* [MPTCP] [PATCH mptcp-net-next 11/14] mptcp: Don't take meta-lock when receiving third ACK
@ 2018-05-03 21:04 Christoph Paasch
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From: Christoph Paasch @ 2018-05-03 21:04 UTC (permalink / raw)
To: mptcp
[-- Attachment #1: Type: text/plain, Size: 9004 bytes --]
Now everything is ready to do this in a lockless way.
Simply, in tcp_v4(6)_rcv, stop taking the meta-level lock.
When creating the initial subflow, we currently are also holding the
meta-level lock. We need to drop this one as soon as we handover control
to the subflow (aka., when exiting mptcp_check_req_master()).
Data-reception however still requires the meta-level lock. Thus, we need
to take it again in tcp_child_process().
Signed-off-by: Christoph Paasch <cpaasch(a)apple.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts(a)tessares.net>
(cherry picked from commit 4966859c2ad3309437caedcc78c948c78eb343f3)
---
net/ipv4/tcp_ipv4.c | 41 ++++-------------------------------------
net/ipv4/tcp_minisocks.c | 9 +++++++--
net/ipv6/tcp_ipv6.c | 41 ++++-------------------------------------
net/mptcp/mptcp_ctrl.c | 13 +++++++++++++
net/mptcp/mptcp_ipv4.c | 5 ++++-
net/mptcp/mptcp_ipv6.c | 4 ++++
6 files changed, 36 insertions(+), 77 deletions(-)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 31c757f862c0..3bec4f0c2c32 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1739,45 +1739,16 @@ int tcp_v4_rcv(struct sk_buff *skb)
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
+ if (unlikely(is_meta_sk(sk) && !mptcp_can_new_subflow(sk))) {
+ inet_csk_reqsk_queue_drop_and_put(sk, req);
+ goto lookup;
+ }
/* We own a reference on the listener, increase it again
* as we might lose it too soon.
*/
sock_hold(sk);
refcounted = true;
- if (is_meta_sk(sk)) {
- bh_lock_sock(sk);
-
- if (!mptcp_can_new_subflow(sk)) {
- inet_csk_reqsk_queue_drop_and_put(sk, req);
- bh_unlock_sock(sk);
-
- goto discard_and_relse;
- }
-
- if (sock_owned_by_user(sk)) {
- th = (const struct tcphdr *)skb->data;
- iph = ip_hdr(skb);
- tcp_v4_fill_cb(skb, iph, th);
-
- skb->sk = sk;
- if (unlikely(sk_add_backlog(sk, skb,
- sk->sk_rcvbuf + sk->sk_sndbuf))) {
- reqsk_put(req);
-
- bh_unlock_sock(sk);
- __NET_INC_STATS(net, LINUX_MIB_TCPBACKLOGDROP);
- goto discard_and_relse;
- }
-
- reqsk_put(req);
- bh_unlock_sock(sk);
- sock_put(sk);
-
- return 0;
- }
- }
-
nsk = NULL;
if (!tcp_filter(sk, skb)) {
th = (const struct tcphdr *)skb->data;
@@ -1787,8 +1758,6 @@ int tcp_v4_rcv(struct sk_buff *skb)
}
if (!nsk) {
reqsk_put(req);
- if (is_meta_sk(sk))
- bh_unlock_sock(sk);
if (req_stolen) {
/* Another cpu got exclusive access to req
* and created a full blown socket.
@@ -1804,8 +1773,6 @@ int tcp_v4_rcv(struct sk_buff *skb)
if (nsk == sk) {
reqsk_put(req);
tcp_v4_restore_cb(skb);
- if (is_meta_sk(sk))
- bh_unlock_sock(sk);
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v4_send_reset(nsk, skb);
goto discard_and_relse;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 94e7bfd8343a..1581b1991733 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -899,6 +899,11 @@ int tcp_child_process(struct sock *parent, struct sock *child,
sk_mark_napi_id(child, skb);
tcp_segs_in(tcp_sk(child), skb);
+ /* The following will be removed when we allow lockless data-reception
+ * on the subflows.
+ */
+ if (mptcp(tcp_sk(child)))
+ bh_lock_sock(meta_sk);
if (!sock_owned_by_user(meta_sk)) {
ret = tcp_rcv_state_process(child, skb);
/* Wakeup parent, send SIGIO */
@@ -914,9 +919,9 @@ int tcp_child_process(struct sock *parent, struct sock *child,
__sk_add_backlog(meta_sk, skb);
}
+ bh_unlock_sock(child);
if (mptcp(tcp_sk(child)))
- bh_unlock_sock(child);
- bh_unlock_sock(meta_sk);
+ bh_unlock_sock(meta_sk);
sock_put(child);
return ret;
}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1b2ce91839df..eea44f1c9084 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1537,42 +1537,13 @@ static int tcp_v6_rcv(struct sk_buff *skb)
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
+ if (unlikely(is_meta_sk(sk) && !mptcp_can_new_subflow(sk))) {
+ inet_csk_reqsk_queue_drop_and_put(sk, req);
+ goto lookup;
+ }
sock_hold(sk);
refcounted = true;
- if (is_meta_sk(sk)) {
- bh_lock_sock(sk);
-
- if (!mptcp_can_new_subflow(sk)) {
- inet_csk_reqsk_queue_drop_and_put(sk, req);
- bh_unlock_sock(sk);
-
- goto discard_and_relse;
- }
-
- if (sock_owned_by_user(sk)) {
- th = (const struct tcphdr *)skb->data;
- hdr = ipv6_hdr(skb);
- tcp_v6_fill_cb(skb, hdr, th);
-
- skb->sk = sk;
- if (unlikely(sk_add_backlog(sk, skb,
- sk->sk_rcvbuf + sk->sk_sndbuf))) {
- reqsk_put(req);
-
- bh_unlock_sock(sk);
- __NET_INC_STATS(net, LINUX_MIB_TCPBACKLOGDROP);
- goto discard_and_relse;
- }
-
- reqsk_put(req);
- bh_unlock_sock(sk);
- sock_put(sk);
-
- return 0;
- }
- }
-
nsk = NULL;
if (!tcp_filter(sk, skb)) {
th = (const struct tcphdr *)skb->data;
@@ -1582,8 +1553,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
}
if (!nsk) {
reqsk_put(req);
- if (is_meta_sk(sk))
- bh_unlock_sock(sk);
if (req_stolen) {
/* Another cpu got exclusive access to req
* and created a full blown socket.
@@ -1598,8 +1567,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
}
if (nsk == sk) {
reqsk_put(req);
- if (is_meta_sk(sk))
- bh_unlock_sock(sk);
tcp_v6_restore_cb(skb);
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v6_send_reset(nsk, skb);
diff --git a/net/mptcp/mptcp_ctrl.c b/net/mptcp/mptcp_ctrl.c
index 925d05d673d8..4be0e5c063ca 100644
--- a/net/mptcp/mptcp_ctrl.c
+++ b/net/mptcp/mptcp_ctrl.c
@@ -1333,6 +1333,7 @@ static u8 mptcp_set_new_pathindex(struct mptcp_cb *mpcb)
return i;
}
+/* May be called without holding the meta-level lock */
int mptcp_add_sock(struct sock *meta_sk, struct sock *sk, u8 loc_id, u8 rem_id,
gfp_t flags)
{
@@ -2109,6 +2110,11 @@ int mptcp_check_req_fastopen(struct sock *child, struct request_sock *req)
/* Handled by the master_sk */
tcp_sk(meta_sk)->fastopen_rsk = NULL;
+ /* Subflow establishment is now lockless, drop the lock here it will
+ * be taken again in tcp_child_process().
+ */
+ bh_unlock_sock(meta_sk);
+
return 0;
}
@@ -2138,9 +2144,15 @@ int mptcp_check_req_master(struct sock *sk, struct sock *child,
inet_csk_reqsk_queue_add(sk, req, meta_sk);
}
+ /* Subflow establishment is now lockless, drop the lock here it will
+ * be taken again in tcp_child_process().
+ */
+ bh_unlock_sock(meta_sk);
+
return 0;
}
+/* May be called without holding the meta-level lock */
struct sock *mptcp_check_req_child(struct sock *meta_sk,
struct sock *child,
struct request_sock *req,
@@ -2383,6 +2395,7 @@ void mptcp_tsq_sub_deferred(struct sock *meta_sk)
}
}
+/* May be called without holding the meta-level lock */
void mptcp_join_reqsk_init(const struct mptcp_cb *mpcb,
const struct request_sock *req,
struct sk_buff *skb)
diff --git a/net/mptcp/mptcp_ipv4.c b/net/mptcp/mptcp_ipv4.c
index 6fce833c6859..c808d10205f5 100644
--- a/net/mptcp/mptcp_ipv4.c
+++ b/net/mptcp/mptcp_ipv4.c
@@ -96,6 +96,7 @@ static u32 mptcp_v4_cookie_init_seq(struct request_sock *req, const struct sock
}
#endif
+/* May be called without holding the meta-level lock */
static int mptcp_v4_join_init_req(struct request_sock *req, const struct sock *meta_sk,
struct sk_buff *skb, bool want_cookie)
{
@@ -141,7 +142,9 @@ struct request_sock_ops mptcp_request_sock_ops __read_mostly = {
.syn_ack_timeout = tcp_syn_ack_timeout,
};
-/* Similar to: tcp_v4_conn_request */
+/* Similar to: tcp_v4_conn_request
+ * May be called without holding the meta-level lock
+ */
static int mptcp_v4_join_request(struct sock *meta_sk, struct sk_buff *skb)
{
return tcp_conn_request(&mptcp_request_sock_ops,
diff --git a/net/mptcp/mptcp_ipv6.c b/net/mptcp/mptcp_ipv6.c
index bd6b16becc49..2d730379d5ed 100644
--- a/net/mptcp/mptcp_ipv6.c
+++ b/net/mptcp/mptcp_ipv6.c
@@ -125,6 +125,7 @@ static u32 mptcp_v6_cookie_init_seq(struct request_sock *req, const struct sock
}
#endif
+/* May be called without holding the meta-level lock */
static int mptcp_v6_join_init_req(struct request_sock *req, const struct sock *meta_sk,
struct sk_buff *skb, bool want_cookie)
{
@@ -170,6 +171,9 @@ struct request_sock_ops mptcp6_request_sock_ops __read_mostly = {
.syn_ack_timeout = tcp_syn_ack_timeout,
};
+/* Similar to: tcp_v6_conn_request
+ * May be called without holding the meta-level lock
+ */
static int mptcp_v6_join_request(struct sock *meta_sk, struct sk_buff *skb)
{
return tcp_conn_request(&mptcp6_request_sock_ops,
--
2.16.2
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