diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
index b319721..ff53d5d 100644
--- a/fs/ext4/bitmap.c
+++ b/fs/ext4/bitmap.c
@@ -13,18 +13,9 @@
 
 #ifdef EXT4FS_DEBUG
 
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
 unsigned int ext4_count_free(struct buffer_head *map, unsigned int numchars)
 {
-	unsigned int i, sum = 0;
-
-	if (!map)
-		return 0;
-	for (i = 0; i < numchars; i++)
-		sum += nibblemap[map->b_data[i] & 0xf] +
-			nibblemap[(map->b_data[i] >> 4) & 0xf];
-	return sum;
+	return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
 }
 
 #endif  /*  EXT4FS_DEBUG  */