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Date: Mon, 6 Jan 2025 07:12:00 +0100
Message-ID: <CALXu0Ucpsd7McaYAVtUU0tCGzRm7p2q74VgBrM8aKVDLVkB=bQ@mail.gmail.com>
Subject: Re: Cygwin copy_file_range() support with sparse
 file+FSCTL_DUPLICATE_EXTENTS_TO_FILE?
To: cygwin AT cygwin DOT com
From: Cedric Blancher via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Cedric Blancher <cedric DOT blancher AT gmail DOT com>
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On Sun, 5 Jan 2025 at 17:31, Brian Inglis via Cygwin <cygwin AT cygwin DOT com> wrote:
>
> On 2025-01-05 06:52, Takeshi Nishimura via Cygwin wrote:
> > On Sun, Jan 5, 2025 at 1:06 PM Václav Haisman via Cygwin wrote:
> >> On 05. 01. 25 7:31, Cedric Blancher via Cygwin wrote:
> >>> 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
>
> Cygwin has supported sparse files since 2000, mount option to enable it for over
> a decade, inode sparse ioctl flag for half that, and automatic support on SSDs
> just over a year ago:
>
> https://cygwin.com/git/?p=newlib-cygwin.git&a=search&st=commit&s=sparse&h=363357
>
> https://cygwin.com/git/?p=newlib-cygwin.git;a=commitdiff;h=05297c
>
> https://cygwin.com/git/?p=newlib-cygwin.git;a=blob_plain;f=winsup/cygwin/include/cygwin/fs.h
>
> It works on NTFS, include remote mounts, but I don't know about other filesystems?

I know about sparse file support in Cygwin. My request was for sparse
file support in copy_file_range() when Cygwin implements this function

Ced
-- 
Cedric Blancher <cedric DOT blancher AT gmail DOT com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur

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