net_sched: htb: do not acquire qdisc lock in dump operations
htb_dump() and htb_dump_class() do not strictly need to acquire qdisc lock to fetch qdisc and/or class parameters. We hold RTNL and no changes can occur. This reduces by 50% qdisc lock pressure while doing tc qdisc|class dump operations. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1062,12 +1062,13 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt)
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static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
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{
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spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);
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struct htb_sched *q = qdisc_priv(sch);
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struct nlattr *nest;
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struct tc_htb_glob gopt;
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spin_lock_bh(root_lock);
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/* Its safe to not acquire qdisc lock. As we hold RTNL,
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* no change can happen on the qdisc parameters.
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*/
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gopt.direct_pkts = q->direct_pkts;
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gopt.version = HTB_VER;
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@ -1081,13 +1082,10 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
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if (nla_put(skb, TCA_HTB_INIT, sizeof(gopt), &gopt) ||
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nla_put_u32(skb, TCA_HTB_DIRECT_QLEN, q->direct_qlen))
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goto nla_put_failure;
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nla_nest_end(skb, nest);
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spin_unlock_bh(root_lock);
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return skb->len;
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return nla_nest_end(skb, nest);
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nla_put_failure:
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spin_unlock_bh(root_lock);
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nla_nest_cancel(skb, nest);
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return -1;
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}
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@ -1096,11 +1094,12 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
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struct sk_buff *skb, struct tcmsg *tcm)
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{
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struct htb_class *cl = (struct htb_class *)arg;
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spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);
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struct nlattr *nest;
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struct tc_htb_opt opt;
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spin_lock_bh(root_lock);
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/* Its safe to not acquire qdisc lock. As we hold RTNL,
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* no change can happen on the class parameters.
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*/
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tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;
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tcm->tcm_handle = cl->common.classid;
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if (!cl->level && cl->un.leaf.q)
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@ -1128,12 +1127,9 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
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nla_put_u64(skb, TCA_HTB_CEIL64, cl->ceil.rate_bytes_ps))
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goto nla_put_failure;
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nla_nest_end(skb, nest);
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spin_unlock_bh(root_lock);
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return skb->len;
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return nla_nest_end(skb, nest);
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nla_put_failure:
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spin_unlock_bh(root_lock);
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nla_nest_cancel(skb, nest);
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return -1;
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}
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