Fix panic of cpu online with memory less node

When a cpu is onlined on memory-less-node box, kernel panics due to touch
NULL pointer of pgdat->kswapd.  Current kswapd runs only nodes which have
memory.  So, calling of set_cpus_allowed() is not necessary for memory-less
node.

This is fix for it.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8fd8ba1c67b4..cb8ad3c6e483 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1694,9 +1694,11 @@ static int __devinit cpu_callback(struct notifier_block *nfb,
 {
         pg_data_t *pgdat;
         cpumask_t mask;
+        int nid;
 
         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
-                for_each_online_pgdat(pgdat) {
+                for_each_node_state(nid, N_HIGH_MEMORY) {
+                        pgdat = NODE_DATA(nid);
                         mask = node_to_cpumask(pgdat->node_id);
                         if (any_online_cpu(mask) != NR_CPUS)
                                 /* One of our CPUs online: restore mask */