mm/swap.c

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