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