lvconvert: fix regression preventing direct striped conversion

Conversion to striped from raid0/raid0_meta is directly possible.

Fix a regression setting superfluous interim raid5_n conversion type
introduced by commit bd7cdd0b09.

Add new test script lvconvert-raid0-striped.sh.

Resolves: rhbz1608067

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 3.0.0
 =============
+  Fix lvconvert raid0/raid0_meta -> striped regression.
   Fix lvconvert --splitmirror for mirror type (2.02.178).
   Do not pair cache policy and cache metadata format.
   lvconvert: reject conversions on raid1 LVs with split tracked SubLVs

lib/metadata/raid_manip.c

@@ -6126,6 +6126,9 @@ static int _set_convenient_raid145610_segtype_to(const struct lv_segment *seg_fr
 		if (seg_from->area_count == 1)
 			seg_flag = SEG_RAID1;
 
+		else if (seg_is_any_raid0(seg_from) && segtype_is_striped(*segtype))
+			;
+
 		/* If this is any raid5 conversion request -> enforce raid5_n, because we convert from striped */
 		else if (((segtype_is_striped(*segtype) && !segtype_is_any_raid0(*segtype)) || segtype_is_any_raid5(*segtype)) &&
 			 !segtype_is_raid5_n(*segtype))

test/shell/lvconvert-raid0-striped.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+# Copyright (C) 2018 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+
+SKIP_WITH_LVMPOLLD=1
+
+. lib/inittest
+
+aux have_raid 1 7 0 || skip
+
+aux prepare_vg 3 16
+
+lvcreate -aey --type raid0 -i 3 -l3 -n $lv $vg
+lvconvert -y --type striped $vg/$lv
+check lv_field $vg/$lv segtype "striped"
+vgremove -ff $vg