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>
29 #include <asm/pgtable.h>
30 #include <asm/tlbflush.h>
31 #include <linux/swapops.h>
33 spinlock_t swaplock = SPIN_LOCK_UNLOCKED;
34 unsigned int nr_swapfiles;
35 long total_swap_pages;
36 static int swap_overflow;
38 EXPORT_SYMBOL(total_swap_pages);
40 static const char Bad_file[] = "Bad swap file entry ";
41 static const char Unused_file[] = "Unused swap file entry ";
42 static const char Bad_offset[] = "Bad swap offset entry ";
43 static const char Unused_offset[] = "Unused swap offset entry ";
45 struct swap_list_t swap_list = {-1, -1};
47 struct swap_info_struct swap_info[MAX_SWAPFILES];
49 static DECLARE_MUTEX(swapon_sem);
52 * We need this because the bdev->unplug_fn can sleep and we cannot
53 * hold swap_list_lock while calling the unplug_fn. And swap_list_lock
54 * cannot be turned into a semaphore.
56 static DECLARE_RWSEM(swap_unplug_sem);
58 #define SWAPFILE_CLUSTER 256
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;
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 above. If
74 * 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 bdi->unplug_io_fn(bdi, page);
83 up_read(&swap_unplug_sem);
86 static inline int scan_swap_map(struct swap_info_struct *si)
90 * We try to cluster swap pages by allocating them
91 * sequentially in swap. Once we've allocated
92 * SWAPFILE_CLUSTER pages this way, however, we resort to
93 * first-free allocation, starting a new cluster. This
94 * prevents us from scattering swap pages all over the entire
95 * swap partition, so that we reduce overall disk seek times
96 * between swap pages. -- sct */
98 while (si->cluster_next <= si->highest_bit) {
99 offset = si->cluster_next++;
100 if (si->swap_map[offset])
106 si->cluster_nr = SWAPFILE_CLUSTER;
108 /* try to find an empty (even not aligned) cluster. */
109 offset = si->lowest_bit;
111 if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
114 for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
115 if (si->swap_map[nr])
118 goto check_next_cluster;
120 /* We found a completly empty cluster, so start
125 /* No luck, so now go finegrined as usual. -Andrea */
126 for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
127 if (si->swap_map[offset])
129 si->lowest_bit = offset+1;
131 if (offset == si->lowest_bit)
133 if (offset == si->highest_bit)
135 if (si->lowest_bit > si->highest_bit) {
136 si->lowest_bit = si->max;
139 si->swap_map[offset] = 1;
142 si->cluster_next = offset+1;
145 si->lowest_bit = si->max;
150 swp_entry_t get_swap_page(void)
152 struct swap_info_struct * p;
153 unsigned long offset;
155 int type, wrapped = 0;
157 entry.val = 0; /* Out of memory */
159 type = swap_list.next;
162 if (nr_swap_pages <= 0)
166 p = &swap_info[type];
167 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
169 offset = scan_swap_map(p);
170 swap_device_unlock(p);
172 entry = swp_entry(type,offset);
173 type = swap_info[type].next;
175 p->prio != swap_info[type].prio) {
176 swap_list.next = swap_list.head;
178 swap_list.next = type;
185 if (type < 0 || p->prio != swap_info[type].prio) {
186 type = swap_list.head;
191 goto out; /* out of swap space */
198 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
200 struct swap_info_struct * p;
201 unsigned long offset, type;
205 type = swp_type(entry);
206 if (type >= nr_swapfiles)
208 p = & swap_info[type];
209 if (!(p->flags & SWP_USED))
211 offset = swp_offset(entry);
212 if (offset >= p->max)
214 if (!p->swap_map[offset])
217 if (p->prio > swap_info[swap_list.next].prio)
218 swap_list.next = type;
223 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
226 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
229 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
232 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
237 static void swap_info_put(struct swap_info_struct * p)
239 swap_device_unlock(p);
243 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
245 int count = p->swap_map[offset];
247 if (count < SWAP_MAP_MAX) {
249 p->swap_map[offset] = count;
251 if (offset < p->lowest_bit)
252 p->lowest_bit = offset;
253 if (offset > p->highest_bit)
254 p->highest_bit = offset;
263 * Caller has made sure that the swapdevice corresponding to entry
264 * is still around or has not been recycled.
266 void swap_free(swp_entry_t entry)
268 struct swap_info_struct * p;
270 p = swap_info_get(entry);
272 swap_entry_free(p, swp_offset(entry));
278 * Check if we're the only user of a swap page,
279 * when the page is locked.
281 static int exclusive_swap_page(struct page *page)
284 struct swap_info_struct * p;
287 entry.val = page->private;
288 p = swap_info_get(entry);
290 /* Is the only swap cache user the cache itself? */
291 if (p->swap_map[swp_offset(entry)] == 1) {
292 /* Recheck the page count with the swapcache lock held.. */
293 spin_lock_irq(&swapper_space.tree_lock);
294 if (page_count(page) == 2)
296 spin_unlock_irq(&swapper_space.tree_lock);
304 * We can use this swap cache entry directly
305 * if there are no other references to it.
307 * Here "exclusive_swap_page()" does the real
308 * work, but we opportunistically check whether
309 * we need to get all the locks first..
311 int can_share_swap_page(struct page *page)
315 if (!PageLocked(page))
317 switch (page_count(page)) {
319 if (!PagePrivate(page))
323 if (!PageSwapCache(page))
325 retval = exclusive_swap_page(page);
328 if (PageReserved(page))
336 * Work out if there are any other processes sharing this
337 * swap cache page. Free it if you can. Return success.
339 int remove_exclusive_swap_page(struct page *page)
342 struct swap_info_struct * p;
345 BUG_ON(PagePrivate(page));
346 BUG_ON(!PageLocked(page));
348 if (!PageSwapCache(page))
350 if (PageWriteback(page))
352 if (page_count(page) != 2) /* 2: us + cache */
355 entry.val = page->private;
356 p = swap_info_get(entry);
360 /* Is the only swap cache user the cache itself? */
362 if (p->swap_map[swp_offset(entry)] == 1) {
363 /* Recheck the page count with the swapcache lock held.. */
364 spin_lock_irq(&swapper_space.tree_lock);
365 if ((page_count(page) == 2) && !PageWriteback(page)) {
366 __delete_from_swap_cache(page);
370 spin_unlock_irq(&swapper_space.tree_lock);
376 page_cache_release(page);
383 * Free the swap entry like above, but also try to
384 * free the page cache entry if it is the last user.
386 void free_swap_and_cache(swp_entry_t entry)
388 struct swap_info_struct * p;
389 struct page *page = NULL;
391 p = swap_info_get(entry);
393 if (swap_entry_free(p, swp_offset(entry)) == 1) {
394 spin_lock_irq(&swapper_space.tree_lock);
395 page = radix_tree_lookup(&swapper_space.page_tree,
397 if (page && TestSetPageLocked(page))
399 spin_unlock_irq(&swapper_space.tree_lock);
406 BUG_ON(PagePrivate(page));
407 page_cache_get(page);
408 one_user = (page_count(page) == 2);
409 /* Only cache user (+us), or swap space full? Free it! */
410 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
411 delete_from_swap_cache(page);
415 page_cache_release(page);
420 * The swap entry has been read in advance, and we return 1 to indicate
421 * that the page has been used or is no longer needed.
423 * Always set the resulting pte to be nowrite (the same as COW pages
424 * after one process has exited). We don't know just how many PTEs will
425 * share this swap entry, so be cautious and let do_wp_page work out
426 * what to do if a write is requested later.
428 /* vma->vm_mm->page_table_lock is held */
430 unuse_pte(struct vm_area_struct *vma, unsigned long address, pte_t *dir,
431 swp_entry_t entry, struct page *page)
435 set_pte(dir, pte_mkold(mk_pte(page, vma->vm_page_prot)));
436 page_add_anon_rmap(page, vma, address);
440 /* vma->vm_mm->page_table_lock is held */
441 static unsigned long unuse_pmd(struct vm_area_struct * vma, pmd_t *dir,
442 unsigned long address, unsigned long size, unsigned long offset,
443 swp_entry_t entry, struct page *page)
447 pte_t swp_pte = swp_entry_to_pte(entry);
456 pte = pte_offset_map(dir, address);
457 offset += address & PMD_MASK;
458 address &= ~PMD_MASK;
459 end = address + size;
464 * swapoff spends a _lot_ of time in this loop!
465 * Test inline before going to call unuse_pte.
467 if (unlikely(pte_same(*pte, swp_pte))) {
468 unuse_pte(vma, offset + address, pte, entry, page);
472 * Move the page to the active list so it is not
473 * immediately swapped out again after swapon.
477 /* add 1 since address may be 0 */
478 return 1 + offset + address;
480 address += PAGE_SIZE;
482 } while (address && (address < end));
487 /* vma->vm_mm->page_table_lock is held */
488 static unsigned long unuse_pgd(struct vm_area_struct * vma, pgd_t *dir,
489 unsigned long address, unsigned long size,
490 swp_entry_t entry, struct page *page)
493 unsigned long offset, end;
494 unsigned long foundaddr;
503 pmd = pmd_offset(dir, address);
504 offset = address & PGDIR_MASK;
505 address &= ~PGDIR_MASK;
506 end = address + size;
507 if (end > PGDIR_SIZE)
512 foundaddr = unuse_pmd(vma, pmd, address, end - address,
513 offset, entry, page);
516 address = (address + PMD_SIZE) & PMD_MASK;
518 } while (address && (address < end));
522 /* vma->vm_mm->page_table_lock is held */
523 static unsigned long unuse_vma(struct vm_area_struct * vma, pgd_t *pgdir,
524 swp_entry_t entry, struct page *page)
526 unsigned long start = vma->vm_start, end = vma->vm_end;
527 unsigned long foundaddr;
532 foundaddr = unuse_pgd(vma, pgdir, start, end - start,
536 start = (start + PGDIR_SIZE) & PGDIR_MASK;
538 } while (start && (start < end));
542 static int unuse_process(struct mm_struct * mm,
543 swp_entry_t entry, struct page* page)
545 struct vm_area_struct* vma;
546 unsigned long foundaddr = 0;
549 * Go through process' page directory.
551 down_read(&mm->mmap_sem);
552 spin_lock(&mm->page_table_lock);
553 for (vma = mm->mmap; vma; vma = vma->vm_next) {
554 if (!is_vm_hugetlb_page(vma)) {
555 pgd_t * pgd = pgd_offset(mm, vma->vm_start);
556 foundaddr = unuse_vma(vma, pgd, entry, page);
561 spin_unlock(&mm->page_table_lock);
562 up_read(&mm->mmap_sem);
564 * Currently unuse_process cannot fail, but leave error handling
565 * at call sites for now, since we change it from time to time.
571 * Scan swap_map from current position to next entry still in use.
572 * Recycle to start on reaching the end, returning 0 when empty.
574 static int find_next_to_unuse(struct swap_info_struct *si, int prev)
581 * No need for swap_device_lock(si) here: we're just looking
582 * for whether an entry is in use, not modifying it; false
583 * hits are okay, and sys_swapoff() has already prevented new
584 * allocations from this area (while holding swap_list_lock()).
593 * No entries in use at top of swap_map,
594 * loop back to start and recheck there.
600 count = si->swap_map[i];
601 if (count && count != SWAP_MAP_BAD)
608 * We completely avoid races by reading each swap page in advance,
609 * and then search for the process using it. All the necessary
610 * page table adjustments can then be made atomically.
612 static int try_to_unuse(unsigned int type)
614 struct swap_info_struct * si = &swap_info[type];
615 struct mm_struct *start_mm;
616 unsigned short *swap_map;
617 unsigned short swcount;
622 int reset_overflow = 0;
626 * When searching mms for an entry, a good strategy is to
627 * start at the first mm we freed the previous entry from
628 * (though actually we don't notice whether we or coincidence
629 * freed the entry). Initialize this start_mm with a hold.
631 * A simpler strategy would be to start at the last mm we
632 * freed the previous entry from; but that would take less
633 * advantage of mmlist ordering (now preserved by swap_out()),
634 * which clusters forked address spaces together, most recent
635 * child immediately after parent. If we race with dup_mmap(),
636 * we very much want to resolve parent before child, otherwise
637 * we may miss some entries: using last mm would invert that.
640 atomic_inc(&init_mm.mm_users);
643 * Keep on scanning until all entries have gone. Usually,
644 * one pass through swap_map is enough, but not necessarily:
645 * mmput() removes mm from mmlist before exit_mmap() and its
646 * zap_page_range(). That's not too bad, those entries are
647 * on their way out, and handled faster there than here.
648 * do_munmap() behaves similarly, taking the range out of mm's
649 * vma list before zap_page_range(). But unfortunately, when
650 * unmapping a part of a vma, it takes the whole out first,
651 * then reinserts what's left after (might even reschedule if
652 * open() method called) - so swap entries may be invisible
653 * to swapoff for a while, then reappear - but that is rare.
655 while ((i = find_next_to_unuse(si, i)) != 0) {
656 if (signal_pending(current)) {
662 * Get a page for the entry, using the existing swap
663 * cache page if there is one. Otherwise, get a clean
664 * page and read the swap into it.
666 swap_map = &si->swap_map[i];
667 entry = swp_entry(type, i);
668 page = read_swap_cache_async(entry, NULL, 0);
671 * Either swap_duplicate() failed because entry
672 * has been freed independently, and will not be
673 * reused since sys_swapoff() already disabled
674 * allocation from here, or alloc_page() failed.
683 * Don't hold on to start_mm if it looks like exiting.
685 if (atomic_read(&start_mm->mm_users) == 1) {
688 atomic_inc(&init_mm.mm_users);
692 * Wait for and lock page. When do_swap_page races with
693 * try_to_unuse, do_swap_page can handle the fault much
694 * faster than try_to_unuse can locate the entry. This
695 * apparently redundant "wait_on_page_locked" lets try_to_unuse
696 * defer to do_swap_page in such a case - in some tests,
697 * do_swap_page and try_to_unuse repeatedly compete.
699 wait_on_page_locked(page);
700 wait_on_page_writeback(page);
702 wait_on_page_writeback(page);
705 * Remove all references to entry, without blocking.
706 * Whenever we reach init_mm, there's no address space
707 * to search, but use it as a reminder to search shmem.
712 if (start_mm == &init_mm)
713 shmem = shmem_unuse(entry, page);
715 retval = unuse_process(start_mm, entry, page);
718 int set_start_mm = (*swap_map >= swcount);
719 struct list_head *p = &start_mm->mmlist;
720 struct mm_struct *new_start_mm = start_mm;
721 struct mm_struct *prev_mm = start_mm;
722 struct mm_struct *mm;
724 atomic_inc(&new_start_mm->mm_users);
725 atomic_inc(&prev_mm->mm_users);
726 spin_lock(&mmlist_lock);
727 while (*swap_map > 1 && !retval &&
728 (p = p->next) != &start_mm->mmlist) {
729 mm = list_entry(p, struct mm_struct, mmlist);
730 atomic_inc(&mm->mm_users);
731 spin_unlock(&mmlist_lock);
740 else if (mm == &init_mm) {
742 shmem = shmem_unuse(entry, page);
744 retval = unuse_process(mm, entry, page);
745 if (set_start_mm && *swap_map < swcount) {
747 atomic_inc(&mm->mm_users);
751 spin_lock(&mmlist_lock);
753 spin_unlock(&mmlist_lock);
756 start_mm = new_start_mm;
760 page_cache_release(page);
765 * How could swap count reach 0x7fff when the maximum
766 * pid is 0x7fff, and there's no way to repeat a swap
767 * page within an mm (except in shmem, where it's the
768 * shared object which takes the reference count)?
769 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
771 * If that's wrong, then we should worry more about
772 * exit_mmap() and do_munmap() cases described above:
773 * we might be resetting SWAP_MAP_MAX too early here.
774 * We know "Undead"s can happen, they're okay, so don't
775 * report them; but do report if we reset SWAP_MAP_MAX.
777 if (*swap_map == SWAP_MAP_MAX) {
778 swap_device_lock(si);
780 swap_device_unlock(si);
785 * If a reference remains (rare), we would like to leave
786 * the page in the swap cache; but try_to_unmap could
787 * then re-duplicate the entry once we drop page lock,
788 * so we might loop indefinitely; also, that page could
789 * not be swapped out to other storage meanwhile. So:
790 * delete from cache even if there's another reference,
791 * after ensuring that the data has been saved to disk -
792 * since if the reference remains (rarer), it will be
793 * read from disk into another page. Splitting into two
794 * pages would be incorrect if swap supported "shared
795 * private" pages, but they are handled by tmpfs files.
797 * Note shmem_unuse already deleted a swappage from
798 * the swap cache, unless the move to filepage failed:
799 * in which case it left swappage in cache, lowered its
800 * swap count to pass quickly through the loops above,
801 * and now we must reincrement count to try again later.
803 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
804 struct writeback_control wbc = {
805 .sync_mode = WB_SYNC_NONE,
808 swap_writepage(page, &wbc);
810 wait_on_page_writeback(page);
812 if (PageSwapCache(page)) {
814 swap_duplicate(entry);
816 delete_from_swap_cache(page);
820 * So we could skip searching mms once swap count went
821 * to 1, we did not mark any present ptes as dirty: must
822 * mark page dirty so shrink_list will preserve it.
826 page_cache_release(page);
829 * Make sure that we aren't completely killing
830 * interactive performance.
836 if (reset_overflow) {
837 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
844 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
845 * corresponds to page offset `offset'.
847 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
849 struct swap_extent *se = sis->curr_swap_extent;
850 struct swap_extent *start_se = se;
853 struct list_head *lh;
855 if (se->start_page <= offset &&
856 offset < (se->start_page + se->nr_pages)) {
857 return se->start_block + (offset - se->start_page);
860 if (lh == &sis->extent_list)
862 se = list_entry(lh, struct swap_extent, list);
863 sis->curr_swap_extent = se;
864 BUG_ON(se == start_se); /* It *must* be present */
869 * Free all of a swapdev's extent information
871 static void destroy_swap_extents(struct swap_info_struct *sis)
873 while (!list_empty(&sis->extent_list)) {
874 struct swap_extent *se;
876 se = list_entry(sis->extent_list.next,
877 struct swap_extent, list);
885 * Add a block range (and the corresponding page range) into this swapdev's
886 * extent list. The extent list is kept sorted in block order.
888 * This function rather assumes that it is called in ascending sector_t order.
889 * It doesn't look for extent coalescing opportunities.
892 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
893 unsigned long nr_pages, sector_t start_block)
895 struct swap_extent *se;
896 struct swap_extent *new_se;
897 struct list_head *lh;
899 lh = sis->extent_list.next; /* The highest-addressed block */
900 while (lh != &sis->extent_list) {
901 se = list_entry(lh, struct swap_extent, list);
902 if (se->start_block + se->nr_pages == start_block &&
903 se->start_page + se->nr_pages == start_page) {
905 se->nr_pages += nr_pages;
912 * No merge. Insert a new extent, preserving ordering.
914 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
917 new_se->start_page = start_page;
918 new_se->nr_pages = nr_pages;
919 new_se->start_block = start_block;
921 lh = sis->extent_list.prev; /* The lowest block */
922 while (lh != &sis->extent_list) {
923 se = list_entry(lh, struct swap_extent, list);
924 if (se->start_block > start_block)
928 list_add_tail(&new_se->list, lh);
934 * A `swap extent' is a simple thing which maps a contiguous range of pages
935 * onto a contiguous range of disk blocks. An ordered list of swap extents
936 * is built at swapon time and is then used at swap_writepage/swap_readpage
937 * time for locating where on disk a page belongs.
939 * If the swapfile is an S_ISBLK block device, a single extent is installed.
940 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
941 * swap files identically.
943 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
944 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
945 * swapfiles are handled *identically* after swapon time.
947 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
948 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
949 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
950 * requirements, they are simply tossed out - we will never use those blocks
953 * For S_ISREG swapfiles we hold i_sem across the life of the swapon. This
954 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
955 * which will scribble on the fs.
957 * The amount of disk space which a single swap extent represents varies.
958 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
959 * extents in the list. To avoid much list walking, we cache the previous
960 * search location in `curr_swap_extent', and start new searches from there.
961 * This is extremely effective. The average number of iterations in
962 * map_swap_page() has been measured at about 0.3 per page. - akpm.
964 static int setup_swap_extents(struct swap_info_struct *sis)
967 unsigned blocks_per_page;
968 unsigned long page_no;
970 sector_t probe_block;
974 inode = sis->swap_file->f_mapping->host;
975 if (S_ISBLK(inode->i_mode)) {
976 ret = add_swap_extent(sis, 0, sis->max, 0);
980 blkbits = inode->i_blkbits;
981 blocks_per_page = PAGE_SIZE >> blkbits;
984 * Map all the blocks into the extent list. This code doesn't try
989 last_block = i_size_read(inode) >> blkbits;
990 while ((probe_block + blocks_per_page) <= last_block &&
991 page_no < sis->max) {
992 unsigned block_in_page;
993 sector_t first_block;
995 first_block = bmap(inode, probe_block);
996 if (first_block == 0)
1000 * It must be PAGE_SIZE aligned on-disk
1002 if (first_block & (blocks_per_page - 1)) {
1007 for (block_in_page = 1; block_in_page < blocks_per_page;
1011 block = bmap(inode, probe_block + block_in_page);
1014 if (block != first_block + block_in_page) {
1022 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1024 ret = add_swap_extent(sis, page_no, 1,
1025 first_block >> (PAGE_SHIFT - blkbits));
1029 probe_block += blocks_per_page;
1037 sis->highest_bit = page_no - 1;
1039 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1040 struct swap_extent, list);
1043 printk(KERN_ERR "swapon: swapfile has holes\n");
1049 #if 0 /* We don't need this yet */
1050 #include <linux/backing-dev.h>
1051 int page_queue_congested(struct page *page)
1053 struct backing_dev_info *bdi;
1055 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1057 if (PageSwapCache(page)) {
1058 swp_entry_t entry = { .val = page->private };
1059 struct swap_info_struct *sis;
1061 sis = get_swap_info_struct(swp_type(entry));
1062 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1064 bdi = page->mapping->backing_dev_info;
1065 return bdi_write_congested(bdi);
1069 asmlinkage long sys_swapoff(const char __user * specialfile)
1071 struct swap_info_struct * p = NULL;
1072 unsigned short *swap_map;
1073 struct file *swap_file, *victim;
1074 struct address_space *mapping;
1075 struct inode *inode;
1080 if (!capable(CAP_SYS_ADMIN))
1083 pathname = getname(specialfile);
1084 err = PTR_ERR(pathname);
1085 if (IS_ERR(pathname))
1088 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1090 err = PTR_ERR(victim);
1094 mapping = victim->f_mapping;
1097 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1098 p = swap_info + type;
1099 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1100 if (p->swap_file->f_mapping == mapping)
1110 if (!security_vm_enough_memory(p->pages))
1111 vm_unacct_memory(p->pages);
1118 swap_list.head = p->next;
1120 swap_info[prev].next = p->next;
1122 if (type == swap_list.next) {
1123 /* just pick something that's safe... */
1124 swap_list.next = swap_list.head;
1126 nr_swap_pages -= p->pages;
1127 total_swap_pages -= p->pages;
1128 p->flags &= ~SWP_WRITEOK;
1130 current->flags |= PF_SWAPOFF;
1131 err = try_to_unuse(type);
1132 current->flags &= ~PF_SWAPOFF;
1134 /* wait for any unplug function to finish */
1135 down_write(&swap_unplug_sem);
1136 up_write(&swap_unplug_sem);
1139 /* re-insert swap space back into swap_list */
1141 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1142 if (p->prio >= swap_info[i].prio)
1146 swap_list.head = swap_list.next = p - swap_info;
1148 swap_info[prev].next = p - swap_info;
1149 nr_swap_pages += p->pages;
1150 total_swap_pages += p->pages;
1151 p->flags |= SWP_WRITEOK;
1157 swap_device_lock(p);
1158 swap_file = p->swap_file;
1159 p->swap_file = NULL;
1161 swap_map = p->swap_map;
1164 destroy_swap_extents(p);
1165 swap_device_unlock(p);
1169 inode = mapping->host;
1170 if (S_ISBLK(inode->i_mode)) {
1171 struct block_device *bdev = I_BDEV(inode);
1172 set_blocksize(bdev, p->old_block_size);
1175 down(&inode->i_sem);
1176 inode->i_flags &= ~S_SWAPFILE;
1179 filp_close(swap_file, NULL);
1183 filp_close(victim, NULL);
1188 #ifdef CONFIG_PROC_FS
1190 static void *swap_start(struct seq_file *swap, loff_t *pos)
1192 struct swap_info_struct *ptr = swap_info;
1198 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1199 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1208 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1210 struct swap_info_struct *ptr = v;
1211 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1213 for (++ptr; ptr < endptr; ptr++) {
1214 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1223 static void swap_stop(struct seq_file *swap, void *v)
1228 static int swap_show(struct seq_file *swap, void *v)
1230 struct swap_info_struct *ptr = v;
1235 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1237 file = ptr->swap_file;
1238 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1239 seq_printf(swap, "%*s%s\t%d\t%ld\t%d\n",
1240 len < 40 ? 40 - len : 1, " ",
1241 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1242 "partition" : "file\t",
1243 ptr->pages << (PAGE_SHIFT - 10),
1244 ptr->inuse_pages << (PAGE_SHIFT - 10),
1249 static struct seq_operations swaps_op = {
1250 .start = swap_start,
1256 static int swaps_open(struct inode *inode, struct file *file)
1258 return seq_open(file, &swaps_op);
1261 static struct file_operations proc_swaps_operations = {
1264 .llseek = seq_lseek,
1265 .release = seq_release,
1268 static int __init procswaps_init(void)
1270 struct proc_dir_entry *entry;
1272 entry = create_proc_entry("swaps", 0, NULL);
1274 entry->proc_fops = &proc_swaps_operations;
1277 __initcall(procswaps_init);
1278 #endif /* CONFIG_PROC_FS */
1281 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1283 * The swapon system call
1285 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1287 struct swap_info_struct * p;
1289 struct block_device *bdev = NULL;
1290 struct file *swap_file = NULL;
1291 struct address_space *mapping;
1295 static int least_priority;
1296 union swap_header *swap_header = NULL;
1297 int swap_header_version;
1298 int nr_good_pages = 0;
1299 unsigned long maxpages = 1;
1301 unsigned short *swap_map;
1302 struct page *page = NULL;
1303 struct inode *inode = NULL;
1306 if (!capable(CAP_SYS_ADMIN))
1310 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1311 if (!(p->flags & SWP_USED))
1315 * Test if adding another swap device is possible. There are
1316 * two limiting factors: 1) the number of bits for the swap
1317 * type swp_entry_t definition and 2) the number of bits for
1318 * the swap type in the swap ptes as defined by the different
1319 * architectures. To honor both limitations a swap entry
1320 * with swap offset 0 and swap type ~0UL is created, encoded
1321 * to a swap pte, decoded to a swp_entry_t again and finally
1322 * the swap type part is extracted. This will mask all bits
1323 * from the initial ~0UL that can't be encoded in either the
1324 * swp_entry_t or the architecture definition of a swap pte.
1326 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1330 if (type >= nr_swapfiles)
1331 nr_swapfiles = type+1;
1332 INIT_LIST_HEAD(&p->extent_list);
1333 p->flags = SWP_USED;
1335 p->swap_file = NULL;
1336 p->old_block_size = 0;
1342 p->sdev_lock = SPIN_LOCK_UNLOCKED;
1344 if (swap_flags & SWAP_FLAG_PREFER) {
1346 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1348 p->prio = --least_priority;
1351 name = getname(specialfile);
1352 error = PTR_ERR(name);
1357 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1358 error = PTR_ERR(swap_file);
1359 if (IS_ERR(swap_file)) {
1364 p->swap_file = swap_file;
1365 mapping = swap_file->f_mapping;
1366 inode = mapping->host;
1369 for (i = 0; i < nr_swapfiles; i++) {
1370 struct swap_info_struct *q = &swap_info[i];
1372 if (i == type || !q->swap_file)
1374 if (mapping == q->swap_file->f_mapping)
1379 if (S_ISBLK(inode->i_mode)) {
1380 bdev = I_BDEV(inode);
1381 error = bd_claim(bdev, sys_swapon);
1386 p->old_block_size = block_size(bdev);
1387 error = set_blocksize(bdev, PAGE_SIZE);
1391 } else if (S_ISREG(inode->i_mode)) {
1392 p->bdev = inode->i_sb->s_bdev;
1393 down(&inode->i_sem);
1395 if (IS_SWAPFILE(inode)) {
1403 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1406 * Read the swap header.
1408 if (!mapping->a_ops->readpage) {
1412 page = read_cache_page(mapping, 0,
1413 (filler_t *)mapping->a_ops->readpage, swap_file);
1415 error = PTR_ERR(page);
1418 wait_on_page_locked(page);
1419 if (!PageUptodate(page))
1422 swap_header = page_address(page);
1424 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1425 swap_header_version = 1;
1426 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1427 swap_header_version = 2;
1429 printk("Unable to find swap-space signature\n");
1434 switch (swap_header_version) {
1436 printk(KERN_ERR "version 0 swap is no longer supported. "
1437 "Use mkswap -v1 %s\n", name);
1441 /* Check the swap header's sub-version and the size of
1442 the swap file and bad block lists */
1443 if (swap_header->info.version != 1) {
1445 "Unable to handle swap header version %d\n",
1446 swap_header->info.version);
1453 * Find out how many pages are allowed for a single swap
1454 * device. There are two limiting factors: 1) the number of
1455 * bits for the swap offset in the swp_entry_t type and
1456 * 2) the number of bits in the a swap pte as defined by
1457 * the different architectures. In order to find the
1458 * largest possible bit mask a swap entry with swap type 0
1459 * and swap offset ~0UL is created, encoded to a swap pte,
1460 * decoded to a swp_entry_t again and finally the swap
1461 * offset is extracted. This will mask all the bits from
1462 * the initial ~0UL mask that can't be encoded in either
1463 * the swp_entry_t or the architecture definition of a
1466 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1467 if (maxpages > swap_header->info.last_page)
1468 maxpages = swap_header->info.last_page;
1469 p->highest_bit = maxpages - 1;
1472 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1475 /* OK, set up the swap map and apply the bad block list */
1476 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1482 memset(p->swap_map, 0, maxpages * sizeof(short));
1483 for (i=0; i<swap_header->info.nr_badpages; i++) {
1484 int page = swap_header->info.badpages[i];
1485 if (page <= 0 || page >= swap_header->info.last_page)
1488 p->swap_map[page] = SWAP_MAP_BAD;
1490 nr_good_pages = swap_header->info.last_page -
1491 swap_header->info.nr_badpages -
1492 1 /* header page */;
1497 if (swapfilesize && maxpages > swapfilesize) {
1499 "Swap area shorter than signature indicates\n");
1503 if (!nr_good_pages) {
1504 printk(KERN_WARNING "Empty swap-file\n");
1508 p->swap_map[0] = SWAP_MAP_BAD;
1510 p->pages = nr_good_pages;
1512 error = setup_swap_extents(p);
1518 swap_device_lock(p);
1519 p->flags = SWP_ACTIVE;
1520 nr_swap_pages += nr_good_pages;
1521 total_swap_pages += nr_good_pages;
1522 printk(KERN_INFO "Adding %dk swap on %s. Priority:%d extents:%d\n",
1523 nr_good_pages<<(PAGE_SHIFT-10), name,
1524 p->prio, p->nr_extents);
1526 /* insert swap space into swap_list: */
1528 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1529 if (p->prio >= swap_info[i].prio) {
1536 swap_list.head = swap_list.next = p - swap_info;
1538 swap_info[prev].next = p - swap_info;
1540 swap_device_unlock(p);
1547 set_blocksize(bdev, p->old_block_size);
1552 swap_map = p->swap_map;
1553 p->swap_file = NULL;
1556 if (!(swap_flags & SWAP_FLAG_PREFER))
1559 destroy_swap_extents(p);
1563 filp_close(swap_file, NULL);
1565 if (page && !IS_ERR(page)) {
1567 page_cache_release(page);
1573 inode->i_flags |= S_SWAPFILE;
1579 void si_swapinfo(struct sysinfo *val)
1582 unsigned long nr_to_be_unused = 0;
1585 for (i = 0; i < nr_swapfiles; i++) {
1586 if (!(swap_info[i].flags & SWP_USED) ||
1587 (swap_info[i].flags & SWP_WRITEOK))
1589 nr_to_be_unused += swap_info[i].inuse_pages;
1591 val->freeswap = nr_swap_pages + nr_to_be_unused;
1592 val->totalswap = total_swap_pages + nr_to_be_unused;
1597 * Verify that a swap entry is valid and increment its swap map count.
1599 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1600 * "permanent", but will be reclaimed by the next swapoff.
1602 int swap_duplicate(swp_entry_t entry)
1604 struct swap_info_struct * p;
1605 unsigned long offset, type;
1608 type = swp_type(entry);
1609 if (type >= nr_swapfiles)
1611 p = type + swap_info;
1612 offset = swp_offset(entry);
1614 swap_device_lock(p);
1615 if (offset < p->max && p->swap_map[offset]) {
1616 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1617 p->swap_map[offset]++;
1619 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1620 if (swap_overflow++ < 5)
1621 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1622 p->swap_map[offset] = SWAP_MAP_MAX;
1626 swap_device_unlock(p);
1631 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1635 struct swap_info_struct *
1636 get_swap_info_struct(unsigned type)
1638 return &swap_info[type];
1642 * swap_device_lock prevents swap_map being freed. Don't grab an extra
1643 * reference on the swaphandle, it doesn't matter if it becomes unused.
1645 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1647 int ret = 0, i = 1 << page_cluster;
1649 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1651 if (!page_cluster) /* no readahead */
1653 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1654 if (!toff) /* first page is swap header */
1658 swap_device_lock(swapdev);
1660 /* Don't read-ahead past the end of the swap area */
1661 if (toff >= swapdev->max)
1663 /* Don't read in free or bad pages */
1664 if (!swapdev->swap_map[toff])
1666 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1671 swap_device_unlock(swapdev);