4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ilya Dryomov <[email protected]>

commit 7b4c443d139f1d2b5570da475f7a9cbcef86740c upstream.

If we go without an established session for a while, backoff delay will
climb to 30 seconds.  The keepalive timeout is also 30 seconds, so it's
pretty easily hit after a prolonged hunting for a monitor: we don't get
a chance to send out a keepalive in time, which means we never get back
a keepalive ack in time, cutting an established session and attempting
to connect to a different monitor every 30 seconds:

  [Sun Apr 1 23:37:05 2018] libceph: mon0 10.80.20.99:6789 session established
  [Sun Apr 1 23:37:36 2018] libceph: mon0 10.80.20.99:6789 session lost, 
hunting for new mon
  [Sun Apr 1 23:37:36 2018] libceph: mon2 10.80.20.103:6789 session established
  [Sun Apr 1 23:38:07 2018] libceph: mon2 10.80.20.103:6789 session lost, 
hunting for new mon
  [Sun Apr 1 23:38:07 2018] libceph: mon1 10.80.20.100:6789 session established
  [Sun Apr 1 23:38:37 2018] libceph: mon1 10.80.20.100:6789 session lost, 
hunting for new mon
  [Sun Apr 1 23:38:37 2018] libceph: mon2 10.80.20.103:6789 session established
  [Sun Apr 1 23:39:08 2018] libceph: mon2 10.80.20.103:6789 session lost, 
hunting for new mon

The regular keepalive interval is 10 seconds.  After ->hunting is
cleared in finish_hunting(), call __schedule_delayed() to ensure we
send out a keepalive after 10 seconds.

Cc: [email protected] # 4.7+
Link: http://tracker.ceph.com/issues/23537
Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Jason Dillaman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 net/ceph/mon_client.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ceph/mon_client.c
+++ b/net/ceph/mon_client.c
@@ -1133,6 +1133,7 @@ static void finish_hunting(struct ceph_m
                monc->hunting = false;
                monc->had_a_connection = true;
                un_backoff(monc);
+               __schedule_delayed(monc);
        }
 }
 


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