netdev - Re: [PATCH net-next 0/7] mptcp: update mptcp ack sequence outside of recv path

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Message-Id: <20200226.204716.756773371437694239.davem@davemloft.net>
Date:   Wed, 26 Feb 2020 20:47:16 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/7] mptcp: update mptcp ack sequence outside
 of recv path

From: Florian Westphal <fw@...len.de>
Date: Wed, 26 Feb 2020 10:14:45 +0100

> This series moves mptcp-level ack sequence update outside of the recvmsg path.
> Current approach has two problems:
> 
> 1. There is delay between arrival of new data and the time we can ack
>    this data.
> 2. If userspace doesn't call recv for some time, mptcp ack_seq is not
>    updated at all, even if this data is queued in the subflow socket
>    receive queue.
> 
> Move skbs from the subflow socket receive queue to the mptcp-level
> receive queue, updating the mptcp-level ack sequence and have recv
> take skbs from the mptcp-level receive queue.
> 
> The first place where we will attempt to update the mptcp level acks
> is from the subflows' data_ready callback, even before we make userspace
> aware of new data.
> 
> Because of possible deadlock (we need to take the mptcp socket lock
> while already holding the subflow sockets lock), we may still need to
> defer the mptcp-level ack update.  In such case, this work will be either
> done from work queue or recv path, depending on which runs sooner.
> 
> In order to avoid pointless scheduling of the work queue, work
> will be queued from the mptcp sockets lock release callback.
> This allows to detect when the socket owner did drain the subflow
> socket receive queue.
> 
> Please see individual patches for more information.

Series applied, thanks Florian.