blob: 763210732b5fd019875cbec86ec136e6c29b1383 [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>
25#include <linux/rmap.h>
26#include <linux/security.h>
27#include <linux/backing-dev.h>
Ingo Molnarfc0abb12006-01-18 17:42:33 -080028#include <linux/mutex.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080029#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070030#include <linux/syscalls.h>
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080031#include <linux/memcontrol.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070032
33#include <asm/pgtable.h>
34#include <asm/tlbflush.h>
35#include <linux/swapops.h>
36
Adrian Bunk7c363b82008-07-25 19:46:24 -070037static DEFINE_SPINLOCK(swap_lock);
38static unsigned int nr_swapfiles;
Hugh Dickinsb9627162009-01-06 14:39:41 -080039long nr_swap_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -070040long total_swap_pages;
41static int swap_overflow;
Hugh Dickins78ecba02008-07-23 21:28:23 -070042static int least_priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
Linus Torvalds1da177e2005-04-16 15:20:36 -070044static const char Bad_file[] = "Bad swap file entry ";
45static const char Unused_file[] = "Unused swap file entry ";
46static const char Bad_offset[] = "Bad swap offset entry ";
47static const char Unused_offset[] = "Unused swap offset entry ";
48
Adrian Bunk7c363b82008-07-25 19:46:24 -070049static struct swap_list_t swap_list = {-1, -1};
Linus Torvalds1da177e2005-04-16 15:20:36 -070050
Rafael J. Wysockif577eb32006-03-23 02:59:59 -080051static struct swap_info_struct swap_info[MAX_SWAPFILES];
Linus Torvalds1da177e2005-04-16 15:20:36 -070052
Ingo Molnarfc0abb12006-01-18 17:42:33 -080053static DEFINE_MUTEX(swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070054
55/*
56 * We need this because the bdev->unplug_fn can sleep and we cannot
Hugh Dickins5d337b92005-09-03 15:54:41 -070057 * hold swap_lock while calling the unplug_fn. And swap_lock
Ingo Molnarfc0abb12006-01-18 17:42:33 -080058 * cannot be turned into a mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 */
60static DECLARE_RWSEM(swap_unplug_sem);
61
Linus Torvalds1da177e2005-04-16 15:20:36 -070062void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
63{
64 swp_entry_t entry;
65
66 down_read(&swap_unplug_sem);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070067 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 if (PageSwapCache(page)) {
69 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
70 struct backing_dev_info *bdi;
71
72 /*
73 * If the page is removed from swapcache from under us (with a
74 * racy try_to_unuse/swapoff) we need an additional reference
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070075 * count to avoid reading garbage from page_private(page) above.
76 * If the WARN_ON triggers during a swapoff it maybe the race
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 * condition and it's harmless. However if it triggers without
78 * swapoff it signals a problem.
79 */
80 WARN_ON(page_count(page) <= 1);
81
82 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
McMullan, Jasonba323112005-05-16 21:53:40 -070083 blk_run_backing_dev(bdi, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 }
85 up_read(&swap_unplug_sem);
86}
87
Hugh Dickins6a6ba832009-01-06 14:39:51 -080088/*
89 * swapon tell device that all the old swap contents can be discarded,
90 * to allow the swap device to optimize its wear-levelling.
91 */
92static int discard_swap(struct swap_info_struct *si)
93{
94 struct swap_extent *se;
95 int err = 0;
96
97 list_for_each_entry(se, &si->extent_list, list) {
98 sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
99 pgoff_t nr_blocks = se->nr_pages << (PAGE_SHIFT - 9);
100
101 if (se->start_page == 0) {
102 /* Do not discard the swap header page! */
103 start_block += 1 << (PAGE_SHIFT - 9);
104 nr_blocks -= 1 << (PAGE_SHIFT - 9);
105 if (!nr_blocks)
106 continue;
107 }
108
109 err = blkdev_issue_discard(si->bdev, start_block,
110 nr_blocks, GFP_KERNEL);
111 if (err)
112 break;
113
114 cond_resched();
115 }
116 return err; /* That will often be -EOPNOTSUPP */
117}
118
Hugh Dickins7992fde2009-01-06 14:39:53 -0800119/*
120 * swap allocation tell device that a cluster of swap can now be discarded,
121 * to allow the swap device to optimize its wear-levelling.
122 */
123static void discard_swap_cluster(struct swap_info_struct *si,
124 pgoff_t start_page, pgoff_t nr_pages)
125{
126 struct swap_extent *se = si->curr_swap_extent;
127 int found_extent = 0;
128
129 while (nr_pages) {
130 struct list_head *lh;
131
132 if (se->start_page <= start_page &&
133 start_page < se->start_page + se->nr_pages) {
134 pgoff_t offset = start_page - se->start_page;
135 sector_t start_block = se->start_block + offset;
136 pgoff_t nr_blocks = se->nr_pages - offset;
137
138 if (nr_blocks > nr_pages)
139 nr_blocks = nr_pages;
140 start_page += nr_blocks;
141 nr_pages -= nr_blocks;
142
143 if (!found_extent++)
144 si->curr_swap_extent = se;
145
146 start_block <<= PAGE_SHIFT - 9;
147 nr_blocks <<= PAGE_SHIFT - 9;
148 if (blkdev_issue_discard(si->bdev, start_block,
149 nr_blocks, GFP_NOIO))
150 break;
151 }
152
153 lh = se->list.next;
154 if (lh == &si->extent_list)
155 lh = lh->next;
156 se = list_entry(lh, struct swap_extent, list);
157 }
158}
159
160static int wait_for_discard(void *word)
161{
162 schedule();
163 return 0;
164}
165
Hugh Dickins048c27f2005-09-03 15:54:40 -0700166#define SWAPFILE_CLUSTER 256
167#define LATENCY_LIMIT 256
168
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700169static inline unsigned long scan_swap_map(struct swap_info_struct *si)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170{
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800171 unsigned long offset;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800172 unsigned long scan_base;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800173 unsigned long last_in_cluster = 0;
Hugh Dickins048c27f2005-09-03 15:54:40 -0700174 int latency_ration = LATENCY_LIMIT;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800175 int found_free_cluster = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800177 /*
Hugh Dickins7dfad412005-09-03 15:54:38 -0700178 * We try to cluster swap pages by allocating them sequentially
179 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
180 * way, however, we resort to first-free allocation, starting
181 * a new cluster. This prevents us from scattering swap pages
182 * all over the entire swap partition, so that we reduce
183 * overall disk seek times between swap pages. -- sct
184 * But we do now try to find an empty cluster. -Andrea
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800185 * And we let swap pages go all over an SSD partition. Hugh
Hugh Dickins7dfad412005-09-03 15:54:38 -0700186 */
187
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700188 si->flags += SWP_SCANNING;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800189 scan_base = offset = si->cluster_next;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800190
191 if (unlikely(!si->cluster_nr--)) {
192 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
193 si->cluster_nr = SWAPFILE_CLUSTER - 1;
194 goto checks;
195 }
Hugh Dickins7992fde2009-01-06 14:39:53 -0800196 if (si->flags & SWP_DISCARDABLE) {
197 /*
198 * Start range check on racing allocations, in case
199 * they overlap the cluster we eventually decide on
200 * (we scan without swap_lock to allow preemption).
201 * It's hardly conceivable that cluster_nr could be
202 * wrapped during our scan, but don't depend on it.
203 */
204 if (si->lowest_alloc)
205 goto checks;
206 si->lowest_alloc = si->max;
207 si->highest_alloc = 0;
208 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700209 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700210
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800211 /*
212 * If seek is expensive, start searching for new cluster from
213 * start of partition, to minimize the span of allocated swap.
214 * But if seek is cheap, search from our current position, so
215 * that swap is allocated from all over the partition: if the
216 * Flash Translation Layer only remaps within limited zones,
217 * we don't want to wear out the first zone too quickly.
218 */
219 if (!(si->flags & SWP_SOLIDSTATE))
220 scan_base = offset = si->lowest_bit;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700221 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
222
223 /* Locate the first empty (unaligned) cluster */
224 for (; last_in_cluster <= si->highest_bit; offset++) {
225 if (si->swap_map[offset])
226 last_in_cluster = offset + SWAPFILE_CLUSTER;
227 else if (offset == last_in_cluster) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700228 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800229 offset -= SWAPFILE_CLUSTER - 1;
230 si->cluster_next = offset;
231 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800232 found_free_cluster = 1;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800233 goto checks;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700235 if (unlikely(--latency_ration < 0)) {
236 cond_resched();
237 latency_ration = LATENCY_LIMIT;
238 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700239 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800240
241 offset = si->lowest_bit;
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800242 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
243
244 /* Locate the first empty (unaligned) cluster */
245 for (; last_in_cluster < scan_base; offset++) {
246 if (si->swap_map[offset])
247 last_in_cluster = offset + SWAPFILE_CLUSTER;
248 else if (offset == last_in_cluster) {
249 spin_lock(&swap_lock);
250 offset -= SWAPFILE_CLUSTER - 1;
251 si->cluster_next = offset;
252 si->cluster_nr = SWAPFILE_CLUSTER - 1;
253 found_free_cluster = 1;
254 goto checks;
255 }
256 if (unlikely(--latency_ration < 0)) {
257 cond_resched();
258 latency_ration = LATENCY_LIMIT;
259 }
260 }
261
262 offset = scan_base;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700263 spin_lock(&swap_lock);
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800264 si->cluster_nr = SWAPFILE_CLUSTER - 1;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800265 si->lowest_alloc = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700267
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800268checks:
269 if (!(si->flags & SWP_WRITEOK))
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700270 goto no_page;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700271 if (!si->highest_bit)
272 goto no_page;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800273 if (offset > si->highest_bit)
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800274 scan_base = offset = si->lowest_bit;
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800275 if (si->swap_map[offset])
276 goto scan;
Hugh Dickins7dfad412005-09-03 15:54:38 -0700277
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800278 if (offset == si->lowest_bit)
279 si->lowest_bit++;
280 if (offset == si->highest_bit)
281 si->highest_bit--;
282 si->inuse_pages++;
283 if (si->inuse_pages == si->pages) {
284 si->lowest_bit = si->max;
285 si->highest_bit = 0;
286 }
287 si->swap_map[offset] = 1;
288 si->cluster_next = offset + 1;
289 si->flags -= SWP_SCANNING;
Hugh Dickins7992fde2009-01-06 14:39:53 -0800290
291 if (si->lowest_alloc) {
292 /*
293 * Only set when SWP_DISCARDABLE, and there's a scan
294 * for a free cluster in progress or just completed.
295 */
296 if (found_free_cluster) {
297 /*
298 * To optimize wear-levelling, discard the
299 * old data of the cluster, taking care not to
300 * discard any of its pages that have already
301 * been allocated by racing tasks (offset has
302 * already stepped over any at the beginning).
303 */
304 if (offset < si->highest_alloc &&
305 si->lowest_alloc <= last_in_cluster)
306 last_in_cluster = si->lowest_alloc - 1;
307 si->flags |= SWP_DISCARDING;
308 spin_unlock(&swap_lock);
309
310 if (offset < last_in_cluster)
311 discard_swap_cluster(si, offset,
312 last_in_cluster - offset + 1);
313
314 spin_lock(&swap_lock);
315 si->lowest_alloc = 0;
316 si->flags &= ~SWP_DISCARDING;
317
318 smp_mb(); /* wake_up_bit advises this */
319 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
320
321 } else if (si->flags & SWP_DISCARDING) {
322 /*
323 * Delay using pages allocated by racing tasks
324 * until the whole discard has been issued. We
325 * could defer that delay until swap_writepage,
326 * but it's easier to keep this self-contained.
327 */
328 spin_unlock(&swap_lock);
329 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
330 wait_for_discard, TASK_UNINTERRUPTIBLE);
331 spin_lock(&swap_lock);
332 } else {
333 /*
334 * Note pages allocated by racing tasks while
335 * scan for a free cluster is in progress, so
336 * that its final discard can exclude them.
337 */
338 if (offset < si->lowest_alloc)
339 si->lowest_alloc = offset;
340 if (offset > si->highest_alloc)
341 si->highest_alloc = offset;
342 }
343 }
Hugh Dickinsebebbbe2009-01-06 14:39:50 -0800344 return offset;
345
346scan:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700347 spin_unlock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700348 while (++offset <= si->highest_bit) {
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700349 if (!si->swap_map[offset]) {
Hugh Dickins5d337b92005-09-03 15:54:41 -0700350 spin_lock(&swap_lock);
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700351 goto checks;
352 }
Hugh Dickins048c27f2005-09-03 15:54:40 -0700353 if (unlikely(--latency_ration < 0)) {
354 cond_resched();
355 latency_ration = LATENCY_LIMIT;
356 }
Hugh Dickins7dfad412005-09-03 15:54:38 -0700357 }
Hugh Dickinsc60aa172009-01-06 14:39:55 -0800358 offset = si->lowest_bit;
359 while (++offset < scan_base) {
360 if (!si->swap_map[offset]) {
361 spin_lock(&swap_lock);
362 goto checks;
363 }
364 if (unlikely(--latency_ration < 0)) {
365 cond_resched();
366 latency_ration = LATENCY_LIMIT;
367 }
368 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700369 spin_lock(&swap_lock);
Hugh Dickins7dfad412005-09-03 15:54:38 -0700370
371no_page:
Hugh Dickins52b7efdb2005-09-03 15:54:39 -0700372 si->flags -= SWP_SCANNING;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373 return 0;
374}
375
376swp_entry_t get_swap_page(void)
377{
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700378 struct swap_info_struct *si;
379 pgoff_t offset;
380 int type, next;
381 int wrapped = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
Hugh Dickins5d337b92005-09-03 15:54:41 -0700383 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 if (nr_swap_pages <= 0)
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700385 goto noswap;
386 nr_swap_pages--;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700388 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
389 si = swap_info + type;
390 next = si->next;
391 if (next < 0 ||
392 (!wrapped && si->prio != swap_info[next].prio)) {
393 next = swap_list.head;
394 wrapped++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700396
397 if (!si->highest_bit)
398 continue;
399 if (!(si->flags & SWP_WRITEOK))
400 continue;
401
402 swap_list.next = next;
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700403 offset = scan_swap_map(si);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700404 if (offset) {
405 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700406 return swp_entry(type, offset);
Hugh Dickins5d337b92005-09-03 15:54:41 -0700407 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700408 next = swap_list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 }
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700410
411 nr_swap_pages++;
412noswap:
Hugh Dickins5d337b92005-09-03 15:54:41 -0700413 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -0700414 return (swp_entry_t) {0};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415}
416
Rafael J. Wysocki3a291a22006-01-06 00:16:37 -0800417swp_entry_t get_swap_page_of_type(int type)
418{
419 struct swap_info_struct *si;
420 pgoff_t offset;
421
422 spin_lock(&swap_lock);
423 si = swap_info + type;
424 if (si->flags & SWP_WRITEOK) {
425 nr_swap_pages--;
426 offset = scan_swap_map(si);
427 if (offset) {
428 spin_unlock(&swap_lock);
429 return swp_entry(type, offset);
430 }
431 nr_swap_pages++;
432 }
433 spin_unlock(&swap_lock);
434 return (swp_entry_t) {0};
435}
436
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437static struct swap_info_struct * swap_info_get(swp_entry_t entry)
438{
439 struct swap_info_struct * p;
440 unsigned long offset, type;
441
442 if (!entry.val)
443 goto out;
444 type = swp_type(entry);
445 if (type >= nr_swapfiles)
446 goto bad_nofile;
447 p = & swap_info[type];
448 if (!(p->flags & SWP_USED))
449 goto bad_device;
450 offset = swp_offset(entry);
451 if (offset >= p->max)
452 goto bad_offset;
453 if (!p->swap_map[offset])
454 goto bad_free;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700455 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 return p;
457
458bad_free:
459 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
460 goto out;
461bad_offset:
462 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
463 goto out;
464bad_device:
465 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
466 goto out;
467bad_nofile:
468 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
469out:
470 return NULL;
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800471}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
474{
475 int count = p->swap_map[offset];
476
477 if (count < SWAP_MAP_MAX) {
478 count--;
479 p->swap_map[offset] = count;
480 if (!count) {
481 if (offset < p->lowest_bit)
482 p->lowest_bit = offset;
483 if (offset > p->highest_bit)
484 p->highest_bit = offset;
Hugh Dickins89d09a22005-09-03 15:54:36 -0700485 if (p->prio > swap_info[swap_list.next].prio)
486 swap_list.next = p - swap_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 nr_swap_pages++;
488 p->inuse_pages--;
489 }
490 }
491 return count;
492}
493
494/*
495 * Caller has made sure that the swapdevice corresponding to entry
496 * is still around or has not been recycled.
497 */
498void swap_free(swp_entry_t entry)
499{
500 struct swap_info_struct * p;
501
502 p = swap_info_get(entry);
503 if (p) {
504 swap_entry_free(p, swp_offset(entry));
Hugh Dickins5d337b92005-09-03 15:54:41 -0700505 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 }
507}
508
509/*
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700510 * How many references to page are currently swapped out?
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700512static inline int page_swapcount(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700514 int count = 0;
515 struct swap_info_struct *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 swp_entry_t entry;
517
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700518 entry.val = page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 p = swap_info_get(entry);
520 if (p) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700521 /* Subtract the 1 for the swap cache itself */
522 count = p->swap_map[swp_offset(entry)] - 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -0700523 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700525 return count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526}
527
528/*
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800529 * We can write to an anon page without COW if there are no other references
530 * to it. And as a side-effect, free up its swap: because the old content
531 * on disk will never be read, and seeking back there to write new content
532 * later would only waste time away from clustering.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 */
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800534int reuse_swap_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535{
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700536 int count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537
Hugh Dickins51726b12009-01-06 14:39:25 -0800538 VM_BUG_ON(!PageLocked(page));
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700539 count = page_mapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800540 if (count <= 1 && PageSwapCache(page)) {
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700541 count += page_swapcount(page);
Hugh Dickins7b1fe592009-01-06 14:39:34 -0800542 if (count == 1 && !PageWriteback(page)) {
543 delete_from_swap_cache(page);
544 SetPageDirty(page);
545 }
546 }
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700547 return count == 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548}
549
550/*
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800551 * If swap is getting full, or if there are no more mappings of this page,
552 * then try_to_free_swap is called to free its swap space.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 */
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800554int try_to_free_swap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555{
Hugh Dickins51726b12009-01-06 14:39:25 -0800556 VM_BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557
558 if (!PageSwapCache(page))
559 return 0;
560 if (PageWriteback(page))
561 return 0;
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800562 if (page_swapcount(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 return 0;
564
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800565 delete_from_swap_cache(page);
566 SetPageDirty(page);
567 return 1;
Rik van Riel68a223942008-10-18 20:26:23 -0700568}
569
570/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 * Free the swap entry like above, but also try to
572 * free the page cache entry if it is the last user.
573 */
574void free_swap_and_cache(swp_entry_t entry)
575{
576 struct swap_info_struct * p;
577 struct page *page = NULL;
578
Christoph Lameter06972122006-06-23 02:03:35 -0700579 if (is_migration_entry(entry))
580 return;
581
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 p = swap_info_get(entry);
583 if (p) {
Nick Piggin93fac702006-03-31 02:29:56 -0800584 if (swap_entry_free(p, swp_offset(entry)) == 1) {
585 page = find_get_page(&swapper_space, entry.val);
Nick Piggin8413ac92008-10-18 20:26:59 -0700586 if (page && !trylock_page(page)) {
Nick Piggin93fac702006-03-31 02:29:56 -0800587 page_cache_release(page);
588 page = NULL;
589 }
590 }
Hugh Dickins5d337b92005-09-03 15:54:41 -0700591 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592 }
593 if (page) {
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800594 /*
595 * Not mapped elsewhere, or swap space full? Free it!
596 * Also recheck PageSwapCache now page is locked (above).
597 */
Nick Piggin93fac702006-03-31 02:29:56 -0800598 if (PageSwapCache(page) && !PageWriteback(page) &&
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -0800599 (!page_mapped(page) || vm_swap_full())) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600 delete_from_swap_cache(page);
601 SetPageDirty(page);
602 }
603 unlock_page(page);
604 page_cache_release(page);
605 }
606}
607
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +0200608#ifdef CONFIG_HIBERNATION
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800609/*
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800610 * Find the swap type that corresponds to given device (if any).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800611 *
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800612 * @offset - number of the PAGE_SIZE-sized block of the device, starting
613 * from 0, in which the swap header is expected to be located.
614 *
615 * This is needed for the suspend to disk (aka swsusp).
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800616 */
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800617int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800618{
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800619 struct block_device *bdev = NULL;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800620 int i;
621
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800622 if (device)
623 bdev = bdget(device);
624
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800625 spin_lock(&swap_lock);
626 for (i = 0; i < nr_swapfiles; i++) {
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800627 struct swap_info_struct *sis = swap_info + i;
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800628
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800629 if (!(sis->flags & SWP_WRITEOK))
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800630 continue;
Rafael J. Wysockib6b5bce2006-08-27 01:23:25 -0700631
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800632 if (!bdev) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800633 if (bdev_p)
634 *bdev_p = sis->bdev;
635
Rafael J. Wysocki6e1819d2006-03-23 03:00:03 -0800636 spin_unlock(&swap_lock);
637 return i;
638 }
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800639 if (bdev == sis->bdev) {
640 struct swap_extent *se;
641
642 se = list_entry(sis->extent_list.next,
643 struct swap_extent, list);
644 if (se->start_block == offset) {
Rafael J. Wysocki7bf23682007-01-05 16:36:28 -0800645 if (bdev_p)
646 *bdev_p = sis->bdev;
647
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800648 spin_unlock(&swap_lock);
649 bdput(bdev);
650 return i;
651 }
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800652 }
653 }
654 spin_unlock(&swap_lock);
Rafael J. Wysocki915bae92006-12-06 20:34:07 -0800655 if (bdev)
656 bdput(bdev);
657
Rafael J. Wysockif577eb32006-03-23 02:59:59 -0800658 return -ENODEV;
659}
660
661/*
662 * Return either the total number of swap pages of given type, or the number
663 * of free pages of that type (depending on @free)
664 *
665 * This is needed for software suspend
666 */
667unsigned int count_swap_pages(int type, int free)
668{
669 unsigned int n = 0;
670
671 if (type < nr_swapfiles) {
672 spin_lock(&swap_lock);
673 if (swap_info[type].flags & SWP_WRITEOK) {
674 n = swap_info[type].pages;
675 if (free)
676 n -= swap_info[type].inuse_pages;
677 }
678 spin_unlock(&swap_lock);
679 }
680 return n;
681}
682#endif
683
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684/*
Hugh Dickins72866f62005-10-29 18:15:55 -0700685 * No need to decide whether this PTE shares the swap entry with others,
686 * just let do_wp_page work it out if a write is requested later - to
687 * force COW, vm_page_prot omits write permission from any private vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688 */
Hugh Dickins044d66c2008-02-07 00:14:04 -0800689static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690 unsigned long addr, swp_entry_t entry, struct page *page)
691{
Hugh Dickins044d66c2008-02-07 00:14:04 -0800692 spinlock_t *ptl;
693 pte_t *pte;
694 int ret = 1;
695
Balbir Singhe1a1cd52008-02-07 00:14:02 -0800696 if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
Hugh Dickins044d66c2008-02-07 00:14:04 -0800697 ret = -ENOMEM;
698
699 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
700 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
701 if (ret > 0)
702 mem_cgroup_uncharge_page(page);
703 ret = 0;
704 goto out;
705 }
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800706
Hugh Dickins42946212005-10-29 18:16:05 -0700707 inc_mm_counter(vma->vm_mm, anon_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708 get_page(page);
709 set_pte_at(vma->vm_mm, addr, pte,
710 pte_mkold(mk_pte(page, vma->vm_page_prot)));
711 page_add_anon_rmap(page, vma, addr);
712 swap_free(entry);
713 /*
714 * Move the page to the active list so it is not
715 * immediately swapped out again after swapon.
716 */
717 activate_page(page);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800718out:
719 pte_unmap_unlock(pte, ptl);
720 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721}
722
723static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
724 unsigned long addr, unsigned long end,
725 swp_entry_t entry, struct page *page)
726{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 pte_t swp_pte = swp_entry_to_pte(entry);
Hugh Dickins705e87c2005-10-29 18:16:27 -0700728 pte_t *pte;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800729 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730
Hugh Dickins044d66c2008-02-07 00:14:04 -0800731 /*
732 * We don't actually need pte lock while scanning for swp_pte: since
733 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
734 * page table while we're scanning; though it could get zapped, and on
735 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
736 * of unmatched parts which look like swp_pte, so unuse_pte must
737 * recheck under pte lock. Scanning without pte lock lets it be
738 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
739 */
740 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741 do {
742 /*
743 * swapoff spends a _lot_ of time in this loop!
744 * Test inline before going to call unuse_pte.
745 */
746 if (unlikely(pte_same(*pte, swp_pte))) {
Hugh Dickins044d66c2008-02-07 00:14:04 -0800747 pte_unmap(pte);
748 ret = unuse_pte(vma, pmd, addr, entry, page);
749 if (ret)
750 goto out;
751 pte = pte_offset_map(pmd, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752 }
753 } while (pte++, addr += PAGE_SIZE, addr != end);
Hugh Dickins044d66c2008-02-07 00:14:04 -0800754 pte_unmap(pte - 1);
755out:
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800756 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757}
758
759static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
760 unsigned long addr, unsigned long end,
761 swp_entry_t entry, struct page *page)
762{
763 pmd_t *pmd;
764 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800765 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766
767 pmd = pmd_offset(pud, addr);
768 do {
769 next = pmd_addr_end(addr, end);
770 if (pmd_none_or_clear_bad(pmd))
771 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800772 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
773 if (ret)
774 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700775 } while (pmd++, addr = next, addr != end);
776 return 0;
777}
778
779static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
780 unsigned long addr, unsigned long end,
781 swp_entry_t entry, struct page *page)
782{
783 pud_t *pud;
784 unsigned long next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800785 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786
787 pud = pud_offset(pgd, addr);
788 do {
789 next = pud_addr_end(addr, end);
790 if (pud_none_or_clear_bad(pud))
791 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800792 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
793 if (ret)
794 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795 } while (pud++, addr = next, addr != end);
796 return 0;
797}
798
799static int unuse_vma(struct vm_area_struct *vma,
800 swp_entry_t entry, struct page *page)
801{
802 pgd_t *pgd;
803 unsigned long addr, end, next;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800804 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805
806 if (page->mapping) {
807 addr = page_address_in_vma(page, vma);
808 if (addr == -EFAULT)
809 return 0;
810 else
811 end = addr + PAGE_SIZE;
812 } else {
813 addr = vma->vm_start;
814 end = vma->vm_end;
815 }
816
817 pgd = pgd_offset(vma->vm_mm, addr);
818 do {
819 next = pgd_addr_end(addr, end);
820 if (pgd_none_or_clear_bad(pgd))
821 continue;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800822 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
823 if (ret)
824 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 } while (pgd++, addr = next, addr != end);
826 return 0;
827}
828
829static int unuse_mm(struct mm_struct *mm,
830 swp_entry_t entry, struct page *page)
831{
832 struct vm_area_struct *vma;
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800833 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834
835 if (!down_read_trylock(&mm->mmap_sem)) {
836 /*
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -0700837 * Activate page so shrink_inactive_list is unlikely to unmap
838 * its ptes while lock is dropped, so swapoff can make progress.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839 */
Hugh Dickinsc475a8a2005-06-21 17:15:12 -0700840 activate_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841 unlock_page(page);
842 down_read(&mm->mmap_sem);
843 lock_page(page);
844 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800846 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700847 break;
848 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 up_read(&mm->mmap_sem);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800850 return (ret < 0)? ret: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700851}
852
853/*
854 * Scan swap_map from current position to next entry still in use.
855 * Recycle to start on reaching the end, returning 0 when empty.
856 */
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700857static unsigned int find_next_to_unuse(struct swap_info_struct *si,
858 unsigned int prev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859{
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700860 unsigned int max = si->max;
861 unsigned int i = prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700862 int count;
863
864 /*
Hugh Dickins5d337b92005-09-03 15:54:41 -0700865 * No need for swap_lock here: we're just looking
Linus Torvalds1da177e2005-04-16 15:20:36 -0700866 * for whether an entry is in use, not modifying it; false
867 * hits are okay, and sys_swapoff() has already prevented new
Hugh Dickins5d337b92005-09-03 15:54:41 -0700868 * allocations from this area (while holding swap_lock).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869 */
870 for (;;) {
871 if (++i >= max) {
872 if (!prev) {
873 i = 0;
874 break;
875 }
876 /*
877 * No entries in use at top of swap_map,
878 * loop back to start and recheck there.
879 */
880 max = prev + 1;
881 prev = 0;
882 i = 1;
883 }
884 count = si->swap_map[i];
885 if (count && count != SWAP_MAP_BAD)
886 break;
887 }
888 return i;
889}
890
891/*
892 * We completely avoid races by reading each swap page in advance,
893 * and then search for the process using it. All the necessary
894 * page table adjustments can then be made atomically.
895 */
896static int try_to_unuse(unsigned int type)
897{
898 struct swap_info_struct * si = &swap_info[type];
899 struct mm_struct *start_mm;
900 unsigned short *swap_map;
901 unsigned short swcount;
902 struct page *page;
903 swp_entry_t entry;
Hugh Dickins6eb396d2005-09-03 15:54:35 -0700904 unsigned int i = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 int retval = 0;
906 int reset_overflow = 0;
907 int shmem;
908
909 /*
910 * When searching mms for an entry, a good strategy is to
911 * start at the first mm we freed the previous entry from
912 * (though actually we don't notice whether we or coincidence
913 * freed the entry). Initialize this start_mm with a hold.
914 *
915 * A simpler strategy would be to start at the last mm we
916 * freed the previous entry from; but that would take less
917 * advantage of mmlist ordering, which clusters forked mms
918 * together, child after parent. If we race with dup_mmap(), we
919 * prefer to resolve parent before child, lest we miss entries
920 * duplicated after we scanned child: using last mm would invert
921 * that. Though it's only a serious concern when an overflowed
922 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
923 */
924 start_mm = &init_mm;
925 atomic_inc(&init_mm.mm_users);
926
927 /*
928 * Keep on scanning until all entries have gone. Usually,
929 * one pass through swap_map is enough, but not necessarily:
930 * there are races when an instance of an entry might be missed.
931 */
932 while ((i = find_next_to_unuse(si, i)) != 0) {
933 if (signal_pending(current)) {
934 retval = -EINTR;
935 break;
936 }
937
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800938 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939 * Get a page for the entry, using the existing swap
940 * cache page if there is one. Otherwise, get a clean
Hugh Dickins886bb7e2009-01-06 14:39:48 -0800941 * page and read the swap into it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 */
943 swap_map = &si->swap_map[i];
944 entry = swp_entry(type, i);
Hugh Dickins02098fe2008-02-04 22:28:42 -0800945 page = read_swap_cache_async(entry,
946 GFP_HIGHUSER_MOVABLE, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 if (!page) {
948 /*
949 * Either swap_duplicate() failed because entry
950 * has been freed independently, and will not be
951 * reused since sys_swapoff() already disabled
952 * allocation from here, or alloc_page() failed.
953 */
954 if (!*swap_map)
955 continue;
956 retval = -ENOMEM;
957 break;
958 }
959
960 /*
961 * Don't hold on to start_mm if it looks like exiting.
962 */
963 if (atomic_read(&start_mm->mm_users) == 1) {
964 mmput(start_mm);
965 start_mm = &init_mm;
966 atomic_inc(&init_mm.mm_users);
967 }
968
969 /*
970 * Wait for and lock page. When do_swap_page races with
971 * try_to_unuse, do_swap_page can handle the fault much
972 * faster than try_to_unuse can locate the entry. This
973 * apparently redundant "wait_on_page_locked" lets try_to_unuse
974 * defer to do_swap_page in such a case - in some tests,
975 * do_swap_page and try_to_unuse repeatedly compete.
976 */
977 wait_on_page_locked(page);
978 wait_on_page_writeback(page);
979 lock_page(page);
980 wait_on_page_writeback(page);
981
982 /*
983 * Remove all references to entry.
984 * Whenever we reach init_mm, there's no address space
985 * to search, but use it as a reminder to search shmem.
986 */
987 shmem = 0;
988 swcount = *swap_map;
989 if (swcount > 1) {
990 if (start_mm == &init_mm)
991 shmem = shmem_unuse(entry, page);
992 else
993 retval = unuse_mm(start_mm, entry, page);
994 }
995 if (*swap_map > 1) {
996 int set_start_mm = (*swap_map >= swcount);
997 struct list_head *p = &start_mm->mmlist;
998 struct mm_struct *new_start_mm = start_mm;
999 struct mm_struct *prev_mm = start_mm;
1000 struct mm_struct *mm;
1001
1002 atomic_inc(&new_start_mm->mm_users);
1003 atomic_inc(&prev_mm->mm_users);
1004 spin_lock(&mmlist_lock);
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001005 while (*swap_map > 1 && !retval && !shmem &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 (p = p->next) != &start_mm->mmlist) {
1007 mm = list_entry(p, struct mm_struct, mmlist);
Hugh Dickins70af7c52006-06-23 02:03:44 -07001008 if (!atomic_inc_not_zero(&mm->mm_users))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 spin_unlock(&mmlist_lock);
1011 mmput(prev_mm);
1012 prev_mm = mm;
1013
1014 cond_resched();
1015
1016 swcount = *swap_map;
1017 if (swcount <= 1)
1018 ;
1019 else if (mm == &init_mm) {
1020 set_start_mm = 1;
1021 shmem = shmem_unuse(entry, page);
1022 } else
1023 retval = unuse_mm(mm, entry, page);
1024 if (set_start_mm && *swap_map < swcount) {
1025 mmput(new_start_mm);
1026 atomic_inc(&mm->mm_users);
1027 new_start_mm = mm;
1028 set_start_mm = 0;
1029 }
1030 spin_lock(&mmlist_lock);
1031 }
1032 spin_unlock(&mmlist_lock);
1033 mmput(prev_mm);
1034 mmput(start_mm);
1035 start_mm = new_start_mm;
1036 }
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001037 if (shmem) {
1038 /* page has already been unlocked and released */
1039 if (shmem > 0)
1040 continue;
1041 retval = shmem;
1042 break;
1043 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044 if (retval) {
1045 unlock_page(page);
1046 page_cache_release(page);
1047 break;
1048 }
1049
1050 /*
1051 * How could swap count reach 0x7fff when the maximum
1052 * pid is 0x7fff, and there's no way to repeat a swap
1053 * page within an mm (except in shmem, where it's the
1054 * shared object which takes the reference count)?
1055 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
1056 *
1057 * If that's wrong, then we should worry more about
1058 * exit_mmap() and do_munmap() cases described above:
1059 * we might be resetting SWAP_MAP_MAX too early here.
1060 * We know "Undead"s can happen, they're okay, so don't
1061 * report them; but do report if we reset SWAP_MAP_MAX.
1062 */
1063 if (*swap_map == SWAP_MAP_MAX) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001064 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065 *swap_map = 1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001066 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 reset_overflow = 1;
1068 }
1069
1070 /*
1071 * If a reference remains (rare), we would like to leave
1072 * the page in the swap cache; but try_to_unmap could
1073 * then re-duplicate the entry once we drop page lock,
1074 * so we might loop indefinitely; also, that page could
1075 * not be swapped out to other storage meanwhile. So:
1076 * delete from cache even if there's another reference,
1077 * after ensuring that the data has been saved to disk -
1078 * since if the reference remains (rarer), it will be
1079 * read from disk into another page. Splitting into two
1080 * pages would be incorrect if swap supported "shared
1081 * private" pages, but they are handled by tmpfs files.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 */
1083 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
1084 struct writeback_control wbc = {
1085 .sync_mode = WB_SYNC_NONE,
1086 };
1087
1088 swap_writepage(page, &wbc);
1089 lock_page(page);
1090 wait_on_page_writeback(page);
1091 }
Hugh Dickins68bdc8d2009-01-06 14:39:37 -08001092
1093 /*
1094 * It is conceivable that a racing task removed this page from
1095 * swap cache just before we acquired the page lock at the top,
1096 * or while we dropped it in unuse_mm(). The page might even
1097 * be back in swap cache on another swap area: that we must not
1098 * delete, since it may not have been written out to swap yet.
1099 */
1100 if (PageSwapCache(page) &&
1101 likely(page_private(page) == entry.val))
Hugh Dickins2e0e26c2008-02-04 22:28:53 -08001102 delete_from_swap_cache(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103
1104 /*
1105 * So we could skip searching mms once swap count went
1106 * to 1, we did not mark any present ptes as dirty: must
Anderson Briglia2706a1b2007-07-15 23:38:09 -07001107 * mark page dirty so shrink_page_list will preserve it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108 */
1109 SetPageDirty(page);
1110 unlock_page(page);
1111 page_cache_release(page);
1112
1113 /*
1114 * Make sure that we aren't completely killing
1115 * interactive performance.
1116 */
1117 cond_resched();
1118 }
1119
1120 mmput(start_mm);
1121 if (reset_overflow) {
1122 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
1123 swap_overflow = 0;
1124 }
1125 return retval;
1126}
1127
1128/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001129 * After a successful try_to_unuse, if no swap is now in use, we know
1130 * we can empty the mmlist. swap_lock must be held on entry and exit.
1131 * Note that mmlist_lock nests inside swap_lock, and an mm must be
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 * added to the mmlist just after page_duplicate - before would be racy.
1133 */
1134static void drain_mmlist(void)
1135{
1136 struct list_head *p, *next;
1137 unsigned int i;
1138
1139 for (i = 0; i < nr_swapfiles; i++)
1140 if (swap_info[i].inuse_pages)
1141 return;
1142 spin_lock(&mmlist_lock);
1143 list_for_each_safe(p, next, &init_mm.mmlist)
1144 list_del_init(p);
1145 spin_unlock(&mmlist_lock);
1146}
1147
1148/*
1149 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1150 * corresponds to page offset `offset'.
1151 */
1152sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
1153{
1154 struct swap_extent *se = sis->curr_swap_extent;
1155 struct swap_extent *start_se = se;
1156
1157 for ( ; ; ) {
1158 struct list_head *lh;
1159
1160 if (se->start_page <= offset &&
1161 offset < (se->start_page + se->nr_pages)) {
1162 return se->start_block + (offset - se->start_page);
1163 }
Hugh Dickins11d31882005-09-03 15:54:34 -07001164 lh = se->list.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165 if (lh == &sis->extent_list)
Hugh Dickins11d31882005-09-03 15:54:34 -07001166 lh = lh->next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 se = list_entry(lh, struct swap_extent, list);
1168 sis->curr_swap_extent = se;
1169 BUG_ON(se == start_se); /* It *must* be present */
1170 }
1171}
1172
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +02001173#ifdef CONFIG_HIBERNATION
Rafael J. Wysocki3aef83e2006-12-06 20:34:10 -08001174/*
1175 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1176 * corresponding to given index in swap_info (swap type).
1177 */
1178sector_t swapdev_block(int swap_type, pgoff_t offset)
1179{
1180 struct swap_info_struct *sis;
1181
1182 if (swap_type >= nr_swapfiles)
1183 return 0;
1184
1185 sis = swap_info + swap_type;
1186 return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
1187}
Rafael J. Wysockib0cb1a12007-07-29 23:24:36 +02001188#endif /* CONFIG_HIBERNATION */
Rafael J. Wysocki3aef83e2006-12-06 20:34:10 -08001189
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190/*
1191 * Free all of a swapdev's extent information
1192 */
1193static void destroy_swap_extents(struct swap_info_struct *sis)
1194{
1195 while (!list_empty(&sis->extent_list)) {
1196 struct swap_extent *se;
1197
1198 se = list_entry(sis->extent_list.next,
1199 struct swap_extent, list);
1200 list_del(&se->list);
1201 kfree(se);
1202 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001203}
1204
1205/*
1206 * Add a block range (and the corresponding page range) into this swapdev's
Hugh Dickins11d31882005-09-03 15:54:34 -07001207 * extent list. The extent list is kept sorted in page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208 *
Hugh Dickins11d31882005-09-03 15:54:34 -07001209 * This function rather assumes that it is called in ascending page order.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210 */
1211static int
1212add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1213 unsigned long nr_pages, sector_t start_block)
1214{
1215 struct swap_extent *se;
1216 struct swap_extent *new_se;
1217 struct list_head *lh;
1218
Hugh Dickins11d31882005-09-03 15:54:34 -07001219 lh = sis->extent_list.prev; /* The highest page extent */
1220 if (lh != &sis->extent_list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221 se = list_entry(lh, struct swap_extent, list);
Hugh Dickins11d31882005-09-03 15:54:34 -07001222 BUG_ON(se->start_page + se->nr_pages != start_page);
1223 if (se->start_block + se->nr_pages == start_block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224 /* Merge it */
1225 se->nr_pages += nr_pages;
1226 return 0;
1227 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 }
1229
1230 /*
1231 * No merge. Insert a new extent, preserving ordering.
1232 */
1233 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1234 if (new_se == NULL)
1235 return -ENOMEM;
1236 new_se->start_page = start_page;
1237 new_se->nr_pages = nr_pages;
1238 new_se->start_block = start_block;
1239
Hugh Dickins11d31882005-09-03 15:54:34 -07001240 list_add_tail(&new_se->list, &sis->extent_list);
Hugh Dickins53092a72005-09-03 15:54:34 -07001241 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242}
1243
1244/*
1245 * A `swap extent' is a simple thing which maps a contiguous range of pages
1246 * onto a contiguous range of disk blocks. An ordered list of swap extents
1247 * is built at swapon time and is then used at swap_writepage/swap_readpage
1248 * time for locating where on disk a page belongs.
1249 *
1250 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1251 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1252 * swap files identically.
1253 *
1254 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1255 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1256 * swapfiles are handled *identically* after swapon time.
1257 *
1258 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1259 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1260 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1261 * requirements, they are simply tossed out - we will never use those blocks
1262 * for swapping.
1263 *
Hugh Dickinsb0d9bcd2005-09-03 15:54:31 -07001264 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1266 * which will scribble on the fs.
1267 *
1268 * The amount of disk space which a single swap extent represents varies.
1269 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1270 * extents in the list. To avoid much list walking, we cache the previous
1271 * search location in `curr_swap_extent', and start new searches from there.
1272 * This is extremely effective. The average number of iterations in
1273 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1274 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001275static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276{
1277 struct inode *inode;
1278 unsigned blocks_per_page;
1279 unsigned long page_no;
1280 unsigned blkbits;
1281 sector_t probe_block;
1282 sector_t last_block;
Hugh Dickins53092a72005-09-03 15:54:34 -07001283 sector_t lowest_block = -1;
1284 sector_t highest_block = 0;
1285 int nr_extents = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 int ret;
1287
1288 inode = sis->swap_file->f_mapping->host;
1289 if (S_ISBLK(inode->i_mode)) {
1290 ret = add_swap_extent(sis, 0, sis->max, 0);
Hugh Dickins53092a72005-09-03 15:54:34 -07001291 *span = sis->pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 goto done;
1293 }
1294
1295 blkbits = inode->i_blkbits;
1296 blocks_per_page = PAGE_SIZE >> blkbits;
1297
1298 /*
1299 * Map all the blocks into the extent list. This code doesn't try
1300 * to be very smart.
1301 */
1302 probe_block = 0;
1303 page_no = 0;
1304 last_block = i_size_read(inode) >> blkbits;
1305 while ((probe_block + blocks_per_page) <= last_block &&
1306 page_no < sis->max) {
1307 unsigned block_in_page;
1308 sector_t first_block;
1309
1310 first_block = bmap(inode, probe_block);
1311 if (first_block == 0)
1312 goto bad_bmap;
1313
1314 /*
1315 * It must be PAGE_SIZE aligned on-disk
1316 */
1317 if (first_block & (blocks_per_page - 1)) {
1318 probe_block++;
1319 goto reprobe;
1320 }
1321
1322 for (block_in_page = 1; block_in_page < blocks_per_page;
1323 block_in_page++) {
1324 sector_t block;
1325
1326 block = bmap(inode, probe_block + block_in_page);
1327 if (block == 0)
1328 goto bad_bmap;
1329 if (block != first_block + block_in_page) {
1330 /* Discontiguity */
1331 probe_block++;
1332 goto reprobe;
1333 }
1334 }
1335
Hugh Dickins53092a72005-09-03 15:54:34 -07001336 first_block >>= (PAGE_SHIFT - blkbits);
1337 if (page_no) { /* exclude the header page */
1338 if (first_block < lowest_block)
1339 lowest_block = first_block;
1340 if (first_block > highest_block)
1341 highest_block = first_block;
1342 }
1343
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 /*
1345 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1346 */
Hugh Dickins53092a72005-09-03 15:54:34 -07001347 ret = add_swap_extent(sis, page_no, 1, first_block);
1348 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 goto out;
Hugh Dickins53092a72005-09-03 15:54:34 -07001350 nr_extents += ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 page_no++;
1352 probe_block += blocks_per_page;
1353reprobe:
1354 continue;
1355 }
Hugh Dickins53092a72005-09-03 15:54:34 -07001356 ret = nr_extents;
1357 *span = 1 + highest_block - lowest_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358 if (page_no == 0)
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001359 page_no = 1; /* force Empty message */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 sis->max = page_no;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001361 sis->pages = page_no - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362 sis->highest_bit = page_no - 1;
1363done:
1364 sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1365 struct swap_extent, list);
1366 goto out;
1367bad_bmap:
1368 printk(KERN_ERR "swapon: swapfile has holes\n");
1369 ret = -EINVAL;
1370out:
1371 return ret;
1372}
1373
1374#if 0 /* We don't need this yet */
1375#include <linux/backing-dev.h>
1376int page_queue_congested(struct page *page)
1377{
1378 struct backing_dev_info *bdi;
1379
Hugh Dickins51726b12009-01-06 14:39:25 -08001380 VM_BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381
1382 if (PageSwapCache(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -07001383 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384 struct swap_info_struct *sis;
1385
1386 sis = get_swap_info_struct(swp_type(entry));
1387 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1388 } else
1389 bdi = page->mapping->backing_dev_info;
1390 return bdi_write_congested(bdi);
1391}
1392#endif
1393
1394asmlinkage long sys_swapoff(const char __user * specialfile)
1395{
1396 struct swap_info_struct * p = NULL;
1397 unsigned short *swap_map;
1398 struct file *swap_file, *victim;
1399 struct address_space *mapping;
1400 struct inode *inode;
1401 char * pathname;
1402 int i, type, prev;
1403 int err;
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001404
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405 if (!capable(CAP_SYS_ADMIN))
1406 return -EPERM;
1407
1408 pathname = getname(specialfile);
1409 err = PTR_ERR(pathname);
1410 if (IS_ERR(pathname))
1411 goto out;
1412
1413 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1414 putname(pathname);
1415 err = PTR_ERR(victim);
1416 if (IS_ERR(victim))
1417 goto out;
1418
1419 mapping = victim->f_mapping;
1420 prev = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001421 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422 for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1423 p = swap_info + type;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001424 if (p->flags & SWP_WRITEOK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425 if (p->swap_file->f_mapping == mapping)
1426 break;
1427 }
1428 prev = type;
1429 }
1430 if (type < 0) {
1431 err = -EINVAL;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001432 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433 goto out_dput;
1434 }
1435 if (!security_vm_enough_memory(p->pages))
1436 vm_unacct_memory(p->pages);
1437 else {
1438 err = -ENOMEM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001439 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440 goto out_dput;
1441 }
1442 if (prev < 0) {
1443 swap_list.head = p->next;
1444 } else {
1445 swap_info[prev].next = p->next;
1446 }
1447 if (type == swap_list.next) {
1448 /* just pick something that's safe... */
1449 swap_list.next = swap_list.head;
1450 }
Hugh Dickins78ecba02008-07-23 21:28:23 -07001451 if (p->prio < 0) {
1452 for (i = p->next; i >= 0; i = swap_info[i].next)
1453 swap_info[i].prio = p->prio--;
1454 least_priority++;
1455 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 nr_swap_pages -= p->pages;
1457 total_swap_pages -= p->pages;
1458 p->flags &= ~SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001459 spin_unlock(&swap_lock);
Hugh Dickinsfb4f88d2005-09-03 15:54:37 -07001460
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461 current->flags |= PF_SWAPOFF;
1462 err = try_to_unuse(type);
1463 current->flags &= ~PF_SWAPOFF;
1464
Linus Torvalds1da177e2005-04-16 15:20:36 -07001465 if (err) {
1466 /* re-insert swap space back into swap_list */
Hugh Dickins5d337b92005-09-03 15:54:41 -07001467 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001468 if (p->prio < 0)
1469 p->prio = --least_priority;
1470 prev = -1;
1471 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472 if (p->prio >= swap_info[i].prio)
1473 break;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001474 prev = i;
1475 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001476 p->next = i;
1477 if (prev < 0)
1478 swap_list.head = swap_list.next = p - swap_info;
1479 else
1480 swap_info[prev].next = p - swap_info;
1481 nr_swap_pages += p->pages;
1482 total_swap_pages += p->pages;
1483 p->flags |= SWP_WRITEOK;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001484 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485 goto out_dput;
1486 }
Hugh Dickins52b7efdb2005-09-03 15:54:39 -07001487
1488 /* wait for any unplug function to finish */
1489 down_write(&swap_unplug_sem);
1490 up_write(&swap_unplug_sem);
1491
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001492 destroy_swap_extents(p);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001493 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001494 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001495 drain_mmlist();
Hugh Dickins5d337b92005-09-03 15:54:41 -07001496
1497 /* wait for anyone still in scan_swap_map */
1498 p->highest_bit = 0; /* cuts scans short */
1499 while (p->flags >= SWP_SCANNING) {
1500 spin_unlock(&swap_lock);
Nishanth Aravamudan13e4b572005-09-10 00:27:25 -07001501 schedule_timeout_uninterruptible(1);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001502 spin_lock(&swap_lock);
1503 }
1504
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 swap_file = p->swap_file;
1506 p->swap_file = NULL;
1507 p->max = 0;
1508 swap_map = p->swap_map;
1509 p->swap_map = NULL;
1510 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001511 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001512 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001513 vfree(swap_map);
1514 inode = mapping->host;
1515 if (S_ISBLK(inode->i_mode)) {
1516 struct block_device *bdev = I_BDEV(inode);
1517 set_blocksize(bdev, p->old_block_size);
1518 bd_release(bdev);
1519 } else {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001520 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001521 inode->i_flags &= ~S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001522 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 }
1524 filp_close(swap_file, NULL);
1525 err = 0;
1526
1527out_dput:
1528 filp_close(victim, NULL);
1529out:
1530 return err;
1531}
1532
1533#ifdef CONFIG_PROC_FS
1534/* iterator */
1535static void *swap_start(struct seq_file *swap, loff_t *pos)
1536{
1537 struct swap_info_struct *ptr = swap_info;
1538 int i;
1539 loff_t l = *pos;
1540
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001541 mutex_lock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001543 if (!l)
1544 return SEQ_START_TOKEN;
1545
Linus Torvalds1da177e2005-04-16 15:20:36 -07001546 for (i = 0; i < nr_swapfiles; i++, ptr++) {
1547 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1548 continue;
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001549 if (!--l)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 return ptr;
1551 }
1552
1553 return NULL;
1554}
1555
1556static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1557{
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001558 struct swap_info_struct *ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559 struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1560
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001561 if (v == SEQ_START_TOKEN)
1562 ptr = swap_info;
1563 else {
1564 ptr = v;
1565 ptr++;
1566 }
1567
1568 for (; ptr < endptr; ptr++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1570 continue;
1571 ++*pos;
1572 return ptr;
1573 }
1574
1575 return NULL;
1576}
1577
1578static void swap_stop(struct seq_file *swap, void *v)
1579{
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001580 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581}
1582
1583static int swap_show(struct seq_file *swap, void *v)
1584{
1585 struct swap_info_struct *ptr = v;
1586 struct file *file;
1587 int len;
1588
Suleiman Souhlal881e4aa2006-12-06 20:32:28 -08001589 if (ptr == SEQ_START_TOKEN) {
1590 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1591 return 0;
1592 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001593
1594 file = ptr->swap_file;
Jan Blunckc32c2f62008-02-14 19:38:43 -08001595 len = seq_path(swap, &file->f_path, " \t\n\\");
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001596 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001597 len < 40 ? 40 - len : 1, " ",
1598 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599 "partition" : "file\t",
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001600 ptr->pages << (PAGE_SHIFT - 10),
1601 ptr->inuse_pages << (PAGE_SHIFT - 10),
1602 ptr->prio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603 return 0;
1604}
1605
Helge Deller15ad7cd2006-12-06 20:40:36 -08001606static const struct seq_operations swaps_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607 .start = swap_start,
1608 .next = swap_next,
1609 .stop = swap_stop,
1610 .show = swap_show
1611};
1612
1613static int swaps_open(struct inode *inode, struct file *file)
1614{
1615 return seq_open(file, &swaps_op);
1616}
1617
Helge Deller15ad7cd2006-12-06 20:40:36 -08001618static const struct file_operations proc_swaps_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619 .open = swaps_open,
1620 .read = seq_read,
1621 .llseek = seq_lseek,
1622 .release = seq_release,
1623};
1624
1625static int __init procswaps_init(void)
1626{
Denis V. Lunev3d71f862008-04-29 01:02:13 -07001627 proc_create("swaps", 0, NULL, &proc_swaps_operations);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628 return 0;
1629}
1630__initcall(procswaps_init);
1631#endif /* CONFIG_PROC_FS */
1632
Jan Beulich17963162008-12-16 11:35:24 +00001633#ifdef MAX_SWAPFILES_CHECK
1634static int __init max_swapfiles_check(void)
1635{
1636 MAX_SWAPFILES_CHECK();
1637 return 0;
1638}
1639late_initcall(max_swapfiles_check);
1640#endif
1641
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642/*
1643 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1644 *
1645 * The swapon system call
1646 */
1647asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1648{
1649 struct swap_info_struct * p;
1650 char *name = NULL;
1651 struct block_device *bdev = NULL;
1652 struct file *swap_file = NULL;
1653 struct address_space *mapping;
1654 unsigned int type;
1655 int i, prev;
1656 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 union swap_header *swap_header = NULL;
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001658 unsigned int nr_good_pages = 0;
1659 int nr_extents = 0;
Hugh Dickins53092a72005-09-03 15:54:34 -07001660 sector_t span;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661 unsigned long maxpages = 1;
Hugh Dickins73fd8742009-01-06 14:39:47 -08001662 unsigned long swapfilepages;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001663 unsigned short *swap_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664 struct page *page = NULL;
1665 struct inode *inode = NULL;
1666 int did_down = 0;
1667
1668 if (!capable(CAP_SYS_ADMIN))
1669 return -EPERM;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001670 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 p = swap_info;
1672 for (type = 0 ; type < nr_swapfiles ; type++,p++)
1673 if (!(p->flags & SWP_USED))
1674 break;
1675 error = -EPERM;
Christoph Lameter06972122006-06-23 02:03:35 -07001676 if (type >= MAX_SWAPFILES) {
Hugh Dickins5d337b92005-09-03 15:54:41 -07001677 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 goto out;
1679 }
1680 if (type >= nr_swapfiles)
1681 nr_swapfiles = type+1;
Hugh Dickins78ecba02008-07-23 21:28:23 -07001682 memset(p, 0, sizeof(*p));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683 INIT_LIST_HEAD(&p->extent_list);
1684 p->flags = SWP_USED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685 p->next = -1;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001686 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001687 name = getname(specialfile);
1688 error = PTR_ERR(name);
1689 if (IS_ERR(name)) {
1690 name = NULL;
1691 goto bad_swap_2;
1692 }
1693 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1694 error = PTR_ERR(swap_file);
1695 if (IS_ERR(swap_file)) {
1696 swap_file = NULL;
1697 goto bad_swap_2;
1698 }
1699
1700 p->swap_file = swap_file;
1701 mapping = swap_file->f_mapping;
1702 inode = mapping->host;
1703
1704 error = -EBUSY;
1705 for (i = 0; i < nr_swapfiles; i++) {
1706 struct swap_info_struct *q = &swap_info[i];
1707
1708 if (i == type || !q->swap_file)
1709 continue;
1710 if (mapping == q->swap_file->f_mapping)
1711 goto bad_swap;
1712 }
1713
1714 error = -EINVAL;
1715 if (S_ISBLK(inode->i_mode)) {
1716 bdev = I_BDEV(inode);
1717 error = bd_claim(bdev, sys_swapon);
1718 if (error < 0) {
1719 bdev = NULL;
Rob Landleyf7b3a432005-09-22 21:44:27 -07001720 error = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001721 goto bad_swap;
1722 }
1723 p->old_block_size = block_size(bdev);
1724 error = set_blocksize(bdev, PAGE_SIZE);
1725 if (error < 0)
1726 goto bad_swap;
1727 p->bdev = bdev;
1728 } else if (S_ISREG(inode->i_mode)) {
1729 p->bdev = inode->i_sb->s_bdev;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001730 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 did_down = 1;
1732 if (IS_SWAPFILE(inode)) {
1733 error = -EBUSY;
1734 goto bad_swap;
1735 }
1736 } else {
1737 goto bad_swap;
1738 }
1739
Hugh Dickins73fd8742009-01-06 14:39:47 -08001740 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741
1742 /*
1743 * Read the swap header.
1744 */
1745 if (!mapping->a_ops->readpage) {
1746 error = -EINVAL;
1747 goto bad_swap;
1748 }
Pekka Enberg090d2b12006-06-23 02:05:08 -07001749 page = read_mapping_page(mapping, 0, swap_file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 if (IS_ERR(page)) {
1751 error = PTR_ERR(page);
1752 goto bad_swap;
1753 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001754 swap_header = kmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755
Hugh Dickins81e33972009-01-06 14:39:49 -08001756 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
Jesper Juhle97a3112006-01-11 01:50:28 +01001757 printk(KERN_ERR "Unable to find swap-space signature\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 error = -EINVAL;
1759 goto bad_swap;
1760 }
Hugh Dickins886bb7e2009-01-06 14:39:48 -08001761
Hugh Dickins81e33972009-01-06 14:39:49 -08001762 /* swap partition endianess hack... */
1763 if (swab32(swap_header->info.version) == 1) {
1764 swab32s(&swap_header->info.version);
1765 swab32s(&swap_header->info.last_page);
1766 swab32s(&swap_header->info.nr_badpages);
1767 for (i = 0; i < swap_header->info.nr_badpages; i++)
1768 swab32s(&swap_header->info.badpages[i]);
1769 }
1770 /* Check the swap header's sub-version */
1771 if (swap_header->info.version != 1) {
1772 printk(KERN_WARNING
1773 "Unable to handle swap header version %d\n",
1774 swap_header->info.version);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775 error = -EINVAL;
1776 goto bad_swap;
Hugh Dickins81e33972009-01-06 14:39:49 -08001777 }
1778
1779 p->lowest_bit = 1;
1780 p->cluster_next = 1;
1781
1782 /*
1783 * Find out how many pages are allowed for a single swap
1784 * device. There are two limiting factors: 1) the number of
1785 * bits for the swap offset in the swp_entry_t type and
1786 * 2) the number of bits in the a swap pte as defined by
1787 * the different architectures. In order to find the
1788 * largest possible bit mask a swap entry with swap type 0
1789 * and swap offset ~0UL is created, encoded to a swap pte,
1790 * decoded to a swp_entry_t again and finally the swap
1791 * offset is extracted. This will mask all the bits from
1792 * the initial ~0UL mask that can't be encoded in either
1793 * the swp_entry_t or the architecture definition of a
1794 * swap pte.
1795 */
1796 maxpages = swp_offset(pte_to_swp_entry(
1797 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1798 if (maxpages > swap_header->info.last_page)
1799 maxpages = swap_header->info.last_page;
1800 p->highest_bit = maxpages - 1;
1801
1802 error = -EINVAL;
1803 if (!maxpages)
1804 goto bad_swap;
1805 if (swapfilepages && maxpages > swapfilepages) {
1806 printk(KERN_WARNING
1807 "Swap area shorter than signature indicates\n");
1808 goto bad_swap;
1809 }
1810 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1811 goto bad_swap;
1812 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1813 goto bad_swap;
1814
1815 /* OK, set up the swap map and apply the bad block list */
1816 swap_map = vmalloc(maxpages * sizeof(short));
1817 if (!swap_map) {
1818 error = -ENOMEM;
1819 goto bad_swap;
1820 }
1821
1822 memset(swap_map, 0, maxpages * sizeof(short));
1823 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1824 int page_nr = swap_header->info.badpages[i];
1825 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826 error = -EINVAL;
1827 goto bad_swap;
1828 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001829 swap_map[page_nr] = SWAP_MAP_BAD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001830 }
Hugh Dickins81e33972009-01-06 14:39:49 -08001831 nr_good_pages = swap_header->info.last_page -
1832 swap_header->info.nr_badpages -
1833 1 /* header page */;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001834
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001835 if (nr_good_pages) {
Hugh Dickins78ecba02008-07-23 21:28:23 -07001836 swap_map[0] = SWAP_MAP_BAD;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001837 p->max = maxpages;
1838 p->pages = nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001839 nr_extents = setup_swap_extents(p, &span);
1840 if (nr_extents < 0) {
1841 error = nr_extents;
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001842 goto bad_swap;
Hugh Dickins53092a72005-09-03 15:54:34 -07001843 }
Hugh Dickinse2244ec2005-09-03 15:54:32 -07001844 nr_good_pages = p->pages;
1845 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001846 if (!nr_good_pages) {
1847 printk(KERN_WARNING "Empty swap-file\n");
1848 error = -EINVAL;
1849 goto bad_swap;
1850 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001851
Hugh Dickins20137a42009-01-06 14:39:54 -08001852 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1853 p->flags |= SWP_SOLIDSTATE;
1854 srandom32((u32)get_seconds());
1855 p->cluster_next = 1 + (random32() % p->highest_bit);
1856 }
Hugh Dickins6a6ba832009-01-06 14:39:51 -08001857 if (discard_swap(p) == 0)
1858 p->flags |= SWP_DISCARDABLE;
1859
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001860 mutex_lock(&swapon_mutex);
Hugh Dickins5d337b92005-09-03 15:54:41 -07001861 spin_lock(&swap_lock);
Hugh Dickins78ecba02008-07-23 21:28:23 -07001862 if (swap_flags & SWAP_FLAG_PREFER)
1863 p->prio =
1864 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1865 else
1866 p->prio = --least_priority;
1867 p->swap_map = swap_map;
Hugh Dickins22c6f8f2009-01-06 14:39:48 -08001868 p->flags |= SWP_WRITEOK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 nr_swap_pages += nr_good_pages;
1870 total_swap_pages += nr_good_pages;
Hugh Dickins53092a72005-09-03 15:54:34 -07001871
Hugh Dickins6eb396d2005-09-03 15:54:35 -07001872 printk(KERN_INFO "Adding %uk swap on %s. "
Hugh Dickins20137a42009-01-06 14:39:54 -08001873 "Priority:%d extents:%d across:%lluk %s%s\n",
Hugh Dickins53092a72005-09-03 15:54:34 -07001874 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
Hugh Dickins6a6ba832009-01-06 14:39:51 -08001875 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
Hugh Dickins20137a42009-01-06 14:39:54 -08001876 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
1877 (p->flags & SWP_DISCARDABLE) ? "D" : "");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878
1879 /* insert swap space into swap_list: */
1880 prev = -1;
1881 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1882 if (p->prio >= swap_info[i].prio) {
1883 break;
1884 }
1885 prev = i;
1886 }
1887 p->next = i;
1888 if (prev < 0) {
1889 swap_list.head = swap_list.next = p - swap_info;
1890 } else {
1891 swap_info[prev].next = p - swap_info;
1892 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001893 spin_unlock(&swap_lock);
Ingo Molnarfc0abb12006-01-18 17:42:33 -08001894 mutex_unlock(&swapon_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001895 error = 0;
1896 goto out;
1897bad_swap:
1898 if (bdev) {
1899 set_blocksize(bdev, p->old_block_size);
1900 bd_release(bdev);
1901 }
Hugh Dickins4cd3bb12005-09-03 15:54:33 -07001902 destroy_swap_extents(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001903bad_swap_2:
Hugh Dickins5d337b92005-09-03 15:54:41 -07001904 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001905 p->swap_file = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001906 p->flags = 0;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001907 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001908 vfree(swap_map);
1909 if (swap_file)
1910 filp_close(swap_file, NULL);
1911out:
1912 if (page && !IS_ERR(page)) {
1913 kunmap(page);
1914 page_cache_release(page);
1915 }
1916 if (name)
1917 putname(name);
1918 if (did_down) {
1919 if (!error)
1920 inode->i_flags |= S_SWAPFILE;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001921 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001922 }
1923 return error;
1924}
1925
1926void si_swapinfo(struct sysinfo *val)
1927{
1928 unsigned int i;
1929 unsigned long nr_to_be_unused = 0;
1930
Hugh Dickins5d337b92005-09-03 15:54:41 -07001931 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001932 for (i = 0; i < nr_swapfiles; i++) {
1933 if (!(swap_info[i].flags & SWP_USED) ||
1934 (swap_info[i].flags & SWP_WRITEOK))
1935 continue;
1936 nr_to_be_unused += swap_info[i].inuse_pages;
1937 }
1938 val->freeswap = nr_swap_pages + nr_to_be_unused;
1939 val->totalswap = total_swap_pages + nr_to_be_unused;
Hugh Dickins5d337b92005-09-03 15:54:41 -07001940 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001941}
1942
1943/*
1944 * Verify that a swap entry is valid and increment its swap map count.
1945 *
1946 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1947 * "permanent", but will be reclaimed by the next swapoff.
1948 */
1949int swap_duplicate(swp_entry_t entry)
1950{
1951 struct swap_info_struct * p;
1952 unsigned long offset, type;
1953 int result = 0;
1954
Christoph Lameter06972122006-06-23 02:03:35 -07001955 if (is_migration_entry(entry))
1956 return 1;
1957
Linus Torvalds1da177e2005-04-16 15:20:36 -07001958 type = swp_type(entry);
1959 if (type >= nr_swapfiles)
1960 goto bad_file;
1961 p = type + swap_info;
1962 offset = swp_offset(entry);
1963
Hugh Dickins5d337b92005-09-03 15:54:41 -07001964 spin_lock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001965 if (offset < p->max && p->swap_map[offset]) {
1966 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1967 p->swap_map[offset]++;
1968 result = 1;
1969 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1970 if (swap_overflow++ < 5)
1971 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1972 p->swap_map[offset] = SWAP_MAP_MAX;
1973 result = 1;
1974 }
1975 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07001976 spin_unlock(&swap_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001977out:
1978 return result;
1979
1980bad_file:
1981 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1982 goto out;
1983}
1984
1985struct swap_info_struct *
1986get_swap_info_struct(unsigned type)
1987{
1988 return &swap_info[type];
1989}
1990
1991/*
Hugh Dickins5d337b92005-09-03 15:54:41 -07001992 * swap_lock prevents swap_map being freed. Don't grab an extra
Linus Torvalds1da177e2005-04-16 15:20:36 -07001993 * reference on the swaphandle, it doesn't matter if it becomes unused.
1994 */
1995int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1996{
Hugh Dickins89528982008-02-04 22:28:45 -08001997 struct swap_info_struct *si;
Hugh Dickins3f9e7942006-09-29 02:01:26 -07001998 int our_page_cluster = page_cluster;
Hugh Dickins89528982008-02-04 22:28:45 -08001999 pgoff_t target, toff;
2000 pgoff_t base, end;
2001 int nr_pages = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002002
Hugh Dickins3f9e7942006-09-29 02:01:26 -07002003 if (!our_page_cluster) /* no readahead */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004 return 0;
Hugh Dickins89528982008-02-04 22:28:45 -08002005
2006 si = &swap_info[swp_type(entry)];
2007 target = swp_offset(entry);
2008 base = (target >> our_page_cluster) << our_page_cluster;
2009 end = base + (1 << our_page_cluster);
2010 if (!base) /* first page is swap header */
2011 base++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012
Hugh Dickins5d337b92005-09-03 15:54:41 -07002013 spin_lock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002014 if (end > si->max) /* don't go beyond end of map */
2015 end = si->max;
2016
2017 /* Count contiguous allocated slots above our target */
2018 for (toff = target; ++toff < end; nr_pages++) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002019 /* Don't read in free or bad pages */
Hugh Dickins89528982008-02-04 22:28:45 -08002020 if (!si->swap_map[toff])
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021 break;
Hugh Dickins89528982008-02-04 22:28:45 -08002022 if (si->swap_map[toff] == SWAP_MAP_BAD)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023 break;
Hugh Dickins89528982008-02-04 22:28:45 -08002024 }
2025 /* Count contiguous allocated slots below our target */
2026 for (toff = target; --toff >= base; nr_pages++) {
2027 /* Don't read in free or bad pages */
2028 if (!si->swap_map[toff])
2029 break;
2030 if (si->swap_map[toff] == SWAP_MAP_BAD)
2031 break;
2032 }
Hugh Dickins5d337b92005-09-03 15:54:41 -07002033 spin_unlock(&swap_lock);
Hugh Dickins89528982008-02-04 22:28:45 -08002034
2035 /*
2036 * Indicate starting offset, and return number of pages to get:
2037 * if only 1, say 0, since there's then no readahead to be done.
2038 */
2039 *offset = ++toff;
2040 return nr_pages? ++nr_pages: 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041}