Re: [Qemu-devel] [Qemu-block] [PATCH v6 03/22] blockdev: Add and parse "lock-mode" option for image locking

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, Sep 06, 2016 at 06:45:55PM +0200, Kevin Wolf wrote:
> Am 08.07.2016 um 15:05 hat Max Reitz geschrieben:
> > I think whether to lock a BDS chain is a host-side property and has not
> > a lot to do with the guest, thus it should be a BDS property. I can
> > imagine that a guest may say that sharing should be disallowed under all
> > circumstances, but a guest is never able to decide to allow sharing.
> 
> Well, yes and no. The decision which lock mode to use is at the node
> level, no doubt. But it's not something that a user can configure.
> Non-raw images simply can't be shared and the user can't do anything
> about it. Why should they have an option to specify a lock mode when
> there is only one correct setting?

I'm not sure that's true for all non-raw images. I understand things like
qcow2 won't work, because of cached metadata which can be updated by QEMU
during writes, but I think the luks format ought to be safe as the cached
metadata is never changed.

Regards,
Daniel
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