linux/mm/compaction.c
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   1/*
   2 * linux/mm/compaction.c
   3 *
   4 * Memory compaction for the reduction of external fragmentation. Note that
   5 * this heavily depends upon page migration to do all the real heavy
   6 * lifting
   7 *
   8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
   9 */
  10#include <linux/swap.h>
  11#include <linux/migrate.h>
  12#include <linux/compaction.h>
  13#include <linux/mm_inline.h>
  14#include <linux/backing-dev.h>
  15#include <linux/sysctl.h>
  16#include <linux/sysfs.h>
  17#include "internal.h"
  18
  19#define CREATE_TRACE_POINTS
  20#include <trace/events/compaction.h>
  21
  22/*
  23 * compact_control is used to track pages being migrated and the free pages
  24 * they are being migrated to during memory compaction. The free_pfn starts
  25 * at the end of a zone and migrate_pfn begins at the start. Movable pages
  26 * are moved to the end of a zone during a compaction run and the run
  27 * completes when free_pfn <= migrate_pfn
  28 */
  29struct compact_control {
  30        struct list_head freepages;     /* List of free pages to migrate to */
  31        struct list_head migratepages;  /* List of pages being migrated */
  32        unsigned long nr_freepages;     /* Number of isolated free pages */
  33        unsigned long nr_migratepages;  /* Number of pages to migrate */
  34        unsigned long free_pfn;         /* isolate_freepages search base */
  35        unsigned long migrate_pfn;      /* isolate_migratepages search base */
  36        bool sync;                      /* Synchronous migration */
  37
  38        /* Account for isolated anon and file pages */
  39        unsigned long nr_anon;
  40        unsigned long nr_file;
  41
  42        unsigned int order;             /* order a direct compactor needs */
  43        int migratetype;                /* MOVABLE, RECLAIMABLE etc */
  44        struct zone *zone;
  45
  46        int compact_mode;
  47};
  48
  49static unsigned long release_freepages(struct list_head *freelist)
  50{
  51        struct page *page, *next;
  52        unsigned long count = 0;
  53
  54        list_for_each_entry_safe(page, next, freelist, lru) {
  55                list_del(&page->lru);
  56                __free_page(page);
  57                count++;
  58        }
  59
  60        return count;
  61}
  62
  63/* Isolate free pages onto a private freelist. Must hold zone->lock */
  64static unsigned long isolate_freepages_block(struct zone *zone,
  65                                unsigned long blockpfn,
  66                                struct list_head *freelist)
  67{
  68        unsigned long zone_end_pfn, end_pfn;
  69        int nr_scanned = 0, total_isolated = 0;
  70        struct page *cursor;
  71
  72        /* Get the last PFN we should scan for free pages at */
  73        zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
  74        end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);
  75
  76        /* Find the first usable PFN in the block to initialse page cursor */
  77        for (; blockpfn < end_pfn; blockpfn++) {
  78                if (pfn_valid_within(blockpfn))
  79                        break;
  80        }
  81        cursor = pfn_to_page(blockpfn);
  82
  83        /* Isolate free pages. This assumes the block is valid */
  84        for (; blockpfn < end_pfn; blockpfn++, cursor++) {
  85                int isolated, i;
  86                struct page *page = cursor;
  87
  88                if (!pfn_valid_within(blockpfn))
  89                        continue;
  90                nr_scanned++;
  91
  92                if (!PageBuddy(page))
  93                        continue;
  94
  95                /* Found a free page, break it into order-0 pages */
  96                isolated = split_free_page(page);
  97                total_isolated += isolated;
  98                for (i = 0; i < isolated; i++) {
  99                        list_add(&page->lru, freelist);
 100                        page++;
 101                }
 102
 103                /* If a page was split, advance to the end of it */
 104                if (isolated) {
 105                        blockpfn += isolated - 1;
 106                        cursor += isolated - 1;
 107                }
 108        }
 109
 110        trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
 111        return total_isolated;
 112}
 113
 114/* Returns true if the page is within a block suitable for migration to */
 115static bool suitable_migration_target(struct page *page)
 116{
 117
 118        int migratetype = get_pageblock_migratetype(page);
 119
 120        /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
 121        if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
 122                return false;
 123
 124        /* If the page is a large free page, then allow migration */
 125        if (PageBuddy(page) && page_order(page) >= pageblock_order)
 126                return true;
 127
 128        /* If the block is MIGRATE_MOVABLE, allow migration */
 129        if (migratetype == MIGRATE_MOVABLE)
 130                return true;
 131
 132        /* Otherwise skip the block */
 133        return false;
 134}
 135
 136/*
 137 * Based on information in the current compact_control, find blocks
 138 * suitable for isolating free pages from and then isolate them.
 139 */
 140static void isolate_freepages(struct zone *zone,
 141                                struct compact_control *cc)
 142{
 143        struct page *page;
 144        unsigned long high_pfn, low_pfn, pfn;
 145        unsigned long flags;
 146        int nr_freepages = cc->nr_freepages;
 147        struct list_head *freelist = &cc->freepages;
 148
 149        pfn = cc->free_pfn;
 150        low_pfn = cc->migrate_pfn + pageblock_nr_pages;
 151        high_pfn = low_pfn;
 152
 153        /*
 154         * Isolate free pages until enough are available to migrate the
 155         * pages on cc->migratepages. We stop searching if the migrate
 156         * and free page scanners meet or enough free pages are isolated.
 157         */
 158        spin_lock_irqsave(&zone->lock, flags);
 159        for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
 160                                        pfn -= pageblock_nr_pages) {
 161                unsigned long isolated;
 162
 163                if (!pfn_valid(pfn))
 164                        continue;
 165
 166                /*
 167                 * Check for overlapping nodes/zones. It's possible on some
 168                 * configurations to have a setup like
 169                 * node0 node1 node0
 170                 * i.e. it's possible that all pages within a zones range of
 171                 * pages do not belong to a single zone.
 172                 */
 173                page = pfn_to_page(pfn);
 174                if (page_zone(page) != zone)
 175                        continue;
 176
 177                /* Check the block is suitable for migration */
 178                if (!suitable_migration_target(page))
 179                        continue;
 180
 181                /* Found a block suitable for isolating free pages from */
 182                isolated = isolate_freepages_block(zone, pfn, freelist);
 183                nr_freepages += isolated;
 184
 185                /*
 186                 * Record the highest PFN we isolated pages from. When next
 187                 * looking for free pages, the search will restart here as
 188                 * page migration may have returned some pages to the allocator
 189                 */
 190                if (isolated)
 191                        high_pfn = max(high_pfn, pfn);
 192        }
 193        spin_unlock_irqrestore(&zone->lock, flags);
 194
 195        /* split_free_page does not map the pages */
 196        list_for_each_entry(page, freelist, lru) {
 197                arch_alloc_page(page, 0);
 198                kernel_map_pages(page, 1, 1);
 199        }
 200
 201        cc->free_pfn = high_pfn;
 202        cc->nr_freepages = nr_freepages;
 203}
 204
 205/* Update the number of anon and file isolated pages in the zone */
 206static void acct_isolated(struct zone *zone, struct compact_control *cc)
 207{
 208        struct page *page;
 209        unsigned int count[NR_LRU_LISTS] = { 0, };
 210
 211        list_for_each_entry(page, &cc->migratepages, lru) {
 212                int lru = page_lru_base_type(page);
 213                count[lru]++;
 214        }
 215
 216        cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
 217        cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
 218        __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
 219        __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
 220}
 221
 222/* Similar to reclaim, but different enough that they don't share logic */
 223static bool too_many_isolated(struct zone *zone)
 224{
 225        unsigned long active, inactive, isolated;
 226
 227        inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
 228                                        zone_page_state(zone, NR_INACTIVE_ANON);
 229        active = zone_page_state(zone, NR_ACTIVE_FILE) +
 230                                        zone_page_state(zone, NR_ACTIVE_ANON);
 231        isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
 232                                        zone_page_state(zone, NR_ISOLATED_ANON);
 233
 234        return isolated > (inactive + active) / 2;
 235}
 236
 237/*
 238 * Isolate all pages that can be migrated from the block pointed to by
 239 * the migrate scanner within compact_control.
 240 */
 241static unsigned long isolate_migratepages(struct zone *zone,
 242                                        struct compact_control *cc)
 243{
 244        unsigned long low_pfn, end_pfn;
 245        unsigned long last_pageblock_nr = 0, pageblock_nr;
 246        unsigned long nr_scanned = 0, nr_isolated = 0;
 247        struct list_head *migratelist = &cc->migratepages;
 248
 249        /* Do not scan outside zone boundaries */
 250        low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
 251
 252        /* Only scan within a pageblock boundary */
 253        end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
 254
 255        /* Do not cross the free scanner or scan within a memory hole */
 256        if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
 257                cc->migrate_pfn = end_pfn;
 258                return 0;
 259        }
 260
 261        /*
 262         * Ensure that there are not too many pages isolated from the LRU
 263         * list by either parallel reclaimers or compaction. If there are,
 264         * delay for some time until fewer pages are isolated
 265         */
 266        while (unlikely(too_many_isolated(zone))) {
 267                congestion_wait(BLK_RW_ASYNC, HZ/10);
 268
 269                if (fatal_signal_pending(current))
 270                        return 0;
 271        }
 272
 273        /* Time to isolate some pages for migration */
 274        spin_lock_irq(&zone->lru_lock);
 275        for (; low_pfn < end_pfn; low_pfn++) {
 276                struct page *page;
 277                if (!pfn_valid_within(low_pfn))
 278                        continue;
 279                nr_scanned++;
 280
 281                /* Get the page and skip if free */
 282                page = pfn_to_page(low_pfn);
 283                if (PageBuddy(page))
 284                        continue;
 285
 286                /*
 287                 * For async migration, also only scan in MOVABLE blocks. Async
 288                 * migration is optimistic to see if the minimum amount of work
 289                 * satisfies the allocation
 290                 */
 291                pageblock_nr = low_pfn >> pageblock_order;
 292                if (!cc->sync && last_pageblock_nr != pageblock_nr &&
 293                                get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
 294                        low_pfn += pageblock_nr_pages;
 295                        low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
 296                        last_pageblock_nr = pageblock_nr;
 297                        continue;
 298                }
 299
 300                if (!PageLRU(page))
 301                        continue;
 302
 303                /*
 304                 * PageLRU is set, and lru_lock excludes isolation,
 305                 * splitting and collapsing (collapsing has already
 306                 * happened if PageLRU is set).
 307                 */
 308                if (PageTransHuge(page)) {
 309                        low_pfn += (1 << compound_order(page)) - 1;
 310                        continue;
 311                }
 312
 313                /* Try isolate the page */
 314                if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
 315                        continue;
 316
 317                VM_BUG_ON(PageTransCompound(page));
 318
 319                /* Successfully isolated */
 320                del_page_from_lru_list(zone, page, page_lru(page));
 321                list_add(&page->lru, migratelist);
 322                cc->nr_migratepages++;
 323                nr_isolated++;
 324
 325                /* Avoid isolating too much */
 326                if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
 327                        break;
 328        }
 329
 330        acct_isolated(zone, cc);
 331
 332        spin_unlock_irq(&zone->lru_lock);
 333        cc->migrate_pfn = low_pfn;
 334
 335        trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 336
 337        return cc->nr_migratepages;
 338}
 339
 340/*
 341 * This is a migrate-callback that "allocates" freepages by taking pages
 342 * from the isolated freelists in the block we are migrating to.
 343 */
 344static struct page *compaction_alloc(struct page *migratepage,
 345                                        unsigned long data,
 346                                        int **result)
 347{
 348        struct compact_control *cc = (struct compact_control *)data;
 349        struct page *freepage;
 350
 351        /* Isolate free pages if necessary */
 352        if (list_empty(&cc->freepages)) {
 353                isolate_freepages(cc->zone, cc);
 354
 355                if (list_empty(&cc->freepages))
 356                        return NULL;
 357        }
 358
 359        freepage = list_entry(cc->freepages.next, struct page, lru);
 360        list_del(&freepage->lru);
 361        cc->nr_freepages--;
 362
 363        return freepage;
 364}
 365
 366/*
 367 * We cannot control nr_migratepages and nr_freepages fully when migration is
 368 * running as migrate_pages() has no knowledge of compact_control. When
 369 * migration is complete, we count the number of pages on the lists by hand.
 370 */
 371static void update_nr_listpages(struct compact_control *cc)
 372{
 373        int nr_migratepages = 0;
 374        int nr_freepages = 0;
 375        struct page *page;
 376
 377        list_for_each_entry(page, &cc->migratepages, lru)
 378                nr_migratepages++;
 379        list_for_each_entry(page, &cc->freepages, lru)
 380                nr_freepages++;
 381
 382        cc->nr_migratepages = nr_migratepages;
 383        cc->nr_freepages = nr_freepages;
 384}
 385
 386static int compact_finished(struct zone *zone,
 387                            struct compact_control *cc)
 388{
 389        unsigned int order;
 390        unsigned long watermark;
 391
 392        if (fatal_signal_pending(current))
 393                return COMPACT_PARTIAL;
 394
 395        /* Compaction run completes if the migrate and free scanner meet */
 396        if (cc->free_pfn <= cc->migrate_pfn)
 397                return COMPACT_COMPLETE;
 398
 399        /* Compaction run is not finished if the watermark is not met */
 400        if (cc->compact_mode != COMPACT_MODE_KSWAPD)
 401                watermark = low_wmark_pages(zone);
 402        else
 403                watermark = high_wmark_pages(zone);
 404        watermark += (1 << cc->order);
 405
 406        if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
 407                return COMPACT_CONTINUE;
 408
 409        /*
 410         * order == -1 is expected when compacting via
 411         * /proc/sys/vm/compact_memory
 412         */
 413        if (cc->order == -1)
 414                return COMPACT_CONTINUE;
 415
 416        /*
 417         * Generating only one page of the right order is not enough
 418         * for kswapd, we must continue until we're above the high
 419         * watermark as a pool for high order GFP_ATOMIC allocations
 420         * too.
 421         */
 422        if (cc->compact_mode == COMPACT_MODE_KSWAPD)
 423                return COMPACT_CONTINUE;
 424
 425        /* Direct compactor: Is a suitable page free? */
 426        for (order = cc->order; order < MAX_ORDER; order++) {
 427                /* Job done if page is free of the right migratetype */
 428                if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
 429                        return COMPACT_PARTIAL;
 430
 431                /* Job done if allocation would set block type */
 432                if (order >= pageblock_order && zone->free_area[order].nr_free)
 433                        return COMPACT_PARTIAL;
 434        }
 435
 436        return COMPACT_CONTINUE;
 437}
 438
 439/*
 440 * compaction_suitable: Is this suitable to run compaction on this zone now?
 441 * Returns
 442 *   COMPACT_SKIPPED  - If there are too few free pages for compaction
 443 *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
 444 *   COMPACT_CONTINUE - If compaction should run now
 445 */
 446unsigned long compaction_suitable(struct zone *zone, int order)
 447{
 448        int fragindex;
 449        unsigned long watermark;
 450
 451        /*
 452         * Watermarks for order-0 must be met for compaction. Note the 2UL.
 453         * This is because during migration, copies of pages need to be
 454         * allocated and for a short time, the footprint is higher
 455         */
 456        watermark = low_wmark_pages(zone) + (2UL << order);
 457        if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
 458                return COMPACT_SKIPPED;
 459
 460        /*
 461         * order == -1 is expected when compacting via
 462         * /proc/sys/vm/compact_memory
 463         */
 464        if (order == -1)
 465                return COMPACT_CONTINUE;
 466
 467        /*
 468         * fragmentation index determines if allocation failures are due to
 469         * low memory or external fragmentation
 470         *
 471         * index of -1 implies allocations might succeed dependingon watermarks
 472         * index towards 0 implies failure is due to lack of memory
 473         * index towards 1000 implies failure is due to fragmentation
 474         *
 475         * Only compact if a failure would be due to fragmentation.
 476         */
 477        fragindex = fragmentation_index(zone, order);
 478        if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
 479                return COMPACT_SKIPPED;
 480
 481        if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0))
 482                return COMPACT_PARTIAL;
 483
 484        return COMPACT_CONTINUE;
 485}
 486
 487static int compact_zone(struct zone *zone, struct compact_control *cc)
 488{
 489        int ret;
 490
 491        ret = compaction_suitable(zone, cc->order);
 492        switch (ret) {
 493        case COMPACT_PARTIAL:
 494        case COMPACT_SKIPPED:
 495                /* Compaction is likely to fail */
 496                return ret;
 497        case COMPACT_CONTINUE:
 498                /* Fall through to compaction */
 499                ;
 500        }
 501
 502        /* Setup to move all movable pages to the end of the zone */
 503        cc->migrate_pfn = zone->zone_start_pfn;
 504        cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
 505        cc->free_pfn &= ~(pageblock_nr_pages-1);
 506
 507        migrate_prep_local();
 508
 509        while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
 510                unsigned long nr_migrate, nr_remaining;
 511
 512                if (!isolate_migratepages(zone, cc))
 513                        continue;
 514
 515                nr_migrate = cc->nr_migratepages;
 516                migrate_pages(&cc->migratepages, compaction_alloc,
 517                                (unsigned long)cc, false,
 518                                cc->sync);
 519                update_nr_listpages(cc);
 520                nr_remaining = cc->nr_migratepages;
 521
 522                count_vm_event(COMPACTBLOCKS);
 523                count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
 524                if (nr_remaining)
 525                        count_vm_events(COMPACTPAGEFAILED, nr_remaining);
 526                trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
 527                                                nr_remaining);
 528
 529                /* Release LRU pages not migrated */
 530                if (!list_empty(&cc->migratepages)) {
 531                        putback_lru_pages(&cc->migratepages);
 532                        cc->nr_migratepages = 0;
 533                }
 534
 535        }
 536
 537        /* Release free pages and check accounting */
 538        cc->nr_freepages -= release_freepages(&cc->freepages);
 539        VM_BUG_ON(cc->nr_freepages != 0);
 540
 541        return ret;
 542}
 543
 544unsigned long compact_zone_order(struct zone *zone,
 545                                 int order, gfp_t gfp_mask,
 546                                 bool sync,
 547                                 int compact_mode)
 548{
 549        struct compact_control cc = {
 550                .nr_freepages = 0,
 551                .nr_migratepages = 0,
 552                .order = order,
 553                .migratetype = allocflags_to_migratetype(gfp_mask),
 554                .zone = zone,
 555                .sync = sync,
 556                .compact_mode = compact_mode,
 557        };
 558        INIT_LIST_HEAD(&cc.freepages);
 559        INIT_LIST_HEAD(&cc.migratepages);
 560
 561        return compact_zone(zone, &cc);
 562}
 563
 564int sysctl_extfrag_threshold = 500;
 565
 566/**
 567 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
 568 * @zonelist: The zonelist used for the current allocation
 569 * @order: The order of the current allocation
 570 * @gfp_mask: The GFP mask of the current allocation
 571 * @nodemask: The allowed nodes to allocate from
 572 * @sync: Whether migration is synchronous or not
 573 *
 574 * This is the main entry point for direct page compaction.
 575 */
 576unsigned long try_to_compact_pages(struct zonelist *zonelist,
 577                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
 578                        bool sync)
 579{
 580        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
 581        int may_enter_fs = gfp_mask & __GFP_FS;
 582        int may_perform_io = gfp_mask & __GFP_IO;
 583        struct zoneref *z;
 584        struct zone *zone;
 585        int rc = COMPACT_SKIPPED;
 586
 587        /*
 588         * Check whether it is worth even starting compaction. The order check is
 589         * made because an assumption is made that the page allocator can satisfy
 590         * the "cheaper" orders without taking special steps
 591         */
 592        if (!order || !may_enter_fs || !may_perform_io)
 593                return rc;
 594
 595        count_vm_event(COMPACTSTALL);
 596
 597        /* Compact each zone in the list */
 598        for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
 599                                                                nodemask) {
 600                int status;
 601
 602                status = compact_zone_order(zone, order, gfp_mask, sync,
 603                                            COMPACT_MODE_DIRECT_RECLAIM);
 604                rc = max(status, rc);
 605
 606                /* If a normal allocation would succeed, stop compacting */
 607                if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
 608                        break;
 609        }
 610
 611        return rc;
 612}
 613
 614
 615/* Compact all zones within a node */
 616static int compact_node(int nid)
 617{
 618        int zoneid;
 619        pg_data_t *pgdat;
 620        struct zone *zone;
 621
 622        if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
 623                return -EINVAL;
 624        pgdat = NODE_DATA(nid);
 625
 626        /* Flush pending updates to the LRU lists */
 627        lru_add_drain_all();
 628
 629        for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
 630                struct compact_control cc = {
 631                        .nr_freepages = 0,
 632                        .nr_migratepages = 0,
 633                        .order = -1,
 634                        .compact_mode = COMPACT_MODE_DIRECT_RECLAIM,
 635                };
 636
 637                zone = &pgdat->node_zones[zoneid];
 638                if (!populated_zone(zone))
 639                        continue;
 640
 641                cc.zone = zone;
 642                INIT_LIST_HEAD(&cc.freepages);
 643                INIT_LIST_HEAD(&cc.migratepages);
 644
 645                compact_zone(zone, &cc);
 646
 647                VM_BUG_ON(!list_empty(&cc.freepages));
 648                VM_BUG_ON(!list_empty(&cc.migratepages));
 649        }
 650
 651        return 0;
 652}
 653
 654/* Compact all nodes in the system */
 655static int compact_nodes(void)
 656{
 657        int nid;
 658
 659        for_each_online_node(nid)
 660                compact_node(nid);
 661
 662        return COMPACT_COMPLETE;
 663}
 664
 665/* The written value is actually unused, all memory is compacted */
 666int sysctl_compact_memory;
 667
 668/* This is the entry point for compacting all nodes via /proc/sys/vm */
 669int sysctl_compaction_handler(struct ctl_table *table, int write,
 670                        void __user *buffer, size_t *length, loff_t *ppos)
 671{
 672        if (write)
 673                return compact_nodes();
 674
 675        return 0;
 676}
 677
 678int sysctl_extfrag_handler(struct ctl_table *table, int write,
 679                        void __user *buffer, size_t *length, loff_t *ppos)
 680{
 681        proc_dointvec_minmax(table, write, buffer, length, ppos);
 682
 683        return 0;
 684}
 685
 686#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 687ssize_t sysfs_compact_node(struct sys_device *dev,
 688                        struct sysdev_attribute *attr,
 689                        const char *buf, size_t count)
 690{
 691        compact_node(dev->id);
 692
 693        return count;
 694}
 695static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
 696
 697int compaction_register_node(struct node *node)
 698{
 699        return sysdev_create_file(&node->sysdev, &attr_compact);
 700}
 701
 702void compaction_unregister_node(struct node *node)
 703{
 704        return sysdev_remove_file(&node->sysdev, &attr_compact);
 705}
 706#endif /* CONFIG_SYSFS && CONFIG_NUMA */
 707