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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 CH3PR12MB7737.namprd12.prod.outlook.com (2603:10b6:610:14d::15) 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 02:12:49 +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 02:12:49 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 26 Oct 2026 22:12:46 -0400 Message-Id: Subject: Re: [PATCH 10/16] mm/shmem: discard whole new large folios on fallocate rollback Cc: , , 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: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-10-703206d5fa0c@kernel.org> In-Reply-To: <20261026-fixes_shmem-v1-10-703206d5fa0c@kernel.org> X-ClientProxiedBy: CH0PR03CA0028.namprd03.prod.outlook.com (2603:10b6:610:b0::33) 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_|CH3PR12MB7737:EE_ X-MS-Office365-Filtering-Correlation-Id: c72f6fd3-e6bd-4fe7-2921-08df33cfcc50 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|23010399003|7416014|1800799024|22082099003|18002099003|261026121527099003|921020|56012099006|4143699003|11063799006|261021123027099003|261021121427099003|10067099003|261022105027099003|261009223027099003|261026140227099003; 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Its second scan instead passes large > folios to truncate_inode_partial_folio(), which does not necessarily > discard the entire large folio, but instead tries splitting it to > discard only the requested range. > > For example, with huge=3Dalways, a failed allocation starting at offset > 4 KiB can leave page 0 allocated in an otherwise empty file. > > Discard the whole folio when unfalloc is set. Note that we enter this > path only for folios that are not uptodate, and can consequently be > dropped without losing any data. > > Fixes: 55ac8bbe358b ("mm/shmem: fix race in shmem_undo_range w/THP") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) > --- > mm/shmem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Reviewed-by: Zi Yan Rebase it on top of mm-stable: diff --git a/mm/shmem.c b/mm/shmem.c index e9f98d526fc52..7cf5a4d9d1ace 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1472,7 +1472,7 @@ static void shmem_undo_range(struct inode *inode, lof= f_t lstart, uoff_t lend, if (!unfalloc && folio_test_large(folio)) folio_mark_dirty(folio); =20 - if (!folio_test_large(folio)) { + if (unfalloc || !folio_test_large(folio)) { truncate_inode_folio(mapping, folio); } else if (truncate_inode_partial_folio(folio, lstart, lend, NULL, NULL)) { --=20 Best Regards, Yan, Zi