Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359

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	[thread overview]
Message-ID: <5812280.fcLxn8YiTP@natalenko.name> (raw)
In-Reply-To: <688a2cb1-5cd8-2c00-889c-4d48021371f8@huawei.com>

On pondělí 19. července 2021 14:08:37 CEST Miaohe Lin wrote:
> On 2021/7/19 19:59, Oleksandr Natalenko wrote:
> > On pondělí 19. července 2021 13:50:07 CEST Miaohe Lin wrote:
> >> 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.
> >>> 
> >>> Oh, so this is a backport problem.  2799e77529c2 was backported without
> >>> its prerequisite 63d8620ecf93.  Greg, probably best to just drop
> >> 
> >> Yes, they're posted as a patch set:
> >> 
> >> https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com
> >> 
> >>> 2799e77529c2 from all stable trees; the race described is not very
> >>> important (swapoff vs reading a page back from that swap device).
> >>> .
> >> 
> >> 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.
> >> 
> >> Sorry for the trouble!
> > 
> > git log --oneline v5.13..v5.13.3 --author="Miaohe Lin"
> > 11ebc09e50dc mm/zswap.c: fix two bugs in zswap_writeback_entry()
> > 95d192da198d mm/z3fold: use release_z3fold_page_locked() to release locked
> > z3fold page
> > ccb7848e2344 mm/z3fold: fix potential memory leak in z3fold_destroy_pool()
> > 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
> > 
> > Do you suggest reverting "mm/shmem: fix shmem_swapin() race with swapoff"
> > as well?
> 
> This patch also rely on its prerequisite 63d8620ecf93. I think we should
> either revert any commit in this series or just backport the entire series.

Then why not just pick up 2 more patches instead of dropping 2 patches. Greg, 
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

-- 
Oleksandr Natalenko (post-factum)