// 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))

/* Free the page without taking locks. Rely on trylock only. */
#define FPI_TRYLOCK             ((__force fpi_t)BIT(2))

/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
static DEFINE_MUTEX(pcp_batch_high_lock);
#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)

#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
/*
 * On SMP, spin_trylock is sufficient protection.
 * On PREEMPT_RT, spin_trylock is equivalent on both SMP and UP.
 */
#define pcp_trylock_prepare(flags)      do { } while (0)
#define pcp_trylock_finish(flag)        do { } while (0)
#else

/* UP spin_trylock always succeeds so disable IRQs to prevent re-entrancy. */
#define pcp_trylock_prepare(flags)      local_irq_save(flags)
#define pcp_trylock_finish(flags)       local_irq_restore(flags)
#endif

/*
 * Locking a pcp requires a PCP lookup followed by a spinlock. To avoid
 * a migration causing the wrong PCP to be locked and remote memory being
 * potentially allocated, pin the task to the CPU for the lookup+lock.
 * preempt_disable is used on !RT because it is faster than migrate_disable.
 * migrate_disable is used on RT because otherwise RT spinlock usage is
 * interfered with and a high priority task cannot preempt the allocator.
 */
#ifndef CONFIG_PREEMPT_RT
#define pcpu_task_pin()         preempt_disable()
#define pcpu_task_unpin()       preempt_enable()
#else
#define pcpu_task_pin()         migrate_disable()
#define pcpu_task_unpin()       migrate_enable()
#endif

/*
 * Generic helper to lookup and a per-cpu variable with an embedded spinlock.
 * Return value should be used with equivalent unlock helper.
 */
#define pcpu_spin_lock(type, member, ptr)                               \
({                                                                      \
        type *_ret;                                                     \
        pcpu_task_pin();                                                \
        _ret = this_cpu_ptr(ptr);                                       \
        spin_lock(&_ret->member);                                       \
        _ret;                                                           \
})

#define pcpu_spin_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;
int defrag_mode;

/* 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 bool cond_accept_memory(struct zone *zone, unsigned int order,
                               int alloc_flags);
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;
}

static inline bool _deferred_grow_zone(struct zone *zone, unsigned int order)
{
        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;
}

static __always_inline bool is_standalone_pb_bit(enum pageblock_bits pb_bit)
{
        return pb_bit > PB_migrate_end && pb_bit < __NR_PAGEBLOCK_BITS;
}

static __always_inline void
get_pfnblock_bitmap_bitidx(const struct page *page, unsigned long pfn,
                           unsigned long **bitmap_word, unsigned long *bitidx)
{
        unsigned long *bitmap;
        unsigned long word_bitidx;

#ifdef CONFIG_MEMORY_ISOLATION
        BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 8);
#else
        BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
#endif
        BUILD_BUG_ON(__MIGRATE_TYPE_END >= (1 << PB_migratetype_bits));
        VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);

        bitmap = get_pageblock_bitmap(page, pfn);
        *bitidx = pfn_to_bitidx(page, pfn);
        word_bitidx = *bitidx / BITS_PER_LONG;
        *bitidx &= (BITS_PER_LONG - 1);
        *bitmap_word = &bitmap[word_bitidx];
}


/**
 * __get_pfnblock_flags_mask - Return the requested group of flags for
 * a 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
 */
static unsigned long __get_pfnblock_flags_mask(const struct page *page,
                                               unsigned long pfn,
                                               unsigned long mask)
{
        unsigned long *bitmap_word;
        unsigned long bitidx;
        unsigned long word;

        get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx);
        /*
         * This races, without locks, with set_pfnblock_migratetype(). Ensure
         * a consistent read of the memory array, so that results, even though
         * racy, are not corrupted.
         */
        word = READ_ONCE(*bitmap_word);
        return (word >> bitidx) & mask;
}

/**
 * get_pfnblock_bit - Check if a standalone bit of a pageblock is set
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 * @pb_bit: pageblock bit to check
 *
 * Return: true if the bit is set, otherwise false
 */
bool get_pfnblock_bit(const struct page *page, unsigned long pfn,
                      enum pageblock_bits pb_bit)
{
        unsigned long *bitmap_word;
        unsigned long bitidx;

        if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit)))
                return false;

        get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx);

        return test_bit(bitidx + pb_bit, bitmap_word);
}

/**
 * get_pfnblock_migratetype - Return the migratetype of a pageblock
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 *
 * Return: The migratetype of the pageblock
 *
 * Use get_pfnblock_migratetype() if caller already has both @page and @pfn
 * to save a call to page_to_pfn().
 */
__always_inline enum migratetype
get_pfnblock_migratetype(const struct page *page, unsigned long pfn)
{
        unsigned long mask = MIGRATETYPE_AND_ISO_MASK;
        unsigned long flags;

        flags = __get_pfnblock_flags_mask(page, pfn, mask);

#ifdef CONFIG_MEMORY_ISOLATION
        if (flags & BIT(PB_migrate_isolate))
                return MIGRATE_ISOLATE;
#endif
        return flags & 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
 * @pfn: The target page frame number
 * @flags: The flags to set
 * @mask: mask of bits that the caller is interested in
 */
static void __set_pfnblock_flags_mask(struct page *page, unsigned long pfn,
                                      unsigned long flags, unsigned long mask)
{
        unsigned long *bitmap_word;
        unsigned long bitidx;
        unsigned long word;

        get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx);

        mask <<= bitidx;
        flags <<= bitidx;

        word = READ_ONCE(*bitmap_word);
        do {
        } while (!try_cmpxchg(bitmap_word, &word, (word & ~mask) | flags));
}

/**
 * set_pfnblock_bit - Set a standalone bit of a pageblock
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 * @pb_bit: pageblock bit to set
 */
void set_pfnblock_bit(const struct page *page, unsigned long pfn,
                      enum pageblock_bits pb_bit)
{
        unsigned long *bitmap_word;
        unsigned long bitidx;

        if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit)))
                return;

        get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx);

        set_bit(bitidx + pb_bit, bitmap_word);
}

/**
 * clear_pfnblock_bit - Clear a standalone bit of a pageblock
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 * @pb_bit: pageblock bit to clear
 */
void clear_pfnblock_bit(const struct page *page, unsigned long pfn,
                        enum pageblock_bits pb_bit)
{
        unsigned long *bitmap_word;
        unsigned long bitidx;

        if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit)))
                return;

        get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx);

        clear_bit(bitidx + pb_bit, bitmap_word);
}

/**
 * set_pageblock_migratetype - Set the migratetype of a pageblock
 * @page: The page within the block of interest
 * @migratetype: migratetype to set
 */
static void set_pageblock_migratetype(struct page *page,
                                      enum migratetype migratetype)
{
        if (unlikely(page_group_by_mobility_disabled &&
                     migratetype < MIGRATE_PCPTYPES))
                migratetype = MIGRATE_UNMOVABLE;

#ifdef CONFIG_MEMORY_ISOLATION
        if (migratetype == MIGRATE_ISOLATE) {
                VM_WARN_ONCE(1,
                        "Use set_pageblock_isolate() for pageblock isolation");
                return;
        }
        VM_WARN_ONCE(get_pfnblock_bit(page, page_to_pfn(page),
                                      PB_migrate_isolate),
                     "Use clear_pageblock_isolate() to unisolate pageblock");
        /* MIGRATETYPE_AND_ISO_MASK clears PB_migrate_isolate if it is set */
#endif
        __set_pfnblock_flags_mask(page, page_to_pfn(page),
                                  (unsigned long)migratetype,
                                  MIGRATETYPE_AND_ISO_MASK);
}

void __meminit init_pageblock_migratetype(struct page *page,
                                          enum migratetype migratetype,
                                          bool isolate)
{
        unsigned long flags;

        if (unlikely(page_group_by_mobility_disabled &&
                     migratetype < MIGRATE_PCPTYPES))
                migratetype = MIGRATE_UNMOVABLE;

        flags = migratetype;

#ifdef CONFIG_MEMORY_ISOLATION
        if (migratetype == MIGRATE_ISOLATE) {
                VM_WARN_ONCE(
                        1,
                        "Set isolate=true to isolate pageblock with a migratetype");
                return;
        }
        if (isolate)
                flags |= BIT(PB_migrate_isolate);
#endif
        __set_pfnblock_flags_mask(page, page_to_pfn(page), flags,
                                  MIGRATETYPE_AND_ISO_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)
{

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        bool movable;
        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;

        if (migratetype != capc->cc->migratetype)
                trace_mm_page_alloc_extfrag(page, capc->cc->order, order,
                                            capc->cc->migratetype, migratetype);

        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)
{
        lockdep_assert_held(&zone->lock);

        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);
        else if (is_migrate_highatomic(migratetype))
                WRITE_ONCE(zone->nr_free_highatomic,
                           zone->nr_free_highatomic + 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];
        int nr_pages = 1 << order;

        VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype,
                     "page type is %d, passed migratetype is %d (nr=%d)\n",
                     get_pageblock_migratetype(page), migratetype, nr_pages);

        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++;

        if (order >= pageblock_order && !is_migrate_isolate(migratetype))
                __mod_zone_page_state(zone, NR_FREE_PAGES_BLOCKS, nr_pages);
}

/*
 * 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];
        int nr_pages = 1 << 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 %d, passed migratetype is %d (nr=%d)\n",
                     get_pageblock_migratetype(page), old_mt, nr_pages);

        list_move_tail(&page->buddy_list, &area->free_list[new_mt]);

        account_freepages(zone, -nr_pages, old_mt);
        account_freepages(zone, nr_pages, new_mt);

        if (order >= pageblock_order &&
            is_migrate_isolate(old_mt) != is_migrate_isolate(new_mt)) {
                if (!is_migrate_isolate(old_mt))
                        nr_pages = -nr_pages;
                __mod_zone_page_state(zone, NR_FREE_PAGES_BLOCKS, nr_pages);
        }
}

static inline void __del_page_from_free_list(struct page *page, struct zone *zone,
                                             unsigned int order, int migratetype)
{
        int nr_pages = 1 << order;

        VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype,
                     "page type is %d, passed migratetype is %d (nr=%d)\n",
                     get_pageblock_migratetype(page), migratetype, nr_pages);

        /* clear reported state and update reported page count */
        if (page_reported(page))
                __ClearPageReported(page);

        list_del(&page->buddy_list);
        __ClearPageBuddy(page);
        set_page_private(page, 0);
        zone->free_area[order].nr_free--;

        if (order >= pageblock_order && !is_migrate_isolate(migratetype))
                __mod_zone_page_state(zone, NR_FREE_PAGES_BLOCKS, -nr_pages);
}

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
                        page_pool_page_is_pp(page) |
                        (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
        if (unlikely(page_pool_page_is_pp(page)))
                bad_reason = "page_pool leak";
        return bad_reason;
}

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 */
        bad_page(page, page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
        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_large_mapcount(folio))) {
                        bad_page(page, "nonzero large_mapcount");
                        goto out;
                }
                if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT) &&
                    unlikely(atomic_read(&folio->_nr_pages_mapped))) {
                        bad_page(page, "nonzero nr_pages_mapped");
                        goto out;
                }
                if (IS_ENABLED(CONFIG_MM_ID)) {
                        if (unlikely(folio->_mm_id_mapcount[0] != -1)) {
                                bad_page(page, "nonzero mm mapcount 0");
                                goto out;
                        }
                        if (unlikely(folio->_mm_id_mapcount[1] != -1)) {
                                bad_page(page, "nonzero mm mapcount 1");
                                goto out;
                        }
                }
                if (IS_ENABLED(CONFIG_64BIT)) {
                        if (unlikely(atomic_read(&folio->_entire_mapcount) + 1)) {
                                bad_page(page, "nonzero entire_mapcount");
                                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;
                }
                if (!IS_ENABLED(CONFIG_64BIT)) {
                        if (unlikely(atomic_read(&folio->_entire_mapcount) + 1)) {
                                bad_page(page, "nonzero entire_mapcount");
                                goto out;
                        }
                        if (unlikely(atomic_read(&folio->_pincount))) {
                                bad_page(page, "nonzero pincount");
                                goto out;
                        }
                }
                break;
        case 3:
                /* the third tail page: hugetlb specifics overlap ->mappings */
                if (IS_ENABLED(CONFIG_HUGETLB_PAGE))
                        break;
                fallthrough;
        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();
}

#ifdef CONFIG_MEM_ALLOC_PROFILING

/* Should be called only if mem_alloc_profiling_enabled() */
void __clear_page_tag_ref(struct page *page)
{
        union pgtag_ref_handle handle;
        union codetag_ref ref;

        if (get_page_tag_ref(page, &ref, &handle)) {
                set_codetag_empty(&ref);
                update_page_tag_ref(handle, &ref);
                put_page_tag_ref(handle);
        }
}

/* Should be called only if mem_alloc_profiling_enabled() */
static noinline
void __pgalloc_tag_add(struct page *page, struct task_struct *task,
                       unsigned int nr)
{
        union pgtag_ref_handle handle;
        union codetag_ref ref;

        if (get_page_tag_ref(page, &ref, &handle)) {
                alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZE * nr);
                update_page_tag_ref(handle, &ref);
                put_page_tag_ref(handle);
        }
}

static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
                                   unsigned int nr)
{
        if (mem_alloc_profiling_enabled())
                __pgalloc_tag_add(page, task, nr);
}

/* Should be called only if mem_alloc_profiling_enabled() */
static noinline
void __pgalloc_tag_sub(struct page *page, unsigned int nr)
{
        union pgtag_ref_handle handle;
        union codetag_ref ref;

        if (get_page_tag_ref(page, &ref, &handle)) {
                alloc_tag_sub(&ref, PAGE_SIZE * nr);
                update_page_tag_ref(handle, &ref);
                put_page_tag_ref(handle);
        }
}

static inline void pgalloc_tag_sub(struct page *page, unsigned int nr)
{
        if (mem_alloc_profiling_enabled())
                __pgalloc_tag_sub(page, nr);
}

/* When tag is not NULL, assuming mem_alloc_profiling_enabled */
static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr)
{
        if (tag)
                this_cpu_sub(tag->counters->bytes, PAGE_SIZE * nr);
}

#else /* CONFIG_MEM_ALLOC_PROFILING */

static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
                                   unsigned int nr) {}
static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) {}
static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr) {}

#endif /* CONFIG_MEM_ALLOC_PROFILING */

__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);
        struct folio *folio = page_folio(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);

        /*
         * In rare cases, when truncation or holepunching raced with
         * munlock after VM_LOCKED was cleared, Mlocked may still be
         * found set here.  This does not indicate a problem, unless
         * "unevictable_pgs_cleared" appears worryingly large.
         */
        if (unlikely(folio_test_mlocked(folio))) {
                long nr_pages = folio_nr_pages(folio);

                __folio_clear_mlocked(folio);
                zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages);
                count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
        }

        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;
#ifdef NR_PAGES_IN_LARGE_FOLIO
                        folio->_nr_pages = 0;
#endif
                }
                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 (folio_test_anon(folio)) {
                mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
                folio->mapping = NULL;
        }
        if (unlikely(page_has_type(page)))
                /* Reset the page_type (which overlays _mapcount) */
                page->page_type = UINT_MAX;

        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);
}

/* 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, fpi_t fpi)
{
        unsigned long end = pfn + (1 << order);

        VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order));
        /* Caller removed page from freelist, buddy info cleared! */
        VM_WARN_ON_ONCE(PageBuddy(page));

        if (order > pageblock_order)
                order = pageblock_order;

        do {
                int mt = get_pfnblock_migratetype(page, pfn);

                __free_one_page(page, pfn, zone, order, mt, fpi);
                pfn += 1 << order;
                if (pfn == end)
                        break;
                page = pfn_to_page(pfn);
        } while (1);
}

static void add_page_to_zone_llist(struct zone *zone, struct page *page,
                                   unsigned int order)
{
        /* Remember the order */
        page->order = order;
        /* Add the page to the free list */
        llist_add(&page->pcp_llist, &zone->trylock_free_pages);
}

static void free_one_page(struct zone *zone, struct page *page,
                          unsigned long pfn, unsigned int order,
                          fpi_t fpi_flags)
{
        struct llist_head *llhead;
        unsigned long flags;

        if (unlikely(fpi_flags & FPI_TRYLOCK)) {
                if (!spin_trylock_irqsave(&zone->lock, flags)) {
                        add_page_to_zone_llist(zone, page, order);
                        return;
                }
        } else {
                spin_lock_irqsave(&zone->lock, flags);
        }

        /* The lock succeeded. Process deferred pages. */
        llhead = &zone->trylock_free_pages;
        if (unlikely(!llist_empty(llhead) && !(fpi_flags & FPI_TRYLOCK))) {
                struct llist_node *llnode;
                struct page *p, *tmp;

                llnode = llist_del_all(llhead);
                llist_for_each_entry_safe(p, tmp, llnode, pcp_llist) {
                        unsigned int p_order = p->order;

                        split_large_buddy(zone, p, page_to_pfn(p), p_order, fpi_flags);
                        __count_vm_events(PGFREE, 1 << p_order);
                }
        }
        split_large_buddy(zone, page, pfn, order, fpi_flags);
        spin_unlock_irqrestore(&zone->lock, flags);

        __count_vm_events(PGFREE, 1 << order);
}

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))
                free_one_page(zone, page, pfn, order, fpi_flags);
}

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);
                }

                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_memory(page_to_phys(page), PAGE_SIZE << 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 unsigned int expand(struct zone *zone, struct page *page, int low,
                                  int high, int migratetype)
{
        unsigned int size = 1 << high;
        unsigned int 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;
        }

        return nr_added;
}

static __always_inline void page_del_and_expand(struct zone *zone,
                                                struct page *page, int low,
                                                int high, int migratetype)
{
        int nr_pages = 1 << high;

        __del_page_from_free_list(page, zone, high, migratetype);
        nr_pages -= expand(zone, page, low, high, migratetype);
        account_freepages(zone, -nr_pages, migratetype);
}

static void check_new_page_bad(struct page *page)
{
        if (unlikely(PageHWPoison(page))) {
                /* 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);

        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;

                page_del_and_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

/*
 * Move all free pages of a block to new type's freelist. Caller needs to
 * change the block type.
 */
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;
        }

        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) || page_has_movable_ops(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;
        int res;

        if (!prep_move_freepages_block(zone, page, &start_pfn, NULL, NULL))
                return -1;

        res = __move_freepages_block(zone, start_pfn, old_mt, new_mt);
        set_pageblock_migratetype(pfn_to_page(start_pfn), new_mt);

        return res;

}

#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;
}

static inline void toggle_pageblock_isolate(struct page *page, bool isolate)
{
        if (isolate)
                set_pfnblock_bit(page, page_to_pfn(page), PB_migrate_isolate);
        else
                clear_pfnblock_bit(page, page_to_pfn(page), PB_migrate_isolate);
}

/**
 * __move_freepages_block_isolate - move free pages in block for page isolation
 * @zone: the zone
 * @page: the pageblock page
 * @isolate: to isolate the given pageblock or unisolate it
 *
 * 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.
 */
static bool __move_freepages_block_isolate(struct zone *zone,
                struct page *page, bool isolate)
{
        unsigned long start_pfn, pfn;
        int from_mt;
        int to_mt;

        if (isolate == get_pageblock_isolate(page)) {
                VM_WARN_ONCE(1, "%s a pageblock that is already in that state",
                             isolate ? "Isolate" : "Unisolate");
                return false;
        }

        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));
                toggle_pageblock_isolate(page, isolate);
                split_large_buddy(zone, buddy, pfn, order, FPI_NONE);
                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));
                toggle_pageblock_isolate(page, isolate);
                split_large_buddy(zone, page, pfn, order, FPI_NONE);
                return true;
        }
move:
        /* Use MIGRATETYPE_MASK to get non-isolate migratetype */
        if (isolate) {
                from_mt = __get_pfnblock_flags_mask(page, page_to_pfn(page),
                                                    MIGRATETYPE_MASK);
                to_mt = MIGRATE_ISOLATE;
        } else {
                from_mt = MIGRATE_ISOLATE;
                to_mt = __get_pfnblock_flags_mask(page, page_to_pfn(page),
                                                  MIGRATETYPE_MASK);
        }

        __move_freepages_block(zone, start_pfn, from_mt, to_mt);
        toggle_pageblock_isolate(pfn_to_page(start_pfn), isolate);

        return true;
}

bool pageblock_isolate_and_move_free_pages(struct zone *zone, struct page *page)
{
        return __move_freepages_block_isolate(zone, page, true);
}

bool pageblock_unisolate_and_move_free_pages(struct zone *zone, struct page *page)
{
        return __move_freepages_block_isolate(zone, page, false);
}

#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;
        }
}

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;
}

/*
 * When we are falling back to another migratetype during allocation, should we
 * try to claim an entire block to satisfy further allocations, instead of
 * polluting multiple pageblocks?
 */
static bool should_try_claim_block(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 claim the 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;

        /*
         * Above a certain threshold, always try to claim, as it's likely there
         * will be more free pages in the pageblock.
         */
        if (order >= pageblock_order / 2)
                return true;

        /*
         * Unmovable/reclaimable allocations would cause permanent
         * fragmentations if they fell back to allocating from a movable block
         * (polluting it), so we try to claim the whole block regardless of the
         * allocation size. Later movable allocations can always steal from this
         * block, which is less problematic.
         */
        if (start_mt == MIGRATE_RECLAIMABLE || start_mt == MIGRATE_UNMOVABLE)
                return true;

        if (page_group_by_mobility_disabled)
                return true;

        /*
         * Movable pages won't cause permanent fragmentation, so when you alloc
         * small pages, we just need to temporarily steal unmovable or
         * reclaimable pages that are closest to the request size. After a
         * while, memory compaction may occur to form large contiguous pages,
         * and the next movable allocation may not need to steal.
         */
        return false;
}

/*
 * Check whether there is a suitable fallback freepage with requested order.
 * If claimable is true, this function returns fallback_mt only if
 * we would do this whole-block claiming. 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 claimable)
{
        int i;

        if (claimable && !should_try_claim_block(order, migratetype))
                return -2;

        if (area->nr_free == 0)
                return -1;

        for (i = 0; i < MIGRATE_PCPTYPES - 1 ; i++) {
                int fallback_mt = fallbacks[migratetype][i];

                if (!free_area_empty(area, fallback_mt))
                        return fallback_mt;
        }

        return -1;
}

/*
 * This function implements actual block claiming 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.
 */
static struct page *
try_to_claim_block(struct zone *zone, struct page *page,
                   int current_order, int order, int start_type,
                   int block_type, unsigned int alloc_flags)
{
        int free_pages, movable_pages, alike_pages;
        unsigned long start_pfn;

        /* Take ownership for orders >= pageblock_order */
        if (current_order >= pageblock_order) {
                unsigned int nr_added;

                del_page_from_free_list(page, zone, current_order, block_type);
                change_pageblock_range(page, current_order, start_type);
                nr_added = expand(zone, page, order, current_order, start_type);
                account_freepages(zone, nr_added, 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);

        /* moving whole block can fail due to zone boundary conditions */
        if (!prep_move_freepages_block(zone, page, &start_pfn, &free_pages,
                                       &movable_pages))
                return NULL;

        /*
         * 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);
                set_pageblock_migratetype(pfn_to_page(start_pfn), start_type);
                return __rmqueue_smallest(zone, order, start_type);
        }

        return NULL;
}

/*
 * Try to allocate from some fallback migratetype by claiming the entire block,
 * i.e. converting it to the allocation's start migratetype.
 *
 * 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_claim(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;

        /*
         * 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, true);

                /* No block in that order */
                if (fallback_mt == -1)
                        continue;

                /* Advanced into orders too low to claim, abort */
                if (fallback_mt == -2)
                        break;

                page = get_page_from_free_area(area, fallback_mt);
                page = try_to_claim_block(zone, page, current_order, order,
                                          start_migratetype, fallback_mt,
                                          alloc_flags);
                if (page) {
                        trace_mm_page_alloc_extfrag(page, order, current_order,
                                                    start_migratetype, fallback_mt);
                        return page;
                }
        }

        return NULL;
}

/*
 * Try to steal a single page from some fallback migratetype. Leave the rest of
 * the block as its current migratetype, potentially causing fragmentation.
 */
static __always_inline struct page *
__rmqueue_steal(struct zone *zone, int order, int start_migratetype)
{
        struct free_area *area;
        int current_order;
        struct page *page;
        int fallback_mt;

        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);
                if (fallback_mt == -1)
                        continue;

                page = get_page_from_free_area(area, fallback_mt);
                page_del_and_expand(zone, page, order, current_order, fallback_mt);
                trace_mm_page_alloc_extfrag(page, order, current_order,
                                            start_migratetype, fallback_mt);
                return page;
        }

        return NULL;
}

enum rmqueue_mode {
        RMQUEUE_NORMAL,
        RMQUEUE_CMA,
        RMQUEUE_CLAIM,
        RMQUEUE_STEAL,
};

/*
 * 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, enum rmqueue_mode *mode)
{
        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;
                }
        }

        /*
         * First try the freelists of the requested migratetype, then try
         * fallbacks modes with increasing levels of fragmentation risk.
         *
         * The fallback logic is expensive and rmqueue_bulk() calls in
         * a loop with the zone->lock held, meaning the freelists are
         * not subject to any outside changes. Remember in *mode where
         * we found pay dirt, to save us the search on the next call.
         */
        switch (*mode) {
        case RMQUEUE_NORMAL:
                page = __rmqueue_smallest(zone, order, migratetype);
                if (page)
                        return page;
                fallthrough;
        case RMQUEUE_CMA:
                if (alloc_flags & ALLOC_CMA) {
                        page = __rmqueue_cma_fallback(zone, order);
                        if (page) {
                                *mode = RMQUEUE_CMA;
                                return page;
                        }
                }
                fallthrough;
        case RMQUEUE_CLAIM:
                page = __rmqueue_claim(zone, order, migratetype, alloc_flags);
                if (page) {
                        /* Replenished preferred freelist, back to normal mode. */
                        *mode = RMQUEUE_NORMAL;
                        return page;
                }
                fallthrough;
        case RMQUEUE_STEAL:
                if (!(alloc_flags & ALLOC_NOFRAGMENT)) {
                        page = __rmqueue_steal(zone, order, migratetype);
                        if (page) {
                                *mode = RMQUEUE_STEAL;
                                return page;
                        }
                }
        }
        return NULL;
}

/*
 * 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)
{
        enum rmqueue_mode rmqm = RMQUEUE_NORMAL;
        unsigned long flags;
        int i;

        if (unlikely(alloc_flags & ALLOC_TRYLOCK)) {
                if (!spin_trylock_irqsave(&zone->lock, flags))
                        return 0;
        } else {
                spin_lock_irqsave(&zone->lock, flags);
        }
        for (i = 0; i < count; ++i) {
                struct page *page = __rmqueue(zone, order, migratetype,
                                              alloc_flags, &rmqm);
                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_frozen_page_commit(struct zone *zone,
                struct per_cpu_pages *pcp, struct page *page, int migratetype,
                unsigned int order, fpi_t fpi_flags)
{
        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->high_min / 2) &&
                             (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
                             (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
                              pcp->count >= 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);

        if (unlikely(fpi_flags & FPI_TRYLOCK)) {
                /*
                 * Do not attempt to take a zone lock. Let pcp->count get
                 * over high mark temporarily.
                 */
                return;
        }
        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
 */
static void __free_frozen_pages(struct page *page, unsigned int order,
                                fpi_t fpi_flags)
{
        unsigned long __maybe_unused UP_flags;
        struct per_cpu_pages *pcp;
        struct zone *zone;
        unsigned long pfn = page_to_pfn(page);
        int migratetype;

        if (!pcp_allowed_order(order)) {
                __free_pages_ok(page, order, fpi_flags);
                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
         */
        zone = page_zone(page);
        migratetype = get_pfnblock_migratetype(page, pfn);
        if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
                if (unlikely(is_migrate_isolate(migratetype))) {
                        free_one_page(zone, page, pfn, order, fpi_flags);
                        return;
                }
                migratetype = MIGRATE_MOVABLE;
        }

        if (unlikely((fpi_flags & FPI_TRYLOCK) && IS_ENABLED(CONFIG_PREEMPT_RT)
                     && (in_nmi() || in_hardirq()))) {
                add_page_to_zone_llist(zone, page, order);
                return;
        }
        pcp_trylock_prepare(UP_flags);
        pcp = pcp_spin_trylock(zone->per_cpu_pageset);
        if (pcp) {
                free_frozen_page_commit(zone, pcp, page, migratetype, order, fpi_flags);
                pcp_spin_unlock(pcp);
        } else {
                free_one_page(zone, page, pfn, order, fpi_flags);
        }
        pcp_trylock_finish(UP_flags);
}

void free_frozen_pages(struct page *page, unsigned int order)
{
        __free_frozen_pages(page, order, FPI_NONE);
}

/*
 * 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);

                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_frozen_pages.
                         */
                        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_frozen_page_commit(zone, pcp, &folio->page, migratetype,
                                        order, FPI_NONE);
        }

        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_folio(page), order, 0);
        split_page_memcg(page, order);
}
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;
                if (unlikely(alloc_flags & ALLOC_TRYLOCK)) {
                        if (!spin_trylock_irqsave(&zone->lock, flags))
                                return NULL;
                } else {
                        spin_lock_irqsave(&zone->lock, flags);
                }
                if (alloc_flags & ALLOC_HIGHATOMIC)
                        page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
                if (!page) {
                        enum rmqueue_mode rmqm = RMQUEUE_NORMAL;

                        page = __rmqueue(zone, order, migratetype, alloc_flags, &rmqm);

                        /*
                         * If the allocation fails, allow OOM handling and
                         * order-0 (atomic) allocs 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|ALLOC_NON_BLOCK)))
                                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_migratetype().
 * 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;

        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;
}

/*
 * 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]);
                        unsigned long size;

                        page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
                        if (!page)
                                continue;

                        size = max(pageblock_nr_pages, 1UL << order);
                        /*
                         * 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.
                         */
                        if (WARN_ON_ONCE(size > zone->nr_reserved_highatomic))
                                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,
                                                           MIGRATE_HIGHATOMIC,
                                                           ac->migratetype);
                        else {
                                move_to_free_list(page, zone, order,
                                                  MIGRATE_HIGHATOMIC,
                                                  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;
}

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 free pages reserved for highatomic.
         */
        if (likely(!(alloc_flags & ALLOC_RESERVES)))
                unusable_free += READ_ONCE(z->nr_free_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;
}

#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);

        if (defrag_mode) {
                alloc_flags |= ALLOC_NOFRAGMENT;
                return alloc_flags;
        }

#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_current_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 && !defrag_mode && nr_online_nodes > 1 &&
                    zone != zonelist_zone(ac->preferred_zoneref)) {
                        int local_nid;

                        /*
                         * If moving to a remote node, retry but allow
                         * fragmenting fallbacks. Locality is more important
                         * than fragmentation avoidance.
                         */
                        local_nid = zonelist_node_idx(ac->preferred_zoneref);
                        if (zone_to_nid(zone) != local_nid) {
                                alloc_flags &= ~ALLOC_NOFRAGMENT;
                                goto retry;
                        }
                }

                cond_accept_memory(zone, order, alloc_flags);

                /*
                 * 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, alloc_flags))
                                goto try_this_zone;

                        /*
                         * 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;
                        }
                        /* 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(zonelist_zone(ac->preferred_zoneref), 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(zonelist_zone(ac->preferred_zoneref), 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, alloc_flags))
                                goto try_this_zone;

                        /* Try again if zone has deferred pages */
                        if (deferred_pages_enabled()) {
                                if (_deferred_grow_zone(zone, order))
                                        goto try_this_zone;
                        }
                }
        }

        /*
         * 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 && !defrag_mode) {
                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