1 files changed, 8 insertions, 4 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 628e50f6f8a8..8e5863e900bf 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -179,21 +179,25 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 
 
+static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
+{
+        return css ? container_of(css, struct blkcg, css) : NULL;
+}
+
 static inline struct blkcg *cgroup_to_blkcg(struct cgroup *cgroup)
 {
-        return container_of(cgroup_css(cgroup, blkio_subsys_id),
-                            struct blkcg, css);
+        return css_to_blkcg(cgroup_css(cgroup, blkio_subsys_id));
 }
 
 static inline struct blkcg *task_blkcg(struct task_struct *tsk)
 {
-        return container_of(task_css(tsk, blkio_subsys_id), struct blkcg, css);
+        return css_to_blkcg(task_css(tsk, blkio_subsys_id));
 }
 
 static inline struct blkcg *bio_blkcg(struct bio *bio)
 {
         if (bio && bio->bi_css)
-                return container_of(bio->bi_css, struct blkcg, css);
+                return css_to_blkcg(bio->bi_css);
         return task_blkcg(current);
 }