4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/hugetlb.h>
10 #include <linux/mman.h>
11 #include <linux/slab.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/swap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/pagemap.h>
16 #include <linux/namei.h>
17 #include <linux/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/writeback.h>
20 #include <linux/proc_fs.h>
21 #include <linux/seq_file.h>
22 #include <linux/init.h>
23 #include <linux/module.h>
24 #include <linux/rmap.h>
25 #include <linux/security.h>
26 #include <linux/backing-dev.h>
27 #include <linux/mutex.h>
28 #include <linux/capability.h>
29 #include <linux/syscalls.h>
30 #include <linux/memcontrol.h>
32 #include <asm/pgtable.h>
33 #include <asm/tlbflush.h>
34 #include <linux/swapops.h>
36 static DEFINE_SPINLOCK(swap_lock);
37 static unsigned int nr_swapfiles;
39 long total_swap_pages;
40 static int swap_overflow;
41 static int least_priority;
43 static const char Bad_file[] = "Bad swap file entry ";
44 static const char Unused_file[] = "Unused swap file entry ";
45 static const char Bad_offset[] = "Bad swap offset entry ";
46 static const char Unused_offset[] = "Unused swap offset entry ";
48 static struct swap_list_t swap_list = {-1, -1};
50 static struct swap_info_struct swap_info[MAX_SWAPFILES];
52 static DEFINE_MUTEX(swapon_mutex);
55 * We need this because the bdev->unplug_fn can sleep and we cannot
56 * hold swap_lock while calling the unplug_fn. And swap_lock
57 * cannot be turned into a mutex.
59 static DECLARE_RWSEM(swap_unplug_sem);
61 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
65 down_read(&swap_unplug_sem);
66 entry.val = page_private(page);
67 if (PageSwapCache(page)) {
68 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
69 struct backing_dev_info *bdi;
72 * If the page is removed from swapcache from under us (with a
73 * racy try_to_unuse/swapoff) we need an additional reference
74 * count to avoid reading garbage from page_private(page) above.
75 * If the WARN_ON triggers during a swapoff it maybe the race
76 * condition and it's harmless. However if it triggers without
77 * swapoff it signals a problem.
79 WARN_ON(page_count(page) <= 1);
81 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
82 blk_run_backing_dev(bdi, page);
84 up_read(&swap_unplug_sem);
87 #define SWAPFILE_CLUSTER 256
88 #define LATENCY_LIMIT 256
90 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
93 unsigned long last_in_cluster;
94 int latency_ration = LATENCY_LIMIT;
97 * We try to cluster swap pages by allocating them sequentially
98 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
99 * way, however, we resort to first-free allocation, starting
100 * a new cluster. This prevents us from scattering swap pages
101 * all over the entire swap partition, so that we reduce
102 * overall disk seek times between swap pages. -- sct
103 * But we do now try to find an empty cluster. -Andrea
106 si->flags += SWP_SCANNING;
107 offset = si->cluster_next;
109 if (unlikely(!si->cluster_nr--)) {
110 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
111 si->cluster_nr = SWAPFILE_CLUSTER - 1;
114 spin_unlock(&swap_lock);
116 offset = si->lowest_bit;
117 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
119 /* Locate the first empty (unaligned) cluster */
120 for (; last_in_cluster <= si->highest_bit; offset++) {
121 if (si->swap_map[offset])
122 last_in_cluster = offset + SWAPFILE_CLUSTER;
123 else if (offset == last_in_cluster) {
124 spin_lock(&swap_lock);
125 offset -= SWAPFILE_CLUSTER - 1;
126 si->cluster_next = offset;
127 si->cluster_nr = SWAPFILE_CLUSTER - 1;
130 if (unlikely(--latency_ration < 0)) {
132 latency_ration = LATENCY_LIMIT;
136 offset = si->lowest_bit;
137 spin_lock(&swap_lock);
138 si->cluster_nr = SWAPFILE_CLUSTER - 1;
142 if (!(si->flags & SWP_WRITEOK))
144 if (!si->highest_bit)
146 if (offset > si->highest_bit)
147 offset = si->lowest_bit;
148 if (si->swap_map[offset])
151 if (offset == si->lowest_bit)
153 if (offset == si->highest_bit)
156 if (si->inuse_pages == si->pages) {
157 si->lowest_bit = si->max;
160 si->swap_map[offset] = 1;
161 si->cluster_next = offset + 1;
162 si->flags -= SWP_SCANNING;
166 spin_unlock(&swap_lock);
167 while (++offset <= si->highest_bit) {
168 if (!si->swap_map[offset]) {
169 spin_lock(&swap_lock);
172 if (unlikely(--latency_ration < 0)) {
174 latency_ration = LATENCY_LIMIT;
177 spin_lock(&swap_lock);
181 si->flags -= SWP_SCANNING;
185 swp_entry_t get_swap_page(void)
187 struct swap_info_struct *si;
192 spin_lock(&swap_lock);
193 if (nr_swap_pages <= 0)
197 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
198 si = swap_info + type;
201 (!wrapped && si->prio != swap_info[next].prio)) {
202 next = swap_list.head;
206 if (!si->highest_bit)
208 if (!(si->flags & SWP_WRITEOK))
211 swap_list.next = next;
212 offset = scan_swap_map(si);
214 spin_unlock(&swap_lock);
215 return swp_entry(type, offset);
217 next = swap_list.next;
222 spin_unlock(&swap_lock);
223 return (swp_entry_t) {0};
226 swp_entry_t get_swap_page_of_type(int type)
228 struct swap_info_struct *si;
231 spin_lock(&swap_lock);
232 si = swap_info + type;
233 if (si->flags & SWP_WRITEOK) {
235 offset = scan_swap_map(si);
237 spin_unlock(&swap_lock);
238 return swp_entry(type, offset);
242 spin_unlock(&swap_lock);
243 return (swp_entry_t) {0};
246 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
248 struct swap_info_struct * p;
249 unsigned long offset, type;
253 type = swp_type(entry);
254 if (type >= nr_swapfiles)
256 p = & swap_info[type];
257 if (!(p->flags & SWP_USED))
259 offset = swp_offset(entry);
260 if (offset >= p->max)
262 if (!p->swap_map[offset])
264 spin_lock(&swap_lock);
268 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
271 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
274 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
277 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
282 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
284 int count = p->swap_map[offset];
286 if (count < SWAP_MAP_MAX) {
288 p->swap_map[offset] = count;
290 if (offset < p->lowest_bit)
291 p->lowest_bit = offset;
292 if (offset > p->highest_bit)
293 p->highest_bit = offset;
294 if (p->prio > swap_info[swap_list.next].prio)
295 swap_list.next = p - swap_info;
304 * Caller has made sure that the swapdevice corresponding to entry
305 * is still around or has not been recycled.
307 void swap_free(swp_entry_t entry)
309 struct swap_info_struct * p;
311 p = swap_info_get(entry);
313 swap_entry_free(p, swp_offset(entry));
314 spin_unlock(&swap_lock);
319 * How many references to page are currently swapped out?
321 static inline int page_swapcount(struct page *page)
324 struct swap_info_struct *p;
327 entry.val = page_private(page);
328 p = swap_info_get(entry);
330 /* Subtract the 1 for the swap cache itself */
331 count = p->swap_map[swp_offset(entry)] - 1;
332 spin_unlock(&swap_lock);
338 * We can write to an anon page without COW if there are no other references
339 * to it. And as a side-effect, free up its swap: because the old content
340 * on disk will never be read, and seeking back there to write new content
341 * later would only waste time away from clustering.
343 int reuse_swap_page(struct page *page)
347 VM_BUG_ON(!PageLocked(page));
348 count = page_mapcount(page);
349 if (count <= 1 && PageSwapCache(page)) {
350 count += page_swapcount(page);
351 if (count == 1 && !PageWriteback(page)) {
352 delete_from_swap_cache(page);
360 * If swap is getting full, or if there are no more mappings of this page,
361 * then try_to_free_swap is called to free its swap space.
363 int try_to_free_swap(struct page *page)
365 VM_BUG_ON(!PageLocked(page));
367 if (!PageSwapCache(page))
369 if (PageWriteback(page))
371 if (page_swapcount(page))
374 delete_from_swap_cache(page);
380 * Free the swap entry like above, but also try to
381 * free the page cache entry if it is the last user.
383 void free_swap_and_cache(swp_entry_t entry)
385 struct swap_info_struct * p;
386 struct page *page = NULL;
388 if (is_migration_entry(entry))
391 p = swap_info_get(entry);
393 if (swap_entry_free(p, swp_offset(entry)) == 1) {
394 page = find_get_page(&swapper_space, entry.val);
395 if (page && !trylock_page(page)) {
396 page_cache_release(page);
400 spin_unlock(&swap_lock);
404 * Not mapped elsewhere, or swap space full? Free it!
405 * Also recheck PageSwapCache now page is locked (above).
407 if (PageSwapCache(page) && !PageWriteback(page) &&
408 (!page_mapped(page) || vm_swap_full())) {
409 delete_from_swap_cache(page);
413 page_cache_release(page);
417 #ifdef CONFIG_HIBERNATION
419 * Find the swap type that corresponds to given device (if any).
421 * @offset - number of the PAGE_SIZE-sized block of the device, starting
422 * from 0, in which the swap header is expected to be located.
424 * This is needed for the suspend to disk (aka swsusp).
426 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
428 struct block_device *bdev = NULL;
432 bdev = bdget(device);
434 spin_lock(&swap_lock);
435 for (i = 0; i < nr_swapfiles; i++) {
436 struct swap_info_struct *sis = swap_info + i;
438 if (!(sis->flags & SWP_WRITEOK))
445 spin_unlock(&swap_lock);
448 if (bdev == sis->bdev) {
449 struct swap_extent *se;
451 se = list_entry(sis->extent_list.next,
452 struct swap_extent, list);
453 if (se->start_block == offset) {
457 spin_unlock(&swap_lock);
463 spin_unlock(&swap_lock);
471 * Return either the total number of swap pages of given type, or the number
472 * of free pages of that type (depending on @free)
474 * This is needed for software suspend
476 unsigned int count_swap_pages(int type, int free)
480 if (type < nr_swapfiles) {
481 spin_lock(&swap_lock);
482 if (swap_info[type].flags & SWP_WRITEOK) {
483 n = swap_info[type].pages;
485 n -= swap_info[type].inuse_pages;
487 spin_unlock(&swap_lock);
494 * No need to decide whether this PTE shares the swap entry with others,
495 * just let do_wp_page work it out if a write is requested later - to
496 * force COW, vm_page_prot omits write permission from any private vma.
498 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
499 unsigned long addr, swp_entry_t entry, struct page *page)
505 if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
508 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
509 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
511 mem_cgroup_uncharge_page(page);
516 inc_mm_counter(vma->vm_mm, anon_rss);
518 set_pte_at(vma->vm_mm, addr, pte,
519 pte_mkold(mk_pte(page, vma->vm_page_prot)));
520 page_add_anon_rmap(page, vma, addr);
523 * Move the page to the active list so it is not
524 * immediately swapped out again after swapon.
528 pte_unmap_unlock(pte, ptl);
532 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
533 unsigned long addr, unsigned long end,
534 swp_entry_t entry, struct page *page)
536 pte_t swp_pte = swp_entry_to_pte(entry);
541 * We don't actually need pte lock while scanning for swp_pte: since
542 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
543 * page table while we're scanning; though it could get zapped, and on
544 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
545 * of unmatched parts which look like swp_pte, so unuse_pte must
546 * recheck under pte lock. Scanning without pte lock lets it be
547 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
549 pte = pte_offset_map(pmd, addr);
552 * swapoff spends a _lot_ of time in this loop!
553 * Test inline before going to call unuse_pte.
555 if (unlikely(pte_same(*pte, swp_pte))) {
557 ret = unuse_pte(vma, pmd, addr, entry, page);
560 pte = pte_offset_map(pmd, addr);
562 } while (pte++, addr += PAGE_SIZE, addr != end);
568 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
569 unsigned long addr, unsigned long end,
570 swp_entry_t entry, struct page *page)
576 pmd = pmd_offset(pud, addr);
578 next = pmd_addr_end(addr, end);
579 if (pmd_none_or_clear_bad(pmd))
581 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
584 } while (pmd++, addr = next, addr != end);
588 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
589 unsigned long addr, unsigned long end,
590 swp_entry_t entry, struct page *page)
596 pud = pud_offset(pgd, addr);
598 next = pud_addr_end(addr, end);
599 if (pud_none_or_clear_bad(pud))
601 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
604 } while (pud++, addr = next, addr != end);
608 static int unuse_vma(struct vm_area_struct *vma,
609 swp_entry_t entry, struct page *page)
612 unsigned long addr, end, next;
616 addr = page_address_in_vma(page, vma);
620 end = addr + PAGE_SIZE;
622 addr = vma->vm_start;
626 pgd = pgd_offset(vma->vm_mm, addr);
628 next = pgd_addr_end(addr, end);
629 if (pgd_none_or_clear_bad(pgd))
631 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
634 } while (pgd++, addr = next, addr != end);
638 static int unuse_mm(struct mm_struct *mm,
639 swp_entry_t entry, struct page *page)
641 struct vm_area_struct *vma;
644 if (!down_read_trylock(&mm->mmap_sem)) {
646 * Activate page so shrink_inactive_list is unlikely to unmap
647 * its ptes while lock is dropped, so swapoff can make progress.
651 down_read(&mm->mmap_sem);
654 for (vma = mm->mmap; vma; vma = vma->vm_next) {
655 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
658 up_read(&mm->mmap_sem);
659 return (ret < 0)? ret: 0;
663 * Scan swap_map from current position to next entry still in use.
664 * Recycle to start on reaching the end, returning 0 when empty.
666 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
669 unsigned int max = si->max;
670 unsigned int i = prev;
674 * No need for swap_lock here: we're just looking
675 * for whether an entry is in use, not modifying it; false
676 * hits are okay, and sys_swapoff() has already prevented new
677 * allocations from this area (while holding swap_lock).
686 * No entries in use at top of swap_map,
687 * loop back to start and recheck there.
693 count = si->swap_map[i];
694 if (count && count != SWAP_MAP_BAD)
701 * We completely avoid races by reading each swap page in advance,
702 * and then search for the process using it. All the necessary
703 * page table adjustments can then be made atomically.
705 static int try_to_unuse(unsigned int type)
707 struct swap_info_struct * si = &swap_info[type];
708 struct mm_struct *start_mm;
709 unsigned short *swap_map;
710 unsigned short swcount;
715 int reset_overflow = 0;
719 * When searching mms for an entry, a good strategy is to
720 * start at the first mm we freed the previous entry from
721 * (though actually we don't notice whether we or coincidence
722 * freed the entry). Initialize this start_mm with a hold.
724 * A simpler strategy would be to start at the last mm we
725 * freed the previous entry from; but that would take less
726 * advantage of mmlist ordering, which clusters forked mms
727 * together, child after parent. If we race with dup_mmap(), we
728 * prefer to resolve parent before child, lest we miss entries
729 * duplicated after we scanned child: using last mm would invert
730 * that. Though it's only a serious concern when an overflowed
731 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
734 atomic_inc(&init_mm.mm_users);
737 * Keep on scanning until all entries have gone. Usually,
738 * one pass through swap_map is enough, but not necessarily:
739 * there are races when an instance of an entry might be missed.
741 while ((i = find_next_to_unuse(si, i)) != 0) {
742 if (signal_pending(current)) {
748 * Get a page for the entry, using the existing swap
749 * cache page if there is one. Otherwise, get a clean
750 * page and read the swap into it.
752 swap_map = &si->swap_map[i];
753 entry = swp_entry(type, i);
754 page = read_swap_cache_async(entry,
755 GFP_HIGHUSER_MOVABLE, NULL, 0);
758 * Either swap_duplicate() failed because entry
759 * has been freed independently, and will not be
760 * reused since sys_swapoff() already disabled
761 * allocation from here, or alloc_page() failed.
770 * Don't hold on to start_mm if it looks like exiting.
772 if (atomic_read(&start_mm->mm_users) == 1) {
775 atomic_inc(&init_mm.mm_users);
779 * Wait for and lock page. When do_swap_page races with
780 * try_to_unuse, do_swap_page can handle the fault much
781 * faster than try_to_unuse can locate the entry. This
782 * apparently redundant "wait_on_page_locked" lets try_to_unuse
783 * defer to do_swap_page in such a case - in some tests,
784 * do_swap_page and try_to_unuse repeatedly compete.
786 wait_on_page_locked(page);
787 wait_on_page_writeback(page);
789 wait_on_page_writeback(page);
792 * Remove all references to entry.
793 * Whenever we reach init_mm, there's no address space
794 * to search, but use it as a reminder to search shmem.
799 if (start_mm == &init_mm)
800 shmem = shmem_unuse(entry, page);
802 retval = unuse_mm(start_mm, entry, page);
805 int set_start_mm = (*swap_map >= swcount);
806 struct list_head *p = &start_mm->mmlist;
807 struct mm_struct *new_start_mm = start_mm;
808 struct mm_struct *prev_mm = start_mm;
809 struct mm_struct *mm;
811 atomic_inc(&new_start_mm->mm_users);
812 atomic_inc(&prev_mm->mm_users);
813 spin_lock(&mmlist_lock);
814 while (*swap_map > 1 && !retval && !shmem &&
815 (p = p->next) != &start_mm->mmlist) {
816 mm = list_entry(p, struct mm_struct, mmlist);
817 if (!atomic_inc_not_zero(&mm->mm_users))
819 spin_unlock(&mmlist_lock);
828 else if (mm == &init_mm) {
830 shmem = shmem_unuse(entry, page);
832 retval = unuse_mm(mm, entry, page);
833 if (set_start_mm && *swap_map < swcount) {
835 atomic_inc(&mm->mm_users);
839 spin_lock(&mmlist_lock);
841 spin_unlock(&mmlist_lock);
844 start_mm = new_start_mm;
847 /* page has already been unlocked and released */
855 page_cache_release(page);
860 * How could swap count reach 0x7fff when the maximum
861 * pid is 0x7fff, and there's no way to repeat a swap
862 * page within an mm (except in shmem, where it's the
863 * shared object which takes the reference count)?
864 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
866 * If that's wrong, then we should worry more about
867 * exit_mmap() and do_munmap() cases described above:
868 * we might be resetting SWAP_MAP_MAX too early here.
869 * We know "Undead"s can happen, they're okay, so don't
870 * report them; but do report if we reset SWAP_MAP_MAX.
872 if (*swap_map == SWAP_MAP_MAX) {
873 spin_lock(&swap_lock);
875 spin_unlock(&swap_lock);
880 * If a reference remains (rare), we would like to leave
881 * the page in the swap cache; but try_to_unmap could
882 * then re-duplicate the entry once we drop page lock,
883 * so we might loop indefinitely; also, that page could
884 * not be swapped out to other storage meanwhile. So:
885 * delete from cache even if there's another reference,
886 * after ensuring that the data has been saved to disk -
887 * since if the reference remains (rarer), it will be
888 * read from disk into another page. Splitting into two
889 * pages would be incorrect if swap supported "shared
890 * private" pages, but they are handled by tmpfs files.
892 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
893 struct writeback_control wbc = {
894 .sync_mode = WB_SYNC_NONE,
897 swap_writepage(page, &wbc);
899 wait_on_page_writeback(page);
903 * It is conceivable that a racing task removed this page from
904 * swap cache just before we acquired the page lock at the top,
905 * or while we dropped it in unuse_mm(). The page might even
906 * be back in swap cache on another swap area: that we must not
907 * delete, since it may not have been written out to swap yet.
909 if (PageSwapCache(page) &&
910 likely(page_private(page) == entry.val))
911 delete_from_swap_cache(page);
914 * So we could skip searching mms once swap count went
915 * to 1, we did not mark any present ptes as dirty: must
916 * mark page dirty so shrink_page_list will preserve it.
920 page_cache_release(page);
923 * Make sure that we aren't completely killing
924 * interactive performance.
930 if (reset_overflow) {
931 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
938 * After a successful try_to_unuse, if no swap is now in use, we know
939 * we can empty the mmlist. swap_lock must be held on entry and exit.
940 * Note that mmlist_lock nests inside swap_lock, and an mm must be
941 * added to the mmlist just after page_duplicate - before would be racy.
943 static void drain_mmlist(void)
945 struct list_head *p, *next;
948 for (i = 0; i < nr_swapfiles; i++)
949 if (swap_info[i].inuse_pages)
951 spin_lock(&mmlist_lock);
952 list_for_each_safe(p, next, &init_mm.mmlist)
954 spin_unlock(&mmlist_lock);
958 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
959 * corresponds to page offset `offset'.
961 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
963 struct swap_extent *se = sis->curr_swap_extent;
964 struct swap_extent *start_se = se;
967 struct list_head *lh;
969 if (se->start_page <= offset &&
970 offset < (se->start_page + se->nr_pages)) {
971 return se->start_block + (offset - se->start_page);
974 if (lh == &sis->extent_list)
976 se = list_entry(lh, struct swap_extent, list);
977 sis->curr_swap_extent = se;
978 BUG_ON(se == start_se); /* It *must* be present */
982 #ifdef CONFIG_HIBERNATION
984 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
985 * corresponding to given index in swap_info (swap type).
987 sector_t swapdev_block(int swap_type, pgoff_t offset)
989 struct swap_info_struct *sis;
991 if (swap_type >= nr_swapfiles)
994 sis = swap_info + swap_type;
995 return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
997 #endif /* CONFIG_HIBERNATION */
1000 * Free all of a swapdev's extent information
1002 static void destroy_swap_extents(struct swap_info_struct *sis)
1004 while (!list_empty(&sis->extent_list)) {
1005 struct swap_extent *se;
1007 se = list_entry(sis->extent_list.next,
1008 struct swap_extent, list);
1009 list_del(&se->list);
1015 * Add a block range (and the corresponding page range) into this swapdev's
1016 * extent list. The extent list is kept sorted in page order.
1018 * This function rather assumes that it is called in ascending page order.
1021 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1022 unsigned long nr_pages, sector_t start_block)
1024 struct swap_extent *se;
1025 struct swap_extent *new_se;
1026 struct list_head *lh;
1028 lh = sis->extent_list.prev; /* The highest page extent */
1029 if (lh != &sis->extent_list) {
1030 se = list_entry(lh, struct swap_extent, list);
1031 BUG_ON(se->start_page + se->nr_pages != start_page);
1032 if (se->start_block + se->nr_pages == start_block) {
1034 se->nr_pages += nr_pages;
1040 * No merge. Insert a new extent, preserving ordering.
1042 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1045 new_se->start_page = start_page;
1046 new_se->nr_pages = nr_pages;
1047 new_se->start_block = start_block;
1049 list_add_tail(&new_se->list, &sis->extent_list);
1054 * A `swap extent' is a simple thing which maps a contiguous range of pages
1055 * onto a contiguous range of disk blocks. An ordered list of swap extents
1056 * is built at swapon time and is then used at swap_writepage/swap_readpage
1057 * time for locating where on disk a page belongs.
1059 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1060 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1061 * swap files identically.
1063 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1064 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1065 * swapfiles are handled *identically* after swapon time.
1067 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1068 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1069 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1070 * requirements, they are simply tossed out - we will never use those blocks
1073 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1074 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1075 * which will scribble on the fs.
1077 * The amount of disk space which a single swap extent represents varies.
1078 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1079 * extents in the list. To avoid much list walking, we cache the previous
1080 * search location in `curr_swap_extent', and start new searches from there.
1081 * This is extremely effective. The average number of iterations in
1082 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1084 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1086 struct inode *inode;
1087 unsigned blocks_per_page;
1088 unsigned long page_no;
1090 sector_t probe_block;
1091 sector_t last_block;
1092 sector_t lowest_block = -1;
1093 sector_t highest_block = 0;
1097 inode = sis->swap_file->f_mapping->host;
1098 if (S_ISBLK(inode->i_mode)) {
1099 ret = add_swap_extent(sis, 0, sis->max, 0);
1104 blkbits = inode->i_blkbits;
1105 blocks_per_page = PAGE_SIZE >> blkbits;
1108 * Map all the blocks into the extent list. This code doesn't try
1113 last_block = i_size_read(inode) >> blkbits;
1114 while ((probe_block + blocks_per_page) <= last_block &&
1115 page_no < sis->max) {
1116 unsigned block_in_page;
1117 sector_t first_block;
1119 first_block = bmap(inode, probe_block);
1120 if (first_block == 0)
1124 * It must be PAGE_SIZE aligned on-disk
1126 if (first_block & (blocks_per_page - 1)) {
1131 for (block_in_page = 1; block_in_page < blocks_per_page;
1135 block = bmap(inode, probe_block + block_in_page);
1138 if (block != first_block + block_in_page) {
1145 first_block >>= (PAGE_SHIFT - blkbits);
1146 if (page_no) { /* exclude the header page */
1147 if (first_block < lowest_block)
1148 lowest_block = first_block;
1149 if (first_block > highest_block)
1150 highest_block = first_block;
1154 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1156 ret = add_swap_extent(sis, page_no, 1, first_block);
1161 probe_block += blocks_per_page;
1166 *span = 1 + highest_block - lowest_block;
1168 page_no = 1; /* force Empty message */
1170 sis->pages = page_no - 1;
1171 sis->highest_bit = page_no - 1;
1173 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1174 struct swap_extent, list);
1177 printk(KERN_ERR "swapon: swapfile has holes\n");
1183 #if 0 /* We don't need this yet */
1184 #include <linux/backing-dev.h>
1185 int page_queue_congested(struct page *page)
1187 struct backing_dev_info *bdi;
1189 VM_BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1191 if (PageSwapCache(page)) {
1192 swp_entry_t entry = { .val = page_private(page) };
1193 struct swap_info_struct *sis;
1195 sis = get_swap_info_struct(swp_type(entry));
1196 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1198 bdi = page->mapping->backing_dev_info;
1199 return bdi_write_congested(bdi);
1203 asmlinkage long sys_swapoff(const char __user * specialfile)
1205 struct swap_info_struct * p = NULL;
1206 unsigned short *swap_map;
1207 struct file *swap_file, *victim;
1208 struct address_space *mapping;
1209 struct inode *inode;
1214 if (!capable(CAP_SYS_ADMIN))
1217 pathname = getname(specialfile);
1218 err = PTR_ERR(pathname);
1219 if (IS_ERR(pathname))
1222 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1224 err = PTR_ERR(victim);
1228 mapping = victim->f_mapping;
1230 spin_lock(&swap_lock);
1231 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1232 p = swap_info + type;
1233 if (p->flags & SWP_WRITEOK) {
1234 if (p->swap_file->f_mapping == mapping)
1241 spin_unlock(&swap_lock);
1244 if (!security_vm_enough_memory(p->pages))
1245 vm_unacct_memory(p->pages);
1248 spin_unlock(&swap_lock);
1252 swap_list.head = p->next;
1254 swap_info[prev].next = p->next;
1256 if (type == swap_list.next) {
1257 /* just pick something that's safe... */
1258 swap_list.next = swap_list.head;
1261 for (i = p->next; i >= 0; i = swap_info[i].next)
1262 swap_info[i].prio = p->prio--;
1265 nr_swap_pages -= p->pages;
1266 total_swap_pages -= p->pages;
1267 p->flags &= ~SWP_WRITEOK;
1268 spin_unlock(&swap_lock);
1270 current->flags |= PF_SWAPOFF;
1271 err = try_to_unuse(type);
1272 current->flags &= ~PF_SWAPOFF;
1275 /* re-insert swap space back into swap_list */
1276 spin_lock(&swap_lock);
1278 p->prio = --least_priority;
1280 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1281 if (p->prio >= swap_info[i].prio)
1287 swap_list.head = swap_list.next = p - swap_info;
1289 swap_info[prev].next = p - swap_info;
1290 nr_swap_pages += p->pages;
1291 total_swap_pages += p->pages;
1292 p->flags |= SWP_WRITEOK;
1293 spin_unlock(&swap_lock);
1297 /* wait for any unplug function to finish */
1298 down_write(&swap_unplug_sem);
1299 up_write(&swap_unplug_sem);
1301 destroy_swap_extents(p);
1302 mutex_lock(&swapon_mutex);
1303 spin_lock(&swap_lock);
1306 /* wait for anyone still in scan_swap_map */
1307 p->highest_bit = 0; /* cuts scans short */
1308 while (p->flags >= SWP_SCANNING) {
1309 spin_unlock(&swap_lock);
1310 schedule_timeout_uninterruptible(1);
1311 spin_lock(&swap_lock);
1314 swap_file = p->swap_file;
1315 p->swap_file = NULL;
1317 swap_map = p->swap_map;
1320 spin_unlock(&swap_lock);
1321 mutex_unlock(&swapon_mutex);
1323 inode = mapping->host;
1324 if (S_ISBLK(inode->i_mode)) {
1325 struct block_device *bdev = I_BDEV(inode);
1326 set_blocksize(bdev, p->old_block_size);
1329 mutex_lock(&inode->i_mutex);
1330 inode->i_flags &= ~S_SWAPFILE;
1331 mutex_unlock(&inode->i_mutex);
1333 filp_close(swap_file, NULL);
1337 filp_close(victim, NULL);
1342 #ifdef CONFIG_PROC_FS
1344 static void *swap_start(struct seq_file *swap, loff_t *pos)
1346 struct swap_info_struct *ptr = swap_info;
1350 mutex_lock(&swapon_mutex);
1353 return SEQ_START_TOKEN;
1355 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1356 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1365 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1367 struct swap_info_struct *ptr;
1368 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1370 if (v == SEQ_START_TOKEN)
1377 for (; ptr < endptr; ptr++) {
1378 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1387 static void swap_stop(struct seq_file *swap, void *v)
1389 mutex_unlock(&swapon_mutex);
1392 static int swap_show(struct seq_file *swap, void *v)
1394 struct swap_info_struct *ptr = v;
1398 if (ptr == SEQ_START_TOKEN) {
1399 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1403 file = ptr->swap_file;
1404 len = seq_path(swap, &file->f_path, " \t\n\\");
1405 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1406 len < 40 ? 40 - len : 1, " ",
1407 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1408 "partition" : "file\t",
1409 ptr->pages << (PAGE_SHIFT - 10),
1410 ptr->inuse_pages << (PAGE_SHIFT - 10),
1415 static const struct seq_operations swaps_op = {
1416 .start = swap_start,
1422 static int swaps_open(struct inode *inode, struct file *file)
1424 return seq_open(file, &swaps_op);
1427 static const struct file_operations proc_swaps_operations = {
1430 .llseek = seq_lseek,
1431 .release = seq_release,
1434 static int __init procswaps_init(void)
1436 proc_create("swaps", 0, NULL, &proc_swaps_operations);
1439 __initcall(procswaps_init);
1440 #endif /* CONFIG_PROC_FS */
1442 #ifdef MAX_SWAPFILES_CHECK
1443 static int __init max_swapfiles_check(void)
1445 MAX_SWAPFILES_CHECK();
1448 late_initcall(max_swapfiles_check);
1452 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1454 * The swapon system call
1456 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1458 struct swap_info_struct * p;
1460 struct block_device *bdev = NULL;
1461 struct file *swap_file = NULL;
1462 struct address_space *mapping;
1466 union swap_header *swap_header = NULL;
1467 unsigned int nr_good_pages = 0;
1470 unsigned long maxpages = 1;
1471 unsigned long swapfilepages;
1472 unsigned short *swap_map = NULL;
1473 struct page *page = NULL;
1474 struct inode *inode = NULL;
1477 if (!capable(CAP_SYS_ADMIN))
1479 spin_lock(&swap_lock);
1481 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1482 if (!(p->flags & SWP_USED))
1485 if (type >= MAX_SWAPFILES) {
1486 spin_unlock(&swap_lock);
1489 if (type >= nr_swapfiles)
1490 nr_swapfiles = type+1;
1491 memset(p, 0, sizeof(*p));
1492 INIT_LIST_HEAD(&p->extent_list);
1493 p->flags = SWP_USED;
1495 spin_unlock(&swap_lock);
1496 name = getname(specialfile);
1497 error = PTR_ERR(name);
1502 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1503 error = PTR_ERR(swap_file);
1504 if (IS_ERR(swap_file)) {
1509 p->swap_file = swap_file;
1510 mapping = swap_file->f_mapping;
1511 inode = mapping->host;
1514 for (i = 0; i < nr_swapfiles; i++) {
1515 struct swap_info_struct *q = &swap_info[i];
1517 if (i == type || !q->swap_file)
1519 if (mapping == q->swap_file->f_mapping)
1524 if (S_ISBLK(inode->i_mode)) {
1525 bdev = I_BDEV(inode);
1526 error = bd_claim(bdev, sys_swapon);
1532 p->old_block_size = block_size(bdev);
1533 error = set_blocksize(bdev, PAGE_SIZE);
1537 } else if (S_ISREG(inode->i_mode)) {
1538 p->bdev = inode->i_sb->s_bdev;
1539 mutex_lock(&inode->i_mutex);
1541 if (IS_SWAPFILE(inode)) {
1549 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1552 * Read the swap header.
1554 if (!mapping->a_ops->readpage) {
1558 page = read_mapping_page(mapping, 0, swap_file);
1560 error = PTR_ERR(page);
1563 swap_header = kmap(page);
1565 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1566 printk(KERN_ERR "Unable to find swap-space signature\n");
1571 /* swap partition endianess hack... */
1572 if (swab32(swap_header->info.version) == 1) {
1573 swab32s(&swap_header->info.version);
1574 swab32s(&swap_header->info.last_page);
1575 swab32s(&swap_header->info.nr_badpages);
1576 for (i = 0; i < swap_header->info.nr_badpages; i++)
1577 swab32s(&swap_header->info.badpages[i]);
1579 /* Check the swap header's sub-version */
1580 if (swap_header->info.version != 1) {
1582 "Unable to handle swap header version %d\n",
1583 swap_header->info.version);
1589 p->cluster_next = 1;
1592 * Find out how many pages are allowed for a single swap
1593 * device. There are two limiting factors: 1) the number of
1594 * bits for the swap offset in the swp_entry_t type and
1595 * 2) the number of bits in the a swap pte as defined by
1596 * the different architectures. In order to find the
1597 * largest possible bit mask a swap entry with swap type 0
1598 * and swap offset ~0UL is created, encoded to a swap pte,
1599 * decoded to a swp_entry_t again and finally the swap
1600 * offset is extracted. This will mask all the bits from
1601 * the initial ~0UL mask that can't be encoded in either
1602 * the swp_entry_t or the architecture definition of a
1605 maxpages = swp_offset(pte_to_swp_entry(
1606 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1607 if (maxpages > swap_header->info.last_page)
1608 maxpages = swap_header->info.last_page;
1609 p->highest_bit = maxpages - 1;
1614 if (swapfilepages && maxpages > swapfilepages) {
1616 "Swap area shorter than signature indicates\n");
1619 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1621 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1624 /* OK, set up the swap map and apply the bad block list */
1625 swap_map = vmalloc(maxpages * sizeof(short));
1631 memset(swap_map, 0, maxpages * sizeof(short));
1632 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1633 int page_nr = swap_header->info.badpages[i];
1634 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1638 swap_map[page_nr] = SWAP_MAP_BAD;
1640 nr_good_pages = swap_header->info.last_page -
1641 swap_header->info.nr_badpages -
1642 1 /* header page */;
1644 if (nr_good_pages) {
1645 swap_map[0] = SWAP_MAP_BAD;
1647 p->pages = nr_good_pages;
1648 nr_extents = setup_swap_extents(p, &span);
1649 if (nr_extents < 0) {
1653 nr_good_pages = p->pages;
1655 if (!nr_good_pages) {
1656 printk(KERN_WARNING "Empty swap-file\n");
1661 mutex_lock(&swapon_mutex);
1662 spin_lock(&swap_lock);
1663 if (swap_flags & SWAP_FLAG_PREFER)
1665 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1667 p->prio = --least_priority;
1668 p->swap_map = swap_map;
1669 p->flags |= SWP_WRITEOK;
1670 nr_swap_pages += nr_good_pages;
1671 total_swap_pages += nr_good_pages;
1673 printk(KERN_INFO "Adding %uk swap on %s. "
1674 "Priority:%d extents:%d across:%lluk\n",
1675 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1676 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1678 /* insert swap space into swap_list: */
1680 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1681 if (p->prio >= swap_info[i].prio) {
1688 swap_list.head = swap_list.next = p - swap_info;
1690 swap_info[prev].next = p - swap_info;
1692 spin_unlock(&swap_lock);
1693 mutex_unlock(&swapon_mutex);
1698 set_blocksize(bdev, p->old_block_size);
1701 destroy_swap_extents(p);
1703 spin_lock(&swap_lock);
1704 p->swap_file = NULL;
1706 spin_unlock(&swap_lock);
1709 filp_close(swap_file, NULL);
1711 if (page && !IS_ERR(page)) {
1713 page_cache_release(page);
1719 inode->i_flags |= S_SWAPFILE;
1720 mutex_unlock(&inode->i_mutex);
1725 void si_swapinfo(struct sysinfo *val)
1728 unsigned long nr_to_be_unused = 0;
1730 spin_lock(&swap_lock);
1731 for (i = 0; i < nr_swapfiles; i++) {
1732 if (!(swap_info[i].flags & SWP_USED) ||
1733 (swap_info[i].flags & SWP_WRITEOK))
1735 nr_to_be_unused += swap_info[i].inuse_pages;
1737 val->freeswap = nr_swap_pages + nr_to_be_unused;
1738 val->totalswap = total_swap_pages + nr_to_be_unused;
1739 spin_unlock(&swap_lock);
1743 * Verify that a swap entry is valid and increment its swap map count.
1745 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1746 * "permanent", but will be reclaimed by the next swapoff.
1748 int swap_duplicate(swp_entry_t entry)
1750 struct swap_info_struct * p;
1751 unsigned long offset, type;
1754 if (is_migration_entry(entry))
1757 type = swp_type(entry);
1758 if (type >= nr_swapfiles)
1760 p = type + swap_info;
1761 offset = swp_offset(entry);
1763 spin_lock(&swap_lock);
1764 if (offset < p->max && p->swap_map[offset]) {
1765 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1766 p->swap_map[offset]++;
1768 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1769 if (swap_overflow++ < 5)
1770 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1771 p->swap_map[offset] = SWAP_MAP_MAX;
1775 spin_unlock(&swap_lock);
1780 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1784 struct swap_info_struct *
1785 get_swap_info_struct(unsigned type)
1787 return &swap_info[type];
1791 * swap_lock prevents swap_map being freed. Don't grab an extra
1792 * reference on the swaphandle, it doesn't matter if it becomes unused.
1794 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1796 struct swap_info_struct *si;
1797 int our_page_cluster = page_cluster;
1798 pgoff_t target, toff;
1802 if (!our_page_cluster) /* no readahead */
1805 si = &swap_info[swp_type(entry)];
1806 target = swp_offset(entry);
1807 base = (target >> our_page_cluster) << our_page_cluster;
1808 end = base + (1 << our_page_cluster);
1809 if (!base) /* first page is swap header */
1812 spin_lock(&swap_lock);
1813 if (end > si->max) /* don't go beyond end of map */
1816 /* Count contiguous allocated slots above our target */
1817 for (toff = target; ++toff < end; nr_pages++) {
1818 /* Don't read in free or bad pages */
1819 if (!si->swap_map[toff])
1821 if (si->swap_map[toff] == SWAP_MAP_BAD)
1824 /* Count contiguous allocated slots below our target */
1825 for (toff = target; --toff >= base; nr_pages++) {
1826 /* Don't read in free or bad pages */
1827 if (!si->swap_map[toff])
1829 if (si->swap_map[toff] == SWAP_MAP_BAD)
1832 spin_unlock(&swap_lock);
1835 * Indicate starting offset, and return number of pages to get:
1836 * if only 1, say 0, since there's then no readahead to be done.
1839 return nr_pages? ++nr_pages: 0;