[SCSI] scsi_dh: Change the scsidh_activate interface to be asynchronous

Make scsi_dh_activate() function asynchronous, by taking in two additional
parameters, one is the callback function and the other is the data to call
the callback function with.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

include/scsi/scsi_device.h

@@ -177,6 +177,7 @@ struct scsi_dh_devlist {
 	char *model;
 };
 
+typedef void (*activate_complete)(void *, int);
 struct scsi_device_handler {
 	/* Used by the infrastructure */
 	struct list_head list; /* list of scsi_device_handlers */
@@ -188,7 +189,7 @@ struct scsi_device_handler {
 	int (*check_sense)(struct scsi_device *, struct scsi_sense_hdr *);
 	int (*attach)(struct scsi_device *);
 	void (*detach)(struct scsi_device *);
-	int (*activate)(struct scsi_device *);
+	int (*activate)(struct scsi_device *, activate_complete, void *);
 	int (*prep_fn)(struct scsi_device *, struct request *);
 	int (*set_params)(struct scsi_device *, const char *);
 };

include/scsi/scsi_dh.h

@@ -56,14 +56,16 @@ enum {
 	SCSI_DH_DRIVER_MAX,
 };
 #if defined(CONFIG_SCSI_DH) || defined(CONFIG_SCSI_DH_MODULE)
-extern int scsi_dh_activate(struct request_queue *);
+extern int scsi_dh_activate(struct request_queue *, activate_complete, void *);
 extern int scsi_dh_handler_exist(const char *);
 extern int scsi_dh_attach(struct request_queue *, const char *);
 extern void scsi_dh_detach(struct request_queue *);
 extern int scsi_dh_set_params(struct request_queue *, const char *);
 #else
-static inline int scsi_dh_activate(struct request_queue *req)
+static inline int scsi_dh_activate(struct request_queue *req,
+					activate_complete fn, void *data)
 {
+	fn(data, 0);
 	return 0;
 }
 static inline int scsi_dh_handler_exist(const char *name)