From 5d5d1db3ca621eb80b9481924d1fc470571cfc09 Mon Sep 17 00:00:00 2001
From: Pavel Cahyna <pcahyna@redhat.com>
Date: Mon, 30 Aug 2021 12:00:43 +0200
Subject: [PATCH] Avoid vgcfgrestore on thin volumes/pools

and any other unsupported volume types.

vgcfgrestore is not supposed to be able to restore any logical volumes
that use kernel metadata. All volume types except linear and striped use
kernel metadata. Main purpose of vgcfgrestore (with mandatory --force
option) is to let users fix existing thin-pool, not to recreate the pool
on empty disks. Do not even try vgcfgrestore on VGs that need any kernel
metadata, because it might lead to an inconsistent state (if there are
data that the kernel might interpret as LV metadata present on the disks).

For VGs that have any volume with kernel metadata and are thus
unsupported by vgcfgrestore, switch automatically to LV creation using
lvcreate, similarly to MIGRATION_MODE.

Avoid vgcfgrestore --force entirely, since it should not be needed now.

This mostly reverts changes in commits
311bfb3da1d5e47a2ff144123a2457e634f67893 and
1b779abfbf56693877fe666f56253ec623599674. The former code is preserved
and gets enabled if FORCE_VGCFGRESTORE=y. This option is on purpose
undocumented though and may be removed in the future.
---
 .../prepare/GNU/Linux/110_include_lvm_code.sh |  8 +++++-
 usr/share/rear/lib/layout-functions.sh        | 26 +++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/usr/share/rear/layout/prepare/GNU/Linux/110_include_lvm_code.sh b/usr/share/rear/layout/prepare/GNU/Linux/110_include_lvm_code.sh
index 5babce228..54a55e688 100644
--- a/usr/share/rear/layout/prepare/GNU/Linux/110_include_lvm_code.sh
+++ b/usr/share/rear/layout/prepare/GNU/Linux/110_include_lvm_code.sh
@@ -83,7 +83,7 @@ EOF
     # '--mirrorlog', etc.
     # Also, we likely do not support every layout yet (e.g. 'cachepool').
 
-    if ! is_true "$MIGRATION_MODE" ; then
+    if ! is_true "$MIGRATION_MODE" && lvmgrp_supports_vgcfgrestore "$vgrp" ; then
         cat >> "$LAYOUT_CODE" <<EOF
 LogPrint "Restoring LVM VG '$vg'"
 if [ -e "$vgrp" ] ; then
@@ -100,6 +100,9 @@ if lvm vgcfgrestore -f "$VAR_DIR/layout/lvm/${vg}.cfg" $vg >&2 ; then
     create_volume_group=( \$( RmInArray "$vg" "\${create_volume_group[@]}" ) )
     create_logical_volumes=( \$( RmInArray "$vg" "\${create_logical_volumes[@]}" ) )
 
+EOF
+        if is_true "${FORCE_VGCFGRESTORE-no}"; then
+            cat >> "$LAYOUT_CODE" <<EOF
 #
 # It failed ... restore layout using 'vgcfgrestore --force', but then remove Thin volumes, they are broken
 #
@@ -124,6 +127,9 @@ elif lvm vgcfgrestore --force -f "$VAR_DIR/layout/lvm/${vg}.cfg" $vg >&2 ; then
     create_volume_group=( \$( RmInArray "$vg" "\${create_volume_group[@]}" ) )
     create_thin_volumes_only+=( "$vg" )
  
+EOF
+        fi
+        cat >> "$LAYOUT_CODE" <<EOF
 #
 # It failed also ... restore using 'vgcreate/lvcreate' commands
 #
diff --git a/usr/share/rear/lib/layout-functions.sh b/usr/share/rear/lib/layout-functions.sh
index 249ad0cd6..77107ae63 100644
--- a/usr/share/rear/lib/layout-functions.sh
+++ b/usr/share/rear/lib/layout-functions.sh
@@ -1387,4 +1387,30 @@ delete_dummy_partitions_and_resize_real_ones() {
     last_partition_number=0
 }
 
+# vgcfgrestore can properly restore only volume groups that do not use
+# any kernel metadata. All volume types except linear and striped use
+# kernel metadata.
+# Check whether a VG (given as /dev/<vgname> in the first argument)
+# doesn't contain any LVs that use kernel metadata.
+# If the function returns true, we can safely use vgcfgrestore to restore the VG.
+function lvmgrp_supports_vgcfgrestore() {
+    if is_true "${FORCE_VGCFGRESTORE-no}"; then
+        # If we are willing to use vgcfgrestore --force and then remove broken volumes,
+        # then everything can be considered supported. Don't do it by default though.
+        return 0
+    fi
+
+    local lvmvol vgrp lvname size layout kval
+
+    local supported_layouts=("linear" "striped")
+
+    while read lvmvol vgrp lvname size layout kval; do
+        [ "$vgrp" == "$1" ] || BugError "vgrp '$vgrp' != '$1'"
+        if ! IsInArray $layout "${supported_layouts[@]}"; then
+            LogPrint "Layout '$layout' of LV '$lvname' in VG '$vgrp' not supported by vgcfgrestore"
+            return 1
+        fi
+    done < <(grep "^lvmvol $1 " "$LAYOUT_FILE")
+}
+
 # vim: set et ts=4 sw=4: