mm: Constify arguments in default pxdp_get()

[PATCH] mm: Constify arguments in default pxdp_get()

Posted by Anshuman Khandual 6 days, 17 hours ago

Generic MM default pxdp_get() helpers fetch the values contained in pgtable
entries via READ_ONCE() without modifying them. Just make their arguments
explicitly 'const' for some additional protection.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: David Hildenbrand <david@kernel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This patch applies on v7.2-rc3 and builds on many platforms. Some earlier
discussion could be found here. Platorm implementations for these helpers
could convert into these "const" format later if required.

https://lore.kernel.org/all/yjqldpl7il6uqfoqrszaopchqthhlffssprmlqjkljvpkbpwkt@zetb5hyvllsl/

 include/linux/pgtable.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2981e386da7b3..f09a91ff5833b 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -490,35 +490,35 @@ 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);
 }
 #endif
 
 #ifndef pmdp_get
-static inline pmd_t pmdp_get(pmd_t *pmdp)
+static inline pmd_t pmdp_get(const pmd_t *pmdp)
 {
 	return READ_ONCE(*pmdp);
 }
 #endif
 
 #ifndef pudp_get
-static inline pud_t pudp_get(pud_t *pudp)
+static inline pud_t pudp_get(const pud_t *pudp)
 {
 	return READ_ONCE(*pudp);
 }
 #endif
 
 #ifndef p4dp_get
-static inline p4d_t p4dp_get(p4d_t *p4dp)
+static inline p4d_t p4dp_get(const p4d_t *p4dp)
 {
 	return READ_ONCE(*p4dp);
 }
 #endif
 
 #ifndef pgdp_get
-static inline pgd_t pgdp_get(pgd_t *pgdp)
+static inline pgd_t pgdp_get(const pgd_t *pgdp)
 {
 	return READ_ONCE(*pgdp);
 }
-- 
2.43.0

Re: [PATCH] mm: Constify arguments in default pxdp_get()

Posted by SJ Park 5 days, 23 hours ago

On Fri, 18 Sep 2026 12:19:28 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:

> Generic MM default pxdp_get() helpers fetch the values contained in pgtable
> entries via READ_ONCE() without modifying them. Just make their arguments
> explicitly 'const' for some additional protection.

Looks good and safe to me.

> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Suggested-by: David Hildenbrand <david@kernel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

Reviewed-by: SJ Park <sj@kernel.org>


Thanks,
SJ

[...]

Re: [PATCH] mm: Constify arguments in default pxdp_get()

Posted by Lorenzo Stoakes (ARM) 6 days, 10 hours ago

On Fri, Sep 18, 2026 at 12:19:28PM +0530, Anshuman Khandual wrote:
> Generic MM default pxdp_get() helpers fetch the values contained in pgtable
> entries via READ_ONCE() without modifying them. Just make their arguments
> explicitly 'const' for some additional protection.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Suggested-by: David Hildenbrand <david@kernel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

LGTM so:

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

> ---
> This patch applies on v7.2-rc3 and builds on many platforms. Some earlier
> discussion could be found here. Platorm implementations for these helpers
> could convert into these "const" format later if required.
>
> https://lore.kernel.org/all/yjqldpl7il6uqfoqrszaopchqthhlffssprmlqjkljvpkbpwkt@zetb5hyvllsl/
>
>  include/linux/pgtable.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 2981e386da7b3..f09a91ff5833b 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -490,35 +490,35 @@ 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);
>  }
>  #endif
>
>  #ifndef pmdp_get
> -static inline pmd_t pmdp_get(pmd_t *pmdp)
> +static inline pmd_t pmdp_get(const pmd_t *pmdp)
>  {
>  	return READ_ONCE(*pmdp);
>  }
>  #endif
>
>  #ifndef pudp_get
> -static inline pud_t pudp_get(pud_t *pudp)
> +static inline pud_t pudp_get(const pud_t *pudp)
>  {
>  	return READ_ONCE(*pudp);
>  }
>  #endif
>
>  #ifndef p4dp_get
> -static inline p4d_t p4dp_get(p4d_t *p4dp)
> +static inline p4d_t p4dp_get(const p4d_t *p4dp)
>  {
>  	return READ_ONCE(*p4dp);
>  }
>  #endif
>
>  #ifndef pgdp_get
> -static inline pgd_t pgdp_get(pgd_t *pgdp)
> +static inline pgd_t pgdp_get(const pgd_t *pgdp)
>  {
>  	return READ_ONCE(*pgdp);
>  }
> --
> 2.43.0
>

--
Cheers, Lorenzo

Re: [PATCH] mm: Constify arguments in default pxdp_get()

Posted by Pedro Falcato 6 days, 11 hours ago

On Fri, Sep 18, 2026 at 12:19:28PM +0530, Anshuman Khandual wrote:
> Generic MM default pxdp_get() helpers fetch the values contained in pgtable
> entries via READ_ONCE() without modifying them. Just make their arguments
> explicitly 'const' for some additional protection.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Suggested-by: David Hildenbrand <david@kernel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

https://lore.kernel.org/linux-mm/20260803164400.531199-1-pfalcato@suse.de/

I'll respin my series, since it addresses every architecture.

(apologies for not doing it yet this merge window, but it has been hectic
downstream)

-- 
Pedro

Re: [PATCH] mm: Constify arguments in default pxdp_get()

Posted by David Hildenbrand (Arm) 6 days, 11 hours ago

On 9/18/26 08:49, Anshuman Khandual wrote:
> Generic MM default pxdp_get() helpers fetch the values contained in pgtable
> entries via READ_ONCE() without modifying them. Just make their arguments
> explicitly 'const' for some additional protection.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Suggested-by: David Hildenbrand <david@kernel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---

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

-- 
Cheers,

David