Merged for Linux 6.13 back in 2024 was multigrain timestamp support for being able to switch between coarse and fine-grained change/modification time reporting on a per-file basis. This is useful if caring about accuracy more than the once-per-jiffy timestamps on files and was originally devised as a way of addressing NFS caching issues. A limitation of multigrain timestamps though has been the lack of user-space to know whether a file's timestamps are multi-grain or not...