[for-next PATCH] infiniband:cma: add a parameter for the packet lifetime

[Chao Leng <lengchao@huawei.com>]

Now the default packet lifetime(CMA_IBOE_PACKET_LIFETIME) is 18.
That means the minimum ack timeout is 2 seconds(2^(18+1)*4us=2.097seconds).
The packet lifetime means the maximum transmission time of packets
on the network, the maximum transmission time of packets is closely
related to the network. 2 seconds is too long for simple lossless networks.
The packet lifetime should allow the user to adjust according to the
network situation.
So add a parameter for the packet lifetime.

Signed-off-by: Chao Leng <lengchao@huawei.com>
---
 drivers/infiniband/core/cma.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index cc2222b85c88..8e2ff5d610e3 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -50,6 +50,10 @@ MODULE_LICENSE("Dual BSD/GPL");
 #define CMA_IBOE_PACKET_LIFETIME 18
 #define CMA_PREFERRED_ROCE_GID_TYPE IB_GID_TYPE_ROCE_UDP_ENCAP
 
+static unsigned char cma_packet_lifetime = CMA_IBOE_PACKET_LIFETIME;
+module_param_named(packet_lifetime, cma_packet_lifetime, byte, 0644);
+MODULE_PARM_DESC(packet_lifetime, "max transmission time of the packet");
+
 static const char * const cma_events[] = {
 	[RDMA_CM_EVENT_ADDR_RESOLVED]	 = "address resolved",
 	[RDMA_CM_EVENT_ADDR_ERROR]	 = "address error",
@@ -3301,7 +3305,7 @@ static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 	if (id_priv->timeout_set && id_priv->timeout)
 		route->path_rec->packet_life_time = id_priv->timeout - 1;
 	else
-		route->path_rec->packet_life_time = CMA_IBOE_PACKET_LIFETIME;
+		route->path_rec->packet_life_time = cma_packet_lifetime;
 	mutex_unlock(&id_priv->qp_mutex);
 
 	if (!route->path_rec->mtu) {
-- 
2.16.4