5 files changed, 263 insertions, 120 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
index 3ee1cbc89479..e19a1a55270c 100644
--- a/drivers/scsi/device_handler/scsi_dh.c
+++ b/drivers/scsi/device_handler/scsi_dh.c
@@ -226,7 +226,7 @@ store_dh_state(struct device *dev, struct device_attribute *attr,
 			 * Activate a device handler
 			 */
 			if (scsi_dh->activate)
-				err = scsi_dh->activate(sdev);
+				err = scsi_dh->activate(sdev, NULL, NULL);
 			else
 				err = 0;
 		}
@@ -304,18 +304,15 @@ static int scsi_dh_notifier(struct notifier_block *nb,
 	sdev = to_scsi_device(dev);
 
 	if (action == BUS_NOTIFY_ADD_DEVICE) {
+		err = device_create_file(dev, &scsi_dh_state_attr);
+		/* don't care about err */
 		devinfo = device_handler_match(NULL, sdev);
-		if (!devinfo)
-			goto out;
-
-		err = scsi_dh_handler_attach(sdev, devinfo);
-		if (!err)
-			err = device_create_file(dev, &scsi_dh_state_attr);
+		if (devinfo)
+			err = scsi_dh_handler_attach(sdev, devinfo);
 	} else if (action == BUS_NOTIFY_DEL_DEVICE) {
 		device_remove_file(dev, &scsi_dh_state_attr);
 		scsi_dh_handler_detach(sdev, NULL);
 	}
-out:
 	return err;
 }
 
@@ -423,10 +420,17 @@ EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);
 /*
  * 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 +449,7 @@ int scsi_dh_activate(struct request_queue *q)
 		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;
 }
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index b5cdefaf2608..4f0d0138f48b 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -60,11 +60,17 @@ struct alua_dh_data {
 	int			bufflen;
 	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
 	int			senselen;
+	struct scsi_device	*sdev;
+	activate_complete	callback_fn;
+	void			*callback_data;
 };
 
 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1
 
+static char print_alua_state(int);
+static int alua_check_sense(struct scsi_device *, struct scsi_sense_hdr *);
+
 static inline struct alua_dh_data *get_alua_data(struct scsi_device *sdev)
 {
 	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
@@ -231,18 +237,71 @@ done:
 }
 
 /*
+ * alua_stpg - Evaluate SET TARGET GROUP STATES
+ * @sdev: the device to be evaluated
+ * @state: the new target group state
+ *
+ * Send a SET TARGET GROUP STATES command to the device.
+ * We only have to test here if we should resubmit the command;
+ * any other error is assumed as a failure.
+ */
+static void stpg_endio(struct request *req, int error)
+{
+	struct alua_dh_data *h = req->end_io_data;
+	struct scsi_sense_hdr sense_hdr;
+	unsigned err = SCSI_DH_IO;
+
+	if (error || host_byte(req->errors) != DID_OK ||
+			msg_byte(req->errors) != COMMAND_COMPLETE)
+		goto done;
+
+	if (err == SCSI_DH_IO && h->senselen > 0) {
+		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
+					   &sense_hdr);
+		if (!err) {
+			err = SCSI_DH_IO;
+			goto done;
+		}
+		err = alua_check_sense(h->sdev, &sense_hdr);
+		if (err == ADD_TO_MLQUEUE) {
+			err = SCSI_DH_RETRY;
+			goto done;
+		}
+		sdev_printk(KERN_INFO, h->sdev,
+			    "%s: stpg sense code: %02x/%02x/%02x\n",
+			    ALUA_DH_NAME, sense_hdr.sense_key,
+			    sense_hdr.asc, sense_hdr.ascq);
+		err = SCSI_DH_IO;
+	}
+	if (err == SCSI_DH_OK) {
+		h->state = TPGS_STATE_OPTIMIZED;
+		sdev_printk(KERN_INFO, h->sdev,
+			    "%s: port group %02x switched to state %c\n",
+			    ALUA_DH_NAME, h->group_id,
+			    print_alua_state(h->state));
+	}
+done:
+	blk_put_request(req);
+	if (h->callback_fn) {
+		h->callback_fn(h->callback_data, err);
+		h->callback_fn = h->callback_data = NULL;
+	}
+	return;
+}
+
+/*
  * submit_stpg - Issue a SET TARGET GROUP STATES command
- * @sdev: sdev the command should be sent to
  *
  * Currently we're only setting the current target port group state
  * to 'active/optimized' and let the array firmware figure out
  * the states of the remaining groups.
  */
-static unsigned submit_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
+static unsigned submit_stpg(struct alua_dh_data *h)
 {
 	struct request *rq;
 	int err = SCSI_DH_RES_TEMP_UNAVAIL;
 	int stpg_len = 8;
+	struct scsi_device *sdev = h->sdev;
 
 	/* Prepare the data buffer */
 	memset(h->buff, 0, stpg_len);
@@ -252,7 +311,7 @@ static unsigned submit_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 
 	rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
 	if (!rq)
-		goto done;
+		return SCSI_DH_RES_TEMP_UNAVAIL;
 
 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_OUT;
@@ -266,17 +325,9 @@ static unsigned submit_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 	rq->sense = h->sense;
 	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	rq->sense_len = h->senselen = 0;
+	rq->end_io_data = h;
 
-	err = blk_execute_rq(rq->q, NULL, rq, 1);
-	if (err == -EIO) {
-		sdev_printk(KERN_INFO, sdev,
-			    "%s: stpg failed with %x\n",
-			    ALUA_DH_NAME, rq->errors);
-		h->senselen = rq->sense_len;
-		err = SCSI_DH_IO;
-	}
-	blk_put_request(rq);
-done:
+	blk_execute_rq_nowait(rq->q, NULL, rq, 1, stpg_endio);
 	return err;
 }
 
@@ -477,50 +528,6 @@ static int alua_check_sense(struct scsi_device *sdev,
 }
 
 /*
- * alua_stpg - Evaluate SET TARGET GROUP STATES
- * @sdev: the device to be evaluated
- * @state: the new target group state
- *
- * Send a SET TARGET GROUP STATES command to the device.
- * We only have to test here if we should resubmit the command;
- * any other error is assumed as a failure.
- */
-static int alua_stpg(struct scsi_device *sdev, int state,
-		     struct alua_dh_data *h)
-{
-	struct scsi_sense_hdr sense_hdr;
-	unsigned err;
-	int retry = ALUA_FAILOVER_RETRIES;
-
- retry:
-	err = submit_stpg(sdev, h);
-	if (err == SCSI_DH_IO && h->senselen > 0) {
-		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-					   &sense_hdr);
-		if (!err)
-			return SCSI_DH_IO;
-		err = alua_check_sense(sdev, &sense_hdr);
-		if (retry > 0 && err == ADD_TO_MLQUEUE) {
-			retry--;
-			goto retry;
-		}
-		sdev_printk(KERN_INFO, sdev,
-			    "%s: stpg sense code: %02x/%02x/%02x\n",
-			    ALUA_DH_NAME, sense_hdr.sense_key,
-			    sense_hdr.asc, sense_hdr.ascq);
-		err = SCSI_DH_IO;
-	}
-	if (err == SCSI_DH_OK) {
-		h->state = state;
-		sdev_printk(KERN_INFO, sdev,
-			    "%s: port group %02x switched to state %c\n",
-			    ALUA_DH_NAME, h->group_id,
-			    print_alua_state(h->state) );
-	}
-	return err;
-}
-
-/*
  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
  * @sdev: the device to be evaluated.
  *
@@ -652,7 +659,8 @@ out:
  * 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;
@@ -663,11 +671,19 @@ static int alua_activate(struct scsi_device *sdev)
 			goto out;
 	}
 
-	if (h->tpgs & TPGS_MODE_EXPLICIT && h->state != TPGS_STATE_OPTIMIZED)
-		err = alua_stpg(sdev, TPGS_STATE_OPTIMIZED, h);
+	if (h->tpgs & TPGS_MODE_EXPLICIT && h->state != TPGS_STATE_OPTIMIZED) {
+		h->callback_fn = fn;
+		h->callback_data = data;
+		err = submit_stpg(h);
+		if (err == SCSI_DH_OK)
+			return 0;
+		h->callback_fn = h->callback_data = NULL;
+	}
 
 out:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 /*
@@ -745,6 +761,7 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	h->rel_port = -1;
 	h->buff = h->inq;
 	h->bufflen = ALUA_INQUIRY_SIZE;
+	h->sdev = sdev;
 
 	err = alua_initialize(sdev, h);
 	if (err != SCSI_DH_OK)
diff --git a/drivers/scsi/device_handler/scsi_dh_emc.c b/drivers/scsi/device_handler/scsi_dh_emc.c
index 0cffe84976fe..61966750bd60 100644
--- a/drivers/scsi/device_handler/scsi_dh_emc.c
+++ b/drivers/scsi/device_handler/scsi_dh_emc.c
@@ -528,7 +528,8 @@ retry:
 	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 @@ done:
 		    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
diff --git a/drivers/scsi/device_handler/scsi_dh_hp_sw.c b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
index f7da7530875e..857fdd6032b2 100644
--- a/drivers/scsi/device_handler/scsi_dh_hp_sw.c
+++ b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
@@ -39,8 +39,14 @@ struct hp_sw_dh_data {
 	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
 	int path_state;
 	int retries;
+	int retry_cnt;
+	struct scsi_device *sdev;
+	activate_complete	callback_fn;
+	void			*callback_data;
 };
 
+static int hp_sw_start_stop(struct hp_sw_dh_data *);
+
 static inline struct hp_sw_dh_data *get_hp_sw_data(struct scsi_device *sdev)
 {
 	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
@@ -191,19 +197,53 @@ static int start_done(struct scsi_device *sdev, unsigned char *sense)
 	return rc;
 }
 
+static void start_stop_endio(struct request *req, int error)
+{
+	struct hp_sw_dh_data *h = req->end_io_data;
+	unsigned err = SCSI_DH_OK;
+
+	if (error || host_byte(req->errors) != DID_OK ||
+			msg_byte(req->errors) != COMMAND_COMPLETE) {
+		sdev_printk(KERN_WARNING, h->sdev,
+			    "%s: sending start_stop_unit failed with %x\n",
+			    HP_SW_NAME, req->errors);
+		err = SCSI_DH_IO;
+		goto done;
+	}
+
+	if (req->sense_len > 0) {
+		err = start_done(h->sdev, h->sense);
+		if (err == SCSI_DH_RETRY) {
+			err = SCSI_DH_IO;
+			if (--h->retry_cnt) {
+				blk_put_request(req);
+				err = hp_sw_start_stop(h);
+				if (err == SCSI_DH_OK)
+					return;
+			}
+		}
+	}
+done:
+	blk_put_request(req);
+	if (h->callback_fn) {
+		h->callback_fn(h->callback_data, err);
+		h->callback_fn = h->callback_data = NULL;
+	}
+	return;
+
+}
+
 /*
  * hp_sw_start_stop - Send START STOP UNIT command
  * @sdev: sdev command should be sent to
  *
  * Sending START STOP UNIT activates the SP.
  */
-static int hp_sw_start_stop(struct scsi_device *sdev, struct hp_sw_dh_data *h)
+static int hp_sw_start_stop(struct hp_sw_dh_data *h)
 {
 	struct request *req;
-	int ret, retry;
 
-retry:
-	req = blk_get_request(sdev->request_queue, WRITE, GFP_NOIO);
+	req = blk_get_request(h->sdev->request_queue, WRITE, GFP_ATOMIC);
 	if (!req)
 		return SCSI_DH_RES_TEMP_UNAVAIL;
 
@@ -217,32 +257,10 @@ retry:
 	req->sense = h->sense;
 	memset(req->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	req->sense_len = 0;
-	retry = h->retries;
-
-	ret = blk_execute_rq(req->q, NULL, req, 1);
-	if (ret == -EIO) {
-		if (req->sense_len > 0) {
-			ret = start_done(sdev, h->sense);
-		} else {
-			sdev_printk(KERN_WARNING, sdev,
-				    "%s: sending start_stop_unit failed with %x\n",
-				    HP_SW_NAME, req->errors);
-			ret = SCSI_DH_IO;
-		}
-	} else
-		ret = SCSI_DH_OK;
+	req->end_io_data = h;
 
-	if (ret == SCSI_DH_RETRY) {
-		if (--retry) {
-			blk_put_request(req);
-			goto retry;
-		}
-		ret = SCSI_DH_IO;
-	}
-
-	blk_put_request(req);
-
-	return ret;
+	blk_execute_rq_nowait(req->q, NULL, req, 1, start_stop_endio);
+	return SCSI_DH_OK;
 }
 
 static int hp_sw_prep_fn(struct scsi_device *sdev, struct request *req)
@@ -268,7 +286,8 @@ static int hp_sw_prep_fn(struct scsi_device *sdev, struct request *req)
  * 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);
@@ -276,14 +295,18 @@ static int hp_sw_activate(struct scsi_device *sdev)
 	ret = hp_sw_tur(sdev, h);
 
 	if (ret == SCSI_DH_OK && h->path_state == HP_SW_PATH_PASSIVE) {
-		ret = hp_sw_start_stop(sdev, h);
+		h->retry_cnt = h->retries;
+		h->callback_fn = fn;
+		h->callback_data = data;
+		ret = hp_sw_start_stop(h);
 		if (ret == SCSI_DH_OK)
-			sdev_printk(KERN_INFO, sdev,
-				    "%s: activated path\n",
-				    HP_SW_NAME);
+			return 0;
+		h->callback_fn = h->callback_data = NULL;
 	}
 
-	return ret;
+	if (fn)
+		fn(data, ret);
+	return 0;
 }
 
 static const struct scsi_dh_devlist hp_sw_dh_data_list[] = {
@@ -326,6 +349,7 @@ static int hp_sw_bus_attach(struct scsi_device *sdev)
 	h = (struct hp_sw_dh_data *) scsi_dh_data->buf;
 	h->path_state = HP_SW_PATH_UNINITIALIZED;
 	h->retries = HP_SW_RETRIES;
+	h->sdev = sdev;
 
 	ret = hp_sw_tur(sdev, h);
 	if (ret != SCSI_DH_OK || h->path_state == HP_SW_PATH_UNINITIALIZED)
diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index 268189d31d9c..47cfe1c49c3e 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -22,6 +22,7 @@
 #include <scsi/scsi.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_dh.h>
+#include <linux/workqueue.h>
 
 #define RDAC_NAME "rdac"
 #define RDAC_RETRY_COUNT 5
@@ -138,7 +139,13 @@ struct rdac_controller {
 	} mode_select;
 	u8	index;
 	u8	array_name[ARRAY_LABEL_LEN];
+	spinlock_t		ms_lock;
+	int			ms_queued;
+	struct work_struct	ms_work;
+	struct scsi_device	*ms_sdev;
+	struct list_head	ms_head;
 };
+
 struct c8_inquiry {
 	u8	peripheral_info;
 	u8	page_code; /* 0xC8 */
@@ -198,8 +205,17 @@ static const char *lun_state[] =
 	"owned (AVT mode)",
 };
 
+struct rdac_queue_data {
+	struct list_head	entry;
+	struct rdac_dh_data	*h;
+	activate_complete	callback_fn;
+	void			*callback_data;
+};
+
 static LIST_HEAD(ctlr_list);
 static DEFINE_SPINLOCK(list_lock);
+static struct workqueue_struct *kmpath_rdacd;
+static void send_mode_select(struct work_struct *work);
 
 /*
  * module parameter to enable rdac debug logging.
@@ -281,7 +297,6 @@ static struct request *rdac_failover_get(struct scsi_device *sdev,
 		rdac_pg->subpage_code = 0x1;
 		rdac_pg->page_len[0] = 0x01;
 		rdac_pg->page_len[1] = 0x28;
-		rdac_pg->lun_table[h->lun] = 0x81;
 	} else {
 		struct rdac_pg_legacy *rdac_pg;
 
@@ -291,7 +306,6 @@ static struct request *rdac_failover_get(struct scsi_device *sdev,
 		common = &rdac_pg->common;
 		rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER;
 		rdac_pg->page_len = 0x68;
-		rdac_pg->lun_table[h->lun] = 0x81;
 	}
 	common->rdac_mode[1] = RDAC_MODE_TRANSFER_SPECIFIED_LUNS;
 	common->quiescence_timeout = RDAC_QUIESCENCE_TIME;
@@ -325,6 +339,7 @@ static void release_controller(struct kref *kref)
 	struct rdac_controller *ctlr;
 	ctlr = container_of(kref, struct rdac_controller, kref);
 
+	flush_workqueue(kmpath_rdacd);
 	spin_lock(&list_lock);
 	list_del(&ctlr->node);
 	spin_unlock(&list_lock);
@@ -363,6 +378,11 @@ static struct rdac_controller *get_controller(u8 *subsys_id, u8 *slot_id,
 
 	kref_init(&ctlr->kref);
 	ctlr->use_ms10 = -1;
+	ctlr->ms_queued = 0;
+	ctlr->ms_sdev = NULL;
+	spin_lock_init(&ctlr->ms_lock);
+	INIT_WORK(&ctlr->ms_work, send_mode_select);
+	INIT_LIST_HEAD(&ctlr->ms_head);
 	list_add(&ctlr->node, &ctlr_list);
 done:
 	spin_unlock(&list_lock);
@@ -490,7 +510,7 @@ static int set_mode_select(struct scsi_device *sdev, struct rdac_dh_data *h)
 }
 
 static int mode_select_handle_sense(struct scsi_device *sdev,
-				    unsigned char *sensebuf)
+					unsigned char *sensebuf)
 {
 	struct scsi_sense_hdr sense_hdr;
 	int err = SCSI_DH_IO, ret;
@@ -533,11 +553,29 @@ done:
 	return err;
 }
 
-static int send_mode_select(struct scsi_device *sdev, struct rdac_dh_data *h)
+static void send_mode_select(struct work_struct *work)
 {
+	struct rdac_controller *ctlr =
+		container_of(work, struct rdac_controller, ms_work);
 	struct request *rq;
+	struct scsi_device *sdev = ctlr->ms_sdev;
+	struct rdac_dh_data *h = get_rdac_data(sdev);
 	struct request_queue *q = sdev->request_queue;
 	int err, retry_cnt = RDAC_RETRY_COUNT;
+	struct rdac_queue_data *tmp, *qdata;
+	LIST_HEAD(list);
+	u8 *lun_table;
+
+	spin_lock(&ctlr->ms_lock);
+	list_splice_init(&ctlr->ms_head, &list);
+	ctlr->ms_queued = 0;
+	ctlr->ms_sdev = NULL;
+	spin_unlock(&ctlr->ms_lock);
+
+	if (ctlr->use_ms10)
+		lun_table = ctlr->mode_select.expanded.lun_table;
+	else
+		lun_table = ctlr->mode_select.legacy.lun_table;
 
 retry:
 	err = SCSI_DH_RES_TEMP_UNAVAIL;
@@ -545,6 +583,10 @@ retry:
 	if (!rq)
 		goto done;
 
+	list_for_each_entry(qdata, &list, entry) {
+		lun_table[qdata->h->lun] = 0x81;
+	}
+
 	RDAC_LOG(RDAC_LOG_FAILOVER, sdev, "array %s, ctlr %d, "
 		"%s MODE_SELECT command",
 		(char *) h->ctlr->array_name, h->ctlr->index,
@@ -565,10 +607,45 @@ retry:
 	}
 
 done:
-	return err;
+	list_for_each_entry_safe(qdata, tmp, &list, entry) {
+		list_del(&qdata->entry);
+		if (err == SCSI_DH_OK)
+			qdata->h->state = RDAC_STATE_ACTIVE;
+		if (qdata->callback_fn)
+			qdata->callback_fn(qdata->callback_data, err);
+		kfree(qdata);
+	}
+	return;
+}
+
+static int queue_mode_select(struct scsi_device *sdev,
+				activate_complete fn, void *data)
+{
+	struct rdac_queue_data *qdata;
+	struct rdac_controller *ctlr;
+
+	qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+	if (!qdata)
+		return SCSI_DH_RETRY;
+
+	qdata->h = get_rdac_data(sdev);
+	qdata->callback_fn = fn;
+	qdata->callback_data = data;
+
+	ctlr = qdata->h->ctlr;
+	spin_lock(&ctlr->ms_lock);
+	list_add_tail(&qdata->entry, &ctlr->ms_head);
+	if (!ctlr->ms_queued) {
+		ctlr->ms_queued = 1;
+		ctlr->ms_sdev = sdev;
+		queue_work(kmpath_rdacd, &ctlr->ms_work);
+	}
+	spin_unlock(&ctlr->ms_lock);
+	return SCSI_DH_OK;
 }
 
-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;
@@ -577,10 +654,15 @@ static int rdac_activate(struct scsi_device *sdev)
 	if (err != SCSI_DH_OK)
 		goto done;
 
-	if (h->lun_state == RDAC_LUN_UNOWNED)
-		err = send_mode_select(sdev, h);
+	if (h->lun_state == RDAC_LUN_UNOWNED) {
+		err = queue_mode_select(sdev, fn, data);
+		if (err == SCSI_DH_OK)
+			return 0;
+	}
 done:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 static int rdac_prep_fn(struct scsi_device *sdev, struct request *req)
@@ -790,13 +872,26 @@ static int __init rdac_init(void)
 	int r;
 
 	r = scsi_register_device_handler(&rdac_dh);
-	if (r != 0)
+	if (r != 0) {
 		printk(KERN_ERR "Failed to register scsi device handler.");
+		goto done;
+	}
+
+	/*
+	 * Create workqueue to handle mode selects for rdac
+	 */
+	kmpath_rdacd = create_singlethread_workqueue("kmpath_rdacd");
+	if (!kmpath_rdacd) {
+		scsi_unregister_device_handler(&rdac_dh);
+		printk(KERN_ERR "kmpath_rdacd creation failed.\n");
+	}
+done:
 	return r;
 }
 
 static void __exit rdac_exit(void)
 {
+	destroy_workqueue(kmpath_rdacd);
 	scsi_unregister_device_handler(&rdac_dh);
 }