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Date: Wed, 27 Jul 2005 18:17:24 -0700
From: Andrew Morton <akpm@osdl.org>
To: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, shai@scalex86.org
Subject: Re: [patch] mm: Ensure proper alignment for node_remap_start_pfn
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Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
>
> While reserving KVA for lmem_maps of node, we have to make sure that
> node_remap_start_pfn[] is aligned to a proper pmd boundary.
> (node_remap_start_pfn[] gets its value from node_end_pfn[])
> 

What are the effects of not having this patch applied?  Does someone's
computer crash, or what?

IOW: what problem is this fixing, precisely?

> 
> Index: linux-2.6.13-rc3/arch/i386/mm/discontig.c
> ===================================================================
> --- linux-2.6.13-rc3.orig/arch/i386/mm/discontig.c	2005-07-26 15:10:25.000000000 -0700
> +++ linux-2.6.13-rc3/arch/i386/mm/discontig.c	2005-07-26 16:27:43.000000000 -0700
> @@ -243,6 +243,14 @@
>  		/* now the roundup is correct, convert to PAGE_SIZE pages */
>  		size = size * PTRS_PER_PTE;
>  
> +		if (node_end_pfn[nid] & (PTRS_PER_PTE-1)) {
> +			/* 
> +			 * Adjust size if node_end_pfn is not on a proper 
> +			 * pmd boundary. remap_numa_kva will barf otherwise.
> +			 */
> +			size +=  node_end_pfn[nid] & (PTRS_PER_PTE-1);
> +		}
> +
>  		/*
>  		 * Validate the region we are allocating only contains valid
>  		 * pages.