Index: linux-2.6.13-ck5/mm/swap_prefetch.c
===================================================================
--- linux-2.6.13-ck5.orig/mm/swap_prefetch.c	2005-09-20 23:33:34.000000000 +1000
+++ linux-2.6.13-ck5/mm/swap_prefetch.c	2005-09-22 22:05:00.000000000 +1000
@@ -20,13 +20,13 @@
 #define PREFETCH_INTERVAL (HZ)
 
 struct swapped_root_t {
+	int 			busy;
+	spinlock_t		busylock;
 	spinlock_t		lock;
+	struct list_head	list;
 	unsigned int		count;
 	unsigned int		maxcount;
 	kmem_cache_t		*cache;
-	struct list_head	list;
-	int 			busy;
-	spinlock_t		busylock;
 };
 
 struct swapped_entry_t {
@@ -35,8 +35,8 @@ struct swapped_entry_t {
 };
 
 static struct swapped_root_t swapped_root = {
-	.count = 0,
 	.list  = LIST_HEAD_INIT(swapped_root.list),
+	.count = 0,
 };
 
 static struct timer_list prefetch_timer;
@@ -175,7 +175,7 @@ static struct page * prefetch_get_page(v
 		(GFP_HIGHUSER & GFP_ZONEMASK);
 
 	for_each_zone(z) {
-		if (z->name == "DMA" || z->present_pages == 0)
+		if (zone_idx(z) == ZONE_DMA || z->present_pages == 0)
 			continue;
 		page = buffered_rmqueue(z, 0, GFP_HIGHUSER);
 		if (page)
@@ -248,7 +248,7 @@ out:
  */
 static int prefetch_suitable(void)
 {
-	unsigned long pending_writes;
+	unsigned long pending_writes, limit;
 	struct zone *z;
 
 	if (test_clear_busy())
@@ -264,10 +264,6 @@ static int prefetch_suitable(void)
 	if (pending_writes > SWAP_CLUSTER_MAX)
 		goto out_delay;
 
-	/* >2/3 of the ram is mapped, we need some free for pagecache */
-	if (read_page_state(nr_mapped) > mapped_limit)
-		goto out_delay;
-
 	/*
 	 * Have some hysteresis between where page reclaiming and prefetching
 	 * will occur to prevent ping-ponging between them.
@@ -279,6 +275,22 @@ static int prefetch_suitable(void)
 			goto out_delay;
 	}
 
+	/* >2/3 of the ram is mapped, we need some free for pagecache */
+	limit = read_page_state(nr_mapped);
+	if (limit > mapped_limit)
+		goto out_delay;
+
+	/*
+	 * Add swapcache to limit as well, but check this last since it needs
+	 * locking
+	 */
+	if (unlikely(!read_trylock(&swapper_space.tree_lock)))
+		goto out_delay;
+	limit += total_swapcache_pages;
+	read_unlock(&swapper_space.tree_lock);
+	if (limit > mapped_limit)
+		goto out_delay;
+
 	/* Survived all that? Hooray we can prefetch! */
 	return 1;