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1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/mm/compaction.c
4 *
5 * Memory compaction for the reduction of external fragmentation. Note that
6 * this heavily depends upon page migration to do all the real heavy
7 * lifting
8 *
9 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
10 */
11 #include <linux/cpu.h>
12 #include <linux/swap.h>
13 #include <linux/migrate.h>
14 #include <linux/compaction.h>
15 #include <linux/mm_inline.h>
16 #include <linux/sched/signal.h>
17 #include <linux/backing-dev.h>
18 #include <linux/sysctl.h>
19 #include <linux/sysfs.h>
20 #include <linux/page-isolation.h>
21 #include <linux/kasan.h>
22 #include <linux/kthread.h>
23 #include <linux/freezer.h>
24 #include <linux/page_owner.h>
25 #include "internal.h"
26
27 #ifdef CONFIG_COMPACTION
28 static inline void count_compact_event(enum vm_event_item item)
29 {
30 count_vm_event(item);
31 }
32
33 static inline void count_compact_events(enum vm_event_item item, long delta)
34 {
35 count_vm_events(item, delta);
36 }
37 #else
38 #define count_compact_event(item) do { } while (0)
39 #define count_compact_events(item, delta) do { } while (0)
40 #endif
41
42 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
43
44 #define CREATE_TRACE_POINTS
45 #include <trace/events/compaction.h>
46
47 #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
48 #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
49 #define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
50 #define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
51
52 static unsigned long release_freepages(struct list_head *freelist)
53 {
54 struct page *page, *next;
55 unsigned long high_pfn = 0;
56
57 list_for_each_entry_safe(page, next, freelist, lru) {
58 unsigned long pfn = page_to_pfn(page);
59 list_del(&page->lru);
60 __free_page(page);
61 if (pfn > high_pfn)
62 high_pfn = pfn;
63 }
64
65 return high_pfn;
66 }
67
68 static void map_pages(struct list_head *list)
69 {
70 unsigned int i, order, nr_pages;
71 struct page *page, *next;
72 LIST_HEAD(tmp_list);
73
74 list_for_each_entry_safe(page, next, list, lru) {
75 list_del(&page->lru);
76
77 order = page_private(page);
78 nr_pages = 1 << order;
79
80 post_alloc_hook(page, order, __GFP_MOVABLE);
81 if (order)
82 split_page(page, order);
83
84 for (i = 0; i < nr_pages; i++) {
85 list_add(&page->lru, &tmp_list);
86 page++;
87 }
88 }
89
90 list_splice(&tmp_list, list);
91 }
92
93 #ifdef CONFIG_COMPACTION
94
95 int PageMovable(struct page *page)
96 {
97 struct address_space *mapping;
98
99 VM_BUG_ON_PAGE(!PageLocked(page), page);
100 if (!__PageMovable(page))
101 return 0;
102
103 mapping = page_mapping(page);
104 if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
105 return 1;
106
107 return 0;
108 }
109 EXPORT_SYMBOL(PageMovable);
110
111 void __SetPageMovable(struct page *page, struct address_space *mapping)
112 {
113 VM_BUG_ON_PAGE(!PageLocked(page), page);
114 VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
115 page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
116 }
117 EXPORT_SYMBOL(__SetPageMovable);
118
119 void __ClearPageMovable(struct page *page)
120 {
121 VM_BUG_ON_PAGE(!PageLocked(page), page);
122 VM_BUG_ON_PAGE(!PageMovable(page), page);
123 /*
124 * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
125 * flag so that VM can catch up released page by driver after isolation.
126 * With it, VM migration doesn't try to put it back.
127 */
128 page->mapping = (void *)((unsigned long)page->mapping &
129 PAGE_MAPPING_MOVABLE);
130 }
131 EXPORT_SYMBOL(__ClearPageMovable);
132
133 /* Do not skip compaction more than 64 times */
134 #define COMPACT_MAX_DEFER_SHIFT 6
135
136 /*
137 * Compaction is deferred when compaction fails to result in a page
138 * allocation success. 1 << compact_defer_limit compactions are skipped up
139 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
140 */
141 void defer_compaction(struct zone *zone, int order)
142 {
143 zone->compact_considered = 0;
144 zone->compact_defer_shift++;
145
146 if (order < zone->compact_order_failed)
147 zone->compact_order_failed = order;
148
149 if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
150 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
151
152 trace_mm_compaction_defer_compaction(zone, order);
153 }
154
155 /* Returns true if compaction should be skipped this time */
156 bool compaction_deferred(struct zone *zone, int order)
157 {
158 unsigned long defer_limit = 1UL << zone->compact_defer_shift;
159
160 if (order < zone->compact_order_failed)
161 return false;
162
163 /* Avoid possible overflow */
164 if (++zone->compact_considered > defer_limit)
165 zone->compact_considered = defer_limit;
166
167 if (zone->compact_considered >= defer_limit)
168 return false;
169
170 trace_mm_compaction_deferred(zone, order);
171
172 return true;
173 }
174
175 /*
176 * Update defer tracking counters after successful compaction of given order,
177 * which means an allocation either succeeded (alloc_success == true) or is
178 * expected to succeed.
179 */
180 void compaction_defer_reset(struct zone *zone, int order,
181 bool alloc_success)
182 {
183 if (alloc_success) {
184 zone->compact_considered = 0;
185 zone->compact_defer_shift = 0;
186 }
187 if (order >= zone->compact_order_failed)
188 zone->compact_order_failed = order + 1;
189
190 trace_mm_compaction_defer_reset(zone, order);
191 }
192
193 /* Returns true if restarting compaction after many failures */
194 bool compaction_restarting(struct zone *zone, int order)
195 {
196 if (order < zone->compact_order_failed)
197 return false;
198
199 return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
200 zone->compact_considered >= 1UL << zone->compact_defer_shift;
201 }
202
203 /* Returns true if the pageblock should be scanned for pages to isolate. */
204 static inline bool isolation_suitable(struct compact_control *cc,
205 struct page *page)
206 {
207 if (cc->ignore_skip_hint)
208 return true;
209
210 return !get_pageblock_skip(page);
211 }
212
213 static void reset_cached_positions(struct zone *zone)
214 {
215 zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
216 zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
217 zone->compact_cached_free_pfn =
218 pageblock_start_pfn(zone_end_pfn(zone) - 1);
219 }
220
221 /*
222 * Compound pages of >= pageblock_order should consistenly be skipped until
223 * released. It is always pointless to compact pages of such order (if they are
224 * migratable), and the pageblocks they occupy cannot contain any free pages.
225 */
226 static bool pageblock_skip_persistent(struct page *page)
227 {
228 if (!PageCompound(page))
229 return false;
230
231 page = compound_head(page);
232
233 if (compound_order(page) >= pageblock_order)
234 return true;
235
236 return false;
237 }
238
239 /*
240 * This function is called to clear all cached information on pageblocks that
241 * should be skipped for page isolation when the migrate and free page scanner
242 * meet.
243 */
244 static void __reset_isolation_suitable(struct zone *zone)
245 {
246 unsigned long start_pfn = zone->zone_start_pfn;
247 unsigned long end_pfn = zone_end_pfn(zone);
248 unsigned long pfn;
249
250 zone->compact_blockskip_flush = false;
251
252 /* Walk the zone and mark every pageblock as suitable for isolation */
253 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
254 struct page *page;
255
256 cond_resched();
257
258 page = pfn_to_online_page(pfn);
259 if (!page)
260 continue;
261 if (zone != page_zone(page))
262 continue;
263 if (pageblock_skip_persistent(page))
264 continue;
265
266 clear_pageblock_skip(page);
267 }
268
269 reset_cached_positions(zone);
270 }
271
272 void reset_isolation_suitable(pg_data_t *pgdat)
273 {
274 int zoneid;
275
276 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
277 struct zone *zone = &pgdat->node_zones[zoneid];
278 if (!populated_zone(zone))
279 continue;
280
281 /* Only flush if a full compaction finished recently */
282 if (zone->compact_blockskip_flush)
283 __reset_isolation_suitable(zone);
284 }
285 }
286
287 /*
288 * If no pages were isolated then mark this pageblock to be skipped in the
289 * future. The information is later cleared by __reset_isolation_suitable().
290 */
291 static void update_pageblock_skip(struct compact_control *cc,
292 struct page *page, unsigned long nr_isolated,
293 bool migrate_scanner)
294 {
295 struct zone *zone = cc->zone;
296 unsigned long pfn;
297
298 if (cc->no_set_skip_hint)
299 return;
300
301 if (!page)
302 return;
303
304 if (nr_isolated)
305 return;
306
307 set_pageblock_skip(page);
308
309 pfn = page_to_pfn(page);
310
311 /* Update where async and sync compaction should restart */
312 if (migrate_scanner) {
313 if (pfn > zone->compact_cached_migrate_pfn[0])
314 zone->compact_cached_migrate_pfn[0] = pfn;
315 if (cc->mode != MIGRATE_ASYNC &&
316 pfn > zone->compact_cached_migrate_pfn[1])
317 zone->compact_cached_migrate_pfn[1] = pfn;
318 } else {
319 if (pfn < zone->compact_cached_free_pfn)
320 zone->compact_cached_free_pfn = pfn;
321 }
322 }
323 #else
324 static inline bool isolation_suitable(struct compact_control *cc,
325 struct page *page)
326 {
327 return true;
328 }
329
330 static inline bool pageblock_skip_persistent(struct page *page)
331 {
332 return false;
333 }
334
335 static inline void update_pageblock_skip(struct compact_control *cc,
336 struct page *page, unsigned long nr_isolated,
337 bool migrate_scanner)
338 {
339 }
340 #endif /* CONFIG_COMPACTION */
341
342 /*
343 * Compaction requires the taking of some coarse locks that are potentially
344 * very heavily contended. For async compaction, back out if the lock cannot
345 * be taken immediately. For sync compaction, spin on the lock if needed.
346 *
347 * Returns true if the lock is held
348 * Returns false if the lock is not held and compaction should abort
349 */
350 static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
351 struct compact_control *cc)
352 {
353 if (cc->mode == MIGRATE_ASYNC) {
354 if (!spin_trylock_irqsave(lock, *flags)) {
355 cc->contended = true;
356 return false;
357 }
358 } else {
359 spin_lock_irqsave(lock, *flags);
360 }
361
362 return true;
363 }
364
365 /*
366 * Compaction requires the taking of some coarse locks that are potentially
367 * very heavily contended. The lock should be periodically unlocked to avoid
368 * having disabled IRQs for a long time, even when there is nobody waiting on
369 * the lock. It might also be that allowing the IRQs will result in
370 * need_resched() becoming true. If scheduling is needed, async compaction
371 * aborts. Sync compaction schedules.
372 * Either compaction type will also abort if a fatal signal is pending.
373 * In either case if the lock was locked, it is dropped and not regained.
374 *
375 * Returns true if compaction should abort due to fatal signal pending, or
376 * async compaction due to need_resched()
377 * Returns false when compaction can continue (sync compaction might have
378 * scheduled)
379 */
380 static bool compact_unlock_should_abort(spinlock_t *lock,
381 unsigned long flags, bool *locked, struct compact_control *cc)
382 {
383 if (*locked) {
384 spin_unlock_irqrestore(lock, flags);
385 *locked = false;
386 }
387
388 if (fatal_signal_pending(current)) {
389 cc->contended = true;
390 return true;
391 }
392
393 if (need_resched()) {
394 if (cc->mode == MIGRATE_ASYNC) {
395 cc->contended = true;
396 return true;
397 }
398 cond_resched();
399 }
400
401 return false;
402 }
403
404 /*
405 * Aside from avoiding lock contention, compaction also periodically checks
406 * need_resched() and either schedules in sync compaction or aborts async
407 * compaction. This is similar to what compact_unlock_should_abort() does, but
408 * is used where no lock is concerned.
409 *
410 * Returns false when no scheduling was needed, or sync compaction scheduled.
411 * Returns true when async compaction should abort.
412 */
413 static inline bool compact_should_abort(struct compact_control *cc)
414 {
415 /* async compaction aborts if contended */
416 if (need_resched()) {
417 if (cc->mode == MIGRATE_ASYNC) {
418 cc->contended = true;
419 return true;
420 }
421
422 cond_resched();
423 }
424
425 return false;
426 }
427
428 /*
429 * Isolate free pages onto a private freelist. If @strict is true, will abort
430 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
431 * (even though it may still end up isolating some pages).
432 */
433 static unsigned long isolate_freepages_block(struct compact_control *cc,
434 unsigned long *start_pfn,
435 unsigned long end_pfn,
436 struct list_head *freelist,
437 bool strict)
438 {
439 int nr_scanned = 0, total_isolated = 0;
440 struct page *cursor, *valid_page = NULL;
441 unsigned long flags = 0;
442 bool locked = false;
443 unsigned long blockpfn = *start_pfn;
444 unsigned int order;
445
446 cursor = pfn_to_page(blockpfn);
447
448 /* Isolate free pages. */
449 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
450 int isolated;
451 struct page *page = cursor;
452
453 /*
454 * Periodically drop the lock (if held) regardless of its
455 * contention, to give chance to IRQs. Abort if fatal signal
456 * pending or async compaction detects need_resched()
457 */
458 if (!(blockpfn % SWAP_CLUSTER_MAX)
459 && compact_unlock_should_abort(&cc->zone->lock, flags,
460 &locked, cc))
461 break;
462
463 nr_scanned++;
464 if (!pfn_valid_within(blockpfn))
465 goto isolate_fail;
466
467 if (!valid_page)
468 valid_page = page;
469
470 /*
471 * For compound pages such as THP and hugetlbfs, we can save
472 * potentially a lot of iterations if we skip them at once.
473 * The check is racy, but we can consider only valid values
474 * and the only danger is skipping too much.
475 */
476 if (PageCompound(page)) {
477 const unsigned int order = compound_order(page);
478
479 if (likely(order < MAX_ORDER)) {
480 blockpfn += (1UL << order) - 1;
481 cursor += (1UL << order) - 1;
482 }
483 goto isolate_fail;
484 }
485
486 if (!PageBuddy(page))
487 goto isolate_fail;
488
489 /*
490 * If we already hold the lock, we can skip some rechecking.
491 * Note that if we hold the lock now, checked_pageblock was
492 * already set in some previous iteration (or strict is true),
493 * so it is correct to skip the suitable migration target
494 * recheck as well.
495 */
496 if (!locked) {
497 /*
498 * The zone lock must be held to isolate freepages.
499 * Unfortunately this is a very coarse lock and can be
500 * heavily contended if there are parallel allocations
501 * or parallel compactions. For async compaction do not
502 * spin on the lock and we acquire the lock as late as
503 * possible.
504 */
505 locked = compact_trylock_irqsave(&cc->zone->lock,
506 &flags, cc);
507 if (!locked)
508 break;
509
510 /* Recheck this is a buddy page under lock */
511 if (!PageBuddy(page))
512 goto isolate_fail;
513 }
514
515 /* Found a free page, will break it into order-0 pages */
516 order = page_order(page);
517 isolated = __isolate_free_page(page, order);
518 if (!isolated)
519 break;
520 set_page_private(page, order);
521
522 total_isolated += isolated;
523 cc->nr_freepages += isolated;
524 list_add_tail(&page->lru, freelist);
525
526 if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
527 blockpfn += isolated;
528 break;
529 }
530 /* Advance to the end of split page */
531 blockpfn += isolated - 1;
532 cursor += isolated - 1;
533 continue;
534
535 isolate_fail:
536 if (strict)
537 break;
538 else
539 continue;
540
541 }
542
543 if (locked)
544 spin_unlock_irqrestore(&cc->zone->lock, flags);
545
546 /*
547 * There is a tiny chance that we have read bogus compound_order(),
548 * so be careful to not go outside of the pageblock.
549 */
550 if (unlikely(blockpfn > end_pfn))
551 blockpfn = end_pfn;
552
553 trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
554 nr_scanned, total_isolated);
555
556 /* Record how far we have got within the block */
557 *start_pfn = blockpfn;
558
559 /*
560 * If strict isolation is requested by CMA then check that all the
561 * pages requested were isolated. If there were any failures, 0 is
562 * returned and CMA will fail.
563 */
564 if (strict && blockpfn < end_pfn)
565 total_isolated = 0;
566
567 /* Update the pageblock-skip if the whole pageblock was scanned */
568 if (blockpfn == end_pfn)
569 update_pageblock_skip(cc, valid_page, total_isolated, false);
570
571 cc->total_free_scanned += nr_scanned;
572 if (total_isolated)
573 count_compact_events(COMPACTISOLATED, total_isolated);
574 return total_isolated;
575 }
576
577 /**
578 * isolate_freepages_range() - isolate free pages.
579 * @start_pfn: The first PFN to start isolating.
580 * @end_pfn: The one-past-last PFN.
581 *
582 * Non-free pages, invalid PFNs, or zone boundaries within the
583 * [start_pfn, end_pfn) range are considered errors, cause function to
584 * undo its actions and return zero.
585 *
586 * Otherwise, function returns one-past-the-last PFN of isolated page
587 * (which may be greater then end_pfn if end fell in a middle of
588 * a free page).
589 */
590 unsigned long
591 isolate_freepages_range(struct compact_control *cc,
592 unsigned long start_pfn, unsigned long end_pfn)
593 {
594 unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
595 LIST_HEAD(freelist);
596
597 pfn = start_pfn;
598 block_start_pfn = pageblock_start_pfn(pfn);
599 if (block_start_pfn < cc->zone->zone_start_pfn)
600 block_start_pfn = cc->zone->zone_start_pfn;
601 block_end_pfn = pageblock_end_pfn(pfn);
602
603 for (; pfn < end_pfn; pfn += isolated,
604 block_start_pfn = block_end_pfn,
605 block_end_pfn += pageblock_nr_pages) {
606 /* Protect pfn from changing by isolate_freepages_block */
607 unsigned long isolate_start_pfn = pfn;
608
609 block_end_pfn = min(block_end_pfn, end_pfn);
610
611 /*
612 * pfn could pass the block_end_pfn if isolated freepage
613 * is more than pageblock order. In this case, we adjust
614 * scanning range to right one.
615 */
616 if (pfn >= block_end_pfn) {
617 block_start_pfn = pageblock_start_pfn(pfn);
618 block_end_pfn = pageblock_end_pfn(pfn);
619 block_end_pfn = min(block_end_pfn, end_pfn);
620 }
621
622 if (!pageblock_pfn_to_page(block_start_pfn,
623 block_end_pfn, cc->zone))
624 break;
625
626 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
627 block_end_pfn, &freelist, true);
628
629 /*
630 * In strict mode, isolate_freepages_block() returns 0 if
631 * there are any holes in the block (ie. invalid PFNs or
632 * non-free pages).
633 */
634 if (!isolated)
635 break;
636
637 /*
638 * If we managed to isolate pages, it is always (1 << n) *
639 * pageblock_nr_pages for some non-negative n. (Max order
640 * page may span two pageblocks).
641 */
642 }
643
644 /* __isolate_free_page() does not map the pages */
645 map_pages(&freelist);
646
647 if (pfn < end_pfn) {
648 /* Loop terminated early, cleanup. */
649 release_freepages(&freelist);
650 return 0;
651 }
652
653 /* We don't use freelists for anything. */
654 return pfn;
655 }
656
657 /* Similar to reclaim, but different enough that they don't share logic */
658 static bool too_many_isolated(struct zone *zone)
659 {
660 unsigned long active, inactive, isolated;
661
662 inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) +
663 node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON);
664 active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) +
665 node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON);
666 isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) +
667 node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON);
668
669 return isolated > (inactive + active) / 2;
670 }
671
672 /**
673 * isolate_migratepages_block() - isolate all migrate-able pages within
674 * a single pageblock
675 * @cc: Compaction control structure.
676 * @low_pfn: The first PFN to isolate
677 * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
678 * @isolate_mode: Isolation mode to be used.
679 *
680 * Isolate all pages that can be migrated from the range specified by
681 * [low_pfn, end_pfn). The range is expected to be within same pageblock.
682 * Returns zero if there is a fatal signal pending, otherwise PFN of the
683 * first page that was not scanned (which may be both less, equal to or more
684 * than end_pfn).
685 *
686 * The pages are isolated on cc->migratepages list (not required to be empty),
687 * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
688 * is neither read nor updated.
689 */
690 static unsigned long
691 isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
692 unsigned long end_pfn, isolate_mode_t isolate_mode)
693 {
694 struct zone *zone = cc->zone;
695 unsigned long nr_scanned = 0, nr_isolated = 0;
696 struct lruvec *lruvec;
697 unsigned long flags = 0;
698 bool locked = false;
699 struct page *page = NULL, *valid_page = NULL;
700 unsigned long start_pfn = low_pfn;
701 bool skip_on_failure = false;
702 unsigned long next_skip_pfn = 0;
703
704 /*
705 * Ensure that there are not too many pages isolated from the LRU
706 * list by either parallel reclaimers or compaction. If there are,
707 * delay for some time until fewer pages are isolated
708 */
709 while (unlikely(too_many_isolated(zone))) {
710 /* async migration should just abort */
711 if (cc->mode == MIGRATE_ASYNC)
712 return 0;
713
714 congestion_wait(BLK_RW_ASYNC, HZ/10);
715
716 if (fatal_signal_pending(current))
717 return 0;
718 }
719
720 if (compact_should_abort(cc))
721 return 0;
722
723 if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
724 skip_on_failure = true;
725 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
726 }
727
728 /* Time to isolate some pages for migration */
729 for (; low_pfn < end_pfn; low_pfn++) {
730
731 if (skip_on_failure && low_pfn >= next_skip_pfn) {
732 /*
733 * We have isolated all migration candidates in the
734 * previous order-aligned block, and did not skip it due
735 * to failure. We should migrate the pages now and
736 * hopefully succeed compaction.
737 */
738 if (nr_isolated)
739 break;
740
741 /*
742 * We failed to isolate in the previous order-aligned
743 * block. Set the new boundary to the end of the
744 * current block. Note we can't simply increase
745 * next_skip_pfn by 1 << order, as low_pfn might have
746 * been incremented by a higher number due to skipping
747 * a compound or a high-order buddy page in the
748 * previous loop iteration.
749 */
750 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
751 }
752
753 /*
754 * Periodically drop the lock (if held) regardless of its
755 * contention, to give chance to IRQs. Abort async compaction
756 * if contended.
757 */
758 if (!(low_pfn % SWAP_CLUSTER_MAX)
759 && compact_unlock_should_abort(zone_lru_lock(zone), flags,
760 &locked, cc))
761 break;
762
763 if (!pfn_valid_within(low_pfn))
764 goto isolate_fail;
765 nr_scanned++;
766
767 page = pfn_to_page(low_pfn);
768
769 if (!valid_page)
770 valid_page = page;
771
772 /*
773 * Skip if free. We read page order here without zone lock
774 * which is generally unsafe, but the race window is small and
775 * the worst thing that can happen is that we skip some
776 * potential isolation targets.
777 */
778 if (PageBuddy(page)) {
779 unsigned long freepage_order = page_order_unsafe(page);
780
781 /*
782 * Without lock, we cannot be sure that what we got is
783 * a valid page order. Consider only values in the
784 * valid order range to prevent low_pfn overflow.
785 */
786 if (freepage_order > 0 && freepage_order < MAX_ORDER)
787 low_pfn += (1UL << freepage_order) - 1;
788 continue;
789 }
790
791 /*
792 * Regardless of being on LRU, compound pages such as THP and
793 * hugetlbfs are not to be compacted. We can potentially save
794 * a lot of iterations if we skip them at once. The check is
795 * racy, but we can consider only valid values and the only
796 * danger is skipping too much.
797 */
798 if (PageCompound(page)) {
799 const unsigned int order = compound_order(page);
800
801 if (likely(order < MAX_ORDER))
802 low_pfn += (1UL << order) - 1;
803 goto isolate_fail;
804 }
805
806 /*
807 * Check may be lockless but that's ok as we recheck later.
808 * It's possible to migrate LRU and non-lru movable pages.
809 * Skip any other type of page
810 */
811 if (!PageLRU(page)) {
812 /*
813 * __PageMovable can return false positive so we need
814 * to verify it under page_lock.
815 */
816 if (unlikely(__PageMovable(page)) &&
817 !PageIsolated(page)) {
818 if (locked) {
819 spin_unlock_irqrestore(zone_lru_lock(zone),
820 flags);
821 locked = false;
822 }
823
824 if (!isolate_movable_page(page, isolate_mode))
825 goto isolate_success;
826 }
827
828 goto isolate_fail;
829 }
830
831 /*
832 * Migration will fail if an anonymous page is pinned in memory,
833 * so avoid taking lru_lock and isolating it unnecessarily in an
834 * admittedly racy check.
835 */
836 if (!page_mapping(page) &&
837 page_count(page) > page_mapcount(page))
838 goto isolate_fail;
839
840 /*
841 * Only allow to migrate anonymous pages in GFP_NOFS context
842 * because those do not depend on fs locks.
843 */
844 if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
845 goto isolate_fail;
846
847 /* If we already hold the lock, we can skip some rechecking */
848 if (!locked) {
849 locked = compact_trylock_irqsave(zone_lru_lock(zone),
850 &flags, cc);
851 if (!locked)
852 break;
853
854 /* Recheck PageLRU and PageCompound under lock */
855 if (!PageLRU(page))
856 goto isolate_fail;
857
858 /*
859 * Page become compound since the non-locked check,
860 * and it's on LRU. It can only be a THP so the order
861 * is safe to read and it's 0 for tail pages.
862 */
863 if (unlikely(PageCompound(page))) {
864 low_pfn += (1UL << compound_order(page)) - 1;
865 goto isolate_fail;
866 }
867 }
868
869 lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
870
871 /* Try isolate the page */
872 if (__isolate_lru_page(page, isolate_mode) != 0)
873 goto isolate_fail;
874
875 VM_BUG_ON_PAGE(PageCompound(page), page);
876
877 /* Successfully isolated */
878 del_page_from_lru_list(page, lruvec, page_lru(page));
879 inc_node_page_state(page,
880 NR_ISOLATED_ANON + page_is_file_cache(page));
881
882 isolate_success:
883 list_add(&page->lru, &cc->migratepages);
884 cc->nr_migratepages++;
885 nr_isolated++;
886
887 /*
888 * Record where we could have freed pages by migration and not
889 * yet flushed them to buddy allocator.
890 * - this is the lowest page that was isolated and likely be
891 * then freed by migration.
892 */
893 if (!cc->last_migrated_pfn)
894 cc->last_migrated_pfn = low_pfn;
895
896 /* Avoid isolating too much */
897 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
898 ++low_pfn;
899 break;
900 }
901
902 continue;
903 isolate_fail:
904 if (!skip_on_failure)
905 continue;
906
907 /*
908 * We have isolated some pages, but then failed. Release them
909 * instead of migrating, as we cannot form the cc->order buddy
910 * page anyway.
911 */
912 if (nr_isolated) {
913 if (locked) {
914 spin_unlock_irqrestore(zone_lru_lock(zone), flags);
915 locked = false;
916 }
917 putback_movable_pages(&cc->migratepages);
918 cc->nr_migratepages = 0;
919 cc->last_migrated_pfn = 0;
920 nr_isolated = 0;
921 }
922
923 if (low_pfn < next_skip_pfn) {
924 low_pfn = next_skip_pfn - 1;
925 /*
926 * The check near the loop beginning would have updated
927 * next_skip_pfn too, but this is a bit simpler.
928 */
929 next_skip_pfn += 1UL << cc->order;
930 }
931 }
932
933 /*
934 * The PageBuddy() check could have potentially brought us outside
935 * the range to be scanned.
936 */
937 if (unlikely(low_pfn > end_pfn))
938 low_pfn = end_pfn;
939
940 if (locked)
941 spin_unlock_irqrestore(zone_lru_lock(zone), flags);
942
943 /*
944 * Update the pageblock-skip information and cached scanner pfn,
945 * if the whole pageblock was scanned without isolating any page.
946 */
947 if (low_pfn == end_pfn)
948 update_pageblock_skip(cc, valid_page, nr_isolated, true);
949
950 trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
951 nr_scanned, nr_isolated);
952
953 cc->total_migrate_scanned += nr_scanned;
954 if (nr_isolated)
955 count_compact_events(COMPACTISOLATED, nr_isolated);
956
957 return low_pfn;
958 }
959
960 /**
961 * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
962 * @cc: Compaction control structure.
963 * @start_pfn: The first PFN to start isolating.
964 * @end_pfn: The one-past-last PFN.
965 *
966 * Returns zero if isolation fails fatally due to e.g. pending signal.
967 * Otherwise, function returns one-past-the-last PFN of isolated page
968 * (which may be greater than end_pfn if end fell in a middle of a THP page).
969 */
970 unsigned long
971 isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
972 unsigned long end_pfn)
973 {
974 unsigned long pfn, block_start_pfn, block_end_pfn;
975
976 /* Scan block by block. First and last block may be incomplete */
977 pfn = start_pfn;
978 block_start_pfn = pageblock_start_pfn(pfn);
979 if (block_start_pfn < cc->zone->zone_start_pfn)
980 block_start_pfn = cc->zone->zone_start_pfn;
981 block_end_pfn = pageblock_end_pfn(pfn);
982
983 for (; pfn < end_pfn; pfn = block_end_pfn,
984 block_start_pfn = block_end_pfn,
985 block_end_pfn += pageblock_nr_pages) {
986
987 block_end_pfn = min(block_end_pfn, end_pfn);
988
989 if (!pageblock_pfn_to_page(block_start_pfn,
990 block_end_pfn, cc->zone))
991 continue;
992
993 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
994 ISOLATE_UNEVICTABLE);
995
996 if (!pfn)
997 break;
998
999 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
1000 break;
1001 }
1002
1003 return pfn;
1004 }
1005
1006 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1007 #ifdef CONFIG_COMPACTION
1008
1009 static bool suitable_migration_source(struct compact_control *cc,
1010 struct page *page)
1011 {
1012 int block_mt;
1013
1014 if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
1015 return true;
1016
1017 block_mt = get_pageblock_migratetype(page);
1018
1019 if (cc->migratetype == MIGRATE_MOVABLE)
1020 return is_migrate_movable(block_mt);
1021 else
1022 return block_mt == cc->migratetype;
1023 }
1024
1025 /* Returns true if the page is within a block suitable for migration to */
1026 static bool suitable_migration_target(struct compact_control *cc,
1027 struct page *page)
1028 {
1029 /* If the page is a large free page, then disallow migration */
1030 if (PageBuddy(page)) {
1031 /*
1032 * We are checking page_order without zone->lock taken. But
1033 * the only small danger is that we skip a potentially suitable
1034 * pageblock, so it's not worth to check order for valid range.
1035 */
1036 if (page_order_unsafe(page) >= pageblock_order)
1037 return false;
1038 }
1039
1040 if (cc->ignore_block_suitable)
1041 return true;
1042
1043 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1044 if (is_migrate_movable(get_pageblock_migratetype(page)))
1045 return true;
1046
1047 /* Otherwise skip the block */
1048 return false;
1049 }
1050
1051 /*
1052 * Test whether the free scanner has reached the same or lower pageblock than
1053 * the migration scanner, and compaction should thus terminate.
1054 */
1055 static inline bool compact_scanners_met(struct compact_control *cc)
1056 {
1057 return (cc->free_pfn >> pageblock_order)
1058 <= (cc->migrate_pfn >> pageblock_order);
1059 }
1060
1061 /*
1062 * Based on information in the current compact_control, find blocks
1063 * suitable for isolating free pages from and then isolate them.
1064 */
1065 static void isolate_freepages(struct compact_control *cc)
1066 {
1067 struct zone *zone = cc->zone;
1068 struct page *page;
1069 unsigned long block_start_pfn; /* start of current pageblock */
1070 unsigned long isolate_start_pfn; /* exact pfn we start at */
1071 unsigned long block_end_pfn; /* end of current pageblock */
1072 unsigned long low_pfn; /* lowest pfn scanner is able to scan */
1073 struct list_head *freelist = &cc->freepages;
1074
1075 /*
1076 * Initialise the free scanner. The starting point is where we last
1077 * successfully isolated from, zone-cached value, or the end of the
1078 * zone when isolating for the first time. For looping we also need
1079 * this pfn aligned down to the pageblock boundary, because we do
1080 * block_start_pfn -= pageblock_nr_pages in the for loop.
1081 * For ending point, take care when isolating in last pageblock of a
1082 * a zone which ends in the middle of a pageblock.
1083 * The low boundary is the end of the pageblock the migration scanner
1084 * is using.
1085 */
1086 isolate_start_pfn = cc->free_pfn;
1087 block_start_pfn = pageblock_start_pfn(cc->free_pfn);
1088 block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1089 zone_end_pfn(zone));
1090 low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1091
1092 /*
1093 * Isolate free pages until enough are available to migrate the
1094 * pages on cc->migratepages. We stop searching if the migrate
1095 * and free page scanners meet or enough free pages are isolated.
1096 */
1097 for (; block_start_pfn >= low_pfn;
1098 block_end_pfn = block_start_pfn,
1099 block_start_pfn -= pageblock_nr_pages,
1100 isolate_start_pfn = block_start_pfn) {
1101 /*
1102 * This can iterate a massively long zone without finding any
1103 * suitable migration targets, so periodically check if we need
1104 * to schedule, or even abort async compaction.
1105 */
1106 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1107 && compact_should_abort(cc))
1108 break;
1109
1110 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1111 zone);
1112 if (!page)
1113 continue;
1114
1115 /* Check the block is suitable for migration */
1116 if (!suitable_migration_target(cc, page))
1117 continue;
1118
1119 /* If isolation recently failed, do not retry */
1120 if (!isolation_suitable(cc, page))
1121 continue;
1122
1123 /* Found a block suitable for isolating free pages from. */
1124 isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn,
1125 freelist, false);
1126
1127 /*
1128 * If we isolated enough freepages, or aborted due to lock
1129 * contention, terminate.
1130 */
1131 if ((cc->nr_freepages >= cc->nr_migratepages)
1132 || cc->contended) {
1133 if (isolate_start_pfn >= block_end_pfn) {
1134 /*
1135 * Restart at previous pageblock if more
1136 * freepages can be isolated next time.
1137 */
1138 isolate_start_pfn =
1139 block_start_pfn - pageblock_nr_pages;
1140 }
1141 break;
1142 } else if (isolate_start_pfn < block_end_pfn) {
1143 /*
1144 * If isolation failed early, do not continue
1145 * needlessly.
1146 */
1147 break;
1148 }
1149 }
1150
1151 /* __isolate_free_page() does not map the pages */
1152 map_pages(freelist);
1153
1154 /*
1155 * Record where the free scanner will restart next time. Either we
1156 * broke from the loop and set isolate_start_pfn based on the last
1157 * call to isolate_freepages_block(), or we met the migration scanner
1158 * and the loop terminated due to isolate_start_pfn < low_pfn
1159 */
1160 cc->free_pfn = isolate_start_pfn;
1161 }
1162
1163 /*
1164 * This is a migrate-callback that "allocates" freepages by taking pages
1165 * from the isolated freelists in the block we are migrating to.
1166 */
1167 static struct page *compaction_alloc(struct page *migratepage,
1168 unsigned long data,
1169 int **result)
1170 {
1171 struct compact_control *cc = (struct compact_control *)data;
1172 struct page *freepage;
1173
1174 /*
1175 * Isolate free pages if necessary, and if we are not aborting due to
1176 * contention.
1177 */
1178 if (list_empty(&cc->freepages)) {
1179 if (!cc->contended)
1180 isolate_freepages(cc);
1181
1182 if (list_empty(&cc->freepages))
1183 return NULL;
1184 }
1185
1186 freepage = list_entry(cc->freepages.next, struct page, lru);
1187 list_del(&freepage->lru);
1188 cc->nr_freepages--;
1189
1190 return freepage;
1191 }
1192
1193 /*
1194 * This is a migrate-callback that "frees" freepages back to the isolated
1195 * freelist. All pages on the freelist are from the same zone, so there is no
1196 * special handling needed for NUMA.
1197 */
1198 static void compaction_free(struct page *page, unsigned long data)
1199 {
1200 struct compact_control *cc = (struct compact_control *)data;
1201
1202 list_add(&page->lru, &cc->freepages);
1203 cc->nr_freepages++;
1204 }
1205
1206 /* possible outcome of isolate_migratepages */
1207 typedef enum {
1208 ISOLATE_ABORT, /* Abort compaction now */
1209 ISOLATE_NONE, /* No pages isolated, continue scanning */
1210 ISOLATE_SUCCESS, /* Pages isolated, migrate */
1211 } isolate_migrate_t;
1212
1213 /*
1214 * Allow userspace to control policy on scanning the unevictable LRU for
1215 * compactable pages.
1216 */
1217 int sysctl_compact_unevictable_allowed __read_mostly = 1;
1218
1219 /*
1220 * Isolate all pages that can be migrated from the first suitable block,
1221 * starting at the block pointed to by the migrate scanner pfn within
1222 * compact_control.
1223 */
1224 static isolate_migrate_t isolate_migratepages(struct zone *zone,
1225 struct compact_control *cc)
1226 {
1227 unsigned long block_start_pfn;
1228 unsigned long block_end_pfn;
1229 unsigned long low_pfn;
1230 struct page *page;
1231 const isolate_mode_t isolate_mode =
1232 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1233 (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1234
1235 /*
1236 * Start at where we last stopped, or beginning of the zone as
1237 * initialized by compact_zone()
1238 */
1239 low_pfn = cc->migrate_pfn;
1240 block_start_pfn = pageblock_start_pfn(low_pfn);
1241 if (block_start_pfn < zone->zone_start_pfn)
1242 block_start_pfn = zone->zone_start_pfn;
1243
1244 /* Only scan within a pageblock boundary */
1245 block_end_pfn = pageblock_end_pfn(low_pfn);
1246
1247 /*
1248 * Iterate over whole pageblocks until we find the first suitable.
1249 * Do not cross the free scanner.
1250 */
1251 for (; block_end_pfn <= cc->free_pfn;
1252 low_pfn = block_end_pfn,
1253 block_start_pfn = block_end_pfn,
1254 block_end_pfn += pageblock_nr_pages) {
1255
1256 /*
1257 * This can potentially iterate a massively long zone with
1258 * many pageblocks unsuitable, so periodically check if we
1259 * need to schedule, or even abort async compaction.
1260 */
1261 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
1262 && compact_should_abort(cc))
1263 break;
1264
1265 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1266 zone);
1267 if (!page)
1268 continue;
1269
1270 /* If isolation recently failed, do not retry */
1271 if (!isolation_suitable(cc, page))
1272 continue;
1273
1274 /*
1275 * For async compaction, also only scan in MOVABLE blocks.
1276 * Async compaction is optimistic to see if the minimum amount
1277 * of work satisfies the allocation.
1278 */
1279 if (!suitable_migration_source(cc, page))
1280 continue;
1281
1282 /* Perform the isolation */
1283 low_pfn = isolate_migratepages_block(cc, low_pfn,
1284 block_end_pfn, isolate_mode);
1285
1286 if (!low_pfn || cc->contended)
1287 return ISOLATE_ABORT;
1288
1289 /*
1290 * Either we isolated something and proceed with migration. Or
1291 * we failed and compact_zone should decide if we should
1292 * continue or not.
1293 */
1294 break;
1295 }
1296
1297 /* Record where migration scanner will be restarted. */
1298 cc->migrate_pfn = low_pfn;
1299
1300 return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1301 }
1302
1303 /*
1304 * order == -1 is expected when compacting via
1305 * /proc/sys/vm/compact_memory
1306 */
1307 static inline bool is_via_compact_memory(int order)
1308 {
1309 return order == -1;
1310 }
1311
1312 static enum compact_result __compact_finished(struct zone *zone,
1313 struct compact_control *cc)
1314 {
1315 unsigned int order;
1316 const int migratetype = cc->migratetype;
1317
1318 if (cc->contended || fatal_signal_pending(current))
1319 return COMPACT_CONTENDED;
1320
1321 /* Compaction run completes if the migrate and free scanner meet */
1322 if (compact_scanners_met(cc)) {
1323 /* Let the next compaction start anew. */
1324 reset_cached_positions(zone);
1325
1326 /*
1327 * Mark that the PG_migrate_skip information should be cleared
1328 * by kswapd when it goes to sleep. kcompactd does not set the
1329 * flag itself as the decision to be clear should be directly
1330 * based on an allocation request.
1331 */
1332 if (cc->direct_compaction)
1333 zone->compact_blockskip_flush = true;
1334
1335 if (cc->whole_zone)
1336 return COMPACT_COMPLETE;
1337 else
1338 return COMPACT_PARTIAL_SKIPPED;
1339 }
1340
1341 if (is_via_compact_memory(cc->order))
1342 return COMPACT_CONTINUE;
1343
1344 if (cc->finishing_block) {
1345 /*
1346 * We have finished the pageblock, but better check again that
1347 * we really succeeded.
1348 */
1349 if (IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
1350 cc->finishing_block = false;
1351 else
1352 return COMPACT_CONTINUE;
1353 }
1354
1355 /* Direct compactor: Is a suitable page free? */
1356 for (order = cc->order; order < MAX_ORDER; order++) {
1357 struct free_area *area = &zone->free_area[order];
1358 bool can_steal;
1359
1360 /* Job done if page is free of the right migratetype */
1361 if (!list_empty(&area->free_list[migratetype]))
1362 return COMPACT_SUCCESS;
1363
1364 #ifdef CONFIG_CMA
1365 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1366 if (migratetype == MIGRATE_MOVABLE &&
1367 !list_empty(&area->free_list[MIGRATE_CMA]))
1368 return COMPACT_SUCCESS;
1369 #endif
1370 /*
1371 * Job done if allocation would steal freepages from
1372 * other migratetype buddy lists.
1373 */
1374 if (find_suitable_fallback(area, order, migratetype,
1375 true, &can_steal) != -1) {
1376
1377 /* movable pages are OK in any pageblock */
1378 if (migratetype == MIGRATE_MOVABLE)
1379 return COMPACT_SUCCESS;
1380
1381 /*
1382 * We are stealing for a non-movable allocation. Make
1383 * sure we finish compacting the current pageblock
1384 * first so it is as free as possible and we won't
1385 * have to steal another one soon. This only applies
1386 * to sync compaction, as async compaction operates
1387 * on pageblocks of the same migratetype.
1388 */
1389 if (cc->mode == MIGRATE_ASYNC ||
1390 IS_ALIGNED(cc->migrate_pfn,
1391 pageblock_nr_pages)) {
1392 return COMPACT_SUCCESS;
1393 }
1394
1395 cc->finishing_block = true;
1396 return COMPACT_CONTINUE;
1397 }
1398 }
1399
1400 return COMPACT_NO_SUITABLE_PAGE;
1401 }
1402
1403 static enum compact_result compact_finished(struct zone *zone,
1404 struct compact_control *cc)
1405 {
1406 int ret;
1407
1408 ret = __compact_finished(zone, cc);
1409 trace_mm_compaction_finished(zone, cc->order, ret);
1410 if (ret == COMPACT_NO_SUITABLE_PAGE)
1411 ret = COMPACT_CONTINUE;
1412
1413 return ret;
1414 }
1415
1416 /*
1417 * compaction_suitable: Is this suitable to run compaction on this zone now?
1418 * Returns
1419 * COMPACT_SKIPPED - If there are too few free pages for compaction
1420 * COMPACT_SUCCESS - If the allocation would succeed without compaction
1421 * COMPACT_CONTINUE - If compaction should run now
1422 */
1423 static enum compact_result __compaction_suitable(struct zone *zone, int order,
1424 unsigned int alloc_flags,
1425 int classzone_idx,
1426 unsigned long wmark_target)
1427 {
1428 unsigned long watermark;
1429
1430 if (is_via_compact_memory(order))
1431 return COMPACT_CONTINUE;
1432
1433 watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
1434 /*
1435 * If watermarks for high-order allocation are already met, there
1436 * should be no need for compaction at all.
1437 */
1438 if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1439 alloc_flags))
1440 return COMPACT_SUCCESS;
1441
1442 /*
1443 * Watermarks for order-0 must be met for compaction to be able to
1444 * isolate free pages for migration targets. This means that the
1445 * watermark and alloc_flags have to match, or be more pessimistic than
1446 * the check in __isolate_free_page(). We don't use the direct
1447 * compactor's alloc_flags, as they are not relevant for freepage
1448 * isolation. We however do use the direct compactor's classzone_idx to
1449 * skip over zones where lowmem reserves would prevent allocation even
1450 * if compaction succeeds.
1451 * For costly orders, we require low watermark instead of min for
1452 * compaction to proceed to increase its chances.
1453 * ALLOC_CMA is used, as pages in CMA pageblocks are considered
1454 * suitable migration targets
1455 */
1456 watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
1457 low_wmark_pages(zone) : min_wmark_pages(zone);
1458 watermark += compact_gap(order);
1459 if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
1460 ALLOC_CMA, wmark_target))
1461 return COMPACT_SKIPPED;
1462
1463 return COMPACT_CONTINUE;
1464 }
1465
1466 enum compact_result compaction_suitable(struct zone *zone, int order,
1467 unsigned int alloc_flags,
1468 int classzone_idx)
1469 {
1470 enum compact_result ret;
1471 int fragindex;
1472
1473 ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
1474 zone_page_state(zone, NR_FREE_PAGES));
1475 /*
1476 * fragmentation index determines if allocation failures are due to
1477 * low memory or external fragmentation
1478 *
1479 * index of -1000 would imply allocations might succeed depending on
1480 * watermarks, but we already failed the high-order watermark check
1481 * index towards 0 implies failure is due to lack of memory
1482 * index towards 1000 implies failure is due to fragmentation
1483 *
1484 * Only compact if a failure would be due to fragmentation. Also
1485 * ignore fragindex for non-costly orders where the alternative to
1486 * a successful reclaim/compaction is OOM. Fragindex and the
1487 * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
1488 * excessive compaction for costly orders, but it should not be at the
1489 * expense of system stability.
1490 */
1491 if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
1492 fragindex = fragmentation_index(zone, order);
1493 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
1494 ret = COMPACT_NOT_SUITABLE_ZONE;
1495 }
1496
1497 trace_mm_compaction_suitable(zone, order, ret);
1498 if (ret == COMPACT_NOT_SUITABLE_ZONE)
1499 ret = COMPACT_SKIPPED;
1500
1501 return ret;
1502 }
1503
1504 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
1505 int alloc_flags)
1506 {
1507 struct zone *zone;
1508 struct zoneref *z;
1509
1510 /*
1511 * Make sure at least one zone would pass __compaction_suitable if we continue
1512 * retrying the reclaim.
1513 */
1514 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1515 ac->nodemask) {
1516 unsigned long available;
1517 enum compact_result compact_result;
1518
1519 /*
1520 * Do not consider all the reclaimable memory because we do not
1521 * want to trash just for a single high order allocation which
1522 * is even not guaranteed to appear even if __compaction_suitable
1523 * is happy about the watermark check.
1524 */
1525 available = zone_reclaimable_pages(zone) / order;
1526 available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
1527 compact_result = __compaction_suitable(zone, order, alloc_flags,
1528 ac_classzone_idx(ac), available);
1529 if (compact_result != COMPACT_SKIPPED)
1530 return true;
1531 }
1532
1533 return false;
1534 }
1535
1536 static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
1537 {
1538 enum compact_result ret;
1539 unsigned long start_pfn = zone->zone_start_pfn;
1540 unsigned long end_pfn = zone_end_pfn(zone);
1541 const bool sync = cc->mode != MIGRATE_ASYNC;
1542
1543 cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
1544 ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
1545 cc->classzone_idx);
1546 /* Compaction is likely to fail */
1547 if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
1548 return ret;
1549
1550 /* huh, compaction_suitable is returning something unexpected */
1551 VM_BUG_ON(ret != COMPACT_CONTINUE);
1552
1553 /*
1554 * Clear pageblock skip if there were failures recently and compaction
1555 * is about to be retried after being deferred.
1556 */
1557 if (compaction_restarting(zone, cc->order))
1558 __reset_isolation_suitable(zone);
1559
1560 /*
1561 * Setup to move all movable pages to the end of the zone. Used cached
1562 * information on where the scanners should start (unless we explicitly
1563 * want to compact the whole zone), but check that it is initialised
1564 * by ensuring the values are within zone boundaries.
1565 */
1566 if (cc->whole_zone) {
1567 cc->migrate_pfn = start_pfn;
1568 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
1569 } else {
1570 cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
1571 cc->free_pfn = zone->compact_cached_free_pfn;
1572 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
1573 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
1574 zone->compact_cached_free_pfn = cc->free_pfn;
1575 }
1576 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
1577 cc->migrate_pfn = start_pfn;
1578 zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
1579 zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
1580 }
1581
1582 if (cc->migrate_pfn == start_pfn)
1583 cc->whole_zone = true;
1584 }
1585
1586 cc->last_migrated_pfn = 0;
1587
1588 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
1589 cc->free_pfn, end_pfn, sync);
1590
1591 migrate_prep_local();
1592
1593 while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
1594 int err;
1595
1596 switch (isolate_migratepages(zone, cc)) {
1597 case ISOLATE_ABORT:
1598 ret = COMPACT_CONTENDED;
1599 putback_movable_pages(&cc->migratepages);
1600 cc->nr_migratepages = 0;
1601 goto out;
1602 case ISOLATE_NONE:
1603 /*
1604 * We haven't isolated and migrated anything, but
1605 * there might still be unflushed migrations from
1606 * previous cc->order aligned block.
1607 */
1608 goto check_drain;
1609 case ISOLATE_SUCCESS:
1610 ;
1611 }
1612
1613 err = migrate_pages(&cc->migratepages, compaction_alloc,
1614 compaction_free, (unsigned long)cc, cc->mode,
1615 MR_COMPACTION);
1616
1617 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
1618 &cc->migratepages);
1619
1620 /* All pages were either migrated or will be released */
1621 cc->nr_migratepages = 0;
1622 if (err) {
1623 putback_movable_pages(&cc->migratepages);
1624 /*
1625 * migrate_pages() may return -ENOMEM when scanners meet
1626 * and we want compact_finished() to detect it
1627 */
1628 if (err == -ENOMEM && !compact_scanners_met(cc)) {
1629 ret = COMPACT_CONTENDED;
1630 goto out;
1631 }
1632 /*
1633 * We failed to migrate at least one page in the current
1634 * order-aligned block, so skip the rest of it.
1635 */
1636 if (cc->direct_compaction &&
1637 (cc->mode == MIGRATE_ASYNC)) {
1638 cc->migrate_pfn = block_end_pfn(
1639 cc->migrate_pfn - 1, cc->order);
1640 /* Draining pcplists is useless in this case */
1641 cc->last_migrated_pfn = 0;
1642
1643 }
1644 }
1645
1646 check_drain:
1647 /*
1648 * Has the migration scanner moved away from the previous
1649 * cc->order aligned block where we migrated from? If yes,
1650 * flush the pages that were freed, so that they can merge and
1651 * compact_finished() can detect immediately if allocation
1652 * would succeed.
1653 */
1654 if (cc->order > 0 && cc->last_migrated_pfn) {
1655 int cpu;
1656 unsigned long current_block_start =
1657 block_start_pfn(cc->migrate_pfn, cc->order);
1658
1659 if (cc->last_migrated_pfn < current_block_start) {
1660 cpu = get_cpu();
1661 lru_add_drain_cpu(cpu);
1662 drain_local_pages(zone);
1663 put_cpu();
1664 /* No more flushing until we migrate again */
1665 cc->last_migrated_pfn = 0;
1666 }
1667 }
1668
1669 }
1670
1671 out:
1672 /*
1673 * Release free pages and update where the free scanner should restart,
1674 * so we don't leave any returned pages behind in the next attempt.
1675 */
1676 if (cc->nr_freepages > 0) {
1677 unsigned long free_pfn = release_freepages(&cc->freepages);
1678
1679 cc->nr_freepages = 0;
1680 VM_BUG_ON(free_pfn == 0);
1681 /* The cached pfn is always the first in a pageblock */
1682 free_pfn = pageblock_start_pfn(free_pfn);
1683 /*
1684 * Only go back, not forward. The cached pfn might have been
1685 * already reset to zone end in compact_finished()
1686 */
1687 if (free_pfn > zone->compact_cached_free_pfn)
1688 zone->compact_cached_free_pfn = free_pfn;
1689 }
1690
1691 count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
1692 count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
1693
1694 trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
1695 cc->free_pfn, end_pfn, sync, ret);
1696
1697 return ret;
1698 }
1699
1700 static enum compact_result compact_zone_order(struct zone *zone, int order,
1701 gfp_t gfp_mask, enum compact_priority prio,
1702 unsigned int alloc_flags, int classzone_idx)
1703 {
1704 enum compact_result ret;
1705 struct compact_control cc = {
1706 .nr_freepages = 0,
1707 .nr_migratepages = 0,
1708 .total_migrate_scanned = 0,
1709 .total_free_scanned = 0,
1710 .order = order,
1711 .gfp_mask = gfp_mask,
1712 .zone = zone,
1713 .mode = (prio == COMPACT_PRIO_ASYNC) ?
1714 MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
1715 .alloc_flags = alloc_flags,
1716 .classzone_idx = classzone_idx,
1717 .direct_compaction = true,
1718 .whole_zone = (prio == MIN_COMPACT_PRIORITY),
1719 .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
1720 .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
1721 };
1722 INIT_LIST_HEAD(&cc.freepages);
1723 INIT_LIST_HEAD(&cc.migratepages);
1724
1725 ret = compact_zone(zone, &cc);
1726
1727 VM_BUG_ON(!list_empty(&cc.freepages));
1728 VM_BUG_ON(!list_empty(&cc.migratepages));
1729
1730 return ret;
1731 }
1732
1733 int sysctl_extfrag_threshold = 500;
1734
1735 /**
1736 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1737 * @gfp_mask: The GFP mask of the current allocation
1738 * @order: The order of the current allocation
1739 * @alloc_flags: The allocation flags of the current allocation
1740 * @ac: The context of current allocation
1741 * @mode: The migration mode for async, sync light, or sync migration
1742 *
1743 * This is the main entry point for direct page compaction.
1744 */
1745 enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
1746 unsigned int alloc_flags, const struct alloc_context *ac,
1747 enum compact_priority prio)
1748 {
1749 int may_perform_io = gfp_mask & __GFP_IO;
1750 struct zoneref *z;
1751 struct zone *zone;
1752 enum compact_result rc = COMPACT_SKIPPED;
1753
1754 /*
1755 * Check if the GFP flags allow compaction - GFP_NOIO is really
1756 * tricky context because the migration might require IO
1757 */
1758 if (!may_perform_io)
1759 return COMPACT_SKIPPED;
1760
1761 trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
1762
1763 /* Compact each zone in the list */
1764 for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
1765 ac->nodemask) {
1766 enum compact_result status;
1767
1768 if (prio > MIN_COMPACT_PRIORITY
1769 && compaction_deferred(zone, order)) {
1770 rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
1771 continue;
1772 }
1773
1774 status = compact_zone_order(zone, order, gfp_mask, prio,
1775 alloc_flags, ac_classzone_idx(ac));
1776 rc = max(status, rc);
1777
1778 /* The allocation should succeed, stop compacting */
1779 if (status == COMPACT_SUCCESS) {
1780 /*
1781 * We think the allocation will succeed in this zone,
1782 * but it is not certain, hence the false. The caller
1783 * will repeat this with true if allocation indeed
1784 * succeeds in this zone.
1785 */
1786 compaction_defer_reset(zone, order, false);
1787
1788 break;
1789 }
1790
1791 if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
1792 status == COMPACT_PARTIAL_SKIPPED))
1793 /*
1794 * We think that allocation won't succeed in this zone
1795 * so we defer compaction there. If it ends up
1796 * succeeding after all, it will be reset.
1797 */
1798 defer_compaction(zone, order);
1799
1800 /*
1801 * We might have stopped compacting due to need_resched() in
1802 * async compaction, or due to a fatal signal detected. In that
1803 * case do not try further zones
1804 */
1805 if ((prio == COMPACT_PRIO_ASYNC && need_resched())
1806 || fatal_signal_pending(current))
1807 break;
1808 }
1809
1810 return rc;
1811 }
1812
1813
1814 /* Compact all zones within a node */
1815 static void compact_node(int nid)
1816 {
1817 pg_data_t *pgdat = NODE_DATA(nid);
1818 int zoneid;
1819 struct zone *zone;
1820 struct compact_control cc = {
1821 .order = -1,
1822 .total_migrate_scanned = 0,
1823 .total_free_scanned = 0,
1824 .mode = MIGRATE_SYNC,
1825 .ignore_skip_hint = true,
1826 .whole_zone = true,
1827 .gfp_mask = GFP_KERNEL,
1828 };
1829
1830
1831 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1832
1833 zone = &pgdat->node_zones[zoneid];
1834 if (!populated_zone(zone))
1835 continue;
1836
1837 cc.nr_freepages = 0;
1838 cc.nr_migratepages = 0;
1839 cc.zone = zone;
1840 INIT_LIST_HEAD(&cc.freepages);
1841 INIT_LIST_HEAD(&cc.migratepages);
1842
1843 compact_zone(zone, &cc);
1844
1845 VM_BUG_ON(!list_empty(&cc.freepages));
1846 VM_BUG_ON(!list_empty(&cc.migratepages));
1847 }
1848 }
1849
1850 /* Compact all nodes in the system */
1851 static void compact_nodes(void)
1852 {
1853 int nid;
1854
1855 /* Flush pending updates to the LRU lists */
1856 lru_add_drain_all();
1857
1858 for_each_online_node(nid)
1859 compact_node(nid);
1860 }
1861
1862 /* The written value is actually unused, all memory is compacted */
1863 int sysctl_compact_memory;
1864
1865 /*
1866 * This is the entry point for compacting all nodes via
1867 * /proc/sys/vm/compact_memory
1868 */
1869 int sysctl_compaction_handler(struct ctl_table *table, int write,
1870 void __user *buffer, size_t *length, loff_t *ppos)
1871 {
1872 if (write)
1873 compact_nodes();
1874
1875 return 0;
1876 }
1877
1878 int sysctl_extfrag_handler(struct ctl_table *table, int write,
1879 void __user *buffer, size_t *length, loff_t *ppos)
1880 {
1881 proc_dointvec_minmax(table, write, buffer, length, ppos);
1882
1883 return 0;
1884 }
1885
1886 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1887 static ssize_t sysfs_compact_node(struct device *dev,
1888 struct device_attribute *attr,
1889 const char *buf, size_t count)
1890 {
1891 int nid = dev->id;
1892
1893 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1894 /* Flush pending updates to the LRU lists */
1895 lru_add_drain_all();
1896
1897 compact_node(nid);
1898 }
1899
1900 return count;
1901 }
1902 static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
1903
1904 int compaction_register_node(struct node *node)
1905 {
1906 return device_create_file(&node->dev, &dev_attr_compact);
1907 }
1908
1909 void compaction_unregister_node(struct node *node)
1910 {
1911 return device_remove_file(&node->dev, &dev_attr_compact);
1912 }
1913 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
1914
1915 static inline bool kcompactd_work_requested(pg_data_t *pgdat)
1916 {
1917 return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
1918 }
1919
1920 static bool kcompactd_node_suitable(pg_data_t *pgdat)
1921 {
1922 int zoneid;
1923 struct zone *zone;
1924 enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
1925
1926 for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
1927 zone = &pgdat->node_zones[zoneid];
1928
1929 if (!populated_zone(zone))
1930 continue;
1931
1932 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
1933 classzone_idx) == COMPACT_CONTINUE)
1934 return true;
1935 }
1936
1937 return false;
1938 }
1939
1940 static void kcompactd_do_work(pg_data_t *pgdat)
1941 {
1942 /*
1943 * With no special task, compact all zones so that a page of requested
1944 * order is allocatable.
1945 */
1946 int zoneid;
1947 struct zone *zone;
1948 struct compact_control cc = {
1949 .order = pgdat->kcompactd_max_order,
1950 .total_migrate_scanned = 0,
1951 .total_free_scanned = 0,
1952 .classzone_idx = pgdat->kcompactd_classzone_idx,
1953 .mode = MIGRATE_SYNC_LIGHT,
1954 .ignore_skip_hint = false,
1955 .gfp_mask = GFP_KERNEL,
1956 };
1957 trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
1958 cc.classzone_idx);
1959 count_compact_event(KCOMPACTD_WAKE);
1960
1961 for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
1962 int status;
1963
1964 zone = &pgdat->node_zones[zoneid];
1965 if (!populated_zone(zone))
1966 continue;
1967
1968 if (compaction_deferred(zone, cc.order))
1969 continue;
1970
1971 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
1972 COMPACT_CONTINUE)
1973 continue;
1974
1975 cc.nr_freepages = 0;
1976 cc.nr_migratepages = 0;
1977 cc.total_migrate_scanned = 0;
1978 cc.total_free_scanned = 0;
1979 cc.zone = zone;
1980 INIT_LIST_HEAD(&cc.freepages);
1981 INIT_LIST_HEAD(&cc.migratepages);
1982
1983 if (kthread_should_stop())
1984 return;
1985 status = compact_zone(zone, &cc);
1986
1987 if (status == COMPACT_SUCCESS) {
1988 compaction_defer_reset(zone, cc.order, false);
1989 } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
1990 /*
1991 * We use sync migration mode here, so we defer like
1992 * sync direct compaction does.
1993 */
1994 defer_compaction(zone, cc.order);
1995 }
1996
1997 count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
1998 cc.total_migrate_scanned);
1999 count_compact_events(KCOMPACTD_FREE_SCANNED,
2000 cc.total_free_scanned);
2001
2002 VM_BUG_ON(!list_empty(&cc.freepages));
2003 VM_BUG_ON(!list_empty(&cc.migratepages));
2004 }
2005
2006 /*
2007 * Regardless of success, we are done until woken up next. But remember
2008 * the requested order/classzone_idx in case it was higher/tighter than
2009 * our current ones
2010 */
2011 if (pgdat->kcompactd_max_order <= cc.order)
2012 pgdat->kcompactd_max_order = 0;
2013 if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
2014 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2015 }
2016
2017 void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
2018 {
2019 if (!order)
2020 return;
2021
2022 if (pgdat->kcompactd_max_order < order)
2023 pgdat->kcompactd_max_order = order;
2024
2025 if (pgdat->kcompactd_classzone_idx > classzone_idx)
2026 pgdat->kcompactd_classzone_idx = classzone_idx;
2027
2028 /*
2029 * Pairs with implicit barrier in wait_event_freezable()
2030 * such that wakeups are not missed.
2031 */
2032 if (!wq_has_sleeper(&pgdat->kcompactd_wait))
2033 return;
2034
2035 if (!kcompactd_node_suitable(pgdat))
2036 return;
2037
2038 trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
2039 classzone_idx);
2040 wake_up_interruptible(&pgdat->kcompactd_wait);
2041 }
2042
2043 /*
2044 * The background compaction daemon, started as a kernel thread
2045 * from the init process.
2046 */
2047 static int kcompactd(void *p)
2048 {
2049 pg_data_t *pgdat = (pg_data_t*)p;
2050 struct task_struct *tsk = current;
2051
2052 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2053
2054 if (!cpumask_empty(cpumask))
2055 set_cpus_allowed_ptr(tsk, cpumask);
2056
2057 set_freezable();
2058
2059 pgdat->kcompactd_max_order = 0;
2060 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2061
2062 while (!kthread_should_stop()) {
2063 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
2064 wait_event_freezable(pgdat->kcompactd_wait,
2065 kcompactd_work_requested(pgdat));
2066
2067 kcompactd_do_work(pgdat);
2068 }
2069
2070 return 0;
2071 }
2072
2073 /*
2074 * This kcompactd start function will be called by init and node-hot-add.
2075 * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2076 */
2077 int kcompactd_run(int nid)
2078 {
2079 pg_data_t *pgdat = NODE_DATA(nid);
2080 int ret = 0;
2081
2082 if (pgdat->kcompactd)
2083 return 0;
2084
2085 pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2086 if (IS_ERR(pgdat->kcompactd)) {
2087 pr_err("Failed to start kcompactd on node %d\n", nid);
2088 ret = PTR_ERR(pgdat->kcompactd);
2089 pgdat->kcompactd = NULL;
2090 }
2091 return ret;
2092 }
2093
2094 /*
2095 * Called by memory hotplug when all memory in a node is offlined. Caller must
2096 * hold mem_hotplug_begin/end().
2097 */
2098 void kcompactd_stop(int nid)
2099 {
2100 struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2101
2102 if (kcompactd) {
2103 kthread_stop(kcompactd);
2104 NODE_DATA(nid)->kcompactd = NULL;
2105 }
2106 }
2107
2108 /*
2109 * It's optimal to keep kcompactd on the same CPUs as their memory, but
2110 * not required for correctness. So if the last cpu in a node goes
2111 * away, we get changed to run anywhere: as the first one comes back,
2112 * restore their cpu bindings.
2113 */
2114 static int kcompactd_cpu_online(unsigned int cpu)
2115 {
2116 int nid;
2117
2118 for_each_node_state(nid, N_MEMORY) {
2119 pg_data_t *pgdat = NODE_DATA(nid);
2120 const struct cpumask *mask;
2121
2122 mask = cpumask_of_node(pgdat->node_id);
2123
2124 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2125 /* One of our CPUs online: restore mask */
2126 set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2127 }
2128 return 0;
2129 }
2130
2131 static int __init kcompactd_init(void)
2132 {
2133 int nid;
2134 int ret;
2135
2136 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
2137 "mm/compaction:online",
2138 kcompactd_cpu_online, NULL);
2139 if (ret < 0) {
2140 pr_err("kcompactd: failed to register hotplug callbacks.\n");
2141 return ret;
2142 }
2143
2144 for_each_node_state(nid, N_MEMORY)
2145 kcompactd_run(nid);
2146 return 0;
2147 }
2148 subsys_initcall(kcompactd_init)
2149
2150 #endif /* CONFIG_COMPACTION */