並行処理の実装パターン

[ubnt-intrepid]

今後のAPI開発を見据え、FUSE 特有の並行処理の実装パターンを整理しておきたい。

あくまで思考整理のためであり、実際に有効なデザインパターンなのかどうかは考えずにいきたい。

[ubnt-intrepid]

1. single-threaded

fn main() -> anyhow::Result<()> {
    let (devfd, mount) = mount("/path/to/mountpoint", MountOptions::default())?;
    let mut conn = Connection::from(devfd);
    
    let session = Session::init(&mut conn, KernelConfig::default())?;
    
    let mut req = session.new_request_buffer()?;
    while session.read_request(&mut conn, &mut req)? {
        match req.operation()? {
            Operation::Lookup(op) => do_lookup(...)?,
            _ => session.reply_error(&mut conn, &req, libc::ENOSYS)?,
        }
    }
    
    mount.unmount()?;

    Ok(())
}

2. per worker thread

fn main() -> anyhow::Result<()> {
    let (conn, session) = /* ...omit... */;

    std::thread::scope(|scope| -> anyhow::Result<()> {
        for i in ..num_worker_threads {
            let session = &session;
            let mut conn = conn.try_ioc_clone()?;
            let mut req = session.new_request_buffer()?;

            scope.spawn(|| {
                while session.read_request(&mut conn, &mut req)? {
                match req.operation()? {
                    Operation::Lookup(op) => do_lookup(...)?,
                    _ => session.reply_error(&mut conn, &req, libc::ENOSYS)?,
                }
            });
        }
        Ok(())
    })?;

    mount.unmount()?;

    Ok(())
}