deprecate RBD plugin from available in-tree drivers

Based on https://groups.google.com/g/kubernetes-sig-storage/c/h5751_B5LQM, the
consensus was to start the deprecation in v1.28.

This commit start the deprecation process of RBD plugin from in-tree
drivers.

ACTION REQUIRED:
   RBD volume plugin ( `kubernetes.io/rbd`) has been deprecated in this release
   and will be removed in a subsequent release. Alternative is to use RBD CSI driver
   (https://github.com/ceph/ceph-csi/) in your Kubernetes Cluster.

Signed-off-by: Humble Chirammal <humble.devassy@gmail.com>

pkg/api/persistentvolume/util.go

@@ -93,8 +93,10 @@ func warningsForPersistentVolumeSpecAndMeta(fieldPath *field.Path, pvSpec *api.P
 		warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.22, non-functional in v1.25+", fieldPath.Child("spec", "persistentVolumeSource").Child("storageOS")))
 	}
 	if pvSpec.Glusterfs != nil {
-		warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.25, non-functional in v1.26+", fieldPath.Child("spec", "persistentVolumeSource").Child("glusterfs")))
+		warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.25, non-functional in v1.26+", fieldPath.Child("spec", "glusterfs")))
+	}
+	if pvSpec.RBD != nil {
+		warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.28, non-functional in v1.31+", fieldPath.Child("spec", "rbd")))
 	}
-
 	return warnings
 }

pkg/api/persistentvolume/util_test.go

@@ -212,6 +212,27 @@ func TestWarnings(t *testing.T) {
 				`spec.persistentVolumeSource.photonPersistentDisk: deprecated in v1.11, non-functional in v1.16+`,
 			},
 		},
+		{
+			name: "PV RBD deprecation warning",
+			template: &api.PersistentVolume{
+				Spec: api.PersistentVolumeSpec{
+					PersistentVolumeSource: api.PersistentVolumeSource{
+						RBD: &api.RBDPersistentVolumeSource{
+							CephMonitors: nil,
+							RBDImage:     "",
+							FSType:       "",
+							RBDPool:      "",
+							RadosUser:    "",
+							Keyring:      "",
+							SecretRef:    nil,
+							ReadOnly:     false,
+						},
+					},
+				},
+			},
+			expected: []string{
+				`spec.rbd: deprecated in v1.28, non-functional in v1.31+`},
+		},
 		{
 			name: "PV ScaleIO deprecation warning",
 			template: &api.PersistentVolume{

pkg/api/pod/warnings.go

@@ -163,6 +163,9 @@ func warningsForPodSpecAndMeta(fieldPath *field.Path, podSpec *api.PodSpec, meta
 		if v.CephFS != nil {
 			warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.28, non-functional in v1.31+", fieldPath.Child("spec", "volumes").Index(i).Child("cephfs")))
 		}
+		if v.RBD != nil {
+			warnings = append(warnings, fmt.Sprintf("%s: deprecated in v1.28, non-functional in v1.31+", fieldPath.Child("spec", "volumes").Index(i).Child("rbd")))
+		}
 	}
 
 	// duplicate hostAliases (#91670, #58477)

pkg/api/pod/warnings_test.go

@@ -224,6 +224,15 @@ func TestWarnings(t *testing.T) {
 			expected: []string{`spec.volumes[0].cephfs: deprecated in v1.28, non-functional in v1.31+`},
 		},
 
+		{
+			name: "rbd",
+			template: &api.PodTemplateSpec{Spec: api.PodSpec{
+				Volumes: []api.Volume{
+					{Name: "s", VolumeSource: api.VolumeSource{RBD: &api.RBDVolumeSource{}}},
+				}},
+			},
+			expected: []string{`spec.volumes[0].rbd: deprecated in v1.28, non-functional in v1.31+`},
+		},
 		{
 			name: "duplicate hostAlias",
 			template: &api.PodTemplateSpec{Spec: api.PodSpec{