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/syscalls.h>
30 #include <asm/pgtable.h>
31 #include <asm/tlbflush.h>
32 #include <linux/swapops.h>
34 DEFINE_SPINLOCK(swaplock);
35 unsigned int nr_swapfiles;
36 long total_swap_pages;
37 static int swap_overflow;
39 EXPORT_SYMBOL(total_swap_pages);
41 static const char Bad_file[] = "Bad swap file entry ";
42 static const char Unused_file[] = "Unused swap file entry ";
43 static const char Bad_offset[] = "Bad swap offset entry ";
44 static const char Unused_offset[] = "Unused swap offset entry ";
46 struct swap_list_t swap_list = {-1, -1};
48 struct swap_info_struct swap_info[MAX_SWAPFILES];
50 static DECLARE_MUTEX(swapon_sem);
53 * We need this because the bdev->unplug_fn can sleep and we cannot
54 * hold swap_list_lock while calling the unplug_fn. And swap_list_lock
55 * cannot be turned into a semaphore.
57 static DECLARE_RWSEM(swap_unplug_sem);
59 #define SWAPFILE_CLUSTER 256
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;
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 above. If
75 * 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 static inline int scan_swap_map(struct swap_info_struct *si)
91 * We try to cluster swap pages by allocating them
92 * sequentially in swap. Once we've allocated
93 * SWAPFILE_CLUSTER pages this way, however, we resort to
94 * first-free allocation, starting a new cluster. This
95 * prevents us from scattering swap pages all over the entire
96 * swap partition, so that we reduce overall disk seek times
97 * between swap pages. -- sct */
99 while (si->cluster_next <= si->highest_bit) {
100 offset = si->cluster_next++;
101 if (si->swap_map[offset])
107 si->cluster_nr = SWAPFILE_CLUSTER;
109 /* try to find an empty (even not aligned) cluster. */
110 offset = si->lowest_bit;
112 if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
115 for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
116 if (si->swap_map[nr])
119 goto check_next_cluster;
121 /* We found a completly empty cluster, so start
126 /* No luck, so now go finegrined as usual. -Andrea */
127 for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
128 if (si->swap_map[offset])
130 si->lowest_bit = offset+1;
132 if (offset == si->lowest_bit)
134 if (offset == si->highest_bit)
136 if (si->lowest_bit > si->highest_bit) {
137 si->lowest_bit = si->max;
140 si->swap_map[offset] = 1;
143 si->cluster_next = offset+1;
146 si->lowest_bit = si->max;
151 swp_entry_t get_swap_page(void)
153 struct swap_info_struct * p;
154 unsigned long offset;
156 int type, wrapped = 0;
158 entry.val = 0; /* Out of memory */
160 type = swap_list.next;
163 if (nr_swap_pages <= 0)
167 p = &swap_info[type];
168 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
170 offset = scan_swap_map(p);
171 swap_device_unlock(p);
173 entry = swp_entry(type,offset);
174 type = swap_info[type].next;
176 p->prio != swap_info[type].prio) {
177 swap_list.next = swap_list.head;
179 swap_list.next = type;
186 if (type < 0 || p->prio != swap_info[type].prio) {
187 type = swap_list.head;
192 goto out; /* out of swap space */
199 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
201 struct swap_info_struct * p;
202 unsigned long offset, type;
206 type = swp_type(entry);
207 if (type >= nr_swapfiles)
209 p = & swap_info[type];
210 if (!(p->flags & SWP_USED))
212 offset = swp_offset(entry);
213 if (offset >= p->max)
215 if (!p->swap_map[offset])
218 if (p->prio > swap_info[swap_list.next].prio)
219 swap_list.next = type;
224 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
227 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
230 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
233 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
238 static void swap_info_put(struct swap_info_struct * p)
240 swap_device_unlock(p);
244 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
246 int count = p->swap_map[offset];
248 if (count < SWAP_MAP_MAX) {
250 p->swap_map[offset] = count;
252 if (offset < p->lowest_bit)
253 p->lowest_bit = offset;
254 if (offset > p->highest_bit)
255 p->highest_bit = offset;
264 * Caller has made sure that the swapdevice corresponding to entry
265 * is still around or has not been recycled.
267 void swap_free(swp_entry_t entry)
269 struct swap_info_struct * p;
271 p = swap_info_get(entry);
273 swap_entry_free(p, swp_offset(entry));
279 * How many references to page are currently swapped out?
281 static inline int page_swapcount(struct page *page)
284 struct swap_info_struct *p;
287 entry.val = page->private;
288 p = swap_info_get(entry);
290 /* Subtract the 1 for the swap cache itself */
291 count = p->swap_map[swp_offset(entry)] - 1;
298 * We can use this swap cache entry directly
299 * if there are no other references to it.
301 int can_share_swap_page(struct page *page)
305 BUG_ON(!PageLocked(page));
306 count = page_mapcount(page);
307 if (count <= 1 && PageSwapCache(page))
308 count += page_swapcount(page);
313 * Work out if there are any other processes sharing this
314 * swap cache page. Free it if you can. Return success.
316 int remove_exclusive_swap_page(struct page *page)
319 struct swap_info_struct * p;
322 BUG_ON(PagePrivate(page));
323 BUG_ON(!PageLocked(page));
325 if (!PageSwapCache(page))
327 if (PageWriteback(page))
329 if (page_count(page) != 2) /* 2: us + cache */
332 entry.val = page->private;
333 p = swap_info_get(entry);
337 /* Is the only swap cache user the cache itself? */
339 if (p->swap_map[swp_offset(entry)] == 1) {
340 /* Recheck the page count with the swapcache lock held.. */
341 write_lock_irq(&swapper_space.tree_lock);
342 if ((page_count(page) == 2) && !PageWriteback(page)) {
343 __delete_from_swap_cache(page);
347 write_unlock_irq(&swapper_space.tree_lock);
353 page_cache_release(page);
360 * Free the swap entry like above, but also try to
361 * free the page cache entry if it is the last user.
363 void free_swap_and_cache(swp_entry_t entry)
365 struct swap_info_struct * p;
366 struct page *page = NULL;
368 p = swap_info_get(entry);
370 if (swap_entry_free(p, swp_offset(entry)) == 1)
371 page = find_trylock_page(&swapper_space, entry.val);
377 BUG_ON(PagePrivate(page));
378 page_cache_get(page);
379 one_user = (page_count(page) == 2);
380 /* Only cache user (+us), or swap space full? Free it! */
381 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
382 delete_from_swap_cache(page);
386 page_cache_release(page);
391 * Always set the resulting pte to be nowrite (the same as COW pages
392 * after one process has exited). We don't know just how many PTEs will
393 * share this swap entry, so be cautious and let do_wp_page work out
394 * what to do if a write is requested later.
396 * vma->vm_mm->page_table_lock is held.
398 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
399 unsigned long addr, swp_entry_t entry, struct page *page)
401 inc_mm_counter(vma->vm_mm, rss);
403 set_pte_at(vma->vm_mm, addr, pte,
404 pte_mkold(mk_pte(page, vma->vm_page_prot)));
405 page_add_anon_rmap(page, vma, addr);
408 * Move the page to the active list so it is not
409 * immediately swapped out again after swapon.
414 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
415 unsigned long addr, unsigned long end,
416 swp_entry_t entry, struct page *page)
419 pte_t swp_pte = swp_entry_to_pte(entry);
421 pte = pte_offset_map(pmd, addr);
424 * swapoff spends a _lot_ of time in this loop!
425 * Test inline before going to call unuse_pte.
427 if (unlikely(pte_same(*pte, swp_pte))) {
428 unuse_pte(vma, pte, addr, entry, page);
432 } while (pte++, addr += PAGE_SIZE, addr != end);
437 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
438 unsigned long addr, unsigned long end,
439 swp_entry_t entry, struct page *page)
444 pmd = pmd_offset(pud, addr);
446 next = pmd_addr_end(addr, end);
447 if (pmd_none_or_clear_bad(pmd))
449 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
451 } while (pmd++, addr = next, addr != end);
455 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
456 unsigned long addr, unsigned long end,
457 swp_entry_t entry, struct page *page)
462 pud = pud_offset(pgd, addr);
464 next = pud_addr_end(addr, end);
465 if (pud_none_or_clear_bad(pud))
467 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
469 } while (pud++, addr = next, addr != end);
473 static int unuse_vma(struct vm_area_struct *vma,
474 swp_entry_t entry, struct page *page)
477 unsigned long addr, end, next;
480 addr = page_address_in_vma(page, vma);
484 end = addr + PAGE_SIZE;
486 addr = vma->vm_start;
490 pgd = pgd_offset(vma->vm_mm, addr);
492 next = pgd_addr_end(addr, end);
493 if (pgd_none_or_clear_bad(pgd))
495 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
497 } while (pgd++, addr = next, addr != end);
501 static int unuse_mm(struct mm_struct *mm,
502 swp_entry_t entry, struct page *page)
504 struct vm_area_struct *vma;
506 if (!down_read_trylock(&mm->mmap_sem)) {
508 * Activate page so shrink_cache is unlikely to unmap its
509 * ptes while lock is dropped, so swapoff can make progress.
513 down_read(&mm->mmap_sem);
516 spin_lock(&mm->page_table_lock);
517 for (vma = mm->mmap; vma; vma = vma->vm_next) {
518 if (vma->anon_vma && unuse_vma(vma, entry, page))
521 spin_unlock(&mm->page_table_lock);
522 up_read(&mm->mmap_sem);
524 * Currently unuse_mm cannot fail, but leave error handling
525 * at call sites for now, since we change it from time to time.
531 * Scan swap_map from current position to next entry still in use.
532 * Recycle to start on reaching the end, returning 0 when empty.
534 static int find_next_to_unuse(struct swap_info_struct *si, int prev)
541 * No need for swap_device_lock(si) here: we're just looking
542 * for whether an entry is in use, not modifying it; false
543 * hits are okay, and sys_swapoff() has already prevented new
544 * allocations from this area (while holding swap_list_lock()).
553 * No entries in use at top of swap_map,
554 * loop back to start and recheck there.
560 count = si->swap_map[i];
561 if (count && count != SWAP_MAP_BAD)
568 * We completely avoid races by reading each swap page in advance,
569 * and then search for the process using it. All the necessary
570 * page table adjustments can then be made atomically.
572 static int try_to_unuse(unsigned int type)
574 struct swap_info_struct * si = &swap_info[type];
575 struct mm_struct *start_mm;
576 unsigned short *swap_map;
577 unsigned short swcount;
582 int reset_overflow = 0;
586 * When searching mms for an entry, a good strategy is to
587 * start at the first mm we freed the previous entry from
588 * (though actually we don't notice whether we or coincidence
589 * freed the entry). Initialize this start_mm with a hold.
591 * A simpler strategy would be to start at the last mm we
592 * freed the previous entry from; but that would take less
593 * advantage of mmlist ordering, which clusters forked mms
594 * together, child after parent. If we race with dup_mmap(), we
595 * prefer to resolve parent before child, lest we miss entries
596 * duplicated after we scanned child: using last mm would invert
597 * that. Though it's only a serious concern when an overflowed
598 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
601 atomic_inc(&init_mm.mm_users);
604 * Keep on scanning until all entries have gone. Usually,
605 * one pass through swap_map is enough, but not necessarily:
606 * there are races when an instance of an entry might be missed.
608 while ((i = find_next_to_unuse(si, i)) != 0) {
609 if (signal_pending(current)) {
615 * Get a page for the entry, using the existing swap
616 * cache page if there is one. Otherwise, get a clean
617 * page and read the swap into it.
619 swap_map = &si->swap_map[i];
620 entry = swp_entry(type, i);
621 page = read_swap_cache_async(entry, NULL, 0);
624 * Either swap_duplicate() failed because entry
625 * has been freed independently, and will not be
626 * reused since sys_swapoff() already disabled
627 * allocation from here, or alloc_page() failed.
636 * Don't hold on to start_mm if it looks like exiting.
638 if (atomic_read(&start_mm->mm_users) == 1) {
641 atomic_inc(&init_mm.mm_users);
645 * Wait for and lock page. When do_swap_page races with
646 * try_to_unuse, do_swap_page can handle the fault much
647 * faster than try_to_unuse can locate the entry. This
648 * apparently redundant "wait_on_page_locked" lets try_to_unuse
649 * defer to do_swap_page in such a case - in some tests,
650 * do_swap_page and try_to_unuse repeatedly compete.
652 wait_on_page_locked(page);
653 wait_on_page_writeback(page);
655 wait_on_page_writeback(page);
658 * Remove all references to entry.
659 * Whenever we reach init_mm, there's no address space
660 * to search, but use it as a reminder to search shmem.
665 if (start_mm == &init_mm)
666 shmem = shmem_unuse(entry, page);
668 retval = unuse_mm(start_mm, entry, page);
671 int set_start_mm = (*swap_map >= swcount);
672 struct list_head *p = &start_mm->mmlist;
673 struct mm_struct *new_start_mm = start_mm;
674 struct mm_struct *prev_mm = start_mm;
675 struct mm_struct *mm;
677 atomic_inc(&new_start_mm->mm_users);
678 atomic_inc(&prev_mm->mm_users);
679 spin_lock(&mmlist_lock);
680 while (*swap_map > 1 && !retval &&
681 (p = p->next) != &start_mm->mmlist) {
682 mm = list_entry(p, struct mm_struct, mmlist);
683 if (atomic_inc_return(&mm->mm_users) == 1) {
684 atomic_dec(&mm->mm_users);
687 spin_unlock(&mmlist_lock);
696 else if (mm == &init_mm) {
698 shmem = shmem_unuse(entry, page);
700 retval = unuse_mm(mm, entry, page);
701 if (set_start_mm && *swap_map < swcount) {
703 atomic_inc(&mm->mm_users);
707 spin_lock(&mmlist_lock);
709 spin_unlock(&mmlist_lock);
712 start_mm = new_start_mm;
716 page_cache_release(page);
721 * How could swap count reach 0x7fff when the maximum
722 * pid is 0x7fff, and there's no way to repeat a swap
723 * page within an mm (except in shmem, where it's the
724 * shared object which takes the reference count)?
725 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
727 * If that's wrong, then we should worry more about
728 * exit_mmap() and do_munmap() cases described above:
729 * we might be resetting SWAP_MAP_MAX too early here.
730 * We know "Undead"s can happen, they're okay, so don't
731 * report them; but do report if we reset SWAP_MAP_MAX.
733 if (*swap_map == SWAP_MAP_MAX) {
734 swap_device_lock(si);
736 swap_device_unlock(si);
741 * If a reference remains (rare), we would like to leave
742 * the page in the swap cache; but try_to_unmap could
743 * then re-duplicate the entry once we drop page lock,
744 * so we might loop indefinitely; also, that page could
745 * not be swapped out to other storage meanwhile. So:
746 * delete from cache even if there's another reference,
747 * after ensuring that the data has been saved to disk -
748 * since if the reference remains (rarer), it will be
749 * read from disk into another page. Splitting into two
750 * pages would be incorrect if swap supported "shared
751 * private" pages, but they are handled by tmpfs files.
753 * Note shmem_unuse already deleted a swappage from
754 * the swap cache, unless the move to filepage failed:
755 * in which case it left swappage in cache, lowered its
756 * swap count to pass quickly through the loops above,
757 * and now we must reincrement count to try again later.
759 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
760 struct writeback_control wbc = {
761 .sync_mode = WB_SYNC_NONE,
764 swap_writepage(page, &wbc);
766 wait_on_page_writeback(page);
768 if (PageSwapCache(page)) {
770 swap_duplicate(entry);
772 delete_from_swap_cache(page);
776 * So we could skip searching mms once swap count went
777 * to 1, we did not mark any present ptes as dirty: must
778 * mark page dirty so shrink_list will preserve it.
782 page_cache_release(page);
785 * Make sure that we aren't completely killing
786 * interactive performance.
792 if (reset_overflow) {
793 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
800 * After a successful try_to_unuse, if no swap is now in use, we know we
801 * can empty the mmlist. swap_list_lock must be held on entry and exit.
802 * Note that mmlist_lock nests inside swap_list_lock, and an mm must be
803 * added to the mmlist just after page_duplicate - before would be racy.
805 static void drain_mmlist(void)
807 struct list_head *p, *next;
810 for (i = 0; i < nr_swapfiles; i++)
811 if (swap_info[i].inuse_pages)
813 spin_lock(&mmlist_lock);
814 list_for_each_safe(p, next, &init_mm.mmlist)
816 spin_unlock(&mmlist_lock);
820 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
821 * corresponds to page offset `offset'.
823 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
825 struct swap_extent *se = sis->curr_swap_extent;
826 struct swap_extent *start_se = se;
829 struct list_head *lh;
831 if (se->start_page <= offset &&
832 offset < (se->start_page + se->nr_pages)) {
833 return se->start_block + (offset - se->start_page);
836 if (lh == &sis->extent_list)
838 se = list_entry(lh, struct swap_extent, list);
839 sis->curr_swap_extent = se;
840 BUG_ON(se == start_se); /* It *must* be present */
845 * Free all of a swapdev's extent information
847 static void destroy_swap_extents(struct swap_info_struct *sis)
849 while (!list_empty(&sis->extent_list)) {
850 struct swap_extent *se;
852 se = list_entry(sis->extent_list.next,
853 struct swap_extent, list);
860 * Add a block range (and the corresponding page range) into this swapdev's
861 * extent list. The extent list is kept sorted in page order.
863 * This function rather assumes that it is called in ascending page order.
866 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
867 unsigned long nr_pages, sector_t start_block)
869 struct swap_extent *se;
870 struct swap_extent *new_se;
871 struct list_head *lh;
873 lh = sis->extent_list.prev; /* The highest page extent */
874 if (lh != &sis->extent_list) {
875 se = list_entry(lh, struct swap_extent, list);
876 BUG_ON(se->start_page + se->nr_pages != start_page);
877 if (se->start_block + se->nr_pages == start_block) {
879 se->nr_pages += nr_pages;
885 * No merge. Insert a new extent, preserving ordering.
887 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
890 new_se->start_page = start_page;
891 new_se->nr_pages = nr_pages;
892 new_se->start_block = start_block;
894 list_add_tail(&new_se->list, &sis->extent_list);
899 * A `swap extent' is a simple thing which maps a contiguous range of pages
900 * onto a contiguous range of disk blocks. An ordered list of swap extents
901 * is built at swapon time and is then used at swap_writepage/swap_readpage
902 * time for locating where on disk a page belongs.
904 * If the swapfile is an S_ISBLK block device, a single extent is installed.
905 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
906 * swap files identically.
908 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
909 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
910 * swapfiles are handled *identically* after swapon time.
912 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
913 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
914 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
915 * requirements, they are simply tossed out - we will never use those blocks
918 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
919 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
920 * which will scribble on the fs.
922 * The amount of disk space which a single swap extent represents varies.
923 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
924 * extents in the list. To avoid much list walking, we cache the previous
925 * search location in `curr_swap_extent', and start new searches from there.
926 * This is extremely effective. The average number of iterations in
927 * map_swap_page() has been measured at about 0.3 per page. - akpm.
929 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
932 unsigned blocks_per_page;
933 unsigned long page_no;
935 sector_t probe_block;
937 sector_t lowest_block = -1;
938 sector_t highest_block = 0;
942 inode = sis->swap_file->f_mapping->host;
943 if (S_ISBLK(inode->i_mode)) {
944 ret = add_swap_extent(sis, 0, sis->max, 0);
949 blkbits = inode->i_blkbits;
950 blocks_per_page = PAGE_SIZE >> blkbits;
953 * Map all the blocks into the extent list. This code doesn't try
958 last_block = i_size_read(inode) >> blkbits;
959 while ((probe_block + blocks_per_page) <= last_block &&
960 page_no < sis->max) {
961 unsigned block_in_page;
962 sector_t first_block;
964 first_block = bmap(inode, probe_block);
965 if (first_block == 0)
969 * It must be PAGE_SIZE aligned on-disk
971 if (first_block & (blocks_per_page - 1)) {
976 for (block_in_page = 1; block_in_page < blocks_per_page;
980 block = bmap(inode, probe_block + block_in_page);
983 if (block != first_block + block_in_page) {
990 first_block >>= (PAGE_SHIFT - blkbits);
991 if (page_no) { /* exclude the header page */
992 if (first_block < lowest_block)
993 lowest_block = first_block;
994 if (first_block > highest_block)
995 highest_block = first_block;
999 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1001 ret = add_swap_extent(sis, page_no, 1, first_block);
1006 probe_block += blocks_per_page;
1011 *span = 1 + highest_block - lowest_block;
1013 page_no = 1; /* force Empty message */
1015 sis->pages = page_no - 1;
1016 sis->highest_bit = page_no - 1;
1018 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1019 struct swap_extent, list);
1022 printk(KERN_ERR "swapon: swapfile has holes\n");
1028 #if 0 /* We don't need this yet */
1029 #include <linux/backing-dev.h>
1030 int page_queue_congested(struct page *page)
1032 struct backing_dev_info *bdi;
1034 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1036 if (PageSwapCache(page)) {
1037 swp_entry_t entry = { .val = page->private };
1038 struct swap_info_struct *sis;
1040 sis = get_swap_info_struct(swp_type(entry));
1041 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1043 bdi = page->mapping->backing_dev_info;
1044 return bdi_write_congested(bdi);
1048 asmlinkage long sys_swapoff(const char __user * specialfile)
1050 struct swap_info_struct * p = NULL;
1051 unsigned short *swap_map;
1052 struct file *swap_file, *victim;
1053 struct address_space *mapping;
1054 struct inode *inode;
1059 if (!capable(CAP_SYS_ADMIN))
1062 pathname = getname(specialfile);
1063 err = PTR_ERR(pathname);
1064 if (IS_ERR(pathname))
1067 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1069 err = PTR_ERR(victim);
1073 mapping = victim->f_mapping;
1076 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1077 p = swap_info + type;
1078 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1079 if (p->swap_file->f_mapping == mapping)
1089 if (!security_vm_enough_memory(p->pages))
1090 vm_unacct_memory(p->pages);
1097 swap_list.head = p->next;
1099 swap_info[prev].next = p->next;
1101 if (type == swap_list.next) {
1102 /* just pick something that's safe... */
1103 swap_list.next = swap_list.head;
1105 nr_swap_pages -= p->pages;
1106 total_swap_pages -= p->pages;
1107 p->flags &= ~SWP_WRITEOK;
1109 current->flags |= PF_SWAPOFF;
1110 err = try_to_unuse(type);
1111 current->flags &= ~PF_SWAPOFF;
1113 /* wait for any unplug function to finish */
1114 down_write(&swap_unplug_sem);
1115 up_write(&swap_unplug_sem);
1118 /* re-insert swap space back into swap_list */
1120 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1121 if (p->prio >= swap_info[i].prio)
1125 swap_list.head = swap_list.next = p - swap_info;
1127 swap_info[prev].next = p - swap_info;
1128 nr_swap_pages += p->pages;
1129 total_swap_pages += p->pages;
1130 p->flags |= SWP_WRITEOK;
1134 destroy_swap_extents(p);
1138 swap_device_lock(p);
1139 swap_file = p->swap_file;
1140 p->swap_file = NULL;
1142 swap_map = p->swap_map;
1145 swap_device_unlock(p);
1149 inode = mapping->host;
1150 if (S_ISBLK(inode->i_mode)) {
1151 struct block_device *bdev = I_BDEV(inode);
1152 set_blocksize(bdev, p->old_block_size);
1155 down(&inode->i_sem);
1156 inode->i_flags &= ~S_SWAPFILE;
1159 filp_close(swap_file, NULL);
1163 filp_close(victim, NULL);
1168 #ifdef CONFIG_PROC_FS
1170 static void *swap_start(struct seq_file *swap, loff_t *pos)
1172 struct swap_info_struct *ptr = swap_info;
1178 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1179 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1188 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1190 struct swap_info_struct *ptr = v;
1191 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1193 for (++ptr; ptr < endptr; ptr++) {
1194 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1203 static void swap_stop(struct seq_file *swap, void *v)
1208 static int swap_show(struct seq_file *swap, void *v)
1210 struct swap_info_struct *ptr = v;
1215 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1217 file = ptr->swap_file;
1218 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1219 seq_printf(swap, "%*s%s\t%d\t%ld\t%d\n",
1220 len < 40 ? 40 - len : 1, " ",
1221 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1222 "partition" : "file\t",
1223 ptr->pages << (PAGE_SHIFT - 10),
1224 ptr->inuse_pages << (PAGE_SHIFT - 10),
1229 static struct seq_operations swaps_op = {
1230 .start = swap_start,
1236 static int swaps_open(struct inode *inode, struct file *file)
1238 return seq_open(file, &swaps_op);
1241 static struct file_operations proc_swaps_operations = {
1244 .llseek = seq_lseek,
1245 .release = seq_release,
1248 static int __init procswaps_init(void)
1250 struct proc_dir_entry *entry;
1252 entry = create_proc_entry("swaps", 0, NULL);
1254 entry->proc_fops = &proc_swaps_operations;
1257 __initcall(procswaps_init);
1258 #endif /* CONFIG_PROC_FS */
1261 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1263 * The swapon system call
1265 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1267 struct swap_info_struct * p;
1269 struct block_device *bdev = NULL;
1270 struct file *swap_file = NULL;
1271 struct address_space *mapping;
1275 static int least_priority;
1276 union swap_header *swap_header = NULL;
1277 int swap_header_version;
1278 int nr_good_pages = 0;
1281 unsigned long maxpages = 1;
1283 unsigned short *swap_map;
1284 struct page *page = NULL;
1285 struct inode *inode = NULL;
1288 if (!capable(CAP_SYS_ADMIN))
1292 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1293 if (!(p->flags & SWP_USED))
1297 * Test if adding another swap device is possible. There are
1298 * two limiting factors: 1) the number of bits for the swap
1299 * type swp_entry_t definition and 2) the number of bits for
1300 * the swap type in the swap ptes as defined by the different
1301 * architectures. To honor both limitations a swap entry
1302 * with swap offset 0 and swap type ~0UL is created, encoded
1303 * to a swap pte, decoded to a swp_entry_t again and finally
1304 * the swap type part is extracted. This will mask all bits
1305 * from the initial ~0UL that can't be encoded in either the
1306 * swp_entry_t or the architecture definition of a swap pte.
1308 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1312 if (type >= nr_swapfiles)
1313 nr_swapfiles = type+1;
1314 INIT_LIST_HEAD(&p->extent_list);
1315 p->flags = SWP_USED;
1316 p->swap_file = NULL;
1317 p->old_block_size = 0;
1323 spin_lock_init(&p->sdev_lock);
1325 if (swap_flags & SWAP_FLAG_PREFER) {
1327 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1329 p->prio = --least_priority;
1332 name = getname(specialfile);
1333 error = PTR_ERR(name);
1338 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1339 error = PTR_ERR(swap_file);
1340 if (IS_ERR(swap_file)) {
1345 p->swap_file = swap_file;
1346 mapping = swap_file->f_mapping;
1347 inode = mapping->host;
1350 for (i = 0; i < nr_swapfiles; i++) {
1351 struct swap_info_struct *q = &swap_info[i];
1353 if (i == type || !q->swap_file)
1355 if (mapping == q->swap_file->f_mapping)
1360 if (S_ISBLK(inode->i_mode)) {
1361 bdev = I_BDEV(inode);
1362 error = bd_claim(bdev, sys_swapon);
1367 p->old_block_size = block_size(bdev);
1368 error = set_blocksize(bdev, PAGE_SIZE);
1372 } else if (S_ISREG(inode->i_mode)) {
1373 p->bdev = inode->i_sb->s_bdev;
1374 down(&inode->i_sem);
1376 if (IS_SWAPFILE(inode)) {
1384 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1387 * Read the swap header.
1389 if (!mapping->a_ops->readpage) {
1393 page = read_cache_page(mapping, 0,
1394 (filler_t *)mapping->a_ops->readpage, swap_file);
1396 error = PTR_ERR(page);
1399 wait_on_page_locked(page);
1400 if (!PageUptodate(page))
1403 swap_header = page_address(page);
1405 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1406 swap_header_version = 1;
1407 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1408 swap_header_version = 2;
1410 printk("Unable to find swap-space signature\n");
1415 switch (swap_header_version) {
1417 printk(KERN_ERR "version 0 swap is no longer supported. "
1418 "Use mkswap -v1 %s\n", name);
1422 /* Check the swap header's sub-version and the size of
1423 the swap file and bad block lists */
1424 if (swap_header->info.version != 1) {
1426 "Unable to handle swap header version %d\n",
1427 swap_header->info.version);
1434 * Find out how many pages are allowed for a single swap
1435 * device. There are two limiting factors: 1) the number of
1436 * bits for the swap offset in the swp_entry_t type and
1437 * 2) the number of bits in the a swap pte as defined by
1438 * the different architectures. In order to find the
1439 * largest possible bit mask a swap entry with swap type 0
1440 * and swap offset ~0UL is created, encoded to a swap pte,
1441 * decoded to a swp_entry_t again and finally the swap
1442 * offset is extracted. This will mask all the bits from
1443 * the initial ~0UL mask that can't be encoded in either
1444 * the swp_entry_t or the architecture definition of a
1447 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1448 if (maxpages > swap_header->info.last_page)
1449 maxpages = swap_header->info.last_page;
1450 p->highest_bit = maxpages - 1;
1455 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1457 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1460 /* OK, set up the swap map and apply the bad block list */
1461 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1467 memset(p->swap_map, 0, maxpages * sizeof(short));
1468 for (i=0; i<swap_header->info.nr_badpages; i++) {
1469 int page = swap_header->info.badpages[i];
1470 if (page <= 0 || page >= swap_header->info.last_page)
1473 p->swap_map[page] = SWAP_MAP_BAD;
1475 nr_good_pages = swap_header->info.last_page -
1476 swap_header->info.nr_badpages -
1477 1 /* header page */;
1482 if (swapfilesize && maxpages > swapfilesize) {
1484 "Swap area shorter than signature indicates\n");
1488 if (nr_good_pages) {
1489 p->swap_map[0] = SWAP_MAP_BAD;
1491 p->pages = nr_good_pages;
1492 nr_extents = setup_swap_extents(p, &span);
1493 if (nr_extents < 0) {
1497 nr_good_pages = p->pages;
1499 if (!nr_good_pages) {
1500 printk(KERN_WARNING "Empty swap-file\n");
1507 swap_device_lock(p);
1508 p->flags = SWP_ACTIVE;
1509 nr_swap_pages += nr_good_pages;
1510 total_swap_pages += nr_good_pages;
1512 printk(KERN_INFO "Adding %dk swap on %s. "
1513 "Priority:%d extents:%d across:%lluk\n",
1514 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1515 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1517 /* insert swap space into swap_list: */
1519 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1520 if (p->prio >= swap_info[i].prio) {
1527 swap_list.head = swap_list.next = p - swap_info;
1529 swap_info[prev].next = p - swap_info;
1531 swap_device_unlock(p);
1538 set_blocksize(bdev, p->old_block_size);
1541 destroy_swap_extents(p);
1544 swap_map = p->swap_map;
1545 p->swap_file = NULL;
1548 if (!(swap_flags & SWAP_FLAG_PREFER))
1553 filp_close(swap_file, NULL);
1555 if (page && !IS_ERR(page)) {
1557 page_cache_release(page);
1563 inode->i_flags |= S_SWAPFILE;
1569 void si_swapinfo(struct sysinfo *val)
1572 unsigned long nr_to_be_unused = 0;
1575 for (i = 0; i < nr_swapfiles; i++) {
1576 if (!(swap_info[i].flags & SWP_USED) ||
1577 (swap_info[i].flags & SWP_WRITEOK))
1579 nr_to_be_unused += swap_info[i].inuse_pages;
1581 val->freeswap = nr_swap_pages + nr_to_be_unused;
1582 val->totalswap = total_swap_pages + nr_to_be_unused;
1587 * Verify that a swap entry is valid and increment its swap map count.
1589 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1590 * "permanent", but will be reclaimed by the next swapoff.
1592 int swap_duplicate(swp_entry_t entry)
1594 struct swap_info_struct * p;
1595 unsigned long offset, type;
1598 type = swp_type(entry);
1599 if (type >= nr_swapfiles)
1601 p = type + swap_info;
1602 offset = swp_offset(entry);
1604 swap_device_lock(p);
1605 if (offset < p->max && p->swap_map[offset]) {
1606 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1607 p->swap_map[offset]++;
1609 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1610 if (swap_overflow++ < 5)
1611 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1612 p->swap_map[offset] = SWAP_MAP_MAX;
1616 swap_device_unlock(p);
1621 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1625 struct swap_info_struct *
1626 get_swap_info_struct(unsigned type)
1628 return &swap_info[type];
1632 * swap_device_lock prevents swap_map being freed. Don't grab an extra
1633 * reference on the swaphandle, it doesn't matter if it becomes unused.
1635 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1637 int ret = 0, i = 1 << page_cluster;
1639 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1641 if (!page_cluster) /* no readahead */
1643 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1644 if (!toff) /* first page is swap header */
1648 swap_device_lock(swapdev);
1650 /* Don't read-ahead past the end of the swap area */
1651 if (toff >= swapdev->max)
1653 /* Don't read in free or bad pages */
1654 if (!swapdev->swap_map[toff])
1656 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1661 swap_device_unlock(swapdev);