Re: 2.6.21-rc3-mm2 (oops in move_freepages)

[mel@skynet.ie (Mel Gorman)]

On (13/03/07 21:52), Bjorn Helgaas didst pronounce:
> FYI, I'm seeing the following oops with 2.6.21-rc3-mm1 (and -mm2)
> on the HP rx2600 and an Intel Tiger (both ia64 boxes).
> 
> I haven't investigated this other than to determine that it
> does not occur with 2.6.21-rc3 or 2.6.20-rc3-mm1, and the
> instruction at move_freepages+0x10 is a load of the value
> pointed to by the third argument (end_page).
> 

Please try the following patch from Yasunori Goto.

>From y-goto@jp.fujitsu.com Thu Mar  8 08:00:15 2007
Date: Thu, 08 Mar 2007 16:39:43 +0900
From: Yasunori Goto <y-goto@jp.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, Mel Gorman <mel@csn.ul.ie>
Subject: [PATCH] fix BUG_ON check at move_freepages() (Re: 2.6.21-rc3-mm2)

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".

This is fix of 2.6.21-rc3-mm2 for it.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>

---
 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)) {