linux-kernel - Re: dpkg fails on sparc64 (was: [PATCH v4 4/7] mm/thp: Carry over dirty bit when thp splits on pmd)

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Date:   Tue, 25 Oct 2022 13:22:45 +0300
From:   Anatoly Pugachev <matorola@...il.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     David Miller <davem@...emloft.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Alistair Popple <apopple@...dia.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Huang Ying <ying.huang@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>, sparclinux@...r.kernel.org
Subject: Re: dpkg fails on sparc64 (was: [PATCH v4 4/7] mm/thp: Carry over
 dirty bit when thp splits on pmd)

On Sun, Oct 23, 2022 at 10:53 PM Peter Xu <peterx@...hat.com> wrote:
> On Fri, Oct 21, 2022 at 07:06:03PM +0300, Anatoly Pugachev wrote:
> >
> >     Link: https://lkml.kernel.org/r/20220811161331.37055-5-peterx@redhat.com
> >
> > So, v6.0-rc3-176-g0d206b5d2e0d) does not segfault dpkg,
> > v6.0-rc3-177-g0ccf7f168e17 segfaults it on package install.
> >
> > dpkg test was (apt) install/remove some packages, segfaults only on install
> > (not remove).
> >
> > Reverted 0ccf7f168e17bb7eb5a322397ba5a841f4fbaccb from top of v6.1-rc1 and
> > tried to compile kernel, but got error
> >
> > mm/huge_memory.c: In function ‘__split_huge_pmd_locked’:
> > mm/huge_memory.c:2129:17: error: ‘dirty’ undeclared (first use in this function)
> >  2129 |                 dirty = is_migration_entry_dirty(entry);
> >       |                 ^~~~~
> > mm/huge_memory.c:2129:17: note: each undeclared identifier is reported only once for each function it appears in
> > make[2]: *** [scripts/Makefile.build:250: mm/huge_memory.o] Error 1
> >
> > So can't test v6.1-rc1 with patch reverted...
>
> Sorry to know this, and thanks for the report and debugging.  The revert
> won't work because dirty variable is used in later patch for the swap path
> too.  I've attached a partial (and minimum) revert, feel free to try.

Peter,

tested again with 6.1.0-rc2 already, non patched kernel segfaulting
dpkg, using your patch makes dpkg
(or kernel) to behave properly.
Thanks!

> I had a feeling that it's somehow related to the special impl of sparc64
> pte_mkdirty() where a kernel patching mechanism is used to share code
> between sun4[uv].  I'd assume your machine is sun4v?  As that's the one
> that needs the patching, iiuc.

kernel boot log reports
ARCH: SUN4V