CSIDriver: allow "StorageCapacity" to be modified

When originally introduced, the field was made immutable to be
consistent with the other fields. But in practice allowing it to be
toggled makes more sense, in particular when considering the rollout
of a CSI driver (let it run without using the published
CSIStorageCapacity object, then flip the field, or upgrading from a
driver without support to one which supports it).

The only consumer of this field, the kube-scheduler, can handle
mutation without problems because it always consults the informer
cache to get the current value.

pkg/apis/storage/types.go

@@ -357,7 +357,7 @@ type CSIDriverSpec struct {
 	// unset or false and it can be flipped later when storage
 	// capacity information has been published.
 	//
-	// This field is immutable.
+	// This field was immutable in Kubernetes <= 1.22 and now is mutable.
 	//
 	// This is a beta field and only available when the CSIStorageCapacity
 	// feature is enabled. The default is false.

pkg/apis/storage/validation/validation.go

@@ -420,13 +420,13 @@ func ValidateCSIDriver(csiDriver *storage.CSIDriver) field.ErrorList {
 // ValidateCSIDriverUpdate validates a CSIDriver.
 func ValidateCSIDriverUpdate(new, old *storage.CSIDriver) field.ErrorList {
 	allErrs := apivalidation.ValidateObjectMetaUpdate(&new.ObjectMeta, &old.ObjectMeta, field.NewPath("metadata"))
+	allErrs = append(allErrs, validateCSIDriverSpec(&new.Spec, field.NewPath("spec"))...)
 
 	// immutable fields should not be mutated.
 	allErrs = append(allErrs, apimachineryvalidation.ValidateImmutableField(new.Spec.AttachRequired, old.Spec.AttachRequired, field.NewPath("spec", "attachedRequired"))...)
 	allErrs = append(allErrs, apimachineryvalidation.ValidateImmutableField(new.Spec.FSGroupPolicy, old.Spec.FSGroupPolicy, field.NewPath("spec", "fsGroupPolicy"))...)
 	allErrs = append(allErrs, apimachineryvalidation.ValidateImmutableField(new.Spec.PodInfoOnMount, old.Spec.PodInfoOnMount, field.NewPath("spec", "podInfoOnMount"))...)
 	allErrs = append(allErrs, apimachineryvalidation.ValidateImmutableField(new.Spec.VolumeLifecycleModes, old.Spec.VolumeLifecycleModes, field.NewPath("spec", "volumeLifecycleModes"))...)
-	allErrs = append(allErrs, apimachineryvalidation.ValidateImmutableField(new.Spec.StorageCapacity, old.Spec.StorageCapacity, field.NewPath("spec", "storageCapacity"))...)
 
 	allErrs = append(allErrs, validateTokenRequests(new.Spec.TokenRequests, field.NewPath("spec", "tokenRequests"))...)
 	return allErrs

pkg/apis/storage/validation/validation_test.go

@@ -1965,6 +1965,12 @@ func TestCSIDriverValidationUpdate(t *testing.T) {
 				new.Spec.RequiresRepublish = &requiresRepublish
 			},
 		},
+		{
+			name: "StorageCapacity changed",
+			modify: func(new *storage.CSIDriver) {
+				new.Spec.StorageCapacity = &notStorageCapacity
+			},
+		},
 	}
 	for _, test := range successCases {
 		t.Run(test.name, func(t *testing.T) {
@@ -2061,18 +2067,18 @@ func TestCSIDriverValidationUpdate(t *testing.T) {
 				new.Spec.FSGroupPolicy = &fileFSGroupPolicy
 			},
 		},
-		{
-			name: "StorageCapacity changed",
-			modify: func(new *storage.CSIDriver) {
-				new.Spec.StorageCapacity = &notStorageCapacity
-			},
-		},
 		{
 			name: "TokenRequests invalidated",
 			modify: func(new *storage.CSIDriver) {
 				new.Spec.TokenRequests = []storage.TokenRequest{{Audience: gcp}, {Audience: gcp}}
 			},
 		},
+		{
+			name: "invalid nil StorageCapacity",
+			modify: func(new *storage.CSIDriver) {
+				new.Spec.StorageCapacity = nil
+			},
+		},
 	}
 
 	for _, test := range errorCases {

staging/src/k8s.io/api/storage/v1/types.go

@@ -341,7 +341,7 @@ type CSIDriverSpec struct {
 	// unset or false and it can be flipped later when storage
 	// capacity information has been published.
 	//
-	// This field is immutable.
+	// This field was immutable in Kubernetes <= 1.22 and now is mutable.
 	//
 	// This is a beta field and only available when the CSIStorageCapacity
 	// feature is enabled. The default is false.

staging/src/k8s.io/api/storage/v1beta1/types.go

@@ -362,7 +362,7 @@ type CSIDriverSpec struct {
 	// unset or false and it can be flipped later when storage
 	// capacity information has been published.
 	//
-	// This field is immutable.
+	// This field was immutable in Kubernetes <= 1.22 and now is mutable.
 	//
 	// This is a beta field and only available when the CSIStorageCapacity
 	// feature is enabled. The default is false.