#define read_swap_cache_async(swp,vma,addr) NULL
#define lookup_swap_cache(swp) NULL
#define valid_swaphandles(swp, off) 0
-#define can_share_swap_page(p) 0
+#define can_share_swap_page(p) (page_mapcount(p) == 1)
#define move_to_swap_cache(p, swp) 1
#define move_from_swap_cache(p, i, m) 1
#define __delete_from_swap_cache(p) /*NOTHING*/