diff --git a/kernel/scheme/debug.rs b/kernel/scheme/debug.rs
index 0dc67267a..c3b77d886 100644
--- a/kernel/scheme/debug.rs
+++ b/kernel/scheme/debug.rs
@@ -62,7 +62,7 @@ impl Scheme for DebugScheme {
         Ok(buffer.len())
     }
 
-    fn fsync(&mut self, file: usize) -> Result<()> {
+    fn fsync(&mut self, _file: usize) -> Result<()> {
         Ok(())
     }
 
diff --git a/kernel/scheme/env.rs b/kernel/scheme/env.rs
index a04142f11..6e5778330 100644
--- a/kernel/scheme/env.rs
+++ b/kernel/scheme/env.rs
@@ -78,7 +78,7 @@ impl Scheme for EnvScheme {
         Err(Error::NotPermitted)
     }
 
-    fn fsync(&mut self, file: usize) -> Result<()> {
+    fn fsync(&mut self, _file: usize) -> Result<()> {
         Ok(())
     }
 
diff --git a/kernel/scheme/initfs.rs b/kernel/scheme/initfs.rs
index 0a33ce781..96d7d35dd 100644
--- a/kernel/scheme/initfs.rs
+++ b/kernel/scheme/initfs.rs
@@ -79,7 +79,7 @@ impl Scheme for InitFsScheme {
         Err(Error::NotPermitted)
     }
 
-    fn fsync(&mut self, file: usize) -> Result<()> {
+    fn fsync(&mut self, _file: usize) -> Result<()> {
         Ok(())
     }
 
diff --git a/kernel/scheme/irq.rs b/kernel/scheme/irq.rs
index 1720d9360..2e762d445 100644
--- a/kernel/scheme/irq.rs
+++ b/kernel/scheme/irq.rs
@@ -20,7 +20,7 @@ impl Scheme for IrqScheme {
     }
 
     fn dup(&mut self, file: usize) -> Result<usize> {
-        Err(Error::NotPermitted)
+        Ok(file)
     }
 
     fn read(&mut self, file: usize, buffer: &mut [u8]) -> Result<usize> {
@@ -32,9 +32,9 @@ impl Scheme for IrqScheme {
                 // Safe if the length of the buffer is larger than the size of a usize
                 assert!(buffer.len() >= mem::size_of::<usize>());
                 unsafe { *(buffer.as_mut_ptr() as *mut usize) = current; }
-                return Ok(mem::size_of::<usize>());
+                Ok(mem::size_of::<usize>())
             } else {
-                return Ok(0);
+                Ok(0)
             }
         } else {
             Err(Error::InvalidValue)
@@ -49,9 +49,9 @@ impl Scheme for IrqScheme {
             if ack == current {
                 ACKS.lock()[file] = ack;
                 unsafe { acknowledge(file); }
-                return Ok(mem::size_of::<usize>());
+                Ok(mem::size_of::<usize>())
             } else {
-                return Ok(0);
+                Ok(0)
             }
         } else {
             Err(Error::InvalidValue)
@@ -62,7 +62,7 @@ impl Scheme for IrqScheme {
         Ok(())
     }
 
-    fn close(&mut self, file: usize) -> Result<()> {
+    fn close(&mut self, _file: usize) -> Result<()> {
         Ok(())
     }
 }