[PATCH v2 0/6] mm: add basic PTE const type-safety

[PATCH v2 0/6] mm: add basic PTE const type-safety

[Pedro Falcato]

Since forever, MM code has thrown pte_t * around with no concern for const
safety, or typesafety of any kind. This is confusing. Attempt to address it
by:
1) Making sure pte_get*() helpers can cope with const pte_t * arguments
2) Constifying the pte_offset_map_ro_nolock() return type, which by definition
already pledges that users will not write to it.

These two simple steps were already able to uncover code smell from
khugepaged + do_swap_page().

Separate steps could include introducing pte_offset_map_ro_lock() for more
widespread usage of this.

Benefits of this include less confusion and better type-safety. It could also
futurely aid in efforts such as [0] which may want semantic annotation of these
accesses.

Based on mm-unstable and compile-tested on a handful of architectures.

No functional changes intended.

[CC list editorially trimmed for brevity reasons; apologies if you're not on it]

Link: https://lore.kernel.org/linux-mm/20260526-kpkeys-v8-0-eaaacdacc67c@arm.com/#t [0]
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Liam R. Howlett" <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-mm@kvack.org
Cc: linux-fsdevel@vger.kernel.org

v2:
 - Small fixups on the arm64 side
 - Re-order patches in a way such that bisection is preserved
 - Pick up Helge's patch dropping parisc ptep_get()
 - Constify s390's ptep_get() as well

Helge Deller (1):
  parisc: Drop own implementations for ptep_get() and
    ptep_test_and_clear_young()

Pedro Falcato (5):
  mm/arm64: constify pte_get*() and contpte get logic
  mm/powerpc/8xx: constify ptep_get() argument
  mm/s390: constify ptep_get() argument
  mm: constify generic pte_get*()
  mm: constify the pte_offset_map_ro_nolock() return value

 arch/arm64/include/asm/pgtable.h             | 10 +++++-----
 arch/arm64/mm/contpte.c                      | 11 ++++++++---
 arch/parisc/include/asm/pgtable.h            | 20 --------------------
 arch/powerpc/include/asm/nohash/32/pte-8xx.h |  2 +-
 arch/powerpc/mm/pgtable.c                    |  2 +-
 arch/s390/include/asm/pgtable.h              |  2 +-
 include/linux/mm.h                           |  4 ++--
 include/linux/pgtable.h                      |  8 ++++----
 mm/filemap.c                                 |  2 +-
 mm/khugepaged.c                              |  2 +-
 mm/pgtable-generic.c                         |  4 ++--
 11 files changed, 26 insertions(+), 41 deletions(-)

-- 
2.55.0

[PATCH v2 1/6] mm/arm64: constify pte_get*() and contpte get logic

[Pedro Falcato]

None of the contpte code needs write access to the PTEs.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/arm64/include/asm/pgtable.h | 10 +++++-----
 arch/arm64/mm/contpte.c          | 11 ++++++++---
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a2681d755358..043bc0649cee 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -378,7 +378,7 @@ static inline void __set_pte(pte_t *ptep, pte_t pte)
 	__set_pte_complete(pte);
 }
 
-static inline pte_t __ptep_get(pte_t *ptep)
+static inline pte_t __ptep_get(const pte_t *ptep)
 {
 	return READ_ONCE(*ptep);
 }
@@ -1652,8 +1652,8 @@ extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte);
 extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte);
-extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte);
-extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep);
+extern pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte);
+extern pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep);
 extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, unsigned int nr);
 extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
@@ -1732,7 +1732,7 @@ static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte)
  */
 
 #define ptep_get ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
+static inline pte_t ptep_get(const pte_t *ptep)
 {
 	pte_t pte = __ptep_get(ptep);
 
@@ -1743,7 +1743,7 @@ static inline pte_t ptep_get(pte_t *ptep)
 }
 
 #define ptep_get_lockless ptep_get_lockless
-static inline pte_t ptep_get_lockless(pte_t *ptep)
+static inline pte_t ptep_get_lockless(const pte_t *ptep)
 {
 	pte_t pte = __ptep_get(ptep);
 
diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 2de12656b4d8..3a5d6937fb51 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -26,6 +26,11 @@ static inline pte_t *contpte_align_down(pte_t *ptep)
 	return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
 }
 
+#define contpte_align_down(ptep)                                                       \
+	_Generic((ptep),                                                               \
+		 const pte_t *: (const pte_t *) contpte_align_down((pte_t *) (ptep)),  \
+		 pte_t *: contpte_align_down((pte_t *) ptep))
+
 static inline pte_t *contpte_align_addr_ptep(unsigned long *start,
 					     unsigned long *end, pte_t *ptep,
 					     unsigned int nr)
@@ -310,7 +315,7 @@ void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL_GPL(__contpte_try_unfold);
 
-pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
+pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte)
 {
 	/*
 	 * Gather access/dirty bits, which may be populated in any of the ptes
@@ -367,7 +372,7 @@ static inline bool contpte_is_consistent(pte_t pte, unsigned long pfn,
 			pgprot_val(prot) == pgprot_val(orig_prot);
 }
 
-pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
+pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep)
 {
 	/*
 	 * The ptep_get_lockless() API requires us to read and return *orig_ptep
@@ -386,10 +391,10 @@ pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
 	 * because it is not part of a contpte range.
 	 */
 
+	const pte_t *ptep;
 	pgprot_t orig_prot;
 	unsigned long pfn;
 	pte_t orig_pte;
-	pte_t *ptep;
 	pte_t pte;
 	int i;
 
-- 
2.55.0

Re: [PATCH v2 1/6] mm/arm64: constify pte_get*() and contpte get logic

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:43:55PM +0100, Pedro Falcato wrote:
> None of the contpte code needs write access to the PTEs.

This seems like a very broad statement? Is that actually true? I see a bunch of
ptep's that aren't const-ified, so you should explain why those couldn't be
converted.

Also you add a new contpte_align_down() macro, you should mention that it the
commit message, explain why it was needed.

In general more needed here :) it'd be ok if it was a truly trivial change that
was all obvious but you're changing some pte_t *'s and not others so it's
clearly not.

>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>
> ---
>  arch/arm64/include/asm/pgtable.h | 10 +++++-----
>  arch/arm64/mm/contpte.c          | 11 ++++++++---
>  2 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index a2681d755358..043bc0649cee 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -378,7 +378,7 @@ static inline void __set_pte(pte_t *ptep, pte_t pte)
>  	__set_pte_complete(pte);
>  }
>
> -static inline pte_t __ptep_get(pte_t *ptep)
> +static inline pte_t __ptep_get(const pte_t *ptep)
>  {
>  	return READ_ONCE(*ptep);
>  }
> @@ -1652,8 +1652,8 @@ extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr,
>  				pte_t *ptep, pte_t pte);
>  extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
>  				pte_t *ptep, pte_t pte);
> -extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte);
> -extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep);
> +extern pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte);
> +extern pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep);

This is (very) nitty but - not sure on the policy on extern's (Will/Catalin?) -
but in mm we drop them when we touch the code since you don't need them these
days :)

>  extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
>  				pte_t *ptep, pte_t pte, unsigned int nr);
>  extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
> @@ -1732,7 +1732,7 @@ static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte)
>   */
>
>  #define ptep_get ptep_get
> -static inline pte_t ptep_get(pte_t *ptep)
> +static inline pte_t ptep_get(const pte_t *ptep)
>  {
>  	pte_t pte = __ptep_get(ptep);
>
> @@ -1743,7 +1743,7 @@ static inline pte_t ptep_get(pte_t *ptep)
>  }
>
>  #define ptep_get_lockless ptep_get_lockless
> -static inline pte_t ptep_get_lockless(pte_t *ptep)
> +static inline pte_t ptep_get_lockless(const pte_t *ptep)
>  {
>  	pte_t pte = __ptep_get(ptep);
>
> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
> index 2de12656b4d8..3a5d6937fb51 100644
> --- a/arch/arm64/mm/contpte.c
> +++ b/arch/arm64/mm/contpte.c
> @@ -26,6 +26,11 @@ static inline pte_t *contpte_align_down(pte_t *ptep)
>  	return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
>  }
>
> +#define contpte_align_down(ptep)                                                       \
> +	_Generic((ptep),                                                               \
> +		 const pte_t *: (const pte_t *) contpte_align_down((pte_t *) (ptep)),  \
> +		 pte_t *: contpte_align_down((pte_t *) ptep))

I really hate these _Generic() helper things. So ugly. And it's a pretty horrid
cast now :(

Was it not possible to const-ify further to just be able to constify
contpte_align_down itself?

It also seems to contradict the claim that contpte doesn't need write-access to
pte's since you're going to lengths to allow non-const pte_t * here.

You should cover off why this was necessary in the commit message as above.

Anyway PTR_ALIGN_DOWN() is already const-safe so couldn't you anyway just
collapse this to:

#define contpte_align_down(ptep) \
	PTR_ALIGN_DOWN(ptep, sizeof(*(ptep)) * CONT_PTES)

Then describe in the commit message why you need to handle both cases?

> +
>  static inline pte_t *contpte_align_addr_ptep(unsigned long *start,
>  					     unsigned long *end, pte_t *ptep,
>  					     unsigned int nr)
> @@ -310,7 +315,7 @@ void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
>  }
>  EXPORT_SYMBOL_GPL(__contpte_try_unfold);
>
> -pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
> +pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte)
>  {
>  	/*
>  	 * Gather access/dirty bits, which may be populated in any of the ptes
> @@ -367,7 +372,7 @@ static inline bool contpte_is_consistent(pte_t pte, unsigned long pfn,
>  			pgprot_val(prot) == pgprot_val(orig_prot);
>  }
>
> -pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
> +pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep)
>  {
>  	/*
>  	 * The ptep_get_lockless() API requires us to read and return *orig_ptep
> @@ -386,10 +391,10 @@ pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
>  	 * because it is not part of a contpte range.
>  	 */
>
> +	const pte_t *ptep;

Nit but this is breaking the reverse xmas tree isn't it?

>  	pgprot_t orig_prot;
>  	unsigned long pfn;
>  	pte_t orig_pte;
> -	pte_t *ptep;
>  	pte_t pte;
>  	int i;
>
> --
> 2.55.0
>

--
Cheers, Lorenzo

[PATCH v2 2/6] parisc: Drop own implementations for ptep_get() and ptep_test_and_clear_young()

[Pedro Falcato]

From: Helge Deller <deller@gmx.de>

Switch to the generic implementations, which are identical.

Suggested-by: Usama Arif <usama.arif@linux.dev>
Suggested-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/parisc/include/asm/pgtable.h | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 467b8547ac8b..d92dee9fef3f 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -432,25 +432,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 	return pte;
 }
 
-static inline pte_t ptep_get(pte_t *ptep)
-{
-	return READ_ONCE(*ptep);
-}
-#define ptep_get ptep_get
-
-static inline bool ptep_test_and_clear_young(struct vm_area_struct *vma,
-		unsigned long addr, pte_t *ptep)
-{
-	pte_t pte;
-
-	pte = ptep_get(ptep);
-	if (!pte_young(pte)) {
-		return false;
-	}
-	set_pte_at(vma->vm_mm, addr, ptep, pte_mkold(pte));
-	return true;
-}
-
 bool ptep_clear_flush_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep);
 pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep);
 
@@ -491,7 +472,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 #define HAVE_ARCH_UNMAPPED_AREA
 #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 
-#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
 #define __HAVE_ARCH_PTEP_CLEAR_FLUSH
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
-- 
2.55.0

Re: [PATCH v2 2/6] parisc: Drop own implementations for ptep_get() and ptep_test_and_clear_young()

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:43:56PM +0100, Pedro Falcato wrote:
> From: Helge Deller <deller@gmx.de>
>
> Switch to the generic implementations, which are identical.

You sure do like succinct commit messages :)

Maybe worth saying by dropping the __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG and
ptep_get defines you get the generic versions from include/pgtable.h which are
functionally identical.

(Being pedantic, they're not quite strictly identical as the
ptep_test_and_clear_young() generic function does some weird unnecessary
indirection with a local variable and the single {} is dropped etc.)

>
> Suggested-by: Usama Arif <usama.arif@linux.dev>
> Suggested-by: John David Anglin <dave.anglin@bell.net>
> Signed-off-by: Helge Deller <deller@gmx.de>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>

Nits above notwithstanding, LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  arch/parisc/include/asm/pgtable.h | 20 --------------------
>  1 file changed, 20 deletions(-)
>
> diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
> index 467b8547ac8b..d92dee9fef3f 100644
> --- a/arch/parisc/include/asm/pgtable.h
> +++ b/arch/parisc/include/asm/pgtable.h
> @@ -432,25 +432,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
>  	return pte;
>  }
>
> -static inline pte_t ptep_get(pte_t *ptep)
> -{
> -	return READ_ONCE(*ptep);
> -}
> -#define ptep_get ptep_get
> -
> -static inline bool ptep_test_and_clear_young(struct vm_area_struct *vma,
> -		unsigned long addr, pte_t *ptep)
> -{
> -	pte_t pte;
> -
> -	pte = ptep_get(ptep);
> -	if (!pte_young(pte)) {
> -		return false;
> -	}
> -	set_pte_at(vma->vm_mm, addr, ptep, pte_mkold(pte));
> -	return true;
> -}
> -
>  bool ptep_clear_flush_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep);
>  pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep);
>
> @@ -491,7 +472,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
>  #define HAVE_ARCH_UNMAPPED_AREA
>  #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
>
> -#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
>  #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
>  #define __HAVE_ARCH_PTEP_CLEAR_FLUSH
>  #define __HAVE_ARCH_PTEP_SET_WRPROTECT
> --
> 2.55.0
>

--
Cheers, Lorenzo

[PATCH v2 3/6] mm/powerpc/8xx: constify ptep_get() argument

[Pedro Falcato]

There is no need for write access to the PTE.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
index e2ea8ba9f8ca..f2bab31040c7 100644
--- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
@@ -226,7 +226,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p
 
 #ifdef CONFIG_PPC_16K_PAGES
 #define ptep_get ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
+static inline pte_t ptep_get(const pte_t *ptep)
 {
 	pte_basic_t val = READ_ONCE(ptep->pte);
 	pte_t pte = {val, val, val, val};
-- 
2.55.0

Re: [PATCH v2 3/6] mm/powerpc/8xx: constify ptep_get() argument

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:43:57PM +0100, Pedro Falcato wrote:
> There is no need for write access to the PTE.
>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>

With below addressed LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> index e2ea8ba9f8ca..f2bab31040c7 100644
> --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> @@ -226,7 +226,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p
>
>  #ifdef CONFIG_PPC_16K_PAGES
>  #define ptep_get ptep_get
> -static inline pte_t ptep_get(pte_t *ptep)
> +static inline pte_t ptep_get(const pte_t *ptep)
>  {
>  	pte_basic_t val = READ_ONCE(ptep->pte);
>  	pte_t pte = {val, val, val, val};

Worth making these const too (that {val, val, val, val} horrifies me btw :)?

> --
> 2.55.0
>

--
Cheers, Lorenzo

[PATCH v2 4/6] mm/s390: constify ptep_get() argument

[Pedro Falcato]

It's a simple READ_ONCE() dereference, therefore it can be const.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/s390/include/asm/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index e882663a58e7..ec331ec92943 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -986,7 +986,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
 }
 
 #define ptep_get ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
+static inline pte_t ptep_get(const pte_t *ptep)
 {
 	return READ_ONCE(*ptep);
 }
-- 
2.55.0

Re: [PATCH v2 4/6] mm/s390: constify ptep_get() argument

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:43:58PM +0100, Pedro Falcato wrote:
> It's a simple READ_ONCE() dereference, therefore it can be const.
>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>

Even I can't be pedantic about this one... :) so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  arch/s390/include/asm/pgtable.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index e882663a58e7..ec331ec92943 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -986,7 +986,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
>  }
>
>  #define ptep_get ptep_get
> -static inline pte_t ptep_get(pte_t *ptep)
> +static inline pte_t ptep_get(const pte_t *ptep)
>  {
>  	return READ_ONCE(*ptep);
>  }
> --
> 2.55.0
>

--
Cheers, Lorenzo

[PATCH v2 5/6] mm: constify generic pte_get*()

[Pedro Falcato]

None of the helpers need write access to the PTE. Constifying the param
allows for const typesafety.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 include/linux/pgtable.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 8c093c119e5a..dc418553e57a 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -490,7 +490,7 @@ static inline int pudp_set_access_flags(struct vm_area_struct *vma,
 #endif
 
 #ifndef ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
+static inline pte_t ptep_get(const pte_t *ptep)
 {
 	return READ_ONCE(*ptep);
 }
@@ -739,7 +739,7 @@ static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
  * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
  * operates on present ptes we're safe.
  */
-static inline pte_t ptep_get_lockless(pte_t *ptep)
+static inline pte_t ptep_get_lockless(const pte_t *ptep)
 {
 	pte_t pte;
 
@@ -777,7 +777,7 @@ static inline pmd_t pmdp_get_lockless(pmd_t *pmdp)
  * We require that the PTE can be read atomically.
  */
 #ifndef ptep_get_lockless
-static inline pte_t ptep_get_lockless(pte_t *ptep)
+static inline pte_t ptep_get_lockless(const pte_t *ptep)
 {
 	return ptep_get(ptep);
 }
-- 
2.55.0

Re: [PATCH v2 5/6] mm: constify generic pte_get*()

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:43:59PM +0100, Pedro Falcato wrote:
> None of the helpers need write access to the PTE. Constifying the param
> allows for const typesafety.

constity?

>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>

LGTM, so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  include/linux/pgtable.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 8c093c119e5a..dc418553e57a 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -490,7 +490,7 @@ static inline int pudp_set_access_flags(struct vm_area_struct *vma,
>  #endif
>
>  #ifndef ptep_get
> -static inline pte_t ptep_get(pte_t *ptep)
> +static inline pte_t ptep_get(const pte_t *ptep)
>  {
>  	return READ_ONCE(*ptep);
>  }
> @@ -739,7 +739,7 @@ static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>   * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
>   * operates on present ptes we're safe.
>   */
> -static inline pte_t ptep_get_lockless(pte_t *ptep)
> +static inline pte_t ptep_get_lockless(const pte_t *ptep)
>  {
>  	pte_t pte;
>
> @@ -777,7 +777,7 @@ static inline pmd_t pmdp_get_lockless(pmd_t *pmdp)
>   * We require that the PTE can be read atomically.
>   */
>  #ifndef ptep_get_lockless
> -static inline pte_t ptep_get_lockless(pte_t *ptep)
> +static inline pte_t ptep_get_lockless(const pte_t *ptep)
>  {
>  	return ptep_get(ptep);
>  }
> --
> 2.55.0
>

--
Cheers, Lorenzo

[PATCH v2 6/6] mm: constify the pte_offset_map_ro_nolock() return value

[Pedro Falcato]

Constify the pte_t * retval from pte_offset_map_ro_nolock(), for which it is
already pledged that accesses must be read-only. With it, convert the three
treewide users to use const pte_t *.

khugepaged passes the result right down to fault code (do_swap_page()). This
leads to a complicated set of conditions that, in order to be correct, must
not install anything into *vmf->pte. This is not trivial to work around in
fault code, and as such just trivially cast to non-const pte_t* in the
meantime.

The other users are far more trivial and the conversion is equally
trivially simple.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/powerpc/mm/pgtable.c | 2 +-
 include/linux/mm.h        | 4 ++--
 include/linux/pgtable.h   | 2 +-
 mm/filemap.c              | 2 +-
 mm/khugepaged.c           | 2 +-
 mm/pgtable-generic.c      | 4 ++--
 6 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index a9be337be3e4..e29db41b6043 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -390,7 +390,7 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
-	pte_t *pte;
+	const pte_t *pte;
 	spinlock_t *ptl;
 
 	if (mm == &init_mm)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7fabe6c66b4b..acf5a5e31d34 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3885,8 +3885,8 @@ static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
 pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
 			   unsigned long addr, spinlock_t **ptlp);
 
-pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
-				unsigned long addr, spinlock_t **ptlp);
+const pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
+				      unsigned long addr, spinlock_t **ptlp);
 pte_t *pte_offset_map_rw_nolock(struct mm_struct *mm, pmd_t *pmd,
 				unsigned long addr, pmd_t *pmdvalp,
 				spinlock_t **ptlp);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index dc418553e57a..dd51e722c535 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -112,7 +112,7 @@ static inline pte_t *__pte_map(pmd_t *pmd, unsigned long address)
 {
 	return pte_offset_kernel(pmd, address);
 }
-static inline void pte_unmap(pte_t *pte)
+static inline void pte_unmap(const pte_t *pte)
 {
 	rcu_read_unlock();
 }
diff --git a/mm/filemap.c b/mm/filemap.c
index 6afec636881f..af5d3fcd1b05 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3490,7 +3490,7 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret = 0;
-	pte_t *ptep;
+	const pte_t *ptep;
 
 	/*
 	 * We might have COW'ed a pagecache folio and might now have an mlocked
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b237f6e7662a..09efac93a8c6 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1170,7 +1170,7 @@ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,
 			 * Here the ptl is only used to check pte_same() in
 			 * do_swap_page(), so readonly version is enough.
 			 */
-			pte = pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);
+			pte = (pte_t *) pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);
 			if (!pte) {
 				mmap_read_unlock(mm);
 				result = SCAN_NO_PTE_TABLE;
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index b91b1a98029c..2cfc6e608ef4 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -308,8 +308,8 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
 	return NULL;
 }
 
-pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
-				unsigned long addr, spinlock_t **ptlp)
+const pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
+				      unsigned long addr, spinlock_t **ptlp)
 {
 	pmd_t pmdval;
 	pte_t *pte;
-- 
2.55.0

Re: [PATCH v2 6/6] mm: constify the pte_offset_map_ro_nolock() return value

[Lorenzo Stoakes (ARM)]

On Mon, Aug 03, 2026 at 05:44:00PM +0100, Pedro Falcato wrote:
> Constify the pte_t * retval from pte_offset_map_ro_nolock(), for which it is
> already pledged that accesses must be read-only. With it, convert the three
> treewide users to use const pte_t *.
>
> khugepaged passes the result right down to fault code (do_swap_page()). This
> leads to a complicated set of conditions that, in order to be correct, must
> not install anything into *vmf->pte. This is not trivial to work around in
> fault code, and as such just trivially cast to non-const pte_t* in the
> meantime.
>
> The other users are far more trivial and the conversion is equally
> trivially simple.

Ah finally more words! :)

>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>

With comment updated as below and nits addressed, LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  arch/powerpc/mm/pgtable.c | 2 +-
>  include/linux/mm.h        | 4 ++--
>  include/linux/pgtable.h   | 2 +-
>  mm/filemap.c              | 2 +-
>  mm/khugepaged.c           | 2 +-
>  mm/pgtable-generic.c      | 4 ++--
>  6 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index a9be337be3e4..e29db41b6043 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -390,7 +390,7 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
>  	p4d_t *p4d;
>  	pud_t *pud;
>  	pmd_t *pmd;
> -	pte_t *pte;
> +	const pte_t *pte;
>  	spinlock_t *ptl;
>
>  	if (mm == &init_mm)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7fabe6c66b4b..acf5a5e31d34 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3885,8 +3885,8 @@ static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
>  pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
>  			   unsigned long addr, spinlock_t **ptlp);
>
> -pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
> -				unsigned long addr, spinlock_t **ptlp);
> +const pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
> +				      unsigned long addr, spinlock_t **ptlp);
>  pte_t *pte_offset_map_rw_nolock(struct mm_struct *mm, pmd_t *pmd,
>  				unsigned long addr, pmd_t *pmdvalp,
>  				spinlock_t **ptlp);
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index dc418553e57a..dd51e722c535 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -112,7 +112,7 @@ static inline pte_t *__pte_map(pmd_t *pmd, unsigned long address)
>  {
>  	return pte_offset_kernel(pmd, address);
>  }
> -static inline void pte_unmap(pte_t *pte)
> +static inline void pte_unmap(const pte_t *pte)

I was going to question this based on whether the contract holds for
CONFIG_HIGHPTE but actually:

#define pte_unmap(pte)	do {	\
	kunmap_local((pte));	\
	rcu_read_unlock();	\
} while (0)

#define kunmap_local(__addr)					\
do {								\
	BUILD_BUG_ON(__same_type((__addr), struct page *));	\
	__kunmap_local(__addr);					\
} while (0)

static inline void __kunmap_local(const void *vaddr) <-- const!
{
	kunmap_local_indexed(vaddr);
}

So nice (CONFIG_HIGHPTE is going to go away at some point though, right? I
hope... :)


>  {
>  	rcu_read_unlock();
>  }
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 6afec636881f..af5d3fcd1b05 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3490,7 +3490,7 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf)
>  {
>  	struct vm_area_struct *vma = vmf->vma;
>  	vm_fault_t ret = 0;
> -	pte_t *ptep;
> +	const pte_t *ptep;
>
>  	/*
>  	 * We might have COW'ed a pagecache folio and might now have an mlocked
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index b237f6e7662a..09efac93a8c6 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1170,7 +1170,7 @@ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,
>  			 * Here the ptl is only used to check pte_same() in
>  			 * do_swap_page(), so readonly version is enough.
>  			 */
> -			pte = pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);
> +			pte = (pte_t *) pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);

Hmm yeah this is nasty, but you explain why in the commit message. Could you
extend the comment to explain it?

>  			if (!pte) {
>  				mmap_read_unlock(mm);
>  				result = SCAN_NO_PTE_TABLE;
> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
> index b91b1a98029c..2cfc6e608ef4 100644
> --- a/mm/pgtable-generic.c
> +++ b/mm/pgtable-generic.c
> @@ -308,8 +308,8 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
>  	return NULL;
>  }
>
> -pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
> -				unsigned long addr, spinlock_t **ptlp)
> +const pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,

Can pmd be const too?

> +				      unsigned long addr, spinlock_t **ptlp)
>  {
>  	pmd_t pmdval;
>  	pte_t *pte;
> --
> 2.55.0
>

--
Cheers, Lorenzo

Re: [PATCH v2 0/6] mm: add basic PTE const type-safety

[Muhammad Usama Anjum]

On 03/08/2026 5:43 pm, Pedro Falcato wrote:
> Since forever, MM code has thrown pte_t * around with no concern for const
> safety, or typesafety of any kind. This is confusing. Attempt to address it
> by:
> 1) Making sure pte_get*() helpers can cope with const pte_t * arguments
> 2) Constifying the pte_offset_map_ro_nolock() return type, which by definition
> already pledges that users will not write to it.
> 
> These two simple steps were already able to uncover code smell from
> khugepaged + do_swap_page().
> 
> Separate steps could include introducing pte_offset_map_ro_lock() for more
> widespread usage of this.
> 
> Benefits of this include less confusion and better type-safety. It could also
> futurely aid in efforts such as [0] which may want semantic annotation of these
> accesses.
> 
> Based on mm-unstable and compile-tested on a handful of architectures.
> 
> No functional changes intended.
I've reviewed the entire series. Hence:

Reviewed-by: Muhammad Usama Anjum <usama.anjum@arm.com>

> 
> [CC list editorially trimmed for brevity reasons; apologies if you're not on it]
> 
> Link: https://lore.kernel.org/linux-mm/20260526-kpkeys-v8-0-eaaacdacc67c@arm.com/#t [0]
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: "Liam R. Howlett" <liam@infradead.org>
> Cc: Vlastimil Babka <vbabka@kernel.org>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Nico Pache <npache@redhat.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Dev Jain <dev.jain@arm.com>
> Cc: Barry Song <baohua@kernel.org>
> Cc: Lance Yang <lance.yang@linux.dev>
> Cc: Usama Arif <usama.arif@linux.dev>
> Cc: Kevin Brodsky <kevin.brodsky@arm.com>
> Cc: Muhammad Usama Anjum <usama.anjum@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-parisc@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-mm@kvack.org
> Cc: linux-fsdevel@vger.kernel.org
> 
> v2:
>  - Small fixups on the arm64 side
>  - Re-order patches in a way such that bisection is preserved
>  - Pick up Helge's patch dropping parisc ptep_get()
>  - Constify s390's ptep_get() as well
> 
> Helge Deller (1):
>   parisc: Drop own implementations for ptep_get() and
>     ptep_test_and_clear_young()
> 
> Pedro Falcato (5):
>   mm/arm64: constify pte_get*() and contpte get logic
>   mm/powerpc/8xx: constify ptep_get() argument
>   mm/s390: constify ptep_get() argument
>   mm: constify generic pte_get*()
>   mm: constify the pte_offset_map_ro_nolock() return value
> 
>  arch/arm64/include/asm/pgtable.h             | 10 +++++-----
>  arch/arm64/mm/contpte.c                      | 11 ++++++++---
>  arch/parisc/include/asm/pgtable.h            | 20 --------------------
>  arch/powerpc/include/asm/nohash/32/pte-8xx.h |  2 +-
>  arch/powerpc/mm/pgtable.c                    |  2 +-
>  arch/s390/include/asm/pgtable.h              |  2 +-
>  include/linux/mm.h                           |  4 ++--
>  include/linux/pgtable.h                      |  8 ++++----
>  mm/filemap.c                                 |  2 +-
>  mm/khugepaged.c                              |  2 +-
>  mm/pgtable-generic.c                         |  4 ++--
>  11 files changed, 26 insertions(+), 41 deletions(-)
> 

-- 
Thanks,
Usama

Re: [PATCH v2 0/6] mm: add basic PTE const type-safety

[Christophe Leroy (CS GROUP)]

Le 03/08/2026 à 18:43, Pedro Falcato a écrit :
> Since forever, MM code has thrown pte_t * around with no concern for const
> safety, or typesafety of any kind. This is confusing. Attempt to address it
> by:

What do you mean by "typesafety of any kind" ?

On powerpc64, pte_t is a struct so you can't play-up too much with it.

On powerpc32, pte_t is a long int because having it as a struct is 
counter-performant, but we have it as a struct when __CHECKER__ is 
defined, ie when doing a sparse check with 'make C=2'.


> 1) Making sure pte_get*() helpers can cope with const pte_t * arguments
> 2) Constifying the pte_offset_map_ro_nolock() return type, which by definition
> already pledges that users will not write to it.
> 
> These two simple steps were already able to uncover code smell from
> khugepaged + do_swap_page().
> 
> Separate steps could include introducing pte_offset_map_ro_lock() for more
> widespread usage of this.
> 
> Benefits of this include less confusion and better type-safety. It could also
> futurely aid in efforts such as [0] which may want semantic annotation of these
> accesses.
> 
> Based on mm-unstable and compile-tested on a handful of architectures.
> 
> No functional changes intended.
> 

For the series,

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>



> [CC list editorially trimmed for brevity reasons; apologies if you're not on it]
> 
> Link: https://lore.kernel.org/linux-mm/20260526-kpkeys-v8-0-eaaacdacc67c@arm.com/#t [0]
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: "Liam R. Howlett" <liam@infradead.org>
> Cc: Vlastimil Babka <vbabka@kernel.org>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Nico Pache <npache@redhat.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Dev Jain <dev.jain@arm.com>
> Cc: Barry Song <baohua@kernel.org>
> Cc: Lance Yang <lance.yang@linux.dev>
> Cc: Usama Arif <usama.arif@linux.dev>
> Cc: Kevin Brodsky <kevin.brodsky@arm.com>
> Cc: Muhammad Usama Anjum <usama.anjum@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-parisc@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-mm@kvack.org
> Cc: linux-fsdevel@vger.kernel.org
> 
> v2:
>   - Small fixups on the arm64 side
>   - Re-order patches in a way such that bisection is preserved
>   - Pick up Helge's patch dropping parisc ptep_get()
>   - Constify s390's ptep_get() as well
> 
> Helge Deller (1):
>    parisc: Drop own implementations for ptep_get() and
>      ptep_test_and_clear_young()
> 
> Pedro Falcato (5):
>    mm/arm64: constify pte_get*() and contpte get logic
>    mm/powerpc/8xx: constify ptep_get() argument
>    mm/s390: constify ptep_get() argument
>    mm: constify generic pte_get*()
>    mm: constify the pte_offset_map_ro_nolock() return value
> 
>   arch/arm64/include/asm/pgtable.h             | 10 +++++-----
>   arch/arm64/mm/contpte.c                      | 11 ++++++++---
>   arch/parisc/include/asm/pgtable.h            | 20 --------------------
>   arch/powerpc/include/asm/nohash/32/pte-8xx.h |  2 +-
>   arch/powerpc/mm/pgtable.c                    |  2 +-
>   arch/s390/include/asm/pgtable.h              |  2 +-
>   include/linux/mm.h                           |  4 ++--
>   include/linux/pgtable.h                      |  8 ++++----
>   mm/filemap.c                                 |  2 +-
>   mm/khugepaged.c                              |  2 +-
>   mm/pgtable-generic.c                         |  4 ++--
>   11 files changed, 26 insertions(+), 41 deletions(-)
>