nvme: factor out a add nvme_is_write helper

Centralize the check if a given NVMe command reads or writes data.
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NJay Freyensee <james.p.freyensee@intel.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/nvme/host/core.c

@@ -193,10 +193,9 @@ EXPORT_SYMBOL_GPL(nvme_requeue_req);
 struct request *nvme_alloc_request(struct request_queue *q,
 		struct nvme_command *cmd, unsigned int flags)
 {
-	bool write = cmd->common.opcode & 1;
 	struct request *req;
 
-	req = blk_mq_alloc_request(q, write, flags);
+	req = blk_mq_alloc_request(q, nvme_is_write(cmd), flags);
 	if (IS_ERR(req))
 		return req;
 
@@ -361,7 +360,7 @@ int __nvme_submit_user_cmd(struct request_queue *q, struct nvme_command *cmd,
 		void __user *meta_buffer, unsigned meta_len, u32 meta_seed,
 		u32 *result, unsigned timeout)
 {
-	bool write = cmd->common.opcode & 1;
+	bool write = nvme_is_write(cmd);
 	struct nvme_completion cqe;
 	struct nvme_ns *ns = q->queuedata;
 	struct gendisk *disk = ns ? ns->disk : NULL;

include/linux/nvme.h

@@ -590,6 +590,11 @@ struct nvme_command {
 	};
 };
 
+static inline bool nvme_is_write(struct nvme_command *cmd)
+{
+	return cmd->common.opcode & 1;
+}
+
 enum {
 	NVME_SC_SUCCESS			= 0x0,
 	NVME_SC_INVALID_OPCODE		= 0x1,