+ if (log->l_mp->m_flags & XFS_MOUNT_BARRIER) {
+ /*
+ * If we have an external log device, flush the data device
+ * before flushing the log to make sure all meta data
+ * written back from the AIL actually made it to disk
+ * before writing out the new log tail LSN in the log buffer.
+ */
+ if (log->l_mp->m_logdev_targp != log->l_mp->m_ddev_targp)
+ xfs_blkdev_issue_flush(log->l_mp->m_ddev_targp);