Re: [pve-devel] [PATCH qemu-server 14/14] qcow2: add external snapshot support

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

> Alexandre Derumier via pve-devel <pve-devel@lists.proxmox.com> hat am 22.04.2025 13:51 CEST geschrieben:

no commit message..

> Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
> ---
>  PVE/QemuConfig.pm       |   4 +-
>  PVE/QemuServer.pm       | 237 +++++++++++++++++++++++++++++++++++-----
>  PVE/QemuServer/Drive.pm |  39 ++++---
>  3 files changed, 239 insertions(+), 41 deletions(-)
> 
> diff --git a/PVE/QemuConfig.pm b/PVE/QemuConfig.pm
> index 2609542c..785c84a2 100644
> --- a/PVE/QemuConfig.pm
> +++ b/PVE/QemuConfig.pm
> @@ -378,7 +378,7 @@ sub __snapshot_create_vol_snapshot {
>  
>      print "snapshotting '$device' ($drive->{file})\n";
>  
> -    PVE::QemuServer::qemu_volume_snapshot($vmid, $device, $storecfg, $volid, $snapname);
> +    PVE::QemuServer::qemu_volume_snapshot($vmid, $device, $storecfg, $drive, $snapname);
>  }
>  
>  sub __snapshot_delete_remove_drive {
> @@ -415,7 +415,7 @@ sub __snapshot_delete_vol_snapshot {
>      my $storecfg = PVE::Storage::config();
>      my $volid = $drive->{file};
>  
> -    PVE::QemuServer::qemu_volume_snapshot_delete($vmid, $storecfg, $volid, $snapname);
> +    PVE::QemuServer::qemu_volume_snapshot_delete($vmid, $storecfg, $drive, $snapname);
>  
>      push @$unused, $volid;
>  }
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 5cce7094..aff430df 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -55,7 +55,7 @@ use PVE::QemuServer::Helpers qw(config_aware_timeout min_version kvm_user_versio
>  use PVE::QemuServer::Cloudinit;
>  use PVE::QemuServer::CGroup;
>  use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options get_cpu_bitness is_native_arch get_amd_sev_object get_amd_sev_type);
> -use PVE::QemuServer::Drive qw(is_valid_drivename checked_volume_format drive_is_cloudinit drive_is_cdrom drive_is_read_only parse_drive print_drive print_drive_throttle_group generate_drive_blockdev generate_throttle_group);
> +use PVE::QemuServer::Drive qw(is_valid_drivename checked_volume_format drive_is_cloudinit drive_is_cdrom drive_is_read_only parse_drive print_drive print_drive_throttle_group generate_drive_blockdev generate_throttle_group generate_blockdev_throttle generate_file_blockdev generate_format_blockdev);
>  use PVE::QemuServer::Machine;
>  use PVE::QemuServer::Memory qw(get_current_memory);
>  use PVE::QemuServer::MetaInfo;
> @@ -4518,20 +4518,193 @@ sub qemu_block_resize {
>  }
>  
>  sub qemu_volume_snapshot {
> -    my ($vmid, $deviceid, $storecfg, $volid, $snap) = @_;
> +    my ($vmid, $deviceid, $storecfg, $drive, $snap) = @_;
>  
> +    my $volid = $drive->{file};
>      my $running = check_running($vmid);
>  
> -    if ($running && do_snapshots_with_qemu($storecfg, $volid, $deviceid)) {
> -	mon_cmd($vmid, 'blockdev-snapshot-internal-sync', device => $deviceid, name => $snap);
> +    my $do_snapshots_with_qemu = do_snapshots_with_qemu($storecfg, $volid, $deviceid);
> +
> +    if ($running && $do_snapshots_with_qemu) {
> +	if ($do_snapshots_with_qemu == 2) {
> +	    print "internal qemu snapshot\n";
> +	    mon_cmd($vmid, 'blockdev-snapshot-internal-sync', device => $deviceid, name => $snap);
> +	} elsif ($do_snapshots_with_qemu == 3) {
> +	    my $storeid = (PVE::Storage::parse_volume_id($volid))[0];
> +	    my $scfg = PVE::Storage::storage_config($storecfg, $storeid);
> +	    print "external qemu snapshot\n";
> +	    my $snapshots = PVE::Storage::volume_snapshot_info($storecfg, $volid);
> +	    my $parent_snap = $snapshots->{'current'}->{parent};
> +	    blockdev_rename($storecfg, $vmid, $deviceid, $drive, 'current', $snap, $parent_snap);
> +	    eval { blockdev_external_snapshot($storecfg, $vmid, $deviceid, $drive, $snap) };
> +	    if ($@) {
> +		print "error creating snapshot. Revert rename\n";
> +		eval { blockdev_rename($storecfg, $vmid, $deviceid, $drive, $snap, 'current', $parent_snap) };
> +	    }
> +	}

this is a very weird interface, because do_snapshots_with_qemu only returns either 2 or 3
or undef.. see the other comment regarding volume_has_features on patch #12

>      } else {
>  	PVE::Storage::volume_snapshot($storecfg, $volid, $snap);
>      }
>  }
>  
> +sub blockdev_external_snapshot {
> +    my ($storecfg, $vmid, $deviceid, $drive, $snap, $size) = @_;
> +
> +    my $volid = $drive->{file};
> +
> +    #preallocate add a new current file with reference to backing-file
> +    PVE::Storage::volume_snapshot($storecfg, $volid, $snap, 1);
> +
> +    #be sure to add drive in write mode
> +    delete($drive->{ro});
> +
> +    my $new_file_blockdev = generate_file_blockdev($storecfg, $drive);
> +    my $new_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $new_file_blockdev);
> +
> +    my $snap_file_blockdev = generate_file_blockdev($storecfg, $drive, $snap);
> +    my $snap_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $snap_file_blockdev, $snap);
> +
> +    #backing need to be forced to undef in blockdev, to avoid reopen of backing-file on blockdev-add
> +    $new_fmt_blockdev->{backing} = undef;
> +
> +    PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-add', %$new_fmt_blockdev);
> +
> +    mon_cmd($vmid, 'blockdev-snapshot', node => $snap_fmt_blockdev->{'node-name'}, overlay => $new_fmt_blockdev->{'node-name'});
> +}
> +
> +sub blockdev_delete {
> +    my ($storecfg, $vmid, $drive, $file_blockdev, $fmt_blockdev, $snap) = @_;
> +
> +    #add eval as reopen is auto removing the old nodename automatically only if it was created at vm start in command line argument
> +    eval { mon_cmd($vmid, 'blockdev-del', 'node-name' => $file_blockdev->{'node-name'}) };
> +    eval { mon_cmd($vmid, 'blockdev-del', 'node-name' => $fmt_blockdev->{'node-name'}) };
> +
> +    #delete the file (don't use vdisk_free as we don't want to delete all snapshot chain)
> +    print"delete old $file_blockdev->{filename}\n";
> +
> +    my $storage_name = PVE::Storage::parse_volume_id($drive->{file});
> +
> +    my $volid = $drive->{file};
> +    PVE::Storage::volume_snapshot_delete($storecfg, $volid, $snap, 1);
> +}
> +
> +sub blockdev_rename {
> +    my ($storecfg, $vmid, $deviceid, $drive, $src_snap, $target_snap, $parent_snap) = @_;
> +
> +    print "rename $src_snap to $target_snap\n";
> +
> +    my $volid = $drive->{file};
> +
> +    my $src_file_blockdev = generate_file_blockdev($storecfg, $drive, $src_snap);
> +    my $src_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $src_file_blockdev, $src_snap);
> +    my $target_file_blockdev = generate_file_blockdev($storecfg, $drive, $target_snap);
> +    my $target_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $target_file_blockdev, $target_snap);
> +
> +    #rename volume image
> +    PVE::Storage::rename_volume($storecfg, $volid, $vmid, undef, $src_snap, $target_snap);
> +
> +    if($target_snap eq 'current' || $src_snap eq 'current') {
> +	#rename from|to current
> +
> +	#add backing to target
> +	if ($parent_snap) {
> +	    my $parent_fmt_nodename = encode_nodename('fmt', $volid, $parent_snap);
> +	    $target_fmt_blockdev->{backing} = $parent_fmt_nodename;
> +	}
> +	PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-add', %$target_fmt_blockdev);
> +
> +	#reopen the current throttlefilter nodename with the target fmt nodename
> +	my $throttle_blockdev = generate_blockdev_throttle($drive, $target_fmt_blockdev->{'node-name'});
> +	PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-reopen', options => [$throttle_blockdev]);
> +    } else {
> +        rename($src_file_blockdev->{filename}, $target_file_blockdev->{filename});
> +
> +	#intermediate snapshot
> +	PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-add', %$target_fmt_blockdev);
> +
> +	#reopen the parent node with the new target fmt backing node
> +	my $parent_file_blockdev = generate_file_blockdev($storecfg, $drive, $parent_snap);
> +	my $parent_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $parent_file_blockdev, $parent_snap);
> +	$parent_fmt_blockdev->{backing} = $target_fmt_blockdev->{'node-name'};
> +	PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-reopen', options => [$parent_fmt_blockdev]);
> +
> +	#change backing-file in qcow2 metadatas
> +	PVE::QemuServer::Monitor::mon_cmd($vmid, 'change-backing-file', device => $deviceid, 'image-node-name' => $parent_fmt_blockdev->{'node-name'}, 'backing-file' => $target_file_blockdev->{filename});
> +    }
> +
> +    # delete old file|fmt nodes
> +    # add eval as reopen is auto removing the old nodename automatically only if it was created at vm start in command line argument
> +    eval { PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-del', 'node-name' => $src_file_blockdev->{'node-name'})};
> +    eval { PVE::QemuServer::Monitor::mon_cmd($vmid, 'blockdev-del', 'node-name' => $src_fmt_blockdev->{'node-name'})};
> +}
> +
> +sub blockdev_commit {
> +    my ($storecfg, $vmid, $deviceid, $drive, $src_snap, $target_snap) = @_;
> +
> +    my $volid = $drive->{file};
> +
> +    print "block-commit $src_snap to base:$target_snap\n";
> +
> +    my $target_file_blockdev = generate_file_blockdev($storecfg, $drive, $target_snap);
> +    my $target_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $target_file_blockdev, $target_snap);
> +
> +    my $src_file_blockdev = generate_file_blockdev($storecfg, $drive, $src_snap);
> +    my $src_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $src_file_blockdev, $src_snap);
> +
> +    my $job_id = "commit-$deviceid";
> +    my $jobs = {};
> +    my $opts = { 'job-id' => $job_id, device => $deviceid };
> +
> +    my $complete = undef;
> +    if ($src_snap && $src_snap ne 'current') {
> +	$complete = 'auto';
> +	$opts->{'top-node'} = $src_fmt_blockdev->{'node-name'};
> +	$opts->{'base-node'} = $target_fmt_blockdev->{'node-name'};
> +    } else {
> +	$complete = 'complete';
> +	$opts->{'base-node'} = $target_fmt_blockdev->{'node-name'};
> +	$opts->{replaces} = $src_fmt_blockdev->{'node-name'};
> +    }
> +
> +    mon_cmd($vmid, "block-commit", %$opts);
> +    $jobs->{$job_id} = {};
> +    qemu_drive_mirror_monitor($vmid, undef, $jobs, $complete, 0, 'commit');
> +
> +    blockdev_delete($storecfg, $vmid, $drive, $src_file_blockdev, $src_fmt_blockdev, $src_snap);
> +}
> +
> +sub blockdev_stream {
> +    my ($storecfg, $vmid, $deviceid, $drive, $snap, $parent_snap, $target_snap) = @_;
> +
> +    my $volid = $drive->{file};
> +    $target_snap = undef if $target_snap eq 'current';
> +
> +    my $parent_file_blockdev = generate_file_blockdev($storecfg, $drive, $parent_snap);
> +    my $parent_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $parent_file_blockdev, $parent_snap);
> +
> +    my $target_file_blockdev = generate_file_blockdev($storecfg, $drive, $target_snap);
> +    my $target_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $target_file_blockdev, $target_snap);
> +
> +    my $snap_file_blockdev = generate_file_blockdev($storecfg, $drive, $snap);
> +    my $snap_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $snap_file_blockdev, $snap);
> +
> +    my $job_id = "stream-$deviceid";
> +    my $jobs = {};
> +    my $options = { 'job-id' => $job_id, device => $target_fmt_blockdev->{'node-name'} };
> +    $options->{'base-node'} = $parent_fmt_blockdev->{'node-name'};
> +    $options->{'backing-file'} = $parent_file_blockdev->{filename};
> +
> +    mon_cmd($vmid, 'block-stream', %$options);
> +    $jobs->{$job_id} = {};
> +    qemu_drive_mirror_monitor($vmid, undef, $jobs, 'auto', 0, 'stream');
> +
> +    blockdev_delete($storecfg, $vmid, $drive, $snap_file_blockdev, $snap_fmt_blockdev, $snap);
> +}
> +
>  sub qemu_volume_snapshot_delete {
> -    my ($vmid, $storecfg, $volid, $snap) = @_;
> +    my ($vmid, $storecfg, $drive, $snap) = @_;
>  
> +    my $volid = $drive->{file};
>      my $running = check_running($vmid);
>      my $attached_deviceid;
>  
> @@ -4543,13 +4716,36 @@ sub qemu_volume_snapshot_delete {
>  	});
>      }
>  
> +    my $do_snapshots_with_qemu = do_snapshots_with_qemu($storecfg, $volid, $attached_deviceid);
> +
>      if ($attached_deviceid && do_snapshots_with_qemu($storecfg, $volid, $attached_deviceid)) {
> -	mon_cmd(
> -	    $vmid,
> -	    'blockdev-snapshot-delete-internal-sync',
> -	    device => $attached_deviceid,
> -	    name => $snap,
> -	);
> +	if ($do_snapshots_with_qemu == 2) {
> +	    mon_cmd(
> +		$vmid,
> +		'blockdev-snapshot-delete-internal-sync',
> +		device => $attached_deviceid,
> +		name => $snap,
> +	    );
> +	} elsif ($do_snapshots_with_qemu == 3) {
> +	    print "delete qemu external snapshot\n";
> +
> +	    my $path = PVE::Storage::path($storecfg, $volid);
> +	    my $snapshots = PVE::Storage::volume_snapshot_info($storecfg, $volid);
> +	    my $parentsnap = $snapshots->{$snap}->{parent};
> +	    my $childsnap = $snapshots->{$snap}->{child};
> +
> +	    # if we delete the first snasphot, we commit because the first snapshot original base image, it should be big.
> +	    # improve-me: if firstsnap > child : commit, if firstsnap < child do a stream.
> +	    if(!$parentsnap) {
> +		print"delete first snapshot $snap\n";
> +		blockdev_commit($storecfg, $vmid, $attached_deviceid, $drive, $childsnap, $snap);
> +		blockdev_rename($storecfg, $vmid, $attached_deviceid, $drive, $snap, $childsnap, $snapshots->{$childsnap}->{child});
> +	    } else {
> +		#intermediate snapshot, we always stream the snapshot to child snapshot
> +		print"stream intermediate snapshot $snap to $childsnap\n";
> +		blockdev_stream($storecfg, $vmid, $attached_deviceid, $drive, $snap, $parentsnap, $childsnap);
> +	    }
> +	}
>      } else {
>  	PVE::Storage::volume_snapshot_delete(
>  	    $storecfg, $volid, $snap, $attached_deviceid ? 1 : undef);
> @@ -7778,27 +7974,16 @@ sub foreach_storage_used_by_vm {
>      }
>  }
>  
> -my $qemu_snap_storage = {
> -    rbd => 1,
> -};
>  sub do_snapshots_with_qemu {
>      my ($storecfg, $volid, $deviceid) = @_;
>  
> -    return if $deviceid =~ m/tpmstate0/;
> +    return if $deviceid && $deviceid =~ m/tpmstate0/;
>  
> -    my $storage_name = PVE::Storage::parse_volume_id($volid);
> -    my $scfg = $storecfg->{ids}->{$storage_name};
> -    die "could not find storage '$storage_name'\n" if !defined($scfg);
> +    my $snapshot_type = PVE::Storage::volume_has_feature($storecfg, 'snapshot', $volid);
>  
> -    if ($qemu_snap_storage->{$scfg->{type}} && !$scfg->{krbd}){
> -	return 1;
> -    }
> +    return $snapshot_type if $snapshot_type == 2 || $snapshot_type == 3;
>  
> -    if ($volid =~ m/\.(qcow2|qed)$/){
> -	return 1;
> -    }
> -
> -    return;
> +    return undef;

previously this returned 1 for rbd and not krbd, and also external plugins with qcow2 or
qed formatted volumes.. now it returns 2 for rbd but not krbd, and undef for such external
plugins?

>  }
>  
>  sub qga_check_running {
> diff --git a/PVE/QemuServer/Drive.pm b/PVE/QemuServer/Drive.pm
> index 0737034d..93903a59 100644
> --- a/PVE/QemuServer/Drive.pm
> +++ b/PVE/QemuServer/Drive.pm
> @@ -27,6 +27,9 @@ print_drive
>  print_drive_throttle_group
>  generate_drive_blockdev
>  generate_throttle_group
> +generate_blockdev_throttle
> +generate_format_blockdev
> +generate_file_blockdev
>  );
>  
>  our $QEMU_FORMAT_RE = qr/raw|qcow|qcow2|qed|vmdk|cloop/;
> @@ -1074,6 +1077,8 @@ sub print_drive_throttle_group {
>  sub generate_file_blockdev {
>      my ($storecfg, $drive, $snap, $nodename) = @_;
>  
> +    $snap = undef if $snap && $snap eq 'current';
> +
>      my $volid = $drive->{file};
>      my $driveid = get_drive_id($drive);
>  
> @@ -1209,6 +1214,8 @@ sub generate_file_blockdev {
>  sub generate_format_blockdev {
>      my ($storecfg, $drive, $file, $snap, $nodename) = @_;
>  
> +    $snap = undef if $snap && $snap eq 'current';
> +
>      my $volid = $drive->{file};
>      #nbd don't support format blockdev, return the fileblockdev
>      return $file if $volid =~ /^nbd:/;
> @@ -1280,6 +1287,15 @@ sub generate_backing_chain_blockdev {
>      return $chain_blockdev;
>  }
>  
> +sub generate_blockdev_throttle {
> +    my ($drive, $blockdev_file) = @_;
> +
> +    my $drive_id = get_drive_id($drive);
> +    #this is the topfilter entry point, use $drive-drive_id as nodename
> +    my $blockdev_throttle = { driver => "throttle", 'node-name' => "drive-$drive_id", 'throttle-group' => "throttle-drive-$drive_id", 'file' => $blockdev_file };
> +    return $blockdev_throttle;
> +}
> +
>  sub generate_drive_blockdev {
>      my ($storecfg, $drive, $live_restore_name) = @_;
>  
> @@ -1303,22 +1319,19 @@ sub generate_drive_blockdev {
>      #pflash0 don't support throttle-filter
>      return $blockdev_format if $drive_id eq 'pflash0';
>  
> -    my $blockdev_live_restore = undef;
> -    if ($live_restore_name) {
> -        die "$drive_id: Proxmox Backup Server backed drive cannot auto-detect the format\n"
> -            if !$drive->{format};
> +    return generate_blockdev_throttle($drive, $blockdev_format) if !$live_restore_name;
>  
> -        $blockdev_live_restore = { 'node-name' => "liverestore-drive-$drive_id",
> -				    backing => $live_restore_name,
> -				    'auto-remove' => 'on', format => "alloc-track",
> -				    file => $blockdev_format };
> -    }
> +    die "$drive_id: Proxmox Backup Server backed drive cannot auto-detect the format\n"
> +        if !$drive->{format};
>  
> -    #this is the topfilter entry point, use $drive-drive_id as nodename
> -    my $blockdev_throttle = { driver => "throttle", 'node-name' => "drive-$drive_id", 'throttle-group' => "throttle-drive-$drive_id" };
>      #put liverestore filter between throttle && format filter
> -    $blockdev_throttle->{file} = $live_restore_name ? $blockdev_live_restore : $blockdev_format;
> -    return $blockdev_throttle,
> +    my $blockdev_live_restore = { 'node-name' => "liverestore-drive-$drive_id",
> +                                  backing => $live_restore_name,
> +                                  'auto-remove' => 'on', format => "alloc-track",
> +                                  file => $blockdev_format };
> +
> +    return generate_blockdev_throttle($drive, $blockdev_live_restore);
> +
>  }
>  
>  sub encode_base62 {
> -- 
> 2.39.5


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