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