diff options
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index b69b7dac0361..b9cf751cc00e 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -313,8 +313,15 @@ static inline bool compact_should_abort(struct compact_control *cc) static bool suitable_migration_target(struct page *page) { /* If the page is a large free page, then disallow migration */ - if (PageBuddy(page) && page_order(page) >= pageblock_order) - return false; + if (PageBuddy(page)) { + /* + * We are checking page_order without zone->lock taken. But + * the only small danger is that we skip a potentially suitable + * pageblock, so it's not worth to check order for valid range. + */ + if (page_order_unsafe(page) >= pageblock_order) + return false; + } /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ if (migrate_async_suitable(get_pageblock_migratetype(page))) @@ -608,11 +615,23 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, valid_page = page; /* - * Skip if free. page_order cannot be used without zone->lock - * as nothing prevents parallel allocations or buddy merging. + * Skip if free. We read page order here without zone lock + * which is generally unsafe, but the race window is small and + * the worst thing that can happen is that we skip some + * potential isolation targets. */ - if (PageBuddy(page)) + if (PageBuddy(page)) { + unsigned long freepage_order = page_order_unsafe(page); + + /* + * Without lock, we cannot be sure that what we got is + * a valid page order. Consider only values in the + * valid order range to prevent low_pfn overflow. + */ + if (freepage_order > 0 && freepage_order < MAX_ORDER) + low_pfn += (1UL << freepage_order) - 1; continue; + } /* * Check may be lockless but that's ok as we recheck later. @@ -698,6 +717,13 @@ isolate_success: } } + /* + * The PageBuddy() check could have potentially brought us outside + * the range to be scanned. + */ + if (unlikely(low_pfn > end_pfn)) + low_pfn = end_pfn; + if (locked) spin_unlock_irqrestore(&zone->lru_lock, flags); |