From dbfc4fb7d578d4f224faa6b60deb40804dfdc1b1 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Sat, 6 Dec 2014 19:19:42 +0100 Subject: [PATCH] dst: no need to take reference on DST_NOCACHE dsts Since commit f8864972126899 ("ipv4: fix dst race in sk_dst_get()") DST_NOCACHE dst_entries get freed by RCU. So there is no need to get a reference on them when we are in rcu protected sections. Cc: Eric Dumazet Cc: Julian Anastasov Signed-off-by: Hannes Frederic Sowa Reviewed-by: Julian Anastasov Signed-off-by: David S. Miller --- include/linux/skbuff.h | 23 ++--------------------- net/core/dst.c | 24 ------------------------ net/netfilter/ipvs/ip_vs_xmit.c | 4 ++-- 3 files changed, 4 insertions(+), 47 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index e9281b5b7f59..ef64cec42804 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -717,9 +717,6 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst) skb->_skb_refdst = (unsigned long)dst; } -void __skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst, - bool force); - /** * skb_dst_set_noref - sets skb dst, hopefully, without taking reference * @skb: buffer @@ -732,24 +729,8 @@ void __skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst, */ static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst) { - __skb_dst_set_noref(skb, dst, false); -} - -/** - * skb_dst_set_noref_force - sets skb dst, without taking reference - * @skb: buffer - * @dst: dst entry - * - * Sets skb dst, assuming a reference was not taken on dst. - * No reference is taken and no dst_release will be called. While for - * cached dsts deferred reclaim is a basic feature, for entries that are - * not cached it is caller's job to guarantee that last dst_release for - * provided dst happens when nobody uses it, eg. after a RCU grace period. - */ -static inline void skb_dst_set_noref_force(struct sk_buff *skb, - struct dst_entry *dst) -{ - __skb_dst_set_noref(skb, dst, true); + WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); + skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF; } /** diff --git a/net/core/dst.c b/net/core/dst.c index a028409ee438..e956ce6d1378 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -327,30 +327,6 @@ void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old) } EXPORT_SYMBOL(__dst_destroy_metrics_generic); -/** - * __skb_dst_set_noref - sets skb dst, without a reference - * @skb: buffer - * @dst: dst entry - * @force: if force is set, use noref version even for DST_NOCACHE entries - * - * Sets skb dst, assuming a reference was not taken on dst - * skb_dst_drop() should not dst_release() this dst - */ -void __skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst, bool force) -{ - WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); - /* If dst not in cache, we must take a reference, because - * dst_release() will destroy dst as soon as its refcount becomes zero - */ - if (unlikely((dst->flags & DST_NOCACHE) && !force)) { - dst_hold(dst); - skb_dst_set(skb, dst); - } else { - skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF; - } -} -EXPORT_SYMBOL(__skb_dst_set_noref); - /* Dirty hack. We did it in 2.2 (in __dst_free), * we have _very_ good reasons not to repeat * this mistake in 2.3, but we have no choice diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c index 1f933136155a..3aedbda7658a 100644 --- a/net/netfilter/ipvs/ip_vs_xmit.c +++ b/net/netfilter/ipvs/ip_vs_xmit.c @@ -343,7 +343,7 @@ __ip_vs_get_out_rt(int skb_af, struct sk_buff *skb, struct ip_vs_dest *dest, skb_dst_drop(skb); if (noref) { if (!local) - skb_dst_set_noref_force(skb, &rt->dst); + skb_dst_set_noref(skb, &rt->dst); else skb_dst_set(skb, dst_clone(&rt->dst)); } else @@ -487,7 +487,7 @@ __ip_vs_get_out_rt_v6(int skb_af, struct sk_buff *skb, struct ip_vs_dest *dest, skb_dst_drop(skb); if (noref) { if (!local) - skb_dst_set_noref_force(skb, &rt->dst); + skb_dst_set_noref(skb, &rt->dst); else skb_dst_set(skb, dst_clone(&rt->dst)); } else -- 2.20.1