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

[Liu Yuan]

On 06/06/2012 09:31 PM, Christoph Hellwig wrote:

> On Wed, Jun 06, 2012 at 09:28:38PM +0800, Liu Yuan wrote:
>> Yes, this patch only serialize the cluster requests on local node, but I
>> think this is good enough. Sheepdog doesn't need to carry on the burden
>> such as name collision detection, which could be handled very well
>> (better) by the administration layer by serious users. Remove
>> block/unblock logic is relatively difficult to understand and possibly
>> risk the cluster to be blocked for ever (assume any bug that blocks the
>> cluster but forget unblock it).
>>
>> By removing it, we get much more (1 simpler code 2 remove deadlock risk)
>> than lose (just leave the burden to upper layer).
> 
> Sheepdog needs to handle concurrent creation of VDIs, for some defintion
> of handling - detecting the case and returning an error would be enough,
> causing silent failures would not.
> 
> 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.

Thanks,
Yuan