[mirror_ubuntu-zesty-kernel.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>

/* 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)) {
			list_move_tail(&page->lru, &zone->lru[LRU_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.
 */
void  rotate_reclaimable_page(struct page *page)
{
	if (!PageLocked(page) && !PageDirty(page) && !PageActive(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);

	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);
		mem_cgroup_move_lists(page, true);
	}
	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) && 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)) {
		ClearPageActive(page);
	}

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

/*
 * 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();
}

#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_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);

/*
 * 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, enum lru_list lru)
{
	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);
		if (is_active_lru(lru))
			SetPageActive(page);
		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)) {
			if (PageSwapCache(page))
				remove_exclusive_swap_page_ref(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 LT	33
	34	/* How many pages do we try to swap or page in/out together? */
	35	int page_cluster;
	36
f04e9ebb	37	static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
f84f9504	38	static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
902aaed0	39
b221385b AB	40	/*
	41	* This path almost never happens for VM activity - pages are normally
	42	* freed via pagevecs. But it gets used by networking.
	43	*/
920c7a5d	44	static void __page_cache_release(struct page *page)
b221385b AB	45	{
	46	if (PageLRU(page)) {
	47	unsigned long flags;
	48	struct zone *zone = page_zone(page);
	49
	50	spin_lock_irqsave(&zone->lru_lock, flags);
	51	VM_BUG_ON(!PageLRU(page));
	52	__ClearPageLRU(page);
	53	del_page_from_lru(zone, page);
	54	spin_unlock_irqrestore(&zone->lru_lock, flags);
	55	}
	56	free_hot_page(page);
	57	}
	58
8519fb30	59	static void put_compound_page(struct page *page)
1da177e4	60	{
d85f3385	61	page = compound_head(page);
8519fb30	62	if (put_page_testzero(page)) {
33f2ef89	63	compound_page_dtor *dtor;
1da177e4	64
33f2ef89	65	dtor = get_compound_page_dtor(page);
8519fb30	66	(*dtor)(page);
1da177e4	67	}
8519fb30 NP	68	}
	69
	70	void put_page(struct page *page)
	71	{
	72	if (unlikely(PageCompound(page)))
	73	put_compound_page(page);
	74	else if (put_page_testzero(page))
1da177e4 LT	75	__page_cache_release(page);
	76	}
	77	EXPORT_SYMBOL(put_page);
1da177e4	78
1d7ea732	79	/**
7682486b RD	80	* put_pages_list() - release a list of pages
7682486b RD	81	* @pages: list of pages threaded on page->lru
1d7ea732 AZ	82	*
	83	* Release a list of pages which are strung together on page.lru. Currently
	84	* used by read_cache_pages() and related error recovery code.
1d7ea732 AZ	85	*/
	86	void put_pages_list(struct list_head *pages)
	87	{
	88	while (!list_empty(pages)) {
	89	struct page *victim;
	90
	91	victim = list_entry(pages->prev, struct page, lru);
	92	list_del(&victim->lru);
	93	page_cache_release(victim);
	94	}
	95	}
	96	EXPORT_SYMBOL(put_pages_list);
	97
902aaed0 HH	98	/*
	99	* pagevec_move_tail() must be called with IRQ disabled.
	100	* Otherwise this may cause nasty races.
	101	*/
	102	static void pagevec_move_tail(struct pagevec *pvec)
	103	{
	104	int i;
	105	int pgmoved = 0;
	106	struct zone *zone = NULL;
	107
	108	for (i = 0; i < pagevec_count(pvec); i++) {
	109	struct page *page = pvec->pages[i];
	110	struct zone *pagezone = page_zone(page);
	111
	112	if (pagezone != zone) {
	113	if (zone)
	114	spin_unlock(&zone->lru_lock);
	115	zone = pagezone;
	116	spin_lock(&zone->lru_lock);
	117	}
	118	if (PageLRU(page) && !PageActive(page)) {
b69408e8	119	list_move_tail(&page->lru, &zone->lru[LRU_INACTIVE].list);
902aaed0 HH	120	pgmoved++;
	121	}
	122	}
	123	if (zone)
	124	spin_unlock(&zone->lru_lock);
	125	__count_vm_events(PGROTATED, pgmoved);
	126	release_pages(pvec->pages, pvec->nr, pvec->cold);
	127	pagevec_reinit(pvec);
	128	}
	129
1da177e4 LT	130	/*
	131	* Writeback is about to end against a page which has been marked for immediate
	132	* reclaim. If it still appears to be reclaimable, move it to the tail of the
902aaed0	133	* inactive list.
1da177e4	134	*/
ac6aadb2	135	void rotate_reclaimable_page(struct page *page)
1da177e4	136	{
ac6aadb2 MS	137	if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
	138	PageLRU(page)) {
	139	struct pagevec *pvec;
	140	unsigned long flags;
	141
	142	page_cache_get(page);
	143	local_irq_save(flags);
	144	pvec = &__get_cpu_var(lru_rotate_pvecs);
	145	if (!pagevec_add(pvec, page))
	146	pagevec_move_tail(pvec);
	147	local_irq_restore(flags);
	148	}
1da177e4 LT	149	}
	150
	151	/*
	152	* FIXME: speed this up?
	153	*/
920c7a5d	154	void activate_page(struct page *page)
1da177e4 LT	155	{
	156	struct zone *zone = page_zone(page);
	157
	158	spin_lock_irq(&zone->lru_lock);
	159	if (PageLRU(page) && !PageActive(page)) {
	160	del_page_from_inactive_list(zone, page);
	161	SetPageActive(page);
	162	add_page_to_active_list(zone, page);
f8891e5e	163	__count_vm_event(PGACTIVATE);
427d5416	164	mem_cgroup_move_lists(page, true);
1da177e4 LT	165	}
	166	spin_unlock_irq(&zone->lru_lock);
	167	}
	168
	169	/*
	170	* Mark a page as having seen activity.
	171	*
	172	* inactive,unreferenced -> inactive,referenced
	173	* inactive,referenced -> active,unreferenced
	174	* active,unreferenced -> active,referenced
	175	*/
920c7a5d	176	void mark_page_accessed(struct page *page)
1da177e4 LT	177	{
	178	if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
	179	activate_page(page);
	180	ClearPageReferenced(page);
	181	} else if (!PageReferenced(page)) {
	182	SetPageReferenced(page);
	183	}
	184	}
	185
	186	EXPORT_SYMBOL(mark_page_accessed);
	187
f04e9ebb	188	void __lru_cache_add(struct page *page, enum lru_list lru)
1da177e4	189	{
f04e9ebb	190	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
1da177e4 LT	191
	192	page_cache_get(page);
	193	if (!pagevec_add(pvec, page))
f04e9ebb	194	____pagevec_lru_add(pvec, lru);
1da177e4 LT	195	put_cpu_var(lru_add_pvecs);
	196	}
	197
f04e9ebb KM	198	/**
	199	* lru_cache_add_lru - add a page to a page list
	200	* @page: the page to be added to the LRU.
	201	* @lru: the LRU list to which the page is added.
	202	*/
	203	void lru_cache_add_lru(struct page *page, enum lru_list lru)
1da177e4	204	{
f04e9ebb KM	205	if (PageActive(page)) {
	206	ClearPageActive(page);
	207	}
1da177e4	208
f04e9ebb KM	209	VM_BUG_ON(PageLRU(page) \|\| PageActive(page));
f04e9ebb KM	210	__lru_cache_add(page, lru);
1da177e4 LT	211	}
1da177e4 LT	212
902aaed0 HH	213	/*
	214	* Drain pages out of the cpu's pagevecs.
	215	* Either "cpu" is the current CPU, and preemption has already been
	216	* disabled; or "cpu" is being hot-unplugged, and is already dead.
	217	*/
	218	static void drain_cpu_pagevecs(int cpu)
1da177e4	219	{
f04e9ebb	220	struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
902aaed0	221	struct pagevec *pvec;
f04e9ebb	222	int lru;
1da177e4	223
f04e9ebb KM	224	for_each_lru(lru) {
	225	pvec = &pvecs[lru - LRU_BASE];
	226	if (pagevec_count(pvec))
	227	____pagevec_lru_add(pvec, lru);
	228	}
902aaed0 HH	229
	230	pvec = &per_cpu(lru_rotate_pvecs, cpu);
	231	if (pagevec_count(pvec)) {
	232	unsigned long flags;
	233
	234	/* No harm done if a racing interrupt already did this */
	235	local_irq_save(flags);
	236	pagevec_move_tail(pvec);
	237	local_irq_restore(flags);
	238	}
80bfed90 AM	239	}
	240
	241	void lru_add_drain(void)
	242	{
902aaed0	243	drain_cpu_pagevecs(get_cpu());
80bfed90	244	put_cpu();
1da177e4 LT	245	}
1da177e4 LT	246
053837fc	247	#ifdef CONFIG_NUMA
c4028958	248	static void lru_add_drain_per_cpu(struct work_struct *dummy)
053837fc NP	249	{
	250	lru_add_drain();
	251	}
	252
	253	/*
	254	* Returns 0 for success
	255	*/
	256	int lru_add_drain_all(void)
	257	{
c4028958	258	return schedule_on_each_cpu(lru_add_drain_per_cpu);
053837fc NP	259	}
	260
	261	#else
	262
	263	/*
	264	* Returns 0 for success
	265	*/
	266	int lru_add_drain_all(void)
	267	{
	268	lru_add_drain();
	269	return 0;
	270	}
	271	#endif
	272
1da177e4 LT	273	/*
	274	* Batched page_cache_release(). Decrement the reference count on all the
	275	* passed pages. If it fell to zero then remove the page from the LRU and
	276	* free it.
	277	*
	278	* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
	279	* for the remainder of the operation.
	280	*
ab33dc09 FLVC	281	* The locking in this function is against shrink_inactive_list(): we recheck
	282	* the page count inside the lock to see whether shrink_inactive_list()
	283	* grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
	284	* will free it.
1da177e4 LT	285	*/
	286	void release_pages(struct page **pages, int nr, int cold)
	287	{
	288	int i;
	289	struct pagevec pages_to_free;
	290	struct zone *zone = NULL;
902aaed0	291	unsigned long uninitialized_var(flags);
1da177e4 LT	292
	293	pagevec_init(&pages_to_free, cold);
	294	for (i = 0; i < nr; i++) {
	295	struct page *page = pages[i];
1da177e4	296
8519fb30 NP	297	if (unlikely(PageCompound(page))) {
8519fb30 NP	298	if (zone) {
902aaed0	299	spin_unlock_irqrestore(&zone->lru_lock, flags);
8519fb30 NP	300	zone = NULL;
	301	}
	302	put_compound_page(page);
	303	continue;
	304	}
	305
b5810039	306	if (!put_page_testzero(page))
1da177e4 LT	307	continue;
1da177e4 LT	308
46453a6e NP	309	if (PageLRU(page)) {
	310	struct zone *pagezone = page_zone(page);
	311	if (pagezone != zone) {
	312	if (zone)
902aaed0 HH	313	spin_unlock_irqrestore(&zone->lru_lock,
902aaed0 HH	314	flags);
46453a6e	315	zone = pagezone;
902aaed0	316	spin_lock_irqsave(&zone->lru_lock, flags);
46453a6e	317	}
725d704e	318	VM_BUG_ON(!PageLRU(page));
67453911	319	__ClearPageLRU(page);
1da177e4	320	del_page_from_lru(zone, page);
46453a6e NP	321	}
	322
	323	if (!pagevec_add(&pages_to_free, page)) {
	324	if (zone) {
902aaed0	325	spin_unlock_irqrestore(&zone->lru_lock, flags);
46453a6e	326	zone = NULL;
1da177e4	327	}
46453a6e NP	328	__pagevec_free(&pages_to_free);
	329	pagevec_reinit(&pages_to_free);
	330	}
1da177e4 LT	331	}
1da177e4 LT	332	if (zone)
902aaed0	333	spin_unlock_irqrestore(&zone->lru_lock, flags);
1da177e4 LT	334
	335	pagevec_free(&pages_to_free);
	336	}
	337
	338	/*
	339	* The pages which we're about to release may be in the deferred lru-addition
	340	* queues. That would prevent them from really being freed right now. That's
	341	* OK from a correctness point of view but is inefficient - those pages may be
	342	* cache-warm and we want to give them back to the page allocator ASAP.
	343	*
	344	* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
	345	* and __pagevec_lru_add_active() call release_pages() directly to avoid
	346	* mutual recursion.
	347	*/
	348	void __pagevec_release(struct pagevec *pvec)
	349	{
	350	lru_add_drain();
	351	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
	352	pagevec_reinit(pvec);
	353	}
	354
7f285701 SF	355	EXPORT_SYMBOL(__pagevec_release);
7f285701 SF	356
1da177e4 LT	357	/*
	358	* pagevec_release() for pages which are known to not be on the LRU
	359	*
	360	* This function reinitialises the caller's pagevec.
	361	*/
	362	void __pagevec_release_nonlru(struct pagevec *pvec)
	363	{
	364	int i;
	365	struct pagevec pages_to_free;
	366
	367	pagevec_init(&pages_to_free, pvec->cold);
1da177e4 LT	368	for (i = 0; i < pagevec_count(pvec); i++) {
	369	struct page *page = pvec->pages[i];
	370
725d704e	371	VM_BUG_ON(PageLRU(page));
1da177e4 LT	372	if (put_page_testzero(page))
	373	pagevec_add(&pages_to_free, page);
	374	}
	375	pagevec_free(&pages_to_free);
	376	pagevec_reinit(pvec);
	377	}
	378
	379	/*
	380	* Add the passed pages to the LRU, then drop the caller's refcount
	381	* on them. Reinitialises the caller's pagevec.
	382	*/
f04e9ebb	383	void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
1da177e4 LT	384	{
	385	int i;
	386	struct zone *zone = NULL;
	387
	388	for (i = 0; i < pagevec_count(pvec); i++) {
	389	struct page *page = pvec->pages[i];
	390	struct zone *pagezone = page_zone(page);
	391
	392	if (pagezone != zone) {
	393	if (zone)
	394	spin_unlock_irq(&zone->lru_lock);
	395	zone = pagezone;
	396	spin_lock_irq(&zone->lru_lock);
	397	}
725d704e	398	VM_BUG_ON(PageLRU(page));
8d438f96	399	SetPageLRU(page);
f04e9ebb KM	400	if (is_active_lru(lru))
	401	SetPageActive(page);
	402	add_page_to_lru_list(zone, page, lru);
1da177e4 LT	403	}
	404	if (zone)
	405	spin_unlock_irq(&zone->lru_lock);
	406	release_pages(pvec->pages, pvec->nr, pvec->cold);
	407	pagevec_reinit(pvec);
	408	}
	409
f04e9ebb	410	EXPORT_SYMBOL(____pagevec_lru_add);
1da177e4 LT	411
	412	/*
	413	* Try to drop buffers from the pages in a pagevec
	414	*/
	415	void pagevec_strip(struct pagevec *pvec)
	416	{
	417	int i;
	418
	419	for (i = 0; i < pagevec_count(pvec); i++) {
	420	struct page *page = pvec->pages[i];
	421
529ae9aa	422	if (PagePrivate(page) && trylock_page(page)) {
5b40dc78 CL	423	if (PagePrivate(page))
5b40dc78 CL	424	try_to_release_page(page, 0);
1da177e4 LT	425	unlock_page(page);
	426	}
	427	}
	428	}
	429
68a22394 RR	430	/**
	431	* pagevec_swap_free - try to free swap space from the pages in a pagevec
	432	* @pvec: pagevec with swapcache pages to free the swap space of
	433	*
	434	* The caller needs to hold an extra reference to each page and
	435	* not hold the page lock on the pages. This function uses a
	436	* trylock on the page lock so it may not always free the swap
	437	* space associated with a page.
	438	*/
	439	void pagevec_swap_free(struct pagevec *pvec)
	440	{
	441	int i;
	442
	443	for (i = 0; i < pagevec_count(pvec); i++) {
	444	struct page *page = pvec->pages[i];
	445
	446	if (PageSwapCache(page) && trylock_page(page)) {
	447	if (PageSwapCache(page))
	448	remove_exclusive_swap_page_ref(page);
	449	unlock_page(page);
	450	}
	451	}
	452	}
	453
1da177e4 LT	454	/**
	455	* pagevec_lookup - gang pagecache lookup
	456	* @pvec: Where the resulting pages are placed
	457	* @mapping: The address_space to search
	458	* @start: The starting page index
	459	* @nr_pages: The maximum number of pages
	460	*
	461	* pagevec_lookup() will search for and return a group of up to @nr_pages pages
	462	* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
	463	* reference against the pages in @pvec.
	464	*
	465	* The search returns a group of mapping-contiguous pages with ascending
	466	* indexes. There may be holes in the indices due to not-present pages.
	467	*
	468	* pagevec_lookup() returns the number of pages which were found.
	469	*/
	470	unsigned pagevec_lookup(struct pagevec pvec, struct address_space mapping,
	471	pgoff_t start, unsigned nr_pages)
	472	{
	473	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
	474	return pagevec_count(pvec);
	475	}
	476
78539fdf CH	477	EXPORT_SYMBOL(pagevec_lookup);
78539fdf CH	478
1da177e4 LT	479	unsigned pagevec_lookup_tag(struct pagevec pvec, struct address_space mapping,
	480	pgoff_t *index, int tag, unsigned nr_pages)
	481	{
	482	pvec->nr = find_get_pages_tag(mapping, index, tag,
	483	nr_pages, pvec->pages);
	484	return pagevec_count(pvec);
	485	}
	486
7f285701	487	EXPORT_SYMBOL(pagevec_lookup_tag);
1da177e4 LT	488
	489	#ifdef CONFIG_SMP
	490	/*
	491	* We tolerate a little inaccuracy to avoid ping-ponging the counter between
	492	* CPUs
	493	*/
	494	#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
	495
f84f9504	496	static DEFINE_PER_CPU(long, committed_space);
1da177e4 LT	497
	498	void vm_acct_memory(long pages)
	499	{
	500	long *local;
	501
	502	preempt_disable();
	503	local = &__get_cpu_var(committed_space);
	504	*local += pages;
	505	if (local > ACCT_THRESHOLD \|\| local < -ACCT_THRESHOLD) {
80119ef5	506	atomic_long_add(*local, &vm_committed_space);
1da177e4 LT	507	*local = 0;
	508	}
	509	preempt_enable();
	510	}
1da177e4 LT	511
1da177e4 LT	512	#ifdef CONFIG_HOTPLUG_CPU
1da177e4 LT	513
	514	/* Drop the CPU's cached committed space back into the central pool. */
	515	static int cpu_swap_callback(struct notifier_block *nfb,
	516	unsigned long action,
	517	void *hcpu)
	518	{
	519	long *committed;
	520
	521	committed = &per_cpu(committed_space, (long)hcpu);
8bb78442	522	if (action == CPU_DEAD \|\| action == CPU_DEAD_FROZEN) {
80119ef5	523	atomic_long_add(*committed, &vm_committed_space);
1da177e4	524	*committed = 0;
902aaed0	525	drain_cpu_pagevecs((long)hcpu);
1da177e4 LT	526	}
	527	return NOTIFY_OK;
	528	}
	529	#endif /* CONFIG_HOTPLUG_CPU */
	530	#endif /* CONFIG_SMP */
	531
1da177e4 LT	532	/*
	533	* Perform any setup for the swap system
	534	*/
	535	void __init swap_setup(void)
	536	{
	537	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
	538
e0bf68dd PZ	539	#ifdef CONFIG_SWAP
	540	bdi_init(swapper_space.backing_dev_info);
	541	#endif
	542
1da177e4 LT	543	/* Use a smaller cluster for small-memory machines */
	544	if (megs < 16)
	545	page_cluster = 2;
	546	else
	547	page_cluster = 3;
	548	/*
	549	* Right now other parts of the system means that we
	550	* _really_ don't want to cluster much more
	551	*/
02316067	552	#ifdef CONFIG_HOTPLUG_CPU
1da177e4	553	hotcpu_notifier(cpu_swap_callback, 0);
02316067	554	#endif
1da177e4	555	}