[PATCH v2 00/10] qemu: add option to process offloaded legacy blockjob event ealier

[Nikolay Shirokovskiy]

On 04.12.2020 18:11, Peter Krempa wrote:
> On Fri, Nov 13, 2020 at 09:53:28 +0300, Nikolay Shirokovskiy wrote:
>> This is successor to [1] but I changed the subject as in the review the patch
>> 'qemu: sync backing chain update in virDomainGetBlockJobInfo' was not
>> considered good one from design POV. However I think the basic patch is helpful
>> to address similar issues. Look at [*] for example, there it allows to sync
>> backing chains during query block stats.
>>
>> In discussion of [1] I stated that first patch will also allow to get rid of
>> stale block job events on reconnection to qemu. But this will require
>> additional work actually so with this patch series stale events are still
>> present. And in the discussion it was also mentioned by Peter that stale events
>> are not harmful for legacy blockjobs code. I also removed previous attempts to
>> eliminate some of stale events.
>>
>> I still keep patch for virDomainGetBlockJobInfo. May be in comparsion to [*]
>> the approach the patch takes will look not so bad :)
>>
>> [1] First version of the patch series
>> https://www.redhat.com/archives/libvir-list/2020-October/msg01133.html
> 
> I had a look at this series and it's just doing too much just to "fix"
> apps which insist on polling especially with pre-blockdev qemu. I simply
> it's not worth adding the complexity you are proposing.
> 
> NACK series.

Ok. By the way what about the issue described in 

[PATCH v2 09/10] qemu: fix race on legacy block completion and quering stats

Are modern blockjobs have similar?

Nikolay

> 
> Instead I propose we add a workaround which will report fake unfinished
> job:
> 
> https://www.redhat.com/archives/libvir-list/2020-December/msg00352.html
> 
> The scope of this is way more limited and it doesn't actually try to
> modify the job code handovers which is very dangerous.
> 
> 
> 
> I had a look at this series and it's just doing too much just to "fix"
> apps which insist on polling especially with pre-blockdev qemu.
> 
> Additionally it adds documentation stating that apps should not poll
> virDomainGetBlockJobInfo.
>