xen-netfront: fix warn message as irq device name has '/'

There is a call trace generated after commit 2d408c0d(
xen-netfront: fix queue name setting). There is no 'device/vif/xx-q0-tx' file found
under /proc/irq/xx/.

This patch only picks up device type and id as its name.

With the patch, now /proc/interrupts looks like below and the warning message gone:
 70:         21          0          0          0   xen-dyn    -event     vif0-q0-tx
 71:         15          0          0          0   xen-dyn    -event     vif0-q0-rx
 72:         14          0          0          0   xen-dyn    -event     vif0-q1-tx
 73:         33          0          0          0   xen-dyn    -event     vif0-q1-rx
 74:         12          0          0          0   xen-dyn    -event     vif0-q2-tx
 75:         24          0          0          0   xen-dyn    -event     vif0-q2-rx
 76:         19          0          0          0   xen-dyn    -event     vif0-q3-tx
 77:         21          0          0          0   xen-dyn    -event     vif0-q3-rx

Below is call trace information without this patch:

name 'device/vif/0-q0-tx'
WARNING: CPU: 2 PID: 37 at fs/proc/generic.c:174 __xlate_proc_name+0x85/0xa0
RIP: 0010:__xlate_proc_name+0x85/0xa0
RSP: 0018:ffffb85c40473c18 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000006
RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff984c7f516930
RBP: ffffb85c40473cb8 R08: 000000000000002c R09: 0000000000000229
R10: 0000000000000000 R11: 0000000000000001 R12: ffffb85c40473c98
R13: ffffb85c40473cb8 R14: ffffb85c40473c50 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff984c7f500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f69b6899038 CR3: 000000001c20a006 CR4: 00000000001606e0
Call Trace:
__proc_create+0x45/0x230
? snprintf+0x49/0x60
proc_mkdir_data+0x35/0x90
register_handler_proc+0xef/0x110
? proc_register+0xfc/0x110
? proc_create_data+0x70/0xb0
__setup_irq+0x39b/0x660
? request_threaded_irq+0xad/0x160
request_threaded_irq+0xf5/0x160
? xennet_tx_buf_gc+0x1d0/0x1d0 [xen_netfront]
bind_evtchn_to_irqhandler+0x3d/0x70
? xenbus_alloc_evtchn+0x41/0xa0
netback_changed+0xa46/0xcda [xen_netfront]
? find_watch+0x40/0x40
xenwatch_thread+0xc5/0x160
? finish_wait+0x80/0x80
kthread+0x112/0x130
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x35/0x40
Code: 81 5c 00 48 85 c0 75 cc 5b 49 89 2e 31 c0 5d 4d 89 3c 24 41 5c 41 5d 41 5e 41 5f c3 4c 89 ee 48 c7 c7 40 4f 0e b4 e8 65 ea d8 ff <0f> 0b b8 fe ff ff ff 5b 5d 41 5c 41 5d 41 5e 41 5f c3 66 0f 1f
---[ end trace 650e5561b0caab3a ]---
Signed-off-by: Xiao Liang <xiliang@redhat.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netfront.c

@@ -1604,14 +1604,16 @@ static int xennet_init_queue(struct netfront_queue *queue)
 {
 	unsigned short i;
 	int err = 0;
+	char *devid;
 
 	spin_lock_init(&queue->tx_lock);
 	spin_lock_init(&queue->rx_lock);
 
 	timer_setup(&queue->rx_refill_timer, rx_refill_timeout, 0);
 
-	snprintf(queue->name, sizeof(queue->name), "%s-q%u",
-		 queue->info->xbdev->nodename, queue->id);
+	devid = strrchr(queue->info->xbdev->nodename, '/') + 1;
+	snprintf(queue->name, sizeof(queue->name), "vif%s-q%u",
+		 devid, queue->id);
 
 	/* Initialise tx_skbs as a free chain containing every entry. */
 	queue->tx_skb_freelist = 0;