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

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Back in 2007, in commit af65bdfce9 ("[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>
This commit is contained in:
Jakub Kicinski 2024-06-06 12:29:06 -07:00 committed by David S. Miller
parent 5380d64f8d
commit 5fbf57a937
2 changed files with 3 additions and 16 deletions
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1
include/linux/netlink.h
View File

@ -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);

18
net/netlink/af_netlink.c
View File

@ -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.