swapfile.c 45.4 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>
#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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static DEFINE_SPINLOCK(swap_lock);
static unsigned int nr_swapfiles;
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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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/*
 * 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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#define SWAPFILE_CLUSTER	256
#define LATENCY_LIMIT		256

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static inline unsigned long scan_swap_map(struct swap_info_struct *si)
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{
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	unsigned long offset, last_in_cluster;
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	int latency_ration = LATENCY_LIMIT;
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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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	si->flags += SWP_SCANNING;
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	if (unlikely(!si->cluster_nr)) {
		si->cluster_nr = SWAPFILE_CLUSTER - 1;
		if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
			goto lowest;
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		spin_unlock(&swap_lock);
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		offset = si->lowest_bit;
		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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				si->cluster_next = offset-SWAPFILE_CLUSTER+1;
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				goto cluster;
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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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		spin_lock(&swap_lock);
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		goto lowest;
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	}
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	si->cluster_nr--;
cluster:
	offset = si->cluster_next;
	if (offset > si->highest_bit)
lowest:		offset = si->lowest_bit;
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checks:	if (!(si->flags & SWP_WRITEOK))
		goto no_page;
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	if (!si->highest_bit)
		goto no_page;
	if (!si->swap_map[offset]) {
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		if (offset == si->lowest_bit)
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			si->lowest_bit++;
		if (offset == si->highest_bit)
			si->highest_bit--;
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		si->inuse_pages++;
		if (si->inuse_pages == si->pages) {
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			si->lowest_bit = si->max;
			si->highest_bit = 0;
		}
		si->swap_map[offset] = 1;
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		si->cluster_next = offset + 1;
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		si->flags -= SWP_SCANNING;
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		return offset;
	}
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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 (unlikely(--latency_ration < 0)) {
			cond_resched();
			latency_ration = LATENCY_LIMIT;
		}
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	}
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	spin_lock(&swap_lock);
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	goto lowest;

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;
		offset = scan_swap_map(si);
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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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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--;
		offset = scan_swap_map(si);
		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;
}	

static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
{
	int count = p->swap_map[offset];

	if (count < SWAP_MAP_MAX) {
		count--;
		p->swap_map[offset] = count;
		if (!count) {
			if (offset < p->lowest_bit)
				p->lowest_bit = offset;
			if (offset > p->highest_bit)
				p->highest_bit = offset;
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			if (p->prio > swap_info[swap_list.next].prio)
				swap_list.next = p - swap_info;
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			nr_swap_pages++;
			p->inuse_pages--;
		}
	}
	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) {
		swap_entry_free(p, swp_offset(entry));
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		spin_unlock(&swap_lock);
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	}
}

/*
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 * How many references to page are currently swapped out?
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 */
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static inline int page_swapcount(struct page *page)
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{
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	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) {
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		/* Subtract the 1 for the swap cache itself */
		count = p->swap_map[swp_offset(entry)] - 1;
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		spin_unlock(&swap_lock);
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	}
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	return count;
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}

/*
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 * 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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 */
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int reuse_swap_page(struct page *page)
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{
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	int count;

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	VM_BUG_ON(!PageLocked(page));
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	count = page_mapcount(page);
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	if (count <= 1 && PageSwapCache(page)) {
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		count += page_swapcount(page);
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		if (count == 1 && !PageWriteback(page)) {
			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
	}
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	return count == 1;
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}

/*
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 * 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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 */
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int try_to_free_swap(struct page *page)
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{
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	VM_BUG_ON(!PageLocked(page));
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	if (!PageSwapCache(page))
		return 0;
	if (PageWriteback(page))
		return 0;
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	if (page_swapcount(page))
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		return 0;

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	delete_from_swap_cache(page);
	SetPageDirty(page);
	return 1;
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}

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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.
 */
void free_swap_and_cache(swp_entry_t entry)
{
	struct swap_info_struct * p;
	struct page *page = NULL;

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	if (is_migration_entry(entry))
		return;

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	p = swap_info_get(entry);
	if (p) {
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		if (swap_entry_free(p, swp_offset(entry)) == 1) {
			page = find_get_page(&swapper_space, entry.val);
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			if (page && !trylock_page(page)) {
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				page_cache_release(page);
				page = NULL;
			}
		}
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		spin_unlock(&swap_lock);
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	}
	if (page) {
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		/*
		 * Not mapped elsewhere, or swap space full? Free it!
		 * Also recheck PageSwapCache now page is locked (above).
		 */
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		if (PageSwapCache(page) && !PageWriteback(page) &&
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				(!page_mapped(page) || vm_swap_full())) {
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			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
		unlock_page(page);
		page_cache_release(page);
	}
}

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#ifdef CONFIG_HIBERNATION
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/*
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 * Find the swap type that corresponds to given device (if any).
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 *
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 * @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).
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 */
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int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
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{
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	struct block_device *bdev = NULL;
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	int i;

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	if (device)
		bdev = bdget(device);

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	spin_lock(&swap_lock);
	for (i = 0; i < nr_swapfiles; i++) {
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		struct swap_info_struct *sis = swap_info + i;
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429
		if (!(sis->flags & SWP_WRITEOK))
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			continue;
431

432
		if (!bdev) {
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			if (bdev_p)
				*bdev_p = sis->bdev;

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			spin_unlock(&swap_lock);
			return i;
		}
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		if (bdev == sis->bdev) {
			struct swap_extent *se;

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

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				spin_unlock(&swap_lock);
				bdput(bdev);
				return i;
			}
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		}
	}
	spin_unlock(&swap_lock);
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	if (bdev)
		bdput(bdev);

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	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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/*
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 * 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.
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 */
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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)
{
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	spinlock_t *ptl;
	pte_t *pte;
	int ret = 1;

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	if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
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		ret = -ENOMEM;

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
		if (ret > 0)
			mem_cgroup_uncharge_page(page);
		ret = 0;
		goto out;
	}
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	inc_mm_counter(vma->vm_mm, anon_rss);
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	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);
	swap_free(entry);
	/*
	 * Move the page to the active list so it is not
	 * immediately swapped out again after swapon.
	 */
	activate_page(page);
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out:
	pte_unmap_unlock(pte, ptl);
	return ret;
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}

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);
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	pte_t *pte;
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	int ret = 0;
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	/*
	 * 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))) {
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			pte_unmap(pte);
			ret = unuse_pte(vma, pmd, addr, entry, page);
			if (ret)
				goto out;
			pte = pte_offset_map(pmd, addr);
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		}
	} while (pte++, addr += PAGE_SIZE, addr != end);
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	pte_unmap(pte - 1);
out:
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	return ret;
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}

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;
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	int ret;
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	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd))
			continue;
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		ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
		if (ret)
			return ret;
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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;
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	int ret;
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	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
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		ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
		if (ret)
			return ret;
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	} 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;
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	int ret;
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	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;
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		ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
		if (ret)
			return ret;
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	} 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;
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	int ret = 0;
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	if (!down_read_trylock(&mm->mmap_sem)) {
		/*
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		 * Activate page so shrink_inactive_list is unlikely to unmap
		 * its ptes while lock is dropped, so swapoff can make progress.
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		 */
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		activate_page(page);
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		unlock_page(page);
		down_read(&mm->mmap_sem);
		lock_page(page);
	}
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
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		if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
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			break;
	}
	up_read(&mm->mmap_sem);
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	return (ret < 0)? ret: 0;
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}

/*
 * Scan swap_map from current position to next entry still in use.
 * Recycle to start on reaching the end, returning 0 when empty.
 */
657 658
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
					unsigned int prev)
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{
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	unsigned int max = si->max;
	unsigned int i = prev;
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	int count;

	/*
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	 * No need for swap_lock here: we're just looking
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	 * for whether an entry is in use, not modifying it; false
	 * hits are okay, and sys_swapoff() has already prevented new
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	 * allocations from this area (while holding swap_lock).
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	 */
	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];
		if (count && count != SWAP_MAP_BAD)
			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;
704
	unsigned int i = 0;
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	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;
		}

		/* 
		 * Get a page for the entry, using the existing swap
		 * cache page if there is one.  Otherwise, get a clean
		 * page and read the swap into it. 
		 */
		swap_map = &si->swap_map[i];
		entry = swp_entry(type, i);
745 746
		page = read_swap_cache_async(entry,
					GFP_HIGHUSER_MOVABLE, NULL, 0);
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		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;
		if (swcount > 1) {
			if (start_mm == &init_mm)
				shmem = shmem_unuse(entry, page);
			else
				retval = unuse_mm(start_mm, entry, page);
		}
		if (*swap_map > 1) {
			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);
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			while (*swap_map > 1 && !retval && !shmem &&
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					(p = p->next) != &start_mm->mmlist) {
				mm = list_entry(p, struct mm_struct, mmlist);
808
				if (!atomic_inc_not_zero(&mm->mm_users))
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					continue;
				spin_unlock(&mmlist_lock);
				mmput(prev_mm);
				prev_mm = mm;

				cond_resched();

				swcount = *swap_map;
				if (swcount <= 1)
					;
				else if (mm == &init_mm) {
					set_start_mm = 1;
					shmem = shmem_unuse(entry, page);
				} else
					retval = unuse_mm(mm, entry, page);
				if (set_start_mm && *swap_map < swcount) {
					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;
		}
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		if (shmem) {
			/* page has already been unlocked and released */
			if (shmem > 0)
				continue;
			retval = shmem;
			break;
		}
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		if (retval) {
			unlock_page(page);
			page_cache_release(page);
			break;
		}

		/*
		 * How could swap count reach 0x7fff when the maximum
		 * pid is 0x7fff, and 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 in Linux 2.4.
		 *
		 * 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.
		 */
		if (*swap_map == SWAP_MAP_MAX) {
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			spin_lock(&swap_lock);
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			*swap_map = 1;
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			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.
		 */
		if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
			struct writeback_control wbc = {
				.sync_mode = WB_SYNC_NONE,
			};

			swap_writepage(page, &wbc);
			lock_page(page);
			wait_on_page_writeback(page);
		}
892 893 894 895 896 897 898 899 900 901

		/*
		 * 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))
902
			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
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		 * mark page dirty so shrink_page_list will preserve it.
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		 */
		SetPageDirty(page);
		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;
}

/*
929 930 931
 * 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);
		}
964
		lh = se->list.next;
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		if (lh == &sis->extent_list)
966
			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 */
	}
}

973
#ifdef CONFIG_HIBERNATION
974 975 976 977 978 979 980 981 982 983 984 985 986 987
/*
 * 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;
}
988
#endif /* CONFIG_HIBERNATION */
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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
1007
 * extent list.  The extent list is kept sorted in page order.
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 *
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 * 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;

1019 1020
	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);
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		BUG_ON(se->start_page + se->nr_pages != start_page);
		if (se->start_block + se->nr_pages == start_block) {
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			/* 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;

1040
	list_add_tail(&new_se->list, &sis->extent_list);
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	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.
 *
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 * 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.
 */
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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;
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	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);
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		*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;
			}
		}

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		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
		 */
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		ret = add_swap_extent(sis, page_no, 1, first_block);
		if (ret < 0)
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			goto out;
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		nr_extents += ret;
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		page_no++;
		probe_block += blocks_per_page;
reprobe:
		continue;
	}
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	ret = nr_extents;
	*span = 1 + highest_block - lowest_block;
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	if (page_no == 0)
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		page_no = 1;	/* force Empty message */
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	sis->max = page_no;
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	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;
}

#if 0	/* We don't need this yet */
#include <linux/backing-dev.h>
int page_queue_congested(struct page *page)
{
	struct backing_dev_info *bdi;

1180
	VM_BUG_ON(!PageLocked(page));	/* It pins the swap_info_struct */
L
Linus Torvalds 已提交
1181 1182

	if (PageSwapCache(page)) {
H
Hugh Dickins 已提交
1183
		swp_entry_t entry = { .val = page_private(page) };
L
Linus Torvalds 已提交
1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220
		struct swap_info_struct *sis;

		sis = get_swap_info_struct(swp_type(entry));
		bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
	} else
		bdi = page->mapping->backing_dev_info;
	return bdi_write_congested(bdi);
}
#endif

asmlinkage long sys_swapoff(const char __user * specialfile)
{
	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;
	
	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;
1221
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1222 1223 1224 1225 1226 1227 1228 1229 1230 1231
	for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
		p = swap_info + type;
		if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
			if (p->swap_file->f_mapping == mapping)
				break;
		}
		prev = type;
	}
	if (type < 0) {
		err = -EINVAL;
1232
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1233 1234 1235 1236 1237 1238
		goto out_dput;
	}
	if (!security_vm_enough_memory(p->pages))
		vm_unacct_memory(p->pages);
	else {
		err = -ENOMEM;
1239
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250
		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;
	}
1251 1252 1253 1254 1255
	if (p->prio < 0) {
		for (i = p->next; i >= 0; i = swap_info[i].next)
			swap_info[i].prio = p->prio--;
		least_priority++;
	}
L
Linus Torvalds 已提交
1256 1257 1258
	nr_swap_pages -= p->pages;
	total_swap_pages -= p->pages;
	p->flags &= ~SWP_WRITEOK;
1259
	spin_unlock(&swap_lock);
1260

L
Linus Torvalds 已提交
1261 1262 1263 1264 1265 1266
	current->flags |= PF_SWAPOFF;
	err = try_to_unuse(type);
	current->flags &= ~PF_SWAPOFF;

	if (err) {
		/* re-insert swap space back into swap_list */
1267
		spin_lock(&swap_lock);
1268 1269 1270 1271
		if (p->prio < 0)
			p->prio = --least_priority;
		prev = -1;
		for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
L
Linus Torvalds 已提交
1272 1273
			if (p->prio >= swap_info[i].prio)
				break;
1274 1275
			prev = i;
		}
L
Linus Torvalds 已提交
1276 1277 1278 1279 1280 1281 1282 1283
		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;
1284
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1285 1286
		goto out_dput;
	}
1287 1288 1289 1290 1291

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

1292
	destroy_swap_extents(p);
I
Ingo Molnar 已提交
1293
	mutex_lock(&swapon_mutex);
1294 1295 1296
	spin_lock(&swap_lock);
	drain_mmlist();

1297 1298 1299
	/* wait for anyone still in scan_swap_map */
	p->highest_bit = 0;		/* cuts scans short */
	while (p->flags >= SWP_SCANNING) {
1300
		spin_unlock(&swap_lock);
1301
		schedule_timeout_uninterruptible(1);
1302
		spin_lock(&swap_lock);
1303 1304
	}

L
Linus Torvalds 已提交
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	swap_file = p->swap_file;
	p->swap_file = NULL;
	p->max = 0;
	swap_map = p->swap_map;
	p->swap_map = NULL;
	p->flags = 0;
1311
	spin_unlock(&swap_lock);
I
Ingo Molnar 已提交
1312
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1313 1314 1315 1316 1317 1318 1319
	vfree(swap_map);
	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 {
1320
		mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
1321
		inode->i_flags &= ~S_SWAPFILE;
1322
		mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
	}
	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;

I
Ingo Molnar 已提交
1341
	mutex_lock(&swapon_mutex);
L
Linus Torvalds 已提交
1342

1343 1344 1345
	if (!l)
		return SEQ_START_TOKEN;

L
Linus Torvalds 已提交
1346 1347 1348
	for (i = 0; i < nr_swapfiles; i++, ptr++) {
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
1349
		if (!--l)
L
Linus Torvalds 已提交
1350 1351 1352 1353 1354 1355 1356 1357
			return ptr;
	}

	return NULL;
}

static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
{
1358
	struct swap_info_struct *ptr;
L
Linus Torvalds 已提交
1359 1360
	struct swap_info_struct *endptr = swap_info + nr_swapfiles;

1361 1362 1363 1364 1365 1366 1367 1368
	if (v == SEQ_START_TOKEN)
		ptr = swap_info;
	else {
		ptr = v;
		ptr++;
	}

	for (; ptr < endptr; ptr++) {
L
Linus Torvalds 已提交
1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379
		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
1380
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1381 1382 1383 1384 1385 1386 1387 1388
}

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

1389 1390 1391 1392
	if (ptr == SEQ_START_TOKEN) {
		seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
		return 0;
	}
L
Linus Torvalds 已提交
1393 1394

	file = ptr->swap_file;
1395
	len = seq_path(swap, &file->f_path, " \t\n\\");
1396
	seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
L
Linus Torvalds 已提交
1397
		       len < 40 ? 40 - len : 1, " ",
1398
		       S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
L
Linus Torvalds 已提交
1399 1400 1401 1402 1403 1404 1405
				"partition" : "file\t",
		       ptr->pages << (PAGE_SHIFT - 10),
		       ptr->inuse_pages << (PAGE_SHIFT - 10),
		       ptr->prio);
	return 0;
}

1406
static const struct seq_operations swaps_op = {
L
Linus Torvalds 已提交
1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417
	.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);
}

1418
static const struct file_operations proc_swaps_operations = {
L
Linus Torvalds 已提交
1419 1420 1421 1422 1423 1424 1425 1426
	.open		= swaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int __init procswaps_init(void)
{
1427
	proc_create("swaps", 0, NULL, &proc_swaps_operations);
L
Linus Torvalds 已提交
1428 1429 1430 1431 1432
	return 0;
}
__initcall(procswaps_init);
#endif /* CONFIG_PROC_FS */

J
Jan Beulich 已提交
1433 1434 1435 1436 1437 1438 1439 1440 1441
#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
1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458
/*
 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
 *
 * The swapon system call
 */
asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
{
	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;
	int swap_header_version;
1459 1460
	unsigned int nr_good_pages = 0;
	int nr_extents = 0;
1461
	sector_t span;
L
Linus Torvalds 已提交
1462 1463
	unsigned long maxpages = 1;
	int swapfilesize;
1464
	unsigned short *swap_map = NULL;
L
Linus Torvalds 已提交
1465 1466 1467 1468 1469 1470
	struct page *page = NULL;
	struct inode *inode = NULL;
	int did_down = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
1471
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1472 1473 1474 1475 1476
	p = swap_info;
	for (type = 0 ; type < nr_swapfiles ; type++,p++)
		if (!(p->flags & SWP_USED))
			break;
	error = -EPERM;
1477
	if (type >= MAX_SWAPFILES) {
1478
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1479 1480 1481 1482
		goto out;
	}
	if (type >= nr_swapfiles)
		nr_swapfiles = type+1;
1483
	memset(p, 0, sizeof(*p));
L
Linus Torvalds 已提交
1484 1485 1486
	INIT_LIST_HEAD(&p->extent_list);
	p->flags = SWP_USED;
	p->next = -1;
1487
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520
	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
1521
			error = -EINVAL;
L
Linus Torvalds 已提交
1522 1523 1524 1525 1526 1527 1528 1529 1530
			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;
1531
		mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549
		did_down = 1;
		if (IS_SWAPFILE(inode)) {
			error = -EBUSY;
			goto bad_swap;
		}
	} else {
		goto bad_swap;
	}

	swapfilesize = i_size_read(inode) >> PAGE_SHIFT;

	/*
	 * Read the swap header.
	 */
	if (!mapping->a_ops->readpage) {
		error = -EINVAL;
		goto bad_swap;
	}
1550
	page = read_mapping_page(mapping, 0, swap_file);
L
Linus Torvalds 已提交
1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562
	if (IS_ERR(page)) {
		error = PTR_ERR(page);
		goto bad_swap;
	}
	kmap(page);
	swap_header = page_address(page);

	if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
		swap_header_version = 1;
	else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
		swap_header_version = 2;
	else {
1563
		printk(KERN_ERR "Unable to find swap-space signature\n");
L
Linus Torvalds 已提交
1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574
		error = -EINVAL;
		goto bad_swap;
	}
	
	switch (swap_header_version) {
	case 1:
		printk(KERN_ERR "version 0 swap is no longer supported. "
			"Use mkswap -v1 %s\n", name);
		error = -EINVAL;
		goto bad_swap;
	case 2:
1575 1576 1577 1578 1579 1580 1581 1582
		/* 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]);
		}
L
Linus Torvalds 已提交
1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593
		/* Check the swap header's sub-version and the size of
                   the swap file and bad block lists */
		if (swap_header->info.version != 1) {
			printk(KERN_WARNING
			       "Unable to handle swap header version %d\n",
			       swap_header->info.version);
			error = -EINVAL;
			goto bad_swap;
		}

		p->lowest_bit  = 1;
1594 1595
		p->cluster_next = 1;

L
Linus Torvalds 已提交
1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615
		/*
		 * 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;

		error = -EINVAL;
1616 1617
		if (!maxpages)
			goto bad_swap;
1618 1619 1620 1621 1622
		if (swapfilesize && maxpages > swapfilesize) {
			printk(KERN_WARNING
			       "Swap area shorter than signature indicates\n");
			goto bad_swap;
		}
1623 1624
		if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
			goto bad_swap;
L
Linus Torvalds 已提交
1625 1626
		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
			goto bad_swap;
1627

L
Linus Torvalds 已提交
1628
		/* OK, set up the swap map and apply the bad block list */
1629 1630
		swap_map = vmalloc(maxpages * sizeof(short));
		if (!swap_map) {
L
Linus Torvalds 已提交
1631 1632 1633 1634 1635
			error = -ENOMEM;
			goto bad_swap;
		}

		error = 0;
1636
		memset(swap_map, 0, maxpages * sizeof(short));
1637 1638 1639
		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)
L
Linus Torvalds 已提交
1640 1641
				error = -EINVAL;
			else
1642
				swap_map[page_nr] = SWAP_MAP_BAD;
L
Linus Torvalds 已提交
1643 1644 1645 1646
		}
		nr_good_pages = swap_header->info.last_page -
				swap_header->info.nr_badpages -
				1 /* header page */;
1647
		if (error)
L
Linus Torvalds 已提交
1648 1649
			goto bad_swap;
	}
1650 1651

	if (nr_good_pages) {
1652
		swap_map[0] = SWAP_MAP_BAD;
1653 1654
		p->max = maxpages;
		p->pages = nr_good_pages;
1655 1656 1657
		nr_extents = setup_swap_extents(p, &span);
		if (nr_extents < 0) {
			error = nr_extents;
1658
			goto bad_swap;
1659
		}
1660 1661
		nr_good_pages = p->pages;
	}
L
Linus Torvalds 已提交
1662 1663 1664 1665 1666 1667
	if (!nr_good_pages) {
		printk(KERN_WARNING "Empty swap-file\n");
		error = -EINVAL;
		goto bad_swap;
	}

I
Ingo Molnar 已提交
1668
	mutex_lock(&swapon_mutex);
1669
	spin_lock(&swap_lock);
1670 1671 1672 1673 1674 1675
	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;
L
Linus Torvalds 已提交
1676 1677 1678
	p->flags = SWP_ACTIVE;
	nr_swap_pages += nr_good_pages;
	total_swap_pages += nr_good_pages;
1679

1680
	printk(KERN_INFO "Adding %uk swap on %s.  "
1681 1682 1683
			"Priority:%d extents:%d across:%lluk\n",
		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
L
Linus Torvalds 已提交
1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698

	/* 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;
	}
1699
	spin_unlock(&swap_lock);
I
Ingo Molnar 已提交
1700
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1701 1702 1703 1704 1705 1706 1707
	error = 0;
	goto out;
bad_swap:
	if (bdev) {
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	}
1708
	destroy_swap_extents(p);
L
Linus Torvalds 已提交
1709
bad_swap_2:
1710
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1711 1712
	p->swap_file = NULL;
	p->flags = 0;
1713
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726
	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;
1727
		mutex_unlock(&inode->i_mutex);
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	}
	return error;
}

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

1737
	spin_lock(&swap_lock);
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	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;
1746
	spin_unlock(&swap_lock);
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}

/*
 * 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.
 */
int swap_duplicate(swp_entry_t entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;
	int result = 0;

1761 1762 1763
	if (is_migration_entry(entry))
		return 1;

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	type = swp_type(entry);
	if (type >= nr_swapfiles)
		goto bad_file;
	p = type + swap_info;
	offset = swp_offset(entry);

1770
	spin_lock(&swap_lock);
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	if (offset < p->max && p->swap_map[offset]) {
		if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
			p->swap_map[offset]++;
			result = 1;
		} else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
			if (swap_overflow++ < 5)
				printk(KERN_WARNING "swap_dup: swap entry overflow\n");
			p->swap_map[offset] = SWAP_MAP_MAX;
			result = 1;
		}
	}
1782
	spin_unlock(&swap_lock);
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out:
	return result;

bad_file:
	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
	goto out;
}

struct swap_info_struct *
get_swap_info_struct(unsigned type)
{
	return &swap_info[type];
}

/*
1798
 * swap_lock prevents swap_map being freed. Don't grab an extra
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 * reference on the swaphandle, it doesn't matter if it becomes unused.
 */
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
1803
	struct swap_info_struct *si;
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1804
	int our_page_cluster = page_cluster;
1805 1806 1807
	pgoff_t target, toff;
	pgoff_t base, end;
	int nr_pages = 0;
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1808

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Hugh Dickins 已提交
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	if (!our_page_cluster)	/* no readahead */
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1810
		return 0;
1811 1812 1813 1814 1815 1816 1817

	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++;
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1819
	spin_lock(&swap_lock);
1820 1821 1822 1823 1824 1825 1826 1827 1828
	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;
		if (si->swap_map[toff] == SWAP_MAP_BAD)
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			break;
1830 1831 1832
	}
	/* Count contiguous allocated slots below our target */
	for (toff = target; --toff >= base; nr_pages++) {
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		/* Don't read in free or bad pages */
1834
		if (!si->swap_map[toff])
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1835
			break;
1836
		if (si->swap_map[toff] == SWAP_MAP_BAD)
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1837
			break;
1838
	}
1839
	spin_unlock(&swap_lock);
1840 1841 1842 1843 1844 1845 1846

	/*
	 * 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;
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}