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emacs 29.1 From: Alistair Popple To: Matthew Wilcox Cc: Sidhartha Kumar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org Subject: Re: [PATCH v2 4/6] mm/migrate_device: convert __migrate_device_pages() to folios Date: Mon, 19 Feb 2024 20:49:07 +1100 In-reply-to: Message-ID: <8734tobx66.fsf@nvdebian.thelocal> Content-Type: text/plain X-ClientProxiedBy: SYBPR01CA0198.ausprd01.prod.outlook.com (2603:10c6:10:16::18) To DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB7726:EE_|CH3PR12MB9252:EE_ X-MS-Office365-Filtering-Correlation-Id: 9b8a8a9b-53dd-4dcc-ce3a-08dc31302b82 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR12MB7726.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(396003)(346002)(136003)(366004)(39860400002)(376002)(230922051799003)(186009)(64100799003)(1800799012)(451199024)(2906002)(5660300002)(26005)(8936002)(316002)(66476007)(6916009)(4326008)(66946007)(66556008)(41300700001)(83380400001)(8676002)(86362001)(38100700002)(9686003)(53546011)(478600001)(6666004)(6486002)(6512007)(6506007);DIR:OUT;SFP:1101; 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Right, at the moment we only create order 0 device private pages. > That might well be true, but I'm *very* uncomfortable with doing a folio > conversion in core MM that won't work with large folios. We need to > consider what will happen with large device folios. Yes. Perhaps it would be better to post these fixes as part of a series introducing multi-page folio support for deivce private pages after all. I don't think we can address your other comments here without first describing how large folios for device private pages would work, and the best way to describe that is with the patches. I doubt I will get those posted this week, but will aim to do so in the next 2-3 weeks. > (for filesystems, I am less bothered. Individual filesystems control > whether they see large folios or not, and for lesser filesystems it may > never be worth converting them to support large folios)