Linux 7.5 To Convey To User-Space Multi-Grain Timestamp Usage On Files

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. With Linux 7.5, via a new statx attribute there will finally be a way for user-space to know if a file's timestamps are multi-grain. Jeff Layton worked out this new STATX_ATTR_MULTIGRAIN_TIMESTAMP attribute for indicating if a file's timestamps are multigrain. The patch is part of the VFS.git tree and thus expected to be submitted for the next merge window for Linux 7.5. A small but useful addition for those making use of multigrain timestamps or developing software and wanting to be aware of its usage or not.