Re: [PATCH 1/1] proc01: Whitelist /proc/fs/nfsd/nfsv4recoverydir

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2024-04-15 at 17:37 +0000, Chuck Lever III wrote:
> 
> > On Apr 15, 2024, at 1:35 PM, Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > On Mon, 2024-04-15 at 17:27 +0000, Chuck Lever III wrote:
> > > 
> > > > On Apr 15, 2024, at 1:21 PM, Petr Vorel <pvorel@suse.cz> wrote:
> > > > 
> > > > /proc/fs/nfsd/nfsv4recoverydir started from kernel 6.8 report EINVAL.
> > > > 
> > > > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > > > ---
> > > > Hi,
> > > > 
> > > > @ Jeff, Chuck, Neil, NFS devs: The patch itself whitelist reading
> > > > /proc/fs/nfsd/nfsv4recoverydir in LTP test. I suspect reading failed
> > > > with EINVAL in 6.8 was a deliberate change and expected behavior when
> > > > CONFIG_NFSD_LEGACY_CLIENT_TRACKING is not set:
> > > 
> > > I'm not sure it was deliberate. This seems like a behavior
> > > regression. Jeff?
> > > 
> > 
> > I don't think I intended to make it return -EINVAL. I guess that's what
> > happens when there is no entry for it in the write_op array.
> > 
> > With CONFIG_NFSD_LEGACY_CLIENT_TRACKING disabled, that file has no
> > meaning or value at all anymore. Maybe we should just remove the dentry
> > altogether when CONFIG_NFSD_LEGACY_CLIENT_TRACKING is disabled?
> 
> My understanding of the rules about modifying this part of
> the kernel-user interface is that the file has to stay, even
> though it's now a no-op.
> 

Does it? Where are these rules written? 

What should we have it do now when read and written? Maybe EOPNOTSUPP
would be better, if we can make it just return an error?

We could also make it just discard written data, and present a blank
string when read. What do the rules say we are required to do here?

-- 
Jeff Layton <jlayton@kernel.org>