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Date:   Tue, 8 Aug 2023 10:03:44 -0400
From:   Chuck Lever <chuck.lever@oracle.com>
To:     Jeff Layton <jlayton@kernel.org>
Cc:     NeilBrown <neilb@suse.de>, Lorenzo Bianconi <lorenzo@kernel.org>,
        linux-nfs@vger.kernel.org, lorenzo.bianconi@redhat.com
Subject: Re: [PATCH] NFSD: add version field to nfsd_rpc_status_show handler
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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.


> 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.

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


-- 
Chuck Lever