blk-mq: introduce blk_mq_complete_request_sync()

Ming Lei · axboe · commit 1b8f21b74c3c · 2019-04-10T09:57:33.000-06:00
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 foundriesio#3 and foundriesio#4, because blk_mq_complete_request() may run q->mq_ops->complete(rq) remotelly and asynchronously, and ->complete(rq) may be run after foundriesio#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>
diff --git a/block/blk-mq.c b/block/blk-mq.c
@@ -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;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
@@ -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);

Original file line number	Diff line number	Diff line change
`@@ -654,6 +654,13 @@ bool blk_mq_complete_request(struct request *rq)`
`654`	`654`	`}`
`655`	`655`	`EXPORT_SYMBOL(blk_mq_complete_request);`
`656`	`656`
	`657`	`+void blk_mq_complete_request_sync(struct request *rq)`
	`658`	`+{`
	`659`	`+ WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);`
	`660`	`+ rq->q->mq_ops->complete(rq);`
	`661`	`+}`
	`662`	`+EXPORT_SYMBOL_GPL(blk_mq_complete_request_sync);`
	`663`	`+`
`657`	`664`	`int blk_mq_request_started(struct request *rq)`
`658`	`665`	`{`
`659`	`666`	`return blk_mq_rq_state(rq) != MQ_RQ_IDLE;`