Commit 1b8f21b7 authored Apr 09, 2019 by Ming Lei Committed by Jens Axboe Apr 10, 2019

blk-mq: introduce blk_mq_complete_request_sync()



In NVMe's error handler, follows the typical steps of tearing down
hardware for recovering controller:

1) stop blk_mq hw queues
2) stop the real hw queues
3) cancel in-flight requests via
	blk_mq_tagset_busy_iter(tags, cancel_request, ...)
cancel_request():
	mark the request as abort
	blk_mq_complete_request(req);
4) destroy real hw queues

However, there may be race between #3 and #4, because blk_mq_complete_request()
may run q->mq_ops->complete(rq) remotelly and asynchronously, and
->complete(rq) may be run after #4.

This patch introduces blk_mq_complete_request_sync() for fixing the
above race.

Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: James Smart <james.smart@broadcom.com>
Cc: linux-nvme@lists.infradead.org
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 1978f30a

block/blk-mq.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -654,6 +654,13 @@ bool blk_mq_complete_request(struct request *rq)
		}
		EXPORT_SYMBOL(blk_mq_complete_request);

		void blk_mq_complete_request_sync(struct request *rq)
		{
		WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
		rq->q->mq_ops->complete(rq);
		}
		EXPORT_SYMBOL_GPL(blk_mq_complete_request_sync);

		int blk_mq_request_started(struct request *rq)
		{
		return blk_mq_rq_state(rq) != MQ_RQ_IDLE;

include/linux/blk-mq.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -302,6 +302,7 @@ void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list);
		void blk_mq_kick_requeue_list(struct request_queue *q);
		void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
		bool blk_mq_complete_request(struct request *rq);
		void blk_mq_complete_request_sync(struct request *rq);
		bool blk_mq_bio_list_merge(struct request_queue q, struct list_head list,
		struct bio *bio);
		bool blk_mq_queue_stopped(struct request_queue *q);

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