storage: add volume_support_qemu_snapshot

Returns if the volume is supporting qemu snapshot:
 'internal' : do the snapshot with qemu internal snapshot
 'external' : do the snapshot with qemu external snapshot
  undef     : does not support qemu snapshot

Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>

ApiChangeLog

@@ -29,6 +29,14 @@ Future changes should be documented in here.
 * Introduce rename_snapshot() plugin method
     This method allow to rename a vm disk snapshot name to a different snapshot name.
 
+* Introduce volume_support_qemu_snapshot() plugin method
+    This method is used to known if the a snapshot need to be done by qemu
+    or by the storage api.
+    returned values are :
+    'internal' : support snapshot with qemu internal snapshot
+    'external' : support snapshot with qemu external snapshot
+    undef      : don't support qemu snapshot
+
 ##  Version 11:
 
 * Allow declaring storage features via plugin data

src/PVE/Storage.pm

@@ -2370,6 +2370,21 @@ sub rename_snapshot {
     );
 }
 
+sub volume_support_qemu_snapshot {
+    my ($cfg, $volid) = @_;
+
+    my ($storeid, $volname) = parse_volume_id($volid, 1);
+
+    if ($storeid) {
+        my $scfg = storage_config($cfg, $storeid);
+
+        my $plugin = PVE::Storage::Plugin->lookup($scfg->{type});
+
+        return $plugin->volume_support_qemu_snapshot($storeid, $scfg, $volname);
+    }
+    return undef;
+}
+
 # Various io-heavy operations require io/bandwidth limits which can be
 # configured on multiple levels: The global defaults in datacenter.cfg, and
 # per-storage overrides. When we want to do a restore from storage A to storage

src/PVE/Storage/DirPlugin.pm

@@ -314,4 +314,14 @@ sub get_import_metadata {
     };
 }
 
+sub volume_support_qemu_snapshot {
+    my ($class, $storeid, $scfg, $volname) = @_;
+
+    my $format = ($class->parse_volname($volname))[6];
+    return if $format ne 'qcow2';
+
+    my $type = $scfg->{'external-snapshots'} ? 'external' : 'internal';
+    return $type;
+}
+
 1;

src/PVE/Storage/LVMPlugin.pm

@@ -872,4 +872,11 @@ sub rename_snapshot {
     die "rename_snapshot is not implemented for $class";
 }
 
+sub volume_support_qemu_snapshot {
+    my ($class, $storeid, $scfg, $volname) = @_;
+
+    my $format = ($class->parse_volname($volname))[6];
+    return 'external' if $format eq 'qcow2';
+}
+
 1;

src/PVE/Storage/Plugin.pm

@@ -2262,6 +2262,26 @@ sub new_backup_provider {
     die "implement me if enabling the feature 'backup-provider' in plugindata()->{features}\n";
 }
 
+=pod
+
+=head3 volume_support_qemu_snapshot
+
+    $blockdev = $plugin->volume_support_qemu_snapshot($storeid, $scfg, $volname)
+
+Returns a string with the type of snapshot that qemu can do for a specific volume
+
+'internal' : support snapshot with qemu internal snapshot
+'external' : support snapshot with qemu external snapshot
+undef      : don't support qemu snapshot
+=cut
+
+sub volume_support_qemu_snapshot {
+    my ($class, $storeid, $scfg, $volname) = @_;
+
+    my $format = ($class->parse_volname($volname))[6];
+    return 'internal' if $format eq 'qcow2';
+}
+
 sub config_aware_base_mkdir {
     my ($class, $scfg, $path) = @_;
 

src/PVE/Storage/RBDPlugin.pm

@@ -1063,4 +1063,10 @@ sub rename_snapshot {
     die "rename_snapshot is not implemented for $class";
 }
 
+sub volume_support_qemu_snapshot {
+    my ($class, $storeid, $scfg, $volname) = @_;
+
+    return 'internal' if !$scfg->{krbd};
+}
+
 1;