diff --git a/scst/src/scst_copy_mgr.c b/scst/src/scst_copy_mgr.c
index e5b939bf9..5c9ce1345 100644
--- a/scst/src/scst_copy_mgr.c
+++ b/scst/src/scst_copy_mgr.c
@@ -2498,7 +2498,6 @@ out_free:
 	goto out;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 static bool scst_cm_is_lun_free(unsigned int lun)
 {
 	bool res = true;
@@ -2507,6 +2506,9 @@ static bool scst_cm_is_lun_free(unsigned int lun)
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
 		if (tgt_dev->lun == lun) {
 			res = false;
@@ -2518,15 +2520,16 @@ static bool scst_cm_is_lun_free(unsigned int lun)
 	return res;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 static unsigned int scst_cm_get_lun(const struct scst_device *dev)
 {
-	unsigned int res = -1;
+	unsigned int res = SCST_MAX_LUN;
 	int i;
-	bool found = false;
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
 		struct list_head *head = &scst_cm_sess->sess_tgt_dev_list[i];
 		struct scst_tgt_dev *tgt_dev;
@@ -2534,7 +2537,6 @@ static unsigned int scst_cm_get_lun(const struct scst_device *dev)
 		list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
 			if (tgt_dev->dev == dev) {
 				res = tgt_dev->lun;
-				found = true;
 				TRACE_DBG("LUN %d found (full LUN %lld)",
 					res, tgt_dev->lun);
 				goto out;
@@ -2542,14 +2544,11 @@ static unsigned int scst_cm_get_lun(const struct scst_device *dev)
 		}
 	}
 
-	sBUG_ON(!found);
-
 out:
 	TRACE_EXIT_RES(res);
 	return res;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 static int scst_cm_dev_register(struct scst_device *dev, uint64_t lun)
 {
 	int res, i;
@@ -2558,6 +2557,9 @@ static int scst_cm_dev_register(struct scst_device *dev, uint64_t lun)
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	TRACE_DBG("dev %s, LUN %ld", dev->virt_name, (unsigned long)lun);
 
 	for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
@@ -2622,7 +2624,6 @@ out_err:
 	goto out;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 static void scst_cm_dev_unregister(struct scst_device *dev, bool del_lun)
 {
 	int i;
@@ -2630,6 +2631,9 @@ static void scst_cm_dev_unregister(struct scst_device *dev, bool del_lun)
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	TRACE_DBG("dev %s, del_lun %d", dev->virt_name, del_lun);
 
 	list_for_each_entry_safe(des, t, &scst_cm_desig_list, cm_desig_list_entry) {
@@ -2696,13 +2700,15 @@ out_unblock:
 	goto out_resume;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 int scst_cm_on_dev_register(struct scst_device *dev)
 {
 	int res = 0;
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	if (!dev->handler->auto_cm_assignment_possible)
 		goto out;
 
@@ -2713,24 +2719,28 @@ out:
 	return res;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 void scst_cm_on_dev_unregister(struct scst_device *dev)
 {
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	scst_cm_dev_unregister(dev, true);
 
 	TRACE_EXIT();
 	return;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 int scst_cm_on_add_acg(struct scst_acg *acg)
 {
 	int res = 0;
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	if (scst_cm_tgt == NULL)
 		goto out;
 
@@ -2748,13 +2758,13 @@ out:
 	return res;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 void scst_cm_on_del_acg(struct scst_acg *acg)
 {
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
 	/* Nothing to do */
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 int scst_cm_on_add_lun(struct scst_acg_dev *acg_dev, uint64_t lun,
 	unsigned int *flags)
 {
@@ -2762,6 +2772,9 @@ int scst_cm_on_add_lun(struct scst_acg_dev *acg_dev, uint64_t lun,
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	if (acg_dev->acg != scst_cm_tgt->default_acg)
 		goto out;
 
@@ -2780,13 +2793,15 @@ out:
 	return res;
 }
 
-/* scst_mutex supposed to be held and activities suspended */
 bool scst_cm_on_del_lun(struct scst_acg_dev *acg_dev, bool gen_report_luns_changed)
 {
 	bool res = gen_report_luns_changed;
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	if (acg_dev->acg != scst_cm_tgt->default_acg)
 		goto out;
 
@@ -2799,7 +2814,6 @@ out:
 	return res;
 }
 
-/* scst_mutex supposed to be locked */
 static bool scst_cm_check_access_acg(const char *initiator_name,
 	const struct scst_device *dev, const struct scst_acg *acg,
 	bool default_acg)
@@ -2809,6 +2823,9 @@ static bool scst_cm_check_access_acg(const char *initiator_name,
 
 	TRACE_ENTRY();
 
+	scst_assert_activity_suspended();
+	lockdep_assert_held(&scst_mutex);
+
 	list_for_each_entry(acg_dev, &acg->acg_dev_list, acg_dev_list_entry) {
 		if (acg_dev->dev == dev) {
 			struct scst_acn *acn;