[PATCH 3.16.y-ckt 015/180] xen-netback: respect user provided max_queues

[Luis Henriques]

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Wei Liu <wei.liu2@xxxxxxxxxx>

commit 4c82ac3c37363e8c4ded6a5fe1ec5fa756b34df3 upstream.

Originally that parameter was always reset to num_online_cpus during
module initialisation, which renders it useless.

The fix is to only set max_queues to num_online_cpus when user has not
provided a value.

Reported-by: Johnny Strom <johnny.strom@xxxxxxxxxxxxxxxxx>
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/net/xen-netback/netback.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 0c1574212162..4a35be8e397c 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -2008,8 +2008,11 @@ static int __init netback_init(void)
 	if (!xen_domain())
 		return -ENODEV;
 
-	/* Allow as many queues as there are CPUs, by default */
-	xenvif_max_queues = num_online_cpus();
+	/* Allow as many queues as there are CPUs if user has not
+	 * specified a value.
+	 */
+	if (xenvif_max_queues == 0)
+		xenvif_max_queues = num_online_cpus();
 
 	if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
 		pr_info("fatal_skb_slots too small (%d), bump it to XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",