Commit 954b4a5c authored by Damien Le Moal's avatar Damien Le Moal Committed by Jens Axboe
Browse files

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: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 61db437d

block/blk-mq.c

+1 −7
Original line number Diff line number Diff line
@@ -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;

block/blk.h

+1 −1
Original line number Diff line number Diff line
@@ -184,7 +184,7 @@ void blk_account_io_done(struct request *req, u64 now); 


void blk_insert_flush(struct request *rq);



int elevator_init_mq(struct request_queue *q);

void elevator_init_mq(struct request_queue *q);

int elevator_switch_mq(struct request_queue *q,

			      struct elevator_type *new_e);

void __elevator_exit(struct request_queue *, struct elevator_queue *);

block/elevator.c

+12 −11
Original line number Diff line number Diff line
@@ -628,34 +628,35 @@ static inline bool elv_support_iosched(struct request_queue *q) 


/*

 * For blk-mq devices supporting IO scheduling, we default to using mq-deadline,

 * if available, for single queue devices. If deadline isn't available OR we

 * have multiple queues, default to "none".

 * if available, for single queue devices. If deadline isn't available OR

 * deadline initialization fails OR we have multiple queues, default to "none".

 */

int elevator_init_mq(struct request_queue *q)

void elevator_init_mq(struct request_queue *q)

{

	struct elevator_type *e;

	int err = 0;

	int err;



	if (!elv_support_iosched(q))

		return 0;

		return;



	if (q->nr_hw_queues != 1)

		return 0;

		return;



	WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags));



	if (unlikely(q->elevator))

		goto out;

		return;



	e = elevator_get(q, "mq-deadline", false);

	if (!e)

		goto out;

		return;



	err = blk_mq_init_sched(q, e);

	if (err)

	if (err) {

		pr_warn("\"%s\" elevator initialization failed, "

			"falling back to \"none\"\n", e->elevator_name);

		elevator_put(e);

out:

	return err;

	}

}