memcg: simplify LRU handling by new rule
[linux-2.6.git] / mm / swapfile.c
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/shmem_fs.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/ksm.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 #include <linux/poll.h>
33 #include <linux/oom.h>
34
35 #include <asm/pgtable.h>
36 #include <asm/tlbflush.h>
37 #include <linux/swapops.h>
38 #include <linux/page_cgroup.h>
39
40 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
41                                  unsigned char);
42 static void free_swap_count_continuations(struct swap_info_struct *);
43 static sector_t map_swap_entry(swp_entry_t, struct block_device**);
44
45 static DEFINE_SPINLOCK(swap_lock);
46 static unsigned int nr_swapfiles;
47 long nr_swap_pages;
48 long total_swap_pages;
49 static int least_priority;
50
51 static const char Bad_file[] = "Bad swap file entry ";
52 static const char Unused_file[] = "Unused swap file entry ";
53 static const char Bad_offset[] = "Bad swap offset entry ";
54 static const char Unused_offset[] = "Unused swap offset entry ";
55
56 static struct swap_list_t swap_list = {-1, -1};
57
58 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
59
60 static DEFINE_MUTEX(swapon_mutex);
61
62 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
63 /* Activity counter to indicate that a swapon or swapoff has occurred */
64 static atomic_t proc_poll_event = ATOMIC_INIT(0);
65
66 static inline unsigned char swap_count(unsigned char ent)
67 {
68         return ent & ~SWAP_HAS_CACHE;   /* may include SWAP_HAS_CONT flag */
69 }
70
71 /* returns 1 if swap entry is freed */
72 static int
73 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
74 {
75         swp_entry_t entry = swp_entry(si->type, offset);
76         struct page *page;
77         int ret = 0;
78
79         page = find_get_page(&swapper_space, entry.val);
80         if (!page)
81                 return 0;
82         /*
83          * This function is called from scan_swap_map() and it's called
84          * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
85          * We have to use trylock for avoiding deadlock. This is a special
86          * case and you should use try_to_free_swap() with explicit lock_page()
87          * in usual operations.
88          */
89         if (trylock_page(page)) {
90                 ret = try_to_free_swap(page);
91                 unlock_page(page);
92         }
93         page_cache_release(page);
94         return ret;
95 }
96
97 /*
98  * swapon tell device that all the old swap contents can be discarded,
99  * to allow the swap device to optimize its wear-levelling.
100  */
101 static int discard_swap(struct swap_info_struct *si)
102 {
103         struct swap_extent *se;
104         sector_t start_block;
105         sector_t nr_blocks;
106         int err = 0;
107
108         /* Do not discard the swap header page! */
109         se = &si->first_swap_extent;
110         start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
111         nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
112         if (nr_blocks) {
113                 err = blkdev_issue_discard(si->bdev, start_block,
114                                 nr_blocks, GFP_KERNEL, 0);
115                 if (err)
116                         return err;
117                 cond_resched();
118         }
119
120         list_for_each_entry(se, &si->first_swap_extent.list, list) {
121                 start_block = se->start_block << (PAGE_SHIFT - 9);
122                 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
123
124                 err = blkdev_issue_discard(si->bdev, start_block,
125                                 nr_blocks, GFP_KERNEL, 0);
126                 if (err)
127                         break;
128
129                 cond_resched();
130         }
131         return err;             /* That will often be -EOPNOTSUPP */
132 }
133
134 /*
135  * swap allocation tell device that a cluster of swap can now be discarded,
136  * to allow the swap device to optimize its wear-levelling.
137  */
138 static void discard_swap_cluster(struct swap_info_struct *si,
139                                  pgoff_t start_page, pgoff_t nr_pages)
140 {
141         struct swap_extent *se = si->curr_swap_extent;
142         int found_extent = 0;
143
144         while (nr_pages) {
145                 struct list_head *lh;
146
147                 if (se->start_page <= start_page &&
148                     start_page < se->start_page + se->nr_pages) {
149                         pgoff_t offset = start_page - se->start_page;
150                         sector_t start_block = se->start_block + offset;
151                         sector_t nr_blocks = se->nr_pages - offset;
152
153                         if (nr_blocks > nr_pages)
154                                 nr_blocks = nr_pages;
155                         start_page += nr_blocks;
156                         nr_pages -= nr_blocks;
157
158                         if (!found_extent++)
159                                 si->curr_swap_extent = se;
160
161                         start_block <<= PAGE_SHIFT - 9;
162                         nr_blocks <<= PAGE_SHIFT - 9;
163                         if (blkdev_issue_discard(si->bdev, start_block,
164                                     nr_blocks, GFP_NOIO, 0))
165                                 break;
166                 }
167
168                 lh = se->list.next;
169                 se = list_entry(lh, struct swap_extent, list);
170         }
171 }
172
173 static int wait_for_discard(void *word)
174 {
175         schedule();
176         return 0;
177 }
178
179 #define SWAPFILE_CLUSTER        256
180 #define LATENCY_LIMIT           256
181
182 static unsigned long scan_swap_map(struct swap_info_struct *si,
183                                    unsigned char usage)
184 {
185         unsigned long offset;
186         unsigned long scan_base;
187         unsigned long last_in_cluster = 0;
188         int latency_ration = LATENCY_LIMIT;
189         int found_free_cluster = 0;
190
191         /*
192          * We try to cluster swap pages by allocating them sequentially
193          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
194          * way, however, we resort to first-free allocation, starting
195          * a new cluster.  This prevents us from scattering swap pages
196          * all over the entire swap partition, so that we reduce
197          * overall disk seek times between swap pages.  -- sct
198          * But we do now try to find an empty cluster.  -Andrea
199          * And we let swap pages go all over an SSD partition.  Hugh
200          */
201
202         si->flags += SWP_SCANNING;
203         scan_base = offset = si->cluster_next;
204
205         if (unlikely(!si->cluster_nr--)) {
206                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
207                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
208                         goto checks;
209                 }
210                 if (si->flags & SWP_DISCARDABLE) {
211                         /*
212                          * Start range check on racing allocations, in case
213                          * they overlap the cluster we eventually decide on
214                          * (we scan without swap_lock to allow preemption).
215                          * It's hardly conceivable that cluster_nr could be
216                          * wrapped during our scan, but don't depend on it.
217                          */
218                         if (si->lowest_alloc)
219                                 goto checks;
220                         si->lowest_alloc = si->max;
221                         si->highest_alloc = 0;
222                 }
223                 spin_unlock(&swap_lock);
224
225                 /*
226                  * If seek is expensive, start searching for new cluster from
227                  * start of partition, to minimize the span of allocated swap.
228                  * But if seek is cheap, search from our current position, so
229                  * that swap is allocated from all over the partition: if the
230                  * Flash Translation Layer only remaps within limited zones,
231                  * we don't want to wear out the first zone too quickly.
232                  */
233                 if (!(si->flags & SWP_SOLIDSTATE))
234                         scan_base = offset = si->lowest_bit;
235                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
236
237                 /* Locate the first empty (unaligned) cluster */
238                 for (; last_in_cluster <= si->highest_bit; offset++) {
239                         if (si->swap_map[offset])
240                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
241                         else if (offset == last_in_cluster) {
242                                 spin_lock(&swap_lock);
243                                 offset -= SWAPFILE_CLUSTER - 1;
244                                 si->cluster_next = offset;
245                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
246                                 found_free_cluster = 1;
247                                 goto checks;
248                         }
249                         if (unlikely(--latency_ration < 0)) {
250                                 cond_resched();
251                                 latency_ration = LATENCY_LIMIT;
252                         }
253                 }
254
255                 offset = si->lowest_bit;
256                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
257
258                 /* Locate the first empty (unaligned) cluster */
259                 for (; last_in_cluster < scan_base; offset++) {
260                         if (si->swap_map[offset])
261                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
262                         else if (offset == last_in_cluster) {
263                                 spin_lock(&swap_lock);
264                                 offset -= SWAPFILE_CLUSTER - 1;
265                                 si->cluster_next = offset;
266                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
267                                 found_free_cluster = 1;
268                                 goto checks;
269                         }
270                         if (unlikely(--latency_ration < 0)) {
271                                 cond_resched();
272                                 latency_ration = LATENCY_LIMIT;
273                         }
274                 }
275
276                 offset = scan_base;
277                 spin_lock(&swap_lock);
278                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
279                 si->lowest_alloc = 0;
280         }
281
282 checks:
283         if (!(si->flags & SWP_WRITEOK))
284                 goto no_page;
285         if (!si->highest_bit)
286                 goto no_page;
287         if (offset > si->highest_bit)
288                 scan_base = offset = si->lowest_bit;
289
290         /* reuse swap entry of cache-only swap if not busy. */
291         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
292                 int swap_was_freed;
293                 spin_unlock(&swap_lock);
294                 swap_was_freed = __try_to_reclaim_swap(si, offset);
295                 spin_lock(&swap_lock);
296                 /* entry was freed successfully, try to use this again */
297                 if (swap_was_freed)
298                         goto checks;
299                 goto scan; /* check next one */
300         }
301
302         if (si->swap_map[offset])
303                 goto scan;
304
305         if (offset == si->lowest_bit)
306                 si->lowest_bit++;
307         if (offset == si->highest_bit)
308                 si->highest_bit--;
309         si->inuse_pages++;
310         if (si->inuse_pages == si->pages) {
311                 si->lowest_bit = si->max;
312                 si->highest_bit = 0;
313         }
314         si->swap_map[offset] = usage;
315         si->cluster_next = offset + 1;
316         si->flags -= SWP_SCANNING;
317
318         if (si->lowest_alloc) {
319                 /*
320                  * Only set when SWP_DISCARDABLE, and there's a scan
321                  * for a free cluster in progress or just completed.
322                  */
323                 if (found_free_cluster) {
324                         /*
325                          * To optimize wear-levelling, discard the
326                          * old data of the cluster, taking care not to
327                          * discard any of its pages that have already
328                          * been allocated by racing tasks (offset has
329                          * already stepped over any at the beginning).
330                          */
331                         if (offset < si->highest_alloc &&
332                             si->lowest_alloc <= last_in_cluster)
333                                 last_in_cluster = si->lowest_alloc - 1;
334                         si->flags |= SWP_DISCARDING;
335                         spin_unlock(&swap_lock);
336
337                         if (offset < last_in_cluster)
338                                 discard_swap_cluster(si, offset,
339                                         last_in_cluster - offset + 1);
340
341                         spin_lock(&swap_lock);
342                         si->lowest_alloc = 0;
343                         si->flags &= ~SWP_DISCARDING;
344
345                         smp_mb();       /* wake_up_bit advises this */
346                         wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
347
348                 } else if (si->flags & SWP_DISCARDING) {
349                         /*
350                          * Delay using pages allocated by racing tasks
351                          * until the whole discard has been issued. We
352                          * could defer that delay until swap_writepage,
353                          * but it's easier to keep this self-contained.
354                          */
355                         spin_unlock(&swap_lock);
356                         wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
357                                 wait_for_discard, TASK_UNINTERRUPTIBLE);
358                         spin_lock(&swap_lock);
359                 } else {
360                         /*
361                          * Note pages allocated by racing tasks while
362                          * scan for a free cluster is in progress, so
363                          * that its final discard can exclude them.
364                          */
365                         if (offset < si->lowest_alloc)
366                                 si->lowest_alloc = offset;
367                         if (offset > si->highest_alloc)
368                                 si->highest_alloc = offset;
369                 }
370         }
371         return offset;
372
373 scan:
374         spin_unlock(&swap_lock);
375         while (++offset <= si->highest_bit) {
376                 if (!si->swap_map[offset]) {
377                         spin_lock(&swap_lock);
378                         goto checks;
379                 }
380                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
381                         spin_lock(&swap_lock);
382                         goto checks;
383                 }
384                 if (unlikely(--latency_ration < 0)) {
385                         cond_resched();
386                         latency_ration = LATENCY_LIMIT;
387                 }
388         }
389         offset = si->lowest_bit;
390         while (++offset < scan_base) {
391                 if (!si->swap_map[offset]) {
392                         spin_lock(&swap_lock);
393                         goto checks;
394                 }
395                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
396                         spin_lock(&swap_lock);
397                         goto checks;
398                 }
399                 if (unlikely(--latency_ration < 0)) {
400                         cond_resched();
401                         latency_ration = LATENCY_LIMIT;
402                 }
403         }
404         spin_lock(&swap_lock);
405
406 no_page:
407         si->flags -= SWP_SCANNING;
408         return 0;
409 }
410
411 swp_entry_t get_swap_page(void)
412 {
413         struct swap_info_struct *si;
414         pgoff_t offset;
415         int type, next;
416         int wrapped = 0;
417
418         spin_lock(&swap_lock);
419         if (nr_swap_pages <= 0)
420                 goto noswap;
421         nr_swap_pages--;
422
423         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
424                 si = swap_info[type];
425                 next = si->next;
426                 if (next < 0 ||
427                     (!wrapped && si->prio != swap_info[next]->prio)) {
428                         next = swap_list.head;
429                         wrapped++;
430                 }
431
432                 if (!si->highest_bit)
433                         continue;
434                 if (!(si->flags & SWP_WRITEOK))
435                         continue;
436
437                 swap_list.next = next;
438                 /* This is called for allocating swap entry for cache */
439                 offset = scan_swap_map(si, SWAP_HAS_CACHE);
440                 if (offset) {
441                         spin_unlock(&swap_lock);
442                         return swp_entry(type, offset);
443                 }
444                 next = swap_list.next;
445         }
446
447         nr_swap_pages++;
448 noswap:
449         spin_unlock(&swap_lock);
450         return (swp_entry_t) {0};
451 }
452
453 /* The only caller of this function is now susupend routine */
454 swp_entry_t get_swap_page_of_type(int type)
455 {
456         struct swap_info_struct *si;
457         pgoff_t offset;
458
459         spin_lock(&swap_lock);
460         si = swap_info[type];
461         if (si && (si->flags & SWP_WRITEOK)) {
462                 nr_swap_pages--;
463                 /* This is called for allocating swap entry, not cache */
464                 offset = scan_swap_map(si, 1);
465                 if (offset) {
466                         spin_unlock(&swap_lock);
467                         return swp_entry(type, offset);
468                 }
469                 nr_swap_pages++;
470         }
471         spin_unlock(&swap_lock);
472         return (swp_entry_t) {0};
473 }
474
475 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
476 {
477         struct swap_info_struct *p;
478         unsigned long offset, type;
479
480         if (!entry.val)
481                 goto out;
482         type = swp_type(entry);
483         if (type >= nr_swapfiles)
484                 goto bad_nofile;
485         p = swap_info[type];
486         if (!(p->flags & SWP_USED))
487                 goto bad_device;
488         offset = swp_offset(entry);
489         if (offset >= p->max)
490                 goto bad_offset;
491         if (!p->swap_map[offset])
492                 goto bad_free;
493         spin_lock(&swap_lock);
494         return p;
495
496 bad_free:
497         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
498         goto out;
499 bad_offset:
500         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
501         goto out;
502 bad_device:
503         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
504         goto out;
505 bad_nofile:
506         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
507 out:
508         return NULL;
509 }
510
511 static unsigned char swap_entry_free(struct swap_info_struct *p,
512                                      swp_entry_t entry, unsigned char usage)
513 {
514         unsigned long offset = swp_offset(entry);
515         unsigned char count;
516         unsigned char has_cache;
517
518         count = p->swap_map[offset];
519         has_cache = count & SWAP_HAS_CACHE;
520         count &= ~SWAP_HAS_CACHE;
521
522         if (usage == SWAP_HAS_CACHE) {
523                 VM_BUG_ON(!has_cache);
524                 has_cache = 0;
525         } else if (count == SWAP_MAP_SHMEM) {
526                 /*
527                  * Or we could insist on shmem.c using a special
528                  * swap_shmem_free() and free_shmem_swap_and_cache()...
529                  */
530                 count = 0;
531         } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
532                 if (count == COUNT_CONTINUED) {
533                         if (swap_count_continued(p, offset, count))
534                                 count = SWAP_MAP_MAX | COUNT_CONTINUED;
535                         else
536                                 count = SWAP_MAP_MAX;
537                 } else
538                         count--;
539         }
540
541         if (!count)
542                 mem_cgroup_uncharge_swap(entry);
543
544         usage = count | has_cache;
545         p->swap_map[offset] = usage;
546
547         /* free if no reference */
548         if (!usage) {
549                 struct gendisk *disk = p->bdev->bd_disk;
550                 if (offset < p->lowest_bit)
551                         p->lowest_bit = offset;
552                 if (offset > p->highest_bit)
553                         p->highest_bit = offset;
554                 if (swap_list.next >= 0 &&
555                     p->prio > swap_info[swap_list.next]->prio)
556                         swap_list.next = p->type;
557                 nr_swap_pages++;
558                 p->inuse_pages--;
559                 if ((p->flags & SWP_BLKDEV) &&
560                                 disk->fops->swap_slot_free_notify)
561                         disk->fops->swap_slot_free_notify(p->bdev, offset);
562         }
563
564         return usage;
565 }
566
567 /*
568  * Caller has made sure that the swapdevice corresponding to entry
569  * is still around or has not been recycled.
570  */
571 void swap_free(swp_entry_t entry)
572 {
573         struct swap_info_struct *p;
574
575         p = swap_info_get(entry);
576         if (p) {
577                 swap_entry_free(p, entry, 1);
578                 spin_unlock(&swap_lock);
579         }
580 }
581
582 /*
583  * Called after dropping swapcache to decrease refcnt to swap entries.
584  */
585 void swapcache_free(swp_entry_t entry, struct page *page)
586 {
587         struct swap_info_struct *p;
588         unsigned char count;
589
590         p = swap_info_get(entry);
591         if (p) {
592                 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
593                 if (page)
594                         mem_cgroup_uncharge_swapcache(page, entry, count != 0);
595                 spin_unlock(&swap_lock);
596         }
597 }
598
599 /*
600  * How many references to page are currently swapped out?
601  * This does not give an exact answer when swap count is continued,
602  * but does include the high COUNT_CONTINUED flag to allow for that.
603  */
604 static inline int page_swapcount(struct page *page)
605 {
606         int count = 0;
607         struct swap_info_struct *p;
608         swp_entry_t entry;
609
610         entry.val = page_private(page);
611         p = swap_info_get(entry);
612         if (p) {
613                 count = swap_count(p->swap_map[swp_offset(entry)]);
614                 spin_unlock(&swap_lock);
615         }
616         return count;
617 }
618
619 /*
620  * We can write to an anon page without COW if there are no other references
621  * to it.  And as a side-effect, free up its swap: because the old content
622  * on disk will never be read, and seeking back there to write new content
623  * later would only waste time away from clustering.
624  */
625 int reuse_swap_page(struct page *page)
626 {
627         int count;
628
629         VM_BUG_ON(!PageLocked(page));
630         if (unlikely(PageKsm(page)))
631                 return 0;
632         count = page_mapcount(page);
633         if (count <= 1 && PageSwapCache(page)) {
634                 count += page_swapcount(page);
635                 if (count == 1 && !PageWriteback(page)) {
636                         delete_from_swap_cache(page);
637                         SetPageDirty(page);
638                 }
639         }
640         return count <= 1;
641 }
642
643 /*
644  * If swap is getting full, or if there are no more mappings of this page,
645  * then try_to_free_swap is called to free its swap space.
646  */
647 int try_to_free_swap(struct page *page)
648 {
649         VM_BUG_ON(!PageLocked(page));
650
651         if (!PageSwapCache(page))
652                 return 0;
653         if (PageWriteback(page))
654                 return 0;
655         if (page_swapcount(page))
656                 return 0;
657
658         /*
659          * Once hibernation has begun to create its image of memory,
660          * there's a danger that one of the calls to try_to_free_swap()
661          * - most probably a call from __try_to_reclaim_swap() while
662          * hibernation is allocating its own swap pages for the image,
663          * but conceivably even a call from memory reclaim - will free
664          * the swap from a page which has already been recorded in the
665          * image as a clean swapcache page, and then reuse its swap for
666          * another page of the image.  On waking from hibernation, the
667          * original page might be freed under memory pressure, then
668          * later read back in from swap, now with the wrong data.
669          *
670          * Hibration suspends storage while it is writing the image
671          * to disk so check that here.
672          */
673         if (pm_suspended_storage())
674                 return 0;
675
676         delete_from_swap_cache(page);
677         SetPageDirty(page);
678         return 1;
679 }
680
681 /*
682  * Free the swap entry like above, but also try to
683  * free the page cache entry if it is the last user.
684  */
685 int free_swap_and_cache(swp_entry_t entry)
686 {
687         struct swap_info_struct *p;
688         struct page *page = NULL;
689
690         if (non_swap_entry(entry))
691                 return 1;
692
693         p = swap_info_get(entry);
694         if (p) {
695                 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
696                         page = find_get_page(&swapper_space, entry.val);
697                         if (page && !trylock_page(page)) {
698                                 page_cache_release(page);
699                                 page = NULL;
700                         }
701                 }
702                 spin_unlock(&swap_lock);
703         }
704         if (page) {
705                 /*
706                  * Not mapped elsewhere, or swap space full? Free it!
707                  * Also recheck PageSwapCache now page is locked (above).
708                  */
709                 if (PageSwapCache(page) && !PageWriteback(page) &&
710                                 (!page_mapped(page) || vm_swap_full())) {
711                         delete_from_swap_cache(page);
712                         SetPageDirty(page);
713                 }
714                 unlock_page(page);
715                 page_cache_release(page);
716         }
717         return p != NULL;
718 }
719
720 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
721 /**
722  * mem_cgroup_count_swap_user - count the user of a swap entry
723  * @ent: the swap entry to be checked
724  * @pagep: the pointer for the swap cache page of the entry to be stored
725  *
726  * Returns the number of the user of the swap entry. The number is valid only
727  * for swaps of anonymous pages.
728  * If the entry is found on swap cache, the page is stored to pagep with
729  * refcount of it being incremented.
730  */
731 int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
732 {
733         struct page *page;
734         struct swap_info_struct *p;
735         int count = 0;
736
737         page = find_get_page(&swapper_space, ent.val);
738         if (page)
739                 count += page_mapcount(page);
740         p = swap_info_get(ent);
741         if (p) {
742                 count += swap_count(p->swap_map[swp_offset(ent)]);
743                 spin_unlock(&swap_lock);
744         }
745
746         *pagep = page;
747         return count;
748 }
749 #endif
750
751 #ifdef CONFIG_HIBERNATION
752 /*
753  * Find the swap type that corresponds to given device (if any).
754  *
755  * @offset - number of the PAGE_SIZE-sized block of the device, starting
756  * from 0, in which the swap header is expected to be located.
757  *
758  * This is needed for the suspend to disk (aka swsusp).
759  */
760 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
761 {
762         struct block_device *bdev = NULL;
763         int type;
764
765         if (device)
766                 bdev = bdget(device);
767
768         spin_lock(&swap_lock);
769         for (type = 0; type < nr_swapfiles; type++) {
770                 struct swap_info_struct *sis = swap_info[type];
771
772                 if (!(sis->flags & SWP_WRITEOK))
773                         continue;
774
775                 if (!bdev) {
776                         if (bdev_p)
777                                 *bdev_p = bdgrab(sis->bdev);
778
779                         spin_unlock(&swap_lock);
780                         return type;
781                 }
782                 if (bdev == sis->bdev) {
783                         struct swap_extent *se = &sis->first_swap_extent;
784
785                         if (se->start_block == offset) {
786                                 if (bdev_p)
787                                         *bdev_p = bdgrab(sis->bdev);
788
789                                 spin_unlock(&swap_lock);
790                                 bdput(bdev);
791                                 return type;
792                         }
793                 }
794         }
795         spin_unlock(&swap_lock);
796         if (bdev)
797                 bdput(bdev);
798
799         return -ENODEV;
800 }
801
802 /*
803  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
804  * corresponding to given index in swap_info (swap type).
805  */
806 sector_t swapdev_block(int type, pgoff_t offset)
807 {
808         struct block_device *bdev;
809
810         if ((unsigned int)type >= nr_swapfiles)
811                 return 0;
812         if (!(swap_info[type]->flags & SWP_WRITEOK))
813                 return 0;
814         return map_swap_entry(swp_entry(type, offset), &bdev);
815 }
816
817 /*
818  * Return either the total number of swap pages of given type, or the number
819  * of free pages of that type (depending on @free)
820  *
821  * This is needed for software suspend
822  */
823 unsigned int count_swap_pages(int type, int free)
824 {
825         unsigned int n = 0;
826
827         spin_lock(&swap_lock);
828         if ((unsigned int)type < nr_swapfiles) {
829                 struct swap_info_struct *sis = swap_info[type];
830
831                 if (sis->flags & SWP_WRITEOK) {
832                         n = sis->pages;
833                         if (free)
834                                 n -= sis->inuse_pages;
835                 }
836         }
837         spin_unlock(&swap_lock);
838         return n;
839 }
840 #endif /* CONFIG_HIBERNATION */
841
842 /*
843  * No need to decide whether this PTE shares the swap entry with others,
844  * just let do_wp_page work it out if a write is requested later - to
845  * force COW, vm_page_prot omits write permission from any private vma.
846  */
847 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
848                 unsigned long addr, swp_entry_t entry, struct page *page)
849 {
850         struct mem_cgroup *memcg;
851         spinlock_t *ptl;
852         pte_t *pte;
853         int ret = 1;
854
855         if (mem_cgroup_try_charge_swapin(vma->vm_mm, page,
856                                          GFP_KERNEL, &memcg)) {
857                 ret = -ENOMEM;
858                 goto out_nolock;
859         }
860
861         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
862         if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
863                 if (ret > 0)
864                         mem_cgroup_cancel_charge_swapin(memcg);
865                 ret = 0;
866                 goto out;
867         }
868
869         dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
870         inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
871         get_page(page);
872         set_pte_at(vma->vm_mm, addr, pte,
873                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
874         page_add_anon_rmap(page, vma, addr);
875         mem_cgroup_commit_charge_swapin(page, memcg);
876         swap_free(entry);
877         /*
878          * Move the page to the active list so it is not
879          * immediately swapped out again after swapon.
880          */
881         activate_page(page);
882 out:
883         pte_unmap_unlock(pte, ptl);
884 out_nolock:
885         return ret;
886 }
887
888 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
889                                 unsigned long addr, unsigned long end,
890                                 swp_entry_t entry, struct page *page)
891 {
892         pte_t swp_pte = swp_entry_to_pte(entry);
893         pte_t *pte;
894         int ret = 0;
895
896         /*
897          * We don't actually need pte lock while scanning for swp_pte: since
898          * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
899          * page table while we're scanning; though it could get zapped, and on
900          * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
901          * of unmatched parts which look like swp_pte, so unuse_pte must
902          * recheck under pte lock.  Scanning without pte lock lets it be
903          * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
904          */
905         pte = pte_offset_map(pmd, addr);
906         do {
907                 /*
908                  * swapoff spends a _lot_ of time in this loop!
909                  * Test inline before going to call unuse_pte.
910                  */
911                 if (unlikely(pte_same(*pte, swp_pte))) {
912                         pte_unmap(pte);
913                         ret = unuse_pte(vma, pmd, addr, entry, page);
914                         if (ret)
915                                 goto out;
916                         pte = pte_offset_map(pmd, addr);
917                 }
918         } while (pte++, addr += PAGE_SIZE, addr != end);
919         pte_unmap(pte - 1);
920 out:
921         return ret;
922 }
923
924 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
925                                 unsigned long addr, unsigned long end,
926                                 swp_entry_t entry, struct page *page)
927 {
928         pmd_t *pmd;
929         unsigned long next;
930         int ret;
931
932         pmd = pmd_offset(pud, addr);
933         do {
934                 next = pmd_addr_end(addr, end);
935                 if (unlikely(pmd_trans_huge(*pmd)))
936                         continue;
937                 if (pmd_none_or_clear_bad(pmd))
938                         continue;
939                 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
940                 if (ret)
941                         return ret;
942         } while (pmd++, addr = next, addr != end);
943         return 0;
944 }
945
946 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
947                                 unsigned long addr, unsigned long end,
948                                 swp_entry_t entry, struct page *page)
949 {
950         pud_t *pud;
951         unsigned long next;
952         int ret;
953
954         pud = pud_offset(pgd, addr);
955         do {
956                 next = pud_addr_end(addr, end);
957                 if (pud_none_or_clear_bad(pud))
958                         continue;
959                 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
960                 if (ret)
961                         return ret;
962         } while (pud++, addr = next, addr != end);
963         return 0;
964 }
965
966 static int unuse_vma(struct vm_area_struct *vma,
967                                 swp_entry_t entry, struct page *page)
968 {
969         pgd_t *pgd;
970         unsigned long addr, end, next;
971         int ret;
972
973         if (page_anon_vma(page)) {
974                 addr = page_address_in_vma(page, vma);
975                 if (addr == -EFAULT)
976                         return 0;
977                 else
978                         end = addr + PAGE_SIZE;
979         } else {
980                 addr = vma->vm_start;
981                 end = vma->vm_end;
982         }
983
984         pgd = pgd_offset(vma->vm_mm, addr);
985         do {
986                 next = pgd_addr_end(addr, end);
987                 if (pgd_none_or_clear_bad(pgd))
988                         continue;
989                 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
990                 if (ret)
991                         return ret;
992         } while (pgd++, addr = next, addr != end);
993         return 0;
994 }
995
996 static int unuse_mm(struct mm_struct *mm,
997                                 swp_entry_t entry, struct page *page)
998 {
999         struct vm_area_struct *vma;
1000         int ret = 0;
1001
1002         if (!down_read_trylock(&mm->mmap_sem)) {
1003                 /*
1004                  * Activate page so shrink_inactive_list is unlikely to unmap
1005                  * its ptes while lock is dropped, so swapoff can make progress.
1006                  */
1007                 activate_page(page);
1008                 unlock_page(page);
1009                 down_read(&mm->mmap_sem);
1010                 lock_page(page);
1011         }
1012         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1013                 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1014                         break;
1015         }
1016         up_read(&mm->mmap_sem);
1017         return (ret < 0)? ret: 0;
1018 }
1019
1020 /*
1021  * Scan swap_map from current position to next entry still in use.
1022  * Recycle to start on reaching the end, returning 0 when empty.
1023  */
1024 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1025                                         unsigned int prev)
1026 {
1027         unsigned int max = si->max;
1028         unsigned int i = prev;
1029         unsigned char count;
1030
1031         /*
1032          * No need for swap_lock here: we're just looking
1033          * for whether an entry is in use, not modifying it; false
1034          * hits are okay, and sys_swapoff() has already prevented new
1035          * allocations from this area (while holding swap_lock).
1036          */
1037         for (;;) {
1038                 if (++i >= max) {
1039                         if (!prev) {
1040                                 i = 0;
1041                                 break;
1042                         }
1043                         /*
1044                          * No entries in use at top of swap_map,
1045                          * loop back to start and recheck there.
1046                          */
1047                         max = prev + 1;
1048                         prev = 0;
1049                         i = 1;
1050                 }
1051                 count = si->swap_map[i];
1052                 if (count && swap_count(count) != SWAP_MAP_BAD)
1053                         break;
1054         }
1055         return i;
1056 }
1057
1058 /*
1059  * We completely avoid races by reading each swap page in advance,
1060  * and then search for the process using it.  All the necessary
1061  * page table adjustments can then be made atomically.
1062  */
1063 static int try_to_unuse(unsigned int type)
1064 {
1065         struct swap_info_struct *si = swap_info[type];
1066         struct mm_struct *start_mm;
1067         unsigned char *swap_map;
1068         unsigned char swcount;
1069         struct page *page;
1070         swp_entry_t entry;
1071         unsigned int i = 0;
1072         int retval = 0;
1073
1074         /*
1075          * When searching mms for an entry, a good strategy is to
1076          * start at the first mm we freed the previous entry from
1077          * (though actually we don't notice whether we or coincidence
1078          * freed the entry).  Initialize this start_mm with a hold.
1079          *
1080          * A simpler strategy would be to start at the last mm we
1081          * freed the previous entry from; but that would take less
1082          * advantage of mmlist ordering, which clusters forked mms
1083          * together, child after parent.  If we race with dup_mmap(), we
1084          * prefer to resolve parent before child, lest we miss entries
1085          * duplicated after we scanned child: using last mm would invert
1086          * that.
1087          */
1088         start_mm = &init_mm;
1089         atomic_inc(&init_mm.mm_users);
1090
1091         /*
1092          * Keep on scanning until all entries have gone.  Usually,
1093          * one pass through swap_map is enough, but not necessarily:
1094          * there are races when an instance of an entry might be missed.
1095          */
1096         while ((i = find_next_to_unuse(si, i)) != 0) {
1097                 if (signal_pending(current)) {
1098                         retval = -EINTR;
1099                         break;
1100                 }
1101
1102                 /*
1103                  * Get a page for the entry, using the existing swap
1104                  * cache page if there is one.  Otherwise, get a clean
1105                  * page and read the swap into it.
1106                  */
1107                 swap_map = &si->swap_map[i];
1108                 entry = swp_entry(type, i);
1109                 page = read_swap_cache_async(entry,
1110                                         GFP_HIGHUSER_MOVABLE, NULL, 0);
1111                 if (!page) {
1112                         /*
1113                          * Either swap_duplicate() failed because entry
1114                          * has been freed independently, and will not be
1115                          * reused since sys_swapoff() already disabled
1116                          * allocation from here, or alloc_page() failed.
1117                          */
1118                         if (!*swap_map)
1119                                 continue;
1120                         retval = -ENOMEM;
1121                         break;
1122                 }
1123
1124                 /*
1125                  * Don't hold on to start_mm if it looks like exiting.
1126                  */
1127                 if (atomic_read(&start_mm->mm_users) == 1) {
1128                         mmput(start_mm);
1129                         start_mm = &init_mm;
1130                         atomic_inc(&init_mm.mm_users);
1131                 }
1132
1133                 /*
1134                  * Wait for and lock page.  When do_swap_page races with
1135                  * try_to_unuse, do_swap_page can handle the fault much
1136                  * faster than try_to_unuse can locate the entry.  This
1137                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
1138                  * defer to do_swap_page in such a case - in some tests,
1139                  * do_swap_page and try_to_unuse repeatedly compete.
1140                  */
1141                 wait_on_page_locked(page);
1142                 wait_on_page_writeback(page);
1143                 lock_page(page);
1144                 wait_on_page_writeback(page);
1145
1146                 /*
1147                  * Remove all references to entry.
1148                  */
1149                 swcount = *swap_map;
1150                 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1151                         retval = shmem_unuse(entry, page);
1152                         /* page has already been unlocked and released */
1153                         if (retval < 0)
1154                                 break;
1155                         continue;
1156                 }
1157                 if (swap_count(swcount) && start_mm != &init_mm)
1158                         retval = unuse_mm(start_mm, entry, page);
1159
1160                 if (swap_count(*swap_map)) {
1161                         int set_start_mm = (*swap_map >= swcount);
1162                         struct list_head *p = &start_mm->mmlist;
1163                         struct mm_struct *new_start_mm = start_mm;
1164                         struct mm_struct *prev_mm = start_mm;
1165                         struct mm_struct *mm;
1166
1167                         atomic_inc(&new_start_mm->mm_users);
1168                         atomic_inc(&prev_mm->mm_users);
1169                         spin_lock(&mmlist_lock);
1170                         while (swap_count(*swap_map) && !retval &&
1171                                         (p = p->next) != &start_mm->mmlist) {
1172                                 mm = list_entry(p, struct mm_struct, mmlist);
1173                                 if (!atomic_inc_not_zero(&mm->mm_users))
1174                                         continue;
1175                                 spin_unlock(&mmlist_lock);
1176                                 mmput(prev_mm);
1177                                 prev_mm = mm;
1178
1179                                 cond_resched();
1180
1181                                 swcount = *swap_map;
1182                                 if (!swap_count(swcount)) /* any usage ? */
1183                                         ;
1184                                 else if (mm == &init_mm)
1185                                         set_start_mm = 1;
1186                                 else
1187                                         retval = unuse_mm(mm, entry, page);
1188
1189                                 if (set_start_mm && *swap_map < swcount) {
1190                                         mmput(new_start_mm);
1191                                         atomic_inc(&mm->mm_users);
1192                                         new_start_mm = mm;
1193                                         set_start_mm = 0;
1194                                 }
1195                                 spin_lock(&mmlist_lock);
1196                         }
1197                         spin_unlock(&mmlist_lock);
1198                         mmput(prev_mm);
1199                         mmput(start_mm);
1200                         start_mm = new_start_mm;
1201                 }
1202                 if (retval) {
1203                         unlock_page(page);
1204                         page_cache_release(page);
1205                         break;
1206                 }
1207
1208                 /*
1209                  * If a reference remains (rare), we would like to leave
1210                  * the page in the swap cache; but try_to_unmap could
1211                  * then re-duplicate the entry once we drop page lock,
1212                  * so we might loop indefinitely; also, that page could
1213                  * not be swapped out to other storage meanwhile.  So:
1214                  * delete from cache even if there's another reference,
1215                  * after ensuring that the data has been saved to disk -
1216                  * since if the reference remains (rarer), it will be
1217                  * read from disk into another page.  Splitting into two
1218                  * pages would be incorrect if swap supported "shared
1219                  * private" pages, but they are handled by tmpfs files.
1220                  *
1221                  * Given how unuse_vma() targets one particular offset
1222                  * in an anon_vma, once the anon_vma has been determined,
1223                  * this splitting happens to be just what is needed to
1224                  * handle where KSM pages have been swapped out: re-reading
1225                  * is unnecessarily slow, but we can fix that later on.
1226                  */
1227                 if (swap_count(*swap_map) &&
1228                      PageDirty(page) && PageSwapCache(page)) {
1229                         struct writeback_control wbc = {
1230                                 .sync_mode = WB_SYNC_NONE,
1231                         };
1232
1233                         swap_writepage(page, &wbc);
1234                         lock_page(page);
1235                         wait_on_page_writeback(page);
1236                 }
1237
1238                 /*
1239                  * It is conceivable that a racing task removed this page from
1240                  * swap cache just before we acquired the page lock at the top,
1241                  * or while we dropped it in unuse_mm().  The page might even
1242                  * be back in swap cache on another swap area: that we must not
1243                  * delete, since it may not have been written out to swap yet.
1244                  */
1245                 if (PageSwapCache(page) &&
1246                     likely(page_private(page) == entry.val))
1247                         delete_from_swap_cache(page);
1248
1249                 /*
1250                  * So we could skip searching mms once swap count went
1251                  * to 1, we did not mark any present ptes as dirty: must
1252                  * mark page dirty so shrink_page_list will preserve it.
1253                  */
1254                 SetPageDirty(page);
1255                 unlock_page(page);
1256                 page_cache_release(page);
1257
1258                 /*
1259                  * Make sure that we aren't completely killing
1260                  * interactive performance.
1261                  */
1262                 cond_resched();
1263         }
1264
1265         mmput(start_mm);
1266         return retval;
1267 }
1268
1269 /*
1270  * After a successful try_to_unuse, if no swap is now in use, we know
1271  * we can empty the mmlist.  swap_lock must be held on entry and exit.
1272  * Note that mmlist_lock nests inside swap_lock, and an mm must be
1273  * added to the mmlist just after page_duplicate - before would be racy.
1274  */
1275 static void drain_mmlist(void)
1276 {
1277         struct list_head *p, *next;
1278         unsigned int type;
1279
1280         for (type = 0; type < nr_swapfiles; type++)
1281                 if (swap_info[type]->inuse_pages)
1282                         return;
1283         spin_lock(&mmlist_lock);
1284         list_for_each_safe(p, next, &init_mm.mmlist)
1285                 list_del_init(p);
1286         spin_unlock(&mmlist_lock);
1287 }
1288
1289 /*
1290  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1291  * corresponds to page offset for the specified swap entry.
1292  * Note that the type of this function is sector_t, but it returns page offset
1293  * into the bdev, not sector offset.
1294  */
1295 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1296 {
1297         struct swap_info_struct *sis;
1298         struct swap_extent *start_se;
1299         struct swap_extent *se;
1300         pgoff_t offset;
1301
1302         sis = swap_info[swp_type(entry)];
1303         *bdev = sis->bdev;
1304
1305         offset = swp_offset(entry);
1306         start_se = sis->curr_swap_extent;
1307         se = start_se;
1308
1309         for ( ; ; ) {
1310                 struct list_head *lh;
1311
1312                 if (se->start_page <= offset &&
1313                                 offset < (se->start_page + se->nr_pages)) {
1314                         return se->start_block + (offset - se->start_page);
1315                 }
1316                 lh = se->list.next;
1317                 se = list_entry(lh, struct swap_extent, list);
1318                 sis->curr_swap_extent = se;
1319                 BUG_ON(se == start_se);         /* It *must* be present */
1320         }
1321 }
1322
1323 /*
1324  * Returns the page offset into bdev for the specified page's swap entry.
1325  */
1326 sector_t map_swap_page(struct page *page, struct block_device **bdev)
1327 {
1328         swp_entry_t entry;
1329         entry.val = page_private(page);
1330         return map_swap_entry(entry, bdev);
1331 }
1332
1333 /*
1334  * Free all of a swapdev's extent information
1335  */
1336 static void destroy_swap_extents(struct swap_info_struct *sis)
1337 {
1338         while (!list_empty(&sis->first_swap_extent.list)) {
1339                 struct swap_extent *se;
1340
1341                 se = list_entry(sis->first_swap_extent.list.next,
1342                                 struct swap_extent, list);
1343                 list_del(&se->list);
1344                 kfree(se);
1345         }
1346 }
1347
1348 /*
1349  * Add a block range (and the corresponding page range) into this swapdev's
1350  * extent list.  The extent list is kept sorted in page order.
1351  *
1352  * This function rather assumes that it is called in ascending page order.
1353  */
1354 static int
1355 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1356                 unsigned long nr_pages, sector_t start_block)
1357 {
1358         struct swap_extent *se;
1359         struct swap_extent *new_se;
1360         struct list_head *lh;
1361
1362         if (start_page == 0) {
1363                 se = &sis->first_swap_extent;
1364                 sis->curr_swap_extent = se;
1365                 se->start_page = 0;
1366                 se->nr_pages = nr_pages;
1367                 se->start_block = start_block;
1368                 return 1;
1369         } else {
1370                 lh = sis->first_swap_extent.list.prev;  /* Highest extent */
1371                 se = list_entry(lh, struct swap_extent, list);
1372                 BUG_ON(se->start_page + se->nr_pages != start_page);
1373                 if (se->start_block + se->nr_pages == start_block) {
1374                         /* Merge it */
1375                         se->nr_pages += nr_pages;
1376                         return 0;
1377                 }
1378         }
1379
1380         /*
1381          * No merge.  Insert a new extent, preserving ordering.
1382          */
1383         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1384         if (new_se == NULL)
1385                 return -ENOMEM;
1386         new_se->start_page = start_page;
1387         new_se->nr_pages = nr_pages;
1388         new_se->start_block = start_block;
1389
1390         list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1391         return 1;
1392 }
1393
1394 /*
1395  * A `swap extent' is a simple thing which maps a contiguous range of pages
1396  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1397  * is built at swapon time and is then used at swap_writepage/swap_readpage
1398  * time for locating where on disk a page belongs.
1399  *
1400  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1401  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1402  * swap files identically.
1403  *
1404  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1405  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1406  * swapfiles are handled *identically* after swapon time.
1407  *
1408  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1409  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1410  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1411  * requirements, they are simply tossed out - we will never use those blocks
1412  * for swapping.
1413  *
1414  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1415  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1416  * which will scribble on the fs.
1417  *
1418  * The amount of disk space which a single swap extent represents varies.
1419  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1420  * extents in the list.  To avoid much list walking, we cache the previous
1421  * search location in `curr_swap_extent', and start new searches from there.
1422  * This is extremely effective.  The average number of iterations in
1423  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1424  */
1425 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1426 {
1427         struct inode *inode;
1428         unsigned blocks_per_page;
1429         unsigned long page_no;
1430         unsigned blkbits;
1431         sector_t probe_block;
1432         sector_t last_block;
1433         sector_t lowest_block = -1;
1434         sector_t highest_block = 0;
1435         int nr_extents = 0;
1436         int ret;
1437
1438         inode = sis->swap_file->f_mapping->host;
1439         if (S_ISBLK(inode->i_mode)) {
1440                 ret = add_swap_extent(sis, 0, sis->max, 0);
1441                 *span = sis->pages;
1442                 goto out;
1443         }
1444
1445         blkbits = inode->i_blkbits;
1446         blocks_per_page = PAGE_SIZE >> blkbits;
1447
1448         /*
1449          * Map all the blocks into the extent list.  This code doesn't try
1450          * to be very smart.
1451          */
1452         probe_block = 0;
1453         page_no = 0;
1454         last_block = i_size_read(inode) >> blkbits;
1455         while ((probe_block + blocks_per_page) <= last_block &&
1456                         page_no < sis->max) {
1457                 unsigned block_in_page;
1458                 sector_t first_block;
1459
1460                 first_block = bmap(inode, probe_block);
1461                 if (first_block == 0)
1462                         goto bad_bmap;
1463
1464                 /*
1465                  * It must be PAGE_SIZE aligned on-disk
1466                  */
1467                 if (first_block & (blocks_per_page - 1)) {
1468                         probe_block++;
1469                         goto reprobe;
1470                 }
1471
1472                 for (block_in_page = 1; block_in_page < blocks_per_page;
1473                                         block_in_page++) {
1474                         sector_t block;
1475
1476                         block = bmap(inode, probe_block + block_in_page);
1477                         if (block == 0)
1478                                 goto bad_bmap;
1479                         if (block != first_block + block_in_page) {
1480                                 /* Discontiguity */
1481                                 probe_block++;
1482                                 goto reprobe;
1483                         }
1484                 }
1485
1486                 first_block >>= (PAGE_SHIFT - blkbits);
1487                 if (page_no) {  /* exclude the header page */
1488                         if (first_block < lowest_block)
1489                                 lowest_block = first_block;
1490                         if (first_block > highest_block)
1491                                 highest_block = first_block;
1492                 }
1493
1494                 /*
1495                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1496                  */
1497                 ret = add_swap_extent(sis, page_no, 1, first_block);
1498                 if (ret < 0)
1499                         goto out;
1500                 nr_extents += ret;
1501                 page_no++;
1502                 probe_block += blocks_per_page;
1503 reprobe:
1504                 continue;
1505         }
1506         ret = nr_extents;
1507         *span = 1 + highest_block - lowest_block;
1508         if (page_no == 0)
1509                 page_no = 1;    /* force Empty message */
1510         sis->max = page_no;
1511         sis->pages = page_no - 1;
1512         sis->highest_bit = page_no - 1;
1513 out:
1514         return ret;
1515 bad_bmap:
1516         printk(KERN_ERR "swapon: swapfile has holes\n");
1517         ret = -EINVAL;
1518         goto out;
1519 }
1520
1521 static void enable_swap_info(struct swap_info_struct *p, int prio,
1522                                 unsigned char *swap_map)
1523 {
1524         int i, prev;
1525
1526         spin_lock(&swap_lock);
1527         if (prio >= 0)
1528                 p->prio = prio;
1529         else
1530                 p->prio = --least_priority;
1531         p->swap_map = swap_map;
1532         p->flags |= SWP_WRITEOK;
1533         nr_swap_pages += p->pages;
1534         total_swap_pages += p->pages;
1535
1536         /* insert swap space into swap_list: */
1537         prev = -1;
1538         for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1539                 if (p->prio >= swap_info[i]->prio)
1540                         break;
1541                 prev = i;
1542         }
1543         p->next = i;
1544         if (prev < 0)
1545                 swap_list.head = swap_list.next = p->type;
1546         else
1547                 swap_info[prev]->next = p->type;
1548         spin_unlock(&swap_lock);
1549 }
1550
1551 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1552 {
1553         struct swap_info_struct *p = NULL;
1554         unsigned char *swap_map;
1555         struct file *swap_file, *victim;
1556         struct address_space *mapping;
1557         struct inode *inode;
1558         char *pathname;
1559         int oom_score_adj;
1560         int i, type, prev;
1561         int err;
1562
1563         if (!capable(CAP_SYS_ADMIN))
1564                 return -EPERM;
1565
1566         pathname = getname(specialfile);
1567         err = PTR_ERR(pathname);
1568         if (IS_ERR(pathname))
1569                 goto out;
1570
1571         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1572         putname(pathname);
1573         err = PTR_ERR(victim);
1574         if (IS_ERR(victim))
1575                 goto out;
1576
1577         mapping = victim->f_mapping;
1578         prev = -1;
1579         spin_lock(&swap_lock);
1580         for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1581                 p = swap_info[type];
1582                 if (p->flags & SWP_WRITEOK) {
1583                         if (p->swap_file->f_mapping == mapping)
1584                                 break;
1585                 }
1586                 prev = type;
1587         }
1588         if (type < 0) {
1589                 err = -EINVAL;
1590                 spin_unlock(&swap_lock);
1591                 goto out_dput;
1592         }
1593         if (!security_vm_enough_memory(p->pages))
1594                 vm_unacct_memory(p->pages);
1595         else {
1596                 err = -ENOMEM;
1597                 spin_unlock(&swap_lock);
1598                 goto out_dput;
1599         }
1600         if (prev < 0)
1601                 swap_list.head = p->next;
1602         else
1603                 swap_info[prev]->next = p->next;
1604         if (type == swap_list.next) {
1605                 /* just pick something that's safe... */
1606                 swap_list.next = swap_list.head;
1607         }
1608         if (p->prio < 0) {
1609                 for (i = p->next; i >= 0; i = swap_info[i]->next)
1610                         swap_info[i]->prio = p->prio--;
1611                 least_priority++;
1612         }
1613         nr_swap_pages -= p->pages;
1614         total_swap_pages -= p->pages;
1615         p->flags &= ~SWP_WRITEOK;
1616         spin_unlock(&swap_lock);
1617
1618         oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
1619         err = try_to_unuse(type);
1620         compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
1621
1622         if (err) {
1623                 /*
1624                  * reading p->prio and p->swap_map outside the lock is
1625                  * safe here because only sys_swapon and sys_swapoff
1626                  * change them, and there can be no other sys_swapon or
1627                  * sys_swapoff for this swap_info_struct at this point.
1628                  */
1629                 /* re-insert swap space back into swap_list */
1630                 enable_swap_info(p, p->prio, p->swap_map);
1631                 goto out_dput;
1632         }
1633
1634         destroy_swap_extents(p);
1635         if (p->flags & SWP_CONTINUED)
1636                 free_swap_count_continuations(p);
1637
1638         mutex_lock(&swapon_mutex);
1639         spin_lock(&swap_lock);
1640         drain_mmlist();
1641
1642         /* wait for anyone still in scan_swap_map */
1643         p->highest_bit = 0;             /* cuts scans short */
1644         while (p->flags >= SWP_SCANNING) {
1645                 spin_unlock(&swap_lock);
1646                 schedule_timeout_uninterruptible(1);
1647                 spin_lock(&swap_lock);
1648         }
1649
1650         swap_file = p->swap_file;
1651         p->swap_file = NULL;
1652         p->max = 0;
1653         swap_map = p->swap_map;
1654         p->swap_map = NULL;
1655         p->flags = 0;
1656         spin_unlock(&swap_lock);
1657         mutex_unlock(&swapon_mutex);
1658         vfree(swap_map);
1659         /* Destroy swap account informatin */
1660         swap_cgroup_swapoff(type);
1661
1662         inode = mapping->host;
1663         if (S_ISBLK(inode->i_mode)) {
1664                 struct block_device *bdev = I_BDEV(inode);
1665                 set_blocksize(bdev, p->old_block_size);
1666                 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1667         } else {
1668                 mutex_lock(&inode->i_mutex);
1669                 inode->i_flags &= ~S_SWAPFILE;
1670                 mutex_unlock(&inode->i_mutex);
1671         }
1672         filp_close(swap_file, NULL);
1673         err = 0;
1674         atomic_inc(&proc_poll_event);
1675         wake_up_interruptible(&proc_poll_wait);
1676
1677 out_dput:
1678         filp_close(victim, NULL);
1679 out:
1680         return err;
1681 }
1682
1683 #ifdef CONFIG_PROC_FS
1684 static unsigned swaps_poll(struct file *file, poll_table *wait)
1685 {
1686         struct seq_file *seq = file->private_data;
1687
1688         poll_wait(file, &proc_poll_wait, wait);
1689
1690         if (seq->poll_event != atomic_read(&proc_poll_event)) {
1691                 seq->poll_event = atomic_read(&proc_poll_event);
1692                 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
1693         }
1694
1695         return POLLIN | POLLRDNORM;
1696 }
1697
1698 /* iterator */
1699 static void *swap_start(struct seq_file *swap, loff_t *pos)
1700 {
1701         struct swap_info_struct *si;
1702         int type;
1703         loff_t l = *pos;
1704
1705         mutex_lock(&swapon_mutex);
1706
1707         if (!l)
1708                 return SEQ_START_TOKEN;
1709
1710         for (type = 0; type < nr_swapfiles; type++) {
1711                 smp_rmb();      /* read nr_swapfiles before swap_info[type] */
1712                 si = swap_info[type];
1713                 if (!(si->flags & SWP_USED) || !si->swap_map)
1714                         continue;
1715                 if (!--l)
1716                         return si;
1717         }
1718
1719         return NULL;
1720 }
1721
1722 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1723 {
1724         struct swap_info_struct *si = v;
1725         int type;
1726
1727         if (v == SEQ_START_TOKEN)
1728                 type = 0;
1729         else
1730                 type = si->type + 1;
1731
1732         for (; type < nr_swapfiles; type++) {
1733                 smp_rmb();      /* read nr_swapfiles before swap_info[type] */
1734                 si = swap_info[type];
1735                 if (!(si->flags & SWP_USED) || !si->swap_map)
1736                         continue;
1737                 ++*pos;
1738                 return si;
1739         }
1740
1741         return NULL;
1742 }
1743
1744 static void swap_stop(struct seq_file *swap, void *v)
1745 {
1746         mutex_unlock(&swapon_mutex);
1747 }
1748
1749 static int swap_show(struct seq_file *swap, void *v)
1750 {
1751         struct swap_info_struct *si = v;
1752         struct file *file;
1753         int len;
1754
1755         if (si == SEQ_START_TOKEN) {
1756                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1757                 return 0;
1758         }
1759
1760         file = si->swap_file;
1761         len = seq_path(swap, &file->f_path, " \t\n\\");
1762         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1763                         len < 40 ? 40 - len : 1, " ",
1764                         S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1765                                 "partition" : "file\t",
1766                         si->pages << (PAGE_SHIFT - 10),
1767                         si->inuse_pages << (PAGE_SHIFT - 10),
1768                         si->prio);
1769         return 0;
1770 }
1771
1772 static const struct seq_operations swaps_op = {
1773         .start =        swap_start,
1774         .next =         swap_next,
1775         .stop =         swap_stop,
1776         .show =         swap_show
1777 };
1778
1779 static int swaps_open(struct inode *inode, struct file *file)
1780 {
1781         struct seq_file *seq;
1782         int ret;
1783
1784         ret = seq_open(file, &swaps_op);
1785         if (ret)
1786                 return ret;
1787
1788         seq = file->private_data;
1789         seq->poll_event = atomic_read(&proc_poll_event);
1790         return 0;
1791 }
1792
1793 static const struct file_operations proc_swaps_operations = {
1794         .open           = swaps_open,
1795         .read           = seq_read,
1796         .llseek         = seq_lseek,
1797         .release        = seq_release,
1798         .poll           = swaps_poll,
1799 };
1800
1801 static int __init procswaps_init(void)
1802 {
1803         proc_create("swaps", 0, NULL, &proc_swaps_operations);
1804         return 0;
1805 }
1806 __initcall(procswaps_init);
1807 #endif /* CONFIG_PROC_FS */
1808
1809 #ifdef MAX_SWAPFILES_CHECK
1810 static int __init max_swapfiles_check(void)
1811 {
1812         MAX_SWAPFILES_CHECK();
1813         return 0;
1814 }
1815 late_initcall(max_swapfiles_check);
1816 #endif
1817
1818 static struct swap_info_struct *alloc_swap_info(void)
1819 {
1820         struct swap_info_struct *p;
1821         unsigned int type;
1822
1823         p = kzalloc(sizeof(*p), GFP_KERNEL);
1824         if (!p)
1825                 return ERR_PTR(-ENOMEM);
1826
1827         spin_lock(&swap_lock);
1828         for (type = 0; type < nr_swapfiles; type++) {
1829                 if (!(swap_info[type]->flags & SWP_USED))
1830                         break;
1831         }
1832         if (type >= MAX_SWAPFILES) {
1833                 spin_unlock(&swap_lock);
1834                 kfree(p);
1835                 return ERR_PTR(-EPERM);
1836         }
1837         if (type >= nr_swapfiles) {
1838                 p->type = type;
1839                 swap_info[type] = p;
1840                 /*
1841                  * Write swap_info[type] before nr_swapfiles, in case a
1842                  * racing procfs swap_start() or swap_next() is reading them.
1843                  * (We never shrink nr_swapfiles, we never free this entry.)
1844                  */
1845                 smp_wmb();
1846                 nr_swapfiles++;
1847         } else {
1848                 kfree(p);
1849                 p = swap_info[type];
1850                 /*
1851                  * Do not memset this entry: a racing procfs swap_next()
1852                  * would be relying on p->type to remain valid.
1853                  */
1854         }
1855         INIT_LIST_HEAD(&p->first_swap_extent.list);
1856         p->flags = SWP_USED;
1857         p->next = -1;
1858         spin_unlock(&swap_lock);
1859
1860         return p;
1861 }
1862
1863 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
1864 {
1865         int error;
1866
1867         if (S_ISBLK(inode->i_mode)) {
1868                 p->bdev = bdgrab(I_BDEV(inode));
1869                 error = blkdev_get(p->bdev,
1870                                    FMODE_READ | FMODE_WRITE | FMODE_EXCL,
1871                                    sys_swapon);
1872                 if (error < 0) {
1873                         p->bdev = NULL;
1874                         return -EINVAL;
1875                 }
1876                 p->old_block_size = block_size(p->bdev);
1877                 error = set_blocksize(p->bdev, PAGE_SIZE);
1878                 if (error < 0)
1879                         return error;
1880                 p->flags |= SWP_BLKDEV;
1881         } else if (S_ISREG(inode->i_mode)) {
1882                 p->bdev = inode->i_sb->s_bdev;
1883                 mutex_lock(&inode->i_mutex);
1884                 if (IS_SWAPFILE(inode))
1885                         return -EBUSY;
1886         } else
1887                 return -EINVAL;
1888
1889         return 0;
1890 }
1891
1892 static unsigned long read_swap_header(struct swap_info_struct *p,
1893                                         union swap_header *swap_header,
1894                                         struct inode *inode)
1895 {
1896         int i;
1897         unsigned long maxpages;
1898         unsigned long swapfilepages;
1899
1900         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1901                 printk(KERN_ERR "Unable to find swap-space signature\n");
1902                 return 0;
1903         }
1904
1905         /* swap partition endianess hack... */
1906         if (swab32(swap_header->info.version) == 1) {
1907                 swab32s(&swap_header->info.version);
1908                 swab32s(&swap_header->info.last_page);
1909                 swab32s(&swap_header->info.nr_badpages);
1910                 for (i = 0; i < swap_header->info.nr_badpages; i++)
1911                         swab32s(&swap_header->info.badpages[i]);
1912         }
1913         /* Check the swap header's sub-version */
1914         if (swap_header->info.version != 1) {
1915                 printk(KERN_WARNING
1916                        "Unable to handle swap header version %d\n",
1917                        swap_header->info.version);
1918                 return 0;
1919         }
1920
1921         p->lowest_bit  = 1;
1922         p->cluster_next = 1;
1923         p->cluster_nr = 0;
1924
1925         /*
1926          * Find out how many pages are allowed for a single swap
1927          * device. There are three limiting factors: 1) the number
1928          * of bits for the swap offset in the swp_entry_t type, and
1929          * 2) the number of bits in the swap pte as defined by the
1930          * the different architectures, and 3) the number of free bits
1931          * in an exceptional radix_tree entry. In order to find the
1932          * largest possible bit mask, a swap entry with swap type 0
1933          * and swap offset ~0UL is created, encoded to a swap pte,
1934          * decoded to a swp_entry_t again, and finally the swap
1935          * offset is extracted. This will mask all the bits from
1936          * the initial ~0UL mask that can't be encoded in either
1937          * the swp_entry_t or the architecture definition of a
1938          * swap pte.  Then the same is done for a radix_tree entry.
1939          */
1940         maxpages = swp_offset(pte_to_swp_entry(
1941                         swp_entry_to_pte(swp_entry(0, ~0UL))));
1942         maxpages = swp_offset(radix_to_swp_entry(
1943                         swp_to_radix_entry(swp_entry(0, maxpages)))) + 1;
1944
1945         if (maxpages > swap_header->info.last_page) {
1946                 maxpages = swap_header->info.last_page + 1;
1947                 /* p->max is an unsigned int: don't overflow it */
1948                 if ((unsigned int)maxpages == 0)
1949                         maxpages = UINT_MAX;
1950         }
1951         p->highest_bit = maxpages - 1;
1952
1953         if (!maxpages)
1954                 return 0;
1955         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1956         if (swapfilepages && maxpages > swapfilepages) {
1957                 printk(KERN_WARNING
1958                        "Swap area shorter than signature indicates\n");
1959                 return 0;
1960         }
1961         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1962                 return 0;
1963         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1964                 return 0;
1965
1966         return maxpages;
1967 }
1968
1969 static int setup_swap_map_and_extents(struct swap_info_struct *p,
1970                                         union swap_header *swap_header,
1971                                         unsigned char *swap_map,
1972                                         unsigned long maxpages,
1973                                         sector_t *span)
1974 {
1975         int i;
1976         unsigned int nr_good_pages;
1977         int nr_extents;
1978
1979         nr_good_pages = maxpages - 1;   /* omit header page */
1980
1981         for (i = 0; i < swap_header->info.nr_badpages; i++) {
1982                 unsigned int page_nr = swap_header->info.badpages[i];
1983                 if (page_nr == 0 || page_nr > swap_header->info.last_page)
1984                         return -EINVAL;
1985                 if (page_nr < maxpages) {
1986                         swap_map[page_nr] = SWAP_MAP_BAD;
1987                         nr_good_pages--;
1988                 }
1989         }
1990
1991         if (nr_good_pages) {
1992                 swap_map[0] = SWAP_MAP_BAD;
1993                 p->max = maxpages;
1994                 p->pages = nr_good_pages;
1995                 nr_extents = setup_swap_extents(p, span);
1996                 if (nr_extents < 0)
1997                         return nr_extents;
1998                 nr_good_pages = p->pages;
1999         }
2000         if (!nr_good_pages) {
2001                 printk(KERN_WARNING "Empty swap-file\n");
2002                 return -EINVAL;
2003         }
2004
2005         return nr_extents;
2006 }
2007
2008 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2009 {
2010         struct swap_info_struct *p;
2011         char *name;
2012         struct file *swap_file = NULL;
2013         struct address_space *mapping;
2014         int i;
2015         int prio;
2016         int error;
2017         union swap_header *swap_header;
2018         int nr_extents;
2019         sector_t span;
2020         unsigned long maxpages;
2021         unsigned char *swap_map = NULL;
2022         struct page *page = NULL;
2023         struct inode *inode = NULL;
2024
2025         if (!capable(CAP_SYS_ADMIN))
2026                 return -EPERM;
2027
2028         p = alloc_swap_info();
2029         if (IS_ERR(p))
2030                 return PTR_ERR(p);
2031
2032         name = getname(specialfile);
2033         if (IS_ERR(name)) {
2034                 error = PTR_ERR(name);
2035                 name = NULL;
2036                 goto bad_swap;
2037         }
2038         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
2039         if (IS_ERR(swap_file)) {
2040                 error = PTR_ERR(swap_file);
2041                 swap_file = NULL;
2042                 goto bad_swap;
2043         }
2044
2045         p->swap_file = swap_file;
2046         mapping = swap_file->f_mapping;
2047
2048         for (i = 0; i < nr_swapfiles; i++) {
2049                 struct swap_info_struct *q = swap_info[i];
2050
2051                 if (q == p || !q->swap_file)
2052                         continue;
2053                 if (mapping == q->swap_file->f_mapping) {
2054                         error = -EBUSY;
2055                         goto bad_swap;
2056                 }
2057         }
2058
2059         inode = mapping->host;
2060         /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
2061         error = claim_swapfile(p, inode);
2062         if (unlikely(error))
2063                 goto bad_swap;
2064
2065         /*
2066          * Read the swap header.
2067          */
2068         if (!mapping->a_ops->readpage) {
2069                 error = -EINVAL;
2070                 goto bad_swap;
2071         }
2072         page = read_mapping_page(mapping, 0, swap_file);
2073         if (IS_ERR(page)) {
2074                 error = PTR_ERR(page);
2075                 goto bad_swap;
2076         }
2077         swap_header = kmap(page);
2078
2079         maxpages = read_swap_header(p, swap_header, inode);
2080         if (unlikely(!maxpages)) {
2081                 error = -EINVAL;
2082                 goto bad_swap;
2083         }
2084
2085         /* OK, set up the swap map and apply the bad block list */
2086         swap_map = vzalloc(maxpages);
2087         if (!swap_map) {
2088                 error = -ENOMEM;
2089                 goto bad_swap;
2090         }
2091
2092         error = swap_cgroup_swapon(p->type, maxpages);
2093         if (error)
2094                 goto bad_swap;
2095
2096         nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2097                 maxpages, &span);
2098         if (unlikely(nr_extents < 0)) {
2099                 error = nr_extents;
2100                 goto bad_swap;
2101         }
2102
2103         if (p->bdev) {
2104                 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2105                         p->flags |= SWP_SOLIDSTATE;
2106                         p->cluster_next = 1 + (random32() % p->highest_bit);
2107                 }
2108                 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
2109                         p->flags |= SWP_DISCARDABLE;
2110         }
2111
2112         mutex_lock(&swapon_mutex);
2113         prio = -1;
2114         if (swap_flags & SWAP_FLAG_PREFER)
2115                 prio =
2116                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2117         enable_swap_info(p, prio, swap_map);
2118
2119         printk(KERN_INFO "Adding %uk swap on %s.  "
2120                         "Priority:%d extents:%d across:%lluk %s%s\n",
2121                 p->pages<<(PAGE_SHIFT-10), name, p->prio,
2122                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2123                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2124                 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2125
2126         mutex_unlock(&swapon_mutex);
2127         atomic_inc(&proc_poll_event);
2128         wake_up_interruptible(&proc_poll_wait);
2129
2130         if (S_ISREG(inode->i_mode))
2131                 inode->i_flags |= S_SWAPFILE;
2132         error = 0;
2133         goto out;
2134 bad_swap:
2135         if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
2136                 set_blocksize(p->bdev, p->old_block_size);
2137                 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2138         }
2139         destroy_swap_extents(p);
2140         swap_cgroup_swapoff(p->type);
2141         spin_lock(&swap_lock);
2142         p->swap_file = NULL;
2143         p->flags = 0;
2144         spin_unlock(&swap_lock);
2145         vfree(swap_map);
2146         if (swap_file) {
2147                 if (inode && S_ISREG(inode->i_mode)) {
2148                         mutex_unlock(&inode->i_mutex);
2149                         inode = NULL;
2150                 }
2151                 filp_close(swap_file, NULL);
2152         }
2153 out:
2154         if (page && !IS_ERR(page)) {
2155                 kunmap(page);
2156                 page_cache_release(page);
2157         }
2158         if (name)
2159                 putname(name);
2160         if (inode && S_ISREG(inode->i_mode))
2161                 mutex_unlock(&inode->i_mutex);
2162         return error;
2163 }
2164
2165 void si_swapinfo(struct sysinfo *val)
2166 {
2167         unsigned int type;
2168         unsigned long nr_to_be_unused = 0;
2169
2170         spin_lock(&swap_lock);
2171         for (type = 0; type < nr_swapfiles; type++) {
2172                 struct swap_info_struct *si = swap_info[type];
2173
2174                 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2175                         nr_to_be_unused += si->inuse_pages;
2176         }
2177         val->freeswap = nr_swap_pages + nr_to_be_unused;
2178         val->totalswap = total_swap_pages + nr_to_be_unused;
2179         spin_unlock(&swap_lock);
2180 }
2181
2182 /*
2183  * Verify that a swap entry is valid and increment its swap map count.
2184  *
2185  * Returns error code in following case.
2186  * - success -> 0
2187  * - swp_entry is invalid -> EINVAL
2188  * - swp_entry is migration entry -> EINVAL
2189  * - swap-cache reference is requested but there is already one. -> EEXIST
2190  * - swap-cache reference is requested but the entry is not used. -> ENOENT
2191  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2192  */
2193 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2194 {
2195         struct swap_info_struct *p;
2196         unsigned long offset, type;
2197         unsigned char count;
2198         unsigned char has_cache;
2199         int err = -EINVAL;
2200
2201         if (non_swap_entry(entry))
2202                 goto out;
2203
2204         type = swp_type(entry);
2205         if (type >= nr_swapfiles)
2206                 goto bad_file;
2207         p = swap_info[type];
2208         offset = swp_offset(entry);
2209
2210         spin_lock(&swap_lock);
2211         if (unlikely(offset >= p->max))
2212                 goto unlock_out;
2213
2214         count = p->swap_map[offset];
2215         has_cache = count & SWAP_HAS_CACHE;
2216         count &= ~SWAP_HAS_CACHE;
2217         err = 0;
2218
2219         if (usage == SWAP_HAS_CACHE) {
2220
2221                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2222                 if (!has_cache && count)
2223                         has_cache = SWAP_HAS_CACHE;
2224                 else if (has_cache)             /* someone else added cache */
2225                         err = -EEXIST;
2226                 else                            /* no users remaining */
2227                         err = -ENOENT;
2228
2229         } else if (count || has_cache) {
2230
2231                 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2232                         count += usage;
2233                 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2234                         err = -EINVAL;
2235                 else if (swap_count_continued(p, offset, count))
2236                         count = COUNT_CONTINUED;
2237                 else
2238                         err = -ENOMEM;
2239         } else
2240                 err = -ENOENT;                  /* unused swap entry */
2241
2242         p->swap_map[offset] = count | has_cache;
2243
2244 unlock_out:
2245         spin_unlock(&swap_lock);
2246 out:
2247         return err;
2248
2249 bad_file:
2250         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2251         goto out;
2252 }
2253
2254 /*
2255  * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2256  * (in which case its reference count is never incremented).
2257  */
2258 void swap_shmem_alloc(swp_entry_t entry)
2259 {
2260         __swap_duplicate(entry, SWAP_MAP_SHMEM);
2261 }
2262
2263 /*
2264  * Increase reference count of swap entry by 1.
2265  * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2266  * but could not be atomically allocated.  Returns 0, just as if it succeeded,
2267  * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2268  * might occur if a page table entry has got corrupted.
2269  */
2270 int swap_duplicate(swp_entry_t entry)
2271 {
2272         int err = 0;
2273
2274         while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2275                 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2276         return err;
2277 }
2278
2279 /*
2280  * @entry: swap entry for which we allocate swap cache.
2281  *
2282  * Called when allocating swap cache for existing swap entry,
2283  * This can return error codes. Returns 0 at success.
2284  * -EBUSY means there is a swap cache.
2285  * Note: return code is different from swap_duplicate().
2286  */
2287 int swapcache_prepare(swp_entry_t entry)
2288 {
2289         return __swap_duplicate(entry, SWAP_HAS_CACHE);
2290 }
2291
2292 /*
2293  * swap_lock prevents swap_map being freed. Don't grab an extra
2294  * reference on the swaphandle, it doesn't matter if it becomes unused.
2295  */
2296 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2297 {
2298         struct swap_info_struct *si;
2299         int our_page_cluster = page_cluster;
2300         pgoff_t target, toff;
2301         pgoff_t base, end;
2302         int nr_pages = 0;
2303
2304         if (!our_page_cluster)  /* no readahead */
2305                 return 0;
2306
2307         si = swap_info[swp_type(entry)];
2308         target = swp_offset(entry);
2309         base = (target >> our_page_cluster) << our_page_cluster;
2310         end = base + (1 << our_page_cluster);
2311         if (!base)              /* first page is swap header */
2312                 base++;
2313
2314         spin_lock(&swap_lock);
2315         if (end > si->max)      /* don't go beyond end of map */
2316                 end = si->max;
2317
2318         /* Count contiguous allocated slots above our target */
2319         for (toff = target; ++toff < end; nr_pages++) {
2320                 /* Don't read in free or bad pages */
2321                 if (!si->swap_map[toff])
2322                         break;
2323                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2324                         break;
2325         }
2326         /* Count contiguous allocated slots below our target */
2327         for (toff = target; --toff >= base; nr_pages++) {
2328                 /* Don't read in free or bad pages */
2329                 if (!si->swap_map[toff])
2330                         break;
2331                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2332                         break;
2333         }
2334         spin_unlock(&swap_lock);
2335
2336         /*
2337          * Indicate starting offset, and return number of pages to get:
2338          * if only 1, say 0, since there's then no readahead to be done.
2339          */
2340         *offset = ++toff;
2341         return nr_pages? ++nr_pages: 0;
2342 }
2343
2344 /*
2345  * add_swap_count_continuation - called when a swap count is duplicated
2346  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2347  * page of the original vmalloc'ed swap_map, to hold the continuation count
2348  * (for that entry and for its neighbouring PAGE_SIZE swap entries).  Called
2349  * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2350  *
2351  * These continuation pages are seldom referenced: the common paths all work
2352  * on the original swap_map, only referring to a continuation page when the
2353  * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2354  *
2355  * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2356  * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2357  * can be called after dropping locks.
2358  */
2359 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2360 {
2361         struct swap_info_struct *si;
2362         struct page *head;
2363         struct page *page;
2364         struct page *list_page;
2365         pgoff_t offset;
2366         unsigned char count;
2367
2368         /*
2369          * When debugging, it's easier to use __GFP_ZERO here; but it's better
2370          * for latency not to zero a page while GFP_ATOMIC and holding locks.
2371          */
2372         page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2373
2374         si = swap_info_get(entry);
2375         if (!si) {
2376                 /*
2377                  * An acceptable race has occurred since the failing
2378                  * __swap_duplicate(): the swap entry has been freed,
2379                  * perhaps even the whole swap_map cleared for swapoff.
2380                  */
2381                 goto outer;
2382         }
2383
2384         offset = swp_offset(entry);
2385         count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2386
2387         if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2388                 /*
2389                  * The higher the swap count, the more likely it is that tasks
2390                  * will race to add swap count continuation: we need to avoid
2391                  * over-provisioning.
2392                  */
2393                 goto out;
2394         }
2395
2396         if (!page) {
2397                 spin_unlock(&swap_lock);
2398                 return -ENOMEM;
2399         }
2400
2401         /*
2402          * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2403          * no architecture is using highmem pages for kernel pagetables: so it
2404          * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2405          */
2406         head = vmalloc_to_page(si->swap_map + offset);
2407         offset &= ~PAGE_MASK;
2408
2409         /*
2410          * Page allocation does not initialize the page's lru field,
2411          * but it does always reset its private field.
2412          */
2413         if (!page_private(head)) {
2414                 BUG_ON(count & COUNT_CONTINUED);
2415                 INIT_LIST_HEAD(&head->lru);
2416                 set_page_private(head, SWP_CONTINUED);
2417                 si->flags |= SWP_CONTINUED;
2418         }
2419
2420         list_for_each_entry(list_page, &head->lru, lru) {
2421                 unsigned char *map;
2422
2423                 /*
2424                  * If the previous map said no continuation, but we've found
2425                  * a continuation page, free our allocation and use this one.
2426                  */
2427                 if (!(count & COUNT_CONTINUED))
2428                         goto out;
2429
2430                 map = kmap_atomic(list_page, KM_USER0) + offset;
2431                 count = *map;
2432                 kunmap_atomic(map, KM_USER0);
2433
2434                 /*
2435                  * If this continuation count now has some space in it,
2436                  * free our allocation and use this one.
2437                  */
2438                 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2439                         goto out;
2440         }
2441
2442         list_add_tail(&page->lru, &head->lru);
2443         page = NULL;                    /* now it's attached, don't free it */
2444 out:
2445         spin_unlock(&swap_lock);
2446 outer:
2447         if (page)
2448                 __free_page(page);
2449         return 0;
2450 }
2451
2452 /*
2453  * swap_count_continued - when the original swap_map count is incremented
2454  * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2455  * into, carry if so, or else fail until a new continuation page is allocated;
2456  * when the original swap_map count is decremented from 0 with continuation,
2457  * borrow from the continuation and report whether it still holds more.
2458  * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2459  */
2460 static bool swap_count_continued(struct swap_info_struct *si,
2461                                  pgoff_t offset, unsigned char count)
2462 {
2463         struct page *head;
2464         struct page *page;
2465         unsigned char *map;
2466
2467         head = vmalloc_to_page(si->swap_map + offset);
2468         if (page_private(head) != SWP_CONTINUED) {
2469                 BUG_ON(count & COUNT_CONTINUED);
2470                 return false;           /* need to add count continuation */
2471         }
2472
2473         offset &= ~PAGE_MASK;
2474         page = list_entry(head->lru.next, struct page, lru);
2475         map = kmap_atomic(page, KM_USER0) + offset;
2476
2477         if (count == SWAP_MAP_MAX)      /* initial increment from swap_map */
2478                 goto init_map;          /* jump over SWAP_CONT_MAX checks */
2479
2480         if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2481                 /*
2482                  * Think of how you add 1 to 999
2483                  */
2484                 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2485                         kunmap_atomic(map, KM_USER0);
2486                         page = list_entry(page->lru.next, struct page, lru);
2487                         BUG_ON(page == head);
2488                         map = kmap_atomic(page, KM_USER0) + offset;
2489                 }
2490                 if (*map == SWAP_CONT_MAX) {
2491                         kunmap_atomic(map, KM_USER0);
2492                         page = list_entry(page->lru.next, struct page, lru);
2493                         if (page == head)
2494                                 return false;   /* add count continuation */
2495                         map = kmap_atomic(page, KM_USER0) + offset;
2496 init_map:               *map = 0;               /* we didn't zero the page */
2497                 }
2498                 *map += 1;
2499                 kunmap_atomic(map, KM_USER0);
2500                 page = list_entry(page->lru.prev, struct page, lru);
2501                 while (page != head) {
2502                         map = kmap_atomic(page, KM_USER0) + offset;
2503                         *map = COUNT_CONTINUED;
2504                         kunmap_atomic(map, KM_USER0);
2505                         page = list_entry(page->lru.prev, struct page, lru);
2506                 }
2507                 return true;                    /* incremented */
2508
2509         } else {                                /* decrementing */
2510                 /*
2511                  * Think of how you subtract 1 from 1000
2512                  */
2513                 BUG_ON(count != COUNT_CONTINUED);
2514                 while (*map == COUNT_CONTINUED) {
2515                         kunmap_atomic(map, KM_USER0);
2516                         page = list_entry(page->lru.next, struct page, lru);
2517                         BUG_ON(page == head);
2518                         map = kmap_atomic(page, KM_USER0) + offset;
2519                 }
2520                 BUG_ON(*map == 0);
2521                 *map -= 1;
2522                 if (*map == 0)
2523                         count = 0;
2524                 kunmap_atomic(map, KM_USER0);
2525                 page = list_entry(page->lru.prev, struct page, lru);
2526                 while (page != head) {
2527                         map = kmap_atomic(page, KM_USER0) + offset;
2528                         *map = SWAP_CONT_MAX | count;
2529                         count = COUNT_CONTINUED;
2530                         kunmap_atomic(map, KM_USER0);
2531                         page = list_entry(page->lru.prev, struct page, lru);
2532                 }
2533                 return count == COUNT_CONTINUED;
2534         }
2535 }
2536
2537 /*
2538  * free_swap_count_continuations - swapoff free all the continuation pages
2539  * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2540  */
2541 static void free_swap_count_continuations(struct swap_info_struct *si)
2542 {
2543         pgoff_t offset;
2544
2545         for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2546                 struct page *head;
2547                 head = vmalloc_to_page(si->swap_map + offset);
2548                 if (page_private(head)) {
2549                         struct list_head *this, *next;
2550                         list_for_each_safe(this, next, &head->lru) {
2551                                 struct page *page;
2552                                 page = list_entry(this, struct page, lru);
2553                                 list_del(this);
2554                                 __free_page(page);
2555                         }
2556                 }
2557         }
2558 }