net: Implement netdev_nl_queue_create_doit

Implement netdev_nl_queue_create_doit which creates a new rx queue in a
virtual netdev and then leases it to a rx queue in a physical netdev.

Example with ynl client:

  # ynl --family netdev --output-json --do queue-create \
        --json '{"ifindex": 8, "type": "rx", "lease": {"ifindex": 4, "queue": {"type": "rx", "id": 15}}}'
  {'id': 1}

Note that the netdevice locking order is always from the virtual to
the physical device.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260402231031.447597-3-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/networking/netdevices.rst b/Documentation/networking/netdevices.rst
index 35704d115312..83e28b96884f 100644
--- a/Documentation/networking/netdevices.rst
+++ b/Documentation/networking/netdevices.rst
@@ -329,6 +329,12 @@ by setting ``request_ops_lock`` to true. Code comments and docs refer
 to drivers which have ops called under the instance lock as "ops locked".
 See also the documentation of the ``lock`` member of struct net_device.
 
+There is also a case of taking two per-netdev locks in sequence when netdev
+queues are leased, that is, the netdev-scope lock is taken for both the
+virtual and the physical device. To prevent deadlocks, the virtual device's
+lock must always be acquired before the physical device's (see
+``netdev_nl_queue_create_doit``).
+
 In the future, there will be an option for individual
 drivers to opt out of using ``rtnl_lock`` and instead perform their control
 operations directly under the netdev instance lock.