diff --git a/kernel/Cargo.lock b/kernel/Cargo.lock
index 742cb60..bf16e11 100644
--- a/kernel/Cargo.lock
+++ b/kernel/Cargo.lock
@@ -337,12 +337,12 @@ dependencies = [
 [[package]]
 name = "rcore-fs"
 version = "0.1.0"
-source = "git+https://github.com/rcore-os/rcore-fs?branch=sefs#0eba40886d36311b28d42ff2a27a0f4292e2ad9f"
+source = "git+https://github.com/rcore-os/rcore-fs?branch=sefs#38dab25178eb25abaab8e6d929af354a56158d5f"
 
 [[package]]
 name = "rcore-fs-sfs"
 version = "0.1.0"
-source = "git+https://github.com/rcore-os/rcore-fs?branch=sefs#0eba40886d36311b28d42ff2a27a0f4292e2ad9f"
+source = "git+https://github.com/rcore-os/rcore-fs?branch=sefs#38dab25178eb25abaab8e6d929af354a56158d5f"
 dependencies = [
  "bitvec 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/kernel/src/fs/file.rs b/kernel/src/fs/file.rs
index f6d3395..fa6d837 100644
--- a/kernel/src/fs/file.rs
+++ b/kernel/src/fs/file.rs
@@ -36,10 +36,7 @@ impl FileHandle {
     }
 
     pub fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
-        if !self.options.read {
-            return Err(FsError::InvalidParam);  // FIXME: => EBADF
-        }
-        let len = self.inode.read_at(self.offset as usize, buf)?;
+        let len = self.read_at(self.offset as usize, buf)?;
         self.offset += len as u64;
         Ok(len)
     }
@@ -53,15 +50,12 @@ impl FileHandle {
     }
 
     pub fn write(&mut self, buf: &[u8]) -> Result<usize> {
-        if !self.options.write {
-            return Err(FsError::InvalidParam);  // FIXME: => EBADF
-        }
-        if self.options.append {
-            let info = self.inode.metadata()?;
-            self.offset = info.size as u64;
-        }
-        let len = self.inode.write_at(self.offset as usize, buf)?;
-        self.offset += len as u64;
+        let offset = match self.options.append {
+            true => self.inode.metadata()?.size as u64,
+            false => self.offset,
+        } as usize;
+        let len = self.write_at(offset, buf)?;
+        self.offset = (offset + len) as u64;
         Ok(len)
     }
 
@@ -91,12 +85,11 @@ impl FileHandle {
     }
 
     pub fn sync_all(&mut self) -> Result<()> {
-        self.inode.sync()
+        self.inode.sync_all()
     }
 
     pub fn sync_data(&mut self) -> Result<()> {
-        // TODO: add sync_data to VFS
-        self.inode.sync()
+        self.inode.sync_data()
     }
 
     pub fn metadata(&self) -> Result<Metadata> {
diff --git a/kernel/src/fs/pipe.rs b/kernel/src/fs/pipe.rs
index c905d03..9521904 100644
--- a/kernel/src/fs/pipe.rs
+++ b/kernel/src/fs/pipe.rs
@@ -58,12 +58,12 @@ impl Pipe {
 macro_rules! impl_inode {
     () => {
         fn metadata(&self) -> Result<Metadata> { Err(FsError::NotSupported) }
-        fn sync(&self) -> Result<()> { Ok(()) }
+        fn sync_all(&self) -> Result<()> { Ok(()) }
+        fn sync_data(&self) -> Result<()> { Ok(()) }
         fn resize(&self, _len: usize) -> Result<()> { Err(FsError::NotSupported) }
         fn create(&self, _name: &str, _type_: FileType, _mode: u32) -> Result<Arc<INode>> { Err(FsError::NotDir) }
         fn unlink(&self, _name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn link(&self, _name: &str, _other: &Arc<INode>) -> Result<()> { Err(FsError::NotDir) }
-        fn rename(&self, _old_name: &str, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn move_(&self, _old_name: &str, _target: &Arc<INode>, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn find(&self, _name: &str) -> Result<Arc<INode>> { Err(FsError::NotDir) }
         fn get_entry(&self, _id: usize) -> Result<String> { Err(FsError::NotDir) }
diff --git a/kernel/src/fs/stdio.rs b/kernel/src/fs/stdio.rs
index bbce87b..4987fe6 100644
--- a/kernel/src/fs/stdio.rs
+++ b/kernel/src/fs/stdio.rs
@@ -53,12 +53,12 @@ lazy_static! {
 macro_rules! impl_inode {
     () => {
         fn metadata(&self) -> Result<Metadata> { Err(FsError::NotSupported) }
-        fn sync(&self) -> Result<()> { Ok(()) }
+        fn sync_all(&self) -> Result<()> { Ok(()) }
+        fn sync_data(&self) -> Result<()> { Ok(()) }
         fn resize(&self, _len: usize) -> Result<()> { Err(FsError::NotSupported) }
         fn create(&self, _name: &str, _type_: FileType, _mode: u32) -> Result<Arc<INode>> { Err(FsError::NotDir) }
         fn unlink(&self, _name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn link(&self, _name: &str, _other: &Arc<INode>) -> Result<()> { Err(FsError::NotDir) }
-        fn rename(&self, _old_name: &str, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn move_(&self, _old_name: &str, _target: &Arc<INode>, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
         fn find(&self, _name: &str) -> Result<Arc<INode>> { Err(FsError::NotDir) }
         fn get_entry(&self, _id: usize) -> Result<String> { Err(FsError::NotDir) }
diff --git a/kernel/src/syscall/fs.rs b/kernel/src/syscall/fs.rs
index ce3c753..378ffac 100644
--- a/kernel/src/syscall/fs.rs
+++ b/kernel/src/syscall/fs.rs
@@ -319,12 +319,7 @@ pub fn sys_open(path: *const u8, flags: usize, mode: usize) -> SysResult {
             Err(e) => return Err(SysError::from(e)),
         }
     } else {
-        // TODO: remove "stdin:" "stdout:"
-        match path.as_str() {
-            "stdin:" => crate::fs::STDIN.clone() as Arc<INode>,
-            "stdout:" => crate::fs::STDOUT.clone() as Arc<INode>,
-            _ => proc.lookup_inode(&path)?,
-        }
+        proc.lookup_inode(&path)?
     };
 
     let fd = proc.get_free_fd();
@@ -502,12 +497,7 @@ pub fn sys_rename(oldpath: *const u8, newpath: *const u8) -> SysResult {
     let (new_dir_path, new_file_name) = split_path(&newpath);
     let old_dir_inode = proc.lookup_inode(old_dir_path)?;
     let new_dir_inode = proc.lookup_inode(new_dir_path)?;
-    // TODO: merge `rename` and `move` in VFS
-    if Arc::ptr_eq(&old_dir_inode, &new_dir_inode) {
-        old_dir_inode.rename(old_file_name, new_file_name)?;
-    } else {
-        old_dir_inode.move_(old_file_name, &new_dir_inode, new_file_name)?;
-    }
+    old_dir_inode.move_(old_file_name, &new_dir_inode, new_file_name)?;
     Ok(0)
 }
 
@@ -526,6 +516,21 @@ pub fn sys_mkdir(path: *const u8, mode: usize) -> SysResult {
     Ok(0)
 }
 
+pub fn sys_rmdir(path: *const u8) -> SysResult {
+    let proc = process();
+    let path = unsafe { proc.memory_set.check_and_clone_cstr(path)? };
+    info!("rmdir: path: {:?}", path);
+
+    let (dir_path, file_name) = split_path(&path);
+    let dir_inode = proc.lookup_inode(dir_path)?;
+    let file_inode = dir_inode.find(file_name)?;
+    if file_inode.metadata()?.type_ != FileType::Dir {
+        return Err(SysError::ENOTDIR);
+    }
+    dir_inode.unlink(file_name)?;
+    Ok(0)
+}
+
 pub fn sys_link(oldpath: *const u8, newpath: *const u8) -> SysResult {
     let proc = process();
     let oldpath = unsafe { proc.memory_set.check_and_clone_cstr(oldpath)? };
@@ -546,6 +551,10 @@ pub fn sys_unlink(path: *const u8) -> SysResult {
 
     let (dir_path, file_name) = split_path(&path);
     let dir_inode = proc.lookup_inode(dir_path)?;
+    let file_inode = dir_inode.find(file_name)?;
+    if file_inode.metadata()?.type_ == FileType::Dir {
+        return Err(SysError::EISDIR);
+    }
     dir_inode.unlink(file_name)?;
     Ok(0)
 }
@@ -556,7 +565,6 @@ pub fn sys_pipe(fds: *mut u32) -> SysResult {
     let mut proc = process();
     proc.memory_set.check_mut_array(fds, 2)?;
     let (read, write) = Pipe::create_pair();
-    let read_fd = proc.get_free_fd();
 
     let read_fd = proc.get_free_fd();
     proc.files.insert(read_fd, FileLike::File(FileHandle::new(Arc::new(read), OpenOptions { read: true, write: false, append: false })));
@@ -574,6 +582,11 @@ pub fn sys_pipe(fds: *mut u32) -> SysResult {
     Ok(0)
 }
 
+pub fn sys_sync() -> SysResult {
+    ROOT_INODE.fs().sync()?;
+    Ok(0)
+}
+
 impl Process {
     fn get_file(&mut self, fd: usize) -> Result<&mut FileHandle, SysError> {
         self.files.get_mut(&fd).ok_or(SysError::EBADF).and_then(|f| {
@@ -856,7 +869,6 @@ impl StatMode {
             FileType::BlockDevice => StatMode::BLOCK,
             FileType::Socket => StatMode::SOCKET,
             FileType::NamedPipe => StatMode::FIFO,
-            _ => StatMode::NULL,
         };
         let mode = StatMode::from_bits_truncate(mode as u32);
         type_ | mode
diff --git a/kernel/src/syscall/mod.rs b/kernel/src/syscall/mod.rs
index 10158ac..09e57ea 100644
--- a/kernel/src/syscall/mod.rs
+++ b/kernel/src/syscall/mod.rs
@@ -99,7 +99,7 @@ pub fn syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> isize {
         SYS_GETPPID => sys_getppid(),
         SYS_SETPRIORITY => sys_set_priority(args[0]),
 //        SYS_SETRLIMIT => sys_setrlimit(),
-//        SYS_SYNC => sys_sync(),
+        SYS_SYNC => sys_sync(),
         SYS_REBOOT => sys_reboot(args[0] as u32, args[1] as u32, args[2] as u32, args[3] as *const u8),
         SYS_GETTID => sys_gettid(),
         SYS_FUTEX => sys_futex(args[0], args[1] as u32, args[2] as i32, args[3] as *const TimeSpec),
@@ -183,10 +183,6 @@ pub fn syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> isize {
             warn!("sys_sigaltstack is unimplemented");
             Ok(0)
         }
-        SYS_SYNC => {
-            warn!("sys_sync is unimplemented");
-            Ok(0)
-        }
         SYS_SET_TID_ADDRESS => {
             warn!("sys_set_tid_address is unimplemented");
             Ok(thread::current().id())
@@ -243,6 +239,7 @@ fn x86_64_syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> Option<Sys
         SYS_VFORK => sys_fork(tf),
         SYS_RENAME => sys_rename(args[0] as *const u8, args[1] as *const u8),
         SYS_MKDIR => sys_mkdir(args[0] as *const u8, args[1]),
+        SYS_RMDIR => sys_rmdir(args[0] as *const u8),
         SYS_LINK => sys_link(args[0] as *const u8, args[1] as *const u8),
         SYS_UNLINK => sys_unlink(args[0] as *const u8),
         SYS_ARCH_PRCTL => sys_arch_prctl(args[0] as i32, args[1], tf),