Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Simon Kirby <sim@hostway.ca>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: Cache flush on file lock
Thread-Topic: Cache flush on file lock
Thread-Index: AQHYF9ij5r5wZxOe10G+VO/hoTSM1KyArgyAgAHmvgA=
Date:   Fri, 4 Feb 2022 00:57:54 +0000
Message-ID: <6E2B4CA1-69D9-4B34-A413-5DD86CFDBA49@oracle.com>
References: <20220202014111.GA7467@hostway.ca>
 <4691F0AB-FCDB-49EF-B62B-51F135F692A5@oracle.com>
In-Reply-To: <4691F0AB-FCDB-49EF-B62B-51F135F692A5@oracle.com>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?SfEqtLuG0jstPW6k2I5nWc7sTlzf1Di4t07AGzP3efoXvfi6LXCeKYtmEm9N?=
 =?us-ascii?Q?XzT96WzGxfZLpYl7mG5bMLwABpXy7N15D9Yn5RvUf7V0gKmXPgw33C5Q+JYi?=
 =?us-ascii?Q?+VYPXHn+/0NnsY6Kq3uUfTc3D6G2bu8FgjwKLMy0hJOKsMlNNvplfeEQCtJ0?=
 =?us-ascii?Q?g53OLt8OkGBC5ibRIom5XXQEXWH5DP/073gHO81QvuKVEbcNdMz0pb8Hxuyr?=
 =?us-ascii?Q?XZMv0OhdZ1Eff8ma/9uDrU7cYcv6S7bvlWdMmtqjvbM2Asqb4TW8eLblBYME?=
 =?us-ascii?Q?ycqmjvZk7ovc6dR6pbRzS5Jt0fUON0WU0JwG3EAcY+Bc1XaI5aY/RLd4oERk?=
 =?us-ascii?Q?VFDwOw230pFDjYUB2gggGuKFF3Q03pIoauNQBr5EA1Ek7s5KIAoJGVB/3g3S?=
 =?us-ascii?Q?edGQpOqczMziqH0WNnPIPbRgqVgYblXhyf1JxS5kNdCQ9QIwcLhIPDF20cTO?=
 =?us-ascii?Q?5EXTCvP8K4qkI9mxsgZTgOO9oV0gtlf6iOdlu3g6yPFqbtINsAd2KasJHFw6?=
 =?us-ascii?Q?w4uvqhoARoysWyz8QcOJxn5mCxxbm768H3ettDGKLLpQq8e9Ov0CMJ7QKv6X?=
 =?us-ascii?Q?09b91kmyK5tq/doDew0WkcxIrar3sUq0x56/cK8vIzNAg5W74mVWGYyFfUfc?=
 =?us-ascii?Q?IaIEYDVjA2LYdVkxUMrxi6upoIfEJU17Q6zNSfLBGy9GWqoZ1ZxqjEnpg+C5?=
 =?us-ascii?Q?UkhHMJstkRCwZoAIiTGFl1FwU+6rYclQ2LMXPHbBVeLCcTFWzdyzbZvfznbx?=
 =?us-ascii?Q?fuGlLFypCH3pbSkNYlDG5i89maGGi0hD3uyEnrRPqO2tChq0rp4wijpWA8Ru?=
 =?us-ascii?Q?0vVMbDThZiljg9JCq78To9H//VnkttCA8ZQBIGSdN6WuLh57clquibaSAg0O?=
 =?us-ascii?Q?baGif0hMuS6V8ShJRbraOWK1WHsm7AbNiLOPqgAvV1INh9MuMXmWGVuj/hHh?=
 =?us-ascii?Q?OLKhofJ1OM7Q8TW0Q3pYq5tAMZMv5jXpD9gDrkp479tQVBdH2s7K529KB8Ye?=
 =?us-ascii?Q?aZEhAL6IDfKCNB7VFXgRnfUPJkow0qiOIe+ZvM5qMjtkGCRR90zfu6NXB1h0?=
 =?us-ascii?Q?wn9cuFvLjr7l2LdcdawYKqzo/kJZB0IaEADB451+woboD1JdRA2MXqrvb691?=
 =?us-ascii?Q?X99qg0oKoqNcUqWA0Fmf0DE7BSdzrVSoYjA6Haa4p8NNyH0TIvI6bZMDL279?=
 =?us-ascii?Q?qpbt+ww/B4xxypHPKZ2++1jZ9PvREcpgcKsYzUNHNJc2VxWS/2XKUVerD1St?=
 =?us-ascii?Q?I9Cx9Ticf8yDk4iyPwuDI3V/PU1abcxX/CIuIwgumhPwaq+s2CzN9uFgaU9O?=
 =?us-ascii?Q?hbze//Mwi08u8OJpvahVcBnPBOaFM7tZjLUV+7+mxSTy+oE0GfIojITPGnUd?=
 =?us-ascii?Q?qMYYJeqRo7eyKCS0Q+Qgh37HOPJgJ0v79DSa8QrJLMA6cjPK5E1SGoZAYmzW?=
 =?us-ascii?Q?4+jSwvM1z5HseDyc2OsBS/bxGtJ9szfjNY1k8jbxK8kNK2NHVjnWc5F0VOsn?=
 =?us-ascii?Q?AzhCkm65xRoYlxy4T1DyhukFPBYn22iHHvKc5uJ+npHIo7JSvgbz116DsAhq?=
 =?us-ascii?Q?J6MeASKPE1wrH9BogZgnsfpjUyQMsPDIQr6/esWq8UHOeA3WSmhXBwgiaX9e?=
 =?us-ascii?Q?YS2op+fXSd61cjfHRPtVe7E=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-ID: <4778866EAD71C84AB44F7DCA7FB0E244@namprd10.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: CH0PR10MB4858.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 0c6db23a-a979-4748-a7ee-08d9e77960ae
X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Feb 2022 00:57:54.7972
 (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: ScQ7p1i+R91Pqc95+iKZVNMr+81ltpbfHtXFoAzd4maaws+1i2L0sB1XDveNb1cxlsvGYuaII9q/vUSNVGQXjA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR10MB5658
X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10247 signatures=673430
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999
 adultscore=0 malwarescore=0 bulkscore=0 suspectscore=0 mlxscore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2201110000 definitions=main-2202040001
X-Proofpoint-GUID: bASAtSCP4AGN-YxiJf6sy7tjFGbMvfWU
X-Proofpoint-ORIG-GUID: bASAtSCP4AGN-YxiJf6sy7tjFGbMvfWU
Precedence: bulk
List-ID: <linux-nfs.vger.kernel.org>
X-Mailing-List: linux-nfs@vger.kernel.org


> On Feb 2, 2022, at 2:55 PM, Chuck Lever III <chuck.lever@oracle.com> wrot=
e:
>=20
>=20
>=20
>> On Feb 1, 2022, at 8:41 PM, Simon Kirby <sim@hostway.ca> wrote:
>>=20
>> How far off would we be from write delegations happening here?
>=20
> We are tracking a "feature request" for write delegation support
> in the Linux NFS server:
>=20
> https://bugzilla.linux-nfs.org/show_bug.cgi?id=3D348
>=20
> At this point the effort is not resourced. It's not clear how
> much benefit it would be.
>=20
> That said, it seems to me that your use case might benefit if
> the Linux NFS server offered a READ delegation for the SQLite
> database file even when it is open R/W. It might be appropriate
> if the server offered such a delegation when there are no other
> clients that have the file open for write or that hold write
> delegations.
>=20
> Patches and performance data are, as always, welcome.

You didn't mention which version of the server you are using.

In fact, commit aba2072f4523 ("nfsd: grant read delegations to
clients holding writes") ought to make the server offer a READ
delegation in this situation. It appears in v5.13, if I'm
reading my "git describe" output correctly.


--
Chuck Lever