swapfile.c 55.2 KB
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/*
 *  linux/mm/swapfile.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/shm.h>
#include <linux/blkdev.h>
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#include <linux/random.h>
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#include <linux/writeback.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/rmap.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
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#include <linux/mutex.h>
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#include <linux/capability.h>
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#include <linux/syscalls.h>
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#include <linux/memcontrol.h>
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#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <linux/swapops.h>
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#include <linux/page_cgroup.h>
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static DEFINE_SPINLOCK(swap_lock);
static unsigned int nr_swapfiles;
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long nr_swap_pages;
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long total_swap_pages;
static int swap_overflow;
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static int least_priority;
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static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
static const char Bad_offset[] = "Bad swap offset entry ";
static const char Unused_offset[] = "Unused swap offset entry ";

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static struct swap_list_t swap_list = {-1, -1};
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static struct swap_info_struct swap_info[MAX_SWAPFILES];
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static DEFINE_MUTEX(swapon_mutex);
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/* For reference count accounting in swap_map */
/* enum for swap_map[] handling. internal use only */
enum {
	SWAP_MAP = 0,	/* ops for reference from swap users */
	SWAP_CACHE,	/* ops for reference from swap cache */
};

static inline int swap_count(unsigned short ent)
{
	return ent & SWAP_COUNT_MASK;
}

static inline bool swap_has_cache(unsigned short ent)
{
	return !!(ent & SWAP_HAS_CACHE);
}

static inline unsigned short encode_swapmap(int count, bool has_cache)
{
	unsigned short ret = count;

	if (has_cache)
		return SWAP_HAS_CACHE | ret;
	return ret;
}

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/* returnes 1 if swap entry is freed */
static int
__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
{
	int type = si - swap_info;
	swp_entry_t entry = swp_entry(type, offset);
	struct page *page;
	int ret = 0;

	page = find_get_page(&swapper_space, entry.val);
	if (!page)
		return 0;
	/*
	 * This function is called from scan_swap_map() and it's called
	 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
	 * We have to use trylock for avoiding deadlock. This is a special
	 * case and you should use try_to_free_swap() with explicit lock_page()
	 * in usual operations.
	 */
	if (trylock_page(page)) {
		ret = try_to_free_swap(page);
		unlock_page(page);
	}
	page_cache_release(page);
	return ret;
}
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/*
 * We need this because the bdev->unplug_fn can sleep and we cannot
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 * hold swap_lock while calling the unplug_fn. And swap_lock
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 * cannot be turned into a mutex.
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 */
static DECLARE_RWSEM(swap_unplug_sem);

void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
{
	swp_entry_t entry;

	down_read(&swap_unplug_sem);
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	entry.val = page_private(page);
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	if (PageSwapCache(page)) {
		struct block_device *bdev = swap_info[swp_type(entry)].bdev;
		struct backing_dev_info *bdi;

		/*
		 * If the page is removed from swapcache from under us (with a
		 * racy try_to_unuse/swapoff) we need an additional reference
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		 * count to avoid reading garbage from page_private(page) above.
		 * If the WARN_ON triggers during a swapoff it maybe the race
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		 * condition and it's harmless. However if it triggers without
		 * swapoff it signals a problem.
		 */
		WARN_ON(page_count(page) <= 1);

		bdi = bdev->bd_inode->i_mapping->backing_dev_info;
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		blk_run_backing_dev(bdi, page);
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	}
	up_read(&swap_unplug_sem);
}

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/*
 * swapon tell device that all the old swap contents can be discarded,
 * to allow the swap device to optimize its wear-levelling.
 */
static int discard_swap(struct swap_info_struct *si)
{
	struct swap_extent *se;
	int err = 0;

	list_for_each_entry(se, &si->extent_list, list) {
		sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
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		sector_t nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
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		if (se->start_page == 0) {
			/* Do not discard the swap header page! */
			start_block += 1 << (PAGE_SHIFT - 9);
			nr_blocks -= 1 << (PAGE_SHIFT - 9);
			if (!nr_blocks)
				continue;
		}

		err = blkdev_issue_discard(si->bdev, start_block,
						nr_blocks, GFP_KERNEL);
		if (err)
			break;

		cond_resched();
	}
	return err;		/* That will often be -EOPNOTSUPP */
}

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/*
 * swap allocation tell device that a cluster of swap can now be discarded,
 * to allow the swap device to optimize its wear-levelling.
 */
static void discard_swap_cluster(struct swap_info_struct *si,
				 pgoff_t start_page, pgoff_t nr_pages)
{
	struct swap_extent *se = si->curr_swap_extent;
	int found_extent = 0;

	while (nr_pages) {
		struct list_head *lh;

		if (se->start_page <= start_page &&
		    start_page < se->start_page + se->nr_pages) {
			pgoff_t offset = start_page - se->start_page;
			sector_t start_block = se->start_block + offset;
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			sector_t nr_blocks = se->nr_pages - offset;
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			if (nr_blocks > nr_pages)
				nr_blocks = nr_pages;
			start_page += nr_blocks;
			nr_pages -= nr_blocks;

			if (!found_extent++)
				si->curr_swap_extent = se;

			start_block <<= PAGE_SHIFT - 9;
			nr_blocks <<= PAGE_SHIFT - 9;
			if (blkdev_issue_discard(si->bdev, start_block,
							nr_blocks, GFP_NOIO))
				break;
		}

		lh = se->list.next;
		if (lh == &si->extent_list)
			lh = lh->next;
		se = list_entry(lh, struct swap_extent, list);
	}
}

static int wait_for_discard(void *word)
{
	schedule();
	return 0;
}

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#define SWAPFILE_CLUSTER	256
#define LATENCY_LIMIT		256

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static inline unsigned long scan_swap_map(struct swap_info_struct *si,
					  int cache)
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{
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	unsigned long offset;
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	unsigned long scan_base;
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	unsigned long last_in_cluster = 0;
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	int latency_ration = LATENCY_LIMIT;
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	int found_free_cluster = 0;
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	/*
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	 * We try to cluster swap pages by allocating them sequentially
	 * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
	 * way, however, we resort to first-free allocation, starting
	 * a new cluster.  This prevents us from scattering swap pages
	 * all over the entire swap partition, so that we reduce
	 * overall disk seek times between swap pages.  -- sct
	 * But we do now try to find an empty cluster.  -Andrea
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	 * And we let swap pages go all over an SSD partition.  Hugh
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	 */

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	si->flags += SWP_SCANNING;
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	scan_base = offset = si->cluster_next;
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	if (unlikely(!si->cluster_nr--)) {
		if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
			si->cluster_nr = SWAPFILE_CLUSTER - 1;
			goto checks;
		}
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		if (si->flags & SWP_DISCARDABLE) {
			/*
			 * Start range check on racing allocations, in case
			 * they overlap the cluster we eventually decide on
			 * (we scan without swap_lock to allow preemption).
			 * It's hardly conceivable that cluster_nr could be
			 * wrapped during our scan, but don't depend on it.
			 */
			if (si->lowest_alloc)
				goto checks;
			si->lowest_alloc = si->max;
			si->highest_alloc = 0;
		}
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		spin_unlock(&swap_lock);
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		/*
		 * If seek is expensive, start searching for new cluster from
		 * start of partition, to minimize the span of allocated swap.
		 * But if seek is cheap, search from our current position, so
		 * that swap is allocated from all over the partition: if the
		 * Flash Translation Layer only remaps within limited zones,
		 * we don't want to wear out the first zone too quickly.
		 */
		if (!(si->flags & SWP_SOLIDSTATE))
			scan_base = offset = si->lowest_bit;
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		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;

		/* Locate the first empty (unaligned) cluster */
		for (; last_in_cluster <= si->highest_bit; offset++) {
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			if (si->swap_map[offset])
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				last_in_cluster = offset + SWAPFILE_CLUSTER;
			else if (offset == last_in_cluster) {
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				spin_lock(&swap_lock);
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				offset -= SWAPFILE_CLUSTER - 1;
				si->cluster_next = offset;
				si->cluster_nr = SWAPFILE_CLUSTER - 1;
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				found_free_cluster = 1;
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				goto checks;
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			}
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			if (unlikely(--latency_ration < 0)) {
				cond_resched();
				latency_ration = LATENCY_LIMIT;
			}
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		}
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		offset = si->lowest_bit;
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		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;

		/* Locate the first empty (unaligned) cluster */
		for (; last_in_cluster < scan_base; offset++) {
			if (si->swap_map[offset])
				last_in_cluster = offset + SWAPFILE_CLUSTER;
			else if (offset == last_in_cluster) {
				spin_lock(&swap_lock);
				offset -= SWAPFILE_CLUSTER - 1;
				si->cluster_next = offset;
				si->cluster_nr = SWAPFILE_CLUSTER - 1;
				found_free_cluster = 1;
				goto checks;
			}
			if (unlikely(--latency_ration < 0)) {
				cond_resched();
				latency_ration = LATENCY_LIMIT;
			}
		}

		offset = scan_base;
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		spin_lock(&swap_lock);
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		si->cluster_nr = SWAPFILE_CLUSTER - 1;
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		si->lowest_alloc = 0;
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	}
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checks:
	if (!(si->flags & SWP_WRITEOK))
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		goto no_page;
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	if (!si->highest_bit)
		goto no_page;
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	if (offset > si->highest_bit)
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		scan_base = offset = si->lowest_bit;
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	/* reuse swap entry of cache-only swap if not busy. */
	if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
		int swap_was_freed;
		spin_unlock(&swap_lock);
		swap_was_freed = __try_to_reclaim_swap(si, offset);
		spin_lock(&swap_lock);
		/* entry was freed successfully, try to use this again */
		if (swap_was_freed)
			goto checks;
		goto scan; /* check next one */
	}

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	if (si->swap_map[offset])
		goto scan;

	if (offset == si->lowest_bit)
		si->lowest_bit++;
	if (offset == si->highest_bit)
		si->highest_bit--;
	si->inuse_pages++;
	if (si->inuse_pages == si->pages) {
		si->lowest_bit = si->max;
		si->highest_bit = 0;
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	}
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	if (cache == SWAP_CACHE) /* at usual swap-out via vmscan.c */
		si->swap_map[offset] = encode_swapmap(0, true);
	else /* at suspend */
		si->swap_map[offset] = encode_swapmap(1, false);
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	si->cluster_next = offset + 1;
	si->flags -= SWP_SCANNING;
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	if (si->lowest_alloc) {
		/*
		 * Only set when SWP_DISCARDABLE, and there's a scan
		 * for a free cluster in progress or just completed.
		 */
		if (found_free_cluster) {
			/*
			 * To optimize wear-levelling, discard the
			 * old data of the cluster, taking care not to
			 * discard any of its pages that have already
			 * been allocated by racing tasks (offset has
			 * already stepped over any at the beginning).
			 */
			if (offset < si->highest_alloc &&
			    si->lowest_alloc <= last_in_cluster)
				last_in_cluster = si->lowest_alloc - 1;
			si->flags |= SWP_DISCARDING;
			spin_unlock(&swap_lock);

			if (offset < last_in_cluster)
				discard_swap_cluster(si, offset,
					last_in_cluster - offset + 1);

			spin_lock(&swap_lock);
			si->lowest_alloc = 0;
			si->flags &= ~SWP_DISCARDING;

			smp_mb();	/* wake_up_bit advises this */
			wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));

		} else if (si->flags & SWP_DISCARDING) {
			/*
			 * Delay using pages allocated by racing tasks
			 * until the whole discard has been issued. We
			 * could defer that delay until swap_writepage,
			 * but it's easier to keep this self-contained.
			 */
			spin_unlock(&swap_lock);
			wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
				wait_for_discard, TASK_UNINTERRUPTIBLE);
			spin_lock(&swap_lock);
		} else {
			/*
			 * Note pages allocated by racing tasks while
			 * scan for a free cluster is in progress, so
			 * that its final discard can exclude them.
			 */
			if (offset < si->lowest_alloc)
				si->lowest_alloc = offset;
			if (offset > si->highest_alloc)
				si->highest_alloc = offset;
		}
	}
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	return offset;
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scan:
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	spin_unlock(&swap_lock);
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	while (++offset <= si->highest_bit) {
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		if (!si->swap_map[offset]) {
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			spin_lock(&swap_lock);
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			goto checks;
		}
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		if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
			spin_lock(&swap_lock);
			goto checks;
		}
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		if (unlikely(--latency_ration < 0)) {
			cond_resched();
			latency_ration = LATENCY_LIMIT;
		}
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	}
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	offset = si->lowest_bit;
	while (++offset < scan_base) {
		if (!si->swap_map[offset]) {
			spin_lock(&swap_lock);
			goto checks;
		}
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		if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
			spin_lock(&swap_lock);
			goto checks;
		}
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		if (unlikely(--latency_ration < 0)) {
			cond_resched();
			latency_ration = LATENCY_LIMIT;
		}
	}
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	spin_lock(&swap_lock);
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no_page:
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	si->flags -= SWP_SCANNING;
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	return 0;
}

swp_entry_t get_swap_page(void)
{
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	struct swap_info_struct *si;
	pgoff_t offset;
	int type, next;
	int wrapped = 0;
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	spin_lock(&swap_lock);
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	if (nr_swap_pages <= 0)
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		goto noswap;
	nr_swap_pages--;

	for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
		si = swap_info + type;
		next = si->next;
		if (next < 0 ||
		    (!wrapped && si->prio != swap_info[next].prio)) {
			next = swap_list.head;
			wrapped++;
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		}
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		if (!si->highest_bit)
			continue;
		if (!(si->flags & SWP_WRITEOK))
			continue;

		swap_list.next = next;
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		/* This is called for allocating swap entry for cache */
		offset = scan_swap_map(si, SWAP_CACHE);
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		if (offset) {
			spin_unlock(&swap_lock);
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			return swp_entry(type, offset);
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		}
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		next = swap_list.next;
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	}
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	nr_swap_pages++;
noswap:
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	spin_unlock(&swap_lock);
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	return (swp_entry_t) {0};
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}

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/* The only caller of this function is now susupend routine */
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swp_entry_t get_swap_page_of_type(int type)
{
	struct swap_info_struct *si;
	pgoff_t offset;

	spin_lock(&swap_lock);
	si = swap_info + type;
	if (si->flags & SWP_WRITEOK) {
		nr_swap_pages--;
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		/* This is called for allocating swap entry, not cache */
		offset = scan_swap_map(si, SWAP_MAP);
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		if (offset) {
			spin_unlock(&swap_lock);
			return swp_entry(type, offset);
		}
		nr_swap_pages++;
	}
	spin_unlock(&swap_lock);
	return (swp_entry_t) {0};
}

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static struct swap_info_struct * swap_info_get(swp_entry_t entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;

	if (!entry.val)
		goto out;
	type = swp_type(entry);
	if (type >= nr_swapfiles)
		goto bad_nofile;
	p = & swap_info[type];
	if (!(p->flags & SWP_USED))
		goto bad_device;
	offset = swp_offset(entry);
	if (offset >= p->max)
		goto bad_offset;
	if (!p->swap_map[offset])
		goto bad_free;
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	spin_lock(&swap_lock);
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	return p;

bad_free:
	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
	goto out;
bad_offset:
	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
	goto out;
bad_device:
	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
	goto out;
bad_nofile:
	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
out:
	return NULL;
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}
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static int swap_entry_free(struct swap_info_struct *p,
			   swp_entry_t ent, int cache)
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{
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	unsigned long offset = swp_offset(ent);
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	int count = swap_count(p->swap_map[offset]);
	bool has_cache;

	has_cache = swap_has_cache(p->swap_map[offset]);

	if (cache == SWAP_MAP) { /* dropping usage count of swap */
		if (count < SWAP_MAP_MAX) {
			count--;
			p->swap_map[offset] = encode_swapmap(count, has_cache);
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		}
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	} else { /* dropping swap cache flag */
		VM_BUG_ON(!has_cache);
		p->swap_map[offset] = encode_swapmap(count, false);

	}
	/* return code. */
	count = p->swap_map[offset];
	/* free if no reference */
	if (!count) {
		if (offset < p->lowest_bit)
			p->lowest_bit = offset;
		if (offset > p->highest_bit)
			p->highest_bit = offset;
		if (p->prio > swap_info[swap_list.next].prio)
			swap_list.next = p - swap_info;
		nr_swap_pages++;
		p->inuse_pages--;
		mem_cgroup_uncharge_swap(ent);
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	}
	return count;
}

/*
 * Caller has made sure that the swapdevice corresponding to entry
 * is still around or has not been recycled.
 */
void swap_free(swp_entry_t entry)
{
	struct swap_info_struct * p;

	p = swap_info_get(entry);
	if (p) {
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		swap_entry_free(p, entry, SWAP_MAP);
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		spin_unlock(&swap_lock);
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	}
}

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/*
 * Called after dropping swapcache to decrease refcnt to swap entries.
 */
void swapcache_free(swp_entry_t entry, struct page *page)
{
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	struct swap_info_struct *p;

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	if (page)
		mem_cgroup_uncharge_swapcache(page, entry);
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	p = swap_info_get(entry);
	if (p) {
		swap_entry_free(p, entry, SWAP_CACHE);
		spin_unlock(&swap_lock);
	}
	return;
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}

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623
/*
624
 * How many references to page are currently swapped out?
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625
 */
626
static inline int page_swapcount(struct page *page)
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627
{
628 629
	int count = 0;
	struct swap_info_struct *p;
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	swp_entry_t entry;

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	entry.val = page_private(page);
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	p = swap_info_get(entry);
	if (p) {
635
		count = swap_count(p->swap_map[swp_offset(entry)]);
636
		spin_unlock(&swap_lock);
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637
	}
638
	return count;
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}

/*
642 643 644 645
 * We can write to an anon page without COW if there are no other references
 * to it.  And as a side-effect, free up its swap: because the old content
 * on disk will never be read, and seeking back there to write new content
 * later would only waste time away from clustering.
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 */
647
int reuse_swap_page(struct page *page)
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{
649 650
	int count;

651
	VM_BUG_ON(!PageLocked(page));
652
	count = page_mapcount(page);
653
	if (count <= 1 && PageSwapCache(page)) {
654
		count += page_swapcount(page);
655 656 657 658 659
		if (count == 1 && !PageWriteback(page)) {
			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
	}
660
	return count == 1;
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}

/*
664 665
 * If swap is getting full, or if there are no more mappings of this page,
 * then try_to_free_swap is called to free its swap space.
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 */
667
int try_to_free_swap(struct page *page)
L
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668
{
669
	VM_BUG_ON(!PageLocked(page));
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	if (!PageSwapCache(page))
		return 0;
	if (PageWriteback(page))
		return 0;
675
	if (page_swapcount(page))
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		return 0;

678 679 680
	delete_from_swap_cache(page);
	SetPageDirty(page);
	return 1;
681 682
}

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/*
 * Free the swap entry like above, but also try to
 * free the page cache entry if it is the last user.
 */
687
int free_swap_and_cache(swp_entry_t entry)
L
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688
{
689
	struct swap_info_struct *p;
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	struct page *page = NULL;

692
	if (is_migration_entry(entry))
693
		return 1;
694

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	p = swap_info_get(entry);
	if (p) {
697
		if (swap_entry_free(p, entry, SWAP_MAP) == SWAP_HAS_CACHE) {
698
			page = find_get_page(&swapper_space, entry.val);
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			if (page && !trylock_page(page)) {
700 701 702 703
				page_cache_release(page);
				page = NULL;
			}
		}
704
		spin_unlock(&swap_lock);
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	}
	if (page) {
707 708 709 710
		/*
		 * Not mapped elsewhere, or swap space full? Free it!
		 * Also recheck PageSwapCache now page is locked (above).
		 */
711
		if (PageSwapCache(page) && !PageWriteback(page) &&
712
				(!page_mapped(page) || vm_swap_full())) {
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			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
		unlock_page(page);
		page_cache_release(page);
	}
719
	return p != NULL;
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}

722
#ifdef CONFIG_HIBERNATION
723
/*
724
 * Find the swap type that corresponds to given device (if any).
725
 *
726 727 728 729
 * @offset - number of the PAGE_SIZE-sized block of the device, starting
 * from 0, in which the swap header is expected to be located.
 *
 * This is needed for the suspend to disk (aka swsusp).
730
 */
731
int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
732
{
733
	struct block_device *bdev = NULL;
734 735
	int i;

736 737 738
	if (device)
		bdev = bdget(device);

739 740
	spin_lock(&swap_lock);
	for (i = 0; i < nr_swapfiles; i++) {
741
		struct swap_info_struct *sis = swap_info + i;
742

743
		if (!(sis->flags & SWP_WRITEOK))
744
			continue;
745

746
		if (!bdev) {
747
			if (bdev_p)
748
				*bdev_p = bdget(sis->bdev->bd_dev);
749

750 751 752
			spin_unlock(&swap_lock);
			return i;
		}
753 754 755 756 757 758
		if (bdev == sis->bdev) {
			struct swap_extent *se;

			se = list_entry(sis->extent_list.next,
					struct swap_extent, list);
			if (se->start_block == offset) {
759
				if (bdev_p)
760
					*bdev_p = bdget(sis->bdev->bd_dev);
761

762 763 764 765
				spin_unlock(&swap_lock);
				bdput(bdev);
				return i;
			}
766 767 768
		}
	}
	spin_unlock(&swap_lock);
769 770 771
	if (bdev)
		bdput(bdev);

772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797
	return -ENODEV;
}

/*
 * Return either the total number of swap pages of given type, or the number
 * of free pages of that type (depending on @free)
 *
 * This is needed for software suspend
 */
unsigned int count_swap_pages(int type, int free)
{
	unsigned int n = 0;

	if (type < nr_swapfiles) {
		spin_lock(&swap_lock);
		if (swap_info[type].flags & SWP_WRITEOK) {
			n = swap_info[type].pages;
			if (free)
				n -= swap_info[type].inuse_pages;
		}
		spin_unlock(&swap_lock);
	}
	return n;
}
#endif

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/*
799 800 801
 * No need to decide whether this PTE shares the swap entry with others,
 * just let do_wp_page work it out if a write is requested later - to
 * force COW, vm_page_prot omits write permission from any private vma.
L
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802
 */
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803
static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
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		unsigned long addr, swp_entry_t entry, struct page *page)
{
806
	struct mem_cgroup *ptr = NULL;
H
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807 808 809 810
	spinlock_t *ptl;
	pte_t *pte;
	int ret = 1;

811
	if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
H
Hugh Dickins 已提交
812
		ret = -ENOMEM;
813 814
		goto out_nolock;
	}
H
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815 816 817 818

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
		if (ret > 0)
819
			mem_cgroup_cancel_charge_swapin(ptr);
H
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820 821 822
		ret = 0;
		goto out;
	}
823

824
	inc_mm_counter(vma->vm_mm, anon_rss);
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825 826 827 828
	get_page(page);
	set_pte_at(vma->vm_mm, addr, pte,
		   pte_mkold(mk_pte(page, vma->vm_page_prot)));
	page_add_anon_rmap(page, vma, addr);
829
	mem_cgroup_commit_charge_swapin(page, ptr);
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830 831 832 833 834 835
	swap_free(entry);
	/*
	 * Move the page to the active list so it is not
	 * immediately swapped out again after swapon.
	 */
	activate_page(page);
H
Hugh Dickins 已提交
836 837
out:
	pte_unmap_unlock(pte, ptl);
838
out_nolock:
H
Hugh Dickins 已提交
839
	return ret;
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840 841 842 843 844 845 846
}

static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pte_t swp_pte = swp_entry_to_pte(entry);
847
	pte_t *pte;
848
	int ret = 0;
L
Linus Torvalds 已提交
849

H
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850 851 852 853 854 855 856 857 858 859
	/*
	 * We don't actually need pte lock while scanning for swp_pte: since
	 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
	 * page table while we're scanning; though it could get zapped, and on
	 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
	 * of unmatched parts which look like swp_pte, so unuse_pte must
	 * recheck under pte lock.  Scanning without pte lock lets it be
	 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
	 */
	pte = pte_offset_map(pmd, addr);
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	do {
		/*
		 * swapoff spends a _lot_ of time in this loop!
		 * Test inline before going to call unuse_pte.
		 */
		if (unlikely(pte_same(*pte, swp_pte))) {
H
Hugh Dickins 已提交
866 867 868 869 870
			pte_unmap(pte);
			ret = unuse_pte(vma, pmd, addr, entry, page);
			if (ret)
				goto out;
			pte = pte_offset_map(pmd, addr);
L
Linus Torvalds 已提交
871 872
		}
	} while (pte++, addr += PAGE_SIZE, addr != end);
H
Hugh Dickins 已提交
873 874
	pte_unmap(pte - 1);
out:
875
	return ret;
L
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876 877 878 879 880 881 882 883
}

static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pmd_t *pmd;
	unsigned long next;
884
	int ret;
L
Linus Torvalds 已提交
885 886 887 888 889 890

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd))
			continue;
891 892 893
		ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
		if (ret)
			return ret;
L
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	} while (pmd++, addr = next, addr != end);
	return 0;
}

static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pud_t *pud;
	unsigned long next;
904
	int ret;
L
Linus Torvalds 已提交
905 906 907 908 909 910

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
911 912 913
		ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
		if (ret)
			return ret;
L
Linus Torvalds 已提交
914 915 916 917 918 919 920 921 922
	} while (pud++, addr = next, addr != end);
	return 0;
}

static int unuse_vma(struct vm_area_struct *vma,
				swp_entry_t entry, struct page *page)
{
	pgd_t *pgd;
	unsigned long addr, end, next;
923
	int ret;
L
Linus Torvalds 已提交
924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940

	if (page->mapping) {
		addr = page_address_in_vma(page, vma);
		if (addr == -EFAULT)
			return 0;
		else
			end = addr + PAGE_SIZE;
	} else {
		addr = vma->vm_start;
		end = vma->vm_end;
	}

	pgd = pgd_offset(vma->vm_mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
941 942 943
		ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
		if (ret)
			return ret;
L
Linus Torvalds 已提交
944 945 946 947 948 949 950 951
	} while (pgd++, addr = next, addr != end);
	return 0;
}

static int unuse_mm(struct mm_struct *mm,
				swp_entry_t entry, struct page *page)
{
	struct vm_area_struct *vma;
952
	int ret = 0;
L
Linus Torvalds 已提交
953 954 955

	if (!down_read_trylock(&mm->mmap_sem)) {
		/*
956 957
		 * Activate page so shrink_inactive_list is unlikely to unmap
		 * its ptes while lock is dropped, so swapoff can make progress.
L
Linus Torvalds 已提交
958
		 */
959
		activate_page(page);
L
Linus Torvalds 已提交
960 961 962 963 964
		unlock_page(page);
		down_read(&mm->mmap_sem);
		lock_page(page);
	}
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
965
		if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
L
Linus Torvalds 已提交
966 967 968
			break;
	}
	up_read(&mm->mmap_sem);
969
	return (ret < 0)? ret: 0;
L
Linus Torvalds 已提交
970 971 972 973 974 975
}

/*
 * Scan swap_map from current position to next entry still in use.
 * Recycle to start on reaching the end, returning 0 when empty.
 */
976 977
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
					unsigned int prev)
L
Linus Torvalds 已提交
978
{
979 980
	unsigned int max = si->max;
	unsigned int i = prev;
L
Linus Torvalds 已提交
981 982 983
	int count;

	/*
984
	 * No need for swap_lock here: we're just looking
L
Linus Torvalds 已提交
985 986
	 * for whether an entry is in use, not modifying it; false
	 * hits are okay, and sys_swapoff() has already prevented new
987
	 * allocations from this area (while holding swap_lock).
L
Linus Torvalds 已提交
988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003
	 */
	for (;;) {
		if (++i >= max) {
			if (!prev) {
				i = 0;
				break;
			}
			/*
			 * No entries in use at top of swap_map,
			 * loop back to start and recheck there.
			 */
			max = prev + 1;
			prev = 0;
			i = 1;
		}
		count = si->swap_map[i];
1004
		if (count && swap_count(count) != SWAP_MAP_BAD)
L
Linus Torvalds 已提交
1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
			break;
	}
	return i;
}

/*
 * We completely avoid races by reading each swap page in advance,
 * and then search for the process using it.  All the necessary
 * page table adjustments can then be made atomically.
 */
static int try_to_unuse(unsigned int type)
{
	struct swap_info_struct * si = &swap_info[type];
	struct mm_struct *start_mm;
	unsigned short *swap_map;
	unsigned short swcount;
	struct page *page;
	swp_entry_t entry;
1023
	unsigned int i = 0;
L
Linus Torvalds 已提交
1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056
	int retval = 0;
	int reset_overflow = 0;
	int shmem;

	/*
	 * When searching mms for an entry, a good strategy is to
	 * start at the first mm we freed the previous entry from
	 * (though actually we don't notice whether we or coincidence
	 * freed the entry).  Initialize this start_mm with a hold.
	 *
	 * A simpler strategy would be to start at the last mm we
	 * freed the previous entry from; but that would take less
	 * advantage of mmlist ordering, which clusters forked mms
	 * together, child after parent.  If we race with dup_mmap(), we
	 * prefer to resolve parent before child, lest we miss entries
	 * duplicated after we scanned child: using last mm would invert
	 * that.  Though it's only a serious concern when an overflowed
	 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
	 */
	start_mm = &init_mm;
	atomic_inc(&init_mm.mm_users);

	/*
	 * Keep on scanning until all entries have gone.  Usually,
	 * one pass through swap_map is enough, but not necessarily:
	 * there are races when an instance of an entry might be missed.
	 */
	while ((i = find_next_to_unuse(si, i)) != 0) {
		if (signal_pending(current)) {
			retval = -EINTR;
			break;
		}

1057
		/*
L
Linus Torvalds 已提交
1058 1059
		 * Get a page for the entry, using the existing swap
		 * cache page if there is one.  Otherwise, get a clean
1060
		 * page and read the swap into it.
L
Linus Torvalds 已提交
1061 1062 1063
		 */
		swap_map = &si->swap_map[i];
		entry = swp_entry(type, i);
1064 1065
		page = read_swap_cache_async(entry,
					GFP_HIGHUSER_MOVABLE, NULL, 0);
L
Linus Torvalds 已提交
1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107
		if (!page) {
			/*
			 * Either swap_duplicate() failed because entry
			 * has been freed independently, and will not be
			 * reused since sys_swapoff() already disabled
			 * allocation from here, or alloc_page() failed.
			 */
			if (!*swap_map)
				continue;
			retval = -ENOMEM;
			break;
		}

		/*
		 * Don't hold on to start_mm if it looks like exiting.
		 */
		if (atomic_read(&start_mm->mm_users) == 1) {
			mmput(start_mm);
			start_mm = &init_mm;
			atomic_inc(&init_mm.mm_users);
		}

		/*
		 * Wait for and lock page.  When do_swap_page races with
		 * try_to_unuse, do_swap_page can handle the fault much
		 * faster than try_to_unuse can locate the entry.  This
		 * apparently redundant "wait_on_page_locked" lets try_to_unuse
		 * defer to do_swap_page in such a case - in some tests,
		 * do_swap_page and try_to_unuse repeatedly compete.
		 */
		wait_on_page_locked(page);
		wait_on_page_writeback(page);
		lock_page(page);
		wait_on_page_writeback(page);

		/*
		 * Remove all references to entry.
		 * Whenever we reach init_mm, there's no address space
		 * to search, but use it as a reminder to search shmem.
		 */
		shmem = 0;
		swcount = *swap_map;
1108
		if (swap_count(swcount)) {
L
Linus Torvalds 已提交
1109 1110 1111 1112 1113
			if (start_mm == &init_mm)
				shmem = shmem_unuse(entry, page);
			else
				retval = unuse_mm(start_mm, entry, page);
		}
1114
		if (swap_count(*swap_map)) {
L
Linus Torvalds 已提交
1115 1116 1117 1118 1119 1120 1121 1122 1123
			int set_start_mm = (*swap_map >= swcount);
			struct list_head *p = &start_mm->mmlist;
			struct mm_struct *new_start_mm = start_mm;
			struct mm_struct *prev_mm = start_mm;
			struct mm_struct *mm;

			atomic_inc(&new_start_mm->mm_users);
			atomic_inc(&prev_mm->mm_users);
			spin_lock(&mmlist_lock);
1124
			while (swap_count(*swap_map) && !retval && !shmem &&
L
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1125 1126
					(p = p->next) != &start_mm->mmlist) {
				mm = list_entry(p, struct mm_struct, mmlist);
1127
				if (!atomic_inc_not_zero(&mm->mm_users))
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Linus Torvalds 已提交
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					continue;
				spin_unlock(&mmlist_lock);
				mmput(prev_mm);
				prev_mm = mm;

				cond_resched();

				swcount = *swap_map;
1136
				if (!swap_count(swcount)) /* any usage ? */
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1137 1138 1139 1140 1141 1142
					;
				else if (mm == &init_mm) {
					set_start_mm = 1;
					shmem = shmem_unuse(entry, page);
				} else
					retval = unuse_mm(mm, entry, page);
1143 1144 1145

				if (set_start_mm &&
				    swap_count(*swap_map) < swcount) {
L
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1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157
					mmput(new_start_mm);
					atomic_inc(&mm->mm_users);
					new_start_mm = mm;
					set_start_mm = 0;
				}
				spin_lock(&mmlist_lock);
			}
			spin_unlock(&mmlist_lock);
			mmput(prev_mm);
			mmput(start_mm);
			start_mm = new_start_mm;
		}
1158 1159 1160 1161 1162 1163 1164
		if (shmem) {
			/* page has already been unlocked and released */
			if (shmem > 0)
				continue;
			retval = shmem;
			break;
		}
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1165 1166 1167 1168 1169 1170 1171
		if (retval) {
			unlock_page(page);
			page_cache_release(page);
			break;
		}

		/*
1172 1173 1174 1175 1176 1177
		 * How could swap count reach 0x7ffe ?
		 * There's no way to repeat a swap page within an mm
		 * (except in shmem, where it's the shared object which takes
		 * the reference count)?
		 * We believe SWAP_MAP_MAX cannot occur.(if occur, unsigned
		 * short is too small....)
L
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		 * If that's wrong, then we should worry more about
		 * exit_mmap() and do_munmap() cases described above:
		 * we might be resetting SWAP_MAP_MAX too early here.
		 * We know "Undead"s can happen, they're okay, so don't
		 * report them; but do report if we reset SWAP_MAP_MAX.
		 */
1184 1185 1186 1187 1188
		/* We might release the lock_page() in unuse_mm(). */
		if (!PageSwapCache(page) || page_private(page) != entry.val)
			goto retry;

		if (swap_count(*swap_map) == SWAP_MAP_MAX) {
1189
			spin_lock(&swap_lock);
1190
			*swap_map = encode_swapmap(0, true);
1191
			spin_unlock(&swap_lock);
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			reset_overflow = 1;
		}

		/*
		 * If a reference remains (rare), we would like to leave
		 * the page in the swap cache; but try_to_unmap could
		 * then re-duplicate the entry once we drop page lock,
		 * so we might loop indefinitely; also, that page could
		 * not be swapped out to other storage meanwhile.  So:
		 * delete from cache even if there's another reference,
		 * after ensuring that the data has been saved to disk -
		 * since if the reference remains (rarer), it will be
		 * read from disk into another page.  Splitting into two
		 * pages would be incorrect if swap supported "shared
		 * private" pages, but they are handled by tmpfs files.
		 */
1208 1209
		if (swap_count(*swap_map) &&
		     PageDirty(page) && PageSwapCache(page)) {
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			struct writeback_control wbc = {
				.sync_mode = WB_SYNC_NONE,
			};

			swap_writepage(page, &wbc);
			lock_page(page);
			wait_on_page_writeback(page);
		}
1218 1219 1220 1221 1222 1223 1224 1225 1226 1227

		/*
		 * It is conceivable that a racing task removed this page from
		 * swap cache just before we acquired the page lock at the top,
		 * or while we dropped it in unuse_mm().  The page might even
		 * be back in swap cache on another swap area: that we must not
		 * delete, since it may not have been written out to swap yet.
		 */
		if (PageSwapCache(page) &&
		    likely(page_private(page) == entry.val))
1228
			delete_from_swap_cache(page);
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		/*
		 * So we could skip searching mms once swap count went
		 * to 1, we did not mark any present ptes as dirty: must
1233
		 * mark page dirty so shrink_page_list will preserve it.
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		 */
		SetPageDirty(page);
1236
retry:
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		unlock_page(page);
		page_cache_release(page);

		/*
		 * Make sure that we aren't completely killing
		 * interactive performance.
		 */
		cond_resched();
	}

	mmput(start_mm);
	if (reset_overflow) {
		printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
		swap_overflow = 0;
	}
	return retval;
}

/*
1256 1257 1258
 * After a successful try_to_unuse, if no swap is now in use, we know
 * we can empty the mmlist.  swap_lock must be held on entry and exit.
 * Note that mmlist_lock nests inside swap_lock, and an mm must be
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 * added to the mmlist just after page_duplicate - before would be racy.
 */
static void drain_mmlist(void)
{
	struct list_head *p, *next;
	unsigned int i;

	for (i = 0; i < nr_swapfiles; i++)
		if (swap_info[i].inuse_pages)
			return;
	spin_lock(&mmlist_lock);
	list_for_each_safe(p, next, &init_mm.mmlist)
		list_del_init(p);
	spin_unlock(&mmlist_lock);
}

/*
 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
 * corresponds to page offset `offset'.
 */
sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
{
	struct swap_extent *se = sis->curr_swap_extent;
	struct swap_extent *start_se = se;

	for ( ; ; ) {
		struct list_head *lh;

		if (se->start_page <= offset &&
				offset < (se->start_page + se->nr_pages)) {
			return se->start_block + (offset - se->start_page);
		}
1291
		lh = se->list.next;
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		if (lh == &sis->extent_list)
1293
			lh = lh->next;
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		se = list_entry(lh, struct swap_extent, list);
		sis->curr_swap_extent = se;
		BUG_ON(se == start_se);		/* It *must* be present */
	}
}

1300
#ifdef CONFIG_HIBERNATION
1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314
/*
 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
 * corresponding to given index in swap_info (swap type).
 */
sector_t swapdev_block(int swap_type, pgoff_t offset)
{
	struct swap_info_struct *sis;

	if (swap_type >= nr_swapfiles)
		return 0;

	sis = swap_info + swap_type;
	return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
}
1315
#endif /* CONFIG_HIBERNATION */
1316

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/*
 * Free all of a swapdev's extent information
 */
static void destroy_swap_extents(struct swap_info_struct *sis)
{
	while (!list_empty(&sis->extent_list)) {
		struct swap_extent *se;

		se = list_entry(sis->extent_list.next,
				struct swap_extent, list);
		list_del(&se->list);
		kfree(se);
	}
}

/*
 * Add a block range (and the corresponding page range) into this swapdev's
1334
 * extent list.  The extent list is kept sorted in page order.
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 *
1336
 * This function rather assumes that it is called in ascending page order.
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 */
static int
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
		unsigned long nr_pages, sector_t start_block)
{
	struct swap_extent *se;
	struct swap_extent *new_se;
	struct list_head *lh;

1346 1347
	lh = sis->extent_list.prev;	/* The highest page extent */
	if (lh != &sis->extent_list) {
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		se = list_entry(lh, struct swap_extent, list);
1349 1350
		BUG_ON(se->start_page + se->nr_pages != start_page);
		if (se->start_block + se->nr_pages == start_block) {
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1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366
			/* Merge it */
			se->nr_pages += nr_pages;
			return 0;
		}
	}

	/*
	 * No merge.  Insert a new extent, preserving ordering.
	 */
	new_se = kmalloc(sizeof(*se), GFP_KERNEL);
	if (new_se == NULL)
		return -ENOMEM;
	new_se->start_page = start_page;
	new_se->nr_pages = nr_pages;
	new_se->start_block = start_block;

1367
	list_add_tail(&new_se->list, &sis->extent_list);
1368
	return 1;
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}

/*
 * A `swap extent' is a simple thing which maps a contiguous range of pages
 * onto a contiguous range of disk blocks.  An ordered list of swap extents
 * is built at swapon time and is then used at swap_writepage/swap_readpage
 * time for locating where on disk a page belongs.
 *
 * If the swapfile is an S_ISBLK block device, a single extent is installed.
 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
 * swap files identically.
 *
 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
 * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
 * swapfiles are handled *identically* after swapon time.
 *
 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
 * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
 * requirements, they are simply tossed out - we will never use those blocks
 * for swapping.
 *
1391
 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
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 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
 * which will scribble on the fs.
 *
 * The amount of disk space which a single swap extent represents varies.
 * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
 * extents in the list.  To avoid much list walking, we cache the previous
 * search location in `curr_swap_extent', and start new searches from there.
 * This is extremely effective.  The average number of iterations in
 * map_swap_page() has been measured at about 0.3 per page.  - akpm.
 */
1402
static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
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{
	struct inode *inode;
	unsigned blocks_per_page;
	unsigned long page_no;
	unsigned blkbits;
	sector_t probe_block;
	sector_t last_block;
1410 1411 1412
	sector_t lowest_block = -1;
	sector_t highest_block = 0;
	int nr_extents = 0;
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	int ret;

	inode = sis->swap_file->f_mapping->host;
	if (S_ISBLK(inode->i_mode)) {
		ret = add_swap_extent(sis, 0, sis->max, 0);
1418
		*span = sis->pages;
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		goto done;
	}

	blkbits = inode->i_blkbits;
	blocks_per_page = PAGE_SIZE >> blkbits;

	/*
	 * Map all the blocks into the extent list.  This code doesn't try
	 * to be very smart.
	 */
	probe_block = 0;
	page_no = 0;
	last_block = i_size_read(inode) >> blkbits;
	while ((probe_block + blocks_per_page) <= last_block &&
			page_no < sis->max) {
		unsigned block_in_page;
		sector_t first_block;

		first_block = bmap(inode, probe_block);
		if (first_block == 0)
			goto bad_bmap;

		/*
		 * It must be PAGE_SIZE aligned on-disk
		 */
		if (first_block & (blocks_per_page - 1)) {
			probe_block++;
			goto reprobe;
		}

		for (block_in_page = 1; block_in_page < blocks_per_page;
					block_in_page++) {
			sector_t block;

			block = bmap(inode, probe_block + block_in_page);
			if (block == 0)
				goto bad_bmap;
			if (block != first_block + block_in_page) {
				/* Discontiguity */
				probe_block++;
				goto reprobe;
			}
		}

1463 1464 1465 1466 1467 1468 1469 1470
		first_block >>= (PAGE_SHIFT - blkbits);
		if (page_no) {	/* exclude the header page */
			if (first_block < lowest_block)
				lowest_block = first_block;
			if (first_block > highest_block)
				highest_block = first_block;
		}

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		/*
		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
		 */
1474 1475
		ret = add_swap_extent(sis, page_no, 1, first_block);
		if (ret < 0)
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			goto out;
1477
		nr_extents += ret;
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		page_no++;
		probe_block += blocks_per_page;
reprobe:
		continue;
	}
1483 1484
	ret = nr_extents;
	*span = 1 + highest_block - lowest_block;
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	if (page_no == 0)
1486
		page_no = 1;	/* force Empty message */
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	sis->max = page_no;
1488
	sis->pages = page_no - 1;
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	sis->highest_bit = page_no - 1;
done:
	sis->curr_swap_extent = list_entry(sis->extent_list.prev,
					struct swap_extent, list);
	goto out;
bad_bmap:
	printk(KERN_ERR "swapon: swapfile has holes\n");
	ret = -EINVAL;
out:
	return ret;
}

1501
SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
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{
	struct swap_info_struct * p = NULL;
	unsigned short *swap_map;
	struct file *swap_file, *victim;
	struct address_space *mapping;
	struct inode *inode;
	char * pathname;
	int i, type, prev;
	int err;
1511

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	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	pathname = getname(specialfile);
	err = PTR_ERR(pathname);
	if (IS_ERR(pathname))
		goto out;

	victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
	putname(pathname);
	err = PTR_ERR(victim);
	if (IS_ERR(victim))
		goto out;

	mapping = victim->f_mapping;
	prev = -1;
1528
	spin_lock(&swap_lock);
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	for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
		p = swap_info + type;
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		if (p->flags & SWP_WRITEOK) {
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			if (p->swap_file->f_mapping == mapping)
				break;
		}
		prev = type;
	}
	if (type < 0) {
		err = -EINVAL;
1539
		spin_unlock(&swap_lock);
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1540 1541 1542 1543 1544 1545
		goto out_dput;
	}
	if (!security_vm_enough_memory(p->pages))
		vm_unacct_memory(p->pages);
	else {
		err = -ENOMEM;
1546
		spin_unlock(&swap_lock);
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		goto out_dput;
	}
	if (prev < 0) {
		swap_list.head = p->next;
	} else {
		swap_info[prev].next = p->next;
	}
	if (type == swap_list.next) {
		/* just pick something that's safe... */
		swap_list.next = swap_list.head;
	}
1558 1559 1560 1561 1562
	if (p->prio < 0) {
		for (i = p->next; i >= 0; i = swap_info[i].next)
			swap_info[i].prio = p->prio--;
		least_priority++;
	}
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	nr_swap_pages -= p->pages;
	total_swap_pages -= p->pages;
	p->flags &= ~SWP_WRITEOK;
1566
	spin_unlock(&swap_lock);
1567

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	current->flags |= PF_SWAPOFF;
	err = try_to_unuse(type);
	current->flags &= ~PF_SWAPOFF;

	if (err) {
		/* re-insert swap space back into swap_list */
1574
		spin_lock(&swap_lock);
1575 1576 1577 1578
		if (p->prio < 0)
			p->prio = --least_priority;
		prev = -1;
		for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
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			if (p->prio >= swap_info[i].prio)
				break;
1581 1582
			prev = i;
		}
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1583 1584 1585 1586 1587 1588 1589 1590
		p->next = i;
		if (prev < 0)
			swap_list.head = swap_list.next = p - swap_info;
		else
			swap_info[prev].next = p - swap_info;
		nr_swap_pages += p->pages;
		total_swap_pages += p->pages;
		p->flags |= SWP_WRITEOK;
1591
		spin_unlock(&swap_lock);
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1592 1593
		goto out_dput;
	}
1594 1595 1596 1597 1598

	/* wait for any unplug function to finish */
	down_write(&swap_unplug_sem);
	up_write(&swap_unplug_sem);

1599
	destroy_swap_extents(p);
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Ingo Molnar 已提交
1600
	mutex_lock(&swapon_mutex);
1601 1602 1603
	spin_lock(&swap_lock);
	drain_mmlist();

1604 1605 1606
	/* wait for anyone still in scan_swap_map */
	p->highest_bit = 0;		/* cuts scans short */
	while (p->flags >= SWP_SCANNING) {
1607
		spin_unlock(&swap_lock);
1608
		schedule_timeout_uninterruptible(1);
1609
		spin_lock(&swap_lock);
1610 1611
	}

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1612 1613 1614 1615 1616 1617
	swap_file = p->swap_file;
	p->swap_file = NULL;
	p->max = 0;
	swap_map = p->swap_map;
	p->swap_map = NULL;
	p->flags = 0;
1618
	spin_unlock(&swap_lock);
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Ingo Molnar 已提交
1619
	mutex_unlock(&swapon_mutex);
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1620
	vfree(swap_map);
1621 1622 1623
	/* Destroy swap account informatin */
	swap_cgroup_swapoff(type);

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1624 1625 1626 1627 1628 1629
	inode = mapping->host;
	if (S_ISBLK(inode->i_mode)) {
		struct block_device *bdev = I_BDEV(inode);
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	} else {
1630
		mutex_lock(&inode->i_mutex);
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1631
		inode->i_flags &= ~S_SWAPFILE;
1632
		mutex_unlock(&inode->i_mutex);
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1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
	}
	filp_close(swap_file, NULL);
	err = 0;

out_dput:
	filp_close(victim, NULL);
out:
	return err;
}

#ifdef CONFIG_PROC_FS
/* iterator */
static void *swap_start(struct seq_file *swap, loff_t *pos)
{
	struct swap_info_struct *ptr = swap_info;
	int i;
	loff_t l = *pos;

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Ingo Molnar 已提交
1651
	mutex_lock(&swapon_mutex);
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1652

1653 1654 1655
	if (!l)
		return SEQ_START_TOKEN;

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1656 1657 1658
	for (i = 0; i < nr_swapfiles; i++, ptr++) {
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
1659
		if (!--l)
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1660 1661 1662 1663 1664 1665 1666 1667
			return ptr;
	}

	return NULL;
}

static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
{
1668
	struct swap_info_struct *ptr;
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1669 1670
	struct swap_info_struct *endptr = swap_info + nr_swapfiles;

1671 1672 1673 1674 1675 1676 1677 1678
	if (v == SEQ_START_TOKEN)
		ptr = swap_info;
	else {
		ptr = v;
		ptr++;
	}

	for (; ptr < endptr; ptr++) {
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1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
		++*pos;
		return ptr;
	}

	return NULL;
}

static void swap_stop(struct seq_file *swap, void *v)
{
I
Ingo Molnar 已提交
1690
	mutex_unlock(&swapon_mutex);
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1691 1692 1693 1694 1695 1696 1697 1698
}

static int swap_show(struct seq_file *swap, void *v)
{
	struct swap_info_struct *ptr = v;
	struct file *file;
	int len;

1699 1700 1701 1702
	if (ptr == SEQ_START_TOKEN) {
		seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
		return 0;
	}
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1703 1704

	file = ptr->swap_file;
1705
	len = seq_path(swap, &file->f_path, " \t\n\\");
1706
	seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1707 1708
			len < 40 ? 40 - len : 1, " ",
			S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
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1709
				"partition" : "file\t",
1710 1711 1712
			ptr->pages << (PAGE_SHIFT - 10),
			ptr->inuse_pages << (PAGE_SHIFT - 10),
			ptr->prio);
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1713 1714 1715
	return 0;
}

1716
static const struct seq_operations swaps_op = {
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	.start =	swap_start,
	.next =		swap_next,
	.stop =		swap_stop,
	.show =		swap_show
};

static int swaps_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &swaps_op);
}

1728
static const struct file_operations proc_swaps_operations = {
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1729 1730 1731 1732 1733 1734 1735 1736
	.open		= swaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int __init procswaps_init(void)
{
1737
	proc_create("swaps", 0, NULL, &proc_swaps_operations);
L
Linus Torvalds 已提交
1738 1739 1740 1741 1742
	return 0;
}
__initcall(procswaps_init);
#endif /* CONFIG_PROC_FS */

J
Jan Beulich 已提交
1743 1744 1745 1746 1747 1748 1749 1750 1751
#ifdef MAX_SWAPFILES_CHECK
static int __init max_swapfiles_check(void)
{
	MAX_SWAPFILES_CHECK();
	return 0;
}
late_initcall(max_swapfiles_check);
#endif

L
Linus Torvalds 已提交
1752 1753 1754 1755 1756
/*
 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
 *
 * The swapon system call
 */
1757
SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
L
Linus Torvalds 已提交
1758 1759 1760 1761 1762 1763 1764 1765 1766 1767
{
	struct swap_info_struct * p;
	char *name = NULL;
	struct block_device *bdev = NULL;
	struct file *swap_file = NULL;
	struct address_space *mapping;
	unsigned int type;
	int i, prev;
	int error;
	union swap_header *swap_header = NULL;
1768 1769
	unsigned int nr_good_pages = 0;
	int nr_extents = 0;
1770
	sector_t span;
L
Linus Torvalds 已提交
1771
	unsigned long maxpages = 1;
1772
	unsigned long swapfilepages;
1773
	unsigned short *swap_map = NULL;
L
Linus Torvalds 已提交
1774 1775 1776 1777 1778 1779
	struct page *page = NULL;
	struct inode *inode = NULL;
	int did_down = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
1780
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1781 1782 1783 1784 1785
	p = swap_info;
	for (type = 0 ; type < nr_swapfiles ; type++,p++)
		if (!(p->flags & SWP_USED))
			break;
	error = -EPERM;
1786
	if (type >= MAX_SWAPFILES) {
1787
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1788 1789 1790 1791
		goto out;
	}
	if (type >= nr_swapfiles)
		nr_swapfiles = type+1;
1792
	memset(p, 0, sizeof(*p));
L
Linus Torvalds 已提交
1793 1794 1795
	INIT_LIST_HEAD(&p->extent_list);
	p->flags = SWP_USED;
	p->next = -1;
1796
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829
	name = getname(specialfile);
	error = PTR_ERR(name);
	if (IS_ERR(name)) {
		name = NULL;
		goto bad_swap_2;
	}
	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
	error = PTR_ERR(swap_file);
	if (IS_ERR(swap_file)) {
		swap_file = NULL;
		goto bad_swap_2;
	}

	p->swap_file = swap_file;
	mapping = swap_file->f_mapping;
	inode = mapping->host;

	error = -EBUSY;
	for (i = 0; i < nr_swapfiles; i++) {
		struct swap_info_struct *q = &swap_info[i];

		if (i == type || !q->swap_file)
			continue;
		if (mapping == q->swap_file->f_mapping)
			goto bad_swap;
	}

	error = -EINVAL;
	if (S_ISBLK(inode->i_mode)) {
		bdev = I_BDEV(inode);
		error = bd_claim(bdev, sys_swapon);
		if (error < 0) {
			bdev = NULL;
R
Rob Landley 已提交
1830
			error = -EINVAL;
L
Linus Torvalds 已提交
1831 1832 1833 1834 1835 1836 1837 1838 1839
			goto bad_swap;
		}
		p->old_block_size = block_size(bdev);
		error = set_blocksize(bdev, PAGE_SIZE);
		if (error < 0)
			goto bad_swap;
		p->bdev = bdev;
	} else if (S_ISREG(inode->i_mode)) {
		p->bdev = inode->i_sb->s_bdev;
1840
		mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
1841 1842 1843 1844 1845 1846 1847 1848 1849
		did_down = 1;
		if (IS_SWAPFILE(inode)) {
			error = -EBUSY;
			goto bad_swap;
		}
	} else {
		goto bad_swap;
	}

1850
	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
L
Linus Torvalds 已提交
1851 1852 1853 1854 1855 1856 1857 1858

	/*
	 * Read the swap header.
	 */
	if (!mapping->a_ops->readpage) {
		error = -EINVAL;
		goto bad_swap;
	}
1859
	page = read_mapping_page(mapping, 0, swap_file);
L
Linus Torvalds 已提交
1860 1861 1862 1863
	if (IS_ERR(page)) {
		error = PTR_ERR(page);
		goto bad_swap;
	}
1864
	swap_header = kmap(page);
L
Linus Torvalds 已提交
1865

1866
	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1867
		printk(KERN_ERR "Unable to find swap-space signature\n");
L
Linus Torvalds 已提交
1868 1869 1870
		error = -EINVAL;
		goto bad_swap;
	}
1871

1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884
	/* swap partition endianess hack... */
	if (swab32(swap_header->info.version) == 1) {
		swab32s(&swap_header->info.version);
		swab32s(&swap_header->info.last_page);
		swab32s(&swap_header->info.nr_badpages);
		for (i = 0; i < swap_header->info.nr_badpages; i++)
			swab32s(&swap_header->info.badpages[i]);
	}
	/* Check the swap header's sub-version */
	if (swap_header->info.version != 1) {
		printk(KERN_WARNING
		       "Unable to handle swap header version %d\n",
		       swap_header->info.version);
L
Linus Torvalds 已提交
1885 1886
		error = -EINVAL;
		goto bad_swap;
1887
	}
L
Linus Torvalds 已提交
1888

1889 1890
	p->lowest_bit  = 1;
	p->cluster_next = 1;
1891

1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910
	/*
	 * Find out how many pages are allowed for a single swap
	 * device. There are two limiting factors: 1) the number of
	 * bits for the swap offset in the swp_entry_t type and
	 * 2) the number of bits in the a swap pte as defined by
	 * the different architectures. In order to find the
	 * largest possible bit mask a swap entry with swap type 0
	 * and swap offset ~0UL is created, encoded to a swap pte,
	 * decoded to a swp_entry_t again and finally the swap
	 * offset is extracted. This will mask all the bits from
	 * the initial ~0UL mask that can't be encoded in either
	 * the swp_entry_t or the architecture definition of a
	 * swap pte.
	 */
	maxpages = swp_offset(pte_to_swp_entry(
			swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
	if (maxpages > swap_header->info.last_page)
		maxpages = swap_header->info.last_page;
	p->highest_bit = maxpages - 1;
L
Linus Torvalds 已提交
1911

1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923
	error = -EINVAL;
	if (!maxpages)
		goto bad_swap;
	if (swapfilepages && maxpages > swapfilepages) {
		printk(KERN_WARNING
		       "Swap area shorter than signature indicates\n");
		goto bad_swap;
	}
	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
		goto bad_swap;
	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
		goto bad_swap;
1924

1925 1926 1927 1928 1929 1930
	/* OK, set up the swap map and apply the bad block list */
	swap_map = vmalloc(maxpages * sizeof(short));
	if (!swap_map) {
		error = -ENOMEM;
		goto bad_swap;
	}
L
Linus Torvalds 已提交
1931

1932 1933 1934 1935 1936
	memset(swap_map, 0, maxpages * sizeof(short));
	for (i = 0; i < swap_header->info.nr_badpages; i++) {
		int page_nr = swap_header->info.badpages[i];
		if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
			error = -EINVAL;
L
Linus Torvalds 已提交
1937
			goto bad_swap;
1938 1939
		}
		swap_map[page_nr] = SWAP_MAP_BAD;
L
Linus Torvalds 已提交
1940
	}
1941 1942 1943 1944 1945

	error = swap_cgroup_swapon(type, maxpages);
	if (error)
		goto bad_swap;

1946 1947 1948
	nr_good_pages = swap_header->info.last_page -
			swap_header->info.nr_badpages -
			1 /* header page */;
1949 1950

	if (nr_good_pages) {
1951
		swap_map[0] = SWAP_MAP_BAD;
1952 1953
		p->max = maxpages;
		p->pages = nr_good_pages;
1954 1955 1956
		nr_extents = setup_swap_extents(p, &span);
		if (nr_extents < 0) {
			error = nr_extents;
1957
			goto bad_swap;
1958
		}
1959 1960
		nr_good_pages = p->pages;
	}
L
Linus Torvalds 已提交
1961 1962 1963 1964 1965 1966
	if (!nr_good_pages) {
		printk(KERN_WARNING "Empty swap-file\n");
		error = -EINVAL;
		goto bad_swap;
	}

1967 1968 1969 1970
	if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
		p->flags |= SWP_SOLIDSTATE;
		p->cluster_next = 1 + (random32() % p->highest_bit);
	}
1971 1972 1973
	if (discard_swap(p) == 0)
		p->flags |= SWP_DISCARDABLE;

I
Ingo Molnar 已提交
1974
	mutex_lock(&swapon_mutex);
1975
	spin_lock(&swap_lock);
1976 1977 1978 1979 1980 1981
	if (swap_flags & SWAP_FLAG_PREFER)
		p->prio =
		  (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
	else
		p->prio = --least_priority;
	p->swap_map = swap_map;
H
Hugh Dickins 已提交
1982
	p->flags |= SWP_WRITEOK;
L
Linus Torvalds 已提交
1983 1984
	nr_swap_pages += nr_good_pages;
	total_swap_pages += nr_good_pages;
1985

1986
	printk(KERN_INFO "Adding %uk swap on %s.  "
1987
			"Priority:%d extents:%d across:%lluk %s%s\n",
1988
		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1989
		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
1990 1991
		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
		(p->flags & SWP_DISCARDABLE) ? "D" : "");
L
Linus Torvalds 已提交
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

	/* insert swap space into swap_list: */
	prev = -1;
	for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
		if (p->prio >= swap_info[i].prio) {
			break;
		}
		prev = i;
	}
	p->next = i;
	if (prev < 0) {
		swap_list.head = swap_list.next = p - swap_info;
	} else {
		swap_info[prev].next = p - swap_info;
	}
2007
	spin_unlock(&swap_lock);
I
Ingo Molnar 已提交
2008
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
2009 2010 2011 2012 2013 2014 2015
	error = 0;
	goto out;
bad_swap:
	if (bdev) {
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	}
2016
	destroy_swap_extents(p);
2017
	swap_cgroup_swapoff(type);
L
Linus Torvalds 已提交
2018
bad_swap_2:
2019
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
2020 2021
	p->swap_file = NULL;
	p->flags = 0;
2022
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
	vfree(swap_map);
	if (swap_file)
		filp_close(swap_file, NULL);
out:
	if (page && !IS_ERR(page)) {
		kunmap(page);
		page_cache_release(page);
	}
	if (name)
		putname(name);
	if (did_down) {
		if (!error)
			inode->i_flags |= S_SWAPFILE;
2036
		mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2037 2038 2039 2040 2041 2042 2043 2044 2045
	}
	return error;
}

void si_swapinfo(struct sysinfo *val)
{
	unsigned int i;
	unsigned long nr_to_be_unused = 0;

2046
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
2047 2048 2049 2050 2051 2052 2053 2054
	for (i = 0; i < nr_swapfiles; i++) {
		if (!(swap_info[i].flags & SWP_USED) ||
		     (swap_info[i].flags & SWP_WRITEOK))
			continue;
		nr_to_be_unused += swap_info[i].inuse_pages;
	}
	val->freeswap = nr_swap_pages + nr_to_be_unused;
	val->totalswap = total_swap_pages + nr_to_be_unused;
2055
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
2056 2057 2058 2059 2060 2061 2062
}

/*
 * Verify that a swap entry is valid and increment its swap map count.
 *
 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
 * "permanent", but will be reclaimed by the next swapoff.
2063 2064 2065 2066 2067 2068
 * Returns error code in following case.
 * - success -> 0
 * - swp_entry is invalid -> EINVAL
 * - swp_entry is migration entry -> EINVAL
 * - swap-cache reference is requested but there is already one. -> EEXIST
 * - swap-cache reference is requested but the entry is not used. -> ENOENT
L
Linus Torvalds 已提交
2069
 */
2070
static int __swap_duplicate(swp_entry_t entry, bool cache)
L
Linus Torvalds 已提交
2071 2072 2073
{
	struct swap_info_struct * p;
	unsigned long offset, type;
2074 2075 2076
	int result = -EINVAL;
	int count;
	bool has_cache;
L
Linus Torvalds 已提交
2077

2078
	if (is_migration_entry(entry))
2079
		return -EINVAL;
2080

L
Linus Torvalds 已提交
2081 2082 2083 2084 2085 2086
	type = swp_type(entry);
	if (type >= nr_swapfiles)
		goto bad_file;
	p = type + swap_info;
	offset = swp_offset(entry);

2087
	spin_lock(&swap_lock);
2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111

	if (unlikely(offset >= p->max))
		goto unlock_out;

	count = swap_count(p->swap_map[offset]);
	has_cache = swap_has_cache(p->swap_map[offset]);

	if (cache == SWAP_CACHE) { /* called for swapcache/swapin-readahead */

		/* set SWAP_HAS_CACHE if there is no cache and entry is used */
		if (!has_cache && count) {
			p->swap_map[offset] = encode_swapmap(count, true);
			result = 0;
		} else if (has_cache) /* someone added cache */
			result = -EEXIST;
		else if (!count) /* no users */
			result = -ENOENT;

	} else if (count || has_cache) {
		if (count < SWAP_MAP_MAX - 1) {
			p->swap_map[offset] = encode_swapmap(count + 1,
							     has_cache);
			result = 0;
		} else if (count <= SWAP_MAP_MAX) {
L
Linus Torvalds 已提交
2112
			if (swap_overflow++ < 5)
2113 2114 2115 2116 2117
				printk(KERN_WARNING
				       "swap_dup: swap entry overflow\n");
			p->swap_map[offset] = encode_swapmap(SWAP_MAP_MAX,
							      has_cache);
			result = 0;
L
Linus Torvalds 已提交
2118
		}
2119 2120 2121
	} else
		result = -ENOENT; /* unused swap entry */
unlock_out:
2122
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
2123 2124 2125 2126 2127 2128 2129
out:
	return result;

bad_file:
	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
	goto out;
}
2130 2131 2132 2133 2134 2135 2136
/*
 * increase reference count of swap entry by 1.
 */
void swap_duplicate(swp_entry_t entry)
{
	__swap_duplicate(entry, SWAP_MAP);
}
L
Linus Torvalds 已提交
2137

2138
/*
2139 2140
 * @entry: swap entry for which we allocate swap cache.
 *
2141
 * Called when allocating swap cache for exising swap entry,
2142 2143 2144
 * This can return error codes. Returns 0 at success.
 * -EBUSY means there is a swap cache.
 * Note: return code is different from swap_duplicate().
2145 2146 2147
 */
int swapcache_prepare(swp_entry_t entry)
{
2148
	return __swap_duplicate(entry, SWAP_CACHE);
2149 2150 2151
}


L
Linus Torvalds 已提交
2152 2153 2154 2155 2156 2157 2158
struct swap_info_struct *
get_swap_info_struct(unsigned type)
{
	return &swap_info[type];
}

/*
2159
 * swap_lock prevents swap_map being freed. Don't grab an extra
L
Linus Torvalds 已提交
2160 2161 2162 2163
 * reference on the swaphandle, it doesn't matter if it becomes unused.
 */
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
2164
	struct swap_info_struct *si;
H
Hugh Dickins 已提交
2165
	int our_page_cluster = page_cluster;
2166 2167 2168
	pgoff_t target, toff;
	pgoff_t base, end;
	int nr_pages = 0;
L
Linus Torvalds 已提交
2169

H
Hugh Dickins 已提交
2170
	if (!our_page_cluster)	/* no readahead */
L
Linus Torvalds 已提交
2171
		return 0;
2172 2173 2174 2175 2176 2177 2178

	si = &swap_info[swp_type(entry)];
	target = swp_offset(entry);
	base = (target >> our_page_cluster) << our_page_cluster;
	end = base + (1 << our_page_cluster);
	if (!base)		/* first page is swap header */
		base++;
L
Linus Torvalds 已提交
2179

2180
	spin_lock(&swap_lock);
2181 2182 2183 2184 2185 2186 2187 2188
	if (end > si->max)	/* don't go beyond end of map */
		end = si->max;

	/* Count contiguous allocated slots above our target */
	for (toff = target; ++toff < end; nr_pages++) {
		/* Don't read in free or bad pages */
		if (!si->swap_map[toff])
			break;
2189
		if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
L
Linus Torvalds 已提交
2190
			break;
2191 2192 2193
	}
	/* Count contiguous allocated slots below our target */
	for (toff = target; --toff >= base; nr_pages++) {
L
Linus Torvalds 已提交
2194
		/* Don't read in free or bad pages */
2195
		if (!si->swap_map[toff])
L
Linus Torvalds 已提交
2196
			break;
2197
		if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
L
Linus Torvalds 已提交
2198
			break;
2199
	}
2200
	spin_unlock(&swap_lock);
2201 2202 2203 2204 2205 2206 2207

	/*
	 * Indicate starting offset, and return number of pages to get:
	 * if only 1, say 0, since there's then no readahead to be done.
	 */
	*offset = ++toff;
	return nr_pages? ++nr_pages: 0;
L
Linus Torvalds 已提交
2208
}