[RFC PATCH V2 1/2] nvmet: rdma: utilize ib_device capability for setting max_queue_size

[Guixin Liu <kanie@linux.alibaba.com>]

Respond with the smaller value between 1024 and the ib_device's
max_qp_wr as the RDMA max queue size.

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
---
 drivers/nvme/target/rdma.c | 17 ++++++++++++++++-
 include/linux/nvme-rdma.h  |  2 ++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 4597bca..d546203 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -2002,7 +2002,22 @@ static u8 nvmet_rdma_get_mdts(const struct nvmet_ctrl *ctrl)
 
 static u16 nvmet_rdma_get_max_queue_size(const struct nvmet_ctrl *ctrl)
 {
-	return NVME_RDMA_MAX_QUEUE_SIZE;
+	struct nvmet_rdma_queue *queue;
+	struct nvmet_port *nport = ctrl->port;
+	int max_qp_wr = 0;
+
+	/* Here nvmet_ctrl's port is already set. */
+	mutex_lock(&nvmet_rdma_queue_mutex);
+	list_for_each_entry(queue, &nvmet_rdma_queue_list, queue_list) {
+		if (queue->port == nport) {
+			max_qp_wr = queue->dev->device->attrs.max_qp_wr;
+			break;
+		}
+	}
+	mutex_unlock(&nvmet_rdma_queue_mutex);
+
+	return (u16)min_t(int, NVMET_QUEUE_SIZE,
+			  max_qp_wr / (NVME_RDMA_SEND_WR_FACTOR + 1));
 }
 
 static const struct nvmet_fabrics_ops nvmet_rdma_ops = {
diff --git a/include/linux/nvme-rdma.h b/include/linux/nvme-rdma.h
index 4dd7e6f..c19858b 100644
--- a/include/linux/nvme-rdma.h
+++ b/include/linux/nvme-rdma.h
@@ -8,6 +8,8 @@
 
 #define NVME_RDMA_MAX_QUEUE_SIZE	128
 
+#define NVME_RDMA_SEND_WR_FACTOR 3  /* MR, SEND, INV */
+
 enum nvme_rdma_cm_fmt {
 	NVME_RDMA_CM_FMT_1_0 = 0x0,
 };
-- 
1.8.3.1