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Date: Fri, 20 Oct 2006 10:46:13 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
To: Andrew Morton <akpm@osdl.org>
Subject: Re: kernel BUG in __cache_alloc_node at linux-2.6.git/mm/slab.c:3177!
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Cc: Jeff Garzik <jeff@garzik.org>, Mel Gorman <mel@csn.ul.ie>,
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Here is the patch:

Slab: Do not fallback to nodes that have not been bootstrapped yet

The zonelist may contain zones of nodes that have not been bootstrapped 
and we will oops if we try to allocate from those zones. So check if the 
node information for the slab and the node have been setup before 
attempting an allocation. If it has not been setup then skip that zone.

Usually we will not encounter this situation since the slab bootstrap
code avoids falling back before we have setup the respective nodes but we 
seem to have a special needs for pppc.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc2-mm1/mm/slab.c
===================================================================
--- linux-2.6.19-rc2-mm1.orig/mm/slab.c	2006-10-20 12:39:02.000000000 -0500
+++ linux-2.6.19-rc2-mm1/mm/slab.c	2006-10-20 12:41:04.137684581 -0500
@@ -3160,12 +3160,15 @@ void *fallback_alloc(struct kmem_cache *
 	struct zone **z;
 	void *obj = NULL;
 
-	for (z = zonelist->zones; *z && !obj; z++)
+	for (z = zonelist->zones; *z && !obj; z++) {
+		int nid = zone_to_nid(*z);
+
 		if (zone_idx(*z) <= ZONE_NORMAL &&
-				cpuset_zone_allowed(*z, flags))
+				cpuset_zone_allowed(*z, flags) &&
+				cache->nodelists[nid])
 			obj = __cache_alloc_node(cache,
-					flags | __GFP_THISNODE,
-					zone_to_nid(*z));
+					flags | __GFP_THISNODE, nid);
+	}
 	return obj;
 }