void read(long addr, byte[] dst, int off, int len) throws IOException {
    if (LOG.isTraceEnabled()) {
      LOG.trace("read:" + this + "," + Thread.currentThread() + "," + len + "," + addr);
    }
    fileChannel.read(ByteBuffer.wrap(dst, off, len), addr);
  }
void read(long addr, byte[] dst, int off, int len)