afae7b1f680b5f4140d305d2a5be7fb476f50fd5
[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_HIBERNATION
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, struct block_device **bdev_p)
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                         if (bdev_p)
454                                 *bdev_p = sis->bdev;
455
456                         spin_unlock(&swap_lock);
457                         return i;
458                 }
459                 if (bdev == sis->bdev) {
460                         struct swap_extent *se;
461
462                         se = list_entry(sis->extent_list.next,
463                                         struct swap_extent, list);
464                         if (se->start_block == offset) {
465                                 if (bdev_p)
466                                         *bdev_p = sis->bdev;
467
468                                 spin_unlock(&swap_lock);
469                                 bdput(bdev);
470                                 return i;
471                         }
472                 }
473         }
474         spin_unlock(&swap_lock);
475         if (bdev)
476                 bdput(bdev);
477
478         return -ENODEV;
479 }
480
481 /*
482  * Return either the total number of swap pages of given type, or the number
483  * of free pages of that type (depending on @free)
484  *
485  * This is needed for software suspend
486  */
487 unsigned int count_swap_pages(int type, int free)
488 {
489         unsigned int n = 0;
490
491         if (type < nr_swapfiles) {
492                 spin_lock(&swap_lock);
493                 if (swap_info[type].flags & SWP_WRITEOK) {
494                         n = swap_info[type].pages;
495                         if (free)
496                                 n -= swap_info[type].inuse_pages;
497                 }
498                 spin_unlock(&swap_lock);
499         }
500         return n;
501 }
502 #endif
503
504 /*
505  * No need to decide whether this PTE shares the swap entry with others,
506  * just let do_wp_page work it out if a write is requested later - to
507  * force COW, vm_page_prot omits write permission from any private vma.
508  */
509 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
510                 unsigned long addr, swp_entry_t entry, struct page *page)
511 {
512         inc_mm_counter(vma->vm_mm, anon_rss);
513         get_page(page);
514         set_pte_at(vma->vm_mm, addr, pte,
515                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
516         page_add_anon_rmap(page, vma, addr);
517         swap_free(entry);
518         /*
519          * Move the page to the active list so it is not
520          * immediately swapped out again after swapon.
521          */
522         activate_page(page);
523 }
524
525 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
526                                 unsigned long addr, unsigned long end,
527                                 swp_entry_t entry, struct page *page)
528 {
529         pte_t swp_pte = swp_entry_to_pte(entry);
530         pte_t *pte;
531         spinlock_t *ptl;
532         int found = 0;
533
534         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
535         do {
536                 /*
537                  * swapoff spends a _lot_ of time in this loop!
538                  * Test inline before going to call unuse_pte.
539                  */
540                 if (unlikely(pte_same(*pte, swp_pte))) {
541                         unuse_pte(vma, pte++, addr, entry, page);
542                         found = 1;
543                         break;
544                 }
545         } while (pte++, addr += PAGE_SIZE, addr != end);
546         pte_unmap_unlock(pte - 1, ptl);
547         return found;
548 }
549
550 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
551                                 unsigned long addr, unsigned long end,
552                                 swp_entry_t entry, struct page *page)
553 {
554         pmd_t *pmd;
555         unsigned long next;
556
557         pmd = pmd_offset(pud, addr);
558         do {
559                 next = pmd_addr_end(addr, end);
560                 if (pmd_none_or_clear_bad(pmd))
561                         continue;
562                 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
563                         return 1;
564         } while (pmd++, addr = next, addr != end);
565         return 0;
566 }
567
568 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
569                                 unsigned long addr, unsigned long end,
570                                 swp_entry_t entry, struct page *page)
571 {
572         pud_t *pud;
573         unsigned long next;
574
575         pud = pud_offset(pgd, addr);
576         do {
577                 next = pud_addr_end(addr, end);
578                 if (pud_none_or_clear_bad(pud))
579                         continue;
580                 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
581                         return 1;
582         } while (pud++, addr = next, addr != end);
583         return 0;
584 }
585
586 static int unuse_vma(struct vm_area_struct *vma,
587                                 swp_entry_t entry, struct page *page)
588 {
589         pgd_t *pgd;
590         unsigned long addr, end, next;
591
592         if (page->mapping) {
593                 addr = page_address_in_vma(page, vma);
594                 if (addr == -EFAULT)
595                         return 0;
596                 else
597                         end = addr + PAGE_SIZE;
598         } else {
599                 addr = vma->vm_start;
600                 end = vma->vm_end;
601         }
602
603         pgd = pgd_offset(vma->vm_mm, addr);
604         do {
605                 next = pgd_addr_end(addr, end);
606                 if (pgd_none_or_clear_bad(pgd))
607                         continue;
608                 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
609                         return 1;
610         } while (pgd++, addr = next, addr != end);
611         return 0;
612 }
613
614 static int unuse_mm(struct mm_struct *mm,
615                                 swp_entry_t entry, struct page *page)
616 {
617         struct vm_area_struct *vma;
618
619         if (!down_read_trylock(&mm->mmap_sem)) {
620                 /*
621                  * Activate page so shrink_cache is unlikely to unmap its
622                  * ptes while lock is dropped, so swapoff can make progress.
623                  */
624                 activate_page(page);
625                 unlock_page(page);
626                 down_read(&mm->mmap_sem);
627                 lock_page(page);
628         }
629         for (vma = mm->mmap; vma; vma = vma->vm_next) {
630                 if (vma->anon_vma && unuse_vma(vma, entry, page))
631                         break;
632         }
633         up_read(&mm->mmap_sem);
634         /*
635          * Currently unuse_mm cannot fail, but leave error handling
636          * at call sites for now, since we change it from time to time.
637          */
638         return 0;
639 }
640
641 /*
642  * Scan swap_map from current position to next entry still in use.
643  * Recycle to start on reaching the end, returning 0 when empty.
644  */
645 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
646                                         unsigned int prev)
647 {
648         unsigned int max = si->max;
649         unsigned int i = prev;
650         int count;
651
652         /*
653          * No need for swap_lock here: we're just looking
654          * for whether an entry is in use, not modifying it; false
655          * hits are okay, and sys_swapoff() has already prevented new
656          * allocations from this area (while holding swap_lock).
657          */
658         for (;;) {
659                 if (++i >= max) {
660                         if (!prev) {
661                                 i = 0;
662                                 break;
663                         }
664                         /*
665                          * No entries in use at top of swap_map,
666                          * loop back to start and recheck there.
667                          */
668                         max = prev + 1;
669                         prev = 0;
670                         i = 1;
671                 }
672                 count = si->swap_map[i];
673                 if (count && count != SWAP_MAP_BAD)
674                         break;
675         }
676         return i;
677 }
678
679 /*
680  * We completely avoid races by reading each swap page in advance,
681  * and then search for the process using it.  All the necessary
682  * page table adjustments can then be made atomically.
683  */
684 static int try_to_unuse(unsigned int type)
685 {
686         struct swap_info_struct * si = &swap_info[type];
687         struct mm_struct *start_mm;
688         unsigned short *swap_map;
689         unsigned short swcount;
690         struct page *page;
691         swp_entry_t entry;
692         unsigned int i = 0;
693         int retval = 0;
694         int reset_overflow = 0;
695         int shmem;
696
697         /*
698          * When searching mms for an entry, a good strategy is to
699          * start at the first mm we freed the previous entry from
700          * (though actually we don't notice whether we or coincidence
701          * freed the entry).  Initialize this start_mm with a hold.
702          *
703          * A simpler strategy would be to start at the last mm we
704          * freed the previous entry from; but that would take less
705          * advantage of mmlist ordering, which clusters forked mms
706          * together, child after parent.  If we race with dup_mmap(), we
707          * prefer to resolve parent before child, lest we miss entries
708          * duplicated after we scanned child: using last mm would invert
709          * that.  Though it's only a serious concern when an overflowed
710          * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
711          */
712         start_mm = &init_mm;
713         atomic_inc(&init_mm.mm_users);
714
715         /*
716          * Keep on scanning until all entries have gone.  Usually,
717          * one pass through swap_map is enough, but not necessarily:
718          * there are races when an instance of an entry might be missed.
719          */
720         while ((i = find_next_to_unuse(si, i)) != 0) {
721                 if (signal_pending(current)) {
722                         retval = -EINTR;
723                         break;
724                 }
725
726                 /* 
727                  * Get a page for the entry, using the existing swap
728                  * cache page if there is one.  Otherwise, get a clean
729                  * page and read the swap into it. 
730                  */
731                 swap_map = &si->swap_map[i];
732                 entry = swp_entry(type, i);
733                 page = read_swap_cache_async(entry,
734                                         GFP_HIGHUSER_MOVABLE, NULL, 0);
735                 if (!page) {
736                         /*
737                          * Either swap_duplicate() failed because entry
738                          * has been freed independently, and will not be
739                          * reused since sys_swapoff() already disabled
740                          * allocation from here, or alloc_page() failed.
741                          */
742                         if (!*swap_map)
743                                 continue;
744                         retval = -ENOMEM;
745                         break;
746                 }
747
748                 /*
749                  * Don't hold on to start_mm if it looks like exiting.
750                  */
751                 if (atomic_read(&start_mm->mm_users) == 1) {
752                         mmput(start_mm);
753                         start_mm = &init_mm;
754                         atomic_inc(&init_mm.mm_users);
755                 }
756
757                 /*
758                  * Wait for and lock page.  When do_swap_page races with
759                  * try_to_unuse, do_swap_page can handle the fault much
760                  * faster than try_to_unuse can locate the entry.  This
761                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
762                  * defer to do_swap_page in such a case - in some tests,
763                  * do_swap_page and try_to_unuse repeatedly compete.
764                  */
765                 wait_on_page_locked(page);
766                 wait_on_page_writeback(page);
767                 lock_page(page);
768                 wait_on_page_writeback(page);
769
770                 /*
771                  * Remove all references to entry.
772                  * Whenever we reach init_mm, there's no address space
773                  * to search, but use it as a reminder to search shmem.
774                  */
775                 shmem = 0;
776                 swcount = *swap_map;
777                 if (swcount > 1) {
778                         if (start_mm == &init_mm)
779                                 shmem = shmem_unuse(entry, page);
780                         else
781                                 retval = unuse_mm(start_mm, entry, page);
782                 }
783                 if (*swap_map > 1) {
784                         int set_start_mm = (*swap_map >= swcount);
785                         struct list_head *p = &start_mm->mmlist;
786                         struct mm_struct *new_start_mm = start_mm;
787                         struct mm_struct *prev_mm = start_mm;
788                         struct mm_struct *mm;
789
790                         atomic_inc(&new_start_mm->mm_users);
791                         atomic_inc(&prev_mm->mm_users);
792                         spin_lock(&mmlist_lock);
793                         while (*swap_map > 1 && !retval && !shmem &&
794                                         (p = p->next) != &start_mm->mmlist) {
795                                 mm = list_entry(p, struct mm_struct, mmlist);
796                                 if (!atomic_inc_not_zero(&mm->mm_users))
797                                         continue;
798                                 spin_unlock(&mmlist_lock);
799                                 mmput(prev_mm);
800                                 prev_mm = mm;
801
802                                 cond_resched();
803
804                                 swcount = *swap_map;
805                                 if (swcount <= 1)
806                                         ;
807                                 else if (mm == &init_mm) {
808                                         set_start_mm = 1;
809                                         shmem = shmem_unuse(entry, page);
810                                 } else
811                                         retval = unuse_mm(mm, entry, page);
812                                 if (set_start_mm && *swap_map < swcount) {
813                                         mmput(new_start_mm);
814                                         atomic_inc(&mm->mm_users);
815                                         new_start_mm = mm;
816                                         set_start_mm = 0;
817                                 }
818                                 spin_lock(&mmlist_lock);
819                         }
820                         spin_unlock(&mmlist_lock);
821                         mmput(prev_mm);
822                         mmput(start_mm);
823                         start_mm = new_start_mm;
824                 }
825                 if (shmem) {
826                         /* page has already been unlocked and released */
827                         if (shmem > 0)
828                                 continue;
829                         retval = shmem;
830                         break;
831                 }
832                 if (retval) {
833                         unlock_page(page);
834                         page_cache_release(page);
835                         break;
836                 }
837
838                 /*
839                  * How could swap count reach 0x7fff when the maximum
840                  * pid is 0x7fff, and there's no way to repeat a swap
841                  * page within an mm (except in shmem, where it's the
842                  * shared object which takes the reference count)?
843                  * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
844                  *
845                  * If that's wrong, then we should worry more about
846                  * exit_mmap() and do_munmap() cases described above:
847                  * we might be resetting SWAP_MAP_MAX too early here.
848                  * We know "Undead"s can happen, they're okay, so don't
849                  * report them; but do report if we reset SWAP_MAP_MAX.
850                  */
851                 if (*swap_map == SWAP_MAP_MAX) {
852                         spin_lock(&swap_lock);
853                         *swap_map = 1;
854                         spin_unlock(&swap_lock);
855                         reset_overflow = 1;
856                 }
857
858                 /*
859                  * If a reference remains (rare), we would like to leave
860                  * the page in the swap cache; but try_to_unmap could
861                  * then re-duplicate the entry once we drop page lock,
862                  * so we might loop indefinitely; also, that page could
863                  * not be swapped out to other storage meanwhile.  So:
864                  * delete from cache even if there's another reference,
865                  * after ensuring that the data has been saved to disk -
866                  * since if the reference remains (rarer), it will be
867                  * read from disk into another page.  Splitting into two
868                  * pages would be incorrect if swap supported "shared
869                  * private" pages, but they are handled by tmpfs files.
870                  */
871                 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
872                         struct writeback_control wbc = {
873                                 .sync_mode = WB_SYNC_NONE,
874                         };
875
876                         swap_writepage(page, &wbc);
877                         lock_page(page);
878                         wait_on_page_writeback(page);
879                 }
880                 if (PageSwapCache(page))
881                         delete_from_swap_cache(page);
882
883                 /*
884                  * So we could skip searching mms once swap count went
885                  * to 1, we did not mark any present ptes as dirty: must
886                  * mark page dirty so shrink_page_list will preserve it.
887                  */
888                 SetPageDirty(page);
889                 unlock_page(page);
890                 page_cache_release(page);
891
892                 /*
893                  * Make sure that we aren't completely killing
894                  * interactive performance.
895                  */
896                 cond_resched();
897         }
898
899         mmput(start_mm);
900         if (reset_overflow) {
901                 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
902                 swap_overflow = 0;
903         }
904         return retval;
905 }
906
907 /*
908  * After a successful try_to_unuse, if no swap is now in use, we know
909  * we can empty the mmlist.  swap_lock must be held on entry and exit.
910  * Note that mmlist_lock nests inside swap_lock, and an mm must be
911  * added to the mmlist just after page_duplicate - before would be racy.
912  */
913 static void drain_mmlist(void)
914 {
915         struct list_head *p, *next;
916         unsigned int i;
917
918         for (i = 0; i < nr_swapfiles; i++)
919                 if (swap_info[i].inuse_pages)
920                         return;
921         spin_lock(&mmlist_lock);
922         list_for_each_safe(p, next, &init_mm.mmlist)
923                 list_del_init(p);
924         spin_unlock(&mmlist_lock);
925 }
926
927 /*
928  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
929  * corresponds to page offset `offset'.
930  */
931 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
932 {
933         struct swap_extent *se = sis->curr_swap_extent;
934         struct swap_extent *start_se = se;
935
936         for ( ; ; ) {
937                 struct list_head *lh;
938
939                 if (se->start_page <= offset &&
940                                 offset < (se->start_page + se->nr_pages)) {
941                         return se->start_block + (offset - se->start_page);
942                 }
943                 lh = se->list.next;
944                 if (lh == &sis->extent_list)
945                         lh = lh->next;
946                 se = list_entry(lh, struct swap_extent, list);
947                 sis->curr_swap_extent = se;
948                 BUG_ON(se == start_se);         /* It *must* be present */
949         }
950 }
951
952 #ifdef CONFIG_HIBERNATION
953 /*
954  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
955  * corresponding to given index in swap_info (swap type).
956  */
957 sector_t swapdev_block(int swap_type, pgoff_t offset)
958 {
959         struct swap_info_struct *sis;
960
961         if (swap_type >= nr_swapfiles)
962                 return 0;
963
964         sis = swap_info + swap_type;
965         return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
966 }
967 #endif /* CONFIG_HIBERNATION */
968
969 /*
970  * Free all of a swapdev's extent information
971  */
972 static void destroy_swap_extents(struct swap_info_struct *sis)
973 {
974         while (!list_empty(&sis->extent_list)) {
975                 struct swap_extent *se;
976
977                 se = list_entry(sis->extent_list.next,
978                                 struct swap_extent, list);
979                 list_del(&se->list);
980                 kfree(se);
981         }
982 }
983
984 /*
985  * Add a block range (and the corresponding page range) into this swapdev's
986  * extent list.  The extent list is kept sorted in page order.
987  *
988  * This function rather assumes that it is called in ascending page order.
989  */
990 static int
991 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
992                 unsigned long nr_pages, sector_t start_block)
993 {
994         struct swap_extent *se;
995         struct swap_extent *new_se;
996         struct list_head *lh;
997
998         lh = sis->extent_list.prev;     /* The highest page extent */
999         if (lh != &sis->extent_list) {
1000                 se = list_entry(lh, struct swap_extent, list);
1001                 BUG_ON(se->start_page + se->nr_pages != start_page);
1002                 if (se->start_block + se->nr_pages == start_block) {
1003                         /* Merge it */
1004                         se->nr_pages += nr_pages;
1005                         return 0;
1006                 }
1007         }
1008
1009         /*
1010          * No merge.  Insert a new extent, preserving ordering.
1011          */
1012         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1013         if (new_se == NULL)
1014                 return -ENOMEM;
1015         new_se->start_page = start_page;
1016         new_se->nr_pages = nr_pages;
1017         new_se->start_block = start_block;
1018
1019         list_add_tail(&new_se->list, &sis->extent_list);
1020         return 1;
1021 }
1022
1023 /*
1024  * A `swap extent' is a simple thing which maps a contiguous range of pages
1025  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1026  * is built at swapon time and is then used at swap_writepage/swap_readpage
1027  * time for locating where on disk a page belongs.
1028  *
1029  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1030  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1031  * swap files identically.
1032  *
1033  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1034  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1035  * swapfiles are handled *identically* after swapon time.
1036  *
1037  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1038  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1039  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1040  * requirements, they are simply tossed out - we will never use those blocks
1041  * for swapping.
1042  *
1043  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1044  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1045  * which will scribble on the fs.
1046  *
1047  * The amount of disk space which a single swap extent represents varies.
1048  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1049  * extents in the list.  To avoid much list walking, we cache the previous
1050  * search location in `curr_swap_extent', and start new searches from there.
1051  * This is extremely effective.  The average number of iterations in
1052  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1053  */
1054 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1055 {
1056         struct inode *inode;
1057         unsigned blocks_per_page;
1058         unsigned long page_no;
1059         unsigned blkbits;
1060         sector_t probe_block;
1061         sector_t last_block;
1062         sector_t lowest_block = -1;
1063         sector_t highest_block = 0;
1064         int nr_extents = 0;
1065         int ret;
1066
1067         inode = sis->swap_file->f_mapping->host;
1068         if (S_ISBLK(inode->i_mode)) {
1069                 ret = add_swap_extent(sis, 0, sis->max, 0);
1070                 *span = sis->pages;
1071                 goto done;
1072         }
1073
1074         blkbits = inode->i_blkbits;
1075         blocks_per_page = PAGE_SIZE >> blkbits;
1076
1077         /*
1078          * Map all the blocks into the extent list.  This code doesn't try
1079          * to be very smart.
1080          */
1081         probe_block = 0;
1082         page_no = 0;
1083         last_block = i_size_read(inode) >> blkbits;
1084         while ((probe_block + blocks_per_page) <= last_block &&
1085                         page_no < sis->max) {
1086                 unsigned block_in_page;
1087                 sector_t first_block;
1088
1089                 first_block = bmap(inode, probe_block);
1090                 if (first_block == 0)
1091                         goto bad_bmap;
1092
1093                 /*
1094                  * It must be PAGE_SIZE aligned on-disk
1095                  */
1096                 if (first_block & (blocks_per_page - 1)) {
1097                         probe_block++;
1098                         goto reprobe;
1099                 }
1100
1101                 for (block_in_page = 1; block_in_page < blocks_per_page;
1102                                         block_in_page++) {
1103                         sector_t block;
1104
1105                         block = bmap(inode, probe_block + block_in_page);
1106                         if (block == 0)
1107                                 goto bad_bmap;
1108                         if (block != first_block + block_in_page) {
1109                                 /* Discontiguity */
1110                                 probe_block++;
1111                                 goto reprobe;
1112                         }
1113                 }
1114
1115                 first_block >>= (PAGE_SHIFT - blkbits);
1116                 if (page_no) {  /* exclude the header page */
1117                         if (first_block < lowest_block)
1118                                 lowest_block = first_block;
1119                         if (first_block > highest_block)
1120                                 highest_block = first_block;
1121                 }
1122
1123                 /*
1124                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1125                  */
1126                 ret = add_swap_extent(sis, page_no, 1, first_block);
1127                 if (ret < 0)
1128                         goto out;
1129                 nr_extents += ret;
1130                 page_no++;
1131                 probe_block += blocks_per_page;
1132 reprobe:
1133                 continue;
1134         }
1135         ret = nr_extents;
1136         *span = 1 + highest_block - lowest_block;
1137         if (page_no == 0)
1138                 page_no = 1;    /* force Empty message */
1139         sis->max = page_no;
1140         sis->pages = page_no - 1;
1141         sis->highest_bit = page_no - 1;
1142 done:
1143         sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1144                                         struct swap_extent, list);
1145         goto out;
1146 bad_bmap:
1147         printk(KERN_ERR "swapon: swapfile has holes\n");
1148         ret = -EINVAL;
1149 out:
1150         return ret;
1151 }
1152
1153 #if 0   /* We don't need this yet */
1154 #include <linux/backing-dev.h>
1155 int page_queue_congested(struct page *page)
1156 {
1157         struct backing_dev_info *bdi;
1158
1159         BUG_ON(!PageLocked(page));      /* It pins the swap_info_struct */
1160
1161         if (PageSwapCache(page)) {
1162                 swp_entry_t entry = { .val = page_private(page) };
1163                 struct swap_info_struct *sis;
1164
1165                 sis = get_swap_info_struct(swp_type(entry));
1166                 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1167         } else
1168                 bdi = page->mapping->backing_dev_info;
1169         return bdi_write_congested(bdi);
1170 }
1171 #endif
1172
1173 asmlinkage long sys_swapoff(const char __user * specialfile)
1174 {
1175         struct swap_info_struct * p = NULL;
1176         unsigned short *swap_map;
1177         struct file *swap_file, *victim;
1178         struct address_space *mapping;
1179         struct inode *inode;
1180         char * pathname;
1181         int i, type, prev;
1182         int err;
1183         
1184         if (!capable(CAP_SYS_ADMIN))
1185                 return -EPERM;
1186
1187         pathname = getname(specialfile);
1188         err = PTR_ERR(pathname);
1189         if (IS_ERR(pathname))
1190                 goto out;
1191
1192         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1193         putname(pathname);
1194         err = PTR_ERR(victim);
1195         if (IS_ERR(victim))
1196                 goto out;
1197
1198         mapping = victim->f_mapping;
1199         prev = -1;
1200         spin_lock(&swap_lock);
1201         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1202                 p = swap_info + type;
1203                 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1204                         if (p->swap_file->f_mapping == mapping)
1205                                 break;
1206                 }
1207                 prev = type;
1208         }
1209         if (type < 0) {
1210                 err = -EINVAL;
1211                 spin_unlock(&swap_lock);
1212                 goto out_dput;
1213         }
1214         if (!security_vm_enough_memory(p->pages))
1215                 vm_unacct_memory(p->pages);
1216         else {
1217                 err = -ENOMEM;
1218                 spin_unlock(&swap_lock);
1219                 goto out_dput;
1220         }
1221         if (prev < 0) {
1222                 swap_list.head = p->next;
1223         } else {
1224                 swap_info[prev].next = p->next;
1225         }
1226         if (type == swap_list.next) {
1227                 /* just pick something that's safe... */
1228                 swap_list.next = swap_list.head;
1229         }
1230         nr_swap_pages -= p->pages;
1231         total_swap_pages -= p->pages;
1232         p->flags &= ~SWP_WRITEOK;
1233         spin_unlock(&swap_lock);
1234
1235         current->flags |= PF_SWAPOFF;
1236         err = try_to_unuse(type);
1237         current->flags &= ~PF_SWAPOFF;
1238
1239         if (err) {
1240                 /* re-insert swap space back into swap_list */
1241                 spin_lock(&swap_lock);
1242                 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1243                         if (p->prio >= swap_info[i].prio)
1244                                 break;
1245                 p->next = i;
1246                 if (prev < 0)
1247                         swap_list.head = swap_list.next = p - swap_info;
1248                 else
1249                         swap_info[prev].next = p - swap_info;
1250                 nr_swap_pages += p->pages;
1251                 total_swap_pages += p->pages;
1252                 p->flags |= SWP_WRITEOK;
1253                 spin_unlock(&swap_lock);
1254                 goto out_dput;
1255         }
1256
1257         /* wait for any unplug function to finish */
1258         down_write(&swap_unplug_sem);
1259         up_write(&swap_unplug_sem);
1260
1261         destroy_swap_extents(p);
1262         mutex_lock(&swapon_mutex);
1263         spin_lock(&swap_lock);
1264         drain_mmlist();
1265
1266         /* wait for anyone still in scan_swap_map */
1267         p->highest_bit = 0;             /* cuts scans short */
1268         while (p->flags >= SWP_SCANNING) {
1269                 spin_unlock(&swap_lock);
1270                 schedule_timeout_uninterruptible(1);
1271                 spin_lock(&swap_lock);
1272         }
1273
1274         swap_file = p->swap_file;
1275         p->swap_file = NULL;
1276         p->max = 0;
1277         swap_map = p->swap_map;
1278         p->swap_map = NULL;
1279         p->flags = 0;
1280         spin_unlock(&swap_lock);
1281         mutex_unlock(&swapon_mutex);
1282         vfree(swap_map);
1283         inode = mapping->host;
1284         if (S_ISBLK(inode->i_mode)) {
1285                 struct block_device *bdev = I_BDEV(inode);
1286                 set_blocksize(bdev, p->old_block_size);
1287                 bd_release(bdev);
1288         } else {
1289                 mutex_lock(&inode->i_mutex);
1290                 inode->i_flags &= ~S_SWAPFILE;
1291                 mutex_unlock(&inode->i_mutex);
1292         }
1293         filp_close(swap_file, NULL);
1294         err = 0;
1295
1296 out_dput:
1297         filp_close(victim, NULL);
1298 out:
1299         return err;
1300 }
1301
1302 #ifdef CONFIG_PROC_FS
1303 /* iterator */
1304 static void *swap_start(struct seq_file *swap, loff_t *pos)
1305 {
1306         struct swap_info_struct *ptr = swap_info;
1307         int i;
1308         loff_t l = *pos;
1309
1310         mutex_lock(&swapon_mutex);
1311
1312         if (!l)
1313                 return SEQ_START_TOKEN;
1314
1315         for (i = 0; i < nr_swapfiles; i++, ptr++) {
1316                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1317                         continue;
1318                 if (!--l)
1319                         return ptr;
1320         }
1321
1322         return NULL;
1323 }
1324
1325 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1326 {
1327         struct swap_info_struct *ptr;
1328         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1329
1330         if (v == SEQ_START_TOKEN)
1331                 ptr = swap_info;
1332         else {
1333                 ptr = v;
1334                 ptr++;
1335         }
1336
1337         for (; ptr < endptr; ptr++) {
1338                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1339                         continue;
1340                 ++*pos;
1341                 return ptr;
1342         }
1343
1344         return NULL;
1345 }
1346
1347 static void swap_stop(struct seq_file *swap, void *v)
1348 {
1349         mutex_unlock(&swapon_mutex);
1350 }
1351
1352 static int swap_show(struct seq_file *swap, void *v)
1353 {
1354         struct swap_info_struct *ptr = v;
1355         struct file *file;
1356         int len;
1357
1358         if (ptr == SEQ_START_TOKEN) {
1359                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1360                 return 0;
1361         }
1362
1363         file = ptr->swap_file;
1364         len = seq_path(swap, file->f_path.mnt, file->f_path.dentry, " \t\n\\");
1365         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1366                        len < 40 ? 40 - len : 1, " ",
1367                        S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1368                                 "partition" : "file\t",
1369                        ptr->pages << (PAGE_SHIFT - 10),
1370                        ptr->inuse_pages << (PAGE_SHIFT - 10),
1371                        ptr->prio);
1372         return 0;
1373 }
1374
1375 static const struct seq_operations swaps_op = {
1376         .start =        swap_start,
1377         .next =         swap_next,
1378         .stop =         swap_stop,
1379         .show =         swap_show
1380 };
1381
1382 static int swaps_open(struct inode *inode, struct file *file)
1383 {
1384         return seq_open(file, &swaps_op);
1385 }
1386
1387 static const struct file_operations proc_swaps_operations = {
1388         .open           = swaps_open,
1389         .read           = seq_read,
1390         .llseek         = seq_lseek,
1391         .release        = seq_release,
1392 };
1393
1394 static int __init procswaps_init(void)
1395 {
1396         struct proc_dir_entry *entry;
1397
1398         entry = create_proc_entry("swaps", 0, NULL);
1399         if (entry)
1400                 entry->proc_fops = &proc_swaps_operations;
1401         return 0;
1402 }
1403 __initcall(procswaps_init);
1404 #endif /* CONFIG_PROC_FS */
1405
1406 /*
1407  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1408  *
1409  * The swapon system call
1410  */
1411 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1412 {
1413         struct swap_info_struct * p;
1414         char *name = NULL;
1415         struct block_device *bdev = NULL;
1416         struct file *swap_file = NULL;
1417         struct address_space *mapping;
1418         unsigned int type;
1419         int i, prev;
1420         int error;
1421         static int least_priority;
1422         union swap_header *swap_header = NULL;
1423         int swap_header_version;
1424         unsigned int nr_good_pages = 0;
1425         int nr_extents = 0;
1426         sector_t span;
1427         unsigned long maxpages = 1;
1428         int swapfilesize;
1429         unsigned short *swap_map;
1430         struct page *page = NULL;
1431         struct inode *inode = NULL;
1432         int did_down = 0;
1433
1434         if (!capable(CAP_SYS_ADMIN))
1435                 return -EPERM;
1436         spin_lock(&swap_lock);
1437         p = swap_info;
1438         for (type = 0 ; type < nr_swapfiles ; type++,p++)
1439                 if (!(p->flags & SWP_USED))
1440                         break;
1441         error = -EPERM;
1442         if (type >= MAX_SWAPFILES) {
1443                 spin_unlock(&swap_lock);
1444                 goto out;
1445         }
1446         if (type >= nr_swapfiles)
1447                 nr_swapfiles = type+1;
1448         INIT_LIST_HEAD(&p->extent_list);
1449         p->flags = SWP_USED;
1450         p->swap_file = NULL;
1451         p->old_block_size = 0;
1452         p->swap_map = NULL;
1453         p->lowest_bit = 0;
1454         p->highest_bit = 0;
1455         p->cluster_nr = 0;
1456         p->inuse_pages = 0;
1457         p->next = -1;
1458         if (swap_flags & SWAP_FLAG_PREFER) {
1459                 p->prio =
1460                   (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1461         } else {
1462                 p->prio = --least_priority;
1463         }
1464         spin_unlock(&swap_lock);
1465         name = getname(specialfile);
1466         error = PTR_ERR(name);
1467         if (IS_ERR(name)) {
1468                 name = NULL;
1469                 goto bad_swap_2;
1470         }
1471         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1472         error = PTR_ERR(swap_file);
1473         if (IS_ERR(swap_file)) {
1474                 swap_file = NULL;
1475                 goto bad_swap_2;
1476         }
1477
1478         p->swap_file = swap_file;
1479         mapping = swap_file->f_mapping;
1480         inode = mapping->host;
1481
1482         error = -EBUSY;
1483         for (i = 0; i < nr_swapfiles; i++) {
1484                 struct swap_info_struct *q = &swap_info[i];
1485
1486                 if (i == type || !q->swap_file)
1487                         continue;
1488                 if (mapping == q->swap_file->f_mapping)
1489                         goto bad_swap;
1490         }
1491
1492         error = -EINVAL;
1493         if (S_ISBLK(inode->i_mode)) {
1494                 bdev = I_BDEV(inode);
1495                 error = bd_claim(bdev, sys_swapon);
1496                 if (error < 0) {
1497                         bdev = NULL;
1498                         error = -EINVAL;
1499                         goto bad_swap;
1500                 }
1501                 p->old_block_size = block_size(bdev);
1502                 error = set_blocksize(bdev, PAGE_SIZE);
1503                 if (error < 0)
1504                         goto bad_swap;
1505                 p->bdev = bdev;
1506         } else if (S_ISREG(inode->i_mode)) {
1507                 p->bdev = inode->i_sb->s_bdev;
1508                 mutex_lock(&inode->i_mutex);
1509                 did_down = 1;
1510                 if (IS_SWAPFILE(inode)) {
1511                         error = -EBUSY;
1512                         goto bad_swap;
1513                 }
1514         } else {
1515                 goto bad_swap;
1516         }
1517
1518         swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1519
1520         /*
1521          * Read the swap header.
1522          */
1523         if (!mapping->a_ops->readpage) {
1524                 error = -EINVAL;
1525                 goto bad_swap;
1526         }
1527         page = read_mapping_page(mapping, 0, swap_file);
1528         if (IS_ERR(page)) {
1529                 error = PTR_ERR(page);
1530                 goto bad_swap;
1531         }
1532         kmap(page);
1533         swap_header = page_address(page);
1534
1535         if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1536                 swap_header_version = 1;
1537         else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1538                 swap_header_version = 2;
1539         else {
1540                 printk(KERN_ERR "Unable to find swap-space signature\n");
1541                 error = -EINVAL;
1542                 goto bad_swap;
1543         }
1544         
1545         switch (swap_header_version) {
1546         case 1:
1547                 printk(KERN_ERR "version 0 swap is no longer supported. "
1548                         "Use mkswap -v1 %s\n", name);
1549                 error = -EINVAL;
1550                 goto bad_swap;
1551         case 2:
1552                 /* Check the swap header's sub-version and the size of
1553                    the swap file and bad block lists */
1554                 if (swap_header->info.version != 1) {
1555                         printk(KERN_WARNING
1556                                "Unable to handle swap header version %d\n",
1557                                swap_header->info.version);
1558                         error = -EINVAL;
1559                         goto bad_swap;
1560                 }
1561
1562                 p->lowest_bit  = 1;
1563                 p->cluster_next = 1;
1564
1565                 /*
1566                  * Find out how many pages are allowed for a single swap
1567                  * device. There are two limiting factors: 1) the number of
1568                  * bits for the swap offset in the swp_entry_t type and
1569                  * 2) the number of bits in the a swap pte as defined by
1570                  * the different architectures. In order to find the
1571                  * largest possible bit mask a swap entry with swap type 0
1572                  * and swap offset ~0UL is created, encoded to a swap pte,
1573                  * decoded to a swp_entry_t again and finally the swap
1574                  * offset is extracted. This will mask all the bits from
1575                  * the initial ~0UL mask that can't be encoded in either
1576                  * the swp_entry_t or the architecture definition of a
1577                  * swap pte.
1578                  */
1579                 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1580                 if (maxpages > swap_header->info.last_page)
1581                         maxpages = swap_header->info.last_page;
1582                 p->highest_bit = maxpages - 1;
1583
1584                 error = -EINVAL;
1585                 if (!maxpages)
1586                         goto bad_swap;
1587                 if (swapfilesize && maxpages > swapfilesize) {
1588                         printk(KERN_WARNING
1589                                "Swap area shorter than signature indicates\n");
1590                         goto bad_swap;
1591                 }
1592                 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1593                         goto bad_swap;
1594                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1595                         goto bad_swap;
1596
1597                 /* OK, set up the swap map and apply the bad block list */
1598                 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1599                         error = -ENOMEM;
1600                         goto bad_swap;
1601                 }
1602
1603                 error = 0;
1604                 memset(p->swap_map, 0, maxpages * sizeof(short));
1605                 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1606                         int page_nr = swap_header->info.badpages[i];
1607                         if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1608                                 error = -EINVAL;
1609                         else
1610                                 p->swap_map[page_nr] = SWAP_MAP_BAD;
1611                 }
1612                 nr_good_pages = swap_header->info.last_page -
1613                                 swap_header->info.nr_badpages -
1614                                 1 /* header page */;
1615                 if (error)
1616                         goto bad_swap;
1617         }
1618
1619         if (nr_good_pages) {
1620                 p->swap_map[0] = SWAP_MAP_BAD;
1621                 p->max = maxpages;
1622                 p->pages = nr_good_pages;
1623                 nr_extents = setup_swap_extents(p, &span);
1624                 if (nr_extents < 0) {
1625                         error = nr_extents;
1626                         goto bad_swap;
1627                 }
1628                 nr_good_pages = p->pages;
1629         }
1630         if (!nr_good_pages) {
1631                 printk(KERN_WARNING "Empty swap-file\n");
1632                 error = -EINVAL;
1633                 goto bad_swap;
1634         }
1635
1636         mutex_lock(&swapon_mutex);
1637         spin_lock(&swap_lock);
1638         p->flags = SWP_ACTIVE;
1639         nr_swap_pages += nr_good_pages;
1640         total_swap_pages += nr_good_pages;
1641
1642         printk(KERN_INFO "Adding %uk swap on %s.  "
1643                         "Priority:%d extents:%d across:%lluk\n",
1644                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1645                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1646
1647         /* insert swap space into swap_list: */
1648         prev = -1;
1649         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1650                 if (p->prio >= swap_info[i].prio) {
1651                         break;
1652                 }
1653                 prev = i;
1654         }
1655         p->next = i;
1656         if (prev < 0) {
1657                 swap_list.head = swap_list.next = p - swap_info;
1658         } else {
1659                 swap_info[prev].next = p - swap_info;
1660         }
1661         spin_unlock(&swap_lock);
1662         mutex_unlock(&swapon_mutex);
1663         error = 0;
1664         goto out;
1665 bad_swap:
1666         if (bdev) {
1667                 set_blocksize(bdev, p->old_block_size);
1668                 bd_release(bdev);
1669         }
1670         destroy_swap_extents(p);
1671 bad_swap_2:
1672         spin_lock(&swap_lock);
1673         swap_map = p->swap_map;
1674         p->swap_file = NULL;
1675         p->swap_map = NULL;
1676         p->flags = 0;
1677         if (!(swap_flags & SWAP_FLAG_PREFER))
1678                 ++least_priority;
1679         spin_unlock(&swap_lock);
1680         vfree(swap_map);
1681         if (swap_file)
1682                 filp_close(swap_file, NULL);
1683 out:
1684         if (page && !IS_ERR(page)) {
1685                 kunmap(page);
1686                 page_cache_release(page);
1687         }
1688         if (name)
1689                 putname(name);
1690         if (did_down) {
1691                 if (!error)
1692                         inode->i_flags |= S_SWAPFILE;
1693                 mutex_unlock(&inode->i_mutex);
1694         }
1695         return error;
1696 }
1697
1698 void si_swapinfo(struct sysinfo *val)
1699 {
1700         unsigned int i;
1701         unsigned long nr_to_be_unused = 0;
1702
1703         spin_lock(&swap_lock);
1704         for (i = 0; i < nr_swapfiles; i++) {
1705                 if (!(swap_info[i].flags & SWP_USED) ||
1706                      (swap_info[i].flags & SWP_WRITEOK))
1707                         continue;
1708                 nr_to_be_unused += swap_info[i].inuse_pages;
1709         }
1710         val->freeswap = nr_swap_pages + nr_to_be_unused;
1711         val->totalswap = total_swap_pages + nr_to_be_unused;
1712         spin_unlock(&swap_lock);
1713 }
1714
1715 /*
1716  * Verify that a swap entry is valid and increment its swap map count.
1717  *
1718  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1719  * "permanent", but will be reclaimed by the next swapoff.
1720  */
1721 int swap_duplicate(swp_entry_t entry)
1722 {
1723         struct swap_info_struct * p;
1724         unsigned long offset, type;
1725         int result = 0;
1726
1727         if (is_migration_entry(entry))
1728                 return 1;
1729
1730         type = swp_type(entry);
1731         if (type >= nr_swapfiles)
1732                 goto bad_file;
1733         p = type + swap_info;
1734         offset = swp_offset(entry);
1735
1736         spin_lock(&swap_lock);
1737         if (offset < p->max && p->swap_map[offset]) {
1738                 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1739                         p->swap_map[offset]++;
1740                         result = 1;
1741                 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1742                         if (swap_overflow++ < 5)
1743                                 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1744                         p->swap_map[offset] = SWAP_MAP_MAX;
1745                         result = 1;
1746                 }
1747         }
1748         spin_unlock(&swap_lock);
1749 out:
1750         return result;
1751
1752 bad_file:
1753         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1754         goto out;
1755 }
1756
1757 struct swap_info_struct *
1758 get_swap_info_struct(unsigned type)
1759 {
1760         return &swap_info[type];
1761 }
1762
1763 /*
1764  * swap_lock prevents swap_map being freed. Don't grab an extra
1765  * reference on the swaphandle, it doesn't matter if it becomes unused.
1766  */
1767 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1768 {
1769         struct swap_info_struct *si;
1770         int our_page_cluster = page_cluster;
1771         pgoff_t target, toff;
1772         pgoff_t base, end;
1773         int nr_pages = 0;
1774
1775         if (!our_page_cluster)  /* no readahead */
1776                 return 0;
1777
1778         si = &swap_info[swp_type(entry)];
1779         target = swp_offset(entry);
1780         base = (target >> our_page_cluster) << our_page_cluster;
1781         end = base + (1 << our_page_cluster);
1782         if (!base)              /* first page is swap header */
1783                 base++;
1784
1785         spin_lock(&swap_lock);
1786         if (end > si->max)      /* don't go beyond end of map */
1787                 end = si->max;
1788
1789         /* Count contiguous allocated slots above our target */
1790         for (toff = target; ++toff < end; nr_pages++) {
1791                 /* Don't read in free or bad pages */
1792                 if (!si->swap_map[toff])
1793                         break;
1794                 if (si->swap_map[toff] == SWAP_MAP_BAD)
1795                         break;
1796         }
1797         /* Count contiguous allocated slots below our target */
1798         for (toff = target; --toff >= base; nr_pages++) {
1799                 /* Don't read in free or bad pages */
1800                 if (!si->swap_map[toff])
1801                         break;
1802                 if (si->swap_map[toff] == SWAP_MAP_BAD)
1803                         break;
1804         }
1805         spin_unlock(&swap_lock);
1806
1807         /*
1808          * Indicate starting offset, and return number of pages to get:
1809          * if only 1, say 0, since there's then no readahead to be done.
1810          */
1811         *offset = ++toff;
1812         return nr_pages? ++nr_pages: 0;
1813 }