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

[Mike Snitzer <snitzer@kernel.org>]

On Wed, Jul 03, 2024 at 03:24:18PM +0000, Chuck Lever III wrote:
> 
> 
> > On Jul 3, 2024, at 11:18 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > The actual way
> > to find the file struct still would be nasty, but I'll try to think of
> > something good for that.
> 
> It is that very code that I've asked to be replaced before this
> series can be merged. We have a set of patches for improving
> that aspect that Neil is working on now.
> 
> When Mike presented LOCALIO to me at LSF, my initial suggestion
> was to use pNFS. I think Jeff had the same reaction.

No, Jeff suggested using a O_TMPFILE based thing for localio
handshake.  But he had the benefit of knowing NFSv3 important for the
intended localio usecase, so I'm not aware of him having pNFS design
ideas.

> IMO the design document should, as part of the problem statement,
> explain why a pNFS-only solution is not workable.

Sure, I can add that.

I explained the NFSv3 requirement when we discussed at LSF.

> I'm also concerned about applications in one container being
> able to reach around existing mount namespace silos into the
> NFS server container's file systems. Obviously the NFS protocol
> has its own authorization that would grant permission for that
> access, but via the network.

Jeff also had concerns there (as did I) but we arrived at NFS having
the ability to do it over network, so doing it with localio ultimately
"OK".  That said, localio isn't taking special action to escape mount
namespaces (that I'm aware of) and in practice there are no
requirements to do so.