Bcache in Ubuntu 18.04 kernel panic

Bcache in Ubuntu 18.04 kernel panic

[Brendan Boerner]

Hi,

I spent the weekend verifying and isolating a kernel panic in bcache
on Ubuntu 18.04 (4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39
UTC 2020).

Is this the place to report it? I have kernel crash dumps.

Thanks!
Brendan

Re: Bcache in Ubuntu 18.04 kernel panic

[Matthias Ferdinand]

On Tue, Sep 01, 2020 at 03:42:54PM -0500, Brendan Boerner wrote:
> Hi,
> 
> I spent the weekend verifying and isolating a kernel panic in bcache
> on Ubuntu 18.04 (4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39
> UTC 2020).
> 
> Is this the place to report it? I have kernel crash dumps.

I'm no bcache developer, but I see there are Ubuntu kernel updates
available, with bcache fixes.

From the changelogs for 4.15.0-113.114:

  * Regression in kernel 4.15.0-91 causes kernel panic with Bcache
    (LP: #1867916)
    - bcache: check and adjust logical block size for backing devices


Perhaps you used unorthodox (neither 512b nor 4k) block sizes at bcache creation?


Regards
Matthias

Re: Bcache in Ubuntu 18.04 kernel panic

[Mauricio Oliveira]

Hi Brendan,

The correct place for Ubuntu bugs is Launchpad, initially.
(It might be the case that it turns out to be an upstream/not
Ubuntu-specific bug, but we'll go from there.)

As Matthias mentioned, recently the patch for the non-512/4k block size
(which was an upstream issue, actually) has been released to Ubuntu
18.04 4.15-based kernel.

You can check if your stack trace is listed in LP#1867916 [1], for example.
And/or test whether the newer kernel version with its fix addresses your issue.

If not, please click 'Report a bug' against the 'linux' package in [2].

Hope this helps,

[1] https://bugs.launchpad.net/bugs/1867916
[2] https://launchpad.net/ubuntu/

On Tue, Sep 1, 2020 at 5:43 PM Brendan Boerner <bboerner.biz@gmail.com> wrote:
>
> Hi,
>
> I spent the weekend verifying and isolating a kernel panic in bcache
> on Ubuntu 18.04 (4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39
> UTC 2020).
>
> Is this the place to report it? I have kernel crash dumps.
>
> Thanks!
> Brendan



-- 
Mauricio Faria de Oliveira

Re: Bcache in Ubuntu 18.04 kernel panic

[Brendan Boerner]

Thank you Matthias and Mauricio for your replies and guidance.

Since I'm not exactly sure it's the same bug I'll open a ticket.

Fwiw mine occurred while rsyncing a large (approx 1.4T) home dir from
an XFS w/no bcache to an XFS on bcache which didn't have a cache set
e.g.  make-bcache -B /dev/vg-bfd02/t3home_bc and not attach a cache
set. With between 100-200GB remaining kernel panic.

I also encountered it with a larger (~2.5T) rsnapshot tree.

I did not encounter it when rsyncing 4.3T tree containing zip files
ranging from 10s of MBs to approx 2GB.

The bcache device was available after reboot and I was able to finish
the rsync.

The obvious workaround was to always ensure the bcache dev is attached
to a cache set. With that configuration full rsyncs completed as
expected.

Regards,
Brendan

On Wed, Sep 2, 2020 at 10:37 AM Mauricio Oliveira
<mauricio.oliveira@canonical.com> wrote:
>
> Hi Brendan,
>
> The correct place for Ubuntu bugs is Launchpad, initially.
> (It might be the case that it turns out to be an upstream/not
> Ubuntu-specific bug, but we'll go from there.)
>
> As Matthias mentioned, recently the patch for the non-512/4k block size
> (which was an upstream issue, actually) has been released to Ubuntu
> 18.04 4.15-based kernel.
>
> You can check if your stack trace is listed in LP#1867916 [1], for example.
> And/or test whether the newer kernel version with its fix addresses your issue.
>
> If not, please click 'Report a bug' against the 'linux' package in [2].
>
> Hope this helps,
>
> [1] https://bugs.launchpad.net/bugs/1867916
> [2] https://launchpad.net/ubuntu/
>
> On Tue, Sep 1, 2020 at 5:43 PM Brendan Boerner <bboerner.biz@gmail.com> wrote:
> >
> > Hi,
> >
> > I spent the weekend verifying and isolating a kernel panic in bcache
> > on Ubuntu 18.04 (4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39
> > UTC 2020).
> >
> > Is this the place to report it? I have kernel crash dumps.
> >
> > Thanks!
> > Brendan
>
>
>
> --
> Mauricio Faria de Oliveira