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Tue, 21 Apr 2026 03:55:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id +2K0C0H15mk2YAAAD6G6ig (envelope-from ); Tue, 21 Apr 2026 03:55:45 +0000 Date: Tue, 21 Apr 2026 05:55:35 +0200 From: Oscar Salvador To: Muchun Song Cc: Andrew Morton , David Hildenbrand , Muchun Song , Michael Ellerman , Madhavan Srinivasan , Mike Rapoport , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/4] mm/sparse-vmemmap: Pass @pgmap argument to memory deactivation paths Message-ID: References: <20260421022044.1217503-1-songmuchun@bytedance.com> <20260421022044.1217503-3-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260421022044.1217503-3-songmuchun@bytedance.com> X-Rspamd-Queue-Id: D60641C0002 X-Stat-Signature: owsjtj1p6gne1ijw33a8ozbzjzky4979 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1776743747-964342 X-HE-Meta: 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 /osSlm2j ezdAV0yvrx4sytSFJ+7m15omdBXfF9sj9cFVY7KXyuTLz5AywtQL4ai2vEy6zZjtBGmKZ7Op+tJ9Wz94ewpNuIk0QoStFoSFRQAJe3MOnlyicrULn+/j1Q1lUSE2llUsANNHiKL9QzNtOODypf5tHeIN31+2wM2oMtVurO5wncuuh3kr7NXjtbw7HpVJuREQ4vVQh1HYn5Fg3XS7jPsQmHY5N46/caww/qp+ujOh1lpiy+dNoCw2EHx49oe2O2Jlk9NZ+xuQOezSFiPzx7UDf3MV1e/xQWvIJzcsXerspt2THRD86ZEe7ps0swA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 21, 2026 at 10:20:42AM +0800, Muchun Song wrote: > Currently, the memory hot-remove call chain -- arch_remove_memory(), > __remove_pages(), sparse_remove_section() and section_deactivate() -- > does not carry the struct dev_pagemap pointer. This prevents the lower > levels from knowing whether the section was originally populated with > vmemmap optimizations (e.g., DAX with vmemmap optimization enabled). > > Without this information, we cannot call vmemmap_can_optimize() to > determine if the vmemmap pages were optimized. As a result, the vmemmap > page accounting during teardown will mistakenly assume a non-optimized > allocation, leading to incorrect memmap statistics. > > To lay the groundwork for fixing the vmemmap page accounting, we need > to pass the @pgmap pointer down to the deactivation location. Plumb the > @pgmap argument through the APIs of arch_remove_memory(), __remove_pages() > and sparse_remove_section(), mirroring the corresponding *_activate() > paths. > > Signed-off-by: Muchun Song > Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Oscar Salvador The change looks good to me, but I was wondering whether we should pass a mhp struct instead to low-level functions like arch_remove_memory and __remove_pages and have __remove_pages then pass the right stuff down the road. That way it would mimic more what we do in hot-add path. -- Oscar Salvador SUSE Labs