mm/compaction.c

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