Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::3:3 as permitted sender) client-ip=2620:137:e000::3:3;
From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Neil Brown <neilb@suse.de>
CC:     Jeff Layton <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Olga Kornievskaia <kolga@netapp.com>,
        Dai Ngo <dai.ngo@oracle.com>, Tom Talpey <tom@talpey.com>
Subject: Re: [PATCH 0/5] sunrpc: not refcounting svc_serv
Thread-Topic: [PATCH 0/5] sunrpc: not refcounting svc_serv
Thread-Index: AQHaCs5Bx30Sst3AQkeWzWCFyIpqgLBkCzaAgABUNQCAAACLgA==
Date:   Tue, 31 Oct 2023 20:42:50 +0000
Message-ID: <C869423C-B578-4D5D-B171-444EDF2D0D02@oracle.com>
References: <20231030011247.9794-1-neilb@suse.de>
 <9BA28F70-A3FC-4EC4-A638-A27C1867F221@oracle.com>
 <169878484259.24305.17786556797570881562@noble.neil.brown.name>
In-Reply-To: <169878484259.24305.17786556797570881562@noble.neil.brown.name>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?k+k47Ou4JyIIbGCS4fVMdcuWmSqUIQUn1b71eheO7ceNzSIFKG/QPn3NrPny?=
 =?us-ascii?Q?xxfkQPiv672B04T78sSftySNcRCT7ANZStmHiZooN2EM25GoDOpz7n9j8YiF?=
 =?us-ascii?Q?K890plBK1MCAkqOGnAm69jUW50TVSZLp49ItqOwF3pwEQLnExmcqE1sPVIQd?=
 =?us-ascii?Q?zgcFtTk994yu28a21NR2h1inHTXyADUOs5HOCEe6USi7tK3yPjEETRkqmizA?=
 =?us-ascii?Q?lIqlpu2L1vFNGHlf5WgEgLZsrqFGYcbFLaOkbR42xeCjnyzs0hYBDIk+WbZ3?=
 =?us-ascii?Q?IUIFgmx+FHUJ9MVk7Dqwx1TVWDYoJ/2lTLkGg8jFzSfsLMEvH8ECGLozLnQr?=
 =?us-ascii?Q?NwgrR6ai7DYTMScQbLbLE0jbBWEcS91tIC5OIIwRTt8hAl1fE8X9HSH4+iBv?=
 =?us-ascii?Q?+flmZwNweNPEVxKhiCgG1uJnC1ioXSr9MWJN43NLwF4LQ0IurA5ZUQVzYb8x?=
 =?us-ascii?Q?HH0FE3P7dyr0giXshFYZUjwYXjIgwV8DVlONFbcsSPkSlPHtrGSvxTfIW9/l?=
 =?us-ascii?Q?AEQHff9ZIsMhrSALlSGBVO4RO+RmCIsIzbyHuz3xfA0/Xn+8g9mIt2t34Luj?=
 =?us-ascii?Q?jt7+i3/FMZYvsTS5qU+02NsZSFQFnlg7a8EzBmT0AR6nd59PHyOZKwH8XSAF?=
 =?us-ascii?Q?nkHLDRqw91gruoLxPLT0VMt3AarOMzcMXgYLJ4teP/0j5NhsmtNK92UwVO13?=
 =?us-ascii?Q?ZexyPVBjja2Sc3MA1wdKY8EaOeg16GZUdxigyXtQnjhuC4/xvjg6wDX94v0l?=
 =?us-ascii?Q?X+1BookT83Iu2SWN5/lgws+4EBkWsoZXRasNm2xuP+Py7/rbIH39madYcto7?=
 =?us-ascii?Q?zQ6fKU8s8M+h4HieQCLJTmYrirjnQOJuKkgq+dJ3N4XaCZzjErh/fTSCEv5E?=
 =?us-ascii?Q?dlMynrgQ9I0HoJe2eDx341MxKsNT3qih9qvz90jqXh3PK3CQ7zYP9dm/0asD?=
 =?us-ascii?Q?4J++3YYW5jfguKBJBEf8RJhLdKtnW9YxMEzEDbcFitxuCnbAuLWHeByzzHKt?=
 =?us-ascii?Q?hTOOixOdIdzKb7y8+ngn8/uP73qYX0+k4sJkzQSPRF7eTy4hc0rriKdaSfkq?=
 =?us-ascii?Q?hh38v8ymf+FAFamf1KY8d2ZaleyGd5mumcpQX59j8klioEnyhU9IoGI6YZ/r?=
 =?us-ascii?Q?H0oCLmc7uD/xRA+iNSGGjN4jQkpUvGVdUleGGVn1un4CspdyU7o22S3QFsHe?=
 =?us-ascii?Q?WXMlGc75DVXz45svCxa5TrWhZxo/yTAcfp+rspfckd+VQpIC8MSAYLRKBK+a?=
 =?us-ascii?Q?HPJ/hJJKMJ0n8RlVIGbGhxAC52edSuS4zCiVvOBfAvax6sNu7MMUHqiFj26L?=
 =?us-ascii?Q?m/19y4QTb3W1xS54TCUAgymiMwsA8ASvPGlmB/haGpFEFzATXNQ36D1dQQm1?=
 =?us-ascii?Q?gT8NjQo268ht7AvrBmwAZg/WoVPrt9d4R4tzpmo8Ah5L5UNyw4yrBnRRTeDw?=
 =?us-ascii?Q?cM92MTGJIyzN9ZDXZBlNRpPAocF8rH7T4EeuPUdrykDaHrwn99NFffBjKlfM?=
 =?us-ascii?Q?YhUt/uTql1lONvBkhJyrYZEYbAA0lg/bW0UyHDCFl8JBncqdSpLHrfz1WMIy?=
 =?us-ascii?Q?kIiw58aF6ZObyt0GFYKWfTI4xMJcmvE230+rrvvtYSC8a4qfD6658SiO1Q8s?=
 =?us-ascii?Q?8Q=3D=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1E7D2DA798E27C4D9D331C6A2EE27C8E@namprd10.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: BN0PR10MB5128.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6e2836e9-488f-4dbf-ee16-08dbda51f31a
X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Oct 2023 20:42:50.8824
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: MRNj0AxAu4cByBrJYj4JivR0ROguJpXVqWOXLZSObJW9SIo7J+fCuQLESqj+7hRs3k9hAZIydv7ZolyWnRF9fQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH0PR10MB5340
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2023-10-31_07,2023-10-31_03,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=0
 malwarescore=0 mlxscore=0 mlxlogscore=850 adultscore=0 phishscore=0
 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2310240000 definitions=main-2310310169
X-Proofpoint-GUID: MV7BwAXa9lEf1cO_DKehOXEslDabhQY3
X-Proofpoint-ORIG-GUID: MV7BwAXa9lEf1cO_DKehOXEslDabhQY3
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email
Precedence: bulk
List-ID: <linux-nfs.vger.kernel.org>
X-Mailing-List: linux-nfs@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Tue, 31 Oct 2023 13:43:21 -0700 (PDT)


> On Oct 31, 2023, at 1:40 PM, NeilBrown <neilb@suse.de> wrote:
>=20
> On Wed, 01 Nov 2023, Chuck Lever III wrote:
>>=20
>>> On Oct 29, 2023, at 6:08 PM, NeilBrown <neilb@suse.de> wrote:
>>>=20
>>> This patch set continues earlier work of improving how threads and
>>> services are managed.  Specifically it drop the refcount.
>>>=20
>>> The refcount is always changed under the mutex, and almost always is
>>> exactly equal to the number of threads.  Those few cases where it is
>>> more than the number of threads can usefully be handled other ways as
>>> see in the patches.
>>>=20
>>> The first patches fixes a potential use-after-free when adding a socket
>>> fails.  This might be the UAF that Jeff mentioned recently.
>>>=20
>>> The second patch which removes the use of a refcount in pool_stats
>>> handling is more complex than I would have liked, but I think it is
>>> worth if for the result seen in 4/5 of substantial simplification.
>>=20
>> So I need a v2 of this series, then...
>>=20
>> - Move 4/5 to the beginning of the series (patch 1 or 2, doesn't matter)
>=20
> I don't understand....  2 and 3 are necessary prerequisites for 4.  The
> remove places where the refcount is used.

Hrm. that's what I was afraid of.

Isn't there a fix in 4/5 that we want applied to stable kernels,
or did I misunderstand the email exchange between you and Jeff?


--
Chuck Lever