Commit 63561a40 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

mptcp: rethink 'is writable' conditional 



Currently, when checking for the 'msk is writable' condition, we
look at the individual subflows write space.
That works well while we send data via a single subflow, but will
not as soon as we will enable concurrent xmit on multiple subflows.

With this change msk becomes writable when the following conditions
hold:
- the socket has some free write space
- there is at least a subflow with write free space

Additionally we need to set the NOSPACE bit on all subflows
before blocking.

Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 26cdb8f7

net/mptcp/protocol.c

+46 −25
Original line number Diff line number Diff line
@@ -472,7 +472,7 @@ void mptcp_data_acked(struct sock *sk) 
{

	mptcp_reset_timer(sk);



	if ((!sk_stream_is_writeable(sk) ||

	if ((!test_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags) ||

	     (inet_sk_state_load(sk) != TCP_ESTABLISHED)) &&

	    schedule_work(&mptcp_sk(sk)->work))

		sock_hold(sk);
@@ -567,6 +567,20 @@ 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);
@@ -609,10 +623,17 @@ out: 
		sk_mem_reclaim_partial(sk);



		/* Only wake up writers if a subflow is ready */

		if (test_bit(MPTCP_SEND_SPACE, &msk->flags))

		if (mptcp_is_writeable(msk)) {

			set_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags);

			smp_mb__after_atomic();



			/* set SEND_SPACE before sk_stream_write_space clears

			 * NOSPACE

			 */

			sk_stream_write_space(sk);

		}

	}

}



/* ensure we get enough memory for the frag hdr, beyond some minimal amount of

 * data
@@ -801,21 +822,31 @@ out: 
	return ret;

}



static void mptcp_nospace(struct mptcp_sock *msk, struct socket *sock)

static void mptcp_nospace(struct mptcp_sock *msk)

{

	struct mptcp_subflow_context *subflow;



	clear_bit(MPTCP_SEND_SPACE, &msk->flags);

	smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */



	/* enables sk->write_space() callbacks */

	mptcp_for_each_subflow(msk, subflow) {

		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

		struct socket *sock = READ_ONCE(ssk->sk_socket);



		/* enables ssk->write_space() callbacks */

		if (sock)

			set_bit(SOCK_NOSPACE, &sock->flags);

	}

}



static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)

{

	struct mptcp_subflow_context *subflow;

	struct sock *sk = (struct sock *)msk;

	struct sock *backup = NULL;

	bool free;



	sock_owned_by_me((const struct sock *)msk);

	sock_owned_by_me(sk);



	if (!mptcp_ext_cache_refill(msk))

		return NULL;
@@ -823,12 +854,9 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk) 
	mptcp_for_each_subflow(msk, subflow) {

		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);



		if (!sk_stream_memory_free(ssk)) {

			struct socket *sock = ssk->sk_socket;



			if (sock)

				mptcp_nospace(msk, sock);



		free = sk_stream_is_writeable(subflow->tcp_sock);

		if (!free) {

			mptcp_nospace(msk);

			return NULL;

		}
@@ -845,16 +873,10 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk) 
	return backup;

}



static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)

static void ssk_check_wmem(struct mptcp_sock *msk)

{

	struct socket *sock;



	if (likely(sk_stream_is_writeable(ssk)))

		return;



	sock = READ_ONCE(ssk->sk_socket);

	if (sock)

		mptcp_nospace(msk, sock);

	if (unlikely(!mptcp_is_writeable(msk)))

		mptcp_nospace(msk);

}



static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
@@ -907,6 +929,7 @@ restart: 
				mptcp_reset_timer(sk);

		}



		mptcp_nospace(msk);

		ret = sk_stream_wait_memory(sk, &timeo);

		if (ret)

			goto out;
@@ -945,7 +968,6 @@ restart: 
		if (!sk_stream_memory_free(ssk) ||

		    !mptcp_page_frag_refill(ssk, pfrag) ||

		    !mptcp_ext_cache_refill(msk)) {

			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);

			tcp_push(ssk, msg->msg_flags, mss_now,

				 tcp_sk(ssk)->nonagle, size_goal);

			mptcp_set_timeout(sk, ssk);
@@ -993,9 +1015,9 @@ restart: 
			mptcp_reset_timer(sk);

	}



	ssk_check_wmem(msk, ssk);

	release_sock(ssk);

out:

	ssk_check_wmem(msk);

	release_sock(sk);

	return copied ? : ret;

}
@@ -2291,8 +2313,7 @@ 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 (sk_stream_is_writeable(sk) &&

		    test_bit(MPTCP_SEND_SPACE, &msk->flags))

		if (test_bit(MPTCP_SEND_SPACE, &msk->flags))

			mask |= EPOLLOUT | EPOLLWRNORM;

	}

	if (sk->sk_shutdown & RCV_SHUTDOWN)

net/mptcp/subflow.c

+4 −2
Original line number Diff line number Diff line
@@ -996,8 +996,10 @@ static void subflow_write_space(struct sock *sk) 
	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);

	struct sock *parent = subflow->conn;



	sk_stream_write_space(sk);

	if (sk_stream_is_writeable(sk)) {

	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 */

CRA Git | Maintained and supported by SUSTech CRA and CCSE