+static void warn_no_callback_path(struct nfs4_client *clp, int reason)
+{
+ dprintk("NFSD: warning: no callback path to client %.*s: error %d\n",
+ (int)clp->cl_name.len, clp->cl_name.data, reason);
+}
+
+static void nfsd4_cb_probe_done(struct rpc_task *task, void *calldata)
+{
+ struct nfs4_client *clp = calldata;
+
+ if (task->tk_status)
+ warn_no_callback_path(clp, task->tk_status);
+ else
+ atomic_set(&clp->cl_cb_conn.cb_set, 1);
+ put_nfs4_client(clp);
+}
+
+static const struct rpc_call_ops nfsd4_cb_probe_ops = {
+ .rpc_call_done = nfsd4_cb_probe_done,
+};
+
+static struct rpc_cred *lookup_cb_cred(struct nfs4_cb_conn *cb)
+{
+ struct auth_cred acred = {
+ .machine_cred = 1
+ };
+
+ /*
+ * Note in the gss case this doesn't actually have to wait for a
+ * gss upcall (or any calls to the client); this just creates a
+ * non-uptodate cred which the rpc state machine will fill in with
+ * a refresh_upcall later.
+ */
+ return rpcauth_lookup_credcache(cb->cb_client->cl_auth, &acred,
+ RPCAUTH_LOOKUP_NEW);
+}
+
+void do_probe_callback(struct nfs4_client *clp)
+{
+ struct nfs4_cb_conn *cb = &clp->cl_cb_conn;
+ struct rpc_message msg = {
+ .rpc_proc = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_NULL],
+ .rpc_argp = clp,
+ };
+ struct rpc_cred *cred;
+ int status;
+
+ cred = lookup_cb_cred(cb);
+ if (IS_ERR(cred)) {
+ status = PTR_ERR(cred);
+ goto out;
+ }
+ cb->cb_cred = cred;
+ msg.rpc_cred = cb->cb_cred;
+ status = rpc_call_async(cb->cb_client, &msg, RPC_TASK_SOFT,
+ &nfsd4_cb_probe_ops, (void *)clp);
+out:
+ if (status) {
+ warn_no_callback_path(clp, status);
+ put_nfs4_client(clp);
+ }
+}
+
+/*
+ * Set up the callback client and put a NFSPROC4_CB_NULL on the wire...
+ */
+void
+nfsd4_probe_callback(struct nfs4_client *clp)
+{
+ int status;
+
+ BUG_ON(atomic_read(&clp->cl_cb_conn.cb_set));
+
+ status = setup_callback_client(clp);
+ if (status) {
+ warn_no_callback_path(clp, status);
+ return;