Index: sys/ufs/ffs/ffs_vnops.c
===================================================================
--- sys/ufs/ffs/ffs_vnops.c
+++ sys/ufs/ffs/ffs_vnops.c
@@ -914,7 +914,8 @@
 			uio->uio_offset -= resid - uio->uio_resid;
 			uio->uio_resid = resid;
 		}
-	} else if (resid > uio->uio_resid && (ioflag & IO_SYNC)) {
+	} else if ((ioflag & IO_SYNC) != 0 && (resid > uio->uio_resid ||
+	    (ip->i_flags & IN_IBLKDATA) != 0)) {
 		error = ffs_update(vp, 1);
 		if (ffs_fsfail_cleanup(VFSTOUFS(vp->v_mount), error))
 			error = ENXIO;