+ mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch added to mm-new branch

+ mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/sparse: move initialization of section metadata to sparse_metadata_init()
has been added to the -mm mm-new branch.  Its filename is
     mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: "David Hildenbrand (Arm)" <david@kernel.org>
Subject: mm/sparse: move initialization of section metadata to sparse_metadata_init()
Date: Mon, 21 Sep 2026 21:58:55 +0200

Let's move the code responsible for initializing sparse metadata (usemap,
memmap) into a helper.  Cleanup the variable while at it (e.g.,
"map_count").

Drop the rather obvious code comments.

No functional change intended.

Link: https://lore.kernel.org/20260921-b4-sparsemem_cleanups-v2-3-54d81d65e125@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
---

 mm/sparse.c |   43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

--- a/mm/sparse.c~mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init
+++ a/mm/sparse.c
@@ -255,38 +255,39 @@ static void __init sparse_init_nid(int n
 	}
 }
 
+static void __init sparse_metadata_init(void)
+{
+	unsigned long start_section_nr = first_present_section_nr();
+	int nid_begin = sparse_early_nid(__nr_to_section(start_section_nr));
+	unsigned long section_nr, nr_sections = 1;
+
+	for_each_present_section_nr(start_section_nr + 1, section_nr) {
+		const int nid = sparse_early_nid(__nr_to_section(section_nr));
+
+		if (nid == nid_begin) {
+			nr_sections++;
+			continue;
+		}
+		sparse_init_nid(nid_begin, start_section_nr, section_nr, nr_sections);
+		nid_begin = nid;
+		start_section_nr = section_nr;
+		nr_sections = 1;
+	}
+	sparse_init_nid(nid_begin, start_section_nr, section_nr, nr_sections);
+}
+
 /*
  * Allocate the accumulated non-linear sections, allocate a mem_map
  * for each and record the physical to section mapping.
  */
 void __init sparse_init(void)
 {
-	unsigned long pnum_end, pnum_begin, map_count = 1;
-	int nid_begin;
-
 	if (compound_info_has_mask()) {
 		VM_WARN_ON_ONCE(!IS_ALIGNED((unsigned long) pfn_to_page(0),
 				    MAX_FOLIO_VMEMMAP_ALIGN));
 	}
 
-	pnum_begin = first_present_section_nr();
-	nid_begin = sparse_early_nid(__nr_to_section(pnum_begin));
-
-	for_each_present_section_nr(pnum_begin + 1, pnum_end) {
-		int nid = sparse_early_nid(__nr_to_section(pnum_end));
-
-		if (nid == nid_begin) {
-			map_count++;
-			continue;
-		}
-		/* Init node with sections in range [pnum_begin, pnum_end) */
-		sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
-		nid_begin = nid;
-		pnum_begin = pnum_end;
-		map_count = 1;
-	}
-	/* cover the last node */
-	sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
+	sparse_metadata_init();
 	sparse_init_subsection_map();
 	vmemmap_populate_print_last();
 }
_

Patches currently in -mm which might be from david@kernel.org are

maintainers-split-up-memory-management-memory-policy-and-migration.patch
maintainers-move-memory-tiering-under-memory-management-numa-placement.patch
maintainers-make-gregory-a-co-maintainer-of-memory-management-numa-placement.patch
selftests-mm-khugepaged-remove-str_dup-usage.patch
mm-sparse-move-mem_section-init-to-sparse_extreme_init.patch
mm-sparse-refactor-sparse_sections_init.patch
mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch
mm-sparse-rename-and-cleanup-sparse_init_nid.patch
mm-sparse-cleanup-sparse_init_one_section.patch
mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr.patch
mm-sparse-remove-pfn_in_present_section.patch
mm-sparse-move-__highest_used_section_nr-handling.patch
scripts-gdb-mmpy-remove-fallbacks-for-section_has_mem_map-and-section_is_early.patch
mm-sparse-remove-section_marked_present.patch
mm-sparse-remove-flags-parameter-from-sparse_init_one_section.patch
fs-proc-page-clarify-comment-in-get_max_dump_pfn.patch
mm-memory_hotplug-drop-config_have_arch_pfn_valid-handling-from-pfn_to_online_page.patch