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On Wed, Jul 05, 2006 at 05:12:54PM -0400, Bill Davidsen wrote: > J. Bruce Fields wrote:> >Or we could add an entirely separate attribute that's guaranteed to > >increase whenever the ctime is updated, and that doesn't necessarily > >have any connection with time--call it a version number or something. > >> There are versions in both VMS and the ISO filesystem. I have a sneaking > suspicion that those of us who ever use them are few and far between. > The other issue is that unless the field is time, programs like make > can't really use it, at least without becoming Linux specific. Sure. > I'm not sure exactly how a "version" value would be used other than > detecting the fact that the file had been changed in some way. I agree. But "detecting the fact that the file has been changed" is a really important use! I think the challenge would be to come up with applications that really depend on timestamps and that use them for anything *other* than detecting when a file has changed. (OK, so make is a special case--it cares not only about whether a file has changed, but also about whether it has changed more recently than some other file. But I'd think a simple version would useful to any network filesystem, or more generally to anything that caches a view of the filesystem either on another machine or in userspace.) > Feel free to show me, I seem to come up empty on using this value. Betraying my own interests--the NFSv4 protocol (unlike v2 or v3) uses a specialized "change" attribute to maintain cache consistency instead of depending on mtime/ctime. So nfsd would be one immediate in-kernel user. Currently we're using ctime, which causes obvious problems. But an improved ctime--one that actually increased whenever the file changed--would also do the job. --b. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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