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Commit f0796d5c authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

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: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Tested-by: default avatarRoss Brattain <ross.b.brattain@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4ef6acff

drivers/net/ixgbe/ixgbe_main.c

+1 −1
Original line number Diff line number Diff line
@@ -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,

include/linux/netdevice.h

+3 −0
Original line number Diff line number Diff line
@@ -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.

include/net/sch_generic.h

+8 −4
Original line number Diff line number Diff line
@@ -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)

{

net/core/dev.c

+18 −0
Original line number Diff line number Diff line
@@ -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)

{