From: Max Gurtovoy <maxg@mellanox.com>
Date: Sun, 8 Mar 2020 12:55:03 +0200
Subject: [PATCH] nvmet: Add get_mdts op for controllers
Git-commit: 02cb00e233ade7c050e0f476902e63847e78114e
Patch-mainline: v5.7-rc1
References: jsc#SLE-15608

Some transports, such as RDMA, would like to set the Maximum Data
Transfer Size (MDTS) according to device/port/ctrl characteristics.
This will enable the transport to set the optimal MDTS according to
controller needs and device capabilities. Add a new nvmet transport
op that is called during ctrl identification. This will not effect
transports that don't implement this option. The return value of the new
op is according to the NVMe spec definition for MDTS.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/nvme/target/admin-cmd.c | 8 ++++++--
 drivers/nvme/target/nvmet.h     | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index c0aa9c34c699..b9ec489dc748 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -369,8 +369,12 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	/* we support multiple ports, multiples hosts and ANA: */
 	id->cmic = (1 << 0) | (1 << 1) | (1 << 3);
 
-	/* no limit on data transfer sizes for now */
-	id->mdts = 0;
+	/* Limit MDTS according to transport capability */
+	if (ctrl->ops->get_mdts)
+		id->mdts = ctrl->ops->get_mdts(ctrl);
+	else
+		id->mdts = 0;
+
 	id->cntlid = cpu_to_le16(ctrl->cntlid);
 	id->ver = cpu_to_le32(ctrl->subsys->ver);
 
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 42ba2ddd9e96..421dff3ea143 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -289,6 +289,7 @@ struct nvmet_fabrics_ops {
 			struct nvmet_port *port, char *traddr);
 	u16 (*install_queue)(struct nvmet_sq *nvme_sq);
 	void (*discovery_chg)(struct nvmet_port *port);
+	u8 (*get_mdts)(const struct nvmet_ctrl *ctrl);
 };
 
 #define NVMET_MAX_INLINE_BIOVEC	8
-- 
2.16.4