when o2hb detect a node down, it first set the dead node to recovery map
and create ocfs2rec which will replay journal for dead node.  o2hb
thread then call dlm_do_local_recovery_cleanup() to delete the lock for
dead node.  After the lock of dead node is gone, locks for other nodes
can be granted and may modify the meta data without replaying journal of
the dead node.  The detail is described as follows.

     N1                         N2                   N3(master)
modify the extent tree of
inode, and commit
dirty metadata to journal,
then goes down.
                                                 o2hb thread detects
                                                 N1 goes down, set
                                                 recovery map and
                                                 delete the lock of N1.

                                                 dlm_thread flush ast
                                                 for the lock of N2.
                        do not detect the death
                        of N1, so recovery map is
                        empty.

                        read inode from disk
                        without replaying
                        the journal of N1 and
                        modify the extent tree
                        of the inode that N1
                        had modified.
                                                 ocfs2rec recover the
                                                 journal of N1.
                                                 The modification of N2
                                                 is lost.

The modification of N1 and N2 are not serial, and it will lead to
read-only file system.  We can set recovery_waiting flag to the lock
resource after delete the lock for dead node to prevent other node from
getting the lock before dlm recovery.  After dlm recovery, the recovery
map on N2 is not empty, ocfs2_inode_lock_full_nested() will wait for ocfs2
recovery.

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