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net: Make ifindex generation per-net namespace 

Strictly speaking this is only _really_ required for checkpoint-restore to
make loopback device always have the same index.

This change appears to be safe wrt "ifindex should be unique per-system"
concept, as all the ifindex usage is either already made per net namespace
of is explicitly limited with init_net only.

There are two cool side effects of this. The first one -- ifindices of
devices in container are always small, regardless of how many containers
we've started (and re-started) so far. The second one is -- we can speed
up the loopback ifidex access as shown in the next patch.

v2: Place ifindex right after dev_base_seq : avoid two holes and use the
    same cache line, dirtied in list_netdevice()/unlist_netdevice()

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pavel Emelyanov 2012-08-08 21:53:19 +00:00 committed by David S. Miller
parent e6f8f1a739
commit aa79e66eee
2 changed files with 3 additions and 2 deletions
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1
include/net/net_namespace.h
View File

@ -66,6 +66,7 @@ struct net {
struct hlist_head *dev_name_head;
struct hlist_head *dev_index_head;
unsigned int dev_base_seq; /* protected by rtnl_mutex */
int ifindex;
/* core fib_rules */
struct list_head rules_ops;

4
net/core/dev.c
View File

@ -5221,12 +5221,12 @@ int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
*/
static int dev_new_index(struct net *net)
{
static int ifindex;
int ifindex = net->ifindex;
for (;;) {
if (++ifindex <= 0)
ifindex = 1;
if (!__dev_get_by_index(net, ifindex))
return ifindex;
return net->ifindex = ifindex;
}
}