netdev - Re: [PATCH net v2 1/2] gianfar: Replace skb_realloc_headroom with skb_cow

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Message-ID: <20201103172741.iia5joaxeww6c454@skbuf>
Date:   Tue, 3 Nov 2020 19:27:41 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Julian Wiedmann <jwi@...ux.ibm.com>
Cc:     Claudiu Manoil <claudiu.manoil@....com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, james.jurack@...tek.com
Subject: Re: [PATCH net v2 1/2] gianfar: Replace skb_realloc_headroom with
 skb_cow_head for PTP

On Tue, Nov 03, 2020 at 07:18:49PM +0200, Vladimir Oltean wrote:
> On Tue, Nov 03, 2020 at 06:36:30PM +0200, Julian Wiedmann wrote:
> > Given the various skb modifications in its xmit path, I wonder why
> > gianfar doesn't clear IFF_TX_SKB_SHARING.
> 
> Thanks for the hint Julian :) I'll try to see if it makes any
> difference.

And unsurprisingly given what Jakub said, it crashed again, even with
this change.

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 41dd3d0f3452..7cc8986910f8 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -3337,6 +3337,7 @@ static int gfar_probe(struct platform_device *ofdev)
 	dev->mtu = 1500;
 	dev->min_mtu = 50;
 	dev->max_mtu = GFAR_JUMBO_FRAME_SIZE - ETH_HLEN;
+	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 	dev->netdev_ops = &gfar_netdev_ops;
 	dev->ethtool_ops = &gfar_ethtool_ops;