linux-kernel - Re: [PATCH v17 5/9] mm: hugetlb: set the PageHWPoison to the raw error page

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Date:   Sun, 7 Mar 2021 19:18:57 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
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        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
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        joao.m.martins@...cle.com, duanxiongchun@...edance.com,
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        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v17 5/9] mm: hugetlb: set the PageHWPoison to the raw
 error page

On Thu, Feb 25, 2021 at 09:21:26PM +0800, Muchun Song wrote:
> Because we reuse the first tail vmemmap page frame and remap it
> with read-only, we cannot set the PageHWPosion on some tail pages.
> So we can use the head[4].private (There are at least 128 struct
> page structures associated with the optimized HugeTLB page, so
> using head[4].private is safe) to record the real error page index
> and set the raw error page PageHWPoison later.
>

Does the hardcoding of 4 come from HUGETLB_CGROUP_MIN_ORDER, if so
do we need to hardcode 4? Also, I am not sure about the comment
on safety and 128 struct pages

Balbir