[libvirt-users] Locking without virtlockd (nor sanlock)?

[Peter Krempa]

On Mon, Jan 06, 2020 at 18:44:31 +0100, Gionatan Danti wrote:
> Il 06-01-2020 10:06 Peter Krempa ha scritto:
> > On Fri, Jan 03, 2020 at 14:08:03 +0000, Daniel Berrange wrote:
> > > As above, QEMU's locking is good enough to rely on for file based
> > > images.
> 
> Hi Daniel, thank you for the direct confirmation.
> 
> > > The flaws I mention with libvirt might actually finally be something
> > > we
> > > have fixed in 5.10.0 with QEMU 4.2.0, since we can finally use
> > > "blockdev"
> > > syntax for configuring disks.  Copying Peter to confirm/deny this...
> > 
> > The main issue was that we were leaking locks on the backing chain. This
> > should be now fixed with -blockdev as we call the appropriate apis to
> > lock/unlock the images but I didn't try it with virtlockd.
> > 
> > Certainly if there's still a problem now we have well defined places
> > where we know what's happening to images so it should be easy to fix
> > them.
> 
> Hi Peter, can I ask what do you mean with "fixed with -blockdev"?

blockdev is the new way to specify disks on qemu command line. It
required quite a lot of internal changes, some of which probably fixed
the block job cooperation with virtlockd. (leaking locks of images).

Blockdev is used starting from libvirt-5.10 and qemu-4.2