修复了unlink彻底删除文件时，没有回收inode的情况

要提交的变更：
      修改：     easy-fs/src/efs.rs
      修改：     easy-fs/src/vfs.rs

easy-fs/src/efs.rs

@@ -153,4 +153,16 @@ impl EasyFileSystem {
             (block_id - self.data_area_start_block) as usize,
         )
     }
+    /// dealloc a inode
+    pub fn dealloc_disk_inode(&mut self, inode_id: u32) {
+        get_block_cache(inode_id as usize, Arc::clone(&self.block_device))
+            .lock()
+            .modify(0, |disk_inode: &mut DataBlock| {
+                disk_inode.iter_mut().for_each(|p| *p = 0);
+            });
+        self.inode_bitmap.dealloc(
+            &self.block_device,
+            (inode_id - self.inode_area_start_block) as usize,
+        );
+    }
 }

easy-fs/src/vfs.rs

@@ -64,9 +64,12 @@ impl Inode {
                 for data_block in data_blocks_dealloc.into_iter() {
                     fs.dealloc_data(data_block);
                 }
-                // fs.inode_bitmap.dealloc(&fs.block_device, self.id() as usize);
             }
         });
+
+        if self.link_cnt() == 0 {
+            fs.dealloc_disk_inode(self.id());
+        }
     }
     #[allow(unused)]
     fn link_cnt(&self) -> usize {