Re: [Qemu-devel] [PATCH v13 15/17] iotests: add simple incremental backup case

[Max Reitz]

On 2015-02-20 at 05:02, Stefan Hajnoczi wrote:
> On Fri, Feb 13, 2015 at 05:08:56PM -0500, John Snow wrote:
> > +    def check_incremental(self, target=None):
> > +        if target is None:
> > +            target = self.bitmaps[-1].last_target()
> > +        self.assertTrue(iotests.compare_images(self.test_img, target))
> > +        return True
> > +
> > +
> > +    def hmp_io_writes(self, drive, patterns):
> > +        for pattern in patterns:
> > +            self.vm.hmp_qemu_io(drive, 'write -P%s %s %s' % pattern)
> > +        self.vm.hmp_qemu_io(drive, 'flush')
> Please don't read image files while the guest is still running.  Image
> formats do not support concurrent readers and writers.

If I'm not mistaken, there is no guest. VMs started using iotests.py 
have -machine accel=qtest set.

Max

> Three options:
> 1. Stop the guest before accessing self.test_img
> 2. Use drive-backup to make a full copy of self.test_img that can be
>     accessed.
> 3. Test specific patterns in the backup file instead of using
>     compare_images (qemu-io -c 'read -P 0xff 0 512' img)