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Thu, 03 Sep 2026 06:36:11 +0000 X-Mizu-Trace-ID: 8473698cd31aeb55 X-Migadu-Flow: FLOW_OUT Message-ID: <3775da0f-4068-4fc4-97a7-135eb975ec65@linux.dev> Date: Thu, 3 Sep 2026 14:36:01 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/11] mm/sparse-vmemmap: prepare DAX vmemmap population for section orders To: Muchun Song , Andrew Morton , David Hildenbrand , 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 , Nicholas Piggin , Christophe Leroy , Randy Dunlap References: <20260831075342.57563-1-songmuchun@bytedance.com> <20260831075342.57563-5-songmuchun@bytedance.com> From: Qi Zheng In-Reply-To: <20260831075342.57563-5-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: szyf44kwpxrticiq481a434eq5qpjdzd X-Rspamd-Queue-Id: 7190AC0003 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788417376-662519 X-HE-Meta: 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 SORL14Iq MSXTrl9lnUo+7nbVUACHTsvkDoSFwctPqwn46dLGx6r4gAu8OunURvneAtUoM/wij5StIZYL00CqLUSESQFEkzbJror0jv2ePJ7eMNB+gKGJQ4TcjDf5xYl/bStH2UrvNdnaxkGJylx4qUoRfEmrieYe9GvzRTWGe1v40Y85LASq1fGnCiJX0Wy/jc4EOITIqvV6IQTa+KJpuJQC2k14qchTVnOvYyL0PuL8ZoHv/RsMgnhHvNmAah55Hd36VW2DO38EuM4F6fxH/F1GMYIY4zW0Sh27eZ5cGODDqiMqZG9gvYsA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/31/26 3:53 PM, Muchun Song wrote: > Device DAX still uses vmemmap_populate_compound_pages() to populate its > compound-page vmemmap mappings. That helper allocates the head and first > tail vmemmap pages explicitly, then reuses the first tail page for the > remaining tail page mappings. > > Device DAX is being moved to the section-based vmemmap optimization > infrastructure, but it cannot switch to the generic section-based > population path yet. Once a later patch records the DAX compound-page > geometry in the section order, DAX head and first-tail PFNs can look > optimizable to the generic helpers as well. > > Add a DAX-specific population flag for this transition. It keeps DAX > head/first-tail allocations on the normal vmemmap allocation path, while > preserving the existing page reference for reused DAX tail mappings. > > Signed-off-by: Muchun Song > --- > mm/sparse-vmemmap.c | 27 +++++++++++++++------------ > 1 file changed, 15 insertions(+), 12 deletions(-) > Acked-by: Qi Zheng Thanks, Qi