Re: [Qemu-devel] [PATCH V6 8/8] block: Use graph node name as reference in bdrv_file_open().

[Max Reitz <mreitz@redhat.com>]

On 24.01.2014 15:48, Kevin Wolf wrote:
> Am 24.01.2014 um 14:37 hat Max Reitz geschrieben:
>> On 24.01.2014 14:26, Kevin Wolf wrote:
>>> Am 23.01.2014 um 21:31 hat Benoît Canet geschrieben:
>>>> Signed-off-by: Benoit Canet <benoit@irqsave.net>
>>>> ---
>>>>   block.c | 6 +++---
>>>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>> I'm not going to merge this one yet. It breaks qemu-iotests case 071,
>>> which would have to be adapted.
>>>
>>> However, first of all I'd like to hear the opinions of at least Eric and
>>> Max on what BlockRef should really refer to. I think node names make
>>> most sense, but perhaps it's a bit inconvenient and the command line
>>> should default to node-name = id when id is set, but node-name isn't?
>> The QAPI schema is pretty clear about this: “references the ID of an
>> existing block device.”
> Sure, that's because I wrote that text before we had a node name.
>
> However, in 1.7 references didn't work yet, so we still have all freedom
> to change the interface as we like.

Yes, that's right.

>> However, if the ID cannot be found, I think
>> we should interpret it as a reference to the node name.
>>
>> Therefore, I'd first try bdrv_find() and if that returns NULL, try
>> again with bdrv_find_node().
> I think I would prefer to avoid such ambiguities. Otherwise a management
> tool that wants to use the node name needs to check first if it's not
> already used as a device name somewhere else and would therefore operate
> on the wrong device.
>
> On the other hand, a management tool using the same names for devices
> and nodes just gets what it deserves.
>
> Perhaps we should use a common namespace for both, i.e. you get an error
> if you try to assign a node name that is already a device name and vice
> versa?

This is what I would go for. However, then I don't really know why we 
should separate the ID and the node name in the first place (although 
that's probably because I haven't followed the discussion around node 
names).

Max