6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jesper Dangaard Brouer hawk@kernel.org
[ Upstream commit 34dd0fecaa02d654c447d43a7e4c72f9b18b7033 ]
The "noqueue" qdisc can either be directly attached, or get default attached if net_device priv_flags has IFF_NO_QUEUE. In both cases, the allocated Qdisc structure gets it's enqueue function pointer reset to NULL by noqueue_init() via noqueue_qdisc_ops.
This is a common case for software virtual net_devices. For these devices with no-queue, the transmission path in __dev_queue_xmit() will bypass the qdisc layer. Directly invoking device drivers ndo_start_xmit (via dev_hard_start_xmit). In this mode the device driver is not allowed to ask for packets to be queued (either via returning NETDEV_TX_BUSY or stopping the TXQ).
The simplest and most reliable way to identify this no-queue case is by checking if enqueue == NULL.
The vrf driver currently open-codes this check (!qdisc->enqueue). While functionally correct, this low-level detail is better encapsulated in a dedicated helper for clarity and long-term maintainability.
To make this behavior more explicit and reusable, this patch introduce a new helper: qdisc_txq_has_no_queue(). Helper will also be used by the veth driver in the next patch, which introduces optional qdisc-based backpressure.
This is a non-functional change.
Reviewed-by: David Ahern dsahern@kernel.org Reviewed-by: Toke Høiland-Jørgensen toke@redhat.com Signed-off-by: Jesper Dangaard Brouer hawk@kernel.org Link: https://patch.msgid.link/174559293172.827981.7583862632045264175.stgit@fires... Signed-off-by: Jakub Kicinski kuba@kernel.org Stable-dep-of: a14602fcae17 ("veth: reduce XDP no_direct return section to fix race") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/vrf.c | 4 +--- include/net/sch_generic.h | 8 ++++++++ 2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c index 89dde220058a2..b62462d8eff26 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -352,15 +352,13 @@ static int vrf_ifindex_lookup_by_table_id(struct net *net, u32 table_id) static bool qdisc_tx_is_default(const struct net_device *dev) { struct netdev_queue *txq; - struct Qdisc *qdisc;
if (dev->num_tx_queues > 1) return false;
txq = netdev_get_tx_queue(dev, 0); - qdisc = rcu_access_pointer(txq->qdisc);
- return !qdisc->enqueue; + return qdisc_txq_has_no_queue(txq); }
/* Local traffic destined to local address. Reinsert the packet to rx diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index a9d7e9ecee6b5..1e002b1dea629 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -803,6 +803,14 @@ static inline bool qdisc_tx_changing(const struct net_device *dev) return false; }
+/* "noqueue" qdisc identified by not having any enqueue, see noqueue_init() */ +static inline bool qdisc_txq_has_no_queue(const struct netdev_queue *txq) +{ + struct Qdisc *qdisc = rcu_access_pointer(txq->qdisc); + + return qdisc->enqueue == NULL; +} + /* Is the device using the noop qdisc on all queues? */ static inline bool qdisc_tx_is_noop(const struct net_device *dev) {