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, 9 insertions, 2 deletions

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index 9d9aa3e..715e01e 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -133,14 +133,20 @@ static void fw_delete_filter(struct rcu_head *head)
 	kfree(f);
 }
 
-static void fw_destroy(struct tcf_proto *tp)
+static bool fw_destroy(struct tcf_proto *tp, bool force)
 {
 	struct fw_head *head = rtnl_dereference(tp->root);
 	struct fw_filter *f;
 	int h;
 
 	if (head == NULL)
-		return;
+		return true;
+
+	if (!force) {
+		for (h = 0; h < HTSIZE; h++)
+			if (rcu_access_pointer(head->ht[h]))
+				return false;
+	}
 
 	for (h = 0; h < HTSIZE; h++) {
 		while ((f = rtnl_dereference(head->ht[h])) != NULL) {
@@ -152,6 +158,7 @@ static void fw_destroy(struct tcf_proto *tp)
 	}
 	RCU_INIT_POINTER(tp->root, NULL);
 	kfree_rcu(head, rcu);
+	return true;
 }
 
 static int fw_delete(struct tcf_proto *tp, unsigned long arg)