+/*
+ * Check if io_u will overlap an in-flight IO in the queue
+ */
+static bool in_flight_overlap(struct io_u_queue *q, struct io_u *io_u)
+{
+ bool overlap;
+ struct io_u *check_io_u;
+ unsigned long long x1, x2, y1, y2;
+ int i;
+
+ x1 = io_u->offset;
+ x2 = io_u->offset + io_u->buflen;
+ overlap = false;
+ io_u_qiter(q, check_io_u, i) {
+ if (check_io_u->flags & IO_U_F_FLIGHT) {
+ y1 = check_io_u->offset;
+ y2 = check_io_u->offset + check_io_u->buflen;
+
+ if (x1 < y2 && y1 < x2) {
+ overlap = true;
+ dprint(FD_IO, "in-flight overlap: %llu/%lu, %llu/%lu\n",
+ x1, io_u->buflen,
+ y1, check_io_u->buflen);
+ break;
+ }
+ }
+ }
+
+ return overlap;
+}
+
+static enum fio_q_status io_u_submit(struct thread_data *td, struct io_u *io_u)
+{
+ /*
+ * Check for overlap if the user asked us to, and we have
+ * at least one IO in flight besides this one.
+ */
+ if (td->o.serialize_overlap && td->cur_depth > 1 &&
+ in_flight_overlap(&td->io_u_all, io_u))
+ return FIO_Q_BUSY;
+
+ return td_io_queue(td, io_u);
+}
+