Index: linux-2.6.17-rc5-mm2/mm/swapfile.c
===================================================================
--- linux-2.6.17-rc5-mm2.orig/mm/swapfile.c	2006-06-01 10:03:07.127259731 -0700
+++ linux-2.6.17-rc5-mm2/mm/swapfile.c	2006-06-05 13:39:26.592396422 -0700
@@ -1392,24 +1392,15 @@ asmlinkage long sys_swapon(const char __
 		if (!(p->flags & SWP_USED))
 			break;
 	error = -EPERM;
-	/*
-	 * Test if adding another swap device is possible. There are
-	 * two limiting factors: 1) the number of bits for the swap
-	 * type swp_entry_t definition and 2) the number of bits for
-	 * the swap type in the swap ptes as defined by the different
-	 * architectures. To honor both limitations a swap entry
-	 * with swap offset 0 and swap type ~0UL is created, encoded
-	 * to a swap pte, decoded to a swp_entry_t again and finally
-	 * the swap type part is extracted. This will mask all bits
-	 * from the initial ~0UL that can't be encoded in either the
-	 * swp_entry_t or the architecture definition of a swap pte.
-	 */
-	if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
-		spin_unlock(&swap_lock);
-		goto out;
-	}
-	if (type >= nr_swapfiles)
+
+	if (type >= nr_swapfiles) {
+		if (nr_swapfiles >= MAX_SWAPFILES) {
+			spin_unlock(&swap_lock);
+			return -E2BIG;
+		}
 		nr_swapfiles = type+1;
+	}
+
 	INIT_LIST_HEAD(&p->extent_list);
 	p->flags = SWP_USED;
 	p->swap_file = NULL;