configfs: switch ->default groups to a linked list

Replace the current NULL-terminated array of default groups with a linked
list.  This gets rid of lots of nasty code to size and/or dynamically
allocate the array.

While we're at it also provide a conveniant helper to remove the default
groups.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Felipe Balbi <balbi@kernel.org>		[drivers/usb/gadget]
Acked-by: Joel Becker <jlbec@evilplan.org>
Acked-by: Nicholas Bellinger <nab@linux-iscsi.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>

drivers/target/iscsi/iscsi_target_configfs.c

@@ -771,21 +771,11 @@ static int lio_target_init_nodeacl(struct se_node_acl *se_nacl,
 {
 	struct iscsi_node_acl *acl =
 		container_of(se_nacl, struct iscsi_node_acl, se_node_acl);
-	struct config_group *stats_cg = &se_nacl->acl_fabric_stat_group;
 
-	stats_cg->default_groups = kmalloc(sizeof(struct config_group *) * 2,
-				GFP_KERNEL);
-	if (!stats_cg->default_groups) {
-		pr_err("Unable to allocate memory for"
-				" stats_cg->default_groups\n");
-		return -ENOMEM;
-	}
-
-	stats_cg->default_groups[0] = &acl->node_stat_grps.iscsi_sess_stats_group;
-	stats_cg->default_groups[1] = NULL;
 	config_group_init_type_name(&acl->node_stat_grps.iscsi_sess_stats_group,
 			"iscsi_sess_stats", &iscsi_stat_sess_cit);
-
+	configfs_add_default_group(&acl->node_stat_grps.iscsi_sess_stats_group,
+			&se_nacl->acl_fabric_stat_group);
 	return 0;
 }
 
@@ -793,17 +783,8 @@ static void lio_target_cleanup_nodeacl( struct se_node_acl *se_nacl)
 {
 	struct iscsi_node_acl *acl = container_of(se_nacl,
 			struct iscsi_node_acl, se_node_acl);
-	struct config_item *df_item;
-	struct config_group *stats_cg;
-	int i;
 
-	stats_cg = &acl->se_node_acl.acl_fabric_stat_group;
-	for (i = 0; stats_cg->default_groups[i]; i++) {
-		df_item = &stats_cg->default_groups[i]->cg_item;
-		stats_cg->default_groups[i] = NULL;
-		config_item_put(df_item);
-	}
-	kfree(stats_cg->default_groups);
+	configfs_remove_default_groups(&acl->se_node_acl.acl_fabric_stat_group);
 }
 
 /* End items for lio_target_acl_cit */
@@ -1260,42 +1241,37 @@ static struct se_wwn *lio_target_call_coreaddtiqn(
 	struct config_group *group,
 	const char *name)
 {
-	struct config_group *stats_cg;
 	struct iscsi_tiqn *tiqn;
 
 	tiqn = iscsit_add_tiqn((unsigned char *)name);
 	if (IS_ERR(tiqn))
 		return ERR_CAST(tiqn);
-	/*
-	 * Setup struct iscsi_wwn_stat_grps for se_wwn->fabric_stat_group.
-	 */
-	stats_cg = &tiqn->tiqn_wwn.fabric_stat_group;
 
-	stats_cg->default_groups = kmalloc(sizeof(struct config_group *) * 6,
-				GFP_KERNEL);
-	if (!stats_cg->default_groups) {
-		pr_err("Unable to allocate memory for"
-				" stats_cg->default_groups\n");
-		iscsit_del_tiqn(tiqn);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	stats_cg->default_groups[0] = &tiqn->tiqn_stat_grps.iscsi_instance_group;
-	stats_cg->default_groups[1] = &tiqn->tiqn_stat_grps.iscsi_sess_err_group;
-	stats_cg->default_groups[2] = &tiqn->tiqn_stat_grps.iscsi_tgt_attr_group;
-	stats_cg->default_groups[3] = &tiqn->tiqn_stat_grps.iscsi_login_stats_group;
-	stats_cg->default_groups[4] = &tiqn->tiqn_stat_grps.iscsi_logout_stats_group;
-	stats_cg->default_groups[5] = NULL;
 	config_group_init_type_name(&tiqn->tiqn_stat_grps.iscsi_instance_group,
 			"iscsi_instance", &iscsi_stat_instance_cit);
+	configfs_add_default_group(&tiqn->tiqn_stat_grps.iscsi_instance_group,
+			&tiqn->tiqn_wwn.fabric_stat_group);
+
 	config_group_init_type_name(&tiqn->tiqn_stat_grps.iscsi_sess_err_group,
 			"iscsi_sess_err", &iscsi_stat_sess_err_cit);
+	configfs_add_default_group(&tiqn->tiqn_stat_grps.iscsi_sess_err_group,
+			&tiqn->tiqn_wwn.fabric_stat_group);
+
 	config_group_init_type_name(&tiqn->tiqn_stat_grps.iscsi_tgt_attr_group,
 			"iscsi_tgt_attr", &iscsi_stat_tgt_attr_cit);
+	configfs_add_default_group(&tiqn->tiqn_stat_grps.iscsi_tgt_attr_group,
+			&tiqn->tiqn_wwn.fabric_stat_group);
+
 	config_group_init_type_name(&tiqn->tiqn_stat_grps.iscsi_login_stats_group,
 			"iscsi_login_stats", &iscsi_stat_login_cit);
+	configfs_add_default_group(&tiqn->tiqn_stat_grps.iscsi_login_stats_group,
+			&tiqn->tiqn_wwn.fabric_stat_group);
+
 	config_group_init_type_name(&tiqn->tiqn_stat_grps.iscsi_logout_stats_group,
 			"iscsi_logout_stats", &iscsi_stat_logout_cit);
+	configfs_add_default_group(&tiqn->tiqn_stat_grps.iscsi_logout_stats_group,
+			&tiqn->tiqn_wwn.fabric_stat_group);
+
 
 	pr_debug("LIO_Target_ConfigFS: REGISTER -> %s\n", tiqn->tiqn);
 	pr_debug("LIO_Target_ConfigFS: REGISTER -> Allocated Node:"
@@ -1307,17 +1283,8 @@ static void lio_target_call_coredeltiqn(
 	struct se_wwn *wwn)
 {
 	struct iscsi_tiqn *tiqn = container_of(wwn, struct iscsi_tiqn, tiqn_wwn);
-	struct config_item *df_item;
-	struct config_group *stats_cg;
-	int i;
 
-	stats_cg = &tiqn->tiqn_wwn.fabric_stat_group;
-	for (i = 0; stats_cg->default_groups[i]; i++) {
-		df_item = &stats_cg->default_groups[i]->cg_item;
-		stats_cg->default_groups[i] = NULL;
-		config_item_put(df_item);
-	}
-	kfree(stats_cg->default_groups);
+	configfs_remove_default_groups(&tiqn->tiqn_wwn.fabric_stat_group);
 
 	pr_debug("LIO_Target_ConfigFS: DEREGISTER -> %s\n",
 			tiqn->tiqn);