On 6/3/19 4:22 PM, Max Reitz wrote:
> QEMU’s always been confused over what a snapshot is: Is it the overlay?
> Is it the backing image?
>
> Confusion is rarely a good thing. I can’t think of any objective reason
> why the overlay would be a snapshot. A snapshot is something that does
> not change over time; the overlay does.
>
> (I suppose historically the reason is that “Taking an overlay” makes no
> sense, so the operations are called “Taking a snapshot”. Somehow, this
> meaning carried over to the new file that is created during that
> operation; if “Creating a snapshot” creates a file, that file must be
> the snapshot, right? Well, no, it isn’t.)
>
> Let’s fix this as best as we can. Better Nate than lever.
>
>
> v2:
> - Don’t break the iotests for a change
> (kept Eric’s R-b, because it felt like the right thing to do)
>
>
> git backport-diff against v1:
>
> Key:
> [----] : patches are identical
> [####] : number of functional differences between upstream/downstream patch
> [down] : patch is downstream-only
> The flags [FC] indicate (F)unctional and (C)ontextual differences,
> respectively
>
> 001/2:[----] [--] 'qapi/block-core: Overlays are not snapshots'
> 002/2:[0010] [FC] 'blockdev: Overlays are not snapshots'
>
>
> Max Reitz (2):
> qapi/block-core: Overlays are not snapshots
> blockdev: Overlays are not snapshots
>
> qapi/block-core.json | 20 ++++++++++----------
> blockdev.c | 10 +++++-----
> tests/qemu-iotests/085.out | 10 +++++-----
> 3 files changed, 20 insertions(+), 20 deletions(-)
>
Makes good sense to me.
There are only 3,283 things named "snapshot" in QEMU so one less is
probably not the worst.
Reviewed-by: John Snow <js...@redhat.com>
