From: Hugh Dickins <hugh@veritas.com>
Date: Tue, 12 Aug 2008 22:08:41 +0000 (-0700)
Subject: memcg: fix oops in mem_cgroup_shrink_usage
X-Git-Tag: v2.6.27-rc3~38
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=9623e078c1f4692a91531af2f639ec8aff8f0472;p=linux-2.6-omap-h63xx.git

memcg: fix oops in mem_cgroup_shrink_usage

Got an oops in mem_cgroup_shrink_usage() when testing loop over tmpfs:
yes, of course, loop0 has no mm: other entry points check but this didn't.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7056c3bdb47..0f1f7a7374b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -796,6 +796,8 @@ int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
 
 	if (mem_cgroup_subsys.disabled)
 		return 0;
+	if (!mm)
+		return 0;
 
 	rcu_read_lock();
 	mem = mem_cgroup_from_task(rcu_dereference(mm->owner));