net_sched: destroy proto tp when all filters are gone

Kernel automatically creates a tp for each
(kind, protocol, priority) tuple, which has handle 0,
when we add a new filter, but it still is left there
after we remove our own, unless we don't specify the
handle (literally means all the filters under
the tuple). For example this one is left:

  # tc filter show dev eth0
  filter parent 8001: protocol arp pref 49152 basic

The user-space is hard to clean up these for kernel
because filters like u32 are organized in a complex way.
So kernel is responsible to remove it after all filters
are gone.  Each type of filter has its own way to
store the filters, so each type has to provide its
way to check if all filters are gone.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim<jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 1 deletions

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 09487afbfd51..375e51b71c80 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -460,13 +460,35 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht)
 	return -ENOENT;
 }
 
-static void u32_destroy(struct tcf_proto *tp)
+static bool ht_empty(struct tc_u_hnode *ht)
+{
+	unsigned int h;
+
+	for (h = 0; h <= ht->divisor; h++)
+		if (rcu_access_pointer(ht->ht[h]))
+			return false;
+
+	return true;
+}
+
+static bool u32_destroy(struct tcf_proto *tp, bool force)
 {
 	struct tc_u_common *tp_c = tp->data;
 	struct tc_u_hnode *root_ht = rtnl_dereference(tp->root);
 
 	WARN_ON(root_ht == NULL);
 
+	if (!force) {
+		if (root_ht) {
+			if (root_ht->refcnt > 1)
+				return false;
+			if (root_ht->refcnt == 1) {
+				if (!ht_empty(root_ht))
+					return false;
+			}
+		}
+	}
+
 	if (root_ht && --root_ht->refcnt == 0)
 		u32_destroy_hnode(tp, root_ht);
 
@@ -491,6 +513,7 @@ static void u32_destroy(struct tcf_proto *tp)
 	}
 
 	tp->data = NULL;
+	return true;
 }
 
 static int u32_delete(struct tcf_proto *tp, unsigned long arg)