linux-kernel - [PATCH 5.10 123/290] net: dsa: tag_gswip: let DSA core deal with TX reallocation

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Date:   Mon, 15 Mar 2021 14:53:36 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hauke Mehrtens <hauke@...ke-m.de>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 123/290] net: dsa: tag_gswip: let DSA core deal with TX reallocation

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Vladimir Oltean <vladimir.oltean@....com>

[ Upstream commit 9b9826ae117f211bcbdc75db844d5fd8b159fc59 ]

Now that we have a central TX reallocation procedure that accounts for
the tagger's needed headroom in a generic way, we can remove the
skb_cow_head call.

This one is interesting, the DSA tag is 8 bytes on RX and 4 bytes on TX.
Because DSA is unaware of asymmetrical tag lengths, the overhead/needed
headroom is declared as 8 bytes and therefore 4 bytes larger than it
needs to be. If this becomes a problem, and the GSWIP driver can't be
converted to a uniform header length, we might need to make DSA aware of
separate RX/TX overhead values.

Cc: Hauke Mehrtens <hauke@...ke-m.de>
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/dsa/tag_gswip.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/net/dsa/tag_gswip.c b/net/dsa/tag_gswip.c
index 408d4af390a0..2f5bd5e338ab 100644
--- a/net/dsa/tag_gswip.c
+++ b/net/dsa/tag_gswip.c
@@ -60,13 +60,8 @@ static struct sk_buff *gswip_tag_xmit(struct sk_buff *skb,
 				      struct net_device *dev)
 {
 	struct dsa_port *dp = dsa_slave_to_port(dev);
-	int err;
 	u8 *gswip_tag;
 
-	err = skb_cow_head(skb, GSWIP_TX_HEADER_LEN);
-	if (err)
-		return NULL;
-
 	skb_push(skb, GSWIP_TX_HEADER_LEN);
 
 	gswip_tag = skb->data;
-- 
2.30.1