Re: [PATCH] fix BUG_ON check at move_freepages() (Re: 2.6.21-rc3-mm2)

[Mel Gorman]

On Thu, 8 Mar 2007, Yasunori Goto wrote:

> Hello.
>
> The BUG_ON() check at move_freepages() is wrong.
> Its end_page is start_page + MAX_ORDER_NR_PAGES. So, it can be
> next zone. BUG_ON() should check "end_page - 1".

You're right on all counts.

> This is fix of 2.6.21-rc3-mm2 for it.
>
> Signed-off-by: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>

Acked-by: Mel Gorman <mel@xxxxxxxxx>

> ---
> mm/page_alloc.c |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: current_test/mm/page_alloc.c
> ===================================================================
> --- current_test.orig/mm/page_alloc.c	2007-03-08 15:44:10.000000000 +0900
> +++ current_test/mm/page_alloc.c	2007-03-08 16:17:29.000000000 +0900
> @@ -707,7 +707,7 @@ int move_freepages(struct zone *zone,
> 	unsigned long order;
> 	int blocks_moved = 0;
>
> -	BUG_ON(page_zone(start_page) != page_zone(end_page));
> +	BUG_ON(page_zone(start_page) != page_zone(end_page - 1));
>
> 	for (page = start_page; page < end_page;) {
> 		if (!PageBuddy(page)) {
>
> --
> Yasunori Goto

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