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

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Message-ID: <CANn89iK61cuFiPRBiF6owS26Em734ioC35tXGV1RMS_WyCZuTg@mail.gmail.com>
Date: Tue, 9 Sep 2025 11:09:04 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, ncardwell@...gle.com, kuniyu@...gle.com, 
	dsahern@...nel.org, 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 Mon, Sep 8, 2025 at 10:50 AM Stanislav Fomichev <sdf@...ichev.me> 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>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>