NFSv4.1: nfs4_proc_bind_conn_to_session must iterate over all connections

Use the new helper to ensure that nfs4_proc_bind_conn_to_session() is called
for all connections.
However ensure that we only set the backchannel flag for the connection
pointed to by rpc_clnt->cl_xprt.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4proc.c

@@ -6783,12 +6783,16 @@ nfs41_same_server_scope(struct nfs41_server_scope *a,
 }
 
 /*
- * nfs4_proc_bind_conn_to_session()
+ * nfs4_proc_bind_one_conn_to_session()
  *
  * The 4.1 client currently uses the same TCP connection for the
  * fore and backchannel.
  */
-int nfs4_proc_bind_conn_to_session(struct nfs_client *clp, struct rpc_cred *cred)
+static
+int nfs4_proc_bind_one_conn_to_session(struct rpc_clnt *clnt,
+		struct rpc_xprt *xprt,
+		struct nfs_client *clp,
+		struct rpc_cred *cred)
 {
 	int status;
 	struct nfs41_bind_conn_to_session_args args = {
@@ -6803,6 +6807,13 @@ int nfs4_proc_bind_conn_to_session(struct nfs_client *clp, struct rpc_cred *cred
 		.rpc_resp = &res,
 		.rpc_cred = cred,
 	};
+	struct rpc_task_setup task_setup_data = {
+		.rpc_client = clnt,
+		.rpc_xprt = xprt,
+		.rpc_message = &msg,
+		.flags = RPC_TASK_TIMEOUT,
+	};
+	struct rpc_task *task;
 
 	dprintk("--> %s\n", __func__);
 
@@ -6810,7 +6821,16 @@ int nfs4_proc_bind_conn_to_session(struct nfs_client *clp, struct rpc_cred *cred
 	if (!(clp->cl_session->flags & SESSION4_BACK_CHAN))
 		args.dir = NFS4_CDFC4_FORE;
 
-	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+	/* Do not set the backchannel flag unless this is clnt->cl_xprt */
+	if (xprt != rcu_access_pointer(clnt->cl_xprt))
+		args.dir = NFS4_CDFC4_FORE;
+
+	task = rpc_run_task(&task_setup_data);
+	if (!IS_ERR(task)) {
+		status = task->tk_status;
+		rpc_put_task(task);
+	} else
+		status = PTR_ERR(task);
 	trace_nfs4_bind_conn_to_session(clp, status);
 	if (status == 0) {
 		if (memcmp(res.sessionid.data,
@@ -6837,6 +6857,31 @@ int nfs4_proc_bind_conn_to_session(struct nfs_client *clp, struct rpc_cred *cred
 	return status;
 }
 
+struct rpc_bind_conn_calldata {
+	struct nfs_client *clp;
+	struct rpc_cred *cred;
+};
+
+static int
+nfs4_proc_bind_conn_to_session_callback(struct rpc_clnt *clnt,
+		struct rpc_xprt *xprt,
+		void *calldata)
+{
+	struct rpc_bind_conn_calldata *p = calldata;
+
+	return nfs4_proc_bind_one_conn_to_session(clnt, xprt, p->clp, p->cred);
+}
+
+int nfs4_proc_bind_conn_to_session(struct nfs_client *clp, struct rpc_cred *cred)
+{
+	struct rpc_bind_conn_calldata data = {
+		.clp = clp,
+		.cred = cred,
+	};
+	return rpc_clnt_iterate_for_each_xprt(clp->cl_rpcclient,
+			nfs4_proc_bind_conn_to_session_callback, &data);
+}
+
 /*
  * Minimum set of SP4_MACH_CRED operations from RFC 5661 in the enforce map
  * and operations we'd like to see to enable certain features in the allow map