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
[off-list ref] 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 [off-list ref] wrote:

quoted

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