Re: [PATCH 7/8] mq-deadline: add blk-mq adaptation of the deadline IO scheduler
From: Paolo Valente <hidden>
Date: 2016-12-22 16:07:14
Also in:
lkml
Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe [off-list ref] ha =
scritto:
=20 This is basically identical to deadline-iosched, except it registers as a MQ capable scheduler. This is still a single queue design. =20 Signed-off-by: Jens Axboe <axboe@fb.com> ---
...
quoted hunk ↗ jump to hunk
diff --git a/block/mq-deadline.c b/block/mq-deadline.c new file mode 100644 index 000000000000..3cb9de21ab21 --- /dev/null +++ b/block/mq-deadline.c... +/* + * remove rq from rbtree and fifo. + */ +static void deadline_remove_request(struct request_queue *q, struct =
request *rq)
+{
+ struct deadline_data *dd =3D q->elevator->elevator_data;
+
+ list_del_init(&rq->queuelist);
+
+ /*
+ * We might not be on the rbtree, if we are doing an insert =merge
+ */ + if (!RB_EMPTY_NODE(&rq->rb_node)) + deadline_del_rq_rb(dd, rq); +
I've been scratching my head on the last three instructions, but at no avail. If I understand correctly, the list_del_init(&rq->queue list); removes rq from the fifo list. But, if so, I don't understand how it could be possible that rq has not been added to the rb_tree too. Another interpretation that I tried is that the above three lines handle correctly the following case where rq has not been inserted at all into deadline fifo queue and rb tree: when dd_insert_request was executed for rq, blk_mq_sched_try_insert_merge succeeded. Yet, the list_del_init(&rq->queue list); does not seem to make sense. Could you please shed some light on this for me? Thanks, Paolo