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SubjectRe: [PATCH V3] mm:add VM_BUG_ON_PAGE() for page_mapcount()
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> 
> This patch add VM_BUG_ON_PAGE() for slab page,
> because _mapcount is an union with slab struct in struct page,
> avoid access _mapcount if this page is a slab page.
> Also remove the unneeded bracket.
>
> Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
> ---
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>

> include/linux/mm.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b464611..a117527 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -449,7 +449,8 @@ static inline void page_mapcount_reset(struct page *page)
>
> static inline int page_mapcount(struct page *page)
> {
> - return atomic_read(&(page)->_mapcount) + 1;
> + VM_BUG_ON_PAGE(PageSlab(page), page);
> + return atomic_read(&page->_mapcount) + 1;
> }
>
> static inline int page_count(struct page *page)
> --
> 2.1.3



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