Patchwork net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()

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Submitter Eric Dumazet
Date Dec. 5, 2010, 11:23 a.m.
Message ID <1291548233.2806.212.camel@edumazet-laptop>
Download mbox | patch
Permalink /patch/74293/
State Accepted
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - Dec. 5, 2010, 11:23 a.m.
Le dimanche 05 décembre 2010 à 09:19 +0100, Eric Dumazet a écrit :

> Hmm..
> 
> If somebody can explain why RTNL is held in arp_ioctl() (and therefore
> in arp_req_delete()), we might first remove RTNL use in arp_ioctl() so
> that your patch can be applied.
> 
> Right now it is not good, because RTNL wont be necessarly held when you
> are going to call arp_invalidate() ?

While doing this analysis, I found a refcount bug in llc, I'll send a
patch for net-2.6

Meanwhile, here is the patch for net-next-2.6

Your patch then can be applied after mine.

Thanks

[PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()

dev_getbyhwaddr() was called under RTNL.

Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
RCU locking instead of RTNL.

Change arp_ioctl() to use RCU instead of RTNL locking.

Note: this fix a dev refcount bug in llc

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 include/linux/netdevice.h      |    3 ++-
 net/core/dev.c                 |   17 +++++++----------
 net/ieee802154/af_ieee802154.c |    6 +++---
 net/ipv4/arp.c                 |   17 +++++++++--------
 net/llc/af_llc.c               |   11 ++++++-----
 5 files changed, 27 insertions(+), 27 deletions(-)



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David Miller - Dec. 8, 2010, 6:05 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sun, 05 Dec 2010 12:23:53 +0100

> [PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
> 
> dev_getbyhwaddr() was called under RTNL.
> 
> Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
> RCU locking instead of RTNL.
> 
> Change arp_ioctl() to use RCU instead of RTNL locking.
> 
> Note: this fix a dev refcount bug in llc
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied, thanks Eric.
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Eric Dumazet - Dec. 8, 2010, 6:07 p.m.
Le mercredi 08 décembre 2010 à 10:05 -0800, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Sun, 05 Dec 2010 12:23:53 +0100
> 
> > [PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
> > 
> > dev_getbyhwaddr() was called under RTNL.
> > 
> > Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
> > RCU locking instead of RTNL.
> > 
> > Change arp_ioctl() to use RCU instead of RTNL locking.
> > 
> > Note: this fix a dev refcount bug in llc
> > 
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> 
> Applied, thanks Eric.

Hmm, dont you want I resubmit it after the "llc: fix a device refcount
imbalance" patch pulled from net-2.6 ?

Sorry for the mess...


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David Miller - Dec. 8, 2010, 6:10 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 08 Dec 2010 19:07:34 +0100

> Le mercredi 08 décembre 2010 à 10:05 -0800, David Miller a écrit :
>> From: Eric Dumazet <eric.dumazet@gmail.com>
>> Date: Sun, 05 Dec 2010 12:23:53 +0100
>> 
>> > [PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
>> > 
>> > dev_getbyhwaddr() was called under RTNL.
>> > 
>> > Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
>> > RCU locking instead of RTNL.
>> > 
>> > Change arp_ioctl() to use RCU instead of RTNL locking.
>> > 
>> > Note: this fix a dev refcount bug in llc
>> > 
>> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
>> 
>> Applied, thanks Eric.
> 
> Hmm, dont you want I resubmit it after the "llc: fix a device refcount
> imbalance" patch pulled from net-2.6 ?
> 
> Sorry for the mess...

I know about the conflict and will resolve it when I do a merge in
the next hour or so.

Don't worry about this.
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Eric Dumazet - Dec. 8, 2010, 6:11 p.m.
Le mercredi 08 décembre 2010 à 10:10 -0800, David Miller a écrit :

> I know about the conflict and will resolve it when I do a merge in
> the next hour or so.
> 
> Don't worry about this.

Ah thats great, thanks !



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Patch

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a9ac5dc..d31bc3c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1360,7 +1360,8 @@  static inline struct net_device *first_net_device(struct net *net)
 
 extern int 			netdev_boot_setup_check(struct net_device *dev);
 extern unsigned long		netdev_boot_base(const char *prefix, int unit);
-extern struct net_device    *dev_getbyhwaddr(struct net *net, unsigned short type, char *hwaddr);
+extern struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
+					      const char *hwaddr);
 extern struct net_device *dev_getfirstbyhwtype(struct net *net, unsigned short type);
 extern struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type);
 extern void		dev_add_pack(struct packet_type *pt);
diff --git a/net/core/dev.c b/net/core/dev.c
index cd24374..8630142 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -743,34 +743,31 @@  struct net_device *dev_get_by_index(struct net *net, int ifindex)
 EXPORT_SYMBOL(dev_get_by_index);
 
 /**
- *	dev_getbyhwaddr - find a device by its hardware address
+ *	dev_getbyhwaddr_rcu - find a device by its hardware address
  *	@net: the applicable net namespace
  *	@type: media type of device
  *	@ha: hardware address
  *
  *	Search for an interface by MAC address. Returns NULL if the device
- *	is not found or a pointer to the device. The caller must hold the
- *	rtnl semaphore. The returned device has not had its ref count increased
+ *	is not found or a pointer to the device. The caller must hold RCU
+ *	The returned device has not had its ref count increased
  *	and the caller must therefore be careful about locking
  *
- *	BUGS:
- *	If the API was consistent this would be __dev_get_by_hwaddr
  */
 
-struct net_device *dev_getbyhwaddr(struct net *net, unsigned short type, char *ha)
+struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
+				       const char *ha)
 {
 	struct net_device *dev;
 
-	ASSERT_RTNL();
-
-	for_each_netdev(net, dev)
+	for_each_netdev_rcu(net, dev)
 		if (dev->type == type &&
 		    !memcmp(dev->dev_addr, ha, dev->addr_len))
 			return dev;
 
 	return NULL;
 }
-EXPORT_SYMBOL(dev_getbyhwaddr);
+EXPORT_SYMBOL(dev_getbyhwaddr_rcu);
 
 struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type)
 {
diff --git a/net/ieee802154/af_ieee802154.c b/net/ieee802154/af_ieee802154.c
index 93c91b6..6df6ecf 100644
--- a/net/ieee802154/af_ieee802154.c
+++ b/net/ieee802154/af_ieee802154.c
@@ -52,11 +52,11 @@  struct net_device *ieee802154_get_dev(struct net *net,
 
 	switch (addr->addr_type) {
 	case IEEE802154_ADDR_LONG:
-		rtnl_lock();
-		dev = dev_getbyhwaddr(net, ARPHRD_IEEE802154, addr->hwaddr);
+		rcu_read_lock();
+		dev = dev_getbyhwaddr_rcu(net, ARPHRD_IEEE802154, addr->hwaddr);
 		if (dev)
 			dev_hold(dev);
-		rtnl_unlock();
+		rcu_read_unlock();
 		break;
 	case IEEE802154_ADDR_SHORT:
 		if (addr->pan_id == 0xffff ||
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 7833f17..ec0966f 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1017,13 +1017,14 @@  static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
 		IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
 		return 0;
 	}
-	if (__in_dev_get_rtnl(dev)) {
-		IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
+	if (__in_dev_get_rcu(dev)) {
+		IN_DEV_CONF_SET(__in_dev_get_rcu(dev), PROXY_ARP, on);
 		return 0;
 	}
 	return -ENXIO;
 }
 
+/* must be called with rcu_read_lock() */
 static int arp_req_set_public(struct net *net, struct arpreq *r,
 		struct net_device *dev)
 {
@@ -1033,7 +1034,7 @@  static int arp_req_set_public(struct net *net, struct arpreq *r,
 	if (mask && mask != htonl(0xFFFFFFFF))
 		return -EINVAL;
 	if (!dev && (r->arp_flags & ATF_COM)) {
-		dev = dev_getbyhwaddr(net, r->arp_ha.sa_family,
+		dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
 				      r->arp_ha.sa_data);
 		if (!dev)
 			return -ENODEV;
@@ -1225,10 +1226,10 @@  int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 	if (!(r.arp_flags & ATF_NETMASK))
 		((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
 							   htonl(0xFFFFFFFFUL);
-	rtnl_lock();
+	rcu_read_lock();
 	if (r.arp_dev[0]) {
 		err = -ENODEV;
-		dev = __dev_get_by_name(net, r.arp_dev);
+		dev = dev_get_by_name_rcu(net, r.arp_dev);
 		if (dev == NULL)
 			goto out;
 
@@ -1252,12 +1253,12 @@  int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 		break;
 	case SIOCGARP:
 		err = arp_req_get(&r, dev);
-		if (!err && copy_to_user(arg, &r, sizeof(r)))
-			err = -EFAULT;
 		break;
 	}
 out:
-	rtnl_unlock();
+	rcu_read_unlock();
+	if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
+		err = -EFAULT;
 	return err;
 }
 
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 5826129..dfd3a64 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -316,9 +316,9 @@  static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
 	if (unlikely(addr->sllc_family != AF_LLC))
 		goto out;
 	rc = -ENODEV;
-	rtnl_lock();
+	rcu_read_lock();
 	if (sk->sk_bound_dev_if) {
-		llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
+		llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
 		if (llc->dev) {
 			if (!addr->sllc_arphrd)
 				addr->sllc_arphrd = llc->dev->type;
@@ -329,14 +329,15 @@  static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
 			    !llc_mac_match(addr->sllc_mac,
 					   llc->dev->dev_addr)) {
 				rc = -EINVAL;
-				dev_put(llc->dev);
 				llc->dev = NULL;
 			}
 		}
 	} else
-		llc->dev = dev_getbyhwaddr(&init_net, addr->sllc_arphrd,
+		llc->dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
 					   addr->sllc_mac);
-	rtnl_unlock();
+	if (llc->dev)
+		dev_hold(llc->dev);
+	rcu_read_unlock();
 	if (!llc->dev)
 		goto out;
 	if (!addr->sllc_sap) {