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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>
This commit is contained in:
Jun'ichi Nomura 2012-10-22 10:15:37 +09:00 committed by Jens Axboe
parent 65635cbc37
commit 65c77fd9e8
1 changed files with 3 additions and 0 deletions
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3
block/blk-cgroup.c
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@ -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;