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