bug#48164: closed (cp --reflink=never no longer works as expected)

[GNU bug Tracking System]

Your message dated Sun, 2 May 2021 21:59:21 +0100
with message-id <b592eb22-e2f3-4ac2-6f3c-2c55854cd921@draigBrady.com>
and subject line Re: bug#48164: cp --reflink=never no longer works as expected
has caused the debbugs.gnu.org bug report #48164,
regarding cp --reflink=never no longer works as expected
to be marked as done.

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48164: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=48164
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> --- Begin Message ---
>
>
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> Subject: 
>
> cp --reflink=never no longer works as expected
>
>
>
>
> Date: 
>
> Sun, 2 May 2021 11:12:27 -0600
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>
>
>
> Hi,
>
> Fedora 34 user 'adrum' reports that 'cp --reflink=never' is performing
> a lightweight copy on Btrfs. And filefrag -v shows the extents are
> shared. Strace shows use of copy_file_range even with --reflink=never
>
> The note for copy_file_range() includes:
>
> copy_file_range() gives filesystems an opportunity to implement
>        "copy acceleration" techniques, such as the use of reflinks
>
>
> Downstream bug
> https://bugzilla.redhat.com/show_bug.cgi?id=1956080
>
> The commit that causes the change in behavior:
> https://src.fedoraproject.org/rpms/coreutils/c/1737e5c81fa82451b510f982499bdedb2a1619d1?branch=rawhide
>
> It references five upstream commits.
>
>
> -- 
> Chris Murphy
>
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#48164: cp --reflink=never no longer works as expected
>
>
>
>
> Date: 
>
> Sun, 2 May 2021 21:59:21 +0100
>
>
>
>
> User-agent: 
>
> Mozilla/5.0 (X11; Linux x86_64; rv:84.0) Gecko/20100101 Thunderbird/84.0
>
>
>
>
> On 02/05/2021 18:12, Chris Murphy wrote:
> > Hi,
> >
> > Fedora 34 user 'adrum' reports that 'cp --reflink=never' is performing
> > a lightweight copy on Btrfs. And filefrag -v shows the extents are
> > shared. Strace shows use of copy_file_range even with --reflink=never
> >
> > The note for copy_file_range() includes:
> >
> > copy_file_range() gives filesystems an opportunity to implement
> >         "copy acceleration" techniques, such as the use of reflinks
> >
> >
> > Downstream bug
> > https://bugzilla.redhat.com/show_bug.cgi?id=1956080
> >
> > The commit that causes the change in behavior:
> > https://src.fedoraproject.org/rpms/coreutils/c/1737e5c81fa82451b510f982499bdedb2a1619d1?branch=rawhide
> >
> > It references five upstream commits.
>
> Thanks for the detailed report. I've fixed this upstream with:
> https://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=v8.32-147-gea9af9923
> Ideally copy_file_range() would take CAN_REFLINK as a flag,
> but for now the patch above avoids the call with --reflink=never.
>
> Note we've not released an official coreutils release with this change yet,
> as we've yet to fully test all variations of this new copying logic.
> There are subtle interactions like this that need to be considered.
> BTW there has been recent discussions on the non generality of
> copy_file_range() at https://lwn.net/Articles/846403/
>
> Marking this as done.
>
> cheers,
> Pádraig
>
>
> --- End Message ---