Fix jbd2 kernel bug in jbd2_journal_commit_transaction+0x120c

In our DB system, we met with a kernel panic when using ext4. After
A deep investigation, it shows that it is caused by a specific usage
of MySQL.
The upstream commit id is deeeaf13 and e7b04ac0.
For more information, please refer to
http://blog.donghao.org/2013/07/17/rhel6%E5%86%8D%E6%AC%A1%E5%8F%91%E7%8E%B0jbd2%E7%9A%84bug/.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>