[PATCH 3/6] mm: page_alloc: move free pages when converting block during isolation

[Johannes Weiner <hannes@cmpxchg.org>]

When claiming a block during compaction isolation, move any remaining
free pages to the correct freelists as well, instead of stranding them
on the wrong list. Otherwise, this encourages incompatible page mixing
down the line, and thus long-term fragmentation.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/page_alloc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3db405414174..f6f658c3d394 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2548,9 +2548,12 @@ int __isolate_free_page(struct page *page, unsigned int order)
 			 * Only change normal pageblocks (i.e., they can merge
 			 * with others)
 			 */
-			if (migratetype_is_mergeable(mt))
+			if (migratetype_is_mergeable(mt)) {
 				set_pageblock_migratetype(page,
 							  MIGRATE_MOVABLE);
+				move_freepages_block(zone, page,
+						     MIGRATE_MOVABLE, NULL);
+			}
 		}
 	}
 
-- 
2.42.0