[sheepdog] [PATCH] sheep: remove block/unblock callbacks

[Liu Yuan]

On 06/06/2012 10:02 PM, Christoph Hellwig wrote:

> On Wed, Jun 06, 2012 at 09:56:00PM +0800, Liu Yuan wrote:
>>> That why I said I like the approch, but issues like the one above need
>>> to be carefully audited and fixed.
>>>
>>
>>
>> Yes, but I can't come up with an easy fix for concurrent VDI creation of
>> the same name inside sheep and the upper software is at a much better
>> place to handle it.
> 
> I don't think it is.  It means you can't ever use sheepdog in a
> distributed environment without a nanny-like higher level, which is
> totally unacceptable.
> 
> I have an idea for management of the VDI bitmap, which basically
> requires:
>  
>   (a) factoring the VDI bitmap implementation into a separate small
>       abstraction. E.g. instead of making the whole VDI creation
>       a blocking operation just grab the VDI inuse bit first, then
>       actually create it and release the inuse flag if it fails
>   (b) move the now nicely separate option into the cluster driver.
>       For corosync it probably means a fairly similar scheme to what
>       we do now, but for zookeeper atomic access to a node is actually
>       part of the concept, so it could be a lot simpler.
> 
> I think this is a bit too much work before the June release, but I'm
> happy to work on it after that.  I'd also very much welcome not breaking
> the existing semantics in fundamental ways until then.
> 


Okay, sounds reasonable. Let's re-visit this patch when the potential
bitmap issue is fixed.

Thanks,
Yuan