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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2016-05-02 18:24:52 (GMT)
committerDavid S. Miller <davem@davemloft.net>2016-05-03 20:03:44 (GMT)
commitbd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e (patch)
tree42b348d05eaf5e948bd694bdbe390ebb6a9c354f /net/rds
parenteb192840266fab3e3da644018121eed30153355d (diff)
downloadlinux-bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e.tar.xz
RDS: TCP: Synchronize accept() and connect() paths on t_conn_lock.
An arbitration scheme for duelling SYNs is implemented as part of commit 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an outgoing socket in rds_tcp_accept_one()") which ensures that both nodes involved will arrive at the same arbitration decision. However, this needs to be synchronized with an outgoing SYN to be generated by rds_tcp_conn_connect(). This commit achieves the synchronization through the t_conn_lock mutex in struct rds_tcp_connection. The rds_conn_state is checked in rds_tcp_conn_connect() after acquiring the t_conn_lock mutex. A SYN is sent out only if the RDS connection is not already UP (an UP would indicate that rds_tcp_accept_one() has completed 3WH, so no SYN needs to be generated). Similarly, the rds_conn_state is checked in rds_tcp_accept_one() after acquiring the t_conn_lock mutex. The only acceptable states (to allow continuation of the arbitration logic) are UP (i.e., outgoing SYN was SYN-ACKed by peer after it sent us the SYN) or CONNECTING (we sent outgoing SYN before we saw incoming SYN). Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds')
-rw-r--r--net/rds/tcp.c1
-rw-r--r--net/rds/tcp.h4
-rw-r--r--net/rds/tcp_connect.c8
-rw-r--r--net/rds/tcp_listen.c30
4 files changed, 33 insertions, 10 deletions
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 9134544..86187da 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -216,6 +216,7 @@ static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
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 rds_tcp_connection {
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 @@ int rds_tcp_conn_connect(struct rds_connection *conn)
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 @@ int rds_tcp_conn_connect(struct rds_connection *conn)
}
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 0896187..be263cd 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -76,7 +76,9 @@ int rds_tcp_accept_one(struct socket *sock)
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,
@@ -116,6 +118,10 @@ int rds_tcp_accept_one(struct socket *sock)
*/
rs_tcp = (struct rds_tcp_connection *)conn->c_transport_data;
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
@@ -126,14 +132,7 @@ int rds_tcp_accept_one(struct socket *sock)
wait_event(conn->c_waitq,
!test_bit(RDS_IN_XMIT, &conn->c_flags));
if (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;
+ goto rst_nsk;
} else if (rs_tcp->t_sock) {
rds_tcp_restore_callbacks(rs_tcp->t_sock, rs_tcp);
conn->c_outgoing = 0;
@@ -143,8 +142,19 @@ int rds_tcp_accept_one(struct socket *sock)
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;