Re: [Qemu-devel] [PATCH v2 2/4] block: in commit, determine base image from the top image

[Eric Blake <eblake@redhat.com>]

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On 10/16/2012 08:44 AM, Jeff Cody wrote:
> This simplifies some code and error checking, and also fixes a bug.
> 
> bdrv_find_backing_image() should only be passed absolute filenames,
> or filenames relative to the chain.  In the QMP message handler for
> block commit, when looking up the base do so from the determined top
> image, so we know it is reachable from top.
> 
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>  block/commit.c |  9 ---------
>  blockdev.c     | 21 +++++++++++----------
>  2 files changed, 11 insertions(+), 19 deletions(-)

As long as you are touching this code:

> @@ -1182,6 +1172,17 @@ void qmp_block_commit(const char *device,
>          return;
>      }
>  
> +    if (base && has_base) {

please swap this to 'has_base && base' to avoid any potential of
valgrind warnings about conditional jump based on uninitialized memory.

Also, I raised another bug[1] about a bad error message regarding
top_bs, if the user passes a different spelling than the canonical name
of the active image.  Is that worth fixing in this series, or is it okay
to leave it until you actually add support for committing the top image?

[1] https://lists.gnu.org/archive/html/qemu-devel/2012-10/msg02067.html
-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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