Re: [PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages

[Hugh Dickins]

On Wed, 25 Mar 2015, Kirill A. Shutemov wrote:
> 
> We only need tail refcounting for THP, so I think this should fix the issue:
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 4a3a38522ab4..9ab432660adb 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -456,7 +456,7 @@ static inline int page_count(struct page *page)
>  
>  static inline bool __compound_tail_refcounted(struct page *page)
>  {
> -       return !PageSlab(page) && !PageHeadHuge(page);
> +       return !PageSlab(page) && !PageHeadHuge(page) && PageAnon(page);
>  }
>  
>  /*

Yes, that should be a good fix for the mapcount issue.
And no coincidence that it's just what I needed too,
when reusing the PG_compound_lock bit: see my 10/24
(which had to rearrange mm.h. not having your 1/16).

Hugh
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