Ocfs2 devel - Aug 2014 - [patch 04/10] ocfs2: o2net: set tcp user timeout to max value

From: Junxiao Bi <junxiao.bi at oracle.com>
Subject: ocfs2: o2net: set tcp user timeout to max value

When tcp retransmit timeout(15mins), the connection will be closed. 
Pending messages may be lost during this time.  So we set tcp user timeout
to override the retransmit timeout to the max value.  This is OK for ocfs2
since we have disk heartbeat, if peer crash, the disk heartbeat will
timeout and it will be evicted, if disk heartbeat not timeout and
connection idle for a long time, then this means the cluster enters
split-brain state, since fence can't happen, we'd better keep the
connection and wait network recover.

Signed-off-by: Junxiao Bi <junxiao.bi at oracle.com>
Reviewed-by: Srinivas Eeda <srinivas.eeda at oracle.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Joseph Qi <joseph.qi at huawei.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 fs/ocfs2/cluster/tcp.c |   20 ++++++++++++++++++++
 fs/ocfs2/cluster/tcp.h |    1 +
 2 files changed, 21 insertions(+)

diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-set-tcp-user-timeout-to-max-value
fs/ocfs2/cluster/tcp.c
--- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-set-tcp-user-timeout-to-max-value
+++ a/fs/ocfs2/cluster/tcp.c
@@ -1480,6 +1480,14 @@ static int o2net_set_nodelay(struct sock
 	return ret;
 }
 
+static int o2net_set_usertimeout(struct socket *sock)
+{
+	int user_timeout = O2NET_TCP_USER_TIMEOUT;
+
+	return kernel_setsockopt(sock, SOL_TCP, TCP_USER_TIMEOUT,
+				(char *)&user_timeout, sizeof(user_timeout));
+}
+
 static void o2net_initialize_handshake(void)
 {
 	o2net_hand->o2hb_heartbeat_timeout_ms = cpu_to_be32(
@@ -1663,6 +1671,12 @@ static void o2net_start_connect(struct w
 		goto out;
 	}
 
+	ret = o2net_set_usertimeout(sock);
+	if (ret) {
+		mlog(ML_ERROR, "set TCP_USER_TIMEOUT failed with %d\n", ret);
+		goto out;
+	}
+
 	o2net_register_callbacks(sc->sc_sock->sk, sc);
 
 	spin_lock(&nn->nn_lock);
@@ -1844,6 +1858,12 @@ static int o2net_accept_one(struct socke
 		goto out;
 	}
 
+	ret = o2net_set_usertimeout(new_sock);
+	if (ret) {
+		mlog(ML_ERROR, "set TCP_USER_TIMEOUT failed with %d\n", ret);
+		goto out;
+	}
+
 	slen = sizeof(sin);
 	ret = new_sock->ops->getname(new_sock, (struct sockaddr *) &sin,
 				       &slen, 1);
diff -puN fs/ocfs2/cluster/tcp.h~ocfs2-o2net-set-tcp-user-timeout-to-max-value
fs/ocfs2/cluster/tcp.h
--- a/fs/ocfs2/cluster/tcp.h~ocfs2-o2net-set-tcp-user-timeout-to-max-value
+++ a/fs/ocfs2/cluster/tcp.h
@@ -63,6 +63,7 @@ typedef void (o2net_post_msg_handler_fun
 #define O2NET_KEEPALIVE_DELAY_MS_DEFAULT	2000
 #define O2NET_IDLE_TIMEOUT_MS_DEFAULT		30000
 
+#define O2NET_TCP_USER_TIMEOUT			0x7fffffff
 
 /* TODO: figure this out.... */
 static inline int o2net_link_down(int err, struct socket *sock)
_

On Wed, Aug 06, 2014 at 01:32:07PM -0700, Andrew Morton
wrote:
> From: Junxiao Bi <junxiao.bi at oracle.com>
> Subject: ocfs2: o2net: set tcp user timeout to max value
> 
> When tcp retransmit timeout(15mins), the connection will be closed. 
> Pending messages may be lost during this time.  So we set tcp user timeout
> to override the retransmit timeout to the max value.  This is OK for ocfs2
> since we have disk heartbeat, if peer crash, the disk heartbeat will
> timeout and it will be evicted, if disk heartbeat not timeout and
> connection idle for a long time, then this means the cluster enters
> split-brain state, since fence can't happen, we'd better keep the
> connection and wait network recover.
That's a heck of a timeout :(

I don't think there's much we can do though with this cluster stack if
we
get into a (true) split brain situation though so this is probably better
than losing messages and crashing the whole thing.

Reviewed-by: Mark Fasheh <mfasheh at suse.de>


--
Mark Fasheh