xen-netback: enable user to unload netback module

This patch enables user to unload netback module, which is useful when user
wants to upgrade to a newer netback module without rebooting the host.

Netfront cannot handle netback removal event. As we cannot fix all possible
frontends we add module get / put along with vif get / put to avoid
mis-unloading of netback. To unload netback module, user needs to shutdown all
VMs or migrate them to another host or unplug all vifs before hand.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>¬
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index d98414168485..82202c2b1bd1 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -316,6 +316,8 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
         if (vif->irq)
                 return 0;
 
+        __module_get(THIS_MODULE);
+
         err = xen_netbk_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
         if (err < 0)
                 goto err;
@@ -343,6 +345,7 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
 err_unmap:
         xen_netbk_unmap_frontend_rings(vif);
 err:
+        module_put(THIS_MODULE);
         return err;
 }
 
@@ -360,18 +363,32 @@ void xenvif_carrier_off(struct xenvif *vif)
 
 void xenvif_disconnect(struct xenvif *vif)
 {
+        /* Disconnect funtion might get called by generic framework
+         * even before vif connects, so we need to check if we really
+         * need to do a module_put.
+         */
+        int need_module_put = 0;
+
         if (netif_carrier_ok(vif->dev))
                 xenvif_carrier_off(vif);
 
         atomic_dec(&vif->refcnt);
         wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
 
-        if (vif->irq)
+        if (vif->irq) {
                 unbind_from_irqhandler(vif->irq, vif);
+                /* vif->irq is valid, we had a module_get in
+                 * xenvif_connect.
+                 */
+                need_module_put = 1;
+        }
 
         unregister_netdev(vif->dev);
 
         xen_netbk_unmap_frontend_rings(vif);
 
         free_netdev(vif->dev);
+
+        if (need_module_put)
+                module_put(THIS_MODULE);
 }