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Date:   Thu, 25 Apr 2019 21:18:04 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Andreas Dilger <adilger@dilger.ca>
Cc:     Jeff Layton <jlayton@redhat.com>,
        "J. Bruce Fields" <bfields@redhat.com>,
        linux-nfs <linux-nfs@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, abe@purdue.edu,
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Subject: Re: [PATCH 08/10] nfsd4: add file to display list of client's opens
Message-ID: <20190426011804.GA12457@fieldses.org>
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On Thu, Apr 25, 2019 at 11:14:23PM +0200, Andreas Dilger wrote:
> On Apr 25, 2019, at 10:14 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > 
> > On Thu, Apr 25, 2019 at 02:04:59PM -0400, Jeff Layton wrote:
> >> More bikeshedding: should we have a "states" file instead of an "opens"
> >> file and print a different set of output for each stateid type?
> > 
> > Sure.  The format of the file could be something like
> > 
> > 	<stateid> open rw -- <openowner>...
> > 	<stateid> lock r 0-EOF <lockowner>...
> > 	<stateid> deleg r
> > 
> > I wonder if we could put owners on separate lines and do some
> > heirarchical thing to show owner-stateid relationships?  Hm.  That's
> > kind of appealing but more work.
> 
> My suggestion here would be to use YAML-formatted output rather than
> space/tab separated positional fields.  That can still be made human
> readable, but also machine parseable and extensible if formatted properly.

Well, anything we do will be machine-parseable.  But I can believe YAML
would make future extension easier.  It doesn't look like it would be
more complicated to generate.  It uses C-style escaping (like \x32) so
there'd be no change to how we format binary blobs.

The field names make it a tad more verbose but I guess it's not too bad.

> Something like the following (use https://yaml-online-parser.appspot.com/
> to validate the formatting):
> 
> - <stateid>: { state: open, mode: rw, owner: <openowner> }
> - <stateid>: { state: lock, mode: r, start: 0, end: EOF, owner: <openowner> }

I haven't noticed other kernel interfaces using YAML.  But I guess I'm
not coming up with any real objection.

--b.