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

/*
 * 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;
unsigned long highest_memmap_pfn __read_mostly;
int percpu_pagelist_fraction;

#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;

unsigned long __meminitdata nr_kernel_pages;
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];
#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
  static unsigned long __meminitdata node_boundary_start_pfn[MAX_NUMNODES];
  static unsigned long __meminitdata node_boundary_end_pfn[MAX_NUMNODES];
#endif /* CONFIG_MEMORY_HOTPLUG_RESERVE */
  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;
EXPORT_SYMBOL(nr_node_ids);
#endif

int page_group_by_mobility_disabled __read_mostly;

static void set_pageblock_migratetype(struct page *page, int migratetype)
{
        set_pageblock_flags_group(page, (unsigned long)migratetype,
                                        PB_migrate, PB_migrate_end);
}

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

        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;

        /*
         * 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));
        printk(KERN_ALERT
                "page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
                page, (void *)page->flags, page_count(page),
                page_mapcount(page), page->mapping, page->index);

        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;
        }
}

#ifdef CONFIG_HUGETLBFS
void prep_compound_gigantic_page(struct page *page, unsigned long order)
{
        int i;
        int nr_pages = 1 << order;
        struct page *p = page + 1;

        set_compound_page_dtor(page, free_compound_page);
        set_compound_order(page, order);
        __SetPageHead(page);
        for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
                __SetPageTail(p);
                p->first_page = page;
        }
}
#endif

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) {
                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)
{
        unsigned long page_idx;
        int order_size = 1 << order;
        int migratetype = get_pageblock_migratetype(page);

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

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

        VM_BUG_ON(page_idx & (order_size - 1));
        VM_BUG_ON(bad_range(zone, page));

        __mod_zone_page_state(zone, NR_FREE_PAGES, order_size);
        while (order < MAX_ORDER-1) {
                unsigned long combined_idx;
                struct page *buddy;

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

static inline int free_pages_check(struct page *page)
{
        free_page_mlock(page);
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_count(page) != 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 list of pages. 
 * 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_pages_bulk(struct zone *zone, int count,
                                        struct list_head *list, int order)
{
        spin_lock(&zone->lock);
        zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
        zone->pages_scanned = 0;
        while (count--) {
                struct page *page;

                VM_BUG_ON(list_empty(list));
                page = list_entry(list->prev, struct page, lru);
                /* have to delete it as __free_one_page list manipulates */
                list_del(&page->lru);
                __free_one_page(page, zone, order);
        }
        spin_unlock(&zone->lock);
}

static void free_one_page(struct zone *zone, struct page *page, int order)
{
        spin_lock(&zone->lock);
        zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
        zone->pages_scanned = 0;
        __free_one_page(page, zone, order);
        spin_unlock(&zone->lock);
}

static void __free_pages_ok(struct page *page, unsigned int order)
{
        unsigned long flags;
        int i;
        int bad = 0;

        for (i = 0 ; i < (1 << order) ; ++i)
                bad += free_pages_check(page + i);
        if (bad)
                return;

        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);

        local_irq_save(flags);
        __count_vm_events(PGFREE, 1 << order);
        free_one_page(page_zone(page), page, order);
        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 int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
{
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_count(page) != 0)  |
                (page->flags & PAGE_FLAGS_CHECK_AT_PREP))) {
                bad_page(page);
                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 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--;
                __mod_zone_page_state(zone, NR_FREE_PAGES, - (1UL << order));
                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);
}

/* Remove an element from the buddy allocator from the fallback list */
static 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) {
                                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)))
                                        set_pageblock_migratetype(page,
                                                                start_migratetype);

                                migratetype = start_migratetype;
                        }

                        /* Remove the page from the freelists */
                        list_del(&page->lru);
                        rmv_page_order(page);
                        __mod_zone_page_state(zone, NR_FREE_PAGES,
                                                        -(1UL << order));

                        if (current_order == pageblock_order)
                                set_pageblock_migratetype(page,
                                                        start_migratetype);

                        expand(zone, page, order, current_order, area, migratetype);
                        return page;
                }
        }

        /* Use MIGRATE_RESERVE rather than fail an allocation */
        return __rmqueue_smallest(zone, order, MIGRATE_RESERVE);
}

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

        page = __rmqueue_smallest(zone, order, migratetype);

        if (unlikely(!page))
                page = __rmqueue_fallback(zone, 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;
        }
        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_pages_bulk(zone, to_drain, &pcp->list, 0);
        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;

                pset = zone_pcp(zone, cpu);

                pcp = &pset->pcp;
                local_irq_save(flags);
                free_pages_bulk(zone, pcp->count, &pcp->list, 0);
                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
 */
static void free_hot_cold_page(struct page *page, int cold)
{
        struct zone *zone = page_zone(page);
        struct per_cpu_pages *pcp;

        unsigned long flags;

        if (PageAnon(page))
                page->mapping = NULL;
        if (free_pages_check(page))
                return;

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

        pcp = &zone_pcp(zone, get_cpu())->pcp;
        local_irq_save(flags);
        __count_vm_event(PGFREE);
        if (cold)
                list_add_tail(&page->lru, &pcp->list);
        else
                list_add(&page->lru, &pcp->list);
        set_page_private(page, get_pageblock_migratetype(page));
        pcp->count++;
        if (pcp->count >= pcp->high) {
                free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
                pcp->count -= pcp->batch;
        }
        local_irq_restore(flags);
        put_cpu();
}

void free_hot_page(struct page *page)
{
        free_hot_cold_page(page, 0);
}
        
void free_cold_page(struct page *page)
{
        free_hot_cold_page(page, 1);
}

/*
 * 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));
        for (i = 1; i < (1 << order); i++)
                set_page_refcounted(page + i);
}

/*
 * 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 struct page *buffered_rmqueue(struct zone *preferred_zone,
                        struct zone *zone, int order, gfp_t gfp_flags)
{
        unsigned long flags;
        struct page *page;
        int cold = !!(gfp_flags & __GFP_COLD);
        int cpu;
        int migratetype = allocflags_to_migratetype(gfp_flags);

again:
        cpu  = get_cpu();
        if (likely(order == 0)) {
                struct per_cpu_pages *pcp;

                pcp = &zone_pcp(zone, cpu)->pcp;
                local_irq_save(flags);
                if (!pcp->count) {
                        pcp->count = rmqueue_bulk(zone, 0,
                                        pcp->batch, &pcp->list,
                                        migratetype, cold);
                        if (unlikely(!pcp->count))
                                goto failed;
                }

                /* Find a page of the appropriate migrate type */
                if (cold) {
                        list_for_each_entry_reverse(page, &pcp->list, lru)
                                if (page_private(page) == migratetype)
                                        break;
                } else {
                        list_for_each_entry(page, &pcp->list, lru)
                                if (page_private(page) == migratetype)
                                        break;
                }

                /* Allocate more to the pcp list if necessary */
                if (unlikely(&page->lru == &pcp->list)) {
                        pcp->count += rmqueue_bulk(zone, 0,
                                        pcp->batch, &pcp->list,
                                        migratetype, cold);
                        page = list_entry(pcp->list.next, struct page, lru);
                }

                list_del(&page->lru);
                pcp->count--;
        } else {
                spin_lock_irqsave(&zone->lock, flags);
                page = __rmqueue(zone, order, migratetype);
                spin_unlock(&zone->lock);
                if (!page)
                        goto failed;
        }

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

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

failed:
        local_irq_restore(flags);
        put_cpu();
        return NULL;
}

#define ALLOC_NO_WATERMARKS     0x01 /* don't check watermarks at all */
#define ALLOC_WMARK_MIN         0x02 /* use pages_min watermark */
#define ALLOC_WMARK_LOW         0x04 /* use pages_low watermark */
#define ALLOC_WMARK_HIGH        0x08 /* use pages_high watermark */
#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 zoneref *z;
        struct page *page = NULL;
        int classzone_idx;
        struct zone *zone, *preferred_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 */

        (void)first_zones_zonelist(zonelist, high_zoneidx, nodemask,
                                                        &preferred_zone);
        if (!preferred_zone)
                return NULL;

        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;

                if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
                        unsigned long mark;
                        int ret;
                        if (alloc_flags & ALLOC_WMARK_MIN)
                                mark = zone->pages_min;
                        else if (alloc_flags & ALLOC_WMARK_LOW)
                                mark = zone->pages_low;
                        else
                                mark = zone->pages_high;

                        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);
                if (page)
                        break;
this_zone_full:
                if (NUMA_BUILD)
                        zlc_mark_zone_full(zonelist, z);
try_next_zone:
                if (NUMA_BUILD && !did_zlc_setup) {
                        /* we do zlc_setup after the first zone is tried */
                        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;
}

/*
 * This is the 'heart' of the zoned buddy allocator.
 */
struct page *
__alloc_pages_internal(gfp_t gfp_mask, unsigned int order,
                        struct zonelist *zonelist, nodemask_t *nodemask)
{
        const gfp_t wait = gfp_mask & __GFP_WAIT;
        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
        struct zoneref *z;
        struct zone *zone;
        struct page *page;
        struct reclaim_state reclaim_state;
        struct task_struct *p = current;
        int do_retry;
        int alloc_flags;
        unsigned long did_some_progress;
        unsigned long pages_reclaimed = 0;

        lockdep_trace_alloc(gfp_mask);

        might_sleep_if(wait);

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

restart:
        z = zonelist->_zonerefs;  /* the list of zones suitable for gfp_mask */

        if (unlikely(!z->zone)) {
                /*
                 * Happens if we have an empty zonelist as a result of
                 * GFP_THISNODE being used on a memoryless node
                 */
                return NULL;
        }

        page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
                        zonelist, high_zoneidx, ALLOC_WMARK_LOW|ALLOC_CPUSET);
        if (page)
                goto got_pg;

        /*
         * 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;

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

        /*
         * 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.
         *
         * 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 = ALLOC_WMARK_MIN;
        if ((unlikely(rt_task(p)) && !in_interrupt()) || !wait)
                alloc_flags |= ALLOC_HARDER;
        if (gfp_mask & __GFP_HIGH)
                alloc_flags |= ALLOC_HIGH;
        if (wait)
                alloc_flags |= ALLOC_CPUSET;

        /*
         * Go through the zonelist again. Let __GFP_HIGH and allocations
         * coming from realtime tasks go deeper into reserves.
         *
         * This is the last chance, in general, before the goto nopage.
         * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
         * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
         */
        page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
                                                high_zoneidx, alloc_flags);
        if (page)
                goto got_pg;

        /* This allocation should allow future memory freeing. */

rebalance:
        if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
                        && !in_interrupt()) {
                if (!(gfp_mask & __GFP_NOMEMALLOC)) {
nofail_alloc:
                        /* go through the zonelist yet again, ignoring mins */
                        page = get_page_from_freelist(gfp_mask, nodemask, order,
                                zonelist, high_zoneidx, ALLOC_NO_WATERMARKS);
                        if (page)
                                goto got_pg;
                        if (gfp_mask & __GFP_NOFAIL) {
                                congestion_wait(WRITE, HZ/50);
                                goto nofail_alloc;
                        }
                }
                goto nopage;
        }

        /* Atomic allocations - we can't balance anything */
        if (!wait)
                goto nopage;

        cond_resched();

        /* We now go into synchronous reclaim */
        cpuset_memory_pressure_bump();
        /*
         * The task's cpuset might have expanded its set of allowable nodes
         */
        cpuset_update_task_memory_state();
        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);
                if (page)
                        goto got_pg;
        } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
                if (!try_set_zone_oom(zonelist, gfp_mask)) {
                        schedule_timeout_uninterruptible(1);
                        goto restart;
                }

                /*
                 * 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);
                if (page) {
                        clear_zonelist_oom(zonelist, gfp_mask);
                        goto got_pg;
                }

                /* The OOM killer will not help higher order allocs so fail */
                if (order > PAGE_ALLOC_COSTLY_ORDER) {
                        clear_zonelist_oom(zonelist, gfp_mask);
                        goto nopage;
                }

                out_of_memory(zonelist, gfp_mask, order);
                clear_zonelist_oom(zonelist, gfp_mask);
                goto restart;
        }

        /*
         * Don't let big-order allocations loop unless the caller explicitly
         * requests that.  Wait for some write requests to complete then retry.
         *
         * In this implementation, order <= PAGE_ALLOC_COSTLY_ORDER
         * means __GFP_NOFAIL, but that may not be true in other
         * implementations.
         *
         * 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.
         */
        pages_reclaimed += did_some_progress;
        do_retry = 0;
        if (!(gfp_mask & __GFP_NORETRY)) {
                if (order <= PAGE_ALLOC_COSTLY_ORDER) {
                        do_retry = 1;
                } else {
                        if (gfp_mask & __GFP_REPEAT &&
                                pages_reclaimed < (1 << order))
                                        do_retry = 1;
                }
                if (gfp_mask & __GFP_NOFAIL)
                        do_retry = 1;
        }
        if (do_retry) {
                congestion_wait(WRITE, HZ/50);
                goto rebalance;
        }

nopage:
        if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit()) {
                printk(KERN_WARNING "%s: page allocation failure."
                        " order:%d, mode:0x%x\n",
                        p->comm, order, gfp_mask);
                dump_stack();
                show_mem();
        }
got_pg:
        return page;
}
EXPORT_SYMBOL(__alloc_pages_internal);

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

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

        page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
        if (page)
                return (unsigned long) page_address(page);
        return 0;
}

EXPORT_SYMBOL(get_zeroed_page);

void __pagevec_free(struct pagevec *pvec)
{
        int i = pagevec_count(pvec);

        while (--i >= 0)
                free_hot_cold_page(pvec->pages[i], pvec->cold);
}

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

EXPORT_SYMBOL(__free_pages);

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

EXPORT_SYMBOL(free_pages);

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

        addr = __get_free_pages(gfp_mask, order);
        if (addr) {
                unsigned long alloc_end = addr + (PAGE_SIZE << order);
                unsigned long used = addr + PAGE_ALIGN(size);

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

        return (void *)addr;
}
EXPORT_SYMBOL(alloc_pages_exact);

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

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

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 = zone->pages_high;
                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

#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.
 */
void show_free_areas(void)
{
        int cpu;
        struct zone *zone;

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

                for_each_online_cpu(cpu) {
                        struct per_cpu_pageset *pageset;

                        pageset = zone_pcp(zone, 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 active_file:%lu inactive_anon:%lu\n"
                " inactive_file:%lu"
//TODO:  check/adjust line lengths
#ifdef CONFIG_UNEVICTABLE_LRU
                " unevictable:%lu"
#endif
                " dirty:%lu writeback:%lu unstable:%lu\n"
                " free:%lu slab:%lu mapped:%lu pagetables:%lu bounce:%lu\n",
                global_page_state(NR_ACTIVE_ANON),
                global_page_state(NR_ACTIVE_FILE),
                global_page_state(NR_INACTIVE_ANON),
                global_page_state(NR_INACTIVE_FILE),
#ifdef CONFIG_UNEVICTABLE_LRU
                global_page_state(NR_UNEVICTABLE),
#endif
                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_PAGETABLE),
                global_page_state(NR_BOUNCE));

        for_each_populated_zone(zone) {
                int i;

                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"
#ifdef CONFIG_UNEVICTABLE_LRU
                        " unevictable:%lukB"
#endif
                        " present:%lukB"
                        " pages_scanned:%lu"
                        " all_unreclaimable? %s"
                        "\n",
                        zone->name,
                        K(zone_page_state(zone, NR_FREE_PAGES)),
                        K(zone->pages_min),
                        K(zone->pages_low),
                        K(zone->pages_high),
                        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)),
#ifdef CONFIG_UNEVICTABLE_LRU
                        K(zone_page_state(zone, NR_UNEVICTABLE)),
#endif
                        K(zone->present_pages),
                        zone->pages_scanned,
                        (zone_is_all_unreclaimable(zone) ? "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;

                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));
        }