pkt_sched: Add and use qdisc_root() and qdisc_root_lock().

When code wants to lock the qdisc tree state, the logic
operation it's doing is locking the top-level qdisc that
sits of the root of the netdev_queue.

Add qdisc_root_lock() to represent this and convert the
easiest cases.

In order for this to work out in all cases, we have to
hook up the noop_qdisc to a dummy netdev_queue.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 8 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index c8ca54cc26b0..ee48457eaa4a 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1039,11 +1039,12 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt)
 
 static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
+        spinlock_t *root_lock = qdisc_root_lock(sch);
         struct htb_sched *q = qdisc_priv(sch);
         struct nlattr *nest;
         struct tc_htb_glob gopt;
 
-        spin_lock_bh(&sch->dev_queue->lock);
+        spin_lock_bh(root_lock);
 
         gopt.direct_pkts = q->direct_pkts;
         gopt.version = HTB_VER;
@@ -1057,11 +1058,11 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
         NLA_PUT(skb, TCA_HTB_INIT, sizeof(gopt), &gopt);
         nla_nest_end(skb, nest);
 
-        spin_unlock_bh(&sch->dev_queue->lock);
+        spin_unlock_bh(root_lock);
         return skb->len;
 
 nla_put_failure:
-        spin_unlock_bh(&sch->dev_queue->lock);
+        spin_unlock_bh(root_lock);
         nla_nest_cancel(skb, nest);
         return -1;
 }
@@ -1070,10 +1071,11 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
                           struct sk_buff *skb, struct tcmsg *tcm)
 {
         struct htb_class *cl = (struct htb_class *)arg;
+        spinlock_t *root_lock = qdisc_root_lock(sch);
         struct nlattr *nest;
         struct tc_htb_opt opt;
 
-        spin_lock_bh(&sch->dev_queue->lock);
+        spin_lock_bh(root_lock);
         tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;
         tcm->tcm_handle = cl->common.classid;
         if (!cl->level && cl->un.leaf.q)
@@ -1095,11 +1097,11 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
         NLA_PUT(skb, TCA_HTB_PARMS, sizeof(opt), &opt);
 
         nla_nest_end(skb, nest);
-        spin_unlock_bh(&sch->dev_queue->lock);
+        spin_unlock_bh(root_lock);
         return skb->len;
 
 nla_put_failure:
-        spin_unlock_bh(&sch->dev_queue->lock);
+        spin_unlock_bh(root_lock);
         nla_nest_cancel(skb, nest);
         return -1;
 }
@@ -1365,7 +1367,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
                         goto failure;
 
                 gen_new_estimator(&cl->bstats, &cl->rate_est,
-                                  &sch->dev_queue->lock,
+                                  qdisc_root_lock(sch),
                                   tca[TCA_RATE] ? : &est.nla);
                 cl->refcnt = 1;
                 cl->children = 0;
@@ -1420,7 +1422,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
         } else {
                 if (tca[TCA_RATE])
                         gen_replace_estimator(&cl->bstats, &cl->rate_est,
-                                              &sch->dev_queue->lock,
+                                              qdisc_root_lock(sch),
                                               tca[TCA_RATE]);
                 sch_tree_lock(sch);
         }