+ if (log->l_mp->m_flags & XFS_MOUNT_BARRIER) {
+ bp->b_flags |= XBF_FUA;
+
+ /*
+ * 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 stamping the new log tail LSN into the
+ * log buffer. For an external log we need to issue the
+ * flush explicitly, and unfortunately synchronously here;
+ * for an internal log we can simply use the block layer
+ * state machine for preflushes.
+ */
+ if (log->l_mp->m_logdev_targp != log->l_mp->m_ddev_targp)
+ xfs_blkdev_issue_flush(log->l_mp->m_ddev_targp);
+ else
+ bp->b_flags |= XBF_FLUSH;
+ }