pciehp: block signals while waiting for command completion

[linux-2.6/mini2440.git] / mm / page_alloc.c

/*
 *  linux/mm/page_alloc.c
 *
 *  Manages the free list, the system allocates free pages here.
 *  Note that kmalloc() lives in slab.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
 *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
 *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
 *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
 *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
 */

#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/jiffies.h>
#include <linux/bootmem.h>
#include <linux/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/memcontrol.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;
long nr_swap_pages;
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 */
  unsigned long __initdata required_kernelcore;
  static unsigned long __initdata required_movablecore;
  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)
{
        void *pc = page_get_page_cgroup(page);

        printk(KERN_EMERG "Bad page state in process '%s'\n" KERN_EMERG
                "page:%p flags:0x%0*lx mapping:%p mapcount:%d count:%d\n",
                current->comm, page, (int)(2*sizeof(unsigned long)),
                (unsigned long)page->flags, page->mapping,
                page_mapcount(page), page_count(page));
        if (pc) {
                printk(KERN_EMERG "cgroup:%p\n", pc);
                page_reset_bad_cgroup(page);
        }
        printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n"
                KERN_EMERG "Backtrace:\n");
        dump_stack();
        page->flags &= ~PAGE_FLAGS_CLEAR_WHEN_BAD;
        set_page_count(page, 0);
        reset_page_mapcount(page);
        page->mapping = NULL;
        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));
}

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

        if (unlikely(compound_order(page) != order))
                bad_page(page);

        if (unlikely(!PageHead(page)))
                        bad_page(page);
        __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);
                __ClearPageTail(p);
        }
}

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)))
                destroy_compound_page(page, order);

        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;          /* Move the buddy up one level. */

                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)
{
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_get_page_cgroup(page) != NULL) |
                (page_count(page) != 0)  |
                (page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
                bad_page(page);
        if (PageDirty(page))
                __ClearPageDirty(page);
        /*
         * For now, we report if PG_reserved was found set, but do not
         * clear it, and do not free the page.  But we shall soon need
         * to do more, for when the ZERO_PAGE count wraps negative.
         */
        return PageReserved(page);
}

/*
 * 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 reserved = 0;

        for (i = 0 ; i < (1 << order) ; ++i)
                reserved += free_pages_check(page + i);
        if (reserved)
                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 __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_get_page_cgroup(page) != NULL) |
                (page_count(page) != 0)  |
                (page->flags & PAGE_FLAGS_CHECK_AT_PREP)))
                bad_page(page);

        /*
         * For now, we report if PG_reserved was found set, but do not
         * clear it, and do not allocate the page: as a safety net.
         */
        if (PageReserved(page))
                return 1;

        page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
                        1 << PG_referenced | 1 << PG_arch_1 |
                        1 << PG_owner_priv_1 | 1 << PG_mappedtodisk);
        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()
 */
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;) {
                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;
}

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 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.
                 */
                list_add(&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_zone(zone) {
                struct per_cpu_pageset *pset;
                struct per_cpu_pages *pcp;

                if (!populated_zone(zone))
                        continue;

                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, 0, 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);
                        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);
                        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;
                        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)) {
                                if (!zone_reclaim_mode ||
                                    !zone_reclaim(zone, gfp_mask, order))
                                        goto this_zone_full;
                        }
                }

                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.
 */
static 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;

        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();
        p->flags |= PF_MEMALLOC;
        reclaim_state.reclaimed_slab = 0;
        p->reclaim_state = &reclaim_state;

        did_some_progress = try_to_free_pages(zonelist, order, gfp_mask);

        p->reclaim_state = NULL;
        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;
}

struct page *
__alloc_pages(gfp_t gfp_mask, unsigned int order,
                struct zonelist *zonelist)
{
        return __alloc_pages_internal(gfp_mask, order, zonelist, NULL);
}

struct page *
__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
                struct zonelist *zonelist, nodemask_t *nodemask)
{
        return __alloc_pages_internal(gfp_mask, order, zonelist, nodemask);
}

EXPORT_SYMBOL(__alloc_pages);

/*
 * 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);

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_zone(zone) {
                if (!populated_zone(zone))
                        continue;

                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:%lu inactive:%lu dirty:%lu writeback:%lu unstable:%lu\n"
                " free:%lu slab:%lu mapped:%lu pagetables:%lu bounce:%lu\n",
                global_page_state(NR_ACTIVE),
                global_page_state(NR_INACTIVE),
                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_zone(zone) {
                int i;

                if (!populated_zone(zone))
                        continue;

                show_node(zone);
                printk("%s"
                        " free:%lukB"
                        " min:%lukB"
                        " low:%lukB"
                        " high:%lukB"
                        " active:%lukB"
                        " inactive:%lukB"
                        " 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)),
                        K(zone_page_state(zone, NR_INACTIVE)),
                        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_zone(zone) {
                unsigned long nr[MAX_ORDER], flags, order, total = 0;

                if (!populated_zone(zone))
                        continue;

                show_node(zone);
                printk("%s: ", zone->name);

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

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

        show_swap_cache_info();
}

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

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

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

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

        } while (zone_type);
        return nr_zones;
}


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

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


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

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

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

static __init int setup_numa_zonelist_order(char *s)
{
        if (s)
                return __parse_numa_zonelist_order(s);
        return 0;
}
early_param("numa_zonelist_order", setup_numa_zonelist_order);

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

        if (write)
                strncpy(saved_string, (char*)table->data,
                        NUMA_ZONELIST_ORDER_LEN);
        ret = proc_dostring(table, write, file, buffer, length, ppos);
        if (ret)
                return ret;
        if (write) {
                int oldval = user_zonelist_order;
                if (__parse_numa_zonelist_order((char*)table->data)) {
                        /*
                         * bogus value.  restore saved string
                         */
                        strncpy((char*)table->data, saved_string,
                                NUMA_ZONELIST_ORDER_LEN);
                        user_zonelist_order = oldval;
                } else if (oldval != user_zonelist_order)
                        build_all_zonelists();
        }
        return 0;
}


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

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

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

        for_each_node_state(n, N_HIGH_MEMORY) {

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

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

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

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

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

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

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

        return best_node;
}


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

        zonelist = &pgdat->node_zonelists[0];
        for (j = 0; zonelist->_zonerefs[j].zone != NULL; j++)
                ;
        j = build_zonelists_node(NODE_DATA(node), zonelist, j,
                                                        MAX_NR_ZONES - 1);
        zonelist->_zonerefs[j].zone = NULL;
        zonelist->_zonerefs[j].zone_idx = 0;
}

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

        zonelist = &pgdat->node_zonelists[1];
        j = build_zonelists_node(pgdat, zonelist, 0, MAX_NR_ZONES - 1);
        zonelist->_zonerefs[j].zone = NULL;
        zonelist->_zonerefs[j].zone_idx = 0;
}

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

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

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

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

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

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

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

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

        memset(node_load, 0, sizeof(node_load));
        memset(node_order, 0, sizeof(node_order));
        j = 0;

        while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
                int distance = node_distance(local_node, node);

                /*
                 * If another node is sufficiently far away then it is better
                 * to reclaim pages in a zone before going off node.
                 */
                if (distance > RECLAIM_DISTANCE)
                        zone_reclaim_mode = 1;

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

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

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

        build_thisnode_zonelists(pgdat);
}

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

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


#else   /* CONFIG_NUMA */

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

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

        local_node = pgdat->node_id;

        zonelist = &pgdat->node_zonelists[0];
        j = build_zonelists_node(pgdat, zonelist, 0, MAX_NR_ZONES - 1);

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

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

/* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
static void build_zonelist_cache(pg_data_t *pgdat)
{
        pgdat->node_zonelists[0].zlcache_ptr = NULL;
        pgdat->node_zonelists[1].zlcache_ptr = NULL;
}

#endif  /* CONFIG_NUMA */

/* return values int ....just for stop_machine_run() */
static int __build_all_zonelists(void *dummy)
{
        int nid;

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

                build_zonelists(pgdat);
                build_zonelist_cache(pgdat);
        }
        return 0;
}

void build_all_zonelists(void)
{
        set_zonelist_order();

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

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

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

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

        pages /= PAGES_PER_WAITQUEUE;

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

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

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

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

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

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

        /* Get the start pfn, end pfn and the number of blocks to reserve */
        start_pfn = zone->zone_start_pfn;
        end_pfn = start_pfn + zone->spanned_pages;
        reserve = roundup(zone->pages_min, pageblock_nr_pages) >>
                                                        pageblock_order;

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

                /* Blocks with reserved pages will never free, skip them. */
                if (PageReserved(page))
                        continue;

                block_migratetype = get_pageblock_migratetype(page);

                /* If this block is reserved, account for it */
                if (reserve > 0 && block_migratetype == MIGRATE_RESERVE) {
                        reserve--;
                        continue;
                }

                /* Suitable for reserving if this block is movable */
                if (reserve > 0 && block_migratetype == MIGRATE_MOVABLE) {
                        set_pageblock_migratetype(page, MIGRATE_RESERVE);
                        move_freepages_block(zone, page, MIGRATE_RESERVE);
                        reserve--;
                        continue;
                }

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

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

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

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

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

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

static int zone_batchsize(struct zone *zone)
{
        int batch;

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

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

        return batch;
}

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

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

        pcp = &p->pcp;
        pcp->count = 0;
        pcp->high = 6 * batch;
        pcp->batch = max(1UL, 1 * batch);
        INIT_LIST_HEAD(&pcp->list);
}

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

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

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


#ifdef CONFIG_NUMA
/*
 * Boot pageset table. One per cpu which is going to be used for all
 * zones and all nodes. The parameters will be set in such a way
 * that an item put on a list will immediately be handed over to
 * the buddy list. This is safe since pageset manipulation is done
 * with interrupts disabled.
 *
 * Some NUMA counter updates may also be caught by the boot pagesets.
 *
 * The boot_pagesets must be kept even after bootup is complete for
 * unused processors and/or zones. They do play a role for bootstrapping
 * hotplugged processors.
 *
 * zoneinfo_show() and maybe other functions do
 * not check if the processor is online before following the pageset pointer.
 * Other parts of the kernel may not check if the zone is available.
 */
static struct per_cpu_pageset boot_pageset[NR_CPUS];

/*
 * Dynamically allocate memory for the
 * per cpu pageset array in struct zone.
 */
static int __cpuinit process_zones(int cpu)
{
        struct zone *zone, *dzone;
        int node = cpu_to_node(cpu);

        node_set_state(node, N_CPU);    /* this node has a cpu */

        for_each_zone(zone) {

                if (!populated_zone(zone))
                        continue;

                zone_pcp(zone, cpu) = kmalloc_node(sizeof(struct per_cpu_pageset),
                                         GFP_KERNEL, node);
                if (!zone_pcp(zone, cpu))
                        goto bad;

                setup_pageset(zone_pcp(zone, cpu), zone_batchsize(zone));

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

        return 0;
bad:
        for_each_zone(dzone) {
                if (!populated_zone(dzone))
                        continue;
                if (dzone == zone)
                        break;
                kfree(zone_pcp(dzone, cpu));
                zone_pcp(dzone, cpu) = NULL;
        }
        return -ENOMEM;
}

static inline void free_zone_pagesets(int cpu)
{
        struct zone *zone;

        for_each_zone(zone) {
                struct per_cpu_pageset *pset = zone_pcp(zone, cpu);

                /* Free per_cpu_pageset if it is slab allocated */
                if (pset != &boot_pageset[cpu])
                        kfree(pset);
                zone_pcp(zone, cpu) = NULL;
        }
}

static int __cpuinit pageset_cpuup_callback(struct notifier_block *nfb,
                unsigned long action,
                void *hcpu)
{
        int cpu = (long)hcpu;
        int ret = NOTIFY_OK;

        switch (action) {
        case CPU_UP_PREPARE:
        case CPU_UP_PREPARE_FROZEN:
                if (process_zones(cpu))
                        ret = NOTIFY_BAD;
                break;
        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                free_zone_pagesets(cpu);
                break;
        default:
                break;
        }
        return ret;
}

static struct notifier_block __cpuinitdata pageset_notifier =
        { &pageset_cpuup_callback, NULL, 0 };

void __init setup_per_cpu_pageset(void)
{
        int err;

        /* Initialize per_cpu_pageset for cpu 0.
         * A cpuup callback will do this for every cpu
         * as it comes online
         */
        err = process_zones(smp_processor_id());
        BUG_ON(err);
        register_cpu_notifier(&pageset_notifier);
}

#endif

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

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

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

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

        return 0;
}

static __meminit void zone_pcp_init(struct zone *zone)
{
        int cpu;
        unsigned long batch = zone_batchsize(zone);

        for (cpu = 0; cpu < NR_CPUS; cpu++) {
#ifdef CONFIG_NUMA
                /* Early boot. Slab allocator not functional yet */
                zone_pcp(zone, cpu) = &boot_pageset[cpu];
                setup_pageset(&boot_pageset[cpu],0);
#else
                setup_pageset(zone_pcp(zone,cpu), batch);
#endif
        }
        if (zone->present_pages)
                printk(KERN_DEBUG "  %s zone: %lu pages, LIFO batch:%lu\n",
                        zone->name, zone->present_pages, batch);
}

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

        zone->zone_start_pfn = zone_start_pfn;

        zone_init_free_lists(zone);

        return 0;
}

#ifdef CONFIG_ARCH_POPULATES_NODE_MAP
/*
 * Basic iterator support. Return the first range of PFNs for a node
 * Note: nid == MAX_NUMNODES returns first region regardless of node
 */
static int __meminit first_active_region_index_in_nid(int nid)
{
        int i;

        for (i = 0; i < nr_nodemap_entries; i++)
                if (nid == MAX_NUMNODES || early_node_map[i].nid == nid)
                        return i;

        return -1;
}

/*
 * Basic iterator support. Return the next active range of PFNs for a node
 * Note: nid == MAX_NUMNODES returns next region regardless of node
 */
static int __meminit next_active_region_index_in_nid(int index, int nid)
{
        for (index = index + 1; index < nr_nodemap_entries; index++)
                if (nid == MAX_NUMNODES || early_node_map[index].nid == nid)
                        return index;

        return -1;
}

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

        for (i = 0; i < nr_nodemap_entries; i++) {
                unsigned long start_pfn = early_node_map[i].start_pfn;
                unsigned long end_pfn = early_node_map[i].end_pfn;

                if (start_pfn <= pfn && pfn < end_pfn)
                        return early_node_map[i].nid;
        }

        return 0;
}
#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */

/* Basic iterator support to walk early_node_map[] */
#define for_each_active_range_index_in_nid(i, nid) \
        for (i = first_active_region_index_in_nid(nid); i != -1; \
                                i = next_active_region_index_in_nid(i, nid))

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

        for_each_active_range_index_in_nid(i, nid) {
                unsigned long size_pages = 0;
                unsigned long end_pfn = early_node_map[i].end_pfn;

                if (early_node_map[i].start_pfn >= max_low_pfn)
                        continue;

                if (end_pfn > max_low_pfn)
                        end_pfn = max_low_pfn;

                size_pages = end_pfn - early_node_map[i].start_pfn;
                free_bootmem_node(NODE_DATA(early_node_map[i].nid),
                                PFN_PHYS(early_node_map[i].start_pfn),
                                size_pages << PAGE_SHIFT);
        }
}

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

        for_each_active_range_index_in_nid(i, nid)
                memory_present(early_node_map[i].nid,
                                early_node_map[i].start_pfn,
                                early_node_map[i].end_pfn);
}

/**
 * push_node_boundaries - Push node boundaries to at least the requested boundary
 * @nid: The nid of the node to push the boundary for
 * @start_pfn: The start pfn of the node
 * @end_pfn: The end pfn of the node
 *
 * In reserve-based hot-add, mem_map is allocated that is unused until hotadd
 * time. Specifically, on x86_64, SRAT will report ranges that can potentially
 * be hotplugged even though no physical memory exists. This function allows
 * an arch to push out the node boundaries so mem_map is allocated that can
 * be used later.
 */
#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
void __init push_node_boundaries(unsigned int nid,
                unsigned long start_pfn, unsigned long end_pfn)
{
        printk(KERN_DEBUG "Entering push_node_boundaries(%u, %lu, %lu)\n",
                        nid, start_pfn, end_pfn);

        /* Initialise the boundary for this node if necessary */
        if (node_boundary_end_pfn[nid] == 0)
                node_boundary_start_pfn[nid] = -1UL;

        /* Update the boundaries */
        if (node_boundary_start_pfn[nid] > start_pfn)
                node_boundary_start_pfn[nid] = start_pfn;
        if (node_boundary_end_pfn[nid] < end_pfn)
                node_boundary_end_pfn[nid] = end_pfn;
}

/* If necessary, push the node boundary out for reserve hotadd */
static void __meminit account_node_boundary(unsigned int nid,
                unsigned long *start_pfn, unsigned long *end_pfn)
{
        printk(KERN_DEBUG "Entering account_node_boundary(%u, %lu, %lu)\n",
                        nid, *start_pfn, *end_pfn);

        /* Return if boundary information has not been provided */
        if (node_boundary_end_pfn[nid] == 0)
                return;

        /* Check the boundaries and update if necessary */
        if (node_boundary_start_pfn[nid] < *start_pfn)
                *start_pfn = node_boundary_start_pfn[nid];
        if (node_boundary_end_pfn[nid] > *end_pfn)
                *end_pfn = node_boundary_end_pfn[nid];
}
#else
void __init push_node_boundaries(unsigned int nid,
                unsigned long start_pfn, unsigned long end_pfn) {}

static void __meminit account_node_boundary(unsigned int nid,
                unsigned long *start_pfn, unsigned long *end_pfn) {}
#endif


/**
 * get_pfn_range_for_nid - Return the start and end page frames for a node
 * @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
 * @start_pfn: Passed by reference. On return, it will have the node start_pfn.
 * @end_pfn: Passed by reference. On return, it will have the node end_pfn.
 *
 * It returns the start and end page frame of a node based on information
 * provided by an arch calling add_active_range(). If called for a node
 * with no available memory, a warning is printed and the start and end
 * PFNs will be 0.
 */
void __meminit get_pfn_range_for_nid(unsigned int nid,
                        unsigned long *start_pfn, unsigned long *end_pfn)
{
        int i;
        *start_pfn = -1UL;
        *end_pfn = 0;

        for_each_active_range_index_in_nid(i, nid) {
                *start_pfn = min(*start_pfn, early_node_map[i].start_pfn);
                *end_pfn = max(*end_pfn, early_node_map[i].end_pfn);
        }

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

        /* Push the node boundaries out if requested */
        account_node_boundary(nid, start_pfn, end_pfn);
}

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

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

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

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

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

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

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

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

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

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

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

/*
 * Return the number of holes in a range on a node. If nid is MAX_NUMNODES,
 * then all holes in the requested range will be accounted for.
 */
unsigned long __meminit __absent_pages_in_range(int nid,
                                unsigned long range_start_pfn,
                                unsigned long range_end_pfn)
{
        int i = 0;
        unsigned long prev_end_pfn = 0, hole_pages = 0;
        unsigned long start_pfn;

        /* Find the end_pfn of the first active range of pfns in the node */
        i = first_active_region_index_in_nid(nid);
        if (i == -1)
                return 0;

        prev_end_pfn = min(early_node_map[i].start_pfn, range_end_pfn);

        /* Account for ranges before physical memory on this node */
        if (early_node_map[i].start_pfn > range_start_pfn)
                hole_pages = prev_end_pfn - range_start_pfn;

        /* Find all holes for the zone within the node */
        for (; i != -1; i = next_active_region_index_in_nid(i, nid)) {

                /* No need to continue if prev_end_pfn is outside the zone */
                if (prev_end_pfn >= range_end_pfn)
                        break;

                /* Make sure the end of the zone is not within the hole */
                start_pfn = min(early_node_map[i].start_pfn, range_end_pfn);
                prev_end_pfn = max(prev_end_pfn, range_start_pfn);

                /* Update the hole size cound and move on */
                if (start_pfn > range_start_pfn) {
                        BUG_ON(prev_end_pfn > start_pfn);
                        hole_pages += start_pfn - prev_end_pfn;
                }
                prev_end_pfn = early_node_map[i].end_pfn;
        }

        /* Account for ranges past physical memory on this node */
        if (range_end_pfn > prev_end_pfn)
                hole_pages += range_end_pfn -
                                max(range_start_pfn, prev_end_pfn);

        return hole_pages;
}

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

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

        get_pfn_range_for_nid(nid, &node_start_pfn, &node_end_pfn);
        zone_start_pfn = max(arch_zone_lowest_possible_pfn[zone_type],
                                                        node_start_pfn);
        zone_end_pfn = min(arch_zone_highest_possible_pfn[zone_type],
                                                        node_end_pfn);

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

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

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

        return zholes_size[zone_type];
}

#endif

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

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

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

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

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

        return usemapsize / 8;
}

static void __init setup_usemap(struct pglist_data *pgdat,
                                struct zone *zone, unsigned long zonesize)
{
        unsigned long usemapsize = usemap_size(zonesize);
        zone->pageblock_flags = NULL;
        if (usemapsize) {
                zone->pageblock_flags = alloc_bootmem_node(pgdat, usemapsize);
                memset(zone->pageblock_flags, 0, usemapsize);
        }
}
#else
static void inline setup_usemap(struct pglist_data *pgdat,
                                struct zone *zone, unsigned long zonesize) {}
#endif /* CONFIG_SPARSEMEM */

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Return a sensible default order for the pageblock size. */
static inline int pageblock_default_order(void)
{
        if (HPAGE_SHIFT > PAGE_SHIFT)
                return HUGETLB_PAGE_ORDER;

        return MAX_ORDER-1;
}

/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
static inline void __init set_pageblock_order(unsigned int order)
{
        /* Check that pageblock_nr_pages has not already been setup */
        if (pageblock_order)
                return;

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

/*
 * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
 * and pageblock_default_order() are unused as pageblock_order is set
 * at compile-time. See include/linux/pageblock-flags.h for the values of
 * pageblock_order based on the kernel config
 */
static inline int pageblock_default_order(unsigned int order)
{
        return MAX_ORDER-1;
}
#define set_pageblock_order(x)  do {} while (0)

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

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

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

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

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

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

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

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

                zone->prev_priority = DEF_PRIORITY;

                zone_pcp_init(zone);
                INIT_LIST_HEAD(&zone->active_list);
                INIT_LIST_HEAD(&zone->inactive_list);
                zone->nr_scan_active = 0;
                zone->nr_scan_inactive = 0;
                zap_zone_vm_stats(zone);
                zone->flags = 0;
                if (!size)
                        continue;

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

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

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

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

void __paginginit free_area_init_node(int nid, struct pglist_data *pgdat,
                unsigned long *zones_size, unsigned long node_start_pfn,
                unsigned long *zholes_size)
{
        pgdat->node_id = nid;
        pgdat->node_start_pfn = node_start_pfn;
        calculate_node_totalpages(pgdat, zones_size, zholes_size);

        alloc_node_mem_map(pgdat);

        free_area_init_core(pgdat, zones_size, zholes_size);
}

#ifdef CONFIG_ARCH_POPULATES_NODE_MAP

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

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

/**
 * add_active_range - Register a range of PFNs backed by physical memory
 * @nid: The node ID the range resides on
 * @start_pfn: The start PFN of the available physical memory
 * @end_pfn: The end PFN of the available physical memory
 *
 * These ranges are stored in an early_node_map[] and later used by
 * free_area_init_nodes() to calculate zone sizes and holes. If the
 * range spans a memory hole, it is up to the architecture to ensure
 * the memory is not freed by the bootmem allocator. If possible
 * the range being registered will be merged with existing ranges.
 */
void __init add_active_range(unsigned int nid, unsigned long start_pfn,
                                                unsigned long end_pfn)
{
        int i;

        printk(KERN_DEBUG "Entering add_active_range(%d, %lu, %lu) "
                          "%d entries of %d used\n",
                          nid, start_pfn, end_pfn,
                          nr_nodemap_entries, MAX_ACTIVE_REGIONS);

        /* Merge with existing active regions if possible */
        for (i = 0; i < nr_nodemap_entries; i++) {
                if (early_node_map[i].nid != nid)
                        continue;

                /* Skip if an existing region covers this new one */
                if (start_pfn >= early_node_map[i].start_pfn &&
                                end_pfn <= early_node_map[i].end_pfn)
                        return;

                /* Merge forward if suitable */
                if (start_pfn <= early_node_map[i].end_pfn &&
                                end_pfn > early_node_map[i].end_pfn) {
                        early_node_map[i].end_pfn = end_pfn;
                        return;
                }

                /* Merge backward if suitable */
                if (start_pfn < early_node_map[i].end_pfn &&
                                end_pfn >= early_node_map[i].start_pfn) {
                        early_node_map[i].start_pfn = start_pfn;
                        return;
                }
        }

        /* Check that early_node_map is large enough */
        if (i >= MAX_ACTIVE_REGIONS) {
                printk(KERN_CRIT "More than %d memory regions, truncating\n",
                                                        MAX_ACTIVE_REGIONS);
                return;
        }

        early_node_map[i].nid = nid;
        early_node_map[i].start_pfn = start_pfn;
        early_node_map[i].end_pfn = end_pfn;
        nr_nodemap_entries = i + 1;
}

/**
 * shrink_active_range - Shrink an existing registered range of PFNs
 * @nid: The node id the range is on that should be shrunk
 * @old_end_pfn: The old end PFN of the range
 * @new_end_pfn: The new PFN of the range
 *
 * i386 with NUMA use alloc_remap() to store a node_mem_map on a local node.
 * The map is kept at the end physical page range that has already been
 * registered with add_active_range(). This function allows an arch to shrink
 * an existing registered range.
 */
void __init shrink_active_range(unsigned int nid, unsigned long old_end_pfn,
                                                unsigned long new_end_pfn)
{
        int i;

        /* Find the old active region end and shrink */
        for_each_active_range_index_in_nid(i, nid)
                if (early_node_map[i].end_pfn == old_end_pfn) {
                        early_node_map[i].end_pfn = new_end_pfn;
                        break;
                }
}

/**
 * remove_all_active_ranges - Remove all currently registered regions
 *
 * During discovery, it may be found that a table like SRAT is invalid
 * and an alternative discovery method must be used. This function removes
 * all currently registered regions.
 */
void __init remove_all_active_ranges(void)
{
        memset(early_node_map, 0, sizeof(early_node_map));
        nr_nodemap_entries = 0;
#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
        memset(node_boundary_start_pfn, 0, sizeof(node_boundary_start_pfn));
        memset(node_boundary_end_pfn, 0, sizeof(node_boundary_end_pfn));
#endif /* CONFIG_MEMORY_HOTPLUG_RESERVE */
}

/* Compare two active node_active_regions */
static int __init cmp_node_active_region(const void *a, const void *b)
{
        struct node_active_region *arange = (struct node_active_region *)a;
        struct node_active_region *brange = (struct node_active_region *)b;

        /* Done this way to avoid overflows */
        if (arange->start_pfn > brange->start_pfn)
                return 1;
        if (arange->start_pfn < brange->start_pfn)
                return -1;

        return 0;
}

/* sort the node_map by start_pfn */
static void __init sort_node_map(void)
{
        sort(early_node_map, (size_t)nr_nodemap_entries,
                        sizeof(struct node_active_region),
                        cmp_node_active_region, NULL);
}

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

        /* Assuming a sorted map, the first range found has the starting pfn */
        for_each_active_range_index_in_nid(i, nid)
                min_pfn = min(min_pfn, early_node_map[i].start_pfn);

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

        return min_pfn;
}

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

/**
 * find_max_pfn_with_active_regions - Find the maximum PFN registered
 *
 * It returns the maximum PFN based on information provided via
 * add_active_range().
 */
unsigned long __init find_max_pfn_with_active_regions(void)
{
        int i;
        unsigned long max_pfn = 0;

        for (i = 0; i < nr_nodemap_entries; i++)
                max_pfn = max(max_pfn, early_node_map[i].end_pfn);

        return max_pfn;
}

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

        for (i = 0; i < nr_nodemap_entries; i++) {
                unsigned long pages = early_node_map[i].end_pfn -
                                                early_node_map[i].start_pfn;
                totalpages += pages;
                if (pages)
                        node_set_state(early_node_map[i].nid, N_HIGH_MEMORY);
        }
        return totalpages;
}

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

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

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

                required_kernelcore = max(required_kernelcore, corepages);
        }

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

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

restart:
        /* Spread kernelcore memory as evenly as possible throughout nodes */
        kernelcore_node = required_kernelcore / usable_nodes;
        for_each_node_state(nid, N_HIGH_MEMORY) {
                /*
                 * Recalculate kernelcore_node if the division per node
                 * now exceeds what is necessary to satisfy the requested
                 * amount of memory for the kernel
                 */
                if (required_kernelcore < kernelcore_node)
                        kernelcore_node = required_kernelcore / usable_nodes;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

        /* Sort early_node_map as initialisation assumes it is sorted */
        sort_node_map();

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

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

        /* Print out the zone ranges */
        printk("Zone PFN ranges:\n");
        for (i = 0; i < MAX_NR_ZONES; i++) {
                if (i == ZONE_MOVABLE)
                        continue;
                printk("  %-8s %8lu -> %8lu\n",
                                zone_names[i],
                                arch_zone_lowest_possible_pfn[i],
                                arch_zone_highest_possible_pfn[i]);
        }

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

        /* Print out the early_node_map[] */
        printk("early_node_map[%d] active PFN ranges\n", nr_nodemap_entries);
        for (i = 0; i < nr_nodemap_entries; i++)
                printk("  %3d: %8lu -> %8lu\n", early_node_map[i].nid,
                                                early_node_map[i].start_pfn,
                                                early_node_map[i].end_pfn);

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

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

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

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

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

        return 0;
}

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

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

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

#endif /* CONFIG_ARCH_POPULATES_NODE_MAP */

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

#ifndef CONFIG_NEED_MULTIPLE_NODES
static bootmem_data_t contig_bootmem_data;
struct pglist_data contig_page_data = { .bdata = &contig_bootmem_data };

EXPORT_SYMBOL(contig_page_data);
#endif

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

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

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

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

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

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

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

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

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

                        /* we treat pages_high as reserved pages. */
                        max += zone->pages_high;

                        if (max > zone->present_pages)
                                max = zone->present_pages;
                        reserve_pages += max;
                }
        }
        totalreserve_pages = reserve_pages;
}

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

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

                        zone->lowmem_reserve[j] = 0;

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

                                idx--;

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

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

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

/**
 * setup_per_zone_pages_min - called when min_free_kbytes changes.
 *
 * Ensures that the pages_{min,low,high} values for each zone are set correctly
 * with respect to min_free_kbytes.
 */
void setup_per_zone_pages_min(void)
{
        unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
        unsigned long lowmem_pages = 0;
        struct zone *zone;
        unsigned long flags;

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

        for_each_zone(zone) {
                u64 tmp;

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

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

                zone->pages_low   = zone->pages_min + (tmp >> 2);
                zone->pages_high  = zone->pages_min + (tmp >> 1);
                setup_zone_migrate_reserve(zone);
                spin_unlock_irqrestore(&zone->lru_lock, flags);
        }

        /* update totalreserve_pages */
        calculate_totalreserve_pages();
}

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

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

        min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
        if (min_free_kbytes < 128)
                min_free_kbytes = 128;
        if (min_free_kbytes > 65536)
                min_free_kbytes = 65536;
        setup_per_zone_pages_min();
        setup_per_zone_lowmem_reserve();
        return 0;
}
module_init(init_per_zone_pages_min)

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

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

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

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

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

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

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

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

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

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

        ret = proc_dointvec_minmax(table, write, file, buffer, length, ppos);
        if (!write || (ret == -EINVAL))
                return ret;
        for_each_zone(zone) {
                for_each_online_cpu(cpu) {
                        unsigned long  high;
                        high = zone->present_pages / percpu_pagelist_fraction;
                        setup_pagelist_highmark(zone_pcp(zone, cpu), high);
                }
        }
        return 0;
}

int hashdist = HASHDIST_DEFAULT;

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

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

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

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

                /* Make sure we've got at least a 0-order allocation.. */
                if (unlikely((numentries * bucketsize) < PAGE_SIZE))
                        numentries = PAGE_SIZE / bucketsize;
        }
        numentries = roundup_pow_of_two(numentries);

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

        if (numentries > max)
                numentries = max;

        log2qty = ilog2(numentries);

        do {
                size = bucketsize << log2qty;
                if (flags & HASH_EARLY)
                        table = alloc_bootmem(size);
                else if (hashdist)
                        table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
                else {
                        unsigned long order = get_order(size);
                        table = (void*) __get_free_pages(GFP_ATOMIC, order);
                        /*
                         * If bucketsize is not a power-of-two, we may free
                         * some pages at the end of hash table.
                         */
                        if (table) {
                                unsigned long alloc_end = (unsigned long)table +
                                                (PAGE_SIZE << order);
                                unsigned long used = (unsigned long)table +
                                                PAGE_ALIGN(size);
                                split_page(virt_to_page(table), order);
                                while (used < alloc_end) {
                                        free_page(used);
                                        used += PAGE_SIZE;
                                }
                        }
                }
        } while (!table && size > PAGE_SIZE && --log2qty);

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

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

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

        return table;
}

#ifdef CONFIG_OUT_OF_LINE_PFN_TO_PAGE
struct page *pfn_to_page(unsigned long pfn)
{
        return __pfn_to_page(pfn);
}
unsigned long page_to_pfn(struct page *page)
{
        return __page_to_pfn(page);
}
EXPORT_SYMBOL(pfn_to_page);
EXPORT_SYMBOL(page_to_pfn);
#endif /* CONFIG_OUT_OF_LINE_PFN_TO_PAGE */

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

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

/**
 * get_pageblock_flags_group - Return the requested group of flags for the pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @start_bitidx: The first bit of interest to retrieve
 * @end_bitidx: The last bit of interest
 * returns pageblock_bits flags
 */
unsigned long get_pageblock_flags_group(struct page *page,
                                        int start_bitidx, int end_bitidx)
{
        struct zone *zone;
        unsigned long *bitmap;
        unsigned long pfn, bitidx;
        unsigned long flags = 0;
        unsigned long value = 1;

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

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

        return flags;
}

/**
 * set_pageblock_flags_group - Set the requested group of flags for a pageblock_nr_pages block of pages
 * @page: The page within the block of interest
 * @start_bitidx: The first bit of interest
 * @end_bitidx: The last bit of interest
 * @flags: The flags to set
 */
void set_pageblock_flags_group(struct page *page, unsigned long flags,
                                        int start_bitidx, int end_bitidx)
{
        struct zone *zone;
        unsigned long *bitmap;
        unsigned long pfn, bitidx;
        unsigned long value = 1;

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

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

/*
 * This is designed as sub function...plz see page_isolation.c also.
 * set/clear page block's type to be ISOLATE.
 * page allocater never alloc memory from ISOLATE block.
 */

int set_migratetype_isolate(struct page *page)
{
        struct zone *zone;
        unsigned long flags;
        int ret = -EBUSY;

        zone = page_zone(page);
        spin_lock_irqsave(&zone->lock, flags);
        /*
         * In future, more migrate types will be able to be isolation target.
         */
        if (get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
                goto out;
        set_pageblock_migratetype(page, MIGRATE_ISOLATE);
        move_freepages_block(zone, page, MIGRATE_ISOLATE);
        ret = 0;
out:
        spin_unlock_irqrestore(&zone->lock, flags);
        if (!ret)
                drain_all_pages();
        return ret;
}

void unset_migratetype_isolate(struct page *page)
{
        struct zone *zone;
        unsigned long flags;
        zone = page_zone(page);
        spin_lock_irqsave(&zone->lock, flags);
        if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
                goto out;
        set_pageblock_migratetype(page, MIGRATE_MOVABLE);
        move_freepages_block(zone, page, MIGRATE_MOVABLE);
out:
        spin_unlock_irqrestore(&zone->lock, flags);
}

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