4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
8 #include <linux/config.h>
10 #include <linux/hugetlb.h>
11 #include <linux/mman.h>
12 #include <linux/slab.h>
13 #include <linux/kernel_stat.h>
14 #include <linux/swap.h>
15 #include <linux/vmalloc.h>
16 #include <linux/pagemap.h>
17 #include <linux/namei.h>
18 #include <linux/shm.h>
19 #include <linux/blkdev.h>
20 #include <linux/writeback.h>
21 #include <linux/proc_fs.h>
22 #include <linux/seq_file.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/rmap.h>
26 #include <linux/security.h>
27 #include <linux/backing-dev.h>
28 #include <linux/mutex.h>
29 #include <linux/capability.h>
30 #include <linux/syscalls.h>
32 #include <asm/pgtable.h>
33 #include <asm/tlbflush.h>
34 #include <linux/swapops.h>
35 #include <linux/vs_memory.h>
37 DEFINE_SPINLOCK(swap_lock);
38 unsigned int nr_swapfiles;
39 long total_swap_pages;
40 static int swap_overflow;
42 static const char Bad_file[] = "Bad swap file entry ";
43 static const char Unused_file[] = "Unused swap file entry ";
44 static const char Bad_offset[] = "Bad swap offset entry ";
45 static const char Unused_offset[] = "Unused swap offset entry ";
47 struct swap_list_t swap_list = {-1, -1};
49 static struct swap_info_struct swap_info[MAX_SWAPFILES];
51 static DEFINE_MUTEX(swapon_mutex);
54 * We need this because the bdev->unplug_fn can sleep and we cannot
55 * hold swap_lock while calling the unplug_fn. And swap_lock
56 * cannot be turned into a mutex.
58 static DECLARE_RWSEM(swap_unplug_sem);
60 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
64 down_read(&swap_unplug_sem);
65 entry.val = page_private(page);
66 if (PageSwapCache(page)) {
67 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
68 struct backing_dev_info *bdi;
71 * If the page is removed from swapcache from under us (with a
72 * racy try_to_unuse/swapoff) we need an additional reference
73 * count to avoid reading garbage from page_private(page) above.
74 * If the WARN_ON triggers during a swapoff it maybe the race
75 * condition and it's harmless. However if it triggers without
76 * swapoff it signals a problem.
78 WARN_ON(page_count(page) <= 1);
80 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
81 blk_run_backing_dev(bdi, page);
83 up_read(&swap_unplug_sem);
86 #define SWAPFILE_CLUSTER 256
87 #define LATENCY_LIMIT 256
89 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
91 unsigned long offset, last_in_cluster;
92 int latency_ration = LATENCY_LIMIT;
95 * We try to cluster swap pages by allocating them sequentially
96 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
97 * way, however, we resort to first-free allocation, starting
98 * a new cluster. This prevents us from scattering swap pages
99 * all over the entire swap partition, so that we reduce
100 * overall disk seek times between swap pages. -- sct
101 * But we do now try to find an empty cluster. -Andrea
104 si->flags += SWP_SCANNING;
105 if (unlikely(!si->cluster_nr)) {
106 si->cluster_nr = SWAPFILE_CLUSTER - 1;
107 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
109 spin_unlock(&swap_lock);
111 offset = si->lowest_bit;
112 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
114 /* Locate the first empty (unaligned) cluster */
115 for (; last_in_cluster <= si->highest_bit; offset++) {
116 if (si->swap_map[offset])
117 last_in_cluster = offset + SWAPFILE_CLUSTER;
118 else if (offset == last_in_cluster) {
119 spin_lock(&swap_lock);
120 si->cluster_next = offset-SWAPFILE_CLUSTER+1;
123 if (unlikely(--latency_ration < 0)) {
125 latency_ration = LATENCY_LIMIT;
128 spin_lock(&swap_lock);
134 offset = si->cluster_next;
135 if (offset > si->highest_bit)
136 lowest: offset = si->lowest_bit;
137 checks: if (!(si->flags & SWP_WRITEOK))
139 if (!si->highest_bit)
141 if (!si->swap_map[offset]) {
142 if (offset == si->lowest_bit)
144 if (offset == si->highest_bit)
147 if (si->inuse_pages == si->pages) {
148 si->lowest_bit = si->max;
151 si->swap_map[offset] = 1;
152 si->cluster_next = offset + 1;
153 si->flags -= SWP_SCANNING;
157 spin_unlock(&swap_lock);
158 while (++offset <= si->highest_bit) {
159 if (!si->swap_map[offset]) {
160 spin_lock(&swap_lock);
163 if (unlikely(--latency_ration < 0)) {
165 latency_ration = LATENCY_LIMIT;
168 spin_lock(&swap_lock);
172 si->flags -= SWP_SCANNING;
176 swp_entry_t get_swap_page(void)
178 struct swap_info_struct *si;
183 spin_lock(&swap_lock);
184 if (nr_swap_pages <= 0)
188 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
189 si = swap_info + type;
192 (!wrapped && si->prio != swap_info[next].prio)) {
193 next = swap_list.head;
197 if (!si->highest_bit)
199 if (!(si->flags & SWP_WRITEOK))
202 swap_list.next = next;
203 offset = scan_swap_map(si);
205 spin_unlock(&swap_lock);
206 return swp_entry(type, offset);
208 next = swap_list.next;
213 spin_unlock(&swap_lock);
214 return (swp_entry_t) {0};
217 swp_entry_t get_swap_page_of_type(int type)
219 struct swap_info_struct *si;
222 spin_lock(&swap_lock);
223 si = swap_info + type;
224 if (si->flags & SWP_WRITEOK) {
226 offset = scan_swap_map(si);
228 spin_unlock(&swap_lock);
229 return swp_entry(type, offset);
233 spin_unlock(&swap_lock);
234 return (swp_entry_t) {0};
237 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
239 struct swap_info_struct * p;
240 unsigned long offset, type;
244 type = swp_type(entry);
245 if (type >= nr_swapfiles)
247 p = & swap_info[type];
248 if (!(p->flags & SWP_USED))
250 offset = swp_offset(entry);
251 if (offset >= p->max)
253 if (!p->swap_map[offset])
255 spin_lock(&swap_lock);
259 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
262 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
265 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
268 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
273 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
275 int count = p->swap_map[offset];
277 if (count < SWAP_MAP_MAX) {
279 p->swap_map[offset] = count;
281 if (offset < p->lowest_bit)
282 p->lowest_bit = offset;
283 if (offset > p->highest_bit)
284 p->highest_bit = offset;
285 if (p->prio > swap_info[swap_list.next].prio)
286 swap_list.next = p - swap_info;
295 * Caller has made sure that the swapdevice corresponding to entry
296 * is still around or has not been recycled.
298 void swap_free(swp_entry_t entry)
300 struct swap_info_struct * p;
302 p = swap_info_get(entry);
304 swap_entry_free(p, swp_offset(entry));
305 spin_unlock(&swap_lock);
310 * How many references to page are currently swapped out?
312 static inline int page_swapcount(struct page *page)
315 struct swap_info_struct *p;
318 entry.val = page_private(page);
319 p = swap_info_get(entry);
321 /* Subtract the 1 for the swap cache itself */
322 count = p->swap_map[swp_offset(entry)] - 1;
323 spin_unlock(&swap_lock);
329 * We can use this swap cache entry directly
330 * if there are no other references to it.
332 int can_share_swap_page(struct page *page)
336 BUG_ON(!PageLocked(page));
337 count = page_mapcount(page);
338 if (count <= 1 && PageSwapCache(page))
339 count += page_swapcount(page);
344 * Work out if there are any other processes sharing this
345 * swap cache page. Free it if you can. Return success.
347 int remove_exclusive_swap_page(struct page *page)
350 struct swap_info_struct * p;
353 BUG_ON(PagePrivate(page));
354 BUG_ON(!PageLocked(page));
356 if (!PageSwapCache(page))
358 if (PageWriteback(page))
360 if (page_count(page) != 2) /* 2: us + cache */
363 entry.val = page_private(page);
364 p = swap_info_get(entry);
368 /* Is the only swap cache user the cache itself? */
370 if (p->swap_map[swp_offset(entry)] == 1) {
371 /* Recheck the page count with the swapcache lock held.. */
372 write_lock_irq(&swapper_space.tree_lock);
373 if ((page_count(page) == 2) && !PageWriteback(page)) {
374 __delete_from_swap_cache(page);
378 write_unlock_irq(&swapper_space.tree_lock);
380 spin_unlock(&swap_lock);
384 page_cache_release(page);
391 * Free the swap entry like above, but also try to
392 * free the page cache entry if it is the last user.
394 void free_swap_and_cache(swp_entry_t entry)
396 struct swap_info_struct * p;
397 struct page *page = NULL;
399 p = swap_info_get(entry);
401 if (swap_entry_free(p, swp_offset(entry)) == 1) {
402 page = find_get_page(&swapper_space, entry.val);
403 if (page && unlikely(TestSetPageLocked(page))) {
404 page_cache_release(page);
408 spin_unlock(&swap_lock);
413 BUG_ON(PagePrivate(page));
414 one_user = (page_count(page) == 2);
415 /* Only cache user (+us), or swap space full? Free it! */
416 /* Also recheck PageSwapCache after page is locked (above) */
417 if (PageSwapCache(page) && !PageWriteback(page) &&
418 (one_user || vm_swap_full())) {
419 delete_from_swap_cache(page);
423 page_cache_release(page);
427 #ifdef CONFIG_SOFTWARE_SUSPEND
429 * Find the swap type that corresponds to given device (if any)
431 * This is needed for software suspend and is done in such a way that inode
432 * aliasing is allowed.
434 int swap_type_of(dev_t device)
438 spin_lock(&swap_lock);
439 for (i = 0; i < nr_swapfiles; i++) {
442 if (!(swap_info[i].flags & SWP_WRITEOK))
445 spin_unlock(&swap_lock);
448 inode = swap_info->swap_file->f_dentry->d_inode;
449 if (S_ISBLK(inode->i_mode) &&
450 device == MKDEV(imajor(inode), iminor(inode))) {
451 spin_unlock(&swap_lock);
455 spin_unlock(&swap_lock);
460 * Return either the total number of swap pages of given type, or the number
461 * of free pages of that type (depending on @free)
463 * This is needed for software suspend
465 unsigned int count_swap_pages(int type, int free)
469 if (type < nr_swapfiles) {
470 spin_lock(&swap_lock);
471 if (swap_info[type].flags & SWP_WRITEOK) {
472 n = swap_info[type].pages;
474 n -= swap_info[type].inuse_pages;
476 spin_unlock(&swap_lock);
483 * No need to decide whether this PTE shares the swap entry with others,
484 * just let do_wp_page work it out if a write is requested later - to
485 * force COW, vm_page_prot omits write permission from any private vma.
487 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
488 unsigned long addr, swp_entry_t entry, struct page *page)
490 inc_mm_counter(vma->vm_mm, anon_rss);
492 set_pte_at(vma->vm_mm, addr, pte,
493 pte_mkold(mk_pte(page, vma->vm_page_prot)));
494 page_add_anon_rmap(page, vma, addr);
497 * Move the page to the active list so it is not
498 * immediately swapped out again after swapon.
503 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
504 unsigned long addr, unsigned long end,
505 swp_entry_t entry, struct page *page)
507 pte_t swp_pte = swp_entry_to_pte(entry);
512 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
515 * swapoff spends a _lot_ of time in this loop!
516 * Test inline before going to call unuse_pte.
518 if (unlikely(pte_same(*pte, swp_pte))) {
519 unuse_pte(vma, pte++, addr, entry, page);
523 } while (pte++, addr += PAGE_SIZE, addr != end);
524 pte_unmap_unlock(pte - 1, ptl);
528 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
529 unsigned long addr, unsigned long end,
530 swp_entry_t entry, struct page *page)
535 pmd = pmd_offset(pud, addr);
537 next = pmd_addr_end(addr, end);
538 if (pmd_none_or_clear_bad(pmd))
540 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
542 } while (pmd++, addr = next, addr != end);
546 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
547 unsigned long addr, unsigned long end,
548 swp_entry_t entry, struct page *page)
553 pud = pud_offset(pgd, addr);
555 next = pud_addr_end(addr, end);
556 if (pud_none_or_clear_bad(pud))
558 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
560 } while (pud++, addr = next, addr != end);
564 static int unuse_vma(struct vm_area_struct *vma,
565 swp_entry_t entry, struct page *page)
568 unsigned long addr, end, next;
571 addr = page_address_in_vma(page, vma);
575 end = addr + PAGE_SIZE;
577 addr = vma->vm_start;
581 pgd = pgd_offset(vma->vm_mm, addr);
583 next = pgd_addr_end(addr, end);
584 if (pgd_none_or_clear_bad(pgd))
586 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
588 } while (pgd++, addr = next, addr != end);
592 static int unuse_mm(struct mm_struct *mm,
593 swp_entry_t entry, struct page *page)
595 struct vm_area_struct *vma;
597 if (!down_read_trylock(&mm->mmap_sem)) {
599 * Activate page so shrink_cache is unlikely to unmap its
600 * ptes while lock is dropped, so swapoff can make progress.
604 down_read(&mm->mmap_sem);
607 for (vma = mm->mmap; vma; vma = vma->vm_next) {
608 if (vma->anon_vma && unuse_vma(vma, entry, page))
611 up_read(&mm->mmap_sem);
613 * Currently unuse_mm cannot fail, but leave error handling
614 * at call sites for now, since we change it from time to time.
619 #ifdef CONFIG_MIGRATION
620 int remove_vma_swap(struct vm_area_struct *vma, struct page *page)
622 swp_entry_t entry = { .val = page_private(page) };
624 return unuse_vma(vma, entry, page);
629 * Scan swap_map from current position to next entry still in use.
630 * Recycle to start on reaching the end, returning 0 when empty.
632 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
635 unsigned int max = si->max;
636 unsigned int i = prev;
640 * No need for swap_lock here: we're just looking
641 * for whether an entry is in use, not modifying it; false
642 * hits are okay, and sys_swapoff() has already prevented new
643 * allocations from this area (while holding swap_lock).
652 * No entries in use at top of swap_map,
653 * loop back to start and recheck there.
659 count = si->swap_map[i];
660 if (count && count != SWAP_MAP_BAD)
667 * We completely avoid races by reading each swap page in advance,
668 * and then search for the process using it. All the necessary
669 * page table adjustments can then be made atomically.
671 static int try_to_unuse(unsigned int type)
673 struct swap_info_struct * si = &swap_info[type];
674 struct mm_struct *start_mm;
675 unsigned short *swap_map;
676 unsigned short swcount;
681 int reset_overflow = 0;
685 * When searching mms for an entry, a good strategy is to
686 * start at the first mm we freed the previous entry from
687 * (though actually we don't notice whether we or coincidence
688 * freed the entry). Initialize this start_mm with a hold.
690 * A simpler strategy would be to start at the last mm we
691 * freed the previous entry from; but that would take less
692 * advantage of mmlist ordering, which clusters forked mms
693 * together, child after parent. If we race with dup_mmap(), we
694 * prefer to resolve parent before child, lest we miss entries
695 * duplicated after we scanned child: using last mm would invert
696 * that. Though it's only a serious concern when an overflowed
697 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
700 atomic_inc(&init_mm.mm_users);
703 * Keep on scanning until all entries have gone. Usually,
704 * one pass through swap_map is enough, but not necessarily:
705 * there are races when an instance of an entry might be missed.
707 while ((i = find_next_to_unuse(si, i)) != 0) {
708 if (signal_pending(current)) {
714 * Get a page for the entry, using the existing swap
715 * cache page if there is one. Otherwise, get a clean
716 * page and read the swap into it.
718 swap_map = &si->swap_map[i];
719 entry = swp_entry(type, i);
721 page = read_swap_cache_async(entry, NULL, 0);
724 * Either swap_duplicate() failed because entry
725 * has been freed independently, and will not be
726 * reused since sys_swapoff() already disabled
727 * allocation from here, or alloc_page() failed.
736 * Don't hold on to start_mm if it looks like exiting.
738 if (atomic_read(&start_mm->mm_users) == 1) {
741 atomic_inc(&init_mm.mm_users);
745 * Wait for and lock page. When do_swap_page races with
746 * try_to_unuse, do_swap_page can handle the fault much
747 * faster than try_to_unuse can locate the entry. This
748 * apparently redundant "wait_on_page_locked" lets try_to_unuse
749 * defer to do_swap_page in such a case - in some tests,
750 * do_swap_page and try_to_unuse repeatedly compete.
752 wait_on_page_locked(page);
753 wait_on_page_writeback(page);
755 if (!PageSwapCache(page)) {
756 /* Page migration has occured */
758 page_cache_release(page);
761 wait_on_page_writeback(page);
764 * Remove all references to entry.
765 * Whenever we reach init_mm, there's no address space
766 * to search, but use it as a reminder to search shmem.
771 if (start_mm == &init_mm)
772 shmem = shmem_unuse(entry, page);
774 retval = unuse_mm(start_mm, entry, page);
777 int set_start_mm = (*swap_map >= swcount);
778 struct list_head *p = &start_mm->mmlist;
779 struct mm_struct *new_start_mm = start_mm;
780 struct mm_struct *prev_mm = start_mm;
781 struct mm_struct *mm;
783 atomic_inc(&new_start_mm->mm_users);
784 atomic_inc(&prev_mm->mm_users);
785 spin_lock(&mmlist_lock);
786 while (*swap_map > 1 && !retval &&
787 (p = p->next) != &start_mm->mmlist) {
788 mm = list_entry(p, struct mm_struct, mmlist);
789 if (atomic_inc_return(&mm->mm_users) == 1) {
790 atomic_dec(&mm->mm_users);
793 spin_unlock(&mmlist_lock);
802 else if (mm == &init_mm) {
804 shmem = shmem_unuse(entry, page);
806 retval = unuse_mm(mm, entry, page);
807 if (set_start_mm && *swap_map < swcount) {
809 atomic_inc(&mm->mm_users);
813 spin_lock(&mmlist_lock);
815 spin_unlock(&mmlist_lock);
818 start_mm = new_start_mm;
822 page_cache_release(page);
827 * How could swap count reach 0x7fff when the maximum
828 * pid is 0x7fff, and there's no way to repeat a swap
829 * page within an mm (except in shmem, where it's the
830 * shared object which takes the reference count)?
831 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
833 * If that's wrong, then we should worry more about
834 * exit_mmap() and do_munmap() cases described above:
835 * we might be resetting SWAP_MAP_MAX too early here.
836 * We know "Undead"s can happen, they're okay, so don't
837 * report them; but do report if we reset SWAP_MAP_MAX.
839 if (*swap_map == SWAP_MAP_MAX) {
840 spin_lock(&swap_lock);
842 spin_unlock(&swap_lock);
847 * If a reference remains (rare), we would like to leave
848 * the page in the swap cache; but try_to_unmap could
849 * then re-duplicate the entry once we drop page lock,
850 * so we might loop indefinitely; also, that page could
851 * not be swapped out to other storage meanwhile. So:
852 * delete from cache even if there's another reference,
853 * after ensuring that the data has been saved to disk -
854 * since if the reference remains (rarer), it will be
855 * read from disk into another page. Splitting into two
856 * pages would be incorrect if swap supported "shared
857 * private" pages, but they are handled by tmpfs files.
859 * Note shmem_unuse already deleted a swappage from
860 * the swap cache, unless the move to filepage failed:
861 * in which case it left swappage in cache, lowered its
862 * swap count to pass quickly through the loops above,
863 * and now we must reincrement count to try again later.
865 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
866 struct writeback_control wbc = {
867 .sync_mode = WB_SYNC_NONE,
870 swap_writepage(page, &wbc);
872 wait_on_page_writeback(page);
874 if (PageSwapCache(page)) {
876 swap_duplicate(entry);
878 delete_from_swap_cache(page);
882 * So we could skip searching mms once swap count went
883 * to 1, we did not mark any present ptes as dirty: must
884 * mark page dirty so shrink_list will preserve it.
888 page_cache_release(page);
891 * Make sure that we aren't completely killing
892 * interactive performance.
898 if (reset_overflow) {
899 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
906 * After a successful try_to_unuse, if no swap is now in use, we know
907 * we can empty the mmlist. swap_lock must be held on entry and exit.
908 * Note that mmlist_lock nests inside swap_lock, and an mm must be
909 * added to the mmlist just after page_duplicate - before would be racy.
911 static void drain_mmlist(void)
913 struct list_head *p, *next;
916 for (i = 0; i < nr_swapfiles; i++)
917 if (swap_info[i].inuse_pages)
919 spin_lock(&mmlist_lock);
920 list_for_each_safe(p, next, &init_mm.mmlist)
922 spin_unlock(&mmlist_lock);
926 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
927 * corresponds to page offset `offset'.
929 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
931 struct swap_extent *se = sis->curr_swap_extent;
932 struct swap_extent *start_se = se;
935 struct list_head *lh;
937 if (se->start_page <= offset &&
938 offset < (se->start_page + se->nr_pages)) {
939 return se->start_block + (offset - se->start_page);
942 if (lh == &sis->extent_list)
944 se = list_entry(lh, struct swap_extent, list);
945 sis->curr_swap_extent = se;
946 BUG_ON(se == start_se); /* It *must* be present */
951 * Free all of a swapdev's extent information
953 static void destroy_swap_extents(struct swap_info_struct *sis)
955 while (!list_empty(&sis->extent_list)) {
956 struct swap_extent *se;
958 se = list_entry(sis->extent_list.next,
959 struct swap_extent, list);
966 * Add a block range (and the corresponding page range) into this swapdev's
967 * extent list. The extent list is kept sorted in page order.
969 * This function rather assumes that it is called in ascending page order.
972 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
973 unsigned long nr_pages, sector_t start_block)
975 struct swap_extent *se;
976 struct swap_extent *new_se;
977 struct list_head *lh;
979 lh = sis->extent_list.prev; /* The highest page extent */
980 if (lh != &sis->extent_list) {
981 se = list_entry(lh, struct swap_extent, list);
982 BUG_ON(se->start_page + se->nr_pages != start_page);
983 if (se->start_block + se->nr_pages == start_block) {
985 se->nr_pages += nr_pages;
991 * No merge. Insert a new extent, preserving ordering.
993 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
996 new_se->start_page = start_page;
997 new_se->nr_pages = nr_pages;
998 new_se->start_block = start_block;
1000 list_add_tail(&new_se->list, &sis->extent_list);
1005 * A `swap extent' is a simple thing which maps a contiguous range of pages
1006 * onto a contiguous range of disk blocks. An ordered list of swap extents
1007 * is built at swapon time and is then used at swap_writepage/swap_readpage
1008 * time for locating where on disk a page belongs.
1010 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1011 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1012 * swap files identically.
1014 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1015 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1016 * swapfiles are handled *identically* after swapon time.
1018 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1019 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1020 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1021 * requirements, they are simply tossed out - we will never use those blocks
1024 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1025 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1026 * which will scribble on the fs.
1028 * The amount of disk space which a single swap extent represents varies.
1029 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1030 * extents in the list. To avoid much list walking, we cache the previous
1031 * search location in `curr_swap_extent', and start new searches from there.
1032 * This is extremely effective. The average number of iterations in
1033 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1035 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1037 struct inode *inode;
1038 unsigned blocks_per_page;
1039 unsigned long page_no;
1041 sector_t probe_block;
1042 sector_t last_block;
1043 sector_t lowest_block = -1;
1044 sector_t highest_block = 0;
1048 inode = sis->swap_file->f_mapping->host;
1049 if (S_ISBLK(inode->i_mode)) {
1050 ret = add_swap_extent(sis, 0, sis->max, 0);
1055 blkbits = inode->i_blkbits;
1056 blocks_per_page = PAGE_SIZE >> blkbits;
1059 * Map all the blocks into the extent list. This code doesn't try
1064 last_block = i_size_read(inode) >> blkbits;
1065 while ((probe_block + blocks_per_page) <= last_block &&
1066 page_no < sis->max) {
1067 unsigned block_in_page;
1068 sector_t first_block;
1070 first_block = bmap(inode, probe_block);
1071 if (first_block == 0)
1075 * It must be PAGE_SIZE aligned on-disk
1077 if (first_block & (blocks_per_page - 1)) {
1082 for (block_in_page = 1; block_in_page < blocks_per_page;
1086 block = bmap(inode, probe_block + block_in_page);
1089 if (block != first_block + block_in_page) {
1096 first_block >>= (PAGE_SHIFT - blkbits);
1097 if (page_no) { /* exclude the header page */
1098 if (first_block < lowest_block)
1099 lowest_block = first_block;
1100 if (first_block > highest_block)
1101 highest_block = first_block;
1105 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1107 ret = add_swap_extent(sis, page_no, 1, first_block);
1112 probe_block += blocks_per_page;
1117 *span = 1 + highest_block - lowest_block;
1119 page_no = 1; /* force Empty message */
1121 sis->pages = page_no - 1;
1122 sis->highest_bit = page_no - 1;
1124 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1125 struct swap_extent, list);
1128 printk(KERN_ERR "swapon: swapfile has holes\n");
1134 #if 0 /* We don't need this yet */
1135 #include <linux/backing-dev.h>
1136 int page_queue_congested(struct page *page)
1138 struct backing_dev_info *bdi;
1140 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1142 if (PageSwapCache(page)) {
1143 swp_entry_t entry = { .val = page_private(page) };
1144 struct swap_info_struct *sis;
1146 sis = get_swap_info_struct(swp_type(entry));
1147 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1149 bdi = page->mapping->backing_dev_info;
1150 return bdi_write_congested(bdi);
1154 asmlinkage long sys_swapoff(const char __user * specialfile)
1156 struct swap_info_struct * p = NULL;
1157 unsigned short *swap_map;
1158 struct file *swap_file, *victim;
1159 struct address_space *mapping;
1160 struct inode *inode;
1165 if (!capable(CAP_SYS_ADMIN))
1168 pathname = getname(specialfile);
1169 err = PTR_ERR(pathname);
1170 if (IS_ERR(pathname))
1173 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1175 err = PTR_ERR(victim);
1179 mapping = victim->f_mapping;
1181 spin_lock(&swap_lock);
1182 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1183 p = swap_info + type;
1184 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1185 if (p->swap_file->f_mapping == mapping)
1192 spin_unlock(&swap_lock);
1195 if (!security_vm_enough_memory(p->pages))
1196 vm_unacct_memory(p->pages);
1199 spin_unlock(&swap_lock);
1203 swap_list.head = p->next;
1205 swap_info[prev].next = p->next;
1207 if (type == swap_list.next) {
1208 /* just pick something that's safe... */
1209 swap_list.next = swap_list.head;
1211 nr_swap_pages -= p->pages;
1212 total_swap_pages -= p->pages;
1213 p->flags &= ~SWP_WRITEOK;
1214 spin_unlock(&swap_lock);
1216 current->flags |= PF_SWAPOFF;
1217 err = try_to_unuse(type);
1218 current->flags &= ~PF_SWAPOFF;
1221 /* re-insert swap space back into swap_list */
1222 spin_lock(&swap_lock);
1223 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1224 if (p->prio >= swap_info[i].prio)
1228 swap_list.head = swap_list.next = p - swap_info;
1230 swap_info[prev].next = p - swap_info;
1231 nr_swap_pages += p->pages;
1232 total_swap_pages += p->pages;
1233 p->flags |= SWP_WRITEOK;
1234 spin_unlock(&swap_lock);
1238 /* wait for any unplug function to finish */
1239 down_write(&swap_unplug_sem);
1240 up_write(&swap_unplug_sem);
1242 destroy_swap_extents(p);
1243 mutex_lock(&swapon_mutex);
1244 spin_lock(&swap_lock);
1247 /* wait for anyone still in scan_swap_map */
1248 p->highest_bit = 0; /* cuts scans short */
1249 while (p->flags >= SWP_SCANNING) {
1250 spin_unlock(&swap_lock);
1251 schedule_timeout_uninterruptible(1);
1252 spin_lock(&swap_lock);
1255 swap_file = p->swap_file;
1256 p->swap_file = NULL;
1258 swap_map = p->swap_map;
1261 spin_unlock(&swap_lock);
1262 mutex_unlock(&swapon_mutex);
1264 inode = mapping->host;
1265 if (S_ISBLK(inode->i_mode)) {
1266 struct block_device *bdev = I_BDEV(inode);
1267 set_blocksize(bdev, p->old_block_size);
1270 mutex_lock(&inode->i_mutex);
1271 inode->i_flags &= ~S_SWAPFILE;
1272 mutex_unlock(&inode->i_mutex);
1274 filp_close(swap_file, NULL);
1278 filp_close(victim, NULL);
1283 #ifdef CONFIG_PROC_FS
1285 static void *swap_start(struct seq_file *swap, loff_t *pos)
1287 struct swap_info_struct *ptr = swap_info;
1291 mutex_lock(&swapon_mutex);
1293 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1294 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1303 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1305 struct swap_info_struct *ptr = v;
1306 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1308 for (++ptr; ptr < endptr; ptr++) {
1309 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1318 static void swap_stop(struct seq_file *swap, void *v)
1320 mutex_unlock(&swapon_mutex);
1323 static int swap_show(struct seq_file *swap, void *v)
1325 struct swap_info_struct *ptr = v;
1330 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1332 file = ptr->swap_file;
1333 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1334 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1335 len < 40 ? 40 - len : 1, " ",
1336 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1337 "partition" : "file\t",
1338 ptr->pages << (PAGE_SHIFT - 10),
1339 ptr->inuse_pages << (PAGE_SHIFT - 10),
1344 static struct seq_operations swaps_op = {
1345 .start = swap_start,
1351 static int swaps_open(struct inode *inode, struct file *file)
1353 return seq_open(file, &swaps_op);
1356 static struct file_operations proc_swaps_operations = {
1359 .llseek = seq_lseek,
1360 .release = seq_release,
1363 static int __init procswaps_init(void)
1365 struct proc_dir_entry *entry;
1367 entry = create_proc_entry("swaps", 0, NULL);
1369 entry->proc_fops = &proc_swaps_operations;
1372 __initcall(procswaps_init);
1373 #endif /* CONFIG_PROC_FS */
1376 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1378 * The swapon system call
1380 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1382 struct swap_info_struct * p;
1384 struct block_device *bdev = NULL;
1385 struct file *swap_file = NULL;
1386 struct address_space *mapping;
1390 static int least_priority;
1391 union swap_header *swap_header = NULL;
1392 int swap_header_version;
1393 unsigned int nr_good_pages = 0;
1396 unsigned long maxpages = 1;
1398 unsigned short *swap_map;
1399 struct page *page = NULL;
1400 struct inode *inode = NULL;
1403 if (!capable(CAP_SYS_ADMIN))
1405 spin_lock(&swap_lock);
1407 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1408 if (!(p->flags & SWP_USED))
1412 * Test if adding another swap device is possible. There are
1413 * two limiting factors: 1) the number of bits for the swap
1414 * type swp_entry_t definition and 2) the number of bits for
1415 * the swap type in the swap ptes as defined by the different
1416 * architectures. To honor both limitations a swap entry
1417 * with swap offset 0 and swap type ~0UL is created, encoded
1418 * to a swap pte, decoded to a swp_entry_t again and finally
1419 * the swap type part is extracted. This will mask all bits
1420 * from the initial ~0UL that can't be encoded in either the
1421 * swp_entry_t or the architecture definition of a swap pte.
1423 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1424 spin_unlock(&swap_lock);
1427 if (type >= nr_swapfiles)
1428 nr_swapfiles = type+1;
1429 INIT_LIST_HEAD(&p->extent_list);
1430 p->flags = SWP_USED;
1431 p->swap_file = NULL;
1432 p->old_block_size = 0;
1439 if (swap_flags & SWAP_FLAG_PREFER) {
1441 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1443 p->prio = --least_priority;
1445 spin_unlock(&swap_lock);
1446 name = getname(specialfile);
1447 error = PTR_ERR(name);
1452 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1453 error = PTR_ERR(swap_file);
1454 if (IS_ERR(swap_file)) {
1459 p->swap_file = swap_file;
1460 mapping = swap_file->f_mapping;
1461 inode = mapping->host;
1464 for (i = 0; i < nr_swapfiles; i++) {
1465 struct swap_info_struct *q = &swap_info[i];
1467 if (i == type || !q->swap_file)
1469 if (mapping == q->swap_file->f_mapping)
1474 if (S_ISBLK(inode->i_mode)) {
1475 bdev = I_BDEV(inode);
1476 error = bd_claim(bdev, sys_swapon);
1482 p->old_block_size = block_size(bdev);
1483 error = set_blocksize(bdev, PAGE_SIZE);
1487 } else if (S_ISREG(inode->i_mode)) {
1488 p->bdev = inode->i_sb->s_bdev;
1489 mutex_lock(&inode->i_mutex);
1491 if (IS_SWAPFILE(inode)) {
1499 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1502 * Read the swap header.
1504 if (!mapping->a_ops->readpage) {
1508 page = read_cache_page(mapping, 0,
1509 (filler_t *)mapping->a_ops->readpage, swap_file);
1511 error = PTR_ERR(page);
1514 wait_on_page_locked(page);
1515 if (!PageUptodate(page))
1518 swap_header = page_address(page);
1520 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1521 swap_header_version = 1;
1522 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1523 swap_header_version = 2;
1525 printk(KERN_ERR "Unable to find swap-space signature\n");
1530 switch (swap_header_version) {
1532 printk(KERN_ERR "version 0 swap is no longer supported. "
1533 "Use mkswap -v1 %s\n", name);
1537 /* Check the swap header's sub-version and the size of
1538 the swap file and bad block lists */
1539 if (swap_header->info.version != 1) {
1541 "Unable to handle swap header version %d\n",
1542 swap_header->info.version);
1548 p->cluster_next = 1;
1551 * Find out how many pages are allowed for a single swap
1552 * device. There are two limiting factors: 1) the number of
1553 * bits for the swap offset in the swp_entry_t type and
1554 * 2) the number of bits in the a swap pte as defined by
1555 * the different architectures. In order to find the
1556 * largest possible bit mask a swap entry with swap type 0
1557 * and swap offset ~0UL is created, encoded to a swap pte,
1558 * decoded to a swp_entry_t again and finally the swap
1559 * offset is extracted. This will mask all the bits from
1560 * the initial ~0UL mask that can't be encoded in either
1561 * the swp_entry_t or the architecture definition of a
1564 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1565 if (maxpages > swap_header->info.last_page)
1566 maxpages = swap_header->info.last_page;
1567 p->highest_bit = maxpages - 1;
1572 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1574 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1577 /* OK, set up the swap map and apply the bad block list */
1578 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1584 memset(p->swap_map, 0, maxpages * sizeof(short));
1585 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1586 int page_nr = swap_header->info.badpages[i];
1587 if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1590 p->swap_map[page_nr] = SWAP_MAP_BAD;
1592 nr_good_pages = swap_header->info.last_page -
1593 swap_header->info.nr_badpages -
1594 1 /* header page */;
1599 if (swapfilesize && maxpages > swapfilesize) {
1601 "Swap area shorter than signature indicates\n");
1605 if (nr_good_pages) {
1606 p->swap_map[0] = SWAP_MAP_BAD;
1608 p->pages = nr_good_pages;
1609 nr_extents = setup_swap_extents(p, &span);
1610 if (nr_extents < 0) {
1614 nr_good_pages = p->pages;
1616 if (!nr_good_pages) {
1617 printk(KERN_WARNING "Empty swap-file\n");
1622 mutex_lock(&swapon_mutex);
1623 spin_lock(&swap_lock);
1624 p->flags = SWP_ACTIVE;
1625 nr_swap_pages += nr_good_pages;
1626 total_swap_pages += nr_good_pages;
1628 printk(KERN_INFO "Adding %uk swap on %s. "
1629 "Priority:%d extents:%d across:%lluk\n",
1630 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1631 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1633 /* insert swap space into swap_list: */
1635 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1636 if (p->prio >= swap_info[i].prio) {
1643 swap_list.head = swap_list.next = p - swap_info;
1645 swap_info[prev].next = p - swap_info;
1647 spin_unlock(&swap_lock);
1648 mutex_unlock(&swapon_mutex);
1653 set_blocksize(bdev, p->old_block_size);
1656 destroy_swap_extents(p);
1658 spin_lock(&swap_lock);
1659 swap_map = p->swap_map;
1660 p->swap_file = NULL;
1663 if (!(swap_flags & SWAP_FLAG_PREFER))
1665 spin_unlock(&swap_lock);
1668 filp_close(swap_file, NULL);
1670 if (page && !IS_ERR(page)) {
1672 page_cache_release(page);
1678 inode->i_flags |= S_SWAPFILE;
1679 mutex_unlock(&inode->i_mutex);
1684 void si_swapinfo(struct sysinfo *val)
1687 unsigned long nr_to_be_unused = 0;
1689 spin_lock(&swap_lock);
1690 for (i = 0; i < nr_swapfiles; i++) {
1691 if (!(swap_info[i].flags & SWP_USED) ||
1692 (swap_info[i].flags & SWP_WRITEOK))
1694 nr_to_be_unused += swap_info[i].inuse_pages;
1696 val->freeswap = nr_swap_pages + nr_to_be_unused;
1697 val->totalswap = total_swap_pages + nr_to_be_unused;
1698 spin_unlock(&swap_lock);
1699 if (vx_flags(VXF_VIRT_MEM, 0))
1700 vx_vsi_swapinfo(val);
1704 * Verify that a swap entry is valid and increment its swap map count.
1706 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1707 * "permanent", but will be reclaimed by the next swapoff.
1709 int swap_duplicate(swp_entry_t entry)
1711 struct swap_info_struct * p;
1712 unsigned long offset, type;
1715 type = swp_type(entry);
1716 if (type >= nr_swapfiles)
1718 p = type + swap_info;
1719 offset = swp_offset(entry);
1721 spin_lock(&swap_lock);
1722 if (offset < p->max && p->swap_map[offset]) {
1723 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1724 p->swap_map[offset]++;
1726 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1727 if (swap_overflow++ < 5)
1728 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1729 p->swap_map[offset] = SWAP_MAP_MAX;
1733 spin_unlock(&swap_lock);
1738 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1742 struct swap_info_struct *
1743 get_swap_info_struct(unsigned type)
1745 return &swap_info[type];
1749 * swap_lock prevents swap_map being freed. Don't grab an extra
1750 * reference on the swaphandle, it doesn't matter if it becomes unused.
1752 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1754 int ret = 0, i = 1 << page_cluster;
1756 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1758 if (!page_cluster) /* no readahead */
1760 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1761 if (!toff) /* first page is swap header */
1765 spin_lock(&swap_lock);
1767 /* Don't read-ahead past the end of the swap area */
1768 if (toff >= swapdev->max)
1770 /* Don't read in free or bad pages */
1771 if (!swapdev->swap_map[toff])
1773 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1778 spin_unlock(&swap_lock);