fix OOM killing processes wrongly thought MPOL_BIND

I only have CONFIG_NUMA=y for build testing: surprised when trying a memhog
to see lots of other processes killed with "No available memory
(MPOL_BIND)".  memhog is killed correctly once we initialize nodemask in
constrained_alloc().
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Acked-by: NWilliam Irwin <bill.irwin@oracle.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -176,6 +176,8 @@ static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
 	struct zone **z;
 	nodemask_t nodes;
 	int node;
+
+	nodes_clear(nodes);
 	/* node has memory ? */
 	for_each_online_node(node)
 		if (NODE_DATA(node)->node_present_pages)