s390/dasd: add safe offline interface

The regular behavior of the DASD device driver when setting a device
offline is to return all outstanding I/O as failed. This behavior is
different from that of other System z operating systems and may lead
to unexpected data loss. Adding an explicit 'safe' offline function
will allow customers to use DASDs in the way they expect them to work.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index 7ff93ee..899e3f5 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -516,6 +516,8 @@
 #define DASD_FLAG_IS_RESERVED	7	/* The device is reserved */
 #define DASD_FLAG_LOCK_STOLEN	8	/* The device lock was stolen */
 #define DASD_FLAG_SUSPENDED	9	/* The device was suspended */
+#define DASD_FLAG_SAFE_OFFLINE	10	/* safe offline processing requested*/
+#define DASD_FLAG_SAFE_OFFLINE_RUNNING	11	/* safe offline running */
 
 
 void dasd_put_device_wake(struct dasd_device *);