blob: 80f948a2028bdc2f850741a802e81b4d207f8f6f [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
Linus Torvalds1da177e2005-04-16 15:20:36 -070039static const char Bad_file[] = "Bad swap file entry ";
40static const char Unused_file[] = "Unused swap file entry ";
41static const char Bad_offset[] = "Bad swap offset entry ";
42static const char Unused_offset[] = "Unused swap offset entry ";
43
44struct swap_list_t swap_list = {-1, -1};
45
46struct swap_info_struct swap_info[MAX_SWAPFILES];
47
48static DECLARE_MUTEX(swapon_sem);
49
50/*
51 * We need this because the bdev->unplug_fn can sleep and we cannot
Hugh Dickins5d337b92005-09-03 15:54:41 -070052 * hold swap_lock while calling the unplug_fn. And swap_lock
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 * cannot be turned into a semaphore.
54 */
55static DECLARE_RWSEM(swap_unplug_sem);
56
Linus Torvalds1da177e2005-04-16 15:20:36 -070057void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
58{
59 swp_entry_t entry;
60
61 down_read(&swap_unplug_sem);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070062 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 if (PageSwapCache(page)) {
64 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
65 struct backing_dev_info *bdi;
66
67 /*
68 * If the page is removed from swapcache from under us (with a
69 * racy try_to_unuse/swapoff) we need an additional reference
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070070 * count to avoid reading garbage from page_private(page) above.
71 * If the WARN_ON triggers during a swapoff it maybe the race
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 * condition and it's harmless. However if it triggers without
73 * swapoff it signals a problem.
74 */
75 WARN_ON(page_count(page) <= 1);
76
77 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -070078 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 }
80 up_read(&swap_unplug_sem);
81}
82
Hugh Dickins048c27f2005-09-03 15:54:40 -070083#define SWAPFILE_CLUSTER 256
84#define LATENCY_LIMIT 256
85
Hugh Dickins6eb396d2005-09-03 15:54:35 -070086static inline unsigned long scan_swap_map(struct swap_info_struct *si)
Linus Torvalds1da177e2005-04-16 15:20:36 -070087{
Hugh Dickins7dfad412005-09-03 15:54:38 -070088 unsigned long offset, last_in_cluster;
Hugh Dickins048c27f2005-09-03 15:54:40 -070089 int latency_ration = LATENCY_LIMIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -070090
Hugh Dickins7dfad412005-09-03 15:54:38 -070091 /*
92 * We try to cluster swap pages by allocating them sequentially
93 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
94 * way, however, we resort to first-free allocation, starting
95 * a new cluster. This prevents us from scattering swap pages
96 * all over the entire swap partition, so that we reduce
97 * overall disk seek times between swap pages. -- sct
98 * But we do now try to find an empty cluster. -Andrea
99 */
100
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700101 si->flags += SWP_SCANNING;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700102 if (unlikely(!si->cluster_nr)) {
103 si->cluster_nr = SWAPFILE_CLUSTER - 1;
104 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
105 goto lowest;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700106 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700107
108 offset = si->lowest_bit;
109 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
110
111 /* Locate the first empty (unaligned) cluster */
112 for (; last_in_cluster <= si->highest_bit; offset++) {
113 if (si->swap_map[offset])
114 last_in_cluster = offset + SWAPFILE_CLUSTER;
115 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700116 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700117 si->cluster_next = offset-SWAPFILE_CLUSTER-1;
118 goto cluster;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700120 if (unlikely(--latency_ration < 0)) {
121 cond_resched();
122 latency_ration = LATENCY_LIMIT;
123 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700124 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700125 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700126 goto lowest;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700128
129 si->cluster_nr--;
130cluster:
131 offset = si->cluster_next;
132 if (offset > si->highest_bit)
133lowest: offset = si->lowest_bit;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700134checks: if (!(si->flags & SWP_WRITEOK))
135 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700136 if (!si->highest_bit)
137 goto no_page;
138 if (!si->swap_map[offset]) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700139 if (offset == si->lowest_bit)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140 si->lowest_bit++;
141 if (offset == si->highest_bit)
142 si->highest_bit--;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700143 si->inuse_pages++;
144 if (si->inuse_pages == si->pages) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 si->lowest_bit = si->max;
146 si->highest_bit = 0;
147 }
148 si->swap_map[offset] = 1;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700149 si->cluster_next = offset + 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700150 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 return offset;
152 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700153
Hugh Dickins5d337b92005-09-03 15:54:41 -0700154 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700155 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700156 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700157 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700158 goto checks;
159 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700160 if (unlikely(--latency_ration < 0)) {
161 cond_resched();
162 latency_ration = LATENCY_LIMIT;
163 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700164 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700165 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700166 goto lowest;
167
168no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700169 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 return 0;
171}
172
173swp_entry_t get_swap_page(void)
174{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700175 struct swap_info_struct *si;
176 pgoff_t offset;
177 int type, next;
178 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179
Hugh Dickins5d337b92005-09-03 15:54:41 -0700180 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700182 goto noswap;
183 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700185 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
186 si = swap_info + type;
187 next = si->next;
188 if (next < 0 ||
189 (!wrapped && si->prio != swap_info[next].prio)) {
190 next = swap_list.head;
191 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700193
194 if (!si->highest_bit)
195 continue;
196 if (!(si->flags & SWP_WRITEOK))
197 continue;
198
199 swap_list.next = next;
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700200 offset = scan_swap_map(si);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700201 if (offset) {
202 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700203 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700204 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700205 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700207
208 nr_swap_pages++;
209noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700210 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700211 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212}
213
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800214swp_entry_t get_swap_page_of_type(int type)
215{
216 struct swap_info_struct *si;
217 pgoff_t offset;
218
219 spin_lock(&swap_lock);
220 si = swap_info + type;
221 if (si->flags & SWP_WRITEOK) {
222 nr_swap_pages--;
223 offset = scan_swap_map(si);
224 if (offset) {
225 spin_unlock(&swap_lock);
226 return swp_entry(type, offset);
227 }
228 nr_swap_pages++;
229 }
230 spin_unlock(&swap_lock);
231 return (swp_entry_t) {0};
232}
233
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234static struct swap_info_struct * swap_info_get(swp_entry_t entry)
235{
236 struct swap_info_struct * p;
237 unsigned long offset, type;
238
239 if (!entry.val)
240 goto out;
241 type = swp_type(entry);
242 if (type >= nr_swapfiles)
243 goto bad_nofile;
244 p = & swap_info[type];
245 if (!(p->flags & SWP_USED))
246 goto bad_device;
247 offset = swp_offset(entry);
248 if (offset >= p->max)
249 goto bad_offset;
250 if (!p->swap_map[offset])
251 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700252 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 return p;
254
255bad_free:
256 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
257 goto out;
258bad_offset:
259 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
260 goto out;
261bad_device:
262 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
263 goto out;
264bad_nofile:
265 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
266out:
267 return NULL;
268}
269
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
271{
272 int count = p->swap_map[offset];
273
274 if (count < SWAP_MAP_MAX) {
275 count--;
276 p->swap_map[offset] = count;
277 if (!count) {
278 if (offset < p->lowest_bit)
279 p->lowest_bit = offset;
280 if (offset > p->highest_bit)
281 p->highest_bit = offset;
Hugh Dickins89d09a22005-09-03 15:54:36 -0700282 if (p->prio > swap_info[swap_list.next].prio)
283 swap_list.next = p - swap_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 nr_swap_pages++;
285 p->inuse_pages--;
286 }
287 }
288 return count;
289}
290
291/*
292 * Caller has made sure that the swapdevice corresponding to entry
293 * is still around or has not been recycled.
294 */
295void swap_free(swp_entry_t entry)
296{
297 struct swap_info_struct * p;
298
299 p = swap_info_get(entry);
300 if (p) {
301 swap_entry_free(p, swp_offset(entry));
Hugh Dickins5d337b92005-09-03 15:54:41 -0700302 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 }
304}
305
306/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700307 * How many references to page are currently swapped out?
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700309static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700311 int count = 0;
312 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 swp_entry_t entry;
314
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700315 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 p = swap_info_get(entry);
317 if (p) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700318 /* Subtract the 1 for the swap cache itself */
319 count = p->swap_map[swp_offset(entry)] - 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700320 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700321 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700322 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323}
324
325/*
326 * We can use this swap cache entry directly
327 * if there are no other references to it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 */
329int can_share_swap_page(struct page *page)
330{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700331 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700333 BUG_ON(!PageLocked(page));
334 count = page_mapcount(page);
335 if (count <= 1 && PageSwapCache(page))
336 count += page_swapcount(page);
337 return count == 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338}
339
340/*
341 * Work out if there are any other processes sharing this
342 * swap cache page. Free it if you can. Return success.
343 */
344int remove_exclusive_swap_page(struct page *page)
345{
346 int retval;
347 struct swap_info_struct * p;
348 swp_entry_t entry;
349
350 BUG_ON(PagePrivate(page));
351 BUG_ON(!PageLocked(page));
352
353 if (!PageSwapCache(page))
354 return 0;
355 if (PageWriteback(page))
356 return 0;
357 if (page_count(page) != 2) /* 2: us + cache */
358 return 0;
359
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700360 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 p = swap_info_get(entry);
362 if (!p)
363 return 0;
364
365 /* Is the only swap cache user the cache itself? */
366 retval = 0;
367 if (p->swap_map[swp_offset(entry)] == 1) {
368 /* Recheck the page count with the swapcache lock held.. */
369 write_lock_irq(&swapper_space.tree_lock);
370 if ((page_count(page) == 2) && !PageWriteback(page)) {
371 __delete_from_swap_cache(page);
372 SetPageDirty(page);
373 retval = 1;
374 }
375 write_unlock_irq(&swapper_space.tree_lock);
376 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700377 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378
379 if (retval) {
380 swap_free(entry);
381 page_cache_release(page);
382 }
383
384 return retval;
385}
386
387/*
388 * Free the swap entry like above, but also try to
389 * free the page cache entry if it is the last user.
390 */
391void free_swap_and_cache(swp_entry_t entry)
392{
393 struct swap_info_struct * p;
394 struct page *page = NULL;
395
396 p = swap_info_get(entry);
397 if (p) {
398 if (swap_entry_free(p, swp_offset(entry)) == 1)
399 page = find_trylock_page(&swapper_space, entry.val);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700400 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 }
402 if (page) {
403 int one_user;
404
405 BUG_ON(PagePrivate(page));
406 page_cache_get(page);
407 one_user = (page_count(page) == 2);
408 /* Only cache user (+us), or swap space full? Free it! */
409 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
410 delete_from_swap_cache(page);
411 SetPageDirty(page);
412 }
413 unlock_page(page);
414 page_cache_release(page);
415 }
416}
417
418/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700419 * No need to decide whether this PTE shares the swap entry with others,
420 * just let do_wp_page work it out if a write is requested later - to
421 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 */
423static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
424 unsigned long addr, swp_entry_t entry, struct page *page)
425{
Hugh Dickins42946212005-10-29 18:16:05 -0700426 inc_mm_counter(vma->vm_mm, anon_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 get_page(page);
428 set_pte_at(vma->vm_mm, addr, pte,
429 pte_mkold(mk_pte(page, vma->vm_page_prot)));
430 page_add_anon_rmap(page, vma, addr);
431 swap_free(entry);
432 /*
433 * Move the page to the active list so it is not
434 * immediately swapped out again after swapon.
435 */
436 activate_page(page);
437}
438
439static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
440 unsigned long addr, unsigned long end,
441 swp_entry_t entry, struct page *page)
442{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700444 pte_t *pte;
445 spinlock_t *ptl;
446 int found = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447
Hugh Dickins705e87c2005-10-29 18:16:27 -0700448 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 do {
450 /*
451 * swapoff spends a _lot_ of time in this loop!
452 * Test inline before going to call unuse_pte.
453 */
454 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins705e87c2005-10-29 18:16:27 -0700455 unuse_pte(vma, pte++, addr, entry, page);
456 found = 1;
457 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 }
459 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700460 pte_unmap_unlock(pte - 1, ptl);
461 return found;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462}
463
464static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
465 unsigned long addr, unsigned long end,
466 swp_entry_t entry, struct page *page)
467{
468 pmd_t *pmd;
469 unsigned long next;
470
471 pmd = pmd_offset(pud, addr);
472 do {
473 next = pmd_addr_end(addr, end);
474 if (pmd_none_or_clear_bad(pmd))
475 continue;
476 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
477 return 1;
478 } while (pmd++, addr = next, addr != end);
479 return 0;
480}
481
482static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
483 unsigned long addr, unsigned long end,
484 swp_entry_t entry, struct page *page)
485{
486 pud_t *pud;
487 unsigned long next;
488
489 pud = pud_offset(pgd, addr);
490 do {
491 next = pud_addr_end(addr, end);
492 if (pud_none_or_clear_bad(pud))
493 continue;
494 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
495 return 1;
496 } while (pud++, addr = next, addr != end);
497 return 0;
498}
499
500static int unuse_vma(struct vm_area_struct *vma,
501 swp_entry_t entry, struct page *page)
502{
503 pgd_t *pgd;
504 unsigned long addr, end, next;
505
506 if (page->mapping) {
507 addr = page_address_in_vma(page, vma);
508 if (addr == -EFAULT)
509 return 0;
510 else
511 end = addr + PAGE_SIZE;
512 } else {
513 addr = vma->vm_start;
514 end = vma->vm_end;
515 }
516
517 pgd = pgd_offset(vma->vm_mm, addr);
518 do {
519 next = pgd_addr_end(addr, end);
520 if (pgd_none_or_clear_bad(pgd))
521 continue;
522 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
523 return 1;
524 } while (pgd++, addr = next, addr != end);
525 return 0;
526}
527
528static int unuse_mm(struct mm_struct *mm,
529 swp_entry_t entry, struct page *page)
530{
531 struct vm_area_struct *vma;
532
533 if (!down_read_trylock(&mm->mmap_sem)) {
534 /*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700535 * Activate page so shrink_cache is unlikely to unmap its
536 * ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700538 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 unlock_page(page);
540 down_read(&mm->mmap_sem);
541 lock_page(page);
542 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 for (vma = mm->mmap; vma; vma = vma->vm_next) {
544 if (vma->anon_vma && unuse_vma(vma, entry, page))
545 break;
546 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547 up_read(&mm->mmap_sem);
548 /*
549 * Currently unuse_mm cannot fail, but leave error handling
550 * at call sites for now, since we change it from time to time.
551 */
552 return 0;
553}
554
555/*
556 * Scan swap_map from current position to next entry still in use.
557 * Recycle to start on reaching the end, returning 0 when empty.
558 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700559static unsigned int find_next_to_unuse(struct swap_info_struct *si,
560 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700562 unsigned int max = si->max;
563 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 int count;
565
566 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700567 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 * for whether an entry is in use, not modifying it; false
569 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -0700570 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 */
572 for (;;) {
573 if (++i >= max) {
574 if (!prev) {
575 i = 0;
576 break;
577 }
578 /*
579 * No entries in use at top of swap_map,
580 * loop back to start and recheck there.
581 */
582 max = prev + 1;
583 prev = 0;
584 i = 1;
585 }
586 count = si->swap_map[i];
587 if (count && count != SWAP_MAP_BAD)
588 break;
589 }
590 return i;
591}
592
593/*
594 * We completely avoid races by reading each swap page in advance,
595 * and then search for the process using it. All the necessary
596 * page table adjustments can then be made atomically.
597 */
598static int try_to_unuse(unsigned int type)
599{
600 struct swap_info_struct * si = &swap_info[type];
601 struct mm_struct *start_mm;
602 unsigned short *swap_map;
603 unsigned short swcount;
604 struct page *page;
605 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700606 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 int retval = 0;
608 int reset_overflow = 0;
609 int shmem;
610
611 /*
612 * When searching mms for an entry, a good strategy is to
613 * start at the first mm we freed the previous entry from
614 * (though actually we don't notice whether we or coincidence
615 * freed the entry). Initialize this start_mm with a hold.
616 *
617 * A simpler strategy would be to start at the last mm we
618 * freed the previous entry from; but that would take less
619 * advantage of mmlist ordering, which clusters forked mms
620 * together, child after parent. If we race with dup_mmap(), we
621 * prefer to resolve parent before child, lest we miss entries
622 * duplicated after we scanned child: using last mm would invert
623 * that. Though it's only a serious concern when an overflowed
624 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
625 */
626 start_mm = &init_mm;
627 atomic_inc(&init_mm.mm_users);
628
629 /*
630 * Keep on scanning until all entries have gone. Usually,
631 * one pass through swap_map is enough, but not necessarily:
632 * there are races when an instance of an entry might be missed.
633 */
634 while ((i = find_next_to_unuse(si, i)) != 0) {
635 if (signal_pending(current)) {
636 retval = -EINTR;
637 break;
638 }
639
640 /*
641 * Get a page for the entry, using the existing swap
642 * cache page if there is one. Otherwise, get a clean
643 * page and read the swap into it.
644 */
645 swap_map = &si->swap_map[i];
646 entry = swp_entry(type, i);
647 page = read_swap_cache_async(entry, NULL, 0);
648 if (!page) {
649 /*
650 * Either swap_duplicate() failed because entry
651 * has been freed independently, and will not be
652 * reused since sys_swapoff() already disabled
653 * allocation from here, or alloc_page() failed.
654 */
655 if (!*swap_map)
656 continue;
657 retval = -ENOMEM;
658 break;
659 }
660
661 /*
662 * Don't hold on to start_mm if it looks like exiting.
663 */
664 if (atomic_read(&start_mm->mm_users) == 1) {
665 mmput(start_mm);
666 start_mm = &init_mm;
667 atomic_inc(&init_mm.mm_users);
668 }
669
670 /*
671 * Wait for and lock page. When do_swap_page races with
672 * try_to_unuse, do_swap_page can handle the fault much
673 * faster than try_to_unuse can locate the entry. This
674 * apparently redundant "wait_on_page_locked" lets try_to_unuse
675 * defer to do_swap_page in such a case - in some tests,
676 * do_swap_page and try_to_unuse repeatedly compete.
677 */
678 wait_on_page_locked(page);
679 wait_on_page_writeback(page);
680 lock_page(page);
681 wait_on_page_writeback(page);
682
683 /*
684 * Remove all references to entry.
685 * Whenever we reach init_mm, there's no address space
686 * to search, but use it as a reminder to search shmem.
687 */
688 shmem = 0;
689 swcount = *swap_map;
690 if (swcount > 1) {
691 if (start_mm == &init_mm)
692 shmem = shmem_unuse(entry, page);
693 else
694 retval = unuse_mm(start_mm, entry, page);
695 }
696 if (*swap_map > 1) {
697 int set_start_mm = (*swap_map >= swcount);
698 struct list_head *p = &start_mm->mmlist;
699 struct mm_struct *new_start_mm = start_mm;
700 struct mm_struct *prev_mm = start_mm;
701 struct mm_struct *mm;
702
703 atomic_inc(&new_start_mm->mm_users);
704 atomic_inc(&prev_mm->mm_users);
705 spin_lock(&mmlist_lock);
706 while (*swap_map > 1 && !retval &&
707 (p = p->next) != &start_mm->mmlist) {
708 mm = list_entry(p, struct mm_struct, mmlist);
709 if (atomic_inc_return(&mm->mm_users) == 1) {
710 atomic_dec(&mm->mm_users);
711 continue;
712 }
713 spin_unlock(&mmlist_lock);
714 mmput(prev_mm);
715 prev_mm = mm;
716
717 cond_resched();
718
719 swcount = *swap_map;
720 if (swcount <= 1)
721 ;
722 else if (mm == &init_mm) {
723 set_start_mm = 1;
724 shmem = shmem_unuse(entry, page);
725 } else
726 retval = unuse_mm(mm, entry, page);
727 if (set_start_mm && *swap_map < swcount) {
728 mmput(new_start_mm);
729 atomic_inc(&mm->mm_users);
730 new_start_mm = mm;
731 set_start_mm = 0;
732 }
733 spin_lock(&mmlist_lock);
734 }
735 spin_unlock(&mmlist_lock);
736 mmput(prev_mm);
737 mmput(start_mm);
738 start_mm = new_start_mm;
739 }
740 if (retval) {
741 unlock_page(page);
742 page_cache_release(page);
743 break;
744 }
745
746 /*
747 * How could swap count reach 0x7fff when the maximum
748 * pid is 0x7fff, and there's no way to repeat a swap
749 * page within an mm (except in shmem, where it's the
750 * shared object which takes the reference count)?
751 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
752 *
753 * If that's wrong, then we should worry more about
754 * exit_mmap() and do_munmap() cases described above:
755 * we might be resetting SWAP_MAP_MAX too early here.
756 * We know "Undead"s can happen, they're okay, so don't
757 * report them; but do report if we reset SWAP_MAP_MAX.
758 */
759 if (*swap_map == SWAP_MAP_MAX) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700760 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 *swap_map = 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700762 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700763 reset_overflow = 1;
764 }
765
766 /*
767 * If a reference remains (rare), we would like to leave
768 * the page in the swap cache; but try_to_unmap could
769 * then re-duplicate the entry once we drop page lock,
770 * so we might loop indefinitely; also, that page could
771 * not be swapped out to other storage meanwhile. So:
772 * delete from cache even if there's another reference,
773 * after ensuring that the data has been saved to disk -
774 * since if the reference remains (rarer), it will be
775 * read from disk into another page. Splitting into two
776 * pages would be incorrect if swap supported "shared
777 * private" pages, but they are handled by tmpfs files.
778 *
779 * Note shmem_unuse already deleted a swappage from
780 * the swap cache, unless the move to filepage failed:
781 * in which case it left swappage in cache, lowered its
782 * swap count to pass quickly through the loops above,
783 * and now we must reincrement count to try again later.
784 */
785 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
786 struct writeback_control wbc = {
787 .sync_mode = WB_SYNC_NONE,
788 };
789
790 swap_writepage(page, &wbc);
791 lock_page(page);
792 wait_on_page_writeback(page);
793 }
794 if (PageSwapCache(page)) {
795 if (shmem)
796 swap_duplicate(entry);
797 else
798 delete_from_swap_cache(page);
799 }
800
801 /*
802 * So we could skip searching mms once swap count went
803 * to 1, we did not mark any present ptes as dirty: must
804 * mark page dirty so shrink_list will preserve it.
805 */
806 SetPageDirty(page);
807 unlock_page(page);
808 page_cache_release(page);
809
810 /*
811 * Make sure that we aren't completely killing
812 * interactive performance.
813 */
814 cond_resched();
815 }
816
817 mmput(start_mm);
818 if (reset_overflow) {
819 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
820 swap_overflow = 0;
821 }
822 return retval;
823}
824
825/*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700826 * After a successful try_to_unuse, if no swap is now in use, we know
827 * we can empty the mmlist. swap_lock must be held on entry and exit.
828 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 * added to the mmlist just after page_duplicate - before would be racy.
830 */
831static void drain_mmlist(void)
832{
833 struct list_head *p, *next;
834 unsigned int i;
835
836 for (i = 0; i < nr_swapfiles; i++)
837 if (swap_info[i].inuse_pages)
838 return;
839 spin_lock(&mmlist_lock);
840 list_for_each_safe(p, next, &init_mm.mmlist)
841 list_del_init(p);
842 spin_unlock(&mmlist_lock);
843}
844
845/*
846 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
847 * corresponds to page offset `offset'.
848 */
849sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
850{
851 struct swap_extent *se = sis->curr_swap_extent;
852 struct swap_extent *start_se = se;
853
854 for ( ; ; ) {
855 struct list_head *lh;
856
857 if (se->start_page <= offset &&
858 offset < (se->start_page + se->nr_pages)) {
859 return se->start_block + (offset - se->start_page);
860 }
Hugh Dickins11d31882005-09-03 15:54:34 -0700861 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700862 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -0700863 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 se = list_entry(lh, struct swap_extent, list);
865 sis->curr_swap_extent = se;
866 BUG_ON(se == start_se); /* It *must* be present */
867 }
868}
869
870/*
871 * Free all of a swapdev's extent information
872 */
873static void destroy_swap_extents(struct swap_info_struct *sis)
874{
875 while (!list_empty(&sis->extent_list)) {
876 struct swap_extent *se;
877
878 se = list_entry(sis->extent_list.next,
879 struct swap_extent, list);
880 list_del(&se->list);
881 kfree(se);
882 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883}
884
885/*
886 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -0700887 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 *
Hugh Dickins11d31882005-09-03 15:54:34 -0700889 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 */
891static int
892add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
893 unsigned long nr_pages, sector_t start_block)
894{
895 struct swap_extent *se;
896 struct swap_extent *new_se;
897 struct list_head *lh;
898
Hugh Dickins11d31882005-09-03 15:54:34 -0700899 lh = sis->extent_list.prev; /* The highest page extent */
900 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -0700902 BUG_ON(se->start_page + se->nr_pages != start_page);
903 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 /* Merge it */
905 se->nr_pages += nr_pages;
906 return 0;
907 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 }
909
910 /*
911 * No merge. Insert a new extent, preserving ordering.
912 */
913 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
914 if (new_se == NULL)
915 return -ENOMEM;
916 new_se->start_page = start_page;
917 new_se->nr_pages = nr_pages;
918 new_se->start_block = start_block;
919
Hugh Dickins11d31882005-09-03 15:54:34 -0700920 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -0700921 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922}
923
924/*
925 * A `swap extent' is a simple thing which maps a contiguous range of pages
926 * onto a contiguous range of disk blocks. An ordered list of swap extents
927 * is built at swapon time and is then used at swap_writepage/swap_readpage
928 * time for locating where on disk a page belongs.
929 *
930 * If the swapfile is an S_ISBLK block device, a single extent is installed.
931 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
932 * swap files identically.
933 *
934 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
935 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
936 * swapfiles are handled *identically* after swapon time.
937 *
938 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
939 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
940 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
941 * requirements, they are simply tossed out - we will never use those blocks
942 * for swapping.
943 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -0700944 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
946 * which will scribble on the fs.
947 *
948 * The amount of disk space which a single swap extent represents varies.
949 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
950 * extents in the list. To avoid much list walking, we cache the previous
951 * search location in `curr_swap_extent', and start new searches from there.
952 * This is extremely effective. The average number of iterations in
953 * map_swap_page() has been measured at about 0.3 per page. - akpm.
954 */
Hugh Dickins53092a72005-09-03 15:54:34 -0700955static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956{
957 struct inode *inode;
958 unsigned blocks_per_page;
959 unsigned long page_no;
960 unsigned blkbits;
961 sector_t probe_block;
962 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -0700963 sector_t lowest_block = -1;
964 sector_t highest_block = 0;
965 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966 int ret;
967
968 inode = sis->swap_file->f_mapping->host;
969 if (S_ISBLK(inode->i_mode)) {
970 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -0700971 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972 goto done;
973 }
974
975 blkbits = inode->i_blkbits;
976 blocks_per_page = PAGE_SIZE >> blkbits;
977
978 /*
979 * Map all the blocks into the extent list. This code doesn't try
980 * to be very smart.
981 */
982 probe_block = 0;
983 page_no = 0;
984 last_block = i_size_read(inode) >> blkbits;
985 while ((probe_block + blocks_per_page) <= last_block &&
986 page_no < sis->max) {
987 unsigned block_in_page;
988 sector_t first_block;
989
990 first_block = bmap(inode, probe_block);
991 if (first_block == 0)
992 goto bad_bmap;
993
994 /*
995 * It must be PAGE_SIZE aligned on-disk
996 */
997 if (first_block & (blocks_per_page - 1)) {
998 probe_block++;
999 goto reprobe;
1000 }
1001
1002 for (block_in_page = 1; block_in_page < blocks_per_page;
1003 block_in_page++) {
1004 sector_t block;
1005
1006 block = bmap(inode, probe_block + block_in_page);
1007 if (block == 0)
1008 goto bad_bmap;
1009 if (block != first_block + block_in_page) {
1010 /* Discontiguity */
1011 probe_block++;
1012 goto reprobe;
1013 }
1014 }
1015
Hugh Dickins53092a72005-09-03 15:54:34 -07001016 first_block >>= (PAGE_SHIFT - blkbits);
1017 if (page_no) { /* exclude the header page */
1018 if (first_block < lowest_block)
1019 lowest_block = first_block;
1020 if (first_block > highest_block)
1021 highest_block = first_block;
1022 }
1023
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 /*
1025 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1026 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001027 ret = add_swap_extent(sis, page_no, 1, first_block);
1028 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001030 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001031 page_no++;
1032 probe_block += blocks_per_page;
1033reprobe:
1034 continue;
1035 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001036 ret = nr_extents;
1037 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001039 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001041 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042 sis->highest_bit = page_no - 1;
1043done:
1044 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1045 struct swap_extent, list);
1046 goto out;
1047bad_bmap:
1048 printk(KERN_ERR "swapon: swapfile has holes\n");
1049 ret = -EINVAL;
1050out:
1051 return ret;
1052}
1053
1054#if 0 /* We don't need this yet */
1055#include <linux/backing-dev.h>
1056int page_queue_congested(struct page *page)
1057{
1058 struct backing_dev_info *bdi;
1059
1060 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1061
1062 if (PageSwapCache(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -07001063 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064 struct swap_info_struct *sis;
1065
1066 sis = get_swap_info_struct(swp_type(entry));
1067 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1068 } else
1069 bdi = page->mapping->backing_dev_info;
1070 return bdi_write_congested(bdi);
1071}
1072#endif
1073
1074asmlinkage long sys_swapoff(const char __user * specialfile)
1075{
1076 struct swap_info_struct * p = NULL;
1077 unsigned short *swap_map;
1078 struct file *swap_file, *victim;
1079 struct address_space *mapping;
1080 struct inode *inode;
1081 char * pathname;
1082 int i, type, prev;
1083 int err;
1084
1085 if (!capable(CAP_SYS_ADMIN))
1086 return -EPERM;
1087
1088 pathname = getname(specialfile);
1089 err = PTR_ERR(pathname);
1090 if (IS_ERR(pathname))
1091 goto out;
1092
1093 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1094 putname(pathname);
1095 err = PTR_ERR(victim);
1096 if (IS_ERR(victim))
1097 goto out;
1098
1099 mapping = victim->f_mapping;
1100 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001101 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1103 p = swap_info + type;
1104 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1105 if (p->swap_file->f_mapping == mapping)
1106 break;
1107 }
1108 prev = type;
1109 }
1110 if (type < 0) {
1111 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001112 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113 goto out_dput;
1114 }
1115 if (!security_vm_enough_memory(p->pages))
1116 vm_unacct_memory(p->pages);
1117 else {
1118 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001119 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001120 goto out_dput;
1121 }
1122 if (prev < 0) {
1123 swap_list.head = p->next;
1124 } else {
1125 swap_info[prev].next = p->next;
1126 }
1127 if (type == swap_list.next) {
1128 /* just pick something that's safe... */
1129 swap_list.next = swap_list.head;
1130 }
1131 nr_swap_pages -= p->pages;
1132 total_swap_pages -= p->pages;
1133 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001134 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001135
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136 current->flags |= PF_SWAPOFF;
1137 err = try_to_unuse(type);
1138 current->flags &= ~PF_SWAPOFF;
1139
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140 if (err) {
1141 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001142 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1144 if (p->prio >= swap_info[i].prio)
1145 break;
1146 p->next = i;
1147 if (prev < 0)
1148 swap_list.head = swap_list.next = p - swap_info;
1149 else
1150 swap_info[prev].next = p - swap_info;
1151 nr_swap_pages += p->pages;
1152 total_swap_pages += p->pages;
1153 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001154 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155 goto out_dput;
1156 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001157
1158 /* wait for any unplug function to finish */
1159 down_write(&swap_unplug_sem);
1160 up_write(&swap_unplug_sem);
1161
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001162 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001164 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001166
1167 /* wait for anyone still in scan_swap_map */
1168 p->highest_bit = 0; /* cuts scans short */
1169 while (p->flags >= SWP_SCANNING) {
1170 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001171 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001172 spin_lock(&swap_lock);
1173 }
1174
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 swap_file = p->swap_file;
1176 p->swap_file = NULL;
1177 p->max = 0;
1178 swap_map = p->swap_map;
1179 p->swap_map = NULL;
1180 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001181 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 up(&swapon_sem);
1183 vfree(swap_map);
1184 inode = mapping->host;
1185 if (S_ISBLK(inode->i_mode)) {
1186 struct block_device *bdev = I_BDEV(inode);
1187 set_blocksize(bdev, p->old_block_size);
1188 bd_release(bdev);
1189 } else {
1190 down(&inode->i_sem);
1191 inode->i_flags &= ~S_SWAPFILE;
1192 up(&inode->i_sem);
1193 }
1194 filp_close(swap_file, NULL);
1195 err = 0;
1196
1197out_dput:
1198 filp_close(victim, NULL);
1199out:
1200 return err;
1201}
1202
1203#ifdef CONFIG_PROC_FS
1204/* iterator */
1205static void *swap_start(struct seq_file *swap, loff_t *pos)
1206{
1207 struct swap_info_struct *ptr = swap_info;
1208 int i;
1209 loff_t l = *pos;
1210
1211 down(&swapon_sem);
1212
1213 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1214 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1215 continue;
1216 if (!l--)
1217 return ptr;
1218 }
1219
1220 return NULL;
1221}
1222
1223static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1224{
1225 struct swap_info_struct *ptr = v;
1226 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1227
1228 for (++ptr; ptr < endptr; ptr++) {
1229 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1230 continue;
1231 ++*pos;
1232 return ptr;
1233 }
1234
1235 return NULL;
1236}
1237
1238static void swap_stop(struct seq_file *swap, void *v)
1239{
1240 up(&swapon_sem);
1241}
1242
1243static int swap_show(struct seq_file *swap, void *v)
1244{
1245 struct swap_info_struct *ptr = v;
1246 struct file *file;
1247 int len;
1248
1249 if (v == swap_info)
1250 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1251
1252 file = ptr->swap_file;
1253 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001254 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 len < 40 ? 40 - len : 1, " ",
1256 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1257 "partition" : "file\t",
1258 ptr->pages << (PAGE_SHIFT - 10),
1259 ptr->inuse_pages << (PAGE_SHIFT - 10),
1260 ptr->prio);
1261 return 0;
1262}
1263
1264static struct seq_operations swaps_op = {
1265 .start = swap_start,
1266 .next = swap_next,
1267 .stop = swap_stop,
1268 .show = swap_show
1269};
1270
1271static int swaps_open(struct inode *inode, struct file *file)
1272{
1273 return seq_open(file, &swaps_op);
1274}
1275
1276static struct file_operations proc_swaps_operations = {
1277 .open = swaps_open,
1278 .read = seq_read,
1279 .llseek = seq_lseek,
1280 .release = seq_release,
1281};
1282
1283static int __init procswaps_init(void)
1284{
1285 struct proc_dir_entry *entry;
1286
1287 entry = create_proc_entry("swaps", 0, NULL);
1288 if (entry)
1289 entry->proc_fops = &proc_swaps_operations;
1290 return 0;
1291}
1292__initcall(procswaps_init);
1293#endif /* CONFIG_PROC_FS */
1294
1295/*
1296 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1297 *
1298 * The swapon system call
1299 */
1300asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1301{
1302 struct swap_info_struct * p;
1303 char *name = NULL;
1304 struct block_device *bdev = NULL;
1305 struct file *swap_file = NULL;
1306 struct address_space *mapping;
1307 unsigned int type;
1308 int i, prev;
1309 int error;
1310 static int least_priority;
1311 union swap_header *swap_header = NULL;
1312 int swap_header_version;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001313 unsigned int nr_good_pages = 0;
1314 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001315 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 unsigned long maxpages = 1;
1317 int swapfilesize;
1318 unsigned short *swap_map;
1319 struct page *page = NULL;
1320 struct inode *inode = NULL;
1321 int did_down = 0;
1322
1323 if (!capable(CAP_SYS_ADMIN))
1324 return -EPERM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001325 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 p = swap_info;
1327 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1328 if (!(p->flags & SWP_USED))
1329 break;
1330 error = -EPERM;
1331 /*
1332 * Test if adding another swap device is possible. There are
1333 * two limiting factors: 1) the number of bits for the swap
1334 * type swp_entry_t definition and 2) the number of bits for
1335 * the swap type in the swap ptes as defined by the different
1336 * architectures. To honor both limitations a swap entry
1337 * with swap offset 0 and swap type ~0UL is created, encoded
1338 * to a swap pte, decoded to a swp_entry_t again and finally
1339 * the swap type part is extracted. This will mask all bits
1340 * from the initial ~0UL that can't be encoded in either the
1341 * swp_entry_t or the architecture definition of a swap pte.
1342 */
1343 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001344 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 goto out;
1346 }
1347 if (type >= nr_swapfiles)
1348 nr_swapfiles = type+1;
1349 INIT_LIST_HEAD(&p->extent_list);
1350 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 p->swap_file = NULL;
1352 p->old_block_size = 0;
1353 p->swap_map = NULL;
1354 p->lowest_bit = 0;
1355 p->highest_bit = 0;
1356 p->cluster_nr = 0;
1357 p->inuse_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358 p->next = -1;
1359 if (swap_flags & SWAP_FLAG_PREFER) {
1360 p->prio =
1361 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1362 } else {
1363 p->prio = --least_priority;
1364 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001365 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366 name = getname(specialfile);
1367 error = PTR_ERR(name);
1368 if (IS_ERR(name)) {
1369 name = NULL;
1370 goto bad_swap_2;
1371 }
1372 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1373 error = PTR_ERR(swap_file);
1374 if (IS_ERR(swap_file)) {
1375 swap_file = NULL;
1376 goto bad_swap_2;
1377 }
1378
1379 p->swap_file = swap_file;
1380 mapping = swap_file->f_mapping;
1381 inode = mapping->host;
1382
1383 error = -EBUSY;
1384 for (i = 0; i < nr_swapfiles; i++) {
1385 struct swap_info_struct *q = &swap_info[i];
1386
1387 if (i == type || !q->swap_file)
1388 continue;
1389 if (mapping == q->swap_file->f_mapping)
1390 goto bad_swap;
1391 }
1392
1393 error = -EINVAL;
1394 if (S_ISBLK(inode->i_mode)) {
1395 bdev = I_BDEV(inode);
1396 error = bd_claim(bdev, sys_swapon);
1397 if (error < 0) {
1398 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001399 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001400 goto bad_swap;
1401 }
1402 p->old_block_size = block_size(bdev);
1403 error = set_blocksize(bdev, PAGE_SIZE);
1404 if (error < 0)
1405 goto bad_swap;
1406 p->bdev = bdev;
1407 } else if (S_ISREG(inode->i_mode)) {
1408 p->bdev = inode->i_sb->s_bdev;
1409 down(&inode->i_sem);
1410 did_down = 1;
1411 if (IS_SWAPFILE(inode)) {
1412 error = -EBUSY;
1413 goto bad_swap;
1414 }
1415 } else {
1416 goto bad_swap;
1417 }
1418
1419 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1420
1421 /*
1422 * Read the swap header.
1423 */
1424 if (!mapping->a_ops->readpage) {
1425 error = -EINVAL;
1426 goto bad_swap;
1427 }
1428 page = read_cache_page(mapping, 0,
1429 (filler_t *)mapping->a_ops->readpage, swap_file);
1430 if (IS_ERR(page)) {
1431 error = PTR_ERR(page);
1432 goto bad_swap;
1433 }
1434 wait_on_page_locked(page);
1435 if (!PageUptodate(page))
1436 goto bad_swap;
1437 kmap(page);
1438 swap_header = page_address(page);
1439
1440 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1441 swap_header_version = 1;
1442 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1443 swap_header_version = 2;
1444 else {
1445 printk("Unable to find swap-space signature\n");
1446 error = -EINVAL;
1447 goto bad_swap;
1448 }
1449
1450 switch (swap_header_version) {
1451 case 1:
1452 printk(KERN_ERR "version 0 swap is no longer supported. "
1453 "Use mkswap -v1 %s\n", name);
1454 error = -EINVAL;
1455 goto bad_swap;
1456 case 2:
1457 /* Check the swap header's sub-version and the size of
1458 the swap file and bad block lists */
1459 if (swap_header->info.version != 1) {
1460 printk(KERN_WARNING
1461 "Unable to handle swap header version %d\n",
1462 swap_header->info.version);
1463 error = -EINVAL;
1464 goto bad_swap;
1465 }
1466
1467 p->lowest_bit = 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001468 p->cluster_next = 1;
1469
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 /*
1471 * Find out how many pages are allowed for a single swap
1472 * device. There are two limiting factors: 1) the number of
1473 * bits for the swap offset in the swp_entry_t type and
1474 * 2) the number of bits in the a swap pte as defined by
1475 * the different architectures. In order to find the
1476 * largest possible bit mask a swap entry with swap type 0
1477 * and swap offset ~0UL is created, encoded to a swap pte,
1478 * decoded to a swp_entry_t again and finally the swap
1479 * offset is extracted. This will mask all the bits from
1480 * the initial ~0UL mask that can't be encoded in either
1481 * the swp_entry_t or the architecture definition of a
1482 * swap pte.
1483 */
1484 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1485 if (maxpages > swap_header->info.last_page)
1486 maxpages = swap_header->info.last_page;
1487 p->highest_bit = maxpages - 1;
1488
1489 error = -EINVAL;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001490 if (!maxpages)
1491 goto bad_swap;
1492 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1493 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1495 goto bad_swap;
Tobias Klausercd105df2006-01-08 01:00:59 -08001496
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 /* OK, set up the swap map and apply the bad block list */
1498 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1499 error = -ENOMEM;
1500 goto bad_swap;
1501 }
1502
1503 error = 0;
1504 memset(p->swap_map, 0, maxpages * sizeof(short));
Tobias Klausercd105df2006-01-08 01:00:59 -08001505 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1506 int page_nr = swap_header->info.badpages[i];
1507 if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 error = -EINVAL;
1509 else
Tobias Klausercd105df2006-01-08 01:00:59 -08001510 p->swap_map[page_nr] = SWAP_MAP_BAD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511 }
1512 nr_good_pages = swap_header->info.last_page -
1513 swap_header->info.nr_badpages -
1514 1 /* header page */;
Tobias Klausercd105df2006-01-08 01:00:59 -08001515 if (error)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001516 goto bad_swap;
1517 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 if (swapfilesize && maxpages > swapfilesize) {
1520 printk(KERN_WARNING
1521 "Swap area shorter than signature indicates\n");
1522 error = -EINVAL;
1523 goto bad_swap;
1524 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001525 if (nr_good_pages) {
1526 p->swap_map[0] = SWAP_MAP_BAD;
1527 p->max = maxpages;
1528 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001529 nr_extents = setup_swap_extents(p, &span);
1530 if (nr_extents < 0) {
1531 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001532 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001533 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001534 nr_good_pages = p->pages;
1535 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001536 if (!nr_good_pages) {
1537 printk(KERN_WARNING "Empty swap-file\n");
1538 error = -EINVAL;
1539 goto bad_swap;
1540 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001541
1542 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001543 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 p->flags = SWP_ACTIVE;
1545 nr_swap_pages += nr_good_pages;
1546 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001547
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001548 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins53092a72005-09-03 15:54:34 -07001549 "Priority:%d extents:%d across:%lluk\n",
1550 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1551 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552
1553 /* insert swap space into swap_list: */
1554 prev = -1;
1555 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1556 if (p->prio >= swap_info[i].prio) {
1557 break;
1558 }
1559 prev = i;
1560 }
1561 p->next = i;
1562 if (prev < 0) {
1563 swap_list.head = swap_list.next = p - swap_info;
1564 } else {
1565 swap_info[prev].next = p - swap_info;
1566 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001567 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568 up(&swapon_sem);
1569 error = 0;
1570 goto out;
1571bad_swap:
1572 if (bdev) {
1573 set_blocksize(bdev, p->old_block_size);
1574 bd_release(bdev);
1575 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001576 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07001578 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001579 swap_map = p->swap_map;
1580 p->swap_file = NULL;
1581 p->swap_map = NULL;
1582 p->flags = 0;
1583 if (!(swap_flags & SWAP_FLAG_PREFER))
1584 ++least_priority;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001585 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 vfree(swap_map);
1587 if (swap_file)
1588 filp_close(swap_file, NULL);
1589out:
1590 if (page && !IS_ERR(page)) {
1591 kunmap(page);
1592 page_cache_release(page);
1593 }
1594 if (name)
1595 putname(name);
1596 if (did_down) {
1597 if (!error)
1598 inode->i_flags |= S_SWAPFILE;
1599 up(&inode->i_sem);
1600 }
1601 return error;
1602}
1603
1604void si_swapinfo(struct sysinfo *val)
1605{
1606 unsigned int i;
1607 unsigned long nr_to_be_unused = 0;
1608
Hugh Dickins5d337b92005-09-03 15:54:41 -07001609 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610 for (i = 0; i < nr_swapfiles; i++) {
1611 if (!(swap_info[i].flags & SWP_USED) ||
1612 (swap_info[i].flags & SWP_WRITEOK))
1613 continue;
1614 nr_to_be_unused += swap_info[i].inuse_pages;
1615 }
1616 val->freeswap = nr_swap_pages + nr_to_be_unused;
1617 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001618 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619}
1620
1621/*
1622 * Verify that a swap entry is valid and increment its swap map count.
1623 *
1624 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1625 * "permanent", but will be reclaimed by the next swapoff.
1626 */
1627int swap_duplicate(swp_entry_t entry)
1628{
1629 struct swap_info_struct * p;
1630 unsigned long offset, type;
1631 int result = 0;
1632
1633 type = swp_type(entry);
1634 if (type >= nr_swapfiles)
1635 goto bad_file;
1636 p = type + swap_info;
1637 offset = swp_offset(entry);
1638
Hugh Dickins5d337b92005-09-03 15:54:41 -07001639 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640 if (offset < p->max && p->swap_map[offset]) {
1641 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1642 p->swap_map[offset]++;
1643 result = 1;
1644 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1645 if (swap_overflow++ < 5)
1646 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1647 p->swap_map[offset] = SWAP_MAP_MAX;
1648 result = 1;
1649 }
1650 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001651 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652out:
1653 return result;
1654
1655bad_file:
1656 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1657 goto out;
1658}
1659
1660struct swap_info_struct *
1661get_swap_info_struct(unsigned type)
1662{
1663 return &swap_info[type];
1664}
1665
1666/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001667 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668 * reference on the swaphandle, it doesn't matter if it becomes unused.
1669 */
1670int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1671{
1672 int ret = 0, i = 1 << page_cluster;
1673 unsigned long toff;
1674 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1675
1676 if (!page_cluster) /* no readahead */
1677 return 0;
1678 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1679 if (!toff) /* first page is swap header */
1680 toff++, i--;
1681 *offset = toff;
1682
Hugh Dickins5d337b92005-09-03 15:54:41 -07001683 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684 do {
1685 /* Don't read-ahead past the end of the swap area */
1686 if (toff >= swapdev->max)
1687 break;
1688 /* Don't read in free or bad pages */
1689 if (!swapdev->swap_map[toff])
1690 break;
1691 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1692 break;
1693 toff++;
1694 ret++;
1695 } while (--i);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001696 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 return ret;
1698}