net/mlx4_en: Fix pages never dma unmapped on rx

This patch fixes a bug introduced by commit 51151a16 (mlx4: allow
order-0 memory allocations in RX path).

dma_unmap_page never reached because condition to detect last fragment
in page is wrong. offset+frag_stride can't be greater than size, need to
make sure no additional frag will fit in page => compare offset +
frag_stride + next_frag_size instead.
next_frag_size is the same as the current one, since page is shared only
with frags of the same size.

CC: Eric Dumazet <edumazet@google.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index 066fc2747854..afe2efa69c86 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -135,9 +135,10 @@ static void mlx4_en_free_frag(struct mlx4_en_priv *priv,
                               int i)
 {
         const struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
+        u32 next_frag_end = frags[i].page_offset + 2 * frag_info->frag_stride;
 
-        if (frags[i].page_offset + frag_info->frag_stride >
-            frags[i].page_size)
+
+        if (next_frag_end > frags[i].page_size)
                 dma_unmap_page(priv->ddev, frags[i].dma, frags[i].page_size,
                                PCI_DMA_FROMDEVICE);