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Howlett" , "Ryan Roberts" , "Dev Jain" , "Barry Song" , "Lance Yang" , "Usama Arif" , "Vlastimil Babka" , "Mike Rapoport" , "Suren Baghdasaryan" , "Michal Hocko" , "Shuah Khan" , "Nico Pache" , , , To: "Kairui Song" From: "Zi Yan" X-Mailer: aerc 0.21.0 References: <20260805-b4-mappingless-swapcache-v1-0-b1d78ba257ca@zohomail.in> <590B3189-5B66-4ECB-84CD-7B7EF18C0E54@nvidia.com> In-Reply-To: X-ClientProxiedBy: MN0P222CA0025.NAMP222.PROD.OUTLOOK.COM (2603:10b6:208:531::33) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) 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: IA0PR12MB8374:EE_|DM4PR12MB7600:EE_ X-MS-Office365-Filtering-Correlation-Id: c022cc04-c775-4a05-a04c-08def48eb35e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|7416014|376014|23010399003|11063799006|4133799003|4143699003|10067099003|56012099006|6133799003|18002099003|22082099003; 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Folios read from = swap >> > but not yet associated with an anon_vma can have the same mappingless >> > swapcache state. folio_check_splittable() currently mistakes both case= s for >> > truncation and rejects the split with -EBUSY. >> > >> > Implement the longstanding TODO for this state. Allow mappingless >> > swapcache folios to use the existing uniform order-0 swapcache split p= ath, >> > while continuing to reject truly truncated folios and unsupported >> > higher-order or non-uniform swapcache splits. >>=20 >> Thank you for your patches. >>=20 >> As Kairui (cc=E2=80=99d) mentioned in [1] (see =E2=80=9CA bit more detai= ls on this=E2=80=9D), >> we might not need to implement this split. I will let Kairui to decide >> how we should deal with this patchset. >>=20 >> [1] https://lore.kernel.org/all/CAMgjq7CHDG8JhesSPMkn1kzG8jKb0BXO756BvxM= QC_MCn2eTyA@mail.gmail.com/ > > Thanks for the CC, this is actually not hard to implement as shown by > Shivam, I just found the code more and more hard to follow and fragile > as we add more logic to it. And we don't have to reject higher order > split either which can be seen easily if the code is cleaner. > > Personally I think doing some cleanup first is better, I haven't post any > code as right now there doesn't seem to be much user of this. It will be > needed if more clean THP swapcache begin to show up due to things like > THP readahead for swap, which isn't here yet. I think I can send an RFC > tomorrow just for reference. I'm fine if we prefer to remove that TODO > using this smaller change first :) Thanks. Can you also help review this patchset? The changes looks good to me but I am not sure if I get all the details about swapcache handling. --=20 Best Regards, Yan, Zi