NFS: disconnect before retrying NFSv4 requests over TCP

RFC3530 section 3.1.1 states an NFSv4 client MUST NOT send a request
twice on the same connection unless it is the NULL procedure.  Section
3.1.1 suggests that the client should disconnect and reconnect if it
wants to retry a request.

Implement this by adding an rpc_clnt flag that an ULP can use to
specify that the underlying transport should be disconnected on a
major timeout.  The NFSv4 client asserts this new flag, and requests
no retries after a minor retransmit timeout.

Note that disconnecting on a retransmit is in general not safe to do
if the RPC client does not reuse the TCP port number when reconnecting.

See http://bugzilla.linux-nfs.org/show_bug.cgi?id=6

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index cf59f7d..1975139 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -735,6 +735,16 @@ void xprt_transmit(struct rpc_task *task)
 			xprt_reset_majortimeo(req);
 			/* Turn off autodisconnect */
 			del_singleshot_timer_sync(&xprt->timer);
+		} else {
+			/* If all request bytes have been sent,
+			 * then we must be retransmitting this one */
+			if (!req->rq_bytes_sent) {
+				if (task->tk_client->cl_discrtry) {
+					xprt_disconnect(xprt);
+					task->tk_status = -ENOTCONN;
+					return;
+				}
+			}
 		}
 	} else if (!req->rq_bytes_sent)
 		return;