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 #include <net/hotdata.h>
   7
   8 struct gro_cell {
   9         struct sk_buff_head     napi_skbs;
  10         struct napi_struct      napi;
  11 };
  12
  13 int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
  14 {
  15         struct net_device *dev = skb->dev;
  16         struct gro_cell *cell;
  17         int res;
  18
  19         rcu_read_lock();
  20         if (unlikely(!(dev->flags & IFF_UP)))
  21                 goto drop;
  22
  23         if (!gcells->cells || skb_cloned(skb) || netif_elide_gro(dev)) {
  24                 res = netif_rx(skb);
  25                 goto unlock;
  26         }
  27
  28         cell = this_cpu_ptr(gcells->cells);
  29
  30         if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(net_hotdata.max_backlog)) {
  31 drop:
  32                 dev_core_stats_rx_dropped_inc(dev);
  33                 kfree_skb(skb);
  34                 res = NET_RX_DROP;
  35                 goto unlock;
  36         }
  37
  38         __skb_queue_tail(&cell->napi_skbs, skb);
  39         if (skb_queue_len(&cell->napi_skbs) == 1)
  40                 napi_schedule(&cell->napi);
  41
  42         res = NET_RX_SUCCESS;
  43
  44 unlock:
  45         rcu_read_unlock();
  46         return res;
  47 }
  48 EXPORT_SYMBOL(gro_cells_receive);
  49
  50 /* called under BH context */
  51 static int gro_cell_poll(struct napi_struct *napi, int budget)
  52 {
  53         struct gro_cell *cell = container_of(napi, struct gro_cell, napi);
  54         struct sk_buff *skb;
  55         int work_done = 0;
  56
  57         while (work_done < budget) {
  58                 skb = __skb_dequeue(&cell->napi_skbs);
  59                 if (!skb)
  60                         break;
  61                 napi_gro_receive(napi, skb);
  62                 work_done++;
  63         }
  64
  65         if (work_done < budget)
  66                 napi_complete_done(napi, work_done);
  67         return work_done;
  68 }
  69
  70 int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
  71 {
  72         int i;
  73
  74         gcells->cells = alloc_percpu(struct gro_cell);
  75         if (!gcells->cells)
  76                 return -ENOMEM;
  77
  78         for_each_possible_cpu(i) {
  79                 struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
  80
  81                 __skb_queue_head_init(&cell->napi_skbs);
  82
  83                 set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);
  84
  85                 netif_napi_add(dev, &cell->napi, gro_cell_poll);
  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);