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: Qingfang Deng <dqfext@gmail.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c
index d2e391c29464e7f9cd38e428a86a5edb60b04427..fb38b7b2bd1801d742d7107a934758183238314b 100644 (file)
--- a/fs/smb/server/transport_tcp.c
+++ b/fs/smb/server/transport_tcp.c
@@ -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;
 }