[RFC V2] mm:add zero_page _mapcount when mapped into user space

[Kirill A. Shutemov]

On Tue, Dec 02, 2014 at 05:27:36PM +0800, Wang, Yalin wrote:
> This patch add/dec zero_page's _mapcount to make sure
> the mapcount is correct for zero_page,
> so that when read from /proc/kpagecount, zero_page's
> mapcount is also correct, userspace process like procrank can
> calculate PSS correctly.

I don't have specific code path to point to, but I would expect zero page
with non-zero mapcount would cause a problem with rmap.

How do you test the change?

-- 
 Kirill A. Shutemov