Need copy_file_range() which uses FSCTL_DUPLICATE_EXTENTS_TO_FILE

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
c
Domain
operating-systems

Research direction

Start by tracing the MSYS2 runtime implementation or entry point for copy_file_range() and how it maps file-copy operations on Windows. Investigate FSCTL_DUPLICATE_EXTENTS_TO_FILE and verify that coreutils cp and mv can use the new behavior on ReFS without breaking ordinary filesystems; done means large-file copies on ReFS use block cloning and retain a fallback.

Written by the indexing model from the issue text.

Description

MSYS2 file copy is EXTREMELY slow for big files on REFS on Windows 11.

Since Win10 is soon End-of-support MSYS2 more and more people use REFS, and there MSYS2 is slow.
It turns out that cmd.exe and powershell.exe cheat a bit when copying files on REFS: They do not copy data, they clone blocks via FSCTL_DUPLICATE_EXTENTS_TO_FILE.

coreutils cp and mv could do the same IF MSYS2 would implement copy_file_range() backed by FSCTL_DUPLICATE_EXTENTS_TO_FILE.

Dominant language
C
Stars
240
Forks
60
Avg merge
2d 3h
Merged PRs (30d)
1

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