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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
55 static const char Bad_file[] = "Bad swap file entry ";
56 static const char Unused_file[] = "Unused swap file entry ";
57 static const char Bad_offset[] = "Bad swap offset entry ";
58 static const char Unused_offset[] = "Unused swap offset entry ";
59
60 /*
61 * all active swap_info_structs
62 * protected with swap_lock, and ordered by priority.
63 */
64 PLIST_HEAD(swap_active_head);
65
66 /*
67 * all available (active, not full) swap_info_structs
68 * protected with swap_avail_lock, ordered by priority.
69 * This is used by get_swap_page() instead of swap_active_head
70 * because swap_active_head includes all swap_info_structs,
71 * but get_swap_page() doesn't need to look at full ones.
72 * This uses its own lock instead of swap_lock because when a
73 * swap_info_struct changes between not-full/full, it needs to
74 * add/remove itself to/from this list, but the swap_info_struct->lock
75 * is held and the locking order requires swap_lock to be taken
76 * before any swap_info_struct->lock.
77 */
78 static PLIST_HEAD(swap_avail_head);
79 static DEFINE_SPINLOCK(swap_avail_lock);
80
81 struct swap_info_struct *swap_info[MAX_SWAPFILES];
82
83 static DEFINE_MUTEX(swapon_mutex);
84
85 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
86 /* Activity counter to indicate that a swapon or swapoff has occurred */
87 static atomic_t proc_poll_event = ATOMIC_INIT(0);
88
89 static inline unsigned char swap_count(unsigned char ent)
90 {
91 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
92 }
93
94 /* returns 1 if swap entry is freed */
95 static int
96 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
97 {
98 swp_entry_t entry = swp_entry(si->type, offset);
99 struct page *page;
100 int ret = 0;
101
102 page = find_get_page(swap_address_space(entry), entry.val);
103 if (!page)
104 return 0;
105 /*
106 * This function is called from scan_swap_map() and it's called
107 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
108 * We have to use trylock for avoiding deadlock. This is a special
109 * case and you should use try_to_free_swap() with explicit lock_page()
110 * in usual operations.
111 */
112 if (trylock_page(page)) {
113 ret = try_to_free_swap(page);
114 unlock_page(page);
115 }
116 page_cache_release(page);
117 return ret;
118 }
119
120 /*
121 * swapon tell device that all the old swap contents can be discarded,
122 * to allow the swap device to optimize its wear-levelling.
123 */
124 static int discard_swap(struct swap_info_struct *si)
125 {
126 struct swap_extent *se;
127 sector_t start_block;
128 sector_t nr_blocks;
129 int err = 0;
130
131 /* Do not discard the swap header page! */
132 se = &si->first_swap_extent;
133 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
134 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
135 if (nr_blocks) {
136 err = blkdev_issue_discard(si->bdev, start_block,
137 nr_blocks, GFP_KERNEL, 0);
138 if (err)
139 return err;
140 cond_resched();
141 }
142
143 list_for_each_entry(se, &si->first_swap_extent.list, list) {
144 start_block = se->start_block << (PAGE_SHIFT - 9);
145 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
146
147 err = blkdev_issue_discard(si->bdev, start_block,
148 nr_blocks, GFP_KERNEL, 0);
149 if (err)
150 break;
151
152 cond_resched();
153 }
154 return err; /* That will often be -EOPNOTSUPP */
155 }
156
157 /*
158 * swap allocation tell device that a cluster of swap can now be discarded,
159 * to allow the swap device to optimize its wear-levelling.
160 */
161 static void discard_swap_cluster(struct swap_info_struct *si,
162 pgoff_t start_page, pgoff_t nr_pages)
163 {
164 struct swap_extent *se = si->curr_swap_extent;
165 int found_extent = 0;
166
167 while (nr_pages) {
168 struct list_head *lh;
169
170 if (se->start_page <= start_page &&
171 start_page < se->start_page + se->nr_pages) {
172 pgoff_t offset = start_page - se->start_page;
173 sector_t start_block = se->start_block + offset;
174 sector_t nr_blocks = se->nr_pages - offset;
175
176 if (nr_blocks > nr_pages)
177 nr_blocks = nr_pages;
178 start_page += nr_blocks;
179 nr_pages -= nr_blocks;
180
181 if (!found_extent++)
182 si->curr_swap_extent = se;
183
184 start_block <<= PAGE_SHIFT - 9;
185 nr_blocks <<= PAGE_SHIFT - 9;
186 if (blkdev_issue_discard(si->bdev, start_block,
187 nr_blocks, GFP_NOIO, 0))
188 break;
189 }
190
191 lh = se->list.next;
192 se = list_entry(lh, struct swap_extent, list);
193 }
194 }
195
196 #define SWAPFILE_CLUSTER 256
197 #define LATENCY_LIMIT 256
198
199 static inline void cluster_set_flag(struct swap_cluster_info *info,
200 unsigned int flag)
201 {
202 info->flags = flag;
203 }
204
205 static inline unsigned int cluster_count(struct swap_cluster_info *info)
206 {
207 return info->data;
208 }
209
210 static inline void cluster_set_count(struct swap_cluster_info *info,
211 unsigned int c)
212 {
213 info->data = c;
214 }
215
216 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
217 unsigned int c, unsigned int f)
218 {
219 info->flags = f;
220 info->data = c;
221 }
222
223 static inline unsigned int cluster_next(struct swap_cluster_info *info)
224 {
225 return info->data;
226 }
227
228 static inline void cluster_set_next(struct swap_cluster_info *info,
229 unsigned int n)
230 {
231 info->data = n;
232 }
233
234 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
235 unsigned int n, unsigned int f)
236 {
237 info->flags = f;
238 info->data = n;
239 }
240
241 static inline bool cluster_is_free(struct swap_cluster_info *info)
242 {
243 return info->flags & CLUSTER_FLAG_FREE;
244 }
245
246 static inline bool cluster_is_null(struct swap_cluster_info *info)
247 {
248 return info->flags & CLUSTER_FLAG_NEXT_NULL;
249 }
250
251 static inline void cluster_set_null(struct swap_cluster_info *info)
252 {
253 info->flags = CLUSTER_FLAG_NEXT_NULL;
254 info->data = 0;
255 }
256
257 /* Add a cluster to discard list and schedule it to do discard */
258 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
259 unsigned int idx)
260 {
261 /*
262 * If scan_swap_map() can't find a free cluster, it will check
263 * si->swap_map directly. To make sure the discarding cluster isn't
264 * taken by scan_swap_map(), mark the swap entries bad (occupied). It
265 * will be cleared after discard
266 */
267 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
268 SWAP_MAP_BAD, SWAPFILE_CLUSTER);
269
270 if (cluster_is_null(&si->discard_cluster_head)) {
271 cluster_set_next_flag(&si->discard_cluster_head,
272 idx, 0);
273 cluster_set_next_flag(&si->discard_cluster_tail,
274 idx, 0);
275 } else {
276 unsigned int tail = cluster_next(&si->discard_cluster_tail);
277 cluster_set_next(&si->cluster_info[tail], idx);
278 cluster_set_next_flag(&si->discard_cluster_tail,
279 idx, 0);
280 }
281
282 schedule_work(&si->discard_work);
283 }
284
285 /*
286 * Doing discard actually. After a cluster discard is finished, the cluster
287 * will be added to free cluster list. caller should hold si->lock.
288 */
289 static void swap_do_scheduled_discard(struct swap_info_struct *si)
290 {
291 struct swap_cluster_info *info;
292 unsigned int idx;
293
294 info = si->cluster_info;
295
296 while (!cluster_is_null(&si->discard_cluster_head)) {
297 idx = cluster_next(&si->discard_cluster_head);
298
299 cluster_set_next_flag(&si->discard_cluster_head,
300 cluster_next(&info[idx]), 0);
301 if (cluster_next(&si->discard_cluster_tail) == idx) {
302 cluster_set_null(&si->discard_cluster_head);
303 cluster_set_null(&si->discard_cluster_tail);
304 }
305 spin_unlock(&si->lock);
306
307 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
308 SWAPFILE_CLUSTER);
309
310 spin_lock(&si->lock);
311 cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
312 if (cluster_is_null(&si->free_cluster_head)) {
313 cluster_set_next_flag(&si->free_cluster_head,
314 idx, 0);
315 cluster_set_next_flag(&si->free_cluster_tail,
316 idx, 0);
317 } else {
318 unsigned int tail;
319
320 tail = cluster_next(&si->free_cluster_tail);
321 cluster_set_next(&info[tail], idx);
322 cluster_set_next_flag(&si->free_cluster_tail,
323 idx, 0);
324 }
325 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
326 0, SWAPFILE_CLUSTER);
327 }
328 }
329
330 static void swap_discard_work(struct work_struct *work)
331 {
332 struct swap_info_struct *si;
333
334 si = container_of(work, struct swap_info_struct, discard_work);
335
336 spin_lock(&si->lock);
337 swap_do_scheduled_discard(si);
338 spin_unlock(&si->lock);
339 }
340
341 /*
342 * The cluster corresponding to page_nr will be used. The cluster will be
343 * removed from free cluster list and its usage counter will be increased.
344 */
345 static void inc_cluster_info_page(struct swap_info_struct *p,
346 struct swap_cluster_info *cluster_info, unsigned long page_nr)
347 {
348 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
349
350 if (!cluster_info)
351 return;
352 if (cluster_is_free(&cluster_info[idx])) {
353 VM_BUG_ON(cluster_next(&p->free_cluster_head) != idx);
354 cluster_set_next_flag(&p->free_cluster_head,
355 cluster_next(&cluster_info[idx]), 0);
356 if (cluster_next(&p->free_cluster_tail) == idx) {
357 cluster_set_null(&p->free_cluster_tail);
358 cluster_set_null(&p->free_cluster_head);
359 }
360 cluster_set_count_flag(&cluster_info[idx], 0, 0);
361 }
362
363 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
364 cluster_set_count(&cluster_info[idx],
365 cluster_count(&cluster_info[idx]) + 1);
366 }
367
368 /*
369 * The cluster corresponding to page_nr decreases one usage. If the usage
370 * counter becomes 0, which means no page in the cluster is in using, we can
371 * optionally discard the cluster and add it to free cluster list.
372 */
373 static void dec_cluster_info_page(struct swap_info_struct *p,
374 struct swap_cluster_info *cluster_info, unsigned long page_nr)
375 {
376 unsigned long idx = page_nr / SWAPFILE_CLUSTER;
377
378 if (!cluster_info)
379 return;
380
381 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
382 cluster_set_count(&cluster_info[idx],
383 cluster_count(&cluster_info[idx]) - 1);
384
385 if (cluster_count(&cluster_info[idx]) == 0) {
386 /*
387 * If the swap is discardable, prepare discard the cluster
388 * instead of free it immediately. The cluster will be freed
389 * after discard.
390 */
391 if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
392 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
393 swap_cluster_schedule_discard(p, idx);
394 return;
395 }
396
397 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
398 if (cluster_is_null(&p->free_cluster_head)) {
399 cluster_set_next_flag(&p->free_cluster_head, idx, 0);
400 cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
401 } else {
402 unsigned int tail = cluster_next(&p->free_cluster_tail);
403 cluster_set_next(&cluster_info[tail], idx);
404 cluster_set_next_flag(&p->free_cluster_tail, idx, 0);
405 }
406 }
407 }
408
409 /*
410 * It's possible scan_swap_map() uses a free cluster in the middle of free
411 * cluster list. Avoiding such abuse to avoid list corruption.
412 */
413 static bool
414 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
415 unsigned long offset)
416 {
417 struct percpu_cluster *percpu_cluster;
418 bool conflict;
419
420 offset /= SWAPFILE_CLUSTER;
421 conflict = !cluster_is_null(&si->free_cluster_head) &&
422 offset != cluster_next(&si->free_cluster_head) &&
423 cluster_is_free(&si->cluster_info[offset]);
424
425 if (!conflict)
426 return false;
427
428 percpu_cluster = this_cpu_ptr(si->percpu_cluster);
429 cluster_set_null(&percpu_cluster->index);
430 return true;
431 }
432
433 /*
434 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
435 * might involve allocating a new cluster for current CPU too.
436 */
437 static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
438 unsigned long *offset, unsigned long *scan_base)
439 {
440 struct percpu_cluster *cluster;
441 bool found_free;
442 unsigned long tmp;
443
444 new_cluster:
445 cluster = this_cpu_ptr(si->percpu_cluster);
446 if (cluster_is_null(&cluster->index)) {
447 if (!cluster_is_null(&si->free_cluster_head)) {
448 cluster->index = si->free_cluster_head;
449 cluster->next = cluster_next(&cluster->index) *
450 SWAPFILE_CLUSTER;
451 } else if (!cluster_is_null(&si->discard_cluster_head)) {
452 /*
453 * we don't have free cluster but have some clusters in
454 * discarding, do discard now and reclaim them
455 */
456 swap_do_scheduled_discard(si);
457 *scan_base = *offset = si->cluster_next;
458 goto new_cluster;
459 } else
460 return;
461 }
462
463 found_free = false;
464
465 /*
466 * Other CPUs can use our cluster if they can't find a free cluster,
467 * check if there is still free entry in the cluster
468 */
469 tmp = cluster->next;
470 while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
471 SWAPFILE_CLUSTER) {
472 if (!si->swap_map[tmp]) {
473 found_free = true;
474 break;
475 }
476 tmp++;
477 }
478 if (!found_free) {
479 cluster_set_null(&cluster->index);
480 goto new_cluster;
481 }
482 cluster->next = tmp + 1;
483 *offset = tmp;
484 *scan_base = tmp;
485 }
486
487 static unsigned long scan_swap_map(struct swap_info_struct *si,
488 unsigned char usage)
489 {
490 unsigned long offset;
491 unsigned long scan_base;
492 unsigned long last_in_cluster = 0;
493 int latency_ration = LATENCY_LIMIT;
494
495 /*
496 * We try to cluster swap pages by allocating them sequentially
497 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
498 * way, however, we resort to first-free allocation, starting
499 * a new cluster. This prevents us from scattering swap pages
500 * all over the entire swap partition, so that we reduce
501 * overall disk seek times between swap pages. -- sct
502 * But we do now try to find an empty cluster. -Andrea
503 * And we let swap pages go all over an SSD partition. Hugh
504 */
505
506 si->flags += SWP_SCANNING;
507 scan_base = offset = si->cluster_next;
508
509 /* SSD algorithm */
510 if (si->cluster_info) {
511 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
512 goto checks;
513 }
514
515 if (unlikely(!si->cluster_nr--)) {
516 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
517 si->cluster_nr = SWAPFILE_CLUSTER - 1;
518 goto checks;
519 }
520
521 spin_unlock(&si->lock);
522
523 /*
524 * If seek is expensive, start searching for new cluster from
525 * start of partition, to minimize the span of allocated swap.
526 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
527 * case, just handled by scan_swap_map_try_ssd_cluster() above.
528 */
529 scan_base = offset = si->lowest_bit;
530 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
531
532 /* Locate the first empty (unaligned) cluster */
533 for (; last_in_cluster <= si->highest_bit; offset++) {
534 if (si->swap_map[offset])
535 last_in_cluster = offset + SWAPFILE_CLUSTER;
536 else if (offset == last_in_cluster) {
537 spin_lock(&si->lock);
538 offset -= SWAPFILE_CLUSTER - 1;
539 si->cluster_next = offset;
540 si->cluster_nr = SWAPFILE_CLUSTER - 1;
541 goto checks;
542 }
543 if (unlikely(--latency_ration < 0)) {
544 cond_resched();
545 latency_ration = LATENCY_LIMIT;
546 }
547 }
548
549 offset = scan_base;
550 spin_lock(&si->lock);
551 si->cluster_nr = SWAPFILE_CLUSTER - 1;
552 }
553
554 checks:
555 if (si->cluster_info) {
556 while (scan_swap_map_ssd_cluster_conflict(si, offset))
557 scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
558 }
559 if (!(si->flags & SWP_WRITEOK))
560 goto no_page;
561 if (!si->highest_bit)
562 goto no_page;
563 if (offset > si->highest_bit)
564 scan_base = offset = si->lowest_bit;
565
566 /* reuse swap entry of cache-only swap if not busy. */
567 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
568 int swap_was_freed;
569 spin_unlock(&si->lock);
570 swap_was_freed = __try_to_reclaim_swap(si, offset);
571 spin_lock(&si->lock);
572 /* entry was freed successfully, try to use this again */
573 if (swap_was_freed)
574 goto checks;
575 goto scan; /* check next one */
576 }
577
578 if (si->swap_map[offset])
579 goto scan;
580
581 if (offset == si->lowest_bit)
582 si->lowest_bit++;
583 if (offset == si->highest_bit)
584 si->highest_bit--;
585 si->inuse_pages++;
586 if (si->inuse_pages == si->pages) {
587 si->lowest_bit = si->max;
588 si->highest_bit = 0;
589 spin_lock(&swap_avail_lock);
590 plist_del(&si->avail_list, &swap_avail_head);
591 spin_unlock(&swap_avail_lock);
592 }
593 si->swap_map[offset] = usage;
594 inc_cluster_info_page(si, si->cluster_info, offset);
595 si->cluster_next = offset + 1;
596 si->flags -= SWP_SCANNING;
597
598 return offset;
599
600 scan:
601 spin_unlock(&si->lock);
602 while (++offset <= si->highest_bit) {
603 if (!si->swap_map[offset]) {
604 spin_lock(&si->lock);
605 goto checks;
606 }
607 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
608 spin_lock(&si->lock);
609 goto checks;
610 }
611 if (unlikely(--latency_ration < 0)) {
612 cond_resched();
613 latency_ration = LATENCY_LIMIT;
614 }
615 }
616 offset = si->lowest_bit;
617 while (offset < scan_base) {
618 if (!si->swap_map[offset]) {
619 spin_lock(&si->lock);
620 goto checks;
621 }
622 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
623 spin_lock(&si->lock);
624 goto checks;
625 }
626 if (unlikely(--latency_ration < 0)) {
627 cond_resched();
628 latency_ration = LATENCY_LIMIT;
629 }
630 offset++;
631 }
632 spin_lock(&si->lock);
633
634 no_page:
635 si->flags -= SWP_SCANNING;
636 return 0;
637 }
638
639 swp_entry_t get_swap_page(void)
640 {
641 struct swap_info_struct *si, *next;
642 pgoff_t offset;
643
644 if (atomic_long_read(&nr_swap_pages) <= 0)
645 goto noswap;
646 atomic_long_dec(&nr_swap_pages);
647
648 spin_lock(&swap_avail_lock);
649
650 start_over:
651 plist_for_each_entry_safe(si, next, &swap_avail_head, avail_list) {
652 /* requeue si to after same-priority siblings */
653 plist_requeue(&si->avail_list, &swap_avail_head);
654 spin_unlock(&swap_avail_lock);
655 spin_lock(&si->lock);
656 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
657 spin_lock(&swap_avail_lock);
658 if (plist_node_empty(&si->avail_list)) {
659 spin_unlock(&si->lock);
660 goto nextsi;
661 }
662 WARN(!si->highest_bit,
663 "swap_info %d in list but !highest_bit\n",
664 si->type);
665 WARN(!(si->flags & SWP_WRITEOK),
666 "swap_info %d in list but !SWP_WRITEOK\n",
667 si->type);
668 plist_del(&si->avail_list, &swap_avail_head);
669 spin_unlock(&si->lock);
670 goto nextsi;
671 }
672
673 /* This is called for allocating swap entry for cache */
674 offset = scan_swap_map(si, SWAP_HAS_CACHE);
675 spin_unlock(&si->lock);
676 if (offset)
677 return swp_entry(si->type, offset);
678 pr_debug("scan_swap_map of si %d failed to find offset\n",
679 si->type);
680 spin_lock(&swap_avail_lock);
681 nextsi:
682 /*
683 * if we got here, it's likely that si was almost full before,
684 * and since scan_swap_map() can drop the si->lock, multiple
685 * callers probably all tried to get a page from the same si
686 * and it filled up before we could get one; or, the si filled
687 * up between us dropping swap_avail_lock and taking si->lock.
688 * Since we dropped the swap_avail_lock, the swap_avail_head
689 * list may have been modified; so if next is still in the
690 * swap_avail_head list then try it, otherwise start over.
691 */
692 if (plist_node_empty(&next->avail_list))
693 goto start_over;
694 }
695
696 spin_unlock(&swap_avail_lock);
697
698 atomic_long_inc(&nr_swap_pages);
699 noswap:
700 return (swp_entry_t) {0};
701 }
702
703 /* The only caller of this function is now suspend routine */
704 swp_entry_t get_swap_page_of_type(int type)
705 {
706 struct swap_info_struct *si;
707 pgoff_t offset;
708
709 si = swap_info[type];
710 spin_lock(&si->lock);
711 if (si && (si->flags & SWP_WRITEOK)) {
712 atomic_long_dec(&nr_swap_pages);
713 /* This is called for allocating swap entry, not cache */
714 offset = scan_swap_map(si, 1);
715 if (offset) {
716 spin_unlock(&si->lock);
717 return swp_entry(type, offset);
718 }
719 atomic_long_inc(&nr_swap_pages);
720 }
721 spin_unlock(&si->lock);
722 return (swp_entry_t) {0};
723 }
724
725 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
726 {
727 struct swap_info_struct *p;
728 unsigned long offset, type;
729
730 if (!entry.val)
731 goto out;
732 type = swp_type(entry);
733 if (type >= nr_swapfiles)
734 goto bad_nofile;
735 p = swap_info[type];
736 if (!(p->flags & SWP_USED))
737 goto bad_device;
738 offset = swp_offset(entry);
739 if (offset >= p->max)
740 goto bad_offset;
741 if (!p->swap_map[offset])
742 goto bad_free;
743 spin_lock(&p->lock);
744 return p;
745
746 bad_free:
747 pr_err("swap_free: %s%08lx\n", Unused_offset, entry.val);
748 goto out;
749 bad_offset:
750 pr_err("swap_free: %s%08lx\n", Bad_offset, entry.val);
751 goto out;
752 bad_device:
753 pr_err("swap_free: %s%08lx\n", Unused_file, entry.val);
754 goto out;
755 bad_nofile:
756 pr_err("swap_free: %s%08lx\n", Bad_file, entry.val);
757 out:
758 return NULL;
759 }
760
761 static unsigned char swap_entry_free(struct swap_info_struct *p,
762 swp_entry_t entry, unsigned char usage)
763 {
764 unsigned long offset = swp_offset(entry);
765 unsigned char count;
766 unsigned char has_cache;
767
768 count = p->swap_map[offset];
769 has_cache = count & SWAP_HAS_CACHE;
770 count &= ~SWAP_HAS_CACHE;
771
772 if (usage == SWAP_HAS_CACHE) {
773 VM_BUG_ON(!has_cache);
774 has_cache = 0;
775 } else if (count == SWAP_MAP_SHMEM) {
776 /*
777 * Or we could insist on shmem.c using a special
778 * swap_shmem_free() and free_shmem_swap_and_cache()...
779 */
780 count = 0;
781 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
782 if (count == COUNT_CONTINUED) {
783 if (swap_count_continued(p, offset, count))
784 count = SWAP_MAP_MAX | COUNT_CONTINUED;
785 else
786 count = SWAP_MAP_MAX;
787 } else
788 count--;
789 }
790
791 if (!count)
792 mem_cgroup_uncharge_swap(entry);
793
794 usage = count | has_cache;
795 p->swap_map[offset] = usage;
796
797 /* free if no reference */
798 if (!usage) {
799 dec_cluster_info_page(p, p->cluster_info, offset);
800 if (offset < p->lowest_bit)
801 p->lowest_bit = offset;
802 if (offset > p->highest_bit) {
803 bool was_full = !p->highest_bit;
804 p->highest_bit = offset;
805 if (was_full && (p->flags & SWP_WRITEOK)) {
806 spin_lock(&swap_avail_lock);
807 WARN_ON(!plist_node_empty(&p->avail_list));
808 if (plist_node_empty(&p->avail_list))
809 plist_add(&p->avail_list,
810 &swap_avail_head);
811 spin_unlock(&swap_avail_lock);
812 }
813 }
814 atomic_long_inc(&nr_swap_pages);
815 p->inuse_pages--;
816 frontswap_invalidate_page(p->type, offset);
817 if (p->flags & SWP_BLKDEV) {
818 struct gendisk *disk = p->bdev->bd_disk;
819 if (disk->fops->swap_slot_free_notify)
820 disk->fops->swap_slot_free_notify(p->bdev,
821 offset);
822 }
823 }
824
825 return usage;
826 }
827
828 /*
829 * Caller has made sure that the swap device corresponding to entry
830 * is still around or has not been recycled.
831 */
832 void swap_free(swp_entry_t entry)
833 {
834 struct swap_info_struct *p;
835
836 p = swap_info_get(entry);
837 if (p) {
838 swap_entry_free(p, entry, 1);
839 spin_unlock(&p->lock);
840 }
841 }
842
843 /*
844 * Called after dropping swapcache to decrease refcnt to swap entries.
845 */
846 void swapcache_free(swp_entry_t entry)
847 {
848 struct swap_info_struct *p;
849
850 p = swap_info_get(entry);
851 if (p) {
852 swap_entry_free(p, entry, SWAP_HAS_CACHE);
853 spin_unlock(&p->lock);
854 }
855 }
856
857 /*
858 * How many references to page are currently swapped out?
859 * This does not give an exact answer when swap count is continued,
860 * but does include the high COUNT_CONTINUED flag to allow for that.
861 */
862 int page_swapcount(struct page *page)
863 {
864 int count = 0;
865 struct swap_info_struct *p;
866 swp_entry_t entry;
867
868 entry.val = page_private(page);
869 p = swap_info_get(entry);
870 if (p) {
871 count = swap_count(p->swap_map[swp_offset(entry)]);
872 spin_unlock(&p->lock);
873 }
874 return count;
875 }
876
877 /*
878 * We can write to an anon page without COW if there are no other references
879 * to it. And as a side-effect, free up its swap: because the old content
880 * on disk will never be read, and seeking back there to write new content
881 * later would only waste time away from clustering.
882 */
883 int reuse_swap_page(struct page *page)
884 {
885 int count;
886
887 VM_BUG_ON_PAGE(!PageLocked(page), page);
888 if (unlikely(PageKsm(page)))
889 return 0;
890 count = page_mapcount(page);
891 if (count <= 1 && PageSwapCache(page)) {
892 count += page_swapcount(page);
893 if (count == 1 && !PageWriteback(page)) {
894 delete_from_swap_cache(page);
895 SetPageDirty(page);
896 }
897 }
898 return count <= 1;
899 }
900
901 /*
902 * If swap is getting full, or if there are no more mappings of this page,
903 * then try_to_free_swap is called to free its swap space.
904 */
905 int try_to_free_swap(struct page *page)
906 {
907 VM_BUG_ON_PAGE(!PageLocked(page), page);
908
909 if (!PageSwapCache(page))
910 return 0;
911 if (PageWriteback(page))
912 return 0;
913 if (page_swapcount(page))
914 return 0;
915
916 /*
917 * Once hibernation has begun to create its image of memory,
918 * there's a danger that one of the calls to try_to_free_swap()
919 * - most probably a call from __try_to_reclaim_swap() while
920 * hibernation is allocating its own swap pages for the image,
921 * but conceivably even a call from memory reclaim - will free
922 * the swap from a page which has already been recorded in the
923 * image as a clean swapcache page, and then reuse its swap for
924 * another page of the image. On waking from hibernation, the
925 * original page might be freed under memory pressure, then
926 * later read back in from swap, now with the wrong data.
927 *
928 * Hibernation suspends storage while it is writing the image
929 * to disk so check that here.
930 */
931 if (pm_suspended_storage())
932 return 0;
933
934 delete_from_swap_cache(page);
935 SetPageDirty(page);
936 return 1;
937 }
938
939 /*
940 * Free the swap entry like above, but also try to
941 * free the page cache entry if it is the last user.
942 */
943 int free_swap_and_cache(swp_entry_t entry)
944 {
945 struct swap_info_struct *p;
946 struct page *page = NULL;
947
948 if (non_swap_entry(entry))
949 return 1;
950
951 p = swap_info_get(entry);
952 if (p) {
953 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
954 page = find_get_page(swap_address_space(entry),
955 entry.val);
956 if (page && !trylock_page(page)) {
957 page_cache_release(page);
958 page = NULL;
959 }
960 }
961 spin_unlock(&p->lock);
962 }
963 if (page) {
964 /*
965 * Not mapped elsewhere, or swap space full? Free it!
966 * Also recheck PageSwapCache now page is locked (above).
967 */
968 if (PageSwapCache(page) && !PageWriteback(page) &&
969 (!page_mapped(page) || vm_swap_full())) {
970 delete_from_swap_cache(page);
971 SetPageDirty(page);
972 }
973 unlock_page(page);
974 page_cache_release(page);
975 }
976 return p != NULL;
977 }
978
979 #ifdef CONFIG_HIBERNATION
980 /*
981 * Find the swap type that corresponds to given device (if any).
982 *
983 * @offset - number of the PAGE_SIZE-sized block of the device, starting
984 * from 0, in which the swap header is expected to be located.
985 *
986 * This is needed for the suspend to disk (aka swsusp).
987 */
988 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
989 {
990 struct block_device *bdev = NULL;
991 int type;
992
993 if (device)
994 bdev = bdget(device);
995
996 spin_lock(&swap_lock);
997 for (type = 0; type < nr_swapfiles; type++) {
998 struct swap_info_struct *sis = swap_info[type];
999
1000 if (!(sis->flags & SWP_WRITEOK))
1001 continue;
1002
1003 if (!bdev) {
1004 if (bdev_p)
1005 *bdev_p = bdgrab(sis->bdev);
1006
1007 spin_unlock(&swap_lock);
1008 return type;
1009 }
1010 if (bdev == sis->bdev) {
1011 struct swap_extent *se = &sis->first_swap_extent;
1012
1013 if (se->start_block == offset) {
1014 if (bdev_p)
1015 *bdev_p = bdgrab(sis->bdev);
1016
1017 spin_unlock(&swap_lock);
1018 bdput(bdev);
1019 return type;
1020 }
1021 }
1022 }
1023 spin_unlock(&swap_lock);
1024 if (bdev)
1025 bdput(bdev);
1026
1027 return -ENODEV;
1028 }
1029
1030 /*
1031 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1032 * corresponding to given index in swap_info (swap type).
1033 */
1034 sector_t swapdev_block(int type, pgoff_t offset)
1035 {
1036 struct block_device *bdev;
1037
1038 if ((unsigned int)type >= nr_swapfiles)
1039 return 0;
1040 if (!(swap_info[type]->flags & SWP_WRITEOK))
1041 return 0;
1042 return map_swap_entry(swp_entry(type, offset), &bdev);
1043 }
1044
1045 /*
1046 * Return either the total number of swap pages of given type, or the number
1047 * of free pages of that type (depending on @free)
1048 *
1049 * This is needed for software suspend
1050 */
1051 unsigned int count_swap_pages(int type, int free)
1052 {
1053 unsigned int n = 0;
1054
1055 spin_lock(&swap_lock);
1056 if ((unsigned int)type < nr_swapfiles) {
1057 struct swap_info_struct *sis = swap_info[type];
1058
1059 spin_lock(&sis->lock);
1060 if (sis->flags & SWP_WRITEOK) {
1061 n = sis->pages;
1062 if (free)
1063 n -= sis->inuse_pages;
1064 }
1065 spin_unlock(&sis->lock);
1066 }
1067 spin_unlock(&swap_lock);
1068 return n;
1069 }
1070 #endif /* CONFIG_HIBERNATION */
1071
1072 static inline int maybe_same_pte(pte_t pte, pte_t swp_pte)
1073 {
1074 #ifdef CONFIG_MEM_SOFT_DIRTY
1075 /*
1076 * When pte keeps soft dirty bit the pte generated
1077 * from swap entry does not has it, still it's same
1078 * pte from logical point of view.
1079 */
1080 pte_t swp_pte_dirty = pte_swp_mksoft_dirty(swp_pte);
1081 return pte_same(pte, swp_pte) || pte_same(pte, swp_pte_dirty);
1082 #else
1083 return pte_same(pte, swp_pte);
1084 #endif
1085 }
1086
1087 /*
1088 * No need to decide whether this PTE shares the swap entry with others,
1089 * just let do_wp_page work it out if a write is requested later - to
1090 * force COW, vm_page_prot omits write permission from any private vma.
1091 */
1092 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1093 unsigned long addr, swp_entry_t entry, struct page *page)
1094 {
1095 struct page *swapcache;
1096 struct mem_cgroup *memcg;
1097 spinlock_t *ptl;
1098 pte_t *pte;
1099 int ret = 1;
1100
1101 swapcache = page;
1102 page = ksm_might_need_to_copy(page, vma, addr);
1103 if (unlikely(!page))
1104 return -ENOMEM;
1105
1106 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg)) {
1107 ret = -ENOMEM;
1108 goto out_nolock;
1109 }
1110
1111 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1112 if (unlikely(!maybe_same_pte(*pte, swp_entry_to_pte(entry)))) {
1113 mem_cgroup_cancel_charge(page, memcg);
1114 ret = 0;
1115 goto out;
1116 }
1117
1118 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1119 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1120 get_page(page);
1121 set_pte_at(vma->vm_mm, addr, pte,
1122 pte_mkold(mk_pte(page, vma->vm_page_prot)));
1123 if (page == swapcache) {
1124 page_add_anon_rmap(page, vma, addr);
1125 mem_cgroup_commit_charge(page, memcg, true);
1126 } else { /* ksm created a completely new copy */
1127 page_add_new_anon_rmap(page, vma, addr);
1128 mem_cgroup_commit_charge(page, memcg, false);
1129 lru_cache_add_active_or_unevictable(page, vma);
1130 }
1131 swap_free(entry);
1132 /*
1133 * Move the page to the active list so it is not
1134 * immediately swapped out again after swapon.
1135 */
1136 activate_page(page);
1137 out:
1138 pte_unmap_unlock(pte, ptl);
1139 out_nolock:
1140 if (page != swapcache) {
1141 unlock_page(page);
1142 put_page(page);
1143 }
1144 return ret;
1145 }
1146
1147 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1148 unsigned long addr, unsigned long end,
1149 swp_entry_t entry, struct page *page)
1150 {
1151 pte_t swp_pte = swp_entry_to_pte(entry);
1152 pte_t *pte;
1153 int ret = 0;
1154
1155 /*
1156 * We don't actually need pte lock while scanning for swp_pte: since
1157 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
1158 * page table while we're scanning; though it could get zapped, and on
1159 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
1160 * of unmatched parts which look like swp_pte, so unuse_pte must
1161 * recheck under pte lock. Scanning without pte lock lets it be
1162 * preemptable whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
1163 */
1164 pte = pte_offset_map(pmd, addr);
1165 do {
1166 /*
1167 * swapoff spends a _lot_ of time in this loop!
1168 * Test inline before going to call unuse_pte.
1169 */
1170 if (unlikely(maybe_same_pte(*pte, swp_pte))) {
1171 pte_unmap(pte);
1172 ret = unuse_pte(vma, pmd, addr, entry, page);
1173 if (ret)
1174 goto out;
1175 pte = pte_offset_map(pmd, addr);
1176 }
1177 } while (pte++, addr += PAGE_SIZE, addr != end);
1178 pte_unmap(pte - 1);
1179 out:
1180 return ret;
1181 }
1182
1183 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
1184 unsigned long addr, unsigned long end,
1185 swp_entry_t entry, struct page *page)
1186 {
1187 pmd_t *pmd;
1188 unsigned long next;
1189 int ret;
1190
1191 pmd = pmd_offset(pud, addr);
1192 do {
1193 next = pmd_addr_end(addr, end);
1194 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1195 continue;
1196 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
1197 if (ret)
1198 return ret;
1199 } while (pmd++, addr = next, addr != end);
1200 return 0;
1201 }
1202
1203 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
1204 unsigned long addr, unsigned long end,
1205 swp_entry_t entry, struct page *page)
1206 {
1207 pud_t *pud;
1208 unsigned long next;
1209 int ret;
1210
1211 pud = pud_offset(pgd, addr);
1212 do {
1213 next = pud_addr_end(addr, end);
1214 if (pud_none_or_clear_bad(pud))
1215 continue;
1216 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
1217 if (ret)
1218 return ret;
1219 } while (pud++, addr = next, addr != end);
1220 return 0;
1221 }
1222
1223 static int unuse_vma(struct vm_area_struct *vma,
1224 swp_entry_t entry, struct page *page)
1225 {
1226 pgd_t *pgd;
1227 unsigned long addr, end, next;
1228 int ret;
1229
1230 if (page_anon_vma(page)) {
1231 addr = page_address_in_vma(page, vma);
1232 if (addr == -EFAULT)
1233 return 0;
1234 else
1235 end = addr + PAGE_SIZE;
1236 } else {
1237 addr = vma->vm_start;
1238 end = vma->vm_end;
1239 }
1240
1241 pgd = pgd_offset(vma->vm_mm, addr);
1242 do {
1243 next = pgd_addr_end(addr, end);
1244 if (pgd_none_or_clear_bad(pgd))
1245 continue;
1246 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
1247 if (ret)
1248 return ret;
1249 } while (pgd++, addr = next, addr != end);
1250 return 0;
1251 }
1252
1253 static int unuse_mm(struct mm_struct *mm,
1254 swp_entry_t entry, struct page *page)
1255 {
1256 struct vm_area_struct *vma;
1257 int ret = 0;
1258
1259 if (!down_read_trylock(&mm->mmap_sem)) {
1260 /*
1261 * Activate page so shrink_inactive_list is unlikely to unmap
1262 * its ptes while lock is dropped, so swapoff can make progress.
1263 */
1264 activate_page(page);
1265 unlock_page(page);
1266 down_read(&mm->mmap_sem);
1267 lock_page(page);
1268 }
1269 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1270 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
1271 break;
1272 }
1273 up_read(&mm->mmap_sem);
1274 return (ret < 0)? ret: 0;
1275 }
1276
1277 /*
1278 * Scan swap_map (or frontswap_map if frontswap parameter is true)
1279 * from current position to next entry still in use.
1280 * Recycle to start on reaching the end, returning 0 when empty.
1281 */
1282 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
1283 unsigned int prev, bool frontswap)
1284 {
1285 unsigned int max = si->max;
1286 unsigned int i = prev;
1287 unsigned char count;
1288
1289 /*
1290 * No need for swap_lock here: we're just looking
1291 * for whether an entry is in use, not modifying it; false
1292 * hits are okay, and sys_swapoff() has already prevented new
1293 * allocations from this area (while holding swap_lock).
1294 */
1295 for (;;) {
1296 if (++i >= max) {
1297 if (!prev) {
1298 i = 0;
1299 break;
1300 }
1301 /*
1302 * No entries in use at top of swap_map,
1303 * loop back to start and recheck there.
1304 */
1305 max = prev + 1;
1306 prev = 0;
1307 i = 1;
1308 }
1309 if (frontswap) {
1310 if (frontswap_test(si, i))
1311 break;
1312 else
1313 continue;
1314 }
1315 count = ACCESS_ONCE(si->swap_map[i]);
1316 if (count && swap_count(count) != SWAP_MAP_BAD)
1317 break;
1318 }
1319 return i;
1320 }
1321
1322 /*
1323 * We completely avoid races by reading each swap page in advance,
1324 * and then search for the process using it. All the necessary
1325 * page table adjustments can then be made atomically.
1326 *
1327 * if the boolean frontswap is true, only unuse pages_to_unuse pages;
1328 * pages_to_unuse==0 means all pages; ignored if frontswap is false
1329 */
1330 int try_to_unuse(unsigned int type, bool frontswap,
1331 unsigned long pages_to_unuse)
1332 {
1333 struct swap_info_struct *si = swap_info[type];
1334 struct mm_struct *start_mm;
1335 volatile unsigned char *swap_map; /* swap_map is accessed without
1336 * locking. Mark it as volatile
1337 * to prevent compiler doing
1338 * something odd.
1339 */
1340 unsigned char swcount;
1341 struct page *page;
1342 swp_entry_t entry;
1343 unsigned int i = 0;
1344 int retval = 0;
1345
1346 /*
1347 * When searching mms for an entry, a good strategy is to
1348 * start at the first mm we freed the previous entry from
1349 * (though actually we don't notice whether we or coincidence
1350 * freed the entry). Initialize this start_mm with a hold.
1351 *
1352 * A simpler strategy would be to start at the last mm we
1353 * freed the previous entry from; but that would take less
1354 * advantage of mmlist ordering, which clusters forked mms
1355 * together, child after parent. If we race with dup_mmap(), we
1356 * prefer to resolve parent before child, lest we miss entries
1357 * duplicated after we scanned child: using last mm would invert
1358 * that.
1359 */
1360 start_mm = &init_mm;
1361 atomic_inc(&init_mm.mm_users);
1362
1363 /*
1364 * Keep on scanning until all entries have gone. Usually,
1365 * one pass through swap_map is enough, but not necessarily:
1366 * there are races when an instance of an entry might be missed.
1367 */
1368 while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
1369 if (signal_pending(current)) {
1370 retval = -EINTR;
1371 break;
1372 }
1373
1374 /*
1375 * Get a page for the entry, using the existing swap
1376 * cache page if there is one. Otherwise, get a clean
1377 * page and read the swap into it.
1378 */
1379 swap_map = &si->swap_map[i];
1380 entry = swp_entry(type, i);
1381 page = read_swap_cache_async(entry,
1382 GFP_HIGHUSER_MOVABLE, NULL, 0);
1383 if (!page) {
1384 /*
1385 * Either swap_duplicate() failed because entry
1386 * has been freed independently, and will not be
1387 * reused since sys_swapoff() already disabled
1388 * allocation from here, or alloc_page() failed.
1389 */
1390 swcount = *swap_map;
1391 /*
1392 * We don't hold lock here, so the swap entry could be
1393 * SWAP_MAP_BAD (when the cluster is discarding).
1394 * Instead of fail out, We can just skip the swap
1395 * entry because swapoff will wait for discarding
1396 * finish anyway.
1397 */
1398 if (!swcount || swcount == SWAP_MAP_BAD)
1399 continue;
1400 retval = -ENOMEM;
1401 break;
1402 }
1403
1404 /*
1405 * Don't hold on to start_mm if it looks like exiting.
1406 */
1407 if (atomic_read(&start_mm->mm_users) == 1) {
1408 mmput(start_mm);
1409 start_mm = &init_mm;
1410 atomic_inc(&init_mm.mm_users);
1411 }
1412
1413 /*
1414 * Wait for and lock page. When do_swap_page races with
1415 * try_to_unuse, do_swap_page can handle the fault much
1416 * faster than try_to_unuse can locate the entry. This
1417 * apparently redundant "wait_on_page_locked" lets try_to_unuse
1418 * defer to do_swap_page in such a case - in some tests,
1419 * do_swap_page and try_to_unuse repeatedly compete.
1420 */
1421 wait_on_page_locked(page);
1422 wait_on_page_writeback(page);
1423 lock_page(page);
1424 wait_on_page_writeback(page);
1425
1426 /*
1427 * Remove all references to entry.
1428 */
1429 swcount = *swap_map;
1430 if (swap_count(swcount) == SWAP_MAP_SHMEM) {
1431 retval = shmem_unuse(entry, page);
1432 /* page has already been unlocked and released */
1433 if (retval < 0)
1434 break;
1435 continue;
1436 }
1437 if (swap_count(swcount) && start_mm != &init_mm)
1438 retval = unuse_mm(start_mm, entry, page);
1439
1440 if (swap_count(*swap_map)) {
1441 int set_start_mm = (*swap_map >= swcount);
1442 struct list_head *p = &start_mm->mmlist;
1443 struct mm_struct *new_start_mm = start_mm;
1444 struct mm_struct *prev_mm = start_mm;
1445 struct mm_struct *mm;
1446
1447 atomic_inc(&new_start_mm->mm_users);
1448 atomic_inc(&prev_mm->mm_users);
1449 spin_lock(&mmlist_lock);
1450 while (swap_count(*swap_map) && !retval &&
1451 (p = p->next) != &start_mm->mmlist) {
1452 mm = list_entry(p, struct mm_struct, mmlist);
1453 if (!atomic_inc_not_zero(&mm->mm_users))
1454 continue;
1455 spin_unlock(&mmlist_lock);
1456 mmput(prev_mm);
1457 prev_mm = mm;
1458
1459 cond_resched();
1460
1461 swcount = *swap_map;
1462 if (!swap_count(swcount)) /* any usage ? */
1463 ;
1464 else if (mm == &init_mm)
1465 set_start_mm = 1;
1466 else
1467 retval = unuse_mm(mm, entry, page);
1468
1469 if (set_start_mm && *swap_map < swcount) {
1470 mmput(new_start_mm);
1471 atomic_inc(&mm->mm_users);
1472 new_start_mm = mm;
1473 set_start_mm = 0;
1474 }
1475 spin_lock(&mmlist_lock);
1476 }
1477 spin_unlock(&mmlist_lock);
1478 mmput(prev_mm);
1479 mmput(start_mm);
1480 start_mm = new_start_mm;
1481 }
1482 if (retval) {
1483 unlock_page(page);
1484 page_cache_release(page);
1485 break;
1486 }
1487
1488 /*
1489 * If a reference remains (rare), we would like to leave
1490 * the page in the swap cache; but try_to_unmap could
1491 * then re-duplicate the entry once we drop page lock,
1492 * so we might loop indefinitely; also, that page could
1493 * not be swapped out to other storage meanwhile. So:
1494 * delete from cache even if there's another reference,
1495 * after ensuring that the data has been saved to disk -
1496 * since if the reference remains (rarer), it will be
1497 * read from disk into another page. Splitting into two
1498 * pages would be incorrect if swap supported "shared
1499 * private" pages, but they are handled by tmpfs files.
1500 *
1501 * Given how unuse_vma() targets one particular offset
1502 * in an anon_vma, once the anon_vma has been determined,
1503 * this splitting happens to be just what is needed to
1504 * handle where KSM pages have been swapped out: re-reading
1505 * is unnecessarily slow, but we can fix that later on.
1506 */
1507 if (swap_count(*swap_map) &&
1508 PageDirty(page) && PageSwapCache(page)) {
1509 struct writeback_control wbc = {
1510 .sync_mode = WB_SYNC_NONE,
1511 };
1512
1513 swap_writepage(page, &wbc);
1514 lock_page(page);
1515 wait_on_page_writeback(page);
1516 }
1517
1518 /*
1519 * It is conceivable that a racing task removed this page from
1520 * swap cache just before we acquired the page lock at the top,
1521 * or while we dropped it in unuse_mm(). The page might even
1522 * be back in swap cache on another swap area: that we must not
1523 * delete, since it may not have been written out to swap yet.
1524 */
1525 if (PageSwapCache(page) &&
1526 likely(page_private(page) == entry.val))
1527 delete_from_swap_cache(page);
1528
1529 /*
1530 * So we could skip searching mms once swap count went
1531 * to 1, we did not mark any present ptes as dirty: must
1532 * mark page dirty so shrink_page_list will preserve it.
1533 */
1534 SetPageDirty(page);
1535 unlock_page(page);
1536 page_cache_release(page);
1537
1538 /*
1539 * Make sure that we aren't completely killing
1540 * interactive performance.
1541 */
1542 cond_resched();
1543 if (frontswap && pages_to_unuse > 0) {
1544 if (!--pages_to_unuse)
1545 break;
1546 }
1547 }
1548
1549 mmput(start_mm);
1550 return retval;
1551 }
1552
1553 /*
1554 * After a successful try_to_unuse, if no swap is now in use, we know
1555 * we can empty the mmlist. swap_lock must be held on entry and exit.
1556 * Note that mmlist_lock nests inside swap_lock, and an mm must be
1557 * added to the mmlist just after page_duplicate - before would be racy.
1558 */
1559 static void drain_mmlist(void)
1560 {
1561 struct list_head *p, *next;
1562 unsigned int type;
1563
1564 for (type = 0; type < nr_swapfiles; type++)
1565 if (swap_info[type]->inuse_pages)
1566 return;
1567 spin_lock(&mmlist_lock);
1568 list_for_each_safe(p, next, &init_mm.mmlist)
1569 list_del_init(p);
1570 spin_unlock(&mmlist_lock);
1571 }
1572
1573 /*
1574 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1575 * corresponds to page offset for the specified swap entry.
1576 * Note that the type of this function is sector_t, but it returns page offset
1577 * into the bdev, not sector offset.
1578 */
1579 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
1580 {
1581 struct swap_info_struct *sis;
1582 struct swap_extent *start_se;
1583 struct swap_extent *se;
1584 pgoff_t offset;
1585
1586 sis = swap_info[swp_type(entry)];
1587 *bdev = sis->bdev;
1588
1589 offset = swp_offset(entry);
1590 start_se = sis->curr_swap_extent;
1591 se = start_se;
1592
1593 for ( ; ; ) {
1594 struct list_head *lh;
1595
1596 if (se->start_page <= offset &&
1597 offset < (se->start_page + se->nr_pages)) {
1598 return se->start_block + (offset - se->start_page);
1599 }
1600 lh = se->list.next;
1601 se = list_entry(lh, struct swap_extent, list);
1602 sis->curr_swap_extent = se;
1603 BUG_ON(se == start_se); /* It *must* be present */
1604 }
1605 }
1606
1607 /*
1608 * Returns the page offset into bdev for the specified page's swap entry.
1609 */
1610 sector_t map_swap_page(struct page *page, struct block_device **bdev)
1611 {
1612 swp_entry_t entry;
1613 entry.val = page_private(page);
1614 return map_swap_entry(entry, bdev);
1615 }
1616
1617 /*
1618 * Free all of a swapdev's extent information
1619 */
1620 static void destroy_swap_extents(struct swap_info_struct *sis)
1621 {
1622 while (!list_empty(&sis->first_swap_extent.list)) {
1623 struct swap_extent *se;
1624
1625 se = list_entry(sis->first_swap_extent.list.next,
1626 struct swap_extent, list);
1627 list_del(&se->list);
1628 kfree(se);
1629 }
1630
1631 if (sis->flags & SWP_FILE) {
1632 struct file *swap_file = sis->swap_file;
1633 struct address_space *mapping = swap_file->f_mapping;
1634
1635 sis->flags &= ~SWP_FILE;
1636 mapping->a_ops->swap_deactivate(swap_file);
1637 }
1638 }
1639
1640 /*
1641 * Add a block range (and the corresponding page range) into this swapdev's
1642 * extent list. The extent list is kept sorted in page order.
1643 *
1644 * This function rather assumes that it is called in ascending page order.
1645 */
1646 int
1647 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1648 unsigned long nr_pages, sector_t start_block)
1649 {
1650 struct swap_extent *se;
1651 struct swap_extent *new_se;
1652 struct list_head *lh;
1653
1654 if (start_page == 0) {
1655 se = &sis->first_swap_extent;
1656 sis->curr_swap_extent = se;
1657 se->start_page = 0;
1658 se->nr_pages = nr_pages;
1659 se->start_block = start_block;
1660 return 1;
1661 } else {
1662 lh = sis->first_swap_extent.list.prev; /* Highest extent */
1663 se = list_entry(lh, struct swap_extent, list);
1664 BUG_ON(se->start_page + se->nr_pages != start_page);
1665 if (se->start_block + se->nr_pages == start_block) {
1666 /* Merge it */
1667 se->nr_pages += nr_pages;
1668 return 0;
1669 }
1670 }
1671
1672 /*
1673 * No merge. Insert a new extent, preserving ordering.
1674 */
1675 new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1676 if (new_se == NULL)
1677 return -ENOMEM;
1678 new_se->start_page = start_page;
1679 new_se->nr_pages = nr_pages;
1680 new_se->start_block = start_block;
1681
1682 list_add_tail(&new_se->list, &sis->first_swap_extent.list);
1683 return 1;
1684 }
1685
1686 /*
1687 * A `swap extent' is a simple thing which maps a contiguous range of pages
1688 * onto a contiguous range of disk blocks. An ordered list of swap extents
1689 * is built at swapon time and is then used at swap_writepage/swap_readpage
1690 * time for locating where on disk a page belongs.
1691 *
1692 * If the swapfile is an S_ISBLK block device, a single extent is installed.
1693 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1694 * swap files identically.
1695 *
1696 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1697 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK
1698 * swapfiles are handled *identically* after swapon time.
1699 *
1700 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1701 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If
1702 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1703 * requirements, they are simply tossed out - we will never use those blocks
1704 * for swapping.
1705 *
1706 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
1707 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1708 * which will scribble on the fs.
1709 *
1710 * The amount of disk space which a single swap extent represents varies.
1711 * Typically it is in the 1-4 megabyte range. So we can have hundreds of
1712 * extents in the list. To avoid much list walking, we cache the previous
1713 * search location in `curr_swap_extent', and start new searches from there.
1714 * This is extremely effective. The average number of iterations in
1715 * map_swap_page() has been measured at about 0.3 per page. - akpm.
1716 */
1717 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1718 {
1719 struct file *swap_file = sis->swap_file;
1720 struct address_space *mapping = swap_file->f_mapping;
1721 struct inode *inode = mapping->host;
1722 int ret;
1723
1724 if (S_ISBLK(inode->i_mode)) {
1725 ret = add_swap_extent(sis, 0, sis->max, 0);
1726 *span = sis->pages;
1727 return ret;
1728 }
1729
1730 if (mapping->a_ops->swap_activate) {
1731 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
1732 if (!ret) {
1733 sis->flags |= SWP_FILE;
1734 ret = add_swap_extent(sis, 0, sis->max, 0);
1735 *span = sis->pages;
1736 }
1737 return ret;
1738 }
1739
1740 return generic_swapfile_activate(sis, swap_file, span);
1741 }
1742
1743 static void _enable_swap_info(struct swap_info_struct *p, int prio,
1744 unsigned char *swap_map,
1745 struct swap_cluster_info *cluster_info)
1746 {
1747 if (prio >= 0)
1748 p->prio = prio;
1749 else
1750 p->prio = --least_priority;
1751 /*
1752 * the plist prio is negated because plist ordering is
1753 * low-to-high, while swap ordering is high-to-low
1754 */
1755 p->list.prio = -p->prio;
1756 p->avail_list.prio = -p->prio;
1757 p->swap_map = swap_map;
1758 p->cluster_info = cluster_info;
1759 p->flags |= SWP_WRITEOK;
1760 atomic_long_add(p->pages, &nr_swap_pages);
1761 total_swap_pages += p->pages;
1762
1763 assert_spin_locked(&swap_lock);
1764 /*
1765 * both lists are plists, and thus priority ordered.
1766 * swap_active_head needs to be priority ordered for swapoff(),
1767 * which on removal of any swap_info_struct with an auto-assigned
1768 * (i.e. negative) priority increments the auto-assigned priority
1769 * of any lower-priority swap_info_structs.
1770 * swap_avail_head needs to be priority ordered for get_swap_page(),
1771 * which allocates swap pages from the highest available priority
1772 * swap_info_struct.
1773 */
1774 plist_add(&p->list, &swap_active_head);
1775 spin_lock(&swap_avail_lock);
1776 plist_add(&p->avail_list, &swap_avail_head);
1777 spin_unlock(&swap_avail_lock);
1778 }
1779
1780 static void enable_swap_info(struct swap_info_struct *p, int prio,
1781 unsigned char *swap_map,
1782 struct swap_cluster_info *cluster_info,
1783 unsigned long *frontswap_map)
1784 {
1785 frontswap_init(p->type, frontswap_map);
1786 spin_lock(&swap_lock);
1787 spin_lock(&p->lock);
1788 _enable_swap_info(p, prio, swap_map, cluster_info);
1789 spin_unlock(&p->lock);
1790 spin_unlock(&swap_lock);
1791 }
1792
1793 static void reinsert_swap_info(struct swap_info_struct *p)
1794 {
1795 spin_lock(&swap_lock);
1796 spin_lock(&p->lock);
1797 _enable_swap_info(p, p->prio, p->swap_map, p->cluster_info);
1798 spin_unlock(&p->lock);
1799 spin_unlock(&swap_lock);
1800 }
1801
1802 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1803 {
1804 struct swap_info_struct *p = NULL;
1805 unsigned char *swap_map;
1806 struct swap_cluster_info *cluster_info;
1807 unsigned long *frontswap_map;
1808 struct file *swap_file, *victim;
1809 struct address_space *mapping;
1810 struct inode *inode;
1811 struct filename *pathname;
1812 int err, found = 0;
1813 unsigned int old_block_size;
1814
1815 if (!capable(CAP_SYS_ADMIN))
1816 return -EPERM;
1817
1818 BUG_ON(!current->mm);
1819
1820 pathname = getname(specialfile);
1821 if (IS_ERR(pathname))
1822 return PTR_ERR(pathname);
1823
1824 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
1825 err = PTR_ERR(victim);
1826 if (IS_ERR(victim))
1827 goto out;
1828
1829 mapping = victim->f_mapping;
1830 spin_lock(&swap_lock);
1831 plist_for_each_entry(p, &swap_active_head, list) {
1832 if (p->flags & SWP_WRITEOK) {
1833 if (p->swap_file->f_mapping == mapping) {
1834 found = 1;
1835 break;
1836 }
1837 }
1838 }
1839 if (!found) {
1840 err = -EINVAL;
1841 spin_unlock(&swap_lock);
1842 goto out_dput;
1843 }
1844 if (!security_vm_enough_memory_mm(current->mm, p->pages))
1845 vm_unacct_memory(p->pages);
1846 else {
1847 err = -ENOMEM;
1848 spin_unlock(&swap_lock);
1849 goto out_dput;
1850 }
1851 spin_lock(&swap_avail_lock);
1852 plist_del(&p->avail_list, &swap_avail_head);
1853 spin_unlock(&swap_avail_lock);
1854 spin_lock(&p->lock);
1855 if (p->prio < 0) {
1856 struct swap_info_struct *si = p;
1857
1858 plist_for_each_entry_continue(si, &swap_active_head, list) {
1859 si->prio++;
1860 si->list.prio--;
1861 si->avail_list.prio--;
1862 }
1863 least_priority++;
1864 }
1865 plist_del(&p->list, &swap_active_head);
1866 atomic_long_sub(p->pages, &nr_swap_pages);
1867 total_swap_pages -= p->pages;
1868 p->flags &= ~SWP_WRITEOK;
1869 spin_unlock(&p->lock);
1870 spin_unlock(&swap_lock);
1871
1872 set_current_oom_origin();
1873 err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
1874 clear_current_oom_origin();
1875
1876 if (err) {
1877 /* re-insert swap space back into swap_list */
1878 reinsert_swap_info(p);
1879 goto out_dput;
1880 }
1881
1882 flush_work(&p->discard_work);
1883
1884 destroy_swap_extents(p);
1885 if (p->flags & SWP_CONTINUED)
1886 free_swap_count_continuations(p);
1887
1888 mutex_lock(&swapon_mutex);
1889 spin_lock(&swap_lock);
1890 spin_lock(&p->lock);
1891 drain_mmlist();
1892
1893 /* wait for anyone still in scan_swap_map */
1894 p->highest_bit = 0; /* cuts scans short */
1895 while (p->flags >= SWP_SCANNING) {
1896 spin_unlock(&p->lock);
1897 spin_unlock(&swap_lock);
1898 schedule_timeout_uninterruptible(1);
1899 spin_lock(&swap_lock);
1900 spin_lock(&p->lock);
1901 }
1902
1903 swap_file = p->swap_file;
1904 old_block_size = p->old_block_size;
1905 p->swap_file = NULL;
1906 p->max = 0;
1907 swap_map = p->swap_map;
1908 p->swap_map = NULL;
1909 cluster_info = p->cluster_info;
1910 p->cluster_info = NULL;
1911 frontswap_map = frontswap_map_get(p);
1912 spin_unlock(&p->lock);
1913 spin_unlock(&swap_lock);
1914 frontswap_invalidate_area(p->type);
1915 frontswap_map_set(p, NULL);
1916 mutex_unlock(&swapon_mutex);
1917 free_percpu(p->percpu_cluster);
1918 p->percpu_cluster = NULL;
1919 vfree(swap_map);
1920 vfree(cluster_info);
1921 vfree(frontswap_map);
1922 /* Destroy swap account information */
1923 swap_cgroup_swapoff(p->type);
1924
1925 inode = mapping->host;
1926 if (S_ISBLK(inode->i_mode)) {
1927 struct block_device *bdev = I_BDEV(inode);
1928 set_blocksize(bdev, old_block_size);
1929 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
1930 } else {
1931 mutex_lock(&inode->i_mutex);
1932 inode->i_flags &= ~S_SWAPFILE;
1933 mutex_unlock(&inode->i_mutex);
1934 }
1935 filp_close(swap_file, NULL);
1936
1937 /*
1938 * Clear the SWP_USED flag after all resources are freed so that swapon
1939 * can reuse this swap_info in alloc_swap_info() safely. It is ok to
1940 * not hold p->lock after we cleared its SWP_WRITEOK.
1941 */
1942 spin_lock(&swap_lock);
1943 p->flags = 0;
1944 spin_unlock(&swap_lock);
1945
1946 err = 0;
1947 atomic_inc(&proc_poll_event);
1948 wake_up_interruptible(&proc_poll_wait);
1949
1950 out_dput:
1951 filp_close(victim, NULL);
1952 out:
1953 putname(pathname);
1954 return err;
1955 }
1956
1957 #ifdef CONFIG_PROC_FS
1958 static unsigned swaps_poll(struct file *file, poll_table *wait)
1959 {
1960 struct seq_file *seq = file->private_data;
1961
1962 poll_wait(file, &proc_poll_wait, wait);
1963
1964 if (seq->poll_event != atomic_read(&proc_poll_event)) {
1965 seq->poll_event = atomic_read(&proc_poll_event);
1966 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
1967 }
1968
1969 return POLLIN | POLLRDNORM;
1970 }
1971
1972 /* iterator */
1973 static void *swap_start(struct seq_file *swap, loff_t *pos)
1974 {
1975 struct swap_info_struct *si;
1976 int type;
1977 loff_t l = *pos;
1978
1979 mutex_lock(&swapon_mutex);
1980
1981 if (!l)
1982 return SEQ_START_TOKEN;
1983
1984 for (type = 0; type < nr_swapfiles; type++) {
1985 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
1986 si = swap_info[type];
1987 if (!(si->flags & SWP_USED) || !si->swap_map)
1988 continue;
1989 if (!--l)
1990 return si;
1991 }
1992
1993 return NULL;
1994 }
1995
1996 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1997 {
1998 struct swap_info_struct *si = v;
1999 int type;
2000
2001 if (v == SEQ_START_TOKEN)
2002 type = 0;
2003 else
2004 type = si->type + 1;
2005
2006 for (; type < nr_swapfiles; type++) {
2007 smp_rmb(); /* read nr_swapfiles before swap_info[type] */
2008 si = swap_info[type];
2009 if (!(si->flags & SWP_USED) || !si->swap_map)
2010 continue;
2011 ++*pos;
2012 return si;
2013 }
2014
2015 return NULL;
2016 }
2017
2018 static void swap_stop(struct seq_file *swap, void *v)
2019 {
2020 mutex_unlock(&swapon_mutex);
2021 }
2022
2023 static int swap_show(struct seq_file *swap, void *v)
2024 {
2025 struct swap_info_struct *si = v;
2026 struct file *file;
2027 int len;
2028
2029 if (si == SEQ_START_TOKEN) {
2030 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
2031 return 0;
2032 }
2033
2034 file = si->swap_file;
2035 len = seq_path(swap, &file->f_path, " \t\n\\");
2036 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
2037 len < 40 ? 40 - len : 1, " ",
2038 S_ISBLK(file_inode(file)->i_mode) ?
2039 "partition" : "file\t",
2040 si->pages << (PAGE_SHIFT - 10),
2041 si->inuse_pages << (PAGE_SHIFT - 10),
2042 si->prio);
2043 return 0;
2044 }
2045
2046 static const struct seq_operations swaps_op = {
2047 .start = swap_start,
2048 .next = swap_next,
2049 .stop = swap_stop,
2050 .show = swap_show
2051 };
2052
2053 static int swaps_open(struct inode *inode, struct file *file)
2054 {
2055 struct seq_file *seq;
2056 int ret;
2057
2058 ret = seq_open(file, &swaps_op);
2059 if (ret)
2060 return ret;
2061
2062 seq = file->private_data;
2063 seq->poll_event = atomic_read(&proc_poll_event);
2064 return 0;
2065 }
2066
2067 static const struct file_operations proc_swaps_operations = {
2068 .open = swaps_open,
2069 .read = seq_read,
2070 .llseek = seq_lseek,
2071 .release = seq_release,
2072 .poll = swaps_poll,
2073 };
2074
2075 static int __init procswaps_init(void)
2076 {
2077 proc_create("swaps", 0, NULL, &proc_swaps_operations);
2078 return 0;
2079 }
2080 __initcall(procswaps_init);
2081 #endif /* CONFIG_PROC_FS */
2082
2083 #ifdef MAX_SWAPFILES_CHECK
2084 static int __init max_swapfiles_check(void)
2085 {
2086 MAX_SWAPFILES_CHECK();
2087 return 0;
2088 }
2089 late_initcall(max_swapfiles_check);
2090 #endif
2091
2092 static struct swap_info_struct *alloc_swap_info(void)
2093 {
2094 struct swap_info_struct *p;
2095 unsigned int type;
2096
2097 p = kzalloc(sizeof(*p), GFP_KERNEL);
2098 if (!p)
2099 return ERR_PTR(-ENOMEM);
2100
2101 spin_lock(&swap_lock);
2102 for (type = 0; type < nr_swapfiles; type++) {
2103 if (!(swap_info[type]->flags & SWP_USED))
2104 break;
2105 }
2106 if (type >= MAX_SWAPFILES) {
2107 spin_unlock(&swap_lock);
2108 kfree(p);
2109 return ERR_PTR(-EPERM);
2110 }
2111 if (type >= nr_swapfiles) {
2112 p->type = type;
2113 swap_info[type] = p;
2114 /*
2115 * Write swap_info[type] before nr_swapfiles, in case a
2116 * racing procfs swap_start() or swap_next() is reading them.
2117 * (We never shrink nr_swapfiles, we never free this entry.)
2118 */
2119 smp_wmb();
2120 nr_swapfiles++;
2121 } else {
2122 kfree(p);
2123 p = swap_info[type];
2124 /*
2125 * Do not memset this entry: a racing procfs swap_next()
2126 * would be relying on p->type to remain valid.
2127 */
2128 }
2129 INIT_LIST_HEAD(&p->first_swap_extent.list);
2130 plist_node_init(&p->list, 0);
2131 plist_node_init(&p->avail_list, 0);
2132 p->flags = SWP_USED;
2133 spin_unlock(&swap_lock);
2134 spin_lock_init(&p->lock);
2135
2136 return p;
2137 }
2138
2139 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2140 {
2141 int error;
2142
2143 if (S_ISBLK(inode->i_mode)) {
2144 p->bdev = bdgrab(I_BDEV(inode));
2145 error = blkdev_get(p->bdev,
2146 FMODE_READ | FMODE_WRITE | FMODE_EXCL,
2147 sys_swapon);
2148 if (error < 0) {
2149 p->bdev = NULL;
2150 return -EINVAL;
2151 }
2152 p->old_block_size = block_size(p->bdev);
2153 error = set_blocksize(p->bdev, PAGE_SIZE);
2154 if (error < 0)
2155 return error;
2156 p->flags |= SWP_BLKDEV;
2157 } else if (S_ISREG(inode->i_mode)) {
2158 p->bdev = inode->i_sb->s_bdev;
2159 mutex_lock(&inode->i_mutex);
2160 if (IS_SWAPFILE(inode))
2161 return -EBUSY;
2162 } else
2163 return -EINVAL;
2164
2165 return 0;
2166 }
2167
2168 static unsigned long read_swap_header(struct swap_info_struct *p,
2169 union swap_header *swap_header,
2170 struct inode *inode)
2171 {
2172 int i;
2173 unsigned long maxpages;
2174 unsigned long swapfilepages;
2175 unsigned long last_page;
2176
2177 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2178 pr_err("Unable to find swap-space signature\n");
2179 return 0;
2180 }
2181
2182 /* swap partition endianess hack... */
2183 if (swab32(swap_header->info.version) == 1) {
2184 swab32s(&swap_header->info.version);
2185 swab32s(&swap_header->info.last_page);
2186 swab32s(&swap_header->info.nr_badpages);
2187 for (i = 0; i < swap_header->info.nr_badpages; i++)
2188 swab32s(&swap_header->info.badpages[i]);
2189 }
2190 /* Check the swap header's sub-version */
2191 if (swap_header->info.version != 1) {
2192 pr_warn("Unable to handle swap header version %d\n",
2193 swap_header->info.version);
2194 return 0;
2195 }
2196
2197 p->lowest_bit = 1;
2198 p->cluster_next = 1;
2199 p->cluster_nr = 0;
2200
2201 /*
2202 * Find out how many pages are allowed for a single swap
2203 * device. There are two limiting factors: 1) the number
2204 * of bits for the swap offset in the swp_entry_t type, and
2205 * 2) the number of bits in the swap pte as defined by the
2206 * different architectures. In order to find the
2207 * largest possible bit mask, a swap entry with swap type 0
2208 * and swap offset ~0UL is created, encoded to a swap pte,
2209 * decoded to a swp_entry_t again, and finally the swap
2210 * offset is extracted. This will mask all the bits from
2211 * the initial ~0UL mask that can't be encoded in either
2212 * the swp_entry_t or the architecture definition of a
2213 * swap pte.
2214 */
2215 maxpages = swp_offset(pte_to_swp_entry(
2216 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2217 last_page = swap_header->info.last_page;
2218 if (last_page > maxpages) {
2219 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2220 maxpages << (PAGE_SHIFT - 10),
2221 last_page << (PAGE_SHIFT - 10));
2222 }
2223 if (maxpages > last_page) {
2224 maxpages = last_page + 1;
2225 /* p->max is an unsigned int: don't overflow it */
2226 if ((unsigned int)maxpages == 0)
2227 maxpages = UINT_MAX;
2228 }
2229 p->highest_bit = maxpages - 1;
2230
2231 if (!maxpages)
2232 return 0;
2233 swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2234 if (swapfilepages && maxpages > swapfilepages) {
2235 pr_warn("Swap area shorter than signature indicates\n");
2236 return 0;
2237 }
2238 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2239 return 0;
2240 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2241 return 0;
2242
2243 return maxpages;
2244 }
2245
2246 static int setup_swap_map_and_extents(struct swap_info_struct *p,
2247 union swap_header *swap_header,
2248 unsigned char *swap_map,
2249 struct swap_cluster_info *cluster_info,
2250 unsigned long maxpages,
2251 sector_t *span)
2252 {
2253 int i;
2254 unsigned int nr_good_pages;
2255 int nr_extents;
2256 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
2257 unsigned long idx = p->cluster_next / SWAPFILE_CLUSTER;
2258
2259 nr_good_pages = maxpages - 1; /* omit header page */
2260
2261 cluster_set_null(&p->free_cluster_head);
2262 cluster_set_null(&p->free_cluster_tail);
2263 cluster_set_null(&p->discard_cluster_head);
2264 cluster_set_null(&p->discard_cluster_tail);
2265
2266 for (i = 0; i < swap_header->info.nr_badpages; i++) {
2267 unsigned int page_nr = swap_header->info.badpages[i];
2268 if (page_nr == 0 || page_nr > swap_header->info.last_page)
2269 return -EINVAL;
2270 if (page_nr < maxpages) {
2271 swap_map[page_nr] = SWAP_MAP_BAD;
2272 nr_good_pages--;
2273 /*
2274 * Haven't marked the cluster free yet, no list
2275 * operation involved
2276 */
2277 inc_cluster_info_page(p, cluster_info, page_nr);
2278 }
2279 }
2280
2281 /* Haven't marked the cluster free yet, no list operation involved */
2282 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
2283 inc_cluster_info_page(p, cluster_info, i);
2284
2285 if (nr_good_pages) {
2286 swap_map[0] = SWAP_MAP_BAD;
2287 /*
2288 * Not mark the cluster free yet, no list
2289 * operation involved
2290 */
2291 inc_cluster_info_page(p, cluster_info, 0);
2292 p->max = maxpages;
2293 p->pages = nr_good_pages;
2294 nr_extents = setup_swap_extents(p, span);
2295 if (nr_extents < 0)
2296 return nr_extents;
2297 nr_good_pages = p->pages;
2298 }
2299 if (!nr_good_pages) {
2300 pr_warn("Empty swap-file\n");
2301 return -EINVAL;
2302 }
2303
2304 if (!cluster_info)
2305 return nr_extents;
2306
2307 for (i = 0; i < nr_clusters; i++) {
2308 if (!cluster_count(&cluster_info[idx])) {
2309 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
2310 if (cluster_is_null(&p->free_cluster_head)) {
2311 cluster_set_next_flag(&p->free_cluster_head,
2312 idx, 0);
2313 cluster_set_next_flag(&p->free_cluster_tail,
2314 idx, 0);
2315 } else {
2316 unsigned int tail;
2317
2318 tail = cluster_next(&p->free_cluster_tail);
2319 cluster_set_next(&cluster_info[tail], idx);
2320 cluster_set_next_flag(&p->free_cluster_tail,
2321 idx, 0);
2322 }
2323 }
2324 idx++;
2325 if (idx == nr_clusters)
2326 idx = 0;
2327 }
2328 return nr_extents;
2329 }
2330
2331 /*
2332 * Helper to sys_swapon determining if a given swap
2333 * backing device queue supports DISCARD operations.
2334 */
2335 static bool swap_discardable(struct swap_info_struct *si)
2336 {
2337 struct request_queue *q = bdev_get_queue(si->bdev);
2338
2339 if (!q || !blk_queue_discard(q))
2340 return false;
2341
2342 return true;
2343 }
2344
2345 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
2346 {
2347 struct swap_info_struct *p;
2348 struct filename *name;
2349 struct file *swap_file = NULL;
2350 struct address_space *mapping;
2351 int i;
2352 int prio;
2353 int error;
2354 union swap_header *swap_header;
2355 int nr_extents;
2356 sector_t span;
2357 unsigned long maxpages;
2358 unsigned char *swap_map = NULL;
2359 struct swap_cluster_info *cluster_info = NULL;
2360 unsigned long *frontswap_map = NULL;
2361 struct page *page = NULL;
2362 struct inode *inode = NULL;
2363
2364 if (swap_flags & ~SWAP_FLAGS_VALID)
2365 return -EINVAL;
2366
2367 if (!capable(CAP_SYS_ADMIN))
2368 return -EPERM;
2369
2370 p = alloc_swap_info();
2371 if (IS_ERR(p))
2372 return PTR_ERR(p);
2373
2374 INIT_WORK(&p->discard_work, swap_discard_work);
2375
2376 name = getname(specialfile);
2377 if (IS_ERR(name)) {
2378 error = PTR_ERR(name);
2379 name = NULL;
2380 goto bad_swap;
2381 }
2382 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
2383 if (IS_ERR(swap_file)) {
2384 error = PTR_ERR(swap_file);
2385 swap_file = NULL;
2386 goto bad_swap;
2387 }
2388
2389 p->swap_file = swap_file;
2390 mapping = swap_file->f_mapping;
2391
2392 for (i = 0; i < nr_swapfiles; i++) {
2393 struct swap_info_struct *q = swap_info[i];
2394
2395 if (q == p || !q->swap_file)
2396 continue;
2397 if (mapping == q->swap_file->f_mapping) {
2398 error = -EBUSY;
2399 goto bad_swap;
2400 }
2401 }
2402
2403 inode = mapping->host;
2404 /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
2405 error = claim_swapfile(p, inode);
2406 if (unlikely(error))
2407 goto bad_swap;
2408
2409 /*
2410 * Read the swap header.
2411 */
2412 if (!mapping->a_ops->readpage) {
2413 error = -EINVAL;
2414 goto bad_swap;
2415 }
2416 page = read_mapping_page(mapping, 0, swap_file);
2417 if (IS_ERR(page)) {
2418 error = PTR_ERR(page);
2419 goto bad_swap;
2420 }
2421 swap_header = kmap(page);
2422
2423 maxpages = read_swap_header(p, swap_header, inode);
2424 if (unlikely(!maxpages)) {
2425 error = -EINVAL;
2426 goto bad_swap;
2427 }
2428
2429 /* OK, set up the swap map and apply the bad block list */
2430 swap_map = vzalloc(maxpages);
2431 if (!swap_map) {
2432 error = -ENOMEM;
2433 goto bad_swap;
2434 }
2435 if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
2436 p->flags |= SWP_SOLIDSTATE;
2437 /*
2438 * select a random position to start with to help wear leveling
2439 * SSD
2440 */
2441 p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
2442
2443 cluster_info = vzalloc(DIV_ROUND_UP(maxpages,
2444 SWAPFILE_CLUSTER) * sizeof(*cluster_info));
2445 if (!cluster_info) {
2446 error = -ENOMEM;
2447 goto bad_swap;
2448 }
2449 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
2450 if (!p->percpu_cluster) {
2451 error = -ENOMEM;
2452 goto bad_swap;
2453 }
2454 for_each_possible_cpu(i) {
2455 struct percpu_cluster *cluster;
2456 cluster = per_cpu_ptr(p->percpu_cluster, i);
2457 cluster_set_null(&cluster->index);
2458 }
2459 }
2460
2461 error = swap_cgroup_swapon(p->type, maxpages);
2462 if (error)
2463 goto bad_swap;
2464
2465 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
2466 cluster_info, maxpages, &span);
2467 if (unlikely(nr_extents < 0)) {
2468 error = nr_extents;
2469 goto bad_swap;
2470 }
2471 /* frontswap enabled? set up bit-per-page map for frontswap */
2472 if (frontswap_enabled)
2473 frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long));
2474
2475 if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
2476 /*
2477 * When discard is enabled for swap with no particular
2478 * policy flagged, we set all swap discard flags here in
2479 * order to sustain backward compatibility with older
2480 * swapon(8) releases.
2481 */
2482 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
2483 SWP_PAGE_DISCARD);
2484
2485 /*
2486 * By flagging sys_swapon, a sysadmin can tell us to
2487 * either do single-time area discards only, or to just
2488 * perform discards for released swap page-clusters.
2489 * Now it's time to adjust the p->flags accordingly.
2490 */
2491 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
2492 p->flags &= ~SWP_PAGE_DISCARD;
2493 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
2494 p->flags &= ~SWP_AREA_DISCARD;
2495
2496 /* issue a swapon-time discard if it's still required */
2497 if (p->flags & SWP_AREA_DISCARD) {
2498 int err = discard_swap(p);
2499 if (unlikely(err))
2500 pr_err("swapon: discard_swap(%p): %d\n",
2501 p, err);
2502 }
2503 }
2504
2505 mutex_lock(&swapon_mutex);
2506 prio = -1;
2507 if (swap_flags & SWAP_FLAG_PREFER)
2508 prio =
2509 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
2510 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
2511
2512 pr_info("Adding %uk swap on %s. "
2513 "Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
2514 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
2515 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
2516 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
2517 (p->flags & SWP_DISCARDABLE) ? "D" : "",
2518 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
2519 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
2520 (frontswap_map) ? "FS" : "");
2521
2522 mutex_unlock(&swapon_mutex);
2523 atomic_inc(&proc_poll_event);
2524 wake_up_interruptible(&proc_poll_wait);
2525
2526 if (S_ISREG(inode->i_mode))
2527 inode->i_flags |= S_SWAPFILE;
2528 error = 0;
2529 goto out;
2530 bad_swap:
2531 free_percpu(p->percpu_cluster);
2532 p->percpu_cluster = NULL;
2533 if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
2534 set_blocksize(p->bdev, p->old_block_size);
2535 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2536 }
2537 destroy_swap_extents(p);
2538 swap_cgroup_swapoff(p->type);
2539 spin_lock(&swap_lock);
2540 p->swap_file = NULL;
2541 p->flags = 0;
2542 spin_unlock(&swap_lock);
2543 vfree(swap_map);
2544 vfree(cluster_info);
2545 if (swap_file) {
2546 if (inode && S_ISREG(inode->i_mode)) {
2547 mutex_unlock(&inode->i_mutex);
2548 inode = NULL;
2549 }
2550 filp_close(swap_file, NULL);
2551 }
2552 out:
2553 if (page && !IS_ERR(page)) {
2554 kunmap(page);
2555 page_cache_release(page);
2556 }
2557 if (name)
2558 putname(name);
2559 if (inode && S_ISREG(inode->i_mode))
2560 mutex_unlock(&inode->i_mutex);
2561 return error;
2562 }
2563
2564 void si_swapinfo(struct sysinfo *val)
2565 {
2566 unsigned int type;
2567 unsigned long nr_to_be_unused = 0;
2568
2569 spin_lock(&swap_lock);
2570 for (type = 0; type < nr_swapfiles; type++) {
2571 struct swap_info_struct *si = swap_info[type];
2572
2573 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
2574 nr_to_be_unused += si->inuse_pages;
2575 }
2576 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
2577 val->totalswap = total_swap_pages + nr_to_be_unused;
2578 spin_unlock(&swap_lock);
2579 }
2580
2581 /*
2582 * Verify that a swap entry is valid and increment its swap map count.
2583 *
2584 * Returns error code in following case.
2585 * - success -> 0
2586 * - swp_entry is invalid -> EINVAL
2587 * - swp_entry is migration entry -> EINVAL
2588 * - swap-cache reference is requested but there is already one. -> EEXIST
2589 * - swap-cache reference is requested but the entry is not used. -> ENOENT
2590 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
2591 */
2592 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2593 {
2594 struct swap_info_struct *p;
2595 unsigned long offset, type;
2596 unsigned char count;
2597 unsigned char has_cache;
2598 int err = -EINVAL;
2599
2600 if (non_swap_entry(entry))
2601 goto out;
2602
2603 type = swp_type(entry);
2604 if (type >= nr_swapfiles)
2605 goto bad_file;
2606 p = swap_info[type];
2607 offset = swp_offset(entry);
2608
2609 spin_lock(&p->lock);
2610 if (unlikely(offset >= p->max))
2611 goto unlock_out;
2612
2613 count = p->swap_map[offset];
2614
2615 /*
2616 * swapin_readahead() doesn't check if a swap entry is valid, so the
2617 * swap entry could be SWAP_MAP_BAD. Check here with lock held.
2618 */
2619 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
2620 err = -ENOENT;
2621 goto unlock_out;
2622 }
2623
2624 has_cache = count & SWAP_HAS_CACHE;
2625 count &= ~SWAP_HAS_CACHE;
2626 err = 0;
2627
2628 if (usage == SWAP_HAS_CACHE) {
2629
2630 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
2631 if (!has_cache && count)
2632 has_cache = SWAP_HAS_CACHE;
2633 else if (has_cache) /* someone else added cache */
2634 err = -EEXIST;
2635 else /* no users remaining */
2636 err = -ENOENT;
2637
2638 } else if (count || has_cache) {
2639
2640 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
2641 count += usage;
2642 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
2643 err = -EINVAL;
2644 else if (swap_count_continued(p, offset, count))
2645 count = COUNT_CONTINUED;
2646 else
2647 err = -ENOMEM;
2648 } else
2649 err = -ENOENT; /* unused swap entry */
2650
2651 p->swap_map[offset] = count | has_cache;
2652
2653 unlock_out:
2654 spin_unlock(&p->lock);
2655 out:
2656 return err;
2657
2658 bad_file:
2659 pr_err("swap_dup: %s%08lx\n", Bad_file, entry.val);
2660 goto out;
2661 }
2662
2663 /*
2664 * Help swapoff by noting that swap entry belongs to shmem/tmpfs
2665 * (in which case its reference count is never incremented).
2666 */
2667 void swap_shmem_alloc(swp_entry_t entry)
2668 {
2669 __swap_duplicate(entry, SWAP_MAP_SHMEM);
2670 }
2671
2672 /*
2673 * Increase reference count of swap entry by 1.
2674 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
2675 * but could not be atomically allocated. Returns 0, just as if it succeeded,
2676 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
2677 * might occur if a page table entry has got corrupted.
2678 */
2679 int swap_duplicate(swp_entry_t entry)
2680 {
2681 int err = 0;
2682
2683 while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
2684 err = add_swap_count_continuation(entry, GFP_ATOMIC);
2685 return err;
2686 }
2687
2688 /*
2689 * @entry: swap entry for which we allocate swap cache.
2690 *
2691 * Called when allocating swap cache for existing swap entry,
2692 * This can return error codes. Returns 0 at success.
2693 * -EBUSY means there is a swap cache.
2694 * Note: return code is different from swap_duplicate().
2695 */
2696 int swapcache_prepare(swp_entry_t entry)
2697 {
2698 return __swap_duplicate(entry, SWAP_HAS_CACHE);
2699 }
2700
2701 struct swap_info_struct *page_swap_info(struct page *page)
2702 {
2703 swp_entry_t swap = { .val = page_private(page) };
2704 BUG_ON(!PageSwapCache(page));
2705 return swap_info[swp_type(swap)];
2706 }
2707
2708 /*
2709 * out-of-line __page_file_ methods to avoid include hell.
2710 */
2711 struct address_space *__page_file_mapping(struct page *page)
2712 {
2713 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2714 return page_swap_info(page)->swap_file->f_mapping;
2715 }
2716 EXPORT_SYMBOL_GPL(__page_file_mapping);
2717
2718 pgoff_t __page_file_index(struct page *page)
2719 {
2720 swp_entry_t swap = { .val = page_private(page) };
2721 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
2722 return swp_offset(swap);
2723 }
2724 EXPORT_SYMBOL_GPL(__page_file_index);
2725
2726 /*
2727 * add_swap_count_continuation - called when a swap count is duplicated
2728 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
2729 * page of the original vmalloc'ed swap_map, to hold the continuation count
2730 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
2731 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
2732 *
2733 * These continuation pages are seldom referenced: the common paths all work
2734 * on the original swap_map, only referring to a continuation page when the
2735 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
2736 *
2737 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
2738 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
2739 * can be called after dropping locks.
2740 */
2741 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
2742 {
2743 struct swap_info_struct *si;
2744 struct page *head;
2745 struct page *page;
2746 struct page *list_page;
2747 pgoff_t offset;
2748 unsigned char count;
2749
2750 /*
2751 * When debugging, it's easier to use __GFP_ZERO here; but it's better
2752 * for latency not to zero a page while GFP_ATOMIC and holding locks.
2753 */
2754 page = alloc_page(gfp_mask | __GFP_HIGHMEM);
2755
2756 si = swap_info_get(entry);
2757 if (!si) {
2758 /*
2759 * An acceptable race has occurred since the failing
2760 * __swap_duplicate(): the swap entry has been freed,
2761 * perhaps even the whole swap_map cleared for swapoff.
2762 */
2763 goto outer;
2764 }
2765
2766 offset = swp_offset(entry);
2767 count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
2768
2769 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
2770 /*
2771 * The higher the swap count, the more likely it is that tasks
2772 * will race to add swap count continuation: we need to avoid
2773 * over-provisioning.
2774 */
2775 goto out;
2776 }
2777
2778 if (!page) {
2779 spin_unlock(&si->lock);
2780 return -ENOMEM;
2781 }
2782
2783 /*
2784 * We are fortunate that although vmalloc_to_page uses pte_offset_map,
2785 * no architecture is using highmem pages for kernel page tables: so it
2786 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
2787 */
2788 head = vmalloc_to_page(si->swap_map + offset);
2789 offset &= ~PAGE_MASK;
2790
2791 /*
2792 * Page allocation does not initialize the page's lru field,
2793 * but it does always reset its private field.
2794 */
2795 if (!page_private(head)) {
2796 BUG_ON(count & COUNT_CONTINUED);
2797 INIT_LIST_HEAD(&head->lru);
2798 set_page_private(head, SWP_CONTINUED);
2799 si->flags |= SWP_CONTINUED;
2800 }
2801
2802 list_for_each_entry(list_page, &head->lru, lru) {
2803 unsigned char *map;
2804
2805 /*
2806 * If the previous map said no continuation, but we've found
2807 * a continuation page, free our allocation and use this one.
2808 */
2809 if (!(count & COUNT_CONTINUED))
2810 goto out;
2811
2812 map = kmap_atomic(list_page) + offset;
2813 count = *map;
2814 kunmap_atomic(map);
2815
2816 /*
2817 * If this continuation count now has some space in it,
2818 * free our allocation and use this one.
2819 */
2820 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
2821 goto out;
2822 }
2823
2824 list_add_tail(&page->lru, &head->lru);
2825 page = NULL; /* now it's attached, don't free it */
2826 out:
2827 spin_unlock(&si->lock);
2828 outer:
2829 if (page)
2830 __free_page(page);
2831 return 0;
2832 }
2833
2834 /*
2835 * swap_count_continued - when the original swap_map count is incremented
2836 * from SWAP_MAP_MAX, check if there is already a continuation page to carry
2837 * into, carry if so, or else fail until a new continuation page is allocated;
2838 * when the original swap_map count is decremented from 0 with continuation,
2839 * borrow from the continuation and report whether it still holds more.
2840 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
2841 */
2842 static bool swap_count_continued(struct swap_info_struct *si,
2843 pgoff_t offset, unsigned char count)
2844 {
2845 struct page *head;
2846 struct page *page;
2847 unsigned char *map;
2848
2849 head = vmalloc_to_page(si->swap_map + offset);
2850 if (page_private(head) != SWP_CONTINUED) {
2851 BUG_ON(count & COUNT_CONTINUED);
2852 return false; /* need to add count continuation */
2853 }
2854
2855 offset &= ~PAGE_MASK;
2856 page = list_entry(head->lru.next, struct page, lru);
2857 map = kmap_atomic(page) + offset;
2858
2859 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
2860 goto init_map; /* jump over SWAP_CONT_MAX checks */
2861
2862 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
2863 /*
2864 * Think of how you add 1 to 999
2865 */
2866 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
2867 kunmap_atomic(map);
2868 page = list_entry(page->lru.next, struct page, lru);
2869 BUG_ON(page == head);
2870 map = kmap_atomic(page) + offset;
2871 }
2872 if (*map == SWAP_CONT_MAX) {
2873 kunmap_atomic(map);
2874 page = list_entry(page->lru.next, struct page, lru);
2875 if (page == head)
2876 return false; /* add count continuation */
2877 map = kmap_atomic(page) + offset;
2878 init_map: *map = 0; /* we didn't zero the page */
2879 }
2880 *map += 1;
2881 kunmap_atomic(map);
2882 page = list_entry(page->lru.prev, struct page, lru);
2883 while (page != head) {
2884 map = kmap_atomic(page) + offset;
2885 *map = COUNT_CONTINUED;
2886 kunmap_atomic(map);
2887 page = list_entry(page->lru.prev, struct page, lru);
2888 }
2889 return true; /* incremented */
2890
2891 } else { /* decrementing */
2892 /*
2893 * Think of how you subtract 1 from 1000
2894 */
2895 BUG_ON(count != COUNT_CONTINUED);
2896 while (*map == COUNT_CONTINUED) {
2897 kunmap_atomic(map);
2898 page = list_entry(page->lru.next, struct page, lru);
2899 BUG_ON(page == head);
2900 map = kmap_atomic(page) + offset;
2901 }
2902 BUG_ON(*map == 0);
2903 *map -= 1;
2904 if (*map == 0)
2905 count = 0;
2906 kunmap_atomic(map);
2907 page = list_entry(page->lru.prev, struct page, lru);
2908 while (page != head) {
2909 map = kmap_atomic(page) + offset;
2910 *map = SWAP_CONT_MAX | count;
2911 count = COUNT_CONTINUED;
2912 kunmap_atomic(map);
2913 page = list_entry(page->lru.prev, struct page, lru);
2914 }
2915 return count == COUNT_CONTINUED;
2916 }
2917 }
2918
2919 /*
2920 * free_swap_count_continuations - swapoff free all the continuation pages
2921 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
2922 */
2923 static void free_swap_count_continuations(struct swap_info_struct *si)
2924 {
2925 pgoff_t offset;
2926
2927 for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
2928 struct page *head;
2929 head = vmalloc_to_page(si->swap_map + offset);
2930 if (page_private(head)) {
2931 struct list_head *this, *next;
2932 list_for_each_safe(this, next, &head->lru) {
2933 struct page *page;
2934 page = list_entry(this, struct page, lru);
2935 list_del(this);
2936 __free_page(page);
2937 }
2938 }
2939 }
2940 }