rbd: add Sparsify implementing rbd_sparsify

The sparsify function can be used to make an image sparse by replacing
runs of zeros with holes. This change adds a wrapper for the basic
rbd_sparsify function and accompanying tests.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

rbd/rbd_nautilus.go

@@ -101,3 +101,17 @@ func (image *Image) GetModifyTimestamp() (Timespec, error) {
 
 	return Timespec(ts.CStructToTimespec(ts.CTimespecPtr(&cts))), nil
 }
+
+// Sparsify makes an image sparse by deallocating runs of zeros.
+// The sparseSize value will be used to find runs of zeros and must be
+// a power of two no less than 4096 and no larger than the image size.
+//
+// Implements:
+//  int rbd_sparsify(rbd_image_t image, size_t sparse_size);
+func (image *Image) Sparsify(sparseSize uint) error {
+	if err := image.validate(imageIsOpen); err != nil {
+		return err
+	}
+
+	return getError(C.rbd_sparsify(image.image, C.size_t(sparseSize)))
+}

rbd/rbd_nautilus_test.go

@@ -77,3 +77,49 @@ func TestClosedImageNautilus(t *testing.T) {
 	_, err = image.GetModifyTimestamp()
 	assert.Error(t, err)
 }
+
+func TestSparsify(t *testing.T) {
+	conn := radosConnect(t)
+	defer conn.Shutdown()
+
+	poolname := GetUUID()
+	err := conn.MakePool(poolname)
+	require.NoError(t, err)
+	defer conn.DeletePool(poolname)
+
+	ioctx, err := conn.OpenIOContext(poolname)
+	require.NoError(t, err)
+	defer ioctx.Destroy()
+
+	name := GetUUID()
+	err = quickCreate(ioctx, name, testImageSize, testImageOrder)
+	require.NoError(t, err)
+	defer func() { assert.NoError(t, RemoveImage(ioctx, name)) }()
+
+	t.Run("valid", func(t *testing.T) {
+		img, err := OpenImage(ioctx, name, NoSnapshot)
+		assert.NoError(t, err)
+		defer func() { assert.NoError(t, img.Close()) }()
+
+		err = img.Sparsify(4096)
+		assert.NoError(t, err)
+	})
+
+	t.Run("invalidValue", func(t *testing.T) {
+		img, err := OpenImage(ioctx, name, NoSnapshot)
+		assert.NoError(t, err)
+		defer func() { assert.NoError(t, img.Close()) }()
+
+		err = img.Sparsify(1024)
+		assert.Error(t, err)
+	})
+
+	t.Run("closedImage", func(t *testing.T) {
+		img, err := OpenImage(ioctx, name, NoSnapshot)
+		assert.NoError(t, err)
+		assert.NoError(t, img.Close())
+
+		err = img.Sparsify(1024)
+		assert.Error(t, err)
+	})
+}