Re: [PATCH 4/4] cifs: remove /proc/fs/cifs/Experimental

[Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

On Tue, 7 Dec 2010 14:31:25 -0600
Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> On Tue, Dec 7, 2010 at 1:10 PM, Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote:
> > On Tue, 7 Dec 2010 10:21:11 -0600
> > Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >
> >> The issue of how to prevent a page from being modified as it is
> >> written out (due to signing in our case) has been discussed on lkml a
> >> few times (e.g. T10 block devices).   We should hold off on changing
> >> this until we have a way of handling the case of:   we calculate the
> >> signature, but just before the page in the cache is remodified, we
> >> send it with the wrong signature ... obviously if we reissue the write
> >> we are fine (the data is fine) but there may be better ways to lock
> >> the page (and some suggestions have been made on lkml for similar
> >> sounding problems).
> >>
> >
> > This behavior has been "Experimental" for years. At what point do we
> > remove this kludge? Who in their right mind is going to turn on a
> > switch called "Experimental" to enable this? As a user, I'd certainly
> > be reticent to do so. It's not clear what turning on "Experimental"
> > would give me.
> 
> 20%+ better write performance
> 
> > If you think this behavior deserves to be switchable then let's put a
> > real usable switch on it. I don't think it ought to be hidden
> > as /proc/fs/cifs/Experimental. Perhaps a module parameter for
> > this would be more appropriate?
> 
> Probably best to work through how to fix the general issue on fsevel
> (ie how to write a presumably unstable page from the cache out)
> 
> 
> 

Obviously there needs to be some sort of endgame for this code. It's
not healthy to keep this under "Experimental" for years on end. That
said, I don't really want to tackle that project at the moment. 

I am however interested in moving this code out from under this
"Experimental" procfile. Would you be amenable to a module option for
this? If so, how would you describe this knob? What name should it have?

The main reason I mention module option is that it's now very helpful
to have this sort of knob based on a file under /proc/fs/cifs. It can't
be set at boot time without a special script.

-- 
Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>