[libvirt] [PATCH] qemu: don't check for backing chains for formats w/o snapshot support

[Eric Blake]

On 04/17/2014 04:20 AM, Martin Kletzander wrote:
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1019926
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=868673
> 
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  src/libvirt_private.syms  |  2 +-
>  src/qemu/qemu_domain.c    |  3 +++
>  src/util/virstoragefile.c | 15 +++++++++++++++
>  src/util/virstoragefile.h |  2 ++
>  4 files changed, 21 insertions(+), 1 deletion(-)


> @@ -1850,7 +1851,6 @@ virStorageSourcePoolModeTypeToString;
>  virStorageTypeFromString;
>  virStorageTypeToString;
> 
> -
>  # util/virstring.h

Spurious whitespace change.


> +
> +bool
> +virStorageFormatMaySupportSnapshots(enum virStorageFileFormat format)
> +{
> +    if (format == VIR_STORAGE_FILE_AUTO ||
> +        format == VIR_STORAGE_FILE_AUTO_SAFE)
> +        return true;
> +
> +    /* Better safe than sorry */
> +    if (format <= VIR_STORAGE_FILE_NONE ||
> +        format >= VIR_STORAGE_FILE_LAST)
> +        return false;
> +
> +    return !!fileTypeInfo[format].getBackingStore;

Hmm, how does this compare with the recent commit db7d7c0e which added
the VIR_STORAGE_FILE_BACKING marker?  I made that separation in order to
state that all formats less than the marker do not have a
getBackingStore callback (well, other than the exceptions of the _AUTO
and _AUTO_SAFE formats which are less than 0), and all formats >= that
marker DO have a potential for a backing store.  Should this code be
using that new constant instead of probing the existence of
getBackingStore?  Or conversely, should the domain_conf.c code that I
touched in that patch instead be using this new function instead of
relying on the VIR_STORAGE_FILE_BACKING marker?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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