[PATCH 3.11 20/66] net/mlx4_en: Fix pages never dma unmapped on rx

[Greg Kroah-Hartman]

3.11-stable review patch.  If anyone has any objections, please let me know.

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

From: Amir Vadai <amirv@xxxxxxxxxxxx>

[ Upstream commit 021f1107ffdae7a82af6c53f4c52654062e365c6 ]

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@xxxxxxxxxx>
Signed-off-by: Amir Vadai <amirv@xxxxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/mellanox/mlx4/en_rx.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- 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 mlx
 			      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);
 


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