[PATCH] RPC: add API to set transport-specific timeouts

 Prepare the way to remove the "xprt->nocong" variable by adding a callout
 to the RPC client transport switch API to handle setting RPC retransmit
 timeouts.

 Add a pair of generic helper functions that provide the ability to set a
 simple fixed timeout, or to set a timeout based on the state of a round-
 trip estimator.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for significant
 regression in performance or client stability.

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 5bb6fed..79433ff 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1047,6 +1047,7 @@
 	.set_buffer_size	= xs_udp_set_buffer_size,
 	.connect		= xs_connect,
 	.send_request		= xs_udp_send_request,
+	.set_retrans_timeout	= xprt_set_retrans_timeout_rtt,
 	.close			= xs_close,
 	.destroy		= xs_destroy,
 };
@@ -1055,6 +1056,7 @@
 	.set_buffer_size	= xs_tcp_set_buffer_size,
 	.connect		= xs_connect,
 	.send_request		= xs_tcp_send_request,
+	.set_retrans_timeout	= xprt_set_retrans_timeout_def,
 	.close			= xs_close,
 	.destroy		= xs_destroy,
 };