diff --git a/mars_device_sio.c b/mars_device_sio.c
index 68b8f8c3..ed7699f1 100644
--- a/mars_device_sio.c
+++ b/mars_device_sio.c
@@ -244,6 +244,22 @@ static void device_sio_ref_io(struct device_sio_output *output, struct mars_ref_
 	int test;
 
 	if (unlikely(!output->filp)) {
+		cb->cb_error = -EINVAL;
+		goto done;
+	}
+
+	/* Shortcut when possible
+	 */
+	if (S_ISBLK(output->filp->f_mapping->host->i_mode) && output->allow_bio) {
+		struct block_device *bdev = output->filp->f_mapping->host->i_bdev;
+#if 0
+		static int count = 10;
+		if (count-- > 0)
+			MARS_INF("AHA: %p\n", bdev);
+#endif
+		bio->bi_bdev = bdev;
+		submit_bio(bio->bi_rw, bio);
+		return;
 	}
 
 	if (barrier) {
@@ -251,11 +267,6 @@ static void device_sio_ref_io(struct device_sio_output *output, struct mars_ref_
 		sync_file(output);
 	}
 
-	if (unlikely(!output->filp)) {
-		cb->cb_error = -EINVAL;
-		goto done;
-	}
-
 	if (rw == READ) {
 		read_aops(output, mref);
 	} else {
@@ -423,6 +434,10 @@ static int device_sio_switch(struct device_sio_brick *brick, bool state)
 	int prot = 0600;
 	mm_segment_t oldfs;
 
+	if (output->o_direct) {
+		flags |= O_DIRECT;
+		MARS_INF("using O_DIRECT on %s\n", path);
+	}
 	if (state) {
 		oldfs = get_fs();
 		set_fs(get_ds());
diff --git a/mars_device_sio.h b/mars_device_sio.h
index 512d9702..103a3f50 100644
--- a/mars_device_sio.h
+++ b/mars_device_sio.h
@@ -28,6 +28,10 @@ struct sio_threadinfo {
 
 struct device_sio_output {
 	MARS_OUTPUT(device_sio);
+	// parameters
+	bool o_direct;
+	bool allow_bio;
+        // private
 	struct file *filp;
 	struct sio_threadinfo tinfo[WITH_THREAD+1];
 	spinlock_t g_lock;
diff --git a/mars_test.c b/mars_test.c
index 6af6d0a2..e7ac3ea2 100644
--- a/mars_test.c
+++ b/mars_test.c
@@ -11,11 +11,12 @@
 #define TRANS_BUFFERS (32)
 #define TRANS_MEM     (1024 / 4)
 
-//#define CONF_TEST
-#define CONF_BUF
-#define CONF_USEBUF
-#define CONF_TRANS
-
+//#define CONF_TEST // use intermediate mars_check bricks
+//#define CONF_BUF
+//#define CONF_USEBUF
+//#define CONF_TRANS
+#define CONF_DIRECT // use O_DIRECT
+//#define CONF_BIO // submit bios directly to device when possible
 
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -46,10 +47,12 @@ static struct trans_logger_brick *_trans_brick = NULL;
 static struct generic_brick *tbuf_brick = NULL;
 static struct buf_brick *_tbuf_brick = NULL;
 static struct generic_brick *tdevice_brick = NULL;
+static struct device_sio_brick *_tdevice_brick = NULL;
 
 static struct generic_brick *buf_brick = NULL;
 static struct buf_brick *_buf_brick = NULL;
 static struct generic_brick *device_brick = NULL;
+static struct device_sio_brick *_device_brick = NULL;
 
 static void test_endio(struct generic_callback *cb)
 {
@@ -124,7 +127,14 @@ void make_test_instance(void)
 	MARS_DBG("starting....\n");
 
 	device_brick = brick(&device_sio_brick_type);
+	_device_brick = (void*)device_brick;
 	device_brick->outputs[0]->output_name = "/tmp/testfile.img";
+#ifdef CONF_DIRECT
+	_device_brick->outputs[0]->o_direct = true;
+#endif
+#ifdef CONF_BIO
+	_device_brick->outputs[0]->allow_bio = true;
+#endif
 	device_brick->ops->brick_switch(device_brick, true);
 
 	if_brick = brick(&if_device_brick_type);
@@ -158,7 +168,14 @@ void make_test_instance(void)
 #ifdef CONF_TRANS // trans_logger plus Infrastruktur zwischenschalten
 
 	tdevice_brick = brick(&device_sio_brick_type);
+	_tdevice_brick = (void*)tdevice_brick;
 	tdevice_brick->outputs[0]->output_name = "/tmp/testfile.log";
+#ifdef CONF_DIRECT
+	_tdevice_brick->outputs[0]->o_direct = true;
+#endif
+#ifdef CONF_BIO
+	_tdevice_brick->outputs[0]->allow_bio = true;
+#endif
 	tdevice_brick->ops->brick_switch(tdevice_brick, true);
 
 	tbuf_brick = brick(&buf_brick_type);