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/*

 *  linux/mm/swap.c

 *

 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds

 */

/*

 * This file contains the default values for the operation of the

 * Linux VM subsystem. Fine-tuning documentation can be found in

 * Documentation/sysctl/vm.txt.

 * Started 18.12.91

 * Swap aging added 23.2.95, Stephen Tweedie.

 * Buffermem limits added 12.3.98, Rik van Riel.

 */

#include <linux/mm.h>

#include <linux/sched.h>

#include <linux/kernel_stat.h>

#include <linux/swap.h>

#include <linux/mman.h>

#include <linux/pagemap.h>

#include <linux/pagevec.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/mm_inline.h>

#include <linux/buffer_head.h>  /* for try_to_release_page() */

#include <linux/percpu_counter.h>

#include <linux/percpu.h>

#include <linux/cpu.h>

#include <linux/notifier.h>

#include <linux/backing-dev.h>

/* How many pages do we try to swap or page in/out together? */

int page_cluster;

static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };

static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };

static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs) = { 0, };

/*

 * This path almost never happens for VM activity - pages are normally

 * freed via pagevecs.  But it gets used by networking.

 */

static void fastcall __page_cache_release(struct page *page)

{

        if (PageLRU(page)) {

                unsigned long flags;

                struct zone *zone = page_zone(page);

                spin_lock_irqsave(&zone->lru_lock, flags);

                VM_BUG_ON(!PageLRU(page));

                __ClearPageLRU(page);

                del_page_from_lru(zone, page);

                spin_unlock_irqrestore(&zone->lru_lock, flags);

        }

        free_hot_page(page);

}

static void put_compound_page(struct page *page)

{

        page = compound_head(page);

        if (put_page_testzero(page)) {

                compound_page_dtor *dtor;

                dtor = get_compound_page_dtor(page);

                (*dtor)(page);

        }

}

void put_page(struct page *page)

{

        if (unlikely(PageCompound(page)))

                put_compound_page(page);

        else if (put_page_testzero(page))

                __page_cache_release(page);

}

EXPORT_SYMBOL(put_page);

/**

 * put_pages_list(): release a list of pages

 *

 * Release a list of pages which are strung together on page.lru.  Currently

 * used by read_cache_pages() and related error recovery code.

 *

 * @pages: list of pages threaded on page->lru

 */

void put_pages_list(struct list_head *pages)

{

        while (!list_empty(pages)) {

                struct page *victim;

                victim = list_entry(pages->prev, struct page, lru);

                list_del(&victim->lru);

                page_cache_release(victim);

        }

}

EXPORT_SYMBOL(put_pages_list);

/*

 * pagevec_move_tail() must be called with IRQ disabled.

 * Otherwise this may cause nasty races.

 */

static void pagevec_move_tail(struct pagevec *pvec)

{

        int i;

        int pgmoved = 0;

        struct zone *zone = NULL;

        for (i = 0; i < pagevec_count(pvec); i++) {

                struct page *page = pvec->pages[i];

                struct zone *pagezone = page_zone(page);

                if (pagezone != zone) {

                        if (zone)

                                spin_unlock(&zone->lru_lock);

                        zone = pagezone;

                        spin_lock(&zone->lru_lock);

                }

                if (PageLRU(page) && !PageActive(page)) {

                        list_move_tail(&page->lru, &zone->inactive_list);

                        pgmoved++;

                }

        }

        if (zone)

                spin_unlock(&zone->lru_lock);

        __count_vm_events(PGROTATED, pgmoved);

        release_pages(pvec->pages, pvec->nr, pvec->cold);

        pagevec_reinit(pvec);

}

/*

 * Writeback is about to end against a page which has been marked for immediate

 * reclaim.  If it still appears to be reclaimable, move it to the tail of the

 * inactive list.

 *

 * Returns zero if it cleared PG_writeback.

 */

int rotate_reclaimable_page(struct page *page)

{

        struct pagevec *pvec;

        unsigned long flags;

        if (PageLocked(page))

                return 1;

        if (PageDirty(page))

                return 1;

        if (PageActive(page))

                return 1;

        if (!PageLRU(page))

                return 1;

        page_cache_get(page);

        local_irq_save(flags);

        pvec = &__get_cpu_var(lru_rotate_pvecs);

        if (!pagevec_add(pvec, page))

                pagevec_move_tail(pvec);

        local_irq_restore(flags);

        if (!test_clear_page_writeback(page))

                BUG();

        return 0;

}

/*

 * FIXME: speed this up?

 */

void fastcall activate_page(struct page *page)

{

        struct zone *zone = page_zone(page);

        spin_lock_irq(&zone->lru_lock);

        if (PageLRU(page) && !PageActive(page)) {

                del_page_from_inactive_list(zone, page);

                SetPageActive(page);

                add_page_to_active_list(zone, page);

                __count_vm_event(PGACTIVATE);

        }

        spin_unlock_irq(&zone->lru_lock);

}

/*

 * Mark a page as having seen activity.

 *

 * inactive,unreferenced        ->      inactive,referenced

 * inactive,referenced          ->      active,unreferenced

 * active,unreferenced          ->      active,referenced

 */

void fastcall mark_page_accessed(struct page *page)

{

        if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {

                activate_page(page);

                ClearPageReferenced(page);

        } else if (!PageReferenced(page)) {

                SetPageReferenced(page);

        }

}

EXPORT_SYMBOL(mark_page_accessed);

/**

 * lru_cache_add: add a page to the page lists

 * @page: the page to add

 */

void fastcall lru_cache_add(struct page *page)

{

        struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);

        page_cache_get(page);

        if (!pagevec_add(pvec, page))

                __pagevec_lru_add(pvec);

        put_cpu_var(lru_add_pvecs);

}

void fastcall lru_cache_add_active(struct page *page)

{

        struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);

        page_cache_get(page);

        if (!pagevec_add(pvec, page))

                __pagevec_lru_add_active(pvec);

        put_cpu_var(lru_add_active_pvecs);

}

/*

 * Drain pages out of the cpu's pagevecs.

 * Either "cpu" is the current CPU, and preemption has already been

 * disabled; or "cpu" is being hot-unplugged, and is already dead.

 */

static void drain_cpu_pagevecs(int cpu)

{

        struct pagevec *pvec;

        pvec = &per_cpu(lru_add_pvecs, cpu);

        if (pagevec_count(pvec))

                __pagevec_lru_add(pvec);

        pvec = &per_cpu(lru_add_active_pvecs, cpu);

        if (pagevec_count(pvec))

                __pagevec_lru_add_active(pvec);

        pvec = &per_cpu(lru_rotate_pvecs, cpu);

        if (pagevec_count(pvec)) {

                unsigned long flags;

                /* No harm done if a racing interrupt already did this */

                local_irq_save(flags);

                pagevec_move_tail(pvec);

                local_irq_restore(flags);

        }

}

void lru_add_drain(void)

{

        drain_cpu_pagevecs(get_cpu());

        put_cpu();

}

#ifdef CONFIG_NUMA

static void lru_add_drain_per_cpu(struct work_struct *dummy)

{

        lru_add_drain();

}

/*

 * Returns 0 for success

 */

int lru_add_drain_all(void)

{

        return schedule_on_each_cpu(lru_add_drain_per_cpu);

}

#else

/*

 * Returns 0 for success

 */

int lru_add_drain_all(void)

{

        lru_add_drain();

        return 0;

}

#endif

/*

 * Batched page_cache_release().  Decrement the reference count on all the

 * passed pages.  If it fell to zero then remove the page from the LRU and

 * free it.

 *

 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it

 * for the remainder of the operation.

 *

 * The locking in this function is against shrink_cache(): we recheck the

 * page count inside the lock to see whether shrink_cache grabbed the page

 * via the LRU.  If it did, give up: shrink_cache will free it.

 */

void release_pages(struct page **pages, int nr, int cold)

{

        int i;

        struct pagevec pages_to_free;

        struct zone *zone = NULL;

        unsigned long uninitialized_var(flags);

        pagevec_init(&pages_to_free, cold);

        for (i = 0; i < nr; i++) {

                struct page *page = pages[i];

                if (unlikely(PageCompound(page))) {

                        if (zone) {

                                spin_unlock_irqrestore(&zone->lru_lock, flags);

                                zone = NULL;

                        }

                        put_compound_page(page);

                        continue;

                }

                if (!put_page_testzero(page))

                        continue;

                if (PageLRU(page)) {

                        struct zone *pagezone = page_zone(page);

                        if (pagezone != zone) {

                                if (zone)

                                        spin_unlock_irqrestore(&zone->lru_lock,

                                                                        flags);

                                zone = pagezone;

                                spin_lock_irqsave(&zone->lru_lock, flags);

                        }

                        VM_BUG_ON(!PageLRU(page));

                        __ClearPageLRU(page);

                        del_page_from_lru(zone, page);

                }

                if (!pagevec_add(&pages_to_free, page)) {

                        if (zone) {

                                spin_unlock_irqrestore(&zone->lru_lock, flags);

                                zone = NULL;

                        }

                        __pagevec_free(&pages_to_free);

                        pagevec_reinit(&pages_to_free);

                }

        }

        if (zone)

                spin_unlock_irqrestore(&zone->lru_lock, flags);

        pagevec_free(&pages_to_free);

}

/*

 * The pages which we're about to release may be in the deferred lru-addition

 * queues.  That would prevent them from really being freed right now.  That's

 * OK from a correctness point of view but is inefficient - those pages may be

 * cache-warm and we want to give them back to the page allocator ASAP.

 *

 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()

 * and __pagevec_lru_add_active() call release_pages() directly to avoid

 * mutual recursion.

 */

void __pagevec_release(struct pagevec *pvec)

{

        lru_add_drain();

        release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);

        pagevec_reinit(pvec);

}

EXPORT_SYMBOL(__pagevec_release);

/*

 * pagevec_release() for pages which are known to not be on the LRU

 *

 * This function reinitialises the caller's pagevec.

 */

void __pagevec_release_nonlru(struct pagevec *pvec)

{

        int i;

        struct pagevec pages_to_free;

        pagevec_init(&pages_to_free, pvec->cold);

        for (i = 0; i < pagevec_count(pvec); i++) {

                struct page *page = pvec->pages[i];

                VM_BUG_ON(PageLRU(page));

                if (put_page_testzero(page))

                        pagevec_add(&pages_to_free, page);

        }

        pagevec_free(&pages_to_free);

        pagevec_reinit(pvec);

}

/*

 * Add the passed pages to the LRU, then drop the caller's refcount

 * on them.  Reinitialises the caller's pagevec.

 */

void __pagevec_lru_add(struct pagevec *pvec)

{

        int i;

        struct zone *zone = NULL;

        for (i = 0; i < pagevec_count(pvec); i++) {

                struct page *page = pvec->pages[i];

                struct zone *pagezone = page_zone(page);

                if (pagezone != zone) {

                        if (zone)

                                spin_unlock_irq(&zone->lru_lock);

                        zone = pagezone;

                        spin_lock_irq(&zone->lru_lock);

                }

                VM_BUG_ON(PageLRU(page));

                SetPageLRU(page);

                add_page_to_inactive_list(zone, page);

        }

        if (zone)

                spin_unlock_irq(&zone->lru_lock);

        release_pages(pvec->pages, pvec->nr, pvec->cold);

        pagevec_reinit(pvec);

}

EXPORT_SYMBOL(__pagevec_lru_add);

void __pagevec_lru_add_active(struct pagevec *pvec)

{

        int i;

        struct zone *zone = NULL;

        for (i = 0; i < pagevec_count(pvec); i++) {

                struct page *page = pvec->pages[i];

                struct zone *pagezone = page_zone(page);

                if (pagezone != zone) {

                        if (zone)

                                spin_unlock_irq(&zone->lru_lock);

                        zone = pagezone;

                        spin_lock_irq(&zone->lru_lock);

                }

                VM_BUG_ON(PageLRU(page));

                SetPageLRU(page);

                VM_BUG_ON(PageActive(page));

                SetPageActive(page);

                add_page_to_active_list(zone, page);

        }

        if (zone)

                spin_unlock_irq(&zone->lru_lock);

        release_pages(pvec->pages, pvec->nr, pvec->cold);

        pagevec_reinit(pvec);

}

/*

 * Try to drop buffers from the pages in a pagevec

 */

void pagevec_strip(struct pagevec *pvec)

{

        int i;

        for (i = 0; i < pagevec_count(pvec); i++) {

                struct page *page = pvec->pages[i];

                if (PagePrivate(page) && !TestSetPageLocked(page)) {

                        if (PagePrivate(page))

                                try_to_release_page(page, 0);

                        unlock_page(page);

                }

        }

}

/**

 * pagevec_lookup - gang pagecache lookup

 * @pvec:       Where the resulting pages are placed

 * @mapping:    The address_space to search

 * @start:      The starting page index

 * @nr_pages:   The maximum number of pages

 *

 * pagevec_lookup() will search for and return a group of up to @nr_pages pages

 * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a

 * reference against the pages in @pvec.

 *

 * The search returns a group of mapping-contiguous pages with ascending

 * indexes.  There may be holes in the indices due to not-present pages.

 *

 * pagevec_lookup() returns the number of pages which were found.

 */

unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,

                pgoff_t start, unsigned nr_pages)

{

        pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);

        return pagevec_count(pvec);

}

EXPORT_SYMBOL(pagevec_lookup);

unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,

                pgoff_t *index, int tag, unsigned nr_pages)

{

        pvec->nr = find_get_pages_tag(mapping, index, tag,

                                        nr_pages, pvec->pages);

        return pagevec_count(pvec);

}

EXPORT_SYMBOL(pagevec_lookup_tag);

#ifdef CONFIG_SMP

/*

 * We tolerate a little inaccuracy to avoid ping-ponging the counter between

 * CPUs

 */

#define ACCT_THRESHOLD  max(16, NR_CPUS * 2)

static DEFINE_PER_CPU(long, committed_space) = 0;

void vm_acct_memory(long pages)

{

        long *local;

        preempt_disable();

        local = &__get_cpu_var(committed_space);

        *local += pages;

        if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {

                atomic_add(*local, &vm_committed_space);

                *local = 0;

        }

        preempt_enable();

}

#ifdef CONFIG_HOTPLUG_CPU

/* Drop the CPU's cached committed space back into the central pool. */

static int cpu_swap_callback(struct notifier_block *nfb,

                             unsigned long action,

                             void *hcpu)

{

        long *committed;

        committed = &per_cpu(committed_space, (long)hcpu);

        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {

                atomic_add(*committed, &vm_committed_space);

                *committed = 0;

                drain_cpu_pagevecs((long)hcpu);

        }

        return NOTIFY_OK;

}

#endif /* CONFIG_HOTPLUG_CPU */

#endif /* CONFIG_SMP */

/*

 * Perform any setup for the swap system

 */

void __init swap_setup(void)

{

        unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);

#ifdef CONFIG_SWAP

        bdi_init(swapper_space.backing_dev_info);

#endif

        /* Use a smaller cluster for small-memory machines */

        if (megs < 16)

                page_cluster = 2;

        else

                page_cluster = 3;

        /*

         * Right now other parts of the system means that we

         * _really_ don't want to cluster much more

         */

#ifdef CONFIG_HOTPLUG_CPU

        hotcpu_notifier(cpu_swap_callback, 0);

#endif

}