[linux-2.6-block.git] / mm / swap.c

/*
 *  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>
#include <linux/memcontrol.h>

#include "internal.h"

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

static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);

/*
 * This path almost never happens for VM activity - pages are normally
 * freed via pagevecs.  But it gets used by networking.
 */
static void __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
 * @pages: list of pages threaded on page->lru
 *
 * Release a list of pages which are strung together on page.lru.  Currently
 * used by read_cache_pages() and related error recovery code.
 */
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) && !PageUnevictable(page)) {
			int lru = page_is_file_cache(page);
			list_move_tail(&page->lru, &zone->lru[lru].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.
 */
void  rotate_reclaimable_page(struct page *page)
{
	if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
	    !PageUnevictable(page) && PageLRU(page)) {
		struct pagevec *pvec;
		unsigned long flags;

		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);
	}
}

/*
 * FIXME: speed this up?
 */
void activate_page(struct page *page)
{
	struct zone *zone = page_zone(page);
	struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;

	spin_lock_irq(&zone->lru_lock);
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = LRU_BASE + file;
		del_page_from_lru_list(zone, page, lru);

		SetPageActive(page);
		lru += LRU_ACTIVE;
		add_page_to_lru_list(zone, page, lru);
		__count_vm_event(PGACTIVATE);

		reclaim_stat->recent_rotated[!!file]++;
		reclaim_stat->recent_scanned[!!file]++;
	}
	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 mark_page_accessed(struct page *page)
{
	if (!PageActive(page) && !PageUnevictable(page) &&
			PageReferenced(page) && PageLRU(page)) {
		activate_page(page);
		ClearPageReferenced(page);
	} else if (!PageReferenced(page)) {
		SetPageReferenced(page);
	}
}

EXPORT_SYMBOL(mark_page_accessed);

void __lru_cache_add(struct page *page, enum lru_list lru)
{
	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];

	page_cache_get(page);
	if (!pagevec_add(pvec, page))
		____pagevec_lru_add(pvec, lru);
	put_cpu_var(lru_add_pvecs);
}

/**
 * lru_cache_add_lru - add a page to a page list
 * @page: the page to be added to the LRU.
 * @lru: the LRU list to which the page is added.
 */
void lru_cache_add_lru(struct page *page, enum lru_list lru)
{
	if (PageActive(page)) {
		VM_BUG_ON(PageUnevictable(page));
		ClearPageActive(page);
	} else if (PageUnevictable(page)) {
		VM_BUG_ON(PageActive(page));
		ClearPageUnevictable(page);
	}

	VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
	__lru_cache_add(page, lru);
}

/**
 * add_page_to_unevictable_list - add a page to the unevictable list
 * @page:  the page to be added to the unevictable list
 *
 * Add page directly to its zone's unevictable list.  To avoid races with
 * tasks that might be making the page evictable, through eg. munlock,
 * munmap or exit, while it's not on the lru, we want to add the page
 * while it's locked or otherwise "invisible" to other tasks.  This is
 * difficult to do when using the pagevec cache, so bypass that.
 */
void add_page_to_unevictable_list(struct page *page)
{
	struct zone *zone = page_zone(page);

	spin_lock_irq(&zone->lru_lock);
	SetPageUnevictable(page);
	SetPageLRU(page);
	add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
	spin_unlock_irq(&zone->lru_lock);
}

/*
 * 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 *pvecs = per_cpu(lru_add_pvecs, cpu);
	struct pagevec *pvec;
	int lru;

	for_each_lru(lru) {
		pvec = &pvecs[lru - LRU_BASE];
		if (pagevec_count(pvec))
			____pagevec_lru_add(pvec, lru);
	}

	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();
}

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);
}

/*
 * 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_inactive_list(): we recheck
 * the page count inside the lock to see whether shrink_inactive_list()
 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 * 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);

/*
 * 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, enum lru_list lru)
{
	int i;
	struct zone *zone = NULL;
	struct zone_reclaim_stat *reclaim_stat = NULL;

	VM_BUG_ON(is_unevictable_lru(lru));

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);
		int file;

		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			reclaim_stat = &zone->reclaim_stat;
			spin_lock_irq(&zone->lru_lock);
		}
		VM_BUG_ON(PageActive(page));
		VM_BUG_ON(PageUnevictable(page));
		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);
		file = is_file_lru(lru);
		reclaim_stat->recent_scanned[file]++;
		if (is_active_lru(lru)) {
			SetPageActive(page);
			reclaim_stat->recent_rotated[file]++;
		}
		add_page_to_lru_list(zone, page, lru);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

EXPORT_SYMBOL(____pagevec_lru_add);

/*
 * 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) && trylock_page(page)) {
			if (PagePrivate(page))
				try_to_release_page(page, 0);
			unlock_page(page);
		}
	}
}

/**
 * pagevec_swap_free - try to free swap space from the pages in a pagevec
 * @pvec: pagevec with swapcache pages to free the swap space of
 *
 * The caller needs to hold an extra reference to each page and
 * not hold the page lock on the pages.  This function uses a
 * trylock on the page lock so it may not always free the swap
 * space associated with a page.
 */
void pagevec_swap_free(struct pagevec *pvec)
{
	int i;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];

		if (PageSwapCache(page) && trylock_page(page)) {
			try_to_free_swap(page);
			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);

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_long_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_long_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
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/mm/swap.c
	3	*
	4	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	5	*/
	6
	7	/*
183ff22b	8	* This file contains the default values for the operation of the
1da177e4 LT	9	* Linux VM subsystem. Fine-tuning documentation can be found in
	10	* Documentation/sysctl/vm.txt.
	11	* Started 18.12.91
	12	* Swap aging added 23.2.95, Stephen Tweedie.
	13	* Buffermem limits added 12.3.98, Rik van Riel.
	14	*/
	15
	16	#include <linux/mm.h>
	17	#include <linux/sched.h>
	18	#include <linux/kernel_stat.h>
	19	#include <linux/swap.h>
	20	#include <linux/mman.h>
	21	#include <linux/pagemap.h>
	22	#include <linux/pagevec.h>
	23	#include <linux/init.h>
	24	#include <linux/module.h>
	25	#include <linux/mm_inline.h>
	26	#include <linux/buffer_head.h> /* for try_to_release_page() */
1da177e4 LT	27	#include <linux/percpu_counter.h>
	28	#include <linux/percpu.h>
	29	#include <linux/cpu.h>
	30	#include <linux/notifier.h>
e0bf68dd	31	#include <linux/backing-dev.h>
66e1707b	32	#include <linux/memcontrol.h>
1da177e4	33
64d6519d LS	34	#include "internal.h"
64d6519d LS	35
1da177e4 LT	36	/* How many pages do we try to swap or page in/out together? */
	37	int page_cluster;
	38
f04e9ebb	39	static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
f84f9504	40	static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
902aaed0	41
b221385b AB	42	/*
	43	* This path almost never happens for VM activity - pages are normally
	44	* freed via pagevecs. But it gets used by networking.
	45	*/
920c7a5d	46	static void __page_cache_release(struct page *page)
b221385b AB	47	{
	48	if (PageLRU(page)) {
	49	unsigned long flags;
	50	struct zone *zone = page_zone(page);
	51
	52	spin_lock_irqsave(&zone->lru_lock, flags);
	53	VM_BUG_ON(!PageLRU(page));
	54	__ClearPageLRU(page);
	55	del_page_from_lru(zone, page);
	56	spin_unlock_irqrestore(&zone->lru_lock, flags);
	57	}
	58	free_hot_page(page);
	59	}
	60
8519fb30	61	static void put_compound_page(struct page *page)
1da177e4	62	{
d85f3385	63	page = compound_head(page);
8519fb30	64	if (put_page_testzero(page)) {
33f2ef89	65	compound_page_dtor *dtor;
1da177e4	66
33f2ef89	67	dtor = get_compound_page_dtor(page);
8519fb30	68	(*dtor)(page);
1da177e4	69	}
8519fb30 NP	70	}
	71
	72	void put_page(struct page *page)
	73	{
	74	if (unlikely(PageCompound(page)))
	75	put_compound_page(page);
	76	else if (put_page_testzero(page))
1da177e4 LT	77	__page_cache_release(page);
	78	}
	79	EXPORT_SYMBOL(put_page);
1da177e4	80
1d7ea732	81	/**
7682486b RD	82	* put_pages_list() - release a list of pages
7682486b RD	83	* @pages: list of pages threaded on page->lru
1d7ea732 AZ	84	*
	85	* Release a list of pages which are strung together on page.lru. Currently
	86	* used by read_cache_pages() and related error recovery code.
1d7ea732 AZ	87	*/
	88	void put_pages_list(struct list_head *pages)
	89	{
	90	while (!list_empty(pages)) {
	91	struct page *victim;
	92
	93	victim = list_entry(pages->prev, struct page, lru);
	94	list_del(&victim->lru);
	95	page_cache_release(victim);
	96	}
	97	}
	98	EXPORT_SYMBOL(put_pages_list);
	99
902aaed0 HH	100	/*
	101	* pagevec_move_tail() must be called with IRQ disabled.
	102	* Otherwise this may cause nasty races.
	103	*/
	104	static void pagevec_move_tail(struct pagevec *pvec)
	105	{
	106	int i;
	107	int pgmoved = 0;
	108	struct zone *zone = NULL;
	109
	110	for (i = 0; i < pagevec_count(pvec); i++) {
	111	struct page *page = pvec->pages[i];
	112	struct zone *pagezone = page_zone(page);
	113
	114	if (pagezone != zone) {
	115	if (zone)
	116	spin_unlock(&zone->lru_lock);
	117	zone = pagezone;
	118	spin_lock(&zone->lru_lock);
	119	}
894bc310	120	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
4f98a2fe RR	121	int lru = page_is_file_cache(page);
4f98a2fe RR	122	list_move_tail(&page->lru, &zone->lru[lru].list);
902aaed0 HH	123	pgmoved++;
	124	}
	125	}
	126	if (zone)
	127	spin_unlock(&zone->lru_lock);
	128	__count_vm_events(PGROTATED, pgmoved);
	129	release_pages(pvec->pages, pvec->nr, pvec->cold);
	130	pagevec_reinit(pvec);
	131	}
	132
1da177e4 LT	133	/*
	134	* Writeback is about to end against a page which has been marked for immediate
	135	* reclaim. If it still appears to be reclaimable, move it to the tail of the
902aaed0	136	* inactive list.
1da177e4	137	*/
ac6aadb2	138	void rotate_reclaimable_page(struct page *page)
1da177e4	139	{
ac6aadb2	140	if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
894bc310	141	!PageUnevictable(page) && PageLRU(page)) {
ac6aadb2 MS	142	struct pagevec *pvec;
	143	unsigned long flags;
	144
	145	page_cache_get(page);
	146	local_irq_save(flags);
	147	pvec = &__get_cpu_var(lru_rotate_pvecs);
	148	if (!pagevec_add(pvec, page))
	149	pagevec_move_tail(pvec);
	150	local_irq_restore(flags);
	151	}
1da177e4 LT	152	}
	153
	154	/*
	155	* FIXME: speed this up?
	156	*/
920c7a5d	157	void activate_page(struct page *page)
1da177e4 LT	158	{
1da177e4 LT	159	struct zone *zone = page_zone(page);
6e901571	160	struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
1da177e4 LT	161
1da177e4 LT	162	spin_lock_irq(&zone->lru_lock);
894bc310	163	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
4f98a2fe RR	164	int file = page_is_file_cache(page);
	165	int lru = LRU_BASE + file;
	166	del_page_from_lru_list(zone, page, lru);
	167
1da177e4	168	SetPageActive(page);
4f98a2fe RR	169	lru += LRU_ACTIVE;
4f98a2fe RR	170	add_page_to_lru_list(zone, page, lru);
f8891e5e	171	__count_vm_event(PGACTIVATE);
4f98a2fe	172
6e901571 KM	173	reclaim_stat->recent_rotated[!!file]++;
6e901571 KM	174	reclaim_stat->recent_scanned[!!file]++;
1da177e4 LT	175	}
	176	spin_unlock_irq(&zone->lru_lock);
	177	}
	178
	179	/*
	180	* Mark a page as having seen activity.
	181	*
	182	* inactive,unreferenced -> inactive,referenced
	183	* inactive,referenced -> active,unreferenced
	184	* active,unreferenced -> active,referenced
	185	*/
920c7a5d	186	void mark_page_accessed(struct page *page)
1da177e4	187	{
894bc310 LS	188	if (!PageActive(page) && !PageUnevictable(page) &&
894bc310 LS	189	PageReferenced(page) && PageLRU(page)) {
1da177e4 LT	190	activate_page(page);
	191	ClearPageReferenced(page);
	192	} else if (!PageReferenced(page)) {
	193	SetPageReferenced(page);
	194	}
	195	}
	196
	197	EXPORT_SYMBOL(mark_page_accessed);
	198
f04e9ebb	199	void __lru_cache_add(struct page *page, enum lru_list lru)
1da177e4	200	{
f04e9ebb	201	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
1da177e4 LT	202
	203	page_cache_get(page);
	204	if (!pagevec_add(pvec, page))
f04e9ebb	205	____pagevec_lru_add(pvec, lru);
1da177e4 LT	206	put_cpu_var(lru_add_pvecs);
	207	}
	208
f04e9ebb KM	209	/**
	210	* lru_cache_add_lru - add a page to a page list
	211	* @page: the page to be added to the LRU.
	212	* @lru: the LRU list to which the page is added.
	213	*/
	214	void lru_cache_add_lru(struct page *page, enum lru_list lru)
1da177e4	215	{
f04e9ebb	216	if (PageActive(page)) {
894bc310	217	VM_BUG_ON(PageUnevictable(page));
f04e9ebb	218	ClearPageActive(page);
894bc310 LS	219	} else if (PageUnevictable(page)) {
	220	VM_BUG_ON(PageActive(page));
	221	ClearPageUnevictable(page);
f04e9ebb	222	}
1da177e4	223
894bc310	224	VM_BUG_ON(PageLRU(page) \|\| PageActive(page) \|\| PageUnevictable(page));
f04e9ebb	225	__lru_cache_add(page, lru);
1da177e4 LT	226	}
1da177e4 LT	227
894bc310 LS	228	/**
	229	* add_page_to_unevictable_list - add a page to the unevictable list
	230	* @page: the page to be added to the unevictable list
	231	*
	232	* Add page directly to its zone's unevictable list. To avoid races with
	233	* tasks that might be making the page evictable, through eg. munlock,
	234	* munmap or exit, while it's not on the lru, we want to add the page
	235	* while it's locked or otherwise "invisible" to other tasks. This is
	236	* difficult to do when using the pagevec cache, so bypass that.
	237	*/
	238	void add_page_to_unevictable_list(struct page *page)
	239	{
	240	struct zone *zone = page_zone(page);
	241
	242	spin_lock_irq(&zone->lru_lock);
	243	SetPageUnevictable(page);
	244	SetPageLRU(page);
	245	add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
	246	spin_unlock_irq(&zone->lru_lock);
	247	}
	248
902aaed0 HH	249	/*
	250	* Drain pages out of the cpu's pagevecs.
	251	* Either "cpu" is the current CPU, and preemption has already been
	252	* disabled; or "cpu" is being hot-unplugged, and is already dead.
	253	*/
	254	static void drain_cpu_pagevecs(int cpu)
1da177e4	255	{
f04e9ebb	256	struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
902aaed0	257	struct pagevec *pvec;
f04e9ebb	258	int lru;
1da177e4	259
f04e9ebb KM	260	for_each_lru(lru) {
	261	pvec = &pvecs[lru - LRU_BASE];
	262	if (pagevec_count(pvec))
	263	____pagevec_lru_add(pvec, lru);
	264	}
902aaed0 HH	265
	266	pvec = &per_cpu(lru_rotate_pvecs, cpu);
	267	if (pagevec_count(pvec)) {
	268	unsigned long flags;
	269
	270	/* No harm done if a racing interrupt already did this */
	271	local_irq_save(flags);
	272	pagevec_move_tail(pvec);
	273	local_irq_restore(flags);
	274	}
80bfed90 AM	275	}
	276
	277	void lru_add_drain(void)
	278	{
902aaed0	279	drain_cpu_pagevecs(get_cpu());
80bfed90	280	put_cpu();
1da177e4 LT	281	}
1da177e4 LT	282
c4028958	283	static void lru_add_drain_per_cpu(struct work_struct *dummy)
053837fc NP	284	{
	285	lru_add_drain();
	286	}
	287
	288	/*
	289	* Returns 0 for success
	290	*/
	291	int lru_add_drain_all(void)
	292	{
c4028958	293	return schedule_on_each_cpu(lru_add_drain_per_cpu);
053837fc NP	294	}
053837fc NP	295
1da177e4 LT	296	/*
	297	* Batched page_cache_release(). Decrement the reference count on all the
	298	* passed pages. If it fell to zero then remove the page from the LRU and
	299	* free it.
	300	*
	301	* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
	302	* for the remainder of the operation.
	303	*
ab33dc09 FLVC	304	* The locking in this function is against shrink_inactive_list(): we recheck
	305	* the page count inside the lock to see whether shrink_inactive_list()
	306	* grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
	307	* will free it.
1da177e4 LT	308	*/
	309	void release_pages(struct page **pages, int nr, int cold)
	310	{
	311	int i;
	312	struct pagevec pages_to_free;
	313	struct zone *zone = NULL;
902aaed0	314	unsigned long uninitialized_var(flags);
1da177e4 LT	315
	316	pagevec_init(&pages_to_free, cold);
	317	for (i = 0; i < nr; i++) {
	318	struct page *page = pages[i];
1da177e4	319
8519fb30 NP	320	if (unlikely(PageCompound(page))) {
8519fb30 NP	321	if (zone) {
902aaed0	322	spin_unlock_irqrestore(&zone->lru_lock, flags);
8519fb30 NP	323	zone = NULL;
	324	}
	325	put_compound_page(page);
	326	continue;
	327	}
	328
b5810039	329	if (!put_page_testzero(page))
1da177e4 LT	330	continue;
1da177e4 LT	331
46453a6e NP	332	if (PageLRU(page)) {
46453a6e NP	333	struct zone *pagezone = page_zone(page);
894bc310	334
46453a6e NP	335	if (pagezone != zone) {
46453a6e NP	336	if (zone)
902aaed0 HH	337	spin_unlock_irqrestore(&zone->lru_lock,
902aaed0 HH	338	flags);
46453a6e	339	zone = pagezone;
902aaed0	340	spin_lock_irqsave(&zone->lru_lock, flags);
46453a6e	341	}
725d704e	342	VM_BUG_ON(!PageLRU(page));
67453911	343	__ClearPageLRU(page);
1da177e4	344	del_page_from_lru(zone, page);
46453a6e NP	345	}
	346
	347	if (!pagevec_add(&pages_to_free, page)) {
	348	if (zone) {
902aaed0	349	spin_unlock_irqrestore(&zone->lru_lock, flags);
46453a6e	350	zone = NULL;
1da177e4	351	}
46453a6e NP	352	__pagevec_free(&pages_to_free);
	353	pagevec_reinit(&pages_to_free);
	354	}
1da177e4 LT	355	}
1da177e4 LT	356	if (zone)
902aaed0	357	spin_unlock_irqrestore(&zone->lru_lock, flags);
1da177e4 LT	358
	359	pagevec_free(&pages_to_free);
	360	}
	361
	362	/*
	363	* The pages which we're about to release may be in the deferred lru-addition
	364	* queues. That would prevent them from really being freed right now. That's
	365	* OK from a correctness point of view but is inefficient - those pages may be
	366	* cache-warm and we want to give them back to the page allocator ASAP.
	367	*
	368	* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
	369	* and __pagevec_lru_add_active() call release_pages() directly to avoid
	370	* mutual recursion.
	371	*/
	372	void __pagevec_release(struct pagevec *pvec)
	373	{
	374	lru_add_drain();
	375	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
	376	pagevec_reinit(pvec);
	377	}
	378
7f285701 SF	379	EXPORT_SYMBOL(__pagevec_release);
7f285701 SF	380
1da177e4 LT	381	/*
	382	* Add the passed pages to the LRU, then drop the caller's refcount
	383	* on them. Reinitialises the caller's pagevec.
	384	*/
f04e9ebb	385	void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
1da177e4 LT	386	{
	387	int i;
	388	struct zone *zone = NULL;
6e901571 KM	389	struct zone_reclaim_stat *reclaim_stat = NULL;
6e901571 KM	390
894bc310	391	VM_BUG_ON(is_unevictable_lru(lru));
1da177e4 LT	392
	393	for (i = 0; i < pagevec_count(pvec); i++) {
	394	struct page *page = pvec->pages[i];
	395	struct zone *pagezone = page_zone(page);
9ff473b9	396	int file;
1da177e4 LT	397
	398	if (pagezone != zone) {
	399	if (zone)
	400	spin_unlock_irq(&zone->lru_lock);
	401	zone = pagezone;
6e901571	402	reclaim_stat = &zone->reclaim_stat;
1da177e4 LT	403	spin_lock_irq(&zone->lru_lock);
1da177e4 LT	404	}
894bc310 LS	405	VM_BUG_ON(PageActive(page));
894bc310 LS	406	VM_BUG_ON(PageUnevictable(page));
725d704e	407	VM_BUG_ON(PageLRU(page));
8d438f96	408	SetPageLRU(page);
9ff473b9	409	file = is_file_lru(lru);
6e901571	410	reclaim_stat->recent_scanned[file]++;
9ff473b9	411	if (is_active_lru(lru)) {
f04e9ebb	412	SetPageActive(page);
6e901571	413	reclaim_stat->recent_rotated[file]++;
9ff473b9	414	}
f04e9ebb	415	add_page_to_lru_list(zone, page, lru);
1da177e4 LT	416	}
	417	if (zone)
	418	spin_unlock_irq(&zone->lru_lock);
	419	release_pages(pvec->pages, pvec->nr, pvec->cold);
	420	pagevec_reinit(pvec);
	421	}
	422
f04e9ebb	423	EXPORT_SYMBOL(____pagevec_lru_add);
1da177e4 LT	424
	425	/*
	426	* Try to drop buffers from the pages in a pagevec
	427	*/
	428	void pagevec_strip(struct pagevec *pvec)
	429	{
	430	int i;
	431
	432	for (i = 0; i < pagevec_count(pvec); i++) {
	433	struct page *page = pvec->pages[i];
	434
529ae9aa	435	if (PagePrivate(page) && trylock_page(page)) {
5b40dc78 CL	436	if (PagePrivate(page))
5b40dc78 CL	437	try_to_release_page(page, 0);
1da177e4 LT	438	unlock_page(page);
	439	}
	440	}
	441	}
	442
68a22394 RR	443	/**
	444	* pagevec_swap_free - try to free swap space from the pages in a pagevec
	445	* @pvec: pagevec with swapcache pages to free the swap space of
	446	*
	447	* The caller needs to hold an extra reference to each page and
	448	* not hold the page lock on the pages. This function uses a
	449	* trylock on the page lock so it may not always free the swap
	450	* space associated with a page.
	451	*/
	452	void pagevec_swap_free(struct pagevec *pvec)
	453	{
	454	int i;
	455
	456	for (i = 0; i < pagevec_count(pvec); i++) {
	457	struct page *page = pvec->pages[i];
	458
	459	if (PageSwapCache(page) && trylock_page(page)) {
a2c43eed	460	try_to_free_swap(page);
68a22394 RR	461	unlock_page(page);
	462	}
	463	}
	464	}
	465
1da177e4 LT	466	/**
	467	* pagevec_lookup - gang pagecache lookup
	468	* @pvec: Where the resulting pages are placed
	469	* @mapping: The address_space to search
	470	* @start: The starting page index
	471	* @nr_pages: The maximum number of pages
	472	*
	473	* pagevec_lookup() will search for and return a group of up to @nr_pages pages
	474	* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
	475	* reference against the pages in @pvec.
	476	*
	477	* The search returns a group of mapping-contiguous pages with ascending
	478	* indexes. There may be holes in the indices due to not-present pages.
	479	*
	480	* pagevec_lookup() returns the number of pages which were found.
	481	*/
	482	unsigned pagevec_lookup(struct pagevec pvec, struct address_space mapping,
	483	pgoff_t start, unsigned nr_pages)
	484	{
	485	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
	486	return pagevec_count(pvec);
	487	}
	488
78539fdf CH	489	EXPORT_SYMBOL(pagevec_lookup);
78539fdf CH	490
1da177e4 LT	491	unsigned pagevec_lookup_tag(struct pagevec pvec, struct address_space mapping,
	492	pgoff_t *index, int tag, unsigned nr_pages)
	493	{
	494	pvec->nr = find_get_pages_tag(mapping, index, tag,
	495	nr_pages, pvec->pages);
	496	return pagevec_count(pvec);
	497	}
	498
7f285701	499	EXPORT_SYMBOL(pagevec_lookup_tag);
1da177e4 LT	500
	501	#ifdef CONFIG_SMP
	502	/*
	503	* We tolerate a little inaccuracy to avoid ping-ponging the counter between
	504	* CPUs
	505	*/
	506	#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
	507
f84f9504	508	static DEFINE_PER_CPU(long, committed_space);
1da177e4 LT	509
	510	void vm_acct_memory(long pages)
	511	{
	512	long *local;
	513
	514	preempt_disable();
	515	local = &__get_cpu_var(committed_space);
	516	*local += pages;
	517	if (local > ACCT_THRESHOLD \|\| local < -ACCT_THRESHOLD) {
80119ef5	518	atomic_long_add(*local, &vm_committed_space);
1da177e4 LT	519	*local = 0;
	520	}
	521	preempt_enable();
	522	}
1da177e4 LT	523
1da177e4 LT	524	#ifdef CONFIG_HOTPLUG_CPU
1da177e4 LT	525
	526	/* Drop the CPU's cached committed space back into the central pool. */
	527	static int cpu_swap_callback(struct notifier_block *nfb,
	528	unsigned long action,
	529	void *hcpu)
	530	{
	531	long *committed;
	532
	533	committed = &per_cpu(committed_space, (long)hcpu);
8bb78442	534	if (action == CPU_DEAD \|\| action == CPU_DEAD_FROZEN) {
80119ef5	535	atomic_long_add(*committed, &vm_committed_space);
1da177e4	536	*committed = 0;
902aaed0	537	drain_cpu_pagevecs((long)hcpu);
1da177e4 LT	538	}
	539	return NOTIFY_OK;
	540	}
	541	#endif /* CONFIG_HOTPLUG_CPU */
	542	#endif /* CONFIG_SMP */
	543
1da177e4 LT	544	/*
	545	* Perform any setup for the swap system
	546	*/
	547	void __init swap_setup(void)
	548	{
	549	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
	550
e0bf68dd PZ	551	#ifdef CONFIG_SWAP
	552	bdi_init(swapper_space.backing_dev_info);
	553	#endif
	554
1da177e4 LT	555	/* Use a smaller cluster for small-memory machines */
	556	if (megs < 16)
	557	page_cluster = 2;
	558	else
	559	page_cluster = 3;
	560	/*
	561	* Right now other parts of the system means that we
	562	* _really_ don't want to cluster much more
	563	*/
02316067	564	#ifdef CONFIG_HOTPLUG_CPU
1da177e4	565	hotcpu_notifier(cpu_swap_callback, 0);
02316067	566	#endif
1da177e4	567	}