diff --git a/scst/include/backport.h b/scst/include/backport.h
index eec927283..98b21fd60 100644
--- a/scst/include/backport.h
+++ b/scst/include/backport.h
@@ -348,6 +348,24 @@ static inline int __must_check kref_get_unless_zero(struct kref *kref)
 }
 #endif
 
+/* <linux/ktime.h> */
+
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 9, 0) &&		\
+	LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 0)) &&	\
+	(!defined(RHEL_MAJOR) || RHEL_MAJOR -0 < 7)
+/**
+ * ktime_before - Compare if a ktime_t value is smaller than another one.
+ * @cmp1:	comparable1
+ * @cmp2:	comparable2
+ *
+ * Return: true if cmp1 happened before cmp2.
+ */
+static inline bool ktime_before(const ktime_t cmp1, const ktime_t cmp2)
+{
+	return ktime_compare(cmp1, cmp2) < 0;
+}
+#endif
+
 /* <linux/list.h> */
 
 #ifndef __list_for_each
@@ -678,19 +696,4 @@ static inline int scsi_bidi_cmnd(struct scsi_cmnd *cmd)
 }
 #endif
 
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 9, 0)) && \
-    (LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 0))
-/**
- * ktime_before - Compare if a ktime_t value is smaller than another one.
- * @cmp1:	comparable1
- * @cmp2:	comparable2
- *
- * Return: true if cmp1 happened before cmp2.
- */
-static inline bool ktime_before(const ktime_t cmp1, const ktime_t cmp2)
-{
-	return ktime_compare(cmp1, cmp2) < 0;
-}
-#endif /* (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 9, 0)) && (LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 0)) */
-
 #endif /* _SCST_BACKPORT_H_ */
diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index e0bd9bedc..d59aa482f 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -631,6 +631,7 @@ static const struct attribute *vdisk_nullio_attrs[] = {
 	&vdev_dummy_attr.attr,
 	&vdev_read_zero_attr.attr,
 	&vdisk_removable_attr.attr,
+	&vdisk_cluster_mode_attr.attr,
 	&vdev_t10_vend_id_attr.attr,
 	&vdev_vend_specific_id_attr.attr,
 	&vdev_prod_id_attr.attr,
@@ -831,6 +832,7 @@ static struct scst_dev_type vdisk_null_devtype = {
 		"dif_mode, "
 		"dif_type, "
 		"dif_static_app_tag, ",
+		"cluster_mode, "
 		"read_only, "
 		"removable, "
 		"rotational, "
@@ -8180,7 +8182,7 @@ static int vdev_nullio_add_device(const char *device_name, char *params)
 	int res = 0;
 	static const char *const allowed_params[] = {
 		"read_only", "dummy", "removable", "blocksize", "rotational",
-		"dif_mode", "dif_type", "dif_static_app_tag",
+		"cluster_mode", "dif_mode", "dif_type", "dif_static_app_tag",
 		"size", "size_mb", "tst", NULL
 	};
 	struct scst_vdisk_dev *virt_dev;
diff --git a/scst/src/scst_sysfs.c b/scst/src/scst_sysfs.c
index d9871a3f9..7c6fdf46e 100644
--- a/scst/src/scst_sysfs.c
+++ b/scst/src/scst_sysfs.c
@@ -2191,7 +2191,7 @@ static int scst_process_ini_group_mgmt_store(char *buffer,
 		TRACE_DBG("Creating group '%s'", p);
 		if (acg != NULL) {
 			PRINT_ERROR("acg name %s exist", p);
-			res = -EINVAL;
+			res = -EEXIST;
 			goto out_unlock;
 		}
 		res = scst_alloc_add_acg(tgt, p, true, &acg);