Re: [Qemu-devel] [PATCH v6] spec: add qcow2 bitmaps extension specification

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

On 11.01.2016 20:07, John Snow wrote:
>
> On 01/11/2016 07:20 AM, Vladimir Sementsov-Ogievskiy wrote:
>> Are you sure? What about creation\last change dates, file links, user
>> data, etc?
>> For now, formally, current "For now, as no extra data is defined,
>> extra_data_size is reserved and must be zero." is equal to such table,
>> but provides more flexibility for future..
> Oh, I see what you're trying to do.
>
> In this case, perhaps we need a versioning system for the type-specific
> data? We won't be able to just add data arbitrarily, we need to change
> some field somewhere.
>
> Maybe we can say something like...
>
> "If extra_data_size is 0, there is no type-specific data and the version
> of that data layout is 0. If extra_data_size is non-zero, the first byte
> of the type-specific-data must be a version number greater than 0 that
> indicates the layout of the data to follow.
>
> For the Dirty Tracking bitmap type, only version 0 is currently valid."
>
> This way it's explicit that data *could* show up for dirty tracking in
> the future, but currently it does not.
>
> --js
It's ok for me.

-- 
Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.