blkcg: fix blkcg->css ref leak in __blkg_lookup_create()

__blkg_lookup_create() leaked blkcg->css ref if blkg allocation
failed.  Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 10 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 82283859727..30a7a9c58b3 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -174,6 +174,7 @@ static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
         __releases(q->queue_lock) __acquires(q->queue_lock)
 {
         struct blkcg_gq *blkg;
+        int ret;
 
         WARN_ON_ONCE(!rcu_read_lock_held());
         lockdep_assert_held(q->queue_lock);
@@ -186,24 +187,22 @@ static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
         if (!css_tryget(&blkcg->css))
                 return ERR_PTR(-EINVAL);
 
-        /*
-         * Allocate and initialize.
-         */
+        /* allocate */
+        ret = -ENOMEM;
         blkg = blkg_alloc(blkcg, q);
-
-        /* did alloc fail? */
-        if (unlikely(!blkg)) {
-                blkg = ERR_PTR(-ENOMEM);
-                goto out;
-        }
+        if (unlikely(!blkg))
+                goto err_put;
 
         /* insert */
         spin_lock(&blkcg->lock);
         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
         list_add(&blkg->q_node, &q->blkg_list);
         spin_unlock(&blkcg->lock);
-out:
         return blkg;
+
+err_put:
+        css_put(&blkcg->css);
+        return ERR_PTR(ret);
 }
 
 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,