This patch series is to fix a possible message lost bug in ocfs2 when
network go bad.  This bug will cause ocfs2 hung forever even network
become good again.

The messages may lost in this case.  After the tcp connection is
established between two nodes, an idle timer will be set to check its
state periodically, if no messages are received during this time, idle
timer will timeout, it will shutdown the connection and try to
reconnect, so pending messages in tcp queues will be lost.  This
messages may be from dlm.  Dlm may get hung in this case.  This may
cause the whole ocfs2 cluster hung.

This is very possible to happen when network state goes bad.  Do the
reconnect is useless, it will fail if network state is still bad.  Just
waiting there for network recovering may be a good idea, it will not
lost messages and some node will be fenced until cluster goes into
split-brain state, for this case, Tcp user timeout is used to override
the tcp retransmit timeout.  It will timeout after 25 days, user should
have notice this through the provided log and fix the network, if they
don't, ocfs2 will fall back to original reconnect way.

This patch (of 3):

Some messages in the tcp queue maybe lost if we shutdown the connection
and reconnect when idle timeout.  If packets lost and reconnect success,
then the ocfs2 cluster maybe hung.

To fix this, we can leave the connection there and do the fence decision
when idle timeout, if network recover before fence dicision is made, the
connection survive without lost any messages.

This bug can be saw when network state go bad.  It may cause ocfs2 hung
forever if some packets lost.  With this fix, ocfs2 will recover from
hung if network becomes good again.

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