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 /*
 240  * get_kernel_pages() - pin kernel pages in memory
 241  * @kiov:       An array of struct kvec structures
 242  * @nr_segs:    number of segments to pin
 243  * @write:      pinning for read/write, currently ignored
 244  * @pages:      array that receives pointers to the pages pinned.
 245  *              Should be at least nr_segs long.
 246  *
 247  * Returns number of pages pinned. This may be fewer than the number
 248  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 249  * were pinned, returns -errno. Each page returned must be released
 250  * with a put_page() call when it is finished with.
 251  */
 252 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
 253                 struct page **pages)
 254 {
 255         int seg;
 256
 257         for (seg = 0; seg < nr_segs; seg++) {
 258                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
 259                         return seg;
 260
 261                 /* virt_to_page sanity checks the PFN */
 262                 pages[seg] = virt_to_page(kiov[seg].iov_base);
 263                 page_cache_get(pages[seg]);
 264         }
 265
 266         return seg;
 267 }
 268 EXPORT_SYMBOL_GPL(get_kernel_pages);
 269
 270 /*
 271  * get_kernel_page() - pin a kernel page in memory
 272  * @start:      starting kernel address
 273  * @write:      pinning for read/write, currently ignored
 274  * @pages:      array that receives pointer to the page pinned.
 275  *              Must be at least nr_segs long.
 276  *
 277  * Returns 1 if page is pinned. If the page was not pinned, returns
 278  * -errno. The page returned must be released with a put_page() call
 279  * when it is finished with.
 280  */
 281 int get_kernel_page(unsigned long start, int write, struct page **pages)
 282 {
 283         const struct kvec kiov = {
 284                 .iov_base = (void *)start,
 285                 .iov_len = PAGE_SIZE
 286         };
 287
 288         return get_kernel_pages(&kiov, 1, write, pages);
 289 }
 290 EXPORT_SYMBOL_GPL(get_kernel_page);
 291
 292 static void pagevec_lru_move_fn(struct pagevec *pvec,
 293         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
 294         void *arg)
 295 {
 296         int i;
 297         struct zone *zone = NULL;
 298         struct lruvec *lruvec;
 299         unsigned long flags = 0;
 300
 301         for (i = 0; i < pagevec_count(pvec); i++) {
 302                 struct page *page = pvec->pages[i];
 303                 struct zone *pagezone = page_zone(page);
 304
 305                 if (pagezone != zone) {
 306                         if (zone)
 307                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 308                         zone = pagezone;
 309                         spin_lock_irqsave(&zone->lru_lock, flags);
 310                 }
 311
 312                 lruvec = mem_cgroup_page_lruvec(page, zone);
 313                 (*move_fn)(page, lruvec, arg);
 314         }
 315         if (zone)
 316                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 317         release_pages(pvec->pages, pvec->nr, pvec->cold);
 318         pagevec_reinit(pvec);
 319 }
 320
 321 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
 322                                  void *arg)
 323 {
 324         int *pgmoved = arg;
 325
 326         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 327                 enum lru_list lru = page_lru_base_type(page);
 328                 list_move_tail(&page->lru, &lruvec->lists[lru]);
 329                 (*pgmoved)++;
 330         }
 331 }
 332
 333 /*
 334  * pagevec_move_tail() must be called with IRQ disabled.
 335  * Otherwise this may cause nasty races.
 336  */
 337 static void pagevec_move_tail(struct pagevec *pvec)
 338 {
 339         int pgmoved = 0;
 340
 341         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
 342         __count_vm_events(PGROTATED, pgmoved);
 343 }
 344
 345 /*
 346  * Writeback is about to end against a page which has been marked for immediate
 347  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 348  * inactive list.
 349  */
 350 void rotate_reclaimable_page(struct page *page)
 351 {
 352         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
 353             !PageUnevictable(page) && PageLRU(page)) {
 354                 struct pagevec *pvec;
 355                 unsigned long flags;
 356
 357                 page_cache_get(page);
 358                 local_irq_save(flags);
 359                 pvec = &__get_cpu_var(lru_rotate_pvecs);
 360                 if (!pagevec_add(pvec, page))
 361                         pagevec_move_tail(pvec);
 362                 local_irq_restore(flags);
 363         }
 364 }
 365
 366 static void update_page_reclaim_stat(struct lruvec *lruvec,
 367                                      int file, int rotated)
 368 {
 369         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 370
 371         reclaim_stat->recent_scanned[file]++;
 372         if (rotated)
 373                 reclaim_stat->recent_rotated[file]++;
 374 }
 375
 376 static void __activate_page(struct page *page, struct lruvec *lruvec,
 377                             void *arg)
 378 {
 379         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 380                 int file = page_is_file_cache(page);
 381                 int lru = page_lru_base_type(page);
 382
 383                 del_page_from_lru_list(page, lruvec, lru);
 384                 SetPageActive(page);
 385                 lru += LRU_ACTIVE;
 386                 add_page_to_lru_list(page, lruvec, lru);
 387
 388                 __count_vm_event(PGACTIVATE);
 389                 update_page_reclaim_stat(lruvec, file, 1);
 390         }
 391 }
 392
 393 #ifdef CONFIG_SMP
 394 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
 395
 396 static void activate_page_drain(int cpu)
 397 {
 398         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
 399
 400         if (pagevec_count(pvec))
 401                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
 402 }
 403
 404 void activate_page(struct page *page)
 405 {
 406         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 407                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
 408
 409                 page_cache_get(page);
 410                 if (!pagevec_add(pvec, page))
 411                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
 412                 put_cpu_var(activate_page_pvecs);
 413         }
 414 }
 415
 416 #else
 417 static inline void activate_page_drain(int cpu)
 418 {
 419 }
 420
 421 void activate_page(struct page *page)
 422 {
 423         struct zone *zone = page_zone(page);
 424
 425         spin_lock_irq(&zone->lru_lock);
 426         __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
 427         spin_unlock_irq(&zone->lru_lock);
 428 }
 429 #endif
 430
 431 /*
 432  * Mark a page as having seen activity.
 433  *
 434  * inactive,unreferenced        ->      inactive,referenced
 435  * inactive,referenced          ->      active,unreferenced
 436  * active,unreferenced          ->      active,referenced
 437  */
 438 void mark_page_accessed(struct page *page)
 439 {
 440         if (!PageActive(page) && !PageUnevictable(page) &&
 441                         PageReferenced(page) && PageLRU(page)) {
 442                 activate_page(page);
 443                 ClearPageReferenced(page);
 444         } else if (!PageReferenced(page)) {
 445                 SetPageReferenced(page);
 446         }
 447 }
 448 EXPORT_SYMBOL(mark_page_accessed);
 449
 450 void __lru_cache_add(struct page *page, enum lru_list lru)
 451 {
 452         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
 453
 454         page_cache_get(page);
 455         if (!pagevec_add(pvec, page))
 456                 __pagevec_lru_add(pvec, lru);
 457         put_cpu_var(lru_add_pvecs);
 458 }
 459 EXPORT_SYMBOL(__lru_cache_add);
 460
 461 /**
 462  * lru_cache_add_lru - add a page to a page list
 463  * @page: the page to be added to the LRU.
 464  * @lru: the LRU list to which the page is added.
 465  */
 466 void lru_cache_add_lru(struct page *page, enum lru_list lru)
 467 {
 468         if (PageActive(page)) {
 469                 VM_BUG_ON(PageUnevictable(page));
 470                 ClearPageActive(page);
 471         } else if (PageUnevictable(page)) {
 472                 VM_BUG_ON(PageActive(page));
 473                 ClearPageUnevictable(page);
 474         }
 475
 476         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
 477         __lru_cache_add(page, lru);
 478 }
 479
 480 /**
 481  * add_page_to_unevictable_list - add a page to the unevictable list
 482  * @page:  the page to be added to the unevictable list
 483  *
 484  * Add page directly to its zone's unevictable list.  To avoid races with
 485  * tasks that might be making the page evictable, through eg. munlock,
 486  * munmap or exit, while it's not on the lru, we want to add the page
 487  * while it's locked or otherwise "invisible" to other tasks.  This is
 488  * difficult to do when using the pagevec cache, so bypass that.
 489  */
 490 void add_page_to_unevictable_list(struct page *page)
 491 {
 492         struct zone *zone = page_zone(page);
 493         struct lruvec *lruvec;
 494
 495         spin_lock_irq(&zone->lru_lock);
 496         lruvec = mem_cgroup_page_lruvec(page, zone);
 497         SetPageUnevictable(page);
 498         SetPageLRU(page);
 499         add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
 500         spin_unlock_irq(&zone->lru_lock);
 501 }
 502
 503 /*
 504  * If the page can not be invalidated, it is moved to the
 505  * inactive list to speed up its reclaim.  It is moved to the
 506  * head of the list, rather than the tail, to give the flusher
 507  * threads some time to write it out, as this is much more
 508  * effective than the single-page writeout from reclaim.
 509  *
 510  * If the page isn't page_mapped and dirty/writeback, the page
 511  * could reclaim asap using PG_reclaim.
 512  *
 513  * 1. active, mapped page -> none
 514  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 515  * 3. inactive, mapped page -> none
 516  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 517  * 5. inactive, clean -> inactive, tail
 518  * 6. Others -> none
 519  *
 520  * In 4, why it moves inactive's head, the VM expects the page would
 521  * be write it out by flusher threads as this is much more effective
 522  * than the single-page writeout from reclaim.
 523  */
 524 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
 525                               void *arg)
 526 {
 527         int lru, file;
 528         bool active;
 529
 530         if (!PageLRU(page))
 531                 return;
 532
 533         if (PageUnevictable(page))
 534                 return;
 535
 536         /* Some processes are using the page */
 537         if (page_mapped(page))
 538                 return;
 539
 540         active = PageActive(page);
 541         file = page_is_file_cache(page);
 542         lru = page_lru_base_type(page);
 543
 544         del_page_from_lru_list(page, lruvec, lru + active);
 545         ClearPageActive(page);
 546         ClearPageReferenced(page);
 547         add_page_to_lru_list(page, lruvec, lru);
 548
 549         if (PageWriteback(page) || PageDirty(page)) {
 550                 /*
 551                  * PG_reclaim could be raced with end_page_writeback
 552                  * It can make readahead confusing.  But race window
 553                  * is _really_ small and  it's non-critical problem.
 554                  */
 555                 SetPageReclaim(page);
 556         } else {
 557                 /*
 558                  * The page's writeback ends up during pagevec
 559                  * We moves tha page into tail of inactive.
 560                  */
 561                 list_move_tail(&page->lru, &lruvec->lists[lru]);
 562                 __count_vm_event(PGROTATED);
 563         }
 564
 565         if (active)
 566                 __count_vm_event(PGDEACTIVATE);
 567         update_page_reclaim_stat(lruvec, file, 0);
 568 }
 569
 570 /*
 571  * Drain pages out of the cpu's pagevecs.
 572  * Either "cpu" is the current CPU, and preemption has already been
 573  * disabled; or "cpu" is being hot-unplugged, and is already dead.
 574  */
 575 void lru_add_drain_cpu(int cpu)
 576 {
 577         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
 578         struct pagevec *pvec;
 579         int lru;
 580
 581         for_each_lru(lru) {
 582                 pvec = &pvecs[lru - LRU_BASE];
 583                 if (pagevec_count(pvec))
 584                         __pagevec_lru_add(pvec, lru);
 585         }
 586
 587         pvec = &per_cpu(lru_rotate_pvecs, cpu);
 588         if (pagevec_count(pvec)) {
 589                 unsigned long flags;
 590
 591                 /* No harm done if a racing interrupt already did this */
 592                 local_irq_save(flags);
 593                 pagevec_move_tail(pvec);
 594                 local_irq_restore(flags);
 595         }
 596
 597         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
 598         if (pagevec_count(pvec))
 599                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 600
 601         activate_page_drain(cpu);
 602 }
 603
 604 /**
 605  * deactivate_page - forcefully deactivate a page
 606  * @page: page to deactivate
 607  *
 608  * This function hints the VM that @page is a good reclaim candidate,
 609  * for example if its invalidation fails due to the page being dirty
 610  * or under writeback.
 611  */
 612 void deactivate_page(struct page *page)
 613 {
 614         /*
 615          * In a workload with many unevictable page such as mprotect, unevictable
 616          * page deactivation for accelerating reclaim is pointless.
 617          */
 618         if (PageUnevictable(page))
 619                 return;
 620
 621         if (likely(get_page_unless_zero(page))) {
 622                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 623
 624                 if (!pagevec_add(pvec, page))
 625                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 626                 put_cpu_var(lru_deactivate_pvecs);
 627         }
 628 }
 629
 630 void lru_add_drain(void)
 631 {
 632         lru_add_drain_cpu(get_cpu());
 633         put_cpu();
 634 }
 635
 636 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 637 {
 638         lru_add_drain();
 639 }
 640
 641 /*
 642  * Returns 0 for success
 643  */
 644 int lru_add_drain_all(void)
 645 {
 646         return schedule_on_each_cpu(lru_add_drain_per_cpu);
 647 }
 648
 649 /*
 650  * Batched page_cache_release().  Decrement the reference count on all the
 651  * passed pages.  If it fell to zero then remove the page from the LRU and
 652  * free it.
 653  *
 654  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 655  * for the remainder of the operation.
 656  *
 657  * The locking in this function is against shrink_inactive_list(): we recheck
 658  * the page count inside the lock to see whether shrink_inactive_list()
 659  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 660  * will free it.
 661  */
 662 void release_pages(struct page **pages, int nr, int cold)
 663 {
 664         int i;
 665         LIST_HEAD(pages_to_free);
 666         struct zone *zone = NULL;
 667         struct lruvec *lruvec;
 668         unsigned long uninitialized_var(flags);
 669
 670         for (i = 0; i < nr; i++) {
 671                 struct page *page = pages[i];
 672
 673                 if (unlikely(PageCompound(page))) {
 674                         if (zone) {
 675                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 676                                 zone = NULL;
 677                         }
 678                         put_compound_page(page);
 679                         continue;
 680                 }
 681
 682                 if (!put_page_testzero(page))
 683                         continue;
 684
 685                 if (PageLRU(page)) {
 686                         struct zone *pagezone = page_zone(page);
 687
 688                         if (pagezone != zone) {
 689                                 if (zone)
 690                                         spin_unlock_irqrestore(&zone->lru_lock,
 691                                                                         flags);
 692                                 zone = pagezone;
 693                                 spin_lock_irqsave(&zone->lru_lock, flags);
 694                         }
 695
 696                         lruvec = mem_cgroup_page_lruvec(page, zone);
 697                         VM_BUG_ON(!PageLRU(page));
 698                         __ClearPageLRU(page);
 699                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
 700                 }
 701
 702                 list_add(&page->lru, &pages_to_free);
 703         }
 704         if (zone)
 705                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 706
 707         free_hot_cold_page_list(&pages_to_free, cold);
 708 }
 709 EXPORT_SYMBOL(release_pages);
 710
 711 /*
 712  * The pages which we're about to release may be in the deferred lru-addition
 713  * queues.  That would prevent them from really being freed right now.  That's
 714  * OK from a correctness point of view but is inefficient - those pages may be
 715  * cache-warm and we want to give them back to the page allocator ASAP.
 716  *
 717  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 718  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 719  * mutual recursion.
 720  */
 721 void __pagevec_release(struct pagevec *pvec)
 722 {
 723         lru_add_drain();
 724         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 725         pagevec_reinit(pvec);
 726 }
 727 EXPORT_SYMBOL(__pagevec_release);
 728
 729 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 730 /* used by __split_huge_page_refcount() */
 731 void lru_add_page_tail(struct page *page, struct page *page_tail,
 732                        struct lruvec *lruvec)
 733 {
 734         int uninitialized_var(active);
 735         enum lru_list lru;
 736         const int file = 0;
 737
 738         VM_BUG_ON(!PageHead(page));
 739         VM_BUG_ON(PageCompound(page_tail));
 740         VM_BUG_ON(PageLRU(page_tail));
 741         VM_BUG_ON(NR_CPUS != 1 &&
 742                   !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
 743
 744         SetPageLRU(page_tail);
 745
 746         if (page_evictable(page_tail, NULL)) {
 747                 if (PageActive(page)) {
 748                         SetPageActive(page_tail);
 749                         active = 1;
 750                         lru = LRU_ACTIVE_ANON;
 751                 } else {
 752                         active = 0;
 753                         lru = LRU_INACTIVE_ANON;
 754                 }
 755         } else {
 756                 SetPageUnevictable(page_tail);
 757                 lru = LRU_UNEVICTABLE;
 758         }
 759
 760         if (likely(PageLRU(page)))
 761                 list_add_tail(&page_tail->lru, &page->lru);
 762         else {
 763                 struct list_head *list_head;
 764                 /*
 765                  * Head page has not yet been counted, as an hpage,
 766                  * so we must account for each subpage individually.
 767                  *
 768                  * Use the standard add function to put page_tail on the list,
 769                  * but then correct its position so they all end up in order.
 770                  */
 771                 add_page_to_lru_list(page_tail, lruvec, lru);
 772                 list_head = page_tail->lru.prev;
 773                 list_move_tail(&page_tail->lru, list_head);
 774         }
 775
 776         if (!PageUnevictable(page))
 777                 update_page_reclaim_stat(lruvec, file, active);
 778 }
 779 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 780
 781 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
 782                                  void *arg)
 783 {
 784         enum lru_list lru = (enum lru_list)arg;
 785         int file = is_file_lru(lru);
 786         int active = is_active_lru(lru);
 787
 788         VM_BUG_ON(PageActive(page));
 789         VM_BUG_ON(PageUnevictable(page));
 790         VM_BUG_ON(PageLRU(page));
 791
 792         SetPageLRU(page);
 793         if (active)
 794                 SetPageActive(page);
 795         add_page_to_lru_list(page, lruvec, lru);
 796         update_page_reclaim_stat(lruvec, file, active);
 797 }
 798
 799 /*
 800  * Add the passed pages to the LRU, then drop the caller's refcount
 801  * on them.  Reinitialises the caller's pagevec.
 802  */
 803 void __pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 804 {
 805         VM_BUG_ON(is_unevictable_lru(lru));
 806
 807         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)lru);
 808 }
 809 EXPORT_SYMBOL(__pagevec_lru_add);
 810
 811 /**
 812  * pagevec_lookup - gang pagecache lookup
 813  * @pvec:       Where the resulting pages are placed
 814  * @mapping:    The address_space to search
 815  * @start:      The starting page index
 816  * @nr_pages:   The maximum number of pages
 817  *
 818  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 819  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 820  * reference against the pages in @pvec.
 821  *
 822  * The search returns a group of mapping-contiguous pages with ascending
 823  * indexes.  There may be holes in the indices due to not-present pages.
 824  *
 825  * pagevec_lookup() returns the number of pages which were found.
 826  */
 827 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 828                 pgoff_t start, unsigned nr_pages)
 829 {
 830         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 831         return pagevec_count(pvec);
 832 }
 833 EXPORT_SYMBOL(pagevec_lookup);
 834
 835 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 836                 pgoff_t *index, int tag, unsigned nr_pages)
 837 {
 838         pvec->nr = find_get_pages_tag(mapping, index, tag,
 839                                         nr_pages, pvec->pages);
 840         return pagevec_count(pvec);
 841 }
 842 EXPORT_SYMBOL(pagevec_lookup_tag);
 843
 844 /*
 845  * Perform any setup for the swap system
 846  */
 847 void __init swap_setup(void)
 848 {
 849         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
 850
 851 #ifdef CONFIG_SWAP
 852         bdi_init(swapper_space.backing_dev_info);
 853 #endif
 854
 855         /* Use a smaller cluster for small-memory machines */
 856         if (megs < 16)
 857                 page_cluster = 2;
 858         else
 859                 page_cluster = 3;
 860         /*
 861          * Right now other parts of the system means that we
 862          * _really_ don't want to cluster much more
 863          */
 864 }