Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: Spurious instability with NFSoRDMA under moderate load
To:     Chuck Lever III <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Olga Kornievskaia <aglo@umich.edu>,
        Dai Ngo <dai.ngo@oracle.com>
References: <4da3b074-a6be-d83f-ccd4-b151557066aa@rothenpieler.org>
 <72ECF9E1-1F6E-44AF-850C-536BED898DDD@oracle.com>
 <e12c24fd-beaf-31ce-cb49-36ad32bd22b3@rothenpieler.org>
 <daae674a-84d4-de36-336d-693dc582e3ef@rothenpieler.org>
 <9355de20-921c-69e0-e5a4-733b64e125e1@rothenpieler.org>
 <a28b403e-42cf-3189-a4db-86d20da1b7aa@rothenpieler.org>
 <4BA2A532-9063-4893-AF53-E1DAB06095CC@oracle.com>
 <c8025457-7376-e1b7-bd6c-e5c6ee5d9ce7@rothenpieler.org>
 <141fdf51-2aa1-6614-fe4e-96f168cbe6cf@rothenpieler.org>
 <99DFF0B0-FE0F-4416-B3F6-1F9535884F39@oracle.com>
 <64F9A492-44B9-4057-ABA5-C8202828A8DD@oracle.com>
 <1b8a24a9-5dba-3faf-8b0a-16e728a6051c@rothenpieler.org>
 <5DD80ADC-0A4B-4D95-8CF7-29096439DE9D@oracle.com>
 <0444ca5c-e8b6-1d80-d8a5-8469daa74970@rothenpieler.org>
 <cc2f55cd-57d4-d7c3-ed83-8b81ea60d821@rothenpieler.org>
 <3AF4F6CA-8B17-4AE9-82E2-21A2B9AA0774@oracle.com>
From:   Timo Rothenpieler <timo@rothenpieler.org>
Message-ID: <4caff277-8e53-3c75-70c1-8938b2a26933@rothenpieler.org>
Date:   Thu, 12 Aug 2021 20:13:39 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.13.0
MIME-Version: 1.0
In-Reply-To: <3AF4F6CA-8B17-4AE9-82E2-21A2B9AA0774@oracle.com>
Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms080403000608050707070209"
Precedence: bulk

This is a cryptographically signed message in MIME format.

--------------ms080403000608050707070209
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: quoted-printable

On 11.08.2021 19:30, Chuck Lever III wrote:
>=20
>=20
>> On Aug 11, 2021, at 12:20 PM, Timo Rothenpieler <timo@rothenpieler.org=
> wrote:
>>
>> resulting dmesg and trace logs of both client and server are attached.=

>>
>> Test procedure:
>>
>> - start tracing on client and server
>> - mount NFS on client
>> - immediately run 'xfs_io -fc "copy_range testfile" testfile.copy' (wh=
ich succeeds)
>> - wait 10~15 minutes for the backchannel to time out (still running 5.=
12.19 with the fix for that reverted)
>> - run xfs_io command again, getting stuck now
>> - let it sit there stuck for a minute, then cancel it
>> - run the command again
>> - while it's still stuck, finished recording the logs and traces
>=20
> The server tries to send CB_OFFLOAD when the offloaded copy
> completes, but finds the backchannel transport is not connected.
>=20
> The server can't report the problem until the client sends a
> SEQUENCE operation, but there's really no other traffic going
> on, so it just waits.
>=20
> The client eventually sends a singleton SEQUENCE to renew its
> lease. The server replies with the SEQ4_STATUS_BACKCHANNEL_FAULT
> flag set at that point. Client's recovery is to destroy that
> session and create a new one. That appears to be successful.

If it re-created the session and the backchannel, shouldn't that mean=20
that after I cancel the first stuck xfs_io command, and try it again=20
immediately (before the backchannel had a chance to timeout again) it=20
should work?
Cause that's explicitly not the case, once the backchannel initially=20
times out, all subsequent commands get stuck, even if the system is=20
seeing other work on the NFS mount being done in parallel, and no matter =

how often I re-try and how long I wait in between or with it stuck.

> But the server doesn't send another CB_OFFLOAD to let the client
> know the copy is complete, so the client hangs.
>=20
> This seems to be peculiar to COPY_OFFLOAD, but I wonder if the
> other CB operations suffer from the same "failed to retransmit
> after the CB path is restored" issue. It might not matter for
> some of them, but for others like CB_RECALL, that could be
> important.
>=20
>=20
> --
> Chuck Lever
>=20
>=20
>=20


--------------ms080403000608050707070209
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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--------------ms080403000608050707070209--