Re: nfsd: add the ability to enable use of RWF_DONTCACHE for all nfsd IO

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2025-02-21 at 10:39 -0500, Chuck Lever wrote:
> On 2/21/25 10:02 AM, Mike Snitzer wrote:
> > On Thu, Feb 20, 2025 at 01:17:42PM -0500, Chuck Lever wrote:
> > > * It might be argued that putting these experimental tunables under /sys
> > >   eliminates the support longevity question, since there aren't strict
> > >   rules about removing files under /sys.
> > 
> > Right, I do think a sysfs knob (that defaults to disabled, requires
> > user opt-in) is a pretty useful and benign means to expose
> > experimental functionality.
> 
> Seems like we want to figure out a blessed way to add this kind of
> experimental "hidden" tunable in a way that can be easily removed
> once we have the answers we need.
> 
> I'd really like to keep the documented administrative interface as
> straightforward as possible, but I agree that having a way to
> experiment is valuable.
> 

We do have this fancy new netlink interface that is extensible.

You could extend the "threads" call to add a server-wide boolean for
this and then extend nfsdctl to set that value in some cases.
-- 
Jeff Layton <jlayton@kernel.org>