[PATCH 1/3] nvme-rdma: limit the maximal queue size for RDMA controllers

[Max Gurtovoy]

Corrent limit of 1024 isn't valid for some of the RDMA based ctrls. In
case the target expose a cap of larger amount of entries (e.g. 1024),
the initiator may fail to create a QP with this size. Thus limit to a
value that works for all RDMA adapters.

Future general solution should use RDMA/core API to calculate this size
according to device capabilities and number of WRs needed per NVMe IO
request.

Signed-off-by: Max Gurtovoy <mgurtovoy at nvidia.com>
---
 drivers/nvme/host/rdma.c  | 7 +++++++
 include/linux/nvme-rdma.h | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index a68704e39084..a2f62eefccd9 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1111,6 +1111,13 @@ static int nvme_rdma_setup_ctrl(struct nvme_rdma_ctrl *ctrl, bool new)
 			ctrl->ctrl.opts->queue_size, ctrl->ctrl.sqsize + 1);
 	}
 
+	if (ctrl->ctrl.sqsize + 1 > NVME_RDMA_MAX_QUEUE_SIZE) {
+		dev_warn(ctrl->ctrl.device,
+			"ctrl sqsize %u > max queue size %u, clamping down\n",
+			ctrl->ctrl.sqsize + 1, NVME_RDMA_MAX_QUEUE_SIZE);
+		ctrl->ctrl.sqsize = NVME_RDMA_MAX_QUEUE_SIZE - 1;
+	}
+
 	if (ctrl->ctrl.sqsize + 1 > ctrl->ctrl.maxcmd) {
 		dev_warn(ctrl->ctrl.device,
 			"sqsize %u > ctrl maxcmd %u, clamping down\n",
diff --git a/include/linux/nvme-rdma.h b/include/linux/nvme-rdma.h
index 3ec8e50efa16..4dd7e6fe92fb 100644
--- a/include/linux/nvme-rdma.h
+++ b/include/linux/nvme-rdma.h
@@ -6,6 +6,8 @@
 #ifndef _LINUX_NVME_RDMA_H
 #define _LINUX_NVME_RDMA_H
 
+#define NVME_RDMA_MAX_QUEUE_SIZE	128
+
 enum nvme_rdma_cm_fmt {
 	NVME_RDMA_CM_FMT_1_0 = 0x0,
 };
-- 
2.18.1