Cygwin copy_file_range() support with sparse file+FSCTL_DUPLICATE_EXTENTS_TO_FILE?

[Takeshi Nishimura]

On Sun, Jan 5, 2025 at 1:06 PM Václav Haisman via Cygwin
<cygwin@cygwin.com> wrote:
>
> On 05. 01. 25 7:31, Cedric Blancher via Cygwin wrote:
> > Good morning!
> >
> > Could Cygwin implement copy_file_range() support, including sparse
> > file support so holes are preserved, and
> > FSCTL_DUPLICATE_EXTENTS_TO_FILE support?
>
> In theory, this could be used to implement that function. In practice,
> the block cloning is only supported by ReFS. See
> <https://learn.microsoft.com/en-us/windows/win32/api/winioctl/ni-winioctl-fsctl_duplicate_extents_to_file>

All Windows Server (2019, 2022) installations we have. and those which
I know about, use ReFS (except in cases where Alternate Streams are
required).
AFAIK SMB3 also support FSCTL_DUPLICATE_EXTENTS_TO_FILE, so this would
be a HUGE win for Cygwin
-- 
Internationalization&localization dev / 大阪大学
Takeshi Nishimura <takeshi.nishimura.linux@gmail.com>