[libvirt] [PATCH] qemu: blockCopy: Allow shallow block copy into a raw image

[Peter Krempa]

On Mon, Apr 27, 2015 at 22:11:40 +0800, Shanzhi Yu wrote:
> 
> 
> On 04/27/2015 08:01 PM, Peter Krempa wrote:
> > The documentation states that for shallow block copy the image has to
> > have the same guest visible content as backing file of the current
> > image. This condition can be achieved also with a raw file (or a qcow
> > without a backing file) so remove the condition that would disallow it.
> >
> > (This patch additionally fixes crash described in
> >  https://bugzilla.redhat.com/show_bug.cgi?id=1215569 since it removes
> >  the code)
> > ---
> >  src/qemu/qemu_driver.c | 10 ----------
> >  1 file changed, 10 deletions(-)
> >
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index 70bf7aa..f979d33 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -16815,16 +16815,6 @@ qemuDomainBlockCopyCommon(virDomainObjPtr vm,
> >      if (qemuDomainDetermineDiskChain(driver, vm, disk, false, true) < 0)
> >          goto endjob;
> >
> > -    if ((flags & VIR_DOMAIN_BLOCK_COPY_SHALLOW) &&
> > -        mirror->format == VIR_STORAGE_FILE_RAW &&
> > -        disk->src->backingStore->path) {
> > -        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> > -                       _("disk '%s' has backing file, so raw shallow copy "
> > -                         "is not possible"),
> > -                       disk->dst);
> > -        goto endjob;
> > -    }
> > -
> 
> Although a shallow blockcopy of file without backing file is
> semantically correct, but still feel a little weird.
> And, a shallow blockcommit of file without backing file will failed with
> error
> "error: invalid argument: top '/var/lib/libvirt/images/raw.img' in chain
> for 'vda' has no backing file"
> 
> Should libvirt post error when try a shallow blockcopy of file without
> backing file, just as shallow blockcommit?

I cannot reproduce the error above, could you please post steps to do
that? or perhaps debug log from libvirt?

When copying from a single layer image with the --shallow flag I'm able
to successfully copy both into a raw and a qcow2 file.

> 
> >      /* Prepare the destination file.  */
> >      /* XXX Allow non-file mirror destinations */
> >      if (!virStorageSourceIsLocalStorage(mirror)) {

Peter
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