iscsi-target: Enforce individual network portal export once per TargetName

This patch enforces individual network portal export on a once per TargetName
basis, thus preventing a network portal from being exported multiple times
across multiple TargetPortalGroups in a single TargetName instance.

This is done in iscsit_tpg_check_network_portal() by walking tiqn->tiqn_tpg_list
and tpg->tpg_gnp_list using iscsit_check_np_match() looking for an existing
network portal mapping from iscsit_tpg_add_network_portal() context, but only
when no pre-existing tpg_np_parent pointer is present.

Reported-by: Andy Grover <agrover@redhat.com>
Tested-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target_tpg.c

@@ -422,6 +422,35 @@ struct iscsi_tpg_np *iscsit_tpg_locate_child_np(
 	return NULL;
 }
 
+static bool iscsit_tpg_check_network_portal(
+	struct iscsi_tiqn *tiqn,
+	struct __kernel_sockaddr_storage *sockaddr,
+	int network_transport)
+{
+	struct iscsi_portal_group *tpg;
+	struct iscsi_tpg_np *tpg_np;
+	struct iscsi_np *np;
+	bool match = false;
+
+	spin_lock(&tiqn->tiqn_tpg_lock);
+	list_for_each_entry(tpg, &tiqn->tiqn_tpg_list, tpg_list) {
+
+		spin_lock(&tpg->tpg_np_lock);
+		list_for_each_entry(tpg_np, &tpg->tpg_gnp_list, tpg_np_list) {
+			np = tpg_np->tpg_np;
+
+			match = iscsit_check_np_match(sockaddr, np,
+						network_transport);
+			if (match == true)
+				break;
+		}
+		spin_unlock(&tpg->tpg_np_lock);
+	}
+	spin_unlock(&tiqn->tiqn_tpg_lock);
+
+	return match;
+}
+
 struct iscsi_tpg_np *iscsit_tpg_add_network_portal(
 	struct iscsi_portal_group *tpg,
 	struct __kernel_sockaddr_storage *sockaddr,
@@ -432,6 +461,16 @@ struct iscsi_tpg_np *iscsit_tpg_add_network_portal(
 	struct iscsi_np *np;
 	struct iscsi_tpg_np *tpg_np;
 
+	if (!tpg_np_parent) {
+		if (iscsit_tpg_check_network_portal(tpg->tpg_tiqn, sockaddr,
+				network_transport) == true) {
+			pr_err("Network Portal: %s already exists on a"
+				" different TPG on %s\n", ip_str,
+				tpg->tpg_tiqn->tiqn);
+			return ERR_PTR(-EEXIST);
+		}
+	}
+
 	tpg_np = kzalloc(sizeof(struct iscsi_tpg_np), GFP_KERNEL);
 	if (!tpg_np) {
 		pr_err("Unable to allocate memory for"