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