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

[Vladimir Sementsov-Ogievskiy]

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 <address@hidden>
>
> 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]

--
Best regards,
Vladimir