[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

[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 <ekffu...@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

[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 <ekffu...@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

[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 <ekffu...@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

[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 <ekffu...@gmail.com>

Reviewed-by: Charlie Jenkins <thecharl...@gmail.com>
Tested-by: Charlie Jenkins <thecharl...@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
>
>

> _______________________________________________
> linux-riscv mailing list
> linux...@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
>

[Andrey Ryabinin]

Sang-Heon Jeon <ekffu...@gmail.com> writes:

> 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 <ekffu...@gmail.com>
> ---
> arch/arm64/mm/kasan_init.c | 3 ---
> 1 file changed, 3 deletions(-)
>

Reviewed-by: Andrey Ryabinin <ryabin...@gmail.com>

[Andrey Ryabinin]

Sang-Heon Jeon <ekffu...@gmail.com> writes:

> 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 <ekffu...@gmail.com>
> ---
> arch/loongarch/mm/kasan_init.c | 3 ---
> 1 file changed, 3 deletions(-)
>

Reviewed-by: Andrey Ryabinin <ryabin...@gmail.com>

[Andrey Ryabinin]

Sang-Heon Jeon <ekffu...@gmail.com> writes:

> 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 <ekffu...@gmail.com>
> ---
> arch/riscv/mm/kasan_init.c | 3 ---
> 1 file changed, 3 deletions(-)
>

Reviewed-by: Andrey Ryabinin <ryabin...@gmail.com>

[Mike Rapoport]

On Sun, 21 Jun 2026 23:59:10 +0900, Sang-Heon Jeon <ekffu...@gmail.com> 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.
>

> [...]

Acked-by: Mike Rapoport (Microsoft) <rp...@kernel.org>

--
Sincerely yours,
Mike.

[Mike Rapoport]

On Sun, Jun 21, 2026 at 11:59:10PM +0900, Sang-Heon Jeon wrote:
> 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.
>

> 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()

I queued this for inclusion into memblock tree.

> 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
>

--
Sincerely yours,
Mike.

[Sang-Heon Jeon]

On Fri, Jun 26, 2026 at 5:23 PM Mike Rapoport <rp...@kernel.org> wrote:
>
> On Sun, Jun 21, 2026 at 11:59:10PM +0900, Sang-Heon Jeon wrote:
> > 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.
> >
> > 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()
>
> I queued this for inclusion into memblock tree.

Thank you, Mike.

Could you please review and queue this patch [1] as well? It does the
same kind of clean up, I just missed it at the time.

[1] https://lore.kernel.org/all/20260626032902.70...@gmail.com/

> > 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
> >
>
> --
> Sincerely yours,
> Mike.

Best Regards,
Sang-Heon Jeon

[Mike Rapoport]

On Fri, Jun 26, 2026 at 07:59:22PM +0900, Sang-Heon Jeon wrote:
> On Fri, Jun 26, 2026 at 5:23 PM Mike Rapoport <rp...@kernel.org> wrote:
> >
> > On Sun, Jun 21, 2026 at 11:59:10PM +0900, Sang-Heon Jeon wrote:
> > > 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.
> > >
> > > 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()
> >
> > I queued this for inclusion into memblock tree.
>
> Thank you, Mike.
>
> Could you please review and queue this patch [1] as well? It does the
> same kind of clean up, I just missed it at the time.

Can you please resend them all as a single set?

> [1] https://lore.kernel.org/all/20260626032902.70...@gmail.com/
>
> > > 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
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
>
> Best Regards,
> Sang-Heon Jeon

--
Sincerely yours,
Mike.

[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

[1] https://lore.kernel.org/all/20260621145919.1...@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 | 3 +--
mm/mm_init.c | 3 +--

9 files changed, 2 insertions(+), 27 deletions(-)

--
2.43.0

[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 <ekffu...@gmail.com>

Reviewed-by: Andrey Ryabinin <ryabin...@gmail.com>
---
arch/arm64/mm/kasan_init.c | 3 ---

1 file changed, 3 deletions(-)

[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 <ekffu...@gmail.com>
Reviewed-by: Andrey Ryabinin <ryabin...@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;
-

[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 <ekffu...@gmail.com>

Reviewed-by: Charlie Jenkins <thecharl...@gmail.com>
Tested-by: Charlie Jenkins <thecharl...@gmail.com>

Reviewed-by: Andrey Ryabinin <ryabin...@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

[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 <ekffu...@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

[Sang-Heon Jeon]

Thanks for considering, Mike.
I've sent v2 patch series [1] that includes the missing patches.

[1] https://lore.kernel.org/all/20260629163736.160...@gmail.com/#t

> > [1] https://lore.kernel.org/all/20260626032902.70...@gmail.com/
> >
> > > > 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
> > > >
> > >
> > > --
> > > Sincerely yours,
> > > Mike.
> >
> > Best Regards,
> > Sang-Heon Jeon
>
> --
> Sincerely yours,
> Mike.

Best Regards,
Sang-Heon Jeon