+ mm-sparse-remove-section_map_size.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/sparse: remove section_map_size()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-sparse-remove-section_map_size.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-sparse-remove-section_map_size.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm/sparse: remove section_map_size()
Date: Thu, 10 Sep 2026 14:32:52 +0800

section_map_size() no longer provides any shared logic.

After the sparse-vmemmap changes, its only remaining user is the
!CONFIG_SPARSEMEM_VMEMMAP path in __populate_section_memmap(), which can
compute the size inline with PAGE_ALIGN(sizeof(struct page) *
PAGES_PER_SECTION).

Remove section_map_size() and inline the remaining calculation.

Link: https://lore.kernel.org/20260910063256.64386-14-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |    1 -
 mm/sparse.c        |   15 ++-------------
 2 files changed, 2 insertions(+), 14 deletions(-)

--- a/include/linux/mm.h~mm-sparse-remove-section_map_size
+++ a/include/linux/mm.h
@@ -5140,7 +5140,6 @@ static inline void print_vma_addr(char *
 }
 #endif
 
-unsigned long section_map_size(void);
 struct page * __populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
 		struct dev_pagemap *pgmap);
--- a/mm/sparse.c~mm-sparse-remove-section_map_size
+++ a/mm/sparse.c
@@ -208,23 +208,12 @@ void __init sparse_sections_init(void)
 		memory_present(nid, start, end);
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-unsigned long __init section_map_size(void)
-{
-	return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
-}
-
-#else
-unsigned long __init section_map_size(void)
-{
-	return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
-}
-
+#ifndef CONFIG_SPARSEMEM_VMEMMAP
 struct page __init *__populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
 		struct dev_pagemap *pgmap)
 {
-	unsigned long size = section_map_size();
+	const unsigned long size = PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
 
 	return memmap_alloc(size, size, __pa(MAX_DMA_ADDRESS), nid, false);
 }
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-sparse-relax-struct-mem_section-size-constraints.patch
mm-sparse-vmemmap-rename-hvo-order-macros.patch
mm-mm_init-skip-initializing-shared-vmemmap-tail-pages.patch
mm-sparse-vmemmap-initialize-shared-tail-vmemmap-pages-on-allocation.patch
mm-sparse-vmemmap-support-section-based-vmemmap-accounting.patch
mm-mm_init-factor-out-pfn_to_zone.patch
mm-sparse-vmemmap-move-helpers-ahead-of-future-callers.patch
mm-sparse-vmemmap-support-section-based-vmemmap-optimization.patch
mm-sparse-initialize-memory-sections-earlier.patch
mm-hugetlb-switch-hugetlb-to-section-based-vmemmap-optimization.patch
mm-sparse-vmemmap-remove-sparsemem_vmemmap_preinit-support.patch
mm-sparse-inline-usemap-allocation-into-sparse_init_nid.patch
mm-sparse-remove-section_map_size.patch
mm-hugetlb-remove-huge_bootmem_hvo.patch
mm-hugetlb-remove-huge_bootmem_cma.patch
mm-hugetlb-localize-struct-huge_bootmem_page.patch
mm-hugetlb-localize-huge_bootmem_zones_valid.patch
mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization.patch
mm-sparse-vmemmap-factor-out-shared-vmemmap-tail-page-allocation.patch
mm-sparse-vmemmap-open-code-init_compound_tail.patch
mm-sparse-vmemmap-prepare-dax-vmemmap-population-for-section-orders.patch
mm-sparse-vmemmap-set-section-order-for-device-dax.patch
mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages.patch
mm-sparse-vmemmap-move-hvo-helpers-to-a-public-header.patch
powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch
mm-sparse-vmemmap-drop-the-extra-tail-page-from-device-dax-reservation.patch
mm-sparse-vmemmap-drop-unused-section_nr_vmemmap_pages-arguments.patch
documentation-mm-update-dax-vmemmap-deduplication-docs.patch