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Shutemov" , Mel Gorman , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Richard Chang , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/4] mm/page_isolation: make page isolation a standalone bit. 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?J3t9hHgYPTv/jm3lt1ITjGzgfZhbdaSXeCofd+hY3Rr+Psmj3jdDTuGoCQAN?= =?us-ascii?Q?S0XqLqtaUdzO/RoOnja7VV642Q2n2fK0dG1i4M/SMKD4uiawtbxT9riASiGO?= =?us-ascii?Q?mTM5i2fM24VEjjY5NFsdksXu7pqFZ+6uh05aRrBaBqOZkWsWjVtfY9jm98u6?= =?us-ascii?Q?XoOlBnzTg1ILdCOFHwVpNGIBPCHrje3Lxn1iYCQjXATuaUgjr+pmGYKAi2F0?= =?us-ascii?Q?TdSUVKBqurn3S0flJKbOzF7keClmGpLzokPgP2X1597dJTyRxD6pkzc9bFrL?= =?us-ascii?Q?5qU92zLVPS5Bs50/33ehdCPilVcoHkaj/F+ZPO9BPQgZZvhj8h5wgeg6//HQ?= =?us-ascii?Q?k9GFLPuLf9zphsXrg5aW2naS6j2cxsUgueu5klqDlkJg5BInLifHx4T1gFF7?= =?us-ascii?Q?kYhH3uoWAodaNWt6kZG4ghpn2sTedn+kCy7n6SZPU3CA37KcQJ+gGYDfX8kn?= =?us-ascii?Q?HOjAMJ14oaxBwmOJEN4JqpZCZAS53shO6pIoCcVEU4cr4BQExoPWmI8bO6gr?= =?us-ascii?Q?KZ54JrAuGHHE5bnyVW7McPPkEmZK3CfMIqbs1H9MUvKgr3efsb6ghPsankGU?= =?us-ascii?Q?W83qX3TGjUPKZCxXdPosOSE2G4U6HuGVzzNSzr0aKtHmDspT+m6eDp4dubIe?= =?us-ascii?Q?NYlaDUDiT932thWMMs1y5hE/uDIgghpdgTgs/nfjudgweXADASLT86bObH97?= =?us-ascii?Q?qsVy8/47L+WoVA6h6rVUKoBPVBTdyAm+8WW7MO4G9B48B3Xddv5weEnzbxGq?= =?us-ascii?Q?0ORs1XW5KMyWlleHB/5Y0YHhVDS+G9GurQQ3hjbYUPwDSWRcCgebH/okbiKz?= =?us-ascii?Q?SE1tSfJa884P8LS56rUjdULjdBOwfYLD8zfgfogKBgE3Jx/DIFUXjjEPnd3U?= =?us-ascii?Q?TwswCm+3x+a0nlJWghpB09KaiF346FbW/GIkL/sOu3d1rAvXPIfLKHoF9goS?= =?us-ascii?Q?HPW3YGknAyF0h34IORF11tOD9SrK4Ty3tg1e1dFoaApHbvoJRY9iZYmSwgGQ?= =?us-ascii?Q?3AO3NVa2QJd03hlRYgx4dy79jaGx4k8PrkxmTa8aItzpOGA+g8mLK0NaTFmY?= =?us-ascii?Q?8LABpZ2E3LBXWkJCVyn4z5CVFV/ARvdV1y+Aq4LPAfXKuwVg6gHypKAKwU4C?= =?us-ascii?Q?9Pt8G3zzPd5iuUOoTW08Vo89e7fshhDV4jAxyuL8LEwSudOnruUtD4EsyFqP?= =?us-ascii?Q?b5PacVrehM0a7ktGwR5eFqcE7mGtMPYxhoxrObLA4opfA6cxl5epz5O7UxOp?= =?us-ascii?Q?CjqckyTVOeCLpstn9CmRGJlw3/YlQyqkeVtBJfb+t9bkKVMxz54nikSr6zZS?= =?us-ascii?Q?7lsGycYql2RCMX8epW78bJt1jbk8i+wxaZUAF98ZGvUbxlw7zvCgttrwnHpb?= =?us-ascii?Q?cMZGY2vd5ymnodSm7MM4gsf9iotXQ/gmUlu+VQPdwAS7nLZuBb3YyxKJ5v23?= =?us-ascii?Q?caKB3yKvrRX0dX45DCLNX05ZCx/q1EHTJIexCM7ks+M78ntGQhJAPhSlx7Dn?= =?us-ascii?Q?63LC37W6oEqErFy5FeyISC+G1JKobiSCSp9j8UBoqpZx68aDK/fNnOucLhqO?= =?us-ascii?Q?so1Y7NWsP1f5fpL8/QzIOuRXKMK6foCpyjrWxFVq?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: f9482061-3e46-4ff0-da85-08dd8e7268d2 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 May 2025 20:53:39.3562 (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: engidktQ+iH0xPuGSuBKO1m/ledvR3nARZazTjPeqhT3cUwXdSWPhyorWddcT0V9 X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6412 On 8 May 2025, at 16:46, Johannes Weiner wrote: > On Thu, May 08, 2025 at 03:17:05PM -0400, Zi Yan wrote: >> >>>>> @@ -426,7 +460,12 @@ void set_pageblock_migratetype(struct page *pa= ge, int migratetype) >>>>> migratetype < MIGRATE_PCPTYPES)) >>>>> migratetype =3D MIGRATE_UNMOVABLE; >>>>> >>>>> - set_pfnblock_flags_mask(page, (unsigned long)migratetype, >>>>> +#ifdef CONFIG_MEMORY_ISOLATION >>>>> + if (migratetype =3D=3D MIGRATE_ISOLATE) >>>>> + set_pageblock_isolate(page); >>>> >>>> Are there paths actually doing this after the second patch? >>>> >>>> There are many instances that want to *read* the migratetype or >>>> MIGRATE_ISOLATE, but only isolation code should be manipulating that= >>>> bit through the dedicated set/toggle_pageblock_isolate API. >>>> >>>> If there isn't one, it might be good to enforce this with a VM_WARN >>>> instead. >>> >>> I checked all set_pageblock_migratetype() callers and do not see >>> one using it for pageblock isolation. Let me replace the code >>> with a VM_WARN and add a comment to tell users to use dedicated >>> pageblock isolation APIs. >>> >> >> Actually, move_freepages_block_isolate() calls __move_freepages_block(= ) >> to move free pages to MIGRATE_ISOLATE pageblock and >> set_pageblock_migratetype() is used inside __move_freepages_block(). >> So the branch has to stay. Will use the suggestion below. > > Ah, good catch. But looking at the callers, it's: > > move_freepages_block() > move_freepages_block_isolate() > try_to_claim_block() > > The last one would benefit from having the set_pageblock_migratetype() > there explicitly, as this is what this function is supposed to do. It > also should never set the isolation bit. > > move_freepages_block_isolate() has two set_pageblock_migratetype() > calls already. And after the series, it should only manipulate the > isolate bit, not change the actual migratetype anymore, right? > > Maybe it makes the most sense to move it into the three callers? > > And then fortify set_pageblock_migratetype() after all. Sounds good to me. Let me update my fixups. Hi Andrew, I will resend new fixups based on Johannes' comment. -- Best Regards, Yan, Zi