Re: [Qemu-devel] [PATCH v2 1/4] qemu-img: add --shrink flag for resize

[Kevin Wolf <kwolf@redhat.com>]

Am 22.06.2017 um 15:54 hat Pavel Butsykin geschrieben:
> On 22.06.2017 01:17, Max Reitz wrote:
> >On 2017-06-13 14:16, Pavel Butsykin wrote:
> >>The flag as additional precaution of data loss. Perhaps in the future the
> >>operation shrink without this flag will be banned, but while we need to
> >>maintain compatibility.
> >>
> >>Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>

> >The functional changes look good to me; even though I'd rather have it
> >an error for qcow2 now (even if that means having to check the image
> >format in img_resize(), and being inconsistent because you wouldn't need
> >--shrink for raw, but for qcow2 you would). But, well, I'm not going to
> >stop this series over that.
> >
> 
> Why shrink for qcow2 image is dangerous, but for raw is not dangerous? I
> think we should provide the same behavior for all formats. When --shrink
> option will become necessary, it also should be the same for all image
> formats.

It is dangerous for both, but for raw we can't enforce the flag
immediately without a deprecation period. With qcow2 we can (because it
is new functionality), so we might as well enforce it from the start.

Kevin