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