swapfile.c 41.9 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/config.h>
#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>
#include <linux/syscalls.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <linux/swapops.h>

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DEFINE_SPINLOCK(swap_lock);
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unsigned int nr_swapfiles;
long total_swap_pages;
static int swap_overflow;

EXPORT_SYMBOL(total_swap_pages);

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 ";

struct swap_list_t swap_list = {-1, -1};

struct swap_info_struct swap_info[MAX_SWAPFILES];

static DECLARE_MUTEX(swapon_sem);

/*
 * 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 semaphore.
 */
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);
	entry.val = page->private;
	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
		 * count to avoid reading garbage from page->private above. If
		 * the WARN_ON triggers during a swapoff it maybe the race
		 * 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;
				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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}

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;

	entry.val = page->private;
	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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}

/*
 * We can use this swap cache entry directly
 * if there are no other references to it.
 */
int can_share_swap_page(struct page *page)
{
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	int count;

	BUG_ON(!PageLocked(page));
	count = page_mapcount(page);
	if (count <= 1 && PageSwapCache(page))
		count += page_swapcount(page);
	return count == 1;
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}

/*
 * Work out if there are any other processes sharing this
 * swap cache page. Free it if you can. Return success.
 */
int remove_exclusive_swap_page(struct page *page)
{
	int retval;
	struct swap_info_struct * p;
	swp_entry_t entry;

	BUG_ON(PagePrivate(page));
	BUG_ON(!PageLocked(page));

	if (!PageSwapCache(page))
		return 0;
	if (PageWriteback(page))
		return 0;
	if (page_count(page) != 2) /* 2: us + cache */
		return 0;

	entry.val = page->private;
	p = swap_info_get(entry);
	if (!p)
		return 0;

	/* Is the only swap cache user the cache itself? */
	retval = 0;
	if (p->swap_map[swp_offset(entry)] == 1) {
		/* Recheck the page count with the swapcache lock held.. */
		write_lock_irq(&swapper_space.tree_lock);
		if ((page_count(page) == 2) && !PageWriteback(page)) {
			__delete_from_swap_cache(page);
			SetPageDirty(page);
			retval = 1;
		}
		write_unlock_irq(&swapper_space.tree_lock);
	}
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	spin_unlock(&swap_lock);
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	if (retval) {
		swap_free(entry);
		page_cache_release(page);
	}

	return retval;
}

/*
 * 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;

	p = swap_info_get(entry);
	if (p) {
		if (swap_entry_free(p, swp_offset(entry)) == 1)
			page = find_trylock_page(&swapper_space, entry.val);
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		spin_unlock(&swap_lock);
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	}
	if (page) {
		int one_user;

		BUG_ON(PagePrivate(page));
		page_cache_get(page);
		one_user = (page_count(page) == 2);
		/* Only cache user (+us), or swap space full? Free it! */
		if (!PageWriteback(page) && (one_user || vm_swap_full())) {
			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
		unlock_page(page);
		page_cache_release(page);
	}
}

/*
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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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 *
 * vma->vm_mm->page_table_lock is held.
 */
static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
		unsigned long addr, swp_entry_t entry, struct page *page)
{
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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);
}

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 *pte;
	pte_t swp_pte = swp_entry_to_pte(entry);

	pte = pte_offset_map(pmd, addr);
	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))) {
			unuse_pte(vma, pte, addr, entry, page);
			pte_unmap(pte);
			return 1;
		}
	} while (pte++, addr += PAGE_SIZE, addr != end);
	pte_unmap(pte - 1);
	return 0;
}

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;

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd))
			continue;
		if (unuse_pte_range(vma, pmd, addr, next, entry, page))
			return 1;
	} 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;

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
		if (unuse_pmd_range(vma, pud, addr, next, entry, page))
			return 1;
	} 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;

	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;
		if (unuse_pud_range(vma, pgd, addr, next, entry, page))
			return 1;
	} 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;

	if (!down_read_trylock(&mm->mmap_sem)) {
		/*
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		 * Activate page so shrink_cache 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);
	}
	spin_lock(&mm->page_table_lock);
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
		if (vma->anon_vma && unuse_vma(vma, entry, page))
			break;
	}
	spin_unlock(&mm->page_table_lock);
	up_read(&mm->mmap_sem);
	/*
	 * Currently unuse_mm cannot fail, but leave error handling
	 * at call sites for now, since we change it from time to time.
	 */
	return 0;
}

/*
 * Scan swap_map from current position to next entry still in use.
 * Recycle to start on reaching the end, returning 0 when empty.
 */
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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;
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	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);
		page = read_swap_cache_async(entry, NULL, 0);
		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);
			while (*swap_map > 1 && !retval &&
					(p = p->next) != &start_mm->mmlist) {
				mm = list_entry(p, struct mm_struct, mmlist);
				if (atomic_inc_return(&mm->mm_users) == 1) {
					atomic_dec(&mm->mm_users);
					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;
		}
		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) {
744
			spin_lock(&swap_lock);
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			*swap_map = 1;
746
			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.
		 *
		 * Note shmem_unuse already deleted a swappage from
		 * the swap cache, unless the move to filepage failed:
		 * in which case it left swappage in cache, lowered its
		 * swap count to pass quickly through the loops above,
		 * and now we must reincrement count to try again later.
		 */
		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);
		}
		if (PageSwapCache(page)) {
			if (shmem)
				swap_duplicate(entry);
			else
				delete_from_swap_cache(page);
		}

		/*
		 * So we could skip searching mms once swap count went
		 * to 1, we did not mark any present ptes as dirty: must
		 * mark page dirty so shrink_list will preserve it.
		 */
		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;
}

/*
810 811 812
 * 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);
		}
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		lh = se->list.next;
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		if (lh == &sis->extent_list)
847
			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 */
	}
}

/*
 * 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
871
 * 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;

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	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;

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	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;
1014
		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;

	BUG_ON(!PageLocked(page));	/* It pins the swap_info_struct */

	if (PageSwapCache(page)) {
		swp_entry_t entry = { .val = page->private };
		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;
1085
	spin_lock(&swap_lock);
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	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;
1096
		spin_unlock(&swap_lock);
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		goto out_dput;
	}
	if (!security_vm_enough_memory(p->pages))
		vm_unacct_memory(p->pages);
	else {
		err = -ENOMEM;
1103
		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;
	}
	nr_swap_pages -= p->pages;
	total_swap_pages -= p->pages;
	p->flags &= ~SWP_WRITEOK;
1118
	spin_unlock(&swap_lock);
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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 */
1126
		spin_lock(&swap_lock);
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		for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
			if (p->prio >= swap_info[i].prio)
				break;
		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;
1138
		spin_unlock(&swap_lock);
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		goto out_dput;
	}
1141 1142 1143 1144 1145

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

1146 1147 1148 1149 1150
	destroy_swap_extents(p);
	down(&swapon_sem);
	spin_lock(&swap_lock);
	drain_mmlist();

1151 1152 1153
	/* wait for anyone still in scan_swap_map */
	p->highest_bit = 0;		/* cuts scans short */
	while (p->flags >= SWP_SCANNING) {
1154
		spin_unlock(&swap_lock);
1155
		schedule_timeout_uninterruptible(1);
1156
		spin_lock(&swap_lock);
1157 1158
	}

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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;
1165
	spin_unlock(&swap_lock);
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	up(&swapon_sem);
	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 {
		down(&inode->i_sem);
		inode->i_flags &= ~S_SWAPFILE;
		up(&inode->i_sem);
	}
	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;

	down(&swapon_sem);

	for (i = 0; i < nr_swapfiles; i++, ptr++) {
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
		if (!l--)
			return ptr;
	}

	return NULL;
}

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

	for (++ptr; ptr < endptr; ptr++) {
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
		++*pos;
		return ptr;
	}

	return NULL;
}

static void swap_stop(struct seq_file *swap, void *v)
{
	up(&swapon_sem);
}

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

	if (v == swap_info)
		seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");

	file = ptr->swap_file;
	len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1238
	seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
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1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296
		       len < 40 ? 40 - len : 1, " ",
		       S_ISBLK(file->f_dentry->d_inode->i_mode) ?
				"partition" : "file\t",
		       ptr->pages << (PAGE_SHIFT - 10),
		       ptr->inuse_pages << (PAGE_SHIFT - 10),
		       ptr->prio);
	return 0;
}

static struct seq_operations swaps_op = {
	.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);
}

static struct file_operations proc_swaps_operations = {
	.open		= swaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int __init procswaps_init(void)
{
	struct proc_dir_entry *entry;

	entry = create_proc_entry("swaps", 0, NULL);
	if (entry)
		entry->proc_fops = &proc_swaps_operations;
	return 0;
}
__initcall(procswaps_init);
#endif /* CONFIG_PROC_FS */

/*
 * 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;
	static int least_priority;
	union swap_header *swap_header = NULL;
	int swap_header_version;
1297 1298
	unsigned int nr_good_pages = 0;
	int nr_extents = 0;
1299
	sector_t span;
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	unsigned long maxpages = 1;
	int swapfilesize;
	unsigned short *swap_map;
	struct page *page = NULL;
	struct inode *inode = NULL;
	int did_down = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
1309
	spin_lock(&swap_lock);
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	p = swap_info;
	for (type = 0 ; type < nr_swapfiles ; type++,p++)
		if (!(p->flags & SWP_USED))
			break;
	error = -EPERM;
	/*
	 * Test if adding another swap device is possible. There are
	 * two limiting factors: 1) the number of bits for the swap
	 * type swp_entry_t definition and 2) the number of bits for
	 * the swap type in the swap ptes as defined by the different
	 * architectures. To honor both limitations a swap entry
	 * with swap offset 0 and swap type ~0UL is created, encoded
	 * to a swap pte, decoded to a swp_entry_t again and finally
	 * the swap type part is extracted. This will mask all bits
	 * from the initial ~0UL that can't be encoded in either the
	 * swp_entry_t or the architecture definition of a swap pte.
	 */
	if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1328
		spin_unlock(&swap_lock);
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		goto out;
	}
	if (type >= nr_swapfiles)
		nr_swapfiles = type+1;
	INIT_LIST_HEAD(&p->extent_list);
	p->flags = SWP_USED;
	p->swap_file = NULL;
	p->old_block_size = 0;
	p->swap_map = NULL;
	p->lowest_bit = 0;
	p->highest_bit = 0;
	p->cluster_nr = 0;
	p->inuse_pages = 0;
	p->next = -1;
	if (swap_flags & SWAP_FLAG_PREFER) {
		p->prio =
		  (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
	} else {
		p->prio = --least_priority;
	}
1349
	spin_unlock(&swap_lock);
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	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;
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			error = -EINVAL;
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1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451
			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;
		down(&inode->i_sem);
		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;
	}
	page = read_cache_page(mapping, 0,
			(filler_t *)mapping->a_ops->readpage, swap_file);
	if (IS_ERR(page)) {
		error = PTR_ERR(page);
		goto bad_swap;
	}
	wait_on_page_locked(page);
	if (!PageUptodate(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 {
		printk("Unable to find swap-space signature\n");
		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:
		/* 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;
1452 1453
		p->cluster_next = 1;

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1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473
		/*
		 * 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;
1474 1475 1476 1477
		if (!maxpages)
			goto bad_swap;
		if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
			goto bad_swap;
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1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501
		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
			goto bad_swap;
		
		/* OK, set up the swap map and apply the bad block list */
		if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
			error = -ENOMEM;
			goto bad_swap;
		}

		error = 0;
		memset(p->swap_map, 0, maxpages * sizeof(short));
		for (i=0; i<swap_header->info.nr_badpages; i++) {
			int page = swap_header->info.badpages[i];
			if (page <= 0 || page >= swap_header->info.last_page)
				error = -EINVAL;
			else
				p->swap_map[page] = SWAP_MAP_BAD;
		}
		nr_good_pages = swap_header->info.last_page -
				swap_header->info.nr_badpages -
				1 /* header page */;
		if (error) 
			goto bad_swap;
	}
1502

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1503 1504 1505 1506 1507 1508
	if (swapfilesize && maxpages > swapfilesize) {
		printk(KERN_WARNING
		       "Swap area shorter than signature indicates\n");
		error = -EINVAL;
		goto bad_swap;
	}
1509 1510 1511 1512
	if (nr_good_pages) {
		p->swap_map[0] = SWAP_MAP_BAD;
		p->max = maxpages;
		p->pages = nr_good_pages;
1513 1514 1515
		nr_extents = setup_swap_extents(p, &span);
		if (nr_extents < 0) {
			error = nr_extents;
1516
			goto bad_swap;
1517
		}
1518 1519
		nr_good_pages = p->pages;
	}
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	if (!nr_good_pages) {
		printk(KERN_WARNING "Empty swap-file\n");
		error = -EINVAL;
		goto bad_swap;
	}

	down(&swapon_sem);
1527
	spin_lock(&swap_lock);
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1528 1529 1530
	p->flags = SWP_ACTIVE;
	nr_swap_pages += nr_good_pages;
	total_swap_pages += nr_good_pages;
1531

1532
	printk(KERN_INFO "Adding %uk swap on %s.  "
1533 1534 1535
			"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));
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	/* 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;
	}
1551
	spin_unlock(&swap_lock);
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1552 1553 1554 1555 1556 1557 1558 1559
	up(&swapon_sem);
	error = 0;
	goto out;
bad_swap:
	if (bdev) {
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	}
1560
	destroy_swap_extents(p);
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bad_swap_2:
1562
	spin_lock(&swap_lock);
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1563 1564 1565 1566 1567 1568
	swap_map = p->swap_map;
	p->swap_file = NULL;
	p->swap_map = NULL;
	p->flags = 0;
	if (!(swap_flags & SWAP_FLAG_PREFER))
		++least_priority;
1569
	spin_unlock(&swap_lock);
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1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592
	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;
		up(&inode->i_sem);
	}
	return error;
}

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

1593
	spin_lock(&swap_lock);
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1594 1595 1596 1597 1598 1599 1600 1601
	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;
1602
	spin_unlock(&swap_lock);
L
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1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622
}

/*
 * 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;

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

1623
	spin_lock(&swap_lock);
L
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1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634
	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;
		}
	}
1635
	spin_unlock(&swap_lock);
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1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
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];
}

/*
1651
 * swap_lock prevents swap_map being freed. Don't grab an extra
L
Linus Torvalds 已提交
1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666
 * reference on the swaphandle, it doesn't matter if it becomes unused.
 */
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
	int ret = 0, i = 1 << page_cluster;
	unsigned long toff;
	struct swap_info_struct *swapdev = swp_type(entry) + swap_info;

	if (!page_cluster)	/* no readahead */
		return 0;
	toff = (swp_offset(entry) >> page_cluster) << page_cluster;
	if (!toff)		/* first page is swap header */
		toff++, i--;
	*offset = toff;

1667
	spin_lock(&swap_lock);
L
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1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679
	do {
		/* Don't read-ahead past the end of the swap area */
		if (toff >= swapdev->max)
			break;
		/* Don't read in free or bad pages */
		if (!swapdev->swap_map[toff])
			break;
		if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
			break;
		toff++;
		ret++;
	} while (--i);
1680
	spin_unlock(&swap_lock);
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1681 1682
	return ret;
}