[PATCH] mm, compaction: fast_find_migrateblock() should return pfn in the target zone

[Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>]

Prevent returning a pfn outside the target zone in case that not
aligned with pageblock boundary.
Otherwise isolate_migratepages_block() would handle pages not in
the target zone.

Signed-off-by: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
---
 mm/compaction.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index fe915db6149b..de42b8e48758 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1858,6 +1858,8 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
 
 				update_fast_start_pfn(cc, free_pfn);
 				pfn = pageblock_start_pfn(free_pfn);
+				if (pfn < cc->zone->zone_start_pfn)
+					pfn = cc->zone->zone_start_pfn;
 				cc->fast_search_fail = 0;
 				found_block = true;
 				set_pageblock_skip(freepage);
-- 
2.27.0