From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Rick Macklem <rmacklem@uoguelph.ca>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: knfsd server returns writeverf of all 0 bits (but was not
 rebooted)
Thread-Topic: knfsd server returns writeverf of all 0 bits (but was not
 rebooted)
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Date:   Mon, 13 Dec 2021 19:42:12 +0000
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Hi Rick-

> On Dec 9, 2021, at 6:15 PM, Rick Macklem <rmacklem@uoguelph.ca> wrote:
>=20
> Hi,
>=20
> When testing against the knfsd in a Linux 5.15.1 kernel, I received a
> write reply with FILE_SYNC and a writeverf of all 0 bytes.
> (Previous write verifiers were not all 0 bytes.)
>=20
> The server seemed to be functioning normally and had not rebooted.
>=20
> Is this intended behaviour?
>=20
> Normally I would not expect the writeverf in a Write operation reply
> to change unless the server had rebooted, but I can see there might
> be circumstances where the knfsd server wants all non-FILE_SYNC
> writes to be redone by the client and would choose to change the
> writeverf.
> However, changing it to all 0 bytes seems particularly odd?

I don't immediately see a code path for WRITE or COMMIT that would
set the verifier to zeroes. When Linux NFSD resets its write verifier,
it sets it to the current time.

Do you have a reproducer you can share?


--
Chuck Lever