blob: 8970c0b74194f45f2bce26592399e9db40f2947b [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);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070064 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 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
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070072 * count to avoid reading garbage from page_private(page) above.
73 * If the WARN_ON triggers during a swapoff it maybe the race
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 * 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
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700297 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 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
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700342 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 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 */
405static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
406 unsigned long addr, swp_entry_t entry, struct page *page)
407{
Hugh Dickins42946212005-10-29 18:16:05 -0700408 inc_mm_counter(vma->vm_mm, anon_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 get_page(page);
410 set_pte_at(vma->vm_mm, addr, pte,
411 pte_mkold(mk_pte(page, vma->vm_page_prot)));
412 page_add_anon_rmap(page, vma, addr);
413 swap_free(entry);
414 /*
415 * Move the page to the active list so it is not
416 * immediately swapped out again after swapon.
417 */
418 activate_page(page);
419}
420
421static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
422 unsigned long addr, unsigned long end,
423 swp_entry_t entry, struct page *page)
424{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700426 pte_t *pte;
427 spinlock_t *ptl;
428 int found = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429
Hugh Dickins705e87c2005-10-29 18:16:27 -0700430 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 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))) {
Hugh Dickins705e87c2005-10-29 18:16:27 -0700437 unuse_pte(vma, pte++, addr, entry, page);
438 found = 1;
439 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 }
441 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700442 pte_unmap_unlock(pte - 1, ptl);
443 return found;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444}
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 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 for (vma = mm->mmap; vma; vma = vma->vm_next) {
526 if (vma->anon_vma && unuse_vma(vma, entry, page))
527 break;
528 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 up_read(&mm->mmap_sem);
530 /*
531 * Currently unuse_mm cannot fail, but leave error handling
532 * at call sites for now, since we change it from time to time.
533 */
534 return 0;
535}
536
537/*
538 * Scan swap_map from current position to next entry still in use.
539 * Recycle to start on reaching the end, returning 0 when empty.
540 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700541static unsigned int find_next_to_unuse(struct swap_info_struct *si,
542 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700544 unsigned int max = si->max;
545 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700546 int count;
547
548 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700549 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 * for whether an entry is in use, not modifying it; false
551 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -0700552 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 */
554 for (;;) {
555 if (++i >= max) {
556 if (!prev) {
557 i = 0;
558 break;
559 }
560 /*
561 * No entries in use at top of swap_map,
562 * loop back to start and recheck there.
563 */
564 max = prev + 1;
565 prev = 0;
566 i = 1;
567 }
568 count = si->swap_map[i];
569 if (count && count != SWAP_MAP_BAD)
570 break;
571 }
572 return i;
573}
574
575/*
576 * We completely avoid races by reading each swap page in advance,
577 * and then search for the process using it. All the necessary
578 * page table adjustments can then be made atomically.
579 */
580static int try_to_unuse(unsigned int type)
581{
582 struct swap_info_struct * si = &swap_info[type];
583 struct mm_struct *start_mm;
584 unsigned short *swap_map;
585 unsigned short swcount;
586 struct page *page;
587 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700588 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 int retval = 0;
590 int reset_overflow = 0;
591 int shmem;
592
593 /*
594 * When searching mms for an entry, a good strategy is to
595 * start at the first mm we freed the previous entry from
596 * (though actually we don't notice whether we or coincidence
597 * freed the entry). Initialize this start_mm with a hold.
598 *
599 * A simpler strategy would be to start at the last mm we
600 * freed the previous entry from; but that would take less
601 * advantage of mmlist ordering, which clusters forked mms
602 * together, child after parent. If we race with dup_mmap(), we
603 * prefer to resolve parent before child, lest we miss entries
604 * duplicated after we scanned child: using last mm would invert
605 * that. Though it's only a serious concern when an overflowed
606 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
607 */
608 start_mm = &init_mm;
609 atomic_inc(&init_mm.mm_users);
610
611 /*
612 * Keep on scanning until all entries have gone. Usually,
613 * one pass through swap_map is enough, but not necessarily:
614 * there are races when an instance of an entry might be missed.
615 */
616 while ((i = find_next_to_unuse(si, i)) != 0) {
617 if (signal_pending(current)) {
618 retval = -EINTR;
619 break;
620 }
621
622 /*
623 * Get a page for the entry, using the existing swap
624 * cache page if there is one. Otherwise, get a clean
625 * page and read the swap into it.
626 */
627 swap_map = &si->swap_map[i];
628 entry = swp_entry(type, i);
629 page = read_swap_cache_async(entry, NULL, 0);
630 if (!page) {
631 /*
632 * Either swap_duplicate() failed because entry
633 * has been freed independently, and will not be
634 * reused since sys_swapoff() already disabled
635 * allocation from here, or alloc_page() failed.
636 */
637 if (!*swap_map)
638 continue;
639 retval = -ENOMEM;
640 break;
641 }
642
643 /*
644 * Don't hold on to start_mm if it looks like exiting.
645 */
646 if (atomic_read(&start_mm->mm_users) == 1) {
647 mmput(start_mm);
648 start_mm = &init_mm;
649 atomic_inc(&init_mm.mm_users);
650 }
651
652 /*
653 * Wait for and lock page. When do_swap_page races with
654 * try_to_unuse, do_swap_page can handle the fault much
655 * faster than try_to_unuse can locate the entry. This
656 * apparently redundant "wait_on_page_locked" lets try_to_unuse
657 * defer to do_swap_page in such a case - in some tests,
658 * do_swap_page and try_to_unuse repeatedly compete.
659 */
660 wait_on_page_locked(page);
661 wait_on_page_writeback(page);
662 lock_page(page);
663 wait_on_page_writeback(page);
664
665 /*
666 * Remove all references to entry.
667 * Whenever we reach init_mm, there's no address space
668 * to search, but use it as a reminder to search shmem.
669 */
670 shmem = 0;
671 swcount = *swap_map;
672 if (swcount > 1) {
673 if (start_mm == &init_mm)
674 shmem = shmem_unuse(entry, page);
675 else
676 retval = unuse_mm(start_mm, entry, page);
677 }
678 if (*swap_map > 1) {
679 int set_start_mm = (*swap_map >= swcount);
680 struct list_head *p = &start_mm->mmlist;
681 struct mm_struct *new_start_mm = start_mm;
682 struct mm_struct *prev_mm = start_mm;
683 struct mm_struct *mm;
684
685 atomic_inc(&new_start_mm->mm_users);
686 atomic_inc(&prev_mm->mm_users);
687 spin_lock(&mmlist_lock);
688 while (*swap_map > 1 && !retval &&
689 (p = p->next) != &start_mm->mmlist) {
690 mm = list_entry(p, struct mm_struct, mmlist);
691 if (atomic_inc_return(&mm->mm_users) == 1) {
692 atomic_dec(&mm->mm_users);
693 continue;
694 }
695 spin_unlock(&mmlist_lock);
696 mmput(prev_mm);
697 prev_mm = mm;
698
699 cond_resched();
700
701 swcount = *swap_map;
702 if (swcount <= 1)
703 ;
704 else if (mm == &init_mm) {
705 set_start_mm = 1;
706 shmem = shmem_unuse(entry, page);
707 } else
708 retval = unuse_mm(mm, entry, page);
709 if (set_start_mm && *swap_map < swcount) {
710 mmput(new_start_mm);
711 atomic_inc(&mm->mm_users);
712 new_start_mm = mm;
713 set_start_mm = 0;
714 }
715 spin_lock(&mmlist_lock);
716 }
717 spin_unlock(&mmlist_lock);
718 mmput(prev_mm);
719 mmput(start_mm);
720 start_mm = new_start_mm;
721 }
722 if (retval) {
723 unlock_page(page);
724 page_cache_release(page);
725 break;
726 }
727
728 /*
729 * How could swap count reach 0x7fff when the maximum
730 * pid is 0x7fff, and there's no way to repeat a swap
731 * page within an mm (except in shmem, where it's the
732 * shared object which takes the reference count)?
733 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
734 *
735 * If that's wrong, then we should worry more about
736 * exit_mmap() and do_munmap() cases described above:
737 * we might be resetting SWAP_MAP_MAX too early here.
738 * We know "Undead"s can happen, they're okay, so don't
739 * report them; but do report if we reset SWAP_MAP_MAX.
740 */
741 if (*swap_map == SWAP_MAP_MAX) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700742 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743 *swap_map = 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700744 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 reset_overflow = 1;
746 }
747
748 /*
749 * If a reference remains (rare), we would like to leave
750 * the page in the swap cache; but try_to_unmap could
751 * then re-duplicate the entry once we drop page lock,
752 * so we might loop indefinitely; also, that page could
753 * not be swapped out to other storage meanwhile. So:
754 * delete from cache even if there's another reference,
755 * after ensuring that the data has been saved to disk -
756 * since if the reference remains (rarer), it will be
757 * read from disk into another page. Splitting into two
758 * pages would be incorrect if swap supported "shared
759 * private" pages, but they are handled by tmpfs files.
760 *
761 * Note shmem_unuse already deleted a swappage from
762 * the swap cache, unless the move to filepage failed:
763 * in which case it left swappage in cache, lowered its
764 * swap count to pass quickly through the loops above,
765 * and now we must reincrement count to try again later.
766 */
767 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
768 struct writeback_control wbc = {
769 .sync_mode = WB_SYNC_NONE,
770 };
771
772 swap_writepage(page, &wbc);
773 lock_page(page);
774 wait_on_page_writeback(page);
775 }
776 if (PageSwapCache(page)) {
777 if (shmem)
778 swap_duplicate(entry);
779 else
780 delete_from_swap_cache(page);
781 }
782
783 /*
784 * So we could skip searching mms once swap count went
785 * to 1, we did not mark any present ptes as dirty: must
786 * mark page dirty so shrink_list will preserve it.
787 */
788 SetPageDirty(page);
789 unlock_page(page);
790 page_cache_release(page);
791
792 /*
793 * Make sure that we aren't completely killing
794 * interactive performance.
795 */
796 cond_resched();
797 }
798
799 mmput(start_mm);
800 if (reset_overflow) {
801 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
802 swap_overflow = 0;
803 }
804 return retval;
805}
806
807/*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700808 * After a successful try_to_unuse, if no swap is now in use, we know
809 * we can empty the mmlist. swap_lock must be held on entry and exit.
810 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811 * added to the mmlist just after page_duplicate - before would be racy.
812 */
813static void drain_mmlist(void)
814{
815 struct list_head *p, *next;
816 unsigned int i;
817
818 for (i = 0; i < nr_swapfiles; i++)
819 if (swap_info[i].inuse_pages)
820 return;
821 spin_lock(&mmlist_lock);
822 list_for_each_safe(p, next, &init_mm.mmlist)
823 list_del_init(p);
824 spin_unlock(&mmlist_lock);
825}
826
827/*
828 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
829 * corresponds to page offset `offset'.
830 */
831sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
832{
833 struct swap_extent *se = sis->curr_swap_extent;
834 struct swap_extent *start_se = se;
835
836 for ( ; ; ) {
837 struct list_head *lh;
838
839 if (se->start_page <= offset &&
840 offset < (se->start_page + se->nr_pages)) {
841 return se->start_block + (offset - se->start_page);
842 }
Hugh Dickins11d31882005-09-03 15:54:34 -0700843 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -0700845 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 se = list_entry(lh, struct swap_extent, list);
847 sis->curr_swap_extent = se;
848 BUG_ON(se == start_se); /* It *must* be present */
849 }
850}
851
852/*
853 * Free all of a swapdev's extent information
854 */
855static void destroy_swap_extents(struct swap_info_struct *sis)
856{
857 while (!list_empty(&sis->extent_list)) {
858 struct swap_extent *se;
859
860 se = list_entry(sis->extent_list.next,
861 struct swap_extent, list);
862 list_del(&se->list);
863 kfree(se);
864 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865}
866
867/*
868 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -0700869 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870 *
Hugh Dickins11d31882005-09-03 15:54:34 -0700871 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 */
873static int
874add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
875 unsigned long nr_pages, sector_t start_block)
876{
877 struct swap_extent *se;
878 struct swap_extent *new_se;
879 struct list_head *lh;
880
Hugh Dickins11d31882005-09-03 15:54:34 -0700881 lh = sis->extent_list.prev; /* The highest page extent */
882 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -0700884 BUG_ON(se->start_page + se->nr_pages != start_page);
885 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886 /* Merge it */
887 se->nr_pages += nr_pages;
888 return 0;
889 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 }
891
892 /*
893 * No merge. Insert a new extent, preserving ordering.
894 */
895 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
896 if (new_se == NULL)
897 return -ENOMEM;
898 new_se->start_page = start_page;
899 new_se->nr_pages = nr_pages;
900 new_se->start_block = start_block;
901
Hugh Dickins11d31882005-09-03 15:54:34 -0700902 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -0700903 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904}
905
906/*
907 * A `swap extent' is a simple thing which maps a contiguous range of pages
908 * onto a contiguous range of disk blocks. An ordered list of swap extents
909 * is built at swapon time and is then used at swap_writepage/swap_readpage
910 * time for locating where on disk a page belongs.
911 *
912 * If the swapfile is an S_ISBLK block device, a single extent is installed.
913 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
914 * swap files identically.
915 *
916 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
917 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
918 * swapfiles are handled *identically* after swapon time.
919 *
920 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
921 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
922 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
923 * requirements, they are simply tossed out - we will never use those blocks
924 * for swapping.
925 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -0700926 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -0700927 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
928 * which will scribble on the fs.
929 *
930 * The amount of disk space which a single swap extent represents varies.
931 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
932 * extents in the list. To avoid much list walking, we cache the previous
933 * search location in `curr_swap_extent', and start new searches from there.
934 * This is extremely effective. The average number of iterations in
935 * map_swap_page() has been measured at about 0.3 per page. - akpm.
936 */
Hugh Dickins53092a72005-09-03 15:54:34 -0700937static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700938{
939 struct inode *inode;
940 unsigned blocks_per_page;
941 unsigned long page_no;
942 unsigned blkbits;
943 sector_t probe_block;
944 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -0700945 sector_t lowest_block = -1;
946 sector_t highest_block = 0;
947 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948 int ret;
949
950 inode = sis->swap_file->f_mapping->host;
951 if (S_ISBLK(inode->i_mode)) {
952 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -0700953 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954 goto done;
955 }
956
957 blkbits = inode->i_blkbits;
958 blocks_per_page = PAGE_SIZE >> blkbits;
959
960 /*
961 * Map all the blocks into the extent list. This code doesn't try
962 * to be very smart.
963 */
964 probe_block = 0;
965 page_no = 0;
966 last_block = i_size_read(inode) >> blkbits;
967 while ((probe_block + blocks_per_page) <= last_block &&
968 page_no < sis->max) {
969 unsigned block_in_page;
970 sector_t first_block;
971
972 first_block = bmap(inode, probe_block);
973 if (first_block == 0)
974 goto bad_bmap;
975
976 /*
977 * It must be PAGE_SIZE aligned on-disk
978 */
979 if (first_block & (blocks_per_page - 1)) {
980 probe_block++;
981 goto reprobe;
982 }
983
984 for (block_in_page = 1; block_in_page < blocks_per_page;
985 block_in_page++) {
986 sector_t block;
987
988 block = bmap(inode, probe_block + block_in_page);
989 if (block == 0)
990 goto bad_bmap;
991 if (block != first_block + block_in_page) {
992 /* Discontiguity */
993 probe_block++;
994 goto reprobe;
995 }
996 }
997
Hugh Dickins53092a72005-09-03 15:54:34 -0700998 first_block >>= (PAGE_SHIFT - blkbits);
999 if (page_no) { /* exclude the header page */
1000 if (first_block < lowest_block)
1001 lowest_block = first_block;
1002 if (first_block > highest_block)
1003 highest_block = first_block;
1004 }
1005
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 /*
1007 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1008 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001009 ret = add_swap_extent(sis, page_no, 1, first_block);
1010 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001012 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013 page_no++;
1014 probe_block += blocks_per_page;
1015reprobe:
1016 continue;
1017 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001018 ret = nr_extents;
1019 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001021 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001023 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 sis->highest_bit = page_no - 1;
1025done:
1026 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1027 struct swap_extent, list);
1028 goto out;
1029bad_bmap:
1030 printk(KERN_ERR "swapon: swapfile has holes\n");
1031 ret = -EINVAL;
1032out:
1033 return ret;
1034}
1035
1036#if 0 /* We don't need this yet */
1037#include <linux/backing-dev.h>
1038int page_queue_congested(struct page *page)
1039{
1040 struct backing_dev_info *bdi;
1041
1042 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1043
1044 if (PageSwapCache(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -07001045 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046 struct swap_info_struct *sis;
1047
1048 sis = get_swap_info_struct(swp_type(entry));
1049 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1050 } else
1051 bdi = page->mapping->backing_dev_info;
1052 return bdi_write_congested(bdi);
1053}
1054#endif
1055
1056asmlinkage long sys_swapoff(const char __user * specialfile)
1057{
1058 struct swap_info_struct * p = NULL;
1059 unsigned short *swap_map;
1060 struct file *swap_file, *victim;
1061 struct address_space *mapping;
1062 struct inode *inode;
1063 char * pathname;
1064 int i, type, prev;
1065 int err;
1066
1067 if (!capable(CAP_SYS_ADMIN))
1068 return -EPERM;
1069
1070 pathname = getname(specialfile);
1071 err = PTR_ERR(pathname);
1072 if (IS_ERR(pathname))
1073 goto out;
1074
1075 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1076 putname(pathname);
1077 err = PTR_ERR(victim);
1078 if (IS_ERR(victim))
1079 goto out;
1080
1081 mapping = victim->f_mapping;
1082 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001083 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1085 p = swap_info + type;
1086 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1087 if (p->swap_file->f_mapping == mapping)
1088 break;
1089 }
1090 prev = type;
1091 }
1092 if (type < 0) {
1093 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001094 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095 goto out_dput;
1096 }
1097 if (!security_vm_enough_memory(p->pages))
1098 vm_unacct_memory(p->pages);
1099 else {
1100 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001101 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 goto out_dput;
1103 }
1104 if (prev < 0) {
1105 swap_list.head = p->next;
1106 } else {
1107 swap_info[prev].next = p->next;
1108 }
1109 if (type == swap_list.next) {
1110 /* just pick something that's safe... */
1111 swap_list.next = swap_list.head;
1112 }
1113 nr_swap_pages -= p->pages;
1114 total_swap_pages -= p->pages;
1115 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001116 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001117
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 current->flags |= PF_SWAPOFF;
1119 err = try_to_unuse(type);
1120 current->flags &= ~PF_SWAPOFF;
1121
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122 if (err) {
1123 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001124 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1126 if (p->prio >= swap_info[i].prio)
1127 break;
1128 p->next = i;
1129 if (prev < 0)
1130 swap_list.head = swap_list.next = p - swap_info;
1131 else
1132 swap_info[prev].next = p - swap_info;
1133 nr_swap_pages += p->pages;
1134 total_swap_pages += p->pages;
1135 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001136 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 goto out_dput;
1138 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001139
1140 /* wait for any unplug function to finish */
1141 down_write(&swap_unplug_sem);
1142 up_write(&swap_unplug_sem);
1143
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001144 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001146 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001148
1149 /* wait for anyone still in scan_swap_map */
1150 p->highest_bit = 0; /* cuts scans short */
1151 while (p->flags >= SWP_SCANNING) {
1152 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001153 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001154 spin_lock(&swap_lock);
1155 }
1156
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 swap_file = p->swap_file;
1158 p->swap_file = NULL;
1159 p->max = 0;
1160 swap_map = p->swap_map;
1161 p->swap_map = NULL;
1162 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001163 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164 up(&swapon_sem);
1165 vfree(swap_map);
1166 inode = mapping->host;
1167 if (S_ISBLK(inode->i_mode)) {
1168 struct block_device *bdev = I_BDEV(inode);
1169 set_blocksize(bdev, p->old_block_size);
1170 bd_release(bdev);
1171 } else {
1172 down(&inode->i_sem);
1173 inode->i_flags &= ~S_SWAPFILE;
1174 up(&inode->i_sem);
1175 }
1176 filp_close(swap_file, NULL);
1177 err = 0;
1178
1179out_dput:
1180 filp_close(victim, NULL);
1181out:
1182 return err;
1183}
1184
1185#ifdef CONFIG_PROC_FS
1186/* iterator */
1187static void *swap_start(struct seq_file *swap, loff_t *pos)
1188{
1189 struct swap_info_struct *ptr = swap_info;
1190 int i;
1191 loff_t l = *pos;
1192
1193 down(&swapon_sem);
1194
1195 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1196 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1197 continue;
1198 if (!l--)
1199 return ptr;
1200 }
1201
1202 return NULL;
1203}
1204
1205static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1206{
1207 struct swap_info_struct *ptr = v;
1208 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1209
1210 for (++ptr; ptr < endptr; ptr++) {
1211 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1212 continue;
1213 ++*pos;
1214 return ptr;
1215 }
1216
1217 return NULL;
1218}
1219
1220static void swap_stop(struct seq_file *swap, void *v)
1221{
1222 up(&swapon_sem);
1223}
1224
1225static int swap_show(struct seq_file *swap, void *v)
1226{
1227 struct swap_info_struct *ptr = v;
1228 struct file *file;
1229 int len;
1230
1231 if (v == swap_info)
1232 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1233
1234 file = ptr->swap_file;
1235 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001236 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237 len < 40 ? 40 - len : 1, " ",
1238 S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1239 "partition" : "file\t",
1240 ptr->pages << (PAGE_SHIFT - 10),
1241 ptr->inuse_pages << (PAGE_SHIFT - 10),
1242 ptr->prio);
1243 return 0;
1244}
1245
1246static struct seq_operations swaps_op = {
1247 .start = swap_start,
1248 .next = swap_next,
1249 .stop = swap_stop,
1250 .show = swap_show
1251};
1252
1253static int swaps_open(struct inode *inode, struct file *file)
1254{
1255 return seq_open(file, &swaps_op);
1256}
1257
1258static struct file_operations proc_swaps_operations = {
1259 .open = swaps_open,
1260 .read = seq_read,
1261 .llseek = seq_lseek,
1262 .release = seq_release,
1263};
1264
1265static int __init procswaps_init(void)
1266{
1267 struct proc_dir_entry *entry;
1268
1269 entry = create_proc_entry("swaps", 0, NULL);
1270 if (entry)
1271 entry->proc_fops = &proc_swaps_operations;
1272 return 0;
1273}
1274__initcall(procswaps_init);
1275#endif /* CONFIG_PROC_FS */
1276
1277/*
1278 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1279 *
1280 * The swapon system call
1281 */
1282asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1283{
1284 struct swap_info_struct * p;
1285 char *name = NULL;
1286 struct block_device *bdev = NULL;
1287 struct file *swap_file = NULL;
1288 struct address_space *mapping;
1289 unsigned int type;
1290 int i, prev;
1291 int error;
1292 static int least_priority;
1293 union swap_header *swap_header = NULL;
1294 int swap_header_version;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001295 unsigned int nr_good_pages = 0;
1296 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001297 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298 unsigned long maxpages = 1;
1299 int swapfilesize;
1300 unsigned short *swap_map;
1301 struct page *page = NULL;
1302 struct inode *inode = NULL;
1303 int did_down = 0;
1304
1305 if (!capable(CAP_SYS_ADMIN))
1306 return -EPERM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001307 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308 p = swap_info;
1309 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1310 if (!(p->flags & SWP_USED))
1311 break;
1312 error = -EPERM;
1313 /*
1314 * Test if adding another swap device is possible. There are
1315 * two limiting factors: 1) the number of bits for the swap
1316 * type swp_entry_t definition and 2) the number of bits for
1317 * the swap type in the swap ptes as defined by the different
1318 * architectures. To honor both limitations a swap entry
1319 * with swap offset 0 and swap type ~0UL is created, encoded
1320 * to a swap pte, decoded to a swp_entry_t again and finally
1321 * the swap type part is extracted. This will mask all bits
1322 * from the initial ~0UL that can't be encoded in either the
1323 * swp_entry_t or the architecture definition of a swap pte.
1324 */
1325 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001326 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 goto out;
1328 }
1329 if (type >= nr_swapfiles)
1330 nr_swapfiles = type+1;
1331 INIT_LIST_HEAD(&p->extent_list);
1332 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333 p->swap_file = NULL;
1334 p->old_block_size = 0;
1335 p->swap_map = NULL;
1336 p->lowest_bit = 0;
1337 p->highest_bit = 0;
1338 p->cluster_nr = 0;
1339 p->inuse_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 p->next = -1;
1341 if (swap_flags & SWAP_FLAG_PREFER) {
1342 p->prio =
1343 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1344 } else {
1345 p->prio = --least_priority;
1346 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001347 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 name = getname(specialfile);
1349 error = PTR_ERR(name);
1350 if (IS_ERR(name)) {
1351 name = NULL;
1352 goto bad_swap_2;
1353 }
1354 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1355 error = PTR_ERR(swap_file);
1356 if (IS_ERR(swap_file)) {
1357 swap_file = NULL;
1358 goto bad_swap_2;
1359 }
1360
1361 p->swap_file = swap_file;
1362 mapping = swap_file->f_mapping;
1363 inode = mapping->host;
1364
1365 error = -EBUSY;
1366 for (i = 0; i < nr_swapfiles; i++) {
1367 struct swap_info_struct *q = &swap_info[i];
1368
1369 if (i == type || !q->swap_file)
1370 continue;
1371 if (mapping == q->swap_file->f_mapping)
1372 goto bad_swap;
1373 }
1374
1375 error = -EINVAL;
1376 if (S_ISBLK(inode->i_mode)) {
1377 bdev = I_BDEV(inode);
1378 error = bd_claim(bdev, sys_swapon);
1379 if (error < 0) {
1380 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001381 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 goto bad_swap;
1383 }
1384 p->old_block_size = block_size(bdev);
1385 error = set_blocksize(bdev, PAGE_SIZE);
1386 if (error < 0)
1387 goto bad_swap;
1388 p->bdev = bdev;
1389 } else if (S_ISREG(inode->i_mode)) {
1390 p->bdev = inode->i_sb->s_bdev;
1391 down(&inode->i_sem);
1392 did_down = 1;
1393 if (IS_SWAPFILE(inode)) {
1394 error = -EBUSY;
1395 goto bad_swap;
1396 }
1397 } else {
1398 goto bad_swap;
1399 }
1400
1401 swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1402
1403 /*
1404 * Read the swap header.
1405 */
1406 if (!mapping->a_ops->readpage) {
1407 error = -EINVAL;
1408 goto bad_swap;
1409 }
1410 page = read_cache_page(mapping, 0,
1411 (filler_t *)mapping->a_ops->readpage, swap_file);
1412 if (IS_ERR(page)) {
1413 error = PTR_ERR(page);
1414 goto bad_swap;
1415 }
1416 wait_on_page_locked(page);
1417 if (!PageUptodate(page))
1418 goto bad_swap;
1419 kmap(page);
1420 swap_header = page_address(page);
1421
1422 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1423 swap_header_version = 1;
1424 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1425 swap_header_version = 2;
1426 else {
1427 printk("Unable to find swap-space signature\n");
1428 error = -EINVAL;
1429 goto bad_swap;
1430 }
1431
1432 switch (swap_header_version) {
1433 case 1:
1434 printk(KERN_ERR "version 0 swap is no longer supported. "
1435 "Use mkswap -v1 %s\n", name);
1436 error = -EINVAL;
1437 goto bad_swap;
1438 case 2:
1439 /* Check the swap header's sub-version and the size of
1440 the swap file and bad block lists */
1441 if (swap_header->info.version != 1) {
1442 printk(KERN_WARNING
1443 "Unable to handle swap header version %d\n",
1444 swap_header->info.version);
1445 error = -EINVAL;
1446 goto bad_swap;
1447 }
1448
1449 p->lowest_bit = 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001450 p->cluster_next = 1;
1451
Linus Torvalds1da177e2005-04-16 15:20:36 -07001452 /*
1453 * Find out how many pages are allowed for a single swap
1454 * device. There are two limiting factors: 1) the number of
1455 * bits for the swap offset in the swp_entry_t type and
1456 * 2) the number of bits in the a swap pte as defined by
1457 * the different architectures. In order to find the
1458 * largest possible bit mask a swap entry with swap type 0
1459 * and swap offset ~0UL is created, encoded to a swap pte,
1460 * decoded to a swp_entry_t again and finally the swap
1461 * offset is extracted. This will mask all the bits from
1462 * the initial ~0UL mask that can't be encoded in either
1463 * the swp_entry_t or the architecture definition of a
1464 * swap pte.
1465 */
1466 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1467 if (maxpages > swap_header->info.last_page)
1468 maxpages = swap_header->info.last_page;
1469 p->highest_bit = maxpages - 1;
1470
1471 error = -EINVAL;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001472 if (!maxpages)
1473 goto bad_swap;
1474 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1475 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001476 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1477 goto bad_swap;
1478
1479 /* OK, set up the swap map and apply the bad block list */
1480 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1481 error = -ENOMEM;
1482 goto bad_swap;
1483 }
1484
1485 error = 0;
1486 memset(p->swap_map, 0, maxpages * sizeof(short));
1487 for (i=0; i<swap_header->info.nr_badpages; i++) {
1488 int page = swap_header->info.badpages[i];
1489 if (page <= 0 || page >= swap_header->info.last_page)
1490 error = -EINVAL;
1491 else
1492 p->swap_map[page] = SWAP_MAP_BAD;
1493 }
1494 nr_good_pages = swap_header->info.last_page -
1495 swap_header->info.nr_badpages -
1496 1 /* header page */;
1497 if (error)
1498 goto bad_swap;
1499 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001500
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501 if (swapfilesize && maxpages > swapfilesize) {
1502 printk(KERN_WARNING
1503 "Swap area shorter than signature indicates\n");
1504 error = -EINVAL;
1505 goto bad_swap;
1506 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001507 if (nr_good_pages) {
1508 p->swap_map[0] = SWAP_MAP_BAD;
1509 p->max = maxpages;
1510 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001511 nr_extents = setup_swap_extents(p, &span);
1512 if (nr_extents < 0) {
1513 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001514 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001515 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001516 nr_good_pages = p->pages;
1517 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518 if (!nr_good_pages) {
1519 printk(KERN_WARNING "Empty swap-file\n");
1520 error = -EINVAL;
1521 goto bad_swap;
1522 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523
1524 down(&swapon_sem);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001525 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 p->flags = SWP_ACTIVE;
1527 nr_swap_pages += nr_good_pages;
1528 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001529
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001530 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins53092a72005-09-03 15:54:34 -07001531 "Priority:%d extents:%d across:%lluk\n",
1532 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1533 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001534
1535 /* insert swap space into swap_list: */
1536 prev = -1;
1537 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1538 if (p->prio >= swap_info[i].prio) {
1539 break;
1540 }
1541 prev = i;
1542 }
1543 p->next = i;
1544 if (prev < 0) {
1545 swap_list.head = swap_list.next = p - swap_info;
1546 } else {
1547 swap_info[prev].next = p - swap_info;
1548 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001549 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 up(&swapon_sem);
1551 error = 0;
1552 goto out;
1553bad_swap:
1554 if (bdev) {
1555 set_blocksize(bdev, p->old_block_size);
1556 bd_release(bdev);
1557 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001558 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07001560 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561 swap_map = p->swap_map;
1562 p->swap_file = NULL;
1563 p->swap_map = NULL;
1564 p->flags = 0;
1565 if (!(swap_flags & SWAP_FLAG_PREFER))
1566 ++least_priority;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001567 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568 vfree(swap_map);
1569 if (swap_file)
1570 filp_close(swap_file, NULL);
1571out:
1572 if (page && !IS_ERR(page)) {
1573 kunmap(page);
1574 page_cache_release(page);
1575 }
1576 if (name)
1577 putname(name);
1578 if (did_down) {
1579 if (!error)
1580 inode->i_flags |= S_SWAPFILE;
1581 up(&inode->i_sem);
1582 }
1583 return error;
1584}
1585
1586void si_swapinfo(struct sysinfo *val)
1587{
1588 unsigned int i;
1589 unsigned long nr_to_be_unused = 0;
1590
Hugh Dickins5d337b92005-09-03 15:54:41 -07001591 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001592 for (i = 0; i < nr_swapfiles; i++) {
1593 if (!(swap_info[i].flags & SWP_USED) ||
1594 (swap_info[i].flags & SWP_WRITEOK))
1595 continue;
1596 nr_to_be_unused += swap_info[i].inuse_pages;
1597 }
1598 val->freeswap = nr_swap_pages + nr_to_be_unused;
1599 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001600 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601}
1602
1603/*
1604 * Verify that a swap entry is valid and increment its swap map count.
1605 *
1606 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1607 * "permanent", but will be reclaimed by the next swapoff.
1608 */
1609int swap_duplicate(swp_entry_t entry)
1610{
1611 struct swap_info_struct * p;
1612 unsigned long offset, type;
1613 int result = 0;
1614
1615 type = swp_type(entry);
1616 if (type >= nr_swapfiles)
1617 goto bad_file;
1618 p = type + swap_info;
1619 offset = swp_offset(entry);
1620
Hugh Dickins5d337b92005-09-03 15:54:41 -07001621 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 if (offset < p->max && p->swap_map[offset]) {
1623 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1624 p->swap_map[offset]++;
1625 result = 1;
1626 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1627 if (swap_overflow++ < 5)
1628 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1629 p->swap_map[offset] = SWAP_MAP_MAX;
1630 result = 1;
1631 }
1632 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001633 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634out:
1635 return result;
1636
1637bad_file:
1638 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1639 goto out;
1640}
1641
1642struct swap_info_struct *
1643get_swap_info_struct(unsigned type)
1644{
1645 return &swap_info[type];
1646}
1647
1648/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001649 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07001650 * reference on the swaphandle, it doesn't matter if it becomes unused.
1651 */
1652int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1653{
1654 int ret = 0, i = 1 << page_cluster;
1655 unsigned long toff;
1656 struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1657
1658 if (!page_cluster) /* no readahead */
1659 return 0;
1660 toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1661 if (!toff) /* first page is swap header */
1662 toff++, i--;
1663 *offset = toff;
1664
Hugh Dickins5d337b92005-09-03 15:54:41 -07001665 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666 do {
1667 /* Don't read-ahead past the end of the swap area */
1668 if (toff >= swapdev->max)
1669 break;
1670 /* Don't read in free or bad pages */
1671 if (!swapdev->swap_map[toff])
1672 break;
1673 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1674 break;
1675 toff++;
1676 ret++;
1677 } while (--i);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001678 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679 return ret;
1680}