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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/mm/page_alloc.c
  *
  *  Manages the free list, the system allocates free pages here.
  *  Note that kmalloc() lives in slab.c
  *
  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  *  Swap reorganised 29.12.95, Stephen Tweedie
  *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
  *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
  *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
  *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
  *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
  *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
  */
 
 #include <linux/stddef.h>
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/interrupt.h>
 #include <linux/pagemap.h>
 #include <linux/jiffies.h>
 #include <linux/memblock.h>
 #include <linux/compiler.h>
 #include <linux/kernel.h>
 #include <linux/kasan.h>
 #include <linux/module.h>
 #include <linux/suspend.h>
 #include <linux/pagevec.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
 #include <linux/ratelimit.h>
 #include <linux/oom.h>
 #include <linux/topology.h>
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
 #include <linux/memory_hotplug.h>
 #include <linux/nodemask.h>
 #include <linux/vmalloc.h>
 #include <linux/vmstat.h>
 #include <linux/mempolicy.h>
 #include <linux/memremap.h>
 #include <linux/stop_machine.h>
 #include <linux/random.h>
 #include <linux/sort.h>
 #include <linux/pfn.h>
 #include <linux/backing-dev.h>
 #include <linux/fault-inject.h>
 #include <linux/page-isolation.h>
 #include <linux/debugobjects.h>
 #include <linux/kmemleak.h>
 #include <linux/compaction.h>
 #include <trace/events/kmem.h>
 #include <trace/events/oom.h>
 #include <linux/prefetch.h>
 #include <linux/mm_inline.h>
 #include <linux/mmu_notifier.h>
 #include <linux/migrate.h>
 #include <linux/hugetlb.h>
 #include <linux/sched/rt.h>
 #include <linux/sched/mm.h>
 #include <linux/page_owner.h>
 #include <linux/page_table_check.h>
 #include <linux/kthread.h>
 #include <linux/memcontrol.h>
 #include <linux/ftrace.h>
 #include <linux/lockdep.h>
 #include <linux/nmi.h>
 #include <linux/psi.h>
 #include <linux/padata.h>
 #include <linux/khugepaged.h>
 #include <linux/buffer_head.h>
 #include <linux/delayacct.h>
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
 #include "internal.h"
 #include "shuffle.h"
 #include "page_reporting.h"
 #include "swap.h"
 
 /* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
 typedef int __bitwise fpi_t;
 
 /* No special request */
 #define FPI_NONE        ((__force fpi_t)0)
 
 /*
  * Skip free page reporting notification for the (possibly merged) page.
  * This does not hinder free page reporting from grabbing the page,
  * reporting it and marking it "reported" -  it only skips notifying
  * the free page reporting infrastructure about a newly freed page. For
  * example, used when temporarily pulling a page from a freelist and
  * putting it back unmodified.
  */
 #define FPI_SKIP_REPORT_NOTIFY  ((__force fpi_t)BIT(0))
 
 /*
  * Place the (possibly merged) page to the tail of the freelist. Will ignore
  * page shuffling (relevant code - e.g., memory onlining - is expected to
  * shuffle the whole zone).
  *
  * Note: No code should rely on this flag for correctness - it's purely
  *       to allow for optimizations when handing back either fresh pages
  *       (memory onlining) or untouched pages (page isolation, free page
  *       reporting).
  */
 #define FPI_TO_TAIL     ((__force fpi_t)BIT(1))
 
 /*
  * Don't poison memory with KASAN (only for the tag-based modes).
  * During boot, all non-reserved memblock memory is exposed to page_alloc.
  * Poisoning all that memory lengthens boot time, especially on systems with
  * large amount of RAM. This flag is used to skip that poisoning.
  * This is only done for the tag-based KASAN modes, as those are able to
  * detect memory corruptions with the memory tags assigned by default.
  * All memory allocated normally after boot gets poisoned as usual.
  */
 #define FPI_SKIP_KASAN_POISON   ((__force fpi_t)BIT(2))
 
 /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
 static DEFINE_MUTEX(pcp_batch_high_lock);
 #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
 
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 /*
  * On SMP, spin_trylock is sufficient protection.
  * On PREEMPT_RT, spin_trylock is equivalent on both SMP and UP.
  */
 #define pcp_trylock_prepare(flags)  do { } while (0)
 #define pcp_trylock_finish(flag)    do { } while (0)
 #else
 
 /* UP spin_trylock always succeeds so disable IRQs to prevent re-entrancy. */
 #define pcp_trylock_prepare(flags)  local_irq_save(flags)
 #define pcp_trylock_finish(flags)   local_irq_restore(flags)
 #endif
 
 /*
  * Locking a pcp requires a PCP lookup followed by a spinlock. To avoid
  * a migration causing the wrong PCP to be locked and remote memory being
  * potentially allocated, pin the task to the CPU for the lookup+lock.
  * preempt_disable is used on !RT because it is faster than migrate_disable.
  * migrate_disable is used on RT because otherwise RT spinlock usage is
  * interfered with and a high priority task cannot preempt the allocator.
  */
 #ifndef CONFIG_PREEMPT_RT
 #define pcpu_task_pin()     preempt_disable()
 #define pcpu_task_unpin()   preempt_enable()
 #else
 #define pcpu_task_pin()     migrate_disable()
 #define pcpu_task_unpin()   migrate_enable()
 #endif
 
 /*
  * Generic helper to lookup and a per-cpu variable with an embedded spinlock.
  * Return value should be used with equivalent unlock helper.
  */
 #define pcpu_spin_lock(type, member, ptr)               \
 ({                                  \
     type *_ret;                         \
     pcpu_task_pin();                        \
     _ret = this_cpu_ptr(ptr);                   \
     spin_lock(&_ret->member);                   \
     _ret;                               \
 })
 
 #define pcpu_spin_lock_irqsave(type, member, ptr, flags)        \
 ({                                  \
     type *_ret;                         \
     pcpu_task_pin();                        \
     _ret = this_cpu_ptr(ptr);                   \
     spin_lock_irqsave(&_ret->member, flags);            \
     _ret;                               \
 })
 
 #define pcpu_spin_trylock_irqsave(type, member, ptr, flags)     \
 ({                                  \
     type *_ret;                         \
     pcpu_task_pin();                        \
     _ret = this_cpu_ptr(ptr);                   \
     if (!spin_trylock_irqsave(&_ret->member, flags)) {      \
         pcpu_task_unpin();                  \
         _ret = NULL;                        \
     }                               \
     _ret;                               \
 })
 
 #define pcpu_spin_unlock(member, ptr)                   \
 ({                                  \
     spin_unlock(&ptr->member);                  \
     pcpu_task_unpin();                      \
 })
 
 #define pcpu_spin_unlock_irqrestore(member, ptr, flags)         \
 ({                                  \
     spin_unlock_irqrestore(&ptr->member, flags);            \
     pcpu_task_unpin();                      \
 })
 
 /* struct per_cpu_pages specific helpers. */
 #define pcp_spin_lock(ptr)                      \
     pcpu_spin_lock(struct per_cpu_pages, lock, ptr)
 
 #define pcp_spin_lock_irqsave(ptr, flags)               \
     pcpu_spin_lock_irqsave(struct per_cpu_pages, lock, ptr, flags)
 
 #define pcp_spin_trylock_irqsave(ptr, flags)                \
     pcpu_spin_trylock_irqsave(struct per_cpu_pages, lock, ptr, flags)
 
 #define pcp_spin_unlock(ptr)                        \
     pcpu_spin_unlock(lock, ptr)
 
 #define pcp_spin_unlock_irqrestore(ptr, flags)              \
     pcpu_spin_unlock_irqrestore(lock, ptr, flags)
 #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
 DEFINE_PER_CPU(int, numa_node);
 EXPORT_PER_CPU_SYMBOL(numa_node);
 #endif
 
 DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 /*
  * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
  * It will not be defined when CONFIG_HAVE_MEMORYLESS_NODES is not defined.
  * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem()
  * defined in <linux/topology.h>.
  */
 DEFINE_PER_CPU(int, _numa_mem_);        /* Kernel "local memory" node */
 EXPORT_PER_CPU_SYMBOL(_numa_mem_);
 #endif
 
 static DEFINE_MUTEX(pcpu_drain_mutex);
 
 #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
 volatile unsigned long latent_entropy __latent_entropy;
 EXPORT_SYMBOL(latent_entropy);
 #endif
 
 /*
  * Array of node states.
  */
 nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
     [N_POSSIBLE] = NODE_MASK_ALL,
     [N_ONLINE] = { { [0] = 1UL } },
 #ifndef CONFIG_NUMA
     [N_NORMAL_MEMORY] = { { [0] = 1UL } },
 #ifdef CONFIG_HIGHMEM
     [N_HIGH_MEMORY] = { { [0] = 1UL } },
 #endif
     [N_MEMORY] = { { [0] = 1UL } },
     [N_CPU] = { { [0] = 1UL } },
 #endif  /* NUMA */
 };
 EXPORT_SYMBOL(node_states);
 
 atomic_long_t _totalram_pages __read_mostly;
 EXPORT_SYMBOL(_totalram_pages);
 unsigned long totalreserve_pages __read_mostly;
 unsigned long totalcma_pages __read_mostly;
 
 int percpu_pagelist_high_fraction;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
 EXPORT_SYMBOL(init_on_alloc);
 
 DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
 EXPORT_SYMBOL(init_on_free);
 
 static bool _init_on_alloc_enabled_early __read_mostly
                 = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);
 static int __init early_init_on_alloc(char *buf)
 {
 
     return kstrtobool(buf, &_init_on_alloc_enabled_early);
 }
 early_param("init_on_alloc", early_init_on_alloc);
 
 static bool _init_on_free_enabled_early __read_mostly
                 = IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON);
 static int __init early_init_on_free(char *buf)
 {
     return kstrtobool(buf, &_init_on_free_enabled_early);
 }
 early_param("init_on_free", early_init_on_free);
 
 /*
  * A cached value of the page's pageblock's migratetype, used when the page is
  * put on a pcplist. Used to avoid the pageblock migratetype lookup when
  * freeing from pcplists in most cases, at the cost of possibly becoming stale.
  * Also the migratetype set in the page does not necessarily match the pcplist
  * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
  * other index - this ensures that it will be put on the correct CMA freelist.
  */
 static inline int get_pcppage_migratetype(struct page *page)
 {
     return page->index;
 }
 
 static inline void set_pcppage_migratetype(struct page *page, int migratetype)
 {
     page->index = migratetype;
 }
 
 #ifdef CONFIG_PM_SLEEP
 /*
  * The following functions are used by the suspend/hibernate code to temporarily
  * change gfp_allowed_mask in order to avoid using I/O during memory allocations
  * while devices are suspended.  To avoid races with the suspend/hibernate code,
  * they should always be called with system_transition_mutex held
  * (gfp_allowed_mask also should only be modified with system_transition_mutex
  * held, unless the suspend/hibernate code is guaranteed not to run in parallel
  * with that modification).
  */
 
 static gfp_t saved_gfp_mask;
 
 void pm_restore_gfp_mask(void)
 {
     WARN_ON(!mutex_is_locked(&system_transition_mutex));
     if (saved_gfp_mask) {
         gfp_allowed_mask = saved_gfp_mask;
         saved_gfp_mask = 0;
     }
 }
 
 void pm_restrict_gfp_mask(void)
 {
     WARN_ON(!mutex_is_locked(&system_transition_mutex));
     WARN_ON(saved_gfp_mask);
     saved_gfp_mask = gfp_allowed_mask;
     gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
 }
 
 bool pm_suspended_storage(void)
 {
     if ((gfp_allowed_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
         return false;
     return true;
 }
 #endif /* CONFIG_PM_SLEEP */
 
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
 unsigned int pageblock_order __read_mostly;
 #endif
 
 static void __free_pages_ok(struct page *page, unsigned int order,
                 fpi_t fpi_flags);
 
 /*
  * results with 256, 32 in the lowmem_reserve sysctl:
  *  1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
  *  1G machine -> (16M dma, 784M normal, 224M high)
  *  NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
  *  HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
  *  HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
  *
  * TBD: should special case ZONE_DMA32 machines here - in those we normally
  * don't need any ZONE_NORMAL reservation
  */
 int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
     [ZONE_DMA] = 256,
 #endif
 #ifdef CONFIG_ZONE_DMA32
     [ZONE_DMA32] = 256,
 #endif
     [ZONE_NORMAL] = 32,
 #ifdef CONFIG_HIGHMEM
     [ZONE_HIGHMEM] = 0,
 #endif
     [ZONE_MOVABLE] = 0,
 };
 
 static char * const zone_names[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
      "DMA",
 #endif
 #ifdef CONFIG_ZONE_DMA32
      "DMA32",
 #endif
      "Normal",
 #ifdef CONFIG_HIGHMEM
      "HighMem",
 #endif
      "Movable",
 #ifdef CONFIG_ZONE_DEVICE
      "Device",
 #endif
 };
 
 const char * const migratetype_names[MIGRATE_TYPES] = {
     "Unmovable",
     "Movable",
     "Reclaimable",
     "HighAtomic",
 #ifdef CONFIG_CMA
     "CMA",
 #endif
 #ifdef CONFIG_MEMORY_ISOLATION
     "Isolate",
 #endif
 };
 
 compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
     [NULL_COMPOUND_DTOR] = NULL,
     [COMPOUND_PAGE_DTOR] = free_compound_page,
 #ifdef CONFIG_HUGETLB_PAGE
     [HUGETLB_PAGE_DTOR] = free_huge_page,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     [TRANSHUGE_PAGE_DTOR] = free_transhuge_page,
 #endif
 };
 
 int min_free_kbytes = 1024;
 int user_min_free_kbytes = -1;
 int watermark_boost_factor __read_mostly = 15000;
 int watermark_scale_factor = 10;
 
 static unsigned long nr_kernel_pages __initdata;
 static unsigned long nr_all_pages __initdata;
 static unsigned long dma_reserve __initdata;
 
 static unsigned long arch_zone_lowest_possible_pfn[MAX_NR_ZONES] __initdata;
 static unsigned long arch_zone_highest_possible_pfn[MAX_NR_ZONES] __initdata;
 static unsigned long required_kernelcore __initdata;
 static unsigned long required_kernelcore_percent __initdata;
 static unsigned long required_movablecore __initdata;
 static unsigned long required_movablecore_percent __initdata;
 static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
 bool mirrored_kernelcore __initdata_memblock;
 
 /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
 int movable_zone;
 EXPORT_SYMBOL(movable_zone);
 
 #if MAX_NUMNODES > 1
 unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
 unsigned int nr_online_nodes __read_mostly = 1;
 EXPORT_SYMBOL(nr_node_ids);
 EXPORT_SYMBOL(nr_online_nodes);
 #endif
 
 int page_group_by_mobility_disabled __read_mostly;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 /*
  * During boot we initialize deferred pages on-demand, as needed, but once
  * page_alloc_init_late() has finished, the deferred pages are all initialized,
  * and we can permanently disable that path.
  */
 static DEFINE_STATIC_KEY_TRUE(deferred_pages);
 
 static inline bool deferred_pages_enabled(void)
 {
     return static_branch_unlikely(&deferred_pages);
 }
 
 /* Returns true if the struct page for the pfn is uninitialised */
 static inline bool __meminit early_page_uninitialised(unsigned long pfn)
 {
     int nid = early_pfn_to_nid(pfn);
 
     if (node_online(nid) && pfn >= NODE_DATA(nid)->first_deferred_pfn)
         return true;
 
     return false;
 }
 
 /*
  * Returns true when the remaining initialisation should be deferred until
  * later in the boot cycle when it can be parallelised.
  */
 static bool __meminit
 defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 {
     static unsigned long prev_end_pfn, nr_initialised;
 
     /*
      * prev_end_pfn static that contains the end of previous zone
      * No need to protect because called very early in boot before smp_init.
      */
     if (prev_end_pfn != end_pfn) {
         prev_end_pfn = end_pfn;
         nr_initialised = 0;
     }
 
     /* Always populate low zones for address-constrained allocations */
     if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
         return false;
 
     if (NODE_DATA(nid)->first_deferred_pfn != ULONG_MAX)
         return true;
     /*
      * We start only with one section of pages, more pages are added as
      * needed until the rest of deferred pages are initialized.
      */
     nr_initialised++;
     if ((nr_initialised > PAGES_PER_SECTION) &&
         (pfn & (PAGES_PER_SECTION - 1)) == 0) {
         NODE_DATA(nid)->first_deferred_pfn = pfn;
         return true;
     }
     return false;
 }
 #else
 static inline bool deferred_pages_enabled(void)
 {
     return false;
 }
 
 static inline bool early_page_uninitialised(unsigned long pfn)
 {
     return false;
 }
 
 static inline bool defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 {
     return false;
 }
 #endif
 
 /* Return a pointer to the bitmap storing bits affecting a block of pages */
 static inline unsigned long *get_pageblock_bitmap(const struct page *page,
                             unsigned long pfn)
 {
 #ifdef CONFIG_SPARSEMEM
     return section_to_usemap(__pfn_to_section(pfn));
 #else
     return page_zone(page)->pageblock_flags;
 #endif /* CONFIG_SPARSEMEM */
 }
 
 static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
 {
 #ifdef CONFIG_SPARSEMEM
     pfn &= (PAGES_PER_SECTION-1);
 #else
     pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
 #endif /* CONFIG_SPARSEMEM */
     return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
 }
 
 static __always_inline
 unsigned long __get_pfnblock_flags_mask(const struct page *page,
                     unsigned long pfn,
                     unsigned long mask)
 {
     unsigned long *bitmap;
     unsigned long bitidx, word_bitidx;
     unsigned long word;
 
     bitmap = get_pageblock_bitmap(page, pfn);
     bitidx = pfn_to_bitidx(page, pfn);
     word_bitidx = bitidx / BITS_PER_LONG;
     bitidx &= (BITS_PER_LONG-1);
     /*
      * This races, without locks, with set_pfnblock_flags_mask(). Ensure
      * a consistent read of the memory array, so that results, even though
      * racy, are not corrupted.
      */
     word = READ_ONCE(bitmap[word_bitidx]);
     return (word >> bitidx) & mask;
 }
 
 /**
  * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
  * @page: The page within the block of interest
  * @pfn: The target page frame number
  * @mask: mask of bits that the caller is interested in
  *
  * Return: pageblock_bits flags
  */
 unsigned long get_pfnblock_flags_mask(const struct page *page,
                     unsigned long pfn, unsigned long mask)
 {
     return __get_pfnblock_flags_mask(page, pfn, mask);
 }
 
 static __always_inline int get_pfnblock_migratetype(const struct page *page,
                     unsigned long pfn)
 {
     return __get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
 }
 
 /**
  * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
  * @page: The page within the block of interest
  * @flags: The flags to set
  * @pfn: The target page frame number
  * @mask: mask of bits that the caller is interested in
  */
 void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
                     unsigned long pfn,
                     unsigned long mask)
 {
     unsigned long *bitmap;
     unsigned long bitidx, word_bitidx;
     unsigned long word;
 
     BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
     BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
 
     bitmap = get_pageblock_bitmap(page, pfn);
     bitidx = pfn_to_bitidx(page, pfn);
     word_bitidx = bitidx / BITS_PER_LONG;
     bitidx &= (BITS_PER_LONG-1);
 
     VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
 
     mask <<= bitidx;
     flags <<= bitidx;
 
     word = READ_ONCE(bitmap[word_bitidx]);
     do {
     } while (!try_cmpxchg(&bitmap[word_bitidx], &word, (word & ~mask) | flags));
 }
 
 void set_pageblock_migratetype(struct page *page, int migratetype)
 {
     if (unlikely(page_group_by_mobility_disabled &&
              migratetype < MIGRATE_PCPTYPES))
         migratetype = MIGRATE_UNMOVABLE;
 
     set_pfnblock_flags_mask(page, (unsigned long)migratetype,
                 page_to_pfn(page), MIGRATETYPE_MASK);
 }
 
 #ifdef CONFIG_DEBUG_VM
 static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 {
     int ret = 0;
     unsigned seq;
     unsigned long pfn = page_to_pfn(page);
     unsigned long sp, start_pfn;
 
     do {
         seq = zone_span_seqbegin(zone);
         start_pfn = zone->zone_start_pfn;
         sp = zone->spanned_pages;
         if (!zone_spans_pfn(zone, pfn))
             ret = 1;
     } while (zone_span_seqretry(zone, seq));
 
     if (ret)
         pr_err("page 0x%lx outside node %d zone %s [ 0x%lx - 0x%lx ]\n",
             pfn, zone_to_nid(zone), zone->name,
             start_pfn, start_pfn + sp);
 
     return ret;
 }
 
 static int page_is_consistent(struct zone *zone, struct page *page)
 {
     if (zone != page_zone(page))
         return 0;
 
     return 1;
 }
 /*
  * Temporary debugging check for pages not lying within a given zone.
  */
 static int __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
     if (page_outside_zone_boundaries(zone, page))
         return 1;
     if (!page_is_consistent(zone, page))
         return 1;
 
     return 0;
 }
 #else
 static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
     return 0;
 }
 #endif
 
 static void bad_page(struct page *page, const char *reason)
 {
     static unsigned long resume;
     static unsigned long nr_shown;
     static unsigned long nr_unshown;
 
     /*
      * Allow a burst of 60 reports, then keep quiet for that minute;
      * or allow a steady drip of one report per second.
      */
     if (nr_shown == 60) {
         if (time_before(jiffies, resume)) {
             nr_unshown++;
             goto out;
         }
         if (nr_unshown) {
             pr_alert(
                   "BUG: Bad page state: %lu messages suppressed\n",
                 nr_unshown);
             nr_unshown = 0;
         }
         nr_shown = 0;
     }
     if (nr_shown++ == 0)
         resume = jiffies + 60 * HZ;
 
     pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
         current->comm, page_to_pfn(page));
     dump_page(page, reason);
 
     print_modules();
     dump_stack();
 out:
     /* Leave bad fields for debug, except PageBuddy could make trouble */
     page_mapcount_reset(page); /* remove PageBuddy */
     add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
 static inline unsigned int order_to_pindex(int migratetype, int order)
 {
     int base = order;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     if (order > PAGE_ALLOC_COSTLY_ORDER) {
         VM_BUG_ON(order != pageblock_order);
         return NR_LOWORDER_PCP_LISTS;
     }
 #else
     VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
 #endif
 
     return (MIGRATE_PCPTYPES * base) + migratetype;
 }
 
 static inline int pindex_to_order(unsigned int pindex)
 {
     int order = pindex / MIGRATE_PCPTYPES;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     if (pindex == NR_LOWORDER_PCP_LISTS)
         order = pageblock_order;
 #else
     VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
 #endif
 
     return order;
 }
 
 static inline bool pcp_allowed_order(unsigned int order)
 {
     if (order <= PAGE_ALLOC_COSTLY_ORDER)
         return true;
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     if (order == pageblock_order)
         return true;
 #endif
     return false;
 }
 
 static inline void free_the_page(struct page *page, unsigned int order)
 {
     if (pcp_allowed_order(order))       /* Via pcp? */
         free_unref_page(page, order);
     else
         __free_pages_ok(page, order, FPI_NONE);
 }
 
 /*
  * Higher-order pages are called "compound pages".  They are structured thusly:
  *
  * The first PAGE_SIZE page is called the "head page" and have PG_head set.
  *
  * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
  * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
  *
  * The first tail page's ->compound_dtor holds the offset in array of compound
  * page destructors. See compound_page_dtors.
  *
  * The first tail page's ->compound_order holds the order of allocation.
  * This usage means that zero-order pages may not be compound.
  */
 
 void free_compound_page(struct page *page)
 {
     mem_cgroup_uncharge(page_folio(page));
     free_the_page(page, compound_order(page));
 }
 
 static void prep_compound_head(struct page *page, unsigned int order)
 {
     set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
     set_compound_order(page, order);
     atomic_set(compound_mapcount_ptr(page), -1);
     atomic_set(compound_pincount_ptr(page), 0);
 }
 
 static void prep_compound_tail(struct page *head, int tail_idx)
 {
     struct page *p = head + tail_idx;
 
     p->mapping = TAIL_MAPPING;
     set_compound_head(p, head);
 }
 
 void prep_compound_page(struct page *page, unsigned int order)
 {
     int i;
     int nr_pages = 1 << order;
 
     __SetPageHead(page);
     for (i = 1; i < nr_pages; i++)
         prep_compound_tail(page, i);
 
     prep_compound_head(page, order);
 }
 
 void destroy_large_folio(struct folio *folio)
 {
     enum compound_dtor_id dtor = folio_page(folio, 1)->compound_dtor;
 
     VM_BUG_ON_FOLIO(dtor >= NR_COMPOUND_DTORS, folio);
     compound_page_dtors[dtor](&folio->page);
 }
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 unsigned int _debug_guardpage_minorder;
 
 bool _debug_pagealloc_enabled_early __read_mostly
             = IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
 EXPORT_SYMBOL(_debug_pagealloc_enabled_early);
 DEFINE_STATIC_KEY_FALSE(_debug_pagealloc_enabled);
 EXPORT_SYMBOL(_debug_pagealloc_enabled);
 
 DEFINE_STATIC_KEY_FALSE(_debug_guardpage_enabled);
 
 static int __init early_debug_pagealloc(char *buf)
 {
     return kstrtobool(buf, &_debug_pagealloc_enabled_early);
 }
 early_param("debug_pagealloc", early_debug_pagealloc);
 
 static int __init debug_guardpage_minorder_setup(char *buf)
 {
     unsigned long res;
 
     if (kstrtoul(buf, 10, &res) < 0 ||  res > MAX_ORDER / 2) {
         pr_err("Bad debug_guardpage_minorder value\n");
         return 0;
     }
     _debug_guardpage_minorder = res;
     pr_info("Setting debug_guardpage_minorder to %lu\n", res);
     return 0;
 }
 early_param("debug_guardpage_minorder", debug_guardpage_minorder_setup);
 
 static inline bool set_page_guard(struct zone *zone, struct page *page,
                 unsigned int order, int migratetype)
 {
     if (!debug_guardpage_enabled())
         return false;
 
     if (order >= debug_guardpage_minorder())
         return false;
 
     __SetPageGuard(page);
     INIT_LIST_HEAD(&page->buddy_list);
     set_page_private(page, order);
     /* Guard pages are not available for any usage */
     __mod_zone_freepage_state(zone, -(1 << order), migratetype);
 
     return true;
 }
 
 static inline void clear_page_guard(struct zone *zone, struct page *page,
                 unsigned int order, int migratetype)
 {
     if (!debug_guardpage_enabled())
         return;
 
     __ClearPageGuard(page);
 
     set_page_private(page, 0);
     if (!is_migrate_isolate(migratetype))
         __mod_zone_freepage_state(zone, (1 << order), migratetype);
 }
 #else
 static inline bool set_page_guard(struct zone *zone, struct page *page,
             unsigned int order, int migratetype) { return false; }
 static inline void clear_page_guard(struct zone *zone, struct page *page,
                 unsigned int order, int migratetype) {}
 #endif
 
 /*
  * Enable static keys related to various memory debugging and hardening options.
  * Some override others, and depend on early params that are evaluated in the
  * order of appearance. So we need to first gather the full picture of what was
  * enabled, and then make decisions.
  */
 void init_mem_debugging_and_hardening(void)
 {
     bool page_poisoning_requested = false;
 
 #ifdef CONFIG_PAGE_POISONING
     /*
      * Page poisoning is debug page alloc for some arches. If
      * either of those options are enabled, enable poisoning.
      */
     if (page_poisoning_enabled() ||
          (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
           debug_pagealloc_enabled())) {
         static_branch_enable(&_page_poisoning_enabled);
         page_poisoning_requested = true;
     }
 #endif
 
     if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) &&
         page_poisoning_requested) {
         pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
             "will take precedence over init_on_alloc and init_on_free\n");
         _init_on_alloc_enabled_early = false;
         _init_on_free_enabled_early = false;
     }
 
     if (_init_on_alloc_enabled_early)
         static_branch_enable(&init_on_alloc);
     else
         static_branch_disable(&init_on_alloc);
 
     if (_init_on_free_enabled_early)
         static_branch_enable(&init_on_free);
     else
         static_branch_disable(&init_on_free);
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
     if (!debug_pagealloc_enabled())
         return;
 
     static_branch_enable(&_debug_pagealloc_enabled);
 
     if (!debug_guardpage_minorder())
         return;
 
     static_branch_enable(&_debug_guardpage_enabled);
 #endif
 }
 
 static inline void set_buddy_order(struct page *page, unsigned int order)
 {
     set_page_private(page, order);
     __SetPageBuddy(page);
 }
 
 #ifdef CONFIG_COMPACTION
 static inline struct capture_control *task_capc(struct zone *zone)
 {
     struct capture_control *capc = current->capture_control;
 
     return unlikely(capc) &&
         !(current->flags & PF_KTHREAD) &&
         !capc->page &&
         capc->cc->zone == zone ? capc : NULL;
 }
 
 static inline bool
 compaction_capture(struct capture_control *capc, struct page *page,
            int order, int migratetype)
 {
     if (!capc || order != capc->cc->order)
         return false;
 
     /* Do not accidentally pollute CMA or isolated regions*/
     if (is_migrate_cma(migratetype) ||
         is_migrate_isolate(migratetype))
         return false;
 
     /*
      * Do not let lower order allocations pollute a movable pageblock.
      * This might let an unmovable request use a reclaimable pageblock
      * and vice-versa but no more than normal fallback logic which can
      * have trouble finding a high-order free page.
      */
     if (order < pageblock_order && migratetype == MIGRATE_MOVABLE)
         return false;
 
     capc->page = page;
     return true;
 }
 
 #else
 static inline struct capture_control *task_capc(struct zone *zone)
 {
     return NULL;
 }
 
 static inline bool
 compaction_capture(struct capture_control *capc, struct page *page,
            int order, int migratetype)
 {
     return false;
 }
 #endif /* CONFIG_COMPACTION */
 
 /* Used for pages not on another list */
 static inline void add_to_free_list(struct page *page, struct zone *zone,
                     unsigned int order, int migratetype)
 {
     struct free_area *area = &zone->free_area[order];
 
     list_add(&page->buddy_list, &area->free_list[migratetype]);
     area->nr_free++;
 }
 
 /* Used for pages not on another list */
 static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
                      unsigned int order, int migratetype)
 {
     struct free_area *area = &zone->free_area[order];
 
     list_add_tail(&page->buddy_list, &area->free_list[migratetype]);
     area->nr_free++;
 }
 
 /*
  * Used for pages which are on another list. Move the pages to the tail
  * of the list - so the moved pages won't immediately be considered for
  * allocation again (e.g., optimization for memory onlining).
  */
 static inline void move_to_free_list(struct page *page, struct zone *zone,
                      unsigned int order, int migratetype)
 {
     struct free_area *area = &zone->free_area[order];
 
     list_move_tail(&page->buddy_list, &area->free_list[migratetype]);
 }
 
 static inline void del_page_from_free_list(struct page *page, struct zone *zone,
                        unsigned int order)
 {
     /* clear reported state and update reported page count */
     if (page_reported(page))
         __ClearPageReported(page);
 
     list_del(&page->buddy_list);
     __ClearPageBuddy(page);
     set_page_private(page, 0);
     zone->free_area[order].nr_free--;
 }
 
 /*
  * If this is not the largest possible page, check if the buddy
  * of the next-highest order is free. If it is, it's possible
  * that pages are being freed that will coalesce soon. In case,
  * that is happening, add the free page to the tail of the list
  * so it's less likely to be used soon and more likely to be merged
  * as a higher order page
  */
 static inline bool
 buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
            struct page *page, unsigned int order)
 {
     unsigned long higher_page_pfn;
     struct page *higher_page;
 
     if (order >= MAX_ORDER - 2)
         return false;
 
     higher_page_pfn = buddy_pfn & pfn;
     higher_page = page + (higher_page_pfn - pfn);
 
     return find_buddy_page_pfn(higher_page, higher_page_pfn, order + 1,
             NULL) != NULL;
 }
 
 /*
  * Freeing function for a buddy system allocator.
  *
  * The concept of a buddy system is to maintain direct-mapped table
  * (containing bit values) for memory blocks of various "orders".
  * The bottom level table contains the map for the smallest allocatable
  * units of memory (here, pages), and each level above it describes
  * pairs of units from the levels below, hence, "buddies".
  * At a high level, all that happens here is marking the table entry
  * at the bottom level available, and propagating the changes upward
  * as necessary, plus some accounting needed to play nicely with other
  * parts of the VM system.
  * At each level, we keep a list of pages, which are heads of continuous
  * free pages of length of (1 << order) and marked with PageBuddy.
  * Page's order is recorded in page_private(page) field.
  * So when we are allocating or freeing one, we can derive the state of the
  * other.  That is, if we allocate a small block, and both were
  * free, the remainder of the region must be split into blocks.
  * If a block is freed, and its buddy is also free, then this
  * triggers coalescing into a block of larger size.
  *
  * -- nyc
  */
 
 static inline void __free_one_page(struct page *page,
         unsigned long pfn,
         struct zone *zone, unsigned int order,
         int migratetype, fpi_t fpi_flags)
 {
     struct capture_control *capc = task_capc(zone);
     unsigned long buddy_pfn;
     unsigned long combined_pfn;
     struct page *buddy;
     bool to_tail;
 
     VM_BUG_ON(!zone_is_initialized(zone));
     VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
 
     VM_BUG_ON(migratetype == -1);
     if (likely(!is_migrate_isolate(migratetype)))
         __mod_zone_freepage_state(zone, 1 << order, migratetype);
 
     VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
     VM_BUG_ON_PAGE(bad_range(zone, page), page);
 
     while (order < MAX_ORDER - 1) {
         if (compaction_capture(capc, page, order, migratetype)) {
             __mod_zone_freepage_state(zone, -(1 << order),
                                 migratetype);
             return;
         }
 
         buddy = find_buddy_page_pfn(page, pfn, order, &buddy_pfn);
         if (!buddy)
             goto done_merging;
 
         if (unlikely(order >= pageblock_order)) {
             /*
              * We want to prevent merge between freepages on pageblock
              * without fallbacks and normal pageblock. Without this,
              * pageblock isolation could cause incorrect freepage or CMA
              * accounting or HIGHATOMIC accounting.
              */
             int buddy_mt = get_pageblock_migratetype(buddy);
 
             if (migratetype != buddy_mt
                     && (!migratetype_is_mergeable(migratetype) ||
                         !migratetype_is_mergeable(buddy_mt)))
                 goto done_merging;
         }
 
         /*
          * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
          * merge with it and move up one order.
          */
         if (page_is_guard(buddy))
             clear_page_guard(zone, buddy, order, migratetype);
         else
             del_page_from_free_list(buddy, zone, order);
         combined_pfn = buddy_pfn & pfn;
         page = page + (combined_pfn - pfn);
         pfn = combined_pfn;
         order++;
     }
 
 done_merging:
     set_buddy_order(page, order);
 
     if (fpi_flags & FPI_TO_TAIL)
         to_tail = true;
     else if (is_shuffle_order(order))
         to_tail = shuffle_pick_tail();
     else
         to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);
 
     if (to_tail)
         add_to_free_list_tail(page, zone, order, migratetype);
     else
         add_to_free_list(page, zone, order, migratetype);
 
     /* Notify page reporting subsystem of freed page */
     if (!(fpi_flags & FPI_SKIP_REPORT_NOTIFY))
         page_reporting_notify_free(order);
 }
 
 /**
  * split_free_page() -- split a free page at split_pfn_offset
  * @free_page:      the original free page
  * @order:      the order of the page
  * @split_pfn_offset:   split offset within the page
  *
  * Return -ENOENT if the free page is changed, otherwise 0
  *
  * It is used when the free page crosses two pageblocks with different migratetypes
  * at split_pfn_offset within the page. The split free page will be put into
  * separate migratetype lists afterwards. Otherwise, the function achieves
  * nothing.
  */
 int split_free_page(struct page *free_page,
             unsigned int order, unsigned long split_pfn_offset)
 {
     struct zone *zone = page_zone(free_page);
     unsigned long free_page_pfn = page_to_pfn(free_page);
     unsigned long pfn;
     unsigned long flags;
     int free_page_order;
     int mt;
     int ret = 0;
 
     if (split_pfn_offset == 0)
         return ret;
 
     spin_lock_irqsave(&zone->lock, flags);
 
     if (!PageBuddy(free_page) || buddy_order(free_page) != order) {
         ret = -ENOENT;
         goto out;
     }
 
     mt = get_pageblock_migratetype(free_page);
     if (likely(!is_migrate_isolate(mt)))
         __mod_zone_freepage_state(zone, -(1UL << order), mt);
 
     del_page_from_free_list(free_page, zone, order);
     for (pfn = free_page_pfn;
          pfn < free_page_pfn + (1UL << order);) {
         int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
 
         free_page_order = min_t(unsigned int,
                     pfn ? __ffs(pfn) : order,
                     __fls(split_pfn_offset));
         __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
                 mt, FPI_NONE);
         pfn += 1UL << free_page_order;
         split_pfn_offset -= (1UL << free_page_order);
         /* we have done the first part, now switch to second part */
         if (split_pfn_offset == 0)
             split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
     }
 out:
     spin_unlock_irqrestore(&zone->lock, flags);
     return ret;
 }
 /*
  * A bad page could be due to a number of fields. Instead of multiple branches,
  * try and check multiple fields with one check. The caller must do a detailed
  * check if necessary.
  */
 static inline bool page_expected_state(struct page *page,
                     unsigned long check_flags)
 {
     if (unlikely(atomic_read(&page->_mapcount) != -1))
         return false;
 
     if (unlikely((unsigned long)page->mapping |
             page_ref_count(page) |
 #ifdef CONFIG_MEMCG
             page->memcg_data |
 #endif
             (page->flags & check_flags)))
         return false;
 
     return true;
 }
 
 static const char *page_bad_reason(struct page *page, unsigned long flags)
 {
     const char *bad_reason = NULL;
 
     if (unlikely(atomic_read(&page->_mapcount) != -1))
         bad_reason = "nonzero mapcount";
     if (unlikely(page->mapping != NULL))
         bad_reason = "non-NULL mapping";
     if (unlikely(page_ref_count(page) != 0))
         bad_reason = "nonzero _refcount";
     if (unlikely(page->flags & flags)) {
         if (flags == PAGE_FLAGS_CHECK_AT_PREP)
             bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag(s) set";
         else
             bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
     }
 #ifdef CONFIG_MEMCG
     if (unlikely(page->memcg_data))
         bad_reason = "page still charged to cgroup";
 #endif
     return bad_reason;
 }
 
 static void check_free_page_bad(struct page *page)
 {
     bad_page(page,
          page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
 }
 
 static inline int check_free_page(struct page *page)
 {
     if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
         return 0;
 
     /* Something has gone sideways, find it */
     check_free_page_bad(page);
     return 1;
 }
 
 static int free_tail_pages_check(struct page *head_page, struct page *page)
 {
     int ret = 1;
 
     /*
      * We rely page->lru.next never has bit 0 set, unless the page
      * is PageTail(). Let's make sure that's true even for poisoned ->lru.
      */
     BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);
 
     if (!IS_ENABLED(CONFIG_DEBUG_VM)) {
         ret = 0;
         goto out;
     }
     switch (page - head_page) {
     case 1:
         /* the first tail page: ->mapping may be compound_mapcount() */
         if (unlikely(compound_mapcount(page))) {
             bad_page(page, "nonzero compound_mapcount");
             goto out;
         }
         break;
     case 2:
         /*
          * the second tail page: ->mapping is
          * deferred_list.next -- ignore value.
          */
         break;
     default:
         if (page->mapping != TAIL_MAPPING) {
             bad_page(page, "corrupted mapping in tail page");
             goto out;
         }
         break;
     }
     if (unlikely(!PageTail(page))) {
         bad_page(page, "PageTail not set");
         goto out;
     }
     if (unlikely(compound_head(page) != head_page)) {
         bad_page(page, "compound_head not consistent");
         goto out;
     }
     ret = 0;
 out:
     page->mapping = NULL;
     clear_compound_head(page);
     return ret;
 }
 
 /*
  * Skip KASAN memory poisoning when either:
  *
  * 1. Deferred memory initialization has not yet completed,
  *    see the explanation below.
  * 2. Skipping poisoning is requested via FPI_SKIP_KASAN_POISON,
  *    see the comment next to it.
  * 3. Skipping poisoning is requested via __GFP_SKIP_KASAN_POISON,
  *    see the comment next to it.
  *
  * Poisoning pages during deferred memory init will greatly lengthen the
  * process and cause problem in large memory systems as the deferred pages
  * initialization is done with interrupt disabled.
  *
  * Assuming that there will be no reference to those newly initialized
  * pages before they are ever allocated, this should have no effect on
  * KASAN memory tracking as the poison will be properly inserted at page
  * allocation time. The only corner case is when pages are allocated by
  * on-demand allocation and then freed again before the deferred pages
  * initialization is done, but this is not likely to happen.
  */
 static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
 {
     return deferred_pages_enabled() ||
            (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
         (fpi_flags & FPI_SKIP_KASAN_POISON)) ||
            PageSkipKASanPoison(page);
 }
 
 static void kernel_init_pages(struct page *page, int numpages)
 {
     int i;
 
     /* s390's use of memset() could override KASAN redzones. */
     kasan_disable_current();
     for (i = 0; i < numpages; i++)
         clear_highpage_kasan_tagged(page + i);
     kasan_enable_current();
 }
 
 static __always_inline bool free_pages_prepare(struct page *page,
             unsigned int order, bool check_free, fpi_t fpi_flags)
 {
     int bad = 0;
     bool init = want_init_on_free();
 
     VM_BUG_ON_PAGE(PageTail(page), page);
 
     trace_mm_page_free(page, order);
 
     if (unlikely(PageHWPoison(page)) && !order) {
         /*
          * Do not let hwpoison pages hit pcplists/buddy
          * Untie memcg state and reset page's owner
          */
         if (memcg_kmem_enabled() && PageMemcgKmem(page))
             __memcg_kmem_uncharge_page(page, order);
         reset_page_owner(page, order);
         page_table_check_free(page, order);
         return false;
     }
 
     /*
      * Check tail pages before head page information is cleared to
      * avoid checking PageCompound for order-0 pages.
      */
     if (unlikely(order)) {
         bool compound = PageCompound(page);
         int i;
 
         VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
         if (compound) {
             ClearPageDoubleMap(page);
             ClearPageHasHWPoisoned(page);
         }
         for (i = 1; i < (1 << order); i++) {
             if (compound)
                 bad += free_tail_pages_check(page, page + i);
             if (unlikely(check_free_page(page + i))) {
                 bad++;
                 continue;
             }
             (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
         }
     }
     if (PageMappingFlags(page))
         page->mapping = NULL;
     if (memcg_kmem_enabled() && PageMemcgKmem(page))
         __memcg_kmem_uncharge_page(page, order);
     if (check_free)
         bad += check_free_page(page);
     if (bad)
         return false;
 
     page_cpupid_reset_last(page);
     page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
     reset_page_owner(page, order);
     page_table_check_free(page, order);
 
     if (!PageHighMem(page)) {
         debug_check_no_locks_freed(page_address(page),
                        PAGE_SIZE << order);
         debug_check_no_obj_freed(page_address(page),
                        PAGE_SIZE << order);
     }
 
     kernel_poison_pages(page, 1 << order);
 
     /*
      * As memory initialization might be integrated into KASAN,
      * KASAN poisoning and memory initialization code must be
      * kept together to avoid discrepancies in behavior.
      *
      * With hardware tag-based KASAN, memory tags must be set before the
      * page becomes unavailable via debug_pagealloc or arch_free_page.
      */
     if (!should_skip_kasan_poison(page, fpi_flags)) {
         kasan_poison_pages(page, order, init);
 
         /* Memory is already initialized if KASAN did it internally. */
         if (kasan_has_integrated_init())
             init = false;
     }
     if (init)
         kernel_init_pages(page, 1 << order);
 
     /*
      * arch_free_page() can make the page's contents inaccessible.  s390
      * does this.  So nothing which can access the page's contents should
      * happen after this.
      */
     arch_free_page(page, order);
 
     debug_pagealloc_unmap_pages(page, 1 << order);
 
     return true;
 }
 
 #ifdef CONFIG_DEBUG_VM
 /*
  * With DEBUG_VM enabled, order-0 pages are checked immediately when being freed
  * to pcp lists. With debug_pagealloc also enabled, they are also rechecked when
  * moved from pcp lists to free lists.
  */
 static bool free_pcp_prepare(struct page *page, unsigned int order)
 {
     return free_pages_prepare(page, order, true, FPI_NONE);
 }
 
 static bool bulkfree_pcp_prepare(struct page *page)
 {
     if (debug_pagealloc_enabled_static())
         return check_free_page(page);
     else
         return false;
 }
 #else
 /*
  * With DEBUG_VM disabled, order-0 pages being freed are checked only when
  * moving from pcp lists to free list in order to reduce overhead. With
  * debug_pagealloc enabled, they are checked also immediately when being freed
  * to the pcp lists.
  */
 static bool free_pcp_prepare(struct page *page, unsigned int order)
 {
     if (debug_pagealloc_enabled_static())
         return free_pages_prepare(page, order, true, FPI_NONE);
     else
         return free_pages_prepare(page, order, false, FPI_NONE);
 }
 
 static bool bulkfree_pcp_prepare(struct page *page)
 {
     return check_free_page(page);
 }
 #endif /* CONFIG_DEBUG_VM */
 
 /*
  * Frees a number of pages from the PCP lists
  * Assumes all pages on list are in same zone.
  * count is the number of pages to free.
  */
 static void free_pcppages_bulk(struct zone *zone, int count,
                     struct per_cpu_pages *pcp,
                     int pindex)
 {
     int min_pindex = 0;
     int max_pindex = NR_PCP_LISTS - 1;
     unsigned int order;
     bool isolated_pageblocks;
     struct page *page;
 
     /*
      * Ensure proper count is passed which otherwise would stuck in the
      * below while (list_empty(list)) loop.
      */
     count = min(pcp->count, count);
 
     /* Ensure requested pindex is drained first. */
     pindex = pindex - 1;
 
     /* Caller must hold IRQ-safe pcp->lock so IRQs are disabled. */
     spin_lock(&zone->lock);
     isolated_pageblocks = has_isolate_pageblock(zone);
 
     while (count > 0) {
         struct list_head *list;
         int nr_pages;
 
         /* Remove pages from lists in a round-robin fashion. */
         do {
             if (++pindex > max_pindex)
                 pindex = min_pindex;
             list = &pcp->lists[pindex];
             if (!list_empty(list))
                 break;
 
             if (pindex == max_pindex)
                 max_pindex--;
             if (pindex == min_pindex)
                 min_pindex++;
         } while (1);
 
         order = pindex_to_order(pindex);
         nr_pages = 1 << order;
         BUILD_BUG_ON(MAX_ORDER >= (1<<NR_PCP_ORDER_WIDTH));
         do {
             int mt;
 
             page = list_last_entry(list, struct page, pcp_list);
             mt = get_pcppage_migratetype(page);
 
             /* must delete to avoid corrupting pcp list */
             list_del(&page->pcp_list);
             count -= nr_pages;
             pcp->count -= nr_pages;
 
             if (bulkfree_pcp_prepare(page))
                 continue;
 
             /* MIGRATE_ISOLATE page should not go to pcplists */
             VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
             /* Pageblock could have been isolated meanwhile */
             if (unlikely(isolated_pageblocks))
                 mt = get_pageblock_migratetype(page);
 
             __free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE);
             trace_mm_page_pcpu_drain(page, order, mt);
         } while (count > 0 && !list_empty(list));
     }
 
     spin_unlock(&zone->lock);
 }
 
 static void free_one_page(struct zone *zone,
                 struct page *page, unsigned long pfn,
                 unsigned int order,
                 int migratetype, fpi_t fpi_flags)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&zone->lock, flags);
     if (unlikely(has_isolate_pageblock(zone) ||
         is_migrate_isolate(migratetype))) {
         migratetype = get_pfnblock_migratetype(page, pfn);
     }
     __free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
     spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 static void __meminit __init_single_page(struct page *page, unsigned long pfn,
                 unsigned long zone, int nid)
 {
     mm_zero_struct_page(page);
     set_page_links(page, zone, nid, pfn);
     init_page_count(page);
     page_mapcount_reset(page);
     page_cpupid_reset_last(page);
     page_kasan_tag_reset(page);
 
     INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
     /* The shift won't overflow because ZONE_NORMAL is below 4G. */
     if (!is_highmem_idx(zone))
         set_page_address(page, __va(pfn << PAGE_SHIFT));
 #endif
 }
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static void __meminit init_reserved_page(unsigned long pfn)
 {
     pg_data_t *pgdat;
     int nid, zid;
 
     if (!early_page_uninitialised(pfn))
         return;
 
     nid = early_pfn_to_nid(pfn);
     pgdat = NODE_DATA(nid);
 
     for (zid = 0; zid < MAX_NR_ZONES; zid++) {
         struct zone *zone = &pgdat->node_zones[zid];
 
         if (zone_spans_pfn(zone, pfn))
             break;
     }
     __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
 }
 #else
 static inline void init_reserved_page(unsigned long pfn)
 {
 }
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 /*
  * Initialised pages do not have PageReserved set. This function is
  * called for each range allocated by the bootmem allocator and
  * marks the pages PageReserved. The remaining valid pages are later
  * sent to the buddy page allocator.
  */
 void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
 {
     unsigned long start_pfn = PFN_DOWN(start);
     unsigned long end_pfn = PFN_UP(end);
 
     for (; start_pfn < end_pfn; start_pfn++) {
         if (pfn_valid(start_pfn)) {
             struct page *page = pfn_to_page(start_pfn);
 
             init_reserved_page(start_pfn);
 
             /* Avoid false-positive PageTail() */
             INIT_LIST_HEAD(&page->lru);
 
             /*
              * no need for atomic set_bit because the struct
              * page is not visible yet so nobody should
              * access it yet.
              */
             __SetPageReserved(page);
         }
     }
 }
 
 static void __free_pages_ok(struct page *page, unsigned int order,
                 fpi_t fpi_flags)
 {
     unsigned long flags;
     int migratetype;
     unsigned long pfn = page_to_pfn(page);
     struct zone *zone = page_zone(page);
 
     if (!free_pages_prepare(page, order, true, fpi_flags))
         return;
 
     migratetype = get_pfnblock_migratetype(page, pfn);
 
     spin_lock_irqsave(&zone->lock, flags);
     if (unlikely(has_isolate_pageblock(zone) ||
         is_migrate_isolate(migratetype))) {
         migratetype = get_pfnblock_migratetype(page, pfn);
     }
     __free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
     spin_unlock_irqrestore(&zone->lock, flags);
 
     __count_vm_events(PGFREE, 1 << order);
 }
 
 void __free_pages_core(struct page *page, unsigned int order)
 {
     unsigned int nr_pages = 1 << order;
     struct page *p = page;
     unsigned int loop;
 
     /*
      * When initializing the memmap, __init_single_page() sets the refcount
      * of all pages to 1 ("allocated"/"not free"). We have to set the
      * refcount of all involved pages to 0.
      */
     prefetchw(p);
     for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
         prefetchw(p + 1);
         __ClearPageReserved(p);
         set_page_count(p, 0);
     }
     __ClearPageReserved(p);
     set_page_count(p, 0);
 
     atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
 
     /*
      * Bypass PCP and place fresh pages right to the tail, primarily
      * relevant for memory onlining.
      */
     __free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
 }
 
 #ifdef CONFIG_NUMA
 
 /*
  * During memory init memblocks map pfns to nids. The search is expensive and
  * this caches recent lookups. The implementation of __early_pfn_to_nid
  * treats start/end as pfns.
  */
 struct mminit_pfnnid_cache {
     unsigned long last_start;
     unsigned long last_end;
     int last_nid;
 };
 
 static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;
 
 /*
  * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
  */
 static int __meminit __early_pfn_to_nid(unsigned long pfn,
                     struct mminit_pfnnid_cache *state)
 {
     unsigned long start_pfn, end_pfn;
     int nid;
 
     if (state->last_start <= pfn && pfn < state->last_end)
         return state->last_nid;
 
     nid = memblock_search_pfn_nid(pfn, &start_pfn, &end_pfn);
     if (nid != NUMA_NO_NODE) {
         state->last_start = start_pfn;
         state->last_end = end_pfn;
         state->last_nid = nid;
     }
 
     return nid;
 }
 
 int __meminit early_pfn_to_nid(unsigned long pfn)
 {
     static DEFINE_SPINLOCK(early_pfn_lock);
     int nid;
 
     spin_lock(&early_pfn_lock);
     nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache);
     if (nid < 0)
         nid = first_online_node;
     spin_unlock(&early_pfn_lock);
 
     return nid;
 }
 #endif /* CONFIG_NUMA */
 
 void __init memblock_free_pages(struct page *page, unsigned long pfn,
                             unsigned int order)
 {
     if (early_page_uninitialised(pfn))
         return;
     __free_pages_core(page, order);
 }
 
 /*
  * Check that the whole (or subset of) a pageblock given by the interval of
  * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
  * with the migration of free compaction scanner.
  *
  * Return struct page pointer of start_pfn, or NULL if checks were not passed.
  *
  * It's possible on some configurations to have a setup like node0 node1 node0
  * i.e. it's possible that all pages within a zones range of pages do not
  * belong to a single zone. We assume that a border between node0 and node1
  * can occur within a single pageblock, but not a node0 node1 node0
  * interleaving within a single pageblock. It is therefore sufficient to check
  * the first and last page of a pageblock and avoid checking each individual
  * page in a pageblock.
  */
 struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
                      unsigned long end_pfn, struct zone *zone)
 {
     struct page *start_page;
     struct page *end_page;
 
     /* end_pfn is one past the range we are checking */
     end_pfn--;
 
     if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
         return NULL;
 
     start_page = pfn_to_online_page(start_pfn);
     if (!start_page)
         return NULL;
 
     if (page_zone(start_page) != zone)
         return NULL;
 
     end_page = pfn_to_page(end_pfn);
 
     /* This gives a shorter code than deriving page_zone(end_page) */
     if (page_zone_id(start_page) != page_zone_id(end_page))
         return NULL;
 
     return start_page;
 }
 
 void set_zone_contiguous(struct zone *zone)
 {
     unsigned long block_start_pfn = zone->zone_start_pfn;
     unsigned long block_end_pfn;
 
     block_end_pfn = ALIGN(block_start_pfn + 1, pageblock_nr_pages);
     for (; block_start_pfn < zone_end_pfn(zone);
             block_start_pfn = block_end_pfn,
              block_end_pfn += pageblock_nr_pages) {
 
         block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));
 
         if (!__pageblock_pfn_to_page(block_start_pfn,
                          block_end_pfn, zone))
             return;
         cond_resched();
     }
 
     /* We confirm that there is no hole */
     zone->contiguous = true;
 }
 
 void clear_zone_contiguous(struct zone *zone)
 {
     zone->contiguous = false;
 }
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static void __init deferred_free_range(unsigned long pfn,
                        unsigned long nr_pages)
 {
     struct page *page;
     unsigned long i;
 
     if (!nr_pages)
         return;
 
     page = pfn_to_page(pfn);
 
     /* Free a large naturally-aligned chunk if possible */
     if (nr_pages == pageblock_nr_pages &&
         (pfn & (pageblock_nr_pages - 1)) == 0) {
         set_pageblock_migratetype(page, MIGRATE_MOVABLE);
         __free_pages_core(page, pageblock_order);
         return;
     }
 
     for (i = 0; i < nr_pages; i++, page++, pfn++) {
         if ((pfn & (pageblock_nr_pages - 1)) == 0)
             set_pageblock_migratetype(page, MIGRATE_MOVABLE);
         __free_pages_core(page, 0);
     }
 }
 
 /* Completion tracking for deferred_init_memmap() threads */
 static atomic_t pgdat_init_n_undone __initdata;
 static __initdata DECLARE_COMPLETION(pgdat_init_all_done_comp);
 
 static inline void __init pgdat_init_report_one_done(void)
 {
     if (atomic_dec_and_test(&pgdat_init_n_undone))
         complete(&pgdat_init_all_done_comp);
 }
 
 /*
  * Returns true if page needs to be initialized or freed to buddy allocator.
  *
  * First we check if pfn is valid on architectures where it is possible to have
  * holes within pageblock_nr_pages. On systems where it is not possible, this
  * function is optimized out.
  *
  * Then, we check if a current large page is valid by only checking the validity
  * of the head pfn.
  */
 static inline bool __init deferred_pfn_valid(unsigned long pfn)
 {
     if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn))
         return false;
     return true;
 }
 
 /*
  * Free pages to buddy allocator. Try to free aligned pages in
  * pageblock_nr_pages sizes.
  */
 static void __init deferred_free_pages(unsigned long pfn,
                        unsigned long end_pfn)
 {
     unsigned long nr_pgmask = pageblock_nr_pages - 1;
     unsigned long nr_free = 0;
 
     for (; pfn < end_pfn; pfn++) {
         if (!deferred_pfn_valid(pfn)) {
             deferred_free_range(pfn - nr_free, nr_free);
             nr_free = 0;
         } else if (!(pfn & nr_pgmask)) {
             deferred_free_range(pfn - nr_free, nr_free);
             nr_free = 1;
         } else {
             nr_free++;
         }
     }
     /* Free the last block of pages to allocator */
     deferred_free_range(pfn - nr_free, nr_free);
 }
 
 /*
  * Initialize struct pages.  We minimize pfn page lookups and scheduler checks
  * by performing it only once every pageblock_nr_pages.
  * Return number of pages initialized.
  */
 static unsigned long  __init deferred_init_pages(struct zone *zone,
                          unsigned long pfn,
                          unsigned long end_pfn)
 {
     unsigned long nr_pgmask = pageblock_nr_pages - 1;
     int nid = zone_to_nid(zone);
     unsigned long nr_pages = 0;
     int zid = zone_idx(zone);
     struct page *page = NULL;
 
     for (; pfn < end_pfn; pfn++) {
         if (!deferred_pfn_valid(pfn)) {
             page = NULL;
             continue;
         } else if (!page || !(pfn & nr_pgmask)) {
             page = pfn_to_page(pfn);
         } else {
             page++;
         }
         __init_single_page(page, pfn, zid, nid);
         nr_pages++;
     }
     return (nr_pages);
 }
 
 /*
  * This function is meant to pre-load the iterator for the zone init.
  * Specifically it walks through the ranges until we are caught up to the
  * first_init_pfn value and exits there. If we never encounter the value we
  * return false indicating there are no valid ranges left.
  */
 static bool __init
 deferred_init_mem_pfn_range_in_zone(u64 *i, struct zone *zone,
                     unsigned long *spfn, unsigned long *epfn,
                     unsigned long first_init_pfn)
 {
     u64 j;
 
     /*
      * Start out by walking through the ranges in this zone that have
      * already been initialized. We don't need to do anything with them
      * so we just need to flush them out of the system.
      */
     for_each_free_mem_pfn_range_in_zone(j, zone, spfn, epfn) {
         if (*epfn <= first_init_pfn)
             continue;
         if (*spfn < first_init_pfn)
             *spfn = first_init_pfn;
         *i = j;
         return true;
     }
 
     return false;
 }
 
 /*
  * Initialize and free pages. We do it in two loops: first we initialize
  * struct page, then free to buddy allocator, because while we are
  * freeing pages we can access pages that are ahead (computing buddy
  * page in __free_one_page()).
  *
  * In order to try and keep some memory in the cache we have the loop
  * broken along max page order boundaries. This way we will not cause
  * any issues with the buddy page computation.
  */
 static unsigned long __init
 deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
                unsigned long *end_pfn)
 {
     unsigned long mo_pfn = ALIGN(*start_pfn + 1, MAX_ORDER_NR_PAGES);
     unsigned long spfn = *start_pfn, epfn = *end_pfn;
     unsigned long nr_pages = 0;
     u64 j = *i;
 
     /* First we loop through and initialize the page values */
     for_each_free_mem_pfn_range_in_zone_from(j, zone, start_pfn, end_pfn) {
         unsigned long t;
 
         if (mo_pfn <= *start_pfn)
             break;
 
         t = min(mo_pfn, *end_pfn);
         nr_pages += deferred_init_pages(zone, *start_pfn, t);
 
         if (mo_pfn < *end_pfn) {
             *start_pfn = mo_pfn;
             break;
         }
     }
 
     /* Reset values and now loop through freeing pages as needed */
     swap(j, *i);
 
     for_each_free_mem_pfn_range_in_zone_from(j, zone, &spfn, &epfn) {
         unsigned long t;
 
         if (mo_pfn <= spfn)
             break;
 
         t = min(mo_pfn, epfn);
         deferred_free_pages(spfn, t);
 
         if (mo_pfn <= epfn)
             break;
     }
 
     return nr_pages;
 }
 
 static void __init
 deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
                void *arg)
 {
     unsigned long spfn, epfn;
     struct zone *zone = arg;
     u64 i;
 
     deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);
 
     /*
      * Initialize and free pages in MAX_ORDER sized increments so that we
      * can avoid introducing any issues with the buddy allocator.
      */
     while (spfn < end_pfn) {
         deferred_init_maxorder(&i, zone, &spfn, &epfn);
         cond_resched();
     }
 }
 
 /* An arch may override for more concurrency. */
 __weak int __init
 deferred_page_init_max_threads(const struct cpumask *node_cpumask)
 {
     return 1;
 }
 
 /* Initialise remaining memory on a node */
 static int __init deferred_init_memmap(void *data)
 {
     pg_data_t *pgdat = data;
     const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
     unsigned long spfn = 0, epfn = 0;
     unsigned long first_init_pfn, flags;
     unsigned long start = jiffies;
     struct zone *zone;
     int zid, max_threads;
     u64 i;
 
     /* Bind memory initialisation thread to a local node if possible */
     if (!cpumask_empty(cpumask))
         set_cpus_allowed_ptr(current, cpumask);
 
     pgdat_resize_lock(pgdat, &flags);
     first_init_pfn = pgdat->first_deferred_pfn;
     if (first_init_pfn == ULONG_MAX) {
         pgdat_resize_unlock(pgdat, &flags);
         pgdat_init_report_one_done();
         return 0;
     }
 
     /* Sanity check boundaries */
     BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn);
     BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
     pgdat->first_deferred_pfn = ULONG_MAX;
 
     /*
      * Once we unlock here, the zone cannot be grown anymore, thus if an
      * interrupt thread must allocate this early in boot, zone must be
      * pre-grown prior to start of deferred page initialization.
      */
     pgdat_resize_unlock(pgdat, &flags);
 
     /* Only the highest zone is deferred so find it */
     for (zid = 0; zid < MAX_NR_ZONES; zid++) {
         zone = pgdat->node_zones + zid;
         if (first_init_pfn < zone_end_pfn(zone))
             break;
     }
 
     /* If the zone is empty somebody else may have cleared out the zone */
     if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                          first_init_pfn))
         goto zone_empty;
 
     max_threads = deferred_page_init_max_threads(cpumask);
 
     while (spfn < epfn) {
         unsigned long epfn_align = ALIGN(epfn, PAGES_PER_SECTION);
         struct padata_mt_job job = {
             .thread_fn   = deferred_init_memmap_chunk,
             .fn_arg      = zone,
             .start       = spfn,
             .size        = epfn_align - spfn,
             .align       = PAGES_PER_SECTION,
             .min_chunk   = PAGES_PER_SECTION,
             .max_threads = max_threads,
         };
 
         padata_do_multithreaded(&job);
         deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                             epfn_align);
     }
 zone_empty:
     /* Sanity check that the next zone really is unpopulated */
     WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));
 
     pr_info("node %d deferred pages initialised in %ums\n",
         pgdat->node_id, jiffies_to_msecs(jiffies - start));
 
     pgdat_init_report_one_done();
     return 0;
 }
 
 /*
  * If this zone has deferred pages, try to grow it by initializing enough
  * deferred pages to satisfy the allocation specified by order, rounded up to
  * the nearest PAGES_PER_SECTION boundary.  So we're adding memory in increments
  * of SECTION_SIZE bytes by initializing struct pages in increments of
  * PAGES_PER_SECTION * sizeof(struct page) bytes.
  *
  * Return true when zone was grown, otherwise return false. We return true even
  * when we grow less than requested, to let the caller decide if there are
  * enough pages to satisfy the allocation.
  *
  * Note: We use noinline because this function is needed only during boot, and
  * it is called from a __ref function _deferred_grow_zone. This way we are
  * making sure that it is not inlined into permanent text section.
  */
 static noinline bool __init
 deferred_grow_zone(struct zone *zone, unsigned int order)
 {
     unsigned long nr_pages_needed = ALIGN(1 << order, PAGES_PER_SECTION);
     pg_data_t *pgdat = zone->zone_pgdat;
     unsigned long first_deferred_pfn = pgdat->first_deferred_pfn;
     unsigned long spfn, epfn, flags;
     unsigned long nr_pages = 0;
     u64 i;
 
     /* Only the last zone may have deferred pages */
     if (zone_end_pfn(zone) != pgdat_end_pfn(pgdat))
         return false;
 
     pgdat_resize_lock(pgdat, &flags);
 
     /*
      * If someone grew this zone while we were waiting for spinlock, return
      * true, as there might be enough pages already.
      */
     if (first_deferred_pfn != pgdat->first_deferred_pfn) {
         pgdat_resize_unlock(pgdat, &flags);
         return true;
     }
 
     /* If the zone is empty somebody else may have cleared out the zone */
     if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
                          first_deferred_pfn)) {
         pgdat->first_deferred_pfn = ULONG_MAX;
         pgdat_resize_unlock(pgdat, &flags);
         /* Retry only once. */
         return first_deferred_pfn != ULONG_MAX;
     }
 
     /*
      * Initialize and free pages in MAX_ORDER sized increments so
      * that we can avoid introducing any issues with the buddy
      * allocator.
      */
     while (spfn < epfn) {
         /* update our first deferred PFN for this section */
         first_deferred_pfn = spfn;
 
         nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
         touch_nmi_watchdog();
 
         /* We should only stop along section boundaries */
         if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)
             continue;
 
         /* If our quota has been met we can stop here */
         if (nr_pages >= nr_pages_needed)
             break;
     }
 
     pgdat->first_deferred_pfn = spfn;
     pgdat_resize_unlock(pgdat, &flags);
 
     return nr_pages > 0;
 }
 
 /*
  * deferred_grow_zone() is __init, but it is called from
  * get_page_from_freelist() during early boot until deferred_pages permanently
  * disables this call. This is why we have refdata wrapper to avoid warning,
  * and to ensure that the function body gets unloaded.
  */
 static bool __ref
 _deferred_grow_zone(struct zone *zone, unsigned int order)
 {
     return deferred_grow_zone(zone, order);
 }
 
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 void __init page_alloc_init_late(void)
 {
     struct zone *zone;
     int nid;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 
     /* There will be num_node_state(N_MEMORY) threads */
     atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
     for_each_node_state(nid, N_MEMORY) {
         kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid);
     }
 
     /* Block until all are initialised */
     wait_for_completion(&pgdat_init_all_done_comp);
 
     /*
      * We initialized the rest of the deferred pages.  Permanently disable
      * on-demand struct page initialization.
      */
     static_branch_disable(&deferred_pages);
 
     /* Reinit limits that are based on free pages after the kernel is up */
     files_maxfiles_init();
 #endif
 
     buffer_init();
 
     /* Discard memblock private memory */
     memblock_discard();
 
     for_each_node_state(nid, N_MEMORY)
         shuffle_free_memory(NODE_DATA(nid));
 
     for_each_populated_zone(zone)
         set_zone_contiguous(zone);
 }
 
 #ifdef CONFIG_CMA
 /* Free whole pageblock and set its migration type to MIGRATE_CMA. */
 void __init init_cma_reserved_pageblock(struct page *page)
 {
     unsigned i = pageblock_nr_pages;
     struct page *p = page;
 
     do {
         __ClearPageReserved(p);
         set_page_count(p, 0);
     } while (++p, --i);
 
     set_pageblock_migratetype(page, MIGRATE_CMA);
     set_page_refcounted(page);
     __free_pages(page, pageblock_order);
 
     adjust_managed_page_count(page, pageblock_nr_pages);
     page_zone(page)->cma_pages += pageblock_nr_pages;
 }
 #endif
 
 /*
  * The order of subdivision here is critical for the IO subsystem.
  * Please do not alter this order without good reasons and regression
  * testing. Specifically, as large blocks of memory are subdivided,
  * the order in which smaller blocks are delivered depends on the order
  * they're subdivided in this function. This is the primary factor
  * influencing the order in which pages are delivered to the IO
  * subsystem according to empirical testing, and this is also justified
  * by considering the behavior of a buddy system containing a single
  * large block of memory acted on by a series of small allocations.
  * This behavior is a critical factor in sglist merging's success.
  *
  * -- nyc
  */
 static inline void expand(struct zone *zone, struct page *page,
     int low, int high, int migratetype)
 {
     unsigned long size = 1 << high;
 
     while (high > low) {
         high--;
         size >>= 1;
         VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
 
         /*
          * Mark as guard pages (or page), that will allow to
          * merge back to allocator when buddy will be freed.
          * Corresponding page table entries will not be touched,
          * pages will stay not present in virtual address space
          */
         if (set_page_guard(zone, &page[size], high, migratetype))
             continue;
 
         add_to_free_list(&page[size], zone, high, migratetype);
         set_buddy_order(&page[size], high);
     }
 }
 
 static void check_new_page_bad(struct page *page)
 {
     if (unlikely(page->flags & __PG_HWPOISON)) {
         /* Don't complain about hwpoisoned pages */
         page_mapcount_reset(page); /* remove PageBuddy */
         return;
     }
 
     bad_page(page,
          page_bad_reason(page, PAGE_FLAGS_CHECK_AT_PREP));
 }
 
 /*
  * This page is about to be returned from the page allocator
  */
 static inline int check_new_page(struct page *page)
 {
     if (likely(page_expected_state(page,
                 PAGE_FLAGS_CHECK_AT_PREP|__PG_HWPOISON)))
         return 0;
 
     check_new_page_bad(page);
     return 1;
 }
 
 static bool check_new_pages(struct page *page, unsigned int order)
 {
     int i;
     for (i = 0; i < (1 << order); i++) {
         struct page *p = page + i;
 
         if (unlikely(check_new_page(p)))
             return true;
     }
 
     return false;
 }
 
 #ifdef CONFIG_DEBUG_VM
 /*
  * With DEBUG_VM enabled, order-0 pages are checked for expected state when
  * being allocated from pcp lists. With debug_pagealloc also enabled, they are
  * also checked when pcp lists are refilled from the free lists.
  */
 static inline bool check_pcp_refill(struct page *page, unsigned int order)
 {
     if (debug_pagealloc_enabled_static())
         return check_new_pages(page, order);
     else
         return false;
 }
 
 static inline bool check_new_pcp(struct page *page, unsigned int order)
 {
     return check_new_pages(page, order);
 }
 #else
 /*
  * With DEBUG_VM disabled, free order-0 pages are checked for expected state
  * when pcp lists are being refilled from the free lists. With debug_pagealloc
  * enabled, they are also checked when being allocated from the pcp lists.
  */
 static inline bool check_pcp_refill(struct page *page, unsigned int order)
 {
     return check_new_pages(page, order);
 }
 static inline bool check_new_pcp(struct page *page, unsigned int order)
 {
     if (debug_pagealloc_enabled_static())
         return check_new_pages(page, order);
     else
         return false;
 }
 #endif /* CONFIG_DEBUG_VM */
 
 static inline bool should_skip_kasan_unpoison(gfp_t flags)
 {
     /* Don't skip if a software KASAN mode is enabled. */
     if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
         IS_ENABLED(CONFIG_KASAN_SW_TAGS))
         return false;
 
     /* Skip, if hardware tag-based KASAN is not enabled. */
     if (!kasan_hw_tags_enabled())
         return true;
 
     /*
      * With hardware tag-based KASAN enabled, skip if this has been
      * requested via __GFP_SKIP_KASAN_UNPOISON.
      */
     return flags & __GFP_SKIP_KASAN_UNPOISON;
 }
 
 static inline bool should_skip_init(gfp_t flags)
 {
     /* Don't skip, if hardware tag-based KASAN is not enabled. */
     if (!kasan_hw_tags_enabled())
         return false;
 
     /* For hardware tag-based KASAN, skip if requested. */
     return (flags & __GFP_SKIP_ZERO);
 }
 
 inline void post_alloc_hook(struct page *page, unsigned int order,
                 gfp_t gfp_flags)
 {
     bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&
             !should_skip_init(gfp_flags);
     bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
     int i;
 
     set_page_private(page, 0);
     set_page_refcounted(page);
 
     arch_alloc_page(page, order);
     debug_pagealloc_map_pages(page, 1 << order);
 
     /*
      * Page unpoisoning must happen before memory initialization.
      * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
      * allocations and the page unpoisoning code will complain.
      */
     kernel_unpoison_pages(page, 1 << order);
 
     /*
      * As memory initialization might be integrated into KASAN,
      * KASAN unpoisoning and memory initializion code must be
      * kept together to avoid discrepancies in behavior.
      */
 
     /*
      * If memory tags should be zeroed (which happens only when memory
      * should be initialized as well).
      */
     if (init_tags) {
         /* Initialize both memory and tags. */
         for (i = 0; i != 1 << order; ++i)
             tag_clear_highpage(page + i);
 
         /* Note that memory is already initialized by the loop above. */
         init = false;
     }
     if (!should_skip_kasan_unpoison(gfp_flags)) {
         /* Unpoison shadow memory or set memory tags. */
         kasan_unpoison_pages(page, order, init);
 
         /* Note that memory is already initialized by KASAN. */
         if (kasan_has_integrated_init())
             init = false;
     } else {
         /* Ensure page_address() dereferencing does not fault. */
         for (i = 0; i != 1 << order; ++i)
             page_kasan_tag_reset(page + i);
     }
     /* If memory is still not initialized, do it now. */
     if (init)
         kernel_init_pages(page, 1 << order);
     /* Propagate __GFP_SKIP_KASAN_POISON to page flags. */
     if (kasan_hw_tags_enabled() && (gfp_flags & __GFP_SKIP_KASAN_POISON))
         SetPageSkipKASanPoison(page);
 
     set_page_owner(page, order, gfp_flags);
     page_table_check_alloc(page, order);
 }
 
 static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
                             unsigned int alloc_flags)
 {
     post_alloc_hook(page, order, gfp_flags);
 
     if (order && (gfp_flags & __GFP_COMP))
         prep_compound_page(page, order);
 
     /*
      * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to
      * allocate the page. The expectation is that the caller is taking
      * steps that will free more memory. The caller should avoid the page
      * being used for !PFMEMALLOC purposes.
      */
     if (alloc_flags & ALLOC_NO_WATERMARKS)
         set_page_pfmemalloc(page);
     else
         clear_page_pfmemalloc(page);
 }
 
 /*
  * Go through the free lists for the given migratetype and remove
  * the smallest available page from the freelists
  */
 static __always_inline
 struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
                         int migratetype)
 {
     unsigned int current_order;
     struct free_area *area;
     struct page *page;
 
     /* Find a page of the appropriate size in the preferred list */
     for (current_order = order; current_order < MAX_ORDER; ++current_order) {
         area = &(zone->free_area[current_order]);
         page = get_page_from_free_area(area, migratetype);
         if (!page)
             continue;
         del_page_from_free_list(page, zone, current_order);
         expand(zone, page, order, current_order, migratetype);
         set_pcppage_migratetype(page, migratetype);
         trace_mm_page_alloc_zone_locked(page, order, migratetype,
                 pcp_allowed_order(order) &&
                 migratetype < MIGRATE_PCPTYPES);
         return page;
     }
 
     return NULL;
 }
 
 
 /*
  * This array describes the order lists are fallen back to when
  * the free lists for the desirable migrate type are depleted
  *
  * The other migratetypes do not have fallbacks.
  */
 static int fallbacks[MIGRATE_TYPES][3] = {
     [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
     [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
     [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
 };
 
 #ifdef CONFIG_CMA
 static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                     unsigned int order)
 {
     return __rmqueue_smallest(zone, order, MIGRATE_CMA);
 }
 #else
 static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                     unsigned int order) { return NULL; }
 #endif
 
 /*
  * Move the free pages in a range to the freelist tail of the requested type.
  * Note that start_page and end_pages are not aligned on a pageblock
  * boundary. If alignment is required, use move_freepages_block()
  */
 static int move_freepages(struct zone *zone,
               unsigned long start_pfn, unsigned long end_pfn,
               int migratetype, int *num_movable)
 {
     struct page *page;
     unsigned long pfn;
     unsigned int order;
     int pages_moved = 0;
 
     for (pfn = start_pfn; pfn <= end_pfn;) {
         page = pfn_to_page(pfn);
         if (!PageBuddy(page)) {
             /*
              * We assume that pages that could be isolated for
              * migration are movable. But we don't actually try
              * isolating, as that would be expensive.
              */
             if (num_movable &&
                     (PageLRU(page) || __PageMovable(page)))
                 (*num_movable)++;
             pfn++;
             continue;
         }
 
         /* Make sure we are not inadvertently changing nodes */
         VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
         VM_BUG_ON_PAGE(page_zone(page) != zone, page);
 
         order = buddy_order(page);
         move_to_free_list(page, zone, order, migratetype);
         pfn += 1 << order;
         pages_moved += 1 << order;
     }
 
     return pages_moved;
 }
 
 int move_freepages_block(struct zone *zone, struct page *page,
                 int migratetype, int *num_movable)
 {
     unsigned long start_pfn, end_pfn, pfn;
 
     if (num_movable)
         *num_movable = 0;
 
     pfn = page_to_pfn(page);
     start_pfn = pfn & ~(pageblock_nr_pages - 1);
     end_pfn = start_pfn + pageblock_nr_pages - 1;
 
     /* Do not cross zone boundaries */
     if (!zone_spans_pfn(zone, start_pfn))
         start_pfn = pfn;
     if (!zone_spans_pfn(zone, end_pfn))
         return 0;
 
     return move_freepages(zone, start_pfn, end_pfn, migratetype,
                                 num_movable);
 }
 
 static void change_pageblock_range(struct page *pageblock_page,
                     int start_order, int migratetype)
 {
     int nr_pageblocks = 1 << (start_order - pageblock_order);
 
     while (nr_pageblocks--) {
         set_pageblock_migratetype(pageblock_page, migratetype);
         pageblock_page += pageblock_nr_pages;
     }
 }
 
 /*
  * When we are falling back to another migratetype during allocation, try to
  * steal extra free pages from the same pageblocks to satisfy further
  * allocations, instead of polluting multiple pageblocks.
  *
  * If we are stealing a relatively large buddy page, it is likely there will
  * be more free pages in the pageblock, so try to steal them all. For
  * reclaimable and unmovable allocations, we steal regardless of page size,
  * as fragmentation caused by those allocations polluting movable pageblocks
  * is worse than movable allocations stealing from unmovable and reclaimable
  * pageblocks.
  */
 static bool can_steal_fallback(unsigned int order, int start_mt)
 {
     /*
      * Leaving this order check is intended, although there is
      * relaxed order check in next check. The reason is that
      * we can actually steal whole pageblock if this condition met,
      * but, below check doesn't guarantee it and that is just heuristic
      * so could be changed anytime.
      */
     if (order >= pageblock_order)
         return true;
 
     if (order >= pageblock_order / 2 ||
         start_mt == MIGRATE_RECLAIMABLE ||
         start_mt == MIGRATE_UNMOVABLE ||
         page_group_by_mobility_disabled)
         return true;
 
     return false;
 }
 
 static inline bool boost_watermark(struct zone *zone)
 {
     unsigned long max_boost;
 
     if (!watermark_boost_factor)
         return false;
     /*
      * Don't bother in zones that are unlikely to produce results.
      * On small machines, including kdump capture kernels running
      * in a small area, boosting the watermark can cause an out of
      * memory situation immediately.
      */
     if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
         return false;
 
     max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
             watermark_boost_factor, 10000);
 
     /*
      * high watermark may be uninitialised if fragmentation occurs
      * very early in boot so do not boost. We do not fall
      * through and boost by pageblock_nr_pages as failing
      * allocations that early means that reclaim is not going
      * to help and it may even be impossible to reclaim the
      * boosted watermark resulting in a hang.
      */
     if (!max_boost)
         return false;
 
     max_boost = max(pageblock_nr_pages, max_boost);
 
     zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages,
         max_boost);
 
     return true;
 }
 
 /*
  * This function implements actual steal behaviour. If order is large enough,
  * we can steal whole pageblock. If not, we first move freepages in this
  * pageblock to our migratetype and determine how many already-allocated pages
  * are there in the pageblock with a compatible migratetype. If at least half
  * of pages are free or compatible, we can change migratetype of the pageblock
  * itself, so pages freed in the future will be put on the correct free list.
  */
 static void steal_suitable_fallback(struct zone *zone, struct page *page,
         unsigned int alloc_flags, int start_type, bool whole_block)
 {
     unsigned int current_order = buddy_order(page);
     int free_pages, movable_pages, alike_pages;
     int old_block_type;
 
     old_block_type = get_pageblock_migratetype(page);
 
     /*
      * This can happen due to races and we want to prevent broken
      * highatomic accounting.
      */
     if (is_migrate_highatomic(old_block_type))
         goto single_page;
 
     /* Take ownership for orders >= pageblock_order */
     if (current_order >= pageblock_order) {
         change_pageblock_range(page, current_order, start_type);
         goto single_page;
     }
 
     /*
      * Boost watermarks to increase reclaim pressure to reduce the
      * likelihood of future fallbacks. Wake kswapd now as the node
      * may be balanced overall and kswapd will not wake naturally.
      */
     if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
         set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 
     /* We are not allowed to try stealing from the whole block */
     if (!whole_block)
         goto single_page;
 
     free_pages = move_freepages_block(zone, page, start_type,
                         &movable_pages);
     /*
      * Determine how many pages are compatible with our allocation.
      * For movable allocation, it's the number of movable pages which
      * we just obtained. For other types it's a bit more tricky.
      */
     if (start_type == MIGRATE_MOVABLE) {
         alike_pages = movable_pages;
     } else {
         /*
          * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
          * to MOVABLE pageblock, consider all non-movable pages as
          * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
          * vice versa, be conservative since we can't distinguish the
          * exact migratetype of non-movable pages.
          */
         if (old_block_type == MIGRATE_MOVABLE)
             alike_pages = pageblock_nr_pages
                         - (free_pages + movable_pages);
         else
             alike_pages = 0;
     }
 
     /* moving whole block can fail due to zone boundary conditions */
     if (!free_pages)
         goto single_page;
 
     /*
      * If a sufficient number of pages in the block are either free or of
      * comparable migratability as our allocation, claim the whole block.
      */
     if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
             page_group_by_mobility_disabled)
         set_pageblock_migratetype(page, start_type);
 
     return;
 
 single_page:
     move_to_free_list(page, zone, current_order, start_type);
 }
 
 /*
  * Check whether there is a suitable fallback freepage with requested order.
  * If only_stealable is true, this function returns fallback_mt only if
  * we can steal other freepages all together. This would help to reduce
  * fragmentation due to mixed migratetype pages in one pageblock.
  */
 int find_suitable_fallback(struct free_area *area, unsigned int order,
             int migratetype, bool only_stealable, bool *can_steal)
 {
     int i;
     int fallback_mt;
 
     if (area->nr_free == 0)
         return -1;
 
     *can_steal = false;
     for (i = 0;; i++) {
         fallback_mt = fallbacks[migratetype][i];
         if (fallback_mt == MIGRATE_TYPES)
             break;
 
         if (free_area_empty(area, fallback_mt))
             continue;
 
         if (can_steal_fallback(order, migratetype))
             *can_steal = true;
 
         if (!only_stealable)
             return fallback_mt;
 
         if (*can_steal)
             return fallback_mt;
     }
 
     return -1;
 }
 
 /*
  * Reserve a pageblock for exclusive use of high-order atomic allocations if
  * there are no empty page blocks that contain a page with a suitable order
  */
 static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
                 unsigned int alloc_order)
 {
     int mt;
     unsigned long max_managed, flags;
 
     /*
      * Limit the number reserved to 1 pageblock or roughly 1% of a zone.
      * Check is race-prone but harmless.
      */
     max_managed = (zone_managed_pages(zone) / 100) + pageblock_nr_pages;
     if (zone->nr_reserved_highatomic >= max_managed)
         return;
 
     spin_lock_irqsave(&zone->lock, flags);
 
     /* Recheck the nr_reserved_highatomic limit under the lock */
     if (zone->nr_reserved_highatomic >= max_managed)
         goto out_unlock;
 
     /* Yoink! */
     mt = get_pageblock_migratetype(page);
     /* Only reserve normal pageblocks (i.e., they can merge with others) */
     if (migratetype_is_mergeable(mt)) {
         zone->nr_reserved_highatomic += pageblock_nr_pages;
         set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
         move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
     }
 
 out_unlock:
     spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 /*
  * Used when an allocation is about to fail under memory pressure. This
  * potentially hurts the reliability of high-order allocations when under
  * intense memory pressure but failed atomic allocations should be easier
  * to recover from than an OOM.
  *
  * If @force is true, try to unreserve a pageblock even though highatomic
  * pageblock is exhausted.
  */
 static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
                         bool force)
 {
     struct zonelist *zonelist = ac->zonelist;
     unsigned long flags;
     struct zoneref *z;
     struct zone *zone;
     struct page *page;
     int order;
     bool ret;
 
     for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->highest_zoneidx,
                                 ac->nodemask) {
         /*
          * Preserve at least one pageblock unless memory pressure
          * is really high.
          */
         if (!force && zone->nr_reserved_highatomic <=
                     pageblock_nr_pages)
             continue;
 
         spin_lock_irqsave(&zone->lock, flags);
         for (order = 0; order < MAX_ORDER; order++) {
             struct free_area *area = &(zone->free_area[order]);
 
             page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
             if (!page)
                 continue;
 
             /*
              * In page freeing path, migratetype change is racy so
              * we can counter several free pages in a pageblock
              * in this loop although we changed the pageblock type
              * from highatomic to ac->migratetype. So we should
              * adjust the count once.
              */
             if (is_migrate_highatomic_page(page)) {
                 /*
                  * It should never happen but changes to
                  * locking could inadvertently allow a per-cpu
                  * drain to add pages to MIGRATE_HIGHATOMIC
                  * while unreserving so be safe and watch for
                  * underflows.
                  */
                 zone->nr_reserved_highatomic -= min(
                         pageblock_nr_pages,
                         zone->nr_reserved_highatomic);
             }
 
             /*
              * Convert to ac->migratetype and avoid the normal
              * pageblock stealing heuristics. Minimally, the caller
              * is doing the work and needs the pages. More
              * importantly, if the block was always converted to
              * MIGRATE_UNMOVABLE or another type then the number
              * of pageblocks that cannot be completely freed
              * may increase.
              */
             set_pageblock_migratetype(page, ac->migratetype);
             ret = move_freepages_block(zone, page, ac->migratetype,
                                     NULL);
             if (ret) {
                 spin_unlock_irqrestore(&zone->lock, flags);
                 return ret;
             }
         }
         spin_unlock_irqrestore(&zone->lock, flags);
     }
 
     return false;
 }
 
 /*
  * Try finding a free buddy page on the fallback list and put it on the free
  * list of requested migratetype, possibly along with other pages from the same
  * block, depending on fragmentation avoidance heuristics. Returns true if
  * fallback was found so that __rmqueue_smallest() can grab it.
  *
  * The use of signed ints for order and current_order is a deliberate
  * deviation from the rest of this file, to make the for loop
  * condition simpler.
  */
 static __always_inline bool
 __rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
                         unsigned int alloc_flags)
 {
     struct free_area *area;
     int current_order;
     int min_order = order;
     struct page *page;
     int fallback_mt;
     bool can_steal;
 
     /*
      * Do not steal pages from freelists belonging to other pageblocks
      * i.e. orders < pageblock_order. If there are no local zones free,
      * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
      */
     if (alloc_flags & ALLOC_NOFRAGMENT)
         min_order = pageblock_order;
 
     /*
      * Find the largest available free page in the other list. This roughly
      * approximates finding the pageblock with the most free pages, which
      * would be too costly to do exactly.
      */
     for (current_order = MAX_ORDER - 1; current_order >= min_order;
                 --current_order) {
         area = &(zone->free_area[current_order]);
         fallback_mt = find_suitable_fallback(area, current_order,
                 start_migratetype, false, &can_steal);
         if (fallback_mt == -1)
             continue;
 
         /*
          * We cannot steal all free pages from the pageblock and the
          * requested migratetype is movable. In that case it's better to
          * steal and split the smallest available page instead of the
          * largest available page, because even if the next movable
          * allocation falls back into a different pageblock than this
          * one, it won't cause permanent fragmentation.
          */
         if (!can_steal && start_migratetype == MIGRATE_MOVABLE
                     && current_order > order)
             goto find_smallest;
 
         goto do_steal;
     }
 
     return false;
 
 find_smallest:
     for (current_order = order; current_order < MAX_ORDER;
                             current_order++) {
         area = &(zone->free_area[current_order]);
         fallback_mt = find_suitable_fallback(area, current_order,
                 start_migratetype, false, &can_steal);
         if (fallback_mt != -1)
             break;
     }
 
     /*
      * This should not happen - we already found a suitable fallback
      * when looking for the largest page.
      */
     VM_BUG_ON(current_order == MAX_ORDER);
 
 do_steal:
     page = get_page_from_free_area(area, fallback_mt);
 
     steal_suitable_fallback(zone, page, alloc_flags, start_migratetype,
                                 can_steal);
 
     trace_mm_page_alloc_extfrag(page, order, current_order,
         start_migratetype, fallback_mt);
 
     return true;
 
 }
 
 /*
  * Do the hard work of removing an element from the buddy allocator.
  * Call me with the zone->lock already held.
  */
 static __always_inline struct page *
 __rmqueue(struct zone *zone, unsigned int order, int migratetype,
                         unsigned int alloc_flags)
 {
     struct page *page;
 
     if (IS_ENABLED(CONFIG_CMA)) {
         /*
          * Balance movable allocations between regular and CMA areas by
          * allocating from CMA when over half of the zone's free memory
          * is in the CMA area.
          */
         if (alloc_flags & ALLOC_CMA &&
             zone_page_state(zone, NR_FREE_CMA_PAGES) >
             zone_page_state(zone, NR_FREE_PAGES) / 2) {
             page = __rmqueue_cma_fallback(zone, order);
             if (page)
                 return page;
         }
     }
 retry:
     page = __rmqueue_smallest(zone, order, migratetype);
     if (unlikely(!page)) {
         if (alloc_flags & ALLOC_CMA)
             page = __rmqueue_cma_fallback(zone, order);
 
         if (!page && __rmqueue_fallback(zone, order, migratetype,
                                 alloc_flags))
             goto retry;
     }
     return page;
 }
 
 /*
  * Obtain a specified number of elements from the buddy allocator, all under
  * a single hold of the lock, for efficiency.  Add them to the supplied list.
  * Returns the number of new pages which were placed at *list.
  */
 static int rmqueue_bulk(struct zone *zone, unsigned int order,
             unsigned long count, struct list_head *list,
             int migratetype, unsigned int alloc_flags)
 {
     int i, allocated = 0;
 
     /* Caller must hold IRQ-safe pcp->lock so IRQs are disabled. */
     spin_lock(&zone->lock);
     for (i = 0; i < count; ++i) {
         struct page *page = __rmqueue(zone, order, migratetype,
                                 alloc_flags);
         if (unlikely(page == NULL))
             break;
 
         if (unlikely(check_pcp_refill(page, order)))
             continue;
 
         /*
          * Split buddy pages returned by expand() are received here in
          * physical page order. The page is added to the tail of
          * caller's list. From the callers perspective, the linked list
          * is ordered by page number under some conditions. This is
          * useful for IO devices that can forward direction from the
          * head, thus also in the physical page order. This is useful
          * for IO devices that can merge IO requests if the physical
          * pages are ordered properly.
          */
         list_add_tail(&page->pcp_list, list);
         allocated++;
         if (is_migrate_cma(get_pcppage_migratetype(page)))
             __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
                           -(1 << order));
     }
 
     /*
      * i pages were removed from the buddy list even if some leak due
      * to check_pcp_refill failing so adjust NR_FREE_PAGES based
      * on i. Do not confuse with 'allocated' which is the number of
      * pages added to the pcp list.
      */
     __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
     spin_unlock(&zone->lock);
     return allocated;
 }
 
 #ifdef CONFIG_NUMA
 /*
  * Called from the vmstat counter updater to drain pagesets of this
  * currently executing processor on remote nodes after they have
  * expired.
  */
 void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
 {
     int to_drain, batch;
 
     batch = READ_ONCE(pcp->batch);
     to_drain = min(pcp->count, batch);
     if (to_drain > 0) {
         unsigned long flags;
 
         /*
          * free_pcppages_bulk expects IRQs disabled for zone->lock
          * so even though pcp->lock is not intended to be IRQ-safe,
          * it's needed in this context.
          */
         spin_lock_irqsave(&pcp->lock, flags);
         free_pcppages_bulk(zone, to_drain, pcp, 0);
         spin_unlock_irqrestore(&pcp->lock, flags);
     }
 }
 #endif
 
 /*
  * Drain pcplists of the indicated processor and zone.
  */
 static void drain_pages_zone(unsigned int cpu, struct zone *zone)
 {
     struct per_cpu_pages *pcp;
 
     pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
     if (pcp->count) {
         unsigned long flags;
 
         /* See drain_zone_pages on why this is disabling IRQs */
         spin_lock_irqsave(&pcp->lock, flags);
         free_pcppages_bulk(zone, pcp->count, pcp, 0);
         spin_unlock_irqrestore(&pcp->lock, flags);
     }
 }
 
 /*
  * Drain pcplists of all zones on the indicated processor.
  */
 static void drain_pages(unsigned int cpu)
 {
     struct zone *zone;
 
     for_each_populated_zone(zone) {
         drain_pages_zone(cpu, zone);
     }
 }
 
 /*
  * Spill all of this CPU's per-cpu pages back into the buddy allocator.
  */
 void drain_local_pages(struct zone *zone)
 {
     int cpu = smp_processor_id();
 
     if (zone)
         drain_pages_zone(cpu, zone);
     else
         drain_pages(cpu);
 }
 
 /*
  * The implementation of drain_all_pages(), exposing an extra parameter to
  * drain on all cpus.
  *
  * drain_all_pages() is optimized to only execute on cpus where pcplists are
  * not empty. The check for non-emptiness can however race with a free to
  * pcplist that has not yet increased the pcp->count from 0 to 1. Callers
  * that need the guarantee that every CPU has drained can disable the
  * optimizing racy check.
  */
 static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
 {
     int cpu;
 
     /*
      * Allocate in the BSS so we won't require allocation in
      * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
      */
     static cpumask_t cpus_with_pcps;
 
     /*
      * Do not drain if one is already in progress unless it's specific to
      * a zone. Such callers are primarily CMA and memory hotplug and need
      * the drain to be complete when the call returns.
      */
     if (unlikely(!mutex_trylock(&pcpu_drain_mutex))) {
         if (!zone)
             return;
         mutex_lock(&pcpu_drain_mutex);
     }
 
     /*
      * We don't care about racing with CPU hotplug event
      * as offline notification will cause the notified
      * cpu to drain that CPU pcps and on_each_cpu_mask
      * disables preemption as part of its processing
      */
     for_each_online_cpu(cpu) {
         struct per_cpu_pages *pcp;
         struct zone *z;
         bool has_pcps = false;
 
         if (force_all_cpus) {
             /*
              * The pcp.count check is racy, some callers need a
              * guarantee that no cpu is missed.
              */
             has_pcps = true;
         } else if (zone) {
             pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
             if (pcp->count)
                 has_pcps = true;
         } else {
             for_each_populated_zone(z) {
                 pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
                 if (pcp->count) {
                     has_pcps = true;
                     break;
                 }
             }
         }
 
         if (has_pcps)
             cpumask_set_cpu(cpu, &cpus_with_pcps);
         else
             cpumask_clear_cpu(cpu, &cpus_with_pcps);
     }
 
     for_each_cpu(cpu, &cpus_with_pcps) {
         if (zone)
             drain_pages_zone(cpu, zone);
         else
             drain_pages(cpu);
     }
 
     mutex_unlock(&pcpu_drain_mutex);
 }
 
 /*
  * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
  *
  * When zone parameter is non-NULL, spill just the single zone's pages.
  */
 void drain_all_pages(struct zone *zone)
 {
     __drain_all_pages(zone, false);
 }
 
 #ifdef CONFIG_HIBERNATION
 
 /*
  * Touch the watchdog for every WD_PAGE_COUNT pages.
  */
 #define WD_PAGE_COUNT   (128*1024)
 
 void mark_free_pages(struct zone *zone)
 {
     unsigned long pfn, max_zone_pfn, page_count = WD_PAGE_COUNT;
     unsigned long flags;
     unsigned int order, t;
     struct page *page;
 
     if (zone_is_empty(zone))
         return;
 
     spin_lock_irqsave(&zone->lock, flags);
 
     max_zone_pfn = zone_end_pfn(zone);
     for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
         if (pfn_valid(pfn)) {
             page = pfn_to_page(pfn);
 
             if (!--page_count) {
                 touch_nmi_watchdog();
                 page_count = WD_PAGE_COUNT;
             }
 
             if (page_zone(page) != zone)
                 continue;
 
             if (!swsusp_page_is_forbidden(page))
                 swsusp_unset_page_free(page);
         }
 
     for_each_migratetype_order(order, t) {
         list_for_each_entry(page,
                 &zone->free_area[order].free_list[t], buddy_list) {
             unsigned long i;
 
             pfn = page_to_pfn(page);
             for (i = 0; i < (1UL << order); i++) {
                 if (!--page_count) {
                     touch_nmi_watchdog();
                     page_count = WD_PAGE_COUNT;
                 }
                 swsusp_set_page_free(pfn_to_page(pfn + i));
             }
         }
     }
     spin_unlock_irqrestore(&zone->lock, flags);
 }
 #endif /* CONFIG_PM */
 
 static bool free_unref_page_prepare(struct page *page, unsigned long pfn,
                             unsigned int order)
 {
     int migratetype;
 
     if (!free_pcp_prepare(page, order))
         return false;
 
     migratetype = get_pfnblock_migratetype(page, pfn);
     set_pcppage_migratetype(page, migratetype);
     return true;
 }
 
 static int nr_pcp_free(struct per_cpu_pages *pcp, int high, int batch,
                bool free_high)
 {
     int min_nr_free, max_nr_free;
 
     /* Free everything if batch freeing high-order pages. */
     if (unlikely(free_high))
         return pcp->count;
 
     /* Check for PCP disabled or boot pageset */
     if (unlikely(high < batch))
         return 1;
 
     /* Leave at least pcp->batch pages on the list */
     min_nr_free = batch;
     max_nr_free = high - batch;
 
     /*
      * Double the number of pages freed each time there is subsequent
      * freeing of pages without any allocation.
      */
     batch <<= pcp->free_factor;
     if (batch < max_nr_free)
         pcp->free_factor++;
     batch = clamp(batch, min_nr_free, max_nr_free);
 
     return batch;
 }
 
 static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone,
                bool free_high)
 {
     int high = READ_ONCE(pcp->high);
 
     if (unlikely(!high || free_high))
         return 0;
 
     if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags))
         return high;
 
     /*
      * If reclaim is active, limit the number of pages that can be
      * stored on pcp lists
      */
     return min(READ_ONCE(pcp->batch) << 2, high);
 }
 
 static void free_unref_page_commit(struct zone *zone, struct per_cpu_pages *pcp,
                    struct page *page, int migratetype,
                    unsigned int order)
 {
     int high;
     int pindex;
     bool free_high;
 
     __count_vm_event(PGFREE);
     pindex = order_to_pindex(migratetype, order);
     list_add(&page->pcp_list, &pcp->lists[pindex]);
     pcp->count += 1 << order;
 
     /*
      * As high-order pages other than THP's stored on PCP can contribute
      * to fragmentation, limit the number stored when PCP is heavily
      * freeing without allocation. The remainder after bulk freeing
      * stops will be drained from vmstat refresh context.
      */
     free_high = (pcp->free_factor && order && order <= PAGE_ALLOC_COSTLY_ORDER);
 
     high = nr_pcp_high(pcp, zone, free_high);
     if (pcp->count >= high) {
         int batch = READ_ONCE(pcp->batch);
 
         free_pcppages_bulk(zone, nr_pcp_free(pcp, high, batch, free_high), pcp, pindex);
     }
 }
 
 /*
  * Free a pcp page
  */
 void free_unref_page(struct page *page, unsigned int order)
 {
     unsigned long flags;
     unsigned long __maybe_unused UP_flags;
     struct per_cpu_pages *pcp;
     struct zone *zone;
     unsigned long pfn = page_to_pfn(page);
     int migratetype;
 
     if (!free_unref_page_prepare(page, pfn, order))
         return;
 
     /*
      * We only track unmovable, reclaimable and movable on pcp lists.
      * Place ISOLATE pages on the isolated list because they are being
      * offlined but treat HIGHATOMIC as movable pages so we can get those
      * areas back if necessary. Otherwise, we may have to free
      * excessively into the page allocator
      */
     migratetype = get_pcppage_migratetype(page);
     if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
         if (unlikely(is_migrate_isolate(migratetype))) {
             free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE);
             return;
         }
         migratetype = MIGRATE_MOVABLE;
     }
 
     zone = page_zone(page);
     pcp_trylock_prepare(UP_flags);
     pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
     if (pcp) {
         free_unref_page_commit(zone, pcp, page, migratetype, order);
         pcp_spin_unlock_irqrestore(pcp, flags);
     } else {
         free_one_page(zone, page, pfn, order, migratetype, FPI_NONE);
     }
     pcp_trylock_finish(UP_flags);
 }
 
 /*
  * Free a list of 0-order pages
  */
 void free_unref_page_list(struct list_head *list)
 {
     struct page *page, *next;
     struct per_cpu_pages *pcp = NULL;
     struct zone *locked_zone = NULL;
     unsigned long flags;
     int batch_count = 0;
     int migratetype;
 
     /* Prepare pages for freeing */
     list_for_each_entry_safe(page, next, list, lru) {
         unsigned long pfn = page_to_pfn(page);
         if (!free_unref_page_prepare(page, pfn, 0)) {
             list_del(&page->lru);
             continue;
         }
 
         /*
          * Free isolated pages directly to the allocator, see
          * comment in free_unref_page.
          */
         migratetype = get_pcppage_migratetype(page);
         if (unlikely(is_migrate_isolate(migratetype))) {
             list_del(&page->lru);
             free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
             continue;
         }
     }
 
     list_for_each_entry_safe(page, next, list, lru) {
         struct zone *zone = page_zone(page);
 
         /* Different zone, different pcp lock. */
         if (zone != locked_zone) {
             if (pcp)
                 pcp_spin_unlock_irqrestore(pcp, flags);
 
             locked_zone = zone;
             pcp = pcp_spin_lock_irqsave(locked_zone->per_cpu_pageset, flags);
         }
 
         /*
          * Non-isolated types over MIGRATE_PCPTYPES get added
          * to the MIGRATE_MOVABLE pcp list.
          */
         migratetype = get_pcppage_migratetype(page);
         if (unlikely(migratetype >= MIGRATE_PCPTYPES))
             migratetype = MIGRATE_MOVABLE;
 
         trace_mm_page_free_batched(page);
         free_unref_page_commit(zone, pcp, page, migratetype, 0);
 
         /*
          * Guard against excessive IRQ disabled times when we get
          * a large list of pages to free.
          */
         if (++batch_count == SWAP_CLUSTER_MAX) {
             pcp_spin_unlock_irqrestore(pcp, flags);
             batch_count = 0;
             pcp = pcp_spin_lock_irqsave(locked_zone->per_cpu_pageset, flags);
         }
     }
 
     if (pcp)
         pcp_spin_unlock_irqrestore(pcp, flags);
 }
 
 /*
  * split_page takes a non-compound higher-order page, and splits it into
  * n (1<<order) sub-pages: page[0..n]
  * Each sub-page must be freed individually.
  *
  * Note: this is probably too low level an operation for use in drivers.
  * Please consult with lkml before using this in your driver.
  */
 void split_page(struct page *page, unsigned int order)
 {
     int i;
 
     VM_BUG_ON_PAGE(PageCompound(page), page);
     VM_BUG_ON_PAGE(!page_count(page), page);
 
     for (i = 1; i < (1 << order); i++)
         set_page_refcounted(page + i);
     split_page_owner(page, 1 << order);
     split_page_memcg(page, 1 << order);
 }
 EXPORT_SYMBOL_GPL(split_page);
 
 int __isolate_free_page(struct page *page, unsigned int order)
 {
     unsigned long watermark;
     struct zone *zone;
     int mt;
 
     BUG_ON(!PageBuddy(page));
 
     zone = page_zone(page);
     mt = get_pageblock_migratetype(page);
 
     if (!is_migrate_isolate(mt)) {
         /*
          * Obey watermarks as if the page was being allocated. We can
          * emulate a high-order watermark check with a raised order-0
          * watermark, because we already know our high-order page
          * exists.
          */
         watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
         if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
             return 0;
 
         __mod_zone_freepage_state(zone, -(1UL << order), mt);
     }
 
     /* Remove page from free list */
 
     del_page_from_free_list(page, zone, order);
 
     /*
      * Set the pageblock if the isolated page is at least half of a
      * pageblock
      */
     if (order >= pageblock_order - 1) {
         struct page *endpage = page + (1 << order) - 1;
         for (; page < endpage; page += pageblock_nr_pages) {
             int mt = get_pageblock_migratetype(page);
             /*
              * Only change normal pageblocks (i.e., they can merge
              * with others)
              */
             if (migratetype_is_mergeable(mt))
                 set_pageblock_migratetype(page,
                               MIGRATE_MOVABLE);
         }
     }
 
 
     return 1UL << order;
 }
 
 /**
  * __putback_isolated_page - Return a now-isolated page back where we got it
  * @page: Page that was isolated
  * @order: Order of the isolated page
  * @mt: The page's pageblock's migratetype
  *
  * This function is meant to return a page pulled from the free lists via
  * __isolate_free_page back to the free lists they were pulled from.
  */
 void __putback_isolated_page(struct page *page, unsigned int order, int mt)
 {
     struct zone *zone = page_zone(page);
 
     /* zone lock should be held when this function is called */
     lockdep_assert_held(&zone->lock);
 
     /* Return isolated page to tail of freelist. */
     __free_one_page(page, page_to_pfn(page), zone, order, mt,
             FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL);
 }
 
 /*
  * Update NUMA hit/miss statistics
  *
  * Must be called with interrupts disabled.
  */
 static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
                    long nr_account)
 {
 #ifdef CONFIG_NUMA
     enum numa_stat_item local_stat = NUMA_LOCAL;
 
     /* skip numa counters update if numa stats is disabled */
     if (!static_branch_likely(&vm_numa_stat_key))
         return;
 
     if (zone_to_nid(z) != numa_node_id())
         local_stat = NUMA_OTHER;
 
     if (zone_to_nid(z) == zone_to_nid(preferred_zone))
         __count_numa_events(z, NUMA_HIT, nr_account);
     else {
         __count_numa_events(z, NUMA_MISS, nr_account);
         __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
     }
     __count_numa_events(z, local_stat, nr_account);
 #endif
 }
 
 static __always_inline
 struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
                unsigned int order, unsigned int alloc_flags,
                int migratetype)
 {
     struct page *page;
     unsigned long flags;
 
     do {
         page = NULL;
         spin_lock_irqsave(&zone->lock, flags);
         /*
          * order-0 request can reach here when the pcplist is skipped
          * due to non-CMA allocation context. HIGHATOMIC area is
          * reserved for high-order atomic allocation, so order-0
          * request should skip it.
          */
         if (order > 0 && alloc_flags & ALLOC_HARDER)
             page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
         if (!page) {
             page = __rmqueue(zone, order, migratetype, alloc_flags);
             if (!page) {
                 spin_unlock_irqrestore(&zone->lock, flags);
                 return NULL;
             }
         }
         __mod_zone_freepage_state(zone, -(1 << order),
                       get_pcppage_migratetype(page));
         spin_unlock_irqrestore(&zone->lock, flags);
     } while (check_new_pages(page, order));
 
     __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
     zone_statistics(preferred_zone, zone, 1);
 
     return page;
 }
 
 /* Remove page from the per-cpu list, caller must protect the list */
 static inline
 struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
             int migratetype,
             unsigned int alloc_flags,
             struct per_cpu_pages *pcp,
             struct list_head *list)
 {
     struct page *page;
 
     do {
         if (list_empty(list)) {
             int batch = READ_ONCE(pcp->batch);
             int alloced;
 
             /*
              * Scale batch relative to order if batch implies
              * free pages can be stored on the PCP. Batch can
              * be 1 for small zones or for boot pagesets which
              * should never store free pages as the pages may
              * belong to arbitrary zones.
              */
             if (batch > 1)
                 batch = max(batch >> order, 2);
             alloced = rmqueue_bulk(zone, order,
                     batch, list,
                     migratetype, alloc_flags);
 
             pcp->count += alloced << order;
             if (unlikely(list_empty(list)))
                 return NULL;
         }
 
         page = list_first_entry(list, struct page, pcp_list);
         list_del(&page->pcp_list);
         pcp->count -= 1 << order;
     } while (check_new_pcp(page, order));
 
     return page;
 }
 
 /* Lock and remove page from the per-cpu list */
 static struct page *rmqueue_pcplist(struct zone *preferred_zone,
             struct zone *zone, unsigned int order,
             gfp_t gfp_flags, int migratetype,
             unsigned int alloc_flags)
 {
     struct per_cpu_pages *pcp;
     struct list_head *list;
     struct page *page;
     unsigned long flags;
     unsigned long __maybe_unused UP_flags;
 
     /*
      * spin_trylock may fail due to a parallel drain. In the future, the
      * trylock will also protect against IRQ reentrancy.
      */
     pcp_trylock_prepare(UP_flags);
     pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
     if (!pcp) {
         pcp_trylock_finish(UP_flags);
         return NULL;
     }
 
     /*
      * On allocation, reduce the number of pages that are batch freed.
      * See nr_pcp_free() where free_factor is increased for subsequent
      * frees.
      */
     pcp->free_factor >>= 1;
     list = &pcp->lists[order_to_pindex(migratetype, order)];
     page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
     pcp_spin_unlock_irqrestore(pcp, flags);
     pcp_trylock_finish(UP_flags);
     if (page) {
         __count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
         zone_statistics(preferred_zone, zone, 1);
     }
     return page;
 }
 
 /*
  * Allocate a page from the given zone. Use pcplists for order-0 allocations.
  */
 static inline
 struct page *rmqueue(struct zone *preferred_zone,
             struct zone *zone, unsigned int order,
             gfp_t gfp_flags, unsigned int alloc_flags,
             int migratetype)
 {
     struct page *page;
 
     /*
      * We most definitely don't want callers attempting to
      * allocate greater than order-1 page units with __GFP_NOFAIL.
      */
     WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
 
     if (likely(pcp_allowed_order(order))) {
         /*
          * MIGRATE_MOVABLE pcplist could have the pages on CMA area and
          * we need to skip it when CMA area isn't allowed.
          */
         if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA ||
                 migratetype != MIGRATE_MOVABLE) {
             page = rmqueue_pcplist(preferred_zone, zone, order,
                     gfp_flags, migratetype, alloc_flags);
             if (likely(page))
                 goto out;
         }
     }
 
     page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
                             migratetype);
 
 out:
     /* Separate test+clear to avoid unnecessary atomics */
     if (unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
         clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
         wakeup_kswapd(zone, 0, 0, zone_idx(zone));
     }
 
     VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
     return page;
 }
 
 #ifdef CONFIG_FAIL_PAGE_ALLOC
 
 static struct {
     struct fault_attr attr;
 
     bool ignore_gfp_highmem;
     bool ignore_gfp_reclaim;
     u32 min_order;
 } fail_page_alloc = {
     .attr = FAULT_ATTR_INITIALIZER,
     .ignore_gfp_reclaim = true,
     .ignore_gfp_highmem = true,
     .min_order = 1,
 };
 
 static int __init setup_fail_page_alloc(char *str)
 {
     return setup_fault_attr(&fail_page_alloc.attr, str);
 }
 __setup("fail_page_alloc=", setup_fail_page_alloc);
 
 static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
     if (order < fail_page_alloc.min_order)
         return false;
     if (gfp_mask & __GFP_NOFAIL)
         return false;
     if (fail_page_alloc.ignore_gfp_highmem && (gfp_mask & __GFP_HIGHMEM))
         return false;
     if (fail_page_alloc.ignore_gfp_reclaim &&
             (gfp_mask & __GFP_DIRECT_RECLAIM))
         return false;
 
     if (gfp_mask & __GFP_NOWARN)
         fail_page_alloc.attr.no_warn = true;
 
     return should_fail(&fail_page_alloc.attr, 1 << order);
 }
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 
 static int __init fail_page_alloc_debugfs(void)
 {
     umode_t mode = S_IFREG | 0600;
     struct dentry *dir;
 
     dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
                     &fail_page_alloc.attr);
 
     debugfs_create_bool("ignore-gfp-wait", mode, dir,
                 &fail_page_alloc.ignore_gfp_reclaim);
     debugfs_create_bool("ignore-gfp-highmem", mode, dir,
                 &fail_page_alloc.ignore_gfp_highmem);
     debugfs_create_u32("min-order", mode, dir, &fail_page_alloc.min_order);
 
     return 0;
 }
 
 late_initcall(fail_page_alloc_debugfs);
 
 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 
 #else /* CONFIG_FAIL_PAGE_ALLOC */
 
 static inline bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
     return false;
 }
 
 #endif /* CONFIG_FAIL_PAGE_ALLOC */
 
 noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
     return __should_fail_alloc_page(gfp_mask, order);
 }
 ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);
 
 static inline long __zone_watermark_unusable_free(struct zone *z,
                 unsigned int order, unsigned int alloc_flags)
 {
     const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
     long unusable_free = (1 << order) - 1;
 
     /*
      * If the caller does not have rights to ALLOC_HARDER then subtract
      * the high-atomic reserves. This will over-estimate the size of the
      * atomic reserve but it avoids a search.
      */
     if (likely(!alloc_harder))
         unusable_free += z->nr_reserved_highatomic;
 
 #ifdef CONFIG_CMA
     /* If allocation can't use CMA areas don't use free CMA pages */
     if (!(alloc_flags & ALLOC_CMA))
         unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
 #endif
 
     return unusable_free;
 }
 
 /*
  * Return true if free base pages are above 'mark'. For high-order checks it
  * will return true of the order-0 watermark is reached and there is at least
  * one free page of a suitable size. Checking now avoids taking the zone lock
  * to check in the allocation paths if no pages are free.
  */
 bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
              int highest_zoneidx, unsigned int alloc_flags,
              long free_pages)
 {
     long min = mark;
     int o;
     const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
 
     /* free_pages may go negative - that's OK */
     free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
 
     if (alloc_flags & ALLOC_HIGH)
         min -= min / 2;
 
     if (unlikely(alloc_harder)) {
         /*
          * OOM victims can try even harder than normal ALLOC_HARDER
          * users on the grounds that it's definitely going to be in
          * the exit path shortly and free memory. Any allocation it
          * makes during the free path will be small and short-lived.
          */
         if (alloc_flags & ALLOC_OOM)
             min -= min / 2;
         else
             min -= min / 4;
     }
 
     /*
      * Check watermarks for an order-0 allocation request. If these
      * are not met, then a high-order request also cannot go ahead
      * even if a suitable page happened to be free.
      */
     if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
         return false;
 
     /* If this is an order-0 request then the watermark is fine */
     if (!order)
         return true;
 
     /* For a high-order request, check at least one suitable page is free */
     for (o = order; o < MAX_ORDER; o++) {
         struct free_area *area = &z->free_area[o];
         int mt;
 
         if (!area->nr_free)
             continue;
 
         for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
             if (!free_area_empty(area, mt))
                 return true;
         }
 
 #ifdef CONFIG_CMA
         if ((alloc_flags & ALLOC_CMA) &&
             !free_area_empty(area, MIGRATE_CMA)) {
             return true;
         }
 #endif
         if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC))
             return true;
     }
     return false;
 }
 
 bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
               int highest_zoneidx, unsigned int alloc_flags)
 {
     return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                     zone_page_state(z, NR_FREE_PAGES));
 }
 
 static inline bool zone_watermark_fast(struct zone *z, unsigned int order,
                 unsigned long mark, int highest_zoneidx,
                 unsigned int alloc_flags, gfp_t gfp_mask)
 {
     long free_pages;
 
     free_pages = zone_page_state(z, NR_FREE_PAGES);
 
     /*
      * Fast check for order-0 only. If this fails then the reserves
      * need to be calculated.
      */
     if (!order) {
         long usable_free;
         long reserved;
 
         usable_free = free_pages;
         reserved = __zone_watermark_unusable_free(z, 0, alloc_flags);
 
         /* reserved may over estimate high-atomic reserves. */
         usable_free -= min(usable_free, reserved);
         if (usable_free > mark + z->lowmem_reserve[highest_zoneidx])
             return true;
     }
 
     if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                     free_pages))
         return true;
     /*
      * Ignore watermark boosting for GFP_ATOMIC order-0 allocations
      * when checking the min watermark. The min watermark is the
      * point where boosting is ignored so that kswapd is woken up
      * when below the low watermark.
      */
     if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost
         && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) {
         mark = z->_watermark[WMARK_MIN];
         return __zone_watermark_ok(z, order, mark, highest_zoneidx,
                     alloc_flags, free_pages);
     }
 
     return false;
 }
 
 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
             unsigned long mark, int highest_zoneidx)
 {
     long free_pages = zone_page_state(z, NR_FREE_PAGES);
 
     if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
         free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);
 
     return __zone_watermark_ok(z, order, mark, highest_zoneidx, 0,
                                 free_pages);
 }
 
 #ifdef CONFIG_NUMA
 int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;
 
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 {
     return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
                 node_reclaim_distance;
 }
 #else   /* CONFIG_NUMA */
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 {
     return true;
 }
 #endif  /* CONFIG_NUMA */
 
 /*
  * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
  * fragmentation is subtle. If the preferred zone was HIGHMEM then
  * premature use of a lower zone may cause lowmem pressure problems that
  * are worse than fragmentation. If the next zone is ZONE_DMA then it is
  * probably too small. It only makes sense to spread allocations to avoid
  * fragmentation between the Normal and DMA32 zones.
  */
 static inline unsigned int
 alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
 {
     unsigned int alloc_flags;
 
     /*
      * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
      * to save a branch.
      */
     alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
 
 #ifdef CONFIG_ZONE_DMA32
     if (!zone)
         return alloc_flags;
 
     if (zone_idx(zone) != ZONE_NORMAL)
         return alloc_flags;
 
     /*
      * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
      * the pointer is within zone->zone_pgdat->node_zones[]. Also assume
      * on UMA that if Normal is populated then so is DMA32.
      */
     BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
     if (nr_online_nodes > 1 && !populated_zone(--zone))
         return alloc_flags;
 
     alloc_flags |= ALLOC_NOFRAGMENT;
 #endif /* CONFIG_ZONE_DMA32 */
     return alloc_flags;
 }
 
 /* Must be called after current_gfp_context() which can change gfp_mask */
 static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
                           unsigned int alloc_flags)
 {
 #ifdef CONFIG_CMA
     if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
         alloc_flags |= ALLOC_CMA;
 #endif
     return alloc_flags;
 }
 
 /*
  * get_page_from_freelist goes through the zonelist trying to allocate
  * a page.
  */
 static struct page *
 get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
                         const struct alloc_context *ac)
 {
     struct zoneref *z;
     struct zone *zone;
     struct pglist_data *last_pgdat = NULL;
     bool last_pgdat_dirty_ok = false;
     bool no_fallback;
 
 retry:
     /*
      * Scan zonelist, looking for a zone with enough free.
      * See also __cpuset_node_allowed() comment in kernel/cgroup/cpuset.c.
      */
     no_fallback = alloc_flags & ALLOC_NOFRAGMENT;
     z = ac->preferred_zoneref;
     for_next_zone_zonelist_nodemask(zone, z, ac->highest_zoneidx,
                     ac->nodemask) {
         struct page *page;
         unsigned long mark;
 
         if (cpusets_enabled() &&
             (alloc_flags & ALLOC_CPUSET) &&
             !__cpuset_zone_allowed(zone, gfp_mask))
                 continue;
         /*
          * When allocating a page cache page for writing, we
          * want to get it from a node that is within its dirty
          * limit, such that no single node holds more than its
          * proportional share of globally allowed dirty pages.
          * The dirty limits take into account the node's
          * lowmem reserves and high watermark so that kswapd
          * should be able to balance it without having to
          * write pages from its LRU list.
          *
          * XXX: For now, allow allocations to potentially
          * exceed the per-node dirty limit in the slowpath
          * (spread_dirty_pages unset) before going into reclaim,
          * which is important when on a NUMA setup the allowed
          * nodes are together not big enough to reach the
          * global limit.  The proper fix for these situations
          * will require awareness of nodes in the
          * dirty-throttling and the flusher threads.
          */
         if (ac->spread_dirty_pages) {
             if (last_pgdat != zone->zone_pgdat) {
                 last_pgdat = zone->zone_pgdat;
                 last_pgdat_dirty_ok = node_dirty_ok(zone->zone_pgdat);
             }
 
             if (!last_pgdat_dirty_ok)
                 continue;
         }
 
         if (no_fallback && nr_online_nodes > 1 &&
             zone != ac->preferred_zoneref->zone) {
             int local_nid;
 
             /*
              * If moving to a remote node, retry but allow
              * fragmenting fallbacks. Locality is more important
              * than fragmentation avoidance.
              */
             local_nid = zone_to_nid(ac->preferred_zoneref->zone);
             if (zone_to_nid(zone) != local_nid) {
                 alloc_flags &= ~ALLOC_NOFRAGMENT;
                 goto retry;
             }
         }
 
         mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
         if (!zone_watermark_fast(zone, order, mark,
                        ac->highest_zoneidx, alloc_flags,
                        gfp_mask)) {
             int ret;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
             /*
              * Watermark failed for this zone, but see if we can
              * grow this zone if it contains deferred pages.
              */
             if (static_branch_unlikely(&deferred_pages)) {
                 if (_deferred_grow_zone(zone, order))
                     goto try_this_zone;
             }
 #endif
             /* Checked here to keep the fast path fast */
             BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
             if (alloc_flags & ALLOC_NO_WATERMARKS)
                 goto try_this_zone;
 
             if (!node_reclaim_enabled() ||
                 !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
                 continue;
 
             ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
             switch (ret) {
             case NODE_RECLAIM_NOSCAN:
                 /* did not scan */
                 continue;
             case NODE_RECLAIM_FULL:
                 /* scanned but unreclaimable */
                 continue;
             default:
                 /* did we reclaim enough */
                 if (zone_watermark_ok(zone, order, mark,
                     ac->highest_zoneidx, alloc_flags))
                     goto try_this_zone;
 
                 continue;
             }
         }
 
 try_this_zone:
         page = rmqueue(ac->preferred_zoneref->zone, zone, order,
                 gfp_mask, alloc_flags, ac->migratetype);
         if (page) {
             prep_new_page(page, order, gfp_mask, alloc_flags);
 
             /*
              * If this is a high-order atomic allocation then check
              * if the pageblock should be reserved for the future
              */
             if (unlikely(order && (alloc_flags & ALLOC_HARDER)))
                 reserve_highatomic_pageblock(page, zone, order);
 
             return page;
         } else {
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
             /* Try again if zone has deferred pages */
             if (static_branch_unlikely(&deferred_pages)) {
                 if (_deferred_grow_zone(zone, order))
                     goto try_this_zone;
             }
 #endif
         }
     }
 
     /*
      * It's possible on a UMA machine to get through all zones that are
      * fragmented. If avoiding fragmentation, reset and try again.
      */
     if (no_fallback) {
         alloc_flags &= ~ALLOC_NOFRAGMENT;
         goto retry;
     }
 
     return NULL;
 }
 
 static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
 {
     unsigned int filter = SHOW_MEM_FILTER_NODES;
 
     /*
      * This documents exceptions given to allocations in certain
      * contexts that are allowed to allocate outside current's set
      * of allowed nodes.
      */
     if (!(gfp_mask & __GFP_NOMEMALLOC))
         if (tsk_is_oom_victim(current) ||
             (current->flags & (PF_MEMALLOC | PF_EXITING)))
             filter &= ~SHOW_MEM_FILTER_NODES;
     if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
         filter &= ~SHOW_MEM_FILTER_NODES;
 
     show_mem(filter, nodemask);
 }
 
 void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
 {
     struct va_format vaf;
     va_list args;
     static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
 
     if ((gfp_mask & __GFP_NOWARN) ||
          !__ratelimit(&nopage_rs) ||
          ((gfp_mask & __GFP_DMA) && !has_managed_dma()))
         return;
 
     va_start(args, fmt);
     vaf.fmt = fmt;
     vaf.va = &args;
     pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
             current->comm, &vaf, gfp_mask, &gfp_mask,
             nodemask_pr_args(nodemask));
     va_end(args);
 
     cpuset_print_current_mems_allowed();
     pr_cont("\n");
     dump_stack();
     warn_alloc_show_mem(gfp_mask, nodemask);
 }
 
 static inline struct page *
 __alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,
                   unsigned int alloc_flags,
                   const struct alloc_context *ac)
 {
     struct page *page;
 
     page = get_page_from_freelist(gfp_mask, order,
             alloc_flags|ALLOC_CPUSET, ac);
     /*
      * fallback to ignore cpuset restriction if our nodes
      * are depleted
      */
     if (!page)
         page = get_page_from_freelist(gfp_mask, order,
                 alloc_flags, ac);
 
     return page;
 }
 
 static inline struct page *
 __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
     const struct alloc_context *ac, unsigned long *did_some_progress)
 {
     struct oom_control oc = {
         .zonelist = ac->zonelist,
         .nodemask = ac->nodemask,
         .memcg = NULL,
         .gfp_mask = gfp_mask,
         .order = order,
     };
     struct page *page;
 
     *did_some_progress = 0;
 
     /*
      * Acquire the oom lock.  If that fails, somebody else is
      * making progress for us.
      */
     if (!mutex_trylock(&oom_lock)) {
         *did_some_progress = 1;
         schedule_timeout_uninterruptible(1);
         return NULL;
     }
 
     /*
      * Go through the zonelist yet one more time, keep very high watermark
      * here, this is only to catch a parallel oom killing, we must fail if
      * we're still under heavy pressure. But make sure that this reclaim
      * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
      * allocation which will never fail due to oom_lock already held.
      */
     page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
                       ~__GFP_DIRECT_RECLAIM, order,
                       ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
     if (page)
         goto out;
 
     /* Coredumps can quickly deplete all memory reserves */
     if (current->flags & PF_DUMPCORE)
         goto out;
     /* The OOM killer will not help higher order allocs */
     if (order > PAGE_ALLOC_COSTLY_ORDER)
         goto out;
     /*
      * We have already exhausted all our reclaim opportunities without any
      * success so it is time to admit defeat. We will skip the OOM killer
      * because it is very likely that the caller has a more reasonable
      * fallback than shooting a random task.
      *
      * The OOM killer may not free memory on a specific node.
      */
     if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
         goto out;
     /* The OOM killer does not needlessly kill tasks for lowmem */
     if (ac->highest_zoneidx < ZONE_NORMAL)
         goto out;
     if (pm_suspended_storage())
         goto out;
     /*
      * XXX: GFP_NOFS allocations should rather fail than rely on
      * other request to make a forward progress.
      * We are in an unfortunate situation where out_of_memory cannot
      * do much for this context but let's try it to at least get
      * access to memory reserved if the current task is killed (see
      * out_of_memory). Once filesystems are ready to handle allocation
      * failures more gracefully we should just bail out here.
      */
 
     /* Exhausted what can be done so it's blame time */
     if (out_of_memory(&oc) ||
         WARN_ON_ONCE_GFP(gfp_mask & __GFP_NOFAIL, gfp_mask)) {
         *did_some_progress = 1;
 
         /*
          * Help non-failing allocations by giving them access to memory
          * reserves
          */
         if (gfp_mask & __GFP_NOFAIL)
             page = __alloc_pages_cpuset_fallback(gfp_mask, order,
                     ALLOC_NO_WATERMARKS, ac);
     }
 out:
     mutex_unlock(&oom_lock);
     return page;
 }
 
 /*
  * Maximum number of compaction retries with a progress before OOM
  * killer is consider as the only way to move forward.
  */
 #define MAX_COMPACT_RETRIES 16
 
 #ifdef CONFIG_COMPACTION
 /* Try memory compaction for high-order allocations before reclaim */
 static struct page *
 __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
         unsigned int alloc_flags, const struct alloc_context *ac,
         enum compact_priority prio, enum compact_result *compact_result)
 {
     struct page *page = NULL;
     unsigned long pflags;
     unsigned int noreclaim_flag;
 
     if (!order)
         return NULL;
 
     psi_memstall_enter(&pflags);
     delayacct_compact_start();
     noreclaim_flag = memalloc_noreclaim_save();
 
     *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
                                 prio, &page);
 
     memalloc_noreclaim_restore(noreclaim_flag);
     psi_memstall_leave(&pflags);
     delayacct_compact_end();
 
     if (*compact_result == COMPACT_SKIPPED)
         return NULL;
     /*
      * At least in one zone compaction wasn't deferred or skipped, so let's
      * count a compaction stall
      */
     count_vm_event(COMPACTSTALL);
 
     /* Prep a captured page if available */
     if (page)
         prep_new_page(page, order, gfp_mask, alloc_flags);
 
     /* Try get a page from the freelist if available */
     if (!page)
         page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
 
     if (page) {
         struct zone *zone = page_zone(page);
 
         zone->compact_blockskip_flush = false;
         compaction_defer_reset(zone, order, true);
         count_vm_event(COMPACTSUCCESS);
         return page;
     }
 
     /*
      * It's bad if compaction run occurs and fails. The most likely reason
      * is that pages exist, but not enough to satisfy watermarks.
      */
     count_vm_event(COMPACTFAIL);
 
     cond_resched();
 
     return NULL;
 }
 
 static inline bool
 should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
              enum compact_result compact_result,
              enum compact_priority *compact_priority,
              int *compaction_retries)
 {
     int max_retries = MAX_COMPACT_RETRIES;
     int min_priority;
     bool ret = false;
     int retries = *compaction_retries;
     enum compact_priority priority = *compact_priority;
 
     if (!order)
         return false;
 
     if (fatal_signal_pending(current))
         return false;
 
     if (compaction_made_progress(compact_result))
         (*compaction_retries)++;
 
     /*
      * compaction considers all the zone as desperately out of memory
      * so it doesn't really make much sense to retry except when the
      * failure could be caused by insufficient priority
      */
     if (compaction_failed(compact_result))
         goto check_priority;
 
     /*
      * compaction was skipped because there are not enough order-0 pages
      * to work with, so we retry only if it looks like reclaim can help.
      */
     if (compaction_needs_reclaim(compact_result)) {
         ret = compaction_zonelist_suitable(ac, order, alloc_flags);
         goto out;
     }
 
     /*
      * make sure the compaction wasn't deferred or didn't bail out early
      * due to locks contention before we declare that we should give up.
      * But the next retry should use a higher priority if allowed, so
      * we don't just keep bailing out endlessly.
      */
     if (compaction_withdrawn(compact_result)) {
         goto check_priority;
     }
 
     /*
      * !costly requests are much more important than __GFP_RETRY_MAYFAIL
      * costly ones because they are de facto nofail and invoke OOM
      * killer to move on while costly can fail and users are ready
      * to cope with that. 1/4 retries is rather arbitrary but we
      * would need much more detailed feedback from compaction to
      * make a better decision.
      */
     if (order > PAGE_ALLOC_COSTLY_ORDER)
         max_retries /= 4;
     if (*compaction_retries <= max_retries) {
         ret = true;
         goto out;
     }
 
     /*
      * Make sure there are attempts at the highest priority if we exhausted
      * all retries or failed at the lower priorities.
      */
 check_priority:
     min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
             MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
 
     if (*compact_priority > min_priority) {
         (*compact_priority)--;
         *compaction_retries = 0;
         ret = true;
     }
 out:
     trace_compact_retry(order, priority, compact_result, retries, max_retries, ret);
     return ret;
 }
 #else
 static inline struct page *
 __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
         unsigned int alloc_flags, const struct alloc_context *ac,
         enum compact_priority prio, enum compact_result *compact_result)
 {
     *compact_result = COMPACT_SKIPPED;
     return NULL;
 }
 
 static inline bool
 should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
              enum compact_result compact_result,
              enum compact_priority *compact_priority,
              int *compaction_retries)
 {
     struct zone *zone;
     struct zoneref *z;
 
     if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
         return false;
 
     /*
      * There are setups with compaction disabled which would prefer to loop
      * inside the allocator rather than hit the oom killer prematurely.
      * Let's give them a good hope and keep retrying while the order-0
      * watermarks are OK.
      */
     for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                 ac->highest_zoneidx, ac->nodemask) {
         if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
                     ac->highest_zoneidx, alloc_flags))
             return true;
     }
     return false;
 }
 #endif /* CONFIG_COMPACTION */
 
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map __fs_reclaim_map =
     STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
 
 static bool __need_reclaim(gfp_t gfp_mask)
 {
     /* no reclaim without waiting on it */
     if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
         return false;
 
     /* this guy won't enter reclaim */
     if (current->flags & PF_MEMALLOC)
         return false;
 
     if (gfp_mask & __GFP_NOLOCKDEP)
         return false;
 
     return true;
 }
 
 void __fs_reclaim_acquire(unsigned long ip)
 {
     lock_acquire_exclusive(&__fs_reclaim_map, 0, 0, NULL, ip);
 }
 
 void __fs_reclaim_release(unsigned long ip)
 {
     lock_release(&__fs_reclaim_map, ip);
 }
 
 void fs_reclaim_acquire(gfp_t gfp_mask)
 {
     gfp_mask = current_gfp_context(gfp_mask);
 
     if (__need_reclaim(gfp_mask)) {
         if (gfp_mask & __GFP_FS)
             __fs_reclaim_acquire(_RET_IP_);
 
 #ifdef CONFIG_MMU_NOTIFIER
         lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
         lock_map_release(&__mmu_notifier_invalidate_range_start_map);
 #endif
 
     }
 }
 EXPORT_SYMBOL_GPL(fs_reclaim_acquire);
 
 void fs_reclaim_release(gfp_t gfp_mask)
 {
     gfp_mask = current_gfp_context(gfp_mask);
 
     if (__need_reclaim(gfp_mask)) {
         if (gfp_mask & __GFP_FS)
             __fs_reclaim_release(_RET_IP_);
     }
 }
 EXPORT_SYMBOL_GPL(fs_reclaim_release);
 #endif
 
 /*
  * Zonelists may change due to hotplug during allocation. Detect when zonelists
  * have been rebuilt so allocation retries. Reader side does not lock and
  * retries the allocation if zonelist changes. Writer side is protected by the
  * embedded spin_lock.
  */
 static DEFINE_SEQLOCK(zonelist_update_seq);
 
 static unsigned int zonelist_iter_begin(void)
 {
     if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
         return read_seqbegin(&zonelist_update_seq);
 
     return 0;
 }
 
 static unsigned int check_retry_zonelist(unsigned int seq)
 {
     if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
         return read_seqretry(&zonelist_update_seq, seq);
 
     return seq;
 }
 
 /* Perform direct synchronous page reclaim */
 static unsigned long
 __perform_reclaim(gfp_t gfp_mask, unsigned int order,
                     const struct alloc_context *ac)
 {
     unsigned int noreclaim_flag;
     unsigned long progress;
 
     cond_resched();
 
     /* We now go into synchronous reclaim */
     cpuset_memory_pressure_bump();
     fs_reclaim_acquire(gfp_mask);
     noreclaim_flag = memalloc_noreclaim_save();
 
     progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
                                 ac->nodemask);
 
     memalloc_noreclaim_restore(noreclaim_flag);
     fs_reclaim_release(gfp_mask);
 
     cond_resched();
 
     return progress;
 }
 
 /* The really slow allocator path where we enter direct reclaim */
 static inline struct page *
 __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
         unsigned int alloc_flags, const struct alloc_context *ac,
         unsigned long *did_some_progress)
 {
     struct page *page = NULL;
     unsigned long pflags;
     bool drained = false;
 
     psi_memstall_enter(&pflags);
     *did_some_progress = __perform_reclaim(gfp_mask, order, ac);
     if (unlikely(!(*did_some_progress)))
         goto out;
 
 retry:
     page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
 
     /*
      * If an allocation failed after direct reclaim, it could be because
      * pages are pinned on the per-cpu lists or in high alloc reserves.
      * Shrink them and try again
      */
     if (!page && !drained) {
         unreserve_highatomic_pageblock(ac, false);
         drain_all_pages(NULL);
         drained = true;
         goto retry;
     }
 out:
     psi_memstall_leave(&pflags);
 
     return page;
 }
 
 static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
                  const struct alloc_context *ac)
 {
     struct zoneref *z;
     struct zone *zone;
     pg_data_t *last_pgdat = NULL;
     enum zone_type highest_zoneidx = ac->highest_zoneidx;
 
     for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
                     ac->nodemask) {
         if (!managed_zone(zone))
             continue;
         if (last_pgdat != zone->zone_pgdat) {
             wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
             last_pgdat = zone->zone_pgdat;
         }
     }
 }
 
 static inline unsigned int
 gfp_to_alloc_flags(gfp_t gfp_mask)
 {
     unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
 
     /*
      * __GFP_HIGH is assumed to be the same as ALLOC_HIGH
      * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
      * to save two branches.
      */
     BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
     BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
 
     /*
      * The caller may dip into page reserves a bit more if the caller
      * cannot run direct reclaim, or if the caller has realtime scheduling
      * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
      * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
      */
     alloc_flags |= (__force int)
         (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
 
     if (gfp_mask & __GFP_ATOMIC) {
         /*
          * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
          * if it can't schedule.
          */
         if (!(gfp_mask & __GFP_NOMEMALLOC))
             alloc_flags |= ALLOC_HARDER;
         /*
          * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
          * comment for __cpuset_node_allowed().
          */
         alloc_flags &= ~ALLOC_CPUSET;
     } else if (unlikely(rt_task(current)) && in_task())
         alloc_flags |= ALLOC_HARDER;
 
     alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags);
 
     return alloc_flags;
 }
 
 static bool oom_reserves_allowed(struct task_struct *tsk)
 {
     if (!tsk_is_oom_victim(tsk))
         return false;
 
     /*
      * !MMU doesn't have oom reaper so give access to memory reserves
      * only to the thread with TIF_MEMDIE set
      */
     if (!IS_ENABLED(CONFIG_MMU) && !test_thread_flag(TIF_MEMDIE))
         return false;
 
     return true;
 }
 
 /*
  * Distinguish requests which really need access to full memory
  * reserves from oom victims which can live with a portion of it
  */
 static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask)
 {
     if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
         return 0;
     if (gfp_mask & __GFP_MEMALLOC)
         return ALLOC_NO_WATERMARKS;
     if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
         return ALLOC_NO_WATERMARKS;
     if (!in_interrupt()) {
         if (current->flags & PF_MEMALLOC)
             return ALLOC_NO_WATERMARKS;
         else if (oom_reserves_allowed(current))
             return ALLOC_OOM;
     }
 
     return 0;
 }
 
 bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
 {
     return !!__gfp_pfmemalloc_flags(gfp_mask);
 }
 
 /*
  * Checks whether it makes sense to retry the reclaim to make a forward progress
  * for the given allocation request.
  *
  * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
  * without success, or when we couldn't even meet the watermark if we
  * reclaimed all remaining pages on the LRU lists.
  *
  * Returns true if a retry is viable or false to enter the oom path.
  */
 static inline bool
 should_reclaim_retry(gfp_t gfp_mask, unsigned order,
              struct alloc_context *ac, int alloc_flags,
              bool did_some_progress, int *no_progress_loops)
 {
     struct zone *zone;
     struct zoneref *z;
     bool ret = false;
 
     /*
      * Costly allocations might have made a progress but this doesn't mean
      * their order will become available due to high fragmentation so
      * always increment the no progress counter for them
      */
     if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
         *no_progress_loops = 0;
     else
         (*no_progress_loops)++;
 
     /*
      * Make sure we converge to OOM if we cannot make any progress
      * several times in the row.
      */
     if (*no_progress_loops > MAX_RECLAIM_RETRIES) {
         /* Before OOM, exhaust highatomic_reserve */
         return unreserve_highatomic_pageblock(ac, true);
     }
 
     /*
      * Keep reclaiming pages while there is a chance this will lead
      * somewhere.  If none of the target zones can satisfy our allocation
      * request even if all reclaimable pages are considered then we are
      * screwed and have to go OOM.
      */
     for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                 ac->highest_zoneidx, ac->nodemask) {
         unsigned long available;
         unsigned long reclaimable;
         unsigned long min_wmark = min_wmark_pages(zone);
         bool wmark;
 
         available = reclaimable = zone_reclaimable_pages(zone);
         available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
 
         /*
          * Would the allocation succeed if we reclaimed all
          * reclaimable pages?
          */
         wmark = __zone_watermark_ok(zone, order, min_wmark,
                 ac->highest_zoneidx, alloc_flags, available);
         trace_reclaim_retry_zone(z, order, reclaimable,
                 available, min_wmark, *no_progress_loops, wmark);
         if (wmark) {
             ret = true;
             break;
         }
     }
 
     /*
      * Memory allocation/reclaim might be called from a WQ context and the
      * current implementation of the WQ concurrency control doesn't
      * recognize that a particular WQ is congested if the worker thread is
      * looping without ever sleeping. Therefore we have to do a short sleep
      * here rather than calling cond_resched().
      */
     if (current->flags & PF_WQ_WORKER)
         schedule_timeout_uninterruptible(1);
     else
         cond_resched();
     return ret;
 }
 
 static inline bool
 check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
 {
     /*
      * It's possible that cpuset's mems_allowed and the nodemask from
      * mempolicy don't intersect. This should be normally dealt with by
      * policy_nodemask(), but it's possible to race with cpuset update in
      * such a way the check therein was true, and then it became false
      * before we got our cpuset_mems_cookie here.
      * This assumes that for all allocations, ac->nodemask can come only
      * from MPOL_BIND mempolicy (whose documented semantics is to be ignored
      * when it does not intersect with the cpuset restrictions) or the
      * caller can deal with a violated nodemask.
      */
     if (cpusets_enabled() && ac->nodemask &&
             !cpuset_nodemask_valid_mems_allowed(ac->nodemask)) {
         ac->nodemask = NULL;
         return true;
     }
 
     /*
      * When updating a task's mems_allowed or mempolicy nodemask, it is
      * possible to race with parallel threads in such a way that our
      * allocation can fail while the mask is being updated. If we are about
      * to fail, check if the cpuset changed during allocation and if so,
      * retry.
      */
     if (read_mems_allowed_retry(cpuset_mems_cookie))
         return true;
 
     return false;
 }
 
 static inline struct page *
 __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                         struct alloc_context *ac)
 {
     bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
     const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
     struct page *page = NULL;
     unsigned int alloc_flags;
     unsigned long did_some_progress;
     enum compact_priority compact_priority;
     enum compact_result compact_result;
     int compaction_retries;
     int no_progress_loops;
     unsigned int cpuset_mems_cookie;
     unsigned int zonelist_iter_cookie;
     int reserve_flags;
 
     /*
      * We also sanity check to catch abuse of atomic reserves being used by
      * callers that are not in atomic context.
      */
     if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
                 (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
         gfp_mask &= ~__GFP_ATOMIC;
 
 restart:
     compaction_retries = 0;
     no_progress_loops = 0;
     compact_priority = DEF_COMPACT_PRIORITY;
     cpuset_mems_cookie = read_mems_allowed_begin();
     zonelist_iter_cookie = zonelist_iter_begin();
 
     /*
      * The fast path uses conservative alloc_flags to succeed only until
      * kswapd needs to be woken up, and to avoid the cost of setting up
      * alloc_flags precisely. So we do that now.
      */
     alloc_flags = gfp_to_alloc_flags(gfp_mask);
 
     /*
      * We need to recalculate the starting point for the zonelist iterator
      * because we might have used different nodemask in the fast path, or
      * there was a cpuset modification and we are retrying - otherwise we
      * could end up iterating over non-eligible zones endlessly.
      */
     ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                     ac->highest_zoneidx, ac->nodemask);
     if (!ac->preferred_zoneref->zone)
         goto nopage;
 
     /*
      * Check for insane configurations where the cpuset doesn't contain
      * any suitable zone to satisfy the request - e.g. non-movable
      * GFP_HIGHUSER allocations from MOVABLE nodes only.
      */
     if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
         struct zoneref *z = first_zones_zonelist(ac->zonelist,
                     ac->highest_zoneidx,
                     &cpuset_current_mems_allowed);
         if (!z->zone)
             goto nopage;
     }
 
     if (alloc_flags & ALLOC_KSWAPD)
         wake_all_kswapds(order, gfp_mask, ac);
 
     /*
      * The adjusted alloc_flags might result in immediate success, so try
      * that first
      */
     page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
     if (page)
         goto got_pg;
 
     /*
      * For costly allocations, try direct compaction first, as it's likely
      * that we have enough base pages and don't need to reclaim. For non-
      * movable high-order allocations, do that as well, as compaction will
      * try prevent permanent fragmentation by migrating from blocks of the
      * same migratetype.
      * Don't try this for allocations that are allowed to ignore
      * watermarks, as the ALLOC_NO_WATERMARKS attempt didn't yet happen.
      */
     if (can_direct_reclaim &&
             (costly_order ||
                (order > 0 && ac->migratetype != MIGRATE_MOVABLE))
             && !gfp_pfmemalloc_allowed(gfp_mask)) {
         page = __alloc_pages_direct_compact(gfp_mask, order,
                         alloc_flags, ac,
                         INIT_COMPACT_PRIORITY,
                         &compact_result);
         if (page)
             goto got_pg;
 
         /*
          * Checks for costly allocations with __GFP_NORETRY, which
          * includes some THP page fault allocations
          */
         if (costly_order && (gfp_mask & __GFP_NORETRY)) {
             /*
              * If allocating entire pageblock(s) and compaction
              * failed because all zones are below low watermarks
              * or is prohibited because it recently failed at this
              * order, fail immediately unless the allocator has
              * requested compaction and reclaim retry.
              *
              * Reclaim is
              *  - potentially very expensive because zones are far
              *    below their low watermarks or this is part of very
              *    bursty high order allocations,
              *  - not guaranteed to help because isolate_freepages()
              *    may not iterate over freed pages as part of its
              *    linear scan, and
              *  - unlikely to make entire pageblocks free on its
              *    own.
              */
             if (compact_result == COMPACT_SKIPPED ||
                 compact_result == COMPACT_DEFERRED)
                 goto nopage;
 
             /*
              * Looks like reclaim/compaction is worth trying, but
              * sync compaction could be very expensive, so keep
              * using async compaction.
              */
             compact_priority = INIT_COMPACT_PRIORITY;
         }
     }
 
 retry:
     /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
     if (alloc_flags & ALLOC_KSWAPD)
         wake_all_kswapds(order, gfp_mask, ac);
 
     reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
     if (reserve_flags)
         alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags);
 
     /*
      * Reset the nodemask and zonelist iterators if memory policies can be
      * ignored. These allocations are high priority and system rather than
      * user oriented.
      */
     if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) {
         ac->nodemask = NULL;
         ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                     ac->highest_zoneidx, ac->nodemask);
     }
 
     /* Attempt with potentially adjusted zonelist and alloc_flags */
     page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
     if (page)
         goto got_pg;
 
     /* Caller is not willing to reclaim, we can't balance anything */
     if (!can_direct_reclaim)
         goto nopage;
 
     /* Avoid recursion of direct reclaim */
     if (current->flags & PF_MEMALLOC)
         goto nopage;
 
     /* Try direct reclaim and then allocating */
     page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
                             &did_some_progress);
     if (page)
         goto got_pg;
 
     /* Try direct compaction and then allocating */
     page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
                     compact_priority, &compact_result);
     if (page)
         goto got_pg;
 
     /* Do not loop if specifically requested */
     if (gfp_mask & __GFP_NORETRY)
         goto nopage;
 
     /*
      * Do not retry costly high order allocations unless they are
      * __GFP_RETRY_MAYFAIL
      */
     if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
         goto nopage;
 
     if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
                  did_some_progress > 0, &no_progress_loops))
         goto retry;
 
     /*
      * It doesn't make any sense to retry for the compaction if the order-0
      * reclaim is not able to make any progress because the current
      * implementation of the compaction depends on the sufficient amount
      * of free memory (see __compaction_suitable)
      */
     if (did_some_progress > 0 &&
             should_compact_retry(ac, order, alloc_flags,
                 compact_result, &compact_priority,
                 &compaction_retries))
         goto retry;
 
 
     /*
      * Deal with possible cpuset update races or zonelist updates to avoid
      * a unnecessary OOM kill.
      */
     if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
         check_retry_zonelist(zonelist_iter_cookie))
         goto restart;
 
     /* Reclaim has failed us, start killing things */
     page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
     if (page)
         goto got_pg;
 
     /* Avoid allocations with no watermarks from looping endlessly */
     if (tsk_is_oom_victim(current) &&
         (alloc_flags & ALLOC_OOM ||
          (gfp_mask & __GFP_NOMEMALLOC)))
         goto nopage;
 
     /* Retry as long as the OOM killer is making progress */
     if (did_some_progress) {
         no_progress_loops = 0;
         goto retry;
     }
 
 nopage:
     /*
      * Deal with possible cpuset update races or zonelist updates to avoid
      * a unnecessary OOM kill.
      */
     if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
         check_retry_zonelist(zonelist_iter_cookie))
         goto restart;
 
     /*
      * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
      * we always retry
      */
     if (gfp_mask & __GFP_NOFAIL) {
         /*
          * All existing users of the __GFP_NOFAIL are blockable, so warn
          * of any new users that actually require GFP_NOWAIT
          */
         if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
             goto fail;
 
         /*
          * PF_MEMALLOC request from this context is rather bizarre
          * because we cannot reclaim anything and only can loop waiting
          * for somebody to do a work for us
          */
         WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
 
         /*
          * non failing costly orders are a hard requirement which we
          * are not prepared for much so let's warn about these users
          * so that we can identify them and convert them to something
          * else.
          */
         WARN_ON_ONCE_GFP(order > PAGE_ALLOC_COSTLY_ORDER, gfp_mask);
 
         /*
          * Help non-failing allocations by giving them access to memory
          * reserves but do not use ALLOC_NO_WATERMARKS because this
          * could deplete whole memory reserves which would just make
          * the situation worse
          */
         page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_HARDER, ac);
         if (page)
             goto got_pg;
 
         cond_resched();
         goto retry;
     }
 fail:
     warn_alloc(gfp_mask, ac->nodemask,
             "page allocation failure: order:%u", order);
 got_pg:
     return page;
 }
 
 static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
         int preferred_nid, nodemask_t *nodemask,
         struct alloc_context *ac, gfp_t *alloc_gfp,
         unsigned int *alloc_flags)
 {
     ac->highest_zoneidx = gfp_zone(gfp_mask);
     ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
     ac->nodemask = nodemask;
     ac->migratetype = gfp_migratetype(gfp_mask);
 
     if (cpusets_enabled()) {
         *alloc_gfp |= __GFP_HARDWALL;
         /*
          * When we are in the interrupt context, it is irrelevant
          * to the current task context. It means that any node ok.
          */
         if (in_task() && !ac->nodemask)
             ac->nodemask = &cpuset_current_mems_allowed;
         else
             *alloc_flags |= ALLOC_CPUSET;
     }
 
     might_alloc(gfp_mask);
 
     if (should_fail_alloc_page(gfp_mask, order))
         return false;
 
     *alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, *alloc_flags);
 
     /* Dirty zone balancing only done in the fast path */
     ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
 
     /*
      * The preferred zone is used for statistics but crucially it is
      * also used as the starting point for the zonelist iterator. It
      * may get reset for allocations that ignore memory policies.
      */
     ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                     ac->highest_zoneidx, ac->nodemask);
 
     return true;
 }
 
 /*
  * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
  * @gfp: GFP flags for the allocation
  * @preferred_nid: The preferred NUMA node ID to allocate from
  * @nodemask: Set of nodes to allocate from, may be NULL
  * @nr_pages: The number of pages desired on the list or array
  * @page_list: Optional list to store the allocated pages
  * @page_array: Optional array to store the pages
  *
  * This is a batched version of the page allocator that attempts to
  * allocate nr_pages quickly. Pages are added to page_list if page_list
  * is not NULL, otherwise it is assumed that the page_array is valid.
  *
  * For lists, nr_pages is the number of pages that should be allocated.
  *
  * For arrays, only NULL elements are populated with pages and nr_pages
  * is the maximum number of pages that will be stored in the array.
  *
  * Returns the number of pages on the list or array.
  */
 unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
             nodemask_t *nodemask, int nr_pages,
             struct list_head *page_list,
             struct page **page_array)
 {
     struct page *page;
     unsigned long flags;
     unsigned long __maybe_unused UP_flags;
     struct zone *zone;
     struct zoneref *z;
     struct per_cpu_pages *pcp;
     struct list_head *pcp_list;
     struct alloc_context ac;
     gfp_t alloc_gfp;
     unsigned int alloc_flags = ALLOC_WMARK_LOW;
     int nr_populated = 0, nr_account = 0;
 
     /*
      * Skip populated array elements to determine if any pages need
      * to be allocated before disabling IRQs.
      */
     while (page_array && nr_populated < nr_pages && page_array[nr_populated])
         nr_populated++;
 
     /* No pages requested? */
     if (unlikely(nr_pages <= 0))
         goto out;
 
     /* Already populated array? */
     if (unlikely(page_array && nr_pages - nr_populated == 0))
         goto out;
 
     /* Bulk allocator does not support memcg accounting. */
     if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT))
         goto failed;
 
     /* Use the single page allocator for one page. */
     if (nr_pages - nr_populated == 1)
         goto failed;
 
 #ifdef CONFIG_PAGE_OWNER
     /*
      * PAGE_OWNER may recurse into the allocator to allocate space to
      * save the stack with pagesets.lock held. Releasing/reacquiring
      * removes much of the performance benefit of bulk allocation so
      * force the caller to allocate one page at a time as it'll have
      * similar performance to added complexity to the bulk allocator.
      */
     if (static_branch_unlikely(&page_owner_inited))
         goto failed;
 #endif
 
     /* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
     gfp &= gfp_allowed_mask;
     alloc_gfp = gfp;
     if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags))
         goto out;
     gfp = alloc_gfp;
 
     /* Find an allowed local zone that meets the low watermark. */
     for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) {
         unsigned long mark;
 
         if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
             !__cpuset_zone_allowed(zone, gfp)) {
             continue;
         }
 
         if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone &&
             zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) {
             goto failed;
         }
 
         mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
         if (zone_watermark_fast(zone, 0,  mark,
                 zonelist_zone_idx(ac.preferred_zoneref),
                 alloc_flags, gfp)) {
             break;
         }
     }
 
     /*
      * If there are no allowed local zones that meets the watermarks then
      * try to allocate a single page and reclaim if necessary.
      */
     if (unlikely(!zone))
         goto failed;
 
     /* Is a parallel drain in progress? */
     pcp_trylock_prepare(UP_flags);
     pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
     if (!pcp)
         goto failed_irq;
 
     /* Attempt the batch allocation */
     pcp_list = &pcp->lists[order_to_pindex(ac.migratetype, 0)];
     while (nr_populated < nr_pages) {
 
         /* Skip existing pages */
         if (page_array && page_array[nr_populated]) {
             nr_populated++;
             continue;
         }
 
         page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
                                 pcp, pcp_list);
         if (unlikely(!page)) {
             /* Try and allocate at least one page */
             if (!nr_account) {
                 pcp_spin_unlock_irqrestore(pcp, flags);
                 goto failed_irq;
             }
             break;
         }
         nr_account++;
 
         prep_new_page(page, 0, gfp, 0);
         if (page_list)
             list_add(&page->lru, page_list);
         else
             page_array[nr_populated] = page;
         nr_populated++;
     }
 
     pcp_spin_unlock_irqrestore(pcp, flags);
     pcp_trylock_finish(UP_flags);
 
     __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
     zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
 
 out:
     return nr_populated;
 
 failed_irq:
     pcp_trylock_finish(UP_flags);
 
 failed:
     page = __alloc_pages(gfp, 0, preferred_nid, nodemask);
     if (page) {
         if (page_list)
             list_add(&page->lru, page_list);
         else
             page_array[nr_populated] = page;
         nr_populated++;
     }
 
     goto out;
 }
 EXPORT_SYMBOL_GPL(__alloc_pages_bulk);
 
 /*
  * This is the 'heart' of the zoned buddy allocator.
  */
 struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
                             nodemask_t *nodemask)
 {
     struct page *page;
     unsigned int alloc_flags = ALLOC_WMARK_LOW;
     gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */
     struct alloc_context ac = { };
 
     /*
      * There are several places where we assume that the order value is sane
      * so bail out early if the request is out of bound.
      */
     if (WARN_ON_ONCE_GFP(order >= MAX_ORDER, gfp))
         return NULL;
 
     gfp &= gfp_allowed_mask;
     /*
      * Apply scoped allocation constraints. This is mainly about GFP_NOFS
      * resp. GFP_NOIO which has to be inherited for all allocation requests
      * from a particular context which has been marked by
      * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures
      * movable zones are not used during allocation.
      */
     gfp = current_gfp_context(gfp);
     alloc_gfp = gfp;
     if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, &ac,
             &alloc_gfp, &alloc_flags))
         return NULL;
 
     /*
      * Forbid the first pass from falling back to types that fragment
      * memory until all local zones are considered.
      */
     alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp);
 
     /* First allocation attempt */
     page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac);
     if (likely(page))
         goto out;
 
     alloc_gfp = gfp;
     ac.spread_dirty_pages = false;
 
     /*
      * Restore the original nodemask if it was potentially replaced with
      * &cpuset_current_mems_allowed to optimize the fast-path attempt.
      */
     ac.nodemask = nodemask;
 
     page = __alloc_pages_slowpath(alloc_gfp, order, &ac);
 
 out:
     if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT) && page &&
         unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
         __free_pages(page, order);
         page = NULL;
     }
 
     trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
 
     return page;
 }
 EXPORT_SYMBOL(__alloc_pages);
 
 struct folio *__folio_alloc(gfp_t gfp, unsigned int order, int preferred_nid,
         nodemask_t *nodemask)
 {
     struct page *page = __alloc_pages(gfp | __GFP_COMP, order,
             preferred_nid, nodemask);
 
     if (page && order > 1)
         prep_transhuge_page(page);
     return (struct folio *)page;
 }
 EXPORT_SYMBOL(__folio_alloc);
 
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
  * address cannot represent highmem pages. Use alloc_pages and then kmap if
  * you need to access high mem.
  */
 unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
 {
     struct page *page;
 
     page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
     if (!page)
         return 0;
     return (unsigned long) page_address(page);
 }
 EXPORT_SYMBOL(__get_free_pages);
 
 unsigned long get_zeroed_page(gfp_t gfp_mask)
 {
     return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
 }
 EXPORT_SYMBOL(get_zeroed_page);
 
 /**
  * __free_pages - Free pages allocated with alloc_pages().
  * @page: The page pointer returned from alloc_pages().
  * @order: The order of the allocation.
  *
  * This function can free multi-page allocations that are not compound
  * pages.  It does not check that the @order passed in matches that of
  * the allocation, so it is easy to leak memory.  Freeing more memory
  * than was allocated will probably emit a warning.
  *
  * If the last reference to this page is speculative, it will be released
  * by put_page() which only frees the first page of a non-compound
  * allocation.  To prevent the remaining pages from being leaked, we free
  * the subsequent pages here.  If you want to use the page's reference
  * count to decide when to free the allocation, you should allocate a
  * compound page, and use put_page() instead of __free_pages().
  *
  * Context: May be called in interrupt context or while holding a normal
  * spinlock, but not in NMI context or while holding a raw spinlock.
  */
 void __free_pages(struct page *page, unsigned int order)
 {
     if (put_page_testzero(page))
         free_the_page(page, order);
     else if (!PageHead(page))
         while (order-- > 0)
             free_the_page(page + (1 << order), order);
 }
 EXPORT_SYMBOL(__free_pages);
 
 void free_pages(unsigned long addr, unsigned int order)
 {
     if (addr != 0) {
         VM_BUG_ON(!virt_addr_valid((void *)addr));
         __free_pages(virt_to_page((void *)addr), order);
     }
 }
 
 EXPORT_SYMBOL(free_pages);
 
 /*
  * Page Fragment:
  *  An arbitrary-length arbitrary-offset area of memory which resides
  *  within a 0 or higher order page.  Multiple fragments within that page
  *  are individually refcounted, in the page's reference counter.
  *
  * The page_frag functions below provide a simple allocation framework for
  * page fragments.  This is used by the network stack and network device
  * drivers to provide a backing region of memory for use as either an
  * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
  */
 static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
                          gfp_t gfp_mask)
 {
     struct page *page = NULL;
     gfp_t gfp = gfp_mask;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
     gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
             __GFP_NOMEMALLOC;
     page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
                 PAGE_FRAG_CACHE_MAX_ORDER);
     nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
 #endif
     if (unlikely(!page))
         page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
 
     nc->va = page ? page_address(page) : NULL;
 
     return page;
 }
 
 void __page_frag_cache_drain(struct page *page, unsigned int count)
 {
     VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
 
     if (page_ref_sub_and_test(page, count))
         free_the_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(__page_frag_cache_drain);
 
 void *page_frag_alloc_align(struct page_frag_cache *nc,
               unsigned int fragsz, gfp_t gfp_mask,
               unsigned int align_mask)
 {
     unsigned int size = PAGE_SIZE;
     struct page *page;
     int offset;
 
     if (unlikely(!nc->va)) {
 refill:
         page = __page_frag_cache_refill(nc, gfp_mask);
         if (!page)
             return NULL;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
         /* if size can vary use size else just use PAGE_SIZE */
         size = nc->size;
 #endif
         /* Even if we own the page, we do not use atomic_set().
          * This would break get_page_unless_zero() users.
          */
         page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
 
         /* reset page count bias and offset to start of new frag */
         nc->pfmemalloc = page_is_pfmemalloc(page);
         nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
         nc->offset = size;
     }
 
     offset = nc->offset - fragsz;
     if (unlikely(offset < 0)) {
         page = virt_to_page(nc->va);
 
         if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
             goto refill;
 
         if (unlikely(nc->pfmemalloc)) {
             free_the_page(page, compound_order(page));
             goto refill;
         }
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
         /* if size can vary use size else just use PAGE_SIZE */
         size = nc->size;
 #endif
         /* OK, page count is 0, we can safely set it */
         set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
 
         /* reset page count bias and offset to start of new frag */
         nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
         offset = size - fragsz;
         if (unlikely(offset < 0)) {
             /*
              * The caller is trying to allocate a fragment
              * with fragsz > PAGE_SIZE but the cache isn't big
              * enough to satisfy the request, this may
              * happen in low memory conditions.
              * We don't release the cache page because
              * it could make memory pressure worse
              * so we simply return NULL here.
              */
             return NULL;
         }
     }
 
     nc->pagecnt_bias--;
     offset &= align_mask;
     nc->offset = offset;
 
     return nc->va + offset;
 }
 EXPORT_SYMBOL(page_frag_alloc_align);
 
 /*
  * Frees a page fragment allocated out of either a compound or order 0 page.
  */
 void page_frag_free(void *addr)
 {
     struct page *page = virt_to_head_page(addr);
 
     if (unlikely(put_page_testzero(page)))
         free_the_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(page_frag_free);
 
 static void *make_alloc_exact(unsigned long addr, unsigned int order,
         size_t size)
 {
     if (addr) {
         unsigned long alloc_end = addr + (PAGE_SIZE << order);
         unsigned long used = addr + PAGE_ALIGN(size);
 
         split_page(virt_to_page((void *)addr), order);
         while (used < alloc_end) {
             free_page(used);
             used += PAGE_SIZE;
         }
     }
     return (void *)addr;
 }
 
 /**
  * alloc_pages_exact - allocate an exact number physically-contiguous pages.
  * @size: the number of bytes to allocate
  * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
  *
  * This function is similar to alloc_pages(), except that it allocates the
  * minimum number of pages to satisfy the request.  alloc_pages() can only
  * allocate memory in power-of-two pages.
  *
  * This function is also limited by MAX_ORDER.
  *
  * Memory allocated by this function must be released by free_pages_exact().
  *
  * Return: pointer to the allocated area or %NULL in case of error.
  */
 void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
 {
     unsigned int order = get_order(size);
     unsigned long addr;
 
     if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
         gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
 
     addr = __get_free_pages(gfp_mask, order);
     return make_alloc_exact(addr, order, size);
 }
 EXPORT_SYMBOL(alloc_pages_exact);
 
 /**
  * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
  *             pages on a node.
  * @nid: the preferred node ID where memory should be allocated
  * @size: the number of bytes to allocate
  * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
  *
  * Like alloc_pages_exact(), but try to allocate on node nid first before falling
  * back.
  *
  * Return: pointer to the allocated area or %NULL in case of error.
  */
 void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
 {
     unsigned int order = get_order(size);
     struct page *p;
 
     if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
         gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
 
     p = alloc_pages_node(nid, gfp_mask, order);
     if (!p)
         return NULL;
     return make_alloc_exact((unsigned long)page_address(p), order, size);
 }
 
 /**
  * free_pages_exact - release memory allocated via alloc_pages_exact()
  * @virt: the value returned by alloc_pages_exact.
  * @size: size of allocation, same value as passed to alloc_pages_exact().
  *
  * Release the memory allocated by a previous call to alloc_pages_exact.
  */
 void free_pages_exact(void *virt, size_t size)
 {
     unsigned long addr = (unsigned long)virt;
     unsigned long end = addr + PAGE_ALIGN(size);
 
     while (addr < end) {
         free_page(addr);
         addr += PAGE_SIZE;
     }
 }
 EXPORT_SYMBOL(free_pages_exact);
 
 /**
  * nr_free_zone_pages - count number of pages beyond high watermark
  * @offset: The zone index of the highest zone
  *
  * nr_free_zone_pages() counts the number of pages which are beyond the
  * high watermark within all zones at or below a given zone index.  For each
  * zone, the number of pages is calculated as:
  *
  *     nr_free_zone_pages = managed_pages - high_pages
  *
  * Return: number of pages beyond high watermark.
  */
 static unsigned long nr_free_zone_pages(int offset)
 {
     struct zoneref *z;
     struct zone *zone;
 
     /* Just pick one node, since fallback list is circular */
     unsigned long sum = 0;
 
     struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);
 
     for_each_zone_zonelist(zone, z, zonelist, offset) {
         unsigned long size = zone_managed_pages(zone);
         unsigned long high = high_wmark_pages(zone);
         if (size > high)
             sum += size - high;
     }
 
     return sum;
 }
 
 /**
  * nr_free_buffer_pages - count number of pages beyond high watermark
  *
  * nr_free_buffer_pages() counts the number of pages which are beyond the high
  * watermark within ZONE_DMA and ZONE_NORMAL.
  *
  * Return: number of pages beyond high watermark within ZONE_DMA and
  * ZONE_NORMAL.
  */
 unsigned long nr_free_buffer_pages(void)
 {
     return nr_free_zone_pages(gfp_zone(GFP_USER));
 }
 EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
 
 static inline void show_node(struct zone *zone)
 {
     if (IS_ENABLED(CONFIG_NUMA))
         printk("Node %d ", zone_to_nid(zone));
 }
 
 long si_mem_available(void)
 {
     long available;
     unsigned long pagecache;
     unsigned long wmark_low = 0;
     unsigned long pages[NR_LRU_LISTS];
     unsigned long reclaimable;
     struct zone *zone;
     int lru;
 
     for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
         pages[lru] = global_node_page_state(NR_LRU_BASE + lru);
 
     for_each_zone(zone)
         wmark_low += low_wmark_pages(zone);
 
     /*
      * Estimate the amount of memory available for userspace allocations,
      * without causing swapping or OOM.
      */
     available = global_zone_page_state(NR_FREE_PAGES) - totalreserve_pages;
 
     /*
      * Not all the page cache can be freed, otherwise the system will
      * start swapping or thrashing. Assume at least half of the page
      * cache, or the low watermark worth of cache, needs to stay.
      */
     pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
     pagecache -= min(pagecache / 2, wmark_low);
     available += pagecache;
 
     /*
      * Part of the reclaimable slab and other kernel memory consists of
      * items that are in use, and cannot be freed. Cap this estimate at the
      * low watermark.
      */
     reclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B) +
         global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
     available += reclaimable - min(reclaimable / 2, wmark_low);
 
     if (available < 0)
         available = 0;
     return available;
 }
 EXPORT_SYMBOL_GPL(si_mem_available);
 
 void si_meminfo(struct sysinfo *val)
 {
     val->totalram = totalram_pages();
     val->sharedram = global_node_page_state(NR_SHMEM);
     val->freeram = global_zone_page_state(NR_FREE_PAGES);
     val->bufferram = nr_blockdev_pages();
     val->totalhigh = totalhigh_pages();
     val->freehigh = nr_free_highpages();
     val->mem_unit = PAGE_SIZE;
 }
 
 EXPORT_SYMBOL(si_meminfo);
 
 #ifdef CONFIG_NUMA
 void si_meminfo_node(struct sysinfo *val, int nid)
 {
     int zone_type;      /* needs to be signed */
     unsigned long managed_pages = 0;
     unsigned long managed_highpages = 0;
     unsigned long free_highpages = 0;
     pg_data_t *pgdat = NODE_DATA(nid);
 
     for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
         managed_pages += zone_managed_pages(&pgdat->node_zones[zone_type]);
     val->totalram = managed_pages;
     val->sharedram = node_page_state(pgdat, NR_SHMEM);
     val->freeram = sum_zone_node_page_state(nid, NR_FREE_PAGES);
 #ifdef CONFIG_HIGHMEM
     for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
         struct zone *zone = &pgdat->node_zones[zone_type];
 
         if (is_highmem(zone)) {
             managed_highpages += zone_managed_pages(zone);
             free_highpages += zone_page_state(zone, NR_FREE_PAGES);
         }
     }
     val->totalhigh = managed_highpages;
     val->freehigh = free_highpages;
 #else
     val->totalhigh = managed_highpages;
     val->freehigh = free_highpages;
 #endif
     val->mem_unit = PAGE_SIZE;
 }
 #endif
 
 /*
  * Determine whether the node should be displayed or not, depending on whether
  * SHOW_MEM_FILTER_NODES was passed to show_free_areas().
  */
 static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask)
 {
     if (!(flags & SHOW_MEM_FILTER_NODES))
         return false;
 
     /*
      * no node mask - aka implicit memory numa policy. Do not bother with
      * the synchronization - read_mems_allowed_begin - because we do not
      * have to be precise here.
      */
     if (!nodemask)
         nodemask = &cpuset_current_mems_allowed;
 
     return !node_isset(nid, *nodemask);
 }
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
 
 static void show_migration_types(unsigned char type)
 {
     static const char types[MIGRATE_TYPES] = {
         [MIGRATE_UNMOVABLE] = 'U',
         [MIGRATE_MOVABLE]   = 'M',
         [MIGRATE_RECLAIMABLE]   = 'E',
         [MIGRATE_HIGHATOMIC]    = 'H',
 #ifdef CONFIG_CMA
         [MIGRATE_CMA]       = 'C',
 #endif
 #ifdef CONFIG_MEMORY_ISOLATION
         [MIGRATE_ISOLATE]   = 'I',
 #endif
     };
     char tmp[MIGRATE_TYPES + 1];
     char *p = tmp;
     int i;
 
     for (i = 0; i < MIGRATE_TYPES; i++) {
         if (type & (1 << i))
             *p++ = types[i];
     }
 
     *p = '\0';
     printk(KERN_CONT "(%s) ", tmp);
 }
 
 /*
  * Show free area list (used inside shift_scroll-lock stuff)
  * We also calculate the percentage fragmentation. We do this by counting the
  * memory on each free list with the exception of the first item on the list.
  *
  * Bits in @filter:
  * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
  *   cpuset.
  */
 void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 {
     unsigned long free_pcp = 0;
     int cpu, nid;
     struct zone *zone;
     pg_data_t *pgdat;
 
     for_each_populated_zone(zone) {
         if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
             continue;
 
         for_each_online_cpu(cpu)
             free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
     }
 
     printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
         " active_file:%lu inactive_file:%lu isolated_file:%lu\n"
         " unevictable:%lu dirty:%lu writeback:%lu\n"
         " slab_reclaimable:%lu slab_unreclaimable:%lu\n"
         " mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
         " kernel_misc_reclaimable:%lu\n"
         " free:%lu free_pcp:%lu free_cma:%lu\n",
         global_node_page_state(NR_ACTIVE_ANON),
         global_node_page_state(NR_INACTIVE_ANON),
         global_node_page_state(NR_ISOLATED_ANON),
         global_node_page_state(NR_ACTIVE_FILE),
         global_node_page_state(NR_INACTIVE_FILE),
         global_node_page_state(NR_ISOLATED_FILE),
         global_node_page_state(NR_UNEVICTABLE),
         global_node_page_state(NR_FILE_DIRTY),
         global_node_page_state(NR_WRITEBACK),
         global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B),
         global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B),
         global_node_page_state(NR_FILE_MAPPED),
         global_node_page_state(NR_SHMEM),
         global_node_page_state(NR_PAGETABLE),
         global_zone_page_state(NR_BOUNCE),
         global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE),
         global_zone_page_state(NR_FREE_PAGES),
         free_pcp,
         global_zone_page_state(NR_FREE_CMA_PAGES));
 
     for_each_online_pgdat(pgdat) {
         if (show_mem_node_skip(filter, pgdat->node_id, nodemask))
             continue;
 
         printk("Node %d"
             " active_anon:%lukB"
             " inactive_anon:%lukB"
             " active_file:%lukB"
             " inactive_file:%lukB"
             " unevictable:%lukB"
             " isolated(anon):%lukB"
             " isolated(file):%lukB"
             " mapped:%lukB"
             " dirty:%lukB"
             " writeback:%lukB"
             " shmem:%lukB"
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
             " shmem_thp: %lukB"
             " shmem_pmdmapped: %lukB"
             " anon_thp: %lukB"
 #endif
             " writeback_tmp:%lukB"
             " kernel_stack:%lukB"
 #ifdef CONFIG_SHADOW_CALL_STACK
             " shadow_call_stack:%lukB"
 #endif
             " pagetables:%lukB"
             " all_unreclaimable? %s"
             "\n",
             pgdat->node_id,
             K(node_page_state(pgdat, NR_ACTIVE_ANON)),
             K(node_page_state(pgdat, NR_INACTIVE_ANON)),
             K(node_page_state(pgdat, NR_ACTIVE_FILE)),
             K(node_page_state(pgdat, NR_INACTIVE_FILE)),
             K(node_page_state(pgdat, NR_UNEVICTABLE)),
             K(node_page_state(pgdat, NR_ISOLATED_ANON)),
             K(node_page_state(pgdat, NR_ISOLATED_FILE)),
             K(node_page_state(pgdat, NR_FILE_MAPPED)),
             K(node_page_state(pgdat, NR_FILE_DIRTY)),
             K(node_page_state(pgdat, NR_WRITEBACK)),
             K(node_page_state(pgdat, NR_SHMEM)),
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
             K(node_page_state(pgdat, NR_SHMEM_THPS)),
             K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
             K(node_page_state(pgdat, NR_ANON_THPS)),
 #endif
             K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
             node_page_state(pgdat, NR_KERNEL_STACK_KB),
 #ifdef CONFIG_SHADOW_CALL_STACK
             node_page_state(pgdat, NR_KERNEL_SCS_KB),
 #endif
             K(node_page_state(pgdat, NR_PAGETABLE)),
             pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
                 "yes" : "no");
     }
 
     for_each_populated_zone(zone) {
         int i;
 
         if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
             continue;
 
         free_pcp = 0;
         for_each_online_cpu(cpu)
             free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
 
         show_node(zone);
         printk(KERN_CONT
             "%s"
             " free:%lukB"
             " boost:%lukB"
             " min:%lukB"
             " low:%lukB"
             " high:%lukB"
             " reserved_highatomic:%luKB"
             " active_anon:%lukB"
             " inactive_anon:%lukB"
             " active_file:%lukB"
             " inactive_file:%lukB"
             " unevictable:%lukB"
             " writepending:%lukB"
             " present:%lukB"
             " managed:%lukB"
             " mlocked:%lukB"
             " bounce:%lukB"
             " free_pcp:%lukB"
             " local_pcp:%ukB"
             " free_cma:%lukB"
             "\n",
             zone->name,
             K(zone_page_state(zone, NR_FREE_PAGES)),
             K(zone->watermark_boost),
             K(min_wmark_pages(zone)),
             K(low_wmark_pages(zone)),
             K(high_wmark_pages(zone)),
             K(zone->nr_reserved_highatomic),
             K(zone_page_state(zone, NR_ZONE_ACTIVE_ANON)),
             K(zone_page_state(zone, NR_ZONE_INACTIVE_ANON)),
             K(zone_page_state(zone, NR_ZONE_ACTIVE_FILE)),
             K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
             K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
             K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
             K(zone->present_pages),
             K(zone_managed_pages(zone)),
             K(zone_page_state(zone, NR_MLOCK)),
             K(zone_page_state(zone, NR_BOUNCE)),
             K(free_pcp),
             K(this_cpu_read(zone->per_cpu_pageset->count)),
             K(zone_page_state(zone, NR_FREE_CMA_PAGES)));
         printk("lowmem_reserve[]:");
         for (i = 0; i < MAX_NR_ZONES; i++)
             printk(KERN_CONT " %ld", zone->lowmem_reserve[i]);
         printk(KERN_CONT "\n");
     }
 
     for_each_populated_zone(zone) {
         unsigned int order;
         unsigned long nr[MAX_ORDER], flags, total = 0;
         unsigned char types[MAX_ORDER];
 
         if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
             continue;
         show_node(zone);
         printk(KERN_CONT "%s: ", zone->name);
 
         spin_lock_irqsave(&zone->lock, flags);
         for (order = 0; order < MAX_ORDER; order++) {
             struct free_area *area = &zone->free_area[order];
             int type;
 
             nr[order] = area->nr_free;
             total += nr[order] << order;
 
             types[order] = 0;
             for (type = 0; type < MIGRATE_TYPES; type++) {
                 if (!free_area_empty(area, type))
                     types[order] |= 1 << type;
             }
         }
         spin_unlock_irqrestore(&zone->lock, flags);
         for (order = 0; order < MAX_ORDER; order++) {
             printk(KERN_CONT "%lu*%lukB ",
                    nr[order], K(1UL) << order);
             if (nr[order])
                 show_migration_types(types[order]);
         }
         printk(KERN_CONT "= %lukB\n", K(total));
     }
 
     for_each_online_node(nid) {
         if (show_mem_node_skip(filter, nid, nodemask))
             continue;
         hugetlb_show_meminfo_node(nid);
     }
 
     printk("%ld total pagecache pages\n", global_node_page_state(NR_FILE_PAGES));
 
     show_swap_cache_info();
 }
 
 static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
 {
     zoneref->zone = zone;
     zoneref->zone_idx = zone_idx(zone);
 }
 
 /*
  * Builds allocation fallback zone lists.
  *
  * Add all populated zones of a node to the zonelist.
  */
 static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
 {
     struct zone *zone;
     enum zone_type zone_type = MAX_NR_ZONES;
     int nr_zones = 0;
 
     do {
         zone_type--;
         zone = pgdat->node_zones + zone_type;
         if (populated_zone(zone)) {
             zoneref_set_zone(zone, &zonerefs[nr_zones++]);
             check_highest_zone(zone_type);
         }
     } while (zone_type);
 
     return nr_zones;
 }
 
 #ifdef CONFIG_NUMA
 
 static int __parse_numa_zonelist_order(char *s)
 {
     /*
      * We used to support different zonelists modes but they turned
      * out to be just not useful. Let's keep the warning in place
      * if somebody still use the cmd line parameter so that we do
      * not fail it silently
      */
     if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {
         pr_warn("Ignoring unsupported numa_zonelist_order value:  %s\n", s);
         return -EINVAL;
     }
     return 0;
 }
 
 char numa_zonelist_order[] = "Node";
 
 /*
  * sysctl handler for numa_zonelist_order
  */
 int numa_zonelist_order_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     if (write)
         return __parse_numa_zonelist_order(buffer);
     return proc_dostring(table, write, buffer, length, ppos);
 }
 
 
 static int node_load[MAX_NUMNODES];
 
 /**
  * find_next_best_node - find the next node that should appear in a given node's fallback list
  * @node: node whose fallback list we're appending
  * @used_node_mask: nodemask_t of already used nodes
  *
  * We use a number of factors to determine which is the next node that should
  * appear on a given node's fallback list.  The node should not have appeared
  * already in @node's fallback list, and it should be the next closest node
  * according to the distance array (which contains arbitrary distance values
  * from each node to each node in the system), and should also prefer nodes
  * with no CPUs, since presumably they'll have very little allocation pressure
  * on them otherwise.
  *
  * Return: node id of the found node or %NUMA_NO_NODE if no node is found.
  */
 int find_next_best_node(int node, nodemask_t *used_node_mask)
 {
     int n, val;
     int min_val = INT_MAX;
     int best_node = NUMA_NO_NODE;
 
     /* Use the local node if we haven't already */
     if (!node_isset(node, *used_node_mask)) {
         node_set(node, *used_node_mask);
         return node;
     }
 
     for_each_node_state(n, N_MEMORY) {
 
         /* Don't want a node to appear more than once */
         if (node_isset(n, *used_node_mask))
             continue;
 
         /* Use the distance array to find the distance */
         val = node_distance(node, n);
 
         /* Penalize nodes under us ("prefer the next node") */
         val += (n < node);
 
         /* Give preference to headless and unused nodes */
         if (!cpumask_empty(cpumask_of_node(n)))
             val += PENALTY_FOR_NODE_WITH_CPUS;
 
         /* Slight preference for less loaded node */
         val *= MAX_NUMNODES;
         val += node_load[n];
 
         if (val < min_val) {
             min_val = val;
             best_node = n;
         }
     }
 
     if (best_node >= 0)
         node_set(best_node, *used_node_mask);
 
     return best_node;
 }
 
 
 /*
  * Build zonelists ordered by node and zones within node.
  * This results in maximum locality--normal zone overflows into local
  * DMA zone, if any--but risks exhausting DMA zone.
  */
 static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
         unsigned nr_nodes)
 {
     struct zoneref *zonerefs;
     int i;
 
     zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
 
     for (i = 0; i < nr_nodes; i++) {
         int nr_zones;
 
         pg_data_t *node = NODE_DATA(node_order[i]);
 
         nr_zones = build_zonerefs_node(node, zonerefs);
         zonerefs += nr_zones;
     }
     zonerefs->zone = NULL;
     zonerefs->zone_idx = 0;
 }
 
 /*
  * Build gfp_thisnode zonelists
  */
 static void build_thisnode_zonelists(pg_data_t *pgdat)
 {
     struct zoneref *zonerefs;
     int nr_zones;
 
     zonerefs = pgdat->node_zonelists[ZONELIST_NOFALLBACK]._zonerefs;
     nr_zones = build_zonerefs_node(pgdat, zonerefs);
     zonerefs += nr_zones;
     zonerefs->zone = NULL;
     zonerefs->zone_idx = 0;
 }
 
 /*
  * Build zonelists ordered by zone and nodes within zones.
  * This results in conserving DMA zone[s] until all Normal memory is
  * exhausted, but results in overflowing to remote node while memory
  * may still exist in local DMA zone.
  */
 
 static void build_zonelists(pg_data_t *pgdat)
 {
     static int node_order[MAX_NUMNODES];
     int node, nr_nodes = 0;
     nodemask_t used_mask = NODE_MASK_NONE;
     int local_node, prev_node;
 
     /* NUMA-aware ordering of nodes */
     local_node = pgdat->node_id;
     prev_node = local_node;
 
     memset(node_order, 0, sizeof(node_order));
     while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
         /*
          * We don't want to pressure a particular node.
          * So adding penalty to the first node in same
          * distance group to make it round-robin.
          */
         if (node_distance(local_node, node) !=
             node_distance(local_node, prev_node))
             node_load[node] += 1;
 
         node_order[nr_nodes++] = node;
         prev_node = node;
     }
 
     build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
     build_thisnode_zonelists(pgdat);
     pr_info("Fallback order for Node %d: ", local_node);
     for (node = 0; node < nr_nodes; node++)
         pr_cont("%d ", node_order[node]);
     pr_cont("\n");
 }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 /*
  * Return node id of node used for "local" allocations.
  * I.e., first node id of first zone in arg node's generic zonelist.
  * Used for initializing percpu 'numa_mem', which is used primarily
  * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
  */
 int local_memory_node(int node)
 {
     struct zoneref *z;
 
     z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
                    gfp_zone(GFP_KERNEL),
                    NULL);
     return zone_to_nid(z->zone);
 }
 #endif
 
 static void setup_min_unmapped_ratio(void);
 static void setup_min_slab_ratio(void);
 #else   /* CONFIG_NUMA */
 
 static void build_zonelists(pg_data_t *pgdat)
 {
     int node, local_node;
     struct zoneref *zonerefs;
     int nr_zones;
 
     local_node = pgdat->node_id;
 
     zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
     nr_zones = build_zonerefs_node(pgdat, zonerefs);
     zonerefs += nr_zones;
 
     /*
      * Now we build the zonelist so that it contains the zones
      * of all the other nodes.
      * We don't want to pressure a particular node, so when
      * building the zones for node N, we make sure that the
      * zones coming right after the local ones are those from
      * node N+1 (modulo N)
      */
     for (node = local_node + 1; node < MAX_NUMNODES; node++) {
         if (!node_online(node))
             continue;
         nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
         zonerefs += nr_zones;
     }
     for (node = 0; node < local_node; node++) {
         if (!node_online(node))
             continue;
         nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
         zonerefs += nr_zones;
     }
 
     zonerefs->zone = NULL;
     zonerefs->zone_idx = 0;
 }
 
 #endif  /* CONFIG_NUMA */
 
 /*
  * Boot pageset table. One per cpu which is going to be used for all
  * zones and all nodes. The parameters will be set in such a way
  * that an item put on a list will immediately be handed over to
  * the buddy list. This is safe since pageset manipulation is done
  * with interrupts disabled.
  *
  * The boot_pagesets must be kept even after bootup is complete for
  * unused processors and/or zones. They do play a role for bootstrapping
  * hotplugged processors.
  *
  * zoneinfo_show() and maybe other functions do
  * not check if the processor is online before following the pageset pointer.
  * Other parts of the kernel may not check if the zone is available.
  */
 static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats);
 /* These effectively disable the pcplists in the boot pageset completely */
 #define BOOT_PAGESET_HIGH   0
 #define BOOT_PAGESET_BATCH  1
 static DEFINE_PER_CPU(struct per_cpu_pages, boot_pageset);
 static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);
 DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
 static void __build_all_zonelists(void *data)
 {
     int nid;
     int __maybe_unused cpu;
     pg_data_t *self = data;
 
     write_seqlock(&zonelist_update_seq);
 
 #ifdef CONFIG_NUMA
     memset(node_load, 0, sizeof(node_load));
 #endif
 
     /*
      * This node is hotadded and no memory is yet present.   So just
      * building zonelists is fine - no need to touch other nodes.
      */
     if (self && !node_online(self->node_id)) {
         build_zonelists(self);
     } else {
         /*
          * All possible nodes have pgdat preallocated
          * in free_area_init
          */
         for_each_node(nid) {
             pg_data_t *pgdat = NODE_DATA(nid);
 
             build_zonelists(pgdat);
         }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
         /*
          * We now know the "local memory node" for each node--
          * i.e., the node of the first zone in the generic zonelist.
          * Set up numa_mem percpu variable for on-line cpus.  During
          * boot, only the boot cpu should be on-line;  we'll init the
          * secondary cpus' numa_mem as they come on-line.  During
          * node/memory hotplug, we'll fixup all on-line cpus.
          */
         for_each_online_cpu(cpu)
             set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
 #endif
     }
 
     write_sequnlock(&zonelist_update_seq);
 }
 
 static noinline void __init
 build_all_zonelists_init(void)
 {
     int cpu;
 
     __build_all_zonelists(NULL);
 
     /*
      * Initialize the boot_pagesets that are going to be used
      * for bootstrapping processors. The real pagesets for
      * each zone will be allocated later when the per cpu
      * allocator is available.
      *
      * boot_pagesets are used also for bootstrapping offline
      * cpus if the system is already booted because the pagesets
      * are needed to initialize allocators on a specific cpu too.
      * F.e. the percpu allocator needs the page allocator which
      * needs the percpu allocator in order to allocate its pagesets
      * (a chicken-egg dilemma).
      */
     for_each_possible_cpu(cpu)
         per_cpu_pages_init(&per_cpu(boot_pageset, cpu), &per_cpu(boot_zonestats, cpu));
 
     mminit_verify_zonelist();
     cpuset_init_current_mems_allowed();
 }
 
 /*
  * unless system_state == SYSTEM_BOOTING.
  *
  * __ref due to call of __init annotated helper build_all_zonelists_init
  * [protected by SYSTEM_BOOTING].
  */
 void __ref build_all_zonelists(pg_data_t *pgdat)
 {
     unsigned long vm_total_pages;
 
     if (system_state == SYSTEM_BOOTING) {
         build_all_zonelists_init();
     } else {
         __build_all_zonelists(pgdat);
         /* cpuset refresh routine should be here */
     }
     /* Get the number of free pages beyond high watermark in all zones. */
     vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
     /*
      * Disable grouping by mobility if the number of pages in the
      * system is too low to allow the mechanism to work. It would be
      * more accurate, but expensive to check per-zone. This check is
      * made on memory-hotadd so a system can start with mobility
      * disabled and enable it later
      */
     if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
         page_group_by_mobility_disabled = 1;
     else
         page_group_by_mobility_disabled = 0;
 
     pr_info("Built %u zonelists, mobility grouping %s.  Total pages: %ld\n",
         nr_online_nodes,
         page_group_by_mobility_disabled ? "off" : "on",
         vm_total_pages);
 #ifdef CONFIG_NUMA
     pr_info("Policy zone: %s\n", zone_names[policy_zone]);
 #endif
 }
 
 /* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped init */
 static bool __meminit
 overlap_memmap_init(unsigned long zone, unsigned long *pfn)
 {
     static struct memblock_region *r;
 
     if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
         if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
             for_each_mem_region(r) {
                 if (*pfn < memblock_region_memory_end_pfn(r))
                     break;
             }
         }
         if (*pfn >= memblock_region_memory_base_pfn(r) &&
             memblock_is_mirror(r)) {
             *pfn = memblock_region_memory_end_pfn(r);
             return true;
         }
     }
     return false;
 }
 
 /*
  * Initially all pages are reserved - free ones are freed
  * up by memblock_free_all() once the early boot process is
  * done. Non-atomic initialization, single-pass.
  *
  * All aligned pageblocks are initialized to the specified migratetype
  * (usually MIGRATE_MOVABLE). Besides setting the migratetype, no related
  * zone stats (e.g., nr_isolate_pageblock) are touched.
  */
 void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone,
         unsigned long start_pfn, unsigned long zone_end_pfn,
         enum meminit_context context,
         struct vmem_altmap *altmap, int migratetype)
 {
     unsigned long pfn, end_pfn = start_pfn + size;
     struct page *page;
 
     if (highest_memmap_pfn < end_pfn - 1)
         highest_memmap_pfn = end_pfn - 1;
 
 #ifdef CONFIG_ZONE_DEVICE
     /*
      * Honor reservation requested by the driver for this ZONE_DEVICE
      * memory. We limit the total number of pages to initialize to just
      * those that might contain the memory mapping. We will defer the
      * ZONE_DEVICE page initialization until after we have released
      * the hotplug lock.
      */
     if (zone == ZONE_DEVICE) {
         if (!altmap)
             return;
 
         if (start_pfn == altmap->base_pfn)
             start_pfn += altmap->reserve;
         end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
     }
 #endif
 
     for (pfn = start_pfn; pfn < end_pfn; ) {
         /*
          * There can be holes in boot-time mem_map[]s handed to this
          * function.  They do not exist on hotplugged memory.
          */
         if (context == MEMINIT_EARLY) {
             if (overlap_memmap_init(zone, &pfn))
                 continue;
             if (defer_init(nid, pfn, zone_end_pfn))
                 break;
         }
 
         page = pfn_to_page(pfn);
         __init_single_page(page, pfn, zone, nid);
         if (context == MEMINIT_HOTPLUG)
             __SetPageReserved(page);
 
         /*
          * Usually, we want to mark the pageblock MIGRATE_MOVABLE,
          * such that unmovable allocations won't be scattered all
          * over the place during system boot.
          */
         if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
             set_pageblock_migratetype(page, migratetype);
             cond_resched();
         }
         pfn++;
     }
 }
 
 #ifdef CONFIG_ZONE_DEVICE
 static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
                       unsigned long zone_idx, int nid,
                       struct dev_pagemap *pgmap)
 {
 
     __init_single_page(page, pfn, zone_idx, nid);
 
     /*
      * Mark page reserved as it will need to wait for onlining
      * phase for it to be fully associated with a zone.
      *
      * We can use the non-atomic __set_bit operation for setting
      * the flag as we are still initializing the pages.
      */
     __SetPageReserved(page);
 
     /*
      * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
      * and zone_device_data.  It is a bug if a ZONE_DEVICE page is
      * ever freed or placed on a driver-private list.
      */
     page->pgmap = pgmap;
     page->zone_device_data = NULL;
 
     /*
      * Mark the block movable so that blocks are reserved for
      * movable at startup. This will force kernel allocations
      * to reserve their blocks rather than leaking throughout
      * the address space during boot when many long-lived
      * kernel allocations are made.
      *
      * Please note that MEMINIT_HOTPLUG path doesn't clear memmap
      * because this is done early in section_activate()
      */
     if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
         set_pageblock_migratetype(page, MIGRATE_MOVABLE);
         cond_resched();
     }
 }
 
 /*
  * With compound page geometry and when struct pages are stored in ram most
  * tail pages are reused. Consequently, the amount of unique struct pages to
  * initialize is a lot smaller that the total amount of struct pages being
  * mapped. This is a paired / mild layering violation with explicit knowledge
  * of how the sparse_vmemmap internals handle compound pages in the lack
  * of an altmap. See vmemmap_populate_compound_pages().
  */
 static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap,
                           unsigned long nr_pages)
 {
     return is_power_of_2(sizeof(struct page)) &&
         !altmap ? 2 * (PAGE_SIZE / sizeof(struct page)) : nr_pages;
 }
 
 static void __ref memmap_init_compound(struct page *head,
                        unsigned long head_pfn,
                        unsigned long zone_idx, int nid,
                        struct dev_pagemap *pgmap,
                        unsigned long nr_pages)
 {
     unsigned long pfn, end_pfn = head_pfn + nr_pages;
     unsigned int order = pgmap->vmemmap_shift;
 
     __SetPageHead(head);
     for (pfn = head_pfn + 1; pfn < end_pfn; pfn++) {
         struct page *page = pfn_to_page(pfn);
 
         __init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
         prep_compound_tail(head, pfn - head_pfn);
         set_page_count(page, 0);
 
         /*
          * The first tail page stores compound_mapcount_ptr() and
          * compound_order() and the second tail page stores
          * compound_pincount_ptr(). Call prep_compound_head() after
          * the first and second tail pages have been initialized to
          * not have the data overwritten.
          */
         if (pfn == head_pfn + 2)
             prep_compound_head(head, order);
     }
 }
 
 void __ref memmap_init_zone_device(struct zone *zone,
                    unsigned long start_pfn,
                    unsigned long nr_pages,
                    struct dev_pagemap *pgmap)
 {
     unsigned long pfn, end_pfn = start_pfn + nr_pages;
     struct pglist_data *pgdat = zone->zone_pgdat;
     struct vmem_altmap *altmap = pgmap_altmap(pgmap);
     unsigned int pfns_per_compound = pgmap_vmemmap_nr(pgmap);
     unsigned long zone_idx = zone_idx(zone);
     unsigned long start = jiffies;
     int nid = pgdat->node_id;
 
     if (WARN_ON_ONCE(!pgmap || zone_idx(zone) != ZONE_DEVICE))
         return;
 
     /*
      * The call to memmap_init should have already taken care
      * of the pages reserved for the memmap, so we can just jump to
      * the end of that region and start processing the device pages.
      */
     if (altmap) {
         start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
         nr_pages = end_pfn - start_pfn;
     }
 
     for (pfn = start_pfn; pfn < end_pfn; pfn += pfns_per_compound) {
         struct page *page = pfn_to_page(pfn);
 
         __init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
 
         if (pfns_per_compound == 1)
             continue;
 
         memmap_init_compound(page, pfn, zone_idx, nid, pgmap,
                      compound_nr_pages(altmap, pfns_per_compound));
     }
 
     pr_info("%s initialised %lu pages in %ums\n", __func__,
         nr_pages, jiffies_to_msecs(jiffies - start));
 }
 
 #endif
 static void __meminit zone_init_free_lists(struct zone *zone)
 {
     unsigned int order, t;
     for_each_migratetype_order(order, t) {
         INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
         zone->free_area[order].nr_free = 0;
     }
 }
 
 /*
  * Only struct pages that correspond to ranges defined by memblock.memory
  * are zeroed and initialized by going through __init_single_page() during
  * memmap_init_zone_range().
  *
  * But, there could be struct pages that correspond to holes in
  * memblock.memory. This can happen because of the following reasons:
  * - physical memory bank size is not necessarily the exact multiple of the
  *   arbitrary section size
  * - early reserved memory may not be listed in memblock.memory
  * - memory layouts defined with memmap= kernel parameter may not align
  *   nicely with memmap sections
  *
  * Explicitly initialize those struct pages so that:
  * - PG_Reserved is set
  * - zone and node links point to zone and node that span the page if the
  *   hole is in the middle of a zone
  * - zone and node links point to adjacent zone/node if the hole falls on
  *   the zone boundary; the pages in such holes will be prepended to the
  *   zone/node above the hole except for the trailing pages in the last
  *   section that will be appended to the zone/node below.
  */
 static void __init init_unavailable_range(unsigned long spfn,
                       unsigned long epfn,
                       int zone, int node)
 {
     unsigned long pfn;
     u64 pgcnt = 0;
 
     for (pfn = spfn; pfn < epfn; pfn++) {
         if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) {
             pfn = ALIGN_DOWN(pfn, pageblock_nr_pages)
                 + pageblock_nr_pages - 1;
             continue;
         }
         __init_single_page(pfn_to_page(pfn), pfn, zone, node);
         __SetPageReserved(pfn_to_page(pfn));
         pgcnt++;
     }
 
     if (pgcnt)
         pr_info("On node %d, zone %s: %lld pages in unavailable ranges",
             node, zone_names[zone], pgcnt);
 }
 
 static void __init memmap_init_zone_range(struct zone *zone,
                       unsigned long start_pfn,
                       unsigned long end_pfn,
                       unsigned long *hole_pfn)
 {
     unsigned long zone_start_pfn = zone->zone_start_pfn;
     unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages;
     int nid = zone_to_nid(zone), zone_id = zone_idx(zone);
 
     start_pfn = clamp(start_pfn, zone_start_pfn, zone_end_pfn);
     end_pfn = clamp(end_pfn, zone_start_pfn, zone_end_pfn);
 
     if (start_pfn >= end_pfn)
         return;
 
     memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
               zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE);
 
     if (*hole_pfn < start_pfn)
         init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);
 
     *hole_pfn = end_pfn;
 }
 
 static void __init memmap_init(void)
 {
     unsigned long start_pfn, end_pfn;
     unsigned long hole_pfn = 0;
     int i, j, zone_id = 0, nid;
 
     for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
         struct pglist_data *node = NODE_DATA(nid);
 
         for (j = 0; j < MAX_NR_ZONES; j++) {
             struct zone *zone = node->node_zones + j;
 
             if (!populated_zone(zone))
                 continue;
 
             memmap_init_zone_range(zone, start_pfn, end_pfn,
                            &hole_pfn);
             zone_id = j;
         }
     }
 
 #ifdef CONFIG_SPARSEMEM
     /*
      * Initialize the memory map for hole in the range [memory_end,
      * section_end].
      * Append the pages in this hole to the highest zone in the last
      * node.
      * The call to init_unavailable_range() is outside the ifdef to
      * silence the compiler warining about zone_id set but not used;
      * for FLATMEM it is a nop anyway
      */
     end_pfn = round_up(end_pfn, PAGES_PER_SECTION);
     if (hole_pfn < end_pfn)
 #endif
         init_unavailable_range(hole_pfn, end_pfn, zone_id, nid);
 }
 
 void __init *memmap_alloc(phys_addr_t size, phys_addr_t align,
               phys_addr_t min_addr, int nid, bool exact_nid)
 {
     void *ptr;
 
     if (exact_nid)
         ptr = memblock_alloc_exact_nid_raw(size, align, min_addr,
                            MEMBLOCK_ALLOC_ACCESSIBLE,
                            nid);
     else
         ptr = memblock_alloc_try_nid_raw(size, align, min_addr,
                          MEMBLOCK_ALLOC_ACCESSIBLE,
                          nid);
 
     if (ptr && size > 0)
         page_init_poison(ptr, size);
 
     return ptr;
 }
 
 static int zone_batchsize(struct zone *zone)
 {
 #ifdef CONFIG_MMU
     int batch;
 
     /*
      * The number of pages to batch allocate is either ~0.1%
      * of the zone or 1MB, whichever is smaller. The batch
      * size is striking a balance between allocation latency
      * and zone lock contention.
      */
     batch = min(zone_managed_pages(zone) >> 10, (1024 * 1024) / PAGE_SIZE);
     batch /= 4;     /* We effectively *= 4 below */
     if (batch < 1)
         batch = 1;
 
     /*
      * Clamp the batch to a 2^n - 1 value. Having a power
      * of 2 value was found to be more likely to have
      * suboptimal cache aliasing properties in some cases.
      *
      * For example if 2 tasks are alternately allocating
      * batches of pages, one task can end up with a lot
      * of pages of one half of the possible page colors
      * and the other with pages of the other colors.
      */
     batch = rounddown_pow_of_two(batch + batch/2) - 1;
 
     return batch;
 
 #else
     /* The deferral and batching of frees should be suppressed under NOMMU
      * conditions.
      *
      * The problem is that NOMMU needs to be able to allocate large chunks
      * of contiguous memory as there's no hardware page translation to
      * assemble apparent contiguous memory from discontiguous pages.
      *
      * Queueing large contiguous runs of pages for batching, however,
      * causes the pages to actually be freed in smaller chunks.  As there
      * can be a significant delay between the individual batches being
      * recycled, this leads to the once large chunks of space being
      * fragmented and becoming unavailable for high-order allocations.
      */
     return 0;
 #endif
 }
 
 static int zone_highsize(struct zone *zone, int batch, int cpu_online)
 {
 #ifdef CONFIG_MMU
     int high;
     int nr_split_cpus;
     unsigned long total_pages;
 
     if (!percpu_pagelist_high_fraction) {
         /*
          * By default, the high value of the pcp is based on the zone
          * low watermark so that if they are full then background
          * reclaim will not be started prematurely.
          */
         total_pages = low_wmark_pages(zone);
     } else {
         /*
          * If percpu_pagelist_high_fraction is configured, the high
          * value is based on a fraction of the managed pages in the
          * zone.
          */
         total_pages = zone_managed_pages(zone) / percpu_pagelist_high_fraction;
     }
 
     /*
      * Split the high value across all online CPUs local to the zone. Note
      * that early in boot that CPUs may not be online yet and that during
      * CPU hotplug that the cpumask is not yet updated when a CPU is being
      * onlined. For memory nodes that have no CPUs, split pcp->high across
      * all online CPUs to mitigate the risk that reclaim is triggered
      * prematurely due to pages stored on pcp lists.
      */
     nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
     if (!nr_split_cpus)
         nr_split_cpus = num_online_cpus();
     high = total_pages / nr_split_cpus;
 
     /*
      * Ensure high is at least batch*4. The multiple is based on the
      * historical relationship between high and batch.
      */
     high = max(high, batch << 2);
 
     return high;
 #else
     return 0;
 #endif
 }
 
 /*
  * pcp->high and pcp->batch values are related and generally batch is lower
  * than high. They are also related to pcp->count such that count is lower
  * than high, and as soon as it reaches high, the pcplist is flushed.
  *
  * However, guaranteeing these relations at all times would require e.g. write
  * barriers here but also careful usage of read barriers at the read side, and
  * thus be prone to error and bad for performance. Thus the update only prevents
  * store tearing. Any new users of pcp->batch and pcp->high should ensure they
  * can cope with those fields changing asynchronously, and fully trust only the
  * pcp->count field on the local CPU with interrupts disabled.
  *
  * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
  * outside of boot time (or some other assurance that no concurrent updaters
  * exist).
  */
 static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
         unsigned long batch)
 {
     WRITE_ONCE(pcp->batch, batch);
     WRITE_ONCE(pcp->high, high);
 }
 
 static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats)
 {
     int pindex;
 
     memset(pcp, 0, sizeof(*pcp));
     memset(pzstats, 0, sizeof(*pzstats));
 
     spin_lock_init(&pcp->lock);
     for (pindex = 0; pindex < NR_PCP_LISTS; pindex++)
         INIT_LIST_HEAD(&pcp->lists[pindex]);
 
     /*
      * Set batch and high values safe for a boot pageset. A true percpu
      * pageset's initialization will update them subsequently. Here we don't
      * need to be as careful as pageset_update() as nobody can access the
      * pageset yet.
      */
     pcp->high = BOOT_PAGESET_HIGH;
     pcp->batch = BOOT_PAGESET_BATCH;
     pcp->free_factor = 0;
 }
 
 static void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high,
         unsigned long batch)
 {
     struct per_cpu_pages *pcp;
     int cpu;
 
     for_each_possible_cpu(cpu) {
         pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
         pageset_update(pcp, high, batch);
     }
 }
 
 /*
  * Calculate and set new high and batch values for all per-cpu pagesets of a
  * zone based on the zone's size.
  */
 static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online)
 {
     int new_high, new_batch;
 
     new_batch = max(1, zone_batchsize(zone));
     new_high = zone_highsize(zone, new_batch, cpu_online);
 
     if (zone->pageset_high == new_high &&
         zone->pageset_batch == new_batch)
         return;
 
     zone->pageset_high = new_high;
     zone->pageset_batch = new_batch;
 
     __zone_set_pageset_high_and_batch(zone, new_high, new_batch);
 }
 
 void __meminit setup_zone_pageset(struct zone *zone)
 {
     int cpu;
 
     /* Size may be 0 on !SMP && !NUMA */
     if (sizeof(struct per_cpu_zonestat) > 0)
         zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
 
     zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
     for_each_possible_cpu(cpu) {
         struct per_cpu_pages *pcp;
         struct per_cpu_zonestat *pzstats;
 
         pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
         pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
         per_cpu_pages_init(pcp, pzstats);
     }
 
     zone_set_pageset_high_and_batch(zone, 0);
 }
 
 /*
  * Allocate per cpu pagesets and initialize them.
  * Before this call only boot pagesets were available.
  */
 void __init setup_per_cpu_pageset(void)
 {
     struct pglist_data *pgdat;
     struct zone *zone;
     int __maybe_unused cpu;
 
     for_each_populated_zone(zone)
         setup_zone_pageset(zone);
 
 #ifdef CONFIG_NUMA
     /*
      * Unpopulated zones continue using the boot pagesets.
      * The numa stats for these pagesets need to be reset.
      * Otherwise, they will end up skewing the stats of
      * the nodes these zones are associated with.
      */
     for_each_possible_cpu(cpu) {
         struct per_cpu_zonestat *pzstats = &per_cpu(boot_zonestats, cpu);
         memset(pzstats->vm_numa_event, 0,
                sizeof(pzstats->vm_numa_event));
     }
 #endif
 
     for_each_online_pgdat(pgdat)
         pgdat->per_cpu_nodestats =
             alloc_percpu(struct per_cpu_nodestat);
 }
 
 static __meminit void zone_pcp_init(struct zone *zone)
 {
     /*
      * per cpu subsystem is not up at this point. The following code
      * relies on the ability of the linker to provide the
      * offset of a (static) per cpu variable into the per cpu area.
      */
     zone->per_cpu_pageset = &boot_pageset;
     zone->per_cpu_zonestats = &boot_zonestats;
     zone->pageset_high = BOOT_PAGESET_HIGH;
     zone->pageset_batch = BOOT_PAGESET_BATCH;
 
     if (populated_zone(zone))
         pr_debug("  %s zone: %lu pages, LIFO batch:%u\n", zone->name,
              zone->present_pages, zone_batchsize(zone));
 }
 
 void __meminit init_currently_empty_zone(struct zone *zone,
                     unsigned long zone_start_pfn,
                     unsigned long size)
 {
     struct pglist_data *pgdat = zone->zone_pgdat;
     int zone_idx = zone_idx(zone) + 1;
 
     if (zone_idx > pgdat->nr_zones)
         pgdat->nr_zones = zone_idx;
 
     zone->zone_start_pfn = zone_start_pfn;
 
     mminit_dprintk(MMINIT_TRACE, "memmap_init",
             "Initialising map node %d zone %lu pfns %lu -> %lu\n",
             pgdat->node_id,
             (unsigned long)zone_idx(zone),
             zone_start_pfn, (zone_start_pfn + size));
 
     zone_init_free_lists(zone);
     zone->initialized = 1;
 }
 
 /**
  * get_pfn_range_for_nid - Return the start and end page frames for a node
  * @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
  * @start_pfn: Passed by reference. On return, it will have the node start_pfn.
  * @end_pfn: Passed by reference. On return, it will have the node end_pfn.
  *
  * It returns the start and end page frame of a node based on information
  * provided by memblock_set_node(). If called for a node
  * with no available memory, a warning is printed and the start and end
  * PFNs will be 0.
  */
 void __init get_pfn_range_for_nid(unsigned int nid,
             unsigned long *start_pfn, unsigned long *end_pfn)
 {
     unsigned long this_start_pfn, this_end_pfn;
     int i;
 
     *start_pfn = -1UL;
     *end_pfn = 0;
 
     for_each_mem_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
         *start_pfn = min(*start_pfn, this_start_pfn);
         *end_pfn = max(*end_pfn, this_end_pfn);
     }
 
     if (*start_pfn == -1UL)
         *start_pfn = 0;
 }
 
 /*
  * This finds a zone that can be used for ZONE_MOVABLE pages. The
  * assumption is made that zones within a node are ordered in monotonic
  * increasing memory addresses so that the "highest" populated zone is used
  */
 static void __init find_usable_zone_for_movable(void)
 {
     int zone_index;
     for (zone_index = MAX_NR_ZONES - 1; zone_index >= 0; zone_index--) {
         if (zone_index == ZONE_MOVABLE)
             continue;
 
         if (arch_zone_highest_possible_pfn[zone_index] >
                 arch_zone_lowest_possible_pfn[zone_index])
             break;
     }
 
     VM_BUG_ON(zone_index == -1);
     movable_zone = zone_index;
 }
 
 /*
  * The zone ranges provided by the architecture do not include ZONE_MOVABLE
  * because it is sized independent of architecture. Unlike the other zones,
  * the starting point for ZONE_MOVABLE is not fixed. It may be different
  * in each node depending on the size of each node and how evenly kernelcore
  * is distributed. This helper function adjusts the zone ranges
  * provided by the architecture for a given node by using the end of the
  * highest usable zone for ZONE_MOVABLE. This preserves the assumption that
  * zones within a node are in order of monotonic increases memory addresses
  */
 static void __init adjust_zone_range_for_zone_movable(int nid,
                     unsigned long zone_type,
                     unsigned long node_start_pfn,
                     unsigned long node_end_pfn,
                     unsigned long *zone_start_pfn,
                     unsigned long *zone_end_pfn)
 {
     /* Only adjust if ZONE_MOVABLE is on this node */
     if (zone_movable_pfn[nid]) {
         /* Size ZONE_MOVABLE */
         if (zone_type == ZONE_MOVABLE) {
             *zone_start_pfn = zone_movable_pfn[nid];
             *zone_end_pfn = min(node_end_pfn,
                 arch_zone_highest_possible_pfn[movable_zone]);
 
         /* Adjust for ZONE_MOVABLE starting within this range */
         } else if (!mirrored_kernelcore &&
             *zone_start_pfn < zone_movable_pfn[nid] &&
             *zone_end_pfn > zone_movable_pfn[nid]) {
             *zone_end_pfn = zone_movable_pfn[nid];
 
         /* Check if this whole range is within ZONE_MOVABLE */
         } else if (*zone_start_pfn >= zone_movable_pfn[nid])
             *zone_start_pfn = *zone_end_pfn;
     }
 }
 
 /*
  * Return the number of pages a zone spans in a node, including holes
  * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
  */
 static unsigned long __init zone_spanned_pages_in_node(int nid,
                     unsigned long zone_type,
                     unsigned long node_start_pfn,
                     unsigned long node_end_pfn,
                     unsigned long *zone_start_pfn,
                     unsigned long *zone_end_pfn)
 {
     unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
     unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
     /* When hotadd a new node from cpu_up(), the node should be empty */
     if (!node_start_pfn && !node_end_pfn)
         return 0;
 
     /* Get the start and end of the zone */
     *zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
     *zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
     adjust_zone_range_for_zone_movable(nid, zone_type,
                 node_start_pfn, node_end_pfn,
                 zone_start_pfn, zone_end_pfn);
 
     /* Check that this node has pages within the zone's required range */
     if (*zone_end_pfn < node_start_pfn || *zone_start_pfn > node_end_pfn)
         return 0;
 
     /* Move the zone boundaries inside the node if necessary */
     *zone_end_pfn = min(*zone_end_pfn, node_end_pfn);
     *zone_start_pfn = max(*zone_start_pfn, node_start_pfn);
 
     /* Return the spanned pages */
     return *zone_end_pfn - *zone_start_pfn;
 }
 
 /*
  * Return the number of holes in a range on a node. If nid is MAX_NUMNODES,
  * then all holes in the requested range will be accounted for.
  */
 unsigned long __init __absent_pages_in_range(int nid,
                 unsigned long range_start_pfn,
                 unsigned long range_end_pfn)
 {
     unsigned long nr_absent = range_end_pfn - range_start_pfn;
     unsigned long start_pfn, end_pfn;
     int i;
 
     for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
         start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
         end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
         nr_absent -= end_pfn - start_pfn;
     }
     return nr_absent;
 }
 
 /**
  * absent_pages_in_range - Return number of page frames in holes within a range
  * @start_pfn: The start PFN to start searching for holes
  * @end_pfn: The end PFN to stop searching for holes
  *
  * Return: the number of pages frames in memory holes within a range.
  */
 unsigned long __init absent_pages_in_range(unsigned long start_pfn,
                             unsigned long end_pfn)
 {
     return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
 }
 
 /* Return the number of page frames in holes in a zone on a node */
 static unsigned long __init zone_absent_pages_in_node(int nid,
                     unsigned long zone_type,
                     unsigned long node_start_pfn,
                     unsigned long node_end_pfn)
 {
     unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
     unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
     unsigned long zone_start_pfn, zone_end_pfn;
     unsigned long nr_absent;
 
     /* When hotadd a new node from cpu_up(), the node should be empty */
     if (!node_start_pfn && !node_end_pfn)
         return 0;
 
     zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
     zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
 
     adjust_zone_range_for_zone_movable(nid, zone_type,
             node_start_pfn, node_end_pfn,
             &zone_start_pfn, &zone_end_pfn);
     nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
 
     /*
      * ZONE_MOVABLE handling.
      * Treat pages to be ZONE_MOVABLE in ZONE_NORMAL as absent pages
      * and vice versa.
      */
     if (mirrored_kernelcore && zone_movable_pfn[nid]) {
         unsigned long start_pfn, end_pfn;
         struct memblock_region *r;
 
         for_each_mem_region(r) {
             start_pfn = clamp(memblock_region_memory_base_pfn(r),
                       zone_start_pfn, zone_end_pfn);
             end_pfn = clamp(memblock_region_memory_end_pfn(r),
                     zone_start_pfn, zone_end_pfn);
 
             if (zone_type == ZONE_MOVABLE &&
                 memblock_is_mirror(r))
                 nr_absent += end_pfn - start_pfn;
 
             if (zone_type == ZONE_NORMAL &&
                 !memblock_is_mirror(r))
                 nr_absent += end_pfn - start_pfn;
         }
     }
 
     return nr_absent;
 }
 
 static void __init calculate_node_totalpages(struct pglist_data *pgdat,
                         unsigned long node_start_pfn,
                         unsigned long node_end_pfn)
 {
     unsigned long realtotalpages = 0, totalpages = 0;
     enum zone_type i;
 
     for (i = 0; i < MAX_NR_ZONES; i++) {
         struct zone *zone = pgdat->node_zones + i;
         unsigned long zone_start_pfn, zone_end_pfn;
         unsigned long spanned, absent;
         unsigned long size, real_size;
 
         spanned = zone_spanned_pages_in_node(pgdat->node_id, i,
                              node_start_pfn,
                              node_end_pfn,
                              &zone_start_pfn,
                              &zone_end_pfn);
         absent = zone_absent_pages_in_node(pgdat->node_id, i,
                            node_start_pfn,
                            node_end_pfn);
 
         size = spanned;
         real_size = size - absent;
 
         if (size)
             zone->zone_start_pfn = zone_start_pfn;
         else
             zone->zone_start_pfn = 0;
         zone->spanned_pages = size;
         zone->present_pages = real_size;
 #if defined(CONFIG_MEMORY_HOTPLUG)
         zone->present_early_pages = real_size;
 #endif
 
         totalpages += size;
         realtotalpages += real_size;
     }
 
     pgdat->node_spanned_pages = totalpages;
     pgdat->node_present_pages = realtotalpages;
     pr_debug("On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages);
 }
 
 #ifndef CONFIG_SPARSEMEM
 /*
  * Calculate the size of the zone->blockflags rounded to an unsigned long
  * Start by making sure zonesize is a multiple of pageblock_order by rounding
  * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally
  * round what is now in bits to nearest long in bits, then return it in
  * bytes.
  */
 static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned long zonesize)
 {
     unsigned long usemapsize;
 
     zonesize += zone_start_pfn & (pageblock_nr_pages-1);
     usemapsize = roundup(zonesize, pageblock_nr_pages);
     usemapsize = usemapsize >> pageblock_order;
     usemapsize *= NR_PAGEBLOCK_BITS;
     usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));
 
     return usemapsize / 8;
 }
 
 static void __ref setup_usemap(struct zone *zone)
 {
     unsigned long usemapsize = usemap_size(zone->zone_start_pfn,
                            zone->spanned_pages);
     zone->pageblock_flags = NULL;
     if (usemapsize) {
         zone->pageblock_flags =
             memblock_alloc_node(usemapsize, SMP_CACHE_BYTES,
                         zone_to_nid(zone));
         if (!zone->pageblock_flags)
             panic("Failed to allocate %ld bytes for zone %s pageblock flags on node %d\n",
                   usemapsize, zone->name, zone_to_nid(zone));
     }
 }
 #else
 static inline void setup_usemap(struct zone *zone) {}
 #endif /* CONFIG_SPARSEMEM */
 
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
 
 /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
 void __init set_pageblock_order(void)
 {
     unsigned int order = MAX_ORDER - 1;
 
     /* Check that pageblock_nr_pages has not already been setup */
     if (pageblock_order)
         return;
 
     /* Don't let pageblocks exceed the maximum allocation granularity. */
     if (HPAGE_SHIFT > PAGE_SHIFT && HUGETLB_PAGE_ORDER < order)
         order = HUGETLB_PAGE_ORDER;
 
     /*
      * Assume the largest contiguous order of interest is a huge page.
      * This value may be variable depending on boot parameters on IA64 and
      * powerpc.
      */
     pageblock_order = order;
 }
 #else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
 /*
  * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
  * is unused as pageblock_order is set at compile-time. See
  * include/linux/pageblock-flags.h for the values of pageblock_order based on
  * the kernel config
  */
 void __init set_pageblock_order(void)
 {
 }
 
 #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
 static unsigned long __init calc_memmap_size(unsigned long spanned_pages,
                         unsigned long present_pages)
 {
     unsigned long pages = spanned_pages;
 
     /*
      * Provide a more accurate estimation if there are holes within
      * the zone and SPARSEMEM is in use. If there are holes within the
      * zone, each populated memory region may cost us one or two extra
      * memmap pages due to alignment because memmap pages for each
      * populated regions may not be naturally aligned on page boundary.
      * So the (present_pages >> 4) heuristic is a tradeoff for that.
      */
     if (spanned_pages > present_pages + (present_pages >> 4) &&
         IS_ENABLED(CONFIG_SPARSEMEM))
         pages = present_pages;
 
     return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void pgdat_init_split_queue(struct pglist_data *pgdat)
 {
     struct deferred_split *ds_queue = &pgdat->deferred_split_queue;
 
     spin_lock_init(&ds_queue->split_queue_lock);
     INIT_LIST_HEAD(&ds_queue->split_queue);
     ds_queue->split_queue_len = 0;
 }
 #else
 static void pgdat_init_split_queue(struct pglist_data *pgdat) {}
 #endif
 
 #ifdef CONFIG_COMPACTION
 static void pgdat_init_kcompactd(struct pglist_data *pgdat)
 {
     init_waitqueue_head(&pgdat->kcompactd_wait);
 }
 #else
 static void pgdat_init_kcompactd(struct pglist_data *pgdat) {}
 #endif
 
 static void __meminit pgdat_init_internals(struct pglist_data *pgdat)
 {
     int i;
 
     pgdat_resize_init(pgdat);
 
     pgdat_init_split_queue(pgdat);
     pgdat_init_kcompactd(pgdat);
 
     init_waitqueue_head(&pgdat->kswapd_wait);
     init_waitqueue_head(&pgdat->pfmemalloc_wait);
 
     for (i = 0; i < NR_VMSCAN_THROTTLE; i++)
         init_waitqueue_head(&pgdat->reclaim_wait[i]);
 
     pgdat_page_ext_init(pgdat);
     lruvec_init(&pgdat->__lruvec);
 }
 
 static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx, int nid,
                             unsigned long remaining_pages)
 {
     atomic_long_set(&zone->managed_pages, remaining_pages);
     zone_set_nid(zone, nid);
     zone->name = zone_names[idx];
     zone->zone_pgdat = NODE_DATA(nid);
     spin_lock_init(&zone->lock);
     zone_seqlock_init(zone);
     zone_pcp_init(zone);
 }
 
 /*
  * Set up the zone data structures
  * - init pgdat internals
  * - init all zones belonging to this node
  *
  * NOTE: this function is only called during memory hotplug
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
 void __ref free_area_init_core_hotplug(struct pglist_data *pgdat)
 {
     int nid = pgdat->node_id;
     enum zone_type z;
     int cpu;
 
     pgdat_init_internals(pgdat);
 
     if (pgdat->per_cpu_nodestats == &boot_nodestats)
         pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat);
 
     /*
      * Reset the nr_zones, order and highest_zoneidx before reuse.
      * Note that kswapd will init kswapd_highest_zoneidx properly
      * when it starts in the near future.
      */
     pgdat->nr_zones = 0;
     pgdat->kswapd_order = 0;
     pgdat->kswapd_highest_zoneidx = 0;
     pgdat->node_start_pfn = 0;
     for_each_online_cpu(cpu) {
         struct per_cpu_nodestat *p;
 
         p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);
         memset(p, 0, sizeof(*p));
     }
 
     for (z = 0; z < MAX_NR_ZONES; z++)
         zone_init_internals(&pgdat->node_zones[z], z, nid, 0);
 }
 #endif
 
 /*
  * Set up the zone data structures:
  *   - mark all pages reserved
  *   - mark all memory queues empty
  *   - clear the memory bitmaps
  *
  * NOTE: pgdat should get zeroed by caller.
  * NOTE: this function is only called during early init.
  */
 static void __init free_area_init_core(struct pglist_data *pgdat)
 {
     enum zone_type j;
     int nid = pgdat->node_id;
 
     pgdat_init_internals(pgdat);
     pgdat->per_cpu_nodestats = &boot_nodestats;
 
     for (j = 0; j < MAX_NR_ZONES; j++) {
         struct zone *zone = pgdat->node_zones + j;
         unsigned long size, freesize, memmap_pages;
 
         size = zone->spanned_pages;
         freesize = zone->present_pages;
 
         /*
          * Adjust freesize so that it accounts for how much memory
          * is used by this zone for memmap. This affects the watermark
          * and per-cpu initialisations
          */
         memmap_pages = calc_memmap_size(size, freesize);
         if (!is_highmem_idx(j)) {
             if (freesize >= memmap_pages) {
                 freesize -= memmap_pages;
                 if (memmap_pages)
                     pr_debug("  %s zone: %lu pages used for memmap\n",
                          zone_names[j], memmap_pages);
             } else
                 pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
                     zone_names[j], memmap_pages, freesize);
         }
 
         /* Account for reserved pages */
         if (j == 0 && freesize > dma_reserve) {
             freesize -= dma_reserve;
             pr_debug("  %s zone: %lu pages reserved\n", zone_names[0], dma_reserve);
         }
 
         if (!is_highmem_idx(j))
             nr_kernel_pages += freesize;
         /* Charge for highmem memmap if there are enough kernel pages */
         else if (nr_kernel_pages > memmap_pages * 2)
             nr_kernel_pages -= memmap_pages;
         nr_all_pages += freesize;
 
         /*
          * Set an approximate value for lowmem here, it will be adjusted
          * when the bootmem allocator frees pages into the buddy system.
          * And all highmem pages will be managed by the buddy system.
          */
         zone_init_internals(zone, j, nid, freesize);
 
         if (!size)
             continue;
 
         set_pageblock_order();
         setup_usemap(zone);
         init_currently_empty_zone(zone, zone->zone_start_pfn, size);
     }
 }
 
 #ifdef CONFIG_FLATMEM
 static void __init alloc_node_mem_map(struct pglist_data *pgdat)
 {
     unsigned long __maybe_unused start = 0;
     unsigned long __maybe_unused offset = 0;
 
     /* Skip empty nodes */
     if (!pgdat->node_spanned_pages)
         return;
 
     start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
     offset = pgdat->node_start_pfn - start;
     /* ia64 gets its own node_mem_map, before this, without bootmem */
     if (!pgdat->node_mem_map) {
         unsigned long size, end;
         struct page *map;
 
         /*
          * The zone's endpoints aren't required to be MAX_ORDER
          * aligned but the node_mem_map endpoints must be in order
          * for the buddy allocator to function correctly.
          */
         end = pgdat_end_pfn(pgdat);
         end = ALIGN(end, MAX_ORDER_NR_PAGES);
         size =  (end - start) * sizeof(struct page);
         map = memmap_alloc(size, SMP_CACHE_BYTES, MEMBLOCK_LOW_LIMIT,
                    pgdat->node_id, false);
         if (!map)
             panic("Failed to allocate %ld bytes for node %d memory map\n",
                   size, pgdat->node_id);
         pgdat->node_mem_map = map + offset;
     }
     pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
                 __func__, pgdat->node_id, (unsigned long)pgdat,
                 (unsigned long)pgdat->node_mem_map);
 #ifndef CONFIG_NUMA
     /*
      * With no DISCONTIG, the global mem_map is just set as node 0's
      */
     if (pgdat == NODE_DATA(0)) {
         mem_map = NODE_DATA(0)->node_mem_map;
         if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
             mem_map -= offset;
     }
 #endif
 }
 #else
 static inline void alloc_node_mem_map(struct pglist_data *pgdat) { }
 #endif /* CONFIG_FLATMEM */
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
 {
     pgdat->first_deferred_pfn = ULONG_MAX;
 }
 #else
 static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
 #endif
 
 static void __init free_area_init_node(int nid)
 {
     pg_data_t *pgdat = NODE_DATA(nid);
     unsigned long start_pfn = 0;
     unsigned long end_pfn = 0;
 
     /* pg_data_t should be reset to zero when it's allocated */
     WARN_ON(pgdat->nr_zones || pgdat->kswapd_highest_zoneidx);
 
     get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
 
     pgdat->node_id = nid;
     pgdat->node_start_pfn = start_pfn;
     pgdat->per_cpu_nodestats = NULL;
 
     if (start_pfn != end_pfn) {
         pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
             (u64)start_pfn << PAGE_SHIFT,
             end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
     } else {
         pr_info("Initmem setup node %d as memoryless\n", nid);
     }
 
     calculate_node_totalpages(pgdat, start_pfn, end_pfn);
 
     alloc_node_mem_map(pgdat);
     pgdat_set_deferred_range(pgdat);
 
     free_area_init_core(pgdat);
 }
 
 static void __init free_area_init_memoryless_node(int nid)
 {
     free_area_init_node(nid);
 }
 
 #if MAX_NUMNODES > 1
 /*
  * Figure out the number of possible node ids.
  */
 void __init setup_nr_node_ids(void)
 {
     unsigned int highest;
 
     highest = find_last_bit(node_possible_map.bits, MAX_NUMNODES);
     nr_node_ids = highest + 1;
 }
 #endif
 
 /**
  * node_map_pfn_alignment - determine the maximum internode alignment
  *
  * This function should be called after node map is populated and sorted.
  * It calculates the maximum power of two alignment which can distinguish
  * all the nodes.
  *
  * For example, if all nodes are 1GiB and aligned to 1GiB, the return value
  * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)).  If the
  * nodes are shifted by 256MiB, 256MiB.  Note that if only the last node is
  * shifted, 1GiB is enough and this function will indicate so.
  *
  * This is used to test whether pfn -> nid mapping of the chosen memory
  * model has fine enough granularity to avoid incorrect mapping for the
  * populated node map.
  *
  * Return: the determined alignment in pfn's.  0 if there is no alignment
  * requirement (single node).
  */
 unsigned long __init node_map_pfn_alignment(void)
 {
     unsigned long accl_mask = 0, last_end = 0;
     unsigned long start, end, mask;
     int last_nid = NUMA_NO_NODE;
     int i, nid;
 
     for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid) {
         if (!start || last_nid < 0 || last_nid == nid) {
             last_nid = nid;
             last_end = end;
             continue;
         }
 
         /*
          * Start with a mask granular enough to pin-point to the
          * start pfn and tick off bits one-by-one until it becomes
          * too coarse to separate the current node from the last.
          */
         mask = ~((1 << __ffs(start)) - 1);
         while (mask && last_end <= (start & (mask << 1)))
             mask <<= 1;
 
         /* accumulate all internode masks */
         accl_mask |= mask;
     }
 
     /* convert mask to number of pages */
     return ~accl_mask + 1;
 }
 
 /**
  * find_min_pfn_with_active_regions - Find the minimum PFN registered
  *
  * Return: the minimum PFN based on information provided via
  * memblock_set_node().
  */
 unsigned long __init find_min_pfn_with_active_regions(void)
 {
     return PHYS_PFN(memblock_start_of_DRAM());
 }
 
 /*
  * early_calculate_totalpages()
  * Sum pages in active regions for movable zone.
  * Populate N_MEMORY for calculating usable_nodes.
  */
 static unsigned long __init early_calculate_totalpages(void)
 {
     unsigned long totalpages = 0;
     unsigned long start_pfn, end_pfn;
     int i, nid;
 
     for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
         unsigned long pages = end_pfn - start_pfn;
 
         totalpages += pages;
         if (pages)
             node_set_state(nid, N_MEMORY);
     }
     return totalpages;
 }
 
 /*
  * Find the PFN the Movable zone begins in each node. Kernel memory
  * is spread evenly between nodes as long as the nodes have enough
  * memory. When they don't, some nodes will have more kernelcore than
  * others
  */
 static void __init find_zone_movable_pfns_for_nodes(void)
 {
     int i, nid;
     unsigned long usable_startpfn;
     unsigned long kernelcore_node, kernelcore_remaining;
     /* save the state before borrow the nodemask */
     nodemask_t saved_node_state = node_states[N_MEMORY];
     unsigned long totalpages = early_calculate_totalpages();
     int usable_nodes = nodes_weight(node_states[N_MEMORY]);
     struct memblock_region *r;
 
     /* Need to find movable_zone earlier when movable_node is specified. */
     find_usable_zone_for_movable();
 
     /*
      * If movable_node is specified, ignore kernelcore and movablecore
      * options.
      */
     if (movable_node_is_enabled()) {
         for_each_mem_region(r) {
             if (!memblock_is_hotpluggable(r))
                 continue;
 
             nid = memblock_get_region_node(r);
 
             usable_startpfn = PFN_DOWN(r->base);
             zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                 min(usable_startpfn, zone_movable_pfn[nid]) :
                 usable_startpfn;
         }
 
         goto out2;
     }
 
     /*
      * If kernelcore=mirror is specified, ignore movablecore option
      */
     if (mirrored_kernelcore) {
         bool mem_below_4gb_not_mirrored = false;
 
         for_each_mem_region(r) {
             if (memblock_is_mirror(r))
                 continue;
 
             nid = memblock_get_region_node(r);
 
             usable_startpfn = memblock_region_memory_base_pfn(r);
 
             if (usable_startpfn < PHYS_PFN(SZ_4G)) {
                 mem_below_4gb_not_mirrored = true;
                 continue;
             }
 
             zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                 min(usable_startpfn, zone_movable_pfn[nid]) :
                 usable_startpfn;
         }
 
         if (mem_below_4gb_not_mirrored)
             pr_warn("This configuration results in unmirrored kernel memory.\n");
 
         goto out2;
     }
 
     /*
      * If kernelcore=nn% or movablecore=nn% was specified, calculate the
      * amount of necessary memory.
      */
     if (required_kernelcore_percent)
         required_kernelcore = (totalpages * 100 * required_kernelcore_percent) /
                        10000UL;
     if (required_movablecore_percent)
         required_movablecore = (totalpages * 100 * required_movablecore_percent) /
                     10000UL;
 
     /*
      * If movablecore= was specified, calculate what size of
      * kernelcore that corresponds so that memory usable for
      * any allocation type is evenly spread. If both kernelcore
      * and movablecore are specified, then the value of kernelcore
      * will be used for required_kernelcore if it's greater than
      * what movablecore would have allowed.
      */
     if (required_movablecore) {
         unsigned long corepages;
 
         /*
          * Round-up so that ZONE_MOVABLE is at least as large as what
          * was requested by the user
          */
         required_movablecore =
             roundup(required_movablecore, MAX_ORDER_NR_PAGES);
         required_movablecore = min(totalpages, required_movablecore);
         corepages = totalpages - required_movablecore;
 
         required_kernelcore = max(required_kernelcore, corepages);
     }
 
     /*
      * If kernelcore was not specified or kernelcore size is larger
      * than totalpages, there is no ZONE_MOVABLE.
      */
     if (!required_kernelcore || required_kernelcore >= totalpages)
         goto out;
 
     /* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
     usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];
 
 restart:
     /* Spread kernelcore memory as evenly as possible throughout nodes */
     kernelcore_node = required_kernelcore / usable_nodes;
     for_each_node_state(nid, N_MEMORY) {
         unsigned long start_pfn, end_pfn;
 
         /*
          * Recalculate kernelcore_node if the division per node
          * now exceeds what is necessary to satisfy the requested
          * amount of memory for the kernel
          */
         if (required_kernelcore < kernelcore_node)
             kernelcore_node = required_kernelcore / usable_nodes;
 
         /*
          * As the map is walked, we track how much memory is usable
          * by the kernel using kernelcore_remaining. When it is
          * 0, the rest of the node is usable by ZONE_MOVABLE
          */
         kernelcore_remaining = kernelcore_node;
 
         /* Go through each range of PFNs within this node */
         for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
             unsigned long size_pages;
 
             start_pfn = max(start_pfn, zone_movable_pfn[nid]);
             if (start_pfn >= end_pfn)
                 continue;
 
             /* Account for what is only usable for kernelcore */
             if (start_pfn < usable_startpfn) {
                 unsigned long kernel_pages;
                 kernel_pages = min(end_pfn, usable_startpfn)
                                 - start_pfn;
 
                 kernelcore_remaining -= min(kernel_pages,
                             kernelcore_remaining);
                 required_kernelcore -= min(kernel_pages,
                             required_kernelcore);
 
                 /* Continue if range is now fully accounted */
                 if (end_pfn <= usable_startpfn) {
 
                     /*
                      * Push zone_movable_pfn to the end so
                      * that if we have to rebalance
                      * kernelcore across nodes, we will
                      * not double account here
                      */
                     zone_movable_pfn[nid] = end_pfn;
                     continue;
                 }
                 start_pfn = usable_startpfn;
             }
 
             /*
              * The usable PFN range for ZONE_MOVABLE is from
              * start_pfn->end_pfn. Calculate size_pages as the
              * number of pages used as kernelcore
              */
             size_pages = end_pfn - start_pfn;
             if (size_pages > kernelcore_remaining)
                 size_pages = kernelcore_remaining;
             zone_movable_pfn[nid] = start_pfn + size_pages;
 
             /*
              * Some kernelcore has been met, update counts and
              * break if the kernelcore for this node has been
              * satisfied
              */
             required_kernelcore -= min(required_kernelcore,
                                 size_pages);
             kernelcore_remaining -= size_pages;
             if (!kernelcore_remaining)
                 break;
         }
     }
 
     /*
      * If there is still required_kernelcore, we do another pass with one
      * less node in the count. This will push zone_movable_pfn[nid] further
      * along on the nodes that still have memory until kernelcore is
      * satisfied
      */
     usable_nodes--;
     if (usable_nodes && required_kernelcore > usable_nodes)
         goto restart;
 
 out2:
     /* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */
     for (nid = 0; nid < MAX_NUMNODES; nid++) {
         unsigned long start_pfn, end_pfn;
 
         zone_movable_pfn[nid] =
             roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);
 
         get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
         if (zone_movable_pfn[nid] >= end_pfn)
             zone_movable_pfn[nid] = 0;
     }
 
 out:
     /* restore the node_state */
     node_states[N_MEMORY] = saved_node_state;
 }
 
 /* Any regular or high memory on that node ? */
 static void check_for_memory(pg_data_t *pgdat, int nid)
 {
     enum zone_type zone_type;
 
     for (zone_type = 0; zone_type <= ZONE_MOVABLE - 1; zone_type++) {
         struct zone *zone = &pgdat->node_zones[zone_type];
         if (populated_zone(zone)) {
             if (IS_ENABLED(CONFIG_HIGHMEM))
                 node_set_state(nid, N_HIGH_MEMORY);
             if (zone_type <= ZONE_NORMAL)
                 node_set_state(nid, N_NORMAL_MEMORY);
             break;
         }
     }
 }
 
 /*
  * Some architectures, e.g. ARC may have ZONE_HIGHMEM below ZONE_NORMAL. For
  * such cases we allow max_zone_pfn sorted in the descending order
  */
 bool __weak arch_has_descending_max_zone_pfns(void)
 {
     return false;
 }
 
 /**
  * free_area_init - Initialise all pg_data_t and zone data
  * @max_zone_pfn: an array of max PFNs for each zone
  *
  * This will call free_area_init_node() for each active node in the system.
  * Using the page ranges provided by memblock_set_node(), the size of each
  * zone in each node and their holes is calculated. If the maximum PFN
  * between two adjacent zones match, it is assumed that the zone is empty.
  * For example, if arch_max_dma_pfn == arch_max_dma32_pfn, it is assumed
  * that arch_max_dma32_pfn has no pages. It is also assumed that a zone
  * starts where the previous one ended. For example, ZONE_DMA32 starts
  * at arch_max_dma_pfn.
  */
 void __init free_area_init(unsigned long *max_zone_pfn)
 {
     unsigned long start_pfn, end_pfn;
     int i, nid, zone;
     bool descending;
 
     /* Record where the zone boundaries are */
     memset(arch_zone_lowest_possible_pfn, 0,
                 sizeof(arch_zone_lowest_possible_pfn));
     memset(arch_zone_highest_possible_pfn, 0,
                 sizeof(arch_zone_highest_possible_pfn));
 
     start_pfn = find_min_pfn_with_active_regions();
     descending = arch_has_descending_max_zone_pfns();
 
     for (i = 0; i < MAX_NR_ZONES; i++) {
         if (descending)
             zone = MAX_NR_ZONES - i - 1;
         else
             zone = i;
 
         if (zone == ZONE_MOVABLE)
             continue;
 
         end_pfn = max(max_zone_pfn[zone], start_pfn);
         arch_zone_lowest_possible_pfn[zone] = start_pfn;
         arch_zone_highest_possible_pfn[zone] = end_pfn;
 
         start_pfn = end_pfn;
     }
 
     /* Find the PFNs that ZONE_MOVABLE begins at in each node */
     memset(zone_movable_pfn, 0, sizeof(zone_movable_pfn));
     find_zone_movable_pfns_for_nodes();
 
     /* Print out the zone ranges */
     pr_info("Zone ranges:\n");
     for (i = 0; i < MAX_NR_ZONES; i++) {
         if (i == ZONE_MOVABLE)
             continue;
         pr_info("  %-8s ", zone_names[i]);
         if (arch_zone_lowest_possible_pfn[i] ==
                 arch_zone_highest_possible_pfn[i])
             pr_cont("empty\n");
         else
             pr_cont("[mem %#018Lx-%#018Lx]\n",
                 (u64)arch_zone_lowest_possible_pfn[i]
                     << PAGE_SHIFT,
                 ((u64)arch_zone_highest_possible_pfn[i]
                     << PAGE_SHIFT) - 1);
     }
 
     /* Print out the PFNs ZONE_MOVABLE begins at in each node */
     pr_info("Movable zone start for each node\n");
     for (i = 0; i < MAX_NUMNODES; i++) {
         if (zone_movable_pfn[i])
             pr_info("  Node %d: %#018Lx\n", i,
                    (u64)zone_movable_pfn[i] << PAGE_SHIFT);
     }
 
     /*
      * Print out the early node map, and initialize the
      * subsection-map relative to active online memory ranges to
      * enable future "sub-section" extensions of the memory map.
      */
     pr_info("Early memory node ranges\n");
     for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
         pr_info("  node %3d: [mem %#018Lx-%#018Lx]\n", nid,
             (u64)start_pfn << PAGE_SHIFT,
             ((u64)end_pfn << PAGE_SHIFT) - 1);
         subsection_map_init(start_pfn, end_pfn - start_pfn);
     }
 
     /* Initialise every node */
     mminit_verify_pageflags_layout();
     setup_nr_node_ids();
     for_each_node(nid) {
         pg_data_t *pgdat;
 
         if (!node_online(nid)) {
             pr_info("Initializing node %d as memoryless\n", nid);
 
             /* Allocator not initialized yet */
             pgdat = arch_alloc_nodedata(nid);
             if (!pgdat) {
                 pr_err("Cannot allocate %zuB for node %d.\n",
                         sizeof(*pgdat), nid);
                 continue;
             }
             arch_refresh_nodedata(nid, pgdat);
             free_area_init_memoryless_node(nid);
 
             /*
              * We do not want to confuse userspace by sysfs
              * files/directories for node without any memory
              * attached to it, so this node is not marked as
              * N_MEMORY and not marked online so that no sysfs
              * hierarchy will be created via register_one_node for
              * it. The pgdat will get fully initialized by
              * hotadd_init_pgdat() when memory is hotplugged into
              * this node.
              */
             continue;
         }
 
         pgdat = NODE_DATA(nid);
         free_area_init_node(nid);
 
         /* Any memory on that node */
         if (pgdat->node_present_pages)
             node_set_state(nid, N_MEMORY);
         check_for_memory(pgdat, nid);
     }
 
     memmap_init();
 }
 
 static int __init cmdline_parse_core(char *p, unsigned long *core,
                      unsigned long *percent)
 {
     unsigned long long coremem;
     char *endptr;
 
     if (!p)
         return -EINVAL;
 
     /* Value may be a percentage of total memory, otherwise bytes */
     coremem = simple_strtoull(p, &endptr, 0);
     if (*endptr == '%') {
         /* Paranoid check for percent values greater than 100 */
         WARN_ON(coremem > 100);
 
         *percent = coremem;
     } else {
         coremem = memparse(p, &p);
         /* Paranoid check that UL is enough for the coremem value */
         WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);
 
         *core = coremem >> PAGE_SHIFT;
         *percent = 0UL;
     }
     return 0;
 }
 
 /*
  * kernelcore=size sets the amount of memory for use for allocations that
  * cannot be reclaimed or migrated.
  */
 static int __init cmdline_parse_kernelcore(char *p)
 {
     /* parse kernelcore=mirror */
     if (parse_option_str(p, "mirror")) {
         mirrored_kernelcore = true;
         return 0;
     }
 
     return cmdline_parse_core(p, &required_kernelcore,
                   &required_kernelcore_percent);
 }
 
 /*
  * movablecore=size sets the amount of memory for use for allocations that
  * can be reclaimed or migrated.
  */
 static int __init cmdline_parse_movablecore(char *p)
 {
     return cmdline_parse_core(p, &required_movablecore,
                   &required_movablecore_percent);
 }
 
 early_param("kernelcore", cmdline_parse_kernelcore);
 early_param("movablecore", cmdline_parse_movablecore);
 
 void adjust_managed_page_count(struct page *page, long count)
 {
     atomic_long_add(count, &page_zone(page)->managed_pages);
     totalram_pages_add(count);
 #ifdef CONFIG_HIGHMEM
     if (PageHighMem(page))
         totalhigh_pages_add(count);
 #endif
 }
 EXPORT_SYMBOL(adjust_managed_page_count);
 
 unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
 {
     void *pos;
     unsigned long pages = 0;
 
     start = (void *)PAGE_ALIGN((unsigned long)start);
     end = (void *)((unsigned long)end & PAGE_MASK);
     for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
         struct page *page = virt_to_page(pos);
         void *direct_map_addr;
 
         /*
          * 'direct_map_addr' might be different from 'pos'
          * because some architectures' virt_to_page()
          * work with aliases.  Getting the direct map
          * address ensures that we get a _writeable_
          * alias for the memset().
          */
         direct_map_addr = page_address(page);
         /*
          * Perform a kasan-unchecked memset() since this memory
          * has not been initialized.
          */
         direct_map_addr = kasan_reset_tag(direct_map_addr);
         if ((unsigned int)poison <= 0xFF)
             memset(direct_map_addr, poison, PAGE_SIZE);
 
         free_reserved_page(page);
     }
 
     if (pages && s)
         pr_info("Freeing %s memory: %ldK\n", s, K(pages));
 
     return pages;
 }
 
 void __init mem_init_print_info(void)
 {
     unsigned long physpages, codesize, datasize, rosize, bss_size;
     unsigned long init_code_size, init_data_size;
 
     physpages = get_num_physpages();
     codesize = _etext - _stext;
     datasize = _edata - _sdata;
     rosize = __end_rodata - __start_rodata;
     bss_size = __bss_stop - __bss_start;
     init_data_size = __init_end - __init_begin;
     init_code_size = _einittext - _sinittext;
 
     /*
      * Detect special cases and adjust section sizes accordingly:
      * 1) .init.* may be embedded into .data sections
      * 2) .init.text.* may be out of [__init_begin, __init_end],
      *    please refer to arch/tile/kernel/vmlinux.lds.S.
      * 3) .rodata.* may be embedded into .text or .data sections.
      */
 #define adj_init_size(start, end, size, pos, adj) \
     do { \
         if (&start[0] <= &pos[0] && &pos[0] < &end[0] && size > adj) \
             size -= adj; \
     } while (0)
 
     adj_init_size(__init_begin, __init_end, init_data_size,
              _sinittext, init_code_size);
     adj_init_size(_stext, _etext, codesize, _sinittext, init_code_size);
     adj_init_size(_sdata, _edata, datasize, __init_begin, init_data_size);
     adj_init_size(_stext, _etext, codesize, __start_rodata, rosize);
     adj_init_size(_sdata, _edata, datasize, __start_rodata, rosize);
 
 #undef  adj_init_size
 
     pr_info("Memory: %luK/%luK available (%luK kernel code, %luK rwdata, %luK rodata, %luK init, %luK bss, %luK reserved, %luK cma-reserved"
 #ifdef  CONFIG_HIGHMEM
         ", %luK highmem"
 #endif
         ")\n",
         K(nr_free_pages()), K(physpages),
         codesize >> 10, datasize >> 10, rosize >> 10,
         (init_data_size + init_code_size) >> 10, bss_size >> 10,
         K(physpages - totalram_pages() - totalcma_pages),
         K(totalcma_pages)
 #ifdef  CONFIG_HIGHMEM
         , K(totalhigh_pages())
 #endif
         );
 }
 
 /**
  * set_dma_reserve - set the specified number of pages reserved in the first zone
  * @new_dma_reserve: The number of pages to mark reserved
  *
  * The per-cpu batchsize and zone watermarks are determined by managed_pages.
  * In the DMA zone, a significant percentage may be consumed by kernel image
  * and other unfreeable allocations which can skew the watermarks badly. This
  * function may optionally be used to account for unfreeable pages in the
  * first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
  * smaller per-cpu batchsize.
  */
 void __init set_dma_reserve(unsigned long new_dma_reserve)
 {
     dma_reserve = new_dma_reserve;
 }
 
 static int page_alloc_cpu_dead(unsigned int cpu)
 {
     struct zone *zone;
 
     lru_add_drain_cpu(cpu);
     mlock_page_drain_remote(cpu);
     drain_pages(cpu);
 
     /*
      * Spill the event counters of the dead processor
      * into the current processors event counters.
      * This artificially elevates the count of the current
      * processor.
      */
     vm_events_fold_cpu(cpu);
 
     /*
      * Zero the differential counters of the dead processor
      * so that the vm statistics are consistent.
      *
      * This is only okay since the processor is dead and cannot
      * race with what we are doing.
      */
     cpu_vm_stats_fold(cpu);
 
     for_each_populated_zone(zone)
         zone_pcp_update(zone, 0);
 
     return 0;
 }
 
 static int page_alloc_cpu_online(unsigned int cpu)
 {
     struct zone *zone;
 
     for_each_populated_zone(zone)
         zone_pcp_update(zone, 1);
     return 0;
 }
 
 #ifdef CONFIG_NUMA
 int hashdist = HASHDIST_DEFAULT;
 
 static int __init set_hashdist(char *str)
 {
     if (!str)
         return 0;
     hashdist = simple_strtoul(str, &str, 0);
     return 1;
 }
 __setup("hashdist=", set_hashdist);
 #endif
 
 void __init page_alloc_init(void)
 {
     int ret;
 
 #ifdef CONFIG_NUMA
     if (num_node_state(N_MEMORY) == 1)
         hashdist = 0;
 #endif
 
     ret = cpuhp_setup_state_nocalls(CPUHP_PAGE_ALLOC,
                     "mm/page_alloc:pcp",
                     page_alloc_cpu_online,
                     page_alloc_cpu_dead);
     WARN_ON(ret < 0);
 }
 
 /*
  * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
  *  or min_free_kbytes changes.
  */
 static void calculate_totalreserve_pages(void)
 {
     struct pglist_data *pgdat;
     unsigned long reserve_pages = 0;
     enum zone_type i, j;
 
     for_each_online_pgdat(pgdat) {
 
         pgdat->totalreserve_pages = 0;
 
         for (i = 0; i < MAX_NR_ZONES; i++) {
             struct zone *zone = pgdat->node_zones + i;
             long max = 0;
             unsigned long managed_pages = zone_managed_pages(zone);
 
             /* Find valid and maximum lowmem_reserve in the zone */
             for (j = i; j < MAX_NR_ZONES; j++) {
                 if (zone->lowmem_reserve[j] > max)
                     max = zone->lowmem_reserve[j];
             }
 
             /* we treat the high watermark as reserved pages. */
             max += high_wmark_pages(zone);
 
             if (max > managed_pages)
                 max = managed_pages;
 
             pgdat->totalreserve_pages += max;
 
             reserve_pages += max;
         }
     }
     totalreserve_pages = reserve_pages;
 }
 
 /*
  * setup_per_zone_lowmem_reserve - called whenever
  *  sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
  *  has a correct pages reserved value, so an adequate number of
  *  pages are left in the zone after a successful __alloc_pages().
  */
 static void setup_per_zone_lowmem_reserve(void)
 {
     struct pglist_data *pgdat;
     enum zone_type i, j;
 
     for_each_online_pgdat(pgdat) {
         for (i = 0; i < MAX_NR_ZONES - 1; i++) {
             struct zone *zone = &pgdat->node_zones[i];
             int ratio = sysctl_lowmem_reserve_ratio[i];
             bool clear = !ratio || !zone_managed_pages(zone);
             unsigned long managed_pages = 0;
 
             for (j = i + 1; j < MAX_NR_ZONES; j++) {
                 struct zone *upper_zone = &pgdat->node_zones[j];
 
                 managed_pages += zone_managed_pages(upper_zone);
 
                 if (clear)
                     zone->lowmem_reserve[j] = 0;
                 else
                     zone->lowmem_reserve[j] = managed_pages / ratio;
             }
         }
     }
 
     /* update totalreserve_pages */
     calculate_totalreserve_pages();
 }
 
 static void __setup_per_zone_wmarks(void)
 {
     unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
     unsigned long lowmem_pages = 0;
     struct zone *zone;
     unsigned long flags;
 
     /* Calculate total number of !ZONE_HIGHMEM pages */
     for_each_zone(zone) {
         if (!is_highmem(zone))
             lowmem_pages += zone_managed_pages(zone);
     }
 
     for_each_zone(zone) {
         u64 tmp;
 
         spin_lock_irqsave(&zone->lock, flags);
         tmp = (u64)pages_min * zone_managed_pages(zone);
         do_div(tmp, lowmem_pages);
         if (is_highmem(zone)) {
             /*
              * __GFP_HIGH and PF_MEMALLOC allocations usually don't
              * need highmem pages, so cap pages_min to a small
              * value here.
              *
              * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
              * deltas control async page reclaim, and so should
              * not be capped for highmem.
              */
             unsigned long min_pages;
 
             min_pages = zone_managed_pages(zone) / 1024;
             min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
             zone->_watermark[WMARK_MIN] = min_pages;
         } else {
             /*
              * If it's a lowmem zone, reserve a number of pages
              * proportionate to the zone's size.
              */
             zone->_watermark[WMARK_MIN] = tmp;
         }
 
         /*
          * Set the kswapd watermarks distance according to the
          * scale factor in proportion to available memory, but
          * ensure a minimum size on small systems.
          */
         tmp = max_t(u64, tmp >> 2,
                 mult_frac(zone_managed_pages(zone),
                       watermark_scale_factor, 10000));
 
         zone->watermark_boost = 0;
         zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
         zone->_watermark[WMARK_HIGH] = low_wmark_pages(zone) + tmp;
         zone->_watermark[WMARK_PROMO] = high_wmark_pages(zone) + tmp;
 
         spin_unlock_irqrestore(&zone->lock, flags);
     }
 
     /* update totalreserve_pages */
     calculate_totalreserve_pages();
 }
 
 /**
  * setup_per_zone_wmarks - called when min_free_kbytes changes
  * or when memory is hot-{added|removed}
  *
  * Ensures that the watermark[min,low,high] values for each zone are set
  * correctly with respect to min_free_kbytes.
  */
 void setup_per_zone_wmarks(void)
 {
     struct zone *zone;
     static DEFINE_SPINLOCK(lock);
 
     spin_lock(&lock);
     __setup_per_zone_wmarks();
     spin_unlock(&lock);
 
     /*
      * The watermark size have changed so update the pcpu batch
      * and high limits or the limits may be inappropriate.
      */
     for_each_zone(zone)
         zone_pcp_update(zone, 0);
 }
 
 /*
  * Initialise min_free_kbytes.
  *
  * For small machines we want it small (128k min).  For large machines
  * we want it large (256MB max).  But it is not linear, because network
  * bandwidth does not increase linearly with machine size.  We use
  *
  *  min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
  *  min_free_kbytes = sqrt(lowmem_kbytes * 16)
  *
  * which yields
  *
  * 16MB:    512k
  * 32MB:    724k
  * 64MB:    1024k
  * 128MB:   1448k
  * 256MB:   2048k
  * 512MB:   2896k
  * 1024MB:  4096k
  * 2048MB:  5792k
  * 4096MB:  8192k
  * 8192MB:  11584k
  * 16384MB: 16384k
  */
 void calculate_min_free_kbytes(void)
 {
     unsigned long lowmem_kbytes;
     int new_min_free_kbytes;
 
     lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
     new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
 
     if (new_min_free_kbytes > user_min_free_kbytes)
         min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
     else
         pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
                 new_min_free_kbytes, user_min_free_kbytes);
 
 }
 
 int __meminit init_per_zone_wmark_min(void)
 {
     calculate_min_free_kbytes();
     setup_per_zone_wmarks();
     refresh_zone_stat_thresholds();
     setup_per_zone_lowmem_reserve();
 
 #ifdef CONFIG_NUMA
     setup_min_unmapped_ratio();
     setup_min_slab_ratio();
 #endif
 
     khugepaged_min_free_kbytes_update();
 
     return 0;
 }
 postcore_initcall(init_per_zone_wmark_min)
 
 /*
  * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
  *  that we can call two helper functions whenever min_free_kbytes
  *  changes.
  */
 int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int rc;
 
     rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (rc)
         return rc;
 
     if (write) {
         user_min_free_kbytes = min_free_kbytes;
         setup_per_zone_wmarks();
     }
     return 0;
 }
 
 int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int rc;
 
     rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (rc)
         return rc;
 
     if (write)
         setup_per_zone_wmarks();
 
     return 0;
 }
 
 #ifdef CONFIG_NUMA
 static void setup_min_unmapped_ratio(void)
 {
     pg_data_t *pgdat;
     struct zone *zone;
 
     for_each_online_pgdat(pgdat)
         pgdat->min_unmapped_pages = 0;
 
     for_each_zone(zone)
         zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) *
                                  sysctl_min_unmapped_ratio) / 100;
 }
 
 
 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int rc;
 
     rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (rc)
         return rc;
 
     setup_min_unmapped_ratio();
 
     return 0;
 }
 
 static void setup_min_slab_ratio(void)
 {
     pg_data_t *pgdat;
     struct zone *zone;
 
     for_each_online_pgdat(pgdat)
         pgdat->min_slab_pages = 0;
 
     for_each_zone(zone)
         zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) *
                              sysctl_min_slab_ratio) / 100;
 }
 
 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int rc;
 
     rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (rc)
         return rc;
 
     setup_min_slab_ratio();
 
     return 0;
 }
 #endif
 
 /*
  * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
  *  proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
  *  whenever sysctl_lowmem_reserve_ratio changes.
  *
  * The reserve ratio obviously has absolutely no relation with the
  * minimum watermarks. The lowmem reserve ratio can only make sense
  * if in function of the boot time zone sizes.
  */
 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int i;
 
     proc_dointvec_minmax(table, write, buffer, length, ppos);
 
     for (i = 0; i < MAX_NR_ZONES; i++) {
         if (sysctl_lowmem_reserve_ratio[i] < 1)
             sysctl_lowmem_reserve_ratio[i] = 0;
     }
 
     setup_per_zone_lowmem_reserve();
     return 0;
 }
 
 /*
  * percpu_pagelist_high_fraction - changes the pcp->high for each zone on each
  * cpu. It is the fraction of total pages in each zone that a hot per cpu
  * pagelist can have before it gets flushed back to buddy allocator.
  */
 int percpu_pagelist_high_fraction_sysctl_handler(struct ctl_table *table,
         int write, void *buffer, size_t *length, loff_t *ppos)
 {
     struct zone *zone;
     int old_percpu_pagelist_high_fraction;
     int ret;
 
     mutex_lock(&pcp_batch_high_lock);
     old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction;
 
     ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (!write || ret < 0)
         goto out;
 
     /* Sanity checking to avoid pcp imbalance */
     if (percpu_pagelist_high_fraction &&
         percpu_pagelist_high_fraction < MIN_PERCPU_PAGELIST_HIGH_FRACTION) {
         percpu_pagelist_high_fraction = old_percpu_pagelist_high_fraction;
         ret = -EINVAL;
         goto out;
     }
 
     /* No change? */
     if (percpu_pagelist_high_fraction == old_percpu_pagelist_high_fraction)
         goto out;
 
     for_each_populated_zone(zone)
         zone_set_pageset_high_and_batch(zone, 0);
 out:
     mutex_unlock(&pcp_batch_high_lock);
     return ret;
 }
 
 #ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES
 /*
  * Returns the number of pages that arch has reserved but
  * is not known to alloc_large_system_hash().
  */
 static unsigned long __init arch_reserved_kernel_pages(void)
 {
     return 0;
 }
 #endif
 
 /*
  * Adaptive scale is meant to reduce sizes of hash tables on large memory
  * machines. As memory size is increased the scale is also increased but at
  * slower pace.  Starting from ADAPT_SCALE_BASE (64G), every time memory
  * quadruples the scale is increased by one, which means the size of hash table
  * only doubles, instead of quadrupling as well.
  * Because 32-bit systems cannot have large physical memory, where this scaling
  * makes sense, it is disabled on such platforms.
  */
 #if __BITS_PER_LONG > 32
 #define ADAPT_SCALE_BASE    (64ul << 30)
 #define ADAPT_SCALE_SHIFT   2
 #define ADAPT_SCALE_NPAGES  (ADAPT_SCALE_BASE >> PAGE_SHIFT)
 #endif
 
 /*
  * allocate a large system hash table from bootmem
  * - it is assumed that the hash table must contain an exact power-of-2
  *   quantity of entries
  * - limit is the number of hash buckets, not the total allocation size
  */
 void *__init alloc_large_system_hash(const char *tablename,
                      unsigned long bucketsize,
                      unsigned long numentries,
                      int scale,
                      int flags,
                      unsigned int *_hash_shift,
                      unsigned int *_hash_mask,
                      unsigned long low_limit,
                      unsigned long high_limit)
 {
     unsigned long long max = high_limit;
     unsigned long log2qty, size;
     void *table = NULL;
     gfp_t gfp_flags;
     bool virt;
     bool huge;
 
     /* allow the kernel cmdline to have a say */
     if (!numentries) {
         /* round applicable memory size up to nearest megabyte */
         numentries = nr_kernel_pages;
         numentries -= arch_reserved_kernel_pages();
 
         /* It isn't necessary when PAGE_SIZE >= 1MB */
         if (PAGE_SHIFT < 20)
             numentries = round_up(numentries, (1<<20)/PAGE_SIZE);
 
 #if __BITS_PER_LONG > 32
         if (!high_limit) {
             unsigned long adapt;
 
             for (adapt = ADAPT_SCALE_NPAGES; adapt < numentries;
                  adapt <<= ADAPT_SCALE_SHIFT)
                 scale++;
         }
 #endif
 
         /* limit to 1 bucket per 2^scale bytes of low memory */
         if (scale > PAGE_SHIFT)
             numentries >>= (scale - PAGE_SHIFT);
         else
             numentries <<= (PAGE_SHIFT - scale);
 
         /* Make sure we've got at least a 0-order allocation.. */
         if (unlikely(flags & HASH_SMALL)) {
             /* Makes no sense without HASH_EARLY */
             WARN_ON(!(flags & HASH_EARLY));
             if (!(numentries >> *_hash_shift)) {
                 numentries = 1UL << *_hash_shift;
                 BUG_ON(!numentries);
             }
         } else if (unlikely((numentries * bucketsize) < PAGE_SIZE))
             numentries = PAGE_SIZE / bucketsize;
     }
     numentries = roundup_pow_of_two(numentries);
 
     /* limit allocation size to 1/16 total memory by default */
     if (max == 0) {
         max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
         do_div(max, bucketsize);
     }
     max = min(max, 0x80000000ULL);
 
     if (numentries < low_limit)
         numentries = low_limit;
     if (numentries > max)
         numentries = max;
 
     log2qty = ilog2(numentries);
 
     gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;
     do {
         virt = false;
         size = bucketsize << log2qty;
         if (flags & HASH_EARLY) {
             if (flags & HASH_ZERO)
                 table = memblock_alloc(size, SMP_CACHE_BYTES);
             else
                 table = memblock_alloc_raw(size,
                                SMP_CACHE_BYTES);
         } else if (get_order(size) >= MAX_ORDER || hashdist) {
             table = vmalloc_huge(size, gfp_flags);
             virt = true;
             if (table)
                 huge = is_vm_area_hugepages(table);
         } else {
             /*
              * If bucketsize is not a power-of-two, we may free
              * some pages at the end of hash table which
              * alloc_pages_exact() automatically does
              */
             table = alloc_pages_exact(size, gfp_flags);
             kmemleak_alloc(table, size, 1, gfp_flags);
         }
     } while (!table && size > PAGE_SIZE && --log2qty);
 
     if (!table)
         panic("Failed to allocate %s hash table\n", tablename);
 
     pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
         tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
         virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");
 
     if (_hash_shift)
         *_hash_shift = log2qty;
     if (_hash_mask)
         *_hash_mask = (1 << log2qty) - 1;
 
     return table;
 }
 
 #ifdef CONFIG_CONTIG_ALLOC
 #if defined(CONFIG_DYNAMIC_DEBUG) || \
     (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
 /* Usage: See admin-guide/dynamic-debug-howto.rst */
 static void alloc_contig_dump_pages(struct list_head *page_list)
 {
     DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, "migrate failure");
 
     if (DYNAMIC_DEBUG_BRANCH(descriptor)) {
         struct page *page;
 
         dump_stack();
         list_for_each_entry(page, page_list, lru)
             dump_page(page, "migration failure");
     }
 }
 #else
 static inline void alloc_contig_dump_pages(struct list_head *page_list)
 {
 }
 #endif
 
 /* [start, end) must belong to a single zone. */
 int __alloc_contig_migrate_range(struct compact_control *cc,
                     unsigned long start, unsigned long end)
 {
     /* This function is based on compact_zone() from compaction.c. */
     unsigned int nr_reclaimed;
     unsigned long pfn = start;
     unsigned int tries = 0;
     int ret = 0;
     struct migration_target_control mtc = {
         .nid = zone_to_nid(cc->zone),
         .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
     };
 
     lru_cache_disable();
 
     while (pfn < end || !list_empty(&cc->migratepages)) {
         if (fatal_signal_pending(current)) {
             ret = -EINTR;
             break;
         }
 
         if (list_empty(&cc->migratepages)) {
             cc->nr_migratepages = 0;
             ret = isolate_migratepages_range(cc, pfn, end);
             if (ret && ret != -EAGAIN)
                 break;
             pfn = cc->migrate_pfn;
             tries = 0;
         } else if (++tries == 5) {
             ret = -EBUSY;
             break;
         }
 
         nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
                             &cc->migratepages);
         cc->nr_migratepages -= nr_reclaimed;
 
         ret = migrate_pages(&cc->migratepages, alloc_migration_target,
             NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE, NULL);
 
         /*
          * On -ENOMEM, migrate_pages() bails out right away. It is pointless
          * to retry again over this error, so do the same here.
          */
         if (ret == -ENOMEM)
             break;
     }
 
     lru_cache_enable();
     if (ret < 0) {
         if (!(cc->gfp_mask & __GFP_NOWARN) && ret == -EBUSY)
             alloc_contig_dump_pages(&cc->migratepages);
         putback_movable_pages(&cc->migratepages);
         return ret;
     }
     return 0;
 }
 
 /**
  * alloc_contig_range() -- tries to allocate given range of pages
  * @start:  start PFN to allocate
  * @end:    one-past-the-last PFN to allocate
  * @migratetype:    migratetype of the underlying pageblocks (either
  *          #MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
  *          in range must have the same migratetype and it must
  *          be either of the two.
  * @gfp_mask:   GFP mask to use during compaction
  *
  * The PFN range does not have to be pageblock aligned. The PFN range must
  * belong to a single zone.
  *
  * The first thing this routine does is attempt to MIGRATE_ISOLATE all
  * pageblocks in the range.  Once isolated, the pageblocks should not
  * be modified by others.
  *
  * Return: zero on success or negative error code.  On success all
  * pages which PFN is in [start, end) are allocated for the caller and
  * need to be freed with free_contig_range().
  */
 int alloc_contig_range(unsigned long start, unsigned long end,
                unsigned migratetype, gfp_t gfp_mask)
 {
     unsigned long outer_start, outer_end;
     int order;
     int ret = 0;
 
     struct compact_control cc = {
         .nr_migratepages = 0,
         .order = -1,
         .zone = page_zone(pfn_to_page(start)),
         .mode = MIGRATE_SYNC,
         .ignore_skip_hint = true,
         .no_set_skip_hint = true,
         .gfp_mask = current_gfp_context(gfp_mask),
         .alloc_contig = true,
     };
     INIT_LIST_HEAD(&cc.migratepages);
 
     /*
      * What we do here is we mark all pageblocks in range as
      * MIGRATE_ISOLATE.  Because pageblock and max order pages may
      * have different sizes, and due to the way page allocator
      * work, start_isolate_page_range() has special handlings for this.
      *
      * Once the pageblocks are marked as MIGRATE_ISOLATE, we
      * migrate the pages from an unaligned range (ie. pages that
      * we are interested in). This will put all the pages in
      * range back to page allocator as MIGRATE_ISOLATE.
      *
      * When this is done, we take the pages in range from page
      * allocator removing them from the buddy system.  This way
      * page allocator will never consider using them.
      *
      * This lets us mark the pageblocks back as
      * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
      * aligned range but not in the unaligned, original range are
      * put back to page allocator so that buddy can use them.
      */
 
     ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
     if (ret)
         goto done;
 
     drain_all_pages(cc.zone);
 
     /*
      * In case of -EBUSY, we'd like to know which page causes problem.
      * So, just fall through. test_pages_isolated() has a tracepoint
      * which will report the busy page.
      *
      * It is possible that busy pages could become available before
      * the call to test_pages_isolated, and the range will actually be
      * allocated.  So, if we fall through be sure to clear ret so that
      * -EBUSY is not accidentally used or returned to caller.
      */
     ret = __alloc_contig_migrate_range(&cc, start, end);
     if (ret && ret != -EBUSY)
         goto done;
     ret = 0;
 
     /*
      * Pages from [start, end) are within a pageblock_nr_pages
      * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
      * more, all pages in [start, end) are free in page allocator.
      * What we are going to do is to allocate all pages from
      * [start, end) (that is remove them from page allocator).
      *
      * The only problem is that pages at the beginning and at the
      * end of interesting range may be not aligned with pages that
      * page allocator holds, ie. they can be part of higher order
      * pages.  Because of this, we reserve the bigger range and
      * once this is done free the pages we are not interested in.
      *
      * We don't have to hold zone->lock here because the pages are
      * isolated thus they won't get removed from buddy.
      */
 
     order = 0;
     outer_start = start;
     while (!PageBuddy(pfn_to_page(outer_start))) {
         if (++order >= MAX_ORDER) {
             outer_start = start;
             break;
         }
         outer_start &= ~0UL << order;
     }
 
     if (outer_start != start) {
         order = buddy_order(pfn_to_page(outer_start));
 
         /*
          * outer_start page could be small order buddy page and
          * it doesn't include start page. Adjust outer_start
          * in this case to report failed page properly
          * on tracepoint in test_pages_isolated()
          */
         if (outer_start + (1UL << order) <= start)
             outer_start = start;
     }
 
     /* Make sure the range is really isolated. */
     if (test_pages_isolated(outer_start, end, 0)) {
         ret = -EBUSY;
         goto done;
     }
 
     /* Grab isolated pages from freelists. */
     outer_end = isolate_freepages_range(&cc, outer_start, end);
     if (!outer_end) {
         ret = -EBUSY;
         goto done;
     }
 
     /* Free head and tail (if any) */
     if (start != outer_start)
         free_contig_range(outer_start, start - outer_start);
     if (end != outer_end)
         free_contig_range(end, outer_end - end);
 
 done:
     undo_isolate_page_range(start, end, migratetype);
     return ret;
 }
 EXPORT_SYMBOL(alloc_contig_range);
 
 static int __alloc_contig_pages(unsigned long start_pfn,
                 unsigned long nr_pages, gfp_t gfp_mask)
 {
     unsigned long end_pfn = start_pfn + nr_pages;
 
     return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
                   gfp_mask);
 }
 
 static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
                    unsigned long nr_pages)
 {
     unsigned long i, end_pfn = start_pfn + nr_pages;
     struct page *page;
 
     for (i = start_pfn; i < end_pfn; i++) {
         page = pfn_to_online_page(i);
         if (!page)
             return false;
 
         if (page_zone(page) != z)
             return false;
 
         if (PageReserved(page))
             return false;
     }
     return true;
 }
 
 static bool zone_spans_last_pfn(const struct zone *zone,
                 unsigned long start_pfn, unsigned long nr_pages)
 {
     unsigned long last_pfn = start_pfn + nr_pages - 1;
 
     return zone_spans_pfn(zone, last_pfn);
 }
 
 /**
  * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
  * @nr_pages:   Number of contiguous pages to allocate
  * @gfp_mask:   GFP mask to limit search and used during compaction
  * @nid:    Target node
  * @nodemask:   Mask for other possible nodes
  *
  * This routine is a wrapper around alloc_contig_range(). It scans over zones
  * on an applicable zonelist to find a contiguous pfn range which can then be
  * tried for allocation with alloc_contig_range(). This routine is intended
  * for allocation requests which can not be fulfilled with the buddy allocator.
  *
  * The allocated memory is always aligned to a page boundary. If nr_pages is a
  * power of two, then allocated range is also guaranteed to be aligned to same
  * nr_pages (e.g. 1GB request would be aligned to 1GB).
  *
  * Allocated pages can be freed with free_contig_range() or by manually calling
  * __free_page() on each allocated page.
  *
  * Return: pointer to contiguous pages on success, or NULL if not successful.
  */
 struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
                 int nid, nodemask_t *nodemask)
 {
     unsigned long ret, pfn, flags;
     struct zonelist *zonelist;
     struct zone *zone;
     struct zoneref *z;
 
     zonelist = node_zonelist(nid, gfp_mask);
     for_each_zone_zonelist_nodemask(zone, z, zonelist,
                     gfp_zone(gfp_mask), nodemask) {
         spin_lock_irqsave(&zone->lock, flags);
 
         pfn = ALIGN(zone->zone_start_pfn, nr_pages);
         while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
             if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
                 /*
                  * We release the zone lock here because
                  * alloc_contig_range() will also lock the zone
                  * at some point. If there's an allocation
                  * spinning on this lock, it may win the race
                  * and cause alloc_contig_range() to fail...
                  */
                 spin_unlock_irqrestore(&zone->lock, flags);
                 ret = __alloc_contig_pages(pfn, nr_pages,
                             gfp_mask);
                 if (!ret)
                     return pfn_to_page(pfn);
                 spin_lock_irqsave(&zone->lock, flags);
             }
             pfn += nr_pages;
         }
         spin_unlock_irqrestore(&zone->lock, flags);
     }
     return NULL;
 }
 #endif /* CONFIG_CONTIG_ALLOC */
 
 void free_contig_range(unsigned long pfn, unsigned long nr_pages)
 {
     unsigned long count = 0;
 
     for (; nr_pages--; pfn++) {
         struct page *page = pfn_to_page(pfn);
 
         count += page_count(page) != 1;
         __free_page(page);
     }
     WARN(count != 0, "%lu pages are still in use!\n", count);
 }
 EXPORT_SYMBOL(free_contig_range);
 
 /*
  * The zone indicated has a new number of managed_pages; batch sizes and percpu
  * page high values need to be recalculated.
  */
 void zone_pcp_update(struct zone *zone, int cpu_online)
 {
     mutex_lock(&pcp_batch_high_lock);
     zone_set_pageset_high_and_batch(zone, cpu_online);
     mutex_unlock(&pcp_batch_high_lock);
 }
 
 /*
  * Effectively disable pcplists for the zone by setting the high limit to 0
  * and draining all cpus. A concurrent page freeing on another CPU that's about
  * to put the page on pcplist will either finish before the drain and the page
  * will be drained, or observe the new high limit and skip the pcplist.
  *
  * Must be paired with a call to zone_pcp_enable().
  */
 void zone_pcp_disable(struct zone *zone)
 {
     mutex_lock(&pcp_batch_high_lock);
     __zone_set_pageset_high_and_batch(zone, 0, 1);
     __drain_all_pages(zone, true);
 }
 
 void zone_pcp_enable(struct zone *zone)
 {
     __zone_set_pageset_high_and_batch(zone, zone->pageset_high, zone->pageset_batch);
     mutex_unlock(&pcp_batch_high_lock);
 }
 
 void zone_pcp_reset(struct zone *zone)
 {
     int cpu;
     struct per_cpu_zonestat *pzstats;
 
     if (zone->per_cpu_pageset != &boot_pageset) {
         for_each_online_cpu(cpu) {
             pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
             drain_zonestat(zone, pzstats);
         }
         free_percpu(zone->per_cpu_pageset);
         free_percpu(zone->per_cpu_zonestats);
         zone->per_cpu_pageset = &boot_pageset;
         zone->per_cpu_zonestats = &boot_zonestats;
     }
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
  * All pages in the range must be in a single zone, must not contain holes,
  * must span full sections, and must be isolated before calling this function.
  */
 void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 {
     unsigned long pfn = start_pfn;
     struct page *page;
     struct zone *zone;
     unsigned int order;
     unsigned long flags;
 
     offline_mem_sections(pfn, end_pfn);
     zone = page_zone(pfn_to_page(pfn));
     spin_lock_irqsave(&zone->lock, flags);
     while (pfn < end_pfn) {
         page = pfn_to_page(pfn);
         /*
          * The HWPoisoned page may be not in buddy system, and
          * page_count() is not 0.
          */
         if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
             pfn++;
             continue;
         }
         /*
          * At this point all remaining PageOffline() pages have a
          * reference count of 0 and can simply be skipped.
          */
         if (PageOffline(page)) {
             BUG_ON(page_count(page));
             BUG_ON(PageBuddy(page));
             pfn++;
             continue;
         }
 
         BUG_ON(page_count(page));
         BUG_ON(!PageBuddy(page));
         order = buddy_order(page);
         del_page_from_free_list(page, zone, order);
         pfn += (1 << order);
     }
     spin_unlock_irqrestore(&zone->lock, flags);
 }
 #endif
 
 /*
  * This function returns a stable result only if called under zone lock.
  */
 bool is_free_buddy_page(struct page *page)
 {
     unsigned long pfn = page_to_pfn(page);
     unsigned int order;
 
     for (order = 0; order < MAX_ORDER; order++) {
         struct page *page_head = page - (pfn & ((1 << order) - 1));
 
         if (PageBuddy(page_head) &&
             buddy_order_unsafe(page_head) >= order)
             break;
     }
 
     return order < MAX_ORDER;
 }
 EXPORT_SYMBOL(is_free_buddy_page);
 
 #ifdef CONFIG_MEMORY_FAILURE
 /*
  * Break down a higher-order page in sub-pages, and keep our target out of
  * buddy allocator.
  */
 static void break_down_buddy_pages(struct zone *zone, struct page *page,
                    struct page *target, int low, int high,
                    int migratetype)
 {
     unsigned long size = 1 << high;
     struct page *current_buddy, *next_page;
 
     while (high > low) {
         high--;
         size >>= 1;
 
         if (target >= &page[size]) {
             next_page = page + size;
             current_buddy = page;
         } else {
             next_page = page;
             current_buddy = page + size;
         }
 
         if (set_page_guard(zone, current_buddy, high, migratetype))
             continue;
 
         if (current_buddy != target) {
             add_to_free_list(current_buddy, zone, high, migratetype);
             set_buddy_order(current_buddy, high);
             page = next_page;
         }
     }
 }
 
 /*
  * Take a page that will be marked as poisoned off the buddy allocator.
  */
 bool take_page_off_buddy(struct page *page)
 {
     struct zone *zone = page_zone(page);
     unsigned long pfn = page_to_pfn(page);
     unsigned long flags;
     unsigned int order;
     bool ret = false;
 
     spin_lock_irqsave(&zone->lock, flags);
     for (order = 0; order < MAX_ORDER; order++) {
         struct page *page_head = page - (pfn & ((1 << order) - 1));
         int page_order = buddy_order(page_head);
 
         if (PageBuddy(page_head) && page_order >= order) {
             unsigned long pfn_head = page_to_pfn(page_head);
             int migratetype = get_pfnblock_migratetype(page_head,
                                    pfn_head);
 
             del_page_from_free_list(page_head, zone, page_order);
             break_down_buddy_pages(zone, page_head, page, 0,
                         page_order, migratetype);
             SetPageHWPoisonTakenOff(page);
             if (!is_migrate_isolate(migratetype))
                 __mod_zone_freepage_state(zone, -1, migratetype);
             ret = true;
             break;
         }
         if (page_count(page_head) > 0)
             break;
     }
     spin_unlock_irqrestore(&zone->lock, flags);
     return ret;
 }
 
 /*
  * Cancel takeoff done by take_page_off_buddy().
  */
 bool put_page_back_buddy(struct page *page)
 {
     struct zone *zone = page_zone(page);
     unsigned long pfn = page_to_pfn(page);
     unsigned long flags;
     int migratetype = get_pfnblock_migratetype(page, pfn);
     bool ret = false;
 
     spin_lock_irqsave(&zone->lock, flags);
     if (put_page_testzero(page)) {
         ClearPageHWPoisonTakenOff(page);
         __free_one_page(page, pfn, zone, 0, migratetype, FPI_NONE);
         if (TestClearPageHWPoison(page)) {
             ret = true;
         }
     }
     spin_unlock_irqrestore(&zone->lock, flags);
 
     return ret;
 }
 #endif
 
 #ifdef CONFIG_ZONE_DMA
 bool has_managed_dma(void)
 {
     struct pglist_data *pgdat;
 
     for_each_online_pgdat(pgdat) {
         struct zone *zone = &pgdat->node_zones[ZONE_DMA];
 
         if (managed_zone(zone))
             return true;
     }
     return false;
 }
 #endif /* CONFIG_ZONE_DMA */