Only `layering` RBD image format 2 feature should be supported for now.

examples/persistent-volume-provisioning/README.md

@@ -220,9 +220,9 @@ parameters:
 * `userId`: Ceph client ID that is used to map the RBD image. Default is the same as `adminId`.
 * `userSecretName`: The name of Ceph Secret for `userId` to map RBD image. It must exist in the same namespace as PVCs. It is required.
 * `imageFormat`: Ceph RBD image format, "1" or "2". Default is "1".
-* `imageFeatures`: Ceph RBD image format 2 features, comma delimited. This is optional, and only be used if you set `imageFormat` to "2". For a complete list of available image features, please refer to [RBD docs](http://docs.ceph.com/docs/master/man/8/rbd/). By default, all features (except for striping) will be enabled.
+* `imageFeatures`: Ceph RBD image format 2 features, comma delimited. This is optional, and only be used if you set `imageFormat` to "2". Currently supported features are `layering` only. Default is "", no features is turned on.
 
-NOTE: If you want to use RBD image format 2, you may need to disable some image features, because some of them are not supported by [Ceph kernel module](https://github.com/ceph/ceph-client). For example, only "layering" feature is supported on Linux 4.9 LTS version, so you need to specify `imageFeatures` to "layering", if set `imageFormat` to "2".
+NOTE: We cannot turn on `exclusive-lock` feature for now (and `object-map`, `fast-diff`, `journaling` which require `exclusive-lock`), because exclusive lock and advisory lock cannot work together. (See [#45805](https://issue.k8s.io/45805))
 
 #### Quobyte
 

pkg/volume/rbd/BUILD

@@ -31,6 +31,7 @@ go_library(
         "//vendor/k8s.io/apimachinery/pkg/api/resource:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/types:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/uuid:go_default_library",
     ],
 )

pkg/volume/rbd/rbd.go

@@ -24,6 +24,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/uuid"
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/clientset"
@@ -35,6 +36,10 @@ import (
 	"k8s.io/kubernetes/pkg/volume/util/volumehelper"
 )
 
+var (
+	supportedFeatures = sets.NewString("layering")
+)
+
 // This is the primary entrypoint for volume plugins.
 func ProbeVolumePlugins() []volume.VolumePlugin {
 	return []volume.VolumePlugin{&rbdPlugin{nil, exec.New()}}
@@ -295,7 +300,11 @@ func (r *rbdVolumeProvisioner) Provision() (*v1.PersistentVolume, error) {
 		case "imagefeatures":
 			arr := dstrings.Split(v, ",")
 			for _, f := range arr {
-				r.imageFeatures = append(r.imageFeatures, f)
+				if !supportedFeatures.Has(f) {
+					return nil, fmt.Errorf("invalid feature %q for volume plugin %s, supported features are: %v", f, r.plugin.GetPluginName(), supportedFeatures)
+				} else {
+					r.imageFeatures = append(r.imageFeatures, f)
+				}
 			}
 		default:
 			return nil, fmt.Errorf("invalid option %q for volume plugin %s", k, r.plugin.GetPluginName())

pkg/volume/rbd/rbd_util.go

@@ -361,10 +361,11 @@ func (util *RBDUtil) CreateImage(p *rbdVolumeProvisioner) (r *v1.RBDVolumeSource
 			glog.V(4).Infof("rbd: create %s size %s format %s using mon %s, pool %s id %s key %s", p.rbdMounter.Image, volSz, p.rbdMounter.imageFormat, mon, p.rbdMounter.Pool, p.rbdMounter.adminId, p.rbdMounter.adminSecret)
 		}
 		args := []string{"create", p.rbdMounter.Image, "--size", volSz, "--pool", p.rbdMounter.Pool, "--id", p.rbdMounter.adminId, "-m", mon, "--key=" + p.rbdMounter.adminSecret, "--image-format", p.rbdMounter.imageFormat}
-		if p.rbdMounter.imageFormat == rbdImageFormat2 && len(p.rbdMounter.imageFeatures) > 0 {
-			for _, f := range p.rbdMounter.imageFeatures {
-				args = append(args, "--image-feature", f)
-			}
+		if p.rbdMounter.imageFormat == rbdImageFormat2 {
+			// if no image features is provided, it results in empty string
+			// which disable all RBD image format 2 features as we expected
+			features := strings.Join(p.rbdMounter.imageFeatures, ",")
+			args = append(args, "--image-feature", features)
 		}
 		output, err = p.rbdMounter.plugin.execCommand("rbd", args)
 		if err == nil {