[libvirt] [PATCH] qemuDomainSnapshotCreateActiveExternal: Remove memory snapshot on failure less frequently

[Michal Privoznik]

On 08/30/2018 12:57 PM, Peter Krempa wrote:
> On Thu, Aug 30, 2018 at 11:22:35 +0200, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1589115
>>
>> When creating a memory snapshot the domain is suspended and qemu
>> is told to dump memory into the desired file. After that we set a
>> flag so that the file is not left behind if a failure occurs at
>> some later point (e.g. when creating disk snapshot fails).
>> However, the way we currently handle the memory snapshot file is
>> way too aggressive. For instance, if resuming domain vCPUs fails
>> after all snapshots were done successfully, we still remove the
>> memory snapshot (even though we leave disk snapshot be).
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>  src/qemu/qemu_driver.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>> index a0f7c71675..2eae3dd49d 100644
>> --- a/src/qemu/qemu_driver.c
>> +++ b/src/qemu/qemu_driver.c
>> @@ -15248,6 +15248,7 @@ qemuDomainSnapshotCreateActiveExternal(virQEMUDriverPtr driver,
>>          virObjectEventStateQueue(driver->domainEventState, event);
>>      }
>>  
>> +    memory_unlink = false;
>>      ret = 0;
> 
> This does not make sense. The snapshot metadata is not saved at this
> point so this file would be left over and could not be used (once we
> implement external snapshot reversion).
> 
> The problem is that you can't get rid of the disk images once the
> transaction is executed, but you can dispose of the memory image.
> 
> The failure points after the disk snapshot is taken are very hard to
> roll back.
> 

So what are you saying is that this is expected behaviour? Okay. Thanks
anyway.

Michal