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b=eryQFDsK8XbiERSwR84WHNpDMzE5PzW2Ardhk9RRQOYTsF5ZNYAsYUTNwxnrO8IJs 4pF3o24oJ+dNKTsPvIBFa7CvmvfCowlF+wh5oBUBDLz4duFK9AGVH8JT/ueUbqsnF7 ZQnN9vpmWzdMu2UbSL9dh0S7xy4SEdCFP0/lBfMYZisKxJkVQFa8adh90Jsp+Hdsdf grXSyKGdotmj1TjbtLy7memifkUshjvj+fwdD5gII7wv7AEeK82aEZfO0aX8u+5fRk kHOknkEF+u5bV6GGr3ZC91nkB1aXFNs2e5o4TGWrX/02jSXQmkMK3/Bj+DRvMSofpX Fgok4KIaAKVaQ== Message-ID: <29717e90-4b4c-4ee4-8a17-20a7b1792000@kernel.org> Date: Tue, 29 Sep 2026 09:45:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 10/12] mm/sparse-vmemmap: drop the extra tail page from device DAX reservation To: Muchun Song , Andrew Morton , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Muchun Song , Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Randy Dunlap , Lance Yang References: <20260927025441.741633-1-songmuchun@bytedance.com> <20260927025441.741633-11-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: udyiksa67h54ijwppamrc4duu8xeadhn X-Rspamd-Queue-Id: 56FC5180003 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790667911-855686 X-HE-Meta: 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 HSMfy0ki fAFKHvIKb8Nt0BQR3WrEyNZvOdekjgwz21yOxGLa1e4/bSmrEXro9eLo2HJhIawcZN+xqiS3w0Bn9cUFaMRh2wo9BPaEM05zgVJ93qWbs9hSbZ2gT+Vy7FXHzq/rr5kps7beufpO/ucx9U3+6V+SGXZp0MRiT8lC8bRlpe1p4G5xGc0lo65Sb3a5lVkLzsGM6EGktJh0jEQX8qH1iMZ8uCT3T2/EfRE24qw2EdJQ5PZ05To7hor/3R2vkxdzQRpKg82J5ucI0bIRgcGNJ0q4F2U8qFd04GL2I7lguvfDU8j8EncnfLJ3XRjVwmQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/27/26 04:54, Muchun Song wrote: > The device DAX vmemmap population still reserves one extra tail vmemmap > page after the head page. > > Drop that extra reservation and let the shared tail page cover all tail > vmemmap pages after the head page, so DAX follows the same reservation > model as HugeTLB. > > This reduces the reserved vmemmap pages for optimized DAX mappings to > one and removes the now-unneeded first-tail population from the generic > and powerpc paths to simplify the code as well. > > Signed-off-by: Muchun Song > Acked-by: Qi Zheng > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David