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

[Mike Snitzer <snitzer@kernel.org>]

On Wed, Jul 03, 2024 at 07:16:31AM -0700, Christoph Hellwig wrote:
> On Wed, Jul 03, 2024 at 04:52:34AM -0400, Mike Snitzer wrote:
> > Ultimately I simply wanted to keep momentum up, I'm sure you can
> > relate to having a vision for phasing changes in without missing a
> > cycle.  But happy to just continue working it into the 6.12
> > development window.
> 
> It just feels really rushed to have something with cross-subsystem
> communication going in past -rc6 in a US holiday week.  Sometimes
> not rushing things too much will lead to much better results.

Yes, I knew it to be very tight given the holiday.  I should've just
yielded to the reality of the calendar and there being some extra
changes needed (remove "fake" svc_rqst in fs/nfsd/localio.c -- I was
hopeful that could be done incrementally after merge but I digress).

Will welcome any help you might offer to optimize localio as much as
possible (doesn't need to be in near-term, whenever you might have
time to look).  Its current approach to use synchronous buffered
read_iter and write_iter, with active waiting, should be improved.

But Dave's idea to go full RMW to be page aligned will complicate a
forecasted NFS roadmap item to allow for: "do-not-cache capabilities,
so that the NFS server can turn off the buffer caching of files on
clients (force O_DIRECT-like writing/reading)".  But even that seems a
catch-22 given the NFS client doesn't enforce DIO alignment.