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

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 10 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index ee605c0867e7..822b15b8d11c 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)
 {