On Wed, Aug 24, 2022 at 08:24:47AM +1000, NeilBrown wrote: > On Tue, 23 Aug 2022, Jeff Layton wrote: > > On Tue, 2022-08-23 at 21:38 +1000, NeilBrown wrote: > > > On Tue, 23 Aug 2022, Jeff Layton wrote: > > > > So, we can refer to that and simply say: > > > > > > > > "If the function updates the mtime or ctime on the inode, then the > > > > i_version should be incremented. If only the atime is being updated, > > > > then the i_version should not be incremented. The exception to this rule > > > > is explicit atime updates via utimes() or similar mechanism, which > > > > should result in the i_version being incremented." > > > > > > Is that exception needed? utimes() updates ctime. > > > > > > https://man7.org/linux/man-pages/man2/utimes.2.html > > > > > > doesn't say that, but > > > > > > https://pubs.opengroup.org/onlinepubs/007904875/functions/utimes.html > > > > > > does, as does the code. > > > > > > > Oh, good point! I think we can leave that out. Even better! > > Further, implicit mtime updates (file_update_time()) also update ctime. > So all you need is > If the function updates the ctime, then i_version should be > incremented. > > and I have to ask - why not just use the ctime? Why have another number > that is parallel? > > Timestamps are updated at HZ (ktime_get_course) which is at most every > millisecond. Kernel time, and therefore timestamps, can go backwards. -Dave. -- Dave Chinner david@xxxxxxxxxxxxx
