lvmplugin: add qcow2 snapshot

we format lvm logical volume with qcow2 to handle snapshot chain.

like for qcow2 file, when a snapshot is taken, the current lvm volume
is renamed to snap volname, and a new current lvm volume is created
with the snap volname as backing file

snapshot volname is similar to lvmthin : snap_${volname}_{$snapname}.qcow2

Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
This commit is contained in:
Alexandre Derumier 2025-07-09 18:22:01 +02:00 committed by Wolfgang Bumiller
parent ccbced53c5
commit eda88c94ed

View File

@ -3,6 +3,7 @@ package PVE::Storage::LVMPlugin;
use strict;
use warnings;
use File::Basename;
use IO::File;
use PVE::Tools qw(run_command trim);
@ -11,6 +12,8 @@ use PVE::JSONSchema qw(get_standard_option);
use PVE::Storage::Common;
use JSON;
use base qw(PVE::Storage::Plugin);
# lvm helper functions
@ -24,6 +27,15 @@ my $ignore_no_medium_warnings = sub {
}
};
my sub fork_cleanup_worker {
my ($cleanup_worker) = @_;
return if !$cleanup_worker;
my $rpcenv = PVE::RPCEnvironment::get();
my $authuser = $rpcenv->get_user();
$rpcenv->fork_worker('imgdel', undef, $authuser, $cleanup_worker);
}
sub lvm_pv_info {
my ($device) = @_;
@ -267,6 +279,73 @@ sub lvm_list_volumes {
return $lvs;
}
my sub free_lvm_volumes {
my ($class, $scfg, $storeid, $volnames) = @_;
my $vg = $scfg->{vgname};
# we need to zero out LVM data for security reasons
# and to allow thin provisioning
my $zero_out_worker = sub {
# wipe throughput up to 10MB/s by default; may be overwritten with saferemove_throughput
my $throughput = '-10485760';
if ($scfg->{saferemove_throughput}) {
$throughput = $scfg->{saferemove_throughput};
}
for my $name (@$volnames) {
print "zero-out data on image $name (/dev/$vg/del-$name)\n";
my $cmd = [
'/usr/bin/cstream',
'-i',
'/dev/zero',
'-o',
"/dev/$vg/del-$name",
'-T',
'10',
'-v',
'1',
'-b',
'1048576',
'-t',
"$throughput",
];
eval {
run_command(
$cmd,
errmsg => "zero out finished (note: 'No space left on device' is ok here)",
);
};
warn $@ if $@;
$class->cluster_lock_storage(
$storeid,
$scfg->{shared},
undef,
sub {
my $cmd = ['/sbin/lvremove', '-f', "$vg/del-$name"];
run_command($cmd, errmsg => "lvremove '$vg/del-$name' error");
},
);
print "successfully removed volume $name ($vg/del-$name)\n";
}
};
if ($scfg->{saferemove}) {
for my $name (@$volnames) {
# avoid long running task, so we only rename here
my $cmd = ['/sbin/lvrename', $vg, $name, "del-$name"];
run_command($cmd, errmsg => "lvrename '$vg/$name' error");
}
return $zero_out_worker;
} else {
for my $name (@$volnames) {
my $cmd = ['/sbin/lvremove', '-f', "$vg/$name"];
run_command($cmd, errmsg => "lvremove '$vg/$name' error");
}
}
}
# Configuration
sub type {
@ -276,6 +355,7 @@ sub type {
sub plugindata {
return {
content => [{ images => 1, rootdir => 1 }, { images => 1 }],
format => [{ raw => 1, qcow2 => 1 }, 'raw'],
'sensitive-properties' => {},
};
}
@ -354,26 +434,76 @@ sub parse_volname {
PVE::Storage::Plugin::parse_lvm_name($volname);
if ($volname =~ m/^(vm-(\d+)-\S+)$/) {
return ('images', $1, $2, undef, undef, undef, 'raw');
my $name = $1;
my $vmid = $2;
my $format = $volname =~ m/\.qcow2$/ ? 'qcow2' : 'raw';
return ('images', $name, $vmid, undef, undef, undef, $format);
}
die "unable to parse lvm volume name '$volname'\n";
}
#return snapshot name from a file path
sub get_snapname_from_path {
my ($class, $volname, $path) = @_;
my $basepath = basename($path);
my $name = ($volname =~ s/\.[^.]+$//r);
if ($basepath =~ m/^snap_${name}_(.*)\.qcow2$/) {
return $1;
} elsif ($basepath eq $volname) {
return 'current';
}
return undef;
}
my sub get_snap_name {
my ($class, $volname, $snapname) = @_;
die "missing snapname\n" if !$snapname;
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
if ($snapname eq 'current') {
return $name;
} else {
$name =~ s/\.[^.]+$//;
return "snap_${name}_${snapname}.qcow2";
}
}
sub get_snap_volname {
my ($class, $volname, $snapname) = @_;
return get_snap_name($class, $volname, $snapname);
}
sub filesystem_path {
my ($class, $scfg, $volname, $snapname) = @_;
die "lvm snapshot is not implemented" if defined($snapname);
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
my ($vtype, $name, $vmid) = $class->parse_volname($volname);
die "snapshot is working with qcow2 format only" if defined($snapname) && $format ne 'qcow2';
my $vg = $scfg->{vgname};
$name = get_snap_name($class, $volname, $snapname) if $snapname;
my $path = "/dev/$vg/$name";
return wantarray ? ($path, $vmid, $vtype) : $path;
}
sub qemu_blockdev_options {
my ($class, $scfg, $storeid, $volname, $machine_version, $options) = @_;
my ($path) = $class->path($scfg, $volname, $storeid, $options->{'snapshot-name'});
my $blockdev = { driver => 'host_device', filename => $path };
return $blockdev;
}
sub create_base {
my ($class, $storeid, $scfg, $volname) = @_;
@ -395,7 +525,11 @@ sub find_free_diskname {
my $disk_list = [keys %{ $lvs->{$vg} }];
return PVE::Storage::Plugin::get_next_vm_diskname($disk_list, $storeid, $vmid, undef, $scfg);
$add_fmt_suffix = $fmt eq 'qcow2' ? 1 : undef;
return PVE::Storage::Plugin::get_next_vm_diskname(
$disk_list, $storeid, $vmid, $fmt, $scfg, $add_fmt_suffix,
);
}
sub lvcreate {
@ -426,7 +560,12 @@ sub lvcreate {
}
sub lvrename {
my ($vg, $oldname, $newname) = @_;
my ($scfg, $oldname, $newname) = @_;
my $vg = $scfg->{vgname};
my $lvs = lvm_list_volumes($vg);
die "target volume '${newname}' already exists\n"
if ($lvs->{$vg}->{$newname});
run_command(
['/sbin/lvrename', $vg, $oldname, $newname],
@ -434,13 +573,46 @@ sub lvrename {
);
}
sub alloc_image {
my ($class, $storeid, $scfg, $vmid, $fmt, $name, $size) = @_;
my sub lvm_qcow2_format {
my ($class, $storeid, $scfg, $name, $fmt, $backing_snap, $size) = @_;
die "unsupported format '$fmt'" if $fmt ne 'raw';
$class->activate_volume($storeid, $scfg, $name);
my $path = $class->path($scfg, $name, $storeid);
die "illegal name '$name' - should be 'vm-$vmid-*'\n"
if $name && $name !~ m/^vm-$vmid-/;
if ($backing_snap) {
my $backing_path = $class->path($scfg, $name, $storeid, $backing_snap);
PVE::Storage::Plugin::qemu_img_create_qcow2_backed($scfg, $path, $backing_path, $fmt);
} else {
PVE::Storage::Plugin::qemu_img_create($scfg, $fmt, $size, $path);
}
}
my sub calculate_lvm_size {
my ($size, $fmt, $backing_snap) = @_;
#input size = qcow2 image size in kb
return $size if $fmt ne 'qcow2';
my $options = $backing_snap ? ['extended_l2=on', 'cluster_size=128k'] : [];
my $json = PVE::Storage::Plugin::qemu_img_measure($size, $fmt, 5, $options);
die "failed to query file information with qemu-img measure\n" if !$json;
my $info = eval { decode_json($json) };
if ($@) {
die "Invalid JSON: $@\n";
}
die "Missing fully-allocated value from json" if !$info->{'fully-allocated'};
return $info->{'fully-allocated'} / 1024;
}
my sub alloc_lvm_image {
my ($class, $storeid, $scfg, $vmid, $fmt, $name, $size, $backing_snap) = @_;
die "unsupported format '$fmt'" if $fmt ne 'raw' && $fmt ne 'qcow2';
$class->parse_volname($name);
my $vgs = lvm_vgs();
@ -449,86 +621,99 @@ sub alloc_image {
die "no such volume group '$vg'\n" if !defined($vgs->{$vg});
my $free = int($vgs->{$vg}->{free});
my $lvmsize = calculate_lvm_size($size, $fmt, $backing_snap);
die "not enough free space ($free < $size)\n" if $free < $size;
$name = $class->find_free_diskname($storeid, $scfg, $vmid)
my $tags = ["pve-vm-$vmid"];
#tags all snapshots volumes with the main volume tag for easier activation of the whole group
push @$tags, "\@pve-$name" if $fmt eq 'qcow2';
lvcreate($vg, $name, $lvmsize, $tags);
return if $fmt ne 'qcow2';
#format the lvm volume with qcow2 format
eval { lvm_qcow2_format($class, $storeid, $scfg, $name, $fmt, $backing_snap, $size) };
if ($@) {
my $err = $@;
#no need to safe cleanup as the volume is still empty
eval {
my $cmd = ['/sbin/lvremove', '-f', "$vg/$name"];
run_command($cmd, errmsg => "lvremove '$vg/$name' error");
};
die $err;
}
}
sub alloc_image {
my ($class, $storeid, $scfg, $vmid, $fmt, $name, $size) = @_;
$name = $class->find_free_diskname($storeid, $scfg, $vmid, $fmt)
if !$name;
lvcreate($vg, $name, $size, ["pve-vm-$vmid"]);
alloc_lvm_image($class, $storeid, $scfg, $vmid, $fmt, $name, $size);
return $name;
}
my sub alloc_snap_image {
my ($class, $storeid, $scfg, $volname, $backing_snap) = @_;
my ($vmid, $format) = ($class->parse_volname($volname))[2, 6];
my $path = $class->path($scfg, $volname, $storeid, $backing_snap);
#we need to use same size than the backing image qcow2 virtual-size
my $size = PVE::Storage::Plugin::file_size_info($path, 5, $format);
$size = $size / 1024; #we use kb in lvcreate
alloc_lvm_image($class, $storeid, $scfg, $vmid, $format, $volname, $size, $backing_snap);
}
my sub free_snap_image {
my ($class, $storeid, $scfg, $volname, $snap) = @_;
#activate only the snapshot volume
my $path = $class->path($scfg, $volname, $storeid, $snap);
my $cmd = ['/sbin/lvchange', '-aly', $path];
run_command($cmd, errmsg => "can't activate LV '$path' to zero-out its data");
$cmd = ['/sbin/lvchange', '--refresh', $path];
run_command($cmd, errmsg => "can't refresh LV '$path' to zero-out its data");
my $snap_volname = get_snap_name($class, $volname, $snap);
return free_lvm_volumes($class, $scfg, $storeid, [$snap_volname]);
}
sub free_image {
my ($class, $storeid, $scfg, $volname, $isBase) = @_;
my ($class, $storeid, $scfg, $volname, $isBase, $format) = @_;
my $vg = $scfg->{vgname};
my $name = ($class->parse_volname($volname))[1];
# we need to zero out LVM data for security reasons
# and to allow thin provisioning
my $volnames = [$volname];
my $zero_out_worker = sub {
print "zero-out data on image $volname (/dev/$vg/del-$volname)\n";
if ($format eq 'qcow2') {
#activate volumes && snapshot volumes
my $path = $class->path($scfg, $volname, $storeid);
$path = "\@pve-$name" if $format && $format eq 'qcow2';
my $cmd = ['/sbin/lvchange', '-aly', $path];
run_command($cmd, errmsg => "can't activate LV '$path' to zero-out its data");
$cmd = ['/sbin/lvchange', '--refresh', $path];
run_command($cmd, errmsg => "can't refresh LV '$path' to zero-out its data");
# wipe throughput up to 10MB/s by default; may be overwritten with saferemove_throughput
my $throughput = '-10485760';
if ($scfg->{saferemove_throughput}) {
$throughput = $scfg->{saferemove_throughput};
my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
for my $snapid (
sort { $snapshots->{$a}->{order} <=> $snapshots->{$b}->{order} }
keys %$snapshots
) {
my $snap = $snapshots->{$snapid};
next if $snapid eq 'current';
next if !$snap->{volid};
my ($snap_storeid, $snap_volname) = PVE::Storage::parse_volume_id($snap->{volid});
push @$volnames, $snap_volname;
}
my $cmd = [
'/usr/bin/cstream',
'-i',
'/dev/zero',
'-o',
"/dev/$vg/del-$volname",
'-T',
'10',
'-v',
'1',
'-b',
'1048576',
'-t',
"$throughput",
];
eval {
run_command(
$cmd,
errmsg => "zero out finished (note: 'No space left on device' is ok here)",
);
};
warn $@ if $@;
$class->cluster_lock_storage(
$storeid,
$scfg->{shared},
undef,
sub {
my $cmd = ['/sbin/lvremove', '-f', "$vg/del-$volname"];
run_command($cmd, errmsg => "lvremove '$vg/del-$volname' error");
},
);
print "successfully removed volume $volname ($vg/del-$volname)\n";
};
my $cmd = ['/sbin/lvchange', '-aly', "$vg/$volname"];
run_command($cmd, errmsg => "can't activate LV '$vg/$volname' to zero-out its data");
$cmd = ['/sbin/lvchange', '--refresh', "$vg/$volname"];
run_command($cmd, errmsg => "can't refresh LV '$vg/$volname' to zero-out its data");
if ($scfg->{saferemove}) {
# avoid long running task, so we only rename here
$cmd = ['/sbin/lvrename', $vg, $volname, "del-$volname"];
run_command($cmd, errmsg => "lvrename '$vg/$volname' error");
return $zero_out_worker;
} else {
my $tmpvg = $scfg->{vgname};
$cmd = ['/sbin/lvremove', '-f', "$tmpvg/$volname"];
run_command($cmd, errmsg => "lvremove '$tmpvg/$volname' error");
}
return undef;
return free_lvm_volumes($class, $scfg, $storeid, $volnames);
}
my $check_tags = sub {
@ -635,6 +820,12 @@ sub activate_volume {
my $lvm_activate_mode = 'ey';
#activate volume && all snapshots volumes by tag
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
$path = "\@pve-$name" if $format eq 'qcow2';
my $cmd = ['/sbin/lvchange', "-a$lvm_activate_mode", $path];
run_command($cmd, errmsg => "can't activate LV '$path'");
$cmd = ['/sbin/lvchange', '--refresh', $path];
@ -647,6 +838,10 @@ sub deactivate_volume {
my $path = $class->path($scfg, $volname, $storeid, $snapname);
return if !-b $path;
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
$path = "\@pve-$name" if $format eq 'qcow2';
my $cmd = ['/sbin/lvchange', '-aln', $path];
run_command($cmd, errmsg => "can't deactivate LV '$path'");
}
@ -654,10 +849,14 @@ sub deactivate_volume {
sub volume_resize {
my ($class, $scfg, $storeid, $volname, $size, $running) = @_;
$size = ($size / 1024 / 1024) . "M";
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
my $lvmsize = calculate_lvm_size($size / 1024, $format);
$lvmsize = "${lvmsize}k";
my $path = $class->path($scfg, $volname);
my $cmd = ['/sbin/lvextend', '-L', $size, $path];
my $cmd = ['/sbin/lvextend', '-L', $lvmsize, $path];
$class->cluster_lock_storage(
$storeid,
@ -668,6 +867,10 @@ sub volume_resize {
},
);
if (!$running && $format eq 'qcow2') {
PVE::Storage::Plugin::qemu_img_resize($scfg, $path, $format, $size, 10);
}
return 1;
}
@ -704,30 +907,205 @@ sub volume_size_info {
sub volume_snapshot {
my ($class, $scfg, $storeid, $volname, $snap, $running) = @_;
die "lvm snapshot is not implemented";
my ($vmid, $format) = ($class->parse_volname($volname))[2, 6];
die "can't snapshot '$format' volume\n" if $format ne 'qcow2';
if ($running) {
#rename with blockdev-reopen is done at qemu level when running
eval { alloc_snap_image($class, $storeid, $scfg, $volname, $snap) };
if ($@) {
die "can't allocate new volume $volname: $@\n";
}
return;
}
#rename current volume to snap volume
eval { $class->rename_snapshot($scfg, $storeid, $volname, 'current', $snap) };
die "error rename $volname to $snap\n" if $@;
eval { alloc_snap_image($class, $storeid, $scfg, $volname, $snap) };
if ($@) {
my $err = $@;
eval { $class->rename_snapshot($scfg, $storeid, $volname, $snap, 'current') };
die $err;
}
}
# Asserts that a rollback to $snap on $volname is possible.
# If certain snapshots are preventing the rollback and $blockers is an array
# reference, the snapshot names can be pushed onto $blockers prior to dying.
sub volume_rollback_is_possible {
my ($class, $scfg, $storeid, $volname, $snap, $blockers) = @_;
my $format = ($class->parse_volname($volname))[6];
die "can't rollback snapshot for '$format' volume\n" if $format ne 'qcow2';
$class->activate_volume($storeid, $scfg, $volname);
my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
my $found;
$blockers //= []; # not guaranteed to be set by caller
for my $snapid (
sort { $snapshots->{$b}->{order} <=> $snapshots->{$a}->{order} }
keys %$snapshots
) {
next if $snapid eq 'current';
if ($snapid eq $snap) {
$found = 1;
} elsif ($found) {
push $blockers->@*, $snapid;
}
}
die "can't rollback, snapshot '$snap' does not exist on '$volname'\n"
if !$found;
die "can't rollback, '$snap' is not most recent snapshot on '$volname'\n"
if scalar($blockers->@*) > 0;
return 1;
}
sub volume_snapshot_rollback {
my ($class, $scfg, $storeid, $volname, $snap) = @_;
die "lvm snapshot rollback is not implemented";
my $format = ($class->parse_volname($volname))[6];
die "can't rollback snapshot for '$format' volume\n" if $format ne 'qcow2';
my $cleanup_worker = eval { free_snap_image($class, $storeid, $scfg, $volname, 'current'); };
die "error deleting snapshot $snap $@\n" if $@;
eval { alloc_snap_image($class, $storeid, $scfg, $volname, $snap) };
fork_cleanup_worker($cleanup_worker);
if ($@) {
die "can't allocate new volume $volname: $@\n";
}
return undef;
}
sub volume_snapshot_delete {
my ($class, $scfg, $storeid, $volname, $snap) = @_;
my ($class, $scfg, $storeid, $volname, $snap, $running) = @_;
die "lvm snapshot delete is not implemented";
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
die "can't delete snapshot for '$format' volume\n" if $format ne 'qcow2';
if ($running) {
my $cleanup_worker = eval { free_snap_image($class, $storeid, $scfg, $volname, $snap); };
die "error deleting snapshot $snap $@\n" if $@;
fork_cleanup_worker($cleanup_worker);
return;
}
my $cmd = "";
my $path = $class->filesystem_path($scfg, $volname);
my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
my $snappath = $snapshots->{$snap}->{file};
my $snapvolname = $snapshots->{$snap}->{volname};
die "volume $snappath is missing" if !-e $snappath;
my $parentsnap = $snapshots->{$snap}->{parent};
my $childsnap = $snapshots->{$snap}->{child};
my $childpath = $snapshots->{$childsnap}->{file};
my $childvolname = $snapshots->{$childsnap}->{volname};
my $err = undef;
#if first snapshot,as it should be bigger, we merge child, and rename the snapshot to child
if (!$parentsnap) {
print "$volname: deleting snapshot '$snap' by commiting snapshot '$childsnap'\n";
print "running 'qemu-img commit $childpath'\n";
#can't use -d here, as it's an lvm volume
$cmd = ['/usr/bin/qemu-img', 'commit', $childpath];
eval { run_command($cmd) };
if ($@) {
warn
"The state of $snap is now invalid. Don't try to clone or rollback it. You can only try to delete it again later\n";
die "error commiting $childsnap to $snap; $@\n";
}
print "delete $childvolname\n";
my $cleanup_worker =
eval { free_snap_image($class, $storeid, $scfg, $volname, $childsnap) };
if ($@) {
die "error delete old snapshot volume $childvolname: $@\n";
}
print "rename $snapvolname to $childvolname\n";
eval { lvrename($scfg, $snapvolname, $childvolname) };
if ($@) {
warn $@;
$err = "error renaming snapshot: $@\n";
}
fork_cleanup_worker($cleanup_worker);
} else {
#we rebase the child image on the parent as new backing image
my $parentpath = $snapshots->{$parentsnap}->{file};
print
"$volname: deleting snapshot '$snap' by rebasing '$childsnap' on top of '$parentsnap'\n";
print "running 'qemu-img rebase -b $parentpath -F qcow -f qcow2 $childpath'\n";
$cmd = [
'/usr/bin/qemu-img',
'rebase',
'-b',
$parentpath,
'-F',
'qcow2',
'-f',
'qcow2',
$childpath,
];
eval { run_command($cmd) };
if ($@) {
#in case of abort, the state of the snap is still clean, just a little bit bigger
die "error rebase $childsnap from $parentsnap; $@\n";
}
#delete the snapshot
my $cleanup_worker = eval { free_snap_image($class, $storeid, $scfg, $volname, $snap); };
if ($@) {
die "error deleting old snapshot volume $snapvolname\n";
}
fork_cleanup_worker($cleanup_worker);
}
die $err if $err;
}
sub volume_has_feature {
my ($class, $scfg, $feature, $storeid, $volname, $snapname, $running) = @_;
my $features = {
copy => { base => 1, current => 1 },
rename => { current => 1 },
copy => {
base => { qcow2 => 1, raw => 1 },
current => { qcow2 => 1, raw => 1 },
snap => { qcow2 => 1 },
},
'rename' => {
current => { qcow2 => 1, raw => 1 },
},
snapshot => {
current => { qcow2 => 1 },
snap => { qcow2 => 1 },
},
# fixme: add later ? (we need to handle basepath, volume activation,...)
# template => {
# current => { raw => 1, qcow2 => 1},
# },
# clone => {
# base => { qcow2 => 1 },
# },
};
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase) = $class->parse_volname($volname);
my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) =
$class->parse_volname($volname);
my $key = undef;
if ($snapname) {
@ -735,7 +1113,7 @@ sub volume_has_feature {
} else {
$key = $isBase ? 'base' : 'current';
}
return 1 if $features->{$feature}->{$key};
return 1 if defined($features->{$feature}->{$key}->{$format});
return undef;
}
@ -829,14 +1207,7 @@ sub volume_import {
if (my $err = $@) {
my $cleanup_worker = eval { $class->free_image($storeid, $scfg, $volname, 0) };
warn $@ if $@;
if ($cleanup_worker) {
my $rpcenv = PVE::RPCEnvironment::get();
my $authuser = $rpcenv->get_user();
$rpcenv->fork_worker('imgdel', undef, $authuser, $cleanup_worker);
}
fork_cleanup_worker($cleanup_worker);
die $err;
}
@ -862,14 +1233,17 @@ sub rename_volume {
die "target volume '${target_volname}' already exists\n"
if ($lvs->{$vg}->{$target_volname});
lvrename($vg, $source_volname, $target_volname);
lvrename($scfg, $source_volname, $target_volname);
return "${storeid}:${target_volname}";
}
sub rename_snapshot {
my ($class, $scfg, $storeid, $volname, $source_snap, $target_snap) = @_;
die "rename_snapshot is not implemented for $class";
my $source_snap_volname = get_snap_name($class, $volname, $source_snap);
my $target_snap_volname = get_snap_name($class, $volname, $target_snap);
lvrename($scfg, $source_snap_volname, $target_snap_volname);
}
sub volume_support_qemu_snapshot {