Merge pull request #55204 from vladimirvivien/k8s-csi-volume-source

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Kubernetes CSI - Persistent Volume Source Type

**What this PR does / why we need it**:
This PR is to track the addition of new API type `CSIPersistentVolumeSource` that will be used as PersistentVolume for storage sources managed by CSI drivers. 

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
xref https://github.com/kubernetes/features/issues/178

**Special notes for your reviewer**:
- Implements API `PersistentVolume` type `CSIPersistentVolumeSource`
- Part of implementation for https://github.com/kubernetes/features/issues/178
- Designed at https://github.com/kubernetes/community/pull/1258

Other CSI Volume Plugin PRs:
- Plugin Mounter/Unmounter https://github.com/kubernetes/kubernetes/pull/54529
- Plugin Attacher/Detacher https://github.com/kubernetes/kubernetes/pull/55809

**Release note**:

```release-note
NONE
```

pkg/apis/core/validation/validation.go

@@ -1318,6 +1318,24 @@ func validateStorageOSPersistentVolumeSource(storageos *core.StorageOSPersistent
 	return allErrs
 }
 
+func validateCSIPersistentVolumeSource(csi *core.CSIPersistentVolumeSource, fldPath *field.Path) field.ErrorList {
+	allErrs := field.ErrorList{}
+
+	if !utilfeature.DefaultFeatureGate.Enabled(features.CSIPersistentVolume) {
+		allErrs = append(allErrs, field.Forbidden(fldPath, "CSIPersistentVolume disabled by feature-gate"))
+	}
+
+	if len(csi.Driver) == 0 {
+		allErrs = append(allErrs, field.Required(fldPath.Child("driver"), ""))
+	}
+
+	if len(csi.VolumeHandle) == 0 {
+		allErrs = append(allErrs, field.Required(fldPath.Child("volumeHandle"), ""))
+	}
+
+	return allErrs
+}
+
 // ValidatePersistentVolumeName checks that a name is appropriate for a
 // PersistentVolumeName object.
 var ValidatePersistentVolumeName = NameIsDNSSubdomain
@@ -1541,6 +1559,15 @@ func ValidatePersistentVolume(pv *core.PersistentVolume) field.ErrorList {
 		}
 	}
 
+	if pv.Spec.CSI != nil {
+		if numVolumes > 0 {
+			allErrs = append(allErrs, field.Forbidden(specPath.Child("csi"), "may not specify more than 1 volume type"))
+		} else {
+			numVolumes++
+			allErrs = append(allErrs, validateCSIPersistentVolumeSource(pv.Spec.CSI, specPath.Child("csi"))...)
+		}
+	}
+
 	if numVolumes == 0 {
 		allErrs = append(allErrs, field.Required(specPath, "must specify a volume type"))
 	}