Re: [Qemu-devel] [PATCH for-2.10 3/3] qemu-img/convert: Move bs_n > 1 && -B check down

[Eric Blake <eblake@redhat.com>]

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On 04/13/2017 03:34 PM, Max Reitz wrote:
> It does not make much sense to use a backing image for the target when
> you concatenate multiple images (because then there is no correspondence
> between the source images' backing files and the target's); but it was
> still possible to give one by using -o backing_file=X instead of -B X.
> 
> Fix this by moving the check.
> 
> (Also, change the error message because -B is not the only way to
>  specify the backing file, evidently.)

For that matter, 'create -B' is intentionally? undocumented in the
qemu-img --help and man page.  (Personally, I don't know why we don't
want it documented - is it because it it not a universal option because
not all formats support backing files?)

> 
> Cc: qemu-stable <qemu-stable@nongnu.org>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  qemu-img.c                 | 14 +++++++-------
>  tests/qemu-iotests/122.out |  4 ++--
>  2 files changed, 9 insertions(+), 9 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

Having a backing file for the destination may still make sense for some
convoluted workflow, but you can get that with a followup qemu-img rebase.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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