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block: Change elevator_init_mq() to always succeed

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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>
This commit is contained in:
Damien Le Moal 2019-09-05 18:51:30 +09:00 committed by Jens Axboe
parent 61db437d1c
commit 954b4a5ce4
3 changed files with 14 additions and 19 deletions
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8
block/blk-mq.c
View File

@ -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;

2
block/blk.h
View File

@ -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 *);

23
block/elevator.c
View File

@ -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;
}
}