linux-kernel - Re: [PATCH 5/5] mm: clear N_HIGH_MEMORY map before se set it again -v2

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Date:	Thu, 14 May 2009 09:54:14 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	mel@....ul.ie, mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
	cl@...ux-foundation.org, suresh.b.siddha@...el.com,
	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	rusty@...tcorp.com.au, steiner@....com, rientjes@...gle.com
Subject: Re: [PATCH 5/5] mm: clear N_HIGH_MEMORY map before se set it again
 -v2

On Thu, 14 May 2009 09:43:22 -0700
Yinghai Lu <yinghai@...nel.org> wrote:

> 
> incase some system strange SRAT table. some kind of small range.
> or with mem= etc
> 

That description is very hard to understand.  Please provide more details.

> 
> Signed-off-by: Yinghai Lu <Yinghai@...nel.org>
> Tested-by: Jack Steiner <steiner@....com>

What reason did Jack have to test this?  Perhaps he hit some bug? 
If so, please fully describe that bug in the changelog.


> Index: linux-2.6/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -4041,6 +4047,11 @@ void __init free_area_init_nodes(unsigne
>  						early_node_map[i].start_pfn,
>  						early_node_map[i].end_pfn);
>  
> +	/*
> +	 * find_zone_movable_pfns_for_nodes/early_calculate_totalpages init
> +	 * that node_mask, clear it at first
> +	 */
> +	nodes_clear(node_states[N_HIGH_MEMORY]);
>  	/* Initialise every node */
>  	mminit_verify_pageflags_layout();
>  	setup_nr_node_ids();

If CONFIG_HIGHMEM=n, this will clear the N_NORMAL_MEMORY entry in
node_states[].  Why is this correct and desirable?

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