[pve-devel] [PATCH v5 container 9/10] migration: fail when aliased volume is detected

[Aaron Lauterer]

Aliased volumes (referencing the same volume multiple times) can lead to
unexpected behavior in a migration.

Therefore, stop the migration in such a case.

The check works by comparing the path returned by the storage plugin.
This means that we should be able to catch the common situations where
it can happen:

* by referencing the same volid multiple times
* having a different volid due to an aliased storage: different storage
name but pointing to the same location.

We decided against checking the storages themselves being aliased. It is
not possible to infer that reliably from just the storage configuration
options alone.

Reviewed-by: Fiona Ebner <f.ebner at proxmox.com>
Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
---
changes since v4: none

 src/PVE/LXC/Migrate.pm | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/PVE/LXC/Migrate.pm b/src/PVE/LXC/Migrate.pm
index 3947227..abef737 100644
--- a/src/PVE/LXC/Migrate.pm
+++ b/src/PVE/LXC/Migrate.pm
@@ -182,6 +182,7 @@ sub phase1 {
     my $volhash = {}; # 'config', 'snapshot' or 'storage' for local volumes
     my $volhash_errors = {};
     my $abort = 0;
+    my $path_to_volid = {};
 
     my $log_error = sub {
 	my ($msg, $volid) = @_;
@@ -231,6 +232,8 @@ sub phase1 {
 	die "owned by other guest (owner = $owner)\n"
 	    if !$owner || ($owner != $self->{vmid});
 
+	$path_to_volid->{$path}->{$volid} = 1;
+
 	if (defined($snapname)) {
 	    # we cannot migrate shapshots on local storage
 	    # exceptions: 'zfspool', 'btrfs'
@@ -277,6 +280,12 @@ sub phase1 {
     # finally all current volumes
     PVE::LXC::Config->foreach_volume_full($conf, { include_unused => 1 }, $test_mp);
 
+    for my $path (keys %$path_to_volid) {
+	my @volids = keys $path_to_volid->{$path}->%*;
+	die "detected not supported aliased volumes: '" . join("', '", @volids) . "'"
+	    if (scalar @volids > 1);
+    }
+
     # additional checks for local storage
     foreach my $volid (keys %$volhash) {
 	eval {
-- 
2.39.2