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Subject: Re: [PATCH v10 01/33] mm: Introduce struct folio
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        akpm@linux-foundation.org
Cc:     linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Jeff Layton <jlayton@kernel.org>
References: <20210511214735.1836149-1-willy@infradead.org>
 <20210511214735.1836149-2-willy@infradead.org>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <ad8cd2e7-4111-f523-bc9c-5702b9071a5f@suse.cz>
Date:   Fri, 14 May 2021 12:40:05 +0200
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On 5/11/21 11:47 PM, Matthew Wilcox (Oracle) wrote:
> +/**
> + * folio_page - Return a page from a folio.
> + * @folio: The folio.
> + * @n: The page number to return.
> + *
> + * @n is relative to the start of the folio.  It should be between
> + * 0 and folio_nr_pages(@folio) - 1, but this is not checked for.
> + */
> +#define folio_page(folio, n)	nth_page(&(folio)->page, n)

BTW, would it make sense to have also a folio_page(folio) wrapper? Or is
"&folio->page" used in later patches sufficiently elegant and stable enough for
the future?

>  static __always_inline int PageTail(struct page *page)
>  {
>  	return READ_ONCE(page->compound_head) & 1;
>