target: Convert se_node_acl->acl_group removal to use ->acl_kref

This patch converts core_tpg_del_initiator_node_acl() shutdown from configfs
context to use se_node_acl->acl_kref and ->acl_free_comp in order to wait for
outstanding fabric callbacks to complete via transport_deregister_session()
callbacks before waking ->acl_free_comp from the last ->acl_kref put.

It also changes core_tpg_del_initiator_node_acl() to setup a local sess_list
with target_get_session() + acl->acl_stop = 1 for active sessions that will
be shutdown, and changes transport_deregister_session_configfs() to check
for ->acl_stop usage.

Cc: Roland Dreier <roland@purestorage.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Joern Engel <joern@logfs.org>
Cc: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_tpg.c

@@ -452,9 +452,10 @@ int core_tpg_del_initiator_node_acl(
 	struct se_node_acl *acl,
 	int force)
 {
+	LIST_HEAD(sess_list);
 	struct se_session *sess, *sess_tmp;
 	unsigned long flags;
-	int dynamic_acl = 0;
+	int dynamic_acl = 0, rc;
 
 	spin_lock_irq(&tpg->acl_node_lock);
 	if (acl->dynamic_node_acl) {
@@ -465,27 +466,34 @@ int core_tpg_del_initiator_node_acl(
 	tpg->num_node_acls--;
 	spin_unlock_irq(&tpg->acl_node_lock);
 
-	spin_lock_irqsave(&tpg->session_lock, flags);
-	list_for_each_entry_safe(sess, sess_tmp,
-				&tpg->tpg_sess_list, sess_list) {
-		if (sess->se_node_acl != acl)
-			continue;
-		/*
-		 * Determine if the session needs to be closed by our context.
-		 */
-		if (!tpg->se_tpg_tfo->shutdown_session(sess))
+	spin_lock_irqsave(&acl->nacl_sess_lock, flags);
+	acl->acl_stop = 1;
+
+	list_for_each_entry_safe(sess, sess_tmp, &acl->acl_sess_list,
+				sess_acl_list) {
+		if (sess->sess_tearing_down != 0)
 			continue;
 
-		spin_unlock_irqrestore(&tpg->session_lock, flags);
-		/*
-		 * If the $FABRIC_MOD session for the Initiator Node ACL exists,
-		 * forcefully shutdown the $FABRIC_MOD session/nexus.
-		 */
-		tpg->se_tpg_tfo->close_session(sess);
+		target_get_session(sess);
+		list_move(&sess->sess_acl_list, &sess_list);
+	}
+	spin_unlock_irqrestore(&acl->nacl_sess_lock, flags);
+
+	list_for_each_entry_safe(sess, sess_tmp, &sess_list, sess_acl_list) {
+		list_del(&sess->sess_acl_list);
 
-		spin_lock_irqsave(&tpg->session_lock, flags);
+		rc = tpg->se_tpg_tfo->shutdown_session(sess);
+		target_put_session(sess);
+		if (!rc)
+			continue;
+		target_put_session(sess);
 	}
-	spin_unlock_irqrestore(&tpg->session_lock, flags);
+	target_put_nacl(acl);
+	/*
+	 * Wait for last target_put_nacl() to complete in target_complete_nacl()
+	 * for active fabric session transport_deregister_session() callbacks.
+	 */
+	wait_for_completion(&acl->acl_free_comp);
 
 	core_tpg_wait_for_nacl_pr_ref(acl);
 	core_clear_initiator_node_from_tpg(acl, tpg);

drivers/target/target_core_transport.c

@@ -360,7 +360,8 @@ void transport_deregister_session_configfs(struct se_session *se_sess)
 	se_nacl = se_sess->se_node_acl;
 	if (se_nacl) {
 		spin_lock_irqsave(&se_nacl->nacl_sess_lock, flags);
-		list_del(&se_sess->sess_acl_list);
+		if (se_nacl->acl_stop == 0)
+			list_del(&se_sess->sess_acl_list);
 		/*
 		 * If the session list is empty, then clear the pointer.
 		 * Otherwise, set the struct se_session pointer from the tail

include/target/target_core_base.h

@@ -620,6 +620,7 @@ struct se_node_acl {
 	char			initiatorname[TRANSPORT_IQN_LEN];
 	/* Used to signal demo mode created ACL, disabled by default */
 	bool			dynamic_node_acl;
+	bool			acl_stop:1;
 	u32			queue_depth;
 	u32			acl_index;
 	u64			num_cmds;