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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 0/2] Do not change split folio target order Date: Fri, 10 Oct 2025 13:39:04 -0400 Message-ID: <20251010173906.3128789-1-ziy@nvidia.com> X-Mailer: git-send-email 2.51.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: BN0PR10CA0003.namprd10.prod.outlook.com (2603:10b6:408:143::35) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) 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: DS7PR12MB9473:EE_|IA1PR12MB8222:EE_ X-MS-Office365-Filtering-Correlation-Id: 4cdf6e03-222d-4b02-a878-08de0823f55f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024; 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When callers expect after-split folios to be order-0, the actual ones are not. The callers might not be able to handle them, since they call huge page and large folio split APIs to get order-0 folios. This issue appears in a recent report on memory_failure()[1], where memory_failure() used split_huge_page() to split a large forlio to order-0, but after a successful split got non order-0 folios. Because memory_failure() can only handle order-0 folios, this caused a WARNING. Fix the issue by not changing split target order and failing the split if min_order_for_split() is greater than the target order. In addition, to avoid wasting memory in memory failure handling, a second patch is added to always split a large folio to min_order_for_split() even if it is not 0, so that folios not containing the poisoned page can be freed for reuse. For soft offline, since the folio is still accessible, do not split if min_order_for_split() is not zero to avoid potential performance loss. [1] https://lore.kernel.org/all/68d2c943.a70a0220.1b52b.02b3.GAE@google.com/ Zi Yan (2): mm/huge_memory: do not change split_huge_page*() target order silently. mm/memory-failure: improve large block size folio handling. include/linux/huge_mm.h | 28 +++++----------------------- mm/huge_memory.c | 9 +-------- mm/memory-failure.c | 25 +++++++++++++++++++++---- mm/truncate.c | 6 ++++-- 4 files changed, 31 insertions(+), 37 deletions(-) -- 2.51.0