@Override
    public Committer closeForCommit() throws IOException {
        lock();
        try {
            uploadCurrentPart();
            return upload.getCommitter();
        } finally {
            unlock();
        }
    }
@Test(expected = IOException.class)
    public void testCloseForCommitOnClosedStreamShouldFail() throws IOException {
        fsDataOutputStream.closeForCommit().commit();
        fsDataOutputStream.closeForCommit().commit();
    }