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-rw-r--r--block/blk-throttle.c10
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)) {