1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * linux/mm/swap.c 4 * 5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 6 */ 7 8/* 9 * This file contains the default values for the operation of the 10 * Linux VM subsystem. Fine-tuning documentation can be found in 11 * Documentation/admin-guide/sysctl/vm.rst. 12 * Started 18.12.91 13 * Swap aging added 23.2.95, Stephen Tweedie. 14 * Buffermem limits added 12.3.98, Rik van Riel. 15 */ 16 17#include <linux/mm.h> 18#include <linux/sched.h> 19#include <linux/kernel_stat.h> 20#include <linux/swap.h> 21#include <linux/mman.h> 22#include <linux/pagemap.h> 23#include <linux/pagevec.h> 24#include <linux/init.h> 25#include <linux/export.h> 26#include <linux/mm_inline.h> 27#include <linux/percpu_counter.h> 28#include <linux/memremap.h> 29#include <linux/percpu.h> 30#include <linux/cpu.h> 31#include <linux/notifier.h> 32#include <linux/backing-dev.h> 33#include <linux/memcontrol.h> 34#include <linux/gfp.h> 35#include <linux/uio.h> 36#include <linux/hugetlb.h> 37#include <linux/page_idle.h> 38#include <linux/local_lock.h> 39#include <linux/buffer_head.h> 40 41#include "internal.h" 42 43#define CREATE_TRACE_POINTS 44#include <trace/events/pagemap.h> 45 46/* How many pages do we try to swap or page in/out together? As a power of 2 */ 47int page_cluster; 48const int page_cluster_max = 31; 49 50/* Protecting only lru_rotate.fbatch which requires disabling interrupts */ 51struct lru_rotate { 52 local_lock_t lock; 53 struct folio_batch fbatch; 54}; 55static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = { 56 .lock = INIT_LOCAL_LOCK(lock), 57}; 58 59/* 60 * The following folio batches are grouped together because they are protected 61 * by disabling preemption (and interrupts remain enabled). 62 */ 63struct cpu_fbatches { 64 local_lock_t lock; 65 struct folio_batch lru_add; 66 struct folio_batch lru_deactivate_file; 67 struct folio_batch lru_deactivate; 68 struct folio_batch lru_lazyfree; 69#ifdef CONFIG_SMP 70 struct folio_batch activate; 71#endif 72}; 73static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = { 74 .lock = INIT_LOCAL_LOCK(lock), 75}; 76 77static void __page_cache_release(struct folio *folio, struct lruvec **lruvecp, 78 unsigned long *flagsp) 79{ 80 if (folio_test_lru(folio)) { 81 folio_lruvec_relock_irqsave(folio, lruvecp, flagsp); 82 lruvec_del_folio(*lruvecp, folio); 83 __folio_clear_lru_flags(folio); 84 } 85 86 /* 87 * In rare cases, when truncation or holepunching raced with 88 * munlock after VM_LOCKED was cleared, Mlocked may still be 89 * found set here. This does not indicate a problem, unless 90 * "unevictable_pgs_cleared" appears worryingly large. 91 */ 92 if (unlikely(folio_test_mlocked(folio))) { 93 long nr_pages = folio_nr_pages(folio); 94 95 __folio_clear_mlocked(folio); 96 zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages); 97 count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages); 98 } 99} 100 101/* 102 * This path almost never happens for VM activity - pages are normally freed 103 * in batches. But it gets used by networking - and for compound pages. 104 */ 105static void page_cache_release(struct folio *folio) 106{ 107 struct lruvec *lruvec = NULL; 108 unsigned long flags; 109 110 __page_cache_release(folio, &lruvec, &flags); 111 if (lruvec) 112 unlock_page_lruvec_irqrestore(lruvec, flags); 113} 114 115static void __folio_put_small(struct folio *folio) 116{ 117 page_cache_release(folio); 118 mem_cgroup_uncharge(folio); 119 free_unref_page(&folio->page, 0); 120} 121 122static void __folio_put_large(struct folio *folio) 123{ 124 /* 125 * __page_cache_release() is supposed to be called for thp, not for 126 * hugetlb. This is because hugetlb page does never have PageLRU set 127 * (it's never listed to any LRU lists) and no memcg routines should 128 * be called for hugetlb (it has a separate hugetlb_cgroup.) 129 */ 130 if (!folio_test_hugetlb(folio)) 131 page_cache_release(folio); 132 destroy_large_folio(folio); 133} 134 135void __folio_put(struct folio *folio) 136{ 137 if (unlikely(folio_is_zone_device(folio))) 138 free_zone_device_page(&folio->page); 139 else if (unlikely(folio_test_large(folio))) 140 __folio_put_large(folio); 141 else 142 __folio_put_small(folio); 143} 144EXPORT_SYMBOL(__folio_put); 145 146/** 147 * put_pages_list() - release a list of pages 148 * @pages: list of pages threaded on page->lru 149 * 150 * Release a list of pages which are strung together on page.lru. 151 */ 152void put_pages_list(struct list_head *pages) 153{ 154 struct folio_batch fbatch; 155 struct folio *folio, *next; 156 157 folio_batch_init(&fbatch); 158 list_for_each_entry_safe(folio, next, pages, lru) { 159 if (!folio_put_testzero(folio)) 160 continue; 161 if (folio_test_large(folio)) { 162 __folio_put_large(folio); 163 continue; 164 } 165 /* LRU flag must be clear because it's passed using the lru */ 166 if (folio_batch_add(&fbatch, folio) > 0) 167 continue; 168 free_unref_folios(&fbatch); 169 } 170 171 if (fbatch.nr) 172 free_unref_folios(&fbatch); 173 INIT_LIST_HEAD(pages); 174} 175EXPORT_SYMBOL(put_pages_list); 176 177typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio); 178 179static void lru_add_fn(struct lruvec *lruvec, struct folio *folio) 180{ 181 int was_unevictable = folio_test_clear_unevictable(folio); 182 long nr_pages = folio_nr_pages(folio); 183 184 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 185 186 /* 187 * Is an smp_mb__after_atomic() still required here, before 188 * folio_evictable() tests the mlocked flag, to rule out the possibility 189 * of stranding an evictable folio on an unevictable LRU? I think 190 * not, because __munlock_folio() only clears the mlocked flag 191 * while the LRU lock is held. 192 * 193 * (That is not true of __page_cache_release(), and not necessarily 194 * true of folios_put(): but those only clear the mlocked flag after 195 * folio_put_testzero() has excluded any other users of the folio.) 196 */ 197 if (folio_evictable(folio)) { 198 if (was_unevictable) 199 __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages); 200 } else { 201 folio_clear_active(folio); 202 folio_set_unevictable(folio); 203 /* 204 * folio->mlock_count = !!folio_test_mlocked(folio)? 205 * But that leaves __mlock_folio() in doubt whether another 206 * actor has already counted the mlock or not. Err on the 207 * safe side, underestimate, let page reclaim fix it, rather 208 * than leaving a page on the unevictable LRU indefinitely. 209 */ 210 folio->mlock_count = 0; 211 if (!was_unevictable) 212 __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages); 213 } 214 215 lruvec_add_folio(lruvec, folio); 216 trace_mm_lru_insertion(folio); 217} 218 219static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn) 220{ 221 int i; 222 struct lruvec *lruvec = NULL; 223 unsigned long flags = 0; 224 225 for (i = 0; i < folio_batch_count(fbatch); i++) { 226 struct folio *folio = fbatch->folios[i]; 227 228 /* block memcg migration while the folio moves between lru */ 229 if (move_fn != lru_add_fn && !folio_test_clear_lru(folio)) 230 continue; 231 232 folio_lruvec_relock_irqsave(folio, &lruvec, &flags); 233 move_fn(lruvec, folio); 234 235 folio_set_lru(folio); 236 } 237 238 if (lruvec) 239 unlock_page_lruvec_irqrestore(lruvec, flags); 240 folios_put(fbatch); 241} 242 243static void folio_batch_add_and_move(struct folio_batch *fbatch, 244 struct folio *folio, move_fn_t move_fn) 245{ 246 if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) && 247 !lru_cache_disabled()) 248 return; 249 folio_batch_move_lru(fbatch, move_fn); 250} 251 252static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio) 253{ 254 if (!folio_test_unevictable(folio)) { 255 lruvec_del_folio(lruvec, folio); 256 folio_clear_active(folio); 257 lruvec_add_folio_tail(lruvec, folio); 258 __count_vm_events(PGROTATED, folio_nr_pages(folio)); 259 } 260} 261 262/* 263 * Writeback is about to end against a folio which has been marked for 264 * immediate reclaim. If it still appears to be reclaimable, move it 265 * to the tail of the inactive list. 266 * 267 * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races. 268 */ 269void folio_rotate_reclaimable(struct folio *folio) 270{ 271 if (!folio_test_locked(folio) && !folio_test_dirty(folio) && 272 !folio_test_unevictable(folio) && folio_test_lru(folio)) { 273 struct folio_batch *fbatch; 274 unsigned long flags; 275 276 folio_get(folio); 277 local_lock_irqsave(&lru_rotate.lock, flags); 278 fbatch = this_cpu_ptr(&lru_rotate.fbatch); 279 folio_batch_add_and_move(fbatch, folio, lru_move_tail_fn); 280 local_unlock_irqrestore(&lru_rotate.lock, flags); 281 } 282} 283 284void lru_note_cost(struct lruvec *lruvec, bool file, 285 unsigned int nr_io, unsigned int nr_rotated) 286{ 287 unsigned long cost; 288 289 /* 290 * Reflect the relative cost of incurring IO and spending CPU 291 * time on rotations. This doesn't attempt to make a precise 292 * comparison, it just says: if reloads are about comparable 293 * between the LRU lists, or rotations are overwhelmingly 294 * different between them, adjust scan balance for CPU work. 295 */ 296 cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated; 297 298 do { 299 unsigned long lrusize; 300 301 /* 302 * Hold lruvec->lru_lock is safe here, since 303 * 1) The pinned lruvec in reclaim, or 304 * 2) From a pre-LRU page during refault (which also holds the 305 * rcu lock, so would be safe even if the page was on the LRU 306 * and could move simultaneously to a new lruvec). 307 */ 308 spin_lock_irq(&lruvec->lru_lock); 309 /* Record cost event */ 310 if (file) 311 lruvec->file_cost += cost; 312 else 313 lruvec->anon_cost += cost; 314 315 /* 316 * Decay previous events 317 * 318 * Because workloads change over time (and to avoid 319 * overflow) we keep these statistics as a floating 320 * average, which ends up weighing recent refaults 321 * more than old ones. 322 */ 323 lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) + 324 lruvec_page_state(lruvec, NR_ACTIVE_ANON) + 325 lruvec_page_state(lruvec, NR_INACTIVE_FILE) + 326 lruvec_page_state(lruvec, NR_ACTIVE_FILE); 327 328 if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) { 329 lruvec->file_cost /= 2; 330 lruvec->anon_cost /= 2; 331 } 332 spin_unlock_irq(&lruvec->lru_lock); 333 } while ((lruvec = parent_lruvec(lruvec))); 334} 335 336void lru_note_cost_refault(struct folio *folio) 337{ 338 lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio), 339 folio_nr_pages(folio), 0); 340} 341 342static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio) 343{ 344 if (!folio_test_active(folio) && !folio_test_unevictable(folio)) { 345 long nr_pages = folio_nr_pages(folio); 346 347 lruvec_del_folio(lruvec, folio); 348 folio_set_active(folio); 349 lruvec_add_folio(lruvec, folio); 350 trace_mm_lru_activate(folio); 351 352 __count_vm_events(PGACTIVATE, nr_pages); 353 __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE, 354 nr_pages); 355 } 356} 357 358#ifdef CONFIG_SMP 359static void folio_activate_drain(int cpu) 360{ 361 struct folio_batch *fbatch = &per_cpu(cpu_fbatches.activate, cpu); 362 363 if (folio_batch_count(fbatch)) 364 folio_batch_move_lru(fbatch, folio_activate_fn); 365} 366 367void folio_activate(struct folio *folio) 368{ 369 if (folio_test_lru(folio) && !folio_test_active(folio) && 370 !folio_test_unevictable(folio)) { 371 struct folio_batch *fbatch; 372 373 folio_get(folio); 374 local_lock(&cpu_fbatches.lock); 375 fbatch = this_cpu_ptr(&cpu_fbatches.activate); 376 folio_batch_add_and_move(fbatch, folio, folio_activate_fn); 377 local_unlock(&cpu_fbatches.lock); 378 } 379} 380 381#else 382static inline void folio_activate_drain(int cpu) 383{ 384} 385 386void folio_activate(struct folio *folio) 387{ 388 struct lruvec *lruvec; 389 390 if (folio_test_clear_lru(folio)) { 391 lruvec = folio_lruvec_lock_irq(folio); 392 folio_activate_fn(lruvec, folio); 393 unlock_page_lruvec_irq(lruvec); 394 folio_set_lru(folio); 395 } 396} 397#endif 398 399static void __lru_cache_activate_folio(struct folio *folio) 400{ 401 struct folio_batch *fbatch; 402 int i; 403 404 local_lock(&cpu_fbatches.lock); 405 fbatch = this_cpu_ptr(&cpu_fbatches.lru_add); 406 407 /* 408 * Search backwards on the optimistic assumption that the folio being 409 * activated has just been added to this batch. Note that only 410 * the local batch is examined as a !LRU folio could be in the 411 * process of being released, reclaimed, migrated or on a remote 412 * batch that is currently being drained. Furthermore, marking 413 * a remote batch's folio active potentially hits a race where 414 * a folio is marked active just after it is added to the inactive 415 * list causing accounting errors and BUG_ON checks to trigger. 416 */ 417 for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) { 418 struct folio *batch_folio = fbatch->folios[i]; 419 420 if (batch_folio == folio) { 421 folio_set_active(folio); 422 break; 423 } 424 } 425 426 local_unlock(&cpu_fbatches.lock); 427} 428 429#ifdef CONFIG_LRU_GEN 430static void folio_inc_refs(struct folio *folio) 431{ 432 unsigned long new_flags, old_flags = READ_ONCE(folio->flags); 433 434 if (folio_test_unevictable(folio)) 435 return; 436 437 if (!folio_test_referenced(folio)) { 438 folio_set_referenced(folio); 439 return; 440 } 441 442 if (!folio_test_workingset(folio)) { 443 folio_set_workingset(folio); 444 return; 445 } 446 447 /* see the comment on MAX_NR_TIERS */ 448 do { 449 new_flags = old_flags & LRU_REFS_MASK; 450 if (new_flags == LRU_REFS_MASK) 451 break; 452 453 new_flags += BIT(LRU_REFS_PGOFF); 454 new_flags |= old_flags & ~LRU_REFS_MASK; 455 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); 456} 457#else 458static void folio_inc_refs(struct folio *folio) 459{ 460} 461#endif /* CONFIG_LRU_GEN */ 462 463/* 464 * Mark a page as having seen activity. 465 * 466 * inactive,unreferenced -> inactive,referenced 467 * inactive,referenced -> active,unreferenced 468 * active,unreferenced -> active,referenced 469 * 470 * When a newly allocated page is not yet visible, so safe for non-atomic ops, 471 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page). 472 */ 473void folio_mark_accessed(struct folio *folio) 474{ 475 if (lru_gen_enabled()) { 476 folio_inc_refs(folio); 477 return; 478 } 479 480 if (!folio_test_referenced(folio)) { 481 folio_set_referenced(folio); 482 } else if (folio_test_unevictable(folio)) { 483 /* 484 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But, 485 * this list is never rotated or maintained, so marking an 486 * unevictable page accessed has no effect. 487 */ 488 } else if (!folio_test_active(folio)) { 489 /* 490 * If the folio is on the LRU, queue it for activation via 491 * cpu_fbatches.activate. Otherwise, assume the folio is in a 492 * folio_batch, mark it active and it'll be moved to the active 493 * LRU on the next drain. 494 */ 495 if (folio_test_lru(folio)) 496 folio_activate(folio); 497 else 498 __lru_cache_activate_folio(folio); 499 folio_clear_referenced(folio); 500 workingset_activation(folio); 501 } 502 if (folio_test_idle(folio)) 503 folio_clear_idle(folio); 504} 505EXPORT_SYMBOL(folio_mark_accessed); 506 507/** 508 * folio_add_lru - Add a folio to an LRU list. 509 * @folio: The folio to be added to the LRU. 510 * 511 * Queue the folio for addition to the LRU. The decision on whether 512 * to add the page to the [in]active [file|anon] list is deferred until the 513 * folio_batch is drained. This gives a chance for the caller of folio_add_lru() 514 * have the folio added to the active list using folio_mark_accessed(). 515 */ 516void folio_add_lru(struct folio *folio) 517{ 518 struct folio_batch *fbatch; 519 520 VM_BUG_ON_FOLIO(folio_test_active(folio) && 521 folio_test_unevictable(folio), folio); 522 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 523 524 /* see the comment in lru_gen_add_folio() */ 525 if (lru_gen_enabled() && !folio_test_unevictable(folio) && 526 lru_gen_in_fault() && !(current->flags & PF_MEMALLOC)) 527 folio_set_active(folio); 528 529 folio_get(folio); 530 local_lock(&cpu_fbatches.lock); 531 fbatch = this_cpu_ptr(&cpu_fbatches.lru_add); 532 folio_batch_add_and_move(fbatch, folio, lru_add_fn); 533 local_unlock(&cpu_fbatches.lock); 534} 535EXPORT_SYMBOL(folio_add_lru); 536 537/** 538 * folio_add_lru_vma() - Add a folio to the appropate LRU list for this VMA. 539 * @folio: The folio to be added to the LRU. 540 * @vma: VMA in which the folio is mapped. 541 * 542 * If the VMA is mlocked, @folio is added to the unevictable list. 543 * Otherwise, it is treated the same way as folio_add_lru(). 544 */ 545void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma) 546{ 547 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 548 549 if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED)) 550 mlock_new_folio(folio); 551 else 552 folio_add_lru(folio); 553} 554 555/* 556 * If the folio cannot be invalidated, it is moved to the 557 * inactive list to speed up its reclaim. It is moved to the 558 * head of the list, rather than the tail, to give the flusher 559 * threads some time to write it out, as this is much more 560 * effective than the single-page writeout from reclaim. 561 * 562 * If the folio isn't mapped and dirty/writeback, the folio 563 * could be reclaimed asap using the reclaim flag. 564 * 565 * 1. active, mapped folio -> none 566 * 2. active, dirty/writeback folio -> inactive, head, reclaim 567 * 3. inactive, mapped folio -> none 568 * 4. inactive, dirty/writeback folio -> inactive, head, reclaim 569 * 5. inactive, clean -> inactive, tail 570 * 6. Others -> none 571 * 572 * In 4, it moves to the head of the inactive list so the folio is 573 * written out by flusher threads as this is much more efficient 574 * than the single-page writeout from reclaim. 575 */ 576static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio) 577{ 578 bool active = folio_test_active(folio); 579 long nr_pages = folio_nr_pages(folio); 580 581 if (folio_test_unevictable(folio)) 582 return; 583 584 /* Some processes are using the folio */ 585 if (folio_mapped(folio)) 586 return; 587 588 lruvec_del_folio(lruvec, folio); 589 folio_clear_active(folio); 590 folio_clear_referenced(folio); 591 592 if (folio_test_writeback(folio) || folio_test_dirty(folio)) { 593 /* 594 * Setting the reclaim flag could race with 595 * folio_end_writeback() and confuse readahead. But the 596 * race window is _really_ small and it's not a critical 597 * problem. 598 */ 599 lruvec_add_folio(lruvec, folio); 600 folio_set_reclaim(folio); 601 } else { 602 /* 603 * The folio's writeback ended while it was in the batch. 604 * We move that folio to the tail of the inactive list. 605 */ 606 lruvec_add_folio_tail(lruvec, folio); 607 __count_vm_events(PGROTATED, nr_pages); 608 } 609 610 if (active) { 611 __count_vm_events(PGDEACTIVATE, nr_pages); 612 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, 613 nr_pages); 614 } 615} 616 617static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio) 618{ 619 if (!folio_test_unevictable(folio) && (folio_test_active(folio) || lru_gen_enabled())) { 620 long nr_pages = folio_nr_pages(folio); 621 622 lruvec_del_folio(lruvec, folio); 623 folio_clear_active(folio); 624 folio_clear_referenced(folio); 625 lruvec_add_folio(lruvec, folio); 626 627 __count_vm_events(PGDEACTIVATE, nr_pages); 628 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, 629 nr_pages); 630 } 631} 632 633static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio) 634{ 635 if (folio_test_anon(folio) && folio_test_swapbacked(folio) && 636 !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) { 637 long nr_pages = folio_nr_pages(folio); 638 639 lruvec_del_folio(lruvec, folio); 640 folio_clear_active(folio); 641 folio_clear_referenced(folio); 642 /* 643 * Lazyfree folios are clean anonymous folios. They have 644 * the swapbacked flag cleared, to distinguish them from normal 645 * anonymous folios 646 */ 647 folio_clear_swapbacked(folio); 648 lruvec_add_folio(lruvec, folio); 649 650 __count_vm_events(PGLAZYFREE, nr_pages); 651 __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE, 652 nr_pages); 653 } 654} 655 656/* 657 * Drain pages out of the cpu's folio_batch. 658 * Either "cpu" is the current CPU, and preemption has already been 659 * disabled; or "cpu" is being hot-unplugged, and is already dead. 660 */ 661void lru_add_drain_cpu(int cpu) 662{ 663 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu); 664 struct folio_batch *fbatch = &fbatches->lru_add; 665 666 if (folio_batch_count(fbatch)) 667 folio_batch_move_lru(fbatch, lru_add_fn); 668 669 fbatch = &per_cpu(lru_rotate.fbatch, cpu); 670 /* Disabling interrupts below acts as a compiler barrier. */ 671 if (data_race(folio_batch_count(fbatch))) { 672 unsigned long flags; 673 674 /* No harm done if a racing interrupt already did this */ 675 local_lock_irqsave(&lru_rotate.lock, flags); 676 folio_batch_move_lru(fbatch, lru_move_tail_fn); 677 local_unlock_irqrestore(&lru_rotate.lock, flags); 678 } 679 680 fbatch = &fbatches->lru_deactivate_file; 681 if (folio_batch_count(fbatch)) 682 folio_batch_move_lru(fbatch, lru_deactivate_file_fn); 683 684 fbatch = &fbatches->lru_deactivate; 685 if (folio_batch_count(fbatch)) 686 folio_batch_move_lru(fbatch, lru_deactivate_fn); 687 688 fbatch = &fbatches->lru_lazyfree; 689 if (folio_batch_count(fbatch)) 690 folio_batch_move_lru(fbatch, lru_lazyfree_fn); 691 692 folio_activate_drain(cpu); 693} 694 695/** 696 * deactivate_file_folio() - Deactivate a file folio. 697 * @folio: Folio to deactivate. 698 * 699 * This function hints to the VM that @folio is a good reclaim candidate, 700 * for example if its invalidation fails due to the folio being dirty 701 * or under writeback. 702 * 703 * Context: Caller holds a reference on the folio. 704 */ 705void deactivate_file_folio(struct folio *folio) 706{ 707 struct folio_batch *fbatch; 708 709 /* Deactivating an unevictable folio will not accelerate reclaim */ 710 if (folio_test_unevictable(folio)) 711 return; 712 713 folio_get(folio); 714 local_lock(&cpu_fbatches.lock); 715 fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file); 716 folio_batch_add_and_move(fbatch, folio, lru_deactivate_file_fn); 717 local_unlock(&cpu_fbatches.lock); 718} 719 720/* 721 * folio_deactivate - deactivate a folio 722 * @folio: folio to deactivate 723 * 724 * folio_deactivate() moves @folio to the inactive list if @folio was on the 725 * active list and was not unevictable. This is done to accelerate the 726 * reclaim of @folio. 727 */ 728void folio_deactivate(struct folio *folio) 729{ 730 if (folio_test_lru(folio) && !folio_test_unevictable(folio) && 731 (folio_test_active(folio) || lru_gen_enabled())) { 732 struct folio_batch *fbatch; 733 734 folio_get(folio); 735 local_lock(&cpu_fbatches.lock); 736 fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate); 737 folio_batch_add_and_move(fbatch, folio, lru_deactivate_fn); 738 local_unlock(&cpu_fbatches.lock); 739 } 740} 741 742/** 743 * folio_mark_lazyfree - make an anon folio lazyfree 744 * @folio: folio to deactivate 745 * 746 * folio_mark_lazyfree() moves @folio to the inactive file list. 747 * This is done to accelerate the reclaim of @folio. 748 */ 749void folio_mark_lazyfree(struct folio *folio) 750{ 751 if (folio_test_lru(folio) && folio_test_anon(folio) && 752 folio_test_swapbacked(folio) && !folio_test_swapcache(folio) && 753 !folio_test_unevictable(folio)) { 754 struct folio_batch *fbatch; 755 756 folio_get(folio); 757 local_lock(&cpu_fbatches.lock); 758 fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree); 759 folio_batch_add_and_move(fbatch, folio, lru_lazyfree_fn); 760 local_unlock(&cpu_fbatches.lock); 761 } 762} 763 764void lru_add_drain(void) 765{ 766 local_lock(&cpu_fbatches.lock); 767 lru_add_drain_cpu(smp_processor_id()); 768 local_unlock(&cpu_fbatches.lock); 769 mlock_drain_local(); 770} 771 772/* 773 * It's called from per-cpu workqueue context in SMP case so 774 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on 775 * the same cpu. It shouldn't be a problem in !SMP case since 776 * the core is only one and the locks will disable preemption. 777 */ 778static void lru_add_and_bh_lrus_drain(void) 779{ 780 local_lock(&cpu_fbatches.lock); 781 lru_add_drain_cpu(smp_processor_id()); 782 local_unlock(&cpu_fbatches.lock); 783 invalidate_bh_lrus_cpu(); 784 mlock_drain_local(); 785} 786 787void lru_add_drain_cpu_zone(struct zone *zone) 788{ 789 local_lock(&cpu_fbatches.lock); 790 lru_add_drain_cpu(smp_processor_id()); 791 drain_local_pages(zone); 792 local_unlock(&cpu_fbatches.lock); 793 mlock_drain_local(); 794} 795 796#ifdef CONFIG_SMP 797 798static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); 799 800static void lru_add_drain_per_cpu(struct work_struct *dummy) 801{ 802 lru_add_and_bh_lrus_drain(); 803} 804 805static bool cpu_needs_drain(unsigned int cpu) 806{ 807 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu); 808 809 /* Check these in order of likelihood that they're not zero */ 810 return folio_batch_count(&fbatches->lru_add) || 811 data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) || 812 folio_batch_count(&fbatches->lru_deactivate_file) || 813 folio_batch_count(&fbatches->lru_deactivate) || 814 folio_batch_count(&fbatches->lru_lazyfree) || 815 folio_batch_count(&fbatches->activate) || 816 need_mlock_drain(cpu) || 817 has_bh_in_lru(cpu, NULL); 818} 819 820/* 821 * Doesn't need any cpu hotplug locking because we do rely on per-cpu 822 * kworkers being shut down before our page_alloc_cpu_dead callback is 823 * executed on the offlined cpu. 824 * Calling this function with cpu hotplug locks held can actually lead 825 * to obscure indirect dependencies via WQ context. 826 */ 827static inline void __lru_add_drain_all(bool force_all_cpus) 828{ 829 /* 830 * lru_drain_gen - Global pages generation number 831 * 832 * (A) Definition: global lru_drain_gen = x implies that all generations 833 * 0 < n <= x are already *scheduled* for draining. 834 * 835 * This is an optimization for the highly-contended use case where a 836 * user space workload keeps constantly generating a flow of pages for 837 * each CPU. 838 */ 839 static unsigned int lru_drain_gen; 840 static struct cpumask has_work; 841 static DEFINE_MUTEX(lock); 842 unsigned cpu, this_gen; 843 844 /* 845 * Make sure nobody triggers this path before mm_percpu_wq is fully 846 * initialized. 847 */ 848 if (WARN_ON(!mm_percpu_wq)) 849 return; 850 851 /* 852 * Guarantee folio_batch counter stores visible by this CPU 853 * are visible to other CPUs before loading the current drain 854 * generation. 855 */ 856 smp_mb(); 857 858 /* 859 * (B) Locally cache global LRU draining generation number 860 * 861 * The read barrier ensures that the counter is loaded before the mutex 862 * is taken. It pairs with smp_mb() inside the mutex critical section 863 * at (D). 864 */ 865 this_gen = smp_load_acquire(&lru_drain_gen); 866 867 mutex_lock(&lock); 868 869 /* 870 * (C) Exit the draining operation if a newer generation, from another 871 * lru_add_drain_all(), was already scheduled for draining. Check (A). 872 */ 873 if (unlikely(this_gen != lru_drain_gen && !force_all_cpus)) 874 goto done; 875 876 /* 877 * (D) Increment global generation number 878 * 879 * Pairs with smp_load_acquire() at (B), outside of the critical 880 * section. Use a full memory barrier to guarantee that the 881 * new global drain generation number is stored before loading 882 * folio_batch counters. 883 * 884 * This pairing must be done here, before the for_each_online_cpu loop 885 * below which drains the page vectors. 886 * 887 * Let x, y, and z represent some system CPU numbers, where x < y < z. 888 * Assume CPU #z is in the middle of the for_each_online_cpu loop 889 * below and has already reached CPU #y's per-cpu data. CPU #x comes 890 * along, adds some pages to its per-cpu vectors, then calls 891 * lru_add_drain_all(). 892 * 893 * If the paired barrier is done at any later step, e.g. after the 894 * loop, CPU #x will just exit at (C) and miss flushing out all of its 895 * added pages. 896 */ 897 WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1); 898 smp_mb(); 899 900 cpumask_clear(&has_work); 901 for_each_online_cpu(cpu) { 902 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); 903 904 if (cpu_needs_drain(cpu)) { 905 INIT_WORK(work, lru_add_drain_per_cpu); 906 queue_work_on(cpu, mm_percpu_wq, work); 907 __cpumask_set_cpu(cpu, &has_work); 908 } 909 } 910 911 for_each_cpu(cpu, &has_work) 912 flush_work(&per_cpu(lru_add_drain_work, cpu)); 913 914done: 915 mutex_unlock(&lock); 916} 917 918void lru_add_drain_all(void) 919{ 920 __lru_add_drain_all(false); 921} 922#else 923void lru_add_drain_all(void) 924{ 925 lru_add_drain(); 926} 927#endif /* CONFIG_SMP */ 928 929atomic_t lru_disable_count = ATOMIC_INIT(0); 930 931/* 932 * lru_cache_disable() needs to be called before we start compiling 933 * a list of pages to be migrated using isolate_lru_page(). 934 * It drains pages on LRU cache and then disable on all cpus until 935 * lru_cache_enable is called. 936 * 937 * Must be paired with a call to lru_cache_enable(). 938 */ 939void lru_cache_disable(void) 940{ 941 atomic_inc(&lru_disable_count); 942 /* 943 * Readers of lru_disable_count are protected by either disabling 944 * preemption or rcu_read_lock: 945 * 946 * preempt_disable, local_irq_disable [bh_lru_lock()] 947 * rcu_read_lock [rt_spin_lock CONFIG_PREEMPT_RT] 948 * preempt_disable [local_lock !CONFIG_PREEMPT_RT] 949 * 950 * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on 951 * preempt_disable() regions of code. So any CPU which sees 952 * lru_disable_count = 0 will have exited the critical 953 * section when synchronize_rcu() returns. 954 */ 955 synchronize_rcu_expedited(); 956#ifdef CONFIG_SMP 957 __lru_add_drain_all(true); 958#else 959 lru_add_and_bh_lrus_drain(); 960#endif 961} 962 963/** 964 * folios_put_refs - Reduce the reference count on a batch of folios. 965 * @folios: The folios. 966 * @refs: The number of refs to subtract from each folio. 967 * 968 * Like folio_put(), but for a batch of folios. This is more efficient 969 * than writing the loop yourself as it will optimise the locks which need 970 * to be taken if the folios are freed. The folios batch is returned 971 * empty and ready to be reused for another batch; there is no need 972 * to reinitialise it. If @refs is NULL, we subtract one from each 973 * folio refcount. 974 * 975 * Context: May be called in process or interrupt context, but not in NMI 976 * context. May be called while holding a spinlock. 977 */ 978void folios_put_refs(struct folio_batch *folios, unsigned int *refs) 979{ 980 int i, j; 981 struct lruvec *lruvec = NULL; 982 unsigned long flags = 0; 983 984 for (i = 0, j = 0; i < folios->nr; i++) { 985 struct folio *folio = folios->folios[i]; 986 unsigned int nr_refs = refs ? refs[i] : 1; 987 988 if (is_huge_zero_page(&folio->page)) 989 continue; 990 991 if (folio_is_zone_device(folio)) { 992 if (lruvec) { 993 unlock_page_lruvec_irqrestore(lruvec, flags); 994 lruvec = NULL; 995 } 996 if (put_devmap_managed_page_refs(&folio->page, nr_refs)) 997 continue; 998 if (folio_ref_sub_and_test(folio, nr_refs)) 999 free_zone_device_page(&folio->page); 1000 continue; 1001 } 1002 1003 if (!folio_ref_sub_and_test(folio, nr_refs)) 1004 continue; 1005 1006 /* hugetlb has its own memcg */ 1007 if (folio_test_hugetlb(folio)) { 1008 if (lruvec) { 1009 unlock_page_lruvec_irqrestore(lruvec, flags); 1010 lruvec = NULL; 1011 } 1012 free_huge_folio(folio); 1013 continue; 1014 } 1015 if (folio_test_large(folio) && 1016 folio_test_large_rmappable(folio)) 1017 folio_undo_large_rmappable(folio); 1018 1019 __page_cache_release(folio, &lruvec, &flags); 1020 1021 if (j != i) 1022 folios->folios[j] = folio; 1023 j++; 1024 } 1025 if (lruvec) 1026 unlock_page_lruvec_irqrestore(lruvec, flags); 1027 if (!j) { 1028 folio_batch_reinit(folios); 1029 return; 1030 } 1031 1032 folios->nr = j; 1033 mem_cgroup_uncharge_folios(folios); 1034 free_unref_folios(folios); 1035} 1036EXPORT_SYMBOL(folios_put_refs); 1037 1038/** 1039 * release_pages - batched put_page() 1040 * @arg: array of pages to release 1041 * @nr: number of pages 1042 * 1043 * Decrement the reference count on all the pages in @arg. If it 1044 * fell to zero, remove the page from the LRU and free it. 1045 * 1046 * Note that the argument can be an array of pages, encoded pages, 1047 * or folio pointers. We ignore any encoded bits, and turn any of 1048 * them into just a folio that gets free'd. 1049 */ 1050void release_pages(release_pages_arg arg, int nr) 1051{ 1052 struct folio_batch fbatch; 1053 int refs[PAGEVEC_SIZE]; 1054 struct encoded_page **encoded = arg.encoded_pages; 1055 int i; 1056 1057 folio_batch_init(&fbatch); 1058 for (i = 0; i < nr; i++) { 1059 /* Turn any of the argument types into a folio */ 1060 struct folio *folio = page_folio(encoded_page_ptr(encoded[i])); 1061 1062 /* Is our next entry actually "nr_pages" -> "nr_refs" ? */ 1063 refs[fbatch.nr] = 1; 1064 if (unlikely(encoded_page_flags(encoded[i]) & 1065 ENCODED_PAGE_BIT_NR_PAGES_NEXT)) 1066 refs[fbatch.nr] = encoded_nr_pages(encoded[++i]); 1067 1068 if (folio_batch_add(&fbatch, folio) > 0) 1069 continue; 1070 folios_put_refs(&fbatch, refs); 1071 } 1072 1073 if (fbatch.nr) 1074 folios_put_refs(&fbatch, refs); 1075} 1076EXPORT_SYMBOL(release_pages); 1077 1078/* 1079 * The folios which we're about to release may be in the deferred lru-addition 1080 * queues. That would prevent them from really being freed right now. That's 1081 * OK from a correctness point of view but is inefficient - those folios may be 1082 * cache-warm and we want to give them back to the page allocator ASAP. 1083 * 1084 * So __folio_batch_release() will drain those queues here. 1085 * folio_batch_move_lru() calls folios_put() directly to avoid 1086 * mutual recursion. 1087 */ 1088void __folio_batch_release(struct folio_batch *fbatch) 1089{ 1090 if (!fbatch->percpu_pvec_drained) { 1091 lru_add_drain(); 1092 fbatch->percpu_pvec_drained = true; 1093 } 1094 folios_put(fbatch); 1095} 1096EXPORT_SYMBOL(__folio_batch_release); 1097 1098/** 1099 * folio_batch_remove_exceptionals() - Prune non-folios from a batch. 1100 * @fbatch: The batch to prune 1101 * 1102 * find_get_entries() fills a batch with both folios and shadow/swap/DAX 1103 * entries. This function prunes all the non-folio entries from @fbatch 1104 * without leaving holes, so that it can be passed on to folio-only batch 1105 * operations. 1106 */ 1107void folio_batch_remove_exceptionals(struct folio_batch *fbatch) 1108{ 1109 unsigned int i, j; 1110 1111 for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) { 1112 struct folio *folio = fbatch->folios[i]; 1113 if (!xa_is_value(folio)) 1114 fbatch->folios[j++] = folio; 1115 } 1116 fbatch->nr = j; 1117} 1118 1119/* 1120 * Perform any setup for the swap system 1121 */ 1122void __init swap_setup(void) 1123{ 1124 unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT); 1125 1126 /* Use a smaller cluster for small-memory machines */ 1127 if (megs < 16) 1128 page_cluster = 2; 1129 else 1130 page_cluster = 3; 1131 /* 1132 * Right now other parts of the system means that we 1133 * _really_ don't want to cluster much more 1134 */ 1135} 1136