rbd/tests: force librbd errors by passing a closed image

In order to get a higher test coverage for rbd/rbd.go, there is a need
to trigger errors for the librbd functions. This makes it possible to
test the error path. The new TestClosedImage() function tricks
RbdImage.validate() into accepting an image that is closed, but still
references the closed image.

librbd is expected to return an error when the image is closed. However,
passing a closed image does not result in stable behavior. Sometimes
librbd causes a panic, at other times there will be a hang and the test
will time-out.

The TestClosedImage() function is disabled, it will skip all testing but
remains available so that it could be enabled in the future.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

rbd/rbd_test.go

@@ -1059,3 +1059,93 @@ func TestImageMetadata(t *testing.T) {
 	conn.DeletePool(poolname)
 	conn.Shutdown()
 }
+
+func TestClosedImage(t *testing.T) {
+	t.Skipf("many of the following functions cause a panic or hang, skip this test")
+
+	conn := radosConnect(t)
+
+	poolname := GetUUID()
+	err := conn.MakePool(poolname)
+	assert.NoError(t, err)
+
+	ioctx, err := conn.OpenIOContext(poolname)
+	require.NoError(t, err)
+
+	name := GetUUID()
+	image, err := Create(ioctx, name, 1<<22, 22)
+	assert.NoError(t, err)
+
+	err = image.Open()
+	assert.NoError(t, err)
+
+	// keep the rbdImage around after close
+	rbdImage := image.image
+
+	// close the image
+	err = image.Close()
+	assert.NoError(t, err)
+
+	// restore the image so image.validate() succeeds
+	image.image = rbdImage
+
+	// functions should now fail with an RBDError
+
+	err = image.Close()
+	assert.Error(t, err)
+
+	err = image.Resize(1 << 22)
+	assert.Error(t, err)
+
+	_, err = image.Stat()
+	assert.Error(t, err)
+
+	_, err = image.IsOldFormat()
+	assert.Error(t, err)
+
+	_, err = image.GetSize()
+	assert.Error(t, err)
+
+	_, err = image.GetFeatures()
+	assert.Error(t, err)
+
+	_, err = image.GetStripeUnit()
+	assert.Error(t, err)
+
+	_, err = image.GetStripeCount()
+	assert.Error(t, err)
+
+	_, err = image.GetOverlap()
+	assert.Error(t, err)
+
+	err = image.Flatten()
+	assert.Error(t, err)
+
+	_, _, err = image.ListChildren()
+	assert.Error(t, err)
+
+	err = image.Flush()
+	assert.Error(t, err)
+
+	_, err = image.GetSnapshotNames()
+	assert.Error(t, err)
+
+	_, err = image.CreateSnapshot("new_snapshot")
+	assert.Error(t, err)
+
+	_, err = image.GetMetadata("metadata-key")
+	assert.Error(t, err)
+
+	err = image.SetMetadata("metadata-key", "metadata-value")
+	assert.Error(t, err)
+
+	err = image.RemoveMetadata("metadata-key")
+	assert.Error(t, err)
+
+	err = image.Remove()
+	assert.NoError(t, err)
+
+	ioctx.Destroy()
+	conn.DeletePool(poolname)
+	conn.Shutdown()
+}