private void updateFirstUnAllocatedOffset(long newValue) {
      //setVolatile even though all updates are under the allocationLock -- because there are a lot of
      // places there we _read_ the value without lock, so visibility must be ensured
      INT64_OVER_BYTE_BUFFER.setVolatile(
        headerPageBuffer,
        NEXT_CHUNK_TO_BE_ALLOCATED_OFFSET,
        newValue
      );
    }
private void updateFirstUnAllocatedOffset(long newValue)