[PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[SF Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Tue, 18 Nov 2014 20:37:05 +0100

The functions free_percpu() and module_put() test whether their argument
is NULL and then return immediately. Thus the test around the call is
not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 net/netfilter/ipvs/ip_vs_ctl.c   | 3 +--
 net/netfilter/ipvs/ip_vs_pe.c    | 3 +--
 net/netfilter/ipvs/ip_vs_sched.c | 3 +--
 net/netfilter/ipvs/ip_vs_sync.c  | 3 +--
 net/netfilter/nf_tables_api.c    | 3 +--
 5 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index fd3f444..7c5e40a 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -465,8 +465,7 @@ __ip_vs_bind_svc(struct ip_vs_dest *dest, struct ip_vs_service *svc)
 
 static void ip_vs_service_free(struct ip_vs_service *svc)
 {
-	if (svc->stats.cpustats)
-		free_percpu(svc->stats.cpustats);
+	free_percpu(svc->stats.cpustats);
 	kfree(svc);
 }
 
diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
index 1a82b29..0df17ca 100644
--- a/net/netfilter/ipvs/ip_vs_pe.c
+++ b/net/netfilter/ipvs/ip_vs_pe.c
@@ -37,8 +37,7 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
 			rcu_read_unlock();
 			return pe;
 		}
-		if (pe->module)
-			module_put(pe->module);
+		module_put(pe->module);
 	}
 	rcu_read_unlock();
 
diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c
index 4dbcda6..199760c 100644
--- a/net/netfilter/ipvs/ip_vs_sched.c
+++ b/net/netfilter/ipvs/ip_vs_sched.c
@@ -104,8 +104,7 @@ static struct ip_vs_scheduler *ip_vs_sched_getbyname(const char *sched_name)
 			mutex_unlock(&ip_vs_sched_mutex);
 			return sched;
 		}
-		if (sched->module)
-			module_put(sched->module);
+		module_put(sched->module);
 	}
 
 	mutex_unlock(&ip_vs_sched_mutex);
diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index eadffb2..cafe28d 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -820,8 +820,7 @@ ip_vs_conn_fill_param_sync(struct net *net, int af, union ip_vs_sync_conn *sc,
 
 		p->pe_data = kmemdup(pe_data, pe_data_len, GFP_ATOMIC);
 		if (!p->pe_data) {
-			if (p->pe->module)
-				module_put(p->pe->module);
+			module_put(p->pe->module);
 			return -ENOMEM;
 		}
 		p->pe_data_len = pe_data_len;
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index deeb95f..b115f54 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3472,8 +3472,7 @@ static int nf_tables_abort(struct sk_buff *skb)
 			break;
 		case NFT_MSG_NEWCHAIN:
 			if (nft_trans_chain_update(trans)) {
-				if (nft_trans_chain_stats(trans))
-					free_percpu(nft_trans_chain_stats(trans));
+				free_percpu(nft_trans_chain_stats(trans));
 
 				nft_trans_destroy(trans);
 			} else {
-- 
2.1.3

Re: [PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[Pablo Neira Ayuso]

On Tue, Nov 18, 2014 at 08:47:31PM +0100, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Tue, 18 Nov 2014 20:37:05 +0100
> 
> The functions free_percpu() and module_put() test whether their argument
> is NULL and then return immediately. Thus the test around the call is
> not needed.

@IPVS folks: Since this involves a nf_tables specific chunk, ack your
chunks and I'll put this into nf-next to speed up things.

Thanks.

> This issue was detected by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c   | 3 +--
>  net/netfilter/ipvs/ip_vs_pe.c    | 3 +--
>  net/netfilter/ipvs/ip_vs_sched.c | 3 +--
>  net/netfilter/ipvs/ip_vs_sync.c  | 3 +--
>  net/netfilter/nf_tables_api.c    | 3 +--
>  5 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index fd3f444..7c5e40a 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -465,8 +465,7 @@ __ip_vs_bind_svc(struct ip_vs_dest *dest, struct ip_vs_service *svc)
>  
>  static void ip_vs_service_free(struct ip_vs_service *svc)
>  {
> -	if (svc->stats.cpustats)
> -		free_percpu(svc->stats.cpustats);
> +	free_percpu(svc->stats.cpustats);
>  	kfree(svc);
>  }
>  
> diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
> index 1a82b29..0df17ca 100644
> --- a/net/netfilter/ipvs/ip_vs_pe.c
> +++ b/net/netfilter/ipvs/ip_vs_pe.c
> @@ -37,8 +37,7 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
>  			rcu_read_unlock();
>  			return pe;
>  		}
> -		if (pe->module)
> -			module_put(pe->module);
> +		module_put(pe->module);
>  	}
>  	rcu_read_unlock();
>  
> diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c
> index 4dbcda6..199760c 100644
> --- a/net/netfilter/ipvs/ip_vs_sched.c
> +++ b/net/netfilter/ipvs/ip_vs_sched.c
> @@ -104,8 +104,7 @@ static struct ip_vs_scheduler *ip_vs_sched_getbyname(const char *sched_name)
>  			mutex_unlock(&ip_vs_sched_mutex);
>  			return sched;
>  		}
> -		if (sched->module)
> -			module_put(sched->module);
> +		module_put(sched->module);
>  	}
>  
>  	mutex_unlock(&ip_vs_sched_mutex);
> diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
> index eadffb2..cafe28d 100644
> --- a/net/netfilter/ipvs/ip_vs_sync.c
> +++ b/net/netfilter/ipvs/ip_vs_sync.c
> @@ -820,8 +820,7 @@ ip_vs_conn_fill_param_sync(struct net *net, int af, union ip_vs_sync_conn *sc,
>  
>  		p->pe_data = kmemdup(pe_data, pe_data_len, GFP_ATOMIC);
>  		if (!p->pe_data) {
> -			if (p->pe->module)
> -				module_put(p->pe->module);
> +			module_put(p->pe->module);
>  			return -ENOMEM;
>  		}
>  		p->pe_data_len = pe_data_len;
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index deeb95f..b115f54 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -3472,8 +3472,7 @@ static int nf_tables_abort(struct sk_buff *skb)
>  			break;
>  		case NFT_MSG_NEWCHAIN:
>  			if (nft_trans_chain_update(trans)) {
> -				if (nft_trans_chain_stats(trans))
> -					free_percpu(nft_trans_chain_stats(trans));
> +				free_percpu(nft_trans_chain_stats(trans));
>  
>  				nft_trans_destroy(trans);
>  			} else {
> -- 
> 2.1.3
> 

Re: [PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[Julian Anastasov]

	Hello,

On Tue, 18 Nov 2014, SF Markus Elfring wrote:

> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Tue, 18 Nov 2014 20:37:05 +0100
> 
> The functions free_percpu() and module_put() test whether their argument
> is NULL and then return immediately. Thus the test around the call is
> not needed.
> 
> This issue was detected by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>

	Pablo, the IPVS parts look ok to me,

Acked-by: Julian Anastasov <ja@ssi.bg>

> ---
>  net/netfilter/ipvs/ip_vs_ctl.c   | 3 +--
>  net/netfilter/ipvs/ip_vs_pe.c    | 3 +--
>  net/netfilter/ipvs/ip_vs_sched.c | 3 +--
>  net/netfilter/ipvs/ip_vs_sync.c  | 3 +--
>  net/netfilter/nf_tables_api.c    | 3 +--
>  5 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index fd3f444..7c5e40a 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -465,8 +465,7 @@ __ip_vs_bind_svc(struct ip_vs_dest *dest, struct ip_vs_service *svc)
>  
>  static void ip_vs_service_free(struct ip_vs_service *svc)
>  {
> -	if (svc->stats.cpustats)
> -		free_percpu(svc->stats.cpustats);
> +	free_percpu(svc->stats.cpustats);
>  	kfree(svc);
>  }
>  
> diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
> index 1a82b29..0df17ca 100644
> --- a/net/netfilter/ipvs/ip_vs_pe.c
> +++ b/net/netfilter/ipvs/ip_vs_pe.c
> @@ -37,8 +37,7 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
>  			rcu_read_unlock();
>  			return pe;
>  		}
> -		if (pe->module)
> -			module_put(pe->module);
> +		module_put(pe->module);
>  	}
>  	rcu_read_unlock();
>  
> diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c
> index 4dbcda6..199760c 100644
> --- a/net/netfilter/ipvs/ip_vs_sched.c
> +++ b/net/netfilter/ipvs/ip_vs_sched.c
> @@ -104,8 +104,7 @@ static struct ip_vs_scheduler *ip_vs_sched_getbyname(const char *sched_name)
>  			mutex_unlock(&ip_vs_sched_mutex);
>  			return sched;
>  		}
> -		if (sched->module)
> -			module_put(sched->module);
> +		module_put(sched->module);
>  	}
>  
>  	mutex_unlock(&ip_vs_sched_mutex);
> diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
> index eadffb2..cafe28d 100644
> --- a/net/netfilter/ipvs/ip_vs_sync.c
> +++ b/net/netfilter/ipvs/ip_vs_sync.c
> @@ -820,8 +820,7 @@ ip_vs_conn_fill_param_sync(struct net *net, int af, union ip_vs_sync_conn *sc,
>  
>  		p->pe_data = kmemdup(pe_data, pe_data_len, GFP_ATOMIC);
>  		if (!p->pe_data) {
> -			if (p->pe->module)
> -				module_put(p->pe->module);
> +			module_put(p->pe->module);
>  			return -ENOMEM;
>  		}
>  		p->pe_data_len = pe_data_len;
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index deeb95f..b115f54 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -3472,8 +3472,7 @@ static int nf_tables_abort(struct sk_buff *skb)
>  			break;
>  		case NFT_MSG_NEWCHAIN:
>  			if (nft_trans_chain_update(trans)) {
> -				if (nft_trans_chain_stats(trans))
> -					free_percpu(nft_trans_chain_stats(trans));
> +				free_percpu(nft_trans_chain_stats(trans));
>  
>  				nft_trans_destroy(trans);
>  			} else {
> -- 
> 2.1.3

Regards

--
Julian Anastasov <ja@ssi.bg>

Re: [PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[Simon Horman]

On Thu, Nov 20, 2014 at 12:26:56AM +0200, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Tue, 18 Nov 2014, SF Markus Elfring wrote:
> 
> > From: Markus Elfring <elfring@users.sourceforge.net>
> > Date: Tue, 18 Nov 2014 20:37:05 +0100
> > 
> > The functions free_percpu() and module_put() test whether their argument
> > is NULL and then return immediately. Thus the test around the call is
> > not needed.
> > 
> > This issue was detected by using the Coccinelle software.
> > 
> > Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> 
> 	Pablo, the IPVS parts look ok to me,
> 
> Acked-by: Julian Anastasov <ja@ssi.bg>

Acked-by: Simon Horman <horms@verge.net.au>

> 
> > ---
> >  net/netfilter/ipvs/ip_vs_ctl.c   | 3 +--
> >  net/netfilter/ipvs/ip_vs_pe.c    | 3 +--
> >  net/netfilter/ipvs/ip_vs_sched.c | 3 +--
> >  net/netfilter/ipvs/ip_vs_sync.c  | 3 +--
> >  net/netfilter/nf_tables_api.c    | 3 +--
> >  5 files changed, 5 insertions(+), 10 deletions(-)
> > 
> > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> > index fd3f444..7c5e40a 100644
> > --- a/net/netfilter/ipvs/ip_vs_ctl.c
> > +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> > @@ -465,8 +465,7 @@ __ip_vs_bind_svc(struct ip_vs_dest *dest, struct ip_vs_service *svc)
> >  
> >  static void ip_vs_service_free(struct ip_vs_service *svc)
> >  {
> > -	if (svc->stats.cpustats)
> > -		free_percpu(svc->stats.cpustats);
> > +	free_percpu(svc->stats.cpustats);
> >  	kfree(svc);
> >  }
> >  
> > diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
> > index 1a82b29..0df17ca 100644
> > --- a/net/netfilter/ipvs/ip_vs_pe.c
> > +++ b/net/netfilter/ipvs/ip_vs_pe.c
> > @@ -37,8 +37,7 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
> >  			rcu_read_unlock();
> >  			return pe;
> >  		}
> > -		if (pe->module)
> > -			module_put(pe->module);
> > +		module_put(pe->module);
> >  	}
> >  	rcu_read_unlock();
> >  
> > diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c
> > index 4dbcda6..199760c 100644
> > --- a/net/netfilter/ipvs/ip_vs_sched.c
> > +++ b/net/netfilter/ipvs/ip_vs_sched.c
> > @@ -104,8 +104,7 @@ static struct ip_vs_scheduler *ip_vs_sched_getbyname(const char *sched_name)
> >  			mutex_unlock(&ip_vs_sched_mutex);
> >  			return sched;
> >  		}
> > -		if (sched->module)
> > -			module_put(sched->module);
> > +		module_put(sched->module);
> >  	}
> >  
> >  	mutex_unlock(&ip_vs_sched_mutex);
> > diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
> > index eadffb2..cafe28d 100644
> > --- a/net/netfilter/ipvs/ip_vs_sync.c
> > +++ b/net/netfilter/ipvs/ip_vs_sync.c
> > @@ -820,8 +820,7 @@ ip_vs_conn_fill_param_sync(struct net *net, int af, union ip_vs_sync_conn *sc,
> >  
> >  		p->pe_data = kmemdup(pe_data, pe_data_len, GFP_ATOMIC);
> >  		if (!p->pe_data) {
> > -			if (p->pe->module)
> > -				module_put(p->pe->module);
> > +			module_put(p->pe->module);
> >  			return -ENOMEM;
> >  		}
> >  		p->pe_data_len = pe_data_len;
> > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > index deeb95f..b115f54 100644
> > --- a/net/netfilter/nf_tables_api.c
> > +++ b/net/netfilter/nf_tables_api.c
> > @@ -3472,8 +3472,7 @@ static int nf_tables_abort(struct sk_buff *skb)
> >  			break;
> >  		case NFT_MSG_NEWCHAIN:
> >  			if (nft_trans_chain_update(trans)) {
> > -				if (nft_trans_chain_stats(trans))
> > -					free_percpu(nft_trans_chain_stats(trans));
> > +				free_percpu(nft_trans_chain_stats(trans));
> >  
> >  				nft_trans_destroy(trans);
> >  			} else {
> > -- 
> > 2.1.3
> 
> Regards
> 
> --
> Julian Anastasov <ja@ssi.bg>
> 

Re: [PATCH 1/1] netfilter: Deletion of unnecessary checks before two function calls

[Pablo Neira Ayuso]

On Thu, Nov 20, 2014 at 10:13:59AM +0900, Simon Horman wrote:
> On Thu, Nov 20, 2014 at 12:26:56AM +0200, Julian Anastasov wrote:
> > 
> > 	Hello,
> > 
> > On Tue, 18 Nov 2014, SF Markus Elfring wrote:
> > 
> > > From: Markus Elfring <elfring@users.sourceforge.net>
> > > Date: Tue, 18 Nov 2014 20:37:05 +0100
> > > 
> > > The functions free_percpu() and module_put() test whether their argument
> > > is NULL and then return immediately. Thus the test around the call is
> > > not needed.
> > > 
> > > This issue was detected by using the Coccinelle software.
> > > 
> > > Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> > 
> > 	Pablo, the IPVS parts look ok to me,
> > 
> > Acked-by: Julian Anastasov <ja@ssi.bg>
> 
> Acked-by: Simon Horman <horms@verge.net.au>

Applied, thanks.

[PATCH] net-ipvs: Delete an unnecessary check before the function call "module_put"

[SF Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Thu, 2 Jul 2015 17:00:14 +0200

The module_put() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 net/netfilter/ipvs/ip_vs_sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c
index 199760c..e50221b 100644
--- a/net/netfilter/ipvs/ip_vs_sched.c
+++ b/net/netfilter/ipvs/ip_vs_sched.c
@@ -137,7 +137,7 @@ struct ip_vs_scheduler *ip_vs_scheduler_get(const char *sched_name)
 
 void ip_vs_scheduler_put(struct ip_vs_scheduler *scheduler)
 {
-	if (scheduler && scheduler->module)
+	if (scheduler)
 		module_put(scheduler->module);
 }
 
-- 
2.4.5

Re: [PATCH] net-ipvs: Delete an unnecessary check before the function call "module_put"

[Simon Horman]

On Thu, Jul 02, 2015 at 05:10:41PM +0200, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Thu, 2 Jul 2015 17:00:14 +0200
> 
> The module_put() function tests whether its argument is NULL and then
> returns immediately. Thus the test around the call is not needed.
> 
> This issue was detected by using the Coccinelle software.

Thanks, applied to ipvs-next for v4.3.

[PATCH] net-ipv6: Delete unnecessary checks before the function call "kfree_skb"

[SF Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Sat, 14 Nov 2015 19:55:00 +0100

The kfree_skb() function tests whether its argument is NULL and then
returns immediately. Thus the test around the calls is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 net/ipv6/af_inet6.c                     | 7 ++-----
 net/ipv6/netfilter/nf_conntrack_reasm.c | 3 +--
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 44bb66b..4cd9259 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -416,12 +416,9 @@ void inet6_destroy_sock(struct sock *sk)
 	/* Release rx options */
 
 	skb = xchg(&np->pktoptions, NULL);
-	if (skb)
-		kfree_skb(skb);
-
+	kfree_skb(skb);
 	skb = xchg(&np->rxpmtu, NULL);
-	if (skb)
-		kfree_skb(skb);
+	kfree_skb(skb);
 
 	/* Free flowlabels */
 	fl6_free_socklist(sk);
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index d5efeb8..dbc013b 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -172,8 +172,7 @@ static unsigned int nf_hashfn(const struct inet_frag_queue *q)
 
 static void nf_skb_free(struct sk_buff *skb)
 {
-	if (NFCT_FRAG6_CB(skb)->orig)
-		kfree_skb(NFCT_FRAG6_CB(skb)->orig);
+	kfree_skb(NFCT_FRAG6_CB(skb)->orig);
 }
 
 static void nf_ct_frag6_expire(unsigned long data)
-- 
2.6.2

Re: [PATCH] net-ipv6: Delete unnecessary checks before the function call "kfree_skb"

[Eric Dumazet]

On Sat, 2015-11-14 at 20:05 +0100, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Sat, 14 Nov 2015 19:55:00 +0100
> 
> The kfree_skb() function tests whether its argument is NULL and then
> returns immediately. Thus the test around the calls is not needed.
> 
> This issue was detected by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  net/ipv6/af_inet6.c                     | 7 ++-----
>  net/ipv6/netfilter/nf_conntrack_reasm.c | 3 +--
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index 44bb66b..4cd9259 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -416,12 +416,9 @@ void inet6_destroy_sock(struct sock *sk)
>  	/* Release rx options */
>  
>  	skb = xchg(&np->pktoptions, NULL);
> -	if (skb)
> -		kfree_skb(skb);
> -
> +	kfree_skb(skb);
>  	skb = xchg(&np->rxpmtu, NULL);
> -	if (skb)
> -		kfree_skb(skb);
> +	kfree_skb(skb);
>  

There is no 'issue' here, or not this one.

In most cases, these pointers are NULL, so the test can be predicted by
the processor.

While if the test is done in kfree_skb(), the branch predictor of the
cpu wont be able to predict things.

By feeding too many NULL pointers to kfree_skb(), we slow down it.

Branch misses and hits were considered important years ago...

But seeing this inet6_destroy_sock() is (ab)using xchg() three times, I
am not sure author cared that much about performance.

Re: net-ipv6: Delete unnecessary checks before the function call "kfree_skb"

[SF Markus Elfring]

> While if the test is done in kfree_skb(), the branch predictor of the
> cpu wont be able to predict things.
> 
> By feeding too many NULL pointers to kfree_skb(), we slow down it.

Would it make sense to annotate checks before such function calls
as "UNLIKELY"?

Regards,
Markus