netdev - [PATCH net V1 2/2] net/mlx4_en: Fix pages never dma unmapped on rx

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Message-Id: <1381145893-20930-3-git-send-email-amirv@mellanox.com>
Date:	Mon,  7 Oct 2013 13:38:13 +0200
From:	Amir Vadai <amirv@...lanox.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Amir Vadai <amirv@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net V1 2/2] 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@...gle.com>
Signed-off-by: Amir Vadai <amirv@...lanox.com>
---
After looking at the code again, need to use 2*frag_stride and not to look at
size of next frag in skb. Changed it accordingly

 drivers/net/ethernet/mellanox/mlx4/en_rx.c | 5 +++--
 1 file 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 066fc27..afe2efa 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);
 
-- 
1.8.3.4

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