[PATCH 5/9] scsi: Do not wait for a request in scsi_eh_lock_door()

[Bart Van Assche <bvanassche@acm.org>]

It is not guaranteed that a request is available when scsi_eh_lock_door()
is called. Hence pass the BLK_MQ_REQ_NOWAIT flag to blk_get_request().
This patch has a second purpose, namely preventing that
scsi_eh_lock_door() deadlocks if sdev->request_queue is frozen and if a
SCSI command is submitted to a SCSI device through a second request queue
that has not been frozen.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Can Guo <cang@codeaurora.org>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_error.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index b197291c631a..f7604d930e3c 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1979,7 +1979,8 @@ static void scsi_eh_lock_door(struct scsi_device *sdev)
 	struct request *req;
 	struct scsi_request *rq;
 
-	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN, 0);
+	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN,
+			      BLK_MQ_REQ_NOWAIT);
 	if (IS_ERR(req))
 		return;
 	rq = scsi_req(req);