[NETNS]: The net-subsys IDs generator.

To make some per-net generic pointers, we need some way to address
them, i.e. - IDs. This is simple IDA-based IDs generator for pernet
subsystems.

Addressing questions about potential checkpoint/restart problems:
these IDs are "lite-offsets" within the net structure and are by no
means supposed to be exported to the userspace.

Since it will be used in the nearest future by devices only (tun,
vlan, tunnels, bridge, etc), I make it resemble the functionality
of register_pernet_device().

The new ids is stored in the *id pointer _before_ calling the init
callback to make this id available in this callback.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index e2aee2689abe1dd8647611746382c2152d55476f..72fad1a0956b86c5502bb85dc634a79cd6dbf46b 100644 (file)
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -185,6 +185,8 @@ extern int register_pernet_subsys(struct pernet_operations *);
 extern void unregister_pernet_subsys(struct pernet_operations *);
 extern int register_pernet_device(struct pernet_operations *);
 extern void unregister_pernet_device(struct pernet_operations *);
+extern int register_pernet_gen_device(int *id, struct pernet_operations *);
+extern void unregister_pernet_gen_device(int id, struct pernet_operations *);
 
 struct ctl_path;
 struct ctl_table;

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 7b660834a4c207a08b23ff6f63fa8ae719ca4fba..2197d51aef3bfed67c29d14bcd1e16120fa28510 100644 (file)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -5,6 +5,7 @@
 #include <linux/list.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
+#include <linux/idr.h>
 #include <net/net_namespace.h>
 
 /*
@@ -253,6 +254,8 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
 }
 #endif
 
+static DEFINE_IDA(net_generic_ids);
+
 /**
  *      register_pernet_subsys - register a network namespace subsystem
  *     @ops:  pernet operations structure for the subsystem
@@ -330,6 +333,30 @@ int register_pernet_device(struct pernet_operations *ops)
 }
 EXPORT_SYMBOL_GPL(register_pernet_device);
 
+int register_pernet_gen_device(int *id, struct pernet_operations *ops)
+{
+       int error;
+       mutex_lock(&net_mutex);
+again:
+       error = ida_get_new_above(&net_generic_ids, 1, id);
+       if (error) {
+               if (error == -EAGAIN) {
+                       ida_pre_get(&net_generic_ids, GFP_KERNEL);
+                       goto again;
+               }
+               goto out;
+       }
+       error = register_pernet_operations(&pernet_list, ops);
+       if (error)
+               ida_remove(&net_generic_ids, *id);
+       else if (first_device == &pernet_list)
+               first_device = &ops->list;
+out:
+       mutex_unlock(&net_mutex);
+       return error;
+}
+EXPORT_SYMBOL_GPL(register_pernet_gen_device);
+
 /**
  *      unregister_pernet_device - unregister a network namespace netdevice
  *     @ops: pernet operations structure to manipulate
@@ -348,3 +375,14 @@ void unregister_pernet_device(struct pernet_operations *ops)
        mutex_unlock(&net_mutex);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_device);
+
+void unregister_pernet_gen_device(int id, struct pernet_operations *ops)
+{
+       mutex_lock(&net_mutex);
+       if (&ops->list == first_device)
+               first_device = first_device->next;
+       unregister_pernet_operations(ops);
+       ida_remove(&net_generic_ids, id);
+       mutex_unlock(&net_mutex);
+}
+EXPORT_SYMBOL_GPL(unregister_pernet_gen_device);