Re: [PATCH 2/3] net/netfilter: refactor notifier registration

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On 22.02.2012 11:54, Eric Dumazet wrote:
Le mercredi 22 février 2012 à 10:48 +0400, Tony Zelenoff a écrit :
* ret variable initialization removed as useless
* Similar code strings concatenated and functions code
   flow became more plain

Signed-off-by: Tony Zelenoff<antonz@xxxxxxxxxxxxx>
---
  net/netfilter/nf_conntrack_ecache.c |   26 ++++++++++----------------
  1 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/net/netfilter/nf_conntrack_ecache.c b/net/netfilter/nf_conntrack_ecache.c
index aa15977..9b8e986 100644
--- a/net/netfilter/nf_conntrack_ecache.c
+++ b/net/netfilter/nf_conntrack_ecache.c
@@ -81,21 +81,18 @@ EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
  int nf_conntrack_register_notifier(struct net *net,
  				   struct nf_ct_event_notifier *new)
  {
-	int ret = 0;
+	int ret;
  	struct nf_ct_event_notifier *notify;

  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
-	if (notify != NULL) {
+	if (likely(!notify)) {
+		rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
+		ret = 0;
+	} else
  		ret = -EBUSY;
-		goto out_unlock;
-	}
-	rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
-	mutex_unlock(&nf_ct_ecache_mutex);
-	return ret;

-out_unlock:
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  }
@@ -118,21 +115,18 @@ EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
  int nf_ct_expect_register_notifier(struct net *net,
  				   struct nf_exp_event_notifier *new)
  {
-	int ret = 0;
+	int ret;
  	struct nf_exp_event_notifier *notify;

  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(net->ct.nf_expect_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
-	if (notify != NULL) {
+	if (likely(!notify)) {
+		rcu_assign_pointer(net->ct.nf_expect_event_cb, new);
+		ret = 0;
+	} else
  		ret = -EBUSY;
-		goto out_unlock;
-	}
-	rcu_assign_pointer(net->ct.nf_expect_event_cb, new);
-	mutex_unlock(&nf_ct_ecache_mutex);
-	return ret;

-out_unlock:
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  }

Please leave the code as is, I find it more readable.

It is standard coding practice, and permits stacking of new init code,
with proper error path.

Do not agree a bit. Of course, the code stacking and so on is good, but there is no reason to write:

	rcu_assign_pointer(net->ct.nf_expect_event_cb, new);
	mutex_unlock(&nf_ct_ecache_mutex);
	return ret;

out_unlock:
   	mutex_unlock(&nf_ct_ecache_mutex);
   	return ret;

if you can do it (without breaking logic and stacking ability and as it done everywhere) this way:

	rcu_assign_pointer(net->ct.nf_expect_event_cb, new);

out_unlock:
   	mutex_unlock(&nf_ct_ecache_mutex);
   	return ret;

with only one exit with proper locks freeing or deinitialization.

Ok, after that i've remove ret initialization at start and without goto this label became unused and compiler warn about it. Thus it was removed.


Dont add likely()/unlikely() clauses in slow path, this obfuscate code
for litle gain.
ok
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