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([2001:67c:2fbc:1:a864:eb02:add4:d64a]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae6e7e910e8sm1235904466b.36.2025.07.16.12.01.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Jul 2025 12:01:26 -0700 (PDT) Message-ID: Date: Wed, 16 Jul 2025 21:01:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: refactor after-split (page) cache code. To: Zi Yan Cc: Andrew Morton , Hugh Dickins , linux-mm@kvack.org, David Hildenbrand , Kirill Shutemov , Lorenzo Stoakes , Dan Carpenter , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , linux-kernel@vger.kernel.org References: <20250716171112.3666150-1-ziy@nvidia.com> Content-Language: en-US From: Antonio Quartulli Autocrypt: addr=antonio@mandelbit.com; keydata= xsFNBFN3k+ABEADEvXdJZVUfqxGOKByfkExNpKzFzAwHYjhOb3MTlzSLlVKLRIHxe/Etj13I X6tcViNYiIiJxmeHAH7FUj/yAISW56lynAEt7OdkGpZf3HGXRQz1Xi0PWuUINa4QW+ipaKmv voR4b1wZQ9cZ787KLmu10VF1duHW/IewDx9GUQIzChqQVI3lSHRCo90Z/NQ75ZL/rbR3UHB+ EWLIh8Lz1cdE47VaVyX6f0yr3Itx0ZuyIWPrctlHwV5bUdA4JnyY3QvJh4yJPYh9I69HZWsj qplU2WxEfM6+OlaM9iKOUhVxjpkFXheD57EGdVkuG0YhizVF4p9MKGB42D70pfS3EiYdTaKf WzbiFUunOHLJ4hyAi75d4ugxU02DsUjw/0t0kfHtj2V0x1169Hp/NTW1jkqgPWtIsjn+dkde dG9mXk5QrvbpihgpcmNbtloSdkRZ02lsxkUzpG8U64X8WK6LuRz7BZ7p5t/WzaR/hCdOiQCG RNup2UTNDrZpWxpwadXMnJsyJcVX4BAKaWGsm5IQyXXBUdguHVa7To/JIBlhjlKackKWoBnI Ojl8VQhVLcD551iJ61w4aQH6bHxdTjz65MT2OrW/mFZbtIwWSeif6axrYpVCyERIDEKrX5AV rOmGEaUGsCd16FueoaM2Hf96BH3SI3/q2w+g058RedLOZVZtyQARAQABzSlBbnRvbmlvIFF1 YXJ0dWxsaSA8YW50b25pb0BtYW5kZWxiaXQuY29tPsLBrQQTAQgAVwIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUJFZDZMhYhBMq9oSggF8JnIZiFx0jwzLaPWdFMBQJhFSq4GBhoa3Bz Oi8va2V5cy5vcGVucGdwLm9yZwAKCRBI8My2j1nRTC6+EACi9cdzbzfIaLxGfn/anoQyiK8r FMgjYmWMSMukJMe0OA+v2+/VTX1Zy8fRwhjniFfiypMjtm08spZpLGZpzTQJ2i07jsAZ+0Kv ybRYBVovJQJeUmlkusY3H4dgodrK8RJ5XK0ukabQlRCe2gbMja3ec/p1sk26z25O/UclB2ti YAKnd/KtD9hoJZsq+sZFvPAhPEeMAxLdhRZRNGib82lU0iiQO+Bbox2+Xnh1+zQypxF6/q7n y5KH/Oa3ruCxo57sc+NDkFC2Q+N4IuMbvtJSpL1j6jRc66K9nwZPO4coffgacjwaD4jX2kAp saRdxTTr8npc1MkZ4N1Z+vJu6SQWVqKqQ6as03pB/FwLZIiU5Mut5RlDAcqXxFHsium+PKl3 UDL1CowLL1/2Sl4NVDJAXSVv7BY51j5HiMuSLnI/+99OeLwoD5j4dnxyUXcTu0h3D8VRlYvz iqg+XY2sFugOouX5UaM00eR3Iw0xzi8SiWYXl2pfeNOwCsl4fy6RmZsoAc/SoU6/mvk82OgN ABHQRWuMOeJabpNyEzA6JISgeIrYWXnn1/KByd+QUIpLJOehSd0o2SSLTHyW4TOq0pJJrz03 oRIe7kuJi8K2igJrfgWxN45ctdxTaNW1S6X1P5AKTs9DlP81ZiUYV9QkZkSS7gxpwvP7CCKF n11s24uF1c44BGhGyuwSCisGAQQBl1UBBQEBB0DIPeCzGpzFfbnob2Usn40WGLsFClyFRq3q ZIA9v7XIJAMBCAfCwXwEGAEIACYWIQTKvaEoIBfCZyGYhcdI8My2j1nRTAUCaEbK7AIbDAUJ AeEzgAAKCRBI8My2j1nRTDKZD/9nW0hlpokzsIfyekOWdvOsj3fxwTRHLlpyvDYRZ3RoYZRp b4v6W7o3WRM5VmJTqueSOJv70VfBbUuEBSIthifY6VWlVPWQFKeJHTQvegTrZSkWBlsPeGvl L+Kjj5kHx998B8PqWUrFtFY0QP1St+JWHTYSBhhLYmbL5XgFPz4okbLE0W/QsVImPBvzNBnm 9VnkU9ixJDklB0DNg2YD31xsuU2nIdvNsevZtevi3xv+uLThLCf4rOmj7zXVb+uSr+YjW/7I z/qjv7TnzqXUxD2bQsyPq8tesEM3SKgZrX/3saE/wu0sTgeWH5LyM9IOf7wGRIHj7gimKNAq 2sCpVNqI/i/djp9qokCs9yHkUcqC76uftsyqiKkqNXMoZReugahQfCPN5o6eefBgy+QMjAeI BbpeDMTllESfZ98SxKdU/MDhCSM/5Bf/lFmgfX3zeBvt45ds/8pCGIfpI7VQECaA8pIpAZEB hi1wlfVsdZhAdO158EagqtuTOSwvlm9N01FwLjj9nm7jKE2YCyrgrrANC7QlsAO/r0nnqM9o Iz6CD01a5JHdc1U66L/QlFXHip3dKeyfCy4XnHL58PShxgEu6SxWYdrgWwmr3XXc6vZ8z7XS 3WbIEhnAgMQEu73PEZRgt6eVr+Ad175SdKz6bJw3SzJr1qE4FMb/nuTvD9pAtw== Organization: Mandelbit SRL In-Reply-To: <20250716171112.3666150-1-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6545F1C0025 X-Stat-Signature: wy4jm5yoyq7998hq6qdxzc6acs48yotn X-Rspam-User: X-HE-Tag: 1752692489-933745 X-HE-Meta: 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 luRE2Tyl 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 16/07/2025 19:11, Zi Yan wrote: > Smatch/coverity checkers report NULL mapping referencing issues[1][2][3] > every time the code is modified, because they do not understand that > mapping cannot be NULL when a folio is in page cache in the code. > Refactor the code to make it explicit. > > No functional change is intended. > > [1]https://lore.kernel.org/linux-mm/2afe3d59-aca5-40f7-82a3-a6d976fb0f4f@stanley.mountain/ > [2]https://lore.kernel.org/oe-kbuild/64b54034-f311-4e7d-b935-c16775dbb642@suswa.mountain/ > [3]https://lore.kernel.org/linux-mm/20250716145804.4836-1-antonio@mandelbit.com/ > > Suggested-by: David Hildenbrand > Signed-off-by: Zi Yan Much easier to grasp - Thanks a lot! I am sure Coverity will be happy too at this point, because the ambiguity has been fully removed. In a previous email you asked me how to prevent Coverity from complaining about certain code: my thinking is fully aligned with Dan's reply. IMHO refactoring the code was the best choice - thanks again. Regards, -- Antonio Quartulli CEO and Co-Founder Mandelbit Srl https://www.mandelbit.com