+/*
+ * Two cases of handling DISCARD merge:
+ * If max_discard_segments > 1, the driver takes every bio
+ * as a range and send them to controller together. The ranges
+ * needn't to be contiguous.
+ * Otherwise, the bios/requests will be handled as same as
+ * others which should be contiguous.
+ */
+static inline bool blk_discard_mergable(struct request *req)
+{
+ if (req_op(req) == REQ_OP_DISCARD &&
+ queue_max_discard_segments(req->q) > 1)
+ return true;
+ return false;
+}
+
+enum elv_merge blk_try_req_merge(struct request *req, struct request *next)
+{
+ if (blk_discard_mergable(req))
+ return ELEVATOR_DISCARD_MERGE;
+ else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
+ return ELEVATOR_BACK_MERGE;
+
+ return ELEVATOR_NO_MERGE;
+}