test: Add a test for the failing pv_read optimisation.

test/shell/mda-rollback.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+# Copyright (C) 2013 Red Hat, Inc. All rights reserved.
+#
+# This copyrighted material is made available to anyone wishing to use,
+# modify, copy, or redistribute it subject to the terms and conditions
+# of the GNU General Public License v.2.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+. lib/test
+
+aux prepare_devs 3
+
+vgcreate --metadatasize 128k $vg1 "$dev1" "$dev2" "$dev3"
+
+vgreduce $vg1 $dev1
+dd if="$dev1" of=badmda bs=256K count=1
+vgextend $vg1 $dev1
+
+dd if=badmda of="$dev1" bs=256K count=1
+
+# dev1 is part of vg1 (as witnessed by metadata on dev2 and dev3), but its mda
+# was corrupt (written over by a backup from time dev1 was an orphan)
+check pv_field $dev1 vg_name $vg1