block: introduce blk_rq_is_passthrough

This can be used to check for fs vs non-fs requests and basically
removes all knowledge of BLOCK_PC specific from the block layer,
as well as preparing for removing the cmd_type field in struct request.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/host/rdma.c

@@ -1423,7 +1423,7 @@ static inline bool nvme_rdma_queue_is_ready(struct nvme_rdma_queue *queue,
 	if (unlikely(!test_bit(NVME_RDMA_Q_LIVE, &queue->flags))) {
 		struct nvme_command *cmd = nvme_req(rq)->cmd;
 
-		if (rq->cmd_type != REQ_TYPE_DRV_PRIV ||
+		if (!blk_rq_is_passthrough(rq) ||
 		    cmd->common.opcode != nvme_fabrics_command ||
 		    cmd->fabrics.fctype != nvme_fabrics_type_connect)
 			return false;
@@ -1522,7 +1522,7 @@ static void nvme_rdma_complete_rq(struct request *rq)
 			return;
 		}
 
-		if (rq->cmd_type == REQ_TYPE_DRV_PRIV)
+		if (blk_rq_is_passthrough(rq))
 			error = rq->errors;
 		else
 			error = nvme_error_status(rq->errors);