[pve-devel] [PATCH container v2 2/2] snapshot creation: fsfreeze mountpoints, if needed

[Stoiko Ivanov]

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 at proxmox.com>
---
 src/PVE/LXC.pm            | 26 +++++++++++++++++++++++---
 src/PVE/LXC/Config.pm     | 19 +++++++++++++++++--
 src/test/snapshot-test.pm | 12 +++++++++++-
 3 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index ee86b37..429da1b 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -1109,8 +1109,20 @@ sub fsfreeze_mountpoint {
     die "fs$op '$path' failed - $ioctl_err\n" if defined $ioctl_err;
 }
 
+sub unfreeze_container_namespace {
+    my ($vmid, $freeze_mountpoints) = @_;
+    my $pid = find_lxc_pid($vmid);
+
+    PVE::Tools::run_fork(sub {
+	&$enter_namespace($vmid, $pid, 'mnt', PVE::Tools::CLONE_NEWNS);
+	foreach my $dir (@$freeze_mountpoints) {
+	    fsfreeze_mountpoint($dir, 1);
+	}
+    });
+}
+
 my $do_syncfs = sub {
-    my ($vmid, $pid, $socket) = @_;
+    my ($vmid, $pid, $socket, $freeze_mountpoints) = @_;
 
     &$enter_namespace($vmid, $pid, 'mnt', PVE::Tools::CLONE_NEWNS);
 
@@ -1143,10 +1155,18 @@ my $do_syncfs = sub {
 	eval { PVE::Tools::sync_mountpoint($dir); };
 	warn $@ if $@;
     }
+
+    # freeze the mountpoints which need it
+    foreach my $dir (@$freeze_mountpoints) {
+	eval {
+	    fsfreeze_mountpoint($dir, 0);
+	};
+	warn $@ if $@;
+    }
 };
 
 sub sync_container_namespace {
-    my ($vmid) = @_;
+    my ($vmid, $freeze_mountpoints) = @_;
     my $pid = find_lxc_pid($vmid);
 
     # SOCK_DGRAM is nicer for barriers but cannot be slurped
@@ -1159,7 +1179,7 @@ sub sync_container_namespace {
     if (!$child) {
 	eval {
 	    close $pfd;
-	    &$do_syncfs($vmid, $pid, $cfd);
+	    &$do_syncfs($vmid, $pid, $cfd, $freeze_mountpoints);
 	};
 	if (my $err = $@) {
 	    warn $err;
diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
index 49f599b..b1a57de 100644
--- a/src/PVE/LXC/Config.pm
+++ b/src/PVE/LXC/Config.pm
@@ -112,12 +112,27 @@ sub __snapshot_check_freeze_needed {
 sub __snapshot_freeze {
     my ($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, $mountpoint->{mp};
+	}
+    });
+
     if ($unfreeze) {
-	eval { PVE::LXC::thaw($vmid); };
+	eval {
+	    PVE::LXC::thaw($vmid);
+	    PVE::LXC::unfreeze_container_namespace($vmid, $freeze_mps);
+	};
 	warn $@ if $@;
     } else {
 	PVE::LXC::freeze($vmid);
-	PVE::LXC::sync_container_namespace($vmid);
+	PVE::LXC::sync_container_namespace($vmid, $freeze_mps);
     }
 }
 
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