mm: migrate: Drop the misplaced pages reference count if the target node is full

If we have to avoid migrating to a node that is nearly full, put page
and return zero.

Signed-off-by: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>

1 files changed, 10 insertions, 7 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index d168aec98427..c7d550011a64 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1489,18 +1489,21 @@ int migrate_misplaced_page(struct page *page, int node)
                 }
                 isolated = 1;
 
-                /*
-                 * Page is isolated which takes a reference count so now the
-                 * callers reference can be safely dropped without the page
-                 * disappearing underneath us during migration
-                 */
-                put_page(page);
-
                 page_lru = page_is_file_cache(page);
                 inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
                 list_add(&page->lru, &migratepages);
         }
 
+        /*
+         * Page is either isolated or there is not enough space on the target
+         * node. If isolated, then it has taken a reference count and the
+         * callers reference can be safely dropped without the page
+         * disappearing underneath us during migration. Otherwise the page is
+         * not to be migrated but the callers reference should still be
+         * dropped so it does not leak.
+         */
+        put_page(page);
+
         if (isolated) {
                 int nr_remaining;