Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sun, 7 Mar 2021 19:18:57 +1100
From:   Balbir Singh <bsingharora@gmail.com>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
        dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org,
        viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
        paulmck@kernel.org, mchehab+huawei@kernel.org,
        pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org,
        oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de,
        almasrymina@google.com, rientjes@google.com, willy@infradead.org,
        osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com,
        david@redhat.com, naoya.horiguchi@nec.com,
        joao.m.martins@oracle.com, duanxiongchun@bytedance.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v17 5/9] mm: hugetlb: set the PageHWPoison to the raw
 error page
Message-ID: <20210307081857.GE1223287@balbir-desktop>
References: <20210225132130.26451-1-songmuchun@bytedance.com>
 <20210225132130.26451-6-songmuchun@bytedance.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210225132130.26451-6-songmuchun@bytedance.com>
Precedence: bulk

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