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dst: no need to take reference on DST_NOCACHE dsts

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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>
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2014-12-06 19:19:42 +01:00 committed by David S. Miller
parent c19be735c9
commit dbfc4fb7d5
3 changed files with 4 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/linux/skbuff.h
View File

@ -717,9 +717,6 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
skb->_skb_refdst = (unsigned long)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_dst_set_noref - sets skb dst, hopefully, without taking reference
* @skb: buffer * @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) static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
{ {
__skb_dst_set_noref(skb, dst, false); WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
} skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
/**
* 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);
} }
/** /**

24
net/core/dst.c
View File

@ -327,30 +327,6 @@ void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
} }
EXPORT_SYMBOL(__dst_destroy_metrics_generic); 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), /* Dirty hack. We did it in 2.2 (in __dst_free),
* we have _very_ good reasons not to repeat * we have _very_ good reasons not to repeat
* this mistake in 2.3, but we have no choice * this mistake in 2.3, but we have no choice

4
net/netfilter/ipvs/ip_vs_xmit.c
View File

@ -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); skb_dst_drop(skb);
if (noref) { if (noref) {
if (!local) if (!local)
skb_dst_set_noref_force(skb, &rt->dst); skb_dst_set_noref(skb, &rt->dst);
else else
skb_dst_set(skb, dst_clone(&rt->dst)); skb_dst_set(skb, dst_clone(&rt->dst));
} else } 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); skb_dst_drop(skb);
if (noref) { if (noref) {
if (!local) if (!local)
skb_dst_set_noref_force(skb, &rt->dst); skb_dst_set_noref(skb, &rt->dst);
else else
skb_dst_set(skb, dst_clone(&rt->dst)); skb_dst_set(skb, dst_clone(&rt->dst));
} else } else