linux-kernel - [PATCH] list_for_each_rcu must die: networking

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Message-ID: <20080515001607.GB20811@linux.vnet.ibm.com>
Date:	Wed, 14 May 2008 17:16:07 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, shemminger@...tta.com,
	linville@...driver.com, sri@...ibm.com, davem@...emloft.net,
	kamalesh@...ux.vnet.ibm.com, adobriyan@...il.com, apw@...dowen.org,
	balbir@...ux.vnet.ibm.com, linuxppc-dev@...abs.org
Subject: [PATCH] list_for_each_rcu must die: networking

All uses of list_for_each_rcu() can be profitably replaced by the
easier-to-use list_for_each_entry_rcu().  This patch makes this change
for networking, in preparation for removing the list_for_each_rcu()
API entirely.

Updated to remove the two now-unused variables as noted by Dave Miller,
and also to fix my bonehead error detected by Kamalesh Babulal and
Alexey Dobriyan.  It now passes LTP on POWER.  And also has valid SOB.
Some days it just doesn't pay to get out of bed...

Acked-by: David S. Miller <davem@...emloft.net> (lkml.org/lkml/2008/4/23/448)
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---

 802/psnap.c     |    4 +---
 ipv4/af_inet.c  |    9 +++------
 ipv6/af_inet6.c |    9 +++------
 3 files changed, 7 insertions(+), 15 deletions(-)

diff -urpNa -X dontdiff linux-2.6.26-rc2/net/802/psnap.c linux-2.6.26-rc2-lfer-net/net/802/psnap.c
--- linux-2.6.26-rc2/net/802/psnap.c	2008-04-16 19:49:44.000000000 -0700
+++ linux-2.6.26-rc2-lfer-net/net/802/psnap.c	2008-05-14 13:38:13.000000000 -0700
@@ -30,11 +30,9 @@ static struct llc_sap *snap_sap;
  */
 static struct datalink_proto *find_snap_client(unsigned char *desc)
 {
-	struct list_head *entry;
 	struct datalink_proto *proto = NULL, *p;
 
-	list_for_each_rcu(entry, &snap_list) {
-		p = list_entry(entry, struct datalink_proto, node);
+	list_for_each_entry_rcu(p, &snap_list, node) {
 		if (!memcmp(p->type, desc, 5)) {
 			proto = p;
 			break;
diff -urpNa -X dontdiff linux-2.6.26-rc2/net/ipv4/af_inet.c linux-2.6.26-rc2-lfer-net/net/ipv4/af_inet.c
--- linux-2.6.26-rc2/net/ipv4/af_inet.c	2008-05-14 13:35:32.000000000 -0700
+++ linux-2.6.26-rc2-lfer-net/net/ipv4/af_inet.c	2008-05-14 13:46:26.000000000 -0700
@@ -267,7 +267,6 @@ static inline int inet_netns_ok(struct n
 static int inet_create(struct net *net, struct socket *sock, int protocol)
 {
 	struct sock *sk;
-	struct list_head *p;
 	struct inet_protosw *answer;
 	struct inet_sock *inet;
 	struct proto *answer_prot;
@@ -284,13 +283,12 @@ static int inet_create(struct net *net, 
 	sock->state = SS_UNCONNECTED;
 
 	/* Look for the requested type/protocol pair. */
-	answer = NULL;
 lookup_protocol:
 	err = -ESOCKTNOSUPPORT;
 	rcu_read_lock();
-	list_for_each_rcu(p, &inetsw[sock->type]) {
-		answer = list_entry(p, struct inet_protosw, list);
+	list_for_each_entry_rcu(answer, &inetsw[sock->type], list) {
 
+		err = 0;
 		/* Check the non-wild match. */
 		if (protocol == answer->protocol) {
 			if (protocol != IPPROTO_IP)
@@ -305,10 +303,9 @@ lookup_protocol:
 				break;
 		}
 		err = -EPROTONOSUPPORT;
-		answer = NULL;
 	}
 
-	if (unlikely(answer == NULL)) {
+	if (unlikely(err)) {
 		if (try_loading_module < 2) {
 			rcu_read_unlock();
 			/*
diff -urpNa -X dontdiff linux-2.6.26-rc2/net/ipv6/af_inet6.c linux-2.6.26-rc2-lfer-net/net/ipv6/af_inet6.c
--- linux-2.6.26-rc2/net/ipv6/af_inet6.c	2008-05-14 13:35:32.000000000 -0700
+++ linux-2.6.26-rc2-lfer-net/net/ipv6/af_inet6.c	2008-05-14 13:45:08.000000000 -0700
@@ -87,7 +87,6 @@ static int inet6_create(struct net *net,
 	struct inet_sock *inet;
 	struct ipv6_pinfo *np;
 	struct sock *sk;
-	struct list_head *p;
 	struct inet_protosw *answer;
 	struct proto *answer_prot;
 	unsigned char answer_flags;
@@ -101,13 +100,12 @@ static int inet6_create(struct net *net,
 		build_ehash_secret();
 
 	/* Look for the requested type/protocol pair. */
-	answer = NULL;
 lookup_protocol:
 	err = -ESOCKTNOSUPPORT;
 	rcu_read_lock();
-	list_for_each_rcu(p, &inetsw6[sock->type]) {
-		answer = list_entry(p, struct inet_protosw, list);
+	list_for_each_entry_rcu(answer, &inetsw6[sock->type], list) {
 
+		err = 0;
 		/* Check the non-wild match. */
 		if (protocol == answer->protocol) {
 			if (protocol != IPPROTO_IP)
@@ -122,10 +120,9 @@ lookup_protocol:
 				break;
 		}
 		err = -EPROTONOSUPPORT;
-		answer = NULL;
 	}
 
-	if (!answer) {
+	if (err) {
 		if (try_loading_module < 2) {
 			rcu_read_unlock();
 			/*
--
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