xref: /linux/mm/vmscan.c (revision 42b16d3ac371a2fac9b6f08fd75f23f34ba3955a)
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 
60 #include <asm/tlbflush.h>
61 #include <asm/div64.h>
62 
63 #include <linux/swapops.h>
64 #include <linux/balloon_compaction.h>
65 #include <linux/sched/sysctl.h>
66 
67 #include "internal.h"
68 #include "swap.h"
69 
70 #define CREATE_TRACE_POINTS
71 #include <trace/events/vmscan.h>
72 
73 struct scan_control {
74 	/* How many pages shrink_list() should reclaim */
75 	unsigned long nr_to_reclaim;
76 
77 	/*
78 	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
79 	 * are scanned.
80 	 */
81 	nodemask_t	*nodemask;
82 
83 	/*
84 	 * The memory cgroup that hit its limit and as a result is the
85 	 * primary target of this reclaim invocation.
86 	 */
87 	struct mem_cgroup *target_mem_cgroup;
88 
89 	/*
90 	 * Scan pressure balancing between anon and file LRUs
91 	 */
92 	unsigned long	anon_cost;
93 	unsigned long	file_cost;
94 
95 #ifdef CONFIG_MEMCG
96 	/* Swappiness value for proactive reclaim. Always use sc_swappiness()! */
97 	int *proactive_swappiness;
98 #endif
99 
100 	/* Can active folios be deactivated as part of reclaim? */
101 #define DEACTIVATE_ANON 1
102 #define DEACTIVATE_FILE 2
103 	unsigned int may_deactivate:2;
104 	unsigned int force_deactivate:1;
105 	unsigned int skipped_deactivate:1;
106 
107 	/* Writepage batching in laptop mode; RECLAIM_WRITE */
108 	unsigned int may_writepage:1;
109 
110 	/* Can mapped folios be reclaimed? */
111 	unsigned int may_unmap:1;
112 
113 	/* Can folios be swapped as part of reclaim? */
114 	unsigned int may_swap:1;
115 
116 	/* Not allow cache_trim_mode to be turned on as part of reclaim? */
117 	unsigned int no_cache_trim_mode:1;
118 
119 	/* Has cache_trim_mode failed at least once? */
120 	unsigned int cache_trim_mode_failed:1;
121 
122 	/* Proactive reclaim invoked by userspace through memory.reclaim */
123 	unsigned int proactive:1;
124 
125 	/*
126 	 * Cgroup memory below memory.low is protected as long as we
127 	 * don't threaten to OOM. If any cgroup is reclaimed at
128 	 * reduced force or passed over entirely due to its memory.low
129 	 * setting (memcg_low_skipped), and nothing is reclaimed as a
130 	 * result, then go back for one more cycle that reclaims the protected
131 	 * memory (memcg_low_reclaim) to avert OOM.
132 	 */
133 	unsigned int memcg_low_reclaim:1;
134 	unsigned int memcg_low_skipped:1;
135 
136 	/* Shared cgroup tree walk failed, rescan the whole tree */
137 	unsigned int memcg_full_walk:1;
138 
139 	unsigned int hibernation_mode:1;
140 
141 	/* One of the zones is ready for compaction */
142 	unsigned int compaction_ready:1;
143 
144 	/* There is easily reclaimable cold cache in the current node */
145 	unsigned int cache_trim_mode:1;
146 
147 	/* The file folios on the current node are dangerously low */
148 	unsigned int file_is_tiny:1;
149 
150 	/* Always discard instead of demoting to lower tier memory */
151 	unsigned int no_demotion:1;
152 
153 	/* Allocation order */
154 	s8 order;
155 
156 	/* Scan (total_size >> priority) pages at once */
157 	s8 priority;
158 
159 	/* The highest zone to isolate folios for reclaim from */
160 	s8 reclaim_idx;
161 
162 	/* This context's GFP mask */
163 	gfp_t gfp_mask;
164 
165 	/* Incremented by the number of inactive pages that were scanned */
166 	unsigned long nr_scanned;
167 
168 	/* Number of pages freed so far during a call to shrink_zones() */
169 	unsigned long nr_reclaimed;
170 
171 	struct {
172 		unsigned int dirty;
173 		unsigned int unqueued_dirty;
174 		unsigned int congested;
175 		unsigned int writeback;
176 		unsigned int immediate;
177 		unsigned int file_taken;
178 		unsigned int taken;
179 	} nr;
180 
181 	/* for recording the reclaimed slab by now */
182 	struct reclaim_state reclaim_state;
183 };
184 
185 #ifdef ARCH_HAS_PREFETCHW
186 #define prefetchw_prev_lru_folio(_folio, _base, _field)			\
187 	do {								\
188 		if ((_folio)->lru.prev != _base) {			\
189 			struct folio *prev;				\
190 									\
191 			prev = lru_to_folio(&(_folio->lru));		\
192 			prefetchw(&prev->_field);			\
193 		}							\
194 	} while (0)
195 #else
196 #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
197 #endif
198 
199 /*
200  * From 0 .. MAX_SWAPPINESS.  Higher means more swappy.
201  */
202 int vm_swappiness = 60;
203 
204 #ifdef CONFIG_MEMCG
205 
206 /* Returns true for reclaim through cgroup limits or cgroup interfaces. */
cgroup_reclaim(struct scan_control * sc)207 static bool cgroup_reclaim(struct scan_control *sc)
208 {
209 	return sc->target_mem_cgroup;
210 }
211 
212 /*
213  * Returns true for reclaim on the root cgroup. This is true for direct
214  * allocator reclaim and reclaim through cgroup interfaces on the root cgroup.
215  */
root_reclaim(struct scan_control * sc)216 static bool root_reclaim(struct scan_control *sc)
217 {
218 	return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup);
219 }
220 
221 /**
222  * writeback_throttling_sane - is the usual dirty throttling mechanism available?
223  * @sc: scan_control in question
224  *
225  * The normal page dirty throttling mechanism in balance_dirty_pages() is
226  * completely broken with the legacy memcg and direct stalling in
227  * shrink_folio_list() is used for throttling instead, which lacks all the
228  * niceties such as fairness, adaptive pausing, bandwidth proportional
229  * allocation and configurability.
230  *
231  * This function tests whether the vmscan currently in progress can assume
232  * that the normal dirty throttling mechanism is operational.
233  */
writeback_throttling_sane(struct scan_control * sc)234 static bool writeback_throttling_sane(struct scan_control *sc)
235 {
236 	if (!cgroup_reclaim(sc))
237 		return true;
238 #ifdef CONFIG_CGROUP_WRITEBACK
239 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
240 		return true;
241 #endif
242 	return false;
243 }
244 
sc_swappiness(struct scan_control * sc,struct mem_cgroup * memcg)245 static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
246 {
247 	if (sc->proactive && sc->proactive_swappiness)
248 		return *sc->proactive_swappiness;
249 	return mem_cgroup_swappiness(memcg);
250 }
251 #else
cgroup_reclaim(struct scan_control * sc)252 static bool cgroup_reclaim(struct scan_control *sc)
253 {
254 	return false;
255 }
256 
root_reclaim(struct scan_control * sc)257 static bool root_reclaim(struct scan_control *sc)
258 {
259 	return true;
260 }
261 
writeback_throttling_sane(struct scan_control * sc)262 static bool writeback_throttling_sane(struct scan_control *sc)
263 {
264 	return true;
265 }
266 
sc_swappiness(struct scan_control * sc,struct mem_cgroup * memcg)267 static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
268 {
269 	return READ_ONCE(vm_swappiness);
270 }
271 #endif
272 
set_task_reclaim_state(struct task_struct * task,struct reclaim_state * rs)273 static void set_task_reclaim_state(struct task_struct *task,
274 				   struct reclaim_state *rs)
275 {
276 	/* Check for an overwrite */
277 	WARN_ON_ONCE(rs && task->reclaim_state);
278 
279 	/* Check for the nulling of an already-nulled member */
280 	WARN_ON_ONCE(!rs && !task->reclaim_state);
281 
282 	task->reclaim_state = rs;
283 }
284 
285 /*
286  * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
287  * scan_control->nr_reclaimed.
288  */
flush_reclaim_state(struct scan_control * sc)289 static void flush_reclaim_state(struct scan_control *sc)
290 {
291 	/*
292 	 * Currently, reclaim_state->reclaimed includes three types of pages
293 	 * freed outside of vmscan:
294 	 * (1) Slab pages.
295 	 * (2) Clean file pages from pruned inodes (on highmem systems).
296 	 * (3) XFS freed buffer pages.
297 	 *
298 	 * For all of these cases, we cannot universally link the pages to a
299 	 * single memcg. For example, a memcg-aware shrinker can free one object
300 	 * charged to the target memcg, causing an entire page to be freed.
301 	 * If we count the entire page as reclaimed from the memcg, we end up
302 	 * overestimating the reclaimed amount (potentially under-reclaiming).
303 	 *
304 	 * Only count such pages for global reclaim to prevent under-reclaiming
305 	 * from the target memcg; preventing unnecessary retries during memcg
306 	 * charging and false positives from proactive reclaim.
307 	 *
308 	 * For uncommon cases where the freed pages were actually mostly
309 	 * charged to the target memcg, we end up underestimating the reclaimed
310 	 * amount. This should be fine. The freed pages will be uncharged
311 	 * anyway, even if they are not counted here properly, and we will be
312 	 * able to make forward progress in charging (which is usually in a
313 	 * retry loop).
314 	 *
315 	 * We can go one step further, and report the uncharged objcg pages in
316 	 * memcg reclaim, to make reporting more accurate and reduce
317 	 * underestimation, but it's probably not worth the complexity for now.
318 	 */
319 	if (current->reclaim_state && root_reclaim(sc)) {
320 		sc->nr_reclaimed += current->reclaim_state->reclaimed;
321 		current->reclaim_state->reclaimed = 0;
322 	}
323 }
324 
can_demote(int nid,struct scan_control * sc)325 static bool can_demote(int nid, struct scan_control *sc)
326 {
327 	if (!numa_demotion_enabled)
328 		return false;
329 	if (sc && sc->no_demotion)
330 		return false;
331 	if (next_demotion_node(nid) == NUMA_NO_NODE)
332 		return false;
333 
334 	return true;
335 }
336 
can_reclaim_anon_pages(struct mem_cgroup * memcg,int nid,struct scan_control * sc)337 static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
338 					  int nid,
339 					  struct scan_control *sc)
340 {
341 	if (memcg == NULL) {
342 		/*
343 		 * For non-memcg reclaim, is there
344 		 * space in any swap device?
345 		 */
346 		if (get_nr_swap_pages() > 0)
347 			return true;
348 	} else {
349 		/* Is the memcg below its swap limit? */
350 		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
351 			return true;
352 	}
353 
354 	/*
355 	 * The page can not be swapped.
356 	 *
357 	 * Can it be reclaimed from this node via demotion?
358 	 */
359 	return can_demote(nid, sc);
360 }
361 
362 /*
363  * This misses isolated folios which are not accounted for to save counters.
364  * As the data only determines if reclaim or compaction continues, it is
365  * not expected that isolated folios will be a dominating factor.
366  */
zone_reclaimable_pages(struct zone * zone)367 unsigned long zone_reclaimable_pages(struct zone *zone)
368 {
369 	unsigned long nr;
370 
371 	nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
372 		zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
373 	if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
374 		nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
375 			zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
376 
377 	return nr;
378 }
379 
380 /**
381  * lruvec_lru_size -  Returns the number of pages on the given LRU list.
382  * @lruvec: lru vector
383  * @lru: lru to use
384  * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
385  */
lruvec_lru_size(struct lruvec * lruvec,enum lru_list lru,int zone_idx)386 static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
387 				     int zone_idx)
388 {
389 	unsigned long size = 0;
390 	int zid;
391 
392 	for (zid = 0; zid <= zone_idx; zid++) {
393 		struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
394 
395 		if (!managed_zone(zone))
396 			continue;
397 
398 		if (!mem_cgroup_disabled())
399 			size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
400 		else
401 			size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
402 	}
403 	return size;
404 }
405 
drop_slab_node(int nid)406 static unsigned long drop_slab_node(int nid)
407 {
408 	unsigned long freed = 0;
409 	struct mem_cgroup *memcg = NULL;
410 
411 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
412 	do {
413 		freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
414 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
415 
416 	return freed;
417 }
418 
drop_slab(void)419 void drop_slab(void)
420 {
421 	int nid;
422 	int shift = 0;
423 	unsigned long freed;
424 
425 	do {
426 		freed = 0;
427 		for_each_online_node(nid) {
428 			if (fatal_signal_pending(current))
429 				return;
430 
431 			freed += drop_slab_node(nid);
432 		}
433 	} while ((freed >> shift++) > 1);
434 }
435 
reclaimer_offset(void)436 static int reclaimer_offset(void)
437 {
438 	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
439 			PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
440 	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
441 			PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
442 	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
443 			PGSCAN_DIRECT - PGSCAN_KSWAPD);
444 	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
445 			PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
446 
447 	if (current_is_kswapd())
448 		return 0;
449 	if (current_is_khugepaged())
450 		return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
451 	return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
452 }
453 
is_page_cache_freeable(struct folio * folio)454 static inline int is_page_cache_freeable(struct folio *folio)
455 {
456 	/*
457 	 * A freeable page cache folio is referenced only by the caller
458 	 * that isolated the folio, the page cache and optional filesystem
459 	 * private data at folio->private.
460 	 */
461 	return folio_ref_count(folio) - folio_test_private(folio) ==
462 		1 + folio_nr_pages(folio);
463 }
464 
465 /*
466  * We detected a synchronous write error writing a folio out.  Probably
467  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
468  * fsync(), msync() or close().
469  *
470  * The tricky part is that after writepage we cannot touch the mapping: nothing
471  * prevents it from being freed up.  But we have a ref on the folio and once
472  * that folio is locked, the mapping is pinned.
473  *
474  * We're allowed to run sleeping folio_lock() here because we know the caller has
475  * __GFP_FS.
476  */
handle_write_error(struct address_space * mapping,struct folio * folio,int error)477 static void handle_write_error(struct address_space *mapping,
478 				struct folio *folio, int error)
479 {
480 	folio_lock(folio);
481 	if (folio_mapping(folio) == mapping)
482 		mapping_set_error(mapping, error);
483 	folio_unlock(folio);
484 }
485 
skip_throttle_noprogress(pg_data_t * pgdat)486 static bool skip_throttle_noprogress(pg_data_t *pgdat)
487 {
488 	int reclaimable = 0, write_pending = 0;
489 	int i;
490 
491 	/*
492 	 * If kswapd is disabled, reschedule if necessary but do not
493 	 * throttle as the system is likely near OOM.
494 	 */
495 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
496 		return true;
497 
498 	/*
499 	 * If there are a lot of dirty/writeback folios then do not
500 	 * throttle as throttling will occur when the folios cycle
501 	 * towards the end of the LRU if still under writeback.
502 	 */
503 	for (i = 0; i < MAX_NR_ZONES; i++) {
504 		struct zone *zone = pgdat->node_zones + i;
505 
506 		if (!managed_zone(zone))
507 			continue;
508 
509 		reclaimable += zone_reclaimable_pages(zone);
510 		write_pending += zone_page_state_snapshot(zone,
511 						  NR_ZONE_WRITE_PENDING);
512 	}
513 	if (2 * write_pending <= reclaimable)
514 		return true;
515 
516 	return false;
517 }
518 
reclaim_throttle(pg_data_t * pgdat,enum vmscan_throttle_state reason)519 void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
520 {
521 	wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
522 	long timeout, ret;
523 	DEFINE_WAIT(wait);
524 
525 	/*
526 	 * Do not throttle user workers, kthreads other than kswapd or
527 	 * workqueues. They may be required for reclaim to make
528 	 * forward progress (e.g. journalling workqueues or kthreads).
529 	 */
530 	if (!current_is_kswapd() &&
531 	    current->flags & (PF_USER_WORKER|PF_KTHREAD)) {
532 		cond_resched();
533 		return;
534 	}
535 
536 	/*
537 	 * These figures are pulled out of thin air.
538 	 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
539 	 * parallel reclaimers which is a short-lived event so the timeout is
540 	 * short. Failing to make progress or waiting on writeback are
541 	 * potentially long-lived events so use a longer timeout. This is shaky
542 	 * logic as a failure to make progress could be due to anything from
543 	 * writeback to a slow device to excessive referenced folios at the tail
544 	 * of the inactive LRU.
545 	 */
546 	switch(reason) {
547 	case VMSCAN_THROTTLE_WRITEBACK:
548 		timeout = HZ/10;
549 
550 		if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
551 			WRITE_ONCE(pgdat->nr_reclaim_start,
552 				node_page_state(pgdat, NR_THROTTLED_WRITTEN));
553 		}
554 
555 		break;
556 	case VMSCAN_THROTTLE_CONGESTED:
557 		fallthrough;
558 	case VMSCAN_THROTTLE_NOPROGRESS:
559 		if (skip_throttle_noprogress(pgdat)) {
560 			cond_resched();
561 			return;
562 		}
563 
564 		timeout = 1;
565 
566 		break;
567 	case VMSCAN_THROTTLE_ISOLATED:
568 		timeout = HZ/50;
569 		break;
570 	default:
571 		WARN_ON_ONCE(1);
572 		timeout = HZ;
573 		break;
574 	}
575 
576 	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
577 	ret = schedule_timeout(timeout);
578 	finish_wait(wqh, &wait);
579 
580 	if (reason == VMSCAN_THROTTLE_WRITEBACK)
581 		atomic_dec(&pgdat->nr_writeback_throttled);
582 
583 	trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
584 				jiffies_to_usecs(timeout - ret),
585 				reason);
586 }
587 
588 /*
589  * Account for folios written if tasks are throttled waiting on dirty
590  * folios to clean. If enough folios have been cleaned since throttling
591  * started then wakeup the throttled tasks.
592  */
__acct_reclaim_writeback(pg_data_t * pgdat,struct folio * folio,int nr_throttled)593 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
594 							int nr_throttled)
595 {
596 	unsigned long nr_written;
597 
598 	node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
599 
600 	/*
601 	 * This is an inaccurate read as the per-cpu deltas may not
602 	 * be synchronised. However, given that the system is
603 	 * writeback throttled, it is not worth taking the penalty
604 	 * of getting an accurate count. At worst, the throttle
605 	 * timeout guarantees forward progress.
606 	 */
607 	nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
608 		READ_ONCE(pgdat->nr_reclaim_start);
609 
610 	if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
611 		wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
612 }
613 
614 /* possible outcome of pageout() */
615 typedef enum {
616 	/* failed to write folio out, folio is locked */
617 	PAGE_KEEP,
618 	/* move folio to the active list, folio is locked */
619 	PAGE_ACTIVATE,
620 	/* folio has been sent to the disk successfully, folio is unlocked */
621 	PAGE_SUCCESS,
622 	/* folio is clean and locked */
623 	PAGE_CLEAN,
624 } pageout_t;
625 
626 /*
627  * pageout is called by shrink_folio_list() for each dirty folio.
628  * Calls ->writepage().
629  */
pageout(struct folio * folio,struct address_space * mapping,struct swap_iocb ** plug,struct list_head * folio_list)630 static pageout_t pageout(struct folio *folio, struct address_space *mapping,
631 			 struct swap_iocb **plug, struct list_head *folio_list)
632 {
633 	/*
634 	 * If the folio is dirty, only perform writeback if that write
635 	 * will be non-blocking.  To prevent this allocation from being
636 	 * stalled by pagecache activity.  But note that there may be
637 	 * stalls if we need to run get_block().  We could test
638 	 * PagePrivate for that.
639 	 *
640 	 * If this process is currently in __generic_file_write_iter() against
641 	 * this folio's queue, we can perform writeback even if that
642 	 * will block.
643 	 *
644 	 * If the folio is swapcache, write it back even if that would
645 	 * block, for some throttling. This happens by accident, because
646 	 * swap_backing_dev_info is bust: it doesn't reflect the
647 	 * congestion state of the swapdevs.  Easy to fix, if needed.
648 	 */
649 	if (!is_page_cache_freeable(folio))
650 		return PAGE_KEEP;
651 	if (!mapping) {
652 		/*
653 		 * Some data journaling orphaned folios can have
654 		 * folio->mapping == NULL while being dirty with clean buffers.
655 		 */
656 		if (folio_test_private(folio)) {
657 			if (try_to_free_buffers(folio)) {
658 				folio_clear_dirty(folio);
659 				pr_info("%s: orphaned folio\n", __func__);
660 				return PAGE_CLEAN;
661 			}
662 		}
663 		return PAGE_KEEP;
664 	}
665 	if (mapping->a_ops->writepage == NULL)
666 		return PAGE_ACTIVATE;
667 
668 	if (folio_clear_dirty_for_io(folio)) {
669 		int res;
670 		struct writeback_control wbc = {
671 			.sync_mode = WB_SYNC_NONE,
672 			.nr_to_write = SWAP_CLUSTER_MAX,
673 			.range_start = 0,
674 			.range_end = LLONG_MAX,
675 			.for_reclaim = 1,
676 			.swap_plug = plug,
677 		};
678 
679 		/*
680 		 * The large shmem folio can be split if CONFIG_THP_SWAP is
681 		 * not enabled or contiguous swap entries are failed to
682 		 * allocate.
683 		 */
684 		if (shmem_mapping(mapping) && folio_test_large(folio))
685 			wbc.list = folio_list;
686 
687 		folio_set_reclaim(folio);
688 		res = mapping->a_ops->writepage(&folio->page, &wbc);
689 		if (res < 0)
690 			handle_write_error(mapping, folio, res);
691 		if (res == AOP_WRITEPAGE_ACTIVATE) {
692 			folio_clear_reclaim(folio);
693 			return PAGE_ACTIVATE;
694 		}
695 
696 		if (!folio_test_writeback(folio)) {
697 			/* synchronous write or broken a_ops? */
698 			folio_clear_reclaim(folio);
699 		}
700 		trace_mm_vmscan_write_folio(folio);
701 		node_stat_add_folio(folio, NR_VMSCAN_WRITE);
702 		return PAGE_SUCCESS;
703 	}
704 
705 	return PAGE_CLEAN;
706 }
707 
708 /*
709  * Same as remove_mapping, but if the folio is removed from the mapping, it
710  * gets returned with a refcount of 0.
711  */
__remove_mapping(struct address_space * mapping,struct folio * folio,bool reclaimed,struct mem_cgroup * target_memcg)712 static int __remove_mapping(struct address_space *mapping, struct folio *folio,
713 			    bool reclaimed, struct mem_cgroup *target_memcg)
714 {
715 	int refcount;
716 	void *shadow = NULL;
717 
718 	BUG_ON(!folio_test_locked(folio));
719 	BUG_ON(mapping != folio_mapping(folio));
720 
721 	if (!folio_test_swapcache(folio))
722 		spin_lock(&mapping->host->i_lock);
723 	xa_lock_irq(&mapping->i_pages);
724 	/*
725 	 * The non racy check for a busy folio.
726 	 *
727 	 * Must be careful with the order of the tests. When someone has
728 	 * a ref to the folio, it may be possible that they dirty it then
729 	 * drop the reference. So if the dirty flag is tested before the
730 	 * refcount here, then the following race may occur:
731 	 *
732 	 * get_user_pages(&page);
733 	 * [user mapping goes away]
734 	 * write_to(page);
735 	 *				!folio_test_dirty(folio)    [good]
736 	 * folio_set_dirty(folio);
737 	 * folio_put(folio);
738 	 *				!refcount(folio)   [good, discard it]
739 	 *
740 	 * [oops, our write_to data is lost]
741 	 *
742 	 * Reversing the order of the tests ensures such a situation cannot
743 	 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
744 	 * load is not satisfied before that of folio->_refcount.
745 	 *
746 	 * Note that if the dirty flag is always set via folio_mark_dirty,
747 	 * and thus under the i_pages lock, then this ordering is not required.
748 	 */
749 	refcount = 1 + folio_nr_pages(folio);
750 	if (!folio_ref_freeze(folio, refcount))
751 		goto cannot_free;
752 	/* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
753 	if (unlikely(folio_test_dirty(folio))) {
754 		folio_ref_unfreeze(folio, refcount);
755 		goto cannot_free;
756 	}
757 
758 	if (folio_test_swapcache(folio)) {
759 		swp_entry_t swap = folio->swap;
760 
761 		if (reclaimed && !mapping_exiting(mapping))
762 			shadow = workingset_eviction(folio, target_memcg);
763 		__delete_from_swap_cache(folio, swap, shadow);
764 		mem_cgroup_swapout(folio, swap);
765 		xa_unlock_irq(&mapping->i_pages);
766 		put_swap_folio(folio, swap);
767 	} else {
768 		void (*free_folio)(struct folio *);
769 
770 		free_folio = mapping->a_ops->free_folio;
771 		/*
772 		 * Remember a shadow entry for reclaimed file cache in
773 		 * order to detect refaults, thus thrashing, later on.
774 		 *
775 		 * But don't store shadows in an address space that is
776 		 * already exiting.  This is not just an optimization,
777 		 * inode reclaim needs to empty out the radix tree or
778 		 * the nodes are lost.  Don't plant shadows behind its
779 		 * back.
780 		 *
781 		 * We also don't store shadows for DAX mappings because the
782 		 * only page cache folios found in these are zero pages
783 		 * covering holes, and because we don't want to mix DAX
784 		 * exceptional entries and shadow exceptional entries in the
785 		 * same address_space.
786 		 */
787 		if (reclaimed && folio_is_file_lru(folio) &&
788 		    !mapping_exiting(mapping) && !dax_mapping(mapping))
789 			shadow = workingset_eviction(folio, target_memcg);
790 		__filemap_remove_folio(folio, shadow);
791 		xa_unlock_irq(&mapping->i_pages);
792 		if (mapping_shrinkable(mapping))
793 			inode_add_lru(mapping->host);
794 		spin_unlock(&mapping->host->i_lock);
795 
796 		if (free_folio)
797 			free_folio(folio);
798 	}
799 
800 	return 1;
801 
802 cannot_free:
803 	xa_unlock_irq(&mapping->i_pages);
804 	if (!folio_test_swapcache(folio))
805 		spin_unlock(&mapping->host->i_lock);
806 	return 0;
807 }
808 
809 /**
810  * remove_mapping() - Attempt to remove a folio from its mapping.
811  * @mapping: The address space.
812  * @folio: The folio to remove.
813  *
814  * If the folio is dirty, under writeback or if someone else has a ref
815  * on it, removal will fail.
816  * Return: The number of pages removed from the mapping.  0 if the folio
817  * could not be removed.
818  * Context: The caller should have a single refcount on the folio and
819  * hold its lock.
820  */
remove_mapping(struct address_space * mapping,struct folio * folio)821 long remove_mapping(struct address_space *mapping, struct folio *folio)
822 {
823 	if (__remove_mapping(mapping, folio, false, NULL)) {
824 		/*
825 		 * Unfreezing the refcount with 1 effectively
826 		 * drops the pagecache ref for us without requiring another
827 		 * atomic operation.
828 		 */
829 		folio_ref_unfreeze(folio, 1);
830 		return folio_nr_pages(folio);
831 	}
832 	return 0;
833 }
834 
835 /**
836  * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
837  * @folio: Folio to be returned to an LRU list.
838  *
839  * Add previously isolated @folio to appropriate LRU list.
840  * The folio may still be unevictable for other reasons.
841  *
842  * Context: lru_lock must not be held, interrupts must be enabled.
843  */
folio_putback_lru(struct folio * folio)844 void folio_putback_lru(struct folio *folio)
845 {
846 	folio_add_lru(folio);
847 	folio_put(folio);		/* drop ref from isolate */
848 }
849 
850 enum folio_references {
851 	FOLIOREF_RECLAIM,
852 	FOLIOREF_RECLAIM_CLEAN,
853 	FOLIOREF_KEEP,
854 	FOLIOREF_ACTIVATE,
855 };
856 
folio_check_references(struct folio * folio,struct scan_control * sc)857 static enum folio_references folio_check_references(struct folio *folio,
858 						  struct scan_control *sc)
859 {
860 	int referenced_ptes, referenced_folio;
861 	unsigned long vm_flags;
862 
863 	referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
864 					   &vm_flags);
865 	referenced_folio = folio_test_clear_referenced(folio);
866 
867 	/*
868 	 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
869 	 * Let the folio, now marked Mlocked, be moved to the unevictable list.
870 	 */
871 	if (vm_flags & VM_LOCKED)
872 		return FOLIOREF_ACTIVATE;
873 
874 	/*
875 	 * There are two cases to consider.
876 	 * 1) Rmap lock contention: rotate.
877 	 * 2) Skip the non-shared swapbacked folio mapped solely by
878 	 *    the exiting or OOM-reaped process.
879 	 */
880 	if (referenced_ptes == -1)
881 		return FOLIOREF_KEEP;
882 
883 	if (referenced_ptes) {
884 		/*
885 		 * All mapped folios start out with page table
886 		 * references from the instantiating fault, so we need
887 		 * to look twice if a mapped file/anon folio is used more
888 		 * than once.
889 		 *
890 		 * Mark it and spare it for another trip around the
891 		 * inactive list.  Another page table reference will
892 		 * lead to its activation.
893 		 *
894 		 * Note: the mark is set for activated folios as well
895 		 * so that recently deactivated but used folios are
896 		 * quickly recovered.
897 		 */
898 		folio_set_referenced(folio);
899 
900 		if (referenced_folio || referenced_ptes > 1)
901 			return FOLIOREF_ACTIVATE;
902 
903 		/*
904 		 * Activate file-backed executable folios after first usage.
905 		 */
906 		if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
907 			return FOLIOREF_ACTIVATE;
908 
909 		return FOLIOREF_KEEP;
910 	}
911 
912 	/* Reclaim if clean, defer dirty folios to writeback */
913 	if (referenced_folio && folio_is_file_lru(folio))
914 		return FOLIOREF_RECLAIM_CLEAN;
915 
916 	return FOLIOREF_RECLAIM;
917 }
918 
919 /* Check if a folio is dirty or under writeback */
folio_check_dirty_writeback(struct folio * folio,bool * dirty,bool * writeback)920 static void folio_check_dirty_writeback(struct folio *folio,
921 				       bool *dirty, bool *writeback)
922 {
923 	struct address_space *mapping;
924 
925 	/*
926 	 * Anonymous folios are not handled by flushers and must be written
927 	 * from reclaim context. Do not stall reclaim based on them.
928 	 * MADV_FREE anonymous folios are put into inactive file list too.
929 	 * They could be mistakenly treated as file lru. So further anon
930 	 * test is needed.
931 	 */
932 	if (!folio_is_file_lru(folio) ||
933 	    (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
934 		*dirty = false;
935 		*writeback = false;
936 		return;
937 	}
938 
939 	/* By default assume that the folio flags are accurate */
940 	*dirty = folio_test_dirty(folio);
941 	*writeback = folio_test_writeback(folio);
942 
943 	/* Verify dirty/writeback state if the filesystem supports it */
944 	if (!folio_test_private(folio))
945 		return;
946 
947 	mapping = folio_mapping(folio);
948 	if (mapping && mapping->a_ops->is_dirty_writeback)
949 		mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
950 }
951 
alloc_migrate_folio(struct folio * src,unsigned long private)952 struct folio *alloc_migrate_folio(struct folio *src, unsigned long private)
953 {
954 	struct folio *dst;
955 	nodemask_t *allowed_mask;
956 	struct migration_target_control *mtc;
957 
958 	mtc = (struct migration_target_control *)private;
959 
960 	allowed_mask = mtc->nmask;
961 	/*
962 	 * make sure we allocate from the target node first also trying to
963 	 * demote or reclaim pages from the target node via kswapd if we are
964 	 * low on free memory on target node. If we don't do this and if
965 	 * we have free memory on the slower(lower) memtier, we would start
966 	 * allocating pages from slower(lower) memory tiers without even forcing
967 	 * a demotion of cold pages from the target memtier. This can result
968 	 * in the kernel placing hot pages in slower(lower) memory tiers.
969 	 */
970 	mtc->nmask = NULL;
971 	mtc->gfp_mask |= __GFP_THISNODE;
972 	dst = alloc_migration_target(src, (unsigned long)mtc);
973 	if (dst)
974 		return dst;
975 
976 	mtc->gfp_mask &= ~__GFP_THISNODE;
977 	mtc->nmask = allowed_mask;
978 
979 	return alloc_migration_target(src, (unsigned long)mtc);
980 }
981 
982 /*
983  * Take folios on @demote_folios and attempt to demote them to another node.
984  * Folios which are not demoted are left on @demote_folios.
985  */
demote_folio_list(struct list_head * demote_folios,struct pglist_data * pgdat)986 static unsigned int demote_folio_list(struct list_head *demote_folios,
987 				     struct pglist_data *pgdat)
988 {
989 	int target_nid = next_demotion_node(pgdat->node_id);
990 	unsigned int nr_succeeded;
991 	nodemask_t allowed_mask;
992 
993 	struct migration_target_control mtc = {
994 		/*
995 		 * Allocate from 'node', or fail quickly and quietly.
996 		 * When this happens, 'page' will likely just be discarded
997 		 * instead of migrated.
998 		 */
999 		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
1000 			__GFP_NOMEMALLOC | GFP_NOWAIT,
1001 		.nid = target_nid,
1002 		.nmask = &allowed_mask,
1003 		.reason = MR_DEMOTION,
1004 	};
1005 
1006 	if (list_empty(demote_folios))
1007 		return 0;
1008 
1009 	if (target_nid == NUMA_NO_NODE)
1010 		return 0;
1011 
1012 	node_get_allowed_targets(pgdat, &allowed_mask);
1013 
1014 	/* Demotion ignores all cpuset and mempolicy settings */
1015 	migrate_pages(demote_folios, alloc_migrate_folio, NULL,
1016 		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
1017 		      &nr_succeeded);
1018 
1019 	return nr_succeeded;
1020 }
1021 
may_enter_fs(struct folio * folio,gfp_t gfp_mask)1022 static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
1023 {
1024 	if (gfp_mask & __GFP_FS)
1025 		return true;
1026 	if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
1027 		return false;
1028 	/*
1029 	 * We can "enter_fs" for swap-cache with only __GFP_IO
1030 	 * providing this isn't SWP_FS_OPS.
1031 	 * ->flags can be updated non-atomicially (scan_swap_map_slots),
1032 	 * but that will never affect SWP_FS_OPS, so the data_race
1033 	 * is safe.
1034 	 */
1035 	return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
1036 }
1037 
1038 /*
1039  * shrink_folio_list() returns the number of reclaimed pages
1040  */
shrink_folio_list(struct list_head * folio_list,struct pglist_data * pgdat,struct scan_control * sc,struct reclaim_stat * stat,bool ignore_references)1041 static unsigned int shrink_folio_list(struct list_head *folio_list,
1042 		struct pglist_data *pgdat, struct scan_control *sc,
1043 		struct reclaim_stat *stat, bool ignore_references)
1044 {
1045 	struct folio_batch free_folios;
1046 	LIST_HEAD(ret_folios);
1047 	LIST_HEAD(demote_folios);
1048 	unsigned int nr_reclaimed = 0;
1049 	unsigned int pgactivate = 0;
1050 	bool do_demote_pass;
1051 	struct swap_iocb *plug = NULL;
1052 
1053 	folio_batch_init(&free_folios);
1054 	memset(stat, 0, sizeof(*stat));
1055 	cond_resched();
1056 	do_demote_pass = can_demote(pgdat->node_id, sc);
1057 
1058 retry:
1059 	while (!list_empty(folio_list)) {
1060 		struct address_space *mapping;
1061 		struct folio *folio;
1062 		enum folio_references references = FOLIOREF_RECLAIM;
1063 		bool dirty, writeback;
1064 		unsigned int nr_pages;
1065 
1066 		cond_resched();
1067 
1068 		folio = lru_to_folio(folio_list);
1069 		list_del(&folio->lru);
1070 
1071 		if (!folio_trylock(folio))
1072 			goto keep;
1073 
1074 		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1075 
1076 		nr_pages = folio_nr_pages(folio);
1077 
1078 		/* Account the number of base pages */
1079 		sc->nr_scanned += nr_pages;
1080 
1081 		if (unlikely(!folio_evictable(folio)))
1082 			goto activate_locked;
1083 
1084 		if (!sc->may_unmap && folio_mapped(folio))
1085 			goto keep_locked;
1086 
1087 		/* folio_update_gen() tried to promote this page? */
1088 		if (lru_gen_enabled() && !ignore_references &&
1089 		    folio_mapped(folio) && folio_test_referenced(folio))
1090 			goto keep_locked;
1091 
1092 		/*
1093 		 * The number of dirty pages determines if a node is marked
1094 		 * reclaim_congested. kswapd will stall and start writing
1095 		 * folios if the tail of the LRU is all dirty unqueued folios.
1096 		 */
1097 		folio_check_dirty_writeback(folio, &dirty, &writeback);
1098 		if (dirty || writeback)
1099 			stat->nr_dirty += nr_pages;
1100 
1101 		if (dirty && !writeback)
1102 			stat->nr_unqueued_dirty += nr_pages;
1103 
1104 		/*
1105 		 * Treat this folio as congested if folios are cycling
1106 		 * through the LRU so quickly that the folios marked
1107 		 * for immediate reclaim are making it to the end of
1108 		 * the LRU a second time.
1109 		 */
1110 		if (writeback && folio_test_reclaim(folio))
1111 			stat->nr_congested += nr_pages;
1112 
1113 		/*
1114 		 * If a folio at the tail of the LRU is under writeback, there
1115 		 * are three cases to consider.
1116 		 *
1117 		 * 1) If reclaim is encountering an excessive number
1118 		 *    of folios under writeback and this folio has both
1119 		 *    the writeback and reclaim flags set, then it
1120 		 *    indicates that folios are being queued for I/O but
1121 		 *    are being recycled through the LRU before the I/O
1122 		 *    can complete. Waiting on the folio itself risks an
1123 		 *    indefinite stall if it is impossible to writeback
1124 		 *    the folio due to I/O error or disconnected storage
1125 		 *    so instead note that the LRU is being scanned too
1126 		 *    quickly and the caller can stall after the folio
1127 		 *    list has been processed.
1128 		 *
1129 		 * 2) Global or new memcg reclaim encounters a folio that is
1130 		 *    not marked for immediate reclaim, or the caller does not
1131 		 *    have __GFP_FS (or __GFP_IO if it's simply going to swap,
1132 		 *    not to fs). In this case mark the folio for immediate
1133 		 *    reclaim and continue scanning.
1134 		 *
1135 		 *    Require may_enter_fs() because we would wait on fs, which
1136 		 *    may not have submitted I/O yet. And the loop driver might
1137 		 *    enter reclaim, and deadlock if it waits on a folio for
1138 		 *    which it is needed to do the write (loop masks off
1139 		 *    __GFP_IO|__GFP_FS for this reason); but more thought
1140 		 *    would probably show more reasons.
1141 		 *
1142 		 * 3) Legacy memcg encounters a folio that already has the
1143 		 *    reclaim flag set. memcg does not have any dirty folio
1144 		 *    throttling so we could easily OOM just because too many
1145 		 *    folios are in writeback and there is nothing else to
1146 		 *    reclaim. Wait for the writeback to complete.
1147 		 *
1148 		 * In cases 1) and 2) we activate the folios to get them out of
1149 		 * the way while we continue scanning for clean folios on the
1150 		 * inactive list and refilling from the active list. The
1151 		 * observation here is that waiting for disk writes is more
1152 		 * expensive than potentially causing reloads down the line.
1153 		 * Since they're marked for immediate reclaim, they won't put
1154 		 * memory pressure on the cache working set any longer than it
1155 		 * takes to write them to disk.
1156 		 */
1157 		if (folio_test_writeback(folio)) {
1158 			/* Case 1 above */
1159 			if (current_is_kswapd() &&
1160 			    folio_test_reclaim(folio) &&
1161 			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1162 				stat->nr_immediate += nr_pages;
1163 				goto activate_locked;
1164 
1165 			/* Case 2 above */
1166 			} else if (writeback_throttling_sane(sc) ||
1167 			    !folio_test_reclaim(folio) ||
1168 			    !may_enter_fs(folio, sc->gfp_mask)) {
1169 				/*
1170 				 * This is slightly racy -
1171 				 * folio_end_writeback() might have
1172 				 * just cleared the reclaim flag, then
1173 				 * setting the reclaim flag here ends up
1174 				 * interpreted as the readahead flag - but
1175 				 * that does not matter enough to care.
1176 				 * What we do want is for this folio to
1177 				 * have the reclaim flag set next time
1178 				 * memcg reclaim reaches the tests above,
1179 				 * so it will then wait for writeback to
1180 				 * avoid OOM; and it's also appropriate
1181 				 * in global reclaim.
1182 				 */
1183 				folio_set_reclaim(folio);
1184 				stat->nr_writeback += nr_pages;
1185 				goto activate_locked;
1186 
1187 			/* Case 3 above */
1188 			} else {
1189 				folio_unlock(folio);
1190 				folio_wait_writeback(folio);
1191 				/* then go back and try same folio again */
1192 				list_add_tail(&folio->lru, folio_list);
1193 				continue;
1194 			}
1195 		}
1196 
1197 		if (!ignore_references)
1198 			references = folio_check_references(folio, sc);
1199 
1200 		switch (references) {
1201 		case FOLIOREF_ACTIVATE:
1202 			goto activate_locked;
1203 		case FOLIOREF_KEEP:
1204 			stat->nr_ref_keep += nr_pages;
1205 			goto keep_locked;
1206 		case FOLIOREF_RECLAIM:
1207 		case FOLIOREF_RECLAIM_CLEAN:
1208 			; /* try to reclaim the folio below */
1209 		}
1210 
1211 		/*
1212 		 * Before reclaiming the folio, try to relocate
1213 		 * its contents to another node.
1214 		 */
1215 		if (do_demote_pass &&
1216 		    (thp_migration_supported() || !folio_test_large(folio))) {
1217 			list_add(&folio->lru, &demote_folios);
1218 			folio_unlock(folio);
1219 			continue;
1220 		}
1221 
1222 		/*
1223 		 * Anonymous process memory has backing store?
1224 		 * Try to allocate it some swap space here.
1225 		 * Lazyfree folio could be freed directly
1226 		 */
1227 		if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
1228 			if (!folio_test_swapcache(folio)) {
1229 				if (!(sc->gfp_mask & __GFP_IO))
1230 					goto keep_locked;
1231 				if (folio_maybe_dma_pinned(folio))
1232 					goto keep_locked;
1233 				if (folio_test_large(folio)) {
1234 					/* cannot split folio, skip it */
1235 					if (!can_split_folio(folio, 1, NULL))
1236 						goto activate_locked;
1237 					/*
1238 					 * Split partially mapped folios right away.
1239 					 * We can free the unmapped pages without IO.
1240 					 */
1241 					if (data_race(!list_empty(&folio->_deferred_list) &&
1242 					    folio_test_partially_mapped(folio)) &&
1243 					    split_folio_to_list(folio, folio_list))
1244 						goto activate_locked;
1245 				}
1246 				if (!add_to_swap(folio)) {
1247 					int __maybe_unused order = folio_order(folio);
1248 
1249 					if (!folio_test_large(folio))
1250 						goto activate_locked_split;
1251 					/* Fallback to swap normal pages */
1252 					if (split_folio_to_list(folio, folio_list))
1253 						goto activate_locked;
1254 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1255 					if (nr_pages >= HPAGE_PMD_NR) {
1256 						count_memcg_folio_events(folio,
1257 							THP_SWPOUT_FALLBACK, 1);
1258 						count_vm_event(THP_SWPOUT_FALLBACK);
1259 					}
1260 					count_mthp_stat(order, MTHP_STAT_SWPOUT_FALLBACK);
1261 #endif
1262 					if (!add_to_swap(folio))
1263 						goto activate_locked_split;
1264 				}
1265 			}
1266 		}
1267 
1268 		/*
1269 		 * If the folio was split above, the tail pages will make
1270 		 * their own pass through this function and be accounted
1271 		 * then.
1272 		 */
1273 		if ((nr_pages > 1) && !folio_test_large(folio)) {
1274 			sc->nr_scanned -= (nr_pages - 1);
1275 			nr_pages = 1;
1276 		}
1277 
1278 		/*
1279 		 * The folio is mapped into the page tables of one or more
1280 		 * processes. Try to unmap it here.
1281 		 */
1282 		if (folio_mapped(folio)) {
1283 			enum ttu_flags flags = TTU_BATCH_FLUSH;
1284 			bool was_swapbacked = folio_test_swapbacked(folio);
1285 
1286 			if (folio_test_pmd_mappable(folio))
1287 				flags |= TTU_SPLIT_HUGE_PMD;
1288 			/*
1289 			 * Without TTU_SYNC, try_to_unmap will only begin to
1290 			 * hold PTL from the first present PTE within a large
1291 			 * folio. Some initial PTEs might be skipped due to
1292 			 * races with parallel PTE writes in which PTEs can be
1293 			 * cleared temporarily before being written new present
1294 			 * values. This will lead to a large folio is still
1295 			 * mapped while some subpages have been partially
1296 			 * unmapped after try_to_unmap; TTU_SYNC helps
1297 			 * try_to_unmap acquire PTL from the first PTE,
1298 			 * eliminating the influence of temporary PTE values.
1299 			 */
1300 			if (folio_test_large(folio))
1301 				flags |= TTU_SYNC;
1302 
1303 			try_to_unmap(folio, flags);
1304 			if (folio_mapped(folio)) {
1305 				stat->nr_unmap_fail += nr_pages;
1306 				if (!was_swapbacked &&
1307 				    folio_test_swapbacked(folio))
1308 					stat->nr_lazyfree_fail += nr_pages;
1309 				goto activate_locked;
1310 			}
1311 		}
1312 
1313 		/*
1314 		 * Folio is unmapped now so it cannot be newly pinned anymore.
1315 		 * No point in trying to reclaim folio if it is pinned.
1316 		 * Furthermore we don't want to reclaim underlying fs metadata
1317 		 * if the folio is pinned and thus potentially modified by the
1318 		 * pinning process as that may upset the filesystem.
1319 		 */
1320 		if (folio_maybe_dma_pinned(folio))
1321 			goto activate_locked;
1322 
1323 		mapping = folio_mapping(folio);
1324 		if (folio_test_dirty(folio)) {
1325 			/*
1326 			 * Only kswapd can writeback filesystem folios
1327 			 * to avoid risk of stack overflow. But avoid
1328 			 * injecting inefficient single-folio I/O into
1329 			 * flusher writeback as much as possible: only
1330 			 * write folios when we've encountered many
1331 			 * dirty folios, and when we've already scanned
1332 			 * the rest of the LRU for clean folios and see
1333 			 * the same dirty folios again (with the reclaim
1334 			 * flag set).
1335 			 */
1336 			if (folio_is_file_lru(folio) &&
1337 			    (!current_is_kswapd() ||
1338 			     !folio_test_reclaim(folio) ||
1339 			     !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1340 				/*
1341 				 * Immediately reclaim when written back.
1342 				 * Similar in principle to folio_deactivate()
1343 				 * except we already have the folio isolated
1344 				 * and know it's dirty
1345 				 */
1346 				node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
1347 						nr_pages);
1348 				folio_set_reclaim(folio);
1349 
1350 				goto activate_locked;
1351 			}
1352 
1353 			if (references == FOLIOREF_RECLAIM_CLEAN)
1354 				goto keep_locked;
1355 			if (!may_enter_fs(folio, sc->gfp_mask))
1356 				goto keep_locked;
1357 			if (!sc->may_writepage)
1358 				goto keep_locked;
1359 
1360 			/*
1361 			 * Folio is dirty. Flush the TLB if a writable entry
1362 			 * potentially exists to avoid CPU writes after I/O
1363 			 * starts and then write it out here.
1364 			 */
1365 			try_to_unmap_flush_dirty();
1366 			switch (pageout(folio, mapping, &plug, folio_list)) {
1367 			case PAGE_KEEP:
1368 				goto keep_locked;
1369 			case PAGE_ACTIVATE:
1370 				/*
1371 				 * If shmem folio is split when writeback to swap,
1372 				 * the tail pages will make their own pass through
1373 				 * this function and be accounted then.
1374 				 */
1375 				if (nr_pages > 1 && !folio_test_large(folio)) {
1376 					sc->nr_scanned -= (nr_pages - 1);
1377 					nr_pages = 1;
1378 				}
1379 				goto activate_locked;
1380 			case PAGE_SUCCESS:
1381 				if (nr_pages > 1 && !folio_test_large(folio)) {
1382 					sc->nr_scanned -= (nr_pages - 1);
1383 					nr_pages = 1;
1384 				}
1385 				stat->nr_pageout += nr_pages;
1386 
1387 				if (folio_test_writeback(folio))
1388 					goto keep;
1389 				if (folio_test_dirty(folio))
1390 					goto keep;
1391 
1392 				/*
1393 				 * A synchronous write - probably a ramdisk.  Go
1394 				 * ahead and try to reclaim the folio.
1395 				 */
1396 				if (!folio_trylock(folio))
1397 					goto keep;
1398 				if (folio_test_dirty(folio) ||
1399 				    folio_test_writeback(folio))
1400 					goto keep_locked;
1401 				mapping = folio_mapping(folio);
1402 				fallthrough;
1403 			case PAGE_CLEAN:
1404 				; /* try to free the folio below */
1405 			}
1406 		}
1407 
1408 		/*
1409 		 * If the folio has buffers, try to free the buffer
1410 		 * mappings associated with this folio. If we succeed
1411 		 * we try to free the folio as well.
1412 		 *
1413 		 * We do this even if the folio is dirty.
1414 		 * filemap_release_folio() does not perform I/O, but it
1415 		 * is possible for a folio to have the dirty flag set,
1416 		 * but it is actually clean (all its buffers are clean).
1417 		 * This happens if the buffers were written out directly,
1418 		 * with submit_bh(). ext3 will do this, as well as
1419 		 * the blockdev mapping.  filemap_release_folio() will
1420 		 * discover that cleanness and will drop the buffers
1421 		 * and mark the folio clean - it can be freed.
1422 		 *
1423 		 * Rarely, folios can have buffers and no ->mapping.
1424 		 * These are the folios which were not successfully
1425 		 * invalidated in truncate_cleanup_folio().  We try to
1426 		 * drop those buffers here and if that worked, and the
1427 		 * folio is no longer mapped into process address space
1428 		 * (refcount == 1) it can be freed.  Otherwise, leave
1429 		 * the folio on the LRU so it is swappable.
1430 		 */
1431 		if (folio_needs_release(folio)) {
1432 			if (!filemap_release_folio(folio, sc->gfp_mask))
1433 				goto activate_locked;
1434 			if (!mapping && folio_ref_count(folio) == 1) {
1435 				folio_unlock(folio);
1436 				if (folio_put_testzero(folio))
1437 					goto free_it;
1438 				else {
1439 					/*
1440 					 * rare race with speculative reference.
1441 					 * the speculative reference will free
1442 					 * this folio shortly, so we may
1443 					 * increment nr_reclaimed here (and
1444 					 * leave it off the LRU).
1445 					 */
1446 					nr_reclaimed += nr_pages;
1447 					continue;
1448 				}
1449 			}
1450 		}
1451 
1452 		if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
1453 			/* follow __remove_mapping for reference */
1454 			if (!folio_ref_freeze(folio, 1))
1455 				goto keep_locked;
1456 			/*
1457 			 * The folio has only one reference left, which is
1458 			 * from the isolation. After the caller puts the
1459 			 * folio back on the lru and drops the reference, the
1460 			 * folio will be freed anyway. It doesn't matter
1461 			 * which lru it goes on. So we don't bother checking
1462 			 * the dirty flag here.
1463 			 */
1464 			count_vm_events(PGLAZYFREED, nr_pages);
1465 			count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
1466 		} else if (!mapping || !__remove_mapping(mapping, folio, true,
1467 							 sc->target_mem_cgroup))
1468 			goto keep_locked;
1469 
1470 		folio_unlock(folio);
1471 free_it:
1472 		/*
1473 		 * Folio may get swapped out as a whole, need to account
1474 		 * all pages in it.
1475 		 */
1476 		nr_reclaimed += nr_pages;
1477 
1478 		folio_undo_large_rmappable(folio);
1479 		if (folio_batch_add(&free_folios, folio) == 0) {
1480 			mem_cgroup_uncharge_folios(&free_folios);
1481 			try_to_unmap_flush();
1482 			free_unref_folios(&free_folios);
1483 		}
1484 		continue;
1485 
1486 activate_locked_split:
1487 		/*
1488 		 * The tail pages that are failed to add into swap cache
1489 		 * reach here.  Fixup nr_scanned and nr_pages.
1490 		 */
1491 		if (nr_pages > 1) {
1492 			sc->nr_scanned -= (nr_pages - 1);
1493 			nr_pages = 1;
1494 		}
1495 activate_locked:
1496 		/* Not a candidate for swapping, so reclaim swap space. */
1497 		if (folio_test_swapcache(folio) &&
1498 		    (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
1499 			folio_free_swap(folio);
1500 		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1501 		if (!folio_test_mlocked(folio)) {
1502 			int type = folio_is_file_lru(folio);
1503 			folio_set_active(folio);
1504 			stat->nr_activate[type] += nr_pages;
1505 			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
1506 		}
1507 keep_locked:
1508 		folio_unlock(folio);
1509 keep:
1510 		list_add(&folio->lru, &ret_folios);
1511 		VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
1512 				folio_test_unevictable(folio), folio);
1513 	}
1514 	/* 'folio_list' is always empty here */
1515 
1516 	/* Migrate folios selected for demotion */
1517 	stat->nr_demoted = demote_folio_list(&demote_folios, pgdat);
1518 	nr_reclaimed += stat->nr_demoted;
1519 	/* Folios that could not be demoted are still in @demote_folios */
1520 	if (!list_empty(&demote_folios)) {
1521 		/* Folios which weren't demoted go back on @folio_list */
1522 		list_splice_init(&demote_folios, folio_list);
1523 
1524 		/*
1525 		 * goto retry to reclaim the undemoted folios in folio_list if
1526 		 * desired.
1527 		 *
1528 		 * Reclaiming directly from top tier nodes is not often desired
1529 		 * due to it breaking the LRU ordering: in general memory
1530 		 * should be reclaimed from lower tier nodes and demoted from
1531 		 * top tier nodes.
1532 		 *
1533 		 * However, disabling reclaim from top tier nodes entirely
1534 		 * would cause ooms in edge scenarios where lower tier memory
1535 		 * is unreclaimable for whatever reason, eg memory being
1536 		 * mlocked or too hot to reclaim. We can disable reclaim
1537 		 * from top tier nodes in proactive reclaim though as that is
1538 		 * not real memory pressure.
1539 		 */
1540 		if (!sc->proactive) {
1541 			do_demote_pass = false;
1542 			goto retry;
1543 		}
1544 	}
1545 
1546 	pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
1547 
1548 	mem_cgroup_uncharge_folios(&free_folios);
1549 	try_to_unmap_flush();
1550 	free_unref_folios(&free_folios);
1551 
1552 	list_splice(&ret_folios, folio_list);
1553 	count_vm_events(PGACTIVATE, pgactivate);
1554 
1555 	if (plug)
1556 		swap_write_unplug(plug);
1557 	return nr_reclaimed;
1558 }
1559 
reclaim_clean_pages_from_list(struct zone * zone,struct list_head * folio_list)1560 unsigned int reclaim_clean_pages_from_list(struct zone *zone,
1561 					   struct list_head *folio_list)
1562 {
1563 	struct scan_control sc = {
1564 		.gfp_mask = GFP_KERNEL,
1565 		.may_unmap = 1,
1566 	};
1567 	struct reclaim_stat stat;
1568 	unsigned int nr_reclaimed;
1569 	struct folio *folio, *next;
1570 	LIST_HEAD(clean_folios);
1571 	unsigned int noreclaim_flag;
1572 
1573 	list_for_each_entry_safe(folio, next, folio_list, lru) {
1574 		if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
1575 		    !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
1576 		    !folio_test_unevictable(folio)) {
1577 			folio_clear_active(folio);
1578 			list_move(&folio->lru, &clean_folios);
1579 		}
1580 	}
1581 
1582 	/*
1583 	 * We should be safe here since we are only dealing with file pages and
1584 	 * we are not kswapd and therefore cannot write dirty file pages. But
1585 	 * call memalloc_noreclaim_save() anyway, just in case these conditions
1586 	 * change in the future.
1587 	 */
1588 	noreclaim_flag = memalloc_noreclaim_save();
1589 	nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
1590 					&stat, true);
1591 	memalloc_noreclaim_restore(noreclaim_flag);
1592 
1593 	list_splice(&clean_folios, folio_list);
1594 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1595 			    -(long)nr_reclaimed);
1596 	/*
1597 	 * Since lazyfree pages are isolated from file LRU from the beginning,
1598 	 * they will rotate back to anonymous LRU in the end if it failed to
1599 	 * discard so isolated count will be mismatched.
1600 	 * Compensate the isolated count for both LRU lists.
1601 	 */
1602 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
1603 			    stat.nr_lazyfree_fail);
1604 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1605 			    -(long)stat.nr_lazyfree_fail);
1606 	return nr_reclaimed;
1607 }
1608 
1609 /*
1610  * Update LRU sizes after isolating pages. The LRU size updates must
1611  * be complete before mem_cgroup_update_lru_size due to a sanity check.
1612  */
update_lru_sizes(struct lruvec * lruvec,enum lru_list lru,unsigned long * nr_zone_taken)1613 static __always_inline void update_lru_sizes(struct lruvec *lruvec,
1614 			enum lru_list lru, unsigned long *nr_zone_taken)
1615 {
1616 	int zid;
1617 
1618 	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1619 		if (!nr_zone_taken[zid])
1620 			continue;
1621 
1622 		update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
1623 	}
1624 
1625 }
1626 
1627 /*
1628  * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1629  *
1630  * lruvec->lru_lock is heavily contended.  Some of the functions that
1631  * shrink the lists perform better by taking out a batch of pages
1632  * and working on them outside the LRU lock.
1633  *
1634  * For pagecache intensive workloads, this function is the hottest
1635  * spot in the kernel (apart from copy_*_user functions).
1636  *
1637  * Lru_lock must be held before calling this function.
1638  *
1639  * @nr_to_scan:	The number of eligible pages to look through on the list.
1640  * @lruvec:	The LRU vector to pull pages from.
1641  * @dst:	The temp list to put pages on to.
1642  * @nr_scanned:	The number of pages that were scanned.
1643  * @sc:		The scan_control struct for this reclaim session
1644  * @lru:	LRU list id for isolating
1645  *
1646  * returns how many pages were moved onto *@dst.
1647  */
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)1648 static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
1649 		struct lruvec *lruvec, struct list_head *dst,
1650 		unsigned long *nr_scanned, struct scan_control *sc,
1651 		enum lru_list lru)
1652 {
1653 	struct list_head *src = &lruvec->lists[lru];
1654 	unsigned long nr_taken = 0;
1655 	unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
1656 	unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
1657 	unsigned long skipped = 0;
1658 	unsigned long scan, total_scan, nr_pages;
1659 	LIST_HEAD(folios_skipped);
1660 
1661 	total_scan = 0;
1662 	scan = 0;
1663 	while (scan < nr_to_scan && !list_empty(src)) {
1664 		struct list_head *move_to = src;
1665 		struct folio *folio;
1666 
1667 		folio = lru_to_folio(src);
1668 		prefetchw_prev_lru_folio(folio, src, flags);
1669 
1670 		nr_pages = folio_nr_pages(folio);
1671 		total_scan += nr_pages;
1672 
1673 		if (folio_zonenum(folio) > sc->reclaim_idx) {
1674 			nr_skipped[folio_zonenum(folio)] += nr_pages;
1675 			move_to = &folios_skipped;
1676 			goto move;
1677 		}
1678 
1679 		/*
1680 		 * Do not count skipped folios because that makes the function
1681 		 * return with no isolated folios if the LRU mostly contains
1682 		 * ineligible folios.  This causes the VM to not reclaim any
1683 		 * folios, triggering a premature OOM.
1684 		 * Account all pages in a folio.
1685 		 */
1686 		scan += nr_pages;
1687 
1688 		if (!folio_test_lru(folio))
1689 			goto move;
1690 		if (!sc->may_unmap && folio_mapped(folio))
1691 			goto move;
1692 
1693 		/*
1694 		 * Be careful not to clear the lru flag until after we're
1695 		 * sure the folio is not being freed elsewhere -- the
1696 		 * folio release code relies on it.
1697 		 */
1698 		if (unlikely(!folio_try_get(folio)))
1699 			goto move;
1700 
1701 		if (!folio_test_clear_lru(folio)) {
1702 			/* Another thread is already isolating this folio */
1703 			folio_put(folio);
1704 			goto move;
1705 		}
1706 
1707 		nr_taken += nr_pages;
1708 		nr_zone_taken[folio_zonenum(folio)] += nr_pages;
1709 		move_to = dst;
1710 move:
1711 		list_move(&folio->lru, move_to);
1712 	}
1713 
1714 	/*
1715 	 * Splice any skipped folios to the start of the LRU list. Note that
1716 	 * this disrupts the LRU order when reclaiming for lower zones but
1717 	 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1718 	 * scanning would soon rescan the same folios to skip and waste lots
1719 	 * of cpu cycles.
1720 	 */
1721 	if (!list_empty(&folios_skipped)) {
1722 		int zid;
1723 
1724 		list_splice(&folios_skipped, src);
1725 		for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1726 			if (!nr_skipped[zid])
1727 				continue;
1728 
1729 			__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
1730 			skipped += nr_skipped[zid];
1731 		}
1732 	}
1733 	*nr_scanned = total_scan;
1734 	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
1735 				    total_scan, skipped, nr_taken, lru);
1736 	update_lru_sizes(lruvec, lru, nr_zone_taken);
1737 	return nr_taken;
1738 }
1739 
1740 /**
1741  * folio_isolate_lru() - Try to isolate a folio from its LRU list.
1742  * @folio: Folio to isolate from its LRU list.
1743  *
1744  * Isolate a @folio from an LRU list and adjust the vmstat statistic
1745  * corresponding to whatever LRU list the folio was on.
1746  *
1747  * The folio will have its LRU flag cleared.  If it was found on the
1748  * active list, it will have the Active flag set.  If it was found on the
1749  * unevictable list, it will have the Unevictable flag set.  These flags
1750  * may need to be cleared by the caller before letting the page go.
1751  *
1752  * Context:
1753  *
1754  * (1) Must be called with an elevated refcount on the folio. This is a
1755  *     fundamental difference from isolate_lru_folios() (which is called
1756  *     without a stable reference).
1757  * (2) The lru_lock must not be held.
1758  * (3) Interrupts must be enabled.
1759  *
1760  * Return: true if the folio was removed from an LRU list.
1761  * false if the folio was not on an LRU list.
1762  */
folio_isolate_lru(struct folio * folio)1763 bool folio_isolate_lru(struct folio *folio)
1764 {
1765 	bool ret = false;
1766 
1767 	VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
1768 
1769 	if (folio_test_clear_lru(folio)) {
1770 		struct lruvec *lruvec;
1771 
1772 		folio_get(folio);
1773 		lruvec = folio_lruvec_lock_irq(folio);
1774 		lruvec_del_folio(lruvec, folio);
1775 		unlock_page_lruvec_irq(lruvec);
1776 		ret = true;
1777 	}
1778 
1779 	return ret;
1780 }
1781 
1782 /*
1783  * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1784  * then get rescheduled. When there are massive number of tasks doing page
1785  * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1786  * the LRU list will go small and be scanned faster than necessary, leading to
1787  * unnecessary swapping, thrashing and OOM.
1788  */
too_many_isolated(struct pglist_data * pgdat,int file,struct scan_control * sc)1789 static bool too_many_isolated(struct pglist_data *pgdat, int file,
1790 		struct scan_control *sc)
1791 {
1792 	unsigned long inactive, isolated;
1793 	bool too_many;
1794 
1795 	if (current_is_kswapd())
1796 		return false;
1797 
1798 	if (!writeback_throttling_sane(sc))
1799 		return false;
1800 
1801 	if (file) {
1802 		inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
1803 		isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
1804 	} else {
1805 		inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
1806 		isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
1807 	}
1808 
1809 	/*
1810 	 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1811 	 * won't get blocked by normal direct-reclaimers, forming a circular
1812 	 * deadlock.
1813 	 */
1814 	if (gfp_has_io_fs(sc->gfp_mask))
1815 		inactive >>= 3;
1816 
1817 	too_many = isolated > inactive;
1818 
1819 	/* Wake up tasks throttled due to too_many_isolated. */
1820 	if (!too_many)
1821 		wake_throttle_isolated(pgdat);
1822 
1823 	return too_many;
1824 }
1825 
1826 /*
1827  * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
1828  *
1829  * Returns the number of pages moved to the given lruvec.
1830  */
move_folios_to_lru(struct lruvec * lruvec,struct list_head * list)1831 static unsigned int move_folios_to_lru(struct lruvec *lruvec,
1832 		struct list_head *list)
1833 {
1834 	int nr_pages, nr_moved = 0;
1835 	struct folio_batch free_folios;
1836 
1837 	folio_batch_init(&free_folios);
1838 	while (!list_empty(list)) {
1839 		struct folio *folio = lru_to_folio(list);
1840 
1841 		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
1842 		list_del(&folio->lru);
1843 		if (unlikely(!folio_evictable(folio))) {
1844 			spin_unlock_irq(&lruvec->lru_lock);
1845 			folio_putback_lru(folio);
1846 			spin_lock_irq(&lruvec->lru_lock);
1847 			continue;
1848 		}
1849 
1850 		/*
1851 		 * The folio_set_lru needs to be kept here for list integrity.
1852 		 * Otherwise:
1853 		 *   #0 move_folios_to_lru             #1 release_pages
1854 		 *   if (!folio_put_testzero())
1855 		 *				      if (folio_put_testzero())
1856 		 *				        !lru //skip lru_lock
1857 		 *     folio_set_lru()
1858 		 *     list_add(&folio->lru,)
1859 		 *                                        list_add(&folio->lru,)
1860 		 */
1861 		folio_set_lru(folio);
1862 
1863 		if (unlikely(folio_put_testzero(folio))) {
1864 			__folio_clear_lru_flags(folio);
1865 
1866 			folio_undo_large_rmappable(folio);
1867 			if (folio_batch_add(&free_folios, folio) == 0) {
1868 				spin_unlock_irq(&lruvec->lru_lock);
1869 				mem_cgroup_uncharge_folios(&free_folios);
1870 				free_unref_folios(&free_folios);
1871 				spin_lock_irq(&lruvec->lru_lock);
1872 			}
1873 
1874 			continue;
1875 		}
1876 
1877 		/*
1878 		 * All pages were isolated from the same lruvec (and isolation
1879 		 * inhibits memcg migration).
1880 		 */
1881 		VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
1882 		lruvec_add_folio(lruvec, folio);
1883 		nr_pages = folio_nr_pages(folio);
1884 		nr_moved += nr_pages;
1885 		if (folio_test_active(folio))
1886 			workingset_age_nonresident(lruvec, nr_pages);
1887 	}
1888 
1889 	if (free_folios.nr) {
1890 		spin_unlock_irq(&lruvec->lru_lock);
1891 		mem_cgroup_uncharge_folios(&free_folios);
1892 		free_unref_folios(&free_folios);
1893 		spin_lock_irq(&lruvec->lru_lock);
1894 	}
1895 
1896 	return nr_moved;
1897 }
1898 
1899 /*
1900  * If a kernel thread (such as nfsd for loop-back mounts) services a backing
1901  * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
1902  * we should not throttle.  Otherwise it is safe to do so.
1903  */
current_may_throttle(void)1904 static int current_may_throttle(void)
1905 {
1906 	return !(current->flags & PF_LOCAL_THROTTLE);
1907 }
1908 
1909 /*
1910  * shrink_inactive_list() is a helper for shrink_node().  It returns the number
1911  * of reclaimed pages
1912  */
shrink_inactive_list(unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc,enum lru_list lru)1913 static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
1914 		struct lruvec *lruvec, struct scan_control *sc,
1915 		enum lru_list lru)
1916 {
1917 	LIST_HEAD(folio_list);
1918 	unsigned long nr_scanned;
1919 	unsigned int nr_reclaimed = 0;
1920 	unsigned long nr_taken;
1921 	struct reclaim_stat stat;
1922 	bool file = is_file_lru(lru);
1923 	enum vm_event_item item;
1924 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
1925 	bool stalled = false;
1926 
1927 	while (unlikely(too_many_isolated(pgdat, file, sc))) {
1928 		if (stalled)
1929 			return 0;
1930 
1931 		/* wait a bit for the reclaimer. */
1932 		stalled = true;
1933 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
1934 
1935 		/* We are about to die and free our memory. Return now. */
1936 		if (fatal_signal_pending(current))
1937 			return SWAP_CLUSTER_MAX;
1938 	}
1939 
1940 	lru_add_drain();
1941 
1942 	spin_lock_irq(&lruvec->lru_lock);
1943 
1944 	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
1945 				     &nr_scanned, sc, lru);
1946 
1947 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
1948 	item = PGSCAN_KSWAPD + reclaimer_offset();
1949 	if (!cgroup_reclaim(sc))
1950 		__count_vm_events(item, nr_scanned);
1951 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
1952 	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
1953 
1954 	spin_unlock_irq(&lruvec->lru_lock);
1955 
1956 	if (nr_taken == 0)
1957 		return 0;
1958 
1959 	nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
1960 
1961 	spin_lock_irq(&lruvec->lru_lock);
1962 	move_folios_to_lru(lruvec, &folio_list);
1963 
1964 	__mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(),
1965 					stat.nr_demoted);
1966 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
1967 	item = PGSTEAL_KSWAPD + reclaimer_offset();
1968 	if (!cgroup_reclaim(sc))
1969 		__count_vm_events(item, nr_reclaimed);
1970 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
1971 	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
1972 	spin_unlock_irq(&lruvec->lru_lock);
1973 
1974 	lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
1975 
1976 	/*
1977 	 * If dirty folios are scanned that are not queued for IO, it
1978 	 * implies that flushers are not doing their job. This can
1979 	 * happen when memory pressure pushes dirty folios to the end of
1980 	 * the LRU before the dirty limits are breached and the dirty
1981 	 * data has expired. It can also happen when the proportion of
1982 	 * dirty folios grows not through writes but through memory
1983 	 * pressure reclaiming all the clean cache. And in some cases,
1984 	 * the flushers simply cannot keep up with the allocation
1985 	 * rate. Nudge the flusher threads in case they are asleep.
1986 	 */
1987 	if (stat.nr_unqueued_dirty == nr_taken) {
1988 		wakeup_flusher_threads(WB_REASON_VMSCAN);
1989 		/*
1990 		 * For cgroupv1 dirty throttling is achieved by waking up
1991 		 * the kernel flusher here and later waiting on folios
1992 		 * which are in writeback to finish (see shrink_folio_list()).
1993 		 *
1994 		 * Flusher may not be able to issue writeback quickly
1995 		 * enough for cgroupv1 writeback throttling to work
1996 		 * on a large system.
1997 		 */
1998 		if (!writeback_throttling_sane(sc))
1999 			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
2000 	}
2001 
2002 	sc->nr.dirty += stat.nr_dirty;
2003 	sc->nr.congested += stat.nr_congested;
2004 	sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
2005 	sc->nr.writeback += stat.nr_writeback;
2006 	sc->nr.immediate += stat.nr_immediate;
2007 	sc->nr.taken += nr_taken;
2008 	if (file)
2009 		sc->nr.file_taken += nr_taken;
2010 
2011 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
2012 			nr_scanned, nr_reclaimed, &stat, sc->priority, file);
2013 	return nr_reclaimed;
2014 }
2015 
2016 /*
2017  * shrink_active_list() moves folios from the active LRU to the inactive LRU.
2018  *
2019  * We move them the other way if the folio is referenced by one or more
2020  * processes.
2021  *
2022  * If the folios are mostly unmapped, the processing is fast and it is
2023  * appropriate to hold lru_lock across the whole operation.  But if
2024  * the folios are mapped, the processing is slow (folio_referenced()), so
2025  * we should drop lru_lock around each folio.  It's impossible to balance
2026  * this, so instead we remove the folios from the LRU while processing them.
2027  * It is safe to rely on the active flag against the non-LRU folios in here
2028  * because nobody will play with that bit on a non-LRU folio.
2029  *
2030  * The downside is that we have to touch folio->_refcount against each folio.
2031  * But we had to alter folio->flags anyway.
2032  */
shrink_active_list(unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc,enum lru_list lru)2033 static void shrink_active_list(unsigned long nr_to_scan,
2034 			       struct lruvec *lruvec,
2035 			       struct scan_control *sc,
2036 			       enum lru_list lru)
2037 {
2038 	unsigned long nr_taken;
2039 	unsigned long nr_scanned;
2040 	unsigned long vm_flags;
2041 	LIST_HEAD(l_hold);	/* The folios which were snipped off */
2042 	LIST_HEAD(l_active);
2043 	LIST_HEAD(l_inactive);
2044 	unsigned nr_deactivate, nr_activate;
2045 	unsigned nr_rotated = 0;
2046 	bool file = is_file_lru(lru);
2047 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2048 
2049 	lru_add_drain();
2050 
2051 	spin_lock_irq(&lruvec->lru_lock);
2052 
2053 	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
2054 				     &nr_scanned, sc, lru);
2055 
2056 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2057 
2058 	if (!cgroup_reclaim(sc))
2059 		__count_vm_events(PGREFILL, nr_scanned);
2060 	__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2061 
2062 	spin_unlock_irq(&lruvec->lru_lock);
2063 
2064 	while (!list_empty(&l_hold)) {
2065 		struct folio *folio;
2066 
2067 		cond_resched();
2068 		folio = lru_to_folio(&l_hold);
2069 		list_del(&folio->lru);
2070 
2071 		if (unlikely(!folio_evictable(folio))) {
2072 			folio_putback_lru(folio);
2073 			continue;
2074 		}
2075 
2076 		if (unlikely(buffer_heads_over_limit)) {
2077 			if (folio_needs_release(folio) &&
2078 			    folio_trylock(folio)) {
2079 				filemap_release_folio(folio, 0);
2080 				folio_unlock(folio);
2081 			}
2082 		}
2083 
2084 		/* Referenced or rmap lock contention: rotate */
2085 		if (folio_referenced(folio, 0, sc->target_mem_cgroup,
2086 				     &vm_flags) != 0) {
2087 			/*
2088 			 * Identify referenced, file-backed active folios and
2089 			 * give them one more trip around the active list. So
2090 			 * that executable code get better chances to stay in
2091 			 * memory under moderate memory pressure.  Anon folios
2092 			 * are not likely to be evicted by use-once streaming
2093 			 * IO, plus JVM can create lots of anon VM_EXEC folios,
2094 			 * so we ignore them here.
2095 			 */
2096 			if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
2097 				nr_rotated += folio_nr_pages(folio);
2098 				list_add(&folio->lru, &l_active);
2099 				continue;
2100 			}
2101 		}
2102 
2103 		folio_clear_active(folio);	/* we are de-activating */
2104 		folio_set_workingset(folio);
2105 		list_add(&folio->lru, &l_inactive);
2106 	}
2107 
2108 	/*
2109 	 * Move folios back to the lru list.
2110 	 */
2111 	spin_lock_irq(&lruvec->lru_lock);
2112 
2113 	nr_activate = move_folios_to_lru(lruvec, &l_active);
2114 	nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
2115 
2116 	__count_vm_events(PGDEACTIVATE, nr_deactivate);
2117 	__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2118 
2119 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2120 	spin_unlock_irq(&lruvec->lru_lock);
2121 
2122 	if (nr_rotated)
2123 		lru_note_cost(lruvec, file, 0, nr_rotated);
2124 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2125 			nr_deactivate, nr_rotated, sc->priority, file);
2126 }
2127 
reclaim_folio_list(struct list_head * folio_list,struct pglist_data * pgdat)2128 static unsigned int reclaim_folio_list(struct list_head *folio_list,
2129 				      struct pglist_data *pgdat)
2130 {
2131 	struct reclaim_stat dummy_stat;
2132 	unsigned int nr_reclaimed;
2133 	struct folio *folio;
2134 	struct scan_control sc = {
2135 		.gfp_mask = GFP_KERNEL,
2136 		.may_writepage = 1,
2137 		.may_unmap = 1,
2138 		.may_swap = 1,
2139 		.no_demotion = 1,
2140 	};
2141 
2142 	nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, true);
2143 	while (!list_empty(folio_list)) {
2144 		folio = lru_to_folio(folio_list);
2145 		list_del(&folio->lru);
2146 		folio_putback_lru(folio);
2147 	}
2148 
2149 	return nr_reclaimed;
2150 }
2151 
reclaim_pages(struct list_head * folio_list)2152 unsigned long reclaim_pages(struct list_head *folio_list)
2153 {
2154 	int nid;
2155 	unsigned int nr_reclaimed = 0;
2156 	LIST_HEAD(node_folio_list);
2157 	unsigned int noreclaim_flag;
2158 
2159 	if (list_empty(folio_list))
2160 		return nr_reclaimed;
2161 
2162 	noreclaim_flag = memalloc_noreclaim_save();
2163 
2164 	nid = folio_nid(lru_to_folio(folio_list));
2165 	do {
2166 		struct folio *folio = lru_to_folio(folio_list);
2167 
2168 		if (nid == folio_nid(folio)) {
2169 			folio_clear_active(folio);
2170 			list_move(&folio->lru, &node_folio_list);
2171 			continue;
2172 		}
2173 
2174 		nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2175 		nid = folio_nid(lru_to_folio(folio_list));
2176 	} while (!list_empty(folio_list));
2177 
2178 	nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2179 
2180 	memalloc_noreclaim_restore(noreclaim_flag);
2181 
2182 	return nr_reclaimed;
2183 }
2184 
shrink_list(enum lru_list lru,unsigned long nr_to_scan,struct lruvec * lruvec,struct scan_control * sc)2185 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2186 				 struct lruvec *lruvec, struct scan_control *sc)
2187 {
2188 	if (is_active_lru(lru)) {
2189 		if (sc->may_deactivate & (1 << is_file_lru(lru)))
2190 			shrink_active_list(nr_to_scan, lruvec, sc, lru);
2191 		else
2192 			sc->skipped_deactivate = 1;
2193 		return 0;
2194 	}
2195 
2196 	return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2197 }
2198 
2199 /*
2200  * The inactive anon list should be small enough that the VM never has
2201  * to do too much work.
2202  *
2203  * The inactive file list should be small enough to leave most memory
2204  * to the established workingset on the scan-resistant active list,
2205  * but large enough to avoid thrashing the aggregate readahead window.
2206  *
2207  * Both inactive lists should also be large enough that each inactive
2208  * folio has a chance to be referenced again before it is reclaimed.
2209  *
2210  * If that fails and refaulting is observed, the inactive list grows.
2211  *
2212  * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2213  * on this LRU, maintained by the pageout code. An inactive_ratio
2214  * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2215  *
2216  * total     target    max
2217  * memory    ratio     inactive
2218  * -------------------------------------
2219  *   10MB       1         5MB
2220  *  100MB       1        50MB
2221  *    1GB       3       250MB
2222  *   10GB      10       0.9GB
2223  *  100GB      31         3GB
2224  *    1TB     101        10GB
2225  *   10TB     320        32GB
2226  */
inactive_is_low(struct lruvec * lruvec,enum lru_list inactive_lru)2227 static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
2228 {
2229 	enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
2230 	unsigned long inactive, active;
2231 	unsigned long inactive_ratio;
2232 	unsigned long gb;
2233 
2234 	inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
2235 	active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
2236 
2237 	gb = (inactive + active) >> (30 - PAGE_SHIFT);
2238 	if (gb)
2239 		inactive_ratio = int_sqrt(10 * gb);
2240 	else
2241 		inactive_ratio = 1;
2242 
2243 	return inactive * inactive_ratio < active;
2244 }
2245 
2246 enum scan_balance {
2247 	SCAN_EQUAL,
2248 	SCAN_FRACT,
2249 	SCAN_ANON,
2250 	SCAN_FILE,
2251 };
2252 
prepare_scan_control(pg_data_t * pgdat,struct scan_control * sc)2253 static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc)
2254 {
2255 	unsigned long file;
2256 	struct lruvec *target_lruvec;
2257 
2258 	if (lru_gen_enabled())
2259 		return;
2260 
2261 	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
2262 
2263 	/*
2264 	 * Flush the memory cgroup stats in rate-limited way as we don't need
2265 	 * most accurate stats here. We may switch to regular stats flushing
2266 	 * in the future once it is cheap enough.
2267 	 */
2268 	mem_cgroup_flush_stats_ratelimited(sc->target_mem_cgroup);
2269 
2270 	/*
2271 	 * Determine the scan balance between anon and file LRUs.
2272 	 */
2273 	spin_lock_irq(&target_lruvec->lru_lock);
2274 	sc->anon_cost = target_lruvec->anon_cost;
2275 	sc->file_cost = target_lruvec->file_cost;
2276 	spin_unlock_irq(&target_lruvec->lru_lock);
2277 
2278 	/*
2279 	 * Target desirable inactive:active list ratios for the anon
2280 	 * and file LRU lists.
2281 	 */
2282 	if (!sc->force_deactivate) {
2283 		unsigned long refaults;
2284 
2285 		/*
2286 		 * When refaults are being observed, it means a new
2287 		 * workingset is being established. Deactivate to get
2288 		 * rid of any stale active pages quickly.
2289 		 */
2290 		refaults = lruvec_page_state(target_lruvec,
2291 				WORKINGSET_ACTIVATE_ANON);
2292 		if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
2293 			inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
2294 			sc->may_deactivate |= DEACTIVATE_ANON;
2295 		else
2296 			sc->may_deactivate &= ~DEACTIVATE_ANON;
2297 
2298 		refaults = lruvec_page_state(target_lruvec,
2299 				WORKINGSET_ACTIVATE_FILE);
2300 		if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
2301 		    inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
2302 			sc->may_deactivate |= DEACTIVATE_FILE;
2303 		else
2304 			sc->may_deactivate &= ~DEACTIVATE_FILE;
2305 	} else
2306 		sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
2307 
2308 	/*
2309 	 * If we have plenty of inactive file pages that aren't
2310 	 * thrashing, try to reclaim those first before touching
2311 	 * anonymous pages.
2312 	 */
2313 	file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
2314 	if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE) &&
2315 	    !sc->no_cache_trim_mode)
2316 		sc->cache_trim_mode = 1;
2317 	else
2318 		sc->cache_trim_mode = 0;
2319 
2320 	/*
2321 	 * Prevent the reclaimer from falling into the cache trap: as
2322 	 * cache pages start out inactive, every cache fault will tip
2323 	 * the scan balance towards the file LRU.  And as the file LRU
2324 	 * shrinks, so does the window for rotation from references.
2325 	 * This means we have a runaway feedback loop where a tiny
2326 	 * thrashing file LRU becomes infinitely more attractive than
2327 	 * anon pages.  Try to detect this based on file LRU size.
2328 	 */
2329 	if (!cgroup_reclaim(sc)) {
2330 		unsigned long total_high_wmark = 0;
2331 		unsigned long free, anon;
2332 		int z;
2333 
2334 		free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2335 		file = node_page_state(pgdat, NR_ACTIVE_FILE) +
2336 			   node_page_state(pgdat, NR_INACTIVE_FILE);
2337 
2338 		for (z = 0; z < MAX_NR_ZONES; z++) {
2339 			struct zone *zone = &pgdat->node_zones[z];
2340 
2341 			if (!managed_zone(zone))
2342 				continue;
2343 
2344 			total_high_wmark += high_wmark_pages(zone);
2345 		}
2346 
2347 		/*
2348 		 * Consider anon: if that's low too, this isn't a
2349 		 * runaway file reclaim problem, but rather just
2350 		 * extreme pressure. Reclaim as per usual then.
2351 		 */
2352 		anon = node_page_state(pgdat, NR_INACTIVE_ANON);
2353 
2354 		sc->file_is_tiny =
2355 			file + free <= total_high_wmark &&
2356 			!(sc->may_deactivate & DEACTIVATE_ANON) &&
2357 			anon >> sc->priority;
2358 	}
2359 }
2360 
2361 /*
2362  * Determine how aggressively the anon and file LRU lists should be
2363  * scanned.
2364  *
2365  * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
2366  * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
2367  */
get_scan_count(struct lruvec * lruvec,struct scan_control * sc,unsigned long * nr)2368 static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
2369 			   unsigned long *nr)
2370 {
2371 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2372 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2373 	unsigned long anon_cost, file_cost, total_cost;
2374 	int swappiness = sc_swappiness(sc, memcg);
2375 	u64 fraction[ANON_AND_FILE];
2376 	u64 denominator = 0;	/* gcc */
2377 	enum scan_balance scan_balance;
2378 	unsigned long ap, fp;
2379 	enum lru_list lru;
2380 
2381 	/* If we have no swap space, do not bother scanning anon folios. */
2382 	if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
2383 		scan_balance = SCAN_FILE;
2384 		goto out;
2385 	}
2386 
2387 	/*
2388 	 * Global reclaim will swap to prevent OOM even with no
2389 	 * swappiness, but memcg users want to use this knob to
2390 	 * disable swapping for individual groups completely when
2391 	 * using the memory controller's swap limit feature would be
2392 	 * too expensive.
2393 	 */
2394 	if (cgroup_reclaim(sc) && !swappiness) {
2395 		scan_balance = SCAN_FILE;
2396 		goto out;
2397 	}
2398 
2399 	/*
2400 	 * Do not apply any pressure balancing cleverness when the
2401 	 * system is close to OOM, scan both anon and file equally
2402 	 * (unless the swappiness setting disagrees with swapping).
2403 	 */
2404 	if (!sc->priority && swappiness) {
2405 		scan_balance = SCAN_EQUAL;
2406 		goto out;
2407 	}
2408 
2409 	/*
2410 	 * If the system is almost out of file pages, force-scan anon.
2411 	 */
2412 	if (sc->file_is_tiny) {
2413 		scan_balance = SCAN_ANON;
2414 		goto out;
2415 	}
2416 
2417 	/*
2418 	 * If there is enough inactive page cache, we do not reclaim
2419 	 * anything from the anonymous working right now.
2420 	 */
2421 	if (sc->cache_trim_mode) {
2422 		scan_balance = SCAN_FILE;
2423 		goto out;
2424 	}
2425 
2426 	scan_balance = SCAN_FRACT;
2427 	/*
2428 	 * Calculate the pressure balance between anon and file pages.
2429 	 *
2430 	 * The amount of pressure we put on each LRU is inversely
2431 	 * proportional to the cost of reclaiming each list, as
2432 	 * determined by the share of pages that are refaulting, times
2433 	 * the relative IO cost of bringing back a swapped out
2434 	 * anonymous page vs reloading a filesystem page (swappiness).
2435 	 *
2436 	 * Although we limit that influence to ensure no list gets
2437 	 * left behind completely: at least a third of the pressure is
2438 	 * applied, before swappiness.
2439 	 *
2440 	 * With swappiness at 100, anon and file have equal IO cost.
2441 	 */
2442 	total_cost = sc->anon_cost + sc->file_cost;
2443 	anon_cost = total_cost + sc->anon_cost;
2444 	file_cost = total_cost + sc->file_cost;
2445 	total_cost = anon_cost + file_cost;
2446 
2447 	ap = swappiness * (total_cost + 1);
2448 	ap /= anon_cost + 1;
2449 
2450 	fp = (MAX_SWAPPINESS - swappiness) * (total_cost + 1);
2451 	fp /= file_cost + 1;
2452 
2453 	fraction[0] = ap;
2454 	fraction[1] = fp;
2455 	denominator = ap + fp;
2456 out:
2457 	for_each_evictable_lru(lru) {
2458 		bool file = is_file_lru(lru);
2459 		unsigned long lruvec_size;
2460 		unsigned long low, min;
2461 		unsigned long scan;
2462 
2463 		lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
2464 		mem_cgroup_protection(sc->target_mem_cgroup, memcg,
2465 				      &min, &low);
2466 
2467 		if (min || low) {
2468 			/*
2469 			 * Scale a cgroup's reclaim pressure by proportioning
2470 			 * its current usage to its memory.low or memory.min
2471 			 * setting.
2472 			 *
2473 			 * This is important, as otherwise scanning aggression
2474 			 * becomes extremely binary -- from nothing as we
2475 			 * approach the memory protection threshold, to totally
2476 			 * nominal as we exceed it.  This results in requiring
2477 			 * setting extremely liberal protection thresholds. It
2478 			 * also means we simply get no protection at all if we
2479 			 * set it too low, which is not ideal.
2480 			 *
2481 			 * If there is any protection in place, we reduce scan
2482 			 * pressure by how much of the total memory used is
2483 			 * within protection thresholds.
2484 			 *
2485 			 * There is one special case: in the first reclaim pass,
2486 			 * we skip over all groups that are within their low
2487 			 * protection. If that fails to reclaim enough pages to
2488 			 * satisfy the reclaim goal, we come back and override
2489 			 * the best-effort low protection. However, we still
2490 			 * ideally want to honor how well-behaved groups are in
2491 			 * that case instead of simply punishing them all
2492 			 * equally. As such, we reclaim them based on how much
2493 			 * memory they are using, reducing the scan pressure
2494 			 * again by how much of the total memory used is under
2495 			 * hard protection.
2496 			 */
2497 			unsigned long cgroup_size = mem_cgroup_size(memcg);
2498 			unsigned long protection;
2499 
2500 			/* memory.low scaling, make sure we retry before OOM */
2501 			if (!sc->memcg_low_reclaim && low > min) {
2502 				protection = low;
2503 				sc->memcg_low_skipped = 1;
2504 			} else {
2505 				protection = min;
2506 			}
2507 
2508 			/* Avoid TOCTOU with earlier protection check */
2509 			cgroup_size = max(cgroup_size, protection);
2510 
2511 			scan = lruvec_size - lruvec_size * protection /
2512 				(cgroup_size + 1);
2513 
2514 			/*
2515 			 * Minimally target SWAP_CLUSTER_MAX pages to keep
2516 			 * reclaim moving forwards, avoiding decrementing
2517 			 * sc->priority further than desirable.
2518 			 */
2519 			scan = max(scan, SWAP_CLUSTER_MAX);
2520 		} else {
2521 			scan = lruvec_size;
2522 		}
2523 
2524 		scan >>= sc->priority;
2525 
2526 		/*
2527 		 * If the cgroup's already been deleted, make sure to
2528 		 * scrape out the remaining cache.
2529 		 */
2530 		if (!scan && !mem_cgroup_online(memcg))
2531 			scan = min(lruvec_size, SWAP_CLUSTER_MAX);
2532 
2533 		switch (scan_balance) {
2534 		case SCAN_EQUAL:
2535 			/* Scan lists relative to size */
2536 			break;
2537 		case SCAN_FRACT:
2538 			/*
2539 			 * Scan types proportional to swappiness and
2540 			 * their relative recent reclaim efficiency.
2541 			 * Make sure we don't miss the last page on
2542 			 * the offlined memory cgroups because of a
2543 			 * round-off error.
2544 			 */
2545 			scan = mem_cgroup_online(memcg) ?
2546 			       div64_u64(scan * fraction[file], denominator) :
2547 			       DIV64_U64_ROUND_UP(scan * fraction[file],
2548 						  denominator);
2549 			break;
2550 		case SCAN_FILE:
2551 		case SCAN_ANON:
2552 			/* Scan one type exclusively */
2553 			if ((scan_balance == SCAN_FILE) != file)
2554 				scan = 0;
2555 			break;
2556 		default:
2557 			/* Look ma, no brain */
2558 			BUG();
2559 		}
2560 
2561 		nr[lru] = scan;
2562 	}
2563 }
2564 
2565 /*
2566  * Anonymous LRU management is a waste if there is
2567  * ultimately no way to reclaim the memory.
2568  */
can_age_anon_pages(struct pglist_data * pgdat,struct scan_control * sc)2569 static bool can_age_anon_pages(struct pglist_data *pgdat,
2570 			       struct scan_control *sc)
2571 {
2572 	/* Aging the anon LRU is valuable if swap is present: */
2573 	if (total_swap_pages > 0)
2574 		return true;
2575 
2576 	/* Also valuable if anon pages can be demoted: */
2577 	return can_demote(pgdat->node_id, sc);
2578 }
2579 
2580 #ifdef CONFIG_LRU_GEN
2581 
2582 #ifdef CONFIG_LRU_GEN_ENABLED
2583 DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
2584 #define get_cap(cap)	static_branch_likely(&lru_gen_caps[cap])
2585 #else
2586 DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
2587 #define get_cap(cap)	static_branch_unlikely(&lru_gen_caps[cap])
2588 #endif
2589 
should_walk_mmu(void)2590 static bool should_walk_mmu(void)
2591 {
2592 	return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK);
2593 }
2594 
should_clear_pmd_young(void)2595 static bool should_clear_pmd_young(void)
2596 {
2597 	return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG);
2598 }
2599 
2600 /******************************************************************************
2601  *                          shorthand helpers
2602  ******************************************************************************/
2603 
2604 #define LRU_REFS_FLAGS	(BIT(PG_referenced) | BIT(PG_workingset))
2605 
2606 #define DEFINE_MAX_SEQ(lruvec)						\
2607 	unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
2608 
2609 #define DEFINE_MIN_SEQ(lruvec)						\
2610 	unsigned long min_seq[ANON_AND_FILE] = {			\
2611 		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]),	\
2612 		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]),	\
2613 	}
2614 
2615 #define for_each_gen_type_zone(gen, type, zone)				\
2616 	for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++)			\
2617 		for ((type) = 0; (type) < ANON_AND_FILE; (type)++)	\
2618 			for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
2619 
2620 #define get_memcg_gen(seq)	((seq) % MEMCG_NR_GENS)
2621 #define get_memcg_bin(bin)	((bin) % MEMCG_NR_BINS)
2622 
get_lruvec(struct mem_cgroup * memcg,int nid)2623 static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
2624 {
2625 	struct pglist_data *pgdat = NODE_DATA(nid);
2626 
2627 #ifdef CONFIG_MEMCG
2628 	if (memcg) {
2629 		struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
2630 
2631 		/* see the comment in mem_cgroup_lruvec() */
2632 		if (!lruvec->pgdat)
2633 			lruvec->pgdat = pgdat;
2634 
2635 		return lruvec;
2636 	}
2637 #endif
2638 	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2639 
2640 	return &pgdat->__lruvec;
2641 }
2642 
get_swappiness(struct lruvec * lruvec,struct scan_control * sc)2643 static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
2644 {
2645 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2646 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2647 
2648 	if (!sc->may_swap)
2649 		return 0;
2650 
2651 	if (!can_demote(pgdat->node_id, sc) &&
2652 	    mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
2653 		return 0;
2654 
2655 	return sc_swappiness(sc, memcg);
2656 }
2657 
get_nr_gens(struct lruvec * lruvec,int type)2658 static int get_nr_gens(struct lruvec *lruvec, int type)
2659 {
2660 	return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
2661 }
2662 
seq_is_valid(struct lruvec * lruvec)2663 static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
2664 {
2665 	/* see the comment on lru_gen_folio */
2666 	return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
2667 	       get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
2668 	       get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
2669 }
2670 
2671 /******************************************************************************
2672  *                          Bloom filters
2673  ******************************************************************************/
2674 
2675 /*
2676  * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
2677  * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
2678  * bits in a bitmap, k is the number of hash functions and n is the number of
2679  * inserted items.
2680  *
2681  * Page table walkers use one of the two filters to reduce their search space.
2682  * To get rid of non-leaf entries that no longer have enough leaf entries, the
2683  * aging uses the double-buffering technique to flip to the other filter each
2684  * time it produces a new generation. For non-leaf entries that have enough
2685  * leaf entries, the aging carries them over to the next generation in
2686  * walk_pmd_range(); the eviction also report them when walking the rmap
2687  * in lru_gen_look_around().
2688  *
2689  * For future optimizations:
2690  * 1. It's not necessary to keep both filters all the time. The spare one can be
2691  *    freed after the RCU grace period and reallocated if needed again.
2692  * 2. And when reallocating, it's worth scaling its size according to the number
2693  *    of inserted entries in the other filter, to reduce the memory overhead on
2694  *    small systems and false positives on large systems.
2695  * 3. Jenkins' hash function is an alternative to Knuth's.
2696  */
2697 #define BLOOM_FILTER_SHIFT	15
2698 
filter_gen_from_seq(unsigned long seq)2699 static inline int filter_gen_from_seq(unsigned long seq)
2700 {
2701 	return seq % NR_BLOOM_FILTERS;
2702 }
2703 
get_item_key(void * item,int * key)2704 static void get_item_key(void *item, int *key)
2705 {
2706 	u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
2707 
2708 	BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
2709 
2710 	key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
2711 	key[1] = hash >> BLOOM_FILTER_SHIFT;
2712 }
2713 
test_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq,void * item)2714 static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2715 			      void *item)
2716 {
2717 	int key[2];
2718 	unsigned long *filter;
2719 	int gen = filter_gen_from_seq(seq);
2720 
2721 	filter = READ_ONCE(mm_state->filters[gen]);
2722 	if (!filter)
2723 		return true;
2724 
2725 	get_item_key(item, key);
2726 
2727 	return test_bit(key[0], filter) && test_bit(key[1], filter);
2728 }
2729 
update_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq,void * item)2730 static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2731 				void *item)
2732 {
2733 	int key[2];
2734 	unsigned long *filter;
2735 	int gen = filter_gen_from_seq(seq);
2736 
2737 	filter = READ_ONCE(mm_state->filters[gen]);
2738 	if (!filter)
2739 		return;
2740 
2741 	get_item_key(item, key);
2742 
2743 	if (!test_bit(key[0], filter))
2744 		set_bit(key[0], filter);
2745 	if (!test_bit(key[1], filter))
2746 		set_bit(key[1], filter);
2747 }
2748 
reset_bloom_filter(struct lru_gen_mm_state * mm_state,unsigned long seq)2749 static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq)
2750 {
2751 	unsigned long *filter;
2752 	int gen = filter_gen_from_seq(seq);
2753 
2754 	filter = mm_state->filters[gen];
2755 	if (filter) {
2756 		bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
2757 		return;
2758 	}
2759 
2760 	filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
2761 			       __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
2762 	WRITE_ONCE(mm_state->filters[gen], filter);
2763 }
2764 
2765 /******************************************************************************
2766  *                          mm_struct list
2767  ******************************************************************************/
2768 
2769 #ifdef CONFIG_LRU_GEN_WALKS_MMU
2770 
get_mm_list(struct mem_cgroup * memcg)2771 static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2772 {
2773 	static struct lru_gen_mm_list mm_list = {
2774 		.fifo = LIST_HEAD_INIT(mm_list.fifo),
2775 		.lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
2776 	};
2777 
2778 #ifdef CONFIG_MEMCG
2779 	if (memcg)
2780 		return &memcg->mm_list;
2781 #endif
2782 	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2783 
2784 	return &mm_list;
2785 }
2786 
get_mm_state(struct lruvec * lruvec)2787 static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2788 {
2789 	return &lruvec->mm_state;
2790 }
2791 
get_next_mm(struct lru_gen_mm_walk * walk)2792 static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2793 {
2794 	int key;
2795 	struct mm_struct *mm;
2796 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
2797 	struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
2798 
2799 	mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
2800 	key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
2801 
2802 	if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
2803 		return NULL;
2804 
2805 	clear_bit(key, &mm->lru_gen.bitmap);
2806 
2807 	return mmget_not_zero(mm) ? mm : NULL;
2808 }
2809 
lru_gen_add_mm(struct mm_struct * mm)2810 void lru_gen_add_mm(struct mm_struct *mm)
2811 {
2812 	int nid;
2813 	struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
2814 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2815 
2816 	VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
2817 #ifdef CONFIG_MEMCG
2818 	VM_WARN_ON_ONCE(mm->lru_gen.memcg);
2819 	mm->lru_gen.memcg = memcg;
2820 #endif
2821 	spin_lock(&mm_list->lock);
2822 
2823 	for_each_node_state(nid, N_MEMORY) {
2824 		struct lruvec *lruvec = get_lruvec(memcg, nid);
2825 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2826 
2827 		/* the first addition since the last iteration */
2828 		if (mm_state->tail == &mm_list->fifo)
2829 			mm_state->tail = &mm->lru_gen.list;
2830 	}
2831 
2832 	list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
2833 
2834 	spin_unlock(&mm_list->lock);
2835 }
2836 
lru_gen_del_mm(struct mm_struct * mm)2837 void lru_gen_del_mm(struct mm_struct *mm)
2838 {
2839 	int nid;
2840 	struct lru_gen_mm_list *mm_list;
2841 	struct mem_cgroup *memcg = NULL;
2842 
2843 	if (list_empty(&mm->lru_gen.list))
2844 		return;
2845 
2846 #ifdef CONFIG_MEMCG
2847 	memcg = mm->lru_gen.memcg;
2848 #endif
2849 	mm_list = get_mm_list(memcg);
2850 
2851 	spin_lock(&mm_list->lock);
2852 
2853 	for_each_node(nid) {
2854 		struct lruvec *lruvec = get_lruvec(memcg, nid);
2855 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2856 
2857 		/* where the current iteration continues after */
2858 		if (mm_state->head == &mm->lru_gen.list)
2859 			mm_state->head = mm_state->head->prev;
2860 
2861 		/* where the last iteration ended before */
2862 		if (mm_state->tail == &mm->lru_gen.list)
2863 			mm_state->tail = mm_state->tail->next;
2864 	}
2865 
2866 	list_del_init(&mm->lru_gen.list);
2867 
2868 	spin_unlock(&mm_list->lock);
2869 
2870 #ifdef CONFIG_MEMCG
2871 	mem_cgroup_put(mm->lru_gen.memcg);
2872 	mm->lru_gen.memcg = NULL;
2873 #endif
2874 }
2875 
2876 #ifdef CONFIG_MEMCG
lru_gen_migrate_mm(struct mm_struct * mm)2877 void lru_gen_migrate_mm(struct mm_struct *mm)
2878 {
2879 	struct mem_cgroup *memcg;
2880 	struct task_struct *task = rcu_dereference_protected(mm->owner, true);
2881 
2882 	VM_WARN_ON_ONCE(task->mm != mm);
2883 	lockdep_assert_held(&task->alloc_lock);
2884 
2885 	/* for mm_update_next_owner() */
2886 	if (mem_cgroup_disabled())
2887 		return;
2888 
2889 	/* migration can happen before addition */
2890 	if (!mm->lru_gen.memcg)
2891 		return;
2892 
2893 	rcu_read_lock();
2894 	memcg = mem_cgroup_from_task(task);
2895 	rcu_read_unlock();
2896 	if (memcg == mm->lru_gen.memcg)
2897 		return;
2898 
2899 	VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
2900 
2901 	lru_gen_del_mm(mm);
2902 	lru_gen_add_mm(mm);
2903 }
2904 #endif
2905 
2906 #else /* !CONFIG_LRU_GEN_WALKS_MMU */
2907 
get_mm_list(struct mem_cgroup * memcg)2908 static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2909 {
2910 	return NULL;
2911 }
2912 
get_mm_state(struct lruvec * lruvec)2913 static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2914 {
2915 	return NULL;
2916 }
2917 
get_next_mm(struct lru_gen_mm_walk * walk)2918 static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2919 {
2920 	return NULL;
2921 }
2922 
2923 #endif
2924 
reset_mm_stats(struct lru_gen_mm_walk * walk,bool last)2925 static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last)
2926 {
2927 	int i;
2928 	int hist;
2929 	struct lruvec *lruvec = walk->lruvec;
2930 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2931 
2932 	lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
2933 
2934 	hist = lru_hist_from_seq(walk->seq);
2935 
2936 	for (i = 0; i < NR_MM_STATS; i++) {
2937 		WRITE_ONCE(mm_state->stats[hist][i],
2938 			   mm_state->stats[hist][i] + walk->mm_stats[i]);
2939 		walk->mm_stats[i] = 0;
2940 	}
2941 
2942 	if (NR_HIST_GENS > 1 && last) {
2943 		hist = lru_hist_from_seq(walk->seq + 1);
2944 
2945 		for (i = 0; i < NR_MM_STATS; i++)
2946 			WRITE_ONCE(mm_state->stats[hist][i], 0);
2947 	}
2948 }
2949 
iterate_mm_list(struct lru_gen_mm_walk * walk,struct mm_struct ** iter)2950 static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **iter)
2951 {
2952 	bool first = false;
2953 	bool last = false;
2954 	struct mm_struct *mm = NULL;
2955 	struct lruvec *lruvec = walk->lruvec;
2956 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2957 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2958 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2959 
2960 	/*
2961 	 * mm_state->seq is incremented after each iteration of mm_list. There
2962 	 * are three interesting cases for this page table walker:
2963 	 * 1. It tries to start a new iteration with a stale max_seq: there is
2964 	 *    nothing left to do.
2965 	 * 2. It started the next iteration: it needs to reset the Bloom filter
2966 	 *    so that a fresh set of PTE tables can be recorded.
2967 	 * 3. It ended the current iteration: it needs to reset the mm stats
2968 	 *    counters and tell its caller to increment max_seq.
2969 	 */
2970 	spin_lock(&mm_list->lock);
2971 
2972 	VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->seq);
2973 
2974 	if (walk->seq <= mm_state->seq)
2975 		goto done;
2976 
2977 	if (!mm_state->head)
2978 		mm_state->head = &mm_list->fifo;
2979 
2980 	if (mm_state->head == &mm_list->fifo)
2981 		first = true;
2982 
2983 	do {
2984 		mm_state->head = mm_state->head->next;
2985 		if (mm_state->head == &mm_list->fifo) {
2986 			WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
2987 			last = true;
2988 			break;
2989 		}
2990 
2991 		/* force scan for those added after the last iteration */
2992 		if (!mm_state->tail || mm_state->tail == mm_state->head) {
2993 			mm_state->tail = mm_state->head->next;
2994 			walk->force_scan = true;
2995 		}
2996 	} while (!(mm = get_next_mm(walk)));
2997 done:
2998 	if (*iter || last)
2999 		reset_mm_stats(walk, last);
3000 
3001 	spin_unlock(&mm_list->lock);
3002 
3003 	if (mm && first)
3004 		reset_bloom_filter(mm_state, walk->seq + 1);
3005 
3006 	if (*iter)
3007 		mmput_async(*iter);
3008 
3009 	*iter = mm;
3010 
3011 	return last;
3012 }
3013 
iterate_mm_list_nowalk(struct lruvec * lruvec,unsigned long seq)3014 static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long seq)
3015 {
3016 	bool success = false;
3017 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3018 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3019 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3020 
3021 	spin_lock(&mm_list->lock);
3022 
3023 	VM_WARN_ON_ONCE(mm_state->seq + 1 < seq);
3024 
3025 	if (seq > mm_state->seq) {
3026 		mm_state->head = NULL;
3027 		mm_state->tail = NULL;
3028 		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3029 		success = true;
3030 	}
3031 
3032 	spin_unlock(&mm_list->lock);
3033 
3034 	return success;
3035 }
3036 
3037 /******************************************************************************
3038  *                          PID controller
3039  ******************************************************************************/
3040 
3041 /*
3042  * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3043  *
3044  * The P term is refaulted/(evicted+protected) from a tier in the generation
3045  * currently being evicted; the I term is the exponential moving average of the
3046  * P term over the generations previously evicted, using the smoothing factor
3047  * 1/2; the D term isn't supported.
3048  *
3049  * The setpoint (SP) is always the first tier of one type; the process variable
3050  * (PV) is either any tier of the other type or any other tier of the same
3051  * type.
3052  *
3053  * The error is the difference between the SP and the PV; the correction is to
3054  * turn off protection when SP>PV or turn on protection when SP<PV.
3055  *
3056  * For future optimizations:
3057  * 1. The D term may discount the other two terms over time so that long-lived
3058  *    generations can resist stale information.
3059  */
3060 struct ctrl_pos {
3061 	unsigned long refaulted;
3062 	unsigned long total;
3063 	int gain;
3064 };
3065 
read_ctrl_pos(struct lruvec * lruvec,int type,int tier,int gain,struct ctrl_pos * pos)3066 static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
3067 			  struct ctrl_pos *pos)
3068 {
3069 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3070 	int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3071 
3072 	pos->refaulted = lrugen->avg_refaulted[type][tier] +
3073 			 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3074 	pos->total = lrugen->avg_total[type][tier] +
3075 		     atomic_long_read(&lrugen->evicted[hist][type][tier]);
3076 	if (tier)
3077 		pos->total += lrugen->protected[hist][type][tier - 1];
3078 	pos->gain = gain;
3079 }
3080 
reset_ctrl_pos(struct lruvec * lruvec,int type,bool carryover)3081 static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
3082 {
3083 	int hist, tier;
3084 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3085 	bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
3086 	unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
3087 
3088 	lockdep_assert_held(&lruvec->lru_lock);
3089 
3090 	if (!carryover && !clear)
3091 		return;
3092 
3093 	hist = lru_hist_from_seq(seq);
3094 
3095 	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
3096 		if (carryover) {
3097 			unsigned long sum;
3098 
3099 			sum = lrugen->avg_refaulted[type][tier] +
3100 			      atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3101 			WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
3102 
3103 			sum = lrugen->avg_total[type][tier] +
3104 			      atomic_long_read(&lrugen->evicted[hist][type][tier]);
3105 			if (tier)
3106 				sum += lrugen->protected[hist][type][tier - 1];
3107 			WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
3108 		}
3109 
3110 		if (clear) {
3111 			atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
3112 			atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
3113 			if (tier)
3114 				WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0);
3115 		}
3116 	}
3117 }
3118 
positive_ctrl_err(struct ctrl_pos * sp,struct ctrl_pos * pv)3119 static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
3120 {
3121 	/*
3122 	 * Return true if the PV has a limited number of refaults or a lower
3123 	 * refaulted/total than the SP.
3124 	 */
3125 	return pv->refaulted < MIN_LRU_BATCH ||
3126 	       pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
3127 	       (sp->refaulted + 1) * pv->total * pv->gain;
3128 }
3129 
3130 /******************************************************************************
3131  *                          the aging
3132  ******************************************************************************/
3133 
3134 /* promote pages accessed through page tables */
folio_update_gen(struct folio * folio,int gen)3135 static int folio_update_gen(struct folio *folio, int gen)
3136 {
3137 	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3138 
3139 	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
3140 	VM_WARN_ON_ONCE(!rcu_read_lock_held());
3141 
3142 	do {
3143 		/* lru_gen_del_folio() has isolated this page? */
3144 		if (!(old_flags & LRU_GEN_MASK)) {
3145 			/* for shrink_folio_list() */
3146 			new_flags = old_flags | BIT(PG_referenced);
3147 			continue;
3148 		}
3149 
3150 		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3151 		new_flags |= (gen + 1UL) << LRU_GEN_PGOFF;
3152 	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3153 
3154 	return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3155 }
3156 
3157 /* protect pages accessed multiple times through file descriptors */
folio_inc_gen(struct lruvec * lruvec,struct folio * folio,bool reclaiming)3158 static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
3159 {
3160 	int type = folio_is_file_lru(folio);
3161 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3162 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3163 	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3164 
3165 	VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
3166 
3167 	do {
3168 		new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3169 		/* folio_update_gen() has promoted this page? */
3170 		if (new_gen >= 0 && new_gen != old_gen)
3171 			return new_gen;
3172 
3173 		new_gen = (old_gen + 1) % MAX_NR_GENS;
3174 
3175 		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3176 		new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
3177 		/* for folio_end_writeback() */
3178 		if (reclaiming)
3179 			new_flags |= BIT(PG_reclaim);
3180 	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3181 
3182 	lru_gen_update_size(lruvec, folio, old_gen, new_gen);
3183 
3184 	return new_gen;
3185 }
3186 
update_batch_size(struct lru_gen_mm_walk * walk,struct folio * folio,int old_gen,int new_gen)3187 static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
3188 			      int old_gen, int new_gen)
3189 {
3190 	int type = folio_is_file_lru(folio);
3191 	int zone = folio_zonenum(folio);
3192 	int delta = folio_nr_pages(folio);
3193 
3194 	VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
3195 	VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
3196 
3197 	walk->batched++;
3198 
3199 	walk->nr_pages[old_gen][type][zone] -= delta;
3200 	walk->nr_pages[new_gen][type][zone] += delta;
3201 }
3202 
reset_batch_size(struct lru_gen_mm_walk * walk)3203 static void reset_batch_size(struct lru_gen_mm_walk *walk)
3204 {
3205 	int gen, type, zone;
3206 	struct lruvec *lruvec = walk->lruvec;
3207 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3208 
3209 	walk->batched = 0;
3210 
3211 	for_each_gen_type_zone(gen, type, zone) {
3212 		enum lru_list lru = type * LRU_INACTIVE_FILE;
3213 		int delta = walk->nr_pages[gen][type][zone];
3214 
3215 		if (!delta)
3216 			continue;
3217 
3218 		walk->nr_pages[gen][type][zone] = 0;
3219 		WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
3220 			   lrugen->nr_pages[gen][type][zone] + delta);
3221 
3222 		if (lru_gen_is_active(lruvec, gen))
3223 			lru += LRU_ACTIVE;
3224 		__update_lru_size(lruvec, lru, zone, delta);
3225 	}
3226 }
3227 
should_skip_vma(unsigned long start,unsigned long end,struct mm_walk * args)3228 static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
3229 {
3230 	struct address_space *mapping;
3231 	struct vm_area_struct *vma = args->vma;
3232 	struct lru_gen_mm_walk *walk = args->private;
3233 
3234 	if (!vma_is_accessible(vma))
3235 		return true;
3236 
3237 	if (is_vm_hugetlb_page(vma))
3238 		return true;
3239 
3240 	if (!vma_has_recency(vma))
3241 		return true;
3242 
3243 	if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
3244 		return true;
3245 
3246 	if (vma == get_gate_vma(vma->vm_mm))
3247 		return true;
3248 
3249 	if (vma_is_anonymous(vma))
3250 		return !walk->can_swap;
3251 
3252 	if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
3253 		return true;
3254 
3255 	mapping = vma->vm_file->f_mapping;
3256 	if (mapping_unevictable(mapping))
3257 		return true;
3258 
3259 	if (shmem_mapping(mapping))
3260 		return !walk->can_swap;
3261 
3262 	/* to exclude special mappings like dax, etc. */
3263 	return !mapping->a_ops->read_folio;
3264 }
3265 
3266 /*
3267  * Some userspace memory allocators map many single-page VMAs. Instead of
3268  * returning back to the PGD table for each of such VMAs, finish an entire PMD
3269  * table to reduce zigzags and improve cache performance.
3270  */
get_next_vma(unsigned long mask,unsigned long size,struct mm_walk * args,unsigned long * vm_start,unsigned long * vm_end)3271 static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
3272 			 unsigned long *vm_start, unsigned long *vm_end)
3273 {
3274 	unsigned long start = round_up(*vm_end, size);
3275 	unsigned long end = (start | ~mask) + 1;
3276 	VMA_ITERATOR(vmi, args->mm, start);
3277 
3278 	VM_WARN_ON_ONCE(mask & size);
3279 	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
3280 
3281 	for_each_vma(vmi, args->vma) {
3282 		if (end && end <= args->vma->vm_start)
3283 			return false;
3284 
3285 		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
3286 			continue;
3287 
3288 		*vm_start = max(start, args->vma->vm_start);
3289 		*vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
3290 
3291 		return true;
3292 	}
3293 
3294 	return false;
3295 }
3296 
get_pte_pfn(pte_t pte,struct vm_area_struct * vma,unsigned long addr)3297 static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
3298 {
3299 	unsigned long pfn = pte_pfn(pte);
3300 
3301 	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3302 
3303 	if (!pte_present(pte) || is_zero_pfn(pfn))
3304 		return -1;
3305 
3306 	if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
3307 		return -1;
3308 
3309 	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3310 		return -1;
3311 
3312 	return pfn;
3313 }
3314 
get_pmd_pfn(pmd_t pmd,struct vm_area_struct * vma,unsigned long addr)3315 static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
3316 {
3317 	unsigned long pfn = pmd_pfn(pmd);
3318 
3319 	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3320 
3321 	if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
3322 		return -1;
3323 
3324 	if (WARN_ON_ONCE(pmd_devmap(pmd)))
3325 		return -1;
3326 
3327 	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3328 		return -1;
3329 
3330 	return pfn;
3331 }
3332 
get_pfn_folio(unsigned long pfn,struct mem_cgroup * memcg,struct pglist_data * pgdat,bool can_swap)3333 static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
3334 				   struct pglist_data *pgdat, bool can_swap)
3335 {
3336 	struct folio *folio;
3337 
3338 	/* try to avoid unnecessary memory loads */
3339 	if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3340 		return NULL;
3341 
3342 	folio = pfn_folio(pfn);
3343 	if (folio_nid(folio) != pgdat->node_id)
3344 		return NULL;
3345 
3346 	if (folio_memcg_rcu(folio) != memcg)
3347 		return NULL;
3348 
3349 	/* file VMAs can contain anon pages from COW */
3350 	if (!folio_is_file_lru(folio) && !can_swap)
3351 		return NULL;
3352 
3353 	return folio;
3354 }
3355 
suitable_to_scan(int total,int young)3356 static bool suitable_to_scan(int total, int young)
3357 {
3358 	int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
3359 
3360 	/* suitable if the average number of young PTEs per cacheline is >=1 */
3361 	return young * n >= total;
3362 }
3363 
walk_pte_range(pmd_t * pmd,unsigned long start,unsigned long end,struct mm_walk * args)3364 static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
3365 			   struct mm_walk *args)
3366 {
3367 	int i;
3368 	pte_t *pte;
3369 	spinlock_t *ptl;
3370 	unsigned long addr;
3371 	int total = 0;
3372 	int young = 0;
3373 	struct lru_gen_mm_walk *walk = args->private;
3374 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3375 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3376 	DEFINE_MAX_SEQ(walk->lruvec);
3377 	int old_gen, new_gen = lru_gen_from_seq(max_seq);
3378 
3379 	pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl);
3380 	if (!pte)
3381 		return false;
3382 	if (!spin_trylock(ptl)) {
3383 		pte_unmap(pte);
3384 		return false;
3385 	}
3386 
3387 	arch_enter_lazy_mmu_mode();
3388 restart:
3389 	for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
3390 		unsigned long pfn;
3391 		struct folio *folio;
3392 		pte_t ptent = ptep_get(pte + i);
3393 
3394 		total++;
3395 		walk->mm_stats[MM_LEAF_TOTAL]++;
3396 
3397 		pfn = get_pte_pfn(ptent, args->vma, addr);
3398 		if (pfn == -1)
3399 			continue;
3400 
3401 		if (!pte_young(ptent)) {
3402 			walk->mm_stats[MM_LEAF_OLD]++;
3403 			continue;
3404 		}
3405 
3406 		folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3407 		if (!folio)
3408 			continue;
3409 
3410 		if (!ptep_test_and_clear_young(args->vma, addr, pte + i))
3411 			VM_WARN_ON_ONCE(true);
3412 
3413 		young++;
3414 		walk->mm_stats[MM_LEAF_YOUNG]++;
3415 
3416 		if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
3417 		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3418 		      !folio_test_swapcache(folio)))
3419 			folio_mark_dirty(folio);
3420 
3421 		old_gen = folio_update_gen(folio, new_gen);
3422 		if (old_gen >= 0 && old_gen != new_gen)
3423 			update_batch_size(walk, folio, old_gen, new_gen);
3424 	}
3425 
3426 	if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
3427 		goto restart;
3428 
3429 	arch_leave_lazy_mmu_mode();
3430 	pte_unmap_unlock(pte, ptl);
3431 
3432 	return suitable_to_scan(total, young);
3433 }
3434 
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)3435 static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
3436 				  struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
3437 {
3438 	int i;
3439 	pmd_t *pmd;
3440 	spinlock_t *ptl;
3441 	struct lru_gen_mm_walk *walk = args->private;
3442 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3443 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3444 	DEFINE_MAX_SEQ(walk->lruvec);
3445 	int old_gen, new_gen = lru_gen_from_seq(max_seq);
3446 
3447 	VM_WARN_ON_ONCE(pud_leaf(*pud));
3448 
3449 	/* try to batch at most 1+MIN_LRU_BATCH+1 entries */
3450 	if (*first == -1) {
3451 		*first = addr;
3452 		bitmap_zero(bitmap, MIN_LRU_BATCH);
3453 		return;
3454 	}
3455 
3456 	i = addr == -1 ? 0 : pmd_index(addr) - pmd_index(*first);
3457 	if (i && i <= MIN_LRU_BATCH) {
3458 		__set_bit(i - 1, bitmap);
3459 		return;
3460 	}
3461 
3462 	pmd = pmd_offset(pud, *first);
3463 
3464 	ptl = pmd_lockptr(args->mm, pmd);
3465 	if (!spin_trylock(ptl))
3466 		goto done;
3467 
3468 	arch_enter_lazy_mmu_mode();
3469 
3470 	do {
3471 		unsigned long pfn;
3472 		struct folio *folio;
3473 
3474 		/* don't round down the first address */
3475 		addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first;
3476 
3477 		pfn = get_pmd_pfn(pmd[i], vma, addr);
3478 		if (pfn == -1)
3479 			goto next;
3480 
3481 		if (!pmd_trans_huge(pmd[i])) {
3482 			if (!walk->force_scan && should_clear_pmd_young())
3483 				pmdp_test_and_clear_young(vma, addr, pmd + i);
3484 			goto next;
3485 		}
3486 
3487 		folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3488 		if (!folio)
3489 			goto next;
3490 
3491 		if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
3492 			goto next;
3493 
3494 		walk->mm_stats[MM_LEAF_YOUNG]++;
3495 
3496 		if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
3497 		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3498 		      !folio_test_swapcache(folio)))
3499 			folio_mark_dirty(folio);
3500 
3501 		old_gen = folio_update_gen(folio, new_gen);
3502 		if (old_gen >= 0 && old_gen != new_gen)
3503 			update_batch_size(walk, folio, old_gen, new_gen);
3504 next:
3505 		i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
3506 	} while (i <= MIN_LRU_BATCH);
3507 
3508 	arch_leave_lazy_mmu_mode();
3509 	spin_unlock(ptl);
3510 done:
3511 	*first = -1;
3512 }
3513 
walk_pmd_range(pud_t * pud,unsigned long start,unsigned long end,struct mm_walk * args)3514 static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
3515 			   struct mm_walk *args)
3516 {
3517 	int i;
3518 	pmd_t *pmd;
3519 	unsigned long next;
3520 	unsigned long addr;
3521 	struct vm_area_struct *vma;
3522 	DECLARE_BITMAP(bitmap, MIN_LRU_BATCH);
3523 	unsigned long first = -1;
3524 	struct lru_gen_mm_walk *walk = args->private;
3525 	struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
3526 
3527 	VM_WARN_ON_ONCE(pud_leaf(*pud));
3528 
3529 	/*
3530 	 * Finish an entire PMD in two passes: the first only reaches to PTE
3531 	 * tables to avoid taking the PMD lock; the second, if necessary, takes
3532 	 * the PMD lock to clear the accessed bit in PMD entries.
3533 	 */
3534 	pmd = pmd_offset(pud, start & PUD_MASK);
3535 restart:
3536 	/* walk_pte_range() may call get_next_vma() */
3537 	vma = args->vma;
3538 	for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
3539 		pmd_t val = pmdp_get_lockless(pmd + i);
3540 
3541 		next = pmd_addr_end(addr, end);
3542 
3543 		if (!pmd_present(val) || is_huge_zero_pmd(val)) {
3544 			walk->mm_stats[MM_LEAF_TOTAL]++;
3545 			continue;
3546 		}
3547 
3548 		if (pmd_trans_huge(val)) {
3549 			unsigned long pfn = pmd_pfn(val);
3550 			struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3551 
3552 			walk->mm_stats[MM_LEAF_TOTAL]++;
3553 
3554 			if (!pmd_young(val)) {
3555 				walk->mm_stats[MM_LEAF_OLD]++;
3556 				continue;
3557 			}
3558 
3559 			/* try to avoid unnecessary memory loads */
3560 			if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3561 				continue;
3562 
3563 			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3564 			continue;
3565 		}
3566 
3567 		walk->mm_stats[MM_NONLEAF_TOTAL]++;
3568 
3569 		if (!walk->force_scan && should_clear_pmd_young()) {
3570 			if (!pmd_young(val))
3571 				continue;
3572 
3573 			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3574 		}
3575 
3576 		if (!walk->force_scan && !test_bloom_filter(mm_state, walk->seq, pmd + i))
3577 			continue;
3578 
3579 		walk->mm_stats[MM_NONLEAF_FOUND]++;
3580 
3581 		if (!walk_pte_range(&val, addr, next, args))
3582 			continue;
3583 
3584 		walk->mm_stats[MM_NONLEAF_ADDED]++;
3585 
3586 		/* carry over to the next generation */
3587 		update_bloom_filter(mm_state, walk->seq + 1, pmd + i);
3588 	}
3589 
3590 	walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first);
3591 
3592 	if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
3593 		goto restart;
3594 }
3595 
walk_pud_range(p4d_t * p4d,unsigned long start,unsigned long end,struct mm_walk * args)3596 static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
3597 			  struct mm_walk *args)
3598 {
3599 	int i;
3600 	pud_t *pud;
3601 	unsigned long addr;
3602 	unsigned long next;
3603 	struct lru_gen_mm_walk *walk = args->private;
3604 
3605 	VM_WARN_ON_ONCE(p4d_leaf(*p4d));
3606 
3607 	pud = pud_offset(p4d, start & P4D_MASK);
3608 restart:
3609 	for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
3610 		pud_t val = READ_ONCE(pud[i]);
3611 
3612 		next = pud_addr_end(addr, end);
3613 
3614 		if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
3615 			continue;
3616 
3617 		walk_pmd_range(&val, addr, next, args);
3618 
3619 		if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
3620 			end = (addr | ~PUD_MASK) + 1;
3621 			goto done;
3622 		}
3623 	}
3624 
3625 	if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
3626 		goto restart;
3627 
3628 	end = round_up(end, P4D_SIZE);
3629 done:
3630 	if (!end || !args->vma)
3631 		return 1;
3632 
3633 	walk->next_addr = max(end, args->vma->vm_start);
3634 
3635 	return -EAGAIN;
3636 }
3637 
walk_mm(struct mm_struct * mm,struct lru_gen_mm_walk * walk)3638 static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
3639 {
3640 	static const struct mm_walk_ops mm_walk_ops = {
3641 		.test_walk = should_skip_vma,
3642 		.p4d_entry = walk_pud_range,
3643 		.walk_lock = PGWALK_RDLOCK,
3644 	};
3645 
3646 	int err;
3647 	struct lruvec *lruvec = walk->lruvec;
3648 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3649 
3650 	walk->next_addr = FIRST_USER_ADDRESS;
3651 
3652 	do {
3653 		DEFINE_MAX_SEQ(lruvec);
3654 
3655 		err = -EBUSY;
3656 
3657 		/* another thread might have called inc_max_seq() */
3658 		if (walk->seq != max_seq)
3659 			break;
3660 
3661 		/* folio_update_gen() requires stable folio_memcg() */
3662 		if (!mem_cgroup_trylock_pages(memcg))
3663 			break;
3664 
3665 		/* the caller might be holding the lock for write */
3666 		if (mmap_read_trylock(mm)) {
3667 			err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
3668 
3669 			mmap_read_unlock(mm);
3670 		}
3671 
3672 		mem_cgroup_unlock_pages();
3673 
3674 		if (walk->batched) {
3675 			spin_lock_irq(&lruvec->lru_lock);
3676 			reset_batch_size(walk);
3677 			spin_unlock_irq(&lruvec->lru_lock);
3678 		}
3679 
3680 		cond_resched();
3681 	} while (err == -EAGAIN);
3682 }
3683 
set_mm_walk(struct pglist_data * pgdat,bool force_alloc)3684 static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc)
3685 {
3686 	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3687 
3688 	if (pgdat && current_is_kswapd()) {
3689 		VM_WARN_ON_ONCE(walk);
3690 
3691 		walk = &pgdat->mm_walk;
3692 	} else if (!walk && force_alloc) {
3693 		VM_WARN_ON_ONCE(current_is_kswapd());
3694 
3695 		walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
3696 	}
3697 
3698 	current->reclaim_state->mm_walk = walk;
3699 
3700 	return walk;
3701 }
3702 
clear_mm_walk(void)3703 static void clear_mm_walk(void)
3704 {
3705 	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3706 
3707 	VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
3708 	VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
3709 
3710 	current->reclaim_state->mm_walk = NULL;
3711 
3712 	if (!current_is_kswapd())
3713 		kfree(walk);
3714 }
3715 
inc_min_seq(struct lruvec * lruvec,int type,bool can_swap)3716 static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
3717 {
3718 	int zone;
3719 	int remaining = MAX_LRU_BATCH;
3720 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3721 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3722 
3723 	if (type == LRU_GEN_ANON && !can_swap)
3724 		goto done;
3725 
3726 	/* prevent cold/hot inversion if force_scan is true */
3727 	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3728 		struct list_head *head = &lrugen->folios[old_gen][type][zone];
3729 
3730 		while (!list_empty(head)) {
3731 			struct folio *folio = lru_to_folio(head);
3732 
3733 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
3734 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
3735 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
3736 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
3737 
3738 			new_gen = folio_inc_gen(lruvec, folio, false);
3739 			list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
3740 
3741 			if (!--remaining)
3742 				return false;
3743 		}
3744 	}
3745 done:
3746 	reset_ctrl_pos(lruvec, type, true);
3747 	WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
3748 
3749 	return true;
3750 }
3751 
try_to_inc_min_seq(struct lruvec * lruvec,bool can_swap)3752 static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
3753 {
3754 	int gen, type, zone;
3755 	bool success = false;
3756 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3757 	DEFINE_MIN_SEQ(lruvec);
3758 
3759 	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3760 
3761 	/* find the oldest populated generation */
3762 	for (type = !can_swap; type < ANON_AND_FILE; type++) {
3763 		while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
3764 			gen = lru_gen_from_seq(min_seq[type]);
3765 
3766 			for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3767 				if (!list_empty(&lrugen->folios[gen][type][zone]))
3768 					goto next;
3769 			}
3770 
3771 			min_seq[type]++;
3772 		}
3773 next:
3774 		;
3775 	}
3776 
3777 	/* see the comment on lru_gen_folio */
3778 	if (can_swap) {
3779 		min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]);
3780 		min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]);
3781 	}
3782 
3783 	for (type = !can_swap; type < ANON_AND_FILE; type++) {
3784 		if (min_seq[type] == lrugen->min_seq[type])
3785 			continue;
3786 
3787 		reset_ctrl_pos(lruvec, type, true);
3788 		WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
3789 		success = true;
3790 	}
3791 
3792 	return success;
3793 }
3794 
inc_max_seq(struct lruvec * lruvec,unsigned long seq,bool can_swap,bool force_scan)3795 static bool inc_max_seq(struct lruvec *lruvec, unsigned long seq,
3796 			bool can_swap, bool force_scan)
3797 {
3798 	bool success;
3799 	int prev, next;
3800 	int type, zone;
3801 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3802 restart:
3803 	if (seq < READ_ONCE(lrugen->max_seq))
3804 		return false;
3805 
3806 	spin_lock_irq(&lruvec->lru_lock);
3807 
3808 	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3809 
3810 	success = seq == lrugen->max_seq;
3811 	if (!success)
3812 		goto unlock;
3813 
3814 	for (type = ANON_AND_FILE - 1; type >= 0; type--) {
3815 		if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
3816 			continue;
3817 
3818 		VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
3819 
3820 		if (inc_min_seq(lruvec, type, can_swap))
3821 			continue;
3822 
3823 		spin_unlock_irq(&lruvec->lru_lock);
3824 		cond_resched();
3825 		goto restart;
3826 	}
3827 
3828 	/*
3829 	 * Update the active/inactive LRU sizes for compatibility. Both sides of
3830 	 * the current max_seq need to be covered, since max_seq+1 can overlap
3831 	 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
3832 	 * overlap, cold/hot inversion happens.
3833 	 */
3834 	prev = lru_gen_from_seq(lrugen->max_seq - 1);
3835 	next = lru_gen_from_seq(lrugen->max_seq + 1);
3836 
3837 	for (type = 0; type < ANON_AND_FILE; type++) {
3838 		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3839 			enum lru_list lru = type * LRU_INACTIVE_FILE;
3840 			long delta = lrugen->nr_pages[prev][type][zone] -
3841 				     lrugen->nr_pages[next][type][zone];
3842 
3843 			if (!delta)
3844 				continue;
3845 
3846 			__update_lru_size(lruvec, lru, zone, delta);
3847 			__update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
3848 		}
3849 	}
3850 
3851 	for (type = 0; type < ANON_AND_FILE; type++)
3852 		reset_ctrl_pos(lruvec, type, false);
3853 
3854 	WRITE_ONCE(lrugen->timestamps[next], jiffies);
3855 	/* make sure preceding modifications appear */
3856 	smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
3857 unlock:
3858 	spin_unlock_irq(&lruvec->lru_lock);
3859 
3860 	return success;
3861 }
3862 
try_to_inc_max_seq(struct lruvec * lruvec,unsigned long seq,bool can_swap,bool force_scan)3863 static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long seq,
3864 			       bool can_swap, bool force_scan)
3865 {
3866 	bool success;
3867 	struct lru_gen_mm_walk *walk;
3868 	struct mm_struct *mm = NULL;
3869 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3870 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3871 
3872 	VM_WARN_ON_ONCE(seq > READ_ONCE(lrugen->max_seq));
3873 
3874 	if (!mm_state)
3875 		return inc_max_seq(lruvec, seq, can_swap, force_scan);
3876 
3877 	/* see the comment in iterate_mm_list() */
3878 	if (seq <= READ_ONCE(mm_state->seq))
3879 		return false;
3880 
3881 	/*
3882 	 * If the hardware doesn't automatically set the accessed bit, fallback
3883 	 * to lru_gen_look_around(), which only clears the accessed bit in a
3884 	 * handful of PTEs. Spreading the work out over a period of time usually
3885 	 * is less efficient, but it avoids bursty page faults.
3886 	 */
3887 	if (!should_walk_mmu()) {
3888 		success = iterate_mm_list_nowalk(lruvec, seq);
3889 		goto done;
3890 	}
3891 
3892 	walk = set_mm_walk(NULL, true);
3893 	if (!walk) {
3894 		success = iterate_mm_list_nowalk(lruvec, seq);
3895 		goto done;
3896 	}
3897 
3898 	walk->lruvec = lruvec;
3899 	walk->seq = seq;
3900 	walk->can_swap = can_swap;
3901 	walk->force_scan = force_scan;
3902 
3903 	do {
3904 		success = iterate_mm_list(walk, &mm);
3905 		if (mm)
3906 			walk_mm(mm, walk);
3907 	} while (mm);
3908 done:
3909 	if (success) {
3910 		success = inc_max_seq(lruvec, seq, can_swap, force_scan);
3911 		WARN_ON_ONCE(!success);
3912 	}
3913 
3914 	return success;
3915 }
3916 
3917 /******************************************************************************
3918  *                          working set protection
3919  ******************************************************************************/
3920 
set_initial_priority(struct pglist_data * pgdat,struct scan_control * sc)3921 static void set_initial_priority(struct pglist_data *pgdat, struct scan_control *sc)
3922 {
3923 	int priority;
3924 	unsigned long reclaimable;
3925 
3926 	if (sc->priority != DEF_PRIORITY || sc->nr_to_reclaim < MIN_LRU_BATCH)
3927 		return;
3928 	/*
3929 	 * Determine the initial priority based on
3930 	 * (total >> priority) * reclaimed_to_scanned_ratio = nr_to_reclaim,
3931 	 * where reclaimed_to_scanned_ratio = inactive / total.
3932 	 */
3933 	reclaimable = node_page_state(pgdat, NR_INACTIVE_FILE);
3934 	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
3935 		reclaimable += node_page_state(pgdat, NR_INACTIVE_ANON);
3936 
3937 	/* round down reclaimable and round up sc->nr_to_reclaim */
3938 	priority = fls_long(reclaimable) - 1 - fls_long(sc->nr_to_reclaim - 1);
3939 
3940 	/*
3941 	 * The estimation is based on LRU pages only, so cap it to prevent
3942 	 * overshoots of shrinker objects by large margins.
3943 	 */
3944 	sc->priority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY);
3945 }
3946 
lruvec_is_sizable(struct lruvec * lruvec,struct scan_control * sc)3947 static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
3948 {
3949 	int gen, type, zone;
3950 	unsigned long total = 0;
3951 	bool can_swap = get_swappiness(lruvec, sc);
3952 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
3953 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3954 	DEFINE_MAX_SEQ(lruvec);
3955 	DEFINE_MIN_SEQ(lruvec);
3956 
3957 	for (type = !can_swap; type < ANON_AND_FILE; type++) {
3958 		unsigned long seq;
3959 
3960 		for (seq = min_seq[type]; seq <= max_seq; seq++) {
3961 			gen = lru_gen_from_seq(seq);
3962 
3963 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
3964 				total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
3965 		}
3966 	}
3967 
3968 	/* whether the size is big enough to be helpful */
3969 	return mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
3970 }
3971 
lruvec_is_reclaimable(struct lruvec * lruvec,struct scan_control * sc,unsigned long min_ttl)3972 static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc,
3973 				  unsigned long min_ttl)
3974 {
3975 	int gen;
3976 	unsigned long birth;
3977 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3978 	DEFINE_MIN_SEQ(lruvec);
3979 
3980 	if (mem_cgroup_below_min(NULL, memcg))
3981 		return false;
3982 
3983 	if (!lruvec_is_sizable(lruvec, sc))
3984 		return false;
3985 
3986 	/* see the comment on lru_gen_folio */
3987 	gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
3988 	birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
3989 
3990 	return time_is_before_jiffies(birth + min_ttl);
3991 }
3992 
3993 /* to protect the working set of the last N jiffies */
3994 static unsigned long lru_gen_min_ttl __read_mostly;
3995 
lru_gen_age_node(struct pglist_data * pgdat,struct scan_control * sc)3996 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
3997 {
3998 	struct mem_cgroup *memcg;
3999 	unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
4000 	bool reclaimable = !min_ttl;
4001 
4002 	VM_WARN_ON_ONCE(!current_is_kswapd());
4003 
4004 	set_initial_priority(pgdat, sc);
4005 
4006 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
4007 	do {
4008 		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4009 
4010 		mem_cgroup_calculate_protection(NULL, memcg);
4011 
4012 		if (!reclaimable)
4013 			reclaimable = lruvec_is_reclaimable(lruvec, sc, min_ttl);
4014 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
4015 
4016 	/*
4017 	 * The main goal is to OOM kill if every generation from all memcgs is
4018 	 * younger than min_ttl. However, another possibility is all memcgs are
4019 	 * either too small or below min.
4020 	 */
4021 	if (!reclaimable && mutex_trylock(&oom_lock)) {
4022 		struct oom_control oc = {
4023 			.gfp_mask = sc->gfp_mask,
4024 		};
4025 
4026 		out_of_memory(&oc);
4027 
4028 		mutex_unlock(&oom_lock);
4029 	}
4030 }
4031 
4032 /******************************************************************************
4033  *                          rmap/PT walk feedback
4034  ******************************************************************************/
4035 
4036 /*
4037  * This function exploits spatial locality when shrink_folio_list() walks the
4038  * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
4039  * the scan was done cacheline efficiently, it adds the PMD entry pointing to
4040  * the PTE table to the Bloom filter. This forms a feedback loop between the
4041  * eviction and the aging.
4042  */
lru_gen_look_around(struct page_vma_mapped_walk * pvmw)4043 void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
4044 {
4045 	int i;
4046 	unsigned long start;
4047 	unsigned long end;
4048 	struct lru_gen_mm_walk *walk;
4049 	int young = 0;
4050 	pte_t *pte = pvmw->pte;
4051 	unsigned long addr = pvmw->address;
4052 	struct vm_area_struct *vma = pvmw->vma;
4053 	struct folio *folio = pfn_folio(pvmw->pfn);
4054 	bool can_swap = !folio_is_file_lru(folio);
4055 	struct mem_cgroup *memcg = folio_memcg(folio);
4056 	struct pglist_data *pgdat = folio_pgdat(folio);
4057 	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4058 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
4059 	DEFINE_MAX_SEQ(lruvec);
4060 	int old_gen, new_gen = lru_gen_from_seq(max_seq);
4061 
4062 	lockdep_assert_held(pvmw->ptl);
4063 	VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
4064 
4065 	if (spin_is_contended(pvmw->ptl))
4066 		return;
4067 
4068 	/* exclude special VMAs containing anon pages from COW */
4069 	if (vma->vm_flags & VM_SPECIAL)
4070 		return;
4071 
4072 	/* avoid taking the LRU lock under the PTL when possible */
4073 	walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
4074 
4075 	start = max(addr & PMD_MASK, vma->vm_start);
4076 	end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1;
4077 
4078 	if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
4079 		if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
4080 			end = start + MIN_LRU_BATCH * PAGE_SIZE;
4081 		else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2)
4082 			start = end - MIN_LRU_BATCH * PAGE_SIZE;
4083 		else {
4084 			start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2;
4085 			end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2;
4086 		}
4087 	}
4088 
4089 	/* folio_update_gen() requires stable folio_memcg() */
4090 	if (!mem_cgroup_trylock_pages(memcg))
4091 		return;
4092 
4093 	arch_enter_lazy_mmu_mode();
4094 
4095 	pte -= (addr - start) / PAGE_SIZE;
4096 
4097 	for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
4098 		unsigned long pfn;
4099 		pte_t ptent = ptep_get(pte + i);
4100 
4101 		pfn = get_pte_pfn(ptent, vma, addr);
4102 		if (pfn == -1)
4103 			continue;
4104 
4105 		if (!pte_young(ptent))
4106 			continue;
4107 
4108 		folio = get_pfn_folio(pfn, memcg, pgdat, can_swap);
4109 		if (!folio)
4110 			continue;
4111 
4112 		if (!ptep_test_and_clear_young(vma, addr, pte + i))
4113 			VM_WARN_ON_ONCE(true);
4114 
4115 		young++;
4116 
4117 		if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
4118 		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4119 		      !folio_test_swapcache(folio)))
4120 			folio_mark_dirty(folio);
4121 
4122 		if (walk) {
4123 			old_gen = folio_update_gen(folio, new_gen);
4124 			if (old_gen >= 0 && old_gen != new_gen)
4125 				update_batch_size(walk, folio, old_gen, new_gen);
4126 
4127 			continue;
4128 		}
4129 
4130 		old_gen = folio_lru_gen(folio);
4131 		if (old_gen < 0)
4132 			folio_set_referenced(folio);
4133 		else if (old_gen != new_gen)
4134 			folio_activate(folio);
4135 	}
4136 
4137 	arch_leave_lazy_mmu_mode();
4138 	mem_cgroup_unlock_pages();
4139 
4140 	/* feedback from rmap walkers to page table walkers */
4141 	if (mm_state && suitable_to_scan(i, young))
4142 		update_bloom_filter(mm_state, max_seq, pvmw->pmd);
4143 }
4144 
4145 /******************************************************************************
4146  *                          memcg LRU
4147  ******************************************************************************/
4148 
4149 /* see the comment on MEMCG_NR_GENS */
4150 enum {
4151 	MEMCG_LRU_NOP,
4152 	MEMCG_LRU_HEAD,
4153 	MEMCG_LRU_TAIL,
4154 	MEMCG_LRU_OLD,
4155 	MEMCG_LRU_YOUNG,
4156 };
4157 
lru_gen_rotate_memcg(struct lruvec * lruvec,int op)4158 static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
4159 {
4160 	int seg;
4161 	int old, new;
4162 	unsigned long flags;
4163 	int bin = get_random_u32_below(MEMCG_NR_BINS);
4164 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4165 
4166 	spin_lock_irqsave(&pgdat->memcg_lru.lock, flags);
4167 
4168 	VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
4169 
4170 	seg = 0;
4171 	new = old = lruvec->lrugen.gen;
4172 
4173 	/* see the comment on MEMCG_NR_GENS */
4174 	if (op == MEMCG_LRU_HEAD)
4175 		seg = MEMCG_LRU_HEAD;
4176 	else if (op == MEMCG_LRU_TAIL)
4177 		seg = MEMCG_LRU_TAIL;
4178 	else if (op == MEMCG_LRU_OLD)
4179 		new = get_memcg_gen(pgdat->memcg_lru.seq);
4180 	else if (op == MEMCG_LRU_YOUNG)
4181 		new = get_memcg_gen(pgdat->memcg_lru.seq + 1);
4182 	else
4183 		VM_WARN_ON_ONCE(true);
4184 
4185 	WRITE_ONCE(lruvec->lrugen.seg, seg);
4186 	WRITE_ONCE(lruvec->lrugen.gen, new);
4187 
4188 	hlist_nulls_del_rcu(&lruvec->lrugen.list);
4189 
4190 	if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD)
4191 		hlist_nulls_add_head_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4192 	else
4193 		hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4194 
4195 	pgdat->memcg_lru.nr_memcgs[old]--;
4196 	pgdat->memcg_lru.nr_memcgs[new]++;
4197 
4198 	if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq))
4199 		WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4200 
4201 	spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags);
4202 }
4203 
4204 #ifdef CONFIG_MEMCG
4205 
lru_gen_online_memcg(struct mem_cgroup * memcg)4206 void lru_gen_online_memcg(struct mem_cgroup *memcg)
4207 {
4208 	int gen;
4209 	int nid;
4210 	int bin = get_random_u32_below(MEMCG_NR_BINS);
4211 
4212 	for_each_node(nid) {
4213 		struct pglist_data *pgdat = NODE_DATA(nid);
4214 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4215 
4216 		spin_lock_irq(&pgdat->memcg_lru.lock);
4217 
4218 		VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
4219 
4220 		gen = get_memcg_gen(pgdat->memcg_lru.seq);
4221 
4222 		lruvec->lrugen.gen = gen;
4223 
4224 		hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]);
4225 		pgdat->memcg_lru.nr_memcgs[gen]++;
4226 
4227 		spin_unlock_irq(&pgdat->memcg_lru.lock);
4228 	}
4229 }
4230 
lru_gen_offline_memcg(struct mem_cgroup * memcg)4231 void lru_gen_offline_memcg(struct mem_cgroup *memcg)
4232 {
4233 	int nid;
4234 
4235 	for_each_node(nid) {
4236 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4237 
4238 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD);
4239 	}
4240 }
4241 
lru_gen_release_memcg(struct mem_cgroup * memcg)4242 void lru_gen_release_memcg(struct mem_cgroup *memcg)
4243 {
4244 	int gen;
4245 	int nid;
4246 
4247 	for_each_node(nid) {
4248 		struct pglist_data *pgdat = NODE_DATA(nid);
4249 		struct lruvec *lruvec = get_lruvec(memcg, nid);
4250 
4251 		spin_lock_irq(&pgdat->memcg_lru.lock);
4252 
4253 		if (hlist_nulls_unhashed(&lruvec->lrugen.list))
4254 			goto unlock;
4255 
4256 		gen = lruvec->lrugen.gen;
4257 
4258 		hlist_nulls_del_init_rcu(&lruvec->lrugen.list);
4259 		pgdat->memcg_lru.nr_memcgs[gen]--;
4260 
4261 		if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))
4262 			WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4263 unlock:
4264 		spin_unlock_irq(&pgdat->memcg_lru.lock);
4265 	}
4266 }
4267 
lru_gen_soft_reclaim(struct mem_cgroup * memcg,int nid)4268 void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
4269 {
4270 	struct lruvec *lruvec = get_lruvec(memcg, nid);
4271 
4272 	/* see the comment on MEMCG_NR_GENS */
4273 	if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_HEAD)
4274 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);
4275 }
4276 
4277 #endif /* CONFIG_MEMCG */
4278 
4279 /******************************************************************************
4280  *                          the eviction
4281  ******************************************************************************/
4282 
sort_folio(struct lruvec * lruvec,struct folio * folio,struct scan_control * sc,int tier_idx)4283 static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
4284 		       int tier_idx)
4285 {
4286 	bool success;
4287 	int gen = folio_lru_gen(folio);
4288 	int type = folio_is_file_lru(folio);
4289 	int zone = folio_zonenum(folio);
4290 	int delta = folio_nr_pages(folio);
4291 	int refs = folio_lru_refs(folio);
4292 	int tier = lru_tier_from_refs(refs);
4293 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4294 
4295 	VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
4296 
4297 	/* unevictable */
4298 	if (!folio_evictable(folio)) {
4299 		success = lru_gen_del_folio(lruvec, folio, true);
4300 		VM_WARN_ON_ONCE_FOLIO(!success, folio);
4301 		folio_set_unevictable(folio);
4302 		lruvec_add_folio(lruvec, folio);
4303 		__count_vm_events(UNEVICTABLE_PGCULLED, delta);
4304 		return true;
4305 	}
4306 
4307 	/* promoted */
4308 	if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
4309 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4310 		return true;
4311 	}
4312 
4313 	/* protected */
4314 	if (tier > tier_idx || refs == BIT(LRU_REFS_WIDTH)) {
4315 		int hist = lru_hist_from_seq(lrugen->min_seq[type]);
4316 
4317 		gen = folio_inc_gen(lruvec, folio, false);
4318 		list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
4319 
4320 		WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
4321 			   lrugen->protected[hist][type][tier - 1] + delta);
4322 		return true;
4323 	}
4324 
4325 	/* ineligible */
4326 	if (!folio_test_lru(folio) || zone > sc->reclaim_idx) {
4327 		gen = folio_inc_gen(lruvec, folio, false);
4328 		list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
4329 		return true;
4330 	}
4331 
4332 	/* waiting for writeback */
4333 	if (folio_test_locked(folio) || folio_test_writeback(folio) ||
4334 	    (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
4335 		gen = folio_inc_gen(lruvec, folio, true);
4336 		list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4337 		return true;
4338 	}
4339 
4340 	return false;
4341 }
4342 
isolate_folio(struct lruvec * lruvec,struct folio * folio,struct scan_control * sc)4343 static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
4344 {
4345 	bool success;
4346 
4347 	/* swap constrained */
4348 	if (!(sc->gfp_mask & __GFP_IO) &&
4349 	    (folio_test_dirty(folio) ||
4350 	     (folio_test_anon(folio) && !folio_test_swapcache(folio))))
4351 		return false;
4352 
4353 	/* raced with release_pages() */
4354 	if (!folio_try_get(folio))
4355 		return false;
4356 
4357 	/* raced with another isolation */
4358 	if (!folio_test_clear_lru(folio)) {
4359 		folio_put(folio);
4360 		return false;
4361 	}
4362 
4363 	/* see the comment on MAX_NR_TIERS */
4364 	if (!folio_test_referenced(folio))
4365 		set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0);
4366 
4367 	/* for shrink_folio_list() */
4368 	folio_clear_reclaim(folio);
4369 	folio_clear_referenced(folio);
4370 
4371 	success = lru_gen_del_folio(lruvec, folio, true);
4372 	VM_WARN_ON_ONCE_FOLIO(!success, folio);
4373 
4374 	return true;
4375 }
4376 
scan_folios(struct lruvec * lruvec,struct scan_control * sc,int type,int tier,struct list_head * list)4377 static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
4378 		       int type, int tier, struct list_head *list)
4379 {
4380 	int i;
4381 	int gen;
4382 	enum vm_event_item item;
4383 	int sorted = 0;
4384 	int scanned = 0;
4385 	int isolated = 0;
4386 	int skipped = 0;
4387 	int remaining = MAX_LRU_BATCH;
4388 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4389 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4390 
4391 	VM_WARN_ON_ONCE(!list_empty(list));
4392 
4393 	if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
4394 		return 0;
4395 
4396 	gen = lru_gen_from_seq(lrugen->min_seq[type]);
4397 
4398 	for (i = MAX_NR_ZONES; i > 0; i--) {
4399 		LIST_HEAD(moved);
4400 		int skipped_zone = 0;
4401 		int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
4402 		struct list_head *head = &lrugen->folios[gen][type][zone];
4403 
4404 		while (!list_empty(head)) {
4405 			struct folio *folio = lru_to_folio(head);
4406 			int delta = folio_nr_pages(folio);
4407 
4408 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4409 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4410 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4411 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4412 
4413 			scanned += delta;
4414 
4415 			if (sort_folio(lruvec, folio, sc, tier))
4416 				sorted += delta;
4417 			else if (isolate_folio(lruvec, folio, sc)) {
4418 				list_add(&folio->lru, list);
4419 				isolated += delta;
4420 			} else {
4421 				list_move(&folio->lru, &moved);
4422 				skipped_zone += delta;
4423 			}
4424 
4425 			if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
4426 				break;
4427 		}
4428 
4429 		if (skipped_zone) {
4430 			list_splice(&moved, head);
4431 			__count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
4432 			skipped += skipped_zone;
4433 		}
4434 
4435 		if (!remaining || isolated >= MIN_LRU_BATCH)
4436 			break;
4437 	}
4438 
4439 	item = PGSCAN_KSWAPD + reclaimer_offset();
4440 	if (!cgroup_reclaim(sc)) {
4441 		__count_vm_events(item, isolated);
4442 		__count_vm_events(PGREFILL, sorted);
4443 	}
4444 	__count_memcg_events(memcg, item, isolated);
4445 	__count_memcg_events(memcg, PGREFILL, sorted);
4446 	__count_vm_events(PGSCAN_ANON + type, isolated);
4447 	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
4448 				scanned, skipped, isolated,
4449 				type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4450 
4451 	/*
4452 	 * There might not be eligible folios due to reclaim_idx. Check the
4453 	 * remaining to prevent livelock if it's not making progress.
4454 	 */
4455 	return isolated || !remaining ? scanned : 0;
4456 }
4457 
get_tier_idx(struct lruvec * lruvec,int type)4458 static int get_tier_idx(struct lruvec *lruvec, int type)
4459 {
4460 	int tier;
4461 	struct ctrl_pos sp, pv;
4462 
4463 	/*
4464 	 * To leave a margin for fluctuations, use a larger gain factor (1:2).
4465 	 * This value is chosen because any other tier would have at least twice
4466 	 * as many refaults as the first tier.
4467 	 */
4468 	read_ctrl_pos(lruvec, type, 0, 1, &sp);
4469 	for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4470 		read_ctrl_pos(lruvec, type, tier, 2, &pv);
4471 		if (!positive_ctrl_err(&sp, &pv))
4472 			break;
4473 	}
4474 
4475 	return tier - 1;
4476 }
4477 
get_type_to_scan(struct lruvec * lruvec,int swappiness,int * tier_idx)4478 static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
4479 {
4480 	int type, tier;
4481 	struct ctrl_pos sp, pv;
4482 	int gain[ANON_AND_FILE] = { swappiness, MAX_SWAPPINESS - swappiness };
4483 
4484 	/*
4485 	 * Compare the first tier of anon with that of file to determine which
4486 	 * type to scan. Also need to compare other tiers of the selected type
4487 	 * with the first tier of the other type to determine the last tier (of
4488 	 * the selected type) to evict.
4489 	 */
4490 	read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
4491 	read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
4492 	type = positive_ctrl_err(&sp, &pv);
4493 
4494 	read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
4495 	for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4496 		read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
4497 		if (!positive_ctrl_err(&sp, &pv))
4498 			break;
4499 	}
4500 
4501 	*tier_idx = tier - 1;
4502 
4503 	return type;
4504 }
4505 
isolate_folios(struct lruvec * lruvec,struct scan_control * sc,int swappiness,int * type_scanned,struct list_head * list)4506 static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
4507 			  int *type_scanned, struct list_head *list)
4508 {
4509 	int i;
4510 	int type;
4511 	int scanned;
4512 	int tier = -1;
4513 	DEFINE_MIN_SEQ(lruvec);
4514 
4515 	/*
4516 	 * Try to make the obvious choice first, and if anon and file are both
4517 	 * available from the same generation,
4518 	 * 1. Interpret swappiness 1 as file first and MAX_SWAPPINESS as anon
4519 	 *    first.
4520 	 * 2. If !__GFP_IO, file first since clean pagecache is more likely to
4521 	 *    exist than clean swapcache.
4522 	 */
4523 	if (!swappiness)
4524 		type = LRU_GEN_FILE;
4525 	else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
4526 		type = LRU_GEN_ANON;
4527 	else if (swappiness == 1)
4528 		type = LRU_GEN_FILE;
4529 	else if (swappiness == MAX_SWAPPINESS)
4530 		type = LRU_GEN_ANON;
4531 	else if (!(sc->gfp_mask & __GFP_IO))
4532 		type = LRU_GEN_FILE;
4533 	else
4534 		type = get_type_to_scan(lruvec, swappiness, &tier);
4535 
4536 	for (i = !swappiness; i < ANON_AND_FILE; i++) {
4537 		if (tier < 0)
4538 			tier = get_tier_idx(lruvec, type);
4539 
4540 		scanned = scan_folios(lruvec, sc, type, tier, list);
4541 		if (scanned)
4542 			break;
4543 
4544 		type = !type;
4545 		tier = -1;
4546 	}
4547 
4548 	*type_scanned = type;
4549 
4550 	return scanned;
4551 }
4552 
evict_folios(struct lruvec * lruvec,struct scan_control * sc,int swappiness)4553 static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
4554 {
4555 	int type;
4556 	int scanned;
4557 	int reclaimed;
4558 	LIST_HEAD(list);
4559 	LIST_HEAD(clean);
4560 	struct folio *folio;
4561 	struct folio *next;
4562 	enum vm_event_item item;
4563 	struct reclaim_stat stat;
4564 	struct lru_gen_mm_walk *walk;
4565 	bool skip_retry = false;
4566 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4567 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4568 
4569 	spin_lock_irq(&lruvec->lru_lock);
4570 
4571 	scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
4572 
4573 	scanned += try_to_inc_min_seq(lruvec, swappiness);
4574 
4575 	if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS)
4576 		scanned = 0;
4577 
4578 	spin_unlock_irq(&lruvec->lru_lock);
4579 
4580 	if (list_empty(&list))
4581 		return scanned;
4582 retry:
4583 	reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
4584 	sc->nr_reclaimed += reclaimed;
4585 	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
4586 			scanned, reclaimed, &stat, sc->priority,
4587 			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4588 
4589 	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
4590 		if (!folio_evictable(folio)) {
4591 			list_del(&folio->lru);
4592 			folio_putback_lru(folio);
4593 			continue;
4594 		}
4595 
4596 		if (folio_test_reclaim(folio) &&
4597 		    (folio_test_dirty(folio) || folio_test_writeback(folio))) {
4598 			/* restore LRU_REFS_FLAGS cleared by isolate_folio() */
4599 			if (folio_test_workingset(folio))
4600 				folio_set_referenced(folio);
4601 			continue;
4602 		}
4603 
4604 		if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
4605 		    folio_mapped(folio) || folio_test_locked(folio) ||
4606 		    folio_test_dirty(folio) || folio_test_writeback(folio)) {
4607 			/* don't add rejected folios to the oldest generation */
4608 			set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
4609 				      BIT(PG_active));
4610 			continue;
4611 		}
4612 
4613 		/* retry folios that may have missed folio_rotate_reclaimable() */
4614 		list_move(&folio->lru, &clean);
4615 	}
4616 
4617 	spin_lock_irq(&lruvec->lru_lock);
4618 
4619 	move_folios_to_lru(lruvec, &list);
4620 
4621 	walk = current->reclaim_state->mm_walk;
4622 	if (walk && walk->batched) {
4623 		walk->lruvec = lruvec;
4624 		reset_batch_size(walk);
4625 	}
4626 
4627 	item = PGSTEAL_KSWAPD + reclaimer_offset();
4628 	if (!cgroup_reclaim(sc))
4629 		__count_vm_events(item, reclaimed);
4630 	__count_memcg_events(memcg, item, reclaimed);
4631 	__count_vm_events(PGSTEAL_ANON + type, reclaimed);
4632 
4633 	spin_unlock_irq(&lruvec->lru_lock);
4634 
4635 	list_splice_init(&clean, &list);
4636 
4637 	if (!list_empty(&list)) {
4638 		skip_retry = true;
4639 		goto retry;
4640 	}
4641 
4642 	return scanned;
4643 }
4644 
should_run_aging(struct lruvec * lruvec,unsigned long max_seq,bool can_swap,unsigned long * nr_to_scan)4645 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
4646 			     bool can_swap, unsigned long *nr_to_scan)
4647 {
4648 	int gen, type, zone;
4649 	unsigned long old = 0;
4650 	unsigned long young = 0;
4651 	unsigned long total = 0;
4652 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4653 	DEFINE_MIN_SEQ(lruvec);
4654 
4655 	/* whether this lruvec is completely out of cold folios */
4656 	if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) {
4657 		*nr_to_scan = 0;
4658 		return true;
4659 	}
4660 
4661 	for (type = !can_swap; type < ANON_AND_FILE; type++) {
4662 		unsigned long seq;
4663 
4664 		for (seq = min_seq[type]; seq <= max_seq; seq++) {
4665 			unsigned long size = 0;
4666 
4667 			gen = lru_gen_from_seq(seq);
4668 
4669 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
4670 				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4671 
4672 			total += size;
4673 			if (seq == max_seq)
4674 				young += size;
4675 			else if (seq + MIN_NR_GENS == max_seq)
4676 				old += size;
4677 		}
4678 	}
4679 
4680 	*nr_to_scan = total;
4681 
4682 	/*
4683 	 * The aging tries to be lazy to reduce the overhead, while the eviction
4684 	 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
4685 	 * ideal number of generations is MIN_NR_GENS+1.
4686 	 */
4687 	if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
4688 		return false;
4689 
4690 	/*
4691 	 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
4692 	 * of the total number of pages for each generation. A reasonable range
4693 	 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
4694 	 * aging cares about the upper bound of hot pages, while the eviction
4695 	 * cares about the lower bound of cold pages.
4696 	 */
4697 	if (young * MIN_NR_GENS > total)
4698 		return true;
4699 	if (old * (MIN_NR_GENS + 2) < total)
4700 		return true;
4701 
4702 	return false;
4703 }
4704 
4705 /*
4706  * For future optimizations:
4707  * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
4708  *    reclaim.
4709  */
get_nr_to_scan(struct lruvec * lruvec,struct scan_control * sc,bool can_swap)4710 static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap)
4711 {
4712 	bool success;
4713 	unsigned long nr_to_scan;
4714 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4715 	DEFINE_MAX_SEQ(lruvec);
4716 
4717 	if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg))
4718 		return -1;
4719 
4720 	success = should_run_aging(lruvec, max_seq, can_swap, &nr_to_scan);
4721 
4722 	/* try to scrape all its memory if this memcg was deleted */
4723 	if (nr_to_scan && !mem_cgroup_online(memcg))
4724 		return nr_to_scan;
4725 
4726 	/* try to get away with not aging at the default priority */
4727 	if (!success || sc->priority == DEF_PRIORITY)
4728 		return nr_to_scan >> sc->priority;
4729 
4730 	/* stop scanning this lruvec as it's low on cold folios */
4731 	return try_to_inc_max_seq(lruvec, max_seq, can_swap, false) ? -1 : 0;
4732 }
4733 
should_abort_scan(struct lruvec * lruvec,struct scan_control * sc)4734 static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
4735 {
4736 	int i;
4737 	enum zone_watermarks mark;
4738 
4739 	/* don't abort memcg reclaim to ensure fairness */
4740 	if (!root_reclaim(sc))
4741 		return false;
4742 
4743 	if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
4744 		return true;
4745 
4746 	/* check the order to exclude compaction-induced reclaim */
4747 	if (!current_is_kswapd() || sc->order)
4748 		return false;
4749 
4750 	mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ?
4751 	       WMARK_PROMO : WMARK_HIGH;
4752 
4753 	for (i = 0; i <= sc->reclaim_idx; i++) {
4754 		struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
4755 		unsigned long size = wmark_pages(zone, mark) + MIN_LRU_BATCH;
4756 
4757 		if (managed_zone(zone) && !zone_watermark_ok(zone, 0, size, sc->reclaim_idx, 0))
4758 			return false;
4759 	}
4760 
4761 	/* kswapd should abort if all eligible zones are safe */
4762 	return true;
4763 }
4764 
try_to_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)4765 static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4766 {
4767 	long nr_to_scan;
4768 	unsigned long scanned = 0;
4769 	int swappiness = get_swappiness(lruvec, sc);
4770 
4771 	while (true) {
4772 		int delta;
4773 
4774 		nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness);
4775 		if (nr_to_scan <= 0)
4776 			break;
4777 
4778 		delta = evict_folios(lruvec, sc, swappiness);
4779 		if (!delta)
4780 			break;
4781 
4782 		scanned += delta;
4783 		if (scanned >= nr_to_scan)
4784 			break;
4785 
4786 		if (should_abort_scan(lruvec, sc))
4787 			break;
4788 
4789 		cond_resched();
4790 	}
4791 
4792 	/* whether this lruvec should be rotated */
4793 	return nr_to_scan < 0;
4794 }
4795 
shrink_one(struct lruvec * lruvec,struct scan_control * sc)4796 static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
4797 {
4798 	bool success;
4799 	unsigned long scanned = sc->nr_scanned;
4800 	unsigned long reclaimed = sc->nr_reclaimed;
4801 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4802 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4803 
4804 	/* lru_gen_age_node() called mem_cgroup_calculate_protection() */
4805 	if (mem_cgroup_below_min(NULL, memcg))
4806 		return MEMCG_LRU_YOUNG;
4807 
4808 	if (mem_cgroup_below_low(NULL, memcg)) {
4809 		/* see the comment on MEMCG_NR_GENS */
4810 		if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL)
4811 			return MEMCG_LRU_TAIL;
4812 
4813 		memcg_memory_event(memcg, MEMCG_LOW);
4814 	}
4815 
4816 	success = try_to_shrink_lruvec(lruvec, sc);
4817 
4818 	shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority);
4819 
4820 	if (!sc->proactive)
4821 		vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned,
4822 			   sc->nr_reclaimed - reclaimed);
4823 
4824 	flush_reclaim_state(sc);
4825 
4826 	if (success && mem_cgroup_online(memcg))
4827 		return MEMCG_LRU_YOUNG;
4828 
4829 	if (!success && lruvec_is_sizable(lruvec, sc))
4830 		return 0;
4831 
4832 	/* one retry if offlined or too small */
4833 	return READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL ?
4834 	       MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
4835 }
4836 
shrink_many(struct pglist_data * pgdat,struct scan_control * sc)4837 static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
4838 {
4839 	int op;
4840 	int gen;
4841 	int bin;
4842 	int first_bin;
4843 	struct lruvec *lruvec;
4844 	struct lru_gen_folio *lrugen;
4845 	struct mem_cgroup *memcg;
4846 	struct hlist_nulls_node *pos;
4847 
4848 	gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
4849 	bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
4850 restart:
4851 	op = 0;
4852 	memcg = NULL;
4853 
4854 	rcu_read_lock();
4855 
4856 	hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) {
4857 		if (op) {
4858 			lru_gen_rotate_memcg(lruvec, op);
4859 			op = 0;
4860 		}
4861 
4862 		mem_cgroup_put(memcg);
4863 		memcg = NULL;
4864 
4865 		if (gen != READ_ONCE(lrugen->gen))
4866 			continue;
4867 
4868 		lruvec = container_of(lrugen, struct lruvec, lrugen);
4869 		memcg = lruvec_memcg(lruvec);
4870 
4871 		if (!mem_cgroup_tryget(memcg)) {
4872 			lru_gen_release_memcg(memcg);
4873 			memcg = NULL;
4874 			continue;
4875 		}
4876 
4877 		rcu_read_unlock();
4878 
4879 		op = shrink_one(lruvec, sc);
4880 
4881 		rcu_read_lock();
4882 
4883 		if (should_abort_scan(lruvec, sc))
4884 			break;
4885 	}
4886 
4887 	rcu_read_unlock();
4888 
4889 	if (op)
4890 		lru_gen_rotate_memcg(lruvec, op);
4891 
4892 	mem_cgroup_put(memcg);
4893 
4894 	if (!is_a_nulls(pos))
4895 		return;
4896 
4897 	/* restart if raced with lru_gen_rotate_memcg() */
4898 	if (gen != get_nulls_value(pos))
4899 		goto restart;
4900 
4901 	/* try the rest of the bins of the current generation */
4902 	bin = get_memcg_bin(bin + 1);
4903 	if (bin != first_bin)
4904 		goto restart;
4905 }
4906 
lru_gen_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)4907 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4908 {
4909 	struct blk_plug plug;
4910 
4911 	VM_WARN_ON_ONCE(root_reclaim(sc));
4912 	VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap);
4913 
4914 	lru_add_drain();
4915 
4916 	blk_start_plug(&plug);
4917 
4918 	set_mm_walk(NULL, sc->proactive);
4919 
4920 	if (try_to_shrink_lruvec(lruvec, sc))
4921 		lru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);
4922 
4923 	clear_mm_walk();
4924 
4925 	blk_finish_plug(&plug);
4926 }
4927 
lru_gen_shrink_node(struct pglist_data * pgdat,struct scan_control * sc)4928 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
4929 {
4930 	struct blk_plug plug;
4931 	unsigned long reclaimed = sc->nr_reclaimed;
4932 
4933 	VM_WARN_ON_ONCE(!root_reclaim(sc));
4934 
4935 	/*
4936 	 * Unmapped clean folios are already prioritized. Scanning for more of
4937 	 * them is likely futile and can cause high reclaim latency when there
4938 	 * is a large number of memcgs.
4939 	 */
4940 	if (!sc->may_writepage || !sc->may_unmap)
4941 		goto done;
4942 
4943 	lru_add_drain();
4944 
4945 	blk_start_plug(&plug);
4946 
4947 	set_mm_walk(pgdat, sc->proactive);
4948 
4949 	set_initial_priority(pgdat, sc);
4950 
4951 	if (current_is_kswapd())
4952 		sc->nr_reclaimed = 0;
4953 
4954 	if (mem_cgroup_disabled())
4955 		shrink_one(&pgdat->__lruvec, sc);
4956 	else
4957 		shrink_many(pgdat, sc);
4958 
4959 	if (current_is_kswapd())
4960 		sc->nr_reclaimed += reclaimed;
4961 
4962 	clear_mm_walk();
4963 
4964 	blk_finish_plug(&plug);
4965 done:
4966 	/* kswapd should never fail */
4967 	pgdat->kswapd_failures = 0;
4968 }
4969 
4970 /******************************************************************************
4971  *                          state change
4972  ******************************************************************************/
4973 
state_is_valid(struct lruvec * lruvec)4974 static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
4975 {
4976 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
4977 
4978 	if (lrugen->enabled) {
4979 		enum lru_list lru;
4980 
4981 		for_each_evictable_lru(lru) {
4982 			if (!list_empty(&lruvec->lists[lru]))
4983 				return false;
4984 		}
4985 	} else {
4986 		int gen, type, zone;
4987 
4988 		for_each_gen_type_zone(gen, type, zone) {
4989 			if (!list_empty(&lrugen->folios[gen][type][zone]))
4990 				return false;
4991 		}
4992 	}
4993 
4994 	return true;
4995 }
4996 
fill_evictable(struct lruvec * lruvec)4997 static bool fill_evictable(struct lruvec *lruvec)
4998 {
4999 	enum lru_list lru;
5000 	int remaining = MAX_LRU_BATCH;
5001 
5002 	for_each_evictable_lru(lru) {
5003 		int type = is_file_lru(lru);
5004 		bool active = is_active_lru(lru);
5005 		struct list_head *head = &lruvec->lists[lru];
5006 
5007 		while (!list_empty(head)) {
5008 			bool success;
5009 			struct folio *folio = lru_to_folio(head);
5010 
5011 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5012 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
5013 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5014 			VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
5015 
5016 			lruvec_del_folio(lruvec, folio);
5017 			success = lru_gen_add_folio(lruvec, folio, false);
5018 			VM_WARN_ON_ONCE(!success);
5019 
5020 			if (!--remaining)
5021 				return false;
5022 		}
5023 	}
5024 
5025 	return true;
5026 }
5027 
drain_evictable(struct lruvec * lruvec)5028 static bool drain_evictable(struct lruvec *lruvec)
5029 {
5030 	int gen, type, zone;
5031 	int remaining = MAX_LRU_BATCH;
5032 
5033 	for_each_gen_type_zone(gen, type, zone) {
5034 		struct list_head *head = &lruvec->lrugen.folios[gen][type][zone];
5035 
5036 		while (!list_empty(head)) {
5037 			bool success;
5038 			struct folio *folio = lru_to_folio(head);
5039 
5040 			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5041 			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
5042 			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5043 			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
5044 
5045 			success = lru_gen_del_folio(lruvec, folio, false);
5046 			VM_WARN_ON_ONCE(!success);
5047 			lruvec_add_folio(lruvec, folio);
5048 
5049 			if (!--remaining)
5050 				return false;
5051 		}
5052 	}
5053 
5054 	return true;
5055 }
5056 
lru_gen_change_state(bool enabled)5057 static void lru_gen_change_state(bool enabled)
5058 {
5059 	static DEFINE_MUTEX(state_mutex);
5060 
5061 	struct mem_cgroup *memcg;
5062 
5063 	cgroup_lock();
5064 	cpus_read_lock();
5065 	get_online_mems();
5066 	mutex_lock(&state_mutex);
5067 
5068 	if (enabled == lru_gen_enabled())
5069 		goto unlock;
5070 
5071 	if (enabled)
5072 		static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5073 	else
5074 		static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5075 
5076 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5077 	do {
5078 		int nid;
5079 
5080 		for_each_node(nid) {
5081 			struct lruvec *lruvec = get_lruvec(memcg, nid);
5082 
5083 			spin_lock_irq(&lruvec->lru_lock);
5084 
5085 			VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
5086 			VM_WARN_ON_ONCE(!state_is_valid(lruvec));
5087 
5088 			lruvec->lrugen.enabled = enabled;
5089 
5090 			while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
5091 				spin_unlock_irq(&lruvec->lru_lock);
5092 				cond_resched();
5093 				spin_lock_irq(&lruvec->lru_lock);
5094 			}
5095 
5096 			spin_unlock_irq(&lruvec->lru_lock);
5097 		}
5098 
5099 		cond_resched();
5100 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5101 unlock:
5102 	mutex_unlock(&state_mutex);
5103 	put_online_mems();
5104 	cpus_read_unlock();
5105 	cgroup_unlock();
5106 }
5107 
5108 /******************************************************************************
5109  *                          sysfs interface
5110  ******************************************************************************/
5111 
min_ttl_ms_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)5112 static ssize_t min_ttl_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5113 {
5114 	return sysfs_emit(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
5115 }
5116 
5117 /* 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)5118 static ssize_t min_ttl_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
5119 				const char *buf, size_t len)
5120 {
5121 	unsigned int msecs;
5122 
5123 	if (kstrtouint(buf, 0, &msecs))
5124 		return -EINVAL;
5125 
5126 	WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
5127 
5128 	return len;
5129 }
5130 
5131 static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR_RW(min_ttl_ms);
5132 
enabled_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)5133 static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5134 {
5135 	unsigned int caps = 0;
5136 
5137 	if (get_cap(LRU_GEN_CORE))
5138 		caps |= BIT(LRU_GEN_CORE);
5139 
5140 	if (should_walk_mmu())
5141 		caps |= BIT(LRU_GEN_MM_WALK);
5142 
5143 	if (should_clear_pmd_young())
5144 		caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
5145 
5146 	return sysfs_emit(buf, "0x%04x\n", caps);
5147 }
5148 
5149 /* 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)5150 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
5151 			     const char *buf, size_t len)
5152 {
5153 	int i;
5154 	unsigned int caps;
5155 
5156 	if (tolower(*buf) == 'n')
5157 		caps = 0;
5158 	else if (tolower(*buf) == 'y')
5159 		caps = -1;
5160 	else if (kstrtouint(buf, 0, &caps))
5161 		return -EINVAL;
5162 
5163 	for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
5164 		bool enabled = caps & BIT(i);
5165 
5166 		if (i == LRU_GEN_CORE)
5167 			lru_gen_change_state(enabled);
5168 		else if (enabled)
5169 			static_branch_enable(&lru_gen_caps[i]);
5170 		else
5171 			static_branch_disable(&lru_gen_caps[i]);
5172 	}
5173 
5174 	return len;
5175 }
5176 
5177 static struct kobj_attribute lru_gen_enabled_attr = __ATTR_RW(enabled);
5178 
5179 static struct attribute *lru_gen_attrs[] = {
5180 	&lru_gen_min_ttl_attr.attr,
5181 	&lru_gen_enabled_attr.attr,
5182 	NULL
5183 };
5184 
5185 static const struct attribute_group lru_gen_attr_group = {
5186 	.name = "lru_gen",
5187 	.attrs = lru_gen_attrs,
5188 };
5189 
5190 /******************************************************************************
5191  *                          debugfs interface
5192  ******************************************************************************/
5193 
lru_gen_seq_start(struct seq_file * m,loff_t * pos)5194 static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
5195 {
5196 	struct mem_cgroup *memcg;
5197 	loff_t nr_to_skip = *pos;
5198 
5199 	m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
5200 	if (!m->private)
5201 		return ERR_PTR(-ENOMEM);
5202 
5203 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5204 	do {
5205 		int nid;
5206 
5207 		for_each_node_state(nid, N_MEMORY) {
5208 			if (!nr_to_skip--)
5209 				return get_lruvec(memcg, nid);
5210 		}
5211 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5212 
5213 	return NULL;
5214 }
5215 
lru_gen_seq_stop(struct seq_file * m,void * v)5216 static void lru_gen_seq_stop(struct seq_file *m, void *v)
5217 {
5218 	if (!IS_ERR_OR_NULL(v))
5219 		mem_cgroup_iter_break(NULL, lruvec_memcg(v));
5220 
5221 	kvfree(m->private);
5222 	m->private = NULL;
5223 }
5224 
lru_gen_seq_next(struct seq_file * m,void * v,loff_t * pos)5225 static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
5226 {
5227 	int nid = lruvec_pgdat(v)->node_id;
5228 	struct mem_cgroup *memcg = lruvec_memcg(v);
5229 
5230 	++*pos;
5231 
5232 	nid = next_memory_node(nid);
5233 	if (nid == MAX_NUMNODES) {
5234 		memcg = mem_cgroup_iter(NULL, memcg, NULL);
5235 		if (!memcg)
5236 			return NULL;
5237 
5238 		nid = first_memory_node;
5239 	}
5240 
5241 	return get_lruvec(memcg, nid);
5242 }
5243 
lru_gen_seq_show_full(struct seq_file * m,struct lruvec * lruvec,unsigned long max_seq,unsigned long * min_seq,unsigned long seq)5244 static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
5245 				  unsigned long max_seq, unsigned long *min_seq,
5246 				  unsigned long seq)
5247 {
5248 	int i;
5249 	int type, tier;
5250 	int hist = lru_hist_from_seq(seq);
5251 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5252 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5253 
5254 	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
5255 		seq_printf(m, "            %10d", tier);
5256 		for (type = 0; type < ANON_AND_FILE; type++) {
5257 			const char *s = "   ";
5258 			unsigned long n[3] = {};
5259 
5260 			if (seq == max_seq) {
5261 				s = "RT ";
5262 				n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
5263 				n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
5264 			} else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
5265 				s = "rep";
5266 				n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
5267 				n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
5268 				if (tier)
5269 					n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]);
5270 			}
5271 
5272 			for (i = 0; i < 3; i++)
5273 				seq_printf(m, " %10lu%c", n[i], s[i]);
5274 		}
5275 		seq_putc(m, '\n');
5276 	}
5277 
5278 	if (!mm_state)
5279 		return;
5280 
5281 	seq_puts(m, "                      ");
5282 	for (i = 0; i < NR_MM_STATS; i++) {
5283 		const char *s = "      ";
5284 		unsigned long n = 0;
5285 
5286 		if (seq == max_seq && NR_HIST_GENS == 1) {
5287 			s = "LOYNFA";
5288 			n = READ_ONCE(mm_state->stats[hist][i]);
5289 		} else if (seq != max_seq && NR_HIST_GENS > 1) {
5290 			s = "loynfa";
5291 			n = READ_ONCE(mm_state->stats[hist][i]);
5292 		}
5293 
5294 		seq_printf(m, " %10lu%c", n, s[i]);
5295 	}
5296 	seq_putc(m, '\n');
5297 }
5298 
5299 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */
lru_gen_seq_show(struct seq_file * m,void * v)5300 static int lru_gen_seq_show(struct seq_file *m, void *v)
5301 {
5302 	unsigned long seq;
5303 	bool full = !debugfs_real_fops(m->file)->write;
5304 	struct lruvec *lruvec = v;
5305 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5306 	int nid = lruvec_pgdat(lruvec)->node_id;
5307 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5308 	DEFINE_MAX_SEQ(lruvec);
5309 	DEFINE_MIN_SEQ(lruvec);
5310 
5311 	if (nid == first_memory_node) {
5312 		const char *path = memcg ? m->private : "";
5313 
5314 #ifdef CONFIG_MEMCG
5315 		if (memcg)
5316 			cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
5317 #endif
5318 		seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
5319 	}
5320 
5321 	seq_printf(m, " node %5d\n", nid);
5322 
5323 	if (!full)
5324 		seq = min_seq[LRU_GEN_ANON];
5325 	else if (max_seq >= MAX_NR_GENS)
5326 		seq = max_seq - MAX_NR_GENS + 1;
5327 	else
5328 		seq = 0;
5329 
5330 	for (; seq <= max_seq; seq++) {
5331 		int type, zone;
5332 		int gen = lru_gen_from_seq(seq);
5333 		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
5334 
5335 		seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
5336 
5337 		for (type = 0; type < ANON_AND_FILE; type++) {
5338 			unsigned long size = 0;
5339 			char mark = full && seq < min_seq[type] ? 'x' : ' ';
5340 
5341 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
5342 				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
5343 
5344 			seq_printf(m, " %10lu%c", size, mark);
5345 		}
5346 
5347 		seq_putc(m, '\n');
5348 
5349 		if (full)
5350 			lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
5351 	}
5352 
5353 	return 0;
5354 }
5355 
5356 static const struct seq_operations lru_gen_seq_ops = {
5357 	.start = lru_gen_seq_start,
5358 	.stop = lru_gen_seq_stop,
5359 	.next = lru_gen_seq_next,
5360 	.show = lru_gen_seq_show,
5361 };
5362 
run_aging(struct lruvec * lruvec,unsigned long seq,bool can_swap,bool force_scan)5363 static int run_aging(struct lruvec *lruvec, unsigned long seq,
5364 		     bool can_swap, bool force_scan)
5365 {
5366 	DEFINE_MAX_SEQ(lruvec);
5367 	DEFINE_MIN_SEQ(lruvec);
5368 
5369 	if (seq < max_seq)
5370 		return 0;
5371 
5372 	if (seq > max_seq)
5373 		return -EINVAL;
5374 
5375 	if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq)
5376 		return -ERANGE;
5377 
5378 	try_to_inc_max_seq(lruvec, max_seq, can_swap, force_scan);
5379 
5380 	return 0;
5381 }
5382 
run_eviction(struct lruvec * lruvec,unsigned long seq,struct scan_control * sc,int swappiness,unsigned long nr_to_reclaim)5383 static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5384 			int swappiness, unsigned long nr_to_reclaim)
5385 {
5386 	DEFINE_MAX_SEQ(lruvec);
5387 
5388 	if (seq + MIN_NR_GENS > max_seq)
5389 		return -EINVAL;
5390 
5391 	sc->nr_reclaimed = 0;
5392 
5393 	while (!signal_pending(current)) {
5394 		DEFINE_MIN_SEQ(lruvec);
5395 
5396 		if (seq < min_seq[!swappiness])
5397 			return 0;
5398 
5399 		if (sc->nr_reclaimed >= nr_to_reclaim)
5400 			return 0;
5401 
5402 		if (!evict_folios(lruvec, sc, swappiness))
5403 			return 0;
5404 
5405 		cond_resched();
5406 	}
5407 
5408 	return -EINTR;
5409 }
5410 
run_cmd(char cmd,int memcg_id,int nid,unsigned long seq,struct scan_control * sc,int swappiness,unsigned long opt)5411 static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
5412 		   struct scan_control *sc, int swappiness, unsigned long opt)
5413 {
5414 	struct lruvec *lruvec;
5415 	int err = -EINVAL;
5416 	struct mem_cgroup *memcg = NULL;
5417 
5418 	if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
5419 		return -EINVAL;
5420 
5421 	if (!mem_cgroup_disabled()) {
5422 		rcu_read_lock();
5423 
5424 		memcg = mem_cgroup_from_id(memcg_id);
5425 		if (!mem_cgroup_tryget(memcg))
5426 			memcg = NULL;
5427 
5428 		rcu_read_unlock();
5429 
5430 		if (!memcg)
5431 			return -EINVAL;
5432 	}
5433 
5434 	if (memcg_id != mem_cgroup_id(memcg))
5435 		goto done;
5436 
5437 	lruvec = get_lruvec(memcg, nid);
5438 
5439 	if (swappiness < MIN_SWAPPINESS)
5440 		swappiness = get_swappiness(lruvec, sc);
5441 	else if (swappiness > MAX_SWAPPINESS)
5442 		goto done;
5443 
5444 	switch (cmd) {
5445 	case '+':
5446 		err = run_aging(lruvec, seq, swappiness, opt);
5447 		break;
5448 	case '-':
5449 		err = run_eviction(lruvec, seq, sc, swappiness, opt);
5450 		break;
5451 	}
5452 done:
5453 	mem_cgroup_put(memcg);
5454 
5455 	return err;
5456 }
5457 
5458 /* 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)5459 static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
5460 				 size_t len, loff_t *pos)
5461 {
5462 	void *buf;
5463 	char *cur, *next;
5464 	unsigned int flags;
5465 	struct blk_plug plug;
5466 	int err = -EINVAL;
5467 	struct scan_control sc = {
5468 		.may_writepage = true,
5469 		.may_unmap = true,
5470 		.may_swap = true,
5471 		.reclaim_idx = MAX_NR_ZONES - 1,
5472 		.gfp_mask = GFP_KERNEL,
5473 	};
5474 
5475 	buf = kvmalloc(len + 1, GFP_KERNEL);
5476 	if (!buf)
5477 		return -ENOMEM;
5478 
5479 	if (copy_from_user(buf, src, len)) {
5480 		kvfree(buf);
5481 		return -EFAULT;
5482 	}
5483 
5484 	set_task_reclaim_state(current, &sc.reclaim_state);
5485 	flags = memalloc_noreclaim_save();
5486 	blk_start_plug(&plug);
5487 	if (!set_mm_walk(NULL, true)) {
5488 		err = -ENOMEM;
5489 		goto done;
5490 	}
5491 
5492 	next = buf;
5493 	next[len] = '\0';
5494 
5495 	while ((cur = strsep(&next, ",;\n"))) {
5496 		int n;
5497 		int end;
5498 		char cmd;
5499 		unsigned int memcg_id;
5500 		unsigned int nid;
5501 		unsigned long seq;
5502 		unsigned int swappiness = -1;
5503 		unsigned long opt = -1;
5504 
5505 		cur = skip_spaces(cur);
5506 		if (!*cur)
5507 			continue;
5508 
5509 		n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
5510 			   &seq, &end, &swappiness, &end, &opt, &end);
5511 		if (n < 4 || cur[end]) {
5512 			err = -EINVAL;
5513 			break;
5514 		}
5515 
5516 		err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
5517 		if (err)
5518 			break;
5519 	}
5520 done:
5521 	clear_mm_walk();
5522 	blk_finish_plug(&plug);
5523 	memalloc_noreclaim_restore(flags);
5524 	set_task_reclaim_state(current, NULL);
5525 
5526 	kvfree(buf);
5527 
5528 	return err ? : len;
5529 }
5530 
lru_gen_seq_open(struct inode * inode,struct file * file)5531 static int lru_gen_seq_open(struct inode *inode, struct file *file)
5532 {
5533 	return seq_open(file, &lru_gen_seq_ops);
5534 }
5535 
5536 static const struct file_operations lru_gen_rw_fops = {
5537 	.open = lru_gen_seq_open,
5538 	.read = seq_read,
5539 	.write = lru_gen_seq_write,
5540 	.llseek = seq_lseek,
5541 	.release = seq_release,
5542 };
5543 
5544 static const struct file_operations lru_gen_ro_fops = {
5545 	.open = lru_gen_seq_open,
5546 	.read = seq_read,
5547 	.llseek = seq_lseek,
5548 	.release = seq_release,
5549 };
5550 
5551 /******************************************************************************
5552  *                          initialization
5553  ******************************************************************************/
5554 
lru_gen_init_pgdat(struct pglist_data * pgdat)5555 void lru_gen_init_pgdat(struct pglist_data *pgdat)
5556 {
5557 	int i, j;
5558 
5559 	spin_lock_init(&pgdat->memcg_lru.lock);
5560 
5561 	for (i = 0; i < MEMCG_NR_GENS; i++) {
5562 		for (j = 0; j < MEMCG_NR_BINS; j++)
5563 			INIT_HLIST_NULLS_HEAD(&pgdat->memcg_lru.fifo[i][j], i);
5564 	}
5565 }
5566 
lru_gen_init_lruvec(struct lruvec * lruvec)5567 void lru_gen_init_lruvec(struct lruvec *lruvec)
5568 {
5569 	int i;
5570 	int gen, type, zone;
5571 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
5572 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5573 
5574 	lrugen->max_seq = MIN_NR_GENS + 1;
5575 	lrugen->enabled = lru_gen_enabled();
5576 
5577 	for (i = 0; i <= MIN_NR_GENS + 1; i++)
5578 		lrugen->timestamps[i] = jiffies;
5579 
5580 	for_each_gen_type_zone(gen, type, zone)
5581 		INIT_LIST_HEAD(&lrugen->folios[gen][type][zone]);
5582 
5583 	if (mm_state)
5584 		mm_state->seq = MIN_NR_GENS;
5585 }
5586 
5587 #ifdef CONFIG_MEMCG
5588 
lru_gen_init_memcg(struct mem_cgroup * memcg)5589 void lru_gen_init_memcg(struct mem_cgroup *memcg)
5590 {
5591 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5592 
5593 	if (!mm_list)
5594 		return;
5595 
5596 	INIT_LIST_HEAD(&mm_list->fifo);
5597 	spin_lock_init(&mm_list->lock);
5598 }
5599 
lru_gen_exit_memcg(struct mem_cgroup * memcg)5600 void lru_gen_exit_memcg(struct mem_cgroup *memcg)
5601 {
5602 	int i;
5603 	int nid;
5604 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5605 
5606 	VM_WARN_ON_ONCE(mm_list && !list_empty(&mm_list->fifo));
5607 
5608 	for_each_node(nid) {
5609 		struct lruvec *lruvec = get_lruvec(memcg, nid);
5610 		struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5611 
5612 		VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
5613 					   sizeof(lruvec->lrugen.nr_pages)));
5614 
5615 		lruvec->lrugen.list.next = LIST_POISON1;
5616 
5617 		if (!mm_state)
5618 			continue;
5619 
5620 		for (i = 0; i < NR_BLOOM_FILTERS; i++) {
5621 			bitmap_free(mm_state->filters[i]);
5622 			mm_state->filters[i] = NULL;
5623 		}
5624 	}
5625 }
5626 
5627 #endif /* CONFIG_MEMCG */
5628 
init_lru_gen(void)5629 static int __init init_lru_gen(void)
5630 {
5631 	BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
5632 	BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
5633 
5634 	if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
5635 		pr_err("lru_gen: failed to create sysfs group\n");
5636 
5637 	debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
5638 	debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
5639 
5640 	return 0;
5641 };
5642 late_initcall(init_lru_gen);
5643 
5644 #else /* !CONFIG_LRU_GEN */
5645 
lru_gen_age_node(struct pglist_data * pgdat,struct scan_control * sc)5646 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
5647 {
5648 	BUILD_BUG();
5649 }
5650 
lru_gen_shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)5651 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5652 {
5653 	BUILD_BUG();
5654 }
5655 
lru_gen_shrink_node(struct pglist_data * pgdat,struct scan_control * sc)5656 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
5657 {
5658 	BUILD_BUG();
5659 }
5660 
5661 #endif /* CONFIG_LRU_GEN */
5662 
shrink_lruvec(struct lruvec * lruvec,struct scan_control * sc)5663 static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5664 {
5665 	unsigned long nr[NR_LRU_LISTS];
5666 	unsigned long targets[NR_LRU_LISTS];
5667 	unsigned long nr_to_scan;
5668 	enum lru_list lru;
5669 	unsigned long nr_reclaimed = 0;
5670 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
5671 	bool proportional_reclaim;
5672 	struct blk_plug plug;
5673 
5674 	if (lru_gen_enabled() && !root_reclaim(sc)) {
5675 		lru_gen_shrink_lruvec(lruvec, sc);
5676 		return;
5677 	}
5678 
5679 	get_scan_count(lruvec, sc, nr);
5680 
5681 	/* Record the original scan target for proportional adjustments later */
5682 	memcpy(targets, nr, sizeof(nr));
5683 
5684 	/*
5685 	 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
5686 	 * event that can occur when there is little memory pressure e.g.
5687 	 * multiple streaming readers/writers. Hence, we do not abort scanning
5688 	 * when the requested number of pages are reclaimed when scanning at
5689 	 * DEF_PRIORITY on the assumption that the fact we are direct
5690 	 * reclaiming implies that kswapd is not keeping up and it is best to
5691 	 * do a batch of work at once. For memcg reclaim one check is made to
5692 	 * abort proportional reclaim if either the file or anon lru has already
5693 	 * dropped to zero at the first pass.
5694 	 */
5695 	proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
5696 				sc->priority == DEF_PRIORITY);
5697 
5698 	blk_start_plug(&plug);
5699 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
5700 					nr[LRU_INACTIVE_FILE]) {
5701 		unsigned long nr_anon, nr_file, percentage;
5702 		unsigned long nr_scanned;
5703 
5704 		for_each_evictable_lru(lru) {
5705 			if (nr[lru]) {
5706 				nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
5707 				nr[lru] -= nr_to_scan;
5708 
5709 				nr_reclaimed += shrink_list(lru, nr_to_scan,
5710 							    lruvec, sc);
5711 			}
5712 		}
5713 
5714 		cond_resched();
5715 
5716 		if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
5717 			continue;
5718 
5719 		/*
5720 		 * For kswapd and memcg, reclaim at least the number of pages
5721 		 * requested. Ensure that the anon and file LRUs are scanned
5722 		 * proportionally what was requested by get_scan_count(). We
5723 		 * stop reclaiming one LRU and reduce the amount scanning
5724 		 * proportional to the original scan target.
5725 		 */
5726 		nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
5727 		nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
5728 
5729 		/*
5730 		 * It's just vindictive to attack the larger once the smaller
5731 		 * has gone to zero.  And given the way we stop scanning the
5732 		 * smaller below, this makes sure that we only make one nudge
5733 		 * towards proportionality once we've got nr_to_reclaim.
5734 		 */
5735 		if (!nr_file || !nr_anon)
5736 			break;
5737 
5738 		if (nr_file > nr_anon) {
5739 			unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
5740 						targets[LRU_ACTIVE_ANON] + 1;
5741 			lru = LRU_BASE;
5742 			percentage = nr_anon * 100 / scan_target;
5743 		} else {
5744 			unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
5745 						targets[LRU_ACTIVE_FILE] + 1;
5746 			lru = LRU_FILE;
5747 			percentage = nr_file * 100 / scan_target;
5748 		}
5749 
5750 		/* Stop scanning the smaller of the LRU */
5751 		nr[lru] = 0;
5752 		nr[lru + LRU_ACTIVE] = 0;
5753 
5754 		/*
5755 		 * Recalculate the other LRU scan count based on its original
5756 		 * scan target and the percentage scanning already complete
5757 		 */
5758 		lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
5759 		nr_scanned = targets[lru] - nr[lru];
5760 		nr[lru] = targets[lru] * (100 - percentage) / 100;
5761 		nr[lru] -= min(nr[lru], nr_scanned);
5762 
5763 		lru += LRU_ACTIVE;
5764 		nr_scanned = targets[lru] - nr[lru];
5765 		nr[lru] = targets[lru] * (100 - percentage) / 100;
5766 		nr[lru] -= min(nr[lru], nr_scanned);
5767 	}
5768 	blk_finish_plug(&plug);
5769 	sc->nr_reclaimed += nr_reclaimed;
5770 
5771 	/*
5772 	 * Even if we did not try to evict anon pages at all, we want to
5773 	 * rebalance the anon lru active/inactive ratio.
5774 	 */
5775 	if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
5776 	    inactive_is_low(lruvec, LRU_INACTIVE_ANON))
5777 		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
5778 				   sc, LRU_ACTIVE_ANON);
5779 }
5780 
5781 /* Use reclaim/compaction for costly allocs or under memory pressure */
in_reclaim_compaction(struct scan_control * sc)5782 static bool in_reclaim_compaction(struct scan_control *sc)
5783 {
5784 	if (gfp_compaction_allowed(sc->gfp_mask) && sc->order &&
5785 			(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
5786 			 sc->priority < DEF_PRIORITY - 2))
5787 		return true;
5788 
5789 	return false;
5790 }
5791 
5792 /*
5793  * Reclaim/compaction is used for high-order allocation requests. It reclaims
5794  * order-0 pages before compacting the zone. should_continue_reclaim() returns
5795  * true if more pages should be reclaimed such that when the page allocator
5796  * calls try_to_compact_pages() that it will have enough free pages to succeed.
5797  * It will give up earlier than that if there is difficulty reclaiming pages.
5798  */
should_continue_reclaim(struct pglist_data * pgdat,unsigned long nr_reclaimed,struct scan_control * sc)5799 static inline bool should_continue_reclaim(struct pglist_data *pgdat,
5800 					unsigned long nr_reclaimed,
5801 					struct scan_control *sc)
5802 {
5803 	unsigned long pages_for_compaction;
5804 	unsigned long inactive_lru_pages;
5805 	int z;
5806 
5807 	/* If not in reclaim/compaction mode, stop */
5808 	if (!in_reclaim_compaction(sc))
5809 		return false;
5810 
5811 	/*
5812 	 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
5813 	 * number of pages that were scanned. This will return to the caller
5814 	 * with the risk reclaim/compaction and the resulting allocation attempt
5815 	 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
5816 	 * allocations through requiring that the full LRU list has been scanned
5817 	 * first, by assuming that zero delta of sc->nr_scanned means full LRU
5818 	 * scan, but that approximation was wrong, and there were corner cases
5819 	 * where always a non-zero amount of pages were scanned.
5820 	 */
5821 	if (!nr_reclaimed)
5822 		return false;
5823 
5824 	/* If compaction would go ahead or the allocation would succeed, stop */
5825 	for (z = 0; z <= sc->reclaim_idx; z++) {
5826 		struct zone *zone = &pgdat->node_zones[z];
5827 		if (!managed_zone(zone))
5828 			continue;
5829 
5830 		/* Allocation can already succeed, nothing to do */
5831 		if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
5832 				      sc->reclaim_idx, 0))
5833 			return false;
5834 
5835 		if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
5836 			return false;
5837 	}
5838 
5839 	/*
5840 	 * If we have not reclaimed enough pages for compaction and the
5841 	 * inactive lists are large enough, continue reclaiming
5842 	 */
5843 	pages_for_compaction = compact_gap(sc->order);
5844 	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
5845 	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
5846 		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
5847 
5848 	return inactive_lru_pages > pages_for_compaction;
5849 }
5850 
shrink_node_memcgs(pg_data_t * pgdat,struct scan_control * sc)5851 static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
5852 {
5853 	struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
5854 	struct mem_cgroup_reclaim_cookie reclaim = {
5855 		.pgdat = pgdat,
5856 	};
5857 	struct mem_cgroup_reclaim_cookie *partial = &reclaim;
5858 	struct mem_cgroup *memcg;
5859 
5860 	/*
5861 	 * In most cases, direct reclaimers can do partial walks
5862 	 * through the cgroup tree, using an iterator state that
5863 	 * persists across invocations. This strikes a balance between
5864 	 * fairness and allocation latency.
5865 	 *
5866 	 * For kswapd, reliable forward progress is more important
5867 	 * than a quick return to idle. Always do full walks.
5868 	 */
5869 	if (current_is_kswapd() || sc->memcg_full_walk)
5870 		partial = NULL;
5871 
5872 	memcg = mem_cgroup_iter(target_memcg, NULL, partial);
5873 	do {
5874 		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
5875 		unsigned long reclaimed;
5876 		unsigned long scanned;
5877 
5878 		/*
5879 		 * This loop can become CPU-bound when target memcgs
5880 		 * aren't eligible for reclaim - either because they
5881 		 * don't have any reclaimable pages, or because their
5882 		 * memory is explicitly protected. Avoid soft lockups.
5883 		 */
5884 		cond_resched();
5885 
5886 		mem_cgroup_calculate_protection(target_memcg, memcg);
5887 
5888 		if (mem_cgroup_below_min(target_memcg, memcg)) {
5889 			/*
5890 			 * Hard protection.
5891 			 * If there is no reclaimable memory, OOM.
5892 			 */
5893 			continue;
5894 		} else if (mem_cgroup_below_low(target_memcg, memcg)) {
5895 			/*
5896 			 * Soft protection.
5897 			 * Respect the protection only as long as
5898 			 * there is an unprotected supply
5899 			 * of reclaimable memory from other cgroups.
5900 			 */
5901 			if (!sc->memcg_low_reclaim) {
5902 				sc->memcg_low_skipped = 1;
5903 				continue;
5904 			}
5905 			memcg_memory_event(memcg, MEMCG_LOW);
5906 		}
5907 
5908 		reclaimed = sc->nr_reclaimed;
5909 		scanned = sc->nr_scanned;
5910 
5911 		shrink_lruvec(lruvec, sc);
5912 
5913 		shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
5914 			    sc->priority);
5915 
5916 		/* Record the group's reclaim efficiency */
5917 		if (!sc->proactive)
5918 			vmpressure(sc->gfp_mask, memcg, false,
5919 				   sc->nr_scanned - scanned,
5920 				   sc->nr_reclaimed - reclaimed);
5921 
5922 		/* If partial walks are allowed, bail once goal is reached */
5923 		if (partial && sc->nr_reclaimed >= sc->nr_to_reclaim) {
5924 			mem_cgroup_iter_break(target_memcg, memcg);
5925 			break;
5926 		}
5927 	} while ((memcg = mem_cgroup_iter(target_memcg, memcg, partial)));
5928 }
5929 
shrink_node(pg_data_t * pgdat,struct scan_control * sc)5930 static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
5931 {
5932 	unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed;
5933 	struct lruvec *target_lruvec;
5934 	bool reclaimable = false;
5935 
5936 	if (lru_gen_enabled() && root_reclaim(sc)) {
5937 		lru_gen_shrink_node(pgdat, sc);
5938 		return;
5939 	}
5940 
5941 	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
5942 
5943 again:
5944 	memset(&sc->nr, 0, sizeof(sc->nr));
5945 
5946 	nr_reclaimed = sc->nr_reclaimed;
5947 	nr_scanned = sc->nr_scanned;
5948 
5949 	prepare_scan_control(pgdat, sc);
5950 
5951 	shrink_node_memcgs(pgdat, sc);
5952 
5953 	flush_reclaim_state(sc);
5954 
5955 	nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed;
5956 
5957 	/* Record the subtree's reclaim efficiency */
5958 	if (!sc->proactive)
5959 		vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
5960 			   sc->nr_scanned - nr_scanned, nr_node_reclaimed);
5961 
5962 	if (nr_node_reclaimed)
5963 		reclaimable = true;
5964 
5965 	if (current_is_kswapd()) {
5966 		/*
5967 		 * If reclaim is isolating dirty pages under writeback,
5968 		 * it implies that the long-lived page allocation rate
5969 		 * is exceeding the page laundering rate. Either the
5970 		 * global limits are not being effective at throttling
5971 		 * processes due to the page distribution throughout
5972 		 * zones or there is heavy usage of a slow backing
5973 		 * device. The only option is to throttle from reclaim
5974 		 * context which is not ideal as there is no guarantee
5975 		 * the dirtying process is throttled in the same way
5976 		 * balance_dirty_pages() manages.
5977 		 *
5978 		 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
5979 		 * count the number of pages under pages flagged for
5980 		 * immediate reclaim and stall if any are encountered
5981 		 * in the nr_immediate check below.
5982 		 */
5983 		if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
5984 			set_bit(PGDAT_WRITEBACK, &pgdat->flags);
5985 
5986 		/* Allow kswapd to start writing pages during reclaim.*/
5987 		if (sc->nr.unqueued_dirty == sc->nr.file_taken)
5988 			set_bit(PGDAT_DIRTY, &pgdat->flags);
5989 
5990 		/*
5991 		 * If kswapd scans pages marked for immediate
5992 		 * reclaim and under writeback (nr_immediate), it
5993 		 * implies that pages are cycling through the LRU
5994 		 * faster than they are written so forcibly stall
5995 		 * until some pages complete writeback.
5996 		 */
5997 		if (sc->nr.immediate)
5998 			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
5999 	}
6000 
6001 	/*
6002 	 * Tag a node/memcg as congested if all the dirty pages were marked
6003 	 * for writeback and immediate reclaim (counted in nr.congested).
6004 	 *
6005 	 * Legacy memcg will stall in page writeback so avoid forcibly
6006 	 * stalling in reclaim_throttle().
6007 	 */
6008 	if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) {
6009 		if (cgroup_reclaim(sc) && writeback_throttling_sane(sc))
6010 			set_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags);
6011 
6012 		if (current_is_kswapd())
6013 			set_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags);
6014 	}
6015 
6016 	/*
6017 	 * Stall direct reclaim for IO completions if the lruvec is
6018 	 * node is congested. Allow kswapd to continue until it
6019 	 * starts encountering unqueued dirty pages or cycling through
6020 	 * the LRU too quickly.
6021 	 */
6022 	if (!current_is_kswapd() && current_may_throttle() &&
6023 	    !sc->hibernation_mode &&
6024 	    (test_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags) ||
6025 	     test_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags)))
6026 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
6027 
6028 	if (should_continue_reclaim(pgdat, nr_node_reclaimed, sc))
6029 		goto again;
6030 
6031 	/*
6032 	 * Kswapd gives up on balancing particular nodes after too
6033 	 * many failures to reclaim anything from them and goes to
6034 	 * sleep. On reclaim progress, reset the failure counter. A
6035 	 * successful direct reclaim run will revive a dormant kswapd.
6036 	 */
6037 	if (reclaimable)
6038 		pgdat->kswapd_failures = 0;
6039 	else if (sc->cache_trim_mode)
6040 		sc->cache_trim_mode_failed = 1;
6041 }
6042 
6043 /*
6044  * Returns true if compaction should go ahead for a costly-order request, or
6045  * the allocation would already succeed without compaction. Return false if we
6046  * should reclaim first.
6047  */
compaction_ready(struct zone * zone,struct scan_control * sc)6048 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
6049 {
6050 	unsigned long watermark;
6051 
6052 	if (!gfp_compaction_allowed(sc->gfp_mask))
6053 		return false;
6054 
6055 	/* Allocation can already succeed, nothing to do */
6056 	if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
6057 			      sc->reclaim_idx, 0))
6058 		return true;
6059 
6060 	/* Compaction cannot yet proceed. Do reclaim. */
6061 	if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
6062 		return false;
6063 
6064 	/*
6065 	 * Compaction is already possible, but it takes time to run and there
6066 	 * are potentially other callers using the pages just freed. So proceed
6067 	 * with reclaim to make a buffer of free pages available to give
6068 	 * compaction a reasonable chance of completing and allocating the page.
6069 	 * Note that we won't actually reclaim the whole buffer in one attempt
6070 	 * as the target watermark in should_continue_reclaim() is lower. But if
6071 	 * we are already above the high+gap watermark, don't reclaim at all.
6072 	 */
6073 	watermark = high_wmark_pages(zone) + compact_gap(sc->order);
6074 
6075 	return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
6076 }
6077 
consider_reclaim_throttle(pg_data_t * pgdat,struct scan_control * sc)6078 static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
6079 {
6080 	/*
6081 	 * If reclaim is making progress greater than 12% efficiency then
6082 	 * wake all the NOPROGRESS throttled tasks.
6083 	 */
6084 	if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
6085 		wait_queue_head_t *wqh;
6086 
6087 		wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
6088 		if (waitqueue_active(wqh))
6089 			wake_up(wqh);
6090 
6091 		return;
6092 	}
6093 
6094 	/*
6095 	 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6096 	 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6097 	 * under writeback and marked for immediate reclaim at the tail of the
6098 	 * LRU.
6099 	 */
6100 	if (current_is_kswapd() || cgroup_reclaim(sc))
6101 		return;
6102 
6103 	/* Throttle if making no progress at high prioities. */
6104 	if (sc->priority == 1 && !sc->nr_reclaimed)
6105 		reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
6106 }
6107 
6108 /*
6109  * This is the direct reclaim path, for page-allocating processes.  We only
6110  * try to reclaim pages from zones which will satisfy the caller's allocation
6111  * request.
6112  *
6113  * If a zone is deemed to be full of pinned pages then just give it a light
6114  * scan then give up on it.
6115  */
shrink_zones(struct zonelist * zonelist,struct scan_control * sc)6116 static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
6117 {
6118 	struct zoneref *z;
6119 	struct zone *zone;
6120 	unsigned long nr_soft_reclaimed;
6121 	unsigned long nr_soft_scanned;
6122 	gfp_t orig_mask;
6123 	pg_data_t *last_pgdat = NULL;
6124 	pg_data_t *first_pgdat = NULL;
6125 
6126 	/*
6127 	 * If the number of buffer_heads in the machine exceeds the maximum
6128 	 * allowed level, force direct reclaim to scan the highmem zone as
6129 	 * highmem pages could be pinning lowmem pages storing buffer_heads
6130 	 */
6131 	orig_mask = sc->gfp_mask;
6132 	if (buffer_heads_over_limit) {
6133 		sc->gfp_mask |= __GFP_HIGHMEM;
6134 		sc->reclaim_idx = gfp_zone(sc->gfp_mask);
6135 	}
6136 
6137 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6138 					sc->reclaim_idx, sc->nodemask) {
6139 		/*
6140 		 * Take care memory controller reclaiming has small influence
6141 		 * to global LRU.
6142 		 */
6143 		if (!cgroup_reclaim(sc)) {
6144 			if (!cpuset_zone_allowed(zone,
6145 						 GFP_KERNEL | __GFP_HARDWALL))
6146 				continue;
6147 
6148 			/*
6149 			 * If we already have plenty of memory free for
6150 			 * compaction in this zone, don't free any more.
6151 			 * Even though compaction is invoked for any
6152 			 * non-zero order, only frequent costly order
6153 			 * reclamation is disruptive enough to become a
6154 			 * noticeable problem, like transparent huge
6155 			 * page allocations.
6156 			 */
6157 			if (IS_ENABLED(CONFIG_COMPACTION) &&
6158 			    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
6159 			    compaction_ready(zone, sc)) {
6160 				sc->compaction_ready = true;
6161 				continue;
6162 			}
6163 
6164 			/*
6165 			 * Shrink each node in the zonelist once. If the
6166 			 * zonelist is ordered by zone (not the default) then a
6167 			 * node may be shrunk multiple times but in that case
6168 			 * the user prefers lower zones being preserved.
6169 			 */
6170 			if (zone->zone_pgdat == last_pgdat)
6171 				continue;
6172 
6173 			/*
6174 			 * This steals pages from memory cgroups over softlimit
6175 			 * and returns the number of reclaimed pages and
6176 			 * scanned pages. This works for global memory pressure
6177 			 * and balancing, not for a memcg's limit.
6178 			 */
6179 			nr_soft_scanned = 0;
6180 			nr_soft_reclaimed = memcg1_soft_limit_reclaim(zone->zone_pgdat,
6181 								      sc->order, sc->gfp_mask,
6182 								      &nr_soft_scanned);
6183 			sc->nr_reclaimed += nr_soft_reclaimed;
6184 			sc->nr_scanned += nr_soft_scanned;
6185 			/* need some check for avoid more shrink_zone() */
6186 		}
6187 
6188 		if (!first_pgdat)
6189 			first_pgdat = zone->zone_pgdat;
6190 
6191 		/* See comment about same check for global reclaim above */
6192 		if (zone->zone_pgdat == last_pgdat)
6193 			continue;
6194 		last_pgdat = zone->zone_pgdat;
6195 		shrink_node(zone->zone_pgdat, sc);
6196 	}
6197 
6198 	if (first_pgdat)
6199 		consider_reclaim_throttle(first_pgdat, sc);
6200 
6201 	/*
6202 	 * Restore to original mask to avoid the impact on the caller if we
6203 	 * promoted it to __GFP_HIGHMEM.
6204 	 */
6205 	sc->gfp_mask = orig_mask;
6206 }
6207 
snapshot_refaults(struct mem_cgroup * target_memcg,pg_data_t * pgdat)6208 static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
6209 {
6210 	struct lruvec *target_lruvec;
6211 	unsigned long refaults;
6212 
6213 	if (lru_gen_enabled())
6214 		return;
6215 
6216 	target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
6217 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
6218 	target_lruvec->refaults[WORKINGSET_ANON] = refaults;
6219 	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
6220 	target_lruvec->refaults[WORKINGSET_FILE] = refaults;
6221 }
6222 
6223 /*
6224  * This is the main entry point to direct page reclaim.
6225  *
6226  * If a full scan of the inactive list fails to free enough memory then we
6227  * are "out of memory" and something needs to be killed.
6228  *
6229  * If the caller is !__GFP_FS then the probability of a failure is reasonably
6230  * high - the zone may be full of dirty or under-writeback pages, which this
6231  * caller can't do much about.  We kick the writeback threads and take explicit
6232  * naps in the hope that some of these pages can be written.  But if the
6233  * allocating task holds filesystem locks which prevent writeout this might not
6234  * work, and the allocation attempt will fail.
6235  *
6236  * returns:	0, if no pages reclaimed
6237  * 		else, the number of pages reclaimed
6238  */
do_try_to_free_pages(struct zonelist * zonelist,struct scan_control * sc)6239 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
6240 					  struct scan_control *sc)
6241 {
6242 	int initial_priority = sc->priority;
6243 	pg_data_t *last_pgdat;
6244 	struct zoneref *z;
6245 	struct zone *zone;
6246 retry:
6247 	delayacct_freepages_start();
6248 
6249 	if (!cgroup_reclaim(sc))
6250 		__count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
6251 
6252 	do {
6253 		if (!sc->proactive)
6254 			vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
6255 					sc->priority);
6256 		sc->nr_scanned = 0;
6257 		shrink_zones(zonelist, sc);
6258 
6259 		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
6260 			break;
6261 
6262 		if (sc->compaction_ready)
6263 			break;
6264 
6265 		/*
6266 		 * If we're getting trouble reclaiming, start doing
6267 		 * writepage even in laptop mode.
6268 		 */
6269 		if (sc->priority < DEF_PRIORITY - 2)
6270 			sc->may_writepage = 1;
6271 	} while (--sc->priority >= 0);
6272 
6273 	last_pgdat = NULL;
6274 	for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
6275 					sc->nodemask) {
6276 		if (zone->zone_pgdat == last_pgdat)
6277 			continue;
6278 		last_pgdat = zone->zone_pgdat;
6279 
6280 		snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
6281 
6282 		if (cgroup_reclaim(sc)) {
6283 			struct lruvec *lruvec;
6284 
6285 			lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
6286 						   zone->zone_pgdat);
6287 			clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6288 		}
6289 	}
6290 
6291 	delayacct_freepages_end();
6292 
6293 	if (sc->nr_reclaimed)
6294 		return sc->nr_reclaimed;
6295 
6296 	/* Aborted reclaim to try compaction? don't OOM, then */
6297 	if (sc->compaction_ready)
6298 		return 1;
6299 
6300 	/*
6301 	 * In most cases, direct reclaimers can do partial walks
6302 	 * through the cgroup tree to meet the reclaim goal while
6303 	 * keeping latency low. Since the iterator state is shared
6304 	 * among all direct reclaim invocations (to retain fairness
6305 	 * among cgroups), though, high concurrency can result in
6306 	 * individual threads not seeing enough cgroups to make
6307 	 * meaningful forward progress. Avoid false OOMs in this case.
6308 	 */
6309 	if (!sc->memcg_full_walk) {
6310 		sc->priority = initial_priority;
6311 		sc->memcg_full_walk = 1;
6312 		goto retry;
6313 	}
6314 
6315 	/*
6316 	 * We make inactive:active ratio decisions based on the node's
6317 	 * composition of memory, but a restrictive reclaim_idx or a
6318 	 * memory.low cgroup setting can exempt large amounts of
6319 	 * memory from reclaim. Neither of which are very common, so
6320 	 * instead of doing costly eligibility calculations of the
6321 	 * entire cgroup subtree up front, we assume the estimates are
6322 	 * good, and retry with forcible deactivation if that fails.
6323 	 */
6324 	if (sc->skipped_deactivate) {
6325 		sc->priority = initial_priority;
6326 		sc->force_deactivate = 1;
6327 		sc->skipped_deactivate = 0;
6328 		goto retry;
6329 	}
6330 
6331 	/* Untapped cgroup reserves?  Don't OOM, retry. */
6332 	if (sc->memcg_low_skipped) {
6333 		sc->priority = initial_priority;
6334 		sc->force_deactivate = 0;
6335 		sc->memcg_low_reclaim = 1;
6336 		sc->memcg_low_skipped = 0;
6337 		goto retry;
6338 	}
6339 
6340 	return 0;
6341 }
6342 
allow_direct_reclaim(pg_data_t * pgdat)6343 static bool allow_direct_reclaim(pg_data_t *pgdat)
6344 {
6345 	struct zone *zone;
6346 	unsigned long pfmemalloc_reserve = 0;
6347 	unsigned long free_pages = 0;
6348 	int i;
6349 	bool wmark_ok;
6350 
6351 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6352 		return true;
6353 
6354 	for (i = 0; i <= ZONE_NORMAL; i++) {
6355 		zone = &pgdat->node_zones[i];
6356 		if (!managed_zone(zone))
6357 			continue;
6358 
6359 		if (!zone_reclaimable_pages(zone))
6360 			continue;
6361 
6362 		pfmemalloc_reserve += min_wmark_pages(zone);
6363 		free_pages += zone_page_state_snapshot(zone, NR_FREE_PAGES);
6364 	}
6365 
6366 	/* If there are no reserves (unexpected config) then do not throttle */
6367 	if (!pfmemalloc_reserve)
6368 		return true;
6369 
6370 	wmark_ok = free_pages > pfmemalloc_reserve / 2;
6371 
6372 	/* kswapd must be awake if processes are being throttled */
6373 	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
6374 		if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
6375 			WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
6376 
6377 		wake_up_interruptible(&pgdat->kswapd_wait);
6378 	}
6379 
6380 	return wmark_ok;
6381 }
6382 
6383 /*
6384  * Throttle direct reclaimers if backing storage is backed by the network
6385  * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6386  * depleted. kswapd will continue to make progress and wake the processes
6387  * when the low watermark is reached.
6388  *
6389  * Returns true if a fatal signal was delivered during throttling. If this
6390  * happens, the page allocator should not consider triggering the OOM killer.
6391  */
throttle_direct_reclaim(gfp_t gfp_mask,struct zonelist * zonelist,nodemask_t * nodemask)6392 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
6393 					nodemask_t *nodemask)
6394 {
6395 	struct zoneref *z;
6396 	struct zone *zone;
6397 	pg_data_t *pgdat = NULL;
6398 
6399 	/*
6400 	 * Kernel threads should not be throttled as they may be indirectly
6401 	 * responsible for cleaning pages necessary for reclaim to make forward
6402 	 * progress. kjournald for example may enter direct reclaim while
6403 	 * committing a transaction where throttling it could forcing other
6404 	 * processes to block on log_wait_commit().
6405 	 */
6406 	if (current->flags & PF_KTHREAD)
6407 		goto out;
6408 
6409 	/*
6410 	 * If a fatal signal is pending, this process should not throttle.
6411 	 * It should return quickly so it can exit and free its memory
6412 	 */
6413 	if (fatal_signal_pending(current))
6414 		goto out;
6415 
6416 	/*
6417 	 * Check if the pfmemalloc reserves are ok by finding the first node
6418 	 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6419 	 * GFP_KERNEL will be required for allocating network buffers when
6420 	 * swapping over the network so ZONE_HIGHMEM is unusable.
6421 	 *
6422 	 * Throttling is based on the first usable node and throttled processes
6423 	 * wait on a queue until kswapd makes progress and wakes them. There
6424 	 * is an affinity then between processes waking up and where reclaim
6425 	 * progress has been made assuming the process wakes on the same node.
6426 	 * More importantly, processes running on remote nodes will not compete
6427 	 * for remote pfmemalloc reserves and processes on different nodes
6428 	 * should make reasonable progress.
6429 	 */
6430 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6431 					gfp_zone(gfp_mask), nodemask) {
6432 		if (zone_idx(zone) > ZONE_NORMAL)
6433 			continue;
6434 
6435 		/* Throttle based on the first usable node */
6436 		pgdat = zone->zone_pgdat;
6437 		if (allow_direct_reclaim(pgdat))
6438 			goto out;
6439 		break;
6440 	}
6441 
6442 	/* If no zone was usable by the allocation flags then do not throttle */
6443 	if (!pgdat)
6444 		goto out;
6445 
6446 	/* Account for the throttling */
6447 	count_vm_event(PGSCAN_DIRECT_THROTTLE);
6448 
6449 	/*
6450 	 * If the caller cannot enter the filesystem, it's possible that it
6451 	 * is due to the caller holding an FS lock or performing a journal
6452 	 * transaction in the case of a filesystem like ext[3|4]. In this case,
6453 	 * it is not safe to block on pfmemalloc_wait as kswapd could be
6454 	 * blocked waiting on the same lock. Instead, throttle for up to a
6455 	 * second before continuing.
6456 	 */
6457 	if (!(gfp_mask & __GFP_FS))
6458 		wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
6459 			allow_direct_reclaim(pgdat), HZ);
6460 	else
6461 		/* Throttle until kswapd wakes the process */
6462 		wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
6463 			allow_direct_reclaim(pgdat));
6464 
6465 	if (fatal_signal_pending(current))
6466 		return true;
6467 
6468 out:
6469 	return false;
6470 }
6471 
try_to_free_pages(struct zonelist * zonelist,int order,gfp_t gfp_mask,nodemask_t * nodemask)6472 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
6473 				gfp_t gfp_mask, nodemask_t *nodemask)
6474 {
6475 	unsigned long nr_reclaimed;
6476 	struct scan_control sc = {
6477 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6478 		.gfp_mask = current_gfp_context(gfp_mask),
6479 		.reclaim_idx = gfp_zone(gfp_mask),
6480 		.order = order,
6481 		.nodemask = nodemask,
6482 		.priority = DEF_PRIORITY,
6483 		.may_writepage = !laptop_mode,
6484 		.may_unmap = 1,
6485 		.may_swap = 1,
6486 	};
6487 
6488 	/*
6489 	 * scan_control uses s8 fields for order, priority, and reclaim_idx.
6490 	 * Confirm they are large enough for max values.
6491 	 */
6492 	BUILD_BUG_ON(MAX_PAGE_ORDER >= S8_MAX);
6493 	BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
6494 	BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
6495 
6496 	/*
6497 	 * Do not enter reclaim if fatal signal was delivered while throttled.
6498 	 * 1 is returned so that the page allocator does not OOM kill at this
6499 	 * point.
6500 	 */
6501 	if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
6502 		return 1;
6503 
6504 	set_task_reclaim_state(current, &sc.reclaim_state);
6505 	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
6506 
6507 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6508 
6509 	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
6510 	set_task_reclaim_state(current, NULL);
6511 
6512 	return nr_reclaimed;
6513 }
6514 
6515 #ifdef CONFIG_MEMCG
6516 
6517 /* 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)6518 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
6519 						gfp_t gfp_mask, bool noswap,
6520 						pg_data_t *pgdat,
6521 						unsigned long *nr_scanned)
6522 {
6523 	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6524 	struct scan_control sc = {
6525 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6526 		.target_mem_cgroup = memcg,
6527 		.may_writepage = !laptop_mode,
6528 		.may_unmap = 1,
6529 		.reclaim_idx = MAX_NR_ZONES - 1,
6530 		.may_swap = !noswap,
6531 	};
6532 
6533 	WARN_ON_ONCE(!current->reclaim_state);
6534 
6535 	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
6536 			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
6537 
6538 	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
6539 						      sc.gfp_mask);
6540 
6541 	/*
6542 	 * NOTE: Although we can get the priority field, using it
6543 	 * here is not a good idea, since it limits the pages we can scan.
6544 	 * if we don't reclaim here, the shrink_node from balance_pgdat
6545 	 * will pick up pages from other mem cgroup's as well. We hack
6546 	 * the priority and make it zero.
6547 	 */
6548 	shrink_lruvec(lruvec, &sc);
6549 
6550 	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
6551 
6552 	*nr_scanned = sc.nr_scanned;
6553 
6554 	return sc.nr_reclaimed;
6555 }
6556 
try_to_free_mem_cgroup_pages(struct mem_cgroup * memcg,unsigned long nr_pages,gfp_t gfp_mask,unsigned int reclaim_options,int * swappiness)6557 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
6558 					   unsigned long nr_pages,
6559 					   gfp_t gfp_mask,
6560 					   unsigned int reclaim_options,
6561 					   int *swappiness)
6562 {
6563 	unsigned long nr_reclaimed;
6564 	unsigned int noreclaim_flag;
6565 	struct scan_control sc = {
6566 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
6567 		.proactive_swappiness = swappiness,
6568 		.gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
6569 				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
6570 		.reclaim_idx = MAX_NR_ZONES - 1,
6571 		.target_mem_cgroup = memcg,
6572 		.priority = DEF_PRIORITY,
6573 		.may_writepage = !laptop_mode,
6574 		.may_unmap = 1,
6575 		.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
6576 		.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
6577 	};
6578 	/*
6579 	 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
6580 	 * equal pressure on all the nodes. This is based on the assumption that
6581 	 * the reclaim does not bail out early.
6582 	 */
6583 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
6584 
6585 	set_task_reclaim_state(current, &sc.reclaim_state);
6586 	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
6587 	noreclaim_flag = memalloc_noreclaim_save();
6588 
6589 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6590 
6591 	memalloc_noreclaim_restore(noreclaim_flag);
6592 	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
6593 	set_task_reclaim_state(current, NULL);
6594 
6595 	return nr_reclaimed;
6596 }
6597 #endif
6598 
kswapd_age_node(struct pglist_data * pgdat,struct scan_control * sc)6599 static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
6600 {
6601 	struct mem_cgroup *memcg;
6602 	struct lruvec *lruvec;
6603 
6604 	if (lru_gen_enabled()) {
6605 		lru_gen_age_node(pgdat, sc);
6606 		return;
6607 	}
6608 
6609 	if (!can_age_anon_pages(pgdat, sc))
6610 		return;
6611 
6612 	lruvec = mem_cgroup_lruvec(NULL, pgdat);
6613 	if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6614 		return;
6615 
6616 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
6617 	do {
6618 		lruvec = mem_cgroup_lruvec(memcg, pgdat);
6619 		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6620 				   sc, LRU_ACTIVE_ANON);
6621 		memcg = mem_cgroup_iter(NULL, memcg, NULL);
6622 	} while (memcg);
6623 }
6624 
pgdat_watermark_boosted(pg_data_t * pgdat,int highest_zoneidx)6625 static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
6626 {
6627 	int i;
6628 	struct zone *zone;
6629 
6630 	/*
6631 	 * Check for watermark boosts top-down as the higher zones
6632 	 * are more likely to be boosted. Both watermarks and boosts
6633 	 * should not be checked at the same time as reclaim would
6634 	 * start prematurely when there is no boosting and a lower
6635 	 * zone is balanced.
6636 	 */
6637 	for (i = highest_zoneidx; i >= 0; i--) {
6638 		zone = pgdat->node_zones + i;
6639 		if (!managed_zone(zone))
6640 			continue;
6641 
6642 		if (zone->watermark_boost)
6643 			return true;
6644 	}
6645 
6646 	return false;
6647 }
6648 
6649 /*
6650  * Returns true if there is an eligible zone balanced for the request order
6651  * and highest_zoneidx
6652  */
pgdat_balanced(pg_data_t * pgdat,int order,int highest_zoneidx)6653 static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
6654 {
6655 	int i;
6656 	unsigned long mark = -1;
6657 	struct zone *zone;
6658 
6659 	/*
6660 	 * Check watermarks bottom-up as lower zones are more likely to
6661 	 * meet watermarks.
6662 	 */
6663 	for (i = 0; i <= highest_zoneidx; i++) {
6664 		zone = pgdat->node_zones + i;
6665 
6666 		if (!managed_zone(zone))
6667 			continue;
6668 
6669 		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
6670 			mark = promo_wmark_pages(zone);
6671 		else
6672 			mark = high_wmark_pages(zone);
6673 		if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
6674 			return true;
6675 	}
6676 
6677 	/*
6678 	 * If a node has no managed zone within highest_zoneidx, it does not
6679 	 * need balancing by definition. This can happen if a zone-restricted
6680 	 * allocation tries to wake a remote kswapd.
6681 	 */
6682 	if (mark == -1)
6683 		return true;
6684 
6685 	return false;
6686 }
6687 
6688 /* Clear pgdat state for congested, dirty or under writeback. */
clear_pgdat_congested(pg_data_t * pgdat)6689 static void clear_pgdat_congested(pg_data_t *pgdat)
6690 {
6691 	struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
6692 
6693 	clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags);
6694 	clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6695 	clear_bit(PGDAT_DIRTY, &pgdat->flags);
6696 	clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
6697 }
6698 
6699 /*
6700  * Prepare kswapd for sleeping. This verifies that there are no processes
6701  * waiting in throttle_direct_reclaim() and that watermarks have been met.
6702  *
6703  * Returns true if kswapd is ready to sleep
6704  */
prepare_kswapd_sleep(pg_data_t * pgdat,int order,int highest_zoneidx)6705 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
6706 				int highest_zoneidx)
6707 {
6708 	/*
6709 	 * The throttled processes are normally woken up in balance_pgdat() as
6710 	 * soon as allow_direct_reclaim() is true. But there is a potential
6711 	 * race between when kswapd checks the watermarks and a process gets
6712 	 * throttled. There is also a potential race if processes get
6713 	 * throttled, kswapd wakes, a large process exits thereby balancing the
6714 	 * zones, which causes kswapd to exit balance_pgdat() before reaching
6715 	 * the wake up checks. If kswapd is going to sleep, no process should
6716 	 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
6717 	 * the wake up is premature, processes will wake kswapd and get
6718 	 * throttled again. The difference from wake ups in balance_pgdat() is
6719 	 * that here we are under prepare_to_wait().
6720 	 */
6721 	if (waitqueue_active(&pgdat->pfmemalloc_wait))
6722 		wake_up_all(&pgdat->pfmemalloc_wait);
6723 
6724 	/* Hopeless node, leave it to direct reclaim */
6725 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6726 		return true;
6727 
6728 	if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
6729 		clear_pgdat_congested(pgdat);
6730 		return true;
6731 	}
6732 
6733 	return false;
6734 }
6735 
6736 /*
6737  * kswapd shrinks a node of pages that are at or below the highest usable
6738  * zone that is currently unbalanced.
6739  *
6740  * Returns true if kswapd scanned at least the requested number of pages to
6741  * reclaim or if the lack of progress was due to pages under writeback.
6742  * This is used to determine if the scanning priority needs to be raised.
6743  */
kswapd_shrink_node(pg_data_t * pgdat,struct scan_control * sc)6744 static bool kswapd_shrink_node(pg_data_t *pgdat,
6745 			       struct scan_control *sc)
6746 {
6747 	struct zone *zone;
6748 	int z;
6749 	unsigned long nr_reclaimed = sc->nr_reclaimed;
6750 
6751 	/* Reclaim a number of pages proportional to the number of zones */
6752 	sc->nr_to_reclaim = 0;
6753 	for (z = 0; z <= sc->reclaim_idx; z++) {
6754 		zone = pgdat->node_zones + z;
6755 		if (!managed_zone(zone))
6756 			continue;
6757 
6758 		sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
6759 	}
6760 
6761 	/*
6762 	 * Historically care was taken to put equal pressure on all zones but
6763 	 * now pressure is applied based on node LRU order.
6764 	 */
6765 	shrink_node(pgdat, sc);
6766 
6767 	/*
6768 	 * Fragmentation may mean that the system cannot be rebalanced for
6769 	 * high-order allocations. If twice the allocation size has been
6770 	 * reclaimed then recheck watermarks only at order-0 to prevent
6771 	 * excessive reclaim. Assume that a process requested a high-order
6772 	 * can direct reclaim/compact.
6773 	 */
6774 	if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
6775 		sc->order = 0;
6776 
6777 	/* account for progress from mm_account_reclaimed_pages() */
6778 	return max(sc->nr_scanned, sc->nr_reclaimed - nr_reclaimed) >= sc->nr_to_reclaim;
6779 }
6780 
6781 /* Page allocator PCP high watermark is lowered if reclaim is active. */
6782 static inline void
update_reclaim_active(pg_data_t * pgdat,int highest_zoneidx,bool active)6783 update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
6784 {
6785 	int i;
6786 	struct zone *zone;
6787 
6788 	for (i = 0; i <= highest_zoneidx; i++) {
6789 		zone = pgdat->node_zones + i;
6790 
6791 		if (!managed_zone(zone))
6792 			continue;
6793 
6794 		if (active)
6795 			set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6796 		else
6797 			clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6798 	}
6799 }
6800 
6801 static inline void
set_reclaim_active(pg_data_t * pgdat,int highest_zoneidx)6802 set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6803 {
6804 	update_reclaim_active(pgdat, highest_zoneidx, true);
6805 }
6806 
6807 static inline void
clear_reclaim_active(pg_data_t * pgdat,int highest_zoneidx)6808 clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6809 {
6810 	update_reclaim_active(pgdat, highest_zoneidx, false);
6811 }
6812 
6813 /*
6814  * For kswapd, balance_pgdat() will reclaim pages across a node from zones
6815  * that are eligible for use by the caller until at least one zone is
6816  * balanced.
6817  *
6818  * Returns the order kswapd finished reclaiming at.
6819  *
6820  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
6821  * zones which have free_pages > high_wmark_pages(zone), but once a zone is
6822  * found to have free_pages <= high_wmark_pages(zone), any page in that zone
6823  * or lower is eligible for reclaim until at least one usable zone is
6824  * balanced.
6825  */
balance_pgdat(pg_data_t * pgdat,int order,int highest_zoneidx)6826 static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
6827 {
6828 	int i;
6829 	unsigned long nr_soft_reclaimed;
6830 	unsigned long nr_soft_scanned;
6831 	unsigned long pflags;
6832 	unsigned long nr_boost_reclaim;
6833 	unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
6834 	bool boosted;
6835 	struct zone *zone;
6836 	struct scan_control sc = {
6837 		.gfp_mask = GFP_KERNEL,
6838 		.order = order,
6839 		.may_unmap = 1,
6840 	};
6841 
6842 	set_task_reclaim_state(current, &sc.reclaim_state);
6843 	psi_memstall_enter(&pflags);
6844 	__fs_reclaim_acquire(_THIS_IP_);
6845 
6846 	count_vm_event(PAGEOUTRUN);
6847 
6848 	/*
6849 	 * Account for the reclaim boost. Note that the zone boost is left in
6850 	 * place so that parallel allocations that are near the watermark will
6851 	 * stall or direct reclaim until kswapd is finished.
6852 	 */
6853 	nr_boost_reclaim = 0;
6854 	for (i = 0; i <= highest_zoneidx; i++) {
6855 		zone = pgdat->node_zones + i;
6856 		if (!managed_zone(zone))
6857 			continue;
6858 
6859 		nr_boost_reclaim += zone->watermark_boost;
6860 		zone_boosts[i] = zone->watermark_boost;
6861 	}
6862 	boosted = nr_boost_reclaim;
6863 
6864 restart:
6865 	set_reclaim_active(pgdat, highest_zoneidx);
6866 	sc.priority = DEF_PRIORITY;
6867 	do {
6868 		unsigned long nr_reclaimed = sc.nr_reclaimed;
6869 		bool raise_priority = true;
6870 		bool balanced;
6871 		bool ret;
6872 		bool was_frozen;
6873 
6874 		sc.reclaim_idx = highest_zoneidx;
6875 
6876 		/*
6877 		 * If the number of buffer_heads exceeds the maximum allowed
6878 		 * then consider reclaiming from all zones. This has a dual
6879 		 * purpose -- on 64-bit systems it is expected that
6880 		 * buffer_heads are stripped during active rotation. On 32-bit
6881 		 * systems, highmem pages can pin lowmem memory and shrinking
6882 		 * buffers can relieve lowmem pressure. Reclaim may still not
6883 		 * go ahead if all eligible zones for the original allocation
6884 		 * request are balanced to avoid excessive reclaim from kswapd.
6885 		 */
6886 		if (buffer_heads_over_limit) {
6887 			for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
6888 				zone = pgdat->node_zones + i;
6889 				if (!managed_zone(zone))
6890 					continue;
6891 
6892 				sc.reclaim_idx = i;
6893 				break;
6894 			}
6895 		}
6896 
6897 		/*
6898 		 * If the pgdat is imbalanced then ignore boosting and preserve
6899 		 * the watermarks for a later time and restart. Note that the
6900 		 * zone watermarks will be still reset at the end of balancing
6901 		 * on the grounds that the normal reclaim should be enough to
6902 		 * re-evaluate if boosting is required when kswapd next wakes.
6903 		 */
6904 		balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
6905 		if (!balanced && nr_boost_reclaim) {
6906 			nr_boost_reclaim = 0;
6907 			goto restart;
6908 		}
6909 
6910 		/*
6911 		 * If boosting is not active then only reclaim if there are no
6912 		 * eligible zones. Note that sc.reclaim_idx is not used as
6913 		 * buffer_heads_over_limit may have adjusted it.
6914 		 */
6915 		if (!nr_boost_reclaim && balanced)
6916 			goto out;
6917 
6918 		/* Limit the priority of boosting to avoid reclaim writeback */
6919 		if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
6920 			raise_priority = false;
6921 
6922 		/*
6923 		 * Do not writeback or swap pages for boosted reclaim. The
6924 		 * intent is to relieve pressure not issue sub-optimal IO
6925 		 * from reclaim context. If no pages are reclaimed, the
6926 		 * reclaim will be aborted.
6927 		 */
6928 		sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
6929 		sc.may_swap = !nr_boost_reclaim;
6930 
6931 		/*
6932 		 * Do some background aging, to give pages a chance to be
6933 		 * referenced before reclaiming. All pages are rotated
6934 		 * regardless of classzone as this is about consistent aging.
6935 		 */
6936 		kswapd_age_node(pgdat, &sc);
6937 
6938 		/*
6939 		 * If we're getting trouble reclaiming, start doing writepage
6940 		 * even in laptop mode.
6941 		 */
6942 		if (sc.priority < DEF_PRIORITY - 2)
6943 			sc.may_writepage = 1;
6944 
6945 		/* Call soft limit reclaim before calling shrink_node. */
6946 		sc.nr_scanned = 0;
6947 		nr_soft_scanned = 0;
6948 		nr_soft_reclaimed = memcg1_soft_limit_reclaim(pgdat, sc.order,
6949 							      sc.gfp_mask, &nr_soft_scanned);
6950 		sc.nr_reclaimed += nr_soft_reclaimed;
6951 
6952 		/*
6953 		 * There should be no need to raise the scanning priority if
6954 		 * enough pages are already being scanned that that high
6955 		 * watermark would be met at 100% efficiency.
6956 		 */
6957 		if (kswapd_shrink_node(pgdat, &sc))
6958 			raise_priority = false;
6959 
6960 		/*
6961 		 * If the low watermark is met there is no need for processes
6962 		 * to be throttled on pfmemalloc_wait as they should not be
6963 		 * able to safely make forward progress. Wake them
6964 		 */
6965 		if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
6966 				allow_direct_reclaim(pgdat))
6967 			wake_up_all(&pgdat->pfmemalloc_wait);
6968 
6969 		/* Check if kswapd should be suspending */
6970 		__fs_reclaim_release(_THIS_IP_);
6971 		ret = kthread_freezable_should_stop(&was_frozen);
6972 		__fs_reclaim_acquire(_THIS_IP_);
6973 		if (was_frozen || ret)
6974 			break;
6975 
6976 		/*
6977 		 * Raise priority if scanning rate is too low or there was no
6978 		 * progress in reclaiming pages
6979 		 */
6980 		nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
6981 		nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
6982 
6983 		/*
6984 		 * If reclaim made no progress for a boost, stop reclaim as
6985 		 * IO cannot be queued and it could be an infinite loop in
6986 		 * extreme circumstances.
6987 		 */
6988 		if (nr_boost_reclaim && !nr_reclaimed)
6989 			break;
6990 
6991 		if (raise_priority || !nr_reclaimed)
6992 			sc.priority--;
6993 	} while (sc.priority >= 1);
6994 
6995 	/*
6996 	 * Restart only if it went through the priority loop all the way,
6997 	 * but cache_trim_mode didn't work.
6998 	 */
6999 	if (!sc.nr_reclaimed && sc.priority < 1 &&
7000 	    !sc.no_cache_trim_mode && sc.cache_trim_mode_failed) {
7001 		sc.no_cache_trim_mode = 1;
7002 		goto restart;
7003 	}
7004 
7005 	if (!sc.nr_reclaimed)
7006 		pgdat->kswapd_failures++;
7007 
7008 out:
7009 	clear_reclaim_active(pgdat, highest_zoneidx);
7010 
7011 	/* If reclaim was boosted, account for the reclaim done in this pass */
7012 	if (boosted) {
7013 		unsigned long flags;
7014 
7015 		for (i = 0; i <= highest_zoneidx; i++) {
7016 			if (!zone_boosts[i])
7017 				continue;
7018 
7019 			/* Increments are under the zone lock */
7020 			zone = pgdat->node_zones + i;
7021 			spin_lock_irqsave(&zone->lock, flags);
7022 			zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
7023 			spin_unlock_irqrestore(&zone->lock, flags);
7024 		}
7025 
7026 		/*
7027 		 * As there is now likely space, wakeup kcompact to defragment
7028 		 * pageblocks.
7029 		 */
7030 		wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
7031 	}
7032 
7033 	snapshot_refaults(NULL, pgdat);
7034 	__fs_reclaim_release(_THIS_IP_);
7035 	psi_memstall_leave(&pflags);
7036 	set_task_reclaim_state(current, NULL);
7037 
7038 	/*
7039 	 * Return the order kswapd stopped reclaiming at as
7040 	 * prepare_kswapd_sleep() takes it into account. If another caller
7041 	 * entered the allocator slow path while kswapd was awake, order will
7042 	 * remain at the higher level.
7043 	 */
7044 	return sc.order;
7045 }
7046 
7047 /*
7048  * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
7049  * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
7050  * not a valid index then either kswapd runs for first time or kswapd couldn't
7051  * sleep after previous reclaim attempt (node is still unbalanced). In that
7052  * case return the zone index of the previous kswapd reclaim cycle.
7053  */
kswapd_highest_zoneidx(pg_data_t * pgdat,enum zone_type prev_highest_zoneidx)7054 static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
7055 					   enum zone_type prev_highest_zoneidx)
7056 {
7057 	enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7058 
7059 	return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
7060 }
7061 
kswapd_try_to_sleep(pg_data_t * pgdat,int alloc_order,int reclaim_order,unsigned int highest_zoneidx)7062 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
7063 				unsigned int highest_zoneidx)
7064 {
7065 	long remaining = 0;
7066 	DEFINE_WAIT(wait);
7067 
7068 	if (freezing(current) || kthread_should_stop())
7069 		return;
7070 
7071 	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7072 
7073 	/*
7074 	 * Try to sleep for a short interval. Note that kcompactd will only be
7075 	 * woken if it is possible to sleep for a short interval. This is
7076 	 * deliberate on the assumption that if reclaim cannot keep an
7077 	 * eligible zone balanced that it's also unlikely that compaction will
7078 	 * succeed.
7079 	 */
7080 	if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7081 		/*
7082 		 * Compaction records what page blocks it recently failed to
7083 		 * isolate pages from and skips them in the future scanning.
7084 		 * When kswapd is going to sleep, it is reasonable to assume
7085 		 * that pages and compaction may succeed so reset the cache.
7086 		 */
7087 		reset_isolation_suitable(pgdat);
7088 
7089 		/*
7090 		 * We have freed the memory, now we should compact it to make
7091 		 * allocation of the requested order possible.
7092 		 */
7093 		wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
7094 
7095 		remaining = schedule_timeout(HZ/10);
7096 
7097 		/*
7098 		 * If woken prematurely then reset kswapd_highest_zoneidx and
7099 		 * order. The values will either be from a wakeup request or
7100 		 * the previous request that slept prematurely.
7101 		 */
7102 		if (remaining) {
7103 			WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
7104 					kswapd_highest_zoneidx(pgdat,
7105 							highest_zoneidx));
7106 
7107 			if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
7108 				WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
7109 		}
7110 
7111 		finish_wait(&pgdat->kswapd_wait, &wait);
7112 		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7113 	}
7114 
7115 	/*
7116 	 * After a short sleep, check if it was a premature sleep. If not, then
7117 	 * go fully to sleep until explicitly woken up.
7118 	 */
7119 	if (!remaining &&
7120 	    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7121 		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
7122 
7123 		/*
7124 		 * vmstat counters are not perfectly accurate and the estimated
7125 		 * value for counters such as NR_FREE_PAGES can deviate from the
7126 		 * true value by nr_online_cpus * threshold. To avoid the zone
7127 		 * watermarks being breached while under pressure, we reduce the
7128 		 * per-cpu vmstat threshold while kswapd is awake and restore
7129 		 * them before going back to sleep.
7130 		 */
7131 		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
7132 
7133 		if (!kthread_should_stop())
7134 			schedule();
7135 
7136 		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
7137 	} else {
7138 		if (remaining)
7139 			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
7140 		else
7141 			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
7142 	}
7143 	finish_wait(&pgdat->kswapd_wait, &wait);
7144 }
7145 
7146 /*
7147  * The background pageout daemon, started as a kernel thread
7148  * from the init process.
7149  *
7150  * This basically trickles out pages so that we have _some_
7151  * free memory available even if there is no other activity
7152  * that frees anything up. This is needed for things like routing
7153  * etc, where we otherwise might have all activity going on in
7154  * asynchronous contexts that cannot page things out.
7155  *
7156  * If there are applications that are active memory-allocators
7157  * (most normal use), this basically shouldn't matter.
7158  */
kswapd(void * p)7159 static int kswapd(void *p)
7160 {
7161 	unsigned int alloc_order, reclaim_order;
7162 	unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
7163 	pg_data_t *pgdat = (pg_data_t *)p;
7164 	struct task_struct *tsk = current;
7165 	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
7166 
7167 	if (!cpumask_empty(cpumask))
7168 		set_cpus_allowed_ptr(tsk, cpumask);
7169 
7170 	/*
7171 	 * Tell the memory management that we're a "memory allocator",
7172 	 * and that if we need more memory we should get access to it
7173 	 * regardless (see "__alloc_pages()"). "kswapd" should
7174 	 * never get caught in the normal page freeing logic.
7175 	 *
7176 	 * (Kswapd normally doesn't need memory anyway, but sometimes
7177 	 * you need a small amount of memory in order to be able to
7178 	 * page out something else, and this flag essentially protects
7179 	 * us from recursively trying to free more memory as we're
7180 	 * trying to free the first piece of memory in the first place).
7181 	 */
7182 	tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
7183 	set_freezable();
7184 
7185 	WRITE_ONCE(pgdat->kswapd_order, 0);
7186 	WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7187 	atomic_set(&pgdat->nr_writeback_throttled, 0);
7188 	for ( ; ; ) {
7189 		bool was_frozen;
7190 
7191 		alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
7192 		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7193 							highest_zoneidx);
7194 
7195 kswapd_try_sleep:
7196 		kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
7197 					highest_zoneidx);
7198 
7199 		/* Read the new order and highest_zoneidx */
7200 		alloc_order = READ_ONCE(pgdat->kswapd_order);
7201 		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7202 							highest_zoneidx);
7203 		WRITE_ONCE(pgdat->kswapd_order, 0);
7204 		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7205 
7206 		if (kthread_freezable_should_stop(&was_frozen))
7207 			break;
7208 
7209 		/*
7210 		 * We can speed up thawing tasks if we don't call balance_pgdat
7211 		 * after returning from the refrigerator
7212 		 */
7213 		if (was_frozen)
7214 			continue;
7215 
7216 		/*
7217 		 * Reclaim begins at the requested order but if a high-order
7218 		 * reclaim fails then kswapd falls back to reclaiming for
7219 		 * order-0. If that happens, kswapd will consider sleeping
7220 		 * for the order it finished reclaiming at (reclaim_order)
7221 		 * but kcompactd is woken to compact for the original
7222 		 * request (alloc_order).
7223 		 */
7224 		trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
7225 						alloc_order);
7226 		reclaim_order = balance_pgdat(pgdat, alloc_order,
7227 						highest_zoneidx);
7228 		if (reclaim_order < alloc_order)
7229 			goto kswapd_try_sleep;
7230 	}
7231 
7232 	tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
7233 
7234 	return 0;
7235 }
7236 
7237 /*
7238  * A zone is low on free memory or too fragmented for high-order memory.  If
7239  * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7240  * pgdat.  It will wake up kcompactd after reclaiming memory.  If kswapd reclaim
7241  * has failed or is not needed, still wake up kcompactd if only compaction is
7242  * needed.
7243  */
wakeup_kswapd(struct zone * zone,gfp_t gfp_flags,int order,enum zone_type highest_zoneidx)7244 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
7245 		   enum zone_type highest_zoneidx)
7246 {
7247 	pg_data_t *pgdat;
7248 	enum zone_type curr_idx;
7249 
7250 	if (!managed_zone(zone))
7251 		return;
7252 
7253 	if (!cpuset_zone_allowed(zone, gfp_flags))
7254 		return;
7255 
7256 	pgdat = zone->zone_pgdat;
7257 	curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7258 
7259 	if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
7260 		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
7261 
7262 	if (READ_ONCE(pgdat->kswapd_order) < order)
7263 		WRITE_ONCE(pgdat->kswapd_order, order);
7264 
7265 	if (!waitqueue_active(&pgdat->kswapd_wait))
7266 		return;
7267 
7268 	/* Hopeless node, leave it to direct reclaim if possible */
7269 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
7270 	    (pgdat_balanced(pgdat, order, highest_zoneidx) &&
7271 	     !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
7272 		/*
7273 		 * There may be plenty of free memory available, but it's too
7274 		 * fragmented for high-order allocations.  Wake up kcompactd
7275 		 * and rely on compaction_suitable() to determine if it's
7276 		 * needed.  If it fails, it will defer subsequent attempts to
7277 		 * ratelimit its work.
7278 		 */
7279 		if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
7280 			wakeup_kcompactd(pgdat, order, highest_zoneidx);
7281 		return;
7282 	}
7283 
7284 	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
7285 				      gfp_flags);
7286 	wake_up_interruptible(&pgdat->kswapd_wait);
7287 }
7288 
7289 #ifdef CONFIG_HIBERNATION
7290 /*
7291  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7292  * freed pages.
7293  *
7294  * Rather than trying to age LRUs the aim is to preserve the overall
7295  * LRU order by reclaiming preferentially
7296  * inactive > active > active referenced > active mapped
7297  */
shrink_all_memory(unsigned long nr_to_reclaim)7298 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
7299 {
7300 	struct scan_control sc = {
7301 		.nr_to_reclaim = nr_to_reclaim,
7302 		.gfp_mask = GFP_HIGHUSER_MOVABLE,
7303 		.reclaim_idx = MAX_NR_ZONES - 1,
7304 		.priority = DEF_PRIORITY,
7305 		.may_writepage = 1,
7306 		.may_unmap = 1,
7307 		.may_swap = 1,
7308 		.hibernation_mode = 1,
7309 	};
7310 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
7311 	unsigned long nr_reclaimed;
7312 	unsigned int noreclaim_flag;
7313 
7314 	fs_reclaim_acquire(sc.gfp_mask);
7315 	noreclaim_flag = memalloc_noreclaim_save();
7316 	set_task_reclaim_state(current, &sc.reclaim_state);
7317 
7318 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
7319 
7320 	set_task_reclaim_state(current, NULL);
7321 	memalloc_noreclaim_restore(noreclaim_flag);
7322 	fs_reclaim_release(sc.gfp_mask);
7323 
7324 	return nr_reclaimed;
7325 }
7326 #endif /* CONFIG_HIBERNATION */
7327 
7328 /*
7329  * This kswapd start function will be called by init and node-hot-add.
7330  */
kswapd_run(int nid)7331 void __meminit kswapd_run(int nid)
7332 {
7333 	pg_data_t *pgdat = NODE_DATA(nid);
7334 
7335 	pgdat_kswapd_lock(pgdat);
7336 	if (!pgdat->kswapd) {
7337 		pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
7338 		if (IS_ERR(pgdat->kswapd)) {
7339 			/* failure at boot is fatal */
7340 			pr_err("Failed to start kswapd on node %d,ret=%ld\n",
7341 				   nid, PTR_ERR(pgdat->kswapd));
7342 			BUG_ON(system_state < SYSTEM_RUNNING);
7343 			pgdat->kswapd = NULL;
7344 		}
7345 	}
7346 	pgdat_kswapd_unlock(pgdat);
7347 }
7348 
7349 /*
7350  * Called by memory hotplug when all memory in a node is offlined.  Caller must
7351  * be holding mem_hotplug_begin/done().
7352  */
kswapd_stop(int nid)7353 void __meminit kswapd_stop(int nid)
7354 {
7355 	pg_data_t *pgdat = NODE_DATA(nid);
7356 	struct task_struct *kswapd;
7357 
7358 	pgdat_kswapd_lock(pgdat);
7359 	kswapd = pgdat->kswapd;
7360 	if (kswapd) {
7361 		kthread_stop(kswapd);
7362 		pgdat->kswapd = NULL;
7363 	}
7364 	pgdat_kswapd_unlock(pgdat);
7365 }
7366 
kswapd_init(void)7367 static int __init kswapd_init(void)
7368 {
7369 	int nid;
7370 
7371 	swap_setup();
7372 	for_each_node_state(nid, N_MEMORY)
7373  		kswapd_run(nid);
7374 	return 0;
7375 }
7376 
7377 module_init(kswapd_init)
7378 
7379 #ifdef CONFIG_NUMA
7380 /*
7381  * Node reclaim mode
7382  *
7383  * If non-zero call node_reclaim when the number of free pages falls below
7384  * the watermarks.
7385  */
7386 int node_reclaim_mode __read_mostly;
7387 
7388 /*
7389  * Priority for NODE_RECLAIM. This determines the fraction of pages
7390  * of a node considered for each zone_reclaim. 4 scans 1/16th of
7391  * a zone.
7392  */
7393 #define NODE_RECLAIM_PRIORITY 4
7394 
7395 /*
7396  * Percentage of pages in a zone that must be unmapped for node_reclaim to
7397  * occur.
7398  */
7399 int sysctl_min_unmapped_ratio = 1;
7400 
7401 /*
7402  * If the number of slab pages in a zone grows beyond this percentage then
7403  * slab reclaim needs to occur.
7404  */
7405 int sysctl_min_slab_ratio = 5;
7406 
node_unmapped_file_pages(struct pglist_data * pgdat)7407 static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
7408 {
7409 	unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
7410 	unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
7411 		node_page_state(pgdat, NR_ACTIVE_FILE);
7412 
7413 	/*
7414 	 * It's possible for there to be more file mapped pages than
7415 	 * accounted for by the pages on the file LRU lists because
7416 	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7417 	 */
7418 	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
7419 }
7420 
7421 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
node_pagecache_reclaimable(struct pglist_data * pgdat)7422 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
7423 {
7424 	unsigned long nr_pagecache_reclaimable;
7425 	unsigned long delta = 0;
7426 
7427 	/*
7428 	 * If RECLAIM_UNMAP is set, then all file pages are considered
7429 	 * potentially reclaimable. Otherwise, we have to worry about
7430 	 * pages like swapcache and node_unmapped_file_pages() provides
7431 	 * a better estimate
7432 	 */
7433 	if (node_reclaim_mode & RECLAIM_UNMAP)
7434 		nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
7435 	else
7436 		nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
7437 
7438 	/* If we can't clean pages, remove dirty pages from consideration */
7439 	if (!(node_reclaim_mode & RECLAIM_WRITE))
7440 		delta += node_page_state(pgdat, NR_FILE_DIRTY);
7441 
7442 	/* Watch for any possible underflows due to delta */
7443 	if (unlikely(delta > nr_pagecache_reclaimable))
7444 		delta = nr_pagecache_reclaimable;
7445 
7446 	return nr_pagecache_reclaimable - delta;
7447 }
7448 
7449 /*
7450  * Try to free up some pages from this node through reclaim.
7451  */
__node_reclaim(struct pglist_data * pgdat,gfp_t gfp_mask,unsigned int order)7452 static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7453 {
7454 	/* Minimum pages needed in order to stay on node */
7455 	const unsigned long nr_pages = 1 << order;
7456 	struct task_struct *p = current;
7457 	unsigned int noreclaim_flag;
7458 	struct scan_control sc = {
7459 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
7460 		.gfp_mask = current_gfp_context(gfp_mask),
7461 		.order = order,
7462 		.priority = NODE_RECLAIM_PRIORITY,
7463 		.may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
7464 		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
7465 		.may_swap = 1,
7466 		.reclaim_idx = gfp_zone(gfp_mask),
7467 	};
7468 	unsigned long pflags;
7469 
7470 	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
7471 					   sc.gfp_mask);
7472 
7473 	cond_resched();
7474 	psi_memstall_enter(&pflags);
7475 	delayacct_freepages_start();
7476 	fs_reclaim_acquire(sc.gfp_mask);
7477 	/*
7478 	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
7479 	 */
7480 	noreclaim_flag = memalloc_noreclaim_save();
7481 	set_task_reclaim_state(p, &sc.reclaim_state);
7482 
7483 	if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
7484 	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
7485 		/*
7486 		 * Free memory by calling shrink node with increasing
7487 		 * priorities until we have enough memory freed.
7488 		 */
7489 		do {
7490 			shrink_node(pgdat, &sc);
7491 		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
7492 	}
7493 
7494 	set_task_reclaim_state(p, NULL);
7495 	memalloc_noreclaim_restore(noreclaim_flag);
7496 	fs_reclaim_release(sc.gfp_mask);
7497 	psi_memstall_leave(&pflags);
7498 	delayacct_freepages_end();
7499 
7500 	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
7501 
7502 	return sc.nr_reclaimed >= nr_pages;
7503 }
7504 
node_reclaim(struct pglist_data * pgdat,gfp_t gfp_mask,unsigned int order)7505 int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7506 {
7507 	int ret;
7508 
7509 	/*
7510 	 * Node reclaim reclaims unmapped file backed pages and
7511 	 * slab pages if we are over the defined limits.
7512 	 *
7513 	 * A small portion of unmapped file backed pages is needed for
7514 	 * file I/O otherwise pages read by file I/O will be immediately
7515 	 * thrown out if the node is overallocated. So we do not reclaim
7516 	 * if less than a specified percentage of the node is used by
7517 	 * unmapped file backed pages.
7518 	 */
7519 	if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
7520 	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
7521 	    pgdat->min_slab_pages)
7522 		return NODE_RECLAIM_FULL;
7523 
7524 	/*
7525 	 * Do not scan if the allocation should not be delayed.
7526 	 */
7527 	if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
7528 		return NODE_RECLAIM_NOSCAN;
7529 
7530 	/*
7531 	 * Only run node reclaim on the local node or on nodes that do not
7532 	 * have associated processors. This will favor the local processor
7533 	 * over remote processors and spread off node memory allocations
7534 	 * as wide as possible.
7535 	 */
7536 	if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
7537 		return NODE_RECLAIM_NOSCAN;
7538 
7539 	if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
7540 		return NODE_RECLAIM_NOSCAN;
7541 
7542 	ret = __node_reclaim(pgdat, gfp_mask, order);
7543 	clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
7544 
7545 	if (ret)
7546 		count_vm_event(PGSCAN_ZONE_RECLAIM_SUCCESS);
7547 	else
7548 		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
7549 
7550 	return ret;
7551 }
7552 #endif
7553 
7554 /**
7555  * check_move_unevictable_folios - Move evictable folios to appropriate zone
7556  * lru list
7557  * @fbatch: Batch of lru folios to check.
7558  *
7559  * Checks folios for evictability, if an evictable folio is in the unevictable
7560  * lru list, moves it to the appropriate evictable lru list. This function
7561  * should be only used for lru folios.
7562  */
check_move_unevictable_folios(struct folio_batch * fbatch)7563 void check_move_unevictable_folios(struct folio_batch *fbatch)
7564 {
7565 	struct lruvec *lruvec = NULL;
7566 	int pgscanned = 0;
7567 	int pgrescued = 0;
7568 	int i;
7569 
7570 	for (i = 0; i < fbatch->nr; i++) {
7571 		struct folio *folio = fbatch->folios[i];
7572 		int nr_pages = folio_nr_pages(folio);
7573 
7574 		pgscanned += nr_pages;
7575 
7576 		/* block memcg migration while the folio moves between lrus */
7577 		if (!folio_test_clear_lru(folio))
7578 			continue;
7579 
7580 		lruvec = folio_lruvec_relock_irq(folio, lruvec);
7581 		if (folio_evictable(folio) && folio_test_unevictable(folio)) {
7582 			lruvec_del_folio(lruvec, folio);
7583 			folio_clear_unevictable(folio);
7584 			lruvec_add_folio(lruvec, folio);
7585 			pgrescued += nr_pages;
7586 		}
7587 		folio_set_lru(folio);
7588 	}
7589 
7590 	if (lruvec) {
7591 		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
7592 		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7593 		unlock_page_lruvec_irq(lruvec);
7594 	} else if (pgscanned) {
7595 		count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7596 	}
7597 }
7598 EXPORT_SYMBOL_GPL(check_move_unevictable_folios);
7599