[linux-2.6.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/config.h>
#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/bootmem.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/topology.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>

#include <asm/tlbflush.h>

DECLARE_BITMAP(node_online_map, MAX_NUMNODES);
struct pglist_data *pgdat_list;
unsigned long totalram_pages;
unsigned long totalhigh_pages;
int nr_swap_pages;
int numnodes = 1;
int sysctl_lower_zone_protection = 0;

EXPORT_SYMBOL(totalram_pages);
EXPORT_SYMBOL(nr_swap_pages);

/*
 * Used by page_zone() to look up the address of the struct zone whose
 * id is encoded in the upper bits of page->flags
 */
struct zone *zone_table[1 << (ZONES_SHIFT + NODES_SHIFT)];
EXPORT_SYMBOL(zone_table);

static char *zone_names[MAX_NR_ZONES] = { "DMA", "Normal", "HighMem" };
int min_free_kbytes = 1024;

/*
 * Temporary debugging check for pages not lying within a given zone.
 */
static int bad_range(struct zone *zone, struct page *page)
{
        if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
                return 1;
        if (page_to_pfn(page) < zone->zone_start_pfn)
                return 1;
        if (zone != page_zone(page))
                return 1;
        return 0;
}

static void bad_page(const char *function, struct page *page)
{
        printk(KERN_EMERG "Bad page state at %s (in process '%s', page %p)\n",
                function, current->comm, page);
        printk(KERN_EMERG "flags:0x%08lx mapping:%p mapcount:%d count:%d\n",
                (unsigned long)page->flags, page->mapping,
                (int)page->mapcount, page_count(page));
        printk(KERN_EMERG "Backtrace:\n");
        dump_stack();
        printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n");
        page->flags &= ~(1 << PG_private        |
                        1 << PG_locked  |
                        1 << PG_lru     |
                        1 << PG_active  |
                        1 << PG_dirty   |
                        1 << PG_maplock |
                        1 << PG_anon    |
                        1 << PG_swapcache |
                        1 << PG_writeback);
        set_page_count(page, 0);
        page->mapping = NULL;
        page->mapcount = 0;
}

#ifndef CONFIG_HUGETLB_PAGE
#define prep_compound_page(page, order) do { } while (0)
#define destroy_compound_page(page, order) do { } while (0)
#else
/*
 * 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 ->mapping, if non-zero, holds the address of the
 * compound page's put_page() function.
 *
 * The order of the allocation is stored in the first tail page's ->index
 * This is only for debug at present.  This usage means that zero-order pages
 * may not be compound.
 */
static void prep_compound_page(struct page *page, unsigned long order)
{
        int i;
        int nr_pages = 1 << order;

        page[1].mapping = 0;
        page[1].index = order;
        for (i = 0; i < nr_pages; i++) {
                struct page *p = page + i;

                SetPageCompound(p);
                p->private = (unsigned long)page;
        }
}

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

        if (!PageCompound(page))
                return;

        if (page[1].index != order)
                bad_page(__FUNCTION__, page);

        for (i = 0; i < nr_pages; i++) {
                struct page *p = page + i;

                if (!PageCompound(p))
                        bad_page(__FUNCTION__, page);
                if (p->private != (unsigned long)page)
                        bad_page(__FUNCTION__, page);
                ClearPageCompound(p);
        }
}
#endif          /* CONFIG_HUGETLB_PAGE */

/*
 * 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 one bit for each pair of blocks, which
 * is set to 1 iff only one of the pair is allocated.  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_pages_bulk (struct page *page, struct page *base,
                struct zone *zone, struct free_area *area, unsigned long mask,
                unsigned int order)
{
        unsigned long page_idx, index;

        if (order)
                destroy_compound_page(page, order);
        page_idx = page - base;
        if (page_idx & ~mask)
                BUG();
        index = page_idx >> (1 + order);

        zone->free_pages -= mask;
        while (mask + (1 << (MAX_ORDER-1))) {
                struct page *buddy1, *buddy2;

                BUG_ON(area >= zone->free_area + MAX_ORDER);
                if (!__test_and_change_bit(index, area->map))
                        /*
                         * the buddy page is still allocated.
                         */
                        break;
                /*
                 * Move the buddy up one level.
                 * This code is taking advantage of the identity:
                 *      -mask = 1+~mask
                 */
                buddy1 = base + (page_idx ^ -mask);
                buddy2 = base + page_idx;
                BUG_ON(bad_range(zone, buddy1));
                BUG_ON(bad_range(zone, buddy2));
                list_del(&buddy1->lru);
                mask <<= 1;
                area++;
                index >>= 1;
                page_idx &= mask;
        }
        list_add(&(base + page_idx)->lru, &area->free_list);
}

static inline void free_pages_check(const char *function, struct page *page)
{
        if (    page_mapped(page) ||
                page->mapping != NULL ||
                page_count(page) != 0 ||
                (page->flags & (
                        1 << PG_lru     |
                        1 << PG_private |
                        1 << PG_locked  |
                        1 << PG_active  |
                        1 << PG_reclaim |
                        1 << PG_slab    |
                        1 << PG_maplock |
                        1 << PG_anon    |
                        1 << PG_swapcache |
                        1 << PG_writeback )))
                bad_page(function, page);
        if (PageDirty(page))
                ClearPageDirty(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, or 0 for all on the list.
 *
 * 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 int
free_pages_bulk(struct zone *zone, int count,
                struct list_head *list, unsigned int order)
{
        unsigned long mask, flags;
        struct free_area *area;
        struct page *base, *page = NULL;
        int ret = 0;

        mask = (~0UL) << order;
        base = zone->zone_mem_map;
        area = zone->free_area + order;
        spin_lock_irqsave(&zone->lock, flags);
        zone->all_unreclaimable = 0;
        zone->pages_scanned = 0;
        while (!list_empty(list) && count--) {
                page = list_entry(list->prev, struct page, lru);
                /* have to delete it as __free_pages_bulk list manipulates */
                list_del(&page->lru);
                __free_pages_bulk(page, base, zone, area, mask, order);
                ret++;
        }
        spin_unlock_irqrestore(&zone->lock, flags);
        return ret;
}

void __free_pages_ok(struct page *page, unsigned int order)
{
        LIST_HEAD(list);
        int i;

        mod_page_state(pgfree, 1 << order);
        for (i = 0 ; i < (1 << order) ; ++i)
                free_pages_check(__FUNCTION__, page + i);
        list_add(&page->lru, &list);
        kernel_map_pages(page, 1<<order, 0);
        free_pages_bulk(page_zone(page), 1, &list, order);
}

#define MARK_USED(index, order, area) \
        __change_bit((index) >> (1+(order)), (area)->map)

static inline struct page *
expand(struct zone *zone, struct page *page,
         unsigned long index, int low, int high, struct free_area *area)
{
        unsigned long size = 1 << high;

        while (high > low) {
                BUG_ON(bad_range(zone, page));
                area--;
                high--;
                size >>= 1;
                list_add(&page->lru, &area->free_list);
                MARK_USED(index, high, area);
                index += size;
                page += size;
        }
        return page;
}

static inline void set_page_refs(struct page *page, int order)
{
#ifdef CONFIG_MMU
        set_page_count(page, 1);
#else
        int i;

        /*
         * We need to reference all the pages for this order, otherwise if
         * anyone accesses one of the pages with (get/put) it will be freed.
         */
        for (i = 0; i < (1 << order); i++)
                set_page_count(page+i, 1);
#endif /* CONFIG_MMU */
}

/*
 * This page is about to be returned from the page allocator
 */
static void prep_new_page(struct page *page, int order)
{
        if (page->mapping || page_mapped(page) ||
            (page->flags & (
                        1 << PG_private |
                        1 << PG_locked  |
                        1 << PG_lru     |
                        1 << PG_active  |
                        1 << PG_dirty   |
                        1 << PG_reclaim |
                        1 << PG_maplock |
                        1 << PG_anon    |
                        1 << PG_swapcache |
                        1 << PG_writeback )))
                bad_page(__FUNCTION__, page);

        page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
                        1 << PG_referenced | 1 << PG_arch_1 |
                        1 << PG_checked | 1 << PG_mappedtodisk);
        page->private = 0;
        set_page_refs(page, order);
}

/* 
 * 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)
{
        struct free_area * area;
        unsigned int current_order;
        struct page *page;
        unsigned int index;

        for (current_order = order; current_order < MAX_ORDER; ++current_order) {
                area = zone->free_area + current_order;
                if (list_empty(&area->free_list))
                        continue;

                page = list_entry(area->free_list.next, struct page, lru);
                list_del(&page->lru);
                index = page - zone->zone_mem_map;
                if (current_order != MAX_ORDER-1)
                        MARK_USED(index, current_order, area);
                zone->free_pages -= 1UL << order;
                return expand(zone, page, index, order, current_order, area);
        }

        return NULL;
}

/* 
 * 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)
{
        unsigned long flags;
        int i;
        int allocated = 0;
        struct page *page;
        
        spin_lock_irqsave(&zone->lock, flags);
        for (i = 0; i < count; ++i) {
                page = __rmqueue(zone, order);
                if (page == NULL)
                        break;
                allocated++;
                list_add_tail(&page->lru, list);
        }
        spin_unlock_irqrestore(&zone->lock, flags);
        return allocated;
}

#if defined(CONFIG_PM) || defined(CONFIG_HOTPLUG_CPU)
static void __drain_pages(unsigned int cpu)
{
        struct zone *zone;
        int i;

        for_each_zone(zone) {
                struct per_cpu_pageset *pset;

                pset = &zone->pageset[cpu];
                for (i = 0; i < ARRAY_SIZE(pset->pcp); i++) {
                        struct per_cpu_pages *pcp;

                        pcp = &pset->pcp[i];
                        pcp->count -= free_pages_bulk(zone, pcp->count,
                                                &pcp->list, 0);
                }
        }
}
#endif /* CONFIG_PM || CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_PM
int is_head_of_free_region(struct page *page)
{
        struct zone *zone = page_zone(page);
        unsigned long flags;
        int order;
        struct list_head *curr;

        /*
         * Should not matter as we need quiescent system for
         * suspend anyway, but...
         */
        spin_lock_irqsave(&zone->lock, flags);
        for (order = MAX_ORDER - 1; order >= 0; --order)
                list_for_each(curr, &zone->free_area[order].free_list)
                        if (page == list_entry(curr, struct page, lru)) {
                                spin_unlock_irqrestore(&zone->lock, flags);
                                return 1 << order;
                        }
        spin_unlock_irqrestore(&zone->lock, flags);
        return 0;
}

/*
 * Spill all of this CPU's per-cpu pages back into the buddy allocator.
 */
void drain_local_pages(void)
{
        unsigned long flags;

        local_irq_save(flags);  
        __drain_pages(smp_processor_id());
        local_irq_restore(flags);       
}
#endif /* CONFIG_PM */

static void zone_statistics(struct zonelist *zonelist, struct zone *z)
{
#ifdef CONFIG_NUMA
        unsigned long flags;
        int cpu;
        pg_data_t *pg = z->zone_pgdat;
        pg_data_t *orig = zonelist->zones[0]->zone_pgdat;
        struct per_cpu_pageset *p;

        local_irq_save(flags);
        cpu = smp_processor_id();
        p = &z->pageset[cpu];
        if (pg == orig) {
                z->pageset[cpu].numa_hit++;
        } else {
                p->numa_miss++;
                zonelist->zones[0]->pageset[cpu].numa_foreign++;
        }
        if (pg == NODE_DATA(numa_node_id()))
                p->local_node++;
        else
                p->other_node++;
        local_irq_restore(flags);
#endif
}

/*
 * Free a 0-order page
 */
static void FASTCALL(free_hot_cold_page(struct page *page, int cold));
static void fastcall free_hot_cold_page(struct page *page, int cold)
{
        struct zone *zone = page_zone(page);
        struct per_cpu_pages *pcp;
        unsigned long flags;

        kernel_map_pages(page, 1, 0);
        inc_page_state(pgfree);
        free_pages_check(__FUNCTION__, page);
        pcp = &zone->pageset[get_cpu()].pcp[cold];
        local_irq_save(flags);
        if (pcp->count >= pcp->high)
                pcp->count -= free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
        list_add(&page->lru, &pcp->list);
        pcp->count++;
        local_irq_restore(flags);
        put_cpu();
}

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

/*
 * 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 *zone, int order, int gfp_flags)
{
        unsigned long flags;
        struct page *page = NULL;
        int cold = !!(gfp_flags & __GFP_COLD);

        if (order == 0) {
                struct per_cpu_pages *pcp;

                pcp = &zone->pageset[get_cpu()].pcp[cold];
                local_irq_save(flags);
                if (pcp->count <= pcp->low)
                        pcp->count += rmqueue_bulk(zone, 0,
                                                pcp->batch, &pcp->list);
                if (pcp->count) {
                        page = list_entry(pcp->list.next, struct page, lru);
                        list_del(&page->lru);
                        pcp->count--;
                }
                local_irq_restore(flags);
                put_cpu();
        }

        if (page == NULL) {
                spin_lock_irqsave(&zone->lock, flags);
                page = __rmqueue(zone, order);
                spin_unlock_irqrestore(&zone->lock, flags);
        }

        if (page != NULL) {
                BUG_ON(bad_range(zone, page));
                mod_page_state_zone(zone, pgalloc, 1 << order);
                prep_new_page(page, order);
                if (order && (gfp_flags & __GFP_COMP))
                        prep_compound_page(page, order);
        }
        return page;
}

/*
 * This is the 'heart' of the zoned buddy allocator.
 *
 * Herein lies the mysterious "incremental min".  That's the
 *
 *      local_low = z->pages_low;
 *      min += local_low;
 *
 * thing.  The intent here is to provide additional protection to low zones for
 * allocation requests which _could_ use higher zones.  So a GFP_HIGHMEM
 * request is not allowed to dip as deeply into the normal zone as a GFP_KERNEL
 * request.  This preserves additional space in those lower zones for requests
 * which really do need memory from those zones.  It means that on a decent
 * sized machine, GFP_HIGHMEM and GFP_KERNEL requests basically leave the DMA
 * zone untouched.
 */
struct page * fastcall
__alloc_pages(unsigned int gfp_mask, unsigned int order,
                struct zonelist *zonelist)
{
        const int wait = gfp_mask & __GFP_WAIT;
        unsigned long min;
        struct zone **zones;
        struct page *page;
        struct reclaim_state reclaim_state;
        struct task_struct *p = current;
        int i;
        int alloc_type;
        int do_retry;

        might_sleep_if(wait);

        zones = zonelist->zones;  /* the list of zones suitable for gfp_mask */
        if (zones[0] == NULL)     /* no zones in the zonelist */
                return NULL;

        alloc_type = zone_idx(zones[0]);

        /* Go through the zonelist once, looking for a zone with enough free */
        for (i = 0; zones[i] != NULL; i++) {
                struct zone *z = zones[i];

                min = (1<<order) + z->protection[alloc_type];

                /*
                 * We let real-time tasks dip their real-time paws a little
                 * deeper into reserves.
                 */
                if (rt_task(p))
                        min -= z->pages_low >> 1;

                if (z->free_pages >= min ||
                                (!wait && z->free_pages >= z->pages_high)) {
                        page = buffered_rmqueue(z, order, gfp_mask);
                        if (page) {
                                zone_statistics(zonelist, z);
                                goto got_pg;
                        }
                }
        }

        /* we're somewhat low on memory, failed to find what we needed */
        for (i = 0; zones[i] != NULL; i++)
                wakeup_kswapd(zones[i]);

        /* Go through the zonelist again, taking __GFP_HIGH into account */
        for (i = 0; zones[i] != NULL; i++) {
                struct zone *z = zones[i];

                min = (1<<order) + z->protection[alloc_type];

                if (gfp_mask & __GFP_HIGH)
                        min -= z->pages_low >> 2;
                if (rt_task(p))
                        min -= z->pages_low >> 1;

                if (z->free_pages >= min ||
                                (!wait && z->free_pages >= z->pages_high)) {
                        page = buffered_rmqueue(z, order, gfp_mask);
                        if (page) {
                                zone_statistics(zonelist, z);
                                goto got_pg;
                        }
                }
        }

        /* here we're in the low on memory slow path */

rebalance:
        if ((p->flags & (PF_MEMALLOC | PF_MEMDIE)) && !in_interrupt()) {
                /* go through the zonelist yet again, ignoring mins */
                for (i = 0; zones[i] != NULL; i++) {
                        struct zone *z = zones[i];

                        page = buffered_rmqueue(z, order, gfp_mask);
                        if (page) {
                                zone_statistics(zonelist, z);
                                goto got_pg;
                        }
                }
                goto nopage;
        }

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

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

        try_to_free_pages(zones, gfp_mask, order);

        p->reclaim_state = NULL;
        p->flags &= ~PF_MEMALLOC;

        /* go through the zonelist yet one more time */
        for (i = 0; zones[i] != NULL; i++) {
                struct zone *z = zones[i];

                min = (1UL << order) + z->protection[alloc_type];

                if (z->free_pages >= min ||
                                (!wait && z->free_pages >= z->pages_high)) {
                        page = buffered_rmqueue(z, order, gfp_mask);
                        if (page) {
                                zone_statistics(zonelist, z);
                                goto got_pg;
                        }
                }
        }

        /*
         * 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, __GFP_REPEAT means __GFP_NOFAIL, but that
         * may not be true in other implementations.
         */
        do_retry = 0;
        if (!(gfp_mask & __GFP_NORETRY)) {
                if ((order <= 3) || (gfp_mask & __GFP_REPEAT))
                        do_retry = 1;
                if (gfp_mask & __GFP_NOFAIL)
                        do_retry = 1;
        }
        if (do_retry) {
                blk_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();
        }
        return NULL;
got_pg:
        kernel_map_pages(page, 1 << order, 1);
        return page;
}

EXPORT_SYMBOL(__alloc_pages);

/*
 * Common helper functions.
 */
fastcall unsigned long __get_free_pages(unsigned int 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);

fastcall unsigned long get_zeroed_page(unsigned int gfp_mask)
{
        struct page * page;

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

        page = alloc_pages(gfp_mask, 0);
        if (page) {
                void *address = page_address(page);
                clear_page(address);
                return (unsigned long) address;
        }
        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);
}

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

EXPORT_SYMBOL(__free_pages);

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

EXPORT_SYMBOL(free_pages);

/*
 * Total amount of free (allocatable) RAM:
 */
unsigned int nr_free_pages(void)
{
        unsigned int sum = 0;
        struct zone *zone;

        for_each_zone(zone)
                sum += zone->free_pages;

        return sum;
}

EXPORT_SYMBOL(nr_free_pages);

unsigned int nr_used_zone_pages(void)
{
        unsigned int pages = 0;
        struct zone *zone;

        for_each_zone(zone)
                pages += zone->nr_active + zone->nr_inactive;

        return pages;
}

#ifdef CONFIG_NUMA
unsigned int nr_free_pages_pgdat(pg_data_t *pgdat)
{
        unsigned int i, sum = 0;

        for (i = 0; i < MAX_NR_ZONES; i++)
                sum += pgdat->node_zones[i].free_pages;

        return sum;
}
#endif

static unsigned int nr_free_zone_pages(int offset)
{
        pg_data_t *pgdat;
        unsigned int sum = 0;

        for_each_pgdat(pgdat) {
                struct zonelist *zonelist = pgdat->node_zonelists + offset;
                struct zone **zonep = zonelist->zones;
                struct zone *zone;

                for (zone = *zonep++; zone; zone = *zonep++) {
                        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_USER & GFP_ZONEMASK);
}

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

#ifdef CONFIG_HIGHMEM
unsigned int nr_free_highpages (void)
{
        pg_data_t *pgdat;
        unsigned int pages = 0;

        for_each_pgdat(pgdat)
                pages += pgdat->node_zones[ZONE_HIGHMEM].free_pages;

        return pages;
}
#endif

#ifdef CONFIG_NUMA
static void show_node(struct zone *zone)
{
        printk("Node %d ", zone->zone_pgdat->node_id);
}
#else
#define show_node(zone) do { } while (0)
#endif

/*
 * Accumulate the page_state information across all CPUs.
 * The result is unavoidably approximate - it can change
 * during and after execution of this function.
 */
DEFINE_PER_CPU(struct page_state, page_states) = {0};
EXPORT_PER_CPU_SYMBOL(page_states);

atomic_t nr_pagecache = ATOMIC_INIT(0);
EXPORT_SYMBOL(nr_pagecache);
#ifdef CONFIG_SMP
DEFINE_PER_CPU(long, nr_pagecache_local) = 0;
#endif

void __get_page_state(struct page_state *ret, int nr)
{
        int cpu = 0;

        memset(ret, 0, sizeof(*ret));
        while (cpu < NR_CPUS) {
                unsigned long *in, *out, off;

                if (!cpu_possible(cpu)) {
                        cpu++;
                        continue;
                }

                in = (unsigned long *)&per_cpu(page_states, cpu);
                cpu++;
                if (cpu < NR_CPUS && cpu_possible(cpu))
                        prefetch(&per_cpu(page_states, cpu));
                out = (unsigned long *)ret;
                for (off = 0; off < nr; off++)
                        *out++ += *in++;
        }
}

void get_page_state(struct page_state *ret)
{
        int nr;

        nr = offsetof(struct page_state, GET_PAGE_STATE_LAST);
        nr /= sizeof(unsigned long);

        __get_page_state(ret, nr + 1);
}

void get_full_page_state(struct page_state *ret)
{
        __get_page_state(ret, sizeof(*ret) / sizeof(unsigned long));
}

unsigned long __read_page_state(unsigned offset)
{
        unsigned long ret = 0;
        int cpu;

        for (cpu = 0; cpu < NR_CPUS; cpu++) {
                unsigned long in;

                if (!cpu_possible(cpu))
                        continue;

                in = (unsigned long)&per_cpu(page_states, cpu) + offset;
                ret += *((unsigned long *)in);
        }
        return ret;
}

void get_zone_counts(unsigned long *active,
                unsigned long *inactive, unsigned long *free)
{
        struct zone *zone;

        *active = 0;
        *inactive = 0;
        *free = 0;
        for_each_zone(zone) {
                *active += zone->nr_active;
                *inactive += zone->nr_inactive;
                *free += zone->free_pages;
        }
}

void si_meminfo(struct sysinfo *val)
{
        val->totalram = totalram_pages;
        val->sharedram = 0;
        val->freeram = nr_free_pages();
        val->bufferram = nr_blockdev_pages();
#ifdef CONFIG_HIGHMEM
        val->totalhigh = totalhigh_pages;
        val->freehigh = nr_free_highpages();
#else
        val->totalhigh = 0;
        val->freehigh = 0;
#endif
        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 = nr_free_pages_pgdat(pgdat);
        val->totalhigh = pgdat->node_zones[ZONE_HIGHMEM].present_pages;
        val->freehigh = pgdat->node_zones[ZONE_HIGHMEM].free_pages;
        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)
{
        struct page_state ps;
        int cpu, temperature;
        unsigned long active;
        unsigned long inactive;
        unsigned long free;
        struct zone *zone;

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

                if (!zone->present_pages) {
                        printk(" empty\n");
                        continue;
                } else
                        printk("\n");

                for (cpu = 0; cpu < NR_CPUS; ++cpu) {
                        struct per_cpu_pageset *pageset;

                        if (!cpu_possible(cpu))
                                continue;

                        pageset = zone->pageset + cpu;

                        for (temperature = 0; temperature < 2; temperature++)
                                printk("cpu %d %s: low %d, high %d, batch %d\n",
                                        cpu,
                                        temperature ? "cold" : "hot",
                                        pageset->pcp[temperature].low,
                                        pageset->pcp[temperature].high,
                                        pageset->pcp[temperature].batch);
                }
        }

        get_page_state(&ps);
        get_zone_counts(&active, &inactive, &free);

        printk("\nFree pages: %11ukB (%ukB HighMem)\n",
                K(nr_free_pages()),
                K(nr_free_highpages()));

        printk("Active:%lu inactive:%lu dirty:%lu writeback:%lu "
                "unstable:%lu free:%u slab:%lu mapped:%lu pagetables:%lu\n",
                active,
                inactive,
                ps.nr_dirty,
                ps.nr_writeback,
                ps.nr_unstable,
                nr_free_pages(),
                ps.nr_slab,
                ps.nr_mapped,
                ps.nr_page_table_pages);

        for_each_zone(zone) {
                int i;

                show_node(zone);
                printk("%s"
                        " free:%lukB"
                        " min:%lukB"
                        " low:%lukB"
                        " high:%lukB"
                        " active:%lukB"
                        " inactive:%lukB"
                        " present:%lukB"
                        "\n",
                        zone->name,
                        K(zone->free_pages),
                        K(zone->pages_min),
                        K(zone->pages_low),
                        K(zone->pages_high),
                        K(zone->nr_active),
                        K(zone->nr_inactive),
                        K(zone->present_pages)
                        );
                printk("protections[]:");
                for (i = 0; i < MAX_NR_ZONES; i++)
                        printk(" %lu", zone->protection[i]);
                printk("\n");
        }

        for_each_zone(zone) {
                struct list_head *elem;
                unsigned long nr, flags, order, total = 0;

                show_node(zone);
                printk("%s: ", zone->name);
                if (!zone->present_pages) {
                        printk("empty\n");
                        continue;
                }

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

        show_swap_cache_info();
}

/*
 * Builds allocation fallback zone lists.
 */
static int __init build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist, int j, int k)
{
        switch (k) {
                struct zone *zone;
        default:
                BUG();
        case ZONE_HIGHMEM:
                zone = pgdat->node_zones + ZONE_HIGHMEM;
                if (zone->present_pages) {
#ifndef CONFIG_HIGHMEM
                        BUG();
#endif
                        zonelist->zones[j++] = zone;
                }
        case ZONE_NORMAL:
                zone = pgdat->node_zones + ZONE_NORMAL;
                if (zone->present_pages)
                        zonelist->zones[j++] = zone;
        case ZONE_DMA:
                zone = pgdat->node_zones + ZONE_DMA;
                if (zone->present_pages)
                        zonelist->zones[j++] = zone;
        }

        return j;
}

#ifdef CONFIG_NUMA
#define MAX_NODE_LOAD (numnodes)
static int __initdata 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: pointer to the bitmap 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 __init find_next_best_node(int node, void *used_node_mask)
{
        int i, n, val;
        int min_val = INT_MAX;
        int best_node = -1;

        for (i = 0; i < numnodes; i++) {
                cpumask_t tmp;

                /* Start from local node */
                n = (node+i)%numnodes;

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

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

                /* Give preference to headless and unused nodes */
                tmp = node_to_cpumask(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)
                set_bit(best_node, used_node_mask);

        return best_node;
}

static void __init build_zonelists(pg_data_t *pgdat)
{
        int i, j, k, node, local_node;
        int prev_node, load;
        struct zonelist *zonelist;
        DECLARE_BITMAP(used_mask, MAX_NUMNODES);

        /* initialize zonelists */
        for (i = 0; i < MAX_NR_ZONES; i++) {
                zonelist = pgdat->node_zonelists + i;
                memset(zonelist, 0, sizeof(*zonelist));
                zonelist->zones[0] = NULL;
        }

        /* NUMA-aware ordering of nodes */
        local_node = pgdat->node_id;
        load = numnodes;
        prev_node = local_node;
        bitmap_zero(used_mask, MAX_NUMNODES);
        while ((node = find_next_best_node(local_node, used_mask)) >= 0) {
                /*
                 * We don't want to pressure a particular node.
                 * So adding penalty to the first node in same
                 * distance group to make it round-robin.
                 */
                if (node_distance(local_node, node) !=
                                node_distance(local_node, prev_node))
                        node_load[node] += load;
                prev_node = node;
                load--;
                for (i = 0; i < MAX_NR_ZONES; i++) {
                        zonelist = pgdat->node_zonelists + i;
                        for (j = 0; zonelist->zones[j] != NULL; j++);

                        k = ZONE_NORMAL;
                        if (i & __GFP_HIGHMEM)
                                k = ZONE_HIGHMEM;
                        if (i & __GFP_DMA)
                                k = ZONE_DMA;

                        j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
                        zonelist->zones[j] = NULL;
                }
        }
}

#else   /* CONFIG_NUMA */

static void __init build_zonelists(pg_data_t *pgdat)
{
        int i, j, k, node, local_node;

        local_node = pgdat->node_id;
        for (i = 0; i < MAX_NR_ZONES; i++) {
                struct zonelist *zonelist;

                zonelist = pgdat->node_zonelists + i;
                memset(zonelist, 0, sizeof(*zonelist));

                j = 0;
                k = ZONE_NORMAL;
                if (i & __GFP_HIGHMEM)
                        k = ZONE_HIGHMEM;
                if (i & __GFP_DMA)
                        k = ZONE_DMA;

                j = build_zonelists_node(pgdat, zonelist, j, k);
                /*
                 * 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 < numnodes; node++)
                        j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
                for (node = 0; node < local_node; node++)
                        j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
 
                zonelist->zones[j] = NULL;
        }
}

#endif  /* CONFIG_NUMA */

void __init build_all_zonelists(void)
{
        int i;

        for(i = 0 ; i < numnodes ; i++)
                build_zonelists(NODE_DATA(i));
        printk("Built %i zonelists\n", numnodes);
}

/*
 * 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

static inline unsigned long wait_table_size(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);
}

/*
 * 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))

static void __init calculate_zone_totalpages(struct pglist_data *pgdat,
                unsigned long *zones_size, unsigned long *zholes_size)
{
        unsigned long realtotalpages, totalpages = 0;
        int i;

        for (i = 0; i < MAX_NR_ZONES; i++)
                totalpages += zones_size[i];
        pgdat->node_spanned_pages = totalpages;

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


/*
 * 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 __init memmap_init_zone(struct page *start, unsigned long size, int nid,
                unsigned long zone, unsigned long start_pfn)
{
        struct page *page;

        for (page = start; page < (start + size); page++) {
                set_page_zone(page, NODEZONE(nid, zone));
                set_page_count(page, 0);
                SetPageReserved(page);
                INIT_LIST_HEAD(&page->lru);
#ifdef WANT_PAGE_VIRTUAL
                /* The shift won't overflow because ZONE_NORMAL is below 4G. */
                if (zone != ZONE_HIGHMEM)
                        set_page_address(page, __va(start_pfn << PAGE_SHIFT));
#endif
                start_pfn++;
        }
}

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

/*
 * Set up the zone data structures:
 *   - mark all pages reserved
 *   - mark all memory queues empty
 *   - clear the memory bitmaps
 */
static void __init free_area_init_core(struct pglist_data *pgdat,
                unsigned long *zones_size, unsigned long *zholes_size)
{
        unsigned long i, j;
        const unsigned long zone_required_alignment = 1UL << (MAX_ORDER-1);
        int cpu, nid = pgdat->node_id;
        struct page *lmem_map = pgdat->node_mem_map;
        unsigned long zone_start_pfn = pgdat->node_start_pfn;

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

                zone_table[NODEZONE(nid, j)] = zone;
                realsize = size = zones_size[j];
                if (zholes_size)
                        realsize -= zholes_size[j];

                zone->spanned_pages = size;
                zone->present_pages = realsize;
                zone->name = zone_names[j];
                spin_lock_init(&zone->lock);
                spin_lock_init(&zone->lru_lock);
                zone->zone_pgdat = pgdat;
                zone->free_pages = 0;

                zone->temp_priority = zone->prev_priority = DEF_PRIORITY;

                /*
                 * The per-cpu-pages pools are set to around 1000th of the
                 * size of the zone.  But no more than 1/4 of a meg - there's
                 * no point in going beyond the size of L2 cache.
                 *
                 * OK, so we don't know how big the cache is.  So guess.
                 */
                batch = zone->present_pages / 1024;
                if (batch * PAGE_SIZE > 256 * 1024)
                        batch = (256 * 1024) / PAGE_SIZE;
                batch /= 4;             /* We effectively *= 4 below */
                if (batch < 1)
                        batch = 1;

                for (cpu = 0; cpu < NR_CPUS; cpu++) {
                        struct per_cpu_pages *pcp;

                        pcp = &zone->pageset[cpu].pcp[0];       /* hot */
                        pcp->count = 0;
                        pcp->low = 2 * batch;
                        pcp->high = 6 * batch;
                        pcp->batch = 1 * batch;
                        INIT_LIST_HEAD(&pcp->list);

                        pcp = &zone->pageset[cpu].pcp[1];       /* cold */
                        pcp->count = 0;
                        pcp->low = 0;
                        pcp->high = 2 * batch;
                        pcp->batch = 1 * batch;
                        INIT_LIST_HEAD(&pcp->list);
                }
                printk("  %s zone: %lu pages, LIFO batch:%lu\n",
                                zone_names[j], realsize, batch);
                INIT_LIST_HEAD(&zone->active_list);
                INIT_LIST_HEAD(&zone->inactive_list);
                atomic_set(&zone->nr_scan_active, 0);
                atomic_set(&zone->nr_scan_inactive, 0);
                zone->nr_active = 0;
                zone->nr_inactive = 0;
                if (!size)
                        continue;

                /*
                 * The per-page waitqueue mechanism uses hashed waitqueues
                 * per zone.
                 */
                zone->wait_table_size = wait_table_size(size);
                zone->wait_table_bits =
                        wait_table_bits(zone->wait_table_size);
                zone->wait_table = (wait_queue_head_t *)
                        alloc_bootmem_node(pgdat, zone->wait_table_size
                                                * sizeof(wait_queue_head_t));

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

                pgdat->nr_zones = j+1;

                zone->zone_mem_map = lmem_map;
                zone->zone_start_pfn = zone_start_pfn;

                if ((zone_start_pfn) & (zone_required_alignment-1))
                        printk("BUG: wrong zone alignment, it will crash\n");

                memmap_init(lmem_map, size, nid, j, zone_start_pfn);

                zone_start_pfn += size;
                lmem_map += size;

                for (i = 0; ; i++) {
                        unsigned long bitmap_size;

                        INIT_LIST_HEAD(&zone->free_area[i].free_list);
                        if (i == MAX_ORDER-1) {
                                zone->free_area[i].map = NULL;
                                break;
                        }

                        /*
                         * Page buddy system uses "index >> (i+1)",
                         * where "index" is at most "size-1".
                         *
                         * The extra "+3" is to round down to byte
                         * size (8 bits per byte assumption). Thus
                         * we get "(size-1) >> (i+4)" as the last byte
                         * we can access.
                         *
                         * The "+1" is because we want to round the
                         * byte allocation up rather than down. So
                         * we should have had a "+7" before we shifted
                         * down by three. Also, we have to add one as
                         * we actually _use_ the last bit (it's [0,n]
                         * inclusive, not [0,n[).
                         *
                         * So we actually had +7+1 before we shift
                         * down by 3. But (n+8) >> 3 == (n >> 3) + 1
                         * (modulo overflows, which we do not have).
                         *
                         * Finally, we LONG_ALIGN because all bitmap
                         * operations are on longs.
                         */
                        bitmap_size = (size-1) >> (i+4);
                        bitmap_size = LONG_ALIGN(bitmap_size+1);
                        zone->free_area[i].map = 
                          (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size);
                }
        }
}

void __init free_area_init_node(int nid, struct pglist_data *pgdat,
                struct page *node_mem_map, unsigned long *zones_size,
                unsigned long node_start_pfn, unsigned long *zholes_size)
{
        unsigned long size;

        pgdat->node_id = nid;
        pgdat->node_start_pfn = node_start_pfn;
        calculate_zone_totalpages(pgdat, zones_size, zholes_size);
        if (!node_mem_map) {
                size = (pgdat->node_spanned_pages + 1) * sizeof(struct page);
                node_mem_map = alloc_bootmem_node(pgdat, size);
        }
        pgdat->node_mem_map = node_mem_map;

        free_area_init_core(pgdat, zones_size, zholes_size);
}

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

EXPORT_SYMBOL(contig_page_data);

void __init free_area_init(unsigned long *zones_size)
{
        free_area_init_node(0, &contig_page_data, NULL, zones_size,
                        __pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
        mem_map = contig_page_data.node_mem_map;
}
#endif

#ifdef CONFIG_PROC_FS

#include <linux/seq_file.h>

static void *frag_start(struct seq_file *m, loff_t *pos)
{
        pg_data_t *pgdat;
        loff_t node = *pos;

        for (pgdat = pgdat_list; pgdat && node; pgdat = pgdat->pgdat_next)
                --node;

        return pgdat;
}

static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
{
        pg_data_t *pgdat = (pg_data_t *)arg;

        (*pos)++;
        return pgdat->pgdat_next;
}

static void frag_stop(struct seq_file *m, void *arg)
{
}

/* 
 * This walks the freelist for each zone. Whilst this is slow, I'd rather 
 * be slow here than slow down the fast path by keeping stats - mjbligh
 */
static int frag_show(struct seq_file *m, void *arg)
{
        pg_data_t *pgdat = (pg_data_t *)arg;
        struct zone *zone;
        struct zone *node_zones = pgdat->node_zones;
        unsigned long flags;
        int order;

        for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
                if (!zone->present_pages)
                        continue;

                spin_lock_irqsave(&zone->lock, flags);
                seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
                for (order = 0; order < MAX_ORDER; ++order) {
                        unsigned long nr_bufs = 0;
                        struct list_head *elem;

                        list_for_each(elem, &(zone->free_area[order].free_list))
                                ++nr_bufs;
                        seq_printf(m, "%6lu ", nr_bufs);
                }
                spin_unlock_irqrestore(&zone->lock, flags);
                seq_putc(m, '\n');
        }
        return 0;
}

struct seq_operations fragmentation_op = {
        .start  = frag_start,
        .next   = frag_next,
        .stop   = frag_stop,
        .show   = frag_show,
};

static char *vmstat_text[] = {
        "nr_dirty",
        "nr_writeback",
        "nr_unstable",
        "nr_page_table_pages",
        "nr_mapped",
        "nr_slab",

        "pgpgin",
        "pgpgout",
        "pswpin",
        "pswpout",
        "pgalloc_high",

        "pgalloc_normal",
        "pgalloc_dma",
        "pgfree",
        "pgactivate",
        "pgdeactivate",

        "pgfault",
        "pgmajfault",
        "pgrefill_high",
        "pgrefill_normal",
        "pgrefill_dma",

        "pgsteal_high",
        "pgsteal_normal",
        "pgsteal_dma",
        "pgscan_kswapd_high",
        "pgscan_kswapd_normal",

        "pgscan_kswapd_dma",
        "pgscan_direct_high",
        "pgscan_direct_normal",
        "pgscan_direct_dma",
        "pginodesteal",

        "slabs_scanned",
        "kswapd_steal",
        "kswapd_inodesteal",
        "pageoutrun",
        "allocstall",

        "pgrotated",
};

static void *vmstat_start(struct seq_file *m, loff_t *pos)
{
        struct page_state *ps;

        if (*pos >= ARRAY_SIZE(vmstat_text))
                return NULL;

        ps = kmalloc(sizeof(*ps), GFP_KERNEL);
        m->private = ps;
        if (!ps)
                return ERR_PTR(-ENOMEM);
        get_full_page_state(ps);
        ps->pgpgin /= 2;                /* sectors -> kbytes */
        ps->pgpgout /= 2;
        return (unsigned long *)ps + *pos;
}

static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
{
        (*pos)++;
        if (*pos >= ARRAY_SIZE(vmstat_text))
                return NULL;
        return (unsigned long *)m->private + *pos;
}

static int vmstat_show(struct seq_file *m, void *arg)
{
        unsigned long *l = arg;
        unsigned long off = l - (unsigned long *)m->private;

        seq_printf(m, "%s %lu\n", vmstat_text[off], *l);
        return 0;
}

static void vmstat_stop(struct seq_file *m, void *arg)
{
        kfree(m->private);
        m->private = NULL;
}

struct seq_operations vmstat_op = {
        .start  = vmstat_start,
        .next   = vmstat_next,
        .stop   = vmstat_stop,
        .show   = vmstat_show,
};

#endif /* CONFIG_PROC_FS */

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

        if (action == CPU_DEAD) {
                /* Drain local pagecache count. */
                count = &per_cpu(nr_pagecache_local, cpu);
                atomic_add(*count, &nr_pagecache);
                *count = 0;
                local_irq_disable();
                __drain_pages(cpu);
                local_irq_enable();
        }
        return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */

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

static unsigned long higherzone_val(struct zone *z, int max_zone,
                                        int alloc_type)
{
        int z_idx = zone_idx(z);
        struct zone *higherzone;
        unsigned long pages;

        /* there is no higher zone to get a contribution from */
        if (z_idx == MAX_NR_ZONES-1)
                return 0;

        higherzone = &z->zone_pgdat->node_zones[z_idx+1];

        /* We always start with the higher zone's protection value */
        pages = higherzone->protection[alloc_type];

        /*
         * We get a lower-zone-protection contribution only if there are
         * pages in the higher zone and if we're not the highest zone
         * in the current zonelist.  e.g., never happens for GFP_DMA. Happens
         * only for ZONE_DMA in a GFP_KERNEL allocation and happens for ZONE_DMA
         * and ZONE_NORMAL for a GFP_HIGHMEM allocation.
         */
        if (higherzone->present_pages && z_idx < alloc_type)
                pages += higherzone->pages_low * sysctl_lower_zone_protection;

        return pages;
}

/*
 * setup_per_zone_protection - called whenver min_free_kbytes or
 *      sysctl_lower_zone_protection changes.  Ensures that each zone
 *      has a correct pages_protected value, so an adequate number of
 *      pages are left in the zone after a successful __alloc_pages().
 *
 *      This algorithm is way confusing.  I tries to keep the same behavior
 *      as we had with the incremental min iterative algorithm.
 */
static void setup_per_zone_protection(void)
{
        struct pglist_data *pgdat;
        struct zone *zones, *zone;
        int max_zone;
        int i, j;

        for_each_pgdat(pgdat) {
                zones = pgdat->node_zones;

                for (i = 0, max_zone = 0; i < MAX_NR_ZONES; i++)
                        if (zones[i].present_pages)
                                max_zone = i;

                /*
                 * For each of the different allocation types:
                 * GFP_DMA -> GFP_KERNEL -> GFP_HIGHMEM
                 */
                for (i = 0; i < MAX_NR_ZONES; i++) {
                        /*
                         * For each of the zones:
                         * ZONE_HIGHMEM -> ZONE_NORMAL -> ZONE_DMA
                         */
                        for (j = MAX_NR_ZONES-1; j >= 0; j--) {
                                zone = &zones[j];

                                /*
                                 * We never protect zones that don't have memory
                                 * in them (j>max_zone) or zones that aren't in
                                 * the zonelists for a certain type of
                                 * allocation (j>i).  We have to assign these to
                                 * zero because the lower zones take
                                 * contributions from the higher zones.
                                 */
                                if (j > max_zone || j > i) {
                                        zone->protection[i] = 0;
                                        continue;
                                }
                                /*
                                 * The contribution of the next higher zone
                                 */
                                zone->protection[i] = higherzone_val(zone,
                                                                max_zone, i);
                                zone->protection[i] += zone->pages_low;
                        }
                }
        }
}

/*
 * 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.
 */
static 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) {
                spin_lock_irqsave(&zone->lru_lock, flags);
                if (is_highmem(zone)) {
                        /*
                         * Often, highmem doesn't need to reserve any pages.
                         * But the pages_min/low/high values are also used for
                         * batching up page reclaim activity so we need a
                         * decent value here.
                         */
                        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 = (pages_min * zone->present_pages) / 
                                           lowmem_pages;
                }

                zone->pages_low = zone->pages_min * 2;
                zone->pages_high = zone->pages_min * 3;
                spin_unlock_irqrestore(&zone->lru_lock, flags);
        }
}

/*
 * Initialise min_free_kbytes.
 *
 * For small machines we want it small (128k min).  For large machines
 * we want it large (16MB max).  But it is not linear, because network
 * bandwidth does not increase linearly with machine size.  We use
 *
 *      min_free_kbytes = sqrt(lowmem_kbytes)
 *
 * which yields
 *
 * 16MB:        128k
 * 32MB:        181k
 * 64MB:        256k
 * 128MB:       362k
 * 256MB:       512k
 * 512MB:       724k
 * 1024MB:      1024k
 * 2048MB:      1448k
 * 4096MB:      2048k
 * 8192MB:      2896k
 * 16384MB:     4096k
 */
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);
        if (min_free_kbytes < 128)
                min_free_kbytes = 128;
        if (min_free_kbytes > 16384)
                min_free_kbytes = 16384;
        setup_per_zone_pages_min();
        setup_per_zone_protection();
        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)
{
        proc_dointvec(table, write, file, buffer, length);
        setup_per_zone_pages_min();
        setup_per_zone_protection();
        return 0;
}

/*
 * lower_zone_protection_sysctl_handler - just a wrapper around
 *      proc_dointvec() so that we can call setup_per_zone_protection()
 *      whenever sysctl_lower_zone_protection changes.
 */
int lower_zone_protection_sysctl_handler(ctl_table *table, int write,
                 struct file *file, void __user *buffer, size_t *length)
{
        proc_dointvec_minmax(table, write, file, buffer, length);
        setup_per_zone_protection();
        return 0;
}