Method fsync

block/src/qcow_sync.rs:238–245

(&mut self, user_data: Option<u64>)

    }

    fn fsync(&mut self, user_data: Option<u64>) -> AsyncIoResult<()> {
        self.metadata.flush().map_err(AsyncIoError::Fsync)?;
        if let Some(user_data) = user_data {
            self.completion_list.push_back((user_data, 0));
            self.eventfd.write(1).unwrap();
        }
        Ok(())
    }

    fn next_completed_request(&mut self) -> Option<(u64, i32)> {
        self.completion_list.pop_front()