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Excerpts from Matthew Booth's message of 2014-06-13 01:40:30 -0700:
> On 12/06/14 21:38, Joshua Harlow wrote:
> > So just a few thoughts before going to far down this path,
> > 
> > Can we make sure we really really understand the use-case where we think
> > this is needed. I think it's fine that this use-case exists, but I just
> > want to make it very clear to others why its needed and why distributing
> > locking is the only *correct* way.
> 
> An example use of this would be side-loading an image from another
> node's image cache rather than fetching it from glance, which would have
> very significant performance benefits in the VMware driver, and possibly
> other places. The copier must take a read lock on the image to prevent
> the owner from ageing it during the copy. Holding a read lock would also
> assure the copier that the image it is copying is complete.

Really? Usually in the unix-inspired world we just open a file and it
stays around until we close it.