handle duplicate vgids

The approach to duplicate VGIDs has been that it is not possible
or not allowed, so the behavior has been undefined.  The actual
result was unpredictable and/or broken, and generally unhelpful.

Improve this by recognizing the problem, displaying the VGs,
and printing a warning to fix the problem.  Beyond this,
using VGs with duplicate VGIDs remains undefined, but should
work well enough to correct the problem with vgchange -u.

It's possible to create this condition without too much difficulty
by cloning PVs, followed by an incomplete attempt at making the two
VGs unique (vgrename and pvchange -u, but missing vgchange -u.)

2 files changed, 68 insertions, 4 deletions

diff --git a/lib/cache/lvmcache.c b/lib/cache/lvmcache.c
index 6569f983d..22edcfd84 100644
--- a/lib/cache/lvmcache.c
+++ b/lib/cache/lvmcache.c
@@ -354,9 +354,11 @@ static struct lvmcache_vginfo *_vginfo_lookup(const char *vgname, const char *vg
 	if (vgid_arg) {
 		if ((vginfo = dm_hash_lookup(_vgid_hash, vgid))) {
 			if (vgname && strcmp(vginfo->vgname, vgname)) {
-				/* should never happen */
-				log_error(INTERNAL_ERROR "vginfo_lookup vgid %s has two names %s %s",
-					  vgid, vginfo->vgname, vgname);
+				log_warn("WARNING: lookup found duplicate VGID %s for VGs %s and %s.", vgid, vginfo->vgname, vgname);
+				if ((vginfo = dm_hash_lookup(_vgname_hash, vgname))) {
+					if (!memcmp(vginfo->vgid, vgid, ID_LEN))
+						return vginfo;
+				}
 				return NULL;
 			}
 			return vginfo;
@@ -1884,7 +1886,17 @@ static int _lvmcache_update_vgname(struct cmd_context *cmd,
 
 	_drop_vginfo(info, info->vginfo);
 
-	if (!(vginfo = lvmcache_vginfo_from_vgid(vgid))) {
+	vginfo = lvmcache_vginfo_from_vgid(vgid);
+	if (vginfo && strcmp(vginfo->vgname, vgname)) {
+		log_warn("WARNING: fix duplicate VGID %s for VGs %s and %s (see vgchange -u).", vgid_dashed, vgname, vginfo->vgname);
+		vginfo = lvmcache_vginfo_from_vgname(vgname, NULL);
+		if (vginfo && memcmp(vginfo->vgid, vgid, ID_LEN)) {
+			log_error("Ignoring %s with conflicting VG info %s %s.", dev_name(info->dev), vgid_dashed, vgname);
+			return_0;
+		}
+	}
+
+	if (!vginfo) {
 		/*
 	 	 * Create a vginfo struct for this VG and put the vginfo
 	 	 * into the hash table.
diff --git a/test/shell/duplicate-vgid.sh b/test/shell/duplicate-vgid.sh
new file mode 100644
index 000000000..12163c2f0
--- /dev/null
+++ b/test/shell/duplicate-vgid.sh
@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+# Copyright (C) 2008-2013 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.
+
+SKIP_WITH_LVMLOCKD=1
+SKIP_WITH_LVMPOLLD=1
+
+. lib/inittest
+
+aux prepare_devs 2
+
+vgcreate $vg1 "$dev1"
+vgchange --setautoactivation n $vg1
+UUID1=$(vgs --noheading -o vg_uuid $vg1 | xargs)
+lvcreate -l1 -an -n $lv1 $vg1
+dd if="$dev1" of="$dev2" bs=1M count=1
+aux disable_dev "$dev1"
+vgrename $vg1 $vg2
+pvchange -u "$dev2"
+aux enable_dev "$dev1"
+
+vgs -o+uuid |tee out
+grep $vg1 out | tee out1
+grep $UUID1 out1
+grep $vg2 out | tee out2
+grep $UUID1 out2
+
+vgs $vg1
+vgs $vg2
+lvs $vg1/$lv1
+lvs $vg2/$lv1
+
+lvremove $vg1/$lv1
+lvremove $vg2/$lv1
+
+lvcreate -l1 -an -n $lv2 $vg1
+lvcreate -l1 -an -n $lv3 $vg2
+
+vgchange -u $vg2
+
+vgs -o uuid $vg1 |tee out
+grep $UUID1 out
+
+vgs -o uuid $vg2 |tee out
+not grep $UUID1 out
+
+vgremove -ff $vg1
+vgremove -ff $vg2