Index: head/sys/cam/scsi/scsi_da.c
===================================================================
--- head/sys/cam/scsi/scsi_da.c
+++ head/sys/cam/scsi/scsi_da.c
@@ -3300,7 +3300,6 @@
 		cam_periph_unlock(periph);
 		xpt_action(start_ccb);
 		cam_periph_lock(periph);
-		softc->refcount--;
 
 		/* May have more work to do, so ensure we stay scheduled */
 		daschedule(periph);
@@ -4443,13 +4442,15 @@
 		softc->flags |= DA_FLAG_WAS_OTAG;
 
 	/*
-	 * We need to call cam_iosched before we call biodone so that we
-	 * don't measure any activity that happens in the completion
-	 * routine, which in the case of sendfile can be quite
-	 * extensive.
+	 * We need to call cam_iosched before we call biodone so that we don't
+	 * measure any activity that happens in the completion routine, which in
+	 * the case of sendfile can be quite extensive. Release the periph
+	 * refcount taken in dastart() for each CCB.
 	 */
 	cam_iosched_bio_complete(softc->cam_iosched, bp, done_ccb);
 	xpt_release_ccb(done_ccb);
+	KASSERT(softc->refcount >= 1, ("dadone softc %p refcount %d", softc, softc->refcount));
+	softc->refcount--;
 	if (state == DA_CCB_DELETE) {
 		TAILQ_HEAD(, bio) queue;