net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath

In sch_handle_egress and sch_handle_ingress tp->q is used only in order
to update stats. So stats and filter list are the only things that are
needed in clsact qdisc fastpath processing. Introduce new mini_Qdisc
struct to hold those items. Also, introduce a helper to swap the
mini_Qdisc structures in case filter list head changes.

This removes need for tp->q usage without added overhead.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5e02f79b2110270c98231e978c196dcd5c40e0a6..7de7656550c29c926d0d4f4fdae501f14b5e5efc 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1559,6 +1559,8 @@ enum netdev_priv_flags {
  *
  *     @rx_handler:            handler for received packets
  *     @rx_handler_data:       XXX: need comments on this one
+ *     @miniq_ingress:         ingress/clsact qdisc specific data for
+ *                             ingress processing
  *     @ingress_queue:         XXX: need comments on this one
  *     @broadcast:             hw bcast address
  *
@@ -1576,7 +1578,8 @@ enum netdev_priv_flags {
  *     @tx_global_lock:        XXX: need comments on this one
  *
  *     @xps_maps:      XXX: need comments on this one
- *
+ *     @miniq_egress:          clsact qdisc specific data for
+ *                             egress processing
  *     @watchdog_timeo:        Represents the timeout that is used by
  *                             the watchdog (see dev_watchdog())
  *     @watchdog_timer:        List of timers
@@ -1795,7 +1798,7 @@ struct net_device {
        void __rcu              *rx_handler_data;
 
 #ifdef CONFIG_NET_CLS_ACT
-       struct tcf_proto __rcu  *ingress_cl_list;
+       struct mini_Qdisc __rcu *miniq_ingress;
 #endif
        struct netdev_queue __rcu *ingress_queue;
 #ifdef CONFIG_NETFILTER_INGRESS
@@ -1826,7 +1829,7 @@ struct net_device {
        struct xps_dev_maps __rcu *xps_maps;
 #endif
 #ifdef CONFIG_NET_CLS_ACT
-       struct tcf_proto __rcu  *egress_cl_list;
+       struct mini_Qdisc __rcu *miniq_egress;
 #endif
 
        /* These may be needed for future network-power-down code. */

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index f230269e0bfb4c8bdf9d235784c4d7ceb675141f..c64e62c9450a8f97cddc96540e16953483c863c7 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -904,4 +904,36 @@ static inline void psched_ratecfg_getrate(struct tc_ratespec *res,
        res->linklayer = (r->linklayer & TC_LINKLAYER_MASK);
 }
 
+/* Mini Qdisc serves for specific needs of ingress/clsact Qdisc.
+ * The fast path only needs to access filter list and to update stats
+ */
+struct mini_Qdisc {
+       struct tcf_proto *filter_list;
+       struct gnet_stats_basic_cpu __percpu *cpu_bstats;
+       struct gnet_stats_queue __percpu *cpu_qstats;
+       struct rcu_head rcu;
+};
+
+static inline void mini_qdisc_bstats_cpu_update(struct mini_Qdisc *miniq,
+                                               const struct sk_buff *skb)
+{
+       bstats_cpu_update(this_cpu_ptr(miniq->cpu_bstats), skb);
+}
+
+static inline void mini_qdisc_qstats_cpu_drop(struct mini_Qdisc *miniq)
+{
+       this_cpu_inc(miniq->cpu_qstats->drops);
+}
+
+struct mini_Qdisc_pair {
+       struct mini_Qdisc miniq1;
+       struct mini_Qdisc miniq2;
+       struct mini_Qdisc __rcu **p_miniq;
+};
+
+void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
+                         struct tcf_proto *tp_head);
+void mini_qdisc_pair_init(struct mini_Qdisc_pair *miniqp, struct Qdisc *qdisc,
+                         struct mini_Qdisc __rcu **p_miniq);
+
 #endif

diff --git a/net/core/dev.c b/net/core/dev.c
index 24ac9083bc132fcdf00ecada5962946a1793468e..1423cf4d695cfebbffc5ad2d50499f581e2641e2 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3274,22 +3274,22 @@ EXPORT_SYMBOL(dev_loopback_xmit);
 static struct sk_buff *
 sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
 {
-       struct tcf_proto *cl = rcu_dereference_bh(dev->egress_cl_list);
+       struct mini_Qdisc *miniq = rcu_dereference_bh(dev->miniq_egress);
        struct tcf_result cl_res;
 
-       if (!cl)
+       if (!miniq)
                return skb;
 
        /* qdisc_skb_cb(skb)->pkt_len was already set by the caller. */
-       qdisc_bstats_cpu_update(cl->q, skb);
+       mini_qdisc_bstats_cpu_update(miniq, skb);
 
-       switch (tcf_classify(skb, cl, &cl_res, false)) {
+       switch (tcf_classify(skb, miniq->filter_list, &cl_res, false)) {
        case TC_ACT_OK:
        case TC_ACT_RECLASSIFY:
                skb->tc_index = TC_H_MIN(cl_res.classid);
                break;
        case TC_ACT_SHOT:
-               qdisc_qstats_cpu_drop(cl->q);
+               mini_qdisc_qstats_cpu_drop(miniq);
                *ret = NET_XMIT_DROP;
                kfree_skb(skb);
                return NULL;
@@ -4189,7 +4189,7 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
                   struct net_device *orig_dev)
 {
 #ifdef CONFIG_NET_CLS_ACT
-       struct tcf_proto *cl = rcu_dereference_bh(skb->dev->ingress_cl_list);
+       struct mini_Qdisc *miniq = rcu_dereference_bh(skb->dev->miniq_ingress);
        struct tcf_result cl_res;
 
        /* If there's at least one ingress present somewhere (so
@@ -4197,8 +4197,9 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
         * that are not configured with an ingress qdisc will bail
         * out here.
         */
-       if (!cl)
+       if (!miniq)
                return skb;
+
        if (*pt_prev) {
                *ret = deliver_skb(skb, *pt_prev, orig_dev);
                *pt_prev = NULL;
@@ -4206,15 +4207,15 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
 
        qdisc_skb_cb(skb)->pkt_len = skb->len;
        skb->tc_at_ingress = 1;
-       qdisc_bstats_cpu_update(cl->q, skb);
+       mini_qdisc_bstats_cpu_update(miniq, skb);
 
-       switch (tcf_classify(skb, cl, &cl_res, false)) {
+       switch (tcf_classify(skb, miniq->filter_list, &cl_res, false)) {
        case TC_ACT_OK:
        case TC_ACT_RECLASSIFY:
                skb->tc_index = TC_H_MIN(cl_res.classid);
                break;
        case TC_ACT_SHOT:
-               qdisc_qstats_cpu_drop(cl->q);
+               mini_qdisc_qstats_cpu_drop(miniq);
                kfree_skb(skb);
                return NULL;
        case TC_ACT_STOLEN:

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index aa74aa42b5d7c07b70527fc0cabca192da70ac65..3839cbbdc32b1eadd2cae6a42a6b8c998ca88a15 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1024,3 +1024,49 @@ void psched_ratecfg_precompute(struct psched_ratecfg *r,
        }
 }
 EXPORT_SYMBOL(psched_ratecfg_precompute);
+
+static void mini_qdisc_rcu_func(struct rcu_head *head)
+{
+}
+
+void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
+                         struct tcf_proto *tp_head)
+{
+       struct mini_Qdisc *miniq_old = rtnl_dereference(*miniqp->p_miniq);
+       struct mini_Qdisc *miniq;
+
+       if (!tp_head) {
+               RCU_INIT_POINTER(*miniqp->p_miniq, NULL);
+               return;
+       }
+
+       miniq = !miniq_old || miniq_old == &miniqp->miniq2 ?
+               &miniqp->miniq1 : &miniqp->miniq2;
+
+       /* We need to make sure that readers won't see the miniq
+        * we are about to modify. So wait until previous call_rcu_bh callback
+        * is done.
+        */
+       rcu_barrier_bh();
+       miniq->filter_list = tp_head;
+       rcu_assign_pointer(*miniqp->p_miniq, miniq);
+
+       if (miniq_old)
+               /* This is counterpart of the rcu barrier above. We need to
+                * block potential new user of miniq_old until all readers
+                * are not seeing it.
+                */
+               call_rcu_bh(&miniq_old->rcu, mini_qdisc_rcu_func);
+}
+EXPORT_SYMBOL(mini_qdisc_pair_swap);
+
+void mini_qdisc_pair_init(struct mini_Qdisc_pair *miniqp, struct Qdisc *qdisc,
+                         struct mini_Qdisc __rcu **p_miniq)
+{
+       miniqp->miniq1.cpu_bstats = qdisc->cpu_bstats;
+       miniqp->miniq1.cpu_qstats = qdisc->cpu_qstats;
+       miniqp->miniq2.cpu_bstats = qdisc->cpu_bstats;
+       miniqp->miniq2.cpu_qstats = qdisc->cpu_qstats;
+       miniqp->p_miniq = p_miniq;
+}
+EXPORT_SYMBOL(mini_qdisc_pair_init);

diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index 811845815b8c3618468efe0173fb3af8f882a43d..5ecc38f35d4774fdfa402d9a4c4a0e655e1c91c2 100644 (file)
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -21,6 +21,7 @@
 struct ingress_sched_data {
        struct tcf_block *block;
        struct tcf_block_ext_info block_info;
+       struct mini_Qdisc_pair miniqp;
 };
 
 static struct Qdisc *ingress_leaf(struct Qdisc *sch, unsigned long arg)
@@ -56,9 +57,9 @@ static struct tcf_block *ingress_tcf_block(struct Qdisc *sch, unsigned long cl)
 
 static void clsact_chain_head_change(struct tcf_proto *tp_head, void *priv)
 {
-       struct tcf_proto __rcu **p_filter_chain = priv;
+       struct mini_Qdisc_pair *miniqp = priv;
 
-       rcu_assign_pointer(*p_filter_chain, tp_head);
+       mini_qdisc_pair_swap(miniqp, tp_head);
 }
 
 static int ingress_init(struct Qdisc *sch, struct nlattr *opt)
@@ -67,9 +68,11 @@ static int ingress_init(struct Qdisc *sch, struct nlattr *opt)
        struct net_device *dev = qdisc_dev(sch);
        int err;
 
+       mini_qdisc_pair_init(&q->miniqp, sch, &dev->miniq_ingress);
+
        q->block_info.binder_type = TCF_BLOCK_BINDER_TYPE_CLSACT_INGRESS;
        q->block_info.chain_head_change = clsact_chain_head_change;
-       q->block_info.chain_head_change_priv = &dev->ingress_cl_list;
+       q->block_info.chain_head_change_priv = &q->miniqp;
 
        err = tcf_block_get_ext(&q->block, sch, &q->block_info);
        if (err)
@@ -128,6 +131,8 @@ struct clsact_sched_data {
        struct tcf_block *egress_block;
        struct tcf_block_ext_info ingress_block_info;
        struct tcf_block_ext_info egress_block_info;
+       struct mini_Qdisc_pair miniqp_ingress;
+       struct mini_Qdisc_pair miniqp_egress;
 };
 
 static unsigned long clsact_find(struct Qdisc *sch, u32 classid)
@@ -167,17 +172,21 @@ static int clsact_init(struct Qdisc *sch, struct nlattr *opt)
        struct net_device *dev = qdisc_dev(sch);
        int err;
 
+       mini_qdisc_pair_init(&q->miniqp_ingress, sch, &dev->miniq_ingress);
+
        q->ingress_block_info.binder_type = TCF_BLOCK_BINDER_TYPE_CLSACT_INGRESS;
        q->ingress_block_info.chain_head_change = clsact_chain_head_change;
-       q->ingress_block_info.chain_head_change_priv = &dev->ingress_cl_list;
+       q->ingress_block_info.chain_head_change_priv = &q->miniqp_ingress;
 
        err = tcf_block_get_ext(&q->ingress_block, sch, &q->ingress_block_info);
        if (err)
                return err;
 
+       mini_qdisc_pair_init(&q->miniqp_egress, sch, &dev->miniq_egress);
+
        q->egress_block_info.binder_type = TCF_BLOCK_BINDER_TYPE_CLSACT_EGRESS;
        q->egress_block_info.chain_head_change = clsact_chain_head_change;
-       q->egress_block_info.chain_head_change_priv = &dev->egress_cl_list;
+       q->egress_block_info.chain_head_change_priv = &q->miniqp_egress;
 
        err = tcf_block_get_ext(&q->egress_block, sch, &q->egress_block_info);
        if (err)