[ 3.8.y.z extended stable ] Patch "atl1c: use custom skb allocator" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    atl1c: use custom skb allocator

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 4d90e6554ca734523c9dcfa5f4f724a8650c7c8f Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Mon, 29 Jul 2013 10:24:04 -0700
Subject: atl1c: use custom skb allocator

[ Upstream commit 7b70176421993866e616f1cbc4d0dd4054f1bf78 ]

We had reports ( https://bugzilla.kernel.org/show_bug.cgi?id=54021 )
that using high order pages for skb allocations is problematic for atl1c

We do not know exactly what the problem is, but we suspect that crossing
4K pages is not well supported by this hardware.

Use a custom allocator, using page allocator and 2K fragments for
optimal stack behavior. We might make this allocator generic
in future kernels.

Signed-off-by: Eric Dumazet <edumazet at google.com>
Cc: Luis Henriques <luis.henriques at canonical.com>
Cc: Neil Horman <nhorman at tuxdriver.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/ethernet/atheros/atl1c/atl1c.h      |  3 ++
 drivers/net/ethernet/atheros/atl1c/atl1c_main.c | 40 ++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c.h b/drivers/net/ethernet/atheros/atl1c/atl1c.h
index b2bf324..0f05565 100644
--- a/drivers/net/ethernet/atheros/atl1c/atl1c.h
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c.h
@@ -520,6 +520,9 @@ struct atl1c_adapter {
 	struct net_device   *netdev;
 	struct pci_dev      *pdev;
 	struct napi_struct  napi;
+	struct page         *rx_page;
+	unsigned int	    rx_page_offset;
+	unsigned int	    rx_frag_size;
 	struct atl1c_hw        hw;
 	struct atl1c_hw_stats  hw_stats;
 	struct mii_if_info  mii;    /* MII interface info */
diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
index bfcb8bc..26a8c62 100644
--- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
@@ -482,10 +482,15 @@ static int atl1c_set_mac_addr(struct net_device *netdev, void *p)
 static void atl1c_set_rxbufsize(struct atl1c_adapter *adapter,
 				struct net_device *dev)
 {
+	unsigned int head_size;
 	int mtu = dev->mtu;

 	adapter->rx_buffer_len = mtu > AT_RX_BUF_SIZE ?
 		roundup(mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN, 8) : AT_RX_BUF_SIZE;
+
+	head_size = SKB_DATA_ALIGN(adapter->rx_buffer_len + NET_SKB_PAD) +
+		    SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	adapter->rx_frag_size = roundup_pow_of_two(head_size);
 }

 static netdev_features_t atl1c_fix_features(struct net_device *netdev,
@@ -953,6 +958,10 @@ static void atl1c_free_ring_resources(struct atl1c_adapter *adapter)
 		kfree(adapter->tpd_ring[0].buffer_info);
 		adapter->tpd_ring[0].buffer_info = NULL;
 	}
+	if (adapter->rx_page) {
+		put_page(adapter->rx_page);
+		adapter->rx_page = NULL;
+	}
 }

 /**
@@ -1642,6 +1651,35 @@ static inline void atl1c_rx_checksum(struct atl1c_adapter *adapter,
 	skb_checksum_none_assert(skb);
 }

+static struct sk_buff *atl1c_alloc_skb(struct atl1c_adapter *adapter)
+{
+	struct sk_buff *skb;
+	struct page *page;
+
+	if (adapter->rx_frag_size > PAGE_SIZE)
+		return netdev_alloc_skb(adapter->netdev,
+					adapter->rx_buffer_len);
+
+	page = adapter->rx_page;
+	if (!page) {
+		adapter->rx_page = page = alloc_page(GFP_ATOMIC);
+		if (unlikely(!page))
+			return NULL;
+		adapter->rx_page_offset = 0;
+	}
+
+	skb = build_skb(page_address(page) + adapter->rx_page_offset,
+			adapter->rx_frag_size);
+	if (likely(skb)) {
+		adapter->rx_page_offset += adapter->rx_frag_size;
+		if (adapter->rx_page_offset >= PAGE_SIZE)
+			adapter->rx_page = NULL;
+		else
+			get_page(page);
+	}
+	return skb;
+}
+
 static int atl1c_alloc_rx_buffer(struct atl1c_adapter *adapter)
 {
 	struct atl1c_rfd_ring *rfd_ring = &adapter->rfd_ring;
@@ -1663,7 +1701,7 @@ static int atl1c_alloc_rx_buffer(struct atl1c_adapter *adapter)
 	while (next_info->flags & ATL1C_BUFFER_FREE) {
 		rfd_desc = ATL1C_RFD_DESC(rfd_ring, rfd_next_to_use);

-		skb = netdev_alloc_skb(adapter->netdev, adapter->rx_buffer_len);
+		skb = atl1c_alloc_skb(adapter);
 		if (unlikely(!skb)) {
 			if (netif_msg_rx_err(adapter))
 				dev_warn(&pdev->dev, "alloc rx buffer failed\n");
--
1.8.1.2