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>
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 93dfd75..f2f3b28 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -112,6 +112,7 @@
 static struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 {
 	struct nfs_client *clp;
+	struct rpc_cred *cred;
 
 	if ((clp = kzalloc(sizeof(*clp), GFP_KERNEL)) == NULL)
 		goto error_0;
@@ -150,6 +151,9 @@
 	clp->cl_boot_time = CURRENT_TIME;
 	clp->cl_state = 1 << NFS4CLNT_LEASE_EXPIRED;
 #endif
+	cred = rpc_lookup_machine_cred();
+	if (!IS_ERR(cred))
+		clp->cl_machine_cred = cred;
 
 	return clp;
 
@@ -191,6 +195,9 @@
 	if (__test_and_clear_bit(NFS_CS_CALLBACK, &clp->cl_res_state))
 		nfs_callback_down();
 
+	if (clp->cl_machine_cred != NULL)
+		put_rpccred(clp->cl_machine_cred);
+
 	kfree(clp->cl_hostname);
 	kfree(clp);