linux-kernel - Re: [PATCH v2 1/4] hugetlbfs: add arch_hugetlb_valid

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Date:   Mon, 13 Apr 2020 10:04:54 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "David S.Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Longpeng <longpeng2@...wei.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Mina Almasry <almasrymina@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 1/4] hugetlbfs: add arch_hugetlb_valid_size

On 4/10/20 12:16 PM, Peter Xu wrote:
> On Wed, Apr 01, 2020 at 11:38:16AM -0700, Mike Kravetz wrote:
>> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
>> index 2eb6c234d594..81606223494f 100644
>> --- a/arch/arm64/include/asm/hugetlb.h
>> +++ b/arch/arm64/include/asm/hugetlb.h
>> @@ -59,6 +59,8 @@ extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>>  extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
>>  				 pte_t *ptep, pte_t pte, unsigned long sz);
>>  #define set_huge_swap_pte_at set_huge_swap_pte_at
>> +bool __init arch_hugetlb_valid_size(unsigned long size);
>> +#define arch_hugetlb_valid_size arch_hugetlb_valid_size
> 
> Sorry for chimming in late.

Thank you for taking a look!

> Since we're working on removing arch-dependent codes after all.. I'm
> thinking whether we can define arch_hugetlb_valid_size() once in the
> common header (e.g. linux/hugetlb.h), then in mm/hugetlb.c:
> 
> bool __init __attribute((weak)) arch_hugetlb_valid_size(unsigned long size)
> {
> 	return size == HPAGE_SIZE;
> }
> 
> We can simply redefine arch_hugetlb_valid_size() in arch specific C
> files where we want to override the default.  Would that be slightly
> cleaner?

I think both the #define X X and weak attribute methods are acceptable.
I went with the #define method only because it was most familiar to me.
Using the weak attribute method does appear to be cleaner.  I'll code it up.

Anyone else have a preference?
-- 
Mike Kravetz