linux-kernel - Re: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad

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Message-Id: <20080328102719.3ab9162b.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 28 Mar 2008 10:27:19 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Yasunori Goto <y-goto@...fujitsu.com>,
	Christoph Lameter <clameter@....com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned
 memory is bad

On Thu, 27 Mar 2008 17:28:38 -0700
Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -784,6 +784,9 @@
>  #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
>  #define PAGE_SECTION_MASK	(~(PAGES_PER_SECTION-1))
>  
> +#define SECTION_SIZE		(1UL << SECTION_SIZE_BITS)
> +#define SECTION_SIZE_MASK	(SECTION_SIZE - 1)
> +
>  #define SECTION_BLOCKFLAGS_BITS \
>  	((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -300,6 +300,11 @@
>  	int ret;
>  	u64 start = res->start;
>  	u64 size = res->end - res->start + 1;
> +
> +	/* Adding non-section-aligned memory will give unexpected
> +	   and unintuitive results. */
> +	WARN_ON((start & SECTION_SIZE_MASK) != 0);
> +	WARN_ON((size & SECTION_SIZE_MASK) != 0);
>  
Why just WARNING ? not BUG_ON?

Thanks,
-Kame

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