1 files changed, 9 insertions, 1 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 381b09bb562b..a89043a3caa4 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -168,7 +168,15 @@ static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
          * tree of blkg (instead of traversing through hash list all
          * the time.
          */
-        tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
+
+        /*
+         * This is the common case when there are no blkio cgroups.
+         * Avoid lookup in this case
+         */
+        if (blkcg == &blkio_root_cgroup)
+                tg = &td->root_tg;
+        else
+                tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
 
         /* Fill in device details for root group */
         if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {