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1 | /* |
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 | |
8 | #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/shmem_fs.h> |
18 | #include <linux/blkdev.h> |
19 | #include <linux/random.h> |
20 | #include <linux/writeback.h> |
21 | #include <linux/proc_fs.h> |
22 | #include <linux/seq_file.h> |
23 | #include <linux/init.h> |
24 | #include <linux/ksm.h> |
25 | #include <linux/rmap.h> |
26 | #include <linux/security.h> |
27 | #include <linux/backing-dev.h> |
28 | #include <linux/mutex.h> |
29 | #include <linux/capability.h> |
30 | #include <linux/syscalls.h> |
31 | #include <linux/memcontrol.h> |
32 | #include <linux/poll.h> |
33 | #include <linux/oom.h> |
34 | #include <linux/frontswap.h> |
35 | #include <linux/swapfile.h> |
36 | #include <linux/export.h> |
37 | |
38 | #include <asm/pgtable.h> |
39 | #include <asm/tlbflush.h> |
40 | #include <linux/swapops.h> |
41 | #include <linux/page_cgroup.h> |
42 | |
43 | static bool swap_count_continued(struct swap_info_struct *, pgoff_t, |
44 | unsigned char); |
45 | static void free_swap_count_continuations(struct swap_info_struct *); |
46 | static sector_t map_swap_entry(swp_entry_t, struct block_device**); |
47 | |
48 | DEFINE_SPINLOCK(swap_lock); |
49 | static unsigned int nr_swapfiles; |
50 | atomic_long_t nr_swap_pages; |
51 | /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ |
52 | long total_swap_pages; |
53 | static int least_priority; |
54 | static atomic_t highest_priority_index = ATOMIC_INIT(-1); |
55 | |
56 | static const char Bad_file[] = "Bad swap file entry "; |
57 | static const char Unused_file[] = "Unused swap file entry "; |
58 | static const char Bad_offset[] = "Bad swap offset entry "; |
59 | static const char Unused_offset[] = "Unused swap offset entry "; |
60 | |
61 | struct swap_list_t swap_list = {-1, -1}; |
62 | |
63 | struct swap_info_struct *swap_info[MAX_SWAPFILES]; |
64 | |
65 | static DEFINE_MUTEX(swapon_mutex); |
66 | |
67 | static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait); |
68 | /* Activity counter to indicate that a swapon or swapoff has occurred */ |
69 | static atomic_t proc_poll_event = ATOMIC_INIT(0); |
70 | |
71 | static inline unsigned char swap_count(unsigned char ent) |
72 | { |
73 | return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */ |
74 | } |
75 | |
76 | /* returns 1 if swap entry is freed */ |
77 | static int |
78 | __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) |
79 | { |
80 | swp_entry_t entry = swp_entry(si->type, offset); |
81 | struct page *page; |
82 | int ret = 0; |
83 | |
84 | page = find_get_page(swap_address_space(entry), entry.val); |
85 | if (!page) |
86 | return 0; |
87 | /* |
88 | * This function is called from scan_swap_map() and it's called |
89 | * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. |
90 | * We have to use trylock for avoiding deadlock. This is a special |
91 | * case and you should use try_to_free_swap() with explicit lock_page() |
92 | * in usual operations. |
93 | */ |
94 | if (trylock_page(page)) { |
95 | ret = try_to_free_swap(page); |
96 | unlock_page(page); |
97 | } |
98 | page_cache_release(page); |
99 | return ret; |
100 | } |
101 | |
102 | /* |
103 | * swapon tell device that all the old swap contents can be discarded, |
104 | * to allow the swap device to optimize its wear-levelling. |
105 | */ |
106 | static int discard_swap(struct swap_info_struct *si) |
107 | { |
108 | struct swap_extent *se; |
109 | sector_t start_block; |
110 | sector_t nr_blocks; |
111 | int err = 0; |
112 | |
113 | /* Do not discard the swap header page! */ |
114 | se = &si->first_swap_extent; |
115 | start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); |
116 | nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); |
117 | if (nr_blocks) { |
118 | err = blkdev_issue_discard(si->bdev, start_block, |
119 | nr_blocks, GFP_KERNEL, 0); |
120 | if (err) |
121 | return err; |
122 | cond_resched(); |
123 | } |
124 | |
125 | list_for_each_entry(se, &si->first_swap_extent.list, list) { |
126 | start_block = se->start_block << (PAGE_SHIFT - 9); |
127 | nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); |
128 | |
129 | err = blkdev_issue_discard(si->bdev, start_block, |
130 | nr_blocks, GFP_KERNEL, 0); |
131 | if (err) |
132 | break; |
133 | |
134 | cond_resched(); |
135 | } |
136 | return err; /* That will often be -EOPNOTSUPP */ |
137 | } |
138 | |
139 | /* |
140 | * swap allocation tell device that a cluster of swap can now be discarded, |
141 | * to allow the swap device to optimize its wear-levelling. |
142 | */ |
143 | static void discard_swap_cluster(struct swap_info_struct *si, |
144 | pgoff_t start_page, pgoff_t nr_pages) |
145 | { |
146 | struct swap_extent *se = si->curr_swap_extent; |
147 | int found_extent = 0; |
148 | |
149 | while (nr_pages) { |
150 | struct list_head *lh; |
151 | |
152 | if (se->start_page <= start_page && |
153 | start_page < se->start_page + se->nr_pages) { |
154 | pgoff_t offset = start_page - se->start_page; |
155 | sector_t start_block = se->start_block + offset; |
156 | sector_t nr_blocks = se->nr_pages - offset; |
157 | |
158 | if (nr_blocks > nr_pages) |
159 | nr_blocks = nr_pages; |
160 | start_page += nr_blocks; |
161 | nr_pages -= nr_blocks; |
162 | |
163 | if (!found_extent++) |
164 | si->curr_swap_extent = se; |
165 | |
166 | start_block <<= PAGE_SHIFT - 9; |
167 | nr_blocks <<= PAGE_SHIFT - 9; |
168 | if (blkdev_issue_discard(si->bdev, start_block, |
169 | nr_blocks, GFP_NOIO, 0)) |
170 | break; |
171 | } |
172 | |
173 | lh = se->list.next; |
174 | se = list_entry(lh, struct swap_extent, list); |
175 | } |
176 | } |
177 | |
178 | static int wait_for_discard(void *word) |
179 | { |
180 | schedule(); |
181 | return 0; |
182 | } |
183 | |
184 | #define SWAPFILE_CLUSTER 256 |
185 | #define LATENCY_LIMIT 256 |
186 | |
187 | static unsigned long scan_swap_map(struct swap_info_struct *si, |
188 | unsigned char usage) |
189 | { |
190 | unsigned long offset; |
191 | unsigned long scan_base; |
192 | unsigned long last_in_cluster = 0; |
193 | int latency_ration = LATENCY_LIMIT; |
194 | int found_free_cluster = 0; |
195 | |
196 | /* |
197 | * We try to cluster swap pages by allocating them sequentially |
198 | * in swap. Once we've allocated SWAPFILE_CLUSTER pages this |
199 | * way, however, we resort to first-free allocation, starting |
200 | * a new cluster. This prevents us from scattering swap pages |
201 | * all over the entire swap partition, so that we reduce |
202 | * overall disk seek times between swap pages. -- sct |
203 | * But we do now try to find an empty cluster. -Andrea |
204 | * And we let swap pages go all over an SSD partition. Hugh |
205 | */ |
206 | |
207 | si->flags += SWP_SCANNING; |
208 | scan_base = offset = si->cluster_next; |
209 | |
210 | if (unlikely(!si->cluster_nr--)) { |
211 | if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { |
212 | si->cluster_nr = SWAPFILE_CLUSTER - 1; |
213 | goto checks; |
214 | } |
215 | if (si->flags & SWP_DISCARDABLE) { |
216 | /* |
217 | * Start range check on racing allocations, in case |
218 | * they overlap the cluster we eventually decide on |
219 | * (we scan without swap_lock to allow preemption). |
220 | * It's hardly conceivable that cluster_nr could be |
221 | * wrapped during our scan, but don't depend on it. |
222 | */ |
223 | if (si->lowest_alloc) |
224 | goto checks; |
225 | si->lowest_alloc = si->max; |
226 | si->highest_alloc = 0; |
227 | } |
228 | spin_unlock(&si->lock); |
229 | |
230 | /* |
231 | * If seek is expensive, start searching for new cluster from |
232 | * start of partition, to minimize the span of allocated swap. |
233 | * But if seek is cheap, search from our current position, so |
234 | * that swap is allocated from all over the partition: if the |
235 | * Flash Translation Layer only remaps within limited zones, |
236 | * we don't want to wear out the first zone too quickly. |
237 | */ |
238 | if (!(si->flags & SWP_SOLIDSTATE)) |
239 | scan_base = offset = si->lowest_bit; |
240 | last_in_cluster = offset + SWAPFILE_CLUSTER - 1; |
241 | |
242 | /* Locate the first empty (unaligned) cluster */ |
243 | for (; last_in_cluster <= si->highest_bit; offset++) { |
244 | if (si->swap_map[offset]) |
245 | last_in_cluster = offset + SWAPFILE_CLUSTER; |
246 | else if (offset == last_in_cluster) { |
247 | spin_lock(&si->lock); |
248 | offset -= SWAPFILE_CLUSTER - 1; |
249 | si->cluster_next = offset; |
250 | si->cluster_nr = SWAPFILE_CLUSTER - 1; |
251 | found_free_cluster = 1; |
252 | goto checks; |
253 | } |
254 | if (unlikely(--latency_ration < 0)) { |
255 | cond_resched(); |
256 | latency_ration = LATENCY_LIMIT; |
257 | } |
258 | } |
259 | |
260 | offset = si->lowest_bit; |
261 | last_in_cluster = offset + SWAPFILE_CLUSTER - 1; |
262 | |
263 | /* Locate the first empty (unaligned) cluster */ |
264 | for (; last_in_cluster < scan_base; offset++) { |
265 | if (si->swap_map[offset]) |
266 | last_in_cluster = offset + SWAPFILE_CLUSTER; |
267 | else if (offset == last_in_cluster) { |
268 | spin_lock(&si->lock); |
269 | offset -= SWAPFILE_CLUSTER - 1; |
270 | si->cluster_next = offset; |
271 | si->cluster_nr = SWAPFILE_CLUSTER - 1; |
272 | found_free_cluster = 1; |
273 | goto checks; |
274 | } |
275 | if (unlikely(--latency_ration < 0)) { |
276 | cond_resched(); |
277 | latency_ration = LATENCY_LIMIT; |
278 | } |
279 | } |
280 | |
281 | offset = scan_base; |
282 | spin_lock(&si->lock); |
283 | si->cluster_nr = SWAPFILE_CLUSTER - 1; |
284 | si->lowest_alloc = 0; |
285 | } |
286 | |
287 | checks: |
288 | if (!(si->flags & SWP_WRITEOK)) |
289 | goto no_page; |
290 | if (!si->highest_bit) |
291 | goto no_page; |
292 | if (offset > si->highest_bit) |
293 | scan_base = offset = si->lowest_bit; |
294 | |
295 | /* reuse swap entry of cache-only swap if not busy. */ |
296 | if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { |
297 | int swap_was_freed; |
298 | spin_unlock(&si->lock); |
299 | swap_was_freed = __try_to_reclaim_swap(si, offset); |
300 | spin_lock(&si->lock); |
301 | /* entry was freed successfully, try to use this again */ |
302 | if (swap_was_freed) |
303 | goto checks; |
304 | goto scan; /* check next one */ |
305 | } |
306 | |
307 | if (si->swap_map[offset]) |
308 | goto scan; |
309 | |
310 | if (offset == si->lowest_bit) |
311 | si->lowest_bit++; |
312 | if (offset == si->highest_bit) |
313 | si->highest_bit--; |
314 | si->inuse_pages++; |
315 | if (si->inuse_pages == si->pages) { |
316 | si->lowest_bit = si->max; |
317 | si->highest_bit = 0; |
318 | } |
319 | si->swap_map[offset] = usage; |
320 | si->cluster_next = offset + 1; |
321 | si->flags -= SWP_SCANNING; |
322 | |
323 | if (si->lowest_alloc) { |
324 | /* |
325 | * Only set when SWP_DISCARDABLE, and there's a scan |
326 | * for a free cluster in progress or just completed. |
327 | */ |
328 | if (found_free_cluster) { |
329 | /* |
330 | * To optimize wear-levelling, discard the |
331 | * old data of the cluster, taking care not to |
332 | * discard any of its pages that have already |
333 | * been allocated by racing tasks (offset has |
334 | * already stepped over any at the beginning). |
335 | */ |
336 | if (offset < si->highest_alloc && |
337 | si->lowest_alloc <= last_in_cluster) |
338 | last_in_cluster = si->lowest_alloc - 1; |
339 | si->flags |= SWP_DISCARDING; |
340 | spin_unlock(&si->lock); |
341 | |
342 | if (offset < last_in_cluster) |
343 | discard_swap_cluster(si, offset, |
344 | last_in_cluster - offset + 1); |
345 | |
346 | spin_lock(&si->lock); |
347 | si->lowest_alloc = 0; |
348 | si->flags &= ~SWP_DISCARDING; |
349 | |
350 | smp_mb(); /* wake_up_bit advises this */ |
351 | wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); |
352 | |
353 | } else if (si->flags & SWP_DISCARDING) { |
354 | /* |
355 | * Delay using pages allocated by racing tasks |
356 | * until the whole discard has been issued. We |
357 | * could defer that delay until swap_writepage, |
358 | * but it's easier to keep this self-contained. |
359 | */ |
360 | spin_unlock(&si->lock); |
361 | wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), |
362 | wait_for_discard, TASK_UNINTERRUPTIBLE); |
363 | spin_lock(&si->lock); |
364 | } else { |
365 | /* |
366 | * Note pages allocated by racing tasks while |
367 | * scan for a free cluster is in progress, so |
368 | * that its final discard can exclude them. |
369 | */ |
370 | if (offset < si->lowest_alloc) |
371 | si->lowest_alloc = offset; |
372 | if (offset > si->highest_alloc) |
373 | si->highest_alloc = offset; |
374 | } |
375 | } |
376 | return offset; |
377 | |
378 | scan: |
379 | spin_unlock(&si->lock); |
380 | while (++offset <= si->highest_bit) { |
381 | if (!si->swap_map[offset]) { |
382 | spin_lock(&si->lock); |
383 | goto checks; |
384 | } |
385 | if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { |
386 | spin_lock(&si->lock); |
387 | goto checks; |
388 | } |
389 | if (unlikely(--latency_ration < 0)) { |
390 | cond_resched(); |
391 | latency_ration = LATENCY_LIMIT; |
392 | } |
393 | } |
394 | offset = si->lowest_bit; |
395 | while (++offset < scan_base) { |
396 | if (!si->swap_map[offset]) { |
397 | spin_lock(&si->lock); |
398 | goto checks; |
399 | } |
400 | if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { |
401 | spin_lock(&si->lock); |
402 | goto checks; |
403 | } |
404 | if (unlikely(--latency_ration < 0)) { |
405 | cond_resched(); |
406 | latency_ration = LATENCY_LIMIT; |
407 | } |
408 | } |
409 | spin_lock(&si->lock); |
410 | |
411 | no_page: |
412 | si->flags -= SWP_SCANNING; |
413 | return 0; |
414 | } |
415 | |
416 | swp_entry_t get_swap_page(void) |
417 | { |
418 | struct swap_info_struct *si; |
419 | pgoff_t offset; |
420 | int type, next; |
421 | int wrapped = 0; |
422 | int hp_index; |
423 | |
424 | spin_lock(&swap_lock); |
425 | if (atomic_long_read(&nr_swap_pages) <= 0) |
426 | goto noswap; |
427 | atomic_long_dec(&nr_swap_pages); |
428 | |
429 | for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { |
430 | hp_index = atomic_xchg(&highest_priority_index, -1); |
431 | /* |
432 | * highest_priority_index records current highest priority swap |
433 | * type which just frees swap entries. If its priority is |
434 | * higher than that of swap_list.next swap type, we use it. It |
435 | * isn't protected by swap_lock, so it can be an invalid value |
436 | * if the corresponding swap type is swapoff. We double check |
437 | * the flags here. It's even possible the swap type is swapoff |
438 | * and swapon again and its priority is changed. In such rare |
439 | * case, low prority swap type might be used, but eventually |
440 | * high priority swap will be used after several rounds of |
441 | * swap. |
442 | */ |
443 | if (hp_index != -1 && hp_index != type && |
444 | swap_info[type]->prio < swap_info[hp_index]->prio && |
445 | (swap_info[hp_index]->flags & SWP_WRITEOK)) { |
446 | type = hp_index; |
447 | swap_list.next = type; |
448 | } |
449 | |
450 | si = swap_info[type]; |
451 | next = si->next; |
452 | if (next < 0 || |
453 | (!wrapped && si->prio != swap_info[next]->prio)) { |
454 | next = swap_list.head; |
455 | wrapped++; |
456 | } |
457 | |
458 | spin_lock(&si->lock); |
459 | if (!si->highest_bit) { |
460 | spin_unlock(&si->lock); |
461 | continue; |
462 | } |
463 | if (!(si->flags & SWP_WRITEOK)) { |
464 | spin_unlock(&si->lock); |
465 | continue; |
466 | } |
467 | |
468 | swap_list.next = next; |
469 | |
470 | spin_unlock(&swap_lock); |
471 | /* This is called for allocating swap entry for cache */ |
472 | offset = scan_swap_map(si, SWAP_HAS_CACHE); |
473 | spin_unlock(&si->lock); |
474 | if (offset) |
475 | return swp_entry(type, offset); |
476 | spin_lock(&swap_lock); |
477 | next = swap_list.next; |
478 | } |
479 | |
480 | atomic_long_inc(&nr_swap_pages); |
481 | noswap: |
482 | spin_unlock(&swap_lock); |
483 | return (swp_entry_t) {0}; |
484 | } |
485 | |
486 | /* The only caller of this function is now susupend routine */ |
487 | swp_entry_t get_swap_page_of_type(int type) |
488 | { |
489 | struct swap_info_struct *si; |
490 | pgoff_t offset; |
491 | |
492 | si = swap_info[type]; |
493 | spin_lock(&si->lock); |
494 | if (si && (si->flags & SWP_WRITEOK)) { |
495 | atomic_long_dec(&nr_swap_pages); |
496 | /* This is called for allocating swap entry, not cache */ |
497 | offset = scan_swap_map(si, 1); |
498 | if (offset) { |
499 | spin_unlock(&si->lock); |
500 | return swp_entry(type, offset); |
501 | } |
502 | atomic_long_inc(&nr_swap_pages); |
503 | } |
504 | spin_unlock(&si->lock); |
505 | return (swp_entry_t) {0}; |
506 | } |
507 | |
508 | static struct swap_info_struct *swap_info_get(swp_entry_t entry) |
509 | { |
510 | struct swap_info_struct *p; |
511 | unsigned long offset, type; |
512 | |
513 | if (!entry.val) |
514 | goto out; |
515 | type = swp_type(entry); |
516 | if (type >= nr_swapfiles) |
517 | goto bad_nofile; |
518 | p = swap_info[type]; |
519 | if (!(p->flags & SWP_USED)) |
520 | goto bad_device; |
521 | offset = swp_offset(entry); |
522 | if (offset >= p->max) |
523 | goto bad_offset; |
524 | if (!p->swap_map[offset]) |
525 | goto bad_free; |
526 | spin_lock(&p->lock); |
527 | return p; |
528 | |
529 | bad_free: |
530 | printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); |
531 | goto out; |
532 | bad_offset: |
533 | printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); |
534 | goto out; |
535 | bad_device: |
536 | printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); |
537 | goto out; |
538 | bad_nofile: |
539 | printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); |
540 | out: |
541 | return NULL; |
542 | } |
543 | |
544 | /* |
545 | * This swap type frees swap entry, check if it is the highest priority swap |
546 | * type which just frees swap entry. get_swap_page() uses |
547 | * highest_priority_index to search highest priority swap type. The |
548 | * swap_info_struct.lock can't protect us if there are multiple swap types |
549 | * active, so we use atomic_cmpxchg. |
550 | */ |
551 | static void set_highest_priority_index(int type) |
552 | { |
553 | int old_hp_index, new_hp_index; |
554 | |
555 | do { |
556 | old_hp_index = atomic_read(&highest_priority_index); |
557 | if (old_hp_index != -1 && |
558 | swap_info[old_hp_index]->prio >= swap_info[type]->prio) |
559 | break; |
560 | new_hp_index = type; |
561 | } while (atomic_cmpxchg(&highest_priority_index, |
562 | old_hp_index, new_hp_index) != old_hp_index); |
563 | } |
564 | |
565 | static unsigned char swap_entry_free(struct swap_info_struct *p, |
566 | swp_entry_t entry, unsigned char usage) |
567 | { |
568 | unsigned long offset = swp_offset(entry); |
569 | unsigned char count; |
570 | unsigned char has_cache; |
571 | |
572 | count = p->swap_map[offset]; |
573 | has_cache = count & SWAP_HAS_CACHE; |
574 | count &= ~SWAP_HAS_CACHE; |
575 | |
576 | if (usage == SWAP_HAS_CACHE) { |
577 | VM_BUG_ON(!has_cache); |
578 | has_cache = 0; |
579 | } else if (count == SWAP_MAP_SHMEM) { |
580 | /* |
581 | * Or we could insist on shmem.c using a special |
582 | * swap_shmem_free() and free_shmem_swap_and_cache()... |
583 | */ |
584 | count = 0; |
585 | } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { |
586 | if (count == COUNT_CONTINUED) { |
587 | if (swap_count_continued(p, offset, count)) |
588 | count = SWAP_MAP_MAX | COUNT_CONTINUED; |
589 | else |
590 | count = SWAP_MAP_MAX; |
591 | } else |
592 | count--; |
593 | } |
594 | |
595 | if (!count) |
596 | mem_cgroup_uncharge_swap(entry); |
597 | |
598 | usage = count | has_cache; |
599 | p->swap_map[offset] = usage; |
600 | |
601 | /* free if no reference */ |
602 | if (!usage) { |
603 | if (offset < p->lowest_bit) |
604 | p->lowest_bit = offset; |
605 | if (offset > p->highest_bit) |
606 | p->highest_bit = offset; |
607 | set_highest_priority_index(p->type); |
608 | atomic_long_inc(&nr_swap_pages); |
609 | p->inuse_pages--; |
610 | frontswap_invalidate_page(p->type, offset); |
611 | if (p->flags & SWP_BLKDEV) { |
612 | struct gendisk *disk = p->bdev->bd_disk; |
613 | if (disk->fops->swap_slot_free_notify) |
614 | disk->fops->swap_slot_free_notify(p->bdev, |
615 | offset); |
616 | } |
617 | } |
618 | |
619 | return usage; |
620 | } |
621 | |
622 | /* |
623 | * Caller has made sure that the swapdevice corresponding to entry |
624 | * is still around or has not been recycled. |
625 | */ |
626 | void swap_free(swp_entry_t entry) |
627 | { |
628 | struct swap_info_struct *p; |
629 | |
630 | p = swap_info_get(entry); |
631 | if (p) { |
632 | swap_entry_free(p, entry, 1); |
633 | spin_unlock(&p->lock); |
634 | } |
635 | } |
636 | |
637 | /* |
638 | * Called after dropping swapcache to decrease refcnt to swap entries. |
639 | */ |
640 | void swapcache_free(swp_entry_t entry, struct page *page) |
641 | { |
642 | struct swap_info_struct *p; |
643 | unsigned char count; |
644 | |
645 | p = swap_info_get(entry); |
646 | if (p) { |
647 | count = swap_entry_free(p, entry, SWAP_HAS_CACHE); |
648 | if (page) |
649 | mem_cgroup_uncharge_swapcache(page, entry, count != 0); |
650 | spin_unlock(&p->lock); |
651 | } |
652 | } |
653 | |
654 | /* |
655 | * How many references to page are currently swapped out? |
656 | * This does not give an exact answer when swap count is continued, |
657 | * but does include the high COUNT_CONTINUED flag to allow for that. |
658 | */ |
659 | int page_swapcount(struct page *page) |
660 | { |
661 | int count = 0; |
662 | struct swap_info_struct *p; |
663 | swp_entry_t entry; |
664 | |
665 | entry.val = page_private(page); |
666 | p = swap_info_get(entry); |
667 | if (p) { |
668 | count = swap_count(p->swap_map[swp_offset(entry)]); |
669 | spin_unlock(&p->lock); |
670 | } |
671 | return count; |
672 | } |
673 | |
674 | /* |
675 | * We can write to an anon page without COW if there are no other references |
676 | * to it. And as a side-effect, free up its swap: because the old content |
677 | * on disk will never be read, and seeking back there to write new content |
678 | * later would only waste time away from clustering. |
679 | */ |
680 | int reuse_swap_page(struct page *page) |
681 | { |
682 | int count; |
683 | |
684 | VM_BUG_ON(!PageLocked(page)); |
685 | if (unlikely(PageKsm(page))) |
686 | return 0; |
687 | count = page_mapcount(page); |
688 | if (count <= 1 && PageSwapCache(page)) { |
689 | count += page_swapcount(page); |
690 | if (count == 1 && !PageWriteback(page)) { |
691 | delete_from_swap_cache(page); |
692 | SetPageDirty(page); |
693 | } |
694 | } |
695 | return count <= 1; |
696 | } |
697 | |
698 | /* |
699 | * If swap is getting full, or if there are no more mappings of this page, |
700 | * then try_to_free_swap is called to free its swap space. |
701 | */ |
702 | int try_to_free_swap(struct page *page) |
703 | { |
704 | VM_BUG_ON(!PageLocked(page)); |
705 | |
706 | if (!PageSwapCache(page)) |
707 | return 0; |
708 | if (PageWriteback(page)) |
709 | return 0; |
710 | if (page_swapcount(page)) |
711 | return 0; |
712 | |
713 | /* |
714 | * Once hibernation has begun to create its image of memory, |
715 | * there's a danger that one of the calls to try_to_free_swap() |
716 | * - most probably a call from __try_to_reclaim_swap() while |
717 | * hibernation is allocating its own swap pages for the image, |
718 | * but conceivably even a call from memory reclaim - will free |
719 | * the swap from a page which has already been recorded in the |
720 | * image as a clean swapcache page, and then reuse its swap for |
721 | * another page of the image. On waking from hibernation, the |
722 | * original page might be freed under memory pressure, then |
723 | * later read back in from swap, now with the wrong data. |
724 | * |
725 | * Hibration suspends storage while it is writing the image |
726 | * to disk so check that here. |
727 | */ |
728 | if (pm_suspended_storage()) |
729 | return 0; |
730 | |
731 | delete_from_swap_cache(page); |
732 | SetPageDirty(page); |
733 | return 1; |
734 | } |
735 | |
736 | /* |
737 | * Free the swap entry like above, but also try to |
738 | * free the page cache entry if it is the last user. |
739 | */ |
740 | int free_swap_and_cache(swp_entry_t entry) |
741 | { |
742 | struct swap_info_struct *p; |
743 | struct page *page = NULL; |
744 | |
745 | if (non_swap_entry(entry)) |
746 | return 1; |
747 | |
748 | p = swap_info_get(entry); |
749 | if (p) { |
750 | if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { |
751 | page = find_get_page(swap_address_space(entry), |
752 | entry.val); |
753 | if (page && !trylock_page(page)) { |
754 | page_cache_release(page); |
755 | page = NULL; |
756 | } |
757 | } |
758 | spin_unlock(&p->lock); |
759 | } |
760 | if (page) { |
761 | /* |
762 | * Not mapped elsewhere, or swap space full? Free it! |
763 | * Also recheck PageSwapCache now page is locked (above). |
764 | */ |
765 | if (PageSwapCache(page) && !PageWriteback(page) && |
766 | (!page_mapped(page) || vm_swap_full())) { |
767 | delete_from_swap_cache(page); |
768 | SetPageDirty(page); |
769 | } |
770 | unlock_page(page); |
771 | page_cache_release(page); |
772 | } |
773 | return p != NULL; |
774 | } |
775 | |
776 | #ifdef CONFIG_HIBERNATION |
777 | /* |
778 | * Find the swap type that corresponds to given device (if any). |
779 | * |
780 | * @offset - number of the PAGE_SIZE-sized block of the device, starting |
781 | * from 0, in which the swap header is expected to be located. |
782 | * |
783 | * This is needed for the suspend to disk (aka swsusp). |
784 | */ |
785 | int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) |
786 | { |
787 | struct block_device *bdev = NULL; |
788 | int type; |
789 | |
790 | if (device) |
791 | bdev = bdget(device); |
792 | |
793 | spin_lock(&swap_lock); |
794 | for (type = 0; type < nr_swapfiles; type++) { |
795 | struct swap_info_struct *sis = swap_info[type]; |
796 | |
797 | if (!(sis->flags & SWP_WRITEOK)) |
798 | continue; |
799 | |
800 | if (!bdev) { |
801 | if (bdev_p) |
802 | *bdev_p = bdgrab(sis->bdev); |
803 | |
804 | spin_unlock(&swap_lock); |
805 | return type; |
806 | } |
807 | if (bdev == sis->bdev) { |
808 | struct swap_extent *se = &sis->first_swap_extent; |
809 | |
810 | if (se->start_block == offset) { |
811 | if (bdev_p) |
812 | *bdev_p = bdgrab(sis->bdev); |
813 | |
814 | spin_unlock(&swap_lock); |
815 | bdput(bdev); |
816 | return type; |
817 | } |
818 | } |
819 | } |
820 | spin_unlock(&swap_lock); |
821 | if (bdev) |
822 | bdput(bdev); |
823 | |
824 | return -ENODEV; |
825 | } |
826 | |
827 | /* |
828 | * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev |
829 | * corresponding to given index in swap_info (swap type). |
830 | */ |
831 | sector_t swapdev_block(int type, pgoff_t offset) |
832 | { |
833 | struct block_device *bdev; |
834 | |
835 | if ((unsigned int)type >= nr_swapfiles) |
836 | return 0; |
837 | if (!(swap_info[type]->flags & SWP_WRITEOK)) |
838 | return 0; |
839 | return map_swap_entry(swp_entry(type, offset), &bdev); |
840 | } |
841 | |
842 | /* |
843 | * Return either the total number of swap pages of given type, or the number |
844 | * of free pages of that type (depending on @free) |
845 | * |
846 | * This is needed for software suspend |
847 | */ |
848 | unsigned int count_swap_pages(int type, int free) |
849 | { |
850 | unsigned int n = 0; |
851 | |
852 | spin_lock(&swap_lock); |
853 | if ((unsigned int)type < nr_swapfiles) { |
854 | struct swap_info_struct *sis = swap_info[type]; |
855 | |
856 | spin_lock(&sis->lock); |
857 | if (sis->flags & SWP_WRITEOK) { |
858 | n = sis->pages; |
859 | if (free) |
860 | n -= sis->inuse_pages; |
861 | } |
862 | spin_unlock(&sis->lock); |
863 | } |
864 | spin_unlock(&swap_lock); |
865 | return n; |
866 | } |
867 | #endif /* CONFIG_HIBERNATION */ |
868 | |
869 | /* |
870 | * No need to decide whether this PTE shares the swap entry with others, |
871 | * just let do_wp_page work it out if a write is requested later - to |
872 | * force COW, vm_page_prot omits write permission from any private vma. |
873 | */ |
874 | static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, |
875 | unsigned long addr, swp_entry_t entry, struct page *page) |
876 | { |
877 | struct page *swapcache; |
878 | struct mem_cgroup *memcg; |
879 | spinlock_t *ptl; |
880 | pte_t *pte; |
881 | int ret = 1; |
882 | |
883 | swapcache = page; |
884 | page = ksm_might_need_to_copy(page, vma, addr); |
885 | if (unlikely(!page)) |
886 | return -ENOMEM; |
887 | |
888 | if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, |
889 | GFP_KERNEL, &memcg)) { |
890 | ret = -ENOMEM; |
891 | goto out_nolock; |
892 | } |
893 | |
894 | pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); |
895 | if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { |
896 | mem_cgroup_cancel_charge_swapin(memcg); |
897 | ret = 0; |
898 | goto out; |
899 | } |
900 | |
901 | dec_mm_counter(vma->vm_mm, MM_SWAPENTS); |
902 | inc_mm_counter(vma->vm_mm, MM_ANONPAGES); |
903 | get_page(page); |
904 | set_pte_at(vma->vm_mm, addr, pte, |
905 | pte_mkold(mk_pte(page, vma->vm_page_prot))); |
906 | if (page == swapcache) |
907 | page_add_anon_rmap(page, vma, addr); |
908 | else /* ksm created a completely new copy */ |
909 | page_add_new_anon_rmap(page, vma, addr); |
910 | mem_cgroup_commit_charge_swapin(page, memcg); |
911 | swap_free(entry); |
912 | /* |
913 | * Move the page to the active list so it is not |
914 | * immediately swapped out again after swapon. |
915 | */ |
916 | activate_page(page); |
917 | out: |
918 | pte_unmap_unlock(pte, ptl); |
919 | out_nolock: |
920 | if (page != swapcache) { |
921 | unlock_page(page); |
922 | put_page(page); |
923 | } |
924 | return ret; |
925 | } |
926 | |
927 | static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, |
928 | unsigned long addr, unsigned long end, |
929 | swp_entry_t entry, struct page *page) |
930 | { |
931 | pte_t swp_pte = swp_entry_to_pte(entry); |
932 | pte_t *pte; |
933 | int ret = 0; |
934 | |
935 | /* |
936 | * We don't actually need pte lock while scanning for swp_pte: since |
937 | * we hold page lock and mmap_sem, swp_pte cannot be inserted into the |
938 | * page table while we're scanning; though it could get zapped, and on |
939 | * some architectures (e.g. x86_32 with PAE) we might catch a glimpse |
940 | * of unmatched parts which look like swp_pte, so unuse_pte must |
941 | * recheck under pte lock. Scanning without pte lock lets it be |
942 | * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. |
943 | */ |
944 | pte = pte_offset_map(pmd, addr); |
945 | do { |
946 | /* |
947 | * swapoff spends a _lot_ of time in this loop! |
948 | * Test inline before going to call unuse_pte. |
949 | */ |
950 | if (unlikely(pte_same(*pte, swp_pte))) { |
951 | pte_unmap(pte); |
952 | ret = unuse_pte(vma, pmd, addr, entry, page); |
953 | if (ret) |
954 | goto out; |
955 | pte = pte_offset_map(pmd, addr); |
956 | } |
957 | } while (pte++, addr += PAGE_SIZE, addr != end); |
958 | pte_unmap(pte - 1); |
959 | out: |
960 | return ret; |
961 | } |
962 | |
963 | static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, |
964 | unsigned long addr, unsigned long end, |
965 | swp_entry_t entry, struct page *page) |
966 | { |
967 | pmd_t *pmd; |
968 | unsigned long next; |
969 | int ret; |
970 | |
971 | pmd = pmd_offset(pud, addr); |
972 | do { |
973 | next = pmd_addr_end(addr, end); |
974 | if (pmd_none_or_trans_huge_or_clear_bad(pmd)) |
975 | continue; |
976 | ret = unuse_pte_range(vma, pmd, addr, next, entry, page); |
977 | if (ret) |
978 | return ret; |
979 | } while (pmd++, addr = next, addr != end); |
980 | return 0; |
981 | } |
982 | |
983 | static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, |
984 | unsigned long addr, unsigned long end, |
985 | swp_entry_t entry, struct page *page) |
986 | { |
987 | pud_t *pud; |
988 | unsigned long next; |
989 | int ret; |
990 | |
991 | pud = pud_offset(pgd, addr); |
992 | do { |
993 | next = pud_addr_end(addr, end); |
994 | if (pud_none_or_clear_bad(pud)) |
995 | continue; |
996 | ret = unuse_pmd_range(vma, pud, addr, next, entry, page); |
997 | if (ret) |
998 | return ret; |
999 | } while (pud++, addr = next, addr != end); |
1000 | return 0; |
1001 | } |
1002 | |
1003 | static int unuse_vma(struct vm_area_struct *vma, |
1004 | swp_entry_t entry, struct page *page) |
1005 | { |
1006 | pgd_t *pgd; |
1007 | unsigned long addr, end, next; |
1008 | int ret; |
1009 | |
1010 | if (page_anon_vma(page)) { |
1011 | addr = page_address_in_vma(page, vma); |
1012 | if (addr == -EFAULT) |
1013 | return 0; |
1014 | else |
1015 | end = addr + PAGE_SIZE; |
1016 | } else { |
1017 | addr = vma->vm_start; |
1018 | end = vma->vm_end; |
1019 | } |
1020 | |
1021 | pgd = pgd_offset(vma->vm_mm, addr); |
1022 | do { |
1023 | next = pgd_addr_end(addr, end); |
1024 | if (pgd_none_or_clear_bad(pgd)) |
1025 | continue; |
1026 | ret = unuse_pud_range(vma, pgd, addr, next, entry, page); |
1027 | if (ret) |
1028 | return ret; |
1029 | } while (pgd++, addr = next, addr != end); |
1030 | return 0; |
1031 | } |
1032 | |
1033 | static int unuse_mm(struct mm_struct *mm, |
1034 | swp_entry_t entry, struct page *page) |
1035 | { |
1036 | struct vm_area_struct *vma; |
1037 | int ret = 0; |
1038 | |
1039 | if (!down_read_trylock(&mm->mmap_sem)) { |
1040 | /* |
1041 | * Activate page so shrink_inactive_list is unlikely to unmap |
1042 | * its ptes while lock is dropped, so swapoff can make progress. |
1043 | */ |
1044 | activate_page(page); |
1045 | unlock_page(page); |
1046 | down_read(&mm->mmap_sem); |
1047 | lock_page(page); |
1048 | } |
1049 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
1050 | if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) |
1051 | break; |
1052 | } |
1053 | up_read(&mm->mmap_sem); |
1054 | return (ret < 0)? ret: 0; |
1055 | } |
1056 | |
1057 | /* |
1058 | * Scan swap_map (or frontswap_map if frontswap parameter is true) |
1059 | * from current position to next entry still in use. |
1060 | * Recycle to start on reaching the end, returning 0 when empty. |
1061 | */ |
1062 | static unsigned int find_next_to_unuse(struct swap_info_struct *si, |
1063 | unsigned int prev, bool frontswap) |
1064 | { |
1065 | unsigned int max = si->max; |
1066 | unsigned int i = prev; |
1067 | unsigned char count; |
1068 | |
1069 | /* |
1070 | * No need for swap_lock here: we're just looking |
1071 | * for whether an entry is in use, not modifying it; false |
1072 | * hits are okay, and sys_swapoff() has already prevented new |
1073 | * allocations from this area (while holding swap_lock). |
1074 | */ |
1075 | for (;;) { |
1076 | if (++i >= max) { |
1077 | if (!prev) { |
1078 | i = 0; |
1079 | break; |
1080 | } |
1081 | /* |
1082 | * No entries in use at top of swap_map, |
1083 | * loop back to start and recheck there. |
1084 | */ |
1085 | max = prev + 1; |
1086 | prev = 0; |
1087 | i = 1; |
1088 | } |
1089 | if (frontswap) { |
1090 | if (frontswap_test(si, i)) |
1091 | break; |
1092 | else |
1093 | continue; |
1094 | } |
1095 | count = si->swap_map[i]; |
1096 | if (count && swap_count(count) != SWAP_MAP_BAD) |
1097 | break; |
1098 | } |
1099 | return i; |
1100 | } |
1101 | |
1102 | /* |
1103 | * We completely avoid races by reading each swap page in advance, |
1104 | * and then search for the process using it. All the necessary |
1105 | * page table adjustments can then be made atomically. |
1106 | * |
1107 | * if the boolean frontswap is true, only unuse pages_to_unuse pages; |
1108 | * pages_to_unuse==0 means all pages; ignored if frontswap is false |
1109 | */ |
1110 | int try_to_unuse(unsigned int type, bool frontswap, |
1111 | unsigned long pages_to_unuse) |
1112 | { |
1113 | struct swap_info_struct *si = swap_info[type]; |
1114 | struct mm_struct *start_mm; |
1115 | unsigned char *swap_map; |
1116 | unsigned char swcount; |
1117 | struct page *page; |
1118 | swp_entry_t entry; |
1119 | unsigned int i = 0; |
1120 | int retval = 0; |
1121 | |
1122 | /* |
1123 | * When searching mms for an entry, a good strategy is to |
1124 | * start at the first mm we freed the previous entry from |
1125 | * (though actually we don't notice whether we or coincidence |
1126 | * freed the entry). Initialize this start_mm with a hold. |
1127 | * |
1128 | * A simpler strategy would be to start at the last mm we |
1129 | * freed the previous entry from; but that would take less |
1130 | * advantage of mmlist ordering, which clusters forked mms |
1131 | * together, child after parent. If we race with dup_mmap(), we |
1132 | * prefer to resolve parent before child, lest we miss entries |
1133 | * duplicated after we scanned child: using last mm would invert |
1134 | * that. |
1135 | */ |
1136 | start_mm = &init_mm; |
1137 | atomic_inc(&init_mm.mm_users); |
1138 | |
1139 | /* |
1140 | * Keep on scanning until all entries have gone. Usually, |
1141 | * one pass through swap_map is enough, but not necessarily: |
1142 | * there are races when an instance of an entry might be missed. |
1143 | */ |
1144 | while ((i = find_next_to_unuse(si, i, frontswap)) != 0) { |
1145 | if (signal_pending(current)) { |
1146 | retval = -EINTR; |
1147 | break; |
1148 | } |
1149 | |
1150 | /* |
1151 | * Get a page for the entry, using the existing swap |
1152 | * cache page if there is one. Otherwise, get a clean |
1153 | * page and read the swap into it. |
1154 | */ |
1155 | swap_map = &si->swap_map[i]; |
1156 | entry = swp_entry(type, i); |
1157 | page = read_swap_cache_async(entry, |
1158 | GFP_HIGHUSER_MOVABLE, NULL, 0); |
1159 | if (!page) { |
1160 | /* |
1161 | * Either swap_duplicate() failed because entry |
1162 | * has been freed independently, and will not be |
1163 | * reused since sys_swapoff() already disabled |
1164 | * allocation from here, or alloc_page() failed. |
1165 | */ |
1166 | if (!*swap_map) |
1167 | continue; |
1168 | retval = -ENOMEM; |
1169 | break; |
1170 | } |
1171 | |
1172 | /* |
1173 | * Don't hold on to start_mm if it looks like exiting. |
1174 | */ |
1175 | if (atomic_read(&start_mm->mm_users) == 1) { |
1176 | mmput(start_mm); |
1177 | start_mm = &init_mm; |
1178 | atomic_inc(&init_mm.mm_users); |
1179 | } |
1180 | |
1181 | /* |
1182 | * Wait for and lock page. When do_swap_page races with |
1183 | * try_to_unuse, do_swap_page can handle the fault much |
1184 | * faster than try_to_unuse can locate the entry. This |
1185 | * apparently redundant "wait_on_page_locked" lets try_to_unuse |
1186 | * defer to do_swap_page in such a case - in some tests, |
1187 | * do_swap_page and try_to_unuse repeatedly compete. |
1188 | */ |
1189 | wait_on_page_locked(page); |
1190 | wait_on_page_writeback(page); |
1191 | lock_page(page); |
1192 | wait_on_page_writeback(page); |
1193 | |
1194 | /* |
1195 | * Remove all references to entry. |
1196 | */ |
1197 | swcount = *swap_map; |
1198 | if (swap_count(swcount) == SWAP_MAP_SHMEM) { |
1199 | retval = shmem_unuse(entry, page); |
1200 | /* page has already been unlocked and released */ |
1201 | if (retval < 0) |
1202 | break; |
1203 | continue; |
1204 | } |
1205 | if (swap_count(swcount) && start_mm != &init_mm) |
1206 | retval = unuse_mm(start_mm, entry, page); |
1207 | |
1208 | if (swap_count(*swap_map)) { |
1209 | int set_start_mm = (*swap_map >= swcount); |
1210 | struct list_head *p = &start_mm->mmlist; |
1211 | struct mm_struct *new_start_mm = start_mm; |
1212 | struct mm_struct *prev_mm = start_mm; |
1213 | struct mm_struct *mm; |
1214 | |
1215 | atomic_inc(&new_start_mm->mm_users); |
1216 | atomic_inc(&prev_mm->mm_users); |
1217 | spin_lock(&mmlist_lock); |
1218 | while (swap_count(*swap_map) && !retval && |
1219 | (p = p->next) != &start_mm->mmlist) { |
1220 | mm = list_entry(p, struct mm_struct, mmlist); |
1221 | if (!atomic_inc_not_zero(&mm->mm_users)) |
1222 | continue; |
1223 | spin_unlock(&mmlist_lock); |
1224 | mmput(prev_mm); |
1225 | prev_mm = mm; |
1226 | |
1227 | cond_resched(); |
1228 | |
1229 | swcount = *swap_map; |
1230 | if (!swap_count(swcount)) /* any usage ? */ |
1231 | ; |
1232 | else if (mm == &init_mm) |
1233 | set_start_mm = 1; |
1234 | else |
1235 | retval = unuse_mm(mm, entry, page); |
1236 | |
1237 | if (set_start_mm && *swap_map < swcount) { |
1238 | mmput(new_start_mm); |
1239 | atomic_inc(&mm->mm_users); |
1240 | new_start_mm = mm; |
1241 | set_start_mm = 0; |
1242 | } |
1243 | spin_lock(&mmlist_lock); |
1244 | } |
1245 | spin_unlock(&mmlist_lock); |
1246 | mmput(prev_mm); |
1247 | mmput(start_mm); |
1248 | start_mm = new_start_mm; |
1249 | } |
1250 | if (retval) { |
1251 | unlock_page(page); |
1252 | page_cache_release(page); |
1253 | break; |
1254 | } |
1255 | |
1256 | /* |
1257 | * If a reference remains (rare), we would like to leave |
1258 | * the page in the swap cache; but try_to_unmap could |
1259 | * then re-duplicate the entry once we drop page lock, |
1260 | * so we might loop indefinitely; also, that page could |
1261 | * not be swapped out to other storage meanwhile. So: |
1262 | * delete from cache even if there's another reference, |
1263 | * after ensuring that the data has been saved to disk - |
1264 | * since if the reference remains (rarer), it will be |
1265 | * read from disk into another page. Splitting into two |
1266 | * pages would be incorrect if swap supported "shared |
1267 | * private" pages, but they are handled by tmpfs files. |
1268 | * |
1269 | * Given how unuse_vma() targets one particular offset |
1270 | * in an anon_vma, once the anon_vma has been determined, |
1271 | * this splitting happens to be just what is needed to |
1272 | * handle where KSM pages have been swapped out: re-reading |
1273 | * is unnecessarily slow, but we can fix that later on. |
1274 | */ |
1275 | if (swap_count(*swap_map) && |
1276 | PageDirty(page) && PageSwapCache(page)) { |
1277 | struct writeback_control wbc = { |
1278 | .sync_mode = WB_SYNC_NONE, |
1279 | }; |
1280 | |
1281 | swap_writepage(page, &wbc); |
1282 | lock_page(page); |
1283 | wait_on_page_writeback(page); |
1284 | } |
1285 | |
1286 | /* |
1287 | * It is conceivable that a racing task removed this page from |
1288 | * swap cache just before we acquired the page lock at the top, |
1289 | * or while we dropped it in unuse_mm(). The page might even |
1290 | * be back in swap cache on another swap area: that we must not |
1291 | * delete, since it may not have been written out to swap yet. |
1292 | */ |
1293 | if (PageSwapCache(page) && |
1294 | likely(page_private(page) == entry.val)) |
1295 | delete_from_swap_cache(page); |
1296 | |
1297 | /* |
1298 | * So we could skip searching mms once swap count went |
1299 | * to 1, we did not mark any present ptes as dirty: must |
1300 | * mark page dirty so shrink_page_list will preserve it. |
1301 | */ |
1302 | SetPageDirty(page); |
1303 | unlock_page(page); |
1304 | page_cache_release(page); |
1305 | |
1306 | /* |
1307 | * Make sure that we aren't completely killing |
1308 | * interactive performance. |
1309 | */ |
1310 | cond_resched(); |
1311 | if (frontswap && pages_to_unuse > 0) { |
1312 | if (!--pages_to_unuse) |
1313 | break; |
1314 | } |
1315 | } |
1316 | |
1317 | mmput(start_mm); |
1318 | return retval; |
1319 | } |
1320 | |
1321 | /* |
1322 | * After a successful try_to_unuse, if no swap is now in use, we know |
1323 | * we can empty the mmlist. swap_lock must be held on entry and exit. |
1324 | * Note that mmlist_lock nests inside swap_lock, and an mm must be |
1325 | * added to the mmlist just after page_duplicate - before would be racy. |
1326 | */ |
1327 | static void drain_mmlist(void) |
1328 | { |
1329 | struct list_head *p, *next; |
1330 | unsigned int type; |
1331 | |
1332 | for (type = 0; type < nr_swapfiles; type++) |
1333 | if (swap_info[type]->inuse_pages) |
1334 | return; |
1335 | spin_lock(&mmlist_lock); |
1336 | list_for_each_safe(p, next, &init_mm.mmlist) |
1337 | list_del_init(p); |
1338 | spin_unlock(&mmlist_lock); |
1339 | } |
1340 | |
1341 | /* |
1342 | * Use this swapdev's extent info to locate the (PAGE_SIZE) block which |
1343 | * corresponds to page offset for the specified swap entry. |
1344 | * Note that the type of this function is sector_t, but it returns page offset |
1345 | * into the bdev, not sector offset. |
1346 | */ |
1347 | static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev) |
1348 | { |
1349 | struct swap_info_struct *sis; |
1350 | struct swap_extent *start_se; |
1351 | struct swap_extent *se; |
1352 | pgoff_t offset; |
1353 | |
1354 | sis = swap_info[swp_type(entry)]; |
1355 | *bdev = sis->bdev; |
1356 | |
1357 | offset = swp_offset(entry); |
1358 | start_se = sis->curr_swap_extent; |
1359 | se = start_se; |
1360 | |
1361 | for ( ; ; ) { |
1362 | struct list_head *lh; |
1363 | |
1364 | if (se->start_page <= offset && |
1365 | offset < (se->start_page + se->nr_pages)) { |
1366 | return se->start_block + (offset - se->start_page); |
1367 | } |
1368 | lh = se->list.next; |
1369 | se = list_entry(lh, struct swap_extent, list); |
1370 | sis->curr_swap_extent = se; |
1371 | BUG_ON(se == start_se); /* It *must* be present */ |
1372 | } |
1373 | } |
1374 | |
1375 | /* |
1376 | * Returns the page offset into bdev for the specified page's swap entry. |
1377 | */ |
1378 | sector_t map_swap_page(struct page *page, struct block_device **bdev) |
1379 | { |
1380 | swp_entry_t entry; |
1381 | entry.val = page_private(page); |
1382 | return map_swap_entry(entry, bdev); |
1383 | } |
1384 | |
1385 | /* |
1386 | * Free all of a swapdev's extent information |
1387 | */ |
1388 | static void destroy_swap_extents(struct swap_info_struct *sis) |
1389 | { |
1390 | while (!list_empty(&sis->first_swap_extent.list)) { |
1391 | struct swap_extent *se; |
1392 | |
1393 | se = list_entry(sis->first_swap_extent.list.next, |
1394 | struct swap_extent, list); |
1395 | list_del(&se->list); |
1396 | kfree(se); |
1397 | } |
1398 | |
1399 | if (sis->flags & SWP_FILE) { |
1400 | struct file *swap_file = sis->swap_file; |
1401 | struct address_space *mapping = swap_file->f_mapping; |
1402 | |
1403 | sis->flags &= ~SWP_FILE; |
1404 | mapping->a_ops->swap_deactivate(swap_file); |
1405 | } |
1406 | } |
1407 | |
1408 | /* |
1409 | * Add a block range (and the corresponding page range) into this swapdev's |
1410 | * extent list. The extent list is kept sorted in page order. |
1411 | * |
1412 | * This function rather assumes that it is called in ascending page order. |
1413 | */ |
1414 | int |
1415 | add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, |
1416 | unsigned long nr_pages, sector_t start_block) |
1417 | { |
1418 | struct swap_extent *se; |
1419 | struct swap_extent *new_se; |
1420 | struct list_head *lh; |
1421 | |
1422 | if (start_page == 0) { |
1423 | se = &sis->first_swap_extent; |
1424 | sis->curr_swap_extent = se; |
1425 | se->start_page = 0; |
1426 | se->nr_pages = nr_pages; |
1427 | se->start_block = start_block; |
1428 | return 1; |
1429 | } else { |
1430 | lh = sis->first_swap_extent.list.prev; /* Highest extent */ |
1431 | se = list_entry(lh, struct swap_extent, list); |
1432 | BUG_ON(se->start_page + se->nr_pages != start_page); |
1433 | if (se->start_block + se->nr_pages == start_block) { |
1434 | /* Merge it */ |
1435 | se->nr_pages += nr_pages; |
1436 | return 0; |
1437 | } |
1438 | } |
1439 | |
1440 | /* |
1441 | * No merge. Insert a new extent, preserving ordering. |
1442 | */ |
1443 | new_se = kmalloc(sizeof(*se), GFP_KERNEL); |
1444 | if (new_se == NULL) |
1445 | return -ENOMEM; |
1446 | new_se->start_page = start_page; |
1447 | new_se->nr_pages = nr_pages; |
1448 | new_se->start_block = start_block; |
1449 | |
1450 | list_add_tail(&new_se->list, &sis->first_swap_extent.list); |
1451 | return 1; |
1452 | } |
1453 | |
1454 | /* |
1455 | * A `swap extent' is a simple thing which maps a contiguous range of pages |
1456 | * onto a contiguous range of disk blocks. An ordered list of swap extents |
1457 | * is built at swapon time and is then used at swap_writepage/swap_readpage |
1458 | * time for locating where on disk a page belongs. |
1459 | * |
1460 | * If the swapfile is an S_ISBLK block device, a single extent is installed. |
1461 | * This is done so that the main operating code can treat S_ISBLK and S_ISREG |
1462 | * swap files identically. |
1463 | * |
1464 | * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap |
1465 | * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK |
1466 | * swapfiles are handled *identically* after swapon time. |
1467 | * |
1468 | * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks |
1469 | * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If |
1470 | * some stray blocks are found which do not fall within the PAGE_SIZE alignment |
1471 | * requirements, they are simply tossed out - we will never use those blocks |
1472 | * for swapping. |
1473 | * |
1474 | * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This |
1475 | * prevents root from shooting her foot off by ftruncating an in-use swapfile, |
1476 | * which will scribble on the fs. |
1477 | * |
1478 | * The amount of disk space which a single swap extent represents varies. |
1479 | * Typically it is in the 1-4 megabyte range. So we can have hundreds of |
1480 | * extents in the list. To avoid much list walking, we cache the previous |
1481 | * search location in `curr_swap_extent', and start new searches from there. |
1482 | * This is extremely effective. The average number of iterations in |
1483 | * map_swap_page() has been measured at about 0.3 per page. - akpm. |
1484 | */ |
1485 | static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) |
1486 | { |
1487 | struct file *swap_file = sis->swap_file; |
1488 | struct address_space *mapping = swap_file->f_mapping; |
1489 | struct inode *inode = mapping->host; |
1490 | int ret; |
1491 | |
1492 | if (S_ISBLK(inode->i_mode)) { |
1493 | ret = add_swap_extent(sis, 0, sis->max, 0); |
1494 | *span = sis->pages; |
1495 | return ret; |
1496 | } |
1497 | |
1498 | if (mapping->a_ops->swap_activate) { |
1499 | ret = mapping->a_ops->swap_activate(sis, swap_file, span); |
1500 | if (!ret) { |
1501 | sis->flags |= SWP_FILE; |
1502 | ret = add_swap_extent(sis, 0, sis->max, 0); |
1503 | *span = sis->pages; |
1504 | } |
1505 | return ret; |
1506 | } |
1507 | |
1508 | return generic_swapfile_activate(sis, swap_file, span); |
1509 | } |
1510 | |
1511 | static void _enable_swap_info(struct swap_info_struct *p, int prio, |
1512 | unsigned char *swap_map, |
1513 | unsigned long *frontswap_map) |
1514 | { |
1515 | int i, prev; |
1516 | |
1517 | if (prio >= 0) |
1518 | p->prio = prio; |
1519 | else |
1520 | p->prio = --least_priority; |
1521 | p->swap_map = swap_map; |
1522 | frontswap_map_set(p, frontswap_map); |
1523 | p->flags |= SWP_WRITEOK; |
1524 | atomic_long_add(p->pages, &nr_swap_pages); |
1525 | total_swap_pages += p->pages; |
1526 | |
1527 | /* insert swap space into swap_list: */ |
1528 | prev = -1; |
1529 | for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { |
1530 | if (p->prio >= swap_info[i]->prio) |
1531 | break; |
1532 | prev = i; |
1533 | } |
1534 | p->next = i; |
1535 | if (prev < 0) |
1536 | swap_list.head = swap_list.next = p->type; |
1537 | else |
1538 | swap_info[prev]->next = p->type; |
1539 | } |
1540 | |
1541 | static void enable_swap_info(struct swap_info_struct *p, int prio, |
1542 | unsigned char *swap_map, |
1543 | unsigned long *frontswap_map) |
1544 | { |
1545 | spin_lock(&swap_lock); |
1546 | spin_lock(&p->lock); |
1547 | _enable_swap_info(p, prio, swap_map, frontswap_map); |
1548 | frontswap_init(p->type); |
1549 | spin_unlock(&p->lock); |
1550 | spin_unlock(&swap_lock); |
1551 | } |
1552 | |
1553 | static void reinsert_swap_info(struct swap_info_struct *p) |
1554 | { |
1555 | spin_lock(&swap_lock); |
1556 | spin_lock(&p->lock); |
1557 | _enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p)); |
1558 | spin_unlock(&p->lock); |
1559 | spin_unlock(&swap_lock); |
1560 | } |
1561 | |
1562 | SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) |
1563 | { |
1564 | struct swap_info_struct *p = NULL; |
1565 | unsigned char *swap_map; |
1566 | struct file *swap_file, *victim; |
1567 | struct address_space *mapping; |
1568 | struct inode *inode; |
1569 | struct filename *pathname; |
1570 | int i, type, prev; |
1571 | int err; |
1572 | |
1573 | if (!capable(CAP_SYS_ADMIN)) |
1574 | return -EPERM; |
1575 | |
1576 | BUG_ON(!current->mm); |
1577 | |
1578 | pathname = getname(specialfile); |
1579 | if (IS_ERR(pathname)) |
1580 | return PTR_ERR(pathname); |
1581 | |
1582 | victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0); |
1583 | err = PTR_ERR(victim); |
1584 | if (IS_ERR(victim)) |
1585 | goto out; |
1586 | |
1587 | mapping = victim->f_mapping; |
1588 | prev = -1; |
1589 | spin_lock(&swap_lock); |
1590 | for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { |
1591 | p = swap_info[type]; |
1592 | if (p->flags & SWP_WRITEOK) { |
1593 | if (p->swap_file->f_mapping == mapping) |
1594 | break; |
1595 | } |
1596 | prev = type; |
1597 | } |
1598 | if (type < 0) { |
1599 | err = -EINVAL; |
1600 | spin_unlock(&swap_lock); |
1601 | goto out_dput; |
1602 | } |
1603 | if (!security_vm_enough_memory_mm(current->mm, p->pages)) |
1604 | vm_unacct_memory(p->pages); |
1605 | else { |
1606 | err = -ENOMEM; |
1607 | spin_unlock(&swap_lock); |
1608 | goto out_dput; |
1609 | } |
1610 | if (prev < 0) |
1611 | swap_list.head = p->next; |
1612 | else |
1613 | swap_info[prev]->next = p->next; |
1614 | if (type == swap_list.next) { |
1615 | /* just pick something that's safe... */ |
1616 | swap_list.next = swap_list.head; |
1617 | } |
1618 | spin_lock(&p->lock); |
1619 | if (p->prio < 0) { |
1620 | for (i = p->next; i >= 0; i = swap_info[i]->next) |
1621 | swap_info[i]->prio = p->prio--; |
1622 | least_priority++; |
1623 | } |
1624 | atomic_long_sub(p->pages, &nr_swap_pages); |
1625 | total_swap_pages -= p->pages; |
1626 | p->flags &= ~SWP_WRITEOK; |
1627 | spin_unlock(&p->lock); |
1628 | spin_unlock(&swap_lock); |
1629 | |
1630 | set_current_oom_origin(); |
1631 | err = try_to_unuse(type, false, 0); /* force all pages to be unused */ |
1632 | clear_current_oom_origin(); |
1633 | |
1634 | if (err) { |
1635 | /* re-insert swap space back into swap_list */ |
1636 | reinsert_swap_info(p); |
1637 | goto out_dput; |
1638 | } |
1639 | |
1640 | destroy_swap_extents(p); |
1641 | if (p->flags & SWP_CONTINUED) |
1642 | free_swap_count_continuations(p); |
1643 | |
1644 | mutex_lock(&swapon_mutex); |
1645 | spin_lock(&swap_lock); |
1646 | spin_lock(&p->lock); |
1647 | drain_mmlist(); |
1648 | |
1649 | /* wait for anyone still in scan_swap_map */ |
1650 | p->highest_bit = 0; /* cuts scans short */ |
1651 | while (p->flags >= SWP_SCANNING) { |
1652 | spin_unlock(&p->lock); |
1653 | spin_unlock(&swap_lock); |
1654 | schedule_timeout_uninterruptible(1); |
1655 | spin_lock(&swap_lock); |
1656 | spin_lock(&p->lock); |
1657 | } |
1658 | |
1659 | swap_file = p->swap_file; |
1660 | p->swap_file = NULL; |
1661 | p->max = 0; |
1662 | swap_map = p->swap_map; |
1663 | p->swap_map = NULL; |
1664 | p->flags = 0; |
1665 | frontswap_invalidate_area(type); |
1666 | spin_unlock(&p->lock); |
1667 | spin_unlock(&swap_lock); |
1668 | mutex_unlock(&swapon_mutex); |
1669 | vfree(swap_map); |
1670 | vfree(frontswap_map_get(p)); |
1671 | /* Destroy swap account informatin */ |
1672 | swap_cgroup_swapoff(type); |
1673 | |
1674 | inode = mapping->host; |
1675 | if (S_ISBLK(inode->i_mode)) { |
1676 | struct block_device *bdev = I_BDEV(inode); |
1677 | set_blocksize(bdev, p->old_block_size); |
1678 | blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); |
1679 | } else { |
1680 | mutex_lock(&inode->i_mutex); |
1681 | inode->i_flags &= ~S_SWAPFILE; |
1682 | mutex_unlock(&inode->i_mutex); |
1683 | } |
1684 | filp_close(swap_file, NULL); |
1685 | err = 0; |
1686 | atomic_inc(&proc_poll_event); |
1687 | wake_up_interruptible(&proc_poll_wait); |
1688 | |
1689 | out_dput: |
1690 | filp_close(victim, NULL); |
1691 | out: |
1692 | putname(pathname); |
1693 | return err; |
1694 | } |
1695 | |
1696 | #ifdef CONFIG_PROC_FS |
1697 | static unsigned swaps_poll(struct file *file, poll_table *wait) |
1698 | { |
1699 | struct seq_file *seq = file->private_data; |
1700 | |
1701 | poll_wait(file, &proc_poll_wait, wait); |
1702 | |
1703 | if (seq->poll_event != atomic_read(&proc_poll_event)) { |
1704 | seq->poll_event = atomic_read(&proc_poll_event); |
1705 | return POLLIN | POLLRDNORM | POLLERR | POLLPRI; |
1706 | } |
1707 | |
1708 | return POLLIN | POLLRDNORM; |
1709 | } |
1710 | |
1711 | /* iterator */ |
1712 | static void *swap_start(struct seq_file *swap, loff_t *pos) |
1713 | { |
1714 | struct swap_info_struct *si; |
1715 | int type; |
1716 | loff_t l = *pos; |
1717 | |
1718 | mutex_lock(&swapon_mutex); |
1719 | |
1720 | if (!l) |
1721 | return SEQ_START_TOKEN; |
1722 | |
1723 | for (type = 0; type < nr_swapfiles; type++) { |
1724 | smp_rmb(); /* read nr_swapfiles before swap_info[type] */ |
1725 | si = swap_info[type]; |
1726 | if (!(si->flags & SWP_USED) || !si->swap_map) |
1727 | continue; |
1728 | if (!--l) |
1729 | return si; |
1730 | } |
1731 | |
1732 | return NULL; |
1733 | } |
1734 | |
1735 | static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) |
1736 | { |
1737 | struct swap_info_struct *si = v; |
1738 | int type; |
1739 | |
1740 | if (v == SEQ_START_TOKEN) |
1741 | type = 0; |
1742 | else |
1743 | type = si->type + 1; |
1744 | |
1745 | for (; type < nr_swapfiles; type++) { |
1746 | smp_rmb(); /* read nr_swapfiles before swap_info[type] */ |
1747 | si = swap_info[type]; |
1748 | if (!(si->flags & SWP_USED) || !si->swap_map) |
1749 | continue; |
1750 | ++*pos; |
1751 | return si; |
1752 | } |
1753 | |
1754 | return NULL; |
1755 | } |
1756 | |
1757 | static void swap_stop(struct seq_file *swap, void *v) |
1758 | { |
1759 | mutex_unlock(&swapon_mutex); |
1760 | } |
1761 | |
1762 | static int swap_show(struct seq_file *swap, void *v) |
1763 | { |
1764 | struct swap_info_struct *si = v; |
1765 | struct file *file; |
1766 | int len; |
1767 | |
1768 | if (si == SEQ_START_TOKEN) { |
1769 | seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); |
1770 | return 0; |
1771 | } |
1772 | |
1773 | file = si->swap_file; |
1774 | len = seq_path(swap, &file->f_path, " \t\n\\"); |
1775 | seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", |
1776 | len < 40 ? 40 - len : 1, " ", |
1777 | S_ISBLK(file_inode(file)->i_mode) ? |
1778 | "partition" : "file\t", |
1779 | si->pages << (PAGE_SHIFT - 10), |
1780 | si->inuse_pages << (PAGE_SHIFT - 10), |
1781 | si->prio); |
1782 | return 0; |
1783 | } |
1784 | |
1785 | static const struct seq_operations swaps_op = { |
1786 | .start = swap_start, |
1787 | .next = swap_next, |
1788 | .stop = swap_stop, |
1789 | .show = swap_show |
1790 | }; |
1791 | |
1792 | static int swaps_open(struct inode *inode, struct file *file) |
1793 | { |
1794 | struct seq_file *seq; |
1795 | int ret; |
1796 | |
1797 | ret = seq_open(file, &swaps_op); |
1798 | if (ret) |
1799 | return ret; |
1800 | |
1801 | seq = file->private_data; |
1802 | seq->poll_event = atomic_read(&proc_poll_event); |
1803 | return 0; |
1804 | } |
1805 | |
1806 | static const struct file_operations proc_swaps_operations = { |
1807 | .open = swaps_open, |
1808 | .read = seq_read, |
1809 | .llseek = seq_lseek, |
1810 | .release = seq_release, |
1811 | .poll = swaps_poll, |
1812 | }; |
1813 | |
1814 | static int __init procswaps_init(void) |
1815 | { |
1816 | proc_create("swaps", 0, NULL, &proc_swaps_operations); |
1817 | return 0; |
1818 | } |
1819 | __initcall(procswaps_init); |
1820 | #endif /* CONFIG_PROC_FS */ |
1821 | |
1822 | #ifdef MAX_SWAPFILES_CHECK |
1823 | static int __init max_swapfiles_check(void) |
1824 | { |
1825 | MAX_SWAPFILES_CHECK(); |
1826 | return 0; |
1827 | } |
1828 | late_initcall(max_swapfiles_check); |
1829 | #endif |
1830 | |
1831 | static struct swap_info_struct *alloc_swap_info(void) |
1832 | { |
1833 | struct swap_info_struct *p; |
1834 | unsigned int type; |
1835 | |
1836 | p = kzalloc(sizeof(*p), GFP_KERNEL); |
1837 | if (!p) |
1838 | return ERR_PTR(-ENOMEM); |
1839 | |
1840 | spin_lock(&swap_lock); |
1841 | for (type = 0; type < nr_swapfiles; type++) { |
1842 | if (!(swap_info[type]->flags & SWP_USED)) |
1843 | break; |
1844 | } |
1845 | if (type >= MAX_SWAPFILES) { |
1846 | spin_unlock(&swap_lock); |
1847 | kfree(p); |
1848 | return ERR_PTR(-EPERM); |
1849 | } |
1850 | 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 | } |
1868 | INIT_LIST_HEAD(&p->first_swap_extent.list); |
1869 | p->flags = SWP_USED; |
1870 | p->next = -1; |
1871 | spin_unlock(&swap_lock); |
1872 | spin_lock_init(&p->lock); |
1873 | |
1874 | return p; |
1875 | } |
1876 | |
1877 | static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) |
1878 | { |
1879 | int error; |
1880 | |
1881 | if (S_ISBLK(inode->i_mode)) { |
1882 | p->bdev = bdgrab(I_BDEV(inode)); |
1883 | error = blkdev_get(p->bdev, |
1884 | FMODE_READ | FMODE_WRITE | FMODE_EXCL, |
1885 | sys_swapon); |
1886 | if (error < 0) { |
1887 | p->bdev = NULL; |
1888 | return -EINVAL; |
1889 | } |
1890 | p->old_block_size = block_size(p->bdev); |
1891 | error = set_blocksize(p->bdev, PAGE_SIZE); |
1892 | if (error < 0) |
1893 | return error; |
1894 | p->flags |= SWP_BLKDEV; |
1895 | } else if (S_ISREG(inode->i_mode)) { |
1896 | p->bdev = inode->i_sb->s_bdev; |
1897 | mutex_lock(&inode->i_mutex); |
1898 | if (IS_SWAPFILE(inode)) |
1899 | return -EBUSY; |
1900 | } else |
1901 | return -EINVAL; |
1902 | |
1903 | return 0; |
1904 | } |
1905 | |
1906 | static unsigned long read_swap_header(struct swap_info_struct *p, |
1907 | union swap_header *swap_header, |
1908 | struct inode *inode) |
1909 | { |
1910 | int i; |
1911 | unsigned long maxpages; |
1912 | unsigned long swapfilepages; |
1913 | |
1914 | if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { |
1915 | printk(KERN_ERR "Unable to find swap-space signature\n"); |
1916 | return 0; |
1917 | } |
1918 | |
1919 | /* swap partition endianess hack... */ |
1920 | if (swab32(swap_header->info.version) == 1) { |
1921 | swab32s(&swap_header->info.version); |
1922 | swab32s(&swap_header->info.last_page); |
1923 | swab32s(&swap_header->info.nr_badpages); |
1924 | for (i = 0; i < swap_header->info.nr_badpages; i++) |
1925 | swab32s(&swap_header->info.badpages[i]); |
1926 | } |
1927 | /* Check the swap header's sub-version */ |
1928 | if (swap_header->info.version != 1) { |
1929 | printk(KERN_WARNING |
1930 | "Unable to handle swap header version %d\n", |
1931 | swap_header->info.version); |
1932 | return 0; |
1933 | } |
1934 | |
1935 | p->lowest_bit = 1; |
1936 | p->cluster_next = 1; |
1937 | p->cluster_nr = 0; |
1938 | |
1939 | /* |
1940 | * Find out how many pages are allowed for a single swap |
1941 | * device. There are two limiting factors: 1) the number |
1942 | * of bits for the swap offset in the swp_entry_t type, and |
1943 | * 2) the number of bits in the swap pte as defined by the |
1944 | * different architectures. In order to find the |
1945 | * largest possible bit mask, a swap entry with swap type 0 |
1946 | * and swap offset ~0UL is created, encoded to a swap pte, |
1947 | * decoded to a swp_entry_t again, and finally the swap |
1948 | * offset is extracted. This will mask all the bits from |
1949 | * the initial ~0UL mask that can't be encoded in either |
1950 | * the swp_entry_t or the architecture definition of a |
1951 | * swap pte. |
1952 | */ |
1953 | maxpages = swp_offset(pte_to_swp_entry( |
1954 | swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; |
1955 | if (maxpages > swap_header->info.last_page) { |
1956 | maxpages = swap_header->info.last_page + 1; |
1957 | /* p->max is an unsigned int: don't overflow it */ |
1958 | if ((unsigned int)maxpages == 0) |
1959 | maxpages = UINT_MAX; |
1960 | } |
1961 | p->highest_bit = maxpages - 1; |
1962 | |
1963 | if (!maxpages) |
1964 | return 0; |
1965 | swapfilepages = i_size_read(inode) >> PAGE_SHIFT; |
1966 | if (swapfilepages && maxpages > swapfilepages) { |
1967 | printk(KERN_WARNING |
1968 | "Swap area shorter than signature indicates\n"); |
1969 | return 0; |
1970 | } |
1971 | if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) |
1972 | return 0; |
1973 | if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) |
1974 | return 0; |
1975 | |
1976 | return maxpages; |
1977 | } |
1978 | |
1979 | static int setup_swap_map_and_extents(struct swap_info_struct *p, |
1980 | union swap_header *swap_header, |
1981 | unsigned char *swap_map, |
1982 | unsigned long maxpages, |
1983 | sector_t *span) |
1984 | { |
1985 | int i; |
1986 | unsigned int nr_good_pages; |
1987 | int nr_extents; |
1988 | |
1989 | nr_good_pages = maxpages - 1; /* omit header page */ |
1990 | |
1991 | for (i = 0; i < swap_header->info.nr_badpages; i++) { |
1992 | unsigned int page_nr = swap_header->info.badpages[i]; |
1993 | if (page_nr == 0 || page_nr > swap_header->info.last_page) |
1994 | return -EINVAL; |
1995 | if (page_nr < maxpages) { |
1996 | swap_map[page_nr] = SWAP_MAP_BAD; |
1997 | nr_good_pages--; |
1998 | } |
1999 | } |
2000 | |
2001 | if (nr_good_pages) { |
2002 | swap_map[0] = SWAP_MAP_BAD; |
2003 | p->max = maxpages; |
2004 | p->pages = nr_good_pages; |
2005 | nr_extents = setup_swap_extents(p, span); |
2006 | if (nr_extents < 0) |
2007 | return nr_extents; |
2008 | nr_good_pages = p->pages; |
2009 | } |
2010 | if (!nr_good_pages) { |
2011 | printk(KERN_WARNING "Empty swap-file\n"); |
2012 | return -EINVAL; |
2013 | } |
2014 | |
2015 | return nr_extents; |
2016 | } |
2017 | |
2018 | SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) |
2019 | { |
2020 | struct swap_info_struct *p; |
2021 | struct filename *name; |
2022 | struct file *swap_file = NULL; |
2023 | struct address_space *mapping; |
2024 | int i; |
2025 | int prio; |
2026 | int error; |
2027 | union swap_header *swap_header; |
2028 | int nr_extents; |
2029 | sector_t span; |
2030 | unsigned long maxpages; |
2031 | unsigned char *swap_map = NULL; |
2032 | unsigned long *frontswap_map = NULL; |
2033 | struct page *page = NULL; |
2034 | struct inode *inode = NULL; |
2035 | |
2036 | if (swap_flags & ~SWAP_FLAGS_VALID) |
2037 | return -EINVAL; |
2038 | |
2039 | if (!capable(CAP_SYS_ADMIN)) |
2040 | return -EPERM; |
2041 | |
2042 | p = alloc_swap_info(); |
2043 | if (IS_ERR(p)) |
2044 | return PTR_ERR(p); |
2045 | |
2046 | name = getname(specialfile); |
2047 | if (IS_ERR(name)) { |
2048 | error = PTR_ERR(name); |
2049 | name = NULL; |
2050 | goto bad_swap; |
2051 | } |
2052 | swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0); |
2053 | if (IS_ERR(swap_file)) { |
2054 | error = PTR_ERR(swap_file); |
2055 | swap_file = NULL; |
2056 | goto bad_swap; |
2057 | } |
2058 | |
2059 | p->swap_file = swap_file; |
2060 | mapping = swap_file->f_mapping; |
2061 | |
2062 | for (i = 0; i < nr_swapfiles; i++) { |
2063 | struct swap_info_struct *q = swap_info[i]; |
2064 | |
2065 | if (q == p || !q->swap_file) |
2066 | continue; |
2067 | if (mapping == q->swap_file->f_mapping) { |
2068 | error = -EBUSY; |
2069 | goto bad_swap; |
2070 | } |
2071 | } |
2072 | |
2073 | inode = mapping->host; |
2074 | /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */ |
2075 | error = claim_swapfile(p, inode); |
2076 | if (unlikely(error)) |
2077 | goto bad_swap; |
2078 | |
2079 | /* |
2080 | * Read the swap header. |
2081 | */ |
2082 | if (!mapping->a_ops->readpage) { |
2083 | error = -EINVAL; |
2084 | goto bad_swap; |
2085 | } |
2086 | page = read_mapping_page(mapping, 0, swap_file); |
2087 | if (IS_ERR(page)) { |
2088 | error = PTR_ERR(page); |
2089 | goto bad_swap; |
2090 | } |
2091 | swap_header = kmap(page); |
2092 | |
2093 | maxpages = read_swap_header(p, swap_header, inode); |
2094 | if (unlikely(!maxpages)) { |
2095 | error = -EINVAL; |
2096 | goto bad_swap; |
2097 | } |
2098 | |
2099 | /* OK, set up the swap map and apply the bad block list */ |
2100 | swap_map = vzalloc(maxpages); |
2101 | if (!swap_map) { |
2102 | error = -ENOMEM; |
2103 | goto bad_swap; |
2104 | } |
2105 | |
2106 | error = swap_cgroup_swapon(p->type, maxpages); |
2107 | if (error) |
2108 | goto bad_swap; |
2109 | |
2110 | nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, |
2111 | maxpages, &span); |
2112 | if (unlikely(nr_extents < 0)) { |
2113 | error = nr_extents; |
2114 | goto bad_swap; |
2115 | } |
2116 | /* frontswap enabled? set up bit-per-page map for frontswap */ |
2117 | if (frontswap_enabled) |
2118 | frontswap_map = vzalloc(maxpages / sizeof(long)); |
2119 | |
2120 | if (p->bdev) { |
2121 | if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { |
2122 | p->flags |= SWP_SOLIDSTATE; |
2123 | p->cluster_next = 1 + (random32() % p->highest_bit); |
2124 | } |
2125 | if ((swap_flags & SWAP_FLAG_DISCARD) && discard_swap(p) == 0) |
2126 | p->flags |= SWP_DISCARDABLE; |
2127 | } |
2128 | |
2129 | mutex_lock(&swapon_mutex); |
2130 | prio = -1; |
2131 | if (swap_flags & SWAP_FLAG_PREFER) |
2132 | prio = |
2133 | (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; |
2134 | enable_swap_info(p, prio, swap_map, frontswap_map); |
2135 | |
2136 | printk(KERN_INFO "Adding %uk swap on %s. " |
2137 | "Priority:%d extents:%d across:%lluk %s%s%s\n", |
2138 | p->pages<<(PAGE_SHIFT-10), name->name, p->prio, |
2139 | nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), |
2140 | (p->flags & SWP_SOLIDSTATE) ? "SS" : "", |
2141 | (p->flags & SWP_DISCARDABLE) ? "D" : "", |
2142 | (frontswap_map) ? "FS" : ""); |
2143 | |
2144 | mutex_unlock(&swapon_mutex); |
2145 | atomic_inc(&proc_poll_event); |
2146 | wake_up_interruptible(&proc_poll_wait); |
2147 | |
2148 | if (S_ISREG(inode->i_mode)) |
2149 | inode->i_flags |= S_SWAPFILE; |
2150 | error = 0; |
2151 | goto out; |
2152 | bad_swap: |
2153 | if (inode && S_ISBLK(inode->i_mode) && p->bdev) { |
2154 | set_blocksize(p->bdev, p->old_block_size); |
2155 | blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); |
2156 | } |
2157 | destroy_swap_extents(p); |
2158 | swap_cgroup_swapoff(p->type); |
2159 | spin_lock(&swap_lock); |
2160 | p->swap_file = NULL; |
2161 | p->flags = 0; |
2162 | spin_unlock(&swap_lock); |
2163 | vfree(swap_map); |
2164 | if (swap_file) { |
2165 | if (inode && S_ISREG(inode->i_mode)) { |
2166 | mutex_unlock(&inode->i_mutex); |
2167 | inode = NULL; |
2168 | } |
2169 | filp_close(swap_file, NULL); |
2170 | } |
2171 | out: |
2172 | if (page && !IS_ERR(page)) { |
2173 | kunmap(page); |
2174 | page_cache_release(page); |
2175 | } |
2176 | if (name) |
2177 | putname(name); |
2178 | if (inode && S_ISREG(inode->i_mode)) |
2179 | mutex_unlock(&inode->i_mutex); |
2180 | return error; |
2181 | } |
2182 | |
2183 | void si_swapinfo(struct sysinfo *val) |
2184 | { |
2185 | unsigned int type; |
2186 | unsigned long nr_to_be_unused = 0; |
2187 | |
2188 | spin_lock(&swap_lock); |
2189 | for (type = 0; type < nr_swapfiles; type++) { |
2190 | struct swap_info_struct *si = swap_info[type]; |
2191 | |
2192 | if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) |
2193 | nr_to_be_unused += si->inuse_pages; |
2194 | } |
2195 | val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused; |
2196 | val->totalswap = total_swap_pages + nr_to_be_unused; |
2197 | spin_unlock(&swap_lock); |
2198 | } |
2199 | |
2200 | /* |
2201 | * Verify that a swap entry is valid and increment its swap map count. |
2202 | * |
2203 | * Returns error code in following case. |
2204 | * - success -> 0 |
2205 | * - swp_entry is invalid -> EINVAL |
2206 | * - swp_entry is migration entry -> EINVAL |
2207 | * - swap-cache reference is requested but there is already one. -> EEXIST |
2208 | * - swap-cache reference is requested but the entry is not used. -> ENOENT |
2209 | * - swap-mapped reference requested but needs continued swap count. -> ENOMEM |
2210 | */ |
2211 | static int __swap_duplicate(swp_entry_t entry, unsigned char usage) |
2212 | { |
2213 | struct swap_info_struct *p; |
2214 | unsigned long offset, type; |
2215 | unsigned char count; |
2216 | unsigned char has_cache; |
2217 | int err = -EINVAL; |
2218 | |
2219 | if (non_swap_entry(entry)) |
2220 | goto out; |
2221 | |
2222 | type = swp_type(entry); |
2223 | if (type >= nr_swapfiles) |
2224 | goto bad_file; |
2225 | p = swap_info[type]; |
2226 | offset = swp_offset(entry); |
2227 | |
2228 | spin_lock(&p->lock); |
2229 | if (unlikely(offset >= p->max)) |
2230 | goto unlock_out; |
2231 | |
2232 | count = p->swap_map[offset]; |
2233 | has_cache = count & SWAP_HAS_CACHE; |
2234 | count &= ~SWAP_HAS_CACHE; |
2235 | err = 0; |
2236 | |
2237 | if (usage == SWAP_HAS_CACHE) { |
2238 | |
2239 | /* set SWAP_HAS_CACHE if there is no cache and entry is used */ |
2240 | if (!has_cache && count) |
2241 | has_cache = SWAP_HAS_CACHE; |
2242 | else if (has_cache) /* someone else added cache */ |
2243 | err = -EEXIST; |
2244 | else /* no users remaining */ |
2245 | err = -ENOENT; |
2246 | |
2247 | } else if (count || has_cache) { |
2248 | |
2249 | if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) |
2250 | count += usage; |
2251 | else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) |
2252 | err = -EINVAL; |
2253 | else if (swap_count_continued(p, offset, count)) |
2254 | count = COUNT_CONTINUED; |
2255 | else |
2256 | err = -ENOMEM; |
2257 | } else |
2258 | err = -ENOENT; /* unused swap entry */ |
2259 | |
2260 | p->swap_map[offset] = count | has_cache; |
2261 | |
2262 | unlock_out: |
2263 | spin_unlock(&p->lock); |
2264 | out: |
2265 | return err; |
2266 | |
2267 | bad_file: |
2268 | printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); |
2269 | goto out; |
2270 | } |
2271 | |
2272 | /* |
2273 | * Help swapoff by noting that swap entry belongs to shmem/tmpfs |
2274 | * (in which case its reference count is never incremented). |
2275 | */ |
2276 | void swap_shmem_alloc(swp_entry_t entry) |
2277 | { |
2278 | __swap_duplicate(entry, SWAP_MAP_SHMEM); |
2279 | } |
2280 | |
2281 | /* |
2282 | * Increase reference count of swap entry by 1. |
2283 | * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required |
2284 | * but could not be atomically allocated. Returns 0, just as if it succeeded, |
2285 | * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which |
2286 | * might occur if a page table entry has got corrupted. |
2287 | */ |
2288 | int swap_duplicate(swp_entry_t entry) |
2289 | { |
2290 | int err = 0; |
2291 | |
2292 | while (!err && __swap_duplicate(entry, 1) == -ENOMEM) |
2293 | err = add_swap_count_continuation(entry, GFP_ATOMIC); |
2294 | return err; |
2295 | } |
2296 | |
2297 | /* |
2298 | * @entry: swap entry for which we allocate swap cache. |
2299 | * |
2300 | * Called when allocating swap cache for existing swap entry, |
2301 | * This can return error codes. Returns 0 at success. |
2302 | * -EBUSY means there is a swap cache. |
2303 | * Note: return code is different from swap_duplicate(). |
2304 | */ |
2305 | int swapcache_prepare(swp_entry_t entry) |
2306 | { |
2307 | return __swap_duplicate(entry, SWAP_HAS_CACHE); |
2308 | } |
2309 | |
2310 | struct swap_info_struct *page_swap_info(struct page *page) |
2311 | { |
2312 | swp_entry_t swap = { .val = page_private(page) }; |
2313 | BUG_ON(!PageSwapCache(page)); |
2314 | return swap_info[swp_type(swap)]; |
2315 | } |
2316 | |
2317 | /* |
2318 | * out-of-line __page_file_ methods to avoid include hell. |
2319 | */ |
2320 | struct address_space *__page_file_mapping(struct page *page) |
2321 | { |
2322 | VM_BUG_ON(!PageSwapCache(page)); |
2323 | return page_swap_info(page)->swap_file->f_mapping; |
2324 | } |
2325 | EXPORT_SYMBOL_GPL(__page_file_mapping); |
2326 | |
2327 | pgoff_t __page_file_index(struct page *page) |
2328 | { |
2329 | swp_entry_t swap = { .val = page_private(page) }; |
2330 | VM_BUG_ON(!PageSwapCache(page)); |
2331 | return swp_offset(swap); |
2332 | } |
2333 | EXPORT_SYMBOL_GPL(__page_file_index); |
2334 | |
2335 | /* |
2336 | * add_swap_count_continuation - called when a swap count is duplicated |
2337 | * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's |
2338 | * page of the original vmalloc'ed swap_map, to hold the continuation count |
2339 | * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called |
2340 | * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. |
2341 | * |
2342 | * These continuation pages are seldom referenced: the common paths all work |
2343 | * on the original swap_map, only referring to a continuation page when the |
2344 | * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. |
2345 | * |
2346 | * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding |
2347 | * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) |
2348 | * can be called after dropping locks. |
2349 | */ |
2350 | int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) |
2351 | { |
2352 | struct swap_info_struct *si; |
2353 | struct page *head; |
2354 | struct page *page; |
2355 | struct page *list_page; |
2356 | pgoff_t offset; |
2357 | unsigned char count; |
2358 | |
2359 | /* |
2360 | * When debugging, it's easier to use __GFP_ZERO here; but it's better |
2361 | * for latency not to zero a page while GFP_ATOMIC and holding locks. |
2362 | */ |
2363 | page = alloc_page(gfp_mask | __GFP_HIGHMEM); |
2364 | |
2365 | si = swap_info_get(entry); |
2366 | if (!si) { |
2367 | /* |
2368 | * An acceptable race has occurred since the failing |
2369 | * __swap_duplicate(): the swap entry has been freed, |
2370 | * perhaps even the whole swap_map cleared for swapoff. |
2371 | */ |
2372 | goto outer; |
2373 | } |
2374 | |
2375 | offset = swp_offset(entry); |
2376 | count = si->swap_map[offset] & ~SWAP_HAS_CACHE; |
2377 | |
2378 | if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { |
2379 | /* |
2380 | * The higher the swap count, the more likely it is that tasks |
2381 | * will race to add swap count continuation: we need to avoid |
2382 | * over-provisioning. |
2383 | */ |
2384 | goto out; |
2385 | } |
2386 | |
2387 | if (!page) { |
2388 | spin_unlock(&si->lock); |
2389 | return -ENOMEM; |
2390 | } |
2391 | |
2392 | /* |
2393 | * We are fortunate that although vmalloc_to_page uses pte_offset_map, |
2394 | * no architecture is using highmem pages for kernel pagetables: so it |
2395 | * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps. |
2396 | */ |
2397 | head = vmalloc_to_page(si->swap_map + offset); |
2398 | offset &= ~PAGE_MASK; |
2399 | |
2400 | /* |
2401 | * Page allocation does not initialize the page's lru field, |
2402 | * but it does always reset its private field. |
2403 | */ |
2404 | if (!page_private(head)) { |
2405 | BUG_ON(count & COUNT_CONTINUED); |
2406 | INIT_LIST_HEAD(&head->lru); |
2407 | set_page_private(head, SWP_CONTINUED); |
2408 | si->flags |= SWP_CONTINUED; |
2409 | } |
2410 | |
2411 | list_for_each_entry(list_page, &head->lru, lru) { |
2412 | unsigned char *map; |
2413 | |
2414 | /* |
2415 | * If the previous map said no continuation, but we've found |
2416 | * a continuation page, free our allocation and use this one. |
2417 | */ |
2418 | if (!(count & COUNT_CONTINUED)) |
2419 | goto out; |
2420 | |
2421 | map = kmap_atomic(list_page) + offset; |
2422 | count = *map; |
2423 | kunmap_atomic(map); |
2424 | |
2425 | /* |
2426 | * If this continuation count now has some space in it, |
2427 | * free our allocation and use this one. |
2428 | */ |
2429 | if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) |
2430 | goto out; |
2431 | } |
2432 | |
2433 | list_add_tail(&page->lru, &head->lru); |
2434 | page = NULL; /* now it's attached, don't free it */ |
2435 | out: |
2436 | spin_unlock(&si->lock); |
2437 | outer: |
2438 | if (page) |
2439 | __free_page(page); |
2440 | return 0; |
2441 | } |
2442 | |
2443 | /* |
2444 | * swap_count_continued - when the original swap_map count is incremented |
2445 | * from SWAP_MAP_MAX, check if there is already a continuation page to carry |
2446 | * into, carry if so, or else fail until a new continuation page is allocated; |
2447 | * when the original swap_map count is decremented from 0 with continuation, |
2448 | * borrow from the continuation and report whether it still holds more. |
2449 | * Called while __swap_duplicate() or swap_entry_free() holds swap_lock. |
2450 | */ |
2451 | static bool swap_count_continued(struct swap_info_struct *si, |
2452 | pgoff_t offset, unsigned char count) |
2453 | { |
2454 | struct page *head; |
2455 | struct page *page; |
2456 | unsigned char *map; |
2457 | |
2458 | head = vmalloc_to_page(si->swap_map + offset); |
2459 | if (page_private(head) != SWP_CONTINUED) { |
2460 | BUG_ON(count & COUNT_CONTINUED); |
2461 | return false; /* need to add count continuation */ |
2462 | } |
2463 | |
2464 | offset &= ~PAGE_MASK; |
2465 | page = list_entry(head->lru.next, struct page, lru); |
2466 | map = kmap_atomic(page) + offset; |
2467 | |
2468 | if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ |
2469 | goto init_map; /* jump over SWAP_CONT_MAX checks */ |
2470 | |
2471 | if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ |
2472 | /* |
2473 | * Think of how you add 1 to 999 |
2474 | */ |
2475 | while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { |
2476 | kunmap_atomic(map); |
2477 | page = list_entry(page->lru.next, struct page, lru); |
2478 | BUG_ON(page == head); |
2479 | map = kmap_atomic(page) + offset; |
2480 | } |
2481 | if (*map == SWAP_CONT_MAX) { |
2482 | kunmap_atomic(map); |
2483 | page = list_entry(page->lru.next, struct page, lru); |
2484 | if (page == head) |
2485 | return false; /* add count continuation */ |
2486 | map = kmap_atomic(page) + offset; |
2487 | init_map: *map = 0; /* we didn't zero the page */ |
2488 | } |
2489 | *map += 1; |
2490 | kunmap_atomic(map); |
2491 | page = list_entry(page->lru.prev, struct page, lru); |
2492 | while (page != head) { |
2493 | map = kmap_atomic(page) + offset; |
2494 | *map = COUNT_CONTINUED; |
2495 | kunmap_atomic(map); |
2496 | page = list_entry(page->lru.prev, struct page, lru); |
2497 | } |
2498 | return true; /* incremented */ |
2499 | |
2500 | } else { /* decrementing */ |
2501 | /* |
2502 | * Think of how you subtract 1 from 1000 |
2503 | */ |
2504 | BUG_ON(count != COUNT_CONTINUED); |
2505 | while (*map == COUNT_CONTINUED) { |
2506 | kunmap_atomic(map); |
2507 | page = list_entry(page->lru.next, struct page, lru); |
2508 | BUG_ON(page == head); |
2509 | map = kmap_atomic(page) + offset; |
2510 | } |
2511 | BUG_ON(*map == 0); |
2512 | *map -= 1; |
2513 | if (*map == 0) |
2514 | count = 0; |
2515 | kunmap_atomic(map); |
2516 | page = list_entry(page->lru.prev, struct page, lru); |
2517 | while (page != head) { |
2518 | map = kmap_atomic(page) + offset; |
2519 | *map = SWAP_CONT_MAX | count; |
2520 | count = COUNT_CONTINUED; |
2521 | kunmap_atomic(map); |
2522 | page = list_entry(page->lru.prev, struct page, lru); |
2523 | } |
2524 | return count == COUNT_CONTINUED; |
2525 | } |
2526 | } |
2527 | |
2528 | /* |
2529 | * free_swap_count_continuations - swapoff free all the continuation pages |
2530 | * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. |
2531 | */ |
2532 | static void free_swap_count_continuations(struct swap_info_struct *si) |
2533 | { |
2534 | pgoff_t offset; |
2535 | |
2536 | for (offset = 0; offset < si->max; offset += PAGE_SIZE) { |
2537 | struct page *head; |
2538 | head = vmalloc_to_page(si->swap_map + offset); |
2539 | if (page_private(head)) { |
2540 | struct list_head *this, *next; |
2541 | list_for_each_safe(this, next, &head->lru) { |
2542 | struct page *page; |
2543 | page = list_entry(this, struct page, lru); |
2544 | list_del(this); |
2545 | __free_page(page); |
2546 | } |
2547 | } |
2548 | } |
2549 | } |
2550 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9