Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20221018200125.848471-1-jthoughton@google.com>
 <20221104021035.GA297167@hori.linux.bs1.fc.nec.co.jp> <Y2UTUNBHVY5U9si2@monkey>
 <20221107042544.GA436198@hori.linux.bs1.fc.nec.co.jp>
In-Reply-To: <20221107042544.GA436198@hori.linux.bs1.fc.nec.co.jp>
From:   Yang Shi <shy828301@gmail.com>
Date:   Mon, 7 Nov 2022 10:50:35 -0800
Message-ID: <CAHbLzkpb5+sPmKLNjoL27mNoVFiKnNCwU6JJY_R7VquJL7VG5Q@mail.gmail.com>
Subject: Re: [PATCH] hugetlbfs: don't delete error page from pagecache
To:     =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= 
        <naoya.horiguchi@nec.com>
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        James Houghton <jthoughton@google.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Axel Rasmussen <axelrasmussen@google.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Sun, Nov 6, 2022 at 8:25 PM HORIGUCHI NAOYA(=E5=A0=80=E5=8F=A3=E3=80=80=
=E7=9B=B4=E4=B9=9F)
<naoya.horiguchi@nec.com> wrote:
>
> On Fri, Nov 04, 2022 at 06:27:44AM -0700, Mike Kravetz wrote:
> > On 11/04/22 02:10, HORIGUCHI NAOYA(=E5=A0=80=E5=8F=A3 =E7=9B=B4=E4=B9=
=9F) wrote:
> > > On Tue, Oct 18, 2022 at 08:01:25PM +0000, James Houghton wrote:
> > > > This change is very similar to the change that was made for shmem [=
1],
> > > > and it solves the same problem but for HugeTLBFS instead.
> > > >
> > > > Currently, when poison is found in a HugeTLB page, the page is remo=
ved
> > > > from the page cache. That means that attempting to map or read that
> > > > hugepage in the future will result in a new hugepage being allocate=
d
> > > > instead of notifying the user that the page was poisoned. As [1] st=
ates,
> > > > this is effectively memory corruption.
> > > >
> > > > The fix is to leave the page in the page cache. If the user attempt=
s to
> > > > use a poisoned HugeTLB page with a syscall, the syscall will fail w=
ith
> > > > EIO, the same error code that shmem uses. For attempts to map the p=
age,
> > > > the thread will get a BUS_MCEERR_AR SIGBUS.
> > > >
> > > > [1]: commit a76054266661 ("mm: shmem: don't truncate page if memory=
 failure happens")
> > > >
> > > > Signed-off-by: James Houghton <jthoughton@google.com>
> > >
> > > I did some testing and found no issue. So I agree with this patch.
> > > Thank you very much.
> > >
> > > Tested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> > > Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> > >
> > > As for whether to go with HGM patchset or not, I have no strong opini=
on.
> > > As you stated in another email this patch is correct without HGM patc=
h,
> > > so it's OK to me to make this merged first.
> >
> > Thanks Naoya.
> >
> > This is a late thought, but ...
> > Should this patch and Yang Shi's shmem patch be backported to stable re=
leases?
> > Both address potential data corruption/loss, so it certainly seems like
> > stable material.
>
> Yes, I agree that backporting these could be helpful.

+1

>
> So I think that I'll try to backport commit a7605426666 and its dependenc=
ies
> to 5.15 (and older LTS if possible).  For this patch, just adding "Cc: st=
able"
> should be enough for now.

Thanks, Naoya.

>
> Thanks,
> Naoya Horiguchi