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 82ed4db499b8 ("block: split scsi_request out of struct request")
Signed-off-by: Bart Van Assche <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: J. Bruce Fields <[e-mail]>
Cc: Jeff Layton <[e-mail]>
Cc: Omar Sandoval <[e-mail]>
Cc: [e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

fs/nfsd/blocklayout.c

···
 	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;