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Subject: Re: [PATCH 3/3] mm/hugetlb: Introduce HAVE_ARCH_CLEAR_HUGEPAGE_FLAGS
To:     Andrew Morton <akpm@linux-foundation.org>
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        Catalin Marinas <catalin.marinas@arm.com>,
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References: <1586864670-21799-1-git-send-email-anshuman.khandual@arm.com>
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 <20200425175511.7a68efb5e2f4436fe0328c1d@linux-foundation.org>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <87d37591-caa2-b82b-392a-3a29b2c7e9a6@arm.com>
Date:   Sun, 26 Apr 2020 08:13:17 +0530
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On 04/26/2020 06:25 AM, Andrew Morton wrote:
> On Tue, 14 Apr 2020 17:14:30 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> 
>> There are multiple similar definitions for arch_clear_hugepage_flags() on
>> various platforms. This introduces HAVE_ARCH_CLEAR_HUGEPAGE_FLAGS for those
>> platforms that need to define their own arch_clear_hugepage_flags() while
>> also providing a generic fallback definition for others to use. This help
>> reduce code duplication.
>>
>> ...
>>
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -544,6 +544,10 @@ static inline int is_hugepage_only_range(struct mm_struct *mm,
>>  }
>>  #endif
>>  
>> +#ifndef HAVE_ARCH_CLEAR_HUGEPAGE_FLAGS
>> +static inline void arch_clear_hugepage_flags(struct page *page) { }
>> +#endif
>> +
>>  #ifndef arch_make_huge_pte
>>  static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
>>  				       struct page *page, int writable)
> 
> This is the rather old-school way of doing it.  The Linus-suggested way is
> 
> #ifndef arch_clear_hugepage_flags
> static inline void arch_clear_hugepage_flags(struct page *page)
> {
> }
> #define arch_clear_hugepage_flags arch_clear_hugepage_flags

Do we need that above line here ? Is not that implicit.

> #endif
> 
> And the various arch headers do
> 
> static inline void arch_clear_hugepage_flags(struct page *page)
> {
> 	<some implementation>
> }
> #define arch_clear_hugepage_flags arch_clear_hugepage_flags
> 
> It's a small difference - mainly to avoid adding two variables to the
> overall namespace where one would do.

Understood, will change and resend.

> 
>