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Thu, 30 Jul 2020 20:53:36 +0000 From: Song Liu To: Andrii Nakryiko CC: Andrii Nakryiko , bpf , Netdev , Alexei Starovoitov , Daniel Borkmann , Kernel Team , =?iso-8859-1?Q?Toke_H=F8iland-J=F8rgensen?= Subject: Re: [PATCH bpf-next 1/5] bpf: add support for forced LINK_DETACH command Thread-Topic: [PATCH bpf-next 1/5] bpf: add support for forced LINK_DETACH command Thread-Index: AQHWZfzM10o3KVlXF0C1TJ9tT1+b76kgZdmAgAAWiYCAAB6ggA== Date: Thu, 30 Jul 2020 20:53:36 +0000 Message-ID: References: <20200729230520.693207-1-andriin@fb.com> <20200729230520.693207-2-andriin@fb.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.80.23.2.2) authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=fb.com; x-originating-ip: [2620:10d:c090:400::5:395d] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: c1c38a8b-b7c0-4437-5e46-08d834caa177 x-ms-traffictypediagnostic: BYAPR15MB3367: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:7691; 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charset="iso-8859-1" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB2999.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: c1c38a8b-b7c0-4437-5e46-08d834caa177 X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Jul 2020 20:53:36.8598 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: vZWOUxbxwxwkAmgTOv97UIn11aojVddheBcYEr3sPvOp/Kb8OR00UQ67Ew2NIpeXdaS2MYUEDBIbmHbtK7yU6A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3367 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-30_15:2020-07-30,2020-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 suspectscore=0 adultscore=0 priorityscore=1501 phishscore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007300147 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org > On Jul 30, 2020, at 12:03 PM, Andrii Nakryiko = wrote: >=20 > On Thu, Jul 30, 2020 at 10:43 AM Song Liu wrote: >>=20 >>=20 >>=20 >>> On Jul 29, 2020, at 4:05 PM, Andrii Nakryiko wrote: >>>=20 >>> Add LINK_DETACH command to force-detach bpf_link without destroying it.= It has >>> the same behavior as auto-detaching of bpf_link due to cgroup dying for >>> bpf_cgroup_link or net_device being destroyed for bpf_xdp_link. In such= case, >>> bpf_link is still a valid kernel object, but is defuncts and doesn't ho= ld BPF >>> program attached to corresponding BPF hook. This functionality allows u= sers >>> with enough access rights to manually force-detach attached bpf_link wi= thout >>> killing respective owner process. >>>=20 >>> This patch implements LINK_DETACH for cgroup, xdp, and netns links, mos= tly >>> re-using existing link release handling code. >>>=20 >>> Signed-off-by: Andrii Nakryiko >>=20 >> The code looks good to me. My only question is, do we need both >> bpf_link_ops->detach and bpf_link_ops->release? >=20 > I think so. release() is mandatory for final clean up, after the last > FD was closed, so every type of bpf_link has to implement this. > detach() is optional, though, and potentially can do different things > than release(). It just so happens right now that three bpf_linkl > types can re-use release as-is (with minimal change to netns release > specifically for detach use case). So I think having two is better and > more flexible. I see. Thanks for the explanation.=20 Acked-by: Song Liu