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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6
[mv-sheeva.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/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/random.h>
20 #include <linux/writeback.h>
21 #include <linux/proc_fs.h>
22 #include <linux/seq_file.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/security.h>
28 #include <linux/backing-dev.h>
29 #include <linux/mutex.h>
30 #include <linux/capability.h>
31 #include <linux/syscalls.h>
32 #include <linux/memcontrol.h>
33
34 #include <asm/pgtable.h>
35 #include <asm/tlbflush.h>
36 #include <linux/swapops.h>
37 #include <linux/page_cgroup.h>
38
39 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
40                                  unsigned char);
41 static void free_swap_count_continuations(struct swap_info_struct *);
42 static sector_t map_swap_entry(swp_entry_t, struct block_device**);
43
44 static DEFINE_SPINLOCK(swap_lock);
45 static unsigned int nr_swapfiles;
46 long nr_swap_pages;
47 long total_swap_pages;
48 static int least_priority;
49
50 static const char Bad_file[] = "Bad swap file entry ";
51 static const char Unused_file[] = "Unused swap file entry ";
52 static const char Bad_offset[] = "Bad swap offset entry ";
53 static const char Unused_offset[] = "Unused swap offset entry ";
54
55 static struct swap_list_t swap_list = {-1, -1};
56
57 static struct swap_info_struct *swap_info[MAX_SWAPFILES];
58
59 static DEFINE_MUTEX(swapon_mutex);
60
61 static inline unsigned char swap_count(unsigned char ent)
62 {
63         return ent & ~SWAP_HAS_CACHE;   /* may include SWAP_HAS_CONT flag */
64 }
65
66 /* returns 1 if swap entry is freed */
67 static int
68 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
69 {
70         swp_entry_t entry = swp_entry(si->type, offset);
71         struct page *page;
72         int ret = 0;
73
74         page = find_get_page(&swapper_space, entry.val);
75         if (!page)
76                 return 0;
77         /*
78          * This function is called from scan_swap_map() and it's called
79          * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
80          * We have to use trylock for avoiding deadlock. This is a special
81          * case and you should use try_to_free_swap() with explicit lock_page()
82          * in usual operations.
83          */
84         if (trylock_page(page)) {
85                 ret = try_to_free_swap(page);
86                 unlock_page(page);
87         }
88         page_cache_release(page);
89         return ret;
90 }
91
92 /*
93  * We need this because the bdev->unplug_fn can sleep and we cannot
94  * hold swap_lock while calling the unplug_fn. And swap_lock
95  * cannot be turned into a mutex.
96  */
97 static DECLARE_RWSEM(swap_unplug_sem);
98
99 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
100 {
101         swp_entry_t entry;
102
103         down_read(&swap_unplug_sem);
104         entry.val = page_private(page);
105         if (PageSwapCache(page)) {
106                 struct block_device *bdev = swap_info[swp_type(entry)]->bdev;
107                 struct backing_dev_info *bdi;
108
109                 /*
110                  * If the page is removed from swapcache from under us (with a
111                  * racy try_to_unuse/swapoff) we need an additional reference
112                  * count to avoid reading garbage from page_private(page) above.
113                  * If the WARN_ON triggers during a swapoff it maybe the race
114                  * condition and it's harmless. However if it triggers without
115                  * swapoff it signals a problem.
116                  */
117                 WARN_ON(page_count(page) <= 1);
118
119                 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
120                 blk_run_backing_dev(bdi, page);
121         }
122         up_read(&swap_unplug_sem);
123 }
124
125 /*
126  * swapon tell device that all the old swap contents can be discarded,
127  * to allow the swap device to optimize its wear-levelling.
128  */
129 static int discard_swap(struct swap_info_struct *si)
130 {
131         struct swap_extent *se;
132         sector_t start_block;
133         sector_t nr_blocks;
134         int err = 0;
135
136         /* Do not discard the swap header page! */
137         se = &si->first_swap_extent;
138         start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
139         nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
140         if (nr_blocks) {
141                 err = blkdev_issue_discard(si->bdev, start_block,
142                                 nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT);
143                 if (err)
144                         return err;
145                 cond_resched();
146         }
147
148         list_for_each_entry(se, &si->first_swap_extent.list, list) {
149                 start_block = se->start_block << (PAGE_SHIFT - 9);
150                 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
151
152                 err = blkdev_issue_discard(si->bdev, start_block,
153                                 nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT);
154                 if (err)
155                         break;
156
157                 cond_resched();
158         }
159         return err;             /* That will often be -EOPNOTSUPP */
160 }
161
162 /*
163  * swap allocation tell device that a cluster of swap can now be discarded,
164  * to allow the swap device to optimize its wear-levelling.
165  */
166 static void discard_swap_cluster(struct swap_info_struct *si,
167                                  pgoff_t start_page, pgoff_t nr_pages)
168 {
169         struct swap_extent *se = si->curr_swap_extent;
170         int found_extent = 0;
171
172         while (nr_pages) {
173                 struct list_head *lh;
174
175                 if (se->start_page <= start_page &&
176                     start_page < se->start_page + se->nr_pages) {
177                         pgoff_t offset = start_page - se->start_page;
178                         sector_t start_block = se->start_block + offset;
179                         sector_t nr_blocks = se->nr_pages - offset;
180
181                         if (nr_blocks > nr_pages)
182                                 nr_blocks = nr_pages;
183                         start_page += nr_blocks;
184                         nr_pages -= nr_blocks;
185
186                         if (!found_extent++)
187                                 si->curr_swap_extent = se;
188
189                         start_block <<= PAGE_SHIFT - 9;
190                         nr_blocks <<= PAGE_SHIFT - 9;
191                         if (blkdev_issue_discard(si->bdev, start_block,
192                                     nr_blocks, GFP_NOIO, BLKDEV_IFL_WAIT))
193                                 break;
194                 }
195
196                 lh = se->list.next;
197                 se = list_entry(lh, struct swap_extent, list);
198         }
199 }
200
201 static int wait_for_discard(void *word)
202 {
203         schedule();
204         return 0;
205 }
206
207 #define SWAPFILE_CLUSTER        256
208 #define LATENCY_LIMIT           256
209
210 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
211                                           unsigned char usage)
212 {
213         unsigned long offset;
214         unsigned long scan_base;
215         unsigned long last_in_cluster = 0;
216         int latency_ration = LATENCY_LIMIT;
217         int found_free_cluster = 0;
218
219         /*
220          * We try to cluster swap pages by allocating them sequentially
221          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
222          * way, however, we resort to first-free allocation, starting
223          * a new cluster.  This prevents us from scattering swap pages
224          * all over the entire swap partition, so that we reduce
225          * overall disk seek times between swap pages.  -- sct
226          * But we do now try to find an empty cluster.  -Andrea
227          * And we let swap pages go all over an SSD partition.  Hugh
228          */
229
230         si->flags += SWP_SCANNING;
231         scan_base = offset = si->cluster_next;
232
233         if (unlikely(!si->cluster_nr--)) {
234                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
235                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
236                         goto checks;
237                 }
238                 if (si->flags & SWP_DISCARDABLE) {
239                         /*
240                          * Start range check on racing allocations, in case
241                          * they overlap the cluster we eventually decide on
242                          * (we scan without swap_lock to allow preemption).
243                          * It's hardly conceivable that cluster_nr could be
244                          * wrapped during our scan, but don't depend on it.
245                          */
246                         if (si->lowest_alloc)
247                                 goto checks;
248                         si->lowest_alloc = si->max;
249                         si->highest_alloc = 0;
250                 }
251                 spin_unlock(&swap_lock);
252
253                 /*
254                  * If seek is expensive, start searching for new cluster from
255                  * start of partition, to minimize the span of allocated swap.
256                  * But if seek is cheap, search from our current position, so
257                  * that swap is allocated from all over the partition: if the
258                  * Flash Translation Layer only remaps within limited zones,
259                  * we don't want to wear out the first zone too quickly.
260                  */
261                 if (!(si->flags & SWP_SOLIDSTATE))
262                         scan_base = offset = si->lowest_bit;
263                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
264
265                 /* Locate the first empty (unaligned) cluster */
266                 for (; last_in_cluster <= si->highest_bit; offset++) {
267                         if (si->swap_map[offset])
268                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
269                         else if (offset == last_in_cluster) {
270                                 spin_lock(&swap_lock);
271                                 offset -= SWAPFILE_CLUSTER - 1;
272                                 si->cluster_next = offset;
273                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
274                                 found_free_cluster = 1;
275                                 goto checks;
276                         }
277                         if (unlikely(--latency_ration < 0)) {
278                                 cond_resched();
279                                 latency_ration = LATENCY_LIMIT;
280                         }
281                 }
282
283                 offset = si->lowest_bit;
284                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
285
286                 /* Locate the first empty (unaligned) cluster */
287                 for (; last_in_cluster < scan_base; offset++) {
288                         if (si->swap_map[offset])
289                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
290                         else if (offset == last_in_cluster) {
291                                 spin_lock(&swap_lock);
292                                 offset -= SWAPFILE_CLUSTER - 1;
293                                 si->cluster_next = offset;
294                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
295                                 found_free_cluster = 1;
296                                 goto checks;
297                         }
298                         if (unlikely(--latency_ration < 0)) {
299                                 cond_resched();
300                                 latency_ration = LATENCY_LIMIT;
301                         }
302                 }
303
304                 offset = scan_base;
305                 spin_lock(&swap_lock);
306                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
307                 si->lowest_alloc = 0;
308         }
309
310 checks:
311         if (!(si->flags & SWP_WRITEOK))
312                 goto no_page;
313         if (!si->highest_bit)
314                 goto no_page;
315         if (offset > si->highest_bit)
316                 scan_base = offset = si->lowest_bit;
317
318         /* reuse swap entry of cache-only swap if not busy. */
319         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
320                 int swap_was_freed;
321                 spin_unlock(&swap_lock);
322                 swap_was_freed = __try_to_reclaim_swap(si, offset);
323                 spin_lock(&swap_lock);
324                 /* entry was freed successfully, try to use this again */
325                 if (swap_was_freed)
326                         goto checks;
327                 goto scan; /* check next one */
328         }
329
330         if (si->swap_map[offset])
331                 goto scan;
332
333         if (offset == si->lowest_bit)
334                 si->lowest_bit++;
335         if (offset == si->highest_bit)
336                 si->highest_bit--;
337         si->inuse_pages++;
338         if (si->inuse_pages == si->pages) {
339                 si->lowest_bit = si->max;
340                 si->highest_bit = 0;
341         }
342         si->swap_map[offset] = usage;
343         si->cluster_next = offset + 1;
344         si->flags -= SWP_SCANNING;
345
346         if (si->lowest_alloc) {
347                 /*
348                  * Only set when SWP_DISCARDABLE, and there's a scan
349                  * for a free cluster in progress or just completed.
350                  */
351                 if (found_free_cluster) {
352                         /*
353                          * To optimize wear-levelling, discard the
354                          * old data of the cluster, taking care not to
355                          * discard any of its pages that have already
356                          * been allocated by racing tasks (offset has
357                          * already stepped over any at the beginning).
358                          */
359                         if (offset < si->highest_alloc &&
360                             si->lowest_alloc <= last_in_cluster)
361                                 last_in_cluster = si->lowest_alloc - 1;
362                         si->flags |= SWP_DISCARDING;
363                         spin_unlock(&swap_lock);
364
365                         if (offset < last_in_cluster)
366                                 discard_swap_cluster(si, offset,
367                                         last_in_cluster - offset + 1);
368
369                         spin_lock(&swap_lock);
370                         si->lowest_alloc = 0;
371                         si->flags &= ~SWP_DISCARDING;
372
373                         smp_mb();       /* wake_up_bit advises this */
374                         wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
375
376                 } else if (si->flags & SWP_DISCARDING) {
377                         /*
378                          * Delay using pages allocated by racing tasks
379                          * until the whole discard has been issued. We
380                          * could defer that delay until swap_writepage,
381                          * but it's easier to keep this self-contained.
382                          */
383                         spin_unlock(&swap_lock);
384                         wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
385                                 wait_for_discard, TASK_UNINTERRUPTIBLE);
386                         spin_lock(&swap_lock);
387                 } else {
388                         /*
389                          * Note pages allocated by racing tasks while
390                          * scan for a free cluster is in progress, so
391                          * that its final discard can exclude them.
392                          */
393                         if (offset < si->lowest_alloc)
394                                 si->lowest_alloc = offset;
395                         if (offset > si->highest_alloc)
396                                 si->highest_alloc = offset;
397                 }
398         }
399         return offset;
400
401 scan:
402         spin_unlock(&swap_lock);
403         while (++offset <= si->highest_bit) {
404                 if (!si->swap_map[offset]) {
405                         spin_lock(&swap_lock);
406                         goto checks;
407                 }
408                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
409                         spin_lock(&swap_lock);
410                         goto checks;
411                 }
412                 if (unlikely(--latency_ration < 0)) {
413                         cond_resched();
414                         latency_ration = LATENCY_LIMIT;
415                 }
416         }
417         offset = si->lowest_bit;
418         while (++offset < scan_base) {
419                 if (!si->swap_map[offset]) {
420                         spin_lock(&swap_lock);
421                         goto checks;
422                 }
423                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
424                         spin_lock(&swap_lock);
425                         goto checks;
426                 }
427                 if (unlikely(--latency_ration < 0)) {
428                         cond_resched();
429                         latency_ration = LATENCY_LIMIT;
430                 }
431         }
432         spin_lock(&swap_lock);
433
434 no_page:
435         si->flags -= SWP_SCANNING;
436         return 0;
437 }
438
439 swp_entry_t get_swap_page(void)
440 {
441         struct swap_info_struct *si;
442         pgoff_t offset;
443         int type, next;
444         int wrapped = 0;
445
446         spin_lock(&swap_lock);
447         if (nr_swap_pages <= 0)
448                 goto noswap;
449         nr_swap_pages--;
450
451         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
452                 si = swap_info[type];
453                 next = si->next;
454                 if (next < 0 ||
455                     (!wrapped && si->prio != swap_info[next]->prio)) {
456                         next = swap_list.head;
457                         wrapped++;
458                 }
459
460                 if (!si->highest_bit)
461                         continue;
462                 if (!(si->flags & SWP_WRITEOK))
463                         continue;
464
465                 swap_list.next = next;
466                 /* This is called for allocating swap entry for cache */
467                 offset = scan_swap_map(si, SWAP_HAS_CACHE);
468                 if (offset) {
469                         spin_unlock(&swap_lock);
470                         return swp_entry(type, offset);
471                 }
472                 next = swap_list.next;
473         }
474
475         nr_swap_pages++;
476 noswap:
477         spin_unlock(&swap_lock);
478         return (swp_entry_t) {0};
479 }
480
481 /* The only caller of this function is now susupend routine */
482 swp_entry_t get_swap_page_of_type(int type)
483 {
484         struct swap_info_struct *si;
485         pgoff_t offset;
486
487         spin_lock(&swap_lock);
488         si = swap_info[type];
489         if (si && (si->flags & SWP_WRITEOK)) {
490                 nr_swap_pages--;
491                 /* This is called for allocating swap entry, not cache */
492                 offset = scan_swap_map(si, 1);
493                 if (offset) {
494                         spin_unlock(&swap_lock);
495                         return swp_entry(type, offset);
496                 }
497                 nr_swap_pages++;
498         }
499         spin_unlock(&swap_lock);
500         return (swp_entry_t) {0};
501 }
502
503 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
504 {
505         struct swap_info_struct *p;
506         unsigned long offset, type;
507
508         if (!entry.val)
509                 goto out;
510         type = swp_type(entry);
511         if (type >= nr_swapfiles)
512                 goto bad_nofile;
513         p = swap_info[type];
514         if (!(p->flags & SWP_USED))
515                 goto bad_device;
516         offset = swp_offset(entry);
517         if (offset >= p->max)
518                 goto bad_offset;
519         if (!p->swap_map[offset])
520                 goto bad_free;
521         spin_lock(&swap_lock);
522         return p;
523
524 bad_free:
525         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
526         goto out;
527 bad_offset:
528         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
529         goto out;
530 bad_device:
531         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
532         goto out;
533 bad_nofile:
534         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
535 out:
536         return NULL;
537 }
538
539 static unsigned char swap_entry_free(struct swap_info_struct *p,
540                                      swp_entry_t entry, unsigned char usage)
541 {
542         unsigned long offset = swp_offset(entry);
543         unsigned char count;
544         unsigned char has_cache;
545
546         count = p->swap_map[offset];
547         has_cache = count & SWAP_HAS_CACHE;
548         count &= ~SWAP_HAS_CACHE;
549
550         if (usage == SWAP_HAS_CACHE) {
551                 VM_BUG_ON(!has_cache);
552                 has_cache = 0;
553         } else if (count == SWAP_MAP_SHMEM) {
554                 /*
555                  * Or we could insist on shmem.c using a special
556                  * swap_shmem_free() and free_shmem_swap_and_cache()...
557                  */
558                 count = 0;
559         } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
560                 if (count == COUNT_CONTINUED) {
561                         if (swap_count_continued(p, offset, count))
562                                 count = SWAP_MAP_MAX | COUNT_CONTINUED;
563                         else
564                                 count = SWAP_MAP_MAX;
565                 } else
566                         count--;
567         }
568
569         if (!count)
570                 mem_cgroup_uncharge_swap(entry);
571
572         usage = count | has_cache;
573         p->swap_map[offset] = usage;
574
575         /* free if no reference */
576         if (!usage) {
577                 struct gendisk *disk = p->bdev->bd_disk;
578                 if (offset < p->lowest_bit)
579                         p->lowest_bit = offset;
580                 if (offset > p->highest_bit)
581                         p->highest_bit = offset;
582                 if (swap_list.next >= 0 &&
583                     p->prio > swap_info[swap_list.next]->prio)
584                         swap_list.next = p->type;
585                 nr_swap_pages++;
586                 p->inuse_pages--;
587                 if ((p->flags & SWP_BLKDEV) &&
588                                 disk->fops->swap_slot_free_notify)
589                         disk->fops->swap_slot_free_notify(p->bdev, offset);
590         }
591
592         return usage;
593 }
594
595 /*
596  * Caller has made sure that the swapdevice corresponding to entry
597  * is still around or has not been recycled.
598  */
599 void swap_free(swp_entry_t entry)
600 {
601         struct swap_info_struct *p;
602
603         p = swap_info_get(entry);
604         if (p) {
605                 swap_entry_free(p, entry, 1);
606                 spin_unlock(&swap_lock);
607         }
608 }
609
610 /*
611  * Called after dropping swapcache to decrease refcnt to swap entries.
612  */
613 void swapcache_free(swp_entry_t entry, struct page *page)
614 {
615         struct swap_info_struct *p;
616         unsigned char count;
617
618         p = swap_info_get(entry);
619         if (p) {
620                 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
621                 if (page)
622                         mem_cgroup_uncharge_swapcache(page, entry, count != 0);
623                 spin_unlock(&swap_lock);
624         }
625 }
626
627 /*
628  * How many references to page are currently swapped out?
629  * This does not give an exact answer when swap count is continued,
630  * but does include the high COUNT_CONTINUED flag to allow for that.
631  */
632 static inline int page_swapcount(struct page *page)
633 {
634         int count = 0;
635         struct swap_info_struct *p;
636         swp_entry_t entry;
637
638         entry.val = page_private(page);
639         p = swap_info_get(entry);
640         if (p) {
641                 count = swap_count(p->swap_map[swp_offset(entry)]);
642                 spin_unlock(&swap_lock);
643         }
644         return count;
645 }
646
647 /*
648  * We can write to an anon page without COW if there are no other references
649  * to it.  And as a side-effect, free up its swap: because the old content
650  * on disk will never be read, and seeking back there to write new content
651  * later would only waste time away from clustering.
652  */
653 int reuse_swap_page(struct page *page)
654 {
655         int count;
656
657         VM_BUG_ON(!PageLocked(page));
658         if (unlikely(PageKsm(page)))
659                 return 0;
660         count = page_mapcount(page);
661         if (count <= 1 && PageSwapCache(page)) {
662                 count += page_swapcount(page);
663                 if (count == 1 && !PageWriteback(page)) {
664                         delete_from_swap_cache(page);
665                         SetPageDirty(page);
666                 }
667         }
668         return count <= 1;
669 }
670
671 /*
672  * If swap is getting full, or if there are no more mappings of this page,
673  * then try_to_free_swap is called to free its swap space.
674  */
675 int try_to_free_swap(struct page *page)
676 {
677         VM_BUG_ON(!PageLocked(page));
678
679         if (!PageSwapCache(page))
680                 return 0;
681         if (PageWriteback(page))
682                 return 0;
683         if (page_swapcount(page))
684                 return 0;
685
686         /*
687          * Once hibernation has begun to create its image of memory,
688          * there's a danger that one of the calls to try_to_free_swap()
689          * - most probably a call from __try_to_reclaim_swap() while
690          * hibernation is allocating its own swap pages for the image,
691          * but conceivably even a call from memory reclaim - will free
692          * the swap from a page which has already been recorded in the
693          * image as a clean swapcache page, and then reuse its swap for
694          * another page of the image.  On waking from hibernation, the
695          * original page might be freed under memory pressure, then
696          * later read back in from swap, now with the wrong data.
697          *
698          * Hibernation clears bits from gfp_allowed_mask to prevent
699          * memory reclaim from writing to disk, so check that here.
700          */
701         if (!(gfp_allowed_mask & __GFP_IO))
702                 return 0;
703
704         delete_from_swap_cache(page);
705         SetPageDirty(page);
706         return 1;
707 }
708
709 /*
710  * Free the swap entry like above, but also try to
711  * free the page cache entry if it is the last user.
712  */
713 int free_swap_and_cache(swp_entry_t entry)
714 {
715         struct swap_info_struct *p;
716         struct page *page = NULL;
717
718         if (non_swap_entry(entry))
719                 return 1;
720
721         p = swap_info_get(entry);
722         if (p) {
723                 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
724                         page = find_get_page(&swapper_space, entry.val);
725                         if (page && !trylock_page(page)) {
726                                 page_cache_release(page);
727                                 page = NULL;
728                         }
729                 }
730                 spin_unlock(&swap_lock);
731         }
732         if (page) {
733                 /*
734                  * Not mapped elsewhere, or swap space full? Free it!
735                  * Also recheck PageSwapCache now page is locked (above).
736                  */
737                 if (PageSwapCache(page) && !PageWriteback(page) &&
738                                 (!page_mapped(page) || vm_swap_full())) {
739                         delete_from_swap_cache(page);
740                         SetPageDirty(page);
741                 }
742                 unlock_page(page);
743                 page_cache_release(page);
744         }
745         return p != NULL;
746 }
747
748 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
749 /**
750  * mem_cgroup_count_swap_user - count the user of a swap entry
751  * @ent: the swap entry to be checked
752  * @pagep: the pointer for the swap cache page of the entry to be stored
753  *
754  * Returns the number of the user of the swap entry. The number is valid only
755  * for swaps of anonymous pages.
756  * If the entry is found on swap cache, the page is stored to pagep with
757  * refcount of it being incremented.
758  */
759 int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
760 {
761         struct page *page;
762         struct swap_info_struct *p;
763         int count = 0;
764
765         page = find_get_page(&swapper_space, ent.val);
766         if (page)
767                 count += page_mapcount(page);
768         p = swap_info_get(ent);
769         if (p) {
770                 count += swap_count(p->swap_map[swp_offset(ent)]);
771                 spin_unlock(&swap_lock);
772         }
773
774         *pagep = page;
775         return count;
776 }
777 #endif
778
779 #ifdef CONFIG_HIBERNATION
780 /*
781  * Find the swap type that corresponds to given device (if any).
782  *
783  * @offset - number of the PAGE_SIZE-sized block of the device, starting
784  * from 0, in which the swap header is expected to be located.
785  *
786  * This is needed for the suspend to disk (aka swsusp).
787  */
788 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
789 {
790         struct block_device *bdev = NULL;
791         int type;
792
793         if (device)
794                 bdev = bdget(device);
795
796         spin_lock(&swap_lock);
797         for (type = 0; type < nr_swapfiles; type++) {
798                 struct swap_info_struct *sis = swap_info[type];
799
800                 if (!(sis->flags & SWP_WRITEOK))
801                         continue;
802
803                 if (!bdev) {
804                         if (bdev_p)
805                                 *bdev_p = bdgrab(sis->bdev);
806
807                         spin_unlock(&swap_lock);
808                         return type;
809                 }
810                 if (bdev == sis->bdev) {
811                         struct swap_extent *se = &sis->first_swap_extent;
812
813                         if (se->start_block == offset) {
814                                 if (bdev_p)
815                                         *bdev_p = bdgrab(sis->bdev);
816
817                                 spin_unlock(&swap_lock);
818                                 bdput(bdev);
819                                 return type;
820                         }
821                 }
822         }
823         spin_unlock(&swap_lock);
824         if (bdev)
825                 bdput(bdev);
826
827         return -ENODEV;
828 }
829
830 /*
831  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
832  * corresponding to given index in swap_info (swap type).
833  */
834 sector_t swapdev_block(int type, pgoff_t offset)
835 {
836         struct block_device *bdev;
837
838         if ((unsigned int)type >= nr_swapfiles)
839                 return 0;
840         if (!(swap_info[type]->flags & SWP_WRITEOK))
841                 return 0;
842         return map_swap_entry(swp_entry(type, offset), &bdev);
843 }
844
845 /*
846  * Return either the total number of swap pages of given type, or the number
847  * of free pages of that type (depending on @free)
848  *
849  * This is needed for software suspend
850  */
851 unsigned int count_swap_pages(int type, int free)
852 {
853         unsigned int n = 0;
854
855         spin_lock(&swap_lock);
856         if ((unsigned int)type < nr_swapfiles) {
857                 struct swap_info_struct *sis = swap_info[type];
858
859                 if (sis->flags & SWP_WRITEOK) {
860                         n = sis->pages;
861                         if (free)
862                                 n -= sis->inuse_pages;
863                 }
864         }
865         spin_unlock(&swap_lock);
866         return n;
867 }
868 #endif /* CONFIG_HIBERNATION */
869
870 /*
871  * No need to decide whether this PTE shares the swap entry with others,
872  * just let do_wp_page work it out if a write is requested later - to
873  * force COW, vm_page_prot omits write permission from any private vma.
874  */
875 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
876                 unsigned long addr, swp_entry_t entry, struct page *page)
877 {
878         struct mem_cgroup *ptr = NULL;
879         spinlock_t *ptl;
880         pte_t *pte;
881         int ret = 1;
882
883         if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
884                 ret = -ENOMEM;
885                 goto out_nolock;
886         }
887
888         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
889         if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
890                 if (ret > 0)
891                         mem_cgroup_cancel_charge_swapin(ptr);
892                 ret = 0;
893                 goto out;
894         }
895
896         dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
897         inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
898         get_page(page);
899         set_pte_at(vma->vm_mm, addr, pte,
900                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
901         page_add_anon_rmap(page, vma, addr);
902         mem_cgroup_commit_charge_swapin(page, ptr);
903         swap_free(entry);
904         /*
905          * Move the page to the active list so it is not
906          * immediately swapped out again after swapon.
907          */
908         activate_page(page);
909 out:
910         pte_unmap_unlock(pte, ptl);
911 out_nolock:
912         return ret;
913 }
914
915 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
916                                 unsigned long addr, unsigned long end,
917                                 swp_entry_t entry, struct page *page)
918 {
919         pte_t swp_pte = swp_entry_to_pte(entry);
920         pte_t *pte;
921         int ret = 0;
922
923         /*
924          * We don't actually need pte lock while scanning for swp_pte: since
925          * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
926          * page table while we're scanning; though it could get zapped, and on
927          * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
928          * of unmatched parts which look like swp_pte, so unuse_pte must
929          * recheck under pte lock.  Scanning without pte lock lets it be
930          * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
931          */
932         pte = pte_offset_map(pmd, addr);
933         do {
934                 /*
935                  * swapoff spends a _lot_ of time in this loop!
936                  * Test inline before going to call unuse_pte.
937                  */
938                 if (unlikely(pte_same(*pte, swp_pte))) {
939                         pte_unmap(pte);
940                         ret = unuse_pte(vma, pmd, addr, entry, page);
941                         if (ret)
942                                 goto out;
943                         pte = pte_offset_map(pmd, addr);
944                 }
945         } while (pte++, addr += PAGE_SIZE, addr != end);
946         pte_unmap(pte - 1);
947 out:
948         return ret;
949 }
950
951 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
952                                 unsigned long addr, unsigned long end,
953                                 swp_entry_t entry, struct page *page)
954 {
955         pmd_t *pmd;
956         unsigned long next;
957         int ret;
958
959         pmd = pmd_offset(pud, addr);
960         do {
961                 next = pmd_addr_end(addr, end);
962                 if (pmd_none_or_clear_bad(pmd))
963                         continue;
964                 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
965                 if (ret)
966                         return ret;
967         } while (pmd++, addr = next, addr != end);
968         return 0;
969 }
970
971 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
972                                 unsigned long addr, unsigned long end,
973                                 swp_entry_t entry, struct page *page)
974 {
975         pud_t *pud;
976         unsigned long next;
977         int ret;
978
979         pud = pud_offset(pgd, addr);
980         do {
981                 next = pud_addr_end(addr, end);
982                 if (pud_none_or_clear_bad(pud))
983                         continue;
984                 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
985                 if (ret)
986                         return ret;
987         } while (pud++, addr = next, addr != end);
988         return 0;
989 }
990
991 static int unuse_vma(struct vm_area_struct *vma,
992                                 swp_entry_t entry, struct page *page)
993 {
994         pgd_t *pgd;
995         unsigned long addr, end, next;
996         int ret;
997
998         if (page_anon_vma(page)) {
999                 addr = page_address_in_vma(page, vma);
1000                 if (addr == -EFAULT)
1001                         return 0;
1002                 else
1003                         end = addr + PAGE_SIZE;
1004         } else {
1005                 addr = vma->vm_start;
1006                 end = vma->vm_end;
1007         }
1008
1009         pgd = pgd_offset(vma->vm_mm, addr);
1010         do {
1011                 next = pgd_addr_end(addr, end);
1012                 if (pgd_none_or_clear_bad(pgd))
1013                         continue;
1014                 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1015                 if (ret)
1016                         return ret;
1017         } while (pgd++, addr = next, addr != end);
1018         return 0;
1019 }
1020
1021 static int unuse_mm(struct mm_struct *mm,
1022                                 swp_entry_t entry, struct page *page)
1023 {
1024         struct vm_area_struct *vma;
1025         int ret = 0;
1026
1027         if (!down_read_trylock(&mm->mmap_sem)) {
1028                 /*
1029                  * Activate page so shrink_inactive_list is unlikely to unmap
1030                  * its ptes while lock is dropped, so swapoff can make progress.
1031                  */
1032                 activate_page(page);
1033                 unlock_page(page);
1034                 down_read(&mm->mmap_sem);
1035                 lock_page(page);
1036         }
1037         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1038                 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1039                         break;
1040         }
1041         up_read(&mm->mmap_sem);
1042         return (ret < 0)? ret: 0;
1043 }
1044
1045 /*
1046  * Scan swap_map from current position to next entry still in use.
1047  * Recycle to start on reaching the end, returning 0 when empty.
1048  */
1049 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1050                                         unsigned int prev)
1051 {
1052         unsigned int max = si->max;
1053         unsigned int i = prev;
1054         unsigned char count;
1055
1056         /*
1057          * No need for swap_lock here: we're just looking
1058          * for whether an entry is in use, not modifying it; false
1059          * hits are okay, and sys_swapoff() has already prevented new
1060          * allocations from this area (while holding swap_lock).
1061          */
1062         for (;;) {
1063                 if (++i >= max) {
1064                         if (!prev) {
1065                                 i = 0;
1066                                 break;
1067                         }
1068                         /*
1069                          * No entries in use at top of swap_map,
1070                          * loop back to start and recheck there.
1071                          */
1072                         max = prev + 1;
1073                         prev = 0;
1074                         i = 1;
1075                 }
1076                 count = si->swap_map[i];
1077                 if (count && swap_count(count) != SWAP_MAP_BAD)
1078                         break;
1079         }
1080         return i;
1081 }
1082
1083 /*
1084  * We completely avoid races by reading each swap page in advance,
1085  * and then search for the process using it.  All the necessary
1086  * page table adjustments can then be made atomically.
1087  */
1088 static int try_to_unuse(unsigned int type)
1089 {
1090         struct swap_info_struct *si = swap_info[type];
1091         struct mm_struct *start_mm;
1092         unsigned char *swap_map;
1093         unsigned char swcount;
1094         struct page *page;
1095         swp_entry_t entry;
1096         unsigned int i = 0;
1097         int retval = 0;
1098
1099         /*
1100          * When searching mms for an entry, a good strategy is to
1101          * start at the first mm we freed the previous entry from
1102          * (though actually we don't notice whether we or coincidence
1103          * freed the entry).  Initialize this start_mm with a hold.
1104          *
1105          * A simpler strategy would be to start at the last mm we
1106          * freed the previous entry from; but that would take less
1107          * advantage of mmlist ordering, which clusters forked mms
1108          * together, child after parent.  If we race with dup_mmap(), we
1109          * prefer to resolve parent before child, lest we miss entries
1110          * duplicated after we scanned child: using last mm would invert
1111          * that.
1112          */
1113         start_mm = &init_mm;
1114         atomic_inc(&init_mm.mm_users);
1115
1116         /*
1117          * Keep on scanning until all entries have gone.  Usually,
1118          * one pass through swap_map is enough, but not necessarily:
1119          * there are races when an instance of an entry might be missed.
1120          */
1121         while ((i = find_next_to_unuse(si, i)) != 0) {
1122                 if (signal_pending(current)) {
1123                         retval = -EINTR;
1124                         break;
1125                 }
1126
1127                 /*
1128                  * Get a page for the entry, using the existing swap
1129                  * cache page if there is one.  Otherwise, get a clean
1130                  * page and read the swap into it.
1131                  */
1132                 swap_map = &si->swap_map[i];
1133                 entry = swp_entry(type, i);
1134                 page = read_swap_cache_async(entry,
1135                                         GFP_HIGHUSER_MOVABLE, NULL, 0);
1136                 if (!page) {
1137                         /*
1138                          * Either swap_duplicate() failed because entry
1139                          * has been freed independently, and will not be
1140                          * reused since sys_swapoff() already disabled
1141                          * allocation from here, or alloc_page() failed.
1142                          */
1143                         if (!*swap_map)
1144                                 continue;
1145                         retval = -ENOMEM;
1146                         break;
1147                 }
1148
1149                 /*
1150                  * Don't hold on to start_mm if it looks like exiting.
1151                  */
1152                 if (atomic_read(&start_mm->mm_users) == 1) {
1153                         mmput(start_mm);
1154                         start_mm = &init_mm;
1155                         atomic_inc(&init_mm.mm_users);
1156                 }
1157
1158                 /*
1159                  * Wait for and lock page.  When do_swap_page races with
1160                  * try_to_unuse, do_swap_page can handle the fault much
1161                  * faster than try_to_unuse can locate the entry.  This
1162                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
1163                  * defer to do_swap_page in such a case - in some tests,
1164                  * do_swap_page and try_to_unuse repeatedly compete.
1165                  */
1166                 wait_on_page_locked(page);
1167                 wait_on_page_writeback(page);
1168                 lock_page(page);
1169                 wait_on_page_writeback(page);
1170
1171                 /*
1172                  * Remove all references to entry.
1173                  */
1174                 swcount = *swap_map;
1175                 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1176                         retval = shmem_unuse(entry, page);
1177                         /* page has already been unlocked and released */
1178                         if (retval < 0)
1179                                 break;
1180                         continue;
1181                 }
1182                 if (swap_count(swcount) && start_mm != &init_mm)
1183                         retval = unuse_mm(start_mm, entry, page);
1184
1185                 if (swap_count(*swap_map)) {
1186                         int set_start_mm = (*swap_map >= swcount);
1187                         struct list_head *p = &start_mm->mmlist;
1188                         struct mm_struct *new_start_mm = start_mm;
1189                         struct mm_struct *prev_mm = start_mm;
1190                         struct mm_struct *mm;
1191
1192                         atomic_inc(&new_start_mm->mm_users);
1193                         atomic_inc(&prev_mm->mm_users);
1194                         spin_lock(&mmlist_lock);
1195                         while (swap_count(*swap_map) && !retval &&
1196                                         (p = p->next) != &start_mm->mmlist) {
1197                                 mm = list_entry(p, struct mm_struct, mmlist);
1198                                 if (!atomic_inc_not_zero(&mm->mm_users))
1199                                         continue;
1200                                 spin_unlock(&mmlist_lock);
1201                                 mmput(prev_mm);
1202                                 prev_mm = mm;
1203
1204                                 cond_resched();
1205
1206                                 swcount = *swap_map;
1207                                 if (!swap_count(swcount)) /* any usage ? */
1208                                         ;
1209                                 else if (mm == &init_mm)
1210                                         set_start_mm = 1;
1211                                 else
1212                                         retval = unuse_mm(mm, entry, page);
1213
1214                                 if (set_start_mm && *swap_map < swcount) {
1215                                         mmput(new_start_mm);
1216                                         atomic_inc(&mm->mm_users);
1217                                         new_start_mm = mm;
1218                                         set_start_mm = 0;
1219                                 }
1220                                 spin_lock(&mmlist_lock);
1221                         }
1222                         spin_unlock(&mmlist_lock);
1223                         mmput(prev_mm);
1224                         mmput(start_mm);
1225                         start_mm = new_start_mm;
1226                 }
1227                 if (retval) {
1228                         unlock_page(page);
1229                         page_cache_release(page);
1230                         break;
1231                 }
1232
1233                 /*
1234                  * If a reference remains (rare), we would like to leave
1235                  * the page in the swap cache; but try_to_unmap could
1236                  * then re-duplicate the entry once we drop page lock,
1237                  * so we might loop indefinitely; also, that page could
1238                  * not be swapped out to other storage meanwhile.  So:
1239                  * delete from cache even if there's another reference,
1240                  * after ensuring that the data has been saved to disk -
1241                  * since if the reference remains (rarer), it will be
1242                  * read from disk into another page.  Splitting into two
1243                  * pages would be incorrect if swap supported "shared
1244                  * private" pages, but they are handled by tmpfs files.
1245                  *
1246                  * Given how unuse_vma() targets one particular offset
1247                  * in an anon_vma, once the anon_vma has been determined,
1248                  * this splitting happens to be just what is needed to
1249                  * handle where KSM pages have been swapped out: re-reading
1250                  * is unnecessarily slow, but we can fix that later on.
1251                  */
1252                 if (swap_count(*swap_map) &&
1253                      PageDirty(page) && PageSwapCache(page)) {
1254                         struct writeback_control wbc = {
1255                                 .sync_mode = WB_SYNC_NONE,
1256                         };
1257
1258                         swap_writepage(page, &wbc);
1259                         lock_page(page);
1260                         wait_on_page_writeback(page);
1261                 }
1262
1263                 /*
1264                  * It is conceivable that a racing task removed this page from
1265                  * swap cache just before we acquired the page lock at the top,
1266                  * or while we dropped it in unuse_mm().  The page might even
1267                  * be back in swap cache on another swap area: that we must not
1268                  * delete, since it may not have been written out to swap yet.
1269                  */
1270                 if (PageSwapCache(page) &&
1271                     likely(page_private(page) == entry.val))
1272                         delete_from_swap_cache(page);
1273
1274                 /*
1275                  * So we could skip searching mms once swap count went
1276                  * to 1, we did not mark any present ptes as dirty: must
1277                  * mark page dirty so shrink_page_list will preserve it.
1278                  */
1279                 SetPageDirty(page);
1280                 unlock_page(page);
1281                 page_cache_release(page);
1282
1283                 /*
1284                  * Make sure that we aren't completely killing
1285                  * interactive performance.
1286                  */
1287                 cond_resched();
1288         }
1289
1290         mmput(start_mm);
1291         return retval;
1292 }
1293
1294 /*
1295  * After a successful try_to_unuse, if no swap is now in use, we know
1296  * we can empty the mmlist.  swap_lock must be held on entry and exit.
1297  * Note that mmlist_lock nests inside swap_lock, and an mm must be
1298  * added to the mmlist just after page_duplicate - before would be racy.
1299  */
1300 static void drain_mmlist(void)
1301 {
1302         struct list_head *p, *next;
1303         unsigned int type;
1304
1305         for (type = 0; type < nr_swapfiles; type++)
1306                 if (swap_info[type]->inuse_pages)
1307                         return;
1308         spin_lock(&mmlist_lock);
1309         list_for_each_safe(p, next, &init_mm.mmlist)
1310                 list_del_init(p);
1311         spin_unlock(&mmlist_lock);
1312 }
1313
1314 /*
1315  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1316  * corresponds to page offset for the specified swap entry.
1317  * Note that the type of this function is sector_t, but it returns page offset
1318  * into the bdev, not sector offset.
1319  */
1320 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1321 {
1322         struct swap_info_struct *sis;
1323         struct swap_extent *start_se;
1324         struct swap_extent *se;
1325         pgoff_t offset;
1326
1327         sis = swap_info[swp_type(entry)];
1328         *bdev = sis->bdev;
1329
1330         offset = swp_offset(entry);
1331         start_se = sis->curr_swap_extent;
1332         se = start_se;
1333
1334         for ( ; ; ) {
1335                 struct list_head *lh;
1336
1337                 if (se->start_page <= offset &&
1338                                 offset < (se->start_page + se->nr_pages)) {
1339                         return se->start_block + (offset - se->start_page);
1340                 }
1341                 lh = se->list.next;
1342                 se = list_entry(lh, struct swap_extent, list);
1343                 sis->curr_swap_extent = se;
1344                 BUG_ON(se == start_se);         /* It *must* be present */
1345         }
1346 }
1347
1348 /*
1349  * Returns the page offset into bdev for the specified page's swap entry.
1350  */
1351 sector_t map_swap_page(struct page *page, struct block_device **bdev)
1352 {
1353         swp_entry_t entry;
1354         entry.val = page_private(page);
1355         return map_swap_entry(entry, bdev);
1356 }
1357
1358 /*
1359  * Free all of a swapdev's extent information
1360  */
1361 static void destroy_swap_extents(struct swap_info_struct *sis)
1362 {
1363         while (!list_empty(&sis->first_swap_extent.list)) {
1364                 struct swap_extent *se;
1365
1366                 se = list_entry(sis->first_swap_extent.list.next,
1367                                 struct swap_extent, list);
1368                 list_del(&se->list);
1369                 kfree(se);
1370         }
1371 }
1372
1373 /*
1374  * Add a block range (and the corresponding page range) into this swapdev's
1375  * extent list.  The extent list is kept sorted in page order.
1376  *
1377  * This function rather assumes that it is called in ascending page order.
1378  */
1379 static int
1380 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1381                 unsigned long nr_pages, sector_t start_block)
1382 {
1383         struct swap_extent *se;
1384         struct swap_extent *new_se;
1385         struct list_head *lh;
1386
1387         if (start_page == 0) {
1388                 se = &sis->first_swap_extent;
1389                 sis->curr_swap_extent = se;
1390                 se->start_page = 0;
1391                 se->nr_pages = nr_pages;
1392                 se->start_block = start_block;
1393                 return 1;
1394         } else {
1395                 lh = sis->first_swap_extent.list.prev;  /* Highest extent */
1396                 se = list_entry(lh, struct swap_extent, list);
1397                 BUG_ON(se->start_page + se->nr_pages != start_page);
1398                 if (se->start_block + se->nr_pages == start_block) {
1399                         /* Merge it */
1400                         se->nr_pages += nr_pages;
1401                         return 0;
1402                 }
1403         }
1404
1405         /*
1406          * No merge.  Insert a new extent, preserving ordering.
1407          */
1408         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1409         if (new_se == NULL)
1410                 return -ENOMEM;
1411         new_se->start_page = start_page;
1412         new_se->nr_pages = nr_pages;
1413         new_se->start_block = start_block;
1414
1415         list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1416         return 1;
1417 }
1418
1419 /*
1420  * A `swap extent' is a simple thing which maps a contiguous range of pages
1421  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1422  * is built at swapon time and is then used at swap_writepage/swap_readpage
1423  * time for locating where on disk a page belongs.
1424  *
1425  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1426  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1427  * swap files identically.
1428  *
1429  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1430  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1431  * swapfiles are handled *identically* after swapon time.
1432  *
1433  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1434  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1435  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1436  * requirements, they are simply tossed out - we will never use those blocks
1437  * for swapping.
1438  *
1439  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1440  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1441  * which will scribble on the fs.
1442  *
1443  * The amount of disk space which a single swap extent represents varies.
1444  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1445  * extents in the list.  To avoid much list walking, we cache the previous
1446  * search location in `curr_swap_extent', and start new searches from there.
1447  * This is extremely effective.  The average number of iterations in
1448  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1449  */
1450 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1451 {
1452         struct inode *inode;
1453         unsigned blocks_per_page;
1454         unsigned long page_no;
1455         unsigned blkbits;
1456         sector_t probe_block;
1457         sector_t last_block;
1458         sector_t lowest_block = -1;
1459         sector_t highest_block = 0;
1460         int nr_extents = 0;
1461         int ret;
1462
1463         inode = sis->swap_file->f_mapping->host;
1464         if (S_ISBLK(inode->i_mode)) {
1465                 ret = add_swap_extent(sis, 0, sis->max, 0);
1466                 *span = sis->pages;
1467                 goto out;
1468         }
1469
1470         blkbits = inode->i_blkbits;
1471         blocks_per_page = PAGE_SIZE >> blkbits;
1472
1473         /*
1474          * Map all the blocks into the extent list.  This code doesn't try
1475          * to be very smart.
1476          */
1477         probe_block = 0;
1478         page_no = 0;
1479         last_block = i_size_read(inode) >> blkbits;
1480         while ((probe_block + blocks_per_page) <= last_block &&
1481                         page_no < sis->max) {
1482                 unsigned block_in_page;
1483                 sector_t first_block;
1484
1485                 first_block = bmap(inode, probe_block);
1486                 if (first_block == 0)
1487                         goto bad_bmap;
1488
1489                 /*
1490                  * It must be PAGE_SIZE aligned on-disk
1491                  */
1492                 if (first_block & (blocks_per_page - 1)) {
1493                         probe_block++;
1494                         goto reprobe;
1495                 }
1496
1497                 for (block_in_page = 1; block_in_page < blocks_per_page;
1498                                         block_in_page++) {
1499                         sector_t block;
1500
1501                         block = bmap(inode, probe_block + block_in_page);
1502                         if (block == 0)
1503                                 goto bad_bmap;
1504                         if (block != first_block + block_in_page) {
1505                                 /* Discontiguity */
1506                                 probe_block++;
1507                                 goto reprobe;
1508                         }
1509                 }
1510
1511                 first_block >>= (PAGE_SHIFT - blkbits);
1512                 if (page_no) {  /* exclude the header page */
1513                         if (first_block < lowest_block)
1514                                 lowest_block = first_block;
1515                         if (first_block > highest_block)
1516                                 highest_block = first_block;
1517                 }
1518
1519                 /*
1520                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1521                  */
1522                 ret = add_swap_extent(sis, page_no, 1, first_block);
1523                 if (ret < 0)
1524                         goto out;
1525                 nr_extents += ret;
1526                 page_no++;
1527                 probe_block += blocks_per_page;
1528 reprobe:
1529                 continue;
1530         }
1531         ret = nr_extents;
1532         *span = 1 + highest_block - lowest_block;
1533         if (page_no == 0)
1534                 page_no = 1;    /* force Empty message */
1535         sis->max = page_no;
1536         sis->pages = page_no - 1;
1537         sis->highest_bit = page_no - 1;
1538 out:
1539         return ret;
1540 bad_bmap:
1541         printk(KERN_ERR "swapon: swapfile has holes\n");
1542         ret = -EINVAL;
1543         goto out;
1544 }
1545
1546 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1547 {
1548         struct swap_info_struct *p = NULL;
1549         unsigned char *swap_map;
1550         struct file *swap_file, *victim;
1551         struct address_space *mapping;
1552         struct inode *inode;
1553         char *pathname;
1554         int i, type, prev;
1555         int err;
1556
1557         if (!capable(CAP_SYS_ADMIN))
1558                 return -EPERM;
1559
1560         pathname = getname(specialfile);
1561         err = PTR_ERR(pathname);
1562         if (IS_ERR(pathname))
1563                 goto out;
1564
1565         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1566         putname(pathname);
1567         err = PTR_ERR(victim);
1568         if (IS_ERR(victim))
1569                 goto out;
1570
1571         mapping = victim->f_mapping;
1572         prev = -1;
1573         spin_lock(&swap_lock);
1574         for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1575                 p = swap_info[type];
1576                 if (p->flags & SWP_WRITEOK) {
1577                         if (p->swap_file->f_mapping == mapping)
1578                                 break;
1579                 }
1580                 prev = type;
1581         }
1582         if (type < 0) {
1583                 err = -EINVAL;
1584                 spin_unlock(&swap_lock);
1585                 goto out_dput;
1586         }
1587         if (!security_vm_enough_memory(p->pages))
1588                 vm_unacct_memory(p->pages);
1589         else {
1590                 err = -ENOMEM;
1591                 spin_unlock(&swap_lock);
1592                 goto out_dput;
1593         }
1594         if (prev < 0)
1595                 swap_list.head = p->next;
1596         else
1597                 swap_info[prev]->next = p->next;
1598         if (type == swap_list.next) {
1599                 /* just pick something that's safe... */
1600                 swap_list.next = swap_list.head;
1601         }
1602         if (p->prio < 0) {
1603                 for (i = p->next; i >= 0; i = swap_info[i]->next)
1604                         swap_info[i]->prio = p->prio--;
1605                 least_priority++;
1606         }
1607         nr_swap_pages -= p->pages;
1608         total_swap_pages -= p->pages;
1609         p->flags &= ~SWP_WRITEOK;
1610         spin_unlock(&swap_lock);
1611
1612         current->flags |= PF_OOM_ORIGIN;
1613         err = try_to_unuse(type);
1614         current->flags &= ~PF_OOM_ORIGIN;
1615
1616         if (err) {
1617                 /* re-insert swap space back into swap_list */
1618                 spin_lock(&swap_lock);
1619                 if (p->prio < 0)
1620                         p->prio = --least_priority;
1621                 prev = -1;
1622                 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1623                         if (p->prio >= swap_info[i]->prio)
1624                                 break;
1625                         prev = i;
1626                 }
1627                 p->next = i;
1628                 if (prev < 0)
1629                         swap_list.head = swap_list.next = type;
1630                 else
1631                         swap_info[prev]->next = type;
1632                 nr_swap_pages += p->pages;
1633                 total_swap_pages += p->pages;
1634                 p->flags |= SWP_WRITEOK;
1635                 spin_unlock(&swap_lock);
1636                 goto out_dput;
1637         }
1638
1639         /* wait for any unplug function to finish */
1640         down_write(&swap_unplug_sem);
1641         up_write(&swap_unplug_sem);
1642
1643         destroy_swap_extents(p);
1644         if (p->flags & SWP_CONTINUED)
1645                 free_swap_count_continuations(p);
1646
1647         mutex_lock(&swapon_mutex);
1648         spin_lock(&swap_lock);
1649         drain_mmlist();
1650
1651         /* wait for anyone still in scan_swap_map */
1652         p->highest_bit = 0;             /* cuts scans short */
1653         while (p->flags >= SWP_SCANNING) {
1654                 spin_unlock(&swap_lock);
1655                 schedule_timeout_uninterruptible(1);
1656                 spin_lock(&swap_lock);
1657         }
1658
1659         swap_file = p->swap_file;
1660         p->swap_file = NULL;
1661         p->max = 0;
1662         swap_map = p->swap_map;
1663         p->swap_map = NULL;
1664         p->flags = 0;
1665         spin_unlock(&swap_lock);
1666         mutex_unlock(&swapon_mutex);
1667         vfree(swap_map);
1668         /* Destroy swap account informatin */
1669         swap_cgroup_swapoff(type);
1670
1671         inode = mapping->host;
1672         if (S_ISBLK(inode->i_mode)) {
1673                 struct block_device *bdev = I_BDEV(inode);
1674                 set_blocksize(bdev, p->old_block_size);
1675                 bd_release(bdev);
1676         } else {
1677                 mutex_lock(&inode->i_mutex);
1678                 inode->i_flags &= ~S_SWAPFILE;
1679                 mutex_unlock(&inode->i_mutex);
1680         }
1681         filp_close(swap_file, NULL);
1682         err = 0;
1683
1684 out_dput:
1685         filp_close(victim, NULL);
1686 out:
1687         return err;
1688 }
1689
1690 #ifdef CONFIG_PROC_FS
1691 /* iterator */
1692 static void *swap_start(struct seq_file *swap, loff_t *pos)
1693 {
1694         struct swap_info_struct *si;
1695         int type;
1696         loff_t l = *pos;
1697
1698         mutex_lock(&swapon_mutex);
1699
1700         if (!l)
1701                 return SEQ_START_TOKEN;
1702
1703         for (type = 0; type < nr_swapfiles; type++) {
1704                 smp_rmb();      /* read nr_swapfiles before swap_info[type] */
1705                 si = swap_info[type];
1706                 if (!(si->flags & SWP_USED) || !si->swap_map)
1707                         continue;
1708                 if (!--l)
1709                         return si;
1710         }
1711
1712         return NULL;
1713 }
1714
1715 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1716 {
1717         struct swap_info_struct *si = v;
1718         int type;
1719
1720         if (v == SEQ_START_TOKEN)
1721                 type = 0;
1722         else
1723                 type = si->type + 1;
1724
1725         for (; type < nr_swapfiles; type++) {
1726                 smp_rmb();      /* read nr_swapfiles before swap_info[type] */
1727                 si = swap_info[type];
1728                 if (!(si->flags & SWP_USED) || !si->swap_map)
1729                         continue;
1730                 ++*pos;
1731                 return si;
1732         }
1733
1734         return NULL;
1735 }
1736
1737 static void swap_stop(struct seq_file *swap, void *v)
1738 {
1739         mutex_unlock(&swapon_mutex);
1740 }
1741
1742 static int swap_show(struct seq_file *swap, void *v)
1743 {
1744         struct swap_info_struct *si = v;
1745         struct file *file;
1746         int len;
1747
1748         if (si == SEQ_START_TOKEN) {
1749                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1750                 return 0;
1751         }
1752
1753         file = si->swap_file;
1754         len = seq_path(swap, &file->f_path, " \t\n\\");
1755         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1756                         len < 40 ? 40 - len : 1, " ",
1757                         S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1758                                 "partition" : "file\t",
1759                         si->pages << (PAGE_SHIFT - 10),
1760                         si->inuse_pages << (PAGE_SHIFT - 10),
1761                         si->prio);
1762         return 0;
1763 }
1764
1765 static const struct seq_operations swaps_op = {
1766         .start =        swap_start,
1767         .next =         swap_next,
1768         .stop =         swap_stop,
1769         .show =         swap_show
1770 };
1771
1772 static int swaps_open(struct inode *inode, struct file *file)
1773 {
1774         return seq_open(file, &swaps_op);
1775 }
1776
1777 static const struct file_operations proc_swaps_operations = {
1778         .open           = swaps_open,
1779         .read           = seq_read,
1780         .llseek         = seq_lseek,
1781         .release        = seq_release,
1782 };
1783
1784 static int __init procswaps_init(void)
1785 {
1786         proc_create("swaps", 0, NULL, &proc_swaps_operations);
1787         return 0;
1788 }
1789 __initcall(procswaps_init);
1790 #endif /* CONFIG_PROC_FS */
1791
1792 #ifdef MAX_SWAPFILES_CHECK
1793 static int __init max_swapfiles_check(void)
1794 {
1795         MAX_SWAPFILES_CHECK();
1796         return 0;
1797 }
1798 late_initcall(max_swapfiles_check);
1799 #endif
1800
1801 /*
1802  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1803  *
1804  * The swapon system call
1805  */
1806 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1807 {
1808         struct swap_info_struct *p;
1809         char *name = NULL;
1810         struct block_device *bdev = NULL;
1811         struct file *swap_file = NULL;
1812         struct address_space *mapping;
1813         unsigned int type;
1814         int i, prev;
1815         int error;
1816         union swap_header *swap_header;
1817         unsigned int nr_good_pages;
1818         int nr_extents = 0;
1819         sector_t span;
1820         unsigned long maxpages;
1821         unsigned long swapfilepages;
1822         unsigned char *swap_map = NULL;
1823         struct page *page = NULL;
1824         struct inode *inode = NULL;
1825         int did_down = 0;
1826
1827         if (!capable(CAP_SYS_ADMIN))
1828                 return -EPERM;
1829
1830         p = kzalloc(sizeof(*p), GFP_KERNEL);
1831         if (!p)
1832                 return -ENOMEM;
1833
1834         spin_lock(&swap_lock);
1835         for (type = 0; type < nr_swapfiles; type++) {
1836                 if (!(swap_info[type]->flags & SWP_USED))
1837                         break;
1838         }
1839         error = -EPERM;
1840         if (type >= MAX_SWAPFILES) {
1841                 spin_unlock(&swap_lock);
1842                 kfree(p);
1843                 goto out;
1844         }
1845         if (type >= nr_swapfiles) {
1846                 p->type = type;
1847                 swap_info[type] = p;
1848                 /*
1849                  * Write swap_info[type] before nr_swapfiles, in case a
1850                  * racing procfs swap_start() or swap_next() is reading them.
1851                  * (We never shrink nr_swapfiles, we never free this entry.)
1852                  */
1853                 smp_wmb();
1854                 nr_swapfiles++;
1855         } else {
1856                 kfree(p);
1857                 p = swap_info[type];
1858                 /*
1859                  * Do not memset this entry: a racing procfs swap_next()
1860                  * would be relying on p->type to remain valid.
1861                  */
1862         }
1863         INIT_LIST_HEAD(&p->first_swap_extent.list);
1864         p->flags = SWP_USED;
1865         p->next = -1;
1866         spin_unlock(&swap_lock);
1867
1868         name = getname(specialfile);
1869         error = PTR_ERR(name);
1870         if (IS_ERR(name)) {
1871                 name = NULL;
1872                 goto bad_swap_2;
1873         }
1874         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1875         error = PTR_ERR(swap_file);
1876         if (IS_ERR(swap_file)) {
1877                 swap_file = NULL;
1878                 goto bad_swap_2;
1879         }
1880
1881         p->swap_file = swap_file;
1882         mapping = swap_file->f_mapping;
1883         inode = mapping->host;
1884
1885         error = -EBUSY;
1886         for (i = 0; i < nr_swapfiles; i++) {
1887                 struct swap_info_struct *q = swap_info[i];
1888
1889                 if (i == type || !q->swap_file)
1890                         continue;
1891                 if (mapping == q->swap_file->f_mapping)
1892                         goto bad_swap;
1893         }
1894
1895         error = -EINVAL;
1896         if (S_ISBLK(inode->i_mode)) {
1897                 bdev = I_BDEV(inode);
1898                 error = bd_claim(bdev, sys_swapon);
1899                 if (error < 0) {
1900                         bdev = NULL;
1901                         error = -EINVAL;
1902                         goto bad_swap;
1903                 }
1904                 p->old_block_size = block_size(bdev);
1905                 error = set_blocksize(bdev, PAGE_SIZE);
1906                 if (error < 0)
1907                         goto bad_swap;
1908                 p->bdev = bdev;
1909                 p->flags |= SWP_BLKDEV;
1910         } else if (S_ISREG(inode->i_mode)) {
1911                 p->bdev = inode->i_sb->s_bdev;
1912                 mutex_lock(&inode->i_mutex);
1913                 did_down = 1;
1914                 if (IS_SWAPFILE(inode)) {
1915                         error = -EBUSY;
1916                         goto bad_swap;
1917                 }
1918         } else {
1919                 goto bad_swap;
1920         }
1921
1922         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1923
1924         /*
1925          * Read the swap header.
1926          */
1927         if (!mapping->a_ops->readpage) {
1928                 error = -EINVAL;
1929                 goto bad_swap;
1930         }
1931         page = read_mapping_page(mapping, 0, swap_file);
1932         if (IS_ERR(page)) {
1933                 error = PTR_ERR(page);
1934                 goto bad_swap;
1935         }
1936         swap_header = kmap(page);
1937
1938         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1939                 printk(KERN_ERR "Unable to find swap-space signature\n");
1940                 error = -EINVAL;
1941                 goto bad_swap;
1942         }
1943
1944         /* swap partition endianess hack... */
1945         if (swab32(swap_header->info.version) == 1) {
1946                 swab32s(&swap_header->info.version);
1947                 swab32s(&swap_header->info.last_page);
1948                 swab32s(&swap_header->info.nr_badpages);
1949                 for (i = 0; i < swap_header->info.nr_badpages; i++)
1950                         swab32s(&swap_header->info.badpages[i]);
1951         }
1952         /* Check the swap header's sub-version */
1953         if (swap_header->info.version != 1) {
1954                 printk(KERN_WARNING
1955                        "Unable to handle swap header version %d\n",
1956                        swap_header->info.version);
1957                 error = -EINVAL;
1958                 goto bad_swap;
1959         }
1960
1961         p->lowest_bit  = 1;
1962         p->cluster_next = 1;
1963         p->cluster_nr = 0;
1964
1965         /*
1966          * Find out how many pages are allowed for a single swap
1967          * device. There are two limiting factors: 1) the number of
1968          * bits for the swap offset in the swp_entry_t type and
1969          * 2) the number of bits in the a swap pte as defined by
1970          * the different architectures. In order to find the
1971          * largest possible bit mask a swap entry with swap type 0
1972          * and swap offset ~0UL is created, encoded to a swap pte,
1973          * decoded to a swp_entry_t again and finally the swap
1974          * offset is extracted. This will mask all the bits from
1975          * the initial ~0UL mask that can't be encoded in either
1976          * the swp_entry_t or the architecture definition of a
1977          * swap pte.
1978          */
1979         maxpages = swp_offset(pte_to_swp_entry(
1980                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
1981         if (maxpages > swap_header->info.last_page) {
1982                 maxpages = swap_header->info.last_page + 1;
1983                 /* p->max is an unsigned int: don't overflow it */
1984                 if ((unsigned int)maxpages == 0)
1985                         maxpages = UINT_MAX;
1986         }
1987         p->highest_bit = maxpages - 1;
1988
1989         error = -EINVAL;
1990         if (!maxpages)
1991                 goto bad_swap;
1992         if (swapfilepages && maxpages > swapfilepages) {
1993                 printk(KERN_WARNING
1994                        "Swap area shorter than signature indicates\n");
1995                 goto bad_swap;
1996         }
1997         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1998                 goto bad_swap;
1999         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2000                 goto bad_swap;
2001
2002         /* OK, set up the swap map and apply the bad block list */
2003         swap_map = vmalloc(maxpages);
2004         if (!swap_map) {
2005                 error = -ENOMEM;
2006                 goto bad_swap;
2007         }
2008
2009         memset(swap_map, 0, maxpages);
2010         nr_good_pages = maxpages - 1;   /* omit header page */
2011
2012         for (i = 0; i < swap_header->info.nr_badpages; i++) {
2013                 unsigned int page_nr = swap_header->info.badpages[i];
2014                 if (page_nr == 0 || page_nr > swap_header->info.last_page) {
2015                         error = -EINVAL;
2016                         goto bad_swap;
2017                 }
2018                 if (page_nr < maxpages) {
2019                         swap_map[page_nr] = SWAP_MAP_BAD;
2020                         nr_good_pages--;
2021                 }
2022         }
2023
2024         error = swap_cgroup_swapon(type, maxpages);
2025         if (error)
2026                 goto bad_swap;
2027
2028         if (nr_good_pages) {
2029                 swap_map[0] = SWAP_MAP_BAD;
2030                 p->max = maxpages;
2031                 p->pages = nr_good_pages;
2032                 nr_extents = setup_swap_extents(p, &span);
2033                 if (nr_extents < 0) {
2034                         error = nr_extents;
2035                         goto bad_swap;
2036                 }
2037                 nr_good_pages = p->pages;
2038         }
2039         if (!nr_good_pages) {
2040                 printk(KERN_WARNING "Empty swap-file\n");
2041                 error = -EINVAL;
2042                 goto bad_swap;
2043         }
2044
2045         if (p->bdev) {
2046                 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2047                         p->flags |= SWP_SOLIDSTATE;
2048                         p->cluster_next = 1 + (random32() % p->highest_bit);
2049                 }
2050                 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
2051                         p->flags |= SWP_DISCARDABLE;
2052         }
2053
2054         mutex_lock(&swapon_mutex);
2055         spin_lock(&swap_lock);
2056         if (swap_flags & SWAP_FLAG_PREFER)
2057                 p->prio =
2058                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2059         else
2060                 p->prio = --least_priority;
2061         p->swap_map = swap_map;
2062         p->flags |= SWP_WRITEOK;
2063         nr_swap_pages += nr_good_pages;
2064         total_swap_pages += nr_good_pages;
2065
2066         printk(KERN_INFO "Adding %uk swap on %s.  "
2067                         "Priority:%d extents:%d across:%lluk %s%s\n",
2068                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
2069                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2070                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2071                 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2072
2073         /* insert swap space into swap_list: */
2074         prev = -1;
2075         for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
2076                 if (p->prio >= swap_info[i]->prio)
2077                         break;
2078                 prev = i;
2079         }
2080         p->next = i;
2081         if (prev < 0)
2082                 swap_list.head = swap_list.next = type;
2083         else
2084                 swap_info[prev]->next = type;
2085         spin_unlock(&swap_lock);
2086         mutex_unlock(&swapon_mutex);
2087         error = 0;
2088         goto out;
2089 bad_swap:
2090         if (bdev) {
2091                 set_blocksize(bdev, p->old_block_size);
2092                 bd_release(bdev);
2093         }
2094         destroy_swap_extents(p);
2095         swap_cgroup_swapoff(type);
2096 bad_swap_2:
2097         spin_lock(&swap_lock);
2098         p->swap_file = NULL;
2099         p->flags = 0;
2100         spin_unlock(&swap_lock);
2101         vfree(swap_map);
2102         if (swap_file)
2103                 filp_close(swap_file, NULL);
2104 out:
2105         if (page && !IS_ERR(page)) {
2106                 kunmap(page);
2107                 page_cache_release(page);
2108         }
2109         if (name)
2110                 putname(name);
2111         if (did_down) {
2112                 if (!error)
2113                         inode->i_flags |= S_SWAPFILE;
2114                 mutex_unlock(&inode->i_mutex);
2115         }
2116         return error;
2117 }
2118
2119 void si_swapinfo(struct sysinfo *val)
2120 {
2121         unsigned int type;
2122         unsigned long nr_to_be_unused = 0;
2123
2124         spin_lock(&swap_lock);
2125         for (type = 0; type < nr_swapfiles; type++) {
2126                 struct swap_info_struct *si = swap_info[type];
2127
2128                 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2129                         nr_to_be_unused += si->inuse_pages;
2130         }
2131         val->freeswap = nr_swap_pages + nr_to_be_unused;
2132         val->totalswap = total_swap_pages + nr_to_be_unused;
2133         spin_unlock(&swap_lock);
2134 }
2135
2136 /*
2137  * Verify that a swap entry is valid and increment its swap map count.
2138  *
2139  * Returns error code in following case.
2140  * - success -> 0
2141  * - swp_entry is invalid -> EINVAL
2142  * - swp_entry is migration entry -> EINVAL
2143  * - swap-cache reference is requested but there is already one. -> EEXIST
2144  * - swap-cache reference is requested but the entry is not used. -> ENOENT
2145  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2146  */
2147 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2148 {
2149         struct swap_info_struct *p;
2150         unsigned long offset, type;
2151         unsigned char count;
2152         unsigned char has_cache;
2153         int err = -EINVAL;
2154
2155         if (non_swap_entry(entry))
2156                 goto out;
2157
2158         type = swp_type(entry);
2159         if (type >= nr_swapfiles)
2160                 goto bad_file;
2161         p = swap_info[type];
2162         offset = swp_offset(entry);
2163
2164         spin_lock(&swap_lock);
2165         if (unlikely(offset >= p->max))
2166                 goto unlock_out;
2167
2168         count = p->swap_map[offset];
2169         has_cache = count & SWAP_HAS_CACHE;
2170         count &= ~SWAP_HAS_CACHE;
2171         err = 0;
2172
2173         if (usage == SWAP_HAS_CACHE) {
2174
2175                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2176                 if (!has_cache && count)
2177                         has_cache = SWAP_HAS_CACHE;
2178                 else if (has_cache)             /* someone else added cache */
2179                         err = -EEXIST;
2180                 else                            /* no users remaining */
2181                         err = -ENOENT;
2182
2183         } else if (count || has_cache) {
2184
2185                 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2186                         count += usage;
2187                 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2188                         err = -EINVAL;
2189                 else if (swap_count_continued(p, offset, count))
2190                         count = COUNT_CONTINUED;
2191                 else
2192                         err = -ENOMEM;
2193         } else
2194                 err = -ENOENT;                  /* unused swap entry */
2195
2196         p->swap_map[offset] = count | has_cache;
2197
2198 unlock_out:
2199         spin_unlock(&swap_lock);
2200 out:
2201         return err;
2202
2203 bad_file:
2204         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2205         goto out;
2206 }
2207
2208 /*
2209  * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2210  * (in which case its reference count is never incremented).
2211  */
2212 void swap_shmem_alloc(swp_entry_t entry)
2213 {
2214         __swap_duplicate(entry, SWAP_MAP_SHMEM);
2215 }
2216
2217 /*
2218  * Increase reference count of swap entry by 1.
2219  * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2220  * but could not be atomically allocated.  Returns 0, just as if it succeeded,
2221  * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2222  * might occur if a page table entry has got corrupted.
2223  */
2224 int swap_duplicate(swp_entry_t entry)
2225 {
2226         int err = 0;
2227
2228         while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2229                 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2230         return err;
2231 }
2232
2233 /*
2234  * @entry: swap entry for which we allocate swap cache.
2235  *
2236  * Called when allocating swap cache for existing swap entry,
2237  * This can return error codes. Returns 0 at success.
2238  * -EBUSY means there is a swap cache.
2239  * Note: return code is different from swap_duplicate().
2240  */
2241 int swapcache_prepare(swp_entry_t entry)
2242 {
2243         return __swap_duplicate(entry, SWAP_HAS_CACHE);
2244 }
2245
2246 /*
2247  * swap_lock prevents swap_map being freed. Don't grab an extra
2248  * reference on the swaphandle, it doesn't matter if it becomes unused.
2249  */
2250 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2251 {
2252         struct swap_info_struct *si;
2253         int our_page_cluster = page_cluster;
2254         pgoff_t target, toff;
2255         pgoff_t base, end;
2256         int nr_pages = 0;
2257
2258         if (!our_page_cluster)  /* no readahead */
2259                 return 0;
2260
2261         si = swap_info[swp_type(entry)];
2262         target = swp_offset(entry);
2263         base = (target >> our_page_cluster) << our_page_cluster;
2264         end = base + (1 << our_page_cluster);
2265         if (!base)              /* first page is swap header */
2266                 base++;
2267
2268         spin_lock(&swap_lock);
2269         if (end > si->max)      /* don't go beyond end of map */
2270                 end = si->max;
2271
2272         /* Count contiguous allocated slots above our target */
2273         for (toff = target; ++toff < end; nr_pages++) {
2274                 /* Don't read in free or bad pages */
2275                 if (!si->swap_map[toff])
2276                         break;
2277                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2278                         break;
2279         }
2280         /* Count contiguous allocated slots below our target */
2281         for (toff = target; --toff >= base; nr_pages++) {
2282                 /* Don't read in free or bad pages */
2283                 if (!si->swap_map[toff])
2284                         break;
2285                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2286                         break;
2287         }
2288         spin_unlock(&swap_lock);
2289
2290         /*
2291          * Indicate starting offset, and return number of pages to get:
2292          * if only 1, say 0, since there's then no readahead to be done.
2293          */
2294         *offset = ++toff;
2295         return nr_pages? ++nr_pages: 0;
2296 }
2297
2298 /*
2299  * add_swap_count_continuation - called when a swap count is duplicated
2300  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2301  * page of the original vmalloc'ed swap_map, to hold the continuation count
2302  * (for that entry and for its neighbouring PAGE_SIZE swap entries).  Called
2303  * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2304  *
2305  * These continuation pages are seldom referenced: the common paths all work
2306  * on the original swap_map, only referring to a continuation page when the
2307  * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2308  *
2309  * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2310  * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2311  * can be called after dropping locks.
2312  */
2313 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2314 {
2315         struct swap_info_struct *si;
2316         struct page *head;
2317         struct page *page;
2318         struct page *list_page;
2319         pgoff_t offset;
2320         unsigned char count;
2321
2322         /*
2323          * When debugging, it's easier to use __GFP_ZERO here; but it's better
2324          * for latency not to zero a page while GFP_ATOMIC and holding locks.
2325          */
2326         page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2327
2328         si = swap_info_get(entry);
2329         if (!si) {
2330                 /*
2331                  * An acceptable race has occurred since the failing
2332                  * __swap_duplicate(): the swap entry has been freed,
2333                  * perhaps even the whole swap_map cleared for swapoff.
2334                  */
2335                 goto outer;
2336         }
2337
2338         offset = swp_offset(entry);
2339         count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2340
2341         if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2342                 /*
2343                  * The higher the swap count, the more likely it is that tasks
2344                  * will race to add swap count continuation: we need to avoid
2345                  * over-provisioning.
2346                  */
2347                 goto out;
2348         }
2349
2350         if (!page) {
2351                 spin_unlock(&swap_lock);
2352                 return -ENOMEM;
2353         }
2354
2355         /*
2356          * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2357          * no architecture is using highmem pages for kernel pagetables: so it
2358          * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2359          */
2360         head = vmalloc_to_page(si->swap_map + offset);
2361         offset &= ~PAGE_MASK;
2362
2363         /*
2364          * Page allocation does not initialize the page's lru field,
2365          * but it does always reset its private field.
2366          */
2367         if (!page_private(head)) {
2368                 BUG_ON(count & COUNT_CONTINUED);
2369                 INIT_LIST_HEAD(&head->lru);
2370                 set_page_private(head, SWP_CONTINUED);
2371                 si->flags |= SWP_CONTINUED;
2372         }
2373
2374         list_for_each_entry(list_page, &head->lru, lru) {
2375                 unsigned char *map;
2376
2377                 /*
2378                  * If the previous map said no continuation, but we've found
2379                  * a continuation page, free our allocation and use this one.
2380                  */
2381                 if (!(count & COUNT_CONTINUED))
2382                         goto out;
2383
2384                 map = kmap_atomic(list_page, KM_USER0) + offset;
2385                 count = *map;
2386                 kunmap_atomic(map, KM_USER0);
2387
2388                 /*
2389                  * If this continuation count now has some space in it,
2390                  * free our allocation and use this one.
2391                  */
2392                 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2393                         goto out;
2394         }
2395
2396         list_add_tail(&page->lru, &head->lru);
2397         page = NULL;                    /* now it's attached, don't free it */
2398 out:
2399         spin_unlock(&swap_lock);
2400 outer:
2401         if (page)
2402                 __free_page(page);
2403         return 0;
2404 }
2405
2406 /*
2407  * swap_count_continued - when the original swap_map count is incremented
2408  * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2409  * into, carry if so, or else fail until a new continuation page is allocated;
2410  * when the original swap_map count is decremented from 0 with continuation,
2411  * borrow from the continuation and report whether it still holds more.
2412  * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2413  */
2414 static bool swap_count_continued(struct swap_info_struct *si,
2415                                  pgoff_t offset, unsigned char count)
2416 {
2417         struct page *head;
2418         struct page *page;
2419         unsigned char *map;
2420
2421         head = vmalloc_to_page(si->swap_map + offset);
2422         if (page_private(head) != SWP_CONTINUED) {
2423                 BUG_ON(count & COUNT_CONTINUED);
2424                 return false;           /* need to add count continuation */
2425         }
2426
2427         offset &= ~PAGE_MASK;
2428         page = list_entry(head->lru.next, struct page, lru);
2429         map = kmap_atomic(page, KM_USER0) + offset;
2430
2431         if (count == SWAP_MAP_MAX)      /* initial increment from swap_map */
2432                 goto init_map;          /* jump over SWAP_CONT_MAX checks */
2433
2434         if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2435                 /*
2436                  * Think of how you add 1 to 999
2437                  */
2438                 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2439                         kunmap_atomic(map, KM_USER0);
2440                         page = list_entry(page->lru.next, struct page, lru);
2441                         BUG_ON(page == head);
2442                         map = kmap_atomic(page, KM_USER0) + offset;
2443                 }
2444                 if (*map == SWAP_CONT_MAX) {
2445                         kunmap_atomic(map, KM_USER0);
2446                         page = list_entry(page->lru.next, struct page, lru);
2447                         if (page == head)
2448                                 return false;   /* add count continuation */
2449                         map = kmap_atomic(page, KM_USER0) + offset;
2450 init_map:               *map = 0;               /* we didn't zero the page */
2451                 }
2452                 *map += 1;
2453                 kunmap_atomic(map, KM_USER0);
2454                 page = list_entry(page->lru.prev, struct page, lru);
2455                 while (page != head) {
2456                         map = kmap_atomic(page, KM_USER0) + offset;
2457                         *map = COUNT_CONTINUED;
2458                         kunmap_atomic(map, KM_USER0);
2459                         page = list_entry(page->lru.prev, struct page, lru);
2460                 }
2461                 return true;                    /* incremented */
2462
2463         } else {                                /* decrementing */
2464                 /*
2465                  * Think of how you subtract 1 from 1000
2466                  */
2467                 BUG_ON(count != COUNT_CONTINUED);
2468                 while (*map == COUNT_CONTINUED) {
2469                         kunmap_atomic(map, KM_USER0);
2470                         page = list_entry(page->lru.next, struct page, lru);
2471                         BUG_ON(page == head);
2472                         map = kmap_atomic(page, KM_USER0) + offset;
2473                 }
2474                 BUG_ON(*map == 0);
2475                 *map -= 1;
2476                 if (*map == 0)
2477                         count = 0;
2478                 kunmap_atomic(map, KM_USER0);
2479                 page = list_entry(page->lru.prev, struct page, lru);
2480                 while (page != head) {
2481                         map = kmap_atomic(page, KM_USER0) + offset;
2482                         *map = SWAP_CONT_MAX | count;
2483                         count = COUNT_CONTINUED;
2484                         kunmap_atomic(map, KM_USER0);
2485                         page = list_entry(page->lru.prev, struct page, lru);
2486                 }
2487                 return count == COUNT_CONTINUED;
2488         }
2489 }
2490
2491 /*
2492  * free_swap_count_continuations - swapoff free all the continuation pages
2493  * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2494  */
2495 static void free_swap_count_continuations(struct swap_info_struct *si)
2496 {
2497         pgoff_t offset;
2498
2499         for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2500                 struct page *head;
2501                 head = vmalloc_to_page(si->swap_map + offset);
2502                 if (page_private(head)) {
2503                         struct list_head *this, *next;
2504                         list_for_each_safe(this, next, &head->lru) {
2505                                 struct page *page;
2506                                 page = list_entry(this, struct page, lru);
2507                                 list_del(this);
2508                                 __free_page(page);
2509                         }
2510                 }
2511         }
2512 }