From: Guillaume Nault <gnault@redhat.com>
To: David Miller <davem@davemloft.net>,
Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: netdev@vger.kernel.org, Nicolas Dichtel <nicolas.dichtel@6wind.com>
Subject: [PATCH net-next 2/3] netns: protect netns ID lookups with RCU
Date: Mon, 13 Jan 2020 22:39:22 +0100 [thread overview]
Message-ID: <44c8f937a2bd6b902b7d4f82261f087b49b5ab29.1578950227.git.gnault@redhat.com> (raw)
In-Reply-To: <cover.1578950227.git.gnault@redhat.com>
__peernet2id() can be protected by RCU as it only calls idr_for_each(),
which is RCU-safe, and never modifies the nsid table.
rtnl_net_dumpid() can also do lockless lookups. It does two nested
idr_for_each() calls on nsid tables (one direct call and one indirect
call because of rtnl_net_dumpid_one() calling __peernet2id()). The
netnsid tables are never updated. Therefore it is safe to not take the
nsid_lock and run within an RCU-critical section instead.
Signed-off-by: Guillaume Nault <gnault@redhat.com>
---
net/core/net_namespace.c | 22 +++++++---------------
1 file changed, 7 insertions(+), 15 deletions(-)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 05e07d24b45b..e7a5ff4966c9 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -211,7 +211,7 @@ static int net_eq_idr(int id, void *net, void *peer)
return 0;
}
-/* Should be called with nsid_lock held. */
+/* Must be called from RCU-critical section or with nsid_lock held */
static int __peernet2id(const struct net *net, struct net *peer)
{
int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);
@@ -272,9 +272,10 @@ int peernet2id(struct net *net, struct net *peer)
{
int id;
- spin_lock_bh(&net->nsid_lock);
+ rcu_read_lock();
id = __peernet2id(net, peer);
- spin_unlock_bh(&net->nsid_lock);
+ rcu_read_unlock();
+
return id;
}
EXPORT_SYMBOL(peernet2id);
@@ -941,6 +942,7 @@ struct rtnl_net_dump_cb {
int s_idx;
};
+/* Runs in RCU-critical section. */
static int rtnl_net_dumpid_one(int id, void *peer, void *data)
{
struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
@@ -1025,19 +1027,9 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb)
goto end;
}
- spin_lock_bh(&net_cb.tgt_net->nsid_lock);
- if (net_cb.fillargs.add_ref &&
- !net_eq(net_cb.ref_net, net_cb.tgt_net) &&
- !spin_trylock_bh(&net_cb.ref_net->nsid_lock)) {
- spin_unlock_bh(&net_cb.tgt_net->nsid_lock);
- err = -EAGAIN;
- goto end;
- }
+ rcu_read_lock();
idr_for_each(&net_cb.tgt_net->netns_ids, rtnl_net_dumpid_one, &net_cb);
- if (net_cb.fillargs.add_ref &&
- !net_eq(net_cb.ref_net, net_cb.tgt_net))
- spin_unlock_bh(&net_cb.ref_net->nsid_lock);
- spin_unlock_bh(&net_cb.tgt_net->nsid_lock);
+ rcu_read_unlock();
cb->args[0] = net_cb.idx;
end:
--
2.21.1
next prev parent reply other threads:[~2020-01-13 21:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 21:39 [PATCH net-next 0/3] netns: Optimise netns ID lookups Guillaume Nault
2020-01-13 21:39 ` [PATCH net-next 1/3] netns: Remove __peernet2id_alloc() Guillaume Nault
2020-01-13 21:39 ` Guillaume Nault [this message]
2020-01-13 21:39 ` [PATCH net-next 3/3] netns: don't disable BHs when locking "nsid_lock" Guillaume Nault
2020-01-14 19:29 ` [PATCH net-next 0/3] netns: Optimise netns ID lookups David Miller
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