Hi Andrew,
I helped Yang clean up his changelog and re-send his patch with a 
reworked title.
The Author is still Yang Zhang.

Thanks,
Changwei

Subject: [PATCH] ocfs2/cluster: close a race that fence can't be triggered

When some nodes of cluster face with TCP connection fault, ocfs2 will
pick up a quorum to continue to work and other nodes will be fenced by
resetting host.
In order to decide which node should be fenced, ocfs2 leverages
o2quo_state::qs_holds. If that variable is reduced to zero, then a try
to decide if fence local node is performed.
However, under a specific scenario that local node is not disconnected
from others at the same time, above method has a problem to reduce
::qs_holds to zero.
Because, o2net 90s idle timer corresponding to different nodes is
triggered one after another.

node 2                          node 3
90s idle timer elapses
clear ::qs_conn_bm
set hold
                                40s is passed
                                90 idle timer elapses
                                clear ::qs_conn_bm
                                set hold
still up timer elapses
clear hold (NOT to zero )
90s idle timer elapses AGAIN
                                still up timer elapses.
                                clear hold
                                still up timer elapses

To solve this issue, a node which has already be evicted from
::qs_conn_bm can't set hold again and again invoked from idle timer.

Signed-off-by: Yang Zhang <zhang.ya...@h3c.com>
Signed-off-by: Changwei Ge <ge.chang...@h3c.com>
---
  fs/ocfs2/cluster/quorum.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/cluster/quorum.c b/fs/ocfs2/cluster/quorum.c
index 62e8ec619b4c..af2e7473956e 100644
--- a/fs/ocfs2/cluster/quorum.c
+++ b/fs/ocfs2/cluster/quorum.c
@@ -314,12 +314,13 @@ void o2quo_conn_err(u8 node)
                                node, qs->qs_connected);

                clear_bit(node, qs->qs_conn_bm);
+
+               if (test_bit(node, qs->qs_hb_bm))
+                       o2quo_set_hold(qs, node);
        }

        mlog(0, "node %u, %d total\n", node, qs->qs_connected);

-       if (test_bit(node, qs->qs_hb_bm))
-               o2quo_set_hold(qs, node);

        spin_unlock(&qs->qs_lock);
  }
-- 
2.11.0



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