netdev - Re: [PATCH net-next] tcp: clear pfmemalloc on outgoing skb

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Message-Id: <20170203.162408.851464918447697481.davem@davemloft.net>
Date:   Fri, 03 Feb 2017 16:24:08 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     jbacik@...com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: clear pfmemalloc on outgoing skb

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 02 Feb 2017 20:40:08 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Josef Bacik diagnosed following problem :
> 
>    I was seeing random disconnects while testing NBD over loopback.
>    This turned out to be because NBD sets pfmemalloc on it's socket,
>    however the receiving side is a user space application so does not
>    have pfmemalloc set on its socket. This means that
>    sk_filter_trim_cap will simply drop this packet, under the
>    assumption that the other side will simply retransmit. Well we do
>    retransmit, and then the packet is just dropped again for the same
>    reason.
> 
> It seems the better way to address this problem is to clear pfmemalloc
> in the TCP transmit path. pfmemalloc strict control really makes sense
> on the receive path. 
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Acked-by: Josef Bacik <jbacik@...com>

Applied.