scsi: core: use blk_mq_requeue_request in __scsi_queue_insert

In scsi core, __scsi_queue_insert should just put request back on the
queue and retry using the same command as before. However, for blk-mq,
scsi_mq_requeue_cmd is employed here which will unprepare the
request. To align with the semantics of __scsi_queue_insert, use
blk_mq_requeue_request with kick_requeue_list == true and put the
reference of scsi_device.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -191,7 +191,19 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
 	 */
 	cmd->result = 0;
 	if (q->mq_ops) {
-		scsi_mq_requeue_cmd(cmd);
+		/*
+		 * Before a SCSI command is dispatched,
+		 * get_device(&sdev->sdev_gendev) is called and the host,
+		 * target and device busy counters are increased. Since
+		 * requeuing a request causes these actions to be repeated and
+		 * since scsi_device_unbusy() has already been called,
+		 * put_device(&device->sdev_gendev) must still be called. Call
+		 * put_device() after blk_mq_requeue_request() to avoid that
+		 * removal of the SCSI device can start before requeueing has
+		 * happened.
+		 */
+		blk_mq_requeue_request(cmd->request, true);
+		put_device(&device->sdev_gendev);
 		return;
 	}
 	spin_lock_irqsave(q->queue_lock, flags);