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-rw-r--r--net/rds/tcp.c78
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)
{