memcg: fix css_id() RCU locking for real

[mv-sheeva.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f4ede99c8b9b5671841021afe04d82bd32dfbda0..595d03f33b2c014aa31def364e2f3df24a4d2727 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -811,10 +811,12 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
         * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
         * hierarchy(even if use_hierarchy is disabled in "mem").
         */
+       rcu_read_lock();
        if (mem->use_hierarchy)
                ret = css_is_ancestor(&curr->css, &mem->css);
        else
                ret = (curr == mem);
+       rcu_read_unlock();
        css_put(&curr->css);
        return ret;
 }
@@ -2429,11 +2431,11 @@ int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
        }
        unlock_page_cgroup(pc);
 
+       *ptr = mem;
        if (mem) {
-               ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false);
+               ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false);
                css_put(&mem->css);
        }
-       *ptr = mem;
        return ret;
 }