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Commit 432e629e authored by Saeed Mahameed's avatar Saeed Mahameed Committed by David S. Miller
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net/mlx4_en: Don't reuse RX page when XDP is set 



When a new rx packet arrives, the rx path will decide whether to reuse
the remainder of the page or not according to one of the below conditions:
1. frag_info->frag_stride == PAGE_SIZE / 2
2. frags->page_offset + frag_info->frag_size > PAGE_SIZE;

The first condition is no met for when XDP is set.
For XDP, page_offset is always set to priv->rx_headroom which is
XDP_PACKET_HEADROOM and frag_info->frag_size is around mtu size + some
padding, still the 2nd release condition will hold since
XDP_PACKET_HEADROOM + 1536 < PAGE_SIZE, as a result the page will not
be released and will be _wrongly_ reused for next free rx descriptor.

In XDP there is an assumption to have a page per packet and reuse can
break such assumption and might cause packet data corruptions.

Fix this by adding an extra condition (!priv->rx_headroom) to the 2nd
case to avoid page reuse when XDP is set, since rx_headroom is set to 0
for non XDP setup and set to XDP_PACKET_HEADROOM for XDP setup.

No additional cache line is required for the new condition.

Fixes: 34db548b ("mlx4: add page recycling in receive path")
Signed-off-by: default avatarSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: default avatarTariq Toukan <tariqt@mellanox.com>
Suggested-by: default avatarMartin KaFai Lau <kafai@fb.com>
CC: Eric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c1334597

drivers/net/ethernet/mellanox/mlx4/en_rx.c

+6 −2
Original line number Diff line number Diff line
@@ -474,10 +474,10 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv, 
{

	const struct mlx4_en_frag_info *frag_info = priv->frag_info;

	unsigned int truesize = 0;

	bool release = true;

	int nr, frag_size;

	struct page *page;

	dma_addr_t dma;

	bool release;



	/* Collect used fragments while replacing them in the HW descriptors */

	for (nr = 0;; frags++) {
@@ -500,7 +500,11 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv, 
			release = page_count(page) != 1 ||

				  page_is_pfmemalloc(page) ||

				  page_to_nid(page) != numa_mem_id();

		} else {

		} else if (!priv->rx_headroom) {

			/* rx_headroom for non XDP setup is always 0.

			 * When XDP is set, the above condition will

			 * guarantee page is always released.

			 */

			u32 sz_align = ALIGN(frag_size, SMP_CACHE_BYTES);



			frags->page_offset += sz_align;