netdev - Re: [PATCH net 1/2] selftests: fix OOM in msg

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Date: Tue, 02 Jul 2024 09:17:56 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: zijianzhang@...edance.com, 
 netdev@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com, 
 cong.wang@...edance.com, 
 xiaochun.lu@...edance.com, 
 Zijian Zhang <zijianzhang@...edance.com>
Subject: Re: [PATCH net 1/2] selftests: fix OOM in msg_zerocopy selftest

zijianzhang@ wrote:
> From: Zijian Zhang <zijianzhang@...edance.com>
> 
> In selftests/net/msg_zerocopy.c, it has a while loop keeps calling sendmsg
> on a socket with MSG_ZEROCOPY flag, and it will recv the notifications
> until the socket is not writable. Typically, it will start the receiving
> process after around 30+ sendmsgs. However, as the introduction of commit
> dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale"), the sender is
> always writable and does not get any chance to run recv notifications.
> The selftest always exits with OUT_OF_MEMORY because the memory used by
> opt_skb exceeds the net.core.optmem_max. Meanwhile, it could be set to a
> different value to trigger OOM on older kernels too.
> 
> Thus, we introduce "cfg_notification_limit" to force sender to receive
> notifications after some number of sendmsgs.
> 
> Fixes: 07b65c5b31ce ("test: add msg_zerocopy test")
> Signed-off-by: Zijian Zhang <zijianzhang@...edance.com>
> Signed-off-by: Xiaochun Lu <xiaochun.lu@...edance.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>