[PATCH 4.19 46/97] mm/memcontrol.c: lost css_put in memcg_expand_shrinker_maps()

[Greg Kroah-Hartman]

From: Vasily Averin <vvs@xxxxxxxxxxxxx>

commit 75866af62b439859d5146b7093ceb6b482852683 upstream.

for_each_mem_cgroup() increases css reference counter for memory cgroup
and requires to use mem_cgroup_iter_break() if the walk is cancelled.

Link: http://lkml.kernel.org/r/c98414fb-7e1f-da0f-867a-9340ec4bd30b@xxxxxxxxxxxxx
Fixes: 0a4465d34028 ("mm, memcg: assign memcg-aware shrinkers bitmap to memcg")
Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Acked-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Roman Gushchin <guro@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/memcontrol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -419,8 +419,10 @@ int memcg_expand_shrinker_maps(int new_i
 		if (mem_cgroup_is_root(memcg))
 			continue;
 		ret = memcg_expand_one_shrinker_map(memcg, size, old_size);
-		if (ret)
+		if (ret) {
+			mem_cgroup_iter_break(NULL, memcg);
 			goto unlock;
+		}
 	}
 unlock:
 	if (!ret)