[PATCH 0/6] treewide: remove unnecessary invalid range checks in memblock iteration loops

[PATCH 0/6] 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 1-4 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 5-6 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.

Sang-Heon Jeon (6):
  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()
  mm: remove unnecessary empty range check in
    early_calculate_totalpages()
  mm/hugetlb: remove unnecessary empty range check in
    hugetlb_bootmem_set_nodes()

 arch/arm64/mm/kasan_init.c     | 3 ---
 arch/loongarch/mm/kasan_init.c | 3 ---
 arch/riscv/mm/init.c           | 2 --
 arch/riscv/mm/kasan_init.c     | 3 ---
 mm/hugetlb.c                   | 3 +--
 mm/mm_init.c                   | 3 +--
 6 files changed, 2 insertions(+), 15 deletions(-)

-- 
2.43.0

[PATCH 0/6] 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 1-4 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 5-6 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.

Sang-Heon Jeon (6):
  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()
  mm: remove unnecessary empty range check in
    early_calculate_totalpages()
  mm/hugetlb: remove unnecessary empty range check in
    hugetlb_bootmem_set_nodes()

 arch/arm64/mm/kasan_init.c     | 3 ---
 arch/loongarch/mm/kasan_init.c | 3 ---
 arch/riscv/mm/init.c           | 2 --
 arch/riscv/mm/kasan_init.c     | 3 ---
 mm/hugetlb.c                   | 3 +--
 mm/mm_init.c                   | 3 +--
 6 files changed, 2 insertions(+), 15 deletions(-)

-- 
2.43.0


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[PATCH 1/6] 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>
---
 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 2/6] LoongArch: remove unreachable invalid range check in kasan_init()

[Sang-Heon Jeon]

kasan_init() populates the linear mapping shadow 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>
---
 arch/loongarch/mm/kasan_init.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
index 0fc02ca06457..92ca0ba86406 100644
--- a/arch/loongarch/mm/kasan_init.c
+++ b/arch/loongarch/mm/kasan_init.c
@@ -305,9 +305,6 @@ void __init kasan_init(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)mem_to_shadow(start),
 			(unsigned long)mem_to_shadow(end), NUMA_NO_NODE);
 	}
-- 
2.43.0

[PATCH 3/6] riscv: remove unreachable invalid range check in create_linear_mapping_page_table()

[Sang-Heon Jeon]

create_linear_mapping_page_table() iterates memblock regions 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>
---
 arch/riscv/mm/init.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 5b1b3c88b4d1..eb93c2ac05a6 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1229,8 +1229,6 @@ static void __init create_linear_mapping_page_table(void)
 
 	/* Map all memory banks in the linear mapping */
 	for_each_mem_range(i, &start, &end) {
-		if (start >= end)
-			break;
 		if (start <= __pa(PAGE_OFFSET) &&
 		    __pa(PAGE_OFFSET) < end)
 			start = __pa(PAGE_OFFSET);
-- 
2.43.0


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[PATCH 4/6] riscv: remove unreachable invalid range check in kasan_init()

[Sang-Heon Jeon]

kasan_init() populates the linear mapping shadow 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>
---
 arch/riscv/mm/kasan_init.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index c4a2a9e5586e..1f3aa9611187 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -512,9 +512,6 @@ void __init kasan_init(void)
 		void *start = (void *)__va(p_start);
 		void *end = (void *)__va(p_end);
 
-		if (start >= end)
-			break;
-
 		kasan_populate(kasan_mem_to_shadow(start), kasan_mem_to_shadow(end));
 	}
 
-- 
2.43.0


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[PATCH 5/6] mm: remove unnecessary empty range check in early_calculate_totalpages()

[Sang-Heon Jeon]

early_calculate_totalpages() iterates the memory ranges with
for_each_mem_pfn_range() and calls node_set_state(nid, N_MEMORY) only when
end_pfn - start_pfn is non-zero. for_each_mem_pfn_range() never returns an
empty range, so start_pfn < end_pfn always.

Therefore the check is unnecessary, so remove it.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 mm/mm_init.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 0f64909e8d20..17498a13eb99 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -332,8 +332,7 @@ static unsigned long __init early_calculate_totalpages(void)
 		unsigned long pages = end_pfn - start_pfn;
 
 		totalpages += pages;
-		if (pages)
-			node_set_state(nid, N_MEMORY);
+		node_set_state(nid, N_MEMORY);
 	}
 	return totalpages;
 }
-- 
2.43.0

[PATCH 6/6] mm/hugetlb: remove unnecessary empty range check in hugetlb_bootmem_set_nodes()

[Sang-Heon Jeon]

hugetlb_bootmem_set_nodes() iterates the memory ranges with
for_each_mem_pfn_range() and calls node_set(nid, hugetlb_bootmem_nodes)
only when end_pfn > start_pfn. for_each_mem_pfn_range() never returns an
empty range, so start_pfn < end_pfn always.

Therefore the check is unnecessary, so remove it.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 mm/hugetlb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 571212b80835..d4d4c9df5f51 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4450,8 +4450,7 @@ void __init hugetlb_bootmem_set_nodes(void)
 		return;
 
 	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
-		if (end_pfn > start_pfn)
-			node_set(nid, hugetlb_bootmem_nodes);
+		node_set(nid, hugetlb_bootmem_nodes);
 	}
 }
 
-- 
2.43.0

Re: [PATCH 3/6] riscv: remove unreachable invalid range check in create_linear_mapping_page_table()

[Charlie Jenkins]

On Sun, Jun 21, 2026 at 11:59:13PM +0900, Sang-Heon Jeon wrote:
> create_linear_mapping_page_table() iterates memblock regions 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: Charlie Jenkins <thecharlesjenkins@gmail.com>
Tested-by: Charlie Jenkins <thecharlesjenkins@gmail.com>

> ---
>  arch/riscv/mm/init.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 5b1b3c88b4d1..eb93c2ac05a6 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1229,8 +1229,6 @@ static void __init create_linear_mapping_page_table(void)
>  
>  	/* Map all memory banks in the linear mapping */
>  	for_each_mem_range(i, &start, &end) {
> -		if (start >= end)
> -			break;
>  		if (start <= __pa(PAGE_OFFSET) &&
>  		    __pa(PAGE_OFFSET) < end)
>  			start = __pa(PAGE_OFFSET);
> -- 
> 2.43.0
> 
> 
> _______________________________________________
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> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 

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Re: [PATCH 4/6] riscv: remove unreachable invalid range check in kasan_init()

[Charlie Jenkins]

On Sun, Jun 21, 2026 at 11:59:14PM +0900, Sang-Heon Jeon wrote:
> kasan_init() populates the linear mapping shadow 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: Charlie Jenkins <thecharlesjenkins@gmail.com>
Tested-by: Charlie Jenkins <thecharlesjenkins@gmail.com>

> ---
>  arch/riscv/mm/kasan_init.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> index c4a2a9e5586e..1f3aa9611187 100644
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@ -512,9 +512,6 @@ void __init kasan_init(void)
>  		void *start = (void *)__va(p_start);
>  		void *end = (void *)__va(p_end);
>  
> -		if (start >= end)
> -			break;
> -
>  		kasan_populate(kasan_mem_to_shadow(start), kasan_mem_to_shadow(end));
>  	}
>  
> -- 
> 2.43.0
> 
> 
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> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 

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Re: [PATCH 6/6] mm/hugetlb: remove unnecessary empty range check in hugetlb_bootmem_set_nodes()

[David Hildenbrand (Arm)]

On 6/21/26 16:59, Sang-Heon Jeon wrote:
> hugetlb_bootmem_set_nodes() iterates the memory ranges with
> for_each_mem_pfn_range() and calls node_set(nid, hugetlb_bootmem_nodes)
> only when end_pfn > start_pfn. for_each_mem_pfn_range() never returns an
> empty range, so start_pfn < end_pfn always.
> 
> Therefore the check is unnecessary, so remove it.
> 
> No functional change.
> 
> Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
> ---
>  mm/hugetlb.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 571212b80835..d4d4c9df5f51 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4450,8 +4450,7 @@ void __init hugetlb_bootmem_set_nodes(void)
>  		return;
>  
>  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
> -		if (end_pfn > start_pfn)
> -			node_set(nid, hugetlb_bootmem_nodes);
> +		node_set(nid, hugetlb_bootmem_nodes);
>  	}
>  }

We have

	if (PFN_UP(r->base) >= PFN_DOWN(r->base + r->size))
		continue;

...

*out_start_pfn = PFN_UP(r->base);
*out_end_pfn = PFN_DOWN(r->base + r->size);

So we should always have *out_start_pfn < *out_end_pfn

Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David