l2tp: delete sessions using work queue

When a tunnel is closed, l2tp_tunnel_closeall closes all sessions in
the tunnel. Move the work of deleting each session to the work queue
so that sessions are deleted using the same codepath whether they are
closed by user API request or their parent tunnel is closing. This
also avoids the locking dance in l2tp_tunnel_closeall where the
tunnel's session list lock was unlocked and relocked in the loop.

In l2tp_exit_net, use drain_workqueue instead of flush_workqueue
because the processing of tunnel_delete work may queue session_delete
work items which must also be processed.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index a01dd891639bbb7552e716800f81da05a3e48876..f6ae18c180bfbafc196b85727e3aeab6be0ef7b1 100644 (file)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1282,18 +1282,8 @@ static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 
        spin_lock_bh(&tunnel->list_lock);
        tunnel->acpt_newsess = false;
-       for (;;) {
-               session = list_first_entry_or_null(&tunnel->session_list,
-                                                  struct l2tp_session, list);
-               if (!session)
-                       break;
-               l2tp_session_inc_refcount(session);
-               list_del_init(&session->list);
-               spin_unlock_bh(&tunnel->list_lock);
+       list_for_each_entry(session, &tunnel->session_list, list)
                l2tp_session_delete(session);
-               spin_lock_bh(&tunnel->list_lock);
-               l2tp_session_dec_refcount(session);
-       }
        spin_unlock_bh(&tunnel->list_lock);
 }
 
@@ -1631,18 +1621,31 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
 
 void l2tp_session_delete(struct l2tp_session *session)
 {
-       if (test_and_set_bit(0, &session->dead))
-               return;
+       if (!test_and_set_bit(0, &session->dead)) {
+               trace_delete_session(session);
+               l2tp_session_inc_refcount(session);
+               queue_work(l2tp_wq, &session->del_work);
+       }
+}
+EXPORT_SYMBOL_GPL(l2tp_session_delete);
+
+/* Workqueue session deletion function */
+static void l2tp_session_del_work(struct work_struct *work)
+{
+       struct l2tp_session *session = container_of(work, struct l2tp_session,
+                                                   del_work);
 
-       trace_delete_session(session);
        l2tp_session_unhash(session);
        l2tp_session_queue_purge(session);
        if (session->session_close)
                (*session->session_close)(session);
 
+       /* drop initial ref */
+       l2tp_session_dec_refcount(session);
+
+       /* drop workqueue ref */
        l2tp_session_dec_refcount(session);
 }
-EXPORT_SYMBOL_GPL(l2tp_session_delete);
 
 /* We come here whenever a session's send_seq, cookie_len or
  * l2specific_type parameters are set.
@@ -1694,6 +1697,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
                INIT_HLIST_NODE(&session->hlist);
                INIT_LIST_HEAD(&session->clist);
                INIT_LIST_HEAD(&session->list);
+               INIT_WORK(&session->del_work, l2tp_session_del_work);
 
                if (cfg) {
                        session->pwtype = cfg->pw_type;
@@ -1751,7 +1755,7 @@ static __net_exit void l2tp_exit_net(struct net *net)
        rcu_read_unlock_bh();
 
        if (l2tp_wq)
-               flush_workqueue(l2tp_wq);
+               drain_workqueue(l2tp_wq);
        rcu_barrier();
 
        idr_destroy(&pn->l2tp_v2_session_idr);

diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 6c62d02a0ae6bd9e466f68ac4dd9e11f0428e4c5..8d7a589ccd2ad758a13683037b55e9fb46aa0e97 100644 (file)
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -102,6 +102,7 @@ struct l2tp_session {
        int                     reorder_skip;   /* set if skip to next nr */
        enum l2tp_pwtype        pwtype;
        struct l2tp_stats       stats;
+       struct work_struct      del_work;
 
        /* Session receive handler for data packets.
         * Each pseudowire implementation should implement this callback in order to