fix: always add to frame owners when installing existing shared page.

src/vm/page.c

@@ -199,12 +199,8 @@ page_load_file (struct page_entry *page)
                   lock_release (&shared_file_pages_lock);
                   return false;
                 }
-              /* First time adding the shared page, so add thread as owner. */
-              if (page->type != PAGE_SHARED)
-                {
               frame_owner_insert (sfp->frame, t);
             }
-            }
             /* Shared page is in swap. Load it. */
             else
               {