Re: [RFC PATCH] NFSD: Add a "file_sync" export option

[Mike Snitzer <snitzer@kernel.org>]

On Thu, Oct 30, 2025 at 03:13:05PM -0400, Chuck Lever wrote:
> On 10/30/25 12:32 PM, Mike Snitzer wrote:
> > On Thu, Oct 30, 2025 at 11:47:15AM -0400, Chuck Lever wrote:
> 
> >> But, in the bigger picture, I think comparison between this approach
> >> and NFSD_IO_DIRECT might be illustrative.
> > 
> > Sure, I'm very interested in the data myself.  A patch to easily
> > enable control is all I'm after. So given what you said above, I'll
> > actually just run with introducing 2 new variants of NFSD_IO_DIRECT
> > for now, so like I mentioned in my previous reply to hch:
> > 
> > NFSD_IO_DIRECT_DATA_SYNC
> > NFSD_IO_DIRECT_FILE_SYNC
> > 
> > Because it sounds like it is only in the context of NFSD_IO_DIRECT
> > where there is any doubt about whether using NFS_FILE_SYNC helpful.
> 
> I'm not sure where you're getting that. FILE_SYNC is interesting for all
> the IO modes, and I'd really like to see specifically the comparison of
> NFSD_IO_BUFFERED with "file_sync" and NFSD_IO_DIRECT with and without
> "file_sync".

I wasn't talking about file_sync being useful or not in general.  I
meant based on what you said with file_sync uniformly hurting
performance (even with tmpfs) that it wouldn't be a question for IO
modes other than NFSD_IO_DIRECT.

Anyway, I can change to implementing the control in terms of an export
option.

Mike