Re: [PATCH] locks: export device name

Andrew Morton
2012-02-15T20:39:32Z

On Wed, 15 Feb 2012 07:42:30 -0500
"J. Bruce Fields" <bfields@fieldses.org> 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!

We can eventually remove the old code - it may take longer than two
years, but whatever. If we go this way, we should arrange for the
kernel to emit a warning (printk_once) into the logs the first time
someone accesses the old file. This will help to prompt people to
migrate off the deprecated interface. After a while, we can add a
config option to make the old interface go away. Distros will start to
disable the feature. Later, we zap it altogether.