Commit 3316a8fc authored by Qingfang Deng's avatar Qingfang Deng Committed by Steve French
Browse files

ksmbd: server: avoid busy polling in accept loop 



The ksmbd listener thread was using busy waiting on a listening socket by
calling kernel_accept() with SOCK_NONBLOCK and retrying every 100ms on
-EAGAIN. Since this thread is dedicated to accepting new connections,
there is no need for non-blocking mode.

Switch to a blocking accept() call instead, allowing the thread to sleep
until a new connection arrives. This avoids unnecessary wakeups and CPU
usage. During teardown, call shutdown() on the listening socket so that
accept() returns -EINVAL and the thread exits cleanly.

The socket release mutex is redundant because kthread_stop() blocks until
the listener thread returns, guaranteeing safe teardown ordering.

Also remove sk_rcvtimeo and sk_sndtimeo assignments, which only caused
accept() to return -EAGAIN prematurely.

Signed-off-by: default avatarQingfang Deng <dqfext@gmail.com>
Reviewed-by: default avatarStefan Metzmacher <metze@samba.org>
Acked-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 5003ad71

fs/smb/server/transport_tcp.c

+6 −35
Original line number Diff line number Diff line
@@ -22,7 +22,6 @@ struct interface { 
	struct socket		*ksmbd_socket;

	struct list_head	entry;

	char			*name;

	struct mutex		sock_release_lock;

	int			state;

};
@@ -56,19 +55,6 @@ static inline void ksmbd_tcp_reuseaddr(struct socket *sock) 
	sock_set_reuseaddr(sock->sk);

}



static inline void ksmbd_tcp_rcv_timeout(struct socket *sock, s64 secs)

{

	if (secs && secs < MAX_SCHEDULE_TIMEOUT / HZ - 1)

		WRITE_ONCE(sock->sk->sk_rcvtimeo, secs * HZ);

	else

		WRITE_ONCE(sock->sk->sk_rcvtimeo, MAX_SCHEDULE_TIMEOUT);

}



static inline void ksmbd_tcp_snd_timeout(struct socket *sock, s64 secs)

{

	sock_set_sndtimeo(sock->sk, secs);

}



static struct tcp_transport *alloc_transport(struct socket *client_sk)

{

	struct tcp_transport *t;
@@ -236,20 +222,14 @@ static int ksmbd_kthread_fn(void *p) 
	unsigned int max_ip_conns;



	while (!kthread_should_stop()) {

		mutex_lock(&iface->sock_release_lock);

		if (!iface->ksmbd_socket) {

			mutex_unlock(&iface->sock_release_lock);

			break;

		}

		ret = kernel_accept(iface->ksmbd_socket, &client_sk,

				    SOCK_NONBLOCK);

		mutex_unlock(&iface->sock_release_lock);

		if (ret) {

			if (ret == -EAGAIN)

				/* check for new connections every 100 msecs */

				schedule_timeout_interruptible(HZ / 10);

		ret = kernel_accept(iface->ksmbd_socket, &client_sk, 0);

		if (ret == -EINVAL)

			break;

		if (ret)

			continue;

		}



		if (!server_conf.max_ip_connections)

			goto skip_max_ip_conns_limit;
@@ -458,10 +438,6 @@ static void tcp_destroy_socket(struct socket *ksmbd_socket) 
	if (!ksmbd_socket)

		return;



	/* set zero to timeout */

	ksmbd_tcp_rcv_timeout(ksmbd_socket, 0);

	ksmbd_tcp_snd_timeout(ksmbd_socket, 0);



	ret = kernel_sock_shutdown(ksmbd_socket, SHUT_RDWR);

	if (ret)

		pr_err("Failed to shutdown socket: %d\n", ret);
@@ -532,9 +508,6 @@ static int create_socket(struct interface *iface) 
		goto out_error;

	}



	ksmbd_socket->sk->sk_rcvtimeo = KSMBD_TCP_RECV_TIMEOUT;

	ksmbd_socket->sk->sk_sndtimeo = KSMBD_TCP_SEND_TIMEOUT;



	ret = kernel_listen(ksmbd_socket, KSMBD_SOCKET_BACKLOG);

	if (ret) {

		pr_err("Port listen() error: %d\n", ret);
@@ -604,12 +577,11 @@ static int ksmbd_netdev_event(struct notifier_block *nb, unsigned long event, 
		if (iface && iface->state == IFACE_STATE_CONFIGURED) {

			ksmbd_debug(CONN, "netdev-down event: netdev(%s) is going down\n",

					iface->name);

			kernel_sock_shutdown(iface->ksmbd_socket, SHUT_RDWR);

			tcp_stop_kthread(iface->ksmbd_kthread);

			iface->ksmbd_kthread = NULL;

			mutex_lock(&iface->sock_release_lock);

			tcp_destroy_socket(iface->ksmbd_socket);

			sock_release(iface->ksmbd_socket);

			iface->ksmbd_socket = NULL;

			mutex_unlock(&iface->sock_release_lock);



			iface->state = IFACE_STATE_DOWN;

			break;
@@ -672,7 +644,6 @@ static struct interface *alloc_iface(char *ifname) 
	iface->name = ifname;

	iface->state = IFACE_STATE_DOWN;

	list_add(&iface->entry, &iface_list);

	mutex_init(&iface->sock_release_lock);

	return iface;

}