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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-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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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