From: Wen Congyang <wency@cn.fujitsu.com>
Date: Fri, 7 Sep 2012 00:17:42 +0000 (+1000)
Subject: memory hotplug: reset pgdat->kswapd to NULL if creating kernel thread fails
X-Git-Tag: next-20120910~2^2~243
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=139ec1bdcc2fd2326556cb7b2e2ee6b8b158f820;p=karo-tx-linux.git

memory hotplug: reset pgdat->kswapd to NULL if creating kernel thread fails

If kthread_run() fails, pgdat->kswapd contains errno.  When we stop this
thread, we only check whether pgdat->kswapd is NULL and access it.  If it
contains errno, it will cause page fault.  Reset pgdat->kswapd to NULL
when creating kernel thread fails can avoid this problem.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8d01243d9560..99b434b674c0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3102,6 +3102,7 @@ int kswapd_run(int nid)
 		/* failure at boot is fatal */
 		BUG_ON(system_state == SYSTEM_BOOTING);
 		printk("Failed to start kswapd on node %d\n",nid);
+		pgdat->kswapd = NULL;
 		ret = -1;
 	}
 	return ret;