On 12/23/25 20:09, Paul Eggert wrote:
On 2025-12-23 04:27, Pádraig Brady wrote:
I don't think it's appropriate for mv to do this expensive/error prone
path manipulation for each file being copied across devices.
IMHO this is more appropriate for the kernel,
which has a more holistic view of the mount space.
Plus, it's not like mv is the only app with this efficiency issue. Why
should all those apps be modified to work around the inefficiency when
the kernel can do the job right once and for all?
yes, that's definitely kernel business.
Even if it's a bind mount and therefore part of the same file system,
it could e.g. be read-only on VFS level:
$ date > /root/file
$ mount --bind -r /root /mnt
$ ls -li /root/file /mnt/file
525930 -rw-r--r-- 1 root root 29 Jan 27 22:50 /mnt/file
525930 -rw-r--r-- 1 root root 29 Jan 27 22:50 /root/file
$ mv /mnt/file /root/file2
mv: cannot remove '/mnt/file': Read-only file system
$ mv /root/file /mnt/file2
mv: inter-device move failed: '/root/file' to '/mnt/file2'; unable to remove
target: Read-only file system
$ mv /mnt/file /mnt/file2
mv: cannot move '/mnt/file' to '/mnt/file2': Read-only file system
$ mv -v /root/file /root/file2
renamed '/root/file' -> '/root/file2'
Have a nice day,
Berny
