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net: add skb_dst_set_noref_force

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Rename skb_dst_set_noref to __skb_dst_set_noref and
add force flag as suggested by David Miller. The new wrapper
skb_dst_set_noref_force will force dst entries that are not
cached to be attached as skb dst without taking reference
as long as provided dst is reclaimed after RCU grace period.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off by: Hans Schillstrom <hans@schillstrom.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Julian Anastasov 2013-03-21 11:57:58 +02:00 committed by Pablo Neira Ayuso
parent e5c5d22e8d
commit 932bc4d7a5
2 changed files with 39 additions and 5 deletions
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35
include/linux/skbuff.h
View File

@ -575,7 +575,40 @@ 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;
} }
extern void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst); extern 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
* @dst: dst entry
*
* Sets skb dst, assuming a reference was not taken on dst.
* If dst entry is cached, we do not take reference and dst_release
* will be avoided by refdst_drop. If dst entry is not cached, we take
* reference, so that last dst_release can destroy the dst immediately.
*/
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);
}
/** /**
* skb_dst_is_noref - Test if skb dst isn't refcounted * skb_dst_is_noref - Test if skb dst isn't refcounted

9
net/core/dst.c
View File

@ -320,27 +320,28 @@ 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_dst_set_noref - sets skb dst, without a reference
* @skb: buffer * @skb: buffer
* @dst: dst entry * @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 * Sets skb dst, assuming a reference was not taken on dst
* skb_dst_drop() should not dst_release() this dst * skb_dst_drop() should not dst_release() this dst
*/ */
void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *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()); WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
/* If dst not in cache, we must take a reference, because /* If dst not in cache, we must take a reference, because
* dst_release() will destroy dst as soon as its refcount becomes zero * dst_release() will destroy dst as soon as its refcount becomes zero
*/ */
if (unlikely(dst->flags & DST_NOCACHE)) { if (unlikely((dst->flags & DST_NOCACHE) && !force)) {
dst_hold(dst); dst_hold(dst);
skb_dst_set(skb, dst); skb_dst_set(skb, dst);
} else { } else {
skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF; skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
} }
} }
EXPORT_SYMBOL(skb_dst_set_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