ocfs2: checkpoint appending truncate log transaction before flushing

Appending truncate log(TA) and and flushing truncate log(TF) are two
separated transactions.  They can be both committed but not checkpointed.
If crash occurs then, both transaction will be replayed with several
already released to global bitmap clusters.  Then truncate log will be
replayed resulting in cluster double free.

To reproduce this issue, just crash the host while punching hole to files.
Signed-off-by: NChangwei Ge <gechangwei@live.cn>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/alloc.c

@@ -5993,6 +5993,7 @@ int __ocfs2_flush_truncate_log(struct ocfs2_super *osb)
 	struct buffer_head *data_alloc_bh = NULL;
 	struct ocfs2_dinode *di;
 	struct ocfs2_truncate_log *tl;
+	struct ocfs2_journal *journal = osb->journal;
 
 	BUG_ON(inode_trylock(tl_inode));
 
@@ -6013,6 +6014,20 @@ int __ocfs2_flush_truncate_log(struct ocfs2_super *osb)
 		goto out;
 	}
 
+	/* Appending truncate log(TA) and and flushing truncate log(TF) are
+	 * two separated transactions. They can be both committed but not
+	 * checkpointed. If crash occurs then, both two transaction will be
+	 * replayed with several already released to global bitmap clusters.
+	 * Then truncate log will be replayed resulting in cluster double free.
+	 */
+	jbd2_journal_lock_updates(journal->j_journal);
+	status = jbd2_journal_flush(journal->j_journal);
+	jbd2_journal_unlock_updates(journal->j_journal);
+	if (status < 0) {
+		mlog_errno(status);
+		goto out;
+	}
+
 	data_alloc_inode = ocfs2_get_system_file_inode(osb,
 						       GLOBAL_BITMAP_SYSTEM_INODE,
 						       OCFS2_INVALID_SLOT);