Re: [PATCH] NFSD: add version field to nfsd_rpc_status_show handler

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-08-08 at 10:03 -0400, Chuck Lever wrote:
> On Tue, Aug 08, 2023 at 09:48:42AM -0400, Jeff Layton wrote:
> > On Tue, 2023-08-08 at 09:24 -0400, Chuck Lever wrote:
> > > On Tue, Aug 08, 2023 at 09:33:23PM +1000, NeilBrown wrote:
> > > > On Tue, 08 Aug 2023, Lorenzo Bianconi wrote:
> > > > > Introduce version field to nfsd_rpc_status handler in order to help
> > > > > the user to maintain backward compatibility.
> > > > 
> > > > I wonder if this really helps.  What do I do if I see a version that I
> > > > don't understand?  Ignore the whole file?  That doesn't make for a good
> > > > user experience.
> > > 
> > > There is no UX consideration here. A user browsing the file directly
> > > will not care about the version.
> > > 
> > > This file is intended to be parsable by scripts and they have to
> > > keep up with the occasional changes in format. Scripts can handle an
> > > unrecogized version however they like.
> > > 
> > > This is what we typically get with a made-up format that isn't .ini
> > > or JSON or XML. The file format isn't self-documenting. The final
> > > field on each row is a variable number of tokens, so it will be
> > > nearly impossible to simply add another field without breaking
> > > something.
> > > 
> > 
> > It shouldn't be a variable number of tokens per line.
> 
> That's how NFSv4 COMPOUND operations are displayed. For example:
> 
> 0x5d58666f 0x000000d1 0x000186a3 NFSv4 COMPOUND 0000062034739371 192.168.103.67 0 192.168.103.56 20049 OP_SEQUENCE OP_PUTFH OP_READ
> 
> The list of operations in the displayed compound are currently
> blank-separated tokens at the end of each row.
> 

Oh! That's a bug in missed in my latest review then. The operations
field was delimited by ':' chars at one point. Lorenzo, did you mean to
change that?

IMO, the list of operations should be one field, separated by a distinct
delimiter (like ':').

> 
> > If there is, then that's a bug, IMO. We do want it to be simple to
> > just add a new field, published version info notwithstanding.
> 
> They could be wrapped in curly braces, or separated by commas, to
> make them all one token.
> 
> I haven't looked at NFSv3 output yet, but I expect those extra
> tokens won't even be there in that case.
> 

That's probably another bug. Anything not a v4 COMPOUND should have
something as a placeholder. It could just be a single '-' character.

> JSON, yaml, or xml would all address the extensibility problem, just
> as an alternative thought.
> 

It would probably be fairly simple to output well-formed yaml instead.
JSON and XML are a bit more of a pain.

For now, we can change the output. We do need to have this settled
before this goes to Linus' tree though.
-- 
Jeff Layton <jlayton@kernel.org>