From: Stephen Hemminger <shemminger@vyatta.com>
To: Li Yang <leoli@freescale.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org,
Li Yang <leoli@freescale.com>
Subject: Re: [PATCH] gianfar: reallocate skb when headroom is not enough for fcb
Date: Wed, 25 Mar 2009 08:53:33 -0700 [thread overview]
Message-ID: <20090325085333.4bb73f55@nehalam> (raw)
In-Reply-To: <1237972533-11195-1-git-send-email-leoli@freescale.com>
On Wed, 25 Mar 2009 17:15:33 +0800
Li Yang <leoli@freescale.com> wrote:
> Gianfar uses a hardware header FCB for offloading. However when used
> with bridging or IP forwarding, TX skb might not have enough headroom
> for the FCB. Reallocate skb for such cases.
>
> Signed-off-by: Li Yang <leoli@freescale.com>
> ---
> drivers/net/gianfar.c | 31 +++++++++++++++++++++----------
> 1 files changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
> index 9831b3f..29dc4ee 100644
> --- a/drivers/net/gianfar.c
> +++ b/drivers/net/gianfar.c
> @@ -1206,10 +1206,19 @@ static int gfar_enet_open(struct net_device *dev)
> return err;
> }
>
> -static inline struct txfcb *gfar_add_fcb(struct sk_buff *skb)
> +static inline struct txfcb *gfar_add_fcb(struct sk_buff **skbp)
> {
> - struct txfcb *fcb = (struct txfcb *)skb_push (skb, GMAC_FCB_LEN);
> -
> + struct txfcb *fcb;
> + struct sk_buff *skb = *skbp;
> +
> + if (unlikely(skb_headroom(skb) < GMAC_FCB_LEN)) {
> + struct sk_buff *old_skb = skb;
> + skb = skb_realloc_headroom(old_skb, GMAC_FCB_LEN);
> + if (!skb)
> + return NULL;
> + dev_kfree_skb_any(old_skb);
> + }
> + fcb = (struct txfcb *)skb_push(skb, GMAC_FCB_LEN);
> cacheable_memzero(fcb, GMAC_FCB_LEN);
>
Overall, this looks like the wrong code (not copying back new skb)
and in awkward place. Also your version doesn't handle case where
skb headroom is not writable.
Why not:
--- a/drivers/net/gianfar.c 2009-03-25 08:39:03.890718197 -0700
+++ b/drivers/net/gianfar.c 2009-03-25 08:51:39.733279404 -0700
@@ -1309,6 +1309,17 @@ static int gfar_start_xmit(struct sk_buf
unsigned long flags;
unsigned int nr_frags, length;
+ /* make sure there is space and can write FCB */
+ if (!skb_clone_writeable(skb, GMAC_FCB_LEN)) {
+ struct sk_buff *skb2;
+
+ skb2 = skb_realloc_headroom(skb, GMAC_FCB_LEN);
+ kfree_skb(skb);
+ if (!skb2)
+ return NETDEV_TX_OK;
+ skb = skb2;
+ }
+
base = priv->tx_bd_base;
/* total number of fragments in the SKB */
next prev parent reply other threads:[~2009-03-25 15:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-20 9:04 [PATCH] net/bridge: use the maximum hard_header_len of ports for bridging device Li Yang
2009-03-23 7:59 ` Li Yang
2009-03-23 8:02 ` David Miller
2009-03-23 8:15 ` Li Yang
2009-03-23 8:16 ` David Miller
2009-03-23 15:51 ` Stephen Hemminger
2009-03-23 22:20 ` David Miller
2009-03-23 22:45 ` Stephen Hemminger
2009-03-23 22:47 ` David Miller
2009-03-25 8:43 ` Li Yang
2009-03-25 21:35 ` David Miller
2009-03-25 6:40 ` David Miller
2009-03-25 7:05 ` Li Yang
2009-03-25 7:06 ` David Miller
2009-03-25 8:38 ` Li Yang
2009-03-25 9:15 ` [PATCH] gianfar: reallocate skb when headroom is not enough for fcb Li Yang
2009-03-25 15:53 ` Stephen Hemminger [this message]
2009-03-25 21:49 ` David Miller
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