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b=VTysHtsFbDZOc9nla0Q2lgBis/brgO6Tu+kf3ZjW0lCZpL1uJplM9eZTkXQhCcum2 UIQVwE1+A3z9/osnfEUHa5wrcr52RX4ivjXktLIzY5oVFuwODBON2ufk5tTgU6mn+R kRQjtEeQq2irifXeO/1G3CFjPn3stmMk/VvAx3qvWB8gbBiWAQl6yd0+kYztL1a+QJ eagSYMaSu7JIt54TiZMwJU+j3SfNPW7mc3mRGstPV06L/k2NOUTqClojWUxdl8PEiw /vumUJqdqpNOYsec/0f6JZTDY41m2mszc4Rs+BB36RPHPk/B4ZAjutUf6q1FNZNSrq eP+Xw8P8QMVAg== Message-ID: <0ecdd75e-ccd8-4217-a409-51da756ff1fe@kernel.org> Date: Fri, 6 Feb 2026 11:42:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 17/17] mm/slab: Use compound_head() in page_slab() To: Kiryl Shutsemau , Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260202155634.650837-1-kas@kernel.org> <20260202155634.650837-18-kas@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E4A2740004 X-Stat-Signature: w9m3hhti47c664zpr7srrtggkyzk1156 X-Rspam-User: X-HE-Tag: 1770374538-159734 X-HE-Meta: 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 eAykrRPS vHc5SOhbyJc5dUR194zD1mT/u1TpKw6nxEDsrRX0eFGfIPU/f+3iACxnZ1d1LpQuvq5HORKLIFVmAujODYMoDhgearITx85OQKJPENo2TlPM/AQtQ0UKC5wvYcQr0ojafvZoinqAh98BVYpvtPzKVws69s+4QuPqvume6fiXBfk6TInXrOhKM0PUGqN0RL7f8xaF0Y21LdDveYlOvtFNnDPpPomS0HGgkNBo4ODwUClPwoA3cvV4wlNfKF/ocIA2gPhUiUeQDNOwgF1aAn2JfpxbdezuthGyixJGIknjxO049dLvT/H9Bn0vgU29rXUJxHrpylvXC/Gaj8dOXok/pHQ8SGjfHgLsq7sFV 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 2/2/26 16:56, Kiryl Shutsemau wrote: > page_slab() contained an open-coded implementation of compound_head(). > > Replace the duplicated code with a direct call to compound_head(). > > Signed-off-by: Kiryl Shutsemau > > --- > > I am not sure if this open-coded version is intentional and required for > memdesc transition. Drop the patch if it is. commit 2bcd3800f2da1be13b972858f63c66d035b1ec6d Author: Matthew Wilcox (Oracle) Date: Thu Nov 13 00:09:15 2025 +0000 slab: Reimplement page_slab() In order to separate slabs from folios, we need to convert from any page in a slab to the slab directly without going through a page to folio conversion first. Up to this point, page_slab() has followed the example of other memdesc converters (page_folio(), page_ptdesc() etc) and just cast the pointer to the requested type, regardless of whether the pointer is actually a pointer to the correct type or not. That changes with this commit; we check that the page actually belongs to a slab and return NULL if it does not. Other memdesc converters will adopt this convention in future. I think using compound_head() is fine. For memdescs the function has to be changed to lookup the memdesc either way, and not go through the head page. Acked-by: David Hildenbrand (Arm) -- Cheers, David