Re: [Qemu-devel] [PATCH v6 12/21] qmp: Add dirty bitmap status field in query-block

[John Snow <jsnow@redhat.com>]

On 04/22/2015 06:18 PM, Eric Blake wrote:
> On 04/17/2015 05:50 PM, John Snow wrote:
>> Add the "frozen" status booleans, to inform clients
>> when a bitmap is occupied doing a task.
>>
>> Signed-off-by: Fam Zheng <famz@redhat.com>
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> Reviewed-by: Max Reitz <mreitz@redhat.com>
>> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> ---
>>   block.c              | 1 +
>>   qapi/block-core.json | 5 ++++-
>>   2 files changed, 5 insertions(+), 1 deletion(-)
>
>> +++ b/qapi/block-core.json
>> @@ -336,10 +336,13 @@
>>   #
>>   # @granularity: granularity of the dirty bitmap in bytes (since 1.4)
>>   #
>> +# @frozen: whether the dirty bitmap is frozen (Since 2.4)
>> +#
>>   # Since: 1.3
>>   ##
>>   { 'type': 'BlockDirtyInfo',
>> -  'data': {'*name': 'str', 'count': 'int', 'granularity': 'uint32'} }
>> +  'data': {'*name': 'str', 'count': 'int', 'granularity': 'uint32',
>> +           'frozen': 'bool'} }
>
> Just thinking aloud here - internally, we have a tri-state situation
> (enabled, disabled, or frozen).  I know we aren't exposing disabled to
> the end user yet (no use case for that), but would it be better to make
> this output an enum type (two values for now, 'enabled' and 'frozen') to
> make it easier to add a third value later, without having to add yet
> another boolean?
>
> But it's not the end of the world to expose a single boolean now (we'd
> just have to maintain it forever, even if we add later states), and
> adding an enum now just adds complexity that we may not need, so:
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>

Hmm..., you have a point!

If there are no further objections to this series as-is, I will author a 
quick follow-up patch to implement that -- possibly when we merge in the 
bitmap migration code.

--js