[PATCH] swsusp: use partition device and offset to identify swap areas
[linux-2.6.git] / mm / swapfile.c
1 /*
2  *  linux/mm/swapfile.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  *  Swap reorganised 29.12.95, Stephen Tweedie
6  */
7
8 #include <linux/mm.h>
9 #include <linux/hugetlb.h>
10 #include <linux/mman.h>
11 #include <linux/slab.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/swap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/pagemap.h>
16 #include <linux/namei.h>
17 #include <linux/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/writeback.h>
20 #include <linux/proc_fs.h>
21 #include <linux/seq_file.h>
22 #include <linux/init.h>
23 #include <linux/module.h>
24 #include <linux/rmap.h>
25 #include <linux/security.h>
26 #include <linux/backing-dev.h>
27 #include <linux/mutex.h>
28 #include <linux/capability.h>
29 #include <linux/syscalls.h>
30
31 #include <asm/pgtable.h>
32 #include <asm/tlbflush.h>
33 #include <linux/swapops.h>
34
35 DEFINE_SPINLOCK(swap_lock);
36 unsigned int nr_swapfiles;
37 long total_swap_pages;
38 static int swap_overflow;
39
40 static const char Bad_file[] = "Bad swap file entry ";
41 static const char Unused_file[] = "Unused swap file entry ";
42 static const char Bad_offset[] = "Bad swap offset entry ";
43 static const char Unused_offset[] = "Unused swap offset entry ";
44
45 struct swap_list_t swap_list = {-1, -1};
46
47 static struct swap_info_struct swap_info[MAX_SWAPFILES];
48
49 static DEFINE_MUTEX(swapon_mutex);
50
51 /*
52  * We need this because the bdev->unplug_fn can sleep and we cannot
53  * hold swap_lock while calling the unplug_fn. And swap_lock
54  * cannot be turned into a mutex.
55  */
56 static DECLARE_RWSEM(swap_unplug_sem);
57
58 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
59 {
60         swp_entry_t entry;
61
62         down_read(&swap_unplug_sem);
63         entry.val = page_private(page);
64         if (PageSwapCache(page)) {
65                 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
66                 struct backing_dev_info *bdi;
67
68                 /*
69                  * If the page is removed from swapcache from under us (with a
70                  * racy try_to_unuse/swapoff) we need an additional reference
71                  * count to avoid reading garbage from page_private(page) above.
72                  * If the WARN_ON triggers during a swapoff it maybe the race
73                  * condition and it's harmless. However if it triggers without
74                  * swapoff it signals a problem.
75                  */
76                 WARN_ON(page_count(page) <= 1);
77
78                 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
79                 blk_run_backing_dev(bdi, page);
80         }
81         up_read(&swap_unplug_sem);
82 }
83
84 #define SWAPFILE_CLUSTER        256
85 #define LATENCY_LIMIT           256
86
87 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
88 {
89         unsigned long offset, last_in_cluster;
90         int latency_ration = LATENCY_LIMIT;
91
92         /* 
93          * We try to cluster swap pages by allocating them sequentially
94          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
95          * way, however, we resort to first-free allocation, starting
96          * a new cluster.  This prevents us from scattering swap pages
97          * all over the entire swap partition, so that we reduce
98          * overall disk seek times between swap pages.  -- sct
99          * But we do now try to find an empty cluster.  -Andrea
100          */
101
102         si->flags += SWP_SCANNING;
103         if (unlikely(!si->cluster_nr)) {
104                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
105                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
106                         goto lowest;
107                 spin_unlock(&swap_lock);
108
109                 offset = si->lowest_bit;
110                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
111
112                 /* Locate the first empty (unaligned) cluster */
113                 for (; last_in_cluster <= si->highest_bit; offset++) {
114                         if (si->swap_map[offset])
115                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
116                         else if (offset == last_in_cluster) {
117                                 spin_lock(&swap_lock);
118                                 si->cluster_next = offset-SWAPFILE_CLUSTER+1;
119                                 goto cluster;
120                         }
121                         if (unlikely(--latency_ration < 0)) {
122                                 cond_resched();
123                                 latency_ration = LATENCY_LIMIT;
124                         }
125                 }
126                 spin_lock(&swap_lock);
127                 goto lowest;
128         }
129
130         si->cluster_nr--;
131 cluster:
132         offset = si->cluster_next;
133         if (offset > si->highest_bit)
134 lowest:         offset = si->lowest_bit;
135 checks: if (!(si->flags & SWP_WRITEOK))
136                 goto no_page;
137         if (!si->highest_bit)
138                 goto no_page;
139         if (!si->swap_map[offset]) {
140                 if (offset == si->lowest_bit)
141                         si->lowest_bit++;
142                 if (offset == si->highest_bit)
143                         si->highest_bit--;
144                 si->inuse_pages++;
145                 if (si->inuse_pages == si->pages) {
146                         si->lowest_bit = si->max;
147                         si->highest_bit = 0;
148                 }
149                 si->swap_map[offset] = 1;
150                 si->cluster_next = offset + 1;
151                 si->flags -= SWP_SCANNING;
152                 return offset;
153         }
154
155         spin_unlock(&swap_lock);
156         while (++offset <= si->highest_bit) {
157                 if (!si->swap_map[offset]) {
158                         spin_lock(&swap_lock);
159                         goto checks;
160                 }
161                 if (unlikely(--latency_ration < 0)) {
162                         cond_resched();
163                         latency_ration = LATENCY_LIMIT;
164                 }
165         }
166         spin_lock(&swap_lock);
167         goto lowest;
168
169 no_page:
170         si->flags -= SWP_SCANNING;
171         return 0;
172 }
173
174 swp_entry_t get_swap_page(void)
175 {
176         struct swap_info_struct *si;
177         pgoff_t offset;
178         int type, next;
179         int wrapped = 0;
180
181         spin_lock(&swap_lock);
182         if (nr_swap_pages <= 0)
183                 goto noswap;
184         nr_swap_pages--;
185
186         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
187                 si = swap_info + type;
188                 next = si->next;
189                 if (next < 0 ||
190                     (!wrapped && si->prio != swap_info[next].prio)) {
191                         next = swap_list.head;
192                         wrapped++;
193                 }
194
195                 if (!si->highest_bit)
196                         continue;
197                 if (!(si->flags & SWP_WRITEOK))
198                         continue;
199
200                 swap_list.next = next;
201                 offset = scan_swap_map(si);
202                 if (offset) {
203                         spin_unlock(&swap_lock);
204                         return swp_entry(type, offset);
205                 }
206                 next = swap_list.next;
207         }
208
209         nr_swap_pages++;
210 noswap:
211         spin_unlock(&swap_lock);
212         return (swp_entry_t) {0};
213 }
214
215 swp_entry_t get_swap_page_of_type(int type)
216 {
217         struct swap_info_struct *si;
218         pgoff_t offset;
219
220         spin_lock(&swap_lock);
221         si = swap_info + type;
222         if (si->flags & SWP_WRITEOK) {
223                 nr_swap_pages--;
224                 offset = scan_swap_map(si);
225                 if (offset) {
226                         spin_unlock(&swap_lock);
227                         return swp_entry(type, offset);
228                 }
229                 nr_swap_pages++;
230         }
231         spin_unlock(&swap_lock);
232         return (swp_entry_t) {0};
233 }
234
235 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
236 {
237         struct swap_info_struct * p;
238         unsigned long offset, type;
239
240         if (!entry.val)
241                 goto out;
242         type = swp_type(entry);
243         if (type >= nr_swapfiles)
244                 goto bad_nofile;
245         p = & swap_info[type];
246         if (!(p->flags & SWP_USED))
247                 goto bad_device;
248         offset = swp_offset(entry);
249         if (offset >= p->max)
250                 goto bad_offset;
251         if (!p->swap_map[offset])
252                 goto bad_free;
253         spin_lock(&swap_lock);
254         return p;
255
256 bad_free:
257         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
258         goto out;
259 bad_offset:
260         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
261         goto out;
262 bad_device:
263         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
264         goto out;
265 bad_nofile:
266         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
267 out:
268         return NULL;
269 }       
270
271 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
272 {
273         int count = p->swap_map[offset];
274
275         if (count < SWAP_MAP_MAX) {
276                 count--;
277                 p->swap_map[offset] = count;
278                 if (!count) {
279                         if (offset < p->lowest_bit)
280                                 p->lowest_bit = offset;
281                         if (offset > p->highest_bit)
282                                 p->highest_bit = offset;
283                         if (p->prio > swap_info[swap_list.next].prio)
284                                 swap_list.next = p - swap_info;
285                         nr_swap_pages++;
286                         p->inuse_pages--;
287                 }
288         }
289         return count;
290 }
291
292 /*
293  * Caller has made sure that the swapdevice corresponding to entry
294  * is still around or has not been recycled.
295  */
296 void swap_free(swp_entry_t entry)
297 {
298         struct swap_info_struct * p;
299
300         p = swap_info_get(entry);
301         if (p) {
302                 swap_entry_free(p, swp_offset(entry));
303                 spin_unlock(&swap_lock);
304         }
305 }
306
307 /*
308  * How many references to page are currently swapped out?
309  */
310 static inline int page_swapcount(struct page *page)
311 {
312         int count = 0;
313         struct swap_info_struct *p;
314         swp_entry_t entry;
315
316         entry.val = page_private(page);
317         p = swap_info_get(entry);
318         if (p) {
319                 /* Subtract the 1 for the swap cache itself */
320                 count = p->swap_map[swp_offset(entry)] - 1;
321                 spin_unlock(&swap_lock);
322         }
323         return count;
324 }
325
326 /*
327  * We can use this swap cache entry directly
328  * if there are no other references to it.
329  */
330 int can_share_swap_page(struct page *page)
331 {
332         int count;
333
334         BUG_ON(!PageLocked(page));
335         count = page_mapcount(page);
336         if (count <= 1 && PageSwapCache(page))
337                 count += page_swapcount(page);
338         return count == 1;
339 }
340
341 /*
342  * Work out if there are any other processes sharing this
343  * swap cache page. Free it if you can. Return success.
344  */
345 int remove_exclusive_swap_page(struct page *page)
346 {
347         int retval;
348         struct swap_info_struct * p;
349         swp_entry_t entry;
350
351         BUG_ON(PagePrivate(page));
352         BUG_ON(!PageLocked(page));
353
354         if (!PageSwapCache(page))
355                 return 0;
356         if (PageWriteback(page))
357                 return 0;
358         if (page_count(page) != 2) /* 2: us + cache */
359                 return 0;
360
361         entry.val = page_private(page);
362         p = swap_info_get(entry);
363         if (!p)
364                 return 0;
365
366         /* Is the only swap cache user the cache itself? */
367         retval = 0;
368         if (p->swap_map[swp_offset(entry)] == 1) {
369                 /* Recheck the page count with the swapcache lock held.. */
370                 write_lock_irq(&swapper_space.tree_lock);
371                 if ((page_count(page) == 2) && !PageWriteback(page)) {
372                         __delete_from_swap_cache(page);
373                         SetPageDirty(page);
374                         retval = 1;
375                 }
376                 write_unlock_irq(&swapper_space.tree_lock);
377         }
378         spin_unlock(&swap_lock);
379
380         if (retval) {
381                 swap_free(entry);
382                 page_cache_release(page);
383         }
384
385         return retval;
386 }
387
388 /*
389  * Free the swap entry like above, but also try to
390  * free the page cache entry if it is the last user.
391  */
392 void free_swap_and_cache(swp_entry_t entry)
393 {
394         struct swap_info_struct * p;
395         struct page *page = NULL;
396
397         if (is_migration_entry(entry))
398                 return;
399
400         p = swap_info_get(entry);
401         if (p) {
402                 if (swap_entry_free(p, swp_offset(entry)) == 1) {
403                         page = find_get_page(&swapper_space, entry.val);
404                         if (page && unlikely(TestSetPageLocked(page))) {
405                                 page_cache_release(page);
406                                 page = NULL;
407                         }
408                 }
409                 spin_unlock(&swap_lock);
410         }
411         if (page) {
412                 int one_user;
413
414                 BUG_ON(PagePrivate(page));
415                 one_user = (page_count(page) == 2);
416                 /* Only cache user (+us), or swap space full? Free it! */
417                 /* Also recheck PageSwapCache after page is locked (above) */
418                 if (PageSwapCache(page) && !PageWriteback(page) &&
419                                         (one_user || vm_swap_full())) {
420                         delete_from_swap_cache(page);
421                         SetPageDirty(page);
422                 }
423                 unlock_page(page);
424                 page_cache_release(page);
425         }
426 }
427
428 #ifdef CONFIG_SOFTWARE_SUSPEND
429 /*
430  * Find the swap type that corresponds to given device (if any).
431  *
432  * @offset - number of the PAGE_SIZE-sized block of the device, starting
433  * from 0, in which the swap header is expected to be located.
434  *
435  * This is needed for the suspend to disk (aka swsusp).
436  */
437 int swap_type_of(dev_t device, sector_t offset)
438 {
439         struct block_device *bdev = NULL;
440         int i;
441
442         if (device)
443                 bdev = bdget(device);
444
445         spin_lock(&swap_lock);
446         for (i = 0; i < nr_swapfiles; i++) {
447                 struct swap_info_struct *sis = swap_info + i;
448
449                 if (!(sis->flags & SWP_WRITEOK))
450                         continue;
451
452                 if (!bdev) {
453                         spin_unlock(&swap_lock);
454                         return i;
455                 }
456                 if (bdev == sis->bdev) {
457                         struct swap_extent *se;
458
459                         se = list_entry(sis->extent_list.next,
460                                         struct swap_extent, list);
461                         if (se->start_block == offset) {
462                                 spin_unlock(&swap_lock);
463                                 bdput(bdev);
464                                 return i;
465                         }
466                 }
467         }
468         spin_unlock(&swap_lock);
469         if (bdev)
470                 bdput(bdev);
471
472         return -ENODEV;
473 }
474
475 /*
476  * Return either the total number of swap pages of given type, or the number
477  * of free pages of that type (depending on @free)
478  *
479  * This is needed for software suspend
480  */
481 unsigned int count_swap_pages(int type, int free)
482 {
483         unsigned int n = 0;
484
485         if (type < nr_swapfiles) {
486                 spin_lock(&swap_lock);
487                 if (swap_info[type].flags & SWP_WRITEOK) {
488                         n = swap_info[type].pages;
489                         if (free)
490                                 n -= swap_info[type].inuse_pages;
491                 }
492                 spin_unlock(&swap_lock);
493         }
494         return n;
495 }
496 #endif
497
498 /*
499  * No need to decide whether this PTE shares the swap entry with others,
500  * just let do_wp_page work it out if a write is requested later - to
501  * force COW, vm_page_prot omits write permission from any private vma.
502  */
503 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
504                 unsigned long addr, swp_entry_t entry, struct page *page)
505 {
506         inc_mm_counter(vma->vm_mm, anon_rss);
507         get_page(page);
508         set_pte_at(vma->vm_mm, addr, pte,
509                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
510         page_add_anon_rmap(page, vma, addr);
511         swap_free(entry);
512         /*
513          * Move the page to the active list so it is not
514          * immediately swapped out again after swapon.
515          */
516         activate_page(page);
517 }
518
519 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
520                                 unsigned long addr, unsigned long end,
521                                 swp_entry_t entry, struct page *page)
522 {
523         pte_t swp_pte = swp_entry_to_pte(entry);
524         pte_t *pte;
525         spinlock_t *ptl;
526         int found = 0;
527
528         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
529         do {
530                 /*
531                  * swapoff spends a _lot_ of time in this loop!
532                  * Test inline before going to call unuse_pte.
533                  */
534                 if (unlikely(pte_same(*pte, swp_pte))) {
535                         unuse_pte(vma, pte++, addr, entry, page);
536                         found = 1;
537                         break;
538                 }
539         } while (pte++, addr += PAGE_SIZE, addr != end);
540         pte_unmap_unlock(pte - 1, ptl);
541         return found;
542 }
543
544 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
545                                 unsigned long addr, unsigned long end,
546                                 swp_entry_t entry, struct page *page)
547 {
548         pmd_t *pmd;
549         unsigned long next;
550
551         pmd = pmd_offset(pud, addr);
552         do {
553                 next = pmd_addr_end(addr, end);
554                 if (pmd_none_or_clear_bad(pmd))
555                         continue;
556                 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
557                         return 1;
558         } while (pmd++, addr = next, addr != end);
559         return 0;
560 }
561
562 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
563                                 unsigned long addr, unsigned long end,
564                                 swp_entry_t entry, struct page *page)
565 {
566         pud_t *pud;
567         unsigned long next;
568
569         pud = pud_offset(pgd, addr);
570         do {
571                 next = pud_addr_end(addr, end);
572                 if (pud_none_or_clear_bad(pud))
573                         continue;
574                 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
575                         return 1;
576         } while (pud++, addr = next, addr != end);
577         return 0;
578 }
579
580 static int unuse_vma(struct vm_area_struct *vma,
581                                 swp_entry_t entry, struct page *page)
582 {
583         pgd_t *pgd;
584         unsigned long addr, end, next;
585
586         if (page->mapping) {
587                 addr = page_address_in_vma(page, vma);
588                 if (addr == -EFAULT)
589                         return 0;
590                 else
591                         end = addr + PAGE_SIZE;
592         } else {
593                 addr = vma->vm_start;
594                 end = vma->vm_end;
595         }
596
597         pgd = pgd_offset(vma->vm_mm, addr);
598         do {
599                 next = pgd_addr_end(addr, end);
600                 if (pgd_none_or_clear_bad(pgd))
601                         continue;
602                 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
603                         return 1;
604         } while (pgd++, addr = next, addr != end);
605         return 0;
606 }
607
608 static int unuse_mm(struct mm_struct *mm,
609                                 swp_entry_t entry, struct page *page)
610 {
611         struct vm_area_struct *vma;
612
613         if (!down_read_trylock(&mm->mmap_sem)) {
614                 /*
615                  * Activate page so shrink_cache is unlikely to unmap its
616                  * ptes while lock is dropped, so swapoff can make progress.
617                  */
618                 activate_page(page);
619                 unlock_page(page);
620                 down_read(&mm->mmap_sem);
621                 lock_page(page);
622         }
623         for (vma = mm->mmap; vma; vma = vma->vm_next) {
624                 if (vma->anon_vma && unuse_vma(vma, entry, page))
625                         break;
626         }
627         up_read(&mm->mmap_sem);
628         /*
629          * Currently unuse_mm cannot fail, but leave error handling
630          * at call sites for now, since we change it from time to time.
631          */
632         return 0;
633 }
634
635 /*
636  * Scan swap_map from current position to next entry still in use.
637  * Recycle to start on reaching the end, returning 0 when empty.
638  */
639 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
640                                         unsigned int prev)
641 {
642         unsigned int max = si->max;
643         unsigned int i = prev;
644         int count;
645
646         /*
647          * No need for swap_lock here: we're just looking
648          * for whether an entry is in use, not modifying it; false
649          * hits are okay, and sys_swapoff() has already prevented new
650          * allocations from this area (while holding swap_lock).
651          */
652         for (;;) {
653                 if (++i >= max) {
654                         if (!prev) {
655                                 i = 0;
656                                 break;
657                         }
658                         /*
659                          * No entries in use at top of swap_map,
660                          * loop back to start and recheck there.
661                          */
662                         max = prev + 1;
663                         prev = 0;
664                         i = 1;
665                 }
666                 count = si->swap_map[i];
667                 if (count && count != SWAP_MAP_BAD)
668                         break;
669         }
670         return i;
671 }
672
673 /*
674  * We completely avoid races by reading each swap page in advance,
675  * and then search for the process using it.  All the necessary
676  * page table adjustments can then be made atomically.
677  */
678 static int try_to_unuse(unsigned int type)
679 {
680         struct swap_info_struct * si = &swap_info[type];
681         struct mm_struct *start_mm;
682         unsigned short *swap_map;
683         unsigned short swcount;
684         struct page *page;
685         swp_entry_t entry;
686         unsigned int i = 0;
687         int retval = 0;
688         int reset_overflow = 0;
689         int shmem;
690
691         /*
692          * When searching mms for an entry, a good strategy is to
693          * start at the first mm we freed the previous entry from
694          * (though actually we don't notice whether we or coincidence
695          * freed the entry).  Initialize this start_mm with a hold.
696          *
697          * A simpler strategy would be to start at the last mm we
698          * freed the previous entry from; but that would take less
699          * advantage of mmlist ordering, which clusters forked mms
700          * together, child after parent.  If we race with dup_mmap(), we
701          * prefer to resolve parent before child, lest we miss entries
702          * duplicated after we scanned child: using last mm would invert
703          * that.  Though it's only a serious concern when an overflowed
704          * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
705          */
706         start_mm = &init_mm;
707         atomic_inc(&init_mm.mm_users);
708
709         /*
710          * Keep on scanning until all entries have gone.  Usually,
711          * one pass through swap_map is enough, but not necessarily:
712          * there are races when an instance of an entry might be missed.
713          */
714         while ((i = find_next_to_unuse(si, i)) != 0) {
715                 if (signal_pending(current)) {
716                         retval = -EINTR;
717                         break;
718                 }
719
720                 /* 
721                  * Get a page for the entry, using the existing swap
722                  * cache page if there is one.  Otherwise, get a clean
723                  * page and read the swap into it. 
724                  */
725                 swap_map = &si->swap_map[i];
726                 entry = swp_entry(type, i);
727                 page = read_swap_cache_async(entry, NULL, 0);
728                 if (!page) {
729                         /*
730                          * Either swap_duplicate() failed because entry
731                          * has been freed independently, and will not be
732                          * reused since sys_swapoff() already disabled
733                          * allocation from here, or alloc_page() failed.
734                          */
735                         if (!*swap_map)
736                                 continue;
737                         retval = -ENOMEM;
738                         break;
739                 }
740
741                 /*
742                  * Don't hold on to start_mm if it looks like exiting.
743                  */
744                 if (atomic_read(&start_mm->mm_users) == 1) {
745                         mmput(start_mm);
746                         start_mm = &init_mm;
747                         atomic_inc(&init_mm.mm_users);
748                 }
749
750                 /*
751                  * Wait for and lock page.  When do_swap_page races with
752                  * try_to_unuse, do_swap_page can handle the fault much
753                  * faster than try_to_unuse can locate the entry.  This
754                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
755                  * defer to do_swap_page in such a case - in some tests,
756                  * do_swap_page and try_to_unuse repeatedly compete.
757                  */
758                 wait_on_page_locked(page);
759                 wait_on_page_writeback(page);
760                 lock_page(page);
761                 wait_on_page_writeback(page);
762
763                 /*
764                  * Remove all references to entry.
765                  * Whenever we reach init_mm, there's no address space
766                  * to search, but use it as a reminder to search shmem.
767                  */
768                 shmem = 0;
769                 swcount = *swap_map;
770                 if (swcount > 1) {
771                         if (start_mm == &init_mm)
772                                 shmem = shmem_unuse(entry, page);
773                         else
774                                 retval = unuse_mm(start_mm, entry, page);
775                 }
776                 if (*swap_map > 1) {
777                         int set_start_mm = (*swap_map >= swcount);
778                         struct list_head *p = &start_mm->mmlist;
779                         struct mm_struct *new_start_mm = start_mm;
780                         struct mm_struct *prev_mm = start_mm;
781                         struct mm_struct *mm;
782
783                         atomic_inc(&new_start_mm->mm_users);
784                         atomic_inc(&prev_mm->mm_users);
785                         spin_lock(&mmlist_lock);
786                         while (*swap_map > 1 && !retval &&
787                                         (p = p->next) != &start_mm->mmlist) {
788                                 mm = list_entry(p, struct mm_struct, mmlist);
789                                 if (!atomic_inc_not_zero(&mm->mm_users))
790                                         continue;
791                                 spin_unlock(&mmlist_lock);
792                                 mmput(prev_mm);
793                                 prev_mm = mm;
794
795                                 cond_resched();
796
797                                 swcount = *swap_map;
798                                 if (swcount <= 1)
799                                         ;
800                                 else if (mm == &init_mm) {
801                                         set_start_mm = 1;
802                                         shmem = shmem_unuse(entry, page);
803                                 } else
804                                         retval = unuse_mm(mm, entry, page);
805                                 if (set_start_mm && *swap_map < swcount) {
806                                         mmput(new_start_mm);
807                                         atomic_inc(&mm->mm_users);
808                                         new_start_mm = mm;
809                                         set_start_mm = 0;
810                                 }
811                                 spin_lock(&mmlist_lock);
812                         }
813                         spin_unlock(&mmlist_lock);
814                         mmput(prev_mm);
815                         mmput(start_mm);
816                         start_mm = new_start_mm;
817                 }
818                 if (retval) {
819                         unlock_page(page);
820                         page_cache_release(page);
821                         break;
822                 }
823
824                 /*
825                  * How could swap count reach 0x7fff when the maximum
826                  * pid is 0x7fff, and there's no way to repeat a swap
827                  * page within an mm (except in shmem, where it's the
828                  * shared object which takes the reference count)?
829                  * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
830                  *
831                  * If that's wrong, then we should worry more about
832                  * exit_mmap() and do_munmap() cases described above:
833                  * we might be resetting SWAP_MAP_MAX too early here.
834                  * We know "Undead"s can happen, they're okay, so don't
835                  * report them; but do report if we reset SWAP_MAP_MAX.
836                  */
837                 if (*swap_map == SWAP_MAP_MAX) {
838                         spin_lock(&swap_lock);
839                         *swap_map = 1;
840                         spin_unlock(&swap_lock);
841                         reset_overflow = 1;
842                 }
843
844                 /*
845                  * If a reference remains (rare), we would like to leave
846                  * the page in the swap cache; but try_to_unmap could
847                  * then re-duplicate the entry once we drop page lock,
848                  * so we might loop indefinitely; also, that page could
849                  * not be swapped out to other storage meanwhile.  So:
850                  * delete from cache even if there's another reference,
851                  * after ensuring that the data has been saved to disk -
852                  * since if the reference remains (rarer), it will be
853                  * read from disk into another page.  Splitting into two
854                  * pages would be incorrect if swap supported "shared
855                  * private" pages, but they are handled by tmpfs files.
856                  *
857                  * Note shmem_unuse already deleted a swappage from
858                  * the swap cache, unless the move to filepage failed:
859                  * in which case it left swappage in cache, lowered its
860                  * swap count to pass quickly through the loops above,
861                  * and now we must reincrement count to try again later.
862                  */
863                 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
864                         struct writeback_control wbc = {
865                                 .sync_mode = WB_SYNC_NONE,
866                         };
867
868                         swap_writepage(page, &wbc);
869                         lock_page(page);
870                         wait_on_page_writeback(page);
871                 }
872                 if (PageSwapCache(page)) {
873                         if (shmem)
874                                 swap_duplicate(entry);
875                         else
876                                 delete_from_swap_cache(page);
877                 }
878
879                 /*
880                  * So we could skip searching mms once swap count went
881                  * to 1, we did not mark any present ptes as dirty: must
882                  * mark page dirty so shrink_list will preserve it.
883                  */
884                 SetPageDirty(page);
885                 unlock_page(page);
886                 page_cache_release(page);
887
888                 /*
889                  * Make sure that we aren't completely killing
890                  * interactive performance.
891                  */
892                 cond_resched();
893         }
894
895         mmput(start_mm);
896         if (reset_overflow) {
897                 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
898                 swap_overflow = 0;
899         }
900         return retval;
901 }
902
903 /*
904  * After a successful try_to_unuse, if no swap is now in use, we know
905  * we can empty the mmlist.  swap_lock must be held on entry and exit.
906  * Note that mmlist_lock nests inside swap_lock, and an mm must be
907  * added to the mmlist just after page_duplicate - before would be racy.
908  */
909 static void drain_mmlist(void)
910 {
911         struct list_head *p, *next;
912         unsigned int i;
913
914         for (i = 0; i < nr_swapfiles; i++)
915                 if (swap_info[i].inuse_pages)
916                         return;
917         spin_lock(&mmlist_lock);
918         list_for_each_safe(p, next, &init_mm.mmlist)
919                 list_del_init(p);
920         spin_unlock(&mmlist_lock);
921 }
922
923 /*
924  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
925  * corresponds to page offset `offset'.
926  */
927 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
928 {
929         struct swap_extent *se = sis->curr_swap_extent;
930         struct swap_extent *start_se = se;
931
932         for ( ; ; ) {
933                 struct list_head *lh;
934
935                 if (se->start_page <= offset &&
936                                 offset < (se->start_page + se->nr_pages)) {
937                         return se->start_block + (offset - se->start_page);
938                 }
939                 lh = se->list.next;
940                 if (lh == &sis->extent_list)
941                         lh = lh->next;
942                 se = list_entry(lh, struct swap_extent, list);
943                 sis->curr_swap_extent = se;
944                 BUG_ON(se == start_se);         /* It *must* be present */
945         }
946 }
947
948 /*
949  * Free all of a swapdev's extent information
950  */
951 static void destroy_swap_extents(struct swap_info_struct *sis)
952 {
953         while (!list_empty(&sis->extent_list)) {
954                 struct swap_extent *se;
955
956                 se = list_entry(sis->extent_list.next,
957                                 struct swap_extent, list);
958                 list_del(&se->list);
959                 kfree(se);
960         }
961 }
962
963 /*
964  * Add a block range (and the corresponding page range) into this swapdev's
965  * extent list.  The extent list is kept sorted in page order.
966  *
967  * This function rather assumes that it is called in ascending page order.
968  */
969 static int
970 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
971                 unsigned long nr_pages, sector_t start_block)
972 {
973         struct swap_extent *se;
974         struct swap_extent *new_se;
975         struct list_head *lh;
976
977         lh = sis->extent_list.prev;     /* The highest page extent */
978         if (lh != &sis->extent_list) {
979                 se = list_entry(lh, struct swap_extent, list);
980                 BUG_ON(se->start_page + se->nr_pages != start_page);
981                 if (se->start_block + se->nr_pages == start_block) {
982                         /* Merge it */
983                         se->nr_pages += nr_pages;
984                         return 0;
985                 }
986         }
987
988         /*
989          * No merge.  Insert a new extent, preserving ordering.
990          */
991         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
992         if (new_se == NULL)
993                 return -ENOMEM;
994         new_se->start_page = start_page;
995         new_se->nr_pages = nr_pages;
996         new_se->start_block = start_block;
997
998         list_add_tail(&new_se->list, &sis->extent_list);
999         return 1;
1000 }
1001
1002 /*
1003  * A `swap extent' is a simple thing which maps a contiguous range of pages
1004  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1005  * is built at swapon time and is then used at swap_writepage/swap_readpage
1006  * time for locating where on disk a page belongs.
1007  *
1008  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1009  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1010  * swap files identically.
1011  *
1012  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1013  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1014  * swapfiles are handled *identically* after swapon time.
1015  *
1016  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1017  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1018  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1019  * requirements, they are simply tossed out - we will never use those blocks
1020  * for swapping.
1021  *
1022  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1023  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1024  * which will scribble on the fs.
1025  *
1026  * The amount of disk space which a single swap extent represents varies.
1027  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1028  * extents in the list.  To avoid much list walking, we cache the previous
1029  * search location in `curr_swap_extent', and start new searches from there.
1030  * This is extremely effective.  The average number of iterations in
1031  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1032  */
1033 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1034 {
1035         struct inode *inode;
1036         unsigned blocks_per_page;
1037         unsigned long page_no;
1038         unsigned blkbits;
1039         sector_t probe_block;
1040         sector_t last_block;
1041         sector_t lowest_block = -1;
1042         sector_t highest_block = 0;
1043         int nr_extents = 0;
1044         int ret;
1045
1046         inode = sis->swap_file->f_mapping->host;
1047         if (S_ISBLK(inode->i_mode)) {
1048                 ret = add_swap_extent(sis, 0, sis->max, 0);
1049                 *span = sis->pages;
1050                 goto done;
1051         }
1052
1053         blkbits = inode->i_blkbits;
1054         blocks_per_page = PAGE_SIZE >> blkbits;
1055
1056         /*
1057          * Map all the blocks into the extent list.  This code doesn't try
1058          * to be very smart.
1059          */
1060         probe_block = 0;
1061         page_no = 0;
1062         last_block = i_size_read(inode) >> blkbits;
1063         while ((probe_block + blocks_per_page) <= last_block &&
1064                         page_no < sis->max) {
1065                 unsigned block_in_page;
1066                 sector_t first_block;
1067
1068                 first_block = bmap(inode, probe_block);
1069                 if (first_block == 0)
1070                         goto bad_bmap;
1071
1072                 /*
1073                  * It must be PAGE_SIZE aligned on-disk
1074                  */
1075                 if (first_block & (blocks_per_page - 1)) {
1076                         probe_block++;
1077                         goto reprobe;
1078                 }
1079
1080                 for (block_in_page = 1; block_in_page < blocks_per_page;
1081                                         block_in_page++) {
1082                         sector_t block;
1083
1084                         block = bmap(inode, probe_block + block_in_page);
1085                         if (block == 0)
1086                                 goto bad_bmap;
1087                         if (block != first_block + block_in_page) {
1088                                 /* Discontiguity */
1089                                 probe_block++;
1090                                 goto reprobe;
1091                         }
1092                 }
1093
1094                 first_block >>= (PAGE_SHIFT - blkbits);
1095                 if (page_no) {  /* exclude the header page */
1096                         if (first_block < lowest_block)
1097                                 lowest_block = first_block;
1098                         if (first_block > highest_block)
1099                                 highest_block = first_block;
1100                 }
1101
1102                 /*
1103                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1104                  */
1105                 ret = add_swap_extent(sis, page_no, 1, first_block);
1106                 if (ret < 0)
1107                         goto out;
1108                 nr_extents += ret;
1109                 page_no++;
1110                 probe_block += blocks_per_page;
1111 reprobe:
1112                 continue;
1113         }
1114         ret = nr_extents;
1115         *span = 1 + highest_block - lowest_block;
1116         if (page_no == 0)
1117                 page_no = 1;    /* force Empty message */
1118         sis->max = page_no;
1119         sis->pages = page_no - 1;
1120         sis->highest_bit = page_no - 1;
1121 done:
1122         sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1123                                         struct swap_extent, list);
1124         goto out;
1125 bad_bmap:
1126         printk(KERN_ERR "swapon: swapfile has holes\n");
1127         ret = -EINVAL;
1128 out:
1129         return ret;
1130 }
1131
1132 #if 0   /* We don't need this yet */
1133 #include <linux/backing-dev.h>
1134 int page_queue_congested(struct page *page)
1135 {
1136         struct backing_dev_info *bdi;
1137
1138         BUG_ON(!PageLocked(page));      /* It pins the swap_info_struct */
1139
1140         if (PageSwapCache(page)) {
1141                 swp_entry_t entry = { .val = page_private(page) };
1142                 struct swap_info_struct *sis;
1143
1144                 sis = get_swap_info_struct(swp_type(entry));
1145                 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1146         } else
1147                 bdi = page->mapping->backing_dev_info;
1148         return bdi_write_congested(bdi);
1149 }
1150 #endif
1151
1152 asmlinkage long sys_swapoff(const char __user * specialfile)
1153 {
1154         struct swap_info_struct * p = NULL;
1155         unsigned short *swap_map;
1156         struct file *swap_file, *victim;
1157         struct address_space *mapping;
1158         struct inode *inode;
1159         char * pathname;
1160         int i, type, prev;
1161         int err;
1162         
1163         if (!capable(CAP_SYS_ADMIN))
1164                 return -EPERM;
1165
1166         pathname = getname(specialfile);
1167         err = PTR_ERR(pathname);
1168         if (IS_ERR(pathname))
1169                 goto out;
1170
1171         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1172         putname(pathname);
1173         err = PTR_ERR(victim);
1174         if (IS_ERR(victim))
1175                 goto out;
1176
1177         mapping = victim->f_mapping;
1178         prev = -1;
1179         spin_lock(&swap_lock);
1180         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1181                 p = swap_info + type;
1182                 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1183                         if (p->swap_file->f_mapping == mapping)
1184                                 break;
1185                 }
1186                 prev = type;
1187         }
1188         if (type < 0) {
1189                 err = -EINVAL;
1190                 spin_unlock(&swap_lock);
1191                 goto out_dput;
1192         }
1193         if (!security_vm_enough_memory(p->pages))
1194                 vm_unacct_memory(p->pages);
1195         else {
1196                 err = -ENOMEM;
1197                 spin_unlock(&swap_lock);
1198                 goto out_dput;
1199         }
1200         if (prev < 0) {
1201                 swap_list.head = p->next;
1202         } else {
1203                 swap_info[prev].next = p->next;
1204         }
1205         if (type == swap_list.next) {
1206                 /* just pick something that's safe... */
1207                 swap_list.next = swap_list.head;
1208         }
1209         nr_swap_pages -= p->pages;
1210         total_swap_pages -= p->pages;
1211         p->flags &= ~SWP_WRITEOK;
1212         spin_unlock(&swap_lock);
1213
1214         current->flags |= PF_SWAPOFF;
1215         err = try_to_unuse(type);
1216         current->flags &= ~PF_SWAPOFF;
1217
1218         if (err) {
1219                 /* re-insert swap space back into swap_list */
1220                 spin_lock(&swap_lock);
1221                 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1222                         if (p->prio >= swap_info[i].prio)
1223                                 break;
1224                 p->next = i;
1225                 if (prev < 0)
1226                         swap_list.head = swap_list.next = p - swap_info;
1227                 else
1228                         swap_info[prev].next = p - swap_info;
1229                 nr_swap_pages += p->pages;
1230                 total_swap_pages += p->pages;
1231                 p->flags |= SWP_WRITEOK;
1232                 spin_unlock(&swap_lock);
1233                 goto out_dput;
1234         }
1235
1236         /* wait for any unplug function to finish */
1237         down_write(&swap_unplug_sem);
1238         up_write(&swap_unplug_sem);
1239
1240         destroy_swap_extents(p);
1241         mutex_lock(&swapon_mutex);
1242         spin_lock(&swap_lock);
1243         drain_mmlist();
1244
1245         /* wait for anyone still in scan_swap_map */
1246         p->highest_bit = 0;             /* cuts scans short */
1247         while (p->flags >= SWP_SCANNING) {
1248                 spin_unlock(&swap_lock);
1249                 schedule_timeout_uninterruptible(1);
1250                 spin_lock(&swap_lock);
1251         }
1252
1253         swap_file = p->swap_file;
1254         p->swap_file = NULL;
1255         p->max = 0;
1256         swap_map = p->swap_map;
1257         p->swap_map = NULL;
1258         p->flags = 0;
1259         spin_unlock(&swap_lock);
1260         mutex_unlock(&swapon_mutex);
1261         vfree(swap_map);
1262         inode = mapping->host;
1263         if (S_ISBLK(inode->i_mode)) {
1264                 struct block_device *bdev = I_BDEV(inode);
1265                 set_blocksize(bdev, p->old_block_size);
1266                 bd_release(bdev);
1267         } else {
1268                 mutex_lock(&inode->i_mutex);
1269                 inode->i_flags &= ~S_SWAPFILE;
1270                 mutex_unlock(&inode->i_mutex);
1271         }
1272         filp_close(swap_file, NULL);
1273         err = 0;
1274
1275 out_dput:
1276         filp_close(victim, NULL);
1277 out:
1278         return err;
1279 }
1280
1281 #ifdef CONFIG_PROC_FS
1282 /* iterator */
1283 static void *swap_start(struct seq_file *swap, loff_t *pos)
1284 {
1285         struct swap_info_struct *ptr = swap_info;
1286         int i;
1287         loff_t l = *pos;
1288
1289         mutex_lock(&swapon_mutex);
1290
1291         if (!l)
1292                 return SEQ_START_TOKEN;
1293
1294         for (i = 0; i < nr_swapfiles; i++, ptr++) {
1295                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1296                         continue;
1297                 if (!--l)
1298                         return ptr;
1299         }
1300
1301         return NULL;
1302 }
1303
1304 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1305 {
1306         struct swap_info_struct *ptr;
1307         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1308
1309         if (v == SEQ_START_TOKEN)
1310                 ptr = swap_info;
1311         else {
1312                 ptr = v;
1313                 ptr++;
1314         }
1315
1316         for (; ptr < endptr; ptr++) {
1317                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1318                         continue;
1319                 ++*pos;
1320                 return ptr;
1321         }
1322
1323         return NULL;
1324 }
1325
1326 static void swap_stop(struct seq_file *swap, void *v)
1327 {
1328         mutex_unlock(&swapon_mutex);
1329 }
1330
1331 static int swap_show(struct seq_file *swap, void *v)
1332 {
1333         struct swap_info_struct *ptr = v;
1334         struct file *file;
1335         int len;
1336
1337         if (ptr == SEQ_START_TOKEN) {
1338                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1339                 return 0;
1340         }
1341
1342         file = ptr->swap_file;
1343         len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1344         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1345                        len < 40 ? 40 - len : 1, " ",
1346                        S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1347                                 "partition" : "file\t",
1348                        ptr->pages << (PAGE_SHIFT - 10),
1349                        ptr->inuse_pages << (PAGE_SHIFT - 10),
1350                        ptr->prio);
1351         return 0;
1352 }
1353
1354 static struct seq_operations swaps_op = {
1355         .start =        swap_start,
1356         .next =         swap_next,
1357         .stop =         swap_stop,
1358         .show =         swap_show
1359 };
1360
1361 static int swaps_open(struct inode *inode, struct file *file)
1362 {
1363         return seq_open(file, &swaps_op);
1364 }
1365
1366 static struct file_operations proc_swaps_operations = {
1367         .open           = swaps_open,
1368         .read           = seq_read,
1369         .llseek         = seq_lseek,
1370         .release        = seq_release,
1371 };
1372
1373 static int __init procswaps_init(void)
1374 {
1375         struct proc_dir_entry *entry;
1376
1377         entry = create_proc_entry("swaps", 0, NULL);
1378         if (entry)
1379                 entry->proc_fops = &proc_swaps_operations;
1380         return 0;
1381 }
1382 __initcall(procswaps_init);
1383 #endif /* CONFIG_PROC_FS */
1384
1385 /*
1386  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1387  *
1388  * The swapon system call
1389  */
1390 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1391 {
1392         struct swap_info_struct * p;
1393         char *name = NULL;
1394         struct block_device *bdev = NULL;
1395         struct file *swap_file = NULL;
1396         struct address_space *mapping;
1397         unsigned int type;
1398         int i, prev;
1399         int error;
1400         static int least_priority;
1401         union swap_header *swap_header = NULL;
1402         int swap_header_version;
1403         unsigned int nr_good_pages = 0;
1404         int nr_extents = 0;
1405         sector_t span;
1406         unsigned long maxpages = 1;
1407         int swapfilesize;
1408         unsigned short *swap_map;
1409         struct page *page = NULL;
1410         struct inode *inode = NULL;
1411         int did_down = 0;
1412
1413         if (!capable(CAP_SYS_ADMIN))
1414                 return -EPERM;
1415         spin_lock(&swap_lock);
1416         p = swap_info;
1417         for (type = 0 ; type < nr_swapfiles ; type++,p++)
1418                 if (!(p->flags & SWP_USED))
1419                         break;
1420         error = -EPERM;
1421         if (type >= MAX_SWAPFILES) {
1422                 spin_unlock(&swap_lock);
1423                 goto out;
1424         }
1425         if (type >= nr_swapfiles)
1426                 nr_swapfiles = type+1;
1427         INIT_LIST_HEAD(&p->extent_list);
1428         p->flags = SWP_USED;
1429         p->swap_file = NULL;
1430         p->old_block_size = 0;
1431         p->swap_map = NULL;
1432         p->lowest_bit = 0;
1433         p->highest_bit = 0;
1434         p->cluster_nr = 0;
1435         p->inuse_pages = 0;
1436         p->next = -1;
1437         if (swap_flags & SWAP_FLAG_PREFER) {
1438                 p->prio =
1439                   (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1440         } else {
1441                 p->prio = --least_priority;
1442         }
1443         spin_unlock(&swap_lock);
1444         name = getname(specialfile);
1445         error = PTR_ERR(name);
1446         if (IS_ERR(name)) {
1447                 name = NULL;
1448                 goto bad_swap_2;
1449         }
1450         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1451         error = PTR_ERR(swap_file);
1452         if (IS_ERR(swap_file)) {
1453                 swap_file = NULL;
1454                 goto bad_swap_2;
1455         }
1456
1457         p->swap_file = swap_file;
1458         mapping = swap_file->f_mapping;
1459         inode = mapping->host;
1460
1461         error = -EBUSY;
1462         for (i = 0; i < nr_swapfiles; i++) {
1463                 struct swap_info_struct *q = &swap_info[i];
1464
1465                 if (i == type || !q->swap_file)
1466                         continue;
1467                 if (mapping == q->swap_file->f_mapping)
1468                         goto bad_swap;
1469         }
1470
1471         error = -EINVAL;
1472         if (S_ISBLK(inode->i_mode)) {
1473                 bdev = I_BDEV(inode);
1474                 error = bd_claim(bdev, sys_swapon);
1475                 if (error < 0) {
1476                         bdev = NULL;
1477                         error = -EINVAL;
1478                         goto bad_swap;
1479                 }
1480                 p->old_block_size = block_size(bdev);
1481                 error = set_blocksize(bdev, PAGE_SIZE);
1482                 if (error < 0)
1483                         goto bad_swap;
1484                 p->bdev = bdev;
1485         } else if (S_ISREG(inode->i_mode)) {
1486                 p->bdev = inode->i_sb->s_bdev;
1487                 mutex_lock(&inode->i_mutex);
1488                 did_down = 1;
1489                 if (IS_SWAPFILE(inode)) {
1490                         error = -EBUSY;
1491                         goto bad_swap;
1492                 }
1493         } else {
1494                 goto bad_swap;
1495         }
1496
1497         swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1498
1499         /*
1500          * Read the swap header.
1501          */
1502         if (!mapping->a_ops->readpage) {
1503                 error = -EINVAL;
1504                 goto bad_swap;
1505         }
1506         page = read_mapping_page(mapping, 0, swap_file);
1507         if (IS_ERR(page)) {
1508                 error = PTR_ERR(page);
1509                 goto bad_swap;
1510         }
1511         wait_on_page_locked(page);
1512         if (!PageUptodate(page))
1513                 goto bad_swap;
1514         kmap(page);
1515         swap_header = page_address(page);
1516
1517         if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1518                 swap_header_version = 1;
1519         else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1520                 swap_header_version = 2;
1521         else {
1522                 printk(KERN_ERR "Unable to find swap-space signature\n");
1523                 error = -EINVAL;
1524                 goto bad_swap;
1525         }
1526         
1527         switch (swap_header_version) {
1528         case 1:
1529                 printk(KERN_ERR "version 0 swap is no longer supported. "
1530                         "Use mkswap -v1 %s\n", name);
1531                 error = -EINVAL;
1532                 goto bad_swap;
1533         case 2:
1534                 /* Check the swap header's sub-version and the size of
1535                    the swap file and bad block lists */
1536                 if (swap_header->info.version != 1) {
1537                         printk(KERN_WARNING
1538                                "Unable to handle swap header version %d\n",
1539                                swap_header->info.version);
1540                         error = -EINVAL;
1541                         goto bad_swap;
1542                 }
1543
1544                 p->lowest_bit  = 1;
1545                 p->cluster_next = 1;
1546
1547                 /*
1548                  * Find out how many pages are allowed for a single swap
1549                  * device. There are two limiting factors: 1) the number of
1550                  * bits for the swap offset in the swp_entry_t type and
1551                  * 2) the number of bits in the a swap pte as defined by
1552                  * the different architectures. In order to find the
1553                  * largest possible bit mask a swap entry with swap type 0
1554                  * and swap offset ~0UL is created, encoded to a swap pte,
1555                  * decoded to a swp_entry_t again and finally the swap
1556                  * offset is extracted. This will mask all the bits from
1557                  * the initial ~0UL mask that can't be encoded in either
1558                  * the swp_entry_t or the architecture definition of a
1559                  * swap pte.
1560                  */
1561                 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1562                 if (maxpages > swap_header->info.last_page)
1563                         maxpages = swap_header->info.last_page;
1564                 p->highest_bit = maxpages - 1;
1565
1566                 error = -EINVAL;
1567                 if (!maxpages)
1568                         goto bad_swap;
1569                 if (swapfilesize && maxpages > swapfilesize) {
1570                         printk(KERN_WARNING
1571                                "Swap area shorter than signature indicates\n");
1572                         goto bad_swap;
1573                 }
1574                 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1575                         goto bad_swap;
1576                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1577                         goto bad_swap;
1578
1579                 /* OK, set up the swap map and apply the bad block list */
1580                 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1581                         error = -ENOMEM;
1582                         goto bad_swap;
1583                 }
1584
1585                 error = 0;
1586                 memset(p->swap_map, 0, maxpages * sizeof(short));
1587                 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1588                         int page_nr = swap_header->info.badpages[i];
1589                         if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1590                                 error = -EINVAL;
1591                         else
1592                                 p->swap_map[page_nr] = SWAP_MAP_BAD;
1593                 }
1594                 nr_good_pages = swap_header->info.last_page -
1595                                 swap_header->info.nr_badpages -
1596                                 1 /* header page */;
1597                 if (error)
1598                         goto bad_swap;
1599         }
1600
1601         if (nr_good_pages) {
1602                 p->swap_map[0] = SWAP_MAP_BAD;
1603                 p->max = maxpages;
1604                 p->pages = nr_good_pages;
1605                 nr_extents = setup_swap_extents(p, &span);
1606                 if (nr_extents < 0) {
1607                         error = nr_extents;
1608                         goto bad_swap;
1609                 }
1610                 nr_good_pages = p->pages;
1611         }
1612         if (!nr_good_pages) {
1613                 printk(KERN_WARNING "Empty swap-file\n");
1614                 error = -EINVAL;
1615                 goto bad_swap;
1616         }
1617
1618         mutex_lock(&swapon_mutex);
1619         spin_lock(&swap_lock);
1620         p->flags = SWP_ACTIVE;
1621         nr_swap_pages += nr_good_pages;
1622         total_swap_pages += nr_good_pages;
1623
1624         printk(KERN_INFO "Adding %uk swap on %s.  "
1625                         "Priority:%d extents:%d across:%lluk\n",
1626                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1627                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1628
1629         /* insert swap space into swap_list: */
1630         prev = -1;
1631         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1632                 if (p->prio >= swap_info[i].prio) {
1633                         break;
1634                 }
1635                 prev = i;
1636         }
1637         p->next = i;
1638         if (prev < 0) {
1639                 swap_list.head = swap_list.next = p - swap_info;
1640         } else {
1641                 swap_info[prev].next = p - swap_info;
1642         }
1643         spin_unlock(&swap_lock);
1644         mutex_unlock(&swapon_mutex);
1645         error = 0;
1646         goto out;
1647 bad_swap:
1648         if (bdev) {
1649                 set_blocksize(bdev, p->old_block_size);
1650                 bd_release(bdev);
1651         }
1652         destroy_swap_extents(p);
1653 bad_swap_2:
1654         spin_lock(&swap_lock);
1655         swap_map = p->swap_map;
1656         p->swap_file = NULL;
1657         p->swap_map = NULL;
1658         p->flags = 0;
1659         if (!(swap_flags & SWAP_FLAG_PREFER))
1660                 ++least_priority;
1661         spin_unlock(&swap_lock);
1662         vfree(swap_map);
1663         if (swap_file)
1664                 filp_close(swap_file, NULL);
1665 out:
1666         if (page && !IS_ERR(page)) {
1667                 kunmap(page);
1668                 page_cache_release(page);
1669         }
1670         if (name)
1671                 putname(name);
1672         if (did_down) {
1673                 if (!error)
1674                         inode->i_flags |= S_SWAPFILE;
1675                 mutex_unlock(&inode->i_mutex);
1676         }
1677         return error;
1678 }
1679
1680 void si_swapinfo(struct sysinfo *val)
1681 {
1682         unsigned int i;
1683         unsigned long nr_to_be_unused = 0;
1684
1685         spin_lock(&swap_lock);
1686         for (i = 0; i < nr_swapfiles; i++) {
1687                 if (!(swap_info[i].flags & SWP_USED) ||
1688                      (swap_info[i].flags & SWP_WRITEOK))
1689                         continue;
1690                 nr_to_be_unused += swap_info[i].inuse_pages;
1691         }
1692         val->freeswap = nr_swap_pages + nr_to_be_unused;
1693         val->totalswap = total_swap_pages + nr_to_be_unused;
1694         spin_unlock(&swap_lock);
1695 }
1696
1697 /*
1698  * Verify that a swap entry is valid and increment its swap map count.
1699  *
1700  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1701  * "permanent", but will be reclaimed by the next swapoff.
1702  */
1703 int swap_duplicate(swp_entry_t entry)
1704 {
1705         struct swap_info_struct * p;
1706         unsigned long offset, type;
1707         int result = 0;
1708
1709         if (is_migration_entry(entry))
1710                 return 1;
1711
1712         type = swp_type(entry);
1713         if (type >= nr_swapfiles)
1714                 goto bad_file;
1715         p = type + swap_info;
1716         offset = swp_offset(entry);
1717
1718         spin_lock(&swap_lock);
1719         if (offset < p->max && p->swap_map[offset]) {
1720                 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1721                         p->swap_map[offset]++;
1722                         result = 1;
1723                 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1724                         if (swap_overflow++ < 5)
1725                                 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1726                         p->swap_map[offset] = SWAP_MAP_MAX;
1727                         result = 1;
1728                 }
1729         }
1730         spin_unlock(&swap_lock);
1731 out:
1732         return result;
1733
1734 bad_file:
1735         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1736         goto out;
1737 }
1738
1739 struct swap_info_struct *
1740 get_swap_info_struct(unsigned type)
1741 {
1742         return &swap_info[type];
1743 }
1744
1745 /*
1746  * swap_lock prevents swap_map being freed. Don't grab an extra
1747  * reference on the swaphandle, it doesn't matter if it becomes unused.
1748  */
1749 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1750 {
1751         int our_page_cluster = page_cluster;
1752         int ret = 0, i = 1 << our_page_cluster;
1753         unsigned long toff;
1754         struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1755
1756         if (!our_page_cluster)  /* no readahead */
1757                 return 0;
1758         toff = (swp_offset(entry) >> our_page_cluster) << our_page_cluster;
1759         if (!toff)              /* first page is swap header */
1760                 toff++, i--;
1761         *offset = toff;
1762
1763         spin_lock(&swap_lock);
1764         do {
1765                 /* Don't read-ahead past the end of the swap area */
1766                 if (toff >= swapdev->max)
1767                         break;
1768                 /* Don't read in free or bad pages */
1769                 if (!swapdev->swap_map[toff])
1770                         break;
1771                 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1772                         break;
1773                 toff++;
1774                 ret++;
1775         } while (--i);
1776         spin_unlock(&swap_lock);
1777         return ret;
1778 }