[libvirt] [PATCH v2 2/2] qemuDomainUndefineFlags: Forbid undefine of active domain with NVRAM

[Michal Privoznik]

On 08/09/2017 02:14 PM, Daniel P. Berrange wrote:
> On Wed, Aug 09, 2017 at 02:00:06PM +0200, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1467245
>>
>> Currently, there's a bug when undefining a domain with NVRAM
>> store. Basically, the unlink() of the NVRAM store file happens
>> during the undefine procedure iff domain is inactive. So, if
>> domain is running and undefine is called the file is left behind.
>> It won't be removed in the domain cleanup process either
>> (qemuProcessStop). To avoid this forbid undefining domain with
>> NVRAM file.
> 
> Why do we need to forbid it ? Even if QEMU still has an open
> file handle, it can continue to write to it after we unlink
> it.
> 
> 

That's what my v1 does. Anyway, there's third option: just recently
Jirka added possibility to do some actions when domain is destroyed. He
needed it for some migration work, but the design is broad enough to fit
this problem too. What we can do is:

if (flags & VIR_DOMAIN_UNDEFINE_NVRAM):
  if domain is running:
    register the callback /* that merely just unlinks the file */
  else:
    unlink
else:
  if (!(flags & VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)):
    error


What do you guys think of this one?

Michal