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Date:   Wed, 16 Dec 2020 22:26:02 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        David Hildenbrand <david@...hat.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v9 10/11] mm/hugetlb: Gather discrete
 indexes of tail page

On Wed, Dec 16, 2020 at 10:03 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Sun, Dec 13, 2020 at 11:45:33PM +0800, Muchun Song wrote:
> > For HugeTLB page, there are more metadata to save in the struct page.
> > But the head struct page cannot meet our needs, so we have to abuse
> > other tail struct page to store the metadata. In order to avoid
> > conflicts caused by subsequent use of more tail struct pages, we can
> > gather these discrete indexes of tail struct page. In this case, it
> > will be easier to add a new tail page index later.
> >
> > There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct
> > page structs can be used when CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, so
> "that can be..."

Thanks.

>
> > add a BUILD_BUG_ON to catch invalid usage of the tail struct page.
> >
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
>
> I think this makes the current situation with metadata usage in sub-pages
> easier to track.

Agree.

>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>

Thank you.

>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun

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