diff options
| author | Jesper Dangaard Brouer <hawk@kernel.org> | 2025-04-25 16:55:31 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-04-28 14:06:58 -0700 |
| commit | 34dd0fecaa02d654c447d43a7e4c72f9b18b7033 (patch) | |
| tree | bf14e87a1e0afe98fa011cb961ab4ec5c1ec8437 | |
| parent | ccc25158c22bf9aaf1242182b852bb6c73e88ac3 (diff) | |
net: sched: generalize check for no-queue qdisc on TX queue
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@firesoul
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/vrf.c | 4 | ||||
| -rw-r--r-- | 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 7168b33adadb..9a4beea6ee0c 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -343,15 +343,13 @@ unlock: 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 d48c657191cd..b6c177f7141c 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) { |