On Fri, Sep 13, 2024 at 01:28:20AM +0200, Pali Rohár wrote: > On Friday 13 September 2024 01:22:07 Pali Rohár wrote: > > 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@xxxxxxxxxx> > > > > --- > > > > 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@xxxxxxx> > > > > > > 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. > > Just very quickly I found this Illumos XDR file for NLM: > https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/rpcsvc/nlm_prot.x > > And it defines NLMv2 with two procedures numbered 17 and 18, plus there > is a comment in file header about v2. > > So probably the best reference would be the Illumos source code. What you see in the Illumos code is not something that is part of the standard NLM protocol, but rather a private upcall protocol between the kernel and user space that is special sauce added by each implementation of NLM/NSM. Also note the way NLMv3 is defined in this file: it defines only a handful of new operations. The other operations are inherited from NLMv1. IMO the comment is accurate and does not warrant a change. -- Chuck Lever
