[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;

void put_page(struct page *page)
{
	if (unlikely(PageCompound(page))) {
		page = (struct page *)page_private(page);
		if (put_page_testzero(page)) {
			void (*dtor)(struct page *page);

			dtor = (void (*)(struct page *))page[1].mapping;
			(*dtor)(page);
		}
		return;
	}
	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();
}

/*
 * 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 (!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)) {
			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);
}

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;
		spin_unlock(&fbc->lock);
		count = 0;
	}
	*pcount = count;
	put_cpu();
}
EXPORT_SYMBOL(percpu_counter_mod);
#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
1da177e4 LT	37	void put_page(struct page *page)
	38	{
	39	if (unlikely(PageCompound(page))) {
4c21e2f2	40	page = (struct page *)page_private(page);
1da177e4 LT	41	if (put_page_testzero(page)) {
	42	void (dtor)(struct page page);
	43
	44	dtor = (void ()(struct page ))page[1].mapping;
	45	(*dtor)(page);
	46	}
	47	return;
	48	}
b5810039	49	if (put_page_testzero(page))
1da177e4 LT	50	__page_cache_release(page);
	51	}
	52	EXPORT_SYMBOL(put_page);
1da177e4 LT	53
	54	/*
	55	* Writeback is about to end against a page which has been marked for immediate
	56	* reclaim. If it still appears to be reclaimable, move it to the tail of the
	57	* inactive list. The page still has PageWriteback set, which will pin it.
	58	*
	59	* We don't expect many pages to come through here, so don't bother batching
	60	* things up.
	61	*
	62	* To avoid placing the page at the tail of the LRU while PG_writeback is still
	63	* set, this function will clear PG_writeback before performing the page
	64	* motion. Do that inside the lru lock because once PG_writeback is cleared
	65	* we may not touch the page.
	66	*
	67	* Returns zero if it cleared PG_writeback.
	68	*/
	69	int rotate_reclaimable_page(struct page *page)
	70	{
	71	struct zone *zone;
	72	unsigned long flags;
	73
	74	if (PageLocked(page))
	75	return 1;
	76	if (PageDirty(page))
	77	return 1;
	78	if (PageActive(page))
	79	return 1;
	80	if (!PageLRU(page))
	81	return 1;
	82
	83	zone = page_zone(page);
	84	spin_lock_irqsave(&zone->lru_lock, flags);
	85	if (PageLRU(page) && !PageActive(page)) {
	86	list_del(&page->lru);
	87	list_add_tail(&page->lru, &zone->inactive_list);
	88	inc_page_state(pgrotated);
	89	}
	90	if (!test_clear_page_writeback(page))
	91	BUG();
	92	spin_unlock_irqrestore(&zone->lru_lock, flags);
	93	return 0;
	94	}
	95
	96	/*
	97	* FIXME: speed this up?
	98	*/
	99	void fastcall activate_page(struct page *page)
	100	{
	101	struct zone *zone = page_zone(page);
	102
	103	spin_lock_irq(&zone->lru_lock);
	104	if (PageLRU(page) && !PageActive(page)) {
	105	del_page_from_inactive_list(zone, page);
	106	SetPageActive(page);
	107	add_page_to_active_list(zone, page);
	108	inc_page_state(pgactivate);
	109	}
	110	spin_unlock_irq(&zone->lru_lock);
	111	}
	112
	113	/*
	114	* Mark a page as having seen activity.
	115	*
	116	* inactive,unreferenced -> inactive,referenced
117	* inactive,referenced -> active,unreferenced
118	* active,unreferenced -> active,referenced
119	*/
120	void fastcall mark_page_accessed(struct page *page)
121	{
122	if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
123	activate_page(page);
124	ClearPageReferenced(page);
125	} else if (!PageReferenced(page)) {
126	SetPageReferenced(page);
127	}
128	}
129
130	EXPORT_SYMBOL(mark_page_accessed);
131
132	/**
133	* lru_cache_add: add a page to the page lists
134	* @page: the page to add
135	*/
136	static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
137	static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
138
139	void fastcall lru_cache_add(struct page *page)
140	{
141	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
142
143	page_cache_get(page);
144	if (!pagevec_add(pvec, page))
145	__pagevec_lru_add(pvec);
146	put_cpu_var(lru_add_pvecs);
147	}
148
149	void fastcall lru_cache_add_active(struct page *page)
150	{
151	struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
152
153	page_cache_get(page);
154	if (!pagevec_add(pvec, page))
155	__pagevec_lru_add_active(pvec);
156	put_cpu_var(lru_add_active_pvecs);
157	}
158
80bfed90	159	static void __lru_add_drain(int cpu)
1da177e4	160	{
80bfed90	161	struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
1da177e4	162
80bfed90	163	/* CPU is dead, so no locking needed. */
1da177e4 LT	164	if (pagevec_count(pvec))
1da177e4 LT	165	__pagevec_lru_add(pvec);
80bfed90	166	pvec = &per_cpu(lru_add_active_pvecs, cpu);
1da177e4 LT	167	if (pagevec_count(pvec))
1da177e4 LT	168	__pagevec_lru_add_active(pvec);
80bfed90 AM	169	}
	170
	171	void lru_add_drain(void)
	172	{
	173	__lru_add_drain(get_cpu());
	174	put_cpu();
1da177e4 LT	175	}
	176
	177	/*
	178	* This path almost never happens for VM activity - pages are normally
	179	* freed via pagevecs. But it gets used by networking.
	180	*/
	181	void fastcall __page_cache_release(struct page *page)
	182	{
	183	unsigned long flags;
	184	struct zone *zone = page_zone(page);
	185
	186	spin_lock_irqsave(&zone->lru_lock, flags);
	187	if (TestClearPageLRU(page))
	188	del_page_from_lru(zone, page);
	189	if (page_count(page) != 0)
	190	page = NULL;
	191	spin_unlock_irqrestore(&zone->lru_lock, flags);
	192	if (page)
	193	free_hot_page(page);
	194	}
	195
	196	EXPORT_SYMBOL(__page_cache_release);
	197
	198	/*
	199	* Batched page_cache_release(). Decrement the reference count on all the
	200	* passed pages. If it fell to zero then remove the page from the LRU and
	201	* free it.
	202	*
	203	* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
	204	* for the remainder of the operation.
	205	*
	206	* The locking in this function is against shrink_cache(): we recheck the
	207	* page count inside the lock to see whether shrink_cache grabbed the page
	208	* via the LRU. If it did, give up: shrink_cache will free it.
	209	*/
	210	void release_pages(struct page **pages, int nr, int cold)
	211	{
	212	int i;
	213	struct pagevec pages_to_free;
	214	struct zone *zone = NULL;
	215
	216	pagevec_init(&pages_to_free, cold);
	217	for (i = 0; i < nr; i++) {
	218	struct page *page = pages[i];
	219	struct zone *pagezone;
	220
b5810039	221	if (!put_page_testzero(page))
1da177e4 LT	222	continue;
	223
	224	pagezone = page_zone(page);
	225	if (pagezone != zone) {
	226	if (zone)
	227	spin_unlock_irq(&zone->lru_lock);
	228	zone = pagezone;
	229	spin_lock_irq(&zone->lru_lock);
	230	}
	231	if (TestClearPageLRU(page))
	232	del_page_from_lru(zone, page);
	233	if (page_count(page) == 0) {
	234	if (!pagevec_add(&pages_to_free, page)) {
	235	spin_unlock_irq(&zone->lru_lock);
	236	__pagevec_free(&pages_to_free);
	237	pagevec_reinit(&pages_to_free);
	238	zone = NULL; /* No lock is held */
	239	}
	240	}
	241	}
	242	if (zone)
	243	spin_unlock_irq(&zone->lru_lock);
	244
	245	pagevec_free(&pages_to_free);
	246	}
	247
	248	/*
	249	* The pages which we're about to release may be in the deferred lru-addition
	250	* queues. That would prevent them from really being freed right now. That's
	251	* OK from a correctness point of view but is inefficient - those pages may be
	252	* cache-warm and we want to give them back to the page allocator ASAP.
	253	*
	254	* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
	255	* and __pagevec_lru_add_active() call release_pages() directly to avoid
	256	* mutual recursion.
	257	*/
	258	void __pagevec_release(struct pagevec *pvec)
	259	{
	260	lru_add_drain();
	261	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
	262	pagevec_reinit(pvec);
	263	}
	264
7f285701 SF	265	EXPORT_SYMBOL(__pagevec_release);
7f285701 SF	266
1da177e4 LT	267	/*
	268	* pagevec_release() for pages which are known to not be on the LRU
	269	*
	270	* This function reinitialises the caller's pagevec.
	271	*/
	272	void __pagevec_release_nonlru(struct pagevec *pvec)
	273	{
	274	int i;
	275	struct pagevec pages_to_free;
	276
	277	pagevec_init(&pages_to_free, pvec->cold);
1da177e4 LT	278	for (i = 0; i < pagevec_count(pvec); i++) {
	279	struct page *page = pvec->pages[i];
	280
	281	BUG_ON(PageLRU(page));
	282	if (put_page_testzero(page))
	283	pagevec_add(&pages_to_free, page);
	284	}
	285	pagevec_free(&pages_to_free);
	286	pagevec_reinit(pvec);
	287	}
	288
	289	/*
	290	* Add the passed pages to the LRU, then drop the caller's refcount
	291	* on them. Reinitialises the caller's pagevec.
	292	*/
	293	void __pagevec_lru_add(struct pagevec *pvec)
	294	{
	295	int i;
	296	struct zone *zone = NULL;
	297
	298	for (i = 0; i < pagevec_count(pvec); i++) {
	299	struct page *page = pvec->pages[i];
	300	struct zone *pagezone = page_zone(page);
	301
	302	if (pagezone != zone) {
	303	if (zone)
	304	spin_unlock_irq(&zone->lru_lock);
	305	zone = pagezone;
	306	spin_lock_irq(&zone->lru_lock);
	307	}
	308	if (TestSetPageLRU(page))
	309	BUG();
	310	add_page_to_inactive_list(zone, page);
	311	}
	312	if (zone)
	313	spin_unlock_irq(&zone->lru_lock);
	314	release_pages(pvec->pages, pvec->nr, pvec->cold);
	315	pagevec_reinit(pvec);
	316	}
	317
	318	EXPORT_SYMBOL(__pagevec_lru_add);
	319
	320	void __pagevec_lru_add_active(struct pagevec *pvec)
	321	{
	322	int i;
	323	struct zone *zone = NULL;
	324
	325	for (i = 0; i < pagevec_count(pvec); i++) {
	326	struct page *page = pvec->pages[i];
	327	struct zone *pagezone = page_zone(page);
	328
	329	if (pagezone != zone) {
	330	if (zone)
	331	spin_unlock_irq(&zone->lru_lock);
	332	zone = pagezone;
	333	spin_lock_irq(&zone->lru_lock);
	334	}
	335	if (TestSetPageLRU(page))
	336	BUG();
	337	if (TestSetPageActive(page))
	338	BUG();
	339	add_page_to_active_list(zone, page);
	340	}
	341	if (zone)
342	spin_unlock_irq(&zone->lru_lock);
343	release_pages(pvec->pages, pvec->nr, pvec->cold);
344	pagevec_reinit(pvec);
345	}
346
347	/*
348	* Try to drop buffers from the pages in a pagevec
349	*/
350	void pagevec_strip(struct pagevec *pvec)
351	{
352	int i;
353
354	for (i = 0; i < pagevec_count(pvec); i++) {
355	struct page *page = pvec->pages[i];
356
357	if (PagePrivate(page) && !TestSetPageLocked(page)) {
358	try_to_release_page(page, 0);
359	unlock_page(page);
360	}
361	}
362	}
363
364	/**
365	* pagevec_lookup - gang pagecache lookup
366	* @pvec: Where the resulting pages are placed
367	* @mapping: The address_space to search
368	* @start: The starting page index
369	* @nr_pages: The maximum number of pages
370	*
371	* pagevec_lookup() will search for and return a group of up to @nr_pages pages
372	* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
373	* reference against the pages in @pvec.
374	*
375	* The search returns a group of mapping-contiguous pages with ascending
376	* indexes. There may be holes in the indices due to not-present pages.
377	*
378	* pagevec_lookup() returns the number of pages which were found.
379	*/
380	unsigned pagevec_lookup(struct pagevec pvec, struct address_space mapping,
381	pgoff_t start, unsigned nr_pages)
382	{
383	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
384	return pagevec_count(pvec);
385	}
386
387	unsigned pagevec_lookup_tag(struct pagevec pvec, struct address_space mapping,
388	pgoff_t *index, int tag, unsigned nr_pages)
389	{
390	pvec->nr = find_get_pages_tag(mapping, index, tag,
391	nr_pages, pvec->pages);
392	return pagevec_count(pvec);
393	}
394
7f285701	395	EXPORT_SYMBOL(pagevec_lookup_tag);
1da177e4 LT	396
	397	#ifdef CONFIG_SMP
	398	/*
	399	* We tolerate a little inaccuracy to avoid ping-ponging the counter between
	400	* CPUs
	401	*/
	402	#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
	403
	404	static DEFINE_PER_CPU(long, committed_space) = 0;
	405
	406	void vm_acct_memory(long pages)
	407	{
	408	long *local;
	409
	410	preempt_disable();
	411	local = &__get_cpu_var(committed_space);
	412	*local += pages;
	413	if (local > ACCT_THRESHOLD \|\| local < -ACCT_THRESHOLD) {
	414	atomic_add(*local, &vm_committed_space);
	415	*local = 0;
	416	}
	417	preempt_enable();
	418	}
1da177e4 LT	419
1da177e4 LT	420	#ifdef CONFIG_HOTPLUG_CPU
1da177e4 LT	421
	422	/* Drop the CPU's cached committed space back into the central pool. */
	423	static int cpu_swap_callback(struct notifier_block *nfb,
	424	unsigned long action,
	425	void *hcpu)
	426	{
	427	long *committed;
	428
	429	committed = &per_cpu(committed_space, (long)hcpu);
	430	if (action == CPU_DEAD) {
	431	atomic_add(*committed, &vm_committed_space);
	432	*committed = 0;
80bfed90	433	__lru_add_drain((long)hcpu);
1da177e4 LT	434	}
	435	return NOTIFY_OK;
	436	}
	437	#endif /* CONFIG_HOTPLUG_CPU */
	438	#endif /* CONFIG_SMP */
	439
	440	#ifdef CONFIG_SMP
	441	void percpu_counter_mod(struct percpu_counter *fbc, long amount)
	442	{
	443	long count;
	444	long *pcount;
	445	int cpu = get_cpu();
	446
	447	pcount = per_cpu_ptr(fbc->counters, cpu);
	448	count = *pcount + amount;
	449	if (count >= FBC_BATCH \|\| count <= -FBC_BATCH) {
	450	spin_lock(&fbc->lock);
	451	fbc->count += count;
	452	spin_unlock(&fbc->lock);
	453	count = 0;
	454	}
	455	*pcount = count;
	456	put_cpu();
	457	}
	458	EXPORT_SYMBOL(percpu_counter_mod);
	459	#endif
	460
	461	/*
	462	* Perform any setup for the swap system
	463	*/
	464	void __init swap_setup(void)
	465	{
	466	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
	467
	468	/* Use a smaller cluster for small-memory machines */
	469	if (megs < 16)
	470	page_cluster = 2;
	471	else
	472	page_cluster = 3;
	473	/*
	474	* Right now other parts of the system means that we
	475	* _really_ don't want to cluster much more
	476	*/
	477	hotcpu_notifier(cpu_swap_callback, 0);
	478	}