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Mon, 17 Nov 2025 00:59:09 -0800 (PST) Received: from gmail.com ([2a09:bac5:1f0a:281e::3ff:5a]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2a49db102f5sm35562982eec.4.2025.11.17.00.59.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Nov 2025 00:59:08 -0800 (PST) From: Qingfang Deng To: Namjae Jeon , Steve French , Sergey Senozhatsky , Tom Talpey , Ronnie Sahlberg , Hyunchul Lee , linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, Stefan Metzmacher , Simon Horman Subject: [PATCH v3] ksmbd: server: avoid busy polling in accept loop Date: Mon, 17 Nov 2025 16:59:00 +0800 Message-ID: <20251117085900.466432-1-dqfext@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Fixes: 0626e6641f6b ("cifsd: add server handler for central processing and tranport layers") Signed-off-by: Qingfang Deng --- v2 -> v3: https://lore.kernel.org/linux-cifs/20251111104750.25739-1-dqfext@gmail.com Remove unused functions. v1 -> v2: https://lore.kernel.org/linux-cifs/20251030064736.24061-1-dqfext@gmail.com Do not remove TCP_NODELAY, as accepted sockets inherits from it. Fix accept() blocking forever on older kernel versions. Remove a redundant mutex fs/smb/server/transport_tcp.c | 41 +++++------------------------------ 1 file changed, 6 insertions(+), 35 deletions(-) diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c index 6e03e93321b8..4bb07937d7ef 100644 --- 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; } -- 2.43.0