[PATCH net-next v3 4/5] TEST ONLY: lan743x: skb_alloc failure test

[Sven Van Asbroeck]

From: Sven Van Asbroeck <thesven73@xxxxxxxxx>

Simulate low-memory in lan743x_rx_allocate_skb(): fail 10
allocations in a row in every 100.

Signed-off-by: Sven Van Asbroeck <thesven73@xxxxxxxxx>
---

To: Bryan Whitehead <bryan.whitehead@xxxxxxxxxxxxx>
To: UNGLinuxDriver@xxxxxxxxxxxxx
To: "David S. Miller" <davem@xxxxxxxxxxxxx>
To: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Andrew Lunn <andrew@xxxxxxx>
Cc: Alexey Denisov <rtgbnm@xxxxxxxxx>
Cc: Sergej Bauer <sbauer@xxxxxxxxxxx>
Cc: Tim Harvey <tharvey@xxxxxxxxxxxxx>
Cc: Anders Rønningen <anders@xxxxxxxxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

 drivers/net/ethernet/microchip/lan743x_main.c | 21 +++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 90738ec5e7ec..6e1b3c996bd7 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -1963,7 +1963,20 @@ static void lan743x_rx_update_tail(struct lan743x_rx *rx, int index)
 				  index);
 }
 
-static int lan743x_rx_init_ring_element(struct lan743x_rx *rx, int index)
+static struct sk_buff *
+lan743x_alloc_skb(struct net_device *netdev, int length, bool can_fail)
+{
+	static int rx_alloc;
+	int counter = rx_alloc++ % 100;
+
+	if (can_fail && counter >= 20 && counter < 30)
+		return NULL;
+
+	return __netdev_alloc_skb(netdev, length, GFP_ATOMIC | GFP_DMA);
+}
+
+static int
+lan743x_rx_init_ring_element(struct lan743x_rx *rx, int index, bool can_fail)
 {
 	struct net_device *netdev = rx->adapter->netdev;
 	struct device *dev = &rx->adapter->pdev->dev;
@@ -1977,7 +1990,7 @@ static int lan743x_rx_init_ring_element(struct lan743x_rx *rx, int index)
 
 	descriptor = &rx->ring_cpu_ptr[index];
 	buffer_info = &rx->buffer_info[index];
-	skb = __netdev_alloc_skb(netdev, buffer_length, GFP_ATOMIC | GFP_DMA);
+	skb = lan743x_alloc_skb(netdev, buffer_length, can_fail);
 	if (!skb)
 		return -ENOMEM;
 	dma_ptr = dma_map_single(dev, skb->data, buffer_length, DMA_FROM_DEVICE);
@@ -2139,7 +2152,7 @@ static int lan743x_rx_process_buffer(struct lan743x_rx *rx)
 
 	/* save existing skb, allocate new skb and map to dma */
 	skb = buffer_info->skb;
-	if (lan743x_rx_init_ring_element(rx, rx->last_head)) {
+	if (lan743x_rx_init_ring_element(rx, rx->last_head, true)) {
 		/* failed to allocate next skb.
 		 * Memory is very low.
 		 * Drop this packet and reuse buffer.
@@ -2344,7 +2357,7 @@ static int lan743x_rx_ring_init(struct lan743x_rx *rx)
 
 	rx->last_head = 0;
 	for (index = 0; index < rx->ring_size; index++) {
-		ret = lan743x_rx_init_ring_element(rx, index);
+		ret = lan743x_rx_init_ring_element(rx, index, false);
 		if (ret)
 			goto cleanup;
 	}
-- 
2.17.1