Re: [PATCH 0/3] umount fixes and cleanups

["Maxim Yu. Osipov" <mosipov@ilbers.de>]

On 12/5/18 3:14 PM, Jan Kiszka wrote:
> On 05.12.18 12:12, Maxim Yu. Osipov wrote:
>> On 12/5/18 12:29 PM, Jan Kiszka wrote:
>>> Patches related to resolving the pending CI issues as well as
>>> simplifying the umounts used during cleanup.
>>
>> Tried to run in patch queue:
>>
>> 027b7cf Remove redundant recursive umounts
>> c1bdc33 isar-events: Improve umount handler
>> b354273 ci: Wait for bitbake worker to finish before deleting artifacts
>> 9cf29e6 isar-bootstrap: Fix and cleanup bind mounting
>> b354026 isar-image: umount base-apt when doing offline build
>> e965c0d gitlab-ci: Switch to ci_build.sh
>> ...
>>
>> After execution of problematic test case (I rebooted PC and executed 
>> steps in clean tree):
>>
>> my stretch Debian system was entered into unusable state
>> as many important mounts were disappeared (see log of mount points
>> before and after execution  of last command attached).
> 
> OK, so I took the time and extracted the root cause. We may see a Debian 
> 4.9 kernel bug here:
> 
> # mkdir my-mnt
> # mount --rbind /sys my-mnt
> # mount --make-rslave my-mnt
> # umount {-R,-l,-R -l} my-mnt
> # rmdir my-mnt
> rmdir: failed to remove 'my-mnt': Device or resource busy
> 
> This works fine on my Leap 15.0 kernel (4.12) as well as the 4.4 kernel 
> (Ubuntu) used on our CI server.

This also works fine on my Debian 4.9 kernel (I've ran this sequence for 
every combination of {-R, -l , -R -l}):

> root@tiberius:~# uname -a
> Linux tiberius 4.9.0-8-amd64 #1 SMP Debian 4.9.110-3+deb9u6 (2018-10-08) x86_64 GNU/Linux
> root@tiberius:~# mkdir my-mnt
> root@tiberius:~# mount --rbind /sys my-mnt
> root@tiberius:~# mount --make-rslave my-mnt
> root@tiberius:~# umount -R my-mnt/
> root@tiberius:~# rmdir my-mnt/
> root@tiberius:~# mkdir my-mnt
> root@tiberius:~# mount --rbind /sys my-mnt
> root@tiberius:~# mount --make-rslave my-mnt
> root@tiberius:~# umount -l my-mnt
> root@tiberius:~# rmdir my-mnt/
> root@tiberius:~# mkdir my-mnt
> root@tiberius:~# mount --rbind /sys my-mnt
> root@tiberius:~# mount --make-rslave my-mnt
> root@tiberius:~# umount -R -l my-mnt
> root@tiberius:~# rmdir my-mnt/
> root@tiberius:~# 


Thanks,
Maxim.

> *This* is information we can base commits on. Also, we can file a bug 
> against Debian with this. Could you do that (keep my in CC)?



> Thanks,
> Jan
> 


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Maxim Osipov
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