scsi_eh_lock_door() is the only function in the SCSI error handler that
calls blk_get_request(). 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().

Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Can Guo <redacted>
Cc: Stanley Chu <redacted>
Cc: Ming Lei <redacted>
Cc: Rafael J. Wysocki <redacted>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
  drivers/scsi/scsi_error.c | 7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index d94449188270..6de6e1bf3dcb 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c

@@ -1993,7 +1993,12 @@ 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);
+	/*
+	 * It is not guaranteed that a request is available nor that
+	 * sdev->request_queue is unfrozen. Hence the BLK_MQ_REQ_NOWAIT below.
+	 */
+	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN,
+			      BLK_MQ_REQ_NOWAIT);
  	if (IS_ERR(req))
  		return;
  	rq = scsi_req(req);