4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
9 #include <linux/hugetlb.h>
10 #include <linux/mman.h>
11 #include <linux/slab.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/swap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/pagemap.h>
16 #include <linux/namei.h>
17 #include <linux/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/random.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>
31 #include <linux/memcontrol.h>
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 #include <linux/page_cgroup.h>
38 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
40 static void free_swap_count_continuations(struct swap_info_struct *);
42 static DEFINE_SPINLOCK(swap_lock);
43 static unsigned int nr_swapfiles;
45 long total_swap_pages;
46 static int least_priority;
48 static const char Bad_file[] = "Bad swap file entry ";
49 static const char Unused_file[] = "Unused swap file entry ";
50 static const char Bad_offset[] = "Bad swap offset entry ";
51 static const char Unused_offset[] = "Unused swap offset entry ";
53 static struct swap_list_t swap_list = {-1, -1};
55 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
57 static DEFINE_MUTEX(swapon_mutex);
59 static inline unsigned char swap_count(unsigned char ent)
61 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
64 /* returns 1 if swap entry is freed */
66 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
68 swp_entry_t entry = swp_entry(si->type, offset);
72 page = find_get_page(&swapper_space, entry.val);
76 * This function is called from scan_swap_map() and it's called
77 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
78 * We have to use trylock for avoiding deadlock. This is a special
79 * case and you should use try_to_free_swap() with explicit lock_page()
80 * in usual operations.
82 if (trylock_page(page)) {
83 ret = try_to_free_swap(page);
86 page_cache_release(page);
91 * We need this because the bdev->unplug_fn can sleep and we cannot
92 * hold swap_lock while calling the unplug_fn. And swap_lock
93 * cannot be turned into a mutex.
95 static DECLARE_RWSEM(swap_unplug_sem);
97 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
101 down_read(&swap_unplug_sem);
102 entry.val = page_private(page);
103 if (PageSwapCache(page)) {
104 struct block_device *bdev = swap_info[swp_type(entry)]->bdev;
105 struct backing_dev_info *bdi;
108 * If the page is removed from swapcache from under us (with a
109 * racy try_to_unuse/swapoff) we need an additional reference
110 * count to avoid reading garbage from page_private(page) above.
111 * If the WARN_ON triggers during a swapoff it maybe the race
112 * condition and it's harmless. However if it triggers without
113 * swapoff it signals a problem.
115 WARN_ON(page_count(page) <= 1);
117 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
118 blk_run_backing_dev(bdi, page);
120 up_read(&swap_unplug_sem);
124 * swapon tell device that all the old swap contents can be discarded,
125 * to allow the swap device to optimize its wear-levelling.
127 static int discard_swap(struct swap_info_struct *si)
129 struct swap_extent *se;
130 sector_t start_block;
134 /* Do not discard the swap header page! */
135 se = &si->first_swap_extent;
136 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
137 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
139 err = blkdev_issue_discard(si->bdev, start_block,
140 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
146 list_for_each_entry(se, &si->first_swap_extent.list, list) {
147 start_block = se->start_block << (PAGE_SHIFT - 9);
148 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
150 err = blkdev_issue_discard(si->bdev, start_block,
151 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
157 return err; /* That will often be -EOPNOTSUPP */
161 * swap allocation tell device that a cluster of swap can now be discarded,
162 * to allow the swap device to optimize its wear-levelling.
164 static void discard_swap_cluster(struct swap_info_struct *si,
165 pgoff_t start_page, pgoff_t nr_pages)
167 struct swap_extent *se = si->curr_swap_extent;
168 int found_extent = 0;
171 struct list_head *lh;
173 if (se->start_page <= start_page &&
174 start_page < se->start_page + se->nr_pages) {
175 pgoff_t offset = start_page - se->start_page;
176 sector_t start_block = se->start_block + offset;
177 sector_t nr_blocks = se->nr_pages - offset;
179 if (nr_blocks > nr_pages)
180 nr_blocks = nr_pages;
181 start_page += nr_blocks;
182 nr_pages -= nr_blocks;
185 si->curr_swap_extent = se;
187 start_block <<= PAGE_SHIFT - 9;
188 nr_blocks <<= PAGE_SHIFT - 9;
189 if (blkdev_issue_discard(si->bdev, start_block,
190 nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER))
195 se = list_entry(lh, struct swap_extent, list);
199 static int wait_for_discard(void *word)
205 #define SWAPFILE_CLUSTER 256
206 #define LATENCY_LIMIT 256
208 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
211 unsigned long offset;
212 unsigned long scan_base;
213 unsigned long last_in_cluster = 0;
214 int latency_ration = LATENCY_LIMIT;
215 int found_free_cluster = 0;
218 * We try to cluster swap pages by allocating them sequentially
219 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
220 * way, however, we resort to first-free allocation, starting
221 * a new cluster. This prevents us from scattering swap pages
222 * all over the entire swap partition, so that we reduce
223 * overall disk seek times between swap pages. -- sct
224 * But we do now try to find an empty cluster. -Andrea
225 * And we let swap pages go all over an SSD partition. Hugh
228 si->flags += SWP_SCANNING;
229 scan_base = offset = si->cluster_next;
231 if (unlikely(!si->cluster_nr--)) {
232 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
233 si->cluster_nr = SWAPFILE_CLUSTER - 1;
236 if (si->flags & SWP_DISCARDABLE) {
238 * Start range check on racing allocations, in case
239 * they overlap the cluster we eventually decide on
240 * (we scan without swap_lock to allow preemption).
241 * It's hardly conceivable that cluster_nr could be
242 * wrapped during our scan, but don't depend on it.
244 if (si->lowest_alloc)
246 si->lowest_alloc = si->max;
247 si->highest_alloc = 0;
249 spin_unlock(&swap_lock);
252 * If seek is expensive, start searching for new cluster from
253 * start of partition, to minimize the span of allocated swap.
254 * But if seek is cheap, search from our current position, so
255 * that swap is allocated from all over the partition: if the
256 * Flash Translation Layer only remaps within limited zones,
257 * we don't want to wear out the first zone too quickly.
259 if (!(si->flags & SWP_SOLIDSTATE))
260 scan_base = offset = si->lowest_bit;
261 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
263 /* Locate the first empty (unaligned) cluster */
264 for (; last_in_cluster <= si->highest_bit; offset++) {
265 if (si->swap_map[offset])
266 last_in_cluster = offset + SWAPFILE_CLUSTER;
267 else if (offset == last_in_cluster) {
268 spin_lock(&swap_lock);
269 offset -= SWAPFILE_CLUSTER - 1;
270 si->cluster_next = offset;
271 si->cluster_nr = SWAPFILE_CLUSTER - 1;
272 found_free_cluster = 1;
275 if (unlikely(--latency_ration < 0)) {
277 latency_ration = LATENCY_LIMIT;
281 offset = si->lowest_bit;
282 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
284 /* Locate the first empty (unaligned) cluster */
285 for (; last_in_cluster < scan_base; offset++) {
286 if (si->swap_map[offset])
287 last_in_cluster = offset + SWAPFILE_CLUSTER;
288 else if (offset == last_in_cluster) {
289 spin_lock(&swap_lock);
290 offset -= SWAPFILE_CLUSTER - 1;
291 si->cluster_next = offset;
292 si->cluster_nr = SWAPFILE_CLUSTER - 1;
293 found_free_cluster = 1;
296 if (unlikely(--latency_ration < 0)) {
298 latency_ration = LATENCY_LIMIT;
303 spin_lock(&swap_lock);
304 si->cluster_nr = SWAPFILE_CLUSTER - 1;
305 si->lowest_alloc = 0;
309 if (!(si->flags & SWP_WRITEOK))
311 if (!si->highest_bit)
313 if (offset > si->highest_bit)
314 scan_base = offset = si->lowest_bit;
316 /* reuse swap entry of cache-only swap if not busy. */
317 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
319 spin_unlock(&swap_lock);
320 swap_was_freed = __try_to_reclaim_swap(si, offset);
321 spin_lock(&swap_lock);
322 /* entry was freed successfully, try to use this again */
325 goto scan; /* check next one */
328 if (si->swap_map[offset])
331 if (offset == si->lowest_bit)
333 if (offset == si->highest_bit)
336 if (si->inuse_pages == si->pages) {
337 si->lowest_bit = si->max;
340 si->swap_map[offset] = usage;
341 si->cluster_next = offset + 1;
342 si->flags -= SWP_SCANNING;
344 if (si->lowest_alloc) {
346 * Only set when SWP_DISCARDABLE, and there's a scan
347 * for a free cluster in progress or just completed.
349 if (found_free_cluster) {
351 * To optimize wear-levelling, discard the
352 * old data of the cluster, taking care not to
353 * discard any of its pages that have already
354 * been allocated by racing tasks (offset has
355 * already stepped over any at the beginning).
357 if (offset < si->highest_alloc &&
358 si->lowest_alloc <= last_in_cluster)
359 last_in_cluster = si->lowest_alloc - 1;
360 si->flags |= SWP_DISCARDING;
361 spin_unlock(&swap_lock);
363 if (offset < last_in_cluster)
364 discard_swap_cluster(si, offset,
365 last_in_cluster - offset + 1);
367 spin_lock(&swap_lock);
368 si->lowest_alloc = 0;
369 si->flags &= ~SWP_DISCARDING;
371 smp_mb(); /* wake_up_bit advises this */
372 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
374 } else if (si->flags & SWP_DISCARDING) {
376 * Delay using pages allocated by racing tasks
377 * until the whole discard has been issued. We
378 * could defer that delay until swap_writepage,
379 * but it's easier to keep this self-contained.
381 spin_unlock(&swap_lock);
382 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
383 wait_for_discard, TASK_UNINTERRUPTIBLE);
384 spin_lock(&swap_lock);
387 * Note pages allocated by racing tasks while
388 * scan for a free cluster is in progress, so
389 * that its final discard can exclude them.
391 if (offset < si->lowest_alloc)
392 si->lowest_alloc = offset;
393 if (offset > si->highest_alloc)
394 si->highest_alloc = offset;
400 spin_unlock(&swap_lock);
401 while (++offset <= si->highest_bit) {
402 if (!si->swap_map[offset]) {
403 spin_lock(&swap_lock);
406 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
407 spin_lock(&swap_lock);
410 if (unlikely(--latency_ration < 0)) {
412 latency_ration = LATENCY_LIMIT;
415 offset = si->lowest_bit;
416 while (++offset < scan_base) {
417 if (!si->swap_map[offset]) {
418 spin_lock(&swap_lock);
421 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
422 spin_lock(&swap_lock);
425 if (unlikely(--latency_ration < 0)) {
427 latency_ration = LATENCY_LIMIT;
430 spin_lock(&swap_lock);
433 si->flags -= SWP_SCANNING;
437 swp_entry_t get_swap_page(void)
439 struct swap_info_struct *si;
444 spin_lock(&swap_lock);
445 if (nr_swap_pages <= 0)
449 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
450 si = swap_info[type];
453 (!wrapped && si->prio != swap_info[next]->prio)) {
454 next = swap_list.head;
458 if (!si->highest_bit)
460 if (!(si->flags & SWP_WRITEOK))
463 swap_list.next = next;
464 /* This is called for allocating swap entry for cache */
465 offset = scan_swap_map(si, SWAP_HAS_CACHE);
467 spin_unlock(&swap_lock);
468 return swp_entry(type, offset);
470 next = swap_list.next;
475 spin_unlock(&swap_lock);
476 return (swp_entry_t) {0};
479 /* The only caller of this function is now susupend routine */
480 swp_entry_t get_swap_page_of_type(int type)
482 struct swap_info_struct *si;
485 spin_lock(&swap_lock);
486 si = swap_info[type];
487 if (si && (si->flags & SWP_WRITEOK)) {
489 /* This is called for allocating swap entry, not cache */
490 offset = scan_swap_map(si, 1);
492 spin_unlock(&swap_lock);
493 return swp_entry(type, offset);
497 spin_unlock(&swap_lock);
498 return (swp_entry_t) {0};
501 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
503 struct swap_info_struct *p;
504 unsigned long offset, type;
508 type = swp_type(entry);
509 if (type >= nr_swapfiles)
512 if (!(p->flags & SWP_USED))
514 offset = swp_offset(entry);
515 if (offset >= p->max)
517 if (!p->swap_map[offset])
519 spin_lock(&swap_lock);
523 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
526 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
529 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
532 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
537 static unsigned char swap_entry_free(struct swap_info_struct *p,
538 swp_entry_t entry, unsigned char usage)
540 unsigned long offset = swp_offset(entry);
542 unsigned char has_cache;
544 count = p->swap_map[offset];
545 has_cache = count & SWAP_HAS_CACHE;
546 count &= ~SWAP_HAS_CACHE;
548 if (usage == SWAP_HAS_CACHE) {
549 VM_BUG_ON(!has_cache);
551 } else if (count == SWAP_MAP_SHMEM) {
553 * Or we could insist on shmem.c using a special
554 * swap_shmem_free() and free_shmem_swap_and_cache()...
557 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
558 if (count == COUNT_CONTINUED) {
559 if (swap_count_continued(p, offset, count))
560 count = SWAP_MAP_MAX | COUNT_CONTINUED;
562 count = SWAP_MAP_MAX;
568 mem_cgroup_uncharge_swap(entry);
570 usage = count | has_cache;
571 p->swap_map[offset] = usage;
573 /* free if no reference */
575 if (offset < p->lowest_bit)
576 p->lowest_bit = offset;
577 if (offset > p->highest_bit)
578 p->highest_bit = offset;
579 if (swap_list.next >= 0 &&
580 p->prio > swap_info[swap_list.next]->prio)
581 swap_list.next = p->type;
590 * Caller has made sure that the swapdevice corresponding to entry
591 * is still around or has not been recycled.
593 void swap_free(swp_entry_t entry)
595 struct swap_info_struct *p;
597 p = swap_info_get(entry);
599 swap_entry_free(p, entry, 1);
600 spin_unlock(&swap_lock);
605 * Called after dropping swapcache to decrease refcnt to swap entries.
607 void swapcache_free(swp_entry_t entry, struct page *page)
609 struct swap_info_struct *p;
612 p = swap_info_get(entry);
614 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
616 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
617 spin_unlock(&swap_lock);
622 * How many references to page are currently swapped out?
623 * This does not give an exact answer when swap count is continued,
624 * but does include the high COUNT_CONTINUED flag to allow for that.
626 static inline int page_swapcount(struct page *page)
629 struct swap_info_struct *p;
632 entry.val = page_private(page);
633 p = swap_info_get(entry);
635 count = swap_count(p->swap_map[swp_offset(entry)]);
636 spin_unlock(&swap_lock);
642 * We can write to an anon page without COW if there are no other references
643 * to it. And as a side-effect, free up its swap: because the old content
644 * on disk will never be read, and seeking back there to write new content
645 * later would only waste time away from clustering.
647 int reuse_swap_page(struct page *page)
651 VM_BUG_ON(!PageLocked(page));
652 count = page_mapcount(page);
653 if (count <= 1 && PageSwapCache(page)) {
654 count += page_swapcount(page);
655 if (count == 1 && !PageWriteback(page)) {
656 delete_from_swap_cache(page);
664 * If swap is getting full, or if there are no more mappings of this page,
665 * then try_to_free_swap is called to free its swap space.
667 int try_to_free_swap(struct page *page)
669 VM_BUG_ON(!PageLocked(page));
671 if (!PageSwapCache(page))
673 if (PageWriteback(page))
675 if (page_swapcount(page))
678 delete_from_swap_cache(page);
684 * Free the swap entry like above, but also try to
685 * free the page cache entry if it is the last user.
687 int free_swap_and_cache(swp_entry_t entry)
689 struct swap_info_struct *p;
690 struct page *page = NULL;
692 if (non_swap_entry(entry))
695 p = swap_info_get(entry);
697 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
698 page = find_get_page(&swapper_space, entry.val);
699 if (page && !trylock_page(page)) {
700 page_cache_release(page);
704 spin_unlock(&swap_lock);
708 * Not mapped elsewhere, or swap space full? Free it!
709 * Also recheck PageSwapCache now page is locked (above).
711 if (PageSwapCache(page) && !PageWriteback(page) &&
712 (!page_mapped(page) || vm_swap_full())) {
713 delete_from_swap_cache(page);
717 page_cache_release(page);
722 #ifdef CONFIG_HIBERNATION
724 * Find the swap type that corresponds to given device (if any).
726 * @offset - number of the PAGE_SIZE-sized block of the device, starting
727 * from 0, in which the swap header is expected to be located.
729 * This is needed for the suspend to disk (aka swsusp).
731 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
733 struct block_device *bdev = NULL;
737 bdev = bdget(device);
739 spin_lock(&swap_lock);
740 for (type = 0; type < nr_swapfiles; type++) {
741 struct swap_info_struct *sis = swap_info[type];
743 if (!(sis->flags & SWP_WRITEOK))
748 *bdev_p = bdgrab(sis->bdev);
750 spin_unlock(&swap_lock);
753 if (bdev == sis->bdev) {
754 struct swap_extent *se = &sis->first_swap_extent;
756 if (se->start_block == offset) {
758 *bdev_p = bdgrab(sis->bdev);
760 spin_unlock(&swap_lock);
766 spin_unlock(&swap_lock);
774 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
775 * corresponding to given index in swap_info (swap type).
777 sector_t swapdev_block(int type, pgoff_t offset)
779 struct block_device *bdev;
781 if ((unsigned int)type >= nr_swapfiles)
783 if (!(swap_info[type]->flags & SWP_WRITEOK))
785 return map_swap_page(swp_entry(type, offset), &bdev);
789 * Return either the total number of swap pages of given type, or the number
790 * of free pages of that type (depending on @free)
792 * This is needed for software suspend
794 unsigned int count_swap_pages(int type, int free)
798 spin_lock(&swap_lock);
799 if ((unsigned int)type < nr_swapfiles) {
800 struct swap_info_struct *sis = swap_info[type];
802 if (sis->flags & SWP_WRITEOK) {
805 n -= sis->inuse_pages;
808 spin_unlock(&swap_lock);
811 #endif /* CONFIG_HIBERNATION */
814 * No need to decide whether this PTE shares the swap entry with others,
815 * just let do_wp_page work it out if a write is requested later - to
816 * force COW, vm_page_prot omits write permission from any private vma.
818 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
819 unsigned long addr, swp_entry_t entry, struct page *page)
821 struct mem_cgroup *ptr = NULL;
826 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
831 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
832 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
834 mem_cgroup_cancel_charge_swapin(ptr);
839 inc_mm_counter(vma->vm_mm, anon_rss);
841 set_pte_at(vma->vm_mm, addr, pte,
842 pte_mkold(mk_pte(page, vma->vm_page_prot)));
843 page_add_anon_rmap(page, vma, addr);
844 mem_cgroup_commit_charge_swapin(page, ptr);
847 * Move the page to the active list so it is not
848 * immediately swapped out again after swapon.
852 pte_unmap_unlock(pte, ptl);
857 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
858 unsigned long addr, unsigned long end,
859 swp_entry_t entry, struct page *page)
861 pte_t swp_pte = swp_entry_to_pte(entry);
866 * We don't actually need pte lock while scanning for swp_pte: since
867 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
868 * page table while we're scanning; though it could get zapped, and on
869 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
870 * of unmatched parts which look like swp_pte, so unuse_pte must
871 * recheck under pte lock. Scanning without pte lock lets it be
872 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
874 pte = pte_offset_map(pmd, addr);
877 * swapoff spends a _lot_ of time in this loop!
878 * Test inline before going to call unuse_pte.
880 if (unlikely(pte_same(*pte, swp_pte))) {
882 ret = unuse_pte(vma, pmd, addr, entry, page);
885 pte = pte_offset_map(pmd, addr);
887 } while (pte++, addr += PAGE_SIZE, addr != end);
893 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
894 unsigned long addr, unsigned long end,
895 swp_entry_t entry, struct page *page)
901 pmd = pmd_offset(pud, addr);
903 next = pmd_addr_end(addr, end);
904 if (pmd_none_or_clear_bad(pmd))
906 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
909 } while (pmd++, addr = next, addr != end);
913 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
914 unsigned long addr, unsigned long end,
915 swp_entry_t entry, struct page *page)
921 pud = pud_offset(pgd, addr);
923 next = pud_addr_end(addr, end);
924 if (pud_none_or_clear_bad(pud))
926 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
929 } while (pud++, addr = next, addr != end);
933 static int unuse_vma(struct vm_area_struct *vma,
934 swp_entry_t entry, struct page *page)
937 unsigned long addr, end, next;
941 addr = page_address_in_vma(page, vma);
945 end = addr + PAGE_SIZE;
947 addr = vma->vm_start;
951 pgd = pgd_offset(vma->vm_mm, addr);
953 next = pgd_addr_end(addr, end);
954 if (pgd_none_or_clear_bad(pgd))
956 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
959 } while (pgd++, addr = next, addr != end);
963 static int unuse_mm(struct mm_struct *mm,
964 swp_entry_t entry, struct page *page)
966 struct vm_area_struct *vma;
969 if (!down_read_trylock(&mm->mmap_sem)) {
971 * Activate page so shrink_inactive_list is unlikely to unmap
972 * its ptes while lock is dropped, so swapoff can make progress.
976 down_read(&mm->mmap_sem);
979 for (vma = mm->mmap; vma; vma = vma->vm_next) {
980 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
983 up_read(&mm->mmap_sem);
984 return (ret < 0)? ret: 0;
988 * Scan swap_map from current position to next entry still in use.
989 * Recycle to start on reaching the end, returning 0 when empty.
991 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
994 unsigned int max = si->max;
995 unsigned int i = prev;
999 * No need for swap_lock here: we're just looking
1000 * for whether an entry is in use, not modifying it; false
1001 * hits are okay, and sys_swapoff() has already prevented new
1002 * allocations from this area (while holding swap_lock).
1011 * No entries in use at top of swap_map,
1012 * loop back to start and recheck there.
1018 count = si->swap_map[i];
1019 if (count && swap_count(count) != SWAP_MAP_BAD)
1026 * We completely avoid races by reading each swap page in advance,
1027 * and then search for the process using it. All the necessary
1028 * page table adjustments can then be made atomically.
1030 static int try_to_unuse(unsigned int type)
1032 struct swap_info_struct *si = swap_info[type];
1033 struct mm_struct *start_mm;
1034 unsigned char *swap_map;
1035 unsigned char swcount;
1042 * When searching mms for an entry, a good strategy is to
1043 * start at the first mm we freed the previous entry from
1044 * (though actually we don't notice whether we or coincidence
1045 * freed the entry). Initialize this start_mm with a hold.
1047 * A simpler strategy would be to start at the last mm we
1048 * freed the previous entry from; but that would take less
1049 * advantage of mmlist ordering, which clusters forked mms
1050 * together, child after parent. If we race with dup_mmap(), we
1051 * prefer to resolve parent before child, lest we miss entries
1052 * duplicated after we scanned child: using last mm would invert
1055 start_mm = &init_mm;
1056 atomic_inc(&init_mm.mm_users);
1059 * Keep on scanning until all entries have gone. Usually,
1060 * one pass through swap_map is enough, but not necessarily:
1061 * there are races when an instance of an entry might be missed.
1063 while ((i = find_next_to_unuse(si, i)) != 0) {
1064 if (signal_pending(current)) {
1070 * Get a page for the entry, using the existing swap
1071 * cache page if there is one. Otherwise, get a clean
1072 * page and read the swap into it.
1074 swap_map = &si->swap_map[i];
1075 entry = swp_entry(type, i);
1076 page = read_swap_cache_async(entry,
1077 GFP_HIGHUSER_MOVABLE, NULL, 0);
1080 * Either swap_duplicate() failed because entry
1081 * has been freed independently, and will not be
1082 * reused since sys_swapoff() already disabled
1083 * allocation from here, or alloc_page() failed.
1092 * Don't hold on to start_mm if it looks like exiting.
1094 if (atomic_read(&start_mm->mm_users) == 1) {
1096 start_mm = &init_mm;
1097 atomic_inc(&init_mm.mm_users);
1101 * Wait for and lock page. When do_swap_page races with
1102 * try_to_unuse, do_swap_page can handle the fault much
1103 * faster than try_to_unuse can locate the entry. This
1104 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1105 * defer to do_swap_page in such a case - in some tests,
1106 * do_swap_page and try_to_unuse repeatedly compete.
1108 wait_on_page_locked(page);
1109 wait_on_page_writeback(page);
1111 wait_on_page_writeback(page);
1114 * Remove all references to entry.
1116 swcount = *swap_map;
1117 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1118 retval = shmem_unuse(entry, page);
1119 /* page has already been unlocked and released */
1124 if (swap_count(swcount) && start_mm != &init_mm)
1125 retval = unuse_mm(start_mm, entry, page);
1127 if (swap_count(*swap_map)) {
1128 int set_start_mm = (*swap_map >= swcount);
1129 struct list_head *p = &start_mm->mmlist;
1130 struct mm_struct *new_start_mm = start_mm;
1131 struct mm_struct *prev_mm = start_mm;
1132 struct mm_struct *mm;
1134 atomic_inc(&new_start_mm->mm_users);
1135 atomic_inc(&prev_mm->mm_users);
1136 spin_lock(&mmlist_lock);
1137 while (swap_count(*swap_map) && !retval &&
1138 (p = p->next) != &start_mm->mmlist) {
1139 mm = list_entry(p, struct mm_struct, mmlist);
1140 if (!atomic_inc_not_zero(&mm->mm_users))
1142 spin_unlock(&mmlist_lock);
1148 swcount = *swap_map;
1149 if (!swap_count(swcount)) /* any usage ? */
1151 else if (mm == &init_mm)
1154 retval = unuse_mm(mm, entry, page);
1156 if (set_start_mm && *swap_map < swcount) {
1157 mmput(new_start_mm);
1158 atomic_inc(&mm->mm_users);
1162 spin_lock(&mmlist_lock);
1164 spin_unlock(&mmlist_lock);
1167 start_mm = new_start_mm;
1171 page_cache_release(page);
1176 * If a reference remains (rare), we would like to leave
1177 * the page in the swap cache; but try_to_unmap could
1178 * then re-duplicate the entry once we drop page lock,
1179 * so we might loop indefinitely; also, that page could
1180 * not be swapped out to other storage meanwhile. So:
1181 * delete from cache even if there's another reference,
1182 * after ensuring that the data has been saved to disk -
1183 * since if the reference remains (rarer), it will be
1184 * read from disk into another page. Splitting into two
1185 * pages would be incorrect if swap supported "shared
1186 * private" pages, but they are handled by tmpfs files.
1188 if (swap_count(*swap_map) &&
1189 PageDirty(page) && PageSwapCache(page)) {
1190 struct writeback_control wbc = {
1191 .sync_mode = WB_SYNC_NONE,
1194 swap_writepage(page, &wbc);
1196 wait_on_page_writeback(page);
1200 * It is conceivable that a racing task removed this page from
1201 * swap cache just before we acquired the page lock at the top,
1202 * or while we dropped it in unuse_mm(). The page might even
1203 * be back in swap cache on another swap area: that we must not
1204 * delete, since it may not have been written out to swap yet.
1206 if (PageSwapCache(page) &&
1207 likely(page_private(page) == entry.val))
1208 delete_from_swap_cache(page);
1211 * So we could skip searching mms once swap count went
1212 * to 1, we did not mark any present ptes as dirty: must
1213 * mark page dirty so shrink_page_list will preserve it.
1217 page_cache_release(page);
1220 * Make sure that we aren't completely killing
1221 * interactive performance.
1231 * After a successful try_to_unuse, if no swap is now in use, we know
1232 * we can empty the mmlist. swap_lock must be held on entry and exit.
1233 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1234 * added to the mmlist just after page_duplicate - before would be racy.
1236 static void drain_mmlist(void)
1238 struct list_head *p, *next;
1241 for (type = 0; type < nr_swapfiles; type++)
1242 if (swap_info[type]->inuse_pages)
1244 spin_lock(&mmlist_lock);
1245 list_for_each_safe(p, next, &init_mm.mmlist)
1247 spin_unlock(&mmlist_lock);
1251 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1252 * corresponds to page offset `offset'. Note that the type of this function
1253 * is sector_t, but it returns page offset into the bdev, not sector offset.
1255 sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev)
1257 struct swap_info_struct *sis;
1258 struct swap_extent *start_se;
1259 struct swap_extent *se;
1262 sis = swap_info[swp_type(entry)];
1265 offset = swp_offset(entry);
1266 start_se = sis->curr_swap_extent;
1270 struct list_head *lh;
1272 if (se->start_page <= offset &&
1273 offset < (se->start_page + se->nr_pages)) {
1274 return se->start_block + (offset - se->start_page);
1277 se = list_entry(lh, struct swap_extent, list);
1278 sis->curr_swap_extent = se;
1279 BUG_ON(se == start_se); /* It *must* be present */
1284 * Free all of a swapdev's extent information
1286 static void destroy_swap_extents(struct swap_info_struct *sis)
1288 while (!list_empty(&sis->first_swap_extent.list)) {
1289 struct swap_extent *se;
1291 se = list_entry(sis->first_swap_extent.list.next,
1292 struct swap_extent, list);
1293 list_del(&se->list);
1299 * Add a block range (and the corresponding page range) into this swapdev's
1300 * extent list. The extent list is kept sorted in page order.
1302 * This function rather assumes that it is called in ascending page order.
1305 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1306 unsigned long nr_pages, sector_t start_block)
1308 struct swap_extent *se;
1309 struct swap_extent *new_se;
1310 struct list_head *lh;
1312 if (start_page == 0) {
1313 se = &sis->first_swap_extent;
1314 sis->curr_swap_extent = se;
1316 se->nr_pages = nr_pages;
1317 se->start_block = start_block;
1320 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1321 se = list_entry(lh, struct swap_extent, list);
1322 BUG_ON(se->start_page + se->nr_pages != start_page);
1323 if (se->start_block + se->nr_pages == start_block) {
1325 se->nr_pages += nr_pages;
1331 * No merge. Insert a new extent, preserving ordering.
1333 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1336 new_se->start_page = start_page;
1337 new_se->nr_pages = nr_pages;
1338 new_se->start_block = start_block;
1340 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1345 * A `swap extent' is a simple thing which maps a contiguous range of pages
1346 * onto a contiguous range of disk blocks. An ordered list of swap extents
1347 * is built at swapon time and is then used at swap_writepage/swap_readpage
1348 * time for locating where on disk a page belongs.
1350 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1351 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1352 * swap files identically.
1354 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1355 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1356 * swapfiles are handled *identically* after swapon time.
1358 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1359 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1360 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1361 * requirements, they are simply tossed out - we will never use those blocks
1364 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1365 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1366 * which will scribble on the fs.
1368 * The amount of disk space which a single swap extent represents varies.
1369 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1370 * extents in the list. To avoid much list walking, we cache the previous
1371 * search location in `curr_swap_extent', and start new searches from there.
1372 * This is extremely effective. The average number of iterations in
1373 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1375 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1377 struct inode *inode;
1378 unsigned blocks_per_page;
1379 unsigned long page_no;
1381 sector_t probe_block;
1382 sector_t last_block;
1383 sector_t lowest_block = -1;
1384 sector_t highest_block = 0;
1388 inode = sis->swap_file->f_mapping->host;
1389 if (S_ISBLK(inode->i_mode)) {
1390 ret = add_swap_extent(sis, 0, sis->max, 0);
1395 blkbits = inode->i_blkbits;
1396 blocks_per_page = PAGE_SIZE >> blkbits;
1399 * Map all the blocks into the extent list. This code doesn't try
1404 last_block = i_size_read(inode) >> blkbits;
1405 while ((probe_block + blocks_per_page) <= last_block &&
1406 page_no < sis->max) {
1407 unsigned block_in_page;
1408 sector_t first_block;
1410 first_block = bmap(inode, probe_block);
1411 if (first_block == 0)
1415 * It must be PAGE_SIZE aligned on-disk
1417 if (first_block & (blocks_per_page - 1)) {
1422 for (block_in_page = 1; block_in_page < blocks_per_page;
1426 block = bmap(inode, probe_block + block_in_page);
1429 if (block != first_block + block_in_page) {
1436 first_block >>= (PAGE_SHIFT - blkbits);
1437 if (page_no) { /* exclude the header page */
1438 if (first_block < lowest_block)
1439 lowest_block = first_block;
1440 if (first_block > highest_block)
1441 highest_block = first_block;
1445 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1447 ret = add_swap_extent(sis, page_no, 1, first_block);
1452 probe_block += blocks_per_page;
1457 *span = 1 + highest_block - lowest_block;
1459 page_no = 1; /* force Empty message */
1461 sis->pages = page_no - 1;
1462 sis->highest_bit = page_no - 1;
1466 printk(KERN_ERR "swapon: swapfile has holes\n");
1471 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1473 struct swap_info_struct *p = NULL;
1474 unsigned char *swap_map;
1475 struct file *swap_file, *victim;
1476 struct address_space *mapping;
1477 struct inode *inode;
1482 if (!capable(CAP_SYS_ADMIN))
1485 pathname = getname(specialfile);
1486 err = PTR_ERR(pathname);
1487 if (IS_ERR(pathname))
1490 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1492 err = PTR_ERR(victim);
1496 mapping = victim->f_mapping;
1498 spin_lock(&swap_lock);
1499 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1500 p = swap_info[type];
1501 if (p->flags & SWP_WRITEOK) {
1502 if (p->swap_file->f_mapping == mapping)
1509 spin_unlock(&swap_lock);
1512 if (!security_vm_enough_memory(p->pages))
1513 vm_unacct_memory(p->pages);
1516 spin_unlock(&swap_lock);
1520 swap_list.head = p->next;
1522 swap_info[prev]->next = p->next;
1523 if (type == swap_list.next) {
1524 /* just pick something that's safe... */
1525 swap_list.next = swap_list.head;
1528 for (i = p->next; i >= 0; i = swap_info[i]->next)
1529 swap_info[i]->prio = p->prio--;
1532 nr_swap_pages -= p->pages;
1533 total_swap_pages -= p->pages;
1534 p->flags &= ~SWP_WRITEOK;
1535 spin_unlock(&swap_lock);
1537 current->flags |= PF_OOM_ORIGIN;
1538 err = try_to_unuse(type);
1539 current->flags &= ~PF_OOM_ORIGIN;
1542 /* re-insert swap space back into swap_list */
1543 spin_lock(&swap_lock);
1545 p->prio = --least_priority;
1547 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1548 if (p->prio >= swap_info[i]->prio)
1554 swap_list.head = swap_list.next = type;
1556 swap_info[prev]->next = type;
1557 nr_swap_pages += p->pages;
1558 total_swap_pages += p->pages;
1559 p->flags |= SWP_WRITEOK;
1560 spin_unlock(&swap_lock);
1564 /* wait for any unplug function to finish */
1565 down_write(&swap_unplug_sem);
1566 up_write(&swap_unplug_sem);
1568 destroy_swap_extents(p);
1569 if (p->flags & SWP_CONTINUED)
1570 free_swap_count_continuations(p);
1572 mutex_lock(&swapon_mutex);
1573 spin_lock(&swap_lock);
1576 /* wait for anyone still in scan_swap_map */
1577 p->highest_bit = 0; /* cuts scans short */
1578 while (p->flags >= SWP_SCANNING) {
1579 spin_unlock(&swap_lock);
1580 schedule_timeout_uninterruptible(1);
1581 spin_lock(&swap_lock);
1584 swap_file = p->swap_file;
1585 p->swap_file = NULL;
1587 swap_map = p->swap_map;
1590 spin_unlock(&swap_lock);
1591 mutex_unlock(&swapon_mutex);
1593 /* Destroy swap account informatin */
1594 swap_cgroup_swapoff(type);
1596 inode = mapping->host;
1597 if (S_ISBLK(inode->i_mode)) {
1598 struct block_device *bdev = I_BDEV(inode);
1599 set_blocksize(bdev, p->old_block_size);
1602 mutex_lock(&inode->i_mutex);
1603 inode->i_flags &= ~S_SWAPFILE;
1604 mutex_unlock(&inode->i_mutex);
1606 filp_close(swap_file, NULL);
1610 filp_close(victim, NULL);
1615 #ifdef CONFIG_PROC_FS
1617 static void *swap_start(struct seq_file *swap, loff_t *pos)
1619 struct swap_info_struct *si;
1623 mutex_lock(&swapon_mutex);
1626 return SEQ_START_TOKEN;
1628 for (type = 0; type < nr_swapfiles; type++) {
1629 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1630 si = swap_info[type];
1631 if (!(si->flags & SWP_USED) || !si->swap_map)
1640 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1642 struct swap_info_struct *si = v;
1645 if (v == SEQ_START_TOKEN)
1648 type = si->type + 1;
1650 for (; type < nr_swapfiles; type++) {
1651 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1652 si = swap_info[type];
1653 if (!(si->flags & SWP_USED) || !si->swap_map)
1662 static void swap_stop(struct seq_file *swap, void *v)
1664 mutex_unlock(&swapon_mutex);
1667 static int swap_show(struct seq_file *swap, void *v)
1669 struct swap_info_struct *si = v;
1673 if (si == SEQ_START_TOKEN) {
1674 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1678 file = si->swap_file;
1679 len = seq_path(swap, &file->f_path, " \t\n\\");
1680 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1681 len < 40 ? 40 - len : 1, " ",
1682 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1683 "partition" : "file\t",
1684 si->pages << (PAGE_SHIFT - 10),
1685 si->inuse_pages << (PAGE_SHIFT - 10),
1690 static const struct seq_operations swaps_op = {
1691 .start = swap_start,
1697 static int swaps_open(struct inode *inode, struct file *file)
1699 return seq_open(file, &swaps_op);
1702 static const struct file_operations proc_swaps_operations = {
1705 .llseek = seq_lseek,
1706 .release = seq_release,
1709 static int __init procswaps_init(void)
1711 proc_create("swaps", 0, NULL, &proc_swaps_operations);
1714 __initcall(procswaps_init);
1715 #endif /* CONFIG_PROC_FS */
1717 #ifdef MAX_SWAPFILES_CHECK
1718 static int __init max_swapfiles_check(void)
1720 MAX_SWAPFILES_CHECK();
1723 late_initcall(max_swapfiles_check);
1727 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1729 * The swapon system call
1731 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1733 struct swap_info_struct *p;
1735 struct block_device *bdev = NULL;
1736 struct file *swap_file = NULL;
1737 struct address_space *mapping;
1741 union swap_header *swap_header = NULL;
1742 unsigned int nr_good_pages = 0;
1745 unsigned long maxpages = 1;
1746 unsigned long swapfilepages;
1747 unsigned char *swap_map = NULL;
1748 struct page *page = NULL;
1749 struct inode *inode = NULL;
1752 if (!capable(CAP_SYS_ADMIN))
1755 p = kzalloc(sizeof(*p), GFP_KERNEL);
1759 spin_lock(&swap_lock);
1760 for (type = 0; type < nr_swapfiles; type++) {
1761 if (!(swap_info[type]->flags & SWP_USED))
1765 if (type >= MAX_SWAPFILES) {
1766 spin_unlock(&swap_lock);
1770 if (type >= nr_swapfiles) {
1772 swap_info[type] = p;
1774 * Write swap_info[type] before nr_swapfiles, in case a
1775 * racing procfs swap_start() or swap_next() is reading them.
1776 * (We never shrink nr_swapfiles, we never free this entry.)
1782 p = swap_info[type];
1784 * Do not memset this entry: a racing procfs swap_next()
1785 * would be relying on p->type to remain valid.
1788 INIT_LIST_HEAD(&p->first_swap_extent.list);
1789 p->flags = SWP_USED;
1791 spin_unlock(&swap_lock);
1793 name = getname(specialfile);
1794 error = PTR_ERR(name);
1799 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1800 error = PTR_ERR(swap_file);
1801 if (IS_ERR(swap_file)) {
1806 p->swap_file = swap_file;
1807 mapping = swap_file->f_mapping;
1808 inode = mapping->host;
1811 for (i = 0; i < nr_swapfiles; i++) {
1812 struct swap_info_struct *q = swap_info[i];
1814 if (i == type || !q->swap_file)
1816 if (mapping == q->swap_file->f_mapping)
1821 if (S_ISBLK(inode->i_mode)) {
1822 bdev = I_BDEV(inode);
1823 error = bd_claim(bdev, sys_swapon);
1829 p->old_block_size = block_size(bdev);
1830 error = set_blocksize(bdev, PAGE_SIZE);
1834 } else if (S_ISREG(inode->i_mode)) {
1835 p->bdev = inode->i_sb->s_bdev;
1836 mutex_lock(&inode->i_mutex);
1838 if (IS_SWAPFILE(inode)) {
1846 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1849 * Read the swap header.
1851 if (!mapping->a_ops->readpage) {
1855 page = read_mapping_page(mapping, 0, swap_file);
1857 error = PTR_ERR(page);
1860 swap_header = kmap(page);
1862 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1863 printk(KERN_ERR "Unable to find swap-space signature\n");
1868 /* swap partition endianess hack... */
1869 if (swab32(swap_header->info.version) == 1) {
1870 swab32s(&swap_header->info.version);
1871 swab32s(&swap_header->info.last_page);
1872 swab32s(&swap_header->info.nr_badpages);
1873 for (i = 0; i < swap_header->info.nr_badpages; i++)
1874 swab32s(&swap_header->info.badpages[i]);
1876 /* Check the swap header's sub-version */
1877 if (swap_header->info.version != 1) {
1879 "Unable to handle swap header version %d\n",
1880 swap_header->info.version);
1886 p->cluster_next = 1;
1890 * Find out how many pages are allowed for a single swap
1891 * device. There are two limiting factors: 1) the number of
1892 * bits for the swap offset in the swp_entry_t type and
1893 * 2) the number of bits in the a swap pte as defined by
1894 * the different architectures. In order to find the
1895 * largest possible bit mask a swap entry with swap type 0
1896 * and swap offset ~0UL is created, encoded to a swap pte,
1897 * decoded to a swp_entry_t again and finally the swap
1898 * offset is extracted. This will mask all the bits from
1899 * the initial ~0UL mask that can't be encoded in either
1900 * the swp_entry_t or the architecture definition of a
1903 maxpages = swp_offset(pte_to_swp_entry(
1904 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1905 if (maxpages > swap_header->info.last_page)
1906 maxpages = swap_header->info.last_page;
1907 p->highest_bit = maxpages - 1;
1912 if (swapfilepages && maxpages > swapfilepages) {
1914 "Swap area shorter than signature indicates\n");
1917 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1919 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1922 /* OK, set up the swap map and apply the bad block list */
1923 swap_map = vmalloc(maxpages);
1929 memset(swap_map, 0, maxpages);
1930 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1931 int page_nr = swap_header->info.badpages[i];
1932 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1936 swap_map[page_nr] = SWAP_MAP_BAD;
1939 error = swap_cgroup_swapon(type, maxpages);
1943 nr_good_pages = swap_header->info.last_page -
1944 swap_header->info.nr_badpages -
1945 1 /* header page */;
1947 if (nr_good_pages) {
1948 swap_map[0] = SWAP_MAP_BAD;
1950 p->pages = nr_good_pages;
1951 nr_extents = setup_swap_extents(p, &span);
1952 if (nr_extents < 0) {
1956 nr_good_pages = p->pages;
1958 if (!nr_good_pages) {
1959 printk(KERN_WARNING "Empty swap-file\n");
1965 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1966 p->flags |= SWP_SOLIDSTATE;
1967 p->cluster_next = 1 + (random32() % p->highest_bit);
1969 if (discard_swap(p) == 0)
1970 p->flags |= SWP_DISCARDABLE;
1973 mutex_lock(&swapon_mutex);
1974 spin_lock(&swap_lock);
1975 if (swap_flags & SWAP_FLAG_PREFER)
1977 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1979 p->prio = --least_priority;
1980 p->swap_map = swap_map;
1981 p->flags |= SWP_WRITEOK;
1982 nr_swap_pages += nr_good_pages;
1983 total_swap_pages += nr_good_pages;
1985 printk(KERN_INFO "Adding %uk swap on %s. "
1986 "Priority:%d extents:%d across:%lluk %s%s\n",
1987 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1988 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
1989 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
1990 (p->flags & SWP_DISCARDABLE) ? "D" : "");
1992 /* insert swap space into swap_list: */
1994 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1995 if (p->prio >= swap_info[i]->prio)
2001 swap_list.head = swap_list.next = type;
2003 swap_info[prev]->next = type;
2004 spin_unlock(&swap_lock);
2005 mutex_unlock(&swapon_mutex);
2010 set_blocksize(bdev, p->old_block_size);
2013 destroy_swap_extents(p);
2014 swap_cgroup_swapoff(type);
2016 spin_lock(&swap_lock);
2017 p->swap_file = NULL;
2019 spin_unlock(&swap_lock);
2022 filp_close(swap_file, NULL);
2024 if (page && !IS_ERR(page)) {
2026 page_cache_release(page);
2032 inode->i_flags |= S_SWAPFILE;
2033 mutex_unlock(&inode->i_mutex);
2038 void si_swapinfo(struct sysinfo *val)
2041 unsigned long nr_to_be_unused = 0;
2043 spin_lock(&swap_lock);
2044 for (type = 0; type < nr_swapfiles; type++) {
2045 struct swap_info_struct *si = swap_info[type];
2047 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2048 nr_to_be_unused += si->inuse_pages;
2050 val->freeswap = nr_swap_pages + nr_to_be_unused;
2051 val->totalswap = total_swap_pages + nr_to_be_unused;
2052 spin_unlock(&swap_lock);
2056 * Verify that a swap entry is valid and increment its swap map count.
2058 * Returns error code in following case.
2060 * - swp_entry is invalid -> EINVAL
2061 * - swp_entry is migration entry -> EINVAL
2062 * - swap-cache reference is requested but there is already one. -> EEXIST
2063 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2064 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2066 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2068 struct swap_info_struct *p;
2069 unsigned long offset, type;
2070 unsigned char count;
2071 unsigned char has_cache;
2074 if (non_swap_entry(entry))
2077 type = swp_type(entry);
2078 if (type >= nr_swapfiles)
2080 p = swap_info[type];
2081 offset = swp_offset(entry);
2083 spin_lock(&swap_lock);
2084 if (unlikely(offset >= p->max))
2087 count = p->swap_map[offset];
2088 has_cache = count & SWAP_HAS_CACHE;
2089 count &= ~SWAP_HAS_CACHE;
2092 if (usage == SWAP_HAS_CACHE) {
2094 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2095 if (!has_cache && count)
2096 has_cache = SWAP_HAS_CACHE;
2097 else if (has_cache) /* someone else added cache */
2099 else /* no users remaining */
2102 } else if (count || has_cache) {
2104 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2106 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2108 else if (swap_count_continued(p, offset, count))
2109 count = COUNT_CONTINUED;
2113 err = -ENOENT; /* unused swap entry */
2115 p->swap_map[offset] = count | has_cache;
2118 spin_unlock(&swap_lock);
2123 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2128 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2129 * (in which case its reference count is never incremented).
2131 void swap_shmem_alloc(swp_entry_t entry)
2133 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2137 * increase reference count of swap entry by 1.
2139 int swap_duplicate(swp_entry_t entry)
2143 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2144 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2149 * @entry: swap entry for which we allocate swap cache.
2151 * Called when allocating swap cache for existing swap entry,
2152 * This can return error codes. Returns 0 at success.
2153 * -EBUSY means there is a swap cache.
2154 * Note: return code is different from swap_duplicate().
2156 int swapcache_prepare(swp_entry_t entry)
2158 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2162 * swap_lock prevents swap_map being freed. Don't grab an extra
2163 * reference on the swaphandle, it doesn't matter if it becomes unused.
2165 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2167 struct swap_info_struct *si;
2168 int our_page_cluster = page_cluster;
2169 pgoff_t target, toff;
2173 if (!our_page_cluster) /* no readahead */
2176 si = swap_info[swp_type(entry)];
2177 target = swp_offset(entry);
2178 base = (target >> our_page_cluster) << our_page_cluster;
2179 end = base + (1 << our_page_cluster);
2180 if (!base) /* first page is swap header */
2183 spin_lock(&swap_lock);
2184 if (end > si->max) /* don't go beyond end of map */
2187 /* Count contiguous allocated slots above our target */
2188 for (toff = target; ++toff < end; nr_pages++) {
2189 /* Don't read in free or bad pages */
2190 if (!si->swap_map[toff])
2192 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2195 /* Count contiguous allocated slots below our target */
2196 for (toff = target; --toff >= base; nr_pages++) {
2197 /* Don't read in free or bad pages */
2198 if (!si->swap_map[toff])
2200 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2203 spin_unlock(&swap_lock);
2206 * Indicate starting offset, and return number of pages to get:
2207 * if only 1, say 0, since there's then no readahead to be done.
2210 return nr_pages? ++nr_pages: 0;
2214 * add_swap_count_continuation - called when a swap count is duplicated
2215 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2216 * page of the original vmalloc'ed swap_map, to hold the continuation count
2217 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2218 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2220 * These continuation pages are seldom referenced: the common paths all work
2221 * on the original swap_map, only referring to a continuation page when the
2222 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2224 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2225 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2226 * can be called after dropping locks.
2228 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2230 struct swap_info_struct *si;
2233 struct page *list_page;
2235 unsigned char count;
2238 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2239 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2241 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2243 si = swap_info_get(entry);
2246 * An acceptable race has occurred since the failing
2247 * __swap_duplicate(): the swap entry has been freed,
2248 * perhaps even the whole swap_map cleared for swapoff.
2253 offset = swp_offset(entry);
2254 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2256 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2258 * The higher the swap count, the more likely it is that tasks
2259 * will race to add swap count continuation: we need to avoid
2260 * over-provisioning.
2266 spin_unlock(&swap_lock);
2271 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2272 * no architecture is using highmem pages for kernel pagetables: so it
2273 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2275 head = vmalloc_to_page(si->swap_map + offset);
2276 offset &= ~PAGE_MASK;
2279 * Page allocation does not initialize the page's lru field,
2280 * but it does always reset its private field.
2282 if (!page_private(head)) {
2283 BUG_ON(count & COUNT_CONTINUED);
2284 INIT_LIST_HEAD(&head->lru);
2285 set_page_private(head, SWP_CONTINUED);
2286 si->flags |= SWP_CONTINUED;
2289 list_for_each_entry(list_page, &head->lru, lru) {
2293 * If the previous map said no continuation, but we've found
2294 * a continuation page, free our allocation and use this one.
2296 if (!(count & COUNT_CONTINUED))
2299 map = kmap_atomic(list_page, KM_USER0) + offset;
2301 kunmap_atomic(map, KM_USER0);
2304 * If this continuation count now has some space in it,
2305 * free our allocation and use this one.
2307 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2311 list_add_tail(&page->lru, &head->lru);
2312 page = NULL; /* now it's attached, don't free it */
2314 spin_unlock(&swap_lock);
2322 * swap_count_continued - when the original swap_map count is incremented
2323 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2324 * into, carry if so, or else fail until a new continuation page is allocated;
2325 * when the original swap_map count is decremented from 0 with continuation,
2326 * borrow from the continuation and report whether it still holds more.
2327 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2329 static bool swap_count_continued(struct swap_info_struct *si,
2330 pgoff_t offset, unsigned char count)
2336 head = vmalloc_to_page(si->swap_map + offset);
2337 if (page_private(head) != SWP_CONTINUED) {
2338 BUG_ON(count & COUNT_CONTINUED);
2339 return false; /* need to add count continuation */
2342 offset &= ~PAGE_MASK;
2343 page = list_entry(head->lru.next, struct page, lru);
2344 map = kmap_atomic(page, KM_USER0) + offset;
2346 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2347 goto init_map; /* jump over SWAP_CONT_MAX checks */
2349 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2351 * Think of how you add 1 to 999
2353 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2354 kunmap_atomic(map, KM_USER0);
2355 page = list_entry(page->lru.next, struct page, lru);
2356 BUG_ON(page == head);
2357 map = kmap_atomic(page, KM_USER0) + offset;
2359 if (*map == SWAP_CONT_MAX) {
2360 kunmap_atomic(map, KM_USER0);
2361 page = list_entry(page->lru.next, struct page, lru);
2363 return false; /* add count continuation */
2364 map = kmap_atomic(page, KM_USER0) + offset;
2365 init_map: *map = 0; /* we didn't zero the page */
2368 kunmap_atomic(map, KM_USER0);
2369 page = list_entry(page->lru.prev, struct page, lru);
2370 while (page != head) {
2371 map = kmap_atomic(page, KM_USER0) + offset;
2372 *map = COUNT_CONTINUED;
2373 kunmap_atomic(map, KM_USER0);
2374 page = list_entry(page->lru.prev, struct page, lru);
2376 return true; /* incremented */
2378 } else { /* decrementing */
2380 * Think of how you subtract 1 from 1000
2382 BUG_ON(count != COUNT_CONTINUED);
2383 while (*map == COUNT_CONTINUED) {
2384 kunmap_atomic(map, KM_USER0);
2385 page = list_entry(page->lru.next, struct page, lru);
2386 BUG_ON(page == head);
2387 map = kmap_atomic(page, KM_USER0) + offset;
2393 kunmap_atomic(map, KM_USER0);
2394 page = list_entry(page->lru.prev, struct page, lru);
2395 while (page != head) {
2396 map = kmap_atomic(page, KM_USER0) + offset;
2397 *map = SWAP_CONT_MAX | count;
2398 count = COUNT_CONTINUED;
2399 kunmap_atomic(map, KM_USER0);
2400 page = list_entry(page->lru.prev, struct page, lru);
2402 return count == COUNT_CONTINUED;
2407 * free_swap_count_continuations - swapoff free all the continuation pages
2408 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2410 static void free_swap_count_continuations(struct swap_info_struct *si)
2414 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2416 head = vmalloc_to_page(si->swap_map + offset);
2417 if (page_private(head)) {
2418 struct list_head *this, *next;
2419 list_for_each_safe(this, next, &head->lru) {
2421 page = list_entry(this, struct page, lru);