Add a shouldDelete method in the provisioner Qualifer interface

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 qualifier, ok := ctrl.provisioner.(Qualifier); ok {
+		if !qualifier.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/controller_test.go

@@ -956,6 +956,10 @@ func (p *testQualifiedProvisioner) ShouldProvision(claim *v1.PersistentVolumeCla
 	return p.answer
 }
 
+func (p *testQualifiedProvisioner) ShouldDelete(claim *v1.PersistentVolume) bool {
+	return p.answer
+}
+
 func newTestBlockProvisioner(answer bool) *testBlockProvisioner {
 	return &testBlockProvisioner{newTestProvisioner(), answer}
 }

controller/volume.go

@@ -45,6 +45,9 @@ type Qualifier interface {
 	// ShouldProvision returns whether provisioning for the claim should
 	// be attempted.
 	ShouldProvision(*v1.PersistentVolumeClaim) bool
+
+	// ShouldDelete returns whether deleting the PV should be attempted.
+	ShouldDelete(volume *v1.PersistentVolume) bool
 }
 
 // BlockProvisioner is an optional interface implemented by provisioners to determine