[Cluster-devel] [DLM PATCH 5/6] DLM: Add locking to protect save callback assignments

[Bob Peterson]

This patch adds write_lock_bh locking to several places in the code
that save and restore the socket callbacks.

Signed-off-by: Bob Peterson <rpete...@redhat.com>
---
 fs/dlm/lowcomms.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index ec5087a..4e82285 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -467,10 +467,17 @@ int dlm_lowcomms_connect_node(int nodeid)
 
 static void lowcomms_error_report(struct sock *sk)
 {
-       struct connection *con = sock2con(sk);
+       struct connection *con;
        struct sockaddr_storage saddr;
        int buflen;
+       void (*orig_report)(struct sock *) = NULL;
+
+       read_lock_bh(&sk->sk_callback_lock);
+       con = sock2con(sk);
+       if (con == NULL)
+               goto out;
 
+       orig_report = con->orig_error_report;
        if (con->sock == NULL ||
            kernel_getpeername(con->sock, (struct sockaddr *)&saddr, &buflen)) {
                printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
@@ -500,22 +507,29 @@ static void lowcomms_error_report(struct sock *sk)
                                   dlm_config.ci_tcp_port, sk->sk_err,
                                   sk->sk_err_soft);
        }
-       con->orig_error_report(sk);
+out:
+       read_unlock_bh(&sk->sk_callback_lock);
+       if (orig_report)
+               orig_report(sk);
 }
 
 /* Make a socket active */
 static void add_sock(struct socket *sock, struct connection *con)
 {
+       struct sock *sk = sock->sk;
+
+       write_lock_bh(&sk->sk_callback_lock);
        con->sock = sock;
 
        /* Install a data_ready callback */
-       con->sock->sk->sk_data_ready = lowcomms_data_ready;
-       con->sock->sk->sk_write_space = lowcomms_write_space;
-       con->sock->sk->sk_state_change = lowcomms_state_change;
-       con->sock->sk->sk_user_data = con;
-       con->sock->sk->sk_allocation = GFP_NOFS;
-       con->orig_error_report = con->sock->sk->sk_error_report;
-       con->sock->sk->sk_error_report = lowcomms_error_report;
+       sk->sk_data_ready = lowcomms_data_ready;
+       sk->sk_write_space = lowcomms_write_space;
+       sk->sk_state_change = lowcomms_state_change;
+       sk->sk_user_data = con;
+       sk->sk_allocation = GFP_NOFS;
+       con->orig_error_report = sk->sk_error_report;
+       sk->sk_error_report = lowcomms_error_report;
+       write_unlock_bh(&sk->sk_callback_lock);
 }
 
 /* Add the port number to an IPv6 or 4 sockaddr and return the address
@@ -1274,6 +1288,7 @@ static int sctp_listen_for_all(void)
        if (result < 0)
                log_print("Could not set SCTP NODELAY error %d\n", result);
 
+       write_lock_bh(&sock->sk->sk_callback_lock);
        /* Init con struct */
        sock->sk->sk_user_data = con;
        con->sock = sock;
@@ -1281,6 +1296,8 @@ static int sctp_listen_for_all(void)
        con->rx_action = sctp_accept_from_sock;
        con->connect_action = sctp_connect_to_sock;
 
+       write_unlock_bh(&sock->sk->sk_callback_lock);
+
        /* Bind to all addresses. */
        if (sctp_bind_addrs(con, dlm_config.ci_tcp_port))
                goto create_delsock;
-- 
2.5.0