From: Gerd Rausch Delegate fan-out to a background worker in order to allow kernel_getpeername() to acquire a lock on the socket. This has become necessary since the introduction of commit "9dfc685e0262d ("inet: remove races in inet{6}_getname()") The socket is already locked in the context that "kernel_getpeername" used to get called by either rds_tcp_recv_path" or "tcp_v{4,6}_rcv", and therefore causing a deadlock. Luckily, the fan-out need not happen in-context nor fast, so we can easily just do the same in a background worker. Also, while we're doing this, we get rid of the unused struct members "t_conn_w", "t_send_w", "t_down_w" & "t_recv_w". Signed-off-by: Gerd Rausch Signed-off-by: Allison Henderson --- net/rds/tcp.c | 3 +++ net/rds/tcp.h | 7 ++---- net/rds/tcp_connect.c | 2 ++ net/rds/tcp_listen.c | 54 +++++++++++++++++++++++++++++++------------ 4 files changed, 46 insertions(+), 20 deletions(-) diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 45484a93d75f..02f8f928c20b 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -358,6 +358,8 @@ static void rds_tcp_conn_free(void *arg) rdsdebug("freeing tc %p\n", tc); + cancel_work_sync(&tc->t_fan_out_w); + spin_lock_irqsave(&rds_tcp_conn_lock, flags); if (!tc->t_tcp_node_detached) list_del(&tc->t_tcp_node); @@ -384,6 +386,7 @@ static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp) tc->t_tinc = NULL; tc->t_tinc_hdr_rem = sizeof(struct rds_header); tc->t_tinc_data_rem = 0; + INIT_WORK(&tc->t_fan_out_w, rds_tcp_fan_out_w); init_waitqueue_head(&tc->t_recv_done_waitq); conn->c_path[i].cp_transport_data = tc; diff --git a/net/rds/tcp.h b/net/rds/tcp.h index 39c86347188c..9ecb0b6b658a 100644 --- a/net/rds/tcp.h +++ b/net/rds/tcp.h @@ -44,11 +44,7 @@ struct rds_tcp_connection { size_t t_tinc_hdr_rem; size_t t_tinc_data_rem; - /* XXX error report? */ - struct work_struct t_conn_w; - struct work_struct t_send_w; - struct work_struct t_down_w; - struct work_struct t_recv_w; + struct work_struct t_fan_out_w; /* for info exporting only */ struct list_head t_list_item; @@ -90,6 +86,7 @@ void rds_tcp_state_change(struct sock *sk); struct socket *rds_tcp_listen_init(struct net *net, bool isv6); void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor); void rds_tcp_listen_data_ready(struct sock *sk); +void rds_tcp_fan_out_w(struct work_struct *work); void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out); int rds_tcp_accept_one(struct rds_tcp_net *rtn); void rds_tcp_keepalive(struct socket *sock); diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c index b77c88ffb199..6954b8c479f1 100644 --- a/net/rds/tcp_connect.c +++ b/net/rds/tcp_connect.c @@ -115,6 +115,8 @@ int rds_tcp_conn_path_connect(struct rds_conn_path *cp) if (cp->cp_index > 0 && cp->cp_conn->c_npaths < 2) return -EAGAIN; + cancel_work_sync(&tc->t_fan_out_w); + mutex_lock(&tc->t_conn_path_lock); if (rds_conn_path_up(cp)) { diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c index 6fb5c928b8fd..8fb8f7d26683 100644 --- a/net/rds/tcp_listen.c +++ b/net/rds/tcp_listen.c @@ -123,27 +123,20 @@ rds_tcp_accept_one_path(struct rds_connection *conn, struct socket *sock) return NULL; } -void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out) +void rds_tcp_fan_out_w(struct work_struct *work) { - struct rds_tcp_connection *tc; - struct rds_tcp_net *rtn; - struct socket *sock; + struct rds_tcp_connection *tc = container_of(work, + struct rds_tcp_connection, + t_fan_out_w); + struct rds_connection *conn = tc->t_cpath->cp_conn; + struct rds_tcp_net *rtn = tc->t_rtn; + struct socket *sock = tc->t_sock; int sport, npaths; - if (rds_destroy_pending(conn)) - return; - - tc = conn->c_path->cp_transport_data; - rtn = tc->t_rtn; - if (!rtn) - return; - - sock = tc->t_sock; - /* During fan-out, check that the connection we already * accepted in slot#0 carried the proper source port modulo. */ - if (fan_out && conn->c_with_sport_idx && sock && + if (conn->c_with_sport_idx && sock && rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) > 0) { /* cp->cp_index is encoded in lowest bits of source-port */ sport = rds_tcp_get_peer_sport(sock); @@ -167,6 +160,37 @@ void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out) rds_tcp_accept_work(rtn); } +void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out) +{ + struct rds_conn_path *cp0; + struct rds_tcp_connection *tc; + struct rds_tcp_net *rtn; + + if (rds_destroy_pending(conn)) + return; + + cp0 = conn->c_path; + tc = cp0->cp_transport_data; + rtn = tc->t_rtn; + if (!rtn) + return; + + if (fan_out) + /* Delegate fan-out to a background worker in order + * to allow "kernel_getpeername" to acquire a lock + * on the socket. + * The socket is already locked in this context + * by either "rds_tcp_recv_path" or "tcp_v{4,6}_rcv", + * depending on the origin of the dequeue-request. + */ + queue_work(cp0->cp_wq, &tc->t_fan_out_w); + else + /* Fan-out either already happened or is unnecessary. + * Just go ahead and attempt to accept more connections + */ + rds_tcp_accept_work(rtn); +} + int rds_tcp_accept_one(struct rds_tcp_net *rtn) { struct socket *listen_sock = rtn->rds_tcp_listen_sock; -- 2.43.0