From 89e2b6e3d345cd4dca822a5ccea764ee7f9e0ae4 Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Mon, 21 Sep 2026 21:58:54 +0200
Subject: [PATCH] mm/sparse: refactor sparse_sections_init()

memory_present() really identifies+prepares all early sections so the
initialization in sparse_init() can properly iterating them to initialize
metadata.

Let's just inline memory_present() into sparse_sections_init() and
cleaning up the code a bit while at it: make it clear that we are
operating on pfns.

Note that we call set_section_nid() now only if the section was not
already created earlier.  Now, there is no more inconsistency between what
we (temporarily) store in ms->section_mem_map and what we store in our
section->nid array.

Link: https://lore.kernel.org/20260921-b4-sparsemem_cleanups-v2-2-54d81d65e125@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>
Acked-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 | 41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 8cd2b06b231a..2b285653abf1 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -179,40 +179,33 @@ static inline unsigned long first_present_section_nr(void)
 	return next_present_section_nr(-1);
 }
 
-/* Record a memory area against a node. */
-static void __init memory_present(int nid, unsigned long start, unsigned long end)
+void __init sparse_sections_init(void)
 {
-	unsigned long pfn;
+	unsigned long pfn, start_pfn, end_pfn;
+	int i, nid;
 
-	start &= PAGE_SECTION_MASK;
-	mminit_validate_memmodel_limits(&start, &end);
-	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
-		unsigned long section_nr = pfn_to_section_nr(pfn);
-		struct mem_section *ms;
+	sparse_extreme_init();
 
-		sparse_index_init(section_nr, nid);
-		set_section_nid(section_nr, nid);
+	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
+		start_pfn &= PAGE_SECTION_MASK;
+		mminit_validate_memmodel_limits(&start_pfn, &end_pfn);
 
-		ms = __nr_to_section(section_nr);
-		if (!ms->section_mem_map) {
+		for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+			unsigned long section_nr = pfn_to_section_nr(pfn);
+			struct mem_section *ms;
+
+			sparse_index_init(section_nr, nid);
+			ms = __nr_to_section(section_nr);
+			if (ms->section_mem_map)
+				continue;
+
+			set_section_nid(section_nr, nid);
 			ms->section_mem_map = sparse_encode_early_nid(nid) |
 							SECTION_IS_ONLINE;
 			__section_mark_present(ms, section_nr);
 		}
 	}
 }
-
-void __init sparse_sections_init(void)
-{
-	unsigned long start, end;
-	int i, nid;
-
-	sparse_extreme_init();
-
-	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
-		memory_present(nid, start, end);
-}
-
 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 struct page __init *__populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,