[pve-devel] [PATCH container v3 2/2] snapshot creation: fsfreeze mountpoints, if needed

[Stoiko Ivanov <s.ivanov@proxmox.com>]

fixes #2991, #2528.

creating a snapshot with rbd, after the syncfs finished successfully does not
guarantee that the snapshot has the state of the filesystem after syncfs.

suggestion taken from #2528 (running fsfreeze -f/-u before snapshotting on
the mountpoints)

added helper PVE::Storage::volume_snapshot_needs_fsfreeze, to indicate
which volumes need to be frozen/thawed. (and mocked it in the tests here).

Added the freeze to sync_container_namespace, since it needs to run inside the
container's mount namespace.

unfreezing happens in a sub of its own.

tests in #2991 seem to indicate that this helps to successfully create backups.

needs a versioned dependency bump on pve-storage

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 src/PVE/LXC/Config.pm     | 28 ++++++++++++++++++++++++++++
 src/test/snapshot-test.pm | 12 +++++++++++-
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
index 0528d51..9834866 100644
--- a/src/PVE/LXC/Config.pm
+++ b/src/PVE/LXC/Config.pm
@@ -2,6 +2,7 @@ package PVE::LXC::Config;
 
 use strict;
 use warnings;
+use Fcntl qw(O_RDONLY);
 
 use PVE::AbstractConfig;
 use PVE::Cluster qw(cfs_register_file);
@@ -131,12 +132,39 @@ sub fsfreeze_mountpoint {
 sub __snapshot_freeze {
     my ($class, $vmid, $unfreeze) = @_;
 
+    my $conf = $class->load_config($vmid);
+    my $storagecfg = PVE::Storage::config();
+
+    my $freeze_mps = [];
+    $class->foreach_volume($conf, sub {
+	my ($ms, $mountpoint) = @_;
+
+	if (PVE::Storage::volume_snapshot_needs_fsfreeze($storagecfg, $mountpoint->{volume})) {
+	    push @$freeze_mps, $mountpoint->{mp};
+	}
+    });
+
+    my $freeze_mountpoints = sub {
+	my ($thaw) = @_;
+
+	return if scalar(@$freeze_mps) == 0;
+
+	my $pid = PVE::LXC::find_lxc_pid($vmid);
+
+	for my $mp (@$freeze_mps) {
+	    eval{ fsfreeze_mountpoint("/proc/${pid}/root/${mp}", $thaw); };
+	    warn $@ if $@;
+	}
+    };
+
     if ($unfreeze) {
 	eval { PVE::LXC::thaw($vmid); };
 	warn $@ if $@;
+	$freeze_mountpoints->(1);
     } else {
 	PVE::LXC::freeze($vmid);
 	PVE::LXC::sync_container_namespace($vmid);
+	$freeze_mountpoints->(0);
     }
 }
 
diff --git a/src/test/snapshot-test.pm b/src/test/snapshot-test.pm
index bfb8551..91a2af9 100644
--- a/src/test/snapshot-test.pm
+++ b/src/test/snapshot-test.pm
@@ -113,6 +113,15 @@ sub mocked_volume_rollback_is_possible {
     die "volume_rollback_is_possible failed\n";
 }
 
+sub mocked_volume_snapshot_needs_fsfreeze {
+    my ($storecfg, $volid) = @_;
+    die "Storage config not mocked! aborting\n"
+	if defined($storecfg);
+    die "volid undefined\n"
+	if !defined($volid);
+    return 0;
+}
+
 sub mocked_vm_stop {
     if ($kill_possible) {
 	$running = 0;
@@ -386,7 +395,8 @@ $storage_module->mock('volume_snapshot', \&mocked_volume_snapshot);
 $storage_module->mock('volume_snapshot_delete', \&mocked_volume_snapshot_delete);
 $storage_module->mock('volume_snapshot_rollback', \&mocked_volume_snapshot_rollback);
 $storage_module->mock('volume_rollback_is_possible', \&mocked_volume_rollback_is_possible);
-printf("\tconfig(), volume_snapshot(), volume_snapshot_delete(), volume_snapshot_rollback() and volume_rollback_is_possible() mocked\n");
+$storage_module->mock('volume_snapshot_needs_fsfreeze', \&mocked_volume_snapshot_needs_fsfreeze);
+printf("\tconfig(), volume_snapshot(), volume_snapshot_delete(), volume_snapshot_rollback(), volume_rollback_is_possible() and volume_snapshot_needs_fsfreeze() mocked\n");
 
 printf("\n");
 printf("Setting up Mocking for PVE::Tools\n");
-- 
2.20.1