blob: 05c85129124146a3e537f71a145a5fd9da3c4643 [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
Hugh Dickins5d337b92005-09-03 15:54:41 -070034DEFINE_SPINLOCK(swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070035unsigned 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
Hugh Dickins5d337b92005-09-03 15:54:41 -070054 * hold swap_lock while calling the unplug_fn. And swap_lock
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 * cannot be turned into a semaphore.
56 */
57static DECLARE_RWSEM(swap_unplug_sem);
58
Linus Torvalds1da177e2005-04-16 15:20:36 -070059void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
60{
61 swp_entry_t entry;
62
63 down_read(&swap_unplug_sem);
64 entry.val = page->private;
65 if (PageSwapCache(page)) {
66 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
67 struct backing_dev_info *bdi;
68
69 /*
70 * If the page is removed from swapcache from under us (with a
71 * racy try_to_unuse/swapoff) we need an additional reference
72 * count to avoid reading garbage from page->private above. If
73 * the WARN_ON triggers during a swapoff it maybe the race
74 * condition and it's harmless. However if it triggers without
75 * swapoff it signals a problem.
76 */
77 WARN_ON(page_count(page) <= 1);
78
79 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -070080 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 }
82 up_read(&swap_unplug_sem);
83}
84
Hugh Dickins048c27f2005-09-03 15:54:40 -070085#define SWAPFILE_CLUSTER 256
86#define LATENCY_LIMIT 256
87
Hugh Dickins6eb396d2005-09-03 15:54:35 -070088static inline unsigned long scan_swap_map(struct swap_info_struct *si)
Linus Torvalds1da177e2005-04-16 15:20:36 -070089{
Hugh Dickins7dfad412005-09-03 15:54:38 -070090 unsigned long offset, last_in_cluster;
Hugh Dickins048c27f2005-09-03 15:54:40 -070091 int latency_ration = LATENCY_LIMIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -070092
Hugh Dickins7dfad412005-09-03 15:54:38 -070093 /*
94 * We try to cluster swap pages by allocating them sequentially
95 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
96 * way, however, we resort to first-free allocation, starting
97 * a new cluster. This prevents us from scattering swap pages
98 * all over the entire swap partition, so that we reduce
99 * overall disk seek times between swap pages. -- sct
100 * But we do now try to find an empty cluster. -Andrea
101 */
102
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700103 si->flags += SWP_SCANNING;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700104 if (unlikely(!si->cluster_nr)) {
105 si->cluster_nr = SWAPFILE_CLUSTER - 1;
106 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
107 goto lowest;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700108 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700109
110 offset = si->lowest_bit;
111 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
112
113 /* Locate the first empty (unaligned) cluster */
114 for (; last_in_cluster <= si->highest_bit; offset++) {
115 if (si->swap_map[offset])
116 last_in_cluster = offset + SWAPFILE_CLUSTER;
117 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700118 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700119 si->cluster_next = offset-SWAPFILE_CLUSTER-1;
120 goto cluster;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700122 if (unlikely(--latency_ration < 0)) {
123 cond_resched();
124 latency_ration = LATENCY_LIMIT;
125 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700126 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700127 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700128 goto lowest;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700130
131 si->cluster_nr--;
132cluster:
133 offset = si->cluster_next;
134 if (offset > si->highest_bit)
135lowest: offset = si->lowest_bit;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700136checks: if (!(si->flags & SWP_WRITEOK))
137 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700138 if (!si->highest_bit)
139 goto no_page;
140 if (!si->swap_map[offset]) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700141 if (offset == si->lowest_bit)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 si->lowest_bit++;
143 if (offset == si->highest_bit)
144 si->highest_bit--;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700145 si->inuse_pages++;
146 if (si->inuse_pages == si->pages) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 si->lowest_bit = si->max;
148 si->highest_bit = 0;
149 }
150 si->swap_map[offset] = 1;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700151 si->cluster_next = offset + 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700152 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 return offset;
154 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700155
Hugh Dickins5d337b92005-09-03 15:54:41 -0700156 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700157 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700158 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700159 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700160 goto checks;
161 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700162 if (unlikely(--latency_ration < 0)) {
163 cond_resched();
164 latency_ration = LATENCY_LIMIT;
165 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700166 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700167 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700168 goto lowest;
169
170no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700171 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 return 0;
173}
174
175swp_entry_t get_swap_page(void)
176{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700177 struct swap_info_struct *si;
178 pgoff_t offset;
179 int type, next;
180 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181
Hugh Dickins5d337b92005-09-03 15:54:41 -0700182 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700184 goto noswap;
185 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700187 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
188 si = swap_info + type;
189 next = si->next;
190 if (next < 0 ||
191 (!wrapped && si->prio != swap_info[next].prio)) {
192 next = swap_list.head;
193 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700195
196 if (!si->highest_bit)
197 continue;
198 if (!(si->flags & SWP_WRITEOK))
199 continue;
200
201 swap_list.next = next;
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700202 offset = scan_swap_map(si);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700203 if (offset) {
204 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700205 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700206 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700207 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700209
210 nr_swap_pages++;
211noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700212 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700213 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214}
215
216static struct swap_info_struct * swap_info_get(swp_entry_t entry)
217{
218 struct swap_info_struct * p;
219 unsigned long offset, type;
220
221 if (!entry.val)
222 goto out;
223 type = swp_type(entry);
224 if (type >= nr_swapfiles)
225 goto bad_nofile;
226 p = & swap_info[type];
227 if (!(p->flags & SWP_USED))
228 goto bad_device;
229 offset = swp_offset(entry);
230 if (offset >= p->max)
231 goto bad_offset;
232 if (!p->swap_map[offset])
233 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700234 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235 return p;
236
237bad_free:
238 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
239 goto out;
240bad_offset:
241 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
242 goto out;
243bad_device:
244 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
245 goto out;
246bad_nofile:
247 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
248out:
249 return NULL;
250}
251
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
253{
254 int count = p->swap_map[offset];
255
256 if (count < SWAP_MAP_MAX) {
257 count--;
258 p->swap_map[offset] = count;
259 if (!count) {
260 if (offset < p->lowest_bit)
261 p->lowest_bit = offset;
262 if (offset > p->highest_bit)
263 p->highest_bit = offset;
Hugh Dickins89d09a22005-09-03 15:54:36 -0700264 if (p->prio > swap_info[swap_list.next].prio)
265 swap_list.next = p - swap_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 nr_swap_pages++;
267 p->inuse_pages--;
268 }
269 }
270 return count;
271}
272
273/*
274 * Caller has made sure that the swapdevice corresponding to entry
275 * is still around or has not been recycled.
276 */
277void swap_free(swp_entry_t entry)
278{
279 struct swap_info_struct * p;
280
281 p = swap_info_get(entry);
282 if (p) {
283 swap_entry_free(p, swp_offset(entry));
Hugh Dickins5d337b92005-09-03 15:54:41 -0700284 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285 }
286}
287
288/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700289 * How many references to page are currently swapped out?
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700291static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700293 int count = 0;
294 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295 swp_entry_t entry;
296
297 entry.val = page->private;
298 p = swap_info_get(entry);
299 if (p) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700300 /* Subtract the 1 for the swap cache itself */
301 count = p->swap_map[swp_offset(entry)] - 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700302 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700304 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305}
306
307/*
308 * We can use this swap cache entry directly
309 * if there are no other references to it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 */
311int can_share_swap_page(struct page *page)
312{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700313 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700315 BUG_ON(!PageLocked(page));
316 count = page_mapcount(page);
317 if (count <= 1 && PageSwapCache(page))
318 count += page_swapcount(page);
319 return count == 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320}
321
322/*
323 * Work out if there are any other processes sharing this
324 * swap cache page. Free it if you can. Return success.
325 */
326int remove_exclusive_swap_page(struct page *page)
327{
328 int retval;
329 struct swap_info_struct * p;
330 swp_entry_t entry;
331
332 BUG_ON(PagePrivate(page));
333 BUG_ON(!PageLocked(page));
334
335 if (!PageSwapCache(page))
336 return 0;
337 if (PageWriteback(page))
338 return 0;
339 if (page_count(page) != 2) /* 2: us + cache */
340 return 0;
341
342 entry.val = page->private;
343 p = swap_info_get(entry);
344 if (!p)
345 return 0;
346
347 /* Is the only swap cache user the cache itself? */
348 retval = 0;
349 if (p->swap_map[swp_offset(entry)] == 1) {
350 /* Recheck the page count with the swapcache lock held.. */
351 write_lock_irq(&swapper_space.tree_lock);
352 if ((page_count(page) == 2) && !PageWriteback(page)) {
353 __delete_from_swap_cache(page);
354 SetPageDirty(page);
355 retval = 1;
356 }
357 write_unlock_irq(&swapper_space.tree_lock);
358 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700359 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360
361 if (retval) {
362 swap_free(entry);
363 page_cache_release(page);
364 }
365
366 return retval;
367}
368
369/*
370 * Free the swap entry like above, but also try to
371 * free the page cache entry if it is the last user.
372 */
373void free_swap_and_cache(swp_entry_t entry)
374{
375 struct swap_info_struct * p;
376 struct page *page = NULL;
377
378 p = swap_info_get(entry);
379 if (p) {
380 if (swap_entry_free(p, swp_offset(entry)) == 1)
381 page = find_trylock_page(&swapper_space, entry.val);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700382 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 }
384 if (page) {
385 int one_user;
386
387 BUG_ON(PagePrivate(page));
388 page_cache_get(page);
389 one_user = (page_count(page) == 2);
390 /* Only cache user (+us), or swap space full? Free it! */
391 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
392 delete_from_swap_cache(page);
393 SetPageDirty(page);
394 }
395 unlock_page(page);
396 page_cache_release(page);
397 }
398}
399
400/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700401 * No need to decide whether this PTE shares the swap entry with others,
402 * just let do_wp_page work it out if a write is requested later - to
403 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 *
405 * vma->vm_mm->page_table_lock is held.
406 */
407static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
408 unsigned long addr, swp_entry_t entry, struct page *page)
409{
410 inc_mm_counter(vma->vm_mm, rss);
411 get_page(page);
412 set_pte_at(vma->vm_mm, addr, pte,
413 pte_mkold(mk_pte(page, vma->vm_page_prot)));
414 page_add_anon_rmap(page, vma, addr);
415 swap_free(entry);
416 /*
417 * Move the page to the active list so it is not
418 * immediately swapped out again after swapon.
419 */
420 activate_page(page);
421}
422
423static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
424 unsigned long addr, unsigned long end,
425 swp_entry_t entry, struct page *page)
426{
427 pte_t *pte;
428 pte_t swp_pte = swp_entry_to_pte(entry);
429
430 pte = pte_offset_map(pmd, addr);
431 do {
432 /*
433 * swapoff spends a _lot_ of time in this loop!
434 * Test inline before going to call unuse_pte.
435 */
436 if (unlikely(pte_same(*pte, swp_pte))) {
437 unuse_pte(vma, pte, addr, entry, page);
438 pte_unmap(pte);
439 return 1;
440 }
441 } while (pte++, addr += PAGE_SIZE, addr != end);
442 pte_unmap(pte - 1);
443 return 0;
444}
445
446static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
447 unsigned long addr, unsigned long end,
448 swp_entry_t entry, struct page *page)
449{
450 pmd_t *pmd;
451 unsigned long next;
452
453 pmd = pmd_offset(pud, addr);
454 do {
455 next = pmd_addr_end(addr, end);
456 if (pmd_none_or_clear_bad(pmd))
457 continue;
458 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
459 return 1;
460 } while (pmd++, addr = next, addr != end);
461 return 0;
462}
463
464static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
465 unsigned long addr, unsigned long end,
466 swp_entry_t entry, struct page *page)
467{
468 pud_t *pud;
469 unsigned long next;
470
471 pud = pud_offset(pgd, addr);
472 do {
473 next = pud_addr_end(addr, end);
474 if (pud_none_or_clear_bad(pud))
475 continue;
476 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
477 return 1;
478 } while (pud++, addr = next, addr != end);
479 return 0;
480}
481
482static int unuse_vma(struct vm_area_struct *vma,
483 swp_entry_t entry, struct page *page)
484{
485 pgd_t *pgd;
486 unsigned long addr, end, next;
487
488 if (page->mapping) {
489 addr = page_address_in_vma(page, vma);
490 if (addr == -EFAULT)
491 return 0;
492 else
493 end = addr + PAGE_SIZE;
494 } else {
495 addr = vma->vm_start;
496 end = vma->vm_end;
497 }
498
499 pgd = pgd_offset(vma->vm_mm, addr);
500 do {
501 next = pgd_addr_end(addr, end);
502 if (pgd_none_or_clear_bad(pgd))
503 continue;
504 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
505 return 1;
506 } while (pgd++, addr = next, addr != end);
507 return 0;
508}
509
510static int unuse_mm(struct mm_struct *mm,
511 swp_entry_t entry, struct page *page)
512{
513 struct vm_area_struct *vma;
514
515 if (!down_read_trylock(&mm->mmap_sem)) {
516 /*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700517 * Activate page so shrink_cache is unlikely to unmap its
518 * ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700520 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 unlock_page(page);
522 down_read(&mm->mmap_sem);
523 lock_page(page);
524 }
525 spin_lock(&mm->page_table_lock);
526 for (vma = mm->mmap; vma; vma = vma->vm_next) {
527 if (vma->anon_vma && unuse_vma(vma, entry, page))
528 break;
529 }
530 spin_unlock(&mm->page_table_lock);
531 up_read(&mm->mmap_sem);
532 /*
533 * Currently unuse_mm cannot fail, but leave error handling
534 * at call sites for now, since we change it from time to time.
535 */
536 return 0;
537}
538
539/*
540 * Scan swap_map from current position to next entry still in use.
541 * Recycle to start on reaching the end, returning 0 when empty.
542 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700543static unsigned int find_next_to_unuse(struct swap_info_struct *si,
544 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700546 unsigned int max = si->max;
547 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548 int count;
549
550 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700551 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 * for whether an entry is in use, not modifying it; false
553 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -0700554 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555 */
556 for (;;) {
557 if (++i >= max) {
558 if (!prev) {
559 i = 0;
560 break;
561 }
562 /*
563 * No entries in use at top of swap_map,
564 * loop back to start and recheck there.
565 */
566 max = prev + 1;
567 prev = 0;
568 i = 1;
569 }
570 count = si->swap_map[i];
571 if (count && count != SWAP_MAP_BAD)
572 break;
573 }
574 return i;
575}
576
577/*
578 * We completely avoid races by reading each swap page in advance,
579 * and then search for the process using it. All the necessary
580 * page table adjustments can then be made atomically.
581 */
582static int try_to_unuse(unsigned int type)
583{
584 struct swap_info_struct * si = &swap_info[type];
585 struct mm_struct *start_mm;
586 unsigned short *swap_map;
587 unsigned short swcount;
588 struct page *page;
589 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700590 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 int retval = 0;
592 int reset_overflow = 0;
593 int shmem;
594
595 /*
596 * When searching mms for an entry, a good strategy is to
597 * start at the first mm we freed the previous entry from
598 * (though actually we don't notice whether we or coincidence
599 * freed the entry). Initialize this start_mm with a hold.
600 *
601 * A simpler strategy would be to start at the last mm we
602 * freed the previous entry from; but that would take less
603 * advantage of mmlist ordering, which clusters forked mms
604 * together, child after parent. If we race with dup_mmap(), we
605 * prefer to resolve parent before child, lest we miss entries
606 * duplicated after we scanned child: using last mm would invert
607 * that. Though it's only a serious concern when an overflowed
608 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
609 */
610 start_mm = &init_mm;
611 atomic_inc(&init_mm.mm_users);
612
613 /*
614 * Keep on scanning until all entries have gone. Usually,
615 * one pass through swap_map is enough, but not necessarily:
616 * there are races when an instance of an entry might be missed.
617 */
618 while ((i = find_next_to_unuse(si, i)) != 0) {
619 if (signal_pending(current)) {
620 retval = -EINTR;
621 break;
622 }
623
624 /*
625 * Get a page for the entry, using the existing swap
626 * cache page if there is one. Otherwise, get a clean
627 * page and read the swap into it.
628 */
629 swap_map = &si->swap_map[i];
630 entry = swp_entry(type, i);
631 page = read_swap_cache_async(entry, NULL, 0);
632 if (!page) {
633 /*
634 * Either swap_duplicate() failed because entry
635 * has been freed independently, and will not be
636 * reused since sys_swapoff() already disabled
637 * allocation from here, or alloc_page() failed.
638 */
639 if (!*swap_map)
640 continue;
641 retval = -ENOMEM;
642 break;
643 }
644
645 /*
646 * Don't hold on to start_mm if it looks like exiting.
647 */
648 if (atomic_read(&start_mm->mm_users) == 1) {
649 mmput(start_mm);
650 start_mm = &init_mm;
651 atomic_inc(&init_mm.mm_users);
652 }
653
654 /*
655 * Wait for and lock page. When do_swap_page races with
656 * try_to_unuse, do_swap_page can handle the fault much
657 * faster than try_to_unuse can locate the entry. This
658 * apparently redundant "wait_on_page_locked" lets try_to_unuse
659 * defer to do_swap_page in such a case - in some tests,
660 * do_swap_page and try_to_unuse repeatedly compete.
661 */
662 wait_on_page_locked(page);
663 wait_on_page_writeback(page);
664 lock_page(page);
665 wait_on_page_writeback(page);
666
667 /*
668 * Remove all references to entry.
669 * Whenever we reach init_mm, there's no address space
670 * to search, but use it as a reminder to search shmem.
671 */
672 shmem = 0;
673 swcount = *swap_map;
674 if (swcount > 1) {
675 if (start_mm == &init_mm)
676 shmem = shmem_unuse(entry, page);
677 else
678 retval = unuse_mm(start_mm, entry, page);
679 }
680 if (*swap_map > 1) {
681 int set_start_mm = (*swap_map >= swcount);
682 struct list_head *p = &start_mm->mmlist;
683 struct mm_struct *new_start_mm = start_mm;
684 struct mm_struct *prev_mm = start_mm;
685 struct mm_struct *mm;
686
687 atomic_inc(&new_start_mm->mm_users);
688 atomic_inc(&prev_mm->mm_users);
689 spin_lock(&mmlist_lock);
690 while (*swap_map > 1 && !retval &&
691 (p = p->next) != &start_mm->mmlist) {
692 mm = list_entry(p, struct mm_struct, mmlist);
693 if (atomic_inc_return(&mm->mm_users) == 1) {
694 atomic_dec(&mm->mm_users);
695 continue;
696 }
697 spin_unlock(&mmlist_lock);
698 mmput(prev_mm);
699 prev_mm = mm;
700
701 cond_resched();
702
703 swcount = *swap_map;
704 if (swcount <= 1)
705 ;
706 else if (mm == &init_mm) {
707 set_start_mm = 1;
708 shmem = shmem_unuse(entry, page);
709 } else
710 retval = unuse_mm(mm, entry, page);
711 if (set_start_mm && *swap_map < swcount) {
712 mmput(new_start_mm);
713 atomic_inc(&mm->mm_users);
714 new_start_mm = mm;
715 set_start_mm = 0;
716 }
717 spin_lock(&mmlist_lock);
718 }
719 spin_unlock(&mmlist_lock);
720 mmput(prev_mm);
721 mmput(start_mm);
722 start_mm = new_start_mm;
723 }
724 if (retval) {
725 unlock_page(page);
726 page_cache_release(page);
727 break;
728 }
729
730 /*
731 * How could swap count reach 0x7fff when the maximum
732 * pid is 0x7fff, and there's no way to repeat a swap
733 * page within an mm (except in shmem, where it's the
734 * shared object which takes the reference count)?
735 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
736 *
737 * If that's wrong, then we should worry more about
738 * exit_mmap() and do_munmap() cases described above:
739 * we might be resetting SWAP_MAP_MAX too early here.
740 * We know "Undead"s can happen, they're okay, so don't
741 * report them; but do report if we reset SWAP_MAP_MAX.
742 */
743 if (*swap_map == SWAP_MAP_MAX) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700744 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 *swap_map = 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700746 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 reset_overflow = 1;
748 }
749
750 /*
751 * If a reference remains (rare), we would like to leave
752 * the page in the swap cache; but try_to_unmap could
753 * then re-duplicate the entry once we drop page lock,
754 * so we might loop indefinitely; also, that page could
755 * not be swapped out to other storage meanwhile. So:
756 * delete from cache even if there's another reference,
757 * after ensuring that the data has been saved to disk -
758 * since if the reference remains (rarer), it will be
759 * read from disk into another page. Splitting into two
760 * pages would be incorrect if swap supported "shared
761 * private" pages, but they are handled by tmpfs files.
762 *
763 * Note shmem_unuse already deleted a swappage from
764 * the swap cache, unless the move to filepage failed:
765 * in which case it left swappage in cache, lowered its
766 * swap count to pass quickly through the loops above,
767 * and now we must reincrement count to try again later.
768 */
769 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
770 struct writeback_control wbc = {
771 .sync_mode = WB_SYNC_NONE,
772 };
773
774 swap_writepage(page, &wbc);
775 lock_page(page);
776 wait_on_page_writeback(page);
777 }
778 if (PageSwapCache(page)) {
779 if (shmem)
780 swap_duplicate(entry);
781 else
782 delete_from_swap_cache(page);
783 }
784
785 /*
786 * So we could skip searching mms once swap count went
787 * to 1, we did not mark any present ptes as dirty: must
788 * mark page dirty so shrink_list will preserve it.
789 */
790 SetPageDirty(page);
791 unlock_page(page);
792 page_cache_release(page);
793
794 /*
795 * Make sure that we aren't completely killing
796 * interactive performance.
797 */
798 cond_resched();
799 }
800
801 mmput(start_mm);
802 if (reset_overflow) {
803 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
804 swap_overflow = 0;
805 }
806 return retval;
807}
808
809/*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700810 * After a successful try_to_unuse, if no swap is now in use, we know
811 * we can empty the mmlist. swap_lock must be held on entry and exit.
812 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813 * added to the mmlist just after page_duplicate - before would be racy.
814 */
815static void drain_mmlist(void)
816{
817 struct list_head *p, *next;
818 unsigned int i;
819
820 for (i = 0; i < nr_swapfiles; i++)
821 if (swap_info[i].inuse_pages)
822 return;
823 spin_lock(&mmlist_lock);
824 list_for_each_safe(p, next, &init_mm.mmlist)
825 list_del_init(p);
826 spin_unlock(&mmlist_lock);
827}
828
829/*
830 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
831 * corresponds to page offset `offset'.
832 */
833sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
834{
835 struct swap_extent *se = sis->curr_swap_extent;
836 struct swap_extent *start_se = se;
837
838 for ( ; ; ) {
839 struct list_head *lh;
840
841 if (se->start_page <= offset &&
842 offset < (se->start_page + se->nr_pages)) {
843 return se->start_block + (offset - se->start_page);
844 }
Hugh Dickins11d31882005-09-03 15:54:34 -0700845 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -0700847 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848 se = list_entry(lh, struct swap_extent, list);
849 sis->curr_swap_extent = se;
850 BUG_ON(se == start_se); /* It *must* be present */
851 }
852}
853
854/*
855 * Free all of a swapdev's extent information
856 */
857static void destroy_swap_extents(struct swap_info_struct *sis)
858{
859 while (!list_empty(&sis->extent_list)) {
860 struct swap_extent *se;
861
862 se = list_entry(sis->extent_list.next,
863 struct swap_extent, list);
864 list_del(&se->list);
865 kfree(se);
866 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700867}
868
869/*
870 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -0700871 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 *
Hugh Dickins11d31882005-09-03 15:54:34 -0700873 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700874 */
875static int
876add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
877 unsigned long nr_pages, sector_t start_block)
878{
879 struct swap_extent *se;
880 struct swap_extent *new_se;
881 struct list_head *lh;
882
Hugh Dickins11d31882005-09-03 15:54:34 -0700883 lh = sis->extent_list.prev; /* The highest page extent */
884 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -0700886 BUG_ON(se->start_page + se->nr_pages != start_page);
887 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 /* Merge it */
889 se->nr_pages += nr_pages;
890 return 0;
891 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700892 }
893
894 /*
895 * No merge. Insert a new extent, preserving ordering.
896 */
897 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
898 if (new_se == NULL)
899 return -ENOMEM;
900 new_se->start_page = start_page;
901 new_se->nr_pages = nr_pages;
902 new_se->start_block = start_block;
903
Hugh Dickins11d31882005-09-03 15:54:34 -0700904 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -0700905 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906}
907
908/*
909 * A `swap extent' is a simple thing which maps a contiguous range of pages
910 * onto a contiguous range of disk blocks. An ordered list of swap extents
911 * is built at swapon time and is then used at swap_writepage/swap_readpage
912 * time for locating where on disk a page belongs.
913 *
914 * If the swapfile is an S_ISBLK block device, a single extent is installed.
915 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
916 * swap files identically.
917 *
918 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
919 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
920 * swapfiles are handled *identically* after swapon time.
921 *
922 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
923 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
924 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
925 * requirements, they are simply tossed out - we will never use those blocks
926 * for swapping.
927 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -0700928 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
930 * which will scribble on the fs.
931 *
932 * The amount of disk space which a single swap extent represents varies.
933 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
934 * extents in the list. To avoid much list walking, we cache the previous
935 * search location in `curr_swap_extent', and start new searches from there.
936 * This is extremely effective. The average number of iterations in
937 * map_swap_page() has been measured at about 0.3 per page. - akpm.
938 */
Hugh Dickins53092a72005-09-03 15:54:34 -0700939static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940{
941 struct inode *inode;
942 unsigned blocks_per_page;
943 unsigned long page_no;
944 unsigned blkbits;
945 sector_t probe_block;
946 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -0700947 sector_t lowest_block = -1;
948 sector_t highest_block = 0;
949 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950 int ret;
951
952 inode = sis->swap_file->f_mapping->host;
953 if (S_ISBLK(inode->i_mode)) {
954 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -0700955 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956 goto done;
957 }
958
959 blkbits = inode->i_blkbits;
960 blocks_per_page = PAGE_SIZE >> blkbits;
961
962 /*
963 * Map all the blocks into the extent list. This code doesn't try
964 * to be very smart.
965 */
966 probe_block = 0;
967 page_no = 0;
968 last_block = i_size_read(inode) >> blkbits;
969 while ((probe_block + blocks_per_page) <= last_block &&
970 page_no < sis->max) {
971 unsigned block_in_page;
972 sector_t first_block;
973
974 first_block = bmap(inode, probe_block);
975 if (first_block == 0)
976 goto bad_bmap;
977
978 /*
979 * It must be PAGE_SIZE aligned on-disk
980 */
981 if (first_block & (blocks_per_page - 1)) {
982 probe_block++;
983 goto reprobe;
984 }
985
986 for (block_in_page = 1; block_in_page < blocks_per_page;
987 block_in_page++) {
988 sector_t block;
989
990 block = bmap(inode, probe_block + block_in_page);
991 if (block == 0)
992 goto bad_bmap;
993 if (block != first_block + block_in_page) {
994 /* Discontiguity */
995 probe_block++;
996 goto reprobe;
997 }
998 }
999
Hugh Dickins53092a72005-09-03 15:54:34 -07001000 first_block >>= (PAGE_SHIFT - blkbits);
1001 if (page_no) { /* exclude the header page */
1002 if (first_block < lowest_block)
1003 lowest_block = first_block;
1004 if (first_block > highest_block)
1005 highest_block = first_block;
1006 }
1007
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 /*
1009 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1010 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001011 ret = add_swap_extent(sis, page_no, 1, first_block);
1012 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001014 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001015 page_no++;
1016 probe_block += blocks_per_page;
1017reprobe:
1018 continue;
1019 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001020 ret = nr_extents;
1021 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001023 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001025 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026 sis->highest_bit = page_no - 1;
1027done:
1028 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1029 struct swap_extent, list);
1030 goto out;
1031bad_bmap:
1032 printk(KERN_ERR "swapon: swapfile has holes\n");
1033 ret = -EINVAL;
1034out:
1035 return ret;
1036}
1037
1038#if 0 /* We don't need this yet */
1039#include <linux/backing-dev.h>
1040int page_queue_congested(struct page *page)
1041{
1042 struct backing_dev_info *bdi;
1043
1044 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1045
1046 if (PageSwapCache(page)) {
1047 swp_entry_t entry = { .val = page->private };
1048 struct swap_info_struct *sis;
1049
1050 sis = get_swap_info_struct(swp_type(entry));
1051 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1052 } else
1053 bdi = page->mapping->backing_dev_info;
1054 return bdi_write_congested(bdi);
1055}
1056#endif
1057
1058asmlinkage long sys_swapoff(const char __user * specialfile)
1059{
1060 struct swap_info_struct * p = NULL;
1061 unsigned short *swap_map;
1062 struct file *swap_file, *victim;
1063 struct address_space *mapping;
1064 struct inode *inode;
1065 char * pathname;
1066 int i, type, prev;
1067 int err;
1068
1069 if (!capable(CAP_SYS_ADMIN))
1070 return -EPERM;
1071
1072 pathname = getname(specialfile);
1073 err = PTR_ERR(pathname);
1074 if (IS_ERR(pathname))
1075 goto out;
1076
1077 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1078 putname(pathname);
1079 err = PTR_ERR(victim);
1080 if (IS_ERR(victim))
1081 goto out;
1082
1083 mapping = victim->f_mapping;
1084 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001085 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1087 p = swap_info + type;
1088 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1089 if (p->swap_file->f_mapping == mapping)
1090 break;
1091 }
1092 prev = type;
1093 }
1094 if (type < 0) {
1095 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001096 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097 goto out_dput;
1098 }
1099 if (!security_vm_enough_memory(p->pages))
1100 vm_unacct_memory(p->pages);
1101 else {
1102 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001103 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104 goto out_dput;
1105 }
1106 if (prev < 0) {
1107 swap_list.head = p->next;
1108 } else {
1109 swap_info[prev].next = p->next;
1110 }
1111 if (type == swap_list.next) {
1112 /* just pick something that's safe... */
1113 swap_list.next = swap_list.head;
1114 }
1115 nr_swap_pages -= p->pages;
1116 total_swap_pages -= p->pages;
1117 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001118 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001119
Linus Torvalds1da177e2005-04-16 15:20:36 -07001120 current->flags |= PF_SWAPOFF;
1121 err = try_to_unuse(type);
1122 current->flags &= ~PF_SWAPOFF;
1123
Linus Torvalds1da177e2005-04-16 15:20:36 -07001124 if (err) {
1125 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001126 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1128 if (p->prio >= swap_info[i].prio)
1129 break;
1130 p->next = i;
1131 if (prev < 0)
1132 swap_list.head = swap_list.next = p - swap_info;
1133 else
1134 swap_info[prev].next = p - swap_info;
1135 nr_swap_pages += p->pages;
1136 total_swap_pages += p->pages;
1137 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001138 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139 goto out_dput;
1140 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001141
1142 /* wait for any unplug function to finish */
1143 down_write(&swap_unplug_sem);
1144 up_write(&swap_unplug_sem);
1145
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001146 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001148 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001150
1151 /* wait for anyone still in scan_swap_map */
1152 p->highest_bit = 0; /* cuts scans short */
1153 while (p->flags >= SWP_SCANNING) {
1154 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001155 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001156 spin_lock(&swap_lock);
1157 }
1158
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159 swap_file = p->swap_file;
1160 p->swap_file = NULL;
1161 p->max = 0;
1162 swap_map = p->swap_map;
1163 p->swap_map = NULL;
1164 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001165 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001166 up(&swapon_sem);
1167 vfree(swap_map);
1168 inode = mapping->host;
1169 if (S_ISBLK(inode->i_mode)) {
1170 struct block_device *bdev = I_BDEV(inode);
1171 set_blocksize(bdev, p->old_block_size);
1172 bd_release(bdev);
1173 } else {
1174 down(&inode->i_sem);
1175 inode->i_flags &= ~S_SWAPFILE;
1176 up(&inode->i_sem);
1177 }
1178 filp_close(swap_file, NULL);
1179 err = 0;
1180
1181out_dput:
1182 filp_close(victim, NULL);
1183out:
1184 return err;
1185}
1186
1187#ifdef CONFIG_PROC_FS
1188/* iterator */
1189static void *swap_start(struct seq_file *swap, loff_t *pos)
1190{
1191 struct swap_info_struct *ptr = swap_info;
1192 int i;
1193 loff_t l = *pos;
1194
1195 down(&swapon_sem);
1196
1197 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1198 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1199 continue;
1200 if (!l--)
1201 return ptr;
1202 }
1203
1204 return NULL;
1205}
1206
1207static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1208{
1209 struct swap_info_struct *ptr = v;
1210 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1211
1212 for (++ptr; ptr < endptr; ptr++) {
1213 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1214 continue;
1215 ++*pos;
1216 return ptr;
1217 }
1218
1219 return NULL;
1220}
1221
1222static void swap_stop(struct seq_file *swap, void *v)
1223{
1224 up(&swapon_sem);
1225}
1226
1227static int swap_show(struct seq_file *swap, void *v)
1228{
1229 struct swap_info_struct *ptr = v;
1230 struct file *file;
1231 int len;
1232
1233 if (v == swap_info)
1234 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1235
1236 file = ptr->swap_file;
1237 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001238 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239 len < 40 ? 40 - len : 1, " ",
1240 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1241 "partition" : "file\t",
1242 ptr->pages << (PAGE_SHIFT - 10),
1243 ptr->inuse_pages << (PAGE_SHIFT - 10),
1244 ptr->prio);
1245 return 0;
1246}
1247
1248static struct seq_operations swaps_op = {
1249 .start = swap_start,
1250 .next = swap_next,
1251 .stop = swap_stop,
1252 .show = swap_show
1253};
1254
1255static int swaps_open(struct inode *inode, struct file *file)
1256{
1257 return seq_open(file, &swaps_op);
1258}
1259
1260static struct file_operations proc_swaps_operations = {
1261 .open = swaps_open,
1262 .read = seq_read,
1263 .llseek = seq_lseek,
1264 .release = seq_release,
1265};
1266
1267static int __init procswaps_init(void)
1268{
1269 struct proc_dir_entry *entry;
1270
1271 entry = create_proc_entry("swaps", 0, NULL);
1272 if (entry)
1273 entry->proc_fops = &proc_swaps_operations;
1274 return 0;
1275}
1276__initcall(procswaps_init);
1277#endif /* CONFIG_PROC_FS */
1278
1279/*
1280 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1281 *
1282 * The swapon system call
1283 */
1284asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1285{
1286 struct swap_info_struct * p;
1287 char *name = NULL;
1288 struct block_device *bdev = NULL;
1289 struct file *swap_file = NULL;
1290 struct address_space *mapping;
1291 unsigned int type;
1292 int i, prev;
1293 int error;
1294 static int least_priority;
1295 union swap_header *swap_header = NULL;
1296 int swap_header_version;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001297 unsigned int nr_good_pages = 0;
1298 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001299 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300 unsigned long maxpages = 1;
1301 int swapfilesize;
1302 unsigned short *swap_map;
1303 struct page *page = NULL;
1304 struct inode *inode = NULL;
1305 int did_down = 0;
1306
1307 if (!capable(CAP_SYS_ADMIN))
1308 return -EPERM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001309 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310 p = swap_info;
1311 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1312 if (!(p->flags & SWP_USED))
1313 break;
1314 error = -EPERM;
1315 /*
1316 * Test if adding another swap device is possible. There are
1317 * two limiting factors: 1) the number of bits for the swap
1318 * type swp_entry_t definition and 2) the number of bits for
1319 * the swap type in the swap ptes as defined by the different
1320 * architectures. To honor both limitations a swap entry
1321 * with swap offset 0 and swap type ~0UL is created, encoded
1322 * to a swap pte, decoded to a swp_entry_t again and finally
1323 * the swap type part is extracted. This will mask all bits
1324 * from the initial ~0UL that can't be encoded in either the
1325 * swp_entry_t or the architecture definition of a swap pte.
1326 */
1327 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001328 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329 goto out;
1330 }
1331 if (type >= nr_swapfiles)
1332 nr_swapfiles = type+1;
1333 INIT_LIST_HEAD(&p->extent_list);
1334 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 p->swap_file = NULL;
1336 p->old_block_size = 0;
1337 p->swap_map = NULL;
1338 p->lowest_bit = 0;
1339 p->highest_bit = 0;
1340 p->cluster_nr = 0;
1341 p->inuse_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 p->next = -1;
1343 if (swap_flags & SWAP_FLAG_PREFER) {
1344 p->prio =
1345 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1346 } else {
1347 p->prio = --least_priority;
1348 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001349 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 name = getname(specialfile);
1351 error = PTR_ERR(name);
1352 if (IS_ERR(name)) {
1353 name = NULL;
1354 goto bad_swap_2;
1355 }
1356 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1357 error = PTR_ERR(swap_file);
1358 if (IS_ERR(swap_file)) {
1359 swap_file = NULL;
1360 goto bad_swap_2;
1361 }
1362
1363 p->swap_file = swap_file;
1364 mapping = swap_file->f_mapping;
1365 inode = mapping->host;
1366
1367 error = -EBUSY;
1368 for (i = 0; i < nr_swapfiles; i++) {
1369 struct swap_info_struct *q = &swap_info[i];
1370
1371 if (i == type || !q->swap_file)
1372 continue;
1373 if (mapping == q->swap_file->f_mapping)
1374 goto bad_swap;
1375 }
1376
1377 error = -EINVAL;
1378 if (S_ISBLK(inode->i_mode)) {
1379 bdev = I_BDEV(inode);
1380 error = bd_claim(bdev, sys_swapon);
1381 if (error < 0) {
1382 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001383 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384 goto bad_swap;
1385 }
1386 p->old_block_size = block_size(bdev);
1387 error = set_blocksize(bdev, PAGE_SIZE);
1388 if (error < 0)
1389 goto bad_swap;
1390 p->bdev = bdev;
1391 } else if (S_ISREG(inode->i_mode)) {
1392 p->bdev = inode->i_sb->s_bdev;
1393 down(&inode->i_sem);
1394 did_down = 1;
1395 if (IS_SWAPFILE(inode)) {
1396 error = -EBUSY;
1397 goto bad_swap;
1398 }
1399 } else {
1400 goto bad_swap;
1401 }
1402
1403 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1404
1405 /*
1406 * Read the swap header.
1407 */
1408 if (!mapping->a_ops->readpage) {
1409 error = -EINVAL;
1410 goto bad_swap;
1411 }
1412 page = read_cache_page(mapping, 0,
1413 (filler_t *)mapping->a_ops->readpage, swap_file);
1414 if (IS_ERR(page)) {
1415 error = PTR_ERR(page);
1416 goto bad_swap;
1417 }
1418 wait_on_page_locked(page);
1419 if (!PageUptodate(page))
1420 goto bad_swap;
1421 kmap(page);
1422 swap_header = page_address(page);
1423
1424 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1425 swap_header_version = 1;
1426 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1427 swap_header_version = 2;
1428 else {
1429 printk("Unable to find swap-space signature\n");
1430 error = -EINVAL;
1431 goto bad_swap;
1432 }
1433
1434 switch (swap_header_version) {
1435 case 1:
1436 printk(KERN_ERR "version 0 swap is no longer supported. "
1437 "Use mkswap -v1 %s\n", name);
1438 error = -EINVAL;
1439 goto bad_swap;
1440 case 2:
1441 /* Check the swap header's sub-version and the size of
1442 the swap file and bad block lists */
1443 if (swap_header->info.version != 1) {
1444 printk(KERN_WARNING
1445 "Unable to handle swap header version %d\n",
1446 swap_header->info.version);
1447 error = -EINVAL;
1448 goto bad_swap;
1449 }
1450
1451 p->lowest_bit = 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001452 p->cluster_next = 1;
1453
Linus Torvalds1da177e2005-04-16 15:20:36 -07001454 /*
1455 * Find out how many pages are allowed for a single swap
1456 * device. There are two limiting factors: 1) the number of
1457 * bits for the swap offset in the swp_entry_t type and
1458 * 2) the number of bits in the a swap pte as defined by
1459 * the different architectures. In order to find the
1460 * largest possible bit mask a swap entry with swap type 0
1461 * and swap offset ~0UL is created, encoded to a swap pte,
1462 * decoded to a swp_entry_t again and finally the swap
1463 * offset is extracted. This will mask all the bits from
1464 * the initial ~0UL mask that can't be encoded in either
1465 * the swp_entry_t or the architecture definition of a
1466 * swap pte.
1467 */
1468 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1469 if (maxpages > swap_header->info.last_page)
1470 maxpages = swap_header->info.last_page;
1471 p->highest_bit = maxpages - 1;
1472
1473 error = -EINVAL;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001474 if (!maxpages)
1475 goto bad_swap;
1476 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1477 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1479 goto bad_swap;
1480
1481 /* OK, set up the swap map and apply the bad block list */
1482 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1483 error = -ENOMEM;
1484 goto bad_swap;
1485 }
1486
1487 error = 0;
1488 memset(p->swap_map, 0, maxpages * sizeof(short));
1489 for (i=0; i<swap_header->info.nr_badpages; i++) {
1490 int page = swap_header->info.badpages[i];
1491 if (page <= 0 || page >= swap_header->info.last_page)
1492 error = -EINVAL;
1493 else
1494 p->swap_map[page] = SWAP_MAP_BAD;
1495 }
1496 nr_good_pages = swap_header->info.last_page -
1497 swap_header->info.nr_badpages -
1498 1 /* header page */;
1499 if (error)
1500 goto bad_swap;
1501 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001502
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 if (swapfilesize && maxpages > swapfilesize) {
1504 printk(KERN_WARNING
1505 "Swap area shorter than signature indicates\n");
1506 error = -EINVAL;
1507 goto bad_swap;
1508 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001509 if (nr_good_pages) {
1510 p->swap_map[0] = SWAP_MAP_BAD;
1511 p->max = maxpages;
1512 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001513 nr_extents = setup_swap_extents(p, &span);
1514 if (nr_extents < 0) {
1515 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001516 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001517 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001518 nr_good_pages = p->pages;
1519 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520 if (!nr_good_pages) {
1521 printk(KERN_WARNING "Empty swap-file\n");
1522 error = -EINVAL;
1523 goto bad_swap;
1524 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525
1526 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001527 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 p->flags = SWP_ACTIVE;
1529 nr_swap_pages += nr_good_pages;
1530 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001531
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001532 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins53092a72005-09-03 15:54:34 -07001533 "Priority:%d extents:%d across:%lluk\n",
1534 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1535 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001536
1537 /* insert swap space into swap_list: */
1538 prev = -1;
1539 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1540 if (p->prio >= swap_info[i].prio) {
1541 break;
1542 }
1543 prev = i;
1544 }
1545 p->next = i;
1546 if (prev < 0) {
1547 swap_list.head = swap_list.next = p - swap_info;
1548 } else {
1549 swap_info[prev].next = p - swap_info;
1550 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001551 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 up(&swapon_sem);
1553 error = 0;
1554 goto out;
1555bad_swap:
1556 if (bdev) {
1557 set_blocksize(bdev, p->old_block_size);
1558 bd_release(bdev);
1559 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001560 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07001562 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 swap_map = p->swap_map;
1564 p->swap_file = NULL;
1565 p->swap_map = NULL;
1566 p->flags = 0;
1567 if (!(swap_flags & SWAP_FLAG_PREFER))
1568 ++least_priority;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001569 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570 vfree(swap_map);
1571 if (swap_file)
1572 filp_close(swap_file, NULL);
1573out:
1574 if (page && !IS_ERR(page)) {
1575 kunmap(page);
1576 page_cache_release(page);
1577 }
1578 if (name)
1579 putname(name);
1580 if (did_down) {
1581 if (!error)
1582 inode->i_flags |= S_SWAPFILE;
1583 up(&inode->i_sem);
1584 }
1585 return error;
1586}
1587
1588void si_swapinfo(struct sysinfo *val)
1589{
1590 unsigned int i;
1591 unsigned long nr_to_be_unused = 0;
1592
Hugh Dickins5d337b92005-09-03 15:54:41 -07001593 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001594 for (i = 0; i < nr_swapfiles; i++) {
1595 if (!(swap_info[i].flags & SWP_USED) ||
1596 (swap_info[i].flags & SWP_WRITEOK))
1597 continue;
1598 nr_to_be_unused += swap_info[i].inuse_pages;
1599 }
1600 val->freeswap = nr_swap_pages + nr_to_be_unused;
1601 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001602 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603}
1604
1605/*
1606 * Verify that a swap entry is valid and increment its swap map count.
1607 *
1608 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1609 * "permanent", but will be reclaimed by the next swapoff.
1610 */
1611int swap_duplicate(swp_entry_t entry)
1612{
1613 struct swap_info_struct * p;
1614 unsigned long offset, type;
1615 int result = 0;
1616
1617 type = swp_type(entry);
1618 if (type >= nr_swapfiles)
1619 goto bad_file;
1620 p = type + swap_info;
1621 offset = swp_offset(entry);
1622
Hugh Dickins5d337b92005-09-03 15:54:41 -07001623 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001624 if (offset < p->max && p->swap_map[offset]) {
1625 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1626 p->swap_map[offset]++;
1627 result = 1;
1628 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1629 if (swap_overflow++ < 5)
1630 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1631 p->swap_map[offset] = SWAP_MAP_MAX;
1632 result = 1;
1633 }
1634 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001635 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636out:
1637 return result;
1638
1639bad_file:
1640 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1641 goto out;
1642}
1643
1644struct swap_info_struct *
1645get_swap_info_struct(unsigned type)
1646{
1647 return &swap_info[type];
1648}
1649
1650/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001651 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 * reference on the swaphandle, it doesn't matter if it becomes unused.
1653 */
1654int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1655{
1656 int ret = 0, i = 1 << page_cluster;
1657 unsigned long toff;
1658 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1659
1660 if (!page_cluster) /* no readahead */
1661 return 0;
1662 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1663 if (!toff) /* first page is swap header */
1664 toff++, i--;
1665 *offset = toff;
1666
Hugh Dickins5d337b92005-09-03 15:54:41 -07001667 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668 do {
1669 /* Don't read-ahead past the end of the swap area */
1670 if (toff >= swapdev->max)
1671 break;
1672 /* Don't read in free or bad pages */
1673 if (!swapdev->swap_map[toff])
1674 break;
1675 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1676 break;
1677 toff++;
1678 ret++;
1679 } while (--i);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001680 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681 return ret;
1682}