[libvirt] [Patch] Libvirt - Fix locking for readonly devices

[Daniel P. Berrange]

On Tue, May 08, 2012 at 09:41:02AM +0000, David Weber wrote:
> Hi,
> 
> I'm currently working on getting sanlock into Debian/Ubuntu.
> While testing, I noticed that I wasn't able to add a readonly 
> or shared device: "internal error unsupported 
> configuration: Readonly leases are not supported".
> 
> After looking into the source, it seems to be the following
> situation:
> - Libvirt passes every device to the sanlock plugin, even if
> it is readonly
> - The sanlock plugin rejects to add a lease for the readonly
> device, returning an error so the machine starts to fail
> 
> The attached patch rejects passing readonly and shared devices 
> to the lock-plugin so they shouldn't be a problem anymore.

This isn't good - the lock manager implementation must be the
one to decide what todo with readonly & shared disks. The sanlock
plugin, however, does not currently support readonly/shared leases
hence why it rejects them. We could probably add a config param
to allow readonly/shared leases to be skipped by the sanlock plugin.

Daniel
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