Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Content-Type: text/plain;
        charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\))
Subject: Re: Lockdep warning on io_file_data_ref_zero() with 5.10-rc5
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <c16232dd-5841-6e87-bbd0-0c18f0fc982b@gmail.com>
Date:   Sat, 28 Nov 2020 16:21:36 -0800
Cc:     linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>
Content-Transfer-Encoding: quoted-printable
Message-Id: <A68B2535-0B9D-43C9-9762-AE8427E64773@gmail.com>
References: <C3012989-5B09-4A88-B271-542C1ED91ABE@gmail.com>
 <c16232dd-5841-6e87-bbd0-0c18f0fc982b@gmail.com>
To:     Pavel Begunkov <asml.silence@gmail.com>
Precedence: bulk

> On Nov 28, 2020, at 4:13 PM, Pavel Begunkov <asml.silence@gmail.com> =
wrote:
>=20
> On 28/11/2020 23:59, Nadav Amit wrote:
>> Hello Pavel,
>>=20
>> I got the following lockdep splat while rebasing my work on 5.10-rc5 =
on the
>> kernel (based on 5.10-rc5+).
>>=20
>> I did not actually confirm that the problem is triggered without my =
changes,
>> as my iouring workload requires some kernel changes (not iouring =
changes),
>> yet IMHO it seems pretty clear that this is a result of your commit
>> e297822b20e7f ("io_uring: order refnode recycling=E2=80=9D), that =
acquires a lock in
>> io_file_data_ref_zero() inside a softirq context.
>=20
> Yeah, that's true. It was already reported by syzkaller and fixed by =
Jens, but
> queued for 5.11. Thanks for letting know anyway!
>=20
> =
https://lore.kernel.org/io-uring/948d2d3b-5f36-034d-28e6-7490343a5b59@kern=
el.dk/T/#t

Thanks for the quick response and sorry for the noise. I should improve =
my
Googling abilities and check the iouring repository the next time.

Regards,
Nadav=