linux-kernel - Re: [PATCH] mm: Drop unused set_pte

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Message-ID: <cae9c32d-c96e-463e-9375-91d9a7ad196a@arm.com>
Date: Tue, 10 Sep 2024 10:08:10 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, "Mike Rapoport (IBM)"
 <rppt@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Drop unused set_pte_safe()

On 10/09/2024 10:04, Anshuman Khandual wrote:
> All set_pte_safe() usage have been dropped after the commit eccd906484d1
> ("x86/mm: Do not use set_{pud, pmd}_safe() when splitting a large page")
> This just drops now unused helper set_pte_safe().

It would be good to add some comment here to mention that the macro was buggy
due to doing direct dereferencing of the pte, and that if it were to be kept, it
should have been updated to use a single call to ptep_get().

With that:

Reviewed-by: Ryan Roberts <ryan.roberts@....com>

Thanks,
Ryan

> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: "Mike Rapoport (IBM)" <rppt@...nel.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  include/linux/pgtable.h | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 2a6a3cccfc36..aeabbf0db7c8 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1058,12 +1058,6 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b)
>   * same value. Otherwise, use the typical "set" helpers and flush the
>   * TLB.
>   */
> -#define set_pte_safe(ptep, pte) \
> -({ \
> -	WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \
> -	set_pte(ptep, pte); \
> -})
> -
>  #define set_pmd_safe(pmdp, pmd) \
>  ({ \
>  	WARN_ON_ONCE(pmd_present(*pmdp) && !pmd_same(*pmdp, pmd)); \