netdev - Re: [PATCH net-next] net: devmem: expose tcp_recvmsg

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Message-ID: <7726e657-585c-42d3-aff2-c991eed42361@kernel.org>
Date: Mon, 8 Sep 2025 14:44:38 -0600
From: David Ahern <dsahern@...nel.org>
To: Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, ncardwell@...gle.com, kuniyu@...gle.com,
 horms@...nel.org, linux-kernel@...r.kernel.org,
 Mina Almasry <almasrymina@...gle.com>
Subject: Re: [PATCH net-next] net: devmem: expose tcp_recvmsg_locked errors

On 9/8/25 11:50 AM, Stanislav Fomichev wrote:
> tcp_recvmsg_dmabuf can export the following errors:
> - EFAULT when linear copy fails
> - ETOOSMALL when cmsg put fails
> - ENODEV if one of the frags is readable
> - ENOMEM on xarray failures
> 
> But they are all ignored and replaced by EFAULT in the caller
> (tcp_recvmsg_locked). Expose real error to the userspace to
> add more transparency on what specifically fails.
> 
> In non-devmem case (skb_copy_datagram_msg) doing `if (!copied)
> copied=-EFAULT` is ok because skb_copy_datagram_msg can return only EFAULT.
> 
> Cc: Mina Almasry <almasrymina@...gle.com>
> Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
> ---
>  net/ipv4/tcp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 


Reviewed-by: David Ahern <dsahern@...nel.org>