s390/dasd: add query host access to volume support

With this feature, applications can query if a DASD volume is online
to another operating system instances by checking the online status of
all attached hosts from the storage server.

Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
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 0f0add9..6132733 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -365,6 +365,8 @@
 	int (*get_uid) (struct dasd_device *, struct dasd_uid *);
 	void (*kick_validate) (struct dasd_device *);
 	int (*check_attention)(struct dasd_device *, __u8);
+	int (*host_access_count)(struct dasd_device *);
+	int (*hosts_print)(struct dasd_device *, struct seq_file *);
 };
 
 extern struct dasd_discipline *dasd_diag_discipline_pointer;
@@ -487,6 +489,7 @@
 	unsigned long blk_timeout;
 
 	struct dentry *debugfs_dentry;
+	struct dentry *hosts_dentry;
 	struct dasd_profile profile;
 };