Re: [PATCH net-next v6 1/4] selftests: fix OOM problem in msg_zerocopy selftest

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

zijianzhang@ wrote:
> From: Zijian Zhang <zijianzhang@bytedance.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, because of the
> 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 core.sysctl_optmem_max.
> 
> According to our experiments, this problem can be mitigated by open the
> DEBUG_LOCKDEP configuration for the kernel. But it will makes the
> notifications disordered even in good commits before
> commit dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale").

Since this is not a real fix, no need to suggest it.
 
> We introduce "cfg_notification_limit" to force sender to receive
> notifications after some number of sendmsgs. And, notifications may not
> come in order, because of the reason we present above. We have order
> checking code managed by cfg_verbose.
> 
> Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
> Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>

Probably just send this as a separate patch to net-next.