blob: 9fc7bac7db0c3b3478b49cbcf33a7f906c170b4c [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>
Hugh Dickins20137a42009-01-06 14:39:54 -080019#include <linux/random.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#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>
Hugh Dickins5ad64682009-12-14 17:59:24 -080025#include <linux/ksm.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/rmap.h>
27#include <linux/security.h>
28#include <linux/backing-dev.h>
Ingo Molnarfc0abb12006-01-18 17:42:33 -080029#include <linux/mutex.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080030#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031#include <linux/syscalls.h>
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080032#include <linux/memcontrol.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033
34#include <asm/pgtable.h>
35#include <asm/tlbflush.h>
36#include <linux/swapops.h>
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -080037#include <linux/page_cgroup.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
Hugh Dickins570a335b2009-12-14 17:58:46 -080039static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
40 unsigned char);
41static void free_swap_count_continuations(struct swap_info_struct *);
Lee Schermerhornd4906e12009-12-14 17:58:49 -080042static sector_t map_swap_entry(swp_entry_t, struct block_device**);
Hugh Dickins570a335b2009-12-14 17:58:46 -080043
Adrian Bunk7c363b82008-07-25 19:46:24 -070044static DEFINE_SPINLOCK(swap_lock);
45static unsigned int nr_swapfiles;
Hugh Dickinsb9627162009-01-06 14:39:41 -080046long nr_swap_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -070047long total_swap_pages;
Hugh Dickins78ecba02008-07-23 21:28:23 -070048static int least_priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
Linus Torvalds1da177e2005-04-16 15:20:36 -070050static const char Bad_file[] = "Bad swap file entry ";
51static const char Unused_file[] = "Unused swap file entry ";
52static const char Bad_offset[] = "Bad swap offset entry ";
53static const char Unused_offset[] = "Unused swap offset entry ";
54
Adrian Bunk7c363b82008-07-25 19:46:24 -070055static struct swap_list_t swap_list = {-1, -1};
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
Hugh Dickinsefa90a92009-12-14 17:58:41 -080057static struct swap_info_struct *swap_info[MAX_SWAPFILES];
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Ingo Molnarfc0abb12006-01-18 17:42:33 -080059static DEFINE_MUTEX(swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Hugh Dickins8d69aae2009-12-14 17:58:45 -080061static inline unsigned char swap_count(unsigned char ent)
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070062{
Hugh Dickins570a335b2009-12-14 17:58:46 -080063 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070064}
65
Hugh Dickinsefa90a92009-12-14 17:58:41 -080066/* returns 1 if swap entry is freed */
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -070067static int
68__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
69{
Hugh Dickinsefa90a92009-12-14 17:58:41 -080070 swp_entry_t entry = swp_entry(si->type, offset);
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -070071 struct page *page;
72 int ret = 0;
73
74 page = find_get_page(&swapper_space, entry.val);
75 if (!page)
76 return 0;
77 /*
78 * This function is called from scan_swap_map() and it's called
79 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
80 * We have to use trylock for avoiding deadlock. This is a special
81 * case and you should use try_to_free_swap() with explicit lock_page()
82 * in usual operations.
83 */
84 if (trylock_page(page)) {
85 ret = try_to_free_swap(page);
86 unlock_page(page);
87 }
88 page_cache_release(page);
89 return ret;
90}
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070091
Linus Torvalds1da177e2005-04-16 15:20:36 -070092/*
93 * We need this because the bdev->unplug_fn can sleep and we cannot
Hugh Dickins5d337b92005-09-03 15:54:41 -070094 * hold swap_lock while calling the unplug_fn. And swap_lock
Ingo Molnarfc0abb12006-01-18 17:42:33 -080095 * cannot be turned into a mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 */
97static DECLARE_RWSEM(swap_unplug_sem);
98
Linus Torvalds1da177e2005-04-16 15:20:36 -070099void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
100{
101 swp_entry_t entry;
102
103 down_read(&swap_unplug_sem);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700104 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 if (PageSwapCache(page)) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800106 struct block_device *bdev = swap_info[swp_type(entry)]->bdev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 struct backing_dev_info *bdi;
108
109 /*
110 * If the page is removed from swapcache from under us (with a
111 * racy try_to_unuse/swapoff) we need an additional reference
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700112 * count to avoid reading garbage from page_private(page) above.
113 * If the WARN_ON triggers during a swapoff it maybe the race
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 * condition and it's harmless. However if it triggers without
115 * swapoff it signals a problem.
116 */
117 WARN_ON(page_count(page) <= 1);
118
119 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -0700120 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 }
122 up_read(&swap_unplug_sem);
123}
124
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800125/*
126 * swapon tell device that all the old swap contents can be discarded,
127 * to allow the swap device to optimize its wear-levelling.
128 */
129static int discard_swap(struct swap_info_struct *si)
130{
131 struct swap_extent *se;
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800132 sector_t start_block;
133 sector_t nr_blocks;
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800134 int err = 0;
135
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800136 /* Do not discard the swap header page! */
137 se = &si->first_swap_extent;
138 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
139 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
140 if (nr_blocks) {
141 err = blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200142 nr_blocks, GFP_KERNEL, 0);
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800143 if (err)
144 return err;
145 cond_resched();
146 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800147
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800148 list_for_each_entry(se, &si->first_swap_extent.list, list) {
149 start_block = se->start_block << (PAGE_SHIFT - 9);
150 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800151
152 err = blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200153 nr_blocks, GFP_KERNEL, 0);
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800154 if (err)
155 break;
156
157 cond_resched();
158 }
159 return err; /* That will often be -EOPNOTSUPP */
160}
161
Hugh Dickins7992fde2009-01-06 14:39:53 -0800162/*
163 * swap allocation tell device that a cluster of swap can now be discarded,
164 * to allow the swap device to optimize its wear-levelling.
165 */
166static void discard_swap_cluster(struct swap_info_struct *si,
167 pgoff_t start_page, pgoff_t nr_pages)
168{
169 struct swap_extent *se = si->curr_swap_extent;
170 int found_extent = 0;
171
172 while (nr_pages) {
173 struct list_head *lh;
174
175 if (se->start_page <= start_page &&
176 start_page < se->start_page + se->nr_pages) {
177 pgoff_t offset = start_page - se->start_page;
178 sector_t start_block = se->start_block + offset;
Hugh Dickins858a29902009-01-06 14:39:56 -0800179 sector_t nr_blocks = se->nr_pages - offset;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800180
181 if (nr_blocks > nr_pages)
182 nr_blocks = nr_pages;
183 start_page += nr_blocks;
184 nr_pages -= nr_blocks;
185
186 if (!found_extent++)
187 si->curr_swap_extent = se;
188
189 start_block <<= PAGE_SHIFT - 9;
190 nr_blocks <<= PAGE_SHIFT - 9;
191 if (blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200192 nr_blocks, GFP_NOIO, 0))
Hugh Dickins7992fde2009-01-06 14:39:53 -0800193 break;
194 }
195
196 lh = se->list.next;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800197 se = list_entry(lh, struct swap_extent, list);
198 }
199}
200
201static int wait_for_discard(void *word)
202{
203 schedule();
204 return 0;
205}
206
Hugh Dickins048c27f2005-09-03 15:54:40 -0700207#define SWAPFILE_CLUSTER 256
208#define LATENCY_LIMIT 256
209
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700210static inline unsigned long scan_swap_map(struct swap_info_struct *si,
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800211 unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212{
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800213 unsigned long offset;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800214 unsigned long scan_base;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800215 unsigned long last_in_cluster = 0;
Hugh Dickins048c27f2005-09-03 15:54:40 -0700216 int latency_ration = LATENCY_LIMIT;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800217 int found_free_cluster = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800219 /*
Hugh Dickins7dfad412005-09-03 15:54:38 -0700220 * We try to cluster swap pages by allocating them sequentially
221 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
222 * way, however, we resort to first-free allocation, starting
223 * a new cluster. This prevents us from scattering swap pages
224 * all over the entire swap partition, so that we reduce
225 * overall disk seek times between swap pages. -- sct
226 * But we do now try to find an empty cluster. -Andrea
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800227 * And we let swap pages go all over an SSD partition. Hugh
Hugh Dickins7dfad412005-09-03 15:54:38 -0700228 */
229
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700230 si->flags += SWP_SCANNING;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800231 scan_base = offset = si->cluster_next;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800232
233 if (unlikely(!si->cluster_nr--)) {
234 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
235 si->cluster_nr = SWAPFILE_CLUSTER - 1;
236 goto checks;
237 }
Hugh Dickins7992fde2009-01-06 14:39:53 -0800238 if (si->flags & SWP_DISCARDABLE) {
239 /*
240 * Start range check on racing allocations, in case
241 * they overlap the cluster we eventually decide on
242 * (we scan without swap_lock to allow preemption).
243 * It's hardly conceivable that cluster_nr could be
244 * wrapped during our scan, but don't depend on it.
245 */
246 if (si->lowest_alloc)
247 goto checks;
248 si->lowest_alloc = si->max;
249 si->highest_alloc = 0;
250 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700251 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700252
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800253 /*
254 * If seek is expensive, start searching for new cluster from
255 * start of partition, to minimize the span of allocated swap.
256 * But if seek is cheap, search from our current position, so
257 * that swap is allocated from all over the partition: if the
258 * Flash Translation Layer only remaps within limited zones,
259 * we don't want to wear out the first zone too quickly.
260 */
261 if (!(si->flags & SWP_SOLIDSTATE))
262 scan_base = offset = si->lowest_bit;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700263 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
264
265 /* Locate the first empty (unaligned) cluster */
266 for (; last_in_cluster <= si->highest_bit; offset++) {
267 if (si->swap_map[offset])
268 last_in_cluster = offset + SWAPFILE_CLUSTER;
269 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700270 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800271 offset -= SWAPFILE_CLUSTER - 1;
272 si->cluster_next = offset;
273 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800274 found_free_cluster = 1;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800275 goto checks;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700277 if (unlikely(--latency_ration < 0)) {
278 cond_resched();
279 latency_ration = LATENCY_LIMIT;
280 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700281 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800282
283 offset = si->lowest_bit;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800284 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
285
286 /* Locate the first empty (unaligned) cluster */
287 for (; last_in_cluster < scan_base; offset++) {
288 if (si->swap_map[offset])
289 last_in_cluster = offset + SWAPFILE_CLUSTER;
290 else if (offset == last_in_cluster) {
291 spin_lock(&swap_lock);
292 offset -= SWAPFILE_CLUSTER - 1;
293 si->cluster_next = offset;
294 si->cluster_nr = SWAPFILE_CLUSTER - 1;
295 found_free_cluster = 1;
296 goto checks;
297 }
298 if (unlikely(--latency_ration < 0)) {
299 cond_resched();
300 latency_ration = LATENCY_LIMIT;
301 }
302 }
303
304 offset = scan_base;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700305 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800306 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800307 si->lowest_alloc = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700309
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800310checks:
311 if (!(si->flags & SWP_WRITEOK))
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700312 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700313 if (!si->highest_bit)
314 goto no_page;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800315 if (offset > si->highest_bit)
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800316 scan_base = offset = si->lowest_bit;
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700317
Hugh Dickinsb73d7fc2010-09-09 16:38:09 -0700318 /* reuse swap entry of cache-only swap if not busy. */
319 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700320 int swap_was_freed;
321 spin_unlock(&swap_lock);
322 swap_was_freed = __try_to_reclaim_swap(si, offset);
323 spin_lock(&swap_lock);
324 /* entry was freed successfully, try to use this again */
325 if (swap_was_freed)
326 goto checks;
327 goto scan; /* check next one */
328 }
329
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800330 if (si->swap_map[offset])
331 goto scan;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700332
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800333 if (offset == si->lowest_bit)
334 si->lowest_bit++;
335 if (offset == si->highest_bit)
336 si->highest_bit--;
337 si->inuse_pages++;
338 if (si->inuse_pages == si->pages) {
339 si->lowest_bit = si->max;
340 si->highest_bit = 0;
341 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800342 si->swap_map[offset] = usage;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800343 si->cluster_next = offset + 1;
344 si->flags -= SWP_SCANNING;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800345
346 if (si->lowest_alloc) {
347 /*
348 * Only set when SWP_DISCARDABLE, and there's a scan
349 * for a free cluster in progress or just completed.
350 */
351 if (found_free_cluster) {
352 /*
353 * To optimize wear-levelling, discard the
354 * old data of the cluster, taking care not to
355 * discard any of its pages that have already
356 * been allocated by racing tasks (offset has
357 * already stepped over any at the beginning).
358 */
359 if (offset < si->highest_alloc &&
360 si->lowest_alloc <= last_in_cluster)
361 last_in_cluster = si->lowest_alloc - 1;
362 si->flags |= SWP_DISCARDING;
363 spin_unlock(&swap_lock);
364
365 if (offset < last_in_cluster)
366 discard_swap_cluster(si, offset,
367 last_in_cluster - offset + 1);
368
369 spin_lock(&swap_lock);
370 si->lowest_alloc = 0;
371 si->flags &= ~SWP_DISCARDING;
372
373 smp_mb(); /* wake_up_bit advises this */
374 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
375
376 } else if (si->flags & SWP_DISCARDING) {
377 /*
378 * Delay using pages allocated by racing tasks
379 * until the whole discard has been issued. We
380 * could defer that delay until swap_writepage,
381 * but it's easier to keep this self-contained.
382 */
383 spin_unlock(&swap_lock);
384 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
385 wait_for_discard, TASK_UNINTERRUPTIBLE);
386 spin_lock(&swap_lock);
387 } else {
388 /*
389 * Note pages allocated by racing tasks while
390 * scan for a free cluster is in progress, so
391 * that its final discard can exclude them.
392 */
393 if (offset < si->lowest_alloc)
394 si->lowest_alloc = offset;
395 if (offset > si->highest_alloc)
396 si->highest_alloc = offset;
397 }
398 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800399 return offset;
400
401scan:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700402 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700403 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700404 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700405 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700406 goto checks;
407 }
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700408 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
409 spin_lock(&swap_lock);
410 goto checks;
411 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700412 if (unlikely(--latency_ration < 0)) {
413 cond_resched();
414 latency_ration = LATENCY_LIMIT;
415 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700416 }
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800417 offset = si->lowest_bit;
418 while (++offset < scan_base) {
419 if (!si->swap_map[offset]) {
420 spin_lock(&swap_lock);
421 goto checks;
422 }
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700423 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
424 spin_lock(&swap_lock);
425 goto checks;
426 }
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800427 if (unlikely(--latency_ration < 0)) {
428 cond_resched();
429 latency_ration = LATENCY_LIMIT;
430 }
431 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700432 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700433
434no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700435 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436 return 0;
437}
438
439swp_entry_t get_swap_page(void)
440{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700441 struct swap_info_struct *si;
442 pgoff_t offset;
443 int type, next;
444 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445
Hugh Dickins5d337b92005-09-03 15:54:41 -0700446 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700448 goto noswap;
449 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700451 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800452 si = swap_info[type];
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700453 next = si->next;
454 if (next < 0 ||
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800455 (!wrapped && si->prio != swap_info[next]->prio)) {
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700456 next = swap_list.head;
457 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700459
460 if (!si->highest_bit)
461 continue;
462 if (!(si->flags & SWP_WRITEOK))
463 continue;
464
465 swap_list.next = next;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700466 /* This is called for allocating swap entry for cache */
Hugh Dickins253d5532009-12-14 17:58:44 -0800467 offset = scan_swap_map(si, SWAP_HAS_CACHE);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700468 if (offset) {
469 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700470 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700471 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700472 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700474
475 nr_swap_pages++;
476noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700477 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700478 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479}
480
Hugh Dickins910321e2010-09-09 16:38:07 -0700481/* The only caller of this function is now susupend routine */
482swp_entry_t get_swap_page_of_type(int type)
483{
484 struct swap_info_struct *si;
485 pgoff_t offset;
486
487 spin_lock(&swap_lock);
488 si = swap_info[type];
489 if (si && (si->flags & SWP_WRITEOK)) {
490 nr_swap_pages--;
491 /* This is called for allocating swap entry, not cache */
492 offset = scan_swap_map(si, 1);
493 if (offset) {
494 spin_unlock(&swap_lock);
495 return swp_entry(type, offset);
496 }
497 nr_swap_pages++;
498 }
499 spin_unlock(&swap_lock);
500 return (swp_entry_t) {0};
501}
502
Hugh Dickins73c34b62009-12-14 17:58:43 -0800503static struct swap_info_struct *swap_info_get(swp_entry_t entry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504{
Hugh Dickins73c34b62009-12-14 17:58:43 -0800505 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 unsigned long offset, type;
507
508 if (!entry.val)
509 goto out;
510 type = swp_type(entry);
511 if (type >= nr_swapfiles)
512 goto bad_nofile;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800513 p = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514 if (!(p->flags & SWP_USED))
515 goto bad_device;
516 offset = swp_offset(entry);
517 if (offset >= p->max)
518 goto bad_offset;
519 if (!p->swap_map[offset])
520 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700521 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 return p;
523
524bad_free:
525 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
526 goto out;
527bad_offset:
528 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
529 goto out;
530bad_device:
531 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
532 goto out;
533bad_nofile:
534 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
535out:
536 return NULL;
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800537}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800539static unsigned char swap_entry_free(struct swap_info_struct *p,
540 swp_entry_t entry, unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541{
Hugh Dickins253d5532009-12-14 17:58:44 -0800542 unsigned long offset = swp_offset(entry);
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800543 unsigned char count;
544 unsigned char has_cache;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700546 count = p->swap_map[offset];
Hugh Dickins253d5532009-12-14 17:58:44 -0800547 has_cache = count & SWAP_HAS_CACHE;
548 count &= ~SWAP_HAS_CACHE;
549
550 if (usage == SWAP_HAS_CACHE) {
551 VM_BUG_ON(!has_cache);
552 has_cache = 0;
Hugh Dickinsaaa46862009-12-14 17:58:47 -0800553 } else if (count == SWAP_MAP_SHMEM) {
554 /*
555 * Or we could insist on shmem.c using a special
556 * swap_shmem_free() and free_shmem_swap_and_cache()...
557 */
558 count = 0;
Hugh Dickins570a335b2009-12-14 17:58:46 -0800559 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
560 if (count == COUNT_CONTINUED) {
561 if (swap_count_continued(p, offset, count))
562 count = SWAP_MAP_MAX | COUNT_CONTINUED;
563 else
564 count = SWAP_MAP_MAX;
565 } else
566 count--;
567 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800568
569 if (!count)
570 mem_cgroup_uncharge_swap(entry);
571
572 usage = count | has_cache;
573 p->swap_map[offset] = usage;
574
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700575 /* free if no reference */
Hugh Dickins253d5532009-12-14 17:58:44 -0800576 if (!usage) {
Nitin Guptab3a27d02010-05-17 11:02:43 +0530577 struct gendisk *disk = p->bdev->bd_disk;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700578 if (offset < p->lowest_bit)
579 p->lowest_bit = offset;
580 if (offset > p->highest_bit)
581 p->highest_bit = offset;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800582 if (swap_list.next >= 0 &&
583 p->prio > swap_info[swap_list.next]->prio)
584 swap_list.next = p->type;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700585 nr_swap_pages++;
586 p->inuse_pages--;
Nitin Guptab3a27d02010-05-17 11:02:43 +0530587 if ((p->flags & SWP_BLKDEV) &&
588 disk->fops->swap_slot_free_notify)
589 disk->fops->swap_slot_free_notify(p->bdev, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800591
592 return usage;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593}
594
595/*
596 * Caller has made sure that the swapdevice corresponding to entry
597 * is still around or has not been recycled.
598 */
599void swap_free(swp_entry_t entry)
600{
Hugh Dickins73c34b62009-12-14 17:58:43 -0800601 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602
603 p = swap_info_get(entry);
604 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800605 swap_entry_free(p, entry, 1);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700606 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 }
608}
609
610/*
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700611 * Called after dropping swapcache to decrease refcnt to swap entries.
612 */
613void swapcache_free(swp_entry_t entry, struct page *page)
614{
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700615 struct swap_info_struct *p;
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800616 unsigned char count;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700617
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700618 p = swap_info_get(entry);
619 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800620 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
621 if (page)
622 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700623 spin_unlock(&swap_lock);
624 }
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700625}
626
627/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700628 * How many references to page are currently swapped out?
Hugh Dickins570a335b2009-12-14 17:58:46 -0800629 * This does not give an exact answer when swap count is continued,
630 * but does include the high COUNT_CONTINUED flag to allow for that.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700632static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700634 int count = 0;
635 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636 swp_entry_t entry;
637
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700638 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639 p = swap_info_get(entry);
640 if (p) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700641 count = swap_count(p->swap_map[swp_offset(entry)]);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700642 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700644 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645}
646
647/*
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800648 * We can write to an anon page without COW if there are no other references
649 * to it. And as a side-effect, free up its swap: because the old content
650 * on disk will never be read, and seeking back there to write new content
651 * later would only waste time away from clustering.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700652 */
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800653int reuse_swap_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700655 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656
Hugh Dickins51726b12009-01-06 14:39:25 -0800657 VM_BUG_ON(!PageLocked(page));
Hugh Dickins5ad64682009-12-14 17:59:24 -0800658 if (unlikely(PageKsm(page)))
659 return 0;
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700660 count = page_mapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800661 if (count <= 1 && PageSwapCache(page)) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700662 count += page_swapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800663 if (count == 1 && !PageWriteback(page)) {
664 delete_from_swap_cache(page);
665 SetPageDirty(page);
666 }
667 }
Hugh Dickins5ad64682009-12-14 17:59:24 -0800668 return count <= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669}
670
671/*
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800672 * If swap is getting full, or if there are no more mappings of this page,
673 * then try_to_free_swap is called to free its swap space.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 */
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800675int try_to_free_swap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676{
Hugh Dickins51726b12009-01-06 14:39:25 -0800677 VM_BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678
679 if (!PageSwapCache(page))
680 return 0;
681 if (PageWriteback(page))
682 return 0;
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800683 if (page_swapcount(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 return 0;
685
Hugh Dickinsb73d7fc2010-09-09 16:38:09 -0700686 /*
687 * Once hibernation has begun to create its image of memory,
688 * there's a danger that one of the calls to try_to_free_swap()
689 * - most probably a call from __try_to_reclaim_swap() while
690 * hibernation is allocating its own swap pages for the image,
691 * but conceivably even a call from memory reclaim - will free
692 * the swap from a page which has already been recorded in the
693 * image as a clean swapcache page, and then reuse its swap for
694 * another page of the image. On waking from hibernation, the
695 * original page might be freed under memory pressure, then
696 * later read back in from swap, now with the wrong data.
697 *
698 * Hibernation clears bits from gfp_allowed_mask to prevent
699 * memory reclaim from writing to disk, so check that here.
700 */
701 if (!(gfp_allowed_mask & __GFP_IO))
702 return 0;
703
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800704 delete_from_swap_cache(page);
705 SetPageDirty(page);
706 return 1;
Rik van Riel68a223942008-10-18 20:26:23 -0700707}
708
709/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 * Free the swap entry like above, but also try to
711 * free the page cache entry if it is the last user.
712 */
Hugh Dickins2509ef22009-01-06 14:40:10 -0800713int free_swap_and_cache(swp_entry_t entry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714{
Hugh Dickins2509ef22009-01-06 14:40:10 -0800715 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 struct page *page = NULL;
717
Andi Kleena7420aa2009-09-16 11:50:05 +0200718 if (non_swap_entry(entry))
Hugh Dickins2509ef22009-01-06 14:40:10 -0800719 return 1;
Christoph Lameter06972122006-06-23 02:03:35 -0700720
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721 p = swap_info_get(entry);
722 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800723 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
Nick Piggin93fac702006-03-31 02:29:56 -0800724 page = find_get_page(&swapper_space, entry.val);
Nick Piggin8413ac92008-10-18 20:26:59 -0700725 if (page && !trylock_page(page)) {
Nick Piggin93fac702006-03-31 02:29:56 -0800726 page_cache_release(page);
727 page = NULL;
728 }
729 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700730 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731 }
732 if (page) {
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800733 /*
734 * Not mapped elsewhere, or swap space full? Free it!
735 * Also recheck PageSwapCache now page is locked (above).
736 */
Nick Piggin93fac702006-03-31 02:29:56 -0800737 if (PageSwapCache(page) && !PageWriteback(page) &&
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800738 (!page_mapped(page) || vm_swap_full())) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 delete_from_swap_cache(page);
740 SetPageDirty(page);
741 }
742 unlock_page(page);
743 page_cache_release(page);
744 }
Hugh Dickins2509ef22009-01-06 14:40:10 -0800745 return p != NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746}
747
Daisuke Nishimura02491442010-03-10 15:22:17 -0800748#ifdef CONFIG_CGROUP_MEM_RES_CTLR
749/**
750 * mem_cgroup_count_swap_user - count the user of a swap entry
751 * @ent: the swap entry to be checked
752 * @pagep: the pointer for the swap cache page of the entry to be stored
753 *
754 * Returns the number of the user of the swap entry. The number is valid only
755 * for swaps of anonymous pages.
756 * If the entry is found on swap cache, the page is stored to pagep with
757 * refcount of it being incremented.
758 */
759int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
760{
761 struct page *page;
762 struct swap_info_struct *p;
763 int count = 0;
764
765 page = find_get_page(&swapper_space, ent.val);
766 if (page)
767 count += page_mapcount(page);
768 p = swap_info_get(ent);
769 if (p) {
770 count += swap_count(p->swap_map[swp_offset(ent)]);
771 spin_unlock(&swap_lock);
772 }
773
774 *pagep = page;
775 return count;
776}
777#endif
778
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200779#ifdef CONFIG_HIBERNATION
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800780/*
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800781 * Find the swap type that corresponds to given device (if any).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800782 *
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800783 * @offset - number of the PAGE_SIZE-sized block of the device, starting
784 * from 0, in which the swap header is expected to be located.
785 *
786 * This is needed for the suspend to disk (aka swsusp).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800787 */
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800788int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800789{
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800790 struct block_device *bdev = NULL;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800791 int type;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800792
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800793 if (device)
794 bdev = bdget(device);
795
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800796 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800797 for (type = 0; type < nr_swapfiles; type++) {
798 struct swap_info_struct *sis = swap_info[type];
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800799
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800800 if (!(sis->flags & SWP_WRITEOK))
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800801 continue;
Rafael J. Wysockib6b5bce2006-08-27 01:23:25 -0700802
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800803 if (!bdev) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800804 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200805 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800806
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800807 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800808 return type;
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800809 }
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800810 if (bdev == sis->bdev) {
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800811 struct swap_extent *se = &sis->first_swap_extent;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800812
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800813 if (se->start_block == offset) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800814 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200815 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800816
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800817 spin_unlock(&swap_lock);
818 bdput(bdev);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800819 return type;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800820 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800821 }
822 }
823 spin_unlock(&swap_lock);
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800824 if (bdev)
825 bdput(bdev);
826
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800827 return -ENODEV;
828}
829
830/*
Hugh Dickins73c34b62009-12-14 17:58:43 -0800831 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
832 * corresponding to given index in swap_info (swap type).
833 */
834sector_t swapdev_block(int type, pgoff_t offset)
835{
836 struct block_device *bdev;
837
838 if ((unsigned int)type >= nr_swapfiles)
839 return 0;
840 if (!(swap_info[type]->flags & SWP_WRITEOK))
841 return 0;
Lee Schermerhornd4906e12009-12-14 17:58:49 -0800842 return map_swap_entry(swp_entry(type, offset), &bdev);
Hugh Dickins73c34b62009-12-14 17:58:43 -0800843}
844
845/*
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800846 * Return either the total number of swap pages of given type, or the number
847 * of free pages of that type (depending on @free)
848 *
849 * This is needed for software suspend
850 */
851unsigned int count_swap_pages(int type, int free)
852{
853 unsigned int n = 0;
854
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800855 spin_lock(&swap_lock);
856 if ((unsigned int)type < nr_swapfiles) {
857 struct swap_info_struct *sis = swap_info[type];
858
859 if (sis->flags & SWP_WRITEOK) {
860 n = sis->pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800861 if (free)
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800862 n -= sis->inuse_pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800863 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800864 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800865 spin_unlock(&swap_lock);
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800866 return n;
867}
Hugh Dickins73c34b62009-12-14 17:58:43 -0800868#endif /* CONFIG_HIBERNATION */
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800869
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700871 * No need to decide whether this PTE shares the swap entry with others,
872 * just let do_wp_page work it out if a write is requested later - to
873 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700874 */
Hugh Dickins044d66c2008-02-07 00:14:04 -0800875static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 unsigned long addr, swp_entry_t entry, struct page *page)
877{
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800878 struct mem_cgroup *ptr = NULL;
Hugh Dickins044d66c2008-02-07 00:14:04 -0800879 spinlock_t *ptl;
880 pte_t *pte;
881 int ret = 1;
882
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800883 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800884 ret = -ENOMEM;
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800885 goto out_nolock;
886 }
Hugh Dickins044d66c2008-02-07 00:14:04 -0800887
888 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
889 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
890 if (ret > 0)
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800891 mem_cgroup_cancel_charge_swapin(ptr);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800892 ret = 0;
893 goto out;
894 }
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800895
KAMEZAWA Hiroyukib084d432010-03-05 13:41:42 -0800896 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -0800897 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 get_page(page);
899 set_pte_at(vma->vm_mm, addr, pte,
900 pte_mkold(mk_pte(page, vma->vm_page_prot)));
901 page_add_anon_rmap(page, vma, addr);
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800902 mem_cgroup_commit_charge_swapin(page, ptr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 swap_free(entry);
904 /*
905 * Move the page to the active list so it is not
906 * immediately swapped out again after swapon.
907 */
908 activate_page(page);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800909out:
910 pte_unmap_unlock(pte, ptl);
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800911out_nolock:
Hugh Dickins044d66c2008-02-07 00:14:04 -0800912 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913}
914
915static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
916 unsigned long addr, unsigned long end,
917 swp_entry_t entry, struct page *page)
918{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700920 pte_t *pte;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800921 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922
Hugh Dickins044d66c2008-02-07 00:14:04 -0800923 /*
924 * We don't actually need pte lock while scanning for swp_pte: since
925 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
926 * page table while we're scanning; though it could get zapped, and on
927 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
928 * of unmatched parts which look like swp_pte, so unuse_pte must
929 * recheck under pte lock. Scanning without pte lock lets it be
930 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
931 */
932 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 do {
934 /*
935 * swapoff spends a _lot_ of time in this loop!
936 * Test inline before going to call unuse_pte.
937 */
938 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800939 pte_unmap(pte);
940 ret = unuse_pte(vma, pmd, addr, entry, page);
941 if (ret)
942 goto out;
943 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 }
945 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800946 pte_unmap(pte - 1);
947out:
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800948 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949}
950
951static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
952 unsigned long addr, unsigned long end,
953 swp_entry_t entry, struct page *page)
954{
955 pmd_t *pmd;
956 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800957 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958
959 pmd = pmd_offset(pud, addr);
960 do {
961 next = pmd_addr_end(addr, end);
962 if (pmd_none_or_clear_bad(pmd))
963 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800964 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
965 if (ret)
966 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967 } while (pmd++, addr = next, addr != end);
968 return 0;
969}
970
971static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
972 unsigned long addr, unsigned long end,
973 swp_entry_t entry, struct page *page)
974{
975 pud_t *pud;
976 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800977 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978
979 pud = pud_offset(pgd, addr);
980 do {
981 next = pud_addr_end(addr, end);
982 if (pud_none_or_clear_bad(pud))
983 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800984 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
985 if (ret)
986 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 } while (pud++, addr = next, addr != end);
988 return 0;
989}
990
991static int unuse_vma(struct vm_area_struct *vma,
992 swp_entry_t entry, struct page *page)
993{
994 pgd_t *pgd;
995 unsigned long addr, end, next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800996 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997
Hugh Dickins3ca7b3c2009-12-14 17:58:57 -0800998 if (page_anon_vma(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999 addr = page_address_in_vma(page, vma);
1000 if (addr == -EFAULT)
1001 return 0;
1002 else
1003 end = addr + PAGE_SIZE;
1004 } else {
1005 addr = vma->vm_start;
1006 end = vma->vm_end;
1007 }
1008
1009 pgd = pgd_offset(vma->vm_mm, addr);
1010 do {
1011 next = pgd_addr_end(addr, end);
1012 if (pgd_none_or_clear_bad(pgd))
1013 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001014 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1015 if (ret)
1016 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017 } while (pgd++, addr = next, addr != end);
1018 return 0;
1019}
1020
1021static int unuse_mm(struct mm_struct *mm,
1022 swp_entry_t entry, struct page *page)
1023{
1024 struct vm_area_struct *vma;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001025 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026
1027 if (!down_read_trylock(&mm->mmap_sem)) {
1028 /*
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -07001029 * Activate page so shrink_inactive_list is unlikely to unmap
1030 * its ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001031 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -07001032 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 unlock_page(page);
1034 down_read(&mm->mmap_sem);
1035 lock_page(page);
1036 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001038 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001039 break;
1040 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 up_read(&mm->mmap_sem);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001042 return (ret < 0)? ret: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043}
1044
1045/*
1046 * Scan swap_map from current position to next entry still in use.
1047 * Recycle to start on reaching the end, returning 0 when empty.
1048 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001049static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1050 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051{
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001052 unsigned int max = si->max;
1053 unsigned int i = prev;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001054 unsigned char count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055
1056 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001057 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 * for whether an entry is in use, not modifying it; false
1059 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -07001060 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061 */
1062 for (;;) {
1063 if (++i >= max) {
1064 if (!prev) {
1065 i = 0;
1066 break;
1067 }
1068 /*
1069 * No entries in use at top of swap_map,
1070 * loop back to start and recheck there.
1071 */
1072 max = prev + 1;
1073 prev = 0;
1074 i = 1;
1075 }
1076 count = si->swap_map[i];
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001077 if (count && swap_count(count) != SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 break;
1079 }
1080 return i;
1081}
1082
1083/*
1084 * We completely avoid races by reading each swap page in advance,
1085 * and then search for the process using it. All the necessary
1086 * page table adjustments can then be made atomically.
1087 */
1088static int try_to_unuse(unsigned int type)
1089{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001090 struct swap_info_struct *si = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091 struct mm_struct *start_mm;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001092 unsigned char *swap_map;
1093 unsigned char swcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094 struct page *page;
1095 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001096 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097 int retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098
1099 /*
1100 * When searching mms for an entry, a good strategy is to
1101 * start at the first mm we freed the previous entry from
1102 * (though actually we don't notice whether we or coincidence
1103 * freed the entry). Initialize this start_mm with a hold.
1104 *
1105 * A simpler strategy would be to start at the last mm we
1106 * freed the previous entry from; but that would take less
1107 * advantage of mmlist ordering, which clusters forked mms
1108 * together, child after parent. If we race with dup_mmap(), we
1109 * prefer to resolve parent before child, lest we miss entries
1110 * duplicated after we scanned child: using last mm would invert
Hugh Dickins570a335b2009-12-14 17:58:46 -08001111 * that.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112 */
1113 start_mm = &init_mm;
1114 atomic_inc(&init_mm.mm_users);
1115
1116 /*
1117 * Keep on scanning until all entries have gone. Usually,
1118 * one pass through swap_map is enough, but not necessarily:
1119 * there are races when an instance of an entry might be missed.
1120 */
1121 while ((i = find_next_to_unuse(si, i)) != 0) {
1122 if (signal_pending(current)) {
1123 retval = -EINTR;
1124 break;
1125 }
1126
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001127 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128 * Get a page for the entry, using the existing swap
1129 * cache page if there is one. Otherwise, get a clean
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001130 * page and read the swap into it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131 */
1132 swap_map = &si->swap_map[i];
1133 entry = swp_entry(type, i);
Hugh Dickins02098fe2008-02-04 22:28:42 -08001134 page = read_swap_cache_async(entry,
1135 GFP_HIGHUSER_MOVABLE, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136 if (!page) {
1137 /*
1138 * Either swap_duplicate() failed because entry
1139 * has been freed independently, and will not be
1140 * reused since sys_swapoff() already disabled
1141 * allocation from here, or alloc_page() failed.
1142 */
1143 if (!*swap_map)
1144 continue;
1145 retval = -ENOMEM;
1146 break;
1147 }
1148
1149 /*
1150 * Don't hold on to start_mm if it looks like exiting.
1151 */
1152 if (atomic_read(&start_mm->mm_users) == 1) {
1153 mmput(start_mm);
1154 start_mm = &init_mm;
1155 atomic_inc(&init_mm.mm_users);
1156 }
1157
1158 /*
1159 * Wait for and lock page. When do_swap_page races with
1160 * try_to_unuse, do_swap_page can handle the fault much
1161 * faster than try_to_unuse can locate the entry. This
1162 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1163 * defer to do_swap_page in such a case - in some tests,
1164 * do_swap_page and try_to_unuse repeatedly compete.
1165 */
1166 wait_on_page_locked(page);
1167 wait_on_page_writeback(page);
1168 lock_page(page);
1169 wait_on_page_writeback(page);
1170
1171 /*
1172 * Remove all references to entry.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174 swcount = *swap_map;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001175 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1176 retval = shmem_unuse(entry, page);
1177 /* page has already been unlocked and released */
1178 if (retval < 0)
1179 break;
1180 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181 }
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001182 if (swap_count(swcount) && start_mm != &init_mm)
1183 retval = unuse_mm(start_mm, entry, page);
1184
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001185 if (swap_count(*swap_map)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 int set_start_mm = (*swap_map >= swcount);
1187 struct list_head *p = &start_mm->mmlist;
1188 struct mm_struct *new_start_mm = start_mm;
1189 struct mm_struct *prev_mm = start_mm;
1190 struct mm_struct *mm;
1191
1192 atomic_inc(&new_start_mm->mm_users);
1193 atomic_inc(&prev_mm->mm_users);
1194 spin_lock(&mmlist_lock);
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001195 while (swap_count(*swap_map) && !retval &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196 (p = p->next) != &start_mm->mmlist) {
1197 mm = list_entry(p, struct mm_struct, mmlist);
Hugh Dickins70af7c52006-06-23 02:03:44 -07001198 if (!atomic_inc_not_zero(&mm->mm_users))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200 spin_unlock(&mmlist_lock);
1201 mmput(prev_mm);
1202 prev_mm = mm;
1203
1204 cond_resched();
1205
1206 swcount = *swap_map;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001207 if (!swap_count(swcount)) /* any usage ? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208 ;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001209 else if (mm == &init_mm)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210 set_start_mm = 1;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001211 else
Linus Torvalds1da177e2005-04-16 15:20:36 -07001212 retval = unuse_mm(mm, entry, page);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001213
Bo Liu32c5fc12009-11-02 16:50:33 +00001214 if (set_start_mm && *swap_map < swcount) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001215 mmput(new_start_mm);
1216 atomic_inc(&mm->mm_users);
1217 new_start_mm = mm;
1218 set_start_mm = 0;
1219 }
1220 spin_lock(&mmlist_lock);
1221 }
1222 spin_unlock(&mmlist_lock);
1223 mmput(prev_mm);
1224 mmput(start_mm);
1225 start_mm = new_start_mm;
1226 }
1227 if (retval) {
1228 unlock_page(page);
1229 page_cache_release(page);
1230 break;
1231 }
1232
1233 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 * If a reference remains (rare), we would like to leave
1235 * the page in the swap cache; but try_to_unmap could
1236 * then re-duplicate the entry once we drop page lock,
1237 * so we might loop indefinitely; also, that page could
1238 * not be swapped out to other storage meanwhile. So:
1239 * delete from cache even if there's another reference,
1240 * after ensuring that the data has been saved to disk -
1241 * since if the reference remains (rarer), it will be
1242 * read from disk into another page. Splitting into two
1243 * pages would be incorrect if swap supported "shared
1244 * private" pages, but they are handled by tmpfs files.
Hugh Dickins5ad64682009-12-14 17:59:24 -08001245 *
1246 * Given how unuse_vma() targets one particular offset
1247 * in an anon_vma, once the anon_vma has been determined,
1248 * this splitting happens to be just what is needed to
1249 * handle where KSM pages have been swapped out: re-reading
1250 * is unnecessarily slow, but we can fix that later on.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251 */
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001252 if (swap_count(*swap_map) &&
1253 PageDirty(page) && PageSwapCache(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001254 struct writeback_control wbc = {
1255 .sync_mode = WB_SYNC_NONE,
1256 };
1257
1258 swap_writepage(page, &wbc);
1259 lock_page(page);
1260 wait_on_page_writeback(page);
1261 }
Hugh Dickins68bdc8d2009-01-06 14:39:37 -08001262
1263 /*
1264 * It is conceivable that a racing task removed this page from
1265 * swap cache just before we acquired the page lock at the top,
1266 * or while we dropped it in unuse_mm(). The page might even
1267 * be back in swap cache on another swap area: that we must not
1268 * delete, since it may not have been written out to swap yet.
1269 */
1270 if (PageSwapCache(page) &&
1271 likely(page_private(page) == entry.val))
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001272 delete_from_swap_cache(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273
1274 /*
1275 * So we could skip searching mms once swap count went
1276 * to 1, we did not mark any present ptes as dirty: must
Anderson Briglia2706a1b2007-07-15 23:38:09 -07001277 * mark page dirty so shrink_page_list will preserve it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278 */
1279 SetPageDirty(page);
1280 unlock_page(page);
1281 page_cache_release(page);
1282
1283 /*
1284 * Make sure that we aren't completely killing
1285 * interactive performance.
1286 */
1287 cond_resched();
1288 }
1289
1290 mmput(start_mm);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001291 return retval;
1292}
1293
1294/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001295 * After a successful try_to_unuse, if no swap is now in use, we know
1296 * we can empty the mmlist. swap_lock must be held on entry and exit.
1297 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298 * added to the mmlist just after page_duplicate - before would be racy.
1299 */
1300static void drain_mmlist(void)
1301{
1302 struct list_head *p, *next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001303 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001305 for (type = 0; type < nr_swapfiles; type++)
1306 if (swap_info[type]->inuse_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 return;
1308 spin_lock(&mmlist_lock);
1309 list_for_each_safe(p, next, &init_mm.mmlist)
1310 list_del_init(p);
1311 spin_unlock(&mmlist_lock);
1312}
1313
1314/*
1315 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001316 * corresponds to page offset for the specified swap entry.
1317 * Note that the type of this function is sector_t, but it returns page offset
1318 * into the bdev, not sector offset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 */
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001320static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321{
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001322 struct swap_info_struct *sis;
1323 struct swap_extent *start_se;
1324 struct swap_extent *se;
1325 pgoff_t offset;
1326
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001327 sis = swap_info[swp_type(entry)];
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001328 *bdev = sis->bdev;
1329
1330 offset = swp_offset(entry);
1331 start_se = sis->curr_swap_extent;
1332 se = start_se;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333
1334 for ( ; ; ) {
1335 struct list_head *lh;
1336
1337 if (se->start_page <= offset &&
1338 offset < (se->start_page + se->nr_pages)) {
1339 return se->start_block + (offset - se->start_page);
1340 }
Hugh Dickins11d31882005-09-03 15:54:34 -07001341 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 se = list_entry(lh, struct swap_extent, list);
1343 sis->curr_swap_extent = se;
1344 BUG_ON(se == start_se); /* It *must* be present */
1345 }
1346}
1347
1348/*
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001349 * Returns the page offset into bdev for the specified page's swap entry.
1350 */
1351sector_t map_swap_page(struct page *page, struct block_device **bdev)
1352{
1353 swp_entry_t entry;
1354 entry.val = page_private(page);
1355 return map_swap_entry(entry, bdev);
1356}
1357
1358/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359 * Free all of a swapdev's extent information
1360 */
1361static void destroy_swap_extents(struct swap_info_struct *sis)
1362{
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001363 while (!list_empty(&sis->first_swap_extent.list)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 struct swap_extent *se;
1365
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001366 se = list_entry(sis->first_swap_extent.list.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 struct swap_extent, list);
1368 list_del(&se->list);
1369 kfree(se);
1370 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371}
1372
1373/*
1374 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -07001375 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376 *
Hugh Dickins11d31882005-09-03 15:54:34 -07001377 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378 */
1379static int
1380add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1381 unsigned long nr_pages, sector_t start_block)
1382{
1383 struct swap_extent *se;
1384 struct swap_extent *new_se;
1385 struct list_head *lh;
1386
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001387 if (start_page == 0) {
1388 se = &sis->first_swap_extent;
1389 sis->curr_swap_extent = se;
1390 se->start_page = 0;
1391 se->nr_pages = nr_pages;
1392 se->start_block = start_block;
1393 return 1;
1394 } else {
1395 lh = sis->first_swap_extent.list.prev; /* Highest extent */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -07001397 BUG_ON(se->start_page + se->nr_pages != start_page);
1398 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001399 /* Merge it */
1400 se->nr_pages += nr_pages;
1401 return 0;
1402 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403 }
1404
1405 /*
1406 * No merge. Insert a new extent, preserving ordering.
1407 */
1408 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1409 if (new_se == NULL)
1410 return -ENOMEM;
1411 new_se->start_page = start_page;
1412 new_se->nr_pages = nr_pages;
1413 new_se->start_block = start_block;
1414
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001415 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
Hugh Dickins53092a72005-09-03 15:54:34 -07001416 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417}
1418
1419/*
1420 * A `swap extent' is a simple thing which maps a contiguous range of pages
1421 * onto a contiguous range of disk blocks. An ordered list of swap extents
1422 * is built at swapon time and is then used at swap_writepage/swap_readpage
1423 * time for locating where on disk a page belongs.
1424 *
1425 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1426 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1427 * swap files identically.
1428 *
1429 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1430 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1431 * swapfiles are handled *identically* after swapon time.
1432 *
1433 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1434 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1435 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1436 * requirements, they are simply tossed out - we will never use those blocks
1437 * for swapping.
1438 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -07001439 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1441 * which will scribble on the fs.
1442 *
1443 * The amount of disk space which a single swap extent represents varies.
1444 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1445 * extents in the list. To avoid much list walking, we cache the previous
1446 * search location in `curr_swap_extent', and start new searches from there.
1447 * This is extremely effective. The average number of iterations in
1448 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1449 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001450static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001451{
1452 struct inode *inode;
1453 unsigned blocks_per_page;
1454 unsigned long page_no;
1455 unsigned blkbits;
1456 sector_t probe_block;
1457 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -07001458 sector_t lowest_block = -1;
1459 sector_t highest_block = 0;
1460 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461 int ret;
1462
1463 inode = sis->swap_file->f_mapping->host;
1464 if (S_ISBLK(inode->i_mode)) {
1465 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -07001466 *span = sis->pages;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001467 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001468 }
1469
1470 blkbits = inode->i_blkbits;
1471 blocks_per_page = PAGE_SIZE >> blkbits;
1472
1473 /*
1474 * Map all the blocks into the extent list. This code doesn't try
1475 * to be very smart.
1476 */
1477 probe_block = 0;
1478 page_no = 0;
1479 last_block = i_size_read(inode) >> blkbits;
1480 while ((probe_block + blocks_per_page) <= last_block &&
1481 page_no < sis->max) {
1482 unsigned block_in_page;
1483 sector_t first_block;
1484
1485 first_block = bmap(inode, probe_block);
1486 if (first_block == 0)
1487 goto bad_bmap;
1488
1489 /*
1490 * It must be PAGE_SIZE aligned on-disk
1491 */
1492 if (first_block & (blocks_per_page - 1)) {
1493 probe_block++;
1494 goto reprobe;
1495 }
1496
1497 for (block_in_page = 1; block_in_page < blocks_per_page;
1498 block_in_page++) {
1499 sector_t block;
1500
1501 block = bmap(inode, probe_block + block_in_page);
1502 if (block == 0)
1503 goto bad_bmap;
1504 if (block != first_block + block_in_page) {
1505 /* Discontiguity */
1506 probe_block++;
1507 goto reprobe;
1508 }
1509 }
1510
Hugh Dickins53092a72005-09-03 15:54:34 -07001511 first_block >>= (PAGE_SHIFT - blkbits);
1512 if (page_no) { /* exclude the header page */
1513 if (first_block < lowest_block)
1514 lowest_block = first_block;
1515 if (first_block > highest_block)
1516 highest_block = first_block;
1517 }
1518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 /*
1520 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1521 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001522 ret = add_swap_extent(sis, page_no, 1, first_block);
1523 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001525 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 page_no++;
1527 probe_block += blocks_per_page;
1528reprobe:
1529 continue;
1530 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001531 ret = nr_extents;
1532 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001534 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001535 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001536 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001537 sis->highest_bit = page_no - 1;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001538out:
1539 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540bad_bmap:
1541 printk(KERN_ERR "swapon: swapfile has holes\n");
1542 ret = -EINVAL;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001543 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544}
1545
Heiko Carstensc4ea37c2009-01-14 14:14:28 +01001546SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001548 struct swap_info_struct *p = NULL;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001549 unsigned char *swap_map;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 struct file *swap_file, *victim;
1551 struct address_space *mapping;
1552 struct inode *inode;
Hugh Dickins73c34b62009-12-14 17:58:43 -08001553 char *pathname;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 int i, type, prev;
1555 int err;
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001556
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557 if (!capable(CAP_SYS_ADMIN))
1558 return -EPERM;
1559
1560 pathname = getname(specialfile);
1561 err = PTR_ERR(pathname);
1562 if (IS_ERR(pathname))
1563 goto out;
1564
1565 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1566 putname(pathname);
1567 err = PTR_ERR(victim);
1568 if (IS_ERR(victim))
1569 goto out;
1570
1571 mapping = victim->f_mapping;
1572 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001573 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001574 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1575 p = swap_info[type];
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001576 if (p->flags & SWP_WRITEOK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577 if (p->swap_file->f_mapping == mapping)
1578 break;
1579 }
1580 prev = type;
1581 }
1582 if (type < 0) {
1583 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001584 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 goto out_dput;
1586 }
1587 if (!security_vm_enough_memory(p->pages))
1588 vm_unacct_memory(p->pages);
1589 else {
1590 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001591 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001592 goto out_dput;
1593 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001594 if (prev < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 swap_list.head = p->next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001596 else
1597 swap_info[prev]->next = p->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598 if (type == swap_list.next) {
1599 /* just pick something that's safe... */
1600 swap_list.next = swap_list.head;
1601 }
Hugh Dickins78ecba02008-07-23 21:28:23 -07001602 if (p->prio < 0) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001603 for (i = p->next; i >= 0; i = swap_info[i]->next)
1604 swap_info[i]->prio = p->prio--;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001605 least_priority++;
1606 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607 nr_swap_pages -= p->pages;
1608 total_swap_pages -= p->pages;
1609 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001610 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001611
Hugh Dickins35451be2009-09-21 17:02:27 -07001612 current->flags |= PF_OOM_ORIGIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 err = try_to_unuse(type);
Hugh Dickins35451be2009-09-21 17:02:27 -07001614 current->flags &= ~PF_OOM_ORIGIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001615
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616 if (err) {
1617 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001618 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001619 if (p->prio < 0)
1620 p->prio = --least_priority;
1621 prev = -1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001622 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1623 if (p->prio >= swap_info[i]->prio)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001624 break;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001625 prev = i;
1626 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 p->next = i;
1628 if (prev < 0)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001629 swap_list.head = swap_list.next = type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 else
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001631 swap_info[prev]->next = type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632 nr_swap_pages += p->pages;
1633 total_swap_pages += p->pages;
1634 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001635 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636 goto out_dput;
1637 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001638
1639 /* wait for any unplug function to finish */
1640 down_write(&swap_unplug_sem);
1641 up_write(&swap_unplug_sem);
1642
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001643 destroy_swap_extents(p);
Hugh Dickins570a335b2009-12-14 17:58:46 -08001644 if (p->flags & SWP_CONTINUED)
1645 free_swap_count_continuations(p);
1646
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001647 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001648 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001650
1651 /* wait for anyone still in scan_swap_map */
1652 p->highest_bit = 0; /* cuts scans short */
1653 while (p->flags >= SWP_SCANNING) {
1654 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001655 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001656 spin_lock(&swap_lock);
1657 }
1658
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 swap_file = p->swap_file;
1660 p->swap_file = NULL;
1661 p->max = 0;
1662 swap_map = p->swap_map;
1663 p->swap_map = NULL;
1664 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001665 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001666 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667 vfree(swap_map);
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08001668 /* Destroy swap account informatin */
1669 swap_cgroup_swapoff(type);
1670
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 inode = mapping->host;
1672 if (S_ISBLK(inode->i_mode)) {
1673 struct block_device *bdev = I_BDEV(inode);
1674 set_blocksize(bdev, p->old_block_size);
1675 bd_release(bdev);
1676 } else {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001677 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 inode->i_flags &= ~S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001679 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 }
1681 filp_close(swap_file, NULL);
1682 err = 0;
1683
1684out_dput:
1685 filp_close(victim, NULL);
1686out:
1687 return err;
1688}
1689
1690#ifdef CONFIG_PROC_FS
1691/* iterator */
1692static void *swap_start(struct seq_file *swap, loff_t *pos)
1693{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001694 struct swap_info_struct *si;
1695 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 loff_t l = *pos;
1697
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001698 mutex_lock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001700 if (!l)
1701 return SEQ_START_TOKEN;
1702
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001703 for (type = 0; type < nr_swapfiles; type++) {
1704 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1705 si = swap_info[type];
1706 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 continue;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001708 if (!--l)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001709 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 }
1711
1712 return NULL;
1713}
1714
1715static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1716{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001717 struct swap_info_struct *si = v;
1718 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001720 if (v == SEQ_START_TOKEN)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001721 type = 0;
1722 else
1723 type = si->type + 1;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001724
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001725 for (; type < nr_swapfiles; type++) {
1726 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1727 si = swap_info[type];
1728 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 continue;
1730 ++*pos;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001731 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 }
1733
1734 return NULL;
1735}
1736
1737static void swap_stop(struct seq_file *swap, void *v)
1738{
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001739 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740}
1741
1742static int swap_show(struct seq_file *swap, void *v)
1743{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001744 struct swap_info_struct *si = v;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001745 struct file *file;
1746 int len;
1747
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001748 if (si == SEQ_START_TOKEN) {
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001749 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1750 return 0;
1751 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001753 file = si->swap_file;
Jan Blunckc32c2f62008-02-14 19:38:43 -08001754 len = seq_path(swap, &file->f_path, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001755 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001756 len < 40 ? 40 - len : 1, " ",
1757 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 "partition" : "file\t",
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001759 si->pages << (PAGE_SHIFT - 10),
1760 si->inuse_pages << (PAGE_SHIFT - 10),
1761 si->prio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 return 0;
1763}
1764
Helge Deller15ad7cd2006-12-06 20:40:36 -08001765static const struct seq_operations swaps_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 .start = swap_start,
1767 .next = swap_next,
1768 .stop = swap_stop,
1769 .show = swap_show
1770};
1771
1772static int swaps_open(struct inode *inode, struct file *file)
1773{
1774 return seq_open(file, &swaps_op);
1775}
1776
Helge Deller15ad7cd2006-12-06 20:40:36 -08001777static const struct file_operations proc_swaps_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001778 .open = swaps_open,
1779 .read = seq_read,
1780 .llseek = seq_lseek,
1781 .release = seq_release,
1782};
1783
1784static int __init procswaps_init(void)
1785{
Denis V. Lunev3d71f862008-04-29 01:02:13 -07001786 proc_create("swaps", 0, NULL, &proc_swaps_operations);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001787 return 0;
1788}
1789__initcall(procswaps_init);
1790#endif /* CONFIG_PROC_FS */
1791
Jan Beulich17963162008-12-16 11:35:24 +00001792#ifdef MAX_SWAPFILES_CHECK
1793static int __init max_swapfiles_check(void)
1794{
1795 MAX_SWAPFILES_CHECK();
1796 return 0;
1797}
1798late_initcall(max_swapfiles_check);
1799#endif
1800
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801/*
1802 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1803 *
1804 * The swapon system call
1805 */
Heiko Carstensc4ea37c2009-01-14 14:14:28 +01001806SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001808 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809 char *name = NULL;
1810 struct block_device *bdev = NULL;
1811 struct file *swap_file = NULL;
1812 struct address_space *mapping;
1813 unsigned int type;
1814 int i, prev;
1815 int error;
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08001816 union swap_header *swap_header;
1817 unsigned int nr_good_pages;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001818 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001819 sector_t span;
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08001820 unsigned long maxpages;
Hugh Dickins73fd8742009-01-06 14:39:47 -08001821 unsigned long swapfilepages;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001822 unsigned char *swap_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 struct page *page = NULL;
1824 struct inode *inode = NULL;
1825 int did_down = 0;
1826
1827 if (!capable(CAP_SYS_ADMIN))
1828 return -EPERM;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001829
1830 p = kzalloc(sizeof(*p), GFP_KERNEL);
1831 if (!p)
1832 return -ENOMEM;
1833
Hugh Dickins5d337b92005-09-03 15:54:41 -07001834 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001835 for (type = 0; type < nr_swapfiles; type++) {
1836 if (!(swap_info[type]->flags & SWP_USED))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 break;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001838 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839 error = -EPERM;
Christoph Lameter06972122006-06-23 02:03:35 -07001840 if (type >= MAX_SWAPFILES) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001841 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001842 kfree(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 goto out;
1844 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001845 if (type >= nr_swapfiles) {
1846 p->type = type;
1847 swap_info[type] = p;
1848 /*
1849 * Write swap_info[type] before nr_swapfiles, in case a
1850 * racing procfs swap_start() or swap_next() is reading them.
1851 * (We never shrink nr_swapfiles, we never free this entry.)
1852 */
1853 smp_wmb();
1854 nr_swapfiles++;
1855 } else {
1856 kfree(p);
1857 p = swap_info[type];
1858 /*
1859 * Do not memset this entry: a racing procfs swap_next()
1860 * would be relying on p->type to remain valid.
1861 */
1862 }
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001863 INIT_LIST_HEAD(&p->first_swap_extent.list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001864 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865 p->next = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001866 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001867
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 name = getname(specialfile);
1869 error = PTR_ERR(name);
1870 if (IS_ERR(name)) {
1871 name = NULL;
1872 goto bad_swap_2;
1873 }
1874 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1875 error = PTR_ERR(swap_file);
1876 if (IS_ERR(swap_file)) {
1877 swap_file = NULL;
1878 goto bad_swap_2;
1879 }
1880
1881 p->swap_file = swap_file;
1882 mapping = swap_file->f_mapping;
1883 inode = mapping->host;
1884
1885 error = -EBUSY;
1886 for (i = 0; i < nr_swapfiles; i++) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001887 struct swap_info_struct *q = swap_info[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888
1889 if (i == type || !q->swap_file)
1890 continue;
1891 if (mapping == q->swap_file->f_mapping)
1892 goto bad_swap;
1893 }
1894
1895 error = -EINVAL;
1896 if (S_ISBLK(inode->i_mode)) {
1897 bdev = I_BDEV(inode);
1898 error = bd_claim(bdev, sys_swapon);
1899 if (error < 0) {
1900 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001901 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001902 goto bad_swap;
1903 }
1904 p->old_block_size = block_size(bdev);
1905 error = set_blocksize(bdev, PAGE_SIZE);
1906 if (error < 0)
1907 goto bad_swap;
1908 p->bdev = bdev;
Nitin Guptab2725642010-05-17 11:02:42 +05301909 p->flags |= SWP_BLKDEV;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910 } else if (S_ISREG(inode->i_mode)) {
1911 p->bdev = inode->i_sb->s_bdev;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001912 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001913 did_down = 1;
1914 if (IS_SWAPFILE(inode)) {
1915 error = -EBUSY;
1916 goto bad_swap;
1917 }
1918 } else {
1919 goto bad_swap;
1920 }
1921
Hugh Dickins73fd8742009-01-06 14:39:47 -08001922 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001923
1924 /*
1925 * Read the swap header.
1926 */
1927 if (!mapping->a_ops->readpage) {
1928 error = -EINVAL;
1929 goto bad_swap;
1930 }
Pekka Enberg090d2b12006-06-23 02:05:08 -07001931 page = read_mapping_page(mapping, 0, swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001932 if (IS_ERR(page)) {
1933 error = PTR_ERR(page);
1934 goto bad_swap;
1935 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001936 swap_header = kmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001937
Hugh Dickins81e33972009-01-06 14:39:49 -08001938 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
Jesper Juhle97a3112006-01-11 01:50:28 +01001939 printk(KERN_ERR "Unable to find swap-space signature\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940 error = -EINVAL;
1941 goto bad_swap;
1942 }
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001943
Hugh Dickins81e33972009-01-06 14:39:49 -08001944 /* swap partition endianess hack... */
1945 if (swab32(swap_header->info.version) == 1) {
1946 swab32s(&swap_header->info.version);
1947 swab32s(&swap_header->info.last_page);
1948 swab32s(&swap_header->info.nr_badpages);
1949 for (i = 0; i < swap_header->info.nr_badpages; i++)
1950 swab32s(&swap_header->info.badpages[i]);
1951 }
1952 /* Check the swap header's sub-version */
1953 if (swap_header->info.version != 1) {
1954 printk(KERN_WARNING
1955 "Unable to handle swap header version %d\n",
1956 swap_header->info.version);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001957 error = -EINVAL;
1958 goto bad_swap;
Hugh Dickins81e33972009-01-06 14:39:49 -08001959 }
1960
1961 p->lowest_bit = 1;
1962 p->cluster_next = 1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001963 p->cluster_nr = 0;
Hugh Dickins81e33972009-01-06 14:39:49 -08001964
1965 /*
1966 * Find out how many pages are allowed for a single swap
1967 * device. There are two limiting factors: 1) the number of
1968 * bits for the swap offset in the swp_entry_t type and
1969 * 2) the number of bits in the a swap pte as defined by
1970 * the different architectures. In order to find the
1971 * largest possible bit mask a swap entry with swap type 0
1972 * and swap offset ~0UL is created, encoded to a swap pte,
1973 * decoded to a swp_entry_t again and finally the swap
1974 * offset is extracted. This will mask all the bits from
1975 * the initial ~0UL mask that can't be encoded in either
1976 * the swp_entry_t or the architecture definition of a
1977 * swap pte.
1978 */
1979 maxpages = swp_offset(pte_to_swp_entry(
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08001980 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
1981 if (maxpages > swap_header->info.last_page) {
1982 maxpages = swap_header->info.last_page + 1;
1983 /* p->max is an unsigned int: don't overflow it */
1984 if ((unsigned int)maxpages == 0)
1985 maxpages = UINT_MAX;
1986 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001987 p->highest_bit = maxpages - 1;
1988
1989 error = -EINVAL;
1990 if (!maxpages)
1991 goto bad_swap;
1992 if (swapfilepages && maxpages > swapfilepages) {
1993 printk(KERN_WARNING
1994 "Swap area shorter than signature indicates\n");
1995 goto bad_swap;
1996 }
1997 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1998 goto bad_swap;
1999 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2000 goto bad_swap;
2001
2002 /* OK, set up the swap map and apply the bad block list */
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002003 swap_map = vmalloc(maxpages);
Hugh Dickins81e33972009-01-06 14:39:49 -08002004 if (!swap_map) {
2005 error = -ENOMEM;
2006 goto bad_swap;
2007 }
2008
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002009 memset(swap_map, 0, maxpages);
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08002010 nr_good_pages = maxpages - 1; /* omit header page */
2011
Hugh Dickins81e33972009-01-06 14:39:49 -08002012 for (i = 0; i < swap_header->info.nr_badpages; i++) {
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08002013 unsigned int page_nr = swap_header->info.badpages[i];
2014 if (page_nr == 0 || page_nr > swap_header->info.last_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 error = -EINVAL;
2016 goto bad_swap;
2017 }
Hugh Dickinsad2bd7e2010-03-05 13:42:12 -08002018 if (page_nr < maxpages) {
2019 swap_map[page_nr] = SWAP_MAP_BAD;
2020 nr_good_pages--;
2021 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022 }
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08002023
2024 error = swap_cgroup_swapon(type, maxpages);
2025 if (error)
2026 goto bad_swap;
2027
Hugh Dickinse2244ec2005-09-03 15:54:32 -07002028 if (nr_good_pages) {
Hugh Dickins78ecba02008-07-23 21:28:23 -07002029 swap_map[0] = SWAP_MAP_BAD;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07002030 p->max = maxpages;
2031 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07002032 nr_extents = setup_swap_extents(p, &span);
2033 if (nr_extents < 0) {
2034 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07002035 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07002036 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07002037 nr_good_pages = p->pages;
2038 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 if (!nr_good_pages) {
2040 printk(KERN_WARNING "Empty swap-file\n");
2041 error = -EINVAL;
2042 goto bad_swap;
2043 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044
Suresh Jayaraman3bd0f0c2009-09-30 10:53:48 +02002045 if (p->bdev) {
2046 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2047 p->flags |= SWP_SOLIDSTATE;
2048 p->cluster_next = 1 + (random32() % p->highest_bit);
2049 }
Hugh Dickins33994462010-09-09 16:38:11 -07002050 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
Suresh Jayaraman3bd0f0c2009-09-30 10:53:48 +02002051 p->flags |= SWP_DISCARDABLE;
Hugh Dickins20137a42009-01-06 14:39:54 -08002052 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -08002053
Ingo Molnarfc0abb12006-01-18 17:42:33 -08002054 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07002055 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07002056 if (swap_flags & SWAP_FLAG_PREFER)
2057 p->prio =
2058 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2059 else
2060 p->prio = --least_priority;
2061 p->swap_map = swap_map;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08002062 p->flags |= SWP_WRITEOK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063 nr_swap_pages += nr_good_pages;
2064 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07002065
Hugh Dickins6eb396d2005-09-03 15:54:35 -07002066 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins20137a42009-01-06 14:39:54 -08002067 "Priority:%d extents:%d across:%lluk %s%s\n",
Hugh Dickins53092a72005-09-03 15:54:34 -07002068 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
Hugh Dickins6a6ba832009-01-06 14:39:51 -08002069 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
Hugh Dickins20137a42009-01-06 14:39:54 -08002070 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2071 (p->flags & SWP_DISCARDABLE) ? "D" : "");
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072
2073 /* insert swap space into swap_list: */
2074 prev = -1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002075 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
2076 if (p->prio >= swap_info[i]->prio)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 prev = i;
2079 }
2080 p->next = i;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002081 if (prev < 0)
2082 swap_list.head = swap_list.next = type;
2083 else
2084 swap_info[prev]->next = type;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002085 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08002086 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 error = 0;
2088 goto out;
2089bad_swap:
2090 if (bdev) {
2091 set_blocksize(bdev, p->old_block_size);
2092 bd_release(bdev);
2093 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07002094 destroy_swap_extents(p);
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08002095 swap_cgroup_swapoff(type);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07002097 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 p->swap_file = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002099 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002100 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 vfree(swap_map);
2102 if (swap_file)
2103 filp_close(swap_file, NULL);
2104out:
2105 if (page && !IS_ERR(page)) {
2106 kunmap(page);
2107 page_cache_release(page);
2108 }
2109 if (name)
2110 putname(name);
2111 if (did_down) {
2112 if (!error)
2113 inode->i_flags |= S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002114 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002115 }
2116 return error;
2117}
2118
2119void si_swapinfo(struct sysinfo *val)
2120{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002121 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122 unsigned long nr_to_be_unused = 0;
2123
Hugh Dickins5d337b92005-09-03 15:54:41 -07002124 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002125 for (type = 0; type < nr_swapfiles; type++) {
2126 struct swap_info_struct *si = swap_info[type];
2127
2128 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2129 nr_to_be_unused += si->inuse_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130 }
2131 val->freeswap = nr_swap_pages + nr_to_be_unused;
2132 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002133 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134}
2135
2136/*
2137 * Verify that a swap entry is valid and increment its swap map count.
2138 *
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002139 * Returns error code in following case.
2140 * - success -> 0
2141 * - swp_entry is invalid -> EINVAL
2142 * - swp_entry is migration entry -> EINVAL
2143 * - swap-cache reference is requested but there is already one. -> EEXIST
2144 * - swap-cache reference is requested but the entry is not used. -> ENOENT
Hugh Dickins570a335b2009-12-14 17:58:46 -08002145 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
Linus Torvalds1da177e2005-04-16 15:20:36 -07002146 */
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002147static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002148{
Hugh Dickins73c34b62009-12-14 17:58:43 -08002149 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002150 unsigned long offset, type;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002151 unsigned char count;
2152 unsigned char has_cache;
Hugh Dickins253d5532009-12-14 17:58:44 -08002153 int err = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154
Andi Kleena7420aa2009-09-16 11:50:05 +02002155 if (non_swap_entry(entry))
Hugh Dickins253d5532009-12-14 17:58:44 -08002156 goto out;
Christoph Lameter06972122006-06-23 02:03:35 -07002157
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 type = swp_type(entry);
2159 if (type >= nr_swapfiles)
2160 goto bad_file;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002161 p = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 offset = swp_offset(entry);
2163
Hugh Dickins5d337b92005-09-03 15:54:41 -07002164 spin_lock(&swap_lock);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002165 if (unlikely(offset >= p->max))
2166 goto unlock_out;
2167
Hugh Dickins253d5532009-12-14 17:58:44 -08002168 count = p->swap_map[offset];
2169 has_cache = count & SWAP_HAS_CACHE;
2170 count &= ~SWAP_HAS_CACHE;
2171 err = 0;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002172
Hugh Dickins253d5532009-12-14 17:58:44 -08002173 if (usage == SWAP_HAS_CACHE) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002174
2175 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
Hugh Dickins253d5532009-12-14 17:58:44 -08002176 if (!has_cache && count)
2177 has_cache = SWAP_HAS_CACHE;
2178 else if (has_cache) /* someone else added cache */
2179 err = -EEXIST;
2180 else /* no users remaining */
2181 err = -ENOENT;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002182
2183 } else if (count || has_cache) {
Hugh Dickins253d5532009-12-14 17:58:44 -08002184
Hugh Dickins570a335b2009-12-14 17:58:46 -08002185 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2186 count += usage;
2187 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
Hugh Dickins253d5532009-12-14 17:58:44 -08002188 err = -EINVAL;
Hugh Dickins570a335b2009-12-14 17:58:46 -08002189 else if (swap_count_continued(p, offset, count))
2190 count = COUNT_CONTINUED;
2191 else
2192 err = -ENOMEM;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002193 } else
Hugh Dickins253d5532009-12-14 17:58:44 -08002194 err = -ENOENT; /* unused swap entry */
2195
2196 p->swap_map[offset] = count | has_cache;
2197
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002198unlock_out:
Hugh Dickins5d337b92005-09-03 15:54:41 -07002199 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002200out:
Hugh Dickins253d5532009-12-14 17:58:44 -08002201 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202
2203bad_file:
2204 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2205 goto out;
2206}
Hugh Dickins253d5532009-12-14 17:58:44 -08002207
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002208/*
Hugh Dickinsaaa46862009-12-14 17:58:47 -08002209 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2210 * (in which case its reference count is never incremented).
2211 */
2212void swap_shmem_alloc(swp_entry_t entry)
2213{
2214 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2215}
2216
2217/*
Hugh Dickins08259d52010-03-05 13:42:25 -08002218 * Increase reference count of swap entry by 1.
2219 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2220 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2221 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2222 * might occur if a page table entry has got corrupted.
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002223 */
Hugh Dickins570a335b2009-12-14 17:58:46 -08002224int swap_duplicate(swp_entry_t entry)
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002225{
Hugh Dickins570a335b2009-12-14 17:58:46 -08002226 int err = 0;
2227
2228 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2229 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2230 return err;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002231}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002233/*
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002234 * @entry: swap entry for which we allocate swap cache.
2235 *
Hugh Dickins73c34b62009-12-14 17:58:43 -08002236 * Called when allocating swap cache for existing swap entry,
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002237 * This can return error codes. Returns 0 at success.
2238 * -EBUSY means there is a swap cache.
2239 * Note: return code is different from swap_duplicate().
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002240 */
2241int swapcache_prepare(swp_entry_t entry)
2242{
Hugh Dickins253d5532009-12-14 17:58:44 -08002243 return __swap_duplicate(entry, SWAP_HAS_CACHE);
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002244}
2245
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07002247 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248 * reference on the swaphandle, it doesn't matter if it becomes unused.
2249 */
2250int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2251{
Hugh Dickins89528982008-02-04 22:28:45 -08002252 struct swap_info_struct *si;
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002253 int our_page_cluster = page_cluster;
Hugh Dickins89528982008-02-04 22:28:45 -08002254 pgoff_t target, toff;
2255 pgoff_t base, end;
2256 int nr_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002258 if (!our_page_cluster) /* no readahead */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 return 0;
Hugh Dickins89528982008-02-04 22:28:45 -08002260
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002261 si = swap_info[swp_type(entry)];
Hugh Dickins89528982008-02-04 22:28:45 -08002262 target = swp_offset(entry);
2263 base = (target >> our_page_cluster) << our_page_cluster;
2264 end = base + (1 << our_page_cluster);
2265 if (!base) /* first page is swap header */
2266 base++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267
Hugh Dickins5d337b92005-09-03 15:54:41 -07002268 spin_lock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002269 if (end > si->max) /* don't go beyond end of map */
2270 end = si->max;
2271
2272 /* Count contiguous allocated slots above our target */
2273 for (toff = target; ++toff < end; nr_pages++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274 /* Don't read in free or bad pages */
Hugh Dickins89528982008-02-04 22:28:45 -08002275 if (!si->swap_map[toff])
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002277 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278 break;
Hugh Dickins89528982008-02-04 22:28:45 -08002279 }
2280 /* Count contiguous allocated slots below our target */
2281 for (toff = target; --toff >= base; nr_pages++) {
2282 /* Don't read in free or bad pages */
2283 if (!si->swap_map[toff])
2284 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002285 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Hugh Dickins89528982008-02-04 22:28:45 -08002286 break;
2287 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07002288 spin_unlock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002289
2290 /*
2291 * Indicate starting offset, and return number of pages to get:
2292 * if only 1, say 0, since there's then no readahead to be done.
2293 */
2294 *offset = ++toff;
2295 return nr_pages? ++nr_pages: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296}
Hugh Dickins570a335b2009-12-14 17:58:46 -08002297
2298/*
2299 * add_swap_count_continuation - called when a swap count is duplicated
2300 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2301 * page of the original vmalloc'ed swap_map, to hold the continuation count
2302 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2303 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2304 *
2305 * These continuation pages are seldom referenced: the common paths all work
2306 * on the original swap_map, only referring to a continuation page when the
2307 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2308 *
2309 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2310 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2311 * can be called after dropping locks.
2312 */
2313int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2314{
2315 struct swap_info_struct *si;
2316 struct page *head;
2317 struct page *page;
2318 struct page *list_page;
2319 pgoff_t offset;
2320 unsigned char count;
2321
2322 /*
2323 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2324 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2325 */
2326 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2327
2328 si = swap_info_get(entry);
2329 if (!si) {
2330 /*
2331 * An acceptable race has occurred since the failing
2332 * __swap_duplicate(): the swap entry has been freed,
2333 * perhaps even the whole swap_map cleared for swapoff.
2334 */
2335 goto outer;
2336 }
2337
2338 offset = swp_offset(entry);
2339 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2340
2341 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2342 /*
2343 * The higher the swap count, the more likely it is that tasks
2344 * will race to add swap count continuation: we need to avoid
2345 * over-provisioning.
2346 */
2347 goto out;
2348 }
2349
2350 if (!page) {
2351 spin_unlock(&swap_lock);
2352 return -ENOMEM;
2353 }
2354
2355 /*
2356 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2357 * no architecture is using highmem pages for kernel pagetables: so it
2358 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2359 */
2360 head = vmalloc_to_page(si->swap_map + offset);
2361 offset &= ~PAGE_MASK;
2362
2363 /*
2364 * Page allocation does not initialize the page's lru field,
2365 * but it does always reset its private field.
2366 */
2367 if (!page_private(head)) {
2368 BUG_ON(count & COUNT_CONTINUED);
2369 INIT_LIST_HEAD(&head->lru);
2370 set_page_private(head, SWP_CONTINUED);
2371 si->flags |= SWP_CONTINUED;
2372 }
2373
2374 list_for_each_entry(list_page, &head->lru, lru) {
2375 unsigned char *map;
2376
2377 /*
2378 * If the previous map said no continuation, but we've found
2379 * a continuation page, free our allocation and use this one.
2380 */
2381 if (!(count & COUNT_CONTINUED))
2382 goto out;
2383
2384 map = kmap_atomic(list_page, KM_USER0) + offset;
2385 count = *map;
2386 kunmap_atomic(map, KM_USER0);
2387
2388 /*
2389 * If this continuation count now has some space in it,
2390 * free our allocation and use this one.
2391 */
2392 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2393 goto out;
2394 }
2395
2396 list_add_tail(&page->lru, &head->lru);
2397 page = NULL; /* now it's attached, don't free it */
2398out:
2399 spin_unlock(&swap_lock);
2400outer:
2401 if (page)
2402 __free_page(page);
2403 return 0;
2404}
2405
2406/*
2407 * swap_count_continued - when the original swap_map count is incremented
2408 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2409 * into, carry if so, or else fail until a new continuation page is allocated;
2410 * when the original swap_map count is decremented from 0 with continuation,
2411 * borrow from the continuation and report whether it still holds more.
2412 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2413 */
2414static bool swap_count_continued(struct swap_info_struct *si,
2415 pgoff_t offset, unsigned char count)
2416{
2417 struct page *head;
2418 struct page *page;
2419 unsigned char *map;
2420
2421 head = vmalloc_to_page(si->swap_map + offset);
2422 if (page_private(head) != SWP_CONTINUED) {
2423 BUG_ON(count & COUNT_CONTINUED);
2424 return false; /* need to add count continuation */
2425 }
2426
2427 offset &= ~PAGE_MASK;
2428 page = list_entry(head->lru.next, struct page, lru);
2429 map = kmap_atomic(page, KM_USER0) + offset;
2430
2431 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2432 goto init_map; /* jump over SWAP_CONT_MAX checks */
2433
2434 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2435 /*
2436 * Think of how you add 1 to 999
2437 */
2438 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2439 kunmap_atomic(map, KM_USER0);
2440 page = list_entry(page->lru.next, struct page, lru);
2441 BUG_ON(page == head);
2442 map = kmap_atomic(page, KM_USER0) + offset;
2443 }
2444 if (*map == SWAP_CONT_MAX) {
2445 kunmap_atomic(map, KM_USER0);
2446 page = list_entry(page->lru.next, struct page, lru);
2447 if (page == head)
2448 return false; /* add count continuation */
2449 map = kmap_atomic(page, KM_USER0) + offset;
2450init_map: *map = 0; /* we didn't zero the page */
2451 }
2452 *map += 1;
2453 kunmap_atomic(map, KM_USER0);
2454 page = list_entry(page->lru.prev, struct page, lru);
2455 while (page != head) {
2456 map = kmap_atomic(page, KM_USER0) + offset;
2457 *map = COUNT_CONTINUED;
2458 kunmap_atomic(map, KM_USER0);
2459 page = list_entry(page->lru.prev, struct page, lru);
2460 }
2461 return true; /* incremented */
2462
2463 } else { /* decrementing */
2464 /*
2465 * Think of how you subtract 1 from 1000
2466 */
2467 BUG_ON(count != COUNT_CONTINUED);
2468 while (*map == COUNT_CONTINUED) {
2469 kunmap_atomic(map, KM_USER0);
2470 page = list_entry(page->lru.next, struct page, lru);
2471 BUG_ON(page == head);
2472 map = kmap_atomic(page, KM_USER0) + offset;
2473 }
2474 BUG_ON(*map == 0);
2475 *map -= 1;
2476 if (*map == 0)
2477 count = 0;
2478 kunmap_atomic(map, KM_USER0);
2479 page = list_entry(page->lru.prev, struct page, lru);
2480 while (page != head) {
2481 map = kmap_atomic(page, KM_USER0) + offset;
2482 *map = SWAP_CONT_MAX | count;
2483 count = COUNT_CONTINUED;
2484 kunmap_atomic(map, KM_USER0);
2485 page = list_entry(page->lru.prev, struct page, lru);
2486 }
2487 return count == COUNT_CONTINUED;
2488 }
2489}
2490
2491/*
2492 * free_swap_count_continuations - swapoff free all the continuation pages
2493 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2494 */
2495static void free_swap_count_continuations(struct swap_info_struct *si)
2496{
2497 pgoff_t offset;
2498
2499 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2500 struct page *head;
2501 head = vmalloc_to_page(si->swap_map + offset);
2502 if (page_private(head)) {
2503 struct list_head *this, *next;
2504 list_for_each_safe(this, next, &head->lru) {
2505 struct page *page;
2506 page = list_entry(this, struct page, lru);
2507 list_del(this);
2508 __free_page(page);
2509 }
2510 }
2511 }
2512}