linux/mm/swap.c
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   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? */
  37int page_cluster;
  38
  39static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
  40static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
  41static 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 */
  47static 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
  63static void __put_single_page(struct page *page)
  64{
  65        __page_cache_release(page);
  66        free_hot_cold_page(page, 0);
  67}
  68
  69static 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
  78static 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);
 116skip_lock:
 117                                if (put_page_testzero(page_head))
 118                                        __put_single_page(page_head);
 119out_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
 140skip_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
 160void 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}
 167EXPORT_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 */
 173bool __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}
 218EXPORT_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 */
 227void 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}
 237EXPORT_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 */
 252int 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                pages[seg] = kmap_to_page(kiov[seg].iov_base);
 262                page_cache_get(pages[seg]);
 263        }
 264
 265        return seg;
 266}
 267EXPORT_SYMBOL_GPL(get_kernel_pages);
 268
 269/*
 270 * get_kernel_page() - pin a kernel page in memory
 271 * @start:      starting kernel address
 272 * @write:      pinning for read/write, currently ignored
 273 * @pages:      array that receives pointer to the page pinned.
 274 *              Must be at least nr_segs long.
 275 *
 276 * Returns 1 if page is pinned. If the page was not pinned, returns
 277 * -errno. The page returned must be released with a put_page() call
 278 * when it is finished with.
 279 */
 280int get_kernel_page(unsigned long start, int write, struct page **pages)
 281{
 282        const struct kvec kiov = {
 283                .iov_base = (void *)start,
 284                .iov_len = PAGE_SIZE
 285        };
 286
 287        return get_kernel_pages(&kiov, 1, write, pages);
 288}
 289EXPORT_SYMBOL_GPL(get_kernel_page);
 290
 291static void pagevec_lru_move_fn(struct pagevec *pvec,
 292        void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
 293        void *arg)
 294{
 295        int i;
 296        struct zone *zone = NULL;
 297        struct lruvec *lruvec;
 298        unsigned long flags = 0;
 299
 300        for (i = 0; i < pagevec_count(pvec); i++) {
 301                struct page *page = pvec->pages[i];
 302                struct zone *pagezone = page_zone(page);
 303
 304                if (pagezone != zone) {
 305                        if (zone)
 306                                spin_unlock_irqrestore(&zone->lru_lock, flags);
 307                        zone = pagezone;
 308                        spin_lock_irqsave(&zone->lru_lock, flags);
 309                }
 310
 311                lruvec = mem_cgroup_page_lruvec(page, zone);
 312                (*move_fn)(page, lruvec, arg);
 313        }
 314        if (zone)
 315                spin_unlock_irqrestore(&zone->lru_lock, flags);
 316        release_pages(pvec->pages, pvec->nr, pvec->cold);
 317        pagevec_reinit(pvec);
 318}
 319
 320static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
 321                                 void *arg)
 322{
 323        int *pgmoved = arg;
 324
 325        if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 326                enum lru_list lru = page_lru_base_type(page);
 327                list_move_tail(&page->lru, &lruvec->lists[lru]);
 328                (*pgmoved)++;
 329        }
 330}
 331
 332/*
 333 * pagevec_move_tail() must be called with IRQ disabled.
 334 * Otherwise this may cause nasty races.
 335 */
 336static void pagevec_move_tail(struct pagevec *pvec)
 337{
 338        int pgmoved = 0;
 339
 340        pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
 341        __count_vm_events(PGROTATED, pgmoved);
 342}
 343
 344/*
 345 * Writeback is about to end against a page which has been marked for immediate
 346 * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 347 * inactive list.
 348 */
 349void rotate_reclaimable_page(struct page *page)
 350{
 351        if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
 352            !PageUnevictable(page) && PageLRU(page)) {
 353                struct pagevec *pvec;
 354                unsigned long flags;
 355
 356                page_cache_get(page);
 357                local_irq_save(flags);
 358                pvec = &__get_cpu_var(lru_rotate_pvecs);
 359                if (!pagevec_add(pvec, page))
 360                        pagevec_move_tail(pvec);
 361                local_irq_restore(flags);
 362        }
 363}
 364
 365static void update_page_reclaim_stat(struct lruvec *lruvec,
 366                                     int file, int rotated)
 367{
 368        struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 369
 370        reclaim_stat->recent_scanned[file]++;
 371        if (rotated)
 372                reclaim_stat->recent_rotated[file]++;
 373}
 374
 375static void __activate_page(struct page *page, struct lruvec *lruvec,
 376                            void *arg)
 377{
 378        if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 379                int file = page_is_file_cache(page);
 380                int lru = page_lru_base_type(page);
 381
 382                del_page_from_lru_list(page, lruvec, lru);
 383                SetPageActive(page);
 384                lru += LRU_ACTIVE;
 385                add_page_to_lru_list(page, lruvec, lru);
 386
 387                __count_vm_event(PGACTIVATE);
 388                update_page_reclaim_stat(lruvec, file, 1);
 389        }
 390}
 391
 392#ifdef CONFIG_SMP
 393static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
 394
 395static void activate_page_drain(int cpu)
 396{
 397        struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
 398
 399        if (pagevec_count(pvec))
 400                pagevec_lru_move_fn(pvec, __activate_page, NULL);
 401}
 402
 403void activate_page(struct page *page)
 404{
 405        if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 406                struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
 407
 408                page_cache_get(page);
 409                if (!pagevec_add(pvec, page))
 410                        pagevec_lru_move_fn(pvec, __activate_page, NULL);
 411                put_cpu_var(activate_page_pvecs);
 412        }
 413}
 414
 415#else
 416static inline void activate_page_drain(int cpu)
 417{
 418}
 419
 420void activate_page(struct page *page)
 421{
 422        struct zone *zone = page_zone(page);
 423
 424        spin_lock_irq(&zone->lru_lock);
 425        __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
 426        spin_unlock_irq(&zone->lru_lock);
 427}
 428#endif
 429
 430/*
 431 * Mark a page as having seen activity.
 432 *
 433 * inactive,unreferenced        ->      inactive,referenced
 434 * inactive,referenced          ->      active,unreferenced
 435 * active,unreferenced          ->      active,referenced
 436 */
 437void mark_page_accessed(struct page *page)
 438{
 439        if (!PageActive(page) && !PageUnevictable(page) &&
 440                        PageReferenced(page) && PageLRU(page)) {
 441                activate_page(page);
 442                ClearPageReferenced(page);
 443        } else if (!PageReferenced(page)) {
 444                SetPageReferenced(page);
 445        }
 446}
 447EXPORT_SYMBOL(mark_page_accessed);
 448
 449/*
 450 * Order of operations is important: flush the pagevec when it's already
 451 * full, not when adding the last page, to make sure that last page is
 452 * not added to the LRU directly when passed to this function. Because
 453 * mark_page_accessed() (called after this when writing) only activates
 454 * pages that are on the LRU, linear writes in subpage chunks would see
 455 * every PAGEVEC_SIZE page activated, which is unexpected.
 456 */
 457void __lru_cache_add(struct page *page, enum lru_list lru)
 458{
 459        struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
 460
 461        page_cache_get(page);
 462        if (!pagevec_space(pvec))
 463                __pagevec_lru_add(pvec, lru);
 464        pagevec_add(pvec, page);
 465        put_cpu_var(lru_add_pvecs);
 466}
 467EXPORT_SYMBOL(__lru_cache_add);
 468
 469/**
 470 * lru_cache_add_lru - add a page to a page list
 471 * @page: the page to be added to the LRU.
 472 * @lru: the LRU list to which the page is added.
 473 */
 474void lru_cache_add_lru(struct page *page, enum lru_list lru)
 475{
 476        if (PageActive(page)) {
 477                VM_BUG_ON(PageUnevictable(page));
 478                ClearPageActive(page);
 479        } else if (PageUnevictable(page)) {
 480                VM_BUG_ON(PageActive(page));
 481                ClearPageUnevictable(page);
 482        }
 483
 484        VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
 485        __lru_cache_add(page, lru);
 486}
 487
 488/**
 489 * add_page_to_unevictable_list - add a page to the unevictable list
 490 * @page:  the page to be added to the unevictable list
 491 *
 492 * Add page directly to its zone's unevictable list.  To avoid races with
 493 * tasks that might be making the page evictable, through eg. munlock,
 494 * munmap or exit, while it's not on the lru, we want to add the page
 495 * while it's locked or otherwise "invisible" to other tasks.  This is
 496 * difficult to do when using the pagevec cache, so bypass that.
 497 */
 498void add_page_to_unevictable_list(struct page *page)
 499{
 500        struct zone *zone = page_zone(page);
 501        struct lruvec *lruvec;
 502
 503        spin_lock_irq(&zone->lru_lock);
 504        lruvec = mem_cgroup_page_lruvec(page, zone);
 505        SetPageUnevictable(page);
 506        SetPageLRU(page);
 507        add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
 508        spin_unlock_irq(&zone->lru_lock);
 509}
 510
 511/*
 512 * If the page can not be invalidated, it is moved to the
 513 * inactive list to speed up its reclaim.  It is moved to the
 514 * head of the list, rather than the tail, to give the flusher
 515 * threads some time to write it out, as this is much more
 516 * effective than the single-page writeout from reclaim.
 517 *
 518 * If the page isn't page_mapped and dirty/writeback, the page
 519 * could reclaim asap using PG_reclaim.
 520 *
 521 * 1. active, mapped page -> none
 522 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 523 * 3. inactive, mapped page -> none
 524 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 525 * 5. inactive, clean -> inactive, tail
 526 * 6. Others -> none
 527 *
 528 * In 4, why it moves inactive's head, the VM expects the page would
 529 * be write it out by flusher threads as this is much more effective
 530 * than the single-page writeout from reclaim.
 531 */
 532static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
 533                              void *arg)
 534{
 535        int lru, file;
 536        bool active;
 537
 538        if (!PageLRU(page))
 539                return;
 540
 541        if (PageUnevictable(page))
 542                return;
 543
 544        /* Some processes are using the page */
 545        if (page_mapped(page))
 546                return;
 547
 548        active = PageActive(page);
 549        file = page_is_file_cache(page);
 550        lru = page_lru_base_type(page);
 551
 552        del_page_from_lru_list(page, lruvec, lru + active);
 553        ClearPageActive(page);
 554        ClearPageReferenced(page);
 555        add_page_to_lru_list(page, lruvec, lru);
 556
 557        if (PageWriteback(page) || PageDirty(page)) {
 558                /*
 559                 * PG_reclaim could be raced with end_page_writeback
 560                 * It can make readahead confusing.  But race window
 561                 * is _really_ small and  it's non-critical problem.
 562                 */
 563                SetPageReclaim(page);
 564        } else {
 565                /*
 566                 * The page's writeback ends up during pagevec
 567                 * We moves tha page into tail of inactive.
 568                 */
 569                list_move_tail(&page->lru, &lruvec->lists[lru]);
 570                __count_vm_event(PGROTATED);
 571        }
 572
 573        if (active)
 574                __count_vm_event(PGDEACTIVATE);
 575        update_page_reclaim_stat(lruvec, file, 0);
 576}
 577
 578/*
 579 * Drain pages out of the cpu's pagevecs.
 580 * Either "cpu" is the current CPU, and preemption has already been
 581 * disabled; or "cpu" is being hot-unplugged, and is already dead.
 582 */
 583void lru_add_drain_cpu(int cpu)
 584{
 585        struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
 586        struct pagevec *pvec;
 587        int lru;
 588
 589        for_each_lru(lru) {
 590                pvec = &pvecs[lru - LRU_BASE];
 591                if (pagevec_count(pvec))
 592                        __pagevec_lru_add(pvec, lru);
 593        }
 594
 595        pvec = &per_cpu(lru_rotate_pvecs, cpu);
 596        if (pagevec_count(pvec)) {
 597                unsigned long flags;
 598
 599                /* No harm done if a racing interrupt already did this */
 600                local_irq_save(flags);
 601                pagevec_move_tail(pvec);
 602                local_irq_restore(flags);
 603        }
 604
 605        pvec = &per_cpu(lru_deactivate_pvecs, cpu);
 606        if (pagevec_count(pvec))
 607                pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 608
 609        activate_page_drain(cpu);
 610}
 611
 612/**
 613 * deactivate_page - forcefully deactivate a page
 614 * @page: page to deactivate
 615 *
 616 * This function hints the VM that @page is a good reclaim candidate,
 617 * for example if its invalidation fails due to the page being dirty
 618 * or under writeback.
 619 */
 620void deactivate_page(struct page *page)
 621{
 622        /*
 623         * In a workload with many unevictable page such as mprotect, unevictable
 624         * page deactivation for accelerating reclaim is pointless.
 625         */
 626        if (PageUnevictable(page))
 627                return;
 628
 629        if (likely(get_page_unless_zero(page))) {
 630                struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 631
 632                if (!pagevec_add(pvec, page))
 633                        pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 634                put_cpu_var(lru_deactivate_pvecs);
 635        }
 636}
 637
 638void lru_add_drain(void)
 639{
 640        lru_add_drain_cpu(get_cpu());
 641        put_cpu();
 642}
 643
 644static void lru_add_drain_per_cpu(struct work_struct *dummy)
 645{
 646        lru_add_drain();
 647}
 648
 649/*
 650 * Returns 0 for success
 651 */
 652int lru_add_drain_all(void)
 653{
 654        return schedule_on_each_cpu(lru_add_drain_per_cpu);
 655}
 656
 657/*
 658 * Batched page_cache_release().  Decrement the reference count on all the
 659 * passed pages.  If it fell to zero then remove the page from the LRU and
 660 * free it.
 661 *
 662 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 663 * for the remainder of the operation.
 664 *
 665 * The locking in this function is against shrink_inactive_list(): we recheck
 666 * the page count inside the lock to see whether shrink_inactive_list()
 667 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 668 * will free it.
 669 */
 670void release_pages(struct page **pages, int nr, int cold)
 671{
 672        int i;
 673        LIST_HEAD(pages_to_free);
 674        struct zone *zone = NULL;
 675        struct lruvec *lruvec;
 676        unsigned long uninitialized_var(flags);
 677
 678        for (i = 0; i < nr; i++) {
 679                struct page *page = pages[i];
 680
 681                if (unlikely(PageCompound(page))) {
 682                        if (zone) {
 683                                spin_unlock_irqrestore(&zone->lru_lock, flags);
 684                                zone = NULL;
 685                        }
 686                        put_compound_page(page);
 687                        continue;
 688                }
 689
 690                if (!put_page_testzero(page))
 691                        continue;
 692
 693                if (PageLRU(page)) {
 694                        struct zone *pagezone = page_zone(page);
 695
 696                        if (pagezone != zone) {
 697                                if (zone)
 698                                        spin_unlock_irqrestore(&zone->lru_lock,
 699                                                                        flags);
 700                                zone = pagezone;
 701                                spin_lock_irqsave(&zone->lru_lock, flags);
 702                        }
 703
 704                        lruvec = mem_cgroup_page_lruvec(page, zone);
 705                        VM_BUG_ON(!PageLRU(page));
 706                        __ClearPageLRU(page);
 707                        del_page_from_lru_list(page, lruvec, page_off_lru(page));
 708                }
 709
 710                list_add(&page->lru, &pages_to_free);
 711        }
 712        if (zone)
 713                spin_unlock_irqrestore(&zone->lru_lock, flags);
 714
 715        free_hot_cold_page_list(&pages_to_free, cold);
 716}
 717EXPORT_SYMBOL(release_pages);
 718
 719/*
 720 * The pages which we're about to release may be in the deferred lru-addition
 721 * queues.  That would prevent them from really being freed right now.  That's
 722 * OK from a correctness point of view but is inefficient - those pages may be
 723 * cache-warm and we want to give them back to the page allocator ASAP.
 724 *
 725 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 726 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 727 * mutual recursion.
 728 */
 729void __pagevec_release(struct pagevec *pvec)
 730{
 731        lru_add_drain();
 732        release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 733        pagevec_reinit(pvec);
 734}
 735EXPORT_SYMBOL(__pagevec_release);
 736
 737#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 738/* used by __split_huge_page_refcount() */
 739void lru_add_page_tail(struct page *page, struct page *page_tail,
 740                       struct lruvec *lruvec)
 741{
 742        int uninitialized_var(active);
 743        enum lru_list lru;
 744        const int file = 0;
 745
 746        VM_BUG_ON(!PageHead(page));
 747        VM_BUG_ON(PageCompound(page_tail));
 748        VM_BUG_ON(PageLRU(page_tail));
 749        VM_BUG_ON(NR_CPUS != 1 &&
 750                  !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
 751
 752        SetPageLRU(page_tail);
 753
 754        if (page_evictable(page_tail)) {
 755                if (PageActive(page)) {
 756                        SetPageActive(page_tail);
 757                        active = 1;
 758                        lru = LRU_ACTIVE_ANON;
 759                } else {
 760                        active = 0;
 761                        lru = LRU_INACTIVE_ANON;
 762                }
 763        } else {
 764                SetPageUnevictable(page_tail);
 765                lru = LRU_UNEVICTABLE;
 766        }
 767
 768        if (likely(PageLRU(page)))
 769                list_add_tail(&page_tail->lru, &page->lru);
 770        else {
 771                struct list_head *list_head;
 772                /*
 773                 * Head page has not yet been counted, as an hpage,
 774                 * so we must account for each subpage individually.
 775                 *
 776                 * Use the standard add function to put page_tail on the list,
 777                 * but then correct its position so they all end up in order.
 778                 */
 779                add_page_to_lru_list(page_tail, lruvec, lru);
 780                list_head = page_tail->lru.prev;
 781                list_move_tail(&page_tail->lru, list_head);
 782        }
 783
 784        if (!PageUnevictable(page))
 785                update_page_reclaim_stat(lruvec, file, active);
 786}
 787#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 788
 789static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
 790                                 void *arg)
 791{
 792        enum lru_list lru = (enum lru_list)arg;
 793        int file = is_file_lru(lru);
 794        int active = is_active_lru(lru);
 795
 796        VM_BUG_ON(PageActive(page));
 797        VM_BUG_ON(PageUnevictable(page));
 798        VM_BUG_ON(PageLRU(page));
 799
 800        SetPageLRU(page);
 801        if (active)
 802                SetPageActive(page);
 803        add_page_to_lru_list(page, lruvec, lru);
 804        update_page_reclaim_stat(lruvec, file, active);
 805}
 806
 807/*
 808 * Add the passed pages to the LRU, then drop the caller's refcount
 809 * on them.  Reinitialises the caller's pagevec.
 810 */
 811void __pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 812{
 813        VM_BUG_ON(is_unevictable_lru(lru));
 814
 815        pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)lru);
 816}
 817EXPORT_SYMBOL(__pagevec_lru_add);
 818
 819/**
 820 * pagevec_lookup - gang pagecache lookup
 821 * @pvec:       Where the resulting pages are placed
 822 * @mapping:    The address_space to search
 823 * @start:      The starting page index
 824 * @nr_pages:   The maximum number of pages
 825 *
 826 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 827 * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 828 * reference against the pages in @pvec.
 829 *
 830 * The search returns a group of mapping-contiguous pages with ascending
 831 * indexes.  There may be holes in the indices due to not-present pages.
 832 *
 833 * pagevec_lookup() returns the number of pages which were found.
 834 */
 835unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 836                pgoff_t start, unsigned nr_pages)
 837{
 838        pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 839        return pagevec_count(pvec);
 840}
 841EXPORT_SYMBOL(pagevec_lookup);
 842
 843unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 844                pgoff_t *index, int tag, unsigned nr_pages)
 845{
 846        pvec->nr = find_get_pages_tag(mapping, index, tag,
 847                                        nr_pages, pvec->pages);
 848        return pagevec_count(pvec);
 849}
 850EXPORT_SYMBOL(pagevec_lookup_tag);
 851
 852/*
 853 * Perform any setup for the swap system
 854 */
 855void __init swap_setup(void)
 856{
 857        unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
 858
 859#ifdef CONFIG_SWAP
 860        bdi_init(swapper_space.backing_dev_info);
 861#endif
 862
 863        /* Use a smaller cluster for small-memory machines */
 864        if (megs < 16)
 865                page_cluster = 2;
 866        else
 867                page_cluster = 3;
 868        /*
 869         * Right now other parts of the system means that we
 870         * _really_ don't want to cluster much more
 871         */
 872}
 873
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