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ksmbd: server: avoid busy polling in accept loop

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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>
This commit is contained in:
Qingfang Deng
2025-11-17 16:59:00 +08:00
committed by Steve French
parent 5003ad718a
commit 3316a8fc84
1 changed files with 6 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
fs/smb/server/transport_tcp.c
View File

@@ -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;
}