[RFC bpf-next 2/6] xsk: refactor xdp_umem_assign_dev()

[Jakub Kicinski]

Return early and only take the ref on dev once there is no possibility
of failing.

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Quentin Monnet <quentin.mon...@netronome.com>
---
 net/xdp/xdp_umem.c | 49 ++++++++++++++++++++--------------------------
 1 file changed, 21 insertions(+), 28 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index f47abb46c587..c199d66b5f3f 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -56,41 +56,34 @@ int xdp_umem_assign_dev(struct xdp_umem *umem, struct 
net_device *dev,
        if (force_copy)
                return 0;
 
-       dev_hold(dev);
+       if (!dev->netdev_ops->ndo_bpf || !dev->netdev_ops->ndo_xsk_async_xmit)
+               return force_zc ? -ENOTSUPP : 0; /* fail or fallback */
 
-       if (dev->netdev_ops->ndo_bpf && dev->netdev_ops->ndo_xsk_async_xmit) {
-               bpf.command = XDP_QUERY_XSK_UMEM;
+       bpf.command = XDP_QUERY_XSK_UMEM;
 
-               rtnl_lock();
-               err = dev->netdev_ops->ndo_bpf(dev, &bpf);
-               rtnl_unlock();
+       rtnl_lock();
+       err = dev->netdev_ops->ndo_bpf(dev, &bpf);
+       rtnl_unlock();
 
-               if (err) {
-                       dev_put(dev);
-                       return force_zc ? -ENOTSUPP : 0;
-               }
+       if (err)
+               return force_zc ? -ENOTSUPP : 0;
 
-               bpf.command = XDP_SETUP_XSK_UMEM;
-               bpf.xsk.umem = umem;
-               bpf.xsk.queue_id = queue_id;
+       bpf.command = XDP_SETUP_XSK_UMEM;
+       bpf.xsk.umem = umem;
+       bpf.xsk.queue_id = queue_id;
 
-               rtnl_lock();
-               err = dev->netdev_ops->ndo_bpf(dev, &bpf);
-               rtnl_unlock();
+       rtnl_lock();
+       err = dev->netdev_ops->ndo_bpf(dev, &bpf);
+       rtnl_unlock();
 
-               if (err) {
-                       dev_put(dev);
-                       return force_zc ? err : 0; /* fail or fallback */
-               }
-
-               umem->dev = dev;
-               umem->queue_id = queue_id;
-               umem->zc = true;
-               return 0;
-       }
+       if (err)
+               return force_zc ? err : 0; /* fail or fallback */
 
-       dev_put(dev);
-       return force_zc ? -ENOTSUPP : 0; /* fail or fallback */
+       dev_hold(dev);
+       umem->dev = dev;
+       umem->queue_id = queue_id;
+       umem->zc = true;
+       return 0;
 }
 
 static void xdp_umem_clear_dev(struct xdp_umem *umem)
-- 
2.17.1