Memoryless nodes: OOM: use N_HIGH_MEMORY map instead of constructing one on the fly

constrained_alloc() builds its own memory map for nodes with memory.  We have
that available in N_HIGH_MEMORY now.  So simplify the code.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>
Acked-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Bob Picco <bob.picco@hp.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@skynet.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -177,14 +177,7 @@ static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
 {
 #ifdef CONFIG_NUMA
 	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)
-			node_set(node, nodes);
+	nodemask_t nodes = node_states[N_HIGH_MEMORY];
 
 	for (z = zonelist->zones; *z; z++)
 		if (cpuset_zone_allowed_softwall(*z, gfp_mask))