/*
 *  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/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/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/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/memory.h>
#include <linux/compaction.h>
#include <trace/events/kmem.h>
#include <linux/ftrace_event.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;
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).
 */
void set_gfp_allowed_mask(gfp_t mask)
{
        WARN_ON(!mutex_is_locked(&pm_mutex));
        gfp_allowed_mask = mask;
}

gfp_t clear_gfp_allowed_mask(gfp_t mask)
{
        gfp_t ret = gfp_allowed_mask;

        WARN_ON(!mutex_is_locked(&pm_mutex));
        gfp_allowed_mask &= ~mask;
        return ret;
}
#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_ARCH_POPULATES_NODE_MAP
  /*
   * MAX_ACTIVE_REGIONS determines the maximum number of distinct
   * ranges of memory (RAM) that may be registered with add_active_range().
   * Ranges passed to add_active_range() will be merged if possible
   * so the number of times add_active_range() can be called is
   * related to the number of nodes and the number of holes
   */
  #ifdef CONFIG_MAX_ACTIVE_REGIONS
    /* Allow an architecture to set MAX_ACTIVE_REGIONS to save memory */
    #define MAX_ACTIVE_REGIONS CONFIG_MAX_ACTIVE_REGIONS
  #else
    #if MAX_NUMNODES >= 32
      /* If there can be many nodes, allow up to 50 holes per node */
      #define MAX_ACTIVE_REGIONS (MAX_NUMNODES*50)
    #else
      /* By default, allow up to 256 distinct regions */
      #define MAX_ACTIVE_REGIONS 256
    #endif
  #endif

  static struct node_active_region __meminitdata early_node_map[MAX_ACTIVE_REGIONS];
  static int __meminitdata nr_nodemap_entries;
  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_ARCH_POPULATES_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;

static 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)) {
                __ClearPageBuddy(page);
                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);

        dump_stack();
out:
        /* Leave bad fields for debug, except PageBuddy could make trouble */
        __ClearPageBuddy(page);
        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 pages have their ->private pointing at
 * the head page (even the head page has this).
 *
 * 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);
                p->first_page = page;
        }
}

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);
}

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 struct page *
__page_find_buddy(struct page *page, unsigned long page_idx, unsigned int order)
{
        unsigned long buddy_idx = page_idx ^ (1 << order);

        return page + (buddy_idx - page_idx);
}

static inline unsigned long
__find_combined_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 use PG_buddy.
 * Setting, clearing, and testing PG_buddy 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 (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 PG_buddy. 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;
        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 = __page_find_buddy(page, page_idx, order);
                if (!page_is_buddy(page, buddy, order))
                        break;

                /* Our buddy is free, merge with it and move up one order. */
                list_del(&buddy->lru);
                zone->free_area[order].nr_free--;
                rmv_page_order(buddy);
                combined_idx = __find_combined_index(page_idx, order);
                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-1) && pfn_valid_within(page_to_pfn(buddy))) {
                struct page *higher_page, *higher_buddy;
                combined_idx = __find_combined_index(page_idx, order);
                higher_page = page + combined_idx - page_idx;
                higher_buddy = __page_find_buddy(higher_page, combined_idx, order + 1);
                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++;
}

/*
 * free_page_mlock() -- clean up attempts to free and mlocked() page.
 * Page should not be on lru, so no need to fix that up.
 * free_pages_check() will verify...
 */
static inline void free_page_mlock(struct page *page)
{
        __dec_zone_page_state(page, NR_MLOCK);
        __count_vm_event(UNEVICTABLE_MLOCKFREED);
}

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))) {
                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;

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

        __mod_zone_page_state(zone, NR_FREE_PAGES, count);
        while (count) {
                struct page *page;
                struct list_head *list;

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

                do {
                        page = list_entry(list->prev, struct page, lru);
                        /* must delete as __free_one_page list manipulates */
                        list_del(&page->lru);
                        /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
                        __free_one_page(page, zone, 0, page_private(page));
                        trace_mm_page_pcpu_drain(page, 0, page_private(page));
                } while (--count && --batch_free && !list_empty(list));
        }
        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;

        __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
        __free_one_page(page, zone, order, migratetype);
        spin_unlock(&zone->lock);
}

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

        trace_mm_page_free_direct(page, order);
        kmemcheck_free_shadow(page, order);

        for (i = 0; i < (1 << order); i++) {
                struct page *pg = page + i;

                if (PageAnon(pg))
                        pg->mapping = NULL;
                bad += free_pages_check(pg);
        }
        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 wasMlocked = __TestClearPageMlocked(page);

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

        local_irq_save(flags);
        if (unlikely(wasMlocked))
                free_page_mlock(page);
        __count_vm_events(PGFREE, 1 << order);
        free_one_page(page_zone(page), page, order,
                                        get_pageblock_migratetype(page));
        local_irq_restore(flags);
}

/*
 * permit the bootmem allocator to evade page validation on high-order frees
 */
void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
{
        if (order == 0) {
                __ClearPageReserved(page);
                set_page_count(page, 0);
                set_page_refcounted(page);
                __free_page(page);
        } else {
                int loop;

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

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

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


/*
 * 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]));
                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))) {
                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][MIGRATE_TYPES-1] = {
        [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_RESERVE },
        [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_RESERVE },
        [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
        [MIGRATE_RESERVE]     = { MIGRATE_RESERVE,     MIGRATE_RESERVE,   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()
 */
static 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_del(&page->lru);
                list_add(&page->lru,
                        &zone->free_area[order].free_list[migratetype]);
                page += 1 << order;
                pages_moved += 1 << order;
        }

        return pages_moved;
}

static 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 < MIGRATE_TYPES - 1; i++) {
                        migratetype = fallbacks[start_migratetype][i];

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

                        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
                         * agressive about taking ownership of free pages
                         */
                        if (unlikely(current_order >= (pageblock_order >> 1)) ||
                                        start_migratetype == MIGRATE_RECLAIMABLE ||
                                        page_group_by_mobility_disabled) {
                                unsigned long 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)
                                change_pageblock_range(page, current_order,
                                                        start_migratetype);

                        expand(zone, page, order, current_order, area, 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 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);
                set_page_private(page, migratetype);
                list = &page->lru;
        }
        __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;
        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;
                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
 */
void drain_all_pages(void)
{
        on_each_cpu(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;
        int wasMlocked = __TestClearPageMlocked(page);

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

        migratetype = get_pageblock_migratetype(page);
        set_page_private(page, migratetype);
        local_irq_save(flags);
        if (unlikely(wasMlocked))
                free_page_mlock(page);
        __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);
}

/*
 * 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 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;
        unsigned long watermark;
        struct zone *zone;

        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);
        __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));

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

        if (order >= pageblock_order - 1) {
                struct page *endpage = page + (1 << order) - 1;
                for (; page < endpage; page += pageblock_nr_pages)
                        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
        }

        return 1 << order;
}

/*
 * 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_page_state(zone, NR_FREE_PAGES, -(1 << order));
        }

        __count_zone_vm_events(PGALLOC, zone, 1 << order);
        zone_statistics(preferred_zone, zone);
        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;
}

/* The ALLOC_WMARK bits are used as an index to zone->watermark */
#define ALLOC_WMARK_MIN         WMARK_MIN
#define ALLOC_WMARK_LOW         WMARK_LOW
#define ALLOC_WMARK_HIGH        WMARK_HIGH
#define ALLOC_NO_WATERMARKS     0x04 /* don't check watermarks at all */

/* Mask to get the watermark bits */
#define ALLOC_WMARK_MASK        (ALLOC_NO_WATERMARKS-1)

#define ALLOC_HARDER            0x10 /* try to alloc harder */
#define ALLOC_HIGH              0x20 /* __GFP_HIGH set */
#define ALLOC_CPUSET            0x40 /* check for correct cpuset */

#ifdef CONFIG_FAIL_PAGE_ALLOC

static struct fail_page_alloc_attr {
        struct fault_attr attr;

        u32 ignore_gfp_highmem;
        u32 ignore_gfp_wait;
        u32 min_order;

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

        struct dentry *ignore_gfp_highmem_file;
        struct dentry *ignore_gfp_wait_file;
        struct dentry *min_order_file;

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */

} 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 int should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        if (order < fail_page_alloc.min_order)
                return 0;
        if (gfp_mask & __GFP_NOFAIL)
                return 0;
        if (fail_page_alloc.ignore_gfp_highmem && (gfp_mask & __GFP_HIGHMEM))
                return 0;
        if (fail_page_alloc.ignore_gfp_wait && (gfp_mask & __GFP_WAIT))
                return 0;

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

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

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

        err = init_fault_attr_dentries(&fail_page_alloc.attr,
                                       "fail_page_alloc");
        if (err)
                return err;
        dir = fail_page_alloc.attr.dentries.dir;

        fail_page_alloc.ignore_gfp_wait_file =
                debugfs_create_bool("ignore-gfp-wait", mode, dir,
                                      &fail_page_alloc.ignore_gfp_wait);

        fail_page_alloc.ignore_gfp_highmem_file =
                debugfs_create_bool("ignore-gfp-highmem", mode, dir,
                                      &fail_page_alloc.ignore_gfp_highmem);
        fail_page_alloc.min_order_file =
                debugfs_create_u32("min-order", mode, dir,
                                   &fail_page_alloc.min_order);

        if (!fail_page_alloc.ignore_gfp_wait_file ||
            !fail_page_alloc.ignore_gfp_highmem_file ||
            !fail_page_alloc.min_order_file) {
                err = -ENOMEM;
                debugfs_remove(fail_page_alloc.ignore_gfp_wait_file);
                debugfs_remove(fail_page_alloc.ignore_gfp_highmem_file);
                debugfs_remove(fail_page_alloc.min_order_file);
                cleanup_fault_attr_dentries(&fail_page_alloc.attr);
        }

        return err;
}

late_initcall(fail_page_alloc_debugfs);

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */

#else /* CONFIG_FAIL_PAGE_ALLOC */

static inline int should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
{
        return 0;
}

#endif /* CONFIG_FAIL_PAGE_ALLOC */

/*
 * Return 1 if free pages are above 'mark'. This takes into account the order
 * of the allocation.
 */
int zone_watermark_ok(struct zone *z, int order, unsigned long mark,
                      int classzone_idx, int alloc_flags)
{
        /* free_pages my go negative - that's OK */
        long min = mark;
        long free_pages = zone_page_state(z, NR_FREE_PAGES) - (1 << order) + 1;
        int o;

        if (alloc_flags & ALLOC_HIGH)
                min -= min / 2;
        if (alloc_flags & ALLOC_HARDER)
                min -= min / 4;

        if (free_pages <= min + z->lowmem_reserve[classzone_idx])
                return 0;
        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 0;
        }
        return 1;
}

#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);
}

#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)
{
}
#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))
                                goto try_next_zone;

                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 (zone_reclaim_mode == 0)
                                goto this_zone_full;

                        ret = zone_reclaim(zone, gfp_mask, order);
                        switch (ret) {
                        case ZONE_RECLAIM_NOSCAN:
                                /* did not scan */
                                goto try_next_zone;
                        case ZONE_RECLAIM_FULL:
                                /* scanned but unreclaimable */
                                goto this_zone_full;
                        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);
try_next_zone:
                if (NUMA_BUILD && !did_zlc_setup && nr_online_nodes > 1) {
                        /*
                         * we do zlc_setup after the first zone is tried but only
                         * if there are multiple nodes make it worthwhile
                         */
                        allowednodes = zlc_setup(zonelist, alloc_flags);
                        zlc_active = 1;
                        did_zlc_setup = 1;
                }
        }

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

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

        /*
         * Don't let big-order allocations loop unless the caller
         * explicitly requests that.
         */
        if (gfp_mask & __GFP_NOFAIL)
                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_zone_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;
                /*
                 * 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);

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, unsigned long *did_some_progress)
{
        struct page *page;

        if (!order || compaction_deferred(preferred_zone))
                return NULL;

        *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
                                                                nodemask);
        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, preferred_zone,
                                migratetype);
                if (page) {
                        preferred_zone->compact_considered = 0;
                        preferred_zone->compact_defer_shift = 0;
                        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);
                defer_compaction(preferred_zone);

                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, unsigned long *did_some_progress)
{
        return NULL;
}
#endif /* CONFIG_COMPACTION */

/* 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;
        struct reclaim_state reclaim_state;
        struct task_struct *p = current;

        cond_resched();

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

        *did_some_progress = try_to_free_pages(zonelist, order, gfp_mask, nodemask);

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

        cond_resched();

        if (order != 0)
                drain_all_pages();

        if (likely(*did_some_progress))
                page = get_page_from_freelist(gfp_mask, nodemask, order,
                                        zonelist, high_zoneidx,
                                        alloc_flags, preferred_zone,
                                        migratetype);
        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)
                        congestion_wait(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)
{
        struct zoneref *z;
        struct zone *zone;

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

static inline int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
        struct task_struct *p = current;
        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 != 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 |= (gfp_mask & __GFP_HIGH);

        if (!wait) {
                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(p)) && !in_interrupt())
                alloc_flags |= ALLOC_HARDER;

        if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
                if (!in_interrupt() &&
                    ((p->flags & PF_MEMALLOC) ||
                     unlikely(test_thread_flag(TIF_MEMDIE))))
                        alloc_flags |= ALLOC_NO_WATERMARKS;
        }

        return alloc_flags;
}

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;
        struct task_struct *p = current;

        /*
         * 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:
        wake_all_kswapd(order, zonelist, high_zoneidx);

        /*
         * 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);

        /* 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;

rebalance: