+static int count_device(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ unsigned *num_devices = data;
+
+ (*num_devices)++;
+
+ return 0;
+}
+
+/*
+ * Check whether a table has no data devices attached using each
+ * target's iterate_devices method.
+ * Returns false if the result is unknown because a target doesn't
+ * support iterate_devices.
+ */
+bool dm_table_has_no_data_devices(struct dm_table *table)
+{
+ struct dm_target *uninitialized_var(ti);
+ unsigned i = 0, num_devices = 0;
+
+ while (i < dm_table_get_num_targets(table)) {
+ ti = dm_table_get_target(table, i++);
+
+ if (!ti->type->iterate_devices)
+ return false;
+
+ ti->type->iterate_devices(ti, count_device, &num_devices);
+ if (num_devices)
+ return false;
+ }
+
+ return true;
+}
+