Re: [PATCH] Fix find_next_best_node (Re: [BUG] 2.6.23-rc3-mm1 Kernel panic - not syncing: DMA: Memory would be corrupted)

[mel@skynet.ie (Mel Gorman)]

On (24/08/07 15:53), Yasunori Goto didst pronounce:
> 
> I found find_next_best_node() was wrong.
> I confirmed boot up by the following patch.
> Mel-san, Kamalesh-san, could you try this?
> 

This boots the IA-64 successful and gets rid of that DMA corrupts
memory message. As a bonus, it fixes up the memoryless nodes (the bug
where Total pages == 0 and there is a BUG in page_alloc.c) by building
zonelists properly. The machine still fails to boot with the more familiar
net/core/skbuff.c:95 but that is a separate problem.

Well spotted Yasunori-san.

Andrew, this fixes a real problem and should be considered a fix to
memoryless-nodes-fixup-uses-of-node_online_map-in-generic-code.patch unless
Christoph Lameter objects.

> Bye.
> ---
> 
> Fix decision of memoryless node in find_next_best_node().
> This can be cause of SW-IOMMU's allocation failure.
> 
> This patch is for 2.6.23-rc3-mm1.
> 
> Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
> 

Acked-by: Mel Gorman <mel@csn.ul.ie>

> ---
>  mm/page_alloc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: current/mm/page_alloc.c
> ===================================================================
> --- current.orig/mm/page_alloc.c	2007-08-24 16:03:17.000000000 +0900
> +++ current/mm/page_alloc.c	2007-08-24 16:04:06.000000000 +0900
> @@ -2136,7 +2136,7 @@ static int find_next_best_node(int node,
>  		 * Note:  N_HIGH_MEMORY state not guaranteed to be
>  		 *        populated yet.
>  		 */
> -		if (pgdat->node_present_pages)
> +		if (!pgdat->node_present_pages)
>  			continue;
>  
>  		/* Don't want a node to appear more than once */
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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