+ hp_index = atomic_xchg(&highest_priority_index, -1);
+ /*
+ * highest_priority_index records current highest priority swap
+ * type which just frees swap entries. If its priority is
+ * higher than that of swap_list.next swap type, we use it. It
+ * isn't protected by swap_lock, so it can be an invalid value
+ * if the corresponding swap type is swapoff. We double check
+ * the flags here. It's even possible the swap type is swapoff
+ * and swapon again and its priority is changed. In such rare
+ * case, low prority swap type might be used, but eventually
+ * high priority swap will be used after several rounds of
+ * swap.
+ */
+ if (hp_index != -1 && hp_index != type &&
+ swap_info[type]->prio < swap_info[hp_index]->prio &&
+ (swap_info[hp_index]->flags & SWP_WRITEOK)) {
+ type = hp_index;
+ swap_list.next = type;
+ }
+