nfs41: add support for callback with RPC version number 4

The NFSv4.1 spec-29 (18.36.3) says that the server MUST use an ONC RPC
(program) version number equal to 4 in callbacks sent to the client.
For now we allow both versions 1 and 4.

Signed-off-by: Alexandros Batsakis <batsakis@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index 76b0aa0f..0fda5e6 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -718,3 +718,10 @@
 	.vs_dispatch = NULL,
 };
 
+struct svc_version nfs4_callback_version4 = {
+	.vs_vers = 4,
+	.vs_nproc = ARRAY_SIZE(nfs4_callback_procedures1),
+	.vs_proc = nfs4_callback_procedures1,
+	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
+	.vs_dispatch = NULL,
+};