[pve-devel] [PATCH v3 qemu-server 3/7] migration: fail when aliased volume is detected

[Aaron Lauterer]

Aliased volids can lead to unexpected behavior in a migration.

An aliased volid can happen if we have two storage configurations,
pointing to the same place. The resulting 'path' for a disk image
will be the same.
Therefore, stop the migration in such a case.

The check works by comparing the path returned by the storage plugin.

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

Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
---
We did discuss moving the check into its own function so that we can
call it in other places as well, for example during the VM start to be
able to show a warning.
I haven't gotten around to it yet, but wanted to get this version of the
sries out so we can review the other parts of the series. Therefore, we could
not apply this and the next patch (maching tests) for now.

 PVE/QemuMigrate.pm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
index 163a721..6148cf5 100644
--- a/PVE/QemuMigrate.pm
+++ b/PVE/QemuMigrate.pm
@@ -299,12 +299,12 @@ sub scan_local_volumes {
 
     my $storecfg = $self->{storecfg};
     eval {
-
 	# found local volumes and their origin
 	my $local_volumes = $self->{local_volumes};
 	my $local_volumes_errors = {};
 	my $other_errors = [];
 	my $abort = 0;
+	my $path_to_volid = {};
 
 	my $log_error = sub {
 	    my ($msg, $volid) = @_;
@@ -391,6 +391,8 @@ sub scan_local_volumes {
 	    die "owned by other VM (owner = VM $owner)\n"
 		if !$owner || ($owner != $vmid);
 
+	    $path_to_volid->{$path}->{$volid} = 1;
+
 	    return if $attr->{is_vmstate};
 
 	    if (defined($snaprefs)) {
@@ -424,6 +426,12 @@ sub scan_local_volumes {
 	    }
         });
 
+	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);
+	}
+
 	foreach my $vol (sort keys %$local_volumes) {
 	    my $type = $replicatable_volumes->{$vol} ? 'local, replicated' : 'local';
 	    my $ref = $local_volumes->{$vol}->{ref};
-- 
2.30.2