diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 16ab8d3..6bc27d5 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -35,14 +35,17 @@
 static int dcssblk_open(struct inode *inode, struct file *filp);
 static int dcssblk_release(struct inode *inode, struct file *filp);
 static int dcssblk_make_request(struct request_queue *q, struct bio *bio);
+static int dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
+				 unsigned long *data);
 
 static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
 
 static int dcssblk_major;
 static struct block_device_operations dcssblk_devops = {
-	.owner   = THIS_MODULE,
-	.open    = dcssblk_open,
-	.release = dcssblk_release,
+	.owner   	= THIS_MODULE,
+	.open    	= dcssblk_open,
+	.release 	= dcssblk_release,
+	.direct_access 	= dcssblk_direct_access,
 };
 
 static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
@@ -641,6 +644,20 @@
 		/* Request beyond end of DCSS segment. */
 		goto fail;
 	}
+	/* verify data transfer direction */
+	if (dev_info->is_shared) {
+		switch (dev_info->segment_type) {
+		case SEG_TYPE_SR:
+		case SEG_TYPE_ER:
+		case SEG_TYPE_SC:
+			/* cannot write to these segments */
+			if (bio_data_dir(bio) == WRITE) {
+				PRINT_WARN("rejecting write to ro segment %s\n", dev_info->dev.bus_id);
+				goto fail;
+			}
+		}
+	}
+
 	index = (bio->bi_sector >> 3);
 	bio_for_each_segment(bvec, bio, i) {
 		page_addr = (unsigned long)
@@ -661,7 +678,26 @@
 	bio_endio(bio, bytes_done, 0);
 	return 0;
 fail:
-	bio_io_error(bio, bytes_done);
+	bio_io_error(bio, bio->bi_size);
+	return 0;
+}
+
+static int
+dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
+			unsigned long *data)
+{
+	struct dcssblk_dev_info *dev_info;
+	unsigned long pgoff;
+
+	dev_info = bdev->bd_disk->private_data;
+	if (!dev_info)
+		return -ENODEV;
+	if (secnum % (PAGE_SIZE/512))
+		return -EINVAL;
+	pgoff = secnum / (PAGE_SIZE / 512);
+	if ((pgoff+1)*PAGE_SIZE-1 > dev_info->end - dev_info->start)
+		return -ERANGE;
+	*data = (unsigned long) (dev_info->start+pgoff*PAGE_SIZE);
 	return 0;
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 83857d8..929bf8d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -885,6 +885,7 @@
 	int (*ioctl) (struct inode *, struct file *, unsigned, unsigned long);
 	long (*unlocked_ioctl) (struct file *, unsigned, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned, unsigned long);
+	int (*direct_access) (struct block_device *, sector_t, unsigned long *);
 	int (*media_changed) (struct gendisk *);
 	int (*revalidate_disk) (struct gendisk *);
 	struct module *owner;