page_alloc.c

Go to the documentation of this file.

/*
 *  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/ftrace_event.h>
#include <linux/memcontrol.h>
#include <linux/prefetch.h>
#include <linux/migrate.h>
#include <linux/page-debug-flags.h>

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

#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_);
#endif

/*
 * Array of node states.
 */
nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
    [N_POSSIBLE] = NODE_MASK_ALL,
    [N_ONLINE] = { { [0] = 1UL } },
#ifndef CONFIG_NUMA
    [N_NORMAL_MEMORY] = { { [0] = 1UL } },
#ifdef CONFIG_HIGHMEM
    [N_HIGH_MEMORY] = { { [0] = 1UL } },
#endif
    [N_CPU] = { { [0] = 1UL } },
#endif  /* NUMA */
};
EXPORT_SYMBOL(node_states);

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;

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;

/*
 * NOTE:
 * Don't use set_pageblock_migratetype(page, MIGRATE_ISOLATE) directly.
 * Instead, use {un}set_pageblock_isolate.
 */
void set_pageblock_migratetype(struct page *page, int migratetype)
{

    if (unlikely(page_group_by_mobility_disabled))
        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);

    do {
        seq = zone_span_seqbegin(zone);
        if (pfn >= zone->zone_start_pfn + zone->spanned_pages)
            ret = 1;
        else if (pfn < zone->zone_start_pfn)
            ret = 1;
    } while (zone_span_seqretry(zone, seq));

    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)
{
    static unsigned long resume;
    static unsigned long nr_shown;
    static unsigned long nr_unshown;

    /* Don't complain about poisoned pages */
    if (PageHWPoison(page)) {
        reset_page_mapcount(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(page);

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

/*
 * 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;
        __SetPageTail(p);
        set_page_count(p, 0);
        p->first_page = page;
    }
}

/* 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) ||
        unlikely(!PageHead(page))) {
        bad_page(page);
        bad++;
    }

    __ClearPageHead(page);

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

        if (unlikely(!PageTail(p) || (p->first_page != page))) {
            bad_page(page);
            bad++;
        }
        __ClearPageTail(p);
    }

    return bad;
}

static inline void prep_zero_page(struct page *page, 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, 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);
}

/*
 * Locate the struct page for both the matching buddy in our
 * pair (buddy1) and the combined O(n+1) page they form (page).
 *
 * 1) Any buddy B1 will have an order O twin B2 which satisfies
 * the following equation:
 *     B2 = B1 ^ (1 << O)
 * For example, if the starting buddy (buddy2) is #8 its order
 * 1 buddy is #10:
 *     B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10
 *
 * 2) Any buddy B will have an order O+1 parent P which
 * satisfies the following equation:
 *     P = B & ~(1 << O)
 *
 * Assumption: *_mem_map is contiguous at least up to MAX_ORDER
 */
static inline unsigned long
__find_buddy_index(unsigned long page_idx, unsigned int order)
{
    return page_idx ^ (1 << order);
}

/*
 * 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 -2.
 * Setting, clearing, and testing _mapcount -2 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,
                                int order)
{
    if (!pfn_valid_within(page_to_pfn(buddy)))
        return 0;

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

    if (page_is_guard(buddy) && page_order(buddy) == order) {
        VM_BUG_ON(page_count(buddy) != 0);
        return 1;
    }

    if (PageBuddy(buddy) && page_order(buddy) == order) {
        VM_BUG_ON(page_count(buddy) != 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 -2. 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.
 *
 * -- wli
 */

static inline void __free_one_page(struct page *page,
        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;

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

    VM_BUG_ON(migratetype == -1);

    page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);

    VM_BUG_ON(page_idx & ((1 << order) - 1));
    VM_BUG_ON(bad_range(zone, 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(page, 0);
            __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)
{
    if (unlikely(page_mapcount(page) |
        (page->mapping != NULL)  |
        (atomic_read(&page->_count) != 0) |
        (page->flags & PAGE_FLAGS_CHECK_AT_FREE) |
        (mem_cgroup_bad_page_check(page)))) {
        bad_page(page);
        return 1;
    }
    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;

    spin_lock(&zone->lock);
    zone->all_unreclaimable = 0;
    zone->pages_scanned = 0;

    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);
            /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
            __free_one_page(page, zone, 0, mt);
            trace_mm_page_pcpu_drain(page, 0, mt);
            if (is_migrate_cma(mt))
                __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1);
        } while (--to_free && --batch_free && !list_empty(list));
    }
    __mod_zone_page_state(zone, NR_FREE_PAGES, count);
    spin_unlock(&zone->lock);
}

static void free_one_page(struct zone *zone, struct page *page, int order,
                int migratetype)
{
    spin_lock(&zone->lock);
    zone->all_unreclaimable = 0;
    zone->pages_scanned = 0;

    __free_one_page(page, zone, order, migratetype);
    if (unlikely(migratetype != MIGRATE_ISOLATE))
        __mod_zone_freepage_state(zone, 1 << 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;

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

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

void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
{
    unsigned int nr_pages = 1 << order;
    unsigned int loop;

    prefetchw(page);
    for (loop = 0; loop < nr_pages; loop++) {
        struct page *p = &page[loop];

        if (loop + 1 < nr_pages)
            prefetchw(p + 1);
        __ClearPageReserved(p);
        set_page_count(p, 0);
    }

    set_page_refcounted(page);
    __free_pages(page, order);
}

#ifdef CONFIG_CMA
/* Free whole pageblock and set it's 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_page_refcounted(page);
    set_pageblock_migratetype(page, MIGRATE_CMA);
    __free_pages(page, pageblock_order);
    totalram_pages += 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.
 *
 * -- wli
 */
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(bad_range(zone, &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)
{
    if (unlikely(page_mapcount(page) |
        (page->mapping != NULL)  |
        (atomic_read(&page->_count) != 0)  |
        (page->flags & PAGE_FLAGS_CHECK_AT_PREP) |
        (mem_cgroup_bad_page_check(page)))) {
        bad_page(page);
        return 1;
    }
    return 0;
}

static int prep_new_page(struct page *page, 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);
        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 */
    [MIGRATE_ISOLATE]     = { MIGRATE_RESERVE }, /* Never used */
};

/*
 * 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
     */
    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_to_nid(page) != zone_to_nid(zone));

        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 (start_pfn < zone->zone_start_pfn)
        start_page = page;
    if (end_pfn >= zone->zone_start_pfn + zone->spanned_pages)
        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;
    }
}

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

    /* Find the largest possible block of pages in the other list */
    for (current_order = MAX_ORDER-1; current_order >= order;
                        --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--;

            /*
             * 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 on different free lists. We don't
             * want unmovable pages to be allocated from
             * MIGRATE_CMA areas.
             */
            if (!is_migrate_cma(migratetype) &&
                (unlikely(current_order >= pageblock_order / 2) ||
                 start_migratetype == MIGRATE_RECLAIMABLE ||
                 page_group_by_mobility_disabled)) {
                int pages;
                pages = move_freepages_block(zone, page,
                                start_migratetype);

                /* 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_migratetype);

                migratetype = start_migratetype;
            }

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

            /* Take ownership for orders >= pageblock_order */
            if (current_order >= pageblock_order &&
                !is_migrate_cma(migratetype))
                change_pageblock_range(page, current_order,
                            start_migratetype);

            expand(zone, page, order, current_order, area,
                   is_migrate_cma(migratetype)
                 ? migratetype : start_migratetype);

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

            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, int cold)
{
    int mt = migratetype, 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 == 0))
            list_add(&page->lru, list);
        else
            list_add_tail(&page->lru, list);
        if (IS_ENABLED(CONFIG_CMA)) {
            mt = get_pageblock_migratetype(page);
            if (!is_migrate_cma(mt) && mt != MIGRATE_ISOLATE)
                mt = migratetype;
        }
        set_freepage_migratetype(page, mt);
        list = &page->lru;
        if (is_migrate_cma(mt))
            __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;

    local_irq_save(flags);
    if (pcp->count >= pcp->batch)
        to_drain = pcp->batch;
    else
        to_drain = pcp->count;
    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;
    int order, t;
    struct list_head *curr;

    if (!zone->spanned_pages)
        return;

    spin_lock_irqsave(&zone->lock, flags);

    max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
    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 == 1 ? free a cold page : free a hot page
 */
void free_hot_cold_page(struct page *page, int cold)
{
    struct zone *zone = page_zone(page);
    struct per_cpu_pages *pcp;
    unsigned long flags;
    int migratetype;

    if (!free_pages_prepare(page, 0))
        return;

    migratetype = get_pageblock_migratetype(page);
    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(migratetype == MIGRATE_ISOLATE)) {
            free_one_page(zone, page, 0, migratetype);
            goto out;
        }
        migratetype = MIGRATE_MOVABLE;
    }

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

out:
    local_irq_restore(flags);
}

/*
 * Free a list of 0-order pages
 */
void free_hot_cold_page_list(struct list_head *list, int 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(PageCompound(page));
    VM_BUG_ON(!page_count(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);
}

/*
 * Similar to the split_page family of functions except that the page
 * required at the given order and being isolated now to prevent races
 * with parallel allocators
 */
int capture_free_page(struct page *page, int alloc_order, int migratetype)
{
    unsigned int order;
    unsigned long watermark;
    struct zone *zone;
    int mt;

    BUG_ON(!PageBuddy(page));

    zone = page_zone(page);
    order = page_order(page);

    /* 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;

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

    mt = get_pageblock_migratetype(page);
    if (unlikely(mt != MIGRATE_ISOLATE))
        __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt);

    if (alloc_order != order)
        expand(zone, page, alloc_order, order,
            &zone->free_area[order], migratetype);

    /* Set the pageblock if the captured 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 (mt != MIGRATE_ISOLATE && !is_migrate_cma(mt))
                set_pageblock_migratetype(page,
                              MIGRATE_MOVABLE);
        }
    }

    return 1UL << alloc_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;

    BUG_ON(!PageBuddy(page));
    order = page_order(page);

    nr_pages = capture_free_page(page, order, 0);
    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, int order, gfp_t gfp_flags,
            int migratetype)
{
    unsigned long flags;
    struct page *page;
    int cold = !!(gfp_flags & __GFP_COLD);

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_pageblock_migratetype(page));
    }

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

    VM_BUG_ON(bad_range(zone, 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, 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;
    long lowmem_reserve = z->lowmem_reserve[classzone_idx];
    int o;

    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_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
#endif
    if (free_pages <= min + lowmem_reserve)
        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;
}

#ifdef CONFIG_MEMORY_ISOLATION
static inline unsigned long nr_zone_isolate_freepages(struct zone *zone)
{
    if (unlikely(zone->nr_pageblock_isolate))
        return zone->nr_pageblock_isolate * pageblock_nr_pages;
    return 0;
}
#else
static inline unsigned long nr_zone_isolate_freepages(struct zone *zone)
{
    return 0;
}
#endif

bool zone_watermark_ok(struct zone *z, 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, 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);

    /*
     * If the zone has MIGRATE_ISOLATE type free pages, we should consider
     * it.  nr_zone_isolate_freepages is never accurate so kswapd might not
     * sleep although it could do so.  But this is more desirable for memory
     * hotplug than sleeping which can cause a livelock in the direct
     * reclaim path.
     */
    free_pages -= nr_zone_isolate_freepages(z);
    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 in zonelist, then
 * returns a pointer to the allowed node mask (either the current
 * tasks mems_allowed, or node_states[N_HIGH_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_HIGH_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_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
    return node_isset(local_zone->node, zone->zone_pgdat->reclaim_nodes);
}

static void __paginginit init_zone_allows_reclaim(int nid)
{
    int i;

    for_each_online_node(i)
        if (node_distance(nid, i) <= RECLAIM_DISTANCE)
            node_set(i, NODE_DATA(nid)->reclaim_nodes);
        else
            zone_reclaim_mode = 1;
}

#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_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
    return true;
}

static inline void init_zone_allows_reclaim(int nid)
{
}
#endif  /* CONFIG_NUMA */

/*
 * get_page_from_freelist goes through the zonelist trying to allocate
 * a page.
 */
static struct page *
get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
        struct zonelist *zonelist, int high_zoneidx, int alloc_flags,
        struct zone *preferred_zone, int migratetype)
{
    struct zoneref *z;
    struct page *page = NULL;
    int classzone_idx;
    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 */

    classzone_idx = zone_idx(preferred_zone);
zonelist_scan:
    /*
     * Scan zonelist, looking for a zone with enough free.
     * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
     */
    for_each_zone_zonelist_nodemask(zone, z, zonelist,
                        high_zoneidx, nodemask) {
        if (NUMA_BUILD && zlc_active &&
            !zlc_zone_worth_trying(zonelist, z, allowednodes))
                continue;
        if ((alloc_flags & ALLOC_CPUSET) &&
            !cpuset_zone_allowed_softwall(zone, gfp_mask))
                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 ((alloc_flags & ALLOC_WMARK_LOW) &&
            (gfp_mask & __GFP_WRITE) && !zone_dirty_ok(zone))
            goto this_zone_full;

        BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
        if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
            unsigned long mark;
            int ret;

            mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
            if (zone_watermark_ok(zone, order, mark,
                    classzone_idx, alloc_flags))
                goto try_this_zone;

            if (NUMA_BUILD && !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 (NUMA_BUILD && 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 this_zone_full;
            }
        }

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

    if (unlikely(NUMA_BUILD && page == NULL && zlc_active)) {
        /* Disable zlc cache for second zonelist scan */
        zlc_active = 0;
        goto zonelist_scan;
    }

    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;
}

/*
 * 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 migratetype)
{
    struct page *page;

    /* Acquire the OOM killer lock for the zones in zonelist */
    if (!try_set_zonelist_oom(zonelist, gfp_mask)) {
        schedule_timeout_uninterruptible(1);
        return NULL;
    }

    /*
     * Go through the zonelist yet one more time, keep very high watermark
     * here, this is only to catch a parallel oom killing, we must fail if
     * we're still under heavy pressure.
     */
    page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask,
        order, zonelist, high_zoneidx,
        ALLOC_WMARK_HIGH|ALLOC_CPUSET,
        preferred_zone, 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:
    clear_zonelist_oom(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 migratetype, bool sync_migration,
    bool *contended_compaction, bool *deferred_compaction,
    unsigned long *did_some_progress)
{
    struct page *page = NULL;

    if (!order)
        return NULL;

    if (compaction_deferred(preferred_zone, order)) {
        *deferred_compaction = true;
        return NULL;
    }

    current->flags |= PF_MEMALLOC;
    *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
                        nodemask, sync_migration,
                        contended_compaction, &page);
    current->flags &= ~PF_MEMALLOC;

    /* If compaction captured a page, prep and use it */
    if (page) {
        prep_new_page(page, order, gfp_mask);
        goto got_page;
    }

    if (*did_some_progress != COMPACT_SKIPPED) {
        /* 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, migratetype);
        if (page) {
got_page:
            preferred_zone->compact_blockskip_flush = false;
            preferred_zone->compact_considered = 0;
            preferred_zone->compact_defer_shift = 0;
            if (order >= preferred_zone->compact_order_failed)
                preferred_zone->compact_order_failed = order + 1;
            count_vm_event(COMPACTSUCCESS);
            return page;
        }

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

        /*
         * As async compaction considers a subset of pageblocks, only
         * defer if the failure was a sync compaction failure.
         */
        if (sync_migration)
            defer_compaction(preferred_zone, order);

        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 migratetype, bool sync_migration,
    bool *contended_compaction, bool *deferred_compaction,
    unsigned long *did_some_progress)
{
    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 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 (NUMA_BUILD)
        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, 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 migratetype)
{
    struct page *page;

    do {
        page = get_page_from_freelist(gfp_mask, nodemask, order,
            zonelist, high_zoneidx, ALLOC_NO_WATERMARKS,
            preferred_zone, 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 inline
void wake_all_kswapd(unsigned int order, struct zonelist *zonelist,
                        enum zone_type high_zoneidx,
                        enum zone_type classzone_idx)
{
    struct zoneref *z;
    struct zone *zone;

    for_each_zone_zonelist(zone, z, zonelist, high_zoneidx)
        wakeup_kswapd(zone, order, classzone_idx);
}

static inline int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
    int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
    const gfp_t wait = gfp_mask & __GFP_WAIT;

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

    if (!wait) {
        /*
         * 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 if GFP_ATOMIC (!wait) rather than fail alloc.
         * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
         */
        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 (allocflags_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 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;
    bool sync_migration = false;
    bool deferred_compaction = false;
    bool contended_compaction = false;

    /*
     * 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 (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
        goto nopage;

restart:
    if (!(gfp_mask & __GFP_NO_KSWAPD))
        wake_all_kswapd(order, zonelist, high_zoneidx,
                        zone_idx(preferred_zone));

    /*
     * 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)
        first_zones_zonelist(zonelist, high_zoneidx, NULL,
                    &preferred_zone);

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, 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, migratetype);
        if (page) {
            goto got_pg;
        }
    }

    /* Atomic allocations - we can't balance anything */
    if (!wait)
        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,
                    migratetype, sync_migration,
                    &contended_compaction,
                    &deferred_compaction,
                    &did_some_progress);
    if (page)
        goto got_pg;
    sync_migration = true;

    /*
     * If compaction is deferred for high-order allocations, it is because
     * sync compaction recently failed. In this is the case and the caller
     * requested a movable allocation that does not heavily disrupt the
     * system then fail the allocation instead of entering direct reclaim.
     */
    if ((deferred_compaction || contended_compaction) &&
                        (gfp_mask & __GFP_NO_KSWAPD))
        goto nopage;

    /* Try direct reclaim and then allocating */
    page = __alloc_pages_direct_reclaim(gfp_mask, order,
                    zonelist, high_zoneidx,
                    nodemask,
                    alloc_flags, preferred_zone,
                    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 ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
            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,
                    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,
                    migratetype, sync_migration,
                    &contended_compaction,
                    &deferred_compaction,
                    &did_some_progress);
        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 page *page = NULL;
    int migratetype = allocflags_to_migratetype(gfp_mask);
    unsigned int cpuset_mems_cookie;
    int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET;

    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;

retry_cpuset:
    cpuset_mems_cookie = get_mems_allowed();

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

#ifdef CONFIG_CMA
    if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
        alloc_flags |= ALLOC_CMA;
#endif
    /* First allocation attempt */
    page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
            zonelist, high_zoneidx, alloc_flags,
            preferred_zone, migratetype);
    if (unlikely(!page))
        page = __alloc_pages_slowpath(gfp_mask, order,
                zonelist, high_zoneidx, nodemask,
                preferred_zone, 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(!put_mems_allowed(cpuset_mems_cookie) && !page))
        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, 0);
        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);

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;
}

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);

void *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);
}
EXPORT_SYMBOL(alloc_pages_exact_nid);

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);

static unsigned int nr_free_zone_pages(int offset)
{
    struct zoneref *z;
    struct zone *zone;

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

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

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

    return sum;
}

/*
 * Amount of free RAM allocatable within ZONE_DMA and ZONE_NORMAL
 */
unsigned int nr_free_buffer_pages(void)
{
    return nr_free_zone_pages(gfp_zone(GFP_USER));
}
EXPORT_SYMBOL_GPL(nr_free_buffer_pages);

/*
 * Amount of free RAM allocatable within all zones
 */
unsigned int nr_free_pagecache_pages(void)
{
    return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
}

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

void si_meminfo(struct sysinfo *val)
{
    val->totalram = totalram_pages;
    val->sharedram = 0;
    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)
{
    pg_data_t *pgdat = NODE_DATA(nid);

    val->totalram = pgdat->node_present_pages;
    val->freeram = node_page_state(nid, NR_FREE_PAGES);
#ifdef CONFIG_HIGHMEM
    val->totalhigh = pgdat->node_zones[ZONE_HIGHMEM].present_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 = get_mems_allowed();
        ret = !node_isset(nid, cpuset_current_mems_allowed);
    } while (!put_mems_allowed(cpuset_mems_cookie));
out:
    return ret;
}

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

/*
 * 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"
            " 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_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)),
            zone->pages_scanned,
            (zone->all_unreclaimable ? "yes" : "no")
            );
        printk("lowmem_reserve[]:");
        for (i = 0; i < MAX_NR_ZONES; i++)
            printk(" %lu", zone->lowmem_reserve[i]);
        printk("\n");
    }

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

        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++) {
            nr[order] = zone->free_area[order].nr_free;
            total += nr[order] << order;
        }
        spin_unlock_irqrestore(&zone->lock, flags);
        for (order = 0; order < MAX_ORDER; order++)
            printk("%lu*%lukB ", nr[order], K(1UL) << order);
        printk("= %lukB\n", K(total));
    }

    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, enum zone_type zone_type)
{
    struct zone *zone;

    BUG_ON(zone_type >= MAX_NR_ZONES);
    zone_type++;

    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(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)
        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;
        if (__parse_numa_zonelist_order((char*)table->data)) {
            /*
             * 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];

static int find_next_best_node(int node, nodemask_t *used_node_mask)
{
    int n, val;
    int min_val = INT_MAX;
    int best_node = -1;
    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_HIGH_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,
                            MAX_NR_ZONES - 1);
    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, MAX_NR_ZONES - 1);
    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;
}

static int default_zonelist_order(void)
{
    int nid, zone_type;
    unsigned long low_kmem_size,total_size;
    struct zone *z;
    int average_size;
    /*
         * ZONE_DMA and ZONE_DMA32 can be very small area in the system.
     * If they are really small and used heavily, the system can fall
     * into OOM very easily.
     * This function detect ZONE_DMA/DMA32 size and configures zone order.
     */
    /* Is there ZONE_NORMAL ? (ex. ppc has only DMA zone..) */
    low_kmem_size = 0;
    total_size = 0;
    for_each_online_node(nid) {
        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
            z = &NODE_DATA(nid)->node_zones[zone_type];
            if (populated_zone(z)) {
                if (zone_type < ZONE_NORMAL)
                    low_kmem_size += z->present_pages;
                total_size += z->present_pages;
            } else if (zone_type == ZONE_NORMAL) {
                /*
                 * If any node has only lowmem, then node order
                 * is preferred to allow kernel allocations
                 * locally; otherwise, they can easily infringe
                 * on other nodes when there is an abundance of
                 * lowmem available to allocate from.
                 */
                return ZONELIST_ORDER_NODE;
            }
        }
    }
    if (!low_kmem_size ||  /* there are no DMA area. */
        low_kmem_size > total_size/2) /* DMA/DMA32 is big. */
        return ZONELIST_ORDER_NODE;
    /*
     * look into each node's config.
     * If there is a node whose DMA/DMA32 memory is very big area on
     * local memory, NODE_ORDER may be suitable.
         */
    average_size = total_size /
                (nodes_weight(node_states[N_HIGH_MEMORY]) + 1);
    for_each_online_node(nid) {
        low_kmem_size = 0;
        total_size = 0;
        for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
            z = &NODE_DATA(nid)->node_zones[zone_type];
            if (populated_zone(z)) {
                if (zone_type < ZONE_NORMAL)
                    low_kmem_size += z->present_pages;
                total_size += z->present_pages;
            }
        }
        if (low_kmem_size &&
            total_size > average_size && /* ignore small node */
            low_kmem_size > total_size * 70/100)
            return ZONELIST_ORDER_NODE;
    }
    return ZONELIST_ORDER_ZONE;
}

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, MAX_NR_ZONES - 1);

    /*
     * 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,
                            MAX_NR_ZONES - 1);
    }
    for (node = 0; node < local_node; node++) {
        if (!node_online(node))
            continue;
        j = build_zonelists_node(NODE_DATA(node), zonelist, j,
                            MAX_NR_ZONES - 1);
    }

    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 {
        /* we have to stop all cpus to guarantee there is no user
           of zonelist */
#ifdef CONFIG_MEMORY_HOTPLUG
        if (zone)
            setup_zone_pageset(zone);
#endif
        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);
}

#define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))

/*
 * 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;

    /*
     * Get the start pfn, end pfn and the number of blocks to reserve
     * We have to be careful to be aligned to pageblock_nr_pages to
     * make sure that we always check pfn_valid for the first page in
     * the block.
     */
    start_pfn = zone->zone_start_pfn;
    end_pfn = start_pfn + zone->spanned_pages;
    start_pfn = roundup(start_pfn, pageblock_nr_pages);
    reserve = roundup(min_wmark_pages(zone), pageblock_nr_pages) >>
                            pageblock_order;

    /*
     * Reserve blocks are generally in place to help high-order atomic
     * allocations that are short-lived. A min_free_kbytes value that
     * would result in more than 2 reserve blocks for atomic allocations
     * is assumed to be in place to help anti-fragmentation for the
     * future allocation of hugepages at runtime.
     */
    reserve = min(2, reserve);

    for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
        if (!pfn_valid(pfn))
            continue;
        page = pfn_to_page(pfn);

        /* Watch out for overlapping nodes */
        if (page_to_nid(page) != zone_to_nid(zone))
            continue;

        block_migratetype = get_pageblock_migratetype(page);

        /* Only test what is necessary when the reserves are not met */
        if (reserve > 0) {
            /*
             * Blocks with reserved pages will never free, skip
             * them.
             */
            block_end_pfn = min(pfn + pageblock_nr_pages, end_pfn);
            if (pageblock_is_reserved(pfn, block_end_pfn))
                continue;

            /* If this block is reserved, account for it */
            if (block_migratetype == MIGRATE_RESERVE) {
                reserve--;
                continue;
            }

            /* Suitable for reserving if this block is movable */
            if (block_migratetype == MIGRATE_MOVABLE) {
                set_pageblock_migratetype(page,
                            MIGRATE_RESERVE);
                move_freepages_block(zone, page,
                            MIGRATE_RESERVE);
                reserve--;
                continue;
            }
        }

        /*
         * If the reserve is met and this is a previous reserved block,
         * take it back
         */
        if (block_migratetype == MIGRATE_RESERVE) {
            set_pageblock_migratetype(page, MIGRATE_MOVABLE);
            move_freepages_block(zone, page, MIGRATE_MOVABLE);
        }
    }
}

/*
 * Initially all pages are reserved - free ones are freed
 * up by free_all_bootmem() once the early boot process is
 * done. Non-atomic initialization, single-pass.
 */
void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
        unsigned long start_pfn, enum memmap_context context)
{
    struct page *page;
    unsigned long end_pfn = start_pfn + size;
    unsigned long pfn;
    struct zone *z;

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

    z = &NODE_DATA(nid)->node_zones[zone];
    for (pfn = start_pfn; pfn < end_pfn; pfn++) {
        /*
         * There can be holes in boot-time mem_map[]s
         * handed to this function.  They do not
         * exist on hotplugged memory.
         */
        if (context == MEMMAP_EARLY) {
            if (!early_pfn_valid(pfn))
                continue;
            if (!early_pfn_in_nid(pfn, nid))
                continue;
        }
        page = pfn_to_page(pfn);
        set_page_links(page, zone, nid, pfn);
        mminit_verify_page_links(page, zone, nid, pfn);
        init_page_count(page);
        reset_page_mapcount(page);
        SetPageReserved(page);
        /*
         * Mark the block movable so that blocks are reserved for
         * movable at startup. This will force kernel allocations
         * to reserve their blocks rather than leaking throughout
         * the address space during boot when many long-lived
         * kernel allocations are made. Later some blocks near
         * the start are marked MIGRATE_RESERVE by
         * setup_zone_migrate_reserve()
         *
         * bitmap is created for zone's valid pfn range. but memmap
         * can be created for invalid pages (for alignment)
         * check here not to call set_pageblock_migratetype() against
         * pfn out of zone.
         */
        if ((z->zone_start_pfn <= pfn)
            && (pfn < z->zone_start_pfn + z->spanned_pages)
            && !(pfn & (pageblock_nr_pages - 1)))
            set_pageblock_migratetype(page, MIGRATE_MOVABLE);

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

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

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

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

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

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

    return batch;

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

static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
{
    struct per_cpu_pages *pcp;
    int migratetype;

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

    pcp = &p->pcp;
    pcp->count = 0;
    pcp->high = 6 * batch;
    pcp->batch = max(1UL, 1 * batch);
    for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
        INIT_LIST_HEAD(&pcp->lists[migratetype]);
}

/*
 * setup_pagelist_highmark() sets the high water mark for hot per_cpu_pagelist
 * to the value high for the pageset p.
 */

static void setup_pagelist_highmark(struct per_cpu_pageset *p,
                unsigned long high)
{
    struct per_cpu_pages *pcp;

    pcp = &p->pcp;
    pcp->high = high;
    pcp->batch = max(1UL, high/4);
    if ((high/4) > (PAGE_SHIFT * 8))
        pcp->batch = PAGE_SHIFT * 8;
}

static void __meminit setup_zone_pageset(struct zone *zone)
{
    int cpu;

    zone->pageset = alloc_percpu(struct per_cpu_pageset);

    for_each_possible_cpu(cpu) {
        struct per_cpu_pageset *pcp = per_cpu_ptr(zone->pageset, cpu);

        setup_pageset(pcp, zone_batchsize(zone));

        if (percpu_pagelist_fraction)
            setup_pagelist_highmark(pcp,
                (zone->present_pages /
                    percpu_pagelist_fraction));
    }
}

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

    for_each_populated_zone(zone)
        setup_zone_pageset(zone);
}

static noinline __init_refok
int zone_wait_table_init(struct zone *zone, unsigned long zone_size_pages)
{
    int i;
    struct pglist_data *pgdat = zone->zone_pgdat;
    size_t alloc_size;

    /*
     * The per-page waitqueue mechanism uses hashed waitqueues
     * per zone.
     */
    zone->wait_table_hash_nr_entries =
         wait_table_hash_nr_entries(zone_size_pages);
    zone->wait_table_bits =
        wait_table_bits(zone->wait_table_hash_nr_entries);
    alloc_size = zone->wait_table_hash_nr_entries
                    * sizeof(wait_queue_head_t);

    if (!slab_is_available()) {
        zone->wait_table = (wait_queue_head_t *)
            alloc_bootmem_node_nopanic(pgdat, alloc_size);
    } else {
        /*
         * This case means that a zone whose size was 0 gets new memory
         * via memory hot-add.
         * But it may be the case that a new node was hot-added.  In
         * this case vmalloc() will not be able to use this new node's
         * memory - this wait_table must be initialized to use this new
         * node itself as well.
         * To use this new node's memory, further consideration will be
         * necessary.
         */
        zone->wait_table = vmalloc(alloc_size);
    }
    if (!zone->wait_table)
        return -ENOMEM;

    for(i = 0; i < zone->wait_table_hash_nr_entries; ++i)
        init_waitqueue_head(zone->wait_table + i);

    return 0;
}

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

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

int __meminit init_currently_empty_zone(struct zone *zone,
                    unsigned long zone_start_pfn,
                    unsigned long size,
                    enum memmap_context context)
{
    struct pglist_data *pgdat = zone->zone_pgdat;
    int ret;
    ret = zone_wait_table_init(zone, size);
    if (ret)
        return ret;
    pgdat->nr_zones = zone_idx(zone) + 1;

    zone->zone_start_pfn = zone_start_pfn;

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

    zone_init_free_lists(zone);

    return 0;
}

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
#ifndef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
/*
 * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
 * Architectures may implement their own version but if add_active_range()
 * was used and there are no special requirements, this is a convenient
 * alternative
 */
int __meminit __early_pfn_to_nid(unsigned long pfn)
{
    unsigned long start_pfn, end_pfn;
    int i, nid;

    for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
        if (start_pfn <= pfn && pfn < end_pfn)
            return nid;
    /* This is a memory hole */
    return -1;
}
#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */

int __meminit early_pfn_to_nid(unsigned long pfn)
{
    int nid;

    nid = __early_pfn_to_nid(pfn);
    if (nid >= 0)
        return nid;
    /* just returns 0 */
    return 0;
}

#ifdef CONFIG_NODES_SPAN_OTHER_NODES
bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
{
    int nid;

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

void __init free_bootmem_with_active_regions(int nid, unsigned long max_low_pfn)
{
    unsigned long start_pfn, end_pfn;
    int i, this_nid;

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

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

void __init sparse_memory_present_with_active_regions(int nid)
{
    unsigned long start_pfn, end_pfn;
    int i, this_nid;

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

void __meminit get_pfn_range_for_nid(unsigned int nid,
            unsigned long *start_pfn, unsigned long *end_pfn)
{
    unsigned long this_start_pfn, this_end_pfn;
    int i;

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

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

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

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

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

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

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

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

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

/*
 * Return the number of pages a zone spans in a node, including holes
 * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
 */
static unsigned long __meminit zone_spanned_pages_in_node(int nid,
                    unsigned long zone_type,
                    unsigned long *ignored)
{
    unsigned long node_start_pfn, node_end_pfn;
    unsigned long zone_start_pfn, zone_end_pfn;

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

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

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

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

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

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

unsigned long __init absent_pages_in_range(unsigned long start_pfn,
                            unsigned long end_pfn)
{
    return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
}

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

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

    adjust_zone_range_for_zone_movable(nid, zone_type,
            node_start_pfn, node_end_pfn,
            &zone_start_pfn, &zone_end_pfn);
    return __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
}

#else /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
static inline unsigned long __meminit zone_spanned_pages_in_node(int nid,
                    unsigned long zone_type,
                    unsigned long *zones_size)
{
    return zones_size[zone_type];
}

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

    return zholes_size[zone_type];
}

#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

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

    for (i = 0; i < MAX_NR_ZONES; i++)
        totalpages += zone_spanned_pages_in_node(pgdat->node_id, i,
                                zones_size);
    pgdat->node_spanned_pages = totalpages;

    realtotalpages = totalpages;
    for (i = 0; i < MAX_NR_ZONES; i++)
        realtotalpages -=
            zone_absent_pages_in_node(pgdat->node_id, i,
                                zholes_size);
    pgdat->node_present_pages = realtotalpages;
    printk(KERN_DEBUG "On node %d totalpages: %lu\n", pgdat->node_id,
                            realtotalpages);
}

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

    usemapsize = roundup(zonesize, pageblock_nr_pages);
    usemapsize = usemapsize >> pageblock_order;
    usemapsize *= NR_PAGEBLOCK_BITS;
    usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));

    return usemapsize / 8;
}

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

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

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

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

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

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

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

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

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

    pgdat_resize_init(pgdat);
    init_waitqueue_head(&pgdat->kswapd_wait);
    init_waitqueue_head(&pgdat->pfmemalloc_wait);
    pgdat_page_cgroup_init(pgdat);

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

        size = zone_spanned_pages_in_node(nid, j, zones_size);
        realsize = size - zone_absent_pages_in_node(nid, j,
                                zholes_size);

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

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

        if (!is_highmem_idx(j))
            nr_kernel_pages += realsize;
        nr_all_pages += realsize;

        zone->spanned_pages = size;
        zone->present_pages = realsize;
#ifdef CONFIG_NUMA
        zone->node = nid;
        zone->min_unmapped_pages = (realsize*sysctl_min_unmapped_ratio)
                        / 100;
        zone->min_slab_pages = (realsize * sysctl_min_slab_ratio) / 100;
#endif
        zone->name = zone_names[j];
        spin_lock_init(&zone->lock);
        spin_lock_init(&zone->lru_lock);
        zone_seqlock_init(zone);
        zone->zone_pgdat = pgdat;

        zone_pcp_init(zone);
        lruvec_init(&zone->lruvec);
        if (!size)
            continue;

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

static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
{
    /* Skip empty nodes */
    if (!pgdat->node_spanned_pages)
        return;

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

        /*
         * The zone's endpoints aren't required to be MAX_ORDER
         * aligned but the node_mem_map endpoints must be in order
         * for the buddy allocator to function correctly.
         */
        start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
        end = pgdat->node_start_pfn + pgdat->node_spanned_pages;
        end = ALIGN(end, MAX_ORDER_NR_PAGES);
        size =  (end - start) * sizeof(struct page);
        map = alloc_remap(pgdat->node_id, size);
        if (!map)
            map = alloc_bootmem_node_nopanic(pgdat, size);
        pgdat->node_mem_map = map + (pgdat->node_start_pfn - start);
    }
#ifndef CONFIG_NEED_MULTIPLE_NODES
    /*
     * With no DISCONTIG, the global mem_map is just set as node 0's
     */
    if (pgdat == NODE_DATA(0)) {
        mem_map = NODE_DATA(0)->node_mem_map;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
        if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
            mem_map -= (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
    }
#endif
#endif /* CONFIG_FLAT_NODE_MEM_MAP */
}

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

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

    pgdat->node_id = nid;
    pgdat->node_start_pfn = node_start_pfn;
    init_zone_allows_reclaim(nid);
    calculate_node_totalpages(pgdat, zones_size, zholes_size);

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

    free_area_init_core(pgdat, zones_size, zholes_size);
}

#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP

#if MAX_NUMNODES > 1
/*
 * Figure out the number of possible node ids.
 */
static void __init setup_nr_node_ids(void)
{
    unsigned int node;
    unsigned int highest = 0;

    for_each_node_mask(node, node_possible_map)
        highest = node;
    nr_node_ids = highest + 1;
}
#else
static inline void setup_nr_node_ids(void)
{
}
#endif

unsigned long __init node_map_pfn_alignment(void)
{
    unsigned long accl_mask = 0, last_end = 0;
    unsigned long start, end, mask;
    int last_nid = -1;
    int i, nid;

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

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

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

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

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

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

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

    return min_pfn;
}

unsigned long __init find_min_pfn_with_active_regions(void)
{
    return find_min_pfn_for_node(MAX_NUMNODES);
}

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

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

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

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

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

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

        required_kernelcore = max(required_kernelcore, corepages);
    }

    /* If kernelcore was not specified, there is no ZONE_MOVABLE */
    if (!required_kernelcore)
        goto out;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/* Any regular memory on that node ? */
static void __init check_for_regular_memory(pg_data_t *pgdat)
{
#ifdef CONFIG_HIGHMEM
    enum zone_type zone_type;

    for (zone_type = 0; zone_type <= ZONE_NORMAL; zone_type++) {
        struct zone *zone = &pgdat->node_zones[zone_type];
        if (zone->present_pages) {
            node_set_state(zone_to_nid(zone), N_NORMAL_MEMORY);
            break;
        }
    }
#endif
}

void __init free_area_init_nodes(unsigned long *max_zone_pfn)
{
    unsigned long start_pfn, end_pfn;
    int i, nid;

    /* Record where the zone boundaries are */
    memset(arch_zone_lowest_possible_pfn, 0,
                sizeof(arch_zone_lowest_possible_pfn));
    memset(arch_zone_highest_possible_pfn, 0,
                sizeof(arch_zone_highest_possible_pfn));
    arch_zone_lowest_possible_pfn[0] = find_min_pfn_with_active_regions();
    arch_zone_highest_possible_pfn[0] = max_zone_pfn[0];
    for (i = 1; i < MAX_NR_ZONES; i++) {
        if (i == ZONE_MOVABLE)
            continue;
        arch_zone_lowest_possible_pfn[i] =
            arch_zone_highest_possible_pfn[i-1];
        arch_zone_highest_possible_pfn[i] =
            max(max_zone_pfn[i], arch_zone_lowest_possible_pfn[i]);
    }
    arch_zone_lowest_possible_pfn[ZONE_MOVABLE] = 0;
    arch_zone_highest_possible_pfn[ZONE_MOVABLE] = 0;

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

    /* Print out the zone ranges */
    printk("Zone ranges:\n");
    for (i = 0; i < MAX_NR_ZONES; i++) {
        if (i == ZONE_MOVABLE)
            continue;
        printk(KERN_CONT "  %-8s ", zone_names[i]);
        if (arch_zone_lowest_possible_pfn[i] ==
                arch_zone_highest_possible_pfn[i])
            printk(KERN_CONT "empty\n");
        else
            printk(KERN_CONT "[mem %0#10lx-%0#10lx]\n",
                arch_zone_lowest_possible_pfn[i] << PAGE_SHIFT,
                (arch_zone_highest_possible_pfn[i]
                    << PAGE_SHIFT) - 1);
    }

    /* Print out the PFNs ZONE_MOVABLE begins at in each node */
    printk("Movable zone start for each node\n");
    for (i = 0; i < MAX_NUMNODES; i++) {
        if (zone_movable_pfn[i])
            printk("  Node %d: %#010lx\n", i,
                   zone_movable_pfn[i] << PAGE_SHIFT);
    }

    /* Print out the early node map */
    printk("Early memory node ranges\n");
    for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
        printk("  node %3d: [mem %#010lx-%#010lx]\n", nid,
               start_pfn << PAGE_SHIFT, (end_pfn << PAGE_SHIFT) - 1);

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

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

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

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

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

    return 0;
}

/*
 * kernelcore=size sets the amount of memory for use for allocations that
 * cannot be reclaimed or migrated.
 */
static int __init cmdline_parse_kernelcore(char *p)
{
    return cmdline_parse_core(p, &required_kernelcore);
}

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

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

#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */

void __init set_dma_reserve(unsigned long new_dma_reserve)
{
    dma_reserve = new_dma_reserve;
}

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

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

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

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

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

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

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

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

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

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

            if (max > zone->present_pages)
                max = zone->present_pages;
            reserve_pages += max;
            /*
             * Lowmem reserves are not available to
             * GFP_HIGHUSER page cache allocations and
             * kswapd tries to balance zones to their high
             * watermark.  As a result, neither should be
             * regarded as dirtyable memory, to prevent a
             * situation where reclaim has to clean pages
             * in order to balance the zones.
             */
            zone->dirty_balance_reserve = max;
        }
    }
    dirty_balance_reserve = reserve_pages;
    totalreserve_pages = reserve_pages;
}

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

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

            zone->lowmem_reserve[j] = 0;

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

                idx--;

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

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

    /* update totalreserve_pages */
    calculate_totalreserve_pages();
}

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

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

    for_each_zone(zone) {
        u64 tmp;

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

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

        zone->watermark[WMARK_LOW]  = min_wmark_pages(zone) + (tmp >> 2);
        zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1);

        zone->watermark[WMARK_MIN] += cma_wmark_pages(zone);
        zone->watermark[WMARK_LOW] += cma_wmark_pages(zone);
        zone->watermark[WMARK_HIGH] += cma_wmark_pages(zone);

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

    /* update totalreserve_pages */
    calculate_totalreserve_pages();
}

void setup_per_zone_wmarks(void)
{
    mutex_lock(&zonelists_mutex);
    __setup_per_zone_wmarks();
    mutex_unlock(&zonelists_mutex);
}

/*
 * The inactive anon list should be small enough that the VM never has to
 * do too much work, but large enough that each inactive page has a chance
 * to be referenced again before it is swapped out.
 *
 * The inactive_anon ratio is the target ratio of ACTIVE_ANON to
 * INACTIVE_ANON pages on this zone's LRU, maintained by the
 * pageout code. A zone->inactive_ratio of 3 means 3:1 or 25% of
 * the anonymous pages are kept on the inactive list.
 *
 * total     target    max
 * memory    ratio     inactive anon
 * -------------------------------------
 *   10MB       1         5MB
 *  100MB       1        50MB
 *    1GB       3       250MB
 *   10GB      10       0.9GB
 *  100GB      31         3GB
 *    1TB     101        10GB
 *   10TB     320        32GB
 */
static void __meminit calculate_zone_inactive_ratio(struct zone *zone)
{
    unsigned int gb, ratio;

    /* Zone size in gigabytes */
    gb = zone->present_pages >> (30 - PAGE_SHIFT);
    if (gb)
        ratio = int_sqrt(10 * gb);
    else
        ratio = 1;

    zone->inactive_ratio = ratio;
}

static void __meminit setup_per_zone_inactive_ratio(void)
{
    struct zone *zone;

    for_each_zone(zone)
        calculate_zone_inactive_ratio(zone);
}

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

    lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);

    min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
    if (min_free_kbytes < 128)
        min_free_kbytes = 128;
    if (min_free_kbytes > 65536)
        min_free_kbytes = 65536;
    setup_per_zone_wmarks();
    refresh_zone_stat_thresholds();
    setup_per_zone_lowmem_reserve();
    setup_per_zone_inactive_ratio();
    return 0;
}
module_init(init_per_zone_wmark_min)

/*
 * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so 
 *  that we can call two helper functions whenever min_free_kbytes
 *  changes.
 */
int min_free_kbytes_sysctl_handler(ctl_table *table, int write, 
    void __user *buffer, size_t *length, loff_t *ppos)
{
    proc_dointvec(table, write, buffer, length, ppos);
    if (write)
        setup_per_zone_wmarks();
    return 0;
}

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

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

    for_each_zone(zone)
        zone->min_unmapped_pages = (zone->present_pages *
                sysctl_min_unmapped_ratio) / 100;
    return 0;
}

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

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

    for_each_zone(zone)
        zone->min_slab_pages = (zone->present_pages *
                sysctl_min_slab_ratio) / 100;
    return 0;
}
#endif

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

/*
 * percpu_pagelist_fraction - changes the pcp->high for each zone on each
 * cpu.  It is the fraction of total pages in each zone that a hot per cpu pagelist
 * can have before it gets flushed back to buddy allocator.
 */

int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
    void __user *buffer, size_t *length, loff_t *ppos)
{
    struct zone *zone;
    unsigned int cpu;
    int ret;

    ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
    if (!write || (ret < 0))
        return ret;
    for_each_populated_zone(zone) {
        for_each_possible_cpu(cpu) {
            unsigned long  high;
            high = zone->present_pages / percpu_pagelist_fraction;
            setup_pagelist_highmark(
                per_cpu_ptr(zone->pageset, cpu), high);
        }
    }
    return 0;
}

int hashdist = HASHDIST_DEFAULT;

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

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

    /* allow the kernel cmdline to have a say */
    if (!numentries) {
        /* round applicable memory size up to nearest megabyte */
        numentries = nr_kernel_pages;
        numentries += (1UL << (20 - PAGE_SHIFT)) - 1;
        numentries >>= 20 - PAGE_SHIFT;
        numentries <<= 20 - PAGE_SHIFT;

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

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

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

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

    log2qty = ilog2(numentries);

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

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

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

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

    return table;
}

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

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

unsigned long get_pageblock_flags_group(struct page *page,
                    int start_bitidx, int end_bitidx)
{
    struct zone *zone;
    unsigned long *bitmap;
    unsigned long pfn, bitidx;
    unsigned long flags = 0;
    unsigned long value = 1;

    zone = page_zone(page);
    pfn = page_to_pfn(page);
    bitmap = get_pageblock_bitmap(zone, pfn);
    bitidx = pfn_to_bitidx(zone, pfn);

    for (; start_bitidx <= end_bitidx; start_bitidx++, value <<= 1)
        if (test_bit(bitidx + start_bitidx, bitmap))
            flags |= value;

    return flags;
}

void set_pageblock_flags_group(struct page *page, unsigned long flags,
                    int start_bitidx, int end_bitidx)
{
    struct zone *zone;
    unsigned long *bitmap;
    unsigned long pfn, bitidx;
    unsigned long value = 1;

    zone = page_zone(page);
    pfn = page_to_pfn(page);
    bitmap = get_pageblock_bitmap(zone, pfn);
    bitidx = pfn_to_bitidx(zone, pfn);
    VM_BUG_ON(pfn < zone->zone_start_pfn);
    VM_BUG_ON(pfn >= zone->zone_start_pfn + zone->spanned_pages);

    for (; start_bitidx <= end_bitidx; start_bitidx++, value <<= 1)
        if (flags & value)
            __set_bit(bitidx + start_bitidx, bitmap);
        else
            __clear_bit(bitidx + start_bitidx, bitmap);
}

/*
 * This function checks whether pageblock includes unmovable pages or not.
 * If @count is not zero, it is okay to include less @count unmovable pages
 *
 * PageLRU check wihtout isolation or lru_lock could race so that
 * MIGRATE_MOVABLE block might include unmovable pages. It means you can't
 * expect this function should be exact.
 */
bool has_unmovable_pages(struct zone *zone, struct page *page, int count)
{
    unsigned long pfn, iter, found;
    int mt;

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

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

        if (!pfn_valid_within(check))
            continue;

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

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

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

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

    zone = page_zone(page);
    pfn = page_to_pfn(page);
    if (zone->zone_start_pfn > pfn ||
            zone->zone_start_pfn + zone->spanned_pages <= pfn)
        return false;

    return !has_unmovable_pages(zone, page, 0);
}

#ifdef CONFIG_CMA

static unsigned long pfn_max_align_down(unsigned long pfn)
{
    return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
                 pageblock_nr_pages) - 1);
}

static unsigned long pfn_max_align_up(unsigned long pfn)
{
    return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
                pageblock_nr_pages));
}

/* [start, end) must belong to a single zone. */
static int __alloc_contig_migrate_range(struct compact_control *cc,
                    unsigned long start, unsigned long end)
{
    /* This function is based on compact_zone() from compaction.c. */
    unsigned long nr_reclaimed;
    unsigned long pfn = start;
    unsigned int tries = 0;
    int ret = 0;

    migrate_prep_local();

    while (pfn < end || !list_empty(&cc->migratepages)) {
        if (fatal_signal_pending(current)) {
            ret = -EINTR;
            break;
        }

        if (list_empty(&cc->migratepages)) {
            cc->nr_migratepages = 0;
            pfn = isolate_migratepages_range(cc->zone, cc,
                             pfn, end, true);
            if (!pfn) {
                ret = -EINTR;
                break;
            }
            tries = 0;
        } else if (++tries == 5) {
            ret = ret < 0 ? ret : -EBUSY;
            break;
        }

        nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
                            &cc->migratepages);
        cc->nr_migratepages -= nr_reclaimed;

        ret = migrate_pages(&cc->migratepages,
                    alloc_migrate_target,
                    0, false, MIGRATE_SYNC);
    }

    putback_lru_pages(&cc->migratepages);
    return ret > 0 ? 0 : ret;
}

/*
 * Update zone's cma pages counter used for watermark level calculation.
 */
static inline void __update_cma_watermarks(struct zone *zone, int count)
{
    unsigned long flags;
    spin_lock_irqsave(&zone->lock, flags);
    zone->min_cma_pages += count;
    spin_unlock_irqrestore(&zone->lock, flags);
    setup_per_zone_wmarks();
}

/*
 * Trigger memory pressure bump to reclaim some pages in order to be able to
 * allocate 'count' pages in single page units. Does similar work as
 *__alloc_pages_slowpath() function.
 */
static int __reclaim_pages(struct zone *zone, gfp_t gfp_mask, int count)
{
    enum zone_type high_zoneidx = gfp_zone(gfp_mask);
    struct zonelist *zonelist = node_zonelist(0, gfp_mask);
    int did_some_progress = 0;
    int order = 1;

    /*
     * Increase level of watermarks to force kswapd do his job
     * to stabilise at new watermark level.
     */
    __update_cma_watermarks(zone, count);

    /* Obey watermarks as if the page was being allocated */
    while (!zone_watermark_ok(zone, 0, low_wmark_pages(zone), 0, 0)) {
        wake_all_kswapd(order, zonelist, high_zoneidx, zone_idx(zone));

        did_some_progress = __perform_reclaim(gfp_mask, order, zonelist,
                              NULL);
        if (!did_some_progress) {
            /* Exhausted what can be done so it's blamo time */
            out_of_memory(zonelist, gfp_mask, order, NULL, false);
        }
    }

    /* Restore original watermark levels. */
    __update_cma_watermarks(zone, -count);

    return count;
}

int alloc_contig_range(unsigned long start, unsigned long end,
               unsigned migratetype)
{
    struct zone *zone = page_zone(pfn_to_page(start));
    unsigned long outer_start, outer_end;
    int ret = 0, order;

    struct compact_control cc = {
        .nr_migratepages = 0,
        .order = -1,
        .zone = page_zone(pfn_to_page(start)),
        .sync = true,
        .ignore_skip_hint = true,
    };
    INIT_LIST_HEAD(&cc.migratepages);

    /*
     * What we do here is we mark all pageblocks in range as
     * MIGRATE_ISOLATE.  Because pageblock and max order pages may
     * have different sizes, and due to the way page allocator
     * work, we align the range to biggest of the two pages so
     * that page allocator won't try to merge buddies from
     * different pageblocks and change MIGRATE_ISOLATE to some
     * other migration type.
     *
     * Once the pageblocks are marked as MIGRATE_ISOLATE, we
     * migrate the pages from an unaligned range (ie. pages that
     * we are interested in).  This will put all the pages in
     * range back to page allocator as MIGRATE_ISOLATE.
     *
     * When this is done, we take the pages in range from page
     * allocator removing them from the buddy system.  This way
     * page allocator will never consider using them.
     *
     * This lets us mark the pageblocks back as
     * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
     * aligned range but not in the unaligned, original range are
     * put back to page allocator so that buddy can use them.
     */

    ret = start_isolate_page_range(pfn_max_align_down(start),
                       pfn_max_align_up(end), migratetype);
    if (ret)
        return ret;

    ret = __alloc_contig_migrate_range(&cc, start, end);
    if (ret)
        goto done;

    /*
     * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
     * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
     * more, all pages in [start, end) are free in page allocator.
     * What we are going to do is to allocate all pages from
     * [start, end) (that is remove them from page allocator).
     *
     * The only problem is that pages at the beginning and at the
     * end of interesting range may be not aligned with pages that
     * page allocator holds, ie. they can be part of higher order
     * pages.  Because of this, we reserve the bigger range and
     * once this is done free the pages we are not interested in.
     *
     * We don't have to hold zone->lock here because the pages are
     * isolated thus they won't get removed from buddy.
     */

    lru_add_drain_all();
    drain_all_pages();

    order = 0;
    outer_start = start;
    while (!PageBuddy(pfn_to_page(outer_start))) {
        if (++order >= MAX_ORDER) {
            ret = -EBUSY;
            goto done;
        }
        outer_start &= ~0UL << order;
    }

    /* Make sure the range is really isolated. */
    if (test_pages_isolated(outer_start, end)) {
        pr_warn("alloc_contig_range test_pages_isolated(%lx, %lx) failed\n",
               outer_start, end);
        ret = -EBUSY;
        goto done;
    }

    /*
     * Reclaim enough pages to make sure that contiguous allocation
     * will not starve the system.
     */
    __reclaim_pages(zone, GFP_HIGHUSER_MOVABLE, end-start);

    /* Grab isolated pages from freelists. */
    outer_end = isolate_freepages_range(&cc, outer_start, end);
    if (!outer_end) {
        ret = -EBUSY;
        goto done;
    }

    /* Free head and tail (if any) */
    if (start != outer_start)
        free_contig_range(outer_start, start - outer_start);
    if (end != outer_end)
        free_contig_range(end, outer_end - end);

done:
    undo_isolate_page_range(pfn_max_align_down(start),
                pfn_max_align_up(end), migratetype);
    return ret;
}

void free_contig_range(unsigned long pfn, unsigned nr_pages)
{
    for (; nr_pages--; ++pfn)
        __free_page(pfn_to_page(pfn));
}
#endif

#ifdef CONFIG_MEMORY_HOTPLUG
static int __meminit __zone_pcp_update(void *data)
{
    struct zone *zone = data;
    int cpu;
    unsigned long batch = zone_batchsize(zone), flags;

    for_each_possible_cpu(cpu) {
        struct per_cpu_pageset *pset;
        struct per_cpu_pages *pcp;

        pset = per_cpu_ptr(zone->pageset, cpu);
        pcp = &pset->pcp;

        local_irq_save(flags);
        if (pcp->count > 0)
            free_pcppages_bulk(zone, pcp->count, pcp);
        drain_zonestat(zone, pset);
        setup_pageset(pset, batch);
        local_irq_restore(flags);
    }
    return 0;
}

void __meminit zone_pcp_update(struct zone *zone)
{
    stop_machine(__zone_pcp_update, zone, NULL);
}
#endif

#ifdef CONFIG_MEMORY_HOTREMOVE
void zone_pcp_reset(struct zone *zone)
{
    unsigned long flags;
    int cpu;
    struct per_cpu_pageset *pset;

    /* avoid races with drain_pages()  */
    local_irq_save(flags);
    if (zone->pageset != &boot_pageset) {
        for_each_online_cpu(cpu) {
            pset = per_cpu_ptr(zone->pageset, cpu);
            drain_zonestat(zone, pset);
        }
        free_percpu(zone->pageset);
        zone->pageset = &boot_pageset;
    }
    local_irq_restore(flags);
}

/*
 * All pages in the range must be isolated before calling this.
 */
void
__offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
{
    struct page *page;
    struct zone *zone;
    int order, i;
    unsigned long pfn;
    unsigned long flags;
    /* find the first valid pfn */
    for (pfn = start_pfn; pfn < end_pfn; pfn++)
        if (pfn_valid(pfn))
            break;
    if (pfn == end_pfn)
        return;
    zone = page_zone(pfn_to_page(pfn));
    spin_lock_irqsave(&zone->lock, flags);
    pfn = start_pfn;
    while (pfn < end_pfn) {
        if (!pfn_valid(pfn)) {
            pfn++;
            continue;
        }
        page = pfn_to_page(pfn);
        BUG_ON(page_count(page));
        BUG_ON(!PageBuddy(page));
        order = page_order(page);
#ifdef CONFIG_DEBUG_VM
        printk(KERN_INFO "remove from free list %lx %d %lx\n",
               pfn, 1 << order, end_pfn);
#endif
        list_del(&page->lru);
        rmv_page_order(page);
        zone->free_area[order].nr_free--;
        __mod_zone_page_state(zone, NR_FREE_PAGES,
                      - (1UL << order));
        for (i = 0; i < (1 << order); i++)
            SetPageReserved((page+i));
        pfn += (1 << order);
    }
    spin_unlock_irqrestore(&zone->lock, flags);
}
#endif

#ifdef CONFIG_MEMORY_FAILURE
bool is_free_buddy_page(struct page *page)
{
    struct zone *zone = page_zone(page);
    unsigned long pfn = page_to_pfn(page);
    unsigned long flags;
    int order;

    spin_lock_irqsave(&zone->lock, flags);
    for (order = 0; order < MAX_ORDER; order++) {
        struct page *page_head = page - (pfn & ((1 << order) - 1));

        if (PageBuddy(page_head) && page_order(page_head) >= order)
            break;
    }
    spin_unlock_irqrestore(&zone->lock, flags);

    return order < MAX_ORDER;
}
#endif

static const struct trace_print_flags pageflag_names[] = {
    {1UL << PG_locked,      "locked"    },
    {1UL << PG_error,       "error"     },
    {1UL << PG_referenced,      "referenced"    },
    {1UL << PG_uptodate,        "uptodate"  },
    {1UL << PG_dirty,       "dirty"     },
    {1UL << PG_lru,         "lru"       },
    {1UL << PG_active,      "active"    },
    {1UL << PG_slab,        "slab"      },
    {1UL << PG_owner_priv_1,    "owner_priv_1"  },
    {1UL << PG_arch_1,      "arch_1"    },
    {1UL << PG_reserved,        "reserved"  },
    {1UL << PG_private,     "private"   },
    {1UL << PG_private_2,       "private_2" },
    {1UL << PG_writeback,       "writeback" },
#ifdef CONFIG_PAGEFLAGS_EXTENDED
    {1UL << PG_head,        "head"      },
    {1UL << PG_tail,        "tail"      },
#else
    {1UL << PG_compound,        "compound"  },
#endif
    {1UL << PG_swapcache,       "swapcache" },
    {1UL << PG_mappedtodisk,    "mappedtodisk"  },
    {1UL << PG_reclaim,     "reclaim"   },
    {1UL << PG_swapbacked,      "swapbacked"    },
    {1UL << PG_unevictable,     "unevictable"   },
#ifdef CONFIG_MMU
    {1UL << PG_mlocked,     "mlocked"   },
#endif
#ifdef CONFIG_ARCH_USES_PG_UNCACHED
    {1UL << PG_uncached,        "uncached"  },
#endif
#ifdef CONFIG_MEMORY_FAILURE
    {1UL << PG_hwpoison,        "hwpoison"  },
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    {1UL << PG_compound_lock,   "compound_lock" },
#endif
};

static void dump_page_flags(unsigned long flags)
{
    const char *delim = "";
    unsigned long mask;
    int i;

    BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS);

    printk(KERN_ALERT "page flags: %#lx(", flags);

    /* remove zone id */
    flags &= (1UL << NR_PAGEFLAGS) - 1;

    for (i = 0; i < ARRAY_SIZE(pageflag_names) && flags; i++) {

        mask = pageflag_names[i].mask;
        if ((flags & mask) != mask)
            continue;

        flags &= ~mask;
        printk("%s%s", delim, pageflag_names[i].name);
        delim = "|";
    }

    /* check for left over flags */
    if (flags)
        printk("%s%#lx", delim, flags);

    printk(")\n");
}

void dump_page(struct page *page)
{
    printk(KERN_ALERT
           "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
        page, atomic_read(&page->_count), page_mapcount(page),
        page->mapping, page->index);
    dump_page_flags(page->flags);
    mem_cgroup_print_bad_page(page);
}