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Message-Id: <61e7462aa9ecfefd71888277134e9a5f9fd6946c.1605175834.git.pabeni@redhat.com>
Date: Thu, 12 Nov 2020 11:48:09 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>, mptcp@...ts.01.org,
Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next 11/13] mptcp: rework poll+nospace handling
From: Florian Westphal <fw@...len.de>
MPTCP maintains a status bit, MPTCP_SEND_SPACE, that is set when at
least one subflow and the mptcp socket itself are writeable.
mptcp_poll returns EPOLLOUT if the bit is set.
mptcp_sendmsg makes sure MPTCP_SEND_SPACE gets cleared when last write
has used up all subflows or the mptcp socket wmem.
This reworks nospace handling as follows:
MPTCP_SEND_SPACE is replaced with MPTCP_NOSPACE, i.e. inverted meaning.
This bit is set when the mptcp socket is not writeable.
The mptcp-level ack path schedule will then schedule the mptcp worker
to allow it to free already-acked data (and reduce wmem usage).
This will then wake userspace processes that wait for a POLLOUT event.
sendmsg will set MPTCP_NOSPACE only when it has to wait for more
wmem (blocking I/O case).
poll path will set MPTCP_NOSPACE in case the mptcp socket is
not writeable.
Normal tcp-level notification (SOCK_NOSPACE) is only enabled
in case the subflow socket has no available wmem.
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
net/mptcp/protocol.c | 92 +++++++++++++++++++++++---------------------
net/mptcp/protocol.h | 2 +-
net/mptcp/subflow.c | 11 +++---
3 files changed, 54 insertions(+), 51 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 86b4b6e2afbc..05b8112050b9 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -730,7 +730,7 @@ void mptcp_data_acked(struct sock *sk)
{
mptcp_reset_timer(sk);
- if ((!test_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags) ||
+ if ((test_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags) ||
mptcp_send_head(sk) ||
(inet_sk_state_load(sk) != TCP_ESTABLISHED)))
mptcp_schedule_work(sk);
@@ -830,20 +830,6 @@ static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
put_page(dfrag->page);
}
-static bool mptcp_is_writeable(struct mptcp_sock *msk)
-{
- struct mptcp_subflow_context *subflow;
-
- if (!sk_stream_is_writeable((struct sock *)msk))
- return false;
-
- mptcp_for_each_subflow(msk, subflow) {
- if (sk_stream_is_writeable(subflow->tcp_sock))
- return true;
- }
- return false;
-}
-
static void mptcp_clean_una(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
@@ -896,13 +882,8 @@ static void mptcp_clean_una_wakeup(struct sock *sk)
mptcp_clean_una(sk);
/* Only wake up writers if a subflow is ready */
- if (mptcp_is_writeable(msk)) {
- set_bit(MPTCP_SEND_SPACE, &msk->flags);
- smp_mb__after_atomic();
-
- /* set SEND_SPACE before sk_stream_write_space clears
- * NOSPACE
- */
+ if (sk_stream_is_writeable(sk)) {
+ clear_bit(MPTCP_NOSPACE, &msk->flags);
sk_stream_write_space(sk);
}
}
@@ -1036,17 +1017,25 @@ static void mptcp_nospace(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
- clear_bit(MPTCP_SEND_SPACE, &msk->flags);
+ set_bit(MPTCP_NOSPACE, &msk->flags);
smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+ bool ssk_writeable = sk_stream_is_writeable(ssk);
struct socket *sock = READ_ONCE(ssk->sk_socket);
+ if (ssk_writeable || !sock)
+ continue;
+
/* enables ssk->write_space() callbacks */
- if (sock)
- set_bit(SOCK_NOSPACE, &sock->flags);
+ set_bit(SOCK_NOSPACE, &sock->flags);
}
+
+ /* mptcp_data_acked() could run just before we set the NOSPACE bit,
+ * so explicitly check for snd_una value
+ */
+ mptcp_clean_una((struct sock *)msk);
}
static bool mptcp_subflow_active(struct mptcp_subflow_context *subflow)
@@ -1150,12 +1139,6 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
return NULL;
}
-static void ssk_check_wmem(struct mptcp_sock *msk)
-{
- if (unlikely(!mptcp_is_writeable(msk)))
- mptcp_nospace(msk);
-}
-
static void mptcp_push_release(struct sock *sk, struct sock *ssk,
struct mptcp_sendmsg_info *info)
{
@@ -1327,7 +1310,6 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
wait_for_memory:
mptcp_nospace(msk);
- mptcp_clean_una(sk);
if (mptcp_timer_pending(sk))
mptcp_reset_timer(sk);
ret = sk_stream_wait_memory(sk, &timeo);
@@ -1339,7 +1321,6 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
mptcp_push_pending(sk, msg->msg_flags);
out:
- ssk_check_wmem(msk);
release_sock(sk);
return copied ? : ret;
}
@@ -1916,7 +1897,6 @@ static int __mptcp_init_sock(struct sock *sk)
INIT_LIST_HEAD(&msk->conn_list);
INIT_LIST_HEAD(&msk->join_list);
INIT_LIST_HEAD(&msk->rtx_queue);
- __set_bit(MPTCP_SEND_SPACE, &msk->flags);
INIT_WORK(&msk->work, mptcp_worker);
msk->out_of_order_queue = RB_ROOT;
msk->first_pending = NULL;
@@ -2612,13 +2592,6 @@ bool mptcp_finish_join(struct sock *ssk)
return true;
}
-static bool mptcp_memory_free(const struct sock *sk, int wake)
-{
- struct mptcp_sock *msk = mptcp_sk(sk);
-
- return wake ? test_bit(MPTCP_SEND_SPACE, &msk->flags) : true;
-}
-
static struct proto mptcp_prot = {
.name = "MPTCP",
.owner = THIS_MODULE,
@@ -2639,7 +2612,6 @@ static struct proto mptcp_prot = {
.sockets_allocated = &mptcp_sockets_allocated,
.memory_allocated = &tcp_memory_allocated,
.memory_pressure = &tcp_memory_pressure,
- .stream_memory_free = mptcp_memory_free,
.sysctl_wmem_offset = offsetof(struct net, ipv4.sysctl_tcp_wmem),
.sysctl_mem = sysctl_tcp_mem,
.obj_size = sizeof(struct mptcp_sock),
@@ -2812,6 +2784,39 @@ static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
0;
}
+static bool __mptcp_check_writeable(struct mptcp_sock *msk)
+{
+ struct sock *sk = (struct sock *)msk;
+ bool mptcp_writable;
+
+ mptcp_clean_una(sk);
+ mptcp_writable = sk_stream_is_writeable(sk);
+ if (!mptcp_writable)
+ mptcp_nospace(msk);
+
+ return mptcp_writable;
+}
+
+static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
+{
+ struct sock *sk = (struct sock *)msk;
+ __poll_t ret = 0;
+ bool slow;
+
+ if (unlikely(sk->sk_shutdown & SEND_SHUTDOWN))
+ return 0;
+
+ if (sk_stream_is_writeable(sk))
+ return EPOLLOUT | EPOLLWRNORM;
+
+ slow = lock_sock_fast(sk);
+ if (__mptcp_check_writeable(msk))
+ ret = EPOLLOUT | EPOLLWRNORM;
+
+ unlock_sock_fast(sk, slow);
+ return ret;
+}
+
static __poll_t mptcp_poll(struct file *file, struct socket *sock,
struct poll_table_struct *wait)
{
@@ -2830,8 +2835,7 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
mask |= mptcp_check_readable(msk);
- if (test_bit(MPTCP_SEND_SPACE, &msk->flags))
- mask |= EPOLLOUT | EPOLLWRNORM;
+ mask |= mptcp_check_writeable(msk);
}
if (sk->sk_shutdown & RCV_SHUTDOWN)
mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index fd9c666aed7f..8345011fc0ba 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -86,7 +86,7 @@
/* MPTCP socket flags */
#define MPTCP_DATA_READY 0
-#define MPTCP_SEND_SPACE 1
+#define MPTCP_NOSPACE 1
#define MPTCP_WORK_RTX 2
#define MPTCP_WORK_EOF 3
#define MPTCP_FALLBACK_DONE 4
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 42581ffb0c7e..794259789194 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -997,17 +997,16 @@ static void subflow_data_ready(struct sock *sk)
static void subflow_write_space(struct sock *sk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ struct socket *sock = READ_ONCE(sk->sk_socket);
struct sock *parent = subflow->conn;
if (!sk_stream_is_writeable(sk))
return;
- if (sk_stream_is_writeable(parent)) {
- set_bit(MPTCP_SEND_SPACE, &mptcp_sk(parent)->flags);
- smp_mb__after_atomic();
- /* set SEND_SPACE before sk_stream_write_space clears NOSPACE */
- sk_stream_write_space(parent);
- }
+ if (sock && sk_stream_is_writeable(parent))
+ clear_bit(SOCK_NOSPACE, &sock->flags);
+
+ sk_stream_write_space(parent);
}
static struct inet_connection_sock_af_ops *
--
2.26.2
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