Commit 29b5e5ef authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

mptcp: implement TCP_NOTSENT_LOWAT support 

Add support for such socket option storing the user-space provided
value in a new msk field, and using such data to implement the
_mptcp_stream_memory_free() helper, similar to the TCP one.

To avoid adding more indirect calls in the fast path, open-code
a variant of sk_stream_memory_free() in mptcp_sendmsg() and add
direct calls to the mptcp stream memory free helper where possible.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/464


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarMat Martineau <martineau@kernel.org>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a7476267

net/mptcp/protocol.c

+34 −5
Original line number Diff line number Diff line
@@ -1762,6 +1762,30 @@ static int do_copy_data_nocache(struct sock *sk, int copy, 
	return 0;

}



/* open-code sk_stream_memory_free() plus sent limit computation to

 * avoid indirect calls in fast-path.

 * Called under the msk socket lock, so we can avoid a bunch of ONCE

 * annotations.

 */

static u32 mptcp_send_limit(const struct sock *sk)

{

	const struct mptcp_sock *msk = mptcp_sk(sk);

	u32 limit, not_sent;



	if (sk->sk_wmem_queued >= READ_ONCE(sk->sk_sndbuf))

		return 0;



	limit = mptcp_notsent_lowat(sk);

	if (limit == UINT_MAX)

		return UINT_MAX;



	not_sent = msk->write_seq - msk->snd_nxt;

	if (not_sent >= limit)

		return 0;



	return limit - not_sent;

}



static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)

{

	struct mptcp_sock *msk = mptcp_sk(sk);
@@ -1806,6 +1830,12 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 
		struct mptcp_data_frag *dfrag;

		bool dfrag_collapsed;

		size_t psize, offset;

		u32 copy_limit;



		/* ensure fitting the notsent_lowat() constraint */

		copy_limit = mptcp_send_limit(sk);

		if (!copy_limit)

			goto wait_for_memory;



		/* reuse tail pfrag, if possible, or carve a new one from the

		 * page allocator
@@ -1813,9 +1843,6 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 
		dfrag = mptcp_pending_tail(sk);

		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);

		if (!dfrag_collapsed) {

			if (!sk_stream_memory_free(sk))

				goto wait_for_memory;



			if (!mptcp_page_frag_refill(sk, pfrag))

				goto wait_for_memory;
@@ -1830,6 +1857,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 
		offset = dfrag->offset + dfrag->data_len;

		psize = pfrag->size - offset;

		psize = min_t(size_t, psize, msg_data_left(msg));

		psize = min_t(size_t, psize, copy_limit);

		total_ts = psize + frag_truesize;



		if (!sk_wmem_schedule(sk, total_ts))
@@ -3760,6 +3788,7 @@ static struct proto mptcp_prot = { 
	.unhash		= mptcp_unhash,

	.get_port	= mptcp_get_port,

	.forward_alloc_get	= mptcp_forward_alloc_get,

	.stream_memory_free	= mptcp_stream_memory_free,

	.sockets_allocated	= &mptcp_sockets_allocated,



	.memory_allocated	= &tcp_memory_allocated,
@@ -3933,12 +3962,12 @@ static __poll_t mptcp_check_writeable(struct mptcp_sock *msk) 
{

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



	if (sk_stream_is_writeable(sk))

	if (__mptcp_stream_is_writeable(sk, 1))

		return EPOLLOUT | EPOLLWRNORM;



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

	smp_mb__after_atomic(); /* NOSPACE is changed by mptcp_write_space() */

	if (sk_stream_is_writeable(sk))

	if (__mptcp_stream_is_writeable(sk, 1))

		return EPOLLOUT | EPOLLWRNORM;



	return 0;

net/mptcp/protocol.h

+27 −1
Original line number Diff line number Diff line
@@ -307,6 +307,7 @@ struct mptcp_sock { 
			in_accept_queue:1,

			free_first:1,

			rcvspace_init:1;

	u32		notsent_lowat;

	struct work_struct work;

	struct sk_buff  *ooo_last_skb;

	struct rb_root  out_of_order_queue;
@@ -807,10 +808,35 @@ static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk) 
	       READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);

}



static inline u32 mptcp_notsent_lowat(const struct sock *sk)

{

	struct net *net = sock_net(sk);

	u32 val;



	val = READ_ONCE(mptcp_sk(sk)->notsent_lowat);

	return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);

}



static inline bool mptcp_stream_memory_free(const struct sock *sk, int wake)

{

	const struct mptcp_sock *msk = mptcp_sk(sk);

	u32 notsent_bytes;



	notsent_bytes = READ_ONCE(msk->write_seq) - READ_ONCE(msk->snd_nxt);

	return (notsent_bytes << wake) < mptcp_notsent_lowat(sk);

}



static inline bool __mptcp_stream_is_writeable(const struct sock *sk, int wake)

{

	return mptcp_stream_memory_free(sk, wake) &&

	       __sk_stream_is_writeable(sk, wake);

}



static inline void mptcp_write_space(struct sock *sk)

{

	/* pairs with memory barrier in mptcp_poll */

	smp_mb();

	if (mptcp_stream_memory_free(sk, 1))

		sk_stream_write_space(sk);

}

net/mptcp/sockopt.c

+12 −0
Original line number Diff line number Diff line
@@ -812,6 +812,16 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname, 
		return 0;

	case TCP_ULP:

		return -EOPNOTSUPP;

	case TCP_NOTSENT_LOWAT:

		ret = mptcp_get_int_option(msk, optval, optlen, &val);

		if (ret)

			return ret;



		lock_sock(sk);

		WRITE_ONCE(msk->notsent_lowat, val);

		mptcp_write_space(sk);

		release_sock(sk);

		return 0;

	case TCP_CONGESTION:

		return mptcp_setsockopt_sol_tcp_congestion(msk, optval, optlen);

	case TCP_CORK:
@@ -1345,6 +1355,8 @@ static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname, 
		return mptcp_put_int_option(msk, optval, optlen, msk->cork);

	case TCP_NODELAY:

		return mptcp_put_int_option(msk, optval, optlen, msk->nodelay);

	case TCP_NOTSENT_LOWAT:

		return mptcp_put_int_option(msk, optval, optlen, msk->notsent_lowat);

	}

	return -EOPNOTSUPP;

}