blob: 6c0585b16418661529ef1c0399450bf4b9128a45 [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,
142 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
143 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,
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800153 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
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,
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800192 nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER))
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
318 /* reuse swap entry of cache-only swap if not busy. */
319 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
320 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
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700481/* The only caller of this function is now susupend routine */
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800482swp_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);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800488 si = swap_info[type];
489 if (si && (si->flags & SWP_WRITEOK)) {
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800490 nr_swap_pages--;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700491 /* This is called for allocating swap entry, not cache */
Hugh Dickins253d5532009-12-14 17:58:44 -0800492 offset = scan_swap_map(si, 1);
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800493 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) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700577 if (offset < p->lowest_bit)
578 p->lowest_bit = offset;
579 if (offset > p->highest_bit)
580 p->highest_bit = offset;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800581 if (swap_list.next >= 0 &&
582 p->prio > swap_info[swap_list.next]->prio)
583 swap_list.next = p->type;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700584 nr_swap_pages++;
585 p->inuse_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800587
588 return usage;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589}
590
591/*
592 * Caller has made sure that the swapdevice corresponding to entry
593 * is still around or has not been recycled.
594 */
595void swap_free(swp_entry_t entry)
596{
Hugh Dickins73c34b62009-12-14 17:58:43 -0800597 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598
599 p = swap_info_get(entry);
600 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800601 swap_entry_free(p, entry, 1);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700602 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603 }
604}
605
606/*
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700607 * Called after dropping swapcache to decrease refcnt to swap entries.
608 */
609void swapcache_free(swp_entry_t entry, struct page *page)
610{
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700611 struct swap_info_struct *p;
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800612 unsigned char count;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700613
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700614 p = swap_info_get(entry);
615 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800616 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
617 if (page)
618 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700619 spin_unlock(&swap_lock);
620 }
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700621}
622
623/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700624 * How many references to page are currently swapped out?
Hugh Dickins570a335b2009-12-14 17:58:46 -0800625 * This does not give an exact answer when swap count is continued,
626 * but does include the high COUNT_CONTINUED flag to allow for that.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700628static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700630 int count = 0;
631 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700632 swp_entry_t entry;
633
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700634 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 p = swap_info_get(entry);
636 if (p) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700637 count = swap_count(p->swap_map[swp_offset(entry)]);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700638 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700640 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641}
642
643/*
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800644 * We can write to an anon page without COW if there are no other references
645 * to it. And as a side-effect, free up its swap: because the old content
646 * on disk will never be read, and seeking back there to write new content
647 * later would only waste time away from clustering.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648 */
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800649int reuse_swap_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700650{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700651 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700652
Hugh Dickins51726b12009-01-06 14:39:25 -0800653 VM_BUG_ON(!PageLocked(page));
Hugh Dickins5ad64682009-12-14 17:59:24 -0800654 if (unlikely(PageKsm(page)))
655 return 0;
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700656 count = page_mapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800657 if (count <= 1 && PageSwapCache(page)) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700658 count += page_swapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800659 if (count == 1 && !PageWriteback(page)) {
660 delete_from_swap_cache(page);
661 SetPageDirty(page);
662 }
663 }
Hugh Dickins5ad64682009-12-14 17:59:24 -0800664 return count <= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700665}
666
667/*
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800668 * If swap is getting full, or if there are no more mappings of this page,
669 * then try_to_free_swap is called to free its swap space.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670 */
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800671int try_to_free_swap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700672{
Hugh Dickins51726b12009-01-06 14:39:25 -0800673 VM_BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674
675 if (!PageSwapCache(page))
676 return 0;
677 if (PageWriteback(page))
678 return 0;
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800679 if (page_swapcount(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 return 0;
681
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800682 delete_from_swap_cache(page);
683 SetPageDirty(page);
684 return 1;
Rik van Riel68a223942008-10-18 20:26:23 -0700685}
686
687/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688 * Free the swap entry like above, but also try to
689 * free the page cache entry if it is the last user.
690 */
Hugh Dickins2509ef22009-01-06 14:40:10 -0800691int free_swap_and_cache(swp_entry_t entry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692{
Hugh Dickins2509ef22009-01-06 14:40:10 -0800693 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 struct page *page = NULL;
695
Andi Kleena7420aa2009-09-16 11:50:05 +0200696 if (non_swap_entry(entry))
Hugh Dickins2509ef22009-01-06 14:40:10 -0800697 return 1;
Christoph Lameter06972122006-06-23 02:03:35 -0700698
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 p = swap_info_get(entry);
700 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800701 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
Nick Piggin93fac702006-03-31 02:29:56 -0800702 page = find_get_page(&swapper_space, entry.val);
Nick Piggin8413ac92008-10-18 20:26:59 -0700703 if (page && !trylock_page(page)) {
Nick Piggin93fac702006-03-31 02:29:56 -0800704 page_cache_release(page);
705 page = NULL;
706 }
707 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700708 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 }
710 if (page) {
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800711 /*
712 * Not mapped elsewhere, or swap space full? Free it!
713 * Also recheck PageSwapCache now page is locked (above).
714 */
Nick Piggin93fac702006-03-31 02:29:56 -0800715 if (PageSwapCache(page) && !PageWriteback(page) &&
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800716 (!page_mapped(page) || vm_swap_full())) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 delete_from_swap_cache(page);
718 SetPageDirty(page);
719 }
720 unlock_page(page);
721 page_cache_release(page);
722 }
Hugh Dickins2509ef22009-01-06 14:40:10 -0800723 return p != NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724}
725
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200726#ifdef CONFIG_HIBERNATION
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800727/*
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800728 * Find the swap type that corresponds to given device (if any).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800729 *
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800730 * @offset - number of the PAGE_SIZE-sized block of the device, starting
731 * from 0, in which the swap header is expected to be located.
732 *
733 * This is needed for the suspend to disk (aka swsusp).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800734 */
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800735int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800736{
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800737 struct block_device *bdev = NULL;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800738 int type;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800739
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800740 if (device)
741 bdev = bdget(device);
742
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800743 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800744 for (type = 0; type < nr_swapfiles; type++) {
745 struct swap_info_struct *sis = swap_info[type];
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800746
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800747 if (!(sis->flags & SWP_WRITEOK))
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800748 continue;
Rafael J. Wysockib6b5bce2006-08-27 01:23:25 -0700749
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800750 if (!bdev) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800751 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200752 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800753
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800754 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800755 return type;
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800756 }
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800757 if (bdev == sis->bdev) {
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800758 struct swap_extent *se = &sis->first_swap_extent;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800759
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800760 if (se->start_block == offset) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800761 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200762 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800763
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800764 spin_unlock(&swap_lock);
765 bdput(bdev);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800766 return type;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800767 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800768 }
769 }
770 spin_unlock(&swap_lock);
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800771 if (bdev)
772 bdput(bdev);
773
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800774 return -ENODEV;
775}
776
777/*
Hugh Dickins73c34b62009-12-14 17:58:43 -0800778 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
779 * corresponding to given index in swap_info (swap type).
780 */
781sector_t swapdev_block(int type, pgoff_t offset)
782{
783 struct block_device *bdev;
784
785 if ((unsigned int)type >= nr_swapfiles)
786 return 0;
787 if (!(swap_info[type]->flags & SWP_WRITEOK))
788 return 0;
Lee Schermerhornd4906e12009-12-14 17:58:49 -0800789 return map_swap_entry(swp_entry(type, offset), &bdev);
Hugh Dickins73c34b62009-12-14 17:58:43 -0800790}
791
792/*
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800793 * Return either the total number of swap pages of given type, or the number
794 * of free pages of that type (depending on @free)
795 *
796 * This is needed for software suspend
797 */
798unsigned int count_swap_pages(int type, int free)
799{
800 unsigned int n = 0;
801
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800802 spin_lock(&swap_lock);
803 if ((unsigned int)type < nr_swapfiles) {
804 struct swap_info_struct *sis = swap_info[type];
805
806 if (sis->flags & SWP_WRITEOK) {
807 n = sis->pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800808 if (free)
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800809 n -= sis->inuse_pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800810 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800811 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800812 spin_unlock(&swap_lock);
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800813 return n;
814}
Hugh Dickins73c34b62009-12-14 17:58:43 -0800815#endif /* CONFIG_HIBERNATION */
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800816
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700818 * No need to decide whether this PTE shares the swap entry with others,
819 * just let do_wp_page work it out if a write is requested later - to
820 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 */
Hugh Dickins044d66c2008-02-07 00:14:04 -0800822static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823 unsigned long addr, swp_entry_t entry, struct page *page)
824{
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800825 struct mem_cgroup *ptr = NULL;
Hugh Dickins044d66c2008-02-07 00:14:04 -0800826 spinlock_t *ptl;
827 pte_t *pte;
828 int ret = 1;
829
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800830 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800831 ret = -ENOMEM;
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800832 goto out_nolock;
833 }
Hugh Dickins044d66c2008-02-07 00:14:04 -0800834
835 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
836 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
837 if (ret > 0)
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800838 mem_cgroup_cancel_charge_swapin(ptr);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800839 ret = 0;
840 goto out;
841 }
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800842
Hugh Dickins42946212005-10-29 18:16:05 -0700843 inc_mm_counter(vma->vm_mm, anon_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844 get_page(page);
845 set_pte_at(vma->vm_mm, addr, pte,
846 pte_mkold(mk_pte(page, vma->vm_page_prot)));
847 page_add_anon_rmap(page, vma, addr);
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800848 mem_cgroup_commit_charge_swapin(page, ptr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 swap_free(entry);
850 /*
851 * Move the page to the active list so it is not
852 * immediately swapped out again after swapon.
853 */
854 activate_page(page);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800855out:
856 pte_unmap_unlock(pte, ptl);
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800857out_nolock:
Hugh Dickins044d66c2008-02-07 00:14:04 -0800858 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859}
860
861static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
862 unsigned long addr, unsigned long end,
863 swp_entry_t entry, struct page *page)
864{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700866 pte_t *pte;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800867 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868
Hugh Dickins044d66c2008-02-07 00:14:04 -0800869 /*
870 * We don't actually need pte lock while scanning for swp_pte: since
871 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
872 * page table while we're scanning; though it could get zapped, and on
873 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
874 * of unmatched parts which look like swp_pte, so unuse_pte must
875 * recheck under pte lock. Scanning without pte lock lets it be
876 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
877 */
878 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 do {
880 /*
881 * swapoff spends a _lot_ of time in this loop!
882 * Test inline before going to call unuse_pte.
883 */
884 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800885 pte_unmap(pte);
886 ret = unuse_pte(vma, pmd, addr, entry, page);
887 if (ret)
888 goto out;
889 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 }
891 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800892 pte_unmap(pte - 1);
893out:
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800894 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895}
896
897static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
898 unsigned long addr, unsigned long end,
899 swp_entry_t entry, struct page *page)
900{
901 pmd_t *pmd;
902 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800903 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904
905 pmd = pmd_offset(pud, addr);
906 do {
907 next = pmd_addr_end(addr, end);
908 if (pmd_none_or_clear_bad(pmd))
909 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800910 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
911 if (ret)
912 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913 } while (pmd++, addr = next, addr != end);
914 return 0;
915}
916
917static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
918 unsigned long addr, unsigned long end,
919 swp_entry_t entry, struct page *page)
920{
921 pud_t *pud;
922 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800923 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700924
925 pud = pud_offset(pgd, addr);
926 do {
927 next = pud_addr_end(addr, end);
928 if (pud_none_or_clear_bad(pud))
929 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800930 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
931 if (ret)
932 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 } while (pud++, addr = next, addr != end);
934 return 0;
935}
936
937static int unuse_vma(struct vm_area_struct *vma,
938 swp_entry_t entry, struct page *page)
939{
940 pgd_t *pgd;
941 unsigned long addr, end, next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800942 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700943
Hugh Dickins3ca7b3c2009-12-14 17:58:57 -0800944 if (page_anon_vma(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 addr = page_address_in_vma(page, vma);
946 if (addr == -EFAULT)
947 return 0;
948 else
949 end = addr + PAGE_SIZE;
950 } else {
951 addr = vma->vm_start;
952 end = vma->vm_end;
953 }
954
955 pgd = pgd_offset(vma->vm_mm, addr);
956 do {
957 next = pgd_addr_end(addr, end);
958 if (pgd_none_or_clear_bad(pgd))
959 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800960 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
961 if (ret)
962 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 } while (pgd++, addr = next, addr != end);
964 return 0;
965}
966
967static int unuse_mm(struct mm_struct *mm,
968 swp_entry_t entry, struct page *page)
969{
970 struct vm_area_struct *vma;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800971 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
973 if (!down_read_trylock(&mm->mmap_sem)) {
974 /*
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -0700975 * Activate page so shrink_inactive_list is unlikely to unmap
976 * its ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700978 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979 unlock_page(page);
980 down_read(&mm->mmap_sem);
981 lock_page(page);
982 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800984 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700985 break;
986 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 up_read(&mm->mmap_sem);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800988 return (ret < 0)? ret: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700989}
990
991/*
992 * Scan swap_map from current position to next entry still in use.
993 * Recycle to start on reaching the end, returning 0 when empty.
994 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700995static unsigned int find_next_to_unuse(struct swap_info_struct *si,
996 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700998 unsigned int max = si->max;
999 unsigned int i = prev;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001000 unsigned char count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001
1002 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001003 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004 * for whether an entry is in use, not modifying it; false
1005 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -07001006 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001007 */
1008 for (;;) {
1009 if (++i >= max) {
1010 if (!prev) {
1011 i = 0;
1012 break;
1013 }
1014 /*
1015 * No entries in use at top of swap_map,
1016 * loop back to start and recheck there.
1017 */
1018 max = prev + 1;
1019 prev = 0;
1020 i = 1;
1021 }
1022 count = si->swap_map[i];
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001023 if (count && swap_count(count) != SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 break;
1025 }
1026 return i;
1027}
1028
1029/*
1030 * We completely avoid races by reading each swap page in advance,
1031 * and then search for the process using it. All the necessary
1032 * page table adjustments can then be made atomically.
1033 */
1034static int try_to_unuse(unsigned int type)
1035{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001036 struct swap_info_struct *si = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 struct mm_struct *start_mm;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001038 unsigned char *swap_map;
1039 unsigned char swcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 struct page *page;
1041 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001042 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043 int retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044
1045 /*
1046 * When searching mms for an entry, a good strategy is to
1047 * start at the first mm we freed the previous entry from
1048 * (though actually we don't notice whether we or coincidence
1049 * freed the entry). Initialize this start_mm with a hold.
1050 *
1051 * A simpler strategy would be to start at the last mm we
1052 * freed the previous entry from; but that would take less
1053 * advantage of mmlist ordering, which clusters forked mms
1054 * together, child after parent. If we race with dup_mmap(), we
1055 * prefer to resolve parent before child, lest we miss entries
1056 * duplicated after we scanned child: using last mm would invert
Hugh Dickins570a335b2009-12-14 17:58:46 -08001057 * that.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 */
1059 start_mm = &init_mm;
1060 atomic_inc(&init_mm.mm_users);
1061
1062 /*
1063 * Keep on scanning until all entries have gone. Usually,
1064 * one pass through swap_map is enough, but not necessarily:
1065 * there are races when an instance of an entry might be missed.
1066 */
1067 while ((i = find_next_to_unuse(si, i)) != 0) {
1068 if (signal_pending(current)) {
1069 retval = -EINTR;
1070 break;
1071 }
1072
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001073 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 * Get a page for the entry, using the existing swap
1075 * cache page if there is one. Otherwise, get a clean
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001076 * page and read the swap into it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 */
1078 swap_map = &si->swap_map[i];
1079 entry = swp_entry(type, i);
Hugh Dickins02098fe2008-02-04 22:28:42 -08001080 page = read_swap_cache_async(entry,
1081 GFP_HIGHUSER_MOVABLE, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 if (!page) {
1083 /*
1084 * Either swap_duplicate() failed because entry
1085 * has been freed independently, and will not be
1086 * reused since sys_swapoff() already disabled
1087 * allocation from here, or alloc_page() failed.
1088 */
1089 if (!*swap_map)
1090 continue;
1091 retval = -ENOMEM;
1092 break;
1093 }
1094
1095 /*
1096 * Don't hold on to start_mm if it looks like exiting.
1097 */
1098 if (atomic_read(&start_mm->mm_users) == 1) {
1099 mmput(start_mm);
1100 start_mm = &init_mm;
1101 atomic_inc(&init_mm.mm_users);
1102 }
1103
1104 /*
1105 * Wait for and lock page. When do_swap_page races with
1106 * try_to_unuse, do_swap_page can handle the fault much
1107 * faster than try_to_unuse can locate the entry. This
1108 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1109 * defer to do_swap_page in such a case - in some tests,
1110 * do_swap_page and try_to_unuse repeatedly compete.
1111 */
1112 wait_on_page_locked(page);
1113 wait_on_page_writeback(page);
1114 lock_page(page);
1115 wait_on_page_writeback(page);
1116
1117 /*
1118 * Remove all references to entry.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001120 swcount = *swap_map;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001121 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1122 retval = shmem_unuse(entry, page);
1123 /* page has already been unlocked and released */
1124 if (retval < 0)
1125 break;
1126 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 }
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001128 if (swap_count(swcount) && start_mm != &init_mm)
1129 retval = unuse_mm(start_mm, entry, page);
1130
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001131 if (swap_count(*swap_map)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 int set_start_mm = (*swap_map >= swcount);
1133 struct list_head *p = &start_mm->mmlist;
1134 struct mm_struct *new_start_mm = start_mm;
1135 struct mm_struct *prev_mm = start_mm;
1136 struct mm_struct *mm;
1137
1138 atomic_inc(&new_start_mm->mm_users);
1139 atomic_inc(&prev_mm->mm_users);
1140 spin_lock(&mmlist_lock);
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001141 while (swap_count(*swap_map) && !retval &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 (p = p->next) != &start_mm->mmlist) {
1143 mm = list_entry(p, struct mm_struct, mmlist);
Hugh Dickins70af7c52006-06-23 02:03:44 -07001144 if (!atomic_inc_not_zero(&mm->mm_users))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 spin_unlock(&mmlist_lock);
1147 mmput(prev_mm);
1148 prev_mm = mm;
1149
1150 cond_resched();
1151
1152 swcount = *swap_map;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001153 if (!swap_count(swcount)) /* any usage ? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001154 ;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001155 else if (mm == &init_mm)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156 set_start_mm = 1;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001157 else
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 retval = unuse_mm(mm, entry, page);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001159
Bo Liu32c5fc12009-11-02 16:50:33 +00001160 if (set_start_mm && *swap_map < swcount) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 mmput(new_start_mm);
1162 atomic_inc(&mm->mm_users);
1163 new_start_mm = mm;
1164 set_start_mm = 0;
1165 }
1166 spin_lock(&mmlist_lock);
1167 }
1168 spin_unlock(&mmlist_lock);
1169 mmput(prev_mm);
1170 mmput(start_mm);
1171 start_mm = new_start_mm;
1172 }
1173 if (retval) {
1174 unlock_page(page);
1175 page_cache_release(page);
1176 break;
1177 }
1178
1179 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 * If a reference remains (rare), we would like to leave
1181 * the page in the swap cache; but try_to_unmap could
1182 * then re-duplicate the entry once we drop page lock,
1183 * so we might loop indefinitely; also, that page could
1184 * not be swapped out to other storage meanwhile. So:
1185 * delete from cache even if there's another reference,
1186 * after ensuring that the data has been saved to disk -
1187 * since if the reference remains (rarer), it will be
1188 * read from disk into another page. Splitting into two
1189 * pages would be incorrect if swap supported "shared
1190 * private" pages, but they are handled by tmpfs files.
Hugh Dickins5ad64682009-12-14 17:59:24 -08001191 *
1192 * Given how unuse_vma() targets one particular offset
1193 * in an anon_vma, once the anon_vma has been determined,
1194 * this splitting happens to be just what is needed to
1195 * handle where KSM pages have been swapped out: re-reading
1196 * is unnecessarily slow, but we can fix that later on.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197 */
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001198 if (swap_count(*swap_map) &&
1199 PageDirty(page) && PageSwapCache(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200 struct writeback_control wbc = {
1201 .sync_mode = WB_SYNC_NONE,
1202 };
1203
1204 swap_writepage(page, &wbc);
1205 lock_page(page);
1206 wait_on_page_writeback(page);
1207 }
Hugh Dickins68bdc8d2009-01-06 14:39:37 -08001208
1209 /*
1210 * It is conceivable that a racing task removed this page from
1211 * swap cache just before we acquired the page lock at the top,
1212 * or while we dropped it in unuse_mm(). The page might even
1213 * be back in swap cache on another swap area: that we must not
1214 * delete, since it may not have been written out to swap yet.
1215 */
1216 if (PageSwapCache(page) &&
1217 likely(page_private(page) == entry.val))
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001218 delete_from_swap_cache(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001219
1220 /*
1221 * So we could skip searching mms once swap count went
1222 * to 1, we did not mark any present ptes as dirty: must
Anderson Briglia2706a1b2007-07-15 23:38:09 -07001223 * mark page dirty so shrink_page_list will preserve it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224 */
1225 SetPageDirty(page);
1226 unlock_page(page);
1227 page_cache_release(page);
1228
1229 /*
1230 * Make sure that we aren't completely killing
1231 * interactive performance.
1232 */
1233 cond_resched();
1234 }
1235
1236 mmput(start_mm);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237 return retval;
1238}
1239
1240/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001241 * After a successful try_to_unuse, if no swap is now in use, we know
1242 * we can empty the mmlist. swap_lock must be held on entry and exit.
1243 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244 * added to the mmlist just after page_duplicate - before would be racy.
1245 */
1246static void drain_mmlist(void)
1247{
1248 struct list_head *p, *next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001249 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001251 for (type = 0; type < nr_swapfiles; type++)
1252 if (swap_info[type]->inuse_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 return;
1254 spin_lock(&mmlist_lock);
1255 list_for_each_safe(p, next, &init_mm.mmlist)
1256 list_del_init(p);
1257 spin_unlock(&mmlist_lock);
1258}
1259
1260/*
1261 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001262 * corresponds to page offset for the specified swap entry.
1263 * Note that the type of this function is sector_t, but it returns page offset
1264 * into the bdev, not sector offset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 */
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001266static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001267{
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001268 struct swap_info_struct *sis;
1269 struct swap_extent *start_se;
1270 struct swap_extent *se;
1271 pgoff_t offset;
1272
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001273 sis = swap_info[swp_type(entry)];
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001274 *bdev = sis->bdev;
1275
1276 offset = swp_offset(entry);
1277 start_se = sis->curr_swap_extent;
1278 se = start_se;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279
1280 for ( ; ; ) {
1281 struct list_head *lh;
1282
1283 if (se->start_page <= offset &&
1284 offset < (se->start_page + se->nr_pages)) {
1285 return se->start_block + (offset - se->start_page);
1286 }
Hugh Dickins11d31882005-09-03 15:54:34 -07001287 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288 se = list_entry(lh, struct swap_extent, list);
1289 sis->curr_swap_extent = se;
1290 BUG_ON(se == start_se); /* It *must* be present */
1291 }
1292}
1293
1294/*
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001295 * Returns the page offset into bdev for the specified page's swap entry.
1296 */
1297sector_t map_swap_page(struct page *page, struct block_device **bdev)
1298{
1299 swp_entry_t entry;
1300 entry.val = page_private(page);
1301 return map_swap_entry(entry, bdev);
1302}
1303
1304/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305 * Free all of a swapdev's extent information
1306 */
1307static void destroy_swap_extents(struct swap_info_struct *sis)
1308{
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001309 while (!list_empty(&sis->first_swap_extent.list)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310 struct swap_extent *se;
1311
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001312 se = list_entry(sis->first_swap_extent.list.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001313 struct swap_extent, list);
1314 list_del(&se->list);
1315 kfree(se);
1316 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317}
1318
1319/*
1320 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -07001321 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 *
Hugh Dickins11d31882005-09-03 15:54:34 -07001323 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 */
1325static int
1326add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1327 unsigned long nr_pages, sector_t start_block)
1328{
1329 struct swap_extent *se;
1330 struct swap_extent *new_se;
1331 struct list_head *lh;
1332
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001333 if (start_page == 0) {
1334 se = &sis->first_swap_extent;
1335 sis->curr_swap_extent = se;
1336 se->start_page = 0;
1337 se->nr_pages = nr_pages;
1338 se->start_block = start_block;
1339 return 1;
1340 } else {
1341 lh = sis->first_swap_extent.list.prev; /* Highest extent */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -07001343 BUG_ON(se->start_page + se->nr_pages != start_page);
1344 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 /* Merge it */
1346 se->nr_pages += nr_pages;
1347 return 0;
1348 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 }
1350
1351 /*
1352 * No merge. Insert a new extent, preserving ordering.
1353 */
1354 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1355 if (new_se == NULL)
1356 return -ENOMEM;
1357 new_se->start_page = start_page;
1358 new_se->nr_pages = nr_pages;
1359 new_se->start_block = start_block;
1360
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001361 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
Hugh Dickins53092a72005-09-03 15:54:34 -07001362 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363}
1364
1365/*
1366 * A `swap extent' is a simple thing which maps a contiguous range of pages
1367 * onto a contiguous range of disk blocks. An ordered list of swap extents
1368 * is built at swapon time and is then used at swap_writepage/swap_readpage
1369 * time for locating where on disk a page belongs.
1370 *
1371 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1372 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1373 * swap files identically.
1374 *
1375 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1376 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1377 * swapfiles are handled *identically* after swapon time.
1378 *
1379 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1380 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1381 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1382 * requirements, they are simply tossed out - we will never use those blocks
1383 * for swapping.
1384 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -07001385 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1387 * which will scribble on the fs.
1388 *
1389 * The amount of disk space which a single swap extent represents varies.
1390 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1391 * extents in the list. To avoid much list walking, we cache the previous
1392 * search location in `curr_swap_extent', and start new searches from there.
1393 * This is extremely effective. The average number of iterations in
1394 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1395 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001396static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001397{
1398 struct inode *inode;
1399 unsigned blocks_per_page;
1400 unsigned long page_no;
1401 unsigned blkbits;
1402 sector_t probe_block;
1403 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -07001404 sector_t lowest_block = -1;
1405 sector_t highest_block = 0;
1406 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 int ret;
1408
1409 inode = sis->swap_file->f_mapping->host;
1410 if (S_ISBLK(inode->i_mode)) {
1411 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -07001412 *span = sis->pages;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001413 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414 }
1415
1416 blkbits = inode->i_blkbits;
1417 blocks_per_page = PAGE_SIZE >> blkbits;
1418
1419 /*
1420 * Map all the blocks into the extent list. This code doesn't try
1421 * to be very smart.
1422 */
1423 probe_block = 0;
1424 page_no = 0;
1425 last_block = i_size_read(inode) >> blkbits;
1426 while ((probe_block + blocks_per_page) <= last_block &&
1427 page_no < sis->max) {
1428 unsigned block_in_page;
1429 sector_t first_block;
1430
1431 first_block = bmap(inode, probe_block);
1432 if (first_block == 0)
1433 goto bad_bmap;
1434
1435 /*
1436 * It must be PAGE_SIZE aligned on-disk
1437 */
1438 if (first_block & (blocks_per_page - 1)) {
1439 probe_block++;
1440 goto reprobe;
1441 }
1442
1443 for (block_in_page = 1; block_in_page < blocks_per_page;
1444 block_in_page++) {
1445 sector_t block;
1446
1447 block = bmap(inode, probe_block + block_in_page);
1448 if (block == 0)
1449 goto bad_bmap;
1450 if (block != first_block + block_in_page) {
1451 /* Discontiguity */
1452 probe_block++;
1453 goto reprobe;
1454 }
1455 }
1456
Hugh Dickins53092a72005-09-03 15:54:34 -07001457 first_block >>= (PAGE_SHIFT - blkbits);
1458 if (page_no) { /* exclude the header page */
1459 if (first_block < lowest_block)
1460 lowest_block = first_block;
1461 if (first_block > highest_block)
1462 highest_block = first_block;
1463 }
1464
Linus Torvalds1da177e2005-04-16 15:20:36 -07001465 /*
1466 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1467 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001468 ret = add_swap_extent(sis, page_no, 1, first_block);
1469 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001471 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472 page_no++;
1473 probe_block += blocks_per_page;
1474reprobe:
1475 continue;
1476 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001477 ret = nr_extents;
1478 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001480 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001481 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001482 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483 sis->highest_bit = page_no - 1;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001484out:
1485 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486bad_bmap:
1487 printk(KERN_ERR "swapon: swapfile has holes\n");
1488 ret = -EINVAL;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001489 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001490}
1491
Heiko Carstensc4ea37c2009-01-14 14:14:28 +01001492SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001494 struct swap_info_struct *p = NULL;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001495 unsigned char *swap_map;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496 struct file *swap_file, *victim;
1497 struct address_space *mapping;
1498 struct inode *inode;
Hugh Dickins73c34b62009-12-14 17:58:43 -08001499 char *pathname;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 int i, type, prev;
1501 int err;
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001502
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 if (!capable(CAP_SYS_ADMIN))
1504 return -EPERM;
1505
1506 pathname = getname(specialfile);
1507 err = PTR_ERR(pathname);
1508 if (IS_ERR(pathname))
1509 goto out;
1510
1511 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1512 putname(pathname);
1513 err = PTR_ERR(victim);
1514 if (IS_ERR(victim))
1515 goto out;
1516
1517 mapping = victim->f_mapping;
1518 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001519 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001520 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1521 p = swap_info[type];
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001522 if (p->flags & SWP_WRITEOK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 if (p->swap_file->f_mapping == mapping)
1524 break;
1525 }
1526 prev = type;
1527 }
1528 if (type < 0) {
1529 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001530 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531 goto out_dput;
1532 }
1533 if (!security_vm_enough_memory(p->pages))
1534 vm_unacct_memory(p->pages);
1535 else {
1536 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001537 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001538 goto out_dput;
1539 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001540 if (prev < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001541 swap_list.head = p->next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001542 else
1543 swap_info[prev]->next = p->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 if (type == swap_list.next) {
1545 /* just pick something that's safe... */
1546 swap_list.next = swap_list.head;
1547 }
Hugh Dickins78ecba02008-07-23 21:28:23 -07001548 if (p->prio < 0) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001549 for (i = p->next; i >= 0; i = swap_info[i]->next)
1550 swap_info[i]->prio = p->prio--;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001551 least_priority++;
1552 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553 nr_swap_pages -= p->pages;
1554 total_swap_pages -= p->pages;
1555 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001556 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001557
Hugh Dickins35451be2009-09-21 17:02:27 -07001558 current->flags |= PF_OOM_ORIGIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559 err = try_to_unuse(type);
Hugh Dickins35451be2009-09-21 17:02:27 -07001560 current->flags &= ~PF_OOM_ORIGIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 if (err) {
1563 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001564 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001565 if (p->prio < 0)
1566 p->prio = --least_priority;
1567 prev = -1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001568 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1569 if (p->prio >= swap_info[i]->prio)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570 break;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001571 prev = i;
1572 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001573 p->next = i;
1574 if (prev < 0)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001575 swap_list.head = swap_list.next = type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576 else
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001577 swap_info[prev]->next = type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001578 nr_swap_pages += p->pages;
1579 total_swap_pages += p->pages;
1580 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001581 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001582 goto out_dput;
1583 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001584
1585 /* wait for any unplug function to finish */
1586 down_write(&swap_unplug_sem);
1587 up_write(&swap_unplug_sem);
1588
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001589 destroy_swap_extents(p);
Hugh Dickins570a335b2009-12-14 17:58:46 -08001590 if (p->flags & SWP_CONTINUED)
1591 free_swap_count_continuations(p);
1592
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001593 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001594 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001596
1597 /* wait for anyone still in scan_swap_map */
1598 p->highest_bit = 0; /* cuts scans short */
1599 while (p->flags >= SWP_SCANNING) {
1600 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001601 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001602 spin_lock(&swap_lock);
1603 }
1604
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 swap_file = p->swap_file;
1606 p->swap_file = NULL;
1607 p->max = 0;
1608 swap_map = p->swap_map;
1609 p->swap_map = NULL;
1610 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001611 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001612 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 vfree(swap_map);
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08001614 /* Destroy swap account informatin */
1615 swap_cgroup_swapoff(type);
1616
Linus Torvalds1da177e2005-04-16 15:20:36 -07001617 inode = mapping->host;
1618 if (S_ISBLK(inode->i_mode)) {
1619 struct block_device *bdev = I_BDEV(inode);
1620 set_blocksize(bdev, p->old_block_size);
1621 bd_release(bdev);
1622 } else {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001623 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001624 inode->i_flags &= ~S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001625 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001626 }
1627 filp_close(swap_file, NULL);
1628 err = 0;
1629
1630out_dput:
1631 filp_close(victim, NULL);
1632out:
1633 return err;
1634}
1635
1636#ifdef CONFIG_PROC_FS
1637/* iterator */
1638static void *swap_start(struct seq_file *swap, loff_t *pos)
1639{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001640 struct swap_info_struct *si;
1641 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 loff_t l = *pos;
1643
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001644 mutex_lock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001646 if (!l)
1647 return SEQ_START_TOKEN;
1648
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001649 for (type = 0; type < nr_swapfiles; type++) {
1650 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1651 si = swap_info[type];
1652 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 continue;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001654 if (!--l)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001655 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 }
1657
1658 return NULL;
1659}
1660
1661static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1662{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001663 struct swap_info_struct *si = v;
1664 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001666 if (v == SEQ_START_TOKEN)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001667 type = 0;
1668 else
1669 type = si->type + 1;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001670
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001671 for (; type < nr_swapfiles; type++) {
1672 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1673 si = swap_info[type];
1674 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675 continue;
1676 ++*pos;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001677 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 }
1679
1680 return NULL;
1681}
1682
1683static void swap_stop(struct seq_file *swap, void *v)
1684{
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001685 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001686}
1687
1688static int swap_show(struct seq_file *swap, void *v)
1689{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001690 struct swap_info_struct *si = v;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 struct file *file;
1692 int len;
1693
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001694 if (si == SEQ_START_TOKEN) {
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001695 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1696 return 0;
1697 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001698
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001699 file = si->swap_file;
Jan Blunckc32c2f62008-02-14 19:38:43 -08001700 len = seq_path(swap, &file->f_path, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001701 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001702 len < 40 ? 40 - len : 1, " ",
1703 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 "partition" : "file\t",
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001705 si->pages << (PAGE_SHIFT - 10),
1706 si->inuse_pages << (PAGE_SHIFT - 10),
1707 si->prio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708 return 0;
1709}
1710
Helge Deller15ad7cd2006-12-06 20:40:36 -08001711static const struct seq_operations swaps_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712 .start = swap_start,
1713 .next = swap_next,
1714 .stop = swap_stop,
1715 .show = swap_show
1716};
1717
1718static int swaps_open(struct inode *inode, struct file *file)
1719{
1720 return seq_open(file, &swaps_op);
1721}
1722
Helge Deller15ad7cd2006-12-06 20:40:36 -08001723static const struct file_operations proc_swaps_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724 .open = swaps_open,
1725 .read = seq_read,
1726 .llseek = seq_lseek,
1727 .release = seq_release,
1728};
1729
1730static int __init procswaps_init(void)
1731{
Denis V. Lunev3d71f862008-04-29 01:02:13 -07001732 proc_create("swaps", 0, NULL, &proc_swaps_operations);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 return 0;
1734}
1735__initcall(procswaps_init);
1736#endif /* CONFIG_PROC_FS */
1737
Jan Beulich17963162008-12-16 11:35:24 +00001738#ifdef MAX_SWAPFILES_CHECK
1739static int __init max_swapfiles_check(void)
1740{
1741 MAX_SWAPFILES_CHECK();
1742 return 0;
1743}
1744late_initcall(max_swapfiles_check);
1745#endif
1746
Linus Torvalds1da177e2005-04-16 15:20:36 -07001747/*
1748 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1749 *
1750 * The swapon system call
1751 */
Heiko Carstensc4ea37c2009-01-14 14:14:28 +01001752SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001754 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 char *name = NULL;
1756 struct block_device *bdev = NULL;
1757 struct file *swap_file = NULL;
1758 struct address_space *mapping;
1759 unsigned int type;
1760 int i, prev;
1761 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 union swap_header *swap_header = NULL;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001763 unsigned int nr_good_pages = 0;
1764 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001765 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 unsigned long maxpages = 1;
Hugh Dickins73fd8742009-01-06 14:39:47 -08001767 unsigned long swapfilepages;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001768 unsigned char *swap_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769 struct page *page = NULL;
1770 struct inode *inode = NULL;
1771 int did_down = 0;
1772
1773 if (!capable(CAP_SYS_ADMIN))
1774 return -EPERM;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001775
1776 p = kzalloc(sizeof(*p), GFP_KERNEL);
1777 if (!p)
1778 return -ENOMEM;
1779
Hugh Dickins5d337b92005-09-03 15:54:41 -07001780 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001781 for (type = 0; type < nr_swapfiles; type++) {
1782 if (!(swap_info[type]->flags & SWP_USED))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783 break;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001784 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001785 error = -EPERM;
Christoph Lameter06972122006-06-23 02:03:35 -07001786 if (type >= MAX_SWAPFILES) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001787 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001788 kfree(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789 goto out;
1790 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001791 if (type >= nr_swapfiles) {
1792 p->type = type;
1793 swap_info[type] = p;
1794 /*
1795 * Write swap_info[type] before nr_swapfiles, in case a
1796 * racing procfs swap_start() or swap_next() is reading them.
1797 * (We never shrink nr_swapfiles, we never free this entry.)
1798 */
1799 smp_wmb();
1800 nr_swapfiles++;
1801 } else {
1802 kfree(p);
1803 p = swap_info[type];
1804 /*
1805 * Do not memset this entry: a racing procfs swap_next()
1806 * would be relying on p->type to remain valid.
1807 */
1808 }
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001809 INIT_LIST_HEAD(&p->first_swap_extent.list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001810 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 p->next = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001812 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001813
Linus Torvalds1da177e2005-04-16 15:20:36 -07001814 name = getname(specialfile);
1815 error = PTR_ERR(name);
1816 if (IS_ERR(name)) {
1817 name = NULL;
1818 goto bad_swap_2;
1819 }
1820 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1821 error = PTR_ERR(swap_file);
1822 if (IS_ERR(swap_file)) {
1823 swap_file = NULL;
1824 goto bad_swap_2;
1825 }
1826
1827 p->swap_file = swap_file;
1828 mapping = swap_file->f_mapping;
1829 inode = mapping->host;
1830
1831 error = -EBUSY;
1832 for (i = 0; i < nr_swapfiles; i++) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001833 struct swap_info_struct *q = swap_info[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834
1835 if (i == type || !q->swap_file)
1836 continue;
1837 if (mapping == q->swap_file->f_mapping)
1838 goto bad_swap;
1839 }
1840
1841 error = -EINVAL;
1842 if (S_ISBLK(inode->i_mode)) {
1843 bdev = I_BDEV(inode);
1844 error = bd_claim(bdev, sys_swapon);
1845 if (error < 0) {
1846 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001847 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848 goto bad_swap;
1849 }
1850 p->old_block_size = block_size(bdev);
1851 error = set_blocksize(bdev, PAGE_SIZE);
1852 if (error < 0)
1853 goto bad_swap;
1854 p->bdev = bdev;
1855 } else if (S_ISREG(inode->i_mode)) {
1856 p->bdev = inode->i_sb->s_bdev;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001857 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 did_down = 1;
1859 if (IS_SWAPFILE(inode)) {
1860 error = -EBUSY;
1861 goto bad_swap;
1862 }
1863 } else {
1864 goto bad_swap;
1865 }
1866
Hugh Dickins73fd8742009-01-06 14:39:47 -08001867 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868
1869 /*
1870 * Read the swap header.
1871 */
1872 if (!mapping->a_ops->readpage) {
1873 error = -EINVAL;
1874 goto bad_swap;
1875 }
Pekka Enberg090d2b12006-06-23 02:05:08 -07001876 page = read_mapping_page(mapping, 0, swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877 if (IS_ERR(page)) {
1878 error = PTR_ERR(page);
1879 goto bad_swap;
1880 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001881 swap_header = kmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001882
Hugh Dickins81e33972009-01-06 14:39:49 -08001883 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
Jesper Juhle97a3112006-01-11 01:50:28 +01001884 printk(KERN_ERR "Unable to find swap-space signature\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885 error = -EINVAL;
1886 goto bad_swap;
1887 }
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001888
Hugh Dickins81e33972009-01-06 14:39:49 -08001889 /* swap partition endianess hack... */
1890 if (swab32(swap_header->info.version) == 1) {
1891 swab32s(&swap_header->info.version);
1892 swab32s(&swap_header->info.last_page);
1893 swab32s(&swap_header->info.nr_badpages);
1894 for (i = 0; i < swap_header->info.nr_badpages; i++)
1895 swab32s(&swap_header->info.badpages[i]);
1896 }
1897 /* Check the swap header's sub-version */
1898 if (swap_header->info.version != 1) {
1899 printk(KERN_WARNING
1900 "Unable to handle swap header version %d\n",
1901 swap_header->info.version);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001902 error = -EINVAL;
1903 goto bad_swap;
Hugh Dickins81e33972009-01-06 14:39:49 -08001904 }
1905
1906 p->lowest_bit = 1;
1907 p->cluster_next = 1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001908 p->cluster_nr = 0;
Hugh Dickins81e33972009-01-06 14:39:49 -08001909
1910 /*
1911 * Find out how many pages are allowed for a single swap
1912 * device. There are two limiting factors: 1) the number of
1913 * bits for the swap offset in the swp_entry_t type and
1914 * 2) the number of bits in the a swap pte as defined by
1915 * the different architectures. In order to find the
1916 * largest possible bit mask a swap entry with swap type 0
1917 * and swap offset ~0UL is created, encoded to a swap pte,
1918 * decoded to a swp_entry_t again and finally the swap
1919 * offset is extracted. This will mask all the bits from
1920 * the initial ~0UL mask that can't be encoded in either
1921 * the swp_entry_t or the architecture definition of a
1922 * swap pte.
1923 */
1924 maxpages = swp_offset(pte_to_swp_entry(
1925 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1926 if (maxpages > swap_header->info.last_page)
1927 maxpages = swap_header->info.last_page;
1928 p->highest_bit = maxpages - 1;
1929
1930 error = -EINVAL;
1931 if (!maxpages)
1932 goto bad_swap;
1933 if (swapfilepages && maxpages > swapfilepages) {
1934 printk(KERN_WARNING
1935 "Swap area shorter than signature indicates\n");
1936 goto bad_swap;
1937 }
1938 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1939 goto bad_swap;
1940 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1941 goto bad_swap;
1942
1943 /* OK, set up the swap map and apply the bad block list */
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001944 swap_map = vmalloc(maxpages);
Hugh Dickins81e33972009-01-06 14:39:49 -08001945 if (!swap_map) {
1946 error = -ENOMEM;
1947 goto bad_swap;
1948 }
1949
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001950 memset(swap_map, 0, maxpages);
Hugh Dickins81e33972009-01-06 14:39:49 -08001951 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1952 int page_nr = swap_header->info.badpages[i];
1953 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954 error = -EINVAL;
1955 goto bad_swap;
1956 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001957 swap_map[page_nr] = SWAP_MAP_BAD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001958 }
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08001959
1960 error = swap_cgroup_swapon(type, maxpages);
1961 if (error)
1962 goto bad_swap;
1963
Hugh Dickins81e33972009-01-06 14:39:49 -08001964 nr_good_pages = swap_header->info.last_page -
1965 swap_header->info.nr_badpages -
1966 1 /* header page */;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001967
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001968 if (nr_good_pages) {
Hugh Dickins78ecba02008-07-23 21:28:23 -07001969 swap_map[0] = SWAP_MAP_BAD;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001970 p->max = maxpages;
1971 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001972 nr_extents = setup_swap_extents(p, &span);
1973 if (nr_extents < 0) {
1974 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001975 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001976 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001977 nr_good_pages = p->pages;
1978 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001979 if (!nr_good_pages) {
1980 printk(KERN_WARNING "Empty swap-file\n");
1981 error = -EINVAL;
1982 goto bad_swap;
1983 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001984
Suresh Jayaraman3bd0f0c2009-09-30 10:53:48 +02001985 if (p->bdev) {
1986 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1987 p->flags |= SWP_SOLIDSTATE;
1988 p->cluster_next = 1 + (random32() % p->highest_bit);
1989 }
1990 if (discard_swap(p) == 0)
1991 p->flags |= SWP_DISCARDABLE;
Hugh Dickins20137a42009-01-06 14:39:54 -08001992 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -08001993
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001994 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001995 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001996 if (swap_flags & SWAP_FLAG_PREFER)
1997 p->prio =
1998 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1999 else
2000 p->prio = --least_priority;
2001 p->swap_map = swap_map;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08002002 p->flags |= SWP_WRITEOK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003 nr_swap_pages += nr_good_pages;
2004 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07002005
Hugh Dickins6eb396d2005-09-03 15:54:35 -07002006 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins20137a42009-01-06 14:39:54 -08002007 "Priority:%d extents:%d across:%lluk %s%s\n",
Hugh Dickins53092a72005-09-03 15:54:34 -07002008 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
Hugh Dickins6a6ba832009-01-06 14:39:51 -08002009 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
Hugh Dickins20137a42009-01-06 14:39:54 -08002010 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2011 (p->flags & SWP_DISCARDABLE) ? "D" : "");
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012
2013 /* insert swap space into swap_list: */
2014 prev = -1;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002015 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
2016 if (p->prio >= swap_info[i]->prio)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018 prev = i;
2019 }
2020 p->next = i;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002021 if (prev < 0)
2022 swap_list.head = swap_list.next = type;
2023 else
2024 swap_info[prev]->next = type;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002025 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08002026 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002027 error = 0;
2028 goto out;
2029bad_swap:
2030 if (bdev) {
2031 set_blocksize(bdev, p->old_block_size);
2032 bd_release(bdev);
2033 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07002034 destroy_swap_extents(p);
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08002035 swap_cgroup_swapoff(type);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002036bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07002037 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002038 p->swap_file = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002040 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 vfree(swap_map);
2042 if (swap_file)
2043 filp_close(swap_file, NULL);
2044out:
2045 if (page && !IS_ERR(page)) {
2046 kunmap(page);
2047 page_cache_release(page);
2048 }
2049 if (name)
2050 putname(name);
2051 if (did_down) {
2052 if (!error)
2053 inode->i_flags |= S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002054 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002055 }
2056 return error;
2057}
2058
2059void si_swapinfo(struct sysinfo *val)
2060{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002061 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002062 unsigned long nr_to_be_unused = 0;
2063
Hugh Dickins5d337b92005-09-03 15:54:41 -07002064 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002065 for (type = 0; type < nr_swapfiles; type++) {
2066 struct swap_info_struct *si = swap_info[type];
2067
2068 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2069 nr_to_be_unused += si->inuse_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002070 }
2071 val->freeswap = nr_swap_pages + nr_to_be_unused;
2072 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002073 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002074}
2075
2076/*
2077 * Verify that a swap entry is valid and increment its swap map count.
2078 *
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002079 * Returns error code in following case.
2080 * - success -> 0
2081 * - swp_entry is invalid -> EINVAL
2082 * - swp_entry is migration entry -> EINVAL
2083 * - swap-cache reference is requested but there is already one. -> EEXIST
2084 * - swap-cache reference is requested but the entry is not used. -> ENOENT
Hugh Dickins570a335b2009-12-14 17:58:46 -08002085 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086 */
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002087static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088{
Hugh Dickins73c34b62009-12-14 17:58:43 -08002089 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090 unsigned long offset, type;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002091 unsigned char count;
2092 unsigned char has_cache;
Hugh Dickins253d5532009-12-14 17:58:44 -08002093 int err = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002094
Andi Kleena7420aa2009-09-16 11:50:05 +02002095 if (non_swap_entry(entry))
Hugh Dickins253d5532009-12-14 17:58:44 -08002096 goto out;
Christoph Lameter06972122006-06-23 02:03:35 -07002097
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 type = swp_type(entry);
2099 if (type >= nr_swapfiles)
2100 goto bad_file;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002101 p = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 offset = swp_offset(entry);
2103
Hugh Dickins5d337b92005-09-03 15:54:41 -07002104 spin_lock(&swap_lock);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002105 if (unlikely(offset >= p->max))
2106 goto unlock_out;
2107
Hugh Dickins253d5532009-12-14 17:58:44 -08002108 count = p->swap_map[offset];
2109 has_cache = count & SWAP_HAS_CACHE;
2110 count &= ~SWAP_HAS_CACHE;
2111 err = 0;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002112
Hugh Dickins253d5532009-12-14 17:58:44 -08002113 if (usage == SWAP_HAS_CACHE) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002114
2115 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
Hugh Dickins253d5532009-12-14 17:58:44 -08002116 if (!has_cache && count)
2117 has_cache = SWAP_HAS_CACHE;
2118 else if (has_cache) /* someone else added cache */
2119 err = -EEXIST;
2120 else /* no users remaining */
2121 err = -ENOENT;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002122
2123 } else if (count || has_cache) {
Hugh Dickins253d5532009-12-14 17:58:44 -08002124
Hugh Dickins570a335b2009-12-14 17:58:46 -08002125 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2126 count += usage;
2127 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
Hugh Dickins253d5532009-12-14 17:58:44 -08002128 err = -EINVAL;
Hugh Dickins570a335b2009-12-14 17:58:46 -08002129 else if (swap_count_continued(p, offset, count))
2130 count = COUNT_CONTINUED;
2131 else
2132 err = -ENOMEM;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002133 } else
Hugh Dickins253d5532009-12-14 17:58:44 -08002134 err = -ENOENT; /* unused swap entry */
2135
2136 p->swap_map[offset] = count | has_cache;
2137
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002138unlock_out:
Hugh Dickins5d337b92005-09-03 15:54:41 -07002139 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002140out:
Hugh Dickins253d5532009-12-14 17:58:44 -08002141 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142
2143bad_file:
2144 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2145 goto out;
2146}
Hugh Dickins253d5532009-12-14 17:58:44 -08002147
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002148/*
Hugh Dickinsaaa46862009-12-14 17:58:47 -08002149 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2150 * (in which case its reference count is never incremented).
2151 */
2152void swap_shmem_alloc(swp_entry_t entry)
2153{
2154 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2155}
2156
2157/*
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002158 * increase reference count of swap entry by 1.
2159 */
Hugh Dickins570a335b2009-12-14 17:58:46 -08002160int swap_duplicate(swp_entry_t entry)
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002161{
Hugh Dickins570a335b2009-12-14 17:58:46 -08002162 int err = 0;
2163
2164 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2165 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2166 return err;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002167}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002168
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002169/*
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002170 * @entry: swap entry for which we allocate swap cache.
2171 *
Hugh Dickins73c34b62009-12-14 17:58:43 -08002172 * Called when allocating swap cache for existing swap entry,
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002173 * This can return error codes. Returns 0 at success.
2174 * -EBUSY means there is a swap cache.
2175 * Note: return code is different from swap_duplicate().
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002176 */
2177int swapcache_prepare(swp_entry_t entry)
2178{
Hugh Dickins253d5532009-12-14 17:58:44 -08002179 return __swap_duplicate(entry, SWAP_HAS_CACHE);
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002180}
2181
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07002183 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 * reference on the swaphandle, it doesn't matter if it becomes unused.
2185 */
2186int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2187{
Hugh Dickins89528982008-02-04 22:28:45 -08002188 struct swap_info_struct *si;
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002189 int our_page_cluster = page_cluster;
Hugh Dickins89528982008-02-04 22:28:45 -08002190 pgoff_t target, toff;
2191 pgoff_t base, end;
2192 int nr_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002193
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002194 if (!our_page_cluster) /* no readahead */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002195 return 0;
Hugh Dickins89528982008-02-04 22:28:45 -08002196
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002197 si = swap_info[swp_type(entry)];
Hugh Dickins89528982008-02-04 22:28:45 -08002198 target = swp_offset(entry);
2199 base = (target >> our_page_cluster) << our_page_cluster;
2200 end = base + (1 << our_page_cluster);
2201 if (!base) /* first page is swap header */
2202 base++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002203
Hugh Dickins5d337b92005-09-03 15:54:41 -07002204 spin_lock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002205 if (end > si->max) /* don't go beyond end of map */
2206 end = si->max;
2207
2208 /* Count contiguous allocated slots above our target */
2209 for (toff = target; ++toff < end; nr_pages++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002210 /* Don't read in free or bad pages */
Hugh Dickins89528982008-02-04 22:28:45 -08002211 if (!si->swap_map[toff])
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002213 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002214 break;
Hugh Dickins89528982008-02-04 22:28:45 -08002215 }
2216 /* Count contiguous allocated slots below our target */
2217 for (toff = target; --toff >= base; nr_pages++) {
2218 /* Don't read in free or bad pages */
2219 if (!si->swap_map[toff])
2220 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002221 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Hugh Dickins89528982008-02-04 22:28:45 -08002222 break;
2223 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07002224 spin_unlock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002225
2226 /*
2227 * Indicate starting offset, and return number of pages to get:
2228 * if only 1, say 0, since there's then no readahead to be done.
2229 */
2230 *offset = ++toff;
2231 return nr_pages? ++nr_pages: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232}
Hugh Dickins570a335b2009-12-14 17:58:46 -08002233
2234/*
2235 * add_swap_count_continuation - called when a swap count is duplicated
2236 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2237 * page of the original vmalloc'ed swap_map, to hold the continuation count
2238 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2239 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2240 *
2241 * These continuation pages are seldom referenced: the common paths all work
2242 * on the original swap_map, only referring to a continuation page when the
2243 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2244 *
2245 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2246 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2247 * can be called after dropping locks.
2248 */
2249int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2250{
2251 struct swap_info_struct *si;
2252 struct page *head;
2253 struct page *page;
2254 struct page *list_page;
2255 pgoff_t offset;
2256 unsigned char count;
2257
2258 /*
2259 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2260 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2261 */
2262 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2263
2264 si = swap_info_get(entry);
2265 if (!si) {
2266 /*
2267 * An acceptable race has occurred since the failing
2268 * __swap_duplicate(): the swap entry has been freed,
2269 * perhaps even the whole swap_map cleared for swapoff.
2270 */
2271 goto outer;
2272 }
2273
2274 offset = swp_offset(entry);
2275 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2276
2277 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2278 /*
2279 * The higher the swap count, the more likely it is that tasks
2280 * will race to add swap count continuation: we need to avoid
2281 * over-provisioning.
2282 */
2283 goto out;
2284 }
2285
2286 if (!page) {
2287 spin_unlock(&swap_lock);
2288 return -ENOMEM;
2289 }
2290
2291 /*
2292 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2293 * no architecture is using highmem pages for kernel pagetables: so it
2294 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2295 */
2296 head = vmalloc_to_page(si->swap_map + offset);
2297 offset &= ~PAGE_MASK;
2298
2299 /*
2300 * Page allocation does not initialize the page's lru field,
2301 * but it does always reset its private field.
2302 */
2303 if (!page_private(head)) {
2304 BUG_ON(count & COUNT_CONTINUED);
2305 INIT_LIST_HEAD(&head->lru);
2306 set_page_private(head, SWP_CONTINUED);
2307 si->flags |= SWP_CONTINUED;
2308 }
2309
2310 list_for_each_entry(list_page, &head->lru, lru) {
2311 unsigned char *map;
2312
2313 /*
2314 * If the previous map said no continuation, but we've found
2315 * a continuation page, free our allocation and use this one.
2316 */
2317 if (!(count & COUNT_CONTINUED))
2318 goto out;
2319
2320 map = kmap_atomic(list_page, KM_USER0) + offset;
2321 count = *map;
2322 kunmap_atomic(map, KM_USER0);
2323
2324 /*
2325 * If this continuation count now has some space in it,
2326 * free our allocation and use this one.
2327 */
2328 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2329 goto out;
2330 }
2331
2332 list_add_tail(&page->lru, &head->lru);
2333 page = NULL; /* now it's attached, don't free it */
2334out:
2335 spin_unlock(&swap_lock);
2336outer:
2337 if (page)
2338 __free_page(page);
2339 return 0;
2340}
2341
2342/*
2343 * swap_count_continued - when the original swap_map count is incremented
2344 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2345 * into, carry if so, or else fail until a new continuation page is allocated;
2346 * when the original swap_map count is decremented from 0 with continuation,
2347 * borrow from the continuation and report whether it still holds more.
2348 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2349 */
2350static bool swap_count_continued(struct swap_info_struct *si,
2351 pgoff_t offset, unsigned char count)
2352{
2353 struct page *head;
2354 struct page *page;
2355 unsigned char *map;
2356
2357 head = vmalloc_to_page(si->swap_map + offset);
2358 if (page_private(head) != SWP_CONTINUED) {
2359 BUG_ON(count & COUNT_CONTINUED);
2360 return false; /* need to add count continuation */
2361 }
2362
2363 offset &= ~PAGE_MASK;
2364 page = list_entry(head->lru.next, struct page, lru);
2365 map = kmap_atomic(page, KM_USER0) + offset;
2366
2367 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2368 goto init_map; /* jump over SWAP_CONT_MAX checks */
2369
2370 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2371 /*
2372 * Think of how you add 1 to 999
2373 */
2374 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2375 kunmap_atomic(map, KM_USER0);
2376 page = list_entry(page->lru.next, struct page, lru);
2377 BUG_ON(page == head);
2378 map = kmap_atomic(page, KM_USER0) + offset;
2379 }
2380 if (*map == SWAP_CONT_MAX) {
2381 kunmap_atomic(map, KM_USER0);
2382 page = list_entry(page->lru.next, struct page, lru);
2383 if (page == head)
2384 return false; /* add count continuation */
2385 map = kmap_atomic(page, KM_USER0) + offset;
2386init_map: *map = 0; /* we didn't zero the page */
2387 }
2388 *map += 1;
2389 kunmap_atomic(map, KM_USER0);
2390 page = list_entry(page->lru.prev, struct page, lru);
2391 while (page != head) {
2392 map = kmap_atomic(page, KM_USER0) + offset;
2393 *map = COUNT_CONTINUED;
2394 kunmap_atomic(map, KM_USER0);
2395 page = list_entry(page->lru.prev, struct page, lru);
2396 }
2397 return true; /* incremented */
2398
2399 } else { /* decrementing */
2400 /*
2401 * Think of how you subtract 1 from 1000
2402 */
2403 BUG_ON(count != COUNT_CONTINUED);
2404 while (*map == COUNT_CONTINUED) {
2405 kunmap_atomic(map, KM_USER0);
2406 page = list_entry(page->lru.next, struct page, lru);
2407 BUG_ON(page == head);
2408 map = kmap_atomic(page, KM_USER0) + offset;
2409 }
2410 BUG_ON(*map == 0);
2411 *map -= 1;
2412 if (*map == 0)
2413 count = 0;
2414 kunmap_atomic(map, KM_USER0);
2415 page = list_entry(page->lru.prev, struct page, lru);
2416 while (page != head) {
2417 map = kmap_atomic(page, KM_USER0) + offset;
2418 *map = SWAP_CONT_MAX | count;
2419 count = COUNT_CONTINUED;
2420 kunmap_atomic(map, KM_USER0);
2421 page = list_entry(page->lru.prev, struct page, lru);
2422 }
2423 return count == COUNT_CONTINUED;
2424 }
2425}
2426
2427/*
2428 * free_swap_count_continuations - swapoff free all the continuation pages
2429 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2430 */
2431static void free_swap_count_continuations(struct swap_info_struct *si)
2432{
2433 pgoff_t offset;
2434
2435 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2436 struct page *head;
2437 head = vmalloc_to_page(si->swap_map + offset);
2438 if (page_private(head)) {
2439 struct list_head *this, *next;
2440 list_for_each_safe(this, next, &head->lru) {
2441 struct page *page;
2442 page = list_entry(this, struct page, lru);
2443 list_del(this);
2444 __free_page(page);
2445 }
2446 }
2447 }
2448}