Re: [Qemu-devel] [PATCH for 2.6 2/3] block: Hide HBitmap in block dirty bitmap interface

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

On 24.11.2015 05:28, Fam Zheng wrote:
> On Mon, 11/23 16:34, John Snow wrote:
>> Hmm, what's the idea, here?
>>
>> This patch does a lot more than just hide hbitmap details from callers
>> of block_dirty_bitmap functions.
>>
>> So we're changing the backing hbitmap to always be one where g=0 and the
>> number of physical bits directly is (now) the same as the number of
>> 'virtual' bits, pre-patch. Then, to compensate, we handle the shift math
>> to convert the bitmap granularity to sector size and vice-versa in the
>> Block Dirty Bitmap layer instead of in the hbitmap layer.
>>
>> What's the benefit? It looks like we just pull all the implementation
>> details up from hbitmap and into BdrvDirtyBitmap, which I am not
>> immediately convinced of as being a benefit.
> It feels counter intuitive to me with hbitmap handling granularity, it makes it
> more like a HGranularityBitmap rather than HBitmap, and is unnecessarily
> complex to work on.
>
> Now it's simplified in that only one BdrvDirtyBitmap needs to care about the
> granularity, and which I think is a big benefit when we are going to extend the
> dirty bitmap interface, for example to serialize and deserialize for
> persistence.
>
> Fam

But what is the relation from this to adding iterator interface? This 
seems like this patch do two different things:
1) granularity changes, described in quotation above
2) adding iterator related things, described in commit message

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