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Peter Anvin" , Arnd Bergmann , Greg Kroah-Hartman , Dan Williams , Vishal Verma , Dave Jiang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Christian Koenig , Huang Rui , Matthew Auld , Matthew Brost , Alexander Viro , Christian Brauner , Jan Kara , Benjamin LaHaise , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Theodore Ts'o , Andreas Dilger , Muchun Song , Oscar Salvador , David Hildenbrand , Konstantin Komarov , Mike Marshall , Martin Brandenburg , Tony Luck , Reinette Chatre , Dave Martin , James Morse , Babu Moger , Carlos Maiolino , Damien Le Moal , Naohiro Aota , Johannes Thumshirn , Matthew Wilcox , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , Zi Yan , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Jann Horn , Pedro Falcato , David Howells , Paul Moore , James Morris , "Serge E . Hallyn" , Yury Norov , Rasmus Villemoes , linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, ntfs3@lists.linux.dev, devel@lists.orangefs.org, linux-xfs@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only Message-ID: <20260120152245.GC1134360@nvidia.com> References: <20260119231403.GS1134360@nvidia.com> <36abc616-471b-4c7b-82f5-db87f324d708@lucifer.local> <20260120133619.GZ1134360@nvidia.com> <488a0fd8-5d64-4907-873b-60cefee96979@lucifer.local> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <488a0fd8-5d64-4907-873b-60cefee96979@lucifer.local> X-ClientProxiedBy: BLAPR03CA0088.namprd03.prod.outlook.com (2603:10b6:208:329::33) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|PH8PR12MB6721:EE_ X-MS-Office365-Filtering-Correlation-Id: 0f23315a-38ff-446d-dcf2-08de5837c3c9 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?/kJlt45gk9FgL+tTa7H+v4SFi+ZNQ9RsaoVOCXb/xzD3J64tWrLguNA96P6G?= =?us-ascii?Q?7SST+nPcDjISbyhaWneiUsBduaQhlMxHIRTYpCbkR5ghoXHbmRxp0h6Y0rI8?= =?us-ascii?Q?5I1vPqVYKd9wyrlZvuBYCEHNhzb8v02soHih+e1jcOYjHaM8tmxBOxxdGYhD?= =?us-ascii?Q?ZOvK6ARaLitcB4xpNvAjr5WcziN3Yr5+LnScixjM7B8SG6vvlppcWDjnjCbd?= =?us-ascii?Q?dUFEizcOiryu8cA0F7idsAn1PHnIIOnG0f09A6dWPRzW4bI8FLBmcfjwGNGK?= =?us-ascii?Q?XUfqdoiwjYbYi7nv4/ewu5UoaVa+xrXof2sLeBHA6i1Q4cMcGcn5Ns1MVEaY?= =?us-ascii?Q?4LHrXFFwn4EzKMdl11tiuzU7ktcWjcpYVN6aGiu83kuICgyBCWqLm2UnD/Ap?= =?us-ascii?Q?6opnmBFoui1CWXhSu14dgJHnnc6tYBgtKn2g71qXeMTGH96nqb8NkyBTkHYE?= =?us-ascii?Q?N7iuF0p3z7zMq7DAiKKcoduoxlaIu2q2gmPqXDH5rgb5Gwy/xX4pkEHiFwov?= =?us-ascii?Q?Ms7jzTk1126qiDQH85lAo1hw7WXFfXgWnGiMNz4OhxT3f47Hjrqu+WkfWWvH?= =?us-ascii?Q?1zdj4r8o+5da5bqEmu/ewgOARhZNK5vMQPKXU9UBWpD7I2wkhUo0UcmlJajN?= =?us-ascii?Q?69fzw/1I8B62NTd052ztVbYcJGHxljEp95ctXYYKZAseaqIGERg3gFk7xcLk?= =?us-ascii?Q?GrMs8EL1aHmD6z4FTIqWFRsG2dhH/cJzSqk80BTXXcYLSW3WRtZmA5kLg8Ax?= =?us-ascii?Q?oltduum7kR6adFTgODVGaw1VtaVUIaV7dTfwu5A3wRIR7ueMTZaKTwUTrOo5?= =?us-ascii?Q?Kl8rixBk2M4PHmnHqWq4uDvsYc7xmy6lE2ZuNPiroHCGDnTfIxXE5eZHM7r4?= =?us-ascii?Q?HpXYmhi80yWHHzWad8ys+ZW5UJ51atEMNawupsF8sC+7pYkI/Pa+vLwx+HcU?= =?us-ascii?Q?FC8qKyyQ64BUxTQBraipnmobWvBdkRmJoPVdH3j0rLsPhaQ2Jb8+y0rGrnu0?= =?us-ascii?Q?EzqOu2cYeTwB2EPwaYgPVnB8eQmDZbrT6uQuQpiizfYA3Do2zC0OOnH3MAgT?= =?us-ascii?Q?vVkuIljFgae+LyGOTwJms0I/DFolgvgDKnUTJMq5GQn1msGNxq/0QT8MI5+s?= =?us-ascii?Q?l+iI9fQt/UfCLcMXmbhMzHq9xUOFG5+p4xKU7fJ1hijPnvjebxCZk6z3SjV3?= =?us-ascii?Q?gqmxfyCNLRswvbcFcnZdcLYfKeL3ZFYyHwZMno9SMSx6FJFekEg2n2pYrmSJ?= =?us-ascii?Q?zgSjrVqnWokOEsj2ZaNfvG9DmXLgQkcb5lr4lw6JzJ4blJg4d+crgXKFj8Dy?= =?us-ascii?Q?WHL1CvzXAOfcXDnziLm3lSiacKn8NBz05dU2yrrymizA1ZGf5KAGE8n6YGSf?= =?us-ascii?Q?o1cx0OAhg1FACHHxiiPEA4Qg6i4p2+FQce47GILPV4Bjs53EZjUUO/cSI5hH?= =?us-ascii?Q?xwQjiswzcAIpAbzs1JENx6Z66ms8wBiQkdk7sK7Z8sEi6k+4L/ogSYjdQWbz?= =?us-ascii?Q?dDFz23ztYtWSvkerx3VZQLAhCTWihWjegdDVYo6cXSZHnbZNkqQBZ14TIkaH?= =?us-ascii?Q?5CI53+w1ySmBL+MLVcOhhjff1gjyRGvkG2MxDfcq468g+7EJLfBBkJZEY3i2?= =?us-ascii?Q?+I41IT+fn0OC9DAkgwtEmEA2gijr0p4+HUXrI49dpu46sp/u5EaCJCUfiwTA?= =?us-ascii?Q?zBeVsIZh82CQ2QIBEdmjeEw41r1+NTsR0fDU/d9ClT3gSK1tKKDGwVswl9Ls?= =?us-ascii?Q?rrTkETDyhg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0f23315a-38ff-446d-dcf2-08de5837c3c9 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Jan 2026 15:22:46.6186 (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: uM8t+KncR+kVgpD+4wjpPyVDfJmX+0Zujuw179fTvzYmv7LFNzC7aE8/u6m8O1mz X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB6721 On Tue, Jan 20, 2026 at 03:10:54PM +0000, Lorenzo Stoakes wrote: > The natural implication of what you're saying is that we can no longer use this > from _anywhere_ because - hey - passing this by value is bad so now _everything_ > has to be re-written as: No, I'm not saying that, I'm saying this specific case where you are making an accessor to reach an unknown value located on the heap should be using a pointer as both a matter of style and to simplify life for the compiler. > vma_flags_t flags_to_set = mk_vma_flags(); > > if (vma_flags_test(&flags, &flags_to_set)) { ... } This is quite a different situation, it is a known const at compile time value located on the stack. > If it was just changing this one function I'd still object as it makes it differ > from _every other test predicate_ using vma_flags_t but maybe to humour you I'd > change it, but surely by this argument you're essentially objecting to the whole > series? I only think that if you are taking a heap input that is not of known value you should continue to pass by pointer as is generally expected in the C style we use. And it isn't saying anything about the overall technique in the series, just a minor note about style. > I am not sure about this 'idiomatic kernel style' thing either, it feels rather > conjured. Yes you wouldn't ordinarily pass something larger than a register size > by-value, but here the intent is for it to be inlined anyway right? Well, exactly, we don't normally pass things larger than an interger by value, that isn't the style, so I don't think it is such a great thing to introduce here kind of unnecessarily. The troubles I recently had were linked to odd things like gcov and very old still supported versions of gcc. Also I saw a power compiler make a very strange choice to not inline something that evaluated to a constant. Jason