memcg: use find_lock_task_mm() in memory cgroups oom

When the OOM killer scans task, it check a task is under memcg or
not when it's called via memcg's context.

But, as Oleg pointed out, a thread group leader may have NULL ->mm
and task_in_mem_cgroup() may do wrong decision. We have to use
find_lock_task_mm() in memcg as generic OOM-Killer does.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/oom.h b/include/linux/oom.h
index f209b683e118..5e3aa8311c5e 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -66,6 +66,8 @@ static inline void oom_killer_enable(void)
 extern unsigned long badness(struct task_struct *p, struct mem_cgroup *mem,
                       const nodemask_t *nodemask, unsigned long uptime);
 
+extern struct task_struct *find_lock_task_mm(struct task_struct *p);
+
 /* sysctls */
 extern int sysctl_oom_dump_tasks;
 extern int sysctl_oom_kill_allocating_task;