linux-kernel - Re: [RFC PATCH 1/3] arm64/hugetlb: Introduce new huge_ptep_get_access

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Date:   Mon, 9 May 2022 12:19:00 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     nh26223@...com, catalin.marinas@....com, will@...nel.org,
        arnd@...db.de, mike.kravetz@...cle.com, akpm@...ux-foundation.org,
        sj@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, Muchun Song <songmuchun@...edance.com>
Subject: Re: [RFC PATCH 1/3] arm64/hugetlb: Introduce new
 huge_ptep_get_access_flags() interface



On 5/9/2022 12:10 PM, nh26223@...com write:
> ----------------8<---------------
>>>>
>>>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>>>> index ca8e65c..ce39699 100644
>>>> --- a/arch/arm64/mm/hugetlbpage.c
>>>> +++ b/arch/arm64/mm/hugetlbpage.c
>>>> @@ -158,6 +158,30 @@ static inline int num_contig_ptes(unsigned long
>>>> size,
>>>> size_t *pgsize) return contig_ptes;
>>>>
>>>>    }
>>>>
>>>> +pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long sz)
>>>
>>> The function name looks to me that it returns access flags of PTE.
>>
>> Yes, not a good name. That's why this is a RFC patch set to get more
>> suggestion :)
>>
>> Maybe huge_ptep_get_with_access_flags()? or do you have some better idea?
> I don't have either. "Naming is hard". :)
> 
>>>> diff --git a/include/asm-generic/hugetlb.h
>>>> b/include/asm-generic/hugetlb.h
>>>> index a57d667..bb77fb0 100644
>>>> --- a/include/asm-generic/hugetlb.h
>>>> +++ b/include/asm-generic/hugetlb.h
>>>> @@ -150,6 +150,13 @@ static inline pte_t huge_ptep_get(pte_t *ptep)
>>>>
>>>>    }
>>>>    #endif
>>>>
>>>> +#ifndef __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS
>>>> +static inline pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned
>>>> long
>>>> sz) +{
>>>> +	return ptep_get(ptep);
>>>
>>> Should be:
>>> 	return huge_ptep_get(ptep) ?
>>
>> I don't think so. If no ARCH-specific definition, the
>> huge_ptep_get_access_flags() implementation should be same as
>> huge_ptep_get(). Thanks for your comments.
> If no __HAVE_ARCH_HUGE_PTEP_GET, huge_ptep_get() is same as
> ptep_get().
> 
> Or it's not possible no __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS
> but with __HAVE_ARCH_HUGE_PTEP_GET?

Yes, I am wrong, shoule be huge_ptep_get(). Thanks for pointing out 
issues :)

PS: I think I will follow Muchun's suggestion in next version, so no 
need to add a new interface.