[Filesystems-devel] Bug#884008: Bug#884008: aufs-dkms: aufs triggers kernel WARN during boot

[Ralf Jung]

Hi,

>> Linux core.hacksaar.de 4.9.0-4-amd64 #1 SMP Debian 4.9.65-3 (2017-12-03)
>> x86_64 GNU/Linux
>>
>> The source download is at the bottom of
>> <https://packages.debian.org/source/stable/linux>
> 
> Hmm, I checked linux-image-4.9.0-4-amd64 pkg and downloaded its
> linux_4.9.65-3.debian.tar.xz, I could not find aufs source files.

Ah, right -- aufs is compiled as a dedicated package via dkms, it is not
part of the Debian kernel.  Sorry for the confusion.  The sources for
that are at <https://packages.debian.org/source/stable/aufs>.

>>> S Sun Dec 10 12:10:27 2017 p4 kernel: WARNING: CPU: 0 PID: 1490 at /var/lib/dkms/aufs/4.9+20161219/build/fs/aufs/cpup.c:423 au_cp_regular+0x16c/0x250 [aufs]
>>> S Sun Dec 10 12:10:27 2017 p4 kernel: .wh..wh.setup_maker_elements-i.ri.0007
>>> Please report this warning to aufs-users ML
> 
> This is an unexpected situation for aufs. It might be related to your
> environment (xen domU?).

Yes, this is a VPS running under Xen.

> The period (10sec) this warning is appearing,
> the performance of the internal file-close operation may get worse a
> little bit. But it is harmless. You can ignore this warning safely.

That is good to know, thanks!

> I know it must be annoying for you, and I am going to comment it out in
> next release. Your report is helpful for me to know the case where this
> warning appears.

I am only getting this warning during a boot, it disappears after a
while -- no idea why.

> By the way, I see all your branches are under "/dev/xvda1
> /var/lib/docker/aufs ext4", it is ok. But what for is
> "shm /var/lib/docker/containers/2b0cb..."?
> Is it totally unused?

TBH I do not know.  Docker is managing all that.  All I did is download
and start a docker image.

Kind regards,
Ralf