Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -778,7 +778,7 @@
 	/*
 	 * Examine the nonempty subtree associated with each bit set in mask.
 	 */
-	do {
+	while (mask != 0) {
 		bit = mask & -mask;
 		digit = bitpos(bit);
 		i = 1 + digit * skip;
@@ -795,7 +795,8 @@
 			}
 		}
 		cursor = blk;
-	} while ((mask ^= bit) != 0);
+		mask ^= bit;
+	}
 
 	/*
 	 * We couldn't allocate count in this subtree.  If the whole tree was