[Patch net 07/15] net_sched: remove RCU callbacks in flow filter

[Cong Wang]

Replace call_rcu() with synchronize_rcu(), except in
flow_destroy() we have to use list_splice_init_rcu().

Reported-by: Chris Mi <chr...@mellanox.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
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 | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/net/sched/cls_flow.c b/net/sched/cls_flow.c
index 2a3a60ec5b86..c33643289fa9 100644
--- a/net/sched/cls_flow.c
+++ b/net/sched/cls_flow.c
@@ -35,7 +35,6 @@
 
 struct flow_head {
        struct list_head        filters;
-       struct rcu_head         rcu;
 };
 
 struct flow_filter {
@@ -57,7 +56,6 @@ struct flow_filter {
        u32                     divisor;
        u32                     baseclass;
        u32                     hashrnd;
-       struct rcu_head         rcu;
 };
 
 static inline u32 addr_fold(void *addr)
@@ -369,10 +367,8 @@ 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(struct flow_filter *f)
 {
-       struct flow_filter *f = container_of(head, struct flow_filter, rcu);
-
        del_timer_sync(&f->perturb_timer);
        tcf_exts_destroy(&f->exts);
        tcf_em_tree_destroy(&f->ematches);
@@ -539,8 +535,10 @@ static int flow_change(struct net *net, struct sk_buff 
*in_skb,
 
        *arg = fnew;
 
-       if (fold)
-               call_rcu(&fold->rcu, flow_destroy_filter);
+       if (fold) {
+               synchronize_rcu();
+               flow_destroy_filter(fold);
+       }
        return 0;
 
 err2:
@@ -557,7 +555,8 @@ static int flow_delete(struct tcf_proto *tp, void *arg, 
bool *last)
        struct flow_filter *f = arg;
 
        list_del_rcu(&f->list);
-       call_rcu(&f->rcu, flow_destroy_filter);
+       synchronize_rcu();
+       flow_destroy_filter(f);
        *last = list_empty(&head->filters);
        return 0;
 }
@@ -578,12 +577,15 @@ static void flow_destroy(struct tcf_proto *tp)
 {
        struct flow_head *head = rtnl_dereference(tp->root);
        struct flow_filter *f, *next;
+       LIST_HEAD(local);
+
+       list_splice_init_rcu(&head->filters, &local, synchronize_rcu);
 
-       list_for_each_entry_safe(f, next, &head->filters, list) {
+       list_for_each_entry_safe(f, next, &local, list) {
                list_del_rcu(&f->list);
-               call_rcu(&f->rcu, flow_destroy_filter);
+               flow_destroy_filter(f);
        }
-       kfree_rcu(head, rcu);
+       kfree(head);
 }
 
 static void *flow_get(struct tcf_proto *tp, u32 handle)
-- 
2.13.0