path: root/block
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authorJun'ichi Nomura <j-nomura@ce.jp.nec.com>2012-10-22 10:15:37 +0900
committerJens Axboe <axboe@kernel.dk>2012-10-22 22:00:26 +0200
commit65c77fd9e8a1c8c3da0bbbea6b7efa3d6ef265f8 (patch)
tree305b08304869b3f8d57a191b4b23968e53b53247 /block
parent65635cbc37e011e71b208257a25e7c1078cd039b (diff)
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 <j-nomura@ce.jp.nec.com> Cc: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
1 files changed, 3 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3ad5e3fbf579..d0b770391ad4 100644
--- 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;

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