[linux.git] / mm / swap_state.c

/*
 *  linux/mm/swap_state.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *
 *  Rewritten to use page cache, (C) 1998 Stephen Tweedie
 */
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/migrate.h>
#include <linux/page_cgroup.h>

#include <asm/pgtable.h>

/*
 * swapper_space is a fiction, retained to simplify the path through
 * vmscan's shrink_page_list, to make sync_page look nicer, and to allow
 * future use of radix_tree tags in the swap cache.
 */
static const struct address_space_operations swap_aops = {
	.writepage	= swap_writepage,
	.sync_page	= block_sync_page,
	.set_page_dirty	= __set_page_dirty_nobuffers,
	.migratepage	= migrate_page,
};

static struct backing_dev_info swap_backing_dev_info = {
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
	.unplug_io_fn	= swap_unplug_io_fn,
};

struct address_space swapper_space = {
	.page_tree	= RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
	.tree_lock	= __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
	.a_ops		= &swap_aops,
	.i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
	.backing_dev_info = &swap_backing_dev_info,
};

#define INC_CACHE_INFO(x)	do { swap_cache_info.x++; } while (0)

static struct {
	unsigned long add_total;
	unsigned long del_total;
	unsigned long find_success;
	unsigned long find_total;
} swap_cache_info;

void show_swap_cache_info(void)
{
	printk("%lu pages in swap cache\n", total_swapcache_pages);
	printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
		swap_cache_info.add_total, swap_cache_info.del_total,
		swap_cache_info.find_success, swap_cache_info.find_total);
	printk("Free swap  = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
	printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
}

/*
 * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
 * but sets SwapCache flag and private instead of mapping and index.
 */
int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
{
	int error;

	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(PageSwapCache(page));
	VM_BUG_ON(!PageSwapBacked(page));

	error = radix_tree_preload(gfp_mask);
	if (!error) {
		page_cache_get(page);
		SetPageSwapCache(page);
		set_page_private(page, entry.val);

		spin_lock_irq(&swapper_space.tree_lock);
		error = radix_tree_insert(&swapper_space.page_tree,
						entry.val, page);
		if (likely(!error)) {
			total_swapcache_pages++;
			__inc_zone_page_state(page, NR_FILE_PAGES);
			INC_CACHE_INFO(add_total);
		}
		spin_unlock_irq(&swapper_space.tree_lock);
		radix_tree_preload_end();

		if (unlikely(error)) {
			set_page_private(page, 0UL);
			ClearPageSwapCache(page);
			page_cache_release(page);
		}
	}
	return error;
}

/*
 * This must be called only on pages that have
 * been verified to be in the swap cache.
 */
void __delete_from_swap_cache(struct page *page)
{
	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(!PageSwapCache(page));
	VM_BUG_ON(PageWriteback(page));

	radix_tree_delete(&swapper_space.page_tree, page_private(page));
	set_page_private(page, 0);
	ClearPageSwapCache(page);
	total_swapcache_pages--;
	__dec_zone_page_state(page, NR_FILE_PAGES);
	INC_CACHE_INFO(del_total);
}

/**
 * add_to_swap - allocate swap space for a page
 * @page: page we want to move to swap
 * @gfp_mask: memory allocation flags
 *
 * Allocate swap space for the page and add the page to the
 * swap cache.  Caller needs to hold the page lock. 
 */
int add_to_swap(struct page *page)
{
	swp_entry_t entry;
	int err;

	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(!PageUptodate(page));

	for (;;) {
		entry = get_swap_page();
		if (!entry.val)
			return 0;

		/*
		 * Radix-tree node allocations from PF_MEMALLOC contexts could
		 * completely exhaust the page allocator. __GFP_NOMEMALLOC
		 * stops emergency reserves from being allocated.
		 *
		 * TODO: this could cause a theoretical memory reclaim
		 * deadlock in the swap out path.
		 */
		/*
		 * Add it to the swap cache and mark it dirty
		 */
		err = add_to_swap_cache(page, entry,
				__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);

		switch (err) {
		case 0:				/* Success */
			SetPageDirty(page);
			return 1;
		case -EEXIST:
			/* Raced with "speculative" read_swap_cache_async */
			swap_free(entry);
			continue;
		default:
			/* -ENOMEM radix-tree allocation failure */
			swap_free(entry);
			return 0;
		}
	}
}

/*
 * This must be called only on pages that have
 * been verified to be in the swap cache and locked.
 * It will never put the page into the free list,
 * the caller has a reference on the page.
 */
void delete_from_swap_cache(struct page *page)
{
	swp_entry_t entry;

	entry.val = page_private(page);

	spin_lock_irq(&swapper_space.tree_lock);
	__delete_from_swap_cache(page);
	spin_unlock_irq(&swapper_space.tree_lock);

	mem_cgroup_uncharge_swapcache(page, entry);
	swap_free(entry);
	page_cache_release(page);
}

/* 
 * If we are the only user, then try to free up the swap cache. 
 * 
 * Its ok to check for PageSwapCache without the page lock
 * here because we are going to recheck again inside
 * try_to_free_swap() _with_ the lock.
 * 					- Marcelo
 */
static inline void free_swap_cache(struct page *page)
{
	if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
		try_to_free_swap(page);
		unlock_page(page);
	}
}

/* 
 * Perform a free_page(), also freeing any swap cache associated with
 * this page if it is the last user of the page.
 */
void free_page_and_swap_cache(struct page *page)
{
	free_swap_cache(page);
	page_cache_release(page);
}

/*
 * Passed an array of pages, drop them all from swapcache and then release
 * them.  They are removed from the LRU and freed if this is their last use.
 */
void free_pages_and_swap_cache(struct page **pages, int nr)
{
	struct page **pagep = pages;

	lru_add_drain();
	while (nr) {
		int todo = min(nr, PAGEVEC_SIZE);
		int i;

		for (i = 0; i < todo; i++)
			free_swap_cache(pagep[i]);
		release_pages(pagep, todo, 0);
		pagep += todo;
		nr -= todo;
	}
}

/*
 * Lookup a swap entry in the swap cache. A found page will be returned
 * unlocked and with its refcount incremented - we rely on the kernel
 * lock getting page table operations atomic even if we drop the page
 * lock before returning.
 */
struct page * lookup_swap_cache(swp_entry_t entry)
{
	struct page *page;

	page = find_get_page(&swapper_space, entry.val);

	if (page)
		INC_CACHE_INFO(find_success);

	INC_CACHE_INFO(find_total);
	return page;
}

/* 
 * Locate a page of swap in physical memory, reserving swap cache space
 * and reading the disk if it is not already cached.
 * A failure return means that either the page allocation failed or that
 * the swap entry is no longer in use.
 */
struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr)
{
	struct page *found_page, *new_page = NULL;
	int err;

	do {
		/*
		 * First check the swap cache.  Since this is normally
		 * called after lookup_swap_cache() failed, re-calling
		 * that would confuse statistics.
		 */
		found_page = find_get_page(&swapper_space, entry.val);
		if (found_page)
			break;

		/*
		 * Get a new page to read into from swap.
		 */
		if (!new_page) {
			new_page = alloc_page_vma(gfp_mask, vma, addr);
			if (!new_page)
				break;		/* Out of memory */
		}

		/*
		 * Swap entry may have been freed since our caller observed it.
		 */
		if (!swap_duplicate(entry))
			break;

		/*
		 * Associate the page with swap entry in the swap cache.
		 * May fail (-EEXIST) if there is already a page associated
		 * with this entry in the swap cache: added by a racing
		 * read_swap_cache_async, or add_to_swap or shmem_writepage
		 * re-using the just freed swap entry for an existing page.
		 * May fail (-ENOMEM) if radix-tree node allocation failed.
		 */
		__set_page_locked(new_page);
		SetPageSwapBacked(new_page);
		err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
		if (likely(!err)) {
			/*
			 * Initiate read into locked page and return.
			 */
			lru_cache_add_anon(new_page);
			swap_readpage(NULL, new_page);
			return new_page;
		}
		ClearPageSwapBacked(new_page);
		__clear_page_locked(new_page);
		swap_free(entry);
	} while (err != -ENOMEM);

	if (new_page)
		page_cache_release(new_page);
	return found_page;
}

/**
 * swapin_readahead - swap in pages in hope we need them soon
 * @entry: swap entry of this memory
 * @gfp_mask: memory allocation flags
 * @vma: user vma this address belongs to
 * @addr: target address for mempolicy
 *
 * Returns the struct page for entry and addr, after queueing swapin.
 *
 * Primitive swap readahead code. We simply read an aligned block of
 * (1 << page_cluster) entries in the swap area. This method is chosen
 * because it doesn't cost us any seek time.  We also make sure to queue
 * the 'original' request together with the readahead ones...
 *
 * This has been extended to use the NUMA policies from the mm triggering
 * the readahead.
 *
 * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
 */
struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr)
{
	int nr_pages;
	struct page *page;
	unsigned long offset;
	unsigned long end_offset;

	/*
	 * Get starting offset for readaround, and number of pages to read.
	 * Adjust starting address by readbehind (for NUMA interleave case)?
	 * No, it's very unlikely that swap layout would follow vma layout,
	 * more likely that neighbouring swap pages came from the same node:
	 * so use the same "addr" to choose the same node for each swap read.
	 */
	nr_pages = valid_swaphandles(entry, &offset);
	for (end_offset = offset + nr_pages; offset < end_offset; offset++) {
		/* Ok, do the async read-ahead now */
		page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
						gfp_mask, vma, addr);
		if (!page)
			break;
		page_cache_release(page);
	}
	lru_add_drain();	/* Push any new pages onto the LRU now */
	return read_swap_cache_async(entry, gfp_mask, vma, addr);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/mm/swap_state.c
	3	*
	4	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	5	* Swap reorganised 29.12.95, Stephen Tweedie
	6	*
	7	* Rewritten to use page cache, (C) 1998 Stephen Tweedie
	8	*/
	9	#include <linux/module.h>
	10	#include <linux/mm.h>
	11	#include <linux/kernel_stat.h>
	12	#include <linux/swap.h>
46017e95	13	#include <linux/swapops.h>
1da177e4 LT	14	#include <linux/init.h>
	15	#include <linux/pagemap.h>
	16	#include <linux/buffer_head.h>
	17	#include <linux/backing-dev.h>
c484d410	18	#include <linux/pagevec.h>
b20a3503	19	#include <linux/migrate.h>
8c7c6e34	20	#include <linux/page_cgroup.h>
1da177e4 LT	21
	22	#include <asm/pgtable.h>
	23
	24	/*
	25	* swapper_space is a fiction, retained to simplify the path through
2706a1b8	26	* vmscan's shrink_page_list, to make sync_page look nicer, and to allow
1da177e4 LT	27	* future use of radix_tree tags in the swap cache.
1da177e4 LT	28	*/
f5e54d6e	29	static const struct address_space_operations swap_aops = {
1da177e4 LT	30	.writepage = swap_writepage,
	31	.sync_page = block_sync_page,
	32	.set_page_dirty = __set_page_dirty_nobuffers,
e965f963	33	.migratepage = migrate_page,
1da177e4 LT	34	};
	35
	36	static struct backing_dev_info swap_backing_dev_info = {
4f98a2fe	37	.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK \| BDI_CAP_SWAP_BACKED,
1da177e4 LT	38	.unplug_io_fn = swap_unplug_io_fn,
	39	};
	40
	41	struct address_space swapper_space = {
	42	.page_tree = RADIX_TREE_INIT(GFP_ATOMIC\|__GFP_NOWARN),
19fd6231	43	.tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
1da177e4 LT	44	.a_ops = &swap_aops,
	45	.i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
	46	.backing_dev_info = &swap_backing_dev_info,
	47	};
1da177e4 LT	48
	49	#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
	50
	51	static struct {
	52	unsigned long add_total;
	53	unsigned long del_total;
	54	unsigned long find_success;
	55	unsigned long find_total;
1da177e4 LT	56	} swap_cache_info;
	57
	58	void show_swap_cache_info(void)
	59	{
2c97b7fc JW	60	printk("%lu pages in swap cache\n", total_swapcache_pages);
2c97b7fc JW	61	printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
1da177e4	62	swap_cache_info.add_total, swap_cache_info.del_total,
bb63be0a	63	swap_cache_info.find_success, swap_cache_info.find_total);
07279cdf	64	printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
1da177e4 LT	65	printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
	66	}
	67
	68	/*
e286781d	69	* add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
1da177e4 LT	70	* but sets SwapCache flag and private instead of mapping and index.
1da177e4 LT	71	*/
73b1262f	72	int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
1da177e4 LT	73	{
	74	int error;
	75
51726b12 HD	76	VM_BUG_ON(!PageLocked(page));
	77	VM_BUG_ON(PageSwapCache(page));
	78	VM_BUG_ON(!PageSwapBacked(page));
	79
35c754d7 BS	80	error = radix_tree_preload(gfp_mask);
35c754d7 BS	81	if (!error) {
e286781d NP	82	page_cache_get(page);
	83	SetPageSwapCache(page);
	84	set_page_private(page, entry.val);
	85
19fd6231	86	spin_lock_irq(&swapper_space.tree_lock);
1da177e4 LT	87	error = radix_tree_insert(&swapper_space.page_tree,
1da177e4 LT	88	entry.val, page);
e286781d	89	if (likely(!error)) {
1da177e4	90	total_swapcache_pages++;
347ce434	91	__inc_zone_page_state(page, NR_FILE_PAGES);
bb63be0a	92	INC_CACHE_INFO(add_total);
1da177e4	93	}
19fd6231	94	spin_unlock_irq(&swapper_space.tree_lock);
1da177e4	95	radix_tree_preload_end();
e286781d NP	96
	97	if (unlikely(error)) {
	98	set_page_private(page, 0UL);
	99	ClearPageSwapCache(page);
	100	page_cache_release(page);
	101	}
fa1de900	102	}
1da177e4 LT	103	return error;
	104	}
	105
1da177e4 LT	106	/*
	107	* This must be called only on pages that have
	108	* been verified to be in the swap cache.
	109	*/
	110	void __delete_from_swap_cache(struct page *page)
	111	{
51726b12 HD	112	VM_BUG_ON(!PageLocked(page));
	113	VM_BUG_ON(!PageSwapCache(page));
	114	VM_BUG_ON(PageWriteback(page));
1da177e4	115
4c21e2f2 HD	116	radix_tree_delete(&swapper_space.page_tree, page_private(page));
4c21e2f2 HD	117	set_page_private(page, 0);
1da177e4 LT	118	ClearPageSwapCache(page);
1da177e4 LT	119	total_swapcache_pages--;
347ce434	120	__dec_zone_page_state(page, NR_FILE_PAGES);
1da177e4 LT	121	INC_CACHE_INFO(del_total);
	122	}
	123
	124	/**
	125	* add_to_swap - allocate swap space for a page
	126	* @page: page we want to move to swap
7682486b	127	* @gfp_mask: memory allocation flags
1da177e4 LT	128	*
	129	* Allocate swap space for the page and add the page to the
	130	* swap cache. Caller needs to hold the page lock.
	131	*/
ac47b003	132	int add_to_swap(struct page *page)
1da177e4 LT	133	{
1da177e4 LT	134	swp_entry_t entry;
1da177e4 LT	135	int err;
1da177e4 LT	136
51726b12 HD	137	VM_BUG_ON(!PageLocked(page));
51726b12 HD	138	VM_BUG_ON(!PageUptodate(page));
1da177e4 LT	139
	140	for (;;) {
	141	entry = get_swap_page();
	142	if (!entry.val)
	143	return 0;
	144
bd53b714 NP	145	/*
	146	* Radix-tree node allocations from PF_MEMALLOC contexts could
	147	* completely exhaust the page allocator. __GFP_NOMEMALLOC
	148	* stops emergency reserves from being allocated.
1da177e4	149	*
bd53b714 NP	150	* TODO: this could cause a theoretical memory reclaim
bd53b714 NP	151	* deadlock in the swap out path.
1da177e4	152	*/
1da177e4 LT	153	/*
	154	* Add it to the swap cache and mark it dirty
	155	*/
f000944d	156	err = add_to_swap_cache(page, entry,
ac47b003	157	__GFP_HIGH\|__GFP_NOMEMALLOC\|__GFP_NOWARN);
1da177e4 LT	158
	159	switch (err) {
	160	case 0: /* Success */
1da177e4	161	SetPageDirty(page);
1da177e4 LT	162	return 1;
	163	case -EEXIST:
	164	/* Raced with "speculative" read_swap_cache_async */
1da177e4 LT	165	swap_free(entry);
	166	continue;
	167	default:
	168	/* -ENOMEM radix-tree allocation failure */
	169	swap_free(entry);
	170	return 0;
	171	}
	172	}
	173	}
	174
	175	/*
	176	* This must be called only on pages that have
	177	* been verified to be in the swap cache and locked.
	178	* It will never put the page into the free list,
	179	* the caller has a reference on the page.
	180	*/
	181	void delete_from_swap_cache(struct page *page)
	182	{
	183	swp_entry_t entry;
	184
4c21e2f2	185	entry.val = page_private(page);
1da177e4	186
19fd6231	187	spin_lock_irq(&swapper_space.tree_lock);
1da177e4	188	__delete_from_swap_cache(page);
19fd6231	189	spin_unlock_irq(&swapper_space.tree_lock);
1da177e4	190
e767e056	191	mem_cgroup_uncharge_swapcache(page, entry);
1da177e4 LT	192	swap_free(entry);
	193	page_cache_release(page);
	194	}
	195
1da177e4 LT	196	/*
	197	* If we are the only user, then try to free up the swap cache.
	198	*
	199	* Its ok to check for PageSwapCache without the page lock
a2c43eed HD	200	* here because we are going to recheck again inside
a2c43eed HD	201	* try_to_free_swap() _with_ the lock.
1da177e4 LT	202	* - Marcelo
	203	*/
	204	static inline void free_swap_cache(struct page *page)
	205	{
a2c43eed HD	206	if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
a2c43eed HD	207	try_to_free_swap(page);
1da177e4 LT	208	unlock_page(page);
	209	}
	210	}
	211
	212	/*
	213	* Perform a free_page(), also freeing any swap cache associated with
b8072f09	214	* this page if it is the last user of the page.
1da177e4 LT	215	*/
	216	void free_page_and_swap_cache(struct page *page)
	217	{
	218	free_swap_cache(page);
	219	page_cache_release(page);
	220	}
	221
	222	/*
	223	* Passed an array of pages, drop them all from swapcache and then release
	224	* them. They are removed from the LRU and freed if this is their last use.
	225	*/
	226	void free_pages_and_swap_cache(struct page **pages, int nr)
	227	{
1da177e4 LT	228	struct page **pagep = pages;
	229
	230	lru_add_drain();
	231	while (nr) {
c484d410	232	int todo = min(nr, PAGEVEC_SIZE);
1da177e4 LT	233	int i;
	234
	235	for (i = 0; i < todo; i++)
	236	free_swap_cache(pagep[i]);
	237	release_pages(pagep, todo, 0);
	238	pagep += todo;
	239	nr -= todo;
	240	}
	241	}
	242
	243	/*
	244	* Lookup a swap entry in the swap cache. A found page will be returned
	245	* unlocked and with its refcount incremented - we rely on the kernel
	246	* lock getting page table operations atomic even if we drop the page
	247	* lock before returning.
	248	*/
	249	struct page * lookup_swap_cache(swp_entry_t entry)
	250	{
	251	struct page *page;
	252
	253	page = find_get_page(&swapper_space, entry.val);
	254
	255	if (page)
	256	INC_CACHE_INFO(find_success);
	257
	258	INC_CACHE_INFO(find_total);
	259	return page;
	260	}
	261
	262	/*
	263	* Locate a page of swap in physical memory, reserving swap cache space
	264	* and reading the disk if it is not already cached.
	265	* A failure return means that either the page allocation failed or that
	266	* the swap entry is no longer in use.
	267	*/
02098fea	268	struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
1da177e4 LT	269	struct vm_area_struct *vma, unsigned long addr)
	270	{
	271	struct page found_page, new_page = NULL;
	272	int err;
	273
	274	do {
	275	/*
	276	* First check the swap cache. Since this is normally
	277	* called after lookup_swap_cache() failed, re-calling
	278	* that would confuse statistics.
	279	*/
	280	found_page = find_get_page(&swapper_space, entry.val);
	281	if (found_page)
	282	break;
	283
	284	/*
	285	* Get a new page to read into from swap.
	286	*/
	287	if (!new_page) {
02098fea	288	new_page = alloc_page_vma(gfp_mask, vma, addr);
1da177e4 LT	289	if (!new_page)
	290	break; /* Out of memory */
	291	}
	292
f000944d HD	293	/*
	294	* Swap entry may have been freed since our caller observed it.
	295	*/
	296	if (!swap_duplicate(entry))
	297	break;
	298
1da177e4 LT	299	/*
1da177e4 LT	300	* Associate the page with swap entry in the swap cache.
f000944d HD	301	* May fail (-EEXIST) if there is already a page associated
	302	* with this entry in the swap cache: added by a racing
	303	* read_swap_cache_async, or add_to_swap or shmem_writepage
	304	* re-using the just freed swap entry for an existing page.
1da177e4 LT	305	* May fail (-ENOMEM) if radix-tree node allocation failed.
1da177e4 LT	306	*/
f45840b5	307	__set_page_locked(new_page);
b2e18538	308	SetPageSwapBacked(new_page);
f000944d	309	err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
529ae9aa	310	if (likely(!err)) {
1da177e4 LT	311	/*
	312	* Initiate read into locked page and return.
	313	*/
c5fdae46	314	lru_cache_add_anon(new_page);
1da177e4 LT	315	swap_readpage(NULL, new_page);
	316	return new_page;
	317	}
b2e18538	318	ClearPageSwapBacked(new_page);
f45840b5	319	__clear_page_locked(new_page);
f000944d HD	320	swap_free(entry);
f000944d HD	321	} while (err != -ENOMEM);
1da177e4 LT	322
	323	if (new_page)
	324	page_cache_release(new_page);
	325	return found_page;
	326	}
46017e95 HD	327
	328	/**
	329	* swapin_readahead - swap in pages in hope we need them soon
	330	* @entry: swap entry of this memory
7682486b	331	* @gfp_mask: memory allocation flags
46017e95 HD	332	* @vma: user vma this address belongs to
	333	* @addr: target address for mempolicy
	334	*
	335	* Returns the struct page for entry and addr, after queueing swapin.
	336	*
	337	* Primitive swap readahead code. We simply read an aligned block of
	338	* (1 << page_cluster) entries in the swap area. This method is chosen
	339	* because it doesn't cost us any seek time. We also make sure to queue
	340	* the 'original' request together with the readahead ones...
	341	*
	342	* This has been extended to use the NUMA policies from the mm triggering
	343	* the readahead.
	344	*
	345	* Caller must hold down_read on the vma->vm_mm if vma is not NULL.
	346	*/
02098fea	347	struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
46017e95 HD	348	struct vm_area_struct *vma, unsigned long addr)
	349	{
	350	int nr_pages;
	351	struct page *page;
	352	unsigned long offset;
	353	unsigned long end_offset;
	354
	355	/*
	356	* Get starting offset for readaround, and number of pages to read.
	357	* Adjust starting address by readbehind (for NUMA interleave case)?
	358	* No, it's very unlikely that swap layout would follow vma layout,
	359	* more likely that neighbouring swap pages came from the same node:
	360	* so use the same "addr" to choose the same node for each swap read.
	361	*/
	362	nr_pages = valid_swaphandles(entry, &offset);
	363	for (end_offset = offset + nr_pages; offset < end_offset; offset++) {
	364	/* Ok, do the async read-ahead now */
	365	page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
02098fea	366	gfp_mask, vma, addr);
46017e95 HD	367	if (!page)
	368	break;
	369	page_cache_release(page);
	370	}
	371	lru_add_drain(); /* Push any new pages onto the LRU now */
02098fea	372	return read_swap_cache_async(entry, gfp_mask, vma, addr);
46017e95	373	}