netdev - [PATCH net] mlx4: reduce OOM risk on arches with large pages

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Date:   Sat, 18 Feb 2017 10:34:18 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [PATCH net] mlx4: reduce OOM risk on arches with large pages

From: Eric Dumazet <edumazet@...gle.com>

Since mlx4 NIC are used on PowerPC with 64K pages, we need to adapt
MLX4_EN_ALLOC_PREFER_ORDER definition.

Otherwise, a fragment sitting in an out of order TCP queue can hold
0.5 Mbytes and it is a serious OOM risk.

Fixes: 51151a16a60f ("mlx4: allow order-0 memory allocations in RX path")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 drivers/net/ethernet/mellanox/mlx4/mlx4_en.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index cec59bc264c9ac197048fd7c98bcd5cf25de0efd..0f6d2f3b7d54f51de359d4ccde21f4585e6b7852 100644
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -102,7 +102,8 @@
 /* Use the maximum between 16384 and a single page */
 #define MLX4_EN_ALLOC_SIZE	PAGE_ALIGN(16384)
 
-#define MLX4_EN_ALLOC_PREFER_ORDER	PAGE_ALLOC_COSTLY_ORDER
+#define MLX4_EN_ALLOC_PREFER_ORDER min_t(int, get_order(32768),		\
+					 PAGE_ALLOC_COSTLY_ORDER)
 
 /* Receive fragment sizes; we use at most 3 fragments (for 9600 byte MTU
  * and 4K allocations) */