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? */ 47 int page_cluster; 48 49 /* Protecting only lru_rotate.pvec which requires disabling interrupts */ 50 struct lru_rotate { 51 local_lock_t lock; 52 struct pagevec pvec; 53 }; 54 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = { 55 .lock = INIT_LOCAL_LOCK(lock), 56 }; 57 58 /* 59 * The following struct pagevec are grouped together because they are protected 60 * by disabling preemption (and interrupts remain enabled). 61 */ 62 struct lru_pvecs { 63 local_lock_t lock; 64 struct pagevec lru_add; 65 struct pagevec lru_deactivate_file; 66 struct pagevec lru_deactivate; 67 struct pagevec lru_lazyfree; 68 #ifdef CONFIG_SMP 69 struct pagevec activate_page; 70 #endif 71 }; 72 static DEFINE_PER_CPU(struct lru_pvecs, lru_pvecs) = { 73 .lock = INIT_LOCAL_LOCK(lock), 74 }; 75 76 /* 77 * This path almost never happens for VM activity - pages are normally 78 * freed via pagevecs. But it gets used by networking. 79 */ 80 static void __page_cache_release(struct page *page) 81 { 82 if (PageLRU(page)) { 83 struct folio *folio = page_folio(page); 84 struct lruvec *lruvec; 85 unsigned long flags; 86 87 lruvec = folio_lruvec_lock_irqsave(folio, &flags); 88 del_page_from_lru_list(page, lruvec); 89 __clear_page_lru_flags(page); 90 unlock_page_lruvec_irqrestore(lruvec, flags); 91 } 92 __ClearPageWaiters(page); 93 } 94 95 static void __put_single_page(struct page *page) 96 { 97 __page_cache_release(page); 98 mem_cgroup_uncharge(page_folio(page)); 99 free_unref_page(page, 0); 100 } 101 102 static void __put_compound_page(struct page *page) 103 { 104 /* 105 * __page_cache_release() is supposed to be called for thp, not for 106 * hugetlb. This is because hugetlb page does never have PageLRU set 107 * (it's never listed to any LRU lists) and no memcg routines should 108 * be called for hugetlb (it has a separate hugetlb_cgroup.) 109 */ 110 if (!PageHuge(page)) 111 __page_cache_release(page); 112 destroy_compound_page(page); 113 } 114 115 void __put_page(struct page *page) 116 { 117 if (is_zone_device_page(page)) { 118 put_dev_pagemap(page->pgmap); 119 120 /* 121 * The page belongs to the device that created pgmap. Do 122 * not return it to page allocator. 123 */ 124 return; 125 } 126 127 if (unlikely(PageCompound(page))) 128 __put_compound_page(page); 129 else 130 __put_single_page(page); 131 } 132 EXPORT_SYMBOL(__put_page); 133 134 /** 135 * put_pages_list() - release a list of pages 136 * @pages: list of pages threaded on page->lru 137 * 138 * Release a list of pages which are strung together on page.lru. Currently 139 * used by read_cache_pages() and related error recovery code. 140 */ 141 void put_pages_list(struct list_head *pages) 142 { 143 while (!list_empty(pages)) { 144 struct page *victim; 145 146 victim = lru_to_page(pages); 147 list_del(&victim->lru); 148 put_page(victim); 149 } 150 } 151 EXPORT_SYMBOL(put_pages_list); 152 153 /* 154 * get_kernel_pages() - pin kernel pages in memory 155 * @kiov: An array of struct kvec structures 156 * @nr_segs: number of segments to pin 157 * @write: pinning for read/write, currently ignored 158 * @pages: array that receives pointers to the pages pinned. 159 * Should be at least nr_segs long. 160 * 161 * Returns number of pages pinned. This may be fewer than the number 162 * requested. If nr_pages is 0 or negative, returns 0. If no pages 163 * were pinned, returns -errno. Each page returned must be released 164 * with a put_page() call when it is finished with. 165 */ 166 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write, 167 struct page **pages) 168 { 169 int seg; 170 171 for (seg = 0; seg < nr_segs; seg++) { 172 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE)) 173 return seg; 174 175 pages[seg] = kmap_to_page(kiov[seg].iov_base); 176 get_page(pages[seg]); 177 } 178 179 return seg; 180 } 181 EXPORT_SYMBOL_GPL(get_kernel_pages); 182 183 static void pagevec_lru_move_fn(struct pagevec *pvec, 184 void (*move_fn)(struct page *page, struct lruvec *lruvec)) 185 { 186 int i; 187 struct lruvec *lruvec = NULL; 188 unsigned long flags = 0; 189 190 for (i = 0; i < pagevec_count(pvec); i++) { 191 struct page *page = pvec->pages[i]; 192 struct folio *folio = page_folio(page); 193 194 /* block memcg migration during page moving between lru */ 195 if (!TestClearPageLRU(page)) 196 continue; 197 198 lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags); 199 (*move_fn)(page, lruvec); 200 201 SetPageLRU(page); 202 } 203 if (lruvec) 204 unlock_page_lruvec_irqrestore(lruvec, flags); 205 release_pages(pvec->pages, pvec->nr); 206 pagevec_reinit(pvec); 207 } 208 209 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec) 210 { 211 struct folio *folio = page_folio(page); 212 213 if (!folio_test_unevictable(folio)) { 214 lruvec_del_folio(lruvec, folio); 215 folio_clear_active(folio); 216 lruvec_add_folio_tail(lruvec, folio); 217 __count_vm_events(PGROTATED, folio_nr_pages(folio)); 218 } 219 } 220 221 /* return true if pagevec needs to drain */ 222 static bool pagevec_add_and_need_flush(struct pagevec *pvec, struct page *page) 223 { 224 bool ret = false; 225 226 if (!pagevec_add(pvec, page) || PageCompound(page) || 227 lru_cache_disabled()) 228 ret = true; 229 230 return ret; 231 } 232 233 /* 234 * Writeback is about to end against a folio which has been marked for 235 * immediate reclaim. If it still appears to be reclaimable, move it 236 * to the tail of the inactive list. 237 * 238 * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races. 239 */ 240 void folio_rotate_reclaimable(struct folio *folio) 241 { 242 if (!folio_test_locked(folio) && !folio_test_dirty(folio) && 243 !folio_test_unevictable(folio) && folio_test_lru(folio)) { 244 struct pagevec *pvec; 245 unsigned long flags; 246 247 folio_get(folio); 248 local_lock_irqsave(&lru_rotate.lock, flags); 249 pvec = this_cpu_ptr(&lru_rotate.pvec); 250 if (pagevec_add_and_need_flush(pvec, &folio->page)) 251 pagevec_lru_move_fn(pvec, pagevec_move_tail_fn); 252 local_unlock_irqrestore(&lru_rotate.lock, flags); 253 } 254 } 255 256 void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages) 257 { 258 do { 259 unsigned long lrusize; 260 261 /* 262 * Hold lruvec->lru_lock is safe here, since 263 * 1) The pinned lruvec in reclaim, or 264 * 2) From a pre-LRU page during refault (which also holds the 265 * rcu lock, so would be safe even if the page was on the LRU 266 * and could move simultaneously to a new lruvec). 267 */ 268 spin_lock_irq(&lruvec->lru_lock); 269 /* Record cost event */ 270 if (file) 271 lruvec->file_cost += nr_pages; 272 else 273 lruvec->anon_cost += nr_pages; 274 275 /* 276 * Decay previous events 277 * 278 * Because workloads change over time (and to avoid 279 * overflow) we keep these statistics as a floating 280 * average, which ends up weighing recent refaults 281 * more than old ones. 282 */ 283 lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) + 284 lruvec_page_state(lruvec, NR_ACTIVE_ANON) + 285 lruvec_page_state(lruvec, NR_INACTIVE_FILE) + 286 lruvec_page_state(lruvec, NR_ACTIVE_FILE); 287 288 if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) { 289 lruvec->file_cost /= 2; 290 lruvec->anon_cost /= 2; 291 } 292 spin_unlock_irq(&lruvec->lru_lock); 293 } while ((lruvec = parent_lruvec(lruvec))); 294 } 295 296 void lru_note_cost_folio(struct folio *folio) 297 { 298 lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio), 299 folio_nr_pages(folio)); 300 } 301 302 static void __folio_activate(struct folio *folio, struct lruvec *lruvec) 303 { 304 if (!folio_test_active(folio) && !folio_test_unevictable(folio)) { 305 long nr_pages = folio_nr_pages(folio); 306 307 lruvec_del_folio(lruvec, folio); 308 folio_set_active(folio); 309 lruvec_add_folio(lruvec, folio); 310 trace_mm_lru_activate(folio); 311 312 __count_vm_events(PGACTIVATE, nr_pages); 313 __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE, 314 nr_pages); 315 } 316 } 317 318 #ifdef CONFIG_SMP 319 static void __activate_page(struct page *page, struct lruvec *lruvec) 320 { 321 return __folio_activate(page_folio(page), lruvec); 322 } 323 324 static void activate_page_drain(int cpu) 325 { 326 struct pagevec *pvec = &per_cpu(lru_pvecs.activate_page, cpu); 327 328 if (pagevec_count(pvec)) 329 pagevec_lru_move_fn(pvec, __activate_page); 330 } 331 332 static bool need_activate_page_drain(int cpu) 333 { 334 return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0; 335 } 336 337 static void folio_activate(struct folio *folio) 338 { 339 if (folio_test_lru(folio) && !folio_test_active(folio) && 340 !folio_test_unevictable(folio)) { 341 struct pagevec *pvec; 342 343 folio_get(folio); 344 local_lock(&lru_pvecs.lock); 345 pvec = this_cpu_ptr(&lru_pvecs.activate_page); 346 if (pagevec_add_and_need_flush(pvec, &folio->page)) 347 pagevec_lru_move_fn(pvec, __activate_page); 348 local_unlock(&lru_pvecs.lock); 349 } 350 } 351 352 #else 353 static inline void activate_page_drain(int cpu) 354 { 355 } 356 357 static void folio_activate(struct folio *folio) 358 { 359 struct lruvec *lruvec; 360 361 if (folio_test_clear_lru(folio)) { 362 lruvec = folio_lruvec_lock_irq(folio); 363 __folio_activate(folio, lruvec); 364 unlock_page_lruvec_irq(lruvec); 365 folio_set_lru(folio); 366 } 367 } 368 #endif 369 370 static void __lru_cache_activate_folio(struct folio *folio) 371 { 372 struct pagevec *pvec; 373 int i; 374 375 local_lock(&lru_pvecs.lock); 376 pvec = this_cpu_ptr(&lru_pvecs.lru_add); 377 378 /* 379 * Search backwards on the optimistic assumption that the page being 380 * activated has just been added to this pagevec. Note that only 381 * the local pagevec is examined as a !PageLRU page could be in the 382 * process of being released, reclaimed, migrated or on a remote 383 * pagevec that is currently being drained. Furthermore, marking 384 * a remote pagevec's page PageActive potentially hits a race where 385 * a page is marked PageActive just after it is added to the inactive 386 * list causing accounting errors and BUG_ON checks to trigger. 387 */ 388 for (i = pagevec_count(pvec) - 1; i >= 0; i--) { 389 struct page *pagevec_page = pvec->pages[i]; 390 391 if (pagevec_page == &folio->page) { 392 folio_set_active(folio); 393 break; 394 } 395 } 396 397 local_unlock(&lru_pvecs.lock); 398 } 399 400 /* 401 * Mark a page as having seen activity. 402 * 403 * inactive,unreferenced -> inactive,referenced 404 * inactive,referenced -> active,unreferenced 405 * active,unreferenced -> active,referenced 406 * 407 * When a newly allocated page is not yet visible, so safe for non-atomic ops, 408 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page). 409 */ 410 void folio_mark_accessed(struct folio *folio) 411 { 412 if (!folio_test_referenced(folio)) { 413 folio_set_referenced(folio); 414 } else if (folio_test_unevictable(folio)) { 415 /* 416 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But, 417 * this list is never rotated or maintained, so marking an 418 * evictable page accessed has no effect. 419 */ 420 } else if (!folio_test_active(folio)) { 421 /* 422 * If the page is on the LRU, queue it for activation via 423 * lru_pvecs.activate_page. Otherwise, assume the page is on a 424 * pagevec, mark it active and it'll be moved to the active 425 * LRU on the next drain. 426 */ 427 if (folio_test_lru(folio)) 428 folio_activate(folio); 429 else 430 __lru_cache_activate_folio(folio); 431 folio_clear_referenced(folio); 432 workingset_activation(folio); 433 } 434 if (folio_test_idle(folio)) 435 folio_clear_idle(folio); 436 } 437 EXPORT_SYMBOL(folio_mark_accessed); 438 439 /** 440 * folio_add_lru - Add a folio to an LRU list. 441 * @folio: The folio to be added to the LRU. 442 * 443 * Queue the folio for addition to the LRU. The decision on whether 444 * to add the page to the [in]active [file|anon] list is deferred until the 445 * pagevec is drained. This gives a chance for the caller of folio_add_lru() 446 * have the folio added to the active list using folio_mark_accessed(). 447 */ 448 void folio_add_lru(struct folio *folio) 449 { 450 struct pagevec *pvec; 451 452 VM_BUG_ON_FOLIO(folio_test_active(folio) && folio_test_unevictable(folio), folio); 453 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 454 455 folio_get(folio); 456 local_lock(&lru_pvecs.lock); 457 pvec = this_cpu_ptr(&lru_pvecs.lru_add); 458 if (pagevec_add_and_need_flush(pvec, &folio->page)) 459 __pagevec_lru_add(pvec); 460 local_unlock(&lru_pvecs.lock); 461 } 462 EXPORT_SYMBOL(folio_add_lru); 463 464 /** 465 * lru_cache_add_inactive_or_unevictable 466 * @page: the page to be added to LRU 467 * @vma: vma in which page is mapped for determining reclaimability 468 * 469 * Place @page on the inactive or unevictable LRU list, depending on its 470 * evictability. 471 */ 472 void lru_cache_add_inactive_or_unevictable(struct page *page, 473 struct vm_area_struct *vma) 474 { 475 bool unevictable; 476 477 VM_BUG_ON_PAGE(PageLRU(page), page); 478 479 unevictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED; 480 if (unlikely(unevictable) && !TestSetPageMlocked(page)) { 481 int nr_pages = thp_nr_pages(page); 482 /* 483 * We use the irq-unsafe __mod_zone_page_state because this 484 * counter is not modified from interrupt context, and the pte 485 * lock is held(spinlock), which implies preemption disabled. 486 */ 487 __mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages); 488 count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages); 489 } 490 lru_cache_add(page); 491 } 492 493 /* 494 * If the page can not be invalidated, it is moved to the 495 * inactive list to speed up its reclaim. It is moved to the 496 * head of the list, rather than the tail, to give the flusher 497 * threads some time to write it out, as this is much more 498 * effective than the single-page writeout from reclaim. 499 * 500 * If the page isn't page_mapped and dirty/writeback, the page 501 * could reclaim asap using PG_reclaim. 502 * 503 * 1. active, mapped page -> none 504 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim 505 * 3. inactive, mapped page -> none 506 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim 507 * 5. inactive, clean -> inactive, tail 508 * 6. Others -> none 509 * 510 * In 4, why it moves inactive's head, the VM expects the page would 511 * be write it out by flusher threads as this is much more effective 512 * than the single-page writeout from reclaim. 513 */ 514 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec) 515 { 516 bool active = PageActive(page); 517 int nr_pages = thp_nr_pages(page); 518 519 if (PageUnevictable(page)) 520 return; 521 522 /* Some processes are using the page */ 523 if (page_mapped(page)) 524 return; 525 526 del_page_from_lru_list(page, lruvec); 527 ClearPageActive(page); 528 ClearPageReferenced(page); 529 530 if (PageWriteback(page) || PageDirty(page)) { 531 /* 532 * PG_reclaim could be raced with end_page_writeback 533 * It can make readahead confusing. But race window 534 * is _really_ small and it's non-critical problem. 535 */ 536 add_page_to_lru_list(page, lruvec); 537 SetPageReclaim(page); 538 } else { 539 /* 540 * The page's writeback ends up during pagevec 541 * We move that page into tail of inactive. 542 */ 543 add_page_to_lru_list_tail(page, lruvec); 544 __count_vm_events(PGROTATED, nr_pages); 545 } 546 547 if (active) { 548 __count_vm_events(PGDEACTIVATE, nr_pages); 549 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, 550 nr_pages); 551 } 552 } 553 554 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec) 555 { 556 if (PageActive(page) && !PageUnevictable(page)) { 557 int nr_pages = thp_nr_pages(page); 558 559 del_page_from_lru_list(page, lruvec); 560 ClearPageActive(page); 561 ClearPageReferenced(page); 562 add_page_to_lru_list(page, lruvec); 563 564 __count_vm_events(PGDEACTIVATE, nr_pages); 565 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, 566 nr_pages); 567 } 568 } 569 570 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec) 571 { 572 if (PageAnon(page) && PageSwapBacked(page) && 573 !PageSwapCache(page) && !PageUnevictable(page)) { 574 int nr_pages = thp_nr_pages(page); 575 576 del_page_from_lru_list(page, lruvec); 577 ClearPageActive(page); 578 ClearPageReferenced(page); 579 /* 580 * Lazyfree pages are clean anonymous pages. They have 581 * PG_swapbacked flag cleared, to distinguish them from normal 582 * anonymous pages 583 */ 584 ClearPageSwapBacked(page); 585 add_page_to_lru_list(page, lruvec); 586 587 __count_vm_events(PGLAZYFREE, nr_pages); 588 __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE, 589 nr_pages); 590 } 591 } 592 593 /* 594 * Drain pages out of the cpu's pagevecs. 595 * Either "cpu" is the current CPU, and preemption has already been 596 * disabled; or "cpu" is being hot-unplugged, and is already dead. 597 */ 598 void lru_add_drain_cpu(int cpu) 599 { 600 struct pagevec *pvec = &per_cpu(lru_pvecs.lru_add, cpu); 601 602 if (pagevec_count(pvec)) 603 __pagevec_lru_add(pvec); 604 605 pvec = &per_cpu(lru_rotate.pvec, cpu); 606 /* Disabling interrupts below acts as a compiler barrier. */ 607 if (data_race(pagevec_count(pvec))) { 608 unsigned long flags; 609 610 /* No harm done if a racing interrupt already did this */ 611 local_lock_irqsave(&lru_rotate.lock, flags); 612 pagevec_lru_move_fn(pvec, pagevec_move_tail_fn); 613 local_unlock_irqrestore(&lru_rotate.lock, flags); 614 } 615 616 pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu); 617 if (pagevec_count(pvec)) 618 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn); 619 620 pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu); 621 if (pagevec_count(pvec)) 622 pagevec_lru_move_fn(pvec, lru_deactivate_fn); 623 624 pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu); 625 if (pagevec_count(pvec)) 626 pagevec_lru_move_fn(pvec, lru_lazyfree_fn); 627 628 activate_page_drain(cpu); 629 } 630 631 /** 632 * deactivate_file_page - forcefully deactivate a file page 633 * @page: page to deactivate 634 * 635 * This function hints the VM that @page is a good reclaim candidate, 636 * for example if its invalidation fails due to the page being dirty 637 * or under writeback. 638 */ 639 void deactivate_file_page(struct page *page) 640 { 641 /* 642 * In a workload with many unevictable page such as mprotect, 643 * unevictable page deactivation for accelerating reclaim is pointless. 644 */ 645 if (PageUnevictable(page)) 646 return; 647 648 if (likely(get_page_unless_zero(page))) { 649 struct pagevec *pvec; 650 651 local_lock(&lru_pvecs.lock); 652 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file); 653 654 if (pagevec_add_and_need_flush(pvec, page)) 655 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn); 656 local_unlock(&lru_pvecs.lock); 657 } 658 } 659 660 /* 661 * deactivate_page - deactivate a page 662 * @page: page to deactivate 663 * 664 * deactivate_page() moves @page to the inactive list if @page was on the active 665 * list and was not an unevictable page. This is done to accelerate the reclaim 666 * of @page. 667 */ 668 void deactivate_page(struct page *page) 669 { 670 if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) { 671 struct pagevec *pvec; 672 673 local_lock(&lru_pvecs.lock); 674 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate); 675 get_page(page); 676 if (pagevec_add_and_need_flush(pvec, page)) 677 pagevec_lru_move_fn(pvec, lru_deactivate_fn); 678 local_unlock(&lru_pvecs.lock); 679 } 680 } 681 682 /** 683 * mark_page_lazyfree - make an anon page lazyfree 684 * @page: page to deactivate 685 * 686 * mark_page_lazyfree() moves @page to the inactive file list. 687 * This is done to accelerate the reclaim of @page. 688 */ 689 void mark_page_lazyfree(struct page *page) 690 { 691 if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && 692 !PageSwapCache(page) && !PageUnevictable(page)) { 693 struct pagevec *pvec; 694 695 local_lock(&lru_pvecs.lock); 696 pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree); 697 get_page(page); 698 if (pagevec_add_and_need_flush(pvec, page)) 699 pagevec_lru_move_fn(pvec, lru_lazyfree_fn); 700 local_unlock(&lru_pvecs.lock); 701 } 702 } 703 704 void lru_add_drain(void) 705 { 706 local_lock(&lru_pvecs.lock); 707 lru_add_drain_cpu(smp_processor_id()); 708 local_unlock(&lru_pvecs.lock); 709 } 710 711 /* 712 * It's called from per-cpu workqueue context in SMP case so 713 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on 714 * the same cpu. It shouldn't be a problem in !SMP case since 715 * the core is only one and the locks will disable preemption. 716 */ 717 static void lru_add_and_bh_lrus_drain(void) 718 { 719 local_lock(&lru_pvecs.lock); 720 lru_add_drain_cpu(smp_processor_id()); 721 local_unlock(&lru_pvecs.lock); 722 invalidate_bh_lrus_cpu(); 723 } 724 725 void lru_add_drain_cpu_zone(struct zone *zone) 726 { 727 local_lock(&lru_pvecs.lock); 728 lru_add_drain_cpu(smp_processor_id()); 729 drain_local_pages(zone); 730 local_unlock(&lru_pvecs.lock); 731 } 732 733 #ifdef CONFIG_SMP 734 735 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); 736 737 static void lru_add_drain_per_cpu(struct work_struct *dummy) 738 { 739 lru_add_and_bh_lrus_drain(); 740 } 741 742 /* 743 * Doesn't need any cpu hotplug locking because we do rely on per-cpu 744 * kworkers being shut down before our page_alloc_cpu_dead callback is 745 * executed on the offlined cpu. 746 * Calling this function with cpu hotplug locks held can actually lead 747 * to obscure indirect dependencies via WQ context. 748 */ 749 inline void __lru_add_drain_all(bool force_all_cpus) 750 { 751 /* 752 * lru_drain_gen - Global pages generation number 753 * 754 * (A) Definition: global lru_drain_gen = x implies that all generations 755 * 0 < n <= x are already *scheduled* for draining. 756 * 757 * This is an optimization for the highly-contended use case where a 758 * user space workload keeps constantly generating a flow of pages for 759 * each CPU. 760 */ 761 static unsigned int lru_drain_gen; 762 static struct cpumask has_work; 763 static DEFINE_MUTEX(lock); 764 unsigned cpu, this_gen; 765 766 /* 767 * Make sure nobody triggers this path before mm_percpu_wq is fully 768 * initialized. 769 */ 770 if (WARN_ON(!mm_percpu_wq)) 771 return; 772 773 /* 774 * Guarantee pagevec counter stores visible by this CPU are visible to 775 * other CPUs before loading the current drain generation. 776 */ 777 smp_mb(); 778 779 /* 780 * (B) Locally cache global LRU draining generation number 781 * 782 * The read barrier ensures that the counter is loaded before the mutex 783 * is taken. It pairs with smp_mb() inside the mutex critical section 784 * at (D). 785 */ 786 this_gen = smp_load_acquire(&lru_drain_gen); 787 788 mutex_lock(&lock); 789 790 /* 791 * (C) Exit the draining operation if a newer generation, from another 792 * lru_add_drain_all(), was already scheduled for draining. Check (A). 793 */ 794 if (unlikely(this_gen != lru_drain_gen && !force_all_cpus)) 795 goto done; 796 797 /* 798 * (D) Increment global generation number 799 * 800 * Pairs with smp_load_acquire() at (B), outside of the critical 801 * section. Use a full memory barrier to guarantee that the new global 802 * drain generation number is stored before loading pagevec counters. 803 * 804 * This pairing must be done here, before the for_each_online_cpu loop 805 * below which drains the page vectors. 806 * 807 * Let x, y, and z represent some system CPU numbers, where x < y < z. 808 * Assume CPU #z is in the middle of the for_each_online_cpu loop 809 * below and has already reached CPU #y's per-cpu data. CPU #x comes 810 * along, adds some pages to its per-cpu vectors, then calls 811 * lru_add_drain_all(). 812 * 813 * If the paired barrier is done at any later step, e.g. after the 814 * loop, CPU #x will just exit at (C) and miss flushing out all of its 815 * added pages. 816 */ 817 WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1); 818 smp_mb(); 819 820 cpumask_clear(&has_work); 821 for_each_online_cpu(cpu) { 822 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); 823 824 if (force_all_cpus || 825 pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) || 826 data_race(pagevec_count(&per_cpu(lru_rotate.pvec, cpu))) || 827 pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) || 828 pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) || 829 pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) || 830 need_activate_page_drain(cpu) || 831 has_bh_in_lru(cpu, NULL)) { 832 INIT_WORK(work, lru_add_drain_per_cpu); 833 queue_work_on(cpu, mm_percpu_wq, work); 834 __cpumask_set_cpu(cpu, &has_work); 835 } 836 } 837 838 for_each_cpu(cpu, &has_work) 839 flush_work(&per_cpu(lru_add_drain_work, cpu)); 840 841 done: 842 mutex_unlock(&lock); 843 } 844 845 void lru_add_drain_all(void) 846 { 847 __lru_add_drain_all(false); 848 } 849 #else 850 void lru_add_drain_all(void) 851 { 852 lru_add_drain(); 853 } 854 #endif /* CONFIG_SMP */ 855 856 atomic_t lru_disable_count = ATOMIC_INIT(0); 857 858 /* 859 * lru_cache_disable() needs to be called before we start compiling 860 * a list of pages to be migrated using isolate_lru_page(). 861 * It drains pages on LRU cache and then disable on all cpus until 862 * lru_cache_enable is called. 863 * 864 * Must be paired with a call to lru_cache_enable(). 865 */ 866 void lru_cache_disable(void) 867 { 868 atomic_inc(&lru_disable_count); 869 #ifdef CONFIG_SMP 870 /* 871 * lru_add_drain_all in the force mode will schedule draining on 872 * all online CPUs so any calls of lru_cache_disabled wrapped by 873 * local_lock or preemption disabled would be ordered by that. 874 * The atomic operation doesn't need to have stronger ordering 875 * requirements because that is enforeced by the scheduling 876 * guarantees. 877 */ 878 __lru_add_drain_all(true); 879 #else 880 lru_add_and_bh_lrus_drain(); 881 #endif 882 } 883 884 /** 885 * release_pages - batched put_page() 886 * @pages: array of pages to release 887 * @nr: number of pages 888 * 889 * Decrement the reference count on all the pages in @pages. If it 890 * fell to zero, remove the page from the LRU and free it. 891 */ 892 void release_pages(struct page **pages, int nr) 893 { 894 int i; 895 LIST_HEAD(pages_to_free); 896 struct lruvec *lruvec = NULL; 897 unsigned long flags = 0; 898 unsigned int lock_batch; 899 900 for (i = 0; i < nr; i++) { 901 struct page *page = pages[i]; 902 struct folio *folio = page_folio(page); 903 904 /* 905 * Make sure the IRQ-safe lock-holding time does not get 906 * excessive with a continuous string of pages from the 907 * same lruvec. The lock is held only if lruvec != NULL. 908 */ 909 if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) { 910 unlock_page_lruvec_irqrestore(lruvec, flags); 911 lruvec = NULL; 912 } 913 914 page = &folio->page; 915 if (is_huge_zero_page(page)) 916 continue; 917 918 if (is_zone_device_page(page)) { 919 if (lruvec) { 920 unlock_page_lruvec_irqrestore(lruvec, flags); 921 lruvec = NULL; 922 } 923 /* 924 * ZONE_DEVICE pages that return 'false' from 925 * page_is_devmap_managed() do not require special 926 * processing, and instead, expect a call to 927 * put_page_testzero(). 928 */ 929 if (page_is_devmap_managed(page)) { 930 put_devmap_managed_page(page); 931 continue; 932 } 933 if (put_page_testzero(page)) 934 put_dev_pagemap(page->pgmap); 935 continue; 936 } 937 938 if (!put_page_testzero(page)) 939 continue; 940 941 if (PageCompound(page)) { 942 if (lruvec) { 943 unlock_page_lruvec_irqrestore(lruvec, flags); 944 lruvec = NULL; 945 } 946 __put_compound_page(page); 947 continue; 948 } 949 950 if (PageLRU(page)) { 951 struct lruvec *prev_lruvec = lruvec; 952 953 lruvec = folio_lruvec_relock_irqsave(folio, lruvec, 954 &flags); 955 if (prev_lruvec != lruvec) 956 lock_batch = 0; 957 958 del_page_from_lru_list(page, lruvec); 959 __clear_page_lru_flags(page); 960 } 961 962 __ClearPageWaiters(page); 963 964 list_add(&page->lru, &pages_to_free); 965 } 966 if (lruvec) 967 unlock_page_lruvec_irqrestore(lruvec, flags); 968 969 mem_cgroup_uncharge_list(&pages_to_free); 970 free_unref_page_list(&pages_to_free); 971 } 972 EXPORT_SYMBOL(release_pages); 973 974 /* 975 * The pages which we're about to release may be in the deferred lru-addition 976 * queues. That would prevent them from really being freed right now. That's 977 * OK from a correctness point of view but is inefficient - those pages may be 978 * cache-warm and we want to give them back to the page allocator ASAP. 979 * 980 * So __pagevec_release() will drain those queues here. __pagevec_lru_add() 981 * and __pagevec_lru_add_active() call release_pages() directly to avoid 982 * mutual recursion. 983 */ 984 void __pagevec_release(struct pagevec *pvec) 985 { 986 if (!pvec->percpu_pvec_drained) { 987 lru_add_drain(); 988 pvec->percpu_pvec_drained = true; 989 } 990 release_pages(pvec->pages, pagevec_count(pvec)); 991 pagevec_reinit(pvec); 992 } 993 EXPORT_SYMBOL(__pagevec_release); 994 995 static void __pagevec_lru_add_fn(struct folio *folio, struct lruvec *lruvec) 996 { 997 int was_unevictable = folio_test_clear_unevictable(folio); 998 long nr_pages = folio_nr_pages(folio); 999 1000 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 1001 1002 /* 1003 * A folio becomes evictable in two ways: 1004 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()]. 1005 * 2) Before acquiring LRU lock to put the folio on the correct LRU 1006 * and then 1007 * a) do PageLRU check with lock [check_move_unevictable_pages] 1008 * b) do PageLRU check before lock [clear_page_mlock] 1009 * 1010 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need 1011 * following strict ordering: 1012 * 1013 * #0: __pagevec_lru_add_fn #1: clear_page_mlock 1014 * 1015 * folio_set_lru() folio_test_clear_mlocked() 1016 * smp_mb() // explicit ordering // above provides strict 1017 * // ordering 1018 * folio_test_mlocked() folio_test_lru() 1019 * 1020 * 1021 * if '#1' does not observe setting of PG_lru by '#0' and 1022 * fails isolation, the explicit barrier will make sure that 1023 * folio_evictable check will put the folio on the correct 1024 * LRU. Without smp_mb(), folio_set_lru() can be reordered 1025 * after folio_test_mlocked() check and can make '#1' fail the 1026 * isolation of the folio whose mlocked bit is cleared (#0 is 1027 * also looking at the same folio) and the evictable folio will 1028 * be stranded on an unevictable LRU. 1029 */ 1030 folio_set_lru(folio); 1031 smp_mb__after_atomic(); 1032 1033 if (folio_evictable(folio)) { 1034 if (was_unevictable) 1035 __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages); 1036 } else { 1037 folio_clear_active(folio); 1038 folio_set_unevictable(folio); 1039 if (!was_unevictable) 1040 __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages); 1041 } 1042 1043 lruvec_add_folio(lruvec, folio); 1044 trace_mm_lru_insertion(folio); 1045 } 1046 1047 /* 1048 * Add the passed pages to the LRU, then drop the caller's refcount 1049 * on them. Reinitialises the caller's pagevec. 1050 */ 1051 void __pagevec_lru_add(struct pagevec *pvec) 1052 { 1053 int i; 1054 struct lruvec *lruvec = NULL; 1055 unsigned long flags = 0; 1056 1057 for (i = 0; i < pagevec_count(pvec); i++) { 1058 struct folio *folio = page_folio(pvec->pages[i]); 1059 1060 lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags); 1061 __pagevec_lru_add_fn(folio, lruvec); 1062 } 1063 if (lruvec) 1064 unlock_page_lruvec_irqrestore(lruvec, flags); 1065 release_pages(pvec->pages, pvec->nr); 1066 pagevec_reinit(pvec); 1067 } 1068 1069 /** 1070 * pagevec_remove_exceptionals - pagevec exceptionals pruning 1071 * @pvec: The pagevec to prune 1072 * 1073 * find_get_entries() fills both pages and XArray value entries (aka 1074 * exceptional entries) into the pagevec. This function prunes all 1075 * exceptionals from @pvec without leaving holes, so that it can be 1076 * passed on to page-only pagevec operations. 1077 */ 1078 void pagevec_remove_exceptionals(struct pagevec *pvec) 1079 { 1080 int i, j; 1081 1082 for (i = 0, j = 0; i < pagevec_count(pvec); i++) { 1083 struct page *page = pvec->pages[i]; 1084 if (!xa_is_value(page)) 1085 pvec->pages[j++] = page; 1086 } 1087 pvec->nr = j; 1088 } 1089 1090 /** 1091 * pagevec_lookup_range - gang pagecache lookup 1092 * @pvec: Where the resulting pages are placed 1093 * @mapping: The address_space to search 1094 * @start: The starting page index 1095 * @end: The final page index 1096 * 1097 * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE 1098 * pages in the mapping starting from index @start and upto index @end 1099 * (inclusive). The pages are placed in @pvec. pagevec_lookup() takes a 1100 * reference against the pages in @pvec. 1101 * 1102 * The search returns a group of mapping-contiguous pages with ascending 1103 * indexes. There may be holes in the indices due to not-present pages. We 1104 * also update @start to index the next page for the traversal. 1105 * 1106 * pagevec_lookup_range() returns the number of pages which were found. If this 1107 * number is smaller than PAGEVEC_SIZE, the end of specified range has been 1108 * reached. 1109 */ 1110 unsigned pagevec_lookup_range(struct pagevec *pvec, 1111 struct address_space *mapping, pgoff_t *start, pgoff_t end) 1112 { 1113 pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE, 1114 pvec->pages); 1115 return pagevec_count(pvec); 1116 } 1117 EXPORT_SYMBOL(pagevec_lookup_range); 1118 1119 unsigned pagevec_lookup_range_tag(struct pagevec *pvec, 1120 struct address_space *mapping, pgoff_t *index, pgoff_t end, 1121 xa_mark_t tag) 1122 { 1123 pvec->nr = find_get_pages_range_tag(mapping, index, end, tag, 1124 PAGEVEC_SIZE, pvec->pages); 1125 return pagevec_count(pvec); 1126 } 1127 EXPORT_SYMBOL(pagevec_lookup_range_tag); 1128 1129 /* 1130 * Perform any setup for the swap system 1131 */ 1132 void __init swap_setup(void) 1133 { 1134 unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT); 1135 1136 /* Use a smaller cluster for small-memory machines */ 1137 if (megs < 16) 1138 page_cluster = 2; 1139 else 1140 page_cluster = 3; 1141 /* 1142 * Right now other parts of the system means that we 1143 * _really_ don't want to cluster much more 1144 */ 1145 } 1146 1147 #ifdef CONFIG_DEV_PAGEMAP_OPS 1148 void put_devmap_managed_page(struct page *page) 1149 { 1150 int count; 1151 1152 if (WARN_ON_ONCE(!page_is_devmap_managed(page))) 1153 return; 1154 1155 count = page_ref_dec_return(page); 1156 1157 /* 1158 * devmap page refcounts are 1-based, rather than 0-based: if 1159 * refcount is 1, then the page is free and the refcount is 1160 * stable because nobody holds a reference on the page. 1161 */ 1162 if (count == 1) 1163 free_devmap_managed_page(page); 1164 else if (!count) 1165 __put_page(page); 1166 } 1167 EXPORT_SYMBOL(put_devmap_managed_page); 1168 #endif 1169