tmpfs: make lseek(SEEK_DATA/SEK_HOLE) return ENXIO with a negative offset

[android-x86/kernel.git] / mm / page_alloc.c

/*
 *  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/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/jiffies.h>
#include <linux/bootmem.h>
#include <linux/memblock.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <linux/kasan.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/oom.h>
#include <linux/notifier.h>
#include <linux/topology.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/memory_hotplug.h>
#include <linux/nodemask.h>
#include <linux/vmalloc.h>
#include <linux/vmstat.h>
#include <linux/mempolicy.h>
#include <linux/memremap.h>
#include <linux/stop_machine.h>
#include <linux/sort.h>
#include <linux/pfn.h>
#include <linux/backing-dev.h>
#include <linux/fault-inject.h>
#include <linux/page-isolation.h>
#include <linux/page_ext.h>
#include <linux/debugobjects.h>
#include <linux/kmemleak.h>
#include <linux/compaction.h>
#include <trace/events/kmem.h>
#include <linux/prefetch.h>
#include <linux/mm_inline.h>
#include <linux/migrate.h>
#include <linux/page_ext.h>
#include <linux/hugetlb.h>
#include <linux/sched/rt.h>
#include <linux/page_owner.h>
#include <linux/kthread.h>
#include <linux/memcontrol.h>

#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
#include "internal.h"

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

#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
#endif

#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_);
int _node_numa_mem_[MAX_NUMNODES];
#endif

#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
#ifdef CONFIG_MOVABLE_NODE
        [N_MEMORY] = { { [0] = 1UL } },
#endif
        [N_CPU] = { { [0] = 1UL } },
#endif  /* NUMA */
};
EXPORT_SYMBOL(node_states);

/* Protect totalram_pages and zone->managed_pages */
static DEFINE_SPINLOCK(managed_page_count_lock);

unsigned long totalram_pages __read_mostly;
unsigned long totalreserve_pages __read_mostly;
unsigned long totalcma_pages __read_mostly;

int percpu_pagelist_fraction;
gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;

/*
 * A cached value of the page's pageblock's migratetype, used when the page is
 * put on a pcplist. Used to avoid the pageblock migratetype lookup when
 * freeing from pcplists in most cases, at the cost of possibly becoming stale.
 * Also the migratetype set in the page does not necessarily match the pcplist
 * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
 * other index - this ensures that it will be put on the correct CMA freelist.
 */
static inline int get_pcppage_migratetype(struct page *page)
{
        return page->index;
}

static inline void set_pcppage_migratetype(struct page *page, int migratetype)
{
        page->index = migratetype;
}

#ifdef CONFIG_PM_SLEEP
/*
 * The following functions are used by the suspend/hibernate code to temporarily
 * change gfp_allowed_mask in order to avoid using I/O during memory allocations
 * while devices are suspended.  To avoid races with the suspend/hibernate code,
 * they should always be called with pm_mutex held (gfp_allowed_mask also should
 * only be modified with pm_mutex held, unless the suspend/hibernate code is
 * guaranteed not to run in parallel with that modification).
 */

static gfp_t saved_gfp_mask;

void pm_restore_gfp_mask(void)
{
        WARN_ON(!mutex_is_locked(&pm_mutex));
        if (saved_gfp_mask) {
                gfp_allowed_mask = saved_gfp_mask;
                saved_gfp_mask = 0;
        }
}

void pm_restrict_gfp_mask(void)
{
        WARN_ON(!mutex_is_locked(&pm_mutex));
        WARN_ON(saved_gfp_mask);
        saved_gfp_mask = gfp_allowed_mask;
        gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
}

bool pm_suspended_storage(void)
{
        if ((gfp_allowed_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
                return false;
        return true;
}
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
unsigned int pageblock_order __read_mostly;
#endif

static void __free_pages_ok(struct page *page, unsigned int order);

/*
 * results with 256, 32 in the lowmem_reserve sysctl:
 *      1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
 *      1G machine -> (16M dma, 784M normal, 224M high)
 *      NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
 *      HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
 *      HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
 *
 * TBD: should special case ZONE_DMA32 machines here - in those we normally
 * don't need any ZONE_NORMAL reservation
 */
int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
#ifdef CONFIG_ZONE_DMA
         256,
#endif
#ifdef CONFIG_ZONE_DMA32
         256,
#endif
#ifdef CONFIG_HIGHMEM
         32,
#endif
         32,
};

EXPORT_SYMBOL(totalram_pages);

static char * const zone_names[MAX_NR_ZONES] = {
#ifdef CONFIG_ZONE_DMA
         "DMA",
#endif
#ifdef CONFIG_ZONE_DMA32
         "DMA32",
#endif
         "Normal",
#ifdef CONFIG_HIGHMEM
         "HighMem",
#endif
         "Movable",
#ifdef CONFIG_ZONE_DEVICE
         "Device",
#endif
};

char * const migratetype_names[MIGRATE_TYPES] = {
        "Unmovable",
        "Movable",
        "Reclaimable",
        "HighAtomic",
#ifdef CONFIG_CMA
        "CMA",
#endif
#ifdef CONFIG_MEMORY_ISOLATION
        "Isolate",
#endif
};

compound_page_dtor * const compound_page_dtors[] = {
        NULL,
        free_compound_page,
#ifdef CONFIG_HUGETLB_PAGE
        free_huge_page,
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        free_transhuge_page,
#endif
};

int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
int watermark_scale_factor = 10;

static unsigned long __meminitdata nr_kernel_pages;
static unsigned long __meminitdata nr_all_pages;
static unsigned long __meminitdata dma_reserve;

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
static unsigned long __meminitdata arch_zone_lowest_possible_pfn[MAX_NR_ZONES];
static unsigned long __meminitdata arch_zone_highest_possible_pfn[MAX_NR_ZONES];
static unsigned long __initdata required_kernelcore;
static unsigned long __initdata required_movablecore;
static unsigned long __meminitdata zone_movable_pfn[MAX_NUMNODES];
static bool mirrored_kernelcore;

/* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
int movable_zone;
EXPORT_SYMBOL(movable_zone);
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

#if MAX_NUMNODES > 1
int nr_node_ids __read_mostly = MAX_NUMNODES;
int nr_online_nodes __read_mostly = 1;
EXPORT_SYMBOL(nr_node_ids);
EXPORT_SYMBOL(nr_online_nodes);
#endif

int page_group_by_mobility_disabled __read_mostly;

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT

/*
 * Determine how many pages need to be initialized durig early boot
 * (non-deferred initialization).
 * The value of first_deferred_pfn will be set later, once non-deferred pages
 * are initialized, but for now set it ULONG_MAX.
 */
static inline void reset_deferred_meminit(pg_data_t *pgdat)
{
        phys_addr_t start_addr, end_addr;
        unsigned long max_pgcnt;
        unsigned long reserved;

        /*
         * Initialise at least 2G of a node but also take into account that
         * two large system hashes that can take up 1GB for 0.25TB/node.
         */
        max_pgcnt = max(2UL << (30 - PAGE_SHIFT),
                        (pgdat->node_spanned_pages >> 8));

        /*
         * Compensate the all the memblock reservations (e.g. crash kernel)
         * from the initial estimation to make sure we will initialize enough
         * memory to boot.
         */
        start_addr = PFN_PHYS(pgdat->node_start_pfn);
        end_addr = PFN_PHYS(pgdat->node_start_pfn + max_pgcnt);
        reserved = memblock_reserved_memory_within(start_addr, end_addr);
        max_pgcnt += PHYS_PFN(reserved);

        pgdat->static_init_pgcnt = min(max_pgcnt, pgdat->node_spanned_pages);
        pgdat->first_deferred_pfn = ULONG_MAX;
}

/* Returns true if the struct page for the pfn is uninitialised */
static inline bool __meminit early_page_uninitialised(unsigned long pfn)
{
        int nid = early_pfn_to_nid(pfn);

        if (node_online(nid) && pfn >= NODE_DATA(nid)->first_deferred_pfn)
                return true;

        return false;
}

/*
 * Returns false when the remaining initialisation should be deferred until
 * later in the boot cycle when it can be parallelised.
 */
static inline bool update_defer_init(pg_data_t *pgdat,
                                unsigned long pfn, unsigned long zone_end,
                                unsigned long *nr_initialised)
{
        /* Always populate low zones for address-contrained allocations */
        if (zone_end < pgdat_end_pfn(pgdat))
                return true;
        (*nr_initialised)++;
        if ((*nr_initialised > pgdat->static_init_pgcnt) &&
            (pfn & (PAGES_PER_SECTION - 1)) == 0) {
                pgdat->first_deferred_pfn = pfn;
                return false;
        }

        return true;
}
#else
static inline void reset_deferred_meminit(pg_data_t *pgdat)
{
}

static inline bool early_page_uninitialised(unsigned long pfn)
{
        return false;
}

static inline bool update_defer_init(pg_data_t *pgdat,
                                unsigned long pfn, unsigned long zone_end,
                                unsigned long *nr_initialised)
{
        return true;
}
#endif

/* Return a pointer to the bitmap storing bits affecting a block of pages */
static inline unsigned long *get_pageblock_bitmap(struct page *page,
                                                        unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
        return __pfn_to_section(pfn)->pageblock_flags;
#else
        return page_zone(page)->pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
}

static inline int pfn_to_bitidx(struct page *page, unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
        pfn &= (PAGES_PER_SECTION-1);
        return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
#else
        pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
        return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
#endif /* CONFIG_SPARSEMEM */
}

/**
 * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @pfn: The target page frame number
 * @end_bitidx: The last bit of interest to retrieve
 * @mask: mask of bits that the caller is interested in
 *
 * Return: pageblock_bits flags
 */
static __always_inline unsigned long __get_pfnblock_flags_mask(struct page *page,
                                        unsigned long pfn,
                                        unsigned long end_bitidx,
                                        unsigned long mask)
{
        unsigned long *bitmap;
        unsigned long bitidx, word_bitidx;
        unsigned long word;

        bitmap = get_pageblock_bitmap(page, pfn);
        bitidx = pfn_to_bitidx(page, pfn);
        word_bitidx = bitidx / BITS_PER_LONG;
        bitidx &= (BITS_PER_LONG-1);

        word = bitmap[word_bitidx];
        bitidx += end_bitidx;
        return (word >> (BITS_PER_LONG - bitidx - 1)) & mask;
}

unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn,
                                        unsigned long end_bitidx,
                                        unsigned long mask)
{
        return __get_pfnblock_flags_mask(page, pfn, end_bitidx, mask);
}

static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
{
        return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK);
}

/**
 * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @flags: The flags to set
 * @pfn: The target page frame number
 * @end_bitidx: The last bit of interest
 * @mask: mask of bits that the caller is interested in
 */
void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
                                        unsigned long pfn,
                                        unsigned long end_bitidx,
                                        unsigned long mask)
{
        unsigned long *bitmap;
        unsigned long bitidx, word_bitidx;
        unsigned long old_word, word;

        BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);

        bitmap = get_pageblock_bitmap(page, pfn);
        bitidx = pfn_to_bitidx(page, pfn);
        word_bitidx = bitidx / BITS_PER_LONG;
        bitidx &= (BITS_PER_LONG-1);

        VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);

        bitidx += end_bitidx;
        mask <<= (BITS_PER_LONG - bitidx - 1);
        flags <<= (BITS_PER_LONG - bitidx - 1);

        word = READ_ONCE(bitmap[word_bitidx]);
        for (;;) {
                old_word = cmpxchg(&bitmap[word_bitidx], word, (word & ~mask) | flags);
                if (word == old_word)
                        break;
                word = old_word;
        }
}

void set_pageblock_migratetype(struct page *page, int migratetype)
{
        if (unlikely(page_group_by_mobility_disabled &&
                     migratetype < MIGRATE_PCPTYPES))
                migratetype = MIGRATE_UNMOVABLE;

        set_pageblock_flags_group(page, (unsigned long)migratetype,
                                        PB_migrate, PB_migrate_end);
}

#ifdef CONFIG_DEBUG_VM
static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
{
        int ret = 0;
        unsigned seq;
        unsigned long pfn = page_to_pfn(page);
        unsigned long sp, start_pfn;

        do {
                seq = zone_span_seqbegin(zone);
                start_pfn = zone->zone_start_pfn;
                sp = zone->spanned_pages;
                if (!zone_spans_pfn(zone, pfn))
                        ret = 1;
        } while (zone_span_seqretry(zone, seq));

        if (ret)
                pr_err("page 0x%lx outside node %d zone %s [ 0x%lx - 0x%lx ]\n",
                        pfn, zone_to_nid(zone), zone->name,
                        start_pfn, start_pfn + sp);

        return ret;
}

static int page_is_consistent(struct zone *zone, struct page *page)
{
        if (!pfn_valid_within(page_to_pfn(page)))
                return 0;
        if (zone != page_zone(page))
                return 0;

        return 1;
}
/*
 * Temporary debugging check for pages not lying within a given zone.
 */
static int bad_range(struct zone *zone, struct page *page)
{
        if (page_outside_zone_boundaries(zone, page))
                return 1;
        if (!page_is_consistent(zone, page))
                return 1;

        return 0;
}
#else
static inline int bad_range(struct zone *zone, struct page *page)
{
        return 0;
}
#endif

static void bad_page(struct page *page, const char *reason,
                unsigned long bad_flags)
{
        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);
        bad_flags &= page->flags;
        if (bad_flags)
                pr_alert("bad because of flags: %#lx(%pGp)\n",
                                                bad_flags, &bad_flags);
        dump_page_owner(page);

        print_modules();
        dump_stack();
out:
        /* Leave bad fields for debug, except PageBuddy could make trouble */
        page_mapcount_reset(page); /* remove PageBuddy */
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}

/*
 * Higher-order pages are called "compound pages".  They are structured thusly:
 *
 * The first PAGE_SIZE page is called the "head page" and have PG_head set.
 *
 * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
 * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
 *
 * The first tail page's ->compound_dtor holds the offset in array of compound
 * page destructors. See compound_page_dtors.
 *
 * The first tail page's ->compound_order holds the order of allocation.
 * This usage means that zero-order pages may not be compound.
 */

void free_compound_page(struct page *page)
{
        __free_pages_ok(page, compound_order(page));
}

void prep_compound_page(struct page *page, unsigned int order)
{
        int i;
        int nr_pages = 1 << order;

        set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
        set_compound_order(page, order);
        __SetPageHead(page);
        for (i = 1; i < nr_pages; i++) {
                struct page *p = page + i;
                set_page_count(p, 0);
                p->mapping = TAIL_MAPPING;
                set_compound_head(p, page);
        }
        atomic_set(compound_mapcount_ptr(page), -1);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
unsigned int _debug_guardpage_minorder;
bool _debug_pagealloc_enabled __read_mostly
                        = IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
EXPORT_SYMBOL(_debug_pagealloc_enabled);
bool _debug_guardpage_enabled __read_mostly;

static int __init early_debug_pagealloc(char *buf)
{
        if (!buf)
                return -EINVAL;
        return kstrtobool(buf, &_debug_pagealloc_enabled);
}
early_param("debug_pagealloc", early_debug_pagealloc);

static bool need_debug_guardpage(void)
{
        /* If we don't use debug_pagealloc, we don't need guard page */
        if (!debug_pagealloc_enabled())
                return false;

        if (!debug_guardpage_minorder())
                return false;

        return true;
}

static void init_debug_guardpage(void)
{
        if (!debug_pagealloc_enabled())
                return;

        if (!debug_guardpage_minorder())
                return;

        _debug_guardpage_enabled = true;
}

struct page_ext_operations debug_guardpage_ops = {
        .need = need_debug_guardpage,
        .init = init_debug_guardpage,
};

static int __init debug_guardpage_minorder_setup(char *buf)
{
        unsigned long res;

        if (kstrtoul(buf, 10, &res) < 0 ||  res > MAX_ORDER / 2) {
                pr_err("Bad debug_guardpage_minorder value\n");
                return 0;
        }
        _debug_guardpage_minorder = res;
        pr_info("Setting debug_guardpage_minorder to %lu\n", res);
        return 0;
}
early_param("debug_guardpage_minorder", debug_guardpage_minorder_setup);

static inline bool set_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype)
{
        struct page_ext *page_ext;

        if (!debug_guardpage_enabled())
                return false;

        if (order >= debug_guardpage_minorder())
                return false;

        page_ext = lookup_page_ext(page);
        if (unlikely(!page_ext))
                return false;

        __set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);

        INIT_LIST_HEAD(&page->lru);
        set_page_private(page, order);
        /* Guard pages are not available for any usage */
        __mod_zone_freepage_state(zone, -(1 << order), migratetype);

        return true;
}

static inline void clear_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype)
{
        struct page_ext *page_ext;

        if (!debug_guardpage_enabled())
                return;

        page_ext = lookup_page_ext(page);
        if (unlikely(!page_ext))
                return;

        __clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);

        set_page_private(page, 0);
        if (!is_migrate_isolate(migratetype))
                __mod_zone_freepage_state(zone, (1 << order), migratetype);
}
#else
struct page_ext_operations debug_guardpage_ops;
static inline bool set_page_guard(struct zone *zone, struct page *page,
                        unsigned int order, int migratetype) { return false; }
static inline void clear_page_guard(struct zone *zone, struct page *page,
                                unsigned int order, int migratetype) {}
#endif

static inline void set_page_order(struct page *page, unsigned int order)
{
        set_page_private(page, order);
        __SetPageBuddy(page);
}

static inline void rmv_page_order(struct page *page)
{
        __ClearPageBuddy(page);
        set_page_private(page, 0);
}

/*
 * This function checks whether a page is free && is the buddy
 * we can do coalesce a page and its buddy if
 * (a) the buddy is not in a hole &&
 * (b) the buddy is in the buddy system &&
 * (c) a page and its buddy have the same order &&
 * (d) a page and its buddy are in the same zone.
 *
 * For recording whether a page is in the buddy system, we set ->_mapcount
 * PAGE_BUDDY_MAPCOUNT_VALUE.
 * Setting, clearing, and testing _mapcount PAGE_BUDDY_MAPCOUNT_VALUE is
 * serialized by zone->lock.
 *
 * For recording page's order, we use page_private(page).
 */
static inline int page_is_buddy(struct page *page, struct page *buddy,
                                                        unsigned int order)
{
        if (!pfn_valid_within(page_to_pfn(buddy)))
                return 0;

        if (page_is_guard(buddy) && page_order(buddy) == order) {
                if (page_zone_id(page) != page_zone_id(buddy))
                        return 0;

                VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);

                return 1;
        }

        if (PageBuddy(buddy) && page_order(buddy) == order) {
                /*
                 * zone check is done late to avoid uselessly
                 * calculating zone/node ids for pages that could
                 * never merge.
                 */
                if (page_zone_id(page) != page_zone_id(buddy))
                        return 0;

                VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);

                return 1;
        }
        return 0;
}

/*
 * 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 _mapcount
 * PAGE_BUDDY_MAPCOUNT_VALUE. 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)
{
        unsigned long page_idx;
        unsigned long combined_idx;
        unsigned long uninitialized_var(buddy_idx);
        struct page *buddy;
        unsigned int max_order;

        max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);

        VM_BUG_ON(!zone_is_initialized(zone));
        VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);

        VM_BUG_ON(migratetype == -1);
        if (likely(!is_migrate_isolate(migratetype)))
                __mod_zone_freepage_state(zone, 1 << order, migratetype);

        page_idx = pfn & ((1 << MAX_ORDER) - 1);

        VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page);
        VM_BUG_ON_PAGE(bad_range(zone, page), page);

continue_merging:
        while (order < max_order - 1) {
                buddy_idx = __find_buddy_index(page_idx, order);
                buddy = page + (buddy_idx - page_idx);
                if (!page_is_buddy(page, buddy, order))
                        goto done_merging;
                /*
                 * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
                 * merge with it and move up one order.
                 */
                if (page_is_guard(buddy)) {
                        clear_page_guard(zone, buddy, order, migratetype);
                } else {
                        list_del(&buddy->lru);
                        zone->free_area[order].nr_free--;
                        rmv_page_order(buddy);
                }
                combined_idx = buddy_idx & page_idx;
                page = page + (combined_idx - page_idx);
                page_idx = combined_idx;
                order++;
        }
        if (max_order < MAX_ORDER) {
                /* If we are here, it means order is >= pageblock_order.
                 * We want to prevent merge between freepages on isolate
                 * pageblock and normal pageblock. Without this, pageblock
                 * isolation could cause incorrect freepage or CMA accounting.
                 *
                 * We don't want to hit this code for the more frequent
                 * low-order merging.
                 */
                if (unlikely(has_isolate_pageblock(zone))) {
                        int buddy_mt;

                        buddy_idx = __find_buddy_index(page_idx, order);
                        buddy = page + (buddy_idx - page_idx);
                        buddy_mt = get_pageblock_migratetype(buddy);

                        if (migratetype != buddy_mt
                                        && (is_migrate_isolate(migratetype) ||
                                                is_migrate_isolate(buddy_mt)))
                                goto done_merging;
                }
                max_order++;
                goto continue_merging;
        }

done_merging:
        set_page_order(page, order);

        /*
         * If this is not the largest possible page, check if the buddy
         * of the next-highest order is free. If it is, it's possible
         * that pages are being freed that will coalesce soon. In case,
         * that is happening, add the free page to the tail of the list
         * so it's less likely to be used soon and more likely to be merged
         * as a higher order page
         */
        if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) {
                struct page *higher_page, *higher_buddy;
                combined_idx = buddy_idx & page_idx;
                higher_page = page + (combined_idx - page_idx);
                buddy_idx = __find_buddy_index(combined_idx, order + 1);
                higher_buddy = higher_page + (buddy_idx - combined_idx);
                if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
                        list_add_tail(&page->lru,
                                &zone->free_area[order].free_list[migratetype]);
                        goto out;
                }
        }

        list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
out:
        zone->free_area[order].nr_free++;
}

/*
 * 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
                        (unsigned long)page->mem_cgroup |
#endif
                        (page->flags & check_flags)))
                return false;

        return true;
}

static void free_pages_check_bad(struct page *page)
{
        const char *bad_reason;
        unsigned long bad_flags;

        bad_reason = NULL;
        bad_flags = 0;

        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 & PAGE_FLAGS_CHECK_AT_FREE)) {
                bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
                bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
        }
#ifdef CONFIG_MEMCG
        if (unlikely(page->mem_cgroup))
                bad_reason = "page still charged to cgroup";
#endif
        bad_page(page, bad_reason, bad_flags);
}

static inline int free_pages_check(struct page *page)
{
        if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
                return 0;

        /* Something has gone sideways, find it */
        free_pages_check_bad(page);
        return 1;
}

static int free_tail_pages_check(struct page *head_page, struct page *page)
{
        int ret = 1;

        /*
         * We rely page->lru.next never has bit 0 set, unless the page
         * is PageTail(). Let's make sure that's true even for poisoned ->lru.
         */
        BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);

        if (!IS_ENABLED(CONFIG_DEBUG_VM)) {
                ret = 0;
                goto out;
        }
        switch (page - head_page) {
        case 1:
                /* the first tail page: ->mapping is compound_mapcount() */
                if (unlikely(compound_mapcount(page))) {
                        bad_page(page, "nonzero compound_mapcount", 0);
                        goto out;
                }
                break;
        case 2:
                /*
                 * the second tail page: ->mapping is
                 * page_deferred_list().next -- ignore value.
                 */
                break;
        default:
                if (page->mapping != TAIL_MAPPING) {
                        bad_page(page, "corrupted mapping in tail page", 0);
                        goto out;
                }
                break;
        }
        if (unlikely(!PageTail(page))) {
                bad_page(page, "PageTail not set", 0);
                goto out;
        }
        if (unlikely(compound_head(page) != head_page)) {
                bad_page(page, "compound_head not consistent", 0);
                goto out;
        }
        ret = 0;
out:
        page->mapping = NULL;
        clear_compound_head(page);
        return ret;
}

static __always_inline bool free_pages_prepare(struct page *page,
                                        unsigned int order, bool check_free)
{
        int bad = 0;

        VM_BUG_ON_PAGE(PageTail(page), page);

        trace_mm_page_free(page, order);
        kmemcheck_free_shadow(page, order);

        /*
         * Check tail pages before head page information is cleared to
         * avoid checking PageCompound for order-0 pages.
         */
        if (unlikely(order)) {
                bool compound = PageCompound(page);
                int i;

                VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);

                if (compound)
                        ClearPageDoubleMap(page);
                for (i = 1; i < (1 << order); i++) {
                        if (compound)
                                bad += free_tail_pages_check(page, page + i);
                        if (unlikely(free_pages_check(page + i))) {
                                bad++;
                                continue;
                        }
                        (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
                }
        }
        if (PageMappingFlags(page))
                page->mapping = NULL;
        if (memcg_kmem_enabled() && PageKmemcg(page))
                memcg_kmem_uncharge(page, order);
        if (check_free)
                bad += free_pages_check(page);
        if (bad)
                return false;

        page_cpupid_reset_last(page);
        page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
        reset_page_owner(page, order);

        if (!PageHighMem(page)) {
                debug_check_no_locks_freed(page_address(page),
                                           PAGE_SIZE << order);
                debug_check_no_obj_freed(page_address(page),
                                           PAGE_SIZE << order);
        }
        arch_free_page(page, order);
        kernel_poison_pages(page, 1 << order, 0);
        kernel_map_pages(page, 1 << order, 0);
        kasan_free_pages(page, order);

        return true;
}

#ifdef CONFIG_DEBUG_VM
static inline bool free_pcp_prepare(struct page *page)
{
        return free_pages_prepare(page, 0, true);
}

static inline bool bulkfree_pcp_prepare(struct page *page)
{
        return false;
}
#else
static bool free_pcp_prepare(struct page *page)
{
        return free_pages_prepare(page, 0, false);
}

static bool bulkfree_pcp_prepare(struct page *page)
{
        return free_pages_check(page);
}
#endif /* CONFIG_DEBUG_VM */

/*
 * Frees a number of pages from the PCP lists
 * Assumes all pages on list are in same zone, and of same order.
 * count is the number of pages to free.
 *
 * If the zone was previously in an "all pages pinned" state then look to
 * see if this freeing clears that state.
 *
 * And clear the zone's pages_scanned counter, to hold off the "all pages are
 * pinned" detection logic.
 */
static void free_pcppages_bulk(struct zone *zone, int count,
                                        struct per_cpu_pages *pcp)
{
        int migratetype = 0;
        int batch_free = 0;
        unsigned long nr_scanned;
        bool isolated_pageblocks;

        spin_lock(&zone->lock);
        isolated_pageblocks = has_isolate_pageblock(zone);
        nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
        if (nr_scanned)
                __mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);

        while (count) {
                struct page *page;
                struct list_head *list;

                /*
                 * Remove pages from lists in a round-robin fashion. A
                 * batch_free count is maintained that is incremented when an
                 * empty list is encountered.  This is so more pages are freed
                 * off fuller lists instead of spinning excessively around empty
                 * lists
                 */
                do {
                        batch_free++;
                        if (++migratetype == MIGRATE_PCPTYPES)
                                migratetype = 0;
                        list = &pcp->lists[migratetype];
                } while (list_empty(list));

                /* This is the only non-empty list. Free them all. */
                if (batch_free == MIGRATE_PCPTYPES)
                        batch_free = count;

                do {
                        int mt; /* migratetype of the to-be-freed page */

                        page = list_last_entry(list, struct page, lru);
                        /* must delete as __free_one_page list manipulates */
                        list_del(&page->lru);

                        mt = get_pcppage_migratetype(page);
                        /* MIGRATE_ISOLATE page should not go to pcplists */
                        VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
                        /* Pageblock could have been isolated meanwhile */
                        if (unlikely(isolated_pageblocks))
                                mt = get_pageblock_migratetype(page);

                        if (bulkfree_pcp_prepare(page))
                                continue;

                        __free_one_page(page, page_to_pfn(page), zone, 0, mt);
                        trace_mm_page_pcpu_drain(page, 0, mt);
                } while (--count && --batch_free && !list_empty(list));
        }
        spin_unlock(&zone->lock);
}

static void free_one_page(struct zone *zone,
                                struct page *page, unsigned long pfn,
                                unsigned int order,
                                int migratetype)
{
        unsigned long nr_scanned;
        spin_lock(&zone->lock);
        nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
        if (nr_scanned)
                __mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);

        if (unlikely(has_isolate_pageblock(zone) ||
                is_migrate_isolate(migratetype))) {
                migratetype = get_pfnblock_migratetype(page, pfn);
        }
        __free_one_page(page, pfn, zone, order, migratetype);
        spin_unlock(&zone->lock);
}

static void __meminit __init_single_page(struct page *page, unsigned long pfn,
                                unsigned long zone, int nid)
{
        set_page_links(page, zone, nid, pfn);
        init_page_count(page);
        page_mapcount_reset(page);
        page_cpupid_reset_last(page);

        INIT_LIST_HEAD(&page->lru);
#ifdef WANT_PAGE_VIRTUAL
        /* The shift won't overflow because ZONE_NORMAL is below 4G. */
        if (!is_highmem_idx(zone))
                set_page_address(page, __va(pfn << PAGE_SHIFT));
#endif
}

static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
                                        int nid)
{
        return __init_single_page(pfn_to_page(pfn), pfn, zone, nid);
}

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static void init_reserved_page(unsigned long pfn)
{
        pg_data_t *pgdat;
        int nid, zid;

        if (!early_page_uninitialised(pfn))
                return;

        nid = early_pfn_to_nid(pfn);
        pgdat = NODE_DATA(nid);

        for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                struct zone *zone = &pgdat->node_zones[zid];

                if (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone))
                        break;
        }
        __init_single_pfn(pfn, zid, nid);
}
#else
static inline void init_reserved_page(unsigned long pfn)
{
}
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

/*
 * Initialised pages do not have PageReserved set. This function is
 * called for each range allocated by the bootmem allocator and
 * marks the pages PageReserved. The remaining valid pages are later
 * sent to the buddy page allocator.
 */
void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
{
        unsigned long start_pfn = PFN_DOWN(start);
        unsigned long end_pfn = PFN_UP(end);

        for (; start_pfn < end_pfn; start_pfn++) {
                if (pfn_valid(start_pfn)) {
                        struct page *page = pfn_to_page(start_pfn);

                        init_reserved_page(start_pfn);

                        /* Avoid false-positive PageTail() */
                        INIT_LIST_HEAD(&page->lru);

                        SetPageReserved(page);
                }
        }
}

static void __free_pages_ok(struct page *page, unsigned int order)
{
        unsigned long flags;
        int migratetype;
        unsigned long pfn = page_to_pfn(page);

        if (!free_pages_prepare(page, order, true))
                return;

        migratetype = get_pfnblock_migratetype(page, pfn);
        local_irq_save(flags);
        __count_vm_events(PGFREE, 1 << order);
        free_one_page(page_zone(page), page, pfn, order, migratetype);
        local_irq_restore(flags);
}

static void __init __free_pages_boot_core(struct page *page, unsigned int order)
{
        unsigned int nr_pages = 1 << order;
        struct page *p = page;
        unsigned int loop;

        prefetchw(p);
        for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
                prefetchw(p + 1);
                __ClearPageReserved(p);
                set_page_count(p, 0);
        }
        __ClearPageReserved(p);
        set_page_count(p, 0);

        page_zone(page)->managed_pages += nr_pages;
        set_page_refcounted(page);
        __free_pages(page, order);
}

#if defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) || \
        defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)

static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;

int __meminit early_pfn_to_nid(unsigned long pfn)
{
        static DEFINE_SPINLOCK(early_pfn_lock);
        int nid;

        spin_lock(&early_pfn_lock);
        nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache);
        if (nid < 0)
                nid = first_online_node;
        spin_unlock(&early_pfn_lock);

        return nid;
}
#endif

#ifdef CONFIG_NODES_SPAN_OTHER_NODES
static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
                                        struct mminit_pfnnid_cache *state)
{
        int nid;

        nid = __early_pfn_to_nid(pfn, state);
        if (nid >= 0 && nid != node)
                return false;
        return true;
}

/* Only safe to use early in boot when initialisation is single-threaded */
static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
{
        return meminit_pfn_in_nid(pfn, node, &early_pfnnid_cache);
}

#else

static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
{
        return true;
}
static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
                                        struct mminit_pfnnid_cache *state)
{
        return true;
}
#endif


void __init __free_pages_bootmem(struct page *page, unsigned long pfn,
                                                        unsigned int order)
{
        if (early_page_uninitialised(pfn))
                return;
        return __free_pages_boot_core(page, order);
}

/*
 * Check that the whole (or subset of) a pageblock given by the interval of
 * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
 * with the migration of free compaction scanner. The scanners then need to
 * use only pfn_valid_within() check for arches that allow holes within
 * pageblocks.
 *
 * Return struct page pointer of start_pfn, or NULL if checks were not passed.
 *
 * It's possible on some configurations to have a setup like node0 node1 node0
 * i.e. it's possible that all pages within a zones range of pages do not
 * belong to a single zone. We assume that a border between node0 and node1
 * can occur within a single pageblock, but not a node0 node1 node0
 * interleaving within a single pageblock. It is therefore sufficient to check
 * the first and last page of a pageblock and avoid checking each individual
 * page in a pageblock.
 */
struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
                                     unsigned long end_pfn, struct zone *zone)
{
        struct page *start_page;
        struct page *end_page;

        /* end_pfn is one past the range we are checking */
        end_pfn--;

        if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
                return NULL;

        start_page = pfn_to_page(start_pfn);

        if (page_zone(start_page) != zone)
                return NULL;

        end_page = pfn_to_page(end_pfn);

        /* This gives a shorter code than deriving page_zone(end_page) */
        if (page_zone_id(start_page) != page_zone_id(end_page))
                return NULL;

        return start_page;
}

void set_zone_contiguous(struct zone *zone)
{
        unsigned long block_start_pfn = zone->zone_start_pfn;
        unsigned long block_end_pfn;

        block_end_pfn = ALIGN(block_start_pfn + 1, pageblock_nr_pages);
        for (; block_start_pfn < zone_end_pfn(zone);
                        block_start_pfn = block_end_pfn,
                         block_end_pfn += pageblock_nr_pages) {

                block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));

                if (!__pageblock_pfn_to_page(block_start_pfn,
                                             block_end_pfn, zone))
                        return;
        }

        /* We confirm that there is no hole */
        zone->contiguous = true;
}

void clear_zone_contiguous(struct zone *zone)
{
        zone->contiguous = false;
}

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static void __init deferred_free_range(struct page *page,
                                        unsigned long pfn, int nr_pages)
{
        int i;

        if (!page)
                return;

        /* Free a large naturally-aligned chunk if possible */
        if (nr_pages == pageblock_nr_pages &&
            (pfn & (pageblock_nr_pages - 1)) == 0) {
                set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                __free_pages_boot_core(page, pageblock_order);
                return;
        }

        for (i = 0; i < nr_pages; i++, page++, pfn++) {
                if ((pfn & (pageblock_nr_pages - 1)) == 0)
                        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                __free_pages_boot_core(page, 0);
        }
}

/* Completion tracking for deferred_init_memmap() threads */
static atomic_t pgdat_init_n_undone __initdata;
static __initdata DECLARE_COMPLETION(pgdat_init_all_done_comp);

static inline void __init pgdat_init_report_one_done(void)
{
        if (atomic_dec_and_test(&pgdat_init_n_undone))
                complete(&pgdat_init_all_done_comp);
}

/* Initialise remaining memory on a node */
static int __init deferred_init_memmap(void *data)
{
        pg_data_t *pgdat = data;
        int nid = pgdat->node_id;
        struct mminit_pfnnid_cache nid_init_state = { };
        unsigned long start = jiffies;
        unsigned long nr_pages = 0;
        unsigned long walk_start, walk_end;
        int i, zid;
        struct zone *zone;
        unsigned long first_init_pfn = pgdat->first_deferred_pfn;
        const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);

        if (first_init_pfn == ULONG_MAX) {
                pgdat_init_report_one_done();
                return 0;
        }

        /* Bind memory initialisation thread to a local node if possible */
        if (!cpumask_empty(cpumask))
                set_cpus_allowed_ptr(current, cpumask);

        /* Sanity check boundaries */
        BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn);
        BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
        pgdat->first_deferred_pfn = ULONG_MAX;

        /* Only the highest zone is deferred so find it */
        for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                zone = pgdat->node_zones + zid;
                if (first_init_pfn < zone_end_pfn(zone))
                        break;
        }

        for_each_mem_pfn_range(i, nid, &walk_start, &walk_end, NULL) {
                unsigned long pfn, end_pfn;
                struct page *page = NULL;
                struct page *free_base_page = NULL;
                unsigned long free_base_pfn = 0;
                int nr_to_free = 0;

                end_pfn = min(walk_end, zone_end_pfn(zone));
                pfn = first_init_pfn;
                if (pfn < walk_start)
                        pfn = walk_start;
                if (pfn < zone->zone_start_pfn)
                        pfn = zone->zone_start_pfn;

                for (; pfn < end_pfn; pfn++) {
                        if (!pfn_valid_within(pfn))
                                goto free_range;

                        /*
                         * Ensure pfn_valid is checked every
                         * pageblock_nr_pages for memory holes
                         */
                        if ((pfn & (pageblock_nr_pages - 1)) == 0) {
                                if (!pfn_valid(pfn)) {
                                        page = NULL;
                                        goto free_range;
                                }
                        }

                        if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state)) {
                                page = NULL;
                                goto free_range;
                        }

                        /* Minimise pfn page lookups and scheduler checks */
                        if (page && (pfn & (pageblock_nr_pages - 1)) != 0) {
                                page++;
                        } else {
                                nr_pages += nr_to_free;
                                deferred_free_range(free_base_page,
                                                free_base_pfn, nr_to_free);
                                free_base_page = NULL;
                                free_base_pfn = nr_to_free = 0;

                                page = pfn_to_page(pfn);
                                cond_resched();
                        }

                        if (page->flags) {
                                VM_BUG_ON(page_zone(page) != zone);
                                goto free_range;
                        }

                        __init_single_page(page, pfn, zid, nid);
                        if (!free_base_page) {
                                free_base_page = page;
                                free_base_pfn = pfn;
                                nr_to_free = 0;
                        }
                        nr_to_free++;

                        /* Where possible, batch up pages for a single free */
                        continue;
free_range:
                        /* Free the current block of pages to allocator */
                        nr_pages += nr_to_free;
                        deferred_free_range(free_base_page, free_base_pfn,
                                                                nr_to_free);
                        free_base_page = NULL;
                        free_base_pfn = nr_to_free = 0;
                }
                /* Free the last block of pages to allocator */
                nr_pages += nr_to_free;
                deferred_free_range(free_base_page, free_base_pfn, nr_to_free);

                first_init_pfn = max(end_pfn, first_init_pfn);
        }

        /* Sanity check that the next zone really is unpopulated */
        WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));

        pr_info("node %d initialised, %lu pages in %ums\n", nid, nr_pages,
                                        jiffies_to_msecs(jiffies - start));

        pgdat_init_report_one_done();
        return 0;
}
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

void __init page_alloc_init_late(void)
{
        struct zone *zone;

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
        int nid;

        /* There will be num_node_state(N_MEMORY) threads */
        atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
        for_each_node_state(nid, N_MEMORY) {
                kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid);
        }

        /* Block until all are initialised */
        wait_for_completion(&pgdat_init_all_done_comp);

        /* Reinit limits that are based on free pages after the kernel is up */
        files_maxfiles_init();
#endif
#ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
        /* Discard memblock private memory */
        memblock_discard();
#endif

        for_each_populated_zone(zone)
                set_zone_contiguous(zone);
}

#ifdef CONFIG_CMA
/* Free whole pageblock and set its migration type to MIGRATE_CMA. */
void __init init_cma_reserved_pageblock(struct page *page)
{
        unsigned i = pageblock_nr_pages;
        struct page *p = page;

        do {
                __ClearPageReserved(p);
                set_page_count(p, 0);
        } while (++p, --i);

        set_pageblock_migratetype(page, MIGRATE_CMA);

        if (pageblock_order >= MAX_ORDER) {
                i = pageblock_nr_pages;
                p = page;
                do {
                        set_page_refcounted(p);
                        __free_pages(p, MAX_ORDER - 1);
                        p += MAX_ORDER_NR_PAGES;
                } while (i -= MAX_ORDER_NR_PAGES);
        } else {
                set_page_refcounted(page);
                __free_pages(page, pageblock_order);
        }

        adjust_managed_page_count(page, pageblock_nr_pages);
}
#endif

/*
 * The order of subdivision here is critical for the IO subsystem.
 * Please do not alter this order without good reasons and regression
 * testing. Specifically, as large blocks of memory are subdivided,
 * the order in which smaller blocks are delivered depends on the order
 * they're subdivided in this function. This is the primary factor
 * influencing the order in which pages are delivered to the IO
 * subsystem according to empirical testing, and this is also justified
 * by considering the behavior of a buddy system containing a single
 * large block of memory acted on by a series of small allocations.
 * This behavior is a critical factor in sglist merging's success.
 *
 * -- nyc
 */
static inline void expand(struct zone *zone, struct page *page,
        int low, int high, struct free_area *area,
        int migratetype)
{
        unsigned long size = 1 << high;

        while (high > low) {
                area--;
                high--;
                size >>= 1;
                VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);

                /*
                 * Mark as guard pages (or page), that will allow to
                 * merge back to allocator when buddy will be freed.
                 * Corresponding page table entries will not be touched,
                 * pages will stay not present in virtual address space
                 */
                if (set_page_guard(zone, &page[size], high, migratetype))
                        continue;

                list_add(&page[size].lru, &area->free_list[migratetype]);
                area->nr_free++;
                set_page_order(&page[size], high);
        }
}

static void check_new_page_bad(struct page *page)
{
        const char *bad_reason = NULL;
        unsigned long bad_flags = 0;

        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 _count";
        if (unlikely(page->flags & __PG_HWPOISON)) {
                bad_reason = "HWPoisoned (hardware-corrupted)";
                bad_flags = __PG_HWPOISON;
                /* Don't complain about hwpoisoned pages */
                page_mapcount_reset(page); /* remove PageBuddy */
                return;
        }
        if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
                bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
                bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
        }
#ifdef CONFIG_MEMCG
        if (unlikely(page->mem_cgroup))
                bad_reason = "page still charged to cgroup";
#endif
        bad_page(page, bad_reason, bad_flags);
}

/*
 * This page is about to be returned from the page allocator
 */
static inline int check_new_page(struct page *page)
{
        if (likely(page_expected_state(page,
                                PAGE_FLAGS_CHECK_AT_PREP|__PG_HWPOISON)))
                return 0;

        check_new_page_bad(page);
        return 1;
}

static inline bool free_pages_prezeroed(bool poisoned)
{
        return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
                page_poisoning_enabled() && poisoned;
}

#ifdef CONFIG_DEBUG_VM
static bool check_pcp_refill(struct page *page)
{
        return false;
}

static bool check_new_pcp(struct page *page)
{
        return check_new_page(page);
}
#else
static bool check_pcp_refill(struct page *page)
{
        return check_new_page(page);
}
static bool check_new_pcp(struct page *page)
{
        return false;
}
#endif /* CONFIG_DEBUG_VM */

static bool check_new_pages(struct page *page, unsigned int order)
{
        int i;
        for (i = 0; i < (1 << order); i++) {
                struct page *p = page + i;

                if (unlikely(check_new_page(p)))
                        return true;
        }

        return false;
}

inline void post_alloc_hook(struct page *page, unsigned int order,
                                gfp_t gfp_flags)
{
        set_page_private(page, 0);
        set_page_refcounted(page);

        arch_alloc_page(page, order);
        kernel_map_pages(page, 1 << order, 1);
        kernel_poison_pages(page, 1 << order, 1);
        kasan_alloc_pages(page, order);
        set_page_owner(page, order, gfp_flags);
}

static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
                                                        unsigned int alloc_flags)
{
        int i;
        bool poisoned = true;

        for (i = 0; i < (1 << order); i++) {
                struct page *p = page + i;
                if (poisoned)
                        poisoned &= page_is_poisoned(p);
        }

        post_alloc_hook(page, order, gfp_flags);

        if (!free_pages_prezeroed(poisoned) && (gfp_flags & __GFP_ZERO))
                for (i = 0; i < (1 << order); i++)
                        clear_highpage(page + i);

        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 inline
struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
                                                int migratetype)
{
        unsigned int current_order;
        struct free_area *area;
        struct page *page;

        /* Find a page of the appropriate size in the preferred list */
        for (current_order = order; current_order < MAX_ORDER; ++current_order) {
                area = &(zone->free_area[current_order]);
                page = list_first_entry_or_null(&area->free_list[migratetype],
                                                        struct page, lru);
                if (!page)
                        continue;
                list_del(&page->lru);
                rmv_page_order(page);
                area->nr_free--;
                expand(zone, page, order, current_order, area, migratetype);
                set_pcppage_migratetype(page, migratetype);
                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
 */
static int fallbacks[MIGRATE_TYPES][4] = {
        [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
        [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
        [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
#ifdef CONFIG_CMA
        [MIGRATE_CMA]         = { MIGRATE_TYPES }, /* Never used */
#endif
#ifdef CONFIG_MEMORY_ISOLATION
        [MIGRATE_ISOLATE]     = { MIGRATE_TYPES }, /* Never used */
#endif
};

#ifdef CONFIG_CMA
static struct page *__rmqueue_cma_fallback(struct zone *zone,
                                        unsigned int order)
{
        return __rmqueue_smallest(zone, order, MIGRATE_CMA);
}
#else
static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
                                        unsigned int order) { return NULL; }
#endif

/*
 * Move the free pages in a range to the free lists of the requested type.
 * Note that start_page and end_pages are not aligned on a pageblock
 * boundary. If alignment is required, use move_freepages_block()
 */
int move_freepages(struct zone *zone,
                          struct page *start_page, struct page *end_page,
                          int migratetype)
{
        struct page *page;
        unsigned int order;
        int pages_moved = 0;

#ifndef CONFIG_HOLES_IN_ZONE
        /*
         * page_zone is not safe to call in this context when
         * CONFIG_HOLES_IN_ZONE is set. This bug check is probably redundant
         * anyway as we check zone boundaries in move_freepages_block().
         * Remove at a later date when no bug reports exist related to
         * grouping pages by mobility
         */
        VM_BUG_ON(page_zone(start_page) != page_zone(end_page));
#endif

        for (page = start_page; page <= end_page;) {
                if (!pfn_valid_within(page_to_pfn(page))) {
                        page++;
                        continue;
                }

                /* Make sure we are not inadvertently changing nodes */
                VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);

                if (!PageBuddy(page)) {
                        page++;
                        continue;
                }

                order = page_order(page);
                list_move(&page->lru,
                          &zone->free_area[order].free_list[migratetype]);
                page += 1 << order;
                pages_moved += 1 << order;
        }

        return pages_moved;
}

int move_freepages_block(struct zone *zone, struct page *page,
                                int migratetype)
{
        unsigned long start_pfn, end_pfn;
        struct page *start_page, *end_page;

        start_pfn = page_to_pfn(page);
        start_pfn = start_pfn & ~(pageblock_nr_pages-1);
        start_page = pfn_to_page(start_pfn);
        end_page = start_page + pageblock_nr_pages - 1;
        end_pfn = start_pfn + pageblock_nr_pages - 1;

        /* Do not cross zone boundaries */
        if (!zone_spans_pfn(zone, start_pfn))
                start_page = page;
        if (!zone_spans_pfn(zone, end_pfn))
                return 0;

        return move_freepages(zone, start_page, end_page, migratetype);
}

static void change_pageblock_range(struct page *pageblock_page,
                                        int start_order, int migratetype)
{
        int nr_pageblocks = 1 << (start_order - pageblock_order);

        while (nr_pageblocks--) {
                set_pageblock_migratetype(pageblock_page, migratetype);
                pageblock_page += pageblock_nr_pages;
        }
}

/*
 * When we are falling back to another migratetype during allocation, try to
 * steal extra free pages from the same pageblocks to satisfy further
 * allocations, instead of polluting multiple pageblocks.
 *
 * If we are stealing a relatively large buddy page, it is likely there will
 * be more free pages in the pageblock, so try to steal them all. For
 * reclaimable and unmovable allocations, we steal regardless of page size,
 * as fragmentation caused by those allocations polluting movable pageblocks
 * is worse than movable allocations stealing from unmovable and reclaimable
 * pageblocks.
 */
static bool can_steal_fallback(unsigned int order, int start_mt)
{
        /*
         * Leaving this order check is intended, although there is
         * relaxed order check in next check. The reason is that
         * we can actually steal whole pageblock if this condition met,
         * but, below check doesn't guarantee it and that is just heuristic
         * so could be changed anytime.
         */
        if (order >= pageblock_order)
                return true;

        if (order >= pageblock_order / 2 ||
                start_mt == MIGRATE_RECLAIMABLE ||
                start_mt == MIGRATE_UNMOVABLE ||
                page_group_by_mobility_disabled)
                return true;

        return false;
}

/*
 * This function implements actual steal behaviour. If order is large enough,
 * we can steal whole pageblock. If not, we first move freepages in this
 * pageblock and check whether half of pages are moved or not. If half of
 * pages are moved, we can change migratetype of pageblock and permanently
 * use it's pages as requested migratetype in the future.
 */
static void steal_suitable_fallback(struct zone *zone, struct page *page,
                                                          int start_type)
{
        unsigned int current_order = page_order(page);
        int pages;

        /* Take ownership for orders >= pageblock_order */
        if (current_order >= pageblock_order) {
                change_pageblock_range(page, current_order, start_type);
                return;
        }

        pages = move_freepages_block(zone, page, start_type);

        /* Claim the whole block if over half of it is free */
        if (pages >= (1 << (pageblock_order-1)) ||
                        page_group_by_mobility_disabled)
                set_pageblock_migratetype(page, start_type);
}

/*
 * Check whether there is a suitable fallback freepage with requested order.
 * If only_stealable is true, this function returns fallback_mt only if
 * we can steal other freepages all together. This would help to reduce
 * fragmentation due to mixed migratetype pages in one pageblock.
 */
int find_suitable_fallback(struct free_area *area, unsigned int order,
                        int migratetype, bool only_stealable, bool *can_steal)
{
        int i;
        int fallback_mt;

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

        *can_steal = false;
        for (i = 0;; i++) {
                fallback_mt = fallbacks[migratetype][i];
                if (fallback_mt == MIGRATE_TYPES)
                        break;

                if (list_empty(&area->free_list[fallback_mt]))
                        continue;

                if (can_steal_fallback(order, migratetype))
                        *can_steal = true;

                if (!only_stealable)
                        return fallback_mt;

                if (*can_steal)
                        return fallback_mt;
        }

        return -1;
}

/*
 * Reserve a pageblock for exclusive use of high-order atomic allocations if
 * there are no empty page blocks that contain a page with a suitable order
 */
static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
                                unsigned int alloc_order)
{
        int mt;
        unsigned long max_managed, flags;

        /*
         * Limit the number reserved to 1 pageblock or roughly 1% of a zone.
         * Check is race-prone but harmless.
         */
        max_managed = (zone->managed_pages / 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);
        if (mt != MIGRATE_HIGHATOMIC &&
                        !is_migrate_isolate(mt) && !is_migrate_cma(mt)) {
                zone->nr_reserved_highatomic += pageblock_nr_pages;
                set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
                move_freepages_block(zone, page, MIGRATE_HIGHATOMIC);
        }

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.
 */
static void unreserve_highatomic_pageblock(const struct alloc_context *ac)
{
        struct zonelist *zonelist = ac->zonelist;
        unsigned long flags;
        struct zoneref *z;
        struct zone *zone;
        struct page *page;
        int order;

        for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->high_zoneidx,
                                                                ac->nodemask) {
                /* Preserve at least one pageblock */
                if (zone->nr_reserved_highatomic <= pageblock_nr_pages)
                        continue;

                spin_lock_irqsave(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        struct free_area *area = &(zone->free_area[order]);

                        page = list_first_entry_or_null(
                                        &area->free_list[MIGRATE_HIGHATOMIC],
                                        struct page, lru);
                        if (!page)
                                continue;

                        /*
                         * In page freeing path, migratetype change is racy so
                         * we can counter several free pages in a pageblock
                         * in this loop althoug we changed the pageblock type
                         * from highatomic to ac->migratetype. So we should
                         * adjust the count once.
                         */
                        if (get_pageblock_migratetype(page) ==
                                                        MIGRATE_HIGHATOMIC) {
                                /*
                                 * It should never happen but changes to
                                 * locking could inadvertently allow a per-cpu
                                 * drain to add pages to MIGRATE_HIGHATOMIC
                                 * while unreserving so be safe and watch for
                                 * underflows.
                                 */
                                zone->nr_reserved_highatomic -= min(
                                                pageblock_nr_pages,
                                                zone->nr_reserved_highatomic);
                        }

                        /*
                         * Convert to ac->migratetype and avoid the normal
                         * pageblock stealing heuristics. Minimally, the caller
                         * is doing the work and needs the pages. More
                         * importantly, if the block was always converted to
                         * MIGRATE_UNMOVABLE or another type then the number
                         * of pageblocks that cannot be completely freed
                         * may increase.
                         */
                        set_pageblock_migratetype(page, ac->migratetype);
                        move_freepages_block(zone, page, ac->migratetype);
                        spin_unlock_irqrestore(&zone->lock, flags);
                        return;
                }
                spin_unlock_irqrestore(&zone->lock, flags);
        }
}

/* Remove an element from the buddy allocator from the fallback list */
static inline struct page *
__rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
{
        struct free_area *area;
        unsigned int current_order;
        struct page *page;
        int fallback_mt;
        bool can_steal;

        /* Find the largest possible block of pages in the other list */
        for (current_order = MAX_ORDER-1;
                                current_order >= order && current_order <= MAX_ORDER-1;
                                --current_order) {
                area = &(zone->free_area[current_order]);
                fallback_mt = find_suitable_fallback(area, current_order,
                                start_migratetype, false, &can_steal);
                if (fallback_mt == -1)
                        continue;

                page = list_first_entry(&area->free_list[fallback_mt],
                                                struct page, lru);
                if (can_steal)
                        steal_suitable_fallback(zone, page, start_migratetype);

                /* Remove the page from the freelists */
                area->nr_free--;
                list_del(&page->lru);
                rmv_page_order(page);

                expand(zone, page, order, current_order, area,
                                        start_migratetype);
                /*
                 * The pcppage_migratetype may differ from pageblock's
                 * migratetype depending on the decisions in
                 * find_suitable_fallback(). This is OK as long as it does not
                 * differ for MIGRATE_CMA pageblocks. Those can be used as
                 * fallback only via special __rmqueue_cma_fallback() function
                 */
                set_pcppage_migratetype(page, start_migratetype);

                trace_mm_page_alloc_extfrag(page, order, current_order,
                        start_migratetype, fallback_mt);

                return page;
        }

        return NULL;
}

/*
 * Do the hard work of removing an element from the buddy allocator.
 * Call me with the zone->lock already held.
 */
static struct page *__rmqueue(struct zone *zone, unsigned int order,
                                int migratetype)
{
        struct page *page;

        page = __rmqueue_smallest(zone, order, migratetype);
        if (unlikely(!page)) {
                if (migratetype == MIGRATE_MOVABLE)
                        page = __rmqueue_cma_fallback(zone, order);

                if (!page)
                        page = __rmqueue_fallback(zone, order, migratetype);
        }

        trace_mm_page_alloc_zone_locked(page, order, migratetype);
        return page;
}

/*
 * Obtain a specified number of elements from the buddy allocator, all under
 * a single hold of the lock, for efficiency.  Add them to the supplied list.
 * Returns the number of new pages which were placed at *list.
 */
static int rmqueue_bulk(struct zone *zone, unsigned int order,
                        unsigned long count, struct list_head *list,
                        int migratetype, bool cold)
{
        int i, alloced = 0;

        spin_lock(&zone->lock);
        for (i = 0; i < count; ++i) {
                struct page *page = __rmqueue(zone, order, migratetype);
                if (unlikely(page == NULL))
                        break;

                if (unlikely(check_pcp_refill(page)))
                        continue;

                /*
                 * Split buddy pages returned by expand() are received here
                 * in physical page order. The page is added to the callers and
                 * list and the list head then moves forward. From the callers
                 * perspective, the linked list is ordered by page number in
                 * some conditions. This is useful for IO devices that can
                 * merge IO requests if the physical pages are ordered
                 * properly.
                 */
                if (likely(!cold))
                        list_add(&page->lru, list);
                else
                        list_add_tail(&page->lru, list);
                list = &page->lru;
                alloced++;
                if (is_migrate_cma(get_pcppage_migratetype(page)))
                        __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
                                              -(1 << order));
        }

        /*
         * i pages were removed from the buddy list even if some leak due
         * to check_pcp_refill failing so adjust NR_FREE_PAGES based
         * on i. Do not confuse with 'alloced' which is the number of
         * pages added to the pcp list.
         */
        __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
        spin_unlock(&zone->lock);
        return alloced;
}

#ifdef CONFIG_NUMA
/*
 * Called from the vmstat counter updater to drain pagesets of this
 * currently executing processor on remote nodes after they have
 * expired.
 *
 * Note that this function must be called with the thread pinned to
 * a single processor.
 */
void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
{
        unsigned long flags;
        int to_drain, batch;

        local_irq_save(flags);
        batch = READ_ONCE(pcp->batch);
        to_drain = min(pcp->count, batch);
        if (to_drain > 0) {
                free_pcppages_bulk(zone, to_drain, pcp);
                pcp->count -= to_drain;
        }
        local_irq_restore(flags);
}
#endif

/*
 * Drain pcplists of the indicated processor and zone.
 *
 * The processor must either be the current processor and the
 * thread pinned to the current processor or a processor that
 * is not online.
 */
static void drain_pages_zone(unsigned int cpu, struct zone *zone)
{
        unsigned long flags;
        struct per_cpu_pageset *pset;
        struct per_cpu_pages *pcp;

        local_irq_save(flags);
        pset = per_cpu_ptr(zone->pageset, cpu);

        pcp = &pset->pcp;
        if (pcp->count) {
                free_pcppages_bulk(zone, pcp->count, pcp);
                pcp->count = 0;
        }
        local_irq_restore(flags);
}

/*
 * Drain pcplists of all zones on the indicated processor.
 *
 * The processor must either be the current processor and the
 * thread pinned to the current processor or a processor that
 * is not online.
 */
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.
 *
 * The CPU has to be pinned. When zone parameter is non-NULL, spill just
 * the single zone's pages.
 */
void drain_local_pages(struct zone *zone)
{
        int cpu = smp_processor_id();

        if (zone)
                drain_pages_zone(cpu, zone);
        else
                drain_pages(cpu);
}

/*
 * 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.
 *
 * Note that this code is protected against sending an IPI to an offline
 * CPU but does not guarantee sending an IPI to newly hotplugged CPUs:
 * on_each_cpu_mask() blocks hotplug and won't talk to offlined CPUs but
 * nothing keeps CPUs from showing up after we populated the cpumask and
 * before the call to on_each_cpu_mask().
 */
void drain_all_pages(struct zone *zone)
{
        int cpu;

        /*
         * Allocate in the BSS so we wont require allocation in
         * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
         */
        static cpumask_t cpus_with_pcps;

        /*
         * 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_pageset *pcp;
                struct zone *z;
                bool has_pcps = false;

                if (zone) {
                        pcp = per_cpu_ptr(zone->pageset, cpu);
                        if (pcp->pcp.count)
                                has_pcps = true;
                } else {
                        for_each_populated_zone(z) {
                                pcp = per_cpu_ptr(z->pageset, cpu);
                                if (pcp->pcp.count) {
                                        has_pcps = true;
                                        break;
                                }
                        }
                }

                if (has_pcps)
                        cpumask_set_cpu(cpu, &cpus_with_pcps);
                else
                        cpumask_clear_cpu(cpu, &cpus_with_pcps);
        }
        on_each_cpu_mask(&cpus_with_pcps, (smp_call_func_t) drain_local_pages,
                                                                zone, 1);
}

#ifdef CONFIG_HIBERNATION

void mark_free_pages(struct zone *zone)
{
        unsigned long pfn, max_zone_pfn;
        unsigned long flags;
        unsigned int order, t;
        struct page *page;

        if (zone_is_empty(zone))
                return;

        spin_lock_irqsave(&zone->lock, flags);

        max_zone_pfn = zone_end_pfn(zone);
        for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                if (pfn_valid(pfn)) {
                        page = pfn_to_page(pfn);

                        if (page_zone(page) != zone)
                                continue;

                        if (!swsusp_page_is_forbidden(page))
                                swsusp_unset_page_free(page);
                }

        for_each_migratetype_order(order, t) {
                list_for_each_entry(page,
                                &zone->free_area[order].free_list[t], lru) {
                        unsigned long i;

                        pfn = page_to_pfn(page);
                        for (i = 0; i < (1UL << order); i++)
                                swsusp_set_page_free(pfn_to_page(pfn + i));
                }
        }
        spin_unlock_irqrestore(&zone->lock, flags);
}
#endif /* CONFIG_PM */

/*
 * Free a 0-order page
 * cold == true ? free a cold page : free a hot page
 */
void free_hot_cold_page(struct page *page, bool cold)
{
        struct zone *zone = page_zone(page);
        struct per_cpu_pages *pcp;
        unsigned long flags;
        unsigned long pfn = page_to_pfn(page);
        int migratetype;

        if (!free_pcp_prepare(page))
                return;

        migratetype = get_pfnblock_migratetype(page, pfn);
        set_pcppage_migratetype(page, migratetype);
        local_irq_save(flags);
        __count_vm_event(PGFREE);

        /*
         * We only track unmovable, reclaimable and movable on pcp lists.
         * Free ISOLATE pages back to the allocator because they are being
         * offlined but treat RESERVE as movable pages so we can get those
         * areas back if necessary. Otherwise, we may have to free
         * excessively into the page allocator
         */
        if (migratetype >= MIGRATE_PCPTYPES) {
                if (unlikely(is_migrate_isolate(migratetype))) {
                        free_one_page(zone, page, pfn, 0, migratetype);
                        goto out;
                }
                migratetype = MIGRATE_MOVABLE;
        }

        pcp = &this_cpu_ptr(zone->pageset)->pcp;
        if (!cold)
                list_add(&page->lru, &pcp->lists[migratetype]);
        else
                list_add_tail(&page->lru, &pcp->lists[migratetype]);
        pcp->count++;
        if (pcp->count >= pcp->high) {
                unsigned long batch = READ_ONCE(pcp->batch);
                free_pcppages_bulk(zone, batch, pcp);
                pcp->count -= batch;
        }

out:
        local_irq_restore(flags);
}

/*
 * Free a list of 0-order pages
 */
void free_hot_cold_page_list(struct list_head *list, bool cold)
{
        struct page *page, *next;

        list_for_each_entry_safe(page, next, list, lru) {
                trace_mm_page_free_batched(page, cold);
                free_hot_cold_page(page, cold);
        }
}

/*
 * 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);

#ifdef CONFIG_KMEMCHECK
        /*
         * Split shadow pages too, because free(page[0]) would
         * otherwise free the whole shadow.
         */
        if (kmemcheck_page_is_tracked(page))
                split_page(virt_to_page(page[0].shadow), order);
#endif

        for (i = 1; i < (1 << order); i++)
                set_page_refcounted(page + i);
        split_page_owner(page, order);
}
EXPORT_SYMBOL_GPL(split_page);

int __isolate_free_page(struct page *page, unsigned int order)
{
        unsigned long watermark;
        struct zone *zone;
        int mt;

        BUG_ON(!PageBuddy(page));

        zone = page_zone(page);
        mt = get_pageblock_migratetype(page);

        if (!is_migrate_isolate(mt)) {
                /*
                 * Obey watermarks as if the page was being allocated. We can
                 * emulate a high-order watermark check with a raised order-0
                 * watermark, because we already know our high-order page
                 * exists.
                 */
                watermark = min_wmark_pages(zone) + (1UL << order);
                if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
                        return 0;

                __mod_zone_freepage_state(zone, -(1UL << order), mt);
        }

        /* Remove page from free list */
        list_del(&page->lru);
        zone->free_area[order].nr_free--;
        rmv_page_order(page);

        /*
         * 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);
                        if (!is_migrate_isolate(mt) && !is_migrate_cma(mt))
                                set_pageblock_migratetype(page,
                                                          MIGRATE_MOVABLE);
                }
        }


        return 1UL << order;
}

/*
 * Update NUMA hit/miss statistics
 *
 * Must be called with interrupts disabled.
 */
static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
                                                                gfp_t flags)
{
#ifdef CONFIG_NUMA
        enum zone_stat_item local_stat = NUMA_LOCAL;

        if (z->node != numa_node_id())
                local_stat = NUMA_OTHER;

        if (z->node == preferred_zone->node)
                __inc_zone_state(z, NUMA_HIT);
        else {
                __inc_zone_state(z, NUMA_MISS);
                __inc_zone_state(preferred_zone, NUMA_FOREIGN);
        }
        __inc_zone_state(z, local_stat);
#endif
}

/*
 * Allocate a page from the given zone. Use pcplists for order-0 allocations.
 */
static inline
struct page *buffered_rmqueue(struct zone *preferred_zone,
                        struct zone *zone, unsigned int order,
                        gfp_t gfp_flags, unsigned int alloc_flags,
                        int migratetype)
{
        unsigned long flags;
        struct page *page;
        bool cold = ((gfp_flags & __GFP_COLD) != 0);

        if (likely(order == 0)) {
                struct per_cpu_pages *pcp;
                struct list_head *list;

                local_irq_save(flags);
                do {
                        pcp = &this_cpu_ptr(zone->pageset)->pcp;
                        list = &pcp->lists[migratetype];
                        if (list_empty(list)) {
                                pcp->count += rmqueue_bulk(zone, 0,
                                                pcp->batch, list,
                                                migratetype, cold);
                                if (unlikely(list_empty(list)))
                                        goto failed;
                        }

                        if (cold)
                                page = list_last_entry(list, struct page, lru);
                        else
                                page = list_first_entry(list, struct page, lru);

                        list_del(&page->lru);
                        pcp->count--;

                } while (check_new_pcp(page));
        } else {
                /*
                 * We most definitely don't want callers attempting to
                 * allocate greater than order-1 page units with __GFP_NOFAIL.
                 */
                WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
                spin_lock_irqsave(&zone->lock, flags);

                do {
                        page = NULL;
                        if (alloc_flags & ALLOC_HARDER) {
                                page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
                                if (page)
                                        trace_mm_page_alloc_zone_locked(page, order, migratetype);
                        }
                        if (!page)
                                page = __rmqueue(zone, order, migratetype);
                } while (page && check_new_pages(page, order));
                spin_unlock(&zone->lock);
                if (!page)
                        goto failed;
                __mod_zone_freepage_state(zone, -(1 << order),
                                          get_pcppage_migratetype(page));
        }

        __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
        zone_statistics(preferred_zone, zone, gfp_flags);
        local_irq_restore(flags);

        VM_BUG_ON_PAGE(bad_range(zone, page), page);
        return page;

failed:
        local_irq_restore(flags);
        return NULL;
}

#ifdef CONFIG_FAIL_PAGE_ALLOC

static struct {
        struct fault_attr attr;

        bool ignore_gfp_highmem;
        bool ignore_gfp_reclaim;
        u32 min_order;
} fail_page_alloc = {
        .attr = FAULT_ATTR_INITIALIZER,
        .ignore_gfp_reclaim = true,
        .ignore_gfp_highmem = true,
        .min_order = 1,
};

static int __init setup_fail_page_alloc(char *str)
{
        return setup_fault_attr(&fail_page_alloc.attr, str);
}
__setup("fail_page_alloc=", setup_fail_page_alloc);

static bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        if (order < fail_page_alloc.min_order)
                return false;
        if (gfp_mask & __GFP_NOFAIL)
                return false;
        if (fail_page_alloc.ignore_gfp_highmem && (gfp_mask & __GFP_HIGHMEM))
                return false;
        if (fail_page_alloc.ignore_gfp_reclaim &&
                        (gfp_mask & __GFP_DIRECT_RECLAIM))
                return false;

        return should_fail(&fail_page_alloc.attr, 1 << order);
}

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

static int __init fail_page_alloc_debugfs(void)
{
        umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
        struct dentry *dir;

        dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
                                        &fail_page_alloc.attr);
        if (IS_ERR(dir))
                return PTR_ERR(dir);

        if (!debugfs_create_bool("ignore-gfp-wait", mode, dir,
                                &fail_page_alloc.ignore_gfp_reclaim))
                goto fail;
        if (!debugfs_create_bool("ignore-gfp-highmem", mode, dir,
                                &fail_page_alloc.ignore_gfp_highmem))
                goto fail;
        if (!debugfs_create_u32("min-order", mode, dir,
                                &fail_page_alloc.min_order))
                goto fail;

        return 0;
fail:
        debugfs_remove_recursive(dir);

        return -ENOMEM;
}

late_initcall(fail_page_alloc_debugfs);

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */

#else /* CONFIG_FAIL_PAGE_ALLOC */

static inline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        return false;
}

#endif /* CONFIG_FAIL_PAGE_ALLOC */

/*
 * 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 classzone_idx, unsigned int alloc_flags,
                         long free_pages)
{
        long min = mark;
        int o;
        const bool alloc_harder = (alloc_flags & ALLOC_HARDER);

        /* free_pages may go negative - that's OK */
        free_pages -= (1 << order) - 1;

        if (alloc_flags & ALLOC_HIGH)
                min -= min / 2;

        /*
         * If the caller does not have rights to ALLOC_HARDER then subtract
         * the high-atomic reserves. This will over-estimate the size of the
         * atomic reserve but it avoids a search.
         */
        if (likely(!alloc_harder))
                free_pages -= z->nr_reserved_highatomic;
        else
                min -= min / 4;

#ifdef CONFIG_CMA
        /* If allocation can't use CMA areas don't use free CMA pages */
        if (!(alloc_flags & ALLOC_CMA))
                free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
#endif

        /*
         * 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[classzone_idx])
                return false;

        /* If this is an order-0 request then the watermark is fine */
        if (!order)
                return true;

        /* For a high-order request, check at least one suitable page is free */
        for (o = order; o < MAX_ORDER; o++) {
                struct free_area *area = &z->free_area[o];
                int mt;

                if (!area->nr_free)
                        continue;

                for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
                        if (!list_empty(&area->free_list[mt]))
                                return true;
                }

#ifdef CONFIG_CMA
                if ((alloc_flags & ALLOC_CMA) &&
                    !list_empty(&area->free_list[MIGRATE_CMA])) {
                        return true;
                }
#endif
                if (alloc_harder &&
                        !list_empty(&area->free_list[MIGRATE_HIGHATOMIC]))
                        return true;
        }
        return false;
}

bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
                      int classzone_idx, unsigned int alloc_flags)
{
        return __zone_watermark_ok(z, order, mark, classzone_idx, 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 classzone_idx, unsigned int alloc_flags)
{
        long free_pages = zone_page_state(z, NR_FREE_PAGES);
        long cma_pages = 0;

#ifdef CONFIG_CMA
        /* If allocation can't use CMA areas don't use free CMA pages */
        if (!(alloc_flags & ALLOC_CMA))
                cma_pages = zone_page_state(z, NR_FREE_CMA_PAGES);
#endif

        /*
         * Fast check for order-0 only. If this fails then the reserves
         * need to be calculated. There is a corner case where the check
         * passes but only the high-order atomic reserve are free. If
         * the caller is !atomic then it'll uselessly search the free
         * list. That corner case is then slower but it is harmless.
         */
        if (!order && (free_pages - cma_pages) > mark + z->lowmem_reserve[classzone_idx])
                return true;

        return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags,
                                        free_pages);
}

bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
                        unsigned long mark, int classzone_idx)
{
        long free_pages = zone_page_state(z, NR_FREE_PAGES);

        if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
                free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);

        return __zone_watermark_ok(z, order, mark, classzone_idx, 0,
                                                                free_pages);
}

#ifdef CONFIG_NUMA
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
        return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
                                RECLAIM_DISTANCE;
}
#else   /* CONFIG_NUMA */
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
        return true;
}
#endif  /* CONFIG_NUMA */

/*
 * 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 = ac->preferred_zoneref;
        struct zone *zone;
        struct pglist_data *last_pgdat_dirty_limit = NULL;

        /*
         * Scan zonelist, looking for a zone with enough free.
         * See also __cpuset_node_allowed() comment in kernel/cpuset.c.
         */
        for_next_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_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_dirty_limit == zone->zone_pgdat)
                                continue;

                        if (!node_dirty_ok(zone->zone_pgdat)) {
                                last_pgdat_dirty_limit = zone->zone_pgdat;
                                continue;
                        }
                }

                mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
                if (!zone_watermark_fast(zone, order, mark,
                                       ac_classzone_idx(ac), alloc_flags)) {
                        int ret;

                        /* 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_mode == 0 ||
                            !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
                                continue;

                        ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
                        switch (ret) {
                        case NODE_RECLAIM_NOSCAN:
                                /* did not scan */
                                continue;
                        case NODE_RECLAIM_FULL:
                                /* scanned but unreclaimable */
                                continue;
                        default:
                                /* did we reclaim enough */
                                if (zone_watermark_ok(zone, order, mark,
                                                ac_classzone_idx(ac), alloc_flags))
                                        goto try_this_zone;

                                continue;
                        }
                }

try_this_zone:
                page = buffered_rmqueue(ac->preferred_zoneref->zone, zone, order,
                                gfp_mask, alloc_flags, ac->migratetype);
                if (page) {
                        prep_new_page(page, order, gfp_mask, alloc_flags);

                        /*
                         * If this is a high-order atomic allocation then check
                         * if the pageblock should be reserved for the future
                         */
                        if (unlikely(order && (alloc_flags & ALLOC_HARDER)))
                                reserve_highatomic_pageblock(page, zone, order);

                        return page;
                }
        }

        return NULL;
}

/*
 * Large machines with many possible nodes should not always dump per-node
 * meminfo in irq context.
 */
static inline bool should_suppress_show_mem(void)
{
        bool ret = false;

#if NODES_SHIFT > 8
        ret = in_interrupt();
#endif
        return ret;
}

static DEFINE_RATELIMIT_STATE(nopage_rs,
                DEFAULT_RATELIMIT_INTERVAL,
                DEFAULT_RATELIMIT_BURST);

void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
{
        unsigned int filter = SHOW_MEM_FILTER_NODES;
        struct va_format vaf;
        va_list args;

        if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
            debug_guardpage_minorder() > 0)
                return;

        /*
         * 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 (test_thread_flag(TIF_MEMDIE) ||
                    (current->flags & (PF_MEMALLOC | PF_EXITING)))
                        filter &= ~SHOW_MEM_FILTER_NODES;
        if (in_interrupt() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
                filter &= ~SHOW_MEM_FILTER_NODES;

        pr_warn("%s: ", current->comm);

        va_start(args, fmt);
        vaf.fmt = fmt;
        vaf.va = &args;
        pr_cont("%pV", &vaf);
        va_end(args);

        pr_cont(", mode:%#x(%pGg)\n", gfp_mask, &gfp_mask);

        dump_stack();
        if (!should_suppress_show_mem())
                show_mem(filter);
}

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.
         */
        page = get_page_from_freelist(gfp_mask | __GFP_HARDWALL, order,
                                        ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
        if (page)
                goto out;

        if (!(gfp_mask & __GFP_NOFAIL)) {
                /* 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;
                /* The OOM killer does not needlessly kill tasks for lowmem */
                if (ac->high_zoneidx < ZONE_NORMAL)
                        goto out;
                if (pm_suspended_storage())
                        goto out;
                /*
                 * XXX: GFP_NOFS allocations should rather fail than rely on
                 * other request to make a forward progress.
                 * We are in an unfortunate situation where out_of_memory cannot
                 * do much for this context but let's try it to at least get
                 * access to memory reserved if the current task is killed (see
                 * out_of_memory). Once filesystems are ready to handle allocation
                 * failures more gracefully we should just bail out here.
                 */

                /* The OOM killer may not free memory on a specific node */
                if (gfp_mask & __GFP_THISNODE)
                        goto out;
        }
        /* Exhausted what can be done so it's blamo time */
        if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
                *did_some_progress = 1;

                if (gfp_mask & __GFP_NOFAIL) {
                        page = get_page_from_freelist(gfp_mask, order,
                                        ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac);
                        /*
                         * fallback to ignore cpuset restriction if our nodes
                         * are depleted
                         */
                        if (!page)
                                page = get_page_from_freelist(gfp_mask, order,
                                        ALLOC_NO_WATERMARKS, ac);
                }
        }
out:
        mutex_unlock(&oom_lock);
        return page;
}

/*
 * Maximum number of compaction retries wit a progress before OOM
 * killer is consider as the only way to move forward.
 */
#define MAX_COMPACT_RETRIES 16

#ifdef CONFIG_COMPACTION
/* Try memory compaction for high-order allocations before reclaim */
static struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                enum compact_priority prio, enum compact_result *compact_result)
{
        struct page *page;
        unsigned int noreclaim_flag = current->flags & PF_MEMALLOC;

        if (!order)
                return NULL;

        current->flags |= PF_MEMALLOC;
        *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
                                                                        prio);
        current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag;

        if (*compact_result <= COMPACT_INACTIVE)
                return NULL;

        /*
         * At least in one zone compaction wasn't deferred or skipped, so let's
         * count a compaction stall
         */
        count_vm_event(COMPACTSTALL);

        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);

        if (page) {
                struct zone *zone = page_zone(page);

                zone->compact_blockskip_flush = false;
                compaction_defer_reset(zone, order, true);
                count_vm_event(COMPACTSUCCESS);
                return page;
        }

        /*
         * It's bad if compaction run occurs and fails. The most likely reason
         * is that pages exist, but not enough to satisfy watermarks.
         */
        count_vm_event(COMPACTFAIL);

        cond_resched();

        return NULL;
}

static inline bool
should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
                     int *compaction_retries)
{
        int max_retries = MAX_COMPACT_RETRIES;
        int min_priority;

        if (!order)
                return false;

        if (compaction_made_progress(compact_result))
                (*compaction_retries)++;

        /*
         * compaction considers all the zone as desperately out of memory
         * so it doesn't really make much sense to retry except when the
         * failure could be caused by insufficient priority
         */
        if (compaction_failed(compact_result))
                goto check_priority;

        /*
         * make sure the compaction wasn't deferred or didn't bail out early
         * due to locks contention before we declare that we should give up.
         * But do not retry if the given zonelist is not suitable for
         * compaction.
         */
        if (compaction_withdrawn(compact_result))
                return compaction_zonelist_suitable(ac, order, alloc_flags);

        /*
         * !costly requests are much more important than __GFP_REPEAT
         * costly ones because they are de facto nofail and invoke OOM
         * killer to move on while costly can fail and users are ready
         * to cope with that. 1/4 retries is rather arbitrary but we
         * would need much more detailed feedback from compaction to
         * make a better decision.
         */
        if (order > PAGE_ALLOC_COSTLY_ORDER)
                max_retries /= 4;
        if (*compaction_retries <= max_retries)
                return true;

        /*
         * Make sure there are attempts at the highest priority if we exhausted
         * all retries or failed at the lower priorities.
         */
check_priority:
        min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
                        MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
        if (*compact_priority > min_priority) {
                (*compact_priority)--;
                *compaction_retries = 0;
                return true;
        }
        return false;
}
#else
static inline struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                enum compact_priority prio, enum compact_result *compact_result)
{
        *compact_result = COMPACT_SKIPPED;
        return NULL;
}

static inline bool
should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
                     int *compaction_retries)
{
        struct zone *zone;
        struct zoneref *z;

        if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
                return false;

        /*
         * There are setups with compaction disabled which would prefer to loop
         * inside the allocator rather than hit the oom killer prematurely.
         * Let's give them a good hope and keep retrying while the order-0
         * watermarks are OK.
         */
        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
                                        ac->nodemask) {
                if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
                                        ac_classzone_idx(ac), alloc_flags))
                        return true;
        }
        return false;
}
#endif /* CONFIG_COMPACTION */

/* Perform direct synchronous page reclaim */
static int
__perform_reclaim(gfp_t gfp_mask, unsigned int order,
                                        const struct alloc_context *ac)
{
        struct reclaim_state reclaim_state;
        int progress;

        cond_resched();

        /* We now go into synchronous reclaim */
        cpuset_memory_pressure_bump();
        current->flags |= PF_MEMALLOC;
        lockdep_set_current_reclaim_state(gfp_mask);
        reclaim_state.reclaimed_slab = 0;
        current->reclaim_state = &reclaim_state;

        progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
                                                                ac->nodemask);

        current->reclaim_state = NULL;
        lockdep_clear_current_reclaim_state();
        current->flags &= ~PF_MEMALLOC;

        cond_resched();

        return progress;
}

/* The really slow allocator path where we enter direct reclaim */
static inline struct page *
__alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
                unsigned int alloc_flags, const struct alloc_context *ac,
                unsigned long *did_some_progress)
{
        struct page *page = NULL;
        bool drained = false;

        *did_some_progress = __perform_reclaim(gfp_mask, order, ac);
        if (unlikely(!(*did_some_progress)))
                return NULL;

retry:
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);

        /*
         * If an allocation failed after direct reclaim, it could be because
         * pages are pinned on the per-cpu lists or in high alloc reserves.
         * Shrink them them and try again
         */
        if (!page && !drained) {
                unreserve_highatomic_pageblock(ac);
                drain_all_pages(NULL);
                drained = true;
                goto retry;
        }

        return page;
}

static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac)
{
        struct zoneref *z;
        struct zone *zone;
        pg_data_t *last_pgdat = NULL;

        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                        ac->high_zoneidx, ac->nodemask) {
                if (last_pgdat != zone->zone_pgdat)
                        wakeup_kswapd(zone, order, ac->high_zoneidx);
                last_pgdat = zone->zone_pgdat;
        }
}

static inline unsigned int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
        unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;

        /* __GFP_HIGH is assumed to be the same as ALLOC_HIGH to save a branch. */
        BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);

        /*
         * The caller may dip into page reserves a bit more if the caller
         * cannot run direct reclaim, or if the caller has realtime scheduling
         * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
         * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
         */
        alloc_flags |= (__force int) (gfp_mask & __GFP_HIGH);

        if (gfp_mask & __GFP_ATOMIC) {
                /*
                 * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
                 * if it can't schedule.
                 */
                if (!(gfp_mask & __GFP_NOMEMALLOC))
                        alloc_flags |= ALLOC_HARDER;
                /*
                 * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
                 * comment for __cpuset_node_allowed().
                 */
                alloc_flags &= ~ALLOC_CPUSET;
        } else if (unlikely(rt_task(current)) && !in_interrupt())
                alloc_flags |= ALLOC_HARDER;

#ifdef CONFIG_CMA
        if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
                alloc_flags |= ALLOC_CMA;
#endif
        return alloc_flags;
}

bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
{
        if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
                return false;

        if (gfp_mask & __GFP_MEMALLOC)
                return true;
        if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
                return true;
        if (!in_interrupt() &&
                        ((current->flags & PF_MEMALLOC) ||
                         unlikely(test_thread_flag(TIF_MEMDIE))))
                return true;

        return false;
}

/*
 * Checks whether it makes sense to retry the reclaim to make a forward progress
 * for the given allocation request.
 * The reclaim feedback represented by did_some_progress (any progress during
 * the last reclaim round) and no_progress_loops (number of reclaim rounds without
 * any progress in a row) is considered as well as the reclaimable pages on the
 * applicable zone list (with a backoff mechanism which is a function of
 * no_progress_loops).
 *
 * Returns true if a retry is viable or false to enter the oom path.
 */
static inline bool
should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                     struct alloc_context *ac, int alloc_flags,
                     bool did_some_progress, int *no_progress_loops)
{
        struct zone *zone;
        struct zoneref *z;

        /*
         * Costly allocations might have made a progress but this doesn't mean
         * their order will become available due to high fragmentation so
         * always increment the no progress counter for them
         */
        if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
                *no_progress_loops = 0;
        else
                (*no_progress_loops)++;

        /*
         * Make sure we converge to OOM if we cannot make any progress
         * several times in the row.
         */
        if (*no_progress_loops > MAX_RECLAIM_RETRIES)
                return false;

        /*
         * Keep reclaiming pages while there is a chance this will lead
         * somewhere.  If none of the target zones can satisfy our allocation
         * request even if all reclaimable pages are considered then we are
         * screwed and have to go OOM.
         */
        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
                                        ac->nodemask) {
                unsigned long available;
                unsigned long reclaimable;

                available = reclaimable = zone_reclaimable_pages(zone);
                available -= DIV_ROUND_UP((*no_progress_loops) * available,
                                          MAX_RECLAIM_RETRIES);
                available += zone_page_state_snapshot(zone, NR_FREE_PAGES);

                /*
                 * Would the allocation succeed if we reclaimed the whole
                 * available?
                 */
                if (__zone_watermark_ok(zone, order, min_wmark_pages(zone),
                                ac_classzone_idx(ac), alloc_flags, available)) {
                        /*
                         * If we didn't make any progress and have a lot of
                         * dirty + writeback pages then we should wait for
                         * an IO to complete to slow down the reclaim and
                         * prevent from pre mature OOM
                         */
                        if (!did_some_progress) {
                                unsigned long write_pending;

                                write_pending = zone_page_state_snapshot(zone,
                                                        NR_ZONE_WRITE_PENDING);

                                if (2 * write_pending > reclaimable) {
                                        congestion_wait(BLK_RW_ASYNC, HZ/10);
                                        return true;
                                }
                        }

                        /*
                         * Memory allocation/reclaim might be called from a WQ
                         * context and the current implementation of the WQ
                         * concurrency control doesn't recognize that
                         * a particular WQ is congested if the worker thread is
                         * looping without ever sleeping. Therefore we have to
                         * do a short sleep here rather than calling
                         * cond_resched().
                         */
                        if (current->flags & PF_WQ_WORKER)
                                schedule_timeout_uninterruptible(1);
                        else
                                cond_resched();

                        return true;
                }
        }

        return false;
}

static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                                                struct alloc_context *ac)
{
        bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
        struct page *page = NULL;
        unsigned int alloc_flags;
        unsigned long did_some_progress;
        enum compact_priority compact_priority;
        enum compact_result compact_result;
        int compaction_retries;
        int no_progress_loops;
        unsigned long alloc_start = jiffies;
        unsigned int stall_timeout = 10 * HZ;
        unsigned int cpuset_mems_cookie;

        /*
         * In the slowpath, we sanity check order to avoid ever trying to
         * reclaim >= MAX_ORDER areas which will never succeed. Callers may
         * be using allocators in order of preference for an area that is
         * too large.
         */
        if (order >= MAX_ORDER) {
                WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
                return NULL;
        }

        /*
         * We also sanity check to catch abuse of atomic reserves being used by
         * callers that are not in atomic context.
         */
        if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
                                (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
                gfp_mask &= ~__GFP_ATOMIC;

retry_cpuset:
        compaction_retries = 0;
        no_progress_loops = 0;
        compact_priority = DEF_COMPACT_PRIORITY;
        cpuset_mems_cookie = read_mems_allowed_begin();
        /*
         * We need to recalculate the starting point for the zonelist iterator
         * because we might have used different nodemask in the fast path, or
         * there was a cpuset modification and we are retrying - otherwise we
         * could end up iterating over non-eligible zones endlessly.
         */
        ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                        ac->high_zoneidx, ac->nodemask);
        if (!ac->preferred_zoneref->zone)
                goto nopage;


        /*
         * The fast path uses conservative alloc_flags to succeed only until
         * kswapd needs to be woken up, and to avoid the cost of setting up
         * alloc_flags precisely. So we do that now.
         */
        alloc_flags = gfp_to_alloc_flags(gfp_mask);

        if (gfp_mask & __GFP_KSWAPD_RECLAIM)
                wake_all_kswapds(order, ac);

        /*
         * The adjusted alloc_flags might result in immediate success, so try
         * that first
         */
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
        if (page)
                goto got_pg;

        /*
         * For costly allocations, try direct compaction first, as it's likely
         * that we have enough base pages and don't need to reclaim. Don't try
         * that for allocations that are allowed to ignore watermarks, as the
         * ALLOC_NO_WATERMARKS attempt didn't yet happen.
         */
        if (can_direct_reclaim && order > PAGE_ALLOC_COSTLY_ORDER &&
                !gfp_pfmemalloc_allowed(gfp_mask)) {
                page = __alloc_pages_direct_compact(gfp_mask, order,
                                                alloc_flags, ac,
                                                INIT_COMPACT_PRIORITY,
                                                &compact_result);
                if (page)
                        goto got_pg;

                /*
                 * Checks for costly allocations with __GFP_NORETRY, which
                 * includes THP page fault allocations
                 */
                if (gfp_mask & __GFP_NORETRY) {
                        /*
                         * If compaction is deferred for high-order allocations,
                         * it is because sync compaction recently failed. If
                         * this is the case and the caller requested a THP
                         * allocation, we do not want to heavily disrupt the
                         * system, so we fail the allocation instead of entering
                         * direct reclaim.
                         */
                        if (compact_result == COMPACT_DEFERRED)
                                goto nopage;

                        /*
                         * Looks like reclaim/compaction is worth trying, but
                         * sync compaction could be very expensive, so keep
                         * using async compaction.
                         */
                        compact_priority = INIT_COMPACT_PRIORITY;
                }
        }

retry:
        /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
        if (gfp_mask & __GFP_KSWAPD_RECLAIM)
                wake_all_kswapds(order, ac);

        if (gfp_pfmemalloc_allowed(gfp_mask))
                alloc_flags = ALLOC_NO_WATERMARKS;

        /*
         * Reset the zonelist iterators if memory policies can be ignored.
         * These allocations are high priority and system rather than user
         * orientated.
         */
        if (!(alloc_flags & ALLOC_CPUSET) || (alloc_flags & ALLOC_NO_WATERMARKS)) {
                ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
                                        ac->high_zoneidx, ac->nodemask);
        }

        /* Attempt with potentially adjusted zonelist and alloc_flags */
        page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
        if (page)
                goto got_pg;

        /* Caller is not willing to reclaim, we can't balance anything */
        if (!can_direct_reclaim) {
                /*
                 * All existing users of the __GFP_NOFAIL are blockable, so warn
                 * of any new users that actually allow this type of allocation
                 * to fail.
                 */
                WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
                goto nopage;
        }

        /* Avoid recursion of direct reclaim */
        if (current->flags & PF_MEMALLOC) {
                /*
                 * __GFP_NOFAIL request from this context is rather bizarre
                 * because we cannot reclaim anything and only can loop waiting
                 * for somebody to do a work for us.
                 */
                if (WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
                        cond_resched();
                        goto retry;
                }
                goto nopage;
        }

        /* Avoid allocations with no watermarks from looping endlessly */
        if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL))
                goto nopage;


        /* Try direct reclaim and then allocating */
        page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
                                                        &did_some_progress);
        if (page)
                goto got_pg;

        /* Try direct compaction and then allocating */
        page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
                                        compact_priority, &compact_result);
        if (page)
                goto got_pg;

        /* Do not loop if specifically requested */
        if (gfp_mask & __GFP_NORETRY)
                goto nopage;

        /*
         * Do not retry costly high order allocations unless they are
         * __GFP_REPEAT
         */
        if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_REPEAT))
                goto nopage;

        /* Make sure we know about allocations which stall for too long */
        if (time_after(jiffies, alloc_start + stall_timeout)) {
                warn_alloc(gfp_mask,
                        "page allocation stalls for %ums, order:%u",
                        jiffies_to_msecs(jiffies-alloc_start), order);
                stall_timeout += 10 * HZ;
        }

        if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
                                 did_some_progress > 0, &no_progress_loops))
                goto retry;

        /*
         * It doesn't make any sense to retry for the compaction if the order-0
         * reclaim is not able to make any progress because the current
         * implementation of the compaction depends on the sufficient amount
         * of free memory (see __compaction_suitable)
         */
        if (did_some_progress > 0 &&
                        should_compact_retry(ac, order, alloc_flags,
                                compact_result, &compact_priority,
                                &compaction_retries))
                goto retry;

        /*
         * It's possible we raced with cpuset update so the OOM would be
         * premature (see below the nopage: label for full explanation).
         */
        if (read_mems_allowed_retry(cpuset_mems_cookie))
                goto retry_cpuset;

        /* Reclaim has failed us, start killing things */
        page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
        if (page)
                goto got_pg;

        /* Retry as long as the OOM killer is making progress */
        if (did_some_progress) {
                no_progress_loops = 0;
                goto retry;
        }

nopage:
        /*
         * When updating a task's mems_allowed or mempolicy nodemask, it is
         * possible to race with parallel threads in such a way that our
         * allocation can fail while the mask is being updated. If we are about
         * to fail, check if the cpuset changed during allocation and if so,
         * retry.
         */
        if (read_mems_allowed_retry(cpuset_mems_cookie))
                goto retry_cpuset;

        warn_alloc(gfp_mask,
                        "page allocation failure: order:%u", order);
got_pg:
        return page;
}

/*
 * This is the 'heart' of the zoned buddy allocator.
 */
struct page *
__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
                        struct zonelist *zonelist, nodemask_t *nodemask)
{
        struct page *page;
        unsigned int alloc_flags = ALLOC_WMARK_LOW;
        gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
        struct alloc_context ac = {
                .high_zoneidx = gfp_zone(gfp_mask),
                .zonelist = zonelist,
                .nodemask = nodemask,
                .migratetype = gfpflags_to_migratetype(gfp_mask),
        };

        if (cpusets_enabled()) {
                alloc_mask |= __GFP_HARDWALL;
                alloc_flags |= ALLOC_CPUSET;
                if (!ac.nodemask)
                        ac.nodemask = &cpuset_current_mems_allowed;
        }

        gfp_mask &= gfp_allowed_mask;

        lockdep_trace_alloc(gfp_mask);

        might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);

        if (should_fail_alloc_page(gfp_mask, order))
                return NULL;

        /*
         * Check the zones suitable for the gfp_mask contain at least one
         * valid zone. It's possible to have an empty zonelist as a result
         * of __GFP_THISNODE and a memoryless node
         */
        if (unlikely(!zonelist->_zonerefs->zone))
                return NULL;

        if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
                alloc_flags |= ALLOC_CMA;

        /* Dirty zone balancing only done in the fast path */
        ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);

        /*
         * The preferred zone is used for statistics but crucially it is
         * also used as the starting point for the zonelist iterator. It
         * may get reset for allocations that ignore memory policies.
         */
        ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
                                        ac.high_zoneidx, ac.nodemask);
        if (!ac.preferred_zoneref->zone) {
                page = NULL;
                /*
                 * This might be due to race with cpuset_current_mems_allowed
                 * update, so make sure we retry with original nodemask in the
                 * slow path.
                 */
                goto no_zone;
        }

        /* First allocation attempt */
        page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
        if (likely(page))
                goto out;

no_zone:
        /*
         * Runtime PM, block IO and its error handling path can deadlock
         * because I/O on the device might not complete.
         */
        alloc_mask = memalloc_noio_flags(gfp_mask);
        ac.spread_dirty_pages = false;

        /*
         * Restore the original nodemask if it was potentially replaced with
         * &cpuset_current_mems_allowed to optimize the fast-path attempt.
         */
        if (unlikely(ac.nodemask != nodemask))
                ac.nodemask = nodemask;

        page = __alloc_pages_slowpath(alloc_mask, order, &ac);

out:
        if (memcg_kmem_enabled() && (gfp_mask & __GFP_ACCOUNT) && page &&
            unlikely(memcg_kmem_charge(page, gfp_mask, order) != 0)) {
                __free_pages(page, order);
                page = NULL;
        }

        if (kmemcheck_enabled && page)
                kmemcheck_pagealloc_alloc(page, order, gfp_mask);

        trace_mm_page_alloc(page, order, alloc_mask, ac.migratetype);

        return page;
}
EXPORT_SYMBOL(__alloc_pages_nodemask);

/*
 * Common helper functions.
 */
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
{
        struct page *page;

        /*
         * __get_free_pages() returns a 32-bit address, which cannot represent
         * a highmem page
         */
        VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);

        page = alloc_pages(gfp_mask, order);
        if (!page)
                return 0;
        return (unsigned long) page_address(page);
}
EXPORT_SYMBOL(__get_free_pages);

unsigned long get_zeroed_page(gfp_t gfp_mask)
{
        return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
}
EXPORT_SYMBOL(get_zeroed_page);

void __free_pages(struct page *page, unsigned int order)
{
        if (put_page_testzero(page)) {
                if (order == 0)
                        free_hot_cold_page(page, false);
                else
                        __free_pages_ok(page, order);
        }
}

EXPORT_SYMBOL(__free_pages);

void free_pages(unsigned long addr, unsigned int order)
{
        if (addr != 0) {
                VM_BUG_ON(!virt_addr_valid((void *)addr));
                __free_pages(virt_to_page((void *)addr), order);
        }
}

EXPORT_SYMBOL(free_pages);

/*
 * Page Fragment:
 *  An arbitrary-length arbitrary-offset area of memory which resides
 *  within a 0 or higher order page.  Multiple fragments within that page
 *  are individually refcounted, in the page's reference counter.
 *
 * The page_frag functions below provide a simple allocation framework for
 * page fragments.  This is used by the network stack and network device
 * drivers to provide a backing region of memory for use as either an
 * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
 */
static struct page *__page_frag_refill(struct page_frag_cache *nc,
                                       gfp_t gfp_mask)
{
        struct page *page = NULL;
        gfp_t gfp = gfp_mask;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
        gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
                    __GFP_NOMEMALLOC;
        page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
                                PAGE_FRAG_CACHE_MAX_ORDER);
        nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
#endif
        if (unlikely(!page))
                page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);

        nc->va = page ? page_address(page) : NULL;

        return page;
}

void *__alloc_page_frag(struct page_frag_cache *nc,
                        unsigned int fragsz, gfp_t gfp_mask)
{
        unsigned int size = PAGE_SIZE;
        struct page *page;
        int offset;

        if (unlikely(!nc->va)) {
refill:
                page = __page_frag_refill(nc, gfp_mask);
                if (!page)
                        return NULL;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                /* if size can vary use size else just use PAGE_SIZE */
                size = nc->size;
#endif
                /* Even if we own the page, we do not use atomic_set().
                 * This would break get_page_unless_zero() users.
                 */
                page_ref_add(page, size - 1);

                /* reset page count bias and offset to start of new frag */
                nc->pfmemalloc = page_is_pfmemalloc(page);
                nc->pagecnt_bias = size;
                nc->offset = size;
        }

        offset = nc->offset - fragsz;
        if (unlikely(offset < 0)) {
                page = virt_to_page(nc->va);

                if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
                        goto refill;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
                /* if size can vary use size else just use PAGE_SIZE */
                size = nc->size;
#endif
                /* OK, page count is 0, we can safely set it */
                set_page_count(page, size);

                /* reset page count bias and offset to start of new frag */
                nc->pagecnt_bias = size;
                offset = size - fragsz;
        }

        nc->pagecnt_bias--;
        nc->offset = offset;

        return nc->va + offset;
}
EXPORT_SYMBOL(__alloc_page_frag);

/*
 * Frees a page fragment allocated out of either a compound or order 0 page.
 */
void __free_page_frag(void *addr)
{
        struct page *page = virt_to_head_page(addr);

        if (unlikely(put_page_testzero(page)))
                __free_pages_ok(page, compound_order(page));
}
EXPORT_SYMBOL(__free_page_frag);

static void *make_alloc_exact(unsigned long addr, unsigned int order,
                size_t size)
{
        if (addr) {
                unsigned long alloc_end = addr + (PAGE_SIZE << order);
                unsigned long used = addr + PAGE_ALIGN(size);

                split_page(virt_to_page((void *)addr), order);
                while (used < alloc_end) {
                        free_page(used);
                        used += PAGE_SIZE;
                }
        }
        return (void *)addr;
}

/**
 * alloc_pages_exact - allocate an exact number physically-contiguous pages.
 * @size: the number of bytes to allocate
 * @gfp_mask: GFP flags for the allocation
 *
 * This function is similar to alloc_pages(), except that it allocates the
 * minimum number of pages to satisfy the request.  alloc_pages() can only
 * allocate memory in power-of-two pages.
 *
 * This function is also limited by MAX_ORDER.
 *
 * Memory allocated by this function must be released by free_pages_exact().
 */
void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
{
        unsigned int order = get_order(size);
        unsigned long addr;

        addr = __get_free_pages(gfp_mask, order);
        return make_alloc_exact(addr, order, size);
}
EXPORT_SYMBOL(alloc_pages_exact);

/**
 * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
 *                         pages on a node.
 * @nid: the preferred node ID where memory should be allocated
 * @size: the number of bytes to allocate
 * @gfp_mask: GFP flags for the allocation
 *
 * Like alloc_pages_exact(), but try to allocate on node nid first before falling
 * back.
 */
void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
{
        unsigned int order = get_order(size);
        struct page *p = alloc_pages_node(nid, gfp_mask, order);
        if (!p)
                return NULL;
        return make_alloc_exact((unsigned long)page_address(p), order, size);
}

/**
 * free_pages_exact - release memory allocated via alloc_pages_exact()
 * @virt: the value returned by alloc_pages_exact.
 * @size: size of allocation, same value as passed to alloc_pages_exact().
 *
 * Release the memory allocated by a previous call to alloc_pages_exact.
 */
void free_pages_exact(void *virt, size_t size)
{
        unsigned long addr = (unsigned long)virt;
        unsigned long end = addr + PAGE_ALIGN(size);

        while (addr < end) {
                free_page(addr);
                addr += PAGE_SIZE;
        }
}
EXPORT_SYMBOL(free_pages_exact);

/**
 * nr_free_zone_pages - count number of pages beyond high watermark
 * @offset: The zone index of the highest zone
 *
 * nr_free_zone_pages() counts the number of counts pages which are beyond the
 * high watermark within all zones at or below a given zone index.  For each
 * zone, the number of pages is calculated as:
 *     managed_pages - high_pages
 */
static unsigned long nr_free_zone_pages(int offset)
{
        struct zoneref *z;
        struct zone *zone;

        /* Just pick one node, since fallback list is circular */
        unsigned long sum = 0;

        struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);

        for_each_zone_zonelist(zone, z, zonelist, offset) {
                unsigned long size = zone->managed_pages;
                unsigned long high = high_wmark_pages(zone);
                if (size > high)
                        sum += size - high;
        }

        return sum;
}

/**
 * nr_free_buffer_pages - count number of pages beyond high watermark
 *
 * nr_free_buffer_pages() counts the number of pages which are beyond the high
 * watermark within ZONE_DMA and ZONE_NORMAL.
 */
unsigned long nr_free_buffer_pages(void)
{
        return nr_free_zone_pages(gfp_zone(GFP_USER));
}
EXPORT_SYMBOL_GPL(nr_free_buffer_pages);

/**
 * nr_free_pagecache_pages - count number of pages beyond high watermark
 *
 * nr_free_pagecache_pages() counts the number of pages which are beyond the
 * high watermark within all zones.
 */
unsigned long nr_free_pagecache_pages(void)
{
        return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
}

static inline void show_node(struct zone *zone)
{
        if (IS_ENABLED(CONFIG_NUMA))
                printk("Node %d ", zone_to_nid(zone));
}

long si_mem_available(void)
{
        long available;
        unsigned long pagecache;
        unsigned long wmark_low = 0;
        unsigned long pages[NR_LRU_LISTS];
        struct zone *zone;
        int lru;

        for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
                pages[lru] = global_node_page_state(NR_LRU_BASE + lru);

        for_each_zone(zone)
                wmark_low += zone->watermark[WMARK_LOW];

        /*
         * Estimate the amount of memory available for userspace allocations,
         * without causing swapping.
         */
        available = global_page_state(NR_FREE_PAGES) - totalreserve_pages;

        /*
         * Not all the page cache can be freed, otherwise the system will
         * start swapping. Assume at least half of the page cache, or the
         * low watermark worth of cache, needs to stay.
         */
        pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
        pagecache -= min(pagecache / 2, wmark_low);
        available += pagecache;

        /*
         * Part of the reclaimable slab consists of items that are in use,
         * and cannot be freed. Cap this estimate at the low watermark.
         */
        available += global_page_state(NR_SLAB_RECLAIMABLE) -
                     min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low);

        if (available < 0)
                available = 0;
        return available;
}
EXPORT_SYMBOL_GPL(si_mem_available);

void si_meminfo(struct sysinfo *val)
{
        val->totalram = totalram_pages;
        val->sharedram = global_node_page_state(NR_SHMEM);
        val->freeram = global_page_state(NR_FREE_PAGES);
        val->bufferram = nr_blockdev_pages();
        val->totalhigh = totalhigh_pages;
        val->freehigh = nr_free_highpages();
        val->mem_unit = PAGE_SIZE;
}

EXPORT_SYMBOL(si_meminfo);

#ifdef CONFIG_NUMA
void si_meminfo_node(struct sysinfo *val, int nid)
{
        int zone_type;          /* needs to be signed */
        unsigned long managed_pages = 0;
        unsigned long managed_highpages = 0;
        unsigned long free_highpages = 0;
        pg_data_t *pgdat = NODE_DATA(nid);

        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
                managed_pages += pgdat->node_zones[zone_type].managed_pages;
        val->totalram = managed_pages;
        val->sharedram = node_page_state(pgdat, NR_SHMEM);
        val->freeram = sum_zone_node_page_state(nid, NR_FREE_PAGES);
#ifdef CONFIG_HIGHMEM
        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
                struct zone *zone = &pgdat->node_zones[zone_type];

                if (is_highmem(zone)) {
                        managed_highpages += zone->managed_pages;
                        free_highpages += zone_page_state(zone, NR_FREE_PAGES);
                }
        }
        val->totalhigh = managed_highpages;
        val->freehigh = free_highpages;
#else
        val->totalhigh = managed_highpages;
        val->freehigh = free_highpages;
#endif
        val->mem_unit = PAGE_SIZE;
}
#endif

/*
 * Determine whether the node should be displayed or not, depending on whether
 * SHOW_MEM_FILTER_NODES was passed to show_free_areas().
 */
bool skip_free_areas_node(unsigned int flags, int nid)
{
        bool ret = false;
        unsigned int cpuset_mems_cookie;

        if (!(flags & SHOW_MEM_FILTER_NODES))
                goto out;

        do {
                cpuset_mems_cookie = read_mems_allowed_begin();
                ret = !node_isset(nid, cpuset_current_mems_allowed);
        } while (read_mems_allowed_retry(cpuset_mems_cookie));
out:
        return ret;
}

#define K(x) ((x) << (PAGE_SHIFT-10))

static void show_migration_types(unsigned char type)
{
        static const char types[MIGRATE_TYPES] = {
                [MIGRATE_UNMOVABLE]     = 'U',
                [MIGRATE_MOVABLE]       = 'M',
                [MIGRATE_RECLAIMABLE]   = 'E',
                [MIGRATE_HIGHATOMIC]    = 'H',
#ifdef CONFIG_CMA
                [MIGRATE_CMA]           = 'C',
#endif
#ifdef CONFIG_MEMORY_ISOLATION
                [MIGRATE_ISOLATE]       = 'I',
#endif
        };
        char tmp[MIGRATE_TYPES + 1];
        char *p = tmp;
        int i;

        for (i = 0; i < MIGRATE_TYPES; i++) {
                if (type & (1 << i))
                        *p++ = types[i];
        }

        *p = '\0';
        printk(KERN_CONT "(%s) ", tmp);
}

/*
 * Show free area list (used inside shift_scroll-lock stuff)
 * We also calculate the percentage fragmentation. We do this by counting the
 * memory on each free list with the exception of the first item on the list.
 *
 * Bits in @filter:
 * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
 *   cpuset.
 */
void show_free_areas(unsigned int filter)
{
        unsigned long free_pcp = 0;
        int cpu;
        struct zone *zone;
        pg_data_t *pgdat;

        for_each_populated_zone(zone) {
                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;

                for_each_online_cpu(cpu)
                        free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;
        }

        printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
                " active_file:%lu inactive_file:%lu isolated_file:%lu\n"
                " unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
                " slab_reclaimable:%lu slab_unreclaimable:%lu\n"
                " mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
                " free:%lu free_pcp:%lu free_cma:%lu\n",
                global_node_page_state(NR_ACTIVE_ANON),
                global_node_page_state(NR_INACTIVE_ANON),
                global_node_page_state(NR_ISOLATED_ANON),
                global_node_page_state(NR_ACTIVE_FILE),
                global_node_page_state(NR_INACTIVE_FILE),
                global_node_page_state(NR_ISOLATED_FILE),
                global_node_page_state(NR_UNEVICTABLE),
                global_node_page_state(NR_FILE_DIRTY),
                global_node_page_state(NR_WRITEBACK),
                global_node_page_state(NR_UNSTABLE_NFS),
                global_page_state(NR_SLAB_RECLAIMABLE),
                global_page_state(NR_SLAB_UNRECLAIMABLE),
                global_node_page_state(NR_FILE_MAPPED),
                global_node_page_state(NR_SHMEM),
                global_page_state(NR_PAGETABLE),
                global_page_state(NR_BOUNCE),
                global_page_state(NR_FREE_PAGES),
                free_pcp,
                global_page_state(NR_FREE_CMA_PAGES));

        for_each_online_pgdat(pgdat) {
                printk("Node %d"
                        " active_anon:%lukB"
                        " inactive_anon:%lukB"
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
                        " isolated(anon):%lukB"
                        " isolated(file):%lukB"
                        " mapped:%lukB"
                        " dirty:%lukB"
                        " writeback:%lukB"
                        " shmem:%lukB"
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
                        " shmem_thp: %lukB"
                        " shmem_pmdmapped: %lukB"
                        " anon_thp: %lukB"
#endif
                        " writeback_tmp:%lukB"
                        " unstable:%lukB"
                        " pages_scanned:%lu"
                        " all_unreclaimable? %s"
                        "\n",
                        pgdat->node_id,
                        K(node_page_state(pgdat, NR_ACTIVE_ANON)),
                        K(node_page_state(pgdat, NR_INACTIVE_ANON)),
                        K(node_page_state(pgdat, NR_ACTIVE_FILE)),
                        K(node_page_state(pgdat, NR_INACTIVE_FILE)),
                        K(node_page_state(pgdat, NR_UNEVICTABLE)),
                        K(node_page_state(pgdat, NR_ISOLATED_ANON)),
                        K(node_page_state(pgdat, NR_ISOLATED_FILE)),
                        K(node_page_state(pgdat, NR_FILE_MAPPED)),
                        K(node_page_state(pgdat, NR_FILE_DIRTY)),
                        K(node_page_state(pgdat, NR_WRITEBACK)),
                        K(node_page_state(pgdat, NR_SHMEM)),
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
                        K(node_page_state(pgdat, NR_SHMEM_THPS) * HPAGE_PMD_NR),
                        K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)
                                        * HPAGE_PMD_NR),
                        K(node_page_state(pgdat, NR_ANON_THPS) * HPAGE_PMD_NR),
#endif
                        K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
                        K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
                        node_page_state(pgdat, NR_PAGES_SCANNED),
                        pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
                                "yes" : "no");
        }

        for_each_populated_zone(zone) {
                int i;

                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;

                free_pcp = 0;
                for_each_online_cpu(cpu)
                        free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;

                show_node(zone);
                printk(KERN_CONT
                        "%s"
                        " free:%lukB"
                        " min:%lukB"
                        " low:%lukB"
                        " high:%lukB"
                        " active_anon:%lukB"
                        " inactive_anon:%lukB"
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
                        " writepending:%lukB"
                        " present:%lukB"
                        " managed:%lukB"
                        " mlocked:%lukB"
                        " slab_reclaimable:%lukB"
                        " slab_unreclaimable:%lukB"
                        " kernel_stack:%lukB"
                        " pagetables:%lukB"
                        " bounce:%lukB"
                        " free_pcp:%lukB"
                        " local_pcp:%ukB"
                        " free_cma:%lukB"
                        "\n",
                        zone->name,
                        K(zone_page_state(zone, NR_FREE_PAGES)),
                        K(min_wmark_pages(zone)),
                        K(low_wmark_pages(zone)),
                        K(high_wmark_pages(zone)),
                        K(zone_page_state(zone, NR_ZONE_ACTIVE_ANON)),
                        K(zone_page_state(zone, NR_ZONE_INACTIVE_ANON)),
                        K(zone_page_state(zone, NR_ZONE_ACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
                        K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
                        K(zone->present_pages),
                        K(zone->managed_pages),
                        K(zone_page_state(zone, NR_MLOCK)),
                        K(zone_page_state(zone, NR_SLAB_RECLAIMABLE)),
                        K(zone_page_state(zone, NR_SLAB_UNRECLAIMABLE)),
                        zone_page_state(zone, NR_KERNEL_STACK_KB),
                        K(zone_page_state(zone, NR_PAGETABLE)),
                        K(zone_page_state(zone, NR_BOUNCE)),
                        K(free_pcp),
                        K(this_cpu_read(zone->pageset->pcp.count)),
                        K(zone_page_state(zone, NR_FREE_CMA_PAGES)));
                printk("lowmem_reserve[]:");
                for (i = 0; i < MAX_NR_ZONES; i++)
                        printk(KERN_CONT " %ld", zone->lowmem_reserve[i]);
                printk(KERN_CONT "\n");
        }

        for_each_populated_zone(zone) {
                unsigned int order;
                unsigned long nr[MAX_ORDER], flags, total = 0;
                unsigned char types[MAX_ORDER];

                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;
                show_node(zone);
                printk(KERN_CONT "%s: ", zone->name);

                spin_lock_irqsave(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        struct free_area *area = &zone->free_area[order];
                        int type;

                        nr[order] = area->nr_free;
                        total += nr[order] << order;

                        types[order] = 0;
                        for (type = 0; type < MIGRATE_TYPES; type++) {
                                if (!list_empty(&area->free_list[type]))
                                        types[order] |= 1 << type;
                        }
                }
                spin_unlock_irqrestore(&zone->lock, flags);
                for (order = 0; order < MAX_ORDER; order++) {
                        printk(KERN_CONT "%lu*%lukB ",
                               nr[order], K(1UL) << order);
                        if (nr[order])
                                show_migration_types(types[order]);
                }
                printk(KERN_CONT "= %lukB\n", K(total));
        }

        hugetlb_show_meminfo();

        printk("%ld total pagecache pages\n", global_node_page_state(NR_FILE_PAGES));

        show_swap_cache_info();
}

static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
{
        zoneref->zone = zone;
        zoneref->zone_idx = zone_idx(zone);
}

/*
 * Builds allocation fallback zone lists.
 *
 * Add all populated zones of a node to the zonelist.
 */
static int build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist,
                                int nr_zones)
{
        struct zone *zone;
        enum zone_type zone_type = MAX_NR_ZONES;

        do {
                zone_type--;
                zone = pgdat->node_zones + zone_type;
                if (managed_zone(zone)) {
                        zoneref_set_zone(zone,
                                &zonelist->_zonerefs[nr_zones++]);
                        check_highest_zone(zone_type);
                }
        } while (zone_type);

        return nr_zones;
}


/*
 *  zonelist_order:
 *  0 = automatic detection of better ordering.
 *  1 = order by ([node] distance, -zonetype)
 *  2 = order by (-zonetype, [node] distance)
 *
 *  If not NUMA, ZONELIST_ORDER_ZONE and ZONELIST_ORDER_NODE will create
 *  the same zonelist. So only NUMA can configure this param.
 */
#define ZONELIST_ORDER_DEFAULT  0
#define ZONELIST_ORDER_NODE     1
#define ZONELIST_ORDER_ZONE     2

/* zonelist order in the kernel.
 * set_zonelist_order() will set this to NODE or ZONE.
 */
static int current_zonelist_order = ZONELIST_ORDER_DEFAULT;
static char zonelist_order_name[3][8] = {"Default", "Node", "Zone"};


#ifdef CONFIG_NUMA
/* The value user specified ....changed by config */
static int user_zonelist_order = ZONELIST_ORDER_DEFAULT;
/* string for sysctl */
#define NUMA_ZONELIST_ORDER_LEN 16
char numa_zonelist_order[16] = "default";

/*
 * interface for configure zonelist ordering.
 * command line option "numa_zonelist_order"
 *      = "[dD]efault   - default, automatic configuration.
 *      = "[nN]ode      - order by node locality, then by zone within node
 *      = "[zZ]one      - order by zone, then by locality within zone
 */

static int __parse_numa_zonelist_order(char *s)
{
        if (*s == 'd' || *s == 'D') {
                user_zonelist_order = ZONELIST_ORDER_DEFAULT;
        } else if (*s == 'n' || *s == 'N') {
                user_zonelist_order = ZONELIST_ORDER_NODE;
        } else if (*s == 'z' || *s == 'Z') {
                user_zonelist_order = ZONELIST_ORDER_ZONE;
        } else {
                pr_warn("Ignoring invalid numa_zonelist_order value:  %s\n", s);
                return -EINVAL;
        }
        return 0;
}

static __init int setup_numa_zonelist_order(char *s)
{
        int ret;

        if (!s)
                return 0;

        ret = __parse_numa_zonelist_order(s);
        if (ret == 0)
                strlcpy(numa_zonelist_order, s, NUMA_ZONELIST_ORDER_LEN);

        return ret;
}
early_param("numa_zonelist_order", setup_numa_zonelist_order);

/*
 * sysctl handler for numa_zonelist_order
 */
int numa_zonelist_order_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *length,
                loff_t *ppos)
{
        char saved_string[NUMA_ZONELIST_ORDER_LEN];
        int ret;
        static DEFINE_MUTEX(zl_order_mutex);

        mutex_lock(&zl_order_mutex);
        if (write) {
                if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) {
                        ret = -EINVAL;
                        goto out;
                }
                strcpy(saved_string, (char *)table->data);
        }
        ret = proc_dostring(table, write, buffer, length, ppos);
        if (ret)
                goto out;
        if (write) {
                int oldval = user_zonelist_order;

                ret = __parse_numa_zonelist_order((char *)table->data);
                if (ret) {
                        /*
                         * bogus value.  restore saved string
                         */
                        strncpy((char *)table->data, saved_string,
                                NUMA_ZONELIST_ORDER_LEN);
                        user_zonelist_order = oldval;
                } else if (oldval != user_zonelist_order) {
                        mutex_lock(&zonelists_mutex);
                        build_all_zonelists(NULL, NULL);
                        mutex_unlock(&zonelists_mutex);
                }
        }
out:
        mutex_unlock(&zl_order_mutex);
        return ret;
}


#define MAX_NODE_LOAD (nr_online_nodes)
static int node_load[MAX_NUMNODES];

/**
 * find_next_best_node - find the next node that should appear in a given node's fallback list
 * @node: node whose fallback list we're appending
 * @used_node_mask: nodemask_t of already used nodes
 *
 * We use a number of factors to determine which is the next node that should
 * appear on a given node's fallback list.  The node should not have appeared
 * already in @node's fallback list, and it should be the next closest node
 * according to the distance array (which contains arbitrary distance values
 * from each node to each node in the system), and should also prefer nodes
 * with no CPUs, since presumably they'll have very little allocation pressure
 * on them otherwise.
 * It returns -1 if no node is found.
 */
static int find_next_best_node(int node, nodemask_t *used_node_mask)
{
        int n, val;
        int min_val = INT_MAX;
        int best_node = NUMA_NO_NODE;
        const struct cpumask *tmp = cpumask_of_node(0);

        /* Use the local node if we haven't already */
        if (!node_isset(node, *used_node_mask)) {
                node_set(node, *used_node_mask);
                return node;
        }

        for_each_node_state(n, N_MEMORY) {

                /* Don't want a node to appear more than once */
                if (node_isset(n, *used_node_mask))
                        continue;

                /* Use the distance array to find the distance */
                val = node_distance(node, n);

                /* Penalize nodes under us ("prefer the next node") */
                val += (n < node);

                /* Give preference to headless and unused nodes */
                tmp = cpumask_of_node(n);
                if (!cpumask_empty(tmp))
                        val += PENALTY_FOR_NODE_WITH_CPUS;

                /* Slight preference for less loaded node */
                val *= (MAX_NODE_LOAD*MAX_NUMNODES);
                val += node_load[n];

                if (val < min_val) {
                        min_val = val;
                        best_node = n;
                }
        }

        if (best_node >= 0)
                node_set(best_node, *used_node_mask);

        return best_node;
}


/*
 * Build zonelists ordered by node and zones within node.
 * This results in maximum locality--normal zone overflows into local
 * DMA zone, if any--but risks exhausting DMA zone.
 */
static void build_zonelists_in_node_order(pg_data_t *pgdat, int node)
{
        int j;
        struct zonelist *zonelist;

        zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
        for (j = 0; zonelist->_zonerefs[j].zone != NULL; j++)
                ;
        j = build_zonelists_node(NODE_DATA(node), zonelist, j);
        zonelist->_zonerefs[j].zone = NULL;
        zonelist->_zonerefs[j].zone_idx = 0;
}

/*
 * Build gfp_thisnode zonelists
 */
static void build_thisnode_zonelists(pg_data_t *pgdat)
{
        int j;
        struct zonelist *zonelist;

        zonelist = &pgdat->node_zonelists[ZONELIST_NOFALLBACK];
        j = build_zonelists_node(pgdat, zonelist, 0);
        zonelist->_zonerefs[j].zone = NULL;
        zonelist->_zonerefs[j].zone_idx = 0;
}

/*
 * Build zonelists ordered by zone and nodes within zones.
 * This results in conserving DMA zone[s] until all Normal memory is
 * exhausted, but results in overflowing to remote node while memory
 * may still exist in local DMA zone.
 */
static int node_order[MAX_NUMNODES];

static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
{
        int pos, j, node;
        int zone_type;          /* needs to be signed */
        struct zone *z;
        struct zonelist *zonelist;

        zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
        pos = 0;
        for (zone_type = MAX_NR_ZONES - 1; zone_type >= 0; zone_type--) {
                for (j = 0; j < nr_nodes; j++) {
                        node = node_order[j];
                        z = &NODE_DATA(node)->node_zones[zone_type];
                        if (managed_zone(z)) {
                                zoneref_set_zone(z,
                                        &zonelist->_zonerefs[pos++]);
                                check_highest_zone(zone_type);
                        }
                }
        }
        zonelist->_zonerefs[pos].zone = NULL;
        zonelist->_zonerefs[pos].zone_idx = 0;
}

#if defined(CONFIG_64BIT)
/*
 * Devices that require DMA32/DMA are relatively rare and do not justify a
 * penalty to every machine in case the specialised case applies. Default
 * to Node-ordering on 64-bit NUMA machines
 */
static int default_zonelist_order(void)
{
        return ZONELIST_ORDER_NODE;
}
#else
/*
 * On 32-bit, the Normal zone needs to be preserved for allocations accessible
 * by the kernel. If processes running on node 0 deplete the low memory zone
 * then reclaim will occur more frequency increasing stalls and potentially
 * be easier to OOM if a large percentage of the zone is under writeback or
 * dirty. The problem is significantly worse if CONFIG_HIGHPTE is not set.
 * Hence, default to zone ordering on 32-bit.
 */
static int default_zonelist_order(void)
{
        return ZONELIST_ORDER_ZONE;
}
#endif /* CONFIG_64BIT */

static void set_zonelist_order(void)
{
        if (user_zonelist_order == ZONELIST_ORDER_DEFAULT)
                current_zonelist_order = default_zonelist_order();
        else
                current_zonelist_order = user_zonelist_order;
}

static void build_zonelists(pg_data_t *pgdat)
{
        int i, node, load;
        nodemask_t used_mask;
        int local_node, prev_node;
        struct zonelist *zonelist;
        unsigned int order = current_zonelist_order;

        /* initialize zonelists */
        for (i = 0; i < MAX_ZONELISTS; i++) {
                zonelist = pgdat->node_zonelists + i;
                zonelist->_zonerefs[0].zone = NULL;
                zonelist->_zonerefs[0].zone_idx = 0;
        }

        /* NUMA-aware ordering of nodes */
        local_node = pgdat->node_id;
        load = nr_online_nodes;
        prev_node = local_node;
        nodes_clear(used_mask);

        memset(node_order, 0, sizeof(node_order));
        i = 0;

        while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
                /*
                 * We don't want to pressure a particular node.
                 * So adding penalty to the first node in same
                 * distance group to make it round-robin.
                 */
                if (node_distance(local_node, node) !=
                    node_distance(local_node, prev_node))
                        node_load[node] = load;

                prev_node = node;
                load--;
                if (order == ZONELIST_ORDER_NODE)
                        build_zonelists_in_node_order(pgdat, node);
                else
                        node_order[i++] = node; /* remember order */
        }

        if (order == ZONELIST_ORDER_ZONE) {
                /* calculate node order -- i.e., DMA last! */
                build_zonelists_in_zone_order(pgdat, i);
        }

        build_thisnode_zonelists(pgdat);
}

#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
 * Return node id of node used for "local" allocations.
 * I.e., first node id of first zone in arg node's generic zonelist.
 * Used for initializing percpu 'numa_mem', which is used primarily
 * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
 */
int local_memory_node(int node)
{
        struct zoneref *z;

        z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
                                   gfp_zone(GFP_KERNEL),
                                   NULL);
        return z->zone->node;
}
#endif

static void setup_min_unmapped_ratio(void);
static void setup_min_slab_ratio(void);
#else   /* CONFIG_NUMA */

static void set_zonelist_order(void)
{
        current_zonelist_order = ZONELIST_ORDER_ZONE;
}

static void build_zonelists(pg_data_t *pgdat)
{
        int node, local_node;
        enum zone_type j;
        struct zonelist *zonelist;

        local_node = pgdat->node_id;

        zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
        j = build_zonelists_node(pgdat, zonelist, 0);

        /*
         * Now we build the zonelist so that it contains the zones
         * of all the other nodes.
         * We don't want to pressure a particular node, so when
         * building the zones for node N, we make sure that the
         * zones coming right after the local ones are those from
         * node N+1 (modulo N)
         */
        for (node = local_node + 1; node < MAX_NUMNODES; node++) {
                if (!node_online(node))
                        continue;
                j = build_zonelists_node(NODE_DATA(node), zonelist, j);
        }
        for (node = 0; node < local_node; node++) {
                if (!node_online(node))
                        continue;
                j = build_zonelists_node(NODE_DATA(node), zonelist, j);
        }

        zonelist->_zonerefs[j].zone = NULL;
        zonelist->_zonerefs[j].zone_idx = 0;
}

#endif  /* CONFIG_NUMA */

/*
 * Boot pageset table. One per cpu which is going to be used for all
 * zones and all nodes. The parameters will be set in such a way
 * that an item put on a list will immediately be handed over to
 * the buddy list. This is safe since pageset manipulation is done
 * with interrupts disabled.
 *
 * The boot_pagesets must be kept even after bootup is complete for
 * unused processors and/or zones. They do play a role for bootstrapping
 * hotplugged processors.
 *
 * zoneinfo_show() and maybe other functions do
 * not check if the processor is online before following the pageset pointer.
 * Other parts of the kernel may not check if the zone is available.
 */
static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
static void setup_zone_pageset(struct zone *zone);

/*
 * Global mutex to protect against size modification of zonelists
 * as well as to serialize pageset setup for the new populated zone.
 */
DEFINE_MUTEX(zonelists_mutex);

/* return values int ....just for stop_machine() */
static int __build_all_zonelists(void *data)
{
        int nid;
        int cpu;
        pg_data_t *self = data;

#ifdef CONFIG_NUMA
        memset(node_load, 0, sizeof(node_load));
#endif

        if (self && !node_online(self->node_id)) {
                build_zonelists(self);
        }

        for_each_online_node(nid) {
                pg_data_t *pgdat = NODE_DATA(nid);

                build_zonelists(pgdat);
        }

        /*
         * Initialize the boot_pagesets that are going to be used
         * for bootstrapping processors. The real pagesets for
         * each zone will be allocated later when the per cpu
         * allocator is available.
         *
         * boot_pagesets are used also for bootstrapping offline
         * cpus if the system is already booted because the pagesets
         * are needed to initialize allocators on a specific cpu too.
         * F.e. the percpu allocator needs the page allocator which
         * needs the percpu allocator in order to allocate its pagesets
         * (a chicken-egg dilemma).
         */
        for_each_possible_cpu(cpu) {
                setup_pageset(&per_cpu(boot_pageset, cpu), 0);

#ifdef CONFIG_HAVE_MEMORYLESS_NODES
                /*
                 * We now know the "local memory node" for each node--
                 * i.e., the node of the first zone in the generic zonelist.
                 * Set up numa_mem percpu variable for on-line cpus.  During
                 * boot, only the boot cpu should be on-line;  we'll init the
                 * secondary cpus' numa_mem as they come on-line.  During
                 * node/memory hotplug, we'll fixup all on-line cpus.
                 */
                if (cpu_online(cpu))
                        set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
#endif
        }

        return 0;
}

static noinline void __init
build_all_zonelists_init(void)
{
        __build_all_zonelists(NULL);
        mminit_verify_zonelist();
        cpuset_init_current_mems_allowed();
}

/*
 * Called with zonelists_mutex held always
 * unless system_state == SYSTEM_BOOTING.
 *
 * __ref due to (1) call of __meminit annotated setup_zone_pageset
 * [we're only called with non-NULL zone through __meminit paths] and
 * (2) call of __init annotated helper build_all_zonelists_init
 * [protected by SYSTEM_BOOTING].
 */
void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone)
{
        set_zonelist_order();

        if (system_state == SYSTEM_BOOTING) {
                build_all_zonelists_init();
        } else {
#ifdef CONFIG_MEMORY_HOTPLUG
                if (zone)
                        setup_zone_pageset(zone);
#endif
                /* we have to stop all cpus to guarantee there is no user
                   of zonelist */
                stop_machine(__build_all_zonelists, pgdat, NULL);
                /* cpuset refresh routine should be here */
        }
        vm_total_pages = nr_free_pagecache_pages();
        /*
         * Disable grouping by mobility if the number of pages in the
         * system is too low to allow the mechanism to work. It would be
         * more accurate, but expensive to check per-zone. This check is
         * made on memory-hotadd so a system can start with mobility
         * disabled and enable it later
         */
        if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
                page_group_by_mobility_disabled = 1;
        else
                page_group_by_mobility_disabled = 0;

        pr_info("Built %i zonelists in %s order, mobility grouping %s.  Total pages: %ld\n",
                nr_online_nodes,
                zonelist_order_name[current_zonelist_order],
                page_group_by_mobility_disabled ? "off" : "on",
                vm_total_pages);
#ifdef CONFIG_NUMA
        pr_info("Policy zone: %s\n", zone_names[policy_zone]);
#endif
}

/*
 * Initially all pages are reserved - free ones are freed
 * up by free_all_bootmem() once the early boot process is
 * done. Non-atomic initialization, single-pass.
 */
void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
                unsigned long start_pfn, enum memmap_context context)
{
        struct vmem_altmap *altmap = to_vmem_altmap(__pfn_to_phys(start_pfn));
        unsigned long end_pfn = start_pfn + size;
        pg_data_t *pgdat = NODE_DATA(nid);
        unsigned long pfn;
        unsigned long nr_initialised = 0;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
        struct memblock_region *r = NULL, *tmp;
#endif

        if (highest_memmap_pfn < end_pfn - 1)
                highest_memmap_pfn = end_pfn - 1;

        /*
         * Honor reservation requested by the driver for this ZONE_DEVICE
         * memory
         */
        if (altmap && start_pfn == altmap->base_pfn)
                start_pfn += altmap->reserve;

        for (pfn = start_pfn; pfn < end_pfn; pfn++) {
                /*
                 * There can be holes in boot-time mem_map[]s handed to this
                 * function.  They do not exist on hotplugged memory.
                 */
                if (context != MEMMAP_EARLY)
                        goto not_early;

                if (!early_pfn_valid(pfn))
                        continue;
                if (!early_pfn_in_nid(pfn, nid))
                        continue;
                if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
                        break;

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
                /*
                 * Check given memblock attribute by firmware which can affect
                 * kernel memory layout.  If zone==ZONE_MOVABLE but memory is
                 * mirrored, it's an overlapped memmap init. skip it.
                 */
                if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
                        if (!r || pfn >= memblock_region_memory_end_pfn(r)) {
                                for_each_memblock(memory, tmp)
                                        if (pfn < memblock_region_memory_end_pfn(tmp))
                                                break;
                                r = tmp;
                        }
                        if (pfn >= memblock_region_memory_base_pfn(r) &&
                            memblock_is_mirror(r)) {
                                /* already initialized as NORMAL */
                                pfn = memblock_region_memory_end_pfn(r);
                                continue;
                        }
                }
#endif

not_early:
                /*
                 * Mark the block movable so that blocks are reserved for
                 * movable at startup. This will force kernel allocations
                 * to reserve their blocks rather than leaking throughout
                 * the address space during boot when many long-lived
                 * kernel allocations are made.
                 *
                 * bitmap is created for zone's valid pfn range. but memmap
                 * can be created for invalid pages (for alignment)
                 * check here not to call set_pageblock_migratetype() against
                 * pfn out of zone.
                 */
                if (!(pfn & (pageblock_nr_pages - 1))) {
                        struct page *page = pfn_to_page(pfn);

                        __init_single_page(page, pfn, zone, nid);
                        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
                } else {
                        __init_single_pfn(pfn, zone, nid);
                }
        }
}

static void __meminit zone_init_free_lists(struct zone *zone)
{
        unsigned int order, t;
        for_each_migratetype_order(order, t) {
                INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
                zone->free_area[order].nr_free = 0;
        }
}

#ifndef __HAVE_ARCH_MEMMAP_INIT
#define memmap_init(size, nid, zone, start_pfn) \
        memmap_init_zone((size), (nid), (zone), (start_pfn), MEMMAP_EARLY)
#endif

static int zone_batchsize(struct zone *zone)
{
#ifdef CONFIG_MMU
        int batch;

        /*
         * The per-cpu-pages pools are set to around 1000th of the
         * size of the zone.  But no more than 1/2 of a meg.
         *
         * OK, so we don't know how big the cache is.  So guess.
         */
        batch = zone->managed_pages / 1024;
        if (batch * PAGE_SIZE > 512 * 1024)
                batch = (512 * 1024) / PAGE_SIZE;
        batch /= 4;             /* We effectively *= 4 below */
        if (batch < 1)
                batch = 1;

        /*
         * Clamp the batch to a 2^n - 1 value. Having a power
         * of 2 value was found to be more likely to have
         * suboptimal cache aliasing properties in some cases.
         *
         * For example if 2 tasks are alternately allocating
         * batches of pages, one task can end up with a lot
         * of pages of one half of the possible page colors
         * and the other with pages of the other colors.
         */
        batch = rounddown_pow_of_two(batch + batch/2) - 1;

        return batch;

#else
        /* The deferral and batching of frees should be suppressed under NOMMU
         * conditions.
         *
         * The problem is that NOMMU needs to be able to allocate large chunks
         * of contiguous memory as there's no hardware page translation to
         * assemble apparent contiguous memory from discontiguous pages.
         *
         * Queueing large contiguous runs of pages for batching, however,
         * causes the pages to actually be freed in smaller chunks.  As there
         * can be a significant delay between the individual batches being
         * recycled, this leads to the once large chunks of space being
         * fragmented and becoming unavailable for high-order allocations.
         */
        return 0;
#endif
}

/*
 * pcp->high and pcp->batch values are related and dependent on one another:
 * ->batch must never be higher then ->high.
 * The following function updates them in a safe manner without read side
 * locking.
 *
 * Any new users of pcp->batch and pcp->high should ensure they can cope with
 * those fields changing asynchronously (acording the the above rule).
 *
 * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
 * outside of boot time (or some other assurance that no concurrent updaters
 * exist).
 */
static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
                unsigned long batch)
{
       /* start with a fail safe value for batch */
        pcp->batch = 1;
        smp_wmb();

       /* Update high, then batch, in order */
        pcp->high = high;
        smp_wmb();

        pcp->batch = batch;
}

/* a companion to pageset_set_high() */
static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
{
        pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch));
}

static void pageset_init(struct per_cpu_pageset *p)
{
        struct per_cpu_pages *pcp;
        int migratetype;

        memset(p, 0, sizeof(*p));

        pcp = &p->pcp;
        pcp->count = 0;
        for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
                INIT_LIST_HEAD(&pcp->lists[migratetype]);
}

static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
{
        pageset_init(p);
        pageset_set_batch(p, batch);
}

/*
 * pageset_set_high() sets the high water mark for hot per_cpu_pagelist
 * to the value high for the pageset p.
 */
static void pageset_set_high(struct per_cpu_pageset *p,
                                unsigned long high)
{
        unsigned long batch = max(1UL, high / 4);
        if ((high / 4) > (PAGE_SHIFT * 8))
                batch = PAGE_SHIFT * 8;

        pageset_update(&p->pcp, high, batch);
}

static void pageset_set_high_and_batch(struct zone *zone,
                                       struct per_cpu_pageset *pcp)
{
        if (percpu_pagelist_fraction)
                pageset_set_high(pcp,
                        (zone->managed_pages /
                                percpu_pagelist_fraction));
        else
                pageset_set_batch(pcp, zone_batchsize(zone));
}

static void __meminit zone_pageset_init(struct zone *zone, int cpu)
{
        struct per_cpu_pageset *pcp = per_cpu_ptr(zone->pageset, cpu);

        pageset_init(pcp);
        pageset_set_high_and_batch(zone, pcp);
}

static void __meminit setup_zone_pageset(struct zone *zone)
{
        int cpu;
        zone->pageset = alloc_percpu(struct per_cpu_pageset);
        for_each_possible_cpu(cpu)
                zone_pageset_init(zone, cpu);
}

/*
 * Allocate per cpu pagesets and initialize them.
 * Before this call only boot pagesets were available.
 */
void __init setup_per_cpu_pageset(void)
{
        struct pglist_data *pgdat;
        struct zone *zone;

        for_each_populated_zone(zone)
                setup_zone_pageset(zone);

        for_each_online_pgdat(pgdat)
                pgdat->per_cpu_nodestats =
                        alloc_percpu(struct per_cpu_nodestat);
}

static __meminit void zone_pcp_init(struct zone *zone)
{
        /*
         * per cpu subsystem is not up at this point. The following code
         * relies on the ability of the linker to provide the
         * offset of a (static) per cpu variable into the per cpu area.
         */
        zone->pageset = &boot_pageset;

        if (populated_zone(zone))
                printk(KERN_DEBUG "  %s zone: %lu pages, LIFO batch:%u\n",
                        zone->name, zone->present_pages,
                                         zone_batchsize(zone));
}

int __meminit init_currently_empty_zone(struct zone *zone,
                                        unsigned long zone_start_pfn,
                                        unsigned long size)
{
        struct pglist_data *pgdat = zone->zone_pgdat;

        pgdat->nr_zones = zone_idx(zone) + 1;

        zone->zone_start_pfn = zone_start_pfn;

        mminit_dprintk(MMINIT_TRACE, "memmap_init",
                        "Initialising map node %d zone %lu pfns %lu -> %lu\n",
                        pgdat->node_id,
                        (unsigned long)zone_idx(zone),
                        zone_start_pfn, (zone_start_pfn + size));

        zone_init_free_lists(zone);
        zone->initialized = 1;

        return 0;
}

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
#ifndef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID

/*
 * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
 */
int __meminit __early_pfn_to_nid(unsigned long pfn,
                                        struct mminit_pfnnid_cache *state)
{
        unsigned long start_pfn, end_pfn;
        int nid;

        if (state->last_start <= pfn && pfn < state->last_end)
                return state->last_nid;

        nid = memblock_search_pfn_nid(pfn, &start_pfn, &end_pfn);
        if (nid != -1) {
                state->last_start = start_pfn;
                state->last_end = end_pfn;
                state->last_nid = nid;
        }

        return nid;
}
#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */

/**
 * free_bootmem_with_active_regions - Call memblock_free_early_nid for each active range
 * @nid: The node to free memory on. If MAX_NUMNODES, all nodes are freed.
 * @max_low_pfn: The highest PFN that will be passed to memblock_free_early_nid
 *
 * If an architecture guarantees that all ranges registered contain no holes
 * and may be freed, this this function may be used instead of calling
 * memblock_free_early_nid() manually.
 */
void __init free_bootmem_with_active_regions(int nid, unsigned long max_low_pfn)
{
        unsigned long start_pfn, end_pfn;
        int i, this_nid;

        for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid) {
                start_pfn = min(start_pfn, max_low_pfn);
                end_pfn = min(end_pfn, max_low_pfn);

                if (start_pfn < end_pfn)
                        memblock_free_early_nid(PFN_PHYS(start_pfn),
                                        (end_pfn - start_pfn) << PAGE_SHIFT,
                                        this_nid);
        }
}

/**
 * sparse_memory_present_with_active_regions - Call memory_present for each active range
 * @nid: The node to call memory_present for. If MAX_NUMNODES, all nodes will be used.
 *
 * If an architecture guarantees that all ranges registered contain no holes and may
 * be freed, this function may be used instead of calling memory_present() manually.
 */
void __init sparse_memory_present_with_active_regions(int nid)
{
        unsigned long start_pfn, end_pfn;
        int i, this_nid;

        for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid)
                memory_present(this_nid, start_pfn, end_pfn);
}

/**
 * get_pfn_range_for_nid - Return the start and end page frames for a node
 * @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
 * @start_pfn: Passed by reference. On return, it will have the node start_pfn.
 * @end_pfn: Passed by reference. On return, it will have the node end_pfn.
 *
 * It returns the start and end page frame of a node based on information
 * provided by memblock_set_node(). If called for a node
 * with no available memory, a warning is printed and the start and end
 * PFNs will be 0.
 */
void __meminit get_pfn_range_for_nid(unsigned int nid,
                        unsigned long *start_pfn, unsigned long *end_pfn)
{
        unsigned long this_start_pfn, this_end_pfn;
        int i;

        *start_pfn = -1UL;
        *end_pfn = 0;

        for_each_mem_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
                *start_pfn = min(*start_pfn, this_start_pfn);
                *end_pfn = max(*end_pfn, this_end_pfn);
        }

        if (*start_pfn == -1UL)
                *start_pfn = 0;
}

/*
 * This finds a zone that can be used for ZONE_MOVABLE pages. The
 * assumption is made that zones within a node are ordered in monotonic
 * increasing memory addresses so that the "highest" populated zone is used
 */
static void __init find_usable_zone_for_movable(void)
{
        int zone_index;
        for (zone_index = MAX_NR_ZONES - 1; zone_index >= 0; zone_index--) {
                if (zone_index == ZONE_MOVABLE)
                        continue;

                if (arch_zone_highest_possible_pfn[zone_index] >
                                arch_zone_lowest_possible_pfn[zone_index])
                        break;
        }

        VM_BUG_ON(zone_index == -1);
        movable_zone = zone_index;
}

/*
 * The zone ranges provided by the architecture do not include ZONE_MOVABLE
 * because it is sized independent of architecture. Unlike the other zones,
 * the starting point for ZONE_MOVABLE is not fixed. It may be different
 * in each node depending on the size of each node and how evenly kernelcore
 * is distributed. This helper function adjusts the zone ranges
 * provided by the architecture for a given node by using the end of the
 * highest usable zone for ZONE_MOVABLE. This preserves the assumption that
 * zones within a node are in order of monotonic increases memory addresses
 */
static void __meminit adjust_zone_range_for_zone_movable(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *zone_start_pfn,
                                        unsigned long *zone_end_pfn)
{
        /* Only adjust if ZONE_MOVABLE is on this node */
        if (zone_movable_pfn[nid]) {
                /* Size ZONE_MOVABLE */
                if (zone_type == ZONE_MOVABLE) {
                        *zone_start_pfn = zone_movable_pfn[nid];
                        *zone_end_pfn = min(node_end_pfn,
                                arch_zone_highest_possible_pfn[movable_zone]);

                /* Adjust for ZONE_MOVABLE starting within this range */
                } else if (!mirrored_kernelcore &&
                        *zone_start_pfn < zone_movable_pfn[nid] &&
                        *zone_end_pfn > zone_movable_pfn[nid]) {
                        *zone_end_pfn = zone_movable_pfn[nid];

                /* Check if this whole range is within ZONE_MOVABLE */
                } else if (*zone_start_pfn >= zone_movable_pfn[nid])
                        *zone_start_pfn = *zone_end_pfn;
        }
}

/*
 * Return the number of pages a zone spans in a node, including holes
 * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
 */
static unsigned long __meminit zone_spanned_pages_in_node(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *zone_start_pfn,
                                        unsigned long *zone_end_pfn,
                                        unsigned long *ignored)
{
        /* When hotadd a new node from cpu_up(), the node should be empty */
        if (!node_start_pfn && !node_end_pfn)
                return 0;

        /* Get the start and end of the zone */
        *zone_start_pfn = arch_zone_lowest_possible_pfn[zone_type];
        *zone_end_pfn = arch_zone_highest_possible_pfn[zone_type];
        adjust_zone_range_for_zone_movable(nid, zone_type,
                                node_start_pfn, node_end_pfn,
                                zone_start_pfn, zone_end_pfn);

        /* Check that this node has pages within the zone's required range */
        if (*zone_end_pfn < node_start_pfn || *zone_start_pfn > node_end_pfn)
                return 0;

        /* Move the zone boundaries inside the node if necessary */
        *zone_end_pfn = min(*zone_end_pfn, node_end_pfn);
        *zone_start_pfn = max(*zone_start_pfn, node_start_pfn);

        /* Return the spanned pages */
        return *zone_end_pfn - *zone_start_pfn;
}

/*
 * Return the number of holes in a range on a node. If nid is MAX_NUMNODES,
 * then all holes in the requested range will be accounted for.
 */
unsigned long __meminit __absent_pages_in_range(int nid,
                                unsigned long range_start_pfn,
                                unsigned long range_end_pfn)
{
        unsigned long nr_absent = range_end_pfn - range_start_pfn;
        unsigned long start_pfn, end_pfn;
        int i;

        for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
                start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
                end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
                nr_absent -= end_pfn - start_pfn;
        }
        return nr_absent;
}

/**
 * absent_pages_in_range - Return number of page frames in holes within a range
 * @start_pfn: The start PFN to start searching for holes
 * @end_pfn: The end PFN to stop searching for holes
 *
 * It returns the number of pages frames in memory holes within a range.
 */
unsigned long __init absent_pages_in_range(unsigned long start_pfn,
                                                        unsigned long end_pfn)
{
        return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
}

/* Return the number of page frames in holes in a zone on a node */
static unsigned long __meminit zone_absent_pages_in_node(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *ignored)
{
        unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
        unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
        unsigned long zone_start_pfn, zone_end_pfn;
        unsigned long nr_absent;

        /* When hotadd a new node from cpu_up(), the node should be empty */
        if (!node_start_pfn && !node_end_pfn)
                return 0;

        zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
        zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);

        adjust_zone_range_for_zone_movable(nid, zone_type,
                        node_start_pfn, node_end_pfn,
                        &zone_start_pfn, &zone_end_pfn);
        nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);

        /*
         * ZONE_MOVABLE handling.
         * Treat pages to be ZONE_MOVABLE in ZONE_NORMAL as absent pages
         * and vice versa.
         */
        if (mirrored_kernelcore && zone_movable_pfn[nid]) {
                unsigned long start_pfn, end_pfn;
                struct memblock_region *r;

                for_each_memblock(memory, r) {
                        start_pfn = clamp(memblock_region_memory_base_pfn(r),
                                          zone_start_pfn, zone_end_pfn);
                        end_pfn = clamp(memblock_region_memory_end_pfn(r),
                                        zone_start_pfn, zone_end_pfn);

                        if (zone_type == ZONE_MOVABLE &&
                            memblock_is_mirror(r))
                                nr_absent += end_pfn - start_pfn;

                        if (zone_type == ZONE_NORMAL &&
                            !memblock_is_mirror(r))
                                nr_absent += end_pfn - start_pfn;
                }
        }

        return nr_absent;
}

#else /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
static inline unsigned long __meminit zone_spanned_pages_in_node(int nid,
                                        unsigned long zone_type,
                                        unsigned long node_start_pfn,
                                        unsigned long node_end_pfn,
                                        unsigned long *zone_start_pfn,
                                        unsigned long *zone_end_pfn,
                                        unsigned long *zones_size)
{
        unsigned int zone;

        *zone_start_pfn = node_start_pfn;
        for (zone = 0; zone < zone_type; zone++)
                *zone_start_pfn += zones_size[zone];

        *zone_end_pfn = *zone_start_pfn + zones_size[zone_type];

        return zones_size[zone_type];
}

static inline unsigned long __meminit zone_absent_pages_in_node(int nid,
                                                unsigned long zone_type,
                                                unsigned long node_start_pfn,
                                                unsigned long node_end_pfn,
                                                unsigned long *zholes_size)
{
        if (!zholes_size)
                return 0;

        return zholes_size[zone_type];
}

#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

static void __meminit calculate_node_totalpages(struct pglist_data *pgdat,
                                                unsigned long node_start_pfn,
                                                unsigned long node_end_pfn,
                                                unsigned long *zones_size,
                                                unsigned long *zholes_size)
{
        unsigned long realtotalpages = 0, totalpages = 0;
        enum zone_type i;

        for (i = 0; i < MAX_NR_ZONES; i++) {
                struct zone *zone = pgdat->node_zones + i;
                unsigned long zone_start_pfn, zone_end_pfn;
                unsigned long size, real_size;

                size = zone_spanned_pages_in_node(pgdat->node_id, i,
                                                  node_start_pfn,
                                                  node_end_pfn,
                                                  &zone_start_pfn,
                                                  &zone_end_pfn,
                                                  zones_size);
                real_size = size - zone_absent_pages_in_node(pgdat->node_id, i,
                                                  node_start_pfn, node_end_pfn,
                                                  zholes_size);
                if (size)
                        zone->zone_start_pfn = zone_start_pfn;
                else
                        zone->zone_start_pfn = 0;
                zone->spanned_pages = size;
                zone->present_pages = real_size;

                totalpages += size;
                realtotalpages += real_size;
        }

        pgdat->node_spanned_pages = totalpages;
        pgdat->node_present_pages = realtotalpages;
        printk(KERN_DEBUG "On node %d totalpages: %lu\n", pgdat->node_id,
                                                        realtotalpages);
}

#ifndef CONFIG_SPARSEMEM
/*
 * Calculate the size of the zone->blockflags rounded to an unsigned long
 * Start by making sure zonesize is a multiple of pageblock_order by rounding
 * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally
 * round what is now in bits to nearest long in bits, then return it in
 * bytes.
 */
static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned long zonesize)
{
        unsigned long usemapsize;

        zonesize += zone_start_pfn & (pageblock_nr_pages-1);
        usemapsize = roundup(zonesize, pageblock_nr_pages);
        usemapsize = usemapsize >> pageblock_order;
        usemapsize *= NR_PAGEBLOCK_BITS;
        usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));

        return usemapsize / 8;
}

static void __init setup_usemap(struct pglist_data *pgdat,
                                struct zone *zone,
                                unsigned long zone_start_pfn,
                                unsigned long zonesize)
{
        unsigned long usemapsize = usemap_size(zone_start_pfn, zonesize);
        zone->pageblock_flags = NULL;
        if (usemapsize)
                zone->pageblock_flags =
                        memblock_virt_alloc_node_nopanic(usemapsize,
                                                         pgdat->node_id);
}
#else
static inline void setup_usemap(struct pglist_data *pgdat, struct zone *zone,
                                unsigned long zone_start_pfn, unsigned long zonesize) {}
#endif /* CONFIG_SPARSEMEM */

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
void __paginginit set_pageblock_order(void)
{
        unsigned int order;

        /* Check that pageblock_nr_pages has not already been setup */
        if (pageblock_order)
                return;

        if (HPAGE_SHIFT > PAGE_SHIFT)
                order = HUGETLB_PAGE_ORDER;
        else
                order = MAX_ORDER - 1;

        /*
         * Assume the largest contiguous order of interest is a huge page.
         * This value may be variable depending on boot parameters on IA64 and
         * powerpc.
         */
        pageblock_order = order;
}
#else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

/*
 * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
 * is unused as pageblock_order is set at compile-time. See
 * include/linux/pageblock-flags.h for the values of pageblock_order based on
 * the kernel config
 */
void __paginginit set_pageblock_order(void)
{
}

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages,
                                                   unsigned long present_pages)
{
        unsigned long pages = spanned_pages;

        /*
         * Provide a more accurate estimation if there are holes within
         * the zone and SPARSEMEM is in use. If there are holes within the
         * zone, each populated memory region may cost us one or two extra
         * memmap pages due to alignment because memmap pages for each
         * populated regions may not naturally algined on page boundary.
         * So the (present_pages >> 4) heuristic is a tradeoff for that.
         */
        if (spanned_pages > present_pages + (present_pages >> 4) &&
            IS_ENABLED(CONFIG_SPARSEMEM))
                pages = present_pages;

        return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
}

/*
 * Set up the zone data structures:
 *   - mark all pages reserved
 *   - mark all memory queues empty
 *   - clear the memory bitmaps
 *
 * NOTE: pgdat should get zeroed by caller.
 */
static void __paginginit free_area_init_core(struct pglist_data *pgdat)
{
        enum zone_type j;
        int nid = pgdat->node_id;
        int ret;

        pgdat_resize_init(pgdat);
#ifdef CONFIG_NUMA_BALANCING
        spin_lock_init(&pgdat->numabalancing_migrate_lock);
        pgdat->numabalancing_migrate_nr_pages = 0;
        pgdat->numabalancing_migrate_next_window = jiffies;
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        spin_lock_init(&pgdat->split_queue_lock);
        INIT_LIST_HEAD(&pgdat->split_queue);
        pgdat->split_queue_len = 0;
#endif
        init_waitqueue_head(&pgdat->kswapd_wait);
        init_waitqueue_head(&pgdat->pfmemalloc_wait);
#ifdef CONFIG_COMPACTION
        init_waitqueue_head(&pgdat->kcompactd_wait);
#endif
        pgdat_page_ext_init(pgdat);
        spin_lock_init(&pgdat->lru_lock);
        lruvec_init(node_lruvec(pgdat));

        for (j = 0; j < MAX_NR_ZONES; j++) {
                struct zone *zone = pgdat->node_zones + j;
                unsigned long size, realsize, freesize, memmap_pages;
                unsigned long zone_start_pfn = zone->zone_start_pfn;

                size = zone->spanned_pages;
                realsize = freesize = zone->present_pages;

                /*
                 * Adjust freesize so that it accounts for how much memory
                 * is used by this zone for memmap. This affects the watermark
                 * and per-cpu initialisations
                 */
                memmap_pages = calc_memmap_size(size, realsize);
                if (!is_highmem_idx(j)) {
                        if (freesize >= memmap_pages) {
                                freesize -= memmap_pages;
                                if (memmap_pages)
                                        printk(KERN_DEBUG
                                               "  %s zone: %lu pages used for memmap\n",
                                               zone_names[j], memmap_pages);
                        } else
                                pr_warn("  %s zone: %lu pages exceeds freesize %lu\n",
                                        zone_names[j], memmap_pages, freesize);
                }

                /* Account for reserved pages */
                if (j == 0 && freesize > dma_reserve) {
                        freesize -= dma_reserve;
                        printk(KERN_DEBUG "  %s zone: %lu pages reserved\n",
                                        zone_names[0], dma_reserve);
                }

                if (!is_highmem_idx(j))
                        nr_kernel_pages += freesize;
                /* Charge for highmem memmap if there are enough kernel pages */
                else if (nr_kernel_pages > memmap_pages * 2)
                        nr_kernel_pages -= memmap_pages;
                nr_all_pages += freesize;

                /*
                 * Set an approximate value for lowmem here, it will be adjusted
                 * when the bootmem allocator frees pages into the buddy system.
                 * And all highmem pages will be managed by the buddy system.
                 */
                zone->managed_pages = is_highmem_idx(j) ? realsize : freesize;
#ifdef CONFIG_NUMA
                zone->node = nid;
#endif
                zone->name = zone_names[j];
                zone->zone_pgdat = pgdat;
                spin_lock_init(&zone->lock);
                zone_seqlock_init(zone);
                zone_pcp_init(zone);

                if (!size)
                        continue;

                set_pageblock_order();
                setup_usemap(pgdat, zone, zone_start_pfn, size);
                ret = init_currently_empty_zone(zone, zone_start_pfn, size);
                BUG_ON(ret);
                memmap_init(size, nid, j, zone_start_pfn);
        }
}

static void __ref alloc_node_mem_map(struct pglist_data *pgdat)
{
        unsigned long __maybe_unused start = 0;
        unsigned long __maybe_unused offset = 0;

        /* Skip empty nodes */
        if (!pgdat->node_spanned_pages)
                return;

#ifdef CONFIG_FLAT_NODE_MEM_MAP
        start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
        offset = pgdat->node_start_pfn - start;
        /* ia64 gets its own node_mem_map, before this, without bootmem */
        if (!pgdat->node_mem_map) {
                unsigned long size, end;
                struct page *map;

                /*
                 * The zone's endpoints aren't required to be MAX_ORDER
                 * aligned but the node_mem_map endpoints must be in order
                 * for the buddy allocator to function correctly.
                 */
                end = pgdat_end_pfn(pgdat);
                end = ALIGN(end, MAX_ORDER_NR_PAGES);
                size =  (end - start) * sizeof(struct page);
                map = alloc_remap(pgdat->node_id, size);
                if (!map)
                        map = memblock_virt_alloc_node_nopanic(size,
                                                               pgdat->node_id);
                pgdat->node_mem_map = map + offset;
        }
#ifndef CONFIG_NEED_MULTIPLE_NODES
        /*
         * With no DISCONTIG, the global mem_map is just set as node 0's
         */
        if (pgdat == NODE_DATA(0)) {
                mem_map = NODE_DATA(0)->node_mem_map;
#if defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) || defined(CONFIG_FLATMEM)
                if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
                        mem_map -= offset;
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
        }
#endif
#endif /* CONFIG_FLAT_NODE_MEM_MAP */
}

void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
                unsigned long node_start_pfn, unsigned long *zholes_size)
{
        pg_data_t *pgdat = NODE_DATA(nid);
        unsigned long start_pfn = 0;
        unsigned long end_pfn = 0;

        /* pg_data_t should be reset to zero when it's allocated */
        WARN_ON(pgdat->nr_zones || pgdat->kswapd_classzone_idx);

        pgdat->node_id = nid;
        pgdat->node_start_pfn = node_start_pfn;
        pgdat->per_cpu_nodestats = NULL;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
        get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
        pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
                (u64)start_pfn << PAGE_SHIFT,
                end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
#else
        start_pfn = node_start_pfn;
#endif
        calculate_node_totalpages(pgdat, start_pfn, end_pfn,
                                  zones_size, zholes_size);

        alloc_node_mem_map(pgdat);
#ifdef CONFIG_FLAT_NODE_MEM_MAP
        printk(KERN_DEBUG "free_area_init_node: node %d, pgdat %08lx, node_mem_map %08lx\n",
                nid, (unsigned long)pgdat,
                (unsigned long)pgdat->node_mem_map);
#endif

        reset_deferred_meminit(pgdat);
        free_area_init_core(pgdat);
}

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP

#if MAX_NUMNODES > 1
/*
 * Figure out the number of possible node ids.
 */
void __init setup_nr_node_ids(void)
{
        unsigned int highest;

        highest = find_last_bit(node_possible_map.bits, MAX_NUMNODES);
        nr_node_ids = highest + 1;
}
#endif

/**
 * node_map_pfn_alignment - determine the maximum internode alignment
 *
 * This function should be called after node map is populated and sorted.
 * It calculates the maximum power of two alignment which can distinguish
 * all the nodes.
 *
 * For example, if all nodes are 1GiB and aligned to 1GiB, the return value
 * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)).  If the
 * nodes are shifted by 256MiB, 256MiB.  Note that if only the last node is
 * shifted, 1GiB is enough and this function will indicate so.
 *
 * This is used to test whether pfn -> nid mapping of the chosen memory
 * model has fine enough granularity to avoid incorrect mapping for the
 * populated node map.
 *
 * Returns the determined alignment in pfn's.  0 if there is no alignment
 * requirement (single node).
 */
unsigned long __init node_map_pfn_alignment(void)
{
        unsigned long accl_mask = 0, last_end = 0;
        unsigned long start, end, mask;
        int last_nid = -1;
        int i, nid;

        for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid) {
                if (!start || last_nid < 0 || last_nid == nid) {
                        last_nid = nid;
                        last_end = end;
                        continue;
                }

                /*
                 * Start with a mask granular enough to pin-point to the
                 * start pfn and tick off bits one-by-one until it becomes
                 * too coarse to separate the current node from the last.
                 */
                mask = ~((1 << __ffs(start)) - 1);
                while (mask && last_end <= (start & (mask << 1)))
                        mask <<= 1;

                /* accumulate all internode masks */
                accl_mask |= mask;
        }

        /* convert mask to number of pages */
        return ~accl_mask + 1;
}

/* Find the lowest pfn for a node */
static unsigned long __init find_min_pfn_for_node(int nid)
{
        unsigned long min_pfn = ULONG_MAX;
        unsigned long start_pfn;
        int i;

        for_each_mem_pfn_range(i, nid, &start_pfn, NULL, NULL)
                min_pfn = min(min_pfn, start_pfn);

        if (min_pfn == ULONG_MAX) {
                pr_warn("Could not find start_pfn for node %d\n", nid);
                return 0;
        }

        return min_pfn;
}

/**
 * find_min_pfn_with_active_regions - Find the minimum PFN registered
 *
 * It returns the minimum PFN based on information provided via
 * memblock_set_node().
 */
unsigned long __init find_min_pfn_with_active_regions(void)
{
        return find_min_pfn_for_node(MAX_NUMNODES);
}

/*
 * early_calculate_totalpages()
 * Sum pages in active regions for movable zone.
 * Populate N_MEMORY for calculating usable_nodes.
 */
static unsigned long __init early_calculate_totalpages(void)
{
        unsigned long totalpages = 0;
        unsigned long start_pfn, end_pfn;
        int i, nid;

        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
                unsigned long pages = end_pfn - start_pfn;

                totalpages += pages;
                if (pages)
                        node_set_state(nid, N_MEMORY);
        }
        return totalpages;
}

/*
 * Find the PFN the Movable zone begins in each node. Kernel memory
 * is spread evenly between nodes as long as the nodes have enough
 * memory. When they don't, some nodes will have more kernelcore than
 * others
 */
static void __init find_zone_movable_pfns_for_nodes(void)
{
        int i, nid;
        unsigned long usable_startpfn;
        unsigned long kernelcore_node, kernelcore_remaining;
        /* save the state before borrow the nodemask */
        nodemask_t saved_node_state = node_states[N_MEMORY];
        unsigned long totalpages = early_calculate_totalpages();
        int usable_nodes = nodes_weight(node_states[N_MEMORY]);
        struct memblock_region *r;

        /* Need to find movable_zone earlier when movable_node is specified. */
        find_usable_zone_for_movable();

        /*
         * If movable_node is specified, ignore kernelcore and movablecore
         * options.
         */
        if (movable_node_is_enabled()) {
                for_each_memblock(memory, r) {
                        if (!memblock_is_hotpluggable(r))
                                continue;

                        nid = r->nid;

                        usable_startpfn = PFN_DOWN(r->base);
                        zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                                min(usable_startpfn, zone_movable_pfn[nid]) :
                                usable_startpfn;
                }

                goto out2;
        }

        /*
         * If kernelcore=mirror is specified, ignore movablecore option
         */
        if (mirrored_kernelcore) {
                bool mem_below_4gb_not_mirrored = false;

                for_each_memblock(memory, r) {
                        if (memblock_is_mirror(r))
                                continue;

                        nid = r->nid;

                        usable_startpfn = memblock_region_memory_base_pfn(r);

                        if (usable_startpfn < 0x100000) {
                                mem_below_4gb_not_mirrored = true;
                                continue;
                        }

                        zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
                                min(usable_startpfn, zone_movable_pfn[nid]) :
                                usable_startpfn;
                }

                if (mem_below_4gb_not_mirrored)
                        pr_warn("This configuration results in unmirrored kernel memory.");

                goto out2;
        }

        /*
         * If movablecore=nn[KMG] was specified, calculate what size of
         * kernelcore that corresponds so that memory usable for
         * any allocation type is evenly spread. If both kernelcore
         * and movablecore are specified, then the value of kernelcore
         * will be used for required_kernelcore if it's greater than
         * what movablecore would have allowed.
         */
        if (required_movablecore) {
                unsigned long corepages;

                /*
                 * Round-up so that ZONE_MOVABLE is at least as large as what
                 * was requested by the user
                 */
                required_movablecore =
                        roundup(required_movablecore, MAX_ORDER_NR_PAGES);
                required_movablecore = min(totalpages, required_movablecore);
                corepages = totalpages - required_movablecore;

                required_kernelcore = max(required_kernelcore, corepages);
        }

        /*
         * If kernelcore was not specified or kernelcore size is larger
         * than totalpages, there is no ZONE_MOVABLE.
         */
        if (!required_kernelcore || required_kernelcore >= totalpages)
                goto out;

        /* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
        usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];

restart:
        /* Spread kernelcore memory as evenly as possible throughout nodes */
        kernelcore_node = required_kernelcore / usable_nodes;
        for_each_node_state(nid, N_MEMORY) {
                unsigned long start_pfn, end_pfn;

                /*
                 * Recalculate kernelcore_node if the division per node
                 * now exceeds what is necessary to satisfy the requested
                 * amount of memory for the kernel
                 */
                if (required_kernelcore < kernelcore_node)
                        kernelcore_node = required_kernelcore / usable_nodes;

                /*
                 * As the map is walked, we track how much memory is usable
                 * by the kernel using kernelcore_remaining. When it is
                 * 0, the rest of the node is usable by ZONE_MOVABLE
                 */
                kernelcore_remaining = kernelcore_node;

                /* Go through each range of PFNs within this node */
                for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
                        unsigned long size_pages;

                        start_pfn = max(start_pfn, zone_movable_pfn[nid]);
                        if (start_pfn >= end_pfn)
                                continue;

                        /* Account for what is only usable for kernelcore */
                        if (start_pfn < usable_startpfn) {
                                unsigned long kernel_pages;
                                kernel_pages = min(end_pfn, usable_startpfn)
                                                                - start_pfn;

                                kernelcore_remaining -= min(kernel_pages,
                                                        kernelcore_remaining);
                                required_kernelcore -= min(kernel_pages,
                                                        required_kernelcore);

                                /* Continue if range is now fully accounted */
                                if (end_pfn <= usable_startpfn) {

                                        /*
                                         * Push zone_movable_pfn to the end so
                                         * that if we have to rebalance
                                         * kernelcore across nodes, we will
                                         * not double account here
                                         */
                                        zone_movable_pfn[nid] = end_pfn;
                                        continue;
                                }
                                start_pfn = usable_startpfn;
                        }

                        /*
                         * The usable PFN range for ZONE_MOVABLE is from
                         * start_pfn->end_pfn. Calculate size_pages as the
                         * number of pages used as kernelcore
                         */
                        size_pages = end_pfn - start_pfn;
                        if (size_pages > kernelcore_remaining)
                                size_pages = kernelcore_remaining;
                        zone_movable_pfn[nid] = start_pfn + size_pages;

                        /*
                         * Some kernelcore has been met, update counts and
                         * break if the kernelcore for this node has been
                         * satisfied
                         */
                        required_kernelcore -= min(required_kernelcore,
                                                                size_pages);
                        kernelcore_remaining -= size_pages;
                        if (!kernelcore_remaining)
                                break;
                }
        }

        /*
         * If there is still required_kernelcore, we do another pass with one
         * less node in the count. This will push zone_movable_pfn[nid] further
         * along on the nodes that still have memory until kernelcore is
         * satisfied
         */
        usable_nodes--;
        if (usable_nodes && required_kernelcore > usable_nodes)
                goto restart;

out2:
        /* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */
        for (nid = 0; nid < MAX_NUMNODES; nid++)
                zone_movable_pfn[nid] =
                        roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);

out:
        /* restore the node_state */
        node_states[N_MEMORY] = saved_node_state;
}

/* Any regular or high memory on that node ? */
static void check_for_memory(pg_data_t *pgdat, int nid)
{
        enum zone_type zone_type;

        if (N_MEMORY == N_NORMAL_MEMORY)
                return;

        for (zone_type = 0; zone_type <= ZONE_MOVABLE - 1; zone_type++) {
                struct zone *zone = &pgdat->node_zones[zone_type];
                if (populated_zone(zone)) {
                        node_set_state(nid, N_HIGH_MEMORY);
                        if (N_NORMAL_MEMORY != N_HIGH_MEMORY &&
                            zone_type <= ZONE_NORMAL)
                                node_set_state(nid, N_NORMAL_MEMORY);
                        break;
                }
        }
}

/**
 * free_area_init_nodes - Initialise all pg_data_t and zone data
 * @max_zone_pfn: an array of max PFNs for each zone
 *
 * This will call free_area_init_node() for each active node in the system.
 * Using the page ranges provided by memblock_set_node(), the size of each
 * zone in each node and their holes is calculated. If the maximum PFN
 * between two adjacent zones match, it is assumed that the zone is empty.
 * For example, if arch_max_dma_pfn == arch_max_dma32_pfn, it is assumed
 * that arch_max_dma32_pfn has no pages. It is also assumed that a zone
 * starts where the previous one ended. For example, ZONE_DMA32 starts
 * at arch_max_dma_pfn.
 */
void __init free_area_init_nodes(unsigned long *max_zone_pfn)
{
        unsigned long start_pfn, end_pfn;
        int i, nid;

        /* Record where the zone boundaries are */
        memset(arch_zone_lowest_possible_pfn, 0,
                                sizeof(arch_zone_lowest_possible_pfn));
        memset(arch_zone_highest_possible_pfn, 0,
                                sizeof(arch_zone_highest_possible_pfn));

        start_pfn = find_min_pfn_with_active_regions();

        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (i == ZONE_MOVABLE)
                        continue;

                end_pfn = max(max_zone_pfn[i], start_pfn);
                arch_zone_lowest_possible_pfn[i] = start_pfn;
                arch_zone_highest_possible_pfn[i] = end_pfn;

                start_pfn = end_pfn;
        }
        arch_zone_lowest_possible_pfn[ZONE_MOVABLE] = 0;
        arch_zone_highest_possible_pfn[ZONE_MOVABLE] = 0;

        /* Find the PFNs that ZONE_MOVABLE begins at in each node */
        memset(zone_movable_pfn, 0, sizeof(zone_movable_pfn));
        find_zone_movable_pfns_for_nodes();

        /* Print out the zone ranges */
        pr_info("Zone ranges:\n");
        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (i == ZONE_MOVABLE)
                        continue;
                pr_info("  %-8s ", zone_names[i]);
                if (arch_zone_lowest_possible_pfn[i] ==
                                arch_zone_highest_possible_pfn[i])
                        pr_cont("empty\n");
                else
                        pr_cont("[mem %#018Lx-%#018Lx]\n",
                                (u64)arch_zone_lowest_possible_pfn[i]
                                        << PAGE_SHIFT,
                                ((u64)arch_zone_highest_possible_pfn[i]
                                        << PAGE_SHIFT) - 1);
        }

        /* Print out the PFNs ZONE_MOVABLE begins at in each node */
        pr_info("Movable zone start for each node\n");
        for (i = 0; i < MAX_NUMNODES; i++) {
                if (zone_movable_pfn[i])
                        pr_info("  Node %d: %#018Lx\n", i,
                               (u64)zone_movable_pfn[i] << PAGE_SHIFT);
        }

        /* Print out the early node map */
        pr_info("Early memory node ranges\n");
        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
                pr_info("  node %3d: [mem %#018Lx-%#018Lx]\n", nid,
                        (u64)start_pfn << PAGE_SHIFT,
                        ((u64)end_pfn << PAGE_SHIFT) - 1);

        /* Initialise every node */
        mminit_verify_pageflags_layout();
        setup_nr_node_ids();
        for_each_online_node(nid) {
                pg_data_t *pgdat = NODE_DATA(nid);
                free_area_init_node(nid, NULL,
                                find_min_pfn_for_node(nid), NULL);

                /* Any memory on that node */
                if (pgdat->node_present_pages)
                        node_set_state(nid, N_MEMORY);
                check_for_memory(pgdat, nid);
        }
}

static int __init cmdline_parse_core(char *p, unsigned long *core)
{
        unsigned long long coremem;
        if (!p)
                return -EINVAL;

        coremem = memparse(p, &p);
        *core = coremem >> PAGE_SHIFT;

        /* Paranoid check that UL is enough for the coremem value */
        WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);

        return 0;
}

/*
 * kernelcore=size sets the amount of memory for use for allocations that
 * cannot be reclaimed or migrated.
 */
static int __init cmdline_parse_kernelcore(char *p)
{
        /* parse kernelcore=mirror */
        if (parse_option_str(p, "mirror")) {
                mirrored_kernelcore = true;
                return 0;
        }

        return cmdline_parse_core(p, &required_kernelcore);
}

/*
 * movablecore=size sets the amount of memory for use for allocations that
 * can be reclaimed or migrated.
 */
static int __init cmdline_parse_movablecore(char *p)
{
        return cmdline_parse_core(p, &required_movablecore);
}

early_param("kernelcore", cmdline_parse_kernelcore);
early_param("movablecore", cmdline_parse_movablecore);

#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

void adjust_managed_page_count(struct page *page, long count)
{
        spin_lock(&managed_page_count_lock);
        page_zone(page)->managed_pages += count;
        totalram_pages += count;
#ifdef CONFIG_HIGHMEM
        if (PageHighMem(page))
                totalhigh_pages += count;
#endif
        spin_unlock(&managed_page_count_lock);
}
EXPORT_SYMBOL(adjust_managed_page_count);

unsigned long free_reserved_area(void *start, void *end, int poison, char *s)
{
        void *pos;
        unsigned long pages = 0;

        start = (void *)PAGE_ALIGN((unsigned long)start);
        end = (void *)((unsigned long)end & PAGE_MASK);
        for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
                if ((unsigned int)poison <= 0xFF)
                        memset(pos, poison, PAGE_SIZE);
                free_reserved_page(virt_to_page(pos));
        }

        if (pages && s)
                pr_info("Freeing %s memory: %ldK\n",
                        s, pages << (PAGE_SHIFT - 10));

        return pages;
}
EXPORT_SYMBOL(free_reserved_area);

#ifdef  CONFIG_HIGHMEM
void free_highmem_page(struct page *page)
{
        __free_reserved_page(page);
        totalram_pages++;
        page_zone(page)->managed_pages++;
        totalhigh_pages++;
}
#endif


void __init mem_init_print_info(const char *str)
{
        unsigned long physpages, codesize, datasize, rosize, bss_size;
        unsigned long init_code_size, init_data_size;

        physpages = get_num_physpages();
        codesize = _etext - _stext;
        datasize = _edata - _sdata;
        rosize = __end_rodata - __start_rodata;
        bss_size = __bss_stop - __bss_start;
        init_data_size = __init_end - __init_begin;
        init_code_size = _einittext - _sinittext;

        /*
         * Detect special cases and adjust section sizes accordingly:
         * 1) .init.* may be embedded into .data sections
         * 2) .init.text.* may be out of [__init_begin, __init_end],
         *    please refer to arch/tile/kernel/vmlinux.lds.S.
         * 3) .rodata.* may be embedded into .text or .data sections.
         */
#define adj_init_size(start, end, size, pos, adj) \
        do { \
                if (start <= pos && pos < end && size > adj) \
                        size -= adj; \
        } while (0)

        adj_init_size(__init_begin, __init_end, init_data_size,
                     _sinittext, init_code_size);
        adj_init_size(_stext, _etext, codesize, _sinittext, init_code_size);
        adj_init_size(_sdata, _edata, datasize, __init_begin, init_data_size);
        adj_init_size(_stext, _etext, codesize, __start_rodata, rosize);
        adj_init_size(_sdata, _edata, datasize, __start_rodata, rosize);

#undef  adj_init_size

        pr_info("Memory: %luK/%luK available (%luK kernel code, %luK rwdata, %luK rodata, %luK init, %luK bss, %luK reserved, %luK cma-reserved"
#ifdef  CONFIG_HIGHMEM
                ", %luK highmem"
#endif
                "%s%s)\n",
                nr_free_pages() << (PAGE_SHIFT - 10),
                physpages << (PAGE_SHIFT - 10),
                codesize >> 10, datasize >> 10, rosize >> 10,
                (init_data_size + init_code_size) >> 10, bss_size >> 10,
                (physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT - 10),
                totalcma_pages << (PAGE_SHIFT - 10),
#ifdef  CONFIG_HIGHMEM
                totalhigh_pages << (PAGE_SHIFT - 10),
#endif
                str ? ", " : "", str ? str : "");
}

/**
 * set_dma_reserve - set the specified number of pages reserved in the first zone
 * @new_dma_reserve: The number of pages to mark reserved
 *
 * The per-cpu batchsize and zone watermarks are determined by managed_pages.
 * In the DMA zone, a significant percentage may be consumed by kernel image
 * and other unfreeable allocations which can skew the watermarks badly. This
 * function may optionally be used to account for unfreeable pages in the
 * first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
 * smaller per-cpu batchsize.
 */
void __init set_dma_reserve(unsigned long new_dma_reserve)
{
        dma_reserve = new_dma_reserve;
}

void __init free_area_init(unsigned long *zones_size)
{
        free_area_init_node(0, zones_size,
                        __pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
}

static int page_alloc_cpu_notify(struct notifier_block *self,
                                 unsigned long action, void *hcpu)
{
        int cpu = (unsigned long)hcpu;

        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
                lru_add_drain_cpu(cpu);
                drain_pages(cpu);

                /*
                 * Spill the event counters of the dead processor
                 * into the current processors event counters.
                 * This artificially elevates the count of the current
                 * processor.
                 */
                vm_events_fold_cpu(cpu);

                /*
                 * Zero the differential counters of the dead processor
                 * so that the vm statistics are consistent.
                 *
                 * This is only okay since the processor is dead and cannot
                 * race with what we are doing.
                 */
                cpu_vm_stats_fold(cpu);
        }
        return NOTIFY_OK;
}

void __init page_alloc_init(void)
{
        hotcpu_notifier(page_alloc_cpu_notify, 0);
}

/*
 * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
 *      or min_free_kbytes changes.
 */
static void calculate_totalreserve_pages(void)
{
        struct pglist_data *pgdat;
        unsigned long reserve_pages = 0;
        enum zone_type i, j;

        for_each_online_pgdat(pgdat) {

                pgdat->totalreserve_pages = 0;

                for (i = 0; i < MAX_NR_ZONES; i++) {
                        struct zone *zone = pgdat->node_zones + i;
                        long max = 0;

                        /* Find valid and maximum lowmem_reserve in the zone */
                        for (j = i; j < MAX_NR_ZONES; j++) {
                                if (zone->lowmem_reserve[j] > max)
                                        max = zone->lowmem_reserve[j];
                        }

                        /* we treat the high watermark as reserved pages. */
                        max += high_wmark_pages(zone);

                        if (max > zone->managed_pages)
                                max = zone->managed_pages;

                        pgdat->totalreserve_pages += max;

                        reserve_pages += max;
                }
        }
        totalreserve_pages = reserve_pages;
}

/*
 * setup_per_zone_lowmem_reserve - called whenever
 *      sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
 *      has a correct pages reserved value, so an adequate number of
 *      pages are left in the zone after a successful __alloc_pages().
 */
static void setup_per_zone_lowmem_reserve(void)
{
        struct pglist_data *pgdat;
        enum zone_type j, idx;

        for_each_online_pgdat(pgdat) {
                for (j = 0; j < MAX_NR_ZONES; j++) {
                        struct zone *zone = pgdat->node_zones + j;
                        unsigned long managed_pages = zone->managed_pages;

                        zone->lowmem_reserve[j] = 0;

                        idx = j;
                        while (idx) {
                                struct zone *lower_zone;

                                idx--;

                                if (sysctl_lowmem_reserve_ratio[idx] < 1)
                                        sysctl_lowmem_reserve_ratio[idx] = 1;

                                lower_zone = pgdat->node_zones + idx;
                                lower_zone->lowmem_reserve[j] = managed_pages /
                                        sysctl_lowmem_reserve_ratio[idx];
                                managed_pages += lower_zone->managed_pages;
                        }
                }
        }

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

static void __setup_per_zone_wmarks(void)
{
        unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
        unsigned long lowmem_pages = 0;
        struct zone *zone;
        unsigned long flags;

        /* Calculate total number of !ZONE_HIGHMEM pages */
        for_each_zone(zone) {
                if (!is_highmem(zone))
                        lowmem_pages += zone->managed_pages;
        }

        for_each_zone(zone) {
                u64 tmp;

                spin_lock_irqsave(&zone->lock, flags);
                tmp = (u64)pages_min * zone->managed_pages;
                do_div(tmp, lowmem_pages);
                if (is_highmem(zone)) {
                        /*
                         * __GFP_HIGH and PF_MEMALLOC allocations usually don't
                         * need highmem pages, so cap pages_min to a small
                         * value here.
                         *
                         * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
                         * deltas control asynch page reclaim, and so should
                         * not be capped for highmem.
                         */
                        unsigned long min_pages;

                        min_pages = zone->managed_pages / 1024;
                        min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
                        zone->watermark[WMARK_MIN] = min_pages;
                } else {
                        /*
                         * If it's a lowmem zone, reserve a number of pages
                         * proportionate to the zone's size.
                         */
                        zone->watermark[WMARK_MIN] = tmp;
                }

                /*
                 * Set the kswapd watermarks distance according to the
                 * scale factor in proportion to available memory, but
                 * ensure a minimum size on small systems.
                 */
                tmp = max_t(u64, tmp >> 2,
                            mult_frac(zone->managed_pages,
                                      watermark_scale_factor, 10000));

                zone->watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
                zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;

                spin_unlock_irqrestore(&zone->lock, flags);
        }

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

/**
 * setup_per_zone_wmarks - called when min_free_kbytes changes
 * or when memory is hot-{added|removed}
 *
 * Ensures that the watermark[min,low,high] values for each zone are set
 * correctly with respect to min_free_kbytes.
 */
void setup_per_zone_wmarks(void)
{
        mutex_lock(&zonelists_mutex);
        __setup_per_zone_wmarks();
        mutex_unlock(&zonelists_mutex);
}

/*
 * Initialise min_free_kbytes.
 *
 * For small machines we want it small (128k min).  For large machines
 * we want it large (64MB max).  But it is not linear, because network
 * bandwidth does not increase linearly with machine size.  We use
 *
 *      min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
 *      min_free_kbytes = sqrt(lowmem_kbytes * 16)
 *
 * which yields
 *
 * 16MB:        512k
 * 32MB:        724k
 * 64MB:        1024k
 * 128MB:       1448k
 * 256MB:       2048k
 * 512MB:       2896k
 * 1024MB:      4096k
 * 2048MB:      5792k
 * 4096MB:      8192k
 * 8192MB:      11584k
 * 16384MB:     16384k
 */
int __meminit init_per_zone_wmark_min(void)
{
        unsigned long lowmem_kbytes;
        int new_min_free_kbytes;

        lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
        new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);

        if (new_min_free_kbytes > user_min_free_kbytes) {
                min_free_kbytes = new_min_free_kbytes;
                if (min_free_kbytes < 128)
                        min_free_kbytes = 128;
                if (min_free_kbytes > 65536)
                        min_free_kbytes = 65536;
        } else {
                pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
                                new_min_free_kbytes, user_min_free_kbytes);
        }
        setup_per_zone_wmarks();
        refresh_zone_stat_thresholds();
        setup_per_zone_lowmem_reserve();

#ifdef CONFIG_NUMA
        setup_min_unmapped_ratio();
        setup_min_slab_ratio();
#endif

        return 0;
}
core_initcall(init_per_zone_wmark_min)

/*
 * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
 *      that we can call two helper functions whenever min_free_kbytes
 *      changes.
 */
int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        if (write) {
                user_min_free_kbytes = min_free_kbytes;
                setup_per_zone_wmarks();
        }
        return 0;
}

int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        if (write)
                setup_per_zone_wmarks();

        return 0;
}

#ifdef CONFIG_NUMA
static void setup_min_unmapped_ratio(void)
{
        pg_data_t *pgdat;
        struct zone *zone;

        for_each_online_pgdat(pgdat)
                pgdat->min_unmapped_pages = 0;

        for_each_zone(zone)
                zone->zone_pgdat->min_unmapped_pages += (zone->managed_pages *
                                sysctl_min_unmapped_ratio) / 100;
}


int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        setup_min_unmapped_ratio();

        return 0;
}

static void setup_min_slab_ratio(void)
{
        pg_data_t *pgdat;
        struct zone *zone;

        for_each_online_pgdat(pgdat)
                pgdat->min_slab_pages = 0;

        for_each_zone(zone)
                zone->zone_pgdat->min_slab_pages += (zone->managed_pages *
                                sysctl_min_slab_ratio) / 100;
}

int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        int rc;

        rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (rc)
                return rc;

        setup_min_slab_ratio();

        return 0;
}
#endif

/*
 * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
 *      proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
 *      whenever sysctl_lowmem_reserve_ratio changes.
 *
 * The reserve ratio obviously has absolutely no relation with the
 * minimum watermarks. The lowmem reserve ratio can only make sense
 * if in function of the boot time zone sizes.
 */
int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        proc_dointvec_minmax(table, write, buffer, length, ppos);
        setup_per_zone_lowmem_reserve();
        return 0;
}

/*
 * percpu_pagelist_fraction - changes the pcp->high for each zone on each
 * cpu.  It is the fraction of total pages in each zone that a hot per cpu
 * pagelist can have before it gets flushed back to buddy allocator.
 */
int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
{
        struct zone *zone;
        int old_percpu_pagelist_fraction;
        int ret;

        mutex_lock(&pcp_batch_high_lock);
        old_percpu_pagelist_fraction = percpu_pagelist_fraction;

        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (!write || ret < 0)
                goto out;

        /* Sanity checking to avoid pcp imbalance */
        if (percpu_pagelist_fraction &&
            percpu_pagelist_fraction < MIN_PERCPU_PAGELIST_FRACTION) {
                percpu_pagelist_fraction = old_percpu_pagelist_fraction;
                ret = -EINVAL;
                goto out;
        }

        /* No change? */
        if (percpu_pagelist_fraction == old_percpu_pagelist_fraction)
                goto out;

        for_each_populated_zone(zone) {
                unsigned int cpu;

                for_each_possible_cpu(cpu)
                        pageset_set_high_and_batch(zone,
                                        per_cpu_ptr(zone->pageset, cpu));
        }
out:
        mutex_unlock(&pcp_batch_high_lock);
        return ret;
}

#ifdef CONFIG_NUMA
int hashdist = HASHDIST_DEFAULT;

static int __init set_hashdist(char *str)
{
        if (!str)
                return 0;
        hashdist = simple_strtoul(str, &str, 0);
        return 1;
}
__setup("hashdist=", set_hashdist);
#endif

#ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES
/*
 * Returns the number of pages that arch has reserved but
 * is not known to alloc_large_system_hash().
 */
static unsigned long __init arch_reserved_kernel_pages(void)
{
        return 0;
}
#endif

/*
 * allocate a large system hash table from bootmem
 * - it is assumed that the hash table must contain an exact power-of-2
 *   quantity of entries
 * - limit is the number of hash buckets, not the total allocation size
 */
void *__init alloc_large_system_hash(const char *tablename,
                                     unsigned long bucketsize,
                                     unsigned long numentries,
                                     int scale,
                                     int flags,
                                     unsigned int *_hash_shift,
                                     unsigned int *_hash_mask,
                                     unsigned long low_limit,
                                     unsigned long high_limit)
{
        unsigned long long max = high_limit;
        unsigned long log2qty, size;
        void *table = NULL;

        /* allow the kernel cmdline to have a say */
        if (!numentries) {
                /* round applicable memory size up to nearest megabyte */
                numentries = nr_kernel_pages;
                numentries -= arch_reserved_kernel_pages();

                /* It isn't necessary when PAGE_SIZE >= 1MB */
                if (PAGE_SHIFT < 20)
                        numentries = round_up(numentries, (1<<20)/PAGE_SIZE);

                /* limit to 1 bucket per 2^scale bytes of low memory */
                if (scale > PAGE_SHIFT)
                        numentries >>= (scale - PAGE_SHIFT);
                else
                        numentries <<= (PAGE_SHIFT - scale);

                /* Make sure we've got at least a 0-order allocation.. */
                if (unlikely(flags & HASH_SMALL)) {
                        /* Makes no sense without HASH_EARLY */
                        WARN_ON(!(flags & HASH_EARLY));
                        if (!(numentries >> *_hash_shift)) {
                                numentries = 1UL << *_hash_shift;
                                BUG_ON(!numentries);
                        }
                } else if (unlikely((numentries * bucketsize) < PAGE_SIZE))
                        numentries = PAGE_SIZE / bucketsize;
        }
        numentries = roundup_pow_of_two(numentries);

        /* limit allocation size to 1/16 total memory by default */
        if (max == 0) {
                max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
                do_div(max, bucketsize);
        }
        max = min(max, 0x80000000ULL);

        if (numentries < low_limit)
                numentries = low_limit;
        if (numentries > max)
                numentries = max;

        log2qty = ilog2(numentries);

        do {
                size = bucketsize << log2qty;
                if (flags & HASH_EARLY)
                        table = memblock_virt_alloc_nopanic(size, 0);
                else if (hashdist)
                        table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
                else {
                        /*
                         * If bucketsize is not a power-of-two, we may free
                         * some pages at the end of hash table which
                         * alloc_pages_exact() automatically does
                         */
                        if (get_order(size) < MAX_ORDER) {
                                table = alloc_pages_exact(size, GFP_ATOMIC);
                                kmemleak_alloc(table, size, 1, GFP_ATOMIC);
                        }
                }
        } while (!table && size > PAGE_SIZE && --log2qty);

        if (!table)
                panic("Failed to allocate %s hash table\n", tablename);

        pr_info("%s hash table entries: %ld (order: %d, %lu bytes)\n",
                tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size);

        if (_hash_shift)
                *_hash_shift = log2qty;
        if (_hash_mask)
                *_hash_mask = (1 << log2qty) - 1;

        return table;
}

/*
 * This function checks whether pageblock includes unmovable pages or not.
 * If @count is not zero, it is okay to include less @count unmovable pages
 *
 * PageLRU check without isolation or lru_lock could race so that
 * MIGRATE_MOVABLE block might include unmovable pages. It means you can't
 * expect this function should be exact.
 */
bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
                         bool skip_hwpoisoned_pages)
{
        unsigned long pfn, iter, found;
        int mt;

        /*
         * For avoiding noise data, lru_add_drain_all() should be called
         * If ZONE_MOVABLE, the zone never contains unmovable pages
         */
        if (zone_idx(zone) == ZONE_MOVABLE)
                return false;
        mt = get_pageblock_migratetype(page);
        if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt))
                return false;

        pfn = page_to_pfn(page);
        for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) {
                unsigned long check = pfn + iter;

                if (!pfn_valid_within(check))
                        continue;

                page = pfn_to_page(check);

                /*
                 * Hugepages are not in LRU lists, but they're movable.
                 * We need not scan over tail pages bacause we don't
                 * handle each tail page individually in migration.
                 */
                if (PageHuge(page)) {
                        iter = round_up(iter + 1, 1<<compound_order(page)) - 1;
                        continue;
                }

                /*
                 * We can't use page_count without pin a page
                 * because another CPU can free compound page.
                 * This check already skips compound tails of THP
                 * because their page->_refcount is zero at all time.
                 */
                if (!page_ref_count(page)) {
                        if (PageBuddy(page))
                                iter += (1 << page_order(page)) - 1;
                        continue;
                }

                /*
                 * The HWPoisoned page may be not in buddy system, and
                 * page_count() is not 0.
                 */
                if (skip_hwpoisoned_pages && PageHWPoison(page))
                        continue;

                if (!PageLRU(page))
                        found++;
                /*
                 * If there are RECLAIMABLE pages, we need to check
                 * it.  But now, memory offline itself doesn't call
                 * shrink_node_slabs() and it still to be fixed.
                 */
                /*
                 * If the page is not RAM, page_count()should be 0.
                 * we don't need more check. This is an _used_ not-movable page.
                 *
                 * The problematic thing here is PG_reserved pages. PG_reserved
                 * is set to both of a memory hole page and a _used_ kernel
                 * page at boot.
                 */
                if (found > count)
                        return true;
        }
        return false;
}

bool is_pageblock_removable_nolock(struct page *page)
{
        struct zone *zone;
        unsigned long pfn;

        /*
         * We have to be careful here because we are iterating over memory
         * sections which are not zone aware so we might end up outside of
         * the zone but still within the section.
         * We have to take care about the node as well. If the node is offline
         * its NODE_DATA will be NULL - see page_zone.
         */
        if (!node_online(page_to_nid(page)))
                return false;

        zone = page_zone(page);
        pfn = page_to_pfn(page);
        if (!zone_spans_pfn(zone, pfn))
                return false;

        return !has_unmovable_pages(zone, page, 0, true);
}

#if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA)

static unsigned long pfn_max_align_down(unsigned long pfn)
{
        return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
                             pageblock_nr_pages) - 1);
}

static unsigned long pfn_max_align_up(unsigned long pfn)
{
        return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
                                pageblock_nr_pages));
}

/* [start, end) must belong to a single zone. */
static int __alloc_contig_migrate_range(struct compact_control *cc,
                                        unsigned long start, unsigned long end)
{
        /* This function is based on compact_zone() from compaction.c. */
        unsigned long nr_reclaimed;
        unsigned long pfn = start;
        unsigned int tries = 0;
        int ret = 0;

        migrate_prep();

        while (pfn < end || !list_empty(&cc->migratepages)) {
                if (fatal_signal_pending(current)) {
                        ret = -EINTR;
                        break;
                }

                if (list_empty(&cc->migratepages)) {
                        cc->nr_migratepages = 0;
                        pfn = isolate_migratepages_range(cc, pfn, end);
                        if (!pfn) {
                                ret = -EINTR;
                                break;
                        }
                        tries = 0;
                } else if (++tries == 5) {
                        ret = ret < 0 ? ret : -EBUSY;
                        break;
                }

                nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
                                                        &cc->migratepages);
                cc->nr_migratepages -= nr_reclaimed;

                ret = migrate_pages(&cc->migratepages, alloc_migrate_target,
                                    NULL, 0, cc->mode, MR_CMA);
        }
        if (ret < 0) {
                putback_movable_pages(&cc->migratepages);
                return ret;
        }
        return 0;
}

/**
 * alloc_contig_range() -- tries to allocate given range of pages
 * @start:      start PFN to allocate
 * @end:        one-past-the-last PFN to allocate
 * @migratetype:        migratetype of the underlaying pageblocks (either
 *                      #MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
 *                      in range must have the same migratetype and it must
 *                      be either of the two.
 *
 * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
 * aligned, however it's the caller's responsibility to guarantee that
 * we are the only thread that changes migrate type of pageblocks the
 * pages fall in.
 *
 * The PFN range must belong to a single zone.
 *
 * Returns zero on success or negative error code.  On success all
 * pages which PFN is in [start, end) are allocated for the caller and
 * need to be freed with free_contig_range().
 */
int alloc_contig_range(unsigned long start, unsigned long end,
                       unsigned migratetype)
{
        unsigned long outer_start, outer_end;
        unsigned int order;
        int ret = 0;

        struct compact_control cc = {
                .nr_migratepages = 0,
                .order = -1,
                .zone = page_zone(pfn_to_page(start)),
                .mode = MIGRATE_SYNC,
                .ignore_skip_hint = true,
        };
        INIT_LIST_HEAD(&cc.migratepages);

        /*
         * What we do here is we mark all pageblocks in range as
         * MIGRATE_ISOLATE.  Because pageblock and max order pages may
         * have different sizes, and due to the way page allocator
         * work, we align the range to biggest of the two pages so
         * that page allocator won't try to merge buddies from
         * different pageblocks and change MIGRATE_ISOLATE to some
         * other migration type.
         *
         * Once the pageblocks are marked as MIGRATE_ISOLATE, we
         * migrate the pages from an unaligned range (ie. pages that
         * we are interested in).  This will put all the pages in
         * range back to page allocator as MIGRATE_ISOLATE.
         *
         * When this is done, we take the pages in range from page
         * allocator removing them from the buddy system.  This way
         * page allocator will never consider using them.
         *
         * This lets us mark the pageblocks back as
         * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
         * aligned range but not in the unaligned, original range are
         * put back to page allocator so that buddy can use them.
         */

        ret = start_isolate_page_range(pfn_max_align_down(start),
                                       pfn_max_align_up(end), migratetype,
                                       false);
        if (ret)
                return ret;

        /*
         * In case of -EBUSY, we'd like to know which page causes problem.
         * So, just fall through. test_pages_isolated() has a tracepoint
         * which will report the busy page.
         *
         * It is possible that busy pages could become available before
         * the call to test_pages_isolated, and the range will actually be
         * allocated.  So, if we fall through be sure to clear ret so that
         * -EBUSY is not accidentally used or returned to caller.
         */
        ret = __alloc_contig_migrate_range(&cc, start, end);
        if (ret && ret != -EBUSY)
                goto done;
        ret =0;

        /*
         * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
         * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
         * more, all pages in [start, end) are free in page allocator.
         * What we are going to do is to allocate all pages from
         * [start, end) (that is remove them from page allocator).
         *
         * The only problem is that pages at the beginning and at the
         * end of interesting range may be not aligned with pages that
         * page allocator holds, ie. they can be part of higher order
         * pages.  Because of this, we reserve the bigger range and
         * once this is done free the pages we are not interested in.
         *
         * We don't have to hold zone->lock here because the pages are
         * isolated thus they won't get removed from buddy.
         */

        lru_add_drain_all();
        drain_all_pages(cc.zone);

        order = 0;
        outer_start = start;
        while (!PageBuddy(pfn_to_page(outer_start))) {
                if (++order >= MAX_ORDER) {
                        outer_start = start;
                        break;
                }
                outer_start &= ~0UL << order;
        }

        if (outer_start != start) {
                order = page_order(pfn_to_page(outer_start));

                /*
                 * outer_start page could be small order buddy page and
                 * it doesn't include start page. Adjust outer_start
                 * in this case to report failed page properly
                 * on tracepoint in test_pages_isolated()
                 */
                if (outer_start + (1UL << order) <= start)
                        outer_start = start;
        }

        /* Make sure the range is really isolated. */
        if (test_pages_isolated(outer_start, end, false)) {
                pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n",
                        __func__, outer_start, end);
                ret = -EBUSY;
                goto done;
        }

        /* Grab isolated pages from freelists. */
        outer_end = isolate_freepages_range(&cc, outer_start, end);
        if (!outer_end) {
                ret = -EBUSY;
                goto done;
        }

        /* Free head and tail (if any) */
        if (start != outer_start)
                free_contig_range(outer_start, start - outer_start);
        if (end != outer_end)
                free_contig_range(end, outer_end - end);

done:
        undo_isolate_page_range(pfn_max_align_down(start),
                                pfn_max_align_up(end), migratetype);
        return ret;
}

void free_contig_range(unsigned long pfn, unsigned nr_pages)
{
        unsigned int count = 0;

        for (; nr_pages--; pfn++) {
                struct page *page = pfn_to_page(pfn);

                count += page_count(page) != 1;
                __free_page(page);
        }
        WARN(count != 0, "%d pages are still in use!\n", count);
}
#endif

#ifdef CONFIG_MEMORY_HOTPLUG
/*
 * The zone indicated has a new number of managed_pages; batch sizes and percpu
 * page high values need to be recalulated.
 */
void __meminit zone_pcp_update(struct zone *zone)
{
        unsigned cpu;
        mutex_lock(&pcp_batch_high_lock);
        for_each_possible_cpu(cpu)
                pageset_set_high_and_batch(zone,
                                per_cpu_ptr(zone->pageset, cpu));
        mutex_unlock(&pcp_batch_high_lock);
}
#endif

void zone_pcp_reset(struct zone *zone)
{
        unsigned long flags;
        int cpu;
        struct per_cpu_pageset *pset;

        /* avoid races with drain_pages()  */
        local_irq_save(flags);
        if (zone->pageset != &boot_pageset) {
                for_each_online_cpu(cpu) {
                        pset = per_cpu_ptr(zone->pageset, cpu);
                        drain_zonestat(zone, pset);
                }
                free_percpu(zone->pageset);
                zone->pageset = &boot_pageset;
        }
        local_irq_restore(flags);
}

#ifdef CONFIG_MEMORY_HOTREMOVE
/*
 * All pages in the range must be in a single zone and isolated
 * before calling this.
 */
void
__offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
{
        struct page *page;
        struct zone *zone;
        unsigned int order, i;
        unsigned long pfn;
        unsigned long flags;
        /* find the first valid pfn */
        for (pfn = start_pfn; pfn < end_pfn; pfn++)
                if (pfn_valid(pfn))
                        break;
        if (pfn == end_pfn)
                return;
        zone = page_zone(pfn_to_page(pfn));
        spin_lock_irqsave(&zone->lock, flags);
        pfn = start_pfn;
        while (pfn < end_pfn) {
                if (!pfn_valid(pfn)) {
                        pfn++;
                        continue;
                }
                page = pfn_to_page(pfn);
                /*
                 * The HWPoisoned page may be not in buddy system, and
                 * page_count() is not 0.
                 */
                if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
                        pfn++;
                        SetPageReserved(page);
                        continue;
                }

                BUG_ON(page_count(page));
                BUG_ON(!PageBuddy(page));
                order = page_order(page);
#ifdef CONFIG_DEBUG_VM
                pr_info("remove from free list %lx %d %lx\n",
                        pfn, 1 << order, end_pfn);
#endif
                list_del(&page->lru);
                rmv_page_order(page);
                zone->free_area[order].nr_free--;
                for (i = 0; i < (1 << order); i++)
                        SetPageReserved((page+i));
                pfn += (1 << order);
        }
        spin_unlock_irqrestore(&zone->lock, flags);
}
#endif

bool is_free_buddy_page(struct page *page)
{
        struct zone *zone = page_zone(page);
        unsigned long pfn = page_to_pfn(page);
        unsigned long flags;
        unsigned int order;

        spin_lock_irqsave(&zone->lock, flags);
        for (order = 0; order < MAX_ORDER; order++) {
                struct page *page_head = page - (pfn & ((1 << order) - 1));

                if (PageBuddy(page_head) && page_order(page_head) >= order)
                        break;
        }
        spin_unlock_irqrestore(&zone->lock, flags);

        return order < MAX_ORDER;
}