block: Disallow snapshots if the overlay doesn't support backing files
This addresses scenarios like this one:
{ 'execute': 'blockdev-add', 'arguments':
{ 'options': { 'driver': 'qcow2',
'node-name': 'new0',
'file': { 'driver': 'file',
'filename': 'new.qcow2',
'node-name': 'file0' } } } }
{ 'execute': 'blockdev-snapshot', 'arguments':
{ 'node': 'virtio0',
'overlay': 'file0' } }
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 3598b01..3197791 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1678,6 +1678,11 @@
if (state->new_bs->backing != NULL) {
error_setg(errp, "The snapshot already has a backing image");
+ return;
+ }
+
+ if (!state->new_bs->drv->supports_backing) {
+ error_setg(errp, "The snapshot does not support backing images");
}
}