ULK关于永久内核映射计数器的解释和源代码以及《深入linux内核架构》上讲的都不一样？

/*

* Virtual_count is not a pure "count".
在源代码（我的是2.6.25）
*  0 means that it is not mapped, and has not been mapped

*    since a TLB flush - it is usable.

*  1 means that there are no users, but it has been mapped

*    since the last TLB flush - so we can't use it. //没有内核成分使用这个页表项，但是从上次刷新TLB以来，它已经被映射。

*  n means that there are (n-1) current users of it.

*/

但是在ULK（第三版，不过这里的内容和第二版一样）中这样说：
  The corresponding Page Table entry does not map any high-memory page frame, but it cannot be used because the corresponding TLB entry has not been flushed since its last usage。（对应的页表项没有映射任何高端内存页框，但是它不能被使用。。。）
  请各位大侠提携小弟，小弟不甚感激，哦，是不胜感激。

深入理解Linux架构，看的云里雾里的，个人感觉还是不如ulk和情景分析经典