feat: remove identity mapping methods from PageNums, as we don't need identity mapping

crates/address/src/physical_page_num.rs

@@ -8,12 +8,6 @@ pub struct PhysicalPageNum(pub usize);
 
 impl_IPageNum!(PhysicalPageNum);
 
-impl PhysicalPageNum {
-    pub fn identity_mapped(self) -> VirtualPageNum {
-        VirtualPageNum::from_usize(self.as_usize())
-    }
-}
-
 #[cfg(test)]
 mod physical_page_num_tests {
     use super::*;
@@ -25,14 +19,6 @@ mod physical_page_num_tests {
         assert_eq!(page_num.as_usize(), 5);
     }
 
-    // Identity mapping 测试
-    #[test]
-    fn test_identity_mapped() {
-        let phys_page = PhysicalPageNum::from_usize(0x1000);
-        let virt_page = phys_page.identity_mapped();
-        assert_eq!(phys_page.as_usize(), virt_page.as_usize());
-    }
-
     // 运算符测试
     #[test]
     fn test_arithmetic_operations() {

crates/address/src/physical_page_num_range.rs

@@ -3,12 +3,3 @@ use crate::*;
 pub type PhysicalPageNumRange = PageNumRange<PhysicalPageNum>;
 
 impl_range_display!(PhysicalPageNumRange);
-
-impl PhysicalPageNumRange {
-    pub fn identity_mapped(&self) -> VirtualPageNumRange {
-        VirtualPageNumRange::from_start_end(
-            self.start().identity_mapped(),
-            self.end().identity_mapped(),
-        )
-    }
-}

crates/address/src/virtual_page_num.rs

@@ -8,10 +8,4 @@ pub struct VirtualPageNum(pub usize);
 
 impl_IPageNum!(VirtualPageNum);
 
-impl VirtualPageNum {
-    pub fn identity_mapped(self) -> PhysicalPageNum {
-        PhysicalPageNum::from_usize(self.as_usize())
-    }
-}
-
 // No need to test VirtualPageNum, as they share the same code as PhysicalPageNum

crates/address/src/virtual_page_num_range.rs

@@ -3,12 +3,3 @@ use crate::*;
 pub type VirtualPageNumRange = PageNumRange<VirtualPageNum>;
 
 impl_range_display!(VirtualPageNumRange);
-
-impl VirtualPageNumRange {
-    pub fn identity_mapped(&self) -> PhysicalPageNumRange {
-        PhysicalPageNumRange::from_start_end(
-            self.start().identity_mapped(),
-            self.end().identity_mapped(),
-        )
-    }
-}