Multi-Grain Timestamps Revived For Linux File-Systems

Last year a new kernel feature merged in Linux 6.6 was multi-grain(ed) timestamps for file-systems as a means of better timestamp handling originally for NFS compared to the existing coarse-grained timestamps with the once per jiffy timestamps being used for invalidating NFS caches. But multi-grain timestamps was reverted just weeks after landing in the mainline kernel due to corner cases like a newer file with a coarse-grained timestamp appearing earlier than another file with a fine-grained timestamp. Due to subtle bugs like that, multi-grain timestamps were dropped before Linux 6.6 was even released while now there is a revised attempt...