[pve-devel] [PATCH v3 qemu-server 10/11] blockdev: add backing_chain support

[Alexandre Derumier via pve-devel <pve-devel@lists.proxmox.com>]

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From: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
To: pve-devel@lists.proxmox.com
Subject: [PATCH v3 qemu-server 10/11] blockdev: add backing_chain support
Date: Mon, 16 Dec 2024 10:12:28 +0100
Message-ID: <20241216091229.3142660-15-alexandre.derumier@groupe-cyllene.com>

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@groupe-cyllene.com>
---
 PVE/QemuServer.pm | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index dc12b38f..3a3feadf 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -1618,6 +1618,38 @@ sub generate_throttle_group {
    return $throttle_group;
 }
 
+sub generate_backing_blockdev {
+    my ($storecfg, $snapshots, $deviceid, $drive, $id) = @_;
+
+    my $snapshot = $snapshots->{$id};
+    my $order = $snapshot->{order};
+    my $parentid = $snapshot->{parent};
+    my $snap_fmt_nodename = "fmt-$deviceid-$order";
+    my $snap_file_nodename = "file-$deviceid-$order";
+
+    my $snap_file_blockdev = generate_file_blockdev($storecfg, $drive, $snap_file_nodename);
+    $snap_file_blockdev->{filename} = $snapshot->{file};
+    my $snap_fmt_blockdev = generate_format_blockdev($storecfg, $drive, $snap_fmt_nodename, $snap_file_blockdev, 1);
+    $snap_fmt_blockdev->{backing} = generate_backing_blockdev($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 $do_snapshots_with_qemu = do_snapshots_with_qemu($storecfg, $volid, $deviceid);
+    return if !$do_snapshots_with_qemu || $do_snapshots_with_qemu != 2;
+
+    my $chain_blockdev = undef;
+    PVE::Storage::activate_volumes($storecfg, [$volid]);
+    #should we use qemu config to list snapshots ?
+    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 $chain_blockdev;
+}
+
 sub generate_file_blockdev {
     my ($storecfg, $drive, $nodename) = @_;
 
@@ -1816,6 +1848,8 @@ sub generate_drive_blockdev {
     my $blockdev_file = generate_file_blockdev($storecfg, $drive, $file_nodename);
     my $fmt_nodename = "fmt-drive-$drive_id";
     my $blockdev_format = generate_format_blockdev($storecfg, $drive, $fmt_nodename, $blockdev_file, $force_readonly);
+    my $backing_chain  = generate_backing_chain_blockdev($storecfg, "drive-$drive_id", $drive);
+    $blockdev_format->{backing} = $backing_chain if $backing_chain;
 
     my $blockdev_live_restore = undef;
     if ($live_restore_name) {
-- 
2.39.5



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