1 files changed, 18 insertions, 0 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 24597309e23d..b26ed58899fe 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -94,8 +94,13 @@ struct blkcg_gq {
         struct list_head                q_node;
         struct hlist_node               blkcg_node;
         struct blkcg                    *blkcg;
+
+        /* all non-root blkcg_gq's are guaranteed to have access to parent */
+        struct blkcg_gq                 *parent;
+
         /* request allocation list for this blkcg-q pair */
         struct request_list             rl;
+
         /* reference count */
         int                             refcnt;
 
@@ -181,6 +186,19 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
 }
 
 /**
+ * blkcg_parent - get the parent of a blkcg
+ * @blkcg: blkcg of interest
+ *
+ * Return the parent blkcg of @blkcg.  Can be called anytime.
+ */
+static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
+{
+        struct cgroup *pcg = blkcg->css.cgroup->parent;
+
+        return pcg ? cgroup_to_blkcg(pcg) : NULL;
+}
+
+/**
  * blkg_to_pdata - get policy private data
  * @blkg: blkg of interest
  * @pol: policy of interest