Re: [PATCH 10/14] net: sched: extend act API for lockless actions

Jiri Pirko
2018-05-16T07:50:06Z

Mon, May 14, 2018 at 04:27:11PM CEST, vladbu@mellanox.com wrote:
>Implement new action API function to atomically delete action with
>specified index and to atomically insert unique action. These functions are
>required to implement init and delete functions for specific actions that
>do not rely on rtnl lock.
>
>Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>---
> include/net/act_api.h | 2 ++
> net/sched/act_api.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)
>
>diff --git a/include/net/act_api.h b/include/net/act_api.h
>index a8c8570..bce0cf1 100644
>--- a/include/net/act_api.h
>+++ b/include/net/act_api.h
>@@ -153,7 +153,9 @@ int tcf_idr_create(struct tc_action_net *tn, u32 index, struct nlattr *est,
> struct tc_action **a, const struct tc_action_ops *ops,
> int bind, bool cpustats);
> void tcf_idr_insert(struct tc_action_net *tn, struct tc_action *a);
>+void tcf_idr_insert_unique(struct tc_action_net *tn, struct tc_action *a);
>
>+int tcf_idr_find_delete(struct tc_action_net *tn, u32 index);
> int __tcf_idr_release(struct tc_action *a, bool bind, bool strict);
>
> static inline int tcf_idr_release(struct tc_action *a, bool bind)
>diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>index 2772276e..a5193dc 100644
>--- a/net/sched/act_api.c
>+++ b/net/sched/act_api.c
>@@ -330,6 +330,41 @@ bool tcf_idr_check(struct tc_action_net *tn, u32 index, struct tc_action **a,
> }
> EXPORT_SYMBOL(tcf_idr_check);
>
>+int tcf_idr_find_delete(struct tc_action_net *tn, u32 index)
>+{
>+ struct tcf_idrinfo *idrinfo = tn->idrinfo;
>+ struct tc_action *p;
>+ int ret = 0;
>+
>+ spin_lock_bh(&idrinfo->lock);

Why "_bh" is needed here?

>+ p = idr_find(&idrinfo->action_idr, index);
>+ if (!p) {
>+ spin_unlock(&idrinfo->lock);
>+ return -ENOENT;
>+ }
>+
>+ if (!atomic_read(&p->tcfa_bindcnt)) {
>+ if (refcount_dec_and_test(&p->tcfa_refcnt)) {
>+ struct module *owner = p->ops->owner;
>+
>+ WARN_ON(p != idr_remove(&idrinfo->action_idr,
>+ p->tcfa_index));
>+ spin_unlock_bh(&idrinfo->lock);
>+
>+ tcf_action_cleanup(p);
>+ module_put(owner);
>+ return 0;
>+ }
>+ ret = 0;
>+ } else {
>+ ret = -EPERM;

I wonder if "-EPERM" is the best error code for this...

>+ }
>+
>+ spin_unlock_bh(&idrinfo->lock);
>+ return ret;
>+}
>+EXPORT_SYMBOL(tcf_idr_find_delete);
>+
> int tcf_idr_create(struct tc_action_net *tn, u32 index, struct nlattr *est,
> struct tc_action **a, const struct tc_action_ops *ops,
> int bind, bool cpustats)
>@@ -407,6 +442,16 @@ void tcf_idr_insert(struct tc_action_net *tn, struct tc_action *a)
> }
> EXPORT_SYMBOL(tcf_idr_insert);
>
>+void tcf_idr_insert_unique(struct tc_action_net *tn, struct tc_action *a)
>+{
>+ struct tcf_idrinfo *idrinfo = tn->idrinfo;
>+
>+ spin_lock_bh(&idrinfo->lock);
>+ WARN_ON(idr_replace(&idrinfo->action_idr, a, a->tcfa_index));

Under which condition this WARN_ON is hit?

>+ spin_unlock_bh(&idrinfo->lock);
>+}
>+EXPORT_SYMBOL(tcf_idr_insert_unique);
>+
> void tcf_idrinfo_destroy(const struct tc_action_ops *ops,
> struct tcf_idrinfo *idrinfo)
> {
>--
>2.7.5
>