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

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Message-ID: <05c53d3b-87d7-4a25-89cb-ae349c901244@arm.com>
Date: Tue, 10 Sep 2024 14:45:54 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ryan Roberts <ryan.roberts@....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 9/10/24 14:38, Ryan Roberts wrote:
> 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().

Makes sense, will update as suggested.

> 
> 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)); \
> 
>