Add a DeletionGuard interface for custom provisioner to implement cus…

…tom shouldDelete logic

controller/controller.go

@@ -848,6 +848,12 @@ func (ctrl *ProvisionController) shouldProvision(claim *v1.PersistentVolumeClaim
 // shouldDelete returns whether a volume should have its backing volume
 // deleted, i.e. whether a Delete is "desired"
 func (ctrl *ProvisionController) shouldDelete(volume *v1.PersistentVolume) bool {
+	if deletionGuard, ok := ctrl.provisioner.(DeletionGuard); ok {
+		if !deletionGuard.ShouldDelete(volume) {
+			return false
+		}
+	}
+
 	// In 1.9+ PV protection means the object will exist briefly with a
 	// deletion timestamp even after our successful Delete. Ignore it.
 	if ctrl.kubeVersion.AtLeast(utilversion.MustParseSemantic("v1.9.0")) {

controller/volume.go

@@ -47,6 +47,13 @@ type Qualifier interface {
 	ShouldProvision(*v1.PersistentVolumeClaim) bool
 }
 
+// DeletionGuard is an optional interface implemented by provisioners to determine
+// whether a PV should be deleted.
+type DeletionGuard interface {
+	// ShouldDelete returns whether deleting the PV should be attempted.
+	ShouldDelete(volume *v1.PersistentVolume) bool
+}
+
 // BlockProvisioner is an optional interface implemented by provisioners to determine
 // whether it supports block volume.
 type BlockProvisioner interface {