[Patch net 09/16] net_sched: use tcf_queue_work() in u32 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_u32.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 10b8d851fc6b..dadd1b344497 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -68,7 +68,10 @@ struct tc_u_knode {
        u32 __percpu            *pcpu_success;
 #endif
        struct tcf_proto        *tp;
-       struct rcu_head         rcu;
+       union {
+               struct work_struct      work;
+               struct rcu_head         rcu;
+       };
        /* The 'sel' field MUST be the last field in structure to allow for
         * tc_u32_keys allocated at end of structure.
         */
@@ -418,11 +421,21 @@ static int u32_destroy_key(struct tcf_proto *tp, struct 
tc_u_knode *n,
  * this the u32_delete_key_rcu variant does not free the percpu
  * statistics.
  */
+static void u32_delete_key_work(struct work_struct *work)
+{
+       struct tc_u_knode *key = container_of(work, struct tc_u_knode, work);
+
+       rtnl_lock();
+       u32_destroy_key(key->tp, key, false);
+       rtnl_unlock();
+}
+
 static void u32_delete_key_rcu(struct rcu_head *rcu)
 {
        struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
 
-       u32_destroy_key(key->tp, key, false);
+       INIT_WORK(&key->work, u32_delete_key_work);
+       tcf_queue_work(&key->work);
 }
 
 /* u32_delete_key_freepf_rcu is the rcu callback variant
@@ -432,11 +445,21 @@ static void u32_delete_key_rcu(struct rcu_head *rcu)
  * for the variant that should be used with keys return from
  * u32_init_knode()
  */
+static void u32_delete_key_freepf_work(struct work_struct *work)
+{
+       struct tc_u_knode *key = container_of(work, struct tc_u_knode, work);
+
+       rtnl_lock();
+       u32_destroy_key(key->tp, key, true);
+       rtnl_unlock();
+}
+
 static void u32_delete_key_freepf_rcu(struct rcu_head *rcu)
 {
        struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
 
-       u32_destroy_key(key->tp, key, true);
+       INIT_WORK(&key->work, u32_delete_key_freepf_work);
+       tcf_queue_work(&key->work);
 }
 
 static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
-- 
2.13.0