[PATCH] NUMA fixes

From: Anton Blanchard <anton@samba.org>


Anton has been testing odd setups:

/* node 0 - no cpus, no memory */
/* node 1 - 1 cpu, no memory */
/* node 2 - 0 cpus, 1GB memory */
/* node 3 - 3 cpus, 3GB memory */

Two things tripped so far.  Firstly the ppc64 debug check for invalid cpus
in cpu_to_node().  Fix that in kernel/sched.c:node_nr_running_init().

The other problem concerned nodes with memory but no cpus.  kswapd tries to
set_cpus_allowed(0) and bad things happen.  So we only set cpu affinity
for kswapd if there are cpus in the node.

kernel/sched.c

@@ -219,8 +219,11 @@ __init void node_nr_running_init(void)
 {
 	int i;
 
-	for (i = 0; i < NR_CPUS; i++)
-		cpu_rq(i)->node_nr_running = &node_nr_running[cpu_to_node(i)];
+	for (i = 0; i < NR_CPUS; i++) {
+		if (cpu_possible(i))
+			cpu_rq(i)->node_nr_running =
+				&node_nr_running[cpu_to_node(i)];
+	}
 }
 
 #else /* !CONFIG_NUMA */

mm/vmscan.c

@@ -956,9 +956,12 @@ int kswapd(void *p)
 	struct reclaim_state reclaim_state = {
 		.reclaimed_slab = 0,
 	};
+	unsigned long cpumask;
 
 	daemonize("kswapd%d", pgdat->node_id);
-	set_cpus_allowed(tsk, node_to_cpumask(pgdat->node_id));
+	cpumask = node_to_cpumask(pgdat->node_id);
+	if (cpumask)
+		set_cpus_allowed(tsk, cpumask);
 	current->reclaim_state = &reclaim_state;
 
 	/*