1 files changed, 10 insertions, 0 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index cafcd7431189..d0b770391ad4 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -285,6 +285,13 @@ static void blkg_destroy_all(struct request_queue *q)
                 blkg_destroy(blkg);
                 spin_unlock(&blkcg->lock);
         }
+
+        /*
+         * root blkg is destroyed.  Just clear the pointer since
+         * root_rl does not take reference on root blkg.
+         */
+        q->root_blkg = NULL;
+        q->root_rl.blkg = NULL;
 }
 
 static void blkg_rcu_free(struct rcu_head *rcu_head)
@@ -326,6 +333,9 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl,
          */
         if (rl == &q->root_rl) {
                 ent = &q->blkg_list;
+                /* There are no more block groups, hence no request lists */
+                if (list_empty(ent))
+                        return NULL;
         } else {
                 blkg = container_of(rl, struct blkcg_gq, rl);
                 ent = &blkg->q_node;