[Patch net 05/16] net_sched: use tcf_queue_work() in flow filter

[Cong Wang]

Defer the tcf_exts_destroy() in RCU callback to
tc filter workqueue and get RTNL lock.

Reported-by: Chris Mi <chr...@mellanox.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Jiri Pirko <j...@resnulli.us>
Cc: John Fastabend <john.fastab...@gmail.com>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 net/sched/cls_flow.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_flow.c b/net/sched/cls_flow.c
index 2a3a60ec5b86..67f3a2af6aab 100644
--- a/net/sched/cls_flow.c
+++ b/net/sched/cls_flow.c
@@ -57,7 +57,10 @@ struct flow_filter {
        u32                     divisor;
        u32                     baseclass;
        u32                     hashrnd;
-       struct rcu_head         rcu;
+       union {
+               struct work_struct      work;
+               struct rcu_head         rcu;
+       };
 };
 
 static inline u32 addr_fold(void *addr)
@@ -369,14 +372,24 @@ static const struct nla_policy flow_policy[TCA_FLOW_MAX + 
1] = {
        [TCA_FLOW_PERTURB]      = { .type = NLA_U32 },
 };
 
-static void flow_destroy_filter(struct rcu_head *head)
+static void flow_destroy_filter_work(struct work_struct *work)
 {
-       struct flow_filter *f = container_of(head, struct flow_filter, rcu);
+       struct flow_filter *f = container_of(work, struct flow_filter, work);
 
+       rtnl_lock();
        del_timer_sync(&f->perturb_timer);
        tcf_exts_destroy(&f->exts);
        tcf_em_tree_destroy(&f->ematches);
        kfree(f);
+       rtnl_unlock();
+}
+
+static void flow_destroy_filter(struct rcu_head *head)
+{
+       struct flow_filter *f = container_of(head, struct flow_filter, rcu);
+
+       INIT_WORK(&f->work, flow_destroy_filter_work);
+       tcf_queue_work(&f->work);
 }
 
 static int flow_change(struct net *net, struct sk_buff *in_skb,
-- 
2.13.0