virtio_net: use dev_kfree_skb_any() in free_old_xmit_skbs()

Because netpoll can call netdevice start_xmit() method with
irqs disabled, drivers should not call kfree_skb() from
their start_xmit(), but use dev_kfree_skb_any() instead.

Oct  8 11:16:52 172.30.1.31 [113074.791813] ------------[ cut here ]------------
Oct  8 11:16:52 172.30.1.31 [113074.791813] WARNING: at net/core/skbuff.c:398 \
                skb_release_head_state+0x64/0xc8()
Oct  8 11:16:52 172.30.1.31 [113074.791813] Hardware name:
Oct  8 11:16:52 172.30.1.31 [113074.791813] Modules linked in: netconsole ocfs2 jbd2 quota_tree \
ocfs2_dlmfs ocfs2_stack_o2cb ocfs2_dlm ocfs2_nodemanager ocfs2_stackglue configfs crc32c drbd cn loop \
serio_raw psmouse snd_pcm snd_timer snd soundcore snd_page_alloc virtio_net pcspkr parport_pc parport \
i2c_piix4 i2c_core button processor evdev ext3 jbd mbcache dm_mirror dm_region_hash dm_log dm_snapshot \
dm_mod ide_cd_mod cdrom ata_generic ata_piix virtio_blk libata scsi_mod piix ide_pci_generic ide_core \
                virtio_pci virtio_ring virtio floppy thermal fan thermal_sys [last unloaded: netconsole]
Oct  8 11:16:52 172.30.1.31 [113074.791813] Pid: 11132, comm: php5-cgi Tainted: G        W  \
                2.6.31.2-vserver #1
Oct  8 11:16:52 172.30.1.31 [113074.791813] Call Trace:
Oct  8 11:16:52 172.30.1.31 [113074.791813] <IRQ>  [<ffffffff81253cd5>] ? \
                skb_release_head_state+0x64/0xc8
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81253cd5>] ? skb_release_head_state+0x64/0xc8
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81049ae1>] ? warn_slowpath_common+0x77/0xa3
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81253cd5>] ? skb_release_head_state+0x64/0xc8
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81253a1a>] ? __kfree_skb+0x9/0x7d
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffffa01cb139>] ? free_old_xmit_skbs+0x51/0x6e \
                [virtio_net]
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffffa01cbc85>] ? start_xmit+0x26/0xf2 [virtio_net]
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8126934f>] ? netpoll_send_skb+0xd2/0x205
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffffa0429216>] ? write_msg+0x90/0xeb [netconsole]
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81049f06>] ? __call_console_drivers+0x5e/0x6f
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8102b49d>] ? kvm_clock_read+0x4d/0x52
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8104a082>] ? release_console_sem+0x115/0x1ba
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8104a632>] ? vprintk+0x2f2/0x34b
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8106b142>] ? vx_update_load+0x18/0x13e
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81308309>] ? printk+0x4e/0x5d
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff8102b49d>] ? kvm_clock_read+0x4d/0x52
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81070b62>] ? getnstimeofday+0x55/0xaf
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81062683>] ? ktime_get_ts+0x21/0x49
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff810626b7>] ? ktime_get+0xc/0x41
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81062788>] ? hrtimer_interrupt+0x9c/0x146
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81024a4b>] ? smp_apic_timer_interrupt+0x80/0x93
Oct  8 11:16:52 172.30.1.31 [113074.791813] [<ffffffff81011663>] ? apic_timer_interrupt+0x13/0x20
Oct  8 11:16:52 172.30.1.31 [113074.791813] <EOI>  [<ffffffff8130a9eb>] ? _spin_unlock_irq+0xd/0x31

Reported-and-tested-by: Massimo Cetra <mcetra@navynet.it>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Bug-Entry: http://bugzilla.kernel.org/show_bug.cgi?id=14378
Signed-off-by: David S. Miller <davem@davemloft.net>