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Commit 45db81e1 authored by Giuseppe CAVALLARO's avatar Giuseppe CAVALLARO Committed by David S. Miller
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stmmac: limit max_mtu in case of 4KiB and use __netdev_alloc_skb (V2) 



Problem using big mtu around 4096 bytes is you end allocating (4096
+NET_SKB_PAD + NET_IP_ALIGN + sizeof(struct skb_shared_info) bytes ->
8192 bytes : order-1 pages

It's better to limit the mtu to SKB_MAX_HEAD(NET_SKB_PAD),
to have no more than one page per skb.

Also the patch changes the netdev_alloc_skb_ip_align() done in
init_dma_desc_rings() and uses a variant allowing GFP_KERNEL allocations
allowing the driver to load even in case of memory pressure.

Reported-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarGiuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 286a8372

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

+4 −2
Original line number Diff line number Diff line
@@ -474,11 +474,13 @@ static void init_dma_desc_rings(struct net_device *dev) 
	for (i = 0; i < rxsize; i++) {

		struct dma_desc *p = priv->dma_rx + i;



		skb = netdev_alloc_skb_ip_align(dev, bfsize);

		skb = __netdev_alloc_skb(dev, bfsize + NET_IP_ALIGN,

					 GFP_KERNEL);

		if (unlikely(skb == NULL)) {

			pr_err("%s: Rx init fails; skb is NULL\n", __func__);

			break;

		}

		skb_reserve(skb, NET_IP_ALIGN);

		priv->rx_skbuff[i] = skb;

		priv->rx_skbuff_dma[i] = dma_map_single(priv->device, skb->data,

						bfsize, DMA_FROM_DEVICE);
@@ -1401,7 +1403,7 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu) 
	if (priv->plat->enh_desc)

		max_mtu = JUMBO_LEN;

	else

		max_mtu = BUF_SIZE_4KiB;

		max_mtu = SKB_MAX_HEAD(NET_SKB_PAD + NET_IP_ALIGN);



	if ((new_mtu < 46) || (new_mtu > max_mtu)) {

		pr_err("%s: invalid MTU, max MTU is: %d\n", dev->name, max_mtu);