[libvirt] Use flock() instead of fcntl()

[Daniel P. Berrange]

On Fri, Jul 26, 2013 at 10:44:24AM +0200, David Weber wrote:
> > Looking again at flock() I see it cannot support locking of ranges, only
> > the entire file. This makes it unsuitable as a replacement for libvirt's
> > use of fcntl() I'm afraid. I can only sugggest you configure OCFS2 so
> > that it supports fcntl(), or setup virtlockd to use separate indirect
> > leases on a diffrent shared filesystem, or perhaps try sanlock instead
> > which doesn't require any special filesystem support.
> 
> It's true that flock() doesn't support locking of ranges but I can't see how 
> this is necessary. 

The code may not currently use ranges, but that doesn't mean it'll stay
that way. By adding support for flock() we're preventing us from making
use of this feature in the future, and I don't want to see that.

Daniel
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