[PATCH] mm/compactoin: Fix edge case of fast_find_migrateblock()
From: Wonhyuk Yang <hidden>
Date: 2021-01-23 15:43:25
Subsystem:
memory management, memory management - page allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Linus Torvalds
In the fast_find_migrateblock(), It iterate freelist to find
proper pageblock. But there are two edge cases. First, if the page
we found is equal to cc->migrate_pfn, it is considered that we
didn't found suitable pageblock. Second, if the loop was terminated
because order is less than PAGE_ALLOC_COSTLY_ORDER, it could
be considered that we found suitable one.
Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate
a migration source")
Signed-off-by: Wonhyuk Yang <redacted>
---
mm/compaction.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index e5acb9714436..46f49e6b7d1a 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c@@ -1742,8 +1742,8 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) distance >>= 2; high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); - for (order = cc->order - 1; - order >= PAGE_ALLOC_COSTLY_ORDER && pfn == cc->migrate_pfn && nr_scanned < limit; + for (order = cc->order - 1, pfn = high_pfn; + order >= PAGE_ALLOC_COSTLY_ORDER && pfn == high_pfn && nr_scanned < limit; order--) { struct free_area *area = &cc->zone->free_area[order]; struct list_head *freelist;
@@ -1785,7 +1785,6 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) } if (nr_scanned >= limit) { - cc->fast_search_fail++; move_freelist_tail(freelist, freepage); break; }
@@ -1799,9 +1798,10 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) * If fast scanning failed then use a cached entry for a page block * that had free pages as the basis for starting a linear scan. */ - if (pfn == cc->migrate_pfn) + if (pfn == high_pfn) { + cc->fast_search_fail++; pfn = reinit_migrate_pfn(cc); - + } return pfn; }
--
2.25.1