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

[Stefan Hajnoczi <stefanha@redhat.com>]

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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.

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)

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