From: Bart Van Assche <bart.vanassche@wdc.com>
Date: Wed, 11 Oct 2017 10:27:29 -0700
Subject: IB/srp: Make CM timeout dependent on subnet timeout
Patch-mainline: v4.15-rc1
Git-commit: 4c532d6ce14bb3fb4e1cb2d29fafdd7d6bded51c
References: bsc#1103992 FATE#326009

For small networks it is safe to reduce the subnet timeout from
its default value (18 for opensm) to 16. Make the SRP CM timeout
dependent on the subnet timeout such that decreasing the subnet
timeout also causes SRP failover and failback to occur faster.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/ulp/srp/ib_srp.c |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -711,6 +711,23 @@ out:
 	return ret;
 }
 
+static u8 srp_get_subnet_timeout(struct srp_host *host)
+{
+	struct ib_port_attr attr;
+	int ret;
+	u8 subnet_timeout = 18;
+
+	ret = ib_query_port(host->srp_dev->dev, host->port, &attr);
+	if (ret == 0)
+		subnet_timeout = attr.subnet_timeout;
+
+	if (unlikely(subnet_timeout < 15))
+		pr_warn("%s: subnet timeout %d may cause SRP login to fail.\n",
+			dev_name(&host->srp_dev->dev->dev), subnet_timeout);
+
+	return subnet_timeout;
+}
+
 static int srp_send_req(struct srp_rdma_ch *ch, bool multich)
 {
 	struct srp_target_port *target = ch->target;
@@ -719,6 +736,9 @@ static int srp_send_req(struct srp_rdma_
 		struct srp_login_req   priv;
 	} *req = NULL;
 	int status;
+	u8 subnet_timeout;
+
+	subnet_timeout = srp_get_subnet_timeout(target->srp_host);
 
 	req = kzalloc(sizeof *req, GFP_KERNEL);
 	if (!req)
@@ -741,8 +761,8 @@ static int srp_send_req(struct srp_rdma_
 	 * module parameters if anyone cared about setting them.
 	 */
 	req->param.responder_resources	      = 4;
-	req->param.remote_cm_response_timeout = 20;
-	req->param.local_cm_response_timeout  = 20;
+	req->param.remote_cm_response_timeout = subnet_timeout + 2;
+	req->param.local_cm_response_timeout  = subnet_timeout + 2;
 	req->param.retry_count                = target->tl_retry_count;
 	req->param.rnr_retry_count 	      = 7;
 	req->param.max_cm_retries 	      = 15;