Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> wrote on 
04/20/2020 11:04:33 AM:

> Yes, the problem is that copy_range subsystem handles block-status, 
> when generic backup copying loop doesn't. I'm not sure that adding 
> fallback into copy-range is a correct thing to do, at least it 
> should be optional, enabled by flag.. But you don't need it for your 
problem,
> as it is already fixed upstream:
> 
> You need to backport my commit 2d57511a88 "block/block-copy: use 
> block_status" (together with 3 preparing patches before it, or with 
> the whole series (including some refactoring after the 2d57511 commit)

Vladimir, thanks for the pointer to the "block/block-copy: use 
block_status" patch set. Those 4 patches do in fact solve the problem we 
were seeing.

- Bryan