mm/swap.c

   1 /*
   2  *  linux/mm/swap.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5  */
   6
   7 /*
   8  * This file contains the default values for the operation of the
   9  * Linux VM subsystem. Fine-tuning documentation can be found in
  10  * Documentation/sysctl/vm.txt.
  11  * Started 18.12.91
  12  * Swap aging added 23.2.95, Stephen Tweedie.
  13  * Buffermem limits added 12.3.98, Rik van Riel.
  14  */
  15
  16 #include <linux/mm.h>
  17 #include <linux/sched.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/swap.h>
  20 #include <linux/mman.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/pagevec.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/mm_inline.h>
  26 #include <linux/buffer_head.h>  /* for try_to_release_page() */
  27 #include <linux/percpu_counter.h>
  28 #include <linux/percpu.h>
  29 #include <linux/cpu.h>
  30 #include <linux/notifier.h>
  31 #include <linux/backing-dev.h>
  32 #include <linux/memcontrol.h>
  33 #include <linux/gfp.h>
  34
  35 #include "internal.h"
  36
  37 /* How many pages do we try to swap or page in/out together? */
  38 int page_cluster;
  39
  40 static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
  41 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
  42
  43 /*
  44  * This path almost never happens for VM activity - pages are normally
  45  * freed via pagevecs.  But it gets used by networking.
  46  */
  47 static void __page_cache_release(struct page *page)
  48 {
  49         if (PageLRU(page)) {
  50                 unsigned long flags;
  51                 struct zone *zone = page_zone(page);
  52
  53                 spin_lock_irqsave(&zone->lru_lock, flags);
  54                 VM_BUG_ON(!PageLRU(page));
  55                 __ClearPageLRU(page);
  56                 del_page_from_lru(zone, page);
  57                 spin_unlock_irqrestore(&zone->lru_lock, flags);
  58         }
  59 }
  60
  61 static void __put_single_page(struct page *page)
  62 {
  63         __page_cache_release(page);
  64         free_hot_cold_page(page, 0);
  65 }
  66
  67 static void __put_compound_page(struct page *page)
  68 {
  69         compound_page_dtor *dtor;
  70
  71         __page_cache_release(page);
  72         dtor = get_compound_page_dtor(page);
  73         (*dtor)(page);
  74 }
  75
  76 static void put_compound_page(struct page *page)
  77 {
  78         if (unlikely(PageTail(page))) {
  79                 /* __split_huge_page_refcount can run under us */
  80                 struct page *page_head = page->first_page;
  81                 smp_rmb();
  82                 /*
  83                  * If PageTail is still set after smp_rmb() we can be sure
  84                  * that the page->first_page we read wasn't a dangling pointer.
  85                  * See __split_huge_page_refcount() smp_wmb().
  86                  */
  87                 if (likely(PageTail(page) && get_page_unless_zero(page_head))) {
  88                         unsigned long flags;
  89                         /*
  90                          * Verify that our page_head wasn't converted
  91                          * to a a regular page before we got a
  92                          * reference on it.
  93                          */
  94                         if (unlikely(!PageHead(page_head))) {
  95                                 /* PageHead is cleared after PageTail */
  96                                 smp_rmb();
  97                                 VM_BUG_ON(PageTail(page));
  98                                 goto out_put_head;
  99                         }
 100                         /*
 101                          * Only run compound_lock on a valid PageHead,
 102                          * after having it pinned with
 103                          * get_page_unless_zero() above.
 104                          */
 105                         smp_mb();
 106                         /* page_head wasn't a dangling pointer */
 107                         flags = compound_lock_irqsave(page_head);
 108                         if (unlikely(!PageTail(page))) {
 109                                 /* __split_huge_page_refcount run before us */
 110                                 compound_unlock_irqrestore(page_head, flags);
 111                                 VM_BUG_ON(PageHead(page_head));
 112                         out_put_head:
 113                                 if (put_page_testzero(page_head))
 114                                         __put_single_page(page_head);
 115                         out_put_single:
 116                                 if (put_page_testzero(page))
 117                                         __put_single_page(page);
 118                                 return;
 119                         }
 120                         VM_BUG_ON(page_head != page->first_page);
 121                         /*
 122                          * We can release the refcount taken by
 123                          * get_page_unless_zero now that
 124                          * split_huge_page_refcount is blocked on the
 125                          * compound_lock.
 126                          */
 127                         if (put_page_testzero(page_head))
 128                                 VM_BUG_ON(1);
 129                         /* __split_huge_page_refcount will wait now */
 130                         VM_BUG_ON(atomic_read(&page->_count) <= 0);
 131                         atomic_dec(&page->_count);
 132                         VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
 133                         compound_unlock_irqrestore(page_head, flags);
 134                         if (put_page_testzero(page_head)) {
 135                                 if (PageHead(page_head))
 136                                         __put_compound_page(page_head);
 137                                 else
 138                                         __put_single_page(page_head);
 139                         }
 140                 } else {
 141                         /* page_head is a dangling pointer */
 142                         VM_BUG_ON(PageTail(page));
 143                         goto out_put_single;
 144                 }
 145         } else if (put_page_testzero(page)) {
 146                 if (PageHead(page))
 147                         __put_compound_page(page);
 148                 else
 149                         __put_single_page(page);
 150         }
 151 }
 152
 153 void put_page(struct page *page)
 154 {
 155         if (unlikely(PageCompound(page)))
 156                 put_compound_page(page);
 157         else if (put_page_testzero(page))
 158                 __put_single_page(page);
 159 }
 160 EXPORT_SYMBOL(put_page);
 161
 162 /**
 163  * put_pages_list() - release a list of pages
 164  * @pages: list of pages threaded on page->lru
 165  *
 166  * Release a list of pages which are strung together on page.lru.  Currently
 167  * used by read_cache_pages() and related error recovery code.
 168  */
 169 void put_pages_list(struct list_head *pages)
 170 {
 171         while (!list_empty(pages)) {
 172                 struct page *victim;
 173
 174                 victim = list_entry(pages->prev, struct page, lru);
 175                 list_del(&victim->lru);
 176                 page_cache_release(victim);
 177         }
 178 }
 179 EXPORT_SYMBOL(put_pages_list);
 180
 181 /*
 182  * pagevec_move_tail() must be called with IRQ disabled.
 183  * Otherwise this may cause nasty races.
 184  */
 185 static void pagevec_move_tail(struct pagevec *pvec)
 186 {
 187         int i;
 188         int pgmoved = 0;
 189         struct zone *zone = NULL;
 190
 191         for (i = 0; i < pagevec_count(pvec); i++) {
 192                 struct page *page = pvec->pages[i];
 193                 struct zone *pagezone = page_zone(page);
 194
 195                 if (pagezone != zone) {
 196                         if (zone)
 197                                 spin_unlock(&zone->lru_lock);
 198                         zone = pagezone;
 199                         spin_lock(&zone->lru_lock);
 200                 }
 201                 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 202                         int lru = page_lru_base_type(page);
 203                         list_move_tail(&page->lru, &zone->lru[lru].list);
 204                         pgmoved++;
 205                 }
 206         }
 207         if (zone)
 208                 spin_unlock(&zone->lru_lock);
 209         __count_vm_events(PGROTATED, pgmoved);
 210         release_pages(pvec->pages, pvec->nr, pvec->cold);
 211         pagevec_reinit(pvec);
 212 }
 213
 214 /*
 215  * Writeback is about to end against a page which has been marked for immediate
 216  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 217  * inactive list.
 218  */
 219 void  rotate_reclaimable_page(struct page *page)
 220 {
 221         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
 222             !PageUnevictable(page) && PageLRU(page)) {
 223                 struct pagevec *pvec;
 224                 unsigned long flags;
 225
 226                 page_cache_get(page);
 227                 local_irq_save(flags);
 228                 pvec = &__get_cpu_var(lru_rotate_pvecs);
 229                 if (!pagevec_add(pvec, page))
 230                         pagevec_move_tail(pvec);
 231                 local_irq_restore(flags);
 232         }
 233 }
 234
 235 static void update_page_reclaim_stat(struct zone *zone, struct page *page,
 236                                      int file, int rotated)
 237 {
 238         struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
 239         struct zone_reclaim_stat *memcg_reclaim_stat;
 240
 241         memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
 242
 243         reclaim_stat->recent_scanned[file]++;
 244         if (rotated)
 245                 reclaim_stat->recent_rotated[file]++;
 246
 247         if (!memcg_reclaim_stat)
 248                 return;
 249
 250         memcg_reclaim_stat->recent_scanned[file]++;
 251         if (rotated)
 252                 memcg_reclaim_stat->recent_rotated[file]++;
 253 }
 254
 255 /*
 256  * FIXME: speed this up?
 257  */
 258 void activate_page(struct page *page)
 259 {
 260         struct zone *zone = page_zone(page);
 261
 262         spin_lock_irq(&zone->lru_lock);
 263         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 264                 int file = page_is_file_cache(page);
 265                 int lru = page_lru_base_type(page);
 266                 del_page_from_lru_list(zone, page, lru);
 267
 268                 SetPageActive(page);
 269                 lru += LRU_ACTIVE;
 270                 add_page_to_lru_list(zone, page, lru);
 271                 __count_vm_event(PGACTIVATE);
 272
 273                 update_page_reclaim_stat(zone, page, file, 1);
 274         }
 275         spin_unlock_irq(&zone->lru_lock);
 276 }
 277
 278 /*
 279  * Mark a page as having seen activity.
 280  *
 281  * inactive,unreferenced        ->      inactive,referenced
 282  * inactive,referenced          ->      active,unreferenced
 283  * active,unreferenced          ->      active,referenced
 284  */
 285 void mark_page_accessed(struct page *page)
 286 {
 287         if (!PageActive(page) && !PageUnevictable(page) &&
 288                         PageReferenced(page) && PageLRU(page)) {
 289                 activate_page(page);
 290                 ClearPageReferenced(page);
 291         } else if (!PageReferenced(page)) {
 292                 SetPageReferenced(page);
 293         }
 294 }
 295
 296 EXPORT_SYMBOL(mark_page_accessed);
 297
 298 void __lru_cache_add(struct page *page, enum lru_list lru)
 299 {
 300         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
 301
 302         page_cache_get(page);
 303         if (!pagevec_add(pvec, page))
 304                 ____pagevec_lru_add(pvec, lru);
 305         put_cpu_var(lru_add_pvecs);
 306 }
 307 EXPORT_SYMBOL(__lru_cache_add);
 308
 309 /**
 310  * lru_cache_add_lru - add a page to a page list
 311  * @page: the page to be added to the LRU.
 312  * @lru: the LRU list to which the page is added.
 313  */
 314 void lru_cache_add_lru(struct page *page, enum lru_list lru)
 315 {
 316         if (PageActive(page)) {
 317                 VM_BUG_ON(PageUnevictable(page));
 318                 ClearPageActive(page);
 319         } else if (PageUnevictable(page)) {
 320                 VM_BUG_ON(PageActive(page));
 321                 ClearPageUnevictable(page);
 322         }
 323
 324         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
 325         __lru_cache_add(page, lru);
 326 }
 327
 328 /**
 329  * add_page_to_unevictable_list - add a page to the unevictable list
 330  * @page:  the page to be added to the unevictable list
 331  *
 332  * Add page directly to its zone's unevictable list.  To avoid races with
 333  * tasks that might be making the page evictable, through eg. munlock,
 334  * munmap or exit, while it's not on the lru, we want to add the page
 335  * while it's locked or otherwise "invisible" to other tasks.  This is
 336  * difficult to do when using the pagevec cache, so bypass that.
 337  */
 338 void add_page_to_unevictable_list(struct page *page)
 339 {
 340         struct zone *zone = page_zone(page);
 341
 342         spin_lock_irq(&zone->lru_lock);
 343         SetPageUnevictable(page);
 344         SetPageLRU(page);
 345         add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
 346         spin_unlock_irq(&zone->lru_lock);
 347 }
 348
 349 /*
 350  * Drain pages out of the cpu's pagevecs.
 351  * Either "cpu" is the current CPU, and preemption has already been
 352  * disabled; or "cpu" is being hot-unplugged, and is already dead.
 353  */
 354 static void drain_cpu_pagevecs(int cpu)
 355 {
 356         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
 357         struct pagevec *pvec;
 358         int lru;
 359
 360         for_each_lru(lru) {
 361                 pvec = &pvecs[lru - LRU_BASE];
 362                 if (pagevec_count(pvec))
 363                         ____pagevec_lru_add(pvec, lru);
 364         }
 365
 366         pvec = &per_cpu(lru_rotate_pvecs, cpu);
 367         if (pagevec_count(pvec)) {
 368                 unsigned long flags;
 369
 370                 /* No harm done if a racing interrupt already did this */
 371                 local_irq_save(flags);
 372                 pagevec_move_tail(pvec);
 373                 local_irq_restore(flags);
 374         }
 375 }
 376
 377 void lru_add_drain(void)
 378 {
 379         drain_cpu_pagevecs(get_cpu());
 380         put_cpu();
 381 }
 382
 383 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 384 {
 385         lru_add_drain();
 386 }
 387
 388 /*
 389  * Returns 0 for success
 390  */
 391 int lru_add_drain_all(void)
 392 {
 393         return schedule_on_each_cpu(lru_add_drain_per_cpu);
 394 }
 395
 396 /*
 397  * Batched page_cache_release().  Decrement the reference count on all the
 398  * passed pages.  If it fell to zero then remove the page from the LRU and
 399  * free it.
 400  *
 401  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 402  * for the remainder of the operation.
 403  *
 404  * The locking in this function is against shrink_inactive_list(): we recheck
 405  * the page count inside the lock to see whether shrink_inactive_list()
 406  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 407  * will free it.
 408  */
 409 void release_pages(struct page **pages, int nr, int cold)
 410 {
 411         int i;
 412         struct pagevec pages_to_free;
 413         struct zone *zone = NULL;
 414         unsigned long uninitialized_var(flags);
 415
 416         pagevec_init(&pages_to_free, cold);
 417         for (i = 0; i < nr; i++) {
 418                 struct page *page = pages[i];
 419
 420                 if (unlikely(PageCompound(page))) {
 421                         if (zone) {
 422                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 423                                 zone = NULL;
 424                         }
 425                         put_compound_page(page);
 426                         continue;
 427                 }
 428
 429                 if (!put_page_testzero(page))
 430                         continue;
 431
 432                 if (PageLRU(page)) {
 433                         struct zone *pagezone = page_zone(page);
 434
 435                         if (pagezone != zone) {
 436                                 if (zone)
 437                                         spin_unlock_irqrestore(&zone->lru_lock,
 438                                                                         flags);
 439                                 zone = pagezone;
 440                                 spin_lock_irqsave(&zone->lru_lock, flags);
 441                         }
 442                         VM_BUG_ON(!PageLRU(page));
 443                         __ClearPageLRU(page);
 444                         del_page_from_lru(zone, page);
 445                 }
 446
 447                 if (!pagevec_add(&pages_to_free, page)) {
 448                         if (zone) {
 449                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 450                                 zone = NULL;
 451                         }
 452                         __pagevec_free(&pages_to_free);
 453                         pagevec_reinit(&pages_to_free);
 454                 }
 455         }
 456         if (zone)
 457                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 458
 459         pagevec_free(&pages_to_free);
 460 }
 461 EXPORT_SYMBOL(release_pages);
 462
 463 /*
 464  * The pages which we're about to release may be in the deferred lru-addition
 465  * queues.  That would prevent them from really being freed right now.  That's
 466  * OK from a correctness point of view but is inefficient - those pages may be
 467  * cache-warm and we want to give them back to the page allocator ASAP.
 468  *
 469  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 470  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 471  * mutual recursion.
 472  */
 473 void __pagevec_release(struct pagevec *pvec)
 474 {
 475         lru_add_drain();
 476         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 477         pagevec_reinit(pvec);
 478 }
 479
 480 EXPORT_SYMBOL(__pagevec_release);
 481
 482 /*
 483  * Add the passed pages to the LRU, then drop the caller's refcount
 484  * on them.  Reinitialises the caller's pagevec.
 485  */
 486 void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 487 {
 488         int i;
 489         struct zone *zone = NULL;
 490
 491         VM_BUG_ON(is_unevictable_lru(lru));
 492
 493         for (i = 0; i < pagevec_count(pvec); i++) {
 494                 struct page *page = pvec->pages[i];
 495                 struct zone *pagezone = page_zone(page);
 496                 int file;
 497                 int active;
 498
 499                 if (pagezone != zone) {
 500                         if (zone)
 501                                 spin_unlock_irq(&zone->lru_lock);
 502                         zone = pagezone;
 503                         spin_lock_irq(&zone->lru_lock);
 504                 }
 505                 VM_BUG_ON(PageActive(page));
 506                 VM_BUG_ON(PageUnevictable(page));
 507                 VM_BUG_ON(PageLRU(page));
 508                 SetPageLRU(page);
 509                 active = is_active_lru(lru);
 510                 file = is_file_lru(lru);
 511                 if (active)
 512                         SetPageActive(page);
 513                 update_page_reclaim_stat(zone, page, file, active);
 514                 add_page_to_lru_list(zone, page, lru);
 515         }
 516         if (zone)
 517                 spin_unlock_irq(&zone->lru_lock);
 518         release_pages(pvec->pages, pvec->nr, pvec->cold);
 519         pagevec_reinit(pvec);
 520 }
 521
 522 EXPORT_SYMBOL(____pagevec_lru_add);
 523
 524 /*
 525  * Try to drop buffers from the pages in a pagevec
 526  */
 527 void pagevec_strip(struct pagevec *pvec)
 528 {
 529         int i;
 530
 531         for (i = 0; i < pagevec_count(pvec); i++) {
 532                 struct page *page = pvec->pages[i];
 533
 534                 if (page_has_private(page) && trylock_page(page)) {
 535                         if (page_has_private(page))
 536                                 try_to_release_page(page, 0);
 537                         unlock_page(page);
 538                 }
 539         }
 540 }
 541
 542 /**
 543  * pagevec_lookup - gang pagecache lookup
 544  * @pvec:       Where the resulting pages are placed
 545  * @mapping:    The address_space to search
 546  * @start:      The starting page index
 547  * @nr_pages:   The maximum number of pages
 548  *
 549  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 550  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 551  * reference against the pages in @pvec.
 552  *
 553  * The search returns a group of mapping-contiguous pages with ascending
 554  * indexes.  There may be holes in the indices due to not-present pages.
 555  *
 556  * pagevec_lookup() returns the number of pages which were found.
 557  */
 558 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 559                 pgoff_t start, unsigned nr_pages)
 560 {
 561         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 562         return pagevec_count(pvec);
 563 }
 564
 565 EXPORT_SYMBOL(pagevec_lookup);
 566
 567 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 568                 pgoff_t *index, int tag, unsigned nr_pages)
 569 {
 570         pvec->nr = find_get_pages_tag(mapping, index, tag,
 571                                         nr_pages, pvec->pages);
 572         return pagevec_count(pvec);
 573 }
 574
 575 EXPORT_SYMBOL(pagevec_lookup_tag);
 576
 577 /*
 578  * Perform any setup for the swap system
 579  */
 580 void __init swap_setup(void)
 581 {
 582         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
 583
 584 #ifdef CONFIG_SWAP
 585         bdi_init(swapper_space.backing_dev_info);
 586 #endif
 587
 588         /* Use a smaller cluster for small-memory machines */
 589         if (megs < 16)
 590                 page_cluster = 2;
 591         else
 592                 page_cluster = 3;
 593         /*
 594          * Right now other parts of the system means that we
 595          * _really_ don't want to cluster much more
 596          */
 597 }