Re: [nfsv4] Spencer Dawkins' Yes on draft-ietf-nfsv4-versioning-09: (with COMMENT)

[Spencer Dawkins at IETF <[e-mail]>]

Dear -versioning- folk,

On Fri, May 12, 2017 at 11:17 AM, Trond Myklebust <[e-mail]> wrote:

> On Fri, 2017-05-12 at 07:36 -0700, Spencer Dawkins wrote:
> >
> > I did have one question that came up during AD Evaluation that I
> > wanted
> > to mention.
> >
> > The first two drafts that used this mechanism (umask and xattrs) used
> > two
> > different idioms for discovering support. The xaddrs draft defines an
> > xaddr_support attribute, while umask does not.
> >
> > In conversations with the working group, the reasoning was that
> > xattrs
> > defines a number of operations, so discovering that the complete
> > mechanism is supported before you start trying to use the attributes
> > makes sense, while umask defines only one attribute, and for any
> > attribute, you can find out if it is supported within a given file
> > system
> > by interrogating the appropriate bit position in the REQUIRED
> > attribute
> > supported_attrs, so there is no advantage to adding a umask_support
> > attribute.
> >
> > That all made perfect sense to me, but the explanation was helpful
> > enough
> > to me that I wonder if it's worth a sentence or two, pointing out
> > that
> > some protocol designers may choose one idiom, while other protocol
> > designers choose the other, and saying that's not a problem.
> >
>
> It's an extra mechanism that could be a convenience, but is not
> something that a client can or should rely on. The only reliable
> mechanism for verifying that the feature is available is to try it, and
> handle the resulting NFS4ERR_NOTSUPP and/or NFS4ERR_OP_ILLEGAL error.
>
> This is how the Linux client handles all the other NFSv4.x optional
> features as well.


This draft was approved on today's telechat, but the secretariat is holding
off sending the approval announcement until I let them know that all the
comments have been addressed.

It looked like David had a plan for this specific comment on idioms for
detecting support, and Trond had a response, so if others have thoughts
that would affect the text that appears in the RFC, it would be great to
hear that, Real Soon Now.

Thanks!

Spencer (D)