If ocfs2_reserve_cluster_bitmap_bits() fails with ENOSPC, it will try to
free truncate log and then retry.  Since ocfs2_try_to_free_truncate_log
will lock/unlock global bitmap inode, we have to unlock it before
calling this function.  But when retry reserve and it fails with no
global bitmap inode lock taken, it will unlock again in error handling
branch and BUG.

This issue also exists if no need retry and then ocfs2_inode_lock fails.
So fix it.

Fixes: 2070ad1aebff ("ocfs2: retry on ENOSPC if sufficient space in truncate log")
Link: http://lkml.kernel.org/r/57D91939.6030809@huawei.com
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Jiufei Xue <xuejiufei@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>