[XFS] Fix a barrier related forced shutdown on mounts with quota enabled.

SGI-PV: 912426
SGI-Modid: xfs-linux-melb:xfs-kern:26622a

Signed-off-by: Nathan Scott <nathans@sgi.com>
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 9bdef9d..4754f34 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -314,6 +314,13 @@
 		return;
 	}
 
+	if (xfs_readonly_buftarg(mp->m_ddev_targp)) {
+		xfs_fs_cmn_err(CE_NOTE, mp,
+		  "Disabling barriers, underlying device is readonly");
+		mp->m_flags &= ~XFS_MOUNT_BARRIER;
+		return;
+	}
+
 	error = xfs_barrier_test(mp);
 	if (error) {
 		xfs_fs_cmn_err(CE_NOTE, mp,