Message ID | 51b54bc66109594459e1a08c9022c5c48f20d910.1417889528.git.hannes@stressinduktion.org |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
Hello, On Sat, 6 Dec 2014, Hannes Frederic Sowa wrote: > 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 <edumazet@google.com> > Cc: Julian Anastasov <ja@ssi.bg> Looks ok to me, Reviewed-by: Julian Anastasov <ja@ssi.bg> For IPVS we still call dst_release from RCU callback ip_vs_dest_dst_rcu_free(). May be I have to create separate patch to move dst_release() from ip_vs_dest_dst_rcu_free() to __ip_vs_dst_cache_reset() and __ip_vs_dst_set() to avoid second callback step. > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> > --- > 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 7691ad5..70ebc79 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -718,9 +718,6 @@ 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 > @@ -733,24 +730,8 @@ 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 a028409..e956ce6 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 1f93313..3aedbda 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 > -- > 1.9.3 Regards -- Julian Anastasov <ja@ssi.bg> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Hannes Frederic Sowa <hannes@stressinduktion.org> Date: Sat, 6 Dec 2014 19:19:42 +0100 > 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 <edumazet@google.com> > Cc: Julian Anastasov <ja@ssi.bg> > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 7691ad5..70ebc79 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -718,9 +718,6 @@ 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 @@ -733,24 +730,8 @@ 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 a028409..e956ce6 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 1f93313..3aedbda 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
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 <edumazet@google.com> Cc: Julian Anastasov <ja@ssi.bg> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> --- 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(-)