Re: [PATCH v4 3/9] block: Make it easier to learn which BDS support bitmaps

[Eric Blake <eblake@redhat.com>]

On 5/14/20 12:19 AM, Vladimir Sementsov-Ogievskiy wrote:

>> In the future, when we improve the ability to look up bitmaps through
>> a filter, we will probably also want to teach the block layer to
>> automatically let filters pass this request on through.
> 
> Hm. I think that bitmap at filter bs is a valid thing (moreover I have a 
> plan to use it for one issue), so I'm not sure that it's good idea to do 
> any generic logic around bitmaps work through filters, better to always 
> address the exact node you mean..

In the immediate term, the only user of this new function is qemu-img, 
and qemu-img is not setting up filters, so whether this callback can see 
through filters is moot (that is, we are always addressing the exact 
node the user passed on the command line, for whatever bitmap operations 
qemu-img does).  In the long term, being able to see bitmaps through 
filters is better addressed after we finally include Max's series that 
include filter handling overall.

> 
>>
>> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Thanks.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org