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Thu, 29 Oct 2026 11:42:39 -0400 (EDT) Date: Thu, 29 Oct 2026 15:42:38 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 42/46] mm/huge_memory: split huge PUDs when adjusting VMA boundaries Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-42-6f74bec9a5bb@kernel.org> <9f4128a4-85fc-4f4b-ac41-b9d348f56e37@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: E028540004 X-Stat-Signature: o56a99z31yigu9yw394apq1c463oxnsw X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793288577-30111 X-HE-Meta: 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 ZyjinRdW JM2K22A5Voj0ZJ0u7p2bbA5ATE7ZlZ9VLi2bzpIoCpZCkM6Oaup15V4qYnaR5ALMYA5YRqjjAibpPOuB0lFhtjZI87R1GG4uZWyuU0kOyvh4CtBkdPf30sc/nIhDetc60WtoDjWYxBC4+BP4hJ3r2WNMwG9Wd5GwX+lBEEC95AcF5e+3YJ8ic4v3fTRQKanUHhya7IareAvMuEC/mxTZpSKJ8Lw3yewvG1yJCZqCWW3sJhdiFxcwdXJxVTDRFriGpUrKjr9/pLqXvaBB18uF7tLZyIRH57gMEs4z/dq/EkGEAsNzHi+IzXPg0JlM/W4FWAUDgDdeQoVG8Oe+FkA9t+xGCqLrLYCMdG15eGiDpCyUb/evnfaH5VwTMMPhQaSth8SGJZkD+GI1qN+v56w2gsa0ntQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Oct 29, 2026 at 04:35:46PM +0100, David Hildenbrand (Arm) wrote: > On 10/29/26 15:40, David Hildenbrand (Arm) wrote: > > On 10/29/26 15:31, Kiryl Shutsemau wrote: > >> On Thu, Oct 29, 2026 at 03:24:29PM +0100, David Hildenbrand (Arm) wrote: > >>> > >>> __split_huge_pud() must split a leave. Either by zapping it (what we do right > >>> now) or by populating page tables (as in Usama's PoC). > >> > >> No, meant the situation when pud_leaf() is true, but split_pud is false, > >> so __split_huge_pud() is never hit. pud_present() is true so we proceed > >> to pmd_offset() > > > > Oh, yeah, I can add a WARN_ON_ONCE() for that, it would be a bug in the software. > > Ah, or I can just drop the split_pud check. Let me do that. Yeah, looks good. -- Kiryl Shutsemau / Kirill A. Shutemov