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Wysocki" , Danilo Krummrich , Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev, linux-kselftest@vger.kernel.org, Laurent Pinchart , Bartosz Golaszewski , Wolfram Sang , Simona Vetter , Dan Williams Subject: Re: [PATCH v6 1/3] revocable: Add fops replacement Message-ID: <20251106154715.GB1732817@nvidia.com> References: <20251106152712.11850-1-tzungbi@kernel.org> <20251106152712.11850-2-tzungbi@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251106152712.11850-2-tzungbi@kernel.org> X-ClientProxiedBy: MN2PR01CA0063.prod.exchangelabs.com (2603:10b6:208:23f::32) To MN2PR12MB3613.namprd12.prod.outlook.com (2603:10b6:208:c1::17) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN2PR12MB3613:EE_|IA1PR12MB7541:EE_ X-MS-Office365-Filtering-Correlation-Id: 74689851-bf93-4f3d-4eb4-08de1d4bc360 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?KTNPkiLxFVHvRlgeWtJqFkqPGf4uPG6KjKnBvJ6svRJAdWdPP/aKsI5vhehE?= =?us-ascii?Q?TVMYepYGFT9Elv1U54SKdmpfvd5pm2xtv4B9DgUNmImum7qVzobK2z+r6iFX?= =?us-ascii?Q?idQjUY3E0/1zbeFQu9ewQ+F4FvvbpTm4C5QIHg0s2IYsvekTXzzrbQ4DK1jc?= =?us-ascii?Q?w3QqxNkVt2j0QfPEpjIsRCBgJ7C+oUYagQkJ0VkeYgxJsHrl3BRIswOyej83?= =?us-ascii?Q?CmI3jbBqMquBPELWDIU3kFVYsULg95VgIqwoqIZPXhLMEWuDSop4w1nXTpyb?= =?us-ascii?Q?IkZWg+8UM6My+eZNNf8rYVb5W7oQAlc+6jyproeV+qxHbkHUV0sRKBhocJNh?= =?us-ascii?Q?9p54doDprc2t710SANufDhBy/nFEZyFQyQhcvS5AAOJHM2J1j9G8LH0D64Z+?= =?us-ascii?Q?kzO+fNo0Eg0EJEj+On6KelUaIrAoMVDmH73sA1Z4W4FUHDxVscoY/5xZLBDY?= =?us-ascii?Q?5y1EBHG0typvatHqP3OP9qt1eG6uOe0xVeNxHXsRkBWMRkmpa7wto9v/2tnZ?= =?us-ascii?Q?RGQqwO3tlRjjwVGYmROCcfK7PKHAbmBIGLwCByYS8o9yjlv27Bv77JGcFoqT?= =?us-ascii?Q?9uu7pET5bNFG4DADMLpJ/NIzvTN49hLtrbZ3yoyHw3OAu9BT9PMZFWdr1he0?= =?us-ascii?Q?xR0SqsJrTGd5Ub6gpY/WvnqaMZdrlniOUsI4KX/FLM1shSTWDte3qj2isI5t?= =?us-ascii?Q?/sIDXMqzTMtpZHBl6naTm0x49NT3pK9UT7Df7F8d+bWF2lGzEG0OgYrp7xhp?= =?us-ascii?Q?FVK9x7hUgMynDDdjisZU9s3eLkOFfFd3b+QZj6ViEYnElq73YAsgNSVqT47Y?= =?us-ascii?Q?MArC2I6NzAEejVuzLwqCwVnMG+Ho6U1Qlvn4SYZhS3NPaTe9C7Fr8nSxBpdA?= =?us-ascii?Q?Qiik7jZ6l6nOHWnSLUcUT4tfFsV5MInQB0SowDy7GXdCBU5CyiOLk4cqHhFH?= =?us-ascii?Q?VXZeBwy1K25IPhSWNY9Bxe/cSqW9bVc9Y2LDTfUX5Dq6njftCIW+4fagVoNR?= =?us-ascii?Q?mPu3UW7hCZQe+NoFy5cANUpIHpNlciWKBw995s1x2sMmDQ/AkQk0F+srb+P6?= =?us-ascii?Q?HQ+Kq3RfBaaFuEspA5ehK0btnzuj6LutKKwB3bDLLQBrcMX6TOfuhMUGikjg?= =?us-ascii?Q?KZ3Io2QiGIhbmUVKINr2TQ292QOoYRxBmBff3ZuIhs9dfPGOYUV+W9UE7jB5?= =?us-ascii?Q?Uo/VvxYvLXtqRSPucR6XfwyRYgYWQiRbb2E+i3Z/0I6Z/Cz/ufXu1oZ/WRDF?= =?us-ascii?Q?2QxGRzDFHaMtIiyz3acK9uxKnPO9yETD96dJE5/5EUpfUHQJ250a69J6TPr6?= =?us-ascii?Q?OEJ9/DMLVlyeNc0Vv6Ws6LOpOVMBnu4j498fxvMhfyReFjo5/rbgXuDpGY/C?= =?us-ascii?Q?7eC+qeqi+voxsDpsgX3pWtEcXMhga3KOgKECyYfyZs18WzFoZm68PIcEYSAo?= =?us-ascii?Q?dcqgu1RNtXjUrayUflGcmp3V20F0gpIRpf43+TOHFOWLAK4fM0/ATMCuEvPR?= =?us-ascii?Q?3iUkDvl5VlK8yfxqWnI9bqpI7a9RmyKsVodl7YBP3asvhvt7QP7XvYjZeKY7?= =?us-ascii?Q?ahhb+/LnfqfR3gbJJz4=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 74689851-bf93-4f3d-4eb4-08de1d4bc360 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB3613.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Nov 2025 15:47:17.2333 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 8IzCT6DEif4V95K1NxZKqcGHwOpA3fzC7S5WgQLvTxxcM/p14ZNxupltu807xnSB X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7541 On Thu, Nov 06, 2025 at 11:27:10PM +0800, Tzung-Bi Shih wrote: > +/* > + * Recover the private_data to its original one. > + */ > +static struct fops_replacement *_recover_private_data(struct file *filp) > +{ > + struct fops_replacement *fr = filp->private_data; > + > + filp->private_data = fr->orig_private_data; > + return fr; > +} > + > +/* > + * Replace the private_data to fops_replacement. > + */ > +static void _replace_private_data(struct fops_replacement *fr) > +{ > + fr->filp->private_data = fr; > +} This switching of private_data isn't reasonable, it breaks too much stuff. I think I showed a better idea in my sketch. I still think this is a bad use case of revocable, we don't need to obfuscate very simple locks in *core* kernel code like this. I'd rather see you propose this series without using it. > +static int fs_revocable_release(struct inode *inode, struct file *filp) > +{ > + struct fops_replacement *fr = _recover_private_data(filp); > + int ret = 0; > + void *any; > + > + filp->f_op = fr->orig_fops; > + > + if (!fr->orig_fops->release) > + goto leave; > + > + REVOCABLE_TRY_ACCESS_SCOPED(fr->rev, any) { > + if (!any) { > + ret = -ENODEV; > + goto leave; > + } > + > + ret = fr->orig_fops->release(inode, filp); > + } This probably doesn't work out, is likely to make a memory leak. It will be hard for the owning driver to free its per-file memory without access to release. Jason