---

 linux-2.6.git-dave/mm/page_alloc.c |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff -puN mm/page_alloc.c~zone-list-seqlock mm/page_alloc.c
--- linux-2.6.git/mm/page_alloc.c~zone-list-seqlock	2008-11-04 08:53:38.000000000 -0800
+++ linux-2.6.git-dave/mm/page_alloc.c	2008-11-04 08:57:04.000000000 -0800
@@ -2378,17 +2378,43 @@ static void build_zonelist_cache(pg_data
 
 #endif	/* CONFIG_NUMA */
 
+/*
+ * This provides a way for other parts of the
+ * system to detect when the list of zones
+ * might have changed underneath them.
+ *
+ * Use this if you are doing a for_each_zone()
+ * or for_each_node() and really, really care
+ * if you miss some memory.
+ */
+static seqlock_t zonelist_seqlock = SEQLOCK_UNLOCKED;
+
+/*
+ * We could #ifdef these under MEMORY_HOTPLUG, but they
+ * are tiny.
+ */
+unsigned zonelist_seqbegin(void)
+{
+        return read_seqbegin(&zonelist_seqlock);
+}
+int zonelist_seqretry(void)
+{
+        return read_seqretry(&zonelist_seqlock, iv);
+}
+
 /* return values int ....just for stop_machine() */
 static int __build_all_zonelists(void *dummy)
 {
 	int nid;
 
+	write_seqlock(&zonelist_seqlock);
 	for_each_online_node(nid) {
 		pg_data_t *pgdat = NODE_DATA(nid);
 
 		build_zonelists(pgdat);
 		build_zonelist_cache(pgdat);
 	}
+	write_sequnlock(&zonelist_seqlock);
 	return 0;
 }
 
_