Memoryless nodes: Fix interleave behavior for memoryless nodes

MPOL_INTERLEAVE currently simply loops over all nodes.  Allocations on
memoryless nodes will be redirected to nodes with memory.  This results in an
imbalance because the neighboring nodes to memoryless nodes will get
significantly more interleave hits that the rest of the nodes on the system.

We can avoid this imbalance by clearing the nodes in the interleave node set
that have no memory.  If we use the node map of the memory nodes instead of
the online nodes then we have only the nodes we want.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NNishanth Aravamudan <nacc@us.ibm.com>
Tested-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: NBob Picco <bob.picco@hp.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@skynet.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

@@ -183,7 +183,9 @@ static struct mempolicy *mpol_new(int mode, nodemask_t *nodes)
 	switch (mode) {
 	case MPOL_INTERLEAVE:
 		policy->v.nodes = *nodes;
-		if (nodes_weight(*nodes) == 0) {
+		nodes_and(policy->v.nodes, policy->v.nodes,
+					node_states[N_HIGH_MEMORY]);
+		if (nodes_weight(policy->v.nodes) == 0) {
 			kmem_cache_free(policy_cache, policy);
 			return ERR_PTR(-EINVAL);
 		}