ia64/linux-2.6.18-xen.hg

view mm/swapfile.c @ 749:2892ca2b9c17

linux/x86: cleanup IO-APIC code

- get 32-bit code in sync with 64-bit wrt ExtINT pin detection being
unnecessary
- eliminate build warnings resulting from c/s 725

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Fri Nov 28 13:31:21 2008 +0000 (2008-11-28)
parents 831230e53067
children cad6f60f0506
line source
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 */
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>
31 #include <asm/pgtable.h>
32 #include <asm/tlbflush.h>
33 #include <linux/swapops.h>
35 DEFINE_SPINLOCK(swap_lock);
36 unsigned int nr_swapfiles;
37 long total_swap_pages;
38 static int swap_overflow;
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 ";
45 struct swap_list_t swap_list = {-1, -1};
47 static struct swap_info_struct swap_info[MAX_SWAPFILES];
49 static DEFINE_MUTEX(swapon_mutex);
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);
58 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
59 {
60 swp_entry_t entry;
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;
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);
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 }
84 #define SWAPFILE_CLUSTER 256
85 #define LATENCY_LIMIT 256
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;
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 */
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);
109 offset = si->lowest_bit;
110 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
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 }
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 }
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;
169 no_page:
170 si->flags -= SWP_SCANNING;
171 return 0;
172 }
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;
181 spin_lock(&swap_lock);
182 if (nr_swap_pages <= 0)
183 goto noswap;
184 nr_swap_pages--;
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 }
195 if (!si->highest_bit)
196 continue;
197 if (!(si->flags & SWP_WRITEOK))
198 continue;
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 }
209 nr_swap_pages++;
210 noswap:
211 spin_unlock(&swap_lock);
212 return (swp_entry_t) {0};
213 }
215 swp_entry_t get_swap_page_of_type(int type)
216 {
217 struct swap_info_struct *si;
218 pgoff_t offset;
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 }
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;
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;
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 }
271 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
272 {
273 int count = p->swap_map[offset];
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 }
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;
300 p = swap_info_get(entry);
301 if (p) {
302 swap_entry_free(p, swp_offset(entry));
303 spin_unlock(&swap_lock);
304 }
305 }
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;
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 }
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;
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 }
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;
351 BUG_ON(PagePrivate(page));
352 BUG_ON(!PageLocked(page));
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;
361 entry.val = page_private(page);
362 p = swap_info_get(entry);
363 if (!p)
364 return 0;
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);
380 if (retval) {
381 swap_free(entry);
382 page_cache_release(page);
383 }
385 return retval;
386 }
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;
397 if (is_migration_entry(entry))
398 return;
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;
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 }
428 #ifdef CONFIG_SOFTWARE_SUSPEND
429 /*
430 * Find the swap type that corresponds to given device (if any)
431 *
432 * This is needed for software suspend and is done in such a way that inode
433 * aliasing is allowed.
434 */
435 int swap_type_of(dev_t device)
436 {
437 int i;
439 spin_lock(&swap_lock);
440 for (i = 0; i < nr_swapfiles; i++) {
441 struct inode *inode;
443 if (!(swap_info[i].flags & SWP_WRITEOK))
444 continue;
446 if (!device) {
447 spin_unlock(&swap_lock);
448 return i;
449 }
450 inode = swap_info[i].swap_file->f_dentry->d_inode;
451 if (S_ISBLK(inode->i_mode) &&
452 device == MKDEV(imajor(inode), iminor(inode))) {
453 spin_unlock(&swap_lock);
454 return i;
455 }
456 }
457 spin_unlock(&swap_lock);
458 return -ENODEV;
459 }
461 /*
462 * Return either the total number of swap pages of given type, or the number
463 * of free pages of that type (depending on @free)
464 *
465 * This is needed for software suspend
466 */
467 unsigned int count_swap_pages(int type, int free)
468 {
469 unsigned int n = 0;
471 if (type < nr_swapfiles) {
472 spin_lock(&swap_lock);
473 if (swap_info[type].flags & SWP_WRITEOK) {
474 n = swap_info[type].pages;
475 if (free)
476 n -= swap_info[type].inuse_pages;
477 }
478 spin_unlock(&swap_lock);
479 }
480 return n;
481 }
482 #endif
484 /*
485 * No need to decide whether this PTE shares the swap entry with others,
486 * just let do_wp_page work it out if a write is requested later - to
487 * force COW, vm_page_prot omits write permission from any private vma.
488 */
489 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
490 unsigned long addr, swp_entry_t entry, struct page *page)
491 {
492 inc_mm_counter(vma->vm_mm, anon_rss);
493 get_page(page);
494 set_pte_at(vma->vm_mm, addr, pte,
495 pte_mkold(mk_pte(page, vma->vm_page_prot)));
496 page_add_anon_rmap(page, vma, addr);
497 swap_free(entry);
498 /*
499 * Move the page to the active list so it is not
500 * immediately swapped out again after swapon.
501 */
502 activate_page(page);
503 }
505 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
506 unsigned long addr, unsigned long end,
507 swp_entry_t entry, struct page *page)
508 {
509 pte_t swp_pte = swp_entry_to_pte(entry);
510 pte_t *pte;
511 spinlock_t *ptl;
512 int found = 0;
514 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
515 do {
516 /*
517 * swapoff spends a _lot_ of time in this loop!
518 * Test inline before going to call unuse_pte.
519 */
520 if (unlikely(pte_same(*pte, swp_pte))) {
521 unuse_pte(vma, pte++, addr, entry, page);
522 found = 1;
523 break;
524 }
525 } while (pte++, addr += PAGE_SIZE, addr != end);
526 pte_unmap_unlock(pte - 1, ptl);
527 return found;
528 }
530 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
531 unsigned long addr, unsigned long end,
532 swp_entry_t entry, struct page *page)
533 {
534 pmd_t *pmd;
535 unsigned long next;
537 pmd = pmd_offset(pud, addr);
538 do {
539 next = pmd_addr_end(addr, end);
540 if (pmd_none_or_clear_bad(pmd))
541 continue;
542 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
543 return 1;
544 } while (pmd++, addr = next, addr != end);
545 return 0;
546 }
548 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
549 unsigned long addr, unsigned long end,
550 swp_entry_t entry, struct page *page)
551 {
552 pud_t *pud;
553 unsigned long next;
555 pud = pud_offset(pgd, addr);
556 do {
557 next = pud_addr_end(addr, end);
558 if (pud_none_or_clear_bad(pud))
559 continue;
560 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
561 return 1;
562 } while (pud++, addr = next, addr != end);
563 return 0;
564 }
566 static int unuse_vma(struct vm_area_struct *vma,
567 swp_entry_t entry, struct page *page)
568 {
569 pgd_t *pgd;
570 unsigned long addr, end, next;
572 if (page->mapping) {
573 addr = page_address_in_vma(page, vma);
574 if (addr == -EFAULT)
575 return 0;
576 else
577 end = addr + PAGE_SIZE;
578 } else {
579 addr = vma->vm_start;
580 end = vma->vm_end;
581 }
583 pgd = pgd_offset(vma->vm_mm, addr);
584 do {
585 next = pgd_addr_end(addr, end);
586 if (pgd_none_or_clear_bad(pgd))
587 continue;
588 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
589 return 1;
590 } while (pgd++, addr = next, addr != end);
591 return 0;
592 }
594 static int unuse_mm(struct mm_struct *mm,
595 swp_entry_t entry, struct page *page)
596 {
597 struct vm_area_struct *vma;
599 if (!down_read_trylock(&mm->mmap_sem)) {
600 /*
601 * Activate page so shrink_cache is unlikely to unmap its
602 * ptes while lock is dropped, so swapoff can make progress.
603 */
604 activate_page(page);
605 unlock_page(page);
606 down_read(&mm->mmap_sem);
607 lock_page(page);
608 }
609 for (vma = mm->mmap; vma; vma = vma->vm_next) {
610 if (vma->anon_vma && unuse_vma(vma, entry, page))
611 break;
612 }
613 up_read(&mm->mmap_sem);
614 /*
615 * Currently unuse_mm cannot fail, but leave error handling
616 * at call sites for now, since we change it from time to time.
617 */
618 return 0;
619 }
621 /*
622 * Scan swap_map from current position to next entry still in use.
623 * Recycle to start on reaching the end, returning 0 when empty.
624 */
625 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
626 unsigned int prev)
627 {
628 unsigned int max = si->max;
629 unsigned int i = prev;
630 int count;
632 /*
633 * No need for swap_lock here: we're just looking
634 * for whether an entry is in use, not modifying it; false
635 * hits are okay, and sys_swapoff() has already prevented new
636 * allocations from this area (while holding swap_lock).
637 */
638 for (;;) {
639 if (++i >= max) {
640 if (!prev) {
641 i = 0;
642 break;
643 }
644 /*
645 * No entries in use at top of swap_map,
646 * loop back to start and recheck there.
647 */
648 max = prev + 1;
649 prev = 0;
650 i = 1;
651 }
652 count = si->swap_map[i];
653 if (count && count != SWAP_MAP_BAD)
654 break;
655 }
656 return i;
657 }
659 /*
660 * We completely avoid races by reading each swap page in advance,
661 * and then search for the process using it. All the necessary
662 * page table adjustments can then be made atomically.
663 */
664 static int try_to_unuse(unsigned int type)
665 {
666 struct swap_info_struct * si = &swap_info[type];
667 struct mm_struct *start_mm;
668 unsigned short *swap_map;
669 unsigned short swcount;
670 struct page *page;
671 swp_entry_t entry;
672 unsigned int i = 0;
673 int retval = 0;
674 int reset_overflow = 0;
675 int shmem;
677 /*
678 * When searching mms for an entry, a good strategy is to
679 * start at the first mm we freed the previous entry from
680 * (though actually we don't notice whether we or coincidence
681 * freed the entry). Initialize this start_mm with a hold.
682 *
683 * A simpler strategy would be to start at the last mm we
684 * freed the previous entry from; but that would take less
685 * advantage of mmlist ordering, which clusters forked mms
686 * together, child after parent. If we race with dup_mmap(), we
687 * prefer to resolve parent before child, lest we miss entries
688 * duplicated after we scanned child: using last mm would invert
689 * that. Though it's only a serious concern when an overflowed
690 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
691 */
692 start_mm = &init_mm;
693 atomic_inc(&init_mm.mm_users);
695 /*
696 * Keep on scanning until all entries have gone. Usually,
697 * one pass through swap_map is enough, but not necessarily:
698 * there are races when an instance of an entry might be missed.
699 */
700 while ((i = find_next_to_unuse(si, i)) != 0) {
701 if (signal_pending(current)) {
702 retval = -EINTR;
703 break;
704 }
706 /*
707 * Get a page for the entry, using the existing swap
708 * cache page if there is one. Otherwise, get a clean
709 * page and read the swap into it.
710 */
711 swap_map = &si->swap_map[i];
712 entry = swp_entry(type, i);
713 page = read_swap_cache_async(entry, NULL, 0);
714 if (!page) {
715 /*
716 * Either swap_duplicate() failed because entry
717 * has been freed independently, and will not be
718 * reused since sys_swapoff() already disabled
719 * allocation from here, or alloc_page() failed.
720 */
721 if (!*swap_map)
722 continue;
723 retval = -ENOMEM;
724 break;
725 }
727 /*
728 * Don't hold on to start_mm if it looks like exiting.
729 */
730 if (atomic_read(&start_mm->mm_users) == 1) {
731 mmput(start_mm);
732 start_mm = &init_mm;
733 atomic_inc(&init_mm.mm_users);
734 }
736 /*
737 * Wait for and lock page. When do_swap_page races with
738 * try_to_unuse, do_swap_page can handle the fault much
739 * faster than try_to_unuse can locate the entry. This
740 * apparently redundant "wait_on_page_locked" lets try_to_unuse
741 * defer to do_swap_page in such a case - in some tests,
742 * do_swap_page and try_to_unuse repeatedly compete.
743 */
744 wait_on_page_locked(page);
745 wait_on_page_writeback(page);
746 lock_page(page);
747 wait_on_page_writeback(page);
749 /*
750 * Remove all references to entry.
751 * Whenever we reach init_mm, there's no address space
752 * to search, but use it as a reminder to search shmem.
753 */
754 shmem = 0;
755 swcount = *swap_map;
756 if (swcount > 1) {
757 if (start_mm == &init_mm)
758 shmem = shmem_unuse(entry, page);
759 else
760 retval = unuse_mm(start_mm, entry, page);
761 }
762 if (*swap_map > 1) {
763 int set_start_mm = (*swap_map >= swcount);
764 struct list_head *p = &start_mm->mmlist;
765 struct mm_struct *new_start_mm = start_mm;
766 struct mm_struct *prev_mm = start_mm;
767 struct mm_struct *mm;
769 atomic_inc(&new_start_mm->mm_users);
770 atomic_inc(&prev_mm->mm_users);
771 spin_lock(&mmlist_lock);
772 while (*swap_map > 1 && !retval &&
773 (p = p->next) != &start_mm->mmlist) {
774 mm = list_entry(p, struct mm_struct, mmlist);
775 if (!atomic_inc_not_zero(&mm->mm_users))
776 continue;
777 spin_unlock(&mmlist_lock);
778 mmput(prev_mm);
779 prev_mm = mm;
781 cond_resched();
783 swcount = *swap_map;
784 if (swcount <= 1)
785 ;
786 else if (mm == &init_mm) {
787 set_start_mm = 1;
788 shmem = shmem_unuse(entry, page);
789 } else
790 retval = unuse_mm(mm, entry, page);
791 if (set_start_mm && *swap_map < swcount) {
792 mmput(new_start_mm);
793 atomic_inc(&mm->mm_users);
794 new_start_mm = mm;
795 set_start_mm = 0;
796 }
797 spin_lock(&mmlist_lock);
798 }
799 spin_unlock(&mmlist_lock);
800 mmput(prev_mm);
801 mmput(start_mm);
802 start_mm = new_start_mm;
803 }
804 if (retval) {
805 unlock_page(page);
806 page_cache_release(page);
807 break;
808 }
810 /*
811 * How could swap count reach 0x7fff when the maximum
812 * pid is 0x7fff, and there's no way to repeat a swap
813 * page within an mm (except in shmem, where it's the
814 * shared object which takes the reference count)?
815 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
816 *
817 * If that's wrong, then we should worry more about
818 * exit_mmap() and do_munmap() cases described above:
819 * we might be resetting SWAP_MAP_MAX too early here.
820 * We know "Undead"s can happen, they're okay, so don't
821 * report them; but do report if we reset SWAP_MAP_MAX.
822 */
823 if (*swap_map == SWAP_MAP_MAX) {
824 spin_lock(&swap_lock);
825 *swap_map = 1;
826 spin_unlock(&swap_lock);
827 reset_overflow = 1;
828 }
830 /*
831 * If a reference remains (rare), we would like to leave
832 * the page in the swap cache; but try_to_unmap could
833 * then re-duplicate the entry once we drop page lock,
834 * so we might loop indefinitely; also, that page could
835 * not be swapped out to other storage meanwhile. So:
836 * delete from cache even if there's another reference,
837 * after ensuring that the data has been saved to disk -
838 * since if the reference remains (rarer), it will be
839 * read from disk into another page. Splitting into two
840 * pages would be incorrect if swap supported "shared
841 * private" pages, but they are handled by tmpfs files.
842 *
843 * Note shmem_unuse already deleted a swappage from
844 * the swap cache, unless the move to filepage failed:
845 * in which case it left swappage in cache, lowered its
846 * swap count to pass quickly through the loops above,
847 * and now we must reincrement count to try again later.
848 */
849 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
850 struct writeback_control wbc = {
851 .sync_mode = WB_SYNC_NONE,
852 };
854 swap_writepage(page, &wbc);
855 lock_page(page);
856 wait_on_page_writeback(page);
857 }
858 if (PageSwapCache(page)) {
859 if (shmem)
860 swap_duplicate(entry);
861 else
862 delete_from_swap_cache(page);
863 }
865 /*
866 * So we could skip searching mms once swap count went
867 * to 1, we did not mark any present ptes as dirty: must
868 * mark page dirty so shrink_list will preserve it.
869 */
870 SetPageDirty(page);
871 unlock_page(page);
872 page_cache_release(page);
874 /*
875 * Make sure that we aren't completely killing
876 * interactive performance.
877 */
878 cond_resched();
879 }
881 mmput(start_mm);
882 if (reset_overflow) {
883 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
884 swap_overflow = 0;
885 }
886 return retval;
887 }
889 /*
890 * After a successful try_to_unuse, if no swap is now in use, we know
891 * we can empty the mmlist. swap_lock must be held on entry and exit.
892 * Note that mmlist_lock nests inside swap_lock, and an mm must be
893 * added to the mmlist just after page_duplicate - before would be racy.
894 */
895 static void drain_mmlist(void)
896 {
897 struct list_head *p, *next;
898 unsigned int i;
900 for (i = 0; i < nr_swapfiles; i++)
901 if (swap_info[i].inuse_pages)
902 return;
903 spin_lock(&mmlist_lock);
904 list_for_each_safe(p, next, &init_mm.mmlist)
905 list_del_init(p);
906 spin_unlock(&mmlist_lock);
907 }
909 /*
910 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
911 * corresponds to page offset `offset'.
912 */
913 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
914 {
915 struct swap_extent *se = sis->curr_swap_extent;
916 struct swap_extent *start_se = se;
918 for ( ; ; ) {
919 struct list_head *lh;
921 if (se->start_page <= offset &&
922 offset < (se->start_page + se->nr_pages)) {
923 return se->start_block + (offset - se->start_page);
924 }
925 lh = se->list.next;
926 if (lh == &sis->extent_list)
927 lh = lh->next;
928 se = list_entry(lh, struct swap_extent, list);
929 sis->curr_swap_extent = se;
930 BUG_ON(se == start_se); /* It *must* be present */
931 }
932 }
934 /*
935 * Free all of a swapdev's extent information
936 */
937 static void destroy_swap_extents(struct swap_info_struct *sis)
938 {
939 while (!list_empty(&sis->extent_list)) {
940 struct swap_extent *se;
942 se = list_entry(sis->extent_list.next,
943 struct swap_extent, list);
944 list_del(&se->list);
945 kfree(se);
946 }
947 }
949 /*
950 * Add a block range (and the corresponding page range) into this swapdev's
951 * extent list. The extent list is kept sorted in page order.
952 *
953 * This function rather assumes that it is called in ascending page order.
954 */
955 static int
956 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
957 unsigned long nr_pages, sector_t start_block)
958 {
959 struct swap_extent *se;
960 struct swap_extent *new_se;
961 struct list_head *lh;
963 lh = sis->extent_list.prev; /* The highest page extent */
964 if (lh != &sis->extent_list) {
965 se = list_entry(lh, struct swap_extent, list);
966 BUG_ON(se->start_page + se->nr_pages != start_page);
967 if (se->start_block + se->nr_pages == start_block) {
968 /* Merge it */
969 se->nr_pages += nr_pages;
970 return 0;
971 }
972 }
974 /*
975 * No merge. Insert a new extent, preserving ordering.
976 */
977 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
978 if (new_se == NULL)
979 return -ENOMEM;
980 new_se->start_page = start_page;
981 new_se->nr_pages = nr_pages;
982 new_se->start_block = start_block;
984 list_add_tail(&new_se->list, &sis->extent_list);
985 return 1;
986 }
988 /*
989 * A `swap extent' is a simple thing which maps a contiguous range of pages
990 * onto a contiguous range of disk blocks. An ordered list of swap extents
991 * is built at swapon time and is then used at swap_writepage/swap_readpage
992 * time for locating where on disk a page belongs.
993 *
994 * If the swapfile is an S_ISBLK block device, a single extent is installed.
995 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
996 * swap files identically.
997 *
998 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
999 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1000 * swapfiles are handled *identically* after swapon time.
1002 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1003 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1004 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1005 * requirements, they are simply tossed out - we will never use those blocks
1006 * for swapping.
1008 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1009 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1010 * which will scribble on the fs.
1012 * The amount of disk space which a single swap extent represents varies.
1013 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1014 * extents in the list. To avoid much list walking, we cache the previous
1015 * search location in `curr_swap_extent', and start new searches from there.
1016 * This is extremely effective. The average number of iterations in
1017 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1018 */
1019 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1021 struct inode *inode;
1022 unsigned blocks_per_page;
1023 unsigned long page_no;
1024 unsigned blkbits;
1025 sector_t probe_block;
1026 sector_t last_block;
1027 sector_t lowest_block = -1;
1028 sector_t highest_block = 0;
1029 int nr_extents = 0;
1030 int ret;
1032 inode = sis->swap_file->f_mapping->host;
1033 if (S_ISBLK(inode->i_mode)) {
1034 ret = add_swap_extent(sis, 0, sis->max, 0);
1035 *span = sis->pages;
1036 goto done;
1039 blkbits = inode->i_blkbits;
1040 blocks_per_page = PAGE_SIZE >> blkbits;
1042 /*
1043 * Map all the blocks into the extent list. This code doesn't try
1044 * to be very smart.
1045 */
1046 probe_block = 0;
1047 page_no = 0;
1048 last_block = i_size_read(inode) >> blkbits;
1049 while ((probe_block + blocks_per_page) <= last_block &&
1050 page_no < sis->max) {
1051 unsigned block_in_page;
1052 sector_t first_block;
1054 first_block = bmap(inode, probe_block);
1055 if (first_block == 0)
1056 goto bad_bmap;
1058 /*
1059 * It must be PAGE_SIZE aligned on-disk
1060 */
1061 if (first_block & (blocks_per_page - 1)) {
1062 probe_block++;
1063 goto reprobe;
1066 for (block_in_page = 1; block_in_page < blocks_per_page;
1067 block_in_page++) {
1068 sector_t block;
1070 block = bmap(inode, probe_block + block_in_page);
1071 if (block == 0)
1072 goto bad_bmap;
1073 if (block != first_block + block_in_page) {
1074 /* Discontiguity */
1075 probe_block++;
1076 goto reprobe;
1080 first_block >>= (PAGE_SHIFT - blkbits);
1081 if (page_no) { /* exclude the header page */
1082 if (first_block < lowest_block)
1083 lowest_block = first_block;
1084 if (first_block > highest_block)
1085 highest_block = first_block;
1088 /*
1089 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1090 */
1091 ret = add_swap_extent(sis, page_no, 1, first_block);
1092 if (ret < 0)
1093 goto out;
1094 nr_extents += ret;
1095 page_no++;
1096 probe_block += blocks_per_page;
1097 reprobe:
1098 continue;
1100 ret = nr_extents;
1101 *span = 1 + highest_block - lowest_block;
1102 if (page_no == 0)
1103 page_no = 1; /* force Empty message */
1104 sis->max = page_no;
1105 sis->pages = page_no - 1;
1106 sis->highest_bit = page_no - 1;
1107 done:
1108 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1109 struct swap_extent, list);
1110 goto out;
1111 bad_bmap:
1112 printk(KERN_ERR "swapon: swapfile has holes\n");
1113 ret = -EINVAL;
1114 out:
1115 return ret;
1118 #if 0 /* We don't need this yet */
1119 #include <linux/backing-dev.h>
1120 int page_queue_congested(struct page *page)
1122 struct backing_dev_info *bdi;
1124 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1126 if (PageSwapCache(page)) {
1127 swp_entry_t entry = { .val = page_private(page) };
1128 struct swap_info_struct *sis;
1130 sis = get_swap_info_struct(swp_type(entry));
1131 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1132 } else
1133 bdi = page->mapping->backing_dev_info;
1134 return bdi_write_congested(bdi);
1136 #endif
1138 asmlinkage long sys_swapoff(const char __user * specialfile)
1140 struct swap_info_struct * p = NULL;
1141 unsigned short *swap_map;
1142 struct file *swap_file, *victim;
1143 struct address_space *mapping;
1144 struct inode *inode;
1145 char * pathname;
1146 int i, type, prev;
1147 int err;
1149 if (!capable(CAP_SYS_ADMIN))
1150 return -EPERM;
1152 pathname = getname(specialfile);
1153 err = PTR_ERR(pathname);
1154 if (IS_ERR(pathname))
1155 goto out;
1157 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1158 putname(pathname);
1159 err = PTR_ERR(victim);
1160 if (IS_ERR(victim))
1161 goto out;
1163 mapping = victim->f_mapping;
1164 prev = -1;
1165 spin_lock(&swap_lock);
1166 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1167 p = swap_info + type;
1168 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1169 if (p->swap_file->f_mapping == mapping)
1170 break;
1172 prev = type;
1174 if (type < 0) {
1175 err = -EINVAL;
1176 spin_unlock(&swap_lock);
1177 goto out_dput;
1179 if (!security_vm_enough_memory(p->pages))
1180 vm_unacct_memory(p->pages);
1181 else {
1182 err = -ENOMEM;
1183 spin_unlock(&swap_lock);
1184 goto out_dput;
1186 if (prev < 0) {
1187 swap_list.head = p->next;
1188 } else {
1189 swap_info[prev].next = p->next;
1191 if (type == swap_list.next) {
1192 /* just pick something that's safe... */
1193 swap_list.next = swap_list.head;
1195 nr_swap_pages -= p->pages;
1196 total_swap_pages -= p->pages;
1197 p->flags &= ~SWP_WRITEOK;
1198 spin_unlock(&swap_lock);
1200 current->flags |= PF_SWAPOFF;
1201 err = try_to_unuse(type);
1202 current->flags &= ~PF_SWAPOFF;
1204 if (err) {
1205 /* re-insert swap space back into swap_list */
1206 spin_lock(&swap_lock);
1207 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1208 if (p->prio >= swap_info[i].prio)
1209 break;
1210 p->next = i;
1211 if (prev < 0)
1212 swap_list.head = swap_list.next = p - swap_info;
1213 else
1214 swap_info[prev].next = p - swap_info;
1215 nr_swap_pages += p->pages;
1216 total_swap_pages += p->pages;
1217 p->flags |= SWP_WRITEOK;
1218 spin_unlock(&swap_lock);
1219 goto out_dput;
1222 /* wait for any unplug function to finish */
1223 down_write(&swap_unplug_sem);
1224 up_write(&swap_unplug_sem);
1226 destroy_swap_extents(p);
1227 mutex_lock(&swapon_mutex);
1228 spin_lock(&swap_lock);
1229 drain_mmlist();
1231 /* wait for anyone still in scan_swap_map */
1232 p->highest_bit = 0; /* cuts scans short */
1233 while (p->flags >= SWP_SCANNING) {
1234 spin_unlock(&swap_lock);
1235 schedule_timeout_uninterruptible(1);
1236 spin_lock(&swap_lock);
1239 swap_file = p->swap_file;
1240 p->swap_file = NULL;
1241 p->max = 0;
1242 swap_map = p->swap_map;
1243 p->swap_map = NULL;
1244 p->flags = 0;
1245 spin_unlock(&swap_lock);
1246 mutex_unlock(&swapon_mutex);
1247 vfree(swap_map);
1248 inode = mapping->host;
1249 if (S_ISBLK(inode->i_mode)) {
1250 struct block_device *bdev = I_BDEV(inode);
1251 set_blocksize(bdev, p->old_block_size);
1252 bd_release(bdev);
1253 } else {
1254 mutex_lock(&inode->i_mutex);
1255 inode->i_flags &= ~S_SWAPFILE;
1256 mutex_unlock(&inode->i_mutex);
1258 filp_close(swap_file, NULL);
1259 err = 0;
1261 out_dput:
1262 filp_close(victim, NULL);
1263 out:
1264 return err;
1267 #ifdef CONFIG_PROC_FS
1268 /* iterator */
1269 static void *swap_start(struct seq_file *swap, loff_t *pos)
1271 struct swap_info_struct *ptr = swap_info;
1272 int i;
1273 loff_t l = *pos;
1275 mutex_lock(&swapon_mutex);
1277 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1278 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1279 continue;
1280 if (!l--)
1281 return ptr;
1284 return NULL;
1287 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1289 struct swap_info_struct *ptr = v;
1290 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1292 for (++ptr; ptr < endptr; ptr++) {
1293 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1294 continue;
1295 ++*pos;
1296 return ptr;
1299 return NULL;
1302 static void swap_stop(struct seq_file *swap, void *v)
1304 mutex_unlock(&swapon_mutex);
1307 static int swap_show(struct seq_file *swap, void *v)
1309 struct swap_info_struct *ptr = v;
1310 struct file *file;
1311 int len;
1313 if (v == swap_info)
1314 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1316 file = ptr->swap_file;
1317 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1318 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1319 len < 40 ? 40 - len : 1, " ",
1320 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1321 "partition" : "file\t",
1322 ptr->pages << (PAGE_SHIFT - 10),
1323 ptr->inuse_pages << (PAGE_SHIFT - 10),
1324 ptr->prio);
1325 return 0;
1328 static struct seq_operations swaps_op = {
1329 .start = swap_start,
1330 .next = swap_next,
1331 .stop = swap_stop,
1332 .show = swap_show
1333 };
1335 static int swaps_open(struct inode *inode, struct file *file)
1337 return seq_open(file, &swaps_op);
1340 static struct file_operations proc_swaps_operations = {
1341 .open = swaps_open,
1342 .read = seq_read,
1343 .llseek = seq_lseek,
1344 .release = seq_release,
1345 };
1347 static int __init procswaps_init(void)
1349 struct proc_dir_entry *entry;
1351 entry = create_proc_entry("swaps", 0, NULL);
1352 if (entry)
1353 entry->proc_fops = &proc_swaps_operations;
1354 return 0;
1356 __initcall(procswaps_init);
1357 #endif /* CONFIG_PROC_FS */
1359 /*
1360 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1362 * The swapon system call
1363 */
1364 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1366 struct swap_info_struct * p;
1367 char *name = NULL;
1368 struct block_device *bdev = NULL;
1369 struct file *swap_file = NULL;
1370 struct address_space *mapping;
1371 unsigned int type;
1372 int i, prev;
1373 int error;
1374 static int least_priority;
1375 union swap_header *swap_header = NULL;
1376 int swap_header_version;
1377 unsigned int nr_good_pages = 0;
1378 int nr_extents = 0;
1379 sector_t span;
1380 unsigned long maxpages = 1;
1381 int swapfilesize;
1382 unsigned short *swap_map;
1383 struct page *page = NULL;
1384 struct inode *inode = NULL;
1385 int did_down = 0;
1387 if (!capable(CAP_SYS_ADMIN))
1388 return -EPERM;
1389 spin_lock(&swap_lock);
1390 p = swap_info;
1391 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1392 if (!(p->flags & SWP_USED))
1393 break;
1394 error = -EPERM;
1395 if (type >= MAX_SWAPFILES) {
1396 spin_unlock(&swap_lock);
1397 goto out;
1399 if (type >= nr_swapfiles)
1400 nr_swapfiles = type+1;
1401 INIT_LIST_HEAD(&p->extent_list);
1402 p->flags = SWP_USED;
1403 p->swap_file = NULL;
1404 p->old_block_size = 0;
1405 p->swap_map = NULL;
1406 p->lowest_bit = 0;
1407 p->highest_bit = 0;
1408 p->cluster_nr = 0;
1409 p->inuse_pages = 0;
1410 p->next = -1;
1411 if (swap_flags & SWAP_FLAG_PREFER) {
1412 p->prio =
1413 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1414 } else {
1415 p->prio = --least_priority;
1417 spin_unlock(&swap_lock);
1418 name = getname(specialfile);
1419 error = PTR_ERR(name);
1420 if (IS_ERR(name)) {
1421 name = NULL;
1422 goto bad_swap_2;
1424 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1425 error = PTR_ERR(swap_file);
1426 if (IS_ERR(swap_file)) {
1427 swap_file = NULL;
1428 goto bad_swap_2;
1431 p->swap_file = swap_file;
1432 mapping = swap_file->f_mapping;
1433 inode = mapping->host;
1435 error = -EBUSY;
1436 for (i = 0; i < nr_swapfiles; i++) {
1437 struct swap_info_struct *q = &swap_info[i];
1439 if (i == type || !q->swap_file)
1440 continue;
1441 if (mapping == q->swap_file->f_mapping)
1442 goto bad_swap;
1445 error = -EINVAL;
1446 if (S_ISBLK(inode->i_mode)) {
1447 bdev = I_BDEV(inode);
1448 error = bd_claim(bdev, sys_swapon);
1449 if (error < 0) {
1450 bdev = NULL;
1451 error = -EINVAL;
1452 goto bad_swap;
1454 p->old_block_size = block_size(bdev);
1455 error = set_blocksize(bdev, PAGE_SIZE);
1456 if (error < 0)
1457 goto bad_swap;
1458 p->bdev = bdev;
1459 } else if (S_ISREG(inode->i_mode)) {
1460 p->bdev = inode->i_sb->s_bdev;
1461 mutex_lock(&inode->i_mutex);
1462 did_down = 1;
1463 if (IS_SWAPFILE(inode)) {
1464 error = -EBUSY;
1465 goto bad_swap;
1467 } else {
1468 goto bad_swap;
1471 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1473 /*
1474 * Read the swap header.
1475 */
1476 if (!mapping->a_ops->readpage) {
1477 error = -EINVAL;
1478 goto bad_swap;
1480 page = read_mapping_page(mapping, 0, swap_file);
1481 if (IS_ERR(page)) {
1482 error = PTR_ERR(page);
1483 goto bad_swap;
1485 wait_on_page_locked(page);
1486 if (!PageUptodate(page))
1487 goto bad_swap;
1488 kmap(page);
1489 swap_header = page_address(page);
1491 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1492 swap_header_version = 1;
1493 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1494 swap_header_version = 2;
1495 else {
1496 printk(KERN_ERR "Unable to find swap-space signature\n");
1497 error = -EINVAL;
1498 goto bad_swap;
1501 switch (swap_header_version) {
1502 case 1:
1503 printk(KERN_ERR "version 0 swap is no longer supported. "
1504 "Use mkswap -v1 %s\n", name);
1505 error = -EINVAL;
1506 goto bad_swap;
1507 case 2:
1508 /* Check the swap header's sub-version and the size of
1509 the swap file and bad block lists */
1510 if (swap_header->info.version != 1) {
1511 printk(KERN_WARNING
1512 "Unable to handle swap header version %d\n",
1513 swap_header->info.version);
1514 error = -EINVAL;
1515 goto bad_swap;
1518 p->lowest_bit = 1;
1519 p->cluster_next = 1;
1521 /*
1522 * Find out how many pages are allowed for a single swap
1523 * device. There are two limiting factors: 1) the number of
1524 * bits for the swap offset in the swp_entry_t type and
1525 * 2) the number of bits in the a swap pte as defined by
1526 * the different architectures. In order to find the
1527 * largest possible bit mask a swap entry with swap type 0
1528 * and swap offset ~0UL is created, encoded to a swap pte,
1529 * decoded to a swp_entry_t again and finally the swap
1530 * offset is extracted. This will mask all the bits from
1531 * the initial ~0UL mask that can't be encoded in either
1532 * the swp_entry_t or the architecture definition of a
1533 * swap pte.
1534 */
1535 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1536 if (maxpages > swap_header->info.last_page)
1537 maxpages = swap_header->info.last_page;
1538 p->highest_bit = maxpages - 1;
1540 error = -EINVAL;
1541 if (!maxpages)
1542 goto bad_swap;
1543 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1544 goto bad_swap;
1545 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1546 goto bad_swap;
1548 /* OK, set up the swap map and apply the bad block list */
1549 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1550 error = -ENOMEM;
1551 goto bad_swap;
1554 error = 0;
1555 memset(p->swap_map, 0, maxpages * sizeof(short));
1556 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1557 int page_nr = swap_header->info.badpages[i];
1558 if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1559 error = -EINVAL;
1560 else
1561 p->swap_map[page_nr] = SWAP_MAP_BAD;
1563 nr_good_pages = swap_header->info.last_page -
1564 swap_header->info.nr_badpages -
1565 1 /* header page */;
1566 if (error)
1567 goto bad_swap;
1570 if (swapfilesize && maxpages > swapfilesize) {
1571 printk(KERN_WARNING
1572 "Swap area shorter than signature indicates\n");
1573 error = -EINVAL;
1574 goto bad_swap;
1576 if (nr_good_pages) {
1577 p->swap_map[0] = SWAP_MAP_BAD;
1578 p->max = maxpages;
1579 p->pages = nr_good_pages;
1580 nr_extents = setup_swap_extents(p, &span);
1581 if (nr_extents < 0) {
1582 error = nr_extents;
1583 goto bad_swap;
1585 nr_good_pages = p->pages;
1587 if (!nr_good_pages) {
1588 printk(KERN_WARNING "Empty swap-file\n");
1589 error = -EINVAL;
1590 goto bad_swap;
1593 mutex_lock(&swapon_mutex);
1594 spin_lock(&swap_lock);
1595 p->flags = SWP_ACTIVE;
1596 nr_swap_pages += nr_good_pages;
1597 total_swap_pages += nr_good_pages;
1599 printk(KERN_INFO "Adding %uk swap on %s. "
1600 "Priority:%d extents:%d across:%lluk\n",
1601 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1602 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1604 /* insert swap space into swap_list: */
1605 prev = -1;
1606 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1607 if (p->prio >= swap_info[i].prio) {
1608 break;
1610 prev = i;
1612 p->next = i;
1613 if (prev < 0) {
1614 swap_list.head = swap_list.next = p - swap_info;
1615 } else {
1616 swap_info[prev].next = p - swap_info;
1618 spin_unlock(&swap_lock);
1619 mutex_unlock(&swapon_mutex);
1620 error = 0;
1621 goto out;
1622 bad_swap:
1623 if (bdev) {
1624 set_blocksize(bdev, p->old_block_size);
1625 bd_release(bdev);
1627 destroy_swap_extents(p);
1628 bad_swap_2:
1629 spin_lock(&swap_lock);
1630 swap_map = p->swap_map;
1631 p->swap_file = NULL;
1632 p->swap_map = NULL;
1633 p->flags = 0;
1634 if (!(swap_flags & SWAP_FLAG_PREFER))
1635 ++least_priority;
1636 spin_unlock(&swap_lock);
1637 vfree(swap_map);
1638 if (swap_file)
1639 filp_close(swap_file, NULL);
1640 out:
1641 if (page && !IS_ERR(page)) {
1642 kunmap(page);
1643 page_cache_release(page);
1645 if (name)
1646 putname(name);
1647 if (did_down) {
1648 if (!error)
1649 inode->i_flags |= S_SWAPFILE;
1650 mutex_unlock(&inode->i_mutex);
1652 return error;
1655 void si_swapinfo(struct sysinfo *val)
1657 unsigned int i;
1658 unsigned long nr_to_be_unused = 0;
1660 spin_lock(&swap_lock);
1661 for (i = 0; i < nr_swapfiles; i++) {
1662 if (!(swap_info[i].flags & SWP_USED) ||
1663 (swap_info[i].flags & SWP_WRITEOK))
1664 continue;
1665 nr_to_be_unused += swap_info[i].inuse_pages;
1667 val->freeswap = nr_swap_pages + nr_to_be_unused;
1668 val->totalswap = total_swap_pages + nr_to_be_unused;
1669 spin_unlock(&swap_lock);
1672 /*
1673 * Verify that a swap entry is valid and increment its swap map count.
1675 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1676 * "permanent", but will be reclaimed by the next swapoff.
1677 */
1678 int swap_duplicate(swp_entry_t entry)
1680 struct swap_info_struct * p;
1681 unsigned long offset, type;
1682 int result = 0;
1684 if (is_migration_entry(entry))
1685 return 1;
1687 type = swp_type(entry);
1688 if (type >= nr_swapfiles)
1689 goto bad_file;
1690 p = type + swap_info;
1691 offset = swp_offset(entry);
1693 spin_lock(&swap_lock);
1694 if (offset < p->max && p->swap_map[offset]) {
1695 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1696 p->swap_map[offset]++;
1697 result = 1;
1698 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1699 if (swap_overflow++ < 5)
1700 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1701 p->swap_map[offset] = SWAP_MAP_MAX;
1702 result = 1;
1705 spin_unlock(&swap_lock);
1706 out:
1707 return result;
1709 bad_file:
1710 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1711 goto out;
1714 struct swap_info_struct *
1715 get_swap_info_struct(unsigned type)
1717 return &swap_info[type];
1720 /*
1721 * swap_lock prevents swap_map being freed. Don't grab an extra
1722 * reference on the swaphandle, it doesn't matter if it becomes unused.
1723 */
1724 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1726 int ret = 0, i = 1 << page_cluster;
1727 unsigned long toff;
1728 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1730 if (!page_cluster) /* no readahead */
1731 return 0;
1732 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1733 if (!toff) /* first page is swap header */
1734 toff++, i--;
1735 *offset = toff;
1737 spin_lock(&swap_lock);
1738 do {
1739 /* Don't read-ahead past the end of the swap area */
1740 if (toff >= swapdev->max)
1741 break;
1742 /* Don't read in free or bad pages */
1743 if (!swapdev->swap_map[toff])
1744 break;
1745 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1746 break;
1747 toff++;
1748 ret++;
1749 } while (--i);
1750 spin_unlock(&swap_lock);
1751 return ret;