Re: [Qemu-devel] [PATCH 3/4] block/vpc: give option to force the current_size field in .bdrv_create

[Jeff Cody <jcody@redhat.com>]

On Wed, Feb 24, 2016 at 11:19:37AM +0100, Kevin Wolf wrote:
> Am 24.02.2016 um 01:47 hat Jeff Cody geschrieben:
> > When QEMU creates a VHD image, it goes by the original spec,
> > calculating the current_size based on the nearest CHS geometry (with an
> > exception for disks > 127GB).
> > 
> > Apparently, Azure will only allow images that are sized to the nearest
> > MB, and the current_size as calculated from CHS cannot guarantee that.
> > 
> > Allow QEMU to create images similar to how Hyper-V creates images, by
> > setting current_size to the specified virtual disk size.  This
> > introduces an option, force_size, to be passed to the vpc format during
> > image creation, e.g.:
> > 
> >     qemu-img convert -f raw -o force_size -O vpc test.img test.vhd
> > 
> > Bug reference: https://bugs.launchpad.net/qemu/+bug/1490611
> > 
> > Signed-off-by: Jeff Cody <jcody@redhat.com>
> 
> We need to set a different creator string here that makes vpc_open()
> recognise the image as current_size based.
> 
> Kevin

How about "qem2"?  I initially thought about just changing the case on
"qemu", but I was afraid some other software may treat the app creator
string as case-insensitive.

I'll also update patch 1, to recognize that string as well.