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Subject: Re: Bisected GFP in bfq_bfqq_expire on v5.1-rc1
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <20190401115509.76310e03@fire.localdomain>
Date:   Mon, 1 Apr 2019 11:01:27 +0200
Cc:     Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        linux-kernel@vger.kernel.org
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Message-Id: <84B0CA50-0ED8-4171-8007-19EA43951735@linaro.org>
References: <20190329160227.7d55c8dd@fire.localdomain>
 <0e203a26-b941-cef4-dff1-013999d4b041@kernel.dk>
 <626EAE58-63C1-4ABA-9040-9D9A61F74A0D@linaro.org>
 <20190401115509.76310e03@fire.localdomain>
To:     Dmitrii Tcvetkov <demfloro@demfloro.ru>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> Il giorno 1 apr 2019, alle ore 10:55, Dmitrii Tcvetkov =
<demfloro@demfloro.ru> ha scritto:
>=20
> On Mon, 1 Apr 2019 09:29:16 +0200
> Paolo Valente <paolo.valente@linaro.org> wrote:
>>=20
>>=20
>>> Il giorno 29 mar 2019, alle ore 15:10, Jens Axboe <axboe@kernel.dk>
>>> ha scritto:
>>>=20
>>> On 3/29/19 7:02 AM, Dmitrii Tcvetkov wrote:
>>>> Hi,
>>>>=20
>>>> I got kernel panic since v5.1-rc1 when working with files on block
>>>> device with BFQ scheduler assigned. I didn't find trivial way to
>>>> reproduce the panic but "git checkout origin/linux-5.0.y"
>>>> on linux-stable-rc[1] git repo on btrfs filesystem reproduces the
>>>> problem 100% of the time on my bare-metal machine and in a VM.
>>>>=20
>>>> Bisect led me to commit 9dee8b3b057e1 (block, bfq: fix queue
>>>> removal from weights tree). After reverting this commit on top of
>>>> current mainline master(9936328b41ce) I can't reproduce the
>>>> problem.
>>>>=20
>>>> dmesg with the panic and bisect log attached.
>>>>=20
>>>> [1]
>>>> =
https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stab=
le-rc.git
>>>=20
>>> Paolo, can you please take a look at this?
>>>=20
>>>=20
>>=20
>> Yep.
>>=20
>> That you very much Dmitrii for also bisecting.  I feel like this
>> failure may be caused by the typo fixed by this patch:
>> https://patchwork.kernel.org/patch/10877113/
>>=20
>> Could you please give this fix a try?
>=20
> Still reproduces with the patch on top of current mainline
> master(v5.1-rc3).
>=20
> Crashes with and without CONFIG_BFQ_GROUP_IOSCHED look same to me.
> Original dmesg was also from kernel with CONFIG_BFQ_GROUP_IOSCHED=3Dn.
>=20
> gpf.txt contains crash with the patch and CONFIG_BFQ_GROUP_IOSCHED=3Dn
> gpf-w-bfq-group-iosched.txt - with the patch and =
CONFIG_BFQ_GROUP_IOSCHED=3Dy
> config.txt - kernel config for the VM with CONFIG_BFQ_GROUP_IOSCHED=3Dn
>=20
>=20

Ok, thank you. Could you please do a

list *(bfq_bfqq_expire+0x1f3)

for me?

Thanks,
Paolo

>=20
> <gpf.txt><gpf-w-bfq-group-iosched.txt><config.txt>