Re: [PATCH v9 10/12] NFSD: Handle kiocb->ki_flags correctly

[Mike Snitzer <snitzer@kernel.org>]

On Mon, Nov 03, 2025 at 11:53:49AM -0500, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> Christoph says:
> > > +	if (file->f_op->fop_flags & FOP_DONTCACHE)
> > > +		kiocb->ki_flags |= IOCB_DONTCACHE;
> > IOCB_DONTCACHE isn't defined for IOCB_DIRECT.  So this should
> > move into a branch just for buffered I/O.
> 
> and
> 
> > > Promoting all NFSD_IO_DIRECT writes to FILE_SYNC was my idea,
> > > based on the assumption that IOCB_DIRECT writes to local file
> > > systems left nothing to be done by a later commit. My assumption
> > > is based on the behavior of O_DIRECT on NFS files.
> > >
> > > If that assumption is not true, then I agree there is no
> > > technical reason to promote NFSD_IO_DIRECT writes to FILE_SYNC,
> > > and I can remove that built-in assumption for v8 of this series.
> >
> > It is not true, or rather only true for a tiny subset of use cases
> > (which NFS can't even query a head of time).
> 
> So, observe the existing setting of ki_flags rather than forcing
> persistence unconditionally, and ensure that DONTCACHE is not set
> for IOCB_DIRECT writes.
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Reviewed-by: Mike Snitzer <snitzer@kernel.org>