[mirror_ubuntu-jammy-kernel.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/mm.h>
#include <linux/gfp.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/init.h>
#include <linux/pagemap.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.
 */
static const struct address_space_operations swap_aops = {
	.writepage	= swap_writepage,
	.set_page_dirty	= __set_page_dirty_no_writeback,
	.migratepage	= migrate_page,
};

static struct backing_dev_info swap_backing_dev_info = {
	.name		= "swap",
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
};

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.
 */
static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
	int error;

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

	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);

	if (unlikely(error)) {
		/*
		 * Only the context which have set SWAP_HAS_CACHE flag
		 * would call add_to_swap_cache().
		 * So add_to_swap_cache() doesn't returns -EEXIST.
		 */
		VM_BUG_ON(error == -EEXIST);
		set_page_private(page, 0UL);
		ClearPageSwapCache(page);
		page_cache_release(page);
	}

	return error;
}


int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
{
	int error;

	error = radix_tree_preload(gfp_mask);
	if (!error) {
		error = __add_to_swap_cache(page, entry);
		radix_tree_preload_end();
	}
	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
 *
 * 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));

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

	if (unlikely(PageTransHuge(page)))
		if (unlikely(split_huge_page(page))) {
			swapcache_free(entry, NULL);
			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);

	if (!err) {	/* Success */
		SetPageDirty(page);
		return 1;
	} else {	/* -ENOMEM radix-tree allocation failure */
		/*
		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
		 * clear SWAP_HAS_CACHE flag.
		 */
		swapcache_free(entry, NULL);
		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);

	swapcache_free(entry, page);
	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 */
		}

		/*
		 * call radix_tree_preload() while we can wait.
		 */
		err = radix_tree_preload(gfp_mask & GFP_KERNEL);
		if (err)
			break;

		/*
		 * Swap entry may have been freed since our caller observed it.
		 */
		err = swapcache_prepare(entry);
		if (err == -EEXIST) {	/* seems racy */
			radix_tree_preload_end();
			continue;
		}
		if (err) {		/* swp entry is obsolete ? */
			radix_tree_preload_end();
			break;
		}

		/* 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);
		if (likely(!err)) {
			radix_tree_preload_end();
			/*
			 * Initiate read into locked page and return.
			 */
			lru_cache_add_anon(new_page);
			swap_readpage(new_page);
			return new_page;
		}
		radix_tree_preload_end();
		ClearPageSwapBacked(new_page);
		__clear_page_locked(new_page);
		/*
		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
		 * clear SWAP_HAS_CACHE flag.
		 */
		swapcache_free(entry, NULL);
	} 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)
{
	struct page *page;
	unsigned long offset = swp_offset(entry);
	unsigned long start_offset, end_offset;
	unsigned long mask = (1UL << page_cluster) - 1;

	/* Read a page_cluster sized and aligned cluster around offset. */
	start_offset = offset & ~mask;
	end_offset = offset | mask;
	if (!start_offset)	/* First page is swap header. */
		start_offset++;

	for (offset = start_offset; 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)
			continue;
		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	*/
1da177e4	9	#include <linux/mm.h>
5a0e3ad6	10	#include <linux/gfp.h>
1da177e4 LT	11	#include <linux/kernel_stat.h>
1da177e4 LT	12	#include <linux/swap.h>
46017e95	13	#include <linux/swapops.h>
1da177e4 LT	14	#include <linux/init.h>
1da177e4 LT	15	#include <linux/pagemap.h>
1da177e4	16	#include <linux/backing-dev.h>
c484d410	17	#include <linux/pagevec.h>
b20a3503	18	#include <linux/migrate.h>
8c7c6e34	19	#include <linux/page_cgroup.h>
1da177e4 LT	20
	21	#include <asm/pgtable.h>
	22
	23	/*
	24	* swapper_space is a fiction, retained to simplify the path through
7eaceacc	25	* vmscan's shrink_page_list.
1da177e4	26	*/
f5e54d6e	27	static const struct address_space_operations swap_aops = {
1da177e4	28	.writepage = swap_writepage,
aca50bd3	29	.set_page_dirty = __set_page_dirty_no_writeback,
e965f963	30	.migratepage = migrate_page,
1da177e4 LT	31	};
	32
	33	static struct backing_dev_info swap_backing_dev_info = {
d993831f	34	.name = "swap",
4f98a2fe	35	.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK \| BDI_CAP_SWAP_BACKED,
1da177e4 LT	36	};
	37
	38	struct address_space swapper_space = {
	39	.page_tree = RADIX_TREE_INIT(GFP_ATOMIC\|__GFP_NOWARN),
19fd6231	40	.tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
1da177e4 LT	41	.a_ops = &swap_aops,
	42	.i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
	43	.backing_dev_info = &swap_backing_dev_info,
	44	};
1da177e4 LT	45
	46	#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
	47
	48	static struct {
	49	unsigned long add_total;
	50	unsigned long del_total;
	51	unsigned long find_success;
	52	unsigned long find_total;
1da177e4 LT	53	} swap_cache_info;
	54
	55	void show_swap_cache_info(void)
	56	{
2c97b7fc JW	57	printk("%lu pages in swap cache\n", total_swapcache_pages);
2c97b7fc JW	58	printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
1da177e4	59	swap_cache_info.add_total, swap_cache_info.del_total,
bb63be0a	60	swap_cache_info.find_success, swap_cache_info.find_total);
07279cdf	61	printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
1da177e4 LT	62	printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
	63	}
	64
	65	/*
31a56396	66	* __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
1da177e4 LT	67	* but sets SwapCache flag and private instead of mapping and index.
1da177e4 LT	68	*/
31a56396	69	static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
1da177e4 LT	70	{
	71	int error;
	72
51726b12 HD	73	VM_BUG_ON(!PageLocked(page));
	74	VM_BUG_ON(PageSwapCache(page));
	75	VM_BUG_ON(!PageSwapBacked(page));
	76
31a56396 DN	77	page_cache_get(page);
	78	SetPageSwapCache(page);
	79	set_page_private(page, entry.val);
	80
	81	spin_lock_irq(&swapper_space.tree_lock);
	82	error = radix_tree_insert(&swapper_space.page_tree, entry.val, page);
	83	if (likely(!error)) {
	84	total_swapcache_pages++;
	85	__inc_zone_page_state(page, NR_FILE_PAGES);
	86	INC_CACHE_INFO(add_total);
	87	}
	88	spin_unlock_irq(&swapper_space.tree_lock);
	89
	90	if (unlikely(error)) {
2ca4532a DN	91	/*
	92	* Only the context which have set SWAP_HAS_CACHE flag
	93	* would call add_to_swap_cache().
	94	* So add_to_swap_cache() doesn't returns -EEXIST.
	95	*/
	96	VM_BUG_ON(error == -EEXIST);
31a56396 DN	97	set_page_private(page, 0UL);
	98	ClearPageSwapCache(page);
	99	page_cache_release(page);
	100	}
	101
	102	return error;
	103	}
	104
	105
	106	int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
	107	{
	108	int error;
	109
35c754d7 BS	110	error = radix_tree_preload(gfp_mask);
35c754d7 BS	111	if (!error) {
31a56396	112	error = __add_to_swap_cache(page, entry);
1da177e4	113	radix_tree_preload_end();
fa1de900	114	}
1da177e4 LT	115	return error;
	116	}
	117
1da177e4 LT	118	/*
	119	* This must be called only on pages that have
	120	* been verified to be in the swap cache.
	121	*/
	122	void __delete_from_swap_cache(struct page *page)
	123	{
51726b12 HD	124	VM_BUG_ON(!PageLocked(page));
	125	VM_BUG_ON(!PageSwapCache(page));
	126	VM_BUG_ON(PageWriteback(page));
1da177e4	127
4c21e2f2 HD	128	radix_tree_delete(&swapper_space.page_tree, page_private(page));
4c21e2f2 HD	129	set_page_private(page, 0);
1da177e4 LT	130	ClearPageSwapCache(page);
1da177e4 LT	131	total_swapcache_pages--;
347ce434	132	__dec_zone_page_state(page, NR_FILE_PAGES);
1da177e4 LT	133	INC_CACHE_INFO(del_total);
	134	}
	135
	136	/**
	137	* add_to_swap - allocate swap space for a page
	138	* @page: page we want to move to swap
	139	*
	140	* Allocate swap space for the page and add the page to the
	141	* swap cache. Caller needs to hold the page lock.
	142	*/
ac47b003	143	int add_to_swap(struct page *page)
1da177e4 LT	144	{
1da177e4 LT	145	swp_entry_t entry;
1da177e4 LT	146	int err;
1da177e4 LT	147
51726b12 HD	148	VM_BUG_ON(!PageLocked(page));
51726b12 HD	149	VM_BUG_ON(!PageUptodate(page));
1da177e4	150
2ca4532a DN	151	entry = get_swap_page();
	152	if (!entry.val)
	153	return 0;
	154
3f04f62f AA	155	if (unlikely(PageTransHuge(page)))
	156	if (unlikely(split_huge_page(page))) {
	157	swapcache_free(entry, NULL);
	158	return 0;
	159	}
	160
2ca4532a DN	161	/*
	162	* Radix-tree node allocations from PF_MEMALLOC contexts could
	163	* completely exhaust the page allocator. __GFP_NOMEMALLOC
	164	* stops emergency reserves from being allocated.
	165	*
	166	* TODO: this could cause a theoretical memory reclaim
	167	* deadlock in the swap out path.
	168	*/
	169	/*
	170	* Add it to the swap cache and mark it dirty
	171	*/
	172	err = add_to_swap_cache(page, entry,
	173	__GFP_HIGH\|__GFP_NOMEMALLOC\|__GFP_NOWARN);
	174
	175	if (!err) { /* Success */
	176	SetPageDirty(page);
	177	return 1;
	178	} else { /* -ENOMEM radix-tree allocation failure */
bd53b714	179	/*
2ca4532a DN	180	* add_to_swap_cache() doesn't return -EEXIST, so we can safely
2ca4532a DN	181	* clear SWAP_HAS_CACHE flag.
1da177e4	182	*/
2ca4532a DN	183	swapcache_free(entry, NULL);
2ca4532a DN	184	return 0;
1da177e4 LT	185	}
	186	}
	187
	188	/*
	189	* This must be called only on pages that have
	190	* been verified to be in the swap cache and locked.
	191	* It will never put the page into the free list,
	192	* the caller has a reference on the page.
	193	*/
	194	void delete_from_swap_cache(struct page *page)
	195	{
	196	swp_entry_t entry;
	197
4c21e2f2	198	entry.val = page_private(page);
1da177e4	199
19fd6231	200	spin_lock_irq(&swapper_space.tree_lock);
1da177e4	201	__delete_from_swap_cache(page);
19fd6231	202	spin_unlock_irq(&swapper_space.tree_lock);
1da177e4	203
cb4b86ba	204	swapcache_free(entry, page);
1da177e4 LT	205	page_cache_release(page);
	206	}
	207
1da177e4 LT	208	/*
	209	* If we are the only user, then try to free up the swap cache.
	210	*
	211	* Its ok to check for PageSwapCache without the page lock
a2c43eed HD	212	* here because we are going to recheck again inside
a2c43eed HD	213	* try_to_free_swap() _with_ the lock.
1da177e4 LT	214	* - Marcelo
	215	*/
	216	static inline void free_swap_cache(struct page *page)
	217	{
a2c43eed HD	218	if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
a2c43eed HD	219	try_to_free_swap(page);
1da177e4 LT	220	unlock_page(page);
	221	}
	222	}
	223
	224	/*
	225	* Perform a free_page(), also freeing any swap cache associated with
b8072f09	226	* this page if it is the last user of the page.
1da177e4 LT	227	*/
	228	void free_page_and_swap_cache(struct page *page)
	229	{
	230	free_swap_cache(page);
	231	page_cache_release(page);
	232	}
	233
	234	/*
	235	* Passed an array of pages, drop them all from swapcache and then release
	236	* them. They are removed from the LRU and freed if this is their last use.
	237	*/
	238	void free_pages_and_swap_cache(struct page **pages, int nr)
	239	{
1da177e4 LT	240	struct page **pagep = pages;
	241
	242	lru_add_drain();
	243	while (nr) {
c484d410	244	int todo = min(nr, PAGEVEC_SIZE);
1da177e4 LT	245	int i;
	246
	247	for (i = 0; i < todo; i++)
	248	free_swap_cache(pagep[i]);
	249	release_pages(pagep, todo, 0);
	250	pagep += todo;
	251	nr -= todo;
	252	}
	253	}
	254
	255	/*
	256	* Lookup a swap entry in the swap cache. A found page will be returned
	257	* unlocked and with its refcount incremented - we rely on the kernel
	258	* lock getting page table operations atomic even if we drop the page
	259	* lock before returning.
	260	*/
	261	struct page * lookup_swap_cache(swp_entry_t entry)
	262	{
	263	struct page *page;
	264
	265	page = find_get_page(&swapper_space, entry.val);
	266
	267	if (page)
	268	INC_CACHE_INFO(find_success);
	269
	270	INC_CACHE_INFO(find_total);
	271	return page;
	272	}
	273
	274	/*
	275	* Locate a page of swap in physical memory, reserving swap cache space
	276	* and reading the disk if it is not already cached.
	277	* A failure return means that either the page allocation failed or that
	278	* the swap entry is no longer in use.
	279	*/
02098fea	280	struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
1da177e4 LT	281	struct vm_area_struct *vma, unsigned long addr)
	282	{
	283	struct page found_page, new_page = NULL;
	284	int err;
	285
	286	do {
	287	/*
	288	* First check the swap cache. Since this is normally
	289	* called after lookup_swap_cache() failed, re-calling
	290	* that would confuse statistics.
	291	*/
	292	found_page = find_get_page(&swapper_space, entry.val);
	293	if (found_page)
	294	break;
	295
	296	/*
	297	* Get a new page to read into from swap.
	298	*/
	299	if (!new_page) {
02098fea	300	new_page = alloc_page_vma(gfp_mask, vma, addr);
1da177e4 LT	301	if (!new_page)
	302	break; /* Out of memory */
	303	}
	304
31a56396 DN	305	/*
	306	* call radix_tree_preload() while we can wait.
	307	*/
	308	err = radix_tree_preload(gfp_mask & GFP_KERNEL);
	309	if (err)
	310	break;
	311
f000944d HD	312	/*
	313	* Swap entry may have been freed since our caller observed it.
	314	*/
355cfa73	315	err = swapcache_prepare(entry);
31a56396 DN	316	if (err == -EEXIST) { /* seems racy */
31a56396 DN	317	radix_tree_preload_end();
355cfa73	318	continue;
31a56396 DN	319	}
	320	if (err) { /* swp entry is obsolete ? */
	321	radix_tree_preload_end();
f000944d	322	break;
31a56396	323	}
f000944d	324
2ca4532a	325	/* May fail (-ENOMEM) if radix-tree node allocation failed. */
f45840b5	326	__set_page_locked(new_page);
b2e18538	327	SetPageSwapBacked(new_page);
31a56396	328	err = __add_to_swap_cache(new_page, entry);
529ae9aa	329	if (likely(!err)) {
31a56396	330	radix_tree_preload_end();
1da177e4 LT	331	/*
	332	* Initiate read into locked page and return.
	333	*/
c5fdae46	334	lru_cache_add_anon(new_page);
aca8bf32	335	swap_readpage(new_page);
1da177e4 LT	336	return new_page;
1da177e4 LT	337	}
31a56396	338	radix_tree_preload_end();
b2e18538	339	ClearPageSwapBacked(new_page);
f45840b5	340	__clear_page_locked(new_page);
2ca4532a DN	341	/*
	342	* add_to_swap_cache() doesn't return -EEXIST, so we can safely
	343	* clear SWAP_HAS_CACHE flag.
	344	*/
cb4b86ba	345	swapcache_free(entry, NULL);
f000944d	346	} while (err != -ENOMEM);
1da177e4 LT	347
	348	if (new_page)
	349	page_cache_release(new_page);
	350	return found_page;
	351	}
46017e95 HD	352
	353	/**
	354	* swapin_readahead - swap in pages in hope we need them soon
	355	* @entry: swap entry of this memory
7682486b	356	* @gfp_mask: memory allocation flags
46017e95 HD	357	* @vma: user vma this address belongs to
	358	* @addr: target address for mempolicy
	359	*
	360	* Returns the struct page for entry and addr, after queueing swapin.
	361	*
	362	* Primitive swap readahead code. We simply read an aligned block of
	363	* (1 << page_cluster) entries in the swap area. This method is chosen
	364	* because it doesn't cost us any seek time. We also make sure to queue
	365	* the 'original' request together with the readahead ones...
	366	*
	367	* This has been extended to use the NUMA policies from the mm triggering
	368	* the readahead.
	369	*
	370	* Caller must hold down_read on the vma->vm_mm if vma is not NULL.
	371	*/
02098fea	372	struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
46017e95 HD	373	struct vm_area_struct *vma, unsigned long addr)
46017e95 HD	374	{
46017e95	375	struct page *page;
67f96aa2 RR	376	unsigned long offset = swp_offset(entry);
	377	unsigned long start_offset, end_offset;
	378	unsigned long mask = (1UL << page_cluster) - 1;
46017e95	379
67f96aa2 RR	380	/* Read a page_cluster sized and aligned cluster around offset. */
	381	start_offset = offset & ~mask;
	382	end_offset = offset \| mask;
	383	if (!start_offset) /* First page is swap header. */
	384	start_offset++;
	385
	386	for (offset = start_offset; offset <= end_offset ; offset++) {
46017e95 HD	387	/* Ok, do the async read-ahead now */
46017e95 HD	388	page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
02098fea	389	gfp_mask, vma, addr);
46017e95	390	if (!page)
67f96aa2	391	continue;
46017e95 HD	392	page_cache_release(page);
	393	}
	394	lru_add_drain(); /* Push any new pages onto the LRU now */
02098fea	395	return read_swap_cache_async(entry, gfp_mask, vma, addr);
46017e95	396	}