Re: BTRFS file clone support for cp

[Jim Meyering]

Giuseppe Scrivano wrote:
> Jim Meyering <address@hidden> writes:
>>> ..., a cloned partially-sparse file on btrfs takes less
>>> space than a fully-sparse copied file.
>>
>> That is not true.  A fully-sparse file takes less space
>> than a partially-sparse one.
>
> Sorry I wasn't clear, I wanted to say that a cloned file in any case
> take less space than really copying it.

That depends on what you mean by "really copying it".
If you copy with --sparse=always and the file has at least
one non-sparse run of zeros, that result will be smaller
than the cloned file.

>> Adding this optimization should not change the meaning of
>> --sparse=always.
>
> So do you want to use it only when --sparse=auto is used?

Precisely.