Re: [PATCH mptcp-net 1/2] mptcp: fix bad RCVPRUNED mib accounting

[Mat Martineau <martineau@kernel.org>]

On Thu, 25 Jul 2024, Paolo Abeni wrote:

> Since its introduction, the mentioned MIB accounted for the wrong
> event: wake-up being skipped as not-needed on some edge condition
> instead of incoming skb being dropped after landing in the (subflow)
> receive queue.
>
> Move the increment in the correct location.
>
> Fixes: ce599c516386 ("mptcp: properly account bulk freed memory")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/mptcp/protocol.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index b3a48d97f009..13777c35496c 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -350,8 +350,10 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
> 	skb_orphan(skb);
>
> 	/* try to fetch required memory from subflow */
> -	if (!mptcp_rmem_schedule(sk, ssk, skb->truesize))
> +	if (!mptcp_rmem_schedule(sk, ssk, skb->truesize)) {
> +		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);

Hi Paolo -

MIB change LGTM:

Reviewed-by: Mat Martineau <martineau@kernel.org>

> 		goto drop;
> +	}
>
> 	has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
>
> @@ -844,10 +846,8 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
> 		sk_rbuf = ssk_rbuf;
>
> 	/* over limit? can't append more skbs to msk, Also, no need to wake-up*/
> -	if (__mptcp_rmem(sk) > sk_rbuf) {
> -		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);
> +	if (__mptcp_rmem(sk) > sk_rbuf)
> 		return;
> -	}
>
> 	/* Wake-up the reader only for in-sequence data */
> 	mptcp_data_lock(sk);