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1/*
2 * linux/mm/compaction.c
3 *
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
6 * lifting
7 *
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
9 */
10#include <linux/swap.h>
11#include <linux/migrate.h>
12#include <linux/compaction.h>
13#include <linux/mm_inline.h>
14#include <linux/backing-dev.h>
15#include <linux/sysctl.h>
16#include <linux/sysfs.h>
17#include <linux/balloon_compaction.h>
18#include <linux/page-isolation.h>
19#include "internal.h"
20
21#ifdef CONFIG_COMPACTION
22static inline void count_compact_event(enum vm_event_item item)
23{
24 count_vm_event(item);
25}
26
27static inline void count_compact_events(enum vm_event_item item, long delta)
28{
29 count_vm_events(item, delta);
30}
31#else
32#define count_compact_event(item) do { } while (0)
33#define count_compact_events(item, delta) do { } while (0)
34#endif
35
36#if defined CONFIG_COMPACTION || defined CONFIG_CMA
37
38#define CREATE_TRACE_POINTS
39#include <trace/events/compaction.h>
40
41static unsigned long release_freepages(struct list_head *freelist)
42{
43 struct page *page, *next;
44 unsigned long count = 0;
45
46 list_for_each_entry_safe(page, next, freelist, lru) {
47 list_del(&page->lru);
48 __free_page(page);
49 count++;
50 }
51
52 return count;
53}
54
55static void map_pages(struct list_head *list)
56{
57 struct page *page;
58
59 list_for_each_entry(page, list, lru) {
60 arch_alloc_page(page, 0);
61 kernel_map_pages(page, 1, 1);
62 }
63}
64
65static inline bool migrate_async_suitable(int migratetype)
66{
67 return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
68}
69
70#ifdef CONFIG_COMPACTION
71/* Returns true if the pageblock should be scanned for pages to isolate. */
72static inline bool isolation_suitable(struct compact_control *cc,
73 struct page *page)
74{
75 if (cc->ignore_skip_hint)
76 return true;
77
78 return !get_pageblock_skip(page);
79}
80
81/*
82 * This function is called to clear all cached information on pageblocks that
83 * should be skipped for page isolation when the migrate and free page scanner
84 * meet.
85 */
86static void __reset_isolation_suitable(struct zone *zone)
87{
88 unsigned long start_pfn = zone->zone_start_pfn;
89 unsigned long end_pfn = zone_end_pfn(zone);
90 unsigned long pfn;
91
92 zone->compact_cached_migrate_pfn = start_pfn;
93 zone->compact_cached_free_pfn = end_pfn;
94 zone->compact_blockskip_flush = false;
95
96 /* Walk the zone and mark every pageblock as suitable for isolation */
97 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
98 struct page *page;
99
100 cond_resched();
101
102 if (!pfn_valid(pfn))
103 continue;
104
105 page = pfn_to_page(pfn);
106 if (zone != page_zone(page))
107 continue;
108
109 clear_pageblock_skip(page);
110 }
111}
112
113void reset_isolation_suitable(pg_data_t *pgdat)
114{
115 int zoneid;
116
117 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
118 struct zone *zone = &pgdat->node_zones[zoneid];
119 if (!populated_zone(zone))
120 continue;
121
122 /* Only flush if a full compaction finished recently */
123 if (zone->compact_blockskip_flush)
124 __reset_isolation_suitable(zone);
125 }
126}
127
128/*
129 * If no pages were isolated then mark this pageblock to be skipped in the
130 * future. The information is later cleared by __reset_isolation_suitable().
131 */
132static void update_pageblock_skip(struct compact_control *cc,
133 struct page *page, unsigned long nr_isolated,
134 bool migrate_scanner)
135{
136 struct zone *zone = cc->zone;
137
138 if (cc->ignore_skip_hint)
139 return;
140
141 if (!page)
142 return;
143
144 if (!nr_isolated) {
145 unsigned long pfn = page_to_pfn(page);
146 set_pageblock_skip(page);
147
148 /* Update where compaction should restart */
149 if (migrate_scanner) {
150 if (!cc->finished_update_migrate &&
151 pfn > zone->compact_cached_migrate_pfn)
152 zone->compact_cached_migrate_pfn = pfn;
153 } else {
154 if (!cc->finished_update_free &&
155 pfn < zone->compact_cached_free_pfn)
156 zone->compact_cached_free_pfn = pfn;
157 }
158 }
159}
160#else
161static inline bool isolation_suitable(struct compact_control *cc,
162 struct page *page)
163{
164 return true;
165}
166
167static void update_pageblock_skip(struct compact_control *cc,
168 struct page *page, unsigned long nr_isolated,
169 bool migrate_scanner)
170{
171}
172#endif /* CONFIG_COMPACTION */
173
174static inline bool should_release_lock(spinlock_t *lock)
175{
176 return need_resched() || spin_is_contended(lock);
177}
178
179/*
180 * Compaction requires the taking of some coarse locks that are potentially
181 * very heavily contended. Check if the process needs to be scheduled or
182 * if the lock is contended. For async compaction, back out in the event
183 * if contention is severe. For sync compaction, schedule.
184 *
185 * Returns true if the lock is held.
186 * Returns false if the lock is released and compaction should abort
187 */
188static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
189 bool locked, struct compact_control *cc)
190{
191 if (should_release_lock(lock)) {
192 if (locked) {
193 spin_unlock_irqrestore(lock, *flags);
194 locked = false;
195 }
196
197 /* async aborts if taking too long or contended */
198 if (!cc->sync) {
199 cc->contended = true;
200 return false;
201 }
202
203 cond_resched();
204 }
205
206 if (!locked)
207 spin_lock_irqsave(lock, *flags);
208 return true;
209}
210
211static inline bool compact_trylock_irqsave(spinlock_t *lock,
212 unsigned long *flags, struct compact_control *cc)
213{
214 return compact_checklock_irqsave(lock, flags, false, cc);
215}
216
217/* Returns true if the page is within a block suitable for migration to */
218static bool suitable_migration_target(struct page *page)
219{
220 /* If the page is a large free page, then disallow migration */
221 if (PageBuddy(page) && page_order(page) >= pageblock_order)
222 return false;
223
224 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
225 if (migrate_async_suitable(get_pageblock_migratetype(page)))
226 return true;
227
228 /* Otherwise skip the block */
229 return false;
230}
231
232/*
233 * Isolate free pages onto a private freelist. If @strict is true, will abort
234 * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
235 * (even though it may still end up isolating some pages).
236 */
237static unsigned long isolate_freepages_block(struct compact_control *cc,
238 unsigned long blockpfn,
239 unsigned long end_pfn,
240 struct list_head *freelist,
241 bool strict)
242{
243 int nr_scanned = 0, total_isolated = 0;
244 struct page *cursor, *valid_page = NULL;
245 unsigned long flags;
246 bool locked = false;
247 bool checked_pageblock = false;
248
249 cursor = pfn_to_page(blockpfn);
250
251 /* Isolate free pages. */
252 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
253 int isolated, i;
254 struct page *page = cursor;
255
256 nr_scanned++;
257 if (!pfn_valid_within(blockpfn))
258 goto isolate_fail;
259
260 if (!valid_page)
261 valid_page = page;
262 if (!PageBuddy(page))
263 goto isolate_fail;
264
265 /*
266 * The zone lock must be held to isolate freepages.
267 * Unfortunately this is a very coarse lock and can be
268 * heavily contended if there are parallel allocations
269 * or parallel compactions. For async compaction do not
270 * spin on the lock and we acquire the lock as late as
271 * possible.
272 */
273 locked = compact_checklock_irqsave(&cc->zone->lock, &flags,
274 locked, cc);
275 if (!locked)
276 break;
277
278 /* Recheck this is a suitable migration target under lock */
279 if (!strict && !checked_pageblock) {
280 /*
281 * We need to check suitability of pageblock only once
282 * and this isolate_freepages_block() is called with
283 * pageblock range, so just check once is sufficient.
284 */
285 checked_pageblock = true;
286 if (!suitable_migration_target(page))
287 break;
288 }
289
290 /* Recheck this is a buddy page under lock */
291 if (!PageBuddy(page))
292 goto isolate_fail;
293
294 /* Found a free page, break it into order-0 pages */
295 isolated = split_free_page(page);
296 total_isolated += isolated;
297 for (i = 0; i < isolated; i++) {
298 list_add(&page->lru, freelist);
299 page++;
300 }
301
302 /* If a page was split, advance to the end of it */
303 if (isolated) {
304 blockpfn += isolated - 1;
305 cursor += isolated - 1;
306 continue;
307 }
308
309isolate_fail:
310 if (strict)
311 break;
312 else
313 continue;
314
315 }
316
317 trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
318
319 /*
320 * If strict isolation is requested by CMA then check that all the
321 * pages requested were isolated. If there were any failures, 0 is
322 * returned and CMA will fail.
323 */
324 if (strict && blockpfn < end_pfn)
325 total_isolated = 0;
326
327 if (locked)
328 spin_unlock_irqrestore(&cc->zone->lock, flags);
329
330 /* Update the pageblock-skip if the whole pageblock was scanned */
331 if (blockpfn == end_pfn)
332 update_pageblock_skip(cc, valid_page, total_isolated, false);
333
334 count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
335 if (total_isolated)
336 count_compact_events(COMPACTISOLATED, total_isolated);
337 return total_isolated;
338}
339
340/**
341 * isolate_freepages_range() - isolate free pages.
342 * @start_pfn: The first PFN to start isolating.
343 * @end_pfn: The one-past-last PFN.
344 *
345 * Non-free pages, invalid PFNs, or zone boundaries within the
346 * [start_pfn, end_pfn) range are considered errors, cause function to
347 * undo its actions and return zero.
348 *
349 * Otherwise, function returns one-past-the-last PFN of isolated page
350 * (which may be greater then end_pfn if end fell in a middle of
351 * a free page).
352 */
353unsigned long
354isolate_freepages_range(struct compact_control *cc,
355 unsigned long start_pfn, unsigned long end_pfn)
356{
357 unsigned long isolated, pfn, block_end_pfn;
358 LIST_HEAD(freelist);
359
360 for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) {
361 if (!pfn_valid(pfn) || cc->zone != page_zone(pfn_to_page(pfn)))
362 break;
363
364 /*
365 * On subsequent iterations ALIGN() is actually not needed,
366 * but we keep it that we not to complicate the code.
367 */
368 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
369 block_end_pfn = min(block_end_pfn, end_pfn);
370
371 isolated = isolate_freepages_block(cc, pfn, block_end_pfn,
372 &freelist, true);
373
374 /*
375 * In strict mode, isolate_freepages_block() returns 0 if
376 * there are any holes in the block (ie. invalid PFNs or
377 * non-free pages).
378 */
379 if (!isolated)
380 break;
381
382 /*
383 * If we managed to isolate pages, it is always (1 << n) *
384 * pageblock_nr_pages for some non-negative n. (Max order
385 * page may span two pageblocks).
386 */
387 }
388
389 /* split_free_page does not map the pages */
390 map_pages(&freelist);
391
392 if (pfn < end_pfn) {
393 /* Loop terminated early, cleanup. */
394 release_freepages(&freelist);
395 return 0;
396 }
397
398 /* We don't use freelists for anything. */
399 return pfn;
400}
401
402/* Update the number of anon and file isolated pages in the zone */
403static void acct_isolated(struct zone *zone, bool locked, struct compact_control *cc)
404{
405 struct page *page;
406 unsigned int count[2] = { 0, };
407
408 list_for_each_entry(page, &cc->migratepages, lru)
409 count[!!page_is_file_cache(page)]++;
410
411 /* If locked we can use the interrupt unsafe versions */
412 if (locked) {
413 __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
414 __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
415 } else {
416 mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
417 mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
418 }
419}
420
421/* Similar to reclaim, but different enough that they don't share logic */
422static bool too_many_isolated(struct zone *zone)
423{
424 unsigned long active, inactive, isolated;
425
426 inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
427 zone_page_state(zone, NR_INACTIVE_ANON);
428 active = zone_page_state(zone, NR_ACTIVE_FILE) +
429 zone_page_state(zone, NR_ACTIVE_ANON);
430 isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
431 zone_page_state(zone, NR_ISOLATED_ANON);
432
433 return isolated > (inactive + active) / 2;
434}
435
436/**
437 * isolate_migratepages_range() - isolate all migrate-able pages in range.
438 * @zone: Zone pages are in.
439 * @cc: Compaction control structure.
440 * @low_pfn: The first PFN of the range.
441 * @end_pfn: The one-past-the-last PFN of the range.
442 * @unevictable: true if it allows to isolate unevictable pages
443 *
444 * Isolate all pages that can be migrated from the range specified by
445 * [low_pfn, end_pfn). Returns zero if there is a fatal signal
446 * pending), otherwise PFN of the first page that was not scanned
447 * (which may be both less, equal to or more then end_pfn).
448 *
449 * Assumes that cc->migratepages is empty and cc->nr_migratepages is
450 * zero.
451 *
452 * Apart from cc->migratepages and cc->nr_migratetypes this function
453 * does not modify any cc's fields, in particular it does not modify
454 * (or read for that matter) cc->migrate_pfn.
455 */
456unsigned long
457isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
458 unsigned long low_pfn, unsigned long end_pfn, bool unevictable)
459{
460 unsigned long last_pageblock_nr = 0, pageblock_nr;
461 unsigned long nr_scanned = 0, nr_isolated = 0;
462 struct list_head *migratelist = &cc->migratepages;
463 struct lruvec *lruvec;
464 unsigned long flags;
465 bool locked = false;
466 struct page *page = NULL, *valid_page = NULL;
467 bool skipped_async_unsuitable = false;
468 const isolate_mode_t mode = (!cc->sync ? ISOLATE_ASYNC_MIGRATE : 0) |
469 (unevictable ? ISOLATE_UNEVICTABLE : 0);
470
471 /*
472 * Ensure that there are not too many pages isolated from the LRU
473 * list by either parallel reclaimers or compaction. If there are,
474 * delay for some time until fewer pages are isolated
475 */
476 while (unlikely(too_many_isolated(zone))) {
477 /* async migration should just abort */
478 if (!cc->sync)
479 return 0;
480
481 congestion_wait(BLK_RW_ASYNC, HZ/10);
482
483 if (fatal_signal_pending(current))
484 return 0;
485 }
486
487 /* Time to isolate some pages for migration */
488 cond_resched();
489 for (; low_pfn < end_pfn; low_pfn++) {
490 /* give a chance to irqs before checking need_resched() */
491 if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
492 if (should_release_lock(&zone->lru_lock)) {
493 spin_unlock_irqrestore(&zone->lru_lock, flags);
494 locked = false;
495 }
496 }
497
498 /*
499 * migrate_pfn does not necessarily start aligned to a
500 * pageblock. Ensure that pfn_valid is called when moving
501 * into a new MAX_ORDER_NR_PAGES range in case of large
502 * memory holes within the zone
503 */
504 if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
505 if (!pfn_valid(low_pfn)) {
506 low_pfn += MAX_ORDER_NR_PAGES - 1;
507 continue;
508 }
509 }
510
511 if (!pfn_valid_within(low_pfn))
512 continue;
513 nr_scanned++;
514
515 /*
516 * Get the page and ensure the page is within the same zone.
517 * See the comment in isolate_freepages about overlapping
518 * nodes. It is deliberate that the new zone lock is not taken
519 * as memory compaction should not move pages between nodes.
520 */
521 page = pfn_to_page(low_pfn);
522 if (page_zone(page) != zone)
523 continue;
524
525 if (!valid_page)
526 valid_page = page;
527
528 /* If isolation recently failed, do not retry */
529 pageblock_nr = low_pfn >> pageblock_order;
530 if (last_pageblock_nr != pageblock_nr) {
531 int mt;
532
533 last_pageblock_nr = pageblock_nr;
534 if (!isolation_suitable(cc, page))
535 goto next_pageblock;
536
537 /*
538 * For async migration, also only scan in MOVABLE
539 * blocks. Async migration is optimistic to see if
540 * the minimum amount of work satisfies the allocation
541 */
542 mt = get_pageblock_migratetype(page);
543 if (!cc->sync && !migrate_async_suitable(mt)) {
544 cc->finished_update_migrate = true;
545 skipped_async_unsuitable = true;
546 goto next_pageblock;
547 }
548 }
549
550 /*
551 * Skip if free. page_order cannot be used without zone->lock
552 * as nothing prevents parallel allocations or buddy merging.
553 */
554 if (PageBuddy(page))
555 continue;
556
557 /*
558 * Check may be lockless but that's ok as we recheck later.
559 * It's possible to migrate LRU pages and balloon pages
560 * Skip any other type of page
561 */
562 if (!PageLRU(page)) {
563 if (unlikely(balloon_page_movable(page))) {
564 if (locked && balloon_page_isolate(page)) {
565 /* Successfully isolated */
566 goto isolate_success;
567 }
568 }
569 continue;
570 }
571
572 /*
573 * PageLRU is set. lru_lock normally excludes isolation
574 * splitting and collapsing (collapsing has already happened
575 * if PageLRU is set) but the lock is not necessarily taken
576 * here and it is wasteful to take it just to check transhuge.
577 * Check TransHuge without lock and skip the whole pageblock if
578 * it's either a transhuge or hugetlbfs page, as calling
579 * compound_order() without preventing THP from splitting the
580 * page underneath us may return surprising results.
581 */
582 if (PageTransHuge(page)) {
583 if (!locked)
584 goto next_pageblock;
585 low_pfn += (1 << compound_order(page)) - 1;
586 continue;
587 }
588
589 /*
590 * Migration will fail if an anonymous page is pinned in memory,
591 * so avoid taking lru_lock and isolating it unnecessarily in an
592 * admittedly racy check.
593 */
594 if (!page_mapping(page) &&
595 page_count(page) > page_mapcount(page))
596 continue;
597
598 /* Check if it is ok to still hold the lock */
599 locked = compact_checklock_irqsave(&zone->lru_lock, &flags,
600 locked, cc);
601 if (!locked || fatal_signal_pending(current))
602 break;
603
604 /* Recheck PageLRU and PageTransHuge under lock */
605 if (!PageLRU(page))
606 continue;
607 if (PageTransHuge(page)) {
608 low_pfn += (1 << compound_order(page)) - 1;
609 continue;
610 }
611
612 lruvec = mem_cgroup_page_lruvec(page, zone);
613
614 /* Try isolate the page */
615 if (__isolate_lru_page(page, mode) != 0)
616 continue;
617
618 VM_BUG_ON_PAGE(PageTransCompound(page), page);
619
620 /* Successfully isolated */
621 del_page_from_lru_list(page, lruvec, page_lru(page));
622
623isolate_success:
624 cc->finished_update_migrate = true;
625 list_add(&page->lru, migratelist);
626 cc->nr_migratepages++;
627 nr_isolated++;
628
629 /* Avoid isolating too much */
630 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
631 ++low_pfn;
632 break;
633 }
634
635 continue;
636
637next_pageblock:
638 low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1;
639 }
640
641 acct_isolated(zone, locked, cc);
642
643 if (locked)
644 spin_unlock_irqrestore(&zone->lru_lock, flags);
645
646 /*
647 * Update the pageblock-skip information and cached scanner pfn,
648 * if the whole pageblock was scanned without isolating any page.
649 * This is not done when pageblock was skipped due to being unsuitable
650 * for async compaction, so that eventual sync compaction can try.
651 */
652 if (low_pfn == end_pfn && !skipped_async_unsuitable)
653 update_pageblock_skip(cc, valid_page, nr_isolated, true);
654
655 trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
656
657 count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
658 if (nr_isolated)
659 count_compact_events(COMPACTISOLATED, nr_isolated);
660
661 return low_pfn;
662}
663
664#endif /* CONFIG_COMPACTION || CONFIG_CMA */
665#ifdef CONFIG_COMPACTION
666/*
667 * Based on information in the current compact_control, find blocks
668 * suitable for isolating free pages from and then isolate them.
669 */
670static void isolate_freepages(struct zone *zone,
671 struct compact_control *cc)
672{
673 struct page *page;
674 unsigned long high_pfn, low_pfn, pfn, z_end_pfn;
675 int nr_freepages = cc->nr_freepages;
676 struct list_head *freelist = &cc->freepages;
677
678 /*
679 * Initialise the free scanner. The starting point is where we last
680 * successfully isolated from, zone-cached value, or the end of the
681 * zone when isolating for the first time. We need this aligned to
682 * the pageblock boundary, because we do pfn -= pageblock_nr_pages
683 * in the for loop.
684 * The low boundary is the end of the pageblock the migration scanner
685 * is using.
686 */
687 pfn = cc->free_pfn & ~(pageblock_nr_pages-1);
688 low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages);
689
690 /*
691 * Take care that if the migration scanner is at the end of the zone
692 * that the free scanner does not accidentally move to the next zone
693 * in the next isolation cycle.
694 */
695 high_pfn = min(low_pfn, pfn);
696
697 z_end_pfn = zone_end_pfn(zone);
698
699 /*
700 * Isolate free pages until enough are available to migrate the
701 * pages on cc->migratepages. We stop searching if the migrate
702 * and free page scanners meet or enough free pages are isolated.
703 */
704 for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages;
705 pfn -= pageblock_nr_pages) {
706 unsigned long isolated;
707 unsigned long end_pfn;
708
709 /*
710 * This can iterate a massively long zone without finding any
711 * suitable migration targets, so periodically check if we need
712 * to schedule.
713 */
714 cond_resched();
715
716 if (!pfn_valid(pfn))
717 continue;
718
719 /*
720 * Check for overlapping nodes/zones. It's possible on some
721 * configurations to have a setup like
722 * node0 node1 node0
723 * i.e. it's possible that all pages within a zones range of
724 * pages do not belong to a single zone.
725 */
726 page = pfn_to_page(pfn);
727 if (page_zone(page) != zone)
728 continue;
729
730 /* Check the block is suitable for migration */
731 if (!suitable_migration_target(page))
732 continue;
733
734 /* If isolation recently failed, do not retry */
735 if (!isolation_suitable(cc, page))
736 continue;
737
738 /* Found a block suitable for isolating free pages from */
739 isolated = 0;
740
741 /*
742 * Take care when isolating in last pageblock of a zone which
743 * ends in the middle of a pageblock.
744 */
745 end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn);
746 isolated = isolate_freepages_block(cc, pfn, end_pfn,
747 freelist, false);
748 nr_freepages += isolated;
749
750 /*
751 * Record the highest PFN we isolated pages from. When next
752 * looking for free pages, the search will restart here as
753 * page migration may have returned some pages to the allocator
754 */
755 if (isolated) {
756 cc->finished_update_free = true;
757 high_pfn = max(high_pfn, pfn);
758 }
759 }
760
761 /* split_free_page does not map the pages */
762 map_pages(freelist);
763
764 /*
765 * If we crossed the migrate scanner, we want to keep it that way
766 * so that compact_finished() may detect this
767 */
768 if (pfn < low_pfn)
769 cc->free_pfn = max(pfn, zone->zone_start_pfn);
770 else
771 cc->free_pfn = high_pfn;
772 cc->nr_freepages = nr_freepages;
773}
774
775/*
776 * This is a migrate-callback that "allocates" freepages by taking pages
777 * from the isolated freelists in the block we are migrating to.
778 */
779static struct page *compaction_alloc(struct page *migratepage,
780 unsigned long data,
781 int **result)
782{
783 struct compact_control *cc = (struct compact_control *)data;
784 struct page *freepage;
785
786 /* Isolate free pages if necessary */
787 if (list_empty(&cc->freepages)) {
788 isolate_freepages(cc->zone, cc);
789
790 if (list_empty(&cc->freepages))
791 return NULL;
792 }
793
794 freepage = list_entry(cc->freepages.next, struct page, lru);
795 list_del(&freepage->lru);
796 cc->nr_freepages--;
797
798 return freepage;
799}
800
801/*
802 * We cannot control nr_migratepages and nr_freepages fully when migration is
803 * running as migrate_pages() has no knowledge of compact_control. When
804 * migration is complete, we count the number of pages on the lists by hand.
805 */
806static void update_nr_listpages(struct compact_control *cc)
807{
808 int nr_migratepages = 0;
809 int nr_freepages = 0;
810 struct page *page;
811
812 list_for_each_entry(page, &cc->migratepages, lru)
813 nr_migratepages++;
814 list_for_each_entry(page, &cc->freepages, lru)
815 nr_freepages++;
816
817 cc->nr_migratepages = nr_migratepages;
818 cc->nr_freepages = nr_freepages;
819}
820
821/* possible outcome of isolate_migratepages */
822typedef enum {
823 ISOLATE_ABORT, /* Abort compaction now */
824 ISOLATE_NONE, /* No pages isolated, continue scanning */
825 ISOLATE_SUCCESS, /* Pages isolated, migrate */
826} isolate_migrate_t;
827
828/*
829 * Isolate all pages that can be migrated from the block pointed to by
830 * the migrate scanner within compact_control.
831 */
832static isolate_migrate_t isolate_migratepages(struct zone *zone,
833 struct compact_control *cc)
834{
835 unsigned long low_pfn, end_pfn;
836
837 /* Do not scan outside zone boundaries */
838 low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
839
840 /* Only scan within a pageblock boundary */
841 end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
842
843 /* Do not cross the free scanner or scan within a memory hole */
844 if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
845 cc->migrate_pfn = end_pfn;
846 return ISOLATE_NONE;
847 }
848
849 /* Perform the isolation */
850 low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn, false);
851 if (!low_pfn || cc->contended)
852 return ISOLATE_ABORT;
853
854 cc->migrate_pfn = low_pfn;
855
856 return ISOLATE_SUCCESS;
857}
858
859static int compact_finished(struct zone *zone,
860 struct compact_control *cc)
861{
862 unsigned int order;
863 unsigned long watermark;
864
865 if (fatal_signal_pending(current))
866 return COMPACT_PARTIAL;
867
868 /* Compaction run completes if the migrate and free scanner meet */
869 if (cc->free_pfn <= cc->migrate_pfn) {
870 /* Let the next compaction start anew. */
871 zone->compact_cached_migrate_pfn = zone->zone_start_pfn;
872 zone->compact_cached_free_pfn = zone_end_pfn(zone);
873
874 /*
875 * Mark that the PG_migrate_skip information should be cleared
876 * by kswapd when it goes to sleep. kswapd does not set the
877 * flag itself as the decision to be clear should be directly
878 * based on an allocation request.
879 */
880 if (!current_is_kswapd())
881 zone->compact_blockskip_flush = true;
882
883 return COMPACT_COMPLETE;
884 }
885
886 /*
887 * order == -1 is expected when compacting via
888 * /proc/sys/vm/compact_memory
889 */
890 if (cc->order == -1)
891 return COMPACT_CONTINUE;
892
893 /* Compaction run is not finished if the watermark is not met */
894 watermark = low_wmark_pages(zone);
895 watermark += (1 << cc->order);
896
897 if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
898 return COMPACT_CONTINUE;
899
900 /* Direct compactor: Is a suitable page free? */
901 for (order = cc->order; order < MAX_ORDER; order++) {
902 struct free_area *area = &zone->free_area[order];
903
904 /* Job done if page is free of the right migratetype */
905 if (!list_empty(&area->free_list[cc->migratetype]))
906 return COMPACT_PARTIAL;
907
908 /* Job done if allocation would set block type */
909 if (cc->order >= pageblock_order && area->nr_free)
910 return COMPACT_PARTIAL;
911 }
912
913 return COMPACT_CONTINUE;
914}
915
916/*
917 * compaction_suitable: Is this suitable to run compaction on this zone now?
918 * Returns
919 * COMPACT_SKIPPED - If there are too few free pages for compaction
920 * COMPACT_PARTIAL - If the allocation would succeed without compaction
921 * COMPACT_CONTINUE - If compaction should run now
922 */
923unsigned long compaction_suitable(struct zone *zone, int order)
924{
925 int fragindex;
926 unsigned long watermark;
927
928 /*
929 * order == -1 is expected when compacting via
930 * /proc/sys/vm/compact_memory
931 */
932 if (order == -1)
933 return COMPACT_CONTINUE;
934
935 /*
936 * Watermarks for order-0 must be met for compaction. Note the 2UL.
937 * This is because during migration, copies of pages need to be
938 * allocated and for a short time, the footprint is higher
939 */
940 watermark = low_wmark_pages(zone) + (2UL << order);
941 if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
942 return COMPACT_SKIPPED;
943
944 /*
945 * fragmentation index determines if allocation failures are due to
946 * low memory or external fragmentation
947 *
948 * index of -1000 implies allocations might succeed depending on
949 * watermarks
950 * index towards 0 implies failure is due to lack of memory
951 * index towards 1000 implies failure is due to fragmentation
952 *
953 * Only compact if a failure would be due to fragmentation.
954 */
955 fragindex = fragmentation_index(zone, order);
956 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
957 return COMPACT_SKIPPED;
958
959 if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
960 0, 0))
961 return COMPACT_PARTIAL;
962
963 return COMPACT_CONTINUE;
964}
965
966static int compact_zone(struct zone *zone, struct compact_control *cc)
967{
968 int ret;
969 unsigned long start_pfn = zone->zone_start_pfn;
970 unsigned long end_pfn = zone_end_pfn(zone);
971
972 ret = compaction_suitable(zone, cc->order);
973 switch (ret) {
974 case COMPACT_PARTIAL:
975 case COMPACT_SKIPPED:
976 /* Compaction is likely to fail */
977 return ret;
978 case COMPACT_CONTINUE:
979 /* Fall through to compaction */
980 ;
981 }
982
983 /*
984 * Clear pageblock skip if there were failures recently and compaction
985 * is about to be retried after being deferred. kswapd does not do
986 * this reset as it'll reset the cached information when going to sleep.
987 */
988 if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
989 __reset_isolation_suitable(zone);
990
991 /*
992 * Setup to move all movable pages to the end of the zone. Used cached
993 * information on where the scanners should start but check that it
994 * is initialised by ensuring the values are within zone boundaries.
995 */
996 cc->migrate_pfn = zone->compact_cached_migrate_pfn;
997 cc->free_pfn = zone->compact_cached_free_pfn;
998 if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
999 cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
1000 zone->compact_cached_free_pfn = cc->free_pfn;
1001 }
1002 if (cc->migrate_pfn < start_pfn || cc->migrate_pfn > end_pfn) {
1003 cc->migrate_pfn = start_pfn;
1004 zone->compact_cached_migrate_pfn = cc->migrate_pfn;
1005 }
1006
1007 trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn);
1008
1009 migrate_prep_local();
1010
1011 while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
1012 unsigned long nr_migrate, nr_remaining;
1013 int err;
1014
1015 switch (isolate_migratepages(zone, cc)) {
1016 case ISOLATE_ABORT:
1017 ret = COMPACT_PARTIAL;
1018 putback_movable_pages(&cc->migratepages);
1019 cc->nr_migratepages = 0;
1020 goto out;
1021 case ISOLATE_NONE:
1022 continue;
1023 case ISOLATE_SUCCESS:
1024 ;
1025 }
1026
1027 nr_migrate = cc->nr_migratepages;
1028 err = migrate_pages(&cc->migratepages, compaction_alloc,
1029 (unsigned long)cc,
1030 cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC,
1031 MR_COMPACTION);
1032 update_nr_listpages(cc);
1033 nr_remaining = cc->nr_migratepages;
1034
1035 trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
1036 nr_remaining);
1037
1038 /* Release isolated pages not migrated */
1039 if (err) {
1040 putback_movable_pages(&cc->migratepages);
1041 cc->nr_migratepages = 0;
1042 /*
1043 * migrate_pages() may return -ENOMEM when scanners meet
1044 * and we want compact_finished() to detect it
1045 */
1046 if (err == -ENOMEM && cc->free_pfn > cc->migrate_pfn) {
1047 ret = COMPACT_PARTIAL;
1048 goto out;
1049 }
1050 }
1051 }
1052
1053out:
1054 /* Release free pages and check accounting */
1055 cc->nr_freepages -= release_freepages(&cc->freepages);
1056 VM_BUG_ON(cc->nr_freepages != 0);
1057
1058 trace_mm_compaction_end(ret);
1059
1060 return ret;
1061}
1062
1063static unsigned long compact_zone_order(struct zone *zone,
1064 int order, gfp_t gfp_mask,
1065 bool sync, bool *contended)
1066{
1067 unsigned long ret;
1068 struct compact_control cc = {
1069 .nr_freepages = 0,
1070 .nr_migratepages = 0,
1071 .order = order,
1072 .migratetype = allocflags_to_migratetype(gfp_mask),
1073 .zone = zone,
1074 .sync = sync,
1075 };
1076 INIT_LIST_HEAD(&cc.freepages);
1077 INIT_LIST_HEAD(&cc.migratepages);
1078
1079 ret = compact_zone(zone, &cc);
1080
1081 VM_BUG_ON(!list_empty(&cc.freepages));
1082 VM_BUG_ON(!list_empty(&cc.migratepages));
1083
1084 *contended = cc.contended;
1085 return ret;
1086}
1087
1088int sysctl_extfrag_threshold = 500;
1089
1090/**
1091 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
1092 * @zonelist: The zonelist used for the current allocation
1093 * @order: The order of the current allocation
1094 * @gfp_mask: The GFP mask of the current allocation
1095 * @nodemask: The allowed nodes to allocate from
1096 * @sync: Whether migration is synchronous or not
1097 * @contended: Return value that is true if compaction was aborted due to lock contention
1098 * @page: Optionally capture a free page of the requested order during compaction
1099 *
1100 * This is the main entry point for direct page compaction.
1101 */
1102unsigned long try_to_compact_pages(struct zonelist *zonelist,
1103 int order, gfp_t gfp_mask, nodemask_t *nodemask,
1104 bool sync, bool *contended)
1105{
1106 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
1107 int may_enter_fs = gfp_mask & __GFP_FS;
1108 int may_perform_io = gfp_mask & __GFP_IO;
1109 struct zoneref *z;
1110 struct zone *zone;
1111 int rc = COMPACT_SKIPPED;
1112 int alloc_flags = 0;
1113
1114 /* Check if the GFP flags allow compaction */
1115 if (!order || !may_enter_fs || !may_perform_io)
1116 return rc;
1117
1118 count_compact_event(COMPACTSTALL);
1119
1120#ifdef CONFIG_CMA
1121 if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
1122 alloc_flags |= ALLOC_CMA;
1123#endif
1124 /* Compact each zone in the list */
1125 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1126 nodemask) {
1127 int status;
1128
1129 status = compact_zone_order(zone, order, gfp_mask, sync,
1130 contended);
1131 rc = max(status, rc);
1132
1133 /* If a normal allocation would succeed, stop compacting */
1134 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0,
1135 alloc_flags))
1136 break;
1137 }
1138
1139 return rc;
1140}
1141
1142
1143/* Compact all zones within a node */
1144static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
1145{
1146 int zoneid;
1147 struct zone *zone;
1148
1149 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
1150
1151 zone = &pgdat->node_zones[zoneid];
1152 if (!populated_zone(zone))
1153 continue;
1154
1155 cc->nr_freepages = 0;
1156 cc->nr_migratepages = 0;
1157 cc->zone = zone;
1158 INIT_LIST_HEAD(&cc->freepages);
1159 INIT_LIST_HEAD(&cc->migratepages);
1160
1161 if (cc->order == -1 || !compaction_deferred(zone, cc->order))
1162 compact_zone(zone, cc);
1163
1164 if (cc->order > 0) {
1165 if (zone_watermark_ok(zone, cc->order,
1166 low_wmark_pages(zone), 0, 0))
1167 compaction_defer_reset(zone, cc->order, false);
1168 /* Currently async compaction is never deferred. */
1169 else if (cc->sync)
1170 defer_compaction(zone, cc->order);
1171 }
1172
1173 VM_BUG_ON(!list_empty(&cc->freepages));
1174 VM_BUG_ON(!list_empty(&cc->migratepages));
1175 }
1176}
1177
1178void compact_pgdat(pg_data_t *pgdat, int order)
1179{
1180 struct compact_control cc = {
1181 .order = order,
1182 .sync = false,
1183 };
1184
1185 if (!order)
1186 return;
1187
1188 __compact_pgdat(pgdat, &cc);
1189}
1190
1191static void compact_node(int nid)
1192{
1193 struct compact_control cc = {
1194 .order = -1,
1195 .sync = true,
1196 .ignore_skip_hint = true,
1197 };
1198
1199 __compact_pgdat(NODE_DATA(nid), &cc);
1200}
1201
1202/* Compact all nodes in the system */
1203static void compact_nodes(void)
1204{
1205 int nid;
1206
1207 /* Flush pending updates to the LRU lists */
1208 lru_add_drain_all();
1209
1210 for_each_online_node(nid)
1211 compact_node(nid);
1212}
1213
1214/* The written value is actually unused, all memory is compacted */
1215int sysctl_compact_memory;
1216
1217/* This is the entry point for compacting all nodes via /proc/sys/vm */
1218int sysctl_compaction_handler(struct ctl_table *table, int write,
1219 void __user *buffer, size_t *length, loff_t *ppos)
1220{
1221 if (write)
1222 compact_nodes();
1223
1224 return 0;
1225}
1226
1227int sysctl_extfrag_handler(struct ctl_table *table, int write,
1228 void __user *buffer, size_t *length, loff_t *ppos)
1229{
1230 proc_dointvec_minmax(table, write, buffer, length, ppos);
1231
1232 return 0;
1233}
1234
1235#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
1236static ssize_t sysfs_compact_node(struct device *dev,
1237 struct device_attribute *attr,
1238 const char *buf, size_t count)
1239{
1240 int nid = dev->id;
1241
1242 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
1243 /* Flush pending updates to the LRU lists */
1244 lru_add_drain_all();
1245
1246 compact_node(nid);
1247 }
1248
1249 return count;
1250}
1251static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
1252
1253int compaction_register_node(struct node *node)
1254{
1255 return device_create_file(&node->dev, &dev_attr_compact);
1256}
1257
1258void compaction_unregister_node(struct node *node)
1259{
1260 return device_remove_file(&node->dev, &dev_attr_compact);
1261}
1262#endif /* CONFIG_SYSFS && CONFIG_NUMA */
1263
1264#endif /* CONFIG_COMPACTION */
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
29static inline void count_compact_event(enum vm_event_item item)
30{
31 count_vm_event(item);
32}
33
34static 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
53static 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
69static 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
96int 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}
110EXPORT_SYMBOL(PageMovable);
111
112void __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}
118EXPORT_SYMBOL(__SetPageMovable);
119
120void __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}
132EXPORT_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 */
142void 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 */
157bool 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 */
181void 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 */
195bool 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. */
205static 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
214static 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 */
227static 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
240static 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 */
317static 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
369void 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 */
388static 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
407static 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 */
428static 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
446static inline bool isolation_suitable(struct compact_control *cc,
447 struct page *page)
448{
449 return true;
450}
451
452static inline bool pageblock_skip_persistent(struct page *page)
453{
454 return false;
455}
456
457static inline void update_pageblock_skip(struct compact_control *cc,
458 struct page *page, unsigned long pfn)
459{
460}
461
462static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
463{
464}
465
466static 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 */
482static 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 */
512static 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 */
535static 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
629isolate_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 */
681unsigned long
682isolate_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 */
749static 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 */
781static unsigned long
782isolate_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
991isolate_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;
1009isolate_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
1045isolate_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
1066fatal_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 */
1084unsigned long
1085isolate_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
1123static 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 */
1143static 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
1168static inline unsigned int
1169freelist_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 */
1180static 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 */
1191static void
1192move_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 */
1209static void
1210move_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
1221static void
1222fast_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 */
1257static 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
1274static unsigned long
1275fast_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 */
1432static 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
1540splitmap:
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 */
1549static 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 */
1574static 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 */
1583typedef 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 */
1593int sysctl_compact_unevictable_allowed __read_mostly = 1;
1594
1595static inline void
1596update_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
1607static inline unsigned long
1608reinit_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 */
1624static 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 */
1741static 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 */
1844static inline bool is_via_compact_memory(int order)
1845{
1846 return order == -1;
1847}
1848
1849static 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
1939static 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 */
1958static 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
2001enum 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
2039bool 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
2071static enum compact_result
2072compact_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
2229check_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
2259out:
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
2288static 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
2327int 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 */
2339enum 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 */
2409static 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 */
2439static 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 */
2451int sysctl_compact_memory;
2452
2453/*
2454 * This is the entry point for compacting all nodes via
2455 * /proc/sys/vm/compact_memory
2456 */
2457int 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)
2467static 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}
2482static DEVICE_ATTR(compact, 0200, NULL, sysfs_compact_node);
2483
2484int compaction_register_node(struct node *node)
2485{
2486 return device_create_file(&node->dev, &dev_attr_compact);
2487}
2488
2489void 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
2495static inline bool kcompactd_work_requested(pg_data_t *pgdat)
2496{
2497 return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
2498}
2499
2500static 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
2520static 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
2598void 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 */
2628static 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 */
2662int 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 */
2683void 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 */
2699static 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
2716static 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}
2733subsys_initcall(kcompactd_init)
2734
2735#endif /* CONFIG_COMPACTION */