From dec827d174d7f76c457238800183ca864a639365 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Tue, 15 Apr 2008 00:36:08 -0700 Subject: [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 Acked-by: Paul E. McKenney Signed-off-by: David S. Miller --- include/net/net_namespace.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/net/net_namespace.h') diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index 72fad1a0956b..f880b0f9f107 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -20,6 +20,7 @@ struct proc_dir_entry; struct net_device; struct sock; struct ctl_table_header; +struct net_generic; struct net { atomic_t count; /* To decided when the network @@ -61,6 +62,7 @@ struct net { #ifdef CONFIG_NETFILTER struct netns_xt xt; #endif + struct net_generic *gen; }; -- cgit v1.2.3