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

[Michael Rodrigues]

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.
>
>> So sanlock is preventing both from running concurrently, but it
>> seems to contradict your statement:
>> "Even if you now pause the VM on node 2, and try to resume node 1,
>> sanlock will still prevent node 1 from running again. It tracks a
>> lock "version" number. The key is that once the original VM is
>> paused, if any other VM runs on that disk, the orignal VM is never
>> allowed to be unpaused again."
> Daniel


-- 
Michael Rodrigues
Interim Help Desk Manager
Gevirtz Graduate School of Education
Education Building 4203
(805) 893-8031
help at education.ucsb.edu