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Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359
To:     Oleksandr Natalenko <oleksandr@natalenko.name>,
        Matthew Wilcox <willy@infradead.org>
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>
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 <YPVgaY6uw59Fqg5x@casper.infradead.org>
 <8058e175-cec5-c243-6499-c1cd4e3c8605@huawei.com>
 <2145858.R0O0FObHBN@natalenko.name>
From:   Miaohe Lin <linmiaohe@huawei.com>
Message-ID: <688a2cb1-5cd8-2c00-889c-4d48021371f8@huawei.com>
Date:   Mon, 19 Jul 2021 20:08:37 +0800
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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.

Many thanks.

>