pktcdvd: Check queue type before attaching to a queue

Since the pktcdvd driver only supports request queues for which
struct scsi_request is the first member of their private request
data, refuse to register block layer queues for which struct
scsi_request is not the first member of the private data.

References: commit 82ed4db499b8 ("block: split scsi_request out of struct request")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/pktcdvd.c

@@ -2583,6 +2583,11 @@ static int pkt_new_dev(struct pktcdvd_device *pd, dev_t dev)
 	bdev = bdget(dev);
 	if (!bdev)
 		return -ENOMEM;
+	if (!blk_queue_scsi_passthrough(bdev_get_queue(bdev))) {
+		WARN_ONCE(true, "Attempt to register a non-SCSI queue\n");
+		bdput(bdev);
+		return -EINVAL;
+	}
 	ret = blkdev_get(bdev, FMODE_READ | FMODE_NDELAY, NULL);
 	if (ret)
 		return ret;