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ip6mr: convert mrt_lock to a spinlock

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mrt_lock is only held in write mode, from process context only.

We can switch to a mere spinlock, and avoid blocking BH.

Also, vif_dev_read() is always called under standard rcu_read_lock().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2022-06-23 04:34:49 +00:00 committed by David S. Miller
parent 3f55211ecf
commit a96f7a6a60
1 changed files with 14 additions and 15 deletions
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29
net/ipv6/ip6mr.c
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@ -62,12 +62,11 @@ struct ip6mr_result {
Note that the changes are semaphored via rtnl_lock.
*/
static DEFINE_RWLOCK(mrt_lock);
static DEFINE_SPINLOCK(mrt_lock);
static struct net_device *vif_dev_read(const struct vif_device *vif)
{
return rcu_dereference_check(vif->dev,
lockdep_is_held(&mrt_lock));
return rcu_dereference(vif->dev);
}
/* Multicast router control variables */
@ -714,7 +713,7 @@ static int mif6_delete(struct mr_table *mrt, int vifi, int notify,
call_ip6mr_vif_entry_notifiers(read_pnet(&mrt->net),
FIB_EVENT_VIF_DEL, v, dev,
vifi, mrt->id);
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
RCU_INIT_POINTER(v->dev, NULL);
#ifdef CONFIG_IPV6_PIMSM_V2
@ -733,7 +732,7 @@ static int mif6_delete(struct mr_table *mrt, int vifi, int notify,
WRITE_ONCE(mrt->maxvif, tmp + 1);
}
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
dev_set_allmulti(dev, -1);
@ -833,7 +832,7 @@ static void ipmr_expire_process(struct timer_list *t)
spin_unlock(&mfc_unres_lock);
}
/* Fill oifs list. It is called under write locked mrt_lock. */
/* Fill oifs list. It is called under locked mrt_lock. */
static void ip6mr_update_thresholds(struct mr_table *mrt,
struct mr_mfc *cache,
@ -919,7 +918,7 @@ static int mif6_add(struct net *net, struct mr_table *mrt,
MIFF_REGISTER);
/* And finish update writing critical data */
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
rcu_assign_pointer(v->dev, dev);
netdev_tracker_alloc(dev, &v->dev_tracker, GFP_ATOMIC);
#ifdef CONFIG_IPV6_PIMSM_V2
@ -928,7 +927,7 @@ static int mif6_add(struct net *net, struct mr_table *mrt,
#endif
if (vifi + 1 > mrt->maxvif)
WRITE_ONCE(mrt->maxvif, vifi + 1);
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
call_ip6mr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD,
v, dev, vifi, mrt->id);
return 0;
@ -1442,12 +1441,12 @@ static int ip6mr_mfc_add(struct net *net, struct mr_table *mrt,
&mfc->mf6cc_mcastgrp.sin6_addr, parent);
rcu_read_unlock();
if (c) {
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
c->_c.mfc_parent = mfc->mf6cc_parent;
ip6mr_update_thresholds(mrt, &c->_c, ttls);
if (!mrtsock)
c->_c.mfc_flags |= MFC_STATIC;
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
call_ip6mr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_REPLACE,
c, mrt->id);
mr6_netlink_event(mrt, c, RTM_NEWROUTE);
@ -1565,7 +1564,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk)
struct net *net = sock_net(sk);
rtnl_lock();
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
if (rtnl_dereference(mrt->mroute_sk)) {
err = -EADDRINUSE;
} else {
@ -1573,7 +1572,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk)
sock_set_flag(sk, SOCK_RCU_FREE);
atomic_inc(&net->ipv6.devconf_all->mc_forwarding);
}
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
if (!err)
inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
@ -1603,14 +1602,14 @@ int ip6mr_sk_done(struct sock *sk)
rtnl_lock();
ip6mr_for_each_table(mrt, net) {
if (sk == rtnl_dereference(mrt->mroute_sk)) {
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
RCU_INIT_POINTER(mrt->mroute_sk, NULL);
/* Note that mroute_sk had SOCK_RCU_FREE set,
* so the RCU grace period before sk freeing
* is guaranteed by sk_destruct()
*/
atomic_dec(&devconf->mc_forwarding);
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
NETCONFA_MC_FORWARDING,
NETCONFA_IFINDEX_ALL,
@ -2097,7 +2096,7 @@ out_free:
return 0;
}
/* Called with mrt_lock or rcu_read_lock() */
/* Called with rcu_read_lock() */
static int ip6mr_find_vif(struct mr_table *mrt, struct net_device *dev)
{
int ct;