[libvirt] [PATCH RFC] storage: Remove 'cow' disk format

Peter Krempa pkrempa at redhat.com
Fri Mar 23 11:43:11 UTC 2018


On Fri, Mar 23, 2018 at 11:37:17 +0000, Daniel Berrange wrote:
> On Fri, Mar 23, 2018 at 12:32:29PM +0100, Peter Krempa wrote:
> > There's no tests for this format and nothing seems to specifically care
> > about this format. QEMU does not even recognize it. Remove it completely.
> 
> This format is from the User Mode Linux driver, not QEMU.

Hmmm. I wanted to delete the UML driver too, but that was slightly more
work and it also looked like it might be possible to build it even now,
but I did not manage to do it.

> 
> > Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> > ---
> >  docs/schemas/storagecommon.rng |  1 -
> >  src/util/virstoragefile.c      | 31 +------------------------------
> >  src/util/virstoragefile.h      |  3 +--
> >  3 files changed, 2 insertions(+), 33 deletions(-)

[...]

> > diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
> > index 596746ccb7..c84e013f46 100644
> > --- a/src/util/virstoragefile.h
> > +++ b/src/util/virstoragefile.h
> > @@ -82,8 +82,7 @@ typedef enum {
> >       * libvirt support for following a backing chain */
> >      VIR_STORAGE_FILE_BACKING,
> > 
> > -    VIR_STORAGE_FILE_COW = VIR_STORAGE_FILE_BACKING,
> > -    VIR_STORAGE_FILE_QCOW,
> > +    VIR_STORAGE_FILE_QCOW = VIR_STORAGE_FILE_BACKING,
> >      VIR_STORAGE_FILE_QCOW2,
> >      VIR_STORAGE_FILE_QED,
> >      VIR_STORAGE_FILE_VMDK,
> 
> Removing this from the XML schema, is akin to deleting an enum
> entry from the public API. This is not something we can do, even if
> we think it is unlikely to be used.

Yes I know. But given the chance to delete unused code I had to try it.
Especially since it was easy and I doubt that anyone would ever care.

> It is of course fine if we generate an error in drivers when trying to use
> it at runtime though. 

Yes. This is the patch I was doing after sending this.
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