Re: [PATCH 2/2] netfilter: conntrack: optional reliable conntrack event delivery

[Pablo Neira Ayuso <pablo@netfilter.org>]

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Patrick McHardy wrote:
> Patrick McHardy wrote:
>> Pablo Neira Ayuso wrote:
>>> Hi Patrick,
>>>
>>> A couple of minor issues related to this patch.
>>>
>>> Patrick McHardy wrote:
>>>>> +    hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
>>>> Why is _rcu used? The lists are never used for a lookup.
>>>
>>> There's no hlist_nulls_del() operation without rcu. I have a patch here
>>> to add hlist_nulls_add_head() and hlist_nulls_del() although I guess
>>> that you are going to tell me that you cannot apply that patch? So,
>>> where to go?
>>
>> Either way is fine I guess. Adding non _rcu function makes sense
>> I think (Eric CCed to correct me :)). But there's also no harm
>> in using the RCU functions as long as you add a comment stating
>> that you don't in fact rely on the RCU properties to avoid confusing
>> people.
> 
> But to clarify: the non-RCU functions would be preferred :)

OK :). Eric, could you tell what if this patch is OK? It's based on the
RCU version.

-- 
"Los honestos son inadaptados sociales" -- Les Luthiers

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list_nulls: add hlist_nulls_add_head and hlist_nulls_del

This patch adds the hlist_nulls_add_head() function which is
based on hlist_nulls_add_head_rcu() but without the use of
rcu_assign_pointer(). It also adds hlist_nulls_del which is
exactly the same hlist_nulls_del_rcu.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---

 include/linux/list_nulls.h |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)


diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index 93150ec..5d10ae3 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -56,6 +56,18 @@ static inline int hlist_nulls_empty(const struct hlist_nulls_head *h)
 	return is_a_nulls(h->first);
 }
 
+static inline void hlist_nulls_add_head(struct hlist_nulls_node *n,
+					struct hlist_nulls_head *h)
+{
+	struct hlist_nulls_node *first = h->first;
+
+	n->next = first;
+	n->pprev = &h->first;
+	h->first = n;
+	if (!is_a_nulls(first))
+		first->pprev = &n->next;
+}
+
 static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
 {
 	struct hlist_nulls_node *next = n->next;
@@ -65,6 +77,12 @@ static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
 		next->pprev = pprev;
 }
 
+static inline void hlist_nulls_del(struct hlist_nulls_node *n)
+{
+	__hlist_nulls_del(n);
+	n->pprev = LIST_POISON2;
+}
+
 /**
  * hlist_nulls_for_each_entry	- iterate over list of given type
  * @tpos:	the type * to use as a loop cursor.