KVM: x86/mmu: Move definition of make_mmu_pages_available() up
[linux-2.6-microblaze.git] / mm / compaction.c
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 <linux/psi.h>
26 #include "internal.h"
27
28 #ifdef CONFIG_COMPACTION
29 static inline void count_compact_event(enum vm_event_item item)
30 {
31         count_vm_event(item);
32 }
33
34 static inline void count_compact_events(enum vm_event_item item, long delta)
35 {
36         count_vm_events(item, delta);
37 }
38 #else
39 #define count_compact_event(item) do { } while (0)
40 #define count_compact_events(item, delta) do { } while (0)
41 #endif
42
43 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
44
45 #define CREATE_TRACE_POINTS
46 #include <trace/events/compaction.h>
47
48 #define block_start_pfn(pfn, order)     round_down(pfn, 1UL << (order))
49 #define block_end_pfn(pfn, order)       ALIGN((pfn) + 1, 1UL << (order))
50 #define pageblock_start_pfn(pfn)        block_start_pfn(pfn, pageblock_order)
51 #define pageblock_end_pfn(pfn)          block_end_pfn(pfn, pageblock_order)
52
53 static unsigned long release_freepages(struct list_head *freelist)
54 {
55         struct page *page, *next;
56         unsigned long high_pfn = 0;
57
58         list_for_each_entry_safe(page, next, freelist, lru) {
59                 unsigned long pfn = page_to_pfn(page);
60                 list_del(&page->lru);
61                 __free_page(page);
62                 if (pfn > high_pfn)
63                         high_pfn = pfn;
64         }
65
66         return high_pfn;
67 }
68
69 static void split_map_pages(struct list_head *list)
70 {
71         unsigned int i, order, nr_pages;
72         struct page *page, *next;
73         LIST_HEAD(tmp_list);
74
75         list_for_each_entry_safe(page, next, list, lru) {
76                 list_del(&page->lru);
77
78                 order = page_private(page);
79                 nr_pages = 1 << order;
80
81                 post_alloc_hook(page, order, __GFP_MOVABLE);
82                 if (order)
83                         split_page(page, order);
84
85                 for (i = 0; i < nr_pages; i++) {
86                         list_add(&page->lru, &tmp_list);
87                         page++;
88                 }
89         }
90
91         list_splice(&tmp_list, list);
92 }
93
94 #ifdef CONFIG_COMPACTION
95
96 int PageMovable(struct page *page)
97 {
98         struct address_space *mapping;
99
100         VM_BUG_ON_PAGE(!PageLocked(page), page);
101         if (!__PageMovable(page))
102                 return 0;
103
104         mapping = page_mapping(page);
105         if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
106                 return 1;
107
108         return 0;
109 }
110 EXPORT_SYMBOL(PageMovable);
111
112 void __SetPageMovable(struct page *page, struct address_space *mapping)
113 {
114         VM_BUG_ON_PAGE(!PageLocked(page), page);
115         VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
116         page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
117 }
118 EXPORT_SYMBOL(__SetPageMovable);
119
120 void __ClearPageMovable(struct page *page)
121 {
122         VM_BUG_ON_PAGE(!PageLocked(page), page);
123         VM_BUG_ON_PAGE(!PageMovable(page), page);
124         /*
125          * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
126          * flag so that VM can catch up released page by driver after isolation.
127          * With it, VM migration doesn't try to put it back.
128          */
129         page->mapping = (void *)((unsigned long)page->mapping &
130                                 PAGE_MAPPING_MOVABLE);
131 }
132 EXPORT_SYMBOL(__ClearPageMovable);
133
134 /* Do not skip compaction more than 64 times */
135 #define COMPACT_MAX_DEFER_SHIFT 6
136
137 /*
138  * Compaction is deferred when compaction fails to result in a page
139  * allocation success. 1 << compact_defer_limit compactions are skipped up
140  * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
141  */
142 void defer_compaction(struct zone *zone, int order)
143 {
144         zone->compact_considered = 0;
145         zone->compact_defer_shift++;
146
147         if (order < zone->compact_order_failed)
148                 zone->compact_order_failed = order;
149
150         if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
151                 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
152
153         trace_mm_compaction_defer_compaction(zone, order);
154 }
155
156 /* Returns true if compaction should be skipped this time */
157 bool compaction_deferred(struct zone *zone, int order)
158 {
159         unsigned long defer_limit = 1UL << zone->compact_defer_shift;
160
161         if (order < zone->compact_order_failed)
162                 return false;
163
164         /* Avoid possible overflow */
165         if (++zone->compact_considered > defer_limit)
166                 zone->compact_considered = defer_limit;
167
168         if (zone->compact_considered >= defer_limit)
169                 return false;
170
171         trace_mm_compaction_deferred(zone, order);
172
173         return true;
174 }
175
176 /*
177  * Update defer tracking counters after successful compaction of given order,
178  * which means an allocation either succeeded (alloc_success == true) or is
179  * expected to succeed.
180  */
181 void compaction_defer_reset(struct zone *zone, int order,
182                 bool alloc_success)
183 {
184         if (alloc_success) {
185                 zone->compact_considered = 0;
186                 zone->compact_defer_shift = 0;
187         }
188         if (order >= zone->compact_order_failed)
189                 zone->compact_order_failed = order + 1;
190
191         trace_mm_compaction_defer_reset(zone, order);
192 }
193
194 /* Returns true if restarting compaction after many failures */
195 bool compaction_restarting(struct zone *zone, int order)
196 {
197         if (order < zone->compact_order_failed)
198                 return false;
199
200         return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
201                 zone->compact_considered >= 1UL << zone->compact_defer_shift;
202 }
203
204 /* Returns true if the pageblock should be scanned for pages to isolate. */
205 static inline bool isolation_suitable(struct compact_control *cc,
206                                         struct page *page)
207 {
208         if (cc->ignore_skip_hint)
209                 return true;
210
211         return !get_pageblock_skip(page);
212 }
213
214 static void reset_cached_positions(struct zone *zone)
215 {
216         zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
217         zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
218         zone->compact_cached_free_pfn =
219                                 pageblock_start_pfn(zone_end_pfn(zone) - 1);
220 }
221
222 /*
223  * Compound pages of >= pageblock_order should consistenly be skipped until
224  * released. It is always pointless to compact pages of such order (if they are
225  * migratable), and the pageblocks they occupy cannot contain any free pages.
226  */
227 static bool pageblock_skip_persistent(struct page *page)
228 {
229         if (!PageCompound(page))
230                 return false;
231
232         page = compound_head(page);
233
234         if (compound_order(page) >= pageblock_order)
235                 return true;
236
237         return false;
238 }
239
240 static bool
241 __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
242                                                         bool check_target)
243 {
244         struct page *page = pfn_to_online_page(pfn);
245         struct page *block_page;
246         struct page *end_page;
247         unsigned long block_pfn;
248
249         if (!page)
250                 return false;
251         if (zone != page_zone(page))
252                 return false;
253         if (pageblock_skip_persistent(page))
254                 return false;
255
256         /*
257          * If skip is already cleared do no further checking once the
258          * restart points have been set.
259          */
260         if (check_source && check_target && !get_pageblock_skip(page))
261                 return true;
262
263         /*
264          * If clearing skip for the target scanner, do not select a
265          * non-movable pageblock as the starting point.
266          */
267         if (!check_source && check_target &&
268             get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
269                 return false;
270
271         /* Ensure the start of the pageblock or zone is online and valid */
272         block_pfn = pageblock_start_pfn(pfn);
273         block_pfn = max(block_pfn, zone->zone_start_pfn);
274         block_page = pfn_to_online_page(block_pfn);
275         if (block_page) {
276                 page = block_page;
277                 pfn = block_pfn;
278         }
279
280         /* Ensure the end of the pageblock or zone is online and valid */
281         block_pfn = pageblock_end_pfn(pfn) - 1;
282         block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
283         end_page = pfn_to_online_page(block_pfn);
284         if (!end_page)
285                 return false;
286
287         /*
288          * Only clear the hint if a sample indicates there is either a
289          * free page or an LRU page in the block. One or other condition
290          * is necessary for the block to be a migration source/target.
291          */
292         do {
293                 if (pfn_valid_within(pfn)) {
294                         if (check_source && PageLRU(page)) {
295                                 clear_pageblock_skip(page);
296                                 return true;
297                         }
298
299                         if (check_target && PageBuddy(page)) {
300                                 clear_pageblock_skip(page);
301                                 return true;
302                         }
303                 }
304
305                 page += (1 << PAGE_ALLOC_COSTLY_ORDER);
306                 pfn += (1 << PAGE_ALLOC_COSTLY_ORDER);
307         } while (page <= end_page);
308
309         return false;
310 }
311
312 /*
313  * This function is called to clear all cached information on pageblocks that
314  * should be skipped for page isolation when the migrate and free page scanner
315  * meet.
316  */
317 static void __reset_isolation_suitable(struct zone *zone)
318 {
319         unsigned long migrate_pfn = zone->zone_start_pfn;
320         unsigned long free_pfn = zone_end_pfn(zone) - 1;
321         unsigned long reset_migrate = free_pfn;
322         unsigned long reset_free = migrate_pfn;
323         bool source_set = false;
324         bool free_set = false;
325
326         if (!zone->compact_blockskip_flush)
327                 return;
328
329         zone->compact_blockskip_flush = false;
330
331         /*
332          * Walk the zone and update pageblock skip information. Source looks
333          * for PageLRU while target looks for PageBuddy. When the scanner
334          * is found, both PageBuddy and PageLRU are checked as the pageblock
335          * is suitable as both source and target.
336          */
337         for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages,
338                                         free_pfn -= pageblock_nr_pages) {
339                 cond_resched();
340
341                 /* Update the migrate PFN */
342                 if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) &&
343                     migrate_pfn < reset_migrate) {
344                         source_set = true;
345                         reset_migrate = migrate_pfn;
346                         zone->compact_init_migrate_pfn = reset_migrate;
347                         zone->compact_cached_migrate_pfn[0] = reset_migrate;
348                         zone->compact_cached_migrate_pfn[1] = reset_migrate;
349                 }
350
351                 /* Update the free PFN */
352                 if (__reset_isolation_pfn(zone, free_pfn, free_set, true) &&
353                     free_pfn > reset_free) {
354                         free_set = true;
355                         reset_free = free_pfn;
356                         zone->compact_init_free_pfn = reset_free;
357                         zone->compact_cached_free_pfn = reset_free;
358                 }
359         }
360
361         /* Leave no distance if no suitable block was reset */
362         if (reset_migrate >= reset_free) {
363                 zone->compact_cached_migrate_pfn[0] = migrate_pfn;
364                 zone->compact_cached_migrate_pfn[1] = migrate_pfn;
365                 zone->compact_cached_free_pfn = free_pfn;
366         }
367 }
368
369 void reset_isolation_suitable(pg_data_t *pgdat)
370 {
371         int zoneid;
372
373         for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
374                 struct zone *zone = &pgdat->node_zones[zoneid];
375                 if (!populated_zone(zone))
376                         continue;
377
378                 /* Only flush if a full compaction finished recently */
379                 if (zone->compact_blockskip_flush)
380                         __reset_isolation_suitable(zone);
381         }
382 }
383
384 /*
385  * Sets the pageblock skip bit if it was clear. Note that this is a hint as
386  * locks are not required for read/writers. Returns true if it was already set.
387  */
388 static bool test_and_set_skip(struct compact_control *cc, struct page *page,
389                                                         unsigned long pfn)
390 {
391         bool skip;
392
393         /* Do no update if skip hint is being ignored */
394         if (cc->ignore_skip_hint)
395                 return false;
396
397         if (!IS_ALIGNED(pfn, pageblock_nr_pages))
398                 return false;
399
400         skip = get_pageblock_skip(page);
401         if (!skip && !cc->no_set_skip_hint)
402                 set_pageblock_skip(page);
403
404         return skip;
405 }
406
407 static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
408 {
409         struct zone *zone = cc->zone;
410
411         pfn = pageblock_end_pfn(pfn);
412
413         /* Set for isolation rather than compaction */
414         if (cc->no_set_skip_hint)
415                 return;
416
417         if (pfn > zone->compact_cached_migrate_pfn[0])
418                 zone->compact_cached_migrate_pfn[0] = pfn;
419         if (cc->mode != MIGRATE_ASYNC &&
420             pfn > zone->compact_cached_migrate_pfn[1])
421                 zone->compact_cached_migrate_pfn[1] = pfn;
422 }
423
424 /*
425  * If no pages were isolated then mark this pageblock to be skipped in the
426  * future. The information is later cleared by __reset_isolation_suitable().
427  */
428 static void update_pageblock_skip(struct compact_control *cc,
429                         struct page *page, unsigned long pfn)
430 {
431         struct zone *zone = cc->zone;
432
433         if (cc->no_set_skip_hint)
434                 return;
435
436         if (!page)
437                 return;
438
439         set_pageblock_skip(page);
440
441         /* Update where async and sync compaction should restart */
442         if (pfn < zone->compact_cached_free_pfn)
443                 zone->compact_cached_free_pfn = pfn;
444 }
445 #else
446 static inline bool isolation_suitable(struct compact_control *cc,
447                                         struct page *page)
448 {
449         return true;
450 }
451
452 static inline bool pageblock_skip_persistent(struct page *page)
453 {
454         return false;
455 }
456
457 static inline void update_pageblock_skip(struct compact_control *cc,
458                         struct page *page, unsigned long pfn)
459 {
460 }
461
462 static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
463 {
464 }
465
466 static bool test_and_set_skip(struct compact_control *cc, struct page *page,
467                                                         unsigned long pfn)
468 {
469         return false;
470 }
471 #endif /* CONFIG_COMPACTION */
472
473 /*
474  * Compaction requires the taking of some coarse locks that are potentially
475  * very heavily contended. For async compaction, trylock and record if the
476  * lock is contended. The lock will still be acquired but compaction will
477  * abort when the current block is finished regardless of success rate.
478  * Sync compaction acquires the lock.
479  *
480  * Always returns true which makes it easier to track lock state in callers.
481  */
482 static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
483                                                 struct compact_control *cc)
484 {
485         /* Track if the lock is contended in async mode */
486         if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
487                 if (spin_trylock_irqsave(lock, *flags))
488                         return true;
489
490                 cc->contended = true;
491         }
492
493         spin_lock_irqsave(lock, *flags);
494         return true;
495 }
496
497 /*
498  * Compaction requires the taking of some coarse locks that are potentially
499  * very heavily contended. The lock should be periodically unlocked to avoid
500  * having disabled IRQs for a long time, even when there is nobody waiting on
501  * the lock. It might also be that allowing the IRQs will result in
502  * need_resched() becoming true. If scheduling is needed, async compaction
503  * aborts. Sync compaction schedules.
504  * Either compaction type will also abort if a fatal signal is pending.
505  * In either case if the lock was locked, it is dropped and not regained.
506  *
507  * Returns true if compaction should abort due to fatal signal pending, or
508  *              async compaction due to need_resched()
509  * Returns false when compaction can continue (sync compaction might have
510  *              scheduled)
511  */
512 static bool compact_unlock_should_abort(spinlock_t *lock,
513                 unsigned long flags, bool *locked, struct compact_control *cc)
514 {
515         if (*locked) {
516                 spin_unlock_irqrestore(lock, flags);
517                 *locked = false;
518         }
519
520         if (fatal_signal_pending(current)) {
521                 cc->contended = true;
522                 return true;
523         }
524
525         cond_resched();
526
527         return false;
528 }
529
530 /*
531  * Isolate free pages onto a private freelist. If @strict is true, will abort
532  * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
533  * (even though it may still end up isolating some pages).
534  */
535 static unsigned long isolate_freepages_block(struct compact_control *cc,
536                                 unsigned long *start_pfn,
537                                 unsigned long end_pfn,
538                                 struct list_head *freelist,
539                                 unsigned int stride,
540                                 bool strict)
541 {
542         int nr_scanned = 0, total_isolated = 0;
543         struct page *cursor;
544         unsigned long flags = 0;
545         bool locked = false;
546         unsigned long blockpfn = *start_pfn;
547         unsigned int order;
548
549         /* Strict mode is for isolation, speed is secondary */
550         if (strict)
551                 stride = 1;
552
553         cursor = pfn_to_page(blockpfn);
554
555         /* Isolate free pages. */
556         for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
557                 int isolated;
558                 struct page *page = cursor;
559
560                 /*
561                  * Periodically drop the lock (if held) regardless of its
562                  * contention, to give chance to IRQs. Abort if fatal signal
563                  * pending or async compaction detects need_resched()
564                  */
565                 if (!(blockpfn % SWAP_CLUSTER_MAX)
566                     && compact_unlock_should_abort(&cc->zone->lock, flags,
567                                                                 &locked, cc))
568                         break;
569
570                 nr_scanned++;
571                 if (!pfn_valid_within(blockpfn))
572                         goto isolate_fail;
573
574                 /*
575                  * For compound pages such as THP and hugetlbfs, we can save
576                  * potentially a lot of iterations if we skip them at once.
577                  * The check is racy, but we can consider only valid values
578                  * and the only danger is skipping too much.
579                  */
580                 if (PageCompound(page)) {
581                         const unsigned int order = compound_order(page);
582
583                         if (likely(order < MAX_ORDER)) {
584                                 blockpfn += (1UL << order) - 1;
585                                 cursor += (1UL << order) - 1;
586                         }
587                         goto isolate_fail;
588                 }
589
590                 if (!PageBuddy(page))
591                         goto isolate_fail;
592
593                 /*
594                  * If we already hold the lock, we can skip some rechecking.
595                  * Note that if we hold the lock now, checked_pageblock was
596                  * already set in some previous iteration (or strict is true),
597                  * so it is correct to skip the suitable migration target
598                  * recheck as well.
599                  */
600                 if (!locked) {
601                         locked = compact_lock_irqsave(&cc->zone->lock,
602                                                                 &flags, cc);
603
604                         /* Recheck this is a buddy page under lock */
605                         if (!PageBuddy(page))
606                                 goto isolate_fail;
607                 }
608
609                 /* Found a free page, will break it into order-0 pages */
610                 order = page_order(page);
611                 isolated = __isolate_free_page(page, order);
612                 if (!isolated)
613                         break;
614                 set_page_private(page, order);
615
616                 total_isolated += isolated;
617                 cc->nr_freepages += isolated;
618                 list_add_tail(&page->lru, freelist);
619
620                 if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
621                         blockpfn += isolated;
622                         break;
623                 }
624                 /* Advance to the end of split page */
625                 blockpfn += isolated - 1;
626                 cursor += isolated - 1;
627                 continue;
628
629 isolate_fail:
630                 if (strict)
631                         break;
632                 else
633                         continue;
634
635         }
636
637         if (locked)
638                 spin_unlock_irqrestore(&cc->zone->lock, flags);
639
640         /*
641          * There is a tiny chance that we have read bogus compound_order(),
642          * so be careful to not go outside of the pageblock.
643          */
644         if (unlikely(blockpfn > end_pfn))
645                 blockpfn = end_pfn;
646
647         trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
648                                         nr_scanned, total_isolated);
649
650         /* Record how far we have got within the block */
651         *start_pfn = blockpfn;
652
653         /*
654          * If strict isolation is requested by CMA then check that all the
655          * pages requested were isolated. If there were any failures, 0 is
656          * returned and CMA will fail.
657          */
658         if (strict && blockpfn < end_pfn)
659                 total_isolated = 0;
660
661         cc->total_free_scanned += nr_scanned;
662         if (total_isolated)
663                 count_compact_events(COMPACTISOLATED, total_isolated);
664         return total_isolated;
665 }
666
667 /**
668  * isolate_freepages_range() - isolate free pages.
669  * @cc:        Compaction control structure.
670  * @start_pfn: The first PFN to start isolating.
671  * @end_pfn:   The one-past-last PFN.
672  *
673  * Non-free pages, invalid PFNs, or zone boundaries within the
674  * [start_pfn, end_pfn) range are considered errors, cause function to
675  * undo its actions and return zero.
676  *
677  * Otherwise, function returns one-past-the-last PFN of isolated page
678  * (which may be greater then end_pfn if end fell in a middle of
679  * a free page).
680  */
681 unsigned long
682 isolate_freepages_range(struct compact_control *cc,
683                         unsigned long start_pfn, unsigned long end_pfn)
684 {
685         unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
686         LIST_HEAD(freelist);
687
688         pfn = start_pfn;
689         block_start_pfn = pageblock_start_pfn(pfn);
690         if (block_start_pfn < cc->zone->zone_start_pfn)
691                 block_start_pfn = cc->zone->zone_start_pfn;
692         block_end_pfn = pageblock_end_pfn(pfn);
693
694         for (; pfn < end_pfn; pfn += isolated,
695                                 block_start_pfn = block_end_pfn,
696                                 block_end_pfn += pageblock_nr_pages) {
697                 /* Protect pfn from changing by isolate_freepages_block */
698                 unsigned long isolate_start_pfn = pfn;
699
700                 block_end_pfn = min(block_end_pfn, end_pfn);
701
702                 /*
703                  * pfn could pass the block_end_pfn if isolated freepage
704                  * is more than pageblock order. In this case, we adjust
705                  * scanning range to right one.
706                  */
707                 if (pfn >= block_end_pfn) {
708                         block_start_pfn = pageblock_start_pfn(pfn);
709                         block_end_pfn = pageblock_end_pfn(pfn);
710                         block_end_pfn = min(block_end_pfn, end_pfn);
711                 }
712
713                 if (!pageblock_pfn_to_page(block_start_pfn,
714                                         block_end_pfn, cc->zone))
715                         break;
716
717                 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
718                                         block_end_pfn, &freelist, 0, true);
719
720                 /*
721                  * In strict mode, isolate_freepages_block() returns 0 if
722                  * there are any holes in the block (ie. invalid PFNs or
723                  * non-free pages).
724                  */
725                 if (!isolated)
726                         break;
727
728                 /*
729                  * If we managed to isolate pages, it is always (1 << n) *
730                  * pageblock_nr_pages for some non-negative n.  (Max order
731                  * page may span two pageblocks).
732                  */
733         }
734
735         /* __isolate_free_page() does not map the pages */
736         split_map_pages(&freelist);
737
738         if (pfn < end_pfn) {
739                 /* Loop terminated early, cleanup. */
740                 release_freepages(&freelist);
741                 return 0;
742         }
743
744         /* We don't use freelists for anything. */
745         return pfn;
746 }
747
748 /* Similar to reclaim, but different enough that they don't share logic */
749 static bool too_many_isolated(pg_data_t *pgdat)
750 {
751         unsigned long active, inactive, isolated;
752
753         inactive = node_page_state(pgdat, NR_INACTIVE_FILE) +
754                         node_page_state(pgdat, NR_INACTIVE_ANON);
755         active = node_page_state(pgdat, NR_ACTIVE_FILE) +
756                         node_page_state(pgdat, NR_ACTIVE_ANON);
757         isolated = node_page_state(pgdat, NR_ISOLATED_FILE) +
758                         node_page_state(pgdat, NR_ISOLATED_ANON);
759
760         return isolated > (inactive + active) / 2;
761 }
762
763 /**
764  * isolate_migratepages_block() - isolate all migrate-able pages within
765  *                                a single pageblock
766  * @cc:         Compaction control structure.
767  * @low_pfn:    The first PFN to isolate
768  * @end_pfn:    The one-past-the-last PFN to isolate, within same pageblock
769  * @isolate_mode: Isolation mode to be used.
770  *
771  * Isolate all pages that can be migrated from the range specified by
772  * [low_pfn, end_pfn). The range is expected to be within same pageblock.
773  * Returns zero if there is a fatal signal pending, otherwise PFN of the
774  * first page that was not scanned (which may be both less, equal to or more
775  * than end_pfn).
776  *
777  * The pages are isolated on cc->migratepages list (not required to be empty),
778  * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
779  * is neither read nor updated.
780  */
781 static unsigned long
782 isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
783                         unsigned long end_pfn, isolate_mode_t isolate_mode)
784 {
785         pg_data_t *pgdat = cc->zone->zone_pgdat;
786         unsigned long nr_scanned = 0, nr_isolated = 0;
787         struct lruvec *lruvec;
788         unsigned long flags = 0;
789         bool locked = false;
790         struct page *page = NULL, *valid_page = NULL;
791         unsigned long start_pfn = low_pfn;
792         bool skip_on_failure = false;
793         unsigned long next_skip_pfn = 0;
794         bool skip_updated = false;
795
796         /*
797          * Ensure that there are not too many pages isolated from the LRU
798          * list by either parallel reclaimers or compaction. If there are,
799          * delay for some time until fewer pages are isolated
800          */
801         while (unlikely(too_many_isolated(pgdat))) {
802                 /* async migration should just abort */
803                 if (cc->mode == MIGRATE_ASYNC)
804                         return 0;
805
806                 congestion_wait(BLK_RW_ASYNC, HZ/10);
807
808                 if (fatal_signal_pending(current))
809                         return 0;
810         }
811
812         cond_resched();
813
814         if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
815                 skip_on_failure = true;
816                 next_skip_pfn = block_end_pfn(low_pfn, cc->order);
817         }
818
819         /* Time to isolate some pages for migration */
820         for (; low_pfn < end_pfn; low_pfn++) {
821
822                 if (skip_on_failure && low_pfn >= next_skip_pfn) {
823                         /*
824                          * We have isolated all migration candidates in the
825                          * previous order-aligned block, and did not skip it due
826                          * to failure. We should migrate the pages now and
827                          * hopefully succeed compaction.
828                          */
829                         if (nr_isolated)
830                                 break;
831
832                         /*
833                          * We failed to isolate in the previous order-aligned
834                          * block. Set the new boundary to the end of the
835                          * current block. Note we can't simply increase
836                          * next_skip_pfn by 1 << order, as low_pfn might have
837                          * been incremented by a higher number due to skipping
838                          * a compound or a high-order buddy page in the
839                          * previous loop iteration.
840                          */
841                         next_skip_pfn = block_end_pfn(low_pfn, cc->order);
842                 }
843
844                 /*
845                  * Periodically drop the lock (if held) regardless of its
846                  * contention, to give chance to IRQs. Abort completely if
847                  * a fatal signal is pending.
848                  */
849                 if (!(low_pfn % SWAP_CLUSTER_MAX)
850                     && compact_unlock_should_abort(&pgdat->lru_lock,
851                                             flags, &locked, cc)) {
852                         low_pfn = 0;
853                         goto fatal_pending;
854                 }
855
856                 if (!pfn_valid_within(low_pfn))
857                         goto isolate_fail;
858                 nr_scanned++;
859
860                 page = pfn_to_page(low_pfn);
861
862                 /*
863                  * Check if the pageblock has already been marked skipped.
864                  * Only the aligned PFN is checked as the caller isolates
865                  * COMPACT_CLUSTER_MAX at a time so the second call must
866                  * not falsely conclude that the block should be skipped.
867                  */
868                 if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
869                         if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
870                                 low_pfn = end_pfn;
871                                 goto isolate_abort;
872                         }
873                         valid_page = page;
874                 }
875
876                 /*
877                  * Skip if free. We read page order here without zone lock
878                  * which is generally unsafe, but the race window is small and
879                  * the worst thing that can happen is that we skip some
880                  * potential isolation targets.
881                  */
882                 if (PageBuddy(page)) {
883                         unsigned long freepage_order = page_order_unsafe(page);
884
885                         /*
886                          * Without lock, we cannot be sure that what we got is
887                          * a valid page order. Consider only values in the
888                          * valid order range to prevent low_pfn overflow.
889                          */
890                         if (freepage_order > 0 && freepage_order < MAX_ORDER)
891                                 low_pfn += (1UL << freepage_order) - 1;
892                         continue;
893                 }
894
895                 /*
896                  * Regardless of being on LRU, compound pages such as THP and
897                  * hugetlbfs are not to be compacted. We can potentially save
898                  * a lot of iterations if we skip them at once. The check is
899                  * racy, but we can consider only valid values and the only
900                  * danger is skipping too much.
901                  */
902                 if (PageCompound(page)) {
903                         const unsigned int order = compound_order(page);
904
905                         if (likely(order < MAX_ORDER))
906                                 low_pfn += (1UL << order) - 1;
907                         goto isolate_fail;
908                 }
909
910                 /*
911                  * Check may be lockless but that's ok as we recheck later.
912                  * It's possible to migrate LRU and non-lru movable pages.
913                  * Skip any other type of page
914                  */
915                 if (!PageLRU(page)) {
916                         /*
917                          * __PageMovable can return false positive so we need
918                          * to verify it under page_lock.
919                          */
920                         if (unlikely(__PageMovable(page)) &&
921                                         !PageIsolated(page)) {
922                                 if (locked) {
923                                         spin_unlock_irqrestore(&pgdat->lru_lock,
924                                                                         flags);
925                                         locked = false;
926                                 }
927
928                                 if (!isolate_movable_page(page, isolate_mode))
929                                         goto isolate_success;
930                         }
931
932                         goto isolate_fail;
933                 }
934
935                 /*
936                  * Migration will fail if an anonymous page is pinned in memory,
937                  * so avoid taking lru_lock and isolating it unnecessarily in an
938                  * admittedly racy check.
939                  */
940                 if (!page_mapping(page) &&
941                     page_count(page) > page_mapcount(page))
942                         goto isolate_fail;
943
944                 /*
945                  * Only allow to migrate anonymous pages in GFP_NOFS context
946                  * because those do not depend on fs locks.
947                  */
948                 if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
949                         goto isolate_fail;
950
951                 /* If we already hold the lock, we can skip some rechecking */
952                 if (!locked) {
953                         locked = compact_lock_irqsave(&pgdat->lru_lock,
954                                                                 &flags, cc);
955
956                         /* Try get exclusive access under lock */
957                         if (!skip_updated) {
958                                 skip_updated = true;
959                                 if (test_and_set_skip(cc, page, low_pfn))
960                                         goto isolate_abort;
961                         }
962
963                         /* Recheck PageLRU and PageCompound under lock */
964                         if (!PageLRU(page))
965                                 goto isolate_fail;
966
967                         /*
968                          * Page become compound since the non-locked check,
969                          * and it's on LRU. It can only be a THP so the order
970                          * is safe to read and it's 0 for tail pages.
971                          */
972                         if (unlikely(PageCompound(page))) {
973                                 low_pfn += compound_nr(page) - 1;
974                                 goto isolate_fail;
975                         }
976                 }
977
978                 lruvec = mem_cgroup_page_lruvec(page, pgdat);
979
980                 /* Try isolate the page */
981                 if (__isolate_lru_page(page, isolate_mode) != 0)
982                         goto isolate_fail;
983
984                 VM_BUG_ON_PAGE(PageCompound(page), page);
985
986                 /* Successfully isolated */
987                 del_page_from_lru_list(page, lruvec, page_lru(page));
988                 inc_node_page_state(page,
989                                 NR_ISOLATED_ANON + page_is_file_cache(page));
990
991 isolate_success:
992                 list_add(&page->lru, &cc->migratepages);
993                 cc->nr_migratepages++;
994                 nr_isolated++;
995
996                 /*
997                  * Avoid isolating too much unless this block is being
998                  * rescanned (e.g. dirty/writeback pages, parallel allocation)
999                  * or a lock is contended. For contention, isolate quickly to
1000                  * potentially remove one source of contention.
1001                  */
1002                 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX &&
1003                     !cc->rescan && !cc->contended) {
1004                         ++low_pfn;
1005                         break;
1006                 }
1007
1008                 continue;
1009 isolate_fail:
1010                 if (!skip_on_failure)
1011                         continue;
1012
1013                 /*
1014                  * We have isolated some pages, but then failed. Release them
1015                  * instead of migrating, as we cannot form the cc->order buddy
1016                  * page anyway.
1017                  */
1018                 if (nr_isolated) {
1019                         if (locked) {
1020                                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
1021                                 locked = false;
1022                         }
1023                         putback_movable_pages(&cc->migratepages);
1024                         cc->nr_migratepages = 0;
1025                         nr_isolated = 0;
1026                 }
1027
1028                 if (low_pfn < next_skip_pfn) {
1029                         low_pfn = next_skip_pfn - 1;
1030                         /*
1031                          * The check near the loop beginning would have updated
1032                          * next_skip_pfn too, but this is a bit simpler.
1033                          */
1034                         next_skip_pfn += 1UL << cc->order;
1035                 }
1036         }
1037
1038         /*
1039          * The PageBuddy() check could have potentially brought us outside
1040          * the range to be scanned.
1041          */
1042         if (unlikely(low_pfn > end_pfn))
1043                 low_pfn = end_pfn;
1044
1045 isolate_abort:
1046         if (locked)
1047                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
1048
1049         /*
1050          * Updated the cached scanner pfn once the pageblock has been scanned
1051          * Pages will either be migrated in which case there is no point
1052          * scanning in the near future or migration failed in which case the
1053          * failure reason may persist. The block is marked for skipping if
1054          * there were no pages isolated in the block or if the block is
1055          * rescanned twice in a row.
1056          */
1057         if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) {
1058                 if (valid_page && !skip_updated)
1059                         set_pageblock_skip(valid_page);
1060                 update_cached_migrate(cc, low_pfn);
1061         }
1062
1063         trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
1064                                                 nr_scanned, nr_isolated);
1065
1066 fatal_pending:
1067         cc->total_migrate_scanned += nr_scanned;
1068         if (nr_isolated)
1069                 count_compact_events(COMPACTISOLATED, nr_isolated);
1070
1071         return low_pfn;
1072 }
1073
1074 /**
1075  * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
1076  * @cc:        Compaction control structure.
1077  * @start_pfn: The first PFN to start isolating.
1078  * @end_pfn:   The one-past-last PFN.
1079  *
1080  * Returns zero if isolation fails fatally due to e.g. pending signal.
1081  * Otherwise, function returns one-past-the-last PFN of isolated page
1082  * (which may be greater than end_pfn if end fell in a middle of a THP page).
1083  */
1084 unsigned long
1085 isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
1086                                                         unsigned long end_pfn)
1087 {
1088         unsigned long pfn, block_start_pfn, block_end_pfn;
1089
1090         /* Scan block by block. First and last block may be incomplete */
1091         pfn = start_pfn;
1092         block_start_pfn = pageblock_start_pfn(pfn);
1093         if (block_start_pfn < cc->zone->zone_start_pfn)
1094                 block_start_pfn = cc->zone->zone_start_pfn;
1095         block_end_pfn = pageblock_end_pfn(pfn);
1096
1097         for (; pfn < end_pfn; pfn = block_end_pfn,
1098                                 block_start_pfn = block_end_pfn,
1099                                 block_end_pfn += pageblock_nr_pages) {
1100
1101                 block_end_pfn = min(block_end_pfn, end_pfn);
1102
1103                 if (!pageblock_pfn_to_page(block_start_pfn,
1104                                         block_end_pfn, cc->zone))
1105                         continue;
1106
1107                 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
1108                                                         ISOLATE_UNEVICTABLE);
1109
1110                 if (!pfn)
1111                         break;
1112
1113                 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
1114                         break;
1115         }
1116
1117         return pfn;
1118 }
1119
1120 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1121 #ifdef CONFIG_COMPACTION
1122
1123 static bool suitable_migration_source(struct compact_control *cc,
1124                                                         struct page *page)
1125 {
1126         int block_mt;
1127
1128         if (pageblock_skip_persistent(page))
1129                 return false;
1130
1131         if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
1132                 return true;
1133
1134         block_mt = get_pageblock_migratetype(page);
1135
1136         if (cc->migratetype == MIGRATE_MOVABLE)
1137                 return is_migrate_movable(block_mt);
1138         else
1139                 return block_mt == cc->migratetype;
1140 }
1141
1142 /* Returns true if the page is within a block suitable for migration to */
1143 static bool suitable_migration_target(struct compact_control *cc,
1144                                                         struct page *page)
1145 {
1146         /* If the page is a large free page, then disallow migration */
1147         if (PageBuddy(page)) {
1148                 /*
1149                  * We are checking page_order without zone->lock taken. But
1150                  * the only small danger is that we skip a potentially suitable
1151                  * pageblock, so it's not worth to check order for valid range.
1152                  */
1153                 if (page_order_unsafe(page) >= pageblock_order)
1154                         return false;
1155         }
1156
1157         if (cc->ignore_block_suitable)
1158                 return true;
1159
1160         /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1161         if (is_migrate_movable(get_pageblock_migratetype(page)))
1162                 return true;
1163
1164         /* Otherwise skip the block */
1165         return false;
1166 }
1167
1168 static inline unsigned int
1169 freelist_scan_limit(struct compact_control *cc)
1170 {
1171         unsigned short shift = BITS_PER_LONG - 1;
1172
1173         return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
1174 }
1175
1176 /*
1177  * Test whether the free scanner has reached the same or lower pageblock than
1178  * the migration scanner, and compaction should thus terminate.
1179  */
1180 static inline bool compact_scanners_met(struct compact_control *cc)
1181 {
1182         return (cc->free_pfn >> pageblock_order)
1183                 <= (cc->migrate_pfn >> pageblock_order);
1184 }
1185
1186 /*
1187  * Used when scanning for a suitable migration target which scans freelists
1188  * in reverse. Reorders the list such as the unscanned pages are scanned
1189  * first on the next iteration of the free scanner
1190  */
1191 static void
1192 move_freelist_head(struct list_head *freelist, struct page *freepage)
1193 {
1194         LIST_HEAD(sublist);
1195
1196         if (!list_is_last(freelist, &freepage->lru)) {
1197                 list_cut_before(&sublist, freelist, &freepage->lru);
1198                 if (!list_empty(&sublist))
1199                         list_splice_tail(&sublist, freelist);
1200         }
1201 }
1202
1203 /*
1204  * Similar to move_freelist_head except used by the migration scanner
1205  * when scanning forward. It's possible for these list operations to
1206  * move against each other if they search the free list exactly in
1207  * lockstep.
1208  */
1209 static void
1210 move_freelist_tail(struct list_head *freelist, struct page *freepage)
1211 {
1212         LIST_HEAD(sublist);
1213
1214         if (!list_is_first(freelist, &freepage->lru)) {
1215                 list_cut_position(&sublist, freelist, &freepage->lru);
1216                 if (!list_empty(&sublist))
1217                         list_splice_tail(&sublist, freelist);
1218         }
1219 }
1220
1221 static void
1222 fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
1223 {
1224         unsigned long start_pfn, end_pfn;
1225         struct page *page = pfn_to_page(pfn);
1226
1227         /* Do not search around if there are enough pages already */
1228         if (cc->nr_freepages >= cc->nr_migratepages)
1229                 return;
1230
1231         /* Minimise scanning during async compaction */
1232         if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC)
1233                 return;
1234
1235         /* Pageblock boundaries */
1236         start_pfn = pageblock_start_pfn(pfn);
1237         end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)) - 1;
1238
1239         /* Scan before */
1240         if (start_pfn != pfn) {
1241                 isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false);
1242                 if (cc->nr_freepages >= cc->nr_migratepages)
1243                         return;
1244         }
1245
1246         /* Scan after */
1247         start_pfn = pfn + nr_isolated;
1248         if (start_pfn < end_pfn)
1249                 isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
1250
1251         /* Skip this pageblock in the future as it's full or nearly full */
1252         if (cc->nr_freepages < cc->nr_migratepages)
1253                 set_pageblock_skip(page);
1254 }
1255
1256 /* Search orders in round-robin fashion */
1257 static int next_search_order(struct compact_control *cc, int order)
1258 {
1259         order--;
1260         if (order < 0)
1261                 order = cc->order - 1;
1262
1263         /* Search wrapped around? */
1264         if (order == cc->search_order) {
1265                 cc->search_order--;
1266                 if (cc->search_order < 0)
1267                         cc->search_order = cc->order - 1;
1268                 return -1;
1269         }
1270
1271         return order;
1272 }
1273
1274 static unsigned long
1275 fast_isolate_freepages(struct compact_control *cc)
1276 {
1277         unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1);
1278         unsigned int nr_scanned = 0;
1279         unsigned long low_pfn, min_pfn, high_pfn = 0, highest = 0;
1280         unsigned long nr_isolated = 0;
1281         unsigned long distance;
1282         struct page *page = NULL;
1283         bool scan_start = false;
1284         int order;
1285
1286         /* Full compaction passes in a negative order */
1287         if (cc->order <= 0)
1288                 return cc->free_pfn;
1289
1290         /*
1291          * If starting the scan, use a deeper search and use the highest
1292          * PFN found if a suitable one is not found.
1293          */
1294         if (cc->free_pfn >= cc->zone->compact_init_free_pfn) {
1295                 limit = pageblock_nr_pages >> 1;
1296                 scan_start = true;
1297         }
1298
1299         /*
1300          * Preferred point is in the top quarter of the scan space but take
1301          * a pfn from the top half if the search is problematic.
1302          */
1303         distance = (cc->free_pfn - cc->migrate_pfn);
1304         low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2));
1305         min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1));
1306
1307         if (WARN_ON_ONCE(min_pfn > low_pfn))
1308                 low_pfn = min_pfn;
1309
1310         /*
1311          * Search starts from the last successful isolation order or the next
1312          * order to search after a previous failure
1313          */
1314         cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
1315
1316         for (order = cc->search_order;
1317              !page && order >= 0;
1318              order = next_search_order(cc, order)) {
1319                 struct free_area *area = &cc->zone->free_area[order];
1320                 struct list_head *freelist;
1321                 struct page *freepage;
1322                 unsigned long flags;
1323                 unsigned int order_scanned = 0;
1324
1325                 if (!area->nr_free)
1326                         continue;
1327
1328                 spin_lock_irqsave(&cc->zone->lock, flags);
1329                 freelist = &area->free_list[MIGRATE_MOVABLE];
1330                 list_for_each_entry_reverse(freepage, freelist, lru) {
1331                         unsigned long pfn;
1332
1333                         order_scanned++;
1334                         nr_scanned++;
1335                         pfn = page_to_pfn(freepage);
1336
1337                         if (pfn >= highest)
1338                                 highest = pageblock_start_pfn(pfn);
1339
1340                         if (pfn >= low_pfn) {
1341                                 cc->fast_search_fail = 0;
1342                                 cc->search_order = order;
1343                                 page = freepage;
1344                                 break;
1345                         }
1346
1347                         if (pfn >= min_pfn && pfn > high_pfn) {
1348                                 high_pfn = pfn;
1349
1350                                 /* Shorten the scan if a candidate is found */
1351                                 limit >>= 1;
1352                         }
1353
1354                         if (order_scanned >= limit)
1355                                 break;
1356                 }
1357
1358                 /* Use a minimum pfn if a preferred one was not found */
1359                 if (!page && high_pfn) {
1360                         page = pfn_to_page(high_pfn);
1361
1362                         /* Update freepage for the list reorder below */
1363                         freepage = page;
1364                 }
1365
1366                 /* Reorder to so a future search skips recent pages */
1367                 move_freelist_head(freelist, freepage);
1368
1369                 /* Isolate the page if available */
1370                 if (page) {
1371                         if (__isolate_free_page(page, order)) {
1372                                 set_page_private(page, order);
1373                                 nr_isolated = 1 << order;
1374                                 cc->nr_freepages += nr_isolated;
1375                                 list_add_tail(&page->lru, &cc->freepages);
1376                                 count_compact_events(COMPACTISOLATED, nr_isolated);
1377                         } else {
1378                                 /* If isolation fails, abort the search */
1379                                 order = cc->search_order + 1;
1380                                 page = NULL;
1381                         }
1382                 }
1383
1384                 spin_unlock_irqrestore(&cc->zone->lock, flags);
1385
1386                 /*
1387                  * Smaller scan on next order so the total scan ig related
1388                  * to freelist_scan_limit.
1389                  */
1390                 if (order_scanned >= limit)
1391                         limit = min(1U, limit >> 1);
1392         }
1393
1394         if (!page) {
1395                 cc->fast_search_fail++;
1396                 if (scan_start) {
1397                         /*
1398                          * Use the highest PFN found above min. If one was
1399                          * not found, be pessemistic for direct compaction
1400                          * and use the min mark.
1401                          */
1402                         if (highest) {
1403                                 page = pfn_to_page(highest);
1404                                 cc->free_pfn = highest;
1405                         } else {
1406                                 if (cc->direct_compaction && pfn_valid(min_pfn)) {
1407                                         page = pfn_to_page(min_pfn);
1408                                         cc->free_pfn = min_pfn;
1409                                 }
1410                         }
1411                 }
1412         }
1413
1414         if (highest && highest >= cc->zone->compact_cached_free_pfn) {
1415                 highest -= pageblock_nr_pages;
1416                 cc->zone->compact_cached_free_pfn = highest;
1417         }
1418
1419         cc->total_free_scanned += nr_scanned;
1420         if (!page)
1421                 return cc->free_pfn;
1422
1423         low_pfn = page_to_pfn(page);
1424         fast_isolate_around(cc, low_pfn, nr_isolated);
1425         return low_pfn;
1426 }
1427
1428 /*
1429  * Based on information in the current compact_control, find blocks
1430  * suitable for isolating free pages from and then isolate them.
1431  */
1432 static void isolate_freepages(struct compact_control *cc)
1433 {
1434         struct zone *zone = cc->zone;
1435         struct page *page;
1436         unsigned long block_start_pfn;  /* start of current pageblock */
1437         unsigned long isolate_start_pfn; /* exact pfn we start at */
1438         unsigned long block_end_pfn;    /* end of current pageblock */
1439         unsigned long low_pfn;       /* lowest pfn scanner is able to scan */
1440         struct list_head *freelist = &cc->freepages;
1441         unsigned int stride;
1442
1443         /* Try a small search of the free lists for a candidate */
1444         isolate_start_pfn = fast_isolate_freepages(cc);
1445         if (cc->nr_freepages)
1446                 goto splitmap;
1447
1448         /*
1449          * Initialise the free scanner. The starting point is where we last
1450          * successfully isolated from, zone-cached value, or the end of the
1451          * zone when isolating for the first time. For looping we also need
1452          * this pfn aligned down to the pageblock boundary, because we do
1453          * block_start_pfn -= pageblock_nr_pages in the for loop.
1454          * For ending point, take care when isolating in last pageblock of a
1455          * a zone which ends in the middle of a pageblock.
1456          * The low boundary is the end of the pageblock the migration scanner
1457          * is using.
1458          */
1459         isolate_start_pfn = cc->free_pfn;
1460         block_start_pfn = pageblock_start_pfn(isolate_start_pfn);
1461         block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1462                                                 zone_end_pfn(zone));
1463         low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1464         stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1;
1465
1466         /*
1467          * Isolate free pages until enough are available to migrate the
1468          * pages on cc->migratepages. We stop searching if the migrate
1469          * and free page scanners meet or enough free pages are isolated.
1470          */
1471         for (; block_start_pfn >= low_pfn;
1472                                 block_end_pfn = block_start_pfn,
1473                                 block_start_pfn -= pageblock_nr_pages,
1474                                 isolate_start_pfn = block_start_pfn) {
1475                 unsigned long nr_isolated;
1476
1477                 /*
1478                  * This can iterate a massively long zone without finding any
1479                  * suitable migration targets, so periodically check resched.
1480                  */
1481                 if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1482                         cond_resched();
1483
1484                 page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1485                                                                         zone);
1486                 if (!page)
1487                         continue;
1488
1489                 /* Check the block is suitable for migration */
1490                 if (!suitable_migration_target(cc, page))
1491                         continue;
1492
1493                 /* If isolation recently failed, do not retry */
1494                 if (!isolation_suitable(cc, page))
1495                         continue;
1496
1497                 /* Found a block suitable for isolating free pages from. */
1498                 nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
1499                                         block_end_pfn, freelist, stride, false);
1500
1501                 /* Update the skip hint if the full pageblock was scanned */
1502                 if (isolate_start_pfn == block_end_pfn)
1503                         update_pageblock_skip(cc, page, block_start_pfn);
1504
1505                 /* Are enough freepages isolated? */
1506                 if (cc->nr_freepages >= cc->nr_migratepages) {
1507                         if (isolate_start_pfn >= block_end_pfn) {
1508                                 /*
1509                                  * Restart at previous pageblock if more
1510                                  * freepages can be isolated next time.
1511                                  */
1512                                 isolate_start_pfn =
1513                                         block_start_pfn - pageblock_nr_pages;
1514                         }
1515                         break;
1516                 } else if (isolate_start_pfn < block_end_pfn) {
1517                         /*
1518                          * If isolation failed early, do not continue
1519                          * needlessly.
1520                          */
1521                         break;
1522                 }
1523
1524                 /* Adjust stride depending on isolation */
1525                 if (nr_isolated) {
1526                         stride = 1;
1527                         continue;
1528                 }
1529                 stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1);
1530         }
1531
1532         /*
1533          * Record where the free scanner will restart next time. Either we
1534          * broke from the loop and set isolate_start_pfn based on the last
1535          * call to isolate_freepages_block(), or we met the migration scanner
1536          * and the loop terminated due to isolate_start_pfn < low_pfn
1537          */
1538         cc->free_pfn = isolate_start_pfn;
1539
1540 splitmap:
1541         /* __isolate_free_page() does not map the pages */
1542         split_map_pages(freelist);
1543 }
1544
1545 /*
1546  * This is a migrate-callback that "allocates" freepages by taking pages
1547  * from the isolated freelists in the block we are migrating to.
1548  */
1549 static struct page *compaction_alloc(struct page *migratepage,
1550                                         unsigned long data)
1551 {
1552         struct compact_control *cc = (struct compact_control *)data;
1553         struct page *freepage;
1554
1555         if (list_empty(&cc->freepages)) {
1556                 isolate_freepages(cc);
1557
1558                 if (list_empty(&cc->freepages))
1559                         return NULL;
1560         }
1561
1562         freepage = list_entry(cc->freepages.next, struct page, lru);
1563         list_del(&freepage->lru);
1564         cc->nr_freepages--;
1565
1566         return freepage;
1567 }
1568
1569 /*
1570  * This is a migrate-callback that "frees" freepages back to the isolated
1571  * freelist.  All pages on the freelist are from the same zone, so there is no
1572  * special handling needed for NUMA.
1573  */
1574 static void compaction_free(struct page *page, unsigned long data)
1575 {
1576         struct compact_control *cc = (struct compact_control *)data;
1577
1578         list_add(&page->lru, &cc->freepages);
1579         cc->nr_freepages++;
1580 }
1581
1582 /* possible outcome of isolate_migratepages */
1583 typedef enum {
1584         ISOLATE_ABORT,          /* Abort compaction now */
1585         ISOLATE_NONE,           /* No pages isolated, continue scanning */
1586         ISOLATE_SUCCESS,        /* Pages isolated, migrate */
1587 } isolate_migrate_t;
1588
1589 /*
1590  * Allow userspace to control policy on scanning the unevictable LRU for
1591  * compactable pages.
1592  */
1593 int sysctl_compact_unevictable_allowed __read_mostly = 1;
1594
1595 static inline void
1596 update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
1597 {
1598         if (cc->fast_start_pfn == ULONG_MAX)
1599                 return;
1600
1601         if (!cc->fast_start_pfn)
1602                 cc->fast_start_pfn = pfn;
1603
1604         cc->fast_start_pfn = min(cc->fast_start_pfn, pfn);
1605 }
1606
1607 static inline unsigned long
1608 reinit_migrate_pfn(struct compact_control *cc)
1609 {
1610         if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX)
1611                 return cc->migrate_pfn;
1612
1613         cc->migrate_pfn = cc->fast_start_pfn;
1614         cc->fast_start_pfn = ULONG_MAX;
1615
1616         return cc->migrate_pfn;
1617 }
1618
1619 /*
1620  * Briefly search the free lists for a migration source that already has
1621  * some free pages to reduce the number of pages that need migration
1622  * before a pageblock is free.
1623  */
1624 static unsigned long fast_find_migrateblock(struct compact_control *cc)
1625 {
1626         unsigned int limit = freelist_scan_limit(cc);
1627         unsigned int nr_scanned = 0;
1628         unsigned long distance;
1629         unsigned long pfn = cc->migrate_pfn;
1630         unsigned long high_pfn;
1631         int order;
1632
1633         /* Skip hints are relied on to avoid repeats on the fast search */
1634         if (cc->ignore_skip_hint)
1635                 return pfn;
1636
1637         /*
1638          * If the migrate_pfn is not at the start of a zone or the start
1639          * of a pageblock then assume this is a continuation of a previous
1640          * scan restarted due to COMPACT_CLUSTER_MAX.
1641          */
1642         if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn))
1643                 return pfn;
1644
1645         /*
1646          * For smaller orders, just linearly scan as the number of pages
1647          * to migrate should be relatively small and does not necessarily
1648          * justify freeing up a large block for a small allocation.
1649          */
1650         if (cc->order <= PAGE_ALLOC_COSTLY_ORDER)
1651                 return pfn;
1652
1653         /*
1654          * Only allow kcompactd and direct requests for movable pages to
1655          * quickly clear out a MOVABLE pageblock for allocation. This
1656          * reduces the risk that a large movable pageblock is freed for
1657          * an unmovable/reclaimable small allocation.
1658          */
1659         if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE)
1660                 return pfn;
1661
1662         /*
1663          * When starting the migration scanner, pick any pageblock within the
1664          * first half of the search space. Otherwise try and pick a pageblock
1665          * within the first eighth to reduce the chances that a migration
1666          * target later becomes a source.
1667          */
1668         distance = (cc->free_pfn - cc->migrate_pfn) >> 1;
1669         if (cc->migrate_pfn != cc->zone->zone_start_pfn)
1670                 distance >>= 2;
1671         high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance);
1672
1673         for (order = cc->order - 1;
1674              order >= PAGE_ALLOC_COSTLY_ORDER && pfn == cc->migrate_pfn && nr_scanned < limit;
1675              order--) {
1676                 struct free_area *area = &cc->zone->free_area[order];
1677                 struct list_head *freelist;
1678                 unsigned long flags;
1679                 struct page *freepage;
1680
1681                 if (!area->nr_free)
1682                         continue;
1683
1684                 spin_lock_irqsave(&cc->zone->lock, flags);
1685                 freelist = &area->free_list[MIGRATE_MOVABLE];
1686                 list_for_each_entry(freepage, freelist, lru) {
1687                         unsigned long free_pfn;
1688
1689                         nr_scanned++;
1690                         free_pfn = page_to_pfn(freepage);
1691                         if (free_pfn < high_pfn) {
1692                                 /*
1693                                  * Avoid if skipped recently. Ideally it would
1694                                  * move to the tail but even safe iteration of
1695                                  * the list assumes an entry is deleted, not
1696                                  * reordered.
1697                                  */
1698                                 if (get_pageblock_skip(freepage)) {
1699                                         if (list_is_last(freelist, &freepage->lru))
1700                                                 break;
1701
1702                                         continue;
1703                                 }
1704
1705                                 /* Reorder to so a future search skips recent pages */
1706                                 move_freelist_tail(freelist, freepage);
1707
1708                                 update_fast_start_pfn(cc, free_pfn);
1709                                 pfn = pageblock_start_pfn(free_pfn);
1710                                 cc->fast_search_fail = 0;
1711                                 set_pageblock_skip(freepage);
1712                                 break;
1713                         }
1714
1715                         if (nr_scanned >= limit) {
1716                                 cc->fast_search_fail++;
1717                                 move_freelist_tail(freelist, freepage);
1718                                 break;
1719                         }
1720                 }
1721                 spin_unlock_irqrestore(&cc->zone->lock, flags);
1722         }
1723
1724         cc->total_migrate_scanned += nr_scanned;
1725
1726         /*
1727          * If fast scanning failed then use a cached entry for a page block
1728          * that had free pages as the basis for starting a linear scan.
1729          */
1730         if (pfn == cc->migrate_pfn)
1731                 pfn = reinit_migrate_pfn(cc);
1732
1733         return pfn;
1734 }
1735
1736 /*
1737  * Isolate all pages that can be migrated from the first suitable block,
1738  * starting at the block pointed to by the migrate scanner pfn within
1739  * compact_control.
1740  */
1741 static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
1742 {
1743         unsigned long block_start_pfn;
1744         unsigned long block_end_pfn;
1745         unsigned long low_pfn;
1746         struct page *page;
1747         const isolate_mode_t isolate_mode =
1748                 (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1749                 (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1750         bool fast_find_block;
1751
1752         /*
1753          * Start at where we last stopped, or beginning of the zone as
1754          * initialized by compact_zone(). The first failure will use
1755          * the lowest PFN as the starting point for linear scanning.
1756          */
1757         low_pfn = fast_find_migrateblock(cc);
1758         block_start_pfn = pageblock_start_pfn(low_pfn);
1759         if (block_start_pfn < cc->zone->zone_start_pfn)
1760                 block_start_pfn = cc->zone->zone_start_pfn;
1761
1762         /*
1763          * fast_find_migrateblock marks a pageblock skipped so to avoid
1764          * the isolation_suitable check below, check whether the fast
1765          * search was successful.
1766          */
1767         fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
1768
1769         /* Only scan within a pageblock boundary */
1770         block_end_pfn = pageblock_end_pfn(low_pfn);
1771
1772         /*
1773          * Iterate over whole pageblocks until we find the first suitable.
1774          * Do not cross the free scanner.
1775          */
1776         for (; block_end_pfn <= cc->free_pfn;
1777                         fast_find_block = false,
1778                         low_pfn = block_end_pfn,
1779                         block_start_pfn = block_end_pfn,
1780                         block_end_pfn += pageblock_nr_pages) {
1781
1782                 /*
1783                  * This can potentially iterate a massively long zone with
1784                  * many pageblocks unsuitable, so periodically check if we
1785                  * need to schedule.
1786                  */
1787                 if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
1788                         cond_resched();
1789
1790                 page = pageblock_pfn_to_page(block_start_pfn,
1791                                                 block_end_pfn, cc->zone);
1792                 if (!page)
1793                         continue;
1794
1795                 /*
1796                  * If isolation recently failed, do not retry. Only check the
1797                  * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
1798                  * to be visited multiple times. Assume skip was checked
1799                  * before making it "skip" so other compaction instances do
1800                  * not scan the same block.
1801                  */
1802                 if (IS_ALIGNED(low_pfn, pageblock_nr_pages) &&
1803                     !fast_find_block && !isolation_suitable(cc, page))
1804                         continue;
1805
1806                 /*
1807                  * For async compaction, also only scan in MOVABLE blocks
1808                  * without huge pages. Async compaction is optimistic to see
1809                  * if the minimum amount of work satisfies the allocation.
1810                  * The cached PFN is updated as it's possible that all
1811                  * remaining blocks between source and target are unsuitable
1812                  * and the compaction scanners fail to meet.
1813                  */
1814                 if (!suitable_migration_source(cc, page)) {
1815                         update_cached_migrate(cc, block_end_pfn);
1816                         continue;
1817                 }
1818
1819                 /* Perform the isolation */
1820                 low_pfn = isolate_migratepages_block(cc, low_pfn,
1821                                                 block_end_pfn, isolate_mode);
1822
1823                 if (!low_pfn)
1824                         return ISOLATE_ABORT;
1825
1826                 /*
1827                  * Either we isolated something and proceed with migration. Or
1828                  * we failed and compact_zone should decide if we should
1829                  * continue or not.
1830                  */
1831                 break;
1832         }
1833
1834         /* Record where migration scanner will be restarted. */
1835         cc->migrate_pfn = low_pfn;
1836
1837         return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1838 }
1839
1840 /*
1841  * order == -1 is expected when compacting via
1842  * /proc/sys/vm/compact_memory
1843  */
1844 static inline bool is_via_compact_memory(int order)
1845 {
1846         return order == -1;
1847 }
1848
1849 static enum compact_result __compact_finished(struct compact_control *cc)
1850 {
1851         unsigned int order;
1852         const int migratetype = cc->migratetype;
1853         int ret;
1854
1855         /* Compaction run completes if the migrate and free scanner meet */
1856         if (compact_scanners_met(cc)) {
1857                 /* Let the next compaction start anew. */
1858                 reset_cached_positions(cc->zone);
1859
1860                 /*
1861                  * Mark that the PG_migrate_skip information should be cleared
1862                  * by kswapd when it goes to sleep. kcompactd does not set the
1863                  * flag itself as the decision to be clear should be directly
1864                  * based on an allocation request.
1865                  */
1866                 if (cc->direct_compaction)
1867                         cc->zone->compact_blockskip_flush = true;
1868
1869                 if (cc->whole_zone)
1870                         return COMPACT_COMPLETE;
1871                 else
1872                         return COMPACT_PARTIAL_SKIPPED;
1873         }
1874
1875         if (is_via_compact_memory(cc->order))
1876                 return COMPACT_CONTINUE;
1877
1878         /*
1879          * Always finish scanning a pageblock to reduce the possibility of
1880          * fallbacks in the future. This is particularly important when
1881          * migration source is unmovable/reclaimable but it's not worth
1882          * special casing.
1883          */
1884         if (!IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
1885                 return COMPACT_CONTINUE;
1886
1887         /* Direct compactor: Is a suitable page free? */
1888         ret = COMPACT_NO_SUITABLE_PAGE;
1889         for (order = cc->order; order < MAX_ORDER; order++) {
1890                 struct free_area *area = &cc->zone->free_area[order];
1891                 bool can_steal;
1892
1893                 /* Job done if page is free of the right migratetype */
1894                 if (!free_area_empty(area, migratetype))
1895                         return COMPACT_SUCCESS;
1896
1897 #ifdef CONFIG_CMA
1898                 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
1899                 if (migratetype == MIGRATE_MOVABLE &&
1900                         !free_area_empty(area, MIGRATE_CMA))
1901                         return COMPACT_SUCCESS;
1902 #endif
1903                 /*
1904                  * Job done if allocation would steal freepages from
1905                  * other migratetype buddy lists.
1906                  */
1907                 if (find_suitable_fallback(area, order, migratetype,
1908                                                 true, &can_steal) != -1) {
1909
1910                         /* movable pages are OK in any pageblock */
1911                         if (migratetype == MIGRATE_MOVABLE)
1912                                 return COMPACT_SUCCESS;
1913
1914                         /*
1915                          * We are stealing for a non-movable allocation. Make
1916                          * sure we finish compacting the current pageblock
1917                          * first so it is as free as possible and we won't
1918                          * have to steal another one soon. This only applies
1919                          * to sync compaction, as async compaction operates
1920                          * on pageblocks of the same migratetype.
1921                          */
1922                         if (cc->mode == MIGRATE_ASYNC ||
1923                                         IS_ALIGNED(cc->migrate_pfn,
1924                                                         pageblock_nr_pages)) {
1925                                 return COMPACT_SUCCESS;
1926                         }
1927
1928                         ret = COMPACT_CONTINUE;
1929                         break;
1930                 }
1931         }
1932
1933         if (cc->contended || fatal_signal_pending(current))
1934                 ret = COMPACT_CONTENDED;
1935
1936         return ret;
1937 }
1938
1939 static enum compact_result compact_finished(struct compact_control *cc)
1940 {
1941         int ret;
1942
1943         ret = __compact_finished(cc);
1944         trace_mm_compaction_finished(cc->zone, cc->order, ret);
1945         if (ret == COMPACT_NO_SUITABLE_PAGE)
1946                 ret = COMPACT_CONTINUE;
1947
1948         return ret;
1949 }
1950
1951 /*
1952  * compaction_suitable: Is this suitable to run compaction on this zone now?
1953  * Returns
1954  *   COMPACT_SKIPPED  - If there are too few free pages for compaction
1955  *   COMPACT_SUCCESS  - If the allocation would succeed without compaction
1956  *   COMPACT_CONTINUE - If compaction should run now
1957  */
1958 static enum compact_result __compaction_suitable(struct zone *zone, int order,
1959                                         unsigned int alloc_flags,
1960                                         int classzone_idx,
1961                                         unsigned long wmark_target)
1962 {
1963         unsigned long watermark;
1964
1965         if (is_via_compact_memory(order))
1966                 return COMPACT_CONTINUE;
1967
1968         watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
1969         /*
1970          * If watermarks for high-order allocation are already met, there
1971          * should be no need for compaction at all.
1972          */
1973         if (zone_watermark_ok(zone, order, watermark, classzone_idx,
1974                                                                 alloc_flags))
1975                 return COMPACT_SUCCESS;
1976
1977         /*
1978          * Watermarks for order-0 must be met for compaction to be able to
1979          * isolate free pages for migration targets. This means that the
1980          * watermark and alloc_flags have to match, or be more pessimistic than
1981          * the check in __isolate_free_page(). We don't use the direct
1982          * compactor's alloc_flags, as they are not relevant for freepage
1983          * isolation. We however do use the direct compactor's classzone_idx to
1984          * skip over zones where lowmem reserves would prevent allocation even
1985          * if compaction succeeds.
1986          * For costly orders, we require low watermark instead of min for
1987          * compaction to proceed to increase its chances.
1988          * ALLOC_CMA is used, as pages in CMA pageblocks are considered
1989          * suitable migration targets
1990          */
1991         watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
1992                                 low_wmark_pages(zone) : min_wmark_pages(zone);
1993         watermark += compact_gap(order);
1994         if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
1995                                                 ALLOC_CMA, wmark_target))
1996                 return COMPACT_SKIPPED;
1997
1998         return COMPACT_CONTINUE;
1999 }
2000
2001 enum compact_result compaction_suitable(struct zone *zone, int order,
2002                                         unsigned int alloc_flags,
2003                                         int classzone_idx)
2004 {
2005         enum compact_result ret;
2006         int fragindex;
2007
2008         ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
2009                                     zone_page_state(zone, NR_FREE_PAGES));
2010         /*
2011          * fragmentation index determines if allocation failures are due to
2012          * low memory or external fragmentation
2013          *
2014          * index of -1000 would imply allocations might succeed depending on
2015          * watermarks, but we already failed the high-order watermark check
2016          * index towards 0 implies failure is due to lack of memory
2017          * index towards 1000 implies failure is due to fragmentation
2018          *
2019          * Only compact if a failure would be due to fragmentation. Also
2020          * ignore fragindex for non-costly orders where the alternative to
2021          * a successful reclaim/compaction is OOM. Fragindex and the
2022          * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
2023          * excessive compaction for costly orders, but it should not be at the
2024          * expense of system stability.
2025          */
2026         if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
2027                 fragindex = fragmentation_index(zone, order);
2028                 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
2029                         ret = COMPACT_NOT_SUITABLE_ZONE;
2030         }
2031
2032         trace_mm_compaction_suitable(zone, order, ret);
2033         if (ret == COMPACT_NOT_SUITABLE_ZONE)
2034                 ret = COMPACT_SKIPPED;
2035
2036         return ret;
2037 }
2038
2039 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
2040                 int alloc_flags)
2041 {
2042         struct zone *zone;
2043         struct zoneref *z;
2044
2045         /*
2046          * Make sure at least one zone would pass __compaction_suitable if we continue
2047          * retrying the reclaim.
2048          */
2049         for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
2050                                         ac->nodemask) {
2051                 unsigned long available;
2052                 enum compact_result compact_result;
2053
2054                 /*
2055                  * Do not consider all the reclaimable memory because we do not
2056                  * want to trash just for a single high order allocation which
2057                  * is even not guaranteed to appear even if __compaction_suitable
2058                  * is happy about the watermark check.
2059                  */
2060                 available = zone_reclaimable_pages(zone) / order;
2061                 available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
2062                 compact_result = __compaction_suitable(zone, order, alloc_flags,
2063                                 ac_classzone_idx(ac), available);
2064                 if (compact_result != COMPACT_SKIPPED)
2065                         return true;
2066         }
2067
2068         return false;
2069 }
2070
2071 static enum compact_result
2072 compact_zone(struct compact_control *cc, struct capture_control *capc)
2073 {
2074         enum compact_result ret;
2075         unsigned long start_pfn = cc->zone->zone_start_pfn;
2076         unsigned long end_pfn = zone_end_pfn(cc->zone);
2077         unsigned long last_migrated_pfn;
2078         const bool sync = cc->mode != MIGRATE_ASYNC;
2079         bool update_cached;
2080
2081         /*
2082          * These counters track activities during zone compaction.  Initialize
2083          * them before compacting a new zone.
2084          */
2085         cc->total_migrate_scanned = 0;
2086         cc->total_free_scanned = 0;
2087         cc->nr_migratepages = 0;
2088         cc->nr_freepages = 0;
2089         INIT_LIST_HEAD(&cc->freepages);
2090         INIT_LIST_HEAD(&cc->migratepages);
2091
2092         cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
2093         ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
2094                                                         cc->classzone_idx);
2095         /* Compaction is likely to fail */
2096         if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
2097                 return ret;
2098
2099         /* huh, compaction_suitable is returning something unexpected */
2100         VM_BUG_ON(ret != COMPACT_CONTINUE);
2101
2102         /*
2103          * Clear pageblock skip if there were failures recently and compaction
2104          * is about to be retried after being deferred.
2105          */
2106         if (compaction_restarting(cc->zone, cc->order))
2107                 __reset_isolation_suitable(cc->zone);
2108
2109         /*
2110          * Setup to move all movable pages to the end of the zone. Used cached
2111          * information on where the scanners should start (unless we explicitly
2112          * want to compact the whole zone), but check that it is initialised
2113          * by ensuring the values are within zone boundaries.
2114          */
2115         cc->fast_start_pfn = 0;
2116         if (cc->whole_zone) {
2117                 cc->migrate_pfn = start_pfn;
2118                 cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2119         } else {
2120                 cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
2121                 cc->free_pfn = cc->zone->compact_cached_free_pfn;
2122                 if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
2123                         cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2124                         cc->zone->compact_cached_free_pfn = cc->free_pfn;
2125                 }
2126                 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
2127                         cc->migrate_pfn = start_pfn;
2128                         cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
2129                         cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
2130                 }
2131
2132                 if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn)
2133                         cc->whole_zone = true;
2134         }
2135
2136         last_migrated_pfn = 0;
2137
2138         /*
2139          * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
2140          * the basis that some migrations will fail in ASYNC mode. However,
2141          * if the cached PFNs match and pageblocks are skipped due to having
2142          * no isolation candidates, then the sync state does not matter.
2143          * Until a pageblock with isolation candidates is found, keep the
2144          * cached PFNs in sync to avoid revisiting the same blocks.
2145          */
2146         update_cached = !sync &&
2147                 cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
2148
2149         trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
2150                                 cc->free_pfn, end_pfn, sync);
2151
2152         migrate_prep_local();
2153
2154         while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
2155                 int err;
2156                 unsigned long start_pfn = cc->migrate_pfn;
2157
2158                 /*
2159                  * Avoid multiple rescans which can happen if a page cannot be
2160                  * isolated (dirty/writeback in async mode) or if the migrated
2161                  * pages are being allocated before the pageblock is cleared.
2162                  * The first rescan will capture the entire pageblock for
2163                  * migration. If it fails, it'll be marked skip and scanning
2164                  * will proceed as normal.
2165                  */
2166                 cc->rescan = false;
2167                 if (pageblock_start_pfn(last_migrated_pfn) ==
2168                     pageblock_start_pfn(start_pfn)) {
2169                         cc->rescan = true;
2170                 }
2171
2172                 switch (isolate_migratepages(cc)) {
2173                 case ISOLATE_ABORT:
2174                         ret = COMPACT_CONTENDED;
2175                         putback_movable_pages(&cc->migratepages);
2176                         cc->nr_migratepages = 0;
2177                         last_migrated_pfn = 0;
2178                         goto out;
2179                 case ISOLATE_NONE:
2180                         if (update_cached) {
2181                                 cc->zone->compact_cached_migrate_pfn[1] =
2182                                         cc->zone->compact_cached_migrate_pfn[0];
2183                         }
2184
2185                         /*
2186                          * We haven't isolated and migrated anything, but
2187                          * there might still be unflushed migrations from
2188                          * previous cc->order aligned block.
2189                          */
2190                         goto check_drain;
2191                 case ISOLATE_SUCCESS:
2192                         update_cached = false;
2193                         last_migrated_pfn = start_pfn;
2194                         ;
2195                 }
2196
2197                 err = migrate_pages(&cc->migratepages, compaction_alloc,
2198                                 compaction_free, (unsigned long)cc, cc->mode,
2199                                 MR_COMPACTION);
2200
2201                 trace_mm_compaction_migratepages(cc->nr_migratepages, err,
2202                                                         &cc->migratepages);
2203
2204                 /* All pages were either migrated or will be released */
2205                 cc->nr_migratepages = 0;
2206                 if (err) {
2207                         putback_movable_pages(&cc->migratepages);
2208                         /*
2209                          * migrate_pages() may return -ENOMEM when scanners meet
2210                          * and we want compact_finished() to detect it
2211                          */
2212                         if (err == -ENOMEM && !compact_scanners_met(cc)) {
2213                                 ret = COMPACT_CONTENDED;
2214                                 goto out;
2215                         }
2216                         /*
2217                          * We failed to migrate at least one page in the current
2218                          * order-aligned block, so skip the rest of it.
2219                          */
2220                         if (cc->direct_compaction &&
2221                                                 (cc->mode == MIGRATE_ASYNC)) {
2222                                 cc->migrate_pfn = block_end_pfn(
2223                                                 cc->migrate_pfn - 1, cc->order);
2224                                 /* Draining pcplists is useless in this case */
2225                                 last_migrated_pfn = 0;
2226                         }
2227                 }
2228
2229 check_drain:
2230                 /*
2231                  * Has the migration scanner moved away from the previous
2232                  * cc->order aligned block where we migrated from? If yes,
2233                  * flush the pages that were freed, so that they can merge and
2234                  * compact_finished() can detect immediately if allocation
2235                  * would succeed.
2236                  */
2237                 if (cc->order > 0 && last_migrated_pfn) {
2238                         int cpu;
2239                         unsigned long current_block_start =
2240                                 block_start_pfn(cc->migrate_pfn, cc->order);
2241
2242                         if (last_migrated_pfn < current_block_start) {
2243                                 cpu = get_cpu();
2244                                 lru_add_drain_cpu(cpu);
2245                                 drain_local_pages(cc->zone);
2246                                 put_cpu();
2247                                 /* No more flushing until we migrate again */
2248                                 last_migrated_pfn = 0;
2249                         }
2250                 }
2251
2252                 /* Stop if a page has been captured */
2253                 if (capc && capc->page) {
2254                         ret = COMPACT_SUCCESS;
2255                         break;
2256                 }
2257         }
2258
2259 out:
2260         /*
2261          * Release free pages and update where the free scanner should restart,
2262          * so we don't leave any returned pages behind in the next attempt.
2263          */
2264         if (cc->nr_freepages > 0) {
2265                 unsigned long free_pfn = release_freepages(&cc->freepages);
2266
2267                 cc->nr_freepages = 0;
2268                 VM_BUG_ON(free_pfn == 0);
2269                 /* The cached pfn is always the first in a pageblock */
2270                 free_pfn = pageblock_start_pfn(free_pfn);
2271                 /*
2272                  * Only go back, not forward. The cached pfn might have been
2273                  * already reset to zone end in compact_finished()
2274                  */
2275                 if (free_pfn > cc->zone->compact_cached_free_pfn)
2276                         cc->zone->compact_cached_free_pfn = free_pfn;
2277         }
2278
2279         count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
2280         count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
2281
2282         trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
2283                                 cc->free_pfn, end_pfn, sync, ret);
2284
2285         return ret;
2286 }
2287
2288 static enum compact_result compact_zone_order(struct zone *zone, int order,
2289                 gfp_t gfp_mask, enum compact_priority prio,
2290                 unsigned int alloc_flags, int classzone_idx,
2291                 struct page **capture)
2292 {
2293         enum compact_result ret;
2294         struct compact_control cc = {
2295                 .order = order,
2296                 .search_order = order,
2297                 .gfp_mask = gfp_mask,
2298                 .zone = zone,
2299                 .mode = (prio == COMPACT_PRIO_ASYNC) ?
2300                                         MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
2301                 .alloc_flags = alloc_flags,
2302                 .classzone_idx = classzone_idx,
2303                 .direct_compaction = true,
2304                 .whole_zone = (prio == MIN_COMPACT_PRIORITY),
2305                 .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
2306                 .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
2307         };
2308         struct capture_control capc = {
2309                 .cc = &cc,
2310                 .page = NULL,
2311         };
2312
2313         if (capture)
2314                 current->capture_control = &capc;
2315
2316         ret = compact_zone(&cc, &capc);
2317
2318         VM_BUG_ON(!list_empty(&cc.freepages));
2319         VM_BUG_ON(!list_empty(&cc.migratepages));
2320
2321         *capture = capc.page;
2322         current->capture_control = NULL;
2323
2324         return ret;
2325 }
2326
2327 int sysctl_extfrag_threshold = 500;
2328
2329 /**
2330  * try_to_compact_pages - Direct compact to satisfy a high-order allocation
2331  * @gfp_mask: The GFP mask of the current allocation
2332  * @order: The order of the current allocation
2333  * @alloc_flags: The allocation flags of the current allocation
2334  * @ac: The context of current allocation
2335  * @prio: Determines how hard direct compaction should try to succeed
2336  *
2337  * This is the main entry point for direct page compaction.
2338  */
2339 enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
2340                 unsigned int alloc_flags, const struct alloc_context *ac,
2341                 enum compact_priority prio, struct page **capture)
2342 {
2343         int may_perform_io = gfp_mask & __GFP_IO;
2344         struct zoneref *z;
2345         struct zone *zone;
2346         enum compact_result rc = COMPACT_SKIPPED;
2347
2348         /*
2349          * Check if the GFP flags allow compaction - GFP_NOIO is really
2350          * tricky context because the migration might require IO
2351          */
2352         if (!may_perform_io)
2353                 return COMPACT_SKIPPED;
2354
2355         trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
2356
2357         /* Compact each zone in the list */
2358         for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
2359                                                                 ac->nodemask) {
2360                 enum compact_result status;
2361
2362                 if (prio > MIN_COMPACT_PRIORITY
2363                                         && compaction_deferred(zone, order)) {
2364                         rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
2365                         continue;
2366                 }
2367
2368                 status = compact_zone_order(zone, order, gfp_mask, prio,
2369                                 alloc_flags, ac_classzone_idx(ac), capture);
2370                 rc = max(status, rc);
2371
2372                 /* The allocation should succeed, stop compacting */
2373                 if (status == COMPACT_SUCCESS) {
2374                         /*
2375                          * We think the allocation will succeed in this zone,
2376                          * but it is not certain, hence the false. The caller
2377                          * will repeat this with true if allocation indeed
2378                          * succeeds in this zone.
2379                          */
2380                         compaction_defer_reset(zone, order, false);
2381
2382                         break;
2383                 }
2384
2385                 if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
2386                                         status == COMPACT_PARTIAL_SKIPPED))
2387                         /*
2388                          * We think that allocation won't succeed in this zone
2389                          * so we defer compaction there. If it ends up
2390                          * succeeding after all, it will be reset.
2391                          */
2392                         defer_compaction(zone, order);
2393
2394                 /*
2395                  * We might have stopped compacting due to need_resched() in
2396                  * async compaction, or due to a fatal signal detected. In that
2397                  * case do not try further zones
2398                  */
2399                 if ((prio == COMPACT_PRIO_ASYNC && need_resched())
2400                                         || fatal_signal_pending(current))
2401                         break;
2402         }
2403
2404         return rc;
2405 }
2406
2407
2408 /* Compact all zones within a node */
2409 static void compact_node(int nid)
2410 {
2411         pg_data_t *pgdat = NODE_DATA(nid);
2412         int zoneid;
2413         struct zone *zone;
2414         struct compact_control cc = {
2415                 .order = -1,
2416                 .mode = MIGRATE_SYNC,
2417                 .ignore_skip_hint = true,
2418                 .whole_zone = true,
2419                 .gfp_mask = GFP_KERNEL,
2420         };
2421
2422
2423         for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2424
2425                 zone = &pgdat->node_zones[zoneid];
2426                 if (!populated_zone(zone))
2427                         continue;
2428
2429                 cc.zone = zone;
2430
2431                 compact_zone(&cc, NULL);
2432
2433                 VM_BUG_ON(!list_empty(&cc.freepages));
2434                 VM_BUG_ON(!list_empty(&cc.migratepages));
2435         }
2436 }
2437
2438 /* Compact all nodes in the system */
2439 static void compact_nodes(void)
2440 {
2441         int nid;
2442
2443         /* Flush pending updates to the LRU lists */
2444         lru_add_drain_all();
2445
2446         for_each_online_node(nid)
2447                 compact_node(nid);
2448 }
2449
2450 /* The written value is actually unused, all memory is compacted */
2451 int sysctl_compact_memory;
2452
2453 /*
2454  * This is the entry point for compacting all nodes via
2455  * /proc/sys/vm/compact_memory
2456  */
2457 int sysctl_compaction_handler(struct ctl_table *table, int write,
2458                         void __user *buffer, size_t *length, loff_t *ppos)
2459 {
2460         if (write)
2461                 compact_nodes();
2462
2463         return 0;
2464 }
2465
2466 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
2467 static ssize_t sysfs_compact_node(struct device *dev,
2468                         struct device_attribute *attr,
2469                         const char *buf, size_t count)
2470 {
2471         int nid = dev->id;
2472
2473         if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
2474                 /* Flush pending updates to the LRU lists */
2475                 lru_add_drain_all();
2476
2477                 compact_node(nid);
2478         }
2479
2480         return count;
2481 }
2482 static DEVICE_ATTR(compact, 0200, NULL, sysfs_compact_node);
2483
2484 int compaction_register_node(struct node *node)
2485 {
2486         return device_create_file(&node->dev, &dev_attr_compact);
2487 }
2488
2489 void compaction_unregister_node(struct node *node)
2490 {
2491         return device_remove_file(&node->dev, &dev_attr_compact);
2492 }
2493 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
2494
2495 static inline bool kcompactd_work_requested(pg_data_t *pgdat)
2496 {
2497         return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
2498 }
2499
2500 static bool kcompactd_node_suitable(pg_data_t *pgdat)
2501 {
2502         int zoneid;
2503         struct zone *zone;
2504         enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
2505
2506         for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
2507                 zone = &pgdat->node_zones[zoneid];
2508
2509                 if (!populated_zone(zone))
2510                         continue;
2511
2512                 if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
2513                                         classzone_idx) == COMPACT_CONTINUE)
2514                         return true;
2515         }
2516
2517         return false;
2518 }
2519
2520 static void kcompactd_do_work(pg_data_t *pgdat)
2521 {
2522         /*
2523          * With no special task, compact all zones so that a page of requested
2524          * order is allocatable.
2525          */
2526         int zoneid;
2527         struct zone *zone;
2528         struct compact_control cc = {
2529                 .order = pgdat->kcompactd_max_order,
2530                 .search_order = pgdat->kcompactd_max_order,
2531                 .classzone_idx = pgdat->kcompactd_classzone_idx,
2532                 .mode = MIGRATE_SYNC_LIGHT,
2533                 .ignore_skip_hint = false,
2534                 .gfp_mask = GFP_KERNEL,
2535         };
2536         trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
2537                                                         cc.classzone_idx);
2538         count_compact_event(KCOMPACTD_WAKE);
2539
2540         for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
2541                 int status;
2542
2543                 zone = &pgdat->node_zones[zoneid];
2544                 if (!populated_zone(zone))
2545                         continue;
2546
2547                 if (compaction_deferred(zone, cc.order))
2548                         continue;
2549
2550                 if (compaction_suitable(zone, cc.order, 0, zoneid) !=
2551                                                         COMPACT_CONTINUE)
2552                         continue;
2553
2554                 if (kthread_should_stop())
2555                         return;
2556
2557                 cc.zone = zone;
2558                 status = compact_zone(&cc, NULL);
2559
2560                 if (status == COMPACT_SUCCESS) {
2561                         compaction_defer_reset(zone, cc.order, false);
2562                 } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
2563                         /*
2564                          * Buddy pages may become stranded on pcps that could
2565                          * otherwise coalesce on the zone's free area for
2566                          * order >= cc.order.  This is ratelimited by the
2567                          * upcoming deferral.
2568                          */
2569                         drain_all_pages(zone);
2570
2571                         /*
2572                          * We use sync migration mode here, so we defer like
2573                          * sync direct compaction does.
2574                          */
2575                         defer_compaction(zone, cc.order);
2576                 }
2577
2578                 count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
2579                                      cc.total_migrate_scanned);
2580                 count_compact_events(KCOMPACTD_FREE_SCANNED,
2581                                      cc.total_free_scanned);
2582
2583                 VM_BUG_ON(!list_empty(&cc.freepages));
2584                 VM_BUG_ON(!list_empty(&cc.migratepages));
2585         }
2586
2587         /*
2588          * Regardless of success, we are done until woken up next. But remember
2589          * the requested order/classzone_idx in case it was higher/tighter than
2590          * our current ones
2591          */
2592         if (pgdat->kcompactd_max_order <= cc.order)
2593                 pgdat->kcompactd_max_order = 0;
2594         if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
2595                 pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2596 }
2597
2598 void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
2599 {
2600         if (!order)
2601                 return;
2602
2603         if (pgdat->kcompactd_max_order < order)
2604                 pgdat->kcompactd_max_order = order;
2605
2606         if (pgdat->kcompactd_classzone_idx > classzone_idx)
2607                 pgdat->kcompactd_classzone_idx = classzone_idx;
2608
2609         /*
2610          * Pairs with implicit barrier in wait_event_freezable()
2611          * such that wakeups are not missed.
2612          */
2613         if (!wq_has_sleeper(&pgdat->kcompactd_wait))
2614                 return;
2615
2616         if (!kcompactd_node_suitable(pgdat))
2617                 return;
2618
2619         trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
2620                                                         classzone_idx);
2621         wake_up_interruptible(&pgdat->kcompactd_wait);
2622 }
2623
2624 /*
2625  * The background compaction daemon, started as a kernel thread
2626  * from the init process.
2627  */
2628 static int kcompactd(void *p)
2629 {
2630         pg_data_t *pgdat = (pg_data_t*)p;
2631         struct task_struct *tsk = current;
2632
2633         const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2634
2635         if (!cpumask_empty(cpumask))
2636                 set_cpus_allowed_ptr(tsk, cpumask);
2637
2638         set_freezable();
2639
2640         pgdat->kcompactd_max_order = 0;
2641         pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
2642
2643         while (!kthread_should_stop()) {
2644                 unsigned long pflags;
2645
2646                 trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
2647                 wait_event_freezable(pgdat->kcompactd_wait,
2648                                 kcompactd_work_requested(pgdat));
2649
2650                 psi_memstall_enter(&pflags);
2651                 kcompactd_do_work(pgdat);
2652                 psi_memstall_leave(&pflags);
2653         }
2654
2655         return 0;
2656 }
2657
2658 /*
2659  * This kcompactd start function will be called by init and node-hot-add.
2660  * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
2661  */
2662 int kcompactd_run(int nid)
2663 {
2664         pg_data_t *pgdat = NODE_DATA(nid);
2665         int ret = 0;
2666
2667         if (pgdat->kcompactd)
2668                 return 0;
2669
2670         pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
2671         if (IS_ERR(pgdat->kcompactd)) {
2672                 pr_err("Failed to start kcompactd on node %d\n", nid);
2673                 ret = PTR_ERR(pgdat->kcompactd);
2674                 pgdat->kcompactd = NULL;
2675         }
2676         return ret;
2677 }
2678
2679 /*
2680  * Called by memory hotplug when all memory in a node is offlined. Caller must
2681  * hold mem_hotplug_begin/end().
2682  */
2683 void kcompactd_stop(int nid)
2684 {
2685         struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
2686
2687         if (kcompactd) {
2688                 kthread_stop(kcompactd);
2689                 NODE_DATA(nid)->kcompactd = NULL;
2690         }
2691 }
2692
2693 /*
2694  * It's optimal to keep kcompactd on the same CPUs as their memory, but
2695  * not required for correctness. So if the last cpu in a node goes
2696  * away, we get changed to run anywhere: as the first one comes back,
2697  * restore their cpu bindings.
2698  */
2699 static int kcompactd_cpu_online(unsigned int cpu)
2700 {
2701         int nid;
2702
2703         for_each_node_state(nid, N_MEMORY) {
2704                 pg_data_t *pgdat = NODE_DATA(nid);
2705                 const struct cpumask *mask;
2706
2707                 mask = cpumask_of_node(pgdat->node_id);
2708
2709                 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2710                         /* One of our CPUs online: restore mask */
2711                         set_cpus_allowed_ptr(pgdat->kcompactd, mask);
2712         }
2713         return 0;
2714 }
2715
2716 static int __init kcompactd_init(void)
2717 {
2718         int nid;
2719         int ret;
2720
2721         ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
2722                                         "mm/compaction:online",
2723                                         kcompactd_cpu_online, NULL);
2724         if (ret < 0) {
2725                 pr_err("kcompactd: failed to register hotplug callbacks.\n");
2726                 return ret;
2727         }
2728
2729         for_each_node_state(nid, N_MEMORY)
2730                 kcompactd_run(nid);
2731         return 0;
2732 }
2733 subsys_initcall(kcompactd_init)
2734
2735 #endif /* CONFIG_COMPACTION */