diff --git a/iscsi-scst/Makefile b/iscsi-scst/Makefile
index d1969de05..745cad781 100644
--- a/iscsi-scst/Makefile
+++ b/iscsi-scst/Makefile
@@ -50,7 +50,7 @@ endif
 INSTALL_DIR := $(INSTALL_MOD_PATH)/lib/modules/$(KVER)/extra
 INFINIBAND_ENABLED := $(shell if grep -q '^CONFIG_INFINIBAND=[my]$$' $(KDIR)/.config; then echo true; else echo false; fi)
 
-all: include/iscsi_scst_itf_ver.h progs mods
+all: progs mods
 
 ISER_SYMVERS:=$(KMOD)/Module.symvers
 OFED_CFLAGS:=
@@ -103,7 +103,7 @@ endif
 CREATE_CQ_FLAG = $(shell $(MAKE) -C $(KDIR) SUBDIRS=$(shell pwd)/conftest/create_cq PRE_CFLAGS="$(OFED_CFLAGS) -Werror" >/dev/null 2>&1 && echo -DIB_CREATE_CQ_HAS_INIT_ATTR)
 PRE_CFLAGS=$(OFED_CFLAGS) $(CREATE_CQ_FLAG) -DOFED_FLAVOR=$(OFED_FLAVOR)
 
-mods: Modules.symvers Module.symvers
+mods: include/iscsi_scst_itf_ver.h Modules.symvers Module.symvers
 	$(MAKE) -C $(KDIR) SCST_INC_DIR=$(SCST_INC_DIR) SUBDIRS=$(KMOD) modules
 	if $(INFINIBAND_ENABLED); then					       \
 	  echo "  Building against $(OFED_FLAVOR) InfiniBand kernel headers."; \
@@ -112,7 +112,7 @@ mods: Modules.symvers Module.symvers
 	  KBUILD_EXTRA_SYMBOLS=$(ISER_SYMVERS) modules;			       \
 	fi
 
-progs:
+progs: include/iscsi_scst_itf_ver.h
 	$(MAKE) -C usr SCST_INC_DIR=$(SCST_INC_DIR)
 
 include/iscsi_scst_itf_ver.h: include/iscsi_scst.h
diff --git a/scst/include/scst.h b/scst/include/scst.h
index 140412c43..3e7288f19 100644
--- a/scst/include/scst.h
+++ b/scst/include/scst.h
@@ -1453,7 +1453,9 @@ struct scst_dev_type {
 	 * be started. Can be used to close open file handlers, which might
 	 * prevent the state switch.
 	 *
-	 * Called under scst_dg_mutex and no activities on the dev handler level.
+	 * Called under scst_dg_mutex and no activities on the dev handler level
+	 * (for implicit ALUA case supposed to be done by the user space via
+	 * "block" sysfs attribute as described in the README).
 	 *
 	 * OPTIONAL
 	 */
@@ -1465,7 +1467,9 @@ struct scst_dev_type {
 	 * be finished. Can be used to (re)open file handlers closed in
 	 * on_alua_state_change_start().
 	 *
-	 * Called under scst_dg_mutex and no activities on the dev handler level.
+	 * Called under scst_dg_mutex and no activities on the dev handler level
+	 * (for implicit ALUA case supposed to be done by the user space via
+	 * "block" sysfs attribute as described in the README).
 	 *
 	 * OPTIONAL
 	 */
diff --git a/scst/src/dev_handlers/scst_user.c b/scst/src/dev_handlers/scst_user.c
index dc2e7e7a3..33a2cc7ed 100644
--- a/scst/src/dev_handlers/scst_user.c
+++ b/scst/src/dev_handlers/scst_user.c
@@ -3533,9 +3533,23 @@ out_put:
 
 static int dev_user_unregister_dev(struct file *file)
 {
+	struct scst_user_dev *dev;
+	int res;
+
+	dev = file->private_data;
+	res = dev_user_check_reg(dev);
+	if (unlikely(res != 0))
+		goto out;
+
 	PRINT_WARNING("SCST_USER_UNREGISTER_DEVICE is obsolete and NOOP. "
 		"Closing fd should be used instead.");
-	return 0;
+
+	/* For backward compatibility unblock possibly blocked sync threads */
+	dev->blocking = 0;
+	wake_up_all(&dev->udev_cmd_threads.cmd_list_waitQ);
+
+out:
+	return res;
 }
 
 static int dev_user_flush_cache(struct file *file)
diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index 9171b1f9f..72df069ef 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -145,6 +145,13 @@ static struct scst_trace_log vdisk_local_trace_tbl[] = {
 
 struct scst_vdisk_dev {
 	uint64_t nblocks;
+
+	/*
+	 * Not protected, because assignments to aligned 64-bit integers are
+	 * atomic. At worst, accesses to it should be covered by ACCESS_ONCE(),
+	 * but not sure if that is really needed, so would prefer to keep it
+	 * away from the fast path.
+	 */
 	loff_t file_size;	/* in bytes */
 
 	/*
diff --git a/scst/src/scst_copy_mgr.c b/scst/src/scst_copy_mgr.c
index 80ca7e8cb..62fdb781a 100644
--- a/scst/src/scst_copy_mgr.c
+++ b/scst/src/scst_copy_mgr.c
@@ -2535,9 +2535,13 @@ static int scst_cm_dev_register(struct scst_device *dev, uint64_t lun)
 
 		list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
 			if (tgt_dev->dev == dev) {
-				PRINT_ERROR("Copy Manager already registered "
+				/*
+				 * It's OK, because the copy manager could
+				 * auto register some devices
+				 */
+				TRACE_DBG("Copy Manager already registered "
 					"device %s", dev->virt_name);
-				res = -EEXIST;
+				res = 0;
 				goto out;
 			}
 		}
diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index 3fb4e0d29..1db5ed914 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -4597,7 +4597,7 @@ out:
 	return res;
 }
 
-/* Either add or replace a LUN. */
+/* Either add or replace a LUN according to flags argument */
 int scst_acg_repl_lun(struct scst_acg *acg, struct kobject *parent,
 		      struct scst_device *dev, uint64_t lun,
 		      unsigned int flags)
diff --git a/scst/src/scst_tg.c b/scst/src/scst_tg.c
index b8cc4456c..cb65574eb 100644
--- a/scst/src/scst_tg.c
+++ b/scst/src/scst_tg.c
@@ -954,7 +954,8 @@ out_fail:
  * group @tg->dg.
  */
 static void __scst_tg_set_state(struct scst_target_group *tg,
-				enum scst_tg_state state)
+				enum scst_tg_state state,
+				bool call_on_alua_state_change)
 {
 	struct scst_dg_dev *dg_dev;
 	struct scst_device *dev;
@@ -1018,7 +1019,7 @@ int scst_tg_set_state(struct scst_target_group *tg, enum scst_tg_state state)
 	if (res)
 		goto out;
 
-	__scst_tg_set_state(tg, state);
+	__scst_tg_set_state(tg, state, true);
 
 	mutex_unlock(&scst_dg_mutex);
 out:
@@ -1325,7 +1326,7 @@ static void __scst_dg_remove(struct scst_dev_group *dg)
 	list_del(&dg->entry);
 	scst_dg_sysfs_del(dg);
 	list_for_each_entry(tg, &dg->tg_list, entry)
-		__scst_tg_set_state(tg, SCST_TG_STATE_OPTIMIZED);
+		__scst_tg_set_state(tg, SCST_TG_STATE_OPTIMIZED, false);
 	while (!list_empty(&dg->dev_list)) {
 		dgdev = list_first_entry(&dg->dev_list, struct scst_dg_dev,
 					 entry);
diff --git a/scstadmin/scstadmin.sysfs/scstadmin b/scstadmin/scstadmin.sysfs/scstadmin
index b6bac0e8d..e65ce3fc8 100755
--- a/scstadmin/scstadmin.sysfs/scstadmin
+++ b/scstadmin/scstadmin.sysfs/scstadmin
@@ -1499,6 +1499,7 @@ sub serializeNkAttr {
 		|| defined($attr_filter)
 		   && defined($$attr_filter{$attribute}))
 	    && !defined($$attributes{$attribute}->{'keys'})
+	    && $attribute ne 'dif_checks_failed'
 	    && $attribute ne 'enabled'
 	    && $attribute ne 'hw_target') {
 	    my $value = $$attributes{$attribute}->{'value'};
diff --git a/usr/fileio/Makefile b/usr/fileio/Makefile
index 6705f3496..231d2d81e 100644
--- a/usr/fileio/Makefile
+++ b/usr/fileio/Makefile
@@ -1,5 +1,5 @@
 #
-#  SCSI target mid-level makefile
+#  Fileio_tgt user space dev handler make file
 #
 #  Copyright (C) 2007 - 2016 Vladislav Bolkhovitin <vst@vlnb.net>
 #  Copyright (C) 2007 - 2016 SanDisk Corporation