linux-kernel - Re: [PATCH -next] arm64: mm: Fix unused variable warning in zone_sizes

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Message-ID: <20191016030830.GA29527@ubuntu-m2-xlarge-x86>
Date:   Tue, 15 Oct 2019 20:08:30 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Will Deacon <will@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] arm64: mm: Fix unused variable warning in
 zone_sizes_init

On Wed, Oct 16, 2019 at 04:00:52AM +0100, Will Deacon wrote:
> On Tue, Oct 15, 2019 at 03:43:04PM -0700, Nathan Chancellor wrote:
> > When building arm64 allnoconfig, CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32
> > get disabled so there is a warning about max_dma being unused.
> > 
> > ../arch/arm64/mm/init.c:215:16: warning: unused variable 'max_dma'
> > [-Wunused-variable]
> >         unsigned long max_dma = min;
> >                       ^
> > 1 warning generated.
> > 
> > Add an ifdef around the variable to fix this.
> > 
> > Fixes: 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32")
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  arch/arm64/mm/init.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 44f07fdf7a59..c3d6657b9942 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -212,7 +212,9 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
> >  	struct memblock_region *reg;
> >  	unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
> >  	unsigned long max_dma32 = min;
> > +#if defined(CONFIG_ZONE_DMA) || defined(CONFIG_ZONE_DMA)
> >  	unsigned long max_dma = min;
> > +#endif
> 
> This looks bogus to me :/ You're referring to CONFIG_ZONE_DMA twice, and I
> can't see how that symbol even exists on arm64.
> 
> Will

Gah, sorry, one of those CONFIGs should be CONFIG_ZONE_DMA32. I will
send a v2 to fix that shortly.

Note, this patch is targetting for-next/zone-dma, which reintroduces
CONFIG_ZONE_DMA. Sorry if the patch tag and Fixes tag didn't make that
clear, let me know how I can better convey that in the future!

Cheers,
Nathan