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1 /*
2 * linux/mm/swapfile.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
6 */
7
8 #include <linux/mm.h>
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>
32
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 #include <linux/page_cgroup.h>
37
38 static DEFINE_SPINLOCK(swap_lock);
39 static unsigned int nr_swapfiles;
40 long nr_swap_pages;
41 long total_swap_pages;
42 static int swap_overflow;
43 static int least_priority;
44
45 static const char Bad_file[] = "Bad swap file entry ";
46 static const char Unused_file[] = "Unused swap file entry ";
47 static const char Bad_offset[] = "Bad swap offset entry ";
48 static const char Unused_offset[] = "Unused swap offset entry ";
49
50 static struct swap_list_t swap_list = {-1, -1};
51
52 static struct swap_info_struct swap_info[MAX_SWAPFILES];
53
54 static DEFINE_MUTEX(swapon_mutex);
55
56 /* For reference count accounting in swap_map */
57 /* enum for swap_map[] handling. internal use only */
58 enum {
59 SWAP_MAP = 0, /* ops for reference from swap users */
60 SWAP_CACHE, /* ops for reference from swap cache */
61 };
62
63 static inline int swap_count(unsigned short ent)
64 {
65 return ent & SWAP_COUNT_MASK;
66 }
67
68 static inline bool swap_has_cache(unsigned short ent)
69 {
70 return !!(ent & SWAP_HAS_CACHE);
71 }
72
73 static inline unsigned short encode_swapmap(int count, bool has_cache)
74 {
75 unsigned short ret = count;
76
77 if (has_cache)
78 return SWAP_HAS_CACHE | ret;
79 return ret;
80 }
81
82 /* returnes 1 if swap entry is freed */
83 static int
84 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
85 {
86 int type = si - swap_info;
87 swp_entry_t entry = swp_entry(type, offset);
88 struct page *page;
89 int ret = 0;
90
91 page = find_get_page(&swapper_space, entry.val);
92 if (!page)
93 return 0;
94 /*
95 * This function is called from scan_swap_map() and it's called
96 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
97 * We have to use trylock for avoiding deadlock. This is a special
98 * case and you should use try_to_free_swap() with explicit lock_page()
99 * in usual operations.
100 */
101 if (trylock_page(page)) {
102 ret = try_to_free_swap(page);
103 unlock_page(page);
104 }
105 page_cache_release(page);
106 return ret;
107 }
108
109 /*
110 * We need this because the bdev->unplug_fn can sleep and we cannot
111 * hold swap_lock while calling the unplug_fn. And swap_lock
112 * cannot be turned into a mutex.
113 */
114 static DECLARE_RWSEM(swap_unplug_sem);
115
116 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
117 {
118 swp_entry_t entry;
119
120 down_read(&swap_unplug_sem);
121 entry.val = page_private(page);
122 if (PageSwapCache(page)) {
123 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
124 struct backing_dev_info *bdi;
125
126 /*
127 * If the page is removed from swapcache from under us (with a
128 * racy try_to_unuse/swapoff) we need an additional reference
129 * count to avoid reading garbage from page_private(page) above.
130 * If the WARN_ON triggers during a swapoff it maybe the race
131 * condition and it's harmless. However if it triggers without
132 * swapoff it signals a problem.
133 */
134 WARN_ON(page_count(page) <= 1);
135
136 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
137 blk_run_backing_dev(bdi, page);
138 }
139 up_read(&swap_unplug_sem);
140 }
141
142 /*
143 * swapon tell device that all the old swap contents can be discarded,
144 * to allow the swap device to optimize its wear-levelling.
145 */
146 static int discard_swap(struct swap_info_struct *si)
147 {
148 struct swap_extent *se;
149 int err = 0;
150
151 list_for_each_entry(se, &si->extent_list, list) {
152 sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
153 sector_t nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
154
155 if (se->start_page == 0) {
156 /* Do not discard the swap header page! */
157 start_block += 1 << (PAGE_SHIFT - 9);
158 nr_blocks -= 1 << (PAGE_SHIFT - 9);
159 if (!nr_blocks)
160 continue;
161 }
162
163 err = blkdev_issue_discard(si->bdev, start_block,
164 nr_blocks, GFP_KERNEL,
165 DISCARD_FL_BARRIER);
166 if (err)
167 break;
168
169 cond_resched();
170 }
171 return err; /* That will often be -EOPNOTSUPP */
172 }
173
174 /*
175 * swap allocation tell device that a cluster of swap can now be discarded,
176 * to allow the swap device to optimize its wear-levelling.
177 */
178 static void discard_swap_cluster(struct swap_info_struct *si,
179 pgoff_t start_page, pgoff_t nr_pages)
180 {
181 struct swap_extent *se = si->curr_swap_extent;
182 int found_extent = 0;
183
184 while (nr_pages) {
185 struct list_head *lh;
186
187 if (se->start_page <= start_page &&
188 start_page < se->start_page + se->nr_pages) {
189 pgoff_t offset = start_page - se->start_page;
190 sector_t start_block = se->start_block + offset;
191 sector_t nr_blocks = se->nr_pages - offset;
192
193 if (nr_blocks > nr_pages)
194 nr_blocks = nr_pages;
195 start_page += nr_blocks;
196 nr_pages -= nr_blocks;
197
198 if (!found_extent++)
199 si->curr_swap_extent = se;
200
201 start_block <<= PAGE_SHIFT - 9;
202 nr_blocks <<= PAGE_SHIFT - 9;
203 if (blkdev_issue_discard(si->bdev, start_block,
204 nr_blocks, GFP_NOIO,
205 DISCARD_FL_BARRIER))
206 break;
207 }
208
209 lh = se->list.next;
210 if (lh == &si->extent_list)
211 lh = lh->next;
212 se = list_entry(lh, struct swap_extent, list);
213 }
214 }
215
216 static int wait_for_discard(void *word)
217 {
218 schedule();
219 return 0;
220 }
221
222 #define SWAPFILE_CLUSTER 256
223 #define LATENCY_LIMIT 256
224
225 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
226 int cache)
227 {
228 unsigned long offset;
229 unsigned long scan_base;
230 unsigned long last_in_cluster = 0;
231 int latency_ration = LATENCY_LIMIT;
232 int found_free_cluster = 0;
233
234 /*
235 * We try to cluster swap pages by allocating them sequentially
236 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
237 * way, however, we resort to first-free allocation, starting
238 * a new cluster. This prevents us from scattering swap pages
239 * all over the entire swap partition, so that we reduce
240 * overall disk seek times between swap pages. -- sct
241 * But we do now try to find an empty cluster. -Andrea
242 * And we let swap pages go all over an SSD partition. Hugh
243 */
244
245 si->flags += SWP_SCANNING;
246 scan_base = offset = si->cluster_next;
247
248 if (unlikely(!si->cluster_nr--)) {
249 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
250 si->cluster_nr = SWAPFILE_CLUSTER - 1;
251 goto checks;
252 }
253 if (si->flags & SWP_DISCARDABLE) {
254 /*
255 * Start range check on racing allocations, in case
256 * they overlap the cluster we eventually decide on
257 * (we scan without swap_lock to allow preemption).
258 * It's hardly conceivable that cluster_nr could be
259 * wrapped during our scan, but don't depend on it.
260 */
261 if (si->lowest_alloc)
262 goto checks;
263 si->lowest_alloc = si->max;
264 si->highest_alloc = 0;
265 }
266 spin_unlock(&swap_lock);
267
268 /*
269 * If seek is expensive, start searching for new cluster from
270 * start of partition, to minimize the span of allocated swap.
271 * But if seek is cheap, search from our current position, so
272 * that swap is allocated from all over the partition: if the
273 * Flash Translation Layer only remaps within limited zones,
274 * we don't want to wear out the first zone too quickly.
275 */
276 if (!(si->flags & SWP_SOLIDSTATE))
277 scan_base = offset = si->lowest_bit;
278 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
279
280 /* Locate the first empty (unaligned) cluster */
281 for (; last_in_cluster <= si->highest_bit; offset++) {
282 if (si->swap_map[offset])
283 last_in_cluster = offset + SWAPFILE_CLUSTER;
284 else if (offset == last_in_cluster) {
285 spin_lock(&swap_lock);
286 offset -= SWAPFILE_CLUSTER - 1;
287 si->cluster_next = offset;
288 si->cluster_nr = SWAPFILE_CLUSTER - 1;
289 found_free_cluster = 1;
290 goto checks;
291 }
292 if (unlikely(--latency_ration < 0)) {
293 cond_resched();
294 latency_ration = LATENCY_LIMIT;
295 }
296 }
297
298 offset = si->lowest_bit;
299 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
300
301 /* Locate the first empty (unaligned) cluster */
302 for (; last_in_cluster < scan_base; offset++) {
303 if (si->swap_map[offset])
304 last_in_cluster = offset + SWAPFILE_CLUSTER;
305 else if (offset == last_in_cluster) {
306 spin_lock(&swap_lock);
307 offset -= SWAPFILE_CLUSTER - 1;
308 si->cluster_next = offset;
309 si->cluster_nr = SWAPFILE_CLUSTER - 1;
310 found_free_cluster = 1;
311 goto checks;
312 }
313 if (unlikely(--latency_ration < 0)) {
314 cond_resched();
315 latency_ration = LATENCY_LIMIT;
316 }
317 }
318
319 offset = scan_base;
320 spin_lock(&swap_lock);
321 si->cluster_nr = SWAPFILE_CLUSTER - 1;
322 si->lowest_alloc = 0;
323 }
324
325 checks:
326 if (!(si->flags & SWP_WRITEOK))
327 goto no_page;
328 if (!si->highest_bit)
329 goto no_page;
330 if (offset > si->highest_bit)
331 scan_base = offset = si->lowest_bit;
332
333 /* reuse swap entry of cache-only swap if not busy. */
334 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
335 int swap_was_freed;
336 spin_unlock(&swap_lock);
337 swap_was_freed = __try_to_reclaim_swap(si, offset);
338 spin_lock(&swap_lock);
339 /* entry was freed successfully, try to use this again */
340 if (swap_was_freed)
341 goto checks;
342 goto scan; /* check next one */
343 }
344
345 if (si->swap_map[offset])
346 goto scan;
347
348 if (offset == si->lowest_bit)
349 si->lowest_bit++;
350 if (offset == si->highest_bit)
351 si->highest_bit--;
352 si->inuse_pages++;
353 if (si->inuse_pages == si->pages) {
354 si->lowest_bit = si->max;
355 si->highest_bit = 0;
356 }
357 if (cache == SWAP_CACHE) /* at usual swap-out via vmscan.c */
358 si->swap_map[offset] = encode_swapmap(0, true);
359 else /* at suspend */
360 si->swap_map[offset] = encode_swapmap(1, false);
361 si->cluster_next = offset + 1;
362 si->flags -= SWP_SCANNING;
363
364 if (si->lowest_alloc) {
365 /*
366 * Only set when SWP_DISCARDABLE, and there's a scan
367 * for a free cluster in progress or just completed.
368 */
369 if (found_free_cluster) {
370 /*
371 * To optimize wear-levelling, discard the
372 * old data of the cluster, taking care not to
373 * discard any of its pages that have already
374 * been allocated by racing tasks (offset has
375 * already stepped over any at the beginning).
376 */
377 if (offset < si->highest_alloc &&
378 si->lowest_alloc <= last_in_cluster)
379 last_in_cluster = si->lowest_alloc - 1;
380 si->flags |= SWP_DISCARDING;
381 spin_unlock(&swap_lock);
382
383 if (offset < last_in_cluster)
384 discard_swap_cluster(si, offset,
385 last_in_cluster - offset + 1);
386
387 spin_lock(&swap_lock);
388 si->lowest_alloc = 0;
389 si->flags &= ~SWP_DISCARDING;
390
391 smp_mb(); /* wake_up_bit advises this */
392 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
393
394 } else if (si->flags & SWP_DISCARDING) {
395 /*
396 * Delay using pages allocated by racing tasks
397 * until the whole discard has been issued. We
398 * could defer that delay until swap_writepage,
399 * but it's easier to keep this self-contained.
400 */
401 spin_unlock(&swap_lock);
402 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
403 wait_for_discard, TASK_UNINTERRUPTIBLE);
404 spin_lock(&swap_lock);
405 } else {
406 /*
407 * Note pages allocated by racing tasks while
408 * scan for a free cluster is in progress, so
409 * that its final discard can exclude them.
410 */
411 if (offset < si->lowest_alloc)
412 si->lowest_alloc = offset;
413 if (offset > si->highest_alloc)
414 si->highest_alloc = offset;
415 }
416 }
417 return offset;
418
419 scan:
420 spin_unlock(&swap_lock);
421 while (++offset <= si->highest_bit) {
422 if (!si->swap_map[offset]) {
423 spin_lock(&swap_lock);
424 goto checks;
425 }
426 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
427 spin_lock(&swap_lock);
428 goto checks;
429 }
430 if (unlikely(--latency_ration < 0)) {
431 cond_resched();
432 latency_ration = LATENCY_LIMIT;
433 }
434 }
435 offset = si->lowest_bit;
436 while (++offset < scan_base) {
437 if (!si->swap_map[offset]) {
438 spin_lock(&swap_lock);
439 goto checks;
440 }
441 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
442 spin_lock(&swap_lock);
443 goto checks;
444 }
445 if (unlikely(--latency_ration < 0)) {
446 cond_resched();
447 latency_ration = LATENCY_LIMIT;
448 }
449 }
450 spin_lock(&swap_lock);
451
452 no_page:
453 si->flags -= SWP_SCANNING;
454 return 0;
455 }
456
457 swp_entry_t get_swap_page(void)
458 {
459 struct swap_info_struct *si;
460 pgoff_t offset;
461 int type, next;
462 int wrapped = 0;
463
464 spin_lock(&swap_lock);
465 if (nr_swap_pages <= 0)
466 goto noswap;
467 nr_swap_pages--;
468
469 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
470 si = swap_info + type;
471 next = si->next;
472 if (next < 0 ||
473 (!wrapped && si->prio != swap_info[next].prio)) {
474 next = swap_list.head;
475 wrapped++;
476 }
477
478 if (!si->highest_bit)
479 continue;
480 if (!(si->flags & SWP_WRITEOK))
481 continue;
482
483 swap_list.next = next;
484 /* This is called for allocating swap entry for cache */
485 offset = scan_swap_map(si, SWAP_CACHE);
486 if (offset) {
487 spin_unlock(&swap_lock);
488 return swp_entry(type, offset);
489 }
490 next = swap_list.next;
491 }
492
493 nr_swap_pages++;
494 noswap:
495 spin_unlock(&swap_lock);
496 return (swp_entry_t) {0};
497 }
498
499 /* The only caller of this function is now susupend routine */
500 swp_entry_t get_swap_page_of_type(int type)
501 {
502 struct swap_info_struct *si;
503 pgoff_t offset;
504
505 spin_lock(&swap_lock);
506 si = swap_info + type;
507 if (si->flags & SWP_WRITEOK) {
508 nr_swap_pages--;
509 /* This is called for allocating swap entry, not cache */
510 offset = scan_swap_map(si, SWAP_MAP);
511 if (offset) {
512 spin_unlock(&swap_lock);
513 return swp_entry(type, offset);
514 }
515 nr_swap_pages++;
516 }
517 spin_unlock(&swap_lock);
518 return (swp_entry_t) {0};
519 }
520
521 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
522 {
523 struct swap_info_struct * p;
524 unsigned long offset, type;
525
526 if (!entry.val)
527 goto out;
528 type = swp_type(entry);
529 if (type >= nr_swapfiles)
530 goto bad_nofile;
531 p = & swap_info[type];
532 if (!(p->flags & SWP_USED))
533 goto bad_device;
534 offset = swp_offset(entry);
535 if (offset >= p->max)
536 goto bad_offset;
537 if (!p->swap_map[offset])
538 goto bad_free;
539 spin_lock(&swap_lock);
540 return p;
541
542 bad_free:
543 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
544 goto out;
545 bad_offset:
546 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
547 goto out;
548 bad_device:
549 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
550 goto out;
551 bad_nofile:
552 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
553 out:
554 return NULL;
555 }
556
557 static int swap_entry_free(struct swap_info_struct *p,
558 swp_entry_t ent, int cache)
559 {
560 unsigned long offset = swp_offset(ent);
561 int count = swap_count(p->swap_map[offset]);
562 bool has_cache;
563
564 has_cache = swap_has_cache(p->swap_map[offset]);
565
566 if (cache == SWAP_MAP) { /* dropping usage count of swap */
567 if (count < SWAP_MAP_MAX) {
568 count--;
569 p->swap_map[offset] = encode_swapmap(count, has_cache);
570 }
571 } else { /* dropping swap cache flag */
572 VM_BUG_ON(!has_cache);
573 p->swap_map[offset] = encode_swapmap(count, false);
574
575 }
576 /* return code. */
577 count = p->swap_map[offset];
578 /* free if no reference */
579 if (!count) {
580 if (offset < p->lowest_bit)
581 p->lowest_bit = offset;
582 if (offset > p->highest_bit)
583 p->highest_bit = offset;
584 if (p->prio > swap_info[swap_list.next].prio)
585 swap_list.next = p - swap_info;
586 nr_swap_pages++;
587 p->inuse_pages--;
588 }
589 if (!swap_count(count))
590 mem_cgroup_uncharge_swap(ent);
591 return count;
592 }
593
594 /*
595 * Caller has made sure that the swapdevice corresponding to entry
596 * is still around or has not been recycled.
597 */
598 void swap_free(swp_entry_t entry)
599 {
600 struct swap_info_struct * p;
601
602 p = swap_info_get(entry);
603 if (p) {
604 swap_entry_free(p, entry, SWAP_MAP);
605 spin_unlock(&swap_lock);
606 }
607 }
608
609 /*
610 * Called after dropping swapcache to decrease refcnt to swap entries.
611 */
612 void swapcache_free(swp_entry_t entry, struct page *page)
613 {
614 struct swap_info_struct *p;
615 int ret;
616
617 p = swap_info_get(entry);
618 if (p) {
619 ret = swap_entry_free(p, entry, SWAP_CACHE);
620 if (page) {
621 bool swapout;
622 if (ret)
623 swapout = true; /* the end of swap out */
624 else
625 swapout = false; /* no more swap users! */
626 mem_cgroup_uncharge_swapcache(page, entry, swapout);
627 }
628 spin_unlock(&swap_lock);
629 }
630 return;
631 }
632
633 /*
634 * How many references to page are currently swapped out?
635 */
636 static inline int page_swapcount(struct page *page)
637 {
638 int count = 0;
639 struct swap_info_struct *p;
640 swp_entry_t entry;
641
642 entry.val = page_private(page);
643 p = swap_info_get(entry);
644 if (p) {
645 count = swap_count(p->swap_map[swp_offset(entry)]);
646 spin_unlock(&swap_lock);
647 }
648 return count;
649 }
650
651 /*
652 * We can write to an anon page without COW if there are no other references
653 * to it. And as a side-effect, free up its swap: because the old content
654 * on disk will never be read, and seeking back there to write new content
655 * later would only waste time away from clustering.
656 */
657 int reuse_swap_page(struct page *page)
658 {
659 int count;
660
661 VM_BUG_ON(!PageLocked(page));
662 count = page_mapcount(page);
663 if (count <= 1 && PageSwapCache(page)) {
664 count += page_swapcount(page);
665 if (count == 1 && !PageWriteback(page)) {
666 delete_from_swap_cache(page);
667 SetPageDirty(page);
668 }
669 }
670 return count == 1;
671 }
672
673 /*
674 * If swap is getting full, or if there are no more mappings of this page,
675 * then try_to_free_swap is called to free its swap space.
676 */
677 int try_to_free_swap(struct page *page)
678 {
679 VM_BUG_ON(!PageLocked(page));
680
681 if (!PageSwapCache(page))
682 return 0;
683 if (PageWriteback(page))
684 return 0;
685 if (page_swapcount(page))
686 return 0;
687
688 delete_from_swap_cache(page);
689 SetPageDirty(page);
690 return 1;
691 }
692
693 /*
694 * Free the swap entry like above, but also try to
695 * free the page cache entry if it is the last user.
696 */
697 int free_swap_and_cache(swp_entry_t entry)
698 {
699 struct swap_info_struct *p;
700 struct page *page = NULL;
701
702 if (non_swap_entry(entry))
703 return 1;
704
705 p = swap_info_get(entry);
706 if (p) {
707 if (swap_entry_free(p, entry, SWAP_MAP) == SWAP_HAS_CACHE) {
708 page = find_get_page(&swapper_space, entry.val);
709 if (page && !trylock_page(page)) {
710 page_cache_release(page);
711 page = NULL;
712 }
713 }
714 spin_unlock(&swap_lock);
715 }
716 if (page) {
717 /*
718 * Not mapped elsewhere, or swap space full? Free it!
719 * Also recheck PageSwapCache now page is locked (above).
720 */
721 if (PageSwapCache(page) && !PageWriteback(page) &&
722 (!page_mapped(page) || vm_swap_full())) {
723 delete_from_swap_cache(page);
724 SetPageDirty(page);
725 }
726 unlock_page(page);
727 page_cache_release(page);
728 }
729 return p != NULL;
730 }
731
732 #ifdef CONFIG_HIBERNATION
733 /*
734 * Find the swap type that corresponds to given device (if any).
735 *
736 * @offset - number of the PAGE_SIZE-sized block of the device, starting
737 * from 0, in which the swap header is expected to be located.
738 *
739 * This is needed for the suspend to disk (aka swsusp).
740 */
741 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
742 {
743 struct block_device *bdev = NULL;
744 int i;
745
746 if (device)
747 bdev = bdget(device);
748
749 spin_lock(&swap_lock);
750 for (i = 0; i < nr_swapfiles; i++) {
751 struct swap_info_struct *sis = swap_info + i;
752
753 if (!(sis->flags & SWP_WRITEOK))
754 continue;
755
756 if (!bdev) {
757 if (bdev_p)
758 *bdev_p = bdgrab(sis->bdev);
759
760 spin_unlock(&swap_lock);
761 return i;
762 }
763 if (bdev == sis->bdev) {
764 struct swap_extent *se;
765
766 se = list_entry(sis->extent_list.next,
767 struct swap_extent, list);
768 if (se->start_block == offset) {
769 if (bdev_p)
770 *bdev_p = bdgrab(sis->bdev);
771
772 spin_unlock(&swap_lock);
773 bdput(bdev);
774 return i;
775 }
776 }
777 }
778 spin_unlock(&swap_lock);
779 if (bdev)
780 bdput(bdev);
781
782 return -ENODEV;
783 }
784
785 /*
786 * Return either the total number of swap pages of given type, or the number
787 * of free pages of that type (depending on @free)
788 *
789 * This is needed for software suspend
790 */
791 unsigned int count_swap_pages(int type, int free)
792 {
793 unsigned int n = 0;
794
795 if (type < nr_swapfiles) {
796 spin_lock(&swap_lock);
797 if (swap_info[type].flags & SWP_WRITEOK) {
798 n = swap_info[type].pages;
799 if (free)
800 n -= swap_info[type].inuse_pages;
801 }
802 spin_unlock(&swap_lock);
803 }
804 return n;
805 }
806 #endif
807
808 /*
809 * No need to decide whether this PTE shares the swap entry with others,
810 * just let do_wp_page work it out if a write is requested later - to
811 * force COW, vm_page_prot omits write permission from any private vma.
812 */
813 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
814 unsigned long addr, swp_entry_t entry, struct page *page)
815 {
816 struct mem_cgroup *ptr = NULL;
817 spinlock_t *ptl;
818 pte_t *pte;
819 int ret = 1;
820
821 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
822 ret = -ENOMEM;
823 goto out_nolock;
824 }
825
826 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
827 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
828 if (ret > 0)
829 mem_cgroup_cancel_charge_swapin(ptr);
830 ret = 0;
831 goto out;
832 }
833
834 inc_mm_counter(vma->vm_mm, anon_rss);
835 get_page(page);
836 set_pte_at(vma->vm_mm, addr, pte,
837 pte_mkold(mk_pte(page, vma->vm_page_prot)));
838 page_add_anon_rmap(page, vma, addr);
839 mem_cgroup_commit_charge_swapin(page, ptr);
840 swap_free(entry);
841 /*
842 * Move the page to the active list so it is not
843 * immediately swapped out again after swapon.
844 */
845 activate_page(page);
846 out:
847 pte_unmap_unlock(pte, ptl);
848 out_nolock:
849 return ret;
850 }
851
852 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
853 unsigned long addr, unsigned long end,
854 swp_entry_t entry, struct page *page)
855 {
856 pte_t swp_pte = swp_entry_to_pte(entry);
857 pte_t *pte;
858 int ret = 0;
859
860 /*
861 * We don't actually need pte lock while scanning for swp_pte: since
862 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
863 * page table while we're scanning; though it could get zapped, and on
864 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
865 * of unmatched parts which look like swp_pte, so unuse_pte must
866 * recheck under pte lock. Scanning without pte lock lets it be
867 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
868 */
869 pte = pte_offset_map(pmd, addr);
870 do {
871 /*
872 * swapoff spends a _lot_ of time in this loop!
873 * Test inline before going to call unuse_pte.
874 */
875 if (unlikely(pte_same(*pte, swp_pte))) {
876 pte_unmap(pte);
877 ret = unuse_pte(vma, pmd, addr, entry, page);
878 if (ret)
879 goto out;
880 pte = pte_offset_map(pmd, addr);
881 }
882 } while (pte++, addr += PAGE_SIZE, addr != end);
883 pte_unmap(pte - 1);
884 out:
885 return ret;
886 }
887
888 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
889 unsigned long addr, unsigned long end,
890 swp_entry_t entry, struct page *page)
891 {
892 pmd_t *pmd;
893 unsigned long next;
894 int ret;
895
896 pmd = pmd_offset(pud, addr);
897 do {
898 next = pmd_addr_end(addr, end);
899 if (pmd_none_or_clear_bad(pmd))
900 continue;
901 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
902 if (ret)
903 return ret;
904 } while (pmd++, addr = next, addr != end);
905 return 0;
906 }
907
908 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
909 unsigned long addr, unsigned long end,
910 swp_entry_t entry, struct page *page)
911 {
912 pud_t *pud;
913 unsigned long next;
914 int ret;
915
916 pud = pud_offset(pgd, addr);
917 do {
918 next = pud_addr_end(addr, end);
919 if (pud_none_or_clear_bad(pud))
920 continue;
921 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
922 if (ret)
923 return ret;
924 } while (pud++, addr = next, addr != end);
925 return 0;
926 }
927
928 static int unuse_vma(struct vm_area_struct *vma,
929 swp_entry_t entry, struct page *page)
930 {
931 pgd_t *pgd;
932 unsigned long addr, end, next;
933 int ret;
934
935 if (page->mapping) {
936 addr = page_address_in_vma(page, vma);
937 if (addr == -EFAULT)
938 return 0;
939 else
940 end = addr + PAGE_SIZE;
941 } else {
942 addr = vma->vm_start;
943 end = vma->vm_end;
944 }
945
946 pgd = pgd_offset(vma->vm_mm, addr);
947 do {
948 next = pgd_addr_end(addr, end);
949 if (pgd_none_or_clear_bad(pgd))
950 continue;
951 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
952 if (ret)
953 return ret;
954 } while (pgd++, addr = next, addr != end);
955 return 0;
956 }
957
958 static int unuse_mm(struct mm_struct *mm,
959 swp_entry_t entry, struct page *page)
960 {
961 struct vm_area_struct *vma;
962 int ret = 0;
963
964 if (!down_read_trylock(&mm->mmap_sem)) {
965 /*
966 * Activate page so shrink_inactive_list is unlikely to unmap
967 * its ptes while lock is dropped, so swapoff can make progress.
968 */
969 activate_page(page);
970 unlock_page(page);
971 down_read(&mm->mmap_sem);
972 lock_page(page);
973 }
974 for (vma = mm->mmap; vma; vma = vma->vm_next) {
975 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
976 break;
977 }
978 up_read(&mm->mmap_sem);
979 return (ret < 0)? ret: 0;
980 }
981
982 /*
983 * Scan swap_map from current position to next entry still in use.
984 * Recycle to start on reaching the end, returning 0 when empty.
985 */
986 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
987 unsigned int prev)
988 {
989 unsigned int max = si->max;
990 unsigned int i = prev;
991 int count;
992
993 /*
994 * No need for swap_lock here: we're just looking
995 * for whether an entry is in use, not modifying it; false
996 * hits are okay, and sys_swapoff() has already prevented new
997 * allocations from this area (while holding swap_lock).
998 */
999 for (;;) {
1000 if (++i >= max) {
1001 if (!prev) {
1002 i = 0;
1003 break;
1004 }
1005 /*
1006 * No entries in use at top of swap_map,
1007 * loop back to start and recheck there.
1008 */
1009 max = prev + 1;
1010 prev = 0;
1011 i = 1;
1012 }
1013 count = si->swap_map[i];
1014 if (count && swap_count(count) != SWAP_MAP_BAD)
1015 break;
1016 }
1017 return i;
1018 }
1019
1020 /*
1021 * We completely avoid races by reading each swap page in advance,
1022 * and then search for the process using it. All the necessary
1023 * page table adjustments can then be made atomically.
1024 */
1025 static int try_to_unuse(unsigned int type)
1026 {
1027 struct swap_info_struct * si = &swap_info[type];
1028 struct mm_struct *start_mm;
1029 unsigned short *swap_map;
1030 unsigned short swcount;
1031 struct page *page;
1032 swp_entry_t entry;
1033 unsigned int i = 0;
1034 int retval = 0;
1035 int reset_overflow = 0;
1036 int shmem;
1037
1038 /*
1039 * When searching mms for an entry, a good strategy is to
1040 * start at the first mm we freed the previous entry from
1041 * (though actually we don't notice whether we or coincidence
1042 * freed the entry). Initialize this start_mm with a hold.
1043 *
1044 * A simpler strategy would be to start at the last mm we
1045 * freed the previous entry from; but that would take less
1046 * advantage of mmlist ordering, which clusters forked mms
1047 * together, child after parent. If we race with dup_mmap(), we
1048 * prefer to resolve parent before child, lest we miss entries
1049 * duplicated after we scanned child: using last mm would invert
1050 * that. Though it's only a serious concern when an overflowed
1051 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
1052 */
1053 start_mm = &init_mm;
1054 atomic_inc(&init_mm.mm_users);
1055
1056 /*
1057 * Keep on scanning until all entries have gone. Usually,
1058 * one pass through swap_map is enough, but not necessarily:
1059 * there are races when an instance of an entry might be missed.
1060 */
1061 while ((i = find_next_to_unuse(si, i)) != 0) {
1062 if (signal_pending(current)) {
1063 retval = -EINTR;
1064 break;
1065 }
1066
1067 /*
1068 * Get a page for the entry, using the existing swap
1069 * cache page if there is one. Otherwise, get a clean
1070 * page and read the swap into it.
1071 */
1072 swap_map = &si->swap_map[i];
1073 entry = swp_entry(type, i);
1074 page = read_swap_cache_async(entry,
1075 GFP_HIGHUSER_MOVABLE, NULL, 0);
1076 if (!page) {
1077 /*
1078 * Either swap_duplicate() failed because entry
1079 * has been freed independently, and will not be
1080 * reused since sys_swapoff() already disabled
1081 * allocation from here, or alloc_page() failed.
1082 */
1083 if (!*swap_map)
1084 continue;
1085 retval = -ENOMEM;
1086 break;
1087 }
1088
1089 /*
1090 * Don't hold on to start_mm if it looks like exiting.
1091 */
1092 if (atomic_read(&start_mm->mm_users) == 1) {
1093 mmput(start_mm);
1094 start_mm = &init_mm;
1095 atomic_inc(&init_mm.mm_users);
1096 }
1097
1098 /*
1099 * Wait for and lock page. When do_swap_page races with
1100 * try_to_unuse, do_swap_page can handle the fault much
1101 * faster than try_to_unuse can locate the entry. This
1102 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1103 * defer to do_swap_page in such a case - in some tests,
1104 * do_swap_page and try_to_unuse repeatedly compete.
1105 */
1106 wait_on_page_locked(page);
1107 wait_on_page_writeback(page);
1108 lock_page(page);
1109 wait_on_page_writeback(page);
1110
1111 /*
1112 * Remove all references to entry.
1113 * Whenever we reach init_mm, there's no address space
1114 * to search, but use it as a reminder to search shmem.
1115 */
1116 shmem = 0;
1117 swcount = *swap_map;
1118 if (swap_count(swcount)) {
1119 if (start_mm == &init_mm)
1120 shmem = shmem_unuse(entry, page);
1121 else
1122 retval = unuse_mm(start_mm, entry, page);
1123 }
1124 if (swap_count(*swap_map)) {
1125 int set_start_mm = (*swap_map >= swcount);
1126 struct list_head *p = &start_mm->mmlist;
1127 struct mm_struct *new_start_mm = start_mm;
1128 struct mm_struct *prev_mm = start_mm;
1129 struct mm_struct *mm;
1130
1131 atomic_inc(&new_start_mm->mm_users);
1132 atomic_inc(&prev_mm->mm_users);
1133 spin_lock(&mmlist_lock);
1134 while (swap_count(*swap_map) && !retval && !shmem &&
1135 (p = p->next) != &start_mm->mmlist) {
1136 mm = list_entry(p, struct mm_struct, mmlist);
1137 if (!atomic_inc_not_zero(&mm->mm_users))
1138 continue;
1139 spin_unlock(&mmlist_lock);
1140 mmput(prev_mm);
1141 prev_mm = mm;
1142
1143 cond_resched();
1144
1145 swcount = *swap_map;
1146 if (!swap_count(swcount)) /* any usage ? */
1147 ;
1148 else if (mm == &init_mm) {
1149 set_start_mm = 1;
1150 shmem = shmem_unuse(entry, page);
1151 } else
1152 retval = unuse_mm(mm, entry, page);
1153
1154 if (set_start_mm && *swap_map < swcount) {
1155 mmput(new_start_mm);
1156 atomic_inc(&mm->mm_users);
1157 new_start_mm = mm;
1158 set_start_mm = 0;
1159 }
1160 spin_lock(&mmlist_lock);
1161 }
1162 spin_unlock(&mmlist_lock);
1163 mmput(prev_mm);
1164 mmput(start_mm);
1165 start_mm = new_start_mm;
1166 }
1167 if (shmem) {
1168 /* page has already been unlocked and released */
1169 if (shmem > 0)
1170 continue;
1171 retval = shmem;
1172 break;
1173 }
1174 if (retval) {
1175 unlock_page(page);
1176 page_cache_release(page);
1177 break;
1178 }
1179
1180 /*
1181 * How could swap count reach 0x7ffe ?
1182 * There's no way to repeat a swap page within an mm
1183 * (except in shmem, where it's the shared object which takes
1184 * the reference count)?
1185 * We believe SWAP_MAP_MAX cannot occur.(if occur, unsigned
1186 * short is too small....)
1187 * If that's wrong, then we should worry more about
1188 * exit_mmap() and do_munmap() cases described above:
1189 * we might be resetting SWAP_MAP_MAX too early here.
1190 * We know "Undead"s can happen, they're okay, so don't
1191 * report them; but do report if we reset SWAP_MAP_MAX.
1192 */
1193 /* We might release the lock_page() in unuse_mm(). */
1194 if (!PageSwapCache(page) || page_private(page) != entry.val)
1195 goto retry;
1196
1197 if (swap_count(*swap_map) == SWAP_MAP_MAX) {
1198 spin_lock(&swap_lock);
1199 *swap_map = encode_swapmap(0, true);
1200 spin_unlock(&swap_lock);
1201 reset_overflow = 1;
1202 }
1203
1204 /*
1205 * If a reference remains (rare), we would like to leave
1206 * the page in the swap cache; but try_to_unmap could
1207 * then re-duplicate the entry once we drop page lock,
1208 * so we might loop indefinitely; also, that page could
1209 * not be swapped out to other storage meanwhile. So:
1210 * delete from cache even if there's another reference,
1211 * after ensuring that the data has been saved to disk -
1212 * since if the reference remains (rarer), it will be
1213 * read from disk into another page. Splitting into two
1214 * pages would be incorrect if swap supported "shared
1215 * private" pages, but they are handled by tmpfs files.
1216 */
1217 if (swap_count(*swap_map) &&
1218 PageDirty(page) && PageSwapCache(page)) {
1219 struct writeback_control wbc = {
1220 .sync_mode = WB_SYNC_NONE,
1221 };
1222
1223 swap_writepage(page, &wbc);
1224 lock_page(page);
1225 wait_on_page_writeback(page);
1226 }
1227
1228 /*
1229 * It is conceivable that a racing task removed this page from
1230 * swap cache just before we acquired the page lock at the top,
1231 * or while we dropped it in unuse_mm(). The page might even
1232 * be back in swap cache on another swap area: that we must not
1233 * delete, since it may not have been written out to swap yet.
1234 */
1235 if (PageSwapCache(page) &&
1236 likely(page_private(page) == entry.val))
1237 delete_from_swap_cache(page);
1238
1239 /*
1240 * So we could skip searching mms once swap count went
1241 * to 1, we did not mark any present ptes as dirty: must
1242 * mark page dirty so shrink_page_list will preserve it.
1243 */
1244 SetPageDirty(page);
1245 retry:
1246 unlock_page(page);
1247 page_cache_release(page);
1248
1249 /*
1250 * Make sure that we aren't completely killing
1251 * interactive performance.
1252 */
1253 cond_resched();
1254 }
1255
1256 mmput(start_mm);
1257 if (reset_overflow) {
1258 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
1259 swap_overflow = 0;
1260 }
1261 return retval;
1262 }
1263
1264 /*
1265 * After a successful try_to_unuse, if no swap is now in use, we know
1266 * we can empty the mmlist. swap_lock must be held on entry and exit.
1267 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1268 * added to the mmlist just after page_duplicate - before would be racy.
1269 */
1270 static void drain_mmlist(void)
1271 {
1272 struct list_head *p, *next;
1273 unsigned int i;
1274
1275 for (i = 0; i < nr_swapfiles; i++)
1276 if (swap_info[i].inuse_pages)
1277 return;
1278 spin_lock(&mmlist_lock);
1279 list_for_each_safe(p, next, &init_mm.mmlist)
1280 list_del_init(p);
1281 spin_unlock(&mmlist_lock);
1282 }
1283
1284 /*
1285 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1286 * corresponds to page offset `offset'. Note that the type of this function
1287 * is sector_t, but it returns page offset into the bdev, not sector offset.
1288 */
1289 sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev)
1290 {
1291 struct swap_info_struct *sis;
1292 struct swap_extent *start_se;
1293 struct swap_extent *se;
1294 pgoff_t offset;
1295
1296 sis = swap_info + swp_type(entry);
1297 *bdev = sis->bdev;
1298
1299 offset = swp_offset(entry);
1300 start_se = sis->curr_swap_extent;
1301 se = start_se;
1302
1303 for ( ; ; ) {
1304 struct list_head *lh;
1305
1306 if (se->start_page <= offset &&
1307 offset < (se->start_page + se->nr_pages)) {
1308 return se->start_block + (offset - se->start_page);
1309 }
1310 lh = se->list.next;
1311 if (lh == &sis->extent_list)
1312 lh = lh->next;
1313 se = list_entry(lh, struct swap_extent, list);
1314 sis->curr_swap_extent = se;
1315 BUG_ON(se == start_se); /* It *must* be present */
1316 }
1317 }
1318
1319 #ifdef CONFIG_HIBERNATION
1320 /*
1321 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1322 * corresponding to given index in swap_info (swap type).
1323 */
1324 sector_t swapdev_block(int swap_type, pgoff_t offset)
1325 {
1326 struct swap_info_struct *sis;
1327 struct block_device *bdev;
1328
1329 if (swap_type >= nr_swapfiles)
1330 return 0;
1331
1332 sis = swap_info + swap_type;
1333 return (sis->flags & SWP_WRITEOK) ?
1334 map_swap_page(swp_entry(swap_type, offset), &bdev) : 0;
1335 }
1336 #endif /* CONFIG_HIBERNATION */
1337
1338 /*
1339 * Free all of a swapdev's extent information
1340 */
1341 static void destroy_swap_extents(struct swap_info_struct *sis)
1342 {
1343 while (!list_empty(&sis->extent_list)) {
1344 struct swap_extent *se;
1345
1346 se = list_entry(sis->extent_list.next,
1347 struct swap_extent, list);
1348 list_del(&se->list);
1349 kfree(se);
1350 }
1351 }
1352
1353 /*
1354 * Add a block range (and the corresponding page range) into this swapdev's
1355 * extent list. The extent list is kept sorted in page order.
1356 *
1357 * This function rather assumes that it is called in ascending page order.
1358 */
1359 static int
1360 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1361 unsigned long nr_pages, sector_t start_block)
1362 {
1363 struct swap_extent *se;
1364 struct swap_extent *new_se;
1365 struct list_head *lh;
1366
1367 lh = sis->extent_list.prev; /* The highest page extent */
1368 if (lh != &sis->extent_list) {
1369 se = list_entry(lh, struct swap_extent, list);
1370 BUG_ON(se->start_page + se->nr_pages != start_page);
1371 if (se->start_block + se->nr_pages == start_block) {
1372 /* Merge it */
1373 se->nr_pages += nr_pages;
1374 return 0;
1375 }
1376 }
1377
1378 /*
1379 * No merge. Insert a new extent, preserving ordering.
1380 */
1381 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1382 if (new_se == NULL)
1383 return -ENOMEM;
1384 new_se->start_page = start_page;
1385 new_se->nr_pages = nr_pages;
1386 new_se->start_block = start_block;
1387
1388 list_add_tail(&new_se->list, &sis->extent_list);
1389 return 1;
1390 }
1391
1392 /*
1393 * A `swap extent' is a simple thing which maps a contiguous range of pages
1394 * onto a contiguous range of disk blocks. An ordered list of swap extents
1395 * is built at swapon time and is then used at swap_writepage/swap_readpage
1396 * time for locating where on disk a page belongs.
1397 *
1398 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1399 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1400 * swap files identically.
1401 *
1402 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1403 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1404 * swapfiles are handled *identically* after swapon time.
1405 *
1406 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1407 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1408 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1409 * requirements, they are simply tossed out - we will never use those blocks
1410 * for swapping.
1411 *
1412 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1413 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1414 * which will scribble on the fs.
1415 *
1416 * The amount of disk space which a single swap extent represents varies.
1417 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1418 * extents in the list. To avoid much list walking, we cache the previous
1419 * search location in `curr_swap_extent', and start new searches from there.
1420 * This is extremely effective. The average number of iterations in
1421 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1422 */
1423 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1424 {
1425 struct inode *inode;
1426 unsigned blocks_per_page;
1427 unsigned long page_no;
1428 unsigned blkbits;
1429 sector_t probe_block;
1430 sector_t last_block;
1431 sector_t lowest_block = -1;
1432 sector_t highest_block = 0;
1433 int nr_extents = 0;
1434 int ret;
1435
1436 inode = sis->swap_file->f_mapping->host;
1437 if (S_ISBLK(inode->i_mode)) {
1438 ret = add_swap_extent(sis, 0, sis->max, 0);
1439 *span = sis->pages;
1440 goto done;
1441 }
1442
1443 blkbits = inode->i_blkbits;
1444 blocks_per_page = PAGE_SIZE >> blkbits;
1445
1446 /*
1447 * Map all the blocks into the extent list. This code doesn't try
1448 * to be very smart.
1449 */
1450 probe_block = 0;
1451 page_no = 0;
1452 last_block = i_size_read(inode) >> blkbits;
1453 while ((probe_block + blocks_per_page) <= last_block &&
1454 page_no < sis->max) {
1455 unsigned block_in_page;
1456 sector_t first_block;
1457
1458 first_block = bmap(inode, probe_block);
1459 if (first_block == 0)
1460 goto bad_bmap;
1461
1462 /*
1463 * It must be PAGE_SIZE aligned on-disk
1464 */
1465 if (first_block & (blocks_per_page - 1)) {
1466 probe_block++;
1467 goto reprobe;
1468 }
1469
1470 for (block_in_page = 1; block_in_page < blocks_per_page;
1471 block_in_page++) {
1472 sector_t block;
1473
1474 block = bmap(inode, probe_block + block_in_page);
1475 if (block == 0)
1476 goto bad_bmap;
1477 if (block != first_block + block_in_page) {
1478 /* Discontiguity */
1479 probe_block++;
1480 goto reprobe;
1481 }
1482 }
1483
1484 first_block >>= (PAGE_SHIFT - blkbits);
1485 if (page_no) { /* exclude the header page */
1486 if (first_block < lowest_block)
1487 lowest_block = first_block;
1488 if (first_block > highest_block)
1489 highest_block = first_block;
1490 }
1491
1492 /*
1493 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1494 */
1495 ret = add_swap_extent(sis, page_no, 1, first_block);
1496 if (ret < 0)
1497 goto out;
1498 nr_extents += ret;
1499 page_no++;
1500 probe_block += blocks_per_page;
1501 reprobe:
1502 continue;
1503 }
1504 ret = nr_extents;
1505 *span = 1 + highest_block - lowest_block;
1506 if (page_no == 0)
1507 page_no = 1; /* force Empty message */
1508 sis->max = page_no;
1509 sis->pages = page_no - 1;
1510 sis->highest_bit = page_no - 1;
1511 done:
1512 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1513 struct swap_extent, list);
1514 goto out;
1515 bad_bmap:
1516 printk(KERN_ERR "swapon: swapfile has holes\n");
1517 ret = -EINVAL;
1518 out:
1519 return ret;
1520 }
1521
1522 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1523 {
1524 struct swap_info_struct * p = NULL;
1525 unsigned short *swap_map;
1526 struct file *swap_file, *victim;
1527 struct address_space *mapping;
1528 struct inode *inode;
1529 char * pathname;
1530 int i, type, prev;
1531 int err;
1532
1533 if (!capable(CAP_SYS_ADMIN))
1534 return -EPERM;
1535
1536 pathname = getname(specialfile);
1537 err = PTR_ERR(pathname);
1538 if (IS_ERR(pathname))
1539 goto out;
1540
1541 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1542 putname(pathname);
1543 err = PTR_ERR(victim);
1544 if (IS_ERR(victim))
1545 goto out;
1546
1547 mapping = victim->f_mapping;
1548 prev = -1;
1549 spin_lock(&swap_lock);
1550 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1551 p = swap_info + type;
1552 if (p->flags & SWP_WRITEOK) {
1553 if (p->swap_file->f_mapping == mapping)
1554 break;
1555 }
1556 prev = type;
1557 }
1558 if (type < 0) {
1559 err = -EINVAL;
1560 spin_unlock(&swap_lock);
1561 goto out_dput;
1562 }
1563 if (!security_vm_enough_memory(p->pages))
1564 vm_unacct_memory(p->pages);
1565 else {
1566 err = -ENOMEM;
1567 spin_unlock(&swap_lock);
1568 goto out_dput;
1569 }
1570 if (prev < 0) {
1571 swap_list.head = p->next;
1572 } else {
1573 swap_info[prev].next = p->next;
1574 }
1575 if (type == swap_list.next) {
1576 /* just pick something that's safe... */
1577 swap_list.next = swap_list.head;
1578 }
1579 if (p->prio < 0) {
1580 for (i = p->next; i >= 0; i = swap_info[i].next)
1581 swap_info[i].prio = p->prio--;
1582 least_priority++;
1583 }
1584 nr_swap_pages -= p->pages;
1585 total_swap_pages -= p->pages;
1586 p->flags &= ~SWP_WRITEOK;
1587 spin_unlock(&swap_lock);
1588
1589 current->flags |= PF_OOM_ORIGIN;
1590 err = try_to_unuse(type);
1591 current->flags &= ~PF_OOM_ORIGIN;
1592
1593 if (err) {
1594 /* re-insert swap space back into swap_list */
1595 spin_lock(&swap_lock);
1596 if (p->prio < 0)
1597 p->prio = --least_priority;
1598 prev = -1;
1599 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1600 if (p->prio >= swap_info[i].prio)
1601 break;
1602 prev = i;
1603 }
1604 p->next = i;
1605 if (prev < 0)
1606 swap_list.head = swap_list.next = p - swap_info;
1607 else
1608 swap_info[prev].next = p - swap_info;
1609 nr_swap_pages += p->pages;
1610 total_swap_pages += p->pages;
1611 p->flags |= SWP_WRITEOK;
1612 spin_unlock(&swap_lock);
1613 goto out_dput;
1614 }
1615
1616 /* wait for any unplug function to finish */
1617 down_write(&swap_unplug_sem);
1618 up_write(&swap_unplug_sem);
1619
1620 destroy_swap_extents(p);
1621 mutex_lock(&swapon_mutex);
1622 spin_lock(&swap_lock);
1623 drain_mmlist();
1624
1625 /* wait for anyone still in scan_swap_map */
1626 p->highest_bit = 0; /* cuts scans short */
1627 while (p->flags >= SWP_SCANNING) {
1628 spin_unlock(&swap_lock);
1629 schedule_timeout_uninterruptible(1);
1630 spin_lock(&swap_lock);
1631 }
1632
1633 swap_file = p->swap_file;
1634 p->swap_file = NULL;
1635 p->max = 0;
1636 swap_map = p->swap_map;
1637 p->swap_map = NULL;
1638 p->flags = 0;
1639 spin_unlock(&swap_lock);
1640 mutex_unlock(&swapon_mutex);
1641 vfree(swap_map);
1642 /* Destroy swap account informatin */
1643 swap_cgroup_swapoff(type);
1644
1645 inode = mapping->host;
1646 if (S_ISBLK(inode->i_mode)) {
1647 struct block_device *bdev = I_BDEV(inode);
1648 set_blocksize(bdev, p->old_block_size);
1649 bd_release(bdev);
1650 } else {
1651 mutex_lock(&inode->i_mutex);
1652 inode->i_flags &= ~S_SWAPFILE;
1653 mutex_unlock(&inode->i_mutex);
1654 }
1655 filp_close(swap_file, NULL);
1656 err = 0;
1657
1658 out_dput:
1659 filp_close(victim, NULL);
1660 out:
1661 return err;
1662 }
1663
1664 #ifdef CONFIG_PROC_FS
1665 /* iterator */
1666 static void *swap_start(struct seq_file *swap, loff_t *pos)
1667 {
1668 struct swap_info_struct *ptr = swap_info;
1669 int i;
1670 loff_t l = *pos;
1671
1672 mutex_lock(&swapon_mutex);
1673
1674 if (!l)
1675 return SEQ_START_TOKEN;
1676
1677 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1678 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1679 continue;
1680 if (!--l)
1681 return ptr;
1682 }
1683
1684 return NULL;
1685 }
1686
1687 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1688 {
1689 struct swap_info_struct *ptr;
1690 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1691
1692 if (v == SEQ_START_TOKEN)
1693 ptr = swap_info;
1694 else {
1695 ptr = v;
1696 ptr++;
1697 }
1698
1699 for (; ptr < endptr; ptr++) {
1700 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1701 continue;
1702 ++*pos;
1703 return ptr;
1704 }
1705
1706 return NULL;
1707 }
1708
1709 static void swap_stop(struct seq_file *swap, void *v)
1710 {
1711 mutex_unlock(&swapon_mutex);
1712 }
1713
1714 static int swap_show(struct seq_file *swap, void *v)
1715 {
1716 struct swap_info_struct *ptr = v;
1717 struct file *file;
1718 int len;
1719
1720 if (ptr == SEQ_START_TOKEN) {
1721 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1722 return 0;
1723 }
1724
1725 file = ptr->swap_file;
1726 len = seq_path(swap, &file->f_path, " \t\n\\");
1727 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1728 len < 40 ? 40 - len : 1, " ",
1729 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1730 "partition" : "file\t",
1731 ptr->pages << (PAGE_SHIFT - 10),
1732 ptr->inuse_pages << (PAGE_SHIFT - 10),
1733 ptr->prio);
1734 return 0;
1735 }
1736
1737 static const struct seq_operations swaps_op = {
1738 .start = swap_start,
1739 .next = swap_next,
1740 .stop = swap_stop,
1741 .show = swap_show
1742 };
1743
1744 static int swaps_open(struct inode *inode, struct file *file)
1745 {
1746 return seq_open(file, &swaps_op);
1747 }
1748
1749 static const struct file_operations proc_swaps_operations = {
1750 .open = swaps_open,
1751 .read = seq_read,
1752 .llseek = seq_lseek,
1753 .release = seq_release,
1754 };
1755
1756 static int __init procswaps_init(void)
1757 {
1758 proc_create("swaps", 0, NULL, &proc_swaps_operations);
1759 return 0;
1760 }
1761 __initcall(procswaps_init);
1762 #endif /* CONFIG_PROC_FS */
1763
1764 #ifdef MAX_SWAPFILES_CHECK
1765 static int __init max_swapfiles_check(void)
1766 {
1767 MAX_SWAPFILES_CHECK();
1768 return 0;
1769 }
1770 late_initcall(max_swapfiles_check);
1771 #endif
1772
1773 /*
1774 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1775 *
1776 * The swapon system call
1777 */
1778 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1779 {
1780 struct swap_info_struct * p;
1781 char *name = NULL;
1782 struct block_device *bdev = NULL;
1783 struct file *swap_file = NULL;
1784 struct address_space *mapping;
1785 unsigned int type;
1786 int i, prev;
1787 int error;
1788 union swap_header *swap_header = NULL;
1789 unsigned int nr_good_pages = 0;
1790 int nr_extents = 0;
1791 sector_t span;
1792 unsigned long maxpages = 1;
1793 unsigned long swapfilepages;
1794 unsigned short *swap_map = NULL;
1795 struct page *page = NULL;
1796 struct inode *inode = NULL;
1797 int did_down = 0;
1798
1799 if (!capable(CAP_SYS_ADMIN))
1800 return -EPERM;
1801 spin_lock(&swap_lock);
1802 p = swap_info;
1803 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1804 if (!(p->flags & SWP_USED))
1805 break;
1806 error = -EPERM;
1807 if (type >= MAX_SWAPFILES) {
1808 spin_unlock(&swap_lock);
1809 goto out;
1810 }
1811 if (type >= nr_swapfiles)
1812 nr_swapfiles = type+1;
1813 memset(p, 0, sizeof(*p));
1814 INIT_LIST_HEAD(&p->extent_list);
1815 p->flags = SWP_USED;
1816 p->next = -1;
1817 spin_unlock(&swap_lock);
1818 name = getname(specialfile);
1819 error = PTR_ERR(name);
1820 if (IS_ERR(name)) {
1821 name = NULL;
1822 goto bad_swap_2;
1823 }
1824 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1825 error = PTR_ERR(swap_file);
1826 if (IS_ERR(swap_file)) {
1827 swap_file = NULL;
1828 goto bad_swap_2;
1829 }
1830
1831 p->swap_file = swap_file;
1832 mapping = swap_file->f_mapping;
1833 inode = mapping->host;
1834
1835 error = -EBUSY;
1836 for (i = 0; i < nr_swapfiles; i++) {
1837 struct swap_info_struct *q = &swap_info[i];
1838
1839 if (i == type || !q->swap_file)
1840 continue;
1841 if (mapping == q->swap_file->f_mapping)
1842 goto bad_swap;
1843 }
1844
1845 error = -EINVAL;
1846 if (S_ISBLK(inode->i_mode)) {
1847 bdev = I_BDEV(inode);
1848 error = bd_claim(bdev, sys_swapon);
1849 if (error < 0) {
1850 bdev = NULL;
1851 error = -EINVAL;
1852 goto bad_swap;
1853 }
1854 p->old_block_size = block_size(bdev);
1855 error = set_blocksize(bdev, PAGE_SIZE);
1856 if (error < 0)
1857 goto bad_swap;
1858 p->bdev = bdev;
1859 } else if (S_ISREG(inode->i_mode)) {
1860 p->bdev = inode->i_sb->s_bdev;
1861 mutex_lock(&inode->i_mutex);
1862 did_down = 1;
1863 if (IS_SWAPFILE(inode)) {
1864 error = -EBUSY;
1865 goto bad_swap;
1866 }
1867 } else {
1868 goto bad_swap;
1869 }
1870
1871 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1872
1873 /*
1874 * Read the swap header.
1875 */
1876 if (!mapping->a_ops->readpage) {
1877 error = -EINVAL;
1878 goto bad_swap;
1879 }
1880 page = read_mapping_page(mapping, 0, swap_file);
1881 if (IS_ERR(page)) {
1882 error = PTR_ERR(page);
1883 goto bad_swap;
1884 }
1885 swap_header = kmap(page);
1886
1887 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1888 printk(KERN_ERR "Unable to find swap-space signature\n");
1889 error = -EINVAL;
1890 goto bad_swap;
1891 }
1892
1893 /* swap partition endianess hack... */
1894 if (swab32(swap_header->info.version) == 1) {
1895 swab32s(&swap_header->info.version);
1896 swab32s(&swap_header->info.last_page);
1897 swab32s(&swap_header->info.nr_badpages);
1898 for (i = 0; i < swap_header->info.nr_badpages; i++)
1899 swab32s(&swap_header->info.badpages[i]);
1900 }
1901 /* Check the swap header's sub-version */
1902 if (swap_header->info.version != 1) {
1903 printk(KERN_WARNING
1904 "Unable to handle swap header version %d\n",
1905 swap_header->info.version);
1906 error = -EINVAL;
1907 goto bad_swap;
1908 }
1909
1910 p->lowest_bit = 1;
1911 p->cluster_next = 1;
1912
1913 /*
1914 * Find out how many pages are allowed for a single swap
1915 * device. There are two limiting factors: 1) the number of
1916 * bits for the swap offset in the swp_entry_t type and
1917 * 2) the number of bits in the a swap pte as defined by
1918 * the different architectures. In order to find the
1919 * largest possible bit mask a swap entry with swap type 0
1920 * and swap offset ~0UL is created, encoded to a swap pte,
1921 * decoded to a swp_entry_t again and finally the swap
1922 * offset is extracted. This will mask all the bits from
1923 * the initial ~0UL mask that can't be encoded in either
1924 * the swp_entry_t or the architecture definition of a
1925 * swap pte.
1926 */
1927 maxpages = swp_offset(pte_to_swp_entry(
1928 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1929 if (maxpages > swap_header->info.last_page)
1930 maxpages = swap_header->info.last_page;
1931 p->highest_bit = maxpages - 1;
1932
1933 error = -EINVAL;
1934 if (!maxpages)
1935 goto bad_swap;
1936 if (swapfilepages && maxpages > swapfilepages) {
1937 printk(KERN_WARNING
1938 "Swap area shorter than signature indicates\n");
1939 goto bad_swap;
1940 }
1941 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1942 goto bad_swap;
1943 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1944 goto bad_swap;
1945
1946 /* OK, set up the swap map and apply the bad block list */
1947 swap_map = vmalloc(maxpages * sizeof(short));
1948 if (!swap_map) {
1949 error = -ENOMEM;
1950 goto bad_swap;
1951 }
1952
1953 memset(swap_map, 0, maxpages * sizeof(short));
1954 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1955 int page_nr = swap_header->info.badpages[i];
1956 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1957 error = -EINVAL;
1958 goto bad_swap;
1959 }
1960 swap_map[page_nr] = SWAP_MAP_BAD;
1961 }
1962
1963 error = swap_cgroup_swapon(type, maxpages);
1964 if (error)
1965 goto bad_swap;
1966
1967 nr_good_pages = swap_header->info.last_page -
1968 swap_header->info.nr_badpages -
1969 1 /* header page */;
1970
1971 if (nr_good_pages) {
1972 swap_map[0] = SWAP_MAP_BAD;
1973 p->max = maxpages;
1974 p->pages = nr_good_pages;
1975 nr_extents = setup_swap_extents(p, &span);
1976 if (nr_extents < 0) {
1977 error = nr_extents;
1978 goto bad_swap;
1979 }
1980 nr_good_pages = p->pages;
1981 }
1982 if (!nr_good_pages) {
1983 printk(KERN_WARNING "Empty swap-file\n");
1984 error = -EINVAL;
1985 goto bad_swap;
1986 }
1987
1988 if (p->bdev) {
1989 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1990 p->flags |= SWP_SOLIDSTATE;
1991 p->cluster_next = 1 + (random32() % p->highest_bit);
1992 }
1993 if (discard_swap(p) == 0)
1994 p->flags |= SWP_DISCARDABLE;
1995 }
1996
1997 mutex_lock(&swapon_mutex);
1998 spin_lock(&swap_lock);
1999 if (swap_flags & SWAP_FLAG_PREFER)
2000 p->prio =
2001 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2002 else
2003 p->prio = --least_priority;
2004 p->swap_map = swap_map;
2005 p->flags |= SWP_WRITEOK;
2006 nr_swap_pages += nr_good_pages;
2007 total_swap_pages += nr_good_pages;
2008
2009 printk(KERN_INFO "Adding %uk swap on %s. "
2010 "Priority:%d extents:%d across:%lluk %s%s\n",
2011 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
2012 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2013 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2014 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2015
2016 /* insert swap space into swap_list: */
2017 prev = -1;
2018 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
2019 if (p->prio >= swap_info[i].prio) {
2020 break;
2021 }
2022 prev = i;
2023 }
2024 p->next = i;
2025 if (prev < 0) {
2026 swap_list.head = swap_list.next = p - swap_info;
2027 } else {
2028 swap_info[prev].next = p - swap_info;
2029 }
2030 spin_unlock(&swap_lock);
2031 mutex_unlock(&swapon_mutex);
2032 error = 0;
2033 goto out;
2034 bad_swap:
2035 if (bdev) {
2036 set_blocksize(bdev, p->old_block_size);
2037 bd_release(bdev);
2038 }
2039 destroy_swap_extents(p);
2040 swap_cgroup_swapoff(type);
2041 bad_swap_2:
2042 spin_lock(&swap_lock);
2043 p->swap_file = NULL;
2044 p->flags = 0;
2045 spin_unlock(&swap_lock);
2046 vfree(swap_map);
2047 if (swap_file)
2048 filp_close(swap_file, NULL);
2049 out:
2050 if (page && !IS_ERR(page)) {
2051 kunmap(page);
2052 page_cache_release(page);
2053 }
2054 if (name)
2055 putname(name);
2056 if (did_down) {
2057 if (!error)
2058 inode->i_flags |= S_SWAPFILE;
2059 mutex_unlock(&inode->i_mutex);
2060 }
2061 return error;
2062 }
2063
2064 void si_swapinfo(struct sysinfo *val)
2065 {
2066 unsigned int i;
2067 unsigned long nr_to_be_unused = 0;
2068
2069 spin_lock(&swap_lock);
2070 for (i = 0; i < nr_swapfiles; i++) {
2071 if (!(swap_info[i].flags & SWP_USED) ||
2072 (swap_info[i].flags & SWP_WRITEOK))
2073 continue;
2074 nr_to_be_unused += swap_info[i].inuse_pages;
2075 }
2076 val->freeswap = nr_swap_pages + nr_to_be_unused;
2077 val->totalswap = total_swap_pages + nr_to_be_unused;
2078 spin_unlock(&swap_lock);
2079 }
2080
2081 /*
2082 * Verify that a swap entry is valid and increment its swap map count.
2083 *
2084 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
2085 * "permanent", but will be reclaimed by the next swapoff.
2086 * Returns error code in following case.
2087 * - success -> 0
2088 * - swp_entry is invalid -> EINVAL
2089 * - swp_entry is migration entry -> EINVAL
2090 * - swap-cache reference is requested but there is already one. -> EEXIST
2091 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2092 */
2093 static int __swap_duplicate(swp_entry_t entry, bool cache)
2094 {
2095 struct swap_info_struct * p;
2096 unsigned long offset, type;
2097 int result = -EINVAL;
2098 int count;
2099 bool has_cache;
2100
2101 if (non_swap_entry(entry))
2102 return -EINVAL;
2103
2104 type = swp_type(entry);
2105 if (type >= nr_swapfiles)
2106 goto bad_file;
2107 p = type + swap_info;
2108 offset = swp_offset(entry);
2109
2110 spin_lock(&swap_lock);
2111
2112 if (unlikely(offset >= p->max))
2113 goto unlock_out;
2114
2115 count = swap_count(p->swap_map[offset]);
2116 has_cache = swap_has_cache(p->swap_map[offset]);
2117
2118 if (cache == SWAP_CACHE) { /* called for swapcache/swapin-readahead */
2119
2120 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2121 if (!has_cache && count) {
2122 p->swap_map[offset] = encode_swapmap(count, true);
2123 result = 0;
2124 } else if (has_cache) /* someone added cache */
2125 result = -EEXIST;
2126 else if (!count) /* no users */
2127 result = -ENOENT;
2128
2129 } else if (count || has_cache) {
2130 if (count < SWAP_MAP_MAX - 1) {
2131 p->swap_map[offset] = encode_swapmap(count + 1,
2132 has_cache);
2133 result = 0;
2134 } else if (count <= SWAP_MAP_MAX) {
2135 if (swap_overflow++ < 5)
2136 printk(KERN_WARNING
2137 "swap_dup: swap entry overflow\n");
2138 p->swap_map[offset] = encode_swapmap(SWAP_MAP_MAX,
2139 has_cache);
2140 result = 0;
2141 }
2142 } else
2143 result = -ENOENT; /* unused swap entry */
2144 unlock_out:
2145 spin_unlock(&swap_lock);
2146 out:
2147 return result;
2148
2149 bad_file:
2150 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2151 goto out;
2152 }
2153 /*
2154 * increase reference count of swap entry by 1.
2155 */
2156 void swap_duplicate(swp_entry_t entry)
2157 {
2158 __swap_duplicate(entry, SWAP_MAP);
2159 }
2160
2161 /*
2162 * @entry: swap entry for which we allocate swap cache.
2163 *
2164 * Called when allocating swap cache for exising swap entry,
2165 * This can return error codes. Returns 0 at success.
2166 * -EBUSY means there is a swap cache.
2167 * Note: return code is different from swap_duplicate().
2168 */
2169 int swapcache_prepare(swp_entry_t entry)
2170 {
2171 return __swap_duplicate(entry, SWAP_CACHE);
2172 }
2173
2174 /*
2175 * swap_lock prevents swap_map being freed. Don't grab an extra
2176 * reference on the swaphandle, it doesn't matter if it becomes unused.
2177 */
2178 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2179 {
2180 struct swap_info_struct *si;
2181 int our_page_cluster = page_cluster;
2182 pgoff_t target, toff;
2183 pgoff_t base, end;
2184 int nr_pages = 0;
2185
2186 if (!our_page_cluster) /* no readahead */
2187 return 0;
2188
2189 si = &swap_info[swp_type(entry)];
2190 target = swp_offset(entry);
2191 base = (target >> our_page_cluster) << our_page_cluster;
2192 end = base + (1 << our_page_cluster);
2193 if (!base) /* first page is swap header */
2194 base++;
2195
2196 spin_lock(&swap_lock);
2197 if (end > si->max) /* don't go beyond end of map */
2198 end = si->max;
2199
2200 /* Count contiguous allocated slots above our target */
2201 for (toff = target; ++toff < end; nr_pages++) {
2202 /* Don't read in free or bad pages */
2203 if (!si->swap_map[toff])
2204 break;
2205 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2206 break;
2207 }
2208 /* Count contiguous allocated slots below our target */
2209 for (toff = target; --toff >= base; nr_pages++) {
2210 /* Don't read in free or bad pages */
2211 if (!si->swap_map[toff])
2212 break;
2213 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2214 break;
2215 }
2216 spin_unlock(&swap_lock);
2217
2218 /*
2219 * Indicate starting offset, and return number of pages to get:
2220 * if only 1, say 0, since there's then no readahead to be done.
2221 */
2222 *offset = ++toff;
2223 return nr_pages? ++nr_pages: 0;
2224 }