blob: 915cb3fc43d7287b738d6c1ba7b5e793402ba60a [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
Linus Torvalds1da177e2005-04-16 15:20:36 -07008#include <linux/mm.h>
9#include <linux/hugetlb.h>
10#include <linux/mman.h>
11#include <linux/slab.h>
12#include <linux/kernel_stat.h>
13#include <linux/swap.h>
14#include <linux/vmalloc.h>
15#include <linux/pagemap.h>
16#include <linux/namei.h>
17#include <linux/shm.h>
18#include <linux/blkdev.h>
19#include <linux/writeback.h>
20#include <linux/proc_fs.h>
21#include <linux/seq_file.h>
22#include <linux/init.h>
23#include <linux/module.h>
24#include <linux/rmap.h>
25#include <linux/security.h>
26#include <linux/backing-dev.h>
Ingo Molnarfc0abb12006-01-18 17:42:33 -080027#include <linux/mutex.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080028#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#include <linux/syscalls.h>
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080030#include <linux/memcontrol.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031
32#include <asm/pgtable.h>
33#include <asm/tlbflush.h>
34#include <linux/swapops.h>
35
Adrian Bunk7c363b82008-07-25 19:46:24 -070036static DEFINE_SPINLOCK(swap_lock);
37static unsigned int nr_swapfiles;
Hugh Dickinsb9627162009-01-06 14:39:41 -080038long nr_swap_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -070039long total_swap_pages;
40static int swap_overflow;
Hugh Dickins78ecba02008-07-23 21:28:23 -070041static int least_priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
Linus Torvalds1da177e2005-04-16 15:20:36 -070043static const char Bad_file[] = "Bad swap file entry ";
44static const char Unused_file[] = "Unused swap file entry ";
45static const char Bad_offset[] = "Bad swap offset entry ";
46static const char Unused_offset[] = "Unused swap offset entry ";
47
Adrian Bunk7c363b82008-07-25 19:46:24 -070048static struct swap_list_t swap_list = {-1, -1};
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
Rafael J. Wysockif577eb32006-03-23 02:59:59 -080050static struct swap_info_struct swap_info[MAX_SWAPFILES];
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
Ingo Molnarfc0abb12006-01-18 17:42:33 -080052static DEFINE_MUTEX(swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54/*
55 * We need this because the bdev->unplug_fn can sleep and we cannot
Hugh Dickins5d337b92005-09-03 15:54:41 -070056 * hold swap_lock while calling the unplug_fn. And swap_lock
Ingo Molnarfc0abb12006-01-18 17:42:33 -080057 * cannot be turned into a mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 */
59static DECLARE_RWSEM(swap_unplug_sem);
60
Linus Torvalds1da177e2005-04-16 15:20:36 -070061void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
62{
63 swp_entry_t entry;
64
65 down_read(&swap_unplug_sem);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070066 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070067 if (PageSwapCache(page)) {
68 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
69 struct backing_dev_info *bdi;
70
71 /*
72 * If the page is removed from swapcache from under us (with a
73 * racy try_to_unuse/swapoff) we need an additional reference
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070074 * count to avoid reading garbage from page_private(page) above.
75 * If the WARN_ON triggers during a swapoff it maybe the race
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 * condition and it's harmless. However if it triggers without
77 * swapoff it signals a problem.
78 */
79 WARN_ON(page_count(page) <= 1);
80
81 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -070082 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 }
84 up_read(&swap_unplug_sem);
85}
86
Hugh Dickins048c27f2005-09-03 15:54:40 -070087#define SWAPFILE_CLUSTER 256
88#define LATENCY_LIMIT 256
89
Hugh Dickins6eb396d2005-09-03 15:54:35 -070090static inline unsigned long scan_swap_map(struct swap_info_struct *si)
Linus Torvalds1da177e2005-04-16 15:20:36 -070091{
Hugh Dickins7dfad412005-09-03 15:54:38 -070092 unsigned long offset, last_in_cluster;
Hugh Dickins048c27f2005-09-03 15:54:40 -070093 int latency_ration = LATENCY_LIMIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Hugh Dickins7dfad412005-09-03 15:54:38 -070095 /*
96 * We try to cluster swap pages by allocating them sequentially
97 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
98 * way, however, we resort to first-free allocation, starting
99 * a new cluster. This prevents us from scattering swap pages
100 * all over the entire swap partition, so that we reduce
101 * overall disk seek times between swap pages. -- sct
102 * But we do now try to find an empty cluster. -Andrea
103 */
104
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700105 si->flags += SWP_SCANNING;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700106 if (unlikely(!si->cluster_nr)) {
107 si->cluster_nr = SWAPFILE_CLUSTER - 1;
108 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
109 goto lowest;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700110 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700111
112 offset = si->lowest_bit;
113 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
114
115 /* Locate the first empty (unaligned) cluster */
116 for (; last_in_cluster <= si->highest_bit; offset++) {
117 if (si->swap_map[offset])
118 last_in_cluster = offset + SWAPFILE_CLUSTER;
119 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700120 spin_lock(&swap_lock);
Akinobu Mita9b65ef52006-03-22 00:09:09 -0800121 si->cluster_next = offset-SWAPFILE_CLUSTER+1;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700122 goto cluster;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700124 if (unlikely(--latency_ration < 0)) {
125 cond_resched();
126 latency_ration = LATENCY_LIMIT;
127 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700128 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700129 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700130 goto lowest;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700132
133 si->cluster_nr--;
134cluster:
135 offset = si->cluster_next;
136 if (offset > si->highest_bit)
137lowest: offset = si->lowest_bit;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700138checks: if (!(si->flags & SWP_WRITEOK))
139 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700140 if (!si->highest_bit)
141 goto no_page;
142 if (!si->swap_map[offset]) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700143 if (offset == si->lowest_bit)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 si->lowest_bit++;
145 if (offset == si->highest_bit)
146 si->highest_bit--;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700147 si->inuse_pages++;
148 if (si->inuse_pages == si->pages) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 si->lowest_bit = si->max;
150 si->highest_bit = 0;
151 }
152 si->swap_map[offset] = 1;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700153 si->cluster_next = offset + 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700154 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 return offset;
156 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700157
Hugh Dickins5d337b92005-09-03 15:54:41 -0700158 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700159 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700160 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700161 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700162 goto checks;
163 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700164 if (unlikely(--latency_ration < 0)) {
165 cond_resched();
166 latency_ration = LATENCY_LIMIT;
167 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700168 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700169 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700170 goto lowest;
171
172no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700173 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 return 0;
175}
176
177swp_entry_t get_swap_page(void)
178{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700179 struct swap_info_struct *si;
180 pgoff_t offset;
181 int type, next;
182 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
Hugh Dickins5d337b92005-09-03 15:54:41 -0700184 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700186 goto noswap;
187 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700189 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
190 si = swap_info + type;
191 next = si->next;
192 if (next < 0 ||
193 (!wrapped && si->prio != swap_info[next].prio)) {
194 next = swap_list.head;
195 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700197
198 if (!si->highest_bit)
199 continue;
200 if (!(si->flags & SWP_WRITEOK))
201 continue;
202
203 swap_list.next = next;
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700204 offset = scan_swap_map(si);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700205 if (offset) {
206 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700207 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700208 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700209 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700211
212 nr_swap_pages++;
213noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700214 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700215 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216}
217
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800218swp_entry_t get_swap_page_of_type(int type)
219{
220 struct swap_info_struct *si;
221 pgoff_t offset;
222
223 spin_lock(&swap_lock);
224 si = swap_info + type;
225 if (si->flags & SWP_WRITEOK) {
226 nr_swap_pages--;
227 offset = scan_swap_map(si);
228 if (offset) {
229 spin_unlock(&swap_lock);
230 return swp_entry(type, offset);
231 }
232 nr_swap_pages++;
233 }
234 spin_unlock(&swap_lock);
235 return (swp_entry_t) {0};
236}
237
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238static struct swap_info_struct * swap_info_get(swp_entry_t entry)
239{
240 struct swap_info_struct * p;
241 unsigned long offset, type;
242
243 if (!entry.val)
244 goto out;
245 type = swp_type(entry);
246 if (type >= nr_swapfiles)
247 goto bad_nofile;
248 p = & swap_info[type];
249 if (!(p->flags & SWP_USED))
250 goto bad_device;
251 offset = swp_offset(entry);
252 if (offset >= p->max)
253 goto bad_offset;
254 if (!p->swap_map[offset])
255 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700256 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 return p;
258
259bad_free:
260 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
261 goto out;
262bad_offset:
263 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
264 goto out;
265bad_device:
266 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
267 goto out;
268bad_nofile:
269 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
270out:
271 return NULL;
272}
273
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
275{
276 int count = p->swap_map[offset];
277
278 if (count < SWAP_MAP_MAX) {
279 count--;
280 p->swap_map[offset] = count;
281 if (!count) {
282 if (offset < p->lowest_bit)
283 p->lowest_bit = offset;
284 if (offset > p->highest_bit)
285 p->highest_bit = offset;
Hugh Dickins89d09a22005-09-03 15:54:36 -0700286 if (p->prio > swap_info[swap_list.next].prio)
287 swap_list.next = p - swap_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 nr_swap_pages++;
289 p->inuse_pages--;
290 }
291 }
292 return count;
293}
294
295/*
296 * Caller has made sure that the swapdevice corresponding to entry
297 * is still around or has not been recycled.
298 */
299void swap_free(swp_entry_t entry)
300{
301 struct swap_info_struct * p;
302
303 p = swap_info_get(entry);
304 if (p) {
305 swap_entry_free(p, swp_offset(entry));
Hugh Dickins5d337b92005-09-03 15:54:41 -0700306 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 }
308}
309
310/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700311 * How many references to page are currently swapped out?
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700313static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700315 int count = 0;
316 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317 swp_entry_t entry;
318
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700319 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 p = swap_info_get(entry);
321 if (p) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700322 /* Subtract the 1 for the swap cache itself */
323 count = p->swap_map[swp_offset(entry)] - 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700324 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700326 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327}
328
329/*
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800330 * We can write to an anon page without COW if there are no other references
331 * to it. And as a side-effect, free up its swap: because the old content
332 * on disk will never be read, and seeking back there to write new content
333 * later would only waste time away from clustering.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334 */
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800335int reuse_swap_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700337 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338
Hugh Dickins51726b12009-01-06 14:39:25 -0800339 VM_BUG_ON(!PageLocked(page));
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700340 count = page_mapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800341 if (count <= 1 && PageSwapCache(page)) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700342 count += page_swapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800343 if (count == 1 && !PageWriteback(page)) {
344 delete_from_swap_cache(page);
345 SetPageDirty(page);
346 }
347 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700348 return count == 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349}
350
351/*
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800352 * If swap is getting full, or if there are no more mappings of this page,
353 * then try_to_free_swap is called to free its swap space.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 */
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800355int try_to_free_swap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356{
Hugh Dickins51726b12009-01-06 14:39:25 -0800357 VM_BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358
359 if (!PageSwapCache(page))
360 return 0;
361 if (PageWriteback(page))
362 return 0;
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800363 if (page_swapcount(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 return 0;
365
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800366 delete_from_swap_cache(page);
367 SetPageDirty(page);
368 return 1;
Rik van Riel68a223942008-10-18 20:26:23 -0700369}
370
371/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 * Free the swap entry like above, but also try to
373 * free the page cache entry if it is the last user.
374 */
375void free_swap_and_cache(swp_entry_t entry)
376{
377 struct swap_info_struct * p;
378 struct page *page = NULL;
379
Christoph Lameter06972122006-06-23 02:03:35 -0700380 if (is_migration_entry(entry))
381 return;
382
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 p = swap_info_get(entry);
384 if (p) {
Nick Piggin93fac702006-03-31 02:29:56 -0800385 if (swap_entry_free(p, swp_offset(entry)) == 1) {
386 page = find_get_page(&swapper_space, entry.val);
Nick Piggin8413ac92008-10-18 20:26:59 -0700387 if (page && !trylock_page(page)) {
Nick Piggin93fac702006-03-31 02:29:56 -0800388 page_cache_release(page);
389 page = NULL;
390 }
391 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700392 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 }
394 if (page) {
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800395 /*
396 * Not mapped elsewhere, or swap space full? Free it!
397 * Also recheck PageSwapCache now page is locked (above).
398 */
Nick Piggin93fac702006-03-31 02:29:56 -0800399 if (PageSwapCache(page) && !PageWriteback(page) &&
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800400 (!page_mapped(page) || vm_swap_full())) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 delete_from_swap_cache(page);
402 SetPageDirty(page);
403 }
404 unlock_page(page);
405 page_cache_release(page);
406 }
407}
408
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200409#ifdef CONFIG_HIBERNATION
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800410/*
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800411 * Find the swap type that corresponds to given device (if any).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800412 *
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800413 * @offset - number of the PAGE_SIZE-sized block of the device, starting
414 * from 0, in which the swap header is expected to be located.
415 *
416 * This is needed for the suspend to disk (aka swsusp).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800417 */
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800418int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800419{
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800420 struct block_device *bdev = NULL;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800421 int i;
422
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800423 if (device)
424 bdev = bdget(device);
425
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800426 spin_lock(&swap_lock);
427 for (i = 0; i < nr_swapfiles; i++) {
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800428 struct swap_info_struct *sis = swap_info + i;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800429
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800430 if (!(sis->flags & SWP_WRITEOK))
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800431 continue;
Rafael J. Wysockib6b5bce2006-08-27 01:23:25 -0700432
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800433 if (!bdev) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800434 if (bdev_p)
435 *bdev_p = sis->bdev;
436
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800437 spin_unlock(&swap_lock);
438 return i;
439 }
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800440 if (bdev == sis->bdev) {
441 struct swap_extent *se;
442
443 se = list_entry(sis->extent_list.next,
444 struct swap_extent, list);
445 if (se->start_block == offset) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800446 if (bdev_p)
447 *bdev_p = sis->bdev;
448
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800449 spin_unlock(&swap_lock);
450 bdput(bdev);
451 return i;
452 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800453 }
454 }
455 spin_unlock(&swap_lock);
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800456 if (bdev)
457 bdput(bdev);
458
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800459 return -ENODEV;
460}
461
462/*
463 * Return either the total number of swap pages of given type, or the number
464 * of free pages of that type (depending on @free)
465 *
466 * This is needed for software suspend
467 */
468unsigned int count_swap_pages(int type, int free)
469{
470 unsigned int n = 0;
471
472 if (type < nr_swapfiles) {
473 spin_lock(&swap_lock);
474 if (swap_info[type].flags & SWP_WRITEOK) {
475 n = swap_info[type].pages;
476 if (free)
477 n -= swap_info[type].inuse_pages;
478 }
479 spin_unlock(&swap_lock);
480 }
481 return n;
482}
483#endif
484
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700486 * No need to decide whether this PTE shares the swap entry with others,
487 * just let do_wp_page work it out if a write is requested later - to
488 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 */
Hugh Dickins044d66c2008-02-07 00:14:04 -0800490static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 unsigned long addr, swp_entry_t entry, struct page *page)
492{
Hugh Dickins044d66c2008-02-07 00:14:04 -0800493 spinlock_t *ptl;
494 pte_t *pte;
495 int ret = 1;
496
Balbir Singhe1a1cd52008-02-07 00:14:02 -0800497 if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
Hugh Dickins044d66c2008-02-07 00:14:04 -0800498 ret = -ENOMEM;
499
500 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
501 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
502 if (ret > 0)
503 mem_cgroup_uncharge_page(page);
504 ret = 0;
505 goto out;
506 }
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800507
Hugh Dickins42946212005-10-29 18:16:05 -0700508 inc_mm_counter(vma->vm_mm, anon_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 get_page(page);
510 set_pte_at(vma->vm_mm, addr, pte,
511 pte_mkold(mk_pte(page, vma->vm_page_prot)));
512 page_add_anon_rmap(page, vma, addr);
513 swap_free(entry);
514 /*
515 * Move the page to the active list so it is not
516 * immediately swapped out again after swapon.
517 */
518 activate_page(page);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800519out:
520 pte_unmap_unlock(pte, ptl);
521 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522}
523
524static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
525 unsigned long addr, unsigned long end,
526 swp_entry_t entry, struct page *page)
527{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700529 pte_t *pte;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800530 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700531
Hugh Dickins044d66c2008-02-07 00:14:04 -0800532 /*
533 * We don't actually need pte lock while scanning for swp_pte: since
534 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
535 * page table while we're scanning; though it could get zapped, and on
536 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
537 * of unmatched parts which look like swp_pte, so unuse_pte must
538 * recheck under pte lock. Scanning without pte lock lets it be
539 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
540 */
541 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 do {
543 /*
544 * swapoff spends a _lot_ of time in this loop!
545 * Test inline before going to call unuse_pte.
546 */
547 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800548 pte_unmap(pte);
549 ret = unuse_pte(vma, pmd, addr, entry, page);
550 if (ret)
551 goto out;
552 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 }
554 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800555 pte_unmap(pte - 1);
556out:
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800557 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700558}
559
560static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
561 unsigned long addr, unsigned long end,
562 swp_entry_t entry, struct page *page)
563{
564 pmd_t *pmd;
565 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800566 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567
568 pmd = pmd_offset(pud, addr);
569 do {
570 next = pmd_addr_end(addr, end);
571 if (pmd_none_or_clear_bad(pmd))
572 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800573 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
574 if (ret)
575 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576 } while (pmd++, addr = next, addr != end);
577 return 0;
578}
579
580static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
581 unsigned long addr, unsigned long end,
582 swp_entry_t entry, struct page *page)
583{
584 pud_t *pud;
585 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800586 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587
588 pud = pud_offset(pgd, addr);
589 do {
590 next = pud_addr_end(addr, end);
591 if (pud_none_or_clear_bad(pud))
592 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800593 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
594 if (ret)
595 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 } while (pud++, addr = next, addr != end);
597 return 0;
598}
599
600static int unuse_vma(struct vm_area_struct *vma,
601 swp_entry_t entry, struct page *page)
602{
603 pgd_t *pgd;
604 unsigned long addr, end, next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800605 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606
607 if (page->mapping) {
608 addr = page_address_in_vma(page, vma);
609 if (addr == -EFAULT)
610 return 0;
611 else
612 end = addr + PAGE_SIZE;
613 } else {
614 addr = vma->vm_start;
615 end = vma->vm_end;
616 }
617
618 pgd = pgd_offset(vma->vm_mm, addr);
619 do {
620 next = pgd_addr_end(addr, end);
621 if (pgd_none_or_clear_bad(pgd))
622 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800623 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
624 if (ret)
625 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 } while (pgd++, addr = next, addr != end);
627 return 0;
628}
629
630static int unuse_mm(struct mm_struct *mm,
631 swp_entry_t entry, struct page *page)
632{
633 struct vm_area_struct *vma;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800634 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635
636 if (!down_read_trylock(&mm->mmap_sem)) {
637 /*
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -0700638 * Activate page so shrink_inactive_list is unlikely to unmap
639 * its ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700641 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642 unlock_page(page);
643 down_read(&mm->mmap_sem);
644 lock_page(page);
645 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700646 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800647 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648 break;
649 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700650 up_read(&mm->mmap_sem);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800651 return (ret < 0)? ret: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700652}
653
654/*
655 * Scan swap_map from current position to next entry still in use.
656 * Recycle to start on reaching the end, returning 0 when empty.
657 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700658static unsigned int find_next_to_unuse(struct swap_info_struct *si,
659 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700660{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700661 unsigned int max = si->max;
662 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700663 int count;
664
665 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700666 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 * for whether an entry is in use, not modifying it; false
668 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -0700669 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670 */
671 for (;;) {
672 if (++i >= max) {
673 if (!prev) {
674 i = 0;
675 break;
676 }
677 /*
678 * No entries in use at top of swap_map,
679 * loop back to start and recheck there.
680 */
681 max = prev + 1;
682 prev = 0;
683 i = 1;
684 }
685 count = si->swap_map[i];
686 if (count && count != SWAP_MAP_BAD)
687 break;
688 }
689 return i;
690}
691
692/*
693 * We completely avoid races by reading each swap page in advance,
694 * and then search for the process using it. All the necessary
695 * page table adjustments can then be made atomically.
696 */
697static int try_to_unuse(unsigned int type)
698{
699 struct swap_info_struct * si = &swap_info[type];
700 struct mm_struct *start_mm;
701 unsigned short *swap_map;
702 unsigned short swcount;
703 struct page *page;
704 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700705 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 int retval = 0;
707 int reset_overflow = 0;
708 int shmem;
709
710 /*
711 * When searching mms for an entry, a good strategy is to
712 * start at the first mm we freed the previous entry from
713 * (though actually we don't notice whether we or coincidence
714 * freed the entry). Initialize this start_mm with a hold.
715 *
716 * A simpler strategy would be to start at the last mm we
717 * freed the previous entry from; but that would take less
718 * advantage of mmlist ordering, which clusters forked mms
719 * together, child after parent. If we race with dup_mmap(), we
720 * prefer to resolve parent before child, lest we miss entries
721 * duplicated after we scanned child: using last mm would invert
722 * that. Though it's only a serious concern when an overflowed
723 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
724 */
725 start_mm = &init_mm;
726 atomic_inc(&init_mm.mm_users);
727
728 /*
729 * Keep on scanning until all entries have gone. Usually,
730 * one pass through swap_map is enough, but not necessarily:
731 * there are races when an instance of an entry might be missed.
732 */
733 while ((i = find_next_to_unuse(si, i)) != 0) {
734 if (signal_pending(current)) {
735 retval = -EINTR;
736 break;
737 }
738
739 /*
740 * Get a page for the entry, using the existing swap
741 * cache page if there is one. Otherwise, get a clean
742 * page and read the swap into it.
743 */
744 swap_map = &si->swap_map[i];
745 entry = swp_entry(type, i);
Hugh Dickins02098fe2008-02-04 22:28:42 -0800746 page = read_swap_cache_async(entry,
747 GFP_HIGHUSER_MOVABLE, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 if (!page) {
749 /*
750 * Either swap_duplicate() failed because entry
751 * has been freed independently, and will not be
752 * reused since sys_swapoff() already disabled
753 * allocation from here, or alloc_page() failed.
754 */
755 if (!*swap_map)
756 continue;
757 retval = -ENOMEM;
758 break;
759 }
760
761 /*
762 * Don't hold on to start_mm if it looks like exiting.
763 */
764 if (atomic_read(&start_mm->mm_users) == 1) {
765 mmput(start_mm);
766 start_mm = &init_mm;
767 atomic_inc(&init_mm.mm_users);
768 }
769
770 /*
771 * Wait for and lock page. When do_swap_page races with
772 * try_to_unuse, do_swap_page can handle the fault much
773 * faster than try_to_unuse can locate the entry. This
774 * apparently redundant "wait_on_page_locked" lets try_to_unuse
775 * defer to do_swap_page in such a case - in some tests,
776 * do_swap_page and try_to_unuse repeatedly compete.
777 */
778 wait_on_page_locked(page);
779 wait_on_page_writeback(page);
780 lock_page(page);
781 wait_on_page_writeback(page);
782
783 /*
784 * Remove all references to entry.
785 * Whenever we reach init_mm, there's no address space
786 * to search, but use it as a reminder to search shmem.
787 */
788 shmem = 0;
789 swcount = *swap_map;
790 if (swcount > 1) {
791 if (start_mm == &init_mm)
792 shmem = shmem_unuse(entry, page);
793 else
794 retval = unuse_mm(start_mm, entry, page);
795 }
796 if (*swap_map > 1) {
797 int set_start_mm = (*swap_map >= swcount);
798 struct list_head *p = &start_mm->mmlist;
799 struct mm_struct *new_start_mm = start_mm;
800 struct mm_struct *prev_mm = start_mm;
801 struct mm_struct *mm;
802
803 atomic_inc(&new_start_mm->mm_users);
804 atomic_inc(&prev_mm->mm_users);
805 spin_lock(&mmlist_lock);
Hugh Dickins2e0e26c2008-02-04 22:28:53 -0800806 while (*swap_map > 1 && !retval && !shmem &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 (p = p->next) != &start_mm->mmlist) {
808 mm = list_entry(p, struct mm_struct, mmlist);
Hugh Dickins70af7c52006-06-23 02:03:44 -0700809 if (!atomic_inc_not_zero(&mm->mm_users))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700810 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811 spin_unlock(&mmlist_lock);
812 mmput(prev_mm);
813 prev_mm = mm;
814
815 cond_resched();
816
817 swcount = *swap_map;
818 if (swcount <= 1)
819 ;
820 else if (mm == &init_mm) {
821 set_start_mm = 1;
822 shmem = shmem_unuse(entry, page);
823 } else
824 retval = unuse_mm(mm, entry, page);
825 if (set_start_mm && *swap_map < swcount) {
826 mmput(new_start_mm);
827 atomic_inc(&mm->mm_users);
828 new_start_mm = mm;
829 set_start_mm = 0;
830 }
831 spin_lock(&mmlist_lock);
832 }
833 spin_unlock(&mmlist_lock);
834 mmput(prev_mm);
835 mmput(start_mm);
836 start_mm = new_start_mm;
837 }
Hugh Dickins2e0e26c2008-02-04 22:28:53 -0800838 if (shmem) {
839 /* page has already been unlocked and released */
840 if (shmem > 0)
841 continue;
842 retval = shmem;
843 break;
844 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 if (retval) {
846 unlock_page(page);
847 page_cache_release(page);
848 break;
849 }
850
851 /*
852 * How could swap count reach 0x7fff when the maximum
853 * pid is 0x7fff, and there's no way to repeat a swap
854 * page within an mm (except in shmem, where it's the
855 * shared object which takes the reference count)?
856 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
857 *
858 * If that's wrong, then we should worry more about
859 * exit_mmap() and do_munmap() cases described above:
860 * we might be resetting SWAP_MAP_MAX too early here.
861 * We know "Undead"s can happen, they're okay, so don't
862 * report them; but do report if we reset SWAP_MAP_MAX.
863 */
864 if (*swap_map == SWAP_MAP_MAX) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700865 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700866 *swap_map = 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700867 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868 reset_overflow = 1;
869 }
870
871 /*
872 * If a reference remains (rare), we would like to leave
873 * the page in the swap cache; but try_to_unmap could
874 * then re-duplicate the entry once we drop page lock,
875 * so we might loop indefinitely; also, that page could
876 * not be swapped out to other storage meanwhile. So:
877 * delete from cache even if there's another reference,
878 * after ensuring that the data has been saved to disk -
879 * since if the reference remains (rarer), it will be
880 * read from disk into another page. Splitting into two
881 * pages would be incorrect if swap supported "shared
882 * private" pages, but they are handled by tmpfs files.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 */
884 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
885 struct writeback_control wbc = {
886 .sync_mode = WB_SYNC_NONE,
887 };
888
889 swap_writepage(page, &wbc);
890 lock_page(page);
891 wait_on_page_writeback(page);
892 }
Hugh Dickins68bdc8d2009-01-06 14:39:37 -0800893
894 /*
895 * It is conceivable that a racing task removed this page from
896 * swap cache just before we acquired the page lock at the top,
897 * or while we dropped it in unuse_mm(). The page might even
898 * be back in swap cache on another swap area: that we must not
899 * delete, since it may not have been written out to swap yet.
900 */
901 if (PageSwapCache(page) &&
902 likely(page_private(page) == entry.val))
Hugh Dickins2e0e26c2008-02-04 22:28:53 -0800903 delete_from_swap_cache(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904
905 /*
906 * So we could skip searching mms once swap count went
907 * to 1, we did not mark any present ptes as dirty: must
Anderson Briglia2706a1b2007-07-15 23:38:09 -0700908 * mark page dirty so shrink_page_list will preserve it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909 */
910 SetPageDirty(page);
911 unlock_page(page);
912 page_cache_release(page);
913
914 /*
915 * Make sure that we aren't completely killing
916 * interactive performance.
917 */
918 cond_resched();
919 }
920
921 mmput(start_mm);
922 if (reset_overflow) {
923 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
924 swap_overflow = 0;
925 }
926 return retval;
927}
928
929/*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700930 * After a successful try_to_unuse, if no swap is now in use, we know
931 * we can empty the mmlist. swap_lock must be held on entry and exit.
932 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 * added to the mmlist just after page_duplicate - before would be racy.
934 */
935static void drain_mmlist(void)
936{
937 struct list_head *p, *next;
938 unsigned int i;
939
940 for (i = 0; i < nr_swapfiles; i++)
941 if (swap_info[i].inuse_pages)
942 return;
943 spin_lock(&mmlist_lock);
944 list_for_each_safe(p, next, &init_mm.mmlist)
945 list_del_init(p);
946 spin_unlock(&mmlist_lock);
947}
948
949/*
950 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
951 * corresponds to page offset `offset'.
952 */
953sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
954{
955 struct swap_extent *se = sis->curr_swap_extent;
956 struct swap_extent *start_se = se;
957
958 for ( ; ; ) {
959 struct list_head *lh;
960
961 if (se->start_page <= offset &&
962 offset < (se->start_page + se->nr_pages)) {
963 return se->start_block + (offset - se->start_page);
964 }
Hugh Dickins11d31882005-09-03 15:54:34 -0700965 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -0700967 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 se = list_entry(lh, struct swap_extent, list);
969 sis->curr_swap_extent = se;
970 BUG_ON(se == start_se); /* It *must* be present */
971 }
972}
973
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200974#ifdef CONFIG_HIBERNATION
Rafael J. Wysocki3aef83e2006-12-06 20:34:10 -0800975/*
976 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
977 * corresponding to given index in swap_info (swap type).
978 */
979sector_t swapdev_block(int swap_type, pgoff_t offset)
980{
981 struct swap_info_struct *sis;
982
983 if (swap_type >= nr_swapfiles)
984 return 0;
985
986 sis = swap_info + swap_type;
987 return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
988}
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200989#endif /* CONFIG_HIBERNATION */
Rafael J. Wysocki3aef83e2006-12-06 20:34:10 -0800990
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991/*
992 * Free all of a swapdev's extent information
993 */
994static void destroy_swap_extents(struct swap_info_struct *sis)
995{
996 while (!list_empty(&sis->extent_list)) {
997 struct swap_extent *se;
998
999 se = list_entry(sis->extent_list.next,
1000 struct swap_extent, list);
1001 list_del(&se->list);
1002 kfree(se);
1003 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004}
1005
1006/*
1007 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -07001008 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009 *
Hugh Dickins11d31882005-09-03 15:54:34 -07001010 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011 */
1012static int
1013add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1014 unsigned long nr_pages, sector_t start_block)
1015{
1016 struct swap_extent *se;
1017 struct swap_extent *new_se;
1018 struct list_head *lh;
1019
Hugh Dickins11d31882005-09-03 15:54:34 -07001020 lh = sis->extent_list.prev; /* The highest page extent */
1021 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -07001023 BUG_ON(se->start_page + se->nr_pages != start_page);
1024 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025 /* Merge it */
1026 se->nr_pages += nr_pages;
1027 return 0;
1028 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029 }
1030
1031 /*
1032 * No merge. Insert a new extent, preserving ordering.
1033 */
1034 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1035 if (new_se == NULL)
1036 return -ENOMEM;
1037 new_se->start_page = start_page;
1038 new_se->nr_pages = nr_pages;
1039 new_se->start_block = start_block;
1040
Hugh Dickins11d31882005-09-03 15:54:34 -07001041 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -07001042 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043}
1044
1045/*
1046 * A `swap extent' is a simple thing which maps a contiguous range of pages
1047 * onto a contiguous range of disk blocks. An ordered list of swap extents
1048 * is built at swapon time and is then used at swap_writepage/swap_readpage
1049 * time for locating where on disk a page belongs.
1050 *
1051 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1052 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1053 * swap files identically.
1054 *
1055 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1056 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1057 * swapfiles are handled *identically* after swapon time.
1058 *
1059 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1060 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1061 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1062 * requirements, they are simply tossed out - we will never use those blocks
1063 * for swapping.
1064 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -07001065 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1067 * which will scribble on the fs.
1068 *
1069 * The amount of disk space which a single swap extent represents varies.
1070 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1071 * extents in the list. To avoid much list walking, we cache the previous
1072 * search location in `curr_swap_extent', and start new searches from there.
1073 * This is extremely effective. The average number of iterations in
1074 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1075 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001076static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077{
1078 struct inode *inode;
1079 unsigned blocks_per_page;
1080 unsigned long page_no;
1081 unsigned blkbits;
1082 sector_t probe_block;
1083 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -07001084 sector_t lowest_block = -1;
1085 sector_t highest_block = 0;
1086 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087 int ret;
1088
1089 inode = sis->swap_file->f_mapping->host;
1090 if (S_ISBLK(inode->i_mode)) {
1091 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -07001092 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001093 goto done;
1094 }
1095
1096 blkbits = inode->i_blkbits;
1097 blocks_per_page = PAGE_SIZE >> blkbits;
1098
1099 /*
1100 * Map all the blocks into the extent list. This code doesn't try
1101 * to be very smart.
1102 */
1103 probe_block = 0;
1104 page_no = 0;
1105 last_block = i_size_read(inode) >> blkbits;
1106 while ((probe_block + blocks_per_page) <= last_block &&
1107 page_no < sis->max) {
1108 unsigned block_in_page;
1109 sector_t first_block;
1110
1111 first_block = bmap(inode, probe_block);
1112 if (first_block == 0)
1113 goto bad_bmap;
1114
1115 /*
1116 * It must be PAGE_SIZE aligned on-disk
1117 */
1118 if (first_block & (blocks_per_page - 1)) {
1119 probe_block++;
1120 goto reprobe;
1121 }
1122
1123 for (block_in_page = 1; block_in_page < blocks_per_page;
1124 block_in_page++) {
1125 sector_t block;
1126
1127 block = bmap(inode, probe_block + block_in_page);
1128 if (block == 0)
1129 goto bad_bmap;
1130 if (block != first_block + block_in_page) {
1131 /* Discontiguity */
1132 probe_block++;
1133 goto reprobe;
1134 }
1135 }
1136
Hugh Dickins53092a72005-09-03 15:54:34 -07001137 first_block >>= (PAGE_SHIFT - blkbits);
1138 if (page_no) { /* exclude the header page */
1139 if (first_block < lowest_block)
1140 lowest_block = first_block;
1141 if (first_block > highest_block)
1142 highest_block = first_block;
1143 }
1144
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 /*
1146 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1147 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001148 ret = add_swap_extent(sis, page_no, 1, first_block);
1149 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001151 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001152 page_no++;
1153 probe_block += blocks_per_page;
1154reprobe:
1155 continue;
1156 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001157 ret = nr_extents;
1158 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001160 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001162 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163 sis->highest_bit = page_no - 1;
1164done:
1165 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1166 struct swap_extent, list);
1167 goto out;
1168bad_bmap:
1169 printk(KERN_ERR "swapon: swapfile has holes\n");
1170 ret = -EINVAL;
1171out:
1172 return ret;
1173}
1174
1175#if 0 /* We don't need this yet */
1176#include <linux/backing-dev.h>
1177int page_queue_congested(struct page *page)
1178{
1179 struct backing_dev_info *bdi;
1180
Hugh Dickins51726b12009-01-06 14:39:25 -08001181 VM_BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182
1183 if (PageSwapCache(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -07001184 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 struct swap_info_struct *sis;
1186
1187 sis = get_swap_info_struct(swp_type(entry));
1188 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1189 } else
1190 bdi = page->mapping->backing_dev_info;
1191 return bdi_write_congested(bdi);
1192}
1193#endif
1194
1195asmlinkage long sys_swapoff(const char __user * specialfile)
1196{
1197 struct swap_info_struct * p = NULL;
1198 unsigned short *swap_map;
1199 struct file *swap_file, *victim;
1200 struct address_space *mapping;
1201 struct inode *inode;
1202 char * pathname;
1203 int i, type, prev;
1204 int err;
1205
1206 if (!capable(CAP_SYS_ADMIN))
1207 return -EPERM;
1208
1209 pathname = getname(specialfile);
1210 err = PTR_ERR(pathname);
1211 if (IS_ERR(pathname))
1212 goto out;
1213
1214 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1215 putname(pathname);
1216 err = PTR_ERR(victim);
1217 if (IS_ERR(victim))
1218 goto out;
1219
1220 mapping = victim->f_mapping;
1221 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001222 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1224 p = swap_info + type;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001225 if (p->flags & SWP_WRITEOK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 if (p->swap_file->f_mapping == mapping)
1227 break;
1228 }
1229 prev = type;
1230 }
1231 if (type < 0) {
1232 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001233 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 goto out_dput;
1235 }
1236 if (!security_vm_enough_memory(p->pages))
1237 vm_unacct_memory(p->pages);
1238 else {
1239 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001240 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241 goto out_dput;
1242 }
1243 if (prev < 0) {
1244 swap_list.head = p->next;
1245 } else {
1246 swap_info[prev].next = p->next;
1247 }
1248 if (type == swap_list.next) {
1249 /* just pick something that's safe... */
1250 swap_list.next = swap_list.head;
1251 }
Hugh Dickins78ecba02008-07-23 21:28:23 -07001252 if (p->prio < 0) {
1253 for (i = p->next; i >= 0; i = swap_info[i].next)
1254 swap_info[i].prio = p->prio--;
1255 least_priority++;
1256 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 nr_swap_pages -= p->pages;
1258 total_swap_pages -= p->pages;
1259 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001260 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001261
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 current->flags |= PF_SWAPOFF;
1263 err = try_to_unuse(type);
1264 current->flags &= ~PF_SWAPOFF;
1265
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266 if (err) {
1267 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001268 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001269 if (p->prio < 0)
1270 p->prio = --least_priority;
1271 prev = -1;
1272 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273 if (p->prio >= swap_info[i].prio)
1274 break;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001275 prev = i;
1276 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001277 p->next = i;
1278 if (prev < 0)
1279 swap_list.head = swap_list.next = p - swap_info;
1280 else
1281 swap_info[prev].next = p - swap_info;
1282 nr_swap_pages += p->pages;
1283 total_swap_pages += p->pages;
1284 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001285 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 goto out_dput;
1287 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001288
1289 /* wait for any unplug function to finish */
1290 down_write(&swap_unplug_sem);
1291 up_write(&swap_unplug_sem);
1292
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001293 destroy_swap_extents(p);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001294 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001295 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001297
1298 /* wait for anyone still in scan_swap_map */
1299 p->highest_bit = 0; /* cuts scans short */
1300 while (p->flags >= SWP_SCANNING) {
1301 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001302 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001303 spin_lock(&swap_lock);
1304 }
1305
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 swap_file = p->swap_file;
1307 p->swap_file = NULL;
1308 p->max = 0;
1309 swap_map = p->swap_map;
1310 p->swap_map = NULL;
1311 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001312 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001313 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314 vfree(swap_map);
1315 inode = mapping->host;
1316 if (S_ISBLK(inode->i_mode)) {
1317 struct block_device *bdev = I_BDEV(inode);
1318 set_blocksize(bdev, p->old_block_size);
1319 bd_release(bdev);
1320 } else {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001321 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 inode->i_flags &= ~S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001323 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 }
1325 filp_close(swap_file, NULL);
1326 err = 0;
1327
1328out_dput:
1329 filp_close(victim, NULL);
1330out:
1331 return err;
1332}
1333
1334#ifdef CONFIG_PROC_FS
1335/* iterator */
1336static void *swap_start(struct seq_file *swap, loff_t *pos)
1337{
1338 struct swap_info_struct *ptr = swap_info;
1339 int i;
1340 loff_t l = *pos;
1341
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001342 mutex_lock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001344 if (!l)
1345 return SEQ_START_TOKEN;
1346
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1348 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1349 continue;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001350 if (!--l)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 return ptr;
1352 }
1353
1354 return NULL;
1355}
1356
1357static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1358{
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001359 struct swap_info_struct *ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1361
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001362 if (v == SEQ_START_TOKEN)
1363 ptr = swap_info;
1364 else {
1365 ptr = v;
1366 ptr++;
1367 }
1368
1369 for (; ptr < endptr; ptr++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1371 continue;
1372 ++*pos;
1373 return ptr;
1374 }
1375
1376 return NULL;
1377}
1378
1379static void swap_stop(struct seq_file *swap, void *v)
1380{
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001381 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382}
1383
1384static int swap_show(struct seq_file *swap, void *v)
1385{
1386 struct swap_info_struct *ptr = v;
1387 struct file *file;
1388 int len;
1389
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001390 if (ptr == SEQ_START_TOKEN) {
1391 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1392 return 0;
1393 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394
1395 file = ptr->swap_file;
Jan Blunckc32c2f62008-02-14 19:38:43 -08001396 len = seq_path(swap, &file->f_path, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001397 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398 len < 40 ? 40 - len : 1, " ",
Josef "Jeff" Sipekd3ac7f82006-12-08 02:36:44 -08001399 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
Linus Torvalds1da177e2005-04-16 15:20:36 -07001400 "partition" : "file\t",
1401 ptr->pages << (PAGE_SHIFT - 10),
1402 ptr->inuse_pages << (PAGE_SHIFT - 10),
1403 ptr->prio);
1404 return 0;
1405}
1406
Helge Deller15ad7cd2006-12-06 20:40:36 -08001407static const struct seq_operations swaps_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 .start = swap_start,
1409 .next = swap_next,
1410 .stop = swap_stop,
1411 .show = swap_show
1412};
1413
1414static int swaps_open(struct inode *inode, struct file *file)
1415{
1416 return seq_open(file, &swaps_op);
1417}
1418
Helge Deller15ad7cd2006-12-06 20:40:36 -08001419static const struct file_operations proc_swaps_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 .open = swaps_open,
1421 .read = seq_read,
1422 .llseek = seq_lseek,
1423 .release = seq_release,
1424};
1425
1426static int __init procswaps_init(void)
1427{
Denis V. Lunev3d71f862008-04-29 01:02:13 -07001428 proc_create("swaps", 0, NULL, &proc_swaps_operations);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001429 return 0;
1430}
1431__initcall(procswaps_init);
1432#endif /* CONFIG_PROC_FS */
1433
Jan Beulich17963162008-12-16 11:35:24 +00001434#ifdef MAX_SWAPFILES_CHECK
1435static int __init max_swapfiles_check(void)
1436{
1437 MAX_SWAPFILES_CHECK();
1438 return 0;
1439}
1440late_initcall(max_swapfiles_check);
1441#endif
1442
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443/*
1444 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1445 *
1446 * The swapon system call
1447 */
1448asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1449{
1450 struct swap_info_struct * p;
1451 char *name = NULL;
1452 struct block_device *bdev = NULL;
1453 struct file *swap_file = NULL;
1454 struct address_space *mapping;
1455 unsigned int type;
1456 int i, prev;
1457 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001458 union swap_header *swap_header = NULL;
1459 int swap_header_version;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001460 unsigned int nr_good_pages = 0;
1461 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001462 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463 unsigned long maxpages = 1;
Hugh Dickins73fd8742009-01-06 14:39:47 -08001464 unsigned long swapfilepages;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001465 unsigned short *swap_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466 struct page *page = NULL;
1467 struct inode *inode = NULL;
1468 int did_down = 0;
1469
1470 if (!capable(CAP_SYS_ADMIN))
1471 return -EPERM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001472 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 p = swap_info;
1474 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1475 if (!(p->flags & SWP_USED))
1476 break;
1477 error = -EPERM;
Christoph Lameter06972122006-06-23 02:03:35 -07001478 if (type >= MAX_SWAPFILES) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001479 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001480 goto out;
1481 }
1482 if (type >= nr_swapfiles)
1483 nr_swapfiles = type+1;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001484 memset(p, 0, sizeof(*p));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485 INIT_LIST_HEAD(&p->extent_list);
1486 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487 p->next = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001488 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489 name = getname(specialfile);
1490 error = PTR_ERR(name);
1491 if (IS_ERR(name)) {
1492 name = NULL;
1493 goto bad_swap_2;
1494 }
1495 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1496 error = PTR_ERR(swap_file);
1497 if (IS_ERR(swap_file)) {
1498 swap_file = NULL;
1499 goto bad_swap_2;
1500 }
1501
1502 p->swap_file = swap_file;
1503 mapping = swap_file->f_mapping;
1504 inode = mapping->host;
1505
1506 error = -EBUSY;
1507 for (i = 0; i < nr_swapfiles; i++) {
1508 struct swap_info_struct *q = &swap_info[i];
1509
1510 if (i == type || !q->swap_file)
1511 continue;
1512 if (mapping == q->swap_file->f_mapping)
1513 goto bad_swap;
1514 }
1515
1516 error = -EINVAL;
1517 if (S_ISBLK(inode->i_mode)) {
1518 bdev = I_BDEV(inode);
1519 error = bd_claim(bdev, sys_swapon);
1520 if (error < 0) {
1521 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001522 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 goto bad_swap;
1524 }
1525 p->old_block_size = block_size(bdev);
1526 error = set_blocksize(bdev, PAGE_SIZE);
1527 if (error < 0)
1528 goto bad_swap;
1529 p->bdev = bdev;
1530 } else if (S_ISREG(inode->i_mode)) {
1531 p->bdev = inode->i_sb->s_bdev;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001532 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533 did_down = 1;
1534 if (IS_SWAPFILE(inode)) {
1535 error = -EBUSY;
1536 goto bad_swap;
1537 }
1538 } else {
1539 goto bad_swap;
1540 }
1541
Hugh Dickins73fd8742009-01-06 14:39:47 -08001542 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543
1544 /*
1545 * Read the swap header.
1546 */
1547 if (!mapping->a_ops->readpage) {
1548 error = -EINVAL;
1549 goto bad_swap;
1550 }
Pekka Enberg090d2b12006-06-23 02:05:08 -07001551 page = read_mapping_page(mapping, 0, swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 if (IS_ERR(page)) {
1553 error = PTR_ERR(page);
1554 goto bad_swap;
1555 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 kmap(page);
1557 swap_header = page_address(page);
1558
1559 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1560 swap_header_version = 1;
1561 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1562 swap_header_version = 2;
1563 else {
Jesper Juhle97a3112006-01-11 01:50:28 +01001564 printk(KERN_ERR "Unable to find swap-space signature\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001565 error = -EINVAL;
1566 goto bad_swap;
1567 }
1568
1569 switch (swap_header_version) {
1570 case 1:
1571 printk(KERN_ERR "version 0 swap is no longer supported. "
1572 "Use mkswap -v1 %s\n", name);
1573 error = -EINVAL;
1574 goto bad_swap;
1575 case 2:
Chris Dearman797df572008-04-28 02:12:19 -07001576 /* swap partition endianess hack... */
1577 if (swab32(swap_header->info.version) == 1) {
1578 swab32s(&swap_header->info.version);
1579 swab32s(&swap_header->info.last_page);
1580 swab32s(&swap_header->info.nr_badpages);
1581 for (i = 0; i < swap_header->info.nr_badpages; i++)
1582 swab32s(&swap_header->info.badpages[i]);
1583 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584 /* Check the swap header's sub-version and the size of
1585 the swap file and bad block lists */
1586 if (swap_header->info.version != 1) {
1587 printk(KERN_WARNING
1588 "Unable to handle swap header version %d\n",
1589 swap_header->info.version);
1590 error = -EINVAL;
1591 goto bad_swap;
1592 }
1593
1594 p->lowest_bit = 1;
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001595 p->cluster_next = 1;
1596
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597 /*
1598 * Find out how many pages are allowed for a single swap
1599 * device. There are two limiting factors: 1) the number of
1600 * bits for the swap offset in the swp_entry_t type and
1601 * 2) the number of bits in the a swap pte as defined by
1602 * the different architectures. In order to find the
1603 * largest possible bit mask a swap entry with swap type 0
1604 * and swap offset ~0UL is created, encoded to a swap pte,
1605 * decoded to a swp_entry_t again and finally the swap
1606 * offset is extracted. This will mask all the bits from
1607 * the initial ~0UL mask that can't be encoded in either
1608 * the swp_entry_t or the architecture definition of a
1609 * swap pte.
1610 */
1611 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1612 if (maxpages > swap_header->info.last_page)
1613 maxpages = swap_header->info.last_page;
1614 p->highest_bit = maxpages - 1;
1615
1616 error = -EINVAL;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001617 if (!maxpages)
1618 goto bad_swap;
Hugh Dickins73fd8742009-01-06 14:39:47 -08001619 if (swapfilepages && maxpages > swapfilepages) {
Eric Sandeen5d1854e2006-12-06 20:33:06 -08001620 printk(KERN_WARNING
1621 "Swap area shorter than signature indicates\n");
1622 goto bad_swap;
1623 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001624 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1625 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001626 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1627 goto bad_swap;
Tobias Klausercd105df2006-01-08 01:00:59 -08001628
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629 /* OK, set up the swap map and apply the bad block list */
Hugh Dickins78ecba02008-07-23 21:28:23 -07001630 swap_map = vmalloc(maxpages * sizeof(short));
1631 if (!swap_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632 error = -ENOMEM;
1633 goto bad_swap;
1634 }
1635
1636 error = 0;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001637 memset(swap_map, 0, maxpages * sizeof(short));
Tobias Klausercd105df2006-01-08 01:00:59 -08001638 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1639 int page_nr = swap_header->info.badpages[i];
1640 if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001641 error = -EINVAL;
1642 else
Hugh Dickins78ecba02008-07-23 21:28:23 -07001643 swap_map[page_nr] = SWAP_MAP_BAD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644 }
1645 nr_good_pages = swap_header->info.last_page -
1646 swap_header->info.nr_badpages -
1647 1 /* header page */;
Tobias Klausercd105df2006-01-08 01:00:59 -08001648 if (error)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 goto bad_swap;
1650 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001651
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001652 if (nr_good_pages) {
Hugh Dickins78ecba02008-07-23 21:28:23 -07001653 swap_map[0] = SWAP_MAP_BAD;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001654 p->max = maxpages;
1655 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001656 nr_extents = setup_swap_extents(p, &span);
1657 if (nr_extents < 0) {
1658 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001659 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001660 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001661 nr_good_pages = p->pages;
1662 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663 if (!nr_good_pages) {
1664 printk(KERN_WARNING "Empty swap-file\n");
1665 error = -EINVAL;
1666 goto bad_swap;
1667 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001669 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001670 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001671 if (swap_flags & SWAP_FLAG_PREFER)
1672 p->prio =
1673 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1674 else
1675 p->prio = --least_priority;
1676 p->swap_map = swap_map;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001677 p->flags |= SWP_WRITEOK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 nr_swap_pages += nr_good_pages;
1679 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001680
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001681 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins53092a72005-09-03 15:54:34 -07001682 "Priority:%d extents:%d across:%lluk\n",
1683 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1684 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685
1686 /* insert swap space into swap_list: */
1687 prev = -1;
1688 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1689 if (p->prio >= swap_info[i].prio) {
1690 break;
1691 }
1692 prev = i;
1693 }
1694 p->next = i;
1695 if (prev < 0) {
1696 swap_list.head = swap_list.next = p - swap_info;
1697 } else {
1698 swap_info[prev].next = p - swap_info;
1699 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001700 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001701 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 error = 0;
1703 goto out;
1704bad_swap:
1705 if (bdev) {
1706 set_blocksize(bdev, p->old_block_size);
1707 bd_release(bdev);
1708 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001709 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07001711 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712 p->swap_file = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001714 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715 vfree(swap_map);
1716 if (swap_file)
1717 filp_close(swap_file, NULL);
1718out:
1719 if (page && !IS_ERR(page)) {
1720 kunmap(page);
1721 page_cache_release(page);
1722 }
1723 if (name)
1724 putname(name);
1725 if (did_down) {
1726 if (!error)
1727 inode->i_flags |= S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001728 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 }
1730 return error;
1731}
1732
1733void si_swapinfo(struct sysinfo *val)
1734{
1735 unsigned int i;
1736 unsigned long nr_to_be_unused = 0;
1737
Hugh Dickins5d337b92005-09-03 15:54:41 -07001738 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 for (i = 0; i < nr_swapfiles; i++) {
1740 if (!(swap_info[i].flags & SWP_USED) ||
1741 (swap_info[i].flags & SWP_WRITEOK))
1742 continue;
1743 nr_to_be_unused += swap_info[i].inuse_pages;
1744 }
1745 val->freeswap = nr_swap_pages + nr_to_be_unused;
1746 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001747 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001748}
1749
1750/*
1751 * Verify that a swap entry is valid and increment its swap map count.
1752 *
1753 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1754 * "permanent", but will be reclaimed by the next swapoff.
1755 */
1756int swap_duplicate(swp_entry_t entry)
1757{
1758 struct swap_info_struct * p;
1759 unsigned long offset, type;
1760 int result = 0;
1761
Christoph Lameter06972122006-06-23 02:03:35 -07001762 if (is_migration_entry(entry))
1763 return 1;
1764
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765 type = swp_type(entry);
1766 if (type >= nr_swapfiles)
1767 goto bad_file;
1768 p = type + swap_info;
1769 offset = swp_offset(entry);
1770
Hugh Dickins5d337b92005-09-03 15:54:41 -07001771 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772 if (offset < p->max && p->swap_map[offset]) {
1773 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1774 p->swap_map[offset]++;
1775 result = 1;
1776 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1777 if (swap_overflow++ < 5)
1778 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1779 p->swap_map[offset] = SWAP_MAP_MAX;
1780 result = 1;
1781 }
1782 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001783 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784out:
1785 return result;
1786
1787bad_file:
1788 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1789 goto out;
1790}
1791
1792struct swap_info_struct *
1793get_swap_info_struct(unsigned type)
1794{
1795 return &swap_info[type];
1796}
1797
1798/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001799 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800 * reference on the swaphandle, it doesn't matter if it becomes unused.
1801 */
1802int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1803{
Hugh Dickins89528982008-02-04 22:28:45 -08001804 struct swap_info_struct *si;
Hugh Dickins3f9e7942006-09-29 02:01:26 -07001805 int our_page_cluster = page_cluster;
Hugh Dickins89528982008-02-04 22:28:45 -08001806 pgoff_t target, toff;
1807 pgoff_t base, end;
1808 int nr_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809
Hugh Dickins3f9e7942006-09-29 02:01:26 -07001810 if (!our_page_cluster) /* no readahead */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 return 0;
Hugh Dickins89528982008-02-04 22:28:45 -08001812
1813 si = &swap_info[swp_type(entry)];
1814 target = swp_offset(entry);
1815 base = (target >> our_page_cluster) << our_page_cluster;
1816 end = base + (1 << our_page_cluster);
1817 if (!base) /* first page is swap header */
1818 base++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819
Hugh Dickins5d337b92005-09-03 15:54:41 -07001820 spin_lock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08001821 if (end > si->max) /* don't go beyond end of map */
1822 end = si->max;
1823
1824 /* Count contiguous allocated slots above our target */
1825 for (toff = target; ++toff < end; nr_pages++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826 /* Don't read in free or bad pages */
Hugh Dickins89528982008-02-04 22:28:45 -08001827 if (!si->swap_map[toff])
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 break;
Hugh Dickins89528982008-02-04 22:28:45 -08001829 if (si->swap_map[toff] == SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001830 break;
Hugh Dickins89528982008-02-04 22:28:45 -08001831 }
1832 /* Count contiguous allocated slots below our target */
1833 for (toff = target; --toff >= base; nr_pages++) {
1834 /* Don't read in free or bad pages */
1835 if (!si->swap_map[toff])
1836 break;
1837 if (si->swap_map[toff] == SWAP_MAP_BAD)
1838 break;
1839 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001840 spin_unlock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08001841
1842 /*
1843 * Indicate starting offset, and return number of pages to get:
1844 * if only 1, say 0, since there's then no readahead to be done.
1845 */
1846 *offset = ++toff;
1847 return nr_pages? ++nr_pages: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848}