netdev - Re: [PATCH] sctp: flush if we can't fit another DATA chunk

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Message-Id: <20160330.154622.1322506750240048120.davem@davemloft.net>
Date:	Wed, 30 Mar 2016 15:46:22 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	marcelo.leitner@...il.com
Cc:	netdev@...r.kernel.org, nhorman@...driver.com, vyasevich@...il.com,
	linux-sctp@...r.kernel.org
Subject: Re: [PATCH] sctp: flush if we can't fit another DATA chunk

From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Date: Tue, 29 Mar 2016 10:41:25 -0300

> There is no point in delaying the packet if we can't fit a single byte
> of data on it anymore. So lets just reduce the threshold by the amount
> that a data chunk with 4 bytes (rounding) would use.
> 
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> ---
>  net/sctp/output.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 97745351d58c2fb32b9f9b57d61831d7724d83b2..c518569123ce42a8f21f80754756306c39875013 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -705,7 +705,8 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
>  	/* Check whether this chunk and all the rest of pending data will fit
>  	 * or delay in hopes of bundling a full sized packet.
>  	 */
> -	if (chunk->skb->len + q->out_qlen >= transport->pathmtu - packet->overhead)
> +	if (chunk->skb->len + q->out_qlen >
> +		maxsize - packet->overhead - sizeof(sctp_data_chunk_t) - 4)

There is no maxsize in this function.

You must generate and test your patches against my networking tree.

Neil, how were you able to see where 'maxsize' is and how it's even
calculated before determining that this change is correct?

Please don't ACK patches you really didn't verify in any way at all,
thanks.  It's better to have no reviews than bad reviews, because ACKs
are supposed to give me a reason to be more confident in the change.

Marcelo, I'm ignoring the rest of your SCTP changes, you have to get
your act together.