linux-kernel - [PATCH 4.9 24/51] net/mlx5e: Do not recycle pages from emergency reserve

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Date:   Thu,  2 Feb 2017 19:37:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 24/51] net/mlx5e: Do not recycle pages from emergency reserve

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

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

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


[ Upstream commit e048fc50d7bde23136e098e04a324d7e3404408d ]

A driver using dev_alloc_page() must not reuse a page allocated from
emergency memory reserve.

Otherwise all packets using this page will be immediately dropped,
unless for very specific sockets having SOCK_MEMALLOC bit set.

This issue might be hard to debug, because only a fraction of received
packets would be dropped.

Fixes: 4415a0319f92 ("net/mlx5e: Implement RX mapped page cache for page recycle")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Tariq Toukan <tariqt@...lanox.com>
Cc: Saeed Mahameed <saeedm@...lanox.com>
Acked-by: Saeed Mahameed <saeedm@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -193,6 +193,9 @@ static inline bool mlx5e_rx_cache_put(st
 		return false;
 	}
 
+	if (unlikely(page_is_pfmemalloc(dma_info->page)))
+		return false;
+
 	cache->page_cache[cache->tail] = *dma_info;
 	cache->tail = tail_next;
 	return true;