nfsd: Check queue type before submitting a SCSI request

Since using scsi_req() is only allowed against request queues for
which struct scsi_request is the first member of their private
request data, refuse to submit SCSI commands against a queue for
which this is not the case.

References: commit 82ed4db ("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>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: Omar Sandoval <osandov@fb.com>
Cc: linux-nfs@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>

fs/nfsd/blocklayout.c

@@ -219,6 +219,9 @@ static int nfsd4_scsi_identify_device(struct block_device *bdev,
 	u8 *buf, *d, type, assoc;
 	int error;
 
+	if (WARN_ON_ONCE(!blk_queue_scsi_passthrough(q)))
+		return -EINVAL;
+
 	buf = kzalloc(bufflen, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;