linux-kernel - Re: [PATCH 1/3] mm,hugetlb: use folio fields in second tail page

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Message-ID: <9de71a55-8f6d-a32e-cd57-f8ab8581e50@google.com>
Date:   Wed, 9 Nov 2022 17:58:17 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
cc:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, Peter Xu <peterx@...hat.com>,
        Yang Shi <shy828301@...il.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Mina Almasry <almasrymina@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/3] mm,hugetlb: use folio fields in second tail page

On Sat, 5 Nov 2022, Kirill A. Shutemov wrote:
> On Wed, Nov 02, 2022 at 06:48:45PM -0700, Hugh Dickins wrote:
> > @@ -260,13 +267,16 @@ struct page {
> >   *    to find how many references there are to this folio.
> >   * @memcg_data: Memory Control Group data.
> >   * @_flags_1: For large folios, additional page flags.
> > - * @__head: Points to the folio.  Do not use.
> > + * @_head_1: Points to the folio.  Do not use.
> >   * @_folio_dtor: Which destructor to use for this folio.
> >   * @_folio_order: Do not use directly, call folio_order().
> >   * @_total_mapcount: Do not use directly, call folio_entire_mapcount().
> >   * @_pincount: Do not use directly, call folio_maybe_dma_pinned().
> >   * @_folio_nr_pages: Do not use directly, call folio_nr_pages().
> > - * @_private_1: Do not use directly, call folio_get_private_1().
> 
> Looks like it misses
> 
>   + * @_flags_2: For large folios, additional page flags.
>   + * @_head_2: Points to the folio.  Do not use.
> 
> to match the first tail page documentation.
> 
> Otherwise the patch looks good to me:
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Many thanks for all your encouragement and reviews, Kirill.

Okay, I've added a couple of lines on those fields; but did not
want to recommend the _flags_2 field for use (by the time we run
out in _flags_1, I hope all this will be gone or look different).

I'm sending an incremental fix, once I've responded to Sidhartha.

Hugh