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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_MMZONE_H
 #define _LINUX_MMZONE_H
 
 #ifndef __ASSEMBLY__
 #ifndef __GENERATING_BOUNDS_H
 
 #include <linux/spinlock.h>
 #include <linux/list.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/cache.h>
 #include <linux/threads.h>
 #include <linux/numa.h>
 #include <linux/init.h>
 #include <linux/seqlock.h>
 #include <linux/nodemask.h>
 #include <linux/pageblock-flags.h>
 #include <linux/page-flags-layout.h>
 #include <linux/atomic.h>
 #include <linux/mm_types.h>
 #include <linux/page-flags.h>
 #include <linux/local_lock.h>
 #include <asm/page.h>
 
 /* Free memory management - zoned buddy allocator.  */
 #ifndef CONFIG_FORCE_MAX_ZONEORDER
 #define MAX_ORDER 11
 #else
 #define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER
 #endif
 #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
 
 /*
  * PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
  * costly to service.  That is between allocation orders which should
  * coalesce naturally under reasonable reclaim pressure and those which
  * will not.
  */
 #define PAGE_ALLOC_COSTLY_ORDER 3
 
 enum migratetype {
     MIGRATE_UNMOVABLE,
     MIGRATE_MOVABLE,
     MIGRATE_RECLAIMABLE,
     MIGRATE_PCPTYPES,   /* the number of types on the pcp lists */
     MIGRATE_HIGHATOMIC = MIGRATE_PCPTYPES,
 #ifdef CONFIG_CMA
     /*
      * MIGRATE_CMA migration type is designed to mimic the way
      * ZONE_MOVABLE works.  Only movable pages can be allocated
      * from MIGRATE_CMA pageblocks and page allocator never
      * implicitly change migration type of MIGRATE_CMA pageblock.
      *
      * The way to use it is to change migratetype of a range of
      * pageblocks to MIGRATE_CMA which can be done by
      * __free_pageblock_cma() function.
      */
     MIGRATE_CMA,
 #endif
 #ifdef CONFIG_MEMORY_ISOLATION
     MIGRATE_ISOLATE,    /* can't allocate from here */
 #endif
     MIGRATE_TYPES
 };
 
 /* In mm/page_alloc.c; keep in sync also with show_migration_types() there */
 extern const char * const migratetype_names[MIGRATE_TYPES];
 
 #ifdef CONFIG_CMA
 #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
 #  define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA)
 #else
 #  define is_migrate_cma(migratetype) false
 #  define is_migrate_cma_page(_page) false
 #endif
 
 static inline bool is_migrate_movable(int mt)
 {
     return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE;
 }
 
 /*
  * Check whether a migratetype can be merged with another migratetype.
  *
  * It is only mergeable when it can fall back to other migratetypes for
  * allocation. See fallbacks[MIGRATE_TYPES][3] in page_alloc.c.
  */
 static inline bool migratetype_is_mergeable(int mt)
 {
     return mt < MIGRATE_PCPTYPES;
 }
 
 #define for_each_migratetype_order(order, type) \
     for (order = 0; order < MAX_ORDER; order++) \
         for (type = 0; type < MIGRATE_TYPES; type++)
 
 extern int page_group_by_mobility_disabled;
 
 #define MIGRATETYPE_MASK ((1UL << PB_migratetype_bits) - 1)
 
 #define get_pageblock_migratetype(page)                 \
     get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK)
 
 struct free_area {
     struct list_head    free_list[MIGRATE_TYPES];
     unsigned long       nr_free;
 };
 
 static inline struct page *get_page_from_free_area(struct free_area *area,
                         int migratetype)
 {
     return list_first_entry_or_null(&area->free_list[migratetype],
                     struct page, lru);
 }
 
 static inline bool free_area_empty(struct free_area *area, int migratetype)
 {
     return list_empty(&area->free_list[migratetype]);
 }
 
 struct pglist_data;
 
 /*
  * Add a wild amount of padding here to ensure data fall into separate
  * cachelines.  There are very few zone structures in the machine, so space
  * consumption is not a concern here.
  */
 #if defined(CONFIG_SMP)
 struct zone_padding {
     char x[0];
 } ____cacheline_internodealigned_in_smp;
 #define ZONE_PADDING(name)  struct zone_padding name;
 #else
 #define ZONE_PADDING(name)
 #endif
 
 #ifdef CONFIG_NUMA
 enum numa_stat_item {
     NUMA_HIT,       /* allocated in intended node */
     NUMA_MISS,      /* allocated in non intended node */
     NUMA_FOREIGN,       /* was intended here, hit elsewhere */
     NUMA_INTERLEAVE_HIT,    /* interleaver preferred this zone */
     NUMA_LOCAL,     /* allocation from local node */
     NUMA_OTHER,     /* allocation from other node */
     NR_VM_NUMA_EVENT_ITEMS
 };
 #else
 #define NR_VM_NUMA_EVENT_ITEMS 0
 #endif
 
 enum zone_stat_item {
     /* First 128 byte cacheline (assuming 64 bit words) */
     NR_FREE_PAGES,
     NR_ZONE_LRU_BASE, /* Used only for compaction and reclaim retry */
     NR_ZONE_INACTIVE_ANON = NR_ZONE_LRU_BASE,
     NR_ZONE_ACTIVE_ANON,
     NR_ZONE_INACTIVE_FILE,
     NR_ZONE_ACTIVE_FILE,
     NR_ZONE_UNEVICTABLE,
     NR_ZONE_WRITE_PENDING,  /* Count of dirty, writeback and unstable pages */
     NR_MLOCK,       /* mlock()ed pages found and moved off LRU */
     /* Second 128 byte cacheline */
     NR_BOUNCE,
 #if IS_ENABLED(CONFIG_ZSMALLOC)
     NR_ZSPAGES,     /* allocated in zsmalloc */
 #endif
     NR_FREE_CMA_PAGES,
     NR_VM_ZONE_STAT_ITEMS };
 
 enum node_stat_item {
     NR_LRU_BASE,
     NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
     NR_ACTIVE_ANON,     /*  "     "     "   "       "         */
     NR_INACTIVE_FILE,   /*  "     "     "   "       "         */
     NR_ACTIVE_FILE,     /*  "     "     "   "       "         */
     NR_UNEVICTABLE,     /*  "     "     "   "       "         */
     NR_SLAB_RECLAIMABLE_B,
     NR_SLAB_UNRECLAIMABLE_B,
     NR_ISOLATED_ANON,   /* Temporary isolated pages from anon lru */
     NR_ISOLATED_FILE,   /* Temporary isolated pages from file lru */
     WORKINGSET_NODES,
     WORKINGSET_REFAULT_BASE,
     WORKINGSET_REFAULT_ANON = WORKINGSET_REFAULT_BASE,
     WORKINGSET_REFAULT_FILE,
     WORKINGSET_ACTIVATE_BASE,
     WORKINGSET_ACTIVATE_ANON = WORKINGSET_ACTIVATE_BASE,
     WORKINGSET_ACTIVATE_FILE,
     WORKINGSET_RESTORE_BASE,
     WORKINGSET_RESTORE_ANON = WORKINGSET_RESTORE_BASE,
     WORKINGSET_RESTORE_FILE,
     WORKINGSET_NODERECLAIM,
     NR_ANON_MAPPED, /* Mapped anonymous pages */
     NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
                only modified from process context */
     NR_FILE_PAGES,
     NR_FILE_DIRTY,
     NR_WRITEBACK,
     NR_WRITEBACK_TEMP,  /* Writeback using temporary buffers */
     NR_SHMEM,       /* shmem pages (included tmpfs/GEM pages) */
     NR_SHMEM_THPS,
     NR_SHMEM_PMDMAPPED,
     NR_FILE_THPS,
     NR_FILE_PMDMAPPED,
     NR_ANON_THPS,
     NR_VMSCAN_WRITE,
     NR_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
     NR_DIRTIED,     /* page dirtyings since bootup */
     NR_WRITTEN,     /* page writings since bootup */
     NR_THROTTLED_WRITTEN,   /* NR_WRITTEN while reclaim throttled */
     NR_KERNEL_MISC_RECLAIMABLE, /* reclaimable non-slab kernel pages */
     NR_FOLL_PIN_ACQUIRED,   /* via: pin_user_page(), gup flag: FOLL_PIN */
     NR_FOLL_PIN_RELEASED,   /* pages returned via unpin_user_page() */
     NR_KERNEL_STACK_KB, /* measured in KiB */
 #if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
     NR_KERNEL_SCS_KB,   /* measured in KiB */
 #endif
     NR_PAGETABLE,       /* used for pagetables */
 #ifdef CONFIG_SWAP
     NR_SWAPCACHE,
 #endif
 #ifdef CONFIG_NUMA_BALANCING
     PGPROMOTE_SUCCESS,  /* promote successfully */
 #endif
     NR_VM_NODE_STAT_ITEMS
 };
 
 /*
  * Returns true if the item should be printed in THPs (/proc/vmstat
  * currently prints number of anon, file and shmem THPs. But the item
  * is charged in pages).
  */
 static __always_inline bool vmstat_item_print_in_thp(enum node_stat_item item)
 {
     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
         return false;
 
     return item == NR_ANON_THPS ||
            item == NR_FILE_THPS ||
            item == NR_SHMEM_THPS ||
            item == NR_SHMEM_PMDMAPPED ||
            item == NR_FILE_PMDMAPPED;
 }
 
 /*
  * Returns true if the value is measured in bytes (most vmstat values are
  * measured in pages). This defines the API part, the internal representation
  * might be different.
  */
 static __always_inline bool vmstat_item_in_bytes(int idx)
 {
     /*
      * Global and per-node slab counters track slab pages.
      * It's expected that changes are multiples of PAGE_SIZE.
      * Internally values are stored in pages.
      *
      * Per-memcg and per-lruvec counters track memory, consumed
      * by individual slab objects. These counters are actually
      * byte-precise.
      */
     return (idx == NR_SLAB_RECLAIMABLE_B ||
         idx == NR_SLAB_UNRECLAIMABLE_B);
 }
 
 /*
  * We do arithmetic on the LRU lists in various places in the code,
  * so it is important to keep the active lists LRU_ACTIVE higher in
  * the array than the corresponding inactive lists, and to keep
  * the *_FILE lists LRU_FILE higher than the corresponding _ANON lists.
  *
  * This has to be kept in sync with the statistics in zone_stat_item
  * above and the descriptions in vmstat_text in mm/vmstat.c
  */
 #define LRU_BASE 0
 #define LRU_ACTIVE 1
 #define LRU_FILE 2
 
 enum lru_list {
     LRU_INACTIVE_ANON = LRU_BASE,
     LRU_ACTIVE_ANON = LRU_BASE + LRU_ACTIVE,
     LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
     LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
     LRU_UNEVICTABLE,
     NR_LRU_LISTS
 };
 
 enum vmscan_throttle_state {
     VMSCAN_THROTTLE_WRITEBACK,
     VMSCAN_THROTTLE_ISOLATED,
     VMSCAN_THROTTLE_NOPROGRESS,
     VMSCAN_THROTTLE_CONGESTED,
     NR_VMSCAN_THROTTLE,
 };
 
 #define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)
 
 #define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
 
 static inline bool is_file_lru(enum lru_list lru)
 {
     return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);
 }
 
 static inline bool is_active_lru(enum lru_list lru)
 {
     return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
 }
 
 #define ANON_AND_FILE 2
 
 enum lruvec_flags {
     LRUVEC_CONGESTED,       /* lruvec has many dirty pages
                      * backed by a congested BDI
                      */
 };
 
 struct lruvec {
     struct list_head        lists[NR_LRU_LISTS];
     /* per lruvec lru_lock for memcg */
     spinlock_t          lru_lock;
     /*
      * These track the cost of reclaiming one LRU - file or anon -
      * over the other. As the observed cost of reclaiming one LRU
      * increases, the reclaim scan balance tips toward the other.
      */
     unsigned long           anon_cost;
     unsigned long           file_cost;
     /* Non-resident age, driven by LRU movement */
     atomic_long_t           nonresident_age;
     /* Refaults at the time of last reclaim cycle */
     unsigned long           refaults[ANON_AND_FILE];
     /* Various lruvec state flags (enum lruvec_flags) */
     unsigned long           flags;
 #ifdef CONFIG_MEMCG
     struct pglist_data *pgdat;
 #endif
 };
 
 /* Isolate unmapped pages */
 #define ISOLATE_UNMAPPED    ((__force isolate_mode_t)0x2)
 /* Isolate for asynchronous migration */
 #define ISOLATE_ASYNC_MIGRATE   ((__force isolate_mode_t)0x4)
 /* Isolate unevictable pages */
 #define ISOLATE_UNEVICTABLE ((__force isolate_mode_t)0x8)
 
 /* LRU Isolation modes. */
 typedef unsigned __bitwise isolate_mode_t;
 
 enum zone_watermarks {
     WMARK_MIN,
     WMARK_LOW,
     WMARK_HIGH,
     WMARK_PROMO,
     NR_WMARK
 };
 
 /*
  * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list
  * for THP which will usually be GFP_MOVABLE. Even if it is another type,
  * it should not contribute to serious fragmentation causing THP allocation
  * failures.
  */
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define NR_PCP_THP 1
 #else
 #define NR_PCP_THP 0
 #endif
 #define NR_LOWORDER_PCP_LISTS (MIGRATE_PCPTYPES * (PAGE_ALLOC_COSTLY_ORDER + 1))
 #define NR_PCP_LISTS (NR_LOWORDER_PCP_LISTS + NR_PCP_THP)
 
 /*
  * Shift to encode migratetype and order in the same integer, with order
  * in the least significant bits.
  */
 #define NR_PCP_ORDER_WIDTH 8
 #define NR_PCP_ORDER_MASK ((1<<NR_PCP_ORDER_WIDTH) - 1)
 
 #define min_wmark_pages(z) (z->_watermark[WMARK_MIN] + z->watermark_boost)
 #define low_wmark_pages(z) (z->_watermark[WMARK_LOW] + z->watermark_boost)
 #define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost)
 #define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost)
 
 /* Fields and list protected by pagesets local_lock in page_alloc.c */
 struct per_cpu_pages {
     spinlock_t lock;    /* Protects lists field */
     int count;      /* number of pages in the list */
     int high;       /* high watermark, emptying needed */
     int batch;      /* chunk size for buddy add/remove */
     short free_factor;  /* batch scaling factor during free */
 #ifdef CONFIG_NUMA
     short expire;       /* When 0, remote pagesets are drained */
 #endif
 
     /* Lists of pages, one per migrate type stored on the pcp-lists */
     struct list_head lists[NR_PCP_LISTS];
 } ____cacheline_aligned_in_smp;
 
 struct per_cpu_zonestat {
 #ifdef CONFIG_SMP
     s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
     s8 stat_threshold;
 #endif
 #ifdef CONFIG_NUMA
     /*
      * Low priority inaccurate counters that are only folded
      * on demand. Use a large type to avoid the overhead of
      * folding during refresh_cpu_vm_stats.
      */
     unsigned long vm_numa_event[NR_VM_NUMA_EVENT_ITEMS];
 #endif
 };
 
 struct per_cpu_nodestat {
     s8 stat_threshold;
     s8 vm_node_stat_diff[NR_VM_NODE_STAT_ITEMS];
 };
 
 #endif /* !__GENERATING_BOUNDS.H */
 
 enum zone_type {
     /*
      * ZONE_DMA and ZONE_DMA32 are used when there are peripherals not able
      * to DMA to all of the addressable memory (ZONE_NORMAL).
      * On architectures where this area covers the whole 32 bit address
      * space ZONE_DMA32 is used. ZONE_DMA is left for the ones with smaller
      * DMA addressing constraints. This distinction is important as a 32bit
      * DMA mask is assumed when ZONE_DMA32 is defined. Some 64-bit
      * platforms may need both zones as they support peripherals with
      * different DMA addressing limitations.
      */
 #ifdef CONFIG_ZONE_DMA
     ZONE_DMA,
 #endif
 #ifdef CONFIG_ZONE_DMA32
     ZONE_DMA32,
 #endif
     /*
      * Normal addressable memory is in ZONE_NORMAL. DMA operations can be
      * performed on pages in ZONE_NORMAL if the DMA devices support
      * transfers to all addressable memory.
      */
     ZONE_NORMAL,
 #ifdef CONFIG_HIGHMEM
     /*
      * A memory area that is only addressable by the kernel through
      * mapping portions into its own address space. This is for example
      * used by i386 to allow the kernel to address the memory beyond
      * 900MB. The kernel will set up special mappings (page
      * table entries on i386) for each page that the kernel needs to
      * access.
      */
     ZONE_HIGHMEM,
 #endif
     /*
      * ZONE_MOVABLE is similar to ZONE_NORMAL, except that it contains
      * movable pages with few exceptional cases described below. Main use
      * cases for ZONE_MOVABLE are to make memory offlining/unplug more
      * likely to succeed, and to locally limit unmovable allocations - e.g.,
      * to increase the number of THP/huge pages. Notable special cases are:
      *
      * 1. Pinned pages: (long-term) pinning of movable pages might
      *    essentially turn such pages unmovable. Therefore, we do not allow
      *    pinning long-term pages in ZONE_MOVABLE. When pages are pinned and
      *    faulted, they come from the right zone right away. However, it is
      *    still possible that address space already has pages in
      *    ZONE_MOVABLE at the time when pages are pinned (i.e. user has
      *    touches that memory before pinning). In such case we migrate them
      *    to a different zone. When migration fails - pinning fails.
      * 2. memblock allocations: kernelcore/movablecore setups might create
      *    situations where ZONE_MOVABLE contains unmovable allocations
      *    after boot. Memory offlining and allocations fail early.
      * 3. Memory holes: kernelcore/movablecore setups might create very rare
      *    situations where ZONE_MOVABLE contains memory holes after boot,
      *    for example, if we have sections that are only partially
      *    populated. Memory offlining and allocations fail early.
      * 4. PG_hwpoison pages: while poisoned pages can be skipped during
      *    memory offlining, such pages cannot be allocated.
      * 5. Unmovable PG_offline pages: in paravirtualized environments,
      *    hotplugged memory blocks might only partially be managed by the
      *    buddy (e.g., via XEN-balloon, Hyper-V balloon, virtio-mem). The
      *    parts not manged by the buddy are unmovable PG_offline pages. In
      *    some cases (virtio-mem), such pages can be skipped during
      *    memory offlining, however, cannot be moved/allocated. These
      *    techniques might use alloc_contig_range() to hide previously
      *    exposed pages from the buddy again (e.g., to implement some sort
      *    of memory unplug in virtio-mem).
      * 6. ZERO_PAGE(0), kernelcore/movablecore setups might create
      *    situations where ZERO_PAGE(0) which is allocated differently
      *    on different platforms may end up in a movable zone. ZERO_PAGE(0)
      *    cannot be migrated.
      * 7. Memory-hotplug: when using memmap_on_memory and onlining the
      *    memory to the MOVABLE zone, the vmemmap pages are also placed in
      *    such zone. Such pages cannot be really moved around as they are
      *    self-stored in the range, but they are treated as movable when
      *    the range they describe is about to be offlined.
      *
      * In general, no unmovable allocations that degrade memory offlining
      * should end up in ZONE_MOVABLE. Allocators (like alloc_contig_range())
      * have to expect that migrating pages in ZONE_MOVABLE can fail (even
      * if has_unmovable_pages() states that there are no unmovable pages,
      * there can be false negatives).
      */
     ZONE_MOVABLE,
 #ifdef CONFIG_ZONE_DEVICE
     ZONE_DEVICE,
 #endif
     __MAX_NR_ZONES
 
 };
 
 #ifndef __GENERATING_BOUNDS_H
 
 #define ASYNC_AND_SYNC 2
 
 struct zone {
     /* Read-mostly fields */
 
     /* zone watermarks, access with *_wmark_pages(zone) macros */
     unsigned long _watermark[NR_WMARK];
     unsigned long watermark_boost;
 
     unsigned long nr_reserved_highatomic;
 
     /*
      * We don't know if the memory that we're going to allocate will be
      * freeable or/and it will be released eventually, so to avoid totally
      * wasting several GB of ram we must reserve some of the lower zone
      * memory (otherwise we risk to run OOM on the lower zones despite
      * there being tons of freeable ram on the higher zones).  This array is
      * recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl
      * changes.
      */
     long lowmem_reserve[MAX_NR_ZONES];
 
 #ifdef CONFIG_NUMA
     int node;
 #endif
     struct pglist_data  *zone_pgdat;
     struct per_cpu_pages    __percpu *per_cpu_pageset;
     struct per_cpu_zonestat __percpu *per_cpu_zonestats;
     /*
      * the high and batch values are copied to individual pagesets for
      * faster access
      */
     int pageset_high;
     int pageset_batch;
 
 #ifndef CONFIG_SPARSEMEM
     /*
      * Flags for a pageblock_nr_pages block. See pageblock-flags.h.
      * In SPARSEMEM, this map is stored in struct mem_section
      */
     unsigned long       *pageblock_flags;
 #endif /* CONFIG_SPARSEMEM */
 
     /* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
     unsigned long       zone_start_pfn;
 
     /*
      * spanned_pages is the total pages spanned by the zone, including
      * holes, which is calculated as:
      *  spanned_pages = zone_end_pfn - zone_start_pfn;
      *
      * present_pages is physical pages existing within the zone, which
      * is calculated as:
      *  present_pages = spanned_pages - absent_pages(pages in holes);
      *
      * present_early_pages is present pages existing within the zone
      * located on memory available since early boot, excluding hotplugged
      * memory.
      *
      * managed_pages is present pages managed by the buddy system, which
      * is calculated as (reserved_pages includes pages allocated by the
      * bootmem allocator):
      *  managed_pages = present_pages - reserved_pages;
      *
      * cma pages is present pages that are assigned for CMA use
      * (MIGRATE_CMA).
      *
      * So present_pages may be used by memory hotplug or memory power
      * management logic to figure out unmanaged pages by checking
      * (present_pages - managed_pages). And managed_pages should be used
      * by page allocator and vm scanner to calculate all kinds of watermarks
      * and thresholds.
      *
      * Locking rules:
      *
      * zone_start_pfn and spanned_pages are protected by span_seqlock.
      * It is a seqlock because it has to be read outside of zone->lock,
      * and it is done in the main allocator path.  But, it is written
      * quite infrequently.
      *
      * The span_seq lock is declared along with zone->lock because it is
      * frequently read in proximity to zone->lock.  It's good to
      * give them a chance of being in the same cacheline.
      *
      * Write access to present_pages at runtime should be protected by
      * mem_hotplug_begin/done(). Any reader who can't tolerant drift of
      * present_pages should use get_online_mems() to get a stable value.
      */
     atomic_long_t       managed_pages;
     unsigned long       spanned_pages;
     unsigned long       present_pages;
 #if defined(CONFIG_MEMORY_HOTPLUG)
     unsigned long       present_early_pages;
 #endif
 #ifdef CONFIG_CMA
     unsigned long       cma_pages;
 #endif
 
     const char      *name;
 
 #ifdef CONFIG_MEMORY_ISOLATION
     /*
      * Number of isolated pageblock. It is used to solve incorrect
      * freepage counting problem due to racy retrieving migratetype
      * of pageblock. Protected by zone->lock.
      */
     unsigned long       nr_isolate_pageblock;
 #endif
 
 #ifdef CONFIG_MEMORY_HOTPLUG
     /* see spanned/present_pages for more description */
     seqlock_t       span_seqlock;
 #endif
 
     int initialized;
 
     /* Write-intensive fields used from the page allocator */
     ZONE_PADDING(_pad1_)
 
     /* free areas of different sizes */
     struct free_area    free_area[MAX_ORDER];
 
     /* zone flags, see below */
     unsigned long       flags;
 
     /* Primarily protects free_area */
     spinlock_t      lock;
 
     /* Write-intensive fields used by compaction and vmstats. */
     ZONE_PADDING(_pad2_)
 
     /*
      * When free pages are below this point, additional steps are taken
      * when reading the number of free pages to avoid per-cpu counter
      * drift allowing watermarks to be breached
      */
     unsigned long percpu_drift_mark;
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
     /* pfn where compaction free scanner should start */
     unsigned long       compact_cached_free_pfn;
     /* pfn where compaction migration scanner should start */
     unsigned long       compact_cached_migrate_pfn[ASYNC_AND_SYNC];
     unsigned long       compact_init_migrate_pfn;
     unsigned long       compact_init_free_pfn;
 #endif
 
 #ifdef CONFIG_COMPACTION
     /*
      * On compaction failure, 1<<compact_defer_shift compactions
      * are skipped before trying again. The number attempted since
      * last failure is tracked with compact_considered.
      * compact_order_failed is the minimum compaction failed order.
      */
     unsigned int        compact_considered;
     unsigned int        compact_defer_shift;
     int         compact_order_failed;
 #endif
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
     /* Set to true when the PG_migrate_skip bits should be cleared */
     bool            compact_blockskip_flush;
 #endif
 
     bool            contiguous;
 
     ZONE_PADDING(_pad3_)
     /* Zone statistics */
     atomic_long_t       vm_stat[NR_VM_ZONE_STAT_ITEMS];
     atomic_long_t       vm_numa_event[NR_VM_NUMA_EVENT_ITEMS];
 } ____cacheline_internodealigned_in_smp;
 
 enum pgdat_flags {
     PGDAT_DIRTY,            /* reclaim scanning has recently found
                      * many dirty file pages at the tail
                      * of the LRU.
                      */
     PGDAT_WRITEBACK,        /* reclaim scanning has recently found
                      * many pages under writeback
                      */
     PGDAT_RECLAIM_LOCKED,       /* prevents concurrent reclaim */
 };
 
 enum zone_flags {
     ZONE_BOOSTED_WATERMARK,     /* zone recently boosted watermarks.
                      * Cleared when kswapd is woken.
                      */
     ZONE_RECLAIM_ACTIVE,        /* kswapd may be scanning the zone. */
 };
 
 static inline unsigned long zone_managed_pages(struct zone *zone)
 {
     return (unsigned long)atomic_long_read(&zone->managed_pages);
 }
 
 static inline unsigned long zone_cma_pages(struct zone *zone)
 {
 #ifdef CONFIG_CMA
     return zone->cma_pages;
 #else
     return 0;
 #endif
 }
 
 static inline unsigned long zone_end_pfn(const struct zone *zone)
 {
     return zone->zone_start_pfn + zone->spanned_pages;
 }
 
 static inline bool zone_spans_pfn(const struct zone *zone, unsigned long pfn)
 {
     return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
 }
 
 static inline bool zone_is_initialized(struct zone *zone)
 {
     return zone->initialized;
 }
 
 static inline bool zone_is_empty(struct zone *zone)
 {
     return zone->spanned_pages == 0;
 }
 
 #ifndef BUILD_VDSO32_64
 /*
  * The zone field is never updated after free_area_init_core()
  * sets it, so none of the operations on it need to be atomic.
  */
 
 /* Page flags: | [SECTION] | [NODE] | ZONE | [LAST_CPUPID] | ... | FLAGS | */
 #define SECTIONS_PGOFF      ((sizeof(unsigned long)*8) - SECTIONS_WIDTH)
 #define NODES_PGOFF     (SECTIONS_PGOFF - NODES_WIDTH)
 #define ZONES_PGOFF     (NODES_PGOFF - ZONES_WIDTH)
 #define LAST_CPUPID_PGOFF   (ZONES_PGOFF - LAST_CPUPID_WIDTH)
 #define KASAN_TAG_PGOFF     (LAST_CPUPID_PGOFF - KASAN_TAG_WIDTH)
 
 /*
  * Define the bit shifts to access each section.  For non-existent
  * sections we define the shift as 0; that plus a 0 mask ensures
  * the compiler will optimise away reference to them.
  */
 #define SECTIONS_PGSHIFT    (SECTIONS_PGOFF * (SECTIONS_WIDTH != 0))
 #define NODES_PGSHIFT       (NODES_PGOFF * (NODES_WIDTH != 0))
 #define ZONES_PGSHIFT       (ZONES_PGOFF * (ZONES_WIDTH != 0))
 #define LAST_CPUPID_PGSHIFT (LAST_CPUPID_PGOFF * (LAST_CPUPID_WIDTH != 0))
 #define KASAN_TAG_PGSHIFT   (KASAN_TAG_PGOFF * (KASAN_TAG_WIDTH != 0))
 
 /* NODE:ZONE or SECTION:ZONE is used to ID a zone for the buddy allocator */
 #ifdef NODE_NOT_IN_PAGE_FLAGS
 #define ZONEID_SHIFT        (SECTIONS_SHIFT + ZONES_SHIFT)
 #define ZONEID_PGOFF        ((SECTIONS_PGOFF < ZONES_PGOFF) ? \
                         SECTIONS_PGOFF : ZONES_PGOFF)
 #else
 #define ZONEID_SHIFT        (NODES_SHIFT + ZONES_SHIFT)
 #define ZONEID_PGOFF        ((NODES_PGOFF < ZONES_PGOFF) ? \
                         NODES_PGOFF : ZONES_PGOFF)
 #endif
 
 #define ZONEID_PGSHIFT      (ZONEID_PGOFF * (ZONEID_SHIFT != 0))
 
 #define ZONES_MASK      ((1UL << ZONES_WIDTH) - 1)
 #define NODES_MASK      ((1UL << NODES_WIDTH) - 1)
 #define SECTIONS_MASK       ((1UL << SECTIONS_WIDTH) - 1)
 #define LAST_CPUPID_MASK    ((1UL << LAST_CPUPID_SHIFT) - 1)
 #define KASAN_TAG_MASK      ((1UL << KASAN_TAG_WIDTH) - 1)
 #define ZONEID_MASK     ((1UL << ZONEID_SHIFT) - 1)
 
 static inline enum zone_type page_zonenum(const struct page *page)
 {
     ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT);
     return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
 }
 
 static inline enum zone_type folio_zonenum(const struct folio *folio)
 {
     return page_zonenum(&folio->page);
 }
 
 #ifdef CONFIG_ZONE_DEVICE
 static inline bool is_zone_device_page(const struct page *page)
 {
     return page_zonenum(page) == ZONE_DEVICE;
 }
 extern void memmap_init_zone_device(struct zone *, unsigned long,
                     unsigned long, struct dev_pagemap *);
 #else
 static inline bool is_zone_device_page(const struct page *page)
 {
     return false;
 }
 #endif
 
 static inline bool folio_is_zone_device(const struct folio *folio)
 {
     return is_zone_device_page(&folio->page);
 }
 
 static inline bool is_zone_movable_page(const struct page *page)
 {
     return page_zonenum(page) == ZONE_MOVABLE;
 }
 #endif
 
 /*
  * Return true if [start_pfn, start_pfn + nr_pages) range has a non-empty
  * intersection with the given zone
  */
 static inline bool zone_intersects(struct zone *zone,
         unsigned long start_pfn, unsigned long nr_pages)
 {
     if (zone_is_empty(zone))
         return false;
     if (start_pfn >= zone_end_pfn(zone) ||
         start_pfn + nr_pages <= zone->zone_start_pfn)
         return false;
 
     return true;
 }
 
 /*
  * The "priority" of VM scanning is how much of the queues we will scan in one
  * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
  * queues ("queue_length >> 12") during an aging round.
  */
 #define DEF_PRIORITY 12
 
 /* Maximum number of zones on a zonelist */
 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
 
 enum {
     ZONELIST_FALLBACK,  /* zonelist with fallback */
 #ifdef CONFIG_NUMA
     /*
      * The NUMA zonelists are doubled because we need zonelists that
      * restrict the allocations to a single node for __GFP_THISNODE.
      */
     ZONELIST_NOFALLBACK,    /* zonelist without fallback (__GFP_THISNODE) */
 #endif
     MAX_ZONELISTS
 };
 
 /*
  * This struct contains information about a zone in a zonelist. It is stored
  * here to avoid dereferences into large structures and lookups of tables
  */
 struct zoneref {
     struct zone *zone;  /* Pointer to actual zone */
     int zone_idx;       /* zone_idx(zoneref->zone) */
 };
 
 /*
  * One allocation request operates on a zonelist. A zonelist
  * is a list of zones, the first one is the 'goal' of the
  * allocation, the other zones are fallback zones, in decreasing
  * priority.
  *
  * To speed the reading of the zonelist, the zonerefs contain the zone index
  * of the entry being read. Helper functions to access information given
  * a struct zoneref are
  *
  * zonelist_zone()  - Return the struct zone * for an entry in _zonerefs
  * zonelist_zone_idx()  - Return the index of the zone for an entry
  * zonelist_node_idx()  - Return the index of the node for an entry
  */
 struct zonelist {
     struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
 };
 
 /*
  * The array of struct pages for flatmem.
  * It must be declared for SPARSEMEM as well because there are configurations
  * that rely on that.
  */
 extern struct page *mem_map;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 struct deferred_split {
     spinlock_t split_queue_lock;
     struct list_head split_queue;
     unsigned long split_queue_len;
 };
 #endif
 
 /*
  * On NUMA machines, each NUMA node would have a pg_data_t to describe
  * it's memory layout. On UMA machines there is a single pglist_data which
  * describes the whole memory.
  *
  * Memory statistics and page replacement data structures are maintained on a
  * per-zone basis.
  */
 typedef struct pglist_data {
     /*
      * node_zones contains just the zones for THIS node. Not all of the
      * zones may be populated, but it is the full list. It is referenced by
      * this node's node_zonelists as well as other node's node_zonelists.
      */
     struct zone node_zones[MAX_NR_ZONES];
 
     /*
      * node_zonelists contains references to all zones in all nodes.
      * Generally the first zones will be references to this node's
      * node_zones.
      */
     struct zonelist node_zonelists[MAX_ZONELISTS];
 
     int nr_zones; /* number of populated zones in this node */
 #ifdef CONFIG_FLATMEM   /* means !SPARSEMEM */
     struct page *node_mem_map;
 #ifdef CONFIG_PAGE_EXTENSION
     struct page_ext *node_page_ext;
 #endif
 #endif
 #if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT)
     /*
      * Must be held any time you expect node_start_pfn,
      * node_present_pages, node_spanned_pages or nr_zones to stay constant.
      * Also synchronizes pgdat->first_deferred_pfn during deferred page
      * init.
      *
      * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
      * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG
      * or CONFIG_DEFERRED_STRUCT_PAGE_INIT.
      *
      * Nests above zone->lock and zone->span_seqlock
      */
     spinlock_t node_size_lock;
 #endif
     unsigned long node_start_pfn;
     unsigned long node_present_pages; /* total number of physical pages */
     unsigned long node_spanned_pages; /* total size of physical page
                          range, including holes */
     int node_id;
     wait_queue_head_t kswapd_wait;
     wait_queue_head_t pfmemalloc_wait;
 
     /* workqueues for throttling reclaim for different reasons. */
     wait_queue_head_t reclaim_wait[NR_VMSCAN_THROTTLE];
 
     atomic_t nr_writeback_throttled;/* nr of writeback-throttled tasks */
     unsigned long nr_reclaim_start; /* nr pages written while throttled
                      * when throttling started. */
     struct task_struct *kswapd; /* Protected by
                        mem_hotplug_begin/done() */
     int kswapd_order;
     enum zone_type kswapd_highest_zoneidx;
 
     int kswapd_failures;        /* Number of 'reclaimed == 0' runs */
 
 #ifdef CONFIG_COMPACTION
     int kcompactd_max_order;
     enum zone_type kcompactd_highest_zoneidx;
     wait_queue_head_t kcompactd_wait;
     struct task_struct *kcompactd;
     bool proactive_compact_trigger;
 #endif
     /*
      * This is a per-node reserve of pages that are not available
      * to userspace allocations.
      */
     unsigned long       totalreserve_pages;
 
 #ifdef CONFIG_NUMA
     /*
      * node reclaim becomes active if more unmapped pages exist.
      */
     unsigned long       min_unmapped_pages;
     unsigned long       min_slab_pages;
 #endif /* CONFIG_NUMA */
 
     /* Write-intensive fields used by page reclaim */
     ZONE_PADDING(_pad1_)
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
     /*
      * If memory initialisation on large machines is deferred then this
      * is the first PFN that needs to be initialised.
      */
     unsigned long first_deferred_pfn;
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     struct deferred_split deferred_split_queue;
 #endif
 
     /* Fields commonly accessed by the page reclaim scanner */
 
     /*
      * NOTE: THIS IS UNUSED IF MEMCG IS ENABLED.
      *
      * Use mem_cgroup_lruvec() to look up lruvecs.
      */
     struct lruvec       __lruvec;
 
     unsigned long       flags;
 
     ZONE_PADDING(_pad2_)
 
     /* Per-node vmstats */
     struct per_cpu_nodestat __percpu *per_cpu_nodestats;
     atomic_long_t       vm_stat[NR_VM_NODE_STAT_ITEMS];
 } pg_data_t;
 
 #define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
 #define node_spanned_pages(nid) (NODE_DATA(nid)->node_spanned_pages)
 
 #define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
 #define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))
 
 static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
 {
     return pgdat->node_start_pfn + pgdat->node_spanned_pages;
 }
 
 static inline bool pgdat_is_empty(pg_data_t *pgdat)
 {
     return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
 }
 
 #include <linux/memory_hotplug.h>
 
 void build_all_zonelists(pg_data_t *pgdat);
 void wakeup_kswapd(struct zone *zone, gfp_t gfp_mask, int order,
            enum zone_type highest_zoneidx);
 bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
              int highest_zoneidx, unsigned int alloc_flags,
              long free_pages);
 bool zone_watermark_ok(struct zone *z, unsigned int order,
         unsigned long mark, int highest_zoneidx,
         unsigned int alloc_flags);
 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
         unsigned long mark, int highest_zoneidx);
 /*
  * Memory initialization context, use to differentiate memory added by
  * the platform statically or via memory hotplug interface.
  */
 enum meminit_context {
     MEMINIT_EARLY,
     MEMINIT_HOTPLUG,
 };
 
 extern void init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
                      unsigned long size);
 
 extern void lruvec_init(struct lruvec *lruvec);
 
 static inline struct pglist_data *lruvec_pgdat(struct lruvec *lruvec)
 {
 #ifdef CONFIG_MEMCG
     return lruvec->pgdat;
 #else
     return container_of(lruvec, struct pglist_data, __lruvec);
 #endif
 }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 int local_memory_node(int node_id);
 #else
 static inline int local_memory_node(int node_id) { return node_id; };
 #endif
 
 /*
  * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
  */
 #define zone_idx(zone)      ((zone) - (zone)->zone_pgdat->node_zones)
 
 #ifdef CONFIG_ZONE_DEVICE
 static inline bool zone_is_zone_device(struct zone *zone)
 {
     return zone_idx(zone) == ZONE_DEVICE;
 }
 #else
 static inline bool zone_is_zone_device(struct zone *zone)
 {
     return false;
 }
 #endif
 
 /*
  * Returns true if a zone has pages managed by the buddy allocator.
  * All the reclaim decisions have to use this function rather than
  * populated_zone(). If the whole zone is reserved then we can easily
  * end up with populated_zone() && !managed_zone().
  */
 static inline bool managed_zone(struct zone *zone)
 {
     return zone_managed_pages(zone);
 }
 
 /* Returns true if a zone has memory */
 static inline bool populated_zone(struct zone *zone)
 {
     return zone->present_pages;
 }
 
 #ifdef CONFIG_NUMA
 static inline int zone_to_nid(struct zone *zone)
 {
     return zone->node;
 }
 
 static inline void zone_set_nid(struct zone *zone, int nid)
 {
     zone->node = nid;
 }
 #else
 static inline int zone_to_nid(struct zone *zone)
 {
     return 0;
 }
 
 static inline void zone_set_nid(struct zone *zone, int nid) {}
 #endif
 
 extern int movable_zone;
 
 static inline int is_highmem_idx(enum zone_type idx)
 {
 #ifdef CONFIG_HIGHMEM
     return (idx == ZONE_HIGHMEM ||
         (idx == ZONE_MOVABLE && movable_zone == ZONE_HIGHMEM));
 #else
     return 0;
 #endif
 }
 
 /**
  * is_highmem - helper function to quickly check if a struct zone is a
  *              highmem zone or not.  This is an attempt to keep references
  *              to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
  * @zone: pointer to struct zone variable
  * Return: 1 for a highmem zone, 0 otherwise
  */
 static inline int is_highmem(struct zone *zone)
 {
     return is_highmem_idx(zone_idx(zone));
 }
 
 #ifdef CONFIG_ZONE_DMA
 bool has_managed_dma(void);
 #else
 static inline bool has_managed_dma(void)
 {
     return false;
 }
 #endif
 
 /* These two functions are used to setup the per zone pages min values */
 struct ctl_table;
 
 int min_free_kbytes_sysctl_handler(struct ctl_table *, int, void *, size_t *,
         loff_t *);
 int watermark_scale_factor_sysctl_handler(struct ctl_table *, int, void *,
         size_t *, loff_t *);
 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES];
 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, void *,
         size_t *, loff_t *);
 int percpu_pagelist_high_fraction_sysctl_handler(struct ctl_table *, int,
         void *, size_t *, loff_t *);
 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
         void *, size_t *, loff_t *);
 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
         void *, size_t *, loff_t *);
 int numa_zonelist_order_handler(struct ctl_table *, int,
         void *, size_t *, loff_t *);
 extern int percpu_pagelist_high_fraction;
 extern char numa_zonelist_order[];
 #define NUMA_ZONELIST_ORDER_LEN 16
 
 #ifndef CONFIG_NUMA
 
 extern struct pglist_data contig_page_data;
 static inline struct pglist_data *NODE_DATA(int nid)
 {
     return &contig_page_data;
 }
 
 #else /* CONFIG_NUMA */
 
 #include <asm/mmzone.h>
 
 #endif /* !CONFIG_NUMA */
 
 extern struct pglist_data *first_online_pgdat(void);
 extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
 extern struct zone *next_zone(struct zone *zone);
 
 /**
  * for_each_online_pgdat - helper macro to iterate over all online nodes
  * @pgdat: pointer to a pg_data_t variable
  */
 #define for_each_online_pgdat(pgdat)            \
     for (pgdat = first_online_pgdat();      \
          pgdat;                 \
          pgdat = next_online_pgdat(pgdat))
 /**
  * for_each_zone - helper macro to iterate over all memory zones
  * @zone: pointer to struct zone variable
  *
  * The user only needs to declare the zone variable, for_each_zone
  * fills it in.
  */
 #define for_each_zone(zone)                 \
     for (zone = (first_online_pgdat())->node_zones; \
          zone;                  \
          zone = next_zone(zone))
 
 #define for_each_populated_zone(zone)               \
     for (zone = (first_online_pgdat())->node_zones; \
          zone;                  \
          zone = next_zone(zone))            \
         if (!populated_zone(zone))      \
             ; /* do nothing */      \
         else
 
 static inline struct zone *zonelist_zone(struct zoneref *zoneref)
 {
     return zoneref->zone;
 }
 
 static inline int zonelist_zone_idx(struct zoneref *zoneref)
 {
     return zoneref->zone_idx;
 }
 
 static inline int zonelist_node_idx(struct zoneref *zoneref)
 {
     return zone_to_nid(zoneref->zone);
 }
 
 struct zoneref *__next_zones_zonelist(struct zoneref *z,
                     enum zone_type highest_zoneidx,
                     nodemask_t *nodes);
 
 /**
  * next_zones_zonelist - Returns the next zone at or below highest_zoneidx within the allowed nodemask using a cursor within a zonelist as a starting point
  * @z: The cursor used as a starting point for the search
  * @highest_zoneidx: The zone index of the highest zone to return
  * @nodes: An optional nodemask to filter the zonelist with
  *
  * This function returns the next zone at or below a given zone index that is
  * within the allowed nodemask using a cursor as the starting point for the
  * search. The zoneref returned is a cursor that represents the current zone
  * being examined. It should be advanced by one before calling
  * next_zones_zonelist again.
  *
  * Return: the next zone at or below highest_zoneidx within the allowed
  * nodemask using a cursor within a zonelist as a starting point
  */
 static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
                     enum zone_type highest_zoneidx,
                     nodemask_t *nodes)
 {
     if (likely(!nodes && zonelist_zone_idx(z) <= highest_zoneidx))
         return z;
     return __next_zones_zonelist(z, highest_zoneidx, nodes);
 }
 
 /**
  * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
  * @zonelist: The zonelist to search for a suitable zone
  * @highest_zoneidx: The zone index of the highest zone to return
  * @nodes: An optional nodemask to filter the zonelist with
  *
  * This function returns the first zone at or below a given zone index that is
  * within the allowed nodemask. The zoneref returned is a cursor that can be
  * used to iterate the zonelist with next_zones_zonelist by advancing it by
  * one before calling.
  *
  * When no eligible zone is found, zoneref->zone is NULL (zoneref itself is
  * never NULL). This may happen either genuinely, or due to concurrent nodemask
  * update due to cpuset modification.
  *
  * Return: Zoneref pointer for the first suitable zone found
  */
 static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
                     enum zone_type highest_zoneidx,
                     nodemask_t *nodes)
 {
     return next_zones_zonelist(zonelist->_zonerefs,
                             highest_zoneidx, nodes);
 }
 
 /**
  * for_each_zone_zonelist_nodemask - helper macro to iterate over valid zones in a zonelist at or below a given zone index and within a nodemask
  * @zone: The current zone in the iterator
  * @z: The current pointer within zonelist->_zonerefs being iterated
  * @zlist: The zonelist being iterated
  * @highidx: The zone index of the highest zone to return
  * @nodemask: Nodemask allowed by the allocator
  *
  * This iterator iterates though all zones at or below a given zone index and
  * within a given nodemask
  */
 #define for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \
     for (z = first_zones_zonelist(zlist, highidx, nodemask), zone = zonelist_zone(z);   \
         zone;                           \
         z = next_zones_zonelist(++z, highidx, nodemask),    \
             zone = zonelist_zone(z))
 
 #define for_next_zone_zonelist_nodemask(zone, z, highidx, nodemask) \
     for (zone = z->zone;    \
         zone;                           \
         z = next_zones_zonelist(++z, highidx, nodemask),    \
             zone = zonelist_zone(z))
 
 
 /**
  * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
  * @zone: The current zone in the iterator
  * @z: The current pointer within zonelist->zones being iterated
  * @zlist: The zonelist being iterated
  * @highidx: The zone index of the highest zone to return
  *
  * This iterator iterates though all zones at or below a given zone index.
  */
 #define for_each_zone_zonelist(zone, z, zlist, highidx) \
     for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)
 
 /* Whether the 'nodes' are all movable nodes */
 static inline bool movable_only_nodes(nodemask_t *nodes)
 {
     struct zonelist *zonelist;
     struct zoneref *z;
     int nid;
 
     if (nodes_empty(*nodes))
         return false;
 
     /*
      * We can chose arbitrary node from the nodemask to get a
      * zonelist as they are interlinked. We just need to find
      * at least one zone that can satisfy kernel allocations.
      */
     nid = first_node(*nodes);
     zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
     z = first_zones_zonelist(zonelist, ZONE_NORMAL, nodes);
     return (!z->zone) ? true : false;
 }
 
 
 #ifdef CONFIG_SPARSEMEM
 #include <asm/sparsemem.h>
 #endif
 
 #ifdef CONFIG_FLATMEM
 #define pfn_to_nid(pfn)     (0)
 #endif
 
 #ifdef CONFIG_SPARSEMEM
 
 /*
  * PA_SECTION_SHIFT     physical address to/from section number
  * PFN_SECTION_SHIFT        pfn to/from section number
  */
 #define PA_SECTION_SHIFT    (SECTION_SIZE_BITS)
 #define PFN_SECTION_SHIFT   (SECTION_SIZE_BITS - PAGE_SHIFT)
 
 #define NR_MEM_SECTIONS     (1UL << SECTIONS_SHIFT)
 
 #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
 #define PAGE_SECTION_MASK   (~(PAGES_PER_SECTION-1))
 
 #define SECTION_BLOCKFLAGS_BITS \
     ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
 
 #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
 #error Allocator MAX_ORDER exceeds SECTION_SIZE
 #endif
 
 static inline unsigned long pfn_to_section_nr(unsigned long pfn)
 {
     return pfn >> PFN_SECTION_SHIFT;
 }
 static inline unsigned long section_nr_to_pfn(unsigned long sec)
 {
     return sec << PFN_SECTION_SHIFT;
 }
 
 #define SECTION_ALIGN_UP(pfn)   (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
 #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)
 
 #define SUBSECTION_SHIFT 21
 #define SUBSECTION_SIZE (1UL << SUBSECTION_SHIFT)
 
 #define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT)
 #define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT)
 #define PAGE_SUBSECTION_MASK (~(PAGES_PER_SUBSECTION-1))
 
 #if SUBSECTION_SHIFT > SECTION_SIZE_BITS
 #error Subsection size exceeds section size
 #else
 #define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT))
 #endif
 
 #define SUBSECTION_ALIGN_UP(pfn) ALIGN((pfn), PAGES_PER_SUBSECTION)
 #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
 
 struct mem_section_usage {
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
     DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
 #endif
     /* See declaration of similar field in struct zone */
     unsigned long pageblock_flags[0];
 };
 
 void subsection_map_init(unsigned long pfn, unsigned long nr_pages);
 
 struct page;
 struct page_ext;
 struct mem_section {
     /*
      * This is, logically, a pointer to an array of struct
      * pages.  However, it is stored with some other magic.
      * (see sparse.c::sparse_init_one_section())
      *
      * Additionally during early boot we encode node id of
      * the location of the section here to guide allocation.
      * (see sparse.c::memory_present())
      *
      * Making it a UL at least makes someone do a cast
      * before using it wrong.
      */
     unsigned long section_mem_map;
 
     struct mem_section_usage *usage;
 #ifdef CONFIG_PAGE_EXTENSION
     /*
      * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use
      * section. (see page_ext.h about this.)
      */
     struct page_ext *page_ext;
     unsigned long pad;
 #endif
     /*
      * WARNING: mem_section must be a power-of-2 in size for the
      * calculation and use of SECTION_ROOT_MASK to make sense.
      */
 };
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
 #define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
 #else
 #define SECTIONS_PER_ROOT   1
 #endif
 
 #define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
 #define NR_SECTION_ROOTS    DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
 #define SECTION_ROOT_MASK   (SECTIONS_PER_ROOT - 1)
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
 extern struct mem_section **mem_section;
 #else
 extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
 #endif
 
 static inline unsigned long *section_to_usemap(struct mem_section *ms)
 {
     return ms->usage->pageblock_flags;
 }
 
 static inline struct mem_section *__nr_to_section(unsigned long nr)
 {
     unsigned long root = SECTION_NR_TO_ROOT(nr);
 
     if (unlikely(root >= NR_SECTION_ROOTS))
         return NULL;
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
     if (!mem_section || !mem_section[root])
         return NULL;
 #endif
     return &mem_section[root][nr & SECTION_ROOT_MASK];
 }
 extern size_t mem_section_usage_size(void);
 
 /*
  * We use the lower bits of the mem_map pointer to store
  * a little bit of information.  The pointer is calculated
  * as mem_map - section_nr_to_pfn(pnum).  The result is
  * aligned to the minimum alignment of the two values:
  *   1. All mem_map arrays are page-aligned.
  *   2. section_nr_to_pfn() always clears PFN_SECTION_SHIFT
  *      lowest bits.  PFN_SECTION_SHIFT is arch-specific
  *      (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the
  *      worst combination is powerpc with 256k pages,
  *      which results in PFN_SECTION_SHIFT equal 6.
  * To sum it up, at least 6 bits are available on all architectures.
  * However, we can exceed 6 bits on some other architectures except
  * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available
  * with the worst case of 64K pages on arm64) if we make sure the
  * exceeded bit is not applicable to powerpc.
  */
 enum {
     SECTION_MARKED_PRESENT_BIT,
     SECTION_HAS_MEM_MAP_BIT,
     SECTION_IS_ONLINE_BIT,
     SECTION_IS_EARLY_BIT,
 #ifdef CONFIG_ZONE_DEVICE
     SECTION_TAINT_ZONE_DEVICE_BIT,
 #endif
     SECTION_MAP_LAST_BIT,
 };
 
 #define SECTION_MARKED_PRESENT      BIT(SECTION_MARKED_PRESENT_BIT)
 #define SECTION_HAS_MEM_MAP     BIT(SECTION_HAS_MEM_MAP_BIT)
 #define SECTION_IS_ONLINE       BIT(SECTION_IS_ONLINE_BIT)
 #define SECTION_IS_EARLY        BIT(SECTION_IS_EARLY_BIT)
 #ifdef CONFIG_ZONE_DEVICE
 #define SECTION_TAINT_ZONE_DEVICE   BIT(SECTION_TAINT_ZONE_DEVICE_BIT)
 #endif
 #define SECTION_MAP_MASK        (~(BIT(SECTION_MAP_LAST_BIT) - 1))
 #define SECTION_NID_SHIFT       SECTION_MAP_LAST_BIT
 
 static inline struct page *__section_mem_map_addr(struct mem_section *section)
 {
     unsigned long map = section->section_mem_map;
     map &= SECTION_MAP_MASK;
     return (struct page *)map;
 }
 
 static inline int present_section(struct mem_section *section)
 {
     return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
 }
 
 static inline int present_section_nr(unsigned long nr)
 {
     return present_section(__nr_to_section(nr));
 }
 
 static inline int valid_section(struct mem_section *section)
 {
     return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
 }
 
 static inline int early_section(struct mem_section *section)
 {
     return (section && (section->section_mem_map & SECTION_IS_EARLY));
 }
 
 static inline int valid_section_nr(unsigned long nr)
 {
     return valid_section(__nr_to_section(nr));
 }
 
 static inline int online_section(struct mem_section *section)
 {
     return (section && (section->section_mem_map & SECTION_IS_ONLINE));
 }
 
 #ifdef CONFIG_ZONE_DEVICE
 static inline int online_device_section(struct mem_section *section)
 {
     unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE;
 
     return section && ((section->section_mem_map & flags) == flags);
 }
 #else
 static inline int online_device_section(struct mem_section *section)
 {
     return 0;
 }
 #endif
 
 static inline int online_section_nr(unsigned long nr)
 {
     return online_section(__nr_to_section(nr));
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
 void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
 #endif
 
 static inline struct mem_section *__pfn_to_section(unsigned long pfn)
 {
     return __nr_to_section(pfn_to_section_nr(pfn));
 }
 
 extern unsigned long __highest_present_section_nr;
 
 static inline int subsection_map_index(unsigned long pfn)
 {
     return (pfn & ~(PAGE_SECTION_MASK)) / PAGES_PER_SUBSECTION;
 }
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
 {
     int idx = subsection_map_index(pfn);
 
     return test_bit(idx, ms->usage->subsection_map);
 }
 #else
 static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
 {
     return 1;
 }
 #endif
 
 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
 /**
  * pfn_valid - check if there is a valid memory map entry for a PFN
  * @pfn: the page frame number to check
  *
  * Check if there is a valid memory map entry aka struct page for the @pfn.
  * Note, that availability of the memory map entry does not imply that
  * there is actual usable memory at that @pfn. The struct page may
  * represent a hole or an unusable page frame.
  *
  * Return: 1 for PFNs that have memory map entries and 0 otherwise
  */
 static inline int pfn_valid(unsigned long pfn)
 {
     struct mem_section *ms;
 
     /*
      * Ensure the upper PAGE_SHIFT bits are clear in the
      * pfn. Else it might lead to false positives when
      * some of the upper bits are set, but the lower bits
      * match a valid pfn.
      */
     if (PHYS_PFN(PFN_PHYS(pfn)) != pfn)
         return 0;
 
     if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
         return 0;
     ms = __pfn_to_section(pfn);
     if (!valid_section(ms))
         return 0;
     /*
      * Traditionally early sections always returned pfn_valid() for
      * the entire section-sized span.
      */
     return early_section(ms) || pfn_section_valid(ms, pfn);
 }
 #endif
 
 static inline int pfn_in_present_section(unsigned long pfn)
 {
     if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
         return 0;
     return present_section(__pfn_to_section(pfn));
 }
 
 static inline unsigned long next_present_section_nr(unsigned long section_nr)
 {
     while (++section_nr <= __highest_present_section_nr) {
         if (present_section_nr(section_nr))
             return section_nr;
     }
 
     return -1;
 }
 
 /*
  * These are _only_ used during initialisation, therefore they
  * can use __initdata ...  They could have names to indicate
  * this restriction.
  */
 #ifdef CONFIG_NUMA
 #define pfn_to_nid(pfn)                         \
 ({                                  \
     unsigned long __pfn_to_nid_pfn = (pfn);             \
     page_to_nid(pfn_to_page(__pfn_to_nid_pfn));         \
 })
 #else
 #define pfn_to_nid(pfn)     (0)
 #endif
 
 void sparse_init(void);
 #else
 #define sparse_init()   do {} while (0)
 #define sparse_index_init(_sec, _nid)  do {} while (0)
 #define pfn_in_present_section pfn_valid
 #define subsection_map_init(_pfn, _nr_pages) do {} while (0)
 #endif /* CONFIG_SPARSEMEM */
 
 #endif /* !__GENERATING_BOUNDS.H */
 #endif /* !__ASSEMBLY__ */
 #endif /* _LINUX_MMZONE_H */

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