net: netlink: remove the cb_mutex "injection" from netlink core

Back in 2007, in commit af65bdfce98d ("[NETLINK]: Switch cb_lock spinlock
to mutex and allow to override it") netlink core was extended to allow
subsystems to replace the dump mutex lock with its own lock.

The mechanism was used by rtnetlink to take rtnl_lock but it isn't
sufficiently flexible for other users. Over the 17 years since
it was added no other user appeared. Since rtnetlink needs conditional
locking now, and doesn't use it either, axe this feature complete.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 5df7340d4dabc0c0b1728dafde43b5522dacd024..b332c2048c75576cd265a2f7940d8cab715beacd 100644 (file)
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -47,7 +47,6 @@ struct netlink_kernel_cfg {
        unsigned int    groups;
        unsigned int    flags;
        void            (*input)(struct sk_buff *skb);
-       struct mutex    *cb_mutex;
        int             (*bind)(struct net *net, int group);
        void            (*unbind)(struct net *net, int group);
        void            (*release) (struct sock *sk, unsigned long *groups);

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 8bbbe75e75dbe8c286f7188a61db35740250514c..0b7a89db3ab74e13837ec697d0343cd9839f38b1 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -636,8 +636,7 @@ static struct proto netlink_proto = {
 };
 
 static int __netlink_create(struct net *net, struct socket *sock,
-                           struct mutex *dump_cb_mutex, int protocol,
-                           int kern)
+                           int protocol, int kern)
 {
        struct sock *sk;
        struct netlink_sock *nlk;
@@ -655,7 +654,6 @@ static int __netlink_create(struct net *net, struct socket *sock,
        lockdep_set_class_and_name(&nlk->nl_cb_mutex,
                                           nlk_cb_mutex_keys + protocol,
                                           nlk_cb_mutex_key_strings[protocol]);
-       nlk->dump_cb_mutex = dump_cb_mutex;
        init_waitqueue_head(&nlk->wait);
 
        sk->sk_destruct = netlink_sock_destruct;
@@ -667,7 +665,6 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
                          int kern)
 {
        struct module *module = NULL;
-       struct mutex *cb_mutex;
        struct netlink_sock *nlk;
        int (*bind)(struct net *net, int group);
        void (*unbind)(struct net *net, int group);
@@ -696,7 +693,6 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
                module = nl_table[protocol].module;
        else
                err = -EPROTONOSUPPORT;
-       cb_mutex = nl_table[protocol].cb_mutex;
        bind = nl_table[protocol].bind;
        unbind = nl_table[protocol].unbind;
        release = nl_table[protocol].release;
@@ -705,7 +701,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
        if (err < 0)
                goto out;
 
-       err = __netlink_create(net, sock, cb_mutex, protocol, kern);
+       err = __netlink_create(net, sock, protocol, kern);
        if (err < 0)
                goto out_module;
 
@@ -2016,7 +2012,6 @@ __netlink_kernel_create(struct net *net, int unit, struct module *module,
        struct sock *sk;
        struct netlink_sock *nlk;
        struct listeners *listeners = NULL;
-       struct mutex *cb_mutex = cfg ? cfg->cb_mutex : NULL;
        unsigned int groups;
 
        BUG_ON(!nl_table);
@@ -2027,7 +2022,7 @@ __netlink_kernel_create(struct net *net, int unit, struct module *module,
        if (sock_create_lite(PF_NETLINK, SOCK_DGRAM, unit, &sock))
                return NULL;
 
-       if (__netlink_create(net, sock, cb_mutex, unit, 1) < 0)
+       if (__netlink_create(net, sock, unit, 1) < 0)
                goto out_sock_release_nosk;
 
        sk = sock->sk;
@@ -2055,7 +2050,6 @@ __netlink_kernel_create(struct net *net, int unit, struct module *module,
        if (!nl_table[unit].registered) {
                nl_table[unit].groups = groups;
                rcu_assign_pointer(nl_table[unit].listeners, listeners);
-               nl_table[unit].cb_mutex = cb_mutex;
                nl_table[unit].module = module;
                if (cfg) {
                        nl_table[unit].bind = cfg->bind;
@@ -2326,15 +2320,9 @@ static int netlink_dump(struct sock *sk, bool lock_taken)
        netlink_skb_set_owner_r(skb, sk);
 
        if (nlk->dump_done_errno > 0) {
-               struct mutex *extra_mutex = nlk->dump_cb_mutex;
-
                cb->extack = &extack;
 
-               if (extra_mutex)
-                       mutex_lock(extra_mutex);
                nlk->dump_done_errno = cb->dump(skb, cb);
-               if (extra_mutex)
-                       mutex_unlock(extra_mutex);
 
                /* EMSGSIZE plus something already in the skb means
                 * that there's more to dump but current skb has filled up.