Commit f3bc78d2 authored Feb 28, 2018 by Damien Le Moal Committed by Jens Axboe Mar 01, 2018

mq-deadline: Make sure to always unlock zones



In case of a failed write request (all retries failed) and when using
libata, the SCSI error handler calls scsi_finish_command(). In the
case of blk-mq this means that scsi_mq_done() does not get called,
that blk_mq_complete_request() does not get called and also that the
mq-deadline .completed_request() method is not called. This results in
the target zone of the failed write request being left in a locked
state, preventing that any new write requests are issued to the same
zone.

Fix this by replacing the .completed_request() method with the
.finish_request() method as this method is always called whether or
not a request completes successfully. Since the .finish_request()
method is only called by the blk-mq core if a .prepare_request()
method exists, add a dummy .prepare_request() method.

Fixes: 5700f691 ("mq-deadline: Introduce zone locking support")
Cc: Hannes Reinecke <hare@suse.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
[ bvanassche: edited patch description ]
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 468f0987

block/mq-deadline.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -535,13 +535,22 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
		spin_unlock(&dd->lock);
		}

		/*
		* Nothing to do here. This is defined only to ensure that .finish_request
		* method is called upon request completion.
		*/
		static void dd_prepare_request(struct request rq, struct bio bio)
		{
		}

		/*
		* For zoned block devices, write unlock the target zone of
		* completed write requests. Do this while holding the zone lock
		* spinlock so that the zone is never unlocked while deadline_fifo_request()
		* while deadline_next_request() are executing.
		* or deadline_next_request() are executing. This function is called for
		* all requests, whether or not these requests complete successfully.
		*/
		static void dd_completed_request(struct request *rq)
		static void dd_finish_request(struct request *rq)
		{
		struct request_queue *q = rq->q;

		@@ -756,7 +765,8 @@ static struct elevator_type mq_deadline = {
		.ops.mq = {
		.insert_requests = dd_insert_requests,
		.dispatch_request = dd_dispatch_request,
		.completed_request = dd_completed_request,
		.prepare_request = dd_prepare_request,
		.finish_request = dd_finish_request,
		.next_request = elv_rb_latter_request,
		.former_request = elv_rb_former_request,
		.bio_merge = dd_bio_merge,

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