Pavel Emelyanov dec827d174 [NETNS]: The generic per-net pointers.
Add the elastic array of void * pointer to the struct net.
The access rules are simple:

 1. register the ops with register_pernet_gen_device to get
    the id of your private pointer
 2. call net_assign_generic() to put the private data on the
    struct net (most preferably this should be done in the
    ->init callback of the ops registered)
 3. do not store any private reference on the net_generic array;
 4. do not change this pointer while the net is alive;
 5. use the net_generic() to get the pointer.

When adding a new pointer, I copy the old array, replace it
with a new one and schedule the old for kfree after an RCU
grace period.

Since the net_generic explores the net->gen array inside rcu
read section and once set the net->gen->ptr[x] pointer never 
changes, this grants us a safe access to generic pointers.

Quoting Paul: "... RCU is protecting -only- the net_generic 
structure that net_generic() is traversing, and the [pointer]
returned by net_generic() is protected by a reference counter 
in the upper-level struct net."

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-04-15 00:36:08 -07:00
..
2008-02-06 19:25:06 -06:00
2007-10-10 16:53:11 -07:00
2006-12-02 21:22:55 -08:00
2007-10-10 16:53:56 -07:00
2008-03-27 17:53:31 -07:00
2008-01-28 15:01:08 -08:00
2008-04-12 13:43:18 +09:00
2008-02-29 11:46:17 -08:00
2008-03-28 16:28:36 -07:00
2008-04-12 13:43:18 +09:00
2008-01-28 15:11:09 -08:00
2007-10-07 23:44:17 -07:00
2008-04-10 01:43:09 -07:00