Re: [libvirt] [PATCH] util: Remove empty resource partition created by libvirt
On 12.08.2015 07:39, Nikunj A Dadhania wrote:
Hi Daniel,
"Daniel P. Berrange" <berrange(a)redhat.com> writes:
> On Tue, Aug 11, 2015 at 04:57:15PM +0530, Nikunj A Dadhania wrote:
>> The default resource partition is created in the domain start path if it
>> is not existing. Even when libvirtd is stopped after shutting down all
>> domains, the resource partition still exists.
>>
>> The patch adds code to removes the default resource partition in the
>> cgroup removal path of the domain. If the default resource partition is
>> found to have no child cgroup, the default resource partition will be
>> removed.
>>
>> Moreover, the code does not remove the user provided resource
>> partitions.
>>
>> Signed-off-by: Nikunj A Dadhania <nikunj(a)linux.vnet.ibm.com>
>
> I don't think we want to be doing this. In non-systemd hosts this will
> be deleting the heirarchy that the sysadmin manually pre-created for
> their VMs. In a systemd host it will also end up deleting slices that
> were created by systemd.
AFAIU, there are three cases here:
1) User created resource partition, for example /production/foo
As this is created by user, we should not touch them. And my patch
does not remove them
2) systemd created /machine.slice
If not libvirt, should systemd clean this up when the libvirtd
service is stopped ?
No, machined should clean that up based on signalization sent by libvirt
when it is started up again. I guess the scenario is as follows:
1) libvirt is starting a container
2) as part of the process, a remote procedure is called (via dbus) on
machined to precreate the machine.slice
3) the container is started
4) libvirtd.service is stopped
5) container is stopped
Now you have dangling machine.slice. But this in fact is correct,
because libvirt needs to clean up its runtime metadata too. Therefore
the process should go on like this:
6) libvirtd.service is started again
7) libvirt notices that the container has stopped
8) as part of cleanup process it instructs machined to remove the
machine.slice
Currently, my patch does remove this when its found empty
3) libvirt created /machine
As this was created manually by libvirt, should we delete it here in
libvirt daemon
This one can make sense.
Michal