linux-kernel - Re: [PATCH V2] x86/mm: Fix zone ranges boot printout

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Message-Id: <20141209145038.6253a2b99379bfb1255fa95e@linux-foundation.org>
Date:	Tue, 9 Dec 2014 14:50:38 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Xishi Qiu <qiuxishi@...wei.com>
Cc:	Ingo Molnar <mingo@...nel.org>, <dave@...1.net>,
	Rik van Riel <riel@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	<linux-tip-commits@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH V2] x86/mm: Fix zone ranges boot printout

On Tue, 9 Dec 2014 11:27:20 +0800 Xishi Qiu <qiuxishi@...wei.com> wrote:

> Changelog:
> V2:
> 	-fix building warnings of min(...).
>
> ...
>
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -674,10 +674,12 @@ void __init zone_sizes_init(void)
>  	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
>  
>  #ifdef CONFIG_ZONE_DMA
> -	max_zone_pfns[ZONE_DMA]		= MAX_DMA_PFN;
> +	max_zone_pfns[ZONE_DMA]		= min_t(unsigned long,
> +						max_low_pfn, MAX_DMA_PFN);

MAX_DMA_PFN has type int.

>  #endif
>  #ifdef CONFIG_ZONE_DMA32
> -	max_zone_pfns[ZONE_DMA32]	= MAX_DMA32_PFN;
> +	max_zone_pfns[ZONE_DMA32]	= min_t(unsigned long,
> +						max_low_pfn, MAX_DMA32_PFN);

MAX_DMA32_PFN has type UL (I think?) so there's no need for min_t here.

>  #endif
>  	max_zone_pfns[ZONE_NORMAL]	= max_low_pfn;
>  #ifdef CONFIG_HIGHMEM


Let's try to get the types correct, rather than hacking around fixing
up fallout from earlier incorrect type choices?

What is the type of a pfn?  Unsigned long, generally, when we bother
thinking about it.

So how about we make MAX_DMA_PFN have type UL?  I assume that fixes the
warning?

If we do this, we should also be able to undo the min_t hackery in
arch/x86/kernel/e820.c:memblock_find_dma_reserve().

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