linux-kernel - Re: linux-5.13.2: warning from kernel/rcu/tree

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Date:   Mon, 19 Jul 2021 20:17:41 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Oleksandr Natalenko <oleksandr@...alenko.name>,
        Matthew Wilcox <willy@...radead.org>
CC:     Boqun Feng <boqun.feng@...il.com>,
        Zhouyi Zhou <zhouzhouyi@...il.com>, <paulmck@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>, Chris Clayton <chris2553@...glemail.com>,
        Chris Rankin <rankincj@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        rcu <rcu@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        "Huang, Ying" <ying.huang@...el.com>, <gregkh@...uxfoundation.org>
Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359

On 2021/7/19 20:12, Oleksandr Natalenko wrote:
> 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
> 

I browsed the previous backport notifying email and found that these two patches are also
backported into 5.10 and 5.12. So we might also need to make sure the whole series from
[1] gets pulled in 5.10 and 5.12.

Thanks.