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