Index: linux-2.6.32-rc5/include/scsi/scsi_dh.h
===================================================================
--- linux-2.6.32-rc5.orig/include/scsi/scsi_dh.h	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/include/scsi/scsi_dh.h	2009-10-20 18:26:14.000000000 -0700
@@ -56,14 +56,16 @@
 	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)
Index: linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/scsi/device_handler/scsi_dh.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh.c	2009-10-20 18:26:14.000000000 -0700
@@ -226,7 +226,7 @@
 			 * Activate a device handler
 			 */
 			if (scsi_dh->activate)
-				err = scsi_dh->activate(sdev);
+				err = scsi_dh->activate(sdev, NULL, NULL);
 			else
 				err = 0;
 		}
@@ -423,10 +423,17 @@
 /*
  * scsi_dh_activate - activate the path associated with the scsi_device
  *      corresponding to the given request queue.
- * @q - Request queue that is associated with the scsi_device to be
- *      activated.
+ *     Returns immediately without waiting for activation to be completed.
+ * @q    - Request queue that is associated with the scsi_device to be
+ *         activated.
+ * @fn   - Function to be called upon completion of the activation.
+ *         Function fn is called with data (below) and the error code.
+ *         Function fn may be called from the same calling context. So,
+ *         do not hold the lock in the caller which may be needed in fn.
+ * @data - data passed to the function fn upon completion.
+ *
  */
-int scsi_dh_activate(struct request_queue *q)
+int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
 {
 	int err = 0;
 	unsigned long flags;
@@ -445,7 +452,7 @@
 		return err;
 
 	if (scsi_dh->activate)
-		err = scsi_dh->activate(sdev);
+		err = scsi_dh->activate(sdev, fn, data);
 	put_device(&sdev->sdev_gendev);
 	return err;
 }
Index: linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_rdac.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/scsi/device_handler/scsi_dh_rdac.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_rdac.c	2009-10-20 18:26:14.000000000 -0700
@@ -568,7 +568,8 @@
 	return err;
 }
 
-static int rdac_activate(struct scsi_device *sdev)
+static int rdac_activate(struct scsi_device *sdev,
+			activate_complete fn, void *data)
 {
 	struct rdac_dh_data *h = get_rdac_data(sdev);
 	int err = SCSI_DH_OK;
@@ -580,7 +581,9 @@
 	if (h->lun_state == RDAC_LUN_UNOWNED)
 		err = send_mode_select(sdev, h);
 done:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 static int rdac_prep_fn(struct scsi_device *sdev, struct request *req)
Index: linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_alua.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/scsi/device_handler/scsi_dh_alua.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_alua.c	2009-10-20 18:26:14.000000000 -0700
@@ -652,7 +652,8 @@
  * based on a certain policy. But until we actually encounter them it
  * should be okay.
  */
-static int alua_activate(struct scsi_device *sdev)
+static int alua_activate(struct scsi_device *sdev,
+			activate_complete fn, void *data)
 {
 	struct alua_dh_data *h = get_alua_data(sdev);
 	int err = SCSI_DH_OK;
@@ -667,7 +668,9 @@
 		err = alua_stpg(sdev, TPGS_STATE_OPTIMIZED, h);
 
 out:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 /*
Index: linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_emc.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/scsi/device_handler/scsi_dh_emc.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_emc.c	2009-10-20 18:26:14.000000000 -0700
@@ -528,7 +528,8 @@
 	return err;
 }
 
-static int clariion_activate(struct scsi_device *sdev)
+static int clariion_activate(struct scsi_device *sdev,
+				activate_complete fn, void *data)
 {
 	struct clariion_dh_data *csdev = get_clariion_data(sdev);
 	int result;
@@ -559,7 +560,9 @@
 		    csdev->port, lun_state[csdev->lun_state],
 		    csdev->default_sp + 'A');
 
-	return result;
+	if (fn)
+		fn(data, result);
+	return 0;
 }
 /*
  * params - parameters in the following format
Index: linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_hp_sw.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/scsi/device_handler/scsi_dh_hp_sw.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/scsi/device_handler/scsi_dh_hp_sw.c	2009-10-20 18:26:14.000000000 -0700
@@ -268,7 +268,8 @@
  * activate the passive path (and deactivate the
  * previously active one).
  */
-static int hp_sw_activate(struct scsi_device *sdev)
+static int hp_sw_activate(struct scsi_device *sdev,
+				activate_complete fn, void *data)
 {
 	int ret = SCSI_DH_OK;
 	struct hp_sw_dh_data *h = get_hp_sw_data(sdev);
@@ -283,7 +284,9 @@
 				    HP_SW_NAME);
 	}
 
-	return ret;
+	if (fn)
+		fn(data, ret);
+	return 0;
 }
 
 static const struct scsi_dh_devlist hp_sw_dh_data_list[] = {
Index: linux-2.6.32-rc5/include/scsi/scsi_device.h
===================================================================
--- linux-2.6.32-rc5.orig/include/scsi/scsi_device.h	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/include/scsi/scsi_device.h	2009-10-20 18:26:14.000000000 -0700
@@ -174,6 +174,7 @@
 	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 */
@@ -185,7 +186,7 @@
 	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 *);
 };
Index: linux-2.6.32-rc5/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.32-rc5.orig/drivers/md/dm-mpath.c	2009-10-20 18:26:03.000000000 -0700
+++ linux-2.6.32-rc5/drivers/md/dm-mpath.c	2009-10-20 18:26:14.000000000 -0700
@@ -1116,8 +1116,9 @@
 	return limit_reached;
 }
 
-static void pg_init_done(struct dm_path *path, int errors)
+static void pg_init_done(void *data, int errors)
 {
+	struct dm_path *path = data;
 	struct pgpath *pgpath = path_to_pgpath(path);
 	struct priority_group *pg = pgpath->pg;
 	struct multipath *m = pg->m;
@@ -1183,12 +1184,11 @@
 
 static void activate_path(struct work_struct *work)
 {
-	int ret;
 	struct pgpath *pgpath =
 		container_of(work, struct pgpath, activate_path);
 
-	ret = scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev));
-	pg_init_done(&pgpath->path, ret);
+	scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
+				pg_init_done, &pgpath->path);
 }
 
 /*
