block: Change elevator_init_mq() to always succeed

If the default elevator chosen is mq-deadline, elevator_init_mq() may
return an error if mq-deadline initialization fails, leading to
blk_mq_init_allocated_queue() returning an error, which in turn will
cause the block device initialization to fail and the device not being
exposed.

Instead of taking such extreme measure, handle mq-deadline
initialization failures in the same manner as when mq-deadline is not
available (no module to load), that is, default to the "none" scheduler.
With this change, elevator_init_mq() return type can be changed to void.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 7 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c3bd5b48a5b1..d10a7ab4207a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2848,8 +2848,6 @@ static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 						  struct request_queue *q)
 {
-	int ret = -ENOMEM;
-
 	/* mark the queue as mq asap */
 	q->mq_ops = set->ops;
 
@@ -2910,14 +2908,10 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	blk_mq_add_queue_tag_set(set, q);
 	blk_mq_map_swqueue(q);
 
-	ret = elevator_init_mq(q);
-	if (ret)
-		goto err_tag_set;
+	elevator_init_mq(q);
 
 	return q;
 
-err_tag_set:
-	blk_mq_del_queue_tag_set(q);
 err_hctxs:
 	kfree(q->queue_hw_ctx);
 	q->nr_hw_queues = 0;