Re: Bisected GFP in bfq_bfqq_expire on v5.1-rc1

Paolo Valente
2019-04-01T09:01:34Z

> Il giorno 1 apr 2019, alle ore 10:55, Dmitrii Tcvetkov <demfloro@demfloro.ru> ha scritto:
>
> On Mon, 1 Apr 2019 09:29:16 +0200
> Paolo Valente <paolo.valente@linaro.org> wrote:
>>
>>
>>> Il giorno 29 mar 2019, alle ore 15:10, Jens Axboe <axboe@kernel.dk>
>>> ha scritto:
>>>
>>> On 3/29/19 7:02 AM, Dmitrii Tcvetkov wrote:
>>>> Hi,
>>>>
>>>> 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.
>>>>
>>>> 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.
>>>>
>>>> dmesg with the panic and bisect log attached.
>>>>
>>>> [1]
>>>> https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
>>>
>>> Paolo, can you please take a look at this?
>>>
>>>
>>
>> Yep.
>>
>> 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/
>>
>> Could you please give this fix a try?
>
> Still reproduces with the patch on top of current mainline
> master(v5.1-rc3).
>
> Crashes with and without CONFIG_BFQ_GROUP_IOSCHED look same to me.
> Original dmesg was also from kernel with CONFIG_BFQ_GROUP_IOSCHED=n.
>
> gpf.txt contains crash with the patch and CONFIG_BFQ_GROUP_IOSCHED=n
> gpf-w-bfq-group-iosched.txt - with the patch and CONFIG_BFQ_GROUP_IOSCHED=y
> config.txt - kernel config for the VM with CONFIG_BFQ_GROUP_IOSCHED=n
>
>

Ok, thank you. Could you please do a

list *(bfq_bfqq_expire+0x1f3)

for me?

Thanks,
Paolo

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