linux-kernel - Re: [PATCH 2/3] arm64/hugetlb: Enable HUGETLB_PAGE_SIZE

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Message-ID: <768e2ee2-93a5-02ec-4842-41e1242a6bef@arm.com>
Date:   Fri, 12 Feb 2021 12:43:27 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, akpm@...ux-foundation.org,
        will@...nel.org, Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        David Hildenbrand <david@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] arm64/hugetlb: Enable HUGETLB_PAGE_SIZE_VARIABLE



On 2/11/21 1:31 PM, Christoph Hellwig wrote:
> On Thu, Feb 11, 2021 at 11:52:10AM +0530, Anshuman Khandual wrote:
>> MAX_ORDER which invariably depends on FORCE_MAX_ZONEORDER can be a variable
>> for a given page size, depending on whether TRANSPARENT_HUGEPAGE is enabled
>> or not. In certain page size and THP combinations HUGETLB_PAGE_ORDER can be
>> greater than MAX_ORDER, making it unusable as pageblock_order.
>>
>> This enables HUGETLB_PAGE_SIZE_VARIABLE making pageblock_order a variable
>> rather than the compile time constant HUGETLB_PAGE_ORDER which could break
>> MAX_ORDER rule for certain configurations.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>  arch/arm64/Kconfig | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index f39568b28ec1..8e3a5578f663 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -1909,6 +1909,10 @@ config ARCH_ENABLE_THP_MIGRATION
>>  	def_bool y
>>  	depends on TRANSPARENT_HUGEPAGE
>>  
>> +config HUGETLB_PAGE_SIZE_VARIABLE
> 
> Please move the definition of HUGETLB_PAGE_SIZE_VARIABLE to
> mm/Kconfig and select it from the arch Kconfigfs instead of duplicating
> the definition.

Sure, will do.