Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/25/2010 04:14 AM, Avi Kivity wrote:
> On 05/24/2010 10:38 PM, Anthony Liguori wrote:
>>
>>> - Building a plugin API seems a bit simpler to me, although I'm to
>>> sure if I'd get the
>>>    idea correctly:
>>>    The block layer has already some kind of api (.bdrv_file_open, 
>>> .bdrv_read). We
>>>    could simply compile the block-drivers as shared objects and 
>>> create a method
>>>    for loading the necessary modules at runtime.
>>
>> That approach would be a recipe for disaster.   We would have to 
>> introduce a new, reduced functionality block API that was supported 
>> for plugins.  Otherwise, the only way a plugin could keep up with our 
>> API changes would be if it was in tree which defeats the purpose of 
>> having plugins.
>
> We could guarantee API/ABI stability in a stable branch but not across 
> releases.

We have releases every six months.  There would be tons of block plugins 
that didn't work for random sets of releases.  That creates a lot of 
user confusion and unhappiness.

Regards,

Anthony Liguori