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Subject: Re: [PATCH] mm,hwpoison: unmap poisoned page before invalidation
From:   Rik van Riel <riel@surriel.com>
To:     Oscar Salvador <osalvador@suse.de>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        kernel-team@fb.com, Miaohe Lin <linmiaohe@huawei.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Mel Gorman <mgorman@suse.de>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        stable@vger.kernel.org
Date:   Tue, 29 Mar 2022 11:49:53 -0400
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On Mon, 2022-03-28 at 11:00 +0200, Oscar Salvador wrote:
> On Fri, Mar 25, 2022 at 04:14:28PM -0400, Rik van Riel wrote:
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (in=
validate_inode_page(page))
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0poisonret =3D VM_FAULT_NOPAGE;
>=20
> What is the effect of returning VM_FAULT_NOPAGE?
> I take that we are cool because the pte has been installed and points
> to
> a new page? (I could not find where that is being done).
>=20
It results in us returning to userspace as if the page
fault had been handled, resulting in a second fault on
the same address.

However, now the page is no longer in the page cache,
and we can read it in from disk, to a page that is not
hardware poisoned, and we can then use that second page
without issues.

--=20
All Rights Reversed.

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