i40e: don't reserve excessive XDP_PACKET_HEADROOM on XSK Rx to skb

stable inclusion
from stable-v5.10.110
commit b2e48cd14110fff7d4b3552515dc73f09eaa76a7
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b2e48cd14110fff7d4b3552515dc73f09eaa76a7

--------------------------------

[ Upstream commit bc97f9c6 ]

{__,}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: 0a714186 ("i40e: add AF_XDP zero-copy Rx support")
Signed-off-by: NAlexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: NMichal Swiatkowski <michal.swiatkowski@linux.intel.com>
Acked-by: NJesper Dangaard Brouer <brouer@redhat.com>
Tested-by: NKiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/intel/i40e/i40e_xsk.c

@@ -252,13 +252,11 @@ 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))
 		return NULL;
 
-	skb_reserve(skb, xdp->data - xdp->data_hard_start);
 	memcpy(__skb_put(skb, datasize), xdp->data, datasize);
 	if (metasize)
 		skb_metadata_set(skb, metasize);