diff --git a/judger/src/filesystem/table/handle.rs b/judger/src/filesystem/table/handle.rs
index b0cc3da..ac75b8d 100644
--- a/judger/src/filesystem/table/handle.rs
+++ b/judger/src/filesystem/table/handle.rs
@@ -1,33 +1,30 @@
 use std::{collections::BTreeMap, sync::atomic::AtomicU64};
 
 use spin::RwLock;
-use tokio::io::{AsyncRead, AsyncSeek};
 
-use crate::filesystem::overlay::*;
-
-pub struct HandleTable<F>
-where
-    F: AsyncRead + AsyncSeek + Unpin + 'static,
-{
+pub struct HandleTable<E: Clone> {
     handle_generator: AtomicU64,
-    table: RwLock<BTreeMap<u64, ArcEntry<F>>>,
+    table: RwLock<BTreeMap<u64, E>>,
 }
 
-impl<F> HandleTable<F>
-where
-    F: AsyncRead + AsyncSeek + Unpin + 'static,
-{
-    pub fn new_handle(&self, entry: ArcEntry<F>) -> u64 {
+impl<E: Clone> HandleTable<E> {
+    pub fn new() -> Self {
+        Self {
+            handle_generator: AtomicU64::new(0),
+            table: RwLock::new(BTreeMap::new()),
+        }
+    }
+    pub fn add(&self, entry: E) -> u64 {
         let handle = self
             .handle_generator
             .fetch_add(1, std::sync::atomic::Ordering::AcqRel);
         self.table.write().insert(handle, entry);
         handle
     }
-    pub fn get_entry(&self, handle: u64) -> Option<ArcEntry<F>> {
+    pub fn get(&self, handle: u64) -> Option<E> {
         self.table.read().get(&handle).cloned()
     }
-    pub fn remove_entry(&self, handle: u64) -> Option<ArcEntry<F>> {
+    pub fn remove(&self, handle: u64) -> Option<E> {
         self.table.write().remove(&handle)
     }
 }
diff --git a/judger/src/filesystem/table/inode.rs b/judger/src/filesystem/table/inode.rs
index 1ae9e5e..846298c 100644
--- a/judger/src/filesystem/table/inode.rs
+++ b/judger/src/filesystem/table/inode.rs
@@ -1,30 +1,62 @@
 use std::{
     collections::BTreeMap,
-    sync::{atomic::AtomicU64, Arc},
+    sync::atomic::{AtomicU64, Ordering},
 };
 
 use spin::RwLock;
-use tokio::io::{AsyncRead, AsyncSeek};
 
-use crate::{filesystem::overlay::ArcEntry, semaphore::Semaphore};
+const MAX_INODE: u64 = 1 << 63;
 
-pub struct INodeTable<F>
-where
-    F: AsyncRead + AsyncSeek + Unpin + 'static,
-{
-    semaphore: Arc<Semaphore>,
-    table: RwLock<BTreeMap<u64, ArcEntry<F>>>,
-    handle_generator: AtomicU64,
+pub trait Identified {
+    fn get_id(&self) -> usize;
 }
 
-impl<F> INodeTable<F>
-where
-    F: AsyncRead + AsyncSeek + Unpin + 'static,
-{
-    pub async fn new_inode(&self, entry: ArcEntry<F>) {
-        let handle = self
-            .handle_generator
+pub struct INodeTable<E: Clone + Identified> {
+    inode: RwLock<BTreeMap<u64, E>>,
+    id: RwLock<BTreeMap<usize, u64>>,
+    inode_generator: AtomicU64,
+}
+
+impl<E: Clone + Identified> INodeTable<E> {
+    pub fn new() -> Self {
+        Self {
+            inode: RwLock::new(BTreeMap::new()),
+            id: RwLock::new(BTreeMap::new()),
+            inode_generator: AtomicU64::new(1),
+        }
+    }
+    pub fn allocate<F>(&self, mut f: F) -> E
+    where
+        F: FnMut(u64) -> E,
+    {
+        let inode = self
+            .inode_generator
             .fetch_add(1, std::sync::atomic::Ordering::AcqRel);
-        self.table.write().insert(handle, entry);
+        let entry = f(inode);
+        match { self.id.read().get(&entry.get_id()) } {
+            Some(&x) => f(x),
+            None => {
+                self.inode.write().insert(inode, entry.clone());
+                entry
+            }
+        }
+    }
+    /// get entry by inode
+    pub fn get(&self, inode: u64) -> Option<E> {
+        self.inode.read().get(&inode).cloned()
+    }
+    /// deallocate inode
+    pub fn remove(&self, inode: u64) {
+        // FIXME: inode should be reused
+        if let Some(e) = { self.inode.write().remove(&inode) } {
+            self.id.write().remove(&e.get_id());
+        }
+    }
+    pub fn get_free_inode(&self) -> u64 {
+        MAX_INODE - self.get_used_inode()
+    }
+    #[inline]
+    pub fn get_used_inode(&self) -> u64 {
+        self.inode_generator.load(Ordering::Acquire)
     }
 }
diff --git a/judger/src/filesystem/table/mod.rs b/judger/src/filesystem/table/mod.rs
index 4a8cd64..397faa9 100644
--- a/judger/src/filesystem/table/mod.rs
+++ b/judger/src/filesystem/table/mod.rs
@@ -2,4 +2,4 @@ mod handle;
 mod inode;
 
 pub use handle::HandleTable;
-pub use inode::INodeTable;
+pub use inode::{INodeTable, Identified};