linux-kernel - [PATCH 5.16 0438/1017] i40e: dont reserve excessive XDP_PACKET

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Message-Id: <20220405070407.295653838@linuxfoundation.org>
Date:   Tue,  5 Apr 2022 09:22:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Kiran Bhandare <kiranx.bhandare@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0438/1017] i40e: dont reserve excessive XDP_PACKET_HEADROOM on XSK Rx to skb

From: Alexander Lobakin <alexandr.lobakin@...el.com>

[ Upstream commit bc97f9c6f988b31b728eb47a94ca825401dbeffe ]

{__,}napi_alloc_skb() allocates and reserves additional NET_SKB_PAD
+ NET_IP_ALIGN for any skb.
OTOH, i40e_construct_skb_zc() currently allocates and reserves
additional `xdp->data - xdp->data_hard_start`, which is
XDP_PACKET_HEADROOM for XSK frames.
There's no need for that at all as the frame is post-XDP and will
go only to the networking stack core.
Pass the size of the actual data only to __napi_alloc_skb() and
don't reserve anything. This will give enough headroom for stack
processing.

Fixes: 0a714186d3c0 ("i40e: add AF_XDP zero-copy Rx support")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/intel/i40e/i40e_xsk.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index ea06e957393e..dff7c7fcc329 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -246,13 +246,11 @@ static struct sk_buff *i40e_construct_skb_zc(struct i40e_ring *rx_ring,
 	struct sk_buff *skb;
 
 	/* allocate a skb to store the frags */
-	skb = __napi_alloc_skb(&rx_ring->q_vector->napi,
-			       xdp->data_end - xdp->data_hard_start,
+	skb = __napi_alloc_skb(&rx_ring->q_vector->napi, datasize,
 			       GFP_ATOMIC | __GFP_NOWARN);
 	if (unlikely(!skb))
 		goto out;
 
-	skb_reserve(skb, xdp->data - xdp->data_hard_start);
 	memcpy(__skb_put(skb, datasize), xdp->data, datasize);
 	if (metasize)
 		skb_metadata_set(skb, metasize);
-- 
2.34.1