fix: synchronise pagedir which now may be accessed by other threads, with a lock

src/vm/page.h

@@ -49,7 +49,8 @@ struct shared_file_page
 };
 
 bool init_pages (struct hash *pages);
-bool page_insert_swapped (void *upage, void *kpage, struct list *owners);
+bool page_insert_swapped (void *upage, void *kpage, struct list *owners,
+                          struct thread *cur);
 struct page_entry *page_insert_file (struct file *file, off_t ofs, void *upage,
                                      uint32_t read_bytes, uint32_t zero_bytes,
                                      bool writable, enum page_type);