[PATCH v2 00/13] mm/sparse: remove SECTION_MARKED_PRESENT and further cleanups

[PATCH v2 00/13] mm/sparse: remove SECTION_MARKED_PRESENT and further cleanups

[David Hildenbrand (Arm)]

SECTION_MARKED_PRESENT is really only needed during boot, where we
can instead just rely on SECTION_IS_EARLY_BIT by setting that flag
earlier.

Some preparations for doing that conversion and some cleanups in the same
(sparse) area.

Tested on x86 with and without memory hotplug through virtio-mem.

---
Changes in v2:
- Rebased to mm-unstable
- Add "scripts/gdb: mm.py: remove fallbacks for SECTION_HAS_MEM_MAP and
  SECTION_IS_EARLY"
- Improve comment in mmzone.h for __highest_used_section_nr
- Improve comment in fs/proc/page.c for get_max_dump_pfn()
- Move __highest_used_section_nr handling directly into
  __section_mark_present() callers and use max()
- Make pfn const in sparse_metadata_init_nid()
- Take care of .clang_format
- Smaller patch description fixes
- Link to v1: https://patch.msgid.link/20260909-b4-sparsemem_cleanups-v1-0-008fc8d579fe@kernel.org

To: Andrew Morton <akpm@linux-foundation.org>
To: David Hildenbrand <david@kernel.org>
To: Lorenzo Stoakes <ljs@kernel.org>
To: "Liam R. Howlett" <liam@infradead.org>
To: Vlastimil Babka <vbabka@kernel.org>
To: Mike Rapoport <rppt@kernel.org>
To: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
To: Kairui Song <kasong@tencent.com>
To: Qi Zheng <qi.zheng@linux.dev>
To: Shakeel Butt <shakeel.butt@linux.dev>
To: Barry Song <baohua@kernel.org>
To: Axel Rasmussen <axelrasmussen@google.com>
To: Yuanchu Xie <yuanchu@google.com>
To: Wei Xu <weixugc@google.com>
To: Baoquan He <baoquan.he@linux.dev>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Brendan Jackman <brendan.jackman@linux.dev>
To: Johannes Weiner <hannes@cmpxchg.org>
To: Zi Yan <ziy@nvidia.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
To: Kieran Bingham <kbingham@kernel.org>
To: Oscar Salvador <osalvador@suse.de>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
To: Danilo Krummrich <dakr@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-cxl@vger.kernel.org
Cc: driver-core@lists.linux.dev
Cc: linux-fsdevel@vger.kernel.org

---

David Hildenbrand (Arm) (13):
      mm/sparse: move mem_section init to sparse_extreme_init()
      mm/sparse: refactor sparse_sections_init()
      mm/sparse: move initialization of section metadata to sparse_metadata_init()
      mm/sparse: rename and cleanup sparse_init_nid()
      mm/sparse: cleanup sparse_init_one_section()
      mm/sparse: rename __highest_present_section_nr to __highest_used_section_nr
      mm/sparse: remove pfn_in_present_section()
      mm/sparse: move __highest_used_section_nr handling
      scripts/gdb: mm.py: remove fallbacks for SECTION_HAS_MEM_MAP and SECTION_IS_EARLY
      mm/sparse: remove SECTION_MARKED_PRESENT
      mm/sparse: remove flags parameter from sparse_init_one_section()
      fs/proc/page: clarify comment in get_max_dump_pfn()
      mm/memory_hotplug: drop CONFIG_HAVE_ARCH_PFN_VALID handling from pfn_to_online_page()

 .clang-format           |   2 +-
 drivers/base/memory.c   |   2 +-
 fs/proc/page.c          |   7 +--
 include/linux/cache.h   |   1 +
 include/linux/mmzone.h  |  43 ++++---------
 mm/compaction.c         |   2 +-
 mm/memory_hotplug.c     |   9 +--
 mm/sparse-vmemmap.c     |   4 +-
 mm/sparse.c             | 160 +++++++++++++++++++++++-------------------------
 mm/sparse.h             |  19 ++----
 scripts/gdb/linux/mm.py |   8 +--
 11 files changed, 108 insertions(+), 149 deletions(-)

---

base-commit: 8d61431ed2607386b427752505379536eb634ce8

change-id: 20260814-b4-sparsemem_cleanups-8bc4b47014c3

--

Cheers,

David

[PATCH v2 01/13] mm/sparse: move mem_section init to sparse_extreme_init()

[David Hildenbrand (Arm)]

Let's just avoid another pair of ifdef inside a function. While at it,
switch to INTERNODE_CACHE_BYTES by just defining a fallback in cache.h
as well, given that the x86 variant already provides one.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 include/linux/cache.h |  1 +
 mm/sparse.c           | 19 ++++++++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/linux/cache.h b/include/linux/cache.h
index e69768f50d532..b6e857b985bca 100644
--- a/include/linux/cache.h
+++ b/include/linux/cache.h
@@ -89,6 +89,7 @@
  */
 #ifndef INTERNODE_CACHE_SHIFT
 #define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
+#define INTERNODE_CACHE_BYTES (1 << INTERNODE_CACHE_SHIFT)
 #endif
 
 #if !defined(____cacheline_internodealigned_in_smp)
diff --git a/mm/sparse.c b/mm/sparse.c
index b75921c622ede..8cd2b06b231ac 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -103,11 +103,22 @@ int __meminit sparse_index_init(unsigned long section_nr, int nid)
 
 	return 0;
 }
+
+static void __init sparse_extreme_init(void)
+{
+	const unsigned long size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
+
+	mem_section = memblock_alloc_or_panic(size, INTERNODE_CACHE_BYTES);
+}
 #else /* !SPARSEMEM_EXTREME */
 int __meminit sparse_index_init(unsigned long section_nr, int nid)
 {
 	return 0;
 }
+
+static void __init sparse_extreme_init(void)
+{
+}
 #endif
 
 /*
@@ -196,13 +207,7 @@ void __init sparse_sections_init(void)
 	unsigned long start, end;
 	int i, nid;
 
-#ifdef CONFIG_SPARSEMEM_EXTREME
-	unsigned long size, align;
-
-	size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
-	align = 1 << (INTERNODE_CACHE_SHIFT);
-	mem_section = memblock_alloc_or_panic(size, align);
-#endif
+	sparse_extreme_init();
 
 	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
 		memory_present(nid, start, end);

-- 
2.43.0

Re: [PATCH v2 01/13] mm/sparse: move mem_section init to sparse_extreme_init()

[Zi Yan]

On Mon Sep 21, 2026 at 3:58 PM EDT, David Hildenbrand (Arm) wrote:
> Let's just avoid another pair of ifdef inside a function. While at it,
> switch to INTERNODE_CACHE_BYTES by just defining a fallback in cache.h
> as well, given that the x86 variant already provides one.
>
> Acked-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
> ---
>  include/linux/cache.h |  1 +
>  mm/sparse.c           | 19 ++++++++++++-------
>  2 files changed, 13 insertions(+), 7 deletions(-)
>
LGTM.

Reviewed-by: Zi Yan <ziy@nvidia.com>

-- 
Best Regards,
Yan, Zi

[PATCH v2 02/13] mm/sparse: refactor sparse_sections_init()

[David Hildenbrand (Arm)]

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.

Acked-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse.c | 41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 8cd2b06b231ac..2b285653abf1e 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;
+
+	sparse_extreme_init();
 
-	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;
+	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);
 
-		sparse_index_init(section_nr, nid);
-		set_section_nid(section_nr, nid);
+		for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+			unsigned long section_nr = pfn_to_section_nr(pfn);
+			struct mem_section *ms;
 
-		ms = __nr_to_section(section_nr);
-		if (!ms->section_mem_map) {
+			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,

-- 
2.43.0

[PATCH v2 03/13] mm/sparse: move initialization of section metadata to sparse_metadata_init()

[David Hildenbrand (Arm)]

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.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse.c | 43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 2b285653abf1e..71288daeb3665 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -255,38 +255,39 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
 	}
 }
 
+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();
 }

-- 
2.43.0

[PATCH v2 04/13] mm/sparse: rename and cleanup sparse_init_nid()

[David Hildenbrand (Arm)]

Let's rename it to "sparse_metadata_init_nid", avoid the "pnum" terminology
and drop the function comment. Further, rename the "map" variable to
"mem_map" for consistency with other functions.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse.c | 41 ++++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 71288daeb3665..3c19d47559090 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -221,36 +221,33 @@ void __weak __meminit vmemmap_populate_print_last(void)
 {
 }
 
-/*
- * Initialize sparse on a specific node. The node spans [pnum_begin, pnum_end)
- * And number of present sections in this node is map_count.
- */
-static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
-				   unsigned long pnum_end,
-				   unsigned long map_count)
+static void __init sparse_metadata_init_nid(int nid,
+		unsigned long start_section_nr, unsigned long end_section_nr,
+		unsigned long nr_sections)
 {
-	unsigned long pnum;
 	struct mem_section_usage *usage;
+	unsigned long section_nr;
 
-	usage = memblock_alloc_node(map_count * mem_section_usage_size(),
+	usage = memblock_alloc_node(nr_sections * mem_section_usage_size(),
 				    SMP_CACHE_BYTES, nid);
 	if (!usage)
 		panic("Failed to allocate usemap for node %d\n", nid);
 
-	for_each_present_section_nr(pnum_begin, pnum) {
-		unsigned long pfn = section_nr_to_pfn(pnum);
-		struct page *map;
+	for_each_present_section_nr(start_section_nr, section_nr) {
+		const unsigned long pfn = section_nr_to_pfn(section_nr);
+		struct page *mem_map;
 
-		if (pnum >= pnum_end)
+		if (section_nr >= end_section_nr)
 			break;
 
-		map = __populate_section_memmap(pfn, PAGES_PER_SECTION,
-						nid, NULL, NULL);
-		if (!map)
-			panic("Failed to allocate memmap for section %lu\n", pnum);
+		mem_map = __populate_section_memmap(pfn, PAGES_PER_SECTION, nid,
+						    NULL, NULL);
+		if (!mem_map)
+			panic("Failed to allocate memmap for section %lu\n",
+			      section_nr);
 		memmap_boot_pages_add(section_nr_vmemmap_pages(pfn, PAGES_PER_SECTION));
-		sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage,
-					SECTION_IS_EARLY);
+		sparse_init_one_section(__nr_to_section(section_nr), section_nr,
+					mem_map, usage, SECTION_IS_EARLY);
 		usage = (void *)usage + mem_section_usage_size();
 	}
 }
@@ -268,12 +265,14 @@ static void __init sparse_metadata_init(void)
 			nr_sections++;
 			continue;
 		}
-		sparse_init_nid(nid_begin, start_section_nr, section_nr, nr_sections);
+		sparse_metadata_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);
+	sparse_metadata_init_nid(nid_begin, start_section_nr, section_nr,
+				 nr_sections);
 }
 
 /*

-- 
2.43.0

[PATCH v2 05/13] mm/sparse: cleanup sparse_init_one_section()

[David Hildenbrand (Arm)]

Let's avoid the "pnum" terminology.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/sparse.h b/mm/sparse.h
index 530692cdd516f..4ee507c34b98d 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -20,7 +20,7 @@ void sparse_sections_init(void);
 int sparse_index_init(unsigned long section_nr, int nid);
 
 static inline void sparse_init_one_section(struct mem_section *ms,
-		unsigned long pnum, struct page *mem_map,
+		unsigned long section_nr, struct page *mem_map,
 		struct mem_section_usage *usage, unsigned long flags)
 {
 	unsigned long coded_mem_map;
@@ -32,7 +32,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 	 * page_to_pfn() on !CONFIG_SPARSEMEM_VMEMMAP can simply subtract it
 	 * from the page pointer to obtain the PFN.
 	 */
-	coded_mem_map = (unsigned long)(mem_map - section_nr_to_pfn(pnum));
+	coded_mem_map = (unsigned long)(mem_map - section_nr_to_pfn(section_nr));
 	VM_WARN_ON_ONCE(coded_mem_map & ~SECTION_MAP_MASK);
 
 	ms->section_mem_map &= ~SECTION_MAP_MASK;

-- 
2.43.0

[PATCH v2 06/13] mm/sparse: rename __highest_present_section_nr to __highest_used_section_nr

[David Hildenbrand (Arm)]

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

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@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(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ebbda6f311392..0c2fea48c261b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2181,7 +2181,7 @@ static inline struct mem_section *__pfn_to_section(unsigned long 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_pfn(unsigned long pfn, unsigned long end
 
 	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(unsigned long pfn)
 
 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;
 	}
diff --git a/mm/compaction.c b/mm/compaction.c
index 4994e200bbecd..f1b2060eb2016 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -216,7 +216,7 @@ static unsigned long skip_offline_sections(unsigned long start_pfn)
 	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);
 	}
diff --git a/mm/sparse.c b/mm/sparse.c
index 3c19d47559090..bb89017254f4d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -164,15 +164,11 @@ static void __init mminit_validate_memmodel_limits(unsigned long *start_pfn,
 }
 
 /*
- * 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)
 {
diff --git a/mm/sparse.h b/mm/sparse.h
index 4ee507c34b98d..242b7bab0013c 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -44,8 +44,8 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 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;
 }

-- 
2.43.0

[PATCH v2 07/13] mm/sparse: remove pfn_in_present_section()

[David Hildenbrand (Arm)]

Unused, let's remove it.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 include/linux/mmzone.h | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 0c2fea48c261b..a3937577fbfb2 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2326,13 +2326,6 @@ static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_
 
 #endif
 
-static inline int pfn_in_present_section(unsigned long pfn)
-{
-	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
-		return 0;
-	return present_section(__pfn_to_section(pfn));
-}
-
 static inline unsigned long next_present_section_nr(unsigned long section_nr)
 {
 	while (++section_nr <= __highest_used_section_nr) {
@@ -2362,9 +2355,6 @@ static inline unsigned long next_present_section_nr(unsigned long section_nr)
 #else
 #define pfn_to_nid(pfn)		(0)
 #endif
-
-#else
-#define pfn_in_present_section pfn_valid
 #endif /* CONFIG_SPARSEMEM */
 
 /*

-- 
2.43.0

[PATCH v2 08/13] mm/sparse: move __highest_used_section_nr handling

[David Hildenbrand (Arm)]

In preparation for removing __section_mark_present(), let's move
__highest_used_section_nr handling into its callers. Verify in
sparse_init_one_section() that it was properly updated.

In sparse_sections_init() we can just set it to the last processed
section_nr.

No functional change intended.

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse-vmemmap.c | 1 +
 mm/sparse.c         | 5 +++--
 mm/sparse.h         | 4 +---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 96506f594924c..e89efb67e8e6d 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -865,6 +865,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 		page_init_poison(memmap, sizeof(struct page) * nr_pages);
 
 	__section_mark_present(ms, section_nr);
+	__highest_used_section_nr = max(section_nr, __highest_used_section_nr);
 
 	/* Align memmap to section boundary in the subsection case */
 	if (section_nr_to_pfn(section_nr) != start_pfn)
diff --git a/mm/sparse.c b/mm/sparse.c
index bb89017254f4d..a0f50ca5acf5a 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -177,7 +177,7 @@ static inline unsigned long first_present_section_nr(void)
 
 void __init sparse_sections_init(void)
 {
-	unsigned long pfn, start_pfn, end_pfn;
+	unsigned long pfn, start_pfn, end_pfn, section_nr;
 	int i, nid;
 
 	sparse_extreme_init();
@@ -187,9 +187,9 @@ void __init sparse_sections_init(void)
 		mminit_validate_memmodel_limits(&start_pfn, &end_pfn);
 
 		for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
-			unsigned long section_nr = pfn_to_section_nr(pfn);
 			struct mem_section *ms;
 
+			section_nr = pfn_to_section_nr(pfn);
 			sparse_index_init(section_nr, nid);
 			ms = __nr_to_section(section_nr);
 			if (ms->section_mem_map)
@@ -201,6 +201,7 @@ void __init sparse_sections_init(void)
 			__section_mark_present(ms, section_nr);
 		}
 	}
+	__highest_used_section_nr = section_nr;
 }
 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 struct page __init *__populate_section_memmap(unsigned long pfn,
diff --git a/mm/sparse.h b/mm/sparse.h
index 242b7bab0013c..c396d5c05cfc8 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -26,6 +26,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 	unsigned long coded_mem_map;
 
 	BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
+	VM_WARN_ON_ONCE(section_nr > __highest_used_section_nr);
 
 	/*
 	 * We encode the start PFN of the section into the mem_map such that
@@ -44,9 +45,6 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 static inline void __section_mark_present(struct mem_section *ms,
 		unsigned long section_nr)
 {
-	if (section_nr > __highest_used_section_nr)
-		__highest_used_section_nr = section_nr;
-
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 }
 

-- 
2.43.0

Re: [PATCH v2 08/13] mm/sparse: move __highest_used_section_nr handling

[Oscar Salvador (SUSE)]

On Mon, Sep 21, 2026 at 09:59:00PM +0200, David Hildenbrand (Arm) wrote:
> In preparation for removing __section_mark_present(), let's move
> __highest_used_section_nr handling into its callers. Verify in
> sparse_init_one_section() that it was properly updated.
> 
> In sparse_sections_init() we can just set it to the last processed
> section_nr.
> 
> No functional change intended.
> 
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Acked-by: Oscar Salvador <osalvador@suse.de>

> ---
...
> --- a/mm/sparse.h
> +++ b/mm/sparse.h
> @@ -26,6 +26,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
>  	unsigned long coded_mem_map;
>  
>  	BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
> +	VM_WARN_ON_ONCE(section_nr > __highest_used_section_nr);

I wonder, have we seen this in the wild?



-- 
Oscar Salvador
SUSE Labs

[PATCH v2 09/13] scripts/gdb: mm.py: remove fallbacks for SECTION_HAS_MEM_MAP and SECTION_IS_EARLY

[David Hildenbrand (Arm)]

There is no reason to handle the absence of the corresponding BIT
values. So let's remove the fallbacks.

Link: https://lore.kernel.org/r/vpz5zqg5nwbpolxbkip45vxxdt3lni7j2haal7q42skc3b57tu@uh4cec4x32dq
Cc: Seongjun Hong <hsj0512@snu.ac.kr>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 scripts/gdb/linux/mm.py | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/scripts/gdb/linux/mm.py b/scripts/gdb/linux/mm.py
index 193a88d763abf..7398105ff3f67 100644
--- a/scripts/gdb/linux/mm.py
+++ b/scripts/gdb/linux/mm.py
@@ -71,12 +71,8 @@ class x86_page_ops():
 
         self.NR_SECTION_ROOTS = DIV_ROUND_UP(self.NR_MEM_SECTIONS, self.SECTIONS_PER_ROOT)
 
-        try:
-            self.SECTION_HAS_MEM_MAP = 1 << int(gdb.parse_and_eval('SECTION_HAS_MEM_MAP_BIT'))
-            self.SECTION_IS_EARLY = 1 << int(gdb.parse_and_eval('SECTION_IS_EARLY_BIT'))
-        except:
-            self.SECTION_HAS_MEM_MAP = 1 << 0
-            self.SECTION_IS_EARLY = 1 << 3
+        self.SECTION_HAS_MEM_MAP = 1 << int(gdb.parse_and_eval('SECTION_HAS_MEM_MAP_BIT'))
+        self.SECTION_IS_EARLY = 1 << int(gdb.parse_and_eval('SECTION_IS_EARLY_BIT'))
 
         self.SUBSECTION_SHIFT = 21
         self.PAGES_PER_SUBSECTION = 1 << (self.SUBSECTION_SHIFT - self.PAGE_SHIFT)

-- 
2.43.0

[PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT

[David Hildenbrand (Arm)]

All present section iterators run before memory hotplug added any
further memory sections, Therefore, we can simply use the SECTION_IS_EARLY
flag by setting that flag earlier in sparse_sections_init().

Get rid of SECTION_MARKED_PRESENT entirely and rename
for_each_present_section_nr() to for_each_early_section_nr().

Take care of the .clang-format for_each_present_section_nr() handling.

No functional change intended.

Acked-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 .clang-format          |  2 +-
 drivers/base/memory.c  |  2 +-
 include/linux/mmzone.h | 27 ++++++++++-----------------
 mm/sparse-vmemmap.c    |  1 -
 mm/sparse.c            | 17 ++++++++---------
 mm/sparse.h            |  6 ------
 6 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/.clang-format b/.clang-format
index 5ef5743b77c95..395292ab2ac63 100644
--- a/.clang-format
+++ b/.clang-format
@@ -282,6 +282,7 @@ ForEachMacros:
   - 'for_each_dpcm_fe'
   - 'for_each_drhd_unit'
   - 'for_each_dss_dev'
+  - 'for_each_early_section_nr'
   - 'for_each_efi_memory_desc'
   - 'for_each_efi_memory_desc_in_map'
   - 'for_each_element'
@@ -403,7 +404,6 @@ ForEachMacros:
   - 'for_each_possible_cpu_wrap'
   - 'for_each_present_blessed_reg'
   - 'for_each_present_cpu'
-  - 'for_each_present_section_nr'
   - 'for_each_prime_number'
   - 'for_each_prime_number_from'
   - 'for_each_probe_cache_entry'
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 5eead3346f1e3..b0338de2f1d82 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -972,7 +972,7 @@ void __init memory_dev_init(void)
 	 * block so that it can be covered.
 	 */
 	block_id = ULONG_MAX;
-	for_each_present_section_nr(0, nr) {
+	for_each_early_section_nr(0, nr) {
 		if (block_id != ULONG_MAX && memory_block_id(nr) == block_id)
 			continue;
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a3937577fbfb2..73d9781cc1510 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2085,7 +2085,6 @@ static inline struct mem_section *__nr_to_section(unsigned long nr)
  * accommodate SECTION_MAP_LAST_BIT. We use BUILD_BUG_ON() to ensure this.
  */
 enum {
-	SECTION_MARKED_PRESENT_BIT,
 	SECTION_HAS_MEM_MAP_BIT,
 	SECTION_IS_ONLINE_BIT,
 	SECTION_IS_EARLY_BIT,
@@ -2095,7 +2094,6 @@ enum {
 	SECTION_MAP_LAST_BIT,
 };
 
-#define SECTION_MARKED_PRESENT		BIT(SECTION_MARKED_PRESENT_BIT)
 #define SECTION_HAS_MEM_MAP		BIT(SECTION_HAS_MEM_MAP_BIT)
 #define SECTION_IS_ONLINE		BIT(SECTION_IS_ONLINE_BIT)
 #define SECTION_IS_EARLY		BIT(SECTION_IS_EARLY_BIT)
@@ -2112,16 +2110,6 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section)
 	return (struct page *)map;
 }
 
-static inline int present_section(const struct mem_section *section)
-{
-	return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
-}
-
-static inline int present_section_nr(unsigned long nr)
-{
-	return present_section(__nr_to_section(nr));
-}
-
 static inline int valid_section(const struct mem_section *section)
 {
 	return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
@@ -2137,6 +2125,11 @@ static inline int valid_section_nr(unsigned long nr)
 	return valid_section(__nr_to_section(nr));
 }
 
+static inline int early_section_nr(unsigned long nr)
+{
+	return early_section(__nr_to_section(nr));
+}
+
 static inline int online_section(const struct mem_section *section)
 {
 	return (section && (section->section_mem_map & SECTION_IS_ONLINE));
@@ -2326,20 +2319,20 @@ static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_
 
 #endif
 
-static inline unsigned long next_present_section_nr(unsigned long section_nr)
+static inline unsigned long next_early_section_nr(unsigned long section_nr)
 {
 	while (++section_nr <= __highest_used_section_nr) {
-		if (present_section_nr(section_nr))
+		if (early_section_nr(section_nr))
 			return section_nr;
 	}
 
 	return -1;
 }
 
-#define for_each_present_section_nr(start, section_nr)		\
-	for (section_nr = next_present_section_nr(start - 1);	\
+#define for_each_early_section_nr(start, section_nr)		\
+	for (section_nr = next_early_section_nr(start - 1);	\
 	     section_nr != -1;					\
-	     section_nr = next_present_section_nr(section_nr))
+	     section_nr = next_early_section_nr(section_nr))
 
 /*
  * These are _only_ used during initialisation, therefore they
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index e89efb67e8e6d..f0db433e0f10b 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -864,7 +864,6 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 	if (!section_vmemmap_optimizable(ms))
 		page_init_poison(memmap, sizeof(struct page) * nr_pages);
 
-	__section_mark_present(ms, section_nr);
 	__highest_used_section_nr = max(section_nr, __highest_used_section_nr);
 
 	/* Align memmap to section boundary in the subsection case */
diff --git a/mm/sparse.c b/mm/sparse.c
index a0f50ca5acf5a..5d2d9f95d4024 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -170,13 +170,14 @@ static void __init mminit_validate_memmodel_limits(unsigned long *start_pfn,
  */
 unsigned long __highest_used_section_nr;
 
-static inline unsigned long first_present_section_nr(void)
+static inline unsigned long first_early_section_nr(void)
 {
-	return next_present_section_nr(-1);
+	return next_early_section_nr(-1);
 }
 
 void __init sparse_sections_init(void)
 {
+	const unsigned long flags = SECTION_IS_EARLY | SECTION_IS_ONLINE;
 	unsigned long pfn, start_pfn, end_pfn, section_nr;
 	int i, nid;
 
@@ -196,9 +197,7 @@ void __init sparse_sections_init(void)
 				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);
+			ms->section_mem_map = sparse_encode_early_nid(nid) | flags;
 		}
 	}
 	__highest_used_section_nr = section_nr;
@@ -230,7 +229,7 @@ static void __init sparse_metadata_init_nid(int nid,
 	if (!usage)
 		panic("Failed to allocate usemap for node %d\n", nid);
 
-	for_each_present_section_nr(start_section_nr, section_nr) {
+	for_each_early_section_nr(start_section_nr, section_nr) {
 		const unsigned long pfn = section_nr_to_pfn(section_nr);
 		struct page *mem_map;
 
@@ -244,18 +243,18 @@ static void __init sparse_metadata_init_nid(int nid,
 			      section_nr);
 		memmap_boot_pages_add(section_nr_vmemmap_pages(pfn, PAGES_PER_SECTION));
 		sparse_init_one_section(__nr_to_section(section_nr), section_nr,
-					mem_map, usage, SECTION_IS_EARLY);
+					mem_map, usage, 0);
 		usage = (void *)usage + mem_section_usage_size();
 	}
 }
 
 static void __init sparse_metadata_init(void)
 {
-	unsigned long start_section_nr = first_present_section_nr();
+	unsigned long start_section_nr = first_early_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) {
+	for_each_early_section_nr(start_section_nr + 1, section_nr) {
 		const int nid = sparse_early_nid(__nr_to_section(section_nr));
 
 		if (nid == nid_begin) {
diff --git a/mm/sparse.h b/mm/sparse.h
index c396d5c05cfc8..19664d702af84 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -42,12 +42,6 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 	ms->usage = usage;
 }
 
-static inline void __section_mark_present(struct mem_section *ms,
-		unsigned long section_nr)
-{
-	ms->section_mem_map |= SECTION_MARKED_PRESENT;
-}
-
 static inline size_t mem_section_usage_size(void)
 {
 	return struct_size_t(struct mem_section_usage, pageblock_flags,

-- 
2.43.0

[PATCH v2 11/13] mm/sparse: remove flags parameter from sparse_init_one_section()

[David Hildenbrand (Arm)]

The last user of the flags parameter that used to pass SECTION_IS_EARLY
was removed, so let's remove the parameter.

Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse-vmemmap.c | 2 +-
 mm/sparse.c         | 2 +-
 mm/sparse.h         | 5 ++---
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index f0db433e0f10b..3267f9362c68b 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -869,7 +869,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 	/* Align memmap to section boundary in the subsection case */
 	if (section_nr_to_pfn(section_nr) != start_pfn)
 		memmap = pfn_to_page(section_nr_to_pfn(section_nr));
-	sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
+	sparse_init_one_section(ms, section_nr, memmap, ms->usage);
 
 	return 0;
 }
diff --git a/mm/sparse.c b/mm/sparse.c
index 5d2d9f95d4024..702904b417006 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -243,7 +243,7 @@ static void __init sparse_metadata_init_nid(int nid,
 			      section_nr);
 		memmap_boot_pages_add(section_nr_vmemmap_pages(pfn, PAGES_PER_SECTION));
 		sparse_init_one_section(__nr_to_section(section_nr), section_nr,
-					mem_map, usage, 0);
+					mem_map, usage);
 		usage = (void *)usage + mem_section_usage_size();
 	}
 }
diff --git a/mm/sparse.h b/mm/sparse.h
index 19664d702af84..fdbc4cacf91d1 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -21,7 +21,7 @@ int sparse_index_init(unsigned long section_nr, int nid);
 
 static inline void sparse_init_one_section(struct mem_section *ms,
 		unsigned long section_nr, struct page *mem_map,
-		struct mem_section_usage *usage, unsigned long flags)
+		struct mem_section_usage *usage)
 {
 	unsigned long coded_mem_map;
 
@@ -37,8 +37,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 	VM_WARN_ON_ONCE(coded_mem_map & ~SECTION_MAP_MASK);
 
 	ms->section_mem_map &= ~SECTION_MAP_MASK;
-	ms->section_mem_map |= coded_mem_map;
-	ms->section_mem_map |= flags | SECTION_HAS_MEM_MAP;
+	ms->section_mem_map |= coded_mem_map | SECTION_HAS_MEM_MAP;
 	ms->usage = usage;
 }
 

-- 
2.43.0

[PATCH v2 12/13] fs/proc/page: clarify comment in get_max_dump_pfn()

[David Hildenbrand (Arm)]

pfn_to_online_page() will only succeed on some PFNs within the same
section, not necessarily all. Let's make that clearer.

While at it, rephrase it to "Allow inspection of".

Acked-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 fs/proc/page.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/proc/page.c b/fs/proc/page.c
index f90e1030825e9..6aa99e42ec222 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -31,10 +31,9 @@ static inline unsigned long get_max_dump_pfn(void)
 {
 #ifdef CONFIG_SPARSEMEM
 	/*
-	 * The memmap of early sections is completely populated and marked
-	 * online even if max_pfn does not fall on a section boundary -
-	 * pfn_to_online_page() will succeed on all pages. Allow inspecting
-	 * these memmaps.
+	 * If max_pfn does not fall on a section boundary, pfn_to_online_page()
+	 * can succeed on PFNs beyond max_pfn within the same section. Allow
+	 * inspection of these memmaps.
 	 */
 	return round_up(max_pfn, PAGES_PER_SECTION);
 #else

-- 
2.43.0

[PATCH v2 13/13] mm/memory_hotplug: drop CONFIG_HAVE_ARCH_PFN_VALID handling from pfn_to_online_page()

[David Hildenbrand (Arm)]

Drop CONFIG_HAVE_ARCH_PFN_VALID handling, as CONFIG_HAVE_ARCH_PFN_VALID
is never used with CONFIG_MEMORY_HOTPLUG, as the latter depends on
CONFIG_SPARSEMEM_VMEMMAP. Make sure it stays that way.

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/memory_hotplug.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index d7a59167bec43..796af1028ee23 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -345,6 +345,8 @@ struct page *pfn_to_online_page(unsigned long pfn)
 	struct dev_pagemap *pgmap;
 	struct mem_section *ms;
 
+	BUILD_BUG_ON(IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID));
+
 	if (nr >= NR_MEM_SECTIONS)
 		return NULL;
 
@@ -352,13 +354,6 @@ struct page *pfn_to_online_page(unsigned long pfn)
 	if (!online_section(ms))
 		return NULL;
 
-	/*
-	 * Save some code text when online_section() +
-	 * pfn_section_valid() are sufficient.
-	 */
-	if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn))
-		return NULL;
-
 	if (!pfn_section_valid(ms, pfn))
 		return NULL;
 

-- 
2.43.0

Re: [PATCH v2 13/13] mm/memory_hotplug: drop CONFIG_HAVE_ARCH_PFN_VALID handling from pfn_to_online_page()

[Oscar Salvador (SUSE)]

On Mon, Sep 21, 2026 at 09:59:05PM +0200, David Hildenbrand (Arm) wrote:
> Drop CONFIG_HAVE_ARCH_PFN_VALID handling, as CONFIG_HAVE_ARCH_PFN_VALID
> is never used with CONFIG_MEMORY_HOTPLUG, as the latter depends on
> CONFIG_SPARSEMEM_VMEMMAP. Make sure it stays that way.
> 
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Acked-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH v2 00/13] mm/sparse: remove SECTION_MARKED_PRESENT and further cleanups

[Andrew Morton]

On Mon, 21 Sep 2026 21:58:52 +0200 "David Hildenbrand (Arm)" <david@kernel.org> wrote:

> SECTION_MARKED_PRESENT is really only needed during boot, where we
> can instead just rely on SECTION_IS_EARLY_BIT by setting that flag
> earlier.
> 
> Some preparations for doing that conversion and some cleanups in the same
> (sparse) area.

Added to mm-new, thanks.