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From:   Oleksandr Natalenko <oleksandr@natalenko.name>
To:     Matthew Wilcox <willy@infradead.org>,
        Miaohe Lin <linmiaohe@huawei.com>
Cc:     Boqun Feng <boqun.feng@gmail.com>,
        Zhouyi Zhou <zhouzhouyi@gmail.com>, paulmck@kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        stable@vger.kernel.org, Chris Clayton <chris2553@googlemail.com>,
        Chris Rankin <rankincj@gmail.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        rcu <rcu@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        "Huang, Ying" <ying.huang@intel.com>, gregkh@linuxfoundation.org
Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359
Date:   Mon, 19 Jul 2021 14:12:15 +0200
Message-ID: <5812280.fcLxn8YiTP@natalenko.name>
In-Reply-To: <688a2cb1-5cd8-2c00-889c-4d48021371f8@huawei.com>
References: <c9fd1311-662c-f993-c8ef-54af036f2f78@googlemail.com> <2145858.R0O0FObHBN@natalenko.name> <688a2cb1-5cd8-2c00-889c-4d48021371f8@huawei.com>
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On pond=C4=9Bl=C3=AD 19. =C4=8Dervence 2021 14:08:37 CEST Miaohe Lin wrote:
> On 2021/7/19 19:59, Oleksandr Natalenko wrote:
> > On pond=C4=9Bl=C3=AD 19. =C4=8Dervence 2021 13:50:07 CEST Miaohe Lin wr=
ote:
> >> On 2021/7/19 19:22, Matthew Wilcox wrote:
> >>> On Mon, Jul 19, 2021 at 07:12:58PM +0800, Miaohe Lin wrote:
> >>>> When in the commit 2799e77529c2a, we're using the percpu_ref to
> >>>> serialize
> >>>> against concurrent swapoff, i.e. there's percpu_ref inside
> >>>> get_swap_device() instead of rcu_read_lock(). Please see commit
> >>>> 63d8620ecf93 ("mm/swapfile: use percpu_ref to serialize against
> >>>> concurrent swapoff") for detail.
> >>>=20
> >>> Oh, so this is a backport problem.  2799e77529c2 was backported witho=
ut
> >>> its prerequisite 63d8620ecf93.  Greg, probably best to just drop
> >>=20
> >> Yes, they're posted as a patch set:
> >>=20
> >> https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com
> >>=20
> >>> 2799e77529c2 from all stable trees; the race described is not very
> >>> important (swapoff vs reading a page back from that swap device).
> >>> .
> >>=20
> >> The swapoff races with reading a page back from that swap device should
> >> be
> >> really uncommon as most users only do swapoff when the system is going=
 to
> >> shutdown.
> >>=20
> >> Sorry for the trouble!
> >=20
> > git log --oneline v5.13..v5.13.3 --author=3D"Miaohe Lin"
> > 11ebc09e50dc mm/zswap.c: fix two bugs in zswap_writeback_entry()
> > 95d192da198d mm/z3fold: use release_z3fold_page_locked() to release loc=
ked
> > z3fold page
> > ccb7848e2344 mm/z3fold: fix potential memory leak in z3fold_destroy_poo=
l()
> > 9f7229c901c1 mm/huge_memory.c: don't discard hugepage if other processes
> > are mapping it
> > f13259175e4f mm/huge_memory.c: add missing read-only THP checking in
> > transparent_hugepage_enabled()
> > afafd371e7de mm/huge_memory.c: remove dedicated macro
> > HPAGE_CACHE_INDEX_MASK a533a21b692f mm/shmem: fix shmem_swapin() race
> > with swapoff
> > c3b39134bbd0 swap: fix do_swap_page() race with swapoff
> >=20
> > Do you suggest reverting "mm/shmem: fix shmem_swapin() race with swapof=
f"
> > as well?
>=20
> This patch also rely on its prerequisite 63d8620ecf93. I think we should
> either revert any commit in this series or just backport the entire serie=
s.

Then why not just pick up 2 more patches instead of dropping 2 patches. Gre=
g,=20
could you please make sure the whole series from [1] gets pulled?

Thanks.

[1] https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com

=2D-=20
Oleksandr Natalenko (post-factum)