[net-next-2.6.git] / mm / swap.c

/*
 *  linux/mm/swap.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 */

/*
 * This file contains the default values for the opereation 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/module.h>
#include <linux/percpu_counter.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/init.h>

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

static void put_compound_page(struct page *page)
{
	page = (struct page *)page_private(page);
	if (put_page_testzero(page)) {
		void (*dtor)(struct page *page);

		dtor = (void (*)(struct page *))page[1].lru.next;
		(*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);

/*
 * 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.  The page still has PageWriteback set, which will pin it.
 *
 * We don't expect many pages to come through here, so don't bother batching
 * things up.
 *
 * To avoid placing the page at the tail of the LRU while PG_writeback is still
 * set, this function will clear PG_writeback before performing the page
 * motion.  Do that inside the lru lock because once PG_writeback is cleared
 * we may not touch the page.
 *
 * Returns zero if it cleared PG_writeback.
 */
int rotate_reclaimable_page(struct page *page)
{
	struct zone *zone;
	unsigned long flags;

	if (PageLocked(page))
		return 1;
	if (PageDirty(page))
		return 1;
	if (PageActive(page))
		return 1;
	if (!PageLRU(page))
		return 1;

	zone = page_zone(page);
	spin_lock_irqsave(&zone->lru_lock, flags);
	if (PageLRU(page) && !PageActive(page)) {
		list_del(&page->lru);
		list_add_tail(&page->lru, &zone->inactive_list);
		inc_page_state(pgrotated);
	}
	if (!test_clear_page_writeback(page))
		BUG();
	spin_unlock_irqrestore(&zone->lru_lock, flags);
	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);
		inc_page_state(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
 */
static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };

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);
}

static void __lru_add_drain(int cpu)
{
	struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);

	/* CPU is dead, so no locking needed. */
	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);
}

void lru_add_drain(void)
{
	__lru_add_drain(get_cpu());
	put_cpu();
}

#ifdef CONFIG_NUMA
static void lru_add_drain_per_cpu(void *dummy)
{
	lru_add_drain();
}

/*
 * Returns 0 for success
 */
int lru_add_drain_all(void)
{
	return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
}

#else

/*
 * Returns 0 for success
 */
int lru_add_drain_all(void)
{
	lru_add_drain();
	return 0;
}
#endif

/*
 * This path almost never happens for VM activity - pages are normally
 * freed via pagevecs.  But it gets used by networking.
 */
void fastcall __page_cache_release(struct page *page)
{
	unsigned long flags;
	struct zone *zone = page_zone(page);

	spin_lock_irqsave(&zone->lru_lock, flags);
	if (TestClearPageLRU(page))
		del_page_from_lru(zone, page);
	if (page_count(page) != 0)
		page = NULL;
	spin_unlock_irqrestore(&zone->lru_lock, flags);
	if (page)
		free_hot_page(page);
}

EXPORT_SYMBOL(__page_cache_release);

/*
 * 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;

	pagevec_init(&pages_to_free, cold);
	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];
		struct zone *pagezone;

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irq(&zone->lru_lock);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		if (!put_page_testzero(page))
			continue;

		pagezone = page_zone(page);
		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		if (TestClearPageLRU(page))
			del_page_from_lru(zone, page);
		if (page_count(page) == 0) {
			if (!pagevec_add(&pages_to_free, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_free(&pages_to_free);
				pagevec_reinit(&pages_to_free);
				zone = NULL;	/* No lock is held */
			}
		}
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);

	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];

		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);
		}
		if (TestSetPageLRU(page))
			BUG();
		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);
		}
		if (TestSetPageLRU(page))
			BUG();
		if (TestSetPageActive(page))
			BUG();
		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) {
		atomic_add(*committed, &vm_committed_space);
		*committed = 0;
		__lru_add_drain((long)hcpu);
	}
	return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */
#endif /* CONFIG_SMP */

#ifdef CONFIG_SMP
void percpu_counter_mod(struct percpu_counter *fbc, long amount)
{
	long count;
	long *pcount;
	int cpu = get_cpu();

	pcount = per_cpu_ptr(fbc->counters, cpu);
	count = *pcount + amount;
	if (count >= FBC_BATCH || count <= -FBC_BATCH) {
		spin_lock(&fbc->lock);
		fbc->count += count;
		*pcount = 0;
		spin_unlock(&fbc->lock);
	} else {
		*pcount = count;
	}
	put_cpu();
}
EXPORT_SYMBOL(percpu_counter_mod);

/*
 * Add up all the per-cpu counts, return the result.  This is a more accurate
 * but much slower version of percpu_counter_read_positive()
 */
long percpu_counter_sum(struct percpu_counter *fbc)
{
	long ret;
	int cpu;

	spin_lock(&fbc->lock);
	ret = fbc->count;
	for_each_cpu(cpu) {
		long *pcount = per_cpu_ptr(fbc->counters, cpu);
		ret += *pcount;
	}
	spin_unlock(&fbc->lock);
	return ret < 0 ? 0 : ret;
}
EXPORT_SYMBOL(percpu_counter_sum);
#endif

/*
 * Perform any setup for the swap system
 */
void __init swap_setup(void)
{
	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);

	/* 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
	 */
	hotcpu_notifier(cpu_swap_callback, 0);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/mm/swap.c
	3	*
	4	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	5	*/
	6
	7	/*
	8	* This file contains the default values for the opereation of the
	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() */
	27	#include <linux/module.h>
	28	#include <linux/percpu_counter.h>
	29	#include <linux/percpu.h>
	30	#include <linux/cpu.h>
	31	#include <linux/notifier.h>
	32	#include <linux/init.h>
	33
	34	/* How many pages do we try to swap or page in/out together? */
	35	int page_cluster;
	36
8519fb30	37	static void put_compound_page(struct page *page)
1da177e4	38	{
8519fb30 NP	39	page = (struct page *)page_private(page);
	40	if (put_page_testzero(page)) {
	41	void (dtor)(struct page page);
1da177e4	42
41d78ba5	43	dtor = (void ()(struct page ))page[1].lru.next;
8519fb30	44	(*dtor)(page);
1da177e4	45	}
8519fb30 NP	46	}
	47
	48	void put_page(struct page *page)
	49	{
	50	if (unlikely(PageCompound(page)))
	51	put_compound_page(page);
	52	else if (put_page_testzero(page))
1da177e4 LT	53	__page_cache_release(page);
	54	}
	55	EXPORT_SYMBOL(put_page);
1da177e4 LT	56
	57	/*
	58	* Writeback is about to end against a page which has been marked for immediate
	59	* reclaim. If it still appears to be reclaimable, move it to the tail of the
	60	* inactive list. The page still has PageWriteback set, which will pin it.
	61	*
	62	* We don't expect many pages to come through here, so don't bother batching
	63	* things up.
	64	*
	65	* To avoid placing the page at the tail of the LRU while PG_writeback is still
	66	* set, this function will clear PG_writeback before performing the page
	67	* motion. Do that inside the lru lock because once PG_writeback is cleared
	68	* we may not touch the page.
	69	*
	70	* Returns zero if it cleared PG_writeback.
	71	*/
	72	int rotate_reclaimable_page(struct page *page)
	73	{
	74	struct zone *zone;
	75	unsigned long flags;
	76
	77	if (PageLocked(page))
	78	return 1;
	79	if (PageDirty(page))
	80	return 1;
	81	if (PageActive(page))
	82	return 1;
	83	if (!PageLRU(page))
	84	return 1;
	85
	86	zone = page_zone(page);
	87	spin_lock_irqsave(&zone->lru_lock, flags);
	88	if (PageLRU(page) && !PageActive(page)) {
	89	list_del(&page->lru);
	90	list_add_tail(&page->lru, &zone->inactive_list);
	91	inc_page_state(pgrotated);
	92	}
	93	if (!test_clear_page_writeback(page))
	94	BUG();
	95	spin_unlock_irqrestore(&zone->lru_lock, flags);
	96	return 0;
	97	}
	98
	99	/*
	100	* FIXME: speed this up?
	101	*/
	102	void fastcall activate_page(struct page *page)
	103	{
	104	struct zone *zone = page_zone(page);
	105
	106	spin_lock_irq(&zone->lru_lock);
	107	if (PageLRU(page) && !PageActive(page)) {
	108	del_page_from_inactive_list(zone, page);
	109	SetPageActive(page);
	110	add_page_to_active_list(zone, page);
	111	inc_page_state(pgactivate);
	112	}
	113	spin_unlock_irq(&zone->lru_lock);
	114	}
	115
	116	/*
	117	* Mark a page as having seen activity.
	118	*
	119	* inactive,unreferenced -> inactive,referenced
120	* inactive,referenced -> active,unreferenced
121	* active,unreferenced -> active,referenced
122	*/
123	void fastcall mark_page_accessed(struct page *page)
124	{
125	if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
126	activate_page(page);
127	ClearPageReferenced(page);
128	} else if (!PageReferenced(page)) {
129	SetPageReferenced(page);
130	}
131	}
132
133	EXPORT_SYMBOL(mark_page_accessed);
134
135	/**
136	* lru_cache_add: add a page to the page lists
137	* @page: the page to add
138	*/
139	static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
140	static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
141
142	void fastcall lru_cache_add(struct page *page)
143	{
144	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
145
146	page_cache_get(page);
147	if (!pagevec_add(pvec, page))
148	__pagevec_lru_add(pvec);
149	put_cpu_var(lru_add_pvecs);
150	}
151
152	void fastcall lru_cache_add_active(struct page *page)
153	{
154	struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
155
156	page_cache_get(page);
157	if (!pagevec_add(pvec, page))
158	__pagevec_lru_add_active(pvec);
159	put_cpu_var(lru_add_active_pvecs);
160	}
161
80bfed90	162	static void __lru_add_drain(int cpu)
1da177e4	163	{
80bfed90	164	struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
1da177e4	165
80bfed90	166	/* CPU is dead, so no locking needed. */
1da177e4 LT	167	if (pagevec_count(pvec))
1da177e4 LT	168	__pagevec_lru_add(pvec);
80bfed90	169	pvec = &per_cpu(lru_add_active_pvecs, cpu);
1da177e4 LT	170	if (pagevec_count(pvec))
1da177e4 LT	171	__pagevec_lru_add_active(pvec);
80bfed90 AM	172	}
	173
	174	void lru_add_drain(void)
	175	{
	176	__lru_add_drain(get_cpu());
	177	put_cpu();
1da177e4 LT	178	}
1da177e4 LT	179
053837fc NP	180	#ifdef CONFIG_NUMA
	181	static void lru_add_drain_per_cpu(void *dummy)
	182	{
	183	lru_add_drain();
	184	}
	185
	186	/*
	187	* Returns 0 for success
	188	*/
	189	int lru_add_drain_all(void)
	190	{
	191	return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
	192	}
	193
	194	#else
	195
	196	/*
	197	* Returns 0 for success
	198	*/
	199	int lru_add_drain_all(void)
	200	{
	201	lru_add_drain();
	202	return 0;
	203	}
	204	#endif
	205
1da177e4 LT	206	/*
	207	* This path almost never happens for VM activity - pages are normally
	208	* freed via pagevecs. But it gets used by networking.
	209	*/
	210	void fastcall __page_cache_release(struct page *page)
	211	{
	212	unsigned long flags;
	213	struct zone *zone = page_zone(page);
	214
	215	spin_lock_irqsave(&zone->lru_lock, flags);
	216	if (TestClearPageLRU(page))
	217	del_page_from_lru(zone, page);
	218	if (page_count(page) != 0)
	219	page = NULL;
	220	spin_unlock_irqrestore(&zone->lru_lock, flags);
	221	if (page)
	222	free_hot_page(page);
	223	}
	224
	225	EXPORT_SYMBOL(__page_cache_release);
	226
	227	/*
	228	* Batched page_cache_release(). Decrement the reference count on all the
	229	* passed pages. If it fell to zero then remove the page from the LRU and
	230	* free it.
	231	*
	232	* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
	233	* for the remainder of the operation.
	234	*
	235	* The locking in this function is against shrink_cache(): we recheck the
	236	* page count inside the lock to see whether shrink_cache grabbed the page
	237	* via the LRU. If it did, give up: shrink_cache will free it.
	238	*/
	239	void release_pages(struct page **pages, int nr, int cold)
	240	{
	241	int i;
	242	struct pagevec pages_to_free;
	243	struct zone *zone = NULL;
	244
	245	pagevec_init(&pages_to_free, cold);
	246	for (i = 0; i < nr; i++) {
	247	struct page *page = pages[i];
	248	struct zone *pagezone;
	249
8519fb30 NP	250	if (unlikely(PageCompound(page))) {
	251	if (zone) {
	252	spin_unlock_irq(&zone->lru_lock);
	253	zone = NULL;
	254	}
	255	put_compound_page(page);
	256	continue;
	257	}
	258
b5810039	259	if (!put_page_testzero(page))
1da177e4 LT	260	continue;
	261
	262	pagezone = page_zone(page);
	263	if (pagezone != zone) {
	264	if (zone)
	265	spin_unlock_irq(&zone->lru_lock);
	266	zone = pagezone;
	267	spin_lock_irq(&zone->lru_lock);
	268	}
	269	if (TestClearPageLRU(page))
	270	del_page_from_lru(zone, page);
	271	if (page_count(page) == 0) {
	272	if (!pagevec_add(&pages_to_free, page)) {
	273	spin_unlock_irq(&zone->lru_lock);
	274	__pagevec_free(&pages_to_free);
	275	pagevec_reinit(&pages_to_free);
	276	zone = NULL; /* No lock is held */
	277	}
	278	}
	279	}
	280	if (zone)
	281	spin_unlock_irq(&zone->lru_lock);
	282
	283	pagevec_free(&pages_to_free);
	284	}
	285
	286	/*
	287	* The pages which we're about to release may be in the deferred lru-addition
	288	* queues. That would prevent them from really being freed right now. That's
	289	* OK from a correctness point of view but is inefficient - those pages may be
	290	* cache-warm and we want to give them back to the page allocator ASAP.
	291	*
	292	* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
	293	* and __pagevec_lru_add_active() call release_pages() directly to avoid
	294	* mutual recursion.
	295	*/
	296	void __pagevec_release(struct pagevec *pvec)
	297	{
	298	lru_add_drain();
	299	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
	300	pagevec_reinit(pvec);
	301	}
	302
7f285701 SF	303	EXPORT_SYMBOL(__pagevec_release);
7f285701 SF	304
1da177e4 LT	305	/*
	306	* pagevec_release() for pages which are known to not be on the LRU
	307	*
	308	* This function reinitialises the caller's pagevec.
	309	*/
	310	void __pagevec_release_nonlru(struct pagevec *pvec)
	311	{
	312	int i;
	313	struct pagevec pages_to_free;
	314
	315	pagevec_init(&pages_to_free, pvec->cold);
1da177e4 LT	316	for (i = 0; i < pagevec_count(pvec); i++) {
	317	struct page *page = pvec->pages[i];
	318
	319	BUG_ON(PageLRU(page));
	320	if (put_page_testzero(page))
	321	pagevec_add(&pages_to_free, page);
	322	}
	323	pagevec_free(&pages_to_free);
	324	pagevec_reinit(pvec);
	325	}
	326
	327	/*
	328	* Add the passed pages to the LRU, then drop the caller's refcount
	329	* on them. Reinitialises the caller's pagevec.
	330	*/
	331	void __pagevec_lru_add(struct pagevec *pvec)
	332	{
	333	int i;
	334	struct zone *zone = NULL;
	335
	336	for (i = 0; i < pagevec_count(pvec); i++) {
	337	struct page *page = pvec->pages[i];
	338	struct zone *pagezone = page_zone(page);
	339
	340	if (pagezone != zone) {
	341	if (zone)
	342	spin_unlock_irq(&zone->lru_lock);
	343	zone = pagezone;
	344	spin_lock_irq(&zone->lru_lock);
	345	}
	346	if (TestSetPageLRU(page))
	347	BUG();
	348	add_page_to_inactive_list(zone, page);
	349	}
	350	if (zone)
	351	spin_unlock_irq(&zone->lru_lock);
	352	release_pages(pvec->pages, pvec->nr, pvec->cold);
	353	pagevec_reinit(pvec);
	354	}
	355
	356	EXPORT_SYMBOL(__pagevec_lru_add);
	357
	358	void __pagevec_lru_add_active(struct pagevec *pvec)
	359	{
	360	int i;
	361	struct zone *zone = NULL;
	362
	363	for (i = 0; i < pagevec_count(pvec); i++) {
	364	struct page *page = pvec->pages[i];
	365	struct zone *pagezone = page_zone(page);
	366
	367	if (pagezone != zone) {
	368	if (zone)
	369	spin_unlock_irq(&zone->lru_lock);
	370	zone = pagezone;
	371	spin_lock_irq(&zone->lru_lock);
	372	}
	373	if (TestSetPageLRU(page))
	374	BUG();
	375	if (TestSetPageActive(page))
	376	BUG();
	377	add_page_to_active_list(zone, page);
	378	}
	379	if (zone)
380	spin_unlock_irq(&zone->lru_lock);
381	release_pages(pvec->pages, pvec->nr, pvec->cold);
382	pagevec_reinit(pvec);
383	}
384
385	/*
386	* Try to drop buffers from the pages in a pagevec
387	*/
388	void pagevec_strip(struct pagevec *pvec)
389	{
390	int i;
391
392	for (i = 0; i < pagevec_count(pvec); i++) {
393	struct page *page = pvec->pages[i];
394
395	if (PagePrivate(page) && !TestSetPageLocked(page)) {
5b40dc78 CL	396	if (PagePrivate(page))
5b40dc78 CL	397	try_to_release_page(page, 0);
1da177e4 LT	398	unlock_page(page);
	399	}
	400	}
	401	}
	402
	403	/**
	404	* pagevec_lookup - gang pagecache lookup
	405	* @pvec: Where the resulting pages are placed
	406	* @mapping: The address_space to search
	407	* @start: The starting page index
	408	* @nr_pages: The maximum number of pages
	409	*
	410	* pagevec_lookup() will search for and return a group of up to @nr_pages pages
	411	* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
	412	* reference against the pages in @pvec.
	413	*
	414	* The search returns a group of mapping-contiguous pages with ascending
	415	* indexes. There may be holes in the indices due to not-present pages.
	416	*
	417	* pagevec_lookup() returns the number of pages which were found.
	418	*/
	419	unsigned pagevec_lookup(struct pagevec pvec, struct address_space mapping,
	420	pgoff_t start, unsigned nr_pages)
	421	{
	422	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
	423	return pagevec_count(pvec);
	424	}
	425
78539fdf CH	426	EXPORT_SYMBOL(pagevec_lookup);
78539fdf CH	427
1da177e4 LT	428	unsigned pagevec_lookup_tag(struct pagevec pvec, struct address_space mapping,
	429	pgoff_t *index, int tag, unsigned nr_pages)
	430	{
	431	pvec->nr = find_get_pages_tag(mapping, index, tag,
	432	nr_pages, pvec->pages);
	433	return pagevec_count(pvec);
	434	}
	435
7f285701	436	EXPORT_SYMBOL(pagevec_lookup_tag);
1da177e4 LT	437
	438	#ifdef CONFIG_SMP
	439	/*
	440	* We tolerate a little inaccuracy to avoid ping-ponging the counter between
	441	* CPUs
	442	*/
	443	#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
	444
	445	static DEFINE_PER_CPU(long, committed_space) = 0;
	446
	447	void vm_acct_memory(long pages)
	448	{
	449	long *local;
	450
	451	preempt_disable();
	452	local = &__get_cpu_var(committed_space);
	453	*local += pages;
	454	if (local > ACCT_THRESHOLD \|\| local < -ACCT_THRESHOLD) {
	455	atomic_add(*local, &vm_committed_space);
	456	*local = 0;
	457	}
	458	preempt_enable();
	459	}
1da177e4 LT	460
1da177e4 LT	461	#ifdef CONFIG_HOTPLUG_CPU
1da177e4 LT	462
	463	/* Drop the CPU's cached committed space back into the central pool. */
	464	static int cpu_swap_callback(struct notifier_block *nfb,
	465	unsigned long action,
	466	void *hcpu)
	467	{
	468	long *committed;
	469
	470	committed = &per_cpu(committed_space, (long)hcpu);
	471	if (action == CPU_DEAD) {
	472	atomic_add(*committed, &vm_committed_space);
	473	*committed = 0;
80bfed90	474	__lru_add_drain((long)hcpu);
1da177e4 LT	475	}
	476	return NOTIFY_OK;
	477	}
	478	#endif /* CONFIG_HOTPLUG_CPU */
	479	#endif /* CONFIG_SMP */
	480
	481	#ifdef CONFIG_SMP
	482	void percpu_counter_mod(struct percpu_counter *fbc, long amount)
	483	{
	484	long count;
	485	long *pcount;
	486	int cpu = get_cpu();
	487
	488	pcount = per_cpu_ptr(fbc->counters, cpu);
	489	count = *pcount + amount;
	490	if (count >= FBC_BATCH \|\| count <= -FBC_BATCH) {
	491	spin_lock(&fbc->lock);
	492	fbc->count += count;
e2bab3d9	493	*pcount = 0;
1da177e4	494	spin_unlock(&fbc->lock);
e2bab3d9 AM	495	} else {
e2bab3d9 AM	496	*pcount = count;
1da177e4	497	}
1da177e4 LT	498	put_cpu();
	499	}
	500	EXPORT_SYMBOL(percpu_counter_mod);
e2bab3d9 AM	501
	502	/*
	503	* Add up all the per-cpu counts, return the result. This is a more accurate
	504	* but much slower version of percpu_counter_read_positive()
	505	*/
	506	long percpu_counter_sum(struct percpu_counter *fbc)
	507	{
	508	long ret;
	509	int cpu;
	510
	511	spin_lock(&fbc->lock);
	512	ret = fbc->count;
	513	for_each_cpu(cpu) {
	514	long *pcount = per_cpu_ptr(fbc->counters, cpu);
	515	ret += *pcount;
	516	}
	517	spin_unlock(&fbc->lock);
	518	return ret < 0 ? 0 : ret;
	519	}
	520	EXPORT_SYMBOL(percpu_counter_sum);
1da177e4 LT	521	#endif
	522
	523	/*
	524	* Perform any setup for the swap system
	525	*/
	526	void __init swap_setup(void)
	527	{
	528	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
	529
	530	/* Use a smaller cluster for small-memory machines */
	531	if (megs < 16)
	532	page_cluster = 2;
	533	else
	534	page_cluster = 3;
	535	/*
	536	* Right now other parts of the system means that we
	537	* _really_ don't want to cluster much more
	538	*/
	539	hotcpu_notifier(cpu_swap_callback, 0);
	540	}