---

yaml
---
r: 210893
b: refs/heads/master
c: 180be2a
h: refs/heads/master
i:
  210891: 123f0c0
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a45dc2d2b8d1afa57c91dcfac224e50ffcd3f805
+refs/heads/master: 180be2a0420a0d680285e9352c0db85016b9ed2a

trunk/block/cfq-iosched.c

@@ -1019,10 +1019,20 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
 	 */
 	atomic_set(&cfqg->ref, 1);
 
-	/* Add group onto cgroup list */
-	sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-	cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+	/*
+	 * Add group onto cgroup list. It might happen that bdi->dev is
+	 * not initiliazed yet. Initialize this new group without major
+	 * and minor info and this info will be filled in once a new thread
+	 * comes for IO. See code above.
+	 */
+	if (bdi->dev) {
+		sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+		cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
 					MKDEV(major, minor));
+	} else
+		cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+					0);
+
 	cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
 
 	/* Add group on cfqd list */