Re: [Qemu-devel] [PATCH for-4.1 0/2] backup: Copy only dirty areas

[Vladimir Sementsov-Ogievskiy]

01.08.2019 18:12, Max Reitz wrote:
> Hi,
> 
> In a discussion with Vladimir today, we noticed that the backup job
> currently is pretty broken when using copy offloading.  I don’t know
> about you, but my local filesystem (XFS) supports copy offloading, so
> the job uses it automatically.  That means, that backup is broken and
> has been broken for a year on my local FS.
> 
> The last working version was 2.12, so this isn’t a regression in 4.1.
> We could thus justify moving it to 4.2.  But I think this should really
> go into 4.1, because this is not really an edge case and as far as I
> know users cannot do anything to prevent the backup job from performing
> copy offloading if the system and all involved block drivers support it.
> I just wonder why nobody has noticed...
> 

Agree. And if this goes into 4.1, I suggest to add
[PATCH 2/3] block/backup: disable copy_range for compressed backup

as for now compressed backup just don't compress anything on FS with
copy offloading supported.

> 
> Max Reitz (2):
>    backup: Copy only dirty areas
>    iotests: Test backup job with two guest writes
> 
>   block/backup.c             | 13 +++++++++++--
>   tests/qemu-iotests/056     | 34 ++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/056.out |  4 ++--
>   3 files changed, 47 insertions(+), 4 deletions(-)
> 


-- 
Best regards,
Vladimir