Reorder extent back refs to differentiate file data from btree blocks

ctree.h

@@ -31,7 +31,7 @@ struct btrfs_trans_handle;
 #define BTRFS_EXTENT_TREE_OBJECTID 2ULL
 #define BTRFS_FS_TREE_OBJECTID 3ULL
 #define BTRFS_ROOT_TREE_DIR_OBJECTID 4ULL
-#define BTRFS_FIRST_FREE_OBJECTID 5ULL
+#define BTRFS_FIRST_FREE_OBJECTID 256ULL
 
 /*
  * we can actually store much bigger names, but lets not confuse the rest

mkfs.c

@@ -353,9 +353,9 @@ int main(int ac, char **av)
 	struct stat st;
 	int ret;
 	int i;
-	u32 leafsize = 8 * 1024;
+	u32 leafsize = 16 * 1024;
 	u32 sectorsize = 4096;
-	u32 nodesize = 8 * 1024;
+	u32 nodesize = 16 * 1024;
 	u32 stripesize = 4096;
 	char *buf = malloc(sectorsize);
 	char *realpath_name;