__swap_offset_to_cluster
struct swap_cluster_info *ci = __swap_offset_to_cluster(si, offset);
return __swap_offset_to_cluster(__swap_entry_to_info(entry),
VM_BUG_ON(ci != __swap_offset_to_cluster(si, offset + nr_pages - 1));
swp_tb = swap_table_get(__swap_offset_to_cluster(si, i),