253     next_free: u32,  field
609                 let next_free: u64 = self.fs_info.0.lock().next_free().unwrap_or(0xffffffff);  in allocate_cluster()  localVariable
610                 if next_free < end_cluster.cluster_num {  in allocate_cluster()
611                     Cluster::new(next_free)  in allocate_cluster()
1258         fsinfo.next_free = cursor.read_u32()?;  in new()
1319     pub fn update_next_free(&mut self, next_free: u32) {  in update_next_free()
1321         self.next_free = next_free;  in update_next_free()
1325     pub fn next_free(&self) -> Option<u64> {  in next_free()  method
1326         match self.next_free {  in next_free()
1352             cursor.write_u32(self.next_free)?;  in flush()
1380             self.next_free = cursor.read_u32()?;  in update()
1867             next_free: RESERVED_CLUSTERS,  in default()