IFF_NO_QUEUE: Fix for drivers not calling ether_setup()

[ Upstream commit a813104d923339144078939175faf4e66aca19b4 ]

My implementation around IFF_NO_QUEUE driver flag assumed that leaving
tx_queue_len untouched (specifically: not setting it to zero) by drivers
would make it possible to assign a regular qdisc to them without having
to worry about setting tx_queue_len to a useful value. This was only
partially true: I overlooked that some drivers don't call ether_setup()
and therefore not initialize tx_queue_len to the default value of 1000.
Consequently, removing the workarounds in place for that case in qdisc
implementations which cared about it (namely, pfifo, bfifo, gred, htb,
plug and sfb) leads to problems with these specific interface types and
qdiscs.

Luckily, there's already a sanitization point for drivers setting
tx_queue_len to zero, which can be reused to assign the fallback value
most qdisc implementations used, which is 1.

Fixes: 348e3435cbefa ("net: sched: drop all special handling of tx_queue_len == 0")
Tested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/core/dev.c b/net/core/dev.c
index 7dc137fba5c15980feb9344ff56a9e9b8d534efd..9efbdb3ff78a0098b83f60e0c626da933035e983 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7128,8 +7128,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
        dev->priv_flags = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM;
        setup(dev);
 
-       if (!dev->tx_queue_len)
+       if (!dev->tx_queue_len) {
                dev->priv_flags |= IFF_NO_QUEUE;
+               dev->tx_queue_len = 1;
+       }
 
        dev->num_tx_queues = txqs;
        dev->real_num_tx_queues = txqs;