1 files changed, 13 insertions, 3 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f65c6f01c475..9eba291eb6fd 100644
--- a/block/cfq-iosched.c
+++ b/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 */