Re: [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification

[Stefan Hajnoczi]

On Thu, Jun 11, 2015 at 12:21:31PM -0400, John Snow wrote:
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> On 06/11/2015 09:03 AM, Stefan Hajnoczi wrote:
> > On Thu, Jun 11, 2015 at 01:19:24PM +0300, Vladimir
> > Sementsov-Ogievskiy wrote:
> >> On 10.06.2015 16:24, Stefan Hajnoczi wrote:
> >>> On Wed, Jun 10, 2015 at 11:19:30AM +0300, Vladimir
> >>> Sementsov-Ogievskiy wrote:
> >>>> On 09.06.2015 20:03, Stefan Hajnoczi wrote:
> >>>>> On Mon, Jun 08, 2015 at 06:21:19PM +0300, Vladimir
> >>>>> Sementsov-Ogievskiy wrote:
> >>>>>> @@ -166,6 +167,19 @@ the header extension data. Each
> >>>>>> entry look like this: terminated if it has full length) 
> >>>>>> +== Dirty bitmaps == + +Dirty bitmaps is an optional
> >>>>>> header extension. It provides a possibility of +storing
> >>>>>> dirty bitmaps in qcow2 image. The fields are: + +
> >>>>>> 0 -  3:  nb_dirty_bitmaps +                   Number of
> >>>>>> dirty bitmaps contained in the image
> >>>>> Is there a maximum?
> >>>> hmm. any proposals for this?
> >>> 65535 seems practical.
> >> 
> >> So, you suggest to reduce this field width to 2b? And additional
> >> 2 bytes reserved field, to achieve 8b-alignment?
> > 
> > No, I would leave it 32-bit but impose a little (which can be

s/little/limit/

> > increased later if necessary).  That's how nb_snapshots works too.
> > 
> 
> Doesn't the code already limit the number of bitmaps via +#define
> QCOW_MAX_DIRTY_BITMAPS 65536, from patch 2?

It needs to be in the specification.

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