update codes

code/lab4/kern/mm/memlayout.h

@@ -98,7 +98,7 @@ struct e820map {
  * that convert Page to other data types, such as phyical address.
  * */
 struct Page {
-    atomic_t ref;                   // page frame's reference counter
+    int ref;                        // page frame's reference counter
     uint32_t flags;                 // array of flags that describe the status of the page frame
     unsigned int property;          // used in buddy system, stores the order (the X in 2^X) of the continuous memory block
     int zone_num;                   // used in buddy system, the No. of zone which the page belongs to

code/lab4/kern/mm/pmm.h

@@ -122,22 +122,24 @@ pde2page(pde_t pde) {
 
 static inline int
 page_ref(struct Page *page) {
-    return atomic_read(&(page->ref));
+    return page->ref;
 }
 
 static inline void
 set_page_ref(struct Page *page, int val) {
-    atomic_set(&(page->ref), val);
+    page->ref = val;
 }
 
 static inline int
 page_ref_inc(struct Page *page) {
-    return atomic_add_return(&(page->ref), 1);
+    page->ref += 1;
+    return page->ref;
 }
 
 static inline int
 page_ref_dec(struct Page *page) {
-    return atomic_sub_return(&(page->ref), 1);
+    page->ref -= 1;
+    return page->ref;
 }
 
 extern char bootstack[], bootstacktop[];