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/export.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 #include <linux/hugetlb.h>
  35
  36 #include "internal.h"
  37
  38 /* How many pages do we try to swap or page in/out together? */
  39 int page_cluster;
  40
  41 static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
  42 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
  43 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
  44
  45 /*
  46  * This path almost never happens for VM activity - pages are normally
  47  * freed via pagevecs.  But it gets used by networking.
  48  */
  49 static void __page_cache_release(struct page *page)
  50 {
  51         if (PageLRU(page)) {
  52                 unsigned long flags;
  53                 struct zone *zone = page_zone(page);
  54
  55                 spin_lock_irqsave(&zone->lru_lock, flags);
  56                 VM_BUG_ON(!PageLRU(page));
  57                 __ClearPageLRU(page);
  58                 del_page_from_lru(zone, page);
  59                 spin_unlock_irqrestore(&zone->lru_lock, flags);
  60         }
  61 }
  62
  63 static void __put_single_page(struct page *page)
  64 {
  65         __page_cache_release(page);
  66         free_hot_cold_page(page, 0);
  67 }
  68
  69 static void __put_compound_page(struct page *page)
  70 {
  71         compound_page_dtor *dtor;
  72
  73         if (!PageHuge(page))
  74                 __page_cache_release(page);
  75         dtor = get_compound_page_dtor(page);
  76         (*dtor)(page);
  77 }
  78
  79 static void put_compound_page(struct page *page)
  80 {
  81         /*
  82          * hugetlbfs pages cannot be split from under us.  If this is a
  83          * hugetlbfs page, check refcount on head page and release the page if
  84          * the refcount becomes zero.
  85          */
  86         if (PageHuge(page)) {
  87                 page = compound_head(page);
  88                 if (put_page_testzero(page))
  89                         __put_compound_page(page);
  90                 return;
  91         }
  92
  93         if (unlikely(PageTail(page))) {
  94                 /* __split_huge_page_refcount can run under us */
  95                 struct page *page_head = compound_trans_head(page);
  96
  97                 if (likely(page != page_head &&
  98                            get_page_unless_zero(page_head))) {
  99                         unsigned long flags;
 100                         /*
 101                          * page_head wasn't a dangling pointer but it
 102                          * may not be a head page anymore by the time
 103                          * we obtain the lock. That is ok as long as it
 104                          * can't be freed from under us.
 105                          */
 106                         flags = compound_lock_irqsave(page_head);
 107                         if (unlikely(!PageTail(page))) {
 108                                 /* __split_huge_page_refcount run before us */
 109                                 compound_unlock_irqrestore(page_head, flags);
 110                                 VM_BUG_ON(PageHead(page_head));
 111                                 if (put_page_testzero(page_head))
 112                                         __put_single_page(page_head);
 113                         out_put_single:
 114                                 if (put_page_testzero(page))
 115                                         __put_single_page(page);
 116                                 return;
 117                         }
 118                         VM_BUG_ON(page_head != page->first_page);
 119                         /*
 120                          * We can release the refcount taken by
 121                          * get_page_unless_zero() now that
 122                          * __split_huge_page_refcount() is blocked on
 123                          * the compound_lock.
 124                          */
 125                         if (put_page_testzero(page_head))
 126                                 VM_BUG_ON(1);
 127                         /* __split_huge_page_refcount will wait now */
 128                         VM_BUG_ON(page_mapcount(page) <= 0);
 129                         atomic_dec(&page->_mapcount);
 130                         VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
 131                         VM_BUG_ON(atomic_read(&page->_count) != 0);
 132                         compound_unlock_irqrestore(page_head, flags);
 133                         if (put_page_testzero(page_head)) {
 134                                 if (PageHead(page_head))
 135                                         __put_compound_page(page_head);
 136                                 else
 137                                         __put_single_page(page_head);
 138                         }
 139                 } else {
 140                         /* page_head is a dangling pointer */
 141                         VM_BUG_ON(PageTail(page));
 142                         goto out_put_single;
 143                 }
 144         } else if (put_page_testzero(page)) {
 145                 if (PageHead(page))
 146                         __put_compound_page(page);
 147                 else
 148                         __put_single_page(page);
 149         }
 150 }
 151
 152 void put_page(struct page *page)
 153 {
 154         if (unlikely(PageCompound(page)))
 155                 put_compound_page(page);
 156         else if (put_page_testzero(page))
 157                 __put_single_page(page);
 158 }
 159 EXPORT_SYMBOL(put_page);
 160
 161 /*
 162  * This function is exported but must not be called by anything other
 163  * than get_page(). It implements the slow path of get_page().
 164  */
 165 bool __get_page_tail(struct page *page)
 166 {
 167         /*
 168          * This takes care of get_page() if run on a tail page
 169          * returned by one of the get_user_pages/follow_page variants.
 170          * get_user_pages/follow_page itself doesn't need the compound
 171          * lock because it runs __get_page_tail_foll() under the
 172          * proper PT lock that already serializes against
 173          * split_huge_page().
 174          */
 175         unsigned long flags;
 176         bool got = false;
 177         struct page *page_head;
 178
 179         /*
 180          * If this is a hugetlbfs page it cannot be split under us.  Simply
 181          * increment refcount for the head page.
 182          */
 183         if (PageHuge(page)) {
 184                 page_head = compound_head(page);
 185                 atomic_inc(&page_head->_count);
 186                 got = true;
 187                 goto out;
 188         }
 189
 190         page_head = compound_trans_head(page);
 191         if (likely(page != page_head && get_page_unless_zero(page_head))) {
 192                 /*
 193                  * page_head wasn't a dangling pointer but it
 194                  * may not be a head page anymore by the time
 195                  * we obtain the lock. That is ok as long as it
 196                  * can't be freed from under us.
 197                  */
 198                 flags = compound_lock_irqsave(page_head);
 199                 /* here __split_huge_page_refcount won't run anymore */
 200                 if (likely(PageTail(page))) {
 201                         __get_page_tail_foll(page, false);
 202                         got = true;
 203                 }
 204                 compound_unlock_irqrestore(page_head, flags);
 205                 if (unlikely(!got))
 206                         put_page(page_head);
 207         }
 208 out:
 209         return got;
 210 }
 211 EXPORT_SYMBOL(__get_page_tail);
 212
 213 /**
 214  * put_pages_list() - release a list of pages
 215  * @pages: list of pages threaded on page->lru
 216  *
 217  * Release a list of pages which are strung together on page.lru.  Currently
 218  * used by read_cache_pages() and related error recovery code.
 219  */
 220 void put_pages_list(struct list_head *pages)
 221 {
 222         while (!list_empty(pages)) {
 223                 struct page *victim;
 224
 225                 victim = list_entry(pages->prev, struct page, lru);
 226                 list_del(&victim->lru);
 227                 page_cache_release(victim);
 228         }
 229 }
 230 EXPORT_SYMBOL(put_pages_list);
 231
 232 static void pagevec_lru_move_fn(struct pagevec *pvec,
 233                                 void (*move_fn)(struct page *page, void *arg),
 234                                 void *arg)
 235 {
 236         int i;
 237         struct zone *zone = NULL;
 238         unsigned long flags = 0;
 239
 240         for (i = 0; i < pagevec_count(pvec); i++) {
 241                 struct page *page = pvec->pages[i];
 242                 struct zone *pagezone = page_zone(page);
 243
 244                 if (pagezone != zone) {
 245                         if (zone)
 246                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 247                         zone = pagezone;
 248                         spin_lock_irqsave(&zone->lru_lock, flags);
 249                 }
 250
 251                 (*move_fn)(page, arg);
 252         }
 253         if (zone)
 254                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 255         release_pages(pvec->pages, pvec->nr, pvec->cold);
 256         pagevec_reinit(pvec);
 257 }
 258
 259 static void pagevec_move_tail_fn(struct page *page, void *arg)
 260 {
 261         int *pgmoved = arg;
 262         struct zone *zone = page_zone(page);
 263
 264         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 265                 enum lru_list lru = page_lru_base_type(page);
 266                 list_move_tail(&page->lru, &zone->lru[lru].list);
 267                 mem_cgroup_rotate_reclaimable_page(page);
 268                 (*pgmoved)++;
 269         }
 270 }
 271
 272 /*
 273  * pagevec_move_tail() must be called with IRQ disabled.
 274  * Otherwise this may cause nasty races.
 275  */
 276 static void pagevec_move_tail(struct pagevec *pvec)
 277 {
 278         int pgmoved = 0;
 279
 280         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
 281         __count_vm_events(PGROTATED, pgmoved);
 282 }
 283
 284 /*
 285  * Writeback is about to end against a page which has been marked for immediate
 286  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 287  * inactive list.
 288  */
 289 void rotate_reclaimable_page(struct page *page)
 290 {
 291         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
 292             !PageUnevictable(page) && PageLRU(page)) {
 293                 struct pagevec *pvec;
 294                 unsigned long flags;
 295
 296                 page_cache_get(page);
 297                 local_irq_save(flags);
 298                 pvec = &__get_cpu_var(lru_rotate_pvecs);
 299                 if (!pagevec_add(pvec, page))
 300                         pagevec_move_tail(pvec);
 301                 local_irq_restore(flags);
 302         }
 303 }
 304
 305 static void update_page_reclaim_stat(struct zone *zone, struct page *page,
 306                                      int file, int rotated)
 307 {
 308         struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
 309         struct zone_reclaim_stat *memcg_reclaim_stat;
 310
 311         memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
 312
 313         reclaim_stat->recent_scanned[file]++;
 314         if (rotated)
 315                 reclaim_stat->recent_rotated[file]++;
 316
 317         if (!memcg_reclaim_stat)
 318                 return;
 319
 320         memcg_reclaim_stat->recent_scanned[file]++;
 321         if (rotated)
 322                 memcg_reclaim_stat->recent_rotated[file]++;
 323 }
 324
 325 static void __activate_page(struct page *page, void *arg)
 326 {
 327         struct zone *zone = page_zone(page);
 328
 329         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 330                 int file = page_is_file_cache(page);
 331                 int lru = page_lru_base_type(page);
 332                 del_page_from_lru_list(zone, page, lru);
 333
 334                 SetPageActive(page);
 335                 lru += LRU_ACTIVE;
 336                 add_page_to_lru_list(zone, page, lru);
 337                 __count_vm_event(PGACTIVATE);
 338
 339                 update_page_reclaim_stat(zone, page, file, 1);
 340         }
 341 }
 342
 343 #ifdef CONFIG_SMP
 344 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
 345
 346 static void activate_page_drain(int cpu)
 347 {
 348         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
 349
 350         if (pagevec_count(pvec))
 351                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
 352 }
 353
 354 void activate_page(struct page *page)
 355 {
 356         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 357                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
 358
 359                 page_cache_get(page);
 360                 if (!pagevec_add(pvec, page))
 361                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
 362                 put_cpu_var(activate_page_pvecs);
 363         }
 364 }
 365
 366 #else
 367 static inline void activate_page_drain(int cpu)
 368 {
 369 }
 370
 371 void activate_page(struct page *page)
 372 {
 373         struct zone *zone = page_zone(page);
 374
 375         spin_lock_irq(&zone->lru_lock);
 376         __activate_page(page, NULL);
 377         spin_unlock_irq(&zone->lru_lock);
 378 }
 379 #endif
 380
 381 /*
 382  * Mark a page as having seen activity.
 383  *
 384  * inactive,unreferenced        ->      inactive,referenced
 385  * inactive,referenced          ->      active,unreferenced
 386  * active,unreferenced          ->      active,referenced
 387  */
 388 void mark_page_accessed(struct page *page)
 389 {
 390         if (!PageActive(page) && !PageUnevictable(page) &&
 391                         PageReferenced(page) && PageLRU(page)) {
 392                 activate_page(page);
 393                 ClearPageReferenced(page);
 394         } else if (!PageReferenced(page)) {
 395                 SetPageReferenced(page);
 396         }
 397 }
 398
 399 EXPORT_SYMBOL(mark_page_accessed);
 400
 401 void __lru_cache_add(struct page *page, enum lru_list lru)
 402 {
 403         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
 404
 405         page_cache_get(page);
 406         if (!pagevec_add(pvec, page))
 407                 ____pagevec_lru_add(pvec, lru);
 408         put_cpu_var(lru_add_pvecs);
 409 }
 410 EXPORT_SYMBOL(__lru_cache_add);
 411
 412 /**
 413  * lru_cache_add_lru - add a page to a page list
 414  * @page: the page to be added to the LRU.
 415  * @lru: the LRU list to which the page is added.
 416  */
 417 void lru_cache_add_lru(struct page *page, enum lru_list lru)
 418 {
 419         if (PageActive(page)) {
 420                 VM_BUG_ON(PageUnevictable(page));
 421                 ClearPageActive(page);
 422         } else if (PageUnevictable(page)) {
 423                 VM_BUG_ON(PageActive(page));
 424                 ClearPageUnevictable(page);
 425         }
 426
 427         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
 428         __lru_cache_add(page, lru);
 429 }
 430
 431 /**
 432  * add_page_to_unevictable_list - add a page to the unevictable list
 433  * @page:  the page to be added to the unevictable list
 434  *
 435  * Add page directly to its zone's unevictable list.  To avoid races with
 436  * tasks that might be making the page evictable, through eg. munlock,
 437  * munmap or exit, while it's not on the lru, we want to add the page
 438  * while it's locked or otherwise "invisible" to other tasks.  This is
 439  * difficult to do when using the pagevec cache, so bypass that.
 440  */
 441 void add_page_to_unevictable_list(struct page *page)
 442 {
 443         struct zone *zone = page_zone(page);
 444
 445         spin_lock_irq(&zone->lru_lock);
 446         SetPageUnevictable(page);
 447         SetPageLRU(page);
 448         add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
 449         spin_unlock_irq(&zone->lru_lock);
 450 }
 451
 452 /*
 453  * If the page can not be invalidated, it is moved to the
 454  * inactive list to speed up its reclaim.  It is moved to the
 455  * head of the list, rather than the tail, to give the flusher
 456  * threads some time to write it out, as this is much more
 457  * effective than the single-page writeout from reclaim.
 458  *
 459  * If the page isn't page_mapped and dirty/writeback, the page
 460  * could reclaim asap using PG_reclaim.
 461  *
 462  * 1. active, mapped page -> none
 463  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 464  * 3. inactive, mapped page -> none
 465  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 466  * 5. inactive, clean -> inactive, tail
 467  * 6. Others -> none
 468  *
 469  * In 4, why it moves inactive's head, the VM expects the page would
 470  * be write it out by flusher threads as this is much more effective
 471  * than the single-page writeout from reclaim.
 472  */
 473 static void lru_deactivate_fn(struct page *page, void *arg)
 474 {
 475         int lru, file;
 476         bool active;
 477         struct zone *zone = page_zone(page);
 478
 479         if (!PageLRU(page))
 480                 return;
 481
 482         if (PageUnevictable(page))
 483                 return;
 484
 485         /* Some processes are using the page */
 486         if (page_mapped(page))
 487                 return;
 488
 489         active = PageActive(page);
 490
 491         file = page_is_file_cache(page);
 492         lru = page_lru_base_type(page);
 493         del_page_from_lru_list(zone, page, lru + active);
 494         ClearPageActive(page);
 495         ClearPageReferenced(page);
 496         add_page_to_lru_list(zone, page, lru);
 497
 498         if (PageWriteback(page) || PageDirty(page)) {
 499                 /*
 500                  * PG_reclaim could be raced with end_page_writeback
 501                  * It can make readahead confusing.  But race window
 502                  * is _really_ small and  it's non-critical problem.
 503                  */
 504                 SetPageReclaim(page);
 505         } else {
 506                 /*
 507                  * The page's writeback ends up during pagevec
 508                  * We moves tha page into tail of inactive.
 509                  */
 510                 list_move_tail(&page->lru, &zone->lru[lru].list);
 511                 mem_cgroup_rotate_reclaimable_page(page);
 512                 __count_vm_event(PGROTATED);
 513         }
 514
 515         if (active)
 516                 __count_vm_event(PGDEACTIVATE);
 517         update_page_reclaim_stat(zone, page, file, 0);
 518 }
 519
 520 /*
 521  * Drain pages out of the cpu's pagevecs.
 522  * Either "cpu" is the current CPU, and preemption has already been
 523  * disabled; or "cpu" is being hot-unplugged, and is already dead.
 524  */
 525 static void drain_cpu_pagevecs(int cpu)
 526 {
 527         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
 528         struct pagevec *pvec;
 529         int lru;
 530
 531         for_each_lru(lru) {
 532                 pvec = &pvecs[lru - LRU_BASE];
 533                 if (pagevec_count(pvec))
 534                         ____pagevec_lru_add(pvec, lru);
 535         }
 536
 537         pvec = &per_cpu(lru_rotate_pvecs, cpu);
 538         if (pagevec_count(pvec)) {
 539                 unsigned long flags;
 540
 541                 /* No harm done if a racing interrupt already did this */
 542                 local_irq_save(flags);
 543                 pagevec_move_tail(pvec);
 544                 local_irq_restore(flags);
 545         }
 546
 547         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
 548         if (pagevec_count(pvec))
 549                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 550
 551         activate_page_drain(cpu);
 552 }
 553
 554 /**
 555  * deactivate_page - forcefully deactivate a page
 556  * @page: page to deactivate
 557  *
 558  * This function hints the VM that @page is a good reclaim candidate,
 559  * for example if its invalidation fails due to the page being dirty
 560  * or under writeback.
 561  */
 562 void deactivate_page(struct page *page)
 563 {
 564         /*
 565          * In a workload with many unevictable page such as mprotect, unevictable
 566          * page deactivation for accelerating reclaim is pointless.
 567          */
 568         if (PageUnevictable(page))
 569                 return;
 570
 571         if (likely(get_page_unless_zero(page))) {
 572                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 573
 574                 if (!pagevec_add(pvec, page))
 575                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 576                 put_cpu_var(lru_deactivate_pvecs);
 577         }
 578 }
 579
 580 void lru_add_drain(void)
 581 {
 582         drain_cpu_pagevecs(get_cpu());
 583         put_cpu();
 584 }
 585
 586 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 587 {
 588         lru_add_drain();
 589 }
 590
 591 /*
 592  * Returns 0 for success
 593  */
 594 int lru_add_drain_all(void)
 595 {
 596         return schedule_on_each_cpu(lru_add_drain_per_cpu);
 597 }
 598
 599 /*
 600  * Batched page_cache_release().  Decrement the reference count on all the
 601  * passed pages.  If it fell to zero then remove the page from the LRU and
 602  * free it.
 603  *
 604  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 605  * for the remainder of the operation.
 606  *
 607  * The locking in this function is against shrink_inactive_list(): we recheck
 608  * the page count inside the lock to see whether shrink_inactive_list()
 609  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 610  * will free it.
 611  */
 612 void release_pages(struct page **pages, int nr, int cold)
 613 {
 614         int i;
 615         struct pagevec pages_to_free;
 616         struct zone *zone = NULL;
 617         unsigned long uninitialized_var(flags);
 618
 619         pagevec_init(&pages_to_free, cold);
 620         for (i = 0; i < nr; i++) {
 621                 struct page *page = pages[i];
 622
 623                 if (unlikely(PageCompound(page))) {
 624                         if (zone) {
 625                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 626                                 zone = NULL;
 627                         }
 628                         put_compound_page(page);
 629                         continue;
 630                 }
 631
 632                 if (!put_page_testzero(page))
 633                         continue;
 634
 635                 if (PageLRU(page)) {
 636                         struct zone *pagezone = page_zone(page);
 637
 638                         if (pagezone != zone) {
 639                                 if (zone)
 640                                         spin_unlock_irqrestore(&zone->lru_lock,
 641                                                                         flags);
 642                                 zone = pagezone;
 643                                 spin_lock_irqsave(&zone->lru_lock, flags);
 644                         }
 645                         VM_BUG_ON(!PageLRU(page));
 646                         __ClearPageLRU(page);
 647                         del_page_from_lru(zone, page);
 648                 }
 649
 650                 if (!pagevec_add(&pages_to_free, page)) {
 651                         if (zone) {
 652                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 653                                 zone = NULL;
 654                         }
 655                         __pagevec_free(&pages_to_free);
 656                         pagevec_reinit(&pages_to_free);
 657                 }
 658         }
 659         if (zone)
 660                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 661
 662         pagevec_free(&pages_to_free);
 663 }
 664 EXPORT_SYMBOL(release_pages);
 665
 666 /*
 667  * The pages which we're about to release may be in the deferred lru-addition
 668  * queues.  That would prevent them from really being freed right now.  That's
 669  * OK from a correctness point of view but is inefficient - those pages may be
 670  * cache-warm and we want to give them back to the page allocator ASAP.
 671  *
 672  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 673  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 674  * mutual recursion.
 675  */
 676 void __pagevec_release(struct pagevec *pvec)
 677 {
 678         lru_add_drain();
 679         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 680         pagevec_reinit(pvec);
 681 }
 682
 683 EXPORT_SYMBOL(__pagevec_release);
 684
 685 /* used by __split_huge_page_refcount() */
 686 void lru_add_page_tail(struct zone* zone,
 687                        struct page *page, struct page *page_tail)
 688 {
 689         int active;
 690         enum lru_list lru;
 691         const int file = 0;
 692         struct list_head *head;
 693
 694         VM_BUG_ON(!PageHead(page));
 695         VM_BUG_ON(PageCompound(page_tail));
 696         VM_BUG_ON(PageLRU(page_tail));
 697         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&zone->lru_lock));
 698
 699         SetPageLRU(page_tail);
 700
 701         if (page_evictable(page_tail, NULL)) {
 702                 if (PageActive(page)) {
 703                         SetPageActive(page_tail);
 704                         active = 1;
 705                         lru = LRU_ACTIVE_ANON;
 706                 } else {
 707                         active = 0;
 708                         lru = LRU_INACTIVE_ANON;
 709                 }
 710                 update_page_reclaim_stat(zone, page_tail, file, active);
 711                 if (likely(PageLRU(page)))
 712                         head = page->lru.prev;
 713                 else
 714                         head = &zone->lru[lru].list;
 715                 __add_page_to_lru_list(zone, page_tail, lru, head);
 716         } else {
 717                 SetPageUnevictable(page_tail);
 718                 add_page_to_lru_list(zone, page_tail, LRU_UNEVICTABLE);
 719         }
 720 }
 721
 722 static void ____pagevec_lru_add_fn(struct page *page, void *arg)
 723 {
 724         enum lru_list lru = (enum lru_list)arg;
 725         struct zone *zone = page_zone(page);
 726         int file = is_file_lru(lru);
 727         int active = is_active_lru(lru);
 728
 729         VM_BUG_ON(PageActive(page));
 730         VM_BUG_ON(PageUnevictable(page));
 731         VM_BUG_ON(PageLRU(page));
 732
 733         SetPageLRU(page);
 734         if (active)
 735                 SetPageActive(page);
 736         update_page_reclaim_stat(zone, page, file, active);
 737         add_page_to_lru_list(zone, page, lru);
 738 }
 739
 740 /*
 741  * Add the passed pages to the LRU, then drop the caller's refcount
 742  * on them.  Reinitialises the caller's pagevec.
 743  */
 744 void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 745 {
 746         VM_BUG_ON(is_unevictable_lru(lru));
 747
 748         pagevec_lru_move_fn(pvec, ____pagevec_lru_add_fn, (void *)lru);
 749 }
 750
 751 EXPORT_SYMBOL(____pagevec_lru_add);
 752
 753 /*
 754  * Try to drop buffers from the pages in a pagevec
 755  */
 756 void pagevec_strip(struct pagevec *pvec)
 757 {
 758         int i;
 759
 760         for (i = 0; i < pagevec_count(pvec); i++) {
 761                 struct page *page = pvec->pages[i];
 762
 763                 if (page_has_private(page) && trylock_page(page)) {
 764                         if (page_has_private(page))
 765                                 try_to_release_page(page, 0);
 766                         unlock_page(page);
 767                 }
 768         }
 769 }
 770
 771 /**
 772  * pagevec_lookup - gang pagecache lookup
 773  * @pvec:       Where the resulting pages are placed
 774  * @mapping:    The address_space to search
 775  * @start:      The starting page index
 776  * @nr_pages:   The maximum number of pages
 777  *
 778  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 779  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 780  * reference against the pages in @pvec.
 781  *
 782  * The search returns a group of mapping-contiguous pages with ascending
 783  * indexes.  There may be holes in the indices due to not-present pages.
 784  *
 785  * pagevec_lookup() returns the number of pages which were found.
 786  */
 787 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 788                 pgoff_t start, unsigned nr_pages)
 789 {
 790         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 791         return pagevec_count(pvec);
 792 }
 793
 794 EXPORT_SYMBOL(pagevec_lookup);
 795
 796 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 797                 pgoff_t *index, int tag, unsigned nr_pages)
 798 {
 799         pvec->nr = find_get_pages_tag(mapping, index, tag,
 800                                         nr_pages, pvec->pages);
 801         return pagevec_count(pvec);
 802 }
 803
 804 EXPORT_SYMBOL(pagevec_lookup_tag);
 805
 806 /*
 807  * Perform any setup for the swap system
 808  */
 809 void __init swap_setup(void)
 810 {
 811         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
 812
 813 #ifdef CONFIG_SWAP
 814         bdi_init(swapper_space.backing_dev_info);
 815 #endif
 816
 817         /* Use a smaller cluster for small-memory machines */
 818         if (megs < 16)
 819                 page_cluster = 2;
 820         else
 821                 page_cluster = 3;
 822         /*
 823          * Right now other parts of the system means that we
 824          * _really_ don't want to cluster much more
 825          */
 826 }