From f0796d5c73e59786d09a1e617689d1d415f2db44 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Thu, 1 Jul 2010 13:21:57 +0000 Subject: [PATCH] net: decreasing real_num_tx_queues needs to flush qdisc Reducing real_num_queues needs to flush the qdisc otherwise skbs with queue_mappings greater then real_num_tx_queues can be sent to the underlying driver. The flow for this is, dev_queue_xmit() dev_pick_tx() skb_tx_hash() => hash using real_num_tx_queues skb_set_queue_mapping() ... qdisc_enqueue_root() => enqueue skb on txq from hash ... dev->real_num_tx_queues -= n ... sch_direct_xmit() dev_hard_start_xmit() ndo_start_xmit(skb,dev) => skb queue set with old hash skbs are enqueued on the qdisc with skb->queue_mapping set 0 < queue_mappings < real_num_tx_queues. When the driver decreases real_num_tx_queues skb's may be dequeued from the qdisc with a queue_mapping greater then real_num_tx_queues. This fixes a case in ixgbe where this was occurring with DCB and FCoE. Because the driver is using queue_mapping to map skbs to tx descriptor rings we can potentially map skbs to rings that no longer exist. Signed-off-by: John Fastabend Tested-by: Ross Brattain Signed-off-by: Jeff Kirsher Signed-off-by: David S. Miller --- drivers/net/ixgbe/ixgbe_main.c | 2 +- include/linux/netdevice.h | 3 +++ include/net/sch_generic.h | 12 ++++++++---- net/core/dev.c | 18 ++++++++++++++++++ 4 files changed, 30 insertions(+), 5 deletions(-) diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c index a0b3316..7b5d976 100644 --- a/drivers/net/ixgbe/ixgbe_main.c +++ b/drivers/net/ixgbe/ixgbe_main.c @@ -4001,7 +4001,7 @@ static void ixgbe_set_num_queues(struct ixgbe_adapter *adapter) done: /* Notify the stack of the (possibly) reduced Tx Queue count. */ - adapter->netdev->real_num_tx_queues = adapter->num_tx_queues; + netif_set_real_num_tx_queues(adapter->netdev, adapter->num_tx_queues); } static void ixgbe_acquire_msix_vectors(struct ixgbe_adapter *adapter, diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 40291f3..5e6188d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1656,6 +1656,9 @@ static inline int netif_is_multiqueue(const struct net_device *dev) return (dev->num_tx_queues > 1); } +extern void netif_set_real_num_tx_queues(struct net_device *dev, + unsigned int txq); + /* Use this variant when it is known for sure that it * is executing from hardware interrupt context or with hardware interrupts * disabled. diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index ba749be..433604b 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -313,13 +313,12 @@ extern void qdisc_calculate_pkt_len(struct sk_buff *skb, extern void tcf_destroy(struct tcf_proto *tp); extern void tcf_destroy_chain(struct tcf_proto **fl); -/* Reset all TX qdiscs of a device. */ -static inline void qdisc_reset_all_tx(struct net_device *dev) +/* Reset all TX qdiscs greater then index of a device. */ +static inline void qdisc_reset_all_tx_gt(struct net_device *dev, unsigned int i) { - unsigned int i; struct Qdisc *qdisc; - for (i = 0; i < dev->num_tx_queues; i++) { + for (; i < dev->num_tx_queues; i++) { qdisc = netdev_get_tx_queue(dev, i)->qdisc; if (qdisc) { spin_lock_bh(qdisc_lock(qdisc)); @@ -329,6 +328,11 @@ static inline void qdisc_reset_all_tx(struct net_device *dev) } } +static inline void qdisc_reset_all_tx(struct net_device *dev) +{ + qdisc_reset_all_tx_gt(dev, 0); +} + /* Are all TX queues of the device empty? */ static inline bool qdisc_all_tx_empty(const struct net_device *dev) { diff --git a/net/core/dev.c b/net/core/dev.c index 2b3bf53..723a347 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1553,6 +1553,24 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev) rcu_read_unlock(); } +/* + * Routine to help set real_num_tx_queues. To avoid skbs mapped to queues + * greater then real_num_tx_queues stale skbs on the qdisc must be flushed. + */ +void netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq) +{ + unsigned int real_num = dev->real_num_tx_queues; + + if (unlikely(txq > dev->num_tx_queues)) + ; + else if (txq > real_num) + dev->real_num_tx_queues = txq; + else if (txq < real_num) { + dev->real_num_tx_queues = txq; + qdisc_reset_all_tx_gt(dev, txq); + } +} +EXPORT_SYMBOL(netif_set_real_num_tx_queues); static inline void __netif_reschedule(struct Qdisc *q) { -- 2.7.4