[NET]: Make NAPI polling independent of struct net_device objects.

Several devices have multiple independant RX queues per net
device, and some have a single interrupt doorbell for several
queues.

In either case, it's easier to support layouts like that if the
structure representing the poll is independant from the net
device itself.

The signature of the ->poll() call back goes from:

	int foo_poll(struct net_device *dev, int *budget)

to

	int foo_poll(struct napi_struct *napi, int budget)

The caller is returned the number of RX packets processed (or
the number of "NAPI credits" consumed if you want to get
abstract).  The callee no longer messes around bumping
dev->quota, *budget, etc. because that is all handled in the
caller upon return.

The napi_struct is to be embedded in the device driver private data
structures.

Furthermore, it is the driver's responsibility to disable all NAPI
instances in it's ->stop() device close handler.  Since the
napi_struct is privatized into the driver's private data structures,
only the driver knows how to get at all of the napi_struct instances
it may have per-device.

With lots of help and suggestions from Rusty Russell, Roland Dreier,
Michael Chan, Jeff Garzik, and Jamal Hadi Salim.

Bug fixes from Thomas Graf, Roland Dreier, Peter Zijlstra,
Joseph Fannin, Scott Wood, Hans J. Koch, and Michael Chan.

[ Ported to current tree and all drivers converted.  Integrated
  Stephen's follow-on kerneldoc additions, and restored poll_list
  handling to the old style to fix mutual exclusion issues.  -DaveM ]

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 330 insertions, 86 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e679b275166..b93575db8cc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -31,6 +31,7 @@
 
 #ifdef __KERNEL__
 #include <linux/timer.h>
+#include <linux/delay.h>
 #include <asm/atomic.h>
 #include <asm/cache.h>
 #include <asm/byteorder.h>
@@ -38,6 +39,7 @@
 #include <linux/device.h>
 #include <linux/percpu.h>
 #include <linux/dmaengine.h>
+#include <linux/workqueue.h>
 
 struct vlan_group;
 struct ethtool_ops;
@@ -258,7 +260,6 @@ enum netdev_state_t
 	__LINK_STATE_PRESENT,
 	__LINK_STATE_SCHED,
 	__LINK_STATE_NOCARRIER,
-	__LINK_STATE_RX_SCHED,
 	__LINK_STATE_LINKWATCH_PENDING,
 	__LINK_STATE_DORMANT,
 	__LINK_STATE_QDISC_RUNNING,
@@ -278,6 +279,110 @@ struct netdev_boot_setup {
 extern int __init netdev_boot_setup(char *str);
 
 /*
+ * Structure for NAPI scheduling similar to tasklet but with weighting
+ */
+struct napi_struct {
+	/* The poll_list must only be managed by the entity which
+	 * changes the state of the NAPI_STATE_SCHED bit.  This means
+	 * whoever atomically sets that bit can add this napi_struct
+	 * to the per-cpu poll_list, and whoever clears that bit
+	 * can remove from the list right before clearing the bit.
+	 */
+	struct list_head	poll_list;
+
+	unsigned long		state;
+	int			weight;
+	int			(*poll)(struct napi_struct *, int);
+#ifdef CONFIG_NETPOLL
+	spinlock_t		poll_lock;
+	int			poll_owner;
+	struct net_device	*dev;
+	struct list_head	dev_list;
+#endif
+};
+
+enum
+{
+	NAPI_STATE_SCHED,	/* Poll is scheduled */
+};
+
+extern void FASTCALL(__napi_schedule(struct napi_struct *n));
+
+/**
+ *	napi_schedule_prep - check if napi can be scheduled
+ *	@n: napi context
+ *
+ * Test if NAPI routine is already running, and if not mark
+ * it as running.  This is used as a condition variable
+ * insure only one NAPI poll instance runs
+ */
+static inline int napi_schedule_prep(struct napi_struct *n)
+{
+	return !test_and_set_bit(NAPI_STATE_SCHED, &n->state);
+}
+
+/**
+ *	napi_schedule - schedule NAPI poll
+ *	@n: napi context
+ *
+ * Schedule NAPI poll routine to be called if it is not already
+ * running.
+ */
+static inline void napi_schedule(struct napi_struct *n)
+{
+	if (napi_schedule_prep(n))
+		__napi_schedule(n);
+}
+
+/**
+ *	napi_complete - NAPI processing complete
+ *	@n: napi context
+ *
+ * Mark NAPI processing as complete.
+ */
+static inline void __napi_complete(struct napi_struct *n)
+{
+	BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
+	list_del(&n->poll_list);
+	smp_mb__before_clear_bit();
+	clear_bit(NAPI_STATE_SCHED, &n->state);
+}
+
+static inline void napi_complete(struct napi_struct *n)
+{
+	local_irq_disable();
+	__napi_complete(n);
+	local_irq_enable();
+}
+
+/**
+ *	napi_disable - prevent NAPI from scheduling
+ *	@n: napi context
+ *
+ * Stop NAPI from being scheduled on this context.
+ * Waits till any outstanding processing completes.
+ */
+static inline void napi_disable(struct napi_struct *n)
+{
+	while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
+		msleep_interruptible(1);
+}
+
+/**
+ *	napi_enable - enable NAPI scheduling
+ *	@n: napi context
+ *
+ * Resume NAPI from being scheduled on this context.
+ * Must be paired with napi_disable.
+ */
+static inline void napi_enable(struct napi_struct *n)
+{
+	BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
+	smp_mb__before_clear_bit();
+	clear_bit(NAPI_STATE_SCHED, &n->state);
+}
+
+/*
  *	The DEVICE structure.
  *	Actually, this whole structure is a big mistake.  It mixes I/O
  *	data with strictly "high-level" data, and it has to know about
@@ -319,6 +424,9 @@ struct net_device
 	unsigned long		state;
 
 	struct list_head	dev_list;
+#ifdef CONFIG_NETPOLL
+	struct list_head	napi_list;
+#endif
 	
 	/* The device initialization function. Called only once. */
 	int			(*init)(struct net_device *dev);
@@ -430,12 +538,6 @@ struct net_device
 /*
  * Cache line mostly used on receive path (including eth_type_trans())
  */
-	struct list_head	poll_list ____cacheline_aligned_in_smp;
-					/* Link to poll list	*/
-
-	int			(*poll) (struct net_device *dev, int *quota);
-	int			quota;
-	int			weight;
 	unsigned long		last_rx;	/* Time of last Rx	*/
 	/* Interface address info used in eth_type_trans() */
 	unsigned char		dev_addr[MAX_ADDR_LEN];	/* hw address, (before bcast 
@@ -582,6 +684,12 @@ struct net_device
 #define	NETDEV_ALIGN		32
 #define	NETDEV_ALIGN_CONST	(NETDEV_ALIGN - 1)
 
+/**
+ *	netdev_priv - access network device private data
+ *	@dev: network device
+ *
+ * Get network device private data
+ */
 static inline void *netdev_priv(const struct net_device *dev)
 {
 	return dev->priv;
@@ -593,6 +701,23 @@ static inline void *netdev_priv(const struct net_device *dev)
  */
 #define SET_NETDEV_DEV(net, pdev)	((net)->dev.parent = (pdev))
 
+static inline void netif_napi_add(struct net_device *dev,
+				  struct napi_struct *napi,
+				  int (*poll)(struct napi_struct *, int),
+				  int weight)
+{
+	INIT_LIST_HEAD(&napi->poll_list);
+	napi->poll = poll;
+	napi->weight = weight;
+#ifdef CONFIG_NETPOLL
+	napi->dev = dev;
+	list_add(&napi->dev_list, &dev->napi_list);
+	spin_lock_init(&napi->poll_lock);
+	napi->poll_owner = -1;
+#endif
+	set_bit(NAPI_STATE_SCHED, &napi->state);
+}
+
 struct packet_type {
 	__be16			type;	/* This is really htons(ether_type). */
 	struct net_device	*dev;	/* NULL is wildcarded here	     */
@@ -678,7 +803,6 @@ static inline int unregister_gifconf(unsigned int family)
  * Incoming packets are placed on per-cpu queues so that
  * no locking is needed.
  */
-
 struct softnet_data
 {
 	struct net_device	*output_queue;
@@ -686,7 +810,7 @@ struct softnet_data
 	struct list_head	poll_list;
 	struct sk_buff		*completion_queue;
 
-	struct net_device	backlog_dev;	/* Sorry. 8) */
+	struct napi_struct	backlog;
 #ifdef CONFIG_NET_DMA
 	struct dma_chan		*net_dma;
 #endif
@@ -704,11 +828,24 @@ static inline void netif_schedule(struct net_device *dev)
 		__netif_schedule(dev);
 }
 
+/**
+ *	netif_start_queue - allow transmit
+ *	@dev: network device
+ *
+ *	Allow upper layers to call the device hard_start_xmit routine.
+ */
 static inline void netif_start_queue(struct net_device *dev)
 {
 	clear_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
+/**
+ *	netif_wake_queue - restart transmit
+ *	@dev: network device
+ *
+ *	Allow upper layers to call the device hard_start_xmit routine.
+ *	Used for flow control when transmit resources are available.
+ */
 static inline void netif_wake_queue(struct net_device *dev)
 {
 #ifdef CONFIG_NETPOLL_TRAP
@@ -721,16 +858,35 @@ static inline void netif_wake_queue(struct net_device *dev)
 		__netif_schedule(dev);
 }
 
+/**
+ *	netif_stop_queue - stop transmitted packets
+ *	@dev: network device
+ *
+ *	Stop upper layers calling the device hard_start_xmit routine.
+ *	Used for flow control when transmit resources are unavailable.
+ */
 static inline void netif_stop_queue(struct net_device *dev)
 {
 	set_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
+/**
+ *	netif_queue_stopped - test if transmit queue is flowblocked
+ *	@dev: network device
+ *
+ *	Test if transmit queue on device is currently unable to send.
+ */
 static inline int netif_queue_stopped(const struct net_device *dev)
 {
 	return test_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
+/**
+ *	netif_running - test if up
+ *	@dev: network device
+ *
+ *	Test if the device has been brought up.
+ */
 static inline int netif_running(const struct net_device *dev)
 {
 	return test_bit(__LINK_STATE_START, &dev->state);
@@ -742,6 +898,14 @@ static inline int netif_running(const struct net_device *dev)
  * done at the overall netdevice level.
  * Also test the device if we're multiqueue.
  */
+
+/**
+ *	netif_start_subqueue - allow sending packets on subqueue
+ *	@dev: network device
+ *	@queue_index: sub queue index
+ *
+ * Start individual transmit queue of a device with multiple transmit queues.
+ */
 static inline void netif_start_subqueue(struct net_device *dev, u16 queue_index)
 {
 #ifdef CONFIG_NETDEVICES_MULTIQUEUE
@@ -749,6 +913,13 @@ static inline void netif_start_subqueue(struct net_device *dev, u16 queue_index)
 #endif
 }
 
+/**
+ *	netif_stop_subqueue - stop sending packets on subqueue
+ *	@dev: network device
+ *	@queue_index: sub queue index
+ *
+ * Stop individual transmit queue of a device with multiple transmit queues.
+ */
 static inline void netif_stop_subqueue(struct net_device *dev, u16 queue_index)
 {
 #ifdef CONFIG_NETDEVICES_MULTIQUEUE
@@ -760,6 +931,13 @@ static inline void netif_stop_subqueue(struct net_device *dev, u16 queue_index)
 #endif
 }
 
+/**
+ *	netif_subqueue_stopped - test status of subqueue
+ *	@dev: network device
+ *	@queue_index: sub queue index
+ *
+ * Check individual transmit queue of a device with multiple transmit queues.
+ */
 static inline int netif_subqueue_stopped(const struct net_device *dev,
 					 u16 queue_index)
 {
@@ -771,6 +949,14 @@ static inline int netif_subqueue_stopped(const struct net_device *dev,
 #endif
 }
 
+
+/**
+ *	netif_wake_subqueue - allow sending packets on subqueue
+ *	@dev: network device
+ *	@queue_index: sub queue index
+ *
+ * Resume individual transmit queue of a device with multiple transmit queues.
+ */
 static inline void netif_wake_subqueue(struct net_device *dev, u16 queue_index)
 {
 #ifdef CONFIG_NETDEVICES_MULTIQUEUE
@@ -784,6 +970,13 @@ static inline void netif_wake_subqueue(struct net_device *dev, u16 queue_index)
 #endif
 }
 
+/**
+ *	netif_is_multiqueue - test if device has multiple transmit queues
+ *	@dev: network device
+ *
+ * Check if device has multiple transmit queues
+ * Always falls if NETDEVICE_MULTIQUEUE is not configured
+ */
 static inline int netif_is_multiqueue(const struct net_device *dev)
 {
 #ifdef CONFIG_NETDEVICES_MULTIQUEUE
@@ -796,20 +989,7 @@ static inline int netif_is_multiqueue(const struct net_device *dev)
 /* Use this variant when it is known for sure that it
  * is executing from interrupt context.
  */
-static inline void dev_kfree_skb_irq(struct sk_buff *skb)
-{
-	if (atomic_dec_and_test(&skb->users)) {
-		struct softnet_data *sd;
-		unsigned long flags;
-
-		local_irq_save(flags);
-		sd = &__get_cpu_var(softnet_data);
-		skb->next = sd->completion_queue;
-		sd->completion_queue = skb;
-		raise_softirq_irqoff(NET_TX_SOFTIRQ);
-		local_irq_restore(flags);
-	}
-}
+extern void dev_kfree_skb_irq(struct sk_buff *skb);
 
 /* Use this variant in places where it could be invoked
  * either from interrupt or non-interrupt context.
@@ -833,18 +1013,28 @@ extern int		dev_set_mac_address(struct net_device *,
 extern int		dev_hard_start_xmit(struct sk_buff *skb,
 					    struct net_device *dev);
 
-extern void		dev_init(void);
-
 extern int		netdev_budget;
 
 /* Called by rtnetlink.c:rtnl_unlock() */
 extern void netdev_run_todo(void);
 
+/**
+ *	dev_put - release reference to device
+ *	@dev: network device
+ *
+ * Hold reference to device to keep it from being freed.
+ */
 static inline void dev_put(struct net_device *dev)
 {
 	atomic_dec(&dev->refcnt);
 }
 
+/**
+ *	dev_hold - get reference to device
+ *	@dev: network device
+ *
+ * Release reference to device to allow it to be freed.
+ */
 static inline void dev_hold(struct net_device *dev)
 {
 	atomic_inc(&dev->refcnt);
@@ -861,6 +1051,12 @@ static inline void dev_hold(struct net_device *dev)
 
 extern void linkwatch_fire_event(struct net_device *dev);
 
+/**
+ *	netif_carrier_ok - test if carrier present
+ *	@dev: network device
+ *
+ * Check if carrier is present on device
+ */
 static inline int netif_carrier_ok(const struct net_device *dev)
 {
 	return !test_bit(__LINK_STATE_NOCARRIER, &dev->state);
@@ -872,30 +1068,66 @@ extern void netif_carrier_on(struct net_device *dev);
 
 extern void netif_carrier_off(struct net_device *dev);
 
+/**
+ *	netif_dormant_on - mark device as dormant.
+ *	@dev: network device
+ *
+ * Mark device as dormant (as per RFC2863).
+ *
+ * The dormant state indicates that the relevant interface is not
+ * actually in a condition to pass packets (i.e., it is not 'up') but is
+ * in a "pending" state, waiting for some external event.  For "on-
+ * demand" interfaces, this new state identifies the situation where the
+ * interface is waiting for events to place it in the up state.
+ *
+ */
 static inline void netif_dormant_on(struct net_device *dev)
 {
 	if (!test_and_set_bit(__LINK_STATE_DORMANT, &dev->state))
 		linkwatch_fire_event(dev);
 }
 
+/**
+ *	netif_dormant_off - set device as not dormant.
+ *	@dev: network device
+ *
+ * Device is not in dormant state.
+ */
 static inline void netif_dormant_off(struct net_device *dev)
 {
 	if (test_and_clear_bit(__LINK_STATE_DORMANT, &dev->state))
 		linkwatch_fire_event(dev);
 }
 
+/**
+ *	netif_dormant - test if carrier present
+ *	@dev: network device
+ *
+ * Check if carrier is present on device
+ */
 static inline int netif_dormant(const struct net_device *dev)
 {
 	return test_bit(__LINK_STATE_DORMANT, &dev->state);
 }
 
 
+/**
+ *	netif_oper_up - test if device is operational
+ *	@dev: network device
+ *
+ * Check if carrier is operational
+ */
 static inline int netif_oper_up(const struct net_device *dev) {
 	return (dev->operstate == IF_OPER_UP ||
 		dev->operstate == IF_OPER_UNKNOWN /* backward compat */);
 }
 
-/* Hot-plugging. */
+/**
+ *	netif_device_present - is device available or removed
+ *	@dev: network device
+ *
+ * Check if device has not been removed from system.
+ */
 static inline int netif_device_present(struct net_device *dev)
 {
 	return test_bit(__LINK_STATE_PRESENT, &dev->state);
@@ -955,46 +1187,38 @@ static inline u32 netif_msg_init(int debug_value, int default_msg_enable_bits)
 	return (1 << debug_value) - 1;
 }
 
-/* Test if receive needs to be scheduled */
-static inline int __netif_rx_schedule_prep(struct net_device *dev)
-{
-	return !test_and_set_bit(__LINK_STATE_RX_SCHED, &dev->state);
-}
-
 /* Test if receive needs to be scheduled but only if up */
-static inline int netif_rx_schedule_prep(struct net_device *dev)
+static inline int netif_rx_schedule_prep(struct net_device *dev,
+					 struct napi_struct *napi)
 {
-	return netif_running(dev) && __netif_rx_schedule_prep(dev);
+	return netif_running(dev) && napi_schedule_prep(napi);
 }
 
 /* Add interface to tail of rx poll list. This assumes that _prep has
  * already been called and returned 1.
  */
-
-extern void __netif_rx_schedule(struct net_device *dev);
+static inline void __netif_rx_schedule(struct net_device *dev,
+				       struct napi_struct *napi)
+{
+	dev_hold(dev);
+	__napi_schedule(napi);
+}
 
 /* Try to reschedule poll. Called by irq handler. */
 
-static inline void netif_rx_schedule(struct net_device *dev)
+static inline void netif_rx_schedule(struct net_device *dev,
+				     struct napi_struct *napi)
 {
-	if (netif_rx_schedule_prep(dev))
-		__netif_rx_schedule(dev);
+	if (netif_rx_schedule_prep(dev, napi))
+		__netif_rx_schedule(dev, napi);
 }
 
-/* Try to reschedule poll. Called by dev->poll() after netif_rx_complete().
- * Do not inline this?
- */
-static inline int netif_rx_reschedule(struct net_device *dev, int undo)
+/* Try to reschedule poll. Called by dev->poll() after netif_rx_complete().  */
+static inline int netif_rx_reschedule(struct net_device *dev,
+				      struct napi_struct *napi)
 {
-	if (netif_rx_schedule_prep(dev)) {
-		unsigned long flags;
-
-		dev->quota += undo;
-
-		local_irq_save(flags);
-		list_add_tail(&dev->poll_list, &__get_cpu_var(softnet_data).poll_list);
-		__raise_softirq_irqoff(NET_RX_SOFTIRQ);
-		local_irq_restore(flags);
+	if (napi_schedule_prep(napi)) {
+		__netif_rx_schedule(dev, napi);
 		return 1;
 	}
 	return 0;
@@ -1003,12 +1227,11 @@ static inline int netif_rx_reschedule(struct net_device *dev, int undo)
 /* same as netif_rx_complete, except that local_irq_save(flags)
  * has already been issued
  */
-static inline void __netif_rx_complete(struct net_device *dev)
+static inline void __netif_rx_complete(struct net_device *dev,
+				       struct napi_struct *napi)
 {
-	BUG_ON(!test_bit(__LINK_STATE_RX_SCHED, &dev->state));
-	list_del(&dev->poll_list);
-	smp_mb__before_clear_bit();
-	clear_bit(__LINK_STATE_RX_SCHED, &dev->state);
+	__napi_complete(napi);
+	dev_put(dev);
 }
 
 /* Remove interface from poll list: it must be in the poll list
@@ -1016,28 +1239,22 @@ static inline void __netif_rx_complete(struct net_device *dev)
  * it completes the work. The device cannot be out of poll list at this
  * moment, it is BUG().
  */
-static inline void netif_rx_complete(struct net_device *dev)
+static inline void netif_rx_complete(struct net_device *dev,
+				     struct napi_struct *napi)
 {
 	unsigned long flags;
 
 	local_irq_save(flags);
-	__netif_rx_complete(dev);
+	__netif_rx_complete(dev, napi);
 	local_irq_restore(flags);
 }
 
-static inline void netif_poll_disable(struct net_device *dev)
-{
-	while (test_and_set_bit(__LINK_STATE_RX_SCHED, &dev->state))
-		/* No hurry. */
-		schedule_timeout_interruptible(1);
-}
-
-static inline void netif_poll_enable(struct net_device *dev)
-{
-	smp_mb__before_clear_bit();
-	clear_bit(__LINK_STATE_RX_SCHED, &dev->state);
-}
-
+/**
+ *	netif_tx_lock - grab network device transmit lock
+ *	@dev: network device
+ *
+ * Get network device transmit lock
+ */
 static inline void netif_tx_lock(struct net_device *dev)
 {
 	spin_lock(&dev->_xmit_lock);
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 29930b71a9a..08dcc39ec18 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -25,8 +25,6 @@ struct netpoll {
 
 struct netpoll_info {
 	atomic_t refcnt;
-	spinlock_t poll_lock;
-	int poll_owner;
 	int rx_flags;
 	spinlock_t rx_lock;
 	struct netpoll *rx_np; /* netpoll that registered an rx_hook */
@@ -64,32 +62,61 @@ static inline int netpoll_rx(struct sk_buff *skb)
 	return ret;
 }
 
-static inline void *netpoll_poll_lock(struct net_device *dev)
+static inline int netpoll_receive_skb(struct sk_buff *skb)
 {
+	if (!list_empty(&skb->dev->napi_list))
+		return netpoll_rx(skb);
+	return 0;
+}
+
+static inline void *netpoll_poll_lock(struct napi_struct *napi)
+{
+	struct net_device *dev = napi->dev;
+
 	rcu_read_lock(); /* deal with race on ->npinfo */
-	if (dev->npinfo) {
-		spin_lock(&dev->npinfo->poll_lock);
-		dev->npinfo->poll_owner = smp_processor_id();
-		return dev->npinfo;
+	if (dev && dev->npinfo) {
+		spin_lock(&napi->poll_lock);
+		napi->poll_owner = smp_processor_id();
+		return napi;
 	}
 	return NULL;
 }
 
 static inline void netpoll_poll_unlock(void *have)
 {
-	struct netpoll_info *npi = have;
+	struct napi_struct *napi = have;
 
-	if (npi) {
-		npi->poll_owner = -1;
-		spin_unlock(&npi->poll_lock);
+	if (napi) {
+		napi->poll_owner = -1;
+		spin_unlock(&napi->poll_lock);
 	}
 	rcu_read_unlock();
 }
 
+static inline void netpoll_netdev_init(struct net_device *dev)
+{
+	INIT_LIST_HEAD(&dev->napi_list);
+}
+
 #else
-#define netpoll_rx(a) 0
-#define netpoll_poll_lock(a) NULL
-#define netpoll_poll_unlock(a)
+static inline int netpoll_rx(struct sk_buff *skb)
+{
+	return 0;
+}
+static inline int netpoll_receive_skb(struct sk_buff *skb)
+{
+	return 0;
+}
+static inline void *netpoll_poll_lock(struct napi_struct *napi)
+{
+	return NULL;
+}
+static inline void netpoll_poll_unlock(void *have)
+{
+}
+static inline void netpoll_netdev_init(struct net_device *dev)
+{
+}
 #endif
 
 #endif