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Date: Mon, 19 Mar 2018 18:13:08 +0300
From: Kirill Tkhai <ktkhai@...tuozzo.com>
To: Sowmini Varadhan <sowmini.varadhan@...cle.com>,
netdev@...r.kernel.org
Cc: davem@...emloft.net, santosh.shilimkar@...cle.com
Subject: Re: [PATCH net-next] rds: tcp: remove register_netdevice_notifier
infrastructure.
On 19.03.2018 16:52, Sowmini Varadhan wrote:
> The netns deletion path does not need to wait for all net_devices
> to be unregistered before dismantling rds_tcp state for the netns
> (we are able to dismantle this state on module unload even when
> all net_devices are active so there is no dependency here).
>
> This patch removes code related to netdevice notifiers and
> refactors all the code needed to dismantle rds_tcp state
> into a ->exit callback for the pernet_operations used with
> register_pernet_device().
>
> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
I just repeat my words:
rds_tcp_listen_sock destruction looks nice and safe, since all
the places the sockets is dereferenced use sk_callback_lock.
So they don't miss rds_tcp_listen_sock = NULL, as rds_tcp_listen_stop()
takes the lock too.
rds_tcp_conn_list is populated from:
1)rds_tcp_accept_one(), which can't happen after we flushed the queue
in rds_tcp_listen_stop();
2)rds_sendmsg(), which is triggered by userspace, and that's impossible,
when net is dead;
3)rds_ib_cm_handle_connect(), which call rds_conn_create() with init_net
argument only. This may race with module unloading only, but this problem
is already solved in RDS by rds_destroy_pending() check, which care about
that.
Reviewed-by: Kirill Tkhai <ktkhai@...tuozzo.com>
(The only thing I don't know is the reason we need to destroy the sockets
before last netdevice, but I haven't dived into that. Just to mention this...).
Thanks, Sowmini.
Kirill
> ---
> net/rds/tcp.c | 93 ++++++++++++++-------------------------------------------
> 1 files changed, 23 insertions(+), 70 deletions(-)
>
> diff --git a/net/rds/tcp.c b/net/rds/tcp.c
> index 08ea9cd..4f3a32c 100644
> --- a/net/rds/tcp.c
> +++ b/net/rds/tcp.c
> @@ -485,40 +485,6 @@ static __net_init int rds_tcp_init_net(struct net *net)
> return err;
> }
>
> -static void __net_exit rds_tcp_exit_net(struct net *net)
> -{
> - struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
> -
> - if (rtn->rds_tcp_sysctl)
> - unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
> -
> - if (net != &init_net && rtn->ctl_table)
> - kfree(rtn->ctl_table);
> -
> - /* If rds_tcp_exit_net() is called as a result of netns deletion,
> - * the rds_tcp_kill_sock() device notifier would already have cleaned
> - * up the listen socket, thus there is no work to do in this function.
> - *
> - * If rds_tcp_exit_net() is called as a result of module unload,
> - * i.e., due to rds_tcp_exit() -> unregister_pernet_subsys(), then
> - * we do need to clean up the listen socket here.
> - */
> - if (rtn->rds_tcp_listen_sock) {
> - struct socket *lsock = rtn->rds_tcp_listen_sock;
> -
> - rtn->rds_tcp_listen_sock = NULL;
> - rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w);
> - }
> -}
> -
> -static struct pernet_operations rds_tcp_net_ops = {
> - .init = rds_tcp_init_net,
> - .exit = rds_tcp_exit_net,
> - .id = &rds_tcp_netid,
> - .size = sizeof(struct rds_tcp_net),
> - .async = true,
> -};
> -
> static void rds_tcp_kill_sock(struct net *net)
> {
> struct rds_tcp_connection *tc, *_tc;
> @@ -546,40 +512,38 @@ static void rds_tcp_kill_sock(struct net *net)
> rds_conn_destroy(tc->t_cpath->cp_conn);
> }
>
> -void *rds_tcp_listen_sock_def_readable(struct net *net)
> +static void __net_exit rds_tcp_exit_net(struct net *net)
> {
> struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
> - struct socket *lsock = rtn->rds_tcp_listen_sock;
>
> - if (!lsock)
> - return NULL;
> + rds_tcp_kill_sock(net);
>
> - return lsock->sk->sk_user_data;
> + if (rtn->rds_tcp_sysctl)
> + unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
> +
> + if (net != &init_net && rtn->ctl_table)
> + kfree(rtn->ctl_table);
> }
>
> -static int rds_tcp_dev_event(struct notifier_block *this,
> - unsigned long event, void *ptr)
> +static struct pernet_operations rds_tcp_net_ops = {
> + .init = rds_tcp_init_net,
> + .exit = rds_tcp_exit_net,
> + .id = &rds_tcp_netid,
> + .size = sizeof(struct rds_tcp_net),
> + .async = true,
> +};
> +
> +void *rds_tcp_listen_sock_def_readable(struct net *net)
> {
> - struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> + struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
> + struct socket *lsock = rtn->rds_tcp_listen_sock;
>
> - /* rds-tcp registers as a pernet subys, so the ->exit will only
> - * get invoked after network acitivity has quiesced. We need to
> - * clean up all sockets to quiesce network activity, and use
> - * the unregistration of the per-net loopback device as a trigger
> - * to start that cleanup.
> - */
> - if (event == NETDEV_UNREGISTER_FINAL &&
> - dev->ifindex == LOOPBACK_IFINDEX)
> - rds_tcp_kill_sock(dev_net(dev));
> + if (!lsock)
> + return NULL;
>
> - return NOTIFY_DONE;
> + return lsock->sk->sk_user_data;
> }
>
> -static struct notifier_block rds_tcp_dev_notifier = {
> - .notifier_call = rds_tcp_dev_event,
> - .priority = -10, /* must be called after other network notifiers */
> -};
> -
> /* when sysctl is used to modify some kernel socket parameters,this
> * function resets the RDS connections in that netns so that we can
> * restart with new parameters. The assumption is that such reset
> @@ -625,9 +589,7 @@ static void rds_tcp_exit(void)
> rds_tcp_set_unloading();
> synchronize_rcu();
> rds_info_deregister_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
> - unregister_pernet_subsys(&rds_tcp_net_ops);
> - if (unregister_netdevice_notifier(&rds_tcp_dev_notifier))
> - pr_warn("could not unregister rds_tcp_dev_notifier\n");
> + unregister_pernet_device(&rds_tcp_net_ops);
> rds_tcp_destroy_conns();
> rds_trans_unregister(&rds_tcp_transport);
> rds_tcp_recv_exit();
> @@ -651,24 +613,15 @@ static int rds_tcp_init(void)
> if (ret)
> goto out_slab;
>
> - ret = register_pernet_subsys(&rds_tcp_net_ops);
> + ret = register_pernet_device(&rds_tcp_net_ops);
> if (ret)
> goto out_recv;
>
> - ret = register_netdevice_notifier(&rds_tcp_dev_notifier);
> - if (ret) {
> - pr_warn("could not register rds_tcp_dev_notifier\n");
> - goto out_pernet;
> - }
> -
> rds_trans_register(&rds_tcp_transport);
>
> rds_info_register_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
>
> goto out;
> -
> -out_pernet:
> - unregister_pernet_subsys(&rds_tcp_net_ops);
> out_recv:
> rds_tcp_recv_exit();
> out_slab:
>
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