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Commit 02875878 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: better IFF_XMIT_DST_RELEASE support 



Testing xmit_more support with netperf and connected UDP sockets,
I found strange dst refcount false sharing.

Current handling of IFF_XMIT_DST_RELEASE is not optimal.

Dropping dst in validate_xmit_skb() is certainly too late in case
packet was queued by cpu X but dequeued by cpu Y

The logical point to take care of drop/force is in __dev_queue_xmit()
before even taking qdisc lock.

As Julian Anastasov pointed out, need for skb_dst() might come from some
packet schedulers or classifiers.

This patch adds new helper to cleanly express needs of various drivers
or qdiscs/classifiers.

Drivers that need skb_dst() in their ndo_start_xmit() should call
following helper in their setup instead of the prior :

	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
->
	netif_keep_dst(dev);

Instead of using a single bit, we use two bits, one being
eventually rebuilt in bonding/team drivers.

The other one, is permanent and blocks IFF_XMIT_DST_RELEASE being
rebuilt in bonding/team. Eventually, we could add something
smarter later.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fe971b95

drivers/infiniband/ulp/ipoib/ipoib_main.c

+1 −1
Original line number Diff line number Diff line
@@ -1364,7 +1364,7 @@ void ipoib_setup(struct net_device *dev) 
	dev->tx_queue_len	 = ipoib_sendq_size * 2;

	dev->features		 = (NETIF_F_VLAN_CHALLENGED	|

				    NETIF_F_HIGHDMA);

	dev->priv_flags		&= ~IFF_XMIT_DST_RELEASE;

	netif_keep_dst(dev);



	memcpy(dev->broadcast, ipv4_bcast_addr, INFINIBAND_ALEN);

drivers/net/appletalk/ipddp.c

+1 −1
Original line number Diff line number Diff line
@@ -74,7 +74,7 @@ static struct net_device * __init ipddp_init(void) 
	if (!dev)

		return ERR_PTR(-ENOMEM);



	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;

	netif_keep_dst(dev);

	strcpy(dev->name, "ipddp%d");



	if (version_printed++ == 0)

drivers/net/bonding/bond_main.c

+6 −3
Original line number Diff line number Diff line
@@ -1002,7 +1002,8 @@ static netdev_features_t bond_fix_features(struct net_device *dev, 


static void bond_compute_features(struct bonding *bond)

{

	unsigned int flags, dst_release_flag = IFF_XMIT_DST_RELEASE;

	unsigned int dst_release_flag = IFF_XMIT_DST_RELEASE |

					IFF_XMIT_DST_RELEASE_PERM;

	netdev_features_t vlan_features = BOND_VLAN_FEATURES;

	netdev_features_t enc_features  = BOND_ENC_FEATURES;

	struct net_device *bond_dev = bond->dev;
@@ -1038,8 +1039,10 @@ static void bond_compute_features(struct bonding *bond) 
	bond_dev->gso_max_segs = gso_max_segs;

	netif_set_gso_max_size(bond_dev, gso_max_size);



	flags = bond_dev->priv_flags & ~IFF_XMIT_DST_RELEASE;

	bond_dev->priv_flags = flags | dst_release_flag;

	bond_dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;

	if ((bond_dev->priv_flags & IFF_XMIT_DST_RELEASE_PERM) &&

	    dst_release_flag == (IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM))

		bond_dev->priv_flags |= IFF_XMIT_DST_RELEASE;



	netdev_change_features(bond_dev);

}

drivers/net/eql.c

+1 −1
Original line number Diff line number Diff line
@@ -199,7 +199,7 @@ static void __init eql_setup(struct net_device *dev) 


	dev->type       	= ARPHRD_SLIP;

	dev->tx_queue_len 	= 5;		/* Hands them off fast */

	dev->priv_flags	       &= ~IFF_XMIT_DST_RELEASE;

	netif_keep_dst(dev);

}



static int eql_open(struct net_device *dev)

drivers/net/ifb.c

+2 −1
Original line number Diff line number Diff line
@@ -185,7 +185,8 @@ static void ifb_setup(struct net_device *dev) 


	dev->flags |= IFF_NOARP;

	dev->flags &= ~IFF_MULTICAST;

	dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_TX_SKB_SHARING);

	dev->priv_flags &= ~IFF_TX_SKB_SHARING;

	netif_keep_dst(dev);

	eth_hw_addr_random(dev);

}