Bug 479107

Summary:	Dolphin does not Copy-on-Write ???? on Btrfs filesystems
Product:	[Frameworks and Libraries] frameworks-kio	Reporter:	landon.carbenia
Component:	general	Assignee:	KIO Bugs <kio-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	task	CC:	kdelibs-bugs, kfm-devel, meven, nate
Priority:	NOR
Version:	5.249.0
Target Milestone:	---
Platform:	Manjaro
OS:	Linux
Latest Commit:		Version Fixed In:

Description landon.carbenia 2023-12-28 04:40:59 UTC

SUMMARY
On a copy-on-write filesystem like Btrfs, Dolphin duplicates the entire file(s) on disk instead of just copying.

STEPS TO REPRODUCE
1. In Dolphin, copy a large directory to another location within the same Btrfs filesystem.
2. Observe that it's taking an unacceptably long time and a lot of disk space & throughput. Cancel the operation.
3. In a terminal, use cp to do the same copy operation.
4. Observe that it took all of four seconds, and used negligible extra diskspace and throughput.

OBSERVED RESULT
Dolphin is wasting time and disk space.

EXPECTED RESULT
A copy-on-write filesystem is actually copy-on-write.

SOFTWARE/OS VERSIONS
Linux Version: 6.6.8-MANJARO (64-bit)
Manjaro Version: 23.1.1
KDE Plasma Version: 5.27.10
KDE Frameworks Version: 5.113.0
Qt Version: 5.15.11
Graphics Platform: X11

Comment 1 Méven Car 2024-02-16 09:05:03 UTC

Well we do have "basic" reflink aka copy-on-write support:
https://bugs.kde.org/show_bug.cgi?id=326880

How large is the directory exactly ? How many files, directories, kind of file size ?
Did you check afterwards using btrfs utility the real space used after the dolphin copy ?
You said cp was 4 seconds long, how long would dolphin take exactly, 10 times slower or even more ?

Either you are hitting a real bug with our reflink support not working (which I find unlikely) or you are hitting a known performance issue we have especially visible with very large number of small files, we haven't yet full solved : https://bugs.kde.org/show_bug.cgi?id=342056

Comment 2 Bug Janitor Service 2024-03-02 03:46:52 UTC

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
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If you have already provided the requested information, please
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Comment 3 Bug Janitor Service 2024-03-17 03:46:33 UTC

This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!