[pve-devel] [PATCH pve-manager v4] postinst: filter rbds in lvm

Stefan Hanreich s.hanreich at proxmox.com
Fri Dec 22 10:58:06 CET 2023

Since LVM 2.03.15 RBD devices are also scanned by default [1]. This
can lead to guest volumes being recognized and displayed on the host
when using KRBD for RBD-backed disks. In order to prevent this we add
an additional filter to the LVM config to avoid scanning rbds.

This also prevents a bug where LVM created a very high amount of
archive entries when there were logical volumes with the same path
available. This could happen when two guests with RBD disks had the
same LVM layout or a guest and host had the same layout.

previous behavior:
If there is no marker in the LVM conf and global_filter does not
contain '/dev/zd.*': replace the global_filter with our version

new behavior:
Replace the global_filter iff:
- There is no marker and global_filter is empty
- The global_filter is exactly the old default

If we don't replace the filter and it is a non-default value: We print
a warning. Addtionally we force this function to run once when
upgrading from older versions.

The previous versions could replace custom global_filters where the
comment had been removed and the zvol directive removed. The new
behavior is slightly more conservative, but works the same in other

[1] https://gitlab.com/lvmteam/lvm2/-/commit/6a431eb24241caf2277d3e5b4718782d92650a2a

Signed-off-by: Stefan Hanreich <s.hanreich at proxmox.com>

Changes from v3 -> v4:
- Move LVM_SUPPRESS_FD_WARNINGS=1 in order to prevent fd warnings from
  the lvmconfig invocation

Changes from v2 -> v3:
- Additionally only change empty values if there is no marker
- Print a warning when encountering a non-default value
- Check the LVM config for validity afterwards and restore it from
  backup if it is invalid

Changes from v1 -> v2:
- changed replacement logic:
  - if there is an existing global_filter, we replace the line
  - if there is no existing global_filter we add a whole 'devices' block
- we only rewrite if there is no global_filter set or if it is the value
we set in versions <= 8.1.3

 debian/postinst | 51 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/debian/postinst b/debian/postinst
index 4c9a1f250..8028e39ee 100755
--- a/debian/postinst
+++ b/debian/postinst
@@ -9,23 +9,33 @@ set -e
 # installed and configured.
 set_lvm_conf() {
+    local FORCE="$1"
     LVM_CONF_MARKER="# added by pve-manager to avoid scanning"
     # keep user changes afterwards provided marker is still there..
-    if grep -qLF "$LVM_CONF_MARKER" /etc/lvm/lvm.conf; then
+    if grep -qLF "$LVM_CONF_MARKER" /etc/lvm/lvm.conf && test -z "$FORCE"; then
         return 0 # only do these changes once
-    OLD_VALUE="$(lvmconfig --typeconfig full devices/global_filter)"
-    NEW_VALUE='global_filter=["r|/dev/zd.*|"]'
-    # check global_filter
-    # keep previous setting from our custom packaging if it is still there
-    if echo "$OLD_VALUE" | grep -qvF 'r|/dev/zd.*|'; then
+    OLD_VALUE="$(lvmconfig --typeconfig diff devices/global_filter || true)"
+    NEW_VALUE='global_filter=["r|/dev/zd.*|","r|/dev/rbd.*|"]'
+    # update global_filter if:
+    # it is empty and there is no marker OR exactly the one we set before 8.1.4
+    if (! grep -qF "$LVM_CONF_MARKER" /etc/lvm/lvm.conf && test -z "$OLD_VALUE")\
+	|| (echo "$OLD_VALUE" | grep -qF '="r|/dev/zd.*|"');
+    then
+    # print warning if global_filter is set but not our old/new default
+    elif test -n "$OLD_VALUE"\
+	&& ! echo "$OLD_VALUE" | grep -qF '="r|/dev/zd.*|"'\
+	&& ! echo "$OLD_VALUE" | grep -qF "$NEW_VALUE";
+    then
+	echo "non-default 'global_filter' value '$OLD_VALUE' in /etc/lvm/lvm.conf, not setting '$NEW_VALUE' automatically"
+	echo "consider adapting your 'global_filter' manually."
     # should be the default since bullseye
     if lvmconfig --typeconfig full devices/scan_lvs | grep -qv 'scan_lvs=0'; then
@@ -37,17 +47,19 @@ set_lvm_conf() {
         cp -vb /etc/lvm/lvm.conf /etc/lvm/lvm.conf.bak
     if test -n "$SET_FILTER"; then
-        echo "Setting 'global_filter' in /etc/lvm/lvm.conf to prevent zvols from being scanned:"
+        echo "Setting 'global_filter' in /etc/lvm/lvm.conf to prevent zvols and rbds from being scanned:"
         echo "$OLD_VALUE => $NEW_VALUE"
-        # comment out existing setting
-        sed -i -e 's/^\([[:space:]]*global_filter[[:space:]]*=\)/#\1/' /etc/lvm/lvm.conf
-        # add new section with our setting
-        cat >> /etc/lvm/lvm.conf <<EOF
+        if test -n "$OLD_VALUE"; then
+            sed -i -e "s/$LVM_CONF_MARKER ZFS zvols/$LVM_CONF_MARKER ZFS zvols and Ceph rbds/" /etc/lvm/lvm.conf
+            sed -i -e "s!^\([[:space:]]*\)\(global_filter[[:space:]]*=.*\)\$!\1# \2\n\1$NEW_VALUE!" /etc/lvm/lvm.conf
+        else
+            cat >> /etc/lvm/lvm.conf <<EOF
 devices {
-     $LVM_CONF_MARKER ZFS zvols
+     $LVM_CONF_MARKER ZFS zvols and Ceph rbds
- }
+        fi
     if test -n "$SET_SCAN_LVS"; then
         echo "Adding scan_lvs=0 setting to /etc/lvm/lvm.conf to prevent LVs from being scanned."
@@ -61,6 +73,11 @@ devices {
+    if ! lvmconfig --validate; then
+	echo "Invalid LVM config detected - restoring from /etc/lvm/lvm.conf.bak"
+	mv /etc/lvm/lvm.conf.bak /etc/lvm/lvm.conf
+    fi
 migrate_apt_auth_conf() {
@@ -165,6 +182,12 @@ case "$1" in
         rm -v "$BETA_SOURCES" || true
+    if test ! -e /proxmox_install_mode && test -n "$2" && dpkg --compare-versions "$2" 'lt' '8.1.4~'; then
+        if test -e /etc/lvm/lvm.conf ; then
+            set_lvm_conf 1
+        fi
+    fi
     if test ! -e /proxmox_install_mode; then

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