Qestion about page->_count and page reclaim

[Li Haifeng]

Hi, all in kernel.

The page->_count is the page frame's usage count.
When page is allocated, the page will be refcounted, and page->_cout will
be set 1.

After be allocated from buddy system, the page will be used by process.
 get_page and put_page/put_page_testzero will used in pairs. is it right?

When the page is reclaimed to buddy system, the page->_count should be 0.
However, Because the initialization of page->_count is 1, get_page() and
put_page() is called in pairs, I coufused how page->_count will be 0?

Thanks.
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