Re: [PATCH v2 2/2] qapi: Allow introspecting fix for savevm's cooperation with blockdev

[Markus Armbruster]

Kevin Wolf <address@hidden> writes:

> Am 11.10.2019 um 08:08 hat Markus Armbruster geschrieben:
>> Kevin Wolf <address@hidden> writes:
>> 
>> > Am 02.10.2019 um 13:57 hat Markus Armbruster geschrieben:
[...]
>> >> So the problem is certain (common & sane) -blockdev use makes savevm
>> >> create additional, unwanted snapshots.
>> >
>> > Actually, the most common protocol driver is file-posix, which doesn't
>> > support snapshots, so usually the result was that savevm just fails
>> > because it can't snapshot something that it (incorrectly) thinks it
>> > should snapshot.
>> 
>> v3's commit message:
>> 
>>     qapi: Allow introspecting fix for savevm's cooperation with blockdev
>>     
>>     'savevm' was buggy as it considered all monitor-owned block device nodes
>>     for snapshot. With introduction of -blockdev the common usage made all
>>     nodes including protocol and backing file nodes monitor-owned and thus
>>     considered for snapshot.
>>     
>>     This is a problem since the 'file' protocol nodes can't have internal
>>     snapshots and it does not make sense to take snapshot of nodes
>>     representing backing files.
>>     
>>     This was fixed by commit 05f4aced658a02b02 clients need to be able to
>>     detect whether this fix is present.
>
> Something is missing in this sentence. I think you lost the "but" from
> the original message.

I fixed this in v4 by inserting a period.  I wasn't aware we had lost a
"but".

>>     Since savevm does not have an QMP alternative, add the feature for the
>>     'human-monitor-command' backdoor which is used to call this command in
>>     modern use.
>>     
>>     Signed-off-by: Peter Krempa <address@hidden>
>>  
>> Kevin, is this explanation sufficiently correct & complete?
>
> Looks good to me otherwise.

Thanks!