GNU bug report logs -
#48164
cp --reflink=never no longer works as expected
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Report forwarded
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bug-coreutils <at> gnu.org
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bug#48164
; Package
coreutils
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(Sun, 02 May 2021 17:13:02 GMT)
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Chris Murphy <lists <at> colorremedies.com>
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New bug report received and forwarded. Copy sent to
bug-coreutils <at> gnu.org
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(Sun, 02 May 2021 17:13:02 GMT)
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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):
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
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Pádraig Brady <P <at> draigBrady.com>
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You have taken responsibility.
(Sun, 02 May 2021 21:00:01 GMT)
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Chris Murphy <lists <at> colorremedies.com>
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bug acknowledged by developer.
(Sun, 02 May 2021 21:00:02 GMT)
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Message #10 received at 48164-done <at> debbugs.gnu.org (full text, mbox):
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
bug archived.
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(Mon, 31 May 2021 11:24:08 GMT)
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This bug report was last modified 2 years and 329 days ago.
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