linux-kernel - Re: [PATCH] lockd: Fix comment about NLMv3 backwards compatibility

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Message-ID: <20240912232207.p3gzw744bwtdmghp@pali>
Date: Fri, 13 Sep 2024 01:22:07 +0200
From: Pali Rohár <pali@...nel.org>
To: NeilBrown <neilb@...e.de>
Cc: Chuck Lever <chuck.lever@...cle.com>, Jeff Layton <jlayton@...nel.org>,
	Olga Kornievskaia <okorniev@...hat.com>,
	Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockd: Fix comment about NLMv3 backwards compatibility

On Friday 13 September 2024 09:10:45 NeilBrown wrote:
> On Fri, 13 Sep 2024, Pali Rohár wrote:
> > NLMv2 is completely different protocol than NLMv1 and NLMv3, and in
> > original Sun implementation is used for RPC loopback callbacks from statd
> > to lockd services. Linux does not use nor does not implement NLMv2.
> > 
> > Hence, NLMv3 is not backward compatible with NLMv2. But NLMv3 is backward
> > compatible with NLMv1. Fix comment.
> > 
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > ---
> >  fs/lockd/clntxdr.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/lockd/clntxdr.c b/fs/lockd/clntxdr.c
> > index a3e97278b997..81ffa521f945 100644
> > --- a/fs/lockd/clntxdr.c
> > +++ b/fs/lockd/clntxdr.c
> > @@ -3,7 +3,9 @@
> >   * linux/fs/lockd/clntxdr.c
> >   *
> >   * XDR functions to encode/decode NLM version 3 RPC arguments and results.
> > - * NLM version 3 is backwards compatible with NLM versions 1 and 2.
> > + * NLM version 3 is backwards compatible with NLM version 1.
> > + * NLM version 2 is different protocol used only for RPC loopback callbacks
> > + * from statd to lockd and is not implemented on Linux.
> >   *
> >   * NLM client-side only.
> >   *
> 
> Reviewed-by: NeilBrown <neilb@...e.de>
> 
> Do you have a reference for that info about v2?  I hadn't heard of it
> before.
> 
> NeilBrown

I have just this information in my notes. I guess it should be possible
to gather more information about v2 from released Sun/Solaris source
code via OpenSolaris / Illumos projects.