1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/mm/vmscan.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 *
7 * Swap reorganised 29.12.95, Stephen Tweedie.
8 * kswapd added: 7.1.96 sct
9 * Removed kswapd_ctl limits, and swap out as many pages as needed
10 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
11 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
12 * Multiqueue VM started 5.8.00, Rik van Riel.
13 */
14
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16
17 #include <linux/mm.h>
18 #include <linux/sched/mm.h>
19 #include <linux/module.h>
20 #include <linux/gfp.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/swap.h>
23 #include <linux/pagemap.h>
24 #include <linux/init.h>
25 #include <linux/highmem.h>
26 #include <linux/vmpressure.h>
27 #include <linux/vmstat.h>
28 #include <linux/file.h>
29 #include <linux/writeback.h>
30 #include <linux/blkdev.h>
31 #include <linux/buffer_head.h> /* for try_to_release_page(),
32 buffer_heads_over_limit */
33 #include <linux/mm_inline.h>
34 #include <linux/backing-dev.h>
35 #include <linux/rmap.h>
36 #include <linux/topology.h>
37 #include <linux/cpu.h>
38 #include <linux/cpuset.h>
39 #include <linux/compaction.h>
40 #include <linux/notifier.h>
41 #include <linux/rwsem.h>
42 #include <linux/delay.h>
43 #include <linux/kthread.h>
44 #include <linux/freezer.h>
45 #include <linux/memcontrol.h>
46 #include <linux/delayacct.h>
47 #include <linux/sysctl.h>
48 #include <linux/oom.h>
49 #include <linux/pagevec.h>
50 #include <linux/prefetch.h>
51 #include <linux/printk.h>
52 #include <linux/dax.h>
53 #include <linux/psi.h>
54
55 #include <asm/tlbflush.h>
56 #include <asm/div64.h>
57
58 #include <linux/swapops.h>
59 #include <linux/balloon_compaction.h>
60
61 #include "internal.h"
62
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/vmscan.h>
65
66 struct scan_control {
67 /* How many pages shrink_list() should reclaim */
68 unsigned long nr_to_reclaim;
69
70 /*
71 * Nodemask of nodes allowed by the caller. If NULL, all nodes
72 * are scanned.
73 */
74 nodemask_t *nodemask;
75
76 /*
77 * The memory cgroup that hit its limit and as a result is the
78 * primary target of this reclaim invocation.
79 */
80 struct mem_cgroup *target_mem_cgroup;
81
82 /* Writepage batching in laptop mode; RECLAIM_WRITE */
83 unsigned int may_writepage:1;
84
85 /* Can mapped pages be reclaimed? */
86 unsigned int may_unmap:1;
87
88 /* Can pages be swapped as part of reclaim? */
89 unsigned int may_swap:1;
90
91 /*
92 * Cgroups are not reclaimed below their configured memory.low,
93 * unless we threaten to OOM. If any cgroups are skipped due to
94 * memory.low and nothing was reclaimed, go back for memory.low.
95 */
96 unsigned int memcg_low_reclaim:1;
97 unsigned int memcg_low_skipped:1;
98
99 unsigned int hibernation_mode:1;
100
101 /* One of the zones is ready for compaction */
102 unsigned int compaction_ready:1;
103
104 /* Allocation order */
105 s8 order;
106
107 /* Scan (total_size >> priority) pages at once */
108 s8 priority;
109
110 /* The highest zone to isolate pages for reclaim from */
111 s8 reclaim_idx;
112
113 /* This context's GFP mask */
114 gfp_t gfp_mask;
115
116 /* Incremented by the number of inactive pages that were scanned */
117 unsigned long nr_scanned;
118
119 /* Number of pages freed so far during a call to shrink_zones() */
120 unsigned long nr_reclaimed;
121
122 struct {
123 unsigned int dirty;
124 unsigned int unqueued_dirty;
125 unsigned int congested;
126 unsigned int writeback;
127 unsigned int immediate;
128 unsigned int file_taken;
129 unsigned int taken;
130 } nr;
131
132 /* for recording the reclaimed slab by now */
133 struct reclaim_state reclaim_state;
134 };
135
136 #ifdef ARCH_HAS_PREFETCH
137 #define prefetch_prev_lru_page(_page, _base, _field) \
138 do { \
139 if ((_page)->lru.prev != _base) { \
140 struct page *prev; \
141 \
142 prev = lru_to_page(&(_page->lru)); \
143 prefetch(&prev->_field); \
144 } \
145 } while (0)
146 #else
147 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
148 #endif
149
150 #ifdef ARCH_HAS_PREFETCHW
151 #define prefetchw_prev_lru_page(_page, _base, _field) \
152 do { \
153 if ((_page)->lru.prev != _base) { \
154 struct page *prev; \
155 \
156 prev = lru_to_page(&(_page->lru)); \
157 prefetchw(&prev->_field); \
158 } \
159 } while (0)
160 #else
161 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
162 #endif
163
164 /*
165 * From 0 .. 100. Higher means more swappy.
166 */
167 int vm_swappiness = 60;
168 /*
169 * The total number of pages which are beyond the high watermark within all
170 * zones.
171 */
172 unsigned long vm_total_pages;
173
174 static void set_task_reclaim_state(struct task_struct *task,
175 struct reclaim_state *rs)
176 {
177 /* Check for an overwrite */
178 WARN_ON_ONCE(rs && task->reclaim_state);
179
180 /* Check for the nulling of an already-nulled member */
181 WARN_ON_ONCE(!rs && !task->reclaim_state);
182
183 task->reclaim_state = rs;
184 }
185
186 static LIST_HEAD(shrinker_list);
187 static DECLARE_RWSEM(shrinker_rwsem);
188
189 #ifdef CONFIG_MEMCG
190 /*
191 * We allow subsystems to populate their shrinker-related
192 * LRU lists before register_shrinker_prepared() is called
193 * for the shrinker, since we don't want to impose
194 * restrictions on their internal registration order.
195 * In this case shrink_slab_memcg() may find corresponding
196 * bit is set in the shrinkers map.
197 *
198 * This value is used by the function to detect registering
199 * shrinkers and to skip do_shrink_slab() calls for them.
200 */
201 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
202
203 static DEFINE_IDR(shrinker_idr);
204 static int shrinker_nr_max;
205
206 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
207 {
208 int id, ret = -ENOMEM;
209
210 down_write(&shrinker_rwsem);
211 /* This may call shrinker, so it must use down_read_trylock() */
212 id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
213 if (id < 0)
214 goto unlock;
215
216 if (id >= shrinker_nr_max) {
217 if (memcg_expand_shrinker_maps(id)) {
218 idr_remove(&shrinker_idr, id);
219 goto unlock;
220 }
221
222 shrinker_nr_max = id + 1;
223 }
224 shrinker->id = id;
225 ret = 0;
226 unlock:
227 up_write(&shrinker_rwsem);
228 return ret;
229 }
230
231 static void unregister_memcg_shrinker(struct shrinker *shrinker)
232 {
233 int id = shrinker->id;
234
235 BUG_ON(id < 0);
236
237 down_write(&shrinker_rwsem);
238 idr_remove(&shrinker_idr, id);
239 up_write(&shrinker_rwsem);
240 }
241
242 static bool global_reclaim(struct scan_control *sc)
243 {
244 return !sc->target_mem_cgroup;
245 }
246
247 /**
248 * sane_reclaim - is the usual dirty throttling mechanism operational?
249 * @sc: scan_control in question
250 *
251 * The normal page dirty throttling mechanism in balance_dirty_pages() is
252 * completely broken with the legacy memcg and direct stalling in
253 * shrink_page_list() is used for throttling instead, which lacks all the
254 * niceties such as fairness, adaptive pausing, bandwidth proportional
255 * allocation and configurability.
256 *
257 * This function tests whether the vmscan currently in progress can assume
258 * that the normal dirty throttling mechanism is operational.
259 */
260 static bool sane_reclaim(struct scan_control *sc)
261 {
262 struct mem_cgroup *memcg = sc->target_mem_cgroup;
263
264 if (!memcg)
265 return true;
266 #ifdef CONFIG_CGROUP_WRITEBACK
267 if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
268 return true;
269 #endif
270 return false;
271 }
272
273 static void set_memcg_congestion(pg_data_t *pgdat,
274 struct mem_cgroup *memcg,
275 bool congested)
276 {
277 struct mem_cgroup_per_node *mn;
278
279 if (!memcg)
280 return;
281
282 mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
283 WRITE_ONCE(mn->congested, congested);
284 }
285
286 static bool memcg_congested(pg_data_t *pgdat,
287 struct mem_cgroup *memcg)
288 {
289 struct mem_cgroup_per_node *mn;
290
291 mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
292 return READ_ONCE(mn->congested);
293
294 }
295 #else
296 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
297 {
298 return 0;
299 }
300
301 static void unregister_memcg_shrinker(struct shrinker *shrinker)
302 {
303 }
304
305 static bool global_reclaim(struct scan_control *sc)
306 {
307 return true;
308 }
309
310 static bool sane_reclaim(struct scan_control *sc)
311 {
312 return true;
313 }
314
315 static inline void set_memcg_congestion(struct pglist_data *pgdat,
316 struct mem_cgroup *memcg, bool congested)
317 {
318 }
319
320 static inline bool memcg_congested(struct pglist_data *pgdat,
321 struct mem_cgroup *memcg)
322 {
323 return false;
324
325 }
326 #endif
327
328 /*
329 * This misses isolated pages which are not accounted for to save counters.
330 * As the data only determines if reclaim or compaction continues, it is
331 * not expected that isolated pages will be a dominating factor.
332 */
333 unsigned long zone_reclaimable_pages(struct zone *zone)
334 {
335 unsigned long nr;
336
337 nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
338 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
339 if (get_nr_swap_pages() > 0)
340 nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
341 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
342
343 return nr;
344 }
345
346 /**
347 * lruvec_lru_size - Returns the number of pages on the given LRU list.
348 * @lruvec: lru vector
349 * @lru: lru to use
350 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
351 */
352 unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx)
353 {
354 unsigned long lru_size = 0;
355 int zid;
356
357 if (!mem_cgroup_disabled()) {
358 for (zid = 0; zid < MAX_NR_ZONES; zid++)
359 lru_size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
360 } else
361 lru_size = node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru);
362
363 for (zid = zone_idx + 1; zid < MAX_NR_ZONES; zid++) {
364 struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
365 unsigned long size;
366
367 if (!managed_zone(zone))
368 continue;
369
370 if (!mem_cgroup_disabled())
371 size = mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
372 else
373 size = zone_page_state(&lruvec_pgdat(lruvec)->node_zones[zid],
374 NR_ZONE_LRU_BASE + lru);
375 lru_size -= min(size, lru_size);
376 }
377
378 return lru_size;
379
380 }
381
382 /*
383 * Add a shrinker callback to be called from the vm.
384 */
385 int prealloc_shrinker(struct shrinker *shrinker)
386 {
387 unsigned int size = sizeof(*shrinker->nr_deferred);
388
389 if (shrinker->flags & SHRINKER_NUMA_AWARE)
390 size *= nr_node_ids;
391
392 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
393 if (!shrinker->nr_deferred)
394 return -ENOMEM;
395
396 if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
397 if (prealloc_memcg_shrinker(shrinker))
398 goto free_deferred;
399 }
400
401 return 0;
402
403 free_deferred:
404 kfree(shrinker->nr_deferred);
405 shrinker->nr_deferred = NULL;
406 return -ENOMEM;
407 }
408
409 void free_prealloced_shrinker(struct shrinker *shrinker)
410 {
411 if (!shrinker->nr_deferred)
412 return;
413
414 if (shrinker->flags & SHRINKER_MEMCG_AWARE)
415 unregister_memcg_shrinker(shrinker);
416
417 kfree(shrinker->nr_deferred);
418 shrinker->nr_deferred = NULL;
419 }
420
421 void register_shrinker_prepared(struct shrinker *shrinker)
422 {
423 down_write(&shrinker_rwsem);
424 list_add_tail(&shrinker->list, &shrinker_list);
425 #ifdef CONFIG_MEMCG
426 if (shrinker->flags & SHRINKER_MEMCG_AWARE)
427 idr_replace(&shrinker_idr, shrinker, shrinker->id);
428 #endif
429 up_write(&shrinker_rwsem);
430 }
431
432 int register_shrinker(struct shrinker *shrinker)
433 {
434 int err = prealloc_shrinker(shrinker);
435
436 if (err)
437 return err;
438 register_shrinker_prepared(shrinker);
439 return 0;
440 }
441 EXPORT_SYMBOL(register_shrinker);
442
443 /*
444 * Remove one
445 */
446 void unregister_shrinker(struct shrinker *shrinker)
447 {
448 if (!shrinker->nr_deferred)
449 return;
450 if (shrinker->flags & SHRINKER_MEMCG_AWARE)
451 unregister_memcg_shrinker(shrinker);
452 down_write(&shrinker_rwsem);
453 list_del(&shrinker->list);
454 up_write(&shrinker_rwsem);
455 kfree(shrinker->nr_deferred);
456 shrinker->nr_deferred = NULL;
457 }
458 EXPORT_SYMBOL(unregister_shrinker);
459
460 #define SHRINK_BATCH 128
461
462 static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
463 struct shrinker *shrinker, int priority)
464 {
465 unsigned long freed = 0;
466 unsigned long long delta;
467 long total_scan;
468 long freeable;
469 long nr;
470 long new_nr;
471 int nid = shrinkctl->nid;
472 long batch_size = shrinker->batch ? shrinker->batch
473 : SHRINK_BATCH;
474 long scanned = 0, next_deferred;
475
476 if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
477 nid = 0;
478
479 freeable = shrinker->count_objects(shrinker, shrinkctl);
480 if (freeable == 0 || freeable == SHRINK_EMPTY)
481 return freeable;
482
483 /*
484 * copy the current shrinker scan count into a local variable
485 * and zero it so that other concurrent shrinker invocations
486 * don't also do this scanning work.
487 */
488 nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
489
490 total_scan = nr;
491 if (shrinker->seeks) {
492 delta = freeable >> priority;
493 delta *= 4;
494 do_div(delta, shrinker->seeks);
495 } else {
496 /*
497 * These objects don't require any IO to create. Trim
498 * them aggressively under memory pressure to keep
499 * them from causing refetches in the IO caches.
500 */
501 delta = freeable / 2;
502 }
503
504 total_scan += delta;
505 if (total_scan < 0) {
506 pr_err("shrink_slab: %pS negative objects to delete nr=%ld\n",
507 shrinker->scan_objects, total_scan);
508 total_scan = freeable;
509 next_deferred = nr;
510 } else
511 next_deferred = total_scan;
512
513 /*
514 * We need to avoid excessive windup on filesystem shrinkers
515 * due to large numbers of GFP_NOFS allocations causing the
516 * shrinkers to return -1 all the time. This results in a large
517 * nr being built up so when a shrink that can do some work
518 * comes along it empties the entire cache due to nr >>>
519 * freeable. This is bad for sustaining a working set in
520 * memory.
521 *
522 * Hence only allow the shrinker to scan the entire cache when
523 * a large delta change is calculated directly.
524 */
525 if (delta < freeable / 4)
526 total_scan = min(total_scan, freeable / 2);
527
528 /*
529 * Avoid risking looping forever due to too large nr value:
530 * never try to free more than twice the estimate number of
531 * freeable entries.
532 */
533 if (total_scan > freeable * 2)
534 total_scan = freeable * 2;
535
536 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
537 freeable, delta, total_scan, priority);
538
539 /*
540 * Normally, we should not scan less than batch_size objects in one
541 * pass to avoid too frequent shrinker calls, but if the slab has less
542 * than batch_size objects in total and we are really tight on memory,
543 * we will try to reclaim all available objects, otherwise we can end
544 * up failing allocations although there are plenty of reclaimable
545 * objects spread over several slabs with usage less than the
546 * batch_size.
547 *
548 * We detect the "tight on memory" situations by looking at the total
549 * number of objects we want to scan (total_scan). If it is greater
550 * than the total number of objects on slab (freeable), we must be
551 * scanning at high prio and therefore should try to reclaim as much as
552 * possible.
553 */
554 while (total_scan >= batch_size ||
555 total_scan >= freeable) {
556 unsigned long ret;
557 unsigned long nr_to_scan = min(batch_size, total_scan);
558
559 shrinkctl->nr_to_scan = nr_to_scan;
560 shrinkctl->nr_scanned = nr_to_scan;
561 ret = shrinker->scan_objects(shrinker, shrinkctl);
562 if (ret == SHRINK_STOP)
563 break;
564 freed += ret;
565
566 count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
567 total_scan -= shrinkctl->nr_scanned;
568 scanned += shrinkctl->nr_scanned;
569
570 cond_resched();
571 }
572
573 if (next_deferred >= scanned)
574 next_deferred -= scanned;
575 else
576 next_deferred = 0;
577 /*
578 * move the unused scan count back into the shrinker in a
579 * manner that handles concurrent updates. If we exhausted the
580 * scan, there is no need to do an update.
581 */
582 if (next_deferred > 0)
583 new_nr = atomic_long_add_return(next_deferred,
584 &shrinker->nr_deferred[nid]);
585 else
586 new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
587
588 trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
589 return freed;
590 }
591
592 #ifdef CONFIG_MEMCG
593 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
594 struct mem_cgroup *memcg, int priority)
595 {
596 struct memcg_shrinker_map *map;
597 unsigned long ret, freed = 0;
598 int i;
599
600 if (!mem_cgroup_online(memcg))
601 return 0;
602
603 if (!down_read_trylock(&shrinker_rwsem))
604 return 0;
605
606 map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map,
607 true);
608 if (unlikely(!map))
609 goto unlock;
610
611 for_each_set_bit(i, map->map, shrinker_nr_max) {
612 struct shrink_control sc = {
613 .gfp_mask = gfp_mask,
614 .nid = nid,
615 .memcg = memcg,
616 };
617 struct shrinker *shrinker;
618
619 shrinker = idr_find(&shrinker_idr, i);
620 if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) {
621 if (!shrinker)
622 clear_bit(i, map->map);
623 continue;
624 }
625
626 /* Call non-slab shrinkers even though kmem is disabled */
627 if (!memcg_kmem_enabled() &&
628 !(shrinker->flags & SHRINKER_NONSLAB))
629 continue;
630
631 ret = do_shrink_slab(&sc, shrinker, priority);
632 if (ret == SHRINK_EMPTY) {
633 clear_bit(i, map->map);
634 /*
635 * After the shrinker reported that it had no objects to
636 * free, but before we cleared the corresponding bit in
637 * the memcg shrinker map, a new object might have been
638 * added. To make sure, we have the bit set in this
639 * case, we invoke the shrinker one more time and reset
640 * the bit if it reports that it is not empty anymore.
641 * The memory barrier here pairs with the barrier in
642 * memcg_set_shrinker_bit():
643 *
644 * list_lru_add() shrink_slab_memcg()
645 * list_add_tail() clear_bit()
646 * <MB> <MB>
647 * set_bit() do_shrink_slab()
648 */
649 smp_mb__after_atomic();
650 ret = do_shrink_slab(&sc, shrinker, priority);
651 if (ret == SHRINK_EMPTY)
652 ret = 0;
653 else
654 memcg_set_shrinker_bit(memcg, nid, i);
655 }
656 freed += ret;
657
658 if (rwsem_is_contended(&shrinker_rwsem)) {
659 freed = freed ? : 1;
660 break;
661 }
662 }
663 unlock:
664 up_read(&shrinker_rwsem);
665 return freed;
666 }
667 #else /* CONFIG_MEMCG */
668 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
669 struct mem_cgroup *memcg, int priority)
670 {
671 return 0;
672 }
673 #endif /* CONFIG_MEMCG */
674
675 /**
676 * shrink_slab - shrink slab caches
677 * @gfp_mask: allocation context
678 * @nid: node whose slab caches to target
679 * @memcg: memory cgroup whose slab caches to target
680 * @priority: the reclaim priority
681 *
682 * Call the shrink functions to age shrinkable caches.
683 *
684 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
685 * unaware shrinkers will receive a node id of 0 instead.
686 *
687 * @memcg specifies the memory cgroup to target. Unaware shrinkers
688 * are called only if it is the root cgroup.
689 *
690 * @priority is sc->priority, we take the number of objects and >> by priority
691 * in order to get the scan target.
692 *
693 * Returns the number of reclaimed slab objects.
694 */
695 static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
696 struct mem_cgroup *memcg,
697 int priority)
698 {
699 unsigned long ret, freed = 0;
700 struct shrinker *shrinker;
701
702 /*
703 * The root memcg might be allocated even though memcg is disabled
704 * via "cgroup_disable=memory" boot parameter. This could make
705 * mem_cgroup_is_root() return false, then just run memcg slab
706 * shrink, but skip global shrink. This may result in premature
707 * oom.
708 */
709 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
710 return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
711
712 if (!down_read_trylock(&shrinker_rwsem))
713 goto out;
714
715 list_for_each_entry(shrinker, &shrinker_list, list) {
716 struct shrink_control sc = {
717 .gfp_mask = gfp_mask,
718 .nid = nid,
719 .memcg = memcg,
720 };
721
722 ret = do_shrink_slab(&sc, shrinker, priority);
723 if (ret == SHRINK_EMPTY)
724 ret = 0;
725 freed += ret;
726 /*
727 * Bail out if someone want to register a new shrinker to
728 * prevent the regsitration from being stalled for long periods
729 * by parallel ongoing shrinking.
730 */
731 if (rwsem_is_contended(&shrinker_rwsem)) {
732 freed = freed ? : 1;
733 break;
734 }
735 }
736
737 up_read(&shrinker_rwsem);
738 out:
739 cond_resched();
740 return freed;
741 }
742
743 void drop_slab_node(int nid)
744 {
745 unsigned long freed;
746
747 do {
748 struct mem_cgroup *memcg = NULL;
749
750 freed = 0;
751 memcg = mem_cgroup_iter(NULL, NULL, NULL);
752 do {
753 freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
754 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
755 } while (freed > 10);
756 }
757
758 void drop_slab(void)
759 {
760 int nid;
761
762 for_each_online_node(nid)
763 drop_slab_node(nid);
764 }
765
766 static inline int is_page_cache_freeable(struct page *page)
767 {
768 /*
769 * A freeable page cache page is referenced only by the caller
770 * that isolated the page, the page cache and optional buffer
771 * heads at page->private.
772 */
773 int page_cache_pins = PageTransHuge(page) && PageSwapCache(page) ?
774 HPAGE_PMD_NR : 1;
775 return page_count(page) - page_has_private(page) == 1 + page_cache_pins;
776 }
777
778 static int may_write_to_inode(struct inode *inode, struct scan_control *sc)
779 {
780 if (current->flags & PF_SWAPWRITE)
781 return 1;
782 if (!inode_write_congested(inode))
783 return 1;
784 if (inode_to_bdi(inode) == current->backing_dev_info)
785 return 1;
786 return 0;
787 }
788
789 /*
790 * We detected a synchronous write error writing a page out. Probably
791 * -ENOSPC. We need to propagate that into the address_space for a subsequent
792 * fsync(), msync() or close().
793 *
794 * The tricky part is that after writepage we cannot touch the mapping: nothing
795 * prevents it from being freed up. But we have a ref on the page and once
796 * that page is locked, the mapping is pinned.
797 *
798 * We're allowed to run sleeping lock_page() here because we know the caller has
799 * __GFP_FS.
800 */
801 static void handle_write_error(struct address_space *mapping,
802 struct page *page, int error)
803 {
804 lock_page(page);
805 if (page_mapping(page) == mapping)
806 mapping_set_error(mapping, error);
807 unlock_page(page);
808 }
809
810 /* possible outcome of pageout() */
811 typedef enum {
812 /* failed to write page out, page is locked */
813 PAGE_KEEP,
814 /* move page to the active list, page is locked */
815 PAGE_ACTIVATE,
816 /* page has been sent to the disk successfully, page is unlocked */
817 PAGE_SUCCESS,
818 /* page is clean and locked */
819 PAGE_CLEAN,
820 } pageout_t;
821
822 /*
823 * pageout is called by shrink_page_list() for each dirty page.
824 * Calls ->writepage().
825 */
826 static pageout_t pageout(struct page *page, struct address_space *mapping,
827 struct scan_control *sc)
828 {
829 /*
830 * If the page is dirty, only perform writeback if that write
831 * will be non-blocking. To prevent this allocation from being
832 * stalled by pagecache activity. But note that there may be
833 * stalls if we need to run get_block(). We could test
834 * PagePrivate for that.
835 *
836 * If this process is currently in __generic_file_write_iter() against
837 * this page's queue, we can perform writeback even if that
838 * will block.
839 *
840 * If the page is swapcache, write it back even if that would
841 * block, for some throttling. This happens by accident, because
842 * swap_backing_dev_info is bust: it doesn't reflect the
843 * congestion state of the swapdevs. Easy to fix, if needed.
844 */
845 if (!is_page_cache_freeable(page))
846 return PAGE_KEEP;
847 if (!mapping) {
848 /*
849 * Some data journaling orphaned pages can have
850 * page->mapping == NULL while being dirty with clean buffers.
851 */
852 if (page_has_private(page)) {
853 if (try_to_free_buffers(page)) {
854 ClearPageDirty(page);
855 pr_info("%s: orphaned page\n", __func__);
856 return PAGE_CLEAN;
857 }
858 }
859 return PAGE_KEEP;
860 }
861 if (mapping->a_ops->writepage == NULL)
862 return PAGE_ACTIVATE;
863 if (!may_write_to_inode(mapping->host, sc))
864 return PAGE_KEEP;
865
866 if (clear_page_dirty_for_io(page)) {
867 int res;
868 struct writeback_control wbc = {
869 .sync_mode = WB_SYNC_NONE,
870 .nr_to_write = SWAP_CLUSTER_MAX,
871 .range_start = 0,
872 .range_end = LLONG_MAX,
873 .for_reclaim = 1,
874 };
875
876 SetPageReclaim(page);
877 res = mapping->a_ops->writepage(page, &wbc);
878 if (res < 0)
879 handle_write_error(mapping, page, res);
880 if (res == AOP_WRITEPAGE_ACTIVATE) {
881 ClearPageReclaim(page);
882 return PAGE_ACTIVATE;
883 }
884
885 if (!PageWriteback(page)) {
886 /* synchronous write or broken a_ops? */
887 ClearPageReclaim(page);
888 }
889 trace_mm_vmscan_writepage(page);
890 inc_node_page_state(page, NR_VMSCAN_WRITE);
891 return PAGE_SUCCESS;
892 }
893
894 return PAGE_CLEAN;
895 }
896
897 /*
898 * Same as remove_mapping, but if the page is removed from the mapping, it
899 * gets returned with a refcount of 0.
900 */
901 static int __remove_mapping(struct address_space *mapping, struct page *page,
902 bool reclaimed)
903 {
904 unsigned long flags;
905 int refcount;
906
907 BUG_ON(!PageLocked(page));
908 BUG_ON(mapping != page_mapping(page));
909
910 xa_lock_irqsave(&mapping->i_pages, flags);
911 /*
912 * The non racy check for a busy page.
913 *
914 * Must be careful with the order of the tests. When someone has
915 * a ref to the page, it may be possible that they dirty it then
916 * drop the reference. So if PageDirty is tested before page_count
917 * here, then the following race may occur:
918 *
919 * get_user_pages(&page);
920 * [user mapping goes away]
921 * write_to(page);
922 * !PageDirty(page) [good]
923 * SetPageDirty(page);
924 * put_page(page);
925 * !page_count(page) [good, discard it]
926 *
927 * [oops, our write_to data is lost]
928 *
929 * Reversing the order of the tests ensures such a situation cannot
930 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
931 * load is not satisfied before that of page->_refcount.
932 *
933 * Note that if SetPageDirty is always performed via set_page_dirty,
934 * and thus under the i_pages lock, then this ordering is not required.
935 */
936 refcount = 1 + compound_nr(page);
937 if (!page_ref_freeze(page, refcount))
938 goto cannot_free;
939 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
940 if (unlikely(PageDirty(page))) {
941 page_ref_unfreeze(page, refcount);
942 goto cannot_free;
943 }
944
945 if (PageSwapCache(page)) {
946 swp_entry_t swap = { .val = page_private(page) };
947 mem_cgroup_swapout(page, swap);
948 __delete_from_swap_cache(page, swap);
949 xa_unlock_irqrestore(&mapping->i_pages, flags);
950 put_swap_page(page, swap);
951 } else {
952 void (*freepage)(struct page *);
953 void *shadow = NULL;
954
955 freepage = mapping->a_ops->freepage;
956 /*
957 * Remember a shadow entry for reclaimed file cache in
958 * order to detect refaults, thus thrashing, later on.
959 *
960 * But don't store shadows in an address space that is
961 * already exiting. This is not just an optizimation,
962 * inode reclaim needs to empty out the radix tree or
963 * the nodes are lost. Don't plant shadows behind its
964 * back.
965 *
966 * We also don't store shadows for DAX mappings because the
967 * only page cache pages found in these are zero pages
968 * covering holes, and because we don't want to mix DAX
969 * exceptional entries and shadow exceptional entries in the
970 * same address_space.
971 */
972 if (reclaimed && page_is_file_cache(page) &&
973 !mapping_exiting(mapping) && !dax_mapping(mapping))
974 shadow = workingset_eviction(page);
975 __delete_from_page_cache(page, shadow);
976 xa_unlock_irqrestore(&mapping->i_pages, flags);
977
978 if (freepage != NULL)
979 freepage(page);
980 }
981
982 return 1;
983
984 cannot_free:
985 xa_unlock_irqrestore(&mapping->i_pages, flags);
986 return 0;
987 }
988
989 /*
990 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
991 * someone else has a ref on the page, abort and return 0. If it was
992 * successfully detached, return 1. Assumes the caller has a single ref on
993 * this page.
994 */
995 int remove_mapping(struct address_space *mapping, struct page *page)
996 {
997 if (__remove_mapping(mapping, page, false)) {
998 /*
999 * Unfreezing the refcount with 1 rather than 2 effectively
1000 * drops the pagecache ref for us without requiring another
1001 * atomic operation.
1002 */
1003 page_ref_unfreeze(page, 1);
1004 return 1;
1005 }
1006 return 0;
1007 }
1008
1009 /**
1010 * putback_lru_page - put previously isolated page onto appropriate LRU list
1011 * @page: page to be put back to appropriate lru list
1012 *
1013 * Add previously isolated @page to appropriate LRU list.
1014 * Page may still be unevictable for other reasons.
1015 *
1016 * lru_lock must not be held, interrupts must be enabled.
1017 */
1018 void putback_lru_page(struct page *page)
1019 {
1020 lru_cache_add(page);
1021 put_page(page); /* drop ref from isolate */
1022 }
1023
1024 enum page_references {
1025 PAGEREF_RECLAIM,
1026 PAGEREF_RECLAIM_CLEAN,
1027 PAGEREF_KEEP,
1028 PAGEREF_ACTIVATE,
1029 };
1030
1031 static enum page_references page_check_references(struct page *page,
1032 struct scan_control *sc)
1033 {
1034 int referenced_ptes, referenced_page;
1035 unsigned long vm_flags;
1036
1037 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
1038 &vm_flags);
1039 referenced_page = TestClearPageReferenced(page);
1040
1041 /*
1042 * Mlock lost the isolation race with us. Let try_to_unmap()
1043 * move the page to the unevictable list.
1044 */
1045 if (vm_flags & VM_LOCKED)
1046 return PAGEREF_RECLAIM;
1047
1048 if (referenced_ptes) {
1049 if (PageSwapBacked(page))
1050 return PAGEREF_ACTIVATE;
1051 /*
1052 * All mapped pages start out with page table
1053 * references from the instantiating fault, so we need
1054 * to look twice if a mapped file page is used more
1055 * than once.
1056 *
1057 * Mark it and spare it for another trip around the
1058 * inactive list. Another page table reference will
1059 * lead to its activation.
1060 *
1061 * Note: the mark is set for activated pages as well
1062 * so that recently deactivated but used pages are
1063 * quickly recovered.
1064 */
1065 SetPageReferenced(page);
1066
1067 if (referenced_page || referenced_ptes > 1)
1068 return PAGEREF_ACTIVATE;
1069
1070 /*
1071 * Activate file-backed executable pages after first usage.
1072 */
1073 if (vm_flags & VM_EXEC)
1074 return PAGEREF_ACTIVATE;
1075
1076 return PAGEREF_KEEP;
1077 }
1078
1079 /* Reclaim if clean, defer dirty pages to writeback */
1080 if (referenced_page && !PageSwapBacked(page))
1081 return PAGEREF_RECLAIM_CLEAN;
1082
1083 return PAGEREF_RECLAIM;
1084 }
1085
1086 /* Check if a page is dirty or under writeback */
1087 static void page_check_dirty_writeback(struct page *page,
1088 bool *dirty, bool *writeback)
1089 {
1090 struct address_space *mapping;
1091
1092 /*
1093 * Anonymous pages are not handled by flushers and must be written
1094 * from reclaim context. Do not stall reclaim based on them
1095 */
1096 if (!page_is_file_cache(page) ||
1097 (PageAnon(page) && !PageSwapBacked(page))) {
1098 *dirty = false;
1099 *writeback = false;
1100 return;
1101 }
1102
1103 /* By default assume that the page flags are accurate */
1104 *dirty = PageDirty(page);
1105 *writeback = PageWriteback(page);
1106
1107 /* Verify dirty/writeback state if the filesystem supports it */
1108 if (!page_has_private(page))
1109 return;
1110
1111 mapping = page_mapping(page);
1112 if (mapping && mapping->a_ops->is_dirty_writeback)
1113 mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
1114 }
1115
1116 /*
1117 * shrink_page_list() returns the number of reclaimed pages
1118 */
1119 static unsigned long shrink_page_list(struct list_head *page_list,
1120 struct pglist_data *pgdat,
1121 struct scan_control *sc,
1122 enum ttu_flags ttu_flags,
1123 struct reclaim_stat *stat,
1124 bool ignore_references)
1125 {
1126 LIST_HEAD(ret_pages);
1127 LIST_HEAD(free_pages);
1128 unsigned nr_reclaimed = 0;
1129 unsigned pgactivate = 0;
1130
1131 memset(stat, 0, sizeof(*stat));
1132 cond_resched();
1133
1134 while (!list_empty(page_list)) {
1135 struct address_space *mapping;
1136 struct page *page;
1137 int may_enter_fs;
1138 enum page_references references = PAGEREF_RECLAIM;
1139 bool dirty, writeback;
1140 unsigned int nr_pages;
1141
1142 cond_resched();
1143
1144 page = lru_to_page(page_list);
1145 list_del(&page->lru);
1146
1147 if (!trylock_page(page))
1148 goto keep;
1149
1150 VM_BUG_ON_PAGE(PageActive(page), page);
1151
1152 nr_pages = compound_nr(page);
1153
1154 /* Account the number of base pages even though THP */
1155 sc->nr_scanned += nr_pages;
1156
1157 if (unlikely(!page_evictable(page)))
1158 goto activate_locked;
1159
1160 if (!sc->may_unmap && page_mapped(page))
1161 goto keep_locked;
1162
1163 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
1164 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
1165
1166 /*
1167 * The number of dirty pages determines if a node is marked
1168 * reclaim_congested which affects wait_iff_congested. kswapd
1169 * will stall and start writing pages if the tail of the LRU
1170 * is all dirty unqueued pages.
1171 */
1172 page_check_dirty_writeback(page, &dirty, &writeback);
1173 if (dirty || writeback)
1174 stat->nr_dirty++;
1175
1176 if (dirty && !writeback)
1177 stat->nr_unqueued_dirty++;
1178
1179 /*
1180 * Treat this page as congested if the underlying BDI is or if
1181 * pages are cycling through the LRU so quickly that the
1182 * pages marked for immediate reclaim are making it to the
1183 * end of the LRU a second time.
1184 */
1185 mapping = page_mapping(page);
1186 if (((dirty || writeback) && mapping &&
1187 inode_write_congested(mapping->host)) ||
1188 (writeback && PageReclaim(page)))
1189 stat->nr_congested++;
1190
1191 /*
1192 * If a page at the tail of the LRU is under writeback, there
1193 * are three cases to consider.
1194 *
1195 * 1) If reclaim is encountering an excessive number of pages
1196 * under writeback and this page is both under writeback and
1197 * PageReclaim then it indicates that pages are being queued
1198 * for IO but are being recycled through the LRU before the
1199 * IO can complete. Waiting on the page itself risks an
1200 * indefinite stall if it is impossible to writeback the
1201 * page due to IO error or disconnected storage so instead
1202 * note that the LRU is being scanned too quickly and the
1203 * caller can stall after page list has been processed.
1204 *
1205 * 2) Global or new memcg reclaim encounters a page that is
1206 * not marked for immediate reclaim, or the caller does not
1207 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1208 * not to fs). In this case mark the page for immediate
1209 * reclaim and continue scanning.
1210 *
1211 * Require may_enter_fs because we would wait on fs, which
1212 * may not have submitted IO yet. And the loop driver might
1213 * enter reclaim, and deadlock if it waits on a page for
1214 * which it is needed to do the write (loop masks off
1215 * __GFP_IO|__GFP_FS for this reason); but more thought
1216 * would probably show more reasons.
1217 *
1218 * 3) Legacy memcg encounters a page that is already marked
1219 * PageReclaim. memcg does not have any dirty pages
1220 * throttling so we could easily OOM just because too many
1221 * pages are in writeback and there is nothing else to
1222 * reclaim. Wait for the writeback to complete.
1223 *
1224 * In cases 1) and 2) we activate the pages to get them out of
1225 * the way while we continue scanning for clean pages on the
1226 * inactive list and refilling from the active list. The
1227 * observation here is that waiting for disk writes is more
1228 * expensive than potentially causing reloads down the line.
1229 * Since they're marked for immediate reclaim, they won't put
1230 * memory pressure on the cache working set any longer than it
1231 * takes to write them to disk.
1232 */
1233 if (PageWriteback(page)) {
1234 /* Case 1 above */
1235 if (current_is_kswapd() &&
1236 PageReclaim(page) &&
1237 test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1238 stat->nr_immediate++;
1239 goto activate_locked;
1240
1241 /* Case 2 above */
1242 } else if (sane_reclaim(sc) ||
1243 !PageReclaim(page) || !may_enter_fs) {
1244 /*
1245 * This is slightly racy - end_page_writeback()
1246 * might have just cleared PageReclaim, then
1247 * setting PageReclaim here end up interpreted
1248 * as PageReadahead - but that does not matter
1249 * enough to care. What we do want is for this
1250 * page to have PageReclaim set next time memcg
1251 * reclaim reaches the tests above, so it will
1252 * then wait_on_page_writeback() to avoid OOM;
1253 * and it's also appropriate in global reclaim.
1254 */
1255 SetPageReclaim(page);
1256 stat->nr_writeback++;
1257 goto activate_locked;
1258
1259 /* Case 3 above */
1260 } else {
1261 unlock_page(page);
1262 wait_on_page_writeback(page);
1263 /* then go back and try same page again */
1264 list_add_tail(&page->lru, page_list);
1265 continue;
1266 }
1267 }
1268
1269 if (!ignore_references)
1270 references = page_check_references(page, sc);
1271
1272 switch (references) {
1273 case PAGEREF_ACTIVATE:
1274 goto activate_locked;
1275 case PAGEREF_KEEP:
1276 stat->nr_ref_keep += nr_pages;
1277 goto keep_locked;
1278 case PAGEREF_RECLAIM:
1279 case PAGEREF_RECLAIM_CLEAN:
1280 ; /* try to reclaim the page below */
1281 }
1282
1283 /*
1284 * Anonymous process memory has backing store?
1285 * Try to allocate it some swap space here.
1286 * Lazyfree page could be freed directly
1287 */
1288 if (PageAnon(page) && PageSwapBacked(page)) {
1289 if (!PageSwapCache(page)) {
1290 if (!(sc->gfp_mask & __GFP_IO))
1291 goto keep_locked;
1292 if (PageTransHuge(page)) {
1293 /* cannot split THP, skip it */
1294 if (!can_split_huge_page(page, NULL))
1295 goto activate_locked;
1296 /*
1297 * Split pages without a PMD map right
1298 * away. Chances are some or all of the
1299 * tail pages can be freed without IO.
1300 */
1301 if (!compound_mapcount(page) &&
1302 split_huge_page_to_list(page,
1303 page_list))
1304 goto activate_locked;
1305 }
1306 if (!add_to_swap(page)) {
1307 if (!PageTransHuge(page))
1308 goto activate_locked_split;
1309 /* Fallback to swap normal pages */
1310 if (split_huge_page_to_list(page,
1311 page_list))
1312 goto activate_locked;
1313 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1314 count_vm_event(THP_SWPOUT_FALLBACK);
1315 #endif
1316 if (!add_to_swap(page))
1317 goto activate_locked_split;
1318 }
1319
1320 may_enter_fs = 1;
1321
1322 /* Adding to swap updated mapping */
1323 mapping = page_mapping(page);
1324 }
1325 } else if (unlikely(PageTransHuge(page))) {
1326 /* Split file THP */
1327 if (split_huge_page_to_list(page, page_list))
1328 goto keep_locked;
1329 }
1330
1331 /*
1332 * THP may get split above, need minus tail pages and update
1333 * nr_pages to avoid accounting tail pages twice.
1334 *
1335 * The tail pages that are added into swap cache successfully
1336 * reach here.
1337 */
1338 if ((nr_pages > 1) && !PageTransHuge(page)) {
1339 sc->nr_scanned -= (nr_pages - 1);
1340 nr_pages = 1;
1341 }
1342
1343 /*
1344 * The page is mapped into the page tables of one or more
1345 * processes. Try to unmap it here.
1346 */
1347 if (page_mapped(page)) {
1348 enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
1349
1350 if (unlikely(PageTransHuge(page)))
1351 flags |= TTU_SPLIT_HUGE_PMD;
1352 if (!try_to_unmap(page, flags)) {
1353 stat->nr_unmap_fail += nr_pages;
1354 goto activate_locked;
1355 }
1356 }
1357
1358 if (PageDirty(page)) {
1359 /*
1360 * Only kswapd can writeback filesystem pages
1361 * to avoid risk of stack overflow. But avoid
1362 * injecting inefficient single-page IO into
1363 * flusher writeback as much as possible: only
1364 * write pages when we've encountered many
1365 * dirty pages, and when we've already scanned
1366 * the rest of the LRU for clean pages and see
1367 * the same dirty pages again (PageReclaim).
1368 */
1369 if (page_is_file_cache(page) &&
1370 (!current_is_kswapd() || !PageReclaim(page) ||
1371 !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1372 /*
1373 * Immediately reclaim when written back.
1374 * Similar in principal to deactivate_page()
1375 * except we already have the page isolated
1376 * and know it's dirty
1377 */
1378 inc_node_page_state(page, NR_VMSCAN_IMMEDIATE);
1379 SetPageReclaim(page);
1380
1381 goto activate_locked;
1382 }
1383
1384 if (references == PAGEREF_RECLAIM_CLEAN)
1385 goto keep_locked;
1386 if (!may_enter_fs)
1387 goto keep_locked;
1388 if (!sc->may_writepage)
1389 goto keep_locked;
1390
1391 /*
1392 * Page is dirty. Flush the TLB if a writable entry
1393 * potentially exists to avoid CPU writes after IO
1394 * starts and then write it out here.
1395 */
1396 try_to_unmap_flush_dirty();
1397 switch (pageout(page, mapping, sc)) {
1398 case PAGE_KEEP:
1399 goto keep_locked;
1400 case PAGE_ACTIVATE:
1401 goto activate_locked;
1402 case PAGE_SUCCESS:
1403 if (PageWriteback(page))
1404 goto keep;
1405 if (PageDirty(page))
1406 goto keep;
1407
1408 /*
1409 * A synchronous write - probably a ramdisk. Go
1410 * ahead and try to reclaim the page.
1411 */
1412 if (!trylock_page(page))
1413 goto keep;
1414 if (PageDirty(page) || PageWriteback(page))
1415 goto keep_locked;
1416 mapping = page_mapping(page);
1417 case PAGE_CLEAN:
1418 ; /* try to free the page below */
1419 }
1420 }
1421
1422 /*
1423 * If the page has buffers, try to free the buffer mappings
1424 * associated with this page. If we succeed we try to free
1425 * the page as well.
1426 *
1427 * We do this even if the page is PageDirty().
1428 * try_to_release_page() does not perform I/O, but it is
1429 * possible for a page to have PageDirty set, but it is actually
1430 * clean (all its buffers are clean). This happens if the
1431 * buffers were written out directly, with submit_bh(). ext3
1432 * will do this, as well as the blockdev mapping.
1433 * try_to_release_page() will discover that cleanness and will
1434 * drop the buffers and mark the page clean - it can be freed.
1435 *
1436 * Rarely, pages can have buffers and no ->mapping. These are
1437 * the pages which were not successfully invalidated in
1438 * truncate_complete_page(). We try to drop those buffers here
1439 * and if that worked, and the page is no longer mapped into
1440 * process address space (page_count == 1) it can be freed.
1441 * Otherwise, leave the page on the LRU so it is swappable.
1442 */
1443 if (page_has_private(page)) {
1444 if (!try_to_release_page(page, sc->gfp_mask))
1445 goto activate_locked;
1446 if (!mapping && page_count(page) == 1) {
1447 unlock_page(page);
1448 if (put_page_testzero(page))
1449 goto free_it;
1450 else {
1451 /*
1452 * rare race with speculative reference.
1453 * the speculative reference will free
1454 * this page shortly, so we may
1455 * increment nr_reclaimed here (and
1456 * leave it off the LRU).
1457 */
1458 nr_reclaimed++;
1459 continue;
1460 }
1461 }
1462 }
1463
1464 if (PageAnon(page) && !PageSwapBacked(page)) {
1465 /* follow __remove_mapping for reference */
1466 if (!page_ref_freeze(page, 1))
1467 goto keep_locked;
1468 if (PageDirty(page)) {
1469 page_ref_unfreeze(page, 1);
1470 goto keep_locked;
1471 }
1472
1473 count_vm_event(PGLAZYFREED);
1474 count_memcg_page_event(page, PGLAZYFREED);
1475 } else if (!mapping || !__remove_mapping(mapping, page, true))
1476 goto keep_locked;
1477
1478 unlock_page(page);
1479 free_it:
1480 /*
1481 * THP may get swapped out in a whole, need account
1482 * all base pages.
1483 */
1484 nr_reclaimed += nr_pages;
1485
1486 /*
1487 * Is there need to periodically free_page_list? It would
1488 * appear not as the counts should be low
1489 */
1490 if (unlikely(PageTransHuge(page)))
1491 (*get_compound_page_dtor(page))(page);
1492 else
1493 list_add(&page->lru, &free_pages);
1494 continue;
1495
1496 activate_locked_split:
1497 /*
1498 * The tail pages that are failed to add into swap cache
1499 * reach here. Fixup nr_scanned and nr_pages.
1500 */
1501 if (nr_pages > 1) {
1502 sc->nr_scanned -= (nr_pages - 1);
1503 nr_pages = 1;
1504 }
1505 activate_locked:
1506 /* Not a candidate for swapping, so reclaim swap space. */
1507 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
1508 PageMlocked(page)))
1509 try_to_free_swap(page);
1510 VM_BUG_ON_PAGE(PageActive(page), page);
1511 if (!PageMlocked(page)) {
1512 int type = page_is_file_cache(page);
1513 SetPageActive(page);
1514 stat->nr_activate[type] += nr_pages;
1515 count_memcg_page_event(page, PGACTIVATE);
1516 }
1517 keep_locked:
1518 unlock_page(page);
1519 keep:
1520 list_add(&page->lru, &ret_pages);
1521 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
1522 }
1523
1524 pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
1525
1526 mem_cgroup_uncharge_list(&free_pages);
1527 try_to_unmap_flush();
1528 free_unref_page_list(&free_pages);
1529
1530 list_splice(&ret_pages, page_list);
1531 count_vm_events(PGACTIVATE, pgactivate);
1532
1533 return nr_reclaimed;
1534 }
1535
1536 unsigned long reclaim_clean_pages_from_list(struct zone *zone,
1537 struct list_head *page_list)
1538 {
1539 struct scan_control sc = {
1540 .gfp_mask = GFP_KERNEL,
1541 .priority = DEF_PRIORITY,
1542 .may_unmap = 1,
1543 };
1544 struct reclaim_stat dummy_stat;
1545 unsigned long ret;
1546 struct page *page, *next;
1547 LIST_HEAD(clean_pages);
1548
1549 list_for_each_entry_safe(page, next, page_list, lru) {
1550 if (page_is_file_cache(page) && !PageDirty(page) &&
1551 !__PageMovable(page) && !PageUnevictable(page)) {
1552 ClearPageActive(page);
1553 list_move(&page->lru, &clean_pages);
1554 }
1555 }
1556
1557 ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
1558 TTU_IGNORE_ACCESS, &dummy_stat, true);
1559 list_splice(&clean_pages, page_list);
1560 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret);
1561 return ret;
1562 }
1563
1564 /*
1565 * Attempt to remove the specified page from its LRU. Only take this page
1566 * if it is of the appropriate PageActive status. Pages which are being
1567 * freed elsewhere are also ignored.
1568 *
1569 * page: page to consider
1570 * mode: one of the LRU isolation modes defined above
1571 *
1572 * returns 0 on success, -ve errno on failure.
1573 */
1574 int __isolate_lru_page(struct page *page, isolate_mode_t mode)
1575 {
1576 int ret = -EINVAL;
1577
1578 /* Only take pages on the LRU. */
1579 if (!PageLRU(page))
1580 return ret;
1581
1582 /* Compaction should not handle unevictable pages but CMA can do so */
1583 if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
1584 return ret;
1585
1586 ret = -EBUSY;
1587
1588 /*
1589 * To minimise LRU disruption, the caller can indicate that it only
1590 * wants to isolate pages it will be able to operate on without
1591 * blocking - clean pages for the most part.
1592 *
1593 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1594 * that it is possible to migrate without blocking
1595 */
1596 if (mode & ISOLATE_ASYNC_MIGRATE) {
1597 /* All the caller can do on PageWriteback is block */
1598 if (PageWriteback(page))
1599 return ret;
1600
1601 if (PageDirty(page)) {
1602 struct address_space *mapping;
1603 bool migrate_dirty;
1604
1605 /*
1606 * Only pages without mappings or that have a
1607 * ->migratepage callback are possible to migrate
1608 * without blocking. However, we can be racing with
1609 * truncation so it's necessary to lock the page
1610 * to stabilise the mapping as truncation holds
1611 * the page lock until after the page is removed
1612 * from the page cache.
1613 */
1614 if (!trylock_page(page))
1615 return ret;
1616
1617 mapping = page_mapping(page);
1618 migrate_dirty = !mapping || mapping->a_ops->migratepage;
1619 unlock_page(page);
1620 if (!migrate_dirty)
1621 return ret;
1622 }
1623 }
1624
1625 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1626 return ret;
1627
1628 if (likely(get_page_unless_zero(page))) {
1629 /*
1630 * Be careful not to clear PageLRU until after we're
1631 * sure the page is not being freed elsewhere -- the
1632 * page release code relies on it.
1633 */
1634 ClearPageLRU(page);
1635 ret = 0;
1636 }
1637
1638 return ret;
1639 }
1640
1641
1642 /*
1643 * Update LRU sizes after isolating pages. The LRU size updates must
1644 * be complete before mem_cgroup_update_lru_size due to a santity check.
1645 */
1646 static __always_inline void update_lru_sizes(struct lruvec *lruvec,
1647 enum lru_list lru, unsigned long *nr_zone_taken)
1648 {
1649 int zid;
1650
1651 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1652 if (!nr_zone_taken[zid])
1653 continue;
1654
1655 __update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
1656 #ifdef CONFIG_MEMCG
1657 mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
1658 #endif
1659 }
1660
1661 }
1662
1663 /**
1664 * pgdat->lru_lock is heavily contended. Some of the functions that
1665 * shrink the lists perform better by taking out a batch of pages
1666 * and working on them outside the LRU lock.
1667 *
1668 * For pagecache intensive workloads, this function is the hottest
1669 * spot in the kernel (apart from copy_*_user functions).
1670 *
1671 * Appropriate locks must be held before calling this function.
1672 *
1673 * @nr_to_scan: The number of eligible pages to look through on the list.
1674 * @lruvec: The LRU vector to pull pages from.
1675 * @dst: The temp list to put pages on to.
1676 * @nr_scanned: The number of pages that were scanned.
1677 * @sc: The scan_control struct for this reclaim session
1678 * @mode: One of the LRU isolation modes
1679 * @lru: LRU list id for isolating
1680 *
1681 * returns how many pages were moved onto *@dst.
1682 */
1683 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1684 struct lruvec *lruvec, struct list_head *dst,
1685 unsigned long *nr_scanned, struct scan_control *sc,
1686 enum lru_list lru)
1687 {
1688 struct list_head *src = &lruvec->lists[lru];
1689 unsigned long nr_taken = 0;
1690 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
1691 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
1692 unsigned long skipped = 0;
1693 unsigned long scan, total_scan, nr_pages;
1694 LIST_HEAD(pages_skipped);
1695 isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED);
1696
1697 total_scan = 0;
1698 scan = 0;
1699 while (scan < nr_to_scan && !list_empty(src)) {
1700 struct page *page;
1701
1702 page = lru_to_page(src);
1703 prefetchw_prev_lru_page(page, src, flags);
1704
1705 VM_BUG_ON_PAGE(!PageLRU(page), page);
1706
1707 nr_pages = compound_nr(page);
1708 total_scan += nr_pages;
1709
1710 if (page_zonenum(page) > sc->reclaim_idx) {
1711 list_move(&page->lru, &pages_skipped);
1712 nr_skipped[page_zonenum(page)] += nr_pages;
1713 continue;
1714 }
1715
1716 /*
1717 * Do not count skipped pages because that makes the function
1718 * return with no isolated pages if the LRU mostly contains
1719 * ineligible pages. This causes the VM to not reclaim any
1720 * pages, triggering a premature OOM.
1721 *
1722 * Account all tail pages of THP. This would not cause
1723 * premature OOM since __isolate_lru_page() returns -EBUSY
1724 * only when the page is being freed somewhere else.
1725 */
1726 scan += nr_pages;
1727 switch (__isolate_lru_page(page, mode)) {
1728 case 0:
1729 nr_taken += nr_pages;
1730 nr_zone_taken[page_zonenum(page)] += nr_pages;
1731 list_move(&page->lru, dst);
1732 break;
1733
1734 case -EBUSY:
1735 /* else it is being freed elsewhere */
1736 list_move(&page->lru, src);
1737 continue;
1738
1739 default:
1740 BUG();
1741 }
1742 }
1743
1744 /*
1745 * Splice any skipped pages to the start of the LRU list. Note that
1746 * this disrupts the LRU order when reclaiming for lower zones but
1747 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1748 * scanning would soon rescan the same pages to skip and put the
1749 * system at risk of premature OOM.
1750 */
1751 if (!list_empty(&pages_skipped)) {
1752 int zid;
1753
1754 list_splice(&pages_skipped, src);
1755 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1756 if (!nr_skipped[zid])
1757 continue;
1758
1759 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
1760 skipped += nr_skipped[zid];
1761 }
1762 }
1763 *nr_scanned = total_scan;
1764 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
1765 total_scan, skipped, nr_taken, mode, lru);
1766 update_lru_sizes(lruvec, lru, nr_zone_taken);
1767 return nr_taken;
1768 }
1769
1770 /**
1771 * isolate_lru_page - tries to isolate a page from its LRU list
1772 * @page: page to isolate from its LRU list
1773 *
1774 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1775 * vmstat statistic corresponding to whatever LRU list the page was on.
1776 *
1777 * Returns 0 if the page was removed from an LRU list.
1778 * Returns -EBUSY if the page was not on an LRU list.
1779 *
1780 * The returned page will have PageLRU() cleared. If it was found on
1781 * the active list, it will have PageActive set. If it was found on
1782 * the unevictable list, it will have the PageUnevictable bit set. That flag
1783 * may need to be cleared by the caller before letting the page go.
1784 *
1785 * The vmstat statistic corresponding to the list on which the page was
1786 * found will be decremented.
1787 *
1788 * Restrictions:
1789 *
1790 * (1) Must be called with an elevated refcount on the page. This is a
1791 * fundamentnal difference from isolate_lru_pages (which is called
1792 * without a stable reference).
1793 * (2) the lru_lock must not be held.
1794 * (3) interrupts must be enabled.
1795 */
1796 int isolate_lru_page(struct page *page)
1797 {
1798 int ret = -EBUSY;
1799
1800 VM_BUG_ON_PAGE(!page_count(page), page);
1801 WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
1802
1803 if (PageLRU(page)) {
1804 pg_data_t *pgdat = page_pgdat(page);
1805 struct lruvec *lruvec;
1806
1807 spin_lock_irq(&pgdat->lru_lock);
1808 lruvec = mem_cgroup_page_lruvec(page, pgdat);
1809 if (PageLRU(page)) {
1810 int lru = page_lru(page);
1811 get_page(page);
1812 ClearPageLRU(page);
1813 del_page_from_lru_list(page, lruvec, lru);
1814 ret = 0;
1815 }
1816 spin_unlock_irq(&pgdat->lru_lock);
1817 }
1818 return ret;
1819 }
1820
1821 /*
1822 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1823 * then get resheduled. When there are massive number of tasks doing page
1824 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1825 * the LRU list will go small and be scanned faster than necessary, leading to
1826 * unnecessary swapping, thrashing and OOM.
1827 */
1828 static int too_many_isolated(struct pglist_data *pgdat, int file,
1829 struct scan_control *sc)
1830 {
1831 unsigned long inactive, isolated;
1832
1833 if (current_is_kswapd())
1834 return 0;
1835
1836 if (!sane_reclaim(sc))
1837 return 0;
1838
1839 if (file) {
1840 inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
1841 isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
1842 } else {
1843 inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
1844 isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
1845 }
1846
1847 /*
1848 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1849 * won't get blocked by normal direct-reclaimers, forming a circular
1850 * deadlock.
1851 */
1852 if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
1853 inactive >>= 3;
1854
1855 return isolated > inactive;
1856 }
1857
1858 /*
1859 * This moves pages from @list to corresponding LRU list.
1860 *
1861 * We move them the other way if the page is referenced by one or more
1862 * processes, from rmap.
1863 *
1864 * If the pages are mostly unmapped, the processing is fast and it is
1865 * appropriate to hold zone_lru_lock across the whole operation. But if
1866 * the pages are mapped, the processing is slow (page_referenced()) so we
1867 * should drop zone_lru_lock around each page. It's impossible to balance
1868 * this, so instead we remove the pages from the LRU while processing them.
1869 * It is safe to rely on PG_active against the non-LRU pages in here because
1870 * nobody will play with that bit on a non-LRU page.
1871 *
1872 * The downside is that we have to touch page->_refcount against each page.
1873 * But we had to alter page->flags anyway.
1874 *
1875 * Returns the number of pages moved to the given lruvec.
1876 */
1877
1878 static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
1879 struct list_head *list)
1880 {
1881 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
1882 int nr_pages, nr_moved = 0;
1883 LIST_HEAD(pages_to_free);
1884 struct page *page;
1885 enum lru_list lru;
1886
1887 while (!list_empty(list)) {
1888 page = lru_to_page(list);
1889 VM_BUG_ON_PAGE(PageLRU(page), page);
1890 if (unlikely(!page_evictable(page))) {
1891 list_del(&page->lru);
1892 spin_unlock_irq(&pgdat->lru_lock);
1893 putback_lru_page(page);
1894 spin_lock_irq(&pgdat->lru_lock);
1895 continue;
1896 }
1897 lruvec = mem_cgroup_page_lruvec(page, pgdat);
1898
1899 SetPageLRU(page);
1900 lru = page_lru(page);
1901
1902 nr_pages = hpage_nr_pages(page);
1903 update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
1904 list_move(&page->lru, &lruvec->lists[lru]);
1905
1906 if (put_page_testzero(page)) {
1907 __ClearPageLRU(page);
1908 __ClearPageActive(page);
1909 del_page_from_lru_list(page, lruvec, lru);
1910
1911 if (unlikely(PageCompound(page))) {
1912 spin_unlock_irq(&pgdat->lru_lock);
1913 (*get_compound_page_dtor(page))(page);
1914 spin_lock_irq(&pgdat->lru_lock);
1915 } else
1916 list_add(&page->lru, &pages_to_free);
1917 } else {
1918 nr_moved += nr_pages;
1919 }
1920 }
1921
1922 /*
1923 * To save our caller's stack, now use input list for pages to free.
1924 */
1925 list_splice(&pages_to_free, list);
1926
1927 return nr_moved;
1928 }
1929
1930 /*
1931 * If a kernel thread (such as nfsd for loop-back mounts) services
1932 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1933 * In that case we should only throttle if the backing device it is
1934 * writing to is congested. In other cases it is safe to throttle.
1935 */
1936 static int current_may_throttle(void)
1937 {
1938 return !(current->flags & PF_LESS_THROTTLE) ||
1939 current->backing_dev_info == NULL ||
1940 bdi_write_congested(current->backing_dev_info);
1941 }
1942
1943 /*
1944 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
1945 * of reclaimed pages
1946 */
1947 static noinline_for_stack unsigned long
1948 shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
1949 struct scan_control *sc, enum lru_list lru)
1950 {
1951 LIST_HEAD(page_list);
1952 unsigned long nr_scanned;
1953 unsigned long nr_reclaimed = 0;
1954 unsigned long nr_taken;
1955 struct reclaim_stat stat;
1956 int file = is_file_lru(lru);
1957 enum vm_event_item item;
1958 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
1959 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1960 bool stalled = false;
1961
1962 while (unlikely(too_many_isolated(pgdat, file, sc))) {
1963 if (stalled)
1964 return 0;
1965
1966 /* wait a bit for the reclaimer. */
1967 msleep(100);
1968 stalled = true;
1969
1970 /* We are about to die and free our memory. Return now. */
1971 if (fatal_signal_pending(current))
1972 return SWAP_CLUSTER_MAX;
1973 }
1974
1975 lru_add_drain();
1976
1977 spin_lock_irq(&pgdat->lru_lock);
1978
1979 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
1980 &nr_scanned, sc, lru);
1981
1982 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
1983 reclaim_stat->recent_scanned[file] += nr_taken;
1984
1985 item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT;
1986 if (global_reclaim(sc))
1987 __count_vm_events(item, nr_scanned);
1988 __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
1989 spin_unlock_irq(&pgdat->lru_lock);
1990
1991 if (nr_taken == 0)
1992 return 0;
1993
1994 nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, 0,
1995 &stat, false);
1996
1997 spin_lock_irq(&pgdat->lru_lock);
1998
1999 item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
2000 if (global_reclaim(sc))
2001 __count_vm_events(item, nr_reclaimed);
2002 __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
2003 reclaim_stat->recent_rotated[0] += stat.nr_activate[0];
2004 reclaim_stat->recent_rotated[1] += stat.nr_activate[1];
2005
2006 move_pages_to_lru(lruvec, &page_list);
2007
2008 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2009
2010 spin_unlock_irq(&pgdat->lru_lock);
2011
2012 mem_cgroup_uncharge_list(&page_list);
2013 free_unref_page_list(&page_list);
2014
2015 /*
2016 * If dirty pages are scanned that are not queued for IO, it
2017 * implies that flushers are not doing their job. This can
2018 * happen when memory pressure pushes dirty pages to the end of
2019 * the LRU before the dirty limits are breached and the dirty
2020 * data has expired. It can also happen when the proportion of
2021 * dirty pages grows not through writes but through memory
2022 * pressure reclaiming all the clean cache. And in some cases,
2023 * the flushers simply cannot keep up with the allocation
2024 * rate. Nudge the flusher threads in case they are asleep.
2025 */
2026 if (stat.nr_unqueued_dirty == nr_taken)
2027 wakeup_flusher_threads(WB_REASON_VMSCAN);
2028
2029 sc->nr.dirty += stat.nr_dirty;
2030 sc->nr.congested += stat.nr_congested;
2031 sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
2032 sc->nr.writeback += stat.nr_writeback;
2033 sc->nr.immediate += stat.nr_immediate;
2034 sc->nr.taken += nr_taken;
2035 if (file)
2036 sc->nr.file_taken += nr_taken;
2037
2038 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
2039 nr_scanned, nr_reclaimed, &stat, sc->priority, file);
2040 return nr_reclaimed;
2041 }
2042
2043 static void shrink_active_list(unsigned long nr_to_scan,
2044 struct lruvec *lruvec,
2045 struct scan_control *sc,
2046 enum lru_list lru)
2047 {
2048 unsigned long nr_taken;
2049 unsigned long nr_scanned;
2050 unsigned long vm_flags;
2051 LIST_HEAD(l_hold); /* The pages which were snipped off */
2052 LIST_HEAD(l_active);
2053 LIST_HEAD(l_inactive);
2054 struct page *page;
2055 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
2056 unsigned nr_deactivate, nr_activate;
2057 unsigned nr_rotated = 0;
2058 int file = is_file_lru(lru);
2059 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2060
2061 lru_add_drain();
2062
2063 spin_lock_irq(&pgdat->lru_lock);
2064
2065 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
2066 &nr_scanned, sc, lru);
2067
2068 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2069 reclaim_stat->recent_scanned[file] += nr_taken;
2070
2071 __count_vm_events(PGREFILL, nr_scanned);
2072 __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2073
2074 spin_unlock_irq(&pgdat->lru_lock);
2075
2076 while (!list_empty(&l_hold)) {
2077 cond_resched();
2078 page = lru_to_page(&l_hold);
2079 list_del(&page->lru);
2080
2081 if (unlikely(!page_evictable(page))) {
2082 putback_lru_page(page);
2083 continue;
2084 }
2085
2086 if (unlikely(buffer_heads_over_limit)) {
2087 if (page_has_private(page) && trylock_page(page)) {
2088 if (page_has_private(page))
2089 try_to_release_page(page, 0);
2090 unlock_page(page);
2091 }
2092 }
2093
2094 if (page_referenced(page, 0, sc->target_mem_cgroup,
2095 &vm_flags)) {
2096 nr_rotated += hpage_nr_pages(page);
2097 /*
2098 * Identify referenced, file-backed active pages and
2099 * give them one more trip around the active list. So
2100 * that executable code get better chances to stay in
2101 * memory under moderate memory pressure. Anon pages
2102 * are not likely to be evicted by use-once streaming
2103 * IO, plus JVM can create lots of anon VM_EXEC pages,
2104 * so we ignore them here.
2105 */
2106 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
2107 list_add(&page->lru, &l_active);
2108 continue;
2109 }
2110 }
2111
2112 ClearPageActive(page); /* we are de-activating */
2113 SetPageWorkingset(page);
2114 list_add(&page->lru, &l_inactive);
2115 }
2116
2117 /*
2118 * Move pages back to the lru list.
2119 */
2120 spin_lock_irq(&pgdat->lru_lock);
2121 /*
2122 * Count referenced pages from currently used mappings as rotated,
2123 * even though only some of them are actually re-activated. This
2124 * helps balance scan pressure between file and anonymous pages in
2125 * get_scan_count.
2126 */
2127 reclaim_stat->recent_rotated[file] += nr_rotated;
2128
2129 nr_activate = move_pages_to_lru(lruvec, &l_active);
2130 nr_deactivate = move_pages_to_lru(lruvec, &l_inactive);
2131 /* Keep all free pages in l_active list */
2132 list_splice(&l_inactive, &l_active);
2133
2134 __count_vm_events(PGDEACTIVATE, nr_deactivate);
2135 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2136
2137 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2138 spin_unlock_irq(&pgdat->lru_lock);
2139
2140 mem_cgroup_uncharge_list(&l_active);
2141 free_unref_page_list(&l_active);
2142 trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2143 nr_deactivate, nr_rotated, sc->priority, file);
2144 }
2145
2146 unsigned long reclaim_pages(struct list_head *page_list)
2147 {
2148 int nid = -1;
2149 unsigned long nr_reclaimed = 0;
2150 LIST_HEAD(node_page_list);
2151 struct reclaim_stat dummy_stat;
2152 struct page *page;
2153 struct scan_control sc = {
2154 .gfp_mask = GFP_KERNEL,
2155 .priority = DEF_PRIORITY,
2156 .may_writepage = 1,
2157 .may_unmap = 1,
2158 .may_swap = 1,
2159 };
2160
2161 while (!list_empty(page_list)) {
2162 page = lru_to_page(page_list);
2163 if (nid == -1) {
2164 nid = page_to_nid(page);
2165 INIT_LIST_HEAD(&node_page_list);
2166 }
2167
2168 if (nid == page_to_nid(page)) {
2169 ClearPageActive(page);
2170 list_move(&page->lru, &node_page_list);
2171 continue;
2172 }
2173
2174 nr_reclaimed += shrink_page_list(&node_page_list,
2175 NODE_DATA(nid),
2176 &sc, 0,
2177 &dummy_stat, false);
2178 while (!list_empty(&node_page_list)) {
2179 page = lru_to_page(&node_page_list);
2180 list_del(&page->lru);
2181 putback_lru_page(page);
2182 }
2183
2184 nid = -1;
2185 }
2186
2187 if (!list_empty(&node_page_list)) {
2188 nr_reclaimed += shrink_page_list(&node_page_list,
2189 NODE_DATA(nid),
2190 &sc, 0,
2191 &dummy_stat, false);
2192 while (!list_empty(&node_page_list)) {
2193 page = lru_to_page(&node_page_list);
2194 list_del(&page->lru);
2195 putback_lru_page(page);
2196 }
2197 }
2198
2199 return nr_reclaimed;
2200 }
2201
2202 /*
2203 * The inactive anon list should be small enough that the VM never has
2204 * to do too much work.
2205 *
2206 * The inactive file list should be small enough to leave most memory
2207 * to the established workingset on the scan-resistant active list,
2208 * but large enough to avoid thrashing the aggregate readahead window.
2209 *
2210 * Both inactive lists should also be large enough that each inactive
2211 * page has a chance to be referenced again before it is reclaimed.
2212 *
2213 * If that fails and refaulting is observed, the inactive list grows.
2214 *
2215 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2216 * on this LRU, maintained by the pageout code. An inactive_ratio
2217 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2218 *
2219 * total target max
2220 * memory ratio inactive
2221 * -------------------------------------
2222 * 10MB 1 5MB
2223 * 100MB 1 50MB
2224 * 1GB 3 250MB
2225 * 10GB 10 0.9GB
2226 * 100GB 31 3GB
2227 * 1TB 101 10GB
2228 * 10TB 320 32GB
2229 */
2230 static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
2231 struct scan_control *sc, bool trace)
2232 {
2233 enum lru_list active_lru = file * LRU_FILE + LRU_ACTIVE;
2234 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2235 enum lru_list inactive_lru = file * LRU_FILE;
2236 unsigned long inactive, active;
2237 unsigned long inactive_ratio;
2238 unsigned long refaults;
2239 unsigned long gb;
2240
2241 /*
2242 * If we don't have swap space, anonymous page deactivation
2243 * is pointless.
2244 */
2245 if (!file && !total_swap_pages)
2246 return false;
2247
2248 inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx);
2249 active = lruvec_lru_size(lruvec, active_lru, sc->reclaim_idx);
2250
2251 /*
2252 * When refaults are being observed, it means a new workingset
2253 * is being established. Disable active list protection to get
2254 * rid of the stale workingset quickly.
2255 */
2256 refaults = lruvec_page_state_local(lruvec, WORKINGSET_ACTIVATE);
2257 if (file && lruvec->refaults != refaults) {
2258 inactive_ratio = 0;
2259 } else {
2260 gb = (inactive + active) >> (30 - PAGE_SHIFT);
2261 if (gb)
2262 inactive_ratio = int_sqrt(10 * gb);
2263 else
2264 inactive_ratio = 1;
2265 }
2266
2267 if (trace)
2268 trace_mm_vmscan_inactive_list_is_low(pgdat->node_id, sc->reclaim_idx,
2269 lruvec_lru_size(lruvec, inactive_lru, MAX_NR_ZONES), inactive,
2270 lruvec_lru_size(lruvec, active_lru, MAX_NR_ZONES), active,
2271 inactive_ratio, file);
2272
2273 return inactive * inactive_ratio < active;
2274 }
2275
2276 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2277 struct lruvec *lruvec, struct scan_control *sc)
2278 {
2279 if (is_active_lru(lru)) {
2280 if (inactive_list_is_low(lruvec, is_file_lru(lru), sc, true))
2281 shrink_active_list(nr_to_scan, lruvec, sc, lru);
2282 return 0;
2283 }
2284
2285 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2286 }
2287
2288 enum scan_balance {
2289 SCAN_EQUAL,
2290 SCAN_FRACT,
2291 SCAN_ANON,
2292 SCAN_FILE,
2293 };
2294
2295 /*
2296 * Determine how aggressively the anon and file LRU lists should be
2297 * scanned. The relative value of each set of LRU lists is determined
2298 * by looking at the fraction of the pages scanned we did rotate back
2299 * onto the active list instead of evict.
2300 *
2301 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2302 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2303 */
2304 static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
2305 struct scan_control *sc, unsigned long *nr,
2306 unsigned long *lru_pages)
2307 {
2308 int swappiness = mem_cgroup_swappiness(memcg);
2309 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
2310 u64 fraction[2];
2311 u64 denominator = 0; /* gcc */
2312 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2313 unsigned long anon_prio, file_prio;
2314 enum scan_balance scan_balance;
2315 unsigned long anon, file;
2316 unsigned long ap, fp;
2317 enum lru_list lru;
2318
2319 /* If we have no swap space, do not bother scanning anon pages. */
2320 if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) {
2321 scan_balance = SCAN_FILE;
2322 goto out;
2323 }
2324
2325 /*
2326 * Global reclaim will swap to prevent OOM even with no
2327 * swappiness, but memcg users want to use this knob to
2328 * disable swapping for individual groups completely when
2329 * using the memory controller's swap limit feature would be
2330 * too expensive.
2331 */
2332 if (!global_reclaim(sc) && !swappiness) {
2333 scan_balance = SCAN_FILE;
2334 goto out;
2335 }
2336
2337 /*
2338 * Do not apply any pressure balancing cleverness when the
2339 * system is close to OOM, scan both anon and file equally
2340 * (unless the swappiness setting disagrees with swapping).
2341 */
2342 if (!sc->priority && swappiness) {
2343 scan_balance = SCAN_EQUAL;
2344 goto out;
2345 }
2346
2347 /*
2348 * Prevent the reclaimer from falling into the cache trap: as
2349 * cache pages start out inactive, every cache fault will tip
2350 * the scan balance towards the file LRU. And as the file LRU
2351 * shrinks, so does the window for rotation from references.
2352 * This means we have a runaway feedback loop where a tiny
2353 * thrashing file LRU becomes infinitely more attractive than
2354 * anon pages. Try to detect this based on file LRU size.
2355 */
2356 if (global_reclaim(sc)) {
2357 unsigned long pgdatfile;
2358 unsigned long pgdatfree;
2359 int z;
2360 unsigned long total_high_wmark = 0;
2361
2362 pgdatfree = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2363 pgdatfile = node_page_state(pgdat, NR_ACTIVE_FILE) +
2364 node_page_state(pgdat, NR_INACTIVE_FILE);
2365
2366 for (z = 0; z < MAX_NR_ZONES; z++) {
2367 struct zone *zone = &pgdat->node_zones[z];
2368 if (!managed_zone(zone))
2369 continue;
2370
2371 total_high_wmark += high_wmark_pages(zone);
2372 }
2373
2374 if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
2375 /*
2376 * Force SCAN_ANON if there are enough inactive
2377 * anonymous pages on the LRU in eligible zones.
2378 * Otherwise, the small LRU gets thrashed.
2379 */
2380 if (!inactive_list_is_low(lruvec, false, sc, false) &&
2381 lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
2382 >> sc->priority) {
2383 scan_balance = SCAN_ANON;
2384 goto out;
2385 }
2386 }
2387 }
2388
2389 /*
2390 * If there is enough inactive page cache, i.e. if the size of the
2391 * inactive list is greater than that of the active list *and* the
2392 * inactive list actually has some pages to scan on this priority, we
2393 * do not reclaim anything from the anonymous working set right now.
2394 * Without the second condition we could end up never scanning an
2395 * lruvec even if it has plenty of old anonymous pages unless the
2396 * system is under heavy pressure.
2397 */
2398 if (!inactive_list_is_low(lruvec, true, sc, false) &&
2399 lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
2400 scan_balance = SCAN_FILE;
2401 goto out;
2402 }
2403
2404 scan_balance = SCAN_FRACT;
2405
2406 /*
2407 * With swappiness at 100, anonymous and file have the same priority.
2408 * This scanning priority is essentially the inverse of IO cost.
2409 */
2410 anon_prio = swappiness;
2411 file_prio = 200 - anon_prio;
2412
2413 /*
2414 * OK, so we have swap space and a fair amount of page cache
2415 * pages. We use the recently rotated / recently scanned
2416 * ratios to determine how valuable each cache is.
2417 *
2418 * Because workloads change over time (and to avoid overflow)
2419 * we keep these statistics as a floating average, which ends
2420 * up weighing recent references more than old ones.
2421 *
2422 * anon in [0], file in [1]
2423 */
2424
2425 anon = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) +
2426 lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES);
2427 file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
2428 lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES);
2429
2430 spin_lock_irq(&pgdat->lru_lock);
2431 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
2432 reclaim_stat->recent_scanned[0] /= 2;
2433 reclaim_stat->recent_rotated[0] /= 2;
2434 }
2435
2436 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
2437 reclaim_stat->recent_scanned[1] /= 2;
2438 reclaim_stat->recent_rotated[1] /= 2;
2439 }
2440
2441 /*
2442 * The amount of pressure on anon vs file pages is inversely
2443 * proportional to the fraction of recently scanned pages on
2444 * each list that were recently referenced and in active use.
2445 */
2446 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
2447 ap /= reclaim_stat->recent_rotated[0] + 1;
2448
2449 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
2450 fp /= reclaim_stat->recent_rotated[1] + 1;
2451 spin_unlock_irq(&pgdat->lru_lock);
2452
2453 fraction[0] = ap;
2454 fraction[1] = fp;
2455 denominator = ap + fp + 1;
2456 out:
2457 *lru_pages = 0;
2458 for_each_evictable_lru(lru) {
2459 int file = is_file_lru(lru);
2460 unsigned long lruvec_size;
2461 unsigned long scan;
2462 unsigned long protection;
2463
2464 lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
2465 protection = mem_cgroup_protection(memcg,
2466 sc->memcg_low_reclaim);
2467
2468 if (protection) {
2469 /*
2470 * Scale a cgroup's reclaim pressure by proportioning
2471 * its current usage to its memory.low or memory.min
2472 * setting.
2473 *
2474 * This is important, as otherwise scanning aggression
2475 * becomes extremely binary -- from nothing as we
2476 * approach the memory protection threshold, to totally
2477 * nominal as we exceed it. This results in requiring
2478 * setting extremely liberal protection thresholds. It
2479 * also means we simply get no protection at all if we
2480 * set it too low, which is not ideal.
2481 *
2482 * If there is any protection in place, we reduce scan
2483 * pressure by how much of the total memory used is
2484 * within protection thresholds.
2485 *
2486 * There is one special case: in the first reclaim pass,
2487 * we skip over all groups that are within their low
2488 * protection. If that fails to reclaim enough pages to
2489 * satisfy the reclaim goal, we come back and override
2490 * the best-effort low protection. However, we still
2491 * ideally want to honor how well-behaved groups are in
2492 * that case instead of simply punishing them all
2493 * equally. As such, we reclaim them based on how much
2494 * memory they are using, reducing the scan pressure
2495 * again by how much of the total memory used is under
2496 * hard protection.
2497 */
2498 unsigned long cgroup_size = mem_cgroup_size(memcg);
2499
2500 /* Avoid TOCTOU with earlier protection check */
2501 cgroup_size = max(cgroup_size, protection);
2502
2503 scan = lruvec_size - lruvec_size * protection /
2504 cgroup_size;
2505
2506 /*
2507 * Minimally target SWAP_CLUSTER_MAX pages to keep
2508 * reclaim moving forwards, avoiding decremeting
2509 * sc->priority further than desirable.
2510 */
2511 scan = max(scan, SWAP_CLUSTER_MAX);
2512 } else {
2513 scan = lruvec_size;
2514 }
2515
2516 scan >>= sc->priority;
2517
2518 /*
2519 * If the cgroup's already been deleted, make sure to
2520 * scrape out the remaining cache.
2521 */
2522 if (!scan && !mem_cgroup_online(memcg))
2523 scan = min(lruvec_size, SWAP_CLUSTER_MAX);
2524
2525 switch (scan_balance) {
2526 case SCAN_EQUAL:
2527 /* Scan lists relative to size */
2528 break;
2529 case SCAN_FRACT:
2530 /*
2531 * Scan types proportional to swappiness and
2532 * their relative recent reclaim efficiency.
2533 * Make sure we don't miss the last page on
2534 * the offlined memory cgroups because of a
2535 * round-off error.
2536 */
2537 scan = mem_cgroup_online(memcg) ?
2538 div64_u64(scan * fraction[file], denominator) :
2539 DIV64_U64_ROUND_UP(scan * fraction[file],
2540 denominator);
2541 break;
2542 case SCAN_FILE:
2543 case SCAN_ANON:
2544 /* Scan one type exclusively */
2545 if ((scan_balance == SCAN_FILE) != file) {
2546 lruvec_size = 0;
2547 scan = 0;
2548 }
2549 break;
2550 default:
2551 /* Look ma, no brain */
2552 BUG();
2553 }
2554
2555 *lru_pages += lruvec_size;
2556 nr[lru] = scan;
2557 }
2558 }
2559
2560 /*
2561 * This is a basic per-node page freer. Used by both kswapd and direct reclaim.
2562 */
2563 static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg,
2564 struct scan_control *sc, unsigned long *lru_pages)
2565 {
2566 struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);
2567 unsigned long nr[NR_LRU_LISTS];
2568 unsigned long targets[NR_LRU_LISTS];
2569 unsigned long nr_to_scan;
2570 enum lru_list lru;
2571 unsigned long nr_reclaimed = 0;
2572 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2573 struct blk_plug plug;
2574 bool scan_adjusted;
2575
2576 get_scan_count(lruvec, memcg, sc, nr, lru_pages);
2577
2578 /* Record the original scan target for proportional adjustments later */
2579 memcpy(targets, nr, sizeof(nr));
2580
2581 /*
2582 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2583 * event that can occur when there is little memory pressure e.g.
2584 * multiple streaming readers/writers. Hence, we do not abort scanning
2585 * when the requested number of pages are reclaimed when scanning at
2586 * DEF_PRIORITY on the assumption that the fact we are direct
2587 * reclaiming implies that kswapd is not keeping up and it is best to
2588 * do a batch of work at once. For memcg reclaim one check is made to
2589 * abort proportional reclaim if either the file or anon lru has already
2590 * dropped to zero at the first pass.
2591 */
2592 scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() &&
2593 sc->priority == DEF_PRIORITY);
2594
2595 blk_start_plug(&plug);
2596 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2597 nr[LRU_INACTIVE_FILE]) {
2598 unsigned long nr_anon, nr_file, percentage;
2599 unsigned long nr_scanned;
2600
2601 for_each_evictable_lru(lru) {
2602 if (nr[lru]) {
2603 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
2604 nr[lru] -= nr_to_scan;
2605
2606 nr_reclaimed += shrink_list(lru, nr_to_scan,
2607 lruvec, sc);
2608 }
2609 }
2610
2611 cond_resched();
2612
2613 if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
2614 continue;
2615
2616 /*
2617 * For kswapd and memcg, reclaim at least the number of pages
2618 * requested. Ensure that the anon and file LRUs are scanned
2619 * proportionally what was requested by get_scan_count(). We
2620 * stop reclaiming one LRU and reduce the amount scanning
2621 * proportional to the original scan target.
2622 */
2623 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
2624 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
2625
2626 /*
2627 * It's just vindictive to attack the larger once the smaller
2628 * has gone to zero. And given the way we stop scanning the
2629 * smaller below, this makes sure that we only make one nudge
2630 * towards proportionality once we've got nr_to_reclaim.
2631 */
2632 if (!nr_file || !nr_anon)
2633 break;
2634
2635 if (nr_file > nr_anon) {
2636 unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
2637 targets[LRU_ACTIVE_ANON] + 1;
2638 lru = LRU_BASE;
2639 percentage = nr_anon * 100 / scan_target;
2640 } else {
2641 unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
2642 targets[LRU_ACTIVE_FILE] + 1;
2643 lru = LRU_FILE;
2644 percentage = nr_file * 100 / scan_target;
2645 }
2646
2647 /* Stop scanning the smaller of the LRU */
2648 nr[lru] = 0;
2649 nr[lru + LRU_ACTIVE] = 0;
2650
2651 /*
2652 * Recalculate the other LRU scan count based on its original
2653 * scan target and the percentage scanning already complete
2654 */
2655 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
2656 nr_scanned = targets[lru] - nr[lru];
2657 nr[lru] = targets[lru] * (100 - percentage) / 100;
2658 nr[lru] -= min(nr[lru], nr_scanned);
2659
2660 lru += LRU_ACTIVE;
2661 nr_scanned = targets[lru] - nr[lru];
2662 nr[lru] = targets[lru] * (100 - percentage) / 100;
2663 nr[lru] -= min(nr[lru], nr_scanned);
2664
2665 scan_adjusted = true;
2666 }
2667 blk_finish_plug(&plug);
2668 sc->nr_reclaimed += nr_reclaimed;
2669
2670 /*
2671 * Even if we did not try to evict anon pages at all, we want to
2672 * rebalance the anon lru active/inactive ratio.
2673 */
2674 if (inactive_list_is_low(lruvec, false, sc, true))
2675 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2676 sc, LRU_ACTIVE_ANON);
2677 }
2678
2679 /* Use reclaim/compaction for costly allocs or under memory pressure */
2680 static bool in_reclaim_compaction(struct scan_control *sc)
2681 {
2682 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
2683 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
2684 sc->priority < DEF_PRIORITY - 2))
2685 return true;
2686
2687 return false;
2688 }
2689
2690 /*
2691 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2692 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2693 * true if more pages should be reclaimed such that when the page allocator
2694 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2695 * It will give up earlier than that if there is difficulty reclaiming pages.
2696 */
2697 static inline bool should_continue_reclaim(struct pglist_data *pgdat,
2698 unsigned long nr_reclaimed,
2699 struct scan_control *sc)
2700 {
2701 unsigned long pages_for_compaction;
2702 unsigned long inactive_lru_pages;
2703 int z;
2704
2705 /* If not in reclaim/compaction mode, stop */
2706 if (!in_reclaim_compaction(sc))
2707 return false;
2708
2709 /*
2710 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
2711 * number of pages that were scanned. This will return to the caller
2712 * with the risk reclaim/compaction and the resulting allocation attempt
2713 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
2714 * allocations through requiring that the full LRU list has been scanned
2715 * first, by assuming that zero delta of sc->nr_scanned means full LRU
2716 * scan, but that approximation was wrong, and there were corner cases
2717 * where always a non-zero amount of pages were scanned.
2718 */
2719 if (!nr_reclaimed)
2720 return false;
2721
2722 /* If compaction would go ahead or the allocation would succeed, stop */
2723 for (z = 0; z <= sc->reclaim_idx; z++) {
2724 struct zone *zone = &pgdat->node_zones[z];
2725 if (!managed_zone(zone))
2726 continue;
2727
2728 switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
2729 case COMPACT_SUCCESS:
2730 case COMPACT_CONTINUE:
2731 return false;
2732 default:
2733 /* check next zone */
2734 ;
2735 }
2736 }
2737
2738 /*
2739 * If we have not reclaimed enough pages for compaction and the
2740 * inactive lists are large enough, continue reclaiming
2741 */
2742 pages_for_compaction = compact_gap(sc->order);
2743 inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
2744 if (get_nr_swap_pages() > 0)
2745 inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
2746
2747 return inactive_lru_pages > pages_for_compaction;
2748 }
2749
2750 static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
2751 {
2752 return test_bit(PGDAT_CONGESTED, &pgdat->flags) ||
2753 (memcg && memcg_congested(pgdat, memcg));
2754 }
2755
2756 static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
2757 {
2758 struct reclaim_state *reclaim_state = current->reclaim_state;
2759 unsigned long nr_reclaimed, nr_scanned;
2760 bool reclaimable = false;
2761
2762 do {
2763 struct mem_cgroup *root = sc->target_mem_cgroup;
2764 unsigned long node_lru_pages = 0;
2765 struct mem_cgroup *memcg;
2766
2767 memset(&sc->nr, 0, sizeof(sc->nr));
2768
2769 nr_reclaimed = sc->nr_reclaimed;
2770 nr_scanned = sc->nr_scanned;
2771
2772 memcg = mem_cgroup_iter(root, NULL, NULL);
2773 do {
2774 unsigned long lru_pages;
2775 unsigned long reclaimed;
2776 unsigned long scanned;
2777
2778 switch (mem_cgroup_protected(root, memcg)) {
2779 case MEMCG_PROT_MIN:
2780 /*
2781 * Hard protection.
2782 * If there is no reclaimable memory, OOM.
2783 */
2784 continue;
2785 case MEMCG_PROT_LOW:
2786 /*
2787 * Soft protection.
2788 * Respect the protection only as long as
2789 * there is an unprotected supply
2790 * of reclaimable memory from other cgroups.
2791 */
2792 if (!sc->memcg_low_reclaim) {
2793 sc->memcg_low_skipped = 1;
2794 continue;
2795 }
2796 memcg_memory_event(memcg, MEMCG_LOW);
2797 break;
2798 case MEMCG_PROT_NONE:
2799 /*
2800 * All protection thresholds breached. We may
2801 * still choose to vary the scan pressure
2802 * applied based on by how much the cgroup in
2803 * question has exceeded its protection
2804 * thresholds (see get_scan_count).
2805 */
2806 break;
2807 }
2808
2809 reclaimed = sc->nr_reclaimed;
2810 scanned = sc->nr_scanned;
2811 shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
2812 node_lru_pages += lru_pages;
2813
2814 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
2815 sc->priority);
2816
2817 /* Record the group's reclaim efficiency */
2818 vmpressure(sc->gfp_mask, memcg, false,
2819 sc->nr_scanned - scanned,
2820 sc->nr_reclaimed - reclaimed);
2821
2822 } while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
2823
2824 if (reclaim_state) {
2825 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2826 reclaim_state->reclaimed_slab = 0;
2827 }
2828
2829 /* Record the subtree's reclaim efficiency */
2830 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
2831 sc->nr_scanned - nr_scanned,
2832 sc->nr_reclaimed - nr_reclaimed);
2833
2834 if (sc->nr_reclaimed - nr_reclaimed)
2835 reclaimable = true;
2836
2837 if (current_is_kswapd()) {
2838 /*
2839 * If reclaim is isolating dirty pages under writeback,
2840 * it implies that the long-lived page allocation rate
2841 * is exceeding the page laundering rate. Either the
2842 * global limits are not being effective at throttling
2843 * processes due to the page distribution throughout
2844 * zones or there is heavy usage of a slow backing
2845 * device. The only option is to throttle from reclaim
2846 * context which is not ideal as there is no guarantee
2847 * the dirtying process is throttled in the same way
2848 * balance_dirty_pages() manages.
2849 *
2850 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
2851 * count the number of pages under pages flagged for
2852 * immediate reclaim and stall if any are encountered
2853 * in the nr_immediate check below.
2854 */
2855 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
2856 set_bit(PGDAT_WRITEBACK, &pgdat->flags);
2857
2858 /*
2859 * Tag a node as congested if all the dirty pages
2860 * scanned were backed by a congested BDI and
2861 * wait_iff_congested will stall.
2862 */
2863 if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
2864 set_bit(PGDAT_CONGESTED, &pgdat->flags);
2865
2866 /* Allow kswapd to start writing pages during reclaim.*/
2867 if (sc->nr.unqueued_dirty == sc->nr.file_taken)
2868 set_bit(PGDAT_DIRTY, &pgdat->flags);
2869
2870 /*
2871 * If kswapd scans pages marked marked for immediate
2872 * reclaim and under writeback (nr_immediate), it
2873 * implies that pages are cycling through the LRU
2874 * faster than they are written so also forcibly stall.
2875 */
2876 if (sc->nr.immediate)
2877 congestion_wait(BLK_RW_ASYNC, HZ/10);
2878 }
2879
2880 /*
2881 * Legacy memcg will stall in page writeback so avoid forcibly
2882 * stalling in wait_iff_congested().
2883 */
2884 if (!global_reclaim(sc) && sane_reclaim(sc) &&
2885 sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
2886 set_memcg_congestion(pgdat, root, true);
2887
2888 /*
2889 * Stall direct reclaim for IO completions if underlying BDIs
2890 * and node is congested. Allow kswapd to continue until it
2891 * starts encountering unqueued dirty pages or cycling through
2892 * the LRU too quickly.
2893 */
2894 if (!sc->hibernation_mode && !current_is_kswapd() &&
2895 current_may_throttle() && pgdat_memcg_congested(pgdat, root))
2896 wait_iff_congested(BLK_RW_ASYNC, HZ/10);
2897
2898 } while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
2899 sc));
2900
2901 /*
2902 * Kswapd gives up on balancing particular nodes after too
2903 * many failures to reclaim anything from them and goes to
2904 * sleep. On reclaim progress, reset the failure counter. A
2905 * successful direct reclaim run will revive a dormant kswapd.
2906 */
2907 if (reclaimable)
2908 pgdat->kswapd_failures = 0;
2909
2910 return reclaimable;
2911 }
2912
2913 /*
2914 * Returns true if compaction should go ahead for a costly-order request, or
2915 * the allocation would already succeed without compaction. Return false if we
2916 * should reclaim first.
2917 */
2918 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
2919 {
2920 unsigned long watermark;
2921 enum compact_result suitable;
2922
2923 suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
2924 if (suitable == COMPACT_SUCCESS)
2925 /* Allocation should succeed already. Don't reclaim. */
2926 return true;
2927 if (suitable == COMPACT_SKIPPED)
2928 /* Compaction cannot yet proceed. Do reclaim. */
2929 return false;
2930
2931 /*
2932 * Compaction is already possible, but it takes time to run and there
2933 * are potentially other callers using the pages just freed. So proceed
2934 * with reclaim to make a buffer of free pages available to give
2935 * compaction a reasonable chance of completing and allocating the page.
2936 * Note that we won't actually reclaim the whole buffer in one attempt
2937 * as the target watermark in should_continue_reclaim() is lower. But if
2938 * we are already above the high+gap watermark, don't reclaim at all.
2939 */
2940 watermark = high_wmark_pages(zone) + compact_gap(sc->order);
2941
2942 return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
2943 }
2944
2945 /*
2946 * This is the direct reclaim path, for page-allocating processes. We only
2947 * try to reclaim pages from zones which will satisfy the caller's allocation
2948 * request.
2949 *
2950 * If a zone is deemed to be full of pinned pages then just give it a light
2951 * scan then give up on it.
2952 */
2953 static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
2954 {
2955 struct zoneref *z;
2956 struct zone *zone;
2957 unsigned long nr_soft_reclaimed;
2958 unsigned long nr_soft_scanned;
2959 gfp_t orig_mask;
2960 pg_data_t *last_pgdat = NULL;
2961
2962 /*
2963 * If the number of buffer_heads in the machine exceeds the maximum
2964 * allowed level, force direct reclaim to scan the highmem zone as
2965 * highmem pages could be pinning lowmem pages storing buffer_heads
2966 */
2967 orig_mask = sc->gfp_mask;
2968 if (buffer_heads_over_limit) {
2969 sc->gfp_mask |= __GFP_HIGHMEM;
2970 sc->reclaim_idx = gfp_zone(sc->gfp_mask);
2971 }
2972
2973 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2974 sc->reclaim_idx, sc->nodemask) {
2975 /*
2976 * Take care memory controller reclaiming has small influence
2977 * to global LRU.
2978 */
2979 if (global_reclaim(sc)) {
2980 if (!cpuset_zone_allowed(zone,
2981 GFP_KERNEL | __GFP_HARDWALL))
2982 continue;
2983
2984 /*
2985 * If we already have plenty of memory free for
2986 * compaction in this zone, don't free any more.
2987 * Even though compaction is invoked for any
2988 * non-zero order, only frequent costly order
2989 * reclamation is disruptive enough to become a
2990 * noticeable problem, like transparent huge
2991 * page allocations.
2992 */
2993 if (IS_ENABLED(CONFIG_COMPACTION) &&
2994 sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2995 compaction_ready(zone, sc)) {
2996 sc->compaction_ready = true;
2997 continue;
2998 }
2999
3000 /*
3001 * Shrink each node in the zonelist once. If the
3002 * zonelist is ordered by zone (not the default) then a
3003 * node may be shrunk multiple times but in that case
3004 * the user prefers lower zones being preserved.
3005 */
3006 if (zone->zone_pgdat == last_pgdat)
3007 continue;
3008
3009 /*
3010 * This steals pages from memory cgroups over softlimit
3011 * and returns the number of reclaimed pages and
3012 * scanned pages. This works for global memory pressure
3013 * and balancing, not for a memcg's limit.
3014 */
3015 nr_soft_scanned = 0;
3016 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
3017 sc->order, sc->gfp_mask,
3018 &nr_soft_scanned);
3019 sc->nr_reclaimed += nr_soft_reclaimed;
3020 sc->nr_scanned += nr_soft_scanned;
3021 /* need some check for avoid more shrink_zone() */
3022 }
3023
3024 /* See comment about same check for global reclaim above */
3025 if (zone->zone_pgdat == last_pgdat)
3026 continue;
3027 last_pgdat = zone->zone_pgdat;
3028 shrink_node(zone->zone_pgdat, sc);
3029 }
3030
3031 /*
3032 * Restore to original mask to avoid the impact on the caller if we
3033 * promoted it to __GFP_HIGHMEM.
3034 */
3035 sc->gfp_mask = orig_mask;
3036 }
3037
3038 static void snapshot_refaults(struct mem_cgroup *root_memcg, pg_data_t *pgdat)
3039 {
3040 struct mem_cgroup *memcg;
3041
3042 memcg = mem_cgroup_iter(root_memcg, NULL, NULL);
3043 do {
3044 unsigned long refaults;
3045 struct lruvec *lruvec;
3046
3047 lruvec = mem_cgroup_lruvec(pgdat, memcg);
3048 refaults = lruvec_page_state_local(lruvec, WORKINGSET_ACTIVATE);
3049 lruvec->refaults = refaults;
3050 } while ((memcg = mem_cgroup_iter(root_memcg, memcg, NULL)));
3051 }
3052
3053 /*
3054 * This is the main entry point to direct page reclaim.
3055 *
3056 * If a full scan of the inactive list fails to free enough memory then we
3057 * are "out of memory" and something needs to be killed.
3058 *
3059 * If the caller is !__GFP_FS then the probability of a failure is reasonably
3060 * high - the zone may be full of dirty or under-writeback pages, which this
3061 * caller can't do much about. We kick the writeback threads and take explicit
3062 * naps in the hope that some of these pages can be written. But if the
3063 * allocating task holds filesystem locks which prevent writeout this might not
3064 * work, and the allocation attempt will fail.
3065 *
3066 * returns: 0, if no pages reclaimed
3067 * else, the number of pages reclaimed
3068 */
3069 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
3070 struct scan_control *sc)
3071 {
3072 int initial_priority = sc->priority;
3073 pg_data_t *last_pgdat;
3074 struct zoneref *z;
3075 struct zone *zone;
3076 retry:
3077 delayacct_freepages_start();
3078
3079 if (global_reclaim(sc))
3080 __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
3081
3082 do {
3083 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
3084 sc->priority);
3085 sc->nr_scanned = 0;
3086 shrink_zones(zonelist, sc);
3087
3088 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
3089 break;
3090
3091 if (sc->compaction_ready)
3092 break;
3093
3094 /*
3095 * If we're getting trouble reclaiming, start doing
3096 * writepage even in laptop mode.
3097 */
3098 if (sc->priority < DEF_PRIORITY - 2)
3099 sc->may_writepage = 1;
3100 } while (--sc->priority >= 0);
3101
3102 last_pgdat = NULL;
3103 for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
3104 sc->nodemask) {
3105 if (zone->zone_pgdat == last_pgdat)
3106 continue;
3107 last_pgdat = zone->zone_pgdat;
3108 snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
3109 set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false);
3110 }
3111
3112 delayacct_freepages_end();
3113
3114 if (sc->nr_reclaimed)
3115 return sc->nr_reclaimed;
3116
3117 /* Aborted reclaim to try compaction? don't OOM, then */
3118 if (sc->compaction_ready)
3119 return 1;
3120
3121 /* Untapped cgroup reserves? Don't OOM, retry. */
3122 if (sc->memcg_low_skipped) {
3123 sc->priority = initial_priority;
3124 sc->memcg_low_reclaim = 1;
3125 sc->memcg_low_skipped = 0;
3126 goto retry;
3127 }
3128
3129 return 0;
3130 }
3131
3132 static bool allow_direct_reclaim(pg_data_t *pgdat)
3133 {
3134 struct zone *zone;
3135 unsigned long pfmemalloc_reserve = 0;
3136 unsigned long free_pages = 0;
3137 int i;
3138 bool wmark_ok;
3139
3140 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
3141 return true;
3142
3143 for (i = 0; i <= ZONE_NORMAL; i++) {
3144 zone = &pgdat->node_zones[i];
3145 if (!managed_zone(zone))
3146 continue;
3147
3148 if (!zone_reclaimable_pages(zone))
3149 continue;
3150
3151 pfmemalloc_reserve += min_wmark_pages(zone);
3152 free_pages += zone_page_state(zone, NR_FREE_PAGES);
3153 }
3154
3155 /* If there are no reserves (unexpected config) then do not throttle */
3156 if (!pfmemalloc_reserve)
3157 return true;
3158
3159 wmark_ok = free_pages > pfmemalloc_reserve / 2;
3160
3161 /* kswapd must be awake if processes are being throttled */
3162 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
3163 pgdat->kswapd_classzone_idx = min(pgdat->kswapd_classzone_idx,
3164 (enum zone_type)ZONE_NORMAL);
3165 wake_up_interruptible(&pgdat->kswapd_wait);
3166 }
3167
3168 return wmark_ok;
3169 }
3170
3171 /*
3172 * Throttle direct reclaimers if backing storage is backed by the network
3173 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3174 * depleted. kswapd will continue to make progress and wake the processes
3175 * when the low watermark is reached.
3176 *
3177 * Returns true if a fatal signal was delivered during throttling. If this
3178 * happens, the page allocator should not consider triggering the OOM killer.
3179 */
3180 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
3181 nodemask_t *nodemask)
3182 {
3183 struct zoneref *z;
3184 struct zone *zone;
3185 pg_data_t *pgdat = NULL;
3186
3187 /*
3188 * Kernel threads should not be throttled as they may be indirectly
3189 * responsible for cleaning pages necessary for reclaim to make forward
3190 * progress. kjournald for example may enter direct reclaim while
3191 * committing a transaction where throttling it could forcing other
3192 * processes to block on log_wait_commit().
3193 */
3194 if (current->flags & PF_KTHREAD)
3195 goto out;
3196
3197 /*
3198 * If a fatal signal is pending, this process should not throttle.
3199 * It should return quickly so it can exit and free its memory
3200 */
3201 if (fatal_signal_pending(current))
3202 goto out;
3203
3204 /*
3205 * Check if the pfmemalloc reserves are ok by finding the first node
3206 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3207 * GFP_KERNEL will be required for allocating network buffers when
3208 * swapping over the network so ZONE_HIGHMEM is unusable.
3209 *
3210 * Throttling is based on the first usable node and throttled processes
3211 * wait on a queue until kswapd makes progress and wakes them. There
3212 * is an affinity then between processes waking up and where reclaim
3213 * progress has been made assuming the process wakes on the same node.
3214 * More importantly, processes running on remote nodes will not compete
3215 * for remote pfmemalloc reserves and processes on different nodes
3216 * should make reasonable progress.
3217 */
3218 for_each_zone_zonelist_nodemask(zone, z, zonelist,
3219 gfp_zone(gfp_mask), nodemask) {
3220 if (zone_idx(zone) > ZONE_NORMAL)
3221 continue;
3222
3223 /* Throttle based on the first usable node */
3224 pgdat = zone->zone_pgdat;
3225 if (allow_direct_reclaim(pgdat))
3226 goto out;
3227 break;
3228 }
3229
3230 /* If no zone was usable by the allocation flags then do not throttle */
3231 if (!pgdat)
3232 goto out;
3233
3234 /* Account for the throttling */
3235 count_vm_event(PGSCAN_DIRECT_THROTTLE);
3236
3237 /*
3238 * If the caller cannot enter the filesystem, it's possible that it
3239 * is due to the caller holding an FS lock or performing a journal
3240 * transaction in the case of a filesystem like ext[3|4]. In this case,
3241 * it is not safe to block on pfmemalloc_wait as kswapd could be
3242 * blocked waiting on the same lock. Instead, throttle for up to a
3243 * second before continuing.
3244 */
3245 if (!(gfp_mask & __GFP_FS)) {
3246 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
3247 allow_direct_reclaim(pgdat), HZ);
3248
3249 goto check_pending;
3250 }
3251
3252 /* Throttle until kswapd wakes the process */
3253 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
3254 allow_direct_reclaim(pgdat));
3255
3256 check_pending:
3257 if (fatal_signal_pending(current))
3258 return true;
3259
3260 out:
3261 return false;
3262 }
3263
3264 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
3265 gfp_t gfp_mask, nodemask_t *nodemask)
3266 {
3267 unsigned long nr_reclaimed;
3268 struct scan_control sc = {
3269 .nr_to_reclaim = SWAP_CLUSTER_MAX,
3270 .gfp_mask = current_gfp_context(gfp_mask),
3271 .reclaim_idx = gfp_zone(gfp_mask),
3272 .order = order,
3273 .nodemask = nodemask,
3274 .priority = DEF_PRIORITY,
3275 .may_writepage = !laptop_mode,
3276 .may_unmap = 1,
3277 .may_swap = 1,
3278 };
3279
3280 /*
3281 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3282 * Confirm they are large enough for max values.
3283 */
3284 BUILD_BUG_ON(MAX_ORDER > S8_MAX);
3285 BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
3286 BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
3287
3288 /*
3289 * Do not enter reclaim if fatal signal was delivered while throttled.
3290 * 1 is returned so that the page allocator does not OOM kill at this
3291 * point.
3292 */
3293 if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
3294 return 1;
3295
3296 set_task_reclaim_state(current, &sc.reclaim_state);
3297 trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
3298
3299 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
3300
3301 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
3302 set_task_reclaim_state(current, NULL);
3303
3304 return nr_reclaimed;
3305 }
3306
3307 #ifdef CONFIG_MEMCG
3308
3309 /* Only used by soft limit reclaim. Do not reuse for anything else. */
3310 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
3311 gfp_t gfp_mask, bool noswap,
3312 pg_data_t *pgdat,
3313 unsigned long *nr_scanned)
3314 {
3315 struct scan_control sc = {
3316 .nr_to_reclaim = SWAP_CLUSTER_MAX,
3317 .target_mem_cgroup = memcg,
3318 .may_writepage = !laptop_mode,
3319 .may_unmap = 1,
3320 .reclaim_idx = MAX_NR_ZONES - 1,
3321 .may_swap = !noswap,
3322 };
3323 unsigned long lru_pages;
3324
3325 WARN_ON_ONCE(!current->reclaim_state);
3326
3327 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
3328 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
3329
3330 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
3331 sc.gfp_mask);
3332
3333 /*
3334 * NOTE: Although we can get the priority field, using it
3335 * here is not a good idea, since it limits the pages we can scan.
3336 * if we don't reclaim here, the shrink_node from balance_pgdat
3337 * will pick up pages from other mem cgroup's as well. We hack
3338 * the priority and make it zero.
3339 */
3340 shrink_node_memcg(pgdat, memcg, &sc, &lru_pages);
3341
3342 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
3343
3344 *nr_scanned = sc.nr_scanned;
3345
3346 return sc.nr_reclaimed;
3347 }
3348
3349 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
3350 unsigned long nr_pages,
3351 gfp_t gfp_mask,
3352 bool may_swap)
3353 {
3354 struct zonelist *zonelist;
3355 unsigned long nr_reclaimed;
3356 unsigned long pflags;
3357 int nid;
3358 unsigned int noreclaim_flag;
3359 struct scan_control sc = {
3360 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
3361 .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
3362 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
3363 .reclaim_idx = MAX_NR_ZONES - 1,
3364 .target_mem_cgroup = memcg,
3365 .priority = DEF_PRIORITY,
3366 .may_writepage = !laptop_mode,
3367 .may_unmap = 1,
3368 .may_swap = may_swap,
3369 };
3370
3371 set_task_reclaim_state(current, &sc.reclaim_state);
3372 /*
3373 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
3374 * take care of from where we get pages. So the node where we start the
3375 * scan does not need to be the current node.
3376 */
3377 nid = mem_cgroup_select_victim_node(memcg);
3378
3379 zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
3380
3381 trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
3382
3383 psi_memstall_enter(&pflags);
3384 noreclaim_flag = memalloc_noreclaim_save();
3385
3386 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
3387
3388 memalloc_noreclaim_restore(noreclaim_flag);
3389 psi_memstall_leave(&pflags);
3390
3391 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
3392 set_task_reclaim_state(current, NULL);
3393
3394 return nr_reclaimed;
3395 }
3396 #endif
3397
3398 static void age_active_anon(struct pglist_data *pgdat,
3399 struct scan_control *sc)
3400 {
3401 struct mem_cgroup *memcg;
3402
3403 if (!total_swap_pages)
3404 return;
3405
3406 memcg = mem_cgroup_iter(NULL, NULL, NULL);
3407 do {
3408 struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);
3409
3410 if (inactive_list_is_low(lruvec, false, sc, true))
3411 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
3412 sc, LRU_ACTIVE_ANON);
3413
3414 memcg = mem_cgroup_iter(NULL, memcg, NULL);
3415 } while (memcg);
3416 }
3417
3418 static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx)
3419 {
3420 int i;
3421 struct zone *zone;
3422
3423 /*
3424 * Check for watermark boosts top-down as the higher zones
3425 * are more likely to be boosted. Both watermarks and boosts
3426 * should not be checked at the time time as reclaim would
3427 * start prematurely when there is no boosting and a lower
3428 * zone is balanced.
3429 */
3430 for (i = classzone_idx; i >= 0; i--) {
3431 zone = pgdat->node_zones + i;
3432 if (!managed_zone(zone))
3433 continue;
3434
3435 if (zone->watermark_boost)
3436 return true;
3437 }
3438
3439 return false;
3440 }
3441
3442 /*
3443 * Returns true if there is an eligible zone balanced for the request order
3444 * and classzone_idx
3445 */
3446 static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
3447 {
3448 int i;
3449 unsigned long mark = -1;
3450 struct zone *zone;
3451
3452 /*
3453 * Check watermarks bottom-up as lower zones are more likely to
3454 * meet watermarks.
3455 */
3456 for (i = 0; i <= classzone_idx; i++) {
3457 zone = pgdat->node_zones + i;
3458
3459 if (!managed_zone(zone))
3460 continue;
3461
3462 mark = high_wmark_pages(zone);
3463 if (zone_watermark_ok_safe(zone, order, mark, classzone_idx))
3464 return true;
3465 }
3466
3467 /*
3468 * If a node has no populated zone within classzone_idx, it does not
3469 * need balancing by definition. This can happen if a zone-restricted
3470 * allocation tries to wake a remote kswapd.
3471 */
3472 if (mark == -1)
3473 return true;
3474
3475 return false;
3476 }
3477
3478 /* Clear pgdat state for congested, dirty or under writeback. */
3479 static void clear_pgdat_congested(pg_data_t *pgdat)
3480 {
3481 clear_bit(PGDAT_CONGESTED, &pgdat->flags);
3482 clear_bit(PGDAT_DIRTY, &pgdat->flags);
3483 clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
3484 }
3485
3486 /*
3487 * Prepare kswapd for sleeping. This verifies that there are no processes
3488 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3489 *
3490 * Returns true if kswapd is ready to sleep
3491 */
3492 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
3493 {
3494 /*
3495 * The throttled processes are normally woken up in balance_pgdat() as
3496 * soon as allow_direct_reclaim() is true. But there is a potential
3497 * race between when kswapd checks the watermarks and a process gets
3498 * throttled. There is also a potential race if processes get
3499 * throttled, kswapd wakes, a large process exits thereby balancing the
3500 * zones, which causes kswapd to exit balance_pgdat() before reaching
3501 * the wake up checks. If kswapd is going to sleep, no process should
3502 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3503 * the wake up is premature, processes will wake kswapd and get
3504 * throttled again. The difference from wake ups in balance_pgdat() is
3505 * that here we are under prepare_to_wait().
3506 */
3507 if (waitqueue_active(&pgdat->pfmemalloc_wait))
3508 wake_up_all(&pgdat->pfmemalloc_wait);
3509
3510 /* Hopeless node, leave it to direct reclaim */
3511 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
3512 return true;
3513
3514 if (pgdat_balanced(pgdat, order, classzone_idx)) {
3515 clear_pgdat_congested(pgdat);
3516 return true;
3517 }
3518
3519 return false;
3520 }
3521
3522 /*
3523 * kswapd shrinks a node of pages that are at or below the highest usable
3524 * zone that is currently unbalanced.
3525 *
3526 * Returns true if kswapd scanned at least the requested number of pages to
3527 * reclaim or if the lack of progress was due to pages under writeback.
3528 * This is used to determine if the scanning priority needs to be raised.
3529 */
3530 static bool kswapd_shrink_node(pg_data_t *pgdat,
3531 struct scan_control *sc)
3532 {
3533 struct zone *zone;
3534 int z;
3535
3536 /* Reclaim a number of pages proportional to the number of zones */
3537 sc->nr_to_reclaim = 0;
3538 for (z = 0; z <= sc->reclaim_idx; z++) {
3539 zone = pgdat->node_zones + z;
3540 if (!managed_zone(zone))
3541 continue;
3542
3543 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
3544 }
3545
3546 /*
3547 * Historically care was taken to put equal pressure on all zones but
3548 * now pressure is applied based on node LRU order.
3549 */
3550 shrink_node(pgdat, sc);
3551
3552 /*
3553 * Fragmentation may mean that the system cannot be rebalanced for
3554 * high-order allocations. If twice the allocation size has been
3555 * reclaimed then recheck watermarks only at order-0 to prevent
3556 * excessive reclaim. Assume that a process requested a high-order
3557 * can direct reclaim/compact.
3558 */
3559 if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
3560 sc->order = 0;
3561
3562 return sc->nr_scanned >= sc->nr_to_reclaim;
3563 }
3564
3565 /*
3566 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3567 * that are eligible for use by the caller until at least one zone is
3568 * balanced.
3569 *
3570 * Returns the order kswapd finished reclaiming at.
3571 *
3572 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3573 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3574 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3575 * or lower is eligible for reclaim until at least one usable zone is
3576 * balanced.
3577 */
3578 static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
3579 {
3580 int i;
3581 unsigned long nr_soft_reclaimed;
3582 unsigned long nr_soft_scanned;
3583 unsigned long pflags;
3584 unsigned long nr_boost_reclaim;
3585 unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
3586 bool boosted;
3587 struct zone *zone;
3588 struct scan_control sc = {
3589 .gfp_mask = GFP_KERNEL,
3590 .order = order,
3591 .may_unmap = 1,
3592 };
3593
3594 set_task_reclaim_state(current, &sc.reclaim_state);
3595 psi_memstall_enter(&pflags);
3596 __fs_reclaim_acquire();
3597
3598 count_vm_event(PAGEOUTRUN);
3599
3600 /*
3601 * Account for the reclaim boost. Note that the zone boost is left in
3602 * place so that parallel allocations that are near the watermark will
3603 * stall or direct reclaim until kswapd is finished.
3604 */
3605 nr_boost_reclaim = 0;
3606 for (i = 0; i <= classzone_idx; i++) {
3607 zone = pgdat->node_zones + i;
3608 if (!managed_zone(zone))
3609 continue;
3610
3611 nr_boost_reclaim += zone->watermark_boost;
3612 zone_boosts[i] = zone->watermark_boost;
3613 }
3614 boosted = nr_boost_reclaim;
3615
3616 restart:
3617 sc.priority = DEF_PRIORITY;
3618 do {
3619 unsigned long nr_reclaimed = sc.nr_reclaimed;
3620 bool raise_priority = true;
3621 bool balanced;
3622 bool ret;
3623
3624 sc.reclaim_idx = classzone_idx;
3625
3626 /*
3627 * If the number of buffer_heads exceeds the maximum allowed
3628 * then consider reclaiming from all zones. This has a dual
3629 * purpose -- on 64-bit systems it is expected that
3630 * buffer_heads are stripped during active rotation. On 32-bit
3631 * systems, highmem pages can pin lowmem memory and shrinking
3632 * buffers can relieve lowmem pressure. Reclaim may still not
3633 * go ahead if all eligible zones for the original allocation
3634 * request are balanced to avoid excessive reclaim from kswapd.
3635 */
3636 if (buffer_heads_over_limit) {
3637 for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
3638 zone = pgdat->node_zones + i;
3639 if (!managed_zone(zone))
3640 continue;
3641
3642 sc.reclaim_idx = i;
3643 break;
3644 }
3645 }
3646
3647 /*
3648 * If the pgdat is imbalanced then ignore boosting and preserve
3649 * the watermarks for a later time and restart. Note that the
3650 * zone watermarks will be still reset at the end of balancing
3651 * on the grounds that the normal reclaim should be enough to
3652 * re-evaluate if boosting is required when kswapd next wakes.
3653 */
3654 balanced = pgdat_balanced(pgdat, sc.order, classzone_idx);
3655 if (!balanced && nr_boost_reclaim) {
3656 nr_boost_reclaim = 0;
3657 goto restart;
3658 }
3659
3660 /*
3661 * If boosting is not active then only reclaim if there are no
3662 * eligible zones. Note that sc.reclaim_idx is not used as
3663 * buffer_heads_over_limit may have adjusted it.
3664 */
3665 if (!nr_boost_reclaim && balanced)
3666 goto out;
3667
3668 /* Limit the priority of boosting to avoid reclaim writeback */
3669 if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
3670 raise_priority = false;
3671
3672 /*
3673 * Do not writeback or swap pages for boosted reclaim. The
3674 * intent is to relieve pressure not issue sub-optimal IO
3675 * from reclaim context. If no pages are reclaimed, the
3676 * reclaim will be aborted.
3677 */
3678 sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
3679 sc.may_swap = !nr_boost_reclaim;
3680
3681 /*
3682 * Do some background aging of the anon list, to give
3683 * pages a chance to be referenced before reclaiming. All
3684 * pages are rotated regardless of classzone as this is
3685 * about consistent aging.
3686 */
3687 age_active_anon(pgdat, &sc);
3688
3689 /*
3690 * If we're getting trouble reclaiming, start doing writepage
3691 * even in laptop mode.
3692 */
3693 if (sc.priority < DEF_PRIORITY - 2)
3694 sc.may_writepage = 1;
3695
3696 /* Call soft limit reclaim before calling shrink_node. */
3697 sc.nr_scanned = 0;
3698 nr_soft_scanned = 0;
3699 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order,
3700 sc.gfp_mask, &nr_soft_scanned);
3701 sc.nr_reclaimed += nr_soft_reclaimed;
3702
3703 /*
3704 * There should be no need to raise the scanning priority if
3705 * enough pages are already being scanned that that high
3706 * watermark would be met at 100% efficiency.
3707 */
3708 if (kswapd_shrink_node(pgdat, &sc))
3709 raise_priority = false;
3710
3711 /*
3712 * If the low watermark is met there is no need for processes
3713 * to be throttled on pfmemalloc_wait as they should not be
3714 * able to safely make forward progress. Wake them
3715 */
3716 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
3717 allow_direct_reclaim(pgdat))
3718 wake_up_all(&pgdat->pfmemalloc_wait);
3719
3720 /* Check if kswapd should be suspending */
3721 __fs_reclaim_release();
3722 ret = try_to_freeze();
3723 __fs_reclaim_acquire();
3724 if (ret || kthread_should_stop())
3725 break;
3726
3727 /*
3728 * Raise priority if scanning rate is too low or there was no
3729 * progress in reclaiming pages
3730 */
3731 nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
3732 nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
3733
3734 /*
3735 * If reclaim made no progress for a boost, stop reclaim as
3736 * IO cannot be queued and it could be an infinite loop in
3737 * extreme circumstances.
3738 */
3739 if (nr_boost_reclaim && !nr_reclaimed)
3740 break;
3741
3742 if (raise_priority || !nr_reclaimed)
3743 sc.priority--;
3744 } while (sc.priority >= 1);
3745
3746 if (!sc.nr_reclaimed)
3747 pgdat->kswapd_failures++;
3748
3749 out:
3750 /* If reclaim was boosted, account for the reclaim done in this pass */
3751 if (boosted) {
3752 unsigned long flags;
3753
3754 for (i = 0; i <= classzone_idx; i++) {
3755 if (!zone_boosts[i])
3756 continue;
3757
3758 /* Increments are under the zone lock */
3759 zone = pgdat->node_zones + i;
3760 spin_lock_irqsave(&zone->lock, flags);
3761 zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
3762 spin_unlock_irqrestore(&zone->lock, flags);
3763 }
3764
3765 /*
3766 * As there is now likely space, wakeup kcompact to defragment
3767 * pageblocks.
3768 */
3769 wakeup_kcompactd(pgdat, pageblock_order, classzone_idx);
3770 }
3771
3772 snapshot_refaults(NULL, pgdat);
3773 __fs_reclaim_release();
3774 psi_memstall_leave(&pflags);
3775 set_task_reclaim_state(current, NULL);
3776
3777 /*
3778 * Return the order kswapd stopped reclaiming at as
3779 * prepare_kswapd_sleep() takes it into account. If another caller
3780 * entered the allocator slow path while kswapd was awake, order will
3781 * remain at the higher level.
3782 */
3783 return sc.order;
3784 }
3785
3786 /*
3787 * The pgdat->kswapd_classzone_idx is used to pass the highest zone index to be
3788 * reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is not
3789 * a valid index then either kswapd runs for first time or kswapd couldn't sleep
3790 * after previous reclaim attempt (node is still unbalanced). In that case
3791 * return the zone index of the previous kswapd reclaim cycle.
3792 */
3793 static enum zone_type kswapd_classzone_idx(pg_data_t *pgdat,
3794 enum zone_type prev_classzone_idx)
3795 {
3796 if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES)
3797 return prev_classzone_idx;
3798 return pgdat->kswapd_classzone_idx;
3799 }
3800
3801 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
3802 unsigned int classzone_idx)
3803 {
3804 long remaining = 0;
3805 DEFINE_WAIT(wait);
3806
3807 if (freezing(current) || kthread_should_stop())
3808 return;
3809
3810 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3811
3812 /*
3813 * Try to sleep for a short interval. Note that kcompactd will only be
3814 * woken if it is possible to sleep for a short interval. This is
3815 * deliberate on the assumption that if reclaim cannot keep an
3816 * eligible zone balanced that it's also unlikely that compaction will
3817 * succeed.
3818 */
3819 if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
3820 /*
3821 * Compaction records what page blocks it recently failed to
3822 * isolate pages from and skips them in the future scanning.
3823 * When kswapd is going to sleep, it is reasonable to assume
3824 * that pages and compaction may succeed so reset the cache.
3825 */
3826 reset_isolation_suitable(pgdat);
3827
3828 /*
3829 * We have freed the memory, now we should compact it to make
3830 * allocation of the requested order possible.
3831 */
3832 wakeup_kcompactd(pgdat, alloc_order, classzone_idx);
3833
3834 remaining = schedule_timeout(HZ/10);
3835
3836 /*
3837 * If woken prematurely then reset kswapd_classzone_idx and
3838 * order. The values will either be from a wakeup request or
3839 * the previous request that slept prematurely.
3840 */
3841 if (remaining) {
3842 pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
3843 pgdat->kswapd_order = max(pgdat->kswapd_order, reclaim_order);
3844 }
3845
3846 finish_wait(&pgdat->kswapd_wait, &wait);
3847 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3848 }
3849
3850 /*
3851 * After a short sleep, check if it was a premature sleep. If not, then
3852 * go fully to sleep until explicitly woken up.
3853 */
3854 if (!remaining &&
3855 prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
3856 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
3857
3858 /*
3859 * vmstat counters are not perfectly accurate and the estimated
3860 * value for counters such as NR_FREE_PAGES can deviate from the
3861 * true value by nr_online_cpus * threshold. To avoid the zone
3862 * watermarks being breached while under pressure, we reduce the
3863 * per-cpu vmstat threshold while kswapd is awake and restore
3864 * them before going back to sleep.
3865 */
3866 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
3867
3868 if (!kthread_should_stop())
3869 schedule();
3870
3871 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
3872 } else {
3873 if (remaining)
3874 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
3875 else
3876 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
3877 }
3878 finish_wait(&pgdat->kswapd_wait, &wait);
3879 }
3880
3881 /*
3882 * The background pageout daemon, started as a kernel thread
3883 * from the init process.
3884 *
3885 * This basically trickles out pages so that we have _some_
3886 * free memory available even if there is no other activity
3887 * that frees anything up. This is needed for things like routing
3888 * etc, where we otherwise might have all activity going on in
3889 * asynchronous contexts that cannot page things out.
3890 *
3891 * If there are applications that are active memory-allocators
3892 * (most normal use), this basically shouldn't matter.
3893 */
3894 static int kswapd(void *p)
3895 {
3896 unsigned int alloc_order, reclaim_order;
3897 unsigned int classzone_idx = MAX_NR_ZONES - 1;
3898 pg_data_t *pgdat = (pg_data_t*)p;
3899 struct task_struct *tsk = current;
3900 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
3901
3902 if (!cpumask_empty(cpumask))
3903 set_cpus_allowed_ptr(tsk, cpumask);
3904
3905 /*
3906 * Tell the memory management that we're a "memory allocator",
3907 * and that if we need more memory we should get access to it
3908 * regardless (see "__alloc_pages()"). "kswapd" should
3909 * never get caught in the normal page freeing logic.
3910 *
3911 * (Kswapd normally doesn't need memory anyway, but sometimes
3912 * you need a small amount of memory in order to be able to
3913 * page out something else, and this flag essentially protects
3914 * us from recursively trying to free more memory as we're
3915 * trying to free the first piece of memory in the first place).
3916 */
3917 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
3918 set_freezable();
3919
3920 pgdat->kswapd_order = 0;
3921 pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
3922 for ( ; ; ) {
3923 bool ret;
3924
3925 alloc_order = reclaim_order = pgdat->kswapd_order;
3926 classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
3927
3928 kswapd_try_sleep:
3929 kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
3930 classzone_idx);
3931
3932 /* Read the new order and classzone_idx */
3933 alloc_order = reclaim_order = pgdat->kswapd_order;
3934 classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
3935 pgdat->kswapd_order = 0;
3936 pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
3937
3938 ret = try_to_freeze();
3939 if (kthread_should_stop())
3940 break;
3941
3942 /*
3943 * We can speed up thawing tasks if we don't call balance_pgdat
3944 * after returning from the refrigerator
3945 */
3946 if (ret)
3947 continue;
3948
3949 /*
3950 * Reclaim begins at the requested order but if a high-order
3951 * reclaim fails then kswapd falls back to reclaiming for
3952 * order-0. If that happens, kswapd will consider sleeping
3953 * for the order it finished reclaiming at (reclaim_order)
3954 * but kcompactd is woken to compact for the original
3955 * request (alloc_order).
3956 */
3957 trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx,
3958 alloc_order);
3959 reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
3960 if (reclaim_order < alloc_order)
3961 goto kswapd_try_sleep;
3962 }
3963
3964 tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
3965
3966 return 0;
3967 }
3968
3969 /*
3970 * A zone is low on free memory or too fragmented for high-order memory. If
3971 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
3972 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
3973 * has failed or is not needed, still wake up kcompactd if only compaction is
3974 * needed.
3975 */
3976 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
3977 enum zone_type classzone_idx)
3978 {
3979 pg_data_t *pgdat;
3980
3981 if (!managed_zone(zone))
3982 return;
3983
3984 if (!cpuset_zone_allowed(zone, gfp_flags))
3985 return;
3986 pgdat = zone->zone_pgdat;
3987
3988 if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES)
3989 pgdat->kswapd_classzone_idx = classzone_idx;
3990 else
3991 pgdat->kswapd_classzone_idx = max(pgdat->kswapd_classzone_idx,
3992 classzone_idx);
3993 pgdat->kswapd_order = max(pgdat->kswapd_order, order);
3994 if (!waitqueue_active(&pgdat->kswapd_wait))
3995 return;
3996
3997 /* Hopeless node, leave it to direct reclaim if possible */
3998 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
3999 (pgdat_balanced(pgdat, order, classzone_idx) &&
4000 !pgdat_watermark_boosted(pgdat, classzone_idx))) {
4001 /*
4002 * There may be plenty of free memory available, but it's too
4003 * fragmented for high-order allocations. Wake up kcompactd
4004 * and rely on compaction_suitable() to determine if it's
4005 * needed. If it fails, it will defer subsequent attempts to
4006 * ratelimit its work.
4007 */
4008 if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
4009 wakeup_kcompactd(pgdat, order, classzone_idx);
4010 return;
4011 }
4012
4013 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, classzone_idx, order,
4014 gfp_flags);
4015 wake_up_interruptible(&pgdat->kswapd_wait);
4016 }
4017
4018 #ifdef CONFIG_HIBERNATION
4019 /*
4020 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
4021 * freed pages.
4022 *
4023 * Rather than trying to age LRUs the aim is to preserve the overall
4024 * LRU order by reclaiming preferentially
4025 * inactive > active > active referenced > active mapped
4026 */
4027 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
4028 {
4029 struct scan_control sc = {
4030 .nr_to_reclaim = nr_to_reclaim,
4031 .gfp_mask = GFP_HIGHUSER_MOVABLE,
4032 .reclaim_idx = MAX_NR_ZONES - 1,
4033 .priority = DEF_PRIORITY,
4034 .may_writepage = 1,
4035 .may_unmap = 1,
4036 .may_swap = 1,
4037 .hibernation_mode = 1,
4038 };
4039 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
4040 unsigned long nr_reclaimed;
4041 unsigned int noreclaim_flag;
4042
4043 fs_reclaim_acquire(sc.gfp_mask);
4044 noreclaim_flag = memalloc_noreclaim_save();
4045 set_task_reclaim_state(current, &sc.reclaim_state);
4046
4047 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
4048
4049 set_task_reclaim_state(current, NULL);
4050 memalloc_noreclaim_restore(noreclaim_flag);
4051 fs_reclaim_release(sc.gfp_mask);
4052
4053 return nr_reclaimed;
4054 }
4055 #endif /* CONFIG_HIBERNATION */
4056
4057 /* It's optimal to keep kswapds on the same CPUs as their memory, but
4058 not required for correctness. So if the last cpu in a node goes
4059 away, we get changed to run anywhere: as the first one comes back,
4060 restore their cpu bindings. */
4061 static int kswapd_cpu_online(unsigned int cpu)
4062 {
4063 int nid;
4064
4065 for_each_node_state(nid, N_MEMORY) {
4066 pg_data_t *pgdat = NODE_DATA(nid);
4067 const struct cpumask *mask;
4068
4069 mask = cpumask_of_node(pgdat->node_id);
4070
4071 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
4072 /* One of our CPUs online: restore mask */
4073 set_cpus_allowed_ptr(pgdat->kswapd, mask);
4074 }
4075 return 0;
4076 }
4077
4078 /*
4079 * This kswapd start function will be called by init and node-hot-add.
4080 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
4081 */
4082 int kswapd_run(int nid)
4083 {
4084 pg_data_t *pgdat = NODE_DATA(nid);
4085 int ret = 0;
4086
4087 if (pgdat->kswapd)
4088 return 0;
4089
4090 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
4091 if (IS_ERR(pgdat->kswapd)) {
4092 /* failure at boot is fatal */
4093 BUG_ON(system_state < SYSTEM_RUNNING);
4094 pr_err("Failed to start kswapd on node %d\n", nid);
4095 ret = PTR_ERR(pgdat->kswapd);
4096 pgdat->kswapd = NULL;
4097 }
4098 return ret;
4099 }
4100
4101 /*
4102 * Called by memory hotplug when all memory in a node is offlined. Caller must
4103 * hold mem_hotplug_begin/end().
4104 */
4105 void kswapd_stop(int nid)
4106 {
4107 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
4108
4109 if (kswapd) {
4110 kthread_stop(kswapd);
4111 NODE_DATA(nid)->kswapd = NULL;
4112 }
4113 }
4114
4115 static int __init kswapd_init(void)
4116 {
4117 int nid, ret;
4118
4119 swap_setup();
4120 for_each_node_state(nid, N_MEMORY)
4121 kswapd_run(nid);
4122 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
4123 "mm/vmscan:online", kswapd_cpu_online,
4124 NULL);
4125 WARN_ON(ret < 0);
4126 return 0;
4127 }
4128
4129 module_init(kswapd_init)
4130
4131 #ifdef CONFIG_NUMA
4132 /*
4133 * Node reclaim mode
4134 *
4135 * If non-zero call node_reclaim when the number of free pages falls below
4136 * the watermarks.
4137 */
4138 int node_reclaim_mode __read_mostly;
4139
4140 #define RECLAIM_OFF 0
4141 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
4142 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
4143 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
4144
4145 /*
4146 * Priority for NODE_RECLAIM. This determines the fraction of pages
4147 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4148 * a zone.
4149 */
4150 #define NODE_RECLAIM_PRIORITY 4
4151
4152 /*
4153 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4154 * occur.
4155 */
4156 int sysctl_min_unmapped_ratio = 1;
4157
4158 /*
4159 * If the number of slab pages in a zone grows beyond this percentage then
4160 * slab reclaim needs to occur.
4161 */
4162 int sysctl_min_slab_ratio = 5;
4163
4164 static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
4165 {
4166 unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
4167 unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
4168 node_page_state(pgdat, NR_ACTIVE_FILE);
4169
4170 /*
4171 * It's possible for there to be more file mapped pages than
4172 * accounted for by the pages on the file LRU lists because
4173 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4174 */
4175 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
4176 }
4177
4178 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4179 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
4180 {
4181 unsigned long nr_pagecache_reclaimable;
4182 unsigned long delta = 0;
4183
4184 /*
4185 * If RECLAIM_UNMAP is set, then all file pages are considered
4186 * potentially reclaimable. Otherwise, we have to worry about
4187 * pages like swapcache and node_unmapped_file_pages() provides
4188 * a better estimate
4189 */
4190 if (node_reclaim_mode & RECLAIM_UNMAP)
4191 nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
4192 else
4193 nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
4194
4195 /* If we can't clean pages, remove dirty pages from consideration */
4196 if (!(node_reclaim_mode & RECLAIM_WRITE))
4197 delta += node_page_state(pgdat, NR_FILE_DIRTY);
4198
4199 /* Watch for any possible underflows due to delta */
4200 if (unlikely(delta > nr_pagecache_reclaimable))
4201 delta = nr_pagecache_reclaimable;
4202
4203 return nr_pagecache_reclaimable - delta;
4204 }
4205
4206 /*
4207 * Try to free up some pages from this node through reclaim.
4208 */
4209 static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
4210 {
4211 /* Minimum pages needed in order to stay on node */
4212 const unsigned long nr_pages = 1 << order;
4213 struct task_struct *p = current;
4214 unsigned int noreclaim_flag;
4215 struct scan_control sc = {
4216 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
4217 .gfp_mask = current_gfp_context(gfp_mask),
4218 .order = order,
4219 .priority = NODE_RECLAIM_PRIORITY,
4220 .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
4221 .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
4222 .may_swap = 1,
4223 .reclaim_idx = gfp_zone(gfp_mask),
4224 };
4225
4226 trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
4227 sc.gfp_mask);
4228
4229 cond_resched();
4230 fs_reclaim_acquire(sc.gfp_mask);
4231 /*
4232 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4233 * and we also need to be able to write out pages for RECLAIM_WRITE
4234 * and RECLAIM_UNMAP.
4235 */
4236 noreclaim_flag = memalloc_noreclaim_save();
4237 p->flags |= PF_SWAPWRITE;
4238 set_task_reclaim_state(p, &sc.reclaim_state);
4239
4240 if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) {
4241 /*
4242 * Free memory by calling shrink node with increasing
4243 * priorities until we have enough memory freed.
4244 */
4245 do {
4246 shrink_node(pgdat, &sc);
4247 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
4248 }
4249
4250 set_task_reclaim_state(p, NULL);
4251 current->flags &= ~PF_SWAPWRITE;
4252 memalloc_noreclaim_restore(noreclaim_flag);
4253 fs_reclaim_release(sc.gfp_mask);
4254
4255 trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
4256
4257 return sc.nr_reclaimed >= nr_pages;
4258 }
4259
4260 int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
4261 {
4262 int ret;
4263
4264 /*
4265 * Node reclaim reclaims unmapped file backed pages and
4266 * slab pages if we are over the defined limits.
4267 *
4268 * A small portion of unmapped file backed pages is needed for
4269 * file I/O otherwise pages read by file I/O will be immediately
4270 * thrown out if the node is overallocated. So we do not reclaim
4271 * if less than a specified percentage of the node is used by
4272 * unmapped file backed pages.
4273 */
4274 if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
4275 node_page_state(pgdat, NR_SLAB_RECLAIMABLE) <= pgdat->min_slab_pages)
4276 return NODE_RECLAIM_FULL;
4277
4278 /*
4279 * Do not scan if the allocation should not be delayed.
4280 */
4281 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
4282 return NODE_RECLAIM_NOSCAN;
4283
4284 /*
4285 * Only run node reclaim on the local node or on nodes that do not
4286 * have associated processors. This will favor the local processor
4287 * over remote processors and spread off node memory allocations
4288 * as wide as possible.
4289 */
4290 if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
4291 return NODE_RECLAIM_NOSCAN;
4292
4293 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
4294 return NODE_RECLAIM_NOSCAN;
4295
4296 ret = __node_reclaim(pgdat, gfp_mask, order);
4297 clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
4298
4299 if (!ret)
4300 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
4301
4302 return ret;
4303 }
4304 #endif
4305
4306 /*
4307 * page_evictable - test whether a page is evictable
4308 * @page: the page to test
4309 *
4310 * Test whether page is evictable--i.e., should be placed on active/inactive
4311 * lists vs unevictable list.
4312 *
4313 * Reasons page might not be evictable:
4314 * (1) page's mapping marked unevictable
4315 * (2) page is part of an mlocked VMA
4316 *
4317 */
4318 int page_evictable(struct page *page)
4319 {
4320 int ret;
4321
4322 /* Prevent address_space of inode and swap cache from being freed */
4323 rcu_read_lock();
4324 ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
4325 rcu_read_unlock();
4326 return ret;
4327 }
4328
4329 /**
4330 * check_move_unevictable_pages - check pages for evictability and move to
4331 * appropriate zone lru list
4332 * @pvec: pagevec with lru pages to check
4333 *
4334 * Checks pages for evictability, if an evictable page is in the unevictable
4335 * lru list, moves it to the appropriate evictable lru list. This function
4336 * should be only used for lru pages.
4337 */
4338 void check_move_unevictable_pages(struct pagevec *pvec)
4339 {
4340 struct lruvec *lruvec;
4341 struct pglist_data *pgdat = NULL;
4342 int pgscanned = 0;
4343 int pgrescued = 0;
4344 int i;
4345
4346 for (i = 0; i < pvec->nr; i++) {
4347 struct page *page = pvec->pages[i];
4348 struct pglist_data *pagepgdat = page_pgdat(page);
4349
4350 pgscanned++;
4351 if (pagepgdat != pgdat) {
4352 if (pgdat)
4353 spin_unlock_irq(&pgdat->lru_lock);
4354 pgdat = pagepgdat;
4355 spin_lock_irq(&pgdat->lru_lock);
4356 }
4357 lruvec = mem_cgroup_page_lruvec(page, pgdat);
4358
4359 if (!PageLRU(page) || !PageUnevictable(page))
4360 continue;
4361
4362 if (page_evictable(page)) {
4363 enum lru_list lru = page_lru_base_type(page);
4364
4365 VM_BUG_ON_PAGE(PageActive(page), page);
4366 ClearPageUnevictable(page);
4367 del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
4368 add_page_to_lru_list(page, lruvec, lru);
4369 pgrescued++;
4370 }
4371 }
4372
4373 if (pgdat) {
4374 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
4375 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
4376 spin_unlock_irq(&pgdat->lru_lock);
4377 }
4378 }
4379 EXPORT_SYMBOL_GPL(check_move_unevictable_pages);