+ mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr.patch added to mm-new branch

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

The patch titled
     Subject: mm/sparse: rename __highest_present_section_nr to __highest_used_section_nr
has been added to the -mm mm-new branch.  Its filename is
     mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr.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: rename __highest_present_section_nr to __highest_used_section_nr
Date: Mon, 21 Sep 2026 21:58:58 +0200

In preparation for getting rid of SECTION_MARKED_PRESENT, rename
__highest_present_section_nr and clarify the comment.

Link: https://lore.kernel.org/20260921-b4-sparsemem_cleanups-v2-6-54d81d65e125@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>
---

 include/linux/mmzone.h |    6 +++---
 mm/compaction.c        |    2 +-
 mm/sparse.c            |   12 ++++--------
 mm/sparse.h            |    4 ++--
 4 files changed, 10 insertions(+), 14 deletions(-)

--- a/include/linux/mmzone.h~mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr
+++ a/include/linux/mmzone.h
@@ -2181,7 +2181,7 @@ static inline struct mem_section *__pfn_
 	return __nr_to_section(pfn_to_section_nr(pfn));
 }
 
-extern unsigned long __highest_present_section_nr;
+extern unsigned long __highest_used_section_nr;
 
 static inline int subsection_map_index(unsigned long pfn)
 {
@@ -2280,7 +2280,7 @@ static inline unsigned long first_valid_
 
 	rcu_read_lock_sched();
 
-	while (nr <= __highest_present_section_nr && pfn < end_pfn) {
+	while (nr <= __highest_used_section_nr && pfn < end_pfn) {
 		struct mem_section *ms = __pfn_to_section(pfn);
 
 		if (valid_section(ms) &&
@@ -2335,7 +2335,7 @@ static inline int pfn_in_present_section
 
 static inline unsigned long next_present_section_nr(unsigned long section_nr)
 {
-	while (++section_nr <= __highest_present_section_nr) {
+	while (++section_nr <= __highest_used_section_nr) {
 		if (present_section_nr(section_nr))
 			return section_nr;
 	}
--- a/mm/compaction.c~mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr
+++ a/mm/compaction.c
@@ -216,7 +216,7 @@ static unsigned long skip_offline_sectio
 	if (online_section_nr(start_nr))
 		return 0;
 
-	while (++start_nr <= __highest_present_section_nr) {
+	while (++start_nr <= __highest_used_section_nr) {
 		if (online_section_nr(start_nr))
 			return section_nr_to_pfn(start_nr);
 	}
--- a/mm/sparse.c~mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr
+++ a/mm/sparse.c
@@ -164,15 +164,11 @@ static void __init mminit_validate_memmo
 }
 
 /*
- * There are a number of times that we loop over NR_MEM_SECTIONS,
- * looking for section_present() on each.  But, when we have very
- * large physical address spaces, NR_MEM_SECTIONS can also be
- * very large which makes the loops quite long.
- *
- * Keeping track of this gives us an easy way to break out of
- * those loops early.
+ * Looping over all possible memory sections is expensive, especially if
+ * NR_MEM_SECTIONS is large but only a fraction is actually used. Keep track of
+ * the highest section number we ever used.
  */
-unsigned long __highest_present_section_nr;
+unsigned long __highest_used_section_nr;
 
 static inline unsigned long first_present_section_nr(void)
 {
--- a/mm/sparse.h~mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr
+++ a/mm/sparse.h
@@ -44,8 +44,8 @@ static inline void sparse_init_one_secti
 static inline void __section_mark_present(struct mem_section *ms,
 		unsigned long section_nr)
 {
-	if (section_nr > __highest_present_section_nr)
-		__highest_present_section_nr = section_nr;
+	if (section_nr > __highest_used_section_nr)
+		__highest_used_section_nr = section_nr;
 
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 }
_

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