TOMOYO Linux Cross Reference
Linux/mm/page_alloc.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    *  linux/mm/page_alloc.c
    *
    *  Manages the free list, the system allocates free pages here.
    *  Note that kmalloc() lives in slab.c
    *
    *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
    *  Swap reorganised 29.12.95, Stephen Tweedie
   *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
   *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
   *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
   *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
   *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
   *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
   */
  
  #include <linux/stddef.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/interrupt.h>
  #include <linux/jiffies.h>
  #include <linux/compiler.h>
  #include <linux/kernel.h>
  #include <linux/kasan.h>
  #include <linux/kmsan.h>
  #include <linux/module.h>
  #include <linux/suspend.h>
  #include <linux/ratelimit.h>
  #include <linux/oom.h>
  #include <linux/topology.h>
  #include <linux/sysctl.h>
  #include <linux/cpu.h>
  #include <linux/cpuset.h>
  #include <linux/pagevec.h>
  #include <linux/memory_hotplug.h>
  #include <linux/nodemask.h>
  #include <linux/vmstat.h>
  #include <linux/fault-inject.h>
  #include <linux/compaction.h>
  #include <trace/events/kmem.h>
  #include <trace/events/oom.h>
  #include <linux/prefetch.h>
  #include <linux/mm_inline.h>
  #include <linux/mmu_notifier.h>
  #include <linux/migrate.h>
  #include <linux/sched/mm.h>
  #include <linux/page_owner.h>
  #include <linux/page_table_check.h>
  #include <linux/memcontrol.h>
  #include <linux/ftrace.h>
  #include <linux/lockdep.h>
  #include <linux/psi.h>
  #include <linux/khugepaged.h>
  #include <linux/delayacct.h>
  #include <linux/cacheinfo.h>
  #include <linux/pgalloc_tag.h>
  #include <asm/div64.h>
  #include "internal.h"
  #include "shuffle.h"
  #include "page_reporting.h"
  
  /* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
  typedef int __bitwise fpi_t;
  
  /* No special request */
  #define FPI_NONE                ((__force fpi_t)0)
  
  /*
   * Skip free page reporting notification for the (possibly merged) page.
   * This does not hinder free page reporting from grabbing the page,
   * reporting it and marking it "reported" -  it only skips notifying
   * the free page reporting infrastructure about a newly freed page. For
   * example, used when temporarily pulling a page from a freelist and
   * putting it back unmodified.
   */
  #define FPI_SKIP_REPORT_NOTIFY  ((__force fpi_t)BIT(0))
  
  /*
   * Place the (possibly merged) page to the tail of the freelist. Will ignore
   * page shuffling (relevant code - e.g., memory onlining - is expected to
   * shuffle the whole zone).
   *
   * Note: No code should rely on this flag for correctness - it's purely
   *       to allow for optimizations when handing back either fresh pages
   *       (memory onlining) or untouched pages (page isolation, free page
   *       reporting).
   */
  #define FPI_TO_TAIL             ((__force fpi_t)BIT(1))
  
  /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
  static DEFINE_MUTEX(pcp_batch_high_lock);
  #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
  
  #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
  /*
   * On SMP, spin_trylock is sufficient protection.
   * On PREEMPT_RT, spin_trylock is equivalent on both SMP and UP.
   */
 #define pcp_trylock_prepare(flags)      do { } while (0)
 #define pcp_trylock_finish(flag)        do { } while (0)
 #else
 
 /* UP spin_trylock always succeeds so disable IRQs to prevent re-entrancy. */
 #define pcp_trylock_prepare(flags)      local_irq_save(flags)
 #define pcp_trylock_finish(flags)       local_irq_restore(flags)
 #endif
 
 /*
  * Locking a pcp requires a PCP lookup followed by a spinlock. To avoid
  * a migration causing the wrong PCP to be locked and remote memory being
  * potentially allocated, pin the task to the CPU for the lookup+lock.
  * preempt_disable is used on !RT because it is faster than migrate_disable.
  * migrate_disable is used on RT because otherwise RT spinlock usage is
  * interfered with and a high priority task cannot preempt the allocator.
  */
 #ifndef CONFIG_PREEMPT_RT
 #define pcpu_task_pin()         preempt_disable()
 #define pcpu_task_unpin()       preempt_enable()
 #else
 #define pcpu_task_pin()         migrate_disable()
 #define pcpu_task_unpin()       migrate_enable()
 #endif
 
 /*
  * Generic helper to lookup and a per-cpu variable with an embedded spinlock.
  * Return value should be used with equivalent unlock helper.
  */
 #define pcpu_spin_lock(type, member, ptr)                               \
 ({                                                                      \
         type *_ret;                                                     \
         pcpu_task_pin();                                                \
         _ret = this_cpu_ptr(ptr);                                       \
         spin_lock(&_ret->member);                                       \
         _ret;                                                           \
 })
 
 #define pcpu_spin_trylock(type, member, ptr)                            \
 ({                                                                      \
         type *_ret;                                                     \
         pcpu_task_pin();                                                \
         _ret = this_cpu_ptr(ptr);                                       \
         if (!spin_trylock(&_ret->member)) {                             \
                 pcpu_task_unpin();                                      \
                 _ret = NULL;                                            \
         }                                                               \
         _ret;                                                           \
 })
 
 #define pcpu_spin_unlock(member, ptr)                                   \
 ({                                                                      \
         spin_unlock(&ptr->member);                                      \
         pcpu_task_unpin();                                              \
 })
 
 /* struct per_cpu_pages specific helpers. */
 #define pcp_spin_lock(ptr)                                              \
         pcpu_spin_lock(struct per_cpu_pages, lock, ptr)
 
 #define pcp_spin_trylock(ptr)                                           \
         pcpu_spin_trylock(struct per_cpu_pages, lock, ptr)
 
 #define pcp_spin_unlock(ptr)                                            \
         pcpu_spin_unlock(lock, ptr)
 
 #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
 DEFINE_PER_CPU(int, numa_node);
 EXPORT_PER_CPU_SYMBOL(numa_node);
 #endif
 
 DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 /*
  * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
  * It will not be defined when CONFIG_HAVE_MEMORYLESS_NODES is not defined.
  * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem()
  * defined in <linux/topology.h>.
  */
 DEFINE_PER_CPU(int, _numa_mem_);                /* Kernel "local memory" node */
 EXPORT_PER_CPU_SYMBOL(_numa_mem_);
 #endif
 
 static DEFINE_MUTEX(pcpu_drain_mutex);
 
 #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
 volatile unsigned long latent_entropy __latent_entropy;
 EXPORT_SYMBOL(latent_entropy);
 #endif
 
 /*
  * Array of node states.
  */
 nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
         [N_POSSIBLE] = NODE_MASK_ALL,
         [N_ONLINE] = { { [0] = 1UL } },
 #ifndef CONFIG_NUMA
         [N_NORMAL_MEMORY] = { { [0] = 1UL } },
 #ifdef CONFIG_HIGHMEM
         [N_HIGH_MEMORY] = { { [0] = 1UL } },
 #endif
         [N_MEMORY] = { { [0] = 1UL } },
         [N_CPU] = { { [0] = 1UL } },
 #endif  /* NUMA */
 };
 EXPORT_SYMBOL(node_states);
 
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
 unsigned int pageblock_order __read_mostly;
 #endif
 
 static void __free_pages_ok(struct page *page, unsigned int order,
                             fpi_t fpi_flags);
 
 /*
  * results with 256, 32 in the lowmem_reserve sysctl:
  *      1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
  *      1G machine -> (16M dma, 784M normal, 224M high)
  *      NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
  *      HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
  *      HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
  *
  * TBD: should special case ZONE_DMA32 machines here - in those we normally
  * don't need any ZONE_NORMAL reservation
  */
 static int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
         [ZONE_DMA] = 256,
 #endif
 #ifdef CONFIG_ZONE_DMA32
         [ZONE_DMA32] = 256,
 #endif
         [ZONE_NORMAL] = 32,
 #ifdef CONFIG_HIGHMEM
         [ZONE_HIGHMEM] = 0,
 #endif
         [ZONE_MOVABLE] = 0,
 };
 
 char * const zone_names[MAX_NR_ZONES] = {
 #ifdef CONFIG_ZONE_DMA
          "DMA",
 #endif
 #ifdef CONFIG_ZONE_DMA32
          "DMA32",
 #endif
          "Normal",
 #ifdef CONFIG_HIGHMEM
          "HighMem",
 #endif
          "Movable",
 #ifdef CONFIG_ZONE_DEVICE
          "Device",
 #endif
 };
 
 const char * const migratetype_names[MIGRATE_TYPES] = {
         "Unmovable",
         "Movable",
         "Reclaimable",
         "HighAtomic",
 #ifdef CONFIG_CMA
         "CMA",
 #endif
 #ifdef CONFIG_MEMORY_ISOLATION
         "Isolate",
 #endif
 };
 
 int min_free_kbytes = 1024;
 int user_min_free_kbytes = -1;
 static int watermark_boost_factor __read_mostly = 15000;
 static int watermark_scale_factor = 10;
 
 /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
 int movable_zone;
 EXPORT_SYMBOL(movable_zone);
 
 #if MAX_NUMNODES > 1
 unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
 unsigned int nr_online_nodes __read_mostly = 1;
 EXPORT_SYMBOL(nr_node_ids);
 EXPORT_SYMBOL(nr_online_nodes);
 #endif
 
 static bool page_contains_unaccepted(struct page *page, unsigned int order);
 static void accept_page(struct page *page, unsigned int order);
 static bool cond_accept_memory(struct zone *zone, unsigned int order);
 static inline bool has_unaccepted_memory(void);
 static bool __free_unaccepted(struct page *page);
 
 int page_group_by_mobility_disabled __read_mostly;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 /*
  * During boot we initialize deferred pages on-demand, as needed, but once
  * page_alloc_init_late() has finished, the deferred pages are all initialized,
  * and we can permanently disable that path.
  */
 DEFINE_STATIC_KEY_TRUE(deferred_pages);
 
 static inline bool deferred_pages_enabled(void)
 {
         return static_branch_unlikely(&deferred_pages);
 }
 
 /*
  * deferred_grow_zone() is __init, but it is called from
  * get_page_from_freelist() during early boot until deferred_pages permanently
  * disables this call. This is why we have refdata wrapper to avoid warning,
  * and to ensure that the function body gets unloaded.
  */
 static bool __ref
 _deferred_grow_zone(struct zone *zone, unsigned int order)
 {
         return deferred_grow_zone(zone, order);
 }
 #else
 static inline bool deferred_pages_enabled(void)
 {
         return false;
 }
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 /* Return a pointer to the bitmap storing bits affecting a block of pages */
 static inline unsigned long *get_pageblock_bitmap(const struct page *page,
                                                         unsigned long pfn)
 {
 #ifdef CONFIG_SPARSEMEM
         return section_to_usemap(__pfn_to_section(pfn));
 #else
         return page_zone(page)->pageblock_flags;
 #endif /* CONFIG_SPARSEMEM */
 }
 
 static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
 {
 #ifdef CONFIG_SPARSEMEM
         pfn &= (PAGES_PER_SECTION-1);
 #else
         pfn = pfn - pageblock_start_pfn(page_zone(page)->zone_start_pfn);
 #endif /* CONFIG_SPARSEMEM */
         return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
 }
 
 /**
  * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
  * @page: The page within the block of interest
  * @pfn: The target page frame number
  * @mask: mask of bits that the caller is interested in
  *
  * Return: pageblock_bits flags
  */
 unsigned long get_pfnblock_flags_mask(const struct page *page,
                                         unsigned long pfn, unsigned long mask)
 {
         unsigned long *bitmap;
         unsigned long bitidx, word_bitidx;
         unsigned long word;
 
         bitmap = get_pageblock_bitmap(page, pfn);
         bitidx = pfn_to_bitidx(page, pfn);
         word_bitidx = bitidx / BITS_PER_LONG;
         bitidx &= (BITS_PER_LONG-1);
         /*
          * This races, without locks, with set_pfnblock_flags_mask(). Ensure
          * a consistent read of the memory array, so that results, even though
          * racy, are not corrupted.
          */
         word = READ_ONCE(bitmap[word_bitidx]);
         return (word >> bitidx) & mask;
 }
 
 static __always_inline int get_pfnblock_migratetype(const struct page *page,
                                         unsigned long pfn)
 {
         return get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
 }
 
 /**
  * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
  * @page: The page within the block of interest
  * @flags: The flags to set
  * @pfn: The target page frame number
  * @mask: mask of bits that the caller is interested in
  */
 void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
                                         unsigned long pfn,
                                         unsigned long mask)
 {
         unsigned long *bitmap;
         unsigned long bitidx, word_bitidx;
         unsigned long word;
 
         BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
         BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
 
         bitmap = get_pageblock_bitmap(page, pfn);
         bitidx = pfn_to_bitidx(page, pfn);
         word_bitidx = bitidx / BITS_PER_LONG;
         bitidx &= (BITS_PER_LONG-1);
 
         VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
 
         mask <<= bitidx;
         flags <<= bitidx;
 
         word = READ_ONCE(bitmap[word_bitidx]);
         do {
         } while (!try_cmpxchg(&bitmap[word_bitidx], &word, (word & ~mask) | flags));
 }
 
 void set_pageblock_migratetype(struct page *page, int migratetype)
 {
         if (unlikely(page_group_by_mobility_disabled &&
                      migratetype < MIGRATE_PCPTYPES))
                 migratetype = MIGRATE_UNMOVABLE;
 
         set_pfnblock_flags_mask(page, (unsigned long)migratetype,
                                 page_to_pfn(page), MIGRATETYPE_MASK);
 }
 
 #ifdef CONFIG_DEBUG_VM
 static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 {
         int ret;
         unsigned seq;
         unsigned long pfn = page_to_pfn(page);
         unsigned long sp, start_pfn;
 
         do {
                 seq = zone_span_seqbegin(zone);
                 start_pfn = zone->zone_start_pfn;
                 sp = zone->spanned_pages;
                 ret = !zone_spans_pfn(zone, pfn);
         } while (zone_span_seqretry(zone, seq));
 
         if (ret)
                 pr_err("page 0x%lx outside node %d zone %s [ 0x%lx - 0x%lx ]\n",
                         pfn, zone_to_nid(zone), zone->name,
                         start_pfn, start_pfn + sp);
 
         return ret;
 }
 
 /*
  * Temporary debugging check for pages not lying within a given zone.
  */
 static bool __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
         if (page_outside_zone_boundaries(zone, page))
                 return true;
         if (zone != page_zone(page))
                 return true;
 
         return false;
 }
 #else
 static inline bool __maybe_unused bad_range(struct zone *zone, struct page *page)
 {
         return false;
 }
 #endif
 
 static void bad_page(struct page *page, const char *reason)
 {
         static unsigned long resume;
         static unsigned long nr_shown;
         static unsigned long nr_unshown;
 
         /*
          * Allow a burst of 60 reports, then keep quiet for that minute;
          * or allow a steady drip of one report per second.
          */
         if (nr_shown == 60) {
                 if (time_before(jiffies, resume)) {
                         nr_unshown++;
                         goto out;
                 }
                 if (nr_unshown) {
                         pr_alert(
                               "BUG: Bad page state: %lu messages suppressed\n",
                                 nr_unshown);
                         nr_unshown = 0;
                 }
                 nr_shown = 0;
         }
         if (nr_shown++ == 0)
                 resume = jiffies + 60 * HZ;
 
         pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
                 current->comm, page_to_pfn(page));
         dump_page(page, reason);
 
         print_modules();
         dump_stack();
 out:
         /* Leave bad fields for debug, except PageBuddy could make trouble */
         if (PageBuddy(page))
                 __ClearPageBuddy(page);
         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
 static inline unsigned int order_to_pindex(int migratetype, int order)
 {
         bool __maybe_unused movable;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         if (order > PAGE_ALLOC_COSTLY_ORDER) {
                 VM_BUG_ON(order != HPAGE_PMD_ORDER);
 
                 movable = migratetype == MIGRATE_MOVABLE;
 
                 return NR_LOWORDER_PCP_LISTS + movable;
         }
 #else
         VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
 #endif
 
         return (MIGRATE_PCPTYPES * order) + migratetype;
 }
 
 static inline int pindex_to_order(unsigned int pindex)
 {
         int order = pindex / MIGRATE_PCPTYPES;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         if (pindex >= NR_LOWORDER_PCP_LISTS)
                 order = HPAGE_PMD_ORDER;
 #else
         VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
 #endif
 
         return order;
 }
 
 static inline bool pcp_allowed_order(unsigned int order)
 {
         if (order <= PAGE_ALLOC_COSTLY_ORDER)
                 return true;
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         if (order == HPAGE_PMD_ORDER)
                 return true;
 #endif
         return false;
 }
 
 /*
  * Higher-order pages are called "compound pages".  They are structured thusly:
  *
  * The first PAGE_SIZE page is called the "head page" and have PG_head set.
  *
  * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
  * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
  *
  * The first tail page's ->compound_order holds the order of allocation.
  * This usage means that zero-order pages may not be compound.
  */
 
 void prep_compound_page(struct page *page, unsigned int order)
 {
         int i;
         int nr_pages = 1 << order;
 
         __SetPageHead(page);
         for (i = 1; i < nr_pages; i++)
                 prep_compound_tail(page, i);
 
         prep_compound_head(page, order);
 }
 
 static inline void set_buddy_order(struct page *page, unsigned int order)
 {
         set_page_private(page, order);
         __SetPageBuddy(page);
 }
 
 #ifdef CONFIG_COMPACTION
 static inline struct capture_control *task_capc(struct zone *zone)
 {
         struct capture_control *capc = current->capture_control;
 
         return unlikely(capc) &&
                 !(current->flags & PF_KTHREAD) &&
                 !capc->page &&
                 capc->cc->zone == zone ? capc : NULL;
 }
 
 static inline bool
 compaction_capture(struct capture_control *capc, struct page *page,
                    int order, int migratetype)
 {
         if (!capc || order != capc->cc->order)
                 return false;
 
         /* Do not accidentally pollute CMA or isolated regions*/
         if (is_migrate_cma(migratetype) ||
             is_migrate_isolate(migratetype))
                 return false;
 
         /*
          * Do not let lower order allocations pollute a movable pageblock
          * unless compaction is also requesting movable pages.
          * This might let an unmovable request use a reclaimable pageblock
          * and vice-versa but no more than normal fallback logic which can
          * have trouble finding a high-order free page.
          */
         if (order < pageblock_order && migratetype == MIGRATE_MOVABLE &&
             capc->cc->migratetype != MIGRATE_MOVABLE)
                 return false;
 
         capc->page = page;
         return true;
 }
 
 #else
 static inline struct capture_control *task_capc(struct zone *zone)
 {
         return NULL;
 }
 
 static inline bool
 compaction_capture(struct capture_control *capc, struct page *page,
                    int order, int migratetype)
 {
         return false;
 }
 #endif /* CONFIG_COMPACTION */
 
 static inline void account_freepages(struct zone *zone, int nr_pages,
                                      int migratetype)
 {
         if (is_migrate_isolate(migratetype))
                 return;
 
         __mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages);
 
         if (is_migrate_cma(migratetype))
                 __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages);
 }
 
 /* Used for pages not on another list */
 static inline void __add_to_free_list(struct page *page, struct zone *zone,
                                       unsigned int order, int migratetype,
                                       bool tail)
 {
         struct free_area *area = &zone->free_area[order];
 
         VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype,
                      "page type is %lu, passed migratetype is %d (nr=%d)\n",
                      get_pageblock_migratetype(page), migratetype, 1 << order);
 
         if (tail)
                 list_add_tail(&page->buddy_list, &area->free_list[migratetype]);
         else
                 list_add(&page->buddy_list, &area->free_list[migratetype]);
         area->nr_free++;
 }
 
 /*
  * Used for pages which are on another list. Move the pages to the tail
  * of the list - so the moved pages won't immediately be considered for
  * allocation again (e.g., optimization for memory onlining).
  */
 static inline void move_to_free_list(struct page *page, struct zone *zone,
                                      unsigned int order, int old_mt, int new_mt)
 {
         struct free_area *area = &zone->free_area[order];
 
         /* Free page moving can fail, so it happens before the type update */
         VM_WARN_ONCE(get_pageblock_migratetype(page) != old_mt,
                      "page type is %lu, passed migratetype is %d (nr=%d)\n",
                      get_pageblock_migratetype(page), old_mt, 1 << order);
 
         list_move_tail(&page->buddy_list, &area->free_list[new_mt]);
 
         account_freepages(zone, -(1 << order), old_mt);
         account_freepages(zone, 1 << order, new_mt);
 }
 
 static inline void __del_page_from_free_list(struct page *page, struct zone *zone,
                                              unsigned int order, int migratetype)
 {
         VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype,
                      "page type is %lu, passed migratetype is %d (nr=%d)\n",
                      get_pageblock_migratetype(page), migratetype, 1 << order);
 
         /* clear reported state and update reported page count */
         if (page_reported(page))
                 __ClearPageReported(page);
 
         list_del(&page->buddy_list);
         __ClearPageBuddy(page);
         set_page_private(page, 0);
         zone->free_area[order].nr_free--;
 }
 
 static inline void del_page_from_free_list(struct page *page, struct zone *zone,
                                            unsigned int order, int migratetype)
 {
         __del_page_from_free_list(page, zone, order, migratetype);
         account_freepages(zone, -(1 << order), migratetype);
 }
 
 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, buddy_list);
 }
 
 /*
  * If this is less than the 2nd largest possible page, check if the buddy
  * of the next-higher order is free. If it is, it's possible
  * that pages are being freed that will coalesce soon. In case,
  * that is happening, add the free page to the tail of the list
  * so it's less likely to be used soon and more likely to be merged
  * as a 2-level higher order page
  */
 static inline bool
 buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
                    struct page *page, unsigned int order)
 {
         unsigned long higher_page_pfn;
         struct page *higher_page;
 
         if (order >= MAX_PAGE_ORDER - 1)
                 return false;
 
         higher_page_pfn = buddy_pfn & pfn;
         higher_page = page + (higher_page_pfn - pfn);
 
         return find_buddy_page_pfn(higher_page, higher_page_pfn, order + 1,
                         NULL) != NULL;
 }
 
 /*
  * Freeing function for a buddy system allocator.
  *
  * The concept of a buddy system is to maintain direct-mapped table
  * (containing bit values) for memory blocks of various "orders".
  * The bottom level table contains the map for the smallest allocatable
  * units of memory (here, pages), and each level above it describes
  * pairs of units from the levels below, hence, "buddies".
  * At a high level, all that happens here is marking the table entry
  * at the bottom level available, and propagating the changes upward
  * as necessary, plus some accounting needed to play nicely with other
  * parts of the VM system.
  * At each level, we keep a list of pages, which are heads of continuous
  * free pages of length of (1 << order) and marked with PageBuddy.
  * Page's order is recorded in page_private(page) field.
  * So when we are allocating or freeing one, we can derive the state of the
  * other.  That is, if we allocate a small block, and both were
  * free, the remainder of the region must be split into blocks.
  * If a block is freed, and its buddy is also free, then this
  * triggers coalescing into a block of larger size.
  *
  * -- nyc
  */
 
 static inline void __free_one_page(struct page *page,
                 unsigned long pfn,
                 struct zone *zone, unsigned int order,
                 int migratetype, fpi_t fpi_flags)
 {
         struct capture_control *capc = task_capc(zone);
         unsigned long buddy_pfn = 0;
         unsigned long combined_pfn;
         struct page *buddy;
         bool to_tail;
 
         VM_BUG_ON(!zone_is_initialized(zone));
         VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
 
         VM_BUG_ON(migratetype == -1);
         VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
         VM_BUG_ON_PAGE(bad_range(zone, page), page);
 
         account_freepages(zone, 1 << order, migratetype);
 
         while (order < MAX_PAGE_ORDER) {
                 int buddy_mt = migratetype;
 
                 if (compaction_capture(capc, page, order, migratetype)) {
                         account_freepages(zone, -(1 << order), migratetype);
                         return;
                 }
 
                 buddy = find_buddy_page_pfn(page, pfn, order, &buddy_pfn);
                 if (!buddy)
                         goto done_merging;
 
                 if (unlikely(order >= pageblock_order)) {
                         /*
                          * We want to prevent merge between freepages on pageblock
                          * without fallbacks and normal pageblock. Without this,
                          * pageblock isolation could cause incorrect freepage or CMA
                          * accounting or HIGHATOMIC accounting.
                          */
                         buddy_mt = get_pfnblock_migratetype(buddy, buddy_pfn);
 
                         if (migratetype != buddy_mt &&
                             (!migratetype_is_mergeable(migratetype) ||
                              !migratetype_is_mergeable(buddy_mt)))
                                 goto done_merging;
                 }
 
                 /*
                  * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
                  * merge with it and move up one order.
                  */
                 if (page_is_guard(buddy))
                         clear_page_guard(zone, buddy, order);
                 else
                         __del_page_from_free_list(buddy, zone, order, buddy_mt);
 
                 if (unlikely(buddy_mt != migratetype)) {
                         /*
                          * Match buddy type. This ensures that an
                          * expand() down the line puts the sub-blocks
                          * on the right freelists.
                          */
                         set_pageblock_migratetype(buddy, migratetype);
                 }
 
                 combined_pfn = buddy_pfn & pfn;
                 page = page + (combined_pfn - pfn);
                 pfn = combined_pfn;
                 order++;
         }
 
 done_merging:
         set_buddy_order(page, order);
 
         if (fpi_flags & FPI_TO_TAIL)
                 to_tail = true;
         else if (is_shuffle_order(order))
                 to_tail = shuffle_pick_tail();
         else
                 to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);
 
         __add_to_free_list(page, zone, order, migratetype, to_tail);
 
         /* Notify page reporting subsystem of freed page */
         if (!(fpi_flags & FPI_SKIP_REPORT_NOTIFY))
                 page_reporting_notify_free(order);
 }
 
 /*
  * A bad page could be due to a number of fields. Instead of multiple branches,
  * try and check multiple fields with one check. The caller must do a detailed
  * check if necessary.
  */
 static inline bool page_expected_state(struct page *page,
                                         unsigned long check_flags)
 {
         if (unlikely(atomic_read(&page->_mapcount) != -1))
                 return false;
 
         if (unlikely((unsigned long)page->mapping |
                         page_ref_count(page) |
 #ifdef CONFIG_MEMCG
                         page->memcg_data |
 #endif
 #ifdef CONFIG_PAGE_POOL
                         ((page->pp_magic & ~0x3UL) == PP_SIGNATURE) |
 #endif
                         (page->flags & check_flags)))
                 return false;
 
         return true;
 }
 
 static const char *page_bad_reason(struct page *page, unsigned long flags)
 {
         const char *bad_reason = NULL;
 
         if (unlikely(atomic_read(&page->_mapcount) != -1))
                 bad_reason = "nonzero mapcount";
         if (unlikely(page->mapping != NULL))
                 bad_reason = "non-NULL mapping";
         if (unlikely(page_ref_count(page) != 0))
                 bad_reason = "nonzero _refcount";
         if (unlikely(page->flags & flags)) {
                 if (flags == PAGE_FLAGS_CHECK_AT_PREP)
                         bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag(s) set";
                 else
                         bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
         }
 #ifdef CONFIG_MEMCG
         if (unlikely(page->memcg_data))
                 bad_reason = "page still charged to cgroup";
 #endif
 #ifdef CONFIG_PAGE_POOL
         if (unlikely((page->pp_magic & ~0x3UL) == PP_SIGNATURE))
                 bad_reason = "page_pool leak";
 #endif
         return bad_reason;
 }
 
 static void free_page_is_bad_report(struct page *page)
 {
         bad_page(page,
                  page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
 }
 
 static inline bool free_page_is_bad(struct page *page)
 {
         if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
                 return false;
 
         /* Something has gone sideways, find it */
         free_page_is_bad_report(page);
         return true;
 }
 
 static inline bool is_check_pages_enabled(void)
 {
         return static_branch_unlikely(&check_pages_enabled);
 }
 
 static int free_tail_page_prepare(struct page *head_page, struct page *page)
 {
         struct folio *folio = (struct folio *)head_page;
         int ret = 1;
 
         /*
          * We rely page->lru.next never has bit 0 set, unless the page
          * is PageTail(). Let's make sure that's true even for poisoned ->lru.
          */
         BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);
 
         if (!is_check_pages_enabled()) {
                 ret = 0;
                 goto out;
         }
         switch (page - head_page) {
         case 1:
                 /* the first tail page: these may be in place of ->mapping */
                 if (unlikely(folio_entire_mapcount(folio))) {
                         bad_page(page, "nonzero entire_mapcount");
                         goto out;
                 }
                 if (unlikely(folio_large_mapcount(folio))) {
                         bad_page(page, "nonzero large_mapcount");
                         goto out;
                 }
                 if (unlikely(atomic_read(&folio->_nr_pages_mapped))) {
                         bad_page(page, "nonzero nr_pages_mapped");
                         goto out;
                 }
                 if (unlikely(atomic_read(&folio->_pincount))) {
                         bad_page(page, "nonzero pincount");
                         goto out;
                 }
                 break;
         case 2:
                 /* the second tail page: deferred_list overlaps ->mapping */
                 if (unlikely(!list_empty(&folio->_deferred_list))) {
                         bad_page(page, "on deferred list");
                         goto out;
                 }
                 break;
         default:
                 if (page->mapping != TAIL_MAPPING) {
                         bad_page(page, "corrupted mapping in tail page");
                         goto out;
                 }
                 break;
         }
         if (unlikely(!PageTail(page))) {
                 bad_page(page, "PageTail not set");
                 goto out;
         }
         if (unlikely(compound_head(page) != head_page)) {
                 bad_page(page, "compound_head not consistent");
                 goto out;
         }
         ret = 0;
 out:
         page->mapping = NULL;
         clear_compound_head(page);
         return ret;
 }
 
 /*
  * Skip KASAN memory poisoning when either:
  *
  * 1. For generic KASAN: deferred memory initialization has not yet completed.
  *    Tag-based KASAN modes skip pages freed via deferred memory initialization
  *    using page tags instead (see below).
  * 2. For tag-based KASAN modes: the page has a match-all KASAN tag, indicating
  *    that error detection is disabled for accesses via the page address.
  *
  * Pages will have match-all tags in the following circumstances:
  *
  * 1. Pages are being initialized for the first time, including during deferred
  *    memory init; see the call to page_kasan_tag_reset in __init_single_page.
  * 2. The allocation was not unpoisoned due to __GFP_SKIP_KASAN, with the
  *    exception of pages unpoisoned by kasan_unpoison_vmalloc.
  * 3. The allocation was excluded from being checked due to sampling,
  *    see the call to kasan_unpoison_pages.
  *
  * Poisoning pages during deferred memory init will greatly lengthen the
  * process and cause problem in large memory systems as the deferred pages
  * initialization is done with interrupt disabled.
  *
  * Assuming that there will be no reference to those newly initialized
  * pages before they are ever allocated, this should have no effect on
  * KASAN memory tracking as the poison will be properly inserted at page
  * allocation time. The only corner case is when pages are allocated by
  * on-demand allocation and then freed again before the deferred pages
  * initialization is done, but this is not likely to happen.
  */
 static inline bool should_skip_kasan_poison(struct page *page)
 {
         if (IS_ENABLED(CONFIG_KASAN_GENERIC))
                 return deferred_pages_enabled();
 
         return page_kasan_tag(page) == KASAN_TAG_KERNEL;
 }
 
 static void kernel_init_pages(struct page *page, int numpages)
 {
         int i;
 
         /* s390's use of memset() could override KASAN redzones. */
         kasan_disable_current();
         for (i = 0; i < numpages; i++)
                 clear_highpage_kasan_tagged(page + i);
         kasan_enable_current();
 }
 
 __always_inline bool free_pages_prepare(struct page *page,
                         unsigned int order)
 {
         int bad = 0;
         bool skip_kasan_poison = should_skip_kasan_poison(page);
         bool init = want_init_on_free();
         bool compound = PageCompound(page);
 
         VM_BUG_ON_PAGE(PageTail(page), page);
 
         trace_mm_page_free(page, order);
         kmsan_free_page(page, order);
 
         if (memcg_kmem_online() && PageMemcgKmem(page))
                 __memcg_kmem_uncharge_page(page, order);
 
         if (unlikely(PageHWPoison(page)) && !order) {
                 /* Do not let hwpoison pages hit pcplists/buddy */
                 reset_page_owner(page, order);
                 page_table_check_free(page, order);
                 pgalloc_tag_sub(page, 1 << order);
 
                 /*
                  * The page is isolated and accounted for.
                  * Mark the codetag as empty to avoid accounting error
                  * when the page is freed by unpoison_memory().
                  */
                 clear_page_tag_ref(page);
                 return false;
         }
 
         VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
         /*
          * Check tail pages before head page information is cleared to
          * avoid checking PageCompound for order-0 pages.
          */
         if (unlikely(order)) {
                 int i;
 
                 if (compound)
                         page[1].flags &= ~PAGE_FLAGS_SECOND;
                 for (i = 1; i < (1 << order); i++) {
                         if (compound)
                                 bad += free_tail_page_prepare(page, page + i);
                         if (is_check_pages_enabled()) {
                                 if (free_page_is_bad(page + i)) {
                                         bad++;
                                         continue;
                                 }
                         }
                         (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
                 }
         }
         if (PageMappingFlags(page))
                 page->mapping = NULL;
         if (is_check_pages_enabled()) {
                 if (free_page_is_bad(page))
                         bad++;
                 if (bad)
                         return false;
         }
 
         page_cpupid_reset_last(page);
         page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
         reset_page_owner(page, order);
         page_table_check_free(page, order);
         pgalloc_tag_sub(page, 1 << order);
 
         if (!PageHighMem(page)) {
                 debug_check_no_locks_freed(page_address(page),
                                            PAGE_SIZE << order);
                 debug_check_no_obj_freed(page_address(page),
                                            PAGE_SIZE << order);
         }
 
         kernel_poison_pages(page, 1 << order);
 
         /*
          * As memory initialization might be integrated into KASAN,
          * KASAN poisoning and memory initialization code must be
          * kept together to avoid discrepancies in behavior.
          *
          * With hardware tag-based KASAN, memory tags must be set before the
          * page becomes unavailable via debug_pagealloc or arch_free_page.
          */
         if (!skip_kasan_poison) {
                 kasan_poison_pages(page, order, init);
 
                 /* Memory is already initialized if KASAN did it internally. */
                 if (kasan_has_integrated_init())
                         init = false;
         }
         if (init)
                 kernel_init_pages(page, 1 << order);
 
         /*
          * arch_free_page() can make the page's contents inaccessible.  s390
          * does this.  So nothing which can access the page's contents should
          * happen after this.
          */
         arch_free_page(page, order);
 
         debug_pagealloc_unmap_pages(page, 1 << order);
 
         return true;
 }
 
 /*
  * Frees a number of pages from the PCP lists
  * Assumes all pages on list are in same zone.
  * count is the number of pages to free.
  */
 static void free_pcppages_bulk(struct zone *zone, int count,
                                         struct per_cpu_pages *pcp,
                                         int pindex)
 {
         unsigned long flags;
         unsigned int order;
         struct page *page;
 
         /*
          * Ensure proper count is passed which otherwise would stuck in the
          * below while (list_empty(list)) loop.
          */
         count = min(pcp->count, count);
 
         /* Ensure requested pindex is drained first. */
         pindex = pindex - 1;
 
         spin_lock_irqsave(&zone->lock, flags);
 
         while (count > 0) {
                 struct list_head *list;
                 int nr_pages;
 
                 /* Remove pages from lists in a round-robin fashion. */
                 do {
                         if (++pindex > NR_PCP_LISTS - 1)
                                 pindex = 0;
                         list = &pcp->lists[pindex];
                 } while (list_empty(list));
 
                 order = pindex_to_order(pindex);
                 nr_pages = 1 << order;
                 do {
                         unsigned long pfn;
                         int mt;
 
                         page = list_last_entry(list, struct page, pcp_list);
                         pfn = page_to_pfn(page);
                         mt = get_pfnblock_migratetype(page, pfn);
 
                         /* must delete to avoid corrupting pcp list */
                         list_del(&page->pcp_list);
                         count -= nr_pages;
                         pcp->count -= nr_pages;
 
                         __free_one_page(page, pfn, zone, order, mt, FPI_NONE);
                         trace_mm_page_pcpu_drain(page, order, mt);
                 } while (count > 0 && !list_empty(list));
         }
 
         spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 static void free_one_page(struct zone *zone, struct page *page,
                           unsigned long pfn, unsigned int order,
                           fpi_t fpi_flags)
 {
         unsigned long flags;
         int migratetype;
 
         spin_lock_irqsave(&zone->lock, flags);
         migratetype = get_pfnblock_migratetype(page, pfn);
         __free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
         spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 static void __free_pages_ok(struct page *page, unsigned int order,
                             fpi_t fpi_flags)
 {
         unsigned long pfn = page_to_pfn(page);
         struct zone *zone = page_zone(page);
 
         if (!free_pages_prepare(page, order))
                 return;
 
         free_one_page(zone, page, pfn, order, fpi_flags);
 
         __count_vm_events(PGFREE, 1 << order);
 }
 
 void __meminit __free_pages_core(struct page *page, unsigned int order,
                 enum meminit_context context)
 {
         unsigned int nr_pages = 1 << order;
         struct page *p = page;
         unsigned int loop;
 
         /*
          * When initializing the memmap, __init_single_page() sets the refcount
          * of all pages to 1 ("allocated"/"not free"). We have to set the
          * refcount of all involved pages to 0.
          *
          * Note that hotplugged memory pages are initialized to PageOffline().
          * Pages freed from memblock might be marked as reserved.
          */
         if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG) &&
             unlikely(context == MEMINIT_HOTPLUG)) {
                 for (loop = 0; loop < nr_pages; loop++, p++) {
                         VM_WARN_ON_ONCE(PageReserved(p));
                         __ClearPageOffline(p);
                         set_page_count(p, 0);
                 }
 
                 /*
                  * Freeing the page with debug_pagealloc enabled will try to
                  * unmap it; some archs don't like double-unmappings, so
                  * map it first.
                  */
                 debug_pagealloc_map_pages(page, nr_pages);
                 adjust_managed_page_count(page, nr_pages);
         } else {
                 for (loop = 0; loop < nr_pages; loop++, p++) {
                         __ClearPageReserved(p);
                         set_page_count(p, 0);
                 }
 
                 /* memblock adjusts totalram_pages() manually. */
                 atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
         }
 
         if (page_contains_unaccepted(page, order)) {
                 if (order == MAX_PAGE_ORDER && __free_unaccepted(page))
                         return;
 
                 accept_page(page, order);
         }
 
         /*
          * Bypass PCP and place fresh pages right to the tail, primarily
          * relevant for memory onlining.
          */
         __free_pages_ok(page, order, FPI_TO_TAIL);
 }
 
 /*
  * Check that the whole (or subset of) a pageblock given by the interval of
  * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
  * with the migration of free compaction scanner.
  *
  * Return struct page pointer of start_pfn, or NULL if checks were not passed.
  *
  * It's possible on some configurations to have a setup like node0 node1 node0
  * i.e. it's possible that all pages within a zones range of pages do not
  * belong to a single zone. We assume that a border between node0 and node1
  * can occur within a single pageblock, but not a node0 node1 node0
  * interleaving within a single pageblock. It is therefore sufficient to check
  * the first and last page of a pageblock and avoid checking each individual
  * page in a pageblock.
  *
  * Note: the function may return non-NULL struct page even for a page block
  * which contains a memory hole (i.e. there is no physical memory for a subset
  * of the pfn range). For example, if the pageblock order is MAX_PAGE_ORDER, which
  * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole
  * even though the start pfn is online and valid. This should be safe most of
  * the time because struct pages are still initialized via init_unavailable_range()
  * and pfn walkers shouldn't touch any physical memory range for which they do
  * not recognize any specific metadata in struct pages.
  */
 struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
                                      unsigned long end_pfn, struct zone *zone)
 {
         struct page *start_page;
         struct page *end_page;
 
         /* end_pfn is one past the range we are checking */
         end_pfn--;
 
         if (!pfn_valid(end_pfn))
                 return NULL;
 
         start_page = pfn_to_online_page(start_pfn);
         if (!start_page)
                 return NULL;
 
         if (page_zone(start_page) != zone)
                 return NULL;
 
         end_page = pfn_to_page(end_pfn);
 
         /* This gives a shorter code than deriving page_zone(end_page) */
         if (page_zone_id(start_page) != page_zone_id(end_page))
                 return NULL;
 
         return start_page;
 }
 
 /*
  * The order of subdivision here is critical for the IO subsystem.
  * Please do not alter this order without good reasons and regression
  * testing. Specifically, as large blocks of memory are subdivided,
  * the order in which smaller blocks are delivered depends on the order
  * they're subdivided in this function. This is the primary factor
  * influencing the order in which pages are delivered to the IO
  * subsystem according to empirical testing, and this is also justified
  * by considering the behavior of a buddy system containing a single
  * large block of memory acted on by a series of small allocations.
  * This behavior is a critical factor in sglist merging's success.
  *
  * -- nyc
  */
 static inline void expand(struct zone *zone, struct page *page,
         int low, int high, int migratetype)
 {
         unsigned long size = 1 << high;
         unsigned long nr_added = 0;
 
         while (high > low) {
                 high--;
                 size >>= 1;
                 VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
 
                 /*
                  * Mark as guard pages (or page), that will allow to
                  * merge back to allocator when buddy will be freed.
                  * Corresponding page table entries will not be touched,
                  * pages will stay not present in virtual address space
                  */
                 if (set_page_guard(zone, &page[size], high))
                         continue;
 
                 __add_to_free_list(&page[size], zone, high, migratetype, false);
                 set_buddy_order(&page[size], high);
                 nr_added += size;
         }
         account_freepages(zone, nr_added, migratetype);
 }
 
 static void check_new_page_bad(struct page *page)
 {
         if (unlikely(page->flags & __PG_HWPOISON)) {
                 /* Don't complain about hwpoisoned pages */
                 if (PageBuddy(page))
                         __ClearPageBuddy(page);
                 return;
         }
 
         bad_page(page,
                  page_bad_reason(page, PAGE_FLAGS_CHECK_AT_PREP));
 }
 
 /*
  * This page is about to be returned from the page allocator
  */
 static bool check_new_page(struct page *page)
 {
         if (likely(page_expected_state(page,
                                 PAGE_FLAGS_CHECK_AT_PREP|__PG_HWPOISON)))
                 return false;
 
         check_new_page_bad(page);
         return true;
 }
 
 static inline bool check_new_pages(struct page *page, unsigned int order)
 {
         if (is_check_pages_enabled()) {
                 for (int i = 0; i < (1 << order); i++) {
                         struct page *p = page + i;
 
                         if (check_new_page(p))
                                 return true;
                 }
         }
 
         return false;
 }
 
 static inline bool should_skip_kasan_unpoison(gfp_t flags)
 {
         /* Don't skip if a software KASAN mode is enabled. */
         if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
             IS_ENABLED(CONFIG_KASAN_SW_TAGS))
                 return false;
 
         /* Skip, if hardware tag-based KASAN is not enabled. */
         if (!kasan_hw_tags_enabled())
                 return true;
 
         /*
          * With hardware tag-based KASAN enabled, skip if this has been
          * requested via __GFP_SKIP_KASAN.
          */
         return flags & __GFP_SKIP_KASAN;
 }
 
 static inline bool should_skip_init(gfp_t flags)
 {
         /* Don't skip, if hardware tag-based KASAN is not enabled. */
         if (!kasan_hw_tags_enabled())
                 return false;
 
         /* For hardware tag-based KASAN, skip if requested. */
         return (flags & __GFP_SKIP_ZERO);
 }
 
 inline void post_alloc_hook(struct page *page, unsigned int order,
                                 gfp_t gfp_flags)
 {
         bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&
                         !should_skip_init(gfp_flags);
         bool zero_tags = init && (gfp_flags & __GFP_ZEROTAGS);
         int i;
 
         set_page_private(page, 0);
         set_page_refcounted(page);
 
         arch_alloc_page(page, order);
         debug_pagealloc_map_pages(page, 1 << order);
 
         /*
          * Page unpoisoning must happen before memory initialization.
          * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
          * allocations and the page unpoisoning code will complain.
          */
         kernel_unpoison_pages(page, 1 << order);
 
         /*
          * As memory initialization might be integrated into KASAN,
          * KASAN unpoisoning and memory initializion code must be
          * kept together to avoid discrepancies in behavior.
          */
 
         /*
          * If memory tags should be zeroed
          * (which happens only when memory should be initialized as well).
          */
         if (zero_tags) {
                 /* Initialize both memory and memory tags. */
                 for (i = 0; i != 1 << order; ++i)
                         tag_clear_highpage(page + i);
 
                 /* Take note that memory was initialized by the loop above. */
                 init = false;
         }
         if (!should_skip_kasan_unpoison(gfp_flags) &&
             kasan_unpoison_pages(page, order, init)) {
                 /* Take note that memory was initialized by KASAN. */
                 if (kasan_has_integrated_init())
                         init = false;
         } else {
                 /*
                  * If memory tags have not been set by KASAN, reset the page
                  * tags to ensure page_address() dereferencing does not fault.
                  */
                 for (i = 0; i != 1 << order; ++i)
                         page_kasan_tag_reset(page + i);
         }
         /* If memory is still not initialized, initialize it now. */
         if (init)
                 kernel_init_pages(page, 1 << order);
 
         set_page_owner(page, order, gfp_flags);
         page_table_check_alloc(page, order);
         pgalloc_tag_add(page, current, 1 << order);
 }
 
 static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
                                                         unsigned int alloc_flags)
 {
         post_alloc_hook(page, order, gfp_flags);
 
         if (order && (gfp_flags & __GFP_COMP))
                 prep_compound_page(page, order);
 
         /*
          * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to
          * allocate the page. The expectation is that the caller is taking
          * steps that will free more memory. The caller should avoid the page
          * being used for !PFMEMALLOC purposes.
          */
         if (alloc_flags & ALLOC_NO_WATERMARKS)
                 set_page_pfmemalloc(page);
         else
                 clear_page_pfmemalloc(page);
 }
 
 /*
  * Go through the free lists for the given migratetype and remove
  * the smallest available page from the freelists
  */
 static __always_inline
 struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
                                                 int migratetype)
 {
         unsigned int current_order;
         struct free_area *area;
         struct page *page;
 
         /* Find a page of the appropriate size in the preferred list */
         for (current_order = order; current_order < NR_PAGE_ORDERS; ++current_order) {
                 area = &(zone->free_area[current_order]);
                 page = get_page_from_free_area(area, migratetype);
                 if (!page)
                         continue;
                 del_page_from_free_list(page, zone, current_order, migratetype);
                 expand(zone, page, order, current_order, migratetype);
                 trace_mm_page_alloc_zone_locked(page, order, migratetype,
                                 pcp_allowed_order(order) &&
                                 migratetype < MIGRATE_PCPTYPES);
                 return page;
         }
 
         return NULL;
 }
 
 
 /*
  * This array describes the order lists are fallen back to when
  * the free lists for the desirable migrate type are depleted
  *
  * The other migratetypes do not have fallbacks.
  */
 static int fallbacks[MIGRATE_PCPTYPES][MIGRATE_PCPTYPES - 1] = {
         [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE   },
         [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE },
         [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE   },
 };
 
 #ifdef CONFIG_CMA
 static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                                         unsigned int order)
 {
         return __rmqueue_smallest(zone, order, MIGRATE_CMA);
 }
 #else
 static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                                         unsigned int order) { return NULL; }
 #endif
 
 /*
  * Change the type of a block and move all its free pages to that
  * type's freelist.
  */
 static int __move_freepages_block(struct zone *zone, unsigned long start_pfn,
                                   int old_mt, int new_mt)
 {
         struct page *page;
         unsigned long pfn, end_pfn;
         unsigned int order;
         int pages_moved = 0;
 
         VM_WARN_ON(start_pfn & (pageblock_nr_pages - 1));
         end_pfn = pageblock_end_pfn(start_pfn);
 
         for (pfn = start_pfn; pfn < end_pfn;) {
                 page = pfn_to_page(pfn);
                 if (!PageBuddy(page)) {
                         pfn++;
                         continue;
                 }
 
                 /* Make sure we are not inadvertently changing nodes */
                 VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
                 VM_BUG_ON_PAGE(page_zone(page) != zone, page);
 
                 order = buddy_order(page);
 
                 move_to_free_list(page, zone, order, old_mt, new_mt);
 
                 pfn += 1 << order;
                 pages_moved += 1 << order;
         }
 
         set_pageblock_migratetype(pfn_to_page(start_pfn), new_mt);
 
         return pages_moved;
 }
 
 static bool prep_move_freepages_block(struct zone *zone, struct page *page,
                                       unsigned long *start_pfn,
                                       int *num_free, int *num_movable)
 {
         unsigned long pfn, start, end;
 
         pfn = page_to_pfn(page);
         start = pageblock_start_pfn(pfn);
         end = pageblock_end_pfn(pfn);
 
         /*
          * The caller only has the lock for @zone, don't touch ranges
          * that straddle into other zones. While we could move part of
          * the range that's inside the zone, this call is usually
          * accompanied by other operations such as migratetype updates
          * which also should be locked.
          */
         if (!zone_spans_pfn(zone, start))
                 return false;
         if (!zone_spans_pfn(zone, end - 1))
                 return false;
 
         *start_pfn = start;
 
         if (num_free) {
                 *num_free = 0;
                 *num_movable = 0;
                 for (pfn = start; pfn < end;) {
                         page = pfn_to_page(pfn);
                         if (PageBuddy(page)) {
                                 int nr = 1 << buddy_order(page);
 
                                 *num_free += nr;
                                 pfn += nr;
                                 continue;
                         }
                         /*
                          * We assume that pages that could be isolated for
                          * migration are movable. But we don't actually try
                          * isolating, as that would be expensive.
                          */
                         if (PageLRU(page) || __PageMovable(page))
                                 (*num_movable)++;
                         pfn++;
                 }
         }
 
         return true;
 }
 
 static int move_freepages_block(struct zone *zone, struct page *page,
                                 int old_mt, int new_mt)
 {
         unsigned long start_pfn;
 
         if (!prep_move_freepages_block(zone, page, &start_pfn, NULL, NULL))
                 return -1;
 
         return __move_freepages_block(zone, start_pfn, old_mt, new_mt);
 }
 
 #ifdef CONFIG_MEMORY_ISOLATION
 /* Look for a buddy that straddles start_pfn */
 static unsigned long find_large_buddy(unsigned long start_pfn)
 {
         int order = 0;
         struct page *page;
         unsigned long pfn = start_pfn;
 
         while (!PageBuddy(page = pfn_to_page(pfn))) {
                 /* Nothing found */
                 if (++order > MAX_PAGE_ORDER)
                         return start_pfn;
                 pfn &= ~0UL << order;
         }
 
         /*
          * Found a preceding buddy, but does it straddle?
          */
         if (pfn + (1 << buddy_order(page)) > start_pfn)
                 return pfn;
 
         /* Nothing found */
         return start_pfn;
 }
 
 /* Split a multi-block free page into its individual pageblocks */
 static void split_large_buddy(struct zone *zone, struct page *page,
                               unsigned long pfn, int order)
 {
         unsigned long end_pfn = pfn + (1 << order);
 
         VM_WARN_ON_ONCE(order <= pageblock_order);
         VM_WARN_ON_ONCE(pfn & (pageblock_nr_pages - 1));
 
         /* Caller removed page from freelist, buddy info cleared! */
         VM_WARN_ON_ONCE(PageBuddy(page));
 
         while (pfn != end_pfn) {
                 int mt = get_pfnblock_migratetype(page, pfn);
 
                 __free_one_page(page, pfn, zone, pageblock_order, mt, FPI_NONE);
                 pfn += pageblock_nr_pages;
                 page = pfn_to_page(pfn);
         }
 }
 
 /**
  * move_freepages_block_isolate - move free pages in block for page isolation
  * @zone: the zone
  * @page: the pageblock page
  * @migratetype: migratetype to set on the pageblock
  *
  * This is similar to move_freepages_block(), but handles the special
  * case encountered in page isolation, where the block of interest
  * might be part of a larger buddy spanning multiple pageblocks.
  *
  * Unlike the regular page allocator path, which moves pages while
  * stealing buddies off the freelist, page isolation is interested in
  * arbitrary pfn ranges that may have overlapping buddies on both ends.
  *
  * This function handles that. Straddling buddies are split into
  * individual pageblocks. Only the block of interest is moved.
  *
  * Returns %true if pages could be moved, %false otherwise.
  */
 bool move_freepages_block_isolate(struct zone *zone, struct page *page,
                                   int migratetype)
 {
         unsigned long start_pfn, pfn;
 
         if (!prep_move_freepages_block(zone, page, &start_pfn, NULL, NULL))
                 return false;
 
         /* No splits needed if buddies can't span multiple blocks */
         if (pageblock_order == MAX_PAGE_ORDER)
                 goto move;
 
         /* We're a tail block in a larger buddy */
         pfn = find_large_buddy(start_pfn);
         if (pfn != start_pfn) {
                 struct page *buddy = pfn_to_page(pfn);
                 int order = buddy_order(buddy);
 
                 del_page_from_free_list(buddy, zone, order,
                                         get_pfnblock_migratetype(buddy, pfn));
                 set_pageblock_migratetype(page, migratetype);
                 split_large_buddy(zone, buddy, pfn, order);
                 return true;
         }
 
         /* We're the starting block of a larger buddy */
         if (PageBuddy(page) && buddy_order(page) > pageblock_order) {
                 int order = buddy_order(page);
 
                 del_page_from_free_list(page, zone, order,
                                         get_pfnblock_migratetype(page, pfn));
                 set_pageblock_migratetype(page, migratetype);
                 split_large_buddy(zone, page, pfn, order);
                 return true;
         }
 move:
         __move_freepages_block(zone, start_pfn,
                                get_pfnblock_migratetype(page, start_pfn),
                                migratetype);
         return true;
 }
 #endif /* CONFIG_MEMORY_ISOLATION */
 
 static void change_pageblock_range(struct page *pageblock_page,
                                         int start_order, int migratetype)
 {
         int nr_pageblocks = 1 << (start_order - pageblock_order);
 
         while (nr_pageblocks--) {
                 set_pageblock_migratetype(pageblock_page, migratetype);
                 pageblock_page += pageblock_nr_pages;
         }
 }
 
 /*
  * When we are falling back to another migratetype during allocation, try to
  * steal extra free pages from the same pageblocks to satisfy further
  * allocations, instead of polluting multiple pageblocks.
  *
  * If we are stealing a relatively large buddy page, it is likely there will
  * be more free pages in the pageblock, so try to steal them all. For
  * reclaimable and unmovable allocations, we steal regardless of page size,
  * as fragmentation caused by those allocations polluting movable pageblocks
  * is worse than movable allocations stealing from unmovable and reclaimable
  * pageblocks.
  */
 static bool can_steal_fallback(unsigned int order, int start_mt)
 {
         /*
          * Leaving this order check is intended, although there is
          * relaxed order check in next check. The reason is that
          * we can actually steal whole pageblock if this condition met,
          * but, below check doesn't guarantee it and that is just heuristic
          * so could be changed anytime.
          */
         if (order >= pageblock_order)
                 return true;
 
         if (order >= pageblock_order / 2 ||
                 start_mt == MIGRATE_RECLAIMABLE ||
                 start_mt == MIGRATE_UNMOVABLE ||
                 page_group_by_mobility_disabled)
                 return true;
 
         return false;
 }
 
 static inline bool boost_watermark(struct zone *zone)
 {
         unsigned long max_boost;
 
         if (!watermark_boost_factor)
                 return false;
         /*
          * Don't bother in zones that are unlikely to produce results.
          * On small machines, including kdump capture kernels running
          * in a small area, boosting the watermark can cause an out of
          * memory situation immediately.
          */
         if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
                 return false;
 
         max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
                         watermark_boost_factor, 10000);
 
         /*
          * high watermark may be uninitialised if fragmentation occurs
          * very early in boot so do not boost. We do not fall
          * through and boost by pageblock_nr_pages as failing
          * allocations that early means that reclaim is not going
          * to help and it may even be impossible to reclaim the
          * boosted watermark resulting in a hang.
          */
         if (!max_boost)
                 return false;
 
         max_boost = max(pageblock_nr_pages, max_boost);
 
         zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages,
                 max_boost);
 
         return true;
 }
 
 /*
  * This function implements actual steal behaviour. If order is large enough, we
  * can claim the whole pageblock for the requested migratetype. If not, we check
  * the pageblock for constituent pages; if at least half of the pages are free
  * or compatible, we can still claim the whole block, so pages freed in the
  * future will be put on the correct free list. Otherwise, we isolate exactly
  * the order we need from the fallback block and leave its migratetype alone.
  */
 static struct page *
 steal_suitable_fallback(struct zone *zone, struct page *page,
                         int current_order, int order, int start_type,
                         unsigned int alloc_flags, bool whole_block)
 {
         int free_pages, movable_pages, alike_pages;
         unsigned long start_pfn;
         int block_type;
 
         block_type = get_pageblock_migratetype(page);
 
         /*
          * This can happen due to races and we want to prevent broken
          * highatomic accounting.
          */
         if (is_migrate_highatomic(block_type))
                 goto single_page;
 
         /* Take ownership for orders >= pageblock_order */
         if (current_order >= pageblock_order) {
                 del_page_from_free_list(page, zone, current_order, block_type);
                 change_pageblock_range(page, current_order, start_type);
                 expand(zone, page, order, current_order, start_type);
                 return page;
         }
 
         /*
          * Boost watermarks to increase reclaim pressure to reduce the
          * likelihood of future fallbacks. Wake kswapd now as the node
          * may be balanced overall and kswapd will not wake naturally.
          */
         if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
                 set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 
         /* We are not allowed to try stealing from the whole block */
         if (!whole_block)
                 goto single_page;
 
         /* moving whole block can fail due to zone boundary conditions */
         if (!prep_move_freepages_block(zone, page, &start_pfn, &free_pages,
                                        &movable_pages))
                 goto single_page;
 
         /*
          * Determine how many pages are compatible with our allocation.
          * For movable allocation, it's the number of movable pages which
          * we just obtained. For other types it's a bit more tricky.
          */
         if (start_type == MIGRATE_MOVABLE) {
                 alike_pages = movable_pages;
         } else {
                 /*
                  * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
                  * to MOVABLE pageblock, consider all non-movable pages as
                  * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
                  * vice versa, be conservative since we can't distinguish the
                  * exact migratetype of non-movable pages.
                  */
                 if (block_type == MIGRATE_MOVABLE)
                         alike_pages = pageblock_nr_pages
                                                 - (free_pages + movable_pages);
                 else
                         alike_pages = 0;
         }
         /*
          * If a sufficient number of pages in the block are either free or of
          * compatible migratability as our allocation, claim the whole block.
          */
         if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
                         page_group_by_mobility_disabled) {
                 __move_freepages_block(zone, start_pfn, block_type, start_type);
                 return __rmqueue_smallest(zone, order, start_type);
         }
 
 single_page:
         del_page_from_free_list(page, zone, current_order, block_type);
         expand(zone, page, order, current_order, block_type);
         return page;
 }
 
 /*
  * Check whether there is a suitable fallback freepage with requested order.
  * If only_stealable is true, this function returns fallback_mt only if
  * we can steal other freepages all together. This would help to reduce
  * fragmentation due to mixed migratetype pages in one pageblock.
  */
 int find_suitable_fallback(struct free_area *area, unsigned int order,
                         int migratetype, bool only_stealable, bool *can_steal)
 {
         int i;
         int fallback_mt;
 
         if (area->nr_free == 0)
                 return -1;
 
         *can_steal = false;
         for (i = 0; i < MIGRATE_PCPTYPES - 1 ; i++) {
                 fallback_mt = fallbacks[migratetype][i];
                 if (free_area_empty(area, fallback_mt))
                         continue;
 
                 if (can_steal_fallback(order, migratetype))
                         *can_steal = true;
 
                 if (!only_stealable)
                         return fallback_mt;
 
                 if (*can_steal)
                         return fallback_mt;
         }
 
         return -1;
 }
 
 /*
  * Reserve the pageblock(s) surrounding an allocation request for
  * exclusive use of high-order atomic allocations if there are no
  * empty page blocks that contain a page with a suitable order
  */
 static void reserve_highatomic_pageblock(struct page *page, int order,
                                          struct zone *zone)
 {
         int mt;
         unsigned long max_managed, flags;
 
         /*
          * The number reserved as: minimum is 1 pageblock, maximum is
          * roughly 1% of a zone. But if 1% of a zone falls below a
          * pageblock size, then don't reserve any pageblocks.
          * Check is race-prone but harmless.
          */
         if ((zone_managed_pages(zone) / 100) < pageblock_nr_pages)
                 return;
         max_managed = ALIGN((zone_managed_pages(zone) / 100), pageblock_nr_pages);
         if (zone->nr_reserved_highatomic >= max_managed)
                 return;
 
         spin_lock_irqsave(&zone->lock, flags);
 
         /* Recheck the nr_reserved_highatomic limit under the lock */
         if (zone->nr_reserved_highatomic >= max_managed)
                 goto out_unlock;
 
         /* Yoink! */
         mt = get_pageblock_migratetype(page);
         /* Only reserve normal pageblocks (i.e., they can merge with others) */
         if (!migratetype_is_mergeable(mt))
                 goto out_unlock;
 
         if (order < pageblock_order) {
                 if (move_freepages_block(zone, page, mt, MIGRATE_HIGHATOMIC) == -1)
                         goto out_unlock;
                 zone->nr_reserved_highatomic += pageblock_nr_pages;
         } else {
                 change_pageblock_range(page, order, MIGRATE_HIGHATOMIC);
                 zone->nr_reserved_highatomic += 1 << order;
         }
 
 out_unlock:
         spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 /*
  * Used when an allocation is about to fail under memory pressure. This
  * potentially hurts the reliability of high-order allocations when under
  * intense memory pressure but failed atomic allocations should be easier
  * to recover from than an OOM.
  *
  * If @force is true, try to unreserve pageblocks even though highatomic
  * pageblock is exhausted.
  */
 static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
                                                 bool force)
 {
         struct zonelist *zonelist = ac->zonelist;
         unsigned long flags;
         struct zoneref *z;
         struct zone *zone;
         struct page *page;
         int order;
         int ret;
 
         for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->highest_zoneidx,
                                                                 ac->nodemask) {
                 /*
                  * Preserve at least one pageblock unless memory pressure
                  * is really high.
                  */
                 if (!force && zone->nr_reserved_highatomic <=
                                         pageblock_nr_pages)
                         continue;
 
                 spin_lock_irqsave(&zone->lock, flags);
                 for (order = 0; order < NR_PAGE_ORDERS; order++) {
                         struct free_area *area = &(zone->free_area[order]);
                         int mt;
 
                         page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
                         if (!page)
                                 continue;
 
                         mt = get_pageblock_migratetype(page);
                         /*
                          * In page freeing path, migratetype change is racy so
                          * we can counter several free pages in a pageblock
                          * in this loop although we changed the pageblock type
                          * from highatomic to ac->migratetype. So we should
                          * adjust the count once.
                          */
                         if (is_migrate_highatomic(mt)) {
                                 unsigned long size;
                                 /*
                                  * It should never happen but changes to
                                  * locking could inadvertently allow a per-cpu
                                  * drain to add pages to MIGRATE_HIGHATOMIC
                                  * while unreserving so be safe and watch for
                                  * underflows.
                                  */
                                 size = max(pageblock_nr_pages, 1UL << order);
                                 size = min(size, zone->nr_reserved_highatomic);
                                 zone->nr_reserved_highatomic -= size;
                         }
 
                         /*
                          * Convert to ac->migratetype and avoid the normal
                          * pageblock stealing heuristics. Minimally, the caller
                          * is doing the work and needs the pages. More
                          * importantly, if the block was always converted to
                          * MIGRATE_UNMOVABLE or another type then the number
                          * of pageblocks that cannot be completely freed
                          * may increase.
                          */
                         if (order < pageblock_order)
                                 ret = move_freepages_block(zone, page, mt,
                                                            ac->migratetype);
                         else {
                                 move_to_free_list(page, zone, order, mt,
                                                   ac->migratetype);
                                 change_pageblock_range(page, order,
                                                        ac->migratetype);
                                 ret = 1;
                         }
                         /*
                          * Reserving the block(s) already succeeded,
                          * so this should not fail on zone boundaries.
                          */
                         WARN_ON_ONCE(ret == -1);
                         if (ret > 0) {
                                 spin_unlock_irqrestore(&zone->lock, flags);
                                 return ret;
                         }
                 }
                 spin_unlock_irqrestore(&zone->lock, flags);
         }
 
         return false;
 }
 
 /*
  * Try finding a free buddy page on the fallback list and put it on the free
  * list of requested migratetype, possibly along with other pages from the same
  * block, depending on fragmentation avoidance heuristics. Returns true if
  * fallback was found so that __rmqueue_smallest() can grab it.
  *
  * The use of signed ints for order and current_order is a deliberate
  * deviation from the rest of this file, to make the for loop
  * condition simpler.
  */
 static __always_inline struct page *
 __rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
                                                 unsigned int alloc_flags)
 {
         struct free_area *area;
         int current_order;
         int min_order = order;
         struct page *page;
         int fallback_mt;
         bool can_steal;
 
         /*
          * Do not steal pages from freelists belonging to other pageblocks
          * i.e. orders < pageblock_order. If there are no local zones free,
          * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
          */
         if (order < pageblock_order && alloc_flags & ALLOC_NOFRAGMENT)
                 min_order = pageblock_order;
 
         /*
          * Find the largest available free page in the other list. This roughly
          * approximates finding the pageblock with the most free pages, which
          * would be too costly to do exactly.
          */
         for (current_order = MAX_PAGE_ORDER; current_order >= min_order;
                                 --current_order) {
                 area = &(zone->free_area[current_order]);
                 fallback_mt = find_suitable_fallback(area, current_order,
                                 start_migratetype, false, &can_steal);
                 if (fallback_mt == -1)
                         continue;
 
                 /*
                  * We cannot steal all free pages from the pageblock and the
                  * requested migratetype is movable. In that case it's better to
                  * steal and split the smallest available page instead of the
                  * largest available page, because even if the next movable
                  * allocation falls back into a different pageblock than this
                  * one, it won't cause permanent fragmentation.
                  */
                 if (!can_steal && start_migratetype == MIGRATE_MOVABLE
                                         && current_order > order)
                         goto find_smallest;
 
                 goto do_steal;
         }
 
         return NULL;
 
 find_smallest:
         for (current_order = order; current_order < NR_PAGE_ORDERS; current_order++) {
                 area = &(zone->free_area[current_order]);
                 fallback_mt = find_suitable_fallback(area, current_order,
                                 start_migratetype, false, &can_steal);
                 if (fallback_mt != -1)
                         break;
         }
 
         /*
          * This should not happen - we already found a suitable fallback
          * when looking for the largest page.
          */
         VM_BUG_ON(current_order > MAX_PAGE_ORDER);
 
 do_steal:
         page = get_page_from_free_area(area, fallback_mt);
 
         /* take off list, maybe claim block, expand remainder */
         page = steal_suitable_fallback(zone, page, current_order, order,
                                        start_migratetype, alloc_flags, can_steal);
 
         trace_mm_page_alloc_extfrag(page, order, current_order,
                 start_migratetype, fallback_mt);
 
         return page;
 }
 
 /*
  * Do the hard work of removing an element from the buddy allocator.
  * Call me with the zone->lock already held.
  */
 static __always_inline struct page *
 __rmqueue(struct zone *zone, unsigned int order, int migratetype,
                                                 unsigned int alloc_flags)
 {
         struct page *page;
 
         if (IS_ENABLED(CONFIG_CMA)) {
                 /*
                  * Balance movable allocations between regular and CMA areas by
                  * allocating from CMA when over half of the zone's free memory
                  * is in the CMA area.
                  */
                 if (alloc_flags & ALLOC_CMA &&
                     zone_page_state(zone, NR_FREE_CMA_PAGES) >
                     zone_page_state(zone, NR_FREE_PAGES) / 2) {
                         page = __rmqueue_cma_fallback(zone, order);
                         if (page)
                                 return page;
                 }
         }
 
         page = __rmqueue_smallest(zone, order, migratetype);
         if (unlikely(!page)) {
                 if (alloc_flags & ALLOC_CMA)
                         page = __rmqueue_cma_fallback(zone, order);
 
                 if (!page)
                         page = __rmqueue_fallback(zone, order, migratetype,
                                                   alloc_flags);
         }
         return page;
 }
 
 /*
  * Obtain a specified number of elements from the buddy allocator, all under
  * a single hold of the lock, for efficiency.  Add them to the supplied list.
  * Returns the number of new pages which were placed at *list.
  */
 static int rmqueue_bulk(struct zone *zone, unsigned int order,
                         unsigned long count, struct list_head *list,
                         int migratetype, unsigned int alloc_flags)
 {
         unsigned long flags;
         int i;
 
         spin_lock_irqsave(&zone->lock, flags);
         for (i = 0; i < count; ++i) {
                 struct page *page = __rmqueue(zone, order, migratetype,
                                                                 alloc_flags);
                 if (unlikely(page == NULL))
                         break;
 
                 /*
                  * Split buddy pages returned by expand() are received here in
                  * physical page order. The page is added to the tail of
                  * caller's list. From the callers perspective, the linked list
                  * is ordered by page number under some conditions. This is
                  * useful for IO devices that can forward direction from the
                  * head, thus also in the physical page order. This is useful
                  * for IO devices that can merge IO requests if the physical
                  * pages are ordered properly.
                  */
                 list_add_tail(&page->pcp_list, list);
         }
         spin_unlock_irqrestore(&zone->lock, flags);
 
         return i;
 }
 
 /*
  * Called from the vmstat counter updater to decay the PCP high.
  * Return whether there are addition works to do.
  */
 int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp)
 {
         int high_min, to_drain, batch;
         int todo = 0;
 
         high_min = READ_ONCE(pcp->high_min);
         batch = READ_ONCE(pcp->batch);
         /*
          * Decrease pcp->high periodically to try to free possible
          * idle PCP pages.  And, avoid to free too many pages to
          * control latency.  This caps pcp->high decrement too.
          */
         if (pcp->high > high_min) {
                 pcp->high = max3(pcp->count - (batch << CONFIG_PCP_BATCH_SCALE_MAX),
                                  pcp->high - (pcp->high >> 3), high_min);
                 if (pcp->high > high_min)
                         todo++;
         }
 
         to_drain = pcp->count - pcp->high;
         if (to_drain > 0) {
                 spin_lock(&pcp->lock);
                 free_pcppages_bulk(zone, to_drain, pcp, 0);
                 spin_unlock(&pcp->lock);
                 todo++;
         }
 
         return todo;
 }
 
 #ifdef CONFIG_NUMA
 /*
  * Called from the vmstat counter updater to drain pagesets of this
  * currently executing processor on remote nodes after they have
  * expired.
  */
 void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
 {
         int to_drain, batch;
 
         batch = READ_ONCE(pcp->batch);
         to_drain = min(pcp->count, batch);
         if (to_drain > 0) {
                 spin_lock(&pcp->lock);
                 free_pcppages_bulk(zone, to_drain, pcp, 0);
                 spin_unlock(&pcp->lock);
         }
 }
 #endif
 
 /*
  * Drain pcplists of the indicated processor and zone.
  */
 static void drain_pages_zone(unsigned int cpu, struct zone *zone)
 {
         struct per_cpu_pages *pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
         int count;
 
         do {
                 spin_lock(&pcp->lock);
                 count = pcp->count;
                 if (count) {
                         int to_drain = min(count,
                                 pcp->batch << CONFIG_PCP_BATCH_SCALE_MAX);
 
                         free_pcppages_bulk(zone, to_drain, pcp, 0);
                         count -= to_drain;
                 }
                 spin_unlock(&pcp->lock);
         } while (count);
 }
 
 /*
  * Drain pcplists of all zones on the indicated processor.
  */
 static void drain_pages(unsigned int cpu)
 {
         struct zone *zone;
 
         for_each_populated_zone(zone) {
                 drain_pages_zone(cpu, zone);
         }
 }
 
 /*
  * Spill all of this CPU's per-cpu pages back into the buddy allocator.
  */
 void drain_local_pages(struct zone *zone)
 {
         int cpu = smp_processor_id();
 
         if (zone)
                 drain_pages_zone(cpu, zone);
         else
                 drain_pages(cpu);
 }
 
 /*
  * The implementation of drain_all_pages(), exposing an extra parameter to
  * drain on all cpus.
  *
  * drain_all_pages() is optimized to only execute on cpus where pcplists are
  * not empty. The check for non-emptiness can however race with a free to
  * pcplist that has not yet increased the pcp->count from 0 to 1. Callers
  * that need the guarantee that every CPU has drained can disable the
  * optimizing racy check.
  */
 static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
 {
         int cpu;
 
         /*
          * Allocate in the BSS so we won't require allocation in
          * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
          */
         static cpumask_t cpus_with_pcps;
 
         /*
          * Do not drain if one is already in progress unless it's specific to
          * a zone. Such callers are primarily CMA and memory hotplug and need
          * the drain to be complete when the call returns.
          */
         if (unlikely(!mutex_trylock(&pcpu_drain_mutex))) {
                 if (!zone)
                         return;
                 mutex_lock(&pcpu_drain_mutex);
         }
 
         /*
          * We don't care about racing with CPU hotplug event
          * as offline notification will cause the notified
          * cpu to drain that CPU pcps and on_each_cpu_mask
          * disables preemption as part of its processing
          */
         for_each_online_cpu(cpu) {
                 struct per_cpu_pages *pcp;
                 struct zone *z;
                 bool has_pcps = false;
 
                 if (force_all_cpus) {
                         /*
                          * The pcp.count check is racy, some callers need a
                          * guarantee that no cpu is missed.
                          */
                         has_pcps = true;
                 } else if (zone) {
                         pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                         if (pcp->count)
                                 has_pcps = true;
                 } else {
                         for_each_populated_zone(z) {
                                 pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
                                 if (pcp->count) {
                                         has_pcps = true;
                                         break;
                                 }
                         }
                 }
 
                 if (has_pcps)
                         cpumask_set_cpu(cpu, &cpus_with_pcps);
                 else
                         cpumask_clear_cpu(cpu, &cpus_with_pcps);
         }
 
         for_each_cpu(cpu, &cpus_with_pcps) {
                 if (zone)
                         drain_pages_zone(cpu, zone);
                 else
                         drain_pages(cpu);
         }
 
         mutex_unlock(&pcpu_drain_mutex);
 }
 
 /*
  * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
  *
  * When zone parameter is non-NULL, spill just the single zone's pages.
  */
 void drain_all_pages(struct zone *zone)
 {
         __drain_all_pages(zone, false);
 }
 
 static int nr_pcp_free(struct per_cpu_pages *pcp, int batch, int high, bool free_high)
 {
         int min_nr_free, max_nr_free;
 
         /* Free as much as possible if batch freeing high-order pages. */
         if (unlikely(free_high))
                 return min(pcp->count, batch << CONFIG_PCP_BATCH_SCALE_MAX);
 
         /* Check for PCP disabled or boot pageset */
         if (unlikely(high < batch))
                 return 1;
 
         /* Leave at least pcp->batch pages on the list */
         min_nr_free = batch;
         max_nr_free = high - batch;
 
         /*
          * Increase the batch number to the number of the consecutive
          * freed pages to reduce zone lock contention.
          */
         batch = clamp_t(int, pcp->free_count, min_nr_free, max_nr_free);
 
         return batch;
 }
 
 static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone,
                        int batch, bool free_high)
 {
         int high, high_min, high_max;
 
         high_min = READ_ONCE(pcp->high_min);
         high_max = READ_ONCE(pcp->high_max);
         high = pcp->high = clamp(pcp->high, high_min, high_max);
 
         if (unlikely(!high))
                 return 0;
 
         if (unlikely(free_high)) {
                 pcp->high = max(high - (batch << CONFIG_PCP_BATCH_SCALE_MAX),
                                 high_min);
                 return 0;
         }
 
         /*
          * If reclaim is active, limit the number of pages that can be
          * stored on pcp lists
          */
         if (test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags)) {
                 int free_count = max_t(int, pcp->free_count, batch);
 
                 pcp->high = max(high - free_count, high_min);
                 return min(batch << 2, pcp->high);
         }
 
         if (high_min == high_max)
                 return high;
 
         if (test_bit(ZONE_BELOW_HIGH, &zone->flags)) {
                 int free_count = max_t(int, pcp->free_count, batch);
 
                 pcp->high = max(high - free_count, high_min);
                 high = max(pcp->count, high_min);
         } else if (pcp->count >= high) {
                 int need_high = pcp->free_count + batch;
 
                 /* pcp->high should be large enough to hold batch freed pages */
                 if (pcp->high < need_high)
                         pcp->high = clamp(need_high, high_min, high_max);
         }
 
         return high;
 }
 
 static void free_unref_page_commit(struct zone *zone, struct per_cpu_pages *pcp,
                                    struct page *page, int migratetype,
                                    unsigned int order)
 {
         int high, batch;
         int pindex;
         bool free_high = false;
 
         /*
          * On freeing, reduce the number of pages that are batch allocated.
          * See nr_pcp_alloc() where alloc_factor is increased for subsequent
          * allocations.
          */
         pcp->alloc_factor >>= 1;
         __count_vm_events(PGFREE, 1 << order);
         pindex = order_to_pindex(migratetype, order);
         list_add(&page->pcp_list, &pcp->lists[pindex]);
         pcp->count += 1 << order;
 
         batch = READ_ONCE(pcp->batch);
         /*
          * As high-order pages other than THP's stored on PCP can contribute
          * to fragmentation, limit the number stored when PCP is heavily
          * freeing without allocation. The remainder after bulk freeing
          * stops will be drained from vmstat refresh context.
          */
         if (order && order <= PAGE_ALLOC_COSTLY_ORDER) {
                 free_high = (pcp->free_count >= batch &&
                              (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
                              (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
                               pcp->count >= READ_ONCE(batch)));
                 pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
         } else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
                 pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;
         }
         if (pcp->free_count < (batch << CONFIG_PCP_BATCH_SCALE_MAX))
                 pcp->free_count += (1 << order);
         high = nr_pcp_high(pcp, zone, batch, free_high);
         if (pcp->count >= high) {
                 free_pcppages_bulk(zone, nr_pcp_free(pcp, batch, high, free_high),
                                    pcp, pindex);
                 if (test_bit(ZONE_BELOW_HIGH, &zone->flags) &&
                     zone_watermark_ok(zone, 0, high_wmark_pages(zone),
                                       ZONE_MOVABLE, 0))
                         clear_bit(ZONE_BELOW_HIGH, &zone->flags);
         }
 }
 
 /*
  * Free a pcp page
  */
 void free_unref_page(struct page *page, unsigned int order)
 {
         unsigned long __maybe_unused UP_flags;
         struct per_cpu_pages *pcp;
         struct zone *zone;
         unsigned long pfn = page_to_pfn(page);
         int migratetype;
 
         if (!pcp_allowed_order(order)) {
                 __free_pages_ok(page, order, FPI_NONE);
                 return;
         }
 
         if (!free_pages_prepare(page, order))
                 return;
 
         /*
          * We only track unmovable, reclaimable and movable on pcp lists.
          * Place ISOLATE pages on the isolated list because they are being
          * offlined but treat HIGHATOMIC and CMA as movable pages so we can
          * get those areas back if necessary. Otherwise, we may have to free
          * excessively into the page allocator
          */
         migratetype = get_pfnblock_migratetype(page, pfn);
         if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
                 if (unlikely(is_migrate_isolate(migratetype))) {
                         free_one_page(page_zone(page), page, pfn, order, FPI_NONE);
                         return;
                 }
                 migratetype = MIGRATE_MOVABLE;
         }
 
         zone = page_zone(page);
         pcp_trylock_prepare(UP_flags);
         pcp = pcp_spin_trylock(zone->per_cpu_pageset);
         if (pcp) {
                 free_unref_page_commit(zone, pcp, page, migratetype, order);
                 pcp_spin_unlock(pcp);
         } else {
                 free_one_page(zone, page, pfn, order, FPI_NONE);
         }
         pcp_trylock_finish(UP_flags);
 }
 
 /*
  * Free a batch of folios
  */
 void free_unref_folios(struct folio_batch *folios)
 {
         unsigned long __maybe_unused UP_flags;
         struct per_cpu_pages *pcp = NULL;
         struct zone *locked_zone = NULL;
         int i, j;
 
         /* Prepare folios for freeing */
         for (i = 0, j = 0; i < folios->nr; i++) {
                 struct folio *folio = folios->folios[i];
                 unsigned long pfn = folio_pfn(folio);
                 unsigned int order = folio_order(folio);
 
                 folio_undo_large_rmappable(folio);
                 if (!free_pages_prepare(&folio->page, order))
                         continue;
                 /*
                  * Free orders not handled on the PCP directly to the
                  * allocator.
                  */
                 if (!pcp_allowed_order(order)) {
                         free_one_page(folio_zone(folio), &folio->page,
                                       pfn, order, FPI_NONE);
                         continue;
                 }
                 folio->private = (void *)(unsigned long)order;
                 if (j != i)
                         folios->folios[j] = folio;
                 j++;
         }
         folios->nr = j;
 
         for (i = 0; i < folios->nr; i++) {
                 struct folio *folio = folios->folios[i];
                 struct zone *zone = folio_zone(folio);
                 unsigned long pfn = folio_pfn(folio);
                 unsigned int order = (unsigned long)folio->private;
                 int migratetype;
 
                 folio->private = NULL;
                 migratetype = get_pfnblock_migratetype(&folio->page, pfn);
 
                 /* Different zone requires a different pcp lock */
                 if (zone != locked_zone ||
                     is_migrate_isolate(migratetype)) {
                         if (pcp) {
                                 pcp_spin_unlock(pcp);
                                 pcp_trylock_finish(UP_flags);
                                 locked_zone = NULL;
                                 pcp = NULL;
                         }
 
                         /*
                          * Free isolated pages directly to the
                          * allocator, see comment in free_unref_page.
                          */
                         if (is_migrate_isolate(migratetype)) {
                                 free_one_page(zone, &folio->page, pfn,
                                               order, FPI_NONE);
                                 continue;
                         }
 
                         /*
                          * trylock is necessary as folios may be getting freed
                          * from IRQ or SoftIRQ context after an IO completion.
                          */
                         pcp_trylock_prepare(UP_flags);
                         pcp = pcp_spin_trylock(zone->per_cpu_pageset);
                         if (unlikely(!pcp)) {
                                 pcp_trylock_finish(UP_flags);
                                 free_one_page(zone, &folio->page, pfn,
                                               order, FPI_NONE);
                                 continue;
                         }
                         locked_zone = zone;
                 }
 
                 /*
                  * Non-isolated types over MIGRATE_PCPTYPES get added
                  * to the MIGRATE_MOVABLE pcp list.
                  */
                 if (unlikely(migratetype >= MIGRATE_PCPTYPES))
                         migratetype = MIGRATE_MOVABLE;
 
                 trace_mm_page_free_batched(&folio->page);
                 free_unref_page_commit(zone, pcp, &folio->page, migratetype,
                                 order);
         }
 
         if (pcp) {
                 pcp_spin_unlock(pcp);
                 pcp_trylock_finish(UP_flags);
         }
         folio_batch_reinit(folios);
 }
 
 /*
  * split_page takes a non-compound higher-order page, and splits it into
  * n (1<<order) sub-pages: page[0..n]
  * Each sub-page must be freed individually.
  *
  * Note: this is probably too low level an operation for use in drivers.
  * Please consult with lkml before using this in your driver.
  */
 void split_page(struct page *page, unsigned int order)
 {
         int i;
 
         VM_BUG_ON_PAGE(PageCompound(page), page);
         VM_BUG_ON_PAGE(!page_count(page), page);
 
         for (i = 1; i < (1 << order); i++)
                 set_page_refcounted(page + i);
         split_page_owner(page, order, 0);
         pgalloc_tag_split(page, 1 << order);
         split_page_memcg(page, order, 0);
 }
 EXPORT_SYMBOL_GPL(split_page);
 
 int __isolate_free_page(struct page *page, unsigned int order)
 {
         struct zone *zone = page_zone(page);
         int mt = get_pageblock_migratetype(page);
 
         if (!is_migrate_isolate(mt)) {
                 unsigned long watermark;
                 /*
                  * Obey watermarks as if the page was being allocated. We can
                  * emulate a high-order watermark check with a raised order-0
                  * watermark, because we already know our high-order page
                  * exists.
                  */
                 watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
                 if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
                         return 0;
         }
 
         del_page_from_free_list(page, zone, order, mt);
 
         /*
          * Set the pageblock if the isolated page is at least half of a
          * pageblock
          */
         if (order >= pageblock_order - 1) {
                 struct page *endpage = page + (1 << order) - 1;
                 for (; page < endpage; page += pageblock_nr_pages) {
                         int mt = get_pageblock_migratetype(page);
                         /*
                          * Only change normal pageblocks (i.e., they can merge
                          * with others)
                          */
                         if (migratetype_is_mergeable(mt))
                                 move_freepages_block(zone, page, mt,
                                                      MIGRATE_MOVABLE);
                 }
         }
 
         return 1UL << order;
 }
 
 /**
  * __putback_isolated_page - Return a now-isolated page back where we got it
  * @page: Page that was isolated
  * @order: Order of the isolated page
  * @mt: The page's pageblock's migratetype
  *
  * This function is meant to return a page pulled from the free lists via
  * __isolate_free_page back to the free lists they were pulled from.
  */
 void __putback_isolated_page(struct page *page, unsigned int order, int mt)
 {
         struct zone *zone = page_zone(page);
 
         /* zone lock should be held when this function is called */
         lockdep_assert_held(&zone->lock);
 
         /* Return isolated page to tail of freelist. */
         __free_one_page(page, page_to_pfn(page), zone, order, mt,
                         FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL);
 }
 
 /*
  * Update NUMA hit/miss statistics
  */
 static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
                                    long nr_account)
 {
 #ifdef CONFIG_NUMA
         enum numa_stat_item local_stat = NUMA_LOCAL;
 
         /* skip numa counters update if numa stats is disabled */
         if (!static_branch_likely(&vm_numa_stat_key))
                 return;
 
         if (zone_to_nid(z) != numa_node_id())
                 local_stat = NUMA_OTHER;
 
         if (zone_to_nid(z) == zone_to_nid(preferred_zone))
                 __count_numa_events(z, NUMA_HIT, nr_account);
         else {
                 __count_numa_events(z, NUMA_MISS, nr_account);
                 __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
         }
         __count_numa_events(z, local_stat, nr_account);
 #endif
 }
 
 static __always_inline
 struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
                            unsigned int order, unsigned int alloc_flags,
                            int migratetype)
 {
         struct page *page;
         unsigned long flags;
 
         do {
                 page = NULL;
                 spin_lock_irqsave(&zone->lock, flags);
                 if (alloc_flags & ALLOC_HIGHATOMIC)
                         page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
                 if (!page) {
                         page = __rmqueue(zone, order, migratetype, alloc_flags);
 
                         /*
                          * If the allocation fails, allow OOM handling access
                          * to HIGHATOMIC reserves as failing now is worse than
                          * failing a high-order atomic allocation in the
                          * future.
                          */
                         if (!page && (alloc_flags & ALLOC_OOM))
                                 page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
 
                         if (!page) {
                                 spin_unlock_irqrestore(&zone->lock, flags);
                                 return NULL;
                         }
                 }
                 spin_unlock_irqrestore(&zone->lock, flags);
         } while (check_new_pages(page, order));
 
         __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
         zone_statistics(preferred_zone, zone, 1);
 
         return page;
 }
 
 static int nr_pcp_alloc(struct per_cpu_pages *pcp, struct zone *zone, int order)
 {
         int high, base_batch, batch, max_nr_alloc;
         int high_max, high_min;
 
         base_batch = READ_ONCE(pcp->batch);
         high_min = READ_ONCE(pcp->high_min);
         high_max = READ_ONCE(pcp->high_max);
         high = pcp->high = clamp(pcp->high, high_min, high_max);
 
         /* Check for PCP disabled or boot pageset */
         if (unlikely(high < base_batch))
                 return 1;
 
         if (order)
                 batch = base_batch;
         else
                 batch = (base_batch << pcp->alloc_factor);
 
         /*
          * If we had larger pcp->high, we could avoid to allocate from
          * zone.
          */
         if (high_min != high_max && !test_bit(ZONE_BELOW_HIGH, &zone->flags))
                 high = pcp->high = min(high + batch, high_max);
 
         if (!order) {
                 max_nr_alloc = max(high - pcp->count - base_batch, base_batch);
                 /*
                  * Double the number of pages allocated each time there is
                  * subsequent allocation of order-0 pages without any freeing.
                  */
                 if (batch <= max_nr_alloc &&
                     pcp->alloc_factor < CONFIG_PCP_BATCH_SCALE_MAX)
                         pcp->alloc_factor++;
                 batch = min(batch, max_nr_alloc);
         }
 
         /*
          * Scale batch relative to order if batch implies free pages
          * can be stored on the PCP. Batch can be 1 for small zones or
          * for boot pagesets which should never store free pages as
          * the pages may belong to arbitrary zones.
          */
         if (batch > 1)
                 batch = max(batch >> order, 2);
 
         return batch;
 }
 
 /* Remove page from the per-cpu list, caller must protect the list */
 static inline
 struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
                         int migratetype,
                         unsigned int alloc_flags,
                         struct per_cpu_pages *pcp,
                         struct list_head *list)
 {
         struct page *page;
 
         do {
                 if (list_empty(list)) {
                         int batch = nr_pcp_alloc(pcp, zone, order);
                         int alloced;
 
                         alloced = rmqueue_bulk(zone, order,
                                         batch, list,
                                         migratetype, alloc_flags);
 
                         pcp->count += alloced << order;
                         if (unlikely(list_empty(list)))
                                 return NULL;
                 }
 
                 page = list_first_entry(list, struct page, pcp_list);
                 list_del(&page->pcp_list);
                 pcp->count -= 1 << order;
         } while (check_new_pages(page, order));
 
         return page;
 }
 
 /* Lock and remove page from the per-cpu list */
 static struct page *rmqueue_pcplist(struct zone *preferred_zone,
                         struct zone *zone, unsigned int order,
                         int migratetype, unsigned int alloc_flags)
 {
         struct per_cpu_pages *pcp;
         struct list_head *list;
         struct page *page;
         unsigned long __maybe_unused UP_flags;
 
         /* spin_trylock may fail due to a parallel drain or IRQ reentrancy. */
         pcp_trylock_prepare(UP_flags);
         pcp = pcp_spin_trylock(zone->per_cpu_pageset);
         if (!pcp) {
                 pcp_trylock_finish(UP_flags);
                 return NULL;
         }
 
         /*
          * On allocation, reduce the number of pages that are batch freed.
          * See nr_pcp_free() where free_factor is increased for subsequent
          * frees.
          */
         pcp->free_count >>= 1;
         list = &pcp->lists[order_to_pindex(migratetype, order)];
         page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
         pcp_spin_unlock(pcp);
         pcp_trylock_finish(UP_flags);
         if (page) {
                 __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
                 zone_statistics(preferred_zone, zone, 1);
         }
         return page;
 }
 
 /*
  * Allocate a page from the given zone.
  * Use pcplists for THP or "cheap" high-order allocations.
  */
 
 /*
  * Do not instrument rmqueue() with KMSAN. This function may call
  * __msan_poison_alloca() through a call to set_pfnblock_flags_mask().
  * If __msan_poison_alloca() attempts to allocate pages for the stack depot, it
  * may call rmqueue() again, which will result in a deadlock.
  */
 __no_sanitize_memory
 static inline
 struct page *rmqueue(struct zone *preferred_zone,
                         struct zone *zone, unsigned int order,
                         gfp_t gfp_flags, unsigned int alloc_flags,
                         int migratetype)
 {
         struct page *page;
 
         /*
          * We most definitely don't want callers attempting to
          * allocate greater than order-1 page units with __GFP_NOFAIL.
          */
         WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
 
         if (likely(pcp_allowed_order(order))) {
                 page = rmqueue_pcplist(preferred_zone, zone, order,
                                        migratetype, alloc_flags);
                 if (likely(page))
                         goto out;
         }
 
         page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
                                                         migratetype);
 
 out:
         /* Separate test+clear to avoid unnecessary atomics */
         if ((alloc_flags & ALLOC_KSWAPD) &&
             unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
                 clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
                 wakeup_kswapd(zone, 0, 0, zone_idx(zone));
         }
 
         VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
         return page;
 }
 
 static inline long __zone_watermark_unusable_free(struct zone *z,
                                 unsigned int order, unsigned int alloc_flags)
 {
         long unusable_free = (1 << order) - 1;
 
         /*
          * If the caller does not have rights to reserves below the min
          * watermark then subtract the high-atomic reserves. This will
          * over-estimate the size of the atomic reserve but it avoids a search.
          */
         if (likely(!(alloc_flags & ALLOC_RESERVES)))
                 unusable_free += z->nr_reserved_highatomic;
 
 #ifdef CONFIG_CMA
         /* If allocation can't use CMA areas don't use free CMA pages */
         if (!(alloc_flags & ALLOC_CMA))
                 unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
 #endif
 
         return unusable_free;
 }
 
 /*
  * Return true if free base pages are above 'mark'. For high-order checks it
  * will return true of the order-0 watermark is reached and there is at least
  * one free page of a suitable size. Checking now avoids taking the zone lock
  * to check in the allocation paths if no pages are free.
  */
 bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
                          int highest_zoneidx, unsigned int alloc_flags,
                          long free_pages)
 {
         long min = mark;
         int o;
 
         /* free_pages may go negative - that's OK */
         free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
 
         if (unlikely(alloc_flags & ALLOC_RESERVES)) {
                 /*
                  * __GFP_HIGH allows access to 50% of the min reserve as well
                  * as OOM.
                  */
                 if (alloc_flags & ALLOC_MIN_RESERVE) {
                         min -= min / 2;
 
                         /*
                          * Non-blocking allocations (e.g. GFP_ATOMIC) can
                          * access more reserves than just __GFP_HIGH. Other
                          * non-blocking allocations requests such as GFP_NOWAIT
                          * or (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) do not get
                          * access to the min reserve.
                          */
                         if (alloc_flags & ALLOC_NON_BLOCK)
                                 min -= min / 4;
                 }
 
                 /*
                  * OOM victims can try even harder than the normal reserve
                  * users on the grounds that it's definitely going to be in
                  * the exit path shortly and free memory. Any allocation it
                  * makes during the free path will be small and short-lived.
                  */
                 if (alloc_flags & ALLOC_OOM)
                         min -= min / 2;
         }
 
         /*
          * Check watermarks for an order-0 allocation request. If these
          * are not met, then a high-order request also cannot go ahead
          * even if a suitable page happened to be free.
          */
         if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
                 return false;
 
         /* If this is an order-0 request then the watermark is fine */
         if (!order)
                 return true;
 
         /* For a high-order request, check at least one suitable page is free */
         for (o = order; o < NR_PAGE_ORDERS; o++) {
                 struct free_area *area = &z->free_area[o];
                 int mt;
 
                 if (!area->nr_free)
                         continue;
 
                 for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
                         if (!free_area_empty(area, mt))
                                 return true;
                 }
 
 #ifdef CONFIG_CMA
                 if ((alloc_flags & ALLOC_CMA) &&
                     !free_area_empty(area, MIGRATE_CMA)) {
                         return true;
                 }
 #endif
                 if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) &&
                     !free_area_empty(area, MIGRATE_HIGHATOMIC)) {
                         return true;
                 }
         }
         return false;
 }
 
 bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
                       int highest_zoneidx, unsigned int alloc_flags)
 {
         return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                                         zone_page_state(z, NR_FREE_PAGES));
 }
 
 static inline bool zone_watermark_fast(struct zone *z, unsigned int order,
                                 unsigned long mark, int highest_zoneidx,
                                 unsigned int alloc_flags, gfp_t gfp_mask)
 {
         long free_pages;
 
         free_pages = zone_page_state(z, NR_FREE_PAGES);
 
         /*
          * Fast check for order-0 only. If this fails then the reserves
          * need to be calculated.
          */
         if (!order) {
                 long usable_free;
                 long reserved;
 
                 usable_free = free_pages;
                 reserved = __zone_watermark_unusable_free(z, 0, alloc_flags);
 
                 /* reserved may over estimate high-atomic reserves. */
                 usable_free -= min(usable_free, reserved);
                 if (usable_free > mark + z->lowmem_reserve[highest_zoneidx])
                         return true;
         }
 
         if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
                                         free_pages))
                 return true;
 
         /*
          * Ignore watermark boosting for __GFP_HIGH order-0 allocations
          * when checking the min watermark. The min watermark is the
          * point where boosting is ignored so that kswapd is woken up
          * when below the low watermark.
          */
         if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost
                 && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) {
                 mark = z->_watermark[WMARK_MIN];
                 return __zone_watermark_ok(z, order, mark, highest_zoneidx,
                                         alloc_flags, free_pages);
         }
 
         return false;
 }
 
 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
                         unsigned long mark, int highest_zoneidx)
 {
         long free_pages = zone_page_state(z, NR_FREE_PAGES);
 
         if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
                 free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);
 
         return __zone_watermark_ok(z, order, mark, highest_zoneidx, 0,
                                                                 free_pages);
 }
 
 #ifdef CONFIG_NUMA
 int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;
 
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 {
         return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
                                 node_reclaim_distance;
 }
 #else   /* CONFIG_NUMA */
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 {
         return true;
 }
 #endif  /* CONFIG_NUMA */
 
 /*
  * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
  * fragmentation is subtle. If the preferred zone was HIGHMEM then
  * premature use of a lower zone may cause lowmem pressure problems that
  * are worse than fragmentation. If the next zone is ZONE_DMA then it is
  * probably too small. It only makes sense to spread allocations to avoid
  * fragmentation between the Normal and DMA32 zones.
  */
 static inline unsigned int
 alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
 {
         unsigned int alloc_flags;
 
         /*
          * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
          * to save a branch.
          */
         alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
 
 #ifdef CONFIG_ZONE_DMA32
         if (!zone)
                 return alloc_flags;
 
         if (zone_idx(zone) != ZONE_NORMAL)
                 return alloc_flags;
 
         /*
          * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
          * the pointer is within zone->zone_pgdat->node_zones[]. Also assume
          * on UMA that if Normal is populated then so is DMA32.
          */
         BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
         if (nr_online_nodes > 1 && !populated_zone(--zone))
                 return alloc_flags;
 
         alloc_flags |= ALLOC_NOFRAGMENT;
 #endif /* CONFIG_ZONE_DMA32 */
         return alloc_flags;
 }
 
 /* Must be called after current_gfp_context() which can change gfp_mask */
 static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
                                                   unsigned int alloc_flags)
 {
 #ifdef CONFIG_CMA
         if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
                 alloc_flags |= ALLOC_CMA;
 #endif
         return alloc_flags;
 }
 
 /*
  * get_page_from_freelist goes through the zonelist trying to allocate
  * a page.
  */
 static struct page *
 get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
                                                 const struct alloc_context *ac)
 {
         struct zoneref *z;
         struct zone *zone;
         struct pglist_data *last_pgdat = NULL;
         bool last_pgdat_dirty_ok = false;
         bool no_fallback;
 
 retry:
         /*
          * Scan zonelist, looking for a zone with enough free.
          * See also cpuset_node_allowed() comment in kernel/cgroup/cpuset.c.
          */
         no_fallback = alloc_flags & ALLOC_NOFRAGMENT;
         z = ac->preferred_zoneref;
         for_next_zone_zonelist_nodemask(zone, z, ac->highest_zoneidx,
                                         ac->nodemask) {
                 struct page *page;
                 unsigned long mark;
 
                 if (cpusets_enabled() &&
                         (alloc_flags & ALLOC_CPUSET) &&
                         !__cpuset_zone_allowed(zone, gfp_mask))
                                 continue;
                 /*
                  * When allocating a page cache page for writing, we
                  * want to get it from a node that is within its dirty
                  * limit, such that no single node holds more than its
                  * proportional share of globally allowed dirty pages.
                  * The dirty limits take into account the node's
                  * lowmem reserves and high watermark so that kswapd
                  * should be able to balance it without having to
                  * write pages from its LRU list.
                  *
                  * XXX: For now, allow allocations to potentially
                  * exceed the per-node dirty limit in the slowpath
                  * (spread_dirty_pages unset) before going into reclaim,
                  * which is important when on a NUMA setup the allowed
                  * nodes are together not big enough to reach the
                  * global limit.  The proper fix for these situations
                  * will require awareness of nodes in the
                  * dirty-throttling and the flusher threads.
                  */
                 if (ac->spread_dirty_pages) {
                         if (last_pgdat != zone->zone_pgdat) {
                                 last_pgdat = zone->zone_pgdat;
                                 last_pgdat_dirty_ok = node_dirty_ok(zone->zone_pgdat);
                         }
 
                         if (!last_pgdat_dirty_ok)
                                 continue;
                 }
 
                 if (no_fallback && nr_online_nodes > 1 &&
                     zone != ac->preferred_zoneref->zone) {
                         int local_nid;
 
                         /*
                          * If moving to a remote node, retry but allow
                          * fragmenting fallbacks. Locality is more important
                          * than fragmentation avoidance.
                          */
                         local_nid = zone_to_nid(ac->preferred_zoneref->zone);
                         if (zone_to_nid(zone) != local_nid) {
                                 alloc_flags &= ~ALLOC_NOFRAGMENT;
                                 goto retry;
                         }
                 }
 
                 cond_accept_memory(zone, order);
 
                 /*
                  * Detect whether the number of free pages is below high
                  * watermark.  If so, we will decrease pcp->high and free
                  * PCP pages in free path to reduce the possibility of
                  * premature page reclaiming.  Detection is done here to
                  * avoid to do that in hotter free path.
                  */
                 if (test_bit(ZONE_BELOW_HIGH, &zone->flags))
                         goto check_alloc_wmark;
 
                 mark = high_wmark_pages(zone);
                 if (zone_watermark_fast(zone, order, mark,
                                         ac->highest_zoneidx, alloc_flags,
                                         gfp_mask))
                         goto try_this_zone;
                 else
                         set_bit(ZONE_BELOW_HIGH, &zone->flags);
 
 check_alloc_wmark:
                 mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
                 if (!zone_watermark_fast(zone, order, mark,
                                        ac->highest_zoneidx, alloc_flags,
                                        gfp_mask)) {
                         int ret;
 
                         if (cond_accept_memory(zone, order))
                                 goto try_this_zone;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
                         /*
                          * Watermark failed for this zone, but see if we can
                          * grow this zone if it contains deferred pages.
                          */
                         if (deferred_pages_enabled()) {
                                 if (_deferred_grow_zone(zone, order))
                                         goto try_this_zone;
                         }
 #endif
                         /* Checked here to keep the fast path fast */
                         BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
                         if (alloc_flags & ALLOC_NO_WATERMARKS)
                                 goto try_this_zone;
 
                         if (!node_reclaim_enabled() ||
                             !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
                                 continue;
 
                         ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
                         switch (ret) {
                         case NODE_RECLAIM_NOSCAN:
                                 /* did not scan */
                                 continue;
                         case NODE_RECLAIM_FULL:
                                 /* scanned but unreclaimable */
                                 continue;
                         default:
                                 /* did we reclaim enough */
                                 if (zone_watermark_ok(zone, order, mark,
                                         ac->highest_zoneidx, alloc_flags))
                                         goto try_this_zone;
 
                                 continue;
                         }
                 }
 
 try_this_zone:
                 page = rmqueue(ac->preferred_zoneref->zone, zone, order,
                                 gfp_mask, alloc_flags, ac->migratetype);
                 if (page) {
                         prep_new_page(page, order, gfp_mask, alloc_flags);
 
                         /*
                          * If this is a high-order atomic allocation then check
                          * if the pageblock should be reserved for the future
                          */
                         if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
                                 reserve_highatomic_pageblock(page, order, zone);
 
                         return page;
                 } else {
                         if (cond_accept_memory(zone, order))
                                 goto try_this_zone;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
                         /* Try again if zone has deferred pages */
                         if (deferred_pages_enabled()) {
                                 if (_deferred_grow_zone(zone, order))
                                         goto try_this_zone;
                         }
 #endif
                 }
         }
 
         /*
          * It's possible on a UMA machine to get through all zones that are
          * fragmented. If avoiding fragmentation, reset and try again.
          */
         if (no_fallback) {
                 alloc_flags &= ~ALLOC_NOFRAGMENT;
                 goto retry;
         }
 
         return NULL;
 }
 
 static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
 {
         unsigned int filter = SHOW_MEM_FILTER_NODES;
 
         /*
          * This documents exceptions given to allocations in certain
          * contexts that are allowed to allocate outside current's set
          * of allowed nodes.
          */
         if (!(gfp_mask & __GFP_NOMEMALLOC))
                 if (tsk_is_oom_victim(current) ||
                     (current->flags & (PF_MEMALLOC | PF_EXITING)))
                         filter &= ~SHOW_MEM_FILTER_NODES;
         if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
                 filter &= ~SHOW_MEM_FILTER_NODES;
 
         __show_mem(filter, nodemask, gfp_zone(gfp_mask));
 }
 
 void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
 {
         struct va_format vaf;
         va_list args;
         static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
 
         if ((gfp_mask & __GFP_NOWARN) ||
              !__ratelimit(&nopage_rs) ||
              ((gfp_mask & __GFP_DMA) && !has_managed_dma()))
                 return;
 
         va_start(args, fmt);
         vaf.fmt = fmt;
         vaf.va = &args;
         pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
                         current->comm, &vaf, gfp_mask, &gfp_mask,
                         nodemask_pr_args(nodemask));
         va_end(args);
 
         cpuset_print_current_mems_allowed();
         pr_cont("\n");
         dump_stack();
         warn_alloc_show_mem(gfp_mask, nodemask);
 }
 
 static inline struct page *
 __alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,
                               unsigned int alloc_flags,
                               const struct alloc_context *ac)
 {
         struct page *page;
 
         page = get_page_from_freelist(gfp_mask, order,
                         alloc_flags|ALLOC_CPUSET, ac);
         /*
          * fallback to ignore cpuset restriction if our nodes
          * are depleted
          */
         if (!page)
                 page = get_page_from_freelist(gfp_mask, order,
                                 alloc_flags, ac);
 
         return page;
 }
 
 static inline struct page *
 __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
         const struct alloc_context *ac, unsigned long *did_some_progress)
 {
         struct oom_control oc = {
                 .zonelist = ac->zonelist,
                 .nodemask = ac->nodemask,
                 .memcg = NULL,
                 .gfp_mask = gfp_mask,
                 .order = order,
         };
         struct page *page;
 
         *did_some_progress = 0;
 
         /*
          * Acquire the oom lock.  If that fails, somebody else is
          * making progress for us.
          */
         if (!mutex_trylock(&oom_lock)) {
                 *did_some_progress = 1;
                 schedule_timeout_uninterruptible(1);
                 return NULL;
         }
 
         /*
          * Go through the zonelist yet one more time, keep very high watermark
          * here, this is only to catch a parallel oom killing, we must fail if
          * we're still under heavy pressure. But make sure that this reclaim
          * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
          * allocation which will never fail due to oom_lock already held.
          */
         page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
                                       ~__GFP_DIRECT_RECLAIM, order,
                                       ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
         if (page)
                 goto out;
 
         /* Coredumps can quickly deplete all memory reserves */
         if (current->flags & PF_DUMPCORE)
                 goto out;
         /* The OOM killer will not help higher order allocs */
         if (order > PAGE_ALLOC_COSTLY_ORDER)
                 goto out;
         /*
          * We have already exhausted all our reclaim opportunities without any
          * success so it is time to admit defeat. We will skip the OOM killer
          * because it is very likely that the caller has a more reasonable
          * fallback than shooting a random task.
          *
          * The OOM killer may not free memory on a specific node.
          */
         if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
                 goto out;
         /* The OOM killer does not needlessly kill tasks for lowmem */
         if (ac->highest_zoneidx < ZONE_NORMAL)
                 goto out;
         if (pm_suspended_storage())
                 goto out;
         /*
          * XXX: GFP_NOFS allocations should rather fail than rely on
          * other request to make a forward progress.
          * We are in an unfortunate situation where out_of_memory cannot
          * do much for this context but let's try it to at least get
          * access to memory reserved if the current task is killed (see
          * out_of_memory). Once filesystems are ready to handle allocation
          * failures more gracefully we should just bail out here.
          */
 
         /* Exhausted what can be done so it's blame time */
         if (out_of_memory(&oc) ||
             WARN_ON_ONCE_GFP(gfp_mask & __GFP_NOFAIL, gfp_mask)) {
                 *did_some_progress = 1;
 
                 /*
                  * Help non-failing allocations by giving them access to memory
                  * reserves
                  */
                 if (gfp_mask & __GFP_NOFAIL)
                         page = __alloc_pages_cpuset_fallback(gfp_mask, order,
                                         ALLOC_NO_WATERMARKS, ac);
         }
 out:
         mutex_unlock(&oom_lock);
         return page;
 }
 
 /*
  * Maximum number of compaction retries with a progress before OOM
  * killer is consider as the only way to move forward.
  */
 #define MAX_COMPACT_RETRIES 16
 
 #ifdef CONFIG_COMPACTION
 /* Try memory compaction for high-order allocations before reclaim */
 static struct page *
 __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                 unsigned int alloc_flags, const struct alloc_context *ac,
                 enum compact_priority prio, enum compact_result *compact_result)
 {
         struct page *page = NULL;
         unsigned long pflags;
         unsigned int noreclaim_flag;
 
         if (!order)
                 return NULL;
 
         psi_memstall_enter(&pflags);
         delayacct_compact_start();
         noreclaim_flag = memalloc_noreclaim_save();
 
         *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
                                                                 prio, &page);
 
         memalloc_noreclaim_restore(noreclaim_flag);
         psi_memstall_leave(&pflags);
         delayacct_compact_end();
 
         if (*compact_result == COMPACT_SKIPPED)
                 return NULL;
         /*
          * At least in one zone compaction wasn't deferred or skipped, so let's
          * count a compaction stall
          */
         count_vm_event(COMPACTSTALL);
 
         /* Prep a captured page if available */
         if (page)
                 prep_new_page(page, order, gfp_mask, alloc_flags);
 
         /* Try get a page from the freelist if available */
         if (!page)
                 page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
 
         if (page) {
                 struct zone *zone = page_zone(page);
 
                 zone->compact_blockskip_flush = false;
                 compaction_defer_reset(zone, order, true);
                 count_vm_event(COMPACTSUCCESS);
                 return page;
         }
 
         /*
          * It's bad if compaction run occurs and fails. The most likely reason
          * is that pages exist, but not enough to satisfy watermarks.
          */
         count_vm_event(COMPACTFAIL);
 
         cond_resched();
 
         return NULL;
 }
 
 static inline bool
 should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
                      enum compact_result compact_result,
                      enum compact_priority *compact_priority,
                      int *compaction_retries)
 {
         int max_retries = MAX_COMPACT_RETRIES;
         int min_priority;
         bool ret = false;
         int retries = *compaction_retries;
         enum compact_priority priority = *compact_priority;
 
         if (!order)
                 return false;
 
         if (fatal_signal_pending(current))
                 return false;
 
         /*
          * Compaction was skipped due to a lack of free order-0
          * migration targets. Continue if reclaim can help.
          */
         if (compact_result == COMPACT_SKIPPED) {
                 ret = compaction_zonelist_suitable(ac, order, alloc_flags);
                 goto out;
         }
 
         /*
          * Compaction managed to coalesce some page blocks, but the
          * allocation failed presumably due to a race. Retry some.
          */
         if (compact_result == COMPACT_SUCCESS) {
                 /*
                  * !costly requests are much more important than
                  * __GFP_RETRY_MAYFAIL costly ones because they are de
                  * facto nofail and invoke OOM killer to move on while
                  * costly can fail and users are ready to cope with
                  * that. 1/4 retries is rather arbitrary but we would
                  * need much more detailed feedback from compaction to
                  * make a better decision.
                  */
                 if (order > PAGE_ALLOC_COSTLY_ORDER)
                         max_retries /= 4;
 
                 if (++(*compaction_retries) <= max_retries) {
                         ret = true;
                         goto out;
                 }
         }
 
         /*
          * Compaction failed. Retry with increasing priority.
          */
         min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
                         MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
 
         if (*compact_priority > min_priority) {
                 (*compact_priority)--;
                 *compaction_retries = 0;
                 ret = true;
         }
 out:
         trace_compact_retry(order, priority, compact_result, retries, max_retries, ret);
         return ret;
 }
 #else
 static inline struct page *
 __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                 unsigned int alloc_flags, const struct alloc_context *ac,
                 enum compact_priority prio, enum compact_result *compact_result)
 {
         *compact_result = COMPACT_SKIPPED;
         return NULL;
 }
 
 static inline bool
 should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
                      enum compact_result compact_result,
                      enum compact_priority *compact_priority,
                      int *compaction_retries)
 {
         struct zone *zone;
         struct zoneref *z;
 
         if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
                 return false;
 
         /*
          * There are setups with compaction disabled which would prefer to loop
          * inside the allocator rather than hit the oom killer prematurely.
          * Let's give them a good hope and keep retrying while the order-0
          * watermarks are OK.
          */
         for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                 ac->highest_zoneidx, ac->nodemask) {
                 if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
                                         ac->highest_zoneidx, alloc_flags))
                         return true;
         }
         return false;
 }
 #endif /* CONFIG_COMPACTION */
 
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map __fs_reclaim_map =
         STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
 
 static bool __need_reclaim(gfp_t gfp_mask)
 {
         /* no reclaim without waiting on it */
         if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
                 return false;
 
         /* this guy won't enter reclaim */
         if (current->flags & PF_MEMALLOC)
                 return false;
 
         if (gfp_mask & __GFP_NOLOCKDEP)
                 return false;
 
         return true;
 }
 
 void __fs_reclaim_acquire(unsigned long ip)
 {
         lock_acquire_exclusive(&__fs_reclaim_map, 0, 0, NULL, ip);
 }
 
 void __fs_reclaim_release(unsigned long ip)
 {
         lock_release(&__fs_reclaim_map, ip);
 }
 
 void fs_reclaim_acquire(gfp_t gfp_mask)
 {
         gfp_mask = current_gfp_context(gfp_mask);
 
         if (__need_reclaim(gfp_mask)) {
                 if (gfp_mask & __GFP_FS)
                         __fs_reclaim_acquire(_RET_IP_);
 
 #ifdef CONFIG_MMU_NOTIFIER
                 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
                 lock_map_release(&__mmu_notifier_invalidate_range_start_map);
 #endif
 
         }
 }
 EXPORT_SYMBOL_GPL(fs_reclaim_acquire);
 
 void fs_reclaim_release(gfp_t gfp_mask)
 {
         gfp_mask = current_gfp_context(gfp_mask);
 
         if (__need_reclaim(gfp_mask)) {
                 if (gfp_mask & __GFP_FS)
                         __fs_reclaim_release(_RET_IP_);
         }
 }
 EXPORT_SYMBOL_GPL(fs_reclaim_release);
 #endif
 
 /*
  * Zonelists may change due to hotplug during allocation. Detect when zonelists
  * have been rebuilt so allocation retries. Reader side does not lock and
  * retries the allocation if zonelist changes. Writer side is protected by the
  * embedded spin_lock.
  */
 static DEFINE_SEQLOCK(zonelist_update_seq);
 
 static unsigned int zonelist_iter_begin(void)
 {
         if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
                 return read_seqbegin(&zonelist_update_seq);
 
         return 0;
 }
 
 static unsigned int check_retry_zonelist(unsigned int seq)
 {
         if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
                 return read_seqretry(&zonelist_update_seq, seq);
 
         return seq;
 }
 
 /* Perform direct synchronous page reclaim */
 static unsigned long
 __perform_reclaim(gfp_t gfp_mask, unsigned int order,
                                         const struct alloc_context *ac)
 {
         unsigned int noreclaim_flag;
         unsigned long progress;
 
         cond_resched();
 
         /* We now go into synchronous reclaim */
         cpuset_memory_pressure_bump();
         fs_reclaim_acquire(gfp_mask);
         noreclaim_flag = memalloc_noreclaim_save();
 
         progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
                                                                 ac->nodemask);
 
         memalloc_noreclaim_restore(noreclaim_flag);
         fs_reclaim_release(gfp_mask);
 
         cond_resched();
 
         return progress;
 }
 
 /* The really slow allocator path where we enter direct reclaim */
 static inline struct page *
 __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
                 unsigned int alloc_flags, const struct alloc_context *ac,
                 unsigned long *did_some_progress)
 {
         struct page *page = NULL;
         unsigned long pflags;
         bool drained = false;
 
         psi_memstall_enter(&pflags);
         *did_some_progress = __perform_reclaim(gfp_mask, order, ac);
         if (unlikely(!(*did_some_progress)))
                 goto out;
 
 retry:
         page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
 
         /*
          * If an allocation failed after direct reclaim, it could be because
          * pages are pinned on the per-cpu lists or in high alloc reserves.
          * Shrink them and try again
          */
         if (!page && !drained) {
                 unreserve_highatomic_pageblock(ac, false);
                 drain_all_pages(NULL);
                 drained = true;
                 goto retry;
         }
 out:
         psi_memstall_leave(&pflags);
 
         return page;
 }
 
 static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
                              const struct alloc_context *ac)
 {
         struct zoneref *z;
         struct zone *zone;
         pg_data_t *last_pgdat = NULL;
         enum zone_type highest_zoneidx = ac->highest_zoneidx;
 
         for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
                                         ac->nodemask) {
                 if (!managed_zone(zone))
                         continue;
                 if (last_pgdat != zone->zone_pgdat) {
                         wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
                         last_pgdat = zone->zone_pgdat;
                 }
         }
 }
 
 static inline unsigned int
 gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order)
 {
         unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
 
         /*
          * __GFP_HIGH is assumed to be the same as ALLOC_MIN_RESERVE
          * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
          * to save two branches.
          */
         BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_MIN_RESERVE);
         BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
 
         /*
          * The caller may dip into page reserves a bit more if the caller
          * cannot run direct reclaim, or if the caller has realtime scheduling
          * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
          * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH).
          */
         alloc_flags |= (__force int)
                 (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
 
         if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {
                 /*
                  * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
                  * if it can't schedule.
                  */
                 if (!(gfp_mask & __GFP_NOMEMALLOC)) {
                         alloc_flags |= ALLOC_NON_BLOCK;
 
                         if (order > 0)
                                 alloc_flags |= ALLOC_HIGHATOMIC;
                 }
 
                 /*
                  * Ignore cpuset mems for non-blocking __GFP_HIGH (probably
                  * GFP_ATOMIC) rather than fail, see the comment for
                  * cpuset_node_allowed().
                  */
                 if (alloc_flags & ALLOC_MIN_RESERVE)
                         alloc_flags &= ~ALLOC_CPUSET;
         } else if (unlikely(rt_task(current)) && in_task())
                 alloc_flags |= ALLOC_MIN_RESERVE;
 
         alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags);
 
         return alloc_flags;
 }
 
 static bool oom_reserves_allowed(struct task_struct *tsk)
 {
         if (!tsk_is_oom_victim(tsk))
                 return false;
 
         /*
          * !MMU doesn't have oom reaper so give access to memory reserves
          * only to the thread with TIF_MEMDIE set
          */
         if (!IS_ENABLED(CONFIG_MMU) && !test_thread_flag(TIF_MEMDIE))
                 return false;
 
         return true;
 }
 
 /*
  * Distinguish requests which really need access to full memory
  * reserves from oom victims which can live with a portion of it
  */
 static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask)
 {
         if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
                 return 0;
         if (gfp_mask & __GFP_MEMALLOC)
                 return ALLOC_NO_WATERMARKS;
         if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
                 return ALLOC_NO_WATERMARKS;
         if (!in_interrupt()) {
                 if (current->flags & PF_MEMALLOC)
                         return ALLOC_NO_WATERMARKS;
                 else if (oom_reserves_allowed(current))
                         return ALLOC_OOM;
         }
 
         return 0;
 }
 
 bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
 {
         return !!__gfp_pfmemalloc_flags(gfp_mask);
 }
 
 /*
  * Checks whether it makes sense to retry the reclaim to make a forward progress
  * for the given allocation request.
  *
  * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
  * without success, or when we couldn't even meet the watermark if we
  * reclaimed all remaining pages on the LRU lists.
  *
  * Returns true if a retry is viable or false to enter the oom path.
  */
 static inline bool
 should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                      struct alloc_context *ac, int alloc_flags,
                      bool did_some_progress, int *no_progress_loops)
 {
         struct zone *zone;
         struct zoneref *z;
         bool ret = false;
 
         /*
          * Costly allocations might have made a progress but this doesn't mean
          * their order will become available due to high fragmentation so
          * always increment the no progress counter for them
          */
         if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
                 *no_progress_loops = 0;
         else
                 (*no_progress_loops)++;
 
         if (*no_progress_loops > MAX_RECLAIM_RETRIES)
                 goto out;
 
 
         /*
          * Keep reclaiming pages while there is a chance this will lead
          * somewhere.  If none of the target zones can satisfy our allocation
          * request even if all reclaimable pages are considered then we are
          * screwed and have to go OOM.
          */
         for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                 ac->highest_zoneidx, ac->nodemask) {
                 unsigned long available;
                 unsigned long reclaimable;
                 unsigned long min_wmark = min_wmark_pages(zone);
                 bool wmark;
 
                 available = reclaimable = zone_reclaimable_pages(zone);
                 available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
 
                 /*
                  * Would the allocation succeed if we reclaimed all
                  * reclaimable pages?
                  */
                 wmark = __zone_watermark_ok(zone, order, min_wmark,
                                 ac->highest_zoneidx, alloc_flags, available);
                 trace_reclaim_retry_zone(z, order, reclaimable,
                                 available, min_wmark, *no_progress_loops, wmark);
                 if (wmark) {
                         ret = true;
                         break;
                 }
         }
 
         /*
          * Memory allocation/reclaim might be called from a WQ context and the
          * current implementation of the WQ concurrency control doesn't
          * recognize that a particular WQ is congested if the worker thread is
          * looping without ever sleeping. Therefore we have to do a short sleep
          * here rather than calling cond_resched().
          */
         if (current->flags & PF_WQ_WORKER)
                 schedule_timeout_uninterruptible(1);
         else
                 cond_resched();
 out:
         /* Before OOM, exhaust highatomic_reserve */
         if (!ret)
                 return unreserve_highatomic_pageblock(ac, true);
 
         return ret;
 }
 
 static inline bool
 check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
 {
         /*
          * It's possible that cpuset's mems_allowed and the nodemask from
          * mempolicy don't intersect. This should be normally dealt with by
          * policy_nodemask(), but it's possible to race with cpuset update in
          * such a way the check therein was true, and then it became false
          * before we got our cpuset_mems_cookie here.
          * This assumes that for all allocations, ac->nodemask can come only
          * from MPOL_BIND mempolicy (whose documented semantics is to be ignored
          * when it does not intersect with the cpuset restrictions) or the
          * caller can deal with a violated nodemask.
          */
         if (cpusets_enabled() && ac->nodemask &&
                         !cpuset_nodemask_valid_mems_allowed(ac->nodemask)) {
                 ac->nodemask = NULL;
                 return true;
         }
 
         /*
          * When updating a task's mems_allowed or mempolicy nodemask, it is
          * possible to race with parallel threads in such a way that our
          * allocation can fail while the mask is being updated. If we are about
          * to fail, check if the cpuset changed during allocation and if so,
          * retry.
          */
         if (read_mems_allowed_retry(cpuset_mems_cookie))
                 return true;
 
         return false;
 }
 
 static inline struct page *
 __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                                                 struct alloc_context *ac)
 {
         bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
         bool can_compact = gfp_compaction_allowed(gfp_mask);
         const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
         struct page *page = NULL;
         unsigned int alloc_flags;
         unsigned long did_some_progress;
         enum compact_priority compact_priority;
         enum compact_result compact_result;
         int compaction_retries;
         int no_progress_loops;
         unsigned int cpuset_mems_cookie;
         unsigned int zonelist_iter_cookie;
         int reserve_flags;
 
 restart:
         compaction_retries = 0;
         no_progress_loops = 0;
         compact_priority = DEF_COMPACT_PRIORITY;
         cpuset_mems_cookie = read_mems_allowed_begin();
         zonelist_iter_cookie = zonelist_iter_begin();
 
         /*
          * The fast path uses conservative alloc_flags to succeed only until
          * kswapd needs to be woken up, and to avoid the cost of setting up
          * alloc_flags precisely. So we do that now.
          */
         alloc_flags = gfp_to_alloc_flags(gfp_mask, order);
 
         /*
          * We need to recalculate the starting point for the zonelist iterator
          * because we might have used different nodemask in the fast path, or
          * there was a cpuset modification and we are retrying - otherwise we
          * could end up iterating over non-eligible zones endlessly.
          */
         ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                         ac->highest_zoneidx, ac->nodemask);
         if (!ac->preferred_zoneref->zone)
                 goto nopage;
 
         /*
          * Check for insane configurations where the cpuset doesn't contain
          * any suitable zone to satisfy the request - e.g. non-movable
          * GFP_HIGHUSER allocations from MOVABLE nodes only.
          */
         if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
                 struct zoneref *z = first_zones_zonelist(ac->zonelist,
                                         ac->highest_zoneidx,
                                         &cpuset_current_mems_allowed);
                 if (!z->zone)
                         goto nopage;
         }
 
         if (alloc_flags & ALLOC_KSWAPD)
                 wake_all_kswapds(order, gfp_mask, ac);
 
         /*
          * The adjusted alloc_flags might result in immediate success, so try
          * that first
          */
         page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
         if (page)
                 goto got_pg;
 
         /*
          * For costly allocations, try direct compaction first, as it's likely
          * that we have enough base pages and don't need to reclaim. For non-
          * movable high-order allocations, do that as well, as compaction will
          * try prevent permanent fragmentation by migrating from blocks of the
          * same migratetype.
          * Don't try this for allocations that are allowed to ignore
          * watermarks, as the ALLOC_NO_WATERMARKS attempt didn't yet happen.
          */
         if (can_direct_reclaim && can_compact &&
                         (costly_order ||
                            (order > 0 && ac->migratetype != MIGRATE_MOVABLE))
                         && !gfp_pfmemalloc_allowed(gfp_mask)) {
                 page = __alloc_pages_direct_compact(gfp_mask, order,
                                                 alloc_flags, ac,
                                                 INIT_COMPACT_PRIORITY,
                                                 &compact_result);
                 if (page)
                         goto got_pg;
 
                 /*
                  * Checks for costly allocations with __GFP_NORETRY, which
                  * includes some THP page fault allocations
                  */
                 if (costly_order && (gfp_mask & __GFP_NORETRY)) {
                         /*
                          * If allocating entire pageblock(s) and compaction
                          * failed because all zones are below low watermarks
                          * or is prohibited because it recently failed at this
                          * order, fail immediately unless the allocator has
                          * requested compaction and reclaim retry.
                          *
                          * Reclaim is
                          *  - potentially very expensive because zones are far
                          *    below their low watermarks or this is part of very
                          *    bursty high order allocations,
                          *  - not guaranteed to help because isolate_freepages()
                          *    may not iterate over freed pages as part of its
                          *    linear scan, and
                          *  - unlikely to make entire pageblocks free on its
                          *    own.
                          */
                         if (compact_result == COMPACT_SKIPPED ||
                             compact_result == COMPACT_DEFERRED)
                                 goto nopage;
 
                         /*
                          * Looks like reclaim/compaction is worth trying, but
                          * sync compaction could be very expensive, so keep
                          * using async compaction.
                          */
                         compact_priority = INIT_COMPACT_PRIORITY;
                 }
         }
 
 retry:
         /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
         if (alloc_flags & ALLOC_KSWAPD)
                 wake_all_kswapds(order, gfp_mask, ac);
 
         reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
         if (reserve_flags)
                 alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags) |
                                           (alloc_flags & ALLOC_KSWAPD);
 
         /*
          * Reset the nodemask and zonelist iterators if memory policies can be
          * ignored. These allocations are high priority and system rather than
          * user oriented.
          */
         if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) {
                 ac->nodemask = NULL;
                 ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                         ac->highest_zoneidx, ac->nodemask);
         }
 
         /* Attempt with potentially adjusted zonelist and alloc_flags */
         page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
         if (page)
                 goto got_pg;
 
         /* Caller is not willing to reclaim, we can't balance anything */
         if (!can_direct_reclaim)
                 goto nopage;
 
         /* Avoid recursion of direct reclaim */
         if (current->flags & PF_MEMALLOC)
                 goto nopage;
 
         /* Try direct reclaim and then allocating */
         page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
                                                         &did_some_progress);
         if (page)
                 goto got_pg;
 
         /* Try direct compaction and then allocating */
         page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
                                         compact_priority, &compact_result);
         if (page)
                 goto got_pg;
 
         /* Do not loop if specifically requested */
         if (gfp_mask & __GFP_NORETRY)
                 goto nopage;
 
         /*
          * Do not retry costly high order allocations unless they are
          * __GFP_RETRY_MAYFAIL and we can compact
          */
         if (costly_order && (!can_compact ||
                              !(gfp_mask & __GFP_RETRY_MAYFAIL)))
                 goto nopage;
 
         if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
                                  did_some_progress > 0, &no_progress_loops))
                 goto retry;
 
         /*
          * It doesn't make any sense to retry for the compaction if the order-0
          * reclaim is not able to make any progress because the current
          * implementation of the compaction depends on the sufficient amount
          * of free memory (see __compaction_suitable)
          */
         if (did_some_progress > 0 && can_compact &&
                         should_compact_retry(ac, order, alloc_flags,
                                 compact_result, &compact_priority,
                                 &compaction_retries))
                 goto retry;
 
 
         /*
          * Deal with possible cpuset update races or zonelist updates to avoid
          * a unnecessary OOM kill.
          */
         if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
             check_retry_zonelist(zonelist_iter_cookie))
                 goto restart;
 
         /* Reclaim has failed us, start killing things */
         page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
         if (page)
                 goto got_pg;
 
         /* Avoid allocations with no watermarks from looping endlessly */
         if (tsk_is_oom_victim(current) &&
             (alloc_flags & ALLOC_OOM ||
              (gfp_mask & __GFP_NOMEMALLOC)))
                 goto nopage;
 
         /* Retry as long as the OOM killer is making progress */
         if (did_some_progress) {
                 no_progress_loops = 0;
                 goto retry;
         }
 
 nopage:
         /*
          * Deal with possible cpuset update races or zonelist updates to avoid
          * a unnecessary OOM kill.
          */
         if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
             check_retry_zonelist(zonelist_iter_cookie))
                 goto restart;
 
         /*
          * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
          * we always retry
          */
         if (gfp_mask & __GFP_NOFAIL) {
                 /*
                  * All existing users of the __GFP_NOFAIL are blockable, so warn
                  * of any new users that actually require GFP_NOWAIT
                  */
                 if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
                         goto fail;
 
                 /*
                  * PF_MEMALLOC request from this context is rather bizarre
                  * because we cannot reclaim anything and only can loop waiting
                  * for somebody to do a work for us
                  */
                 WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
 
                 /*
                  * non failing costly orders are a hard requirement which we
                  * are not prepared for much so let's warn about these users
                  * so that we can identify them and convert them to something
                  * else.
                  */
                 WARN_ON_ONCE_GFP(costly_order, gfp_mask);
 
                 /*
                  * Help non-failing allocations by giving some access to memory
                  * reserves normally used for high priority non-blocking
                  * allocations but do not use ALLOC_NO_WATERMARKS because this
                  * could deplete whole memory reserves which would just make
                  * the situation worse.
                  */
                 page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE, ac);
                 if (page)
                         goto got_pg;
 
                 cond_resched();
                 goto retry;
         }
 fail:
         warn_alloc(gfp_mask, ac->nodemask,
                         "page allocation failure: order:%u", order);
 got_pg:
         return page;
 }
 
 static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
                 int preferred_nid, nodemask_t *nodemask,
                 struct alloc_context *ac, gfp_t *alloc_gfp,
                 unsigned int *alloc_flags)
 {
         ac->highest_zoneidx = gfp_zone(gfp_mask);
         ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
         ac->nodemask = nodemask;
         ac->migratetype = gfp_migratetype(gfp_mask);
 
         if (cpusets_enabled()) {
                 *alloc_gfp |= __GFP_HARDWALL;
                 /*
                  * When we are in the interrupt context, it is irrelevant
                  * to the current task context. It means that any node ok.
                  */
                 if (in_task() && !ac->nodemask)
                         ac->nodemask = &cpuset_current_mems_allowed;
                 else
                         *alloc_flags |= ALLOC_CPUSET;
         }
 
         might_alloc(gfp_mask);
 
         if (should_fail_alloc_page(gfp_mask, order))
                 return false;
 
         *alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, *alloc_flags);
 
         /* Dirty zone balancing only done in the fast path */
         ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
 
         /*
          * The preferred zone is used for statistics but crucially it is
          * also used as the starting point for the zonelist iterator. It
          * may get reset for allocations that ignore memory policies.
          */
         ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                         ac->highest_zoneidx, ac->nodemask);
 
         return true;
 }
 
 /*
  * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
  * @gfp: GFP flags for the allocation
  * @preferred_nid: The preferred NUMA node ID to allocate from
  * @nodemask: Set of nodes to allocate from, may be NULL
  * @nr_pages: The number of pages desired on the list or array
  * @page_list: Optional list to store the allocated pages
  * @page_array: Optional array to store the pages
  *
  * This is a batched version of the page allocator that attempts to
  * allocate nr_pages quickly. Pages are added to page_list if page_list
  * is not NULL, otherwise it is assumed that the page_array is valid.
  *
  * For lists, nr_pages is the number of pages that should be allocated.
  *
  * For arrays, only NULL elements are populated with pages and nr_pages
  * is the maximum number of pages that will be stored in the array.
  *
  * Returns the number of pages on the list or array.
  */
 unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
                         nodemask_t *nodemask, int nr_pages,
                         struct list_head *page_list,
                         struct page **page_array)
 {
         struct page *page;
         unsigned long __maybe_unused UP_flags;
         struct zone *zone;
         struct zoneref *z;
         struct per_cpu_pages *pcp;
         struct list_head *pcp_list;
         struct alloc_context ac;
         gfp_t alloc_gfp;
         unsigned int alloc_flags = ALLOC_WMARK_LOW;
         int nr_populated = 0, nr_account = 0;
 
         /*
          * Skip populated array elements to determine if any pages need
          * to be allocated before disabling IRQs.
          */
         while (page_array && nr_populated < nr_pages && page_array[nr_populated])
                 nr_populated++;
 
         /* No pages requested? */
         if (unlikely(nr_pages <= 0))
                 goto out;
 
         /* Already populated array? */
         if (unlikely(page_array && nr_pages - nr_populated == 0))
                 goto out;
 
         /* Bulk allocator does not support memcg accounting. */
         if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT))
                 goto failed;
 
         /* Use the single page allocator for one page. */
         if (nr_pages - nr_populated == 1)
                 goto failed;
 
 #ifdef CONFIG_PAGE_OWNER
         /*
          * PAGE_OWNER may recurse into the allocator to allocate space to
          * save the stack with pagesets.lock held. Releasing/reacquiring
          * removes much of the performance benefit of bulk allocation so
          * force the caller to allocate one page at a time as it'll have
          * similar performance to added complexity to the bulk allocator.
          */
         if (static_branch_unlikely(&page_owner_inited))
                 goto failed;
 #endif
 
         /* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
         gfp &= gfp_allowed_mask;
         alloc_gfp = gfp;
         if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags))
                 goto out;
         gfp = alloc_gfp;
 
         /* Find an allowed local zone that meets the low watermark. */
         for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) {
                 unsigned long mark;
 
                 if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
                     !__cpuset_zone_allowed(zone, gfp)) {
                         continue;
                 }
 
                 if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone &&
                     zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) {
                         goto failed;
                 }
 
                 mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
                 if (zone_watermark_fast(zone, 0,  mark,
                                 zonelist_zone_idx(ac.preferred_zoneref),
                                 alloc_flags, gfp)) {
                         break;
                 }
         }
 
         /*
          * If there are no allowed local zones that meets the watermarks then
          * try to allocate a single page and reclaim if necessary.
          */
         if (unlikely(!zone))
                 goto failed;
 
         /* spin_trylock may fail due to a parallel drain or IRQ reentrancy. */
         pcp_trylock_prepare(UP_flags);
         pcp = pcp_spin_trylock(zone->per_cpu_pageset);
         if (!pcp)
                 goto failed_irq;
 
         /* Attempt the batch allocation */
         pcp_list = &pcp->lists[order_to_pindex(ac.migratetype, 0)];
         while (nr_populated < nr_pages) {
 
                 /* Skip existing pages */
                 if (page_array && page_array[nr_populated]) {
                         nr_populated++;
                         continue;
                 }
 
                 page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
                                                                 pcp, pcp_list);
                 if (unlikely(!page)) {
                         /* Try and allocate at least one page */
                         if (!nr_account) {
                                 pcp_spin_unlock(pcp);
                                 goto failed_irq;
                         }
                         break;
                 }
                 nr_account++;
 
                 prep_new_page(page, 0, gfp, 0);
                 if (page_list)
                         list_add(&page->lru, page_list);
                 else
                         page_array[nr_populated] = page;
                 nr_populated++;
         }
 
         pcp_spin_unlock(pcp);
         pcp_trylock_finish(UP_flags);
 
         __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
         zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
 
 out:
         return nr_populated;
 
 failed_irq:
         pcp_trylock_finish(UP_flags);
 
 failed:
         page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask);
         if (page) {
                 if (page_list)
                         list_add(&page->lru, page_list);
                 else
                         page_array[nr_populated] = page;
                 nr_populated++;
         }
 
         goto out;
 }
 EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
 
 /*
  * This is the 'heart' of the zoned buddy allocator.
  */
 struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order,
                                       int preferred_nid, nodemask_t *nodemask)
 {
         struct page *page;
         unsigned int alloc_flags = ALLOC_WMARK_LOW;
         gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */
         struct alloc_context ac = { };
 
         /*
          * There are several places where we assume that the order value is sane
          * so bail out early if the request is out of bound.
          */
         if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp))
                 return NULL;
 
         gfp &= gfp_allowed_mask;
         /*
          * Apply scoped allocation constraints. This is mainly about GFP_NOFS
          * resp. GFP_NOIO which has to be inherited for all allocation requests
          * from a particular context which has been marked by
          * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures
          * movable zones are not used during allocation.
          */
         gfp = current_gfp_context(gfp);
         alloc_gfp = gfp;
         if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, &ac,
                         &alloc_gfp, &alloc_flags))
                 return NULL;
 
         /*
          * Forbid the first pass from falling back to types that fragment
          * memory until all local zones are considered.
          */
         alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp);
 
         /* First allocation attempt */
         page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac);
         if (likely(page))
                 goto out;
 
         alloc_gfp = gfp;
         ac.spread_dirty_pages = false;
 
         /*
          * Restore the original nodemask if it was potentially replaced with
          * &cpuset_current_mems_allowed to optimize the fast-path attempt.
          */
         ac.nodemask = nodemask;
 
         page = __alloc_pages_slowpath(alloc_gfp, order, &ac);
 
 out:
         if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT) && page &&
             unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
                 __free_pages(page, order);
                 page = NULL;
         }
 
         trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
         kmsan_alloc_page(page, order, alloc_gfp);
 
         return page;
 }
 EXPORT_SYMBOL(__alloc_pages_noprof);
 
 struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
                 nodemask_t *nodemask)
 {
         struct page *page = __alloc_pages_noprof(gfp | __GFP_COMP, order,
                                         preferred_nid, nodemask);
         return page_rmappable_folio(page);
 }
 EXPORT_SYMBOL(__folio_alloc_noprof);
 
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
  * address cannot represent highmem pages. Use alloc_pages and then kmap if
  * you need to access high mem.
  */
 unsigned long get_free_pages_noprof(gfp_t gfp_mask, unsigned int order)
 {
         struct page *page;
 
         page = alloc_pages_noprof(gfp_mask & ~__GFP_HIGHMEM, order);
         if (!page)
                 return 0;
         return (unsigned long) page_address(page);
 }
 EXPORT_SYMBOL(get_free_pages_noprof);
 
 unsigned long get_zeroed_page_noprof(gfp_t gfp_mask)
 {
         return get_free_pages_noprof(gfp_mask | __GFP_ZERO, 0);
 }
 EXPORT_SYMBOL(get_zeroed_page_noprof);
 
 /**
  * __free_pages - Free pages allocated with alloc_pages().
  * @page: The page pointer returned from alloc_pages().
  * @order: The order of the allocation.
  *
  * This function can free multi-page allocations that are not compound
  * pages.  It does not check that the @order passed in matches that of
  * the allocation, so it is easy to leak memory.  Freeing more memory
  * than was allocated will probably emit a warning.
  *
  * If the last reference to this page is speculative, it will be released
  * by put_page() which only frees the first page of a non-compound
  * allocation.  To prevent the remaining pages from being leaked, we free
  * the subsequent pages here.  If you want to use the page's reference
  * count to decide when to free the allocation, you should allocate a
  * compound page, and use put_page() instead of __free_pages().
  *
  * Context: May be called in interrupt context or while holding a normal
  * spinlock, but not in NMI context or while holding a raw spinlock.
  */
 void __free_pages(struct page *page, unsigned int order)
 {
         /* get PageHead before we drop reference */
         int head = PageHead(page);
         struct alloc_tag *tag = pgalloc_tag_get(page);
 
         if (put_page_testzero(page))
                 free_unref_page(page, order);
         else if (!head) {
                 pgalloc_tag_sub_pages(tag, (1 << order) - 1);
                 while (order-- > 0)
                         free_unref_page(page + (1 << order), order);
         }
 }
 EXPORT_SYMBOL(__free_pages);
 
 void free_pages(unsigned long addr, unsigned int order)
 {
         if (addr != 0) {
                 VM_BUG_ON(!virt_addr_valid((void *)addr));
                 __free_pages(virt_to_page((void *)addr), order);
         }
 }
 
 EXPORT_SYMBOL(free_pages);
 
 /*
  * Page Fragment:
  *  An arbitrary-length arbitrary-offset area of memory which resides
  *  within a 0 or higher order page.  Multiple fragments within that page
  *  are individually refcounted, in the page's reference counter.
  *
  * The page_frag functions below provide a simple allocation framework for
  * page fragments.  This is used by the network stack and network device
  * drivers to provide a backing region of memory for use as either an
  * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
  */
 static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
                                              gfp_t gfp_mask)
 {
         struct page *page = NULL;
         gfp_t gfp = gfp_mask;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
         gfp_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) |  __GFP_COMP |
                    __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
         page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
                                 PAGE_FRAG_CACHE_MAX_ORDER);
         nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
 #endif
         if (unlikely(!page))
                 page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
 
         nc->va = page ? page_address(page) : NULL;
 
         return page;
 }
 
 void page_frag_cache_drain(struct page_frag_cache *nc)
 {
         if (!nc->va)
                 return;
 
         __page_frag_cache_drain(virt_to_head_page(nc->va), nc->pagecnt_bias);
         nc->va = NULL;
 }
 EXPORT_SYMBOL(page_frag_cache_drain);
 
 void __page_frag_cache_drain(struct page *page, unsigned int count)
 {
         VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
 
         if (page_ref_sub_and_test(page, count))
                 free_unref_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(__page_frag_cache_drain);
 
 void *__page_frag_alloc_align(struct page_frag_cache *nc,
                               unsigned int fragsz, gfp_t gfp_mask,
                               unsigned int align_mask)
 {
         unsigned int size = PAGE_SIZE;
         struct page *page;
         int offset;
 
         if (unlikely(!nc->va)) {
 refill:
                 page = __page_frag_cache_refill(nc, gfp_mask);
                 if (!page)
                         return NULL;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                 /* if size can vary use size else just use PAGE_SIZE */
                 size = nc->size;
 #endif
                 /* Even if we own the page, we do not use atomic_set().
                  * This would break get_page_unless_zero() users.
                  */
                 page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
 
                 /* reset page count bias and offset to start of new frag */
                 nc->pfmemalloc = page_is_pfmemalloc(page);
                 nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                 nc->offset = size;
         }
 
         offset = nc->offset - fragsz;
         if (unlikely(offset < 0)) {
                 page = virt_to_page(nc->va);
 
                 if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
                         goto refill;
 
                 if (unlikely(nc->pfmemalloc)) {
                         free_unref_page(page, compound_order(page));
                         goto refill;
                 }
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                 /* if size can vary use size else just use PAGE_SIZE */
                 size = nc->size;
 #endif
                 /* OK, page count is 0, we can safely set it */
                 set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
 
                 /* reset page count bias and offset to start of new frag */
                 nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
                 offset = size - fragsz;
                 if (unlikely(offset < 0)) {
                         /*
                          * The caller is trying to allocate a fragment
                          * with fragsz > PAGE_SIZE but the cache isn't big
                          * enough to satisfy the request, this may
                          * happen in low memory conditions.
                          * We don't release the cache page because
                          * it could make memory pressure worse
                          * so we simply return NULL here.
                          */
                         return NULL;
                 }
         }
 
         nc->pagecnt_bias--;
         offset &= align_mask;
         nc->offset = offset;
 
         return nc->va + offset;
 }
 EXPORT_SYMBOL(__page_frag_alloc_align);
 
 /*
  * Frees a page fragment allocated out of either a compound or order 0 page.
  */
 void page_frag_free(void *addr)
 {
         struct page *page = virt_to_head_page(addr);
 
         if (unlikely(put_page_testzero(page)))
                 free_unref_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(page_frag_free);
 
 static void *make_alloc_exact(unsigned long addr, unsigned int order,
                 size_t size)
 {
         if (addr) {
                 unsigned long nr = DIV_ROUND_UP(size, PAGE_SIZE);
                 struct page *page = virt_to_page((void *)addr);
                 struct page *last = page + nr;
 
                 split_page_owner(page, order, 0);
                 pgalloc_tag_split(page, 1 << order);
                 split_page_memcg(page, order, 0);
                 while (page < --last)
                         set_page_refcounted(last);
 
                 last = page + (1UL << order);
                 for (page += nr; page < last; page++)
                         __free_pages_ok(page, 0, FPI_TO_TAIL);
         }
         return (void *)addr;
 }
 
 /**
  * alloc_pages_exact - allocate an exact number physically-contiguous pages.
  * @size: the number of bytes to allocate
  * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
  *
  * This function is similar to alloc_pages(), except that it allocates the
  * minimum number of pages to satisfy the request.  alloc_pages() can only
  * allocate memory in power-of-two pages.
  *
  * This function is also limited by MAX_PAGE_ORDER.
  *
  * Memory allocated by this function must be released by free_pages_exact().
  *
  * Return: pointer to the allocated area or %NULL in case of error.
  */
 void *alloc_pages_exact_noprof(size_t size, gfp_t gfp_mask)
 {
         unsigned int order = get_order(size);
         unsigned long addr;
 
         if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
                 gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
 
         addr = get_free_pages_noprof(gfp_mask, order);
         return make_alloc_exact(addr, order, size);
 }
 EXPORT_SYMBOL(alloc_pages_exact_noprof);
 
 /**
  * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
  *                         pages on a node.
  * @nid: the preferred node ID where memory should be allocated
  * @size: the number of bytes to allocate
  * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
  *
  * Like alloc_pages_exact(), but try to allocate on node nid first before falling
  * back.
  *
  * Return: pointer to the allocated area or %NULL in case of error.
  */
 void * __meminit alloc_pages_exact_nid_noprof(int nid, size_t size, gfp_t gfp_mask)
 {
         unsigned int order = get_order(size);
         struct page *p;
 
         if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
                 gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
 
         p = alloc_pages_node_noprof(nid, gfp_mask, order);
         if (!p)
                 return NULL;
         return make_alloc_exact((unsigned long)page_address(p), order, size);
 }
 
 /**
  * free_pages_exact - release memory allocated via alloc_pages_exact()
  * @virt: the value returned by alloc_pages_exact.
  * @size: size of allocation, same value as passed to alloc_pages_exact().
  *
  * Release the memory allocated by a previous call to alloc_pages_exact.
  */
 void free_pages_exact(void *virt, size_t size)
 {
         unsigned long addr = (unsigned long)virt;
         unsigned long end = addr + PAGE_ALIGN(size);
 
         while (addr < end) {
                 free_page(addr);
                 addr += PAGE_SIZE;
         }
 }
 EXPORT_SYMBOL(free_pages_exact);
 
 /**
  * nr_free_zone_pages - count number of pages beyond high watermark
  * @offset: The zone index of the highest zone
  *
  * nr_free_zone_pages() counts the number of pages which are beyond the
  * high watermark within all zones at or below a given zone index.  For each
  * zone, the number of pages is calculated as:
  *
  *     nr_free_zone_pages = managed_pages - high_pages
  *
  * Return: number of pages beyond high watermark.
  */
 static unsigned long nr_free_zone_pages(int offset)
 {
         struct zoneref *z;
         struct zone *zone;
 
         /* Just pick one node, since fallback list is circular */
         unsigned long sum = 0;
 
         struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);
 
         for_each_zone_zonelist(zone, z, zonelist, offset) {
                 unsigned long size = zone_managed_pages(zone);
                 unsigned long high = high_wmark_pages(zone);
                 if (size > high)
                         sum += size - high;
         }
 
         return sum;
 }
 
 /**
  * nr_free_buffer_pages - count number of pages beyond high watermark
  *
  * nr_free_buffer_pages() counts the number of pages which are beyond the high
  * watermark within ZONE_DMA and ZONE_NORMAL.
  *
  * Return: number of pages beyond high watermark within ZONE_DMA and
  * ZONE_NORMAL.
  */
 unsigned long nr_free_buffer_pages(void)
 {
         return nr_free_zone_pages(gfp_zone(GFP_USER));
 }
 EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
 
 static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
 {
         zoneref->zone = zone;
         zoneref->zone_idx = zone_idx(zone);
 }
 
 /*
  * Builds allocation fallback zone lists.
  *
  * Add all populated zones of a node to the zonelist.
  */
 static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
 {
         struct zone *zone;
         enum zone_type zone_type = MAX_NR_ZONES;
         int nr_zones = 0;
 
         do {
                 zone_type--;
                 zone = pgdat->node_zones + zone_type;
                 if (populated_zone(zone)) {
                         zoneref_set_zone(zone, &zonerefs[nr_zones++]);
                         check_highest_zone(zone_type);
                 }
         } while (zone_type);
 
         return nr_zones;
 }
 
 #ifdef CONFIG_NUMA
 
 static int __parse_numa_zonelist_order(char *s)
 {
         /*
          * We used to support different zonelists modes but they turned
          * out to be just not useful. Let's keep the warning in place
          * if somebody still use the cmd line parameter so that we do
          * not fail it silently
          */
         if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {
                 pr_warn("Ignoring unsupported numa_zonelist_order value:  %s\n", s);
                 return -EINVAL;
         }
         return 0;
 }
 
 static char numa_zonelist_order[] = "Node";
 #define NUMA_ZONELIST_ORDER_LEN 16
 /*
  * sysctl handler for numa_zonelist_order
  */
 static int numa_zonelist_order_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         if (write)
                 return __parse_numa_zonelist_order(buffer);
         return proc_dostring(table, write, buffer, length, ppos);
 }
 
 static int node_load[MAX_NUMNODES];
 
 /**
  * find_next_best_node - find the next node that should appear in a given node's fallback list
  * @node: node whose fallback list we're appending
  * @used_node_mask: nodemask_t of already used nodes
  *
  * We use a number of factors to determine which is the next node that should
  * appear on a given node's fallback list.  The node should not have appeared
  * already in @node's fallback list, and it should be the next closest node
  * according to the distance array (which contains arbitrary distance values
  * from each node to each node in the system), and should also prefer nodes
  * with no CPUs, since presumably they'll have very little allocation pressure
  * on them otherwise.
  *
  * Return: node id of the found node or %NUMA_NO_NODE if no node is found.
  */
 int find_next_best_node(int node, nodemask_t *used_node_mask)
 {
         int n, val;
         int min_val = INT_MAX;
         int best_node = NUMA_NO_NODE;
 
         /*
          * Use the local node if we haven't already, but for memoryless local
          * node, we should skip it and fall back to other nodes.
          */
         if (!node_isset(node, *used_node_mask) && node_state(node, N_MEMORY)) {
                 node_set(node, *used_node_mask);
                 return node;
         }
 
         for_each_node_state(n, N_MEMORY) {
 
                 /* Don't want a node to appear more than once */
                 if (node_isset(n, *used_node_mask))
                         continue;
 
                 /* Use the distance array to find the distance */
                 val = node_distance(node, n);
 
                 /* Penalize nodes under us ("prefer the next node") */
                 val += (n < node);
 
                 /* Give preference to headless and unused nodes */
                 if (!cpumask_empty(cpumask_of_node(n)))
                         val += PENALTY_FOR_NODE_WITH_CPUS;
 
                 /* Slight preference for less loaded node */
                 val *= MAX_NUMNODES;
                 val += node_load[n];
 
                 if (val < min_val) {
                         min_val = val;
                         best_node = n;
                 }
         }
 
         if (best_node >= 0)
                 node_set(best_node, *used_node_mask);
 
         return best_node;
 }
 
 
 /*
  * Build zonelists ordered by node and zones within node.
  * This results in maximum locality--normal zone overflows into local
  * DMA zone, if any--but risks exhausting DMA zone.
  */
 static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
                 unsigned nr_nodes)
 {
         struct zoneref *zonerefs;
         int i;
 
         zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
 
         for (i = 0; i < nr_nodes; i++) {
                 int nr_zones;
 
                 pg_data_t *node = NODE_DATA(node_order[i]);
 
                 nr_zones = build_zonerefs_node(node, zonerefs);
                 zonerefs += nr_zones;
         }
         zonerefs->zone = NULL;
         zonerefs->zone_idx = 0;
 }
 
 /*
  * Build __GFP_THISNODE zonelists
  */
 static void build_thisnode_zonelists(pg_data_t *pgdat)
 {
         struct zoneref *zonerefs;
         int nr_zones;
 
         zonerefs = pgdat->node_zonelists[ZONELIST_NOFALLBACK]._zonerefs;
         nr_zones = build_zonerefs_node(pgdat, zonerefs);
         zonerefs += nr_zones;
         zonerefs->zone = NULL;
         zonerefs->zone_idx = 0;
 }
 
 /*
  * Build zonelists ordered by zone and nodes within zones.
  * This results in conserving DMA zone[s] until all Normal memory is
  * exhausted, but results in overflowing to remote node while memory
  * may still exist in local DMA zone.
  */
 
 static void build_zonelists(pg_data_t *pgdat)
 {
         static int node_order[MAX_NUMNODES];
         int node, nr_nodes = 0;
         nodemask_t used_mask = NODE_MASK_NONE;
         int local_node, prev_node;
 
         /* NUMA-aware ordering of nodes */
         local_node = pgdat->node_id;
         prev_node = local_node;
 
         memset(node_order, 0, sizeof(node_order));
         while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
                 /*
                  * We don't want to pressure a particular node.
                  * So adding penalty to the first node in same
                  * distance group to make it round-robin.
                  */
                 if (node_distance(local_node, node) !=
                     node_distance(local_node, prev_node))
                         node_load[node] += 1;
 
                 node_order[nr_nodes++] = node;
                 prev_node = node;
         }
 
         build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
         build_thisnode_zonelists(pgdat);
         pr_info("Fallback order for Node %d: ", local_node);
         for (node = 0; node < nr_nodes; node++)
                 pr_cont("%d ", node_order[node]);
         pr_cont("\n");
 }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 /*
  * Return node id of node used for "local" allocations.
  * I.e., first node id of first zone in arg node's generic zonelist.
  * Used for initializing percpu 'numa_mem', which is used primarily
  * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
  */
 int local_memory_node(int node)
 {
         struct zoneref *z;
 
         z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
                                    gfp_zone(GFP_KERNEL),
                                    NULL);
         return zone_to_nid(z->zone);
 }
 #endif
 
 static void setup_min_unmapped_ratio(void);
 static void setup_min_slab_ratio(void);
 #else   /* CONFIG_NUMA */
 
 static void build_zonelists(pg_data_t *pgdat)
 {
         struct zoneref *zonerefs;
         int nr_zones;
 
         zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
         nr_zones = build_zonerefs_node(pgdat, zonerefs);
         zonerefs += nr_zones;
 
         zonerefs->zone = NULL;
         zonerefs->zone_idx = 0;
 }
 
 #endif  /* CONFIG_NUMA */
 
 /*
  * Boot pageset table. One per cpu which is going to be used for all
  * zones and all nodes. The parameters will be set in such a way
  * that an item put on a list will immediately be handed over to
  * the buddy list. This is safe since pageset manipulation is done
  * with interrupts disabled.
  *
  * The boot_pagesets must be kept even after bootup is complete for
  * unused processors and/or zones. They do play a role for bootstrapping
  * hotplugged processors.
  *
  * zoneinfo_show() and maybe other functions do
  * not check if the processor is online before following the pageset pointer.
  * Other parts of the kernel may not check if the zone is available.
  */
 static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats);
 /* These effectively disable the pcplists in the boot pageset completely */
 #define BOOT_PAGESET_HIGH       0
 #define BOOT_PAGESET_BATCH      1
 static DEFINE_PER_CPU(struct per_cpu_pages, boot_pageset);
 static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);
 
 static void __build_all_zonelists(void *data)
 {
         int nid;
         int __maybe_unused cpu;
         pg_data_t *self = data;
         unsigned long flags;
 
         /*
          * The zonelist_update_seq must be acquired with irqsave because the
          * reader can be invoked from IRQ with GFP_ATOMIC.
          */
         write_seqlock_irqsave(&zonelist_update_seq, flags);
         /*
          * Also disable synchronous printk() to prevent any printk() from
          * trying to hold port->lock, for
          * tty_insert_flip_string_and_push_buffer() on other CPU might be
          * calling kmalloc(GFP_ATOMIC | __GFP_NOWARN) with port->lock held.
          */
         printk_deferred_enter();
 
 #ifdef CONFIG_NUMA
         memset(node_load, 0, sizeof(node_load));
 #endif
 
         /*
          * This node is hotadded and no memory is yet present.   So just
          * building zonelists is fine - no need to touch other nodes.
          */
         if (self && !node_online(self->node_id)) {
                 build_zonelists(self);
         } else {
                 /*
                  * All possible nodes have pgdat preallocated
                  * in free_area_init
                  */
                 for_each_node(nid) {
                         pg_data_t *pgdat = NODE_DATA(nid);
 
                         build_zonelists(pgdat);
                 }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
                 /*
                  * We now know the "local memory node" for each node--
                  * i.e., the node of the first zone in the generic zonelist.
                  * Set up numa_mem percpu variable for on-line cpus.  During
                  * boot, only the boot cpu should be on-line;  we'll init the
                  * secondary cpus' numa_mem as they come on-line.  During
                  * node/memory hotplug, we'll fixup all on-line cpus.
                  */
                 for_each_online_cpu(cpu)
                         set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
 #endif
         }
 
         printk_deferred_exit();
         write_sequnlock_irqrestore(&zonelist_update_seq, flags);
 }
 
 static noinline void __init
 build_all_zonelists_init(void)
 {
         int cpu;
 
         __build_all_zonelists(NULL);
 
         /*
          * Initialize the boot_pagesets that are going to be used
          * for bootstrapping processors. The real pagesets for
          * each zone will be allocated later when the per cpu
          * allocator is available.
          *
          * boot_pagesets are used also for bootstrapping offline
          * cpus if the system is already booted because the pagesets
          * are needed to initialize allocators on a specific cpu too.
          * F.e. the percpu allocator needs the page allocator which
          * needs the percpu allocator in order to allocate its pagesets
          * (a chicken-egg dilemma).
          */
         for_each_possible_cpu(cpu)
                 per_cpu_pages_init(&per_cpu(boot_pageset, cpu), &per_cpu(boot_zonestats, cpu));
 
         mminit_verify_zonelist();
         cpuset_init_current_mems_allowed();
 }
 
 /*
  * unless system_state == SYSTEM_BOOTING.
  *
  * __ref due to call of __init annotated helper build_all_zonelists_init
  * [protected by SYSTEM_BOOTING].
  */
 void __ref build_all_zonelists(pg_data_t *pgdat)
 {
         unsigned long vm_total_pages;
 
         if (system_state == SYSTEM_BOOTING) {
                 build_all_zonelists_init();
         } else {
                 __build_all_zonelists(pgdat);
                 /* cpuset refresh routine should be here */
         }
         /* Get the number of free pages beyond high watermark in all zones. */
         vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
         /*
          * Disable grouping by mobility if the number of pages in the
          * system is too low to allow the mechanism to work. It would be
          * more accurate, but expensive to check per-zone. This check is
          * made on memory-hotadd so a system can start with mobility
          * disabled and enable it later
          */
         if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
                 page_group_by_mobility_disabled = 1;
         else
                 page_group_by_mobility_disabled = 0;
 
         pr_info("Built %u zonelists, mobility grouping %s.  Total pages: %ld\n",
                 nr_online_nodes,
                 page_group_by_mobility_disabled ? "off" : "on",
                 vm_total_pages);
 #ifdef CONFIG_NUMA
         pr_info("Policy zone: %s\n", zone_names[policy_zone]);
 #endif
 }
 
 static int zone_batchsize(struct zone *zone)
 {
 #ifdef CONFIG_MMU
         int batch;
 
         /*
          * The number of pages to batch allocate is either ~0.1%
          * of the zone or 1MB, whichever is smaller. The batch
          * size is striking a balance between allocation latency
          * and zone lock contention.
          */
         batch = min(zone_managed_pages(zone) >> 10, SZ_1M / PAGE_SIZE);
         batch /= 4;             /* We effectively *= 4 below */
         if (batch < 1)
                 batch = 1;
 
         /*
          * Clamp the batch to a 2^n - 1 value. Having a power
          * of 2 value was found to be more likely to have
          * suboptimal cache aliasing properties in some cases.
          *
          * For example if 2 tasks are alternately allocating
          * batches of pages, one task can end up with a lot
          * of pages of one half of the possible page colors
          * and the other with pages of the other colors.
          */
         batch = rounddown_pow_of_two(batch + batch/2) - 1;
 
         return batch;
 
 #else
         /* The deferral and batching of frees should be suppressed under NOMMU
          * conditions.
          *
          * The problem is that NOMMU needs to be able to allocate large chunks
          * of contiguous memory as there's no hardware page translation to
          * assemble apparent contiguous memory from discontiguous pages.
          *
          * Queueing large contiguous runs of pages for batching, however,
          * causes the pages to actually be freed in smaller chunks.  As there
          * can be a significant delay between the individual batches being
          * recycled, this leads to the once large chunks of space being
          * fragmented and becoming unavailable for high-order allocations.
          */
         return 0;
 #endif
 }
 
 static int percpu_pagelist_high_fraction;
 static int zone_highsize(struct zone *zone, int batch, int cpu_online,
                          int high_fraction)
 {
 #ifdef CONFIG_MMU
         int high;
         int nr_split_cpus;
         unsigned long total_pages;
 
         if (!high_fraction) {
                 /*
                  * By default, the high value of the pcp is based on the zone
                  * low watermark so that if they are full then background
                  * reclaim will not be started prematurely.
                  */
                 total_pages = low_wmark_pages(zone);
         } else {
                 /*
                  * If percpu_pagelist_high_fraction is configured, the high
                  * value is based on a fraction of the managed pages in the
                  * zone.
                  */
                 total_pages = zone_managed_pages(zone) / high_fraction;
         }
 
         /*
          * Split the high value across all online CPUs local to the zone. Note
          * that early in boot that CPUs may not be online yet and that during
          * CPU hotplug that the cpumask is not yet updated when a CPU is being
          * onlined. For memory nodes that have no CPUs, split the high value
          * across all online CPUs to mitigate the risk that reclaim is triggered
          * prematurely due to pages stored on pcp lists.
          */
         nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
         if (!nr_split_cpus)
                 nr_split_cpus = num_online_cpus();
         high = total_pages / nr_split_cpus;
 
         /*
          * Ensure high is at least batch*4. The multiple is based on the
          * historical relationship between high and batch.
          */
         high = max(high, batch << 2);
 
         return high;
 #else
         return 0;
 #endif
 }
 
 /*
  * pcp->high and pcp->batch values are related and generally batch is lower
  * than high. They are also related to pcp->count such that count is lower
  * than high, and as soon as it reaches high, the pcplist is flushed.
  *
  * However, guaranteeing these relations at all times would require e.g. write
  * barriers here but also careful usage of read barriers at the read side, and
  * thus be prone to error and bad for performance. Thus the update only prevents
  * store tearing. Any new users of pcp->batch, pcp->high_min and pcp->high_max
  * should ensure they can cope with those fields changing asynchronously, and
  * fully trust only the pcp->count field on the local CPU with interrupts
  * disabled.
  *
  * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
  * outside of boot time (or some other assurance that no concurrent updaters
  * exist).
  */
 static void pageset_update(struct per_cpu_pages *pcp, unsigned long high_min,
                            unsigned long high_max, unsigned long batch)
 {
         WRITE_ONCE(pcp->batch, batch);
         WRITE_ONCE(pcp->high_min, high_min);
         WRITE_ONCE(pcp->high_max, high_max);
 }
 
 static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats)
 {
         int pindex;
 
         memset(pcp, 0, sizeof(*pcp));
         memset(pzstats, 0, sizeof(*pzstats));
 
         spin_lock_init(&pcp->lock);
         for (pindex = 0; pindex < NR_PCP_LISTS; pindex++)
                 INIT_LIST_HEAD(&pcp->lists[pindex]);
 
         /*
          * Set batch and high values safe for a boot pageset. A true percpu
          * pageset's initialization will update them subsequently. Here we don't
          * need to be as careful as pageset_update() as nobody can access the
          * pageset yet.
          */
         pcp->high_min = BOOT_PAGESET_HIGH;
         pcp->high_max = BOOT_PAGESET_HIGH;
         pcp->batch = BOOT_PAGESET_BATCH;
         pcp->free_count = 0;
 }
 
 static void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high_min,
                                               unsigned long high_max, unsigned long batch)
 {
         struct per_cpu_pages *pcp;
         int cpu;
 
         for_each_possible_cpu(cpu) {
                 pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                 pageset_update(pcp, high_min, high_max, batch);
         }
 }
 
 /*
  * Calculate and set new high and batch values for all per-cpu pagesets of a
  * zone based on the zone's size.
  */
 static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online)
 {
         int new_high_min, new_high_max, new_batch;
 
         new_batch = max(1, zone_batchsize(zone));
         if (percpu_pagelist_high_fraction) {
                 new_high_min = zone_highsize(zone, new_batch, cpu_online,
                                              percpu_pagelist_high_fraction);
                 /*
                  * PCP high is tuned manually, disable auto-tuning via
                  * setting high_min and high_max to the manual value.
                  */
                 new_high_max = new_high_min;
         } else {
                 new_high_min = zone_highsize(zone, new_batch, cpu_online, 0);
                 new_high_max = zone_highsize(zone, new_batch, cpu_online,
                                              MIN_PERCPU_PAGELIST_HIGH_FRACTION);
         }
 
         if (zone->pageset_high_min == new_high_min &&
             zone->pageset_high_max == new_high_max &&
             zone->pageset_batch == new_batch)
                 return;
 
         zone->pageset_high_min = new_high_min;
         zone->pageset_high_max = new_high_max;
         zone->pageset_batch = new_batch;
 
         __zone_set_pageset_high_and_batch(zone, new_high_min, new_high_max,
                                           new_batch);
 }
 
 void __meminit setup_zone_pageset(struct zone *zone)
 {
         int cpu;
 
         /* Size may be 0 on !SMP && !NUMA */
         if (sizeof(struct per_cpu_zonestat) > 0)
                 zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
 
         zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
         for_each_possible_cpu(cpu) {
                 struct per_cpu_pages *pcp;
                 struct per_cpu_zonestat *pzstats;
 
                 pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
                 pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
                 per_cpu_pages_init(pcp, pzstats);
         }
 
         zone_set_pageset_high_and_batch(zone, 0);
 }
 
 /*
  * The zone indicated has a new number of managed_pages; batch sizes and percpu
  * page high values need to be recalculated.
  */
 static void zone_pcp_update(struct zone *zone, int cpu_online)
 {
         mutex_lock(&pcp_batch_high_lock);
         zone_set_pageset_high_and_batch(zone, cpu_online);
         mutex_unlock(&pcp_batch_high_lock);
 }
 
 static void zone_pcp_update_cacheinfo(struct zone *zone, unsigned int cpu)
 {
         struct per_cpu_pages *pcp;
         struct cpu_cacheinfo *cci;
 
         pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
         cci = get_cpu_cacheinfo(cpu);
         /*
          * If data cache slice of CPU is large enough, "pcp->batch"
          * pages can be preserved in PCP before draining PCP for
          * consecutive high-order pages freeing without allocation.
          * This can reduce zone lock contention without hurting
          * cache-hot pages sharing.
          */
         spin_lock(&pcp->lock);
         if ((cci->per_cpu_data_slice_size >> PAGE_SHIFT) > 3 * pcp->batch)
                 pcp->flags |= PCPF_FREE_HIGH_BATCH;
         else
                 pcp->flags &= ~PCPF_FREE_HIGH_BATCH;
         spin_unlock(&pcp->lock);
 }
 
 void setup_pcp_cacheinfo(unsigned int cpu)
 {
         struct zone *zone;
 
         for_each_populated_zone(zone)
                 zone_pcp_update_cacheinfo(zone, cpu);
 }
 
 /*
  * Allocate per cpu pagesets and initialize them.
  * Before this call only boot pagesets were available.
  */
 void __init setup_per_cpu_pageset(void)
 {
         struct pglist_data *pgdat;
         struct zone *zone;
         int __maybe_unused cpu;
 
         for_each_populated_zone(zone)
                 setup_zone_pageset(zone);
 
 #ifdef CONFIG_NUMA
         /*
          * Unpopulated zones continue using the boot pagesets.
          * The numa stats for these pagesets need to be reset.
          * Otherwise, they will end up skewing the stats of
          * the nodes these zones are associated with.
          */
         for_each_possible_cpu(cpu) {
                 struct per_cpu_zonestat *pzstats = &per_cpu(boot_zonestats, cpu);
                 memset(pzstats->vm_numa_event, 0,
                        sizeof(pzstats->vm_numa_event));
         }
 #endif
 
         for_each_online_pgdat(pgdat)
                 pgdat->per_cpu_nodestats =
                         alloc_percpu(struct per_cpu_nodestat);
 }
 
 __meminit void zone_pcp_init(struct zone *zone)
 {
         /*
          * per cpu subsystem is not up at this point. The following code
          * relies on the ability of the linker to provide the
          * offset of a (static) per cpu variable into the per cpu area.
          */
         zone->per_cpu_pageset = &boot_pageset;
         zone->per_cpu_zonestats = &boot_zonestats;
         zone->pageset_high_min = BOOT_PAGESET_HIGH;
         zone->pageset_high_max = BOOT_PAGESET_HIGH;
         zone->pageset_batch = BOOT_PAGESET_BATCH;
 
         if (populated_zone(zone))
                 pr_debug("  %s zone: %lu pages, LIFO batch:%u\n", zone->name,
                          zone->present_pages, zone_batchsize(zone));
 }
 
 void adjust_managed_page_count(struct page *page, long count)
 {
         atomic_long_add(count, &page_zone(page)->managed_pages);
         totalram_pages_add(count);
 }
 EXPORT_SYMBOL(adjust_managed_page_count);
 
 unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
 {
         void *pos;
         unsigned long pages = 0;
 
         start = (void *)PAGE_ALIGN((unsigned long)start);
         end = (void *)((unsigned long)end & PAGE_MASK);
         for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
                 struct page *page = virt_to_page(pos);
                 void *direct_map_addr;
 
                 /*
                  * 'direct_map_addr' might be different from 'pos'
                  * because some architectures' virt_to_page()
                  * work with aliases.  Getting the direct map
                  * address ensures that we get a _writeable_
                  * alias for the memset().
                  */
                 direct_map_addr = page_address(page);
                 /*
                  * Perform a kasan-unchecked memset() since this memory
                  * has not been initialized.
                  */
                 direct_map_addr = kasan_reset_tag(direct_map_addr);
                 if ((unsigned int)poison <= 0xFF)
                         memset(direct_map_addr, poison, PAGE_SIZE);
 
                 free_reserved_page(page);
         }
 
         if (pages && s)
                 pr_info("Freeing %s memory: %ldK\n", s, K(pages));
 
         return pages;
 }
 
 void free_reserved_page(struct page *page)
 {
         clear_page_tag_ref(page);
         ClearPageReserved(page);
         init_page_count(page);
         __free_page(page);
         adjust_managed_page_count(page, 1);
 }
 EXPORT_SYMBOL(free_reserved_page);
 
 static int page_alloc_cpu_dead(unsigned int cpu)
 {
         struct zone *zone;
 
         lru_add_drain_cpu(cpu);
         mlock_drain_remote(cpu);
         drain_pages(cpu);
 
         /*
          * Spill the event counters of the dead processor
          * into the current processors event counters.
          * This artificially elevates the count of the current
          * processor.
          */
         vm_events_fold_cpu(cpu);
 
         /*
          * Zero the differential counters of the dead processor
          * so that the vm statistics are consistent.
          *
          * This is only okay since the processor is dead and cannot
          * race with what we are doing.
          */
         cpu_vm_stats_fold(cpu);
 
         for_each_populated_zone(zone)
                 zone_pcp_update(zone, 0);
 
         return 0;
 }
 
 static int page_alloc_cpu_online(unsigned int cpu)
 {
         struct zone *zone;
 
         for_each_populated_zone(zone)
                 zone_pcp_update(zone, 1);
         return 0;
 }
 
 void __init page_alloc_init_cpuhp(void)
 {
         int ret;
 
         ret = cpuhp_setup_state_nocalls(CPUHP_PAGE_ALLOC,
                                         "mm/page_alloc:pcp",
                                         page_alloc_cpu_online,
                                         page_alloc_cpu_dead);
         WARN_ON(ret < 0);
 }
 
 /*
  * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
  *      or min_free_kbytes changes.
  */
 static void calculate_totalreserve_pages(void)
 {
         struct pglist_data *pgdat;
         unsigned long reserve_pages = 0;
         enum zone_type i, j;
 
         for_each_online_pgdat(pgdat) {
 
                 pgdat->totalreserve_pages = 0;
 
                 for (i = 0; i < MAX_NR_ZONES; i++) {
                         struct zone *zone = pgdat->node_zones + i;
                         long max = 0;
                         unsigned long managed_pages = zone_managed_pages(zone);
 
                         /* Find valid and maximum lowmem_reserve in the zone */
                         for (j = i; j < MAX_NR_ZONES; j++) {
                                 if (zone->lowmem_reserve[j] > max)
                                         max = zone->lowmem_reserve[j];
                         }
 
                         /* we treat the high watermark as reserved pages. */
                         max += high_wmark_pages(zone);
 
                         if (max > managed_pages)
                                 max = managed_pages;
 
                         pgdat->totalreserve_pages += max;
 
                         reserve_pages += max;
                 }
         }
         totalreserve_pages = reserve_pages;
 }
 
 /*
  * setup_per_zone_lowmem_reserve - called whenever
  *      sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
  *      has a correct pages reserved value, so an adequate number of
  *      pages are left in the zone after a successful __alloc_pages().
  */
 static void setup_per_zone_lowmem_reserve(void)
 {
         struct pglist_data *pgdat;
         enum zone_type i, j;
 
         for_each_online_pgdat(pgdat) {
                 for (i = 0; i < MAX_NR_ZONES - 1; i++) {
                         struct zone *zone = &pgdat->node_zones[i];
                         int ratio = sysctl_lowmem_reserve_ratio[i];
                         bool clear = !ratio || !zone_managed_pages(zone);
                         unsigned long managed_pages = 0;
 
                         for (j = i + 1; j < MAX_NR_ZONES; j++) {
                                 struct zone *upper_zone = &pgdat->node_zones[j];
                                 bool empty = !zone_managed_pages(upper_zone);
 
                                 managed_pages += zone_managed_pages(upper_zone);
 
                                 if (clear || empty)
                                         zone->lowmem_reserve[j] = 0;
                                 else
                                         zone->lowmem_reserve[j] = managed_pages / ratio;
                         }
                 }
         }
 
         /* update totalreserve_pages */
         calculate_totalreserve_pages();
 }
 
 static void __setup_per_zone_wmarks(void)
 {
         unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
         unsigned long lowmem_pages = 0;
         struct zone *zone;
         unsigned long flags;
 
         /* Calculate total number of !ZONE_HIGHMEM and !ZONE_MOVABLE pages */
         for_each_zone(zone) {
                 if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
                         lowmem_pages += zone_managed_pages(zone);
         }
 
         for_each_zone(zone) {
                 u64 tmp;
 
                 spin_lock_irqsave(&zone->lock, flags);
                 tmp = (u64)pages_min * zone_managed_pages(zone);
                 tmp = div64_ul(tmp, lowmem_pages);
                 if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
                         /*
                          * __GFP_HIGH and PF_MEMALLOC allocations usually don't
                          * need highmem and movable zones pages, so cap pages_min
                          * to a small  value here.
                          *
                          * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
                          * deltas control async page reclaim, and so should
                          * not be capped for highmem and movable zones.
                          */
                         unsigned long min_pages;
 
                         min_pages = zone_managed_pages(zone) / 1024;
                         min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
                         zone->_watermark[WMARK_MIN] = min_pages;
                 } else {
                         /*
                          * If it's a lowmem zone, reserve a number of pages
                          * proportionate to the zone's size.
                          */
                         zone->_watermark[WMARK_MIN] = tmp;
                 }
 
                 /*
                  * Set the kswapd watermarks distance according to the
                  * scale factor in proportion to available memory, but
                  * ensure a minimum size on small systems.
                  */
                 tmp = max_t(u64, tmp >> 2,
                             mult_frac(zone_managed_pages(zone),
                                       watermark_scale_factor, 10000));
 
                 zone->watermark_boost = 0;
                 zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
                 zone->_watermark[WMARK_HIGH] = low_wmark_pages(zone) + tmp;
                 zone->_watermark[WMARK_PROMO] = high_wmark_pages(zone) + tmp;
 
                 spin_unlock_irqrestore(&zone->lock, flags);
         }
 
         /* update totalreserve_pages */
         calculate_totalreserve_pages();
 }
 
 /**
  * setup_per_zone_wmarks - called when min_free_kbytes changes
  * or when memory is hot-{added|removed}
  *
  * Ensures that the watermark[min,low,high] values for each zone are set
  * correctly with respect to min_free_kbytes.
  */
 void setup_per_zone_wmarks(void)
 {
         struct zone *zone;
         static DEFINE_SPINLOCK(lock);
 
         spin_lock(&lock);
         __setup_per_zone_wmarks();
         spin_unlock(&lock);
 
         /*
          * The watermark size have changed so update the pcpu batch
          * and high limits or the limits may be inappropriate.
          */
         for_each_zone(zone)
                 zone_pcp_update(zone, 0);
 }
 
 /*
  * Initialise min_free_kbytes.
  *
  * For small machines we want it small (128k min).  For large machines
  * we want it large (256MB max).  But it is not linear, because network
  * bandwidth does not increase linearly with machine size.  We use
  *
  *      min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
  *      min_free_kbytes = sqrt(lowmem_kbytes * 16)
  *
  * which yields
  *
  * 16MB:        512k
  * 32MB:        724k
  * 64MB:        1024k
  * 128MB:       1448k
  * 256MB:       2048k
  * 512MB:       2896k
  * 1024MB:      4096k
  * 2048MB:      5792k
  * 4096MB:      8192k
  * 8192MB:      11584k
  * 16384MB:     16384k
  */
 void calculate_min_free_kbytes(void)
 {
         unsigned long lowmem_kbytes;
         int new_min_free_kbytes;
 
         lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
         new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
 
         if (new_min_free_kbytes > user_min_free_kbytes)
                 min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
         else
                 pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
                                 new_min_free_kbytes, user_min_free_kbytes);
 
 }
 
 int __meminit init_per_zone_wmark_min(void)
 {
         calculate_min_free_kbytes();
         setup_per_zone_wmarks();
         refresh_zone_stat_thresholds();
         setup_per_zone_lowmem_reserve();
 
 #ifdef CONFIG_NUMA
         setup_min_unmapped_ratio();
         setup_min_slab_ratio();
 #endif
 
         khugepaged_min_free_kbytes_update();
 
         return 0;
 }
 postcore_initcall(init_per_zone_wmark_min)
 
 /*
  * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
  *      that we can call two helper functions whenever min_free_kbytes
  *      changes.
  */
 static int min_free_kbytes_sysctl_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         int rc;
 
         rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
         if (rc)
                 return rc;
 
         if (write) {
                 user_min_free_kbytes = min_free_kbytes;
                 setup_per_zone_wmarks();
         }
         return 0;
 }
 
 static int watermark_scale_factor_sysctl_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         int rc;
 
         rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
         if (rc)
                 return rc;
 
         if (write)
                 setup_per_zone_wmarks();
 
         return 0;
 }
 
 #ifdef CONFIG_NUMA
 static void setup_min_unmapped_ratio(void)
 {
         pg_data_t *pgdat;
         struct zone *zone;
 
         for_each_online_pgdat(pgdat)
                 pgdat->min_unmapped_pages = 0;
 
         for_each_zone(zone)
                 zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) *
                                                          sysctl_min_unmapped_ratio) / 100;
 }
 
 
 static int sysctl_min_unmapped_ratio_sysctl_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         int rc;
 
         rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
         if (rc)
                 return rc;
 
         setup_min_unmapped_ratio();
 
         return 0;
 }
 
 static void setup_min_slab_ratio(void)
 {
         pg_data_t *pgdat;
         struct zone *zone;
 
         for_each_online_pgdat(pgdat)
                 pgdat->min_slab_pages = 0;
 
         for_each_zone(zone)
                 zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) *
                                                      sysctl_min_slab_ratio) / 100;
 }
 
 static int sysctl_min_slab_ratio_sysctl_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         int rc;
 
         rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
         if (rc)
                 return rc;
 
         setup_min_slab_ratio();
 
         return 0;
 }
 #endif
 
 /*
  * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
  *      proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
  *      whenever sysctl_lowmem_reserve_ratio changes.
  *
  * The reserve ratio obviously has absolutely no relation with the
  * minimum watermarks. The lowmem reserve ratio can only make sense
  * if in function of the boot time zone sizes.
  */
 static int lowmem_reserve_ratio_sysctl_handler(const struct ctl_table *table,
                 int write, void *buffer, size_t *length, loff_t *ppos)
 {
         int i;
 
         proc_dointvec_minmax(table, write, buffer, length, ppos);
 
         for (i = 0; i < MAX_NR_ZONES; i++) {
                 if (sysctl_lowmem_reserve_ratio[i] < 1)
                         sysctl_lowmem_reserve_ratio[i] = 0;
         }
 
         setup_per_zone_lowmem_reserve();
         return 0;
 }
 
 /*
  * percpu_pagelist_high_fraction - changes the pcp->high for each zone on each
  * cpu. It is the fraction of total pages in each zone that a hot per cpu
  * pagelist can have before it gets flushed back to buddy allocator.
  */
 static int percpu_pagelist_high_fraction_sysctl_handler(const struct ctl_table *table,
                 int write, void *buffer, size_t *length, loff_t *ppos)
 {
         struct zone *zone;
         int old_percpu_pagelist_high_fraction;
         int ret;
 
         mutex_lock(&pcp_batch_high_lock);
         old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction;
 
         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
         if (!write || ret < 0)
                 goto out;
 
         /* Sanity checking to avoid pcp imbalance */
         if (percpu_pagelist_high_fraction &&
             percpu_pagelist_high_fraction < MIN_PERCPU_PAGELIST_HIGH_FRACTION) {
                 percpu_pagelist_high_fraction = old_percpu_pagelist_high_fraction;
                 ret = -EINVAL;
                 goto out;
         }
 
         /* No change? */
         if (percpu_pagelist_high_fraction == old_percpu_pagelist_high_fraction)
                 goto out;
 
         for_each_populated_zone(zone)
                 zone_set_pageset_high_and_batch(zone, 0);
 out:
         mutex_unlock(&pcp_batch_high_lock);
         return ret;
 }
 
 static struct ctl_table page_alloc_sysctl_table[] = {
         {
                 .procname       = "min_free_kbytes",
                 .data           = &min_free_kbytes,
                 .maxlen         = sizeof(min_free_kbytes),
                 .mode           = 0644,
                 .proc_handler   = min_free_kbytes_sysctl_handler,
                 .extra1         = SYSCTL_ZERO,
         },
         {
                 .procname       = "watermark_boost_factor",
                 .data           = &watermark_boost_factor,
                 .maxlen         = sizeof(watermark_boost_factor),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_minmax,
                 .extra1         = SYSCTL_ZERO,
         },
         {
                 .procname       = "watermark_scale_factor",
                 .data           = &watermark_scale_factor,
                 .maxlen         = sizeof(watermark_scale_factor),
                 .mode           = 0644,
                 .proc_handler   = watermark_scale_factor_sysctl_handler,
                 .extra1         = SYSCTL_ONE,
                 .extra2         = SYSCTL_THREE_THOUSAND,
         },
         {
                 .procname       = "percpu_pagelist_high_fraction",
                 .data           = &percpu_pagelist_high_fraction,
                 .maxlen         = sizeof(percpu_pagelist_high_fraction),
                 .mode           = 0644,
                 .proc_handler   = percpu_pagelist_high_fraction_sysctl_handler,
                 .extra1         = SYSCTL_ZERO,
         },
         {
                 .procname       = "lowmem_reserve_ratio",
                 .data           = &sysctl_lowmem_reserve_ratio,
                 .maxlen         = sizeof(sysctl_lowmem_reserve_ratio),
                 .mode           = 0644,
                 .proc_handler   = lowmem_reserve_ratio_sysctl_handler,
         },
 #ifdef CONFIG_NUMA
         {
                 .procname       = "numa_zonelist_order",
                 .data           = &numa_zonelist_order,
                 .maxlen         = NUMA_ZONELIST_ORDER_LEN,
                 .mode           = 0644,
                 .proc_handler   = numa_zonelist_order_handler,
         },
         {
                 .procname       = "min_unmapped_ratio",
                 .data           = &sysctl_min_unmapped_ratio,
                 .maxlen         = sizeof(sysctl_min_unmapped_ratio),
                 .mode           = 0644,
                 .proc_handler   = sysctl_min_unmapped_ratio_sysctl_handler,
                 .extra1         = SYSCTL_ZERO,
                 .extra2         = SYSCTL_ONE_HUNDRED,
         },
         {
                 .procname       = "min_slab_ratio",
                 .data           = &sysctl_min_slab_ratio,
                 .maxlen         = sizeof(sysctl_min_slab_ratio),
                 .mode           = 0644,
                 .proc_handler   = sysctl_min_slab_ratio_sysctl_handler,
                 .extra1         = SYSCTL_ZERO,
                 .extra2         = SYSCTL_ONE_HUNDRED,
         },
 #endif
 };
 
 void __init page_alloc_sysctl_init(void)
 {
         register_sysctl_init("vm", page_alloc_sysctl_table);
 }
 
 #ifdef CONFIG_CONTIG_ALLOC
 /* Usage: See admin-guide/dynamic-debug-howto.rst */
 static void alloc_contig_dump_pages(struct list_head *page_list)
 {
         DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, "migrate failure");
 
         if (DYNAMIC_DEBUG_BRANCH(descriptor)) {
                 struct page *page;
 
                 dump_stack();
                 list_for_each_entry(page, page_list, lru)
                         dump_page(page, "migration failure");
         }
 }
 
 /*
  * [start, end) must belong to a single zone.
  * @migratetype: using migratetype to filter the type of migration in
  *              trace_mm_alloc_contig_migrate_range_info.
  */
 int __alloc_contig_migrate_range(struct compact_control *cc,
                                         unsigned long start, unsigned long end,
                                         int migratetype)
 {
         /* This function is based on compact_zone() from compaction.c. */
         unsigned int nr_reclaimed;
         unsigned long pfn = start;
         unsigned int tries = 0;
         int ret = 0;
         struct migration_target_control mtc = {
                 .nid = zone_to_nid(cc->zone),
                 .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
                 .reason = MR_CONTIG_RANGE,
         };
         struct page *page;
         unsigned long total_mapped = 0;
         unsigned long total_migrated = 0;
         unsigned long total_reclaimed = 0;
 
         lru_cache_disable();
 
         while (pfn < end || !list_empty(&cc->migratepages)) {
                 if (fatal_signal_pending(current)) {
                         ret = -EINTR;
                         break;
                 }
 
                 if (list_empty(&cc->migratepages)) {
                         cc->nr_migratepages = 0;
                         ret = isolate_migratepages_range(cc, pfn, end);
                         if (ret && ret != -EAGAIN)
                                 break;
                         pfn = cc->migrate_pfn;
                         tries = 0;
                 } else if (++tries == 5) {
                         ret = -EBUSY;
                         break;
                 }
 
                 nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
                                                         &cc->migratepages);
                 cc->nr_migratepages -= nr_reclaimed;
 
                 if (trace_mm_alloc_contig_migrate_range_info_enabled()) {
                         total_reclaimed += nr_reclaimed;
                         list_for_each_entry(page, &cc->migratepages, lru) {
                                 struct folio *folio = page_folio(page);
 
                                 total_mapped += folio_mapped(folio) *
                                                 folio_nr_pages(folio);
                         }
                 }
 
                 ret = migrate_pages(&cc->migratepages, alloc_migration_target,
                         NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE, NULL);
 
                 if (trace_mm_alloc_contig_migrate_range_info_enabled() && !ret)
                         total_migrated += cc->nr_migratepages;
 
                 /*
                  * On -ENOMEM, migrate_pages() bails out right away. It is pointless
                  * to retry again over this error, so do the same here.
                  */
                 if (ret == -ENOMEM)
                         break;
         }
 
         lru_cache_enable();
         if (ret < 0) {
                 if (!(cc->gfp_mask & __GFP_NOWARN) && ret == -EBUSY)
                         alloc_contig_dump_pages(&cc->migratepages);
                 putback_movable_pages(&cc->migratepages);
         }
 
         trace_mm_alloc_contig_migrate_range_info(start, end, migratetype,
                                                  total_migrated,
                                                  total_reclaimed,
                                                  total_mapped);
         return (ret < 0) ? ret : 0;
 }
 
 /**
  * alloc_contig_range() -- tries to allocate given range of pages
  * @start:      start PFN to allocate
  * @end:        one-past-the-last PFN to allocate
  * @migratetype:        migratetype of the underlying pageblocks (either
  *                      #MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
  *                      in range must have the same migratetype and it must
  *                      be either of the two.
  * @gfp_mask:   GFP mask to use during compaction
  *
  * The PFN range does not have to be pageblock aligned. The PFN range must
  * belong to a single zone.
  *
  * The first thing this routine does is attempt to MIGRATE_ISOLATE all
  * pageblocks in the range.  Once isolated, the pageblocks should not
  * be modified by others.
  *
  * Return: zero on success or negative error code.  On success all
  * pages which PFN is in [start, end) are allocated for the caller and
  * need to be freed with free_contig_range().
  */
 int alloc_contig_range_noprof(unsigned long start, unsigned long end,
                        unsigned migratetype, gfp_t gfp_mask)
 {
         unsigned long outer_start, outer_end;
         int ret = 0;
 
         struct compact_control cc = {
                 .nr_migratepages = 0,
                 .order = -1,
                 .zone = page_zone(pfn_to_page(start)),
                 .mode = MIGRATE_SYNC,
                 .ignore_skip_hint = true,
                 .no_set_skip_hint = true,
                 .gfp_mask = current_gfp_context(gfp_mask),
                 .alloc_contig = true,
         };
         INIT_LIST_HEAD(&cc.migratepages);
 
         /*
          * What we do here is we mark all pageblocks in range as
          * MIGRATE_ISOLATE.  Because pageblock and max order pages may
          * have different sizes, and due to the way page allocator
          * work, start_isolate_page_range() has special handlings for this.
          *
          * Once the pageblocks are marked as MIGRATE_ISOLATE, we
          * migrate the pages from an unaligned range (ie. pages that
          * we are interested in). This will put all the pages in
          * range back to page allocator as MIGRATE_ISOLATE.
          *
          * When this is done, we take the pages in range from page
          * allocator removing them from the buddy system.  This way
          * page allocator will never consider using them.
          *
          * This lets us mark the pageblocks back as
          * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
          * aligned range but not in the unaligned, original range are
          * put back to page allocator so that buddy can use them.
          */
 
         ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
         if (ret)
                 goto done;
 
         drain_all_pages(cc.zone);
 
         /*
          * In case of -EBUSY, we'd like to know which page causes problem.
          * So, just fall through. test_pages_isolated() has a tracepoint
          * which will report the busy page.
          *
          * It is possible that busy pages could become available before
          * the call to test_pages_isolated, and the range will actually be
          * allocated.  So, if we fall through be sure to clear ret so that
          * -EBUSY is not accidentally used or returned to caller.
          */
         ret = __alloc_contig_migrate_range(&cc, start, end, migratetype);
         if (ret && ret != -EBUSY)
                 goto done;
         ret = 0;
 
         /*
          * Pages from [start, end) are within a pageblock_nr_pages
          * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
          * more, all pages in [start, end) are free in page allocator.
          * What we are going to do is to allocate all pages from
          * [start, end) (that is remove them from page allocator).
          *
          * The only problem is that pages at the beginning and at the
          * end of interesting range may be not aligned with pages that
          * page allocator holds, ie. they can be part of higher order
          * pages.  Because of this, we reserve the bigger range and
          * once this is done free the pages we are not interested in.
          *
          * We don't have to hold zone->lock here because the pages are
          * isolated thus they won't get removed from buddy.
          */
         outer_start = find_large_buddy(start);
 
         /* Make sure the range is really isolated. */
         if (test_pages_isolated(outer_start, end, 0)) {
                 ret = -EBUSY;
                 goto done;
         }
 
         /* Grab isolated pages from freelists. */
         outer_end = isolate_freepages_range(&cc, outer_start, end);
         if (!outer_end) {
                 ret = -EBUSY;
                 goto done;
         }
 
         /* Free head and tail (if any) */
         if (start != outer_start)
                 free_contig_range(outer_start, start - outer_start);
         if (end != outer_end)
                 free_contig_range(end, outer_end - end);
 
 done:
         undo_isolate_page_range(start, end, migratetype);
         return ret;
 }
 EXPORT_SYMBOL(alloc_contig_range_noprof);
 
 static int __alloc_contig_pages(unsigned long start_pfn,
                                 unsigned long nr_pages, gfp_t gfp_mask)
 {
         unsigned long end_pfn = start_pfn + nr_pages;
 
         return alloc_contig_range_noprof(start_pfn, end_pfn, MIGRATE_MOVABLE,
                                    gfp_mask);
 }
 
 static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
                                    unsigned long nr_pages)
 {
         unsigned long i, end_pfn = start_pfn + nr_pages;
         struct page *page;
 
         for (i = start_pfn; i < end_pfn; i++) {
                 page = pfn_to_online_page(i);
                 if (!page)
                         return false;
 
                 if (page_zone(page) != z)
                         return false;
 
                 if (PageReserved(page))
                         return false;
 
                 if (PageHuge(page))
                         return false;
         }
         return true;
 }
 
 static bool zone_spans_last_pfn(const struct zone *zone,
                                 unsigned long start_pfn, unsigned long nr_pages)
 {
         unsigned long last_pfn = start_pfn + nr_pages - 1;
 
         return zone_spans_pfn(zone, last_pfn);
 }
 
 /**
  * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
  * @nr_pages:   Number of contiguous pages to allocate
  * @gfp_mask:   GFP mask to limit search and used during compaction
  * @nid:        Target node
  * @nodemask:   Mask for other possible nodes
  *
  * This routine is a wrapper around alloc_contig_range(). It scans over zones
  * on an applicable zonelist to find a contiguous pfn range which can then be
  * tried for allocation with alloc_contig_range(). This routine is intended
  * for allocation requests which can not be fulfilled with the buddy allocator.
  *
  * The allocated memory is always aligned to a page boundary. If nr_pages is a
  * power of two, then allocated range is also guaranteed to be aligned to same
  * nr_pages (e.g. 1GB request would be aligned to 1GB).
  *
  * Allocated pages can be freed with free_contig_range() or by manually calling
  * __free_page() on each allocated page.
  *
  * Return: pointer to contiguous pages on success, or NULL if not successful.
  */
 struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask,
                                  int nid, nodemask_t *nodemask)
 {
         unsigned long ret, pfn, flags;
         struct zonelist *zonelist;
         struct zone *zone;
         struct zoneref *z;
 
         zonelist = node_zonelist(nid, gfp_mask);
         for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                         gfp_zone(gfp_mask), nodemask) {
                 spin_lock_irqsave(&zone->lock, flags);
 
                 pfn = ALIGN(zone->zone_start_pfn, nr_pages);
                 while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
                         if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
                                 /*
                                  * We release the zone lock here because
                                  * alloc_contig_range() will also lock the zone
                                  * at some point. If there's an allocation
                                  * spinning on this lock, it may win the race
                                  * and cause alloc_contig_range() to fail...
                                  */
                                 spin_unlock_irqrestore(&zone->lock, flags);
                                 ret = __alloc_contig_pages(pfn, nr_pages,
                                                         gfp_mask);
                                 if (!ret)
                                         return pfn_to_page(pfn);
                                 spin_lock_irqsave(&zone->lock, flags);
                         }
                         pfn += nr_pages;
                 }
                 spin_unlock_irqrestore(&zone->lock, flags);
         }
         return NULL;
 }
 #endif /* CONFIG_CONTIG_ALLOC */
 
 void free_contig_range(unsigned long pfn, unsigned long nr_pages)
 {
         unsigned long count = 0;
 
         for (; nr_pages--; pfn++) {
                 struct page *page = pfn_to_page(pfn);
 
                 count += page_count(page) != 1;
                 __free_page(page);
         }
         WARN(count != 0, "%lu pages are still in use!\n", count);
 }
 EXPORT_SYMBOL(free_contig_range);
 
 /*
  * Effectively disable pcplists for the zone by setting the high limit to 0
  * and draining all cpus. A concurrent page freeing on another CPU that's about
  * to put the page on pcplist will either finish before the drain and the page
  * will be drained, or observe the new high limit and skip the pcplist.
  *
  * Must be paired with a call to zone_pcp_enable().
  */
 void zone_pcp_disable(struct zone *zone)
 {
         mutex_lock(&pcp_batch_high_lock);
         __zone_set_pageset_high_and_batch(zone, 0, 0, 1);
         __drain_all_pages(zone, true);
 }
 
 void zone_pcp_enable(struct zone *zone)
 {
         __zone_set_pageset_high_and_batch(zone, zone->pageset_high_min,
                 zone->pageset_high_max, zone->pageset_batch);
         mutex_unlock(&pcp_batch_high_lock);
 }
 
 void zone_pcp_reset(struct zone *zone)
 {
         int cpu;
         struct per_cpu_zonestat *pzstats;
 
         if (zone->per_cpu_pageset != &boot_pageset) {
                 for_each_online_cpu(cpu) {
                         pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
                         drain_zonestat(zone, pzstats);
                 }
                 free_percpu(zone->per_cpu_pageset);
                 zone->per_cpu_pageset = &boot_pageset;
                 if (zone->per_cpu_zonestats != &boot_zonestats) {
                         free_percpu(zone->per_cpu_zonestats);
                         zone->per_cpu_zonestats = &boot_zonestats;
                 }
         }
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
  * All pages in the range must be in a single zone, must not contain holes,
  * must span full sections, and must be isolated before calling this function.
  *
  * Returns the number of managed (non-PageOffline()) pages in the range: the
  * number of pages for which memory offlining code must adjust managed page
  * counters using adjust_managed_page_count().
  */
 unsigned long __offline_isolated_pages(unsigned long start_pfn,
                 unsigned long end_pfn)
 {
         unsigned long already_offline = 0, flags;
         unsigned long pfn = start_pfn;
         struct page *page;
         struct zone *zone;
         unsigned int order;
 
         offline_mem_sections(pfn, end_pfn);
         zone = page_zone(pfn_to_page(pfn));
         spin_lock_irqsave(&zone->lock, flags);
         while (pfn < end_pfn) {
                 page = pfn_to_page(pfn);
                 /*
                  * The HWPoisoned page may be not in buddy system, and
                  * page_count() is not 0.
                  */
                 if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
                         pfn++;
                         continue;
                 }
                 /*
                  * At this point all remaining PageOffline() pages have a
                  * reference count of 0 and can simply be skipped.
                  */
                 if (PageOffline(page)) {
                         BUG_ON(page_count(page));
                         BUG_ON(PageBuddy(page));
                         already_offline++;
                         pfn++;
                         continue;
                 }
 
                 BUG_ON(page_count(page));
                 BUG_ON(!PageBuddy(page));
                 VM_WARN_ON(get_pageblock_migratetype(page) != MIGRATE_ISOLATE);
                 order = buddy_order(page);
                 del_page_from_free_list(page, zone, order, MIGRATE_ISOLATE);
                 pfn += (1 << order);
         }
         spin_unlock_irqrestore(&zone->lock, flags);
 
         return end_pfn - start_pfn - already_offline;
 }
 #endif
 
 /*
  * This function returns a stable result only if called under zone lock.
  */
 bool is_free_buddy_page(const struct page *page)
 {
         unsigned long pfn = page_to_pfn(page);
         unsigned int order;
 
         for (order = 0; order < NR_PAGE_ORDERS; order++) {
                 const struct page *head = page - (pfn & ((1 << order) - 1));
 
                 if (PageBuddy(head) &&
                     buddy_order_unsafe(head) >= order)
                         break;
         }
 
         return order <= MAX_PAGE_ORDER;
 }
 EXPORT_SYMBOL(is_free_buddy_page);
 
 #ifdef CONFIG_MEMORY_FAILURE
 static inline void add_to_free_list(struct page *page, struct zone *zone,
                                     unsigned int order, int migratetype,
                                     bool tail)
 {
         __add_to_free_list(page, zone, order, migratetype, tail);
         account_freepages(zone, 1 << order, migratetype);
 }
 
 /*
  * Break down a higher-order page in sub-pages, and keep our target out of
  * buddy allocator.
  */
 static void break_down_buddy_pages(struct zone *zone, struct page *page,
                                    struct page *target, int low, int high,
                                    int migratetype)
 {
         unsigned long size = 1 << high;
         struct page *current_buddy;
 
         while (high > low) {
                 high--;
                 size >>= 1;
 
                 if (target >= &page[size]) {
                         current_buddy = page;
                         page = page + size;
                 } else {
                         current_buddy = page + size;
                 }
 
                 if (set_page_guard(zone, current_buddy, high))
                         continue;
 
                 add_to_free_list(current_buddy, zone, high, migratetype, false);
                 set_buddy_order(current_buddy, high);
         }
 }
 
 /*
  * Take a page that will be marked as poisoned off the buddy allocator.
  */
 bool take_page_off_buddy(struct page *page)
 {
         struct zone *zone = page_zone(page);
         unsigned long pfn = page_to_pfn(page);
         unsigned long flags;
         unsigned int order;
         bool ret = false;
 
         spin_lock_irqsave(&zone->lock, flags);
         for (order = 0; order < NR_PAGE_ORDERS; order++) {
                 struct page *page_head = page - (pfn & ((1 << order) - 1));
                 int page_order = buddy_order(page_head);
 
                 if (PageBuddy(page_head) && page_order >= order) {
                         unsigned long pfn_head = page_to_pfn(page_head);
                         int migratetype = get_pfnblock_migratetype(page_head,
                                                                    pfn_head);
 
                         del_page_from_free_list(page_head, zone, page_order,
                                                 migratetype);
                         break_down_buddy_pages(zone, page_head, page, 0,
                                                 page_order, migratetype);
                         SetPageHWPoisonTakenOff(page);
                         ret = true;
                         break;
                 }
                 if (page_count(page_head) > 0)
                         break;
         }
         spin_unlock_irqrestore(&zone->lock, flags);
         return ret;
 }
 
 /*
  * Cancel takeoff done by take_page_off_buddy().
  */
 bool put_page_back_buddy(struct page *page)
 {
         struct zone *zone = page_zone(page);
         unsigned long flags;
         bool ret = false;
 
         spin_lock_irqsave(&zone->lock, flags);
         if (put_page_testzero(page)) {
                 unsigned long pfn = page_to_pfn(page);
                 int migratetype = get_pfnblock_migratetype(page, pfn);
 
                 ClearPageHWPoisonTakenOff(page);
                 __free_one_page(page, pfn, zone, 0, migratetype, FPI_NONE);
                 if (TestClearPageHWPoison(page)) {
                         ret = true;
                 }
         }
         spin_unlock_irqrestore(&zone->lock, flags);
 
         return ret;
 }
 #endif
 
 #ifdef CONFIG_ZONE_DMA
 bool has_managed_dma(void)
 {
         struct pglist_data *pgdat;
 
         for_each_online_pgdat(pgdat) {
                 struct zone *zone = &pgdat->node_zones[ZONE_DMA];
 
                 if (managed_zone(zone))
                         return true;
         }
         return false;
 }
 #endif /* CONFIG_ZONE_DMA */
 
 #ifdef CONFIG_UNACCEPTED_MEMORY
 
 /* Counts number of zones with unaccepted pages. */
 static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
 
 static bool lazy_accept = true;
 
 static int __init accept_memory_parse(char *p)
 {
         if (!strcmp(p, "lazy")) {
                 lazy_accept = true;
                 return 0;
         } else if (!strcmp(p, "eager")) {
                 lazy_accept = false;
                 return 0;
         } else {
                 return -EINVAL;
         }
 }
 early_param("accept_memory", accept_memory_parse);
 
 static bool page_contains_unaccepted(struct page *page, unsigned int order)
 {
         phys_addr_t start = page_to_phys(page);
         phys_addr_t end = start + (PAGE_SIZE << order);
 
         return range_contains_unaccepted_memory(start, end);
 }
 
 static void accept_page(struct page *page, unsigned int order)
 {
         phys_addr_t start = page_to_phys(page);
 
         accept_memory(start, start + (PAGE_SIZE << order));
 }
 
 static bool try_to_accept_memory_one(struct zone *zone)
 {
         unsigned long flags;
         struct page *page;
         bool last;
 
         spin_lock_irqsave(&zone->lock, flags);
         page = list_first_entry_or_null(&zone->unaccepted_pages,
                                         struct page, lru);
         if (!page) {
                 spin_unlock_irqrestore(&zone->lock, flags);
                 return false;
         }
 
         list_del(&page->lru);
         last = list_empty(&zone->unaccepted_pages);
 
         account_freepages(zone, -MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
         __mod_zone_page_state(zone, NR_UNACCEPTED, -MAX_ORDER_NR_PAGES);
         spin_unlock_irqrestore(&zone->lock, flags);
 
         accept_page(page, MAX_PAGE_ORDER);
 
         __free_pages_ok(page, MAX_PAGE_ORDER, FPI_TO_TAIL);
 
         if (last)
                 static_branch_dec(&zones_with_unaccepted_pages);
 
         return true;
 }
 
 static bool cond_accept_memory(struct zone *zone, unsigned int order)
 {
         long to_accept;
         bool ret = false;
 
         if (!has_unaccepted_memory())
                 return false;
 
         if (list_empty(&zone->unaccepted_pages))
                 return false;
 
         /* How much to accept to get to high watermark? */
         to_accept = high_wmark_pages(zone) -
                     (zone_page_state(zone, NR_FREE_PAGES) -
                     __zone_watermark_unusable_free(zone, order, 0) -
                     zone_page_state(zone, NR_UNACCEPTED));
 
         while (to_accept > 0) {
                 if (!try_to_accept_memory_one(zone))
                         break;
                 ret = true;
                 to_accept -= MAX_ORDER_NR_PAGES;
         }
 
         return ret;
 }
 
 static inline bool has_unaccepted_memory(void)
 {
         return static_branch_unlikely(&zones_with_unaccepted_pages);
 }
 
 static bool __free_unaccepted(struct page *page)
 {
         struct zone *zone = page_zone(page);
         unsigned long flags;
         bool first = false;
 
         if (!lazy_accept)
                 return false;
 
         spin_lock_irqsave(&zone->lock, flags);
         first = list_empty(&zone->unaccepted_pages);
         list_add_tail(&page->lru, &zone->unaccepted_pages);
         account_freepages(zone, MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
         __mod_zone_page_state(zone, NR_UNACCEPTED, MAX_ORDER_NR_PAGES);
         spin_unlock_irqrestore(&zone->lock, flags);
 
         if (first)
                 static_branch_inc(&zones_with_unaccepted_pages);
 
         return true;
 }
 
 #else
 
 static bool page_contains_unaccepted(struct page *page, unsigned int order)
 {
         return false;
 }
 
 static void accept_page(struct page *page, unsigned int order)
 {
 }
 
 static bool cond_accept_memory(struct zone *zone, unsigned int order)
 {
         return false;
 }
 
 static inline bool has_unaccepted_memory(void)
 {
         return false;
 }
 
 static bool __free_unaccepted(struct page *page)
 {
         BUILD_BUG();
         return false;
 }
 
 #endif /* CONFIG_UNACCEPTED_MEMORY */