diff --git a/os/src/fs/mod.rs b/os/src/fs/mod.rs
index 853ef41a..60c89bd3 100644
--- a/os/src/fs/mod.rs
+++ b/os/src/fs/mod.rs
@@ -2,19 +2,9 @@ mod pipe;
 mod stdio;
 
 use crate::mm::UserBuffer;
-use core::any::Any;
-
-pub trait File : Any + Send + Sync {
+pub trait File : Send + Sync {
     fn read(&self, buf: UserBuffer) -> usize;
     fn write(&self, buf: UserBuffer) -> usize;
-    fn as_any_ref(&self) -> &dyn Any;
-}
-
-impl dyn File {
-    #[allow(unused)]
-    pub fn downcast_ref<T: File>(&self) -> Option<&T> {
-        self.as_any_ref().downcast_ref::<T>()
-    }
 }
 
 pub use pipe::{Pipe, make_pipe};
diff --git a/os/src/fs/pipe.rs b/os/src/fs/pipe.rs
index ccbc53e0..6f5c1f33 100644
--- a/os/src/fs/pipe.rs
+++ b/os/src/fs/pipe.rs
@@ -5,7 +5,6 @@ use crate::mm::{
     UserBuffer,
 };
 use crate::task::suspend_current_and_run_next;
-use core::any::Any;
 
 pub struct Pipe {
     readable: bool,
@@ -163,5 +162,4 @@ impl File for Pipe {
             }
         }
     }
-    fn as_any_ref(&self) -> &dyn Any { self }
 }
\ No newline at end of file
diff --git a/os/src/fs/stdio.rs b/os/src/fs/stdio.rs
index 841849ef..b87d185b 100644
--- a/os/src/fs/stdio.rs
+++ b/os/src/fs/stdio.rs
@@ -2,7 +2,6 @@ use super::File;
 use crate::mm::{UserBuffer};
 use crate::sbi::console_getchar;
 use crate::task::suspend_current_and_run_next;
-use core::any::Any;
 
 pub struct Stdin;
 
@@ -29,7 +28,6 @@ impl File for Stdin {
     fn write(&self, _user_buf: UserBuffer) -> usize {
         panic!("Cannot write to stdin!");
     }
-    fn as_any_ref(&self) -> &dyn Any { self }
 }
 
 impl File for Stdout {
@@ -42,5 +40,4 @@ impl File for Stdout {
         }
         user_buf.len()
     }
-    fn as_any_ref(&self) -> &dyn Any { self }
 }
\ No newline at end of file