[PATCH v4 qemu-server 2/3] pbs-restore: set 'no-cache' on block devices backed by zfspool

[Christian Ebner <c.ebner@proxmox.com>]

Skip the host page cache for restores on zvols, as page writeback
after filling the buffers can cause I/O delay on other ZFS-backed VMs
on certain setups, as reported in enterprise support and reproduced
internally. The restored data is not to be read back from cache
during restore anyways.

Keep for other storage types for now to reduce regression potential.

Version bump in d/control assures feature compatibility for
pbs-restore.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
changes since version 3:
- drop package version comparison checks
- bump d/control dependency for pve-qemu-kvm

 debian/control        | 2 +-
 src/PVE/QemuServer.pm | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/debian/control b/debian/control
index 97049e1d..a9949d5a 100644
--- a/debian/control
+++ b/debian/control
@@ -61,7 +61,7 @@ Depends: conntrack,
          pve-edk2-firmware-ovmf (>= 4.2025.05-2) [amd64],
          pve-firewall (>= 6.0.3),
          pve-ha-manager (>= 5.0.3),
-         pve-qemu-kvm (>= 7.1~),
+         pve-qemu-kvm (>= 11.0.3-3),
          python3-virt-firmware,
          socat,
          swtpm,
diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 2f43faa7..317aeaac 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -7090,6 +7090,13 @@ sub restore_proxmox_backup_archive {
             if (PVE::Storage::volume_has_feature($storecfg, 'sparseinit', $volid)) {
                 push @$pbs_restore_cmd, '--skip-zero';
             }
+            my ($target_storeid) = PVE::Storage::parse_volume_id($volid, 1);
+            my $target_scfg = PVE::Storage::storage_config($storecfg, $target_storeid);
+
+            if ($target_scfg->{type} eq 'zfspool') {
+                #TODO: potentially extend to other storage types
+                push @$pbs_restore_cmd, '--no-cache';
+            }
 
             my $dbg_cmdstring = PVE::Tools::cmd2string($pbs_restore_cmd);
             print "restore proxmox backup image: $dbg_cmdstring\n";
-- 
2.47.3