15.02.2019 21:56, Remi Gauvin пишет:
> On 2019-02-15 1:38 p.m., Chris Murphy wrote:
>>
>> Well I'd say maybe use -vvv and --no-data instead of -f and see what
>> it's doing. It sounds like the former has no payload, just difference
>> information, and the latter has a payload. I don't know why.
>>
>>
> 
> 
> Both have all the payload they need to re-create the subvolumes.  The
> first one correctly CoW's the file from subvolume a.. the second one
> stuffs it in the output... Why is indeed the question.
> 

The last extent is incomplete which causes btrfs to not attempt cloning.