Re: [Qemu-devel] [PATCH RFC v2 8/8] migration: add migration/dirty-bitmap.c

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

On 16.02.2015 21:18, John Snow wrote:
>
>
> On 02/16/2015 07:06 AM, Vladimir Sementsov-Ogievskiy wrote:
>> On 13.02.2015 23:22, John Snow wrote:
>>>
>>>
>>> On 02/13/2015 03:19 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>> On 11.02.2015 00:33, John Snow wrote:

>>>> So in summary:
>>>> using device names is probably fine for now, as it matches the current
>>>> use case of bitmaps as well as drive migration; but using node names
>>>> may give us more power and precision later.
>>>>
>>>> I talked to Max about it, and he is leaning towards using device names
>>>> for now and switching to node names if we decide we want that power.
>>>>
>>>> (...I wonder if we could use a flag, for now, that says we're
>>>> including DEVICE names. Later, we could add a flag that says we're
>>>> using NODE names and add an option to toggle as the usage case sees 
>>>> fit.)
>>>>
>>>>
>>>> Are you confused yet? :D
>> O, thanks for the explanation). Are we really need this flag? As Markus
>> wrote, nodes and devices are sharing namespaces.. We can use
>> bdrv_lookup_bs(name, name, errp)..
>
> what 'name' are you using here, though? It looked to me like in your 
> backup routine we got a list of BDS entries and get the name *from* 
> the BDS, so we still have to think about how we want to /get/ the name.
>
>>
>> Also, we can, for example, send bitmaps as follows:
>>
>> if node has name - send bitmap with this name
>> if node is root, but hasn't name - send it with blk name
>> otherwise - don't send the bitmap
>
> The node a bitmap is attached to should always have a name -- it would 
> not be possible via the existing interface to attach it to a node 
> without a name.
>
> I *think* the root node should always have a name, but I am actually 
> less sure of that.
>
Hmm.. No? bitmap is attached using bdrv_lookup_bs(name, name, errp), 
which can find device with this name. qemu option -drive 
file=...,id=disk creates blk named 'disk' and attached node with no name.


-- 
Best regards,
Vladimir