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Date:   Tue, 25 Aug 2020 17:44:10 +1000
From:   Stephen Rothwell <sfr@canb.auug.org.au>
To:     Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     Matthew Wilcox <willy@infradead.org>,
        linux-mm <linux-mm@kvack.org>,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        lkft-triage@lists.linaro.org,
        Andrew Morton <akpm@linux-foundation.org>,
        LTP List <ltp@lists.linux.it>, Arnd Bergmann <arnd@arndb.de>,
        Russell King - ARM Linux <linux@armlinux.org.uk>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christoph Hellwig <hch@lst.de>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Xu <peterx@redhat.com>, opendmb@gmail.com,
        Linus Walleij <linus.walleij@linaro.org>,
        afzal.mohd.ma@gmail.com, Will Deacon <will@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: BUG: Bad page state in process true pfn:a8fed on arm
Message-ID: <20200825174410.1af823db@canb.auug.org.au>
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Hi all,

On Tue, 25 Aug 2020 13:03:53 +0530 Naresh Kamboju <naresh.kamboju@linaro.or=
g> wrote:
>
> On Mon, 24 Aug 2020 at 16:36, Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Mon, Aug 24, 2020 at 03:14:55PM +0530, Naresh Kamboju wrote: =20
> > > [   67.545247] BUG: Bad page state in process true  pfn:a8fed
> > > [   67.550767] page:9640c0ab refcount:0 mapcount:-1024 =20
> >
> > Somebody freed a page table without calling __ClearPageTable() on it. =
=20
>=20
> After running git bisect on this problem,
> The first suspecting of this problem on arm architecture this patch.
> 424efe723f7717430bec7c93b4d28bba73e31cf6
> ("mm: account PMD tables like PTE tables ")
>=20
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Reported-by: Anders Roxell <anders.roxell@linaro.org>
>=20
> Additional information:
> We have tested linux next by reverting this patch and confirmed
> that the reported BUG is not reproduced.
>=20
> These configs enabled on the running device,
>=20
> CONFIG_TRANSPARENT_HUGEPAGE=3Dy
> CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=3Dy
>=20
>=20
> -- Suspecting patch --
> commit 424efe723f7717430bec7c93b4d28bba73e31cf6
> Author: Matthew Wilcox <willy@infradead.org>
> Date:   Thu Aug 20 10:01:30 2020 +1000
>=20
>     mm: account PMD tables like PTE tables

OK, I have reverted that patch from todays' linux-next.

--=20
Cheers,
Stephen Rothwell

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