Ocfs2 devel - Aug 2013 - [patch 16/22] ocfs2/dlm: force clean refmap when doing local cleanup

From: Xue jiufei <xuejiufei at huawei.com>
Subject: ocfs2/dlm: force clean refmap when doing local cleanup

dlm_do_local_recovery_cleanup() should force clean refmap if the owner of
lockres is UNKNOWN.  Otherwise node may hang when umounting filesystems. 
Here's the situation:

	Node1                                    Node2
dlmlock()
  -> dlm_get_lock_resource()
send DLM_MASTER_REQUEST_MSG to
other nodes.

                                       trying to master this lockres,
                                       return MAYBE.

selected as the master of lockresA,
set mle->master to Node1,
and do assert_master,
send DLM_ASSERT_MASTER_MSG to Node2.
                                       Node 2 has interest on lockresA
                                       and return
                                       DLM_ASSERT_RESPONSE_MASTERY_REF
                                       then something happened and
                                       Node2 crashed.

Receiving DLM_ASSERT_RESPONSE_MASTERY_REF, set Node2 into refmap, and keep
sending DLM_ASSERT_MASTER_MSG to other nodes

o2hb found node2 down, calling dlm_hb_node_down() -->
dlm_do_local_recovery_cleanup() the master of lockresA is still UNKNOWN,
no need to call dlm_free_dead_locks().

Set the master of lockresA to Node1, but Node2 stills remains in refmap.

When Node1 umount, it found that the refmap of lockresA is not empty and
attempted to migrate it to Node2, But Node2 is already down, so umount
hang, trying to migrate lockresA again and again.

Signed-off-by: joyce <xuejiufei at huawei.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Jie Liu <jeff.liu at oracle.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 fs/ocfs2/dlm/dlmrecovery.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff -puN
fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-force-clean-refmap-when-doing-local-cleanup
fs/ocfs2/dlm/dlmrecovery.c
---
a/fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-force-clean-refmap-when-doing-local-cleanup
+++ a/fs/ocfs2/dlm/dlmrecovery.c
@@ -2331,6 +2331,14 @@ static void dlm_do_local_recovery_cleanu
 			} else if (res->owner == dlm->node_num) {
 				dlm_free_dead_locks(dlm, res, dead_node);
 				__dlm_lockres_calc_usage(dlm, res);
+			} else if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
+				if (test_bit(dead_node, res->refmap)) {
+					mlog(0, "%s:%.*s: dead node %u had a ref, but had "
+						"no locks and had not purged before dying\n",
+						dlm->name, res->lockname.len,
+						res->lockname.name, dead_node);
+					dlm_lockres_clear_refmap_bit(dlm, res, dead_node);
+				}
 			}
 			spin_unlock(&res->spinlock);
 		}
_