NFS test session trunking with exchange id

Use an async exchange id call to test for session trunking

To conform with RFC 5661 section 18.35.4, the Non-Update on
Existing Clientid case, save the exchange id verifier in
cl_confirm and use it for the session trunking exhange id test.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 6914d4b..a2c9654 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -637,9 +637,10 @@
 }
 
 /**
- * nfs4_detect_session_trunking - Checks for session trunking called
- * after a successful EXCHANGE_ID testing a multi-addr connection to be
- * potentially added as a session trunk
+ * nfs4_detect_session_trunking - Checks for session trunking.
+ *
+ * Called after a successful EXCHANGE_ID on a multi-addr connection.
+ * Upon success, add the transport.
  *
  * @clp:    original mount nfs_client
  * @res:    result structure from an exchange_id using the original mount
@@ -673,6 +674,9 @@
 	if (!nfs4_check_server_scope(clp->cl_serverscope, res->server_scope))
 		goto out_err;
 
+	/* Session trunking passed, add the xprt */
+	rpc_clnt_xprt_switch_add_xprt(clp->cl_rpcclient, xprt);
+
 	pr_info("NFS:  %s: Session trunking succeeded for %s\n",
 		clp->cl_hostname,
 		xprt->address_strings[RPC_DISPLAY_ADDR]);