Commit 5f3e915c authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

Merge branch 'mptcp-avoid-workqueue-usage-for-data' 

Paolo Abeni says:

====================
mptcp: avoid workqueue usage for data

The current locking schema used to protect the MPTCP data-path
requires the usage of the MPTCP workqueue to process the incoming
data, depending on trylock result.

The above poses scalability limits and introduces random delays
in MPTCP-level acks.

With this series we use a single spinlock to protect the MPTCP
data-path, removing the need for workqueue and delayed ack usage.

This additionally reduces the number of atomic operations required
per packet and cleans-up considerably the poll/wake-up code.
====================

Link: https://lore.kernel.org/r/cover.1606413118.git.pabeni@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parents be572424 6e628cd3

include/net/sock.h

+1 −0
Original line number Diff line number Diff line
@@ -1590,6 +1590,7 @@ static inline void lock_sock(struct sock *sk) 
	lock_sock_nested(sk, 0);

}



void __lock_sock(struct sock *sk);

void __release_sock(struct sock *sk);

void release_sock(struct sock *sk);

net/core/sock.c

+1 −1
Original line number Diff line number Diff line
@@ -2486,7 +2486,7 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag) 
}

EXPORT_SYMBOL(sk_page_frag_refill);



static void __lock_sock(struct sock *sk)

void __lock_sock(struct sock *sk)

	__releases(&sk->sk_lock.slock)

	__acquires(&sk->sk_lock.slock)

{

net/mptcp/mptcp_diag.c

+1 −1
Original line number Diff line number Diff line
@@ -140,7 +140,7 @@ static void mptcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r, 
	info->mptcpi_flags = flags;

	info->mptcpi_token = READ_ONCE(msk->token);

	info->mptcpi_write_seq = READ_ONCE(msk->write_seq);

	info->mptcpi_snd_una = atomic64_read(&msk->snd_una);

	info->mptcpi_snd_una = READ_ONCE(msk->snd_una);

	info->mptcpi_rcv_nxt = READ_ONCE(msk->ack_seq);

	unlock_sock_fast(sk, slow);

}

net/mptcp/options.c

+25 −22
Original line number Diff line number Diff line
@@ -830,18 +830,20 @@ static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit) 
}



static void ack_update_msk(struct mptcp_sock *msk,

			   const struct sock *ssk,

			   struct sock *ssk,

			   struct mptcp_options_received *mp_opt)

{

	u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);

	u64 new_wnd_end, wnd_end, old_wnd_end = atomic64_read(&msk->wnd_end);

	u64 snd_nxt = READ_ONCE(msk->snd_nxt);

	u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);

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

	u64 old_snd_una;



	mptcp_data_lock(sk);



	/* avoid ack expansion on update conflict, to reduce the risk of

	 * wrongly expanding to a future ack sequence number, which is way

	 * more dangerous than missing an ack

	 */

	old_snd_una = msk->snd_una;

	new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);



	/* ACK for data not even sent yet? Ignore. */
@@ -850,26 +852,16 @@ static void ack_update_msk(struct mptcp_sock *msk, 


	new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;



	while (after64(new_wnd_end, old_wnd_end)) {

		wnd_end = old_wnd_end;

		old_wnd_end = atomic64_cmpxchg(&msk->wnd_end, wnd_end,

					       new_wnd_end);

		if (old_wnd_end == wnd_end) {

			if (mptcp_send_head(sk))

				mptcp_schedule_work(sk);

			break;

		}

	if (after64(new_wnd_end, msk->wnd_end)) {

		msk->wnd_end = new_wnd_end;

		__mptcp_wnd_updated(sk, ssk);

	}



	while (after64(new_snd_una, old_snd_una)) {

		snd_una = old_snd_una;

		old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,

					       new_snd_una);

		if (old_snd_una == snd_una) {

			mptcp_data_acked(sk);

			break;

		}

	if (after64(new_snd_una, old_snd_una)) {

		msk->snd_una = new_snd_una;

		__mptcp_data_acked(sk);

	}

	mptcp_data_unlock(sk);

}



bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
@@ -922,8 +914,19 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) 
	struct mptcp_options_received mp_opt;

	struct mptcp_ext *mpext;



	if (__mptcp_check_fallback(msk))

	if (__mptcp_check_fallback(msk)) {

		/* Keep it simple and unconditionally trigger send data cleanup and

		 * pending queue spooling. We will need to acquire the data lock

		 * for more accurate checks, and once the lock is acquired, such

		 * helpers are cheap.

		 */

		mptcp_data_lock(subflow->conn);

		if (mptcp_send_head(subflow->conn))

			__mptcp_wnd_updated(subflow->conn, sk);

		__mptcp_data_acked(subflow->conn);

		mptcp_data_unlock(subflow->conn);

		return;

	}



	mptcp_get_options(skb, &mp_opt);

	if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))

net/mptcp/protocol.c

+539 −194

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