Re: [PATCH v1 00/42] Update NFSD XDR functions

Trond Myklebust
2021-01-08T22:55:46Z

On Fri, 2021-01-08 at 13:08 -0500, bfields@fieldses.org wrote:
> On Fri, Jan 08, 2021 at 04:35:50PM +0000, Trond Myklebust wrote:
> > Just ignore generic/465. As far as NFS is concerned, the test has
> > utterly borked assumptions about O_DIRECT ordering.
>
> Thanks, adding to my list of tests to skip.  Should we report it as
> an
> xfstests bug?
>
> (Is the test just wrong, or is this some non-standard but documented
> NFS
> behavior, or something else?)
>
> --b.

I'm not sure who decided the ordering requirements for O_DIRECT, but in
order to fix the generic/465 case, I'd either have to order all reads
with all outstanding writes or implement some kind of range locking to
do it in a more fine-grained way.

We do order buffered I/O and O_DIRECT, so that backup programs can do
their thing on databases that use O_DIRECT. However we do assume that
anyone using O_DIRECT for I/O is doing their own synchronisation.

--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com