linux-kernel - Re: [PATCH v2] hugetlb: allow to free gigantic pages regardless of the configuration

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Date:   Thu, 14 Feb 2019 11:49:19 +0100
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] hugetlb: allow to free gigantic pages regardless of
 the configuration


On 02/13/2019 08:30 PM, Dave Hansen wrote:
>> -#if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA)
>> +#ifdef CONFIG_COMPACTION_CORE
>>   static __init int gigantic_pages_init(void)
>>   {
>>   	/* With compaction or CMA we can allocate gigantic pages at runtime */
>> diff --git a/fs/Kconfig b/fs/Kconfig
>> index ac474a61be37..8fecd3ea5563 100644
>> --- a/fs/Kconfig
>> +++ b/fs/Kconfig
>> @@ -207,8 +207,9 @@ config HUGETLB_PAGE
>>   config MEMFD_CREATE
>>   	def_bool TMPFS || HUGETLBFS
>>   
>> -config ARCH_HAS_GIGANTIC_PAGE
>> +config COMPACTION_CORE
>>   	bool
>> +	default y if (MEMORY_ISOLATION && MIGRATION) || CMA
> This takes a hard dependency (#if) and turns it into a Kconfig *default*
> that can be overridden.  That seems like trouble.
>
> Shouldn't it be:
>
> config COMPACTION_CORE
> 	def_bool y
> 	depends on (MEMORY_ISOLATION && MIGRATION) || CMA
>
> ?

Thanks for that,

Alex