linux-kernel - Re: [PATCH net RFC] net: Clear IFF_TX_SKB_SHARING for all Ethernet devices using skb

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Message-ID: <20201022082239.2ae23264@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date:   Thu, 22 Oct 2020 08:22:39 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Xie He <xie.he.0141@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH net RFC] net: Clear IFF_TX_SKB_SHARING for all Ethernet
 devices using skb_padto

On Thu, 22 Oct 2020 00:46:38 -0700 Xie He wrote:
> It was very hard for me to attempt fixing. There are too many drivers
> that need to be fixed. Fixing them is very time-consuming and may also
> be error-prone. So I think it may be better to just remove
> IFF_TX_SKB_SHARING from ether_setup. Drivers that support this feature
> should add this flag by themselves. This also makes our code cleaner.

Are most of these drivers using skb_padto()? Is that the reason they
can't be sharing the SKB?

I think the IFF_TX_SKB_SHARING flag is only used by pktgen, so perhaps
we can make sure pktgen doesn't generate skbs < dev->min_mtu, and then
the drivers won't pad?