NFSv4: Reintroduce machine creds

We need to try to ensure that we always use the same credentials whenever
we re-establish the clientid on the server. If not, the server won't
recognise that we're the same client, and so may not allow us to recover
state.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/nfs_fs_sb.h

@@ -32,6 +32,8 @@ struct nfs_client {
 	const struct nfs_rpc_ops *rpc_ops;	/* NFS protocol vector */
 	int			cl_proto;	/* Network transport protocol */
 
+	struct rpc_cred		*cl_machine_cred;
+
 #ifdef CONFIG_NFS_V4
 	u64			cl_clientid;	/* constant */
 	nfs4_verifier		cl_confirm;