diff options
Diffstat (limited to 'net/rds/tcp.c')
| -rw-r--r-- | net/rds/tcp.c | 78 |
1 files changed, 75 insertions, 3 deletions
diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 86187dad1440..74ee126a6fe6 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -126,9 +126,81 @@ void rds_tcp_restore_callbacks(struct socket *sock, } /* - * This is the only path that sets tc->t_sock. Send and receive trust that - * it is set. The RDS_CONN_UP bit protects those paths from being - * called while it isn't set. + * rds_tcp_reset_callbacks() switches the to the new sock and + * returns the existing tc->t_sock. + * + * The only functions that set tc->t_sock are rds_tcp_set_callbacks + * and rds_tcp_reset_callbacks. Send and receive trust that + * it is set. The absence of RDS_CONN_UP bit protects those paths + * from being called while it isn't set. + */ +void rds_tcp_reset_callbacks(struct socket *sock, + struct rds_connection *conn) +{ + struct rds_tcp_connection *tc = conn->c_transport_data; + struct socket *osock = tc->t_sock; + + if (!osock) + goto newsock; + + /* Need to resolve a duelling SYN between peers. + * We have an outstanding SYN to this peer, which may + * potentially have transitioned to the RDS_CONN_UP state, + * so we must quiesce any send threads before resetting + * c_transport_data. We quiesce these threads by setting + * c_state to something other than RDS_CONN_UP, and then + * waiting for any existing threads in rds_send_xmit to + * complete release_in_xmit(). (Subsequent threads entering + * rds_send_xmit() will bail on !rds_conn_up(). + * + * However an incoming syn-ack at this point would end up + * marking the conn as RDS_CONN_UP, and would again permit + * rds_send_xmi() threads through, so ideally we would + * synchronize on RDS_CONN_UP after lock_sock(), but cannot + * do that: waiting on !RDS_IN_XMIT after lock_sock() may + * end up deadlocking with tcp_sendmsg(), and the RDS_IN_XMIT + * would not get set. As a result, we set c_state to + * RDS_CONN_RESETTTING, to ensure that rds_tcp_state_change + * cannot mark rds_conn_path_up() in the window before lock_sock() + */ + atomic_set(&conn->c_state, RDS_CONN_RESETTING); + wait_event(conn->c_waitq, !test_bit(RDS_IN_XMIT, &conn->c_flags)); + lock_sock(osock->sk); + /* reset receive side state for rds_tcp_data_recv() for osock */ + if (tc->t_tinc) { + rds_inc_put(&tc->t_tinc->ti_inc); + tc->t_tinc = NULL; + } + tc->t_tinc_hdr_rem = sizeof(struct rds_header); + tc->t_tinc_data_rem = 0; + tc->t_sock = NULL; + + write_lock_bh(&osock->sk->sk_callback_lock); + + osock->sk->sk_user_data = NULL; + osock->sk->sk_data_ready = tc->t_orig_data_ready; + osock->sk->sk_write_space = tc->t_orig_write_space; + osock->sk->sk_state_change = tc->t_orig_state_change; + write_unlock_bh(&osock->sk->sk_callback_lock); + release_sock(osock->sk); + sock_release(osock); +newsock: + rds_send_reset(conn); + lock_sock(sock->sk); + write_lock_bh(&sock->sk->sk_callback_lock); + tc->t_sock = sock; + sock->sk->sk_user_data = conn; + sock->sk->sk_data_ready = rds_tcp_data_ready; + sock->sk->sk_write_space = rds_tcp_write_space; + sock->sk->sk_state_change = rds_tcp_state_change; + + write_unlock_bh(&sock->sk->sk_callback_lock); + release_sock(sock->sk); +} + +/* Add tc to rds_tcp_tc_list and set tc->t_sock. See comments + * above rds_tcp_reset_callbacks for notes about synchronization + * with data path */ void rds_tcp_set_callbacks(struct socket *sock, struct rds_connection *conn) { |