blob: 62e0da8f7e6eeb8aa0f7c99475b61dae8619eda9 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/config.h>
9#include <linux/mm.h>
10#include <linux/hugetlb.h>
11#include <linux/mman.h>
12#include <linux/slab.h>
13#include <linux/kernel_stat.h>
14#include <linux/swap.h>
15#include <linux/vmalloc.h>
16#include <linux/pagemap.h>
17#include <linux/namei.h>
18#include <linux/shm.h>
19#include <linux/blkdev.h>
20#include <linux/writeback.h>
21#include <linux/proc_fs.h>
22#include <linux/seq_file.h>
23#include <linux/init.h>
24#include <linux/module.h>
25#include <linux/rmap.h>
26#include <linux/security.h>
27#include <linux/backing-dev.h>
28#include <linux/syscalls.h>
29
30#include <asm/pgtable.h>
31#include <asm/tlbflush.h>
32#include <linux/swapops.h>
33
34DEFINE_SPINLOCK(swaplock);
35unsigned int nr_swapfiles;
36long total_swap_pages;
37static int swap_overflow;
38
39EXPORT_SYMBOL(total_swap_pages);
40
41static const char Bad_file[] = "Bad swap file entry ";
42static const char Unused_file[] = "Unused swap file entry ";
43static const char Bad_offset[] = "Bad swap offset entry ";
44static const char Unused_offset[] = "Unused swap offset entry ";
45
46struct swap_list_t swap_list = {-1, -1};
47
48struct swap_info_struct swap_info[MAX_SWAPFILES];
49
50static DECLARE_MUTEX(swapon_sem);
51
52/*
53 * We need this because the bdev->unplug_fn can sleep and we cannot
54 * hold swap_list_lock while calling the unplug_fn. And swap_list_lock
55 * cannot be turned into a semaphore.
56 */
57static DECLARE_RWSEM(swap_unplug_sem);
58
59#define SWAPFILE_CLUSTER 256
60
61void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
62{
63 swp_entry_t entry;
64
65 down_read(&swap_unplug_sem);
66 entry.val = page->private;
67 if (PageSwapCache(page)) {
68 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
69 struct backing_dev_info *bdi;
70
71 /*
72 * If the page is removed from swapcache from under us (with a
73 * racy try_to_unuse/swapoff) we need an additional reference
74 * count to avoid reading garbage from page->private above. If
75 * the WARN_ON triggers during a swapoff it maybe the race
76 * condition and it's harmless. However if it triggers without
77 * swapoff it signals a problem.
78 */
79 WARN_ON(page_count(page) <= 1);
80
81 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -070082 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 }
84 up_read(&swap_unplug_sem);
85}
86
Hugh Dickins6eb396d2005-09-03 15:54:35 -070087static inline unsigned long scan_swap_map(struct swap_info_struct *si)
Linus Torvalds1da177e2005-04-16 15:20:36 -070088{
89 unsigned long offset;
90 /*
91 * We try to cluster swap pages by allocating them
92 * sequentially in swap. Once we've allocated
93 * SWAPFILE_CLUSTER pages this way, however, we resort to
94 * first-free allocation, starting a new cluster. This
95 * prevents us from scattering swap pages all over the entire
96 * swap partition, so that we reduce overall disk seek times
97 * between swap pages. -- sct */
98 if (si->cluster_nr) {
99 while (si->cluster_next <= si->highest_bit) {
100 offset = si->cluster_next++;
101 if (si->swap_map[offset])
102 continue;
103 si->cluster_nr--;
104 goto got_page;
105 }
106 }
107 si->cluster_nr = SWAPFILE_CLUSTER;
108
109 /* try to find an empty (even not aligned) cluster. */
110 offset = si->lowest_bit;
111 check_next_cluster:
112 if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
113 {
114 unsigned long nr;
115 for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
116 if (si->swap_map[nr])
117 {
118 offset = nr+1;
119 goto check_next_cluster;
120 }
121 /* We found a completly empty cluster, so start
122 * using it.
123 */
124 goto got_page;
125 }
126 /* No luck, so now go finegrined as usual. -Andrea */
127 for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
128 if (si->swap_map[offset])
129 continue;
130 si->lowest_bit = offset+1;
131 got_page:
132 if (offset == si->lowest_bit)
133 si->lowest_bit++;
134 if (offset == si->highest_bit)
135 si->highest_bit--;
136 if (si->lowest_bit > si->highest_bit) {
137 si->lowest_bit = si->max;
138 si->highest_bit = 0;
139 }
140 si->swap_map[offset] = 1;
141 si->inuse_pages++;
142 nr_swap_pages--;
143 si->cluster_next = offset+1;
144 return offset;
145 }
146 si->lowest_bit = si->max;
147 si->highest_bit = 0;
148 return 0;
149}
150
151swp_entry_t get_swap_page(void)
152{
153 struct swap_info_struct * p;
154 unsigned long offset;
155 swp_entry_t entry;
156 int type, wrapped = 0;
157
158 entry.val = 0; /* Out of memory */
159 swap_list_lock();
160 type = swap_list.next;
161 if (type < 0)
162 goto out;
163 if (nr_swap_pages <= 0)
164 goto out;
165
166 while (1) {
167 p = &swap_info[type];
168 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
169 swap_device_lock(p);
170 offset = scan_swap_map(p);
171 swap_device_unlock(p);
172 if (offset) {
173 entry = swp_entry(type,offset);
174 type = swap_info[type].next;
175 if (type < 0 ||
176 p->prio != swap_info[type].prio) {
177 swap_list.next = swap_list.head;
178 } else {
179 swap_list.next = type;
180 }
181 goto out;
182 }
183 }
184 type = p->next;
185 if (!wrapped) {
186 if (type < 0 || p->prio != swap_info[type].prio) {
187 type = swap_list.head;
188 wrapped = 1;
189 }
190 } else
191 if (type < 0)
192 goto out; /* out of swap space */
193 }
194out:
195 swap_list_unlock();
196 return entry;
197}
198
199static struct swap_info_struct * swap_info_get(swp_entry_t entry)
200{
201 struct swap_info_struct * p;
202 unsigned long offset, type;
203
204 if (!entry.val)
205 goto out;
206 type = swp_type(entry);
207 if (type >= nr_swapfiles)
208 goto bad_nofile;
209 p = & swap_info[type];
210 if (!(p->flags & SWP_USED))
211 goto bad_device;
212 offset = swp_offset(entry);
213 if (offset >= p->max)
214 goto bad_offset;
215 if (!p->swap_map[offset])
216 goto bad_free;
217 swap_list_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 swap_device_lock(p);
219 return p;
220
221bad_free:
222 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
223 goto out;
224bad_offset:
225 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
226 goto out;
227bad_device:
228 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
229 goto out;
230bad_nofile:
231 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
232out:
233 return NULL;
234}
235
236static void swap_info_put(struct swap_info_struct * p)
237{
238 swap_device_unlock(p);
239 swap_list_unlock();
240}
241
242static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
243{
244 int count = p->swap_map[offset];
245
246 if (count < SWAP_MAP_MAX) {
247 count--;
248 p->swap_map[offset] = count;
249 if (!count) {
250 if (offset < p->lowest_bit)
251 p->lowest_bit = offset;
252 if (offset > p->highest_bit)
253 p->highest_bit = offset;
Hugh Dickins89d09a22005-09-03 15:54:36 -0700254 if (p->prio > swap_info[swap_list.next].prio)
255 swap_list.next = p - swap_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 nr_swap_pages++;
257 p->inuse_pages--;
258 }
259 }
260 return count;
261}
262
263/*
264 * Caller has made sure that the swapdevice corresponding to entry
265 * is still around or has not been recycled.
266 */
267void swap_free(swp_entry_t entry)
268{
269 struct swap_info_struct * p;
270
271 p = swap_info_get(entry);
272 if (p) {
273 swap_entry_free(p, swp_offset(entry));
274 swap_info_put(p);
275 }
276}
277
278/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700279 * How many references to page are currently swapped out?
Linus Torvalds1da177e2005-04-16 15:20:36 -0700280 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700281static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700283 int count = 0;
284 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285 swp_entry_t entry;
286
287 entry.val = page->private;
288 p = swap_info_get(entry);
289 if (p) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700290 /* Subtract the 1 for the swap cache itself */
291 count = p->swap_map[swp_offset(entry)] - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 swap_info_put(p);
293 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700294 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295}
296
297/*
298 * We can use this swap cache entry directly
299 * if there are no other references to it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300 */
301int can_share_swap_page(struct page *page)
302{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700303 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700305 BUG_ON(!PageLocked(page));
306 count = page_mapcount(page);
307 if (count <= 1 && PageSwapCache(page))
308 count += page_swapcount(page);
309 return count == 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310}
311
312/*
313 * Work out if there are any other processes sharing this
314 * swap cache page. Free it if you can. Return success.
315 */
316int remove_exclusive_swap_page(struct page *page)
317{
318 int retval;
319 struct swap_info_struct * p;
320 swp_entry_t entry;
321
322 BUG_ON(PagePrivate(page));
323 BUG_ON(!PageLocked(page));
324
325 if (!PageSwapCache(page))
326 return 0;
327 if (PageWriteback(page))
328 return 0;
329 if (page_count(page) != 2) /* 2: us + cache */
330 return 0;
331
332 entry.val = page->private;
333 p = swap_info_get(entry);
334 if (!p)
335 return 0;
336
337 /* Is the only swap cache user the cache itself? */
338 retval = 0;
339 if (p->swap_map[swp_offset(entry)] == 1) {
340 /* Recheck the page count with the swapcache lock held.. */
341 write_lock_irq(&swapper_space.tree_lock);
342 if ((page_count(page) == 2) && !PageWriteback(page)) {
343 __delete_from_swap_cache(page);
344 SetPageDirty(page);
345 retval = 1;
346 }
347 write_unlock_irq(&swapper_space.tree_lock);
348 }
349 swap_info_put(p);
350
351 if (retval) {
352 swap_free(entry);
353 page_cache_release(page);
354 }
355
356 return retval;
357}
358
359/*
360 * Free the swap entry like above, but also try to
361 * free the page cache entry if it is the last user.
362 */
363void free_swap_and_cache(swp_entry_t entry)
364{
365 struct swap_info_struct * p;
366 struct page *page = NULL;
367
368 p = swap_info_get(entry);
369 if (p) {
370 if (swap_entry_free(p, swp_offset(entry)) == 1)
371 page = find_trylock_page(&swapper_space, entry.val);
372 swap_info_put(p);
373 }
374 if (page) {
375 int one_user;
376
377 BUG_ON(PagePrivate(page));
378 page_cache_get(page);
379 one_user = (page_count(page) == 2);
380 /* Only cache user (+us), or swap space full? Free it! */
381 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
382 delete_from_swap_cache(page);
383 SetPageDirty(page);
384 }
385 unlock_page(page);
386 page_cache_release(page);
387 }
388}
389
390/*
391 * Always set the resulting pte to be nowrite (the same as COW pages
392 * after one process has exited). We don't know just how many PTEs will
393 * share this swap entry, so be cautious and let do_wp_page work out
394 * what to do if a write is requested later.
395 *
396 * vma->vm_mm->page_table_lock is held.
397 */
398static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
399 unsigned long addr, swp_entry_t entry, struct page *page)
400{
401 inc_mm_counter(vma->vm_mm, rss);
402 get_page(page);
403 set_pte_at(vma->vm_mm, addr, pte,
404 pte_mkold(mk_pte(page, vma->vm_page_prot)));
405 page_add_anon_rmap(page, vma, addr);
406 swap_free(entry);
407 /*
408 * Move the page to the active list so it is not
409 * immediately swapped out again after swapon.
410 */
411 activate_page(page);
412}
413
414static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
415 unsigned long addr, unsigned long end,
416 swp_entry_t entry, struct page *page)
417{
418 pte_t *pte;
419 pte_t swp_pte = swp_entry_to_pte(entry);
420
421 pte = pte_offset_map(pmd, addr);
422 do {
423 /*
424 * swapoff spends a _lot_ of time in this loop!
425 * Test inline before going to call unuse_pte.
426 */
427 if (unlikely(pte_same(*pte, swp_pte))) {
428 unuse_pte(vma, pte, addr, entry, page);
429 pte_unmap(pte);
430 return 1;
431 }
432 } while (pte++, addr += PAGE_SIZE, addr != end);
433 pte_unmap(pte - 1);
434 return 0;
435}
436
437static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
438 unsigned long addr, unsigned long end,
439 swp_entry_t entry, struct page *page)
440{
441 pmd_t *pmd;
442 unsigned long next;
443
444 pmd = pmd_offset(pud, addr);
445 do {
446 next = pmd_addr_end(addr, end);
447 if (pmd_none_or_clear_bad(pmd))
448 continue;
449 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
450 return 1;
451 } while (pmd++, addr = next, addr != end);
452 return 0;
453}
454
455static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
456 unsigned long addr, unsigned long end,
457 swp_entry_t entry, struct page *page)
458{
459 pud_t *pud;
460 unsigned long next;
461
462 pud = pud_offset(pgd, addr);
463 do {
464 next = pud_addr_end(addr, end);
465 if (pud_none_or_clear_bad(pud))
466 continue;
467 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
468 return 1;
469 } while (pud++, addr = next, addr != end);
470 return 0;
471}
472
473static int unuse_vma(struct vm_area_struct *vma,
474 swp_entry_t entry, struct page *page)
475{
476 pgd_t *pgd;
477 unsigned long addr, end, next;
478
479 if (page->mapping) {
480 addr = page_address_in_vma(page, vma);
481 if (addr == -EFAULT)
482 return 0;
483 else
484 end = addr + PAGE_SIZE;
485 } else {
486 addr = vma->vm_start;
487 end = vma->vm_end;
488 }
489
490 pgd = pgd_offset(vma->vm_mm, addr);
491 do {
492 next = pgd_addr_end(addr, end);
493 if (pgd_none_or_clear_bad(pgd))
494 continue;
495 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
496 return 1;
497 } while (pgd++, addr = next, addr != end);
498 return 0;
499}
500
501static int unuse_mm(struct mm_struct *mm,
502 swp_entry_t entry, struct page *page)
503{
504 struct vm_area_struct *vma;
505
506 if (!down_read_trylock(&mm->mmap_sem)) {
507 /*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700508 * Activate page so shrink_cache is unlikely to unmap its
509 * ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700511 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 unlock_page(page);
513 down_read(&mm->mmap_sem);
514 lock_page(page);
515 }
516 spin_lock(&mm->page_table_lock);
517 for (vma = mm->mmap; vma; vma = vma->vm_next) {
518 if (vma->anon_vma && unuse_vma(vma, entry, page))
519 break;
520 }
521 spin_unlock(&mm->page_table_lock);
522 up_read(&mm->mmap_sem);
523 /*
524 * Currently unuse_mm cannot fail, but leave error handling
525 * at call sites for now, since we change it from time to time.
526 */
527 return 0;
528}
529
530/*
531 * Scan swap_map from current position to next entry still in use.
532 * Recycle to start on reaching the end, returning 0 when empty.
533 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700534static unsigned int find_next_to_unuse(struct swap_info_struct *si,
535 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700537 unsigned int max = si->max;
538 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 int count;
540
541 /*
542 * No need for swap_device_lock(si) here: we're just looking
543 * for whether an entry is in use, not modifying it; false
544 * hits are okay, and sys_swapoff() has already prevented new
545 * allocations from this area (while holding swap_list_lock()).
546 */
547 for (;;) {
548 if (++i >= max) {
549 if (!prev) {
550 i = 0;
551 break;
552 }
553 /*
554 * No entries in use at top of swap_map,
555 * loop back to start and recheck there.
556 */
557 max = prev + 1;
558 prev = 0;
559 i = 1;
560 }
561 count = si->swap_map[i];
562 if (count && count != SWAP_MAP_BAD)
563 break;
564 }
565 return i;
566}
567
568/*
569 * We completely avoid races by reading each swap page in advance,
570 * and then search for the process using it. All the necessary
571 * page table adjustments can then be made atomically.
572 */
573static int try_to_unuse(unsigned int type)
574{
575 struct swap_info_struct * si = &swap_info[type];
576 struct mm_struct *start_mm;
577 unsigned short *swap_map;
578 unsigned short swcount;
579 struct page *page;
580 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700581 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 int retval = 0;
583 int reset_overflow = 0;
584 int shmem;
585
586 /*
587 * When searching mms for an entry, a good strategy is to
588 * start at the first mm we freed the previous entry from
589 * (though actually we don't notice whether we or coincidence
590 * freed the entry). Initialize this start_mm with a hold.
591 *
592 * A simpler strategy would be to start at the last mm we
593 * freed the previous entry from; but that would take less
594 * advantage of mmlist ordering, which clusters forked mms
595 * together, child after parent. If we race with dup_mmap(), we
596 * prefer to resolve parent before child, lest we miss entries
597 * duplicated after we scanned child: using last mm would invert
598 * that. Though it's only a serious concern when an overflowed
599 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
600 */
601 start_mm = &init_mm;
602 atomic_inc(&init_mm.mm_users);
603
604 /*
605 * Keep on scanning until all entries have gone. Usually,
606 * one pass through swap_map is enough, but not necessarily:
607 * there are races when an instance of an entry might be missed.
608 */
609 while ((i = find_next_to_unuse(si, i)) != 0) {
610 if (signal_pending(current)) {
611 retval = -EINTR;
612 break;
613 }
614
615 /*
616 * Get a page for the entry, using the existing swap
617 * cache page if there is one. Otherwise, get a clean
618 * page and read the swap into it.
619 */
620 swap_map = &si->swap_map[i];
621 entry = swp_entry(type, i);
622 page = read_swap_cache_async(entry, NULL, 0);
623 if (!page) {
624 /*
625 * Either swap_duplicate() failed because entry
626 * has been freed independently, and will not be
627 * reused since sys_swapoff() already disabled
628 * allocation from here, or alloc_page() failed.
629 */
630 if (!*swap_map)
631 continue;
632 retval = -ENOMEM;
633 break;
634 }
635
636 /*
637 * Don't hold on to start_mm if it looks like exiting.
638 */
639 if (atomic_read(&start_mm->mm_users) == 1) {
640 mmput(start_mm);
641 start_mm = &init_mm;
642 atomic_inc(&init_mm.mm_users);
643 }
644
645 /*
646 * Wait for and lock page. When do_swap_page races with
647 * try_to_unuse, do_swap_page can handle the fault much
648 * faster than try_to_unuse can locate the entry. This
649 * apparently redundant "wait_on_page_locked" lets try_to_unuse
650 * defer to do_swap_page in such a case - in some tests,
651 * do_swap_page and try_to_unuse repeatedly compete.
652 */
653 wait_on_page_locked(page);
654 wait_on_page_writeback(page);
655 lock_page(page);
656 wait_on_page_writeback(page);
657
658 /*
659 * Remove all references to entry.
660 * Whenever we reach init_mm, there's no address space
661 * to search, but use it as a reminder to search shmem.
662 */
663 shmem = 0;
664 swcount = *swap_map;
665 if (swcount > 1) {
666 if (start_mm == &init_mm)
667 shmem = shmem_unuse(entry, page);
668 else
669 retval = unuse_mm(start_mm, entry, page);
670 }
671 if (*swap_map > 1) {
672 int set_start_mm = (*swap_map >= swcount);
673 struct list_head *p = &start_mm->mmlist;
674 struct mm_struct *new_start_mm = start_mm;
675 struct mm_struct *prev_mm = start_mm;
676 struct mm_struct *mm;
677
678 atomic_inc(&new_start_mm->mm_users);
679 atomic_inc(&prev_mm->mm_users);
680 spin_lock(&mmlist_lock);
681 while (*swap_map > 1 && !retval &&
682 (p = p->next) != &start_mm->mmlist) {
683 mm = list_entry(p, struct mm_struct, mmlist);
684 if (atomic_inc_return(&mm->mm_users) == 1) {
685 atomic_dec(&mm->mm_users);
686 continue;
687 }
688 spin_unlock(&mmlist_lock);
689 mmput(prev_mm);
690 prev_mm = mm;
691
692 cond_resched();
693
694 swcount = *swap_map;
695 if (swcount <= 1)
696 ;
697 else if (mm == &init_mm) {
698 set_start_mm = 1;
699 shmem = shmem_unuse(entry, page);
700 } else
701 retval = unuse_mm(mm, entry, page);
702 if (set_start_mm && *swap_map < swcount) {
703 mmput(new_start_mm);
704 atomic_inc(&mm->mm_users);
705 new_start_mm = mm;
706 set_start_mm = 0;
707 }
708 spin_lock(&mmlist_lock);
709 }
710 spin_unlock(&mmlist_lock);
711 mmput(prev_mm);
712 mmput(start_mm);
713 start_mm = new_start_mm;
714 }
715 if (retval) {
716 unlock_page(page);
717 page_cache_release(page);
718 break;
719 }
720
721 /*
722 * How could swap count reach 0x7fff when the maximum
723 * pid is 0x7fff, and there's no way to repeat a swap
724 * page within an mm (except in shmem, where it's the
725 * shared object which takes the reference count)?
726 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
727 *
728 * If that's wrong, then we should worry more about
729 * exit_mmap() and do_munmap() cases described above:
730 * we might be resetting SWAP_MAP_MAX too early here.
731 * We know "Undead"s can happen, they're okay, so don't
732 * report them; but do report if we reset SWAP_MAP_MAX.
733 */
734 if (*swap_map == SWAP_MAP_MAX) {
735 swap_device_lock(si);
736 *swap_map = 1;
737 swap_device_unlock(si);
738 reset_overflow = 1;
739 }
740
741 /*
742 * If a reference remains (rare), we would like to leave
743 * the page in the swap cache; but try_to_unmap could
744 * then re-duplicate the entry once we drop page lock,
745 * so we might loop indefinitely; also, that page could
746 * not be swapped out to other storage meanwhile. So:
747 * delete from cache even if there's another reference,
748 * after ensuring that the data has been saved to disk -
749 * since if the reference remains (rarer), it will be
750 * read from disk into another page. Splitting into two
751 * pages would be incorrect if swap supported "shared
752 * private" pages, but they are handled by tmpfs files.
753 *
754 * Note shmem_unuse already deleted a swappage from
755 * the swap cache, unless the move to filepage failed:
756 * in which case it left swappage in cache, lowered its
757 * swap count to pass quickly through the loops above,
758 * and now we must reincrement count to try again later.
759 */
760 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
761 struct writeback_control wbc = {
762 .sync_mode = WB_SYNC_NONE,
763 };
764
765 swap_writepage(page, &wbc);
766 lock_page(page);
767 wait_on_page_writeback(page);
768 }
769 if (PageSwapCache(page)) {
770 if (shmem)
771 swap_duplicate(entry);
772 else
773 delete_from_swap_cache(page);
774 }
775
776 /*
777 * So we could skip searching mms once swap count went
778 * to 1, we did not mark any present ptes as dirty: must
779 * mark page dirty so shrink_list will preserve it.
780 */
781 SetPageDirty(page);
782 unlock_page(page);
783 page_cache_release(page);
784
785 /*
786 * Make sure that we aren't completely killing
787 * interactive performance.
788 */
789 cond_resched();
790 }
791
792 mmput(start_mm);
793 if (reset_overflow) {
794 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
795 swap_overflow = 0;
796 }
797 return retval;
798}
799
800/*
801 * After a successful try_to_unuse, if no swap is now in use, we know we
802 * can empty the mmlist. swap_list_lock must be held on entry and exit.
803 * Note that mmlist_lock nests inside swap_list_lock, and an mm must be
804 * added to the mmlist just after page_duplicate - before would be racy.
805 */
806static void drain_mmlist(void)
807{
808 struct list_head *p, *next;
809 unsigned int i;
810
811 for (i = 0; i < nr_swapfiles; i++)
812 if (swap_info[i].inuse_pages)
813 return;
814 spin_lock(&mmlist_lock);
815 list_for_each_safe(p, next, &init_mm.mmlist)
816 list_del_init(p);
817 spin_unlock(&mmlist_lock);
818}
819
820/*
821 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
822 * corresponds to page offset `offset'.
823 */
824sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
825{
826 struct swap_extent *se = sis->curr_swap_extent;
827 struct swap_extent *start_se = se;
828
829 for ( ; ; ) {
830 struct list_head *lh;
831
832 if (se->start_page <= offset &&
833 offset < (se->start_page + se->nr_pages)) {
834 return se->start_block + (offset - se->start_page);
835 }
Hugh Dickins11d31882005-09-03 15:54:34 -0700836 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700837 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -0700838 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839 se = list_entry(lh, struct swap_extent, list);
840 sis->curr_swap_extent = se;
841 BUG_ON(se == start_se); /* It *must* be present */
842 }
843}
844
845/*
846 * Free all of a swapdev's extent information
847 */
848static void destroy_swap_extents(struct swap_info_struct *sis)
849{
850 while (!list_empty(&sis->extent_list)) {
851 struct swap_extent *se;
852
853 se = list_entry(sis->extent_list.next,
854 struct swap_extent, list);
855 list_del(&se->list);
856 kfree(se);
857 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858}
859
860/*
861 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -0700862 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 *
Hugh Dickins11d31882005-09-03 15:54:34 -0700864 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 */
866static int
867add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
868 unsigned long nr_pages, sector_t start_block)
869{
870 struct swap_extent *se;
871 struct swap_extent *new_se;
872 struct list_head *lh;
873
Hugh Dickins11d31882005-09-03 15:54:34 -0700874 lh = sis->extent_list.prev; /* The highest page extent */
875 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -0700877 BUG_ON(se->start_page + se->nr_pages != start_page);
878 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 /* Merge it */
880 se->nr_pages += nr_pages;
881 return 0;
882 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 }
884
885 /*
886 * No merge. Insert a new extent, preserving ordering.
887 */
888 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
889 if (new_se == NULL)
890 return -ENOMEM;
891 new_se->start_page = start_page;
892 new_se->nr_pages = nr_pages;
893 new_se->start_block = start_block;
894
Hugh Dickins11d31882005-09-03 15:54:34 -0700895 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -0700896 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897}
898
899/*
900 * A `swap extent' is a simple thing which maps a contiguous range of pages
901 * onto a contiguous range of disk blocks. An ordered list of swap extents
902 * is built at swapon time and is then used at swap_writepage/swap_readpage
903 * time for locating where on disk a page belongs.
904 *
905 * If the swapfile is an S_ISBLK block device, a single extent is installed.
906 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
907 * swap files identically.
908 *
909 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
910 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
911 * swapfiles are handled *identically* after swapon time.
912 *
913 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
914 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
915 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
916 * requirements, they are simply tossed out - we will never use those blocks
917 * for swapping.
918 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -0700919 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
921 * which will scribble on the fs.
922 *
923 * The amount of disk space which a single swap extent represents varies.
924 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
925 * extents in the list. To avoid much list walking, we cache the previous
926 * search location in `curr_swap_extent', and start new searches from there.
927 * This is extremely effective. The average number of iterations in
928 * map_swap_page() has been measured at about 0.3 per page. - akpm.
929 */
Hugh Dickins53092a72005-09-03 15:54:34 -0700930static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931{
932 struct inode *inode;
933 unsigned blocks_per_page;
934 unsigned long page_no;
935 unsigned blkbits;
936 sector_t probe_block;
937 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -0700938 sector_t lowest_block = -1;
939 sector_t highest_block = 0;
940 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941 int ret;
942
943 inode = sis->swap_file->f_mapping->host;
944 if (S_ISBLK(inode->i_mode)) {
945 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -0700946 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 goto done;
948 }
949
950 blkbits = inode->i_blkbits;
951 blocks_per_page = PAGE_SIZE >> blkbits;
952
953 /*
954 * Map all the blocks into the extent list. This code doesn't try
955 * to be very smart.
956 */
957 probe_block = 0;
958 page_no = 0;
959 last_block = i_size_read(inode) >> blkbits;
960 while ((probe_block + blocks_per_page) <= last_block &&
961 page_no < sis->max) {
962 unsigned block_in_page;
963 sector_t first_block;
964
965 first_block = bmap(inode, probe_block);
966 if (first_block == 0)
967 goto bad_bmap;
968
969 /*
970 * It must be PAGE_SIZE aligned on-disk
971 */
972 if (first_block & (blocks_per_page - 1)) {
973 probe_block++;
974 goto reprobe;
975 }
976
977 for (block_in_page = 1; block_in_page < blocks_per_page;
978 block_in_page++) {
979 sector_t block;
980
981 block = bmap(inode, probe_block + block_in_page);
982 if (block == 0)
983 goto bad_bmap;
984 if (block != first_block + block_in_page) {
985 /* Discontiguity */
986 probe_block++;
987 goto reprobe;
988 }
989 }
990
Hugh Dickins53092a72005-09-03 15:54:34 -0700991 first_block >>= (PAGE_SHIFT - blkbits);
992 if (page_no) { /* exclude the header page */
993 if (first_block < lowest_block)
994 lowest_block = first_block;
995 if (first_block > highest_block)
996 highest_block = first_block;
997 }
998
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999 /*
1000 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1001 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001002 ret = add_swap_extent(sis, page_no, 1, first_block);
1003 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001005 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 page_no++;
1007 probe_block += blocks_per_page;
1008reprobe:
1009 continue;
1010 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001011 ret = nr_extents;
1012 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001014 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001015 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001016 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017 sis->highest_bit = page_no - 1;
1018done:
1019 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1020 struct swap_extent, list);
1021 goto out;
1022bad_bmap:
1023 printk(KERN_ERR "swapon: swapfile has holes\n");
1024 ret = -EINVAL;
1025out:
1026 return ret;
1027}
1028
1029#if 0 /* We don't need this yet */
1030#include <linux/backing-dev.h>
1031int page_queue_congested(struct page *page)
1032{
1033 struct backing_dev_info *bdi;
1034
1035 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1036
1037 if (PageSwapCache(page)) {
1038 swp_entry_t entry = { .val = page->private };
1039 struct swap_info_struct *sis;
1040
1041 sis = get_swap_info_struct(swp_type(entry));
1042 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1043 } else
1044 bdi = page->mapping->backing_dev_info;
1045 return bdi_write_congested(bdi);
1046}
1047#endif
1048
1049asmlinkage long sys_swapoff(const char __user * specialfile)
1050{
1051 struct swap_info_struct * p = NULL;
1052 unsigned short *swap_map;
1053 struct file *swap_file, *victim;
1054 struct address_space *mapping;
1055 struct inode *inode;
1056 char * pathname;
1057 int i, type, prev;
1058 int err;
1059
1060 if (!capable(CAP_SYS_ADMIN))
1061 return -EPERM;
1062
1063 pathname = getname(specialfile);
1064 err = PTR_ERR(pathname);
1065 if (IS_ERR(pathname))
1066 goto out;
1067
1068 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1069 putname(pathname);
1070 err = PTR_ERR(victim);
1071 if (IS_ERR(victim))
1072 goto out;
1073
1074 mapping = victim->f_mapping;
1075 prev = -1;
1076 swap_list_lock();
1077 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1078 p = swap_info + type;
1079 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1080 if (p->swap_file->f_mapping == mapping)
1081 break;
1082 }
1083 prev = type;
1084 }
1085 if (type < 0) {
1086 err = -EINVAL;
1087 swap_list_unlock();
1088 goto out_dput;
1089 }
1090 if (!security_vm_enough_memory(p->pages))
1091 vm_unacct_memory(p->pages);
1092 else {
1093 err = -ENOMEM;
1094 swap_list_unlock();
1095 goto out_dput;
1096 }
1097 if (prev < 0) {
1098 swap_list.head = p->next;
1099 } else {
1100 swap_info[prev].next = p->next;
1101 }
1102 if (type == swap_list.next) {
1103 /* just pick something that's safe... */
1104 swap_list.next = swap_list.head;
1105 }
1106 nr_swap_pages -= p->pages;
1107 total_swap_pages -= p->pages;
1108 p->flags &= ~SWP_WRITEOK;
1109 swap_list_unlock();
1110 current->flags |= PF_SWAPOFF;
1111 err = try_to_unuse(type);
1112 current->flags &= ~PF_SWAPOFF;
1113
1114 /* wait for any unplug function to finish */
1115 down_write(&swap_unplug_sem);
1116 up_write(&swap_unplug_sem);
1117
1118 if (err) {
1119 /* re-insert swap space back into swap_list */
1120 swap_list_lock();
1121 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1122 if (p->prio >= swap_info[i].prio)
1123 break;
1124 p->next = i;
1125 if (prev < 0)
1126 swap_list.head = swap_list.next = p - swap_info;
1127 else
1128 swap_info[prev].next = p - swap_info;
1129 nr_swap_pages += p->pages;
1130 total_swap_pages += p->pages;
1131 p->flags |= SWP_WRITEOK;
1132 swap_list_unlock();
1133 goto out_dput;
1134 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001135 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136 down(&swapon_sem);
1137 swap_list_lock();
1138 drain_mmlist();
1139 swap_device_lock(p);
1140 swap_file = p->swap_file;
1141 p->swap_file = NULL;
1142 p->max = 0;
1143 swap_map = p->swap_map;
1144 p->swap_map = NULL;
1145 p->flags = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 swap_device_unlock(p);
1147 swap_list_unlock();
1148 up(&swapon_sem);
1149 vfree(swap_map);
1150 inode = mapping->host;
1151 if (S_ISBLK(inode->i_mode)) {
1152 struct block_device *bdev = I_BDEV(inode);
1153 set_blocksize(bdev, p->old_block_size);
1154 bd_release(bdev);
1155 } else {
1156 down(&inode->i_sem);
1157 inode->i_flags &= ~S_SWAPFILE;
1158 up(&inode->i_sem);
1159 }
1160 filp_close(swap_file, NULL);
1161 err = 0;
1162
1163out_dput:
1164 filp_close(victim, NULL);
1165out:
1166 return err;
1167}
1168
1169#ifdef CONFIG_PROC_FS
1170/* iterator */
1171static void *swap_start(struct seq_file *swap, loff_t *pos)
1172{
1173 struct swap_info_struct *ptr = swap_info;
1174 int i;
1175 loff_t l = *pos;
1176
1177 down(&swapon_sem);
1178
1179 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1180 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1181 continue;
1182 if (!l--)
1183 return ptr;
1184 }
1185
1186 return NULL;
1187}
1188
1189static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1190{
1191 struct swap_info_struct *ptr = v;
1192 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1193
1194 for (++ptr; ptr < endptr; ptr++) {
1195 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1196 continue;
1197 ++*pos;
1198 return ptr;
1199 }
1200
1201 return NULL;
1202}
1203
1204static void swap_stop(struct seq_file *swap, void *v)
1205{
1206 up(&swapon_sem);
1207}
1208
1209static int swap_show(struct seq_file *swap, void *v)
1210{
1211 struct swap_info_struct *ptr = v;
1212 struct file *file;
1213 int len;
1214
1215 if (v == swap_info)
1216 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1217
1218 file = ptr->swap_file;
1219 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001220 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221 len < 40 ? 40 - len : 1, " ",
1222 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1223 "partition" : "file\t",
1224 ptr->pages << (PAGE_SHIFT - 10),
1225 ptr->inuse_pages << (PAGE_SHIFT - 10),
1226 ptr->prio);
1227 return 0;
1228}
1229
1230static struct seq_operations swaps_op = {
1231 .start = swap_start,
1232 .next = swap_next,
1233 .stop = swap_stop,
1234 .show = swap_show
1235};
1236
1237static int swaps_open(struct inode *inode, struct file *file)
1238{
1239 return seq_open(file, &swaps_op);
1240}
1241
1242static struct file_operations proc_swaps_operations = {
1243 .open = swaps_open,
1244 .read = seq_read,
1245 .llseek = seq_lseek,
1246 .release = seq_release,
1247};
1248
1249static int __init procswaps_init(void)
1250{
1251 struct proc_dir_entry *entry;
1252
1253 entry = create_proc_entry("swaps", 0, NULL);
1254 if (entry)
1255 entry->proc_fops = &proc_swaps_operations;
1256 return 0;
1257}
1258__initcall(procswaps_init);
1259#endif /* CONFIG_PROC_FS */
1260
1261/*
1262 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1263 *
1264 * The swapon system call
1265 */
1266asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1267{
1268 struct swap_info_struct * p;
1269 char *name = NULL;
1270 struct block_device *bdev = NULL;
1271 struct file *swap_file = NULL;
1272 struct address_space *mapping;
1273 unsigned int type;
1274 int i, prev;
1275 int error;
1276 static int least_priority;
1277 union swap_header *swap_header = NULL;
1278 int swap_header_version;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001279 unsigned int nr_good_pages = 0;
1280 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001281 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282 unsigned long maxpages = 1;
1283 int swapfilesize;
1284 unsigned short *swap_map;
1285 struct page *page = NULL;
1286 struct inode *inode = NULL;
1287 int did_down = 0;
1288
1289 if (!capable(CAP_SYS_ADMIN))
1290 return -EPERM;
1291 swap_list_lock();
1292 p = swap_info;
1293 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1294 if (!(p->flags & SWP_USED))
1295 break;
1296 error = -EPERM;
1297 /*
1298 * Test if adding another swap device is possible. There are
1299 * two limiting factors: 1) the number of bits for the swap
1300 * type swp_entry_t definition and 2) the number of bits for
1301 * the swap type in the swap ptes as defined by the different
1302 * architectures. To honor both limitations a swap entry
1303 * with swap offset 0 and swap type ~0UL is created, encoded
1304 * to a swap pte, decoded to a swp_entry_t again and finally
1305 * the swap type part is extracted. This will mask all bits
1306 * from the initial ~0UL that can't be encoded in either the
1307 * swp_entry_t or the architecture definition of a swap pte.
1308 */
1309 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1310 swap_list_unlock();
1311 goto out;
1312 }
1313 if (type >= nr_swapfiles)
1314 nr_swapfiles = type+1;
1315 INIT_LIST_HEAD(&p->extent_list);
1316 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317 p->swap_file = NULL;
1318 p->old_block_size = 0;
1319 p->swap_map = NULL;
1320 p->lowest_bit = 0;
1321 p->highest_bit = 0;
1322 p->cluster_nr = 0;
1323 p->inuse_pages = 0;
1324 spin_lock_init(&p->sdev_lock);
1325 p->next = -1;
1326 if (swap_flags & SWAP_FLAG_PREFER) {
1327 p->prio =
1328 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1329 } else {
1330 p->prio = --least_priority;
1331 }
1332 swap_list_unlock();
1333 name = getname(specialfile);
1334 error = PTR_ERR(name);
1335 if (IS_ERR(name)) {
1336 name = NULL;
1337 goto bad_swap_2;
1338 }
1339 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1340 error = PTR_ERR(swap_file);
1341 if (IS_ERR(swap_file)) {
1342 swap_file = NULL;
1343 goto bad_swap_2;
1344 }
1345
1346 p->swap_file = swap_file;
1347 mapping = swap_file->f_mapping;
1348 inode = mapping->host;
1349
1350 error = -EBUSY;
1351 for (i = 0; i < nr_swapfiles; i++) {
1352 struct swap_info_struct *q = &swap_info[i];
1353
1354 if (i == type || !q->swap_file)
1355 continue;
1356 if (mapping == q->swap_file->f_mapping)
1357 goto bad_swap;
1358 }
1359
1360 error = -EINVAL;
1361 if (S_ISBLK(inode->i_mode)) {
1362 bdev = I_BDEV(inode);
1363 error = bd_claim(bdev, sys_swapon);
1364 if (error < 0) {
1365 bdev = NULL;
1366 goto bad_swap;
1367 }
1368 p->old_block_size = block_size(bdev);
1369 error = set_blocksize(bdev, PAGE_SIZE);
1370 if (error < 0)
1371 goto bad_swap;
1372 p->bdev = bdev;
1373 } else if (S_ISREG(inode->i_mode)) {
1374 p->bdev = inode->i_sb->s_bdev;
1375 down(&inode->i_sem);
1376 did_down = 1;
1377 if (IS_SWAPFILE(inode)) {
1378 error = -EBUSY;
1379 goto bad_swap;
1380 }
1381 } else {
1382 goto bad_swap;
1383 }
1384
1385 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1386
1387 /*
1388 * Read the swap header.
1389 */
1390 if (!mapping->a_ops->readpage) {
1391 error = -EINVAL;
1392 goto bad_swap;
1393 }
1394 page = read_cache_page(mapping, 0,
1395 (filler_t *)mapping->a_ops->readpage, swap_file);
1396 if (IS_ERR(page)) {
1397 error = PTR_ERR(page);
1398 goto bad_swap;
1399 }
1400 wait_on_page_locked(page);
1401 if (!PageUptodate(page))
1402 goto bad_swap;
1403 kmap(page);
1404 swap_header = page_address(page);
1405
1406 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1407 swap_header_version = 1;
1408 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1409 swap_header_version = 2;
1410 else {
1411 printk("Unable to find swap-space signature\n");
1412 error = -EINVAL;
1413 goto bad_swap;
1414 }
1415
1416 switch (swap_header_version) {
1417 case 1:
1418 printk(KERN_ERR "version 0 swap is no longer supported. "
1419 "Use mkswap -v1 %s\n", name);
1420 error = -EINVAL;
1421 goto bad_swap;
1422 case 2:
1423 /* Check the swap header's sub-version and the size of
1424 the swap file and bad block lists */
1425 if (swap_header->info.version != 1) {
1426 printk(KERN_WARNING
1427 "Unable to handle swap header version %d\n",
1428 swap_header->info.version);
1429 error = -EINVAL;
1430 goto bad_swap;
1431 }
1432
1433 p->lowest_bit = 1;
1434 /*
1435 * Find out how many pages are allowed for a single swap
1436 * device. There are two limiting factors: 1) the number of
1437 * bits for the swap offset in the swp_entry_t type and
1438 * 2) the number of bits in the a swap pte as defined by
1439 * the different architectures. In order to find the
1440 * largest possible bit mask a swap entry with swap type 0
1441 * and swap offset ~0UL is created, encoded to a swap pte,
1442 * decoded to a swp_entry_t again and finally the swap
1443 * offset is extracted. This will mask all the bits from
1444 * the initial ~0UL mask that can't be encoded in either
1445 * the swp_entry_t or the architecture definition of a
1446 * swap pte.
1447 */
1448 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1449 if (maxpages > swap_header->info.last_page)
1450 maxpages = swap_header->info.last_page;
1451 p->highest_bit = maxpages - 1;
1452
1453 error = -EINVAL;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001454 if (!maxpages)
1455 goto bad_swap;
1456 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1457 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001458 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1459 goto bad_swap;
1460
1461 /* OK, set up the swap map and apply the bad block list */
1462 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1463 error = -ENOMEM;
1464 goto bad_swap;
1465 }
1466
1467 error = 0;
1468 memset(p->swap_map, 0, maxpages * sizeof(short));
1469 for (i=0; i<swap_header->info.nr_badpages; i++) {
1470 int page = swap_header->info.badpages[i];
1471 if (page <= 0 || page >= swap_header->info.last_page)
1472 error = -EINVAL;
1473 else
1474 p->swap_map[page] = SWAP_MAP_BAD;
1475 }
1476 nr_good_pages = swap_header->info.last_page -
1477 swap_header->info.nr_badpages -
1478 1 /* header page */;
1479 if (error)
1480 goto bad_swap;
1481 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001482
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483 if (swapfilesize && maxpages > swapfilesize) {
1484 printk(KERN_WARNING
1485 "Swap area shorter than signature indicates\n");
1486 error = -EINVAL;
1487 goto bad_swap;
1488 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001489 if (nr_good_pages) {
1490 p->swap_map[0] = SWAP_MAP_BAD;
1491 p->max = maxpages;
1492 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001493 nr_extents = setup_swap_extents(p, &span);
1494 if (nr_extents < 0) {
1495 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001496 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001497 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001498 nr_good_pages = p->pages;
1499 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 if (!nr_good_pages) {
1501 printk(KERN_WARNING "Empty swap-file\n");
1502 error = -EINVAL;
1503 goto bad_swap;
1504 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505
1506 down(&swapon_sem);
1507 swap_list_lock();
1508 swap_device_lock(p);
1509 p->flags = SWP_ACTIVE;
1510 nr_swap_pages += nr_good_pages;
1511 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001512
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001513 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins53092a72005-09-03 15:54:34 -07001514 "Priority:%d extents:%d across:%lluk\n",
1515 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1516 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517
1518 /* insert swap space into swap_list: */
1519 prev = -1;
1520 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1521 if (p->prio >= swap_info[i].prio) {
1522 break;
1523 }
1524 prev = i;
1525 }
1526 p->next = i;
1527 if (prev < 0) {
1528 swap_list.head = swap_list.next = p - swap_info;
1529 } else {
1530 swap_info[prev].next = p - swap_info;
1531 }
1532 swap_device_unlock(p);
1533 swap_list_unlock();
1534 up(&swapon_sem);
1535 error = 0;
1536 goto out;
1537bad_swap:
1538 if (bdev) {
1539 set_blocksize(bdev, p->old_block_size);
1540 bd_release(bdev);
1541 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001542 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543bad_swap_2:
1544 swap_list_lock();
1545 swap_map = p->swap_map;
1546 p->swap_file = NULL;
1547 p->swap_map = NULL;
1548 p->flags = 0;
1549 if (!(swap_flags & SWAP_FLAG_PREFER))
1550 ++least_priority;
1551 swap_list_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 vfree(swap_map);
1553 if (swap_file)
1554 filp_close(swap_file, NULL);
1555out:
1556 if (page && !IS_ERR(page)) {
1557 kunmap(page);
1558 page_cache_release(page);
1559 }
1560 if (name)
1561 putname(name);
1562 if (did_down) {
1563 if (!error)
1564 inode->i_flags |= S_SWAPFILE;
1565 up(&inode->i_sem);
1566 }
1567 return error;
1568}
1569
1570void si_swapinfo(struct sysinfo *val)
1571{
1572 unsigned int i;
1573 unsigned long nr_to_be_unused = 0;
1574
1575 swap_list_lock();
1576 for (i = 0; i < nr_swapfiles; i++) {
1577 if (!(swap_info[i].flags & SWP_USED) ||
1578 (swap_info[i].flags & SWP_WRITEOK))
1579 continue;
1580 nr_to_be_unused += swap_info[i].inuse_pages;
1581 }
1582 val->freeswap = nr_swap_pages + nr_to_be_unused;
1583 val->totalswap = total_swap_pages + nr_to_be_unused;
1584 swap_list_unlock();
1585}
1586
1587/*
1588 * Verify that a swap entry is valid and increment its swap map count.
1589 *
1590 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1591 * "permanent", but will be reclaimed by the next swapoff.
1592 */
1593int swap_duplicate(swp_entry_t entry)
1594{
1595 struct swap_info_struct * p;
1596 unsigned long offset, type;
1597 int result = 0;
1598
1599 type = swp_type(entry);
1600 if (type >= nr_swapfiles)
1601 goto bad_file;
1602 p = type + swap_info;
1603 offset = swp_offset(entry);
1604
1605 swap_device_lock(p);
1606 if (offset < p->max && p->swap_map[offset]) {
1607 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1608 p->swap_map[offset]++;
1609 result = 1;
1610 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1611 if (swap_overflow++ < 5)
1612 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1613 p->swap_map[offset] = SWAP_MAP_MAX;
1614 result = 1;
1615 }
1616 }
1617 swap_device_unlock(p);
1618out:
1619 return result;
1620
1621bad_file:
1622 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1623 goto out;
1624}
1625
1626struct swap_info_struct *
1627get_swap_info_struct(unsigned type)
1628{
1629 return &swap_info[type];
1630}
1631
1632/*
1633 * swap_device_lock prevents swap_map being freed. Don't grab an extra
1634 * reference on the swaphandle, it doesn't matter if it becomes unused.
1635 */
1636int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1637{
1638 int ret = 0, i = 1 << page_cluster;
1639 unsigned long toff;
1640 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1641
1642 if (!page_cluster) /* no readahead */
1643 return 0;
1644 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1645 if (!toff) /* first page is swap header */
1646 toff++, i--;
1647 *offset = toff;
1648
1649 swap_device_lock(swapdev);
1650 do {
1651 /* Don't read-ahead past the end of the swap area */
1652 if (toff >= swapdev->max)
1653 break;
1654 /* Don't read in free or bad pages */
1655 if (!swapdev->swap_map[toff])
1656 break;
1657 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1658 break;
1659 toff++;
1660 ret++;
1661 } while (--i);
1662 swap_device_unlock(swapdev);
1663 return ret;
1664}