/*
 *  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/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/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_cgroup.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-debug-flags.h>
#include <linux/hugetlb.h>
#include <linux/sched/rt.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

/*
 * 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;
/*
 * When calculating the number of globally allowed dirty pages, there
 * is a certain number of per-zone reserves that should not be
 * considered dirtyable memory.  This is the sum of those reserves
 * over all existing zones that contribute dirtyable memory.
 */
unsigned long dirty_balance_reserve __read_mostly;

int percpu_pagelist_fraction;
gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;

#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_IOFS;
}

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

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
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 (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",
};

int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;

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];

/* 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;

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);
}

bool oom_killer_disabled __read_mostly;

#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;

        /* Don't complain about poisoned pages */
        if (PageHWPoison(page)) {
                page_mapcount_reset(page); /* remove PageBuddy */
                return;
        }

        /*
         * 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) {
                        printk(KERN_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;

        printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
                current->comm, page_to_pfn(page));
        dump_page_badflags(page, reason, bad_flags);

        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".
 *
 * The remaining PAGE_SIZE pages are called "tail pages".
 *
 * All pages have PG_compound set.  All tail pages have their ->first_page
 * pointing at the head page.
 *
 * The first tail page's ->lru.next holds the address of the compound page's
 * put_page() function.  Its ->lru.prev holds the order of allocation.
 * This usage means that zero-order pages may not be compound.
 */

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

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

        set_compound_page_dtor(page, free_compound_page);
        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->first_page = page;
                /* Make sure p->first_page is always valid for PageTail() */
                smp_wmb();
                __SetPageTail(p);
        }
}

/* update __split_huge_page_refcount if you change this function */
static int destroy_compound_page(struct page *page, unsigned long order)
{
        int i;
        int nr_pages = 1 << order;
        int bad = 0;

        if (unlikely(compound_order(page) != order)) {
                bad_page(page, "wrong compound order", 0);
                bad++;
        }

        __ClearPageHead(page);

        for (i = 1; i < nr_pages; i++) {
                struct page *p = page + i;

                if (unlikely(!PageTail(p))) {
                        bad_page(page, "PageTail not set", 0);
                        bad++;
                } else if (unlikely(p->first_page != page)) {
                        bad_page(page, "first_page not consistent", 0);
                        bad++;
                }
                __ClearPageTail(p);
        }

        return bad;
}

static inline void prep_zero_page(struct page *page, unsigned int order,
                                                        gfp_t gfp_flags)
{
        int i;

        /*
         * clear_highpage() will use KM_USER0, so it's a bug to use __GFP_ZERO
         * and __GFP_HIGHMEM from hard or soft interrupt context.
         */
        VM_BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());
        for (i = 0; i < (1 << order); i++)
                clear_highpage(page + i);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
unsigned int _debug_guardpage_minorder;

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

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

static inline void set_page_guard_flag(struct page *page)
{
        __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags);
}

static inline void clear_page_guard_flag(struct page *page)
{
        __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags);
}
#else
static inline void set_page_guard_flag(struct page *page) { }
static inline void clear_page_guard_flag(struct page *page) { }
#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) {
                VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);

                if (page_zone_id(page) != page_zone_id(buddy))
                        return 0;

                return 1;
        }

        if (PageBuddy(buddy) && page_order(buddy) == order) {
                VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);

                /*
                 * 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;

                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;
        int max_order = MAX_ORDER;

        VM_BUG_ON(!zone_is_initialized(zone));

        if (unlikely(PageCompound(page)))
                if (unlikely(destroy_compound_page(page, order)))
                        return;

        VM_BUG_ON(migratetype == -1);
        if (is_migrate_isolate(migratetype)) {
                /*
                 * We restrict max order of merging to prevent merge
                 * between freepages on isolate pageblock and normal
                 * pageblock. Without this, pageblock isolation
                 * could cause incorrect freepage accounting.
                 */
                max_order = min(MAX_ORDER, pageblock_order + 1);
        } else {
                __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);

        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))
                        break;
                /*
                 * 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_flag(buddy);
                        set_page_private(buddy, 0);
                        if (!is_migrate_isolate(migratetype)) {
                                __mod_zone_freepage_state(zone, 1 << 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++;
        }
        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++;
}

static inline int free_pages_check(struct page *page)
{
        const char *bad_reason = NULL;
        unsigned long bad_flags = 0;

        if (unlikely(page_mapcount(page)))
                bad_reason = "nonzero mapcount";
        if (unlikely(page->mapping != NULL))
                bad_reason = "non-NULL mapping";
        if (unlikely(atomic_read(&page->_count) != 0))
                bad_reason = "nonzero _count";
        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;
        }
        if (unlikely(mem_cgroup_bad_page_check(page)))
                bad_reason = "cgroup check failed";
        if (unlikely(bad_reason)) {
                bad_page(page, bad_reason, bad_flags);
                return 1;
        }
        page_cpupid_reset_last(page);
        if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
                page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
        return 0;
}

/*
 * 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;
        int to_free = count;
        unsigned long nr_scanned;

        spin_lock(&zone->lock);
        nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
        if (nr_scanned)
                __mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);

        while (to_free) {
                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 = to_free;

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

                        page = list_entry(list->prev, struct page, lru);
                        /* must delete as __free_one_page list manipulates */
                        list_del(&page->lru);
                        mt = get_freepage_migratetype(page);
                        if (unlikely(has_isolate_pageblock(zone)))
                                mt = get_pageblock_migratetype(page);

                        /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
                        __free_one_page(page, page_to_pfn(page), zone, 0, mt);
                        trace_mm_page_pcpu_drain(page, 0, mt);
                } while (--to_free && --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 = zone_page_state(zone, NR_PAGES_SCANNED);
        if (nr_scanned)
                __mod_zone_page_state(zone, 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 bool free_pages_prepare(struct page *page, unsigned int order)
{
        int i;
        int bad = 0;

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

        if (PageAnon(page))
                page->mapping = NULL;
        for (i = 0; i < (1 << order); i++)
                bad += free_pages_check(page + i);
        if (bad)
                return false;

        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_map_pages(page, 1 << order, 0);

        return true;
}

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))
                return;

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

void __init __free_pages_bootmem(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);
}

#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]);

#ifdef CONFIG_DEBUG_PAGEALLOC
                if (high < debug_guardpage_minorder()) {
                        /*
                         * 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
                         */
                        INIT_LIST_HEAD(&page[size].lru);
                        set_page_guard_flag(&page[size]);
                        set_page_private(&page[size], high);
                        /* Guard pages are not available for any usage */
                        __mod_zone_freepage_state(zone, -(1 << high),
                                                  migratetype);
                        continue;
                }
#endif
                list_add(&page[size].lru, &area->free_list[migratetype]);
                area->nr_free++;
                set_page_order(&page[size], high);
        }
}

/*
 * This page is about to be returned from the page allocator
 */
static inline int check_new_page(struct page *page)
{
        const char *bad_reason = NULL;
        unsigned long bad_flags = 0;

        if (unlikely(page_mapcount(page)))
                bad_reason = "nonzero mapcount";
        if (unlikely(page->mapping != NULL))
                bad_reason = "non-NULL mapping";
        if (unlikely(atomic_read(&page->_count) != 0))
                bad_reason = "nonzero _count";
        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;
        }
        if (unlikely(mem_cgroup_bad_page_check(page)))
                bad_reason = "cgroup check failed";
        if (unlikely(bad_reason)) {
                bad_page(page, bad_reason, bad_flags);
                return 1;
        }
        return 0;
}

static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags)
{
        int i;

        for (i = 0; i < (1 << order); i++) {
                struct page *p = page + i;
                if (unlikely(check_new_page(p)))
                        return 1;
        }

        set_page_private(page, 0);
        set_page_refcounted(page);

        arch_alloc_page(page, order);
        kernel_map_pages(page, 1 << order, 1);

        if (gfp_flags & __GFP_ZERO)
                prep_zero_page(page, order, gfp_flags);

        if (order && (gfp_flags & __GFP_COMP))
                prep_compound_page(page, order);

        return 0;
}

/*
 * 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]);
                if (list_empty(&area->free_list[migratetype]))
                        continue;

                page = list_entry(area->free_list[migratetype].next,
                                                        struct page, lru);
                list_del(&page->lru);
                rmv_page_order(page);
                area->nr_free--;
                expand(zone, page, order, current_order, area, migratetype);
                set_freepage_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_RESERVE },
        [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,     MIGRATE_RESERVE },
#ifdef CONFIG_CMA
        [MIGRATE_MOVABLE]     = { MIGRATE_CMA,         MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
        [MIGRATE_CMA]         = { MIGRATE_RESERVE }, /* Never used */
#else
        [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,   MIGRATE_RESERVE },
#endif
        [MIGRATE_RESERVE]     = { MIGRATE_RESERVE }, /* Never used */
#ifdef CONFIG_MEMORY_ISOLATION
        [MIGRATE_ISOLATE]     = { MIGRATE_RESERVE }, /* Never used */
#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 long 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;) {
                /* Make sure we are not inadvertently changing nodes */
                VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);

                if (!pfn_valid_within(page_to_pfn(page))) {
                        page++;
                        continue;
                }

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

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

/*
 * If breaking a large block of pages, move all free pages to the preferred
 * allocation list. If falling back for a reclaimable kernel allocation, be
 * more aggressive about taking ownership of free pages.
 *
 * On the other hand, never change migration type of MIGRATE_CMA pageblocks
 * nor move CMA pages to different free lists. We don't want unmovable pages
 * to be allocated from MIGRATE_CMA areas.
 *
 * Returns the new migratetype of the pageblock (or the same old migratetype
 * if it was unchanged).
 */
static int try_to_steal_freepages(struct zone *zone, struct page *page,
                                  int start_type, int fallback_type)
{
        int current_order = page_order(page);

        /*
         * When borrowing from MIGRATE_CMA, we need to release the excess
         * buddy pages to CMA itself. We also ensure the freepage_migratetype
         * is set to CMA so it is returned to the correct freelist in case
         * the page ends up being not actually allocated from the pcp lists.
         */
        if (is_migrate_cma(fallback_type))
                return fallback_type;

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

        if (current_order >= pageblock_order / 2 ||
            start_type == MIGRATE_RECLAIMABLE ||
            page_group_by_mobility_disabled) {
                int pages;

                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);
                        return start_type;
                }

        }

        return fallback_type;
}

/* 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 migratetype, new_type, i;

        /* 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) {
                for (i = 0;; i++) {
                        migratetype = fallbacks[start_migratetype][i];

                        /* MIGRATE_RESERVE handled later if necessary */
                        if (migratetype == MIGRATE_RESERVE)
                                break;

                        area = &(zone->free_area[current_order]);
                        if (list_empty(&area->free_list[migratetype]))
                                continue;

                        page = list_entry(area->free_list[migratetype].next,
                                        struct page, lru);
                        area->nr_free--;

                        new_type = try_to_steal_freepages(zone, page,
                                                          start_migratetype,
                                                          migratetype);

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

                        expand(zone, page, order, current_order, area,
                               new_type);
                        /* The freepage_migratetype may differ from pageblock's
                         * migratetype depending on the decisions in
                         * try_to_steal_freepages. This is OK as long as it does
                         * not differ for MIGRATE_CMA type.
                         */
                        set_freepage_migratetype(page, new_type);

                        trace_mm_page_alloc_extfrag(page, order, current_order,
                                start_migratetype, migratetype, new_type);

                        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;

retry_reserve:
        page = __rmqueue_smallest(zone, order, migratetype);

        if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
                page = __rmqueue_fallback(zone, order, migratetype);

                /*
                 * Use MIGRATE_RESERVE rather than fail an allocation. goto
                 * is used because __rmqueue_smallest is an inline function
                 * and we want just one call site
                 */
                if (!page) {
                        migratetype = MIGRATE_RESERVE;
                        goto retry_reserve;
                }
        }

        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;

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

                /*
                 * 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;
                if (is_migrate_cma(get_freepage_migratetype(page)))
                        __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
                                              -(1 << order));
        }
        __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
        spin_unlock(&zone->lock);
        return i;
}

#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 = ACCESS_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 pages of 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)
{
        unsigned long flags;
        struct zone *zone;

        for_each_populated_zone(zone) {
                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);
        }
}

/*
 * Spill all of this CPU's per-cpu pages back into the buddy allocator.
 */
void drain_local_pages(void *arg)
{
        drain_pages(smp_processor_id());
}

/*
 * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
 *
 * 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(void)
{
        int cpu;
        struct per_cpu_pageset *pcp;
        struct zone *zone;

        /*
         * 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) {
                bool has_pcps = false;
                for_each_populated_zone(zone) {
                        pcp = per_cpu_ptr(zone->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, drain_local_pages, NULL, 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 list_head *curr;

        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)) {
                        struct page *page = pfn_to_page(pfn);

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

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

                        pfn = page_to_pfn(list_entry(curr, struct page, lru));
                        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_pages_prepare(page, 0))
                return;

        migratetype = get_pfnblock_migratetype(page, pfn);
        set_freepage_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 = ACCESS_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);
}
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 */
                watermark = low_wmark_pages(zone) + (1 << order);
                if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
                        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 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;
}

/*
 * Similar to split_page except the page is already free. As this is only
 * being used for migration, the migratetype of the block also changes.
 * As this is called with interrupts disabled, the caller is responsible
 * for calling arch_alloc_page() and kernel_map_page() after interrupts
 * are enabled.
 *
 * Note: this is probably too low level an operation for use in drivers.
 * Please consult with lkml before using this in your driver.
 */
int split_free_page(struct page *page)
{
        unsigned int order;
        int nr_pages;

        order = page_order(page);

        nr_pages = __isolate_free_page(page, order);
        if (!nr_pages)
                return 0;

        /* Split into individual pages */
        set_page_refcounted(page);
        split_page(page, order);
        return nr_pages;
}

/*
 * Really, prep_compound_page() should be called from __rmqueue_bulk().  But
 * we cheat by calling it from here, in the order > 0 path.  Saves a branch
 * or two.
 */
static inline
struct page *buffered_rmqueue(struct zone *preferred_zone,
                        struct zone *zone, unsigned int order,
                        gfp_t gfp_flags, int migratetype)
{
        unsigned long flags;
        struct page *page;
        bool cold = ((gfp_flags & __GFP_COLD) != 0);

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

                local_irq_save(flags);
                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_entry(list->prev, struct page, lru);
                else
                        page = list_entry(list->next, struct page, lru);

                list_del(&page->lru);
                pcp->count--;
        } else {
                if (unlikely(gfp_flags & __GFP_NOFAIL)) {
                        /*
                         * __GFP_NOFAIL is not to be used in new code.
                         *
                         * All __GFP_NOFAIL callers should be fixed so that they
                         * properly detect and handle allocation failures.
                         *
                         * We most definitely don't want callers attempting to
                         * allocate greater than order-1 page units with
                         * __GFP_NOFAIL.
                         */
                        WARN_ON_ONCE(order > 1);
                }
                spin_lock_irqsave(&zone->lock, flags);
                page = __rmqueue(zone, order, migratetype);
                spin_unlock(&zone->lock);
                if (!page)
                        goto failed;
                __mod_zone_freepage_state(zone, -(1 << order),
                                          get_freepage_migratetype(page));
        }

        __mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
        if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0 &&
            !test_bit(ZONE_FAIR_DEPLETED, &zone->flags))
                set_bit(ZONE_FAIR_DEPLETED, &zone->flags);

        __count_zone_vm_events(PGALLOC, zone, 1 << order);
        zone_statistics(preferred_zone, zone, gfp_flags);
        local_irq_restore(flags);

        VM_BUG_ON_PAGE(bad_range(zone, page), page);
        if (prep_new_page(page, order, gfp_flags))
                goto again;
        return page;

failed:
        local_irq_restore(flags);
        return NULL;
}

#ifdef CONFIG_FAIL_PAGE_ALLOC

static struct {
        struct fault_attr attr;

        u32 ignore_gfp_highmem;
        u32 ignore_gfp_wait;
        u32 min_order;
} fail_page_alloc = {
        .attr = FAULT_ATTR_INITIALIZER,
        .ignore_gfp_wait = 1,
        .ignore_gfp_highmem = 1,
        .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_wait && (gfp_mask & __GFP_WAIT))
                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_wait))
                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 pages are above 'mark'. This takes into account the order
 * of the allocation.
 */
static bool __zone_watermark_ok(struct zone *z, unsigned int order,
                        unsigned long mark, int classzone_idx, int alloc_flags,
                        long free_pages)
{
        /* free_pages my go negative - that's OK */
        long min = mark;
        int o;
        long free_cma = 0;

        free_pages -= (1 << order) - 1;
        if (alloc_flags & ALLOC_HIGH)
                min -= min / 2;
        if (alloc_flags & ALLOC_HARDER)
                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_cma = zone_page_state(z, NR_FREE_CMA_PAGES);
#endif

        if (free_pages - free_cma <= min + z->lowmem_reserve[classzone_idx])
                return false;
        for (o = 0; o < order; o++) {
                /* At the next order, this order's pages become unavailable */
                free_pages -= z->free_area[o].nr_free << o;

                /* Require fewer higher order pages to be free */
                min >>= 1;

                if (free_pages <= min)
                        return false;
        }
        return true;
}

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

bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
                        unsigned long mark, int classzone_idx, int alloc_flags)
{
        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, alloc_flags,
                                                                free_pages);
}

#ifdef CONFIG_NUMA
/*
 * zlc_setup - Setup for "zonelist cache".  Uses cached zone data to
 * skip over zones that are not allowed by the cpuset, or that have
 * been recently (in last second) found to be nearly full.  See further
 * comments in mmzone.h.  Reduces cache footprint of zonelist scans
 * that have to skip over a lot of full or unallowed zones.
 *
 * If the zonelist cache is present in the passed zonelist, then
 * returns a pointer to the allowed node mask (either the current
 * tasks mems_allowed, or node_states[N_MEMORY].)
 *
 * If the zonelist cache is not available for this zonelist, does
 * nothing and returns NULL.
 *
 * If the fullzones BITMAP in the zonelist cache is stale (more than
 * a second since last zap'd) then we zap it out (clear its bits.)
 *
 * We hold off even calling zlc_setup, until after we've checked the
 * first zone in the zonelist, on the theory that most allocations will
 * be satisfied from that first zone, so best to examine that zone as
 * quickly as we can.
 */
static nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
{
        struct zonelist_cache *zlc;     /* cached zonelist speedup info */
        nodemask_t *allowednodes;       /* zonelist_cache approximation */

        zlc = zonelist->zlcache_ptr;
        if (!zlc)
                return NULL;

        if (time_after(jiffies, zlc->last_full_zap + HZ)) {
                bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
                zlc->last_full_zap = jiffies;
        }

        allowednodes = !in_interrupt() && (alloc_flags & ALLOC_CPUSET) ?
                                        &cpuset_current_mems_allowed :
                                        &node_states[N_MEMORY];
        return allowednodes;
}

/*
 * Given 'z' scanning a zonelist, run a couple of quick checks to see
 * if it is worth looking at further for free memory:
 *  1) Check that the zone isn't thought to be full (doesn't have its
 *     bit set in the zonelist_cache fullzones BITMAP).
 *  2) Check that the zones node (obtained from the zonelist_cache
 *     z_to_n[] mapping) is allowed in the passed in allowednodes mask.
 * Return true (non-zero) if zone is worth looking at further, or
 * else return false (zero) if it is not.
 *
 * This check -ignores- the distinction between various watermarks,
 * such as GFP_HIGH, GFP_ATOMIC, PF_MEMALLOC, ...  If a zone is
 * found to be full for any variation of these watermarks, it will
 * be considered full for up to one second by all requests, unless
 * we are so low on memory on all allowed nodes that we are forced
 * into the second scan of the zonelist.
 *
 * In the second scan we ignore this zonelist cache and exactly
 * apply the watermarks to all zones, even it is slower to do so.
 * We are low on memory in the second scan, and should leave no stone
 * unturned looking for a free page.
 */
static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zoneref *z,
                                                nodemask_t *allowednodes)
{
        struct zonelist_cache *zlc;     /* cached zonelist speedup info */
        int i;                          /* index of *z in zonelist zones */
        int n;                          /* node that zone *z is on */

        zlc = zonelist->zlcache_ptr;
        if (!zlc)
                return 1;

        i = z - zonelist->_zonerefs;
        n = zlc->z_to_n[i];

        /* This zone is worth trying if it is allowed but not full */
        return node_isset(n, *allowednodes) && !test_bit(i, zlc->fullzones);
}

/*
 * Given 'z' scanning a zonelist, set the corresponding bit in
 * zlc->fullzones, so that subsequent attempts to allocate a page
 * from that zone don't waste time re-examining it.
 */
static void zlc_mark_zone_full(struct zonelist *zonelist, struct zoneref *z)
{
        struct zonelist_cache *zlc;     /* cached zonelist speedup info */
        int i;                          /* index of *z in zonelist zones */

        zlc = zonelist->zlcache_ptr;
        if (!zlc)
                return;

        i = z - zonelist->_zonerefs;

        set_bit(i, zlc->fullzones);
}

/*
 * clear all zones full, called after direct reclaim makes progress so that
 * a zone that was recently full is not skipped over for up to a second
 */
static void zlc_clear_zones_full(struct zonelist *zonelist)
{
        struct zonelist_cache *zlc;     /* cached zonelist speedup info */

        zlc = zonelist->zlcache_ptr;
        if (!zlc)
                return;

        bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
}

static bool zone_local(struct zone *local_zone, struct zone *zone)
{
        return local_zone->node == zone->node;
}

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 nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
{
        return NULL;
}

static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zoneref *z,
                                nodemask_t *allowednodes)
{
        return 1;
}

static void zlc_mark_zone_full(struct zonelist *zonelist, struct zoneref *z)
{
}

static void zlc_clear_zones_full(struct zonelist *zonelist)
{
}

static bool zone_local(struct zone *local_zone, struct zone *zone)
{
        return true;
}

static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
        return true;
}

#endif  /* CONFIG_NUMA */

static void reset_alloc_batches(struct zone *preferred_zone)
{
        struct zone *zone = preferred_zone->zone_pgdat->node_zones;

        do {
                mod_zone_page_state(zone, NR_ALLOC_BATCH,
                        high_wmark_pages(zone) - low_wmark_pages(zone) -
                        atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
                clear_bit(ZONE_FAIR_DEPLETED, &zone->flags);
        } while (zone++ != preferred_zone);
}

/*
 * get_page_from_freelist goes through the zonelist trying to allocate
 * a page.
 */
static struct page *
get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
                struct zonelist *zonelist, int high_zoneidx, int alloc_flags,
                struct zone *preferred_zone, int classzone_idx, int migratetype)
{
        struct zoneref *z;
        struct page *page = NULL;
        struct zone *zone;
        nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
        int zlc_active = 0;             /* set if using zonelist_cache */
        int did_zlc_setup = 0;          /* just call zlc_setup() one time */
        bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
                                (gfp_mask & __GFP_WRITE);
        int nr_fair_skipped = 0;
        bool zonelist_rescan;

zonelist_scan:
        zonelist_rescan = false;

        /*
         * Scan zonelist, looking for a zone with enough free.
         * See also __cpuset_node_allowed_softwall() comment in kernel/cpuset.c.
         */
        for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                                high_zoneidx, nodemask) {
                unsigned long mark;

                if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
                        !zlc_zone_worth_trying(zonelist, z, allowednodes))
                                continue;
                if (cpusets_enabled() &&
                        (alloc_flags & ALLOC_CPUSET) &&
                        !cpuset_zone_allowed_softwall(zone, gfp_mask))
                                continue;
                /*
                 * Distribute pages in proportion to the individual
                 * zone size to ensure fair page aging.  The zone a
                 * page was allocated in should have no effect on the
                 * time the page has in memory before being reclaimed.
                 */
                if (alloc_flags & ALLOC_FAIR) {
                        if (!zone_local(preferred_zone, zone))
                                break;
                        if (test_bit(ZONE_FAIR_DEPLETED, &zone->flags)) {
                                nr_fair_skipped++;
                                continue;
                        }
                }
                /*
                 * When allocating a page cache page for writing, we
                 * want to get it from a zone that is within its dirty
                 * limit, such that no single zone holds more than its
                 * proportional share of globally allowed dirty pages.
                 * The dirty limits take into account the zone's
                 * lowmem reserves and high watermark so that kswapd
                 * should be able to balance it without having to
                 * write pages from its LRU list.
                 *
                 * This may look like it could increase pressure on
                 * lower zones by failing allocations in higher zones
                 * before they are full.  But the pages that do spill
                 * over are limited as the lower zones are protected
                 * by this very same mechanism.  It should not become
                 * a practical burden to them.
                 *
                 * XXX: For now, allow allocations to potentially

                 * exceed the per-zone dirty limit in the slowpath
                 * (ALLOC_WMARK_LOW unset) before going into reclaim,
                 * which is important when on a NUMA setup the allowed
                 * zones are together not big enough to reach the
                 * global limit.  The proper fix for these situations
                 * will require awareness of zones in the
                 * dirty-throttling and the flusher threads.
                 */
                if (consider_zone_dirty && !zone_dirty_ok(zone))
                        continue;

                mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
                if (!zone_watermark_ok(zone, order, mark,
                                       classzone_idx, 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 (IS_ENABLED(CONFIG_NUMA) &&
                                        !did_zlc_setup && nr_online_nodes > 1) {
                                /*
                                 * we do zlc_setup if there are multiple nodes
                                 * and before considering the first zone allowed
                                 * by the cpuset.
                                 */
                                allowednodes = zlc_setup(zonelist, alloc_flags);
                                zlc_active = 1;
                                did_zlc_setup = 1;
                        }

                        if (zone_reclaim_mode == 0 ||
                            !zone_allows_reclaim(preferred_zone, zone))
                                goto this_zone_full;

                        /*
                         * As we may have just activated ZLC, check if the first
                         * eligible zone has failed zone_reclaim recently.
                         */
                        if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
                                !zlc_zone_worth_trying(zonelist, z, allowednodes))
                                continue;

                        ret = zone_reclaim(zone, gfp_mask, order);
                        switch (ret) {
                        case ZONE_RECLAIM_NOSCAN:
                                /* did not scan */
                                continue;
                        case ZONE_RECLAIM_FULL:
                                /* scanned but unreclaimable */
                                continue;
                        default:
                                /* did we reclaim enough */
                                if (zone_watermark_ok(zone, order, mark,
                                                classzone_idx, alloc_flags))
                                        goto try_this_zone;

                                /*
                                 * Failed to reclaim enough to meet watermark.
                                 * Only mark the zone full if checking the min
                                 * watermark or if we failed to reclaim just
                                 * 1<<order pages or else the page allocator
                                 * fastpath will prematurely mark zones full
                                 * when the watermark is between the low and
                                 * min watermarks.
                                 */
                                if (((alloc_flags & ALLOC_WMARK_MASK) == ALLOC_WMARK_MIN) ||
                                    ret == ZONE_RECLAIM_SOME)
                                        goto this_zone_full;

                                continue;
                        }
                }

try_this_zone:
                page = buffered_rmqueue(preferred_zone, zone, order,
                                                gfp_mask, migratetype);
                if (page)
                        break;
this_zone_full:
                if (IS_ENABLED(CONFIG_NUMA) && zlc_active)
                        zlc_mark_zone_full(zonelist, z);
        }

        if (page) {
                /*
                 * page->pfmemalloc is set 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.
                 */
                page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);
                return page;
        }

        /*
         * The first pass makes sure allocations are spread fairly within the
         * local node.  However, the local node might have free pages left
         * after the fairness batches are exhausted, and remote zones haven't
         * even been considered yet.  Try once more without fairness, and
         * include remote zones now, before entering the slowpath and waking
         * kswapd: prefer spilling to a remote zone over swapping locally.
         */
        if (alloc_flags & ALLOC_FAIR) {
                alloc_flags &= ~ALLOC_FAIR;
                if (nr_fair_skipped) {
                        zonelist_rescan = true;
                        reset_alloc_batches(preferred_zone);
                }
                if (nr_online_nodes > 1)
                        zonelist_rescan = true;
        }

        if (unlikely(IS_ENABLED(CONFIG_NUMA) && zlc_active)) {
                /* Disable zlc cache for second zonelist scan */
                zlc_active = 0;
                zonelist_rescan = true;
        }

        if (zonelist_rescan)
                goto zonelist_scan;

        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_failed(gfp_t gfp_mask, int order, const char *fmt, ...)
{
        unsigned int filter = SHOW_MEM_FILTER_NODES;

        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_WAIT))
                filter &= ~SHOW_MEM_FILTER_NODES;

        if (fmt) {
                struct va_format vaf;
                va_list args;

                va_start(args, fmt);

                vaf.fmt = fmt;
                vaf.va = &args;

                pr_warn("%pV", &vaf);

                va_end(args);
        }

        pr_warn("%s: page allocation failure: order:%d, mode:0x%x\n",
                current->comm, order, gfp_mask);

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

static inline int
should_alloc_retry(gfp_t gfp_mask, unsigned int order,
                                unsigned long did_some_progress,
                                unsigned long pages_reclaimed)
{
        /* Do not loop if specifically requested */
        if (gfp_mask & __GFP_NORETRY)
                return 0;

        /* Always retry if specifically requested */
        if (gfp_mask & __GFP_NOFAIL)
                return 1;

        /*
         * Suspend converts GFP_KERNEL to __GFP_WAIT which can prevent reclaim
         * making forward progress without invoking OOM. Suspend also disables
         * storage devices so kswapd will not help. Bail if we are suspending.
         */
        if (!did_some_progress && pm_suspended_storage())
                return 0;

        /*
         * In this implementation, order <= PAGE_ALLOC_COSTLY_ORDER
         * means __GFP_NOFAIL, but that may not be true in other
         * implementations.
         */
        if (order <= PAGE_ALLOC_COSTLY_ORDER)
                return 1;

        /*
         * For order > PAGE_ALLOC_COSTLY_ORDER, if __GFP_REPEAT is
         * specified, then we retry until we no longer reclaim any pages
         * (above), or we've reclaimed an order of pages at least as
         * large as the allocation's order. In both cases, if the
         * allocation still fails, we stop retrying.
         */
        if (gfp_mask & __GFP_REPEAT && pages_reclaimed < (1 << order))
                return 1;

        return 0;
}

static inline struct page *
__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, struct zone *preferred_zone,
        int classzone_idx, int migratetype)
{
        struct page *page;

        /* Acquire the per-zone oom lock for each zone */
        if (!oom_zonelist_trylock(zonelist, gfp_mask)) {
                schedule_timeout_uninterruptible(1);
                return NULL;
        }

        /*
         * PM-freezer should be notified that there might be an OOM killer on
         * its way to kill and wake somebody up. This is too early and we might
         * end up not killing anything but false positives are acceptable.
         * See freeze_processes.
         */
        note_oom_kill();

        /*
         * 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, nodemask,
                order, zonelist, high_zoneidx,
                ALLOC_WMARK_HIGH|ALLOC_CPUSET,
                preferred_zone, classzone_idx, migratetype);
        if (page)
                goto out;

        if (!(gfp_mask & __GFP_NOFAIL)) {
                /* 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 (high_zoneidx < ZONE_NORMAL)
                        goto out;
                /*
                 * GFP_THISNODE contains __GFP_NORETRY and we never hit this.
                 * Sanity check for bare calls of __GFP_THISNODE, not real OOM.
                 * The caller should handle page allocation failure by itself if
                 * it specifies __GFP_THISNODE.
                 * Note: Hugepage uses it but will hit PAGE_ALLOC_COSTLY_ORDER.
                 */
                if (gfp_mask & __GFP_THISNODE)
                        goto out;
        }
        /* Exhausted what can be done so it's blamo time */
        out_of_memory(zonelist, gfp_mask, order, nodemask, false);

out:
        oom_zonelist_unlock(zonelist, gfp_mask);
        return page;
}

#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,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
        int classzone_idx, int migratetype, enum migrate_mode mode,
        int *contended_compaction, bool *deferred_compaction)
{
        struct zone *last_compact_zone = NULL;
        unsigned long compact_result;
        struct page *page;

        if (!order)
                return NULL;

        current->flags |= PF_MEMALLOC;
        compact_result = try_to_compact_pages(zonelist, order, gfp_mask,
                                                nodemask, mode,
                                                contended_compaction,
                                                &last_compact_zone);
        current->flags &= ~PF_MEMALLOC;

        switch (compact_result) {
        case COMPACT_DEFERRED:
                *deferred_compaction = true;
                /* fall-through */
        case COMPACT_SKIPPED:
                return NULL;
        default:
                break;
        }

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

        /* Page migration frees to the PCP lists but we want merging */
        drain_pages(get_cpu());
        put_cpu();

        page = get_page_from_freelist(gfp_mask, nodemask,
                        order, zonelist, high_zoneidx,
                        alloc_flags & ~ALLOC_NO_WATERMARKS,
                        preferred_zone, classzone_idx, migratetype);

        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;
        }

        /*
         * last_compact_zone is where try_to_compact_pages thought allocation
         * should succeed, so it did not defer compaction. But here we know
         * that it didn't succeed, so we do the defer.
         */
        if (last_compact_zone && mode != MIGRATE_ASYNC)
                defer_compaction(last_compact_zone, order);

        /*
         * 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;
}
#else
static inline struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
        int classzone_idx, int migratetype, enum migrate_mode mode,
        int *contended_compaction, bool *deferred_compaction)
{
        return NULL;
}
#endif /* CONFIG_COMPACTION */

/* Perform direct synchronous page reclaim */
static int
__perform_reclaim(gfp_t gfp_mask, unsigned int order, struct zonelist *zonelist,
                  nodemask_t *nodemask)
{
        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(zonelist, order, gfp_mask, 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,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
        int classzone_idx, int migratetype, unsigned long *did_some_progress)
{
        struct page *page = NULL;
        bool drained = false;

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

        /* After successful reclaim, reconsider all zones for allocation */
        if (IS_ENABLED(CONFIG_NUMA))
                zlc_clear_zones_full(zonelist);

retry:
        page = get_page_from_freelist(gfp_mask, nodemask, order,
                                        zonelist, high_zoneidx,
                                        alloc_flags & ~ALLOC_NO_WATERMARKS,
                                        preferred_zone, classzone_idx,
                                        migratetype);

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

        return page;
}

/*
 * This is called in the allocator slow-path if the allocation request is of
 * sufficient urgency to ignore watermarks and take other desperate measures
 */
static inline struct page *
__alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, struct zone *preferred_zone,
        int classzone_idx, int migratetype)
{
        struct page *page;

        do {
                page = get_page_from_freelist(gfp_mask, nodemask, order,
                        zonelist, high_zoneidx, ALLOC_NO_WATERMARKS,
                        preferred_zone, classzone_idx, migratetype);

                if (!page && gfp_mask & __GFP_NOFAIL)
                        wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/50);
        } while (!page && (gfp_mask & __GFP_NOFAIL));

        return page;
}

static void wake_all_kswapds(unsigned int order,
                             struct zonelist *zonelist,
                             enum zone_type high_zoneidx,
                             struct zone *preferred_zone,
                             nodemask_t *nodemask)
{
        struct zoneref *z;
        struct zone *zone;

        for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                                high_zoneidx, nodemask)
                wakeup_kswapd(zone, order, zone_idx(preferred_zone));
}

static inline int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
        int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
        const bool atomic = !(gfp_mask & (__GFP_WAIT | __GFP_NO_KSWAPD));

        /* __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 (atomic == true) and ALLOC_HIGH (__GFP_HIGH).
         */
        alloc_flags |= (__force int) (gfp_mask & __GFP_HIGH);

        if (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_softwall().
                 */
                alloc_flags &= ~ALLOC_CPUSET;
        } else if (unlikely(rt_task(current)) && !in_interrupt())
                alloc_flags |= ALLOC_HARDER;

        if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
                if (gfp_mask & __GFP_MEMALLOC)
                        alloc_flags |= ALLOC_NO_WATERMARKS;
                else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
                        alloc_flags |= ALLOC_NO_WATERMARKS;
                else if (!in_interrupt() &&
                                ((current->flags & PF_MEMALLOC) ||
                                 unlikely(test_thread_flag(TIF_MEMDIE))))
                        alloc_flags |= ALLOC_NO_WATERMARKS;
        }
#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)
{
        return !!(gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);
}

static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, struct zone *preferred_zone,
        int classzone_idx, int migratetype)
{
        const gfp_t wait = gfp_mask & __GFP_WAIT;
        struct page *page = NULL;
        int alloc_flags;
        unsigned long pages_reclaimed = 0;
        unsigned long did_some_progress;
        enum migrate_mode migration_mode = MIGRATE_ASYNC;
        bool deferred_compaction = false;
        int contended_compaction = COMPACT_CONTENDED_NONE;

        /*
         * 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;
        }

        /*
         * GFP_THISNODE (meaning __GFP_THISNODE, __GFP_NORETRY and
         * __GFP_NOWARN set) should not cause reclaim since the subsystem
         * (f.e. slab) using GFP_THISNODE may choose to trigger reclaim
         * using a larger set of nodes after it has established that the
         * allowed per node queues are empty and that nodes are
         * over allocated.
         */
        if (IS_ENABLED(CONFIG_NUMA) &&
            (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
                goto nopage;

restart:
        if (!(gfp_mask & __GFP_NO_KSWAPD))
                wake_all_kswapds(order, zonelist, high_zoneidx,
                                preferred_zone, nodemask);

        /*
         * OK, we're below the kswapd watermark and have kicked background
         * reclaim. Now things get more complex, so set up alloc_flags according
         * to how we want to proceed.
         */
        alloc_flags = gfp_to_alloc_flags(gfp_mask);

        /*
         * Find the true preferred zone if the allocation is unconstrained by
         * cpusets.
         */
        if (!(alloc_flags & ALLOC_CPUSET) && !nodemask) {
                struct zoneref *preferred_zoneref;
                preferred_zoneref = first_zones_zonelist(zonelist, high_zoneidx,
                                NULL, &preferred_zone);
                classzone_idx = zonelist_zone_idx(preferred_zoneref);
        }

rebalance:
        /* This is the last chance, in general, before the goto nopage. */
        page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
                        high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS,
                        preferred_zone, classzone_idx, migratetype);
        if (page)
                goto got_pg;

        /* Allocate without watermarks if the context allows */
        if (alloc_flags & ALLOC_NO_WATERMARKS) {
                /*
                 * Ignore mempolicies if ALLOC_NO_WATERMARKS on the grounds
                 * the allocation is high priority and these type of
                 * allocations are system rather than user orientated
                 */
                zonelist = node_zonelist(numa_node_id(), gfp_mask);

                page = __alloc_pages_high_priority(gfp_mask, order,
                                zonelist, high_zoneidx, nodemask,
                                preferred_zone, classzone_idx, migratetype);
                if (page) {
                        goto got_pg;
                }
        }

        /* Atomic allocations - we can't balance anything */
        if (!wait) {
                /*
                 * All existing users of the deprecated __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)
                goto nopage;

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

        /*
         * Try direct compaction. The first pass is asynchronous. Subsequent
         * attempts after direct reclaim are synchronous
         */
        page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
                                        high_zoneidx, nodemask, alloc_flags,
                                        preferred_zone,
                                        classzone_idx, migratetype,
                                        migration_mode, &contended_compaction,
                                        &deferred_compaction);
        if (page)
                goto got_pg;

        /* Checks for THP-specific high-order allocations */
        if ((gfp_mask & GFP_TRANSHUGE) == GFP_TRANSHUGE) {
                /*
                 * 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 (deferred_compaction)
                        goto nopage;

                /*
                 * In all zones where compaction was attempted (and not
                 * deferred or skipped), lock contention has been detected.
                 * For THP allocation we do not want to disrupt the others
                 * so we fallback to base pages instead.
                 */
                if (contended_compaction == COMPACT_CONTENDED_LOCK)
                        goto nopage;

                /*
                 * If compaction was aborted due to need_resched(), we do not
                 * want to further increase allocation latency, unless it is
                 * khugepaged trying to collapse.
                 */
                if (contended_compaction == COMPACT_CONTENDED_SCHED
                        && !(current->flags & PF_KTHREAD))
                        goto nopage;
        }

        /*
         * It can become very expensive to allocate transparent hugepages at
         * fault, so use asynchronous memory compaction for THP unless it is
         * khugepaged trying to collapse.
         */
        if ((gfp_mask & GFP_TRANSHUGE) != GFP_TRANSHUGE ||
                                                (current->flags & PF_KTHREAD))
                migration_mode = MIGRATE_SYNC_LIGHT;

        /* Try direct reclaim and then allocating */
        page = __alloc_pages_direct_reclaim(gfp_mask, order,
                                        zonelist, high_zoneidx,
                                        nodemask,
                                        alloc_flags, preferred_zone,
                                        classzone_idx, migratetype,
                                        &did_some_progress);
        if (page)
                goto got_pg;

        /*
         * If we failed to make any progress reclaiming, then we are
         * running out of options and have to consider going OOM
         */
        if (!did_some_progress) {
                if (oom_gfp_allowed(gfp_mask)) {
                        if (oom_killer_disabled)
                                goto nopage;
                        /* Coredumps can quickly deplete all memory reserves */
                        if ((current->flags & PF_DUMPCORE) &&
                            !(gfp_mask & __GFP_NOFAIL))
                                goto nopage;
                        page = __alloc_pages_may_oom(gfp_mask, order,
                                        zonelist, high_zoneidx,
                                        nodemask, preferred_zone,
                                        classzone_idx, migratetype);
                        if (page)
                                goto got_pg;

                        if (!(gfp_mask & __GFP_NOFAIL)) {
                                /*
                                 * The oom killer is not called for high-order
                                 * allocations that may fail, so if no progress
                                 * is being made, there are no other options and
                                 * retrying is unlikely to help.
                                 */
                                if (order > PAGE_ALLOC_COSTLY_ORDER)
                                        goto nopage;
                                /*
                                 * The oom killer is not called for lowmem
                                 * allocations to prevent needlessly killing
                                 * innocent tasks.
                                 */
                                if (high_zoneidx < ZONE_NORMAL)
                                        goto nopage;
                        }

                        goto restart;
                }
        }

        /* Check if we should retry the allocation */
        pages_reclaimed += did_some_progress;
        if (should_alloc_retry(gfp_mask, order, did_some_progress,
                                                pages_reclaimed)) {
                /* Wait for some write requests to complete then retry */
                wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/50);
                goto rebalance;
        } else {
                /*
                 * High-order allocations do not necessarily loop after
                 * direct reclaim and reclaim/compaction depends on compaction
                 * being called after reclaim so call directly if necessary
                 */
                page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
                                        high_zoneidx, nodemask, alloc_flags,
                                        preferred_zone,
                                        classzone_idx, migratetype,
                                        migration_mode, &contended_compaction,
                                        &deferred_compaction);
                if (page)
                        goto got_pg;
        }

nopage:
        warn_alloc_failed(gfp_mask, order, NULL);
        return page;
got_pg:
        if (kmemcheck_enabled)
                kmemcheck_pagealloc_alloc(page, order, gfp_mask);

        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)
{
        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
        struct zone *preferred_zone;
        struct zoneref *preferred_zoneref;
        struct page *page = NULL;
        int migratetype = gfpflags_to_migratetype(gfp_mask);
        unsigned int cpuset_mems_cookie;
        int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR;
        int classzone_idx;

        gfp_mask &= gfp_allowed_mask;

        lockdep_trace_alloc(gfp_mask);

        might_sleep_if(gfp_mask & __GFP_WAIT);

        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) && migratetype == MIGRATE_MOVABLE)
                alloc_flags |= ALLOC_CMA;

retry_cpuset:
        cpuset_mems_cookie = read_mems_allowed_begin();

        /* The preferred zone is used for statistics later */
        preferred_zoneref = first_zones_zonelist(zonelist, high_zoneidx,
                                nodemask ? : &cpuset_current_mems_allowed,
                                &preferred_zone);
        if (!preferred_zone)
                goto out;
        classzone_idx = zonelist_zone_idx(preferred_zoneref);

        /* First allocation attempt */
        page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
                        zonelist, high_zoneidx, alloc_flags,
                        preferred_zone, classzone_idx, migratetype);
        if (unlikely(!page)) {
                /*
                 * Runtime PM, block IO and its error handling path
                 * can deadlock because I/O on the device might not
                 * complete.
                 */
                gfp_mask = memalloc_noio_flags(gfp_mask);
                page = __alloc_pages_slowpath(gfp_mask, order,
                                zonelist, high_zoneidx, nodemask,
                                preferred_zone, classzone_idx, migratetype);
        }

        trace_mm_page_alloc(page, order, gfp_mask, migratetype);

out:
        /*
         * When updating a task's mems_allowed, it is possible to race with
         * parallel threads in such a way that an allocation can fail while
         * the mask is being updated. If a page allocation is about to fail,
         * check if the cpuset changed during allocation and if so, retry.
         */
        if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
                goto retry_cpuset;

        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);

/*
 * alloc_kmem_pages charges newly allocated pages to the kmem resource counter
 * of the current memory cgroup.
 *
 * It should be used when the caller would like to use kmalloc, but since the
 * allocation is large, it has to fall back to the page allocator.
 */
struct page *alloc_kmem_pages(gfp_t gfp_mask, unsigned int order)
{
        struct page *page;
        struct mem_cgroup *memcg = NULL;

        if (!memcg_kmem_newpage_charge(gfp_mask, &memcg, order))
                return NULL;
        page = alloc_pages(gfp_mask, order);
        memcg_kmem_commit_charge(page, memcg, order);
        return page;
}

struct page *alloc_kmem_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
{
        struct page *page;
        struct mem_cgroup *memcg = NULL;

        if (!memcg_kmem_newpage_charge(gfp_mask, &memcg, order))
                return NULL;
        page = alloc_pages_node(nid, gfp_mask, order);
        memcg_kmem_commit_charge(page, memcg, order);
        return page;
}

/*
 * __free_kmem_pages and free_kmem_pages will free pages allocated with
 * alloc_kmem_pages.
 */
void __free_kmem_pages(struct page *page, unsigned int order)
{
        memcg_kmem_uncharge_pages(page, order);
        __free_pages(page, order);
}

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

static void *make_alloc_exact(unsigned long addr, unsigned 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.

 * Note this is not alloc_pages_exact_node() which allocates on a specific node,
 * but is not exact.
 */
void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
{
        unsigned 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));
}

void si_meminfo(struct sysinfo *val)
{
        val->totalram = totalram_pages;
        val->sharedram = global_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;
        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(nid, NR_SHMEM);
        val->freeram = node_page_state(nid, NR_FREE_PAGES);
#ifdef CONFIG_HIGHMEM
        val->totalhigh = pgdat->node_zones[ZONE_HIGHMEM].managed_pages;
        val->freehigh = zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
                        NR_FREE_PAGES);
#else
        val->totalhigh = 0;
        val->freehigh = 0;
#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_RECLAIMABLE]   = 'E',
                [MIGRATE_MOVABLE]       = 'M',
                [MIGRATE_RESERVE]       = 'R',
#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("(%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.
 * Suppresses nodes that are not allowed by current's cpuset if
 * SHOW_MEM_FILTER_NODES is passed.
 */
void show_free_areas(unsigned int filter)
{
        int cpu;
        struct zone *zone;

        for_each_populated_zone(zone) {
                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;
                show_node(zone);
                printk("%s per-cpu:\n", zone->name);

                for_each_online_cpu(cpu) {
                        struct per_cpu_pageset *pageset;

                        pageset = per_cpu_ptr(zone->pageset, cpu);

                        printk("CPU %4d: hi:%5d, btch:%4d usd:%4d\n",
                               cpu, pageset->pcp.high,
                               pageset->pcp.batch, pageset->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"
                " free:%lu slab_reclaimable:%lu slab_unreclaimable:%lu\n"
                " mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
                " free_cma:%lu\n",
                global_page_state(NR_ACTIVE_ANON),
                global_page_state(NR_INACTIVE_ANON),
                global_page_state(NR_ISOLATED_ANON),
                global_page_state(NR_ACTIVE_FILE),
                global_page_state(NR_INACTIVE_FILE),
                global_page_state(NR_ISOLATED_FILE),
                global_page_state(NR_UNEVICTABLE),
                global_page_state(NR_FILE_DIRTY),
                global_page_state(NR_WRITEBACK),
                global_page_state(NR_UNSTABLE_NFS),
                global_page_state(NR_FREE_PAGES),
                global_page_state(NR_SLAB_RECLAIMABLE),
                global_page_state(NR_SLAB_UNRECLAIMABLE),
                global_page_state(NR_FILE_MAPPED),
                global_page_state(NR_SHMEM),
                global_page_state(NR_PAGETABLE),
                global_page_state(NR_BOUNCE),
                global_page_state(NR_FREE_CMA_PAGES));

        for_each_populated_zone(zone) {
                int i;

                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;
                show_node(zone);
                printk("%s"
                        " free:%lukB"
                        " min:%lukB"
                        " low:%lukB"
                        " high:%lukB"
                        " active_anon:%lukB"
                        " inactive_anon:%lukB"
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
                        " isolated(anon):%lukB"
                        " isolated(file):%lukB"
                        " present:%lukB"
                        " managed:%lukB"
                        " mlocked:%lukB"
                        " dirty:%lukB"
                        " writeback:%lukB"
                        " mapped:%lukB"
                        " shmem:%lukB"
                        " slab_reclaimable:%lukB"
                        " slab_unreclaimable:%lukB"
                        " kernel_stack:%lukB"
                        " pagetables:%lukB"
                        " unstable:%lukB"
                        " bounce:%lukB"
                        " free_cma:%lukB"
                        " writeback_tmp:%lukB"
                        " pages_scanned:%lu"
                        " all_unreclaimable? %s"
                        "\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_ACTIVE_ANON)),
                        K(zone_page_state(zone, NR_INACTIVE_ANON)),
                        K(zone_page_state(zone, NR_ACTIVE_FILE)),
                        K(zone_page_state(zone, NR_INACTIVE_FILE)),
                        K(zone_page_state(zone, NR_UNEVICTABLE)),
                        K(zone_page_state(zone, NR_ISOLATED_ANON)),
                        K(zone_page_state(zone, NR_ISOLATED_FILE)),
                        K(zone->present_pages),
                        K(zone->managed_pages),
                        K(zone_page_state(zone, NR_MLOCK)),
                        K(zone_page_state(zone, NR_FILE_DIRTY)),
                        K(zone_page_state(zone, NR_WRITEBACK)),
                        K(zone_page_state(zone, NR_FILE_MAPPED)),
                        K(zone_page_state(zone, NR_SHMEM)),
                        K(zone_page_state(zone, NR_SLAB_RECLAIMABLE)),
                        K(zone_page_state(zone, NR_SLAB_UNRECLAIMABLE)),
                        zone_page_state(zone, NR_KERNEL_STACK) *
                                THREAD_SIZE / 1024,
                        K(zone_page_state(zone, NR_PAGETABLE)),
                        K(zone_page_state(zone, NR_UNSTABLE_NFS)),
                        K(zone_page_state(zone, NR_BOUNCE)),
                        K(zone_page_state(zone, NR_FREE_CMA_PAGES)),
                        K(zone_page_state(zone, NR_WRITEBACK_TEMP)),
                        K(zone_page_state(zone, NR_PAGES_SCANNED)),
                        (!zone_reclaimable(zone) ? "yes" : "no")
                        );
                printk("lowmem_reserve[]:");
                for (i = 0; i < MAX_NR_ZONES; i++)
                        printk(" %ld", zone->lowmem_reserve[i]);
                printk("\n");
        }

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

                if (skip_free_areas_node(filter, zone_to_nid(zone)))
                        continue;
                show_node(zone);
                printk("%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("%lu*%lukB ", nr[order], K(1UL) << order);
                        if (nr[order])
                                show_migration_types(types[order]);
                }
                printk("= %lukB\n", K(total));
        }

        hugetlb_show_meminfo();

        printk("%ld total pagecache pages\n", global_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 (populated_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 {
                printk(KERN_WARNING
                        "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[0];
        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[1];
        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[0];
        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 (populated_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 j, node, load;
        enum zone_type i;
        nodemask_t used_mask;
        int local_node, prev_node;
        struct zonelist *zonelist;
        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));
        j = 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[j++] = node; /* remember order */
        }

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

        build_thisnode_zonelists(pgdat);
}

/* Construct the zonelist performance cache - see further mmzone.h */
static void build_zonelist_cache(pg_data_t *pgdat)
{
        struct zonelist *zonelist;
        struct zonelist_cache *zlc;
        struct zoneref *z;

        zonelist = &pgdat->node_zonelists[0];
        zonelist->zlcache_ptr = zlc = &zonelist->zlcache;
        bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
        for (z = zonelist->_zonerefs; z->zone; z++)
                zlc->z_to_n[z - zonelist->_zonerefs] = zonelist_node_idx(z);
}

#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 zone *zone;

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

#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[0];
        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;
}

/* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
static void build_zonelist_cache(pg_data_t *pgdat)
{
        pgdat->node_zonelists[0].zlcache_ptr = NULL;
}

#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);
                build_zonelist_cache(self);
        }

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

                build_zonelists(pgdat);
                build_zonelist_cache(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;
}

/*
 * Called with zonelists_mutex held always
 * unless system_state == 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(NULL);
                mminit_verify_zonelist();
                cpuset_init_current_mems_allowed();
        } 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;

        printk("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
        printk("Policy zone: %s\n", zone_names[policy_zone]);
#endif
}

/*
 * Helper functions to size the waitqueue hash table.
 * Essentially these want to choose hash table sizes sufficiently
 * large so that collisions trying to wait on pages are rare.
 * But in fact, the number of active page waitqueues on typical
 * systems is ridiculously low, less than 200. So this is even
 * conservative, even though it seems large.
 *
 * The constant PAGES_PER_WAITQUEUE specifies the ratio of pages to
 * waitqueues, i.e. the size of the waitq table given the number of pages.
 */
#define PAGES_PER_WAITQUEUE     256

#ifndef CONFIG_MEMORY_HOTPLUG
static inline unsigned long wait_table_hash_nr_entries(unsigned long pages)
{
        unsigned long size = 1;

        pages /= PAGES_PER_WAITQUEUE;

        while (size < pages)
                size <<= 1;

        /*
         * Once we have dozens or even hundreds of threads sleeping
         * on IO we've got bigger problems than wait queue collision.
         * Limit the size of the wait table to a reasonable size.
         */
        size = min(size, 4096UL);

        return max(size, 4UL);
}
#else
/*
 * A zone's size might be changed by hot-add, so it is not possible to determine
 * a suitable size for its wait_table.  So we use the maximum size now.
 *
 * The max wait table size = 4096 x sizeof(wait_queue_head_t).   ie:
 *
 *    i386 (preemption config)    : 4096 x 16 = 64Kbyte.
 *    ia64, x86-64 (no preemption): 4096 x 20 = 80Kbyte.
 *    ia64, x86-64 (preemption)   : 4096 x 24 = 96Kbyte.
 *
 * The maximum entries are prepared when a zone's memory is (512K + 256) pages
 * or more by the traditional way. (See above).  It equals:
 *
 *    i386, x86-64, powerpc(4K page size) : =  ( 2G + 1M)byte.
 *    ia64(16K page size)                 : =  ( 8G + 4M)byte.
 *    powerpc (64K page size)             : =  (32G +16M)byte.
 */
static inline unsigned long wait_table_hash_nr_entries(unsigned long pages)
{
        return 4096UL;
}
#endif

/*
 * This is an integer logarithm so that shifts can be used later
 * to extract the more random high bits from the multiplicative
 * hash function before the remainder is taken.
 */
static inline unsigned long wait_table_bits(unsigned long size)
{
        return ffz(~size);
}

/*
 * Check if a pageblock contains reserved pages
 */
static int pageblock_is_reserved(unsigned long start_pfn, unsigned long end_pfn)
{
        unsigned long pfn;

        for (pfn = start_pfn; pfn < end_pfn; pfn++) {
                if (!pfn_valid_within(pfn) || PageReserved(pfn_to_page(pfn)))
                        return 1;
        }
        return 0;
}

/*
 * Mark a number of pageblocks as MIGRATE_RESERVE. The number
 * of blocks reserved is based on min_wmark_pages(zone). The memory within
 * the reserve will tend to store contiguous free pages. Setting min_free_kbytes
 * higher will lead to a bigger reserve which will get freed as contiguous
 * blocks as reclaim kicks in
 */
static void setup_zone_migrate_reserve(struct zone *zone)
{
        unsigned long start_pfn, pfn, end_pfn, block_end_pfn;
        struct page *page;
        unsigned long block_migratetype;
        int reserve;
        int old_reserve;