disk: support automatic name generation for swap devices

This commit adds support for automatic geneation of names for
an lv swap devices. This saves the users of advanced blueprints
some typing.

pkg/disk/lvm.go

@@ -110,12 +110,15 @@ func (vg *LVMVolumeGroup) CreateLogicalVolume(lvName string, size uint64, payloa
 
 	if lvName == "" {
 		// generate a name based on the payload's mountpoint
-		mntble, ok := payload.(Mountable)
-		if !ok {
+		switch ent := payload.(type) {
+		case Mountable:
+			lvName = ent.GetMountpoint()
+		case *Swap:
+			lvName = "swap"
+		default:
 			return nil, fmt.Errorf("could not create logical volume: no name provided and payload is not mountable")
 		}
-		mountpoint := mntble.GetMountpoint()
-		autoName, err := vg.genLVName(mountpoint)
+		autoName, err := vg.genLVName(lvName)
 		if err != nil {
 			return nil, err
 		}

pkg/disk/lvm_test.go

@@ -39,6 +39,21 @@ func TestLVMVCreateMountpoint(t *testing.T) {
 	assert.Error(err)
 }
 
+func TestLVMVCreateLogicalVolumeSwap(t *testing.T) {
+	vg := &LVMVolumeGroup{
+		Name:        "root",
+		Description: "root volume group",
+	}
+	swap := &Swap{}
+	lv, err := vg.CreateLogicalVolume("", 12345, swap)
+	assert.NoError(t, err)
+	assert.Equal(t, "swaplv", lv.Name)
+	// one more
+	lv2, err := vg.CreateLogicalVolume("", 12345, swap)
+	assert.NoError(t, err)
+	assert.Equal(t, "swaplv00", lv2.Name)
+}
+
 func TestImplementsInterfacesCompileTimeCheckLVM(t *testing.T) {
 	var _ = Container(&LVMVolumeGroup{})
 	var _ = Sizeable(&LVMLogicalVolume{})