diff --git a/easy-fs/Cargo.toml b/easy-fs/Cargo.toml
index 3beb3ff2..16ffc303 100644
--- a/easy-fs/Cargo.toml
+++ b/easy-fs/Cargo.toml
@@ -7,4 +7,6 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-spin = "0.7.0"
\ No newline at end of file
+spin = "0.7.0"
+#lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
+lazy_static = "1.4.0"
\ No newline at end of file
diff --git a/easy-fs/src/bin/main.rs b/easy-fs/src/bin/main.rs
index 3af832aa..1a8061fd 100644
--- a/easy-fs/src/bin/main.rs
+++ b/easy-fs/src/bin/main.rs
@@ -4,7 +4,6 @@ extern crate alloc;
 use easy_fs::{
     BlockDevice,
     EasyFileSystem,
-    Inode,
 };
 use std::fs::{File, OpenOptions};
 use std::io::{Read, Write, Seek, SeekFrom};
@@ -54,7 +53,7 @@ fn easy_fs_pack() -> std::io::Result<()> {
     root_inode.create("filea");
     root_inode.create("fileb");
     for name in root_inode.ls() {
-        println!("name");
+        println!("{}", name);
     }
     Ok(())
 }
\ No newline at end of file
diff --git a/easy-fs/src/block_cache.rs b/easy-fs/src/block_cache.rs
new file mode 100644
index 00000000..34450f63
--- /dev/null
+++ b/easy-fs/src/block_cache.rs
@@ -0,0 +1,86 @@
+use super::{
+    BlockDevice,
+    BLOCK_SZ,
+};
+use alloc::sync::{Arc, Weak};
+use alloc::collections::BTreeMap;
+use lazy_static::*;
+use spin::Mutex;
+
+pub struct BlockCache {
+    cache: [u8; BLOCK_SZ],
+    block_id: usize,
+    block_device: Arc<dyn BlockDevice>,
+}
+
+impl BlockCache {
+    pub fn new(block_id: usize, block_device: Arc<dyn BlockDevice>) -> Self {
+        let mut cache = [0u8; BLOCK_SZ];
+        block_device.read_block(block_id, &mut cache);
+        Self {
+            cache,
+            block_id,
+            block_device,
+        }
+    }
+    pub fn start_addr(&self, offset: usize) -> usize {
+        &self.cache[offset] as *const _ as usize
+    }
+}
+
+impl Drop for BlockCache {
+    fn drop(&mut self) {
+        // write back
+        self.block_device.write_block(self.block_id, &self.cache);
+        // invalid in block cache manager
+        BLOCK_CACHE_MANAGER.lock().invalid(self.block_id);
+    }
+}
+
+pub struct BlockCacheManager {
+    map: BTreeMap<usize, Weak<BlockCache>>,
+}
+
+lazy_static! {
+    static ref BLOCK_CACHE_MANAGER: Mutex<BlockCacheManager> = Mutex::new(
+        BlockCacheManager::new()
+    );
+}
+
+impl BlockCacheManager {
+    pub fn new() -> Self {
+        Self { map: BTreeMap::new() }
+    }
+    pub fn get(
+        &mut self,
+        block_id: usize,
+        block_device: Arc<dyn BlockDevice>
+    ) -> Arc<BlockCache> {
+        if let Some(block_cache) = self.map.get(&block_id) {
+            // return cloned
+            block_cache.upgrade().unwrap().clone()
+        } else {
+            // fetch from disk
+            let block_cache = Arc::new(BlockCache::new(
+                block_id,
+                block_device.clone()
+            ));
+            self.map.insert(
+                block_id,
+                Arc::downgrade(&block_cache),
+            );
+            // return
+            block_cache
+        }
+    }
+    pub fn invalid(&mut self, block_id: usize) {
+        assert!(self.map.remove(&block_id).is_some());
+    }
+}
+
+pub fn get_block_cache(
+    block_id: usize,
+    block_device: Arc<dyn BlockDevice>
+) -> Arc<BlockCache> {
+    BLOCK_CACHE_MANAGER.lock().get(block_id, block_device)
+}
\ No newline at end of file
diff --git a/easy-fs/src/dirty.rs b/easy-fs/src/dirty.rs
index 8fa7a895..fc02aab4 100644
--- a/easy-fs/src/dirty.rs
+++ b/easy-fs/src/dirty.rs
@@ -1,45 +1,38 @@
-use super::BlockDevice;
-use super::BLOCK_SZ;
+use super::{
+    BlockDevice,
+    BLOCK_SZ,
+    BlockCache,
+    get_block_cache,
+};
 use alloc::sync::Arc;
 use core::marker::PhantomData;
 
 pub struct Dirty<T> {
-    block_id: usize,
-    block_cache: [u8; BLOCK_SZ],
+    block_cache: Arc<BlockCache>,
     offset: usize,
-    dirty: bool,
-    block_device: Arc<dyn BlockDevice>,
     phantom: PhantomData<T>,
 }
 
 impl<T> Dirty<T> where T: Sized {
     pub fn new(block_id: usize, offset: usize, block_device: Arc<dyn BlockDevice>) -> Self {
         Self {
-            block_id,
-            block_cache: {
-                let mut cache = [0u8; BLOCK_SZ];
-                block_device.read_block(block_id as usize, &mut cache);
-                cache
-            },
+            block_cache: get_block_cache(block_id, block_device.clone()),
             offset,
-            dirty: false,
-            block_device,
             phantom: PhantomData,
         }
     }
     pub fn get_mut(&mut self) -> &mut T {
-        self.dirty = true;
         let type_size = core::mem::size_of::<T>();
         // assert that the struct is inside a block
         assert!(self.offset + type_size <= BLOCK_SZ);
-        let start_addr = &self.block_cache[self.offset] as *const _ as usize;
+        let start_addr = self.block_cache.start_addr(self.offset);
         unsafe { &mut *(start_addr as *mut T) }
     }
     pub fn get_ref(&self) -> &T {
         let type_size = core::mem::size_of::<T>();
         // assert that the struct is inside a block
         assert!(self.offset + type_size <= BLOCK_SZ);
-        let start_addr = &self.block_cache[self.offset] as *const _ as usize;
+        let start_addr = self.block_cache.start_addr(self.offset);
         unsafe { &*(start_addr as *const T) }
     }
     pub fn read<V>(&self, f: impl FnOnce(&T) -> V) -> V {
@@ -48,16 +41,4 @@ impl<T> Dirty<T> where T: Sized {
     pub fn modify(&mut self, f: impl FnOnce(&mut T)) {
         f(self.get_mut());
     }
-    pub fn write_back(&mut self) {
-        if self.dirty {
-            self.block_device
-                .write_block(self.block_id as usize, &self.block_cache);
-        }
-    }
 }
-
-impl<T> Drop for Dirty<T> {
-    fn drop(&mut self) {
-        self.write_back();
-    }
-}
\ No newline at end of file
diff --git a/easy-fs/src/layout.rs b/easy-fs/src/layout.rs
index 174d64cf..d262f354 100644
--- a/easy-fs/src/layout.rs
+++ b/easy-fs/src/layout.rs
@@ -247,7 +247,7 @@ pub struct DirEntry {
 
 pub const DIRENT_SZ: usize = 32;
 
-pub type DirentBlock = [DirEntry; BLOCK_SZ / DIRENT_SZ];
+//pub type DirentBlock = [DirEntry; BLOCK_SZ / DIRENT_SZ];
 pub type DirentBytes = [u8; DIRENT_SZ];
 
 impl DirEntry {
diff --git a/easy-fs/src/lib.rs b/easy-fs/src/lib.rs
index 4202fb4b..dfd1725e 100644
--- a/easy-fs/src/lib.rs
+++ b/easy-fs/src/lib.rs
@@ -6,6 +6,7 @@ mod efs;
 mod dirty;
 mod bitmap;
 mod vfs;
+mod block_cache;
 
 pub const BLOCK_SZ: usize = 512;
 pub use block_dev::BlockDevice;
@@ -13,4 +14,5 @@ pub use efs::EasyFileSystem;
 pub use vfs::Inode;
 use layout::*;
 use dirty::Dirty;
-use bitmap::Bitmap;
\ No newline at end of file
+use bitmap::Bitmap;
+use block_cache::{BlockCache, get_block_cache};
\ No newline at end of file
diff --git a/easy-fs/src/vfs.rs b/easy-fs/src/vfs.rs
index 2a989f99..30b31cf9 100644
--- a/easy-fs/src/vfs.rs
+++ b/easy-fs/src/vfs.rs
@@ -6,13 +6,11 @@ use super::{
     DirEntry,
     DirentBytes,
     EasyFileSystem,
-    BLOCK_SZ,
     DIRENT_SZ,
 };
 use alloc::sync::Arc;
 use alloc::string::String;
 use alloc::vec::Vec;
-use crate::layout::DiskInodeType::Directory;
 use spin::{Mutex, MutexGuard};
 
 pub struct Inode {