Am 02.09.2021 um 11:37 hat Vladimir Sementsov-Ogievskiy geschrieben: > First, this permission never protected a node from being changed, as > generic child-replacing functions don't check it. > > Second, it's a strange thing: it presents a permission of parent node > to change its child. But generally, children are replaced by different > mechanisms, like jobs or qmp commands, not by nodes. > > Graph-mod permission is hard to understand. All other permissions > describe operations which done by parent node on its child: read, > write, resize. Graph modification operations are something completely > different. > > The only place where BLK_PERM_GRAPH_MOD is used as "perm" (not shared > perm) is mirror_start_job, for s->target. Still modern code should use > bdrv_freeze_backing_chain() to protect from graph modification, if we > don't do it somewhere it may be considered as a bug. So, it's a bit > risky to drop GRAPH_MOD, and analyzing of possible loss of protection > is hard. But one day we should do it, let's do it now. > > One more bit of information is that locking the corresponding byte in > file-posix doesn't make sense at all. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Thanks, applied to the block branch. Kevin
