csi: add nodeExpandSecret support for CSI client

CSI spec 1.5 enhanced the spec to add optional secrets field to
NodeExpandVolumeRequest. This commit adds NodeExpandSecret to the
CSI PV source and also derive the expansion secret in csiclient to
send it out as part of the nodeexpand request.

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>
Signed-off-by: zhucan <zhucan.k8s@gmail.com>

pkg/api/persistentvolume/util.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package persistentvolume
+
+import (
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
+	api "k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/features"
+)
+
+// DropDisabledFields removes disabled fields from the pv spec.
+// This should be called from PrepareForCreate/PrepareForUpdate for all resources containing a pv spec.
+func DropDisabledFields(pvSpec *api.PersistentVolumeSpec, oldPVSpec *api.PersistentVolumeSpec) {
+	if !utilfeature.DefaultFeatureGate.Enabled(features.CSINodeExpandSecret) && !hasNodeExpansionSecrets(oldPVSpec) {
+		if pvSpec.CSI != nil {
+			pvSpec.CSI.NodeExpandSecretRef = nil
+		}
+	}
+}
+
+func hasNodeExpansionSecrets(oldPVSpec *api.PersistentVolumeSpec) bool {
+	if oldPVSpec == nil || oldPVSpec.CSI == nil {
+		return false
+	}
+
+	if oldPVSpec.CSI.NodeExpandSecretRef != nil {
+		return true
+	}
+	return false
+}