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/rwsem.h>
  39#include <linux/delay.h>
  40#include <linux/kthread.h>
  41#include <linux/freezer.h>
  42#include <linux/memcontrol.h>
  43#include <linux/migrate.h>
  44#include <linux/delayacct.h>
  45#include <linux/sysctl.h>
  46#include <linux/memory-tiers.h>
  47#include <linux/oom.h>
  48#include <linux/pagevec.h>
  49#include <linux/prefetch.h>
  50#include <linux/printk.h>
  51#include <linux/dax.h>
  52#include <linux/psi.h>
  53#include <linux/pagewalk.h>
  54#include <linux/shmem_fs.h>
  55#include <linux/ctype.h>
  56#include <linux/debugfs.h>
  57#include <linux/khugepaged.h>
  58
  59#include <asm/tlbflush.h>
  60#include <asm/div64.h>
  61
  62#include <linux/swapops.h>
  63#include <linux/balloon_compaction.h>
  64#include <linux/sched/sysctl.h>
  65
  66#include "internal.h"
  67#include "swap.h"
  68
  69#define CREATE_TRACE_POINTS
  70#include <trace/events/vmscan.h>
  71
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  72struct scan_control {
 
 
 
 
 
 
  73	/* How many pages shrink_list() should reclaim */
  74	unsigned long nr_to_reclaim;
  75
  76	/*
  77	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
  78	 * are scanned.
  79	 */
  80	nodemask_t	*nodemask;
  81
  82	/*
  83	 * The memory cgroup that hit its limit and as a result is the
  84	 * primary target of this reclaim invocation.
  85	 */
  86	struct mem_cgroup *target_mem_cgroup;
  87
  88	/*
  89	 * Scan pressure balancing between anon and file LRUs
  90	 */
  91	unsigned long	anon_cost;
  92	unsigned long	file_cost;
  93
  94	/* Can active folios be deactivated as part of reclaim? */
  95#define DEACTIVATE_ANON 1
  96#define DEACTIVATE_FILE 2
  97	unsigned int may_deactivate:2;
  98	unsigned int force_deactivate:1;
  99	unsigned int skipped_deactivate:1;
 100
 101	/* Writepage batching in laptop mode; RECLAIM_WRITE */
 102	unsigned int may_writepage:1;
 103
 104	/* Can mapped folios be reclaimed? */
 105	unsigned int may_unmap:1;
 106
 107	/* Can folios be swapped as part of reclaim? */
 108	unsigned int may_swap:1;
 109
 110	/* Proactive reclaim invoked by userspace through memory.reclaim */
 111	unsigned int proactive:1;
 112
 113	/*
 114	 * Cgroup memory below memory.low is protected as long as we
 115	 * don't threaten to OOM. If any cgroup is reclaimed at
 116	 * reduced force or passed over entirely due to its memory.low
 117	 * setting (memcg_low_skipped), and nothing is reclaimed as a
 118	 * result, then go back for one more cycle that reclaims the protected
 119	 * memory (memcg_low_reclaim) to avert OOM.
 120	 */
 121	unsigned int memcg_low_reclaim:1;
 122	unsigned int memcg_low_skipped:1;
 123
 124	unsigned int hibernation_mode:1;
 125
 126	/* One of the zones is ready for compaction */
 127	unsigned int compaction_ready:1;
 128
 129	/* There is easily reclaimable cold cache in the current node */
 130	unsigned int cache_trim_mode:1;
 131
 132	/* The file folios on the current node are dangerously low */
 133	unsigned int file_is_tiny:1;
 
 134
 135	/* Always discard instead of demoting to lower tier memory */
 136	unsigned int no_demotion:1;
 137
 138#ifdef CONFIG_LRU_GEN
 139	/* help kswapd make better choices among multiple memcgs */
 140	unsigned int memcgs_need_aging:1;
 141	unsigned long last_reclaimed;
 
 
 
 
 
 
 
 
 142#endif
 143
 144	/* Allocation order */
 145	s8 order;
 146
 147	/* Scan (total_size >> priority) pages at once */
 148	s8 priority;
 149
 150	/* The highest zone to isolate folios for reclaim from */
 151	s8 reclaim_idx;
 152
 153	/* This context's GFP mask */
 154	gfp_t gfp_mask;
 155
 156	/* Incremented by the number of inactive pages that were scanned */
 157	unsigned long nr_scanned;
 158
 159	/* Number of pages freed so far during a call to shrink_zones() */
 160	unsigned long nr_reclaimed;
 161
 162	struct {
 163		unsigned int dirty;
 164		unsigned int unqueued_dirty;
 165		unsigned int congested;
 166		unsigned int writeback;
 167		unsigned int immediate;
 168		unsigned int file_taken;
 169		unsigned int taken;
 170	} nr;
 171
 172	/* for recording the reclaimed slab by now */
 173	struct reclaim_state reclaim_state;
 174};
 175
 176#ifdef ARCH_HAS_PREFETCHW
 177#define prefetchw_prev_lru_folio(_folio, _base, _field)			\
 178	do {								\
 179		if ((_folio)->lru.prev != _base) {			\
 180			struct folio *prev;				\
 181									\
 182			prev = lru_to_folio(&(_folio->lru));		\
 183			prefetchw(&prev->_field);			\
 184		}							\
 185	} while (0)
 186#else
 187#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
 188#endif
 189
 190/*
 191 * From 0 .. 200.  Higher means more swappy.
 192 */
 193int vm_swappiness = 60;
 
 194
 195static void set_task_reclaim_state(struct task_struct *task,
 196				   struct reclaim_state *rs)
 197{
 198	/* Check for an overwrite */
 199	WARN_ON_ONCE(rs && task->reclaim_state);
 200
 201	/* Check for the nulling of an already-nulled member */
 202	WARN_ON_ONCE(!rs && !task->reclaim_state);
 203
 204	task->reclaim_state = rs;
 205}
 206
 207LIST_HEAD(shrinker_list);
 208DECLARE_RWSEM(shrinker_rwsem);
 209
 210#ifdef CONFIG_MEMCG
 211static int shrinker_nr_max;
 212
 213/* The shrinker_info is expanded in a batch of BITS_PER_LONG */
 214static inline int shrinker_map_size(int nr_items)
 215{
 216	return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
 217}
 218
 219static inline int shrinker_defer_size(int nr_items)
 220{
 221	return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t));
 222}
 223
 224static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
 225						     int nid)
 226{
 227	return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
 228					 lockdep_is_held(&shrinker_rwsem));
 229}
 230
 231static int expand_one_shrinker_info(struct mem_cgroup *memcg,
 232				    int map_size, int defer_size,
 233				    int old_map_size, int old_defer_size)
 234{
 235	struct shrinker_info *new, *old;
 236	struct mem_cgroup_per_node *pn;
 237	int nid;
 238	int size = map_size + defer_size;
 239
 240	for_each_node(nid) {
 241		pn = memcg->nodeinfo[nid];
 242		old = shrinker_info_protected(memcg, nid);
 243		/* Not yet online memcg */
 244		if (!old)
 245			return 0;
 246
 247		new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
 248		if (!new)
 249			return -ENOMEM;
 250
 251		new->nr_deferred = (atomic_long_t *)(new + 1);
 252		new->map = (void *)new->nr_deferred + defer_size;
 253
 254		/* map: set all old bits, clear all new bits */
 255		memset(new->map, (int)0xff, old_map_size);
 256		memset((void *)new->map + old_map_size, 0, map_size - old_map_size);
 257		/* nr_deferred: copy old values, clear all new values */
 258		memcpy(new->nr_deferred, old->nr_deferred, old_defer_size);
 259		memset((void *)new->nr_deferred + old_defer_size, 0,
 260		       defer_size - old_defer_size);
 261
 262		rcu_assign_pointer(pn->shrinker_info, new);
 263		kvfree_rcu(old, rcu);
 264	}
 265
 266	return 0;
 267}
 268
 269void free_shrinker_info(struct mem_cgroup *memcg)
 270{
 271	struct mem_cgroup_per_node *pn;
 272	struct shrinker_info *info;
 273	int nid;
 274
 275	for_each_node(nid) {
 276		pn = memcg->nodeinfo[nid];
 277		info = rcu_dereference_protected(pn->shrinker_info, true);
 278		kvfree(info);
 279		rcu_assign_pointer(pn->shrinker_info, NULL);
 280	}
 281}
 282
 283int alloc_shrinker_info(struct mem_cgroup *memcg)
 284{
 285	struct shrinker_info *info;
 286	int nid, size, ret = 0;
 287	int map_size, defer_size = 0;
 288
 289	down_write(&shrinker_rwsem);
 290	map_size = shrinker_map_size(shrinker_nr_max);
 291	defer_size = shrinker_defer_size(shrinker_nr_max);
 292	size = map_size + defer_size;
 293	for_each_node(nid) {
 294		info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
 295		if (!info) {
 296			free_shrinker_info(memcg);
 297			ret = -ENOMEM;
 298			break;
 299		}
 300		info->nr_deferred = (atomic_long_t *)(info + 1);
 301		info->map = (void *)info->nr_deferred + defer_size;
 302		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
 303	}
 304	up_write(&shrinker_rwsem);
 305
 306	return ret;
 307}
 308
 309static inline bool need_expand(int nr_max)
 310{
 311	return round_up(nr_max, BITS_PER_LONG) >
 312	       round_up(shrinker_nr_max, BITS_PER_LONG);
 313}
 314
 315static int expand_shrinker_info(int new_id)
 316{
 317	int ret = 0;
 318	int new_nr_max = new_id + 1;
 319	int map_size, defer_size = 0;
 320	int old_map_size, old_defer_size = 0;
 321	struct mem_cgroup *memcg;
 322
 323	if (!need_expand(new_nr_max))
 324		goto out;
 325
 326	if (!root_mem_cgroup)
 327		goto out;
 328
 329	lockdep_assert_held(&shrinker_rwsem);
 330
 331	map_size = shrinker_map_size(new_nr_max);
 332	defer_size = shrinker_defer_size(new_nr_max);
 333	old_map_size = shrinker_map_size(shrinker_nr_max);
 334	old_defer_size = shrinker_defer_size(shrinker_nr_max);
 335
 336	memcg = mem_cgroup_iter(NULL, NULL, NULL);
 337	do {
 338		ret = expand_one_shrinker_info(memcg, map_size, defer_size,
 339					       old_map_size, old_defer_size);
 340		if (ret) {
 341			mem_cgroup_iter_break(NULL, memcg);
 342			goto out;
 343		}
 344	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 345out:
 346	if (!ret)
 347		shrinker_nr_max = new_nr_max;
 348
 349	return ret;
 350}
 351
 352void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
 353{
 354	if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
 355		struct shrinker_info *info;
 356
 357		rcu_read_lock();
 358		info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
 359		/* Pairs with smp mb in shrink_slab() */
 360		smp_mb__before_atomic();
 361		set_bit(shrinker_id, info->map);
 362		rcu_read_unlock();
 363	}
 364}
 365
 366static DEFINE_IDR(shrinker_idr);
 367
 368static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 369{
 370	int id, ret = -ENOMEM;
 371
 372	if (mem_cgroup_disabled())
 373		return -ENOSYS;
 374
 375	down_write(&shrinker_rwsem);
 376	/* This may call shrinker, so it must use down_read_trylock() */
 377	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
 378	if (id < 0)
 379		goto unlock;
 380
 381	if (id >= shrinker_nr_max) {
 382		if (expand_shrinker_info(id)) {
 383			idr_remove(&shrinker_idr, id);
 384			goto unlock;
 385		}
 386	}
 387	shrinker->id = id;
 388	ret = 0;
 389unlock:
 390	up_write(&shrinker_rwsem);
 391	return ret;
 392}
 393
 394static void unregister_memcg_shrinker(struct shrinker *shrinker)
 395{
 396	int id = shrinker->id;
 397
 398	BUG_ON(id < 0);
 399
 400	lockdep_assert_held(&shrinker_rwsem);
 401
 402	idr_remove(&shrinker_idr, id);
 403}
 404
 405static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
 406				   struct mem_cgroup *memcg)
 407{
 408	struct shrinker_info *info;
 409
 410	info = shrinker_info_protected(memcg, nid);
 411	return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
 412}
 413
 414static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
 415				  struct mem_cgroup *memcg)
 416{
 417	struct shrinker_info *info;
 418
 419	info = shrinker_info_protected(memcg, nid);
 420	return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
 421}
 422
 423void reparent_shrinker_deferred(struct mem_cgroup *memcg)
 424{
 425	int i, nid;
 426	long nr;
 427	struct mem_cgroup *parent;
 428	struct shrinker_info *child_info, *parent_info;
 429
 430	parent = parent_mem_cgroup(memcg);
 431	if (!parent)
 432		parent = root_mem_cgroup;
 433
 434	/* Prevent from concurrent shrinker_info expand */
 435	down_read(&shrinker_rwsem);
 436	for_each_node(nid) {
 437		child_info = shrinker_info_protected(memcg, nid);
 438		parent_info = shrinker_info_protected(parent, nid);
 439		for (i = 0; i < shrinker_nr_max; i++) {
 440			nr = atomic_long_read(&child_info->nr_deferred[i]);
 441			atomic_long_add(nr, &parent_info->nr_deferred[i]);
 442		}
 443	}
 444	up_read(&shrinker_rwsem);
 445}
 446
 447static bool cgroup_reclaim(struct scan_control *sc)
 448{
 449	return sc->target_mem_cgroup;
 450}
 451
 452/**
 453 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
 454 * @sc: scan_control in question
 455 *
 456 * The normal page dirty throttling mechanism in balance_dirty_pages() is
 457 * completely broken with the legacy memcg and direct stalling in
 458 * shrink_folio_list() is used for throttling instead, which lacks all the
 459 * niceties such as fairness, adaptive pausing, bandwidth proportional
 460 * allocation and configurability.
 461 *
 462 * This function tests whether the vmscan currently in progress can assume
 463 * that the normal dirty throttling mechanism is operational.
 464 */
 465static bool writeback_throttling_sane(struct scan_control *sc)
 466{
 467	if (!cgroup_reclaim(sc))
 468		return true;
 469#ifdef CONFIG_CGROUP_WRITEBACK
 470	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 471		return true;
 472#endif
 473	return false;
 474}
 475#else
 476static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 477{
 478	return -ENOSYS;
 479}
 480
 481static void unregister_memcg_shrinker(struct shrinker *shrinker)
 482{
 483}
 484
 485static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
 486				   struct mem_cgroup *memcg)
 487{
 488	return 0;
 489}
 490
 491static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
 492				  struct mem_cgroup *memcg)
 493{
 494	return 0;
 495}
 496
 497static bool cgroup_reclaim(struct scan_control *sc)
 498{
 499	return false;
 500}
 501
 502static bool writeback_throttling_sane(struct scan_control *sc)
 503{
 504	return true;
 505}
 506#endif
 507
 508static long xchg_nr_deferred(struct shrinker *shrinker,
 509			     struct shrink_control *sc)
 510{
 511	int nid = sc->nid;
 512
 513	if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
 514		nid = 0;
 515
 516	if (sc->memcg &&
 517	    (shrinker->flags & SHRINKER_MEMCG_AWARE))
 518		return xchg_nr_deferred_memcg(nid, shrinker,
 519					      sc->memcg);
 520
 521	return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
 522}
 523
 524
 525static long add_nr_deferred(long nr, struct shrinker *shrinker,
 526			    struct shrink_control *sc)
 527{
 528	int nid = sc->nid;
 529
 530	if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
 531		nid = 0;
 532
 533	if (sc->memcg &&
 534	    (shrinker->flags & SHRINKER_MEMCG_AWARE))
 535		return add_nr_deferred_memcg(nr, nid, shrinker,
 536					     sc->memcg);
 537
 538	return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
 539}
 540
 541static bool can_demote(int nid, struct scan_control *sc)
 542{
 543	if (!numa_demotion_enabled)
 544		return false;
 545	if (sc && sc->no_demotion)
 546		return false;
 547	if (next_demotion_node(nid) == NUMA_NO_NODE)
 548		return false;
 549
 550	return true;
 551}
 552
 553static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
 554					  int nid,
 555					  struct scan_control *sc)
 556{
 557	if (memcg == NULL) {
 558		/*
 559		 * For non-memcg reclaim, is there
 560		 * space in any swap device?
 561		 */
 562		if (get_nr_swap_pages() > 0)
 563			return true;
 564	} else {
 565		/* Is the memcg below its swap limit? */
 566		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
 567			return true;
 568	}
 569
 570	/*
 571	 * The page can not be swapped.
 572	 *
 573	 * Can it be reclaimed from this node via demotion?
 574	 */
 575	return can_demote(nid, sc);
 576}
 577
 578/*
 579 * This misses isolated folios which are not accounted for to save counters.
 580 * As the data only determines if reclaim or compaction continues, it is
 581 * not expected that isolated folios will be a dominating factor.
 582 */
 583unsigned long zone_reclaimable_pages(struct zone *zone)
 584{
 585	unsigned long nr;
 586
 587	nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
 588		zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
 589	if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
 590		nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
 591			zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
 592
 593	return nr;
 594}
 595
 596/**
 597 * lruvec_lru_size -  Returns the number of pages on the given LRU list.
 598 * @lruvec: lru vector
 599 * @lru: lru to use
 600 * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
 601 */
 602static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
 603				     int zone_idx)
 604{
 605	unsigned long size = 0;
 606	int zid;
 607
 608	for (zid = 0; zid <= zone_idx; zid++) {
 609		struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
 610
 611		if (!managed_zone(zone))
 612			continue;
 613
 614		if (!mem_cgroup_disabled())
 615			size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
 616		else
 617			size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
 618	}
 619	return size;
 620}
 621
 622/*
 623 * Add a shrinker callback to be called from the vm.
 624 */
 625static int __prealloc_shrinker(struct shrinker *shrinker)
 626{
 627	unsigned int size;
 628	int err;
 629
 630	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
 631		err = prealloc_memcg_shrinker(shrinker);
 632		if (err != -ENOSYS)
 633			return err;
 634
 635		shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
 636	}
 637
 638	size = sizeof(*shrinker->nr_deferred);
 639	if (shrinker->flags & SHRINKER_NUMA_AWARE)
 640		size *= nr_node_ids;
 641
 642	shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
 643	if (!shrinker->nr_deferred)
 644		return -ENOMEM;
 645
 646	return 0;
 647}
 648
 649#ifdef CONFIG_SHRINKER_DEBUG
 650int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
 651{
 652	va_list ap;
 653	int err;
 654
 655	va_start(ap, fmt);
 656	shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
 657	va_end(ap);
 658	if (!shrinker->name)
 659		return -ENOMEM;
 660
 661	err = __prealloc_shrinker(shrinker);
 662	if (err) {
 663		kfree_const(shrinker->name);
 664		shrinker->name = NULL;
 665	}
 666
 667	return err;
 668}
 669#else
 670int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
 671{
 672	return __prealloc_shrinker(shrinker);
 673}
 674#endif
 675
 676void free_prealloced_shrinker(struct shrinker *shrinker)
 677{
 678#ifdef CONFIG_SHRINKER_DEBUG
 679	kfree_const(shrinker->name);
 680	shrinker->name = NULL;
 681#endif
 682	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
 683		down_write(&shrinker_rwsem);
 684		unregister_memcg_shrinker(shrinker);
 685		up_write(&shrinker_rwsem);
 686		return;
 687	}
 688
 689	kfree(shrinker->nr_deferred);
 690	shrinker->nr_deferred = NULL;
 691}
 692
 693void register_shrinker_prepared(struct shrinker *shrinker)
 694{
 
 695	down_write(&shrinker_rwsem);
 696	list_add_tail(&shrinker->list, &shrinker_list);
 697	shrinker->flags |= SHRINKER_REGISTERED;
 698	shrinker_debugfs_add(shrinker);
 699	up_write(&shrinker_rwsem);
 700}
 701
 702static int __register_shrinker(struct shrinker *shrinker)
 703{
 704	int err = __prealloc_shrinker(shrinker);
 705
 706	if (err)
 707		return err;
 708	register_shrinker_prepared(shrinker);
 709	return 0;
 710}
 711
 712#ifdef CONFIG_SHRINKER_DEBUG
 713int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
 714{
 715	va_list ap;
 716	int err;
 717
 718	va_start(ap, fmt);
 719	shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
 720	va_end(ap);
 721	if (!shrinker->name)
 722		return -ENOMEM;
 723
 724	err = __register_shrinker(shrinker);
 725	if (err) {
 726		kfree_const(shrinker->name);
 727		shrinker->name = NULL;
 728	}
 729	return err;
 730}
 731#else
 732int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
 733{
 734	return __register_shrinker(shrinker);
 735}
 736#endif
 737EXPORT_SYMBOL(register_shrinker);
 738
 739/*
 740 * Remove one
 741 */
 742void unregister_shrinker(struct shrinker *shrinker)
 743{
 744	struct dentry *debugfs_entry;
 745
 746	if (!(shrinker->flags & SHRINKER_REGISTERED))
 747		return;
 748
 749	down_write(&shrinker_rwsem);
 750	list_del(&shrinker->list);
 751	shrinker->flags &= ~SHRINKER_REGISTERED;
 752	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 753		unregister_memcg_shrinker(shrinker);
 754	debugfs_entry = shrinker_debugfs_remove(shrinker);
 755	up_write(&shrinker_rwsem);
 756
 757	debugfs_remove_recursive(debugfs_entry);
 758
 759	kfree(shrinker->nr_deferred);
 760	shrinker->nr_deferred = NULL;
 761}
 762EXPORT_SYMBOL(unregister_shrinker);
 763
 764/**
 765 * synchronize_shrinkers - Wait for all running shrinkers to complete.
 766 *
 767 * This is equivalent to calling unregister_shrink() and register_shrinker(),
 768 * but atomically and with less overhead. This is useful to guarantee that all
 769 * shrinker invocations have seen an update, before freeing memory, similar to
 770 * rcu.
 771 */
 772void synchronize_shrinkers(void)
 773{
 774	down_write(&shrinker_rwsem);
 775	up_write(&shrinker_rwsem);
 776}
 777EXPORT_SYMBOL(synchronize_shrinkers);
 778
 779#define SHRINK_BATCH 128
 780
 781static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 782				    struct shrinker *shrinker, int priority)
 783{
 784	unsigned long freed = 0;
 785	unsigned long long delta;
 786	long total_scan;
 787	long freeable;
 788	long nr;
 789	long new_nr;
 790	long batch_size = shrinker->batch ? shrinker->batch
 791					  : SHRINK_BATCH;
 792	long scanned = 0, next_deferred;
 793
 794	freeable = shrinker->count_objects(shrinker, shrinkctl);
 795	if (freeable == 0 || freeable == SHRINK_EMPTY)
 796		return freeable;
 797
 798	/*
 799	 * copy the current shrinker scan count into a local variable
 800	 * and zero it so that other concurrent shrinker invocations
 801	 * don't also do this scanning work.
 802	 */
 803	nr = xchg_nr_deferred(shrinker, shrinkctl);
 804
 805	if (shrinker->seeks) {
 806		delta = freeable >> priority;
 807		delta *= 4;
 808		do_div(delta, shrinker->seeks);
 809	} else {
 810		/*
 811		 * These objects don't require any IO to create. Trim
 812		 * them aggressively under memory pressure to keep
 813		 * them from causing refetches in the IO caches.
 814		 */
 815		delta = freeable / 2;
 816	}
 817
 818	total_scan = nr >> priority;
 819	total_scan += delta;
 820	total_scan = min(total_scan, (2 * freeable));
 821
 822	trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
 823				   freeable, delta, total_scan, priority);
 824
 825	/*
 826	 * Normally, we should not scan less than batch_size objects in one
 827	 * pass to avoid too frequent shrinker calls, but if the slab has less
 828	 * than batch_size objects in total and we are really tight on memory,
 829	 * we will try to reclaim all available objects, otherwise we can end
 830	 * up failing allocations although there are plenty of reclaimable
 831	 * objects spread over several slabs with usage less than the
 832	 * batch_size.
 833	 *
 834	 * We detect the "tight on memory" situations by looking at the total
 835	 * number of objects we want to scan (total_scan). If it is greater
 836	 * than the total number of objects on slab (freeable), we must be
 837	 * scanning at high prio and therefore should try to reclaim as much as
 838	 * possible.
 839	 */
 840	while (total_scan >= batch_size ||
 841	       total_scan >= freeable) {
 842		unsigned long ret;
 843		unsigned long nr_to_scan = min(batch_size, total_scan);
 844
 845		shrinkctl->nr_to_scan = nr_to_scan;
 846		shrinkctl->nr_scanned = nr_to_scan;
 847		ret = shrinker->scan_objects(shrinker, shrinkctl);
 848		if (ret == SHRINK_STOP)
 849			break;
 850		freed += ret;
 851
 852		count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
 853		total_scan -= shrinkctl->nr_scanned;
 854		scanned += shrinkctl->nr_scanned;
 855
 856		cond_resched();
 857	}
 858
 859	/*
 860	 * The deferred work is increased by any new work (delta) that wasn't
 861	 * done, decreased by old deferred work that was done now.
 862	 *
 863	 * And it is capped to two times of the freeable items.
 864	 */
 865	next_deferred = max_t(long, (nr + delta - scanned), 0);
 866	next_deferred = min(next_deferred, (2 * freeable));
 867
 868	/*
 869	 * move the unused scan count back into the shrinker in a
 870	 * manner that handles concurrent updates.
 871	 */
 872	new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
 873
 874	trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
 875	return freed;
 876}
 877
 878#ifdef CONFIG_MEMCG
 879static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
 880			struct mem_cgroup *memcg, int priority)
 881{
 882	struct shrinker_info *info;
 883	unsigned long ret, freed = 0;
 884	int i;
 885
 886	if (!mem_cgroup_online(memcg))
 887		return 0;
 888
 889	if (!down_read_trylock(&shrinker_rwsem))
 890		return 0;
 891
 892	info = shrinker_info_protected(memcg, nid);
 893	if (unlikely(!info))
 894		goto unlock;
 895
 896	for_each_set_bit(i, info->map, shrinker_nr_max) {
 897		struct shrink_control sc = {
 898			.gfp_mask = gfp_mask,
 899			.nid = nid,
 900			.memcg = memcg,
 901		};
 902		struct shrinker *shrinker;
 903
 904		shrinker = idr_find(&shrinker_idr, i);
 905		if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
 906			if (!shrinker)
 907				clear_bit(i, info->map);
 908			continue;
 909		}
 910
 911		/* Call non-slab shrinkers even though kmem is disabled */
 912		if (!memcg_kmem_enabled() &&
 913		    !(shrinker->flags & SHRINKER_NONSLAB))
 914			continue;
 915
 916		ret = do_shrink_slab(&sc, shrinker, priority);
 917		if (ret == SHRINK_EMPTY) {
 918			clear_bit(i, info->map);
 919			/*
 920			 * After the shrinker reported that it had no objects to
 921			 * free, but before we cleared the corresponding bit in
 922			 * the memcg shrinker map, a new object might have been
 923			 * added. To make sure, we have the bit set in this
 924			 * case, we invoke the shrinker one more time and reset
 925			 * the bit if it reports that it is not empty anymore.
 926			 * The memory barrier here pairs with the barrier in
 927			 * set_shrinker_bit():
 928			 *
 929			 * list_lru_add()     shrink_slab_memcg()
 930			 *   list_add_tail()    clear_bit()
 931			 *   <MB>               <MB>
 932			 *   set_bit()          do_shrink_slab()
 933			 */
 934			smp_mb__after_atomic();
 935			ret = do_shrink_slab(&sc, shrinker, priority);
 936			if (ret == SHRINK_EMPTY)
 937				ret = 0;
 938			else
 939				set_shrinker_bit(memcg, nid, i);
 940		}
 941		freed += ret;
 942
 943		if (rwsem_is_contended(&shrinker_rwsem)) {
 944			freed = freed ? : 1;
 945			break;
 946		}
 947	}
 948unlock:
 949	up_read(&shrinker_rwsem);
 950	return freed;
 951}
 952#else /* CONFIG_MEMCG */
 953static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
 954			struct mem_cgroup *memcg, int priority)
 955{
 956	return 0;
 957}
 958#endif /* CONFIG_MEMCG */
 959
 960/**
 961 * shrink_slab - shrink slab caches
 962 * @gfp_mask: allocation context
 963 * @nid: node whose slab caches to target
 964 * @memcg: memory cgroup whose slab caches to target
 965 * @priority: the reclaim priority
 966 *
 967 * Call the shrink functions to age shrinkable caches.
 
 
 
 968 *
 969 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
 970 * unaware shrinkers will receive a node id of 0 instead.
 971 *
 972 * @memcg specifies the memory cgroup to target. Unaware shrinkers
 973 * are called only if it is the root cgroup.
 974 *
 975 * @priority is sc->priority, we take the number of objects and >> by priority
 976 * in order to get the scan target.
 
 977 *
 978 * Returns the number of reclaimed slab objects.
 979 */
 980static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 981				 struct mem_cgroup *memcg,
 982				 int priority)
 983{
 984	unsigned long ret, freed = 0;
 985	struct shrinker *shrinker;
 
 986
 987	/*
 988	 * The root memcg might be allocated even though memcg is disabled
 989	 * via "cgroup_disable=memory" boot parameter.  This could make
 990	 * mem_cgroup_is_root() return false, then just run memcg slab
 991	 * shrink, but skip global shrink.  This may result in premature
 992	 * oom.
 993	 */
 994	if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
 995		return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
 996
 997	if (!down_read_trylock(&shrinker_rwsem))
 
 
 998		goto out;
 
 999
1000	list_for_each_entry(shrinker, &shrinker_list, list) {
1001		struct shrink_control sc = {
1002			.gfp_mask = gfp_mask,
1003			.nid = nid,
1004			.memcg = memcg,
1005		};
 
 
 
1006
1007		ret = do_shrink_slab(&sc, shrinker, priority);
1008		if (ret == SHRINK_EMPTY)
1009			ret = 0;
1010		freed += ret;
1011		/*
1012		 * Bail out if someone want to register a new shrinker to
1013		 * prevent the registration from being stalled for long periods
1014		 * by parallel ongoing shrinking.
1015		 */
1016		if (rwsem_is_contended(&shrinker_rwsem)) {
1017			freed = freed ? : 1;
1018			break;
1019		}
1020	}
1021
1022	up_read(&shrinker_rwsem);
1023out:
1024	cond_resched();
1025	return freed;
1026}
 
 
 
 
 
 
 
1027
1028static unsigned long drop_slab_node(int nid)
1029{
1030	unsigned long freed = 0;
1031	struct mem_cgroup *memcg = NULL;
 
 
 
 
 
 
 
 
 
 
1032
1033	memcg = mem_cgroup_iter(NULL, NULL, NULL);
1034	do {
1035		freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
1036	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 
 
 
1037
1038	return freed;
1039}
 
1040
1041void drop_slab(void)
1042{
1043	int nid;
1044	int shift = 0;
1045	unsigned long freed;
1046
1047	do {
1048		freed = 0;
1049		for_each_online_node(nid) {
1050			if (fatal_signal_pending(current))
1051				return;
1052
1053			freed += drop_slab_node(nid);
1054		}
1055	} while ((freed >> shift++) > 1);
1056}
1057
1058static int reclaimer_offset(void)
1059{
1060	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
1061			PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
1062	BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
1063			PGSCAN_DIRECT - PGSCAN_KSWAPD);
1064	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
1065			PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
1066	BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
1067			PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
1068
1069	if (current_is_kswapd())
1070		return 0;
1071	if (current_is_khugepaged())
1072		return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
1073	return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
1074}
1075
1076static inline int is_page_cache_freeable(struct folio *folio)
1077{
1078	/*
1079	 * A freeable page cache folio is referenced only by the caller
1080	 * that isolated the folio, the page cache and optional filesystem
1081	 * private data at folio->private.
1082	 */
1083	return folio_ref_count(folio) - folio_test_private(folio) ==
1084		1 + folio_nr_pages(folio);
1085}
 
1086
1087/*
1088 * We detected a synchronous write error writing a folio out.  Probably
1089 * -ENOSPC.  We need to propagate that into the address_space for a subsequent
1090 * fsync(), msync() or close().
1091 *
1092 * The tricky part is that after writepage we cannot touch the mapping: nothing
1093 * prevents it from being freed up.  But we have a ref on the folio and once
1094 * that folio is locked, the mapping is pinned.
1095 *
1096 * We're allowed to run sleeping folio_lock() here because we know the caller has
1097 * __GFP_FS.
1098 */
1099static void handle_write_error(struct address_space *mapping,
1100				struct folio *folio, int error)
1101{
1102	folio_lock(folio);
1103	if (folio_mapping(folio) == mapping)
1104		mapping_set_error(mapping, error);
1105	folio_unlock(folio);
1106}
1107
1108static bool skip_throttle_noprogress(pg_data_t *pgdat)
 
1109{
1110	int reclaimable = 0, write_pending = 0;
1111	int i;
1112
1113	/*
1114	 * If kswapd is disabled, reschedule if necessary but do not
1115	 * throttle as the system is likely near OOM.
 
1116	 */
1117	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
1118		return true;
 
 
1119
1120	/*
1121	 * If there are a lot of dirty/writeback folios then do not
1122	 * throttle as throttling will occur when the folios cycle
1123	 * towards the end of the LRU if still under writeback.
1124	 */
1125	for (i = 0; i < MAX_NR_ZONES; i++) {
1126		struct zone *zone = pgdat->node_zones + i;
1127
1128		if (!managed_zone(zone))
1129			continue;
1130
1131		reclaimable += zone_reclaimable_pages(zone);
1132		write_pending += zone_page_state_snapshot(zone,
1133						  NR_ZONE_WRITE_PENDING);
1134	}
1135	if (2 * write_pending <= reclaimable)
1136		return true;
1137
1138	return false;
1139}
1140
1141void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
1142{
1143	wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
1144	long timeout, ret;
1145	DEFINE_WAIT(wait);
1146
1147	/*
1148	 * Do not throttle IO workers, kthreads other than kswapd or
1149	 * workqueues. They may be required for reclaim to make
1150	 * forward progress (e.g. journalling workqueues or kthreads).
1151	 */
1152	if (!current_is_kswapd() &&
1153	    current->flags & (PF_IO_WORKER|PF_KTHREAD)) {
1154		cond_resched();
1155		return;
1156	}
1157
 
 
1158	/*
1159	 * These figures are pulled out of thin air.
1160	 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
1161	 * parallel reclaimers which is a short-lived event so the timeout is
1162	 * short. Failing to make progress or waiting on writeback are
1163	 * potentially long-lived events so use a longer timeout. This is shaky
1164	 * logic as a failure to make progress could be due to anything from
1165	 * writeback to a slow device to excessive referenced folios at the tail
1166	 * of the inactive LRU.
1167	 */
1168	switch(reason) {
1169	case VMSCAN_THROTTLE_WRITEBACK:
1170		timeout = HZ/10;
1171
1172		if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
1173			WRITE_ONCE(pgdat->nr_reclaim_start,
1174				node_page_state(pgdat, NR_THROTTLED_WRITTEN));
1175		}
1176
1177		break;
1178	case VMSCAN_THROTTLE_CONGESTED:
1179		fallthrough;
1180	case VMSCAN_THROTTLE_NOPROGRESS:
1181		if (skip_throttle_noprogress(pgdat)) {
1182			cond_resched();
1183			return;
1184		}
1185
1186		timeout = 1;
1187
1188		break;
1189	case VMSCAN_THROTTLE_ISOLATED:
1190		timeout = HZ/50;
1191		break;
1192	default:
1193		WARN_ON_ONCE(1);
1194		timeout = HZ;
1195		break;
1196	}
1197
1198	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1199	ret = schedule_timeout(timeout);
1200	finish_wait(wqh, &wait);
1201
1202	if (reason == VMSCAN_THROTTLE_WRITEBACK)
1203		atomic_dec(&pgdat->nr_writeback_throttled);
 
 
 
 
 
 
 
1204
1205	trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
1206				jiffies_to_usecs(timeout - ret),
1207				reason);
 
1208}
1209
1210/*
1211 * Account for folios written if tasks are throttled waiting on dirty
1212 * folios to clean. If enough folios have been cleaned since throttling
1213 * started then wakeup the throttled tasks.
 
 
 
 
 
 
 
1214 */
1215void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
1216							int nr_throttled)
1217{
1218	unsigned long nr_written;
1219
1220	node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
1221
1222	/*
1223	 * This is an inaccurate read as the per-cpu deltas may not
1224	 * be synchronised. However, given that the system is
1225	 * writeback throttled, it is not worth taking the penalty
1226	 * of getting an accurate count. At worst, the throttle
1227	 * timeout guarantees forward progress.
1228	 */
1229	nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
1230		READ_ONCE(pgdat->nr_reclaim_start);
1231
1232	if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
1233		wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
1234}
1235
1236/* possible outcome of pageout() */
1237typedef enum {
1238	/* failed to write folio out, folio is locked */
1239	PAGE_KEEP,
1240	/* move folio to the active list, folio is locked */
1241	PAGE_ACTIVATE,
1242	/* folio has been sent to the disk successfully, folio is unlocked */
1243	PAGE_SUCCESS,
1244	/* folio is clean and locked */
1245	PAGE_CLEAN,
1246} pageout_t;
1247
1248/*
1249 * pageout is called by shrink_folio_list() for each dirty folio.
1250 * Calls ->writepage().
1251 */
1252static pageout_t pageout(struct folio *folio, struct address_space *mapping,
1253			 struct swap_iocb **plug)
1254{
1255	/*
1256	 * If the folio is dirty, only perform writeback if that write
1257	 * will be non-blocking.  To prevent this allocation from being
1258	 * stalled by pagecache activity.  But note that there may be
1259	 * stalls if we need to run get_block().  We could test
1260	 * PagePrivate for that.
1261	 *
1262	 * If this process is currently in __generic_file_write_iter() against
1263	 * this folio's queue, we can perform writeback even if that
1264	 * will block.
1265	 *
1266	 * If the folio is swapcache, write it back even if that would
1267	 * block, for some throttling. This happens by accident, because
1268	 * swap_backing_dev_info is bust: it doesn't reflect the
1269	 * congestion state of the swapdevs.  Easy to fix, if needed.
1270	 */
1271	if (!is_page_cache_freeable(folio))
1272		return PAGE_KEEP;
1273	if (!mapping) {
1274		/*
1275		 * Some data journaling orphaned folios can have
1276		 * folio->mapping == NULL while being dirty with clean buffers.
1277		 */
1278		if (folio_test_private(folio)) {
1279			if (try_to_free_buffers(folio)) {
1280				folio_clear_dirty(folio);
1281				pr_info("%s: orphaned folio\n", __func__);
1282				return PAGE_CLEAN;
1283			}
1284		}
1285		return PAGE_KEEP;
1286	}
1287	if (mapping->a_ops->writepage == NULL)
1288		return PAGE_ACTIVATE;
 
 
1289
1290	if (folio_clear_dirty_for_io(folio)) {
1291		int res;
1292		struct writeback_control wbc = {
1293			.sync_mode = WB_SYNC_NONE,
1294			.nr_to_write = SWAP_CLUSTER_MAX,
1295			.range_start = 0,
1296			.range_end = LLONG_MAX,
1297			.for_reclaim = 1,
1298			.swap_plug = plug,
1299		};
1300
1301		folio_set_reclaim(folio);
1302		res = mapping->a_ops->writepage(&folio->page, &wbc);
1303		if (res < 0)
1304			handle_write_error(mapping, folio, res);
1305		if (res == AOP_WRITEPAGE_ACTIVATE) {
1306			folio_clear_reclaim(folio);
1307			return PAGE_ACTIVATE;
1308		}
1309
1310		if (!folio_test_writeback(folio)) {
 
 
 
 
 
 
 
 
 
1311			/* synchronous write or broken a_ops? */
1312			folio_clear_reclaim(folio);
1313		}
1314		trace_mm_vmscan_write_folio(folio);
1315		node_stat_add_folio(folio, NR_VMSCAN_WRITE);
 
1316		return PAGE_SUCCESS;
1317	}
1318
1319	return PAGE_CLEAN;
1320}
1321
1322/*
1323 * Same as remove_mapping, but if the folio is removed from the mapping, it
1324 * gets returned with a refcount of 0.
1325 */
1326static int __remove_mapping(struct address_space *mapping, struct folio *folio,
1327			    bool reclaimed, struct mem_cgroup *target_memcg)
1328{
1329	int refcount;
1330	void *shadow = NULL;
1331
1332	BUG_ON(!folio_test_locked(folio));
1333	BUG_ON(mapping != folio_mapping(folio));
1334
1335	if (!folio_test_swapcache(folio))
1336		spin_lock(&mapping->host->i_lock);
1337	xa_lock_irq(&mapping->i_pages);
1338	/*
1339	 * The non racy check for a busy folio.
1340	 *
1341	 * Must be careful with the order of the tests. When someone has
1342	 * a ref to the folio, it may be possible that they dirty it then
1343	 * drop the reference. So if the dirty flag is tested before the
1344	 * refcount here, then the following race may occur:
1345	 *
1346	 * get_user_pages(&page);
1347	 * [user mapping goes away]
1348	 * write_to(page);
1349	 *				!folio_test_dirty(folio)    [good]
1350	 * folio_set_dirty(folio);
1351	 * folio_put(folio);
1352	 *				!refcount(folio)   [good, discard it]
1353	 *
1354	 * [oops, our write_to data is lost]
1355	 *
1356	 * Reversing the order of the tests ensures such a situation cannot
1357	 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
1358	 * load is not satisfied before that of folio->_refcount.
1359	 *
1360	 * Note that if the dirty flag is always set via folio_mark_dirty,
1361	 * and thus under the i_pages lock, then this ordering is not required.
1362	 */
1363	refcount = 1 + folio_nr_pages(folio);
1364	if (!folio_ref_freeze(folio, refcount))
1365		goto cannot_free;
1366	/* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
1367	if (unlikely(folio_test_dirty(folio))) {
1368		folio_ref_unfreeze(folio, refcount);
1369		goto cannot_free;
1370	}
1371
1372	if (folio_test_swapcache(folio)) {
1373		swp_entry_t swap = folio_swap_entry(folio);
1374
1375		if (reclaimed && !mapping_exiting(mapping))
1376			shadow = workingset_eviction(folio, target_memcg);
1377		__delete_from_swap_cache(folio, swap, shadow);
1378		mem_cgroup_swapout(folio, swap);
1379		xa_unlock_irq(&mapping->i_pages);
1380		put_swap_folio(folio, swap);
1381	} else {
1382		void (*free_folio)(struct folio *);
1383
1384		free_folio = mapping->a_ops->free_folio;
1385		/*
1386		 * Remember a shadow entry for reclaimed file cache in
1387		 * order to detect refaults, thus thrashing, later on.
1388		 *
1389		 * But don't store shadows in an address space that is
1390		 * already exiting.  This is not just an optimization,
1391		 * inode reclaim needs to empty out the radix tree or
1392		 * the nodes are lost.  Don't plant shadows behind its
1393		 * back.
1394		 *
1395		 * We also don't store shadows for DAX mappings because the
1396		 * only page cache folios found in these are zero pages
1397		 * covering holes, and because we don't want to mix DAX
1398		 * exceptional entries and shadow exceptional entries in the
1399		 * same address_space.
1400		 */
1401		if (reclaimed && folio_is_file_lru(folio) &&
1402		    !mapping_exiting(mapping) && !dax_mapping(mapping))
1403			shadow = workingset_eviction(folio, target_memcg);
1404		__filemap_remove_folio(folio, shadow);
1405		xa_unlock_irq(&mapping->i_pages);
1406		if (mapping_shrinkable(mapping))
1407			inode_add_lru(mapping->host);
1408		spin_unlock(&mapping->host->i_lock);
1409
1410		if (free_folio)
1411			free_folio(folio);
 
 
 
 
1412	}
1413
1414	return 1;
1415
1416cannot_free:
1417	xa_unlock_irq(&mapping->i_pages);
1418	if (!folio_test_swapcache(folio))
1419		spin_unlock(&mapping->host->i_lock);
1420	return 0;
1421}
1422
1423/**
1424 * remove_mapping() - Attempt to remove a folio from its mapping.
1425 * @mapping: The address space.
1426 * @folio: The folio to remove.
1427 *
1428 * If the folio is dirty, under writeback or if someone else has a ref
1429 * on it, removal will fail.
1430 * Return: The number of pages removed from the mapping.  0 if the folio
1431 * could not be removed.
1432 * Context: The caller should have a single refcount on the folio and
1433 * hold its lock.
1434 */
1435long remove_mapping(struct address_space *mapping, struct folio *folio)
1436{
1437	if (__remove_mapping(mapping, folio, false, NULL)) {
1438		/*
1439		 * Unfreezing the refcount with 1 effectively
1440		 * drops the pagecache ref for us without requiring another
1441		 * atomic operation.
1442		 */
1443		folio_ref_unfreeze(folio, 1);
1444		return folio_nr_pages(folio);
1445	}
1446	return 0;
1447}
1448
1449/**
1450 * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
1451 * @folio: Folio to be returned to an LRU list.
1452 *
1453 * Add previously isolated @folio to appropriate LRU list.
1454 * The folio may still be unevictable for other reasons.
1455 *
1456 * Context: lru_lock must not be held, interrupts must be enabled.
1457 */
1458void folio_putback_lru(struct folio *folio)
1459{
1460	folio_add_lru(folio);
1461	folio_put(folio);		/* drop ref from isolate */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1462}
1463
1464enum folio_references {
1465	FOLIOREF_RECLAIM,
1466	FOLIOREF_RECLAIM_CLEAN,
1467	FOLIOREF_KEEP,
1468	FOLIOREF_ACTIVATE,
1469};
1470
1471static enum folio_references folio_check_references(struct folio *folio,
1472						  struct scan_control *sc)
1473{
1474	int referenced_ptes, referenced_folio;
1475	unsigned long vm_flags;
1476
1477	referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
1478					   &vm_flags);
1479	referenced_folio = folio_test_clear_referenced(folio);
 
 
 
1480
1481	/*
1482	 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
1483	 * Let the folio, now marked Mlocked, be moved to the unevictable list.
1484	 */
1485	if (vm_flags & VM_LOCKED)
1486		return FOLIOREF_ACTIVATE;
1487
1488	/* rmap lock contention: rotate */
1489	if (referenced_ptes == -1)
1490		return FOLIOREF_KEEP;
1491
1492	if (referenced_ptes) {
 
 
1493		/*
1494		 * All mapped folios start out with page table
1495		 * references from the instantiating fault, so we need
1496		 * to look twice if a mapped file/anon folio is used more
1497		 * than once.
1498		 *
1499		 * Mark it and spare it for another trip around the
1500		 * inactive list.  Another page table reference will
1501		 * lead to its activation.
1502		 *
1503		 * Note: the mark is set for activated folios as well
1504		 * so that recently deactivated but used folios are
1505		 * quickly recovered.
1506		 */
1507		folio_set_referenced(folio);
1508
1509		if (referenced_folio || referenced_ptes > 1)
1510			return FOLIOREF_ACTIVATE;
1511
1512		/*
1513		 * Activate file-backed executable folios after first usage.
1514		 */
1515		if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
1516			return FOLIOREF_ACTIVATE;
1517
1518		return FOLIOREF_KEEP;
1519	}
1520
1521	/* Reclaim if clean, defer dirty folios to writeback */
1522	if (referenced_folio && folio_is_file_lru(folio))
1523		return FOLIOREF_RECLAIM_CLEAN;
1524
1525	return FOLIOREF_RECLAIM;
1526}
1527
1528/* Check if a folio is dirty or under writeback */
1529static void folio_check_dirty_writeback(struct folio *folio,
1530				       bool *dirty, bool *writeback)
1531{
1532	struct address_space *mapping;
1533
1534	/*
1535	 * Anonymous folios are not handled by flushers and must be written
1536	 * from reclaim context. Do not stall reclaim based on them.
1537	 * MADV_FREE anonymous folios are put into inactive file list too.
1538	 * They could be mistakenly treated as file lru. So further anon
1539	 * test is needed.
1540	 */
1541	if (!folio_is_file_lru(folio) ||
1542	    (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
1543		*dirty = false;
1544		*writeback = false;
1545		return;
1546	}
1547
1548	/* By default assume that the folio flags are accurate */
1549	*dirty = folio_test_dirty(folio);
1550	*writeback = folio_test_writeback(folio);
1551
1552	/* Verify dirty/writeback state if the filesystem supports it */
1553	if (!folio_test_private(folio))
1554		return;
1555
1556	mapping = folio_mapping(folio);
1557	if (mapping && mapping->a_ops->is_dirty_writeback)
1558		mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
1559}
1560
1561static struct page *alloc_demote_page(struct page *page, unsigned long private)
1562{
1563	struct page *target_page;
1564	nodemask_t *allowed_mask;
1565	struct migration_target_control *mtc;
1566
1567	mtc = (struct migration_target_control *)private;
1568
1569	allowed_mask = mtc->nmask;
1570	/*
1571	 * make sure we allocate from the target node first also trying to
1572	 * demote or reclaim pages from the target node via kswapd if we are
1573	 * low on free memory on target node. If we don't do this and if
1574	 * we have free memory on the slower(lower) memtier, we would start
1575	 * allocating pages from slower(lower) memory tiers without even forcing
1576	 * a demotion of cold pages from the target memtier. This can result
1577	 * in the kernel placing hot pages in slower(lower) memory tiers.
1578	 */
1579	mtc->nmask = NULL;
1580	mtc->gfp_mask |= __GFP_THISNODE;
1581	target_page = alloc_migration_target(page, (unsigned long)mtc);
1582	if (target_page)
1583		return target_page;
1584
1585	mtc->gfp_mask &= ~__GFP_THISNODE;
1586	mtc->nmask = allowed_mask;
1587
1588	return alloc_migration_target(page, (unsigned long)mtc);
1589}
1590
1591/*
1592 * Take folios on @demote_folios and attempt to demote them to another node.
1593 * Folios which are not demoted are left on @demote_folios.
1594 */
1595static unsigned int demote_folio_list(struct list_head *demote_folios,
1596				     struct pglist_data *pgdat)
 
1597{
1598	int target_nid = next_demotion_node(pgdat->node_id);
1599	unsigned int nr_succeeded;
1600	nodemask_t allowed_mask;
1601
1602	struct migration_target_control mtc = {
1603		/*
1604		 * Allocate from 'node', or fail quickly and quietly.
1605		 * When this happens, 'page' will likely just be discarded
1606		 * instead of migrated.
1607		 */
1608		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
1609			__GFP_NOMEMALLOC | GFP_NOWAIT,
1610		.nid = target_nid,
1611		.nmask = &allowed_mask
1612	};
1613
1614	if (list_empty(demote_folios))
1615		return 0;
1616
1617	if (target_nid == NUMA_NO_NODE)
1618		return 0;
1619
1620	node_get_allowed_targets(pgdat, &allowed_mask);
1621
1622	/* Demotion ignores all cpuset and mempolicy settings */
1623	migrate_pages(demote_folios, alloc_demote_page, NULL,
1624		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
1625		      &nr_succeeded);
1626
1627	__count_vm_events(PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded);
1628
1629	return nr_succeeded;
1630}
1631
1632static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
1633{
1634	if (gfp_mask & __GFP_FS)
1635		return true;
1636	if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
1637		return false;
1638	/*
1639	 * We can "enter_fs" for swap-cache with only __GFP_IO
1640	 * providing this isn't SWP_FS_OPS.
1641	 * ->flags can be updated non-atomicially (scan_swap_map_slots),
1642	 * but that will never affect SWP_FS_OPS, so the data_race
1643	 * is safe.
1644	 */
1645	return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
1646}
1647
1648/*
1649 * shrink_folio_list() returns the number of reclaimed pages
1650 */
1651static unsigned int shrink_folio_list(struct list_head *folio_list,
1652		struct pglist_data *pgdat, struct scan_control *sc,
1653		struct reclaim_stat *stat, bool ignore_references)
1654{
1655	LIST_HEAD(ret_folios);
1656	LIST_HEAD(free_folios);
1657	LIST_HEAD(demote_folios);
1658	unsigned int nr_reclaimed = 0;
1659	unsigned int pgactivate = 0;
1660	bool do_demote_pass;
1661	struct swap_iocb *plug = NULL;
1662
1663	memset(stat, 0, sizeof(*stat));
1664	cond_resched();
1665	do_demote_pass = can_demote(pgdat->node_id, sc);
1666
1667retry:
1668	while (!list_empty(folio_list)) {
1669		struct address_space *mapping;
1670		struct folio *folio;
1671		enum folio_references references = FOLIOREF_RECLAIM;
1672		bool dirty, writeback;
1673		unsigned int nr_pages;
1674
1675		cond_resched();
1676
1677		folio = lru_to_folio(folio_list);
1678		list_del(&folio->lru);
1679
1680		if (!folio_trylock(folio))
1681			goto keep;
1682
1683		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1684
1685		nr_pages = folio_nr_pages(folio);
1686
1687		/* Account the number of base pages */
1688		sc->nr_scanned += nr_pages;
1689
1690		if (unlikely(!folio_evictable(folio)))
1691			goto activate_locked;
1692
1693		if (!sc->may_unmap && folio_mapped(folio))
1694			goto keep_locked;
1695
1696		/* folio_update_gen() tried to promote this page? */
1697		if (lru_gen_enabled() && !ignore_references &&
1698		    folio_mapped(folio) && folio_test_referenced(folio))
1699			goto keep_locked;
1700
1701		/*
1702		 * The number of dirty pages determines if a node is marked
1703		 * reclaim_congested. kswapd will stall and start writing
1704		 * folios if the tail of the LRU is all dirty unqueued folios.
1705		 */
1706		folio_check_dirty_writeback(folio, &dirty, &writeback);
1707		if (dirty || writeback)
1708			stat->nr_dirty += nr_pages;
1709
1710		if (dirty && !writeback)
1711			stat->nr_unqueued_dirty += nr_pages;
1712
1713		/*
1714		 * Treat this folio as congested if folios are cycling
1715		 * through the LRU so quickly that the folios marked
1716		 * for immediate reclaim are making it to the end of
1717		 * the LRU a second time.
1718		 */
1719		if (writeback && folio_test_reclaim(folio))
1720			stat->nr_congested += nr_pages;
1721
1722		/*
1723		 * If a folio at the tail of the LRU is under writeback, there
1724		 * are three cases to consider.
1725		 *
1726		 * 1) If reclaim is encountering an excessive number
1727		 *    of folios under writeback and this folio has both
1728		 *    the writeback and reclaim flags set, then it
1729		 *    indicates that folios are being queued for I/O but
1730		 *    are being recycled through the LRU before the I/O
1731		 *    can complete. Waiting on the folio itself risks an
1732		 *    indefinite stall if it is impossible to writeback
1733		 *    the folio due to I/O error or disconnected storage
1734		 *    so instead note that the LRU is being scanned too
1735		 *    quickly and the caller can stall after the folio
1736		 *    list has been processed.
1737		 *
1738		 * 2) Global or new memcg reclaim encounters a folio that is
1739		 *    not marked for immediate reclaim, or the caller does not
1740		 *    have __GFP_FS (or __GFP_IO if it's simply going to swap,
1741		 *    not to fs). In this case mark the folio for immediate
1742		 *    reclaim and continue scanning.
1743		 *
1744		 *    Require may_enter_fs() because we would wait on fs, which
1745		 *    may not have submitted I/O yet. And the loop driver might
1746		 *    enter reclaim, and deadlock if it waits on a folio for
1747		 *    which it is needed to do the write (loop masks off
1748		 *    __GFP_IO|__GFP_FS for this reason); but more thought
1749		 *    would probably show more reasons.
1750		 *
1751		 * 3) Legacy memcg encounters a folio that already has the
1752		 *    reclaim flag set. memcg does not have any dirty folio
1753		 *    throttling so we could easily OOM just because too many
1754		 *    folios are in writeback and there is nothing else to
1755		 *    reclaim. Wait for the writeback to complete.
1756		 *
1757		 * In cases 1) and 2) we activate the folios to get them out of
1758		 * the way while we continue scanning for clean folios on the
1759		 * inactive list and refilling from the active list. The
1760		 * observation here is that waiting for disk writes is more
1761		 * expensive than potentially causing reloads down the line.
1762		 * Since they're marked for immediate reclaim, they won't put
1763		 * memory pressure on the cache working set any longer than it
1764		 * takes to write them to disk.
1765		 */
1766		if (folio_test_writeback(folio)) {
1767			/* Case 1 above */
1768			if (current_is_kswapd() &&
1769			    folio_test_reclaim(folio) &&
1770			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1771				stat->nr_immediate += nr_pages;
1772				goto activate_locked;
1773
1774			/* Case 2 above */
1775			} else if (writeback_throttling_sane(sc) ||
1776			    !folio_test_reclaim(folio) ||
1777			    !may_enter_fs(folio, sc->gfp_mask)) {
1778				/*
1779				 * This is slightly racy -
1780				 * folio_end_writeback() might have
1781				 * just cleared the reclaim flag, then
1782				 * setting the reclaim flag here ends up
1783				 * interpreted as the readahead flag - but
1784				 * that does not matter enough to care.
1785				 * What we do want is for this folio to
1786				 * have the reclaim flag set next time
1787				 * memcg reclaim reaches the tests above,
1788				 * so it will then wait for writeback to
1789				 * avoid OOM; and it's also appropriate
1790				 * in global reclaim.
1791				 */
1792				folio_set_reclaim(folio);
1793				stat->nr_writeback += nr_pages;
1794				goto activate_locked;
1795
1796			/* Case 3 above */
1797			} else {
1798				folio_unlock(folio);
1799				folio_wait_writeback(folio);
1800				/* then go back and try same folio again */
1801				list_add_tail(&folio->lru, folio_list);
1802				continue;
1803			}
1804		}
1805
1806		if (!ignore_references)
1807			references = folio_check_references(folio, sc);
1808
1809		switch (references) {
1810		case FOLIOREF_ACTIVATE:
1811			goto activate_locked;
1812		case FOLIOREF_KEEP:
1813			stat->nr_ref_keep += nr_pages;
1814			goto keep_locked;
1815		case FOLIOREF_RECLAIM:
1816		case FOLIOREF_RECLAIM_CLEAN:
1817			; /* try to reclaim the folio below */
1818		}
1819
1820		/*
1821		 * Before reclaiming the folio, try to relocate
1822		 * its contents to another node.
1823		 */
1824		if (do_demote_pass &&
1825		    (thp_migration_supported() || !folio_test_large(folio))) {
1826			list_add(&folio->lru, &demote_folios);
1827			folio_unlock(folio);
1828			continue;
1829		}
1830
1831		/*
1832		 * Anonymous process memory has backing store?
1833		 * Try to allocate it some swap space here.
1834		 * Lazyfree folio could be freed directly
1835		 */
1836		if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
1837			if (!folio_test_swapcache(folio)) {
1838				if (!(sc->gfp_mask & __GFP_IO))
1839					goto keep_locked;
1840				if (folio_maybe_dma_pinned(folio))
1841					goto keep_locked;
1842				if (folio_test_large(folio)) {
1843					/* cannot split folio, skip it */
1844					if (!can_split_folio(folio, NULL))
1845						goto activate_locked;
1846					/*
1847					 * Split folios without a PMD map right
1848					 * away. Chances are some or all of the
1849					 * tail pages can be freed without IO.
1850					 */
1851					if (!folio_entire_mapcount(folio) &&
1852					    split_folio_to_list(folio,
1853								folio_list))
1854						goto activate_locked;
1855				}
1856				if (!add_to_swap(folio)) {
1857					if (!folio_test_large(folio))
1858						goto activate_locked_split;
1859					/* Fallback to swap normal pages */
1860					if (split_folio_to_list(folio,
1861								folio_list))
1862						goto activate_locked;
1863#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1864					count_vm_event(THP_SWPOUT_FALLBACK);
1865#endif
1866					if (!add_to_swap(folio))
1867						goto activate_locked_split;
1868				}
1869			}
1870		} else if (folio_test_swapbacked(folio) &&
1871			   folio_test_large(folio)) {
1872			/* Split shmem folio */
1873			if (split_folio_to_list(folio, folio_list))
1874				goto keep_locked;
 
 
 
1875		}
1876
1877		/*
1878		 * If the folio was split above, the tail pages will make
1879		 * their own pass through this function and be accounted
1880		 * then.
1881		 */
1882		if ((nr_pages > 1) && !folio_test_large(folio)) {
1883			sc->nr_scanned -= (nr_pages - 1);
1884			nr_pages = 1;
1885		}
1886
1887		/*
1888		 * The folio is mapped into the page tables of one or more
1889		 * processes. Try to unmap it here.
1890		 */
1891		if (folio_mapped(folio)) {
1892			enum ttu_flags flags = TTU_BATCH_FLUSH;
1893			bool was_swapbacked = folio_test_swapbacked(folio);
1894
1895			if (folio_test_pmd_mappable(folio))
1896				flags |= TTU_SPLIT_HUGE_PMD;
1897
1898			try_to_unmap(folio, flags);
1899			if (folio_mapped(folio)) {
1900				stat->nr_unmap_fail += nr_pages;
1901				if (!was_swapbacked &&
1902				    folio_test_swapbacked(folio))
1903					stat->nr_lazyfree_fail += nr_pages;
1904				goto activate_locked;
 
 
 
 
 
 
1905			}
1906		}
1907
1908		mapping = folio_mapping(folio);
1909		if (folio_test_dirty(folio)) {
1910			/*
1911			 * Only kswapd can writeback filesystem folios
1912			 * to avoid risk of stack overflow. But avoid
1913			 * injecting inefficient single-folio I/O into
1914			 * flusher writeback as much as possible: only
1915			 * write folios when we've encountered many
1916			 * dirty folios, and when we've already scanned
1917			 * the rest of the LRU for clean folios and see
1918			 * the same dirty folios again (with the reclaim
1919			 * flag set).
1920			 */
1921			if (folio_is_file_lru(folio) &&
1922			    (!current_is_kswapd() ||
1923			     !folio_test_reclaim(folio) ||
1924			     !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1925				/*
1926				 * Immediately reclaim when written back.
1927				 * Similar in principle to deactivate_page()
1928				 * except we already have the folio isolated
1929				 * and know it's dirty
1930				 */
1931				node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
1932						nr_pages);
1933				folio_set_reclaim(folio);
1934
1935				goto activate_locked;
1936			}
1937
1938			if (references == FOLIOREF_RECLAIM_CLEAN)
1939				goto keep_locked;
1940			if (!may_enter_fs(folio, sc->gfp_mask))
1941				goto keep_locked;
1942			if (!sc->may_writepage)
1943				goto keep_locked;
1944
1945			/*
1946			 * Folio is dirty. Flush the TLB if a writable entry
1947			 * potentially exists to avoid CPU writes after I/O
1948			 * starts and then write it out here.
1949			 */
1950			try_to_unmap_flush_dirty();
1951			switch (pageout(folio, mapping, &plug)) {
1952			case PAGE_KEEP:
 
1953				goto keep_locked;
1954			case PAGE_ACTIVATE:
1955				goto activate_locked;
1956			case PAGE_SUCCESS:
1957				stat->nr_pageout += nr_pages;
1958
1959				if (folio_test_writeback(folio))
1960					goto keep;
1961				if (folio_test_dirty(folio))
1962					goto keep;
1963
1964				/*
1965				 * A synchronous write - probably a ramdisk.  Go
1966				 * ahead and try to reclaim the folio.
1967				 */
1968				if (!folio_trylock(folio))
1969					goto keep;
1970				if (folio_test_dirty(folio) ||
1971				    folio_test_writeback(folio))
1972					goto keep_locked;
1973				mapping = folio_mapping(folio);
1974				fallthrough;
1975			case PAGE_CLEAN:
1976				; /* try to free the folio below */
1977			}
1978		}
1979
1980		/*
1981		 * If the folio has buffers, try to free the buffer
1982		 * mappings associated with this folio. If we succeed
1983		 * we try to free the folio as well.
1984		 *
1985		 * We do this even if the folio is dirty.
1986		 * filemap_release_folio() does not perform I/O, but it
1987		 * is possible for a folio to have the dirty flag set,
1988		 * but it is actually clean (all its buffers are clean).
1989		 * This happens if the buffers were written out directly,
1990		 * with submit_bh(). ext3 will do this, as well as
1991		 * the blockdev mapping.  filemap_release_folio() will
1992		 * discover that cleanness and will drop the buffers
1993		 * and mark the folio clean - it can be freed.
1994		 *
1995		 * Rarely, folios can have buffers and no ->mapping.
1996		 * These are the folios which were not successfully
1997		 * invalidated in truncate_cleanup_folio().  We try to
1998		 * drop those buffers here and if that worked, and the
1999		 * folio is no longer mapped into process address space
2000		 * (refcount == 1) it can be freed.  Otherwise, leave
2001		 * the folio on the LRU so it is swappable.
2002		 */
2003		if (folio_has_private(folio)) {
2004			if (!filemap_release_folio(folio, sc->gfp_mask))
2005				goto activate_locked;
2006			if (!mapping && folio_ref_count(folio) == 1) {
2007				folio_unlock(folio);
2008				if (folio_put_testzero(folio))
2009					goto free_it;
2010				else {
2011					/*
2012					 * rare race with speculative reference.
2013					 * the speculative reference will free
2014					 * this folio shortly, so we may
2015					 * increment nr_reclaimed here (and
2016					 * leave it off the LRU).
2017					 */
2018					nr_reclaimed += nr_pages;
2019					continue;
2020				}
2021			}
2022		}
2023
2024		if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
2025			/* follow __remove_mapping for reference */
2026			if (!folio_ref_freeze(folio, 1))
2027				goto keep_locked;
2028			/*
2029			 * The folio has only one reference left, which is
2030			 * from the isolation. After the caller puts the
2031			 * folio back on the lru and drops the reference, the
2032			 * folio will be freed anyway. It doesn't matter
2033			 * which lru it goes on. So we don't bother checking
2034			 * the dirty flag here.
2035			 */
2036			count_vm_events(PGLAZYFREED, nr_pages);
2037			count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
2038		} else if (!mapping || !__remove_mapping(mapping, folio, true,
2039							 sc->target_mem_cgroup))
2040			goto keep_locked;
2041
2042		folio_unlock(folio);
2043free_it:
2044		/*
2045		 * Folio may get swapped out as a whole, need to account
2046		 * all pages in it.
 
 
 
2047		 */
2048		nr_reclaimed += nr_pages;
 
 
2049
2050		/*
2051		 * Is there need to periodically free_folio_list? It would
2052		 * appear not as the counts should be low
2053		 */
2054		if (unlikely(folio_test_large(folio)))
2055			destroy_large_folio(folio);
2056		else
2057			list_add(&folio->lru, &free_folios);
 
 
 
 
 
2058		continue;
2059
2060activate_locked_split:
2061		/*
2062		 * The tail pages that are failed to add into swap cache
2063		 * reach here.  Fixup nr_scanned and nr_pages.
2064		 */
2065		if (nr_pages > 1) {
2066			sc->nr_scanned -= (nr_pages - 1);
2067			nr_pages = 1;
2068		}
2069activate_locked:
2070		/* Not a candidate for swapping, so reclaim swap space. */
2071		if (folio_test_swapcache(folio) &&
2072		    (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
2073			folio_free_swap(folio);
2074		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
2075		if (!folio_test_mlocked(folio)) {
2076			int type = folio_is_file_lru(folio);
2077			folio_set_active(folio);
2078			stat->nr_activate[type] += nr_pages;
2079			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
2080		}
2081keep_locked:
2082		folio_unlock(folio);
2083keep:
2084		list_add(&folio->lru, &ret_folios);
2085		VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
2086				folio_test_unevictable(folio), folio);
2087	}
2088	/* 'folio_list' is always empty here */
2089
2090	/* Migrate folios selected for demotion */
2091	nr_reclaimed += demote_folio_list(&demote_folios, pgdat);
2092	/* Folios that could not be demoted are still in @demote_folios */
2093	if (!list_empty(&demote_folios)) {
2094		/* Folios which weren't demoted go back on @folio_list */
2095		list_splice_init(&demote_folios, folio_list);
2096
2097		/*
2098		 * goto retry to reclaim the undemoted folios in folio_list if
2099		 * desired.
2100		 *
2101		 * Reclaiming directly from top tier nodes is not often desired
2102		 * due to it breaking the LRU ordering: in general memory
2103		 * should be reclaimed from lower tier nodes and demoted from
2104		 * top tier nodes.
2105		 *
2106		 * However, disabling reclaim from top tier nodes entirely
2107		 * would cause ooms in edge scenarios where lower tier memory
2108		 * is unreclaimable for whatever reason, eg memory being
2109		 * mlocked or too hot to reclaim. We can disable reclaim
2110		 * from top tier nodes in proactive reclaim though as that is
2111		 * not real memory pressure.
2112		 */
2113		if (!sc->proactive) {
2114			do_demote_pass = false;
2115			goto retry;
2116		}
2117	}
2118
2119	pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
 
 
 
 
 
 
 
2120
2121	mem_cgroup_uncharge_list(&free_folios);
2122	try_to_unmap_flush();
2123	free_unref_page_list(&free_folios);
2124
2125	list_splice(&ret_folios, folio_list);
2126	count_vm_events(PGACTIVATE, pgactivate);
2127
2128	if (plug)
2129		swap_write_unplug(plug);
2130	return nr_reclaimed;
2131}
2132
2133unsigned int reclaim_clean_pages_from_list(struct zone *zone,
2134					   struct list_head *folio_list)
 
 
 
 
 
 
 
 
 
2135{
2136	struct scan_control sc = {
2137		.gfp_mask = GFP_KERNEL,
2138		.may_unmap = 1,
2139	};
2140	struct reclaim_stat stat;
2141	unsigned int nr_reclaimed;
2142	struct folio *folio, *next;
2143	LIST_HEAD(clean_folios);
2144	unsigned int noreclaim_flag;
2145
2146	list_for_each_entry_safe(folio, next, folio_list, lru) {
2147		if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
2148		    !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
2149		    !folio_test_unevictable(folio)) {
2150			folio_clear_active(folio);
2151			list_move(&folio->lru, &clean_folios);
2152		}
2153	}
2154
2155	/*
2156	 * We should be safe here since we are only dealing with file pages and
2157	 * we are not kswapd and therefore cannot write dirty file pages. But
2158	 * call memalloc_noreclaim_save() anyway, just in case these conditions
2159	 * change in the future.
2160	 */
2161	noreclaim_flag = memalloc_noreclaim_save();
2162	nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
2163					&stat, true);
2164	memalloc_noreclaim_restore(noreclaim_flag);
2165
2166	list_splice(&clean_folios, folio_list);
2167	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
2168			    -(long)nr_reclaimed);
2169	/*
2170	 * Since lazyfree pages are isolated from file LRU from the beginning,
2171	 * they will rotate back to anonymous LRU in the end if it failed to
2172	 * discard so isolated count will be mismatched.
2173	 * Compensate the isolated count for both LRU lists.
2174	 */
2175	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
2176			    stat.nr_lazyfree_fail);
2177	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
2178			    -(long)stat.nr_lazyfree_fail);
2179	return nr_reclaimed;
2180}
2181
2182/*
2183 * Update LRU sizes after isolating pages. The LRU size updates must
2184 * be complete before mem_cgroup_update_lru_size due to a sanity check.
2185 */
2186static __always_inline void update_lru_sizes(struct lruvec *lruvec,
2187			enum lru_list lru, unsigned long *nr_zone_taken)
2188{
2189	int zid;
2190
2191	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
2192		if (!nr_zone_taken[zid])
2193			continue;
2194
2195		update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
 
 
 
 
 
 
 
2196	}
2197
 
2198}
2199
2200/*
2201 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
2202 *
2203 * lruvec->lru_lock is heavily contended.  Some of the functions that
2204 * shrink the lists perform better by taking out a batch of pages
2205 * and working on them outside the LRU lock.
2206 *
2207 * For pagecache intensive workloads, this function is the hottest
2208 * spot in the kernel (apart from copy_*_user functions).
2209 *
2210 * Lru_lock must be held before calling this function.
2211 *
2212 * @nr_to_scan:	The number of eligible pages to look through on the list.
2213 * @lruvec:	The LRU vector to pull pages from.
2214 * @dst:	The temp list to put pages on to.
2215 * @nr_scanned:	The number of pages that were scanned.
2216 * @sc:		The scan_control struct for this reclaim session
2217 * @lru:	LRU list id for isolating
 
2218 *
2219 * returns how many pages were moved onto *@dst.
2220 */
2221static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
2222		struct lruvec *lruvec, struct list_head *dst,
2223		unsigned long *nr_scanned, struct scan_control *sc,
2224		enum lru_list lru)
2225{
2226	struct list_head *src = &lruvec->lists[lru];
2227	unsigned long nr_taken = 0;
2228	unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
2229	unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
2230	unsigned long skipped = 0;
2231	unsigned long scan, total_scan, nr_pages;
2232	LIST_HEAD(folios_skipped);
2233
2234	total_scan = 0;
2235	scan = 0;
2236	while (scan < nr_to_scan && !list_empty(src)) {
2237		struct list_head *move_to = src;
2238		struct folio *folio;
2239
2240		folio = lru_to_folio(src);
2241		prefetchw_prev_lru_folio(folio, src, flags);
2242
2243		nr_pages = folio_nr_pages(folio);
2244		total_scan += nr_pages;
 
 
 
 
 
 
 
 
 
 
 
 
 
2245
2246		if (folio_zonenum(folio) > sc->reclaim_idx) {
2247			nr_skipped[folio_zonenum(folio)] += nr_pages;
2248			move_to = &folios_skipped;
2249			goto move;
2250		}
2251
 
 
 
2252		/*
2253		 * Do not count skipped folios because that makes the function
2254		 * return with no isolated folios if the LRU mostly contains
2255		 * ineligible folios.  This causes the VM to not reclaim any
2256		 * folios, triggering a premature OOM.
2257		 * Account all pages in a folio.
2258		 */
2259		scan += nr_pages;
 
 
 
 
 
 
 
2260
2261		if (!folio_test_lru(folio))
2262			goto move;
2263		if (!sc->may_unmap && folio_mapped(folio))
2264			goto move;
2265
2266		/*
2267		 * Be careful not to clear the lru flag until after we're
2268		 * sure the folio is not being freed elsewhere -- the
2269		 * folio release code relies on it.
2270		 */
2271		if (unlikely(!folio_try_get(folio)))
2272			goto move;
2273
2274		if (!folio_test_clear_lru(folio)) {
2275			/* Another thread is already isolating this folio */
2276			folio_put(folio);
2277			goto move;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2278		}
2279
2280		nr_taken += nr_pages;
2281		nr_zone_taken[folio_zonenum(folio)] += nr_pages;
2282		move_to = dst;
2283move:
2284		list_move(&folio->lru, move_to);
2285	}
2286
2287	/*
2288	 * Splice any skipped folios to the start of the LRU list. Note that
2289	 * this disrupts the LRU order when reclaiming for lower zones but
2290	 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
2291	 * scanning would soon rescan the same folios to skip and waste lots
2292	 * of cpu cycles.
2293	 */
2294	if (!list_empty(&folios_skipped)) {
2295		int zid;
2296
2297		list_splice(&folios_skipped, src);
2298		for (zid = 0; zid < MAX_NR_ZONES; zid++) {
2299			if (!nr_skipped[zid])
2300				continue;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2301
2302			__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
2303			skipped += nr_skipped[zid];
 
 
 
 
 
2304		}
 
 
2305	}
2306	*nr_scanned = total_scan;
2307	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
2308				    total_scan, skipped, nr_taken,
2309				    sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru);
2310	update_lru_sizes(lruvec, lru, nr_zone_taken);
2311	return nr_taken;
2312}
2313
2314/**
2315 * folio_isolate_lru() - Try to isolate a folio from its LRU list.
2316 * @folio: Folio to isolate from its LRU list.
2317 *
2318 * Isolate a @folio from an LRU list and adjust the vmstat statistic
2319 * corresponding to whatever LRU list the folio was on.
2320 *
2321 * The folio will have its LRU flag cleared.  If it was found on the
2322 * active list, it will have the Active flag set.  If it was found on the
2323 * unevictable list, it will have the Unevictable flag set.  These flags
 
 
 
2324 * may need to be cleared by the caller before letting the page go.
2325 *
2326 * Context:
 
2327 *
2328 * (1) Must be called with an elevated refcount on the folio. This is a
2329 *     fundamental difference from isolate_lru_folios() (which is called
 
2330 *     without a stable reference).
2331 * (2) The lru_lock must not be held.
2332 * (3) Interrupts must be enabled.
2333 *
2334 * Return: 0 if the folio was removed from an LRU list.
2335 * -EBUSY if the folio was not on an LRU list.
2336 */
2337int folio_isolate_lru(struct folio *folio)
2338{
2339	int ret = -EBUSY;
2340
2341	VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
2342
2343	if (folio_test_clear_lru(folio)) {
2344		struct lruvec *lruvec;
2345
2346		folio_get(folio);
2347		lruvec = folio_lruvec_lock_irq(folio);
2348		lruvec_del_folio(lruvec, folio);
2349		unlock_page_lruvec_irq(lruvec);
2350		ret = 0;
2351	}
2352
 
 
 
 
2353	return ret;
2354}
2355
2356/*
2357 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
2358 * then get rescheduled. When there are massive number of tasks doing page
2359 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
2360 * the LRU list will go small and be scanned faster than necessary, leading to
2361 * unnecessary swapping, thrashing and OOM.
2362 */
2363static int too_many_isolated(struct pglist_data *pgdat, int file,
2364		struct scan_control *sc)
2365{
2366	unsigned long inactive, isolated;
2367	bool too_many;
2368
2369	if (current_is_kswapd())
2370		return 0;
2371
2372	if (!writeback_throttling_sane(sc))
2373		return 0;
2374
2375	if (file) {
2376		inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
2377		isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
2378	} else {
2379		inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
2380		isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
2381	}
2382
2383	/*
2384	 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2385	 * won't get blocked by normal direct-reclaimers, forming a circular
2386	 * deadlock.
2387	 */
2388	if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
2389		inactive >>= 3;
2390
2391	too_many = isolated > inactive;
2392
2393	/* Wake up tasks throttled due to too_many_isolated. */
2394	if (!too_many)
2395		wake_throttle_isolated(pgdat);
2396
2397	return too_many;
2398}
2399
2400/*
2401 * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
2402 * On return, @list is reused as a list of folios to be freed by the caller.
2403 *
2404 * Returns the number of pages moved to the given lruvec.
2405 */
2406static unsigned int move_folios_to_lru(struct lruvec *lruvec,
2407		struct list_head *list)
 
 
2408{
2409	int nr_pages, nr_moved = 0;
2410	LIST_HEAD(folios_to_free);
2411
2412	while (!list_empty(list)) {
2413		struct folio *folio = lru_to_folio(list);
2414
2415		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
2416		list_del(&folio->lru);
2417		if (unlikely(!folio_evictable(folio))) {
2418			spin_unlock_irq(&lruvec->lru_lock);
2419			folio_putback_lru(folio);
2420			spin_lock_irq(&lruvec->lru_lock);
2421			continue;
2422		}
2423
2424		/*
2425		 * The folio_set_lru needs to be kept here for list integrity.
2426		 * Otherwise:
2427		 *   #0 move_folios_to_lru             #1 release_pages
2428		 *   if (!folio_put_testzero())
2429		 *				      if (folio_put_testzero())
2430		 *				        !lru //skip lru_lock
2431		 *     folio_set_lru()
2432		 *     list_add(&folio->lru,)
2433		 *                                        list_add(&folio->lru,)
2434		 */
2435		folio_set_lru(folio);
2436
2437		if (unlikely(folio_put_testzero(folio))) {
2438			__folio_clear_lru_flags(folio);
2439
2440			if (unlikely(folio_test_large(folio))) {
2441				spin_unlock_irq(&lruvec->lru_lock);
2442				destroy_large_folio(folio);
2443				spin_lock_irq(&lruvec->lru_lock);
2444			} else
2445				list_add(&folio->lru, &folios_to_free);
2446
2447			continue;
2448		}
2449
2450		/*
2451		 * All pages were isolated from the same lruvec (and isolation
2452		 * inhibits memcg migration).
2453		 */
2454		VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
2455		lruvec_add_folio(lruvec, folio);
2456		nr_pages = folio_nr_pages(folio);
2457		nr_moved += nr_pages;
2458		if (folio_test_active(folio))
2459			workingset_age_nonresident(lruvec, nr_pages);
2460	}
2461
2462	/*
2463	 * To save our caller's stack, now use input list for pages to free.
2464	 */
2465	list_splice(&folios_to_free, list);
2466
2467	return nr_moved;
2468}
2469
2470/*
2471 * If a kernel thread (such as nfsd for loop-back mounts) services a backing
2472 * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
2473 * we should not throttle.  Otherwise it is safe to do so.
2474 */
2475static int current_may_throttle(void)
2476{
2477	return !(current->flags & PF_LOCAL_THROTTLE);
2478}
2479
2480/*
2481 * shrink_inactive_list() is a helper for shrink_node().  It returns the number
2482 * of reclaimed pages
2483 */
2484static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
2485		struct lruvec *lruvec, struct scan_control *sc,
2486		enum lru_list lru)
2487{
2488	LIST_HEAD(folio_list);
2489	unsigned long nr_scanned;
2490	unsigned int nr_reclaimed = 0;
2491	unsigned long nr_taken;
2492	struct reclaim_stat stat;
2493	bool file = is_file_lru(lru);
2494	enum vm_event_item item;
2495	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2496	bool stalled = false;
2497
2498	while (unlikely(too_many_isolated(pgdat, file, sc))) {
2499		if (stalled)
2500			return 0;
2501
2502		/* wait a bit for the reclaimer. */
2503		stalled = true;
2504		reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
2505
2506		/* We are about to die and free our memory. Return now. */
2507		if (fatal_signal_pending(current))
2508			return SWAP_CLUSTER_MAX;
2509	}
2510
2511	lru_add_drain();
2512
2513	spin_lock_irq(&lruvec->lru_lock);
2514
2515	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
2516				     &nr_scanned, sc, lru);
2517
2518	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2519	item = PGSCAN_KSWAPD + reclaimer_offset();
2520	if (!cgroup_reclaim(sc))
2521		__count_vm_events(item, nr_scanned);
2522	__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
2523	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
2524
2525	spin_unlock_irq(&lruvec->lru_lock);
2526
2527	if (nr_taken == 0)
2528		return 0;
2529
2530	nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
2531
2532	spin_lock_irq(&lruvec->lru_lock);
2533	move_folios_to_lru(lruvec, &folio_list);
2534
2535	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2536	item = PGSTEAL_KSWAPD + reclaimer_offset();
2537	if (!cgroup_reclaim(sc))
2538		__count_vm_events(item, nr_reclaimed);
2539	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
2540	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
2541	spin_unlock_irq(&lruvec->lru_lock);
2542
2543	lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
2544	mem_cgroup_uncharge_list(&folio_list);
2545	free_unref_page_list(&folio_list);
2546
2547	/*
2548	 * If dirty folios are scanned that are not queued for IO, it
2549	 * implies that flushers are not doing their job. This can
2550	 * happen when memory pressure pushes dirty folios to the end of
2551	 * the LRU before the dirty limits are breached and the dirty
2552	 * data has expired. It can also happen when the proportion of
2553	 * dirty folios grows not through writes but through memory
2554	 * pressure reclaiming all the clean cache. And in some cases,
2555	 * the flushers simply cannot keep up with the allocation
2556	 * rate. Nudge the flusher threads in case they are asleep.
2557	 */
2558	if (stat.nr_unqueued_dirty == nr_taken) {
2559		wakeup_flusher_threads(WB_REASON_VMSCAN);
2560		/*
2561		 * For cgroupv1 dirty throttling is achieved by waking up
2562		 * the kernel flusher here and later waiting on folios
2563		 * which are in writeback to finish (see shrink_folio_list()).
2564		 *
2565		 * Flusher may not be able to issue writeback quickly
2566		 * enough for cgroupv1 writeback throttling to work
2567		 * on a large system.
2568		 */
2569		if (!writeback_throttling_sane(sc))
2570			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
2571	}
2572
2573	sc->nr.dirty += stat.nr_dirty;
2574	sc->nr.congested += stat.nr_congested;
2575	sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
2576	sc->nr.writeback += stat.nr_writeback;
2577	sc->nr.immediate += stat.nr_immediate;
2578	sc->nr.taken += nr_taken;
2579	if (file)
2580		sc->nr.file_taken += nr_taken;
2581
2582	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
2583			nr_scanned, nr_reclaimed, &stat, sc->priority, file);
2584	return nr_reclaimed;
2585}
2586
2587/*
2588 * shrink_active_list() moves folios from the active LRU to the inactive LRU.
2589 *
2590 * We move them the other way if the folio is referenced by one or more
2591 * processes.
2592 *
2593 * If the folios are mostly unmapped, the processing is fast and it is
2594 * appropriate to hold lru_lock across the whole operation.  But if
2595 * the folios are mapped, the processing is slow (folio_referenced()), so
2596 * we should drop lru_lock around each folio.  It's impossible to balance
2597 * this, so instead we remove the folios from the LRU while processing them.
2598 * It is safe to rely on the active flag against the non-LRU folios in here
2599 * because nobody will play with that bit on a non-LRU folio.
2600 *
2601 * The downside is that we have to touch folio->_refcount against each folio.
2602 * But we had to alter folio->flags anyway.
2603 */
2604static void shrink_active_list(unsigned long nr_to_scan,
2605			       struct lruvec *lruvec,
2606			       struct scan_control *sc,
2607			       enum lru_list lru)
2608{
2609	unsigned long nr_taken;
2610	unsigned long nr_scanned;
2611	unsigned long vm_flags;
2612	LIST_HEAD(l_hold);	/* The folios which were snipped off */
2613	LIST_HEAD(l_active);
2614	LIST_HEAD(l_inactive);
2615	unsigned nr_deactivate, nr_activate;
2616	unsigned nr_rotated = 0;
2617	int file = is_file_lru(lru);
2618	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2619
2620	lru_add_drain();
2621
2622	spin_lock_irq(&lruvec->lru_lock);
2623
2624	nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
2625				     &nr_scanned, sc, lru);
2626
2627	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2628
2629	if (!cgroup_reclaim(sc))
2630		__count_vm_events(PGREFILL, nr_scanned);
2631	__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2632
2633	spin_unlock_irq(&lruvec->lru_lock);
2634
2635	while (!list_empty(&l_hold)) {
2636		struct folio *folio;
2637
2638		cond_resched();
2639		folio = lru_to_folio(&l_hold);
2640		list_del(&folio->lru);
2641
2642		if (unlikely(!folio_evictable(folio))) {
2643			folio_putback_lru(folio);
2644			continue;
2645		}
2646
2647		if (unlikely(buffer_heads_over_limit)) {
2648			if (folio_test_private(folio) && folio_trylock(folio)) {
2649				if (folio_test_private(folio))
2650					filemap_release_folio(folio, 0);
2651				folio_unlock(folio);
2652			}
2653		}
2654
2655		/* Referenced or rmap lock contention: rotate */
2656		if (folio_referenced(folio, 0, sc->target_mem_cgroup,
2657				     &vm_flags) != 0) {
2658			/*
2659			 * Identify referenced, file-backed active folios and
2660			 * give them one more trip around the active list. So
2661			 * that executable code get better chances to stay in
2662			 * memory under moderate memory pressure.  Anon folios
2663			 * are not likely to be evicted by use-once streaming
2664			 * IO, plus JVM can create lots of anon VM_EXEC folios,
2665			 * so we ignore them here.
2666			 */
2667			if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
2668				nr_rotated += folio_nr_pages(folio);
2669				list_add(&folio->lru, &l_active);
2670				continue;
2671			}
2672		}
2673
2674		folio_clear_active(folio);	/* we are de-activating */
2675		folio_set_workingset(folio);
2676		list_add(&folio->lru, &l_inactive);
2677	}
 
 
2678
2679	/*
2680	 * Move folios back to the lru list.
2681	 */
2682	spin_lock_irq(&lruvec->lru_lock);
2683
2684	nr_activate = move_folios_to_lru(lruvec, &l_active);
2685	nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
2686	/* Keep all free folios in l_active list */
2687	list_splice(&l_inactive, &l_active);
2688
2689	__count_vm_events(PGDEACTIVATE, nr_deactivate);
2690	__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2691
2692	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2693	spin_unlock_irq(&lruvec->lru_lock);
2694
2695	if (nr_rotated)
2696		lru_note_cost(lruvec, file, 0, nr_rotated);
2697	mem_cgroup_uncharge_list(&l_active);
2698	free_unref_page_list(&l_active);
2699	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2700			nr_deactivate, nr_rotated, sc->priority, file);
2701}
2702
2703static unsigned int reclaim_folio_list(struct list_head *folio_list,
2704				      struct pglist_data *pgdat)
 
 
 
2705{
2706	struct reclaim_stat dummy_stat;
2707	unsigned int nr_reclaimed;
2708	struct folio *folio;
2709	struct scan_control sc = {
2710		.gfp_mask = GFP_KERNEL,
2711		.may_writepage = 1,
2712		.may_unmap = 1,
2713		.may_swap = 1,
2714		.no_demotion = 1,
2715	};
2716
2717	nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
2718	while (!list_empty(folio_list)) {
2719		folio = lru_to_folio(folio_list);
2720		list_del(&folio->lru);
2721		folio_putback_lru(folio);
2722	}
2723
2724	return nr_reclaimed;
2725}
2726
2727unsigned long reclaim_pages(struct list_head *folio_list)
2728{
2729	int nid;
2730	unsigned int nr_reclaimed = 0;
2731	LIST_HEAD(node_folio_list);
2732	unsigned int noreclaim_flag;
2733
2734	if (list_empty(folio_list))
2735		return nr_reclaimed;
2736
2737	noreclaim_flag = memalloc_noreclaim_save();
2738
2739	nid = folio_nid(lru_to_folio(folio_list));
2740	do {
2741		struct folio *folio = lru_to_folio(folio_list);
2742
2743		if (nid == folio_nid(folio)) {
2744			folio_clear_active(folio);
2745			list_move(&folio->lru, &node_folio_list);
2746			continue;
2747		}
2748
2749		nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2750		nid = folio_nid(lru_to_folio(folio_list));
2751	} while (!list_empty(folio_list));
 
2752
2753	nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2754
2755	memalloc_noreclaim_restore(noreclaim_flag);
2756
2757	return nr_reclaimed;
2758}
2759
2760static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2761				 struct lruvec *lruvec, struct scan_control *sc)
2762{
2763	if (is_active_lru(lru)) {
2764		if (sc->may_deactivate & (1 << is_file_lru(lru)))
2765			shrink_active_list(nr_to_scan, lruvec, sc, lru);
2766		else
2767			sc->skipped_deactivate = 1;
2768		return 0;
2769	}
2770
2771	return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2772}
2773
2774/*
2775 * The inactive anon list should be small enough that the VM never has
2776 * to do too much work.
2777 *
2778 * The inactive file list should be small enough to leave most memory
2779 * to the established workingset on the scan-resistant active list,
2780 * but large enough to avoid thrashing the aggregate readahead window.
2781 *
2782 * Both inactive lists should also be large enough that each inactive
2783 * folio has a chance to be referenced again before it is reclaimed.
2784 *
2785 * If that fails and refaulting is observed, the inactive list grows.
2786 *
2787 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2788 * on this LRU, maintained by the pageout code. An inactive_ratio
2789 * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2790 *
2791 * total     target    max
2792 * memory    ratio     inactive
2793 * -------------------------------------
2794 *   10MB       1         5MB
2795 *  100MB       1        50MB
2796 *    1GB       3       250MB
2797 *   10GB      10       0.9GB
2798 *  100GB      31         3GB
2799 *    1TB     101        10GB
2800 *   10TB     320        32GB
2801 */
2802static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
2803{
2804	enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
2805	unsigned long inactive, active;
2806	unsigned long inactive_ratio;
2807	unsigned long gb;
2808
2809	inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
2810	active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
2811
2812	gb = (inactive + active) >> (30 - PAGE_SHIFT);
2813	if (gb)
2814		inactive_ratio = int_sqrt(10 * gb);
2815	else
2816		inactive_ratio = 1;
2817
2818	return inactive * inactive_ratio < active;
2819}
2820
2821enum scan_balance {
2822	SCAN_EQUAL,
2823	SCAN_FRACT,
2824	SCAN_ANON,
2825	SCAN_FILE,
2826};
2827
2828static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
2829{
2830	unsigned long file;
2831	struct lruvec *target_lruvec;
2832
2833	if (lru_gen_enabled())
2834		return;
2835
2836	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
2837
2838	/*
2839	 * Flush the memory cgroup stats, so that we read accurate per-memcg
2840	 * lruvec stats for heuristics.
2841	 */
2842	mem_cgroup_flush_stats();
2843
2844	/*
2845	 * Determine the scan balance between anon and file LRUs.
2846	 */
2847	spin_lock_irq(&target_lruvec->lru_lock);
2848	sc->anon_cost = target_lruvec->anon_cost;
2849	sc->file_cost = target_lruvec->file_cost;
2850	spin_unlock_irq(&target_lruvec->lru_lock);
2851
2852	/*
2853	 * Target desirable inactive:active list ratios for the anon
2854	 * and file LRU lists.
2855	 */
2856	if (!sc->force_deactivate) {
2857		unsigned long refaults;
2858
2859		/*
2860		 * When refaults are being observed, it means a new
2861		 * workingset is being established. Deactivate to get
2862		 * rid of any stale active pages quickly.
2863		 */
2864		refaults = lruvec_page_state(target_lruvec,
2865				WORKINGSET_ACTIVATE_ANON);
2866		if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
2867			inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
2868			sc->may_deactivate |= DEACTIVATE_ANON;
2869		else
2870			sc->may_deactivate &= ~DEACTIVATE_ANON;
2871
2872		refaults = lruvec_page_state(target_lruvec,
2873				WORKINGSET_ACTIVATE_FILE);
2874		if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
2875		    inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
2876			sc->may_deactivate |= DEACTIVATE_FILE;
2877		else
2878			sc->may_deactivate &= ~DEACTIVATE_FILE;
2879	} else
2880		sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
2881
2882	/*
2883	 * If we have plenty of inactive file pages that aren't
2884	 * thrashing, try to reclaim those first before touching
2885	 * anonymous pages.
 
2886	 */
2887	file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
2888	if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
2889		sc->cache_trim_mode = 1;
2890	else
2891		sc->cache_trim_mode = 0;
2892
2893	/*
2894	 * Prevent the reclaimer from falling into the cache trap: as
2895	 * cache pages start out inactive, every cache fault will tip
2896	 * the scan balance towards the file LRU.  And as the file LRU
2897	 * shrinks, so does the window for rotation from references.
2898	 * This means we have a runaway feedback loop where a tiny
2899	 * thrashing file LRU becomes infinitely more attractive than
2900	 * anon pages.  Try to detect this based on file LRU size.
2901	 */
2902	if (!cgroup_reclaim(sc)) {
2903		unsigned long total_high_wmark = 0;
2904		unsigned long free, anon;
2905		int z;
2906
2907		free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2908		file = node_page_state(pgdat, NR_ACTIVE_FILE) +
2909			   node_page_state(pgdat, NR_INACTIVE_FILE);
2910
2911		for (z = 0; z < MAX_NR_ZONES; z++) {
2912			struct zone *zone = &pgdat->node_zones[z];
2913
2914			if (!managed_zone(zone))
2915				continue;
2916
2917			total_high_wmark += high_wmark_pages(zone);
2918		}
2919
2920		/*
2921		 * Consider anon: if that's low too, this isn't a
2922		 * runaway file reclaim problem, but rather just
2923		 * extreme pressure. Reclaim as per usual then.
2924		 */
2925		anon = node_page_state(pgdat, NR_INACTIVE_ANON);
2926
2927		sc->file_is_tiny =
2928			file + free <= total_high_wmark &&
2929			!(sc->may_deactivate & DEACTIVATE_ANON) &&
2930			anon >> sc->priority;
2931	}
2932}
2933
2934/*
2935 * Determine how aggressively the anon and file LRU lists should be
2936 * scanned.
2937 *
2938 * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
2939 * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
2940 */
2941static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
2942			   unsigned long *nr)
 
2943{
2944	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2945	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2946	unsigned long anon_cost, file_cost, total_cost;
2947	int swappiness = mem_cgroup_swappiness(memcg);
2948	u64 fraction[ANON_AND_FILE];
2949	u64 denominator = 0;	/* gcc */
2950	enum scan_balance scan_balance;
2951	unsigned long ap, fp;
2952	enum lru_list lru;
2953
2954	/* If we have no swap space, do not bother scanning anon folios. */
2955	if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
2956		scan_balance = SCAN_FILE;
2957		goto out;
2958	}
2959
2960	/*
2961	 * Global reclaim will swap to prevent OOM even with no
2962	 * swappiness, but memcg users want to use this knob to
2963	 * disable swapping for individual groups completely when
2964	 * using the memory controller's swap limit feature would be
2965	 * too expensive.
2966	 */
2967	if (cgroup_reclaim(sc) && !swappiness) {
2968		scan_balance = SCAN_FILE;
2969		goto out;
2970	}
2971
2972	/*
2973	 * Do not apply any pressure balancing cleverness when the
2974	 * system is close to OOM, scan both anon and file equally
2975	 * (unless the swappiness setting disagrees with swapping).
2976	 */
2977	if (!sc->priority && swappiness) {
2978		scan_balance = SCAN_EQUAL;
2979		goto out;
2980	}
2981
2982	/*
2983	 * If the system is almost out of file pages, force-scan anon.
2984	 */
2985	if (sc->file_is_tiny) {
2986		scan_balance = SCAN_ANON;
2987		goto out;
2988	}
2989
2990	/*
2991	 * If there is enough inactive page cache, we do not reclaim
2992	 * anything from the anonymous working right now.
2993	 */
2994	if (sc->cache_trim_mode) {
2995		scan_balance = SCAN_FILE;
2996		goto out;
2997	}
2998
2999	scan_balance = SCAN_FRACT;
3000	/*
3001	 * Calculate the pressure balance between anon and file pages.
3002	 *
3003	 * The amount of pressure we put on each LRU is inversely
3004	 * proportional to the cost of reclaiming each list, as
3005	 * determined by the share of pages that are refaulting, times
3006	 * the relative IO cost of bringing back a swapped out
3007	 * anonymous page vs reloading a filesystem page (swappiness).
3008	 *
3009	 * Although we limit that influence to ensure no list gets
3010	 * left behind completely: at least a third of the pressure is
3011	 * applied, before swappiness.
3012	 *
3013	 * With swappiness at 100, anon and file have equal IO cost.
3014	 */
3015	total_cost = sc->anon_cost + sc->file_cost;
3016	anon_cost = total_cost + sc->anon_cost;
3017	file_cost = total_cost + sc->file_cost;
3018	total_cost = anon_cost + file_cost;
3019
3020	ap = swappiness * (total_cost + 1);
3021	ap /= anon_cost + 1;
3022
3023	fp = (200 - swappiness) * (total_cost + 1);
3024	fp /= file_cost + 1;
3025
3026	fraction[0] = ap;
3027	fraction[1] = fp;
3028	denominator = ap + fp;
3029out:
3030	for_each_evictable_lru(lru) {
3031		int file = is_file_lru(lru);
3032		unsigned long lruvec_size;
3033		unsigned long low, min;
3034		unsigned long scan;
3035
3036		lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
3037		mem_cgroup_protection(sc->target_mem_cgroup, memcg,
3038				      &min, &low);
3039
3040		if (min || low) {
3041			/*
3042			 * Scale a cgroup's reclaim pressure by proportioning
3043			 * its current usage to its memory.low or memory.min
3044			 * setting.
3045			 *
3046			 * This is important, as otherwise scanning aggression
3047			 * becomes extremely binary -- from nothing as we
3048			 * approach the memory protection threshold, to totally
3049			 * nominal as we exceed it.  This results in requiring
3050			 * setting extremely liberal protection thresholds. It
3051			 * also means we simply get no protection at all if we
3052			 * set it too low, which is not ideal.
3053			 *
3054			 * If there is any protection in place, we reduce scan
3055			 * pressure by how much of the total memory used is
3056			 * within protection thresholds.
3057			 *
3058			 * There is one special case: in the first reclaim pass,
3059			 * we skip over all groups that are within their low
3060			 * protection. If that fails to reclaim enough pages to
3061			 * satisfy the reclaim goal, we come back and override
3062			 * the best-effort low protection. However, we still
3063			 * ideally want to honor how well-behaved groups are in
3064			 * that case instead of simply punishing them all
3065			 * equally. As such, we reclaim them based on how much
3066			 * memory they are using, reducing the scan pressure
3067			 * again by how much of the total memory used is under
3068			 * hard protection.
3069			 */
3070			unsigned long cgroup_size = mem_cgroup_size(memcg);
3071			unsigned long protection;
3072
3073			/* memory.low scaling, make sure we retry before OOM */
3074			if (!sc->memcg_low_reclaim && low > min) {
3075				protection = low;
3076				sc->memcg_low_skipped = 1;
3077			} else {
3078				protection = min;
3079			}
3080
3081			/* Avoid TOCTOU with earlier protection check */
3082			cgroup_size = max(cgroup_size, protection);
3083
3084			scan = lruvec_size - lruvec_size * protection /
3085				(cgroup_size + 1);
3086
3087			/*
3088			 * Minimally target SWAP_CLUSTER_MAX pages to keep
3089			 * reclaim moving forwards, avoiding decrementing
3090			 * sc->priority further than desirable.
3091			 */
3092			scan = max(scan, SWAP_CLUSTER_MAX);
3093		} else {
3094			scan = lruvec_size;
3095		}
3096
3097		scan >>= sc->priority;
3098
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3099		/*
3100		 * If the cgroup's already been deleted, make sure to
3101		 * scrape out the remaining cache.
3102		 */
3103		if (!scan && !mem_cgroup_online(memcg))
3104			scan = min(lruvec_size, SWAP_CLUSTER_MAX);
3105
3106		switch (scan_balance) {
3107		case SCAN_EQUAL:
3108			/* Scan lists relative to size */
3109			break;
3110		case SCAN_FRACT:
3111			/*
3112			 * Scan types proportional to swappiness and
3113			 * their relative recent reclaim efficiency.
3114			 * Make sure we don't miss the last page on
3115			 * the offlined memory cgroups because of a
3116			 * round-off error.
3117			 */
3118			scan = mem_cgroup_online(memcg) ?
3119			       div64_u64(scan * fraction[file], denominator) :
3120			       DIV64_U64_ROUND_UP(scan * fraction[file],
3121						  denominator);
3122			break;
3123		case SCAN_FILE:
3124		case SCAN_ANON:
3125			/* Scan one type exclusively */
3126			if ((scan_balance == SCAN_FILE) != file)
3127				scan = 0;
3128			break;
3129		default:
3130			/* Look ma, no brain */
3131			BUG();
3132		}
3133
3134		nr[lru] = scan;
3135	}
3136}
3137
3138/*
3139 * Anonymous LRU management is a waste if there is
3140 * ultimately no way to reclaim the memory.
3141 */
3142static bool can_age_anon_pages(struct pglist_data *pgdat,
3143			       struct scan_control *sc)
3144{
3145	/* Aging the anon LRU is valuable if swap is present: */
3146	if (total_swap_pages > 0)
3147		return true;
3148
3149	/* Also valuable if anon pages can be demoted: */
3150	return can_demote(pgdat->node_id, sc);
3151}
3152
3153#ifdef CONFIG_LRU_GEN
3154
3155#ifdef CONFIG_LRU_GEN_ENABLED
3156DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
3157#define get_cap(cap)	static_branch_likely(&lru_gen_caps[cap])
3158#else
3159DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
3160#define get_cap(cap)	static_branch_unlikely(&lru_gen_caps[cap])
3161#endif
3162
3163/******************************************************************************
3164 *                          shorthand helpers
3165 ******************************************************************************/
3166
3167#define LRU_REFS_FLAGS	(BIT(PG_referenced) | BIT(PG_workingset))
3168
3169#define DEFINE_MAX_SEQ(lruvec)						\
3170	unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
3171
3172#define DEFINE_MIN_SEQ(lruvec)						\
3173	unsigned long min_seq[ANON_AND_FILE] = {			\
3174		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]),	\
3175		READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]),	\
3176	}
3177
3178#define for_each_gen_type_zone(gen, type, zone)				\
3179	for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++)			\
3180		for ((type) = 0; (type) < ANON_AND_FILE; (type)++)	\
3181			for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
3182
3183static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
3184{
3185	struct pglist_data *pgdat = NODE_DATA(nid);
3186
3187#ifdef CONFIG_MEMCG
3188	if (memcg) {
3189		struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
3190
3191		/* see the comment in mem_cgroup_lruvec() */
3192		if (!lruvec->pgdat)
3193			lruvec->pgdat = pgdat;
3194
3195		return lruvec;
3196	}
3197#endif
3198	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3199
3200	return &pgdat->__lruvec;
3201}
3202
3203static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
3204{
3205	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3206	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
3207
3208	if (!can_demote(pgdat->node_id, sc) &&
3209	    mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
3210		return 0;
3211
3212	return mem_cgroup_swappiness(memcg);
3213}
3214
3215static int get_nr_gens(struct lruvec *lruvec, int type)
3216{
3217	return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
3218}
3219
3220static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
3221{
3222	/* see the comment on lru_gen_struct */
3223	return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
3224	       get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
3225	       get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
3226}
3227
3228/******************************************************************************
3229 *                          mm_struct list
3230 ******************************************************************************/
3231
3232static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
3233{
3234	static struct lru_gen_mm_list mm_list = {
3235		.fifo = LIST_HEAD_INIT(mm_list.fifo),
3236		.lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
3237	};
3238
3239#ifdef CONFIG_MEMCG
3240	if (memcg)
3241		return &memcg->mm_list;
3242#endif
3243	VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3244
3245	return &mm_list;
3246}
3247
3248void lru_gen_add_mm(struct mm_struct *mm)
3249{
3250	int nid;
3251	struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
3252	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3253
3254	VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
3255#ifdef CONFIG_MEMCG
3256	VM_WARN_ON_ONCE(mm->lru_gen.memcg);
3257	mm->lru_gen.memcg = memcg;
3258#endif
3259	spin_lock(&mm_list->lock);
3260
3261	for_each_node_state(nid, N_MEMORY) {
3262		struct lruvec *lruvec = get_lruvec(memcg, nid);
3263
3264		/* the first addition since the last iteration */
3265		if (lruvec->mm_state.tail == &mm_list->fifo)
3266			lruvec->mm_state.tail = &mm->lru_gen.list;
3267	}
3268
3269	list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
3270
3271	spin_unlock(&mm_list->lock);
3272}
3273
3274void lru_gen_del_mm(struct mm_struct *mm)
3275{
3276	int nid;
3277	struct lru_gen_mm_list *mm_list;
3278	struct mem_cgroup *memcg = NULL;
3279
3280	if (list_empty(&mm->lru_gen.list))
3281		return;
3282
3283#ifdef CONFIG_MEMCG
3284	memcg = mm->lru_gen.memcg;
3285#endif
3286	mm_list = get_mm_list(memcg);
3287
3288	spin_lock(&mm_list->lock);
3289
3290	for_each_node(nid) {
3291		struct lruvec *lruvec = get_lruvec(memcg, nid);
3292
3293		/* where the last iteration ended (exclusive) */
3294		if (lruvec->mm_state.tail == &mm->lru_gen.list)
3295			lruvec->mm_state.tail = lruvec->mm_state.tail->next;
3296
3297		/* where the current iteration continues (inclusive) */
3298		if (lruvec->mm_state.head != &mm->lru_gen.list)
3299			continue;
3300
3301		lruvec->mm_state.head = lruvec->mm_state.head->next;
3302		/* the deletion ends the current iteration */
3303		if (lruvec->mm_state.head == &mm_list->fifo)
3304			WRITE_ONCE(lruvec->mm_state.seq, lruvec->mm_state.seq + 1);
3305	}
3306
3307	list_del_init(&mm->lru_gen.list);
3308
3309	spin_unlock(&mm_list->lock);
3310
3311#ifdef CONFIG_MEMCG
3312	mem_cgroup_put(mm->lru_gen.memcg);
3313	mm->lru_gen.memcg = NULL;
3314#endif
3315}
3316
3317#ifdef CONFIG_MEMCG
3318void lru_gen_migrate_mm(struct mm_struct *mm)
3319{
3320	struct mem_cgroup *memcg;
3321	struct task_struct *task = rcu_dereference_protected(mm->owner, true);
3322
3323	VM_WARN_ON_ONCE(task->mm != mm);
3324	lockdep_assert_held(&task->alloc_lock);
3325
3326	/* for mm_update_next_owner() */
3327	if (mem_cgroup_disabled())
3328		return;
3329
3330	/* migration can happen before addition */
3331	if (!mm->lru_gen.memcg)
3332		return;
3333
3334	rcu_read_lock();
3335	memcg = mem_cgroup_from_task(task);
3336	rcu_read_unlock();
3337	if (memcg == mm->lru_gen.memcg)
3338		return;
3339
3340	VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
3341
3342	lru_gen_del_mm(mm);
3343	lru_gen_add_mm(mm);
 
 
 
 
3344}
3345#endif
3346
3347/*
3348 * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
3349 * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
3350 * bits in a bitmap, k is the number of hash functions and n is the number of
3351 * inserted items.
3352 *
3353 * Page table walkers use one of the two filters to reduce their search space.
3354 * To get rid of non-leaf entries that no longer have enough leaf entries, the
3355 * aging uses the double-buffering technique to flip to the other filter each
3356 * time it produces a new generation. For non-leaf entries that have enough
3357 * leaf entries, the aging carries them over to the next generation in
3358 * walk_pmd_range(); the eviction also report them when walking the rmap
3359 * in lru_gen_look_around().
3360 *
3361 * For future optimizations:
3362 * 1. It's not necessary to keep both filters all the time. The spare one can be
3363 *    freed after the RCU grace period and reallocated if needed again.
3364 * 2. And when reallocating, it's worth scaling its size according to the number
3365 *    of inserted entries in the other filter, to reduce the memory overhead on
3366 *    small systems and false positives on large systems.
3367 * 3. Jenkins' hash function is an alternative to Knuth's.
3368 */
3369#define BLOOM_FILTER_SHIFT	15
3370
3371static inline int filter_gen_from_seq(unsigned long seq)
3372{
3373	return seq % NR_BLOOM_FILTERS;
3374}
3375
3376static void get_item_key(void *item, int *key)
3377{
3378	u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
3379
3380	BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
3381
3382	key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
3383	key[1] = hash >> BLOOM_FILTER_SHIFT;
3384}
3385
3386static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq)
3387{
3388	unsigned long *filter;
3389	int gen = filter_gen_from_seq(seq);
3390
3391	filter = lruvec->mm_state.filters[gen];
3392	if (filter) {
3393		bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
3394		return;
3395	}
3396
3397	filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
3398			       __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
3399	WRITE_ONCE(lruvec->mm_state.filters[gen], filter);
3400}
3401
3402static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
3403{
3404	int key[2];
3405	unsigned long *filter;
3406	int gen = filter_gen_from_seq(seq);
3407
3408	filter = READ_ONCE(lruvec->mm_state.filters[gen]);
3409	if (!filter)
3410		return;
3411
3412	get_item_key(item, key);
3413
3414	if (!test_bit(key[0], filter))
3415		set_bit(key[0], filter);
3416	if (!test_bit(key[1], filter))
3417		set_bit(key[1], filter);
3418}
3419
3420static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
3421{
3422	int key[2];
3423	unsigned long *filter;
3424	int gen = filter_gen_from_seq(seq);
3425
3426	filter = READ_ONCE(lruvec->mm_state.filters[gen]);
3427	if (!filter)
3428		return true;
3429
3430	get_item_key(item, key);
3431
3432	return test_bit(key[0], filter) && test_bit(key[1], filter);
3433}
3434
3435static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
3436{
3437	int i;
3438	int hist;
3439
3440	lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
3441
3442	if (walk) {
3443		hist = lru_hist_from_seq(walk->max_seq);
3444
3445		for (i = 0; i < NR_MM_STATS; i++) {
3446			WRITE_ONCE(lruvec->mm_state.stats[hist][i],
3447				   lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]);
3448			walk->mm_stats[i] = 0;
3449		}
3450	}
3451
3452	if (NR_HIST_GENS > 1 && last) {
3453		hist = lru_hist_from_seq(lruvec->mm_state.seq + 1);
3454
3455		for (i = 0; i < NR_MM_STATS; i++)
3456			WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0);
3457	}
3458}
3459
3460static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
3461{
3462	int type;
3463	unsigned long size = 0;
3464	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3465	int key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
3466
3467	if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
3468		return true;
3469
3470	clear_bit(key, &mm->lru_gen.bitmap);
3471
3472	for (type = !walk->can_swap; type < ANON_AND_FILE; type++) {
3473		size += type ? get_mm_counter(mm, MM_FILEPAGES) :
3474			       get_mm_counter(mm, MM_ANONPAGES) +
3475			       get_mm_counter(mm, MM_SHMEMPAGES);
3476	}
3477
3478	if (size < MIN_LRU_BATCH)
3479		return true;
3480
3481	return !mmget_not_zero(mm);
3482}
3483
3484static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
3485			    struct mm_struct **iter)
3486{
3487	bool first = false;
3488	bool last = true;
3489	struct mm_struct *mm = NULL;
3490	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3491	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3492	struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
3493
3494	/*
3495	 * There are four interesting cases for this page table walker:
3496	 * 1. It tries to start a new iteration of mm_list with a stale max_seq;
3497	 *    there is nothing left to do.
3498	 * 2. It's the first of the current generation, and it needs to reset
3499	 *    the Bloom filter for the next generation.
3500	 * 3. It reaches the end of mm_list, and it needs to increment
3501	 *    mm_state->seq; the iteration is done.
3502	 * 4. It's the last of the current generation, and it needs to reset the
3503	 *    mm stats counters for the next generation.
3504	 */
3505	spin_lock(&mm_list->lock);
3506
3507	VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq);
3508	VM_WARN_ON_ONCE(*iter && mm_state->seq > walk->max_seq);
3509	VM_WARN_ON_ONCE(*iter && !mm_state->nr_walkers);
3510
3511	if (walk->max_seq <= mm_state->seq) {
3512		if (!*iter)
3513			last = false;
3514		goto done;
3515	}
3516
3517	if (!mm_state->nr_walkers) {
3518		VM_WARN_ON_ONCE(mm_state->head && mm_state->head != &mm_list->fifo);
3519
3520		mm_state->head = mm_list->fifo.next;
3521		first = true;
3522	}
3523
3524	while (!mm && mm_state->head != &mm_list->fifo) {
3525		mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
3526
3527		mm_state->head = mm_state->head->next;
3528
3529		/* force scan for those added after the last iteration */
3530		if (!mm_state->tail || mm_state->tail == &mm->lru_gen.list) {
3531			mm_state->tail = mm_state->head;
3532			walk->force_scan = true;
3533		}
3534
3535		if (should_skip_mm(mm, walk))
3536			mm = NULL;
3537	}
3538
3539	if (mm_state->head == &mm_list->fifo)
3540		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3541done:
3542	if (*iter && !mm)
3543		mm_state->nr_walkers--;
3544	if (!*iter && mm)
3545		mm_state->nr_walkers++;
3546
3547	if (mm_state->nr_walkers)
3548		last = false;
3549
3550	if (*iter || last)
3551		reset_mm_stats(lruvec, walk, last);
3552
3553	spin_unlock(&mm_list->lock);
3554
3555	if (mm && first)
3556		reset_bloom_filter(lruvec, walk->max_seq + 1);
3557
3558	if (*iter)
3559		mmput_async(*iter);
3560
3561	*iter = mm;
3562
3563	return last;
3564}
3565
3566static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
3567{
3568	bool success = false;
3569	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3570	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3571	struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
3572
3573	spin_lock(&mm_list->lock);
3574
3575	VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq);
3576
3577	if (max_seq > mm_state->seq && !mm_state->nr_walkers) {
3578		VM_WARN_ON_ONCE(mm_state->head && mm_state->head != &mm_list->fifo);
3579
3580		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3581		reset_mm_stats(lruvec, NULL, true);
3582		success = true;
3583	}
3584
3585	spin_unlock(&mm_list->lock);
3586
3587	return success;
3588}
3589
3590/******************************************************************************
3591 *                          refault feedback loop
3592 ******************************************************************************/
3593
3594/*
3595 * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3596 *
3597 * The P term is refaulted/(evicted+protected) from a tier in the generation
3598 * currently being evicted; the I term is the exponential moving average of the
3599 * P term over the generations previously evicted, using the smoothing factor
3600 * 1/2; the D term isn't supported.
3601 *
3602 * The setpoint (SP) is always the first tier of one type; the process variable
3603 * (PV) is either any tier of the other type or any other tier of the same
3604 * type.
3605 *
3606 * The error is the difference between the SP and the PV; the correction is to
3607 * turn off protection when SP>PV or turn on protection when SP<PV.
3608 *
3609 * For future optimizations:
3610 * 1. The D term may discount the other two terms over time so that long-lived
3611 *    generations can resist stale information.
3612 */
3613struct ctrl_pos {
3614	unsigned long refaulted;
3615	unsigned long total;
3616	int gain;
3617};
3618
3619static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
3620			  struct ctrl_pos *pos)
3621{
3622	struct lru_gen_struct *lrugen = &lruvec->lrugen;
3623	int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3624
3625	pos->refaulted = lrugen->avg_refaulted[type][tier] +
3626			 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3627	pos->total = lrugen->avg_total[type][tier] +
3628		     atomic_long_read(&lrugen->evicted[hist][type][tier]);
3629	if (tier)
3630		pos->total += lrugen->protected[hist][type][tier - 1];
3631	pos->gain = gain;
3632}
3633
3634static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
3635{
3636	int hist, tier;
3637	struct lru_gen_struct *lrugen = &lruvec->lrugen;
3638	bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
3639	unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
3640
3641	lockdep_assert_held(&lruvec->lru_lock);
3642
3643	if (!carryover && !clear)
3644		return;
3645
3646	hist = lru_hist_from_seq(seq);
3647
3648	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
3649		if (carryover) {
3650			unsigned long sum;
3651
3652			sum = lrugen->avg_refaulted[type][tier] +
3653			      atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3654			WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
3655
3656			sum = lrugen->avg_total[type][tier] +
3657			      atomic_long_read(&lrugen->evicted[hist][type][tier]);
3658			if (tier)
3659				sum += lrugen->protected[hist][type][tier - 1];
3660			WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
3661		}
3662
3663		if (clear) {
3664			atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
3665			atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
3666			if (tier)
3667				WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0);
3668		}
3669	}
3670}
3671
3672static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
3673{
3674	/*
3675	 * Return true if the PV has a limited number of refaults or a lower
3676	 * refaulted/total than the SP.
3677	 */
3678	return pv->refaulted < MIN_LRU_BATCH ||
3679	       pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
3680	       (sp->refaulted + 1) * pv->total * pv->gain;
3681}
3682
3683/******************************************************************************
3684 *                          the aging
3685 ******************************************************************************/
3686
3687/* promote pages accessed through page tables */
3688static int folio_update_gen(struct folio *folio, int gen)
3689{
3690	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3691
3692	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
3693	VM_WARN_ON_ONCE(!rcu_read_lock_held());
3694
3695	do {
3696		/* lru_gen_del_folio() has isolated this page? */
3697		if (!(old_flags & LRU_GEN_MASK)) {
3698			/* for shrink_folio_list() */
3699			new_flags = old_flags | BIT(PG_referenced);
3700			continue;
3701		}
3702
3703		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3704		new_flags |= (gen + 1UL) << LRU_GEN_PGOFF;
3705	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3706
3707	return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3708}
3709
3710/* protect pages accessed multiple times through file descriptors */
3711static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
3712{
3713	int type = folio_is_file_lru(folio);
3714	struct lru_gen_struct *lrugen = &lruvec->lrugen;
3715	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3716	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3717
3718	VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
3719
3720	do {
3721		new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3722		/* folio_update_gen() has promoted this page? */
3723		if (new_gen >= 0 && new_gen != old_gen)
3724			return new_gen;
3725
3726		new_gen = (old_gen + 1) % MAX_NR_GENS;
3727
3728		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3729		new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
3730		/* for folio_end_writeback() */
3731		if (reclaiming)
3732			new_flags |= BIT(PG_reclaim);
3733	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3734
3735	lru_gen_update_size(lruvec, folio, old_gen, new_gen);
3736
3737	return new_gen;
3738}
3739
3740static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
3741			      int old_gen, int new_gen)
3742{
3743	int type = folio_is_file_lru(folio);
3744	int zone = folio_zonenum(folio);
3745	int delta = folio_nr_pages(folio);
3746
3747	VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
3748	VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
3749
3750	walk->batched++;
3751
3752	walk->nr_pages[old_gen][type][zone] -= delta;
3753	walk->nr_pages[new_gen][type][zone] += delta;
3754}
3755
3756static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
3757{
3758	int gen, type, zone;
3759	struct lru_gen_struct *lrugen = &lruvec->lrugen;
3760
3761	walk->batched = 0;
3762
3763	for_each_gen_type_zone(gen, type, zone) {
3764		enum lru_list lru = type * LRU_INACTIVE_FILE;
3765		int delta = walk->nr_pages[gen][type][zone];
3766
3767		if (!delta)
3768			continue;
3769
3770		walk->nr_pages[gen][type][zone] = 0;
3771		WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
3772			   lrugen->nr_pages[gen][type][zone] + delta);
3773
3774		if (lru_gen_is_active(lruvec, gen))
3775			lru += LRU_ACTIVE;
3776		__update_lru_size(lruvec, lru, zone, delta);
3777	}
3778}
3779
3780static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
3781{
3782	struct address_space *mapping;
3783	struct vm_area_struct *vma = args->vma;
3784	struct lru_gen_mm_walk *walk = args->private;
3785
3786	if (!vma_is_accessible(vma))
3787		return true;
3788
3789	if (is_vm_hugetlb_page(vma))
3790		return true;
3791
3792	if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ))
3793		return true;
3794
3795	if (vma == get_gate_vma(vma->vm_mm))
3796		return true;
3797
3798	if (vma_is_anonymous(vma))
3799		return !walk->can_swap;
3800
3801	if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
3802		return true;
3803
3804	mapping = vma->vm_file->f_mapping;
3805	if (mapping_unevictable(mapping))
3806		return true;
3807
3808	if (shmem_mapping(mapping))
3809		return !walk->can_swap;
3810
3811	/* to exclude special mappings like dax, etc. */
3812	return !mapping->a_ops->read_folio;
3813}
3814
3815/*
3816 * Some userspace memory allocators map many single-page VMAs. Instead of
3817 * returning back to the PGD table for each of such VMAs, finish an entire PMD
3818 * table to reduce zigzags and improve cache performance.
3819 */
3820static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
3821			 unsigned long *vm_start, unsigned long *vm_end)
3822{
3823	unsigned long start = round_up(*vm_end, size);
3824	unsigned long end = (start | ~mask) + 1;
3825	VMA_ITERATOR(vmi, args->mm, start);
3826
3827	VM_WARN_ON_ONCE(mask & size);
3828	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
3829
3830	for_each_vma(vmi, args->vma) {
3831		if (end && end <= args->vma->vm_start)
3832			return false;
3833
3834		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
3835			continue;
3836
3837		*vm_start = max(start, args->vma->vm_start);
3838		*vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
3839
3840		return true;
3841	}
3842
3843	return false;
3844}
3845
3846static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
3847{
3848	unsigned long pfn = pte_pfn(pte);
3849
3850	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3851
3852	if (!pte_present(pte) || is_zero_pfn(pfn))
3853		return -1;
3854
3855	if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
3856		return -1;
3857
3858	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3859		return -1;
3860
3861	return pfn;
3862}
3863
3864#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
3865static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
3866{
3867	unsigned long pfn = pmd_pfn(pmd);
3868
3869	VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3870
3871	if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
3872		return -1;
3873
3874	if (WARN_ON_ONCE(pmd_devmap(pmd)))
3875		return -1;
3876
3877	if (WARN_ON_ONCE(!pfn_valid(pfn)))
3878		return -1;
3879
3880	return pfn;
3881}
3882#endif
3883
3884static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
3885				   struct pglist_data *pgdat, bool can_swap)
3886{
3887	struct folio *folio;
3888
3889	/* try to avoid unnecessary memory loads */
3890	if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3891		return NULL;
3892
3893	folio = pfn_folio(pfn);
3894	if (folio_nid(folio) != pgdat->node_id)
3895		return NULL;
3896
3897	if (folio_memcg_rcu(folio) != memcg)
3898		return NULL;
3899
3900	/* file VMAs can contain anon pages from COW */
3901	if (!folio_is_file_lru(folio) && !can_swap)
3902		return NULL;
3903
3904	return folio;
3905}
3906
3907static bool suitable_to_scan(int total, int young)
3908{
3909	int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
3910
3911	/* suitable if the average number of young PTEs per cacheline is >=1 */
3912	return young * n >= total;
3913}
3914
3915static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
3916			   struct mm_walk *args)
 
3917{
3918	int i;
3919	pte_t *pte;
3920	spinlock_t *ptl;
3921	unsigned long addr;
3922	int total = 0;
3923	int young = 0;
3924	struct lru_gen_mm_walk *walk = args->private;
3925	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3926	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3927	int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3928
3929	VM_WARN_ON_ONCE(pmd_leaf(*pmd));
3930
3931	ptl = pte_lockptr(args->mm, pmd);
3932	if (!spin_trylock(ptl))
3933		return false;
3934
3935	arch_enter_lazy_mmu_mode();
3936
3937	pte = pte_offset_map(pmd, start & PMD_MASK);
3938restart:
3939	for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
3940		unsigned long pfn;
3941		struct folio *folio;
3942
3943		total++;
3944		walk->mm_stats[MM_LEAF_TOTAL]++;
3945
3946		pfn = get_pte_pfn(pte[i], args->vma, addr);
3947		if (pfn == -1)
3948			continue;
3949
3950		if (!pte_young(pte[i])) {
3951			walk->mm_stats[MM_LEAF_OLD]++;
3952			continue;
 
 
 
3953		}
3954
3955		folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3956		if (!folio)
3957			continue;
3958
3959		if (!ptep_test_and_clear_young(args->vma, addr, pte + i))
3960			VM_WARN_ON_ONCE(true);
3961
3962		young++;
3963		walk->mm_stats[MM_LEAF_YOUNG]++;
3964
3965		if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
3966		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3967		      !folio_test_swapcache(folio)))
3968			folio_mark_dirty(folio);
3969
3970		old_gen = folio_update_gen(folio, new_gen);
3971		if (old_gen >= 0 && old_gen != new_gen)
3972			update_batch_size(walk, folio, old_gen, new_gen);
3973	}
3974
3975	if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
3976		goto restart;
3977
3978	pte_unmap(pte);
3979
3980	arch_leave_lazy_mmu_mode();
3981	spin_unlock(ptl);
3982
3983	return suitable_to_scan(total, young);
3984}
3985
3986#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
3987static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
3988				  struct mm_walk *args, unsigned long *bitmap, unsigned long *start)
3989{
3990	int i;
3991	pmd_t *pmd;
3992	spinlock_t *ptl;
3993	struct lru_gen_mm_walk *walk = args->private;
3994	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3995	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3996	int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3997
3998	VM_WARN_ON_ONCE(pud_leaf(*pud));
3999
4000	/* try to batch at most 1+MIN_LRU_BATCH+1 entries */
4001	if (*start == -1) {
4002		*start = next;
4003		return;
4004	}
4005
4006	i = next == -1 ? 0 : pmd_index(next) - pmd_index(*start);
4007	if (i && i <= MIN_LRU_BATCH) {
4008		__set_bit(i - 1, bitmap);
4009		return;
4010	}
4011
4012	pmd = pmd_offset(pud, *start);
4013
4014	ptl = pmd_lockptr(args->mm, pmd);
4015	if (!spin_trylock(ptl))
4016		goto done;
4017
4018	arch_enter_lazy_mmu_mode();
4019
4020	do {
4021		unsigned long pfn;
4022		struct folio *folio;
4023		unsigned long addr = i ? (*start & PMD_MASK) + i * PMD_SIZE : *start;
4024
4025		pfn = get_pmd_pfn(pmd[i], vma, addr);
4026		if (pfn == -1)
4027			goto next;
4028
4029		if (!pmd_trans_huge(pmd[i])) {
4030			if (arch_has_hw_nonleaf_pmd_young() &&
4031			    get_cap(LRU_GEN_NONLEAF_YOUNG))
4032				pmdp_test_and_clear_young(vma, addr, pmd + i);
4033			goto next;
4034		}
4035
4036		folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
4037		if (!folio)
4038			goto next;
4039
4040		if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
4041			goto next;
4042
4043		walk->mm_stats[MM_LEAF_YOUNG]++;
4044
4045		if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
4046		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4047		      !folio_test_swapcache(folio)))
4048			folio_mark_dirty(folio);
4049
4050		old_gen = folio_update_gen(folio, new_gen);
4051		if (old_gen >= 0 && old_gen != new_gen)
4052			update_batch_size(walk, folio, old_gen, new_gen);
4053next:
4054		i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
4055	} while (i <= MIN_LRU_BATCH);
4056
4057	arch_leave_lazy_mmu_mode();
4058	spin_unlock(ptl);
4059done:
4060	*start = -1;
4061	bitmap_zero(bitmap, MIN_LRU_BATCH);
4062}
4063#else
4064static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
4065				  struct mm_walk *args, unsigned long *bitmap, unsigned long *start)
4066{
4067}
4068#endif
4069
4070static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
4071			   struct mm_walk *args)
4072{
4073	int i;
4074	pmd_t *pmd;
4075	unsigned long next;
4076	unsigned long addr;
4077	struct vm_area_struct *vma;
4078	unsigned long pos = -1;
4079	struct lru_gen_mm_walk *walk = args->private;
4080	unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {};
4081
4082	VM_WARN_ON_ONCE(pud_leaf(*pud));
4083
4084	/*
4085	 * Finish an entire PMD in two passes: the first only reaches to PTE
4086	 * tables to avoid taking the PMD lock; the second, if necessary, takes
4087	 * the PMD lock to clear the accessed bit in PMD entries.
4088	 */
4089	pmd = pmd_offset(pud, start & PUD_MASK);
4090restart:
4091	/* walk_pte_range() may call get_next_vma() */
4092	vma = args->vma;
4093	for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
4094		pmd_t val = pmdp_get_lockless(pmd + i);
4095
4096		next = pmd_addr_end(addr, end);
4097
4098		if (!pmd_present(val) || is_huge_zero_pmd(val)) {
4099			walk->mm_stats[MM_LEAF_TOTAL]++;
4100			continue;
4101		}
4102
4103#ifdef CONFIG_TRANSPARENT_HUGEPAGE
4104		if (pmd_trans_huge(val)) {
4105			unsigned long pfn = pmd_pfn(val);
4106			struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
4107
4108			walk->mm_stats[MM_LEAF_TOTAL]++;
4109
4110			if (!pmd_young(val)) {
4111				walk->mm_stats[MM_LEAF_OLD]++;
4112				continue;
4113			}
4114
4115			/* try to avoid unnecessary memory loads */
4116			if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
4117				continue;
4118
4119			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos);
4120			continue;
4121		}
4122#endif
4123		walk->mm_stats[MM_NONLEAF_TOTAL]++;
4124
4125		if (arch_has_hw_nonleaf_pmd_young() &&
4126		    get_cap(LRU_GEN_NONLEAF_YOUNG)) {
4127			if (!pmd_young(val))
4128				continue;
4129
4130			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos);
4131		}
4132
4133		if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq, pmd + i))
4134			continue;
4135
4136		walk->mm_stats[MM_NONLEAF_FOUND]++;
4137
4138		if (!walk_pte_range(&val, addr, next, args))
4139			continue;
4140
4141		walk->mm_stats[MM_NONLEAF_ADDED]++;
4142
4143		/* carry over to the next generation */
4144		update_bloom_filter(walk->lruvec, walk->max_seq + 1, pmd + i);
4145	}
4146
4147	walk_pmd_range_locked(pud, -1, vma, args, bitmap, &pos);
4148
4149	if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
4150		goto restart;
4151}
4152
4153static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
4154			  struct mm_walk *args)
4155{
4156	int i;
4157	pud_t *pud;
4158	unsigned long addr;
4159	unsigned long next;
4160	struct lru_gen_mm_walk *walk = args->private;
4161
4162	VM_WARN_ON_ONCE(p4d_leaf(*p4d));
4163
4164	pud = pud_offset(p4d, start & P4D_MASK);
4165restart:
4166	for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
4167		pud_t val = READ_ONCE(pud[i]);
4168
4169		next = pud_addr_end(addr, end);
4170
4171		if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
4172			continue;
4173
4174		walk_pmd_range(&val, addr, next, args);
4175
4176		/* a racy check to curtail the waiting time */
4177		if (wq_has_sleeper(&walk->lruvec->mm_state.wait))
4178			return 1;
4179
4180		if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
4181			end = (addr | ~PUD_MASK) + 1;
4182			goto done;
4183		}
 
 
 
 
 
 
 
 
 
 
 
 
 
4184	}
4185
4186	if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
4187		goto restart;
4188
4189	end = round_up(end, P4D_SIZE);
4190done:
4191	if (!end || !args->vma)
4192		return 1;
4193
4194	walk->next_addr = max(end, args->vma->vm_start);
4195
4196	return -EAGAIN;
4197}
4198
4199static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
4200{
4201	static const struct mm_walk_ops mm_walk_ops = {
4202		.test_walk = should_skip_vma,
4203		.p4d_entry = walk_pud_range,
4204	};
4205
4206	int err;
4207	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4208
4209	walk->next_addr = FIRST_USER_ADDRESS;
4210
4211	do {
4212		err = -EBUSY;
4213
4214		/* folio_update_gen() requires stable folio_memcg() */
4215		if (!mem_cgroup_trylock_pages(memcg))
4216			break;
4217
4218		/* the caller might be holding the lock for write */
4219		if (mmap_read_trylock(mm)) {
4220			err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
4221
4222			mmap_read_unlock(mm);
4223		}
4224
4225		mem_cgroup_unlock_pages();
4226
4227		if (walk->batched) {
4228			spin_lock_irq(&lruvec->lru_lock);
4229			reset_batch_size(lruvec, walk);
4230			spin_unlock_irq(&lruvec->lru_lock);
4231		}
4232
 
4233		cond_resched();
4234	} while (err == -EAGAIN);
4235}
4236
4237static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat)
4238{
4239	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
4240
4241	if (pgdat && current_is_kswapd()) {
4242		VM_WARN_ON_ONCE(walk);
4243
4244		walk = &pgdat->mm_walk;
4245	} else if (!pgdat && !walk) {
4246		VM_WARN_ON_ONCE(current_is_kswapd());
4247
4248		walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
4249	}
4250
4251	current->reclaim_state->mm_walk = walk;
4252
4253	return walk;
4254}
4255
4256static void clear_mm_walk(void)
4257{
4258	struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
4259
4260	VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
4261	VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
4262
4263	current->reclaim_state->mm_walk = NULL;
4264
4265	if (!current_is_kswapd())
4266		kfree(walk);
4267}
4268
4269static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
4270{
4271	int zone;
4272	int remaining = MAX_LRU_BATCH;
4273	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4274	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
4275
4276	if (type == LRU_GEN_ANON && !can_swap)
4277		goto done;
4278
4279	/* prevent cold/hot inversion if force_scan is true */
4280	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4281		struct list_head *head = &lrugen->lists[old_gen][type][zone];
4282
4283		while (!list_empty(head)) {
4284			struct folio *folio = lru_to_folio(head);
4285
4286			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4287			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4288			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4289			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4290
4291			new_gen = folio_inc_gen(lruvec, folio, false);
4292			list_move_tail(&folio->lru, &lrugen->lists[new_gen][type][zone]);
4293
4294			if (!--remaining)
4295				return false;
4296		}
4297	}
4298done:
4299	reset_ctrl_pos(lruvec, type, true);
4300	WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
4301
4302	return true;
4303}
4304
4305static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
4306{
4307	int gen, type, zone;
4308	bool success = false;
4309	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4310	DEFINE_MIN_SEQ(lruvec);
4311
4312	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
4313
4314	/* find the oldest populated generation */
4315	for (type = !can_swap; type < ANON_AND_FILE; type++) {
4316		while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
4317			gen = lru_gen_from_seq(min_seq[type]);
4318
4319			for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4320				if (!list_empty(&lrugen->lists[gen][type][zone]))
4321					goto next;
4322			}
4323
4324			min_seq[type]++;
4325		}
4326next:
4327		;
4328	}
4329
4330	/* see the comment on lru_gen_struct */
4331	if (can_swap) {
4332		min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]);
4333		min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]);
4334	}
4335
4336	for (type = !can_swap; type < ANON_AND_FILE; type++) {
4337		if (min_seq[type] == lrugen->min_seq[type])
4338			continue;
4339
4340		reset_ctrl_pos(lruvec, type, true);
4341		WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
4342		success = true;
4343	}
4344
4345	return success;
4346}
4347
4348static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan)
4349{
4350	int prev, next;
4351	int type, zone;
4352	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4353
4354	spin_lock_irq(&lruvec->lru_lock);
4355
4356	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
4357
4358	for (type = ANON_AND_FILE - 1; type >= 0; type--) {
4359		if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
4360			continue;
4361
4362		VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
4363
4364		while (!inc_min_seq(lruvec, type, can_swap)) {
4365			spin_unlock_irq(&lruvec->lru_lock);
4366			cond_resched();
4367			spin_lock_irq(&lruvec->lru_lock);
4368		}
4369	}
4370
4371	/*
4372	 * Update the active/inactive LRU sizes for compatibility. Both sides of
4373	 * the current max_seq need to be covered, since max_seq+1 can overlap
4374	 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
4375	 * overlap, cold/hot inversion happens.
4376	 */
4377	prev = lru_gen_from_seq(lrugen->max_seq - 1);
4378	next = lru_gen_from_seq(lrugen->max_seq + 1);
4379
4380	for (type = 0; type < ANON_AND_FILE; type++) {
4381		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4382			enum lru_list lru = type * LRU_INACTIVE_FILE;
4383			long delta = lrugen->nr_pages[prev][type][zone] -
4384				     lrugen->nr_pages[next][type][zone];
4385
4386			if (!delta)
 
 
 
 
 
 
 
 
 
 
 
 
4387				continue;
4388
4389			__update_lru_size(lruvec, lru, zone, delta);
4390			__update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
4391		}
4392	}
4393
4394	for (type = 0; type < ANON_AND_FILE; type++)
4395		reset_ctrl_pos(lruvec, type, false);
4396
4397	WRITE_ONCE(lrugen->timestamps[next], jiffies);
4398	/* make sure preceding modifications appear */
4399	smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
4400
4401	spin_unlock_irq(&lruvec->lru_lock);
4402}
4403
4404static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
4405			       struct scan_control *sc, bool can_swap, bool force_scan)
4406{
4407	bool success;
4408	struct lru_gen_mm_walk *walk;
4409	struct mm_struct *mm = NULL;
4410	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4411
4412	VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq));
4413
4414	/* see the comment in iterate_mm_list() */
4415	if (max_seq <= READ_ONCE(lruvec->mm_state.seq)) {
4416		success = false;
4417		goto done;
4418	}
4419
4420	/*
4421	 * If the hardware doesn't automatically set the accessed bit, fallback
4422	 * to lru_gen_look_around(), which only clears the accessed bit in a
4423	 * handful of PTEs. Spreading the work out over a period of time usually
4424	 * is less efficient, but it avoids bursty page faults.
4425	 */
4426	if (!force_scan && !(arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))) {
4427		success = iterate_mm_list_nowalk(lruvec, max_seq);
4428		goto done;
4429	}
4430
4431	walk = set_mm_walk(NULL);
4432	if (!walk) {
4433		success = iterate_mm_list_nowalk(lruvec, max_seq);
4434		goto done;
4435	}
4436
4437	walk->lruvec = lruvec;
4438	walk->max_seq = max_seq;
4439	walk->can_swap = can_swap;
4440	walk->force_scan = force_scan;
4441
4442	do {
4443		success = iterate_mm_list(lruvec, walk, &mm);
4444		if (mm)
4445			walk_mm(lruvec, mm, walk);
4446
4447		cond_resched();
4448	} while (mm);
4449done:
4450	if (!success) {
4451		if (sc->priority <= DEF_PRIORITY - 2)
4452			wait_event_killable(lruvec->mm_state.wait,
4453					    max_seq < READ_ONCE(lrugen->max_seq));
4454
4455		return max_seq < READ_ONCE(lrugen->max_seq);
4456	}
4457
4458	VM_WARN_ON_ONCE(max_seq != READ_ONCE(lrugen->max_seq));
4459
4460	inc_max_seq(lruvec, can_swap, force_scan);
4461	/* either this sees any waiters or they will see updated max_seq */
4462	if (wq_has_sleeper(&lruvec->mm_state.wait))
4463		wake_up_all(&lruvec->mm_state.wait);
4464
4465	return true;
4466}
4467
4468static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, unsigned long *min_seq,
4469			     struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan)
4470{
4471	int gen, type, zone;
4472	unsigned long old = 0;
4473	unsigned long young = 0;
4474	unsigned long total = 0;
4475	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4476	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4477
4478	for (type = !can_swap; type < ANON_AND_FILE; type++) {
4479		unsigned long seq;
4480
4481		for (seq = min_seq[type]; seq <= max_seq; seq++) {
4482			unsigned long size = 0;
4483
4484			gen = lru_gen_from_seq(seq);
4485
4486			for (zone = 0; zone < MAX_NR_ZONES; zone++)
4487				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4488
4489			total += size;
4490			if (seq == max_seq)
4491				young += size;
4492			else if (seq + MIN_NR_GENS == max_seq)
4493				old += size;
4494		}
4495	}
4496
4497	/* try to scrape all its memory if this memcg was deleted */
4498	*nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
4499
4500	/*
4501	 * The aging tries to be lazy to reduce the overhead, while the eviction
4502	 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
4503	 * ideal number of generations is MIN_NR_GENS+1.
4504	 */
4505	if (min_seq[!can_swap] + MIN_NR_GENS > max_seq)
4506		return true;
4507	if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
4508		return false;
4509
4510	/*
4511	 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
4512	 * of the total number of pages for each generation. A reasonable range
4513	 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
4514	 * aging cares about the upper bound of hot pages, while the eviction
4515	 * cares about the lower bound of cold pages.
4516	 */
4517	if (young * MIN_NR_GENS > total)
4518		return true;
4519	if (old * (MIN_NR_GENS + 2) < total)
4520		return true;
4521
4522	return false;
4523}
4524
4525static bool age_lruvec(struct lruvec *lruvec, struct scan_control *sc, unsigned long min_ttl)
4526{
4527	bool need_aging;
4528	unsigned long nr_to_scan;
4529	int swappiness = get_swappiness(lruvec, sc);
4530	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4531	DEFINE_MAX_SEQ(lruvec);
4532	DEFINE_MIN_SEQ(lruvec);
4533
4534	VM_WARN_ON_ONCE(sc->memcg_low_reclaim);
4535
4536	mem_cgroup_calculate_protection(NULL, memcg);
4537
4538	if (mem_cgroup_below_min(NULL, memcg))
4539		return false;
4540
4541	need_aging = should_run_aging(lruvec, max_seq, min_seq, sc, swappiness, &nr_to_scan);
4542
4543	if (min_ttl) {
4544		int gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
4545		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
4546
4547		if (time_is_after_jiffies(birth + min_ttl))
4548			return false;
4549
4550		/* the size is likely too small to be helpful */
4551		if (!nr_to_scan && sc->priority != DEF_PRIORITY)
4552			return false;
4553	}
4554
4555	if (need_aging)
4556		try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false);
4557
4558	return true;
4559}
4560
4561/* to protect the working set of the last N jiffies */
4562static unsigned long lru_gen_min_ttl __read_mostly;
4563
4564static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
4565{
4566	struct mem_cgroup *memcg;
4567	bool success = false;
4568	unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
4569
4570	VM_WARN_ON_ONCE(!current_is_kswapd());
4571
4572	sc->last_reclaimed = sc->nr_reclaimed;
4573
4574	/*
4575	 * To reduce the chance of going into the aging path, which can be
4576	 * costly, optimistically skip it if the flag below was cleared in the
4577	 * eviction path. This improves the overall performance when multiple
4578	 * memcgs are available.
4579	 */
4580	if (!sc->memcgs_need_aging) {
4581		sc->memcgs_need_aging = true;
4582		return;
4583	}
4584
4585	set_mm_walk(pgdat);
4586
4587	memcg = mem_cgroup_iter(NULL, NULL, NULL);
4588	do {
4589		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4590
4591		if (age_lruvec(lruvec, sc, min_ttl))
4592			success = true;
4593
4594		cond_resched();
4595	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
4596
4597	clear_mm_walk();
4598
4599	/* check the order to exclude compaction-induced reclaim */
4600	if (success || !min_ttl || sc->order)
4601		return;
4602
4603	/*
4604	 * The main goal is to OOM kill if every generation from all memcgs is
4605	 * younger than min_ttl. However, another possibility is all memcgs are
4606	 * either below min or empty.
4607	 */
4608	if (mutex_trylock(&oom_lock)) {
4609		struct oom_control oc = {
4610			.gfp_mask = sc->gfp_mask,
4611		};
4612
4613		out_of_memory(&oc);
4614
4615		mutex_unlock(&oom_lock);
4616	}
4617}
4618
4619/*
4620 * This function exploits spatial locality when shrink_folio_list() walks the
4621 * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
4622 * the scan was done cacheline efficiently, it adds the PMD entry pointing to
4623 * the PTE table to the Bloom filter. This forms a feedback loop between the
4624 * eviction and the aging.
4625 */
4626void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
4627{
4628	int i;
4629	pte_t *pte;
4630	unsigned long start;
4631	unsigned long end;
4632	unsigned long addr;
4633	struct lru_gen_mm_walk *walk;
4634	int young = 0;
4635	unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {};
4636	struct folio *folio = pfn_folio(pvmw->pfn);
4637	struct mem_cgroup *memcg = folio_memcg(folio);
4638	struct pglist_data *pgdat = folio_pgdat(folio);
4639	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4640	DEFINE_MAX_SEQ(lruvec);
4641	int old_gen, new_gen = lru_gen_from_seq(max_seq);
4642
4643	lockdep_assert_held(pvmw->ptl);
4644	VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
4645
4646	if (spin_is_contended(pvmw->ptl))
4647		return;
4648
4649	/* avoid taking the LRU lock under the PTL when possible */
4650	walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
4651
4652	start = max(pvmw->address & PMD_MASK, pvmw->vma->vm_start);
4653	end = min(pvmw->address | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1;
4654
4655	if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
4656		if (pvmw->address - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
4657			end = start + MIN_LRU_BATCH * PAGE_SIZE;
4658		else if (end - pvmw->address < MIN_LRU_BATCH * PAGE_SIZE / 2)
4659			start = end - MIN_LRU_BATCH * PAGE_SIZE;
4660		else {
4661			start = pvmw->address - MIN_LRU_BATCH * PAGE_SIZE / 2;
4662			end = pvmw->address + MIN_LRU_BATCH * PAGE_SIZE / 2;
4663		}
4664	}
4665
4666	pte = pvmw->pte - (pvmw->address - start) / PAGE_SIZE;
4667
4668	rcu_read_lock();
4669	arch_enter_lazy_mmu_mode();
4670
4671	for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
4672		unsigned long pfn;
4673
4674		pfn = get_pte_pfn(pte[i], pvmw->vma, addr);
4675		if (pfn == -1)
4676			continue;
4677
4678		if (!pte_young(pte[i]))
4679			continue;
4680
4681		folio = get_pfn_folio(pfn, memcg, pgdat, !walk || walk->can_swap);
4682		if (!folio)
4683			continue;
4684
4685		if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i))
4686			VM_WARN_ON_ONCE(true);
4687
4688		young++;
4689
4690		if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
4691		    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4692		      !folio_test_swapcache(folio)))
4693			folio_mark_dirty(folio);
4694
4695		old_gen = folio_lru_gen(folio);
4696		if (old_gen < 0)
4697			folio_set_referenced(folio);
4698		else if (old_gen != new_gen)
4699			__set_bit(i, bitmap);
4700	}
4701
4702	arch_leave_lazy_mmu_mode();
4703	rcu_read_unlock();
4704
4705	/* feedback from rmap walkers to page table walkers */
4706	if (suitable_to_scan(i, young))
4707		update_bloom_filter(lruvec, max_seq, pvmw->pmd);
4708
4709	if (!walk && bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) {
4710		for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
4711			folio = pfn_folio(pte_pfn(pte[i]));
4712			folio_activate(folio);
4713		}
4714		return;
4715	}
4716
4717	/* folio_update_gen() requires stable folio_memcg() */
4718	if (!mem_cgroup_trylock_pages(memcg))
4719		return;
4720
4721	if (!walk) {
4722		spin_lock_irq(&lruvec->lru_lock);
4723		new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq);
4724	}
4725
4726	for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
4727		folio = pfn_folio(pte_pfn(pte[i]));
4728		if (folio_memcg_rcu(folio) != memcg)
4729			continue;
4730
4731		old_gen = folio_update_gen(folio, new_gen);
4732		if (old_gen < 0 || old_gen == new_gen)
4733			continue;
4734
4735		if (walk)
4736			update_batch_size(walk, folio, old_gen, new_gen);
4737		else
4738			lru_gen_update_size(lruvec, folio, old_gen, new_gen);
4739	}
4740
4741	if (!walk)
4742		spin_unlock_irq(&lruvec->lru_lock);
4743
4744	mem_cgroup_unlock_pages();
4745}
4746
4747/******************************************************************************
4748 *                          the eviction
4749 ******************************************************************************/
4750
4751static bool sort_folio(struct lruvec *lruvec, struct folio *folio, int tier_idx)
4752{
4753	bool success;
4754	int gen = folio_lru_gen(folio);
4755	int type = folio_is_file_lru(folio);
4756	int zone = folio_zonenum(folio);
4757	int delta = folio_nr_pages(folio);
4758	int refs = folio_lru_refs(folio);
4759	int tier = lru_tier_from_refs(refs);
4760	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4761
4762	VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
4763
4764	/* unevictable */
4765	if (!folio_evictable(folio)) {
4766		success = lru_gen_del_folio(lruvec, folio, true);
4767		VM_WARN_ON_ONCE_FOLIO(!success, folio);
4768		folio_set_unevictable(folio);
4769		lruvec_add_folio(lruvec, folio);
4770		__count_vm_events(UNEVICTABLE_PGCULLED, delta);
4771		return true;
4772	}
4773
4774	/* dirty lazyfree */
4775	if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) {
4776		success = lru_gen_del_folio(lruvec, folio, true);
4777		VM_WARN_ON_ONCE_FOLIO(!success, folio);
4778		folio_set_swapbacked(folio);
4779		lruvec_add_folio_tail(lruvec, folio);
4780		return true;
4781	}
4782
4783	/* promoted */
4784	if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
4785		list_move(&folio->lru, &lrugen->lists[gen][type][zone]);
4786		return true;
4787	}
4788
4789	/* protected */
4790	if (tier > tier_idx) {
4791		int hist = lru_hist_from_seq(lrugen->min_seq[type]);
4792
4793		gen = folio_inc_gen(lruvec, folio, false);
4794		list_move_tail(&folio->lru, &lrugen->lists[gen][type][zone]);
4795
4796		WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
4797			   lrugen->protected[hist][type][tier - 1] + delta);
4798		__mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
4799		return true;
4800	}
4801
4802	/* waiting for writeback */
4803	if (folio_test_locked(folio) || folio_test_writeback(folio) ||
4804	    (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
4805		gen = folio_inc_gen(lruvec, folio, true);
4806		list_move(&folio->lru, &lrugen->lists[gen][type][zone]);
4807		return true;
4808	}
4809
4810	return false;
4811}
4812
4813static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
4814{
4815	bool success;
4816
4817	/* unmapping inhibited */
4818	if (!sc->may_unmap && folio_mapped(folio))
4819		return false;
4820
4821	/* swapping inhibited */
4822	if (!(sc->may_writepage && (sc->gfp_mask & __GFP_IO)) &&
4823	    (folio_test_dirty(folio) ||
4824	     (folio_test_anon(folio) && !folio_test_swapcache(folio))))
4825		return false;
4826
4827	/* raced with release_pages() */
4828	if (!folio_try_get(folio))
4829		return false;
4830
4831	/* raced with another isolation */
4832	if (!folio_test_clear_lru(folio)) {
4833		folio_put(folio);
4834		return false;
4835	}
4836
4837	/* see the comment on MAX_NR_TIERS */
4838	if (!folio_test_referenced(folio))
4839		set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0);
4840
4841	/* for shrink_folio_list() */
4842	folio_clear_reclaim(folio);
4843	folio_clear_referenced(folio);
4844
4845	success = lru_gen_del_folio(lruvec, folio, true);
4846	VM_WARN_ON_ONCE_FOLIO(!success, folio);
4847
4848	return true;
4849}
4850
4851static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
4852		       int type, int tier, struct list_head *list)
4853{
4854	int gen, zone;
4855	enum vm_event_item item;
4856	int sorted = 0;
4857	int scanned = 0;
4858	int isolated = 0;
4859	int remaining = MAX_LRU_BATCH;
4860	struct lru_gen_struct *lrugen = &lruvec->lrugen;
4861	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4862
4863	VM_WARN_ON_ONCE(!list_empty(list));
4864
4865	if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
4866		return 0;
4867
4868	gen = lru_gen_from_seq(lrugen->min_seq[type]);
4869
4870	for (zone = sc->reclaim_idx; zone >= 0; zone--) {
4871		LIST_HEAD(moved);
4872		int skipped = 0;
4873		struct list_head *head = &lrugen->lists[gen][type][zone];
4874
4875		while (!list_empty(head)) {
4876			struct folio *folio = lru_to_folio(head);
4877			int delta = folio_nr_pages(folio);
4878
4879			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4880			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4881			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4882			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4883
4884			scanned += delta;
4885
4886			if (sort_folio(lruvec, folio, tier))
4887				sorted += delta;
4888			else if (isolate_folio(lruvec, folio, sc)) {
4889				list_add(&folio->lru, list);
4890				isolated += delta;
4891			} else {
4892				list_move(&folio->lru, &moved);
4893				skipped += delta;
4894			}
4895
4896			if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
4897				break;
4898		}
4899
4900		if (skipped) {
4901			list_splice(&moved, head);
4902			__count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
4903		}
4904
4905		if (!remaining || isolated >= MIN_LRU_BATCH)
4906			break;
4907	}
4908
4909	item = PGSCAN_KSWAPD + reclaimer_offset();
4910	if (!cgroup_reclaim(sc)) {
4911		__count_vm_events(item, isolated);
4912		__count_vm_events(PGREFILL, sorted);
4913	}
4914	__count_memcg_events(memcg, item, isolated);
4915	__count_memcg_events(memcg, PGREFILL, sorted);
4916	__count_vm_events(PGSCAN_ANON + type, isolated);
4917
4918	/*
4919	 * There might not be eligible pages due to reclaim_idx, may_unmap and
4920	 * may_writepage. Check the remaining to prevent livelock if it's not
4921	 * making progress.
4922	 */
4923	return isolated || !remaining ? scanned : 0;
4924}
4925
4926static int get_tier_idx(struct lruvec *lruvec, int type)
4927{
4928	int tier;
4929	struct ctrl_pos sp, pv;
4930
4931	/*
4932	 * To leave a margin for fluctuations, use a larger gain factor (1:2).
4933	 * This value is chosen because any other tier would have at least twice
4934	 * as many refaults as the first tier.
 
4935	 */
4936	read_ctrl_pos(lruvec, type, 0, 1, &sp);
4937	for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4938		read_ctrl_pos(lruvec, type, tier, 2, &pv);
4939		if (!positive_ctrl_err(&sp, &pv))
4940			break;
4941	}
4942
4943	return tier - 1;
 
 
 
 
 
4944}
4945
4946static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
 
4947{
4948	int type, tier;
4949	struct ctrl_pos sp, pv;
4950	int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness };
4951
4952	/*
4953	 * Compare the first tier of anon with that of file to determine which
4954	 * type to scan. Also need to compare other tiers of the selected type
4955	 * with the first tier of the other type to determine the last tier (of
4956	 * the selected type) to evict.
4957	 */
4958	read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
4959	read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
4960	type = positive_ctrl_err(&sp, &pv);
4961
4962	read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
4963	for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4964		read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
4965		if (!positive_ctrl_err(&sp, &pv))
4966			break;
4967	}
4968
4969	*tier_idx = tier - 1;
4970
4971	return type;
4972}
4973
4974static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
4975			  int *type_scanned, struct list_head *list)
4976{
4977	int i;
4978	int type;
4979	int scanned;
4980	int tier = -1;
4981	DEFINE_MIN_SEQ(lruvec);
4982
4983	/*
4984	 * Try to make the obvious choice first. When anon and file are both
4985	 * available from the same generation, interpret swappiness 1 as file
4986	 * first and 200 as anon first.
4987	 */
4988	if (!swappiness)
4989		type = LRU_GEN_FILE;
4990	else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
4991		type = LRU_GEN_ANON;
4992	else if (swappiness == 1)
4993		type = LRU_GEN_FILE;
4994	else if (swappiness == 200)
4995		type = LRU_GEN_ANON;
4996	else
4997		type = get_type_to_scan(lruvec, swappiness, &tier);
4998
4999	for (i = !swappiness; i < ANON_AND_FILE; i++) {
5000		if (tier < 0)
5001			tier = get_tier_idx(lruvec, type);
5002
5003		scanned = scan_folios(lruvec, sc, type, tier, list);
5004		if (scanned)
5005			break;
5006
5007		type = !type;
5008		tier = -1;
5009	}
5010
5011	*type_scanned = type;
5012
5013	return scanned;
5014}
5015
5016static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
5017			bool *need_swapping)
5018{
5019	int type;
5020	int scanned;
5021	int reclaimed;
5022	LIST_HEAD(list);
5023	LIST_HEAD(clean);
5024	struct folio *folio;
5025	struct folio *next;
5026	enum vm_event_item item;
5027	struct reclaim_stat stat;
5028	struct lru_gen_mm_walk *walk;
5029	bool skip_retry = false;
5030	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5031	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
5032
5033	spin_lock_irq(&lruvec->lru_lock);
5034
5035	scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
5036
5037	scanned += try_to_inc_min_seq(lruvec, swappiness);
5038
5039	if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS)
5040		scanned = 0;
5041
5042	spin_unlock_irq(&lruvec->lru_lock);
5043
5044	if (list_empty(&list))
5045		return scanned;
5046retry:
5047	reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
5048	sc->nr_reclaimed += reclaimed;
5049
5050	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
5051		if (!folio_evictable(folio)) {
5052			list_del(&folio->lru);
5053			folio_putback_lru(folio);
5054			continue;
5055		}
5056
5057		if (folio_test_reclaim(folio) &&
5058		    (folio_test_dirty(folio) || folio_test_writeback(folio))) {
5059			/* restore LRU_REFS_FLAGS cleared by isolate_folio() */
5060			if (folio_test_workingset(folio))
5061				folio_set_referenced(folio);
5062			continue;
5063		}
5064
5065		if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
5066		    folio_mapped(folio) || folio_test_locked(folio) ||
5067		    folio_test_dirty(folio) || folio_test_writeback(folio)) {
5068			/* don't add rejected folios to the oldest generation */
5069			set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
5070				      BIT(PG_active));
5071			continue;
5072		}
5073
5074		/* retry folios that may have missed folio_rotate_reclaimable() */
5075		list_move(&folio->lru, &clean);
5076		sc->nr_scanned -= folio_nr_pages(folio);
5077	}
5078
5079	spin_lock_irq(&lruvec->lru_lock);
5080
5081	move_folios_to_lru(lruvec, &list);
5082
5083	walk = current->reclaim_state->mm_walk;
5084	if (walk && walk->batched)
5085		reset_batch_size(lruvec, walk);
5086
5087	item = PGSTEAL_KSWAPD + reclaimer_offset();
5088	if (!cgroup_reclaim(sc))
5089		__count_vm_events(item, reclaimed);
5090	__count_memcg_events(memcg, item, reclaimed);
5091	__count_vm_events(PGSTEAL_ANON + type, reclaimed);
5092
5093	spin_unlock_irq(&lruvec->lru_lock);
5094
5095	mem_cgroup_uncharge_list(&list);
5096	free_unref_page_list(&list);
5097
5098	INIT_LIST_HEAD(&list);
5099	list_splice_init(&clean, &list);
5100
5101	if (!list_empty(&list)) {
5102		skip_retry = true;
5103		goto retry;
5104	}
5105
5106	if (need_swapping && type == LRU_GEN_ANON)
5107		*need_swapping = true;
5108
5109	return scanned;
5110}
5111
5112/*
5113 * For future optimizations:
5114 * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
5115 *    reclaim.
 
 
 
5116 */
5117static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc,
5118				    bool can_swap, bool *need_aging)
5119{
5120	unsigned long nr_to_scan;
5121	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5122	DEFINE_MAX_SEQ(lruvec);
5123	DEFINE_MIN_SEQ(lruvec);
5124
5125	if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg) ||
5126	    (mem_cgroup_below_low(sc->target_mem_cgroup, memcg) &&
5127	     !sc->memcg_low_reclaim))
5128		return 0;
5129
5130	*need_aging = should_run_aging(lruvec, max_seq, min_seq, sc, can_swap, &nr_to_scan);
5131	if (!*need_aging)
5132		return nr_to_scan;
5133
5134	/* skip the aging path at the default priority */
5135	if (sc->priority == DEF_PRIORITY)
5136		goto done;
5137
5138	/* leave the work to lru_gen_age_node() */
5139	if (current_is_kswapd())
5140		return 0;
5141
5142	if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false))
5143		return nr_to_scan;
5144done:
5145	return min_seq[!can_swap] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0;
5146}
5147
5148static bool should_abort_scan(struct lruvec *lruvec, unsigned long seq,
5149			      struct scan_control *sc, bool need_swapping)
5150{
5151	int i;
5152	DEFINE_MAX_SEQ(lruvec);
5153
5154	if (!current_is_kswapd()) {
5155		/* age each memcg at most once to ensure fairness */
5156		if (max_seq - seq > 1)
5157			return true;
5158
5159		/* over-swapping can increase allocation latency */
5160		if (sc->nr_reclaimed >= sc->nr_to_reclaim && need_swapping)
5161			return true;
5162
5163		/* give this thread a chance to exit and free its memory */
5164		if (fatal_signal_pending(current)) {
5165			sc->nr_reclaimed += MIN_LRU_BATCH;
5166			return true;
5167		}
5168
5169		if (cgroup_reclaim(sc))
5170			return false;
5171	} else if (sc->nr_reclaimed - sc->last_reclaimed < sc->nr_to_reclaim)
5172		return false;
5173
5174	/* keep scanning at low priorities to ensure fairness */
5175	if (sc->priority > DEF_PRIORITY - 2)
5176		return false;
5177
5178	/*
5179	 * A minimum amount of work was done under global memory pressure. For
5180	 * kswapd, it may be overshooting. For direct reclaim, the allocation
5181	 * may succeed if all suitable zones are somewhat safe. In either case,
5182	 * it's better to stop now, and restart later if necessary.
5183	 */
5184	for (i = 0; i <= sc->reclaim_idx; i++) {
5185		unsigned long wmark;
5186		struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
5187
5188		if (!managed_zone(zone))
5189			continue;
5190
5191		wmark = current_is_kswapd() ? high_wmark_pages(zone) : low_wmark_pages(zone);
5192		if (wmark > zone_page_state(zone, NR_FREE_PAGES))
5193			return false;
5194	}
5195
5196	sc->nr_reclaimed += MIN_LRU_BATCH;
5197
5198	return true;
5199}
5200
5201static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5202{
5203	struct blk_plug plug;
5204	bool need_aging = false;
5205	bool need_swapping = false;
5206	unsigned long scanned = 0;
5207	unsigned long reclaimed = sc->nr_reclaimed;
5208	DEFINE_MAX_SEQ(lruvec);
5209
5210	lru_add_drain();
5211
5212	blk_start_plug(&plug);
5213
5214	set_mm_walk(lruvec_pgdat(lruvec));
5215
5216	while (true) {
5217		int delta;
5218		int swappiness;
5219		unsigned long nr_to_scan;
5220
5221		if (sc->may_swap)
5222			swappiness = get_swappiness(lruvec, sc);
5223		else if (!cgroup_reclaim(sc) && get_swappiness(lruvec, sc))
5224			swappiness = 1;
5225		else
5226			swappiness = 0;
5227
5228		nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness, &need_aging);
5229		if (!nr_to_scan)
5230			goto done;
5231
5232		delta = evict_folios(lruvec, sc, swappiness, &need_swapping);
5233		if (!delta)
5234			goto done;
5235
5236		scanned += delta;
5237		if (scanned >= nr_to_scan)
5238			break;
5239
5240		if (should_abort_scan(lruvec, max_seq, sc, need_swapping))
5241			break;
5242
5243		cond_resched();
5244	}
5245
5246	/* see the comment in lru_gen_age_node() */
5247	if (sc->nr_reclaimed - reclaimed >= MIN_LRU_BATCH && !need_aging)
5248		sc->memcgs_need_aging = false;
5249done:
5250	clear_mm_walk();
5251
5252	blk_finish_plug(&plug);
5253}
5254
5255/******************************************************************************
5256 *                          state change
5257 ******************************************************************************/
5258
5259static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
5260{
5261	struct lru_gen_struct *lrugen = &lruvec->lrugen;
5262
5263	if (lrugen->enabled) {
5264		enum lru_list lru;
5265
5266		for_each_evictable_lru(lru) {
5267			if (!list_empty(&lruvec->lists[lru]))
5268				return false;
5269		}
5270	} else {
5271		int gen, type, zone;
5272
5273		for_each_gen_type_zone(gen, type, zone) {
5274			if (!list_empty(&lrugen->lists[gen][type][zone]))
5275				return false;
5276		}
5277	}
5278
5279	return true;
5280}
5281
5282static bool fill_evictable(struct lruvec *lruvec)
5283{
5284	enum lru_list lru;
5285	int remaining = MAX_LRU_BATCH;
5286
5287	for_each_evictable_lru(lru) {
5288		int type = is_file_lru(lru);
5289		bool active = is_active_lru(lru);
5290		struct list_head *head = &lruvec->lists[lru];
5291
5292		while (!list_empty(head)) {
5293			bool success;
5294			struct folio *folio = lru_to_folio(head);
5295
5296			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5297			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
5298			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5299			VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
5300
5301			lruvec_del_folio(lruvec, folio);
5302			success = lru_gen_add_folio(lruvec, folio, false);
5303			VM_WARN_ON_ONCE(!success);
5304
5305			if (!--remaining)
5306				return false;
5307		}
5308	}
5309
5310	return true;
5311}
5312
5313static bool drain_evictable(struct lruvec *lruvec)
5314{
5315	int gen, type, zone;
5316	int remaining = MAX_LRU_BATCH;
5317
5318	for_each_gen_type_zone(gen, type, zone) {
5319		struct list_head *head = &lruvec->lrugen.lists[gen][type][zone];
5320
5321		while (!list_empty(head)) {
5322			bool success;
5323			struct folio *folio = lru_to_folio(head);
5324
5325			VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5326			VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
5327			VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5328			VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
5329
5330			success = lru_gen_del_folio(lruvec, folio, false);
5331			VM_WARN_ON_ONCE(!success);
5332			lruvec_add_folio(lruvec, folio);
5333
5334			if (!--remaining)
5335				return false;
5336		}
5337	}
5338
5339	return true;
5340}
5341
5342static void lru_gen_change_state(bool enabled)
5343{
5344	static DEFINE_MUTEX(state_mutex);
5345
5346	struct mem_cgroup *memcg;
5347
5348	cgroup_lock();
5349	cpus_read_lock();
5350	get_online_mems();
5351	mutex_lock(&state_mutex);
5352
5353	if (enabled == lru_gen_enabled())
5354		goto unlock;
5355
5356	if (enabled)
5357		static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5358	else
5359		static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5360
5361	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5362	do {
5363		int nid;
5364
5365		for_each_node(nid) {
5366			struct lruvec *lruvec = get_lruvec(memcg, nid);
5367
5368			spin_lock_irq(&lruvec->lru_lock);
5369
5370			VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
5371			VM_WARN_ON_ONCE(!state_is_valid(lruvec));
5372
5373			lruvec->lrugen.enabled = enabled;
5374
5375			while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
5376				spin_unlock_irq(&lruvec->lru_lock);
5377				cond_resched();
5378				spin_lock_irq(&lruvec->lru_lock);
5379			}
5380
5381			spin_unlock_irq(&lruvec->lru_lock);
5382		}
5383
5384		cond_resched();
5385	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5386unlock:
5387	mutex_unlock(&state_mutex);
5388	put_online_mems();
5389	cpus_read_unlock();
5390	cgroup_unlock();
5391}
5392
5393/******************************************************************************
5394 *                          sysfs interface
5395 ******************************************************************************/
5396
5397static ssize_t show_min_ttl(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5398{
5399	return sprintf(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
5400}
5401
5402/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5403static ssize_t store_min_ttl(struct kobject *kobj, struct kobj_attribute *attr,
5404			     const char *buf, size_t len)
5405{
5406	unsigned int msecs;
5407
5408	if (kstrtouint(buf, 0, &msecs))
5409		return -EINVAL;
5410
5411	WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
5412
5413	return len;
5414}
5415
5416static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR(
5417	min_ttl_ms, 0644, show_min_ttl, store_min_ttl
5418);
5419
5420static ssize_t show_enabled(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5421{
5422	unsigned int caps = 0;
5423
5424	if (get_cap(LRU_GEN_CORE))
5425		caps |= BIT(LRU_GEN_CORE);
5426
5427	if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))
5428		caps |= BIT(LRU_GEN_MM_WALK);
5429
5430	if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG))
5431		caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
5432
5433	return sysfs_emit(buf, "0x%04x\n", caps);
5434}
5435
5436/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5437static ssize_t store_enabled(struct kobject *kobj, struct kobj_attribute *attr,
5438			     const char *buf, size_t len)
5439{
5440	int i;
5441	unsigned int caps;
5442
5443	if (tolower(*buf) == 'n')
5444		caps = 0;
5445	else if (tolower(*buf) == 'y')
5446		caps = -1;
5447	else if (kstrtouint(buf, 0, &caps))
5448		return -EINVAL;
5449
5450	for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
5451		bool enabled = caps & BIT(i);
5452
5453		if (i == LRU_GEN_CORE)
5454			lru_gen_change_state(enabled);
5455		else if (enabled)
5456			static_branch_enable(&lru_gen_caps[i]);
5457		else
5458			static_branch_disable(&lru_gen_caps[i]);
5459	}
5460
5461	return len;
5462}
5463
5464static struct kobj_attribute lru_gen_enabled_attr = __ATTR(
5465	enabled, 0644, show_enabled, store_enabled
5466);
5467
5468static struct attribute *lru_gen_attrs[] = {
5469	&lru_gen_min_ttl_attr.attr,
5470	&lru_gen_enabled_attr.attr,
5471	NULL
5472};
5473
5474static struct attribute_group lru_gen_attr_group = {
5475	.name = "lru_gen",
5476	.attrs = lru_gen_attrs,
5477};
5478
5479/******************************************************************************
5480 *                          debugfs interface
5481 ******************************************************************************/
5482
5483static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
5484{
5485	struct mem_cgroup *memcg;
5486	loff_t nr_to_skip = *pos;
5487
5488	m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
5489	if (!m->private)
5490		return ERR_PTR(-ENOMEM);
5491
5492	memcg = mem_cgroup_iter(NULL, NULL, NULL);
5493	do {
5494		int nid;
5495
5496		for_each_node_state(nid, N_MEMORY) {
5497			if (!nr_to_skip--)
5498				return get_lruvec(memcg, nid);
5499		}
5500	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5501
5502	return NULL;
5503}
5504
5505static void lru_gen_seq_stop(struct seq_file *m, void *v)
 
5506{
5507	if (!IS_ERR_OR_NULL(v))
5508		mem_cgroup_iter_break(NULL, lruvec_memcg(v));
5509
5510	kvfree(m->private);
5511	m->private = NULL;
5512}
 
5513
5514static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
5515{
5516	int nid = lruvec_pgdat(v)->node_id;
5517	struct mem_cgroup *memcg = lruvec_memcg(v);
5518
5519	++*pos;
5520
5521	nid = next_memory_node(nid);
5522	if (nid == MAX_NUMNODES) {
5523		memcg = mem_cgroup_iter(NULL, memcg, NULL);
5524		if (!memcg)
5525			return NULL;
5526
5527		nid = first_memory_node;
5528	}
5529
5530	return get_lruvec(memcg, nid);
5531}
5532
5533static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
5534				  unsigned long max_seq, unsigned long *min_seq,
5535				  unsigned long seq)
 
 
 
 
 
 
 
 
 
 
 
 
 
5536{
5537	int i;
5538	int type, tier;
5539	int hist = lru_hist_from_seq(seq);
5540	struct lru_gen_struct *lrugen = &lruvec->lrugen;
5541
5542	for (tier = 0; tier < MAX_NR_TIERS; tier++) {
5543		seq_printf(m, "            %10d", tier);
5544		for (type = 0; type < ANON_AND_FILE; type++) {
5545			const char *s = "   ";
5546			unsigned long n[3] = {};
5547
5548			if (seq == max_seq) {
5549				s = "RT ";
5550				n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
5551				n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
5552			} else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
5553				s = "rep";
5554				n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
5555				n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
5556				if (tier)
5557					n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]);
5558			}
5559
5560			for (i = 0; i < 3; i++)
5561				seq_printf(m, " %10lu%c", n[i], s[i]);
5562		}
5563		seq_putc(m, '\n');
5564	}
5565
5566	seq_puts(m, "                      ");
5567	for (i = 0; i < NR_MM_STATS; i++) {
5568		const char *s = "      ";
5569		unsigned long n = 0;
5570
5571		if (seq == max_seq && NR_HIST_GENS == 1) {
5572			s = "LOYNFA";
5573			n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
5574		} else if (seq != max_seq && NR_HIST_GENS > 1) {
5575			s = "loynfa";
5576			n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
5577		}
5578
5579		seq_printf(m, " %10lu%c", n, s[i]);
5580	}
5581	seq_putc(m, '\n');
5582}
5583
5584/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5585static int lru_gen_seq_show(struct seq_file *m, void *v)
5586{
5587	unsigned long seq;
5588	bool full = !debugfs_real_fops(m->file)->write;
5589	struct lruvec *lruvec = v;
5590	struct lru_gen_struct *lrugen = &lruvec->lrugen;
5591	int nid = lruvec_pgdat(lruvec)->node_id;
5592	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5593	DEFINE_MAX_SEQ(lruvec);
5594	DEFINE_MIN_SEQ(lruvec);
5595
5596	if (nid == first_memory_node) {
5597		const char *path = memcg ? m->private : "";
5598
5599#ifdef CONFIG_MEMCG
5600		if (memcg)
5601			cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
5602#endif
5603		seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
5604	}
5605
5606	seq_printf(m, " node %5d\n", nid);
5607
5608	if (!full)
5609		seq = min_seq[LRU_GEN_ANON];
5610	else if (max_seq >= MAX_NR_GENS)
5611		seq = max_seq - MAX_NR_GENS + 1;
5612	else
5613		seq = 0;
5614
5615	for (; seq <= max_seq; seq++) {
5616		int type, zone;
5617		int gen = lru_gen_from_seq(seq);
5618		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
5619
5620		seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
5621
5622		for (type = 0; type < ANON_AND_FILE; type++) {
5623			unsigned long size = 0;
5624			char mark = full && seq < min_seq[type] ? 'x' : ' ';
5625
5626			for (zone = 0; zone < MAX_NR_ZONES; zone++)
5627				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
5628
5629			seq_printf(m, " %10lu%c", size, mark);
5630		}
5631
5632		seq_putc(m, '\n');
5633
5634		if (full)
5635			lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
5636	}
5637
5638	return 0;
5639}
5640
5641static const struct seq_operations lru_gen_seq_ops = {
5642	.start = lru_gen_seq_start,
5643	.stop = lru_gen_seq_stop,
5644	.next = lru_gen_seq_next,
5645	.show = lru_gen_seq_show,
5646};
5647
5648static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5649		     bool can_swap, bool force_scan)
5650{
5651	DEFINE_MAX_SEQ(lruvec);
5652	DEFINE_MIN_SEQ(lruvec);
5653
5654	if (seq < max_seq)
 
 
5655		return 0;
5656
5657	if (seq > max_seq)
5658		return -EINVAL;
5659
5660	if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq)
5661		return -ERANGE;
5662
5663	try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan);
5664
5665	return 0;
5666}
5667
5668static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5669			int swappiness, unsigned long nr_to_reclaim)
5670{
5671	DEFINE_MAX_SEQ(lruvec);
5672
5673	if (seq + MIN_NR_GENS > max_seq)
5674		return -EINVAL;
5675
5676	sc->nr_reclaimed = 0;
5677
5678	while (!signal_pending(current)) {
5679		DEFINE_MIN_SEQ(lruvec);
5680
5681		if (seq < min_seq[!swappiness])
5682			return 0;
5683
5684		if (sc->nr_reclaimed >= nr_to_reclaim)
5685			return 0;
5686
5687		if (!evict_folios(lruvec, sc, swappiness, NULL))
5688			return 0;
5689
5690		cond_resched();
5691	}
5692
5693	return -EINTR;
5694}
5695
5696static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
5697		   struct scan_control *sc, int swappiness, unsigned long opt)
5698{
5699	struct lruvec *lruvec;
5700	int err = -EINVAL;
5701	struct mem_cgroup *memcg = NULL;
5702
5703	if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
5704		return -EINVAL;
5705
5706	if (!mem_cgroup_disabled()) {
5707		rcu_read_lock();
5708		memcg = mem_cgroup_from_id(memcg_id);
5709#ifdef CONFIG_MEMCG
5710		if (memcg && !css_tryget(&memcg->css))
5711			memcg = NULL;
5712#endif
5713		rcu_read_unlock();
5714
5715		if (!memcg)
5716			return -EINVAL;
5717	}
5718
5719	if (memcg_id != mem_cgroup_id(memcg))
5720		goto done;
5721
5722	lruvec = get_lruvec(memcg, nid);
5723
5724	if (swappiness < 0)
5725		swappiness = get_swappiness(lruvec, sc);
5726	else if (swappiness > 200)
5727		goto done;
5728
5729	switch (cmd) {
5730	case '+':
5731		err = run_aging(lruvec, seq, sc, swappiness, opt);
5732		break;
5733	case '-':
5734		err = run_eviction(lruvec, seq, sc, swappiness, opt);
5735		break;
5736	}
5737done:
5738	mem_cgroup_put(memcg);
5739
5740	return err;
5741}
5742
5743/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5744static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
5745				 size_t len, loff_t *pos)
 
 
 
 
 
 
 
5746{
5747	void *buf;
5748	char *cur, *next;
5749	unsigned int flags;
5750	struct blk_plug plug;
5751	int err = -EINVAL;
5752	struct scan_control sc = {
5753		.may_writepage = true,
5754		.may_unmap = true,
5755		.may_swap = true,
5756		.reclaim_idx = MAX_NR_ZONES - 1,
5757		.gfp_mask = GFP_KERNEL,
5758	};
5759
5760	buf = kvmalloc(len + 1, GFP_KERNEL);
5761	if (!buf)
5762		return -ENOMEM;
5763
5764	if (copy_from_user(buf, src, len)) {
5765		kvfree(buf);
5766		return -EFAULT;
5767	}
5768
5769	set_task_reclaim_state(current, &sc.reclaim_state);
5770	flags = memalloc_noreclaim_save();
5771	blk_start_plug(&plug);
5772	if (!set_mm_walk(NULL)) {
5773		err = -ENOMEM;
5774		goto done;
5775	}
5776
5777	next = buf;
5778	next[len] = '\0';
5779
5780	while ((cur = strsep(&next, ",;\n"))) {
5781		int n;
5782		int end;
5783		char cmd;
5784		unsigned int memcg_id;
5785		unsigned int nid;
5786		unsigned long seq;
5787		unsigned int swappiness = -1;
5788		unsigned long opt = -1;
5789
5790		cur = skip_spaces(cur);
5791		if (!*cur)
5792			continue;
5793
5794		n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
5795			   &seq, &end, &swappiness, &end, &opt, &end);
5796		if (n < 4 || cur[end]) {
5797			err = -EINVAL;
5798			break;
5799		}
5800
5801		err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
5802		if (err)
5803			break;
5804	}
5805done:
5806	clear_mm_walk();
5807	blk_finish_plug(&plug);
5808	memalloc_noreclaim_restore(flags);
5809	set_task_reclaim_state(current, NULL);
5810
5811	kvfree(buf);
5812
5813	return err ? : len;
5814}
5815
5816static int lru_gen_seq_open(struct inode *inode, struct file *file)
5817{
5818	return seq_open(file, &lru_gen_seq_ops);
5819}
5820
5821static const struct file_operations lru_gen_rw_fops = {
5822	.open = lru_gen_seq_open,
5823	.read = seq_read,
5824	.write = lru_gen_seq_write,
5825	.llseek = seq_lseek,
5826	.release = seq_release,
5827};
5828
5829static const struct file_operations lru_gen_ro_fops = {
5830	.open = lru_gen_seq_open,
5831	.read = seq_read,
5832	.llseek = seq_lseek,
5833	.release = seq_release,
5834};
5835
5836/******************************************************************************
5837 *                          initialization
5838 ******************************************************************************/
5839
5840void lru_gen_init_lruvec(struct lruvec *lruvec)
5841{
5842	int i;
5843	int gen, type, zone;
5844	struct lru_gen_struct *lrugen = &lruvec->lrugen;
5845
5846	lrugen->max_seq = MIN_NR_GENS + 1;
5847	lrugen->enabled = lru_gen_enabled();
5848
5849	for (i = 0; i <= MIN_NR_GENS + 1; i++)
5850		lrugen->timestamps[i] = jiffies;
5851
5852	for_each_gen_type_zone(gen, type, zone)
5853		INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]);
5854
5855	lruvec->mm_state.seq = MIN_NR_GENS;
5856	init_waitqueue_head(&lruvec->mm_state.wait);
5857}
5858
5859#ifdef CONFIG_MEMCG
5860void lru_gen_init_memcg(struct mem_cgroup *memcg)
5861{
5862	INIT_LIST_HEAD(&memcg->mm_list.fifo);
5863	spin_lock_init(&memcg->mm_list.lock);
5864}
5865
5866void lru_gen_exit_memcg(struct mem_cgroup *memcg)
5867{
5868	int i;
5869	int nid;
5870
5871	for_each_node(nid) {
5872		struct lruvec *lruvec = get_lruvec(memcg, nid);
5873
5874		VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
5875					   sizeof(lruvec->lrugen.nr_pages)));
5876
5877		for (i = 0; i < NR_BLOOM_FILTERS; i++) {
5878			bitmap_free(lruvec->mm_state.filters[i]);
5879			lruvec->mm_state.filters[i] = NULL;
5880		}
5881	}
5882}
5883#endif
5884
5885static int __init init_lru_gen(void)
5886{
5887	BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
5888	BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
5889
5890	if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
5891		pr_err("lru_gen: failed to create sysfs group\n");
5892
5893	debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
5894	debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
5895
5896	return 0;
5897};
5898late_initcall(init_lru_gen);
5899
5900#else /* !CONFIG_LRU_GEN */
5901
5902static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
5903{
5904}
5905
5906static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5907{
5908}
5909
5910#endif /* CONFIG_LRU_GEN */
5911
5912static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5913{
5914	unsigned long nr[NR_LRU_LISTS];
5915	unsigned long targets[NR_LRU_LISTS];
5916	unsigned long nr_to_scan;
5917	enum lru_list lru;
5918	unsigned long nr_reclaimed = 0;
5919	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
5920	bool proportional_reclaim;
5921	struct blk_plug plug;
5922
5923	if (lru_gen_enabled()) {
5924		lru_gen_shrink_lruvec(lruvec, sc);
5925		return;
 
 
 
 
 
 
 
 
 
 
 
 
5926	}
5927
5928	get_scan_count(lruvec, sc, nr);
5929
5930	/* Record the original scan target for proportional adjustments later */
5931	memcpy(targets, nr, sizeof(nr));
5932
5933	/*
5934	 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
5935	 * event that can occur when there is little memory pressure e.g.
5936	 * multiple streaming readers/writers. Hence, we do not abort scanning
5937	 * when the requested number of pages are reclaimed when scanning at
5938	 * DEF_PRIORITY on the assumption that the fact we are direct
5939	 * reclaiming implies that kswapd is not keeping up and it is best to
5940	 * do a batch of work at once. For memcg reclaim one check is made to
5941	 * abort proportional reclaim if either the file or anon lru has already
5942	 * dropped to zero at the first pass.
5943	 */
5944	proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
5945				sc->priority == DEF_PRIORITY);
5946
5947	blk_start_plug(&plug);
5948	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
5949					nr[LRU_INACTIVE_FILE]) {
5950		unsigned long nr_anon, nr_file, percentage;
5951		unsigned long nr_scanned;
5952
5953		for_each_evictable_lru(lru) {
5954			if (nr[lru]) {
5955				nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
5956				nr[lru] -= nr_to_scan;
5957
5958				nr_reclaimed += shrink_list(lru, nr_to_scan,
5959							    lruvec, sc);
5960			}
5961		}
5962
5963		cond_resched();
5964
5965		if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
5966			continue;
5967
5968		/*
5969		 * For kswapd and memcg, reclaim at least the number of pages
5970		 * requested. Ensure that the anon and file LRUs are scanned
5971		 * proportionally what was requested by get_scan_count(). We
5972		 * stop reclaiming one LRU and reduce the amount scanning
5973		 * proportional to the original scan target.
5974		 */
5975		nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
5976		nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
5977
5978		/*
5979		 * It's just vindictive to attack the larger once the smaller
5980		 * has gone to zero.  And given the way we stop scanning the
5981		 * smaller below, this makes sure that we only make one nudge
5982		 * towards proportionality once we've got nr_to_reclaim.
5983		 */
5984		if (!nr_file || !nr_anon)
5985			break;
5986
5987		if (nr_file > nr_anon) {
5988			unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
5989						targets[LRU_ACTIVE_ANON] + 1;
5990			lru = LRU_BASE;
5991			percentage = nr_anon * 100 / scan_target;
5992		} else {
5993			unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
5994						targets[LRU_ACTIVE_FILE] + 1;
5995			lru = LRU_FILE;
5996			percentage = nr_file * 100 / scan_target;
5997		}
5998
5999		/* Stop scanning the smaller of the LRU */
6000		nr[lru] = 0;
6001		nr[lru + LRU_ACTIVE] = 0;
6002
6003		/*
6004		 * Recalculate the other LRU scan count based on its original
6005		 * scan target and the percentage scanning already complete
 
 
 
 
 
6006		 */
6007		lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
6008		nr_scanned = targets[lru] - nr[lru];
6009		nr[lru] = targets[lru] * (100 - percentage) / 100;
6010		nr[lru] -= min(nr[lru], nr_scanned);
6011
6012		lru += LRU_ACTIVE;
6013		nr_scanned = targets[lru] - nr[lru];
6014		nr[lru] = targets[lru] * (100 - percentage) / 100;
6015		nr[lru] -= min(nr[lru], nr_scanned);
6016	}
6017	blk_finish_plug(&plug);
6018	sc->nr_reclaimed += nr_reclaimed;
6019
6020	/*
6021	 * Even if we did not try to evict anon pages at all, we want to
6022	 * rebalance the anon lru active/inactive ratio.
6023	 */
6024	if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
6025	    inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6026		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6027				   sc, LRU_ACTIVE_ANON);
6028}
6029
6030/* Use reclaim/compaction for costly allocs or under memory pressure */
6031static bool in_reclaim_compaction(struct scan_control *sc)
6032{
6033	if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
6034			(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
6035			 sc->priority < DEF_PRIORITY - 2))
6036		return true;
6037
6038	return false;
6039}
6040
6041/*
6042 * Reclaim/compaction is used for high-order allocation requests. It reclaims
6043 * order-0 pages before compacting the zone. should_continue_reclaim() returns
6044 * true if more pages should be reclaimed such that when the page allocator
6045 * calls try_to_compact_pages() that it will have enough free pages to succeed.
6046 * It will give up earlier than that if there is difficulty reclaiming pages.
6047 */
6048static inline bool should_continue_reclaim(struct pglist_data *pgdat,
6049					unsigned long nr_reclaimed,
 
6050					struct scan_control *sc)
6051{
6052	unsigned long pages_for_compaction;
6053	unsigned long inactive_lru_pages;
6054	int z;
6055
6056	/* If not in reclaim/compaction mode, stop */
6057	if (!in_reclaim_compaction(sc))
6058		return false;
6059
6060	/*
6061	 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
6062	 * number of pages that were scanned. This will return to the caller
6063	 * with the risk reclaim/compaction and the resulting allocation attempt
6064	 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
6065	 * allocations through requiring that the full LRU list has been scanned
6066	 * first, by assuming that zero delta of sc->nr_scanned means full LRU
6067	 * scan, but that approximation was wrong, and there were corner cases
6068	 * where always a non-zero amount of pages were scanned.
6069	 */
6070	if (!nr_reclaimed)
6071		return false;
6072
6073	/* If compaction would go ahead or the allocation would succeed, stop */
6074	for (z = 0; z <= sc->reclaim_idx; z++) {
6075		struct zone *zone = &pgdat->node_zones[z];
6076		if (!managed_zone(zone))
6077			continue;
6078
6079		switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
6080		case COMPACT_SUCCESS:
6081		case COMPACT_CONTINUE:
6082			return false;
6083		default:
6084			/* check next zone */
6085			;
6086		}
6087	}
6088
6089	/*
6090	 * If we have not reclaimed enough pages for compaction and the
6091	 * inactive lists are large enough, continue reclaiming
6092	 */
6093	pages_for_compaction = compact_gap(sc->order);
6094	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
6095	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
6096		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
6097
6098	return inactive_lru_pages > pages_for_compaction;
6099}
6100
6101static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
6102{
6103	struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
6104	struct mem_cgroup *memcg;
6105
6106	memcg = mem_cgroup_iter(target_memcg, NULL, NULL);
6107	do {
6108		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6109		unsigned long reclaimed;
6110		unsigned long scanned;
6111
6112		/*
6113		 * This loop can become CPU-bound when target memcgs
6114		 * aren't eligible for reclaim - either because they
6115		 * don't have any reclaimable pages, or because their
6116		 * memory is explicitly protected. Avoid soft lockups.
6117		 */
6118		cond_resched();
6119
6120		mem_cgroup_calculate_protection(target_memcg, memcg);
6121
6122		if (mem_cgroup_below_min(target_memcg, memcg)) {
6123			/*
6124			 * Hard protection.
6125			 * If there is no reclaimable memory, OOM.
6126			 */
6127			continue;
6128		} else if (mem_cgroup_below_low(target_memcg, memcg)) {
6129			/*
6130			 * Soft protection.
6131			 * Respect the protection only as long as
6132			 * there is an unprotected supply
6133			 * of reclaimable memory from other cgroups.
6134			 */
6135			if (!sc->memcg_low_reclaim) {
6136				sc->memcg_low_skipped = 1;
6137				continue;
6138			}
6139			memcg_memory_event(memcg, MEMCG_LOW);
6140		}
6141
6142		reclaimed = sc->nr_reclaimed;
6143		scanned = sc->nr_scanned;
6144
6145		shrink_lruvec(lruvec, sc);
6146
6147		shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
6148			    sc->priority);
6149
6150		/* Record the group's reclaim efficiency */
6151		if (!sc->proactive)
6152			vmpressure(sc->gfp_mask, memcg, false,
6153				   sc->nr_scanned - scanned,
6154				   sc->nr_reclaimed - reclaimed);
6155
6156	} while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL)));
 
 
 
 
 
 
 
6157}
6158
6159static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 
 
 
 
6160{
6161	struct reclaim_state *reclaim_state = current->reclaim_state;
 
 
6162	unsigned long nr_reclaimed, nr_scanned;
6163	struct lruvec *target_lruvec;
6164	bool reclaimable = false;
6165
6166	target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
6167
6168again:
6169	memset(&sc->nr, 0, sizeof(sc->nr));
6170
6171	nr_reclaimed = sc->nr_reclaimed;
 
6172	nr_scanned = sc->nr_scanned;
 
6173
6174	prepare_scan_count(pgdat, sc);
6175
6176	shrink_node_memcgs(pgdat, sc);
 
 
 
 
6177
6178	if (reclaim_state) {
6179		sc->nr_reclaimed += reclaim_state->reclaimed_slab;
6180		reclaim_state->reclaimed_slab = 0;
6181	}
6182
6183	/* Record the subtree's reclaim efficiency */
6184	if (!sc->proactive)
6185		vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
6186			   sc->nr_scanned - nr_scanned,
6187			   sc->nr_reclaimed - nr_reclaimed);
6188
6189	if (sc->nr_reclaimed - nr_reclaimed)
6190		reclaimable = true;
6191
6192	if (current_is_kswapd()) {
6193		/*
6194		 * If reclaim is isolating dirty pages under writeback,
6195		 * it implies that the long-lived page allocation rate
6196		 * is exceeding the page laundering rate. Either the
6197		 * global limits are not being effective at throttling
6198		 * processes due to the page distribution throughout
6199		 * zones or there is heavy usage of a slow backing
6200		 * device. The only option is to throttle from reclaim
6201		 * context which is not ideal as there is no guarantee
6202		 * the dirtying process is throttled in the same way
6203		 * balance_dirty_pages() manages.
6204		 *
6205		 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
6206		 * count the number of pages under pages flagged for
6207		 * immediate reclaim and stall if any are encountered
6208		 * in the nr_immediate check below.
6209		 */
6210		if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
6211			set_bit(PGDAT_WRITEBACK, &pgdat->flags);
6212
6213		/* Allow kswapd to start writing pages during reclaim.*/
6214		if (sc->nr.unqueued_dirty == sc->nr.file_taken)
6215			set_bit(PGDAT_DIRTY, &pgdat->flags);
6216
6217		/*
6218		 * If kswapd scans pages marked for immediate
6219		 * reclaim and under writeback (nr_immediate), it
6220		 * implies that pages are cycling through the LRU
6221		 * faster than they are written so forcibly stall
6222		 * until some pages complete writeback.
6223		 */
6224		if (sc->nr.immediate)
6225			reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
6226	}
 
6227
6228	/*
6229	 * Tag a node/memcg as congested if all the dirty pages were marked
6230	 * for writeback and immediate reclaim (counted in nr.congested).
6231	 *
6232	 * Legacy memcg will stall in page writeback so avoid forcibly
6233	 * stalling in reclaim_throttle().
6234	 */
6235	if ((current_is_kswapd() ||
6236	     (cgroup_reclaim(sc) && writeback_throttling_sane(sc))) &&
6237	    sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
6238		set_bit(LRUVEC_CONGESTED, &target_lruvec->flags);
6239
6240	/*
6241	 * Stall direct reclaim for IO completions if the lruvec is
6242	 * node is congested. Allow kswapd to continue until it
6243	 * starts encountering unqueued dirty pages or cycling through
6244	 * the LRU too quickly.
6245	 */
6246	if (!current_is_kswapd() && current_may_throttle() &&
6247	    !sc->hibernation_mode &&
6248	    test_bit(LRUVEC_CONGESTED, &target_lruvec->flags))
6249		reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
6250
6251	if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
6252				    sc))
6253		goto again;
6254
6255	/*
6256	 * Kswapd gives up on balancing particular nodes after too
6257	 * many failures to reclaim anything from them and goes to
6258	 * sleep. On reclaim progress, reset the failure counter. A
6259	 * successful direct reclaim run will revive a dormant kswapd.
6260	 */
6261	if (reclaimable)
6262		pgdat->kswapd_failures = 0;
6263}
6264
6265/*
6266 * Returns true if compaction should go ahead for a costly-order request, or
6267 * the allocation would already succeed without compaction. Return false if we
6268 * should reclaim first.
6269 */
6270static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
6271{
6272	unsigned long watermark;
6273	enum compact_result suitable;
6274
6275	suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
6276	if (suitable == COMPACT_SUCCESS)
6277		/* Allocation should succeed already. Don't reclaim. */
6278		return true;
6279	if (suitable == COMPACT_SKIPPED)
6280		/* Compaction cannot yet proceed. Do reclaim. */
6281		return false;
6282
6283	/*
6284	 * Compaction is already possible, but it takes time to run and there
6285	 * are potentially other callers using the pages just freed. So proceed
6286	 * with reclaim to make a buffer of free pages available to give
6287	 * compaction a reasonable chance of completing and allocating the page.
6288	 * Note that we won't actually reclaim the whole buffer in one attempt
6289	 * as the target watermark in should_continue_reclaim() is lower. But if
6290	 * we are already above the high+gap watermark, don't reclaim at all.
6291	 */
6292	watermark = high_wmark_pages(zone) + compact_gap(sc->order);
6293
6294	return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
6295}
6296
6297static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
6298{
6299	/*
6300	 * If reclaim is making progress greater than 12% efficiency then
6301	 * wake all the NOPROGRESS throttled tasks.
6302	 */
6303	if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
6304		wait_queue_head_t *wqh;
6305
6306		wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
6307		if (waitqueue_active(wqh))
6308			wake_up(wqh);
6309
6310		return;
6311	}
6312
6313	/*
6314	 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6315	 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6316	 * under writeback and marked for immediate reclaim at the tail of the
6317	 * LRU.
6318	 */
6319	if (current_is_kswapd() || cgroup_reclaim(sc))
6320		return;
6321
6322	/* Throttle if making no progress at high prioities. */
6323	if (sc->priority == 1 && !sc->nr_reclaimed)
6324		reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
6325}
6326
6327/*
6328 * This is the direct reclaim path, for page-allocating processes.  We only
6329 * try to reclaim pages from zones which will satisfy the caller's allocation
6330 * request.
6331 *
 
 
 
 
 
 
 
 
6332 * If a zone is deemed to be full of pinned pages then just give it a light
6333 * scan then give up on it.
6334 */
6335static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 
6336{
6337	struct zoneref *z;
6338	struct zone *zone;
6339	unsigned long nr_soft_reclaimed;
6340	unsigned long nr_soft_scanned;
6341	gfp_t orig_mask;
6342	pg_data_t *last_pgdat = NULL;
6343	pg_data_t *first_pgdat = NULL;
6344
6345	/*
6346	 * If the number of buffer_heads in the machine exceeds the maximum
6347	 * allowed level, force direct reclaim to scan the highmem zone as
6348	 * highmem pages could be pinning lowmem pages storing buffer_heads
6349	 */
6350	orig_mask = sc->gfp_mask;
6351	if (buffer_heads_over_limit) {
6352		sc->gfp_mask |= __GFP_HIGHMEM;
6353		sc->reclaim_idx = gfp_zone(sc->gfp_mask);
6354	}
6355
6356	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6357					sc->reclaim_idx, sc->nodemask) {
 
 
6358		/*
6359		 * Take care memory controller reclaiming has small influence
6360		 * to global LRU.
6361		 */
6362		if (!cgroup_reclaim(sc)) {
6363			if (!cpuset_zone_allowed(zone,
6364						 GFP_KERNEL | __GFP_HARDWALL))
6365				continue;
6366
6367			/*
6368			 * If we already have plenty of memory free for
6369			 * compaction in this zone, don't free any more.
6370			 * Even though compaction is invoked for any
6371			 * non-zero order, only frequent costly order
6372			 * reclamation is disruptive enough to become a
6373			 * noticeable problem, like transparent huge
6374			 * page allocations.
6375			 */
6376			if (IS_ENABLED(CONFIG_COMPACTION) &&
6377			    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
6378			    compaction_ready(zone, sc)) {
6379				sc->compaction_ready = true;
6380				continue;
6381			}
6382
6383			/*
6384			 * Shrink each node in the zonelist once. If the
6385			 * zonelist is ordered by zone (not the default) then a
6386			 * node may be shrunk multiple times but in that case
6387			 * the user prefers lower zones being preserved.
6388			 */
6389			if (zone->zone_pgdat == last_pgdat)
6390				continue;
6391
6392			/*
6393			 * This steals pages from memory cgroups over softlimit
6394			 * and returns the number of reclaimed pages and
6395			 * scanned pages. This works for global memory pressure
6396			 * and balancing, not for a memcg's limit.
6397			 */
6398			nr_soft_scanned = 0;
6399			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
6400						sc->order, sc->gfp_mask,
6401						&nr_soft_scanned);
6402			sc->nr_reclaimed += nr_soft_reclaimed;
6403			sc->nr_scanned += nr_soft_scanned;
6404			/* need some check for avoid more shrink_zone() */
6405		}
6406
6407		if (!first_pgdat)
6408			first_pgdat = zone->zone_pgdat;
6409
6410		/* See comment about same check for global reclaim above */
6411		if (zone->zone_pgdat == last_pgdat)
6412			continue;
6413		last_pgdat = zone->zone_pgdat;
6414		shrink_node(zone->zone_pgdat, sc);
6415	}
 
6416
6417	if (first_pgdat)
6418		consider_reclaim_throttle(first_pgdat, sc);
6419
6420	/*
6421	 * Restore to original mask to avoid the impact on the caller if we
6422	 * promoted it to __GFP_HIGHMEM.
6423	 */
6424	sc->gfp_mask = orig_mask;
6425}
6426
6427static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
 
 
6428{
6429	struct lruvec *target_lruvec;
6430	unsigned long refaults;
6431
6432	if (lru_gen_enabled())
6433		return;
 
 
 
 
 
 
 
6434
6435	target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
6436	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
6437	target_lruvec->refaults[WORKINGSET_ANON] = refaults;
6438	refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
6439	target_lruvec->refaults[WORKINGSET_FILE] = refaults;
6440}
6441
6442/*
6443 * This is the main entry point to direct page reclaim.
6444 *
6445 * If a full scan of the inactive list fails to free enough memory then we
6446 * are "out of memory" and something needs to be killed.
6447 *
6448 * If the caller is !__GFP_FS then the probability of a failure is reasonably
6449 * high - the zone may be full of dirty or under-writeback pages, which this
6450 * caller can't do much about.  We kick the writeback threads and take explicit
6451 * naps in the hope that some of these pages can be written.  But if the
6452 * allocating task holds filesystem locks which prevent writeout this might not
6453 * work, and the allocation attempt will fail.
6454 *
6455 * returns:	0, if no pages reclaimed
6456 * 		else, the number of pages reclaimed
6457 */
6458static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
6459					  struct scan_control *sc)
 
6460{
6461	int initial_priority = sc->priority;
6462	pg_data_t *last_pgdat;
 
6463	struct zoneref *z;
6464	struct zone *zone;
6465retry:
 
 
6466	delayacct_freepages_start();
6467
6468	if (!cgroup_reclaim(sc))
6469		__count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
6470
6471	do {
6472		if (!sc->proactive)
6473			vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
6474					sc->priority);
6475		sc->nr_scanned = 0;
6476		shrink_zones(zonelist, sc);
 
 
 
 
 
 
 
 
 
 
 
 
6477
6478		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
6479			break;
6480
6481		if (sc->compaction_ready)
6482			break;
 
 
 
 
 
 
 
6483
6484		/*
6485		 * If we're getting trouble reclaiming, start doing
6486		 * writepage even in laptop mode.
6487		 */
6488		if (sc->priority < DEF_PRIORITY - 2)
 
 
 
 
 
6489			sc->may_writepage = 1;
6490	} while (--sc->priority >= 0);
6491
6492	last_pgdat = NULL;
6493	for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
6494					sc->nodemask) {
6495		if (zone->zone_pgdat == last_pgdat)
6496			continue;
6497		last_pgdat = zone->zone_pgdat;
6498
6499		snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
6500
6501		if (cgroup_reclaim(sc)) {
6502			struct lruvec *lruvec;
6503
6504			lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
6505						   zone->zone_pgdat);
6506			clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
 
 
 
 
 
 
6507		}
6508	}
6509
 
6510	delayacct_freepages_end();
 
6511
6512	if (sc->nr_reclaimed)
6513		return sc->nr_reclaimed;
6514
6515	/* Aborted reclaim to try compaction? don't OOM, then */
6516	if (sc->compaction_ready)
6517		return 1;
6518
6519	/*
6520	 * We make inactive:active ratio decisions based on the node's
6521	 * composition of memory, but a restrictive reclaim_idx or a
6522	 * memory.low cgroup setting can exempt large amounts of
6523	 * memory from reclaim. Neither of which are very common, so
6524	 * instead of doing costly eligibility calculations of the
6525	 * entire cgroup subtree up front, we assume the estimates are
6526	 * good, and retry with forcible deactivation if that fails.
6527	 */
6528	if (sc->skipped_deactivate) {
6529		sc->priority = initial_priority;
6530		sc->force_deactivate = 1;
6531		sc->skipped_deactivate = 0;
6532		goto retry;
6533	}
6534
6535	/* Untapped cgroup reserves?  Don't OOM, retry. */
6536	if (sc->memcg_low_skipped) {
6537		sc->priority = initial_priority;
6538		sc->force_deactivate = 0;
6539		sc->memcg_low_reclaim = 1;
6540		sc->memcg_low_skipped = 0;
6541		goto retry;
6542	}
6543
6544	return 0;
6545}
6546
6547static bool allow_direct_reclaim(pg_data_t *pgdat)
6548{
6549	struct zone *zone;
6550	unsigned long pfmemalloc_reserve = 0;
6551	unsigned long free_pages = 0;
6552	int i;
6553	bool wmark_ok;
6554
6555	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6556		return true;
6557
6558	for (i = 0; i <= ZONE_NORMAL; i++) {
6559		zone = &pgdat->node_zones[i];
6560		if (!managed_zone(zone))
6561			continue;
6562
6563		if (!zone_reclaimable_pages(zone))
6564			continue;
6565
6566		pfmemalloc_reserve += min_wmark_pages(zone);
6567		free_pages += zone_page_state(zone, NR_FREE_PAGES);
6568	}
6569
6570	/* If there are no reserves (unexpected config) then do not throttle */
6571	if (!pfmemalloc_reserve)
6572		return true;
6573
6574	wmark_ok = free_pages > pfmemalloc_reserve / 2;
6575
6576	/* kswapd must be awake if processes are being throttled */
6577	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
6578		if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
6579			WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
6580
6581		wake_up_interruptible(&pgdat->kswapd_wait);
6582	}
6583
6584	return wmark_ok;
6585}
6586
6587/*
6588 * Throttle direct reclaimers if backing storage is backed by the network
6589 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6590 * depleted. kswapd will continue to make progress and wake the processes
6591 * when the low watermark is reached.
6592 *
6593 * Returns true if a fatal signal was delivered during throttling. If this
6594 * happens, the page allocator should not consider triggering the OOM killer.
6595 */
6596static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
6597					nodemask_t *nodemask)
6598{
6599	struct zoneref *z;
6600	struct zone *zone;
6601	pg_data_t *pgdat = NULL;
6602
6603	/*
6604	 * Kernel threads should not be throttled as they may be indirectly
6605	 * responsible for cleaning pages necessary for reclaim to make forward
6606	 * progress. kjournald for example may enter direct reclaim while
6607	 * committing a transaction where throttling it could forcing other
6608	 * processes to block on log_wait_commit().
6609	 */
6610	if (current->flags & PF_KTHREAD)
6611		goto out;
6612
6613	/*
6614	 * If a fatal signal is pending, this process should not throttle.
6615	 * It should return quickly so it can exit and free its memory
6616	 */
6617	if (fatal_signal_pending(current))
6618		goto out;
6619
6620	/*
6621	 * Check if the pfmemalloc reserves are ok by finding the first node
6622	 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6623	 * GFP_KERNEL will be required for allocating network buffers when
6624	 * swapping over the network so ZONE_HIGHMEM is unusable.
6625	 *
6626	 * Throttling is based on the first usable node and throttled processes
6627	 * wait on a queue until kswapd makes progress and wakes them. There
6628	 * is an affinity then between processes waking up and where reclaim
6629	 * progress has been made assuming the process wakes on the same node.
6630	 * More importantly, processes running on remote nodes will not compete
6631	 * for remote pfmemalloc reserves and processes on different nodes
6632	 * should make reasonable progress.
6633	 */
6634	for_each_zone_zonelist_nodemask(zone, z, zonelist,
6635					gfp_zone(gfp_mask), nodemask) {
6636		if (zone_idx(zone) > ZONE_NORMAL)
6637			continue;
6638
6639		/* Throttle based on the first usable node */
6640		pgdat = zone->zone_pgdat;
6641		if (allow_direct_reclaim(pgdat))
6642			goto out;
6643		break;
6644	}
6645
6646	/* If no zone was usable by the allocation flags then do not throttle */
6647	if (!pgdat)
6648		goto out;
6649
6650	/* Account for the throttling */
6651	count_vm_event(PGSCAN_DIRECT_THROTTLE);
6652
6653	/*
6654	 * If the caller cannot enter the filesystem, it's possible that it
6655	 * is due to the caller holding an FS lock or performing a journal
6656	 * transaction in the case of a filesystem like ext[3|4]. In this case,
6657	 * it is not safe to block on pfmemalloc_wait as kswapd could be
6658	 * blocked waiting on the same lock. Instead, throttle for up to a
6659	 * second before continuing.
6660	 */
6661	if (!(gfp_mask & __GFP_FS))
6662		wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
6663			allow_direct_reclaim(pgdat), HZ);
6664	else
6665		/* Throttle until kswapd wakes the process */
6666		wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
6667			allow_direct_reclaim(pgdat));
6668
6669	if (fatal_signal_pending(current))
6670		return true;
6671
6672out:
6673	return false;
6674}
6675
6676unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
6677				gfp_t gfp_mask, nodemask_t *nodemask)
6678{
6679	unsigned long nr_reclaimed;
6680	struct scan_control sc = {
6681		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6682		.gfp_mask = current_gfp_context(gfp_mask),
6683		.reclaim_idx = gfp_zone(gfp_mask),
6684		.order = order,
6685		.nodemask = nodemask,
6686		.priority = DEF_PRIORITY,
6687		.may_writepage = !laptop_mode,
 
6688		.may_unmap = 1,
6689		.may_swap = 1,
 
 
 
 
 
 
6690	};
6691
6692	/*
6693	 * scan_control uses s8 fields for order, priority, and reclaim_idx.
6694	 * Confirm they are large enough for max values.
6695	 */
6696	BUILD_BUG_ON(MAX_ORDER > S8_MAX);
6697	BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
6698	BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
6699
6700	/*
6701	 * Do not enter reclaim if fatal signal was delivered while throttled.
6702	 * 1 is returned so that the page allocator does not OOM kill at this
6703	 * point.
6704	 */
6705	if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
6706		return 1;
6707
6708	set_task_reclaim_state(current, &sc.reclaim_state);
6709	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
6710
6711	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6712
6713	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
6714	set_task_reclaim_state(current, NULL);
6715
6716	return nr_reclaimed;
6717}
6718
6719#ifdef CONFIG_MEMCG
6720
6721/* Only used by soft limit reclaim. Do not reuse for anything else. */
6722unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
6723						gfp_t gfp_mask, bool noswap,
6724						pg_data_t *pgdat,
6725						unsigned long *nr_scanned)
6726{
6727	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6728	struct scan_control sc = {
 
6729		.nr_to_reclaim = SWAP_CLUSTER_MAX,
6730		.target_mem_cgroup = memcg,
6731		.may_writepage = !laptop_mode,
6732		.may_unmap = 1,
6733		.reclaim_idx = MAX_NR_ZONES - 1,
6734		.may_swap = !noswap,
 
 
6735	};
6736
6737	WARN_ON_ONCE(!current->reclaim_state);
6738
6739	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
6740			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
6741
6742	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
 
6743						      sc.gfp_mask);
6744
6745	/*
6746	 * NOTE: Although we can get the priority field, using it
6747	 * here is not a good idea, since it limits the pages we can scan.
6748	 * if we don't reclaim here, the shrink_node from balance_pgdat
6749	 * will pick up pages from other mem cgroup's as well. We hack
6750	 * the priority and make it zero.
6751	 */
6752	shrink_lruvec(lruvec, &sc);
6753
6754	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
6755
6756	*nr_scanned = sc.nr_scanned;
6757
6758	return sc.nr_reclaimed;
6759}
6760
6761unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
6762					   unsigned long nr_pages,
6763					   gfp_t gfp_mask,
6764					   unsigned int reclaim_options)
6765{
 
6766	unsigned long nr_reclaimed;
6767	unsigned int noreclaim_flag;
6768	struct scan_control sc = {
6769		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
6770		.gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
6771				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
6772		.reclaim_idx = MAX_NR_ZONES - 1,
6773		.target_mem_cgroup = memcg,
6774		.priority = DEF_PRIORITY,
6775		.may_writepage = !laptop_mode,
6776		.may_unmap = 1,
6777		.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
6778		.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
 
 
 
 
 
 
 
 
6779	};
 
6780	/*
6781	 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
6782	 * equal pressure on all the nodes. This is based on the assumption that
6783	 * the reclaim does not bail out early.
6784	 */
6785	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
 
 
6786
6787	set_task_reclaim_state(current, &sc.reclaim_state);
6788	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
6789	noreclaim_flag = memalloc_noreclaim_save();
6790
6791	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6792
6793	memalloc_noreclaim_restore(noreclaim_flag);
6794	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
6795	set_task_reclaim_state(current, NULL);
6796
6797	return nr_reclaimed;
6798}
6799#endif
6800
6801static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
6802{
6803	struct mem_cgroup *memcg;
6804	struct lruvec *lruvec;
6805
6806	if (lru_gen_enabled()) {
6807		lru_gen_age_node(pgdat, sc);
6808		return;
6809	}
6810
6811	if (!can_age_anon_pages(pgdat, sc))
6812		return;
6813
6814	lruvec = mem_cgroup_lruvec(NULL, pgdat);
6815	if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6816		return;
6817
6818	memcg = mem_cgroup_iter(NULL, NULL, NULL);
6819	do {
6820		lruvec = mem_cgroup_lruvec(memcg, pgdat);
6821		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6822				   sc, LRU_ACTIVE_ANON);
6823		memcg = mem_cgroup_iter(NULL, memcg, NULL);
6824	} while (memcg);
6825}
6826
6827static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
6828{
6829	int i;
6830	struct zone *zone;
6831
6832	/*
6833	 * Check for watermark boosts top-down as the higher zones
6834	 * are more likely to be boosted. Both watermarks and boosts
6835	 * should not be checked at the same time as reclaim would
6836	 * start prematurely when there is no boosting and a lower
6837	 * zone is balanced.
6838	 */
6839	for (i = highest_zoneidx; i >= 0; i--) {
6840		zone = pgdat->node_zones + i;
6841		if (!managed_zone(zone))
6842			continue;
6843
6844		if (zone->watermark_boost)
6845			return true;
6846	}
6847
6848	return false;
6849}
6850
6851/*
6852 * Returns true if there is an eligible zone balanced for the request order
6853 * and highest_zoneidx
 
 
 
 
 
 
 
 
 
 
 
 
6854 */
6855static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
 
6856{
 
6857	int i;
6858	unsigned long mark = -1;
6859	struct zone *zone;
6860
6861	/*
6862	 * Check watermarks bottom-up as lower zones are more likely to
6863	 * meet watermarks.
6864	 */
6865	for (i = 0; i <= highest_zoneidx; i++) {
6866		zone = pgdat->node_zones + i;
6867
6868		if (!managed_zone(zone))
6869			continue;
6870
6871		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
6872			mark = wmark_pages(zone, WMARK_PROMO);
6873		else
6874			mark = high_wmark_pages(zone);
6875		if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
6876			return true;
6877	}
6878
6879	/*
6880	 * If a node has no managed zone within highest_zoneidx, it does not
6881	 * need balancing by definition. This can happen if a zone-restricted
6882	 * allocation tries to wake a remote kswapd.
6883	 */
6884	if (mark == -1)
6885		return true;
6886
6887	return false;
 
6888}
6889
6890/* Clear pgdat state for congested, dirty or under writeback. */
6891static void clear_pgdat_congested(pg_data_t *pgdat)
 
6892{
6893	struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
6894
6895	clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
6896	clear_bit(PGDAT_DIRTY, &pgdat->flags);
6897	clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
6898}
6899
6900/*
6901 * Prepare kswapd for sleeping. This verifies that there are no processes
6902 * waiting in throttle_direct_reclaim() and that watermarks have been met.
6903 *
6904 * Returns true if kswapd is ready to sleep
6905 */
6906static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
6907				int highest_zoneidx)
6908{
6909	/*
6910	 * The throttled processes are normally woken up in balance_pgdat() as
6911	 * soon as allow_direct_reclaim() is true. But there is a potential
6912	 * race between when kswapd checks the watermarks and a process gets
6913	 * throttled. There is also a potential race if processes get
6914	 * throttled, kswapd wakes, a large process exits thereby balancing the
6915	 * zones, which causes kswapd to exit balance_pgdat() before reaching
6916	 * the wake up checks. If kswapd is going to sleep, no process should
6917	 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
6918	 * the wake up is premature, processes will wake kswapd and get
6919	 * throttled again. The difference from wake ups in balance_pgdat() is
6920	 * that here we are under prepare_to_wait().
6921	 */
6922	if (waitqueue_active(&pgdat->pfmemalloc_wait))
6923		wake_up_all(&pgdat->pfmemalloc_wait);
6924
6925	/* Hopeless node, leave it to direct reclaim */
6926	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6927		return true;
6928
6929	if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
6930		clear_pgdat_congested(pgdat);
6931		return true;
6932	}
6933
6934	return false;
6935}
6936
6937/*
6938 * kswapd shrinks a node of pages that are at or below the highest usable
6939 * zone that is currently unbalanced.
6940 *
6941 * Returns true if kswapd scanned at least the requested number of pages to
6942 * reclaim or if the lack of progress was due to pages under writeback.
6943 * This is used to determine if the scanning priority needs to be raised.
6944 */
6945static bool kswapd_shrink_node(pg_data_t *pgdat,
6946			       struct scan_control *sc)
6947{
6948	struct zone *zone;
6949	int z;
6950
6951	/* Reclaim a number of pages proportional to the number of zones */
6952	sc->nr_to_reclaim = 0;
6953	for (z = 0; z <= sc->reclaim_idx; z++) {
6954		zone = pgdat->node_zones + z;
6955		if (!managed_zone(zone))
6956			continue;
6957
6958		sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
6959	}
6960
6961	/*
6962	 * Historically care was taken to put equal pressure on all zones but
6963	 * now pressure is applied based on node LRU order.
6964	 */
6965	shrink_node(pgdat, sc);
6966
6967	/*
6968	 * Fragmentation may mean that the system cannot be rebalanced for
6969	 * high-order allocations. If twice the allocation size has been
6970	 * reclaimed then recheck watermarks only at order-0 to prevent
6971	 * excessive reclaim. Assume that a process requested a high-order
6972	 * can direct reclaim/compact.
6973	 */
6974	if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
6975		sc->order = 0;
6976
6977	return sc->nr_scanned >= sc->nr_to_reclaim;
6978}
6979
6980/* Page allocator PCP high watermark is lowered if reclaim is active. */
6981static inline void
6982update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
6983{
6984	int i;
6985	struct zone *zone;
6986
6987	for (i = 0; i <= highest_zoneidx; i++) {
6988		zone = pgdat->node_zones + i;
6989
6990		if (!managed_zone(zone))
6991			continue;
 
6992
6993		if (active)
6994			set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
 
6995		else
6996			clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6997	}
6998}
6999
7000static inline void
7001set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
7002{
7003	update_reclaim_active(pgdat, highest_zoneidx, true);
7004}
7005
7006static inline void
7007clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
7008{
7009	update_reclaim_active(pgdat, highest_zoneidx, false);
7010}
7011
7012/*
7013 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
7014 * that are eligible for use by the caller until at least one zone is
7015 * balanced.
7016 *
7017 * Returns the order kswapd finished reclaiming at.
 
 
 
 
 
 
 
 
7018 *
7019 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
7020 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
7021 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
7022 * or lower is eligible for reclaim until at least one usable zone is
7023 * balanced.
7024 */
7025static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
7026{
 
 
 
 
 
7027	int i;
 
 
 
7028	unsigned long nr_soft_reclaimed;
7029	unsigned long nr_soft_scanned;
7030	unsigned long pflags;
7031	unsigned long nr_boost_reclaim;
7032	unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
7033	bool boosted;
7034	struct zone *zone;
7035	struct scan_control sc = {
7036		.gfp_mask = GFP_KERNEL,
7037		.order = order,
7038		.may_unmap = 1,
 
 
 
 
 
 
 
 
7039	};
 
 
 
 
 
 
 
 
7040
7041	set_task_reclaim_state(current, &sc.reclaim_state);
7042	psi_memstall_enter(&pflags);
7043	__fs_reclaim_acquire(_THIS_IP_);
7044
7045	count_vm_event(PAGEOUTRUN);
 
 
7046
7047	/*
7048	 * Account for the reclaim boost. Note that the zone boost is left in
7049	 * place so that parallel allocations that are near the watermark will
7050	 * stall or direct reclaim until kswapd is finished.
7051	 */
7052	nr_boost_reclaim = 0;
7053	for (i = 0; i <= highest_zoneidx; i++) {
7054		zone = pgdat->node_zones + i;
7055		if (!managed_zone(zone))
7056			continue;
7057
7058		nr_boost_reclaim += zone->watermark_boost;
7059		zone_boosts[i] = zone->watermark_boost;
7060	}
7061	boosted = nr_boost_reclaim;
 
 
7062
7063restart:
7064	set_reclaim_active(pgdat, highest_zoneidx);
7065	sc.priority = DEF_PRIORITY;
7066	do {
7067		unsigned long nr_reclaimed = sc.nr_reclaimed;
7068		bool raise_priority = true;
7069		bool balanced;
7070		bool ret;
7071
7072		sc.reclaim_idx = highest_zoneidx;
7073
7074		/*
7075		 * If the number of buffer_heads exceeds the maximum allowed
7076		 * then consider reclaiming from all zones. This has a dual
7077		 * purpose -- on 64-bit systems it is expected that
7078		 * buffer_heads are stripped during active rotation. On 32-bit
7079		 * systems, highmem pages can pin lowmem memory and shrinking
7080		 * buffers can relieve lowmem pressure. Reclaim may still not
7081		 * go ahead if all eligible zones for the original allocation
7082		 * request are balanced to avoid excessive reclaim from kswapd.
7083		 */
7084		if (buffer_heads_over_limit) {
7085			for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
7086				zone = pgdat->node_zones + i;
7087				if (!managed_zone(zone))
7088					continue;
7089
7090				sc.reclaim_idx = i;
 
 
 
 
 
 
 
 
 
 
 
 
 
7091				break;
 
 
 
7092			}
7093		}
 
 
7094
7095		/*
7096		 * If the pgdat is imbalanced then ignore boosting and preserve
7097		 * the watermarks for a later time and restart. Note that the
7098		 * zone watermarks will be still reset at the end of balancing
7099		 * on the grounds that the normal reclaim should be enough to
7100		 * re-evaluate if boosting is required when kswapd next wakes.
7101		 */
7102		balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
7103		if (!balanced && nr_boost_reclaim) {
7104			nr_boost_reclaim = 0;
7105			goto restart;
7106		}
7107
7108		/*
7109		 * If boosting is not active then only reclaim if there are no
7110		 * eligible zones. Note that sc.reclaim_idx is not used as
7111		 * buffer_heads_over_limit may have adjusted it.
7112		 */
7113		if (!nr_boost_reclaim && balanced)
7114			goto out;
 
 
 
 
 
 
7115
7116		/* Limit the priority of boosting to avoid reclaim writeback */
7117		if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
7118			raise_priority = false;
7119
7120		/*
7121		 * Do not writeback or swap pages for boosted reclaim. The
7122		 * intent is to relieve pressure not issue sub-optimal IO
7123		 * from reclaim context. If no pages are reclaimed, the
7124		 * reclaim will be aborted.
7125		 */
7126		sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
7127		sc.may_swap = !nr_boost_reclaim;
7128
7129		/*
7130		 * Do some background aging, to give pages a chance to be
7131		 * referenced before reclaiming. All pages are rotated
7132		 * regardless of classzone as this is about consistent aging.
7133		 */
7134		kswapd_age_node(pgdat, &sc);
7135
7136		/*
7137		 * If we're getting trouble reclaiming, start doing writepage
7138		 * even in laptop mode.
7139		 */
7140		if (sc.priority < DEF_PRIORITY - 2)
7141			sc.may_writepage = 1;
 
 
 
7142
7143		/* Call soft limit reclaim before calling shrink_node. */
7144		sc.nr_scanned = 0;
7145		nr_soft_scanned = 0;
7146		nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order,
7147						sc.gfp_mask, &nr_soft_scanned);
7148		sc.nr_reclaimed += nr_soft_reclaimed;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7149
7150		/*
7151		 * There should be no need to raise the scanning priority if
7152		 * enough pages are already being scanned that that high
7153		 * watermark would be met at 100% efficiency.
7154		 */
7155		if (kswapd_shrink_node(pgdat, &sc))
7156			raise_priority = false;
7157
7158		/*
7159		 * If the low watermark is met there is no need for processes
7160		 * to be throttled on pfmemalloc_wait as they should not be
7161		 * able to safely make forward progress. Wake them
7162		 */
7163		if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
7164				allow_direct_reclaim(pgdat))
7165			wake_up_all(&pgdat->pfmemalloc_wait);
 
 
 
 
 
 
7166
7167		/* Check if kswapd should be suspending */
7168		__fs_reclaim_release(_THIS_IP_);
7169		ret = try_to_freeze();
7170		__fs_reclaim_acquire(_THIS_IP_);
7171		if (ret || kthread_should_stop())
7172			break;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7173
 
 
 
7174		/*
7175		 * Raise priority if scanning rate is too low or there was no
7176		 * progress in reclaiming pages
7177		 */
7178		nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
7179		nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
 
 
 
 
7180
7181		/*
7182		 * If reclaim made no progress for a boost, stop reclaim as
7183		 * IO cannot be queued and it could be an infinite loop in
7184		 * extreme circumstances.
 
7185		 */
7186		if (nr_boost_reclaim && !nr_reclaimed)
7187			break;
7188
7189		if (raise_priority || !nr_reclaimed)
7190			sc.priority--;
7191	} while (sc.priority >= 1);
7192
7193	if (!sc.nr_reclaimed)
7194		pgdat->kswapd_failures++;
7195
7196out:
7197	clear_reclaim_active(pgdat, highest_zoneidx);
7198
7199	/* If reclaim was boosted, account for the reclaim done in this pass */
7200	if (boosted) {
7201		unsigned long flags;
7202
7203		for (i = 0; i <= highest_zoneidx; i++) {
7204			if (!zone_boosts[i])
7205				continue;
7206
7207			/* Increments are under the zone lock */
7208			zone = pgdat->node_zones + i;
7209			spin_lock_irqsave(&zone->lock, flags);
7210			zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
7211			spin_unlock_irqrestore(&zone->lock, flags);
7212		}
7213
7214		/*
7215		 * As there is now likely space, wakeup kcompact to defragment
7216		 * pageblocks.
 
 
 
 
 
 
 
 
 
 
7217		 */
7218		wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
7219	}
7220
7221	snapshot_refaults(NULL, pgdat);
7222	__fs_reclaim_release(_THIS_IP_);
7223	psi_memstall_leave(&pflags);
7224	set_task_reclaim_state(current, NULL);
7225
7226	/*
7227	 * Return the order kswapd stopped reclaiming at as
7228	 * prepare_kswapd_sleep() takes it into account. If another caller
7229	 * entered the allocator slow path while kswapd was awake, order will
7230	 * remain at the higher level.
 
 
7231	 */
7232	return sc.order;
7233}
 
7234
7235/*
7236 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
7237 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
7238 * not a valid index then either kswapd runs for first time or kswapd couldn't
7239 * sleep after previous reclaim attempt (node is still unbalanced). In that
7240 * case return the zone index of the previous kswapd reclaim cycle.
7241 */
7242static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
7243					   enum zone_type prev_highest_zoneidx)
7244{
7245	enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
 
 
 
 
 
 
7246
7247	return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
 
 
 
 
 
 
 
7248}
7249
7250static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
7251				unsigned int highest_zoneidx)
7252{
7253	long remaining = 0;
7254	DEFINE_WAIT(wait);
7255
7256	if (freezing(current) || kthread_should_stop())
7257		return;
7258
7259	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7260
7261	/*
7262	 * Try to sleep for a short interval. Note that kcompactd will only be
7263	 * woken if it is possible to sleep for a short interval. This is
7264	 * deliberate on the assumption that if reclaim cannot keep an
7265	 * eligible zone balanced that it's also unlikely that compaction will
7266	 * succeed.
7267	 */
7268	if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7269		/*
7270		 * Compaction records what page blocks it recently failed to
7271		 * isolate pages from and skips them in the future scanning.
7272		 * When kswapd is going to sleep, it is reasonable to assume
7273		 * that pages and compaction may succeed so reset the cache.
7274		 */
7275		reset_isolation_suitable(pgdat);
7276
7277		/*
7278		 * We have freed the memory, now we should compact it to make
7279		 * allocation of the requested order possible.
7280		 */
7281		wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
7282
7283		remaining = schedule_timeout(HZ/10);
7284
7285		/*
7286		 * If woken prematurely then reset kswapd_highest_zoneidx and
7287		 * order. The values will either be from a wakeup request or
7288		 * the previous request that slept prematurely.
7289		 */
7290		if (remaining) {
7291			WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
7292					kswapd_highest_zoneidx(pgdat,
7293							highest_zoneidx));
7294
7295			if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
7296				WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
7297		}
7298
7299		finish_wait(&pgdat->kswapd_wait, &wait);
7300		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7301	}
7302
7303	/*
7304	 * After a short sleep, check if it was a premature sleep. If not, then
7305	 * go fully to sleep until explicitly woken up.
7306	 */
7307	if (!remaining &&
7308	    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7309		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
7310
7311		/*
7312		 * vmstat counters are not perfectly accurate and the estimated
7313		 * value for counters such as NR_FREE_PAGES can deviate from the
7314		 * true value by nr_online_cpus * threshold. To avoid the zone
7315		 * watermarks being breached while under pressure, we reduce the
7316		 * per-cpu vmstat threshold while kswapd is awake and restore
7317		 * them before going back to sleep.
7318		 */
7319		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
7320
7321		if (!kthread_should_stop())
7322			schedule();
7323
7324		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
7325	} else {
7326		if (remaining)
7327			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
7328		else
7329			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
7330	}
7331	finish_wait(&pgdat->kswapd_wait, &wait);
7332}
7333
7334/*
7335 * The background pageout daemon, started as a kernel thread
7336 * from the init process.
7337 *
7338 * This basically trickles out pages so that we have _some_
7339 * free memory available even if there is no other activity
7340 * that frees anything up. This is needed for things like routing
7341 * etc, where we otherwise might have all activity going on in
7342 * asynchronous contexts that cannot page things out.
7343 *
7344 * If there are applications that are active memory-allocators
7345 * (most normal use), this basically shouldn't matter.
7346 */
7347static int kswapd(void *p)
7348{
7349	unsigned int alloc_order, reclaim_order;
7350	unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
7351	pg_data_t *pgdat = (pg_data_t *)p;
7352	struct task_struct *tsk = current;
 
 
 
 
7353	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
7354
 
 
7355	if (!cpumask_empty(cpumask))
7356		set_cpus_allowed_ptr(tsk, cpumask);
 
7357
7358	/*
7359	 * Tell the memory management that we're a "memory allocator",
7360	 * and that if we need more memory we should get access to it
7361	 * regardless (see "__alloc_pages()"). "kswapd" should
7362	 * never get caught in the normal page freeing logic.
7363	 *
7364	 * (Kswapd normally doesn't need memory anyway, but sometimes
7365	 * you need a small amount of memory in order to be able to
7366	 * page out something else, and this flag essentially protects
7367	 * us from recursively trying to free more memory as we're
7368	 * trying to free the first piece of memory in the first place).
7369	 */
7370	tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
7371	set_freezable();
7372
7373	WRITE_ONCE(pgdat->kswapd_order, 0);
7374	WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7375	atomic_set(&pgdat->nr_writeback_throttled, 0);
7376	for ( ; ; ) {
7377		bool ret;
 
 
 
 
 
 
 
 
 
 
 
 
7378
7379		alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
7380		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7381							highest_zoneidx);
7382
7383kswapd_try_sleep:
7384		kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
7385					highest_zoneidx);
7386
7387		/* Read the new order and highest_zoneidx */
7388		alloc_order = READ_ONCE(pgdat->kswapd_order);
7389		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7390							highest_zoneidx);
7391		WRITE_ONCE(pgdat->kswapd_order, 0);
7392		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7393
7394		ret = try_to_freeze();
7395		if (kthread_should_stop())
7396			break;
7397
7398		/*
7399		 * We can speed up thawing tasks if we don't call balance_pgdat
7400		 * after returning from the refrigerator
7401		 */
7402		if (ret)
7403			continue;
7404
7405		/*
7406		 * Reclaim begins at the requested order but if a high-order
7407		 * reclaim fails then kswapd falls back to reclaiming for
7408		 * order-0. If that happens, kswapd will consider sleeping
7409		 * for the order it finished reclaiming at (reclaim_order)
7410		 * but kcompactd is woken to compact for the original
7411		 * request (alloc_order).
7412		 */
7413		trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
7414						alloc_order);
7415		reclaim_order = balance_pgdat(pgdat, alloc_order,
7416						highest_zoneidx);
7417		if (reclaim_order < alloc_order)
7418			goto kswapd_try_sleep;
7419	}
7420
7421	tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
7422
7423	return 0;
7424}
7425
7426/*
7427 * A zone is low on free memory or too fragmented for high-order memory.  If
7428 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7429 * pgdat.  It will wake up kcompactd after reclaiming memory.  If kswapd reclaim
7430 * has failed or is not needed, still wake up kcompactd if only compaction is
7431 * needed.
7432 */
7433void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
7434		   enum zone_type highest_zoneidx)
7435{
7436	pg_data_t *pgdat;
7437	enum zone_type curr_idx;
7438
7439	if (!managed_zone(zone))
7440		return;
7441
7442	if (!cpuset_zone_allowed(zone, gfp_flags))
7443		return;
7444
7445	pgdat = zone->zone_pgdat;
7446	curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7447
7448	if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
7449		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
7450
7451	if (READ_ONCE(pgdat->kswapd_order) < order)
7452		WRITE_ONCE(pgdat->kswapd_order, order);
7453
7454	if (!waitqueue_active(&pgdat->kswapd_wait))
7455		return;
7456
7457	/* Hopeless node, leave it to direct reclaim if possible */
7458	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
7459	    (pgdat_balanced(pgdat, order, highest_zoneidx) &&
7460	     !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
7461		/*
7462		 * There may be plenty of free memory available, but it's too
7463		 * fragmented for high-order allocations.  Wake up kcompactd
7464		 * and rely on compaction_suitable() to determine if it's
7465		 * needed.  If it fails, it will defer subsequent attempts to
7466		 * ratelimit its work.
7467		 */
7468		if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
7469			wakeup_kcompactd(pgdat, order, highest_zoneidx);
7470		return;
7471	}
7472
7473	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
7474				      gfp_flags);
7475	wake_up_interruptible(&pgdat->kswapd_wait);
7476}
7477
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7478#ifdef CONFIG_HIBERNATION
7479/*
7480 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7481 * freed pages.
7482 *
7483 * Rather than trying to age LRUs the aim is to preserve the overall
7484 * LRU order by reclaiming preferentially
7485 * inactive > active > active referenced > active mapped
7486 */
7487unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
7488{
 
7489	struct scan_control sc = {
7490		.nr_to_reclaim = nr_to_reclaim,
7491		.gfp_mask = GFP_HIGHUSER_MOVABLE,
7492		.reclaim_idx = MAX_NR_ZONES - 1,
7493		.priority = DEF_PRIORITY,
7494		.may_writepage = 1,
7495		.may_unmap = 1,
7496		.may_swap = 1,
 
 
 
7497		.hibernation_mode = 1,
 
 
 
 
7498	};
7499	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
 
7500	unsigned long nr_reclaimed;
7501	unsigned int noreclaim_flag;
7502
7503	fs_reclaim_acquire(sc.gfp_mask);
7504	noreclaim_flag = memalloc_noreclaim_save();
7505	set_task_reclaim_state(current, &sc.reclaim_state);
7506
7507	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
7508
7509	set_task_reclaim_state(current, NULL);
7510	memalloc_noreclaim_restore(noreclaim_flag);
7511	fs_reclaim_release(sc.gfp_mask);
 
 
 
 
 
 
 
7512
7513	return nr_reclaimed;
7514}
7515#endif /* CONFIG_HIBERNATION */
7516
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7517/*
7518 * This kswapd start function will be called by init and node-hot-add.
 
7519 */
7520void kswapd_run(int nid)
7521{
7522	pg_data_t *pgdat = NODE_DATA(nid);
 
7523
7524	pgdat_kswapd_lock(pgdat);
7525	if (!pgdat->kswapd) {
7526		pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
7527		if (IS_ERR(pgdat->kswapd)) {
7528			/* failure at boot is fatal */
7529			BUG_ON(system_state < SYSTEM_RUNNING);
7530			pr_err("Failed to start kswapd on node %d\n", nid);
7531			pgdat->kswapd = NULL;
7532		}
7533	}
7534	pgdat_kswapd_unlock(pgdat);
7535}
7536
7537/*
7538 * Called by memory hotplug when all memory in a node is offlined.  Caller must
7539 * be holding mem_hotplug_begin/done().
7540 */
7541void kswapd_stop(int nid)
7542{
7543	pg_data_t *pgdat = NODE_DATA(nid);
7544	struct task_struct *kswapd;
7545
7546	pgdat_kswapd_lock(pgdat);
7547	kswapd = pgdat->kswapd;
7548	if (kswapd) {
7549		kthread_stop(kswapd);
7550		pgdat->kswapd = NULL;
7551	}
7552	pgdat_kswapd_unlock(pgdat);
7553}
7554
7555static int __init kswapd_init(void)
7556{
7557	int nid;
7558
7559	swap_setup();
7560	for_each_node_state(nid, N_MEMORY)
7561 		kswapd_run(nid);
 
7562	return 0;
7563}
7564
7565module_init(kswapd_init)
7566
7567#ifdef CONFIG_NUMA
7568/*
7569 * Node reclaim mode
7570 *
7571 * If non-zero call node_reclaim when the number of free pages falls below
7572 * the watermarks.
7573 */
7574int node_reclaim_mode __read_mostly;
 
 
 
 
 
7575
7576/*
7577 * Priority for NODE_RECLAIM. This determines the fraction of pages
7578 * of a node considered for each zone_reclaim. 4 scans 1/16th of
7579 * a zone.
7580 */
7581#define NODE_RECLAIM_PRIORITY 4
7582
7583/*
7584 * Percentage of pages in a zone that must be unmapped for node_reclaim to
7585 * occur.
7586 */
7587int sysctl_min_unmapped_ratio = 1;
7588
7589/*
7590 * If the number of slab pages in a zone grows beyond this percentage then
7591 * slab reclaim needs to occur.
7592 */
7593int sysctl_min_slab_ratio = 5;
7594
7595static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
7596{
7597	unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
7598	unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
7599		node_page_state(pgdat, NR_ACTIVE_FILE);
7600
7601	/*
7602	 * It's possible for there to be more file mapped pages than
7603	 * accounted for by the pages on the file LRU lists because
7604	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7605	 */
7606	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
7607}
7608
7609/* Work out how many page cache pages we can reclaim in this reclaim_mode */
7610static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
7611{
7612	unsigned long nr_pagecache_reclaimable;
7613	unsigned long delta = 0;
7614
7615	/*
7616	 * If RECLAIM_UNMAP is set, then all file pages are considered
7617	 * potentially reclaimable. Otherwise, we have to worry about
7618	 * pages like swapcache and node_unmapped_file_pages() provides
7619	 * a better estimate
7620	 */
7621	if (node_reclaim_mode & RECLAIM_UNMAP)
7622		nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
7623	else
7624		nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
7625
7626	/* If we can't clean pages, remove dirty pages from consideration */
7627	if (!(node_reclaim_mode & RECLAIM_WRITE))
7628		delta += node_page_state(pgdat, NR_FILE_DIRTY);
7629
7630	/* Watch for any possible underflows due to delta */
7631	if (unlikely(delta > nr_pagecache_reclaimable))
7632		delta = nr_pagecache_reclaimable;
7633
7634	return nr_pagecache_reclaimable - delta;
7635}
7636
7637/*
7638 * Try to free up some pages from this node through reclaim.
7639 */
7640static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7641{
7642	/* Minimum pages needed in order to stay on node */
7643	const unsigned long nr_pages = 1 << order;
7644	struct task_struct *p = current;
7645	unsigned int noreclaim_flag;
 
7646	struct scan_control sc = {
7647		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
7648		.gfp_mask = current_gfp_context(gfp_mask),
7649		.order = order,
7650		.priority = NODE_RECLAIM_PRIORITY,
7651		.may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
7652		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
7653		.may_swap = 1,
7654		.reclaim_idx = gfp_zone(gfp_mask),
 
 
 
7655	};
7656	unsigned long pflags;
7657
7658	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
7659					   sc.gfp_mask);
7660
7661	cond_resched();
7662	psi_memstall_enter(&pflags);
7663	fs_reclaim_acquire(sc.gfp_mask);
7664	/*
7665	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
7666	 */
7667	noreclaim_flag = memalloc_noreclaim_save();
7668	set_task_reclaim_state(p, &sc.reclaim_state);
 
 
 
 
7669
7670	if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
7671	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
7672		/*
7673		 * Free memory by calling shrink node with increasing
7674		 * priorities until we have enough memory freed.
7675		 */
 
7676		do {
7677			shrink_node(pgdat, &sc);
7678		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
 
7679	}
7680
7681	set_task_reclaim_state(p, NULL);
7682	memalloc_noreclaim_restore(noreclaim_flag);
7683	fs_reclaim_release(sc.gfp_mask);
7684	psi_memstall_leave(&pflags);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7685
7686	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
 
 
 
 
 
7687
 
 
 
 
 
 
 
 
 
 
 
 
7688	return sc.nr_reclaimed >= nr_pages;
7689}
7690
7691int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7692{
 
7693	int ret;
7694
7695	/*
7696	 * Node reclaim reclaims unmapped file backed pages and
7697	 * slab pages if we are over the defined limits.
7698	 *
7699	 * A small portion of unmapped file backed pages is needed for
7700	 * file I/O otherwise pages read by file I/O will be immediately
7701	 * thrown out if the node is overallocated. So we do not reclaim
7702	 * if less than a specified percentage of the node is used by
7703	 * unmapped file backed pages.
7704	 */
7705	if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
7706	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
7707	    pgdat->min_slab_pages)
7708		return NODE_RECLAIM_FULL;
 
 
7709
7710	/*
7711	 * Do not scan if the allocation should not be delayed.
7712	 */
7713	if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
7714		return NODE_RECLAIM_NOSCAN;
7715
7716	/*
7717	 * Only run node reclaim on the local node or on nodes that do not
7718	 * have associated processors. This will favor the local processor
7719	 * over remote processors and spread off node memory allocations
7720	 * as wide as possible.
7721	 */
7722	if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
7723		return NODE_RECLAIM_NOSCAN;
 
7724
7725	if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
7726		return NODE_RECLAIM_NOSCAN;
7727
7728	ret = __node_reclaim(pgdat, gfp_mask, order);
7729	clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
7730
7731	if (!ret)
7732		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
7733
7734	return ret;
7735}
7736#endif
7737
7738void check_move_unevictable_pages(struct pagevec *pvec)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7739{
7740	struct folio_batch fbatch;
7741	unsigned i;
7742
7743	folio_batch_init(&fbatch);
7744	for (i = 0; i < pvec->nr; i++) {
7745		struct page *page = pvec->pages[i];
7746
7747		if (PageTransTail(page))
7748			continue;
7749		folio_batch_add(&fbatch, page_folio(page));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7750	}
7751	check_move_unevictable_folios(&fbatch);
7752}
7753EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
7754
7755/**
7756 * check_move_unevictable_folios - Move evictable folios to appropriate zone
7757 * lru list
7758 * @fbatch: Batch of lru folios to check.
7759 *
7760 * Checks folios for evictability, if an evictable folio is in the unevictable
7761 * lru list, moves it to the appropriate evictable lru list. This function
7762 * should be only used for lru folios.
7763 */
7764void check_move_unevictable_folios(struct folio_batch *fbatch)
7765{
7766	struct lruvec *lruvec = NULL;
7767	int pgscanned = 0;
7768	int pgrescued = 0;
7769	int i;
7770
7771	for (i = 0; i < fbatch->nr; i++) {
7772		struct folio *folio = fbatch->folios[i];
7773		int nr_pages = folio_nr_pages(folio);
7774
7775		pgscanned += nr_pages;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7776
7777		/* block memcg migration while the folio moves between lrus */
7778		if (!folio_test_clear_lru(folio))
7779			continue;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7780
7781		lruvec = folio_lruvec_relock_irq(folio, lruvec);
7782		if (folio_evictable(folio) && folio_test_unevictable(folio)) {
7783			lruvec_del_folio(lruvec, folio);
7784			folio_clear_unevictable(folio);
7785			lruvec_add_folio(lruvec, folio);
7786			pgrescued += nr_pages;
7787		}
7788		folio_set_lru(folio);
 
 
7789	}
 
7790
7791	if (lruvec) {
7792		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
7793		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7794		unlock_page_lruvec_irq(lruvec);
7795	} else if (pgscanned) {
7796		count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
 
 
 
 
 
 
 
 
 
 
 
 
7797	}
7798}
7799EXPORT_SYMBOL_GPL(check_move_unevictable_folios);