From: Nikolay Aleksandrov Date: Mon, 29 Nov 2021 12:09:24 +0000 (+0200) Subject: net: nexthop: reduce rcu synchronizations when replacing resilient groups X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=7709efa62c4fd2a79d154579ea19be34f9fa9a31;p=linux.git net: nexthop: reduce rcu synchronizations when replacing resilient groups We can optimize resilient nexthop group replaces by reducing the number of synchronize_net calls. After commit 1005f19b9357 ("net: nexthop: release IPv6 per-cpu dsts when replacing a nexthop group") we always do a synchronize_net because we must ensure no new dsts can be created for the replaced group's removed nexthops, but we already did that when replacing resilient groups, so if we always call synchronize_net after any group type replacement we'll take care of both cases and reduce synchronize_net calls for resilient groups. Suggested-by: Ido Schimmel Signed-off-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Tested-by: Ido Schimmel Reviewed-by: David Ahern Signed-off-by: David S. Miller --- diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index 5dbd4b5505eba..1319d093cddaf 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -1918,9 +1918,6 @@ static void nh_rt_cache_flush(struct net *net, struct nexthop *nh, if (!replaced_nh->is_group) return; - /* new dsts must use only the new nexthop group */ - synchronize_net(); - nhg = rtnl_dereference(replaced_nh->nh_grp); for (i = 0; i < nhg->num_nh; i++) { struct nh_grp_entry *nhge = &nhg->nh_entries[i]; @@ -2002,9 +1999,10 @@ static int replace_nexthop_grp(struct net *net, struct nexthop *old, rcu_assign_pointer(old->nh_grp, newg); + /* Make sure concurrent readers are not using 'oldg' anymore. */ + synchronize_net(); + if (newg->resilient) { - /* Make sure concurrent readers are not using 'oldg' anymore. */ - synchronize_net(); rcu_assign_pointer(oldg->res_table, tmp_table); rcu_assign_pointer(oldg->spare->res_table, tmp_table); }