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Subject: Re: [PATCH v1 00/42] Update NFSD XDR functions
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <6c36769a8e9e47cdd26e3f818917401ba69ff390.camel@hammerspace.com>
Date:   Sat, 9 Jan 2021 11:43:05 -0500
Cc:     Bruce Fields <bfields@fieldses.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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To:     Trond Myklebust <trondmy@hammerspace.com>
Precedence: bulk


> On Jan 8, 2021, at 5:54 PM, Trond Myklebust <trondmy@hammerspace.com> =
wrote:
>=20
> 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.
>>=20
>> Thanks, adding to my list of tests to skip.  Should we report it as
>> an
>> xfstests bug?
>>=20
>> (Is the test just wrong, or is this some non-standard but documented
>> NFS
>> behavior, or something else?)
>>=20
>> --b.
>=20
> 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.
>=20
> 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.

Perhaps the best approach would be to add generic/465 to the exempt-list
for NFS.


--
Chuck Lever