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>
diff --git a/block/elevator.c b/block/elevator.c
index 4721834..2944c12 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -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;
+ }
}
