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Tue, 11 Nov 2025 02:47:57 -0800 (PST) Received: from gmail.com ([2a09:bac1:19c0:20::4:2ee]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7b0ccd4edc3sm14912911b3a.66.2025.11.11.02.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Nov 2025 02:47:56 -0800 (PST) From: Qingfang Deng To: Namjae Jeon , Steve French , Sergey Senozhatsky , Tom Talpey , Hyunchul Lee , Ronnie Sahlberg , linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, Stefan Metzmacher Subject: [PATCH v2] ksmbd: server: avoid busy polling in accept loop Date: Tue, 11 Nov 2025 18:47:49 +0800 Message-ID: <20251111104750.25739-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- 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 | 28 ++++++---------------------- 1 file changed, 6 insertions(+), 22 deletions(-) diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c index 6e03e93321b8..79319815b2fc 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; }; =20 @@ -236,20 +235,14 @@ static int ksmbd_kthread_fn(void *p) unsigned int max_ip_conns; =20 while (!kthread_should_stop()) { - mutex_lock(&iface->sock_release_lock); if (!iface->ksmbd_socket) { - mutex_unlock(&iface->sock_release_lock); break; } - ret =3D kernel_accept(iface->ksmbd_socket, &client_sk, - SOCK_NONBLOCK); - mutex_unlock(&iface->sock_release_lock); - if (ret) { - if (ret =3D=3D -EAGAIN) - /* check for new connections every 100 msecs */ - schedule_timeout_interruptible(HZ / 10); + ret =3D kernel_accept(iface->ksmbd_socket, &client_sk, 0); + if (ret =3D=3D -EINVAL) + break; + if (ret) continue; - } =20 if (!server_conf.max_ip_connections) goto skip_max_ip_conns_limit; @@ -458,10 +451,6 @@ static void tcp_destroy_socket(struct socket *ksmbd_so= cket) if (!ksmbd_socket) return; =20 - /* set zero to timeout */ - ksmbd_tcp_rcv_timeout(ksmbd_socket, 0); - ksmbd_tcp_snd_timeout(ksmbd_socket, 0); - ret =3D kernel_sock_shutdown(ksmbd_socket, SHUT_RDWR); if (ret) pr_err("Failed to shutdown socket: %d\n", ret); @@ -532,9 +521,6 @@ static int create_socket(struct interface *iface) goto out_error; } =20 - ksmbd_socket->sk->sk_rcvtimeo =3D KSMBD_TCP_RECV_TIMEOUT; - ksmbd_socket->sk->sk_sndtimeo =3D KSMBD_TCP_SEND_TIMEOUT; - ret =3D kernel_listen(ksmbd_socket, KSMBD_SOCKET_BACKLOG); if (ret) { pr_err("Port listen() error: %d\n", ret); @@ -604,12 +590,11 @@ static int ksmbd_netdev_event(struct notifier_block *= nb, unsigned long event, if (iface && iface->state =3D=3D 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 =3D NULL; - mutex_lock(&iface->sock_release_lock); - tcp_destroy_socket(iface->ksmbd_socket); + sock_release(iface->ksmbd_socket); iface->ksmbd_socket =3D NULL; - mutex_unlock(&iface->sock_release_lock); =20 iface->state =3D IFACE_STATE_DOWN; break; @@ -672,7 +657,6 @@ static struct interface *alloc_iface(char *ifname) iface->name =3D ifname; iface->state =3D IFACE_STATE_DOWN; list_add(&iface->entry, &iface_list); - mutex_init(&iface->sock_release_lock); return iface; } =20 --=20 2.43.0