[XFS] Put back the QUEUE_ORDERED_NONE test in the barrier check.

Put back the QUEUE_ORDERED_NONE test which caused us grief in sles when it
was taken out as, IIRC, it allowed md/lvm to be thought of as supporting
barriers when they weren't in some configurations. This patch will be
reverting what went in as part of a change for the SGI-pv 964544
(SGI-Modid: xfs-linux-melb:xfs-kern:28568a).

SGI-PV: 971783
SGI-Modid: xfs-linux-melb:xfs-kern:29882a
Signed-off-by: Tim Shimmin <tes@sgi.com>
Signed-off-by: David Chinner <dgc@sgi.com>

fs/xfs/linux-2.6/xfs_super.c

@@ -303,6 +303,14 @@ xfs_mountfs_check_barriers(xfs_mount_t *mp)
 		return;
 	}
 
+	if (mp->m_ddev_targp->bt_bdev->bd_disk->queue->ordered ==
+					QUEUE_ORDERED_NONE) {
+		xfs_fs_cmn_err(CE_NOTE, mp,
+		  "Disabling barriers, not supported by the underlying device");
+		mp->m_flags &= ~XFS_MOUNT_BARRIER;
+		return;
+	}
+
 	if (xfs_readonly_buftarg(mp->m_ddev_targp)) {
 		xfs_fs_cmn_err(CE_NOTE, mp,
 		  "Disabling barriers, underlying device is readonly");