[PATCH qemu-server 13/14] blockdev: add backing_chain support

[Alexandre Derumier]

We need to define name-nodes for all backing chain images,
to be able to live rename them with blockdev-reopen

For linked clone, we don't need to definebase image(s) chain.
They are auto added with #block nodename.

Signed-off-by: Alexandre Derumier <alexandre.derumier at groupe-cyllene.com>
---
 PVE/QemuServer/Drive.pm | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/PVE/QemuServer/Drive.pm b/PVE/QemuServer/Drive.pm
index 08b893a1..0737034d 100644
--- a/PVE/QemuServer/Drive.pm
+++ b/PVE/QemuServer/Drive.pm
@@ -1249,6 +1249,37 @@ sub generate_format_blockdev {
     return $blockdev;
 }
 
+sub generate_backing_blockdev {
+    my ($storecfg, $snapshots, $deviceid, $drive, $snap_id) = @_;
+
+    my $snapshot = $snapshots->{$snap_id};
+    my $parentid = $snapshot->{parent};
+
+    my $volid = $drive->{file};
+
+    my $snap_file_blockdev = generate_file_blockdev($storecfg, $drive, $snap_id);
+    $snap_file_blockdev->{filename} = $snapshot->{file};
+    $drive->{ro} = 1;
+    my $snap_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $snap_file_blockdev, $snap_id);
+    $snap_fmt_blockdev->{backing} = generate_backing_blockdev($storecfg, $snapshots, $deviceid, $drive, $parentid) if $parentid;
+    return $snap_fmt_blockdev;
+}
+
+sub generate_backing_chain_blockdev {
+    my ($storecfg, $deviceid, $drive) = @_;
+
+    my $volid = $drive->{file};
+    my $snapshot_type = PVE::Storage::volume_has_feature($storecfg, 'snapshot', $volid);
+    return if !$snapshot_type || $snapshot_type != 3;
+
+    my $chain_blockdev = undef;
+    PVE::Storage::activate_volumes($storecfg, [$volid]);
+    my $snapshots = PVE::Storage::volume_snapshot_info($storecfg, $volid);
+    my $parentid = $snapshots->{'current'}->{parent};
+    $chain_blockdev = generate_backing_blockdev($storecfg, $snapshots, $deviceid, $drive, $parentid) if $parentid;
+    return $chain_blockdev;
+}
+
 sub generate_drive_blockdev {
     my ($storecfg, $drive, $live_restore_name) = @_;
 
@@ -1266,6 +1297,8 @@ sub generate_drive_blockdev {
 
     my $blockdev_file = generate_file_blockdev($storecfg, $drive);
     my $blockdev_format = generate_format_blockdev($storecfg, $drive, $blockdev_file);
+    my $backing_chain  = generate_backing_chain_blockdev($storecfg, "drive-$drive_id", $drive);
+    $blockdev_format->{backing} = $backing_chain if $backing_chain;
 
     #pflash0 don't support throttle-filter
     return $blockdev_format if $drive_id eq 'pflash0';
-- 
2.39.5