blkcg: stop iteration early if root_rl is the only request list

__blk_queue_next_rl() finds next request list based on blkg_list while skipping root_blkg in the list. OTOH, root_rl is special as it may exist even without root_blkg. Though the later part of the function handles such a case correctly, exiting early is good for readability of the code. Signed-off-by: Jun'ichi Nomura <[email protected]> Cc: Tejun Heo <[email protected]> Acked-by: Vivek Goyal <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
btm · Oct 22, 2012 · 65c77fd · 65c77fd
1 parent 65635cb
commit 65c77fd
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
@@ -333,6 +333,9 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl,
 	 */
 	if (rl == &q->root_rl) {
 		ent = &q->blkg_list;
+		/* There are no more block groups, hence no request lists */
+		if (list_empty(ent))
+			return NULL;
 	} else {
 		blkg = container_of(rl, struct blkcg_gq, rl);
 		ent = &blkg->q_node;