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From: Muchun Song In-Reply-To: <20260804035535.2846016-4-songmuchun@bytedance.com> Date: Tue, 11 Aug 2026 11:40:35 +0800 Cc: Andrew Morton , Oscar Salvador , David Hildenbrand , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Michal Hocko , David Laight , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit Message-Id: References: <20260804035535.2846016-1-songmuchun@bytedance.com> <20260804035535.2846016-4-songmuchun@bytedance.com> To: Muchun Song X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 3E190140004 X-Stat-Signature: ts7u48ctnhxxpxi8nh3jia6j6de9q18u X-HE-Tag: 1786419655-131442 X-HE-Meta: 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 ykcvhB3Z jkaOaZi5+BQO8L7EmRwh8cG2QSMY32laTV7PSPrKd370K4A3BNAnYr2nkQqmLeRHRLGPwATilcReF88N6eqXZrXM/7zNiXM4nPlepK5dD2xWDJ/RIvO7CBRSLrmx+GNvkIRmtnyqzyBzo2L/OAxwmi/3wMM1LYkYgwsfHyTdmBlisQT8dVGv8pXzlGKdgAodqFwPO1wKDU/GZfIdSrPzQOci2F9txxdnwDMILnr/XqaDeml9Ts9FB0k0KezV89zIjfMob81nWEaHB1miiDCsxbh8TDihBhroVh4zP701+Tvjw6Cuaha/4maJbTlqlVrNgikrv6LXVyo2oOqdHbvtQ6LxC7kP3xpg37BIlNVr4l1BGh7q84VOvdOyUHIdjjOj9yc49 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Aug 4, 2026, at 11:55, Muchun Song wrote: > > memmap_init_range() initializes every struct page in the target range. > For compound pages with vmemmap optimization, the tail struct pages are > backed by a shared vmemmap page. > > Initializing those tail struct pages would overwrite the shared > vmemmap page contents, requiring users such as HugeTLB to restore the > metadata afterwards. > > Track the compound order for HVO-backed sections and use that metadata > to detect struct pages that fall into the shared tail vmemmap range. > Skip those shared tail pages in memmap_init_range(), then initialize > pageblock migratetypes for the processed range with a helper after the > per-page initialization loop. > > Keep direct mem_section access inside sparse helpers by exposing > pfn_to_section_order() to users that only need the order associated with > a PFN. This lets memmap_init_range() skip shared tail vmemmap pages > without exposing __pfn_to_section() to !SPARSEMEM builds. > > This is a preparatory change for consolidating handling across users of > vmemmap optimization, and it also avoids redundant initialization of > shared tail vmemmap pages during early boot. > > Signed-off-by: Muchun Song Sashiko said there is a missing assignment for the new order field in struct mem_section. This is just an observation, not an issue, because assignment is placed in patch 10. There's no extra action to take for this report. Thanks.