From: Sha Zhengju <redacted>

We should call mem_cgroup_begin_update_page_stat() before
mem_cgroup_update_page_stat() to get proper locks, however the
latter doesn't do any checking that we use proper locking, which
would be hard. Suggested by Michal Hock we could at least test for
rcu_read_lock_held() because RCU is held if !mem_cgroup_disabled().

Signed-off-by: Sha Zhengju <redacted>
Acked-by: Michal Hocko <redacted>
Reviewed-by: Greg Thelen <redacted>
---
 mm/memcontrol.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 24d6d02..0a50871 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -2249,6 +2249,7 @@ void mem_cgroup_update_page_stat(struct page *page,
 	if (mem_cgroup_disabled())
 		return;
 
+	VM_BUG_ON(!rcu_read_lock_held());
 	memcg = pc->mem_cgroup;
 	if (unlikely(!memcg || !PageCgroupUsed(pc)))
 		return;

-- 
1.7.9.5

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>