[PATCH v3 0/8] treewide: remove unnecessary invalid range checks in memblock iteration loops

[PATCH v3 0/8] treewide: remove unnecessary invalid range checks in memblock iteration loops

[Sang-Heon Jeon]

The memblock API guarantees that for_each_mem_range() and
for_each_mem_pfn_range() never return an invalid range, meaning start is
always less than end.

Several memblock callers still have unnecessary invalid range checks in
their loop bodies, so remove them.

Patches 1-6 cover for_each_mem_range() callers. memblock never stores a
zero-size region, so the range it returns always has start < end. Some
callers apply __va() or __phys_to_virt() before comparing, but these keep
start < end too, so the check is unreachable.

Patches 7-8 cover for_each_mem_pfn_range() callers. __next_mem_pfn_range()
skips any region that contains no whole page, so it only ever returns
start_pfn < end_pfn and the check is unnecessary.

For reference, commit 36ca7f4be809 ("arm64: mm: Remove bogus stop
condition from map_mem() loop") did a similar cleanup in arm64 map_mem().

All these checks are in different trees, so I split the change into one
patch per arch/subsystem. The patches are independent and can be applied
separately.

---
Changes from v1 [1]
- Add review-by, tested-by tags from v1
- Add missing simliar patches(5,6) to patch series
- Change base to rppt/for-next

Changes from v2 [2]
- Remove unused local variable and braces

[1] https://lore.kernel.org/all/20260621145919.1453-1-ekffu200098@gmail.com/
[2] https://lore.kernel.org/all/20260629163736.1606688-1-ekffu200098@gmail.com/
---

Sang-Heon Jeon (8):
  arm64: mm: remove unreachable invalid range check in
    kasan_init_shadow()
  LoongArch: remove unreachable invalid range check in kasan_init()
  riscv: remove unreachable invalid range check in
    create_linear_mapping_page_table()
  riscv: remove unreachable invalid range check in kasan_init()
  ARM: remove unreachable invalid range check in kasan_init()
  powerpc64/kasan: Remove unreachable invalid range check in
    kasan_init_phys_region()
  mm: remove unnecessary empty range check in
    early_calculate_totalpages()
  mm/hugetlb: remove unnecessary empty range check in
    hugetlb_bootmem_set_nodes()

 arch/arm/mm/kasan_init.c               | 6 ------
 arch/arm64/mm/kasan_init.c             | 3 ---
 arch/loongarch/mm/kasan_init.c         | 3 ---
 arch/powerpc/mm/kasan/init_book3e_64.c | 3 ---
 arch/powerpc/mm/kasan/init_book3s_64.c | 3 ---
 arch/riscv/mm/init.c                   | 2 --
 arch/riscv/mm/kasan_init.c             | 3 ---
 mm/hugetlb.c                           | 7 ++-----
 mm/mm_init.c                           | 3 +--
 9 files changed, 3 insertions(+), 30 deletions(-)

-- 
2.43.0

[PATCH v3 1/8] arm64: mm: remove unreachable invalid range check in kasan_init_shadow()

[Sang-Heon Jeon]

kasan_init_shadow() maps each memblock region with for_each_mem_range()
and breaks the loop when start >= end. for_each_mem_range() never returns
an invalid range, so start < end always.

Therefore the start >= end check is unreachable, so remove it.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Reviewed-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
---
 arch/arm64/mm/kasan_init.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 3fcad956fdf7..45fbdce684c8 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -353,9 +353,6 @@ static void __init kasan_init_shadow(void)
 		void *start = (void *)__phys_to_virt(pa_start);
 		void *end = (void *)__phys_to_virt(pa_end);
 
-		if (start >= end)
-			break;
-
 		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
 				   (unsigned long)kasan_mem_to_shadow(end),
 				   early_pfn_to_nid(virt_to_pfn(start)));
-- 
2.43.0

[PATCH v3 5/8] ARM: remove unreachable invalid range check in kasan_init()

[Sang-Heon Jeon]

kasan_init() maps each memblock region with for_each_mem_range(), which
guarantees pa_start < pa_end. Then it skips any region with
pa_start >= arm_lowmem_limit, so pa_start < arm_lowmem_limit is guaranteed
as well.

When pa_end <= arm_lowmem_limit, pa_start < pa_end means start < end, so
the start >= end check is unreachable.

When pa_end > arm_lowmem_limit, end is clamped to __va(arm_lowmem_limit),
and pa_start < arm_lowmem_limit means start < end, so the check is
unreachable as well.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 arch/arm/mm/kasan_init.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
index c6625e808bf8..1f7c74c5df9e 100644
--- a/arch/arm/mm/kasan_init.c
+++ b/arch/arm/mm/kasan_init.c
@@ -262,12 +262,6 @@ void __init kasan_init(void)
 				&pa_start, &pa_end, &arm_lowmem_limit);
 			end = __va(arm_lowmem_limit);
 		}
-		if (start >= end) {
-			pr_info("Skipping invalid memory block %pa-%pa (virtual %p-%p)\n",
-				&pa_start, &pa_end, start, end);
-			continue;
-		}
-
 		create_mapping(start, end);
 	}
 
-- 
2.43.0

Re: [PATCH v3 0/8] treewide: remove unnecessary invalid range checks in memblock iteration loops

[Mike Rapoport]

On Wed, 01 Jul 2026 00:04:05 +0900, Sang-Heon Jeon wrote:
> treewide: remove unnecessary invalid range checks in memblock iteration loops
> 
> The memblock API guarantees that for_each_mem_range() and
> for_each_mem_pfn_range() never return an invalid range, meaning start is
> always less than end.
> 
> Several memblock callers still have unnecessary invalid range checks in
> their loop bodies, so remove them.
> 
> [...]

Applied to range-checks branch of memblock.git tree, thanks!

[1/8] arm64: mm: remove unreachable invalid range check in kasan_init_shadow()
      commit: f6e6c57f2e100813be6d5882060fef81cb6f32de
[2/8] LoongArch: remove unreachable invalid range check in kasan_init()
      commit: 68d3b7d58237b8794d9343210d4c90b8381cfa96
[3/8] riscv: remove unreachable invalid range check in create_linear_mapping_page_table()
      commit: 99e60ebe108817fd48791f2cb81f1e672ad8285b
[4/8] riscv: remove unreachable invalid range check in kasan_init()
      commit: 8008f6995d0c0cf22e7b4d60e95fe14085c10f35
[5/8] ARM: remove unreachable invalid range check in kasan_init()
      commit: 3db1a9ccf9290ea3fe01aadf3bd743ef7032b24a
[6/8] powerpc64/kasan: Remove unreachable invalid range check in kasan_init_phys_region()
      commit: 21e95a4b6f34770571eeeaa6adb535efba1b7281
[7/8] mm: remove unnecessary empty range check in early_calculate_totalpages()
      commit: c6af91e48594191f62ad3c1fcc8269b1eb539ef8
[8/8] mm/hugetlb: remove unnecessary empty range check in hugetlb_bootmem_set_nodes()
      commit: 2db44dc8bdd3cfc933a3193724f4d38b03e35b80

tree: https://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock
branch: range-checks

--
Sincerely yours,
Mike.