xref: /linux/mm/vmscan.c (revision 2c1ed907520c50326b8f604907a8478b27881a2e)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
4  *
5  *  Swap reorganised 29.12.95, Stephen Tweedie.
6  *  kswapd added: 7.1.96  sct
7  *  Removed kswapd_ctl limits, and swap out as many pages as needed
8  *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9  *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10  *  Multiqueue VM started 5.8.00, Rik van Riel.
11  */
12 
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14 
15 #include <linux/mm.h>
16 #include <linux/sched/mm.h>
17 #include <linux/module.h>
18 #include <linux/gfp.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/pagemap.h>
22 #include <linux/init.h>
23 #include <linux/highmem.h>
24 #include <linux/vmpressure.h>
25 #include <linux/vmstat.h>
26 #include <linux/file.h>
27 #include <linux/writeback.h>
28 #include <linux/blkdev.h>
29 #include <linux/buffer_head.h>	/* for buffer_heads_over_limit */
30 #include <linux/mm_inline.h>
31 #include <linux/backing-dev.h>
32 #include <linux/rmap.h>
33 #include <linux/topology.h>
34 #include <linux/cpu.h>
35 #include <linux/cpuset.h>
36 #include <linux/compaction.h>
37 #include <linux/notifier.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/migrate.h>
43 #include <linux/delayacct.h>
44 #include <linux/sysctl.h>
45 #include <linux/memory-tiers.h>
46 #include <linux/oom.h>
47 #include <linux/pagevec.h>
48 #include <linux/prefetch.h>
49 #include <linux/printk.h>
50 #include <linux/dax.h>
51 #include <linux/psi.h>
52 #include <linux/pagewalk.h>
53 #include <linux/shmem_fs.h>
54 #include <linux/ctype.h>
55 #include <linux/debugfs.h>
56 #include <linux/khugepaged.h>
57 #include <linux/rculist_nulls.h>
58 #include <linux/random.h>
59 #include <linux/mmu_notifier.h>
60 
61 #include <asm/tlbflush.h>
62 #include <asm/div64.h>
63 
64 #include <linux/swapops.h>
65 #include <linux/balloon_compaction.h>
66 #include <linux/sched/sysctl.h>
67 
68 #include "internal.h"
69 #include "swap.h"
70 
71 #define CREATE_TRACE_POINTS
72 #include <trace/events/vmscan.h>
73 
74 struct scan_control {
75 	/* How many pages shrink_list() should reclaim */
76 	unsigned long nr_to_reclaim;
77 
78 	/*
79 	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
80 	 * are scanned.
81 	 */
82 	nodemask_t	*nodemask;
83 
84 	/*
85 	 * The memory cgroup that hit its limit and as a result is the
86 	 * primary target of this reclaim invocation.
87 	 */
88 	struct mem_cgroup *target_mem_cgroup;
89 
90 	/*
91 	 * Scan pressure balancing between anon and file LRUs
92 	 */
93 	unsigned long	anon_cost;
94 	unsigned long	file_cost;
95 
96 #ifdef CONFIG_MEMCG
97 	/* Swappiness value for proactive reclaim. Always use sc_swappiness()! */
98 	int *proactive_swappiness;
99 #endif
100 
101 	/* Can active folios be deactivated as part of reclaim? */
102 #define DEACTIVATE_ANON 1
103 #define DEACTIVATE_FILE 2
104 	unsigned int may_deactivate:2;
105 	unsigned int force_deactivate:1;
106 	unsigned int skipped_deactivate:1;
107 
108 	/* Writepage batching in laptop mode; RECLAIM_WRITE */
109 	unsigned int may_writepage:1;
110 
111 	/* Can mapped folios be reclaimed? */
112 	unsigned int may_unmap:1;
113 
114 	/* Can folios be swapped as part of reclaim? */
115 	unsigned int may_swap:1;
116 
117 	/* Not allow cache_trim_mode to be turned on as part of reclaim? */
118 	unsigned int no_cache_trim_mode:1;
119 
120 	/* Has cache_trim_mode failed at least once? */
121 	unsigned int cache_trim_mode_failed:1;
122 
123 	/* Proactive reclaim invoked by userspace through memory.reclaim */
124 	unsigned int proactive:1;
125 
126 	/*
127 	 * Cgroup memory below memory.low is protected as long as we
128 	 * don't threaten to OOM. If any cgroup is reclaimed at
129 	 * reduced force or passed over entirely due to its memory.low
130 	 * setting (memcg_low_skipped), and nothing is reclaimed as a
131 	 * result, then go back for one more cycle that reclaims the protected
132 	 * memory (memcg_low_reclaim) to avert OOM.
133 	 */
134 	unsigned int memcg_low_reclaim:1;
135 	unsigned int memcg_low_skipped:1;
136 
137 	/* Shared cgroup tree walk failed, rescan the whole tree */
138 	unsigned int memcg_full_walk:1;
139 
140 	unsigned int hibernation_mode:1;
141 
142 	/* One of the zones is ready for compaction */
143 	unsigned int compaction_ready:1;
144 
145 	/* There is easily reclaimable cold cache in the current node */
146 	unsigned int cache_trim_mode:1;
147 
148 	/* The file folios on the current node are dangerously low */
149 	unsigned int file_is_tiny:1;
150 
151 	/* Always discard instead of demoting to lower tier memory */
152 	unsigned int no_demotion:1;
153 
154 	/* Allocation order */
155 	s8 order;
156 
157 	/* Scan (total_size >> priority) pages at once */
158 	s8 priority;
159 
160 	/* The highest zone to isolate folios for reclaim from */
161 	s8 reclaim_idx;
162 
163 	/* This context's GFP mask */
164 	gfp_t gfp_mask;
165 
166 	/* Incremented by the number of inactive pages that were scanned */
167 	unsigned long nr_scanned;
168 
169 	/* Number of pages freed so far during a call to shrink_zones() */
170 	unsigned long nr_reclaimed;
171 
172 	struct {
173 		unsigned int dirty;
174 		unsigned int unqueued_dirty;
175 		unsigned int congested;
176 		unsigned int writeback;
177 		unsigned int immediate;
178 		unsigned int file_taken;
179 		unsigned int taken;
180 	} nr;
181 
182 	/* for recording the reclaimed slab by now */
183 	struct reclaim_state reclaim_state;
184 };
185 
186 #ifdef ARCH_HAS_PREFETCHW
187 #define prefetchw_prev_lru_folio(_folio, _base, _field)			\
188 	do {								\
189 		if ((_folio)->lru.prev != _base) {			\
190 			struct folio *prev;				\
191 									\
192 			prev = lru_to_folio(&(_folio->lru));		\
193 			prefetchw(&prev->_field);			\
194 		}							\
195 	} while (0)
196 #else
197 #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
198 #endif
199 
200 /*
201  * From 0 .. MAX_SWAPPINESS.  Higher means more swappy.
202  */
203 int vm_swappiness = 60;
204 
205 #ifdef CONFIG_MEMCG
206 
207 /* Returns true for reclaim through cgroup limits or cgroup interfaces. */
cgroup_reclaim(struct scan_control * sc)208 static bool cgroup_reclaim(struct scan_control *sc)
209 {
210 	return sc->target_mem_cgroup;
211 }
212 
213 /*
214  * Returns true for reclaim on the root cgroup. This is true for direct
215  * allocator reclaim and reclaim through cgroup interfaces on the root cgroup.
216  */
root_reclaim(struct scan_control * sc)217 static bool root_reclaim(struct scan_control *sc)
218 {
219 	return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup);
220 }
221 
222 /**
223  * writeback_throttling_sane - is the usual dirty throttling mechanism available?
224  * @sc: scan_control in question
225  *
226  * The normal page dirty throttling mechanism in balance_dirty_pages() is
227  * completely broken with the legacy memcg and direct stalling in
228  * shrink_folio_list() is used for throttling instead, which lacks all the
229  * niceties such as fairness, adaptive pausing, bandwidth proportional
230  * allocation and configurability.
231  *
232  * This function tests whether the vmscan currently in progress can assume
233  * that the normal dirty throttling mechanism is operational.
234  */
writeback_throttling_sane(struct scan_control * sc)235 static bool writeback_throttling_sane(struct scan_control *sc)
236 {
237 	if (!cgroup_reclaim(sc))
238 		return true;
239 #ifdef CONFIG_CGROUP_WRITEBACK
240 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
241 		return true;
242 #endif
243 	return false;
244 }
245 
sc_swappiness(struct scan_control * sc,struct mem_cgroup * memcg)246 static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
247 {
248 	if (sc->proactive && sc->proactive_swappiness)
249 		return *sc->proactive_swappiness;
250 	return mem_cgroup_swappiness(memcg);
251 }
252 #else
cgroup_reclaim(struct scan_control * sc)253 static bool cgroup_reclaim(struct scan_control *sc)
254 {
255 	return false;
256 }
257 
root_reclaim(struct scan_control * sc)258 static bool root_reclaim(struct scan_control *sc)
259 {
260 	return true;
261 }
262 
writeback_throttling_sane(struct scan_control * sc)263 static bool writeback_throttling_sane(struct scan_control *sc)
264 {
265 	return true;
266 }
267 
sc_swappiness(struct scan_control * sc,struct mem_cgroup * memcg)268 static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
269 {
270 	return READ_ONCE(vm_swappiness);
271 }
272 #endif
273 
set_task_reclaim_state(struct task_struct * task,struct reclaim_state * rs)274 static void set_task_reclaim_state(struct task_struct *task,
275 				   struct reclaim_state *rs)
276 {
277 	/* Check for an overwrite */
278 	WARN_ON_ONCE(rs && task->reclaim_state);
279 
280 	/* Check for the nulling of an already-nulled member */
281 	WARN_ON_ONCE(!rs && !task->reclaim_state);
282 
283 	task->reclaim_state = rs;
284 }
285 
286 /*
287  * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
288  * scan_control->nr_reclaimed.
289  */
flush_reclaim_state(struct scan_control * sc)290 static void flush_reclaim_state(struct scan_control *sc)
291 {
292 	/*
293 	 * Currently, reclaim_state->reclaimed includes three types of pages
294 	 * freed outside of vmscan:
295 	 * (1) Slab pages.
296 	 * (2) Clean file pages from pruned inodes (on highmem systems).
297 	 * (3) XFS freed buffer pages.
298 	 *
299 	 * For all of these cases, we cannot universally link the pages to a
300 	 * single memcg. For example, a memcg-aware shrinker can free one object
301 	 * charged to the target memcg, causing an entire page to be freed.
302 	 * If we count the entire page as reclaimed from the memcg, we end up
303 	 * overestimating the reclaimed amount (potentially under-reclaiming).
304 	 *
305 	 * Only count such pages for global reclaim to prevent under-reclaiming
306 	 * from the target memcg; preventing unnecessary retries during memcg
307 	 * charging and false positives from proactive reclaim.
308 	 *
309 	 * For uncommon cases where the freed pages were actually mostly
310 	 * charged to the target memcg, we end up underestimating the reclaimed
311 	 * amount. This should be fine. The freed pages will be uncharged
312 	 * anyway, even if they are not counted here properly, and we will be
313 	 * able to make forward progress in charging (which is usually in a
314 	 * retry loop).
315 	 *
316 	 * We can go one step further, and report the uncharged objcg pages in
317 	 * memcg reclaim, to make reporting more accurate and reduce
318 	 * underestimation, but it's probably not worth the complexity for now.
319 	 */
320 	if (current->reclaim_state && root_reclaim(sc)) {
321 		sc->nr_reclaimed += current->reclaim_state->reclaimed;
322 		current->reclaim_state->reclaimed = 0;
323 	}
324 }
325 
can_demote(int nid,struct scan_control * sc)326 static bool can_demote(int nid, struct scan_control *sc)
327 {
328 	if (!numa_demotion_enabled)
329 		return false;
330 	if (sc && sc->no_demotion)
331 		return false;
332 	if (next_demotion_node(nid) == NUMA_NO_NODE)
333 		return false;
334 
335 	return true;
336 }
337 
can_reclaim_anon_pages(struct mem_cgroup * memcg,int nid,struct scan_control * sc)338 static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
339 					  int nid,
340 					  struct scan_control *sc)
341 {
342 	if (memcg == NULL) {
343 		/*
344 		 * For non-memcg reclaim, is there
345 		 * space in any swap device?
346 		 */
347 		if (get_nr_swap_pages() > 0)
348 			return true;
349 	} else {
350 		/* Is the memcg below its swap limit? */
351 		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
352 			return true;
353 	}
354 
355 	/*
356 	 * The page can not be swapped.
357 	 *
358 	 * Can it be reclaimed from this node via demotion?
359 	 */
360 	return can_demote(nid, sc);
361 }
362 
363 /*
364  * This misses isolated folios which are not accounted for to save counters.
365  * As the data only determines if reclaim or compaction continues, it is
366  * not expected that isolated folios will be a dominating factor.
367  */
zone_reclaimable_pages(struct zone * zone)368 unsigned long zone_reclaimable_pages(struct zone *zone)
369 {
370 	unsigned long nr;
371 
372 	nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
373 		zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
374 	if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
375 		nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
376 			zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
377 	/*
378 	 * If there are no reclaimable file-backed or anonymous pages,
379 	 * ensure zones with sufficient free pages are not skipped.
380 	 * This prevents zones like DMA32 from being ignored in reclaim
381 	 * scenarios where they can still help alleviate memory pressure.
382 	 */
383 	if (nr == 0)
384 		nr = zone_page_state_snapshot(zone, NR_FREE_PAGES);
385 	return nr;
386 }
387 
388 /**
389  * lruvec_lru_size -  Returns the number of pages on the given LRU list.
390  * @lruvec: lru vector
391  * @lru: lru to use
392  * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
393  */
lruvec_lru_size(struct lruvec * lruvec,enum lru_list lru,int zone_idx)394 static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
395 				     int zone_idx)
396 {
397 	unsigned long size = 0;
398 	int zid;
399 
400 	for (zid = 0; zid <= zone_idx; zid++) {
401 		struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
402 
403 		if (!managed_zone(zone))
404 			continue;
405 
406 		if (!mem_cgroup_disabled())
407 			size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
408 		else
409 			size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
410 	}
411 	return size;
412 }
413 
drop_slab_node(int nid)414 static unsigned long drop_slab_node(int nid)
415 {
416 	unsigned long freed = 0;
417 	struct mem_cgroup *memcg = NULL;
418 
419 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
420 	do {
421 		freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
422 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
423 
424 	return freed;
425 }
426 
drop_slab(void)427 void drop_slab(void)
428 {
429 	int nid;
430 	int shift = 0;
431 	unsigned long freed;
432 
433 	do {
434 		freed = 0;
435 		for_each_online_node(nid) {
436 			if (fatal_signal_pending(current))
437 				return;
438 
439 			freed += drop_slab_node(nid);
440 		}
441 	} while ((freed >> shift++) > 1);
442 }
443 
reclaimer_offset(void)444 static int reclaimer_offset(void)
445 {
446 	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
447 			PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
448 	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
449 			PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
450 	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
451 			PGSCAN_DIRECT - PGSCAN_KSWAPD);
452 	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
453 			PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
454 
455 	if (current_is_kswapd())
456 		return 0;
457 	if (current_is_khugepaged())
458 		return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
459 	return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
460 }
461 
is_page_cache_freeable(struct folio * folio)462 static inline int is_page_cache_freeable(struct folio *folio)
463 {
464 	/*
465 	 * A freeable page cache folio is referenced only by the caller
466 	 * that isolated the folio, the page cache and optional filesystem
467 	 * private data at folio->private.
468 	 */
469 	return folio_ref_count(folio) - folio_test_private(folio) ==
470 		1 + folio_nr_pages(folio);
471 }
472 
473 /*
474  * We detected a synchronous write error writing a folio out.  Probably
475  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
476  * fsync(), msync() or close().
477  *
478  * The tricky part is that after writepage we cannot touch the mapping: nothing
479  * prevents it from being freed up.  But we have a ref on the folio and once
480  * that folio is locked, the mapping is pinned.
481  *
482  * We're allowed to run sleeping folio_lock() here because we know the caller has
483  * __GFP_FS.
484  */
handle_write_error(struct address_space * mapping,struct folio * folio,int error)485 static void handle_write_error(struct address_space *mapping,
486 				struct folio *folio, int error)
487 {
488 	folio_lock(folio);
489 	if (folio_mapping(folio) == mapping)
490 		mapping_set_error(mapping, error);
491 	folio_unlock(folio);
492 }
493 
skip_throttle_noprogress(pg_data_t * pgdat)494 static bool skip_throttle_noprogress(pg_data_t *pgdat)
495 {
496 	int reclaimable = 0, write_pending = 0;
497 	int i;
498 
499 	/*
500 	 * If kswapd is disabled, reschedule if necessary but do not
501 	 * throttle as the system is likely near OOM.
502 	 */
503 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
504 		return true;
505 
506 	/*
507 	 * If there are a lot of dirty/writeback folios then do not
508 	 * throttle as throttling will occur when the folios cycle
509 	 * towards the end of the LRU if still under writeback.
510 	 */
511 	for (i = 0; i < MAX_NR_ZONES; i++) {
512 		struct zone *zone = pgdat->node_zones + i;
513 
514 		if (!managed_zone(zone))
515 			continue;
516 
517 		reclaimable += zone_reclaimable_pages(zone);
518 		write_pending += zone_page_state_snapshot(zone,
519 						  NR_ZONE_WRITE_PENDING);
520 	}
521 	if (2 * write_pending <= reclaimable)
522 		return true;
523 
524 	return false;
525 }
526 
reclaim_throttle(pg_data_t * pgdat,enum vmscan_throttle_state reason)527 void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
528 {
529 	wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
530 	long timeout, ret;
531 	DEFINE_WAIT(wait);
532 
533 	/*
534 	 * Do not throttle user workers, kthreads other than kswapd or
535 	 * workqueues. They may be required for reclaim to make
536 	 * forward progress (e.g. journalling workqueues or kthreads).
537 	 */
538 	if (!current_is_kswapd() &&
539 	    current->flags & (PF_USER_WORKER|PF_KTHREAD)) {
540 		cond_resched();
541 		return;
542 	}
543 
544 	/*
545 	 * These figures are pulled out of thin air.
546 	 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
547 	 * parallel reclaimers which is a short-lived event so the timeout is
548 	 * short. Failing to make progress or waiting on writeback are
549 	 * potentially long-lived events so use a longer timeout. This is shaky
550 	 * logic as a failure to make progress could be due to anything from
551 	 * writeback to a slow device to excessive referenced folios at the tail
552 	 * of the inactive LRU.
553 	 */
554 	switch(reason) {
555 	case VMSCAN_THROTTLE_WRITEBACK:
556 		timeout = HZ/10;
557 
558 		if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
559 			WRITE_ONCE(pgdat->nr_reclaim_start,
560 				node_page_state(pgdat, NR_THROTTLED_WRITTEN));
561 		}
562 
563 		break;
564 	case VMSCAN_THROTTLE_CONGESTED:
565 		fallthrough;
566 	case VMSCAN_THROTTLE_NOPROGRESS:
567 		if (skip_throttle_noprogress(pgdat)) {
568 			cond_resched();
569 			return;
570 		}
571 
572 		timeout = 1;
573 
574 		break;
575 	case VMSCAN_THROTTLE_ISOLATED:
576 		timeout = HZ/50;
577 		break;
578 	default:
579 		WARN_ON_ONCE(1);
580 		timeout = HZ;
581 		break;
582 	}
583 
584 	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
585 	ret = schedule_timeout(timeout);
586 	finish_wait(wqh, &wait);
587 
588 	if (reason == VMSCAN_THROTTLE_WRITEBACK)
589 		atomic_dec(&pgdat->nr_writeback_throttled);
590 
591 	trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
592 				jiffies_to_usecs(timeout - ret),
593 				reason);
594 }
595 
596 /*
597  * Account for folios written if tasks are throttled waiting on dirty
598  * folios to clean. If enough folios have been cleaned since throttling
599  * started then wakeup the throttled tasks.
600  */
__acct_reclaim_writeback(pg_data_t * pgdat,struct folio * folio,int nr_throttled)601 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
602 							int nr_throttled)
603 {
604 	unsigned long nr_written;
605 
606 	node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
607 
608 	/*
609 	 * This is an inaccurate read as the per-cpu deltas may not
610 	 * be synchronised. However, given that the system is
611 	 * writeback throttled, it is not worth taking the penalty
612 	 * of getting an accurate count. At worst, the throttle
613 	 * timeout guarantees forward progress.
614 	 */
615 	nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
616 		READ_ONCE(pgdat->nr_reclaim_start);
617 
618 	if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
619 		wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
620 }
621 
622 /* possible outcome of pageout() */
623 typedef enum {
624 	/* failed to write folio out, folio is locked */
625 	PAGE_KEEP,
626 	/* move folio to the active list, folio is locked */
627 	PAGE_ACTIVATE,
628 	/* folio has been sent to the disk successfully, folio is unlocked */
629 	PAGE_SUCCESS,
630 	/* folio is clean and locked */
631 	PAGE_CLEAN,
632 } pageout_t;
633 
634 /*
635  * pageout is called by shrink_folio_list() for each dirty folio.
636  * Calls ->writepage().
637  */
pageout(struct folio * folio,struct address_space * mapping,struct swap_iocb ** plug,struct list_head * folio_list)638 static pageout_t pageout(struct folio *folio, struct address_space *mapping,
639 			 struct swap_iocb **plug, struct list_head *folio_list)
640 {
641 	/*
642 	 * If the folio is dirty, only perform writeback if that write
643 	 * will be non-blocking.  To prevent this allocation from being
644 	 * stalled by pagecache activity.  But note that there may be
645 	 * stalls if we need to run get_block().  We could test
646 	 * PagePrivate for that.
647 	 *
648 	 * If this process is currently in __generic_file_write_iter() against
649 	 * this folio's queue, we can perform writeback even if that
650 	 * will block.
651 	 *
652 	 * If the folio is swapcache, write it back even if that would
653 	 * block, for some throttling. This happens by accident, because
654 	 * swap_backing_dev_info is bust: it doesn't reflect the
655 	 * congestion state of the swapdevs.  Easy to fix, if needed.
656 	 */
657 	if (!is_page_cache_freeable(folio))
658 		return PAGE_KEEP;
659 	if (!mapping) {
660 		/*
661 		 * Some data journaling orphaned folios can have
662 		 * folio->mapping == NULL while being dirty with clean buffers.
663 		 */
664 		if (folio_test_private(folio)) {
665 			if (try_to_free_buffers(folio)) {
666 				folio_clear_dirty(folio);
667 				pr_info("%s: orphaned folio\n", __func__);
668 				return PAGE_CLEAN;
669 			}
670 		}
671 		return PAGE_KEEP;
672 	}
673 	if (mapping->a_ops->writepage == NULL)
674 		return PAGE_ACTIVATE;
675 
676 	if (folio_clear_dirty_for_io(folio)) {
677 		int res;
678 		struct writeback_control wbc = {
679 			.sync_mode = WB_SYNC_NONE,
680 			.nr_to_write = SWAP_CLUSTER_MAX,
681 			.range_start = 0,
682 			.range_end = LLONG_MAX,
683 			.for_reclaim = 1,
684 			.swap_plug = plug,
685 		};
686 
687 		/*
688 		 * The large shmem folio can be split if CONFIG_THP_SWAP is
689 		 * not enabled or contiguous swap entries are failed to
690 		 * allocate.
691 		 */
692 		if (shmem_mapping(mapping) && folio_test_large(folio))
693 			wbc.list = folio_list;
694 
695 		folio_set_reclaim(folio);
696 		res = mapping->a_ops->writepage(&folio->page, &wbc);
697 		if (res < 0)
698 			handle_write_error(mapping, folio, res);
699 		if (res == AOP_WRITEPAGE_ACTIVATE) {
700 			folio_clear_reclaim(folio);
701 			return PAGE_ACTIVATE;
702 		}
703 
704 		if (!folio_test_writeback(folio)) {
705 			/* synchronous write or broken a_ops? */
706 			folio_clear_reclaim(folio);
707 		}
708 		trace_mm_vmscan_write_folio(folio);
709 		node_stat_add_folio(folio, NR_VMSCAN_WRITE);
710 		return PAGE_SUCCESS;
711 	}
712 
713 	return PAGE_CLEAN;
714 }
715 
716 /*
717  * Same as remove_mapping, but if the folio is removed from the mapping, it
718  * gets returned with a refcount of 0.
719  */
__remove_mapping(struct address_space * mapping,struct folio * folio,bool reclaimed,struct mem_cgroup * target_memcg)720 static int __remove_mapping(struct address_space *mapping, struct folio *folio,
721 			    bool reclaimed, struct mem_cgroup *target_memcg)
722 {
723 	int refcount;
724 	void *shadow = NULL;
725 
726 	BUG_ON(!folio_test_locked(folio));
727 	BUG_ON(mapping != folio_mapping(folio));
728 
729 	if (!folio_test_swapcache(folio))
730 		spin_lock(&mapping->host->i_lock);
731 	xa_lock_irq(&mapping->i_pages);
732 	/*
733 	 * The non racy check for a busy folio.
734 	 *
735 	 * Must be careful with the order of the tests. When someone has
736 	 * a ref to the folio, it may be possible that they dirty it then
737 	 * drop the reference. So if the dirty flag is tested before the
738 	 * refcount here, then the following race may occur:
739 	 *
740 	 * get_user_pages(&page);
741 	 * [user mapping goes away]
742 	 * write_to(page);
743 	 *				!folio_test_dirty(folio)    [good]
744 	 * folio_set_dirty(folio);
745 	 * folio_put(folio);
746 	 *				!refcount(folio)   [good, discard it]
747 	 *
748 	 * [oops, our write_to data is lost]
749 	 *
750 	 * Reversing the order of the tests ensures such a situation cannot
751 	 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
752 	 * load is not satisfied before that of folio->_refcount.
753 	 *
754 	 * Note that if the dirty flag is always set via folio_mark_dirty,
755 	 * and thus under the i_pages lock, then this ordering is not required.
756 	 */
757 	refcount = 1 + folio_nr_pages(folio);
758 	if (!folio_ref_freeze(folio, refcount))
759 		goto cannot_free;
760 	/* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
761 	if (unlikely(folio_test_dirty(folio))) {
762 		folio_ref_unfreeze(folio, refcount);
763 		goto cannot_free;
764 	}
765 
766 	if (folio_test_swapcache(folio)) {
767 		swp_entry_t swap = folio->swap;
768 
769 		if (reclaimed && !mapping_exiting(mapping))
770 			shadow = workingset_eviction(folio, target_memcg);
771 		__delete_from_swap_cache(folio, swap, shadow);
772 		mem_cgroup_swapout(folio, swap);
773 		xa_unlock_irq(&mapping->i_pages);
774 		put_swap_folio(folio, swap);
775 	} else {
776 		void (*free_folio)(struct folio *);
777 
778 		free_folio = mapping->a_ops->free_folio;
779 		/*
780 		 * Remember a shadow entry for reclaimed file cache in
781 		 * order to detect refaults, thus thrashing, later on.
782 		 *
783 		 * But don't store shadows in an address space that is
784 		 * already exiting.  This is not just an optimization,
785 		 * inode reclaim needs to empty out the radix tree or
786 		 * the nodes are lost.  Don't plant shadows behind its
787 		 * back.
788 		 *
789 		 * We also don't store shadows for DAX mappings because the
790 		 * only page cache folios found in these are zero pages
791 		 * covering holes, and because we don't want to mix DAX
792 		 * exceptional entries and shadow exceptional entries in the
793 		 * same address_space.
794 		 */
795 		if (reclaimed && folio_is_file_lru(folio) &&
796 		    !mapping_exiting(mapping) && !dax_mapping(mapping))
797 			shadow = workingset_eviction(folio, target_memcg);
798 		__filemap_remove_folio(folio, shadow);
799 		xa_unlock_irq(&mapping->i_pages);
800 		if (mapping_shrinkable(mapping))
801 			inode_add_lru(mapping->host);
802 		spin_unlock(&mapping->host->i_lock);
803 
804 		if (free_folio)
805 			free_folio(folio);
806 	}
807 
808 	return 1;
809 
810 cannot_free:
811 	xa_unlock_irq(&mapping->i_pages);
812 	if (!folio_test_swapcache(folio))
813 		spin_unlock(&mapping->host->i_lock);
814 	return 0;
815 }
816 
817 /**
818  * remove_mapping() - Attempt to remove a folio from its mapping.
819  * @mapping: The address space.
820  * @folio: The folio to remove.
821  *
822  * If the folio is dirty, under writeback or if someone else has a ref
823  * on it, removal will fail.
824  * Return: The number of pages removed from the mapping.  0 if the folio
825  * could not be removed.
826  * Context: The caller should have a single refcount on the folio and
827  * hold its lock.
828  */
remove_mapping(struct address_space * mapping,struct folio * folio)829 long remove_mapping(struct address_space *mapping, struct folio *folio)
830 {
831 	if (__remove_mapping(mapping, folio, false, NULL)) {
832 		/*
833 		 * Unfreezing the refcount with 1 effectively
834 		 * drops the pagecache ref for us without requiring another
835 		 * atomic operation.
836 		 */
837 		folio_ref_unfreeze(folio, 1);
838 		return folio_nr_pages(folio);
839 	}
840 	return 0;
841 }
842 
843 /**
844  * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
845  * @folio: Folio to be returned to an LRU list.
846  *
847  * Add previously isolated @folio to appropriate LRU list.
848  * The folio may still be unevictable for other reasons.
849  *
850  * Context: lru_lock must not be held, interrupts must be enabled.
851  */
folio_putback_lru(struct folio * folio)852 void folio_putback_lru(struct folio *folio)
853 {
854 	folio_add_lru(folio);
855 	folio_put(folio);		/* drop ref from isolate */
856 }
857 
858 enum folio_references {
859 	FOLIOREF_RECLAIM,
860 	FOLIOREF_RECLAIM_CLEAN,
861 	FOLIOREF_KEEP,
862 	FOLIOREF_ACTIVATE,
863 };
864 
865 #ifdef CONFIG_LRU_GEN
866 /*
867  * Only used on a mapped folio in the eviction (rmap walk) path, where promotion
868  * needs to be done by taking the folio off the LRU list and then adding it back
869  * with PG_active set. In contrast, the aging (page table walk) path uses
870  * folio_update_gen().
871  */
lru_gen_set_refs(struct folio * folio)872 static bool lru_gen_set_refs(struct folio *folio)
873 {
874 	/* see the comment on LRU_REFS_FLAGS */
875 	if (!folio_test_referenced(folio) && !folio_test_workingset(folio)) {
876 		set_mask_bits(&folio->flags, LRU_REFS_MASK, BIT(PG_referenced));
877 		return false;
878 	}
879 
880 	set_mask_bits(&folio->flags, LRU_REFS_FLAGS, BIT(PG_workingset));
881 	return true;
882 }
883 #else
lru_gen_set_refs(struct folio * folio)884 static bool lru_gen_set_refs(struct folio *folio)
885 {
886 	return false;
887 }
888 #endif /* CONFIG_LRU_GEN */
889 
folio_check_references(struct folio * folio,struct scan_control * sc)890 static enum folio_references folio_check_references(struct folio *folio,
891 						  struct scan_control *sc)
892 {
893 	int referenced_ptes, referenced_folio;
894 	unsigned long vm_flags;
895 
896 	referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
897 					   &vm_flags);
898 
899 	/*
900 	 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
901 	 * Let the folio, now marked Mlocked, be moved to the unevictable list.
902 	 */
903 	if (vm_flags & VM_LOCKED)
904 		return FOLIOREF_ACTIVATE;
905 
906 	/*
907 	 * There are two cases to consider.
908 	 * 1) Rmap lock contention: rotate.
909 	 * 2) Skip the non-shared swapbacked folio mapped solely by
910 	 *    the exiting or OOM-reaped process.
911 	 */
912 	if (referenced_ptes == -1)
913 		return FOLIOREF_KEEP;
914 
915 	if (lru_gen_enabled()) {
916 		if (!referenced_ptes)
917 			return FOLIOREF_RECLAIM;
918 
919 		return lru_gen_set_refs(folio) ? FOLIOREF_ACTIVATE : FOLIOREF_KEEP;
920 	}
921 
922 	referenced_folio = folio_test_clear_referenced(folio);
923 
924 	if (referenced_ptes) {
925 		/*
926 		 * All mapped folios start out with page table
927 		 * references from the instantiating fault, so we need
928 		 * to look twice if a mapped file/anon folio is used more
929 		 * than once.
930 		 *
931 		 * Mark it and spare it for another trip around the
932 		 * inactive list.  Another page table reference will
933 		 * lead to its activation.
934 		 *
935 		 * Note: the mark is set for activated folios as well
936 		 * so that recently deactivated but used folios are
937 		 * quickly recovered.
938 		 */
939 		folio_set_referenced(folio);
940 
941 		if (referenced_folio || referenced_ptes > 1)
942 			return FOLIOREF_ACTIVATE;
943 
944 		/*
945 		 * Activate file-backed executable folios after first usage.
946 		 */
947 		if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
948 			return FOLIOREF_ACTIVATE;
949 
950 		return FOLIOREF_KEEP;
951 	}
952 
953 	/* Reclaim if clean, defer dirty folios to writeback */
954 	if (referenced_folio && folio_is_file_lru(folio))
955 		return FOLIOREF_RECLAIM_CLEAN;
956 
957 	return FOLIOREF_RECLAIM;
958 }
959 
960 /* Check if a folio is dirty or under writeback */
folio_check_dirty_writeback(struct folio * folio,bool * dirty,bool * writeback)961 static void folio_check_dirty_writeback(struct folio *folio,
962 				       bool *dirty, bool *writeback)
963 {
964 	struct address_space *mapping;
965 
966 	/*
967 	 * Anonymous folios are not handled by flushers and must be written
968 	 * from reclaim context. Do not stall reclaim based on them.
969 	 * MADV_FREE anonymous folios are put into inactive file list too.
970 	 * They could be mistakenly treated as file lru. So further anon
971 	 * test is needed.
972 	 */
973 	if (!folio_is_file_lru(folio) ||
974 	    (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
975 		*dirty = false;
976 		*writeback = false;
977 		return;
978 	}
979 
980 	/* By default assume that the folio flags are accurate */
981 	*dirty = folio_test_dirty(folio);
982 	*writeback = folio_test_writeback(folio);
983 
984 	/* Verify dirty/writeback state if the filesystem supports it */
985 	if (!folio_test_private(folio))
986 		return;
987 
988 	mapping = folio_mapping(folio);
989 	if (mapping && mapping->a_ops->is_dirty_writeback)
990 		mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
991 }
992 
alloc_migrate_folio(struct folio * src,unsigned long private)993 struct folio *alloc_migrate_folio(struct folio *src, unsigned long private)
994 {
995 	struct folio *dst;
996 	nodemask_t *allowed_mask;
997 	struct migration_target_control *mtc;
998 
999 	mtc = (struct migration_target_control *)private;
1000 
1001 	allowed_mask = mtc->nmask;
1002 	/*
1003 	 * make sure we allocate from the target node first also trying to
1004 	 * demote or reclaim pages from the target node via kswapd if we are
1005 	 * low on free memory on target node. If we don't do this and if
1006 	 * we have free memory on the slower(lower) memtier, we would start
1007 	 * allocating pages from slower(lower) memory tiers without even forcing
1008 	 * a demotion of cold pages from the target memtier. This can result
1009 	 * in the kernel placing hot pages in slower(lower) memory tiers.
1010 	 */
1011 	mtc->nmask = NULL;
1012 	mtc->gfp_mask |= __GFP_THISNODE;
1013 	dst = alloc_migration_target(src, (unsigned long)mtc);
1014 	if (dst)
1015 		return dst;
1016 
1017 	mtc->gfp_mask &= ~__GFP_THISNODE;
1018 	mtc->nmask = allowed_mask;
1019 
1020 	return alloc_migration_target(src, (unsigned long)mtc);
1021 }
1022 
1023 /*
1024  * Take folios on @demote_folios and attempt to demote them to another node.
1025  * Folios which are not demoted are left on @demote_folios.
1026  */
demote_folio_list(struct list_head * demote_folios,struct pglist_data * pgdat)1027 static unsigned int demote_folio_list(struct list_head *demote_folios,
1028 				     struct pglist_data *pgdat)
1029 {
1030 	int target_nid = next_demotion_node(pgdat->node_id);
1031 	unsigned int nr_succeeded;
1032 	nodemask_t allowed_mask;
1033 
1034 	struct migration_target_control mtc = {
1035 		/*
1036 		 * Allocate from 'node', or fail quickly and quietly.
1037 		 * When this happens, 'page' will likely just be discarded
1038 		 * instead of migrated.
1039 		 */
1040 		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
1041 			__GFP_NOMEMALLOC | GFP_NOWAIT,
1042 		.nid = target_nid,
1043 		.nmask = &allowed_mask,
1044 		.reason = MR_DEMOTION,
1045 	};
1046 
1047 	if (list_empty(demote_folios))
1048 		return 0;
1049 
1050 	if (target_nid == NUMA_NO_NODE)
1051 		return 0;
1052 
1053 	node_get_allowed_targets(pgdat, &allowed_mask);
1054 
1055 	/* Demotion ignores all cpuset and mempolicy settings */
1056 	migrate_pages(demote_folios, alloc_migrate_folio, NULL,
1057 		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
1058 		      &nr_succeeded);
1059 
1060 	return nr_succeeded;
1061 }
1062 
may_enter_fs(struct folio * folio,gfp_t gfp_mask)1063 static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
1064 {
1065 	if (gfp_mask & __GFP_FS)
1066 		return true;
1067 	if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
1068 		return false;
1069 	/*
1070 	 * We can "enter_fs" for swap-cache with only __GFP_IO
1071 	 * providing this isn't SWP_FS_OPS.
1072 	 * ->flags can be updated non-atomicially (scan_swap_map_slots),
1073 	 * but that will never affect SWP_FS_OPS, so the data_race
1074 	 * is safe.
1075 	 */
1076 	return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
1077 }
1078 
1079 /*
1080  * shrink_folio_list() returns the number of reclaimed pages
1081  */
shrink_folio_list(struct list_head * folio_list,struct pglist_data * pgdat,struct scan_control * sc,struct reclaim_stat * stat,bool ignore_references)1082 static unsigned int shrink_folio_list(struct list_head *folio_list,
1083 		struct pglist_data *pgdat, struct scan_control *sc,
1084 		struct reclaim_stat *stat, bool ignore_references)
1085 {
1086 	struct folio_batch free_folios;
1087 	LIST_HEAD(ret_folios);
1088 	LIST_HEAD(demote_folios);
1089 	unsigned int nr_reclaimed = 0, nr_demoted = 0;
1090 	unsigned int pgactivate = 0;
1091 	bool do_demote_pass;
1092 	struct swap_iocb *plug = NULL;
1093 
1094 	folio_batch_init(&free_folios);
1095 	memset(stat, 0, sizeof(*stat));
1096 	cond_resched();
1097 	do_demote_pass = can_demote(pgdat->node_id, sc);
1098 
1099 retry:
1100 	while (!list_empty(folio_list)) {
1101 		struct address_space *mapping;
1102 		struct folio *folio;
1103 		enum folio_references references = FOLIOREF_RECLAIM;
1104 		bool dirty, writeback;
1105 		unsigned int nr_pages;
1106 
1107 		cond_resched();
1108 
1109 		folio = lru_to_folio(folio_list);
1110 		list_del(&folio->lru);
1111 
1112 		if (!folio_trylock(folio))
1113 			goto keep;
1114 
1115 		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1116 
1117 		nr_pages = folio_nr_pages(folio);
1118 
1119 		/* Account the number of base pages */
1120 		sc->nr_scanned += nr_pages;
1121 
1122 		if (unlikely(!folio_evictable(folio)))
1123 			goto activate_locked;
1124 
1125 		if (!sc->may_unmap && folio_mapped(folio))
1126 			goto keep_locked;
1127 
1128 		/*
1129 		 * The number of dirty pages determines if a node is marked
1130 		 * reclaim_congested. kswapd will stall and start writing
1131 		 * folios if the tail of the LRU is all dirty unqueued folios.
1132 		 */
1133 		folio_check_dirty_writeback(folio, &dirty, &writeback);
1134 		if (dirty || writeback)
1135 			stat->nr_dirty += nr_pages;
1136 
1137 		if (dirty && !writeback)
1138 			stat->nr_unqueued_dirty += nr_pages;
1139 
1140 		/*
1141 		 * Treat this folio as congested if folios are cycling
1142 		 * through the LRU so quickly that the folios marked
1143 		 * for immediate reclaim are making it to the end of
1144 		 * the LRU a second time.
1145 		 */
1146 		if (writeback && folio_test_reclaim(folio))
1147 			stat->nr_congested += nr_pages;
1148 
1149 		/*
1150 		 * If a folio at the tail of the LRU is under writeback, there
1151 		 * are three cases to consider.
1152 		 *
1153 		 * 1) If reclaim is encountering an excessive number
1154 		 *    of folios under writeback and this folio has both
1155 		 *    the writeback and reclaim flags set, then it
1156 		 *    indicates that folios are being queued for I/O but
1157 		 *    are being recycled through the LRU before the I/O
1158 		 *    can complete. Waiting on the folio itself risks an
1159 		 *    indefinite stall if it is impossible to writeback
1160 		 *    the folio due to I/O error or disconnected storage
1161 		 *    so instead note that the LRU is being scanned too
1162 		 *    quickly and the caller can stall after the folio
1163 		 *    list has been processed.
1164 		 *
1165 		 * 2) Global or new memcg reclaim encounters a folio that is
1166 		 *    not marked for immediate reclaim, or the caller does not
1167 		 *    have __GFP_FS (or __GFP_IO if it's simply going to swap,
1168 		 *    not to fs). In this case mark the folio for immediate
1169 		 *    reclaim and continue scanning.
1170 		 *
1171 		 *    Require may_enter_fs() because we would wait on fs, which
1172 		 *    may not have submitted I/O yet. And the loop driver might
1173 		 *    enter reclaim, and deadlock if it waits on a folio for
1174 		 *    which it is needed to do the write (loop masks off
1175 		 *    __GFP_IO|__GFP_FS for this reason); but more thought
1176 		 *    would probably show more reasons.
1177 		 *
1178 		 * 3) Legacy memcg encounters a folio that already has the
1179 		 *    reclaim flag set. memcg does not have any dirty folio
1180 		 *    throttling so we could easily OOM just because too many
1181 		 *    folios are in writeback and there is nothing else to
1182 		 *    reclaim. Wait for the writeback to complete.
1183 		 *
1184 		 * In cases 1) and 2) we activate the folios to get them out of
1185 		 * the way while we continue scanning for clean folios on the
1186 		 * inactive list and refilling from the active list. The
1187 		 * observation here is that waiting for disk writes is more
1188 		 * expensive than potentially causing reloads down the line.
1189 		 * Since they're marked for immediate reclaim, they won't put
1190 		 * memory pressure on the cache working set any longer than it
1191 		 * takes to write them to disk.
1192 		 */
1193 		if (folio_test_writeback(folio)) {
1194 			/* Case 1 above */
1195 			if (current_is_kswapd() &&
1196 			    folio_test_reclaim(folio) &&
1197 			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1198 				stat->nr_immediate += nr_pages;
1199 				goto activate_locked;
1200 
1201 			/* Case 2 above */
1202 			} else if (writeback_throttling_sane(sc) ||
1203 			    !folio_test_reclaim(folio) ||
1204 			    !may_enter_fs(folio, sc->gfp_mask)) {
1205 				/*
1206 				 * This is slightly racy -
1207 				 * folio_end_writeback() might have
1208 				 * just cleared the reclaim flag, then
1209 				 * setting the reclaim flag here ends up
1210 				 * interpreted as the readahead flag - but
1211 				 * that does not matter enough to care.
1212 				 * What we do want is for this folio to
1213 				 * have the reclaim flag set next time
1214 				 * memcg reclaim reaches the tests above,
1215 				 * so it will then wait for writeback to
1216 				 * avoid OOM; and it's also appropriate
1217 				 * in global reclaim.
1218 				 */
1219 				folio_set_reclaim(folio);
1220 				stat->nr_writeback += nr_pages;
1221 				goto activate_locked;
1222 
1223 			/* Case 3 above */
1224 			} else {
1225 				folio_unlock(folio);
1226 				folio_wait_writeback(folio);
1227 				/* then go back and try same folio again */
1228 				list_add_tail(&folio->lru, folio_list);
1229 				continue;
1230 			}
1231 		}
1232 
1233 		if (!ignore_references)
1234 			references = folio_check_references(folio, sc);
1235 
1236 		switch (references) {
1237 		case FOLIOREF_ACTIVATE:
1238 			goto activate_locked;
1239 		case FOLIOREF_KEEP:
1240 			stat->nr_ref_keep += nr_pages;
1241 			goto keep_locked;
1242 		case FOLIOREF_RECLAIM:
1243 		case FOLIOREF_RECLAIM_CLEAN:
1244 			; /* try to reclaim the folio below */
1245 		}
1246 
1247 		/*
1248 		 * Before reclaiming the folio, try to relocate
1249 		 * its contents to another node.
1250 		 */
1251 		if (do_demote_pass &&
1252 		    (thp_migration_supported() || !folio_test_large(folio))) {
1253 			list_add(&folio->lru, &demote_folios);
1254 			folio_unlock(folio);
1255 			continue;
1256 		}
1257 
1258 		/*
1259 		 * Anonymous process memory has backing store?
1260 		 * Try to allocate it some swap space here.
1261 		 * Lazyfree folio could be freed directly
1262 		 */
1263 		if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
1264 			if (!folio_test_swapcache(folio)) {
1265 				if (!(sc->gfp_mask & __GFP_IO))
1266 					goto keep_locked;
1267 				if (folio_maybe_dma_pinned(folio))
1268 					goto keep_locked;
1269 				if (folio_test_large(folio)) {
1270 					/* cannot split folio, skip it */
1271 					if (!can_split_folio(folio, 1, NULL))
1272 						goto activate_locked;
1273 					/*
1274 					 * Split partially mapped folios right away.
1275 					 * We can free the unmapped pages without IO.
1276 					 */
1277 					if (data_race(!list_empty(&folio->_deferred_list) &&
1278 					    folio_test_partially_mapped(folio)) &&
1279 					    split_folio_to_list(folio, folio_list))
1280 						goto activate_locked;
1281 				}
1282 				if (!add_to_swap(folio)) {
1283 					int __maybe_unused order = folio_order(folio);
1284 
1285 					if (!folio_test_large(folio))
1286 						goto activate_locked_split;
1287 					/* Fallback to swap normal pages */
1288 					if (split_folio_to_list(folio, folio_list))
1289 						goto activate_locked;
1290 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1291 					if (nr_pages >= HPAGE_PMD_NR) {
1292 						count_memcg_folio_events(folio,
1293 							THP_SWPOUT_FALLBACK, 1);
1294 						count_vm_event(THP_SWPOUT_FALLBACK);
1295 					}
1296 #endif
1297 					count_mthp_stat(order, MTHP_STAT_SWPOUT_FALLBACK);
1298 					if (!add_to_swap(folio))
1299 						goto activate_locked_split;
1300 				}
1301 			}
1302 		}
1303 
1304 		/*
1305 		 * If the folio was split above, the tail pages will make
1306 		 * their own pass through this function and be accounted
1307 		 * then.
1308 		 */
1309 		if ((nr_pages > 1) && !folio_test_large(folio)) {
1310 			sc->nr_scanned -= (nr_pages - 1);
1311 			nr_pages = 1;
1312 		}
1313 
1314 		/*
1315 		 * The folio is mapped into the page tables of one or more
1316 		 * processes. Try to unmap it here.
1317 		 */
1318 		if (folio_mapped(folio)) {
1319 			enum ttu_flags flags = TTU_BATCH_FLUSH;
1320 			bool was_swapbacked = folio_test_swapbacked(folio);
1321 
1322 			if (folio_test_pmd_mappable(folio))
1323 				flags |= TTU_SPLIT_HUGE_PMD;
1324 			/*
1325 			 * Without TTU_SYNC, try_to_unmap will only begin to
1326 			 * hold PTL from the first present PTE within a large
1327 			 * folio. Some initial PTEs might be skipped due to
1328 			 * races with parallel PTE writes in which PTEs can be
1329 			 * cleared temporarily before being written new present
1330 			 * values. This will lead to a large folio is still
1331 			 * mapped while some subpages have been partially
1332 			 * unmapped after try_to_unmap; TTU_SYNC helps
1333 			 * try_to_unmap acquire PTL from the first PTE,
1334 			 * eliminating the influence of temporary PTE values.
1335 			 */
1336 			if (folio_test_large(folio))
1337 				flags |= TTU_SYNC;
1338 
1339 			try_to_unmap(folio, flags);
1340 			if (folio_mapped(folio)) {
1341 				stat->nr_unmap_fail += nr_pages;
1342 				if (!was_swapbacked &&
1343 				    folio_test_swapbacked(folio))
1344 					stat->nr_lazyfree_fail += nr_pages;
1345 				goto activate_locked;
1346 			}
1347 		}
1348 
1349 		/*
1350 		 * Folio is unmapped now so it cannot be newly pinned anymore.
1351 		 * No point in trying to reclaim folio if it is pinned.
1352 		 * Furthermore we don't want to reclaim underlying fs metadata
1353 		 * if the folio is pinned and thus potentially modified by the
1354 		 * pinning process as that may upset the filesystem.
1355 		 */
1356 		if (folio_maybe_dma_pinned(folio))
1357 			goto activate_locked;
1358 
1359 		mapping = folio_mapping(folio);
1360 		if (folio_test_dirty(folio)) {
1361 			/*
1362 			 * Only kswapd can writeback filesystem folios
1363 			 * to avoid risk of stack overflow. But avoid
1364 			 * injecting inefficient single-folio I/O into
1365 			 * flusher writeback as much as possible: only
1366 			 * write folios when we've encountered many
1367 			 * dirty folios, and when we've already scanned
1368 			 * the rest of the LRU for clean folios and see
1369 			 * the same dirty folios again (with the reclaim
1370 			 * flag set).
1371 			 */
1372 			if (folio_is_file_lru(folio) &&
1373 			    (!current_is_kswapd() ||
1374 			     !folio_test_reclaim(folio) ||
1375 			     !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1376 				/*
1377 				 * Immediately reclaim when written back.
1378 				 * Similar in principle to folio_deactivate()
1379 				 * except we already have the folio isolated
1380 				 * and know it's dirty
1381 				 */
1382 				node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
1383 						nr_pages);
1384 				folio_set_reclaim(folio);
1385 
1386 				goto activate_locked;
1387 			}
1388 
1389 			if (references == FOLIOREF_RECLAIM_CLEAN)
1390 				goto keep_locked;
1391 			if (!may_enter_fs(folio, sc->gfp_mask))
1392 				goto keep_locked;
1393 			if (!sc->may_writepage)
1394 				goto keep_locked;
1395 
1396 			/*
1397 			 * Folio is dirty. Flush the TLB if a writable entry
1398 			 * potentially exists to avoid CPU writes after I/O
1399 			 * starts and then write it out here.
1400 			 */
1401 			try_to_unmap_flush_dirty();
1402 			switch (pageout(folio, mapping, &plug, folio_list)) {
1403 			case PAGE_KEEP:
1404 				goto keep_locked;
1405 			case PAGE_ACTIVATE:
1406 				/*
1407 				 * If shmem folio is split when writeback to swap,
1408 				 * the tail pages will make their own pass through
1409 				 * this function and be accounted then.
1410 				 */
1411 				if (nr_pages > 1 && !folio_test_large(folio)) {
1412 					sc->nr_scanned -= (nr_pages - 1);
1413 					nr_pages = 1;
1414 				}
1415 				goto activate_locked;
1416 			case PAGE_SUCCESS:
1417 				if (nr_pages > 1 && !folio_test_large(folio)) {
1418 					sc->nr_scanned -= (nr_pages - 1);
1419 					nr_pages = 1;
1420 				}
1421 				stat->nr_pageout += nr_pages;
1422 
1423 				if (folio_test_writeback(folio))
1424 					goto keep;
1425 				if (folio_test_dirty(folio))
1426 					goto keep;
1427 
1428 				/*
1429 				 * A synchronous write - probably a ramdisk.  Go
1430 				 * ahead and try to reclaim the folio.
1431 				 */
1432 				if (!folio_trylock(folio))
1433 					goto keep;
1434 				if (folio_test_dirty(folio) ||
1435 				    folio_test_writeback(folio))
1436 					goto keep_locked;
1437 				mapping = folio_mapping(folio);
1438 				fallthrough;
1439 			case PAGE_CLEAN:
1440 				; /* try to free the folio below */
1441 			}
1442 		}
1443 
1444 		/*
1445 		 * If the folio has buffers, try to free the buffer
1446 		 * mappings associated with this folio. If we succeed
1447 		 * we try to free the folio as well.
1448 		 *
1449 		 * We do this even if the folio is dirty.
1450 		 * filemap_release_folio() does not perform I/O, but it
1451 		 * is possible for a folio to have the dirty flag set,
1452 		 * but it is actually clean (all its buffers are clean).
1453 		 * This happens if the buffers were written out directly,
1454 		 * with submit_bh(). ext3 will do this, as well as
1455 		 * the blockdev mapping.  filemap_release_folio() will
1456 		 * discover that cleanness and will drop the buffers
1457 		 * and mark the folio clean - it can be freed.
1458 		 *
1459 		 * Rarely, folios can have buffers and no ->mapping.
1460 		 * These are the folios which were not successfully
1461 		 * invalidated in truncate_cleanup_folio().  We try to
1462 		 * drop those buffers here and if that worked, and the
1463 		 * folio is no longer mapped into process address space
1464 		 * (refcount == 1) it can be freed.  Otherwise, leave
1465 		 * the folio on the LRU so it is swappable.
1466 		 */
1467 		if (folio_needs_release(folio)) {
1468 			if (!filemap_release_folio(folio, sc->gfp_mask))
1469 				goto activate_locked;
1470 			if (!mapping && folio_ref_count(folio) == 1) {
1471 				folio_unlock(folio);
1472 				if (folio_put_testzero(folio))
1473 					goto free_it;
1474 				else {
1475 					/*
1476 					 * rare race with speculative reference.
1477 					 * the speculative reference will free
1478 					 * this folio shortly, so we may
1479 					 * increment nr_reclaimed here (and
1480 					 * leave it off the LRU).
1481 					 */
1482 					nr_reclaimed += nr_pages;
1483 					continue;
1484 				}
1485 			}
1486 		}
1487 
1488 		if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
1489 			/* follow __remove_mapping for reference */
1490 			if (!folio_ref_freeze(folio, 1))
1491 				goto keep_locked;
1492 			/*
1493 			 * The folio has only one reference left, which is
1494 			 * from the isolation. After the caller puts the
1495 			 * folio back on the lru and drops the reference, the
1496 			 * folio will be freed anyway. It doesn't matter
1497 			 * which lru it goes on. So we don't bother checking
1498 			 * the dirty flag here.
1499 			 */
1500 			count_vm_events(PGLAZYFREED, nr_pages);
1501 			count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
1502 		} else if (!mapping || !__remove_mapping(mapping, folio, true,
1503 							 sc->target_mem_cgroup))
1504 			goto keep_locked;
1505 
1506 		folio_unlock(folio);
1507 free_it:
1508 		/*
1509 		 * Folio may get swapped out as a whole, need to account
1510 		 * all pages in it.
1511 		 */
1512 		nr_reclaimed += nr_pages;
1513 
1514 		folio_unqueue_deferred_split(folio);
1515 		if (folio_batch_add(&free_folios, folio) == 0) {
1516 			mem_cgroup_uncharge_folios(&free_folios);
1517 			try_to_unmap_flush();
1518 			free_unref_folios(&free_folios);
1519 		}
1520 		continue;
1521 
1522 activate_locked_split:
1523 		/*
1524 		 * The tail pages that are failed to add into swap cache
1525 		 * reach here.  Fixup nr_scanned and nr_pages.
1526 		 */
1527 		if (nr_pages > 1) {
1528 			sc->nr_scanned -= (nr_pages - 1);
1529 			nr_pages = 1;
1530 		}
1531 activate_locked:
1532 		/* Not a candidate for swapping, so reclaim swap space. */
1533 		if (folio_test_swapcache(folio) &&
1534 		    (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
1535 			folio_free_swap(folio);
1536 		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1537 		if (!folio_test_mlocked(folio)) {
1538 			int type = folio_is_file_lru(folio);
1539 			folio_set_active(folio);
1540 			stat->nr_activate[type] += nr_pages;
1541 			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
1542 		}
1543 keep_locked:
1544 		folio_unlock(folio);
1545 keep:
1546 		list_add(&folio->lru, &ret_folios);
1547 		VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
1548 				folio_test_unevictable(folio), folio);
1549 	}
1550 	/* 'folio_list' is always empty here */
1551 
1552 	/* Migrate folios selected for demotion */
1553 	nr_demoted = demote_folio_list(&demote_folios, pgdat);
1554 	nr_reclaimed += nr_demoted;
1555 	stat->nr_demoted += nr_demoted;
1556 	/* Folios that could not be demoted are still in @demote_folios */
1557 	if (!list_empty(&demote_folios)) {
1558 		/* Folios which weren't demoted go back on @folio_list */
1559 		list_splice_init(&demote_folios, folio_list);
1560 
1561 		/*
1562 		 * goto retry to reclaim the undemoted folios in folio_list if
1563 		 * desired.
1564 		 *
1565 		 * Reclaiming directly from top tier nodes is not often desired
1566 		 * due to it breaking the LRU ordering: in general memory
1567 		 * should be reclaimed from lower tier nodes and demoted from
1568 		 * top tier nodes.
1569 		 *
1570 		 * However, disabling reclaim from top tier nodes entirely
1571 		 * would cause ooms in edge scenarios where lower tier memory
1572 		 * is unreclaimable for whatever reason, eg memory being
1573 		 * mlocked or too hot to reclaim. We can disable reclaim
1574 		 * from top tier nodes in proactive reclaim though as that is
1575 		 * not real memory pressure.
1576 		 */
1577 		if (!sc->proactive) {
1578 			do_demote_pass = false;
1579 			goto retry;
1580 		}
1581 	}
1582 
1583 	pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
1584 
1585 	mem_cgroup_uncharge_folios(&free_folios);
1586 	try_to_unmap_flush();
1587 	free_unref_folios(&free_folios);
1588 
1589 	list_splice(&ret_folios, folio_list);
1590 	count_vm_events(PGACTIVATE, pgactivate);
1591 
1592 	if (plug)
1593 		swap_write_unplug(plug);
1594 	return nr_reclaimed;
1595 }
1596 
reclaim_clean_pages_from_list(struct zone * zone,struct list_head * folio_list)1597 unsigned int reclaim_clean_pages_from_list(struct zone *zone,
1598 					   struct list_head *folio_list)
1599 {
1600 	struct scan_control sc = {
1601 		.gfp_mask = GFP_KERNEL,
1602 		.may_unmap = 1,
1603 	};
1604 	struct reclaim_stat stat;
1605 	unsigned int nr_reclaimed;
1606 	struct folio *folio, *next;
1607 	LIST_HEAD(clean_folios);
1608 	unsigned int noreclaim_flag;
1609 
1610 	list_for_each_entry_safe(folio, next, folio_list, lru) {
1611 		if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
1612 		    !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
1613 		    !folio_test_unevictable(folio)) {
1614 			folio_clear_active(folio);
1615 			list_move(&folio->lru, &clean_folios);
1616 		}
1617 	}
1618 
1619 	/*
1620 	 * We should be safe here since we are only dealing with file pages and
1621 	 * we are not kswapd and therefore cannot write dirty file pages. But
1622 	 * call memalloc_noreclaim_save() anyway, just in case these conditions
1623 	 * change in the future.
1624 	 */
1625 	noreclaim_flag = memalloc_noreclaim_save();
1626 	nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
1627 					&stat, true);
1628 	memalloc_noreclaim_restore(noreclaim_flag);
1629 
1630 	list_splice(&clean_folios, folio_list);
1631 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1632 			    -(long)nr_reclaimed);
1633 	/*
1634 	 * Since lazyfree pages are isolated from file LRU from the beginning,
1635 	 * they will rotate back to anonymous LRU in the end if it failed to
1636 	 * discard so isolated count will be mismatched.
1637 	 * Compensate the isolated count for both LRU lists.
1638 	 */
1639 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
1640 			    stat.nr_lazyfree_fail);
1641 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1642 			    -(long)stat.nr_lazyfree_fail);
1643 	return nr_reclaimed;
1644 }
1645 
1646 /*
1647  * Update LRU sizes after isolating pages. The LRU size updates must
1648  * be complete before mem_cgroup_update_lru_size due to a sanity check.
1649  */
update_lru_sizes(struct lruvec * lruvec,enum lru_list lru,unsigned long * nr_zone_taken)1650 static __always_inline void update_lru_sizes(struct lruvec *lruvec,
1651 			enum lru_list lru, unsigned long *nr_zone_taken)
1652 {
1653 	int zid;
1654 
1655 	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1656 		if (!nr_zone_taken[zid])
1657 			continue;
1658 
1659 		update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
1660 	}
1661 
1662 }
1663 
1664 /*
1665  * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1666  *
1667  * lruvec->lru_lock is heavily contended.  Some of the functions that
1668  * shrink the lists perform better by taking out a batch of pages
1669  * and working on them outside the LRU lock.
1670  *
1671  * For pagecache intensive workloads, this function is the hottest
1672  * spot in the kernel (apart from copy_*_user functions).
1673  *
1674  * Lru_lock must be held before calling this function.
1675  *
1676  * @nr_to_scan:	The number of eligible pages to look through on the list.
1677  * @lruvec:	The LRU vector to pull pages from.
1678  * @dst:	The temp list to put pages on to.
1679  * @nr_scanned:	The number of pages that were scanned.
1680  * @sc:		The scan_control struct for this reclaim session
1681  * @lru:	LRU list id for isolating
1682  *
1683  * returns how many pages were moved onto *@dst.
1684  */
isolate_lru_folios(unsigned long nr_to_scan,struct lruvec * lruvec,struct list_head * dst,unsigned long * nr_scanned,struct scan_control * sc,enum lru_list lru)1685 static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
1686 		struct lruvec *lruvec, struct list_head *dst,
1687 		unsigned long *nr_scanned, struct scan_control *sc,
1688 		enum lru_list lru)
1689 {
1690 	struct list_head *src = &lruvec->lists[lru];
1691 	unsigned long nr_taken = 0;
1692 	unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
1693 	unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
1694 	unsigned long skipped = 0;
1695 	unsigned long scan, total_scan, nr_pages;
1696 	unsigned long max_nr_skipped = 0;
1697 	LIST_HEAD(folios_skipped);
1698 
1699 	total_scan = 0;
1700 	scan = 0;
1701 	while (scan < nr_to_scan && !list_empty(src)) {
1702 		struct list_head *move_to = src;
1703 		struct folio *folio;
1704 
1705 		folio = lru_to_folio(src);
1706 		prefetchw_prev_lru_folio(folio, src, flags);
1707 
1708 		nr_pages = folio_nr_pages(folio);
1709 		total_scan += nr_pages;
1710 
1711 		/* Using max_nr_skipped to prevent hard LOCKUP*/
1712 		if (max_nr_skipped < SWAP_CLUSTER_MAX_SKIPPED &&
1713 		    (folio_zonenum(folio) > sc->reclaim_idx)) {
1714 			nr_skipped[folio_zonenum(folio)] += nr_pages;
1715 			move_to = &folios_skipped;
1716 			max_nr_skipped++;
1717 			goto move;
1718 		}
1719 
1720 		/*
1721 		 * Do not count skipped folios because that makes the function
1722 		 * return with no isolated folios if the LRU mostly contains
1723 		 * ineligible folios.  This causes the VM to not reclaim any
1724 		 * folios, triggering a premature OOM.
1725 		 * Account all pages in a folio.
1726 		 */
1727 		scan += nr_pages;
1728 
1729 		if (!folio_test_lru(folio))
1730 			goto move;
1731 		if (!sc->may_unmap && folio_mapped(folio))
1732 			goto move;
1733 
1734 		/*
1735 		 * Be careful not to clear the lru flag until after we're
1736 		 * sure the folio is not being freed elsewhere -- the
1737 		 * folio release code relies on it.
1738 		 */
1739 		if (unlikely(!folio_try_get(folio)))
1740 			goto move;
1741 
1742 		if (!folio_test_clear_lru(folio)) {
1743 			/* Another thread is already isolating this folio */
1744 			folio_put(folio);
1745 			goto move;
1746 		}
1747 
1748 		nr_taken += nr_pages;
1749 		nr_zone_taken[folio_zonenum(folio)] += nr_pages;
1750 		move_to = dst;
1751 move:
1752 		list_move(&folio->lru, move_to);
1753 	}
1754 
1755 	/*
1756 	 * Splice any skipped folios to the start of the LRU list. Note that
1757 	 * this disrupts the LRU order when reclaiming for lower zones but
1758 	 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1759 	 * scanning would soon rescan the same folios to skip and waste lots
1760 	 * of cpu cycles.
1761 	 */
1762 	if (!list_empty(&folios_skipped)) {
1763 		int zid;
1764 
1765 		list_splice(&folios_skipped, src);
1766 		for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1767 			if (!nr_skipped[zid])
1768 				continue;
1769 
1770 			__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
1771 			skipped += nr_skipped[zid];
1772 		}
1773 	}
1774 	*nr_scanned = total_scan;
1775 	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
1776 				    total_scan, skipped, nr_taken, lru);
1777 	update_lru_sizes(lruvec, lru, nr_zone_taken);
1778 	return nr_taken;
1779 }
1780 
1781 /**
1782  * folio_isolate_lru() - Try to isolate a folio from its LRU list.
1783  * @folio: Folio to isolate from its LRU list.
1784  *
1785  * Isolate a @folio from an LRU list and adjust the vmstat statistic
1786  * corresponding to whatever LRU list the folio was on.
1787  *
1788  * The folio will have its LRU flag cleared.  If it was found on the
1789  * active list, it will have the Active flag set.  If it was found on the
1790  * unevictable list, it will have the Unevictable flag set.  These flags
1791  * may need to be cleared by the caller before letting the page go.
1792  *
1793  * Context:
1794  *
1795  * (1) Must be called with an elevated refcount on the folio. This is a
1796  *     fundamental difference from isolate_lru_folios() (which is called
1797  *     without a stable reference).
1798  * (2) The lru_lock must not be held.
1799  * (3) Interrupts must be enabled.
1800  *
1801  * Return: true if the folio was removed from an LRU list.
1802  * false if the folio was not on an LRU list.
1803  */
folio_isolate_lru(struct folio * folio)1804 bool folio_isolate_lru(struct folio *folio)
1805 {
1806 	bool ret = false;
1807 
1808 	VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
1809 
1810 	if (folio_test_clear_lru(folio)) {
1811 		struct lruvec *lruvec;
1812 
1813 		folio_get(folio);
1814 		lruvec = folio_lruvec_lock_irq(folio);
1815 		lruvec_del_folio(lruvec, folio);
1816 		unlock_page_lruvec_irq(lruvec);
1817 		ret = true;
1818 	}
1819 
1820 	return ret;
1821 }
1822 
1823 /*
1824  * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1825  * then get rescheduled. When there are massive number of tasks doing page
1826  * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1827  * the LRU list will go small and be scanned faster than necessary, leading to
1828  * unnecessary swapping, thrashing and OOM.
1829  */
too_many_isolated(struct pglist_data * pgdat,int file,struct scan_control * sc)1830 static bool too_many_isolated(struct pglist_data *pgdat, int file,
1831 		struct scan_control *sc)
1832 {
1833 	unsigned long inactive, isolated;
1834 	bool too_many;
1835 
1836 	if (current_is_kswapd())
1837 		return false;
1838 
1839 	if (!writeback_throttling_sane(sc))
1840 		return false;
1841 
1842 	if (file) {
1843 		inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
1844 		isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
1845 	} else {
1846 		inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
1847 		isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
1848 	}
1849 
1850 	/*
1851 	 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1852 	 * won't get blocked by normal direct-reclaimers, forming a circular
1853 	 * deadlock.
1854 	 */
1855 	if (gfp_has_io_fs(sc->gfp_mask))
1856 		inactive >>= 3;
1857 
1858 	too_many = isolated > inactive;
1859 
1860 	/* Wake up tasks throttled due to too_many_isolated. */
1861 	if (!too_many)
1862 		wake_throttle_isolated(pgdat);
1863 
1864 	return too_many;
1865 }
1866 
1867 /*
1868  * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
1869  *
1870  * Returns the number of pages moved to the given lruvec.
1871  */
move_folios_to_lru(struct lruvec * lruvec,struct list_head * list)1872 static unsigned int move_folios_to_lru(struct lruvec *lruvec,
1873 		struct list_head *list)
1874 {
1875 	int nr_pages, nr_moved = 0;
1876 	struct folio_batch free_folios;
1877 
1878 	folio_batch_init(&free_folios);
1879 	while (!list_empty(list)) {
1880 		struct folio *folio = lru_to_folio(list);
1881 
1882 		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
1883 		list_del(&folio->lru);
1884 		if (unlikely(!folio_evictable(folio))) {
1885 			spin_unlock_irq(&lruvec->lru_lock);
1886 			folio_putback_lru(folio);
1887 			spin_lock_irq(&lruvec->lru_lock);
1888 			continue;
1889 		}
1890 
1891 		/*
1892 		 * The folio_set_lru needs to be kept here for list integrity.
1893 		 * Otherwise:
1894 		 *   #0 move_folios_to_lru             #1 release_pages
1895 		 *   if (!folio_put_testzero())
1896 		 *				      if (folio_put_testzero())
1897 		 *				        !lru //skip lru_lock
1898 		 *     folio_set_lru()
1899 		 *     list_add(&folio->lru,)
1900 		 *                                        list_add(&folio->lru,)
1901 		 */
1902 		folio_set_lru(folio);
1903 
1904 		if (unlikely(folio_put_testzero(folio))) {
1905 			__folio_clear_lru_flags(folio);
1906 
1907 			folio_unqueue_deferred_split(folio);
1908 			if (folio_batch_add(&free_folios, folio) == 0) {
1909 				spin_unlock_irq(&lruvec->lru_lock);
1910 				mem_cgroup_uncharge_folios(&free_folios);
1911 				free_unref_folios(&free_folios);
1912 				spin_lock_irq(&lruvec->lru_lock);
1913 			}
1914 
1915 			continue;
1916 		}
1917 
1918 		/*
1919 		 * All pages were isolated from the same lruvec (and isolation
1920 		 * inhibits memcg migration).
1921 		 */
1922 		VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
1923 		lruvec_add_folio(lruvec, folio);
1924 		nr_pages = folio_nr_pages(folio);
1925 		nr_moved += nr_pages;
1926 		if (folio_test_active(folio))
1927 			workingset_age_nonresident(lruvec, nr_pages);
1928 	}
1929 
1930 	if (free_folios.nr) {
1931 		spin_unlock_irq(&lruvec->lru_lock);
1932 		mem_cgroup_uncharge_folios(&free_folios);
1933 		free_unref_folios(&free_folios);
1934 		spin_lock_irq(&lruvec->lru_lock);
1935 	}
1936 
1937 	return nr_moved;
1938 }
1939 
1940 /*
1941  * If a kernel thread (such as nfsd for loop-back mounts) services a backing
1942  * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
1943  * we should not throttle.  Otherwise it is safe to do so.
1944  */
current_may_throttle(void)1945 static int current_may_throttle(void)
1946 {
1947 	return !(current->flags & PF_LOCAL_THROTTLE);
1948 }
1949 
1950 /*
1951  * shrink_inactive_list() is a helper for shrink_node().  It returns the number
1952  * of reclaimed pages
1953  */
shrink_inactive_list(unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc,enum lru_list lru)1954 static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
1955 		struct lruvec *lruvec, struct scan_control *sc,
1956 		enum lru_list lru)
1957 {
1958 	LIST_HEAD(folio_list);
1959 	unsigned long nr_scanned;
1960 	unsigned int nr_reclaimed = 0;
1961 	unsigned long nr_taken;
1962 	struct reclaim_stat stat;
1963 	bool file = is_file_lru(lru);
1964 	enum vm_event_item item;
1965 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
1966 	bool stalled = false;
1967 
1968 	while (unlikely(too_many_isolated(pgdat, file, sc))) {
1969 		if (stalled)
1970 			return 0;
1971 
1972 		/* wait a bit for the reclaimer. */
1973 		stalled = true;
1974 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
1975 
1976 		/* We are about to die and free our memory. Return now. */
1977 		if (fatal_signal_pending(current))
1978 			return SWAP_CLUSTER_MAX;
1979 	}
1980 
1981 	lru_add_drain();
1982 
1983 	spin_lock_irq(&lruvec->lru_lock);
1984 
1985 	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
1986 				     &nr_scanned, sc, lru);
1987 
1988 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
1989 	item = PGSCAN_KSWAPD + reclaimer_offset();
1990 	if (!cgroup_reclaim(sc))
1991 		__count_vm_events(item, nr_scanned);
1992 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
1993 	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
1994 
1995 	spin_unlock_irq(&lruvec->lru_lock);
1996 
1997 	if (nr_taken == 0)
1998 		return 0;
1999 
2000 	nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
2001 
2002 	spin_lock_irq(&lruvec->lru_lock);
2003 	move_folios_to_lru(lruvec, &folio_list);
2004 
2005 	__mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(),
2006 					stat.nr_demoted);
2007 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2008 	item = PGSTEAL_KSWAPD + reclaimer_offset();
2009 	if (!cgroup_reclaim(sc))
2010 		__count_vm_events(item, nr_reclaimed);
2011 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
2012 	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
2013 	spin_unlock_irq(&lruvec->lru_lock);
2014 
2015 	lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
2016 
2017 	/*
2018 	 * If dirty folios are scanned that are not queued for IO, it
2019 	 * implies that flushers are not doing their job. This can
2020 	 * happen when memory pressure pushes dirty folios to the end of
2021 	 * the LRU before the dirty limits are breached and the dirty
2022 	 * data has expired. It can also happen when the proportion of
2023 	 * dirty folios grows not through writes but through memory
2024 	 * pressure reclaiming all the clean cache. And in some cases,
2025 	 * the flushers simply cannot keep up with the allocation
2026 	 * rate. Nudge the flusher threads in case they are asleep.
2027 	 */
2028 	if (stat.nr_unqueued_dirty == nr_taken) {
2029 		wakeup_flusher_threads(WB_REASON_VMSCAN);
2030 		/*
2031 		 * For cgroupv1 dirty throttling is achieved by waking up
2032 		 * the kernel flusher here and later waiting on folios
2033 		 * which are in writeback to finish (see shrink_folio_list()).
2034 		 *
2035 		 * Flusher may not be able to issue writeback quickly
2036 		 * enough for cgroupv1 writeback throttling to work
2037 		 * on a large system.
2038 		 */
2039 		if (!writeback_throttling_sane(sc))
2040 			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
2041 	}
2042 
2043 	sc->nr.dirty += stat.nr_dirty;
2044 	sc->nr.congested += stat.nr_congested;
2045 	sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
2046 	sc->nr.writeback += stat.nr_writeback;
2047 	sc->nr.immediate += stat.nr_immediate;
2048 	sc->nr.taken += nr_taken;
2049 	if (file)
2050 		sc->nr.file_taken += nr_taken;
2051 
2052 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
2053 			nr_scanned, nr_reclaimed, &stat, sc->priority, file);
2054 	return nr_reclaimed;
2055 }
2056 
2057 /*
2058  * shrink_active_list() moves folios from the active LRU to the inactive LRU.
2059  *
2060  * We move them the other way if the folio is referenced by one or more
2061  * processes.
2062  *
2063  * If the folios are mostly unmapped, the processing is fast and it is
2064  * appropriate to hold lru_lock across the whole operation.  But if
2065  * the folios are mapped, the processing is slow (folio_referenced()), so
2066  * we should drop lru_lock around each folio.  It's impossible to balance
2067  * this, so instead we remove the folios from the LRU while processing them.
2068  * It is safe to rely on the active flag against the non-LRU folios in here
2069  * because nobody will play with that bit on a non-LRU folio.
2070  *
2071  * The downside is that we have to touch folio->_refcount against each folio.
2072  * But we had to alter folio->flags anyway.
2073  */
shrink_active_list(unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc,enum lru_list lru)2074 static void shrink_active_list(unsigned long nr_to_scan,
2075 			       struct lruvec *lruvec,
2076 			       struct scan_control *sc,
2077 			       enum lru_list lru)
2078 {
2079 	unsigned long nr_taken;
2080 	unsigned long nr_scanned;
2081 	unsigned long vm_flags;
2082 	LIST_HEAD(l_hold);	/* The folios which were snipped off */
2083 	LIST_HEAD(l_active);
2084 	LIST_HEAD(l_inactive);
2085 	unsigned nr_deactivate, nr_activate;
2086 	unsigned nr_rotated = 0;
2087 	bool file = is_file_lru(lru);
2088 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2089 
2090 	lru_add_drain();
2091 
2092 	spin_lock_irq(&lruvec->lru_lock);
2093 
2094 	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
2095 				     &nr_scanned, sc, lru);
2096 
2097 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2098 
2099 	if (!cgroup_reclaim(sc))
2100 		__count_vm_events(PGREFILL, nr_scanned);
2101 	__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2102 
2103 	spin_unlock_irq(&lruvec->lru_lock);
2104 
2105 	while (!list_empty(&l_hold)) {
2106 		struct folio *folio;
2107 
2108 		cond_resched();
2109 		folio = lru_to_folio(&l_hold);
2110 		list_del(&folio->lru);
2111 
2112 		if (unlikely(!folio_evictable(folio))) {
2113 			folio_putback_lru(folio);
2114 			continue;
2115 		}
2116 
2117 		if (unlikely(buffer_heads_over_limit)) {
2118 			if (folio_needs_release(folio) &&
2119 			    folio_trylock(folio)) {
2120 				filemap_release_folio(folio, 0);
2121 				folio_unlock(folio);
2122 			}
2123 		}
2124 
2125 		/* Referenced or rmap lock contention: rotate */
2126 		if (folio_referenced(folio, 0, sc->target_mem_cgroup,
2127 				     &vm_flags) != 0) {
2128 			/*
2129 			 * Identify referenced, file-backed active folios and
2130 			 * give them one more trip around the active list. So
2131 			 * that executable code get better chances to stay in
2132 			 * memory under moderate memory pressure.  Anon folios
2133 			 * are not likely to be evicted by use-once streaming
2134 			 * IO, plus JVM can create lots of anon VM_EXEC folios,
2135 			 * so we ignore them here.
2136 			 */
2137 			if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
2138 				nr_rotated += folio_nr_pages(folio);
2139 				list_add(&folio->lru, &l_active);
2140 				continue;
2141 			}
2142 		}
2143 
2144 		folio_clear_active(folio);	/* we are de-activating */
2145 		folio_set_workingset(folio);
2146 		list_add(&folio->lru, &l_inactive);
2147 	}
2148 
2149 	/*
2150 	 * Move folios back to the lru list.
2151 	 */
2152 	spin_lock_irq(&lruvec->lru_lock);
2153 
2154 	nr_activate = move_folios_to_lru(lruvec, &l_active);
2155 	nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
2156 
2157 	__count_vm_events(PGDEACTIVATE, nr_deactivate);
2158 	__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2159 
2160 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2161 	spin_unlock_irq(&lruvec->lru_lock);
2162 
2163 	if (nr_rotated)
2164 		lru_note_cost(lruvec, file, 0, nr_rotated);
2165 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2166 			nr_deactivate, nr_rotated, sc->priority, file);
2167 }
2168 
reclaim_folio_list(struct list_head * folio_list,struct pglist_data * pgdat)2169 static unsigned int reclaim_folio_list(struct list_head *folio_list,
2170 				      struct pglist_data *pgdat)
2171 {
2172 	struct reclaim_stat stat;
2173 	unsigned int nr_reclaimed;
2174 	struct folio *folio;
2175 	struct scan_control sc = {
2176 		.gfp_mask = GFP_KERNEL,
2177 		.may_writepage = 1,
2178 		.may_unmap = 1,
2179 		.may_swap = 1,
2180 		.no_demotion = 1,
2181 	};
2182 
2183 	nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &stat, true);
2184 	while (!list_empty(folio_list)) {
2185 		folio = lru_to_folio(folio_list);
2186 		list_del(&folio->lru);
2187 		folio_putback_lru(folio);
2188 	}
2189 	trace_mm_vmscan_reclaim_pages(pgdat->node_id, sc.nr_scanned, nr_reclaimed, &stat);
2190 
2191 	return nr_reclaimed;
2192 }
2193 
reclaim_pages(struct list_head * folio_list)2194 unsigned long reclaim_pages(struct list_head *folio_list)
2195 {
2196 	int nid;
2197 	unsigned int nr_reclaimed = 0;
2198 	LIST_HEAD(node_folio_list);
2199 	unsigned int noreclaim_flag;
2200 
2201 	if (list_empty(folio_list))
2202 		return nr_reclaimed;
2203 
2204 	noreclaim_flag = memalloc_noreclaim_save();
2205 
2206 	nid = folio_nid(lru_to_folio(folio_list));
2207 	do {
2208 		struct folio *folio = lru_to_folio(folio_list);
2209 
2210 		if (nid == folio_nid(folio)) {
2211 			folio_clear_active(folio);
2212 			list_move(&folio->lru, &node_folio_list);
2213 			continue;
2214 		}
2215 
2216 		nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2217 		nid = folio_nid(lru_to_folio(folio_list));
2218 	} while (!list_empty(folio_list));
2219 
2220 	nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2221 
2222 	memalloc_noreclaim_restore(noreclaim_flag);
2223 
2224 	return nr_reclaimed;
2225 }
2226 
shrink_list(enum lru_list lru,unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc)2227 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2228 				 struct lruvec *lruvec, struct scan_control *sc)
2229 {
2230 	if (is_active_lru(lru)) {
2231 		if (sc->may_deactivate & (1 << is_file_lru(lru)))
2232 			shrink_active_list(nr_to_scan, lruvec, sc, lru);
2233 		else
2234 			sc->skipped_deactivate = 1;
2235 		return 0;
2236 	}
2237 
2238 	return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2239 }
2240 
2241 /*
2242  * The inactive anon list should be small enough that the VM never has
2243  * to do too much work.
2244  *
2245  * The inactive file list should be small enough to leave most memory
2246  * to the established workingset on the scan-resistant active list,
2247  * but large enough to avoid thrashing the aggregate readahead window.
2248  *
2249  * Both inactive lists should also be large enough that each inactive
2250  * folio has a chance to be referenced again before it is reclaimed.
2251  *
2252  * If that fails and refaulting is observed, the inactive list grows.
2253  *
2254  * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2255  * on this LRU, maintained by the pageout code. An inactive_ratio
2256  * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2257  *
2258  * total     target    max
2259  * memory    ratio     inactive
2260  * -------------------------------------
2261  *   10MB       1         5MB
2262  *  100MB       1        50MB
2263  *    1GB       3       250MB
2264  *   10GB      10       0.9GB
2265  *  100GB      31         3GB
2266  *    1TB     101        10GB
2267  *   10TB     320        32GB
2268  */
inactive_is_low(struct lruvec * lruvec,enum lru_list inactive_lru)2269 static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
2270 {
2271 	enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
2272 	unsigned long inactive, active;
2273 	unsigned long inactive_ratio;
2274 	unsigned long gb;
2275 
2276 	inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
2277 	active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
2278 
2279 	gb = (inactive + active) >> (30 - PAGE_SHIFT);
2280 	if (gb)
2281 		inactive_ratio = int_sqrt(10 * gb);
2282 	else
2283 		inactive_ratio = 1;
2284 
2285 	return inactive * inactive_ratio < active;
2286 }
2287 
2288 enum scan_balance {
2289 	SCAN_EQUAL,
2290 	SCAN_FRACT,
2291 	SCAN_ANON,
2292 	SCAN_FILE,
2293 };
2294 
prepare_scan_control(pg_data_t * pgdat,struct scan_control * sc)2295 static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc)
2296 {
2297 	unsigned long file;
2298 	struct lruvec *target_lruvec;
2299 
2300 	if (lru_gen_enabled())
2301 		return;
2302 
2303 	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
2304 
2305 	/*
2306 	 * Flush the memory cgroup stats in rate-limited way as we don't need
2307 	 * most accurate stats here. We may switch to regular stats flushing
2308 	 * in the future once it is cheap enough.
2309 	 */
2310 	mem_cgroup_flush_stats_ratelimited(sc->target_mem_cgroup);
2311 
2312 	/*
2313 	 * Determine the scan balance between anon and file LRUs.
2314 	 */
2315 	spin_lock_irq(&target_lruvec->lru_lock);
2316 	sc->anon_cost = target_lruvec->anon_cost;
2317 	sc->file_cost = target_lruvec->file_cost;
2318 	spin_unlock_irq(&target_lruvec->lru_lock);
2319 
2320 	/*
2321 	 * Target desirable inactive:active list ratios for the anon
2322 	 * and file LRU lists.
2323 	 */
2324 	if (!sc->force_deactivate) {
2325 		unsigned long refaults;
2326 
2327 		/*
2328 		 * When refaults are being observed, it means a new
2329 		 * workingset is being established. Deactivate to get
2330 		 * rid of any stale active pages quickly.
2331 		 */
2332 		refaults = lruvec_page_state(target_lruvec,
2333 				WORKINGSET_ACTIVATE_ANON);
2334 		if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
2335 			inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
2336 			sc->may_deactivate |= DEACTIVATE_ANON;
2337 		else
2338 			sc->may_deactivate &= ~DEACTIVATE_ANON;
2339 
2340 		refaults = lruvec_page_state(target_lruvec,
2341 				WORKINGSET_ACTIVATE_FILE);
2342 		if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
2343 		    inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
2344 			sc->may_deactivate |= DEACTIVATE_FILE;
2345 		else
2346 			sc->may_deactivate &= ~DEACTIVATE_FILE;
2347 	} else
2348 		sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
2349 
2350 	/*
2351 	 * If we have plenty of inactive file pages that aren't
2352 	 * thrashing, try to reclaim those first before touching
2353 	 * anonymous pages.
2354 	 */
2355 	file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
2356 	if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE) &&
2357 	    !sc->no_cache_trim_mode)
2358 		sc->cache_trim_mode = 1;
2359 	else
2360 		sc->cache_trim_mode = 0;
2361 
2362 	/*
2363 	 * Prevent the reclaimer from falling into the cache trap: as
2364 	 * cache pages start out inactive, every cache fault will tip
2365 	 * the scan balance towards the file LRU.  And as the file LRU
2366 	 * shrinks, so does the window for rotation from references.
2367 	 * This means we have a runaway feedback loop where a tiny
2368 	 * thrashing file LRU becomes infinitely more attractive than
2369 	 * anon pages.  Try to detect this based on file LRU size.
2370 	 */
2371 	if (!cgroup_reclaim(sc)) {
2372 		unsigned long total_high_wmark = 0;
2373 		unsigned long free, anon;
2374 		int z;
2375 
2376 		free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2377 		file = node_page_state(pgdat, NR_ACTIVE_FILE) +
2378 			   node_page_state(pgdat, NR_INACTIVE_FILE);
2379 
2380 		for (z = 0; z < MAX_NR_ZONES; z++) {
2381 			struct zone *zone = &pgdat->node_zones[z];
2382 
2383 			if (!managed_zone(zone))
2384 				continue;
2385 
2386 			total_high_wmark += high_wmark_pages(zone);
2387 		}
2388 
2389 		/*
2390 		 * Consider anon: if that's low too, this isn't a
2391 		 * runaway file reclaim problem, but rather just
2392 		 * extreme pressure. Reclaim as per usual then.
2393 		 */
2394 		anon = node_page_state(pgdat, NR_INACTIVE_ANON);
2395 
2396 		sc->file_is_tiny =
2397 			file + free <= total_high_wmark &&
2398 			!(sc->may_deactivate & DEACTIVATE_ANON) &&
2399 			anon >> sc->priority;
2400 	}
2401 }
2402 
2403 /*
2404  * Determine how aggressively the anon and file LRU lists should be
2405  * scanned.
2406  *
2407  * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
2408  * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
2409  */
get_scan_count(struct lruvec * lruvec,struct scan_control * sc,unsigned long * nr)2410 static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
2411 			   unsigned long *nr)
2412 {
2413 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2414 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2415 	unsigned long anon_cost, file_cost, total_cost;
2416 	int swappiness = sc_swappiness(sc, memcg);
2417 	u64 fraction[ANON_AND_FILE];
2418 	u64 denominator = 0;	/* gcc */
2419 	enum scan_balance scan_balance;
2420 	unsigned long ap, fp;
2421 	enum lru_list lru;
2422 
2423 	/* If we have no swap space, do not bother scanning anon folios. */
2424 	if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
2425 		scan_balance = SCAN_FILE;
2426 		goto out;
2427 	}
2428 
2429 	/*
2430 	 * Global reclaim will swap to prevent OOM even with no
2431 	 * swappiness, but memcg users want to use this knob to
2432 	 * disable swapping for individual groups completely when
2433 	 * using the memory controller's swap limit feature would be
2434 	 * too expensive.
2435 	 */
2436 	if (cgroup_reclaim(sc) && !swappiness) {
2437 		scan_balance = SCAN_FILE;
2438 		goto out;
2439 	}
2440 
2441 	/*
2442 	 * Do not apply any pressure balancing cleverness when the
2443 	 * system is close to OOM, scan both anon and file equally
2444 	 * (unless the swappiness setting disagrees with swapping).
2445 	 */
2446 	if (!sc->priority && swappiness) {
2447 		scan_balance = SCAN_EQUAL;
2448 		goto out;
2449 	}
2450 
2451 	/*
2452 	 * If the system is almost out of file pages, force-scan anon.
2453 	 */
2454 	if (sc->file_is_tiny) {
2455 		scan_balance = SCAN_ANON;
2456 		goto out;
2457 	}
2458 
2459 	/*
2460 	 * If there is enough inactive page cache, we do not reclaim
2461 	 * anything from the anonymous working right now.
2462 	 */
2463 	if (sc->cache_trim_mode) {
2464 		scan_balance = SCAN_FILE;
2465 		goto out;
2466 	}
2467 
2468 	scan_balance = SCAN_FRACT;
2469 	/*
2470 	 * Calculate the pressure balance between anon and file pages.
2471 	 *
2472 	 * The amount of pressure we put on each LRU is inversely
2473 	 * proportional to the cost of reclaiming each list, as
2474 	 * determined by the share of pages that are refaulting, times
2475 	 * the relative IO cost of bringing back a swapped out
2476 	 * anonymous page vs reloading a filesystem page (swappiness).
2477 	 *
2478 	 * Although we limit that influence to ensure no list gets
2479 	 * left behind completely: at least a third of the pressure is
2480 	 * applied, before swappiness.
2481 	 *
2482 	 * With swappiness at 100, anon and file have equal IO cost.
2483 	 */
2484 	total_cost = sc->anon_cost + sc->file_cost;
2485 	anon_cost = total_cost + sc->anon_cost;
2486 	file_cost = total_cost + sc->file_cost;
2487 	total_cost = anon_cost + file_cost;
2488 
2489 	ap = swappiness * (total_cost + 1);
2490 	ap /= anon_cost + 1;
2491 
2492 	fp = (MAX_SWAPPINESS - swappiness) * (total_cost + 1);
2493 	fp /= file_cost + 1;
2494 
2495 	fraction[0] = ap;
2496 	fraction[1] = fp;
2497 	denominator = ap + fp;
2498 out:
2499 	for_each_evictable_lru(lru) {
2500 		bool file = is_file_lru(lru);
2501 		unsigned long lruvec_size;
2502 		unsigned long low, min;
2503 		unsigned long scan;
2504 
2505 		lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
2506 		mem_cgroup_protection(sc->target_mem_cgroup, memcg,
2507 				      &min, &low);
2508 
2509 		if (min || low) {
2510 			/*
2511 			 * Scale a cgroup's reclaim pressure by proportioning
2512 			 * its current usage to its memory.low or memory.min
2513 			 * setting.
2514 			 *
2515 			 * This is important, as otherwise scanning aggression
2516 			 * becomes extremely binary -- from nothing as we
2517 			 * approach the memory protection threshold, to totally
2518 			 * nominal as we exceed it.  This results in requiring
2519 			 * setting extremely liberal protection thresholds. It
2520 			 * also means we simply get no protection at all if we
2521 			 * set it too low, which is not ideal.
2522 			 *
2523 			 * If there is any protection in place, we reduce scan
2524 			 * pressure by how much of the total memory used is
2525 			 * within protection thresholds.
2526 			 *
2527 			 * There is one special case: in the first reclaim pass,
2528 			 * we skip over all groups that are within their low
2529 			 * protection. If that fails to reclaim enough pages to
2530 			 * satisfy the reclaim goal, we come back and override
2531 			 * the best-effort low protection. However, we still
2532 			 * ideally want to honor how well-behaved groups are in
2533 			 * that case instead of simply punishing them all
2534 			 * equally. As such, we reclaim them based on how much
2535 			 * memory they are using, reducing the scan pressure
2536 			 * again by how much of the total memory used is under
2537 			 * hard protection.
2538 			 */
2539 			unsigned long cgroup_size = mem_cgroup_size(memcg);
2540 			unsigned long protection;
2541 
2542 			/* memory.low scaling, make sure we retry before OOM */
2543 			if (!sc->memcg_low_reclaim && low > min) {
2544 				protection = low;
2545 				sc->memcg_low_skipped = 1;
2546 			} else {
2547 				protection = min;
2548 			}
2549 
2550 			/* Avoid TOCTOU with earlier protection check */
2551 			cgroup_size = max(cgroup_size, protection);
2552 
2553 			scan = lruvec_size - lruvec_size * protection /
2554 				(cgroup_size + 1);
2555 
2556 			/*
2557 			 * Minimally target SWAP_CLUSTER_MAX pages to keep
2558 			 * reclaim moving forwards, avoiding decrementing
2559 			 * sc->priority further than desirable.
2560 			 */
2561 			scan = max(scan, SWAP_CLUSTER_MAX);
2562 		} else {
2563 			scan = lruvec_size;
2564 		}
2565 
2566 		scan >>= sc->priority;
2567 
2568 		/*
2569 		 * If the cgroup's already been deleted, make sure to
2570 		 * scrape out the remaining cache.
2571 		 */
2572 		if (!scan && !mem_cgroup_online(memcg))
2573 			scan = min(lruvec_size, SWAP_CLUSTER_MAX);
2574 
2575 		switch (scan_balance) {
2576 		case SCAN_EQUAL:
2577 			/* Scan lists relative to size */
2578 			break;
2579 		case SCAN_FRACT:
2580 			/*
2581 			 * Scan types proportional to swappiness and
2582 			 * their relative recent reclaim efficiency.
2583 			 * Make sure we don't miss the last page on
2584 			 * the offlined memory cgroups because of a
2585 			 * round-off error.
2586 			 */
2587 			scan = mem_cgroup_online(memcg) ?
2588 			       div64_u64(scan * fraction[file], denominator) :
2589 			       DIV64_U64_ROUND_UP(scan * fraction[file],
2590 						  denominator);
2591 			break;
2592 		case SCAN_FILE:
2593 		case SCAN_ANON:
2594 			/* Scan one type exclusively */
2595 			if ((scan_balance == SCAN_FILE) != file)
2596 				scan = 0;
2597 			break;
2598 		default:
2599 			/* Look ma, no brain */
2600 			BUG();
2601 		}
2602 
2603 		nr[lru] = scan;
2604 	}
2605 }
2606 
2607 /*
2608  * Anonymous LRU management is a waste if there is
2609  * ultimately no way to reclaim the memory.
2610  */
can_age_anon_pages(struct pglist_data * pgdat,struct scan_control * sc)2611 static bool can_age_anon_pages(struct pglist_data *pgdat,
2612 			       struct scan_control *sc)
2613 {
2614 	/* Aging the anon LRU is valuable if swap is present: */
2615 	if (total_swap_pages > 0)
2616 		return true;
2617 
2618 	/* Also valuable if anon pages can be demoted: */
2619 	return can_demote(pgdat->node_id, sc);
2620 }
2621 
2622 #ifdef CONFIG_LRU_GEN
2623 
2624 #ifdef CONFIG_LRU_GEN_ENABLED
2625 DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
2626 #define get_cap(cap)	static_branch_likely(&lru_gen_caps[cap])
2627 #else
2628 DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
2629 #define get_cap(cap)	static_branch_unlikely(&lru_gen_caps[cap])
2630 #endif
2631 
should_walk_mmu(void)2632 static bool should_walk_mmu(void)
2633 {
2634 	return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK);
2635 }
2636 
should_clear_pmd_young(void)2637 static bool should_clear_pmd_young(void)
2638 {
2639 	return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG);
2640 }
2641 
2642 /******************************************************************************
2643  *                          shorthand helpers
2644  ******************************************************************************/
2645 
2646 #define DEFINE_MAX_SEQ(lruvec)						\
2647 	unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
2648 
2649 #define DEFINE_MIN_SEQ(lruvec)						\
2650 	unsigned long min_seq[ANON_AND_FILE] = {			\
2651 		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]),	\
2652 		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]),	\
2653 	}
2654 
2655 #define evictable_min_seq(min_seq, swappiness)				\
2656 	min((min_seq)[!(swappiness)], (min_seq)[(swappiness) <= MAX_SWAPPINESS])
2657 
2658 #define for_each_gen_type_zone(gen, type, zone)				\
2659 	for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++)			\
2660 		for ((type) = 0; (type) < ANON_AND_FILE; (type)++)	\
2661 			for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
2662 
2663 #define for_each_evictable_type(type, swappiness)			\
2664 	for ((type) = !(swappiness); (type) <= ((swappiness) <= MAX_SWAPPINESS); (type)++)
2665 
2666 #define get_memcg_gen(seq)	((seq) % MEMCG_NR_GENS)
2667 #define get_memcg_bin(bin)	((bin) % MEMCG_NR_BINS)
2668 
get_lruvec(struct mem_cgroup * memcg,int nid)2669 static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
2670 {
2671 	struct pglist_data *pgdat = NODE_DATA(nid);
2672 
2673 #ifdef CONFIG_MEMCG
2674 	if (memcg) {
2675 		struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
2676 
2677 		/* see the comment in mem_cgroup_lruvec() */
2678 		if (!lruvec->pgdat)
2679 			lruvec->pgdat = pgdat;
2680 
2681 		return lruvec;
2682 	}
2683 #endif
2684 	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2685 
2686 	return &pgdat->__lruvec;
2687 }
2688 
get_swappiness(struct lruvec * lruvec,struct scan_control * sc)2689 static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
2690 {
2691 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2692 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2693 
2694 	if (!sc->may_swap)
2695 		return 0;
2696 
2697 	if (!can_demote(pgdat->node_id, sc) &&
2698 	    mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
2699 		return 0;
2700 
2701 	return sc_swappiness(sc, memcg);
2702 }
2703 
get_nr_gens(struct lruvec * lruvec,int type)2704 static int get_nr_gens(struct lruvec *lruvec, int type)
2705 {
2706 	return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
2707 }
2708 
seq_is_valid(struct lruvec * lruvec)2709 static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
2710 {
2711 	int type;
2712 
2713 	for (type = 0; type < ANON_AND_FILE; type++) {
2714 		int n = get_nr_gens(lruvec, type);
2715 
2716 		if (n < MIN_NR_GENS || n > MAX_NR_GENS)
2717 			return false;
2718 	}
2719 
2720 	return true;
2721 }
2722 
2723 /******************************************************************************
2724  *                          Bloom filters
2725  ******************************************************************************/
2726 
2727 /*
2728  * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
2729  * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
2730  * bits in a bitmap, k is the number of hash functions and n is the number of
2731  * inserted items.
2732  *
2733  * Page table walkers use one of the two filters to reduce their search space.
2734  * To get rid of non-leaf entries that no longer have enough leaf entries, the
2735  * aging uses the double-buffering technique to flip to the other filter each
2736  * time it produces a new generation. For non-leaf entries that have enough
2737  * leaf entries, the aging carries them over to the next generation in
2738  * walk_pmd_range(); the eviction also report them when walking the rmap
2739  * in lru_gen_look_around().
2740  *
2741  * For future optimizations:
2742  * 1. It's not necessary to keep both filters all the time. The spare one can be
2743  *    freed after the RCU grace period and reallocated if needed again.
2744  * 2. And when reallocating, it's worth scaling its size according to the number
2745  *    of inserted entries in the other filter, to reduce the memory overhead on
2746  *    small systems and false positives on large systems.
2747  * 3. Jenkins' hash function is an alternative to Knuth's.
2748  */
2749 #define BLOOM_FILTER_SHIFT	15
2750 
filter_gen_from_seq(unsigned long seq)2751 static inline int filter_gen_from_seq(unsigned long seq)
2752 {
2753 	return seq % NR_BLOOM_FILTERS;
2754 }
2755 
get_item_key(void * item,int * key)2756 static void get_item_key(void *item, int *key)
2757 {
2758 	u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
2759 
2760 	BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
2761 
2762 	key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
2763 	key[1] = hash >> BLOOM_FILTER_SHIFT;
2764 }
2765 
test_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq,void * item)2766 static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2767 			      void *item)
2768 {
2769 	int key[2];
2770 	unsigned long *filter;
2771 	int gen = filter_gen_from_seq(seq);
2772 
2773 	filter = READ_ONCE(mm_state->filters[gen]);
2774 	if (!filter)
2775 		return true;
2776 
2777 	get_item_key(item, key);
2778 
2779 	return test_bit(key[0], filter) && test_bit(key[1], filter);
2780 }
2781 
update_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq,void * item)2782 static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2783 				void *item)
2784 {
2785 	int key[2];
2786 	unsigned long *filter;
2787 	int gen = filter_gen_from_seq(seq);
2788 
2789 	filter = READ_ONCE(mm_state->filters[gen]);
2790 	if (!filter)
2791 		return;
2792 
2793 	get_item_key(item, key);
2794 
2795 	if (!test_bit(key[0], filter))
2796 		set_bit(key[0], filter);
2797 	if (!test_bit(key[1], filter))
2798 		set_bit(key[1], filter);
2799 }
2800 
reset_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq)2801 static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq)
2802 {
2803 	unsigned long *filter;
2804 	int gen = filter_gen_from_seq(seq);
2805 
2806 	filter = mm_state->filters[gen];
2807 	if (filter) {
2808 		bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
2809 		return;
2810 	}
2811 
2812 	filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
2813 			       __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
2814 	WRITE_ONCE(mm_state->filters[gen], filter);
2815 }
2816 
2817 /******************************************************************************
2818  *                          mm_struct list
2819  ******************************************************************************/
2820 
2821 #ifdef CONFIG_LRU_GEN_WALKS_MMU
2822 
get_mm_list(struct mem_cgroup * memcg)2823 static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2824 {
2825 	static struct lru_gen_mm_list mm_list = {
2826 		.fifo = LIST_HEAD_INIT(mm_list.fifo),
2827 		.lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
2828 	};
2829 
2830 #ifdef CONFIG_MEMCG
2831 	if (memcg)
2832 		return &memcg->mm_list;
2833 #endif
2834 	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2835 
2836 	return &mm_list;
2837 }
2838 
get_mm_state(struct lruvec * lruvec)2839 static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2840 {
2841 	return &lruvec->mm_state;
2842 }
2843 
get_next_mm(struct lru_gen_mm_walk * walk)2844 static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2845 {
2846 	int key;
2847 	struct mm_struct *mm;
2848 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
2849 	struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
2850 
2851 	mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
2852 	key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
2853 
2854 	if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
2855 		return NULL;
2856 
2857 	clear_bit(key, &mm->lru_gen.bitmap);
2858 
2859 	return mmget_not_zero(mm) ? mm : NULL;
2860 }
2861 
lru_gen_add_mm(struct mm_struct * mm)2862 void lru_gen_add_mm(struct mm_struct *mm)
2863 {
2864 	int nid;
2865 	struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
2866 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2867 
2868 	VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
2869 #ifdef CONFIG_MEMCG
2870 	VM_WARN_ON_ONCE(mm->lru_gen.memcg);
2871 	mm->lru_gen.memcg = memcg;
2872 #endif
2873 	spin_lock(&mm_list->lock);
2874 
2875 	for_each_node_state(nid, N_MEMORY) {
2876 		struct lruvec *lruvec = get_lruvec(memcg, nid);
2877 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2878 
2879 		/* the first addition since the last iteration */
2880 		if (mm_state->tail == &mm_list->fifo)
2881 			mm_state->tail = &mm->lru_gen.list;
2882 	}
2883 
2884 	list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
2885 
2886 	spin_unlock(&mm_list->lock);
2887 }
2888 
lru_gen_del_mm(struct mm_struct * mm)2889 void lru_gen_del_mm(struct mm_struct *mm)
2890 {
2891 	int nid;
2892 	struct lru_gen_mm_list *mm_list;
2893 	struct mem_cgroup *memcg = NULL;
2894 
2895 	if (list_empty(&mm->lru_gen.list))
2896 		return;
2897 
2898 #ifdef CONFIG_MEMCG
2899 	memcg = mm->lru_gen.memcg;
2900 #endif
2901 	mm_list = get_mm_list(memcg);
2902 
2903 	spin_lock(&mm_list->lock);
2904 
2905 	for_each_node(nid) {
2906 		struct lruvec *lruvec = get_lruvec(memcg, nid);
2907 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2908 
2909 		/* where the current iteration continues after */
2910 		if (mm_state->head == &mm->lru_gen.list)
2911 			mm_state->head = mm_state->head->prev;
2912 
2913 		/* where the last iteration ended before */
2914 		if (mm_state->tail == &mm->lru_gen.list)
2915 			mm_state->tail = mm_state->tail->next;
2916 	}
2917 
2918 	list_del_init(&mm->lru_gen.list);
2919 
2920 	spin_unlock(&mm_list->lock);
2921 
2922 #ifdef CONFIG_MEMCG
2923 	mem_cgroup_put(mm->lru_gen.memcg);
2924 	mm->lru_gen.memcg = NULL;
2925 #endif
2926 }
2927 
2928 #ifdef CONFIG_MEMCG
lru_gen_migrate_mm(struct mm_struct * mm)2929 void lru_gen_migrate_mm(struct mm_struct *mm)
2930 {
2931 	struct mem_cgroup *memcg;
2932 	struct task_struct *task = rcu_dereference_protected(mm->owner, true);
2933 
2934 	VM_WARN_ON_ONCE(task->mm != mm);
2935 	lockdep_assert_held(&task->alloc_lock);
2936 
2937 	/* for mm_update_next_owner() */
2938 	if (mem_cgroup_disabled())
2939 		return;
2940 
2941 	/* migration can happen before addition */
2942 	if (!mm->lru_gen.memcg)
2943 		return;
2944 
2945 	rcu_read_lock();
2946 	memcg = mem_cgroup_from_task(task);
2947 	rcu_read_unlock();
2948 	if (memcg == mm->lru_gen.memcg)
2949 		return;
2950 
2951 	VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
2952 
2953 	lru_gen_del_mm(mm);
2954 	lru_gen_add_mm(mm);
2955 }
2956 #endif
2957 
2958 #else /* !CONFIG_LRU_GEN_WALKS_MMU */
2959 
get_mm_list(struct mem_cgroup * memcg)2960 static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2961 {
2962 	return NULL;
2963 }
2964 
get_mm_state(struct lruvec * lruvec)2965 static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2966 {
2967 	return NULL;
2968 }
2969 
get_next_mm(struct lru_gen_mm_walk * walk)2970 static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2971 {
2972 	return NULL;
2973 }
2974 
2975 #endif
2976 
reset_mm_stats(struct lru_gen_mm_walk * walk,bool last)2977 static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last)
2978 {
2979 	int i;
2980 	int hist;
2981 	struct lruvec *lruvec = walk->lruvec;
2982 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2983 
2984 	lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
2985 
2986 	hist = lru_hist_from_seq(walk->seq);
2987 
2988 	for (i = 0; i < NR_MM_STATS; i++) {
2989 		WRITE_ONCE(mm_state->stats[hist][i],
2990 			   mm_state->stats[hist][i] + walk->mm_stats[i]);
2991 		walk->mm_stats[i] = 0;
2992 	}
2993 
2994 	if (NR_HIST_GENS > 1 && last) {
2995 		hist = lru_hist_from_seq(walk->seq + 1);
2996 
2997 		for (i = 0; i < NR_MM_STATS; i++)
2998 			WRITE_ONCE(mm_state->stats[hist][i], 0);
2999 	}
3000 }
3001 
iterate_mm_list(struct lru_gen_mm_walk * walk,struct mm_struct ** iter)3002 static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **iter)
3003 {
3004 	bool first = false;
3005 	bool last = false;
3006 	struct mm_struct *mm = NULL;
3007 	struct lruvec *lruvec = walk->lruvec;
3008 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3009 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3010 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3011 
3012 	/*
3013 	 * mm_state->seq is incremented after each iteration of mm_list. There
3014 	 * are three interesting cases for this page table walker:
3015 	 * 1. It tries to start a new iteration with a stale max_seq: there is
3016 	 *    nothing left to do.
3017 	 * 2. It started the next iteration: it needs to reset the Bloom filter
3018 	 *    so that a fresh set of PTE tables can be recorded.
3019 	 * 3. It ended the current iteration: it needs to reset the mm stats
3020 	 *    counters and tell its caller to increment max_seq.
3021 	 */
3022 	spin_lock(&mm_list->lock);
3023 
3024 	VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->seq);
3025 
3026 	if (walk->seq <= mm_state->seq)
3027 		goto done;
3028 
3029 	if (!mm_state->head)
3030 		mm_state->head = &mm_list->fifo;
3031 
3032 	if (mm_state->head == &mm_list->fifo)
3033 		first = true;
3034 
3035 	do {
3036 		mm_state->head = mm_state->head->next;
3037 		if (mm_state->head == &mm_list->fifo) {
3038 			WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3039 			last = true;
3040 			break;
3041 		}
3042 
3043 		/* force scan for those added after the last iteration */
3044 		if (!mm_state->tail || mm_state->tail == mm_state->head) {
3045 			mm_state->tail = mm_state->head->next;
3046 			walk->force_scan = true;
3047 		}
3048 	} while (!(mm = get_next_mm(walk)));
3049 done:
3050 	if (*iter || last)
3051 		reset_mm_stats(walk, last);
3052 
3053 	spin_unlock(&mm_list->lock);
3054 
3055 	if (mm && first)
3056 		reset_bloom_filter(mm_state, walk->seq + 1);
3057 
3058 	if (*iter)
3059 		mmput_async(*iter);
3060 
3061 	*iter = mm;
3062 
3063 	return last;
3064 }
3065 
iterate_mm_list_nowalk(struct lruvec * lruvec,unsigned long seq)3066 static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long seq)
3067 {
3068 	bool success = false;
3069 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3070 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3071 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3072 
3073 	spin_lock(&mm_list->lock);
3074 
3075 	VM_WARN_ON_ONCE(mm_state->seq + 1 < seq);
3076 
3077 	if (seq > mm_state->seq) {
3078 		mm_state->head = NULL;
3079 		mm_state->tail = NULL;
3080 		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3081 		success = true;
3082 	}
3083 
3084 	spin_unlock(&mm_list->lock);
3085 
3086 	return success;
3087 }
3088 
3089 /******************************************************************************
3090  *                          PID controller
3091  ******************************************************************************/
3092 
3093 /*
3094  * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3095  *
3096  * The P term is refaulted/(evicted+protected) from a tier in the generation
3097  * currently being evicted; the I term is the exponential moving average of the
3098  * P term over the generations previously evicted, using the smoothing factor
3099  * 1/2; the D term isn't supported.
3100  *
3101  * The setpoint (SP) is always the first tier of one type; the process variable
3102  * (PV) is either any tier of the other type or any other tier of the same
3103  * type.
3104  *
3105  * The error is the difference between the SP and the PV; the correction is to
3106  * turn off protection when SP>PV or turn on protection when SP<PV.
3107  *
3108  * For future optimizations:
3109  * 1. The D term may discount the other two terms over time so that long-lived
3110  *    generations can resist stale information.
3111  */
3112 struct ctrl_pos {
3113 	unsigned long refaulted;
3114 	unsigned long total;
3115 	int gain;
3116 };
3117 
read_ctrl_pos(struct lruvec * lruvec,int type,int tier,int gain,struct ctrl_pos * pos)3118 static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
3119 			  struct ctrl_pos *pos)
3120 {
3121 	int i;
3122 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3123 	int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3124 
3125 	pos->gain = gain;
3126 	pos->refaulted = pos->total = 0;
3127 
3128 	for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) {
3129 		pos->refaulted += lrugen->avg_refaulted[type][i] +
3130 				  atomic_long_read(&lrugen->refaulted[hist][type][i]);
3131 		pos->total += lrugen->avg_total[type][i] +
3132 			      lrugen->protected[hist][type][i] +
3133 			      atomic_long_read(&lrugen->evicted[hist][type][i]);
3134 	}
3135 }
3136 
reset_ctrl_pos(struct lruvec * lruvec,int type,bool carryover)3137 static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
3138 {
3139 	int hist, tier;
3140 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3141 	bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
3142 	unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
3143 
3144 	lockdep_assert_held(&lruvec->lru_lock);
3145 
3146 	if (!carryover && !clear)
3147 		return;
3148 
3149 	hist = lru_hist_from_seq(seq);
3150 
3151 	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
3152 		if (carryover) {
3153 			unsigned long sum;
3154 
3155 			sum = lrugen->avg_refaulted[type][tier] +
3156 			      atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3157 			WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
3158 
3159 			sum = lrugen->avg_total[type][tier] +
3160 			      lrugen->protected[hist][type][tier] +
3161 			      atomic_long_read(&lrugen->evicted[hist][type][tier]);
3162 			WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
3163 		}
3164 
3165 		if (clear) {
3166 			atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
3167 			atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
3168 			WRITE_ONCE(lrugen->protected[hist][type][tier], 0);
3169 		}
3170 	}
3171 }
3172 
positive_ctrl_err(struct ctrl_pos * sp,struct ctrl_pos * pv)3173 static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
3174 {
3175 	/*
3176 	 * Return true if the PV has a limited number of refaults or a lower
3177 	 * refaulted/total than the SP.
3178 	 */
3179 	return pv->refaulted < MIN_LRU_BATCH ||
3180 	       pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
3181 	       (sp->refaulted + 1) * pv->total * pv->gain;
3182 }
3183 
3184 /******************************************************************************
3185  *                          the aging
3186  ******************************************************************************/
3187 
3188 /* promote pages accessed through page tables */
folio_update_gen(struct folio * folio,int gen)3189 static int folio_update_gen(struct folio *folio, int gen)
3190 {
3191 	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3192 
3193 	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
3194 
3195 	/* see the comment on LRU_REFS_FLAGS */
3196 	if (!folio_test_referenced(folio) && !folio_test_workingset(folio)) {
3197 		set_mask_bits(&folio->flags, LRU_REFS_MASK, BIT(PG_referenced));
3198 		return -1;
3199 	}
3200 
3201 	do {
3202 		/* lru_gen_del_folio() has isolated this page? */
3203 		if (!(old_flags & LRU_GEN_MASK))
3204 			return -1;
3205 
3206 		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_FLAGS);
3207 		new_flags |= ((gen + 1UL) << LRU_GEN_PGOFF) | BIT(PG_workingset);
3208 	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3209 
3210 	return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3211 }
3212 
3213 /* protect pages accessed multiple times through file descriptors */
folio_inc_gen(struct lruvec * lruvec,struct folio * folio,bool reclaiming)3214 static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
3215 {
3216 	int type = folio_is_file_lru(folio);
3217 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3218 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3219 	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3220 
3221 	VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
3222 
3223 	do {
3224 		new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3225 		/* folio_update_gen() has promoted this page? */
3226 		if (new_gen >= 0 && new_gen != old_gen)
3227 			return new_gen;
3228 
3229 		new_gen = (old_gen + 1) % MAX_NR_GENS;
3230 
3231 		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_FLAGS);
3232 		new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
3233 		/* for folio_end_writeback() */
3234 		if (reclaiming)
3235 			new_flags |= BIT(PG_reclaim);
3236 	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3237 
3238 	lru_gen_update_size(lruvec, folio, old_gen, new_gen);
3239 
3240 	return new_gen;
3241 }
3242 
update_batch_size(struct lru_gen_mm_walk * walk,struct folio * folio,int old_gen,int new_gen)3243 static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
3244 			      int old_gen, int new_gen)
3245 {
3246 	int type = folio_is_file_lru(folio);
3247 	int zone = folio_zonenum(folio);
3248 	int delta = folio_nr_pages(folio);
3249 
3250 	VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
3251 	VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
3252 
3253 	walk->batched++;
3254 
3255 	walk->nr_pages[old_gen][type][zone] -= delta;
3256 	walk->nr_pages[new_gen][type][zone] += delta;
3257 }
3258 
reset_batch_size(struct lru_gen_mm_walk * walk)3259 static void reset_batch_size(struct lru_gen_mm_walk *walk)
3260 {
3261 	int gen, type, zone;
3262 	struct lruvec *lruvec = walk->lruvec;
3263 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3264 
3265 	walk->batched = 0;
3266 
3267 	for_each_gen_type_zone(gen, type, zone) {
3268 		enum lru_list lru = type * LRU_INACTIVE_FILE;
3269 		int delta = walk->nr_pages[gen][type][zone];
3270 
3271 		if (!delta)
3272 			continue;
3273 
3274 		walk->nr_pages[gen][type][zone] = 0;
3275 		WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
3276 			   lrugen->nr_pages[gen][type][zone] + delta);
3277 
3278 		if (lru_gen_is_active(lruvec, gen))
3279 			lru += LRU_ACTIVE;
3280 		__update_lru_size(lruvec, lru, zone, delta);
3281 	}
3282 }
3283 
should_skip_vma(unsigned long start,unsigned long end,struct mm_walk * args)3284 static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
3285 {
3286 	struct address_space *mapping;
3287 	struct vm_area_struct *vma = args->vma;
3288 	struct lru_gen_mm_walk *walk = args->private;
3289 
3290 	if (!vma_is_accessible(vma))
3291 		return true;
3292 
3293 	if (is_vm_hugetlb_page(vma))
3294 		return true;
3295 
3296 	if (!vma_has_recency(vma))
3297 		return true;
3298 
3299 	if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
3300 		return true;
3301 
3302 	if (vma == get_gate_vma(vma->vm_mm))
3303 		return true;
3304 
3305 	if (vma_is_anonymous(vma))
3306 		return !walk->swappiness;
3307 
3308 	if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
3309 		return true;
3310 
3311 	mapping = vma->vm_file->f_mapping;
3312 	if (mapping_unevictable(mapping))
3313 		return true;
3314 
3315 	if (shmem_mapping(mapping))
3316 		return !walk->swappiness;
3317 
3318 	if (walk->swappiness > MAX_SWAPPINESS)
3319 		return true;
3320 
3321 	/* to exclude special mappings like dax, etc. */
3322 	return !mapping->a_ops->read_folio;
3323 }
3324 
3325 /*
3326  * Some userspace memory allocators map many single-page VMAs. Instead of
3327  * returning back to the PGD table for each of such VMAs, finish an entire PMD
3328  * table to reduce zigzags and improve cache performance.
3329  */
get_next_vma(unsigned long mask,unsigned long size,struct mm_walk * args,unsigned long * vm_start,unsigned long * vm_end)3330 static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
3331 			 unsigned long *vm_start, unsigned long *vm_end)
3332 {
3333 	unsigned long start = round_up(*vm_end, size);
3334 	unsigned long end = (start | ~mask) + 1;
3335 	VMA_ITERATOR(vmi, args->mm, start);
3336 
3337 	VM_WARN_ON_ONCE(mask & size);
3338 	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
3339 
3340 	for_each_vma(vmi, args->vma) {
3341 		if (end && end <= args->vma->vm_start)
3342 			return false;
3343 
3344 		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
3345 			continue;
3346 
3347 		*vm_start = max(start, args->vma->vm_start);
3348 		*vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
3349 
3350 		return true;
3351 	}
3352 
3353 	return false;
3354 }
3355 
get_pte_pfn(pte_t pte,struct vm_area_struct * vma,unsigned long addr,struct pglist_data * pgdat)3356 static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr,
3357 				 struct pglist_data *pgdat)
3358 {
3359 	unsigned long pfn = pte_pfn(pte);
3360 
3361 	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3362 
3363 	if (!pte_present(pte) || is_zero_pfn(pfn))
3364 		return -1;
3365 
3366 	if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
3367 		return -1;
3368 
3369 	if (!pte_young(pte) && !mm_has_notifiers(vma->vm_mm))
3370 		return -1;
3371 
3372 	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3373 		return -1;
3374 
3375 	if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3376 		return -1;
3377 
3378 	return pfn;
3379 }
3380 
get_pmd_pfn(pmd_t pmd,struct vm_area_struct * vma,unsigned long addr,struct pglist_data * pgdat)3381 static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr,
3382 				 struct pglist_data *pgdat)
3383 {
3384 	unsigned long pfn = pmd_pfn(pmd);
3385 
3386 	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3387 
3388 	if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
3389 		return -1;
3390 
3391 	if (WARN_ON_ONCE(pmd_devmap(pmd)))
3392 		return -1;
3393 
3394 	if (!pmd_young(pmd) && !mm_has_notifiers(vma->vm_mm))
3395 		return -1;
3396 
3397 	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3398 		return -1;
3399 
3400 	if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3401 		return -1;
3402 
3403 	return pfn;
3404 }
3405 
get_pfn_folio(unsigned long pfn,struct mem_cgroup * memcg,struct pglist_data * pgdat)3406 static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
3407 				   struct pglist_data *pgdat)
3408 {
3409 	struct folio *folio = pfn_folio(pfn);
3410 
3411 	if (folio_lru_gen(folio) < 0)
3412 		return NULL;
3413 
3414 	if (folio_nid(folio) != pgdat->node_id)
3415 		return NULL;
3416 
3417 	if (folio_memcg(folio) != memcg)
3418 		return NULL;
3419 
3420 	return folio;
3421 }
3422 
suitable_to_scan(int total,int young)3423 static bool suitable_to_scan(int total, int young)
3424 {
3425 	int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
3426 
3427 	/* suitable if the average number of young PTEs per cacheline is >=1 */
3428 	return young * n >= total;
3429 }
3430 
walk_update_folio(struct lru_gen_mm_walk * walk,struct folio * folio,int new_gen,bool dirty)3431 static void walk_update_folio(struct lru_gen_mm_walk *walk, struct folio *folio,
3432 			      int new_gen, bool dirty)
3433 {
3434 	int old_gen;
3435 
3436 	if (!folio)
3437 		return;
3438 
3439 	if (dirty && !folio_test_dirty(folio) &&
3440 	    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3441 	      !folio_test_swapcache(folio)))
3442 		folio_mark_dirty(folio);
3443 
3444 	if (walk) {
3445 		old_gen = folio_update_gen(folio, new_gen);
3446 		if (old_gen >= 0 && old_gen != new_gen)
3447 			update_batch_size(walk, folio, old_gen, new_gen);
3448 	} else if (lru_gen_set_refs(folio)) {
3449 		old_gen = folio_lru_gen(folio);
3450 		if (old_gen >= 0 && old_gen != new_gen)
3451 			folio_activate(folio);
3452 	}
3453 }
3454 
walk_pte_range(pmd_t * pmd,unsigned long start,unsigned long end,struct mm_walk * args)3455 static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
3456 			   struct mm_walk *args)
3457 {
3458 	int i;
3459 	bool dirty;
3460 	pte_t *pte;
3461 	spinlock_t *ptl;
3462 	unsigned long addr;
3463 	int total = 0;
3464 	int young = 0;
3465 	struct folio *last = NULL;
3466 	struct lru_gen_mm_walk *walk = args->private;
3467 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3468 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3469 	DEFINE_MAX_SEQ(walk->lruvec);
3470 	int gen = lru_gen_from_seq(max_seq);
3471 	pmd_t pmdval;
3472 
3473 	pte = pte_offset_map_rw_nolock(args->mm, pmd, start & PMD_MASK, &pmdval, &ptl);
3474 	if (!pte)
3475 		return false;
3476 
3477 	if (!spin_trylock(ptl)) {
3478 		pte_unmap(pte);
3479 		return true;
3480 	}
3481 
3482 	if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) {
3483 		pte_unmap_unlock(pte, ptl);
3484 		return false;
3485 	}
3486 
3487 	arch_enter_lazy_mmu_mode();
3488 restart:
3489 	for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
3490 		unsigned long pfn;
3491 		struct folio *folio;
3492 		pte_t ptent = ptep_get(pte + i);
3493 
3494 		total++;
3495 		walk->mm_stats[MM_LEAF_TOTAL]++;
3496 
3497 		pfn = get_pte_pfn(ptent, args->vma, addr, pgdat);
3498 		if (pfn == -1)
3499 			continue;
3500 
3501 		folio = get_pfn_folio(pfn, memcg, pgdat);
3502 		if (!folio)
3503 			continue;
3504 
3505 		if (!ptep_clear_young_notify(args->vma, addr, pte + i))
3506 			continue;
3507 
3508 		if (last != folio) {
3509 			walk_update_folio(walk, last, gen, dirty);
3510 
3511 			last = folio;
3512 			dirty = false;
3513 		}
3514 
3515 		if (pte_dirty(ptent))
3516 			dirty = true;
3517 
3518 		young++;
3519 		walk->mm_stats[MM_LEAF_YOUNG]++;
3520 	}
3521 
3522 	walk_update_folio(walk, last, gen, dirty);
3523 	last = NULL;
3524 
3525 	if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
3526 		goto restart;
3527 
3528 	arch_leave_lazy_mmu_mode();
3529 	pte_unmap_unlock(pte, ptl);
3530 
3531 	return suitable_to_scan(total, young);
3532 }
3533 
walk_pmd_range_locked(pud_t * pud,unsigned long addr,struct vm_area_struct * vma,struct mm_walk * args,unsigned long * bitmap,unsigned long * first)3534 static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
3535 				  struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
3536 {
3537 	int i;
3538 	bool dirty;
3539 	pmd_t *pmd;
3540 	spinlock_t *ptl;
3541 	struct folio *last = NULL;
3542 	struct lru_gen_mm_walk *walk = args->private;
3543 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3544 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3545 	DEFINE_MAX_SEQ(walk->lruvec);
3546 	int gen = lru_gen_from_seq(max_seq);
3547 
3548 	VM_WARN_ON_ONCE(pud_leaf(*pud));
3549 
3550 	/* try to batch at most 1+MIN_LRU_BATCH+1 entries */
3551 	if (*first == -1) {
3552 		*first = addr;
3553 		bitmap_zero(bitmap, MIN_LRU_BATCH);
3554 		return;
3555 	}
3556 
3557 	i = addr == -1 ? 0 : pmd_index(addr) - pmd_index(*first);
3558 	if (i && i <= MIN_LRU_BATCH) {
3559 		__set_bit(i - 1, bitmap);
3560 		return;
3561 	}
3562 
3563 	pmd = pmd_offset(pud, *first);
3564 
3565 	ptl = pmd_lockptr(args->mm, pmd);
3566 	if (!spin_trylock(ptl))
3567 		goto done;
3568 
3569 	arch_enter_lazy_mmu_mode();
3570 
3571 	do {
3572 		unsigned long pfn;
3573 		struct folio *folio;
3574 
3575 		/* don't round down the first address */
3576 		addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first;
3577 
3578 		if (!pmd_present(pmd[i]))
3579 			goto next;
3580 
3581 		if (!pmd_trans_huge(pmd[i])) {
3582 			if (!walk->force_scan && should_clear_pmd_young() &&
3583 			    !mm_has_notifiers(args->mm))
3584 				pmdp_test_and_clear_young(vma, addr, pmd + i);
3585 			goto next;
3586 		}
3587 
3588 		pfn = get_pmd_pfn(pmd[i], vma, addr, pgdat);
3589 		if (pfn == -1)
3590 			goto next;
3591 
3592 		folio = get_pfn_folio(pfn, memcg, pgdat);
3593 		if (!folio)
3594 			goto next;
3595 
3596 		if (!pmdp_clear_young_notify(vma, addr, pmd + i))
3597 			goto next;
3598 
3599 		if (last != folio) {
3600 			walk_update_folio(walk, last, gen, dirty);
3601 
3602 			last = folio;
3603 			dirty = false;
3604 		}
3605 
3606 		if (pmd_dirty(pmd[i]))
3607 			dirty = true;
3608 
3609 		walk->mm_stats[MM_LEAF_YOUNG]++;
3610 next:
3611 		i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
3612 	} while (i <= MIN_LRU_BATCH);
3613 
3614 	walk_update_folio(walk, last, gen, dirty);
3615 
3616 	arch_leave_lazy_mmu_mode();
3617 	spin_unlock(ptl);
3618 done:
3619 	*first = -1;
3620 }
3621 
walk_pmd_range(pud_t * pud,unsigned long start,unsigned long end,struct mm_walk * args)3622 static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
3623 			   struct mm_walk *args)
3624 {
3625 	int i;
3626 	pmd_t *pmd;
3627 	unsigned long next;
3628 	unsigned long addr;
3629 	struct vm_area_struct *vma;
3630 	DECLARE_BITMAP(bitmap, MIN_LRU_BATCH);
3631 	unsigned long first = -1;
3632 	struct lru_gen_mm_walk *walk = args->private;
3633 	struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
3634 
3635 	VM_WARN_ON_ONCE(pud_leaf(*pud));
3636 
3637 	/*
3638 	 * Finish an entire PMD in two passes: the first only reaches to PTE
3639 	 * tables to avoid taking the PMD lock; the second, if necessary, takes
3640 	 * the PMD lock to clear the accessed bit in PMD entries.
3641 	 */
3642 	pmd = pmd_offset(pud, start & PUD_MASK);
3643 restart:
3644 	/* walk_pte_range() may call get_next_vma() */
3645 	vma = args->vma;
3646 	for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
3647 		pmd_t val = pmdp_get_lockless(pmd + i);
3648 
3649 		next = pmd_addr_end(addr, end);
3650 
3651 		if (!pmd_present(val) || is_huge_zero_pmd(val)) {
3652 			walk->mm_stats[MM_LEAF_TOTAL]++;
3653 			continue;
3654 		}
3655 
3656 		if (pmd_trans_huge(val)) {
3657 			struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3658 			unsigned long pfn = get_pmd_pfn(val, vma, addr, pgdat);
3659 
3660 			walk->mm_stats[MM_LEAF_TOTAL]++;
3661 
3662 			if (pfn != -1)
3663 				walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3664 			continue;
3665 		}
3666 
3667 		if (!walk->force_scan && should_clear_pmd_young() &&
3668 		    !mm_has_notifiers(args->mm)) {
3669 			if (!pmd_young(val))
3670 				continue;
3671 
3672 			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3673 		}
3674 
3675 		if (!walk->force_scan && !test_bloom_filter(mm_state, walk->seq, pmd + i))
3676 			continue;
3677 
3678 		walk->mm_stats[MM_NONLEAF_FOUND]++;
3679 
3680 		if (!walk_pte_range(&val, addr, next, args))
3681 			continue;
3682 
3683 		walk->mm_stats[MM_NONLEAF_ADDED]++;
3684 
3685 		/* carry over to the next generation */
3686 		update_bloom_filter(mm_state, walk->seq + 1, pmd + i);
3687 	}
3688 
3689 	walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first);
3690 
3691 	if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
3692 		goto restart;
3693 }
3694 
walk_pud_range(p4d_t * p4d,unsigned long start,unsigned long end,struct mm_walk * args)3695 static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
3696 			  struct mm_walk *args)
3697 {
3698 	int i;
3699 	pud_t *pud;
3700 	unsigned long addr;
3701 	unsigned long next;
3702 	struct lru_gen_mm_walk *walk = args->private;
3703 
3704 	VM_WARN_ON_ONCE(p4d_leaf(*p4d));
3705 
3706 	pud = pud_offset(p4d, start & P4D_MASK);
3707 restart:
3708 	for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
3709 		pud_t val = READ_ONCE(pud[i]);
3710 
3711 		next = pud_addr_end(addr, end);
3712 
3713 		if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
3714 			continue;
3715 
3716 		walk_pmd_range(&val, addr, next, args);
3717 
3718 		if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
3719 			end = (addr | ~PUD_MASK) + 1;
3720 			goto done;
3721 		}
3722 	}
3723 
3724 	if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
3725 		goto restart;
3726 
3727 	end = round_up(end, P4D_SIZE);
3728 done:
3729 	if (!end || !args->vma)
3730 		return 1;
3731 
3732 	walk->next_addr = max(end, args->vma->vm_start);
3733 
3734 	return -EAGAIN;
3735 }
3736 
walk_mm(struct mm_struct * mm,struct lru_gen_mm_walk * walk)3737 static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
3738 {
3739 	static const struct mm_walk_ops mm_walk_ops = {
3740 		.test_walk = should_skip_vma,
3741 		.p4d_entry = walk_pud_range,
3742 		.walk_lock = PGWALK_RDLOCK,
3743 	};
3744 	int err;
3745 	struct lruvec *lruvec = walk->lruvec;
3746 
3747 	walk->next_addr = FIRST_USER_ADDRESS;
3748 
3749 	do {
3750 		DEFINE_MAX_SEQ(lruvec);
3751 
3752 		err = -EBUSY;
3753 
3754 		/* another thread might have called inc_max_seq() */
3755 		if (walk->seq != max_seq)
3756 			break;
3757 
3758 		/* the caller might be holding the lock for write */
3759 		if (mmap_read_trylock(mm)) {
3760 			err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
3761 
3762 			mmap_read_unlock(mm);
3763 		}
3764 
3765 		if (walk->batched) {
3766 			spin_lock_irq(&lruvec->lru_lock);
3767 			reset_batch_size(walk);
3768 			spin_unlock_irq(&lruvec->lru_lock);
3769 		}
3770 
3771 		cond_resched();
3772 	} while (err == -EAGAIN);
3773 }
3774 
set_mm_walk(struct pglist_data * pgdat,bool force_alloc)3775 static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc)
3776 {
3777 	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3778 
3779 	if (pgdat && current_is_kswapd()) {
3780 		VM_WARN_ON_ONCE(walk);
3781 
3782 		walk = &pgdat->mm_walk;
3783 	} else if (!walk && force_alloc) {
3784 		VM_WARN_ON_ONCE(current_is_kswapd());
3785 
3786 		walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
3787 	}
3788 
3789 	current->reclaim_state->mm_walk = walk;
3790 
3791 	return walk;
3792 }
3793 
clear_mm_walk(void)3794 static void clear_mm_walk(void)
3795 {
3796 	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3797 
3798 	VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
3799 	VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
3800 
3801 	current->reclaim_state->mm_walk = NULL;
3802 
3803 	if (!current_is_kswapd())
3804 		kfree(walk);
3805 }
3806 
inc_min_seq(struct lruvec * lruvec,int type,int swappiness)3807 static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness)
3808 {
3809 	int zone;
3810 	int remaining = MAX_LRU_BATCH;
3811 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3812 	int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3813 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3814 
3815 	if (type ? swappiness > MAX_SWAPPINESS : !swappiness)
3816 		goto done;
3817 
3818 	/* prevent cold/hot inversion if the type is evictable */
3819 	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3820 		struct list_head *head = &lrugen->folios[old_gen][type][zone];
3821 
3822 		while (!list_empty(head)) {
3823 			struct folio *folio = lru_to_folio(head);
3824 			int refs = folio_lru_refs(folio);
3825 			bool workingset = folio_test_workingset(folio);
3826 
3827 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
3828 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
3829 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
3830 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
3831 
3832 			new_gen = folio_inc_gen(lruvec, folio, false);
3833 			list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
3834 
3835 			/* don't count the workingset being lazily promoted */
3836 			if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) {
3837 				int tier = lru_tier_from_refs(refs, workingset);
3838 				int delta = folio_nr_pages(folio);
3839 
3840 				WRITE_ONCE(lrugen->protected[hist][type][tier],
3841 					   lrugen->protected[hist][type][tier] + delta);
3842 			}
3843 
3844 			if (!--remaining)
3845 				return false;
3846 		}
3847 	}
3848 done:
3849 	reset_ctrl_pos(lruvec, type, true);
3850 	WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
3851 
3852 	return true;
3853 }
3854 
try_to_inc_min_seq(struct lruvec * lruvec,int swappiness)3855 static bool try_to_inc_min_seq(struct lruvec *lruvec, int swappiness)
3856 {
3857 	int gen, type, zone;
3858 	bool success = false;
3859 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3860 	DEFINE_MIN_SEQ(lruvec);
3861 
3862 	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3863 
3864 	/* find the oldest populated generation */
3865 	for_each_evictable_type(type, swappiness) {
3866 		while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
3867 			gen = lru_gen_from_seq(min_seq[type]);
3868 
3869 			for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3870 				if (!list_empty(&lrugen->folios[gen][type][zone]))
3871 					goto next;
3872 			}
3873 
3874 			min_seq[type]++;
3875 		}
3876 next:
3877 		;
3878 	}
3879 
3880 	/* see the comment on lru_gen_folio */
3881 	if (swappiness && swappiness <= MAX_SWAPPINESS) {
3882 		unsigned long seq = lrugen->max_seq - MIN_NR_GENS;
3883 
3884 		if (min_seq[LRU_GEN_ANON] > seq && min_seq[LRU_GEN_FILE] < seq)
3885 			min_seq[LRU_GEN_ANON] = seq;
3886 		else if (min_seq[LRU_GEN_FILE] > seq && min_seq[LRU_GEN_ANON] < seq)
3887 			min_seq[LRU_GEN_FILE] = seq;
3888 	}
3889 
3890 	for_each_evictable_type(type, swappiness) {
3891 		if (min_seq[type] <= lrugen->min_seq[type])
3892 			continue;
3893 
3894 		reset_ctrl_pos(lruvec, type, true);
3895 		WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
3896 		success = true;
3897 	}
3898 
3899 	return success;
3900 }
3901 
inc_max_seq(struct lruvec * lruvec,unsigned long seq,int swappiness)3902 static bool inc_max_seq(struct lruvec *lruvec, unsigned long seq, int swappiness)
3903 {
3904 	bool success;
3905 	int prev, next;
3906 	int type, zone;
3907 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3908 restart:
3909 	if (seq < READ_ONCE(lrugen->max_seq))
3910 		return false;
3911 
3912 	spin_lock_irq(&lruvec->lru_lock);
3913 
3914 	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3915 
3916 	success = seq == lrugen->max_seq;
3917 	if (!success)
3918 		goto unlock;
3919 
3920 	for (type = 0; type < ANON_AND_FILE; type++) {
3921 		if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
3922 			continue;
3923 
3924 		if (inc_min_seq(lruvec, type, swappiness))
3925 			continue;
3926 
3927 		spin_unlock_irq(&lruvec->lru_lock);
3928 		cond_resched();
3929 		goto restart;
3930 	}
3931 
3932 	/*
3933 	 * Update the active/inactive LRU sizes for compatibility. Both sides of
3934 	 * the current max_seq need to be covered, since max_seq+1 can overlap
3935 	 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
3936 	 * overlap, cold/hot inversion happens.
3937 	 */
3938 	prev = lru_gen_from_seq(lrugen->max_seq - 1);
3939 	next = lru_gen_from_seq(lrugen->max_seq + 1);
3940 
3941 	for (type = 0; type < ANON_AND_FILE; type++) {
3942 		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3943 			enum lru_list lru = type * LRU_INACTIVE_FILE;
3944 			long delta = lrugen->nr_pages[prev][type][zone] -
3945 				     lrugen->nr_pages[next][type][zone];
3946 
3947 			if (!delta)
3948 				continue;
3949 
3950 			__update_lru_size(lruvec, lru, zone, delta);
3951 			__update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
3952 		}
3953 	}
3954 
3955 	for (type = 0; type < ANON_AND_FILE; type++)
3956 		reset_ctrl_pos(lruvec, type, false);
3957 
3958 	WRITE_ONCE(lrugen->timestamps[next], jiffies);
3959 	/* make sure preceding modifications appear */
3960 	smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
3961 unlock:
3962 	spin_unlock_irq(&lruvec->lru_lock);
3963 
3964 	return success;
3965 }
3966 
try_to_inc_max_seq(struct lruvec * lruvec,unsigned long seq,int swappiness,bool force_scan)3967 static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long seq,
3968 			       int swappiness, bool force_scan)
3969 {
3970 	bool success;
3971 	struct lru_gen_mm_walk *walk;
3972 	struct mm_struct *mm = NULL;
3973 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3974 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3975 
3976 	VM_WARN_ON_ONCE(seq > READ_ONCE(lrugen->max_seq));
3977 
3978 	if (!mm_state)
3979 		return inc_max_seq(lruvec, seq, swappiness);
3980 
3981 	/* see the comment in iterate_mm_list() */
3982 	if (seq <= READ_ONCE(mm_state->seq))
3983 		return false;
3984 
3985 	/*
3986 	 * If the hardware doesn't automatically set the accessed bit, fallback
3987 	 * to lru_gen_look_around(), which only clears the accessed bit in a
3988 	 * handful of PTEs. Spreading the work out over a period of time usually
3989 	 * is less efficient, but it avoids bursty page faults.
3990 	 */
3991 	if (!should_walk_mmu()) {
3992 		success = iterate_mm_list_nowalk(lruvec, seq);
3993 		goto done;
3994 	}
3995 
3996 	walk = set_mm_walk(NULL, true);
3997 	if (!walk) {
3998 		success = iterate_mm_list_nowalk(lruvec, seq);
3999 		goto done;
4000 	}
4001 
4002 	walk->lruvec = lruvec;
4003 	walk->seq = seq;
4004 	walk->swappiness = swappiness;
4005 	walk->force_scan = force_scan;
4006 
4007 	do {
4008 		success = iterate_mm_list(walk, &mm);
4009 		if (mm)
4010 			walk_mm(mm, walk);
4011 	} while (mm);
4012 done:
4013 	if (success) {
4014 		success = inc_max_seq(lruvec, seq, swappiness);
4015 		WARN_ON_ONCE(!success);
4016 	}
4017 
4018 	return success;
4019 }
4020 
4021 /******************************************************************************
4022  *                          working set protection
4023  ******************************************************************************/
4024 
set_initial_priority(struct pglist_data * pgdat,struct scan_control * sc)4025 static void set_initial_priority(struct pglist_data *pgdat, struct scan_control *sc)
4026 {
4027 	int priority;
4028 	unsigned long reclaimable;
4029 
4030 	if (sc->priority != DEF_PRIORITY || sc->nr_to_reclaim < MIN_LRU_BATCH)
4031 		return;
4032 	/*
4033 	 * Determine the initial priority based on
4034 	 * (total >> priority) * reclaimed_to_scanned_ratio = nr_to_reclaim,
4035 	 * where reclaimed_to_scanned_ratio = inactive / total.
4036 	 */
4037 	reclaimable = node_page_state(pgdat, NR_INACTIVE_FILE);
4038 	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
4039 		reclaimable += node_page_state(pgdat, NR_INACTIVE_ANON);
4040 
4041 	/* round down reclaimable and round up sc->nr_to_reclaim */
4042 	priority = fls_long(reclaimable) - 1 - fls_long(sc->nr_to_reclaim - 1);
4043 
4044 	/*
4045 	 * The estimation is based on LRU pages only, so cap it to prevent
4046 	 * overshoots of shrinker objects by large margins.
4047 	 */
4048 	sc->priority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY);
4049 }
4050 
lruvec_is_sizable(struct lruvec * lruvec,struct scan_control * sc)4051 static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
4052 {
4053 	int gen, type, zone;
4054 	unsigned long total = 0;
4055 	int swappiness = get_swappiness(lruvec, sc);
4056 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4057 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4058 	DEFINE_MAX_SEQ(lruvec);
4059 	DEFINE_MIN_SEQ(lruvec);
4060 
4061 	for_each_evictable_type(type, swappiness) {
4062 		unsigned long seq;
4063 
4064 		for (seq = min_seq[type]; seq <= max_seq; seq++) {
4065 			gen = lru_gen_from_seq(seq);
4066 
4067 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
4068 				total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4069 		}
4070 	}
4071 
4072 	/* whether the size is big enough to be helpful */
4073 	return mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
4074 }
4075 
lruvec_is_reclaimable(struct lruvec * lruvec,struct scan_control * sc,unsigned long min_ttl)4076 static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc,
4077 				  unsigned long min_ttl)
4078 {
4079 	int gen;
4080 	unsigned long birth;
4081 	int swappiness = get_swappiness(lruvec, sc);
4082 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4083 	DEFINE_MIN_SEQ(lruvec);
4084 
4085 	if (mem_cgroup_below_min(NULL, memcg))
4086 		return false;
4087 
4088 	if (!lruvec_is_sizable(lruvec, sc))
4089 		return false;
4090 
4091 	gen = lru_gen_from_seq(evictable_min_seq(min_seq, swappiness));
4092 	birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
4093 
4094 	return time_is_before_jiffies(birth + min_ttl);
4095 }
4096 
4097 /* to protect the working set of the last N jiffies */
4098 static unsigned long lru_gen_min_ttl __read_mostly;
4099 
lru_gen_age_node(struct pglist_data * pgdat,struct scan_control * sc)4100 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
4101 {
4102 	struct mem_cgroup *memcg;
4103 	unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
4104 	bool reclaimable = !min_ttl;
4105 
4106 	VM_WARN_ON_ONCE(!current_is_kswapd());
4107 
4108 	set_initial_priority(pgdat, sc);
4109 
4110 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
4111 	do {
4112 		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4113 
4114 		mem_cgroup_calculate_protection(NULL, memcg);
4115 
4116 		if (!reclaimable)
4117 			reclaimable = lruvec_is_reclaimable(lruvec, sc, min_ttl);
4118 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
4119 
4120 	/*
4121 	 * The main goal is to OOM kill if every generation from all memcgs is
4122 	 * younger than min_ttl. However, another possibility is all memcgs are
4123 	 * either too small or below min.
4124 	 */
4125 	if (!reclaimable && mutex_trylock(&oom_lock)) {
4126 		struct oom_control oc = {
4127 			.gfp_mask = sc->gfp_mask,
4128 		};
4129 
4130 		out_of_memory(&oc);
4131 
4132 		mutex_unlock(&oom_lock);
4133 	}
4134 }
4135 
4136 /******************************************************************************
4137  *                          rmap/PT walk feedback
4138  ******************************************************************************/
4139 
4140 /*
4141  * This function exploits spatial locality when shrink_folio_list() walks the
4142  * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
4143  * the scan was done cacheline efficiently, it adds the PMD entry pointing to
4144  * the PTE table to the Bloom filter. This forms a feedback loop between the
4145  * eviction and the aging.
4146  */
lru_gen_look_around(struct page_vma_mapped_walk * pvmw)4147 bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
4148 {
4149 	int i;
4150 	bool dirty;
4151 	unsigned long start;
4152 	unsigned long end;
4153 	struct lru_gen_mm_walk *walk;
4154 	struct folio *last = NULL;
4155 	int young = 1;
4156 	pte_t *pte = pvmw->pte;
4157 	unsigned long addr = pvmw->address;
4158 	struct vm_area_struct *vma = pvmw->vma;
4159 	struct folio *folio = pfn_folio(pvmw->pfn);
4160 	struct mem_cgroup *memcg = folio_memcg(folio);
4161 	struct pglist_data *pgdat = folio_pgdat(folio);
4162 	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4163 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
4164 	DEFINE_MAX_SEQ(lruvec);
4165 	int gen = lru_gen_from_seq(max_seq);
4166 
4167 	lockdep_assert_held(pvmw->ptl);
4168 	VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
4169 
4170 	if (!ptep_clear_young_notify(vma, addr, pte))
4171 		return false;
4172 
4173 	if (spin_is_contended(pvmw->ptl))
4174 		return true;
4175 
4176 	/* exclude special VMAs containing anon pages from COW */
4177 	if (vma->vm_flags & VM_SPECIAL)
4178 		return true;
4179 
4180 	/* avoid taking the LRU lock under the PTL when possible */
4181 	walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
4182 
4183 	start = max(addr & PMD_MASK, vma->vm_start);
4184 	end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1;
4185 
4186 	if (end - start == PAGE_SIZE)
4187 		return true;
4188 
4189 	if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
4190 		if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
4191 			end = start + MIN_LRU_BATCH * PAGE_SIZE;
4192 		else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2)
4193 			start = end - MIN_LRU_BATCH * PAGE_SIZE;
4194 		else {
4195 			start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2;
4196 			end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2;
4197 		}
4198 	}
4199 
4200 	arch_enter_lazy_mmu_mode();
4201 
4202 	pte -= (addr - start) / PAGE_SIZE;
4203 
4204 	for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
4205 		unsigned long pfn;
4206 		pte_t ptent = ptep_get(pte + i);
4207 
4208 		pfn = get_pte_pfn(ptent, vma, addr, pgdat);
4209 		if (pfn == -1)
4210 			continue;
4211 
4212 		folio = get_pfn_folio(pfn, memcg, pgdat);
4213 		if (!folio)
4214 			continue;
4215 
4216 		if (!ptep_clear_young_notify(vma, addr, pte + i))
4217 			continue;
4218 
4219 		if (last != folio) {
4220 			walk_update_folio(walk, last, gen, dirty);
4221 
4222 			last = folio;
4223 			dirty = false;
4224 		}
4225 
4226 		if (pte_dirty(ptent))
4227 			dirty = true;
4228 
4229 		young++;
4230 	}
4231 
4232 	walk_update_folio(walk, last, gen, dirty);
4233 
4234 	arch_leave_lazy_mmu_mode();
4235 
4236 	/* feedback from rmap walkers to page table walkers */
4237 	if (mm_state && suitable_to_scan(i, young))
4238 		update_bloom_filter(mm_state, max_seq, pvmw->pmd);
4239 
4240 	return true;
4241 }
4242 
4243 /******************************************************************************
4244  *                          memcg LRU
4245  ******************************************************************************/
4246 
4247 /* see the comment on MEMCG_NR_GENS */
4248 enum {
4249 	MEMCG_LRU_NOP,
4250 	MEMCG_LRU_HEAD,
4251 	MEMCG_LRU_TAIL,
4252 	MEMCG_LRU_OLD,
4253 	MEMCG_LRU_YOUNG,
4254 };
4255 
lru_gen_rotate_memcg(struct lruvec * lruvec,int op)4256 static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
4257 {
4258 	int seg;
4259 	int old, new;
4260 	unsigned long flags;
4261 	int bin = get_random_u32_below(MEMCG_NR_BINS);
4262 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4263 
4264 	spin_lock_irqsave(&pgdat->memcg_lru.lock, flags);
4265 
4266 	VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
4267 
4268 	seg = 0;
4269 	new = old = lruvec->lrugen.gen;
4270 
4271 	/* see the comment on MEMCG_NR_GENS */
4272 	if (op == MEMCG_LRU_HEAD)
4273 		seg = MEMCG_LRU_HEAD;
4274 	else if (op == MEMCG_LRU_TAIL)
4275 		seg = MEMCG_LRU_TAIL;
4276 	else if (op == MEMCG_LRU_OLD)
4277 		new = get_memcg_gen(pgdat->memcg_lru.seq);
4278 	else if (op == MEMCG_LRU_YOUNG)
4279 		new = get_memcg_gen(pgdat->memcg_lru.seq + 1);
4280 	else
4281 		VM_WARN_ON_ONCE(true);
4282 
4283 	WRITE_ONCE(lruvec->lrugen.seg, seg);
4284 	WRITE_ONCE(lruvec->lrugen.gen, new);
4285 
4286 	hlist_nulls_del_rcu(&lruvec->lrugen.list);
4287 
4288 	if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD)
4289 		hlist_nulls_add_head_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4290 	else
4291 		hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4292 
4293 	pgdat->memcg_lru.nr_memcgs[old]--;
4294 	pgdat->memcg_lru.nr_memcgs[new]++;
4295 
4296 	if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq))
4297 		WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4298 
4299 	spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags);
4300 }
4301 
4302 #ifdef CONFIG_MEMCG
4303 
lru_gen_online_memcg(struct mem_cgroup * memcg)4304 void lru_gen_online_memcg(struct mem_cgroup *memcg)
4305 {
4306 	int gen;
4307 	int nid;
4308 	int bin = get_random_u32_below(MEMCG_NR_BINS);
4309 
4310 	for_each_node(nid) {
4311 		struct pglist_data *pgdat = NODE_DATA(nid);
4312 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4313 
4314 		spin_lock_irq(&pgdat->memcg_lru.lock);
4315 
4316 		VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
4317 
4318 		gen = get_memcg_gen(pgdat->memcg_lru.seq);
4319 
4320 		lruvec->lrugen.gen = gen;
4321 
4322 		hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]);
4323 		pgdat->memcg_lru.nr_memcgs[gen]++;
4324 
4325 		spin_unlock_irq(&pgdat->memcg_lru.lock);
4326 	}
4327 }
4328 
lru_gen_offline_memcg(struct mem_cgroup * memcg)4329 void lru_gen_offline_memcg(struct mem_cgroup *memcg)
4330 {
4331 	int nid;
4332 
4333 	for_each_node(nid) {
4334 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4335 
4336 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD);
4337 	}
4338 }
4339 
lru_gen_release_memcg(struct mem_cgroup * memcg)4340 void lru_gen_release_memcg(struct mem_cgroup *memcg)
4341 {
4342 	int gen;
4343 	int nid;
4344 
4345 	for_each_node(nid) {
4346 		struct pglist_data *pgdat = NODE_DATA(nid);
4347 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4348 
4349 		spin_lock_irq(&pgdat->memcg_lru.lock);
4350 
4351 		if (hlist_nulls_unhashed(&lruvec->lrugen.list))
4352 			goto unlock;
4353 
4354 		gen = lruvec->lrugen.gen;
4355 
4356 		hlist_nulls_del_init_rcu(&lruvec->lrugen.list);
4357 		pgdat->memcg_lru.nr_memcgs[gen]--;
4358 
4359 		if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))
4360 			WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4361 unlock:
4362 		spin_unlock_irq(&pgdat->memcg_lru.lock);
4363 	}
4364 }
4365 
lru_gen_soft_reclaim(struct mem_cgroup * memcg,int nid)4366 void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
4367 {
4368 	struct lruvec *lruvec = get_lruvec(memcg, nid);
4369 
4370 	/* see the comment on MEMCG_NR_GENS */
4371 	if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_HEAD)
4372 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);
4373 }
4374 
4375 #endif /* CONFIG_MEMCG */
4376 
4377 /******************************************************************************
4378  *                          the eviction
4379  ******************************************************************************/
4380 
sort_folio(struct lruvec * lruvec,struct folio * folio,struct scan_control * sc,int tier_idx)4381 static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
4382 		       int tier_idx)
4383 {
4384 	bool success;
4385 	bool dirty, writeback;
4386 	int gen = folio_lru_gen(folio);
4387 	int type = folio_is_file_lru(folio);
4388 	int zone = folio_zonenum(folio);
4389 	int delta = folio_nr_pages(folio);
4390 	int refs = folio_lru_refs(folio);
4391 	bool workingset = folio_test_workingset(folio);
4392 	int tier = lru_tier_from_refs(refs, workingset);
4393 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4394 
4395 	VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
4396 
4397 	/* unevictable */
4398 	if (!folio_evictable(folio)) {
4399 		success = lru_gen_del_folio(lruvec, folio, true);
4400 		VM_WARN_ON_ONCE_FOLIO(!success, folio);
4401 		folio_set_unevictable(folio);
4402 		lruvec_add_folio(lruvec, folio);
4403 		__count_vm_events(UNEVICTABLE_PGCULLED, delta);
4404 		return true;
4405 	}
4406 
4407 	/* promoted */
4408 	if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
4409 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4410 		return true;
4411 	}
4412 
4413 	/* protected */
4414 	if (tier > tier_idx || refs + workingset == BIT(LRU_REFS_WIDTH) + 1) {
4415 		gen = folio_inc_gen(lruvec, folio, false);
4416 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4417 
4418 		/* don't count the workingset being lazily promoted */
4419 		if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) {
4420 			int hist = lru_hist_from_seq(lrugen->min_seq[type]);
4421 
4422 			WRITE_ONCE(lrugen->protected[hist][type][tier],
4423 				   lrugen->protected[hist][type][tier] + delta);
4424 		}
4425 		return true;
4426 	}
4427 
4428 	/* ineligible */
4429 	if (!folio_test_lru(folio) || zone > sc->reclaim_idx) {
4430 		gen = folio_inc_gen(lruvec, folio, false);
4431 		list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
4432 		return true;
4433 	}
4434 
4435 	dirty = folio_test_dirty(folio);
4436 	writeback = folio_test_writeback(folio);
4437 	if (type == LRU_GEN_FILE && dirty) {
4438 		sc->nr.file_taken += delta;
4439 		if (!writeback)
4440 			sc->nr.unqueued_dirty += delta;
4441 	}
4442 
4443 	/* waiting for writeback */
4444 	if (writeback || (type == LRU_GEN_FILE && dirty)) {
4445 		gen = folio_inc_gen(lruvec, folio, true);
4446 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4447 		return true;
4448 	}
4449 
4450 	return false;
4451 }
4452 
isolate_folio(struct lruvec * lruvec,struct folio * folio,struct scan_control * sc)4453 static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
4454 {
4455 	bool success;
4456 
4457 	/* swap constrained */
4458 	if (!(sc->gfp_mask & __GFP_IO) &&
4459 	    (folio_test_dirty(folio) ||
4460 	     (folio_test_anon(folio) && !folio_test_swapcache(folio))))
4461 		return false;
4462 
4463 	/* raced with release_pages() */
4464 	if (!folio_try_get(folio))
4465 		return false;
4466 
4467 	/* raced with another isolation */
4468 	if (!folio_test_clear_lru(folio)) {
4469 		folio_put(folio);
4470 		return false;
4471 	}
4472 
4473 	/* see the comment on LRU_REFS_FLAGS */
4474 	if (!folio_test_referenced(folio))
4475 		set_mask_bits(&folio->flags, LRU_REFS_MASK, 0);
4476 
4477 	/* for shrink_folio_list() */
4478 	folio_clear_reclaim(folio);
4479 
4480 	success = lru_gen_del_folio(lruvec, folio, true);
4481 	VM_WARN_ON_ONCE_FOLIO(!success, folio);
4482 
4483 	return true;
4484 }
4485 
scan_folios(struct lruvec * lruvec,struct scan_control * sc,int type,int tier,struct list_head * list)4486 static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
4487 		       int type, int tier, struct list_head *list)
4488 {
4489 	int i;
4490 	int gen;
4491 	enum vm_event_item item;
4492 	int sorted = 0;
4493 	int scanned = 0;
4494 	int isolated = 0;
4495 	int skipped = 0;
4496 	int remaining = MAX_LRU_BATCH;
4497 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4498 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4499 
4500 	VM_WARN_ON_ONCE(!list_empty(list));
4501 
4502 	if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
4503 		return 0;
4504 
4505 	gen = lru_gen_from_seq(lrugen->min_seq[type]);
4506 
4507 	for (i = MAX_NR_ZONES; i > 0; i--) {
4508 		LIST_HEAD(moved);
4509 		int skipped_zone = 0;
4510 		int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
4511 		struct list_head *head = &lrugen->folios[gen][type][zone];
4512 
4513 		while (!list_empty(head)) {
4514 			struct folio *folio = lru_to_folio(head);
4515 			int delta = folio_nr_pages(folio);
4516 
4517 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4518 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4519 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4520 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4521 
4522 			scanned += delta;
4523 
4524 			if (sort_folio(lruvec, folio, sc, tier))
4525 				sorted += delta;
4526 			else if (isolate_folio(lruvec, folio, sc)) {
4527 				list_add(&folio->lru, list);
4528 				isolated += delta;
4529 			} else {
4530 				list_move(&folio->lru, &moved);
4531 				skipped_zone += delta;
4532 			}
4533 
4534 			if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
4535 				break;
4536 		}
4537 
4538 		if (skipped_zone) {
4539 			list_splice(&moved, head);
4540 			__count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
4541 			skipped += skipped_zone;
4542 		}
4543 
4544 		if (!remaining || isolated >= MIN_LRU_BATCH)
4545 			break;
4546 	}
4547 
4548 	item = PGSCAN_KSWAPD + reclaimer_offset();
4549 	if (!cgroup_reclaim(sc)) {
4550 		__count_vm_events(item, isolated);
4551 		__count_vm_events(PGREFILL, sorted);
4552 	}
4553 	__count_memcg_events(memcg, item, isolated);
4554 	__count_memcg_events(memcg, PGREFILL, sorted);
4555 	__count_vm_events(PGSCAN_ANON + type, isolated);
4556 	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
4557 				scanned, skipped, isolated,
4558 				type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4559 	if (type == LRU_GEN_FILE)
4560 		sc->nr.file_taken += isolated;
4561 	/*
4562 	 * There might not be eligible folios due to reclaim_idx. Check the
4563 	 * remaining to prevent livelock if it's not making progress.
4564 	 */
4565 	return isolated || !remaining ? scanned : 0;
4566 }
4567 
get_tier_idx(struct lruvec * lruvec,int type)4568 static int get_tier_idx(struct lruvec *lruvec, int type)
4569 {
4570 	int tier;
4571 	struct ctrl_pos sp, pv;
4572 
4573 	/*
4574 	 * To leave a margin for fluctuations, use a larger gain factor (2:3).
4575 	 * This value is chosen because any other tier would have at least twice
4576 	 * as many refaults as the first tier.
4577 	 */
4578 	read_ctrl_pos(lruvec, type, 0, 2, &sp);
4579 	for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4580 		read_ctrl_pos(lruvec, type, tier, 3, &pv);
4581 		if (!positive_ctrl_err(&sp, &pv))
4582 			break;
4583 	}
4584 
4585 	return tier - 1;
4586 }
4587 
get_type_to_scan(struct lruvec * lruvec,int swappiness)4588 static int get_type_to_scan(struct lruvec *lruvec, int swappiness)
4589 {
4590 	struct ctrl_pos sp, pv;
4591 
4592 	if (swappiness <= MIN_SWAPPINESS + 1)
4593 		return LRU_GEN_FILE;
4594 
4595 	if (swappiness >= MAX_SWAPPINESS)
4596 		return LRU_GEN_ANON;
4597 	/*
4598 	 * Compare the sum of all tiers of anon with that of file to determine
4599 	 * which type to scan.
4600 	 */
4601 	read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp);
4602 	read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv);
4603 
4604 	return positive_ctrl_err(&sp, &pv);
4605 }
4606 
isolate_folios(struct lruvec * lruvec,struct scan_control * sc,int swappiness,int * type_scanned,struct list_head * list)4607 static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
4608 			  int *type_scanned, struct list_head *list)
4609 {
4610 	int i;
4611 	int type = get_type_to_scan(lruvec, swappiness);
4612 
4613 	for_each_evictable_type(i, swappiness) {
4614 		int scanned;
4615 		int tier = get_tier_idx(lruvec, type);
4616 
4617 		*type_scanned = type;
4618 
4619 		scanned = scan_folios(lruvec, sc, type, tier, list);
4620 		if (scanned)
4621 			return scanned;
4622 
4623 		type = !type;
4624 	}
4625 
4626 	return 0;
4627 }
4628 
evict_folios(struct lruvec * lruvec,struct scan_control * sc,int swappiness)4629 static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
4630 {
4631 	int type;
4632 	int scanned;
4633 	int reclaimed;
4634 	LIST_HEAD(list);
4635 	LIST_HEAD(clean);
4636 	struct folio *folio;
4637 	struct folio *next;
4638 	enum vm_event_item item;
4639 	struct reclaim_stat stat;
4640 	struct lru_gen_mm_walk *walk;
4641 	bool skip_retry = false;
4642 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4643 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4644 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4645 
4646 	spin_lock_irq(&lruvec->lru_lock);
4647 
4648 	scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
4649 
4650 	scanned += try_to_inc_min_seq(lruvec, swappiness);
4651 
4652 	if (evictable_min_seq(lrugen->min_seq, swappiness) + MIN_NR_GENS > lrugen->max_seq)
4653 		scanned = 0;
4654 
4655 	spin_unlock_irq(&lruvec->lru_lock);
4656 
4657 	if (list_empty(&list))
4658 		return scanned;
4659 retry:
4660 	reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
4661 	sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
4662 	sc->nr_reclaimed += reclaimed;
4663 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
4664 			scanned, reclaimed, &stat, sc->priority,
4665 			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4666 
4667 	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
4668 		DEFINE_MIN_SEQ(lruvec);
4669 
4670 		if (!folio_evictable(folio)) {
4671 			list_del(&folio->lru);
4672 			folio_putback_lru(folio);
4673 			continue;
4674 		}
4675 
4676 		/* retry folios that may have missed folio_rotate_reclaimable() */
4677 		if (!skip_retry && !folio_test_active(folio) && !folio_mapped(folio) &&
4678 		    !folio_test_dirty(folio) && !folio_test_writeback(folio)) {
4679 			list_move(&folio->lru, &clean);
4680 			continue;
4681 		}
4682 
4683 		/* don't add rejected folios to the oldest generation */
4684 		if (lru_gen_folio_seq(lruvec, folio, false) == min_seq[type])
4685 			set_mask_bits(&folio->flags, LRU_REFS_FLAGS, BIT(PG_active));
4686 	}
4687 
4688 	spin_lock_irq(&lruvec->lru_lock);
4689 
4690 	move_folios_to_lru(lruvec, &list);
4691 
4692 	walk = current->reclaim_state->mm_walk;
4693 	if (walk && walk->batched) {
4694 		walk->lruvec = lruvec;
4695 		reset_batch_size(walk);
4696 	}
4697 
4698 	__mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(),
4699 					stat.nr_demoted);
4700 
4701 	item = PGSTEAL_KSWAPD + reclaimer_offset();
4702 	if (!cgroup_reclaim(sc))
4703 		__count_vm_events(item, reclaimed);
4704 	__count_memcg_events(memcg, item, reclaimed);
4705 	__count_vm_events(PGSTEAL_ANON + type, reclaimed);
4706 
4707 	spin_unlock_irq(&lruvec->lru_lock);
4708 
4709 	list_splice_init(&clean, &list);
4710 
4711 	if (!list_empty(&list)) {
4712 		skip_retry = true;
4713 		goto retry;
4714 	}
4715 
4716 	return scanned;
4717 }
4718 
should_run_aging(struct lruvec * lruvec,unsigned long max_seq,int swappiness,unsigned long * nr_to_scan)4719 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
4720 			     int swappiness, unsigned long *nr_to_scan)
4721 {
4722 	int gen, type, zone;
4723 	unsigned long size = 0;
4724 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4725 	DEFINE_MIN_SEQ(lruvec);
4726 
4727 	*nr_to_scan = 0;
4728 	/* have to run aging, since eviction is not possible anymore */
4729 	if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS > max_seq)
4730 		return true;
4731 
4732 	for_each_evictable_type(type, swappiness) {
4733 		unsigned long seq;
4734 
4735 		for (seq = min_seq[type]; seq <= max_seq; seq++) {
4736 			gen = lru_gen_from_seq(seq);
4737 
4738 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
4739 				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4740 		}
4741 	}
4742 
4743 	*nr_to_scan = size;
4744 	/* better to run aging even though eviction is still possible */
4745 	return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq;
4746 }
4747 
4748 /*
4749  * For future optimizations:
4750  * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
4751  *    reclaim.
4752  */
get_nr_to_scan(struct lruvec * lruvec,struct scan_control * sc,int swappiness)4753 static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
4754 {
4755 	bool success;
4756 	unsigned long nr_to_scan;
4757 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4758 	DEFINE_MAX_SEQ(lruvec);
4759 
4760 	if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg))
4761 		return -1;
4762 
4763 	success = should_run_aging(lruvec, max_seq, swappiness, &nr_to_scan);
4764 
4765 	/* try to scrape all its memory if this memcg was deleted */
4766 	if (nr_to_scan && !mem_cgroup_online(memcg))
4767 		return nr_to_scan;
4768 
4769 	/* try to get away with not aging at the default priority */
4770 	if (!success || sc->priority == DEF_PRIORITY)
4771 		return nr_to_scan >> sc->priority;
4772 
4773 	/* stop scanning this lruvec as it's low on cold folios */
4774 	return try_to_inc_max_seq(lruvec, max_seq, swappiness, false) ? -1 : 0;
4775 }
4776 
should_abort_scan(struct lruvec * lruvec,struct scan_control * sc)4777 static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
4778 {
4779 	int i;
4780 	enum zone_watermarks mark;
4781 
4782 	/* don't abort memcg reclaim to ensure fairness */
4783 	if (!root_reclaim(sc))
4784 		return false;
4785 
4786 	if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
4787 		return true;
4788 
4789 	/* check the order to exclude compaction-induced reclaim */
4790 	if (!current_is_kswapd() || sc->order)
4791 		return false;
4792 
4793 	mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ?
4794 	       WMARK_PROMO : WMARK_HIGH;
4795 
4796 	for (i = 0; i <= sc->reclaim_idx; i++) {
4797 		struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
4798 		unsigned long size = wmark_pages(zone, mark) + MIN_LRU_BATCH;
4799 
4800 		if (managed_zone(zone) && !zone_watermark_ok(zone, 0, size, sc->reclaim_idx, 0))
4801 			return false;
4802 	}
4803 
4804 	/* kswapd should abort if all eligible zones are safe */
4805 	return true;
4806 }
4807 
try_to_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)4808 static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4809 {
4810 	long nr_to_scan;
4811 	unsigned long scanned = 0;
4812 	int swappiness = get_swappiness(lruvec, sc);
4813 
4814 	while (true) {
4815 		int delta;
4816 
4817 		nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness);
4818 		if (nr_to_scan <= 0)
4819 			break;
4820 
4821 		delta = evict_folios(lruvec, sc, swappiness);
4822 		if (!delta)
4823 			break;
4824 
4825 		scanned += delta;
4826 		if (scanned >= nr_to_scan)
4827 			break;
4828 
4829 		if (should_abort_scan(lruvec, sc))
4830 			break;
4831 
4832 		cond_resched();
4833 	}
4834 
4835 	/*
4836 	 * If too many file cache in the coldest generation can't be evicted
4837 	 * due to being dirty, wake up the flusher.
4838 	 */
4839 	if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty == sc->nr.file_taken)
4840 		wakeup_flusher_threads(WB_REASON_VMSCAN);
4841 
4842 	/* whether this lruvec should be rotated */
4843 	return nr_to_scan < 0;
4844 }
4845 
shrink_one(struct lruvec * lruvec,struct scan_control * sc)4846 static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
4847 {
4848 	bool success;
4849 	unsigned long scanned = sc->nr_scanned;
4850 	unsigned long reclaimed = sc->nr_reclaimed;
4851 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4852 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4853 
4854 	/* lru_gen_age_node() called mem_cgroup_calculate_protection() */
4855 	if (mem_cgroup_below_min(NULL, memcg))
4856 		return MEMCG_LRU_YOUNG;
4857 
4858 	if (mem_cgroup_below_low(NULL, memcg)) {
4859 		/* see the comment on MEMCG_NR_GENS */
4860 		if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL)
4861 			return MEMCG_LRU_TAIL;
4862 
4863 		memcg_memory_event(memcg, MEMCG_LOW);
4864 	}
4865 
4866 	success = try_to_shrink_lruvec(lruvec, sc);
4867 
4868 	shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority);
4869 
4870 	if (!sc->proactive)
4871 		vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned,
4872 			   sc->nr_reclaimed - reclaimed);
4873 
4874 	flush_reclaim_state(sc);
4875 
4876 	if (success && mem_cgroup_online(memcg))
4877 		return MEMCG_LRU_YOUNG;
4878 
4879 	if (!success && lruvec_is_sizable(lruvec, sc))
4880 		return 0;
4881 
4882 	/* one retry if offlined or too small */
4883 	return READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL ?
4884 	       MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
4885 }
4886 
shrink_many(struct pglist_data * pgdat,struct scan_control * sc)4887 static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
4888 {
4889 	int op;
4890 	int gen;
4891 	int bin;
4892 	int first_bin;
4893 	struct lruvec *lruvec;
4894 	struct lru_gen_folio *lrugen;
4895 	struct mem_cgroup *memcg;
4896 	struct hlist_nulls_node *pos;
4897 
4898 	gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
4899 	bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
4900 restart:
4901 	op = 0;
4902 	memcg = NULL;
4903 
4904 	rcu_read_lock();
4905 
4906 	hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) {
4907 		if (op) {
4908 			lru_gen_rotate_memcg(lruvec, op);
4909 			op = 0;
4910 		}
4911 
4912 		mem_cgroup_put(memcg);
4913 		memcg = NULL;
4914 
4915 		if (gen != READ_ONCE(lrugen->gen))
4916 			continue;
4917 
4918 		lruvec = container_of(lrugen, struct lruvec, lrugen);
4919 		memcg = lruvec_memcg(lruvec);
4920 
4921 		if (!mem_cgroup_tryget(memcg)) {
4922 			lru_gen_release_memcg(memcg);
4923 			memcg = NULL;
4924 			continue;
4925 		}
4926 
4927 		rcu_read_unlock();
4928 
4929 		op = shrink_one(lruvec, sc);
4930 
4931 		rcu_read_lock();
4932 
4933 		if (should_abort_scan(lruvec, sc))
4934 			break;
4935 	}
4936 
4937 	rcu_read_unlock();
4938 
4939 	if (op)
4940 		lru_gen_rotate_memcg(lruvec, op);
4941 
4942 	mem_cgroup_put(memcg);
4943 
4944 	if (!is_a_nulls(pos))
4945 		return;
4946 
4947 	/* restart if raced with lru_gen_rotate_memcg() */
4948 	if (gen != get_nulls_value(pos))
4949 		goto restart;
4950 
4951 	/* try the rest of the bins of the current generation */
4952 	bin = get_memcg_bin(bin + 1);
4953 	if (bin != first_bin)
4954 		goto restart;
4955 }
4956 
lru_gen_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)4957 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4958 {
4959 	struct blk_plug plug;
4960 
4961 	VM_WARN_ON_ONCE(root_reclaim(sc));
4962 	VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap);
4963 
4964 	lru_add_drain();
4965 
4966 	blk_start_plug(&plug);
4967 
4968 	set_mm_walk(NULL, sc->proactive);
4969 
4970 	if (try_to_shrink_lruvec(lruvec, sc))
4971 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);
4972 
4973 	clear_mm_walk();
4974 
4975 	blk_finish_plug(&plug);
4976 }
4977 
lru_gen_shrink_node(struct pglist_data * pgdat,struct scan_control * sc)4978 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
4979 {
4980 	struct blk_plug plug;
4981 	unsigned long reclaimed = sc->nr_reclaimed;
4982 
4983 	VM_WARN_ON_ONCE(!root_reclaim(sc));
4984 
4985 	/*
4986 	 * Unmapped clean folios are already prioritized. Scanning for more of
4987 	 * them is likely futile and can cause high reclaim latency when there
4988 	 * is a large number of memcgs.
4989 	 */
4990 	if (!sc->may_writepage || !sc->may_unmap)
4991 		goto done;
4992 
4993 	lru_add_drain();
4994 
4995 	blk_start_plug(&plug);
4996 
4997 	set_mm_walk(pgdat, sc->proactive);
4998 
4999 	set_initial_priority(pgdat, sc);
5000 
5001 	if (current_is_kswapd())
5002 		sc->nr_reclaimed = 0;
5003 
5004 	if (mem_cgroup_disabled())
5005 		shrink_one(&pgdat->__lruvec, sc);
5006 	else
5007 		shrink_many(pgdat, sc);
5008 
5009 	if (current_is_kswapd())
5010 		sc->nr_reclaimed += reclaimed;
5011 
5012 	clear_mm_walk();
5013 
5014 	blk_finish_plug(&plug);
5015 done:
5016 	if (sc->nr_reclaimed > reclaimed)
5017 		pgdat->kswapd_failures = 0;
5018 }
5019 
5020 /******************************************************************************
5021  *                          state change
5022  ******************************************************************************/
5023 
state_is_valid(struct lruvec * lruvec)5024 static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
5025 {
5026 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5027 
5028 	if (lrugen->enabled) {
5029 		enum lru_list lru;
5030 
5031 		for_each_evictable_lru(lru) {
5032 			if (!list_empty(&lruvec->lists[lru]))
5033 				return false;
5034 		}
5035 	} else {
5036 		int gen, type, zone;
5037 
5038 		for_each_gen_type_zone(gen, type, zone) {
5039 			if (!list_empty(&lrugen->folios[gen][type][zone]))
5040 				return false;
5041 		}
5042 	}
5043 
5044 	return true;
5045 }
5046 
fill_evictable(struct lruvec * lruvec)5047 static bool fill_evictable(struct lruvec *lruvec)
5048 {
5049 	enum lru_list lru;
5050 	int remaining = MAX_LRU_BATCH;
5051 
5052 	for_each_evictable_lru(lru) {
5053 		int type = is_file_lru(lru);
5054 		bool active = is_active_lru(lru);
5055 		struct list_head *head = &lruvec->lists[lru];
5056 
5057 		while (!list_empty(head)) {
5058 			bool success;
5059 			struct folio *folio = lru_to_folio(head);
5060 
5061 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5062 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
5063 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5064 			VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
5065 
5066 			lruvec_del_folio(lruvec, folio);
5067 			success = lru_gen_add_folio(lruvec, folio, false);
5068 			VM_WARN_ON_ONCE(!success);
5069 
5070 			if (!--remaining)
5071 				return false;
5072 		}
5073 	}
5074 
5075 	return true;
5076 }
5077 
drain_evictable(struct lruvec * lruvec)5078 static bool drain_evictable(struct lruvec *lruvec)
5079 {
5080 	int gen, type, zone;
5081 	int remaining = MAX_LRU_BATCH;
5082 
5083 	for_each_gen_type_zone(gen, type, zone) {
5084 		struct list_head *head = &lruvec->lrugen.folios[gen][type][zone];
5085 
5086 		while (!list_empty(head)) {
5087 			bool success;
5088 			struct folio *folio = lru_to_folio(head);
5089 
5090 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5091 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
5092 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5093 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
5094 
5095 			success = lru_gen_del_folio(lruvec, folio, false);
5096 			VM_WARN_ON_ONCE(!success);
5097 			lruvec_add_folio(lruvec, folio);
5098 
5099 			if (!--remaining)
5100 				return false;
5101 		}
5102 	}
5103 
5104 	return true;
5105 }
5106 
lru_gen_change_state(bool enabled)5107 static void lru_gen_change_state(bool enabled)
5108 {
5109 	static DEFINE_MUTEX(state_mutex);
5110 
5111 	struct mem_cgroup *memcg;
5112 
5113 	cgroup_lock();
5114 	cpus_read_lock();
5115 	get_online_mems();
5116 	mutex_lock(&state_mutex);
5117 
5118 	if (enabled == lru_gen_enabled())
5119 		goto unlock;
5120 
5121 	if (enabled)
5122 		static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5123 	else
5124 		static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5125 
5126 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5127 	do {
5128 		int nid;
5129 
5130 		for_each_node(nid) {
5131 			struct lruvec *lruvec = get_lruvec(memcg, nid);
5132 
5133 			spin_lock_irq(&lruvec->lru_lock);
5134 
5135 			VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
5136 			VM_WARN_ON_ONCE(!state_is_valid(lruvec));
5137 
5138 			lruvec->lrugen.enabled = enabled;
5139 
5140 			while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
5141 				spin_unlock_irq(&lruvec->lru_lock);
5142 				cond_resched();
5143 				spin_lock_irq(&lruvec->lru_lock);
5144 			}
5145 
5146 			spin_unlock_irq(&lruvec->lru_lock);
5147 		}
5148 
5149 		cond_resched();
5150 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5151 unlock:
5152 	mutex_unlock(&state_mutex);
5153 	put_online_mems();
5154 	cpus_read_unlock();
5155 	cgroup_unlock();
5156 }
5157 
5158 /******************************************************************************
5159  *                          sysfs interface
5160  ******************************************************************************/
5161 
min_ttl_ms_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)5162 static ssize_t min_ttl_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5163 {
5164 	return sysfs_emit(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
5165 }
5166 
5167 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
min_ttl_ms_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t len)5168 static ssize_t min_ttl_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
5169 				const char *buf, size_t len)
5170 {
5171 	unsigned int msecs;
5172 
5173 	if (kstrtouint(buf, 0, &msecs))
5174 		return -EINVAL;
5175 
5176 	WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
5177 
5178 	return len;
5179 }
5180 
5181 static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR_RW(min_ttl_ms);
5182 
enabled_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)5183 static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5184 {
5185 	unsigned int caps = 0;
5186 
5187 	if (get_cap(LRU_GEN_CORE))
5188 		caps |= BIT(LRU_GEN_CORE);
5189 
5190 	if (should_walk_mmu())
5191 		caps |= BIT(LRU_GEN_MM_WALK);
5192 
5193 	if (should_clear_pmd_young())
5194 		caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
5195 
5196 	return sysfs_emit(buf, "0x%04x\n", caps);
5197 }
5198 
5199 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
enabled_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t len)5200 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
5201 			     const char *buf, size_t len)
5202 {
5203 	int i;
5204 	unsigned int caps;
5205 
5206 	if (tolower(*buf) == 'n')
5207 		caps = 0;
5208 	else if (tolower(*buf) == 'y')
5209 		caps = -1;
5210 	else if (kstrtouint(buf, 0, &caps))
5211 		return -EINVAL;
5212 
5213 	for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
5214 		bool enabled = caps & BIT(i);
5215 
5216 		if (i == LRU_GEN_CORE)
5217 			lru_gen_change_state(enabled);
5218 		else if (enabled)
5219 			static_branch_enable(&lru_gen_caps[i]);
5220 		else
5221 			static_branch_disable(&lru_gen_caps[i]);
5222 	}
5223 
5224 	return len;
5225 }
5226 
5227 static struct kobj_attribute lru_gen_enabled_attr = __ATTR_RW(enabled);
5228 
5229 static struct attribute *lru_gen_attrs[] = {
5230 	&lru_gen_min_ttl_attr.attr,
5231 	&lru_gen_enabled_attr.attr,
5232 	NULL
5233 };
5234 
5235 static const struct attribute_group lru_gen_attr_group = {
5236 	.name = "lru_gen",
5237 	.attrs = lru_gen_attrs,
5238 };
5239 
5240 /******************************************************************************
5241  *                          debugfs interface
5242  ******************************************************************************/
5243 
lru_gen_seq_start(struct seq_file * m,loff_t * pos)5244 static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
5245 {
5246 	struct mem_cgroup *memcg;
5247 	loff_t nr_to_skip = *pos;
5248 
5249 	m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
5250 	if (!m->private)
5251 		return ERR_PTR(-ENOMEM);
5252 
5253 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5254 	do {
5255 		int nid;
5256 
5257 		for_each_node_state(nid, N_MEMORY) {
5258 			if (!nr_to_skip--)
5259 				return get_lruvec(memcg, nid);
5260 		}
5261 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5262 
5263 	return NULL;
5264 }
5265 
lru_gen_seq_stop(struct seq_file * m,void * v)5266 static void lru_gen_seq_stop(struct seq_file *m, void *v)
5267 {
5268 	if (!IS_ERR_OR_NULL(v))
5269 		mem_cgroup_iter_break(NULL, lruvec_memcg(v));
5270 
5271 	kvfree(m->private);
5272 	m->private = NULL;
5273 }
5274 
lru_gen_seq_next(struct seq_file * m,void * v,loff_t * pos)5275 static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
5276 {
5277 	int nid = lruvec_pgdat(v)->node_id;
5278 	struct mem_cgroup *memcg = lruvec_memcg(v);
5279 
5280 	++*pos;
5281 
5282 	nid = next_memory_node(nid);
5283 	if (nid == MAX_NUMNODES) {
5284 		memcg = mem_cgroup_iter(NULL, memcg, NULL);
5285 		if (!memcg)
5286 			return NULL;
5287 
5288 		nid = first_memory_node;
5289 	}
5290 
5291 	return get_lruvec(memcg, nid);
5292 }
5293 
lru_gen_seq_show_full(struct seq_file * m,struct lruvec * lruvec,unsigned long max_seq,unsigned long * min_seq,unsigned long seq)5294 static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
5295 				  unsigned long max_seq, unsigned long *min_seq,
5296 				  unsigned long seq)
5297 {
5298 	int i;
5299 	int type, tier;
5300 	int hist = lru_hist_from_seq(seq);
5301 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5302 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5303 
5304 	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
5305 		seq_printf(m, "            %10d", tier);
5306 		for (type = 0; type < ANON_AND_FILE; type++) {
5307 			const char *s = "xxx";
5308 			unsigned long n[3] = {};
5309 
5310 			if (seq == max_seq) {
5311 				s = "RTx";
5312 				n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
5313 				n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
5314 			} else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
5315 				s = "rep";
5316 				n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
5317 				n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
5318 				n[2] = READ_ONCE(lrugen->protected[hist][type][tier]);
5319 			}
5320 
5321 			for (i = 0; i < 3; i++)
5322 				seq_printf(m, " %10lu%c", n[i], s[i]);
5323 		}
5324 		seq_putc(m, '\n');
5325 	}
5326 
5327 	if (!mm_state)
5328 		return;
5329 
5330 	seq_puts(m, "                      ");
5331 	for (i = 0; i < NR_MM_STATS; i++) {
5332 		const char *s = "xxxx";
5333 		unsigned long n = 0;
5334 
5335 		if (seq == max_seq && NR_HIST_GENS == 1) {
5336 			s = "TYFA";
5337 			n = READ_ONCE(mm_state->stats[hist][i]);
5338 		} else if (seq != max_seq && NR_HIST_GENS > 1) {
5339 			s = "tyfa";
5340 			n = READ_ONCE(mm_state->stats[hist][i]);
5341 		}
5342 
5343 		seq_printf(m, " %10lu%c", n, s[i]);
5344 	}
5345 	seq_putc(m, '\n');
5346 }
5347 
5348 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
lru_gen_seq_show(struct seq_file * m,void * v)5349 static int lru_gen_seq_show(struct seq_file *m, void *v)
5350 {
5351 	unsigned long seq;
5352 	bool full = !debugfs_real_fops(m->file)->write;
5353 	struct lruvec *lruvec = v;
5354 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5355 	int nid = lruvec_pgdat(lruvec)->node_id;
5356 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5357 	DEFINE_MAX_SEQ(lruvec);
5358 	DEFINE_MIN_SEQ(lruvec);
5359 
5360 	if (nid == first_memory_node) {
5361 		const char *path = memcg ? m->private : "";
5362 
5363 #ifdef CONFIG_MEMCG
5364 		if (memcg)
5365 			cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
5366 #endif
5367 		seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
5368 	}
5369 
5370 	seq_printf(m, " node %5d\n", nid);
5371 
5372 	if (!full)
5373 		seq = evictable_min_seq(min_seq, MAX_SWAPPINESS / 2);
5374 	else if (max_seq >= MAX_NR_GENS)
5375 		seq = max_seq - MAX_NR_GENS + 1;
5376 	else
5377 		seq = 0;
5378 
5379 	for (; seq <= max_seq; seq++) {
5380 		int type, zone;
5381 		int gen = lru_gen_from_seq(seq);
5382 		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
5383 
5384 		seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
5385 
5386 		for (type = 0; type < ANON_AND_FILE; type++) {
5387 			unsigned long size = 0;
5388 			char mark = full && seq < min_seq[type] ? 'x' : ' ';
5389 
5390 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
5391 				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
5392 
5393 			seq_printf(m, " %10lu%c", size, mark);
5394 		}
5395 
5396 		seq_putc(m, '\n');
5397 
5398 		if (full)
5399 			lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
5400 	}
5401 
5402 	return 0;
5403 }
5404 
5405 static const struct seq_operations lru_gen_seq_ops = {
5406 	.start = lru_gen_seq_start,
5407 	.stop = lru_gen_seq_stop,
5408 	.next = lru_gen_seq_next,
5409 	.show = lru_gen_seq_show,
5410 };
5411 
run_aging(struct lruvec * lruvec,unsigned long seq,int swappiness,bool force_scan)5412 static int run_aging(struct lruvec *lruvec, unsigned long seq,
5413 		     int swappiness, bool force_scan)
5414 {
5415 	DEFINE_MAX_SEQ(lruvec);
5416 
5417 	if (seq > max_seq)
5418 		return -EINVAL;
5419 
5420 	return try_to_inc_max_seq(lruvec, max_seq, swappiness, force_scan) ? 0 : -EEXIST;
5421 }
5422 
run_eviction(struct lruvec * lruvec,unsigned long seq,struct scan_control * sc,int swappiness,unsigned long nr_to_reclaim)5423 static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5424 			int swappiness, unsigned long nr_to_reclaim)
5425 {
5426 	DEFINE_MAX_SEQ(lruvec);
5427 
5428 	if (seq + MIN_NR_GENS > max_seq)
5429 		return -EINVAL;
5430 
5431 	sc->nr_reclaimed = 0;
5432 
5433 	while (!signal_pending(current)) {
5434 		DEFINE_MIN_SEQ(lruvec);
5435 
5436 		if (seq < evictable_min_seq(min_seq, swappiness))
5437 			return 0;
5438 
5439 		if (sc->nr_reclaimed >= nr_to_reclaim)
5440 			return 0;
5441 
5442 		if (!evict_folios(lruvec, sc, swappiness))
5443 			return 0;
5444 
5445 		cond_resched();
5446 	}
5447 
5448 	return -EINTR;
5449 }
5450 
run_cmd(char cmd,int memcg_id,int nid,unsigned long seq,struct scan_control * sc,int swappiness,unsigned long opt)5451 static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
5452 		   struct scan_control *sc, int swappiness, unsigned long opt)
5453 {
5454 	struct lruvec *lruvec;
5455 	int err = -EINVAL;
5456 	struct mem_cgroup *memcg = NULL;
5457 
5458 	if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
5459 		return -EINVAL;
5460 
5461 	if (!mem_cgroup_disabled()) {
5462 		rcu_read_lock();
5463 
5464 		memcg = mem_cgroup_from_id(memcg_id);
5465 		if (!mem_cgroup_tryget(memcg))
5466 			memcg = NULL;
5467 
5468 		rcu_read_unlock();
5469 
5470 		if (!memcg)
5471 			return -EINVAL;
5472 	}
5473 
5474 	if (memcg_id != mem_cgroup_id(memcg))
5475 		goto done;
5476 
5477 	lruvec = get_lruvec(memcg, nid);
5478 
5479 	if (swappiness < MIN_SWAPPINESS)
5480 		swappiness = get_swappiness(lruvec, sc);
5481 	else if (swappiness > MAX_SWAPPINESS + 1)
5482 		goto done;
5483 
5484 	switch (cmd) {
5485 	case '+':
5486 		err = run_aging(lruvec, seq, swappiness, opt);
5487 		break;
5488 	case '-':
5489 		err = run_eviction(lruvec, seq, sc, swappiness, opt);
5490 		break;
5491 	}
5492 done:
5493 	mem_cgroup_put(memcg);
5494 
5495 	return err;
5496 }
5497 
5498 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
lru_gen_seq_write(struct file * file,const char __user * src,size_t len,loff_t * pos)5499 static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
5500 				 size_t len, loff_t *pos)
5501 {
5502 	void *buf;
5503 	char *cur, *next;
5504 	unsigned int flags;
5505 	struct blk_plug plug;
5506 	int err = -EINVAL;
5507 	struct scan_control sc = {
5508 		.may_writepage = true,
5509 		.may_unmap = true,
5510 		.may_swap = true,
5511 		.reclaim_idx = MAX_NR_ZONES - 1,
5512 		.gfp_mask = GFP_KERNEL,
5513 	};
5514 
5515 	buf = kvmalloc(len + 1, GFP_KERNEL);
5516 	if (!buf)
5517 		return -ENOMEM;
5518 
5519 	if (copy_from_user(buf, src, len)) {
5520 		kvfree(buf);
5521 		return -EFAULT;
5522 	}
5523 
5524 	set_task_reclaim_state(current, &sc.reclaim_state);
5525 	flags = memalloc_noreclaim_save();
5526 	blk_start_plug(&plug);
5527 	if (!set_mm_walk(NULL, true)) {
5528 		err = -ENOMEM;
5529 		goto done;
5530 	}
5531 
5532 	next = buf;
5533 	next[len] = '\0';
5534 
5535 	while ((cur = strsep(&next, ",;\n"))) {
5536 		int n;
5537 		int end;
5538 		char cmd;
5539 		unsigned int memcg_id;
5540 		unsigned int nid;
5541 		unsigned long seq;
5542 		unsigned int swappiness = -1;
5543 		unsigned long opt = -1;
5544 
5545 		cur = skip_spaces(cur);
5546 		if (!*cur)
5547 			continue;
5548 
5549 		n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
5550 			   &seq, &end, &swappiness, &end, &opt, &end);
5551 		if (n < 4 || cur[end]) {
5552 			err = -EINVAL;
5553 			break;
5554 		}
5555 
5556 		err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
5557 		if (err)
5558 			break;
5559 	}
5560 done:
5561 	clear_mm_walk();
5562 	blk_finish_plug(&plug);
5563 	memalloc_noreclaim_restore(flags);
5564 	set_task_reclaim_state(current, NULL);
5565 
5566 	kvfree(buf);
5567 
5568 	return err ? : len;
5569 }
5570 
lru_gen_seq_open(struct inode * inode,struct file * file)5571 static int lru_gen_seq_open(struct inode *inode, struct file *file)
5572 {
5573 	return seq_open(file, &lru_gen_seq_ops);
5574 }
5575 
5576 static const struct file_operations lru_gen_rw_fops = {
5577 	.open = lru_gen_seq_open,
5578 	.read = seq_read,
5579 	.write = lru_gen_seq_write,
5580 	.llseek = seq_lseek,
5581 	.release = seq_release,
5582 };
5583 
5584 static const struct file_operations lru_gen_ro_fops = {
5585 	.open = lru_gen_seq_open,
5586 	.read = seq_read,
5587 	.llseek = seq_lseek,
5588 	.release = seq_release,
5589 };
5590 
5591 /******************************************************************************
5592  *                          initialization
5593  ******************************************************************************/
5594 
lru_gen_init_pgdat(struct pglist_data * pgdat)5595 void lru_gen_init_pgdat(struct pglist_data *pgdat)
5596 {
5597 	int i, j;
5598 
5599 	spin_lock_init(&pgdat->memcg_lru.lock);
5600 
5601 	for (i = 0; i < MEMCG_NR_GENS; i++) {
5602 		for (j = 0; j < MEMCG_NR_BINS; j++)
5603 			INIT_HLIST_NULLS_HEAD(&pgdat->memcg_lru.fifo[i][j], i);
5604 	}
5605 }
5606 
lru_gen_init_lruvec(struct lruvec * lruvec)5607 void lru_gen_init_lruvec(struct lruvec *lruvec)
5608 {
5609 	int i;
5610 	int gen, type, zone;
5611 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5612 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5613 
5614 	lrugen->max_seq = MIN_NR_GENS + 1;
5615 	lrugen->enabled = lru_gen_enabled();
5616 
5617 	for (i = 0; i <= MIN_NR_GENS + 1; i++)
5618 		lrugen->timestamps[i] = jiffies;
5619 
5620 	for_each_gen_type_zone(gen, type, zone)
5621 		INIT_LIST_HEAD(&lrugen->folios[gen][type][zone]);
5622 
5623 	if (mm_state)
5624 		mm_state->seq = MIN_NR_GENS;
5625 }
5626 
5627 #ifdef CONFIG_MEMCG
5628 
lru_gen_init_memcg(struct mem_cgroup * memcg)5629 void lru_gen_init_memcg(struct mem_cgroup *memcg)
5630 {
5631 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5632 
5633 	if (!mm_list)
5634 		return;
5635 
5636 	INIT_LIST_HEAD(&mm_list->fifo);
5637 	spin_lock_init(&mm_list->lock);
5638 }
5639 
lru_gen_exit_memcg(struct mem_cgroup * memcg)5640 void lru_gen_exit_memcg(struct mem_cgroup *memcg)
5641 {
5642 	int i;
5643 	int nid;
5644 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5645 
5646 	VM_WARN_ON_ONCE(mm_list && !list_empty(&mm_list->fifo));
5647 
5648 	for_each_node(nid) {
5649 		struct lruvec *lruvec = get_lruvec(memcg, nid);
5650 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5651 
5652 		VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
5653 					   sizeof(lruvec->lrugen.nr_pages)));
5654 
5655 		lruvec->lrugen.list.next = LIST_POISON1;
5656 
5657 		if (!mm_state)
5658 			continue;
5659 
5660 		for (i = 0; i < NR_BLOOM_FILTERS; i++) {
5661 			bitmap_free(mm_state->filters[i]);
5662 			mm_state->filters[i] = NULL;
5663 		}
5664 	}
5665 }
5666 
5667 #endif /* CONFIG_MEMCG */
5668 
init_lru_gen(void)5669 static int __init init_lru_gen(void)
5670 {
5671 	BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
5672 	BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
5673 
5674 	if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
5675 		pr_err("lru_gen: failed to create sysfs group\n");
5676 
5677 	debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
5678 	debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
5679 
5680 	return 0;
5681 };
5682 late_initcall(init_lru_gen);
5683 
5684 #else /* !CONFIG_LRU_GEN */
5685 
lru_gen_age_node(struct pglist_data * pgdat,struct scan_control * sc)5686 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
5687 {
5688 	BUILD_BUG();
5689 }
5690 
lru_gen_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)5691 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5692 {
5693 	BUILD_BUG();
5694 }
5695 
lru_gen_shrink_node(struct pglist_data * pgdat,struct scan_control * sc)5696 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
5697 {
5698 	BUILD_BUG();
5699 }
5700 
5701 #endif /* CONFIG_LRU_GEN */
5702 
shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)5703 static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5704 {
5705 	unsigned long nr[NR_LRU_LISTS];
5706 	unsigned long targets[NR_LRU_LISTS];
5707 	unsigned long nr_to_scan;
5708 	enum lru_list lru;
5709 	unsigned long nr_reclaimed = 0;
5710 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
5711 	bool proportional_reclaim;
5712 	struct blk_plug plug;
5713 
5714 	if (lru_gen_enabled() && !root_reclaim(sc)) {
5715 		lru_gen_shrink_lruvec(lruvec, sc);
5716 		return;
5717 	}
5718 
5719 	get_scan_count(lruvec, sc, nr);
5720 
5721 	/* Record the original scan target for proportional adjustments later */
5722 	memcpy(targets, nr, sizeof(nr));
5723 
5724 	/*
5725 	 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
5726 	 * event that can occur when there is little memory pressure e.g.
5727 	 * multiple streaming readers/writers. Hence, we do not abort scanning
5728 	 * when the requested number of pages are reclaimed when scanning at
5729 	 * DEF_PRIORITY on the assumption that the fact we are direct
5730 	 * reclaiming implies that kswapd is not keeping up and it is best to
5731 	 * do a batch of work at once. For memcg reclaim one check is made to
5732 	 * abort proportional reclaim if either the file or anon lru has already
5733 	 * dropped to zero at the first pass.
5734 	 */
5735 	proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
5736 				sc->priority == DEF_PRIORITY);
5737 
5738 	blk_start_plug(&plug);
5739 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
5740 					nr[LRU_INACTIVE_FILE]) {
5741 		unsigned long nr_anon, nr_file, percentage;
5742 		unsigned long nr_scanned;
5743 
5744 		for_each_evictable_lru(lru) {
5745 			if (nr[lru]) {
5746 				nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
5747 				nr[lru] -= nr_to_scan;
5748 
5749 				nr_reclaimed += shrink_list(lru, nr_to_scan,
5750 							    lruvec, sc);
5751 			}
5752 		}
5753 
5754 		cond_resched();
5755 
5756 		if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
5757 			continue;
5758 
5759 		/*
5760 		 * For kswapd and memcg, reclaim at least the number of pages
5761 		 * requested. Ensure that the anon and file LRUs are scanned
5762 		 * proportionally what was requested by get_scan_count(). We
5763 		 * stop reclaiming one LRU and reduce the amount scanning
5764 		 * proportional to the original scan target.
5765 		 */
5766 		nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
5767 		nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
5768 
5769 		/*
5770 		 * It's just vindictive to attack the larger once the smaller
5771 		 * has gone to zero.  And given the way we stop scanning the
5772 		 * smaller below, this makes sure that we only make one nudge
5773 		 * towards proportionality once we've got nr_to_reclaim.
5774 		 */
5775 		if (!nr_file || !nr_anon)
5776 			break;
5777 
5778 		if (nr_file > nr_anon) {
5779 			unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
5780 						targets[LRU_ACTIVE_ANON] + 1;
5781 			lru = LRU_BASE;
5782 			percentage = nr_anon * 100 / scan_target;
5783 		} else {
5784 			unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
5785 						targets[LRU_ACTIVE_FILE] + 1;
5786 			lru = LRU_FILE;
5787 			percentage = nr_file * 100 / scan_target;
5788 		}
5789 
5790 		/* Stop scanning the smaller of the LRU */
5791 		nr[lru] = 0;
5792 		nr[lru + LRU_ACTIVE] = 0;
5793 
5794 		/*
5795 		 * Recalculate the other LRU scan count based on its original
5796 		 * scan target and the percentage scanning already complete
5797 		 */
5798 		lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
5799 		nr_scanned = targets[lru] - nr[lru];
5800 		nr[lru] = targets[lru] * (100 - percentage) / 100;
5801 		nr[lru] -= min(nr[lru], nr_scanned);
5802 
5803 		lru += LRU_ACTIVE;
5804 		nr_scanned = targets[lru] - nr[lru];
5805 		nr[lru] = targets[lru] * (100 - percentage) / 100;
5806 		nr[lru] -= min(nr[lru], nr_scanned);
5807 	}
5808 	blk_finish_plug(&plug);
5809 	sc->nr_reclaimed += nr_reclaimed;
5810 
5811 	/*
5812 	 * Even if we did not try to evict anon pages at all, we want to
5813 	 * rebalance the anon lru active/inactive ratio.
5814 	 */
5815 	if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
5816 	    inactive_is_low(lruvec, LRU_INACTIVE_ANON))
5817 		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
5818 				   sc, LRU_ACTIVE_ANON);
5819 }
5820 
5821 /* Use reclaim/compaction for costly allocs or under memory pressure */
in_reclaim_compaction(struct scan_control * sc)5822 static bool in_reclaim_compaction(struct scan_control *sc)
5823 {
5824 	if (gfp_compaction_allowed(sc->gfp_mask) && sc->order &&
5825 			(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
5826 			 sc->priority < DEF_PRIORITY - 2))
5827 		return true;
5828 
5829 	return false;
5830 }
5831 
5832 /*
5833  * Reclaim/compaction is used for high-order allocation requests. It reclaims
5834  * order-0 pages before compacting the zone. should_continue_reclaim() returns
5835  * true if more pages should be reclaimed such that when the page allocator
5836  * calls try_to_compact_pages() that it will have enough free pages to succeed.
5837  * It will give up earlier than that if there is difficulty reclaiming pages.
5838  */
should_continue_reclaim(struct pglist_data * pgdat,unsigned long nr_reclaimed,struct scan_control * sc)5839 static inline bool should_continue_reclaim(struct pglist_data *pgdat,
5840 					unsigned long nr_reclaimed,
5841 					struct scan_control *sc)
5842 {
5843 	unsigned long pages_for_compaction;
5844 	unsigned long inactive_lru_pages;
5845 	int z;
5846 
5847 	/* If not in reclaim/compaction mode, stop */
5848 	if (!in_reclaim_compaction(sc))
5849 		return false;
5850 
5851 	/*
5852 	 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
5853 	 * number of pages that were scanned. This will return to the caller
5854 	 * with the risk reclaim/compaction and the resulting allocation attempt
5855 	 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
5856 	 * allocations through requiring that the full LRU list has been scanned
5857 	 * first, by assuming that zero delta of sc->nr_scanned means full LRU
5858 	 * scan, but that approximation was wrong, and there were corner cases
5859 	 * where always a non-zero amount of pages were scanned.
5860 	 */
5861 	if (!nr_reclaimed)
5862 		return false;
5863 
5864 	/* If compaction would go ahead or the allocation would succeed, stop */
5865 	for (z = 0; z <= sc->reclaim_idx; z++) {
5866 		struct zone *zone = &pgdat->node_zones[z];
5867 		if (!managed_zone(zone))
5868 			continue;
5869 
5870 		/* Allocation can already succeed, nothing to do */
5871 		if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
5872 				      sc->reclaim_idx, 0))
5873 			return false;
5874 
5875 		if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
5876 			return false;
5877 	}
5878 
5879 	/*
5880 	 * If we have not reclaimed enough pages for compaction and the
5881 	 * inactive lists are large enough, continue reclaiming
5882 	 */
5883 	pages_for_compaction = compact_gap(sc->order);
5884 	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
5885 	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
5886 		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
5887 
5888 	return inactive_lru_pages > pages_for_compaction;
5889 }
5890 
shrink_node_memcgs(pg_data_t * pgdat,struct scan_control * sc)5891 static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
5892 {
5893 	struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
5894 	struct mem_cgroup_reclaim_cookie reclaim = {
5895 		.pgdat = pgdat,
5896 	};
5897 	struct mem_cgroup_reclaim_cookie *partial = &reclaim;
5898 	struct mem_cgroup *memcg;
5899 
5900 	/*
5901 	 * In most cases, direct reclaimers can do partial walks
5902 	 * through the cgroup tree, using an iterator state that
5903 	 * persists across invocations. This strikes a balance between
5904 	 * fairness and allocation latency.
5905 	 *
5906 	 * For kswapd, reliable forward progress is more important
5907 	 * than a quick return to idle. Always do full walks.
5908 	 */
5909 	if (current_is_kswapd() || sc->memcg_full_walk)
5910 		partial = NULL;
5911 
5912 	memcg = mem_cgroup_iter(target_memcg, NULL, partial);
5913 	do {
5914 		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
5915 		unsigned long reclaimed;
5916 		unsigned long scanned;
5917 
5918 		/*
5919 		 * This loop can become CPU-bound when target memcgs
5920 		 * aren't eligible for reclaim - either because they
5921 		 * don't have any reclaimable pages, or because their
5922 		 * memory is explicitly protected. Avoid soft lockups.
5923 		 */
5924 		cond_resched();
5925 
5926 		mem_cgroup_calculate_protection(target_memcg, memcg);
5927 
5928 		if (mem_cgroup_below_min(target_memcg, memcg)) {
5929 			/*
5930 			 * Hard protection.
5931 			 * If there is no reclaimable memory, OOM.
5932 			 */
5933 			continue;
5934 		} else if (mem_cgroup_below_low(target_memcg, memcg)) {
5935 			/*
5936 			 * Soft protection.
5937 			 * Respect the protection only as long as
5938 			 * there is an unprotected supply
5939 			 * of reclaimable memory from other cgroups.
5940 			 */
5941 			if (!sc->memcg_low_reclaim) {
5942 				sc->memcg_low_skipped = 1;
5943 				continue;
5944 			}
5945 			memcg_memory_event(memcg, MEMCG_LOW);
5946 		}
5947 
5948 		reclaimed = sc->nr_reclaimed;
5949 		scanned = sc->nr_scanned;
5950 
5951 		shrink_lruvec(lruvec, sc);
5952 
5953 		shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
5954 			    sc->priority);
5955 
5956 		/* Record the group's reclaim efficiency */
5957 		if (!sc->proactive)
5958 			vmpressure(sc->gfp_mask, memcg, false,
5959 				   sc->nr_scanned - scanned,
5960 				   sc->nr_reclaimed - reclaimed);
5961 
5962 		/* If partial walks are allowed, bail once goal is reached */
5963 		if (partial && sc->nr_reclaimed >= sc->nr_to_reclaim) {
5964 			mem_cgroup_iter_break(target_memcg, memcg);
5965 			break;
5966 		}
5967 	} while ((memcg = mem_cgroup_iter(target_memcg, memcg, partial)));
5968 }
5969 
shrink_node(pg_data_t * pgdat,struct scan_control * sc)5970 static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
5971 {
5972 	unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed;
5973 	struct lruvec *target_lruvec;
5974 	bool reclaimable = false;
5975 
5976 	if (lru_gen_enabled() && root_reclaim(sc)) {
5977 		memset(&sc->nr, 0, sizeof(sc->nr));
5978 		lru_gen_shrink_node(pgdat, sc);
5979 		return;
5980 	}
5981 
5982 	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
5983 
5984 again:
5985 	memset(&sc->nr, 0, sizeof(sc->nr));
5986 
5987 	nr_reclaimed = sc->nr_reclaimed;
5988 	nr_scanned = sc->nr_scanned;
5989 
5990 	prepare_scan_control(pgdat, sc);
5991 
5992 	shrink_node_memcgs(pgdat, sc);
5993 
5994 	flush_reclaim_state(sc);
5995 
5996 	nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed;
5997 
5998 	/* Record the subtree's reclaim efficiency */
5999 	if (!sc->proactive)
6000 		vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
6001 			   sc->nr_scanned - nr_scanned, nr_node_reclaimed);
6002 
6003 	if (nr_node_reclaimed)
6004 		reclaimable = true;
6005 
6006 	if (current_is_kswapd()) {
6007 		/*
6008 		 * If reclaim is isolating dirty pages under writeback,
6009 		 * it implies that the long-lived page allocation rate
6010 		 * is exceeding the page laundering rate. Either the
6011 		 * global limits are not being effective at throttling
6012 		 * processes due to the page distribution throughout
6013 		 * zones or there is heavy usage of a slow backing
6014 		 * device. The only option is to throttle from reclaim
6015 		 * context which is not ideal as there is no guarantee
6016 		 * the dirtying process is throttled in the same way
6017 		 * balance_dirty_pages() manages.
6018 		 *
6019 		 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
6020 		 * count the number of pages under pages flagged for
6021 		 * immediate reclaim and stall if any are encountered
6022 		 * in the nr_immediate check below.
6023 		 */
6024 		if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
6025 			set_bit(PGDAT_WRITEBACK, &pgdat->flags);
6026 
6027 		/* Allow kswapd to start writing pages during reclaim.*/
6028 		if (sc->nr.unqueued_dirty &&
6029 			sc->nr.unqueued_dirty == sc->nr.file_taken)
6030 			set_bit(PGDAT_DIRTY, &pgdat->flags);
6031 
6032 		/*
6033 		 * If kswapd scans pages marked for immediate
6034 		 * reclaim and under writeback (nr_immediate), it
6035 		 * implies that pages are cycling through the LRU
6036 		 * faster than they are written so forcibly stall
6037 		 * until some pages complete writeback.
6038 		 */
6039 		if (sc->nr.immediate)
6040 			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
6041 	}
6042 
6043 	/*
6044 	 * Tag a node/memcg as congested if all the dirty pages were marked
6045 	 * for writeback and immediate reclaim (counted in nr.congested).
6046 	 *
6047 	 * Legacy memcg will stall in page writeback so avoid forcibly
6048 	 * stalling in reclaim_throttle().
6049 	 */
6050 	if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) {
6051 		if (cgroup_reclaim(sc) && writeback_throttling_sane(sc))
6052 			set_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags);
6053 
6054 		if (current_is_kswapd())
6055 			set_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags);
6056 	}
6057 
6058 	/*
6059 	 * Stall direct reclaim for IO completions if the lruvec is
6060 	 * node is congested. Allow kswapd to continue until it
6061 	 * starts encountering unqueued dirty pages or cycling through
6062 	 * the LRU too quickly.
6063 	 */
6064 	if (!current_is_kswapd() && current_may_throttle() &&
6065 	    !sc->hibernation_mode &&
6066 	    (test_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags) ||
6067 	     test_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags)))
6068 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
6069 
6070 	if (should_continue_reclaim(pgdat, nr_node_reclaimed, sc))
6071 		goto again;
6072 
6073 	/*
6074 	 * Kswapd gives up on balancing particular nodes after too
6075 	 * many failures to reclaim anything from them and goes to
6076 	 * sleep. On reclaim progress, reset the failure counter. A
6077 	 * successful direct reclaim run will revive a dormant kswapd.
6078 	 */
6079 	if (reclaimable)
6080 		pgdat->kswapd_failures = 0;
6081 	else if (sc->cache_trim_mode)
6082 		sc->cache_trim_mode_failed = 1;
6083 }
6084 
6085 /*
6086  * Returns true if compaction should go ahead for a costly-order request, or
6087  * the allocation would already succeed without compaction. Return false if we
6088  * should reclaim first.
6089  */
compaction_ready(struct zone * zone,struct scan_control * sc)6090 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
6091 {
6092 	unsigned long watermark;
6093 
6094 	if (!gfp_compaction_allowed(sc->gfp_mask))
6095 		return false;
6096 
6097 	/* Allocation can already succeed, nothing to do */
6098 	if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
6099 			      sc->reclaim_idx, 0))
6100 		return true;
6101 
6102 	/* Compaction cannot yet proceed. Do reclaim. */
6103 	if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
6104 		return false;
6105 
6106 	/*
6107 	 * Compaction is already possible, but it takes time to run and there
6108 	 * are potentially other callers using the pages just freed. So proceed
6109 	 * with reclaim to make a buffer of free pages available to give
6110 	 * compaction a reasonable chance of completing and allocating the page.
6111 	 * Note that we won't actually reclaim the whole buffer in one attempt
6112 	 * as the target watermark in should_continue_reclaim() is lower. But if
6113 	 * we are already above the high+gap watermark, don't reclaim at all.
6114 	 */
6115 	watermark = high_wmark_pages(zone) + compact_gap(sc->order);
6116 
6117 	return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
6118 }
6119 
consider_reclaim_throttle(pg_data_t * pgdat,struct scan_control * sc)6120 static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
6121 {
6122 	/*
6123 	 * If reclaim is making progress greater than 12% efficiency then
6124 	 * wake all the NOPROGRESS throttled tasks.
6125 	 */
6126 	if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
6127 		wait_queue_head_t *wqh;
6128 
6129 		wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
6130 		if (waitqueue_active(wqh))
6131 			wake_up(wqh);
6132 
6133 		return;
6134 	}
6135 
6136 	/*
6137 	 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6138 	 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6139 	 * under writeback and marked for immediate reclaim at the tail of the
6140 	 * LRU.
6141 	 */
6142 	if (current_is_kswapd() || cgroup_reclaim(sc))
6143 		return;
6144 
6145 	/* Throttle if making no progress at high prioities. */
6146 	if (sc->priority == 1 && !sc->nr_reclaimed)
6147 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
6148 }
6149 
6150 /*
6151  * This is the direct reclaim path, for page-allocating processes.  We only
6152  * try to reclaim pages from zones which will satisfy the caller's allocation
6153  * request.
6154  *
6155  * If a zone is deemed to be full of pinned pages then just give it a light
6156  * scan then give up on it.
6157  */
shrink_zones(struct zonelist * zonelist,struct scan_control * sc)6158 static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
6159 {
6160 	struct zoneref *z;
6161 	struct zone *zone;
6162 	unsigned long nr_soft_reclaimed;
6163 	unsigned long nr_soft_scanned;
6164 	gfp_t orig_mask;
6165 	pg_data_t *last_pgdat = NULL;
6166 	pg_data_t *first_pgdat = NULL;
6167 
6168 	/*
6169 	 * If the number of buffer_heads in the machine exceeds the maximum
6170 	 * allowed level, force direct reclaim to scan the highmem zone as
6171 	 * highmem pages could be pinning lowmem pages storing buffer_heads
6172 	 */
6173 	orig_mask = sc->gfp_mask;
6174 	if (buffer_heads_over_limit) {
6175 		sc->gfp_mask |= __GFP_HIGHMEM;
6176 		sc->reclaim_idx = gfp_zone(sc->gfp_mask);
6177 	}
6178 
6179 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6180 					sc->reclaim_idx, sc->nodemask) {
6181 		/*
6182 		 * Take care memory controller reclaiming has small influence
6183 		 * to global LRU.
6184 		 */
6185 		if (!cgroup_reclaim(sc)) {
6186 			if (!cpuset_zone_allowed(zone,
6187 						 GFP_KERNEL | __GFP_HARDWALL))
6188 				continue;
6189 
6190 			/*
6191 			 * If we already have plenty of memory free for
6192 			 * compaction in this zone, don't free any more.
6193 			 * Even though compaction is invoked for any
6194 			 * non-zero order, only frequent costly order
6195 			 * reclamation is disruptive enough to become a
6196 			 * noticeable problem, like transparent huge
6197 			 * page allocations.
6198 			 */
6199 			if (IS_ENABLED(CONFIG_COMPACTION) &&
6200 			    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
6201 			    compaction_ready(zone, sc)) {
6202 				sc->compaction_ready = true;
6203 				continue;
6204 			}
6205 
6206 			/*
6207 			 * Shrink each node in the zonelist once. If the
6208 			 * zonelist is ordered by zone (not the default) then a
6209 			 * node may be shrunk multiple times but in that case
6210 			 * the user prefers lower zones being preserved.
6211 			 */
6212 			if (zone->zone_pgdat == last_pgdat)
6213 				continue;
6214 
6215 			/*
6216 			 * This steals pages from memory cgroups over softlimit
6217 			 * and returns the number of reclaimed pages and
6218 			 * scanned pages. This works for global memory pressure
6219 			 * and balancing, not for a memcg's limit.
6220 			 */
6221 			nr_soft_scanned = 0;
6222 			nr_soft_reclaimed = memcg1_soft_limit_reclaim(zone->zone_pgdat,
6223 								      sc->order, sc->gfp_mask,
6224 								      &nr_soft_scanned);
6225 			sc->nr_reclaimed += nr_soft_reclaimed;
6226 			sc->nr_scanned += nr_soft_scanned;
6227 			/* need some check for avoid more shrink_zone() */
6228 		}
6229 
6230 		if (!first_pgdat)
6231 			first_pgdat = zone->zone_pgdat;
6232 
6233 		/* See comment about same check for global reclaim above */
6234 		if (zone->zone_pgdat == last_pgdat)
6235 			continue;
6236 		last_pgdat = zone->zone_pgdat;
6237 		shrink_node(zone->zone_pgdat, sc);
6238 	}
6239 
6240 	if (first_pgdat)
6241 		consider_reclaim_throttle(first_pgdat, sc);
6242 
6243 	/*
6244 	 * Restore to original mask to avoid the impact on the caller if we
6245 	 * promoted it to __GFP_HIGHMEM.
6246 	 */
6247 	sc->gfp_mask = orig_mask;
6248 }
6249 
snapshot_refaults(struct mem_cgroup * target_memcg,pg_data_t * pgdat)6250 static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
6251 {
6252 	struct lruvec *target_lruvec;
6253 	unsigned long refaults;
6254 
6255 	if (lru_gen_enabled())
6256 		return;
6257 
6258 	target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
6259 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
6260 	target_lruvec->refaults[WORKINGSET_ANON] = refaults;
6261 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
6262 	target_lruvec->refaults[WORKINGSET_FILE] = refaults;
6263 }
6264 
6265 /*
6266  * This is the main entry point to direct page reclaim.
6267  *
6268  * If a full scan of the inactive list fails to free enough memory then we
6269  * are "out of memory" and something needs to be killed.
6270  *
6271  * If the caller is !__GFP_FS then the probability of a failure is reasonably
6272  * high - the zone may be full of dirty or under-writeback pages, which this
6273  * caller can't do much about.  We kick the writeback threads and take explicit
6274  * naps in the hope that some of these pages can be written.  But if the
6275  * allocating task holds filesystem locks which prevent writeout this might not
6276  * work, and the allocation attempt will fail.
6277  *
6278  * returns:	0, if no pages reclaimed
6279  * 		else, the number of pages reclaimed
6280  */
do_try_to_free_pages(struct zonelist * zonelist,struct scan_control * sc)6281 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
6282 					  struct scan_control *sc)
6283 {
6284 	int initial_priority = sc->priority;
6285 	pg_data_t *last_pgdat;
6286 	struct zoneref *z;
6287 	struct zone *zone;
6288 retry:
6289 	delayacct_freepages_start();
6290 
6291 	if (!cgroup_reclaim(sc))
6292 		__count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
6293 
6294 	do {
6295 		if (!sc->proactive)
6296 			vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
6297 					sc->priority);
6298 		sc->nr_scanned = 0;
6299 		shrink_zones(zonelist, sc);
6300 
6301 		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
6302 			break;
6303 
6304 		if (sc->compaction_ready)
6305 			break;
6306 
6307 		/*
6308 		 * If we're getting trouble reclaiming, start doing
6309 		 * writepage even in laptop mode.
6310 		 */
6311 		if (sc->priority < DEF_PRIORITY - 2)
6312 			sc->may_writepage = 1;
6313 	} while (--sc->priority >= 0);
6314 
6315 	last_pgdat = NULL;
6316 	for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
6317 					sc->nodemask) {
6318 		if (zone->zone_pgdat == last_pgdat)
6319 			continue;
6320 		last_pgdat = zone->zone_pgdat;
6321 
6322 		snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
6323 
6324 		if (cgroup_reclaim(sc)) {
6325 			struct lruvec *lruvec;
6326 
6327 			lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
6328 						   zone->zone_pgdat);
6329 			clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6330 		}
6331 	}
6332 
6333 	delayacct_freepages_end();
6334 
6335 	if (sc->nr_reclaimed)
6336 		return sc->nr_reclaimed;
6337 
6338 	/* Aborted reclaim to try compaction? don't OOM, then */
6339 	if (sc->compaction_ready)
6340 		return 1;
6341 
6342 	/*
6343 	 * In most cases, direct reclaimers can do partial walks
6344 	 * through the cgroup tree to meet the reclaim goal while
6345 	 * keeping latency low. Since the iterator state is shared
6346 	 * among all direct reclaim invocations (to retain fairness
6347 	 * among cgroups), though, high concurrency can result in
6348 	 * individual threads not seeing enough cgroups to make
6349 	 * meaningful forward progress. Avoid false OOMs in this case.
6350 	 */
6351 	if (!sc->memcg_full_walk) {
6352 		sc->priority = initial_priority;
6353 		sc->memcg_full_walk = 1;
6354 		goto retry;
6355 	}
6356 
6357 	/*
6358 	 * We make inactive:active ratio decisions based on the node's
6359 	 * composition of memory, but a restrictive reclaim_idx or a
6360 	 * memory.low cgroup setting can exempt large amounts of
6361 	 * memory from reclaim. Neither of which are very common, so
6362 	 * instead of doing costly eligibility calculations of the
6363 	 * entire cgroup subtree up front, we assume the estimates are
6364 	 * good, and retry with forcible deactivation if that fails.
6365 	 */
6366 	if (sc->skipped_deactivate) {
6367 		sc->priority = initial_priority;
6368 		sc->force_deactivate = 1;
6369 		sc->skipped_deactivate = 0;
6370 		goto retry;
6371 	}
6372 
6373 	/* Untapped cgroup reserves?  Don't OOM, retry. */
6374 	if (sc->memcg_low_skipped) {
6375 		sc->priority = initial_priority;
6376 		sc->force_deactivate = 0;
6377 		sc->memcg_low_reclaim = 1;
6378 		sc->memcg_low_skipped = 0;
6379 		goto retry;
6380 	}
6381 
6382 	return 0;
6383 }
6384 
allow_direct_reclaim(pg_data_t * pgdat)6385 static bool allow_direct_reclaim(pg_data_t *pgdat)
6386 {
6387 	struct zone *zone;
6388 	unsigned long pfmemalloc_reserve = 0;
6389 	unsigned long free_pages = 0;
6390 	int i;
6391 	bool wmark_ok;
6392 
6393 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6394 		return true;
6395 
6396 	for (i = 0; i <= ZONE_NORMAL; i++) {
6397 		zone = &pgdat->node_zones[i];
6398 		if (!managed_zone(zone))
6399 			continue;
6400 
6401 		if (!zone_reclaimable_pages(zone))
6402 			continue;
6403 
6404 		pfmemalloc_reserve += min_wmark_pages(zone);
6405 		free_pages += zone_page_state_snapshot(zone, NR_FREE_PAGES);
6406 	}
6407 
6408 	/* If there are no reserves (unexpected config) then do not throttle */
6409 	if (!pfmemalloc_reserve)
6410 		return true;
6411 
6412 	wmark_ok = free_pages > pfmemalloc_reserve / 2;
6413 
6414 	/* kswapd must be awake if processes are being throttled */
6415 	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
6416 		if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
6417 			WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
6418 
6419 		wake_up_interruptible(&pgdat->kswapd_wait);
6420 	}
6421 
6422 	return wmark_ok;
6423 }
6424 
6425 /*
6426  * Throttle direct reclaimers if backing storage is backed by the network
6427  * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6428  * depleted. kswapd will continue to make progress and wake the processes
6429  * when the low watermark is reached.
6430  *
6431  * Returns true if a fatal signal was delivered during throttling. If this
6432  * happens, the page allocator should not consider triggering the OOM killer.
6433  */
throttle_direct_reclaim(gfp_t gfp_mask,struct zonelist * zonelist,nodemask_t * nodemask)6434 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
6435 					nodemask_t *nodemask)
6436 {
6437 	struct zoneref *z;
6438 	struct zone *zone;
6439 	pg_data_t *pgdat = NULL;
6440 
6441 	/*
6442 	 * Kernel threads should not be throttled as they may be indirectly
6443 	 * responsible for cleaning pages necessary for reclaim to make forward
6444 	 * progress. kjournald for example may enter direct reclaim while
6445 	 * committing a transaction where throttling it could forcing other
6446 	 * processes to block on log_wait_commit().
6447 	 */
6448 	if (current->flags & PF_KTHREAD)
6449 		goto out;
6450 
6451 	/*
6452 	 * If a fatal signal is pending, this process should not throttle.
6453 	 * It should return quickly so it can exit and free its memory
6454 	 */
6455 	if (fatal_signal_pending(current))
6456 		goto out;
6457 
6458 	/*
6459 	 * Check if the pfmemalloc reserves are ok by finding the first node
6460 	 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6461 	 * GFP_KERNEL will be required for allocating network buffers when
6462 	 * swapping over the network so ZONE_HIGHMEM is unusable.
6463 	 *
6464 	 * Throttling is based on the first usable node and throttled processes
6465 	 * wait on a queue until kswapd makes progress and wakes them. There
6466 	 * is an affinity then between processes waking up and where reclaim
6467 	 * progress has been made assuming the process wakes on the same node.
6468 	 * More importantly, processes running on remote nodes will not compete
6469 	 * for remote pfmemalloc reserves and processes on different nodes
6470 	 * should make reasonable progress.
6471 	 */
6472 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6473 					gfp_zone(gfp_mask), nodemask) {
6474 		if (zone_idx(zone) > ZONE_NORMAL)
6475 			continue;
6476 
6477 		/* Throttle based on the first usable node */
6478 		pgdat = zone->zone_pgdat;
6479 		if (allow_direct_reclaim(pgdat))
6480 			goto out;
6481 		break;
6482 	}
6483 
6484 	/* If no zone was usable by the allocation flags then do not throttle */
6485 	if (!pgdat)
6486 		goto out;
6487 
6488 	/* Account for the throttling */
6489 	count_vm_event(PGSCAN_DIRECT_THROTTLE);
6490 
6491 	/*
6492 	 * If the caller cannot enter the filesystem, it's possible that it
6493 	 * is due to the caller holding an FS lock or performing a journal
6494 	 * transaction in the case of a filesystem like ext[3|4]. In this case,
6495 	 * it is not safe to block on pfmemalloc_wait as kswapd could be
6496 	 * blocked waiting on the same lock. Instead, throttle for up to a
6497 	 * second before continuing.
6498 	 */
6499 	if (!(gfp_mask & __GFP_FS))
6500 		wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
6501 			allow_direct_reclaim(pgdat), HZ);
6502 	else
6503 		/* Throttle until kswapd wakes the process */
6504 		wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
6505 			allow_direct_reclaim(pgdat));
6506 
6507 	if (fatal_signal_pending(current))
6508 		return true;
6509 
6510 out:
6511 	return false;
6512 }
6513 
try_to_free_pages(struct zonelist * zonelist,int order,gfp_t gfp_mask,nodemask_t * nodemask)6514 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
6515 				gfp_t gfp_mask, nodemask_t *nodemask)
6516 {
6517 	unsigned long nr_reclaimed;
6518 	struct scan_control sc = {
6519 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6520 		.gfp_mask = current_gfp_context(gfp_mask),
6521 		.reclaim_idx = gfp_zone(gfp_mask),
6522 		.order = order,
6523 		.nodemask = nodemask,
6524 		.priority = DEF_PRIORITY,
6525 		.may_writepage = !laptop_mode,
6526 		.may_unmap = 1,
6527 		.may_swap = 1,
6528 	};
6529 
6530 	/*
6531 	 * scan_control uses s8 fields for order, priority, and reclaim_idx.
6532 	 * Confirm they are large enough for max values.
6533 	 */
6534 	BUILD_BUG_ON(MAX_PAGE_ORDER >= S8_MAX);
6535 	BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
6536 	BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
6537 
6538 	/*
6539 	 * Do not enter reclaim if fatal signal was delivered while throttled.
6540 	 * 1 is returned so that the page allocator does not OOM kill at this
6541 	 * point.
6542 	 */
6543 	if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
6544 		return 1;
6545 
6546 	set_task_reclaim_state(current, &sc.reclaim_state);
6547 	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
6548 
6549 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6550 
6551 	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
6552 	set_task_reclaim_state(current, NULL);
6553 
6554 	return nr_reclaimed;
6555 }
6556 
6557 #ifdef CONFIG_MEMCG
6558 
6559 /* Only used by soft limit reclaim. Do not reuse for anything else. */
mem_cgroup_shrink_node(struct mem_cgroup * memcg,gfp_t gfp_mask,bool noswap,pg_data_t * pgdat,unsigned long * nr_scanned)6560 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
6561 						gfp_t gfp_mask, bool noswap,
6562 						pg_data_t *pgdat,
6563 						unsigned long *nr_scanned)
6564 {
6565 	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6566 	struct scan_control sc = {
6567 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6568 		.target_mem_cgroup = memcg,
6569 		.may_writepage = !laptop_mode,
6570 		.may_unmap = 1,
6571 		.reclaim_idx = MAX_NR_ZONES - 1,
6572 		.may_swap = !noswap,
6573 	};
6574 
6575 	WARN_ON_ONCE(!current->reclaim_state);
6576 
6577 	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
6578 			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
6579 
6580 	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
6581 						      sc.gfp_mask);
6582 
6583 	/*
6584 	 * NOTE: Although we can get the priority field, using it
6585 	 * here is not a good idea, since it limits the pages we can scan.
6586 	 * if we don't reclaim here, the shrink_node from balance_pgdat
6587 	 * will pick up pages from other mem cgroup's as well. We hack
6588 	 * the priority and make it zero.
6589 	 */
6590 	shrink_lruvec(lruvec, &sc);
6591 
6592 	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
6593 
6594 	*nr_scanned = sc.nr_scanned;
6595 
6596 	return sc.nr_reclaimed;
6597 }
6598 
try_to_free_mem_cgroup_pages(struct mem_cgroup * memcg,unsigned long nr_pages,gfp_t gfp_mask,unsigned int reclaim_options,int * swappiness)6599 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
6600 					   unsigned long nr_pages,
6601 					   gfp_t gfp_mask,
6602 					   unsigned int reclaim_options,
6603 					   int *swappiness)
6604 {
6605 	unsigned long nr_reclaimed;
6606 	unsigned int noreclaim_flag;
6607 	struct scan_control sc = {
6608 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
6609 		.proactive_swappiness = swappiness,
6610 		.gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
6611 				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
6612 		.reclaim_idx = MAX_NR_ZONES - 1,
6613 		.target_mem_cgroup = memcg,
6614 		.priority = DEF_PRIORITY,
6615 		.may_writepage = !laptop_mode,
6616 		.may_unmap = 1,
6617 		.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
6618 		.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
6619 	};
6620 	/*
6621 	 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
6622 	 * equal pressure on all the nodes. This is based on the assumption that
6623 	 * the reclaim does not bail out early.
6624 	 */
6625 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
6626 
6627 	set_task_reclaim_state(current, &sc.reclaim_state);
6628 	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
6629 	noreclaim_flag = memalloc_noreclaim_save();
6630 
6631 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6632 
6633 	memalloc_noreclaim_restore(noreclaim_flag);
6634 	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
6635 	set_task_reclaim_state(current, NULL);
6636 
6637 	return nr_reclaimed;
6638 }
6639 #endif
6640 
kswapd_age_node(struct pglist_data * pgdat,struct scan_control * sc)6641 static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
6642 {
6643 	struct mem_cgroup *memcg;
6644 	struct lruvec *lruvec;
6645 
6646 	if (lru_gen_enabled()) {
6647 		lru_gen_age_node(pgdat, sc);
6648 		return;
6649 	}
6650 
6651 	if (!can_age_anon_pages(pgdat, sc))
6652 		return;
6653 
6654 	lruvec = mem_cgroup_lruvec(NULL, pgdat);
6655 	if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6656 		return;
6657 
6658 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
6659 	do {
6660 		lruvec = mem_cgroup_lruvec(memcg, pgdat);
6661 		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6662 				   sc, LRU_ACTIVE_ANON);
6663 		memcg = mem_cgroup_iter(NULL, memcg, NULL);
6664 	} while (memcg);
6665 }
6666 
pgdat_watermark_boosted(pg_data_t * pgdat,int highest_zoneidx)6667 static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
6668 {
6669 	int i;
6670 	struct zone *zone;
6671 
6672 	/*
6673 	 * Check for watermark boosts top-down as the higher zones
6674 	 * are more likely to be boosted. Both watermarks and boosts
6675 	 * should not be checked at the same time as reclaim would
6676 	 * start prematurely when there is no boosting and a lower
6677 	 * zone is balanced.
6678 	 */
6679 	for (i = highest_zoneidx; i >= 0; i--) {
6680 		zone = pgdat->node_zones + i;
6681 		if (!managed_zone(zone))
6682 			continue;
6683 
6684 		if (zone->watermark_boost)
6685 			return true;
6686 	}
6687 
6688 	return false;
6689 }
6690 
6691 /*
6692  * Returns true if there is an eligible zone balanced for the request order
6693  * and highest_zoneidx
6694  */
pgdat_balanced(pg_data_t * pgdat,int order,int highest_zoneidx)6695 static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
6696 {
6697 	int i;
6698 	unsigned long mark = -1;
6699 	struct zone *zone;
6700 
6701 	/*
6702 	 * Check watermarks bottom-up as lower zones are more likely to
6703 	 * meet watermarks.
6704 	 */
6705 	for (i = 0; i <= highest_zoneidx; i++) {
6706 		zone = pgdat->node_zones + i;
6707 
6708 		if (!managed_zone(zone))
6709 			continue;
6710 
6711 		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
6712 			mark = promo_wmark_pages(zone);
6713 		else
6714 			mark = high_wmark_pages(zone);
6715 		if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
6716 			return true;
6717 	}
6718 
6719 	/*
6720 	 * If a node has no managed zone within highest_zoneidx, it does not
6721 	 * need balancing by definition. This can happen if a zone-restricted
6722 	 * allocation tries to wake a remote kswapd.
6723 	 */
6724 	if (mark == -1)
6725 		return true;
6726 
6727 	return false;
6728 }
6729 
6730 /* Clear pgdat state for congested, dirty or under writeback. */
clear_pgdat_congested(pg_data_t * pgdat)6731 static void clear_pgdat_congested(pg_data_t *pgdat)
6732 {
6733 	struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
6734 
6735 	clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags);
6736 	clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6737 	clear_bit(PGDAT_DIRTY, &pgdat->flags);
6738 	clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
6739 }
6740 
6741 /*
6742  * Prepare kswapd for sleeping. This verifies that there are no processes
6743  * waiting in throttle_direct_reclaim() and that watermarks have been met.
6744  *
6745  * Returns true if kswapd is ready to sleep
6746  */
prepare_kswapd_sleep(pg_data_t * pgdat,int order,int highest_zoneidx)6747 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
6748 				int highest_zoneidx)
6749 {
6750 	/*
6751 	 * The throttled processes are normally woken up in balance_pgdat() as
6752 	 * soon as allow_direct_reclaim() is true. But there is a potential
6753 	 * race between when kswapd checks the watermarks and a process gets
6754 	 * throttled. There is also a potential race if processes get
6755 	 * throttled, kswapd wakes, a large process exits thereby balancing the
6756 	 * zones, which causes kswapd to exit balance_pgdat() before reaching
6757 	 * the wake up checks. If kswapd is going to sleep, no process should
6758 	 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
6759 	 * the wake up is premature, processes will wake kswapd and get
6760 	 * throttled again. The difference from wake ups in balance_pgdat() is
6761 	 * that here we are under prepare_to_wait().
6762 	 */
6763 	if (waitqueue_active(&pgdat->pfmemalloc_wait))
6764 		wake_up_all(&pgdat->pfmemalloc_wait);
6765 
6766 	/* Hopeless node, leave it to direct reclaim */
6767 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6768 		return true;
6769 
6770 	if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
6771 		clear_pgdat_congested(pgdat);
6772 		return true;
6773 	}
6774 
6775 	return false;
6776 }
6777 
6778 /*
6779  * kswapd shrinks a node of pages that are at or below the highest usable
6780  * zone that is currently unbalanced.
6781  *
6782  * Returns true if kswapd scanned at least the requested number of pages to
6783  * reclaim or if the lack of progress was due to pages under writeback.
6784  * This is used to determine if the scanning priority needs to be raised.
6785  */
kswapd_shrink_node(pg_data_t * pgdat,struct scan_control * sc)6786 static bool kswapd_shrink_node(pg_data_t *pgdat,
6787 			       struct scan_control *sc)
6788 {
6789 	struct zone *zone;
6790 	int z;
6791 	unsigned long nr_reclaimed = sc->nr_reclaimed;
6792 
6793 	/* Reclaim a number of pages proportional to the number of zones */
6794 	sc->nr_to_reclaim = 0;
6795 	for (z = 0; z <= sc->reclaim_idx; z++) {
6796 		zone = pgdat->node_zones + z;
6797 		if (!managed_zone(zone))
6798 			continue;
6799 
6800 		sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
6801 	}
6802 
6803 	/*
6804 	 * Historically care was taken to put equal pressure on all zones but
6805 	 * now pressure is applied based on node LRU order.
6806 	 */
6807 	shrink_node(pgdat, sc);
6808 
6809 	/*
6810 	 * Fragmentation may mean that the system cannot be rebalanced for
6811 	 * high-order allocations. If twice the allocation size has been
6812 	 * reclaimed then recheck watermarks only at order-0 to prevent
6813 	 * excessive reclaim. Assume that a process requested a high-order
6814 	 * can direct reclaim/compact.
6815 	 */
6816 	if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
6817 		sc->order = 0;
6818 
6819 	/* account for progress from mm_account_reclaimed_pages() */
6820 	return max(sc->nr_scanned, sc->nr_reclaimed - nr_reclaimed) >= sc->nr_to_reclaim;
6821 }
6822 
6823 /* Page allocator PCP high watermark is lowered if reclaim is active. */
6824 static inline void
update_reclaim_active(pg_data_t * pgdat,int highest_zoneidx,bool active)6825 update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
6826 {
6827 	int i;
6828 	struct zone *zone;
6829 
6830 	for (i = 0; i <= highest_zoneidx; i++) {
6831 		zone = pgdat->node_zones + i;
6832 
6833 		if (!managed_zone(zone))
6834 			continue;
6835 
6836 		if (active)
6837 			set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6838 		else
6839 			clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6840 	}
6841 }
6842 
6843 static inline void
set_reclaim_active(pg_data_t * pgdat,int highest_zoneidx)6844 set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6845 {
6846 	update_reclaim_active(pgdat, highest_zoneidx, true);
6847 }
6848 
6849 static inline void
clear_reclaim_active(pg_data_t * pgdat,int highest_zoneidx)6850 clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6851 {
6852 	update_reclaim_active(pgdat, highest_zoneidx, false);
6853 }
6854 
6855 /*
6856  * For kswapd, balance_pgdat() will reclaim pages across a node from zones
6857  * that are eligible for use by the caller until at least one zone is
6858  * balanced.
6859  *
6860  * Returns the order kswapd finished reclaiming at.
6861  *
6862  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
6863  * zones which have free_pages > high_wmark_pages(zone), but once a zone is
6864  * found to have free_pages <= high_wmark_pages(zone), any page in that zone
6865  * or lower is eligible for reclaim until at least one usable zone is
6866  * balanced.
6867  */
balance_pgdat(pg_data_t * pgdat,int order,int highest_zoneidx)6868 static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
6869 {
6870 	int i;
6871 	unsigned long nr_soft_reclaimed;
6872 	unsigned long nr_soft_scanned;
6873 	unsigned long pflags;
6874 	unsigned long nr_boost_reclaim;
6875 	unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
6876 	bool boosted;
6877 	struct zone *zone;
6878 	struct scan_control sc = {
6879 		.gfp_mask = GFP_KERNEL,
6880 		.order = order,
6881 		.may_unmap = 1,
6882 	};
6883 
6884 	set_task_reclaim_state(current, &sc.reclaim_state);
6885 	psi_memstall_enter(&pflags);
6886 	__fs_reclaim_acquire(_THIS_IP_);
6887 
6888 	count_vm_event(PAGEOUTRUN);
6889 
6890 	/*
6891 	 * Account for the reclaim boost. Note that the zone boost is left in
6892 	 * place so that parallel allocations that are near the watermark will
6893 	 * stall or direct reclaim until kswapd is finished.
6894 	 */
6895 	nr_boost_reclaim = 0;
6896 	for (i = 0; i <= highest_zoneidx; i++) {
6897 		zone = pgdat->node_zones + i;
6898 		if (!managed_zone(zone))
6899 			continue;
6900 
6901 		nr_boost_reclaim += zone->watermark_boost;
6902 		zone_boosts[i] = zone->watermark_boost;
6903 	}
6904 	boosted = nr_boost_reclaim;
6905 
6906 restart:
6907 	set_reclaim_active(pgdat, highest_zoneidx);
6908 	sc.priority = DEF_PRIORITY;
6909 	do {
6910 		unsigned long nr_reclaimed = sc.nr_reclaimed;
6911 		bool raise_priority = true;
6912 		bool balanced;
6913 		bool ret;
6914 		bool was_frozen;
6915 
6916 		sc.reclaim_idx = highest_zoneidx;
6917 
6918 		/*
6919 		 * If the number of buffer_heads exceeds the maximum allowed
6920 		 * then consider reclaiming from all zones. This has a dual
6921 		 * purpose -- on 64-bit systems it is expected that
6922 		 * buffer_heads are stripped during active rotation. On 32-bit
6923 		 * systems, highmem pages can pin lowmem memory and shrinking
6924 		 * buffers can relieve lowmem pressure. Reclaim may still not
6925 		 * go ahead if all eligible zones for the original allocation
6926 		 * request are balanced to avoid excessive reclaim from kswapd.
6927 		 */
6928 		if (buffer_heads_over_limit) {
6929 			for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
6930 				zone = pgdat->node_zones + i;
6931 				if (!managed_zone(zone))
6932 					continue;
6933 
6934 				sc.reclaim_idx = i;
6935 				break;
6936 			}
6937 		}
6938 
6939 		/*
6940 		 * If the pgdat is imbalanced then ignore boosting and preserve
6941 		 * the watermarks for a later time and restart. Note that the
6942 		 * zone watermarks will be still reset at the end of balancing
6943 		 * on the grounds that the normal reclaim should be enough to
6944 		 * re-evaluate if boosting is required when kswapd next wakes.
6945 		 */
6946 		balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
6947 		if (!balanced && nr_boost_reclaim) {
6948 			nr_boost_reclaim = 0;
6949 			goto restart;
6950 		}
6951 
6952 		/*
6953 		 * If boosting is not active then only reclaim if there are no
6954 		 * eligible zones. Note that sc.reclaim_idx is not used as
6955 		 * buffer_heads_over_limit may have adjusted it.
6956 		 */
6957 		if (!nr_boost_reclaim && balanced)
6958 			goto out;
6959 
6960 		/* Limit the priority of boosting to avoid reclaim writeback */
6961 		if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
6962 			raise_priority = false;
6963 
6964 		/*
6965 		 * Do not writeback or swap pages for boosted reclaim. The
6966 		 * intent is to relieve pressure not issue sub-optimal IO
6967 		 * from reclaim context. If no pages are reclaimed, the
6968 		 * reclaim will be aborted.
6969 		 */
6970 		sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
6971 		sc.may_swap = !nr_boost_reclaim;
6972 
6973 		/*
6974 		 * Do some background aging, to give pages a chance to be
6975 		 * referenced before reclaiming. All pages are rotated
6976 		 * regardless of classzone as this is about consistent aging.
6977 		 */
6978 		kswapd_age_node(pgdat, &sc);
6979 
6980 		/*
6981 		 * If we're getting trouble reclaiming, start doing writepage
6982 		 * even in laptop mode.
6983 		 */
6984 		if (sc.priority < DEF_PRIORITY - 2)
6985 			sc.may_writepage = 1;
6986 
6987 		/* Call soft limit reclaim before calling shrink_node. */
6988 		sc.nr_scanned = 0;
6989 		nr_soft_scanned = 0;
6990 		nr_soft_reclaimed = memcg1_soft_limit_reclaim(pgdat, sc.order,
6991 							      sc.gfp_mask, &nr_soft_scanned);
6992 		sc.nr_reclaimed += nr_soft_reclaimed;
6993 
6994 		/*
6995 		 * There should be no need to raise the scanning priority if
6996 		 * enough pages are already being scanned that that high
6997 		 * watermark would be met at 100% efficiency.
6998 		 */
6999 		if (kswapd_shrink_node(pgdat, &sc))
7000 			raise_priority = false;
7001 
7002 		/*
7003 		 * If the low watermark is met there is no need for processes
7004 		 * to be throttled on pfmemalloc_wait as they should not be
7005 		 * able to safely make forward progress. Wake them
7006 		 */
7007 		if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
7008 				allow_direct_reclaim(pgdat))
7009 			wake_up_all(&pgdat->pfmemalloc_wait);
7010 
7011 		/* Check if kswapd should be suspending */
7012 		__fs_reclaim_release(_THIS_IP_);
7013 		ret = kthread_freezable_should_stop(&was_frozen);
7014 		__fs_reclaim_acquire(_THIS_IP_);
7015 		if (was_frozen || ret)
7016 			break;
7017 
7018 		/*
7019 		 * Raise priority if scanning rate is too low or there was no
7020 		 * progress in reclaiming pages
7021 		 */
7022 		nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
7023 		nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
7024 
7025 		/*
7026 		 * If reclaim made no progress for a boost, stop reclaim as
7027 		 * IO cannot be queued and it could be an infinite loop in
7028 		 * extreme circumstances.
7029 		 */
7030 		if (nr_boost_reclaim && !nr_reclaimed)
7031 			break;
7032 
7033 		if (raise_priority || !nr_reclaimed)
7034 			sc.priority--;
7035 	} while (sc.priority >= 1);
7036 
7037 	/*
7038 	 * Restart only if it went through the priority loop all the way,
7039 	 * but cache_trim_mode didn't work.
7040 	 */
7041 	if (!sc.nr_reclaimed && sc.priority < 1 &&
7042 	    !sc.no_cache_trim_mode && sc.cache_trim_mode_failed) {
7043 		sc.no_cache_trim_mode = 1;
7044 		goto restart;
7045 	}
7046 
7047 	if (!sc.nr_reclaimed)
7048 		pgdat->kswapd_failures++;
7049 
7050 out:
7051 	clear_reclaim_active(pgdat, highest_zoneidx);
7052 
7053 	/* If reclaim was boosted, account for the reclaim done in this pass */
7054 	if (boosted) {
7055 		unsigned long flags;
7056 
7057 		for (i = 0; i <= highest_zoneidx; i++) {
7058 			if (!zone_boosts[i])
7059 				continue;
7060 
7061 			/* Increments are under the zone lock */
7062 			zone = pgdat->node_zones + i;
7063 			spin_lock_irqsave(&zone->lock, flags);
7064 			zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
7065 			spin_unlock_irqrestore(&zone->lock, flags);
7066 		}
7067 
7068 		/*
7069 		 * As there is now likely space, wakeup kcompact to defragment
7070 		 * pageblocks.
7071 		 */
7072 		wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
7073 	}
7074 
7075 	snapshot_refaults(NULL, pgdat);
7076 	__fs_reclaim_release(_THIS_IP_);
7077 	psi_memstall_leave(&pflags);
7078 	set_task_reclaim_state(current, NULL);
7079 
7080 	/*
7081 	 * Return the order kswapd stopped reclaiming at as
7082 	 * prepare_kswapd_sleep() takes it into account. If another caller
7083 	 * entered the allocator slow path while kswapd was awake, order will
7084 	 * remain at the higher level.
7085 	 */
7086 	return sc.order;
7087 }
7088 
7089 /*
7090  * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
7091  * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
7092  * not a valid index then either kswapd runs for first time or kswapd couldn't
7093  * sleep after previous reclaim attempt (node is still unbalanced). In that
7094  * case return the zone index of the previous kswapd reclaim cycle.
7095  */
kswapd_highest_zoneidx(pg_data_t * pgdat,enum zone_type prev_highest_zoneidx)7096 static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
7097 					   enum zone_type prev_highest_zoneidx)
7098 {
7099 	enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7100 
7101 	return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
7102 }
7103 
kswapd_try_to_sleep(pg_data_t * pgdat,int alloc_order,int reclaim_order,unsigned int highest_zoneidx)7104 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
7105 				unsigned int highest_zoneidx)
7106 {
7107 	long remaining = 0;
7108 	DEFINE_WAIT(wait);
7109 
7110 	if (freezing(current) || kthread_should_stop())
7111 		return;
7112 
7113 	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7114 
7115 	/*
7116 	 * Try to sleep for a short interval. Note that kcompactd will only be
7117 	 * woken if it is possible to sleep for a short interval. This is
7118 	 * deliberate on the assumption that if reclaim cannot keep an
7119 	 * eligible zone balanced that it's also unlikely that compaction will
7120 	 * succeed.
7121 	 */
7122 	if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7123 		/*
7124 		 * Compaction records what page blocks it recently failed to
7125 		 * isolate pages from and skips them in the future scanning.
7126 		 * When kswapd is going to sleep, it is reasonable to assume
7127 		 * that pages and compaction may succeed so reset the cache.
7128 		 */
7129 		reset_isolation_suitable(pgdat);
7130 
7131 		/*
7132 		 * We have freed the memory, now we should compact it to make
7133 		 * allocation of the requested order possible.
7134 		 */
7135 		wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
7136 
7137 		remaining = schedule_timeout(HZ/10);
7138 
7139 		/*
7140 		 * If woken prematurely then reset kswapd_highest_zoneidx and
7141 		 * order. The values will either be from a wakeup request or
7142 		 * the previous request that slept prematurely.
7143 		 */
7144 		if (remaining) {
7145 			WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
7146 					kswapd_highest_zoneidx(pgdat,
7147 							highest_zoneidx));
7148 
7149 			if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
7150 				WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
7151 		}
7152 
7153 		finish_wait(&pgdat->kswapd_wait, &wait);
7154 		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7155 	}
7156 
7157 	/*
7158 	 * After a short sleep, check if it was a premature sleep. If not, then
7159 	 * go fully to sleep until explicitly woken up.
7160 	 */
7161 	if (!remaining &&
7162 	    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7163 		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
7164 
7165 		/*
7166 		 * vmstat counters are not perfectly accurate and the estimated
7167 		 * value for counters such as NR_FREE_PAGES can deviate from the
7168 		 * true value by nr_online_cpus * threshold. To avoid the zone
7169 		 * watermarks being breached while under pressure, we reduce the
7170 		 * per-cpu vmstat threshold while kswapd is awake and restore
7171 		 * them before going back to sleep.
7172 		 */
7173 		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
7174 
7175 		if (!kthread_should_stop())
7176 			schedule();
7177 
7178 		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
7179 	} else {
7180 		if (remaining)
7181 			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
7182 		else
7183 			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
7184 	}
7185 	finish_wait(&pgdat->kswapd_wait, &wait);
7186 }
7187 
7188 /*
7189  * The background pageout daemon, started as a kernel thread
7190  * from the init process.
7191  *
7192  * This basically trickles out pages so that we have _some_
7193  * free memory available even if there is no other activity
7194  * that frees anything up. This is needed for things like routing
7195  * etc, where we otherwise might have all activity going on in
7196  * asynchronous contexts that cannot page things out.
7197  *
7198  * If there are applications that are active memory-allocators
7199  * (most normal use), this basically shouldn't matter.
7200  */
kswapd(void * p)7201 static int kswapd(void *p)
7202 {
7203 	unsigned int alloc_order, reclaim_order;
7204 	unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
7205 	pg_data_t *pgdat = (pg_data_t *)p;
7206 	struct task_struct *tsk = current;
7207 
7208 	/*
7209 	 * Tell the memory management that we're a "memory allocator",
7210 	 * and that if we need more memory we should get access to it
7211 	 * regardless (see "__alloc_pages()"). "kswapd" should
7212 	 * never get caught in the normal page freeing logic.
7213 	 *
7214 	 * (Kswapd normally doesn't need memory anyway, but sometimes
7215 	 * you need a small amount of memory in order to be able to
7216 	 * page out something else, and this flag essentially protects
7217 	 * us from recursively trying to free more memory as we're
7218 	 * trying to free the first piece of memory in the first place).
7219 	 */
7220 	tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
7221 	set_freezable();
7222 
7223 	WRITE_ONCE(pgdat->kswapd_order, 0);
7224 	WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7225 	atomic_set(&pgdat->nr_writeback_throttled, 0);
7226 	for ( ; ; ) {
7227 		bool was_frozen;
7228 
7229 		alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
7230 		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7231 							highest_zoneidx);
7232 
7233 kswapd_try_sleep:
7234 		kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
7235 					highest_zoneidx);
7236 
7237 		/* Read the new order and highest_zoneidx */
7238 		alloc_order = READ_ONCE(pgdat->kswapd_order);
7239 		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7240 							highest_zoneidx);
7241 		WRITE_ONCE(pgdat->kswapd_order, 0);
7242 		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7243 
7244 		if (kthread_freezable_should_stop(&was_frozen))
7245 			break;
7246 
7247 		/*
7248 		 * We can speed up thawing tasks if we don't call balance_pgdat
7249 		 * after returning from the refrigerator
7250 		 */
7251 		if (was_frozen)
7252 			continue;
7253 
7254 		/*
7255 		 * Reclaim begins at the requested order but if a high-order
7256 		 * reclaim fails then kswapd falls back to reclaiming for
7257 		 * order-0. If that happens, kswapd will consider sleeping
7258 		 * for the order it finished reclaiming at (reclaim_order)
7259 		 * but kcompactd is woken to compact for the original
7260 		 * request (alloc_order).
7261 		 */
7262 		trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
7263 						alloc_order);
7264 		reclaim_order = balance_pgdat(pgdat, alloc_order,
7265 						highest_zoneidx);
7266 		if (reclaim_order < alloc_order)
7267 			goto kswapd_try_sleep;
7268 	}
7269 
7270 	tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
7271 
7272 	return 0;
7273 }
7274 
7275 /*
7276  * A zone is low on free memory or too fragmented for high-order memory.  If
7277  * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7278  * pgdat.  It will wake up kcompactd after reclaiming memory.  If kswapd reclaim
7279  * has failed or is not needed, still wake up kcompactd if only compaction is
7280  * needed.
7281  */
wakeup_kswapd(struct zone * zone,gfp_t gfp_flags,int order,enum zone_type highest_zoneidx)7282 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
7283 		   enum zone_type highest_zoneidx)
7284 {
7285 	pg_data_t *pgdat;
7286 	enum zone_type curr_idx;
7287 
7288 	if (!managed_zone(zone))
7289 		return;
7290 
7291 	if (!cpuset_zone_allowed(zone, gfp_flags))
7292 		return;
7293 
7294 	pgdat = zone->zone_pgdat;
7295 	curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7296 
7297 	if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
7298 		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
7299 
7300 	if (READ_ONCE(pgdat->kswapd_order) < order)
7301 		WRITE_ONCE(pgdat->kswapd_order, order);
7302 
7303 	if (!waitqueue_active(&pgdat->kswapd_wait))
7304 		return;
7305 
7306 	/* Hopeless node, leave it to direct reclaim if possible */
7307 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
7308 	    (pgdat_balanced(pgdat, order, highest_zoneidx) &&
7309 	     !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
7310 		/*
7311 		 * There may be plenty of free memory available, but it's too
7312 		 * fragmented for high-order allocations.  Wake up kcompactd
7313 		 * and rely on compaction_suitable() to determine if it's
7314 		 * needed.  If it fails, it will defer subsequent attempts to
7315 		 * ratelimit its work.
7316 		 */
7317 		if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
7318 			wakeup_kcompactd(pgdat, order, highest_zoneidx);
7319 		return;
7320 	}
7321 
7322 	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
7323 				      gfp_flags);
7324 	wake_up_interruptible(&pgdat->kswapd_wait);
7325 }
7326 
7327 #ifdef CONFIG_HIBERNATION
7328 /*
7329  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7330  * freed pages.
7331  *
7332  * Rather than trying to age LRUs the aim is to preserve the overall
7333  * LRU order by reclaiming preferentially
7334  * inactive > active > active referenced > active mapped
7335  */
shrink_all_memory(unsigned long nr_to_reclaim)7336 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
7337 {
7338 	struct scan_control sc = {
7339 		.nr_to_reclaim = nr_to_reclaim,
7340 		.gfp_mask = GFP_HIGHUSER_MOVABLE,
7341 		.reclaim_idx = MAX_NR_ZONES - 1,
7342 		.priority = DEF_PRIORITY,
7343 		.may_writepage = 1,
7344 		.may_unmap = 1,
7345 		.may_swap = 1,
7346 		.hibernation_mode = 1,
7347 	};
7348 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
7349 	unsigned long nr_reclaimed;
7350 	unsigned int noreclaim_flag;
7351 
7352 	fs_reclaim_acquire(sc.gfp_mask);
7353 	noreclaim_flag = memalloc_noreclaim_save();
7354 	set_task_reclaim_state(current, &sc.reclaim_state);
7355 
7356 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
7357 
7358 	set_task_reclaim_state(current, NULL);
7359 	memalloc_noreclaim_restore(noreclaim_flag);
7360 	fs_reclaim_release(sc.gfp_mask);
7361 
7362 	return nr_reclaimed;
7363 }
7364 #endif /* CONFIG_HIBERNATION */
7365 
7366 /*
7367  * This kswapd start function will be called by init and node-hot-add.
7368  */
kswapd_run(int nid)7369 void __meminit kswapd_run(int nid)
7370 {
7371 	pg_data_t *pgdat = NODE_DATA(nid);
7372 
7373 	pgdat_kswapd_lock(pgdat);
7374 	if (!pgdat->kswapd) {
7375 		pgdat->kswapd = kthread_create_on_node(kswapd, pgdat, nid, "kswapd%d", nid);
7376 		if (IS_ERR(pgdat->kswapd)) {
7377 			/* failure at boot is fatal */
7378 			pr_err("Failed to start kswapd on node %d,ret=%ld\n",
7379 				   nid, PTR_ERR(pgdat->kswapd));
7380 			BUG_ON(system_state < SYSTEM_RUNNING);
7381 			pgdat->kswapd = NULL;
7382 		} else {
7383 			wake_up_process(pgdat->kswapd);
7384 		}
7385 	}
7386 	pgdat_kswapd_unlock(pgdat);
7387 }
7388 
7389 /*
7390  * Called by memory hotplug when all memory in a node is offlined.  Caller must
7391  * be holding mem_hotplug_begin/done().
7392  */
kswapd_stop(int nid)7393 void __meminit kswapd_stop(int nid)
7394 {
7395 	pg_data_t *pgdat = NODE_DATA(nid);
7396 	struct task_struct *kswapd;
7397 
7398 	pgdat_kswapd_lock(pgdat);
7399 	kswapd = pgdat->kswapd;
7400 	if (kswapd) {
7401 		kthread_stop(kswapd);
7402 		pgdat->kswapd = NULL;
7403 	}
7404 	pgdat_kswapd_unlock(pgdat);
7405 }
7406 
kswapd_init(void)7407 static int __init kswapd_init(void)
7408 {
7409 	int nid;
7410 
7411 	swap_setup();
7412 	for_each_node_state(nid, N_MEMORY)
7413  		kswapd_run(nid);
7414 	return 0;
7415 }
7416 
7417 module_init(kswapd_init)
7418 
7419 #ifdef CONFIG_NUMA
7420 /*
7421  * Node reclaim mode
7422  *
7423  * If non-zero call node_reclaim when the number of free pages falls below
7424  * the watermarks.
7425  */
7426 int node_reclaim_mode __read_mostly;
7427 
7428 /*
7429  * Priority for NODE_RECLAIM. This determines the fraction of pages
7430  * of a node considered for each zone_reclaim. 4 scans 1/16th of
7431  * a zone.
7432  */
7433 #define NODE_RECLAIM_PRIORITY 4
7434 
7435 /*
7436  * Percentage of pages in a zone that must be unmapped for node_reclaim to
7437  * occur.
7438  */
7439 int sysctl_min_unmapped_ratio = 1;
7440 
7441 /*
7442  * If the number of slab pages in a zone grows beyond this percentage then
7443  * slab reclaim needs to occur.
7444  */
7445 int sysctl_min_slab_ratio = 5;
7446 
node_unmapped_file_pages(struct pglist_data * pgdat)7447 static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
7448 {
7449 	unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
7450 	unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
7451 		node_page_state(pgdat, NR_ACTIVE_FILE);
7452 
7453 	/*
7454 	 * It's possible for there to be more file mapped pages than
7455 	 * accounted for by the pages on the file LRU lists because
7456 	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7457 	 */
7458 	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
7459 }
7460 
7461 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
node_pagecache_reclaimable(struct pglist_data * pgdat)7462 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
7463 {
7464 	unsigned long nr_pagecache_reclaimable;
7465 	unsigned long delta = 0;
7466 
7467 	/*
7468 	 * If RECLAIM_UNMAP is set, then all file pages are considered
7469 	 * potentially reclaimable. Otherwise, we have to worry about
7470 	 * pages like swapcache and node_unmapped_file_pages() provides
7471 	 * a better estimate
7472 	 */
7473 	if (node_reclaim_mode & RECLAIM_UNMAP)
7474 		nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
7475 	else
7476 		nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
7477 
7478 	/* If we can't clean pages, remove dirty pages from consideration */
7479 	if (!(node_reclaim_mode & RECLAIM_WRITE))
7480 		delta += node_page_state(pgdat, NR_FILE_DIRTY);
7481 
7482 	/* Watch for any possible underflows due to delta */
7483 	if (unlikely(delta > nr_pagecache_reclaimable))
7484 		delta = nr_pagecache_reclaimable;
7485 
7486 	return nr_pagecache_reclaimable - delta;
7487 }
7488 
7489 /*
7490  * Try to free up some pages from this node through reclaim.
7491  */
__node_reclaim(struct pglist_data * pgdat,gfp_t gfp_mask,unsigned int order)7492 static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7493 {
7494 	/* Minimum pages needed in order to stay on node */
7495 	const unsigned long nr_pages = 1 << order;
7496 	struct task_struct *p = current;
7497 	unsigned int noreclaim_flag;
7498 	struct scan_control sc = {
7499 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
7500 		.gfp_mask = current_gfp_context(gfp_mask),
7501 		.order = order,
7502 		.priority = NODE_RECLAIM_PRIORITY,
7503 		.may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
7504 		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
7505 		.may_swap = 1,
7506 		.reclaim_idx = gfp_zone(gfp_mask),
7507 	};
7508 	unsigned long pflags;
7509 
7510 	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
7511 					   sc.gfp_mask);
7512 
7513 	cond_resched();
7514 	psi_memstall_enter(&pflags);
7515 	delayacct_freepages_start();
7516 	fs_reclaim_acquire(sc.gfp_mask);
7517 	/*
7518 	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
7519 	 */
7520 	noreclaim_flag = memalloc_noreclaim_save();
7521 	set_task_reclaim_state(p, &sc.reclaim_state);
7522 
7523 	if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
7524 	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
7525 		/*
7526 		 * Free memory by calling shrink node with increasing
7527 		 * priorities until we have enough memory freed.
7528 		 */
7529 		do {
7530 			shrink_node(pgdat, &sc);
7531 		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
7532 	}
7533 
7534 	set_task_reclaim_state(p, NULL);
7535 	memalloc_noreclaim_restore(noreclaim_flag);
7536 	fs_reclaim_release(sc.gfp_mask);
7537 	psi_memstall_leave(&pflags);
7538 	delayacct_freepages_end();
7539 
7540 	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
7541 
7542 	return sc.nr_reclaimed >= nr_pages;
7543 }
7544 
node_reclaim(struct pglist_data * pgdat,gfp_t gfp_mask,unsigned int order)7545 int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7546 {
7547 	int ret;
7548 
7549 	/*
7550 	 * Node reclaim reclaims unmapped file backed pages and
7551 	 * slab pages if we are over the defined limits.
7552 	 *
7553 	 * A small portion of unmapped file backed pages is needed for
7554 	 * file I/O otherwise pages read by file I/O will be immediately
7555 	 * thrown out if the node is overallocated. So we do not reclaim
7556 	 * if less than a specified percentage of the node is used by
7557 	 * unmapped file backed pages.
7558 	 */
7559 	if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
7560 	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
7561 	    pgdat->min_slab_pages)
7562 		return NODE_RECLAIM_FULL;
7563 
7564 	/*
7565 	 * Do not scan if the allocation should not be delayed.
7566 	 */
7567 	if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
7568 		return NODE_RECLAIM_NOSCAN;
7569 
7570 	/*
7571 	 * Only run node reclaim on the local node or on nodes that do not
7572 	 * have associated processors. This will favor the local processor
7573 	 * over remote processors and spread off node memory allocations
7574 	 * as wide as possible.
7575 	 */
7576 	if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
7577 		return NODE_RECLAIM_NOSCAN;
7578 
7579 	if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
7580 		return NODE_RECLAIM_NOSCAN;
7581 
7582 	ret = __node_reclaim(pgdat, gfp_mask, order);
7583 	clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
7584 
7585 	if (ret)
7586 		count_vm_event(PGSCAN_ZONE_RECLAIM_SUCCESS);
7587 	else
7588 		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
7589 
7590 	return ret;
7591 }
7592 #endif
7593 
7594 /**
7595  * check_move_unevictable_folios - Move evictable folios to appropriate zone
7596  * lru list
7597  * @fbatch: Batch of lru folios to check.
7598  *
7599  * Checks folios for evictability, if an evictable folio is in the unevictable
7600  * lru list, moves it to the appropriate evictable lru list. This function
7601  * should be only used for lru folios.
7602  */
check_move_unevictable_folios(struct folio_batch * fbatch)7603 void check_move_unevictable_folios(struct folio_batch *fbatch)
7604 {
7605 	struct lruvec *lruvec = NULL;
7606 	int pgscanned = 0;
7607 	int pgrescued = 0;
7608 	int i;
7609 
7610 	for (i = 0; i < fbatch->nr; i++) {
7611 		struct folio *folio = fbatch->folios[i];
7612 		int nr_pages = folio_nr_pages(folio);
7613 
7614 		pgscanned += nr_pages;
7615 
7616 		/* block memcg migration while the folio moves between lrus */
7617 		if (!folio_test_clear_lru(folio))
7618 			continue;
7619 
7620 		lruvec = folio_lruvec_relock_irq(folio, lruvec);
7621 		if (folio_evictable(folio) && folio_test_unevictable(folio)) {
7622 			lruvec_del_folio(lruvec, folio);
7623 			folio_clear_unevictable(folio);
7624 			lruvec_add_folio(lruvec, folio);
7625 			pgrescued += nr_pages;
7626 		}
7627 		folio_set_lru(folio);
7628 	}
7629 
7630 	if (lruvec) {
7631 		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
7632 		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7633 		unlock_page_lruvec_irq(lruvec);
7634 	} else if (pgscanned) {
7635 		count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7636 	}
7637 }
7638 EXPORT_SYMBOL_GPL(check_move_unevictable_folios);
7639