Re: [PATCH v11 00/20] nfs/nfsd: add support for localio

Mike Snitzer
2024-07-05T14:15:47Z

On Fri, Jul 05, 2024 at 01:35:18PM +0000, Chuck Lever III wrote:
>
>
> > On Jul 5, 2024, at 1:18 AM, Christoph Hellwig <hch@infradead.org> wrote:
> >
> > On Thu, Jul 04, 2024 at 02:31:46PM -0400, Mike Snitzer wrote:
> >> Some new layout misses the entire point of having localio work for
> >> NFSv3 and NFSv4. NFSv3 is very ubiquitous.
> >
> > I'm getting tird of bringing up this "oh NFSv3" again and again without
> > any explanation of why that matters for communication insides the
> > same Linux kernel instance with a kernel that obviously requires
> > patching. Why is running an obsolete protocol inside the same OS
> > instance required. Maybe it is, but if so it needs a very good
> > explanation.
>
> I agree: I think the requirement for NFSv3 in this situation
> needs a clear justification. Both peers are recent vintage
> Linux kernels; both peers can use NFSv4.x, there's no
> explicit need for backwards compatibility in the use cases
> that have been provided so far.
>
> Generally I do agree with Neil's "why not NFSv3, we still
> support it" argument. But with NFSv4, you get better locking
> semantics, delegation, pNFS (possibly), and proper protocol
> extensibility. There are really strong reasons to restrict
> this facility to NFSv4.

NFSv3 is needed because NFSv3 is used to initiate IO to NFSv3 knfsd on
the same host.