Re: [PATCH v9 3/8] mm: Move set/get_pcppage_migratetype to mmzone.h

[Kirill A. Shutemov]

On Sat, Sep 07, 2019 at 10:25:28AM -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> 
> In order to support page reporting it will be necessary to store and
> retrieve the migratetype of a page. To enable that I am moving the set and
> get operations for pcppage_migratetype into the mm/internal.h header so
> that they can be used outside of the page_alloc.c file.
> 
> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>

I'm not sure that it's great idea to export this functionality beyond
mm/page_alloc.c without any additional safeguards. How would we avoid to
messing with ->index when the page is not in the right state of its
life-cycle. Can we add some VM_BUG_ON()s here?

-- 
 Kirill A. Shutemov