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mptcp: refine mptcp_cleanup_rbuf

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The current cleanup rbuf tries a bit too hard to avoid acquiring
the subflow socket lock. We may end-up delaying the needed ack,
or skip acking a blocked subflow.

Address the above extending the conditions used to trigger the cleanup
to reflect more closely what TCP does and invoking tcp_cleanup_rbuf()
on all the active subflows.

Note that we can't replicate the exact tests implemented in
tcp_cleanup_rbuf(), as MPTCP lacks some of the required info - e.g.
ping-pong mode.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2021-06-22 12:25:23 -07:00 committed by David S. Miller
parent d8e336f77e
commit fde56eea01
2 changed files with 23 additions and 34 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

56
net/mptcp/protocol.c
View file

@ -442,49 +442,46 @@ static void mptcp_send_ack(struct mptcp_sock *msk)
}
}
static bool mptcp_subflow_cleanup_rbuf(struct sock *ssk)
static void mptcp_subflow_cleanup_rbuf(struct sock *ssk)
{
bool slow;
int ret;
slow = lock_sock_fast(ssk);
ret = tcp_can_send_ack(ssk);
if (ret)
if (tcp_can_send_ack(ssk))
tcp_cleanup_rbuf(ssk, 1);
unlock_sock_fast(ssk, slow);
return ret;
}
static bool mptcp_subflow_could_cleanup(const struct sock *ssk, bool rx_empty)
{
const struct inet_connection_sock *icsk = inet_csk(ssk);
bool ack_pending = READ_ONCE(icsk->icsk_ack.pending);
const struct tcp_sock *tp = tcp_sk(ssk);
return (ack_pending & ICSK_ACK_SCHED) &&
((READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->rcv_wup) >
READ_ONCE(icsk->icsk_ack.rcv_mss)) ||
(rx_empty && ack_pending &
(ICSK_ACK_PUSHED2 | ICSK_ACK_PUSHED)));
}
static void mptcp_cleanup_rbuf(struct mptcp_sock *msk)
{
struct sock *ack_hint = READ_ONCE(msk->ack_hint);
int old_space = READ_ONCE(msk->old_wspace);
struct mptcp_subflow_context *subflow;
struct sock *sk = (struct sock *)msk;
bool cleanup;
int space = __mptcp_space(sk);
bool cleanup, rx_empty;
/* this is a simple superset of what tcp_cleanup_rbuf() implements
* so that we don't have to acquire the ssk socket lock most of the time
* to do actually nothing
*/
cleanup = __mptcp_space(sk) - old_space >= max(0, old_space);
if (!cleanup)
return;
cleanup = (space > 0) && (space >= (old_space << 1));
rx_empty = !atomic_read(&sk->sk_rmem_alloc);
/* if the hinted ssk is still active, try to use it */
if (likely(ack_hint)) {
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
if (ack_hint == ssk && mptcp_subflow_cleanup_rbuf(ssk))
return;
}
if (cleanup || mptcp_subflow_could_cleanup(ssk, rx_empty))
mptcp_subflow_cleanup_rbuf(ssk);
}
/* otherwise pick the first active subflow */
mptcp_for_each_subflow(msk, subflow)
if (mptcp_subflow_cleanup_rbuf(mptcp_subflow_tcp_sock(subflow)))
return;
}
static bool mptcp_check_data_fin(struct sock *sk)
@ -629,7 +626,6 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
break;
}
} while (more_data_avail);
WRITE_ONCE(msk->ack_hint, ssk);
*bytes += moved;
return done;
@ -1910,7 +1906,6 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk)
__mptcp_update_rmem(sk);
done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
mptcp_data_unlock(sk);
tcp_cleanup_rbuf(ssk, moved);
if (unlikely(ssk->sk_err))
__mptcp_error_report(sk);
@ -1926,7 +1921,6 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk)
ret |= __mptcp_ofo_queue(msk);
__mptcp_splice_receive_queue(sk);
mptcp_data_unlock(sk);
mptcp_cleanup_rbuf(msk);
}
if (ret)
mptcp_check_data_fin((struct sock *)msk);
@ -2175,9 +2169,6 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
if (ssk == msk->last_snd)
msk->last_snd = NULL;
if (ssk == msk->ack_hint)
msk->ack_hint = NULL;
if (ssk == msk->first)
msk->first = NULL;
@ -2392,7 +2383,6 @@ static int __mptcp_init_sock(struct sock *sk)
msk->rmem_released = 0;
msk->tx_pending_data = 0;
msk->ack_hint = NULL;
msk->first = NULL;
inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));

1
net/mptcp/protocol.h
View file

@ -243,7 +243,6 @@ struct mptcp_sock {
bool use_64bit_ack; /* Set when we received a 64-bit DSN */
bool csum_enabled;
spinlock_t join_list_lock;
struct sock *ack_hint;
struct work_struct work;
struct sk_buff *ooo_last_skb;
struct rb_root out_of_order_queue;