blob: d537d29e9b7bb5d9364b531e17f972618a5cad4b [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>
Kay Sievers66d7dd52010-10-26 14:22:06 -070033#include <linux/poll.h>
David Rientjes72788c32011-05-24 17:11:40 -070034#include <linux/oom.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070035
36#include <asm/pgtable.h>
37#include <asm/tlbflush.h>
38#include <linux/swapops.h>
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -080039#include <linux/page_cgroup.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070040
Hugh Dickins570a3352009-12-14 17:58:46 -080041static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
42 unsigned char);
43static void free_swap_count_continuations(struct swap_info_struct *);
Lee Schermerhornd4906e12009-12-14 17:58:49 -080044static sector_t map_swap_entry(swp_entry_t, struct block_device**);
Hugh Dickins570a3352009-12-14 17:58:46 -080045
Adrian Bunk7c363b82008-07-25 19:46:24 -070046static DEFINE_SPINLOCK(swap_lock);
47static unsigned int nr_swapfiles;
Hugh Dickinsb9627162009-01-06 14:39:41 -080048long nr_swap_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -070049long total_swap_pages;
Hugh Dickins78ecba02008-07-23 21:28:23 -070050static int least_priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
Linus Torvalds1da177e2005-04-16 15:20:36 -070052static const char Bad_file[] = "Bad swap file entry ";
53static const char Unused_file[] = "Unused swap file entry ";
54static const char Bad_offset[] = "Bad swap offset entry ";
55static const char Unused_offset[] = "Unused swap offset entry ";
56
Adrian Bunk7c363b82008-07-25 19:46:24 -070057static struct swap_list_t swap_list = {-1, -1};
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Hugh Dickinsefa90a92009-12-14 17:58:41 -080059static struct swap_info_struct *swap_info[MAX_SWAPFILES];
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Ingo Molnarfc0abb12006-01-18 17:42:33 -080061static DEFINE_MUTEX(swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070062
Kay Sievers66d7dd52010-10-26 14:22:06 -070063static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
64/* Activity counter to indicate that a swapon or swapoff has occurred */
65static atomic_t proc_poll_event = ATOMIC_INIT(0);
66
Hugh Dickins8d69aae2009-12-14 17:58:45 -080067static inline unsigned char swap_count(unsigned char ent)
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070068{
Hugh Dickins570a3352009-12-14 17:58:46 -080069 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070070}
71
Hugh Dickinsefa90a92009-12-14 17:58:41 -080072/* returns 1 if swap entry is freed */
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -070073static int
74__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
75{
Hugh Dickinsefa90a92009-12-14 17:58:41 -080076 swp_entry_t entry = swp_entry(si->type, offset);
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -070077 struct page *page;
78 int ret = 0;
79
80 page = find_get_page(&swapper_space, entry.val);
81 if (!page)
82 return 0;
83 /*
84 * This function is called from scan_swap_map() and it's called
85 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
86 * We have to use trylock for avoiding deadlock. This is a special
87 * case and you should use try_to_free_swap() with explicit lock_page()
88 * in usual operations.
89 */
90 if (trylock_page(page)) {
91 ret = try_to_free_swap(page);
92 unlock_page(page);
93 }
94 page_cache_release(page);
95 return ret;
96}
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -070097
Linus Torvalds1da177e2005-04-16 15:20:36 -070098/*
Hugh Dickins6a6ba832009-01-06 14:39:51 -080099 * swapon tell device that all the old swap contents can be discarded,
100 * to allow the swap device to optimize its wear-levelling.
101 */
102static int discard_swap(struct swap_info_struct *si)
103{
104 struct swap_extent *se;
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800105 sector_t start_block;
106 sector_t nr_blocks;
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800107 int err = 0;
108
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800109 /* Do not discard the swap header page! */
110 se = &si->first_swap_extent;
111 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
112 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
113 if (nr_blocks) {
114 err = blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200115 nr_blocks, GFP_KERNEL, 0);
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800116 if (err)
117 return err;
118 cond_resched();
119 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800120
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800121 list_for_each_entry(se, &si->first_swap_extent.list, list) {
122 start_block = se->start_block << (PAGE_SHIFT - 9);
123 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800124
125 err = blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200126 nr_blocks, GFP_KERNEL, 0);
Hugh Dickins6a6ba832009-01-06 14:39:51 -0800127 if (err)
128 break;
129
130 cond_resched();
131 }
132 return err; /* That will often be -EOPNOTSUPP */
133}
134
Hugh Dickins7992fde2009-01-06 14:39:53 -0800135/*
136 * swap allocation tell device that a cluster of swap can now be discarded,
137 * to allow the swap device to optimize its wear-levelling.
138 */
139static void discard_swap_cluster(struct swap_info_struct *si,
140 pgoff_t start_page, pgoff_t nr_pages)
141{
142 struct swap_extent *se = si->curr_swap_extent;
143 int found_extent = 0;
144
145 while (nr_pages) {
146 struct list_head *lh;
147
148 if (se->start_page <= start_page &&
149 start_page < se->start_page + se->nr_pages) {
150 pgoff_t offset = start_page - se->start_page;
151 sector_t start_block = se->start_block + offset;
Hugh Dickins858a29902009-01-06 14:39:56 -0800152 sector_t nr_blocks = se->nr_pages - offset;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800153
154 if (nr_blocks > nr_pages)
155 nr_blocks = nr_pages;
156 start_page += nr_blocks;
157 nr_pages -= nr_blocks;
158
159 if (!found_extent++)
160 si->curr_swap_extent = se;
161
162 start_block <<= PAGE_SHIFT - 9;
163 nr_blocks <<= PAGE_SHIFT - 9;
164 if (blkdev_issue_discard(si->bdev, start_block,
Christoph Hellwigdd3932e2010-09-16 20:51:46 +0200165 nr_blocks, GFP_NOIO, 0))
Hugh Dickins7992fde2009-01-06 14:39:53 -0800166 break;
167 }
168
169 lh = se->list.next;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800170 se = list_entry(lh, struct swap_extent, list);
171 }
172}
173
174static int wait_for_discard(void *word)
175{
176 schedule();
177 return 0;
178}
179
Hugh Dickins048c27f2005-09-03 15:54:40 -0700180#define SWAPFILE_CLUSTER 256
181#define LATENCY_LIMIT 256
182
Cesar Eduardo Barros24b8ff72011-03-22 16:33:38 -0700183static unsigned long scan_swap_map(struct swap_info_struct *si,
184 unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185{
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800186 unsigned long offset;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800187 unsigned long scan_base;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800188 unsigned long last_in_cluster = 0;
Hugh Dickins048c27f2005-09-03 15:54:40 -0700189 int latency_ration = LATENCY_LIMIT;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800190 int found_free_cluster = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800192 /*
Hugh Dickins7dfad412005-09-03 15:54:38 -0700193 * We try to cluster swap pages by allocating them sequentially
194 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
195 * way, however, we resort to first-free allocation, starting
196 * a new cluster. This prevents us from scattering swap pages
197 * all over the entire swap partition, so that we reduce
198 * overall disk seek times between swap pages. -- sct
199 * But we do now try to find an empty cluster. -Andrea
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800200 * And we let swap pages go all over an SSD partition. Hugh
Hugh Dickins7dfad412005-09-03 15:54:38 -0700201 */
202
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700203 si->flags += SWP_SCANNING;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800204 scan_base = offset = si->cluster_next;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800205
206 if (unlikely(!si->cluster_nr--)) {
207 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
208 si->cluster_nr = SWAPFILE_CLUSTER - 1;
209 goto checks;
210 }
Hugh Dickins7992fde2009-01-06 14:39:53 -0800211 if (si->flags & SWP_DISCARDABLE) {
212 /*
213 * Start range check on racing allocations, in case
214 * they overlap the cluster we eventually decide on
215 * (we scan without swap_lock to allow preemption).
216 * It's hardly conceivable that cluster_nr could be
217 * wrapped during our scan, but don't depend on it.
218 */
219 if (si->lowest_alloc)
220 goto checks;
221 si->lowest_alloc = si->max;
222 si->highest_alloc = 0;
223 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700224 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700225
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800226 /*
227 * If seek is expensive, start searching for new cluster from
228 * start of partition, to minimize the span of allocated swap.
229 * But if seek is cheap, search from our current position, so
230 * that swap is allocated from all over the partition: if the
231 * Flash Translation Layer only remaps within limited zones,
232 * we don't want to wear out the first zone too quickly.
233 */
234 if (!(si->flags & SWP_SOLIDSTATE))
235 scan_base = offset = si->lowest_bit;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700236 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
237
238 /* Locate the first empty (unaligned) cluster */
239 for (; last_in_cluster <= si->highest_bit; offset++) {
240 if (si->swap_map[offset])
241 last_in_cluster = offset + SWAPFILE_CLUSTER;
242 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700243 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800244 offset -= SWAPFILE_CLUSTER - 1;
245 si->cluster_next = offset;
246 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800247 found_free_cluster = 1;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800248 goto checks;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700250 if (unlikely(--latency_ration < 0)) {
251 cond_resched();
252 latency_ration = LATENCY_LIMIT;
253 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700254 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800255
256 offset = si->lowest_bit;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800257 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
258
259 /* Locate the first empty (unaligned) cluster */
260 for (; last_in_cluster < scan_base; offset++) {
261 if (si->swap_map[offset])
262 last_in_cluster = offset + SWAPFILE_CLUSTER;
263 else if (offset == last_in_cluster) {
264 spin_lock(&swap_lock);
265 offset -= SWAPFILE_CLUSTER - 1;
266 si->cluster_next = offset;
267 si->cluster_nr = SWAPFILE_CLUSTER - 1;
268 found_free_cluster = 1;
269 goto checks;
270 }
271 if (unlikely(--latency_ration < 0)) {
272 cond_resched();
273 latency_ration = LATENCY_LIMIT;
274 }
275 }
276
277 offset = scan_base;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700278 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800279 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800280 si->lowest_alloc = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700282
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800283checks:
284 if (!(si->flags & SWP_WRITEOK))
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700285 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700286 if (!si->highest_bit)
287 goto no_page;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800288 if (offset > si->highest_bit)
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800289 scan_base = offset = si->lowest_bit;
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700290
Hugh Dickinsb73d7fc2010-09-09 16:38:09 -0700291 /* reuse swap entry of cache-only swap if not busy. */
292 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700293 int swap_was_freed;
294 spin_unlock(&swap_lock);
295 swap_was_freed = __try_to_reclaim_swap(si, offset);
296 spin_lock(&swap_lock);
297 /* entry was freed successfully, try to use this again */
298 if (swap_was_freed)
299 goto checks;
300 goto scan; /* check next one */
301 }
302
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800303 if (si->swap_map[offset])
304 goto scan;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700305
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800306 if (offset == si->lowest_bit)
307 si->lowest_bit++;
308 if (offset == si->highest_bit)
309 si->highest_bit--;
310 si->inuse_pages++;
311 if (si->inuse_pages == si->pages) {
312 si->lowest_bit = si->max;
313 si->highest_bit = 0;
314 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800315 si->swap_map[offset] = usage;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800316 si->cluster_next = offset + 1;
317 si->flags -= SWP_SCANNING;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800318
319 if (si->lowest_alloc) {
320 /*
321 * Only set when SWP_DISCARDABLE, and there's a scan
322 * for a free cluster in progress or just completed.
323 */
324 if (found_free_cluster) {
325 /*
326 * To optimize wear-levelling, discard the
327 * old data of the cluster, taking care not to
328 * discard any of its pages that have already
329 * been allocated by racing tasks (offset has
330 * already stepped over any at the beginning).
331 */
332 if (offset < si->highest_alloc &&
333 si->lowest_alloc <= last_in_cluster)
334 last_in_cluster = si->lowest_alloc - 1;
335 si->flags |= SWP_DISCARDING;
336 spin_unlock(&swap_lock);
337
338 if (offset < last_in_cluster)
339 discard_swap_cluster(si, offset,
340 last_in_cluster - offset + 1);
341
342 spin_lock(&swap_lock);
343 si->lowest_alloc = 0;
344 si->flags &= ~SWP_DISCARDING;
345
346 smp_mb(); /* wake_up_bit advises this */
347 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
348
349 } else if (si->flags & SWP_DISCARDING) {
350 /*
351 * Delay using pages allocated by racing tasks
352 * until the whole discard has been issued. We
353 * could defer that delay until swap_writepage,
354 * but it's easier to keep this self-contained.
355 */
356 spin_unlock(&swap_lock);
357 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
358 wait_for_discard, TASK_UNINTERRUPTIBLE);
359 spin_lock(&swap_lock);
360 } else {
361 /*
362 * Note pages allocated by racing tasks while
363 * scan for a free cluster is in progress, so
364 * that its final discard can exclude them.
365 */
366 if (offset < si->lowest_alloc)
367 si->lowest_alloc = offset;
368 if (offset > si->highest_alloc)
369 si->highest_alloc = offset;
370 }
371 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800372 return offset;
373
374scan:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700375 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700376 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700377 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700378 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700379 goto checks;
380 }
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700381 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
382 spin_lock(&swap_lock);
383 goto checks;
384 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700385 if (unlikely(--latency_ration < 0)) {
386 cond_resched();
387 latency_ration = LATENCY_LIMIT;
388 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700389 }
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800390 offset = si->lowest_bit;
391 while (++offset < scan_base) {
392 if (!si->swap_map[offset]) {
393 spin_lock(&swap_lock);
394 goto checks;
395 }
KAMEZAWA Hiroyukic9e44412009-06-16 15:32:54 -0700396 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
397 spin_lock(&swap_lock);
398 goto checks;
399 }
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800400 if (unlikely(--latency_ration < 0)) {
401 cond_resched();
402 latency_ration = LATENCY_LIMIT;
403 }
404 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700405 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700406
407no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700408 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 return 0;
410}
411
412swp_entry_t get_swap_page(void)
413{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700414 struct swap_info_struct *si;
415 pgoff_t offset;
416 int type, next;
417 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700418
Hugh Dickins5d337b92005-09-03 15:54:41 -0700419 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700421 goto noswap;
422 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700424 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800425 si = swap_info[type];
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700426 next = si->next;
427 if (next < 0 ||
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800428 (!wrapped && si->prio != swap_info[next]->prio)) {
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700429 next = swap_list.head;
430 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700432
433 if (!si->highest_bit)
434 continue;
435 if (!(si->flags & SWP_WRITEOK))
436 continue;
437
438 swap_list.next = next;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700439 /* This is called for allocating swap entry for cache */
Hugh Dickins253d5532009-12-14 17:58:44 -0800440 offset = scan_swap_map(si, SWAP_HAS_CACHE);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700441 if (offset) {
442 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700443 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700444 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700445 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700447
448 nr_swap_pages++;
449noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700450 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700451 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452}
453
Hugh Dickins910321e2010-09-09 16:38:07 -0700454/* The only caller of this function is now susupend routine */
455swp_entry_t get_swap_page_of_type(int type)
456{
457 struct swap_info_struct *si;
458 pgoff_t offset;
459
460 spin_lock(&swap_lock);
461 si = swap_info[type];
462 if (si && (si->flags & SWP_WRITEOK)) {
463 nr_swap_pages--;
464 /* This is called for allocating swap entry, not cache */
465 offset = scan_swap_map(si, 1);
466 if (offset) {
467 spin_unlock(&swap_lock);
468 return swp_entry(type, offset);
469 }
470 nr_swap_pages++;
471 }
472 spin_unlock(&swap_lock);
473 return (swp_entry_t) {0};
474}
475
Hugh Dickins73c34b62009-12-14 17:58:43 -0800476static struct swap_info_struct *swap_info_get(swp_entry_t entry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477{
Hugh Dickins73c34b62009-12-14 17:58:43 -0800478 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479 unsigned long offset, type;
480
481 if (!entry.val)
482 goto out;
483 type = swp_type(entry);
484 if (type >= nr_swapfiles)
485 goto bad_nofile;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800486 p = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 if (!(p->flags & SWP_USED))
488 goto bad_device;
489 offset = swp_offset(entry);
490 if (offset >= p->max)
491 goto bad_offset;
492 if (!p->swap_map[offset])
493 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700494 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495 return p;
496
497bad_free:
498 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
499 goto out;
500bad_offset:
501 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
502 goto out;
503bad_device:
504 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
505 goto out;
506bad_nofile:
507 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
508out:
509 return NULL;
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800510}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800512static unsigned char swap_entry_free(struct swap_info_struct *p,
513 swp_entry_t entry, unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514{
Hugh Dickins253d5532009-12-14 17:58:44 -0800515 unsigned long offset = swp_offset(entry);
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800516 unsigned char count;
517 unsigned char has_cache;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700519 count = p->swap_map[offset];
Hugh Dickins253d5532009-12-14 17:58:44 -0800520 has_cache = count & SWAP_HAS_CACHE;
521 count &= ~SWAP_HAS_CACHE;
522
523 if (usage == SWAP_HAS_CACHE) {
524 VM_BUG_ON(!has_cache);
525 has_cache = 0;
Hugh Dickinsaaa46862009-12-14 17:58:47 -0800526 } else if (count == SWAP_MAP_SHMEM) {
527 /*
528 * Or we could insist on shmem.c using a special
529 * swap_shmem_free() and free_shmem_swap_and_cache()...
530 */
531 count = 0;
Hugh Dickins570a3352009-12-14 17:58:46 -0800532 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
533 if (count == COUNT_CONTINUED) {
534 if (swap_count_continued(p, offset, count))
535 count = SWAP_MAP_MAX | COUNT_CONTINUED;
536 else
537 count = SWAP_MAP_MAX;
538 } else
539 count--;
540 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800541
542 if (!count)
543 mem_cgroup_uncharge_swap(entry);
544
545 usage = count | has_cache;
546 p->swap_map[offset] = usage;
547
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700548 /* free if no reference */
Hugh Dickins253d5532009-12-14 17:58:44 -0800549 if (!usage) {
Nitin Guptab3a27d02010-05-17 11:02:43 +0530550 struct gendisk *disk = p->bdev->bd_disk;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700551 if (offset < p->lowest_bit)
552 p->lowest_bit = offset;
553 if (offset > p->highest_bit)
554 p->highest_bit = offset;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800555 if (swap_list.next >= 0 &&
556 p->prio > swap_info[swap_list.next]->prio)
557 swap_list.next = p->type;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700558 nr_swap_pages++;
559 p->inuse_pages--;
Nitin Guptab3a27d02010-05-17 11:02:43 +0530560 if ((p->flags & SWP_BLKDEV) &&
561 disk->fops->swap_slot_free_notify)
562 disk->fops->swap_slot_free_notify(p->bdev, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 }
Hugh Dickins253d5532009-12-14 17:58:44 -0800564
565 return usage;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566}
567
568/*
569 * Caller has made sure that the swapdevice corresponding to entry
570 * is still around or has not been recycled.
571 */
572void swap_free(swp_entry_t entry)
573{
Hugh Dickins73c34b62009-12-14 17:58:43 -0800574 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575
576 p = swap_info_get(entry);
577 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800578 swap_entry_free(p, entry, 1);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700579 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 }
581}
582
583/*
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700584 * Called after dropping swapcache to decrease refcnt to swap entries.
585 */
586void swapcache_free(swp_entry_t entry, struct page *page)
587{
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700588 struct swap_info_struct *p;
Hugh Dickins8d69aae2009-12-14 17:58:45 -0800589 unsigned char count;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700590
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700591 p = swap_info_get(entry);
592 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800593 count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
594 if (page)
595 mem_cgroup_uncharge_swapcache(page, entry, count != 0);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700596 spin_unlock(&swap_lock);
597 }
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -0700598}
599
600/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700601 * How many references to page are currently swapped out?
Hugh Dickins570a3352009-12-14 17:58:46 -0800602 * This does not give an exact answer when swap count is continued,
603 * but does include the high COUNT_CONTINUED flag to allow for that.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700605static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700607 int count = 0;
608 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 swp_entry_t entry;
610
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700611 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612 p = swap_info_get(entry);
613 if (p) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -0700614 count = swap_count(p->swap_map[swp_offset(entry)]);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700615 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700617 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618}
619
620/*
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800621 * We can write to an anon page without COW if there are no other references
622 * to it. And as a side-effect, free up its swap: because the old content
623 * on disk will never be read, and seeking back there to write new content
624 * later would only waste time away from clustering.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 */
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800626int reuse_swap_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700628 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629
Hugh Dickins51726b12009-01-06 14:39:25 -0800630 VM_BUG_ON(!PageLocked(page));
Hugh Dickins5ad64682009-12-14 17:59:24 -0800631 if (unlikely(PageKsm(page)))
632 return 0;
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700633 count = page_mapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800634 if (count <= 1 && PageSwapCache(page)) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700635 count += page_swapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800636 if (count == 1 && !PageWriteback(page)) {
637 delete_from_swap_cache(page);
638 SetPageDirty(page);
639 }
640 }
Hugh Dickins5ad64682009-12-14 17:59:24 -0800641 return count <= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642}
643
644/*
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800645 * If swap is getting full, or if there are no more mappings of this page,
646 * then try_to_free_swap is called to free its swap space.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 */
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800648int try_to_free_swap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649{
Hugh Dickins51726b12009-01-06 14:39:25 -0800650 VM_BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651
652 if (!PageSwapCache(page))
653 return 0;
654 if (PageWriteback(page))
655 return 0;
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800656 if (page_swapcount(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657 return 0;
658
Hugh Dickinsb73d7fc2010-09-09 16:38:09 -0700659 /*
660 * Once hibernation has begun to create its image of memory,
661 * there's a danger that one of the calls to try_to_free_swap()
662 * - most probably a call from __try_to_reclaim_swap() while
663 * hibernation is allocating its own swap pages for the image,
664 * but conceivably even a call from memory reclaim - will free
665 * the swap from a page which has already been recorded in the
666 * image as a clean swapcache page, and then reuse its swap for
667 * another page of the image. On waking from hibernation, the
668 * original page might be freed under memory pressure, then
669 * later read back in from swap, now with the wrong data.
670 *
671 * Hibernation clears bits from gfp_allowed_mask to prevent
672 * memory reclaim from writing to disk, so check that here.
673 */
674 if (!(gfp_allowed_mask & __GFP_IO))
675 return 0;
676
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800677 delete_from_swap_cache(page);
678 SetPageDirty(page);
679 return 1;
Rik van Riel68a223942008-10-18 20:26:23 -0700680}
681
682/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 * Free the swap entry like above, but also try to
684 * free the page cache entry if it is the last user.
685 */
Hugh Dickins2509ef22009-01-06 14:40:10 -0800686int free_swap_and_cache(swp_entry_t entry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687{
Hugh Dickins2509ef22009-01-06 14:40:10 -0800688 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689 struct page *page = NULL;
690
Andi Kleena7420aa2009-09-16 11:50:05 +0200691 if (non_swap_entry(entry))
Hugh Dickins2509ef22009-01-06 14:40:10 -0800692 return 1;
Christoph Lameter06972122006-06-23 02:03:35 -0700693
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 p = swap_info_get(entry);
695 if (p) {
Hugh Dickins253d5532009-12-14 17:58:44 -0800696 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
Nick Piggin93fac702006-03-31 02:29:56 -0800697 page = find_get_page(&swapper_space, entry.val);
Nick Piggin8413ac92008-10-18 20:26:59 -0700698 if (page && !trylock_page(page)) {
Nick Piggin93fac702006-03-31 02:29:56 -0800699 page_cache_release(page);
700 page = NULL;
701 }
702 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700703 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 }
705 if (page) {
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800706 /*
707 * Not mapped elsewhere, or swap space full? Free it!
708 * Also recheck PageSwapCache now page is locked (above).
709 */
Nick Piggin93fac702006-03-31 02:29:56 -0800710 if (PageSwapCache(page) && !PageWriteback(page) &&
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800711 (!page_mapped(page) || vm_swap_full())) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712 delete_from_swap_cache(page);
713 SetPageDirty(page);
714 }
715 unlock_page(page);
716 page_cache_release(page);
717 }
Hugh Dickins2509ef22009-01-06 14:40:10 -0800718 return p != NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719}
720
Daisuke Nishimura02491442010-03-10 15:22:17 -0800721#ifdef CONFIG_CGROUP_MEM_RES_CTLR
722/**
723 * mem_cgroup_count_swap_user - count the user of a swap entry
724 * @ent: the swap entry to be checked
725 * @pagep: the pointer for the swap cache page of the entry to be stored
726 *
727 * Returns the number of the user of the swap entry. The number is valid only
728 * for swaps of anonymous pages.
729 * If the entry is found on swap cache, the page is stored to pagep with
730 * refcount of it being incremented.
731 */
732int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
733{
734 struct page *page;
735 struct swap_info_struct *p;
736 int count = 0;
737
738 page = find_get_page(&swapper_space, ent.val);
739 if (page)
740 count += page_mapcount(page);
741 p = swap_info_get(ent);
742 if (p) {
743 count += swap_count(p->swap_map[swp_offset(ent)]);
744 spin_unlock(&swap_lock);
745 }
746
747 *pagep = page;
748 return count;
749}
750#endif
751
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200752#ifdef CONFIG_HIBERNATION
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800753/*
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800754 * Find the swap type that corresponds to given device (if any).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800755 *
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800756 * @offset - number of the PAGE_SIZE-sized block of the device, starting
757 * from 0, in which the swap header is expected to be located.
758 *
759 * This is needed for the suspend to disk (aka swsusp).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800760 */
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800761int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800762{
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800763 struct block_device *bdev = NULL;
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800764 int type;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800765
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800766 if (device)
767 bdev = bdget(device);
768
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800769 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800770 for (type = 0; type < nr_swapfiles; type++) {
771 struct swap_info_struct *sis = swap_info[type];
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800772
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800773 if (!(sis->flags & SWP_WRITEOK))
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800774 continue;
Rafael J. Wysockib6b5bce2006-08-27 01:23:25 -0700775
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800776 if (!bdev) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800777 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200778 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800779
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800780 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800781 return type;
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800782 }
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800783 if (bdev == sis->bdev) {
Hugh Dickins9625a5f2009-12-14 17:58:42 -0800784 struct swap_extent *se = &sis->first_swap_extent;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800785
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800786 if (se->start_block == offset) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800787 if (bdev_p)
Alan Jenkinsdddac6a2009-07-29 21:07:55 +0200788 *bdev_p = bdgrab(sis->bdev);
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800789
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800790 spin_unlock(&swap_lock);
791 bdput(bdev);
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800792 return type;
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800793 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800794 }
795 }
796 spin_unlock(&swap_lock);
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800797 if (bdev)
798 bdput(bdev);
799
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800800 return -ENODEV;
801}
802
803/*
Hugh Dickins73c34b62009-12-14 17:58:43 -0800804 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
805 * corresponding to given index in swap_info (swap type).
806 */
807sector_t swapdev_block(int type, pgoff_t offset)
808{
809 struct block_device *bdev;
810
811 if ((unsigned int)type >= nr_swapfiles)
812 return 0;
813 if (!(swap_info[type]->flags & SWP_WRITEOK))
814 return 0;
Lee Schermerhornd4906e12009-12-14 17:58:49 -0800815 return map_swap_entry(swp_entry(type, offset), &bdev);
Hugh Dickins73c34b62009-12-14 17:58:43 -0800816}
817
818/*
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800819 * Return either the total number of swap pages of given type, or the number
820 * of free pages of that type (depending on @free)
821 *
822 * This is needed for software suspend
823 */
824unsigned int count_swap_pages(int type, int free)
825{
826 unsigned int n = 0;
827
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800828 spin_lock(&swap_lock);
829 if ((unsigned int)type < nr_swapfiles) {
830 struct swap_info_struct *sis = swap_info[type];
831
832 if (sis->flags & SWP_WRITEOK) {
833 n = sis->pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800834 if (free)
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800835 n -= sis->inuse_pages;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800836 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800837 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -0800838 spin_unlock(&swap_lock);
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800839 return n;
840}
Hugh Dickins73c34b62009-12-14 17:58:43 -0800841#endif /* CONFIG_HIBERNATION */
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800842
Linus Torvalds1da177e2005-04-16 15:20:36 -0700843/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700844 * No need to decide whether this PTE shares the swap entry with others,
845 * just let do_wp_page work it out if a write is requested later - to
846 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700847 */
Hugh Dickins044d66c2008-02-07 00:14:04 -0800848static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 unsigned long addr, swp_entry_t entry, struct page *page)
850{
KAMEZAWA Hiroyuki56039ef2011-03-23 16:42:19 -0700851 struct mem_cgroup *ptr;
Hugh Dickins044d66c2008-02-07 00:14:04 -0800852 spinlock_t *ptl;
853 pte_t *pte;
854 int ret = 1;
855
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800856 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800857 ret = -ENOMEM;
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800858 goto out_nolock;
859 }
Hugh Dickins044d66c2008-02-07 00:14:04 -0800860
861 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
862 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
863 if (ret > 0)
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800864 mem_cgroup_cancel_charge_swapin(ptr);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800865 ret = 0;
866 goto out;
867 }
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800868
KAMEZAWA Hiroyukib084d432010-03-05 13:41:42 -0800869 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -0800870 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 get_page(page);
872 set_pte_at(vma->vm_mm, addr, pte,
873 pte_mkold(mk_pte(page, vma->vm_page_prot)));
874 page_add_anon_rmap(page, vma, addr);
KAMEZAWA Hiroyuki7a81b882009-01-07 18:07:48 -0800875 mem_cgroup_commit_charge_swapin(page, ptr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 swap_free(entry);
877 /*
878 * Move the page to the active list so it is not
879 * immediately swapped out again after swapon.
880 */
881 activate_page(page);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800882out:
883 pte_unmap_unlock(pte, ptl);
KAMEZAWA Hiroyuki85d9fc82009-01-29 14:25:13 -0800884out_nolock:
Hugh Dickins044d66c2008-02-07 00:14:04 -0800885 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886}
887
888static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
889 unsigned long addr, unsigned long end,
890 swp_entry_t entry, struct page *page)
891{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700892 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700893 pte_t *pte;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800894 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895
Hugh Dickins044d66c2008-02-07 00:14:04 -0800896 /*
897 * We don't actually need pte lock while scanning for swp_pte: since
898 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
899 * page table while we're scanning; though it could get zapped, and on
900 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
901 * of unmatched parts which look like swp_pte, so unuse_pte must
902 * recheck under pte lock. Scanning without pte lock lets it be
903 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
904 */
905 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906 do {
907 /*
908 * swapoff spends a _lot_ of time in this loop!
909 * Test inline before going to call unuse_pte.
910 */
911 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800912 pte_unmap(pte);
913 ret = unuse_pte(vma, pmd, addr, entry, page);
914 if (ret)
915 goto out;
916 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917 }
918 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800919 pte_unmap(pte - 1);
920out:
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800921 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922}
923
924static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
925 unsigned long addr, unsigned long end,
926 swp_entry_t entry, struct page *page)
927{
928 pmd_t *pmd;
929 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800930 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931
932 pmd = pmd_offset(pud, addr);
933 do {
934 next = pmd_addr_end(addr, end);
Andrea Arcangeli3f04f622011-01-13 15:46:47 -0800935 if (unlikely(pmd_trans_huge(*pmd)))
936 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937 if (pmd_none_or_clear_bad(pmd))
938 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800939 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
940 if (ret)
941 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 } while (pmd++, addr = next, addr != end);
943 return 0;
944}
945
946static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
947 unsigned long addr, unsigned long end,
948 swp_entry_t entry, struct page *page)
949{
950 pud_t *pud;
951 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800952 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700953
954 pud = pud_offset(pgd, addr);
955 do {
956 next = pud_addr_end(addr, end);
957 if (pud_none_or_clear_bad(pud))
958 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800959 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
960 if (ret)
961 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700962 } while (pud++, addr = next, addr != end);
963 return 0;
964}
965
966static int unuse_vma(struct vm_area_struct *vma,
967 swp_entry_t entry, struct page *page)
968{
969 pgd_t *pgd;
970 unsigned long addr, end, next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800971 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
Hugh Dickins3ca7b3c2009-12-14 17:58:57 -0800973 if (page_anon_vma(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 addr = page_address_in_vma(page, vma);
975 if (addr == -EFAULT)
976 return 0;
977 else
978 end = addr + PAGE_SIZE;
979 } else {
980 addr = vma->vm_start;
981 end = vma->vm_end;
982 }
983
984 pgd = pgd_offset(vma->vm_mm, addr);
985 do {
986 next = pgd_addr_end(addr, end);
987 if (pgd_none_or_clear_bad(pgd))
988 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800989 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
990 if (ret)
991 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992 } while (pgd++, addr = next, addr != end);
993 return 0;
994}
995
996static int unuse_mm(struct mm_struct *mm,
997 swp_entry_t entry, struct page *page)
998{
999 struct vm_area_struct *vma;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001000 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001
1002 if (!down_read_trylock(&mm->mmap_sem)) {
1003 /*
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -07001004 * Activate page so shrink_inactive_list is unlikely to unmap
1005 * its ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -07001007 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 unlock_page(page);
1009 down_read(&mm->mmap_sem);
1010 lock_page(page);
1011 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001013 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 break;
1015 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016 up_read(&mm->mmap_sem);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -08001017 return (ret < 0)? ret: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001018}
1019
1020/*
1021 * Scan swap_map from current position to next entry still in use.
1022 * Recycle to start on reaching the end, returning 0 when empty.
1023 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001024static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1025 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026{
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001027 unsigned int max = si->max;
1028 unsigned int i = prev;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001029 unsigned char count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030
1031 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001032 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 * for whether an entry is in use, not modifying it; false
1034 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -07001035 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 */
1037 for (;;) {
1038 if (++i >= max) {
1039 if (!prev) {
1040 i = 0;
1041 break;
1042 }
1043 /*
1044 * No entries in use at top of swap_map,
1045 * loop back to start and recheck there.
1046 */
1047 max = prev + 1;
1048 prev = 0;
1049 i = 1;
1050 }
1051 count = si->swap_map[i];
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001052 if (count && swap_count(count) != SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 break;
1054 }
1055 return i;
1056}
1057
1058/*
1059 * We completely avoid races by reading each swap page in advance,
1060 * and then search for the process using it. All the necessary
1061 * page table adjustments can then be made atomically.
1062 */
1063static int try_to_unuse(unsigned int type)
1064{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001065 struct swap_info_struct *si = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 struct mm_struct *start_mm;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001067 unsigned char *swap_map;
1068 unsigned char swcount;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 struct page *page;
1070 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001071 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001072 int retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001073
1074 /*
1075 * When searching mms for an entry, a good strategy is to
1076 * start at the first mm we freed the previous entry from
1077 * (though actually we don't notice whether we or coincidence
1078 * freed the entry). Initialize this start_mm with a hold.
1079 *
1080 * A simpler strategy would be to start at the last mm we
1081 * freed the previous entry from; but that would take less
1082 * advantage of mmlist ordering, which clusters forked mms
1083 * together, child after parent. If we race with dup_mmap(), we
1084 * prefer to resolve parent before child, lest we miss entries
1085 * duplicated after we scanned child: using last mm would invert
Hugh Dickins570a3352009-12-14 17:58:46 -08001086 * that.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087 */
1088 start_mm = &init_mm;
1089 atomic_inc(&init_mm.mm_users);
1090
1091 /*
1092 * Keep on scanning until all entries have gone. Usually,
1093 * one pass through swap_map is enough, but not necessarily:
1094 * there are races when an instance of an entry might be missed.
1095 */
1096 while ((i = find_next_to_unuse(si, i)) != 0) {
1097 if (signal_pending(current)) {
1098 retval = -EINTR;
1099 break;
1100 }
1101
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001102 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 * Get a page for the entry, using the existing swap
1104 * cache page if there is one. Otherwise, get a clean
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001105 * page and read the swap into it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 */
1107 swap_map = &si->swap_map[i];
1108 entry = swp_entry(type, i);
Hugh Dickins02098fe2008-02-04 22:28:42 -08001109 page = read_swap_cache_async(entry,
1110 GFP_HIGHUSER_MOVABLE, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 if (!page) {
1112 /*
1113 * Either swap_duplicate() failed because entry
1114 * has been freed independently, and will not be
1115 * reused since sys_swapoff() already disabled
1116 * allocation from here, or alloc_page() failed.
1117 */
1118 if (!*swap_map)
1119 continue;
1120 retval = -ENOMEM;
1121 break;
1122 }
1123
1124 /*
1125 * Don't hold on to start_mm if it looks like exiting.
1126 */
1127 if (atomic_read(&start_mm->mm_users) == 1) {
1128 mmput(start_mm);
1129 start_mm = &init_mm;
1130 atomic_inc(&init_mm.mm_users);
1131 }
1132
1133 /*
1134 * Wait for and lock page. When do_swap_page races with
1135 * try_to_unuse, do_swap_page can handle the fault much
1136 * faster than try_to_unuse can locate the entry. This
1137 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1138 * defer to do_swap_page in such a case - in some tests,
1139 * do_swap_page and try_to_unuse repeatedly compete.
1140 */
1141 wait_on_page_locked(page);
1142 wait_on_page_writeback(page);
1143 lock_page(page);
1144 wait_on_page_writeback(page);
1145
1146 /*
1147 * Remove all references to entry.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149 swcount = *swap_map;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001150 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1151 retval = shmem_unuse(entry, page);
1152 /* page has already been unlocked and released */
1153 if (retval < 0)
1154 break;
1155 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156 }
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001157 if (swap_count(swcount) && start_mm != &init_mm)
1158 retval = unuse_mm(start_mm, entry, page);
1159
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001160 if (swap_count(*swap_map)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 int set_start_mm = (*swap_map >= swcount);
1162 struct list_head *p = &start_mm->mmlist;
1163 struct mm_struct *new_start_mm = start_mm;
1164 struct mm_struct *prev_mm = start_mm;
1165 struct mm_struct *mm;
1166
1167 atomic_inc(&new_start_mm->mm_users);
1168 atomic_inc(&prev_mm->mm_users);
1169 spin_lock(&mmlist_lock);
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001170 while (swap_count(*swap_map) && !retval &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171 (p = p->next) != &start_mm->mmlist) {
1172 mm = list_entry(p, struct mm_struct, mmlist);
Hugh Dickins70af7c52006-06-23 02:03:44 -07001173 if (!atomic_inc_not_zero(&mm->mm_users))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 spin_unlock(&mmlist_lock);
1176 mmput(prev_mm);
1177 prev_mm = mm;
1178
1179 cond_resched();
1180
1181 swcount = *swap_map;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001182 if (!swap_count(swcount)) /* any usage ? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 ;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001184 else if (mm == &init_mm)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 set_start_mm = 1;
Hugh Dickinsaaa46862009-12-14 17:58:47 -08001186 else
Linus Torvalds1da177e2005-04-16 15:20:36 -07001187 retval = unuse_mm(mm, entry, page);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001188
Bo Liu32c5fc12009-11-02 16:50:33 +00001189 if (set_start_mm && *swap_map < swcount) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190 mmput(new_start_mm);
1191 atomic_inc(&mm->mm_users);
1192 new_start_mm = mm;
1193 set_start_mm = 0;
1194 }
1195 spin_lock(&mmlist_lock);
1196 }
1197 spin_unlock(&mmlist_lock);
1198 mmput(prev_mm);
1199 mmput(start_mm);
1200 start_mm = new_start_mm;
1201 }
1202 if (retval) {
1203 unlock_page(page);
1204 page_cache_release(page);
1205 break;
1206 }
1207
1208 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001209 * If a reference remains (rare), we would like to leave
1210 * the page in the swap cache; but try_to_unmap could
1211 * then re-duplicate the entry once we drop page lock,
1212 * so we might loop indefinitely; also, that page could
1213 * not be swapped out to other storage meanwhile. So:
1214 * delete from cache even if there's another reference,
1215 * after ensuring that the data has been saved to disk -
1216 * since if the reference remains (rarer), it will be
1217 * read from disk into another page. Splitting into two
1218 * pages would be incorrect if swap supported "shared
1219 * private" pages, but they are handled by tmpfs files.
Hugh Dickins5ad64682009-12-14 17:59:24 -08001220 *
1221 * Given how unuse_vma() targets one particular offset
1222 * in an anon_vma, once the anon_vma has been determined,
1223 * this splitting happens to be just what is needed to
1224 * handle where KSM pages have been swapped out: re-reading
1225 * is unnecessarily slow, but we can fix that later on.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 */
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07001227 if (swap_count(*swap_map) &&
1228 PageDirty(page) && PageSwapCache(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 struct writeback_control wbc = {
1230 .sync_mode = WB_SYNC_NONE,
1231 };
1232
1233 swap_writepage(page, &wbc);
1234 lock_page(page);
1235 wait_on_page_writeback(page);
1236 }
Hugh Dickins68bdc8d2009-01-06 14:39:37 -08001237
1238 /*
1239 * It is conceivable that a racing task removed this page from
1240 * swap cache just before we acquired the page lock at the top,
1241 * or while we dropped it in unuse_mm(). The page might even
1242 * be back in swap cache on another swap area: that we must not
1243 * delete, since it may not have been written out to swap yet.
1244 */
1245 if (PageSwapCache(page) &&
1246 likely(page_private(page) == entry.val))
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001247 delete_from_swap_cache(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248
1249 /*
1250 * So we could skip searching mms once swap count went
1251 * to 1, we did not mark any present ptes as dirty: must
Anderson Briglia2706a1b2007-07-15 23:38:09 -07001252 * mark page dirty so shrink_page_list will preserve it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 */
1254 SetPageDirty(page);
1255 unlock_page(page);
1256 page_cache_release(page);
1257
1258 /*
1259 * Make sure that we aren't completely killing
1260 * interactive performance.
1261 */
1262 cond_resched();
1263 }
1264
1265 mmput(start_mm);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266 return retval;
1267}
1268
1269/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001270 * After a successful try_to_unuse, if no swap is now in use, we know
1271 * we can empty the mmlist. swap_lock must be held on entry and exit.
1272 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273 * added to the mmlist just after page_duplicate - before would be racy.
1274 */
1275static void drain_mmlist(void)
1276{
1277 struct list_head *p, *next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001278 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001280 for (type = 0; type < nr_swapfiles; type++)
1281 if (swap_info[type]->inuse_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282 return;
1283 spin_lock(&mmlist_lock);
1284 list_for_each_safe(p, next, &init_mm.mmlist)
1285 list_del_init(p);
1286 spin_unlock(&mmlist_lock);
1287}
1288
1289/*
1290 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001291 * corresponds to page offset for the specified swap entry.
1292 * Note that the type of this function is sector_t, but it returns page offset
1293 * into the bdev, not sector offset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294 */
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001295static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296{
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001297 struct swap_info_struct *sis;
1298 struct swap_extent *start_se;
1299 struct swap_extent *se;
1300 pgoff_t offset;
1301
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001302 sis = swap_info[swp_type(entry)];
Hugh Dickinsf29ad6a2009-12-14 17:58:40 -08001303 *bdev = sis->bdev;
1304
1305 offset = swp_offset(entry);
1306 start_se = sis->curr_swap_extent;
1307 se = start_se;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308
1309 for ( ; ; ) {
1310 struct list_head *lh;
1311
1312 if (se->start_page <= offset &&
1313 offset < (se->start_page + se->nr_pages)) {
1314 return se->start_block + (offset - se->start_page);
1315 }
Hugh Dickins11d31882005-09-03 15:54:34 -07001316 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317 se = list_entry(lh, struct swap_extent, list);
1318 sis->curr_swap_extent = se;
1319 BUG_ON(se == start_se); /* It *must* be present */
1320 }
1321}
1322
1323/*
Lee Schermerhornd4906e12009-12-14 17:58:49 -08001324 * Returns the page offset into bdev for the specified page's swap entry.
1325 */
1326sector_t map_swap_page(struct page *page, struct block_device **bdev)
1327{
1328 swp_entry_t entry;
1329 entry.val = page_private(page);
1330 return map_swap_entry(entry, bdev);
1331}
1332
1333/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 * Free all of a swapdev's extent information
1335 */
1336static void destroy_swap_extents(struct swap_info_struct *sis)
1337{
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001338 while (!list_empty(&sis->first_swap_extent.list)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 struct swap_extent *se;
1340
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001341 se = list_entry(sis->first_swap_extent.list.next,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 struct swap_extent, list);
1343 list_del(&se->list);
1344 kfree(se);
1345 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346}
1347
1348/*
1349 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -07001350 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 *
Hugh Dickins11d31882005-09-03 15:54:34 -07001352 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 */
1354static int
1355add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1356 unsigned long nr_pages, sector_t start_block)
1357{
1358 struct swap_extent *se;
1359 struct swap_extent *new_se;
1360 struct list_head *lh;
1361
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001362 if (start_page == 0) {
1363 se = &sis->first_swap_extent;
1364 sis->curr_swap_extent = se;
1365 se->start_page = 0;
1366 se->nr_pages = nr_pages;
1367 se->start_block = start_block;
1368 return 1;
1369 } else {
1370 lh = sis->first_swap_extent.list.prev; /* Highest extent */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -07001372 BUG_ON(se->start_page + se->nr_pages != start_page);
1373 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 /* Merge it */
1375 se->nr_pages += nr_pages;
1376 return 0;
1377 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378 }
1379
1380 /*
1381 * No merge. Insert a new extent, preserving ordering.
1382 */
1383 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1384 if (new_se == NULL)
1385 return -ENOMEM;
1386 new_se->start_page = start_page;
1387 new_se->nr_pages = nr_pages;
1388 new_se->start_block = start_block;
1389
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001390 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
Hugh Dickins53092a72005-09-03 15:54:34 -07001391 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392}
1393
1394/*
1395 * A `swap extent' is a simple thing which maps a contiguous range of pages
1396 * onto a contiguous range of disk blocks. An ordered list of swap extents
1397 * is built at swapon time and is then used at swap_writepage/swap_readpage
1398 * time for locating where on disk a page belongs.
1399 *
1400 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1401 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1402 * swap files identically.
1403 *
1404 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1405 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1406 * swapfiles are handled *identically* after swapon time.
1407 *
1408 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1409 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1410 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1411 * requirements, they are simply tossed out - we will never use those blocks
1412 * for swapping.
1413 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -07001414 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -07001415 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1416 * which will scribble on the fs.
1417 *
1418 * The amount of disk space which a single swap extent represents varies.
1419 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1420 * extents in the list. To avoid much list walking, we cache the previous
1421 * search location in `curr_swap_extent', and start new searches from there.
1422 * This is extremely effective. The average number of iterations in
1423 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1424 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001425static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426{
1427 struct inode *inode;
1428 unsigned blocks_per_page;
1429 unsigned long page_no;
1430 unsigned blkbits;
1431 sector_t probe_block;
1432 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -07001433 sector_t lowest_block = -1;
1434 sector_t highest_block = 0;
1435 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436 int ret;
1437
1438 inode = sis->swap_file->f_mapping->host;
1439 if (S_ISBLK(inode->i_mode)) {
1440 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -07001441 *span = sis->pages;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001442 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 }
1444
1445 blkbits = inode->i_blkbits;
1446 blocks_per_page = PAGE_SIZE >> blkbits;
1447
1448 /*
1449 * Map all the blocks into the extent list. This code doesn't try
1450 * to be very smart.
1451 */
1452 probe_block = 0;
1453 page_no = 0;
1454 last_block = i_size_read(inode) >> blkbits;
1455 while ((probe_block + blocks_per_page) <= last_block &&
1456 page_no < sis->max) {
1457 unsigned block_in_page;
1458 sector_t first_block;
1459
1460 first_block = bmap(inode, probe_block);
1461 if (first_block == 0)
1462 goto bad_bmap;
1463
1464 /*
1465 * It must be PAGE_SIZE aligned on-disk
1466 */
1467 if (first_block & (blocks_per_page - 1)) {
1468 probe_block++;
1469 goto reprobe;
1470 }
1471
1472 for (block_in_page = 1; block_in_page < blocks_per_page;
1473 block_in_page++) {
1474 sector_t block;
1475
1476 block = bmap(inode, probe_block + block_in_page);
1477 if (block == 0)
1478 goto bad_bmap;
1479 if (block != first_block + block_in_page) {
1480 /* Discontiguity */
1481 probe_block++;
1482 goto reprobe;
1483 }
1484 }
1485
Hugh Dickins53092a72005-09-03 15:54:34 -07001486 first_block >>= (PAGE_SHIFT - blkbits);
1487 if (page_no) { /* exclude the header page */
1488 if (first_block < lowest_block)
1489 lowest_block = first_block;
1490 if (first_block > highest_block)
1491 highest_block = first_block;
1492 }
1493
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494 /*
1495 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1496 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001497 ret = add_swap_extent(sis, page_no, 1, first_block);
1498 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001500 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501 page_no++;
1502 probe_block += blocks_per_page;
1503reprobe:
1504 continue;
1505 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001506 ret = nr_extents;
1507 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001509 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001511 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512 sis->highest_bit = page_no - 1;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001513out:
1514 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515bad_bmap:
1516 printk(KERN_ERR "swapon: swapfile has holes\n");
1517 ret = -EINVAL;
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001518 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519}
1520
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07001521static void enable_swap_info(struct swap_info_struct *p, int prio,
1522 unsigned char *swap_map)
1523{
1524 int i, prev;
1525
1526 spin_lock(&swap_lock);
1527 if (prio >= 0)
1528 p->prio = prio;
1529 else
1530 p->prio = --least_priority;
1531 p->swap_map = swap_map;
1532 p->flags |= SWP_WRITEOK;
1533 nr_swap_pages += p->pages;
1534 total_swap_pages += p->pages;
1535
1536 /* insert swap space into swap_list: */
1537 prev = -1;
1538 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
1539 if (p->prio >= swap_info[i]->prio)
1540 break;
1541 prev = i;
1542 }
1543 p->next = i;
1544 if (prev < 0)
1545 swap_list.head = swap_list.next = p->type;
1546 else
1547 swap_info[prev]->next = p->type;
1548 spin_unlock(&swap_lock);
1549}
1550
Heiko Carstensc4ea37c2009-01-14 14:14:28 +01001551SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001553 struct swap_info_struct *p = NULL;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08001554 unsigned char *swap_map;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 struct file *swap_file, *victim;
1556 struct address_space *mapping;
1557 struct inode *inode;
Hugh Dickins73c34b62009-12-14 17:58:43 -08001558 char *pathname;
David Rientjes72788c32011-05-24 17:11:40 -07001559 int oom_score_adj;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560 int i, type, prev;
1561 int err;
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001562
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 if (!capable(CAP_SYS_ADMIN))
1564 return -EPERM;
1565
1566 pathname = getname(specialfile);
1567 err = PTR_ERR(pathname);
1568 if (IS_ERR(pathname))
1569 goto out;
1570
1571 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1572 putname(pathname);
1573 err = PTR_ERR(victim);
1574 if (IS_ERR(victim))
1575 goto out;
1576
1577 mapping = victim->f_mapping;
1578 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001579 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001580 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
1581 p = swap_info[type];
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001582 if (p->flags & SWP_WRITEOK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001583 if (p->swap_file->f_mapping == mapping)
1584 break;
1585 }
1586 prev = type;
1587 }
1588 if (type < 0) {
1589 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001590 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 goto out_dput;
1592 }
1593 if (!security_vm_enough_memory(p->pages))
1594 vm_unacct_memory(p->pages);
1595 else {
1596 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001597 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598 goto out_dput;
1599 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001600 if (prev < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601 swap_list.head = p->next;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001602 else
1603 swap_info[prev]->next = p->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604 if (type == swap_list.next) {
1605 /* just pick something that's safe... */
1606 swap_list.next = swap_list.head;
1607 }
Hugh Dickins78ecba02008-07-23 21:28:23 -07001608 if (p->prio < 0) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001609 for (i = p->next; i >= 0; i = swap_info[i]->next)
1610 swap_info[i]->prio = p->prio--;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001611 least_priority++;
1612 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 nr_swap_pages -= p->pages;
1614 total_swap_pages -= p->pages;
1615 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001616 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001617
David Rientjes72788c32011-05-24 17:11:40 -07001618 oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619 err = try_to_unuse(type);
David Rientjes72788c32011-05-24 17:11:40 -07001620 test_set_oom_score_adj(oom_score_adj);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 if (err) {
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07001623 /*
1624 * reading p->prio and p->swap_map outside the lock is
1625 * safe here because only sys_swapon and sys_swapoff
1626 * change them, and there can be no other sys_swapon or
1627 * sys_swapoff for this swap_info_struct at this point.
1628 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629 /* re-insert swap space back into swap_list */
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07001630 enable_swap_info(p, p->prio, p->swap_map);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631 goto out_dput;
1632 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001633
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001634 destroy_swap_extents(p);
Hugh Dickins570a3352009-12-14 17:58:46 -08001635 if (p->flags & SWP_CONTINUED)
1636 free_swap_count_continuations(p);
1637
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001638 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001639 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001641
1642 /* wait for anyone still in scan_swap_map */
1643 p->highest_bit = 0; /* cuts scans short */
1644 while (p->flags >= SWP_SCANNING) {
1645 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001646 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001647 spin_lock(&swap_lock);
1648 }
1649
Linus Torvalds1da177e2005-04-16 15:20:36 -07001650 swap_file = p->swap_file;
1651 p->swap_file = NULL;
1652 p->max = 0;
1653 swap_map = p->swap_map;
1654 p->swap_map = NULL;
1655 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001656 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001657 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658 vfree(swap_map);
KAMEZAWA Hiroyuki27a7faa2009-01-07 18:07:58 -08001659 /* Destroy swap account informatin */
1660 swap_cgroup_swapoff(type);
1661
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 inode = mapping->host;
1663 if (S_ISBLK(inode->i_mode)) {
1664 struct block_device *bdev = I_BDEV(inode);
1665 set_blocksize(bdev, p->old_block_size);
Tejun Heoe525fd82010-11-13 11:55:17 +01001666 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667 } else {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001668 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 inode->i_flags &= ~S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001670 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 }
1672 filp_close(swap_file, NULL);
1673 err = 0;
Kay Sievers66d7dd52010-10-26 14:22:06 -07001674 atomic_inc(&proc_poll_event);
1675 wake_up_interruptible(&proc_poll_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676
1677out_dput:
1678 filp_close(victim, NULL);
1679out:
1680 return err;
1681}
1682
1683#ifdef CONFIG_PROC_FS
Kay Sievers66d7dd52010-10-26 14:22:06 -07001684struct proc_swaps {
1685 struct seq_file seq;
1686 int event;
1687};
1688
1689static unsigned swaps_poll(struct file *file, poll_table *wait)
1690{
1691 struct proc_swaps *s = file->private_data;
1692
1693 poll_wait(file, &proc_poll_wait, wait);
1694
1695 if (s->event != atomic_read(&proc_poll_event)) {
1696 s->event = atomic_read(&proc_poll_event);
1697 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
1698 }
1699
1700 return POLLIN | POLLRDNORM;
1701}
1702
Linus Torvalds1da177e2005-04-16 15:20:36 -07001703/* iterator */
1704static void *swap_start(struct seq_file *swap, loff_t *pos)
1705{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001706 struct swap_info_struct *si;
1707 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708 loff_t l = *pos;
1709
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001710 mutex_lock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001712 if (!l)
1713 return SEQ_START_TOKEN;
1714
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001715 for (type = 0; type < nr_swapfiles; type++) {
1716 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1717 si = swap_info[type];
1718 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719 continue;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001720 if (!--l)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001721 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722 }
1723
1724 return NULL;
1725}
1726
1727static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1728{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001729 struct swap_info_struct *si = v;
1730 int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001732 if (v == SEQ_START_TOKEN)
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001733 type = 0;
1734 else
1735 type = si->type + 1;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001736
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001737 for (; type < nr_swapfiles; type++) {
1738 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1739 si = swap_info[type];
1740 if (!(si->flags & SWP_USED) || !si->swap_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741 continue;
1742 ++*pos;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001743 return si;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001744 }
1745
1746 return NULL;
1747}
1748
1749static void swap_stop(struct seq_file *swap, void *v)
1750{
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001751 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752}
1753
1754static int swap_show(struct seq_file *swap, void *v)
1755{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001756 struct swap_info_struct *si = v;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757 struct file *file;
1758 int len;
1759
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001760 if (si == SEQ_START_TOKEN) {
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001761 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1762 return 0;
1763 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001765 file = si->swap_file;
Jan Blunckc32c2f62008-02-14 19:38:43 -08001766 len = seq_path(swap, &file->f_path, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001767 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001768 len < 40 ? 40 - len : 1, " ",
1769 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770 "partition" : "file\t",
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001771 si->pages << (PAGE_SHIFT - 10),
1772 si->inuse_pages << (PAGE_SHIFT - 10),
1773 si->prio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774 return 0;
1775}
1776
Helge Deller15ad7cd2006-12-06 20:40:36 -08001777static const struct seq_operations swaps_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001778 .start = swap_start,
1779 .next = swap_next,
1780 .stop = swap_stop,
1781 .show = swap_show
1782};
1783
1784static int swaps_open(struct inode *inode, struct file *file)
1785{
Kay Sievers66d7dd52010-10-26 14:22:06 -07001786 struct proc_swaps *s;
1787 int ret;
1788
1789 s = kmalloc(sizeof(struct proc_swaps), GFP_KERNEL);
1790 if (!s)
1791 return -ENOMEM;
1792
1793 file->private_data = s;
1794
1795 ret = seq_open(file, &swaps_op);
1796 if (ret) {
1797 kfree(s);
1798 return ret;
1799 }
1800
1801 s->seq.private = s;
1802 s->event = atomic_read(&proc_poll_event);
1803 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804}
1805
Helge Deller15ad7cd2006-12-06 20:40:36 -08001806static const struct file_operations proc_swaps_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807 .open = swaps_open,
1808 .read = seq_read,
1809 .llseek = seq_lseek,
1810 .release = seq_release,
Kay Sievers66d7dd52010-10-26 14:22:06 -07001811 .poll = swaps_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001812};
1813
1814static int __init procswaps_init(void)
1815{
Denis V. Lunev3d71f862008-04-29 01:02:13 -07001816 proc_create("swaps", 0, NULL, &proc_swaps_operations);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817 return 0;
1818}
1819__initcall(procswaps_init);
1820#endif /* CONFIG_PROC_FS */
1821
Jan Beulich17963162008-12-16 11:35:24 +00001822#ifdef MAX_SWAPFILES_CHECK
1823static int __init max_swapfiles_check(void)
1824{
1825 MAX_SWAPFILES_CHECK();
1826 return 0;
1827}
1828late_initcall(max_swapfiles_check);
1829#endif
1830
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07001831static struct swap_info_struct *alloc_swap_info(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001832{
Hugh Dickins73c34b62009-12-14 17:58:43 -08001833 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834 unsigned int type;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001835
1836 p = kzalloc(sizeof(*p), GFP_KERNEL);
1837 if (!p)
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07001838 return ERR_PTR(-ENOMEM);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001839
Hugh Dickins5d337b92005-09-03 15:54:41 -07001840 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001841 for (type = 0; type < nr_swapfiles; type++) {
1842 if (!(swap_info[type]->flags & SWP_USED))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 break;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001844 }
Christoph Lameter06972122006-06-23 02:03:35 -07001845 if (type >= MAX_SWAPFILES) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001846 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001847 kfree(p);
Cesar Eduardo Barros730c0582011-03-22 16:33:19 -07001848 return ERR_PTR(-EPERM);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 }
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001850 if (type >= nr_swapfiles) {
1851 p->type = type;
1852 swap_info[type] = p;
1853 /*
1854 * Write swap_info[type] before nr_swapfiles, in case a
1855 * racing procfs swap_start() or swap_next() is reading them.
1856 * (We never shrink nr_swapfiles, we never free this entry.)
1857 */
1858 smp_wmb();
1859 nr_swapfiles++;
1860 } else {
1861 kfree(p);
1862 p = swap_info[type];
1863 /*
1864 * Do not memset this entry: a racing procfs swap_next()
1865 * would be relying on p->type to remain valid.
1866 */
1867 }
Hugh Dickins9625a5f2009-12-14 17:58:42 -08001868 INIT_LIST_HEAD(&p->first_swap_extent.list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870 p->next = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001871 spin_unlock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08001872
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07001873 return p;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07001874}
1875
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07001876static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
1877{
1878 int error;
1879
1880 if (S_ISBLK(inode->i_mode)) {
1881 p->bdev = bdgrab(I_BDEV(inode));
1882 error = blkdev_get(p->bdev,
1883 FMODE_READ | FMODE_WRITE | FMODE_EXCL,
1884 sys_swapon);
1885 if (error < 0) {
1886 p->bdev = NULL;
Cesar Eduardo Barros87ade722011-03-22 16:33:27 -07001887 return -EINVAL;
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07001888 }
1889 p->old_block_size = block_size(p->bdev);
1890 error = set_blocksize(p->bdev, PAGE_SIZE);
1891 if (error < 0)
Cesar Eduardo Barros87ade722011-03-22 16:33:27 -07001892 return error;
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07001893 p->flags |= SWP_BLKDEV;
1894 } else if (S_ISREG(inode->i_mode)) {
1895 p->bdev = inode->i_sb->s_bdev;
1896 mutex_lock(&inode->i_mutex);
Cesar Eduardo Barros87ade722011-03-22 16:33:27 -07001897 if (IS_SWAPFILE(inode))
1898 return -EBUSY;
1899 } else
1900 return -EINVAL;
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07001901
1902 return 0;
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07001903}
1904
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001905static unsigned long read_swap_header(struct swap_info_struct *p,
1906 union swap_header *swap_header,
1907 struct inode *inode)
1908{
1909 int i;
1910 unsigned long maxpages;
1911 unsigned long swapfilepages;
1912
1913 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1914 printk(KERN_ERR "Unable to find swap-space signature\n");
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001915 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001916 }
1917
1918 /* swap partition endianess hack... */
1919 if (swab32(swap_header->info.version) == 1) {
1920 swab32s(&swap_header->info.version);
1921 swab32s(&swap_header->info.last_page);
1922 swab32s(&swap_header->info.nr_badpages);
1923 for (i = 0; i < swap_header->info.nr_badpages; i++)
1924 swab32s(&swap_header->info.badpages[i]);
1925 }
1926 /* Check the swap header's sub-version */
1927 if (swap_header->info.version != 1) {
1928 printk(KERN_WARNING
1929 "Unable to handle swap header version %d\n",
1930 swap_header->info.version);
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001931 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001932 }
1933
1934 p->lowest_bit = 1;
1935 p->cluster_next = 1;
1936 p->cluster_nr = 0;
1937
1938 /*
1939 * Find out how many pages are allowed for a single swap
1940 * device. There are two limiting factors: 1) the number of
1941 * bits for the swap offset in the swp_entry_t type and
1942 * 2) the number of bits in the a swap pte as defined by
1943 * the different architectures. In order to find the
1944 * largest possible bit mask a swap entry with swap type 0
1945 * and swap offset ~0UL is created, encoded to a swap pte,
1946 * decoded to a swp_entry_t again and finally the swap
1947 * offset is extracted. This will mask all the bits from
1948 * the initial ~0UL mask that can't be encoded in either
1949 * the swp_entry_t or the architecture definition of a
1950 * swap pte.
1951 */
1952 maxpages = swp_offset(pte_to_swp_entry(
1953 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
1954 if (maxpages > swap_header->info.last_page) {
1955 maxpages = swap_header->info.last_page + 1;
1956 /* p->max is an unsigned int: don't overflow it */
1957 if ((unsigned int)maxpages == 0)
1958 maxpages = UINT_MAX;
1959 }
1960 p->highest_bit = maxpages - 1;
1961
1962 if (!maxpages)
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001963 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001964 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1965 if (swapfilepages && maxpages > swapfilepages) {
1966 printk(KERN_WARNING
1967 "Swap area shorter than signature indicates\n");
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001968 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001969 }
1970 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001971 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001972 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
Cesar Eduardo Barros38719022011-03-22 16:33:30 -07001973 return 0;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001974
1975 return maxpages;
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07001976}
1977
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07001978static int setup_swap_map_and_extents(struct swap_info_struct *p,
1979 union swap_header *swap_header,
1980 unsigned char *swap_map,
1981 unsigned long maxpages,
1982 sector_t *span)
1983{
1984 int i;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07001985 unsigned int nr_good_pages;
1986 int nr_extents;
1987
1988 nr_good_pages = maxpages - 1; /* omit header page */
1989
1990 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1991 unsigned int page_nr = swap_header->info.badpages[i];
Cesar Eduardo Barrosbdb8e3f2011-03-22 16:33:33 -07001992 if (page_nr == 0 || page_nr > swap_header->info.last_page)
1993 return -EINVAL;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07001994 if (page_nr < maxpages) {
1995 swap_map[page_nr] = SWAP_MAP_BAD;
1996 nr_good_pages--;
1997 }
1998 }
1999
2000 if (nr_good_pages) {
2001 swap_map[0] = SWAP_MAP_BAD;
2002 p->max = maxpages;
2003 p->pages = nr_good_pages;
2004 nr_extents = setup_swap_extents(p, span);
Cesar Eduardo Barrosbdb8e3f2011-03-22 16:33:33 -07002005 if (nr_extents < 0)
2006 return nr_extents;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07002007 nr_good_pages = p->pages;
2008 }
2009 if (!nr_good_pages) {
2010 printk(KERN_WARNING "Empty swap-file\n");
Cesar Eduardo Barrosbdb8e3f2011-03-22 16:33:33 -07002011 return -EINVAL;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07002012 }
2013
2014 return nr_extents;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07002015}
2016
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002017SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2018{
2019 struct swap_info_struct *p;
Cesar Eduardo Barros28b36bd2011-03-22 16:33:20 -07002020 char *name;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002021 struct file *swap_file = NULL;
2022 struct address_space *mapping;
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07002023 int i;
2024 int prio;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002025 int error;
2026 union swap_header *swap_header;
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07002027 int nr_extents;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002028 sector_t span;
2029 unsigned long maxpages;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002030 unsigned char *swap_map = NULL;
2031 struct page *page = NULL;
2032 struct inode *inode = NULL;
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002033
2034 if (!capable(CAP_SYS_ADMIN))
2035 return -EPERM;
2036
2037 p = alloc_swap_info();
Cesar Eduardo Barros2542e5132011-03-22 16:33:18 -07002038 if (IS_ERR(p))
2039 return PTR_ERR(p);
Cesar Eduardo Barros53cbb242011-03-22 16:33:17 -07002040
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 name = getname(specialfile);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042 if (IS_ERR(name)) {
Cesar Eduardo Barros7de7fb62011-03-22 16:33:22 -07002043 error = PTR_ERR(name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044 name = NULL;
Cesar Eduardo Barrosbd690102011-03-22 16:33:25 -07002045 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 }
2047 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 if (IS_ERR(swap_file)) {
Cesar Eduardo Barros7de7fb62011-03-22 16:33:22 -07002049 error = PTR_ERR(swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 swap_file = NULL;
Cesar Eduardo Barrosbd690102011-03-22 16:33:25 -07002051 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052 }
2053
2054 p->swap_file = swap_file;
2055 mapping = swap_file->f_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057 for (i = 0; i < nr_swapfiles; i++) {
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002058 struct swap_info_struct *q = swap_info[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07002059
Cesar Eduardo Barrose8e6c2e2011-03-22 16:33:16 -07002060 if (q == p || !q->swap_file)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061 continue;
Cesar Eduardo Barros7de7fb62011-03-22 16:33:22 -07002062 if (mapping == q->swap_file->f_mapping) {
2063 error = -EBUSY;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064 goto bad_swap;
Cesar Eduardo Barros7de7fb62011-03-22 16:33:22 -07002065 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002066 }
2067
Cesar Eduardo Barros21307812011-03-22 23:03:13 -03002068 inode = mapping->host;
2069 /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
Cesar Eduardo Barros4d0e1e12011-03-22 16:33:26 -07002070 error = claim_swapfile(p, inode);
2071 if (unlikely(error))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072 goto bad_swap;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002073
Linus Torvalds1da177e2005-04-16 15:20:36 -07002074 /*
2075 * Read the swap header.
2076 */
2077 if (!mapping->a_ops->readpage) {
2078 error = -EINVAL;
2079 goto bad_swap;
2080 }
Pekka Enberg090d2b12006-06-23 02:05:08 -07002081 page = read_mapping_page(mapping, 0, swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002082 if (IS_ERR(page)) {
2083 error = PTR_ERR(page);
2084 goto bad_swap;
2085 }
Hugh Dickins81e33972009-01-06 14:39:49 -08002086 swap_header = kmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087
Cesar Eduardo Barrosca8bd382011-03-22 16:33:29 -07002088 maxpages = read_swap_header(p, swap_header, inode);
2089 if (unlikely(!maxpages)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090 error = -EINVAL;
2091 goto bad_swap;
2092 }
Hugh Dickins886bb7e2009-01-06 14:39:48 -08002093
Hugh Dickins81e33972009-01-06 14:39:49 -08002094 /* OK, set up the swap map and apply the bad block list */
Cesar Eduardo Barros803d0c832011-03-22 16:33:14 -07002095 swap_map = vzalloc(maxpages);
Hugh Dickins81e33972009-01-06 14:39:49 -08002096 if (!swap_map) {
2097 error = -ENOMEM;
2098 goto bad_swap;
2099 }
2100
Cesar Eduardo Barros1421ef32011-03-22 16:33:31 -07002101 error = swap_cgroup_swapon(p->type, maxpages);
2102 if (error)
2103 goto bad_swap;
2104
Cesar Eduardo Barros915d4d72011-03-22 16:33:32 -07002105 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2106 maxpages, &span);
2107 if (unlikely(nr_extents < 0)) {
2108 error = nr_extents;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109 goto bad_swap;
2110 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002111
Suresh Jayaraman3bd0f0c2009-09-30 10:53:48 +02002112 if (p->bdev) {
2113 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2114 p->flags |= SWP_SOLIDSTATE;
2115 p->cluster_next = 1 + (random32() % p->highest_bit);
2116 }
Hugh Dickins33994462010-09-09 16:38:11 -07002117 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
Suresh Jayaraman3bd0f0c2009-09-30 10:53:48 +02002118 p->flags |= SWP_DISCARDABLE;
Hugh Dickins20137a42009-01-06 14:39:54 -08002119 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -08002120
Ingo Molnarfc0abb12006-01-18 17:42:33 -08002121 mutex_lock(&swapon_mutex);
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07002122 prio = -1;
Hugh Dickins78ecba02008-07-23 21:28:23 -07002123 if (swap_flags & SWAP_FLAG_PREFER)
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07002124 prio =
Hugh Dickins78ecba02008-07-23 21:28:23 -07002125 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
Cesar Eduardo Barros40531542011-03-22 16:33:37 -07002126 enable_swap_info(p, prio, swap_map);
Cesar Eduardo Barrosc69dbfb2011-03-22 16:33:35 -07002127
2128 printk(KERN_INFO "Adding %uk swap on %s. "
2129 "Priority:%d extents:%d across:%lluk %s%s\n",
2130 p->pages<<(PAGE_SHIFT-10), name, p->prio,
2131 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2132 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2133 (p->flags & SWP_DISCARDABLE) ? "D" : "");
2134
Ingo Molnarfc0abb12006-01-18 17:42:33 -08002135 mutex_unlock(&swapon_mutex);
Kay Sievers66d7dd52010-10-26 14:22:06 -07002136 atomic_inc(&proc_poll_event);
2137 wake_up_interruptible(&proc_poll_wait);
2138
Cesar Eduardo Barros9b01c352011-03-22 16:33:24 -07002139 if (S_ISREG(inode->i_mode))
2140 inode->i_flags |= S_SWAPFILE;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002141 error = 0;
2142 goto out;
2143bad_swap:
Cesar Eduardo Barrosbd690102011-03-22 16:33:25 -07002144 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
Cesar Eduardo Barrosf2090d22011-03-22 16:33:23 -07002145 set_blocksize(p->bdev, p->old_block_size);
2146 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07002148 destroy_swap_extents(p);
Cesar Eduardo Barrose8e6c2e2011-03-22 16:33:16 -07002149 swap_cgroup_swapoff(p->type);
Hugh Dickins5d337b92005-09-03 15:54:41 -07002150 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 p->swap_file = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002153 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154 vfree(swap_map);
Mel Gorman52c50562011-03-22 16:30:08 -07002155 if (swap_file) {
Cesar Eduardo Barros21307812011-03-22 23:03:13 -03002156 if (inode && S_ISREG(inode->i_mode)) {
Mel Gorman52c50562011-03-22 16:30:08 -07002157 mutex_unlock(&inode->i_mutex);
Cesar Eduardo Barros21307812011-03-22 23:03:13 -03002158 inode = NULL;
2159 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160 filp_close(swap_file, NULL);
Mel Gorman52c50562011-03-22 16:30:08 -07002161 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162out:
2163 if (page && !IS_ERR(page)) {
2164 kunmap(page);
2165 page_cache_release(page);
2166 }
2167 if (name)
2168 putname(name);
Cesar Eduardo Barros9b01c352011-03-22 16:33:24 -07002169 if (inode && S_ISREG(inode->i_mode))
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002170 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171 return error;
2172}
2173
2174void si_swapinfo(struct sysinfo *val)
2175{
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002176 unsigned int type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002177 unsigned long nr_to_be_unused = 0;
2178
Hugh Dickins5d337b92005-09-03 15:54:41 -07002179 spin_lock(&swap_lock);
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002180 for (type = 0; type < nr_swapfiles; type++) {
2181 struct swap_info_struct *si = swap_info[type];
2182
2183 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2184 nr_to_be_unused += si->inuse_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185 }
2186 val->freeswap = nr_swap_pages + nr_to_be_unused;
2187 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07002188 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189}
2190
2191/*
2192 * Verify that a swap entry is valid and increment its swap map count.
2193 *
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002194 * Returns error code in following case.
2195 * - success -> 0
2196 * - swp_entry is invalid -> EINVAL
2197 * - swp_entry is migration entry -> EINVAL
2198 * - swap-cache reference is requested but there is already one. -> EEXIST
2199 * - swap-cache reference is requested but the entry is not used. -> ENOENT
Hugh Dickins570a3352009-12-14 17:58:46 -08002200 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 */
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002202static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002203{
Hugh Dickins73c34b62009-12-14 17:58:43 -08002204 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205 unsigned long offset, type;
Hugh Dickins8d69aae2009-12-14 17:58:45 -08002206 unsigned char count;
2207 unsigned char has_cache;
Hugh Dickins253d5532009-12-14 17:58:44 -08002208 int err = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209
Andi Kleena7420aa2009-09-16 11:50:05 +02002210 if (non_swap_entry(entry))
Hugh Dickins253d5532009-12-14 17:58:44 -08002211 goto out;
Christoph Lameter06972122006-06-23 02:03:35 -07002212
Linus Torvalds1da177e2005-04-16 15:20:36 -07002213 type = swp_type(entry);
2214 if (type >= nr_swapfiles)
2215 goto bad_file;
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002216 p = swap_info[type];
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217 offset = swp_offset(entry);
2218
Hugh Dickins5d337b92005-09-03 15:54:41 -07002219 spin_lock(&swap_lock);
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002220 if (unlikely(offset >= p->max))
2221 goto unlock_out;
2222
Hugh Dickins253d5532009-12-14 17:58:44 -08002223 count = p->swap_map[offset];
2224 has_cache = count & SWAP_HAS_CACHE;
2225 count &= ~SWAP_HAS_CACHE;
2226 err = 0;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002227
Hugh Dickins253d5532009-12-14 17:58:44 -08002228 if (usage == SWAP_HAS_CACHE) {
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002229
2230 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
Hugh Dickins253d5532009-12-14 17:58:44 -08002231 if (!has_cache && count)
2232 has_cache = SWAP_HAS_CACHE;
2233 else if (has_cache) /* someone else added cache */
2234 err = -EEXIST;
2235 else /* no users remaining */
2236 err = -ENOENT;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002237
2238 } else if (count || has_cache) {
Hugh Dickins253d5532009-12-14 17:58:44 -08002239
Hugh Dickins570a3352009-12-14 17:58:46 -08002240 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2241 count += usage;
2242 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
Hugh Dickins253d5532009-12-14 17:58:44 -08002243 err = -EINVAL;
Hugh Dickins570a3352009-12-14 17:58:46 -08002244 else if (swap_count_continued(p, offset, count))
2245 count = COUNT_CONTINUED;
2246 else
2247 err = -ENOMEM;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002248 } else
Hugh Dickins253d5532009-12-14 17:58:44 -08002249 err = -ENOENT; /* unused swap entry */
2250
2251 p->swap_map[offset] = count | has_cache;
2252
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002253unlock_out:
Hugh Dickins5d337b92005-09-03 15:54:41 -07002254 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255out:
Hugh Dickins253d5532009-12-14 17:58:44 -08002256 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257
2258bad_file:
2259 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
2260 goto out;
2261}
Hugh Dickins253d5532009-12-14 17:58:44 -08002262
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002263/*
Hugh Dickinsaaa46862009-12-14 17:58:47 -08002264 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2265 * (in which case its reference count is never incremented).
2266 */
2267void swap_shmem_alloc(swp_entry_t entry)
2268{
2269 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2270}
2271
2272/*
Hugh Dickins08259d52010-03-05 13:42:25 -08002273 * Increase reference count of swap entry by 1.
2274 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2275 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2276 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2277 * might occur if a page table entry has got corrupted.
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002278 */
Hugh Dickins570a3352009-12-14 17:58:46 -08002279int swap_duplicate(swp_entry_t entry)
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002280{
Hugh Dickins570a3352009-12-14 17:58:46 -08002281 int err = 0;
2282
2283 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2284 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2285 return err;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002286}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002288/*
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002289 * @entry: swap entry for which we allocate swap cache.
2290 *
Hugh Dickins73c34b62009-12-14 17:58:43 -08002291 * Called when allocating swap cache for existing swap entry,
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002292 * This can return error codes. Returns 0 at success.
2293 * -EBUSY means there is a swap cache.
2294 * Note: return code is different from swap_duplicate().
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002295 */
2296int swapcache_prepare(swp_entry_t entry)
2297{
Hugh Dickins253d5532009-12-14 17:58:44 -08002298 return __swap_duplicate(entry, SWAP_HAS_CACHE);
KAMEZAWA Hiroyukicb4b86b2009-06-16 15:32:52 -07002299}
2300
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07002302 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303 * reference on the swaphandle, it doesn't matter if it becomes unused.
2304 */
2305int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
2306{
Hugh Dickins89528982008-02-04 22:28:45 -08002307 struct swap_info_struct *si;
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002308 int our_page_cluster = page_cluster;
Hugh Dickins89528982008-02-04 22:28:45 -08002309 pgoff_t target, toff;
2310 pgoff_t base, end;
2311 int nr_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002312
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002313 if (!our_page_cluster) /* no readahead */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002314 return 0;
Hugh Dickins89528982008-02-04 22:28:45 -08002315
Hugh Dickinsefa90a92009-12-14 17:58:41 -08002316 si = swap_info[swp_type(entry)];
Hugh Dickins89528982008-02-04 22:28:45 -08002317 target = swp_offset(entry);
2318 base = (target >> our_page_cluster) << our_page_cluster;
2319 end = base + (1 << our_page_cluster);
2320 if (!base) /* first page is swap header */
2321 base++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002322
Hugh Dickins5d337b92005-09-03 15:54:41 -07002323 spin_lock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002324 if (end > si->max) /* don't go beyond end of map */
2325 end = si->max;
2326
2327 /* Count contiguous allocated slots above our target */
2328 for (toff = target; ++toff < end; nr_pages++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002329 /* Don't read in free or bad pages */
Hugh Dickins89528982008-02-04 22:28:45 -08002330 if (!si->swap_map[toff])
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002332 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002333 break;
Hugh Dickins89528982008-02-04 22:28:45 -08002334 }
2335 /* Count contiguous allocated slots below our target */
2336 for (toff = target; --toff >= base; nr_pages++) {
2337 /* Don't read in free or bad pages */
2338 if (!si->swap_map[toff])
2339 break;
KAMEZAWA Hiroyuki355cfa72009-06-16 15:32:53 -07002340 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
Hugh Dickins89528982008-02-04 22:28:45 -08002341 break;
2342 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07002343 spin_unlock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002344
2345 /*
2346 * Indicate starting offset, and return number of pages to get:
2347 * if only 1, say 0, since there's then no readahead to be done.
2348 */
2349 *offset = ++toff;
2350 return nr_pages? ++nr_pages: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002351}
Hugh Dickins570a3352009-12-14 17:58:46 -08002352
2353/*
2354 * add_swap_count_continuation - called when a swap count is duplicated
2355 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2356 * page of the original vmalloc'ed swap_map, to hold the continuation count
2357 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2358 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2359 *
2360 * These continuation pages are seldom referenced: the common paths all work
2361 * on the original swap_map, only referring to a continuation page when the
2362 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2363 *
2364 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2365 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2366 * can be called after dropping locks.
2367 */
2368int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2369{
2370 struct swap_info_struct *si;
2371 struct page *head;
2372 struct page *page;
2373 struct page *list_page;
2374 pgoff_t offset;
2375 unsigned char count;
2376
2377 /*
2378 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2379 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2380 */
2381 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2382
2383 si = swap_info_get(entry);
2384 if (!si) {
2385 /*
2386 * An acceptable race has occurred since the failing
2387 * __swap_duplicate(): the swap entry has been freed,
2388 * perhaps even the whole swap_map cleared for swapoff.
2389 */
2390 goto outer;
2391 }
2392
2393 offset = swp_offset(entry);
2394 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2395
2396 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2397 /*
2398 * The higher the swap count, the more likely it is that tasks
2399 * will race to add swap count continuation: we need to avoid
2400 * over-provisioning.
2401 */
2402 goto out;
2403 }
2404
2405 if (!page) {
2406 spin_unlock(&swap_lock);
2407 return -ENOMEM;
2408 }
2409
2410 /*
2411 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2412 * no architecture is using highmem pages for kernel pagetables: so it
2413 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps.
2414 */
2415 head = vmalloc_to_page(si->swap_map + offset);
2416 offset &= ~PAGE_MASK;
2417
2418 /*
2419 * Page allocation does not initialize the page's lru field,
2420 * but it does always reset its private field.
2421 */
2422 if (!page_private(head)) {
2423 BUG_ON(count & COUNT_CONTINUED);
2424 INIT_LIST_HEAD(&head->lru);
2425 set_page_private(head, SWP_CONTINUED);
2426 si->flags |= SWP_CONTINUED;
2427 }
2428
2429 list_for_each_entry(list_page, &head->lru, lru) {
2430 unsigned char *map;
2431
2432 /*
2433 * If the previous map said no continuation, but we've found
2434 * a continuation page, free our allocation and use this one.
2435 */
2436 if (!(count & COUNT_CONTINUED))
2437 goto out;
2438
2439 map = kmap_atomic(list_page, KM_USER0) + offset;
2440 count = *map;
2441 kunmap_atomic(map, KM_USER0);
2442
2443 /*
2444 * If this continuation count now has some space in it,
2445 * free our allocation and use this one.
2446 */
2447 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2448 goto out;
2449 }
2450
2451 list_add_tail(&page->lru, &head->lru);
2452 page = NULL; /* now it's attached, don't free it */
2453out:
2454 spin_unlock(&swap_lock);
2455outer:
2456 if (page)
2457 __free_page(page);
2458 return 0;
2459}
2460
2461/*
2462 * swap_count_continued - when the original swap_map count is incremented
2463 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2464 * into, carry if so, or else fail until a new continuation page is allocated;
2465 * when the original swap_map count is decremented from 0 with continuation,
2466 * borrow from the continuation and report whether it still holds more.
2467 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2468 */
2469static bool swap_count_continued(struct swap_info_struct *si,
2470 pgoff_t offset, unsigned char count)
2471{
2472 struct page *head;
2473 struct page *page;
2474 unsigned char *map;
2475
2476 head = vmalloc_to_page(si->swap_map + offset);
2477 if (page_private(head) != SWP_CONTINUED) {
2478 BUG_ON(count & COUNT_CONTINUED);
2479 return false; /* need to add count continuation */
2480 }
2481
2482 offset &= ~PAGE_MASK;
2483 page = list_entry(head->lru.next, struct page, lru);
2484 map = kmap_atomic(page, KM_USER0) + offset;
2485
2486 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2487 goto init_map; /* jump over SWAP_CONT_MAX checks */
2488
2489 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2490 /*
2491 * Think of how you add 1 to 999
2492 */
2493 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2494 kunmap_atomic(map, KM_USER0);
2495 page = list_entry(page->lru.next, struct page, lru);
2496 BUG_ON(page == head);
2497 map = kmap_atomic(page, KM_USER0) + offset;
2498 }
2499 if (*map == SWAP_CONT_MAX) {
2500 kunmap_atomic(map, KM_USER0);
2501 page = list_entry(page->lru.next, struct page, lru);
2502 if (page == head)
2503 return false; /* add count continuation */
2504 map = kmap_atomic(page, KM_USER0) + offset;
2505init_map: *map = 0; /* we didn't zero the page */
2506 }
2507 *map += 1;
2508 kunmap_atomic(map, KM_USER0);
2509 page = list_entry(page->lru.prev, struct page, lru);
2510 while (page != head) {
2511 map = kmap_atomic(page, KM_USER0) + offset;
2512 *map = COUNT_CONTINUED;
2513 kunmap_atomic(map, KM_USER0);
2514 page = list_entry(page->lru.prev, struct page, lru);
2515 }
2516 return true; /* incremented */
2517
2518 } else { /* decrementing */
2519 /*
2520 * Think of how you subtract 1 from 1000
2521 */
2522 BUG_ON(count != COUNT_CONTINUED);
2523 while (*map == COUNT_CONTINUED) {
2524 kunmap_atomic(map, KM_USER0);
2525 page = list_entry(page->lru.next, struct page, lru);
2526 BUG_ON(page == head);
2527 map = kmap_atomic(page, KM_USER0) + offset;
2528 }
2529 BUG_ON(*map == 0);
2530 *map -= 1;
2531 if (*map == 0)
2532 count = 0;
2533 kunmap_atomic(map, KM_USER0);
2534 page = list_entry(page->lru.prev, struct page, lru);
2535 while (page != head) {
2536 map = kmap_atomic(page, KM_USER0) + offset;
2537 *map = SWAP_CONT_MAX | count;
2538 count = COUNT_CONTINUED;
2539 kunmap_atomic(map, KM_USER0);
2540 page = list_entry(page->lru.prev, struct page, lru);
2541 }
2542 return count == COUNT_CONTINUED;
2543 }
2544}
2545
2546/*
2547 * free_swap_count_continuations - swapoff free all the continuation pages
2548 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2549 */
2550static void free_swap_count_continuations(struct swap_info_struct *si)
2551{
2552 pgoff_t offset;
2553
2554 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2555 struct page *head;
2556 head = vmalloc_to_page(si->swap_map + offset);
2557 if (page_private(head)) {
2558 struct list_head *this, *next;
2559 list_for_each_safe(this, next, &head->lru) {
2560 struct page *page;
2561 page = list_entry(this, struct page, lru);
2562 list_del(this);
2563 __free_page(page);
2564 }
2565 }
2566 }
2567}