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dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) by IA4PR12MB243497.namprd12.prod.outlook.com (2603:10b6:207:12b::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.546.22; Tue, 27 Oct 2026 21:07:02 +0000 Received: from IA0PR12MB8374.namprd12.prod.outlook.com ([fe80::d85f:4c87:ae84:3f16]) by IA0PR12MB8374.namprd12.prod.outlook.com ([fe80::d85f:4c87:ae84:3f16%6]) with mapi id 15.21.0546.021; Tue, 27 Oct 2026 21:07:02 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 27 Oct 2026 17:07:00 -0400 Message-Id: Subject: Re: [PATCH v2 09/14] mm/shmem: rescan after nonuniform folio splitting Cc: , , , "Kiryl Shutsemau (Meta)" To: "David Hildenbrand (Arm)" , "Andrew Morton" , "Gregory Price" , "Joshua Hahn" , "Rakie Kim" , "Ying Huang" , "Johannes Weiner" , "Vladimir Davydov" , "Michal Hocko" , "Hugh Dickins" , "Baolin Wang" , "Lukas Czerner" , "Carlos Maiolino" , "Christian Brauner" , "Jan Kara" , "Daniel Verkamp" , "Jeff Xu" , "Muchun Song" , "Oscar Salvador" , "David Stevens" , "Matthew Wilcox (Oracle)" , "William Kucharski" , "Chris Li" , "Kairui Song" , "Nhat Pham" , "Miaohe Lin" , "Naoya Horiguchi" From: "Zi Yan" X-Mailer: aerc 0.22.0 References: <20261027-fixes_shmem-v2-0-86a00952acb9@kernel.org> <20261027-fixes_shmem-v2-9-86a00952acb9@kernel.org> In-Reply-To: <20261027-fixes_shmem-v2-9-86a00952acb9@kernel.org> X-ClientProxiedBy: YQZPR01CA0044.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:86::23) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|IA4PR12MB243497:EE_ X-MS-Office365-Filtering-Correlation-Id: 0ca80da6-9edb-4719-5e61-08df346e3f64 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|376014|7416014|366016|921020|261026121527099003|4143699003|56012099006|11063799006|261021123027099003|261022105027099003|261021121427099003|18002099003|22082099003|6133799003|10067099003|261026140227099003; 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A nonuniform split can > leave that folio large, so the scan skips the newly created folios. > Hole punching then leaves pages within the hole allocated even though > they could be discarded. > > For example, a fault below the hole can allocate a 2 MiB folio after > boundary handling. Punching a 1 MiB hole at offset 64 KiB splits the > folio successfully but leaves the original folio at order 4. The scan > continues past all 512 pages, leaving 2 MiB allocated instead of 1 MiB. > The hole reads as zero, but the pages and their block charges remain. > > Fixes: 7460b470a131 ("mm/truncate: use folio_split() in truncate operatio= n") > Cc: stable@vger.kernel.org > Reviewed-by: Baolin Wang > Acked-by: Kiryl Shutsemau (Meta) > Tested-by: Gregory Price (Meta) > Signed-off-by: David Hildenbrand (Arm) > --- > mm/shmem.c | 16 +++++----------- > 1 file changed, 5 insertions(+), 11 deletions(-) > Reviewed-by: Zi Yan --=20 Best Regards, Yan, Zi