memcg: fix oom killing a child process in an other cgroup

Presently the oom-killer is memcg aware and it finds the worst process
from processes under memcg(s) in oom.  Then, it kills victim's child
first.

It may kill a child in another cgroup and may not be any help for
recovery.  And it will break the assumption users have.

This patch fixes it.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
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/mm/oom_kill.c b/mm/oom_kill.c
index f52481b1c1e5..237050478f28 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -459,6 +459,8 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
         list_for_each_entry(c, &p->children, sibling) {
                 if (c->mm == p->mm)
                         continue;
+                if (mem && !task_in_mem_cgroup(c, mem))
+                        continue;
                 if (!oom_kill_task(c))
                         return 0;
         }