linux-kernel - Re: [RESEND PATCH 2/2] arm64: make WANT_HUGE_PMD_SHARE depends on HUGETLB

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Message-ID: <20161216123512.GF13191@arm.com>
Date:   Fri, 16 Dec 2016 12:35:12 +0000
From:   Will Deacon <will.deacon@....com>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     catalin.marinas@....com, rrichter@...ium.com, mark.rutland@....com,
        arnd@...db.de, ard.biesheuvel@...aro.org, robh+dt@...nel.org,
        dwoods@...hip.com, jeremy.linton@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH 2/2] arm64: make WANT_HUGE_PMD_SHARE depends on
 HUGETLB_PAGE

On Fri, Dec 16, 2016 at 05:10:05PM +0800, zhong jiang wrote:
> On 2016/12/14 22:19, zhongjiang wrote:
> > From: zhong jiang <zhongjiang@...wei.com>
> >
> > when HUGETLB_PAGE is disable, WANT_HUGE_PMD_SHARE contains the
> > fuctions should not be use. therefore, we add the dependency.
> >
> > Signed-off-by: zhong jiang <zhongjiang@...wei.com>
> > ---
> >  arch/arm64/Kconfig | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 969ef88..694ca73 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -640,6 +640,7 @@ config SYS_SUPPORTS_HUGETLBFS
> >  
> >  config ARCH_WANT_HUGE_PMD_SHARE
> >  	def_bool y if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
> > +	depends on HUGETLB_PAGE
> >  
> >  config ARCH_HAS_CACHE_LINE_SIZE
> >  	def_bool y
> Hi,
>       I still think it is a issue. Perhaps above changelog is unclear.  Further explain is as follows.
>  when hugetlb_pages is disable and arch_want_huge_pmd_share is enable,   we maybe call
>  huge_pmd_sahre in hugetlbpage.c, but the function actually is not definition as it is not
>  exported.  is it right ??

The only users of ARCH_WANT_HUGE_PMD_SHARE on arm64 are:

arch/arm64/mm/hugetlbpage.c:            if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
mm/hugetlb.c:#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
mm/hugetlb.c:#else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
mm/hugetlb.c:#endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */

and neither of those files are compiled if !HUGETLB_PAGE.

Are you actually seeing a problem here?

Will