Re: [PATCH 06/14] net: sched: implement reference counted action release

Jiri Pirko
2018-05-14T16:47:57Z

Mon, May 14, 2018 at 04:27:07PM CEST, vladbu@mellanox.com wrote:

[...]

>+static int tcf_action_del_1(struct net *net, char *kind, u32 index,
>+ struct netlink_ext_ack *extack)
>+{
>+ const struct tc_action_ops *ops;
>+ int err = -EINVAL;
>+
>+ ops = tc_lookup_action_n(kind);
>+ if (!ops) {

How this can happen? Apparently you hold reference to the module since
you put it couple lines below. In that case, I don't really understand
why you need to lookup and just don't use "ops" pointer you have in
tcf_action_delete().

>+ NL_SET_ERR_MSG(extack, "Specified TC action not found");
>+ goto err_out;
>+ }
>+
>+ if (ops->delete)
>+ err = ops->delete(net, index);
>+
>+ module_put(ops->owner);
>+err_out:
>+ return err;
>+}
>+
> static int tca_action_flush(struct net *net, struct nlattr *nla,
> struct nlmsghdr *n, u32 portid,
> struct netlink_ext_ack *extack)
>@@ -1052,6 +1088,36 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
> return err;
> }
>
>+static int tcf_action_delete(struct net *net, struct list_head *actions,
>+ struct netlink_ext_ack *extack)
>+{
>+ int ret;
>+ struct tc_action *a, *tmp;
>+ char kind[IFNAMSIZ];
>+ u32 act_index;
>+
>+ list_for_each_entry_safe(a, tmp, actions, list) {
>+ const struct tc_action_ops *ops = a->ops;
>+
>+ /* Actions can be deleted concurrently
>+ * so we must save their type and id to search again
>+ * after reference is released.
>+ */
>+ strncpy(kind, a->ops->kind, sizeof(kind) - 1);
>+ act_index = a->tcfa_index;
>+
>+ list_del(&a->list);
>+ if (tcf_action_put(a))
>+ module_put(ops->owner);
>+
>+ /* now do the delete */
>+ ret = tcf_action_del_1(net, kind, act_index, extack);
>+ if (ret < 0)
>+ return ret;
>+ }
>+ return 0;
>+}
>+ …