From: Oleg Nesterov <oleg@redhat.com>
To: Mateusz Guzik <mjguzik@gmail.com>, Hillf Danton <hdanton@sina.com>
Cc: paulmck@kernel.org, Christian Brauner <brauner@kernel.org>,
rcu@vger.kernel.org
Subject: Re: rcu_sync_dtor() warning question
Date: Sun, 28 Jul 2024 15:41:01 +0200 [thread overview]
Message-ID: <20240728134101.GA8691@redhat.com> (raw)
In-Reply-To: <CAGudoHGznS_Br2gxu=BWsDaCbHmMWRTCmoZDniyFFrDOs9VD5A@mail.gmail.com>
Sorry for late reply.
You do not need my help, I know nothing about fs ;) but just in case...
On 07/26, Mateusz Guzik wrote:
>
> Welp.
>
> syzbot did the bisect, it's not any of the above, instead:
>
> commit b62e71be2110d8b52bf5faf3c3ed7ca1a0c113a5
> Author: Chao Yu <chao@kernel.org>
> Date: Sun Apr 23 15:49:15 2023 +0000
>
> f2fs: support errors=remount-ro|continue|panic mountoption
>
> https://lore.kernel.org/linux-fsdevel/0000000000004ff2dc061e281637@google.com/T/#m90c03813e12e5cdff1eeada8f9ab581d5f039c76
>
> That said, the stuff I mentioned still looks highly suspicious so I
> have to something to investigate regardless.
Did you see the patch from Hillf ?
https://lore.kernel.org/all/20240727011616.2144-1-hdanton@sina.com/
it seems to fix the problem...
Of course I don't understand this patch, but afaics SB_RDONLY can confuse
thaw_super_locked(). If sb_rdonly() is true, thaw_super_locked() assumes
that freeze_super() didn't call sb_wait_write() -> percpu_down_write().
So in this case thaw_super_locked() just clears sb->s_writers.frozen and
goes to the "out_deactivate" label bypassing sb_freeze_unlock().
Oleg.
next prev parent reply other threads:[~2024-07-28 13:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240726-ansonsten-piste-c4f04d4909fc@brauner>
2024-07-26 18:02 ` rcu_sync_dtor() warning question Paul E. McKenney
2024-07-26 18:39 ` Mateusz Guzik
2024-07-26 18:43 ` Mateusz Guzik
2024-07-26 20:21 ` Paul E. McKenney
2024-07-28 13:41 ` Oleg Nesterov [this message]
2024-07-29 8:25 ` Christian Brauner
2024-07-29 9:02 ` Oleg Nesterov
2024-07-29 8:28 ` Christian Brauner
2024-07-29 8:26 ` Christian Brauner
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