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Date:   Fri, 22 May 2020 20:15:17 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 06/36] mm: Introduce offset_in_thp
Message-ID: <20200522171517.dltsre7vfdvcrd2m@box>
References: <20200515131656.12890-1-willy@infradead.org>
 <20200515131656.12890-7-willy@infradead.org>
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On Fri, May 15, 2020 at 06:16:26AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> Mirroring offset_in_page(), this gives you the offset within this
> particular page, no matter what size page it is.  It optimises down
> to offset_in_page() if CONFIG_TRANSPARENT_HUGEPAGE is not set.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/mm.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 088acbda722d..9a55dce6a535 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1577,6 +1577,7 @@ static inline void clear_page_pfmemalloc(struct page *page)
>  extern void pagefault_out_of_memory(void);
>  
>  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
> +#define offset_in_thp(page, p)	((unsigned long)(p) & (thp_size(page) - 1))

Looks like thp_mask() would be handy here.

-- 
 Kirill A. Shutemov