On Thu, 16 Feb 2012 23:37:11 +0100 Davidlohr Bueso <dave@xxxxxxx> wrote: > On Wed, 2012-02-15 at 12:39 -0800, Andrew Morton wrote: > > On Wed, 15 Feb 2012 07:42:30 -0500 > > "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > > > > > > > Perhaps safest would be to replace /proc/locks by another interface and > > > > > deprecate this one. > > > > > > > > If exporting the name in the current /proc/locks file is out of the > > > > question, then IMHO I don't think it would be worth adding a new > > > > interface just for such a small change. > > > > > > OK. > > > > > > If you want to just change this over, I guess the thing to do would be > > > to stick something in feature-removal-schedule.txt saying "we'll switch > > > this in 2 years" (or however long you think before there are > > > realistically no more lslk users left), then do it then. > > > > > > Switching to a new api would be better as we could warn users of the old > > > api then. Maybe it'd be worth it if there was some other change we'd > > > been wanting to make? Can't think of anything off the top of my head. > > > > > > We may be adding more lock types--will lslk and lslocks handle that > > > gracefully? > > > > Adding a whole new interface is pretty attractive. It lets us get it > > right this time. In particular, something which is extensible given > > certain simple rules. As we've learned, the current /proc/locks didn't > > get that right! > > Ok, however I'm a bit confused on what you mean by extensible; since > what we decide to export to userspace is pretty much permanent, how can > we change (extend) it later? We'd pretty much be running into > the /proc/locks situation now. Mainly by avoiding the use of implicit identification via fixed positions. Look at /proc/stat and weep. If we use a name:value format then we can add new fields later and things work OK. We add stuff to /proc/meminfo and /proc/vmstat all the time. Removing things is of course much harder. The best fix is to avoid adding things which we might ever have a reason for removing! If we have a field which we simply can no longer support and which we think we must retain for back-compat reasons then we just have to find some way to emulate it. In extremis we could hardwire the value to "0" so tools won't crash. sysfs has a different convention: one-value-per-file. That means there's no need for the name part of name:value. Extensibility means "go add another sysfs file". -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
