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Date: Fri, 25 Feb 2011 10:05:12 +0100
From: Tejun Heo <tj@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>, Yinghai Lu <yinghai@kernel.org>,
        tglx@linutronix.de, "H. Peter Anvin" <hpa@zytor.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [patch] x86, mm: Fix size of numa_distance array
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Hello,

On Thu, Feb 24, 2011 at 03:31:24PM -0800, David Rientjes wrote:
> > -	size = ++cnt * sizeof(numa_distance[0]);
> > +	size = cnt * cnt * sizeof(numa_distance[0]);
> >  
> >  	phys = memblock_find_in_range(0, (u64)max_pfn_mapped << PAGE_SHIFT,
> >  				      size, PAGE_SIZE);
> > 
> 
> This also looks like it needs the following to not erroneously consider a 
> node id to be out of bounds.  Why were we oversizing cnt in the old code 
> above by 1?

Umm... because @cnt should be length not the last index?

> diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
> --- a/arch/x86/mm/numa_64.c
> +++ b/arch/x86/mm/numa_64.c
> @@ -454,7 +454,7 @@ void __init numa_set_distance(int from, int to, int distance)
>  	if (!numa_distance && numa_alloc_distance() < 0)
>  		return;
>  
> -	if (from >= numa_distance_cnt || to >= numa_distance_cnt) {
> +	if (from > numa_distance_cnt || to > numa_distance_cnt) {
>  		printk_once(KERN_DEBUG "NUMA: Debug: distance out of bound, from=%d to=%d distance=%d\n",
>  			    from, to, distance);
>  		return;
> @@ -472,7 +472,7 @@ void __init numa_set_distance(int from, int to, int distance)
>  
>  int __node_distance(int from, int to)
>  {
> -	if (from >= numa_distance_cnt || to >= numa_distance_cnt)
> +	if (from > numa_distance_cnt || to > numa_distance_cnt)

Again, numa_distance_cnt is the number of elements in one dimension of
the table not the index, while @from and @to are 0 based index.

Thanks.

-- 
tejun