On Mon, Aug 02, 2021 at 02:18:29PM +1000, NeilBrown wrote:

For btrfs, the "location" is root.objectid ++ file.objectid.  I think
the inode should become (file.objectid ^ swab64(root.objectid)).  This
will provide numbers that are unique until you get very large subvols,
and very many subvols.

If you snapshot a filesystem, I'd expect, at least by default, that
inodes in the snapshot to stay the same as in the snapshotted
filesystem.

--b.