r8169: improve rx buffer allocation

8 years ago, as part of 6f0333b8fde4 ("r8169: use 50% less ram for RX
ring"), the alignment requirement for rx buffers was silently changed
from 8 bytes to 16 bytes. I found nothing explaining this, also the
chip specs I have only mention an 8 byte requirement.
AFAICS kmalloc_node() guarantees allocated memory to be at least
"long long" aligned, what is 8 bytes on a 32 bit machine.
So we can take this memory as-is and avoid some overhead by changing
the alignment requirement back to 8 bytes.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index e790a4116f1e2874c764977813762a68d79f5d08..970c82694d4d964937bf1a007f3a2eff171d27ab 100644 (file)
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -5659,11 +5659,6 @@ static inline void rtl8169_mark_to_asic(struct RxDesc *desc)
        desc->opts1 = cpu_to_le32(DescOwn | eor | R8169_RX_BUF_SIZE);
 }
 
-static inline void *rtl8169_align(void *data)
-{
-       return (void *)ALIGN((long)data, 16);
-}
-
 static struct sk_buff *rtl8169_alloc_rx_data(struct rtl8169_private *tp,
                                             struct RxDesc *desc)
 {
@@ -5676,15 +5671,13 @@ static struct sk_buff *rtl8169_alloc_rx_data(struct rtl8169_private *tp,
        if (!data)
                return NULL;
 
-       if (rtl8169_align(data) != data) {
-               kfree(data);
-               data = kmalloc_node(R8169_RX_BUF_SIZE + 15, GFP_KERNEL, node);
-               if (!data)
-                       return NULL;
+       /* Memory should be properly aligned, but better check. */
+       if (!IS_ALIGNED((unsigned long)data, 8)) {
+               netdev_err_once(tp->dev, "RX buffer not 8-byte-aligned\n");
+               goto err_out;
        }
 
-       mapping = dma_map_single(d, rtl8169_align(data), R8169_RX_BUF_SIZE,
-                                DMA_FROM_DEVICE);
+       mapping = dma_map_single(d, data, R8169_RX_BUF_SIZE, DMA_FROM_DEVICE);
        if (unlikely(dma_mapping_error(d, mapping))) {
                if (net_ratelimit())
                        netif_err(tp, drv, tp->dev, "Failed to map RX DMA!\n");
@@ -6290,7 +6283,6 @@ static struct sk_buff *rtl8169_try_rx_copy(void *data,
        struct sk_buff *skb;
        struct device *d = tp_to_dev(tp);
 
-       data = rtl8169_align(data);
        dma_sync_single_for_cpu(d, addr, pkt_size, DMA_FROM_DEVICE);
        prefetch(data);
        skb = napi_alloc_skb(&tp->napi, pkt_size);