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