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 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
  43
  44 /*
  45  * This path almost never happens for VM activity - pages are normally
  46  * freed via pagevecs.  But it gets used by networking.
  47  */
  48 static void __page_cache_release(struct page *page)
  49 {
  50         if (PageLRU(page)) {
  51                 unsigned long flags;
  52                 struct zone *zone = page_zone(page);
  53
  54                 spin_lock_irqsave(&zone->lru_lock, flags);
  55                 VM_BUG_ON(!PageLRU(page));
  56                 __ClearPageLRU(page);
  57                 del_page_from_lru(zone, page);
  58                 spin_unlock_irqrestore(&zone->lru_lock, flags);
  59         }
  60 }
  61
  62 static void __put_single_page(struct page *page)
  63 {
  64         __page_cache_release(page);
  65         free_hot_cold_page(page, 0);
  66 }
  67
  68 static void __put_compound_page(struct page *page)
  69 {
  70         compound_page_dtor *dtor;
  71
  72         __page_cache_release(page);
  73         dtor = get_compound_page_dtor(page);
  74         (*dtor)(page);
  75 }
  76
  77 static void put_compound_page(struct page *page)
  78 {
  79         if (unlikely(PageTail(page))) {
  80                 /* __split_huge_page_refcount can run under us */
  81                 struct page *page_head = page->first_page;
  82                 smp_rmb();
  83                 /*
  84                  * If PageTail is still set after smp_rmb() we can be sure
  85                  * that the page->first_page we read wasn't a dangling pointer.
  86                  * See __split_huge_page_refcount() smp_wmb().
  87                  */
  88                 if (likely(PageTail(page) && get_page_unless_zero(page_head))) {
  89                         unsigned long flags;
  90                         /*
  91                          * Verify that our page_head wasn't converted
  92                          * to a a regular page before we got a
  93                          * reference on it.
  94                          */
  95                         if (unlikely(!PageHead(page_head))) {
  96                                 /* PageHead is cleared after PageTail */
  97                                 smp_rmb();
  98                                 VM_BUG_ON(PageTail(page));
  99                                 goto out_put_head;
 100                         }
 101                         /*
 102                          * Only run compound_lock on a valid PageHead,
 103                          * after having it pinned with
 104                          * get_page_unless_zero() above.
 105                          */
 106                         smp_mb();
 107                         /* page_head wasn't a dangling pointer */
 108                         flags = compound_lock_irqsave(page_head);
 109                         if (unlikely(!PageTail(page))) {
 110                                 /* __split_huge_page_refcount run before us */
 111                                 compound_unlock_irqrestore(page_head, flags);
 112                                 VM_BUG_ON(PageHead(page_head));
 113                         out_put_head:
 114                                 if (put_page_testzero(page_head))
 115                                         __put_single_page(page_head);
 116                         out_put_single:
 117                                 if (put_page_testzero(page))
 118                                         __put_single_page(page);
 119                                 return;
 120                         }
 121                         VM_BUG_ON(page_head != page->first_page);
 122                         /*
 123                          * We can release the refcount taken by
 124                          * get_page_unless_zero now that
 125                          * split_huge_page_refcount is blocked on the
 126                          * compound_lock.
 127                          */
 128                         if (put_page_testzero(page_head))
 129                                 VM_BUG_ON(1);
 130                         /* __split_huge_page_refcount will wait now */
 131                         VM_BUG_ON(atomic_read(&page->_count) <= 0);
 132                         atomic_dec(&page->_count);
 133                         VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
 134                         compound_unlock_irqrestore(page_head, flags);
 135                         if (put_page_testzero(page_head)) {
 136                                 if (PageHead(page_head))
 137                                         __put_compound_page(page_head);
 138                                 else
 139                                         __put_single_page(page_head);
 140                         }
 141                 } else {
 142                         /* page_head is a dangling pointer */
 143                         VM_BUG_ON(PageTail(page));
 144                         goto out_put_single;
 145                 }
 146         } else if (put_page_testzero(page)) {
 147                 if (PageHead(page))
 148                         __put_compound_page(page);
 149                 else
 150                         __put_single_page(page);
 151         }
 152 }
 153
 154 void put_page(struct page *page)
 155 {
 156         if (unlikely(PageCompound(page)))
 157                 put_compound_page(page);
 158         else if (put_page_testzero(page))
 159                 __put_single_page(page);
 160 }
 161 EXPORT_SYMBOL(put_page);
 162
 163 /**
 164  * put_pages_list() - release a list of pages
 165  * @pages: list of pages threaded on page->lru
 166  *
 167  * Release a list of pages which are strung together on page.lru.  Currently
 168  * used by read_cache_pages() and related error recovery code.
 169  */
 170 void put_pages_list(struct list_head *pages)
 171 {
 172         while (!list_empty(pages)) {
 173                 struct page *victim;
 174
 175                 victim = list_entry(pages->prev, struct page, lru);
 176                 list_del(&victim->lru);
 177                 page_cache_release(victim);
 178         }
 179 }
 180 EXPORT_SYMBOL(put_pages_list);
 181
 182 static void pagevec_lru_move_fn(struct pagevec *pvec,
 183                                 void (*move_fn)(struct page *page, void *arg),
 184                                 void *arg)
 185 {
 186         int i;
 187         struct zone *zone = 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 zone *pagezone = page_zone(page);
 193
 194                 if (pagezone != zone) {
 195                         if (zone)
 196                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 197                         zone = pagezone;
 198                         spin_lock_irqsave(&zone->lru_lock, flags);
 199                 }
 200
 201                 (*move_fn)(page, arg);
 202         }
 203         if (zone)
 204                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 205         release_pages(pvec->pages, pvec->nr, pvec->cold);
 206         pagevec_reinit(pvec);
 207 }
 208
 209 static void pagevec_move_tail_fn(struct page *page, void *arg)
 210 {
 211         int *pgmoved = arg;
 212         struct zone *zone = page_zone(page);
 213
 214         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 215                 enum lru_list lru = page_lru_base_type(page);
 216                 list_move_tail(&page->lru, &zone->lru[lru].list);
 217                 mem_cgroup_rotate_reclaimable_page(page);
 218                 (*pgmoved)++;
 219         }
 220 }
 221
 222 /*
 223  * pagevec_move_tail() must be called with IRQ disabled.
 224  * Otherwise this may cause nasty races.
 225  */
 226 static void pagevec_move_tail(struct pagevec *pvec)
 227 {
 228         int pgmoved = 0;
 229
 230         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
 231         __count_vm_events(PGROTATED, pgmoved);
 232 }
 233
 234 /*
 235  * Writeback is about to end against a page which has been marked for immediate
 236  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 237  * inactive list.
 238  */
 239 void rotate_reclaimable_page(struct page *page)
 240 {
 241         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
 242             !PageUnevictable(page) && PageLRU(page)) {
 243                 struct pagevec *pvec;
 244                 unsigned long flags;
 245
 246                 page_cache_get(page);
 247                 local_irq_save(flags);
 248                 pvec = &__get_cpu_var(lru_rotate_pvecs);
 249                 if (!pagevec_add(pvec, page))
 250                         pagevec_move_tail(pvec);
 251                 local_irq_restore(flags);
 252         }
 253 }
 254
 255 static void update_page_reclaim_stat(struct zone *zone, struct page *page,
 256                                      int file, int rotated)
 257 {
 258         struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
 259         struct zone_reclaim_stat *memcg_reclaim_stat;
 260
 261         memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
 262
 263         reclaim_stat->recent_scanned[file]++;
 264         if (rotated)
 265                 reclaim_stat->recent_rotated[file]++;
 266
 267         if (!memcg_reclaim_stat)
 268                 return;
 269
 270         memcg_reclaim_stat->recent_scanned[file]++;
 271         if (rotated)
 272                 memcg_reclaim_stat->recent_rotated[file]++;
 273 }
 274
 275 static void __activate_page(struct page *page, void *arg)
 276 {
 277         struct zone *zone = page_zone(page);
 278
 279         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 280                 int file = page_is_file_cache(page);
 281                 int lru = page_lru_base_type(page);
 282                 del_page_from_lru_list(zone, page, lru);
 283
 284                 SetPageActive(page);
 285                 lru += LRU_ACTIVE;
 286                 add_page_to_lru_list(zone, page, lru);
 287                 __count_vm_event(PGACTIVATE);
 288
 289                 update_page_reclaim_stat(zone, page, file, 1);
 290         }
 291 }
 292
 293 #ifdef CONFIG_SMP
 294 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
 295
 296 static void activate_page_drain(int cpu)
 297 {
 298         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
 299
 300         if (pagevec_count(pvec))
 301                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
 302 }
 303
 304 void activate_page(struct page *page)
 305 {
 306         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 307                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
 308
 309                 page_cache_get(page);
 310                 if (!pagevec_add(pvec, page))
 311                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
 312                 put_cpu_var(activate_page_pvecs);
 313         }
 314 }
 315
 316 #else
 317 static inline void activate_page_drain(int cpu)
 318 {
 319 }
 320
 321 void activate_page(struct page *page)
 322 {
 323         struct zone *zone = page_zone(page);
 324
 325         spin_lock_irq(&zone->lru_lock);
 326         __activate_page(page, NULL);
 327         spin_unlock_irq(&zone->lru_lock);
 328 }
 329 #endif
 330
 331 /*
 332  * Mark a page as having seen activity.
 333  *
 334  * inactive,unreferenced        ->      inactive,referenced
 335  * inactive,referenced          ->      active,unreferenced
 336  * active,unreferenced          ->      active,referenced
 337  */
 338 void mark_page_accessed(struct page *page)
 339 {
 340         if (!PageActive(page) && !PageUnevictable(page) &&
 341                         PageReferenced(page) && PageLRU(page)) {
 342                 activate_page(page);
 343                 ClearPageReferenced(page);
 344         } else if (!PageReferenced(page)) {
 345                 SetPageReferenced(page);
 346         }
 347 }
 348
 349 EXPORT_SYMBOL(mark_page_accessed);
 350
 351 void __lru_cache_add(struct page *page, enum lru_list lru)
 352 {
 353         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
 354
 355         page_cache_get(page);
 356         if (!pagevec_add(pvec, page))
 357                 ____pagevec_lru_add(pvec, lru);
 358         put_cpu_var(lru_add_pvecs);
 359 }
 360 EXPORT_SYMBOL(__lru_cache_add);
 361
 362 /**
 363  * lru_cache_add_lru - add a page to a page list
 364  * @page: the page to be added to the LRU.
 365  * @lru: the LRU list to which the page is added.
 366  */
 367 void lru_cache_add_lru(struct page *page, enum lru_list lru)
 368 {
 369         if (PageActive(page)) {
 370                 VM_BUG_ON(PageUnevictable(page));
 371                 ClearPageActive(page);
 372         } else if (PageUnevictable(page)) {
 373                 VM_BUG_ON(PageActive(page));
 374                 ClearPageUnevictable(page);
 375         }
 376
 377         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
 378         __lru_cache_add(page, lru);
 379 }
 380
 381 /**
 382  * add_page_to_unevictable_list - add a page to the unevictable list
 383  * @page:  the page to be added to the unevictable list
 384  *
 385  * Add page directly to its zone's unevictable list.  To avoid races with
 386  * tasks that might be making the page evictable, through eg. munlock,
 387  * munmap or exit, while it's not on the lru, we want to add the page
 388  * while it's locked or otherwise "invisible" to other tasks.  This is
 389  * difficult to do when using the pagevec cache, so bypass that.
 390  */
 391 void add_page_to_unevictable_list(struct page *page)
 392 {
 393         struct zone *zone = page_zone(page);
 394
 395         spin_lock_irq(&zone->lru_lock);
 396         SetPageUnevictable(page);
 397         SetPageLRU(page);
 398         add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
 399         spin_unlock_irq(&zone->lru_lock);
 400 }
 401
 402 /*
 403  * If the page can not be invalidated, it is moved to the
 404  * inactive list to speed up its reclaim.  It is moved to the
 405  * head of the list, rather than the tail, to give the flusher
 406  * threads some time to write it out, as this is much more
 407  * effective than the single-page writeout from reclaim.
 408  *
 409  * If the page isn't page_mapped and dirty/writeback, the page
 410  * could reclaim asap using PG_reclaim.
 411  *
 412  * 1. active, mapped page -> none
 413  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 414  * 3. inactive, mapped page -> none
 415  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 416  * 5. inactive, clean -> inactive, tail
 417  * 6. Others -> none
 418  *
 419  * In 4, why it moves inactive's head, the VM expects the page would
 420  * be write it out by flusher threads as this is much more effective
 421  * than the single-page writeout from reclaim.
 422  */
 423 static void lru_deactivate_fn(struct page *page, void *arg)
 424 {
 425         int lru, file;
 426         bool active;
 427         struct zone *zone = page_zone(page);
 428
 429         if (!PageLRU(page))
 430                 return;
 431
 432         if (PageUnevictable(page))
 433                 return;
 434
 435         /* Some processes are using the page */
 436         if (page_mapped(page))
 437                 return;
 438
 439         active = PageActive(page);
 440
 441         file = page_is_file_cache(page);
 442         lru = page_lru_base_type(page);
 443         del_page_from_lru_list(zone, page, lru + active);
 444         ClearPageActive(page);
 445         ClearPageReferenced(page);
 446         add_page_to_lru_list(zone, page, lru);
 447
 448         if (PageWriteback(page) || PageDirty(page)) {
 449                 /*
 450                  * PG_reclaim could be raced with end_page_writeback
 451                  * It can make readahead confusing.  But race window
 452                  * is _really_ small and  it's non-critical problem.
 453                  */
 454                 SetPageReclaim(page);
 455         } else {
 456                 /*
 457                  * The page's writeback ends up during pagevec
 458                  * We moves tha page into tail of inactive.
 459                  */
 460                 list_move_tail(&page->lru, &zone->lru[lru].list);
 461                 mem_cgroup_rotate_reclaimable_page(page);
 462                 __count_vm_event(PGROTATED);
 463         }
 464
 465         if (active)
 466                 __count_vm_event(PGDEACTIVATE);
 467         update_page_reclaim_stat(zone, page, file, 0);
 468 }
 469
 470 /*
 471  * Drain pages out of the cpu's pagevecs.
 472  * Either "cpu" is the current CPU, and preemption has already been
 473  * disabled; or "cpu" is being hot-unplugged, and is already dead.
 474  */
 475 static void drain_cpu_pagevecs(int cpu)
 476 {
 477         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
 478         struct pagevec *pvec;
 479         int lru;
 480
 481         for_each_lru(lru) {
 482                 pvec = &pvecs[lru - LRU_BASE];
 483                 if (pagevec_count(pvec))
 484                         ____pagevec_lru_add(pvec, lru);
 485         }
 486
 487         pvec = &per_cpu(lru_rotate_pvecs, cpu);
 488         if (pagevec_count(pvec)) {
 489                 unsigned long flags;
 490
 491                 /* No harm done if a racing interrupt already did this */
 492                 local_irq_save(flags);
 493                 pagevec_move_tail(pvec);
 494                 local_irq_restore(flags);
 495         }
 496
 497         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
 498         if (pagevec_count(pvec))
 499                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 500
 501         activate_page_drain(cpu);
 502 }
 503
 504 /**
 505  * deactivate_page - forcefully deactivate a page
 506  * @page: page to deactivate
 507  *
 508  * This function hints the VM that @page is a good reclaim candidate,
 509  * for example if its invalidation fails due to the page being dirty
 510  * or under writeback.
 511  */
 512 void deactivate_page(struct page *page)
 513 {
 514         /*
 515          * In a workload with many unevictable page such as mprotect, unevictable
 516          * page deactivation for accelerating reclaim is pointless.
 517          */
 518         if (PageUnevictable(page))
 519                 return;
 520
 521         if (likely(get_page_unless_zero(page))) {
 522                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 523
 524                 if (!pagevec_add(pvec, page))
 525                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 526                 put_cpu_var(lru_deactivate_pvecs);
 527         }
 528 }
 529
 530 void lru_add_drain(void)
 531 {
 532         drain_cpu_pagevecs(get_cpu());
 533         put_cpu();
 534 }
 535
 536 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 537 {
 538         lru_add_drain();
 539 }
 540
 541 /*
 542  * Returns 0 for success
 543  */
 544 int lru_add_drain_all(void)
 545 {
 546         return schedule_on_each_cpu(lru_add_drain_per_cpu);
 547 }
 548
 549 /*
 550  * Batched page_cache_release().  Decrement the reference count on all the
 551  * passed pages.  If it fell to zero then remove the page from the LRU and
 552  * free it.
 553  *
 554  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 555  * for the remainder of the operation.
 556  *
 557  * The locking in this function is against shrink_inactive_list(): we recheck
 558  * the page count inside the lock to see whether shrink_inactive_list()
 559  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 560  * will free it.
 561  */
 562 void release_pages(struct page **pages, int nr, int cold)
 563 {
 564         int i;
 565         struct pagevec pages_to_free;
 566         struct zone *zone = NULL;
 567         unsigned long uninitialized_var(flags);
 568
 569         pagevec_init(&pages_to_free, cold);
 570         for (i = 0; i < nr; i++) {
 571                 struct page *page = pages[i];
 572
 573                 if (unlikely(PageCompound(page))) {
 574                         if (zone) {
 575                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 576                                 zone = NULL;
 577                         }
 578                         put_compound_page(page);
 579                         continue;
 580                 }
 581
 582                 if (!put_page_testzero(page))
 583                         continue;
 584
 585                 if (PageLRU(page)) {
 586                         struct zone *pagezone = page_zone(page);
 587
 588                         if (pagezone != zone) {
 589                                 if (zone)
 590                                         spin_unlock_irqrestore(&zone->lru_lock,
 591                                                                         flags);
 592                                 zone = pagezone;
 593                                 spin_lock_irqsave(&zone->lru_lock, flags);
 594                         }
 595                         VM_BUG_ON(!PageLRU(page));
 596                         __ClearPageLRU(page);
 597                         del_page_from_lru(zone, page);
 598                 }
 599
 600                 if (!pagevec_add(&pages_to_free, page)) {
 601                         if (zone) {
 602                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 603                                 zone = NULL;
 604                         }
 605                         __pagevec_free(&pages_to_free);
 606                         pagevec_reinit(&pages_to_free);
 607                 }
 608         }
 609         if (zone)
 610                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 611
 612         pagevec_free(&pages_to_free);
 613 }
 614 EXPORT_SYMBOL(release_pages);
 615
 616 /*
 617  * The pages which we're about to release may be in the deferred lru-addition
 618  * queues.  That would prevent them from really being freed right now.  That's
 619  * OK from a correctness point of view but is inefficient - those pages may be
 620  * cache-warm and we want to give them back to the page allocator ASAP.
 621  *
 622  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 623  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 624  * mutual recursion.
 625  */
 626 void __pagevec_release(struct pagevec *pvec)
 627 {
 628         lru_add_drain();
 629         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 630         pagevec_reinit(pvec);
 631 }
 632
 633 EXPORT_SYMBOL(__pagevec_release);
 634
 635 /* used by __split_huge_page_refcount() */
 636 void lru_add_page_tail(struct zone* zone,
 637                        struct page *page, struct page *page_tail)
 638 {
 639         int active;
 640         enum lru_list lru;
 641         const int file = 0;
 642         struct list_head *head;
 643
 644         VM_BUG_ON(!PageHead(page));
 645         VM_BUG_ON(PageCompound(page_tail));
 646         VM_BUG_ON(PageLRU(page_tail));
 647         VM_BUG_ON(!spin_is_locked(&zone->lru_lock));
 648
 649         SetPageLRU(page_tail);
 650
 651         if (page_evictable(page_tail, NULL)) {
 652                 if (PageActive(page)) {
 653                         SetPageActive(page_tail);
 654                         active = 1;
 655                         lru = LRU_ACTIVE_ANON;
 656                 } else {
 657                         active = 0;
 658                         lru = LRU_INACTIVE_ANON;
 659                 }
 660                 update_page_reclaim_stat(zone, page_tail, file, active);
 661                 if (likely(PageLRU(page)))
 662                         head = page->lru.prev;
 663                 else
 664                         head = &zone->lru[lru].list;
 665                 __add_page_to_lru_list(zone, page_tail, lru, head);
 666         } else {
 667                 SetPageUnevictable(page_tail);
 668                 add_page_to_lru_list(zone, page_tail, LRU_UNEVICTABLE);
 669         }
 670 }
 671
 672 static void ____pagevec_lru_add_fn(struct page *page, void *arg)
 673 {
 674         enum lru_list lru = (enum lru_list)arg;
 675         struct zone *zone = page_zone(page);
 676         int file = is_file_lru(lru);
 677         int active = is_active_lru(lru);
 678
 679         VM_BUG_ON(PageActive(page));
 680         VM_BUG_ON(PageUnevictable(page));
 681         VM_BUG_ON(PageLRU(page));
 682
 683         SetPageLRU(page);
 684         if (active)
 685                 SetPageActive(page);
 686         update_page_reclaim_stat(zone, page, file, active);
 687         add_page_to_lru_list(zone, page, lru);
 688 }
 689
 690 /*
 691  * Add the passed pages to the LRU, then drop the caller's refcount
 692  * on them.  Reinitialises the caller's pagevec.
 693  */
 694 void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 695 {
 696         VM_BUG_ON(is_unevictable_lru(lru));
 697
 698         pagevec_lru_move_fn(pvec, ____pagevec_lru_add_fn, (void *)lru);
 699 }
 700
 701 EXPORT_SYMBOL(____pagevec_lru_add);
 702
 703 /*
 704  * Try to drop buffers from the pages in a pagevec
 705  */
 706 void pagevec_strip(struct pagevec *pvec)
 707 {
 708         int i;
 709
 710         for (i = 0; i < pagevec_count(pvec); i++) {
 711                 struct page *page = pvec->pages[i];
 712
 713                 if (page_has_private(page) && trylock_page(page)) {
 714                         if (page_has_private(page))
 715                                 try_to_release_page(page, 0);
 716                         unlock_page(page);
 717                 }
 718         }
 719 }
 720
 721 /**
 722  * pagevec_lookup - gang pagecache lookup
 723  * @pvec:       Where the resulting pages are placed
 724  * @mapping:    The address_space to search
 725  * @start:      The starting page index
 726  * @nr_pages:   The maximum number of pages
 727  *
 728  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 729  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 730  * reference against the pages in @pvec.
 731  *
 732  * The search returns a group of mapping-contiguous pages with ascending
 733  * indexes.  There may be holes in the indices due to not-present pages.
 734  *
 735  * pagevec_lookup() returns the number of pages which were found.
 736  */
 737 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 738                 pgoff_t start, unsigned nr_pages)
 739 {
 740         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 741         return pagevec_count(pvec);
 742 }
 743
 744 EXPORT_SYMBOL(pagevec_lookup);
 745
 746 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 747                 pgoff_t *index, int tag, unsigned nr_pages)
 748 {
 749         pvec->nr = find_get_pages_tag(mapping, index, tag,
 750                                         nr_pages, pvec->pages);
 751         return pagevec_count(pvec);
 752 }
 753
 754 EXPORT_SYMBOL(pagevec_lookup_tag);
 755
 756 /*
 757  * Perform any setup for the swap system
 758  */
 759 void __init swap_setup(void)
 760 {
 761         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
 762
 763 #ifdef CONFIG_SWAP
 764         bdi_init(swapper_space.backing_dev_info);
 765 #endif
 766
 767         /* Use a smaller cluster for small-memory machines */
 768         if (megs < 16)
 769                 page_cluster = 2;
 770         else
 771                 page_cluster = 3;
 772         /*
 773          * Right now other parts of the system means that we
 774          * _really_ don't want to cluster much more
 775          */
 776 }