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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/memory_hotplug.c
  *
  *  Copyright (C)
  */
 
 #include <linux/stddef.h>
 #include <linux/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/swap.h>
 #include <linux/interrupt.h>
 #include <linux/pagemap.h>
 #include <linux/compiler.h>
 #include <linux/export.h>
 #include <linux/pagevec.h>
 #include <linux/writeback.h>
 #include <linux/slab.h>
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
 #include <linux/memory.h>
 #include <linux/memremap.h>
 #include <linux/memory_hotplug.h>
 #include <linux/vmalloc.h>
 #include <linux/ioport.h>
 #include <linux/delay.h>
 #include <linux/migrate.h>
 #include <linux/page-isolation.h>
 #include <linux/pfn.h>
 #include <linux/suspend.h>
 #include <linux/mm_inline.h>
 #include <linux/firmware-map.h>
 #include <linux/stop_machine.h>
 #include <linux/hugetlb.h>
 #include <linux/memblock.h>
 #include <linux/compaction.h>
 #include <linux/rmap.h>
 #include <linux/module.h>
 
 #include <asm/tlbflush.h>
 
 #include "internal.h"
 #include "shuffle.h"
 
 #ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
 /*
  * memory_hotplug.memmap_on_memory parameter
  */
 static bool memmap_on_memory __ro_after_init;
 module_param(memmap_on_memory, bool, 0444);
 MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
 
 static inline bool mhp_memmap_on_memory(void)
 {
     return memmap_on_memory;
 }
 #else
 static inline bool mhp_memmap_on_memory(void)
 {
     return false;
 }
 #endif
 
 enum {
     ONLINE_POLICY_CONTIG_ZONES = 0,
     ONLINE_POLICY_AUTO_MOVABLE,
 };
 
 static const char * const online_policy_to_str[] = {
     [ONLINE_POLICY_CONTIG_ZONES] = "contig-zones",
     [ONLINE_POLICY_AUTO_MOVABLE] = "auto-movable",
 };
 
 static int set_online_policy(const char *val, const struct kernel_param *kp)
 {
     int ret = sysfs_match_string(online_policy_to_str, val);
 
     if (ret < 0)
         return ret;
     *((int *)kp->arg) = ret;
     return 0;
 }
 
 static int get_online_policy(char *buffer, const struct kernel_param *kp)
 {
     return sprintf(buffer, "%s\n", online_policy_to_str[*((int *)kp->arg)]);
 }
 
 /*
  * memory_hotplug.online_policy: configure online behavior when onlining without
  * specifying a zone (MMOP_ONLINE)
  *
  * "contig-zones": keep zone contiguous
  * "auto-movable": online memory to ZONE_MOVABLE if the configuration
  *                 (auto_movable_ratio, auto_movable_numa_aware) allows for it
  */
 static int online_policy __read_mostly = ONLINE_POLICY_CONTIG_ZONES;
 static const struct kernel_param_ops online_policy_ops = {
     .set = set_online_policy,
     .get = get_online_policy,
 };
 module_param_cb(online_policy, &online_policy_ops, &online_policy, 0644);
 MODULE_PARM_DESC(online_policy,
         "Set the online policy (\"contig-zones\", \"auto-movable\") "
         "Default: \"contig-zones\"");
 
 /*
  * memory_hotplug.auto_movable_ratio: specify maximum MOVABLE:KERNEL ratio
  *
  * The ratio represent an upper limit and the kernel might decide to not
  * online some memory to ZONE_MOVABLE -- e.g., because hotplugged KERNEL memory
  * doesn't allow for more MOVABLE memory.
  */
 static unsigned int auto_movable_ratio __read_mostly = 301;
 module_param(auto_movable_ratio, uint, 0644);
 MODULE_PARM_DESC(auto_movable_ratio,
         "Set the maximum ratio of MOVABLE:KERNEL memory in the system "
         "in percent for \"auto-movable\" online policy. Default: 301");
 
 /*
  * memory_hotplug.auto_movable_numa_aware: consider numa node stats
  */
 #ifdef CONFIG_NUMA
 static bool auto_movable_numa_aware __read_mostly = true;
 module_param(auto_movable_numa_aware, bool, 0644);
 MODULE_PARM_DESC(auto_movable_numa_aware,
         "Consider numa node stats in addition to global stats in "
         "\"auto-movable\" online policy. Default: true");
 #endif /* CONFIG_NUMA */
 
 /*
  * online_page_callback contains pointer to current page onlining function.
  * Initially it is generic_online_page(). If it is required it could be
  * changed by calling set_online_page_callback() for callback registration
  * and restore_online_page_callback() for generic callback restore.
  */
 
 static online_page_callback_t online_page_callback = generic_online_page;
 static DEFINE_MUTEX(online_page_callback_lock);
 
 DEFINE_STATIC_PERCPU_RWSEM(mem_hotplug_lock);
 
 void get_online_mems(void)
 {
     percpu_down_read(&mem_hotplug_lock);
 }
 
 void put_online_mems(void)
 {
     percpu_up_read(&mem_hotplug_lock);
 }
 
 bool movable_node_enabled = false;
 
 #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE
 int mhp_default_online_type = MMOP_OFFLINE;
 #else
 int mhp_default_online_type = MMOP_ONLINE;
 #endif
 
 static int __init setup_memhp_default_state(char *str)
 {
     const int online_type = mhp_online_type_from_str(str);
 
     if (online_type >= 0)
         mhp_default_online_type = online_type;
 
     return 1;
 }
 __setup("memhp_default_state=", setup_memhp_default_state);
 
 void mem_hotplug_begin(void)
 {
     cpus_read_lock();
     percpu_down_write(&mem_hotplug_lock);
 }
 
 void mem_hotplug_done(void)
 {
     percpu_up_write(&mem_hotplug_lock);
     cpus_read_unlock();
 }
 
 u64 max_mem_size = U64_MAX;
 
 /* add this memory to iomem resource */
 static struct resource *register_memory_resource(u64 start, u64 size,
                          const char *resource_name)
 {
     struct resource *res;
     unsigned long flags =  IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
     if (strcmp(resource_name, "System RAM"))
         flags |= IORESOURCE_SYSRAM_DRIVER_MANAGED;
 
     if (!mhp_range_allowed(start, size, true))
         return ERR_PTR(-E2BIG);
 
     /*
      * Make sure value parsed from 'mem=' only restricts memory adding
      * while booting, so that memory hotplug won't be impacted. Please
      * refer to document of 'mem=' in kernel-parameters.txt for more
      * details.
      */
     if (start + size > max_mem_size && system_state < SYSTEM_RUNNING)
         return ERR_PTR(-E2BIG);
 
     /*
      * Request ownership of the new memory range.  This might be
      * a child of an existing resource that was present but
      * not marked as busy.
      */
     res = __request_region(&iomem_resource, start, size,
                    resource_name, flags);
 
     if (!res) {
         pr_debug("Unable to reserve System RAM region: %016llx->%016llx\n",
                 start, start + size);
         return ERR_PTR(-EEXIST);
     }
     return res;
 }
 
 static void release_memory_resource(struct resource *res)
 {
     if (!res)
         return;
     release_resource(res);
     kfree(res);
 }
 
 static int check_pfn_span(unsigned long pfn, unsigned long nr_pages)
 {
     /*
      * Disallow all operations smaller than a sub-section and only
      * allow operations smaller than a section for
      * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
      * enforces a larger memory_block_size_bytes() granularity for
      * memory that will be marked online, so this check should only
      * fire for direct arch_{add,remove}_memory() users outside of
      * add_memory_resource().
      */
     unsigned long min_align;
 
     if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
         min_align = PAGES_PER_SUBSECTION;
     else
         min_align = PAGES_PER_SECTION;
     if (!IS_ALIGNED(pfn | nr_pages, min_align))
         return -EINVAL;
     return 0;
 }
 
 /*
  * Return page for the valid pfn only if the page is online. All pfn
  * walkers which rely on the fully initialized page->flags and others
  * should use this rather than pfn_valid && pfn_to_page
  */
 struct page *pfn_to_online_page(unsigned long pfn)
 {
     unsigned long nr = pfn_to_section_nr(pfn);
     struct dev_pagemap *pgmap;
     struct mem_section *ms;
 
     if (nr >= NR_MEM_SECTIONS)
         return NULL;
 
     ms = __nr_to_section(nr);
     if (!online_section(ms))
         return NULL;
 
     /*
      * Save some code text when online_section() +
      * pfn_section_valid() are sufficient.
      */
     if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn))
         return NULL;
 
     if (!pfn_section_valid(ms, pfn))
         return NULL;
 
     if (!online_device_section(ms))
         return pfn_to_page(pfn);
 
     /*
      * Slowpath: when ZONE_DEVICE collides with
      * ZONE_{NORMAL,MOVABLE} within the same section some pfns in
      * the section may be 'offline' but 'valid'. Only
      * get_dev_pagemap() can determine sub-section online status.
      */
     pgmap = get_dev_pagemap(pfn, NULL);
     put_dev_pagemap(pgmap);
 
     /* The presence of a pgmap indicates ZONE_DEVICE offline pfn */
     if (pgmap)
         return NULL;
 
     return pfn_to_page(pfn);
 }
 EXPORT_SYMBOL_GPL(pfn_to_online_page);
 
 int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
         struct mhp_params *params)
 {
     const unsigned long end_pfn = pfn + nr_pages;
     unsigned long cur_nr_pages;
     int err;
     struct vmem_altmap *altmap = params->altmap;
 
     if (WARN_ON_ONCE(!pgprot_val(params->pgprot)))
         return -EINVAL;
 
     VM_BUG_ON(!mhp_range_allowed(PFN_PHYS(pfn), nr_pages * PAGE_SIZE, false));
 
     if (altmap) {
         /*
          * Validate altmap is within bounds of the total request
          */
         if (altmap->base_pfn != pfn
                 || vmem_altmap_offset(altmap) > nr_pages) {
             pr_warn_once("memory add fail, invalid altmap\n");
             return -EINVAL;
         }
         altmap->alloc = 0;
     }
 
     if (check_pfn_span(pfn, nr_pages)) {
         WARN(1, "Misaligned %s start: %#lx end: #%lx\n", __func__, pfn, pfn + nr_pages - 1);
         return -EINVAL;
     }
 
     for (; pfn < end_pfn; pfn += cur_nr_pages) {
         /* Select all remaining pages up to the next section boundary */
         cur_nr_pages = min(end_pfn - pfn,
                    SECTION_ALIGN_UP(pfn + 1) - pfn);
         err = sparse_add_section(nid, pfn, cur_nr_pages, altmap,
                      params->pgmap);
         if (err)
             break;
         cond_resched();
     }
     vmemmap_populate_print_last();
     return err;
 }
 
 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
 static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
                      unsigned long start_pfn,
                      unsigned long end_pfn)
 {
     for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUBSECTION) {
         if (unlikely(!pfn_to_online_page(start_pfn)))
             continue;
 
         if (unlikely(pfn_to_nid(start_pfn) != nid))
             continue;
 
         if (zone != page_zone(pfn_to_page(start_pfn)))
             continue;
 
         return start_pfn;
     }
 
     return 0;
 }
 
 /* find the biggest valid pfn in the range [start_pfn, end_pfn). */
 static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,
                     unsigned long start_pfn,
                     unsigned long end_pfn)
 {
     unsigned long pfn;
 
     /* pfn is the end pfn of a memory section. */
     pfn = end_pfn - 1;
     for (; pfn >= start_pfn; pfn -= PAGES_PER_SUBSECTION) {
         if (unlikely(!pfn_to_online_page(pfn)))
             continue;
 
         if (unlikely(pfn_to_nid(pfn) != nid))
             continue;
 
         if (zone != page_zone(pfn_to_page(pfn)))
             continue;
 
         return pfn;
     }
 
     return 0;
 }
 
 static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
                  unsigned long end_pfn)
 {
     unsigned long pfn;
     int nid = zone_to_nid(zone);
 
     if (zone->zone_start_pfn == start_pfn) {
         /*
          * If the section is smallest section in the zone, it need
          * shrink zone->zone_start_pfn and zone->zone_spanned_pages.
          * In this case, we find second smallest valid mem_section
          * for shrinking zone.
          */
         pfn = find_smallest_section_pfn(nid, zone, end_pfn,
                         zone_end_pfn(zone));
         if (pfn) {
             zone->spanned_pages = zone_end_pfn(zone) - pfn;
             zone->zone_start_pfn = pfn;
         } else {
             zone->zone_start_pfn = 0;
             zone->spanned_pages = 0;
         }
     } else if (zone_end_pfn(zone) == end_pfn) {
         /*
          * If the section is biggest section in the zone, it need
          * shrink zone->spanned_pages.
          * In this case, we find second biggest valid mem_section for
          * shrinking zone.
          */
         pfn = find_biggest_section_pfn(nid, zone, zone->zone_start_pfn,
                            start_pfn);
         if (pfn)
             zone->spanned_pages = pfn - zone->zone_start_pfn + 1;
         else {
             zone->zone_start_pfn = 0;
             zone->spanned_pages = 0;
         }
     }
 }
 
 static void update_pgdat_span(struct pglist_data *pgdat)
 {
     unsigned long node_start_pfn = 0, node_end_pfn = 0;
     struct zone *zone;
 
     for (zone = pgdat->node_zones;
          zone < pgdat->node_zones + MAX_NR_ZONES; zone++) {
         unsigned long end_pfn = zone_end_pfn(zone);
 
         /* No need to lock the zones, they can't change. */
         if (!zone->spanned_pages)
             continue;
         if (!node_end_pfn) {
             node_start_pfn = zone->zone_start_pfn;
             node_end_pfn = end_pfn;
             continue;
         }
 
         if (end_pfn > node_end_pfn)
             node_end_pfn = end_pfn;
         if (zone->zone_start_pfn < node_start_pfn)
             node_start_pfn = zone->zone_start_pfn;
     }
 
     pgdat->node_start_pfn = node_start_pfn;
     pgdat->node_spanned_pages = node_end_pfn - node_start_pfn;
 }
 
 void __ref remove_pfn_range_from_zone(struct zone *zone,
                       unsigned long start_pfn,
                       unsigned long nr_pages)
 {
     const unsigned long end_pfn = start_pfn + nr_pages;
     struct pglist_data *pgdat = zone->zone_pgdat;
     unsigned long pfn, cur_nr_pages;
 
     /* Poison struct pages because they are now uninitialized again. */
     for (pfn = start_pfn; pfn < end_pfn; pfn += cur_nr_pages) {
         cond_resched();
 
         /* Select all remaining pages up to the next section boundary */
         cur_nr_pages =
             min(end_pfn - pfn, SECTION_ALIGN_UP(pfn + 1) - pfn);
         page_init_poison(pfn_to_page(pfn),
                  sizeof(struct page) * cur_nr_pages);
     }
 
     /*
      * Zone shrinking code cannot properly deal with ZONE_DEVICE. So
      * we will not try to shrink the zones - which is okay as
      * set_zone_contiguous() cannot deal with ZONE_DEVICE either way.
      */
     if (zone_is_zone_device(zone))
         return;
 
     clear_zone_contiguous(zone);
 
     shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);
     update_pgdat_span(pgdat);
 
     set_zone_contiguous(zone);
 }
 
 static void __remove_section(unsigned long pfn, unsigned long nr_pages,
                  unsigned long map_offset,
                  struct vmem_altmap *altmap)
 {
     struct mem_section *ms = __pfn_to_section(pfn);
 
     if (WARN_ON_ONCE(!valid_section(ms)))
         return;
 
     sparse_remove_section(ms, pfn, nr_pages, map_offset, altmap);
 }
 
 /**
  * __remove_pages() - remove sections of pages
  * @pfn: starting pageframe (must be aligned to start of a section)
  * @nr_pages: number of pages to remove (must be multiple of section size)
  * @altmap: alternative device page map or %NULL if default memmap is used
  *
  * Generic helper function to remove section mappings and sysfs entries
  * for the section of the memory we are removing. Caller needs to make
  * sure that pages are marked reserved and zones are adjust properly by
  * calling offline_pages().
  */
 void __remove_pages(unsigned long pfn, unsigned long nr_pages,
             struct vmem_altmap *altmap)
 {
     const unsigned long end_pfn = pfn + nr_pages;
     unsigned long cur_nr_pages;
     unsigned long map_offset = 0;
 
     map_offset = vmem_altmap_offset(altmap);
 
     if (check_pfn_span(pfn, nr_pages)) {
         WARN(1, "Misaligned %s start: %#lx end: #%lx\n", __func__, pfn, pfn + nr_pages - 1);
         return;
     }
 
     for (; pfn < end_pfn; pfn += cur_nr_pages) {
         cond_resched();
         /* Select all remaining pages up to the next section boundary */
         cur_nr_pages = min(end_pfn - pfn,
                    SECTION_ALIGN_UP(pfn + 1) - pfn);
         __remove_section(pfn, cur_nr_pages, map_offset, altmap);
         map_offset = 0;
     }
 }
 
 int set_online_page_callback(online_page_callback_t callback)
 {
     int rc = -EINVAL;
 
     get_online_mems();
     mutex_lock(&online_page_callback_lock);
 
     if (online_page_callback == generic_online_page) {
         online_page_callback = callback;
         rc = 0;
     }
 
     mutex_unlock(&online_page_callback_lock);
     put_online_mems();
 
     return rc;
 }
 EXPORT_SYMBOL_GPL(set_online_page_callback);
 
 int restore_online_page_callback(online_page_callback_t callback)
 {
     int rc = -EINVAL;
 
     get_online_mems();
     mutex_lock(&online_page_callback_lock);
 
     if (online_page_callback == callback) {
         online_page_callback = generic_online_page;
         rc = 0;
     }
 
     mutex_unlock(&online_page_callback_lock);
     put_online_mems();
 
     return rc;
 }
 EXPORT_SYMBOL_GPL(restore_online_page_callback);
 
 void generic_online_page(struct page *page, unsigned int order)
 {
     /*
      * Freeing the page with debug_pagealloc enabled will try to unmap it,
      * so we should map it first. This is better than introducing a special
      * case in page freeing fast path.
      */
     debug_pagealloc_map_pages(page, 1 << order);
     __free_pages_core(page, order);
     totalram_pages_add(1UL << order);
 }
 EXPORT_SYMBOL_GPL(generic_online_page);
 
 static void online_pages_range(unsigned long start_pfn, unsigned long nr_pages)
 {
     const unsigned long end_pfn = start_pfn + nr_pages;
     unsigned long pfn;
 
     /*
      * Online the pages in MAX_ORDER - 1 aligned chunks. The callback might
      * decide to not expose all pages to the buddy (e.g., expose them
      * later). We account all pages as being online and belonging to this
      * zone ("present").
      * When using memmap_on_memory, the range might not be aligned to
      * MAX_ORDER_NR_PAGES - 1, but pageblock aligned. __ffs() will detect
      * this and the first chunk to online will be pageblock_nr_pages.
      */
     for (pfn = start_pfn; pfn < end_pfn;) {
         int order = min(MAX_ORDER - 1UL, __ffs(pfn));
 
         (*online_page_callback)(pfn_to_page(pfn), order);
         pfn += (1UL << order);
     }
 
     /* mark all involved sections as online */
     online_mem_sections(start_pfn, end_pfn);
 }
 
 /* check which state of node_states will be changed when online memory */
 static void node_states_check_changes_online(unsigned long nr_pages,
     struct zone *zone, struct memory_notify *arg)
 {
     int nid = zone_to_nid(zone);
 
     arg->status_change_nid = NUMA_NO_NODE;
     arg->status_change_nid_normal = NUMA_NO_NODE;
 
     if (!node_state(nid, N_MEMORY))
         arg->status_change_nid = nid;
     if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
         arg->status_change_nid_normal = nid;
 }
 
 static void node_states_set_node(int node, struct memory_notify *arg)
 {
     if (arg->status_change_nid_normal >= 0)
         node_set_state(node, N_NORMAL_MEMORY);
 
     if (arg->status_change_nid >= 0)
         node_set_state(node, N_MEMORY);
 }
 
 static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,
         unsigned long nr_pages)
 {
     unsigned long old_end_pfn = zone_end_pfn(zone);
 
     if (zone_is_empty(zone) || start_pfn < zone->zone_start_pfn)
         zone->zone_start_pfn = start_pfn;
 
     zone->spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - zone->zone_start_pfn;
 }
 
 static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned long start_pfn,
                                      unsigned long nr_pages)
 {
     unsigned long old_end_pfn = pgdat_end_pfn(pgdat);
 
     if (!pgdat->node_spanned_pages || start_pfn < pgdat->node_start_pfn)
         pgdat->node_start_pfn = start_pfn;
 
     pgdat->node_spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - pgdat->node_start_pfn;
 
 }
 
 #ifdef CONFIG_ZONE_DEVICE
 static void section_taint_zone_device(unsigned long pfn)
 {
     struct mem_section *ms = __pfn_to_section(pfn);
 
     ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE;
 }
 #else
 static inline void section_taint_zone_device(unsigned long pfn)
 {
 }
 #endif
 
 /*
  * Associate the pfn range with the given zone, initializing the memmaps
  * and resizing the pgdat/zone data to span the added pages. After this
  * call, all affected pages are PG_reserved.
  *
  * 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 __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
                   unsigned long nr_pages,
                   struct vmem_altmap *altmap, int migratetype)
 {
     struct pglist_data *pgdat = zone->zone_pgdat;
     int nid = pgdat->node_id;
 
     clear_zone_contiguous(zone);
 
     if (zone_is_empty(zone))
         init_currently_empty_zone(zone, start_pfn, nr_pages);
     resize_zone_range(zone, start_pfn, nr_pages);
     resize_pgdat_range(pgdat, start_pfn, nr_pages);
 
     /*
      * Subsection population requires care in pfn_to_online_page().
      * Set the taint to enable the slow path detection of
      * ZONE_DEVICE pages in an otherwise  ZONE_{NORMAL,MOVABLE}
      * section.
      */
     if (zone_is_zone_device(zone)) {
         if (!IS_ALIGNED(start_pfn, PAGES_PER_SECTION))
             section_taint_zone_device(start_pfn);
         if (!IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION))
             section_taint_zone_device(start_pfn + nr_pages);
     }
 
     /*
      * TODO now we have a visible range of pages which are not associated
      * with their zone properly. Not nice but set_pfnblock_flags_mask
      * expects the zone spans the pfn range. All the pages in the range
      * are reserved so nobody should be touching them so we should be safe
      */
     memmap_init_range(nr_pages, nid, zone_idx(zone), start_pfn, 0,
              MEMINIT_HOTPLUG, altmap, migratetype);
 
     set_zone_contiguous(zone);
 }
 
 struct auto_movable_stats {
     unsigned long kernel_early_pages;
     unsigned long movable_pages;
 };
 
 static void auto_movable_stats_account_zone(struct auto_movable_stats *stats,
                         struct zone *zone)
 {
     if (zone_idx(zone) == ZONE_MOVABLE) {
         stats->movable_pages += zone->present_pages;
     } else {
         stats->kernel_early_pages += zone->present_early_pages;
 #ifdef CONFIG_CMA
         /*
          * CMA pages (never on hotplugged memory) behave like
          * ZONE_MOVABLE.
          */
         stats->movable_pages += zone->cma_pages;
         stats->kernel_early_pages -= zone->cma_pages;
 #endif /* CONFIG_CMA */
     }
 }
 struct auto_movable_group_stats {
     unsigned long movable_pages;
     unsigned long req_kernel_early_pages;
 };
 
 static int auto_movable_stats_account_group(struct memory_group *group,
                        void *arg)
 {
     const int ratio = READ_ONCE(auto_movable_ratio);
     struct auto_movable_group_stats *stats = arg;
     long pages;
 
     /*
      * We don't support modifying the config while the auto-movable online
      * policy is already enabled. Just avoid the division by zero below.
      */
     if (!ratio)
         return 0;
 
     /*
      * Calculate how many early kernel pages this group requires to
      * satisfy the configured zone ratio.
      */
     pages = group->present_movable_pages * 100 / ratio;
     pages -= group->present_kernel_pages;
 
     if (pages > 0)
         stats->req_kernel_early_pages += pages;
     stats->movable_pages += group->present_movable_pages;
     return 0;
 }
 
 static bool auto_movable_can_online_movable(int nid, struct memory_group *group,
                         unsigned long nr_pages)
 {
     unsigned long kernel_early_pages, movable_pages;
     struct auto_movable_group_stats group_stats = {};
     struct auto_movable_stats stats = {};
     pg_data_t *pgdat = NODE_DATA(nid);
     struct zone *zone;
     int i;
 
     /* Walk all relevant zones and collect MOVABLE vs. KERNEL stats. */
     if (nid == NUMA_NO_NODE) {
         /* TODO: cache values */
         for_each_populated_zone(zone)
             auto_movable_stats_account_zone(&stats, zone);
     } else {
         for (i = 0; i < MAX_NR_ZONES; i++) {
             zone = pgdat->node_zones + i;
             if (populated_zone(zone))
                 auto_movable_stats_account_zone(&stats, zone);
         }
     }
 
     kernel_early_pages = stats.kernel_early_pages;
     movable_pages = stats.movable_pages;
 
     /*
      * Kernel memory inside dynamic memory group allows for more MOVABLE
      * memory within the same group. Remove the effect of all but the
      * current group from the stats.
      */
     walk_dynamic_memory_groups(nid, auto_movable_stats_account_group,
                    group, &group_stats);
     if (kernel_early_pages <= group_stats.req_kernel_early_pages)
         return false;
     kernel_early_pages -= group_stats.req_kernel_early_pages;
     movable_pages -= group_stats.movable_pages;
 
     if (group && group->is_dynamic)
         kernel_early_pages += group->present_kernel_pages;
 
     /*
      * Test if we could online the given number of pages to ZONE_MOVABLE
      * and still stay in the configured ratio.
      */
     movable_pages += nr_pages;
     return movable_pages <= (auto_movable_ratio * kernel_early_pages) / 100;
 }
 
 /*
  * Returns a default kernel memory zone for the given pfn range.
  * If no kernel zone covers this pfn range it will automatically go
  * to the ZONE_NORMAL.
  */
 static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn,
         unsigned long nr_pages)
 {
     struct pglist_data *pgdat = NODE_DATA(nid);
     int zid;
 
     for (zid = 0; zid < ZONE_NORMAL; zid++) {
         struct zone *zone = &pgdat->node_zones[zid];
 
         if (zone_intersects(zone, start_pfn, nr_pages))
             return zone;
     }
 
     return &pgdat->node_zones[ZONE_NORMAL];
 }
 
 /*
  * Determine to which zone to online memory dynamically based on user
  * configuration and system stats. We care about the following ratio:
  *
  *   MOVABLE : KERNEL
  *
  * Whereby MOVABLE is memory in ZONE_MOVABLE and KERNEL is memory in
  * one of the kernel zones. CMA pages inside one of the kernel zones really
  * behaves like ZONE_MOVABLE, so we treat them accordingly.
  *
  * We don't allow for hotplugged memory in a KERNEL zone to increase the
  * amount of MOVABLE memory we can have, so we end up with:
  *
  *   MOVABLE : KERNEL_EARLY
  *
  * Whereby KERNEL_EARLY is memory in one of the kernel zones, available sinze
  * boot. We base our calculation on KERNEL_EARLY internally, because:
  *
  * a) Hotplugged memory in one of the kernel zones can sometimes still get
  *    hotunplugged, especially when hot(un)plugging individual memory blocks.
  *    There is no coordination across memory devices, therefore "automatic"
  *    hotunplugging, as implemented in hypervisors, could result in zone
  *    imbalances.
  * b) Early/boot memory in one of the kernel zones can usually not get
  *    hotunplugged again (e.g., no firmware interface to unplug, fragmented
  *    with unmovable allocations). While there are corner cases where it might
  *    still work, it is barely relevant in practice.
  *
  * Exceptions are dynamic memory groups, which allow for more MOVABLE
  * memory within the same memory group -- because in that case, there is
  * coordination within the single memory device managed by a single driver.
  *
  * We rely on "present pages" instead of "managed pages", as the latter is
  * highly unreliable and dynamic in virtualized environments, and does not
  * consider boot time allocations. For example, memory ballooning adjusts the
  * managed pages when inflating/deflating the balloon, and balloon compaction
  * can even migrate inflated pages between zones.
  *
  * Using "present pages" is better but some things to keep in mind are:
  *
  * a) Some memblock allocations, such as for the crashkernel area, are
  *    effectively unused by the kernel, yet they account to "present pages".
  *    Fortunately, these allocations are comparatively small in relevant setups
  *    (e.g., fraction of system memory).
  * b) Some hotplugged memory blocks in virtualized environments, esecially
  *    hotplugged by virtio-mem, look like they are completely present, however,
  *    only parts of the memory block are actually currently usable.
  *    "present pages" is an upper limit that can get reached at runtime. As
  *    we base our calculations on KERNEL_EARLY, this is not an issue.
  */
 static struct zone *auto_movable_zone_for_pfn(int nid,
                           struct memory_group *group,
                           unsigned long pfn,
                           unsigned long nr_pages)
 {
     unsigned long online_pages = 0, max_pages, end_pfn;
     struct page *page;
 
     if (!auto_movable_ratio)
         goto kernel_zone;
 
     if (group && !group->is_dynamic) {
         max_pages = group->s.max_pages;
         online_pages = group->present_movable_pages;
 
         /* If anything is !MOVABLE online the rest !MOVABLE. */
         if (group->present_kernel_pages)
             goto kernel_zone;
     } else if (!group || group->d.unit_pages == nr_pages) {
         max_pages = nr_pages;
     } else {
         max_pages = group->d.unit_pages;
         /*
          * Take a look at all online sections in the current unit.
          * We can safely assume that all pages within a section belong
          * to the same zone, because dynamic memory groups only deal
          * with hotplugged memory.
          */
         pfn = ALIGN_DOWN(pfn, group->d.unit_pages);
         end_pfn = pfn + group->d.unit_pages;
         for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
             page = pfn_to_online_page(pfn);
             if (!page)
                 continue;
             /* If anything is !MOVABLE online the rest !MOVABLE. */
             if (!is_zone_movable_page(page))
                 goto kernel_zone;
             online_pages += PAGES_PER_SECTION;
         }
     }
 
     /*
      * Online MOVABLE if we could *currently* online all remaining parts
      * MOVABLE. We expect to (add+) online them immediately next, so if
      * nobody interferes, all will be MOVABLE if possible.
      */
     nr_pages = max_pages - online_pages;
     if (!auto_movable_can_online_movable(NUMA_NO_NODE, group, nr_pages))
         goto kernel_zone;
 
 #ifdef CONFIG_NUMA
     if (auto_movable_numa_aware &&
         !auto_movable_can_online_movable(nid, group, nr_pages))
         goto kernel_zone;
 #endif /* CONFIG_NUMA */
 
     return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
 kernel_zone:
     return default_kernel_zone_for_pfn(nid, pfn, nr_pages);
 }
 
 static inline struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
         unsigned long nr_pages)
 {
     struct zone *kernel_zone = default_kernel_zone_for_pfn(nid, start_pfn,
             nr_pages);
     struct zone *movable_zone = &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
     bool in_kernel = zone_intersects(kernel_zone, start_pfn, nr_pages);
     bool in_movable = zone_intersects(movable_zone, start_pfn, nr_pages);
 
     /*
      * We inherit the existing zone in a simple case where zones do not
      * overlap in the given range
      */
     if (in_kernel ^ in_movable)
         return (in_kernel) ? kernel_zone : movable_zone;
 
     /*
      * If the range doesn't belong to any zone or two zones overlap in the
      * given range then we use movable zone only if movable_node is
      * enabled because we always online to a kernel zone by default.
      */
     return movable_node_enabled ? movable_zone : kernel_zone;
 }
 
 struct zone *zone_for_pfn_range(int online_type, int nid,
         struct memory_group *group, unsigned long start_pfn,
         unsigned long nr_pages)
 {
     if (online_type == MMOP_ONLINE_KERNEL)
         return default_kernel_zone_for_pfn(nid, start_pfn, nr_pages);
 
     if (online_type == MMOP_ONLINE_MOVABLE)
         return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
 
     if (online_policy == ONLINE_POLICY_AUTO_MOVABLE)
         return auto_movable_zone_for_pfn(nid, group, start_pfn, nr_pages);
 
     return default_zone_for_pfn(nid, start_pfn, nr_pages);
 }
 
 /*
  * This function should only be called by memory_block_{online,offline},
  * and {online,offline}_pages.
  */
 void adjust_present_page_count(struct page *page, struct memory_group *group,
                    long nr_pages)
 {
     struct zone *zone = page_zone(page);
     const bool movable = zone_idx(zone) == ZONE_MOVABLE;
 
     /*
      * We only support onlining/offlining/adding/removing of complete
      * memory blocks; therefore, either all is either early or hotplugged.
      */
     if (early_section(__pfn_to_section(page_to_pfn(page))))
         zone->present_early_pages += nr_pages;
     zone->present_pages += nr_pages;
     zone->zone_pgdat->node_present_pages += nr_pages;
 
     if (group && movable)
         group->present_movable_pages += nr_pages;
     else if (group && !movable)
         group->present_kernel_pages += nr_pages;
 }
 
 int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
                   struct zone *zone)
 {
     unsigned long end_pfn = pfn + nr_pages;
     int ret, i;
 
     ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
     if (ret)
         return ret;
 
     move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
 
     for (i = 0; i < nr_pages; i++)
         SetPageVmemmapSelfHosted(pfn_to_page(pfn + i));
 
     /*
      * It might be that the vmemmap_pages fully span sections. If that is
      * the case, mark those sections online here as otherwise they will be
      * left offline.
      */
     if (nr_pages >= PAGES_PER_SECTION)
             online_mem_sections(pfn, ALIGN_DOWN(end_pfn, PAGES_PER_SECTION));
 
     return ret;
 }
 
 void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long nr_pages)
 {
     unsigned long end_pfn = pfn + nr_pages;
 
     /*
      * It might be that the vmemmap_pages fully span sections. If that is
      * the case, mark those sections offline here as otherwise they will be
      * left online.
      */
     if (nr_pages >= PAGES_PER_SECTION)
         offline_mem_sections(pfn, ALIGN_DOWN(end_pfn, PAGES_PER_SECTION));
 
         /*
      * The pages associated with this vmemmap have been offlined, so
      * we can reset its state here.
      */
     remove_pfn_range_from_zone(page_zone(pfn_to_page(pfn)), pfn, nr_pages);
     kasan_remove_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
 }
 
 int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
                struct zone *zone, struct memory_group *group)
 {
     unsigned long flags;
     int need_zonelists_rebuild = 0;
     const int nid = zone_to_nid(zone);
     int ret;
     struct memory_notify arg;
 
     /*
      * {on,off}lining is constrained to full memory sections (or more
      * precisely to memory blocks from the user space POV).
      * memmap_on_memory is an exception because it reserves initial part
      * of the physical memory space for vmemmaps. That space is pageblock
      * aligned.
      */
     if (WARN_ON_ONCE(!nr_pages ||
              !IS_ALIGNED(pfn, pageblock_nr_pages) ||
              !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
         return -EINVAL;
 
     mem_hotplug_begin();
 
     /* associate pfn range with the zone */
     move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_ISOLATE);
 
     arg.start_pfn = pfn;
     arg.nr_pages = nr_pages;
     node_states_check_changes_online(nr_pages, zone, &arg);
 
     ret = memory_notify(MEM_GOING_ONLINE, &arg);
     ret = notifier_to_errno(ret);
     if (ret)
         goto failed_addition;
 
     /*
      * Fixup the number of isolated pageblocks before marking the sections
      * onlining, such that undo_isolate_page_range() works correctly.
      */
     spin_lock_irqsave(&zone->lock, flags);
     zone->nr_isolate_pageblock += nr_pages / pageblock_nr_pages;
     spin_unlock_irqrestore(&zone->lock, flags);
 
     /*
      * If this zone is not populated, then it is not in zonelist.
      * This means the page allocator ignores this zone.
      * So, zonelist must be updated after online.
      */
     if (!populated_zone(zone)) {
         need_zonelists_rebuild = 1;
         setup_zone_pageset(zone);
     }
 
     online_pages_range(pfn, nr_pages);
     adjust_present_page_count(pfn_to_page(pfn), group, nr_pages);
 
     node_states_set_node(nid, &arg);
     if (need_zonelists_rebuild)
         build_all_zonelists(NULL);
 
     /* Basic onlining is complete, allow allocation of onlined pages. */
     undo_isolate_page_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE);
 
     /*
      * Freshly onlined pages aren't shuffled (e.g., all pages are placed to
      * the tail of the freelist when undoing isolation). Shuffle the whole
      * zone to make sure the just onlined pages are properly distributed
      * across the whole freelist - to create an initial shuffle.
      */
     shuffle_zone(zone);
 
     /* reinitialise watermarks and update pcp limits */
     init_per_zone_wmark_min();
 
     kswapd_run(nid);
     kcompactd_run(nid);
 
     writeback_set_ratelimit();
 
     memory_notify(MEM_ONLINE, &arg);
     mem_hotplug_done();
     return 0;
 
 failed_addition:
     pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
          (unsigned long long) pfn << PAGE_SHIFT,
          (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
     memory_notify(MEM_CANCEL_ONLINE, &arg);
     remove_pfn_range_from_zone(zone, pfn, nr_pages);
     mem_hotplug_done();
     return ret;
 }
 
 static void reset_node_present_pages(pg_data_t *pgdat)
 {
     struct zone *z;
 
     for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
         z->present_pages = 0;
 
     pgdat->node_present_pages = 0;
 }
 
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 static pg_data_t __ref *hotadd_init_pgdat(int nid)
 {
     struct pglist_data *pgdat;
 
     /*
      * NODE_DATA is preallocated (free_area_init) but its internal
      * state is not allocated completely. Add missing pieces.
      * Completely offline nodes stay around and they just need
      * reintialization.
      */
     pgdat = NODE_DATA(nid);
 
     /* init node's zones as empty zones, we don't have any present pages.*/
     free_area_init_core_hotplug(pgdat);
 
     /*
      * The node we allocated has no zone fallback lists. For avoiding
      * to access not-initialized zonelist, build here.
      */
     build_all_zonelists(pgdat);
 
     /*
      * When memory is hot-added, all the memory is in offline state. So
      * clear all zones' present_pages because they will be updated in
      * online_pages() and offline_pages().
      * TODO: should be in free_area_init_core_hotplug?
      */
     reset_node_managed_pages(pgdat);
     reset_node_present_pages(pgdat);
 
     return pgdat;
 }
 
 /*
  * __try_online_node - online a node if offlined
  * @nid: the node ID
  * @set_node_online: Whether we want to online the node
  * called by cpu_up() to online a node without onlined memory.
  *
  * Returns:
  * 1 -> a new node has been allocated
  * 0 -> the node is already online
  * -ENOMEM -> the node could not be allocated
  */
 static int __try_online_node(int nid, bool set_node_online)
 {
     pg_data_t *pgdat;
     int ret = 1;
 
     if (node_online(nid))
         return 0;
 
     pgdat = hotadd_init_pgdat(nid);
     if (!pgdat) {
         pr_err("Cannot online node %d due to NULL pgdat\n", nid);
         ret = -ENOMEM;
         goto out;
     }
 
     if (set_node_online) {
         node_set_online(nid);
         ret = register_one_node(nid);
         BUG_ON(ret);
     }
 out:
     return ret;
 }
 
 /*
  * Users of this function always want to online/register the node
  */
 int try_online_node(int nid)
 {
     int ret;
 
     mem_hotplug_begin();
     ret =  __try_online_node(nid, true);
     mem_hotplug_done();
     return ret;
 }
 
 static int check_hotplug_memory_range(u64 start, u64 size)
 {
     /* memory range must be block size aligned */
     if (!size || !IS_ALIGNED(start, memory_block_size_bytes()) ||
         !IS_ALIGNED(size, memory_block_size_bytes())) {
         pr_err("Block size [%#lx] unaligned hotplug range: start %#llx, size %#llx",
                memory_block_size_bytes(), start, size);
         return -EINVAL;
     }
 
     return 0;
 }
 
 static int online_memory_block(struct memory_block *mem, void *arg)
 {
     mem->online_type = mhp_default_online_type;
     return device_online(&mem->dev);
 }
 
 bool mhp_supports_memmap_on_memory(unsigned long size)
 {
     unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
     unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
     unsigned long remaining_size = size - vmemmap_size;
 
     /*
      * Besides having arch support and the feature enabled at runtime, we
      * need a few more assumptions to hold true:
      *
      * a) We span a single memory block: memory onlining/offlinin;g happens
      *    in memory block granularity. We don't want the vmemmap of online
      *    memory blocks to reside on offline memory blocks. In the future,
      *    we might want to support variable-sized memory blocks to make the
      *    feature more versatile.
      *
      * b) The vmemmap pages span complete PMDs: We don't want vmemmap code
      *    to populate memory from the altmap for unrelated parts (i.e.,
      *    other memory blocks)
      *
      * c) The vmemmap pages (and thereby the pages that will be exposed to
      *    the buddy) have to cover full pageblocks: memory onlining/offlining
      *    code requires applicable ranges to be page-aligned, for example, to
      *    set the migratetypes properly.
      *
      * TODO: Although we have a check here to make sure that vmemmap pages
      *       fully populate a PMD, it is not the right place to check for
      *       this. A much better solution involves improving vmemmap code
      *       to fallback to base pages when trying to populate vmemmap using
      *       altmap as an alternative source of memory, and we do not exactly
      *       populate a single PMD.
      */
     return mhp_memmap_on_memory() &&
            size == memory_block_size_bytes() &&
            IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
            IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
 }
 
 /*
  * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
  * and online/offline operations (triggered e.g. by sysfs).
  *
  * we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG
  */
 int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
 {
     struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
     enum memblock_flags memblock_flags = MEMBLOCK_NONE;
     struct vmem_altmap mhp_altmap = {};
     struct memory_group *group = NULL;
     u64 start, size;
     bool new_node = false;
     int ret;
 
     start = res->start;
     size = resource_size(res);
 
     ret = check_hotplug_memory_range(start, size);
     if (ret)
         return ret;
 
     if (mhp_flags & MHP_NID_IS_MGID) {
         group = memory_group_find_by_id(nid);
         if (!group)
             return -EINVAL;
         nid = group->nid;
     }
 
     if (!node_possible(nid)) {
         WARN(1, "node %d was absent from the node_possible_map\n", nid);
         return -EINVAL;
     }
 
     mem_hotplug_begin();
 
     if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
         if (res->flags & IORESOURCE_SYSRAM_DRIVER_MANAGED)
             memblock_flags = MEMBLOCK_DRIVER_MANAGED;
         ret = memblock_add_node(start, size, nid, memblock_flags);
         if (ret)
             goto error_mem_hotplug_end;
     }
 
     ret = __try_online_node(nid, false);
     if (ret < 0)
         goto error;
     new_node = ret;
 
     /*
      * Self hosted memmap array
      */
     if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
         if (!mhp_supports_memmap_on_memory(size)) {
             ret = -EINVAL;
             goto error;
         }
         mhp_altmap.free = PHYS_PFN(size);
         mhp_altmap.base_pfn = PHYS_PFN(start);
         params.altmap = &mhp_altmap;
     }
 
     /* call arch's memory hotadd */
     ret = arch_add_memory(nid, start, size, &params);
     if (ret < 0)
         goto error;
 
     /* create memory block devices after memory was added */
     ret = create_memory_block_devices(start, size, mhp_altmap.alloc,
                       group);
     if (ret) {
         arch_remove_memory(start, size, NULL);
         goto error;
     }
 
     if (new_node) {
         /* If sysfs file of new node can't be created, cpu on the node
          * can't be hot-added. There is no rollback way now.
          * So, check by BUG_ON() to catch it reluctantly..
          * We online node here. We can't roll back from here.
          */
         node_set_online(nid);
         ret = __register_one_node(nid);
         BUG_ON(ret);
     }
 
     register_memory_blocks_under_node(nid, PFN_DOWN(start),
                       PFN_UP(start + size - 1),
                       MEMINIT_HOTPLUG);
 
     /* create new memmap entry */
     if (!strcmp(res->name, "System RAM"))
         firmware_map_add_hotplug(start, start + size, "System RAM");
 
     /* device_online() will take the lock when calling online_pages() */
     mem_hotplug_done();
 
     /*
      * In case we're allowed to merge the resource, flag it and trigger
      * merging now that adding succeeded.
      */
     if (mhp_flags & MHP_MERGE_RESOURCE)
         merge_system_ram_resource(res);
 
     /* online pages if requested */
     if (mhp_default_online_type != MMOP_OFFLINE)
         walk_memory_blocks(start, size, NULL, online_memory_block);
 
     return ret;
 error:
     if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
         memblock_remove(start, size);
 error_mem_hotplug_end:
     mem_hotplug_done();
     return ret;
 }
 
 /* requires device_hotplug_lock, see add_memory_resource() */
 int __ref __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)
 {
     struct resource *res;
     int ret;
 
     res = register_memory_resource(start, size, "System RAM");
     if (IS_ERR(res))
         return PTR_ERR(res);
 
     ret = add_memory_resource(nid, res, mhp_flags);
     if (ret < 0)
         release_memory_resource(res);
     return ret;
 }
 
 int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)
 {
     int rc;
 
     lock_device_hotplug();
     rc = __add_memory(nid, start, size, mhp_flags);
     unlock_device_hotplug();
 
     return rc;
 }
 EXPORT_SYMBOL_GPL(add_memory);
 
 /*
  * Add special, driver-managed memory to the system as system RAM. Such
  * memory is not exposed via the raw firmware-provided memmap as system
  * RAM, instead, it is detected and added by a driver - during cold boot,
  * after a reboot, and after kexec.
  *
  * Reasons why this memory should not be used for the initial memmap of a
  * kexec kernel or for placing kexec images:
  * - The booting kernel is in charge of determining how this memory will be
  *   used (e.g., use persistent memory as system RAM)
  * - Coordination with a hypervisor is required before this memory
  *   can be used (e.g., inaccessible parts).
  *
  * For this memory, no entries in /sys/firmware/memmap ("raw firmware-provided
  * memory map") are created. Also, the created memory resource is flagged
  * with IORESOURCE_SYSRAM_DRIVER_MANAGED, so in-kernel users can special-case
  * this memory as well (esp., not place kexec images onto it).
  *
  * The resource_name (visible via /proc/iomem) has to have the format
  * "System RAM ($DRIVER)".
  */
 int add_memory_driver_managed(int nid, u64 start, u64 size,
                   const char *resource_name, mhp_t mhp_flags)
 {
     struct resource *res;
     int rc;
 
     if (!resource_name ||
         strstr(resource_name, "System RAM (") != resource_name ||
         resource_name[strlen(resource_name) - 1] != ')')
         return -EINVAL;
 
     lock_device_hotplug();
 
     res = register_memory_resource(start, size, resource_name);
     if (IS_ERR(res)) {
         rc = PTR_ERR(res);
         goto out_unlock;
     }
 
     rc = add_memory_resource(nid, res, mhp_flags);
     if (rc < 0)
         release_memory_resource(res);
 
 out_unlock:
     unlock_device_hotplug();
     return rc;
 }
 EXPORT_SYMBOL_GPL(add_memory_driver_managed);
 
 /*
  * Platforms should define arch_get_mappable_range() that provides
  * maximum possible addressable physical memory range for which the
  * linear mapping could be created. The platform returned address
  * range must adhere to these following semantics.
  *
  * - range.start <= range.end
  * - Range includes both end points [range.start..range.end]
  *
  * There is also a fallback definition provided here, allowing the
  * entire possible physical address range in case any platform does
  * not define arch_get_mappable_range().
  */
 struct range __weak arch_get_mappable_range(void)
 {
     struct range mhp_range = {
         .start = 0UL,
         .end = -1ULL,
     };
     return mhp_range;
 }
 
 struct range mhp_get_pluggable_range(bool need_mapping)
 {
     const u64 max_phys = (1ULL << MAX_PHYSMEM_BITS) - 1;
     struct range mhp_range;
 
     if (need_mapping) {
         mhp_range = arch_get_mappable_range();
         if (mhp_range.start > max_phys) {
             mhp_range.start = 0;
             mhp_range.end = 0;
         }
         mhp_range.end = min_t(u64, mhp_range.end, max_phys);
     } else {
         mhp_range.start = 0;
         mhp_range.end = max_phys;
     }
     return mhp_range;
 }
 EXPORT_SYMBOL_GPL(mhp_get_pluggable_range);
 
 bool mhp_range_allowed(u64 start, u64 size, bool need_mapping)
 {
     struct range mhp_range = mhp_get_pluggable_range(need_mapping);
     u64 end = start + size;
 
     if (start < end && start >= mhp_range.start && (end - 1) <= mhp_range.end)
         return true;
 
     pr_warn("Hotplug memory [%#llx-%#llx] exceeds maximum addressable range [%#llx-%#llx]\n",
         start, end, mhp_range.start, mhp_range.end);
     return false;
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
  * Scan pfn range [start,end) to find movable/migratable pages (LRU pages,
  * non-lru movable pages and hugepages). Will skip over most unmovable
  * pages (esp., pages that can be skipped when offlining), but bail out on
  * definitely unmovable pages.
  *
  * Returns:
  *  0 in case a movable page is found and movable_pfn was updated.
  *  -ENOENT in case no movable page was found.
  *  -EBUSY in case a definitely unmovable page was found.
  */
 static int scan_movable_pages(unsigned long start, unsigned long end,
                   unsigned long *movable_pfn)
 {
     unsigned long pfn;
 
     for (pfn = start; pfn < end; pfn++) {
         struct page *page, *head;
         unsigned long skip;
 
         if (!pfn_valid(pfn))
             continue;
         page = pfn_to_page(pfn);
         if (PageLRU(page))
             goto found;
         if (__PageMovable(page))
             goto found;
 
         /*
          * PageOffline() pages that are not marked __PageMovable() and
          * have a reference count > 0 (after MEM_GOING_OFFLINE) are
          * definitely unmovable. If their reference count would be 0,
          * they could at least be skipped when offlining memory.
          */
         if (PageOffline(page) && page_count(page))
             return -EBUSY;
 
         if (!PageHuge(page))
             continue;
         head = compound_head(page);
         /*
          * This test is racy as we hold no reference or lock.  The
          * hugetlb page could have been free'ed and head is no longer
          * a hugetlb page before the following check.  In such unlikely
          * cases false positives and negatives are possible.  Calling
          * code must deal with these scenarios.
          */
         if (HPageMigratable(head))
             goto found;
         skip = compound_nr(head) - (page - head);
         pfn += skip - 1;
     }
     return -ENOENT;
 found:
     *movable_pfn = pfn;
     return 0;
 }
 
 static int
 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 {
     unsigned long pfn;
     struct page *page, *head;
     int ret = 0;
     LIST_HEAD(source);
     static DEFINE_RATELIMIT_STATE(migrate_rs, DEFAULT_RATELIMIT_INTERVAL,
                       DEFAULT_RATELIMIT_BURST);
 
     for (pfn = start_pfn; pfn < end_pfn; pfn++) {
         struct folio *folio;
 
         if (!pfn_valid(pfn))
             continue;
         page = pfn_to_page(pfn);
         folio = page_folio(page);
         head = &folio->page;
 
         if (PageHuge(page)) {
             pfn = page_to_pfn(head) + compound_nr(head) - 1;
             isolate_hugetlb(head, &source);
             continue;
         } else if (PageTransHuge(page))
             pfn = page_to_pfn(head) + thp_nr_pages(page) - 1;
 
         /*
          * HWPoison pages have elevated reference counts so the migration would
          * fail on them. It also doesn't make any sense to migrate them in the
          * first place. Still try to unmap such a page in case it is still mapped
          * (e.g. current hwpoison implementation doesn't unmap KSM pages but keep
          * the unmap as the catch all safety net).
          */
         if (PageHWPoison(page)) {
             if (WARN_ON(folio_test_lru(folio)))
                 folio_isolate_lru(folio);
             if (folio_mapped(folio))
                 try_to_unmap(folio, TTU_IGNORE_MLOCK);
             continue;
         }
 
         if (!get_page_unless_zero(page))
             continue;
         /*
          * We can skip free pages. And we can deal with pages on
          * LRU and non-lru movable pages.
          */
         if (PageLRU(page))
             ret = isolate_lru_page(page);
         else
             ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
         if (!ret) { /* Success */
             list_add_tail(&page->lru, &source);
             if (!__PageMovable(page))
                 inc_node_page_state(page, NR_ISOLATED_ANON +
                             page_is_file_lru(page));
 
         } else {
             if (__ratelimit(&migrate_rs)) {
                 pr_warn("failed to isolate pfn %lx\n", pfn);
                 dump_page(page, "isolation failed");
             }
         }
         put_page(page);
     }
     if (!list_empty(&source)) {
         nodemask_t nmask = node_states[N_MEMORY];
         struct migration_target_control mtc = {
             .nmask = &nmask,
             .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
         };
 
         /*
          * We have checked that migration range is on a single zone so
          * we can use the nid of the first page to all the others.
          */
         mtc.nid = page_to_nid(list_first_entry(&source, struct page, lru));
 
         /*
          * try to allocate from a different node but reuse this node
          * if there are no other online nodes to be used (e.g. we are
          * offlining a part of the only existing node)
          */
         node_clear(mtc.nid, nmask);
         if (nodes_empty(nmask))
             node_set(mtc.nid, nmask);
         ret = migrate_pages(&source, alloc_migration_target, NULL,
             (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG, NULL);
         if (ret) {
             list_for_each_entry(page, &source, lru) {
                 if (__ratelimit(&migrate_rs)) {
                     pr_warn("migrating pfn %lx failed ret:%d\n",
                         page_to_pfn(page), ret);
                     dump_page(page, "migration failure");
                 }
             }
             putback_movable_pages(&source);
         }
     }
 
     return ret;
 }
 
 static int __init cmdline_parse_movable_node(char *p)
 {
     movable_node_enabled = true;
     return 0;
 }
 early_param("movable_node", cmdline_parse_movable_node);
 
 /* check which state of node_states will be changed when offline memory */
 static void node_states_check_changes_offline(unsigned long nr_pages,
         struct zone *zone, struct memory_notify *arg)
 {
     struct pglist_data *pgdat = zone->zone_pgdat;
     unsigned long present_pages = 0;
     enum zone_type zt;
 
     arg->status_change_nid = NUMA_NO_NODE;
     arg->status_change_nid_normal = NUMA_NO_NODE;
 
     /*
      * Check whether node_states[N_NORMAL_MEMORY] will be changed.
      * If the memory to be offline is within the range
      * [0..ZONE_NORMAL], and it is the last present memory there,
      * the zones in that range will become empty after the offlining,
      * thus we can determine that we need to clear the node from
      * node_states[N_NORMAL_MEMORY].
      */
     for (zt = 0; zt <= ZONE_NORMAL; zt++)
         present_pages += pgdat->node_zones[zt].present_pages;
     if (zone_idx(zone) <= ZONE_NORMAL && nr_pages >= present_pages)
         arg->status_change_nid_normal = zone_to_nid(zone);
 
     /*
      * We have accounted the pages from [0..ZONE_NORMAL); ZONE_HIGHMEM
      * does not apply as we don't support 32bit.
      * Here we count the possible pages from ZONE_MOVABLE.
      * If after having accounted all the pages, we see that the nr_pages
      * to be offlined is over or equal to the accounted pages,
      * we know that the node will become empty, and so, we can clear
      * it for N_MEMORY as well.
      */
     present_pages += pgdat->node_zones[ZONE_MOVABLE].present_pages;
 
     if (nr_pages >= present_pages)
         arg->status_change_nid = zone_to_nid(zone);
 }
 
 static void node_states_clear_node(int node, struct memory_notify *arg)
 {
     if (arg->status_change_nid_normal >= 0)
         node_clear_state(node, N_NORMAL_MEMORY);
 
     if (arg->status_change_nid >= 0)
         node_clear_state(node, N_MEMORY);
 }
 
 static int count_system_ram_pages_cb(unsigned long start_pfn,
                      unsigned long nr_pages, void *data)
 {
     unsigned long *nr_system_ram_pages = data;
 
     *nr_system_ram_pages += nr_pages;
     return 0;
 }
 
 int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
             struct zone *zone, struct memory_group *group)
 {
     const unsigned long end_pfn = start_pfn + nr_pages;
     unsigned long pfn, system_ram_pages = 0;
     const int node = zone_to_nid(zone);
     unsigned long flags;
     struct memory_notify arg;
     char *reason;
     int ret;
 
     /*
      * {on,off}lining is constrained to full memory sections (or more
      * precisely to memory blocks from the user space POV).
      * memmap_on_memory is an exception because it reserves initial part
      * of the physical memory space for vmemmaps. That space is pageblock
      * aligned.
      */
     if (WARN_ON_ONCE(!nr_pages ||
              !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
              !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
         return -EINVAL;
 
     mem_hotplug_begin();
 
     /*
      * Don't allow to offline memory blocks that contain holes.
      * Consequently, memory blocks with holes can never get onlined
      * via the hotplug path - online_pages() - as hotplugged memory has
      * no holes. This way, we e.g., don't have to worry about marking
      * memory holes PG_reserved, don't need pfn_valid() checks, and can
      * avoid using walk_system_ram_range() later.
      */
     walk_system_ram_range(start_pfn, nr_pages, &system_ram_pages,
                   count_system_ram_pages_cb);
     if (system_ram_pages != nr_pages) {
         ret = -EINVAL;
         reason = "memory holes";
         goto failed_removal;
     }
 
     /*
      * We only support offlining of memory blocks managed by a single zone,
      * checked by calling code. This is just a sanity check that we might
      * want to remove in the future.
      */
     if (WARN_ON_ONCE(page_zone(pfn_to_page(start_pfn)) != zone ||
              page_zone(pfn_to_page(end_pfn - 1)) != zone)) {
         ret = -EINVAL;
         reason = "multizone range";
         goto failed_removal;
     }
 
     /*
      * Disable pcplists so that page isolation cannot race with freeing
      * in a way that pages from isolated pageblock are left on pcplists.
      */
     zone_pcp_disable(zone);
     lru_cache_disable();
 
     /* set above range as isolated */
     ret = start_isolate_page_range(start_pfn, end_pfn,
                        MIGRATE_MOVABLE,
                        MEMORY_OFFLINE | REPORT_FAILURE,
                        GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL);
     if (ret) {
         reason = "failure to isolate range";
         goto failed_removal_pcplists_disabled;
     }
 
     arg.start_pfn = start_pfn;
     arg.nr_pages = nr_pages;
     node_states_check_changes_offline(nr_pages, zone, &arg);
 
     ret = memory_notify(MEM_GOING_OFFLINE, &arg);
     ret = notifier_to_errno(ret);
     if (ret) {
         reason = "notifier failure";
         goto failed_removal_isolated;
     }
 
     do {
         pfn = start_pfn;
         do {
             if (signal_pending(current)) {
                 ret = -EINTR;
                 reason = "signal backoff";
                 goto failed_removal_isolated;
             }
 
             cond_resched();
 
             ret = scan_movable_pages(pfn, end_pfn, &pfn);
             if (!ret) {
                 /*
                  * TODO: fatal migration failures should bail
                  * out
                  */
                 do_migrate_range(pfn, end_pfn);
             }
         } while (!ret);
 
         if (ret != -ENOENT) {
             reason = "unmovable page";
             goto failed_removal_isolated;
         }
 
         /*
          * Dissolve free hugepages in the memory block before doing
          * offlining actually in order to make hugetlbfs's object
          * counting consistent.
          */
         ret = dissolve_free_huge_pages(start_pfn, end_pfn);
         if (ret) {
             reason = "failure to dissolve huge pages";
             goto failed_removal_isolated;
         }
 
         ret = test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE);
 
     } while (ret);
 
     /* Mark all sections offline and remove free pages from the buddy. */
     __offline_isolated_pages(start_pfn, end_pfn);
     pr_debug("Offlined Pages %ld\n", nr_pages);
 
     /*
      * The memory sections are marked offline, and the pageblock flags
      * effectively stale; nobody should be touching them. Fixup the number
      * of isolated pageblocks, memory onlining will properly revert this.
      */
     spin_lock_irqsave(&zone->lock, flags);
     zone->nr_isolate_pageblock -= nr_pages / pageblock_nr_pages;
     spin_unlock_irqrestore(&zone->lock, flags);
 
     lru_cache_enable();
     zone_pcp_enable(zone);
 
     /* removal success */
     adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
     adjust_present_page_count(pfn_to_page(start_pfn), group, -nr_pages);
 
     /* reinitialise watermarks and update pcp limits */
     init_per_zone_wmark_min();
 
     if (!populated_zone(zone)) {
         zone_pcp_reset(zone);
         build_all_zonelists(NULL);
     }
 
     node_states_clear_node(node, &arg);
     if (arg.status_change_nid >= 0) {
         kswapd_stop(node);
         kcompactd_stop(node);
     }
 
     writeback_set_ratelimit();
 
     memory_notify(MEM_OFFLINE, &arg);
     remove_pfn_range_from_zone(zone, start_pfn, nr_pages);
     mem_hotplug_done();
     return 0;
 
 failed_removal_isolated:
     /* pushback to free area */
     undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
     memory_notify(MEM_CANCEL_OFFLINE, &arg);
 failed_removal_pcplists_disabled:
     lru_cache_enable();
     zone_pcp_enable(zone);
 failed_removal:
     pr_debug("memory offlining [mem %#010llx-%#010llx] failed due to %s\n",
          (unsigned long long) start_pfn << PAGE_SHIFT,
          ((unsigned long long) end_pfn << PAGE_SHIFT) - 1,
          reason);
     mem_hotplug_done();
     return ret;
 }
 
 static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
 {
     int ret = !is_memblock_offlined(mem);
     int *nid = arg;
 
     *nid = mem->nid;
     if (unlikely(ret)) {
         phys_addr_t beginpa, endpa;
 
         beginpa = PFN_PHYS(section_nr_to_pfn(mem->start_section_nr));
         endpa = beginpa + memory_block_size_bytes() - 1;
         pr_warn("removing memory fails, because memory [%pa-%pa] is onlined\n",
             &beginpa, &endpa);
 
         return -EBUSY;
     }
     return 0;
 }
 
 static int get_nr_vmemmap_pages_cb(struct memory_block *mem, void *arg)
 {
     /*
      * If not set, continue with the next block.
      */
     return mem->nr_vmemmap_pages;
 }
 
 static int check_cpu_on_node(int nid)
 {
     int cpu;
 
     for_each_present_cpu(cpu) {
         if (cpu_to_node(cpu) == nid)
             /*
              * the cpu on this node isn't removed, and we can't
              * offline this node.
              */
             return -EBUSY;
     }
 
     return 0;
 }
 
 static int check_no_memblock_for_node_cb(struct memory_block *mem, void *arg)
 {
     int nid = *(int *)arg;
 
     /*
      * If a memory block belongs to multiple nodes, the stored nid is not
      * reliable. However, such blocks are always online (e.g., cannot get
      * offlined) and, therefore, are still spanned by the node.
      */
     return mem->nid == nid ? -EEXIST : 0;
 }
 
 /**
  * try_offline_node
  * @nid: the node ID
  *
  * Offline a node if all memory sections and cpus of the node are removed.
  *
  * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
  * and online/offline operations before this call.
  */
 void try_offline_node(int nid)
 {
     int rc;
 
     /*
      * If the node still spans pages (especially ZONE_DEVICE), don't
      * offline it. A node spans memory after move_pfn_range_to_zone(),
      * e.g., after the memory block was onlined.
      */
     if (node_spanned_pages(nid))
         return;
 
     /*
      * Especially offline memory blocks might not be spanned by the
      * node. They will get spanned by the node once they get onlined.
      * However, they link to the node in sysfs and can get onlined later.
      */
     rc = for_each_memory_block(&nid, check_no_memblock_for_node_cb);
     if (rc)
         return;
 
     if (check_cpu_on_node(nid))
         return;
 
     /*
      * all memory/cpu of this node are removed, we can offline this
      * node now.
      */
     node_set_offline(nid);
     unregister_one_node(nid);
 }
 EXPORT_SYMBOL(try_offline_node);
 
 static int __ref try_remove_memory(u64 start, u64 size)
 {
     struct vmem_altmap mhp_altmap = {};
     struct vmem_altmap *altmap = NULL;
     unsigned long nr_vmemmap_pages;
     int rc = 0, nid = NUMA_NO_NODE;
 
     BUG_ON(check_hotplug_memory_range(start, size));
 
     /*
      * All memory blocks must be offlined before removing memory.  Check
      * whether all memory blocks in question are offline and return error
      * if this is not the case.
      *
      * While at it, determine the nid. Note that if we'd have mixed nodes,
      * we'd only try to offline the last determined one -- which is good
      * enough for the cases we care about.
      */
     rc = walk_memory_blocks(start, size, &nid, check_memblock_offlined_cb);
     if (rc)
         return rc;
 
     /*
      * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in
      * the same granularity it was added - a single memory block.
      */
     if (mhp_memmap_on_memory()) {
         nr_vmemmap_pages = walk_memory_blocks(start, size, NULL,
                               get_nr_vmemmap_pages_cb);
         if (nr_vmemmap_pages) {
             if (size != memory_block_size_bytes()) {
                 pr_warn("Refuse to remove %#llx - %#llx,"
                     "wrong granularity\n",
                     start, start + size);
                 return -EINVAL;
             }
 
             /*
              * Let remove_pmd_table->free_hugepage_table do the
              * right thing if we used vmem_altmap when hot-adding
              * the range.
              */
             mhp_altmap.alloc = nr_vmemmap_pages;
             altmap = &mhp_altmap;
         }
     }
 
     /* remove memmap entry */
     firmware_map_remove(start, start + size, "System RAM");
 
     /*
      * Memory block device removal under the device_hotplug_lock is
      * a barrier against racing online attempts.
      */
     remove_memory_block_devices(start, size);
 
     mem_hotplug_begin();
 
     arch_remove_memory(start, size, altmap);
 
     if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
         memblock_phys_free(start, size);
         memblock_remove(start, size);
     }
 
     release_mem_region_adjustable(start, size);
 
     if (nid != NUMA_NO_NODE)
         try_offline_node(nid);
 
     mem_hotplug_done();
     return 0;
 }
 
 /**
  * __remove_memory - Remove memory if every memory block is offline
  * @start: physical address of the region to remove
  * @size: size of the region to remove
  *
  * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
  * and online/offline operations before this call, as required by
  * try_offline_node().
  */
 void __remove_memory(u64 start, u64 size)
 {
 
     /*
      * trigger BUG() if some memory is not offlined prior to calling this
      * function
      */
     if (try_remove_memory(start, size))
         BUG();
 }
 
 /*
  * Remove memory if every memory block is offline, otherwise return -EBUSY is
  * some memory is not offline
  */
 int remove_memory(u64 start, u64 size)
 {
     int rc;
 
     lock_device_hotplug();
     rc = try_remove_memory(start, size);
     unlock_device_hotplug();
 
     return rc;
 }
 EXPORT_SYMBOL_GPL(remove_memory);
 
 static int try_offline_memory_block(struct memory_block *mem, void *arg)
 {
     uint8_t online_type = MMOP_ONLINE_KERNEL;
     uint8_t **online_types = arg;
     struct page *page;
     int rc;
 
     /*
      * Sense the online_type via the zone of the memory block. Offlining
      * with multiple zones within one memory block will be rejected
      * by offlining code ... so we don't care about that.
      */
     page = pfn_to_online_page(section_nr_to_pfn(mem->start_section_nr));
     if (page && zone_idx(page_zone(page)) == ZONE_MOVABLE)
         online_type = MMOP_ONLINE_MOVABLE;
 
     rc = device_offline(&mem->dev);
     /*
      * Default is MMOP_OFFLINE - change it only if offlining succeeded,
      * so try_reonline_memory_block() can do the right thing.
      */
     if (!rc)
         **online_types = online_type;
 
     (*online_types)++;
     /* Ignore if already offline. */
     return rc < 0 ? rc : 0;
 }
 
 static int try_reonline_memory_block(struct memory_block *mem, void *arg)
 {
     uint8_t **online_types = arg;
     int rc;
 
     if (**online_types != MMOP_OFFLINE) {
         mem->online_type = **online_types;
         rc = device_online(&mem->dev);
         if (rc < 0)
             pr_warn("%s: Failed to re-online memory: %d",
                 __func__, rc);
     }
 
     /* Continue processing all remaining memory blocks. */
     (*online_types)++;
     return 0;
 }
 
 /*
  * Try to offline and remove memory. Might take a long time to finish in case
  * memory is still in use. Primarily useful for memory devices that logically
  * unplugged all memory (so it's no longer in use) and want to offline + remove
  * that memory.
  */
 int offline_and_remove_memory(u64 start, u64 size)
 {
     const unsigned long mb_count = size / memory_block_size_bytes();
     uint8_t *online_types, *tmp;
     int rc;
 
     if (!IS_ALIGNED(start, memory_block_size_bytes()) ||
         !IS_ALIGNED(size, memory_block_size_bytes()) || !size)
         return -EINVAL;
 
     /*
      * We'll remember the old online type of each memory block, so we can
      * try to revert whatever we did when offlining one memory block fails
      * after offlining some others succeeded.
      */
     online_types = kmalloc_array(mb_count, sizeof(*online_types),
                      GFP_KERNEL);
     if (!online_types)
         return -ENOMEM;
     /*
      * Initialize all states to MMOP_OFFLINE, so when we abort processing in
      * try_offline_memory_block(), we'll skip all unprocessed blocks in
      * try_reonline_memory_block().
      */
     memset(online_types, MMOP_OFFLINE, mb_count);
 
     lock_device_hotplug();
 
     tmp = online_types;
     rc = walk_memory_blocks(start, size, &tmp, try_offline_memory_block);
 
     /*
      * In case we succeeded to offline all memory, remove it.
      * This cannot fail as it cannot get onlined in the meantime.
      */
     if (!rc) {
         rc = try_remove_memory(start, size);
         if (rc)
             pr_err("%s: Failed to remove memory: %d", __func__, rc);
     }
 
     /*
      * Rollback what we did. While memory onlining might theoretically fail
      * (nacked by a notifier), it barely ever happens.
      */
     if (rc) {
         tmp = online_types;
         walk_memory_blocks(start, size, &tmp,
                    try_reonline_memory_block);
     }
     unlock_device_hotplug();
 
     kfree(online_types);
     return rc;
 }
 EXPORT_SYMBOL_GPL(offline_and_remove_memory);
 #endif /* CONFIG_MEMORY_HOTREMOVE */

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