src/userprog/exception.c

@@ -24,7 +24,7 @@ static void page_fault (struct intr_frame *);
 
 static bool is_valid_stack_access (const void *fault_addr, const void *esp);
 static bool grow_stack (void *upage);
-bool try_fetch_page (void *upage, bool write);
+bool fetch_page (void *upage, bool write);
 
 /* Registers handlers for interrupts that can be caused by user
    programs.
@@ -167,29 +167,14 @@ page_fault (struct intr_frame *f)
    be just that the stack needs to grow or that it needs to be lazily loaded.
    So we attempt to grow the stack. If this does not work, we check our SPT to
    see if the page is expected to have data loaded in memory. */
-  struct thread *t = thread_current ();
   void *upage = pg_round_down (fault_addr);
   if (not_present && is_user_vaddr (upage) && upage != NULL)
     {
-      /* Check if the non-present user page is in the swap partition.
-         If so, swap it back into main memory, updating the PTE for
-         the faulted virtual address to point to the newly allocated
-         frame. */
-      if (page_in_swap (t, fault_addr))
-        {
-          size_t swap_slot = page_get_swap (t, fault_addr);
-          void *kpage = frame_alloc (0, upage, t);
-          swap_in (kpage, swap_slot);
-
-          bool writeable = pagedir_is_writable (t->pagedir, upage);
-          if (pagedir_set_page (t->pagedir, upage, kpage, writeable)) return;
-        }
-
       if (is_valid_stack_access (fault_addr, esp))
           if (grow_stack (upage))
             return;
 
-      if (try_fetch_page (upage, write))
+      if (fetch_page (upage, write))
         return;
     }
 
@@ -262,8 +247,24 @@ grow_stack (void *upage)
 }
 
 bool
-try_fetch_page (void *upage, bool write)
+fetch_page (void *upage, bool write)
 {
+  /* Check if the non-present user page is in the swap partition.
+   If so, swap it back into main memory, updating the PTE for
+   the faulted virtual address to point to the newly allocated
+   frame. */
+  struct thread *t = thread_current ();
+  if (page_in_swap (t, upage))
+  {
+    size_t swap_slot = page_get_swap (t, upage);
+    void *kpage = frame_alloc (0, upage, t);
+    swap_in (kpage, swap_slot);
+
+    bool writeable = pagedir_is_writable (t->pagedir, upage);
+    if (pagedir_set_page (t->pagedir, upage, kpage, writeable))
+      return true;
+  }
+
   /* Check if the page is in the supplemental page table. That is, it is a page
      that is expected to be in memory. */
   struct page_entry *page = page_get (upage);