[PATCH net-next 1/5] net: napi: Make napi_defer_hard_irqs per-NAPI

[Joe Damato <jdamato@fastly.com>]

Allow per-NAPI defer_hard_irqs setting.

The existing sysfs parameter is respected; writes to sysfs will write to
all NAPI structs for the device and the net_device defer_hard_irq field.
Reads from sysfs will read from the net_device field.

sysfs code was updated to guard against what appears to be a potential
overflow as the field is an int, but the value passed in is an unsigned
long.

The ability to set defer_hard_irqs on specific NAPI instances will be
added in a later commit, via netdev-genl.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Martin Karsten <mkarsten@uwaterloo.ca>
Tested-by: Martin Karsten <mkarsten@uwaterloo.ca>
---
 include/linux/netdevice.h | 23 +++++++++++++++++++++++
 net/core/dev.c            | 29 ++++++++++++++++++++++++++---
 net/core/net-sysfs.c      |  5 ++++-
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fce70990b209..7d53380da4c0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -371,6 +371,7 @@ struct napi_struct {
 	struct list_head	rx_list; /* Pending GRO_NORMAL skbs */
 	int			rx_count; /* length of rx_list */
 	unsigned int		napi_id;
+	int			defer_hard_irqs;
 	struct hrtimer		timer;
 	struct task_struct	*thread;
 	/* control-path-only fields follow */
@@ -534,6 +535,28 @@ static inline void napi_schedule_irqoff(struct napi_struct *n)
 		__napi_schedule_irqoff(n);
 }
 
+/**
+ * napi_get_defer_hard_irqs - get the NAPI's defer_hard_irqs
+ * @n: napi struct to get the defer_hard_irqs field from
+ *
+ * Returns the per-NAPI value of the defar_hard_irqs field.
+ */
+int napi_get_defer_hard_irqs(const struct napi_struct *n);
+
+/**
+ * napi_set_defer_hard_irqs - set the defer_hard_irqs for a napi
+ * @n: napi_struct to set the defer_hard_irqs field
+ * @defer: the value the field should be set to
+ */
+void napi_set_defer_hard_irqs(struct napi_struct *n, int defer);
+
+/**
+ * netdev_set_defer_hard_irqs - set defer_hard_irqs for all NAPIs of a netdev
+ * @netdev: the net_device for which all NAPIs will have their defer_hard_irqs set
+ * @defer: the defer_hard_irqs value to set
+ */
+void netdev_set_defer_hard_irqs(struct net_device *netdev, int defer);
+
 /**
  * napi_complete_done - NAPI processing complete
  * @n: NAPI context
diff --git a/net/core/dev.c b/net/core/dev.c
index 63987b8b7c85..f7baff0da057 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6212,6 +6212,28 @@ void __napi_schedule_irqoff(struct napi_struct *n)
 }
 EXPORT_SYMBOL(__napi_schedule_irqoff);
 
+int napi_get_defer_hard_irqs(const struct napi_struct *n)
+{
+	return READ_ONCE(n->defer_hard_irqs);
+}
+EXPORT_SYMBOL_GPL(napi_get_defer_hard_irqs);
+
+void napi_set_defer_hard_irqs(struct napi_struct *n, int defer)
+{
+	WRITE_ONCE(n->defer_hard_irqs, defer);
+}
+EXPORT_SYMBOL_GPL(napi_set_defer_hard_irqs);
+
+void netdev_set_defer_hard_irqs(struct net_device *netdev, int defer)
+{
+	struct napi_struct *napi;
+
+	WRITE_ONCE(netdev->napi_defer_hard_irqs, defer);
+	list_for_each_entry(napi, &netdev->napi_list, dev_list)
+		napi_set_defer_hard_irqs(napi, defer);
+}
+EXPORT_SYMBOL_GPL(netdev_set_defer_hard_irqs);
+
 bool napi_complete_done(struct napi_struct *n, int work_done)
 {
 	unsigned long flags, val, new, timeout = 0;
@@ -6230,7 +6252,7 @@ bool napi_complete_done(struct napi_struct *n, int work_done)
 	if (work_done) {
 		if (n->gro_bitmask)
 			timeout = READ_ONCE(n->dev->gro_flush_timeout);
-		n->defer_hard_irqs_count = READ_ONCE(n->dev->napi_defer_hard_irqs);
+		n->defer_hard_irqs_count = napi_get_defer_hard_irqs(n);
 	}
 	if (n->defer_hard_irqs_count > 0) {
 		n->defer_hard_irqs_count--;
@@ -6368,7 +6390,7 @@ static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock,
 	bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
 
 	if (flags & NAPI_F_PREFER_BUSY_POLL) {
-		napi->defer_hard_irqs_count = READ_ONCE(napi->dev->napi_defer_hard_irqs);
+		napi->defer_hard_irqs_count = napi_get_defer_hard_irqs(napi);
 		timeout = READ_ONCE(napi->dev->gro_flush_timeout);
 		if (napi->defer_hard_irqs_count && timeout) {
 			hrtimer_start(&napi->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED);
@@ -6650,6 +6672,7 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
 	INIT_HLIST_NODE(&napi->napi_hash_node);
 	hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
 	napi->timer.function = napi_watchdog;
+	napi_set_defer_hard_irqs(napi, READ_ONCE(dev->napi_defer_hard_irqs));
 	init_gro_hash(napi);
 	napi->skb = NULL;
 	INIT_LIST_HEAD(&napi->rx_list);
@@ -11032,7 +11055,7 @@ void netdev_sw_irq_coalesce_default_on(struct net_device *dev)
 
 	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
 		dev->gro_flush_timeout = 20000;
-		dev->napi_defer_hard_irqs = 1;
+		netdev_set_defer_hard_irqs(dev, 1);
 	}
 }
 EXPORT_SYMBOL_GPL(netdev_sw_irq_coalesce_default_on);
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 0e2084ce7b75..8272f0144d81 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -425,7 +425,10 @@ NETDEVICE_SHOW_RW(gro_flush_timeout, fmt_ulong);
 
 static int change_napi_defer_hard_irqs(struct net_device *dev, unsigned long val)
 {
-	WRITE_ONCE(dev->napi_defer_hard_irqs, val);
+	if (val > S32_MAX)
+		return -EINVAL;
+
+	netdev_set_defer_hard_irqs(dev, (int)val);
 	return 0;
 }
 
-- 
2.25.1