Zone reclaim for headless nodes.

Zone reclaim is usually only run on the local node. Headless nodes do not have
any local processors. This patch checks for headless nodes and performs zone
reclaim on them.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.16-rc1-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.16-rc1-mm1.orig/mm/vmscan.c	2006-01-19 11:12:31.000000000 -0800
+++ linux-2.6.16-rc1-mm1/mm/vmscan.c	2006-01-19 11:18:37.000000000 -0800
@@ -1842,7 +1842,8 @@ int zone_reclaim(struct zone *zone, gfp_
 			return 0;
 
 	if (!(gfp_mask & __GFP_WAIT) ||
-		zone->zone_pgdat->node_id != numa_node_id() ||
+		(!cpus_empty(node_to_cpumask(zone->zone_pgdat->node_id)) &&
+			 zone->zone_pgdat->node_id != numa_node_id()) ||
 		zone->all_unreclaimable ||
 		atomic_read(&zone->reclaim_in_progress) > 0)
 			return 0;