[libvirt-users] Sanlock gives up lock when VM is paused

[Michael Rodrigues]

In doing more testing I notice that the resource listed by 'sanlock 
client status' disappears when the VM is paused. I haven't yet found 
anything about lock versions yet though.

However, even if sanlock behaved as you said, preventing the unpausing 
of a VM once another one has used it's disk, this could still cause 
damage to the filesystem if the VM is paused during write operations and 
never allowed to finish (after the subsequent VM using the same storage 
takes over). I would think the ideal behavior would be keeping the lock 
until the VM is completely off. I don't see why this would get in the 
way of migration as the filesystem shouldn't need to be accessed until 
the RAM contents have been migrated to the other machine, but then again 
I'm not writing the code.


Thanks,
Michael

On 1/31/2013 3:56 PM, Michael Rodrigues wrote:
> Just for follow up and future reference:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=906590
>
> Thanks,
> Michael
>
> On 1/31/2013 12:03 PM, Daniel P. Berrange wrote:
>> On Thu, Jan 31, 2013 at 11:02:15AM -0800, Michael Rodrigues wrote:
>>> On 1/31/2013 10:40 AM, Daniel P. Berrange wrote:
>>>> On Thu, Jan 31, 2013 at 10:35:17AM -0800, Michael Rodrigues wrote:
>>>>> Hi Daniel,
>>>>>
>>>>> I thought migration might be the reason, but I'm still not seeing
>>>>> the behavior you describe with regards to pausing. I saw the
>>>>> following behavior:
>>>>>
>>>>> 1. Created VM on node 1
>>>>> 2. Started VM on node 1
>>>>> 3. Migrated VM to node 2, node 1 is now shutdown, node 2 is running
>>>>> 4. I paused node 2
>>>>> 5. I started node 1, no error
>>>>> 6. Paused node 1
>>>>> 7. Unpaused node 2, no err
>>>>>
>>>>> I thought maybe the original VM had to be paused first, so I tried
>>>>> that as well:
>>>>>
>>>>> 1. Created VM on node 1
>>>>> 2. Started VM on node 1
>>>>> 3. Migrated to node 2, node 1 is now shutdown, node 2 is running
>>>>> 4. I shutdown node 2 instead of pausing
>>>>> 5. I started node 1
>>>>> 6. I paused node 1
>>>>> 7. Started node 2
>>>>> 8. Paused node 2
>>>>> 9. Started node 1
>>>> Hmm, that isn't supposed to be possible. When you paused node 1
>>>> in step 6, it was supposed to record the lease version number.
>>>> When you resume in step 9, the version number should mis-match
>>>> due to step 7, and thus sandlock ought to have caused an error
>>>> at step 9. If that didn't happen, then I believe we have a bug
>>> Should I file a report? I'm not really a developer but I can provide
>>> whatever information is necessary for a proper report. I don't have
>>> RHEL or a bugzilla account.
>> Yes, please do file a bug report including this scenario to
>> reproduce
>>
>> Daniel
>
>


-- 
Michael Rodrigues
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Gevirtz Graduate School of Education
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