cgroup: add freeze_thaw implementation

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

diff --git a/src/PVE/LXC/CGroup.pm b/src/PVE/LXC/CGroup.pm
index ee5ea16565d4c65a1fe7a6498592a5f91c2998b5..5db1d486b7288d48f2ff2e932b6d7e7652db9a73 100644 (file)
--- a/src/PVE/LXC/CGroup.pm
+++ b/src/PVE/LXC/CGroup.pm
@@ -12,6 +12,8 @@ package PVE::LXC::CGroup;
 use strict;
 use warnings;
 
+use IO::File;
+use IO::Select;
 use POSIX qw();
 
 use PVE::ProcFSTools;
@@ -510,4 +512,72 @@ sub change_cpu_shares {
     return 1;
 }
 
+my sub v1_freeze_thaw {
+    my ($self, $controller_path, $freeze) = @_;
+    my $path = get_subdir($self, 'freezer', 1)
+       or die "trying to freeze container: container not running\n";
+    $path = "$controller_path/$path/freezer.state";
+
+    my $data = $freeze ? 'FROZEN' : 'THAWED';
+    PVE::ProcFSTools::write_proc_entry($path, $data);
+
+    # Here we just poll the freezer.state once per second.
+    while (1) {
+       my $state = file_get_contents($path);
+       chomp $state;
+       last if $state eq $data;
+    }
+}
+
+my sub v2_freeze_thaw {
+    my ($self, $controller_path, $freeze) = @_;
+    my $path = get_subdir($self, undef, 1)
+       or die "trying to freeze container: container not running\n";
+    $path = "$controller_path/$path";
+
+    my $desired_state = $freeze ? 1 : 0;
+
+    # cgroupv2 supports poll events on cgroup.events which contains the frozen
+    # state.
+    my $fh = IO::File->new("$path/cgroup.events", 'r')
+       or die "failed to open $path/cgroup.events file: $!\n";
+    my $select = IO::Select->new();
+    $select->add($fh);
+
+    PVE::ProcFSTools::write_proc_entry("$path/cgroup.freeze", $desired_state);
+    while (1) {
+       my @handles = $select->can_read();
+       next if !@handles;
+       open(my $dup, '<&', $fh)
+           or die "failed to reopen cgroup.events file: $!\n";
+       seek($dup, 0, 0)
+           or die "failed to rewind cgroup.events file: $!\n";
+       my $data = do {
+           local $/ = undef;
+           <$dup>
+       };
+       $data = parse_flat_keyed_file($data);
+       last if $data->{frozen} == $desired_state;
+    }
+}
+
+# Freeze or unfreeze a container.
+#
+# This will freeze the container at its outer (limiting) cgroup path. We use
+# this instead of `lxc-freeze` as `lxc-freeze` from lxc4 will not be able to
+# fetch the cgroup path from contaienrs still running on lxc3.
+sub freeze_thaw {
+    my ($self, $freeze) = @_;
+
+    my $controller_path = find_cgroup_controller('freezer');
+    if (defined($controller_path)) {
+       return v1_freeze_thaw($self, $controller_path, $freeze);
+    } else {
+       # cgroupv2 always has a freezer, there can be both cgv1 and cgv2
+       # freezers, but we'll prefer v1 when it's available as that's what lxc
+       # does as well...
+       return v2_freeze_thaw($self, cgroupv2_base_path(), $freeze);
+    }
+}
+
 1;