Re: [Qemu-devel] [Qemu-block] [PATCH v2 0/2] blockdev: Overlays are not snapshots

[John Snow]

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 <address@hidden>