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Date: Fri, 09 Apr 2010 13:43:47 +0800
From: Cong Wang <amwang@...hat.com>
To: Stephen Hemminger <shemminger@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
bridge@...ts.linux-foundation.org,
Andy Gospodarek <gospo@...hat.com>,
Neil Horman <nhorman@...driver.com>,
Jeff Moyer <jmoyer@...hat.com>, Matt Mackall <mpm@...enic.com>,
bonding-devel@...ts.sourceforge.net,
Jay Vosburgh <fubar@...ibm.com>,
David Miller <davem@...emloft.net>
Subject: Re: [v3 Patch 2/3] bridge: make bridge support netpoll
Stephen Hemminger wrote:
> On Thu, 8 Apr 2010 02:18:58 -0400
> Amerigo Wang <amwang@...hat.com> wrote:
>
>> Based on the previous patch, make bridge support netpoll by:
>>
>> 1) implement the 2 methods to support netpoll for bridge;
>>
>> 2) modify netpoll during forwarding packets via bridge;
>>
>> 3) disable netpoll support of bridge when a netpoll-unabled device
>> is added to bridge;
>>
>> 4) enable netpoll support when all underlying devices support netpoll.
>>
>> Cc: David Miller <davem@...emloft.net>
>> Cc: Neil Horman <nhorman@...driver.com>
>> Cc: Stephen Hemminger <shemminger@...ux-foundation.org>
>> Cc: Matt Mackall <mpm@...enic.com>
>> Signed-off-by: WANG Cong <amwang@...hat.com>
>>
>> ---
>>
>> Index: linux-2.6/net/bridge/br_device.c
>> ===================================================================
>> --- linux-2.6.orig/net/bridge/br_device.c
>> +++ linux-2.6/net/bridge/br_device.c
>> @@ -13,8 +13,10 @@
>>
>> #include <linux/kernel.h>
>> #include <linux/netdevice.h>
>> +#include <linux/netpoll.h>
>> #include <linux/etherdevice.h>
>> #include <linux/ethtool.h>
>> +#include <linux/list.h>
>>
>> #include <asm/uaccess.h>
>> #include "br_private.h"
>> @@ -162,6 +164,59 @@ static int br_set_tx_csum(struct net_dev
>> return 0;
>> }
>>
>> +#ifdef CONFIG_NET_POLL_CONTROLLER
>> +bool br_devices_support_netpoll(struct net_bridge *br)
>> +{
>> + struct net_bridge_port *p;
>> + bool ret = true;
>> + int count = 0;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&br->lock, flags);
>> + list_for_each_entry(p, &br->port_list, list) {
>> + count++;
>> + if (p->dev->priv_flags & IFF_DISABLE_NETPOLL
>> + || !p->dev->netdev_ops->ndo_poll_controller)
>> + ret = false;
>> + }
>> + spin_unlock_irqrestore(&br->lock, flags);
>> + return count != 0 && ret;
>> +}
>> +
>> +static void br_poll_controller(struct net_device *br_dev)
>> +{
>> + struct netpoll *np = br_dev->npinfo->netpoll;
>> +
>> + if (np->real_dev != br_dev)
>> + netpoll_poll_dev(np->real_dev);
>> +}
>> +
>> +void br_netpoll_cleanup(struct net_device *br_dev)
>> +{
>> + struct net_bridge *br = netdev_priv(br_dev);
>> + struct net_bridge_port *p, *n;
>> + const struct net_device_ops *ops;
>> +
>> + br->dev->npinfo = NULL;
>> + list_for_each_entry_safe(p, n, &br->port_list, list) {
>> + if (p->dev) {
>> + ops = p->dev->netdev_ops;
>> + if (ops->ndo_netpoll_cleanup)
>> + ops->ndo_netpoll_cleanup(p->dev);
>> + else
>> + p->dev->npinfo = NULL;
>> + }
>> + }
>> +}
>> +
>> +#else
>> +
>> +void br_netpoll_cleanup(struct net_device *br_dev)
>> +{
>> +}
>> +
>> +#endif
>
> Could you use more stub functions to eliminate #ifdef's in code.
Probably no, because only br_netpoll_cleanup() will be called
no matter if CONFIG_NET_POLL_CONTROLLER is defined.
>> @@ -50,7 +51,13 @@ int br_dev_queue_push_xmit(struct sk_buf
>> else {
>> skb_push(skb, ETH_HLEN);
>>
>> - dev_queue_xmit(skb);
>> +#ifdef CONFIG_NET_POLL_CONTROLLER
>> + if (skb->dev->priv_flags & IFF_IN_NETPOLL) {
>> + netpoll_send_skb(skb->dev->npinfo->netpoll, skb);
>> + skb->dev->priv_flags &= ~IFF_IN_NETPOLL;
>> + } else
>> +#endif
>
> There is no protection on dev->priv_flags for SMP access.
> It would better bit value in dev->state if you are using it as control flag.
>
> Then you could use
> if (unlikely(test_and_clear_bit(__IN_NETPOLL, &skb->dev->state)))
> netpoll_send_skb(...)
>
Yes? netpoll_send_skb() needs to see IFF_IN_NETPOLL is set, so
we can't clear this bit before calling it.
But we do need a find a safe way to check/set this flag.
>> static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
>> {
>> +#ifdef CONFIG_NET_POLL_CONTROLLER
>> + struct net_bridge *br = to->br;
>> + if (br->dev->priv_flags & IFF_IN_NETPOLL) {
>> + struct netpoll *np;
>> + to->dev->npinfo = skb->dev->npinfo;
>> + np = skb->dev->npinfo->netpoll;
>> + np->real_dev = np->dev = to->dev;
>> + to->dev->priv_flags |= IFF_IN_NETPOLL;
>> + }
>> +#endif
>
> This is n hot path, so use unlikely()
Ok, good point.
>> +#ifdef CONFIG_NET_POLL_CONTROLLER
>> + if (br_devices_support_netpoll(br)) {
>> + br->dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
>> + if (br->dev->npinfo)
>> + dev->npinfo = br->dev->npinfo;
>> + } else if (!(br->dev->priv_flags & IFF_DISABLE_NETPOLL)) {
>> + br->dev->priv_flags |= IFF_DISABLE_NETPOLL;
>> + printk(KERN_INFO "New device %s does not support netpoll\n",
>> + dev->name);
>> + printk(KERN_INFO "Disabling netpoll for %s\n",
>> + br->dev->name);
>
> One message is sufficient.
>
Yes? The first messages explains the reason for the second message.
Thanks.
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