ksmbd: convert tree_conns_lock to rw_semaphore

Converts tree_conns_lock to an rw_semaphore to allow sleeping while
the lock is held. Additionally, it simplifies the locking logic in
ksmbd_tree_conn_session_logoff() and introduces
__ksmbd_tree_conn_disconnect() to avoid redundant locking.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/mgmt/tree_connect.c

@@ -80,8 +80,10 @@ ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name)
 	status.tree_conn = tree_conn;
 	atomic_set(&tree_conn->refcount, 1);
 
+	down_write(&sess->tree_conns_lock);
 	ret = xa_err(xa_store(&sess->tree_conns, tree_conn->id, tree_conn,
 			      KSMBD_DEFAULT_GFP));
+	up_write(&sess->tree_conns_lock);
 	if (ret) {
 		status.ret = -ENOMEM;
 		goto out_error;
@@ -105,15 +107,11 @@ void ksmbd_tree_connect_put(struct ksmbd_tree_connect *tcon)
 		kfree(tcon);
 }
 
-int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
-			       struct ksmbd_tree_connect *tree_conn)
+static int __ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
+					struct ksmbd_tree_connect *tree_conn)
 {
 	int ret;
 
-	write_lock(&sess->tree_conns_lock);
-	xa_erase(&sess->tree_conns, tree_conn->id);
-	write_unlock(&sess->tree_conns_lock);
-
 	ret = ksmbd_ipc_tree_disconnect_request(sess->id, tree_conn->id);
 	ksmbd_release_tree_conn_id(sess, tree_conn->id);
 	ksmbd_share_config_put(tree_conn->share_conf);
@@ -123,20 +121,30 @@ int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
 	return ret;
 }
 
+int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
+			       struct ksmbd_tree_connect *tree_conn)
+{
+	down_write(&sess->tree_conns_lock);
+	xa_erase(&sess->tree_conns, tree_conn->id);
+	up_write(&sess->tree_conns_lock);
+
+	return __ksmbd_tree_conn_disconnect(sess, tree_conn);
+}
+
 struct ksmbd_tree_connect *ksmbd_tree_conn_lookup(struct ksmbd_session *sess,
 						  unsigned int id)
 {
 	struct ksmbd_tree_connect *tcon;
 
-	read_lock(&sess->tree_conns_lock);
+	down_read(&sess->tree_conns_lock);
 	tcon = xa_load(&sess->tree_conns, id);
 	if (tcon) {
 		if (tcon->t_state != TREE_CONNECTED)
 			tcon = NULL;
 		else if (!atomic_inc_not_zero(&tcon->refcount))
 			tcon = NULL;
 	}
-	read_unlock(&sess->tree_conns_lock);
+	up_read(&sess->tree_conns_lock);
 
 	return tcon;
 }
@@ -150,18 +158,19 @@ int ksmbd_tree_conn_session_logoff(struct ksmbd_session *sess)
 	if (!sess)
 		return -EINVAL;
 
+	down_write(&sess->tree_conns_lock);
 	xa_for_each(&sess->tree_conns, id, tc) {
-		write_lock(&sess->tree_conns_lock);
 		if (tc->t_state == TREE_DISCONNECTED) {
-			write_unlock(&sess->tree_conns_lock);
 			ret = -ENOENT;
 			continue;
 		}
 		tc->t_state = TREE_DISCONNECTED;
-		write_unlock(&sess->tree_conns_lock);
 
-		ret |= ksmbd_tree_conn_disconnect(sess, tc);
+		xa_erase(&sess->tree_conns, tc->id);
+		ret |= __ksmbd_tree_conn_disconnect(sess, tc);
 	}
 	xa_destroy(&sess->tree_conns);
+	up_write(&sess->tree_conns_lock);
+
 	return ret;
 }

fs/smb/server/mgmt/user_session.c

@@ -135,6 +135,7 @@ static int show_proc_session(struct seq_file *m, void *v)
 	seq_printf(m, "%-20s\t%d\n", "channels", i);
 
 	i = 0;
+	down_read(&sess->tree_conns_lock);
 	xa_for_each(&sess->tree_conns, id, tree_conn) {
 		share_conf = tree_conn->share_conf;
 		seq_printf(m, "%-20s\t%s\t%8d", "share",
@@ -145,6 +146,7 @@ static int show_proc_session(struct seq_file *m, void *v)
 			seq_printf(m, " %s ", "disk");
 		seq_putc(m, '\n');
 	}
+	up_read(&sess->tree_conns_lock);
 
 	ksmbd_user_session_put(sess);
 	return 0;
@@ -673,8 +675,8 @@ static struct ksmbd_session *__session_create(int protocol)
 	xa_init(&sess->ksmbd_chann_list);
 	xa_init(&sess->rpc_handle_list);
 	sess->sequence_number = 1;
-	rwlock_init(&sess->tree_conns_lock);
 	atomic_set(&sess->refcnt, 2);
+	init_rwsem(&sess->tree_conns_lock);
 	init_rwsem(&sess->rpc_lock);
 	init_rwsem(&sess->chann_lock);
 

fs/smb/server/mgmt/user_session.h

@@ -60,7 +60,7 @@ struct ksmbd_session {
 
 	struct ksmbd_file_table		file_table;
 	unsigned long			last_active;
-	rwlock_t			tree_conns_lock;
+	struct rw_semaphore		tree_conns_lock;
 
 #ifdef CONFIG_PROC_FS
 	struct proc_dir_entry		*proc_entry;

fs/smb/server/smb2pdu.c

@@ -2037,9 +2037,9 @@ int smb2_tree_connect(struct ksmbd_work *work)
 	if (conn->posix_ext_supported)
 		status.tree_conn->posix_extensions = true;
 
-	write_lock(&sess->tree_conns_lock);
+	down_write(&sess->tree_conns_lock);
 	status.tree_conn->t_state = TREE_CONNECTED;
-	write_unlock(&sess->tree_conns_lock);
+	up_write(&sess->tree_conns_lock);
 	rsp->StructureSize = cpu_to_le16(16);
 out_err1:
 	if (server_conf.flags & KSMBD_GLOBAL_FLAG_DURABLE_HANDLE && share &&
@@ -2193,16 +2193,16 @@ int smb2_tree_disconnect(struct ksmbd_work *work)
 
 	ksmbd_close_tree_conn_fds(work);
 
-	write_lock(&sess->tree_conns_lock);
+	down_write(&sess->tree_conns_lock);
 	if (tcon->t_state == TREE_DISCONNECTED) {
-		write_unlock(&sess->tree_conns_lock);
+		up_write(&sess->tree_conns_lock);
 		rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
 		err = -ENOENT;
 		goto err_out;
 	}
 
 	tcon->t_state = TREE_DISCONNECTED;
-	write_unlock(&sess->tree_conns_lock);
+	up_write(&sess->tree_conns_lock);
 
 	err = ksmbd_tree_conn_disconnect(sess, tcon);
 	if (err) {