[pve-devel] [PATCH qemu-server 07/11] cfg2cmd: allow PBS snapshots as backing files for drives
Thomas Lamprecht
t.lamprecht at proxmox.com
Thu Jan 28 17:25:33 CET 2021
On 11.01.21 12:14, Stefan Reiter wrote:
> Uses the custom 'alloc-track' filter node to redirect writes to the
> original drives target, while unwritten blocks will be read from the
> specified PBS snapshot.
>
> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> ---
> PVE/QemuServer.pm | 42 +++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 39 insertions(+), 3 deletions(-)
>
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index d517dae..6de6ff6 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -3022,7 +3022,8 @@ sub query_understood_cpu_flags {
> }
>
> sub config_to_command {
> - my ($storecfg, $vmid, $conf, $defaults, $forcemachine, $forcecpu) = @_;
> + my ($storecfg, $vmid, $conf, $defaults, $forcemachine, $forcecpu,
> + $pbs_backing) = @_;
>
> my $cmd = [];
> my $globalFlags = [];
> @@ -3521,6 +3522,32 @@ sub config_to_command {
> my $drive_cmd = print_drive_commandline_full($storecfg, $vmid, $drive);
> $drive_cmd .= ',readonly' if PVE::QemuConfig->is_template($conf);
>
> + if ($pbs_backing && defined($pbs_backing->{$ds})) {
please avoid extending config_to_command to much, move to own method.
> + my $pbs_conf = $pbs_backing->{$ds};
> + my $pbs_name = "drive-$ds-pbs";
> +
> + # add PBS block device to access snapshot from QEMU
> + my $blockdev = "driver=pbs,node-name=$pbs_name,read-only=on";
> + $blockdev .= ",repository=$pbs_conf->{repository}";
> + $blockdev .= ",snapshot=$pbs_conf->{snapshot}";
> + $blockdev .= ",archive=$pbs_conf->{archive}";
> + $blockdev .= ",keyfile=$pbs_conf->{keyfile}" if $pbs_conf->{keyfile};
> + push @$devices, '-blockdev', $blockdev;
> +
> + # modify drive command to put the desired target file behind an
> + # 'alloc-track' node
> + $drive_cmd =~ s/file=([^,]+)/file.file.filename=$1/;
> + $drive_cmd =~ s/,format=([^,]+)/,file.driver=$1,format=alloc-track/;
This seems really fragile and hacky, please avoid string replacements on variables
we assemble ourself.
> + $drive_cmd .= ",backing=$pbs_name";
> + $drive_cmd .= ",auto-remove=on";
> +
> + # note: 'cache' and 'aio' directly affect the 'drive' parameter, so
> + # we don't need to change them to 'file.', but 'detect-zeroes' works
> + # per blockdev and we want it to persist after the alloc-track is
> + # removed, so put it on 'file' directly
> + $drive_cmd =~ s/,detect-zeroes=([^,]+)/,file.detect-zeroes=$1/;
> + }
> +
> push @$devices, '-drive',$drive_cmd;
> push @$devices, '-device', print_drivedevice_full(
> $storecfg, $conf, $vmid, $drive, $bridges, $arch, $machine_type);
> @@ -4915,6 +4942,15 @@ sub vm_start {
> # timeout => in seconds
> # paused => start VM in paused state (backup)
> # resume => resume from hibernation
> +# pbs-backing => {
> +# sata0 => {
> +# repository
> +# snapshot
> +# keyfile
> +# archive
> +# },
> +# virtio2 => ...
> +# }
> # migrate_opts:
> # nbd => volumes for NBD exports (vm_migrate_alloc_nbd_disks)
> # migratedfrom => source node
> @@ -4961,8 +4997,8 @@ sub vm_start_nolock {
> print "Resuming suspended VM\n";
> }
>
> - my ($cmd, $vollist, $spice_port) =
> - config_to_command($storecfg, $vmid, $conf, $defaults, $forcemachine, $forcecpu);
> + my ($cmd, $vollist, $spice_port) = config_to_command($storecfg, $vmid,
> + $conf, $defaults, $forcemachine, $forcecpu, $params->{'pbs-backing'});
>
> my $migration_ip;
> my $get_migration_ip = sub {
>
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