Re: What is needed for ZFS block cloning to work?

On Sun, Jul 12, 2026 at 5:22=E2=80=AFPM Rob Norris <[email protected]> w=
rote:
>
> On Mon, 13 Jul 2026, at 10:18 AM, Rick Macklem wrote:
>
> For FreeBSD, if cloning or failure of the copy_file_range(2) syscall is
> desired, the flag argument COPY_FILE_RANGE_CLONE can be specified.
> (to avoid the fallback to the copy loop in the kernel syscall)
>
>
> Oh, interesting! That wasn't there when we first wired it up (pretty sure=
). I'll check if that's working properly against ZFS. At minimum, I'll re-w=
ork the FICLONERANGE tests to use it.

It went into FreeBSD's main on Aug. 9, 2025. But there is no change to the
ZFS code. It just makes vn_generic_copy_file_range() fail, since that is th=
e
fallback. If zfs_copy_file_range() learns how to do a non-block-cloning "co=
py",
then this will need to change.

rick

>
> Rob.