On Fri 06 Nov 2020 01:42:37 PM CET, Vladimir Sementsov-Ogievskiy wrote: > First, permission update loop tries to do iterations transactionally, > but the whole update is not transactional: nobody roll-back successful > loop iterations when some iteration fails. > > Second, in the iteration we have nested permission update: > c->klass->update_filename may point to bdrv_child_cb_update_filename() > which calls bdrv_backing_update_filename(), which may do node reopen to > RW. > > Permission update system is not prepared to nested updates, at least it > has intermediate permission-update state stored in BdrvChild > structures: has_backup_perm, backup_perm and backup_shared_perm. > > So, let's first do bdrv_replace_node_common() (which is more > transactional than open-coded update in bdrv_drop_intermediate()) and > then call update_filename() in separate. We still do not rollback > changes in case of update_filename() failure but it's not much worse > than pre-patch behavior. > > Note that bdrv_replace_node_common() does check for frozen children, > so corresponding check is dropped in bdrv_drop_intermediate(). > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Reviewed-by: Alberto Garcia <be...@igalia.com> Berto
