Re: [PATCH] qemu: migration: don't open storage driver too early
On Mon, Oct 12, 2020 at 10:55:52AM +0200, Michal Privoznik wrote:
On 10/12/20 10:50 AM, Daniel P. Berrangé wrote:
> On Sun, Oct 11, 2020 at 07:44:36PM -0400, Cole Robinson wrote:
> > If storage migration is requested, and the destination storage does
> > not exist on the remote host, qemu's migration support will call
> > into the libvirt storage driver to precreate the destination storage.
> >
> > The storage driver virConnectPtr is opened too early though, adding
> > an unnecessary dependency on the storage driver for several cases
> > that don't require it. This currently requires kubevirt to install
> > the storage driver even though they aren't actually using it.
> >
> > Push the virGetConnectStorage calls to right before the cases they are
> > actually needed.
>
> This pushes the connection open attempts inside a loop body. So if the
> VM has multiple disks, then we're going to be repeatedly opening and
> closing the connection which is not desirable.
>
> I think we need a global connection across all disks, which is lazy
> opened on first access.
Doesn't virGetConnectStorage() cache the connection?
Yes & no.
You can call virSetConnectStorage(conn) to populate the cache with a
pre-opened connection. If you haven't done that, then a new connection
will be opened every time. The ltter is what this code will be doing.
Regards,
Daniel
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