TrackWriter return incorrect written_size

[nooberfsh]

#[tokio::main]
async fn main() -> Result<()> {
    let wsize = Arc::new(AtomicI64::new(0));
    let mut w = make_writer(wsize.clone()).await?;

    let data = "hello, opendal";
    for _ in 0..1_000_000 {
        w.write_all(data.as_bytes()).await?
    }

    w.shutdown().await?;
    let wsize = wsize.load(std::sync::atomic::Ordering::SeqCst);
    println!("written size: {wsize}");

    Ok(())
}

async fn make_writer(wsize: Arc<AtomicI64>) -> Result<TrackWriter> {
    let mut builder = Fs::default();
    builder.root(".");
    let op: Operator = Operator::new(builder)?.finish();

    let w = op
        .writer("test.txt")
        .await
        .unwrap()
        .into_futures_async_write();
    Ok(TrackWriter::new(w, wsize))
}

Full code can be found in this repo

The above code write a simple string literal "hello, opendal" to local file test.txt 1_000_000 times using TrackWriter.
The expected written_size should be 14000000, but the above code print 14000326 on my machine which does not match the file size.

Related code:

icelake/icelake/src/io_v2/file_writer/track_writer.rs

Lines 30 to 33 in 07d5389

	match Pin::new(&mut self.writer).poll_write(cx, buf) {
	std::task::Poll::Ready(Ok(n)) => {
	self.written_size
	.fetch_add(buf.len() as i64, std::sync::atomic::Ordering::Relaxed);