[Patch net 03/15] net_sched: remove RCU callbacks in flower filter

[Cong Wang]

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

As a bonus, this also drops the ugly code in commit
d936377414fa ("net, sched: respect rcu grace period on cls destruction").

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_flower.c | 46 ++++++++++++++--------------------------------
 1 file changed, 14 insertions(+), 32 deletions(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index b480d7c792ba..ad33bd00b4f0 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -61,7 +61,6 @@ struct fl_flow_mask_range {
 struct fl_flow_mask {
        struct fl_flow_key key;
        struct fl_flow_mask_range range;
-       struct rcu_head rcu;
 };
 
 struct cls_fl_head {
@@ -71,10 +70,6 @@ struct cls_fl_head {
        bool mask_assigned;
        struct list_head filters;
        struct rhashtable_params ht_params;
-       union {
-               struct work_struct work;
-               struct rcu_head rcu;
-       };
        struct idr handle_idr;
 };
 
@@ -87,7 +82,6 @@ struct cls_fl_filter {
        struct list_head list;
        u32 handle;
        u32 flags;
-       struct rcu_head rcu;
        struct net_device *hw_dev;
 };
 
@@ -215,10 +209,8 @@ static int fl_init(struct tcf_proto *tp)
        return 0;
 }
 
-static void fl_destroy_filter(struct rcu_head *head)
+static void fl_destroy_filter(struct cls_fl_filter *f)
 {
-       struct cls_fl_filter *f = container_of(head, struct cls_fl_filter, rcu);
-
        tcf_exts_destroy(&f->exts);
        kfree(f);
 }
@@ -305,38 +297,25 @@ static void __fl_delete(struct tcf_proto *tp, struct 
cls_fl_filter *f)
        if (!tc_skip_hw(f->flags))
                fl_hw_destroy_filter(tp, f);
        tcf_unbind_filter(tp, &f->res);
-       call_rcu(&f->rcu, fl_destroy_filter);
-}
-
-static void fl_destroy_sleepable(struct work_struct *work)
-{
-       struct cls_fl_head *head = container_of(work, struct cls_fl_head,
-                                               work);
-       if (head->mask_assigned)
-               rhashtable_destroy(&head->ht);
-       kfree(head);
-       module_put(THIS_MODULE);
-}
-
-static void fl_destroy_rcu(struct rcu_head *rcu)
-{
-       struct cls_fl_head *head = container_of(rcu, struct cls_fl_head, rcu);
-
-       INIT_WORK(&head->work, fl_destroy_sleepable);
-       schedule_work(&head->work);
 }
 
 static void fl_destroy(struct tcf_proto *tp)
 {
        struct cls_fl_head *head = rtnl_dereference(tp->root);
        struct cls_fl_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) {
                __fl_delete(tp, f);
+               fl_destroy_filter(f);
+       }
        idr_destroy(&head->handle_idr);
 
-       __module_get(THIS_MODULE);
-       call_rcu(&head->rcu, fl_destroy_rcu);
+       if (head->mask_assigned)
+               rhashtable_destroy(&head->ht);
+       kfree(head);
 }
 
 static void *fl_get(struct tcf_proto *tp, u32 handle)
@@ -975,7 +954,8 @@ static int fl_change(struct net *net, struct sk_buff 
*in_skb,
                idr_replace_ext(&head->handle_idr, fnew, fnew->handle);
                list_replace_rcu(&fold->list, &fnew->list);
                tcf_unbind_filter(tp, &fold->res);
-               call_rcu(&fold->rcu, fl_destroy_filter);
+               synchronize_rcu();
+               fl_destroy_filter(fold);
        } else {
                list_add_tail_rcu(&fnew->list, &head->filters);
        }
@@ -1003,6 +983,8 @@ static int fl_delete(struct tcf_proto *tp, void *arg, bool 
*last)
                rhashtable_remove_fast(&head->ht, &f->ht_node,
                                       head->ht_params);
        __fl_delete(tp, f);
+       synchronize_rcu();
+       fl_destroy_filter(f);
        *last = list_empty(&head->filters);
        return 0;
 }
-- 
2.13.0