netdev - Re: [PATCH net] tun: fix return value when the number of iovs exceeds MAX_SKB

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Date:   Thu, 24 Dec 2020 10:56:16 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     wangyunjian <wangyunjian@...wei.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        virtualization@...ts.linux-foundation.org,
        "Lilijun (Jerry)" <jerry.lilijun@...wei.com>,
        chenchanghu <chenchanghu@...wei.com>,
        xudingke <xudingke@...wei.com>,
        "huangbin (J)" <brian.huangbin@...wei.com>
Subject: Re: [PATCH net] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

On Thu, Dec 24, 2020 at 6:51 AM wangyunjian <wangyunjian@...wei.com> wrote:
>
> From: Yunjian Wang <wangyunjian@...wei.com>
>
> Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
> number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
> we should use -EMSGSIZE instead of -ENOMEM.
>
> Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>

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

It might be good to explain why the distinction matters: one denotes a
transient failure that the caller (specifically vhost_net) can retry,
the other a persistent failure due to bad packet geometry that should
be dropped.