[PATCH qemu-server 8/8] fix #7383: agent: fsfreeze: skip freeze if already frozen

[Fiona Ebner <f.ebner@proxmox.com>]

This avoids the following error message about the command being
disallowed which can be hard to interpret for users:
> Command guest-fsfreeze-freeze has been disabled: the command is not allowed

It's disallowed, because the fs is already frozen, but the error
message does not indicate this. Instead avoid the error by skipping if
already frozen and log it if that is the case.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/QemuServer/Agent.pm | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/PVE/QemuServer/Agent.pm b/src/PVE/QemuServer/Agent.pm
index 12f9f9d5..54e30bcf 100644
--- a/src/PVE/QemuServer/Agent.pm
+++ b/src/PVE/QemuServer/Agent.pm
@@ -289,6 +289,25 @@ sub guest_fsthaw {
     return;
 }
 
+=head3 guest_fs_is_frozen
+
+    if (guest_fs_is_frozen($vmid)) {
+        print "skipping guest fs freeze - already frozen\n";
+    }
+
+Check if the file systems of the guest C<$vmid> is currently frozen.
+
+=cut
+
+sub guest_fs_is_frozen {
+    my ($vmid) = @_;
+
+    my $status = PVE::QemuServer::Monitor::mon_cmd($vmid, "guest-fsfreeze-status");
+    check_agent_error($status, "unable to check guest filesystem freeze status");
+
+    return $status eq 'frozen';
+}
+
 =head3 guest_fsfreeze_applicable
 
     if (guest_fsfreeze_applicable($agent_str, $vmid, $logfunc, $is_backup)) {
@@ -296,10 +315,10 @@ sub guest_fsthaw {
     }
 
 Check if the file systems of the guest C<$vmid> should be frozen according to the guest agent
-property string C<$agent_str> and if freezing is actionable in practice, i.e. guest agent running.
-Logs a message if skipped. Using a custom log function via C<$logfunc> is supported. Otherwise,
-C<print()> and C<warn()> will be used. In the context of backup tasks, C<$is_backup> must be
-specified.
+property string C<$agent_str> and if freezing is actionable in practice, i.e. guest agent running
+and file system not already frozen. Logs a message if skipped. Using a custom log function via
+C<$logfunc> is supported. Otherwise, C<print()> and C<warn()> will be used. In the context of backup
+tasks, C<$is_backup> must be specified.
 
 =cut
 
@@ -331,6 +350,14 @@ sub guest_fsfreeze_applicable {
         return;
     }
 
+    my $frozen = eval { PVE::QemuServer::Agent::guest_fs_is_frozen($vmid) };
+    $logfunc->('warn', "unable to check guest fs freeze status - $@") if $@;
+
+    if ($frozen) {
+        $logfunc->('info', "skipping guest filesystem freeze - already frozen");
+        return;
+    }
+
     return 1;
 }
 
-- 
2.47.3