gro_cells.c

  1// SPDX-License-Identifier: GPL-2.0
  2#include <linux/skbuff.h>
  3#include <linux/slab.h>
  4#include <linux/netdevice.h>
  5#include <net/gro_cells.h>
  6#include <net/hotdata.h>
  7
  8struct gro_cell {
  9	struct sk_buff_head	napi_skbs;
 10	struct napi_struct	napi;
 11	local_lock_t		bh_lock;
 12};
 13
 14int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
 15{
 16	struct net_device *dev = skb->dev;
 17	bool have_bh_lock = false;
 18	struct gro_cell *cell;
 19	int res;
 20
 21	rcu_read_lock();
 22	if (unlikely(!(dev->flags & IFF_UP)))
 23		goto drop;
 24
 25	if (!gcells->cells || skb_cloned(skb) || netif_elide_gro(dev)) {
 26		res = netif_rx(skb);
 27		goto unlock;
 28	}
 29
 30	local_lock_nested_bh(&gcells->cells->bh_lock);
 31	have_bh_lock = true;
 32	cell = this_cpu_ptr(gcells->cells);
 33
 34	if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(net_hotdata.max_backlog)) {
 35drop:
 36		dev_core_stats_rx_dropped_inc(dev);
 37		kfree_skb(skb);
 38		res = NET_RX_DROP;
 39		goto unlock;
 40	}
 41
 42	__skb_queue_tail(&cell->napi_skbs, skb);
 43	if (skb_queue_len(&cell->napi_skbs) == 1)
 44		napi_schedule(&cell->napi);
 45
 46	res = NET_RX_SUCCESS;
 47
 48unlock:
 49	if (have_bh_lock)
 50		local_unlock_nested_bh(&gcells->cells->bh_lock);
 51	rcu_read_unlock();
 52	return res;
 53}
 54EXPORT_SYMBOL(gro_cells_receive);
 55
 56/* called under BH context */
 57static int gro_cell_poll(struct napi_struct *napi, int budget)
 58{
 59	struct gro_cell *cell = container_of(napi, struct gro_cell, napi);
 60	struct sk_buff *skb;
 61	int work_done = 0;
 62
 63	while (work_done < budget) {
 64		__local_lock_nested_bh(&cell->bh_lock);
 65		skb = __skb_dequeue(&cell->napi_skbs);
 66		__local_unlock_nested_bh(&cell->bh_lock);
 67		if (!skb)
 68			break;
 69		napi_gro_receive(napi, skb);
 70		work_done++;
 71	}
 72
 73	if (work_done < budget)
 74		napi_complete_done(napi, work_done);
 75	return work_done;
 76}
 77
 78int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
 79{
 80	int i;
 81
 82	gcells->cells = alloc_percpu(struct gro_cell);
 83	if (!gcells->cells)
 84		return -ENOMEM;
 85
 86	for_each_possible_cpu(i) {
 87		struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
 88
 89		__skb_queue_head_init(&cell->napi_skbs);
 90		local_lock_init(&cell->bh_lock);
 91
 92		set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);
 93
 94		netif_napi_add(dev, &cell->napi, gro_cell_poll);
 95		napi_enable(&cell->napi);
 96	}
 97	return 0;
 98}
 99EXPORT_SYMBOL(gro_cells_init);
100
101struct percpu_free_defer {
102	struct rcu_head rcu;
103	void __percpu	*ptr;
104};
105
106static void percpu_free_defer_callback(struct rcu_head *head)
107{
108	struct percpu_free_defer *defer;
109
110	defer = container_of(head, struct percpu_free_defer, rcu);
111	free_percpu(defer->ptr);
112	kfree(defer);
113}
114
115void gro_cells_destroy(struct gro_cells *gcells)
116{
117	struct percpu_free_defer *defer;
118	int i;
119
120	if (!gcells->cells)
121		return;
122	for_each_possible_cpu(i) {
123		struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
124
125		napi_disable(&cell->napi);
126		__netif_napi_del(&cell->napi);
127		__skb_queue_purge(&cell->napi_skbs);
128	}
129	/* We need to observe an rcu grace period before freeing ->cells,
130	 * because netpoll could access dev->napi_list under rcu protection.
131	 * Try hard using call_rcu() instead of synchronize_rcu(),
132	 * because we might be called from cleanup_net(), and we
133	 * definitely do not want to block this critical task.
134	 */
135	defer = kmalloc(sizeof(*defer), GFP_KERNEL | __GFP_NOWARN);
136	if (likely(defer)) {
137		defer->ptr = gcells->cells;
138		call_rcu(&defer->rcu, percpu_free_defer_callback);
139	} else {
140		/* We do not hold RTNL at this point, synchronize_net()
141		 * would not be able to expedite this sync.
142		 */
143		synchronize_rcu_expedited();
144		free_percpu(gcells->cells);
145	}
146	gcells->cells = NULL;
147}
148EXPORT_SYMBOL(gro_cells_destroy);