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ipv6: Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE.

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Now we are ready to remove RTNL from SIOCADDRT and RTM_NEWROUTE.

The remaining things to do are

  1. pass false to lwtunnel_valid_encap_type_attr()
  2. use rcu_dereference_rtnl() in fib6_check_nexthop()
  3. place rcu_read_lock() before ip6_route_info_create_nh().

Let's complete the RTNL-free conversion.

When each CPU-X adds 100000 routes on table-X in a batch
concurrently on c7a.metal-48xl EC2 instance with 192 CPUs,

without this series:

  $ sudo ./route_test.sh
  ...
  added 19200000 routes (100000 routes * 192 tables).
  time elapsed: 191577 milliseconds.

with this series:

  $ sudo ./route_test.sh
  ...
  added 19200000 routes (100000 routes * 192 tables).
  time elapsed: 62854 milliseconds.

I changed the number of routes in each table (1000 ~ 100000)
and consistently saw it finish 3x faster with this series.

Note that now every caller of lwtunnel_valid_encap_type() passes
false as the last argument, and this can be removed later.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250418000443.43734-16-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2025-04-17 17:03:56 -07:00 • committed by Paolo Abeni
parent 081efd1832
commit 169fd62799
2 changed files with 14 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
net/ipv4/nexthop.c
View file

@ -1556,12 +1556,12 @@ int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg,
if (nh->is_group) {
struct nh_group *nhg;
nhg = rtnl_dereference(nh->nh_grp);
nhg = rcu_dereference_rtnl(nh->nh_grp);
if (nhg->has_v4)
goto no_v4_nh;
is_fdb_nh = nhg->fdb_nh;
} else {
nhi = rtnl_dereference(nh->nh_info);
nhi = rcu_dereference_rtnl(nh->nh_info);
if (nhi->family == AF_INET)
goto no_v4_nh;
is_fdb_nh = nhi->fdb_nh;

18
net/ipv6/route.c
View file

@ -3903,12 +3903,16 @@ int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
if (IS_ERR(rt))
return PTR_ERR(rt);
rcu_read_lock();
err = ip6_route_info_create_nh(rt, cfg, extack);
if (err)
return err;
goto unlock;
err = __ip6_ins_rt(rt, &cfg->fc_nlinfo, extack);
fib6_info_release(rt);
unlock:
rcu_read_unlock();
return err;
}
@ -4529,12 +4533,10 @@ int ipv6_route_ioctl(struct net *net, unsigned int cmd, struct in6_rtmsg *rtmsg)
switch (cmd) {
case SIOCADDRT:
rtnl_lock();
/* Only do the default setting of fc_metric in route adding */
if (cfg.fc_metric == 0)
cfg.fc_metric = IP6_RT_PRIO_USER;
err = ip6_route_add(&cfg, GFP_KERNEL, NULL);
rtnl_unlock();
break;
case SIOCDELRT:
err = ip6_route_del(&cfg, NULL);
@ -5113,7 +5115,7 @@ static int rtm_to_fib6_multipath_config(struct fib6_config *cfg,
} while (rtnh_ok(rtnh, remaining));
return lwtunnel_valid_encap_type_attr(cfg->fc_mp, cfg->fc_mp_len,
extack, newroute);
extack, false);
}
static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
@ -5251,7 +5253,7 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
cfg->fc_encap_type = nla_get_u16(tb[RTA_ENCAP_TYPE]);
err = lwtunnel_valid_encap_type(cfg->fc_encap_type,
extack, newroute);
extack, false);
if (err < 0)
goto errout;
}
@ -5518,6 +5520,8 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
if (err)
return err;
rcu_read_lock();
err = ip6_route_mpath_info_create_nh(&rt6_nh_list, extack);
if (err)
goto cleanup;
@ -5609,6 +5613,8 @@ add_errout:
}
cleanup:
rcu_read_unlock();
list_for_each_entry_safe(nh, nh_safe, &rt6_nh_list, list) {
fib6_info_release(nh->fib6_info);
list_del(&nh->list);
@ -6891,7 +6897,7 @@ static void bpf_iter_unregister(void)
static const struct rtnl_msg_handler ip6_route_rtnl_msg_handlers[] __initconst_or_module = {
{.owner = THIS_MODULE, .protocol = PF_INET6, .msgtype = RTM_NEWROUTE,
.doit = inet6_rtm_newroute},
.doit = inet6_rtm_newroute, .flags = RTNL_FLAG_DOIT_UNLOCKED},
{.owner = THIS_MODULE, .protocol = PF_INET6, .msgtype = RTM_DELROUTE,
.doit = inet6_rtm_delroute, .flags = RTNL_FLAG_DOIT_UNLOCKED},
{.owner = THIS_MODULE, .protocol = PF_INET6, .msgtype = RTM_GETROUTE,