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