drm/radeon: set fb aperture sizes for framebuffer handoff.
[linux-2.6] / 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/rmap.h>
26 #include <linux/security.h>
27 #include <linux/backing-dev.h>
28 #include <linux/mutex.h>
29 #include <linux/capability.h>
30 #include <linux/syscalls.h>
31 #include <linux/memcontrol.h>
32
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 #include <linux/page_cgroup.h>
37
38 static DEFINE_SPINLOCK(swap_lock);
39 static unsigned int nr_swapfiles;
40 long nr_swap_pages;
41 long total_swap_pages;
42 static int swap_overflow;
43 static int least_priority;
44
45 static const char Bad_file[] = "Bad swap file entry ";
46 static const char Unused_file[] = "Unused swap file entry ";
47 static const char Bad_offset[] = "Bad swap offset entry ";
48 static const char Unused_offset[] = "Unused swap offset entry ";
49
50 static struct swap_list_t swap_list = {-1, -1};
51
52 static struct swap_info_struct swap_info[MAX_SWAPFILES];
53
54 static DEFINE_MUTEX(swapon_mutex);
55
56 /* For reference count accounting in swap_map */
57 /* enum for swap_map[] handling. internal use only */
58 enum {
59         SWAP_MAP = 0,   /* ops for reference from swap users */
60         SWAP_CACHE,     /* ops for reference from swap cache */
61 };
62
63 static inline int swap_count(unsigned short ent)
64 {
65         return ent & SWAP_COUNT_MASK;
66 }
67
68 static inline bool swap_has_cache(unsigned short ent)
69 {
70         return !!(ent & SWAP_HAS_CACHE);
71 }
72
73 static inline unsigned short encode_swapmap(int count, bool has_cache)
74 {
75         unsigned short ret = count;
76
77         if (has_cache)
78                 return SWAP_HAS_CACHE | ret;
79         return ret;
80 }
81
82 /* returnes 1 if swap entry is freed */
83 static int
84 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
85 {
86         int type = si - swap_info;
87         swp_entry_t entry = swp_entry(type, offset);
88         struct page *page;
89         int ret = 0;
90
91         page = find_get_page(&swapper_space, entry.val);
92         if (!page)
93                 return 0;
94         /*
95          * This function is called from scan_swap_map() and it's called
96          * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
97          * We have to use trylock for avoiding deadlock. This is a special
98          * case and you should use try_to_free_swap() with explicit lock_page()
99          * in usual operations.
100          */
101         if (trylock_page(page)) {
102                 ret = try_to_free_swap(page);
103                 unlock_page(page);
104         }
105         page_cache_release(page);
106         return ret;
107 }
108
109 /*
110  * We need this because the bdev->unplug_fn can sleep and we cannot
111  * hold swap_lock while calling the unplug_fn. And swap_lock
112  * cannot be turned into a mutex.
113  */
114 static DECLARE_RWSEM(swap_unplug_sem);
115
116 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
117 {
118         swp_entry_t entry;
119
120         down_read(&swap_unplug_sem);
121         entry.val = page_private(page);
122         if (PageSwapCache(page)) {
123                 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
124                 struct backing_dev_info *bdi;
125
126                 /*
127                  * If the page is removed from swapcache from under us (with a
128                  * racy try_to_unuse/swapoff) we need an additional reference
129                  * count to avoid reading garbage from page_private(page) above.
130                  * If the WARN_ON triggers during a swapoff it maybe the race
131                  * condition and it's harmless. However if it triggers without
132                  * swapoff it signals a problem.
133                  */
134                 WARN_ON(page_count(page) <= 1);
135
136                 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
137                 blk_run_backing_dev(bdi, page);
138         }
139         up_read(&swap_unplug_sem);
140 }
141
142 /*
143  * swapon tell device that all the old swap contents can be discarded,
144  * to allow the swap device to optimize its wear-levelling.
145  */
146 static int discard_swap(struct swap_info_struct *si)
147 {
148         struct swap_extent *se;
149         int err = 0;
150
151         list_for_each_entry(se, &si->extent_list, list) {
152                 sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
153                 sector_t nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
154
155                 if (se->start_page == 0) {
156                         /* Do not discard the swap header page! */
157                         start_block += 1 << (PAGE_SHIFT - 9);
158                         nr_blocks -= 1 << (PAGE_SHIFT - 9);
159                         if (!nr_blocks)
160                                 continue;
161                 }
162
163                 err = blkdev_issue_discard(si->bdev, start_block,
164                                                 nr_blocks, GFP_KERNEL);
165                 if (err)
166                         break;
167
168                 cond_resched();
169         }
170         return err;             /* That will often be -EOPNOTSUPP */
171 }
172
173 /*
174  * swap allocation tell device that a cluster of swap can now be discarded,
175  * to allow the swap device to optimize its wear-levelling.
176  */
177 static void discard_swap_cluster(struct swap_info_struct *si,
178                                  pgoff_t start_page, pgoff_t nr_pages)
179 {
180         struct swap_extent *se = si->curr_swap_extent;
181         int found_extent = 0;
182
183         while (nr_pages) {
184                 struct list_head *lh;
185
186                 if (se->start_page <= start_page &&
187                     start_page < se->start_page + se->nr_pages) {
188                         pgoff_t offset = start_page - se->start_page;
189                         sector_t start_block = se->start_block + offset;
190                         sector_t nr_blocks = se->nr_pages - offset;
191
192                         if (nr_blocks > nr_pages)
193                                 nr_blocks = nr_pages;
194                         start_page += nr_blocks;
195                         nr_pages -= nr_blocks;
196
197                         if (!found_extent++)
198                                 si->curr_swap_extent = se;
199
200                         start_block <<= PAGE_SHIFT - 9;
201                         nr_blocks <<= PAGE_SHIFT - 9;
202                         if (blkdev_issue_discard(si->bdev, start_block,
203                                                         nr_blocks, GFP_NOIO))
204                                 break;
205                 }
206
207                 lh = se->list.next;
208                 if (lh == &si->extent_list)
209                         lh = lh->next;
210                 se = list_entry(lh, struct swap_extent, list);
211         }
212 }
213
214 static int wait_for_discard(void *word)
215 {
216         schedule();
217         return 0;
218 }
219
220 #define SWAPFILE_CLUSTER        256
221 #define LATENCY_LIMIT           256
222
223 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
224                                           int cache)
225 {
226         unsigned long offset;
227         unsigned long scan_base;
228         unsigned long last_in_cluster = 0;
229         int latency_ration = LATENCY_LIMIT;
230         int found_free_cluster = 0;
231
232         /*
233          * We try to cluster swap pages by allocating them sequentially
234          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
235          * way, however, we resort to first-free allocation, starting
236          * a new cluster.  This prevents us from scattering swap pages
237          * all over the entire swap partition, so that we reduce
238          * overall disk seek times between swap pages.  -- sct
239          * But we do now try to find an empty cluster.  -Andrea
240          * And we let swap pages go all over an SSD partition.  Hugh
241          */
242
243         si->flags += SWP_SCANNING;
244         scan_base = offset = si->cluster_next;
245
246         if (unlikely(!si->cluster_nr--)) {
247                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
248                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
249                         goto checks;
250                 }
251                 if (si->flags & SWP_DISCARDABLE) {
252                         /*
253                          * Start range check on racing allocations, in case
254                          * they overlap the cluster we eventually decide on
255                          * (we scan without swap_lock to allow preemption).
256                          * It's hardly conceivable that cluster_nr could be
257                          * wrapped during our scan, but don't depend on it.
258                          */
259                         if (si->lowest_alloc)
260                                 goto checks;
261                         si->lowest_alloc = si->max;
262                         si->highest_alloc = 0;
263                 }
264                 spin_unlock(&swap_lock);
265
266                 /*
267                  * If seek is expensive, start searching for new cluster from
268                  * start of partition, to minimize the span of allocated swap.
269                  * But if seek is cheap, search from our current position, so
270                  * that swap is allocated from all over the partition: if the
271                  * Flash Translation Layer only remaps within limited zones,
272                  * we don't want to wear out the first zone too quickly.
273                  */
274                 if (!(si->flags & SWP_SOLIDSTATE))
275                         scan_base = offset = si->lowest_bit;
276                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
277
278                 /* Locate the first empty (unaligned) cluster */
279                 for (; last_in_cluster <= si->highest_bit; offset++) {
280                         if (si->swap_map[offset])
281                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
282                         else if (offset == last_in_cluster) {
283                                 spin_lock(&swap_lock);
284                                 offset -= SWAPFILE_CLUSTER - 1;
285                                 si->cluster_next = offset;
286                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
287                                 found_free_cluster = 1;
288                                 goto checks;
289                         }
290                         if (unlikely(--latency_ration < 0)) {
291                                 cond_resched();
292                                 latency_ration = LATENCY_LIMIT;
293                         }
294                 }
295
296                 offset = si->lowest_bit;
297                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
298
299                 /* Locate the first empty (unaligned) cluster */
300                 for (; last_in_cluster < scan_base; offset++) {
301                         if (si->swap_map[offset])
302                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
303                         else if (offset == last_in_cluster) {
304                                 spin_lock(&swap_lock);
305                                 offset -= SWAPFILE_CLUSTER - 1;
306                                 si->cluster_next = offset;
307                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
308                                 found_free_cluster = 1;
309                                 goto checks;
310                         }
311                         if (unlikely(--latency_ration < 0)) {
312                                 cond_resched();
313                                 latency_ration = LATENCY_LIMIT;
314                         }
315                 }
316
317                 offset = scan_base;
318                 spin_lock(&swap_lock);
319                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
320                 si->lowest_alloc = 0;
321         }
322
323 checks:
324         if (!(si->flags & SWP_WRITEOK))
325                 goto no_page;
326         if (!si->highest_bit)
327                 goto no_page;
328         if (offset > si->highest_bit)
329                 scan_base = offset = si->lowest_bit;
330
331         /* reuse swap entry of cache-only swap if not busy. */
332         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
333                 int swap_was_freed;
334                 spin_unlock(&swap_lock);
335                 swap_was_freed = __try_to_reclaim_swap(si, offset);
336                 spin_lock(&swap_lock);
337                 /* entry was freed successfully, try to use this again */
338                 if (swap_was_freed)
339                         goto checks;
340                 goto scan; /* check next one */
341         }
342
343         if (si->swap_map[offset])
344                 goto scan;
345
346         if (offset == si->lowest_bit)
347                 si->lowest_bit++;
348         if (offset == si->highest_bit)
349                 si->highest_bit--;
350         si->inuse_pages++;
351         if (si->inuse_pages == si->pages) {
352                 si->lowest_bit = si->max;
353                 si->highest_bit = 0;
354         }
355         if (cache == SWAP_CACHE) /* at usual swap-out via vmscan.c */
356                 si->swap_map[offset] = encode_swapmap(0, true);
357         else /* at suspend */
358                 si->swap_map[offset] = encode_swapmap(1, false);
359         si->cluster_next = offset + 1;
360         si->flags -= SWP_SCANNING;
361
362         if (si->lowest_alloc) {
363                 /*
364                  * Only set when SWP_DISCARDABLE, and there's a scan
365                  * for a free cluster in progress or just completed.
366                  */
367                 if (found_free_cluster) {
368                         /*
369                          * To optimize wear-levelling, discard the
370                          * old data of the cluster, taking care not to
371                          * discard any of its pages that have already
372                          * been allocated by racing tasks (offset has
373                          * already stepped over any at the beginning).
374                          */
375                         if (offset < si->highest_alloc &&
376                             si->lowest_alloc <= last_in_cluster)
377                                 last_in_cluster = si->lowest_alloc - 1;
378                         si->flags |= SWP_DISCARDING;
379                         spin_unlock(&swap_lock);
380
381                         if (offset < last_in_cluster)
382                                 discard_swap_cluster(si, offset,
383                                         last_in_cluster - offset + 1);
384
385                         spin_lock(&swap_lock);
386                         si->lowest_alloc = 0;
387                         si->flags &= ~SWP_DISCARDING;
388
389                         smp_mb();       /* wake_up_bit advises this */
390                         wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
391
392                 } else if (si->flags & SWP_DISCARDING) {
393                         /*
394                          * Delay using pages allocated by racing tasks
395                          * until the whole discard has been issued. We
396                          * could defer that delay until swap_writepage,
397                          * but it's easier to keep this self-contained.
398                          */
399                         spin_unlock(&swap_lock);
400                         wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
401                                 wait_for_discard, TASK_UNINTERRUPTIBLE);
402                         spin_lock(&swap_lock);
403                 } else {
404                         /*
405                          * Note pages allocated by racing tasks while
406                          * scan for a free cluster is in progress, so
407                          * that its final discard can exclude them.
408                          */
409                         if (offset < si->lowest_alloc)
410                                 si->lowest_alloc = offset;
411                         if (offset > si->highest_alloc)
412                                 si->highest_alloc = offset;
413                 }
414         }
415         return offset;
416
417 scan:
418         spin_unlock(&swap_lock);
419         while (++offset <= si->highest_bit) {
420                 if (!si->swap_map[offset]) {
421                         spin_lock(&swap_lock);
422                         goto checks;
423                 }
424                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
425                         spin_lock(&swap_lock);
426                         goto checks;
427                 }
428                 if (unlikely(--latency_ration < 0)) {
429                         cond_resched();
430                         latency_ration = LATENCY_LIMIT;
431                 }
432         }
433         offset = si->lowest_bit;
434         while (++offset < scan_base) {
435                 if (!si->swap_map[offset]) {
436                         spin_lock(&swap_lock);
437                         goto checks;
438                 }
439                 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
440                         spin_lock(&swap_lock);
441                         goto checks;
442                 }
443                 if (unlikely(--latency_ration < 0)) {
444                         cond_resched();
445                         latency_ration = LATENCY_LIMIT;
446                 }
447         }
448         spin_lock(&swap_lock);
449
450 no_page:
451         si->flags -= SWP_SCANNING;
452         return 0;
453 }
454
455 swp_entry_t get_swap_page(void)
456 {
457         struct swap_info_struct *si;
458         pgoff_t offset;
459         int type, next;
460         int wrapped = 0;
461
462         spin_lock(&swap_lock);
463         if (nr_swap_pages <= 0)
464                 goto noswap;
465         nr_swap_pages--;
466
467         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
468                 si = swap_info + type;
469                 next = si->next;
470                 if (next < 0 ||
471                     (!wrapped && si->prio != swap_info[next].prio)) {
472                         next = swap_list.head;
473                         wrapped++;
474                 }
475
476                 if (!si->highest_bit)
477                         continue;
478                 if (!(si->flags & SWP_WRITEOK))
479                         continue;
480
481                 swap_list.next = next;
482                 /* This is called for allocating swap entry for cache */
483                 offset = scan_swap_map(si, SWAP_CACHE);
484                 if (offset) {
485                         spin_unlock(&swap_lock);
486                         return swp_entry(type, offset);
487                 }
488                 next = swap_list.next;
489         }
490
491         nr_swap_pages++;
492 noswap:
493         spin_unlock(&swap_lock);
494         return (swp_entry_t) {0};
495 }
496
497 /* The only caller of this function is now susupend routine */
498 swp_entry_t get_swap_page_of_type(int type)
499 {
500         struct swap_info_struct *si;
501         pgoff_t offset;
502
503         spin_lock(&swap_lock);
504         si = swap_info + type;
505         if (si->flags & SWP_WRITEOK) {
506                 nr_swap_pages--;
507                 /* This is called for allocating swap entry, not cache */
508                 offset = scan_swap_map(si, SWAP_MAP);
509                 if (offset) {
510                         spin_unlock(&swap_lock);
511                         return swp_entry(type, offset);
512                 }
513                 nr_swap_pages++;
514         }
515         spin_unlock(&swap_lock);
516         return (swp_entry_t) {0};
517 }
518
519 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
520 {
521         struct swap_info_struct * p;
522         unsigned long offset, type;
523
524         if (!entry.val)
525                 goto out;
526         type = swp_type(entry);
527         if (type >= nr_swapfiles)
528                 goto bad_nofile;
529         p = & swap_info[type];
530         if (!(p->flags & SWP_USED))
531                 goto bad_device;
532         offset = swp_offset(entry);
533         if (offset >= p->max)
534                 goto bad_offset;
535         if (!p->swap_map[offset])
536                 goto bad_free;
537         spin_lock(&swap_lock);
538         return p;
539
540 bad_free:
541         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
542         goto out;
543 bad_offset:
544         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
545         goto out;
546 bad_device:
547         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
548         goto out;
549 bad_nofile:
550         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
551 out:
552         return NULL;
553 }
554
555 static int swap_entry_free(struct swap_info_struct *p,
556                            swp_entry_t ent, int cache)
557 {
558         unsigned long offset = swp_offset(ent);
559         int count = swap_count(p->swap_map[offset]);
560         bool has_cache;
561
562         has_cache = swap_has_cache(p->swap_map[offset]);
563
564         if (cache == SWAP_MAP) { /* dropping usage count of swap */
565                 if (count < SWAP_MAP_MAX) {
566                         count--;
567                         p->swap_map[offset] = encode_swapmap(count, has_cache);
568                 }
569         } else { /* dropping swap cache flag */
570                 VM_BUG_ON(!has_cache);
571                 p->swap_map[offset] = encode_swapmap(count, false);
572
573         }
574         /* return code. */
575         count = p->swap_map[offset];
576         /* free if no reference */
577         if (!count) {
578                 if (offset < p->lowest_bit)
579                         p->lowest_bit = offset;
580                 if (offset > p->highest_bit)
581                         p->highest_bit = offset;
582                 if (p->prio > swap_info[swap_list.next].prio)
583                         swap_list.next = p - swap_info;
584                 nr_swap_pages++;
585                 p->inuse_pages--;
586         }
587         if (!swap_count(count))
588                 mem_cgroup_uncharge_swap(ent);
589         return count;
590 }
591
592 /*
593  * Caller has made sure that the swapdevice corresponding to entry
594  * is still around or has not been recycled.
595  */
596 void swap_free(swp_entry_t entry)
597 {
598         struct swap_info_struct * p;
599
600         p = swap_info_get(entry);
601         if (p) {
602                 swap_entry_free(p, entry, SWAP_MAP);
603                 spin_unlock(&swap_lock);
604         }
605 }
606
607 /*
608  * Called after dropping swapcache to decrease refcnt to swap entries.
609  */
610 void swapcache_free(swp_entry_t entry, struct page *page)
611 {
612         struct swap_info_struct *p;
613         int ret;
614
615         p = swap_info_get(entry);
616         if (p) {
617                 ret = swap_entry_free(p, entry, SWAP_CACHE);
618                 if (page) {
619                         bool swapout;
620                         if (ret)
621                                 swapout = true; /* the end of swap out */
622                         else
623                                 swapout = false; /* no more swap users! */
624                         mem_cgroup_uncharge_swapcache(page, entry, swapout);
625                 }
626                 spin_unlock(&swap_lock);
627         }
628         return;
629 }
630
631 /*
632  * How many references to page are currently swapped out?
633  */
634 static inline int page_swapcount(struct page *page)
635 {
636         int count = 0;
637         struct swap_info_struct *p;
638         swp_entry_t entry;
639
640         entry.val = page_private(page);
641         p = swap_info_get(entry);
642         if (p) {
643                 count = swap_count(p->swap_map[swp_offset(entry)]);
644                 spin_unlock(&swap_lock);
645         }
646         return count;
647 }
648
649 /*
650  * We can write to an anon page without COW if there are no other references
651  * to it.  And as a side-effect, free up its swap: because the old content
652  * on disk will never be read, and seeking back there to write new content
653  * later would only waste time away from clustering.
654  */
655 int reuse_swap_page(struct page *page)
656 {
657         int count;
658
659         VM_BUG_ON(!PageLocked(page));
660         count = page_mapcount(page);
661         if (count <= 1 && PageSwapCache(page)) {
662                 count += page_swapcount(page);
663                 if (count == 1 && !PageWriteback(page)) {
664                         delete_from_swap_cache(page);
665                         SetPageDirty(page);
666                 }
667         }
668         return count == 1;
669 }
670
671 /*
672  * If swap is getting full, or if there are no more mappings of this page,
673  * then try_to_free_swap is called to free its swap space.
674  */
675 int try_to_free_swap(struct page *page)
676 {
677         VM_BUG_ON(!PageLocked(page));
678
679         if (!PageSwapCache(page))
680                 return 0;
681         if (PageWriteback(page))
682                 return 0;
683         if (page_swapcount(page))
684                 return 0;
685
686         delete_from_swap_cache(page);
687         SetPageDirty(page);
688         return 1;
689 }
690
691 /*
692  * Free the swap entry like above, but also try to
693  * free the page cache entry if it is the last user.
694  */
695 int free_swap_and_cache(swp_entry_t entry)
696 {
697         struct swap_info_struct *p;
698         struct page *page = NULL;
699
700         if (is_migration_entry(entry))
701                 return 1;
702
703         p = swap_info_get(entry);
704         if (p) {
705                 if (swap_entry_free(p, entry, SWAP_MAP) == SWAP_HAS_CACHE) {
706                         page = find_get_page(&swapper_space, entry.val);
707                         if (page && !trylock_page(page)) {
708                                 page_cache_release(page);
709                                 page = NULL;
710                         }
711                 }
712                 spin_unlock(&swap_lock);
713         }
714         if (page) {
715                 /*
716                  * Not mapped elsewhere, or swap space full? Free it!
717                  * Also recheck PageSwapCache now page is locked (above).
718                  */
719                 if (PageSwapCache(page) && !PageWriteback(page) &&
720                                 (!page_mapped(page) || vm_swap_full())) {
721                         delete_from_swap_cache(page);
722                         SetPageDirty(page);
723                 }
724                 unlock_page(page);
725                 page_cache_release(page);
726         }
727         return p != NULL;
728 }
729
730 #ifdef CONFIG_HIBERNATION
731 /*
732  * Find the swap type that corresponds to given device (if any).
733  *
734  * @offset - number of the PAGE_SIZE-sized block of the device, starting
735  * from 0, in which the swap header is expected to be located.
736  *
737  * This is needed for the suspend to disk (aka swsusp).
738  */
739 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
740 {
741         struct block_device *bdev = NULL;
742         int i;
743
744         if (device)
745                 bdev = bdget(device);
746
747         spin_lock(&swap_lock);
748         for (i = 0; i < nr_swapfiles; i++) {
749                 struct swap_info_struct *sis = swap_info + i;
750
751                 if (!(sis->flags & SWP_WRITEOK))
752                         continue;
753
754                 if (!bdev) {
755                         if (bdev_p)
756                                 *bdev_p = bdget(sis->bdev->bd_dev);
757
758                         spin_unlock(&swap_lock);
759                         return i;
760                 }
761                 if (bdev == sis->bdev) {
762                         struct swap_extent *se;
763
764                         se = list_entry(sis->extent_list.next,
765                                         struct swap_extent, list);
766                         if (se->start_block == offset) {
767                                 if (bdev_p)
768                                         *bdev_p = bdget(sis->bdev->bd_dev);
769
770                                 spin_unlock(&swap_lock);
771                                 bdput(bdev);
772                                 return i;
773                         }
774                 }
775         }
776         spin_unlock(&swap_lock);
777         if (bdev)
778                 bdput(bdev);
779
780         return -ENODEV;
781 }
782
783 /*
784  * Return either the total number of swap pages of given type, or the number
785  * of free pages of that type (depending on @free)
786  *
787  * This is needed for software suspend
788  */
789 unsigned int count_swap_pages(int type, int free)
790 {
791         unsigned int n = 0;
792
793         if (type < nr_swapfiles) {
794                 spin_lock(&swap_lock);
795                 if (swap_info[type].flags & SWP_WRITEOK) {
796                         n = swap_info[type].pages;
797                         if (free)
798                                 n -= swap_info[type].inuse_pages;
799                 }
800                 spin_unlock(&swap_lock);
801         }
802         return n;
803 }
804 #endif
805
806 /*
807  * No need to decide whether this PTE shares the swap entry with others,
808  * just let do_wp_page work it out if a write is requested later - to
809  * force COW, vm_page_prot omits write permission from any private vma.
810  */
811 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
812                 unsigned long addr, swp_entry_t entry, struct page *page)
813 {
814         struct mem_cgroup *ptr = NULL;
815         spinlock_t *ptl;
816         pte_t *pte;
817         int ret = 1;
818
819         if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
820                 ret = -ENOMEM;
821                 goto out_nolock;
822         }
823
824         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
825         if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
826                 if (ret > 0)
827                         mem_cgroup_cancel_charge_swapin(ptr);
828                 ret = 0;
829                 goto out;
830         }
831
832         inc_mm_counter(vma->vm_mm, anon_rss);
833         get_page(page);
834         set_pte_at(vma->vm_mm, addr, pte,
835                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
836         page_add_anon_rmap(page, vma, addr);
837         mem_cgroup_commit_charge_swapin(page, ptr);
838         swap_free(entry);
839         /*
840          * Move the page to the active list so it is not
841          * immediately swapped out again after swapon.
842          */
843         activate_page(page);
844 out:
845         pte_unmap_unlock(pte, ptl);
846 out_nolock:
847         return ret;
848 }
849
850 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
851                                 unsigned long addr, unsigned long end,
852                                 swp_entry_t entry, struct page *page)
853 {
854         pte_t swp_pte = swp_entry_to_pte(entry);
855         pte_t *pte;
856         int ret = 0;
857
858         /*
859          * We don't actually need pte lock while scanning for swp_pte: since
860          * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
861          * page table while we're scanning; though it could get zapped, and on
862          * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
863          * of unmatched parts which look like swp_pte, so unuse_pte must
864          * recheck under pte lock.  Scanning without pte lock lets it be
865          * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
866          */
867         pte = pte_offset_map(pmd, addr);
868         do {
869                 /*
870                  * swapoff spends a _lot_ of time in this loop!
871                  * Test inline before going to call unuse_pte.
872                  */
873                 if (unlikely(pte_same(*pte, swp_pte))) {
874                         pte_unmap(pte);
875                         ret = unuse_pte(vma, pmd, addr, entry, page);
876                         if (ret)
877                                 goto out;
878                         pte = pte_offset_map(pmd, addr);
879                 }
880         } while (pte++, addr += PAGE_SIZE, addr != end);
881         pte_unmap(pte - 1);
882 out:
883         return ret;
884 }
885
886 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
887                                 unsigned long addr, unsigned long end,
888                                 swp_entry_t entry, struct page *page)
889 {
890         pmd_t *pmd;
891         unsigned long next;
892         int ret;
893
894         pmd = pmd_offset(pud, addr);
895         do {
896                 next = pmd_addr_end(addr, end);
897                 if (pmd_none_or_clear_bad(pmd))
898                         continue;
899                 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
900                 if (ret)
901                         return ret;
902         } while (pmd++, addr = next, addr != end);
903         return 0;
904 }
905
906 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
907                                 unsigned long addr, unsigned long end,
908                                 swp_entry_t entry, struct page *page)
909 {
910         pud_t *pud;
911         unsigned long next;
912         int ret;
913
914         pud = pud_offset(pgd, addr);
915         do {
916                 next = pud_addr_end(addr, end);
917                 if (pud_none_or_clear_bad(pud))
918                         continue;
919                 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
920                 if (ret)
921                         return ret;
922         } while (pud++, addr = next, addr != end);
923         return 0;
924 }
925
926 static int unuse_vma(struct vm_area_struct *vma,
927                                 swp_entry_t entry, struct page *page)
928 {
929         pgd_t *pgd;
930         unsigned long addr, end, next;
931         int ret;
932
933         if (page->mapping) {
934                 addr = page_address_in_vma(page, vma);
935                 if (addr == -EFAULT)
936                         return 0;
937                 else
938                         end = addr + PAGE_SIZE;
939         } else {
940                 addr = vma->vm_start;
941                 end = vma->vm_end;
942         }
943
944         pgd = pgd_offset(vma->vm_mm, addr);
945         do {
946                 next = pgd_addr_end(addr, end);
947                 if (pgd_none_or_clear_bad(pgd))
948                         continue;
949                 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
950                 if (ret)
951                         return ret;
952         } while (pgd++, addr = next, addr != end);
953         return 0;
954 }
955
956 static int unuse_mm(struct mm_struct *mm,
957                                 swp_entry_t entry, struct page *page)
958 {
959         struct vm_area_struct *vma;
960         int ret = 0;
961
962         if (!down_read_trylock(&mm->mmap_sem)) {
963                 /*
964                  * Activate page so shrink_inactive_list is unlikely to unmap
965                  * its ptes while lock is dropped, so swapoff can make progress.
966                  */
967                 activate_page(page);
968                 unlock_page(page);
969                 down_read(&mm->mmap_sem);
970                 lock_page(page);
971         }
972         for (vma = mm->mmap; vma; vma = vma->vm_next) {
973                 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
974                         break;
975         }
976         up_read(&mm->mmap_sem);
977         return (ret < 0)? ret: 0;
978 }
979
980 /*
981  * Scan swap_map from current position to next entry still in use.
982  * Recycle to start on reaching the end, returning 0 when empty.
983  */
984 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
985                                         unsigned int prev)
986 {
987         unsigned int max = si->max;
988         unsigned int i = prev;
989         int count;
990
991         /*
992          * No need for swap_lock here: we're just looking
993          * for whether an entry is in use, not modifying it; false
994          * hits are okay, and sys_swapoff() has already prevented new
995          * allocations from this area (while holding swap_lock).
996          */
997         for (;;) {
998                 if (++i >= max) {
999                         if (!prev) {
1000                                 i = 0;
1001                                 break;
1002                         }
1003                         /*
1004                          * No entries in use at top of swap_map,
1005                          * loop back to start and recheck there.
1006                          */
1007                         max = prev + 1;
1008                         prev = 0;
1009                         i = 1;
1010                 }
1011                 count = si->swap_map[i];
1012                 if (count && swap_count(count) != SWAP_MAP_BAD)
1013                         break;
1014         }
1015         return i;
1016 }
1017
1018 /*
1019  * We completely avoid races by reading each swap page in advance,
1020  * and then search for the process using it.  All the necessary
1021  * page table adjustments can then be made atomically.
1022  */
1023 static int try_to_unuse(unsigned int type)
1024 {
1025         struct swap_info_struct * si = &swap_info[type];
1026         struct mm_struct *start_mm;
1027         unsigned short *swap_map;
1028         unsigned short swcount;
1029         struct page *page;
1030         swp_entry_t entry;
1031         unsigned int i = 0;
1032         int retval = 0;
1033         int reset_overflow = 0;
1034         int shmem;
1035
1036         /*
1037          * When searching mms for an entry, a good strategy is to
1038          * start at the first mm we freed the previous entry from
1039          * (though actually we don't notice whether we or coincidence
1040          * freed the entry).  Initialize this start_mm with a hold.
1041          *
1042          * A simpler strategy would be to start at the last mm we
1043          * freed the previous entry from; but that would take less
1044          * advantage of mmlist ordering, which clusters forked mms
1045          * together, child after parent.  If we race with dup_mmap(), we
1046          * prefer to resolve parent before child, lest we miss entries
1047          * duplicated after we scanned child: using last mm would invert
1048          * that.  Though it's only a serious concern when an overflowed
1049          * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
1050          */
1051         start_mm = &init_mm;
1052         atomic_inc(&init_mm.mm_users);
1053
1054         /*
1055          * Keep on scanning until all entries have gone.  Usually,
1056          * one pass through swap_map is enough, but not necessarily:
1057          * there are races when an instance of an entry might be missed.
1058          */
1059         while ((i = find_next_to_unuse(si, i)) != 0) {
1060                 if (signal_pending(current)) {
1061                         retval = -EINTR;
1062                         break;
1063                 }
1064
1065                 /*
1066                  * Get a page for the entry, using the existing swap
1067                  * cache page if there is one.  Otherwise, get a clean
1068                  * page and read the swap into it.
1069                  */
1070                 swap_map = &si->swap_map[i];
1071                 entry = swp_entry(type, i);
1072                 page = read_swap_cache_async(entry,
1073                                         GFP_HIGHUSER_MOVABLE, NULL, 0);
1074                 if (!page) {
1075                         /*
1076                          * Either swap_duplicate() failed because entry
1077                          * has been freed independently, and will not be
1078                          * reused since sys_swapoff() already disabled
1079                          * allocation from here, or alloc_page() failed.
1080                          */
1081                         if (!*swap_map)
1082                                 continue;
1083                         retval = -ENOMEM;
1084                         break;
1085                 }
1086
1087                 /*
1088                  * Don't hold on to start_mm if it looks like exiting.
1089                  */
1090                 if (atomic_read(&start_mm->mm_users) == 1) {
1091                         mmput(start_mm);
1092                         start_mm = &init_mm;
1093                         atomic_inc(&init_mm.mm_users);
1094                 }
1095
1096                 /*
1097                  * Wait for and lock page.  When do_swap_page races with
1098                  * try_to_unuse, do_swap_page can handle the fault much
1099                  * faster than try_to_unuse can locate the entry.  This
1100                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
1101                  * defer to do_swap_page in such a case - in some tests,
1102                  * do_swap_page and try_to_unuse repeatedly compete.
1103                  */
1104                 wait_on_page_locked(page);
1105                 wait_on_page_writeback(page);
1106                 lock_page(page);
1107                 wait_on_page_writeback(page);
1108
1109                 /*
1110                  * Remove all references to entry.
1111                  * Whenever we reach init_mm, there's no address space
1112                  * to search, but use it as a reminder to search shmem.
1113                  */
1114                 shmem = 0;
1115                 swcount = *swap_map;
1116                 if (swap_count(swcount)) {
1117                         if (start_mm == &init_mm)
1118                                 shmem = shmem_unuse(entry, page);
1119                         else
1120                                 retval = unuse_mm(start_mm, entry, page);
1121                 }
1122                 if (swap_count(*swap_map)) {
1123                         int set_start_mm = (*swap_map >= swcount);
1124                         struct list_head *p = &start_mm->mmlist;
1125                         struct mm_struct *new_start_mm = start_mm;
1126                         struct mm_struct *prev_mm = start_mm;
1127                         struct mm_struct *mm;
1128
1129                         atomic_inc(&new_start_mm->mm_users);
1130                         atomic_inc(&prev_mm->mm_users);
1131                         spin_lock(&mmlist_lock);
1132                         while (swap_count(*swap_map) && !retval && !shmem &&
1133                                         (p = p->next) != &start_mm->mmlist) {
1134                                 mm = list_entry(p, struct mm_struct, mmlist);
1135                                 if (!atomic_inc_not_zero(&mm->mm_users))
1136                                         continue;
1137                                 spin_unlock(&mmlist_lock);
1138                                 mmput(prev_mm);
1139                                 prev_mm = mm;
1140
1141                                 cond_resched();
1142
1143                                 swcount = *swap_map;
1144                                 if (!swap_count(swcount)) /* any usage ? */
1145                                         ;
1146                                 else if (mm == &init_mm) {
1147                                         set_start_mm = 1;
1148                                         shmem = shmem_unuse(entry, page);
1149                                 } else
1150                                         retval = unuse_mm(mm, entry, page);
1151
1152                                 if (set_start_mm &&
1153                                     swap_count(*swap_map) < swcount) {
1154                                         mmput(new_start_mm);
1155                                         atomic_inc(&mm->mm_users);
1156                                         new_start_mm = mm;
1157                                         set_start_mm = 0;
1158                                 }
1159                                 spin_lock(&mmlist_lock);
1160                         }
1161                         spin_unlock(&mmlist_lock);
1162                         mmput(prev_mm);
1163                         mmput(start_mm);
1164                         start_mm = new_start_mm;
1165                 }
1166                 if (shmem) {
1167                         /* page has already been unlocked and released */
1168                         if (shmem > 0)
1169                                 continue;
1170                         retval = shmem;
1171                         break;
1172                 }
1173                 if (retval) {
1174                         unlock_page(page);
1175                         page_cache_release(page);
1176                         break;
1177                 }
1178
1179                 /*
1180                  * How could swap count reach 0x7ffe ?
1181                  * There's no way to repeat a swap page within an mm
1182                  * (except in shmem, where it's the shared object which takes
1183                  * the reference count)?
1184                  * We believe SWAP_MAP_MAX cannot occur.(if occur, unsigned
1185                  * short is too small....)
1186                  * If that's wrong, then we should worry more about
1187                  * exit_mmap() and do_munmap() cases described above:
1188                  * we might be resetting SWAP_MAP_MAX too early here.
1189                  * We know "Undead"s can happen, they're okay, so don't
1190                  * report them; but do report if we reset SWAP_MAP_MAX.
1191                  */
1192                 /* We might release the lock_page() in unuse_mm(). */
1193                 if (!PageSwapCache(page) || page_private(page) != entry.val)
1194                         goto retry;
1195
1196                 if (swap_count(*swap_map) == SWAP_MAP_MAX) {
1197                         spin_lock(&swap_lock);
1198                         *swap_map = encode_swapmap(0, true);
1199                         spin_unlock(&swap_lock);
1200                         reset_overflow = 1;
1201                 }
1202
1203                 /*
1204                  * If a reference remains (rare), we would like to leave
1205                  * the page in the swap cache; but try_to_unmap could
1206                  * then re-duplicate the entry once we drop page lock,
1207                  * so we might loop indefinitely; also, that page could
1208                  * not be swapped out to other storage meanwhile.  So:
1209                  * delete from cache even if there's another reference,
1210                  * after ensuring that the data has been saved to disk -
1211                  * since if the reference remains (rarer), it will be
1212                  * read from disk into another page.  Splitting into two
1213                  * pages would be incorrect if swap supported "shared
1214                  * private" pages, but they are handled by tmpfs files.
1215                  */
1216                 if (swap_count(*swap_map) &&
1217                      PageDirty(page) && PageSwapCache(page)) {
1218                         struct writeback_control wbc = {
1219                                 .sync_mode = WB_SYNC_NONE,
1220                         };
1221
1222                         swap_writepage(page, &wbc);
1223                         lock_page(page);
1224                         wait_on_page_writeback(page);
1225                 }
1226
1227                 /*
1228                  * It is conceivable that a racing task removed this page from
1229                  * swap cache just before we acquired the page lock at the top,
1230                  * or while we dropped it in unuse_mm().  The page might even
1231                  * be back in swap cache on another swap area: that we must not
1232                  * delete, since it may not have been written out to swap yet.
1233                  */
1234                 if (PageSwapCache(page) &&
1235                     likely(page_private(page) == entry.val))
1236                         delete_from_swap_cache(page);
1237
1238                 /*
1239                  * So we could skip searching mms once swap count went
1240                  * to 1, we did not mark any present ptes as dirty: must
1241                  * mark page dirty so shrink_page_list will preserve it.
1242                  */
1243                 SetPageDirty(page);
1244 retry:
1245                 unlock_page(page);
1246                 page_cache_release(page);
1247
1248                 /*
1249                  * Make sure that we aren't completely killing
1250                  * interactive performance.
1251                  */
1252                 cond_resched();
1253         }
1254
1255         mmput(start_mm);
1256         if (reset_overflow) {
1257                 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
1258                 swap_overflow = 0;
1259         }
1260         return retval;
1261 }
1262
1263 /*
1264  * After a successful try_to_unuse, if no swap is now in use, we know
1265  * we can empty the mmlist.  swap_lock must be held on entry and exit.
1266  * Note that mmlist_lock nests inside swap_lock, and an mm must be
1267  * added to the mmlist just after page_duplicate - before would be racy.
1268  */
1269 static void drain_mmlist(void)
1270 {
1271         struct list_head *p, *next;
1272         unsigned int i;
1273
1274         for (i = 0; i < nr_swapfiles; i++)
1275                 if (swap_info[i].inuse_pages)
1276                         return;
1277         spin_lock(&mmlist_lock);
1278         list_for_each_safe(p, next, &init_mm.mmlist)
1279                 list_del_init(p);
1280         spin_unlock(&mmlist_lock);
1281 }
1282
1283 /*
1284  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1285  * corresponds to page offset `offset'.
1286  */
1287 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
1288 {
1289         struct swap_extent *se = sis->curr_swap_extent;
1290         struct swap_extent *start_se = se;
1291
1292         for ( ; ; ) {
1293                 struct list_head *lh;
1294
1295                 if (se->start_page <= offset &&
1296                                 offset < (se->start_page + se->nr_pages)) {
1297                         return se->start_block + (offset - se->start_page);
1298                 }
1299                 lh = se->list.next;
1300                 if (lh == &sis->extent_list)
1301                         lh = lh->next;
1302                 se = list_entry(lh, struct swap_extent, list);
1303                 sis->curr_swap_extent = se;
1304                 BUG_ON(se == start_se);         /* It *must* be present */
1305         }
1306 }
1307
1308 #ifdef CONFIG_HIBERNATION
1309 /*
1310  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1311  * corresponding to given index in swap_info (swap type).
1312  */
1313 sector_t swapdev_block(int swap_type, pgoff_t offset)
1314 {
1315         struct swap_info_struct *sis;
1316
1317         if (swap_type >= nr_swapfiles)
1318                 return 0;
1319
1320         sis = swap_info + swap_type;
1321         return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
1322 }
1323 #endif /* CONFIG_HIBERNATION */
1324
1325 /*
1326  * Free all of a swapdev's extent information
1327  */
1328 static void destroy_swap_extents(struct swap_info_struct *sis)
1329 {
1330         while (!list_empty(&sis->extent_list)) {
1331                 struct swap_extent *se;
1332
1333                 se = list_entry(sis->extent_list.next,
1334                                 struct swap_extent, list);
1335                 list_del(&se->list);
1336                 kfree(se);
1337         }
1338 }
1339
1340 /*
1341  * Add a block range (and the corresponding page range) into this swapdev's
1342  * extent list.  The extent list is kept sorted in page order.
1343  *
1344  * This function rather assumes that it is called in ascending page order.
1345  */
1346 static int
1347 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1348                 unsigned long nr_pages, sector_t start_block)
1349 {
1350         struct swap_extent *se;
1351         struct swap_extent *new_se;
1352         struct list_head *lh;
1353
1354         lh = sis->extent_list.prev;     /* The highest page extent */
1355         if (lh != &sis->extent_list) {
1356                 se = list_entry(lh, struct swap_extent, list);
1357                 BUG_ON(se->start_page + se->nr_pages != start_page);
1358                 if (se->start_block + se->nr_pages == start_block) {
1359                         /* Merge it */
1360                         se->nr_pages += nr_pages;
1361                         return 0;
1362                 }
1363         }
1364
1365         /*
1366          * No merge.  Insert a new extent, preserving ordering.
1367          */
1368         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1369         if (new_se == NULL)
1370                 return -ENOMEM;
1371         new_se->start_page = start_page;
1372         new_se->nr_pages = nr_pages;
1373         new_se->start_block = start_block;
1374
1375         list_add_tail(&new_se->list, &sis->extent_list);
1376         return 1;
1377 }
1378
1379 /*
1380  * A `swap extent' is a simple thing which maps a contiguous range of pages
1381  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1382  * is built at swapon time and is then used at swap_writepage/swap_readpage
1383  * time for locating where on disk a page belongs.
1384  *
1385  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1386  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1387  * swap files identically.
1388  *
1389  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1390  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1391  * swapfiles are handled *identically* after swapon time.
1392  *
1393  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1394  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1395  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1396  * requirements, they are simply tossed out - we will never use those blocks
1397  * for swapping.
1398  *
1399  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1400  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1401  * which will scribble on the fs.
1402  *
1403  * The amount of disk space which a single swap extent represents varies.
1404  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1405  * extents in the list.  To avoid much list walking, we cache the previous
1406  * search location in `curr_swap_extent', and start new searches from there.
1407  * This is extremely effective.  The average number of iterations in
1408  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1409  */
1410 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1411 {
1412         struct inode *inode;
1413         unsigned blocks_per_page;
1414         unsigned long page_no;
1415         unsigned blkbits;
1416         sector_t probe_block;
1417         sector_t last_block;
1418         sector_t lowest_block = -1;
1419         sector_t highest_block = 0;
1420         int nr_extents = 0;
1421         int ret;
1422
1423         inode = sis->swap_file->f_mapping->host;
1424         if (S_ISBLK(inode->i_mode)) {
1425                 ret = add_swap_extent(sis, 0, sis->max, 0);
1426                 *span = sis->pages;
1427                 goto done;
1428         }
1429
1430         blkbits = inode->i_blkbits;
1431         blocks_per_page = PAGE_SIZE >> blkbits;
1432
1433         /*
1434          * Map all the blocks into the extent list.  This code doesn't try
1435          * to be very smart.
1436          */
1437         probe_block = 0;
1438         page_no = 0;
1439         last_block = i_size_read(inode) >> blkbits;
1440         while ((probe_block + blocks_per_page) <= last_block &&
1441                         page_no < sis->max) {
1442                 unsigned block_in_page;
1443                 sector_t first_block;
1444
1445                 first_block = bmap(inode, probe_block);
1446                 if (first_block == 0)
1447                         goto bad_bmap;
1448
1449                 /*
1450                  * It must be PAGE_SIZE aligned on-disk
1451                  */
1452                 if (first_block & (blocks_per_page - 1)) {
1453                         probe_block++;
1454                         goto reprobe;
1455                 }
1456
1457                 for (block_in_page = 1; block_in_page < blocks_per_page;
1458                                         block_in_page++) {
1459                         sector_t block;
1460
1461                         block = bmap(inode, probe_block + block_in_page);
1462                         if (block == 0)
1463                                 goto bad_bmap;
1464                         if (block != first_block + block_in_page) {
1465                                 /* Discontiguity */
1466                                 probe_block++;
1467                                 goto reprobe;
1468                         }
1469                 }
1470
1471                 first_block >>= (PAGE_SHIFT - blkbits);
1472                 if (page_no) {  /* exclude the header page */
1473                         if (first_block < lowest_block)
1474                                 lowest_block = first_block;
1475                         if (first_block > highest_block)
1476                                 highest_block = first_block;
1477                 }
1478
1479                 /*
1480                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1481                  */
1482                 ret = add_swap_extent(sis, page_no, 1, first_block);
1483                 if (ret < 0)
1484                         goto out;
1485                 nr_extents += ret;
1486                 page_no++;
1487                 probe_block += blocks_per_page;
1488 reprobe:
1489                 continue;
1490         }
1491         ret = nr_extents;
1492         *span = 1 + highest_block - lowest_block;
1493         if (page_no == 0)
1494                 page_no = 1;    /* force Empty message */
1495         sis->max = page_no;
1496         sis->pages = page_no - 1;
1497         sis->highest_bit = page_no - 1;
1498 done:
1499         sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1500                                         struct swap_extent, list);
1501         goto out;
1502 bad_bmap:
1503         printk(KERN_ERR "swapon: swapfile has holes\n");
1504         ret = -EINVAL;
1505 out:
1506         return ret;
1507 }
1508
1509 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1510 {
1511         struct swap_info_struct * p = NULL;
1512         unsigned short *swap_map;
1513         struct file *swap_file, *victim;
1514         struct address_space *mapping;
1515         struct inode *inode;
1516         char * pathname;
1517         int i, type, prev;
1518         int err;
1519
1520         if (!capable(CAP_SYS_ADMIN))
1521                 return -EPERM;
1522
1523         pathname = getname(specialfile);
1524         err = PTR_ERR(pathname);
1525         if (IS_ERR(pathname))
1526                 goto out;
1527
1528         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1529         putname(pathname);
1530         err = PTR_ERR(victim);
1531         if (IS_ERR(victim))
1532                 goto out;
1533
1534         mapping = victim->f_mapping;
1535         prev = -1;
1536         spin_lock(&swap_lock);
1537         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1538                 p = swap_info + type;
1539                 if (p->flags & SWP_WRITEOK) {
1540                         if (p->swap_file->f_mapping == mapping)
1541                                 break;
1542                 }
1543                 prev = type;
1544         }
1545         if (type < 0) {
1546                 err = -EINVAL;
1547                 spin_unlock(&swap_lock);
1548                 goto out_dput;
1549         }
1550         if (!security_vm_enough_memory(p->pages))
1551                 vm_unacct_memory(p->pages);
1552         else {
1553                 err = -ENOMEM;
1554                 spin_unlock(&swap_lock);
1555                 goto out_dput;
1556         }
1557         if (prev < 0) {
1558                 swap_list.head = p->next;
1559         } else {
1560                 swap_info[prev].next = p->next;
1561         }
1562         if (type == swap_list.next) {
1563                 /* just pick something that's safe... */
1564                 swap_list.next = swap_list.head;
1565         }
1566         if (p->prio < 0) {
1567                 for (i = p->next; i >= 0; i = swap_info[i].next)
1568                         swap_info[i].prio = p->prio--;
1569                 least_priority++;
1570         }
1571         nr_swap_pages -= p->pages;
1572         total_swap_pages -= p->pages;
1573         p->flags &= ~SWP_WRITEOK;
1574         spin_unlock(&swap_lock);
1575
1576         current->flags |= PF_SWAPOFF;
1577         err = try_to_unuse(type);
1578         current->flags &= ~PF_SWAPOFF;
1579
1580         if (err) {
1581                 /* re-insert swap space back into swap_list */
1582                 spin_lock(&swap_lock);
1583                 if (p->prio < 0)
1584                         p->prio = --least_priority;
1585                 prev = -1;
1586                 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1587                         if (p->prio >= swap_info[i].prio)
1588                                 break;
1589                         prev = i;
1590                 }
1591                 p->next = i;
1592                 if (prev < 0)
1593                         swap_list.head = swap_list.next = p - swap_info;
1594                 else
1595                         swap_info[prev].next = p - swap_info;
1596                 nr_swap_pages += p->pages;
1597                 total_swap_pages += p->pages;
1598                 p->flags |= SWP_WRITEOK;
1599                 spin_unlock(&swap_lock);
1600                 goto out_dput;
1601         }
1602
1603         /* wait for any unplug function to finish */
1604         down_write(&swap_unplug_sem);
1605         up_write(&swap_unplug_sem);
1606
1607         destroy_swap_extents(p);
1608         mutex_lock(&swapon_mutex);
1609         spin_lock(&swap_lock);
1610         drain_mmlist();
1611
1612         /* wait for anyone still in scan_swap_map */
1613         p->highest_bit = 0;             /* cuts scans short */
1614         while (p->flags >= SWP_SCANNING) {
1615                 spin_unlock(&swap_lock);
1616                 schedule_timeout_uninterruptible(1);
1617                 spin_lock(&swap_lock);
1618         }
1619
1620         swap_file = p->swap_file;
1621         p->swap_file = NULL;
1622         p->max = 0;
1623         swap_map = p->swap_map;
1624         p->swap_map = NULL;
1625         p->flags = 0;
1626         spin_unlock(&swap_lock);
1627         mutex_unlock(&swapon_mutex);
1628         vfree(swap_map);
1629         /* Destroy swap account informatin */
1630         swap_cgroup_swapoff(type);
1631
1632         inode = mapping->host;
1633         if (S_ISBLK(inode->i_mode)) {
1634                 struct block_device *bdev = I_BDEV(inode);
1635                 set_blocksize(bdev, p->old_block_size);
1636                 bd_release(bdev);
1637         } else {
1638                 mutex_lock(&inode->i_mutex);
1639                 inode->i_flags &= ~S_SWAPFILE;
1640                 mutex_unlock(&inode->i_mutex);
1641         }
1642         filp_close(swap_file, NULL);
1643         err = 0;
1644
1645 out_dput:
1646         filp_close(victim, NULL);
1647 out:
1648         return err;
1649 }
1650
1651 #ifdef CONFIG_PROC_FS
1652 /* iterator */
1653 static void *swap_start(struct seq_file *swap, loff_t *pos)
1654 {
1655         struct swap_info_struct *ptr = swap_info;
1656         int i;
1657         loff_t l = *pos;
1658
1659         mutex_lock(&swapon_mutex);
1660
1661         if (!l)
1662                 return SEQ_START_TOKEN;
1663
1664         for (i = 0; i < nr_swapfiles; i++, ptr++) {
1665                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1666                         continue;
1667                 if (!--l)
1668                         return ptr;
1669         }
1670
1671         return NULL;
1672 }
1673
1674 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1675 {
1676         struct swap_info_struct *ptr;
1677         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1678
1679         if (v == SEQ_START_TOKEN)
1680                 ptr = swap_info;
1681         else {
1682                 ptr = v;
1683                 ptr++;
1684         }
1685
1686         for (; ptr < endptr; ptr++) {
1687                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1688                         continue;
1689                 ++*pos;
1690                 return ptr;
1691         }
1692
1693         return NULL;
1694 }
1695
1696 static void swap_stop(struct seq_file *swap, void *v)
1697 {
1698         mutex_unlock(&swapon_mutex);
1699 }
1700
1701 static int swap_show(struct seq_file *swap, void *v)
1702 {
1703         struct swap_info_struct *ptr = v;
1704         struct file *file;
1705         int len;
1706
1707         if (ptr == SEQ_START_TOKEN) {
1708                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1709                 return 0;
1710         }
1711
1712         file = ptr->swap_file;
1713         len = seq_path(swap, &file->f_path, " \t\n\\");
1714         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1715                         len < 40 ? 40 - len : 1, " ",
1716                         S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1717                                 "partition" : "file\t",
1718                         ptr->pages << (PAGE_SHIFT - 10),
1719                         ptr->inuse_pages << (PAGE_SHIFT - 10),
1720                         ptr->prio);
1721         return 0;
1722 }
1723
1724 static const struct seq_operations swaps_op = {
1725         .start =        swap_start,
1726         .next =         swap_next,
1727         .stop =         swap_stop,
1728         .show =         swap_show
1729 };
1730
1731 static int swaps_open(struct inode *inode, struct file *file)
1732 {
1733         return seq_open(file, &swaps_op);
1734 }
1735
1736 static const struct file_operations proc_swaps_operations = {
1737         .open           = swaps_open,
1738         .read           = seq_read,
1739         .llseek         = seq_lseek,
1740         .release        = seq_release,
1741 };
1742
1743 static int __init procswaps_init(void)
1744 {
1745         proc_create("swaps", 0, NULL, &proc_swaps_operations);
1746         return 0;
1747 }
1748 __initcall(procswaps_init);
1749 #endif /* CONFIG_PROC_FS */
1750
1751 #ifdef MAX_SWAPFILES_CHECK
1752 static int __init max_swapfiles_check(void)
1753 {
1754         MAX_SWAPFILES_CHECK();
1755         return 0;
1756 }
1757 late_initcall(max_swapfiles_check);
1758 #endif
1759
1760 /*
1761  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1762  *
1763  * The swapon system call
1764  */
1765 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1766 {
1767         struct swap_info_struct * p;
1768         char *name = NULL;
1769         struct block_device *bdev = NULL;
1770         struct file *swap_file = NULL;
1771         struct address_space *mapping;
1772         unsigned int type;
1773         int i, prev;
1774         int error;
1775         union swap_header *swap_header = NULL;
1776         unsigned int nr_good_pages = 0;
1777         int nr_extents = 0;
1778         sector_t span;
1779         unsigned long maxpages = 1;
1780         unsigned long swapfilepages;
1781         unsigned short *swap_map = NULL;
1782         struct page *page = NULL;
1783         struct inode *inode = NULL;
1784         int did_down = 0;
1785
1786         if (!capable(CAP_SYS_ADMIN))
1787                 return -EPERM;
1788         spin_lock(&swap_lock);
1789         p = swap_info;
1790         for (type = 0 ; type < nr_swapfiles ; type++,p++)
1791                 if (!(p->flags & SWP_USED))
1792                         break;
1793         error = -EPERM;
1794         if (type >= MAX_SWAPFILES) {
1795                 spin_unlock(&swap_lock);
1796                 goto out;
1797         }
1798         if (type >= nr_swapfiles)
1799                 nr_swapfiles = type+1;
1800         memset(p, 0, sizeof(*p));
1801         INIT_LIST_HEAD(&p->extent_list);
1802         p->flags = SWP_USED;
1803         p->next = -1;
1804         spin_unlock(&swap_lock);
1805         name = getname(specialfile);
1806         error = PTR_ERR(name);
1807         if (IS_ERR(name)) {
1808                 name = NULL;
1809                 goto bad_swap_2;
1810         }
1811         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1812         error = PTR_ERR(swap_file);
1813         if (IS_ERR(swap_file)) {
1814                 swap_file = NULL;
1815                 goto bad_swap_2;
1816         }
1817
1818         p->swap_file = swap_file;
1819         mapping = swap_file->f_mapping;
1820         inode = mapping->host;
1821
1822         error = -EBUSY;
1823         for (i = 0; i < nr_swapfiles; i++) {
1824                 struct swap_info_struct *q = &swap_info[i];
1825
1826                 if (i == type || !q->swap_file)
1827                         continue;
1828                 if (mapping == q->swap_file->f_mapping)
1829                         goto bad_swap;
1830         }
1831
1832         error = -EINVAL;
1833         if (S_ISBLK(inode->i_mode)) {
1834                 bdev = I_BDEV(inode);
1835                 error = bd_claim(bdev, sys_swapon);
1836                 if (error < 0) {
1837                         bdev = NULL;
1838                         error = -EINVAL;
1839                         goto bad_swap;
1840                 }
1841                 p->old_block_size = block_size(bdev);
1842                 error = set_blocksize(bdev, PAGE_SIZE);
1843                 if (error < 0)
1844                         goto bad_swap;
1845                 p->bdev = bdev;
1846         } else if (S_ISREG(inode->i_mode)) {
1847                 p->bdev = inode->i_sb->s_bdev;
1848                 mutex_lock(&inode->i_mutex);
1849                 did_down = 1;
1850                 if (IS_SWAPFILE(inode)) {
1851                         error = -EBUSY;
1852                         goto bad_swap;
1853                 }
1854         } else {
1855                 goto bad_swap;
1856         }
1857
1858         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1859
1860         /*
1861          * Read the swap header.
1862          */
1863         if (!mapping->a_ops->readpage) {
1864                 error = -EINVAL;
1865                 goto bad_swap;
1866         }
1867         page = read_mapping_page(mapping, 0, swap_file);
1868         if (IS_ERR(page)) {
1869                 error = PTR_ERR(page);
1870                 goto bad_swap;
1871         }
1872         swap_header = kmap(page);
1873
1874         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1875                 printk(KERN_ERR "Unable to find swap-space signature\n");
1876                 error = -EINVAL;
1877                 goto bad_swap;
1878         }
1879
1880         /* swap partition endianess hack... */
1881         if (swab32(swap_header->info.version) == 1) {
1882                 swab32s(&swap_header->info.version);
1883                 swab32s(&swap_header->info.last_page);
1884                 swab32s(&swap_header->info.nr_badpages);
1885                 for (i = 0; i < swap_header->info.nr_badpages; i++)
1886                         swab32s(&swap_header->info.badpages[i]);
1887         }
1888         /* Check the swap header's sub-version */
1889         if (swap_header->info.version != 1) {
1890                 printk(KERN_WARNING
1891                        "Unable to handle swap header version %d\n",
1892                        swap_header->info.version);
1893                 error = -EINVAL;
1894                 goto bad_swap;
1895         }
1896
1897         p->lowest_bit  = 1;
1898         p->cluster_next = 1;
1899
1900         /*
1901          * Find out how many pages are allowed for a single swap
1902          * device. There are two limiting factors: 1) the number of
1903          * bits for the swap offset in the swp_entry_t type and
1904          * 2) the number of bits in the a swap pte as defined by
1905          * the different architectures. In order to find the
1906          * largest possible bit mask a swap entry with swap type 0
1907          * and swap offset ~0UL is created, encoded to a swap pte,
1908          * decoded to a swp_entry_t again and finally the swap
1909          * offset is extracted. This will mask all the bits from
1910          * the initial ~0UL mask that can't be encoded in either
1911          * the swp_entry_t or the architecture definition of a
1912          * swap pte.
1913          */
1914         maxpages = swp_offset(pte_to_swp_entry(
1915                         swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1916         if (maxpages > swap_header->info.last_page)
1917                 maxpages = swap_header->info.last_page;
1918         p->highest_bit = maxpages - 1;
1919
1920         error = -EINVAL;
1921         if (!maxpages)
1922                 goto bad_swap;
1923         if (swapfilepages && maxpages > swapfilepages) {
1924                 printk(KERN_WARNING
1925                        "Swap area shorter than signature indicates\n");
1926                 goto bad_swap;
1927         }
1928         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1929                 goto bad_swap;
1930         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1931                 goto bad_swap;
1932
1933         /* OK, set up the swap map and apply the bad block list */
1934         swap_map = vmalloc(maxpages * sizeof(short));
1935         if (!swap_map) {
1936                 error = -ENOMEM;
1937                 goto bad_swap;
1938         }
1939
1940         memset(swap_map, 0, maxpages * sizeof(short));
1941         for (i = 0; i < swap_header->info.nr_badpages; i++) {
1942                 int page_nr = swap_header->info.badpages[i];
1943                 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1944                         error = -EINVAL;
1945                         goto bad_swap;
1946                 }
1947                 swap_map[page_nr] = SWAP_MAP_BAD;
1948         }
1949
1950         error = swap_cgroup_swapon(type, maxpages);
1951         if (error)
1952                 goto bad_swap;
1953
1954         nr_good_pages = swap_header->info.last_page -
1955                         swap_header->info.nr_badpages -
1956                         1 /* header page */;
1957
1958         if (nr_good_pages) {
1959                 swap_map[0] = SWAP_MAP_BAD;
1960                 p->max = maxpages;
1961                 p->pages = nr_good_pages;
1962                 nr_extents = setup_swap_extents(p, &span);
1963                 if (nr_extents < 0) {
1964                         error = nr_extents;
1965                         goto bad_swap;
1966                 }
1967                 nr_good_pages = p->pages;
1968         }
1969         if (!nr_good_pages) {
1970                 printk(KERN_WARNING "Empty swap-file\n");
1971                 error = -EINVAL;
1972                 goto bad_swap;
1973         }
1974
1975         if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1976                 p->flags |= SWP_SOLIDSTATE;
1977                 p->cluster_next = 1 + (random32() % p->highest_bit);
1978         }
1979         if (discard_swap(p) == 0)
1980                 p->flags |= SWP_DISCARDABLE;
1981
1982         mutex_lock(&swapon_mutex);
1983         spin_lock(&swap_lock);
1984         if (swap_flags & SWAP_FLAG_PREFER)
1985                 p->prio =
1986                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1987         else
1988                 p->prio = --least_priority;
1989         p->swap_map = swap_map;
1990         p->flags |= SWP_WRITEOK;
1991         nr_swap_pages += nr_good_pages;
1992         total_swap_pages += nr_good_pages;
1993
1994         printk(KERN_INFO "Adding %uk swap on %s.  "
1995                         "Priority:%d extents:%d across:%lluk %s%s\n",
1996                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1997                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
1998                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
1999                 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2000
2001         /* insert swap space into swap_list: */
2002         prev = -1;
2003         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
2004                 if (p->prio >= swap_info[i].prio) {
2005                         break;
2006                 }
2007                 prev = i;
2008         }
2009         p->next = i;
2010         if (prev < 0) {
2011                 swap_list.head = swap_list.next = p - swap_info;
2012         } else {
2013                 swap_info[prev].next = p - swap_info;
2014         }
2015         spin_unlock(&swap_lock);
2016         mutex_unlock(&swapon_mutex);
2017         error = 0;
2018         goto out;
2019 bad_swap:
2020         if (bdev) {
2021                 set_blocksize(bdev, p->old_block_size);
2022                 bd_release(bdev);
2023         }
2024         destroy_swap_extents(p);
2025         swap_cgroup_swapoff(type);
2026 bad_swap_2:
2027         spin_lock(&swap_lock);
2028         p->swap_file = NULL;
2029         p->flags = 0;
2030         spin_unlock(&swap_lock);
2031         vfree(swap_map);
2032         if (swap_file)
2033                 filp_close(swap_file, NULL);
2034 out:
2035         if (page && !IS_ERR(page)) {
2036                 kunmap(page);
2037                 page_cache_release(page);
2038         }
2039         if (name)
2040                 putname(name);
2041         if (did_down) {
2042                 if (!error)
2043                         inode->i_flags |= S_SWAPFILE;
2044                 mutex_unlock(&inode->i_mutex);
2045         }
2046         return error;
2047 }
2048
2049 void si_swapinfo(struct sysinfo *val)
2050 {
2051         unsigned int i;
2052         unsigned long nr_to_be_unused = 0;
2053
2054         spin_lock(&swap_lock);
2055         for (i = 0; i < nr_swapfiles; i++) {
2056                 if (!(swap_info[i].flags & SWP_USED) ||
2057                      (swap_info[i].flags & SWP_WRITEOK))
2058                         continue;
2059                 nr_to_be_unused += swap_info[i].inuse_pages;
2060         }
2061         val->freeswap = nr_swap_pages + nr_to_be_unused;
2062         val->totalswap = total_swap_pages + nr_to_be_unused;
2063         spin_unlock(&swap_lock);
2064 }
2065
2066 /*
2067  * Verify that a swap entry is valid and increment its swap map count.
2068  *
2069  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
2070  * "permanent", but will be reclaimed by the next swapoff.
2071  * Returns error code in following case.
2072  * - success -> 0
2073  * - swp_entry is invalid -> EINVAL
2074  * - swp_entry is migration entry -> EINVAL
2075  * - swap-cache reference is requested but there is already one. -> EEXIST
2076  * - swap-cache reference is requested but the entry is not used. -> ENOENT
2077  */
2078 static int __swap_duplicate(swp_entry_t entry, bool cache)
2079 {
2080         struct swap_info_struct * p;
2081         unsigned long offset, type;
2082         int result = -EINVAL;
2083         int count;
2084         bool has_cache;
2085
2086         if (is_migration_entry(entry))
2087                 return -EINVAL;
2088
2089         type = swp_type(entry);
2090         if (type >= nr_swapfiles)
2091                 goto bad_file;
2092         p = type + swap_info;
2093         offset = swp_offset(entry);
2094
2095         spin_lock(&swap_lock);
2096
2097         if (unlikely(offset >= p->max))
2098                 goto unlock_out;
2099
2100         count = swap_count(p->swap_map[offset]);
2101         has_cache = swap_has_cache(p->swap_map[offset]);
2102
2103         if (cache == SWAP_CACHE) { /* called for swapcache/swapin-readahead */
2104
2105                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2106                 if (!has_cache && count) {
2107                         p->swap_map[offset] = encode_swapmap(count, true);
2108                         result = 0;
2109                 } else if (has_cache) /* someone added cache */
2110                         result = -EEXIST;
2111                 else if (!count) /* no users */
2112                         result = -ENOENT;
2113
2114         } else if (count || has_cache) {
2115                 if (count < SWAP_MAP_MAX - 1) {
2116                         p->swap_map[offset] = encode_swapmap(count + 1,
2117                                                              has_cache);
2118                         result = 0;
2119                 } else if (count <= SWAP_MAP_MAX) {
2120                         if (swap_overflow++ < 5)
2121                                 printk(KERN_WARNING
2122                                        "swap_dup: swap entry overflow\n");
2123                         p->swap_map[offset] = encode_swapmap(SWAP_MAP_MAX,
2124                                                               has_cache);
2125                         result = 0;
2126                 }
2127         } else
2128                 result = -ENOENT; /* unused swap entry */
2129 unlock_out:
2130         spin_unlock(&swap_lock);
2131 out:
2132         return result;
2133
2134 bad_file:
2135         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2136         goto out;
2137 }
2138 /*
2139  * increase reference count of swap entry by 1.
2140  */
2141 void swap_duplicate(swp_entry_t entry)
2142 {
2143         __swap_duplicate(entry, SWAP_MAP);
2144 }
2145
2146 /*
2147  * @entry: swap entry for which we allocate swap cache.
2148  *
2149  * Called when allocating swap cache for exising swap entry,
2150  * This can return error codes. Returns 0 at success.
2151  * -EBUSY means there is a swap cache.
2152  * Note: return code is different from swap_duplicate().
2153  */
2154 int swapcache_prepare(swp_entry_t entry)
2155 {
2156         return __swap_duplicate(entry, SWAP_CACHE);
2157 }
2158
2159
2160 struct swap_info_struct *
2161 get_swap_info_struct(unsigned type)
2162 {
2163         return &swap_info[type];
2164 }
2165
2166 /*
2167  * swap_lock prevents swap_map being freed. Don't grab an extra
2168  * reference on the swaphandle, it doesn't matter if it becomes unused.
2169  */
2170 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2171 {
2172         struct swap_info_struct *si;
2173         int our_page_cluster = page_cluster;
2174         pgoff_t target, toff;
2175         pgoff_t base, end;
2176         int nr_pages = 0;
2177
2178         if (!our_page_cluster)  /* no readahead */
2179                 return 0;
2180
2181         si = &swap_info[swp_type(entry)];
2182         target = swp_offset(entry);
2183         base = (target >> our_page_cluster) << our_page_cluster;
2184         end = base + (1 << our_page_cluster);
2185         if (!base)              /* first page is swap header */
2186                 base++;
2187
2188         spin_lock(&swap_lock);
2189         if (end > si->max)      /* don't go beyond end of map */
2190                 end = si->max;
2191
2192         /* Count contiguous allocated slots above our target */
2193         for (toff = target; ++toff < end; nr_pages++) {
2194                 /* Don't read in free or bad pages */
2195                 if (!si->swap_map[toff])
2196                         break;
2197                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2198                         break;
2199         }
2200         /* Count contiguous allocated slots below our target */
2201         for (toff = target; --toff >= base; nr_pages++) {
2202                 /* Don't read in free or bad pages */
2203                 if (!si->swap_map[toff])
2204                         break;
2205                 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
2206                         break;
2207         }
2208         spin_unlock(&swap_lock);
2209
2210         /*
2211          * Indicate starting offset, and return number of pages to get:
2212          * if only 1, say 0, since there's then no readahead to be done.
2213          */
2214         *offset = ++toff;
2215         return nr_pages? ++nr_pages: 0;
2216 }