Merge branch 'rds-fixes'
Sowmini Varadhan says:
====================
RDS: TCP: sychronization during connection startup
This patch series ensures that the passive (accept) side of the
TCP connection used for RDS-TCP is correctly synchronized with
any concurrent active (connect) attempts for a given pair of peers.
Patch 1 in the series makes sure that the t_sock in struct
rds_tcp_connection is only reset after any threads in rds_tcp_xmit
have completed (otherwise a null-ptr deref may be encountered).
Patch 2 synchronizes rds_tcp_accept_one() with the rds_tcp*connect()
path.
v2: review comments from Santosh Shilimkar, other spelling corrections
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 61ed2a8..86187da 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -127,7 +127,7 @@
/*
* This is the only path that sets tc->t_sock. Send and receive trust that
- * it is set. The RDS_CONN_CONNECTED bit protects those paths from being
+ * it is set. The RDS_CONN_UP bit protects those paths from being
* called while it isn't set.
*/
void rds_tcp_set_callbacks(struct socket *sock, struct rds_connection *conn)
@@ -216,6 +216,7 @@
if (!tc)
return -ENOMEM;
+ mutex_init(&tc->t_conn_lock);
tc->t_sock = NULL;
tc->t_tinc = NULL;
tc->t_tinc_hdr_rem = sizeof(struct rds_header);
diff --git a/net/rds/tcp.h b/net/rds/tcp.h
index 64f873c..41c2283 100644
--- a/net/rds/tcp.h
+++ b/net/rds/tcp.h
@@ -12,6 +12,10 @@
struct list_head t_tcp_node;
struct rds_connection *conn;
+ /* t_conn_lock synchronizes the connection establishment between
+ * rds_tcp_accept_one and rds_tcp_conn_connect
+ */
+ struct mutex t_conn_lock;
struct socket *t_sock;
void *t_orig_write_space;
void *t_orig_data_ready;
diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c
index 5cb1687..49a3fcf 100644
--- a/net/rds/tcp_connect.c
+++ b/net/rds/tcp_connect.c
@@ -78,7 +78,14 @@
struct socket *sock = NULL;
struct sockaddr_in src, dest;
int ret;
+ struct rds_tcp_connection *tc = conn->c_transport_data;
+ mutex_lock(&tc->t_conn_lock);
+
+ if (rds_conn_up(conn)) {
+ mutex_unlock(&tc->t_conn_lock);
+ return 0;
+ }
ret = sock_create_kern(rds_conn_net(conn), PF_INET,
SOCK_STREAM, IPPROTO_TCP, &sock);
if (ret < 0)
@@ -120,6 +127,7 @@
}
out:
+ mutex_unlock(&tc->t_conn_lock);
if (sock)
sock_release(sock);
return ret;
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 0936a4a..be263cd 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -76,7 +76,9 @@
struct rds_connection *conn;
int ret;
struct inet_sock *inet;
- struct rds_tcp_connection *rs_tcp;
+ struct rds_tcp_connection *rs_tcp = NULL;
+ int conn_state;
+ struct sock *nsk;
ret = sock_create_kern(sock_net(sock->sk), sock->sk->sk_family,
sock->sk->sk_type, sock->sk->sk_protocol,
@@ -115,28 +117,44 @@
* rds_tcp_state_change() will do that cleanup
*/
rs_tcp = (struct rds_tcp_connection *)conn->c_transport_data;
- if (rs_tcp->t_sock &&
- ntohl(inet->inet_saddr) < ntohl(inet->inet_daddr)) {
- struct sock *nsk = new_sock->sk;
-
- nsk->sk_user_data = NULL;
- nsk->sk_prot->disconnect(nsk, 0);
- tcp_done(nsk);
- new_sock = NULL;
- ret = 0;
- goto out;
- } else if (rs_tcp->t_sock) {
- rds_tcp_restore_callbacks(rs_tcp->t_sock, rs_tcp);
- conn->c_outgoing = 0;
- }
-
rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING);
+ mutex_lock(&rs_tcp->t_conn_lock);
+ conn_state = rds_conn_state(conn);
+ if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_UP)
+ goto rst_nsk;
+ if (rs_tcp->t_sock) {
+ /* 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.
+ */
+ wait_event(conn->c_waitq,
+ !test_bit(RDS_IN_XMIT, &conn->c_flags));
+ if (ntohl(inet->inet_saddr) < ntohl(inet->inet_daddr)) {
+ goto rst_nsk;
+ } else if (rs_tcp->t_sock) {
+ rds_tcp_restore_callbacks(rs_tcp->t_sock, rs_tcp);
+ conn->c_outgoing = 0;
+ }
+ }
rds_tcp_set_callbacks(new_sock, conn);
- rds_connect_complete(conn);
+ rds_connect_complete(conn); /* marks RDS_CONN_UP */
new_sock = NULL;
ret = 0;
-
+ goto out;
+rst_nsk:
+ /* reset the newly returned accept sock and bail */
+ nsk = new_sock->sk;
+ rds_tcp_stats_inc(s_tcp_listen_closed_stale);
+ nsk->sk_user_data = NULL;
+ nsk->sk_prot->disconnect(nsk, 0);
+ tcp_done(nsk);
+ new_sock = NULL;
+ ret = 0;
out:
+ if (rs_tcp)
+ mutex_unlock(&rs_tcp->t_conn_lock);
if (new_sock)
sock_release(new_sock);
return ret;