bug#60416: [PATCH] copy: attempt copy offload with sparse files

[Pádraig Brady]

On 31/12/2022 01:36, Paul Eggert wrote:
> On 2022-12-30 16:23, Pádraig Brady wrote:
> > I may follow up with a related patch to
> > ensure we _don't_ use copy_file_range with --sparse=never.
>
> Not sure it's worth the bother. A file system that would create holes
> with copy_file_range could also do so with plain 'write', no?

Well copy_file_range() would be lower level and within its
remit to propagate holes. The FreeBSD docs allude to this also.

But yes, our use of copy_file_range() is generally restricted
to non holes, so less of an issue for us.

Also there may be users using `cp --sparse=never` to avoid
the perf issue currently, like we saw on the OP web thread.

I'll hold off on that change so.

Hopefully copy_file_range() flags are introduced to give
control over this (like I suggested on lkml years ago).

cheers,
Pádraig