Re: [Qemu-devel] [PATCH 3/4] nbd/server: implement dirty bitmap export

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

22.03.2018 18:26, Vladimir Sementsov-Ogievskiy wrote:
> 21.03.2018 19:57, Eric Blake wrote:
>> On 03/21/2018 07:19 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>
>> Rather sparse on the details in the commit message; I had to read the 
>> patch to even learn what the new namespace is.
>
> oh, yes, sorry :(
>
>>> @@ -92,6 +101,7 @@ typedef struct NBDExportMetaContexts {
>>>       bool valid; /* means that negotiation of the option finished 
>>> without
>>>                      errors */
>>>       bool base_allocation; /* export base:allocation context (block 
>>> status) */
>>> +    bool dirty_bitmap; /* export 
>>> qemu-dirty-bitmap:<export_bitmap_name> */
>>
>> That's a LONG namespace name, and it does not lend itself well to 
>> other qemu extensions; so future qemu BLOCK_STATUS additions would 
>> require consuming yet another namespace and additional upstream NBD 
>> registration.  Wouldn't it be better to have the namespace be 'qemu:' 
>> (which we register with upstream NBD just once), where we are then 
>> free to document leafnames to look like 'dirty-bitmap:name' or 
>> 'foo:bar'?
>
> No doubts. (and this shows, that we may want namespaces in namespaces, 
> so we'll parse ':' anyway).
>
> Only one note here (I'm ashamed): 'qemu-dirty-bitmap' namespace is 
> used in Virtuozzo for the feature, yes, without 'x-' prefix. It's my 
> fault, and it should not influence final solution. The probability of 
> problems is near to zero (especially if we decide now to use 'qemu:' 
> namespace for all qemu-specific things. But I'm not sure about, should 
> we mention this fact in the spec.
> [cc NBD list]
>

Looks like at this point, we can safely move to qemu:dirty-bitmap:name, 
or any other thing, and we don't need to support my first variant.

-- 
Best regards,
Vladimir