AuFS 中如何打破自上而下的文件创建策略与父文件创建策略之间的联系？

Question

这金沙澳门官网 手动的说：

创建 create=tdp | top-down-parent 的策略

Selects the highest writable branch where the parent dir exists. If
the parent dir does not exist on a writable branch, then the internal
copyup will happen. The policy for this copyup is always ’bottom-up.’
This is the default policy.

如果父目录存在多个可写分支会发生什么情况？