address review comments

Signed-off-by: ylzh10 <[email protected]>

Author: ylzh10

src/address_allocator.rs

@@ -67,15 +67,19 @@ impl AddressAllocator {
     ) -> Result<RangeInclusive> {
         let constraint = Constraint::new(size, alignment, policy)?;
         let allocated = self.interval_tree.allocate(constraint)?;
-        self.used.checked_add(allocated.len() as usize).expect("Failed to calculate used memory");
+        self.used
+            .checked_add(allocated.len() as usize)
+            .expect("Failed to calculate used memory");
         Ok(allocated)
     }
 
     /// Deletes the specified memory slot or returns `ResourceNotAvailable` if
     /// the node was not allocated before.
     pub fn free(&mut self, key: &RangeInclusive) -> Result<()> {
         self.interval_tree.free(key)?;
-        self.used.checked_sub(key.len() as usize).expect("Failed to calculate used memory");
+        self.used
+            .checked_sub(key.len() as usize)
+            .expect("Failed to calculate used memory");
         Ok(())
     }