Hi Simon,
On Fri, Mar 29, 2013 at 01:11:18PM +0900, Simon Horman wrote:
> From: Julian Anastasov <ja@xxxxxx>
>
> 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@xxxxxx>
> Signed-off by: Hans Schillstrom <hans@xxxxxxxxxxxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
I think was acked by David, right?
> ---
> include/linux/skbuff.h | 35 ++++++++++++++++++++++++++++++++++-
> net/core/dst.c | 9 +++++----
> 2 files changed, 39 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 878e0ee..364e244 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -575,7 +575,40 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *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
> diff --git a/net/core/dst.c b/net/core/dst.c
> index 35fd12f..df9cc81 100644
> --- a/net/core/dst.c
> +++ b/net/core/dst.c
> @@ -320,27 +320,28 @@ 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_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)
> +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)) {
> + 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);
> +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
> --
> 1.7.10.4
>
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