Re: [Qemu-devel] [PATCH 01/10] qcow2: Write feature table only for v3 images

[Kevin Wolf <kwolf@redhat.com>]

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Am 22.12.2015 um 21:20 hat Eric Blake geschrieben:
> On 12/22/2015 09:46 AM, Kevin Wolf wrote:
> > Version 2 images don't have feature bits, so writing a feature table to
> > those images is kind of pointless.
> 
> Fortunately, it is also harmless; even the v2 spec allowed for unknown
> extension headers.

With 512 byte clusters it could use up important space that you wanted
to use for the backing file path!

Okay, okay, maybe not that critical... ;-)

> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  block/qcow2.c              | 48 ++++++++++++++++++++++++----------------------
> >  tests/qemu-iotests/031.out | 12 +-----------
> >  tests/qemu-iotests/061.out | 15 ---------------
> >  3 files changed, 26 insertions(+), 49 deletions(-)
> > 
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> Did you test that amend'ing an image from v2 to v3 adds the table, and
> downgrading from v3 to v2 drops the table?

I'm not sure if I tested it manually, but I'm updating the results of
test case 061, which tests both upgrades and downgrades, so if your
review was thorough enough, the answer is yes.

Kevin

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