On Thu, Sep 10, 2015 at 03:35:20PM -0300, Marcelo Ricardo Leitner wrote:
> On Thu, Sep 10, 2015 at 01:24:54PM -0300, Marcelo Ricardo Leitner wrote:
> > On Thu, Sep 10, 2015 at 11:50:06AM -0400, Vlad Yasevich wrote:
> > > On 09/10/2015 10:22 AM, Marcelo Ricardo Leitner wrote:
> > > > Em 10-09-2015 10:24, Vlad Yasevich escreveu:
> > ...
> > > >> Then you can order sctp_net_init() such that it happens first, then
> > > >> protosw registration
> > > >> happens, then control socket initialization happens, then inet
> > > >> protocol registration
> > > >> happens.
> > > >>
> > > >> This way, we are always guaranteed that by the time user calls
> > > >> socket(), protocol
> > > >> defaults are fully initialized.
> > > >
> > > > Okay, that works for module loading stage, but then how would we handle
> > > > new netns's? We
> > > > have to create the control socket per netns and AFAICT sctp_net_init()
> > > > is the only hook
> > > > called when a new netns is being created.
> > > >
> > > > Then if we move it a workqueue that is scheduled by sctp_net_init(), we
> > > > loose the ability
> > > > to handle its errors by propagating through sctp_net_init() return
> > > > value, not good.
> > >
> > > Here is kind of what I had in mind. It's incomplete and completely
> > > untested (not even
> > > compiled), but good enough to describe the idea:
> > ...
> >
> > Ohh, ok now I get it, thanks. If having two pernet_subsys for a given
> > module is fine, that works for me. It's clearer and has no moment of
> > temporary failure.
> >
> > I can finish this patch if everybody agrees with it.
> >
> > > >>> I used the list pointer because that's null as that memory is
> > > >>> entirely zeroed when alloced
> > > >>> and, after initialization, it's never null again. Works like a
> > > >>> lock/condition without
> > > >>> using an extra field.
> > > >>>
> > > >>
> > > >> I understand this a well. What I don't particularly like is that we
> > > >> are re-using
> > > >> a list without really stating why it's now done this way.
> > > >> Additionally, it's not really
> > > >> the last that happens so it's seems kind of hacky... If we need to
> > > >> add new
> > > >> per-net initializers, we now need to make sure that the code is put in
> > > >> the right
> > > >> place. I'd just really like to have a cleaner solution...
> > > >
> > > > Ok, got you. We could add a dedicated flag/bit for that then, if
> > > > reusing the list is not
> > > > clear enough. Or, as we are discussing on the other part of thread, we
> > > > could make it block
> > > > and wait for the initialization, probably using some wait_queue. I'm
> > > > still thinking on
> > > > something this way, likely something more below than sctp then.
> > > >
> > >
> > > I think if we don the above, the second process calling socket() will
> > > either find the
> > > the protosw or will try to load the module also. I think either is ok
> > > after
> > > request_module returns we'll look at the protosw and will find find
> > > things.
> >
> > Seems so, yes. Nice.
>
> I was testing with it, something is not good. I finished your patch and
> testing with a flooder like:
This is the patch I used. Mostly just fixed a few typos and added error
handling.
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 4345790ad326..8930046eaa1b 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1178,7 +1178,7 @@ static void sctp_v4_del_protocol(void)
unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
}
-static int __net_init sctp_net_init(struct net *net)
+static int __net_init sctp_defaults_init(struct net *net)
{
int status;
@@ -1271,12 +1271,6 @@ static int __net_init sctp_net_init(struct net *net)
sctp_dbg_objcnt_init(net);
- /* Initialize the control inode/socket for handling OOTB packets. */
- if ((status = sctp_ctl_sock_init(net))) {
- pr_err("Failed to initialize the SCTP control sock\n");
- goto err_ctl_sock_init;
- }
-
/* Initialize the local address list. */
INIT_LIST_HEAD(&net->sctp.local_addr_list);
spin_lock_init(&net->sctp.local_addr_lock);
@@ -1292,9 +1286,6 @@ static int __net_init sctp_net_init(struct net *net)
return 0;
-err_ctl_sock_init:
- sctp_dbg_objcnt_exit(net);
- sctp_proc_exit(net);
err_init_proc:
cleanup_sctp_mibs(net);
err_init_mibs:
@@ -1303,15 +1294,12 @@ err_sysctl_register:
return status;
}
-static void __net_exit sctp_net_exit(struct net *net)
+static void __net_exit sctp_defaults_exit(struct net *net)
{
/* Free the local address list */
sctp_free_addr_wq(net);
sctp_free_local_addr_list(net);
- /* Free the control endpoint. */
- inet_ctl_sock_destroy(net->sctp.ctl_sock);
-
sctp_dbg_objcnt_exit(net);
sctp_proc_exit(net);
@@ -1319,9 +1307,32 @@ static void __net_exit sctp_net_exit(struct net *net)
sctp_sysctl_net_unregister(net);
}
-static struct pernet_operations sctp_net_ops = {
- .init = sctp_net_init,
- .exit = sctp_net_exit,
+static struct pernet_operations sctp_defaults_ops = {
+ .init = sctp_defaults_init,
+ .exit = sctp_defaults_exit,
+};
+
+static int __net_init sctp_ctrlsock_init(struct net *net)
+{
+ int status;
+
+ /* Initialize the control inode/socket for handling OOTB packets. */
+ status = sctp_ctl_sock_init(net);
+ if (status)
+ pr_err("Failed to initialize the SCTP control sock\n");
+
+ return status;
+}
+
+static void __net_init sctp_ctrlsock_exit(struct net *net)
+{
+ /* Free the control endpoint. */
+ inet_ctl_sock_destroy(net->sctp.ctl_sock);
+}
+
+static struct pernet_operations sctp_ctrlsock_ops = {
+ .init = sctp_ctrlsock_init,
+ .exit = sctp_ctrlsock_exit,
};
/* Initialize the universe into something sensible. */
@@ -1454,8 +1465,11 @@ static __init int sctp_init(void)
sctp_v4_pf_init();
sctp_v6_pf_init();
- status = sctp_v4_protosw_init();
+ status = register_pernet_subsys(&sctp_defaults_ops);
+ if (status)
+ goto err_register_defaults;
+ status = sctp_v4_protosw_init();
if (status)
goto err_protosw_init;
@@ -1463,9 +1477,9 @@ static __init int sctp_init(void)
if (status)
goto err_v6_protosw_init;
- status = register_pernet_subsys(&sctp_net_ops);
+ status = register_pernet_subsys(&sctp_ctrlsock_ops);
if (status)
- goto err_register_pernet_subsys;
+ goto err_register_ctrlsock;
status = sctp_v4_add_protocol();
if (status)
@@ -1481,12 +1495,14 @@ out:
err_v6_add_protocol:
sctp_v4_del_protocol();
err_add_protocol:
- unregister_pernet_subsys(&sctp_net_ops);
-err_register_pernet_subsys:
+ unregister_pernet_subsys(&sctp_ctrlsock_ops);
+err_register_ctrlsock:
sctp_v6_protosw_exit();
err_v6_protosw_init:
sctp_v4_protosw_exit();
err_protosw_init:
+ unregister_pernet_subsys(&sctp_defaults_ops);
+err_register_defaults:
sctp_v4_pf_exit();
sctp_v6_pf_exit();
sctp_sysctl_unregister();
@@ -1519,12 +1535,14 @@ static __exit void sctp_exit(void)
sctp_v6_del_protocol();
sctp_v4_del_protocol();
- unregister_pernet_subsys(&sctp_net_ops);
+ unregister_pernet_subsys(&sctp_ctrlsock_ops);
/* Free protosw registrations */
sctp_v6_protosw_exit();
sctp_v4_protosw_exit();
+ unregister_pernet_subsys(&sctp_defaults_ops);
+
/* Unregister with socket layer. */
sctp_v6_pf_exit();
sctp_v4_pf_exit();
--
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