1 files changed, 20 insertions, 0 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a388888b6fcf..d3c5de47ff6d 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1005,6 +1005,26 @@ int do_migrate_pages(struct mm_struct *mm,
                 int dest = 0;
 
                 for_each_node_mask(s, tmp) {
+
+                        /*
+                         * do_migrate_pages() tries to maintain the relative
+                         * node relationship of the pages established between
+                         * threads and memory areas.
+                         *
+                         * However if the number of source nodes is not equal to
+                         * the number of destination nodes we can not preserve
+                         * this node relative relationship.  In that case, skip
+                         * copying memory from a node that is in the destination
+                         * mask.
+                         *
+                         * Example: [2,3,4] -> [3,4,5] moves everything.
+                         *          [0-7] - > [3,4,5] moves only 0,1,2,6,7.
+                         */
+
+                        if ((nodes_weight(*from_nodes) != nodes_weight(*to_nodes)) &&
+                                                (node_isset(s, *to_nodes)))
+                                continue;
+
                         d = node_remap(s, *from_nodes, *to_nodes);
                         if (s == d)
                                 continue;