[libvirt] [PATCH] spec: Remove qemu-img dependency from storage driver

[Daniel P. Berrange]

On Thu, Dec 04, 2014 at 02:42:31PM +0100, Jiri Denemark wrote:
> On Wed, Dec 03, 2014 at 15:58:45 +0000, Daniel Berrange wrote:
> > On Wed, Dec 03, 2014 at 04:52:25PM +0100, Jiri Denemark wrote:
> > > Both qemu-img and its stripped down version qcow-create are searched for
> > > dynamically with virFindFileInPath, functions using them report errors
> > > when the required binary is not present, and we don't compile in a fixed
> > > path detected by configure anymore. So I don't see a reason for keeping
> > > the dependencies for our storage driver. Moreover, it's weired when the
> > > dependencies (of the storage driver) change depending on wheter a
> > > particular hypervisor driver (xen/qemu) is enabled or not.
> > > 
> > > Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> > > ---
> > >  libvirt.spec.in | 18 ------------------
> > >  1 file changed, 18 deletions(-)
> > 
> > Even if using the Xen hypervisor, you can use the qemu-img binary
> > for creating volumes. Since the qemu-img binary is in a separate
> > RPM from the main QEMU emulator binaries, it makes sense to depend
> > on qemu-img if we're enabling QEMU support in libvirt. Similarly the
> > LXC driver can make use of qemu-img for creating images that are then
> > used via qemu-nbd.
> > 
> > So I think our current Requires deps are actually correct here - they
> > ensure that the qemu-img binary is always pulled into the host, no
> > matter what daemon-driver-XXX is installed.
> 
> But it still feels wrong. A choice of what hypervisor driver is enabled
> should not influence dependencies of a storage driver. If we want the
> storage driver to depend on qemu-img, I think the dependency should be
> enabled by a separate switch, so that one can enable qemu-img support
> without enabling qemu driver. Or am I just over-engineering it based on
> my confusion why storage deps change depending on enabled HV drivers?

I can see the argument that we should use a separate conditional
for enabling qemu-img, because it is possible that there are architectures
where qemu-img is built, but the qemu emulators are not built. So we would
wnat the dep on qemu-img, even if qemu was disabled in libvirt.

Regards,
Daniel
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