// SPDX-License-Identifier: GPL-2.0
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <net/gro_cells.h>
#include <net/hotdata.h>

struct gro_cell {
        struct sk_buff_head     napi_skbs;
        struct napi_struct      napi;
        local_lock_t            bh_lock;
};

int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        bool have_bh_lock = false;
        struct gro_cell *cell;
        int res;

        rcu_read_lock();
        if (unlikely(!(dev->flags & IFF_UP)))
                goto drop;

        if (!gcells->cells || skb_cloned(skb) || netif_elide_gro(dev)) {
                res = netif_rx(skb);
                goto unlock;
        }

        local_lock_nested_bh(&gcells->cells->bh_lock);
        have_bh_lock = true;
        cell = this_cpu_ptr(gcells->cells);

        if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(net_hotdata.max_backlog)) {
drop:
                dev_core_stats_rx_dropped_inc(dev);
                kfree_skb(skb);
                res = NET_RX_DROP;
                goto unlock;
        }

        __skb_queue_tail(&cell->napi_skbs, skb);
        if (skb_queue_len(&cell->napi_skbs) == 1)
                napi_schedule(&cell->napi);

        res = NET_RX_SUCCESS;

unlock:
        if (have_bh_lock)
                local_unlock_nested_bh(&gcells->cells->bh_lock);
        rcu_read_unlock();
        return res;
}
EXPORT_SYMBOL(gro_cells_receive);

/* called under BH context */
static int gro_cell_poll(struct napi_struct *napi, int budget)
{
        struct gro_cell *cell = container_of(napi, struct gro_cell, napi);
        struct sk_buff *skb;
        int work_done = 0;

        while (work_done < budget) {
                __local_lock_nested_bh(&cell->bh_lock);
                skb = __skb_dequeue(&cell->napi_skbs);
                __local_unlock_nested_bh(&cell->bh_lock);
                if (!skb)
                        break;
                napi_gro_receive(napi, skb);
                work_done++;
        }

        if (work_done < budget)
                napi_complete_done(napi, work_done);
        return work_done;
}

int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
{
        int i;

        gcells->cells = alloc_percpu(struct gro_cell);
        if (!gcells->cells)
                return -ENOMEM;

        for_each_possible_cpu(i) {
                struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);

                __skb_queue_head_init(&cell->napi_skbs);
                local_lock_init(&cell->bh_lock);

                set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);

                netif_napi_add(dev, &cell->napi, gro_cell_poll);
                napi_enable(&cell->napi);
        }
        return 0;
}
EXPORT_SYMBOL(gro_cells_init);

struct percpu_free_defer {
        struct rcu_head rcu;
        void __percpu   *ptr;
};

static void percpu_free_defer_callback(struct rcu_head *head)
{
        struct percpu_free_defer *defer;

        defer = container_of(head, struct percpu_free_defer, rcu);
        free_percpu(defer->ptr);
        kfree(defer);
}

void gro_cells_destroy(struct gro_cells *gcells)
{
        struct percpu_free_defer *defer;
        int i;

        if (!gcells->cells)
                return;
        for_each_possible_cpu(i) {
                struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);

                napi_disable(&cell->napi);
                __netif_napi_del(&cell->napi);
                __skb_queue_purge(&cell->napi_skbs);
        }
        /* We need to observe an rcu grace period before freeing ->cells,
         * because netpoll could access dev->napi_list under rcu protection.
         * Try hard using call_rcu() instead of synchronize_rcu(),
         * because we might be called from cleanup_net(), and we
         * definitely do not want to block this critical task.
         */
        defer = kmalloc_obj(*defer, GFP_KERNEL | __GFP_NOWARN);
        if (likely(defer)) {
                defer->ptr = gcells->cells;
                call_rcu(&defer->rcu, percpu_free_defer_callback);
        } else {
                /* We do not hold RTNL at this point, synchronize_net()
                 * would not be able to expedite this sync.
                 */
                synchronize_rcu_expedited();
                free_percpu(gcells->cells);
        }
        gcells->cells = NULL;
}
EXPORT_SYMBOL(gro_cells_destroy);