SUNRPC: new interface to force an RPC rebind

 We'd like to hide fields in rpc_xprt and rpc_clnt from upper layer protocols.
 Start by creating an API to force RPC rebind, replacing logic that simply
 sets cl_port to zero.

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon
 with UDP and TCP.  NFSv2/3 and NFSv4 mounting should be carefully checked.
 Probably need to rig a server where certain services aren't running, or
 that returns an error for some typical operation.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/lockd/host.c

@@ -177,7 +177,7 @@ nlm_bind_host(struct nlm_host *host)
 	if ((clnt = host->h_rpcclnt) != NULL) {
 		xprt = clnt->cl_xprt;
 		if (time_after_eq(jiffies, host->h_nextrebind)) {
-			clnt->cl_port = 0;
+			rpc_force_rebind(clnt);
 			host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 			dprintk("lockd: next rebind in %ld jiffies\n",
 					host->h_nextrebind - jiffies);
@@ -217,7 +217,7 @@ nlm_rebind_host(struct nlm_host *host)
 {
 	dprintk("lockd: rebind host %s\n", host->h_name);
 	if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
-		host->h_rpcclnt->cl_port = 0;
+		rpc_force_rebind(host->h_rpcclnt);
 		host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 	}
 }

include/linux/sunrpc/clnt.h

@@ -135,6 +135,7 @@ void		rpc_clnt_sigmask(struct rpc_clnt *clnt, sigset_t *oldset);
 void		rpc_clnt_sigunmask(struct rpc_clnt *clnt, sigset_t *oldset);
 void		rpc_setbufsize(struct rpc_clnt *, unsigned int, unsigned int);
 size_t		rpc_max_payload(struct rpc_clnt *);
+void		rpc_force_rebind(struct rpc_clnt *);
 int		rpc_ping(struct rpc_clnt *clnt, int flags);
 
 static __inline__

net/sunrpc/clnt.c

@@ -538,6 +538,18 @@ size_t rpc_max_payload(struct rpc_clnt *clnt)
 }
 EXPORT_SYMBOL(rpc_max_payload);
 
+/**
+ * rpc_force_rebind - force transport to check that remote port is unchanged
+ * @clnt: client to rebind
+ *
+ */
+void rpc_force_rebind(struct rpc_clnt *clnt)
+{
+	if (clnt->cl_autobind)
+		clnt->cl_port = 0;
+}
+EXPORT_SYMBOL(rpc_force_rebind);
+
 /*
  * Restart an (async) RPC call. Usually called from within the
  * exit handler.
@@ -853,8 +865,7 @@ call_connect_status(struct rpc_task *task)
 	}
 
 	/* Something failed: remote service port may have changed */
-	if (clnt->cl_autobind)
-		clnt->cl_port = 0;
+	rpc_force_rebind(clnt);
 
 	switch (status) {
 	case -ENOTCONN:
@@ -935,8 +946,7 @@ call_status(struct rpc_task *task)
 		break;
 	case -ECONNREFUSED:
 	case -ENOTCONN:
-		if (clnt->cl_autobind)
-			clnt->cl_port = 0;
+		rpc_force_rebind(clnt);
 		task->tk_action = call_bind;
 		break;
 	case -EAGAIN:
@@ -995,8 +1005,7 @@ call_timeout(struct rpc_task *task)
 		printk(KERN_NOTICE "%s: server %s not responding, still trying\n",
 			clnt->cl_protname, clnt->cl_server);
 	}
-	if (clnt->cl_autobind)
-		clnt->cl_port = 0;
+	rpc_force_rebind(clnt);
 
 retry:
 	clnt->cl_stats->rpcretrans++;