[S390] dasd: automatic recognition of read-only devices

In z/VM it is possible to attach a device as read-only. To prevent
unintentional write requests and subsequent I/O errors, we can detect
this configuration using the z/VM DIAG 210 interface and set the
respective linux block device to read-only as well.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd_fba.c b/drivers/s390/block/dasd_fba.c
index 0f15244..37282b9 100644
--- a/drivers/s390/block/dasd_fba.c
+++ b/drivers/s390/block/dasd_fba.c
@@ -124,6 +124,7 @@
 	struct dasd_fba_private *private;
 	struct ccw_device *cdev = device->cdev;
 	int rc;
+	int readonly;
 
 	private = (struct dasd_fba_private *) device->private;
 	if (!private) {
@@ -162,16 +163,21 @@
 		return rc;
 	}
 
+	readonly = dasd_device_is_ro(device);
+	if (readonly)
+		set_bit(DASD_FLAG_DEVICE_RO, &device->flags);
+
 	dev_info(&device->cdev->dev,
 		 "New FBA DASD %04X/%02X (CU %04X/%02X) with %d MB "
-		 "and %d B/blk\n",
+		 "and %d B/blk%s\n",
 		 cdev->id.dev_type,
 		 cdev->id.dev_model,
 		 cdev->id.cu_type,
 		 cdev->id.cu_model,
 		 ((private->rdc_data.blk_bdsa *
 		   (private->rdc_data.blk_size >> 9)) >> 11),
-		 private->rdc_data.blk_size);
+		 private->rdc_data.blk_size,
+		 readonly ? ", read-only device" : "");
 	return 0;
 }