/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (c) 2016 Qualcomm Atheros, Inc
 *
 * Based on net/sched/sch_fq_codel.c
 */
#ifndef __NET_SCHED_FQ_IMPL_H
#define __NET_SCHED_FQ_IMPL_H

#include <net/fq.h>

/* functions that are embedded into includer */


static void
__fq_adjust_removal(struct fq *fq, struct fq_flow *flow, unsigned int packets,
                    unsigned int bytes, unsigned int truesize)
{
        struct fq_tin *tin = flow->tin;
        int idx;

        tin->backlog_bytes -= bytes;
        tin->backlog_packets -= packets;
        flow->backlog -= bytes;
        fq->backlog -= packets;
        fq->memory_usage -= truesize;

        if (flow->backlog)
                return;

        if (flow == &tin->default_flow) {
                list_del_init(&tin->tin_list);
                return;
        }

        idx = flow - fq->flows;
        __clear_bit(idx, fq->flows_bitmap);
}

static void fq_adjust_removal(struct fq *fq,
                              struct fq_flow *flow,
                              struct sk_buff *skb)
{
        __fq_adjust_removal(fq, flow, 1, skb->len, skb->truesize);
}

static struct sk_buff *fq_flow_dequeue(struct fq *fq,
                                       struct fq_flow *flow)
{
        struct sk_buff *skb;

        lockdep_assert_held(&fq->lock);

        skb = __skb_dequeue(&flow->queue);
        if (!skb)
                return NULL;

        fq_adjust_removal(fq, flow, skb);

        return skb;
}

static int fq_flow_drop(struct fq *fq, struct fq_flow *flow,
                        fq_skb_free_t free_func)
{
        unsigned int packets = 0, bytes = 0, truesize = 0;
        struct fq_tin *tin = flow->tin;
        struct sk_buff *skb;
        int pending;

        lockdep_assert_held(&fq->lock);

        pending = min_t(int, 32, skb_queue_len(&flow->queue) / 2);
        do {
                skb = __skb_dequeue(&flow->queue);
                if (!skb)
                        break;

                packets++;
                bytes += skb->len;
                truesize += skb->truesize;
                free_func(fq, tin, flow, skb);
        } while (packets < pending);

        __fq_adjust_removal(fq, flow, packets, bytes, truesize);

        return packets;
}

static struct sk_buff *fq_tin_dequeue(struct fq *fq,
                                      struct fq_tin *tin,
                                      fq_tin_dequeue_t dequeue_func)
{
        struct fq_flow *flow;
        struct list_head *head;
        struct sk_buff *skb;

        lockdep_assert_held(&fq->lock);

begin:
        head = &tin->new_flows;
        if (list_empty(head)) {
                head = &tin->old_flows;
                if (list_empty(head))
                        return NULL;
        }

        flow = list_first_entry(head, struct fq_flow, flowchain);

        if (flow->deficit <= 0) {
                flow->deficit += fq->quantum;
                list_move_tail(&flow->flowchain,
                               &tin->old_flows);
                goto begin;
        }

        skb = dequeue_func(fq, tin, flow);
        if (!skb) {
                /* force a pass through old_flows to prevent starvation */
                if ((head == &tin->new_flows) &&
                    !list_empty(&tin->old_flows)) {
                        list_move_tail(&flow->flowchain, &tin->old_flows);
                } else {
                        list_del_init(&flow->flowchain);
                        flow->tin = NULL;
                }
                goto begin;
        }

        flow->deficit -= skb->len;
        tin->tx_bytes += skb->len;
        tin->tx_packets++;

        return skb;
}

static u32 fq_flow_idx(struct fq *fq, struct sk_buff *skb)
{
        u32 hash = skb_get_hash(skb);

        return reciprocal_scale(hash, fq->flows_cnt);
}

static struct fq_flow *fq_flow_classify(struct fq *fq,
                                        struct fq_tin *tin, u32 idx,
                                        struct sk_buff *skb)
{
        struct fq_flow *flow;

        lockdep_assert_held(&fq->lock);

        flow = &fq->flows[idx];
        if (flow->tin && flow->tin != tin) {
                flow = &tin->default_flow;
                tin->collisions++;
                fq->collisions++;
        }

        if (!flow->tin)
                tin->flows++;

        return flow;
}

static struct fq_flow *fq_find_fattest_flow(struct fq *fq)
{
        struct fq_tin *tin;
        struct fq_flow *flow = NULL;
        u32 len = 0;
        int i;

        for_each_set_bit(i, fq->flows_bitmap, fq->flows_cnt) {
                struct fq_flow *cur = &fq->flows[i];
                unsigned int cur_len;

                cur_len = cur->backlog;
                if (cur_len <= len)
                        continue;

                flow = cur;
                len = cur_len;
        }

        list_for_each_entry(tin, &fq->tin_backlog, tin_list) {
                unsigned int cur_len = tin->default_flow.backlog;

                if (cur_len <= len)
                        continue;

                flow = &tin->default_flow;
                len = cur_len;
        }

        return flow;
}

static void fq_tin_enqueue(struct fq *fq,
                           struct fq_tin *tin, u32 idx,
                           struct sk_buff *skb,
                           fq_skb_free_t free_func)
{
        struct fq_flow *flow;
        struct sk_buff *next;
        bool oom;

        lockdep_assert_held(&fq->lock);

        flow = fq_flow_classify(fq, tin, idx, skb);

        if (!flow->backlog) {
                if (flow != &tin->default_flow)
                        __set_bit(idx, fq->flows_bitmap);
                else if (list_empty(&tin->tin_list))
                        list_add(&tin->tin_list, &fq->tin_backlog);
        }

        flow->tin = tin;
        skb_list_walk_safe(skb, skb, next) {
                skb_mark_not_on_list(skb);
                flow->backlog += skb->len;
                tin->backlog_bytes += skb->len;
                tin->backlog_packets++;
                fq->memory_usage += skb->truesize;
                fq->backlog++;
                __skb_queue_tail(&flow->queue, skb);
        }

        if (list_empty(&flow->flowchain)) {
                flow->deficit = fq->quantum;
                list_add_tail(&flow->flowchain,
                              &tin->new_flows);
        }

        oom = (fq->memory_usage > fq->memory_limit);
        while (fq->backlog > fq->limit || oom) {
                flow = fq_find_fattest_flow(fq);
                if (!flow)
                        return;

                if (!fq_flow_drop(fq, flow, free_func))
                        return;

                flow->tin->overlimit++;
                fq->overlimit++;
                if (oom) {
                        fq->overmemory++;
                        oom = (fq->memory_usage > fq->memory_limit);
                }
        }
}

static void fq_flow_filter(struct fq *fq,
                           struct fq_flow *flow,
                           fq_skb_filter_t filter_func,
                           void *filter_data,
                           fq_skb_free_t free_func)
{
        struct fq_tin *tin = flow->tin;
        struct sk_buff *skb, *tmp;

        lockdep_assert_held(&fq->lock);

        skb_queue_walk_safe(&flow->queue, skb, tmp) {
                if (!filter_func(fq, tin, flow, skb, filter_data))
                        continue;

                __skb_unlink(skb, &flow->queue);
                fq_adjust_removal(fq, flow, skb);
                free_func(fq, tin, flow, skb);
        }
}

static void fq_tin_filter(struct fq *fq,
                          struct fq_tin *tin,
                          fq_skb_filter_t filter_func,
                          void *filter_data,
                          fq_skb_free_t free_func)
{
        struct fq_flow *flow;

        lockdep_assert_held(&fq->lock);

        list_for_each_entry(flow, &tin->new_flows, flowchain)
                fq_flow_filter(fq, flow, filter_func, filter_data, free_func);
        list_for_each_entry(flow, &tin->old_flows, flowchain)
                fq_flow_filter(fq, flow, filter_func, filter_data, free_func);
}

static void fq_flow_reset(struct fq *fq,
                          struct fq_flow *flow,
                          fq_skb_free_t free_func)
{
        struct fq_tin *tin = flow->tin;
        struct sk_buff *skb;

        while ((skb = fq_flow_dequeue(fq, flow)))
                free_func(fq, tin, flow, skb);

        if (!list_empty(&flow->flowchain)) {
                list_del_init(&flow->flowchain);
                if (list_empty(&tin->new_flows) &&
                    list_empty(&tin->old_flows))
                        list_del_init(&tin->tin_list);
        }

        flow->tin = NULL;

        WARN_ON_ONCE(flow->backlog);
}

static void fq_tin_reset(struct fq *fq,
                         struct fq_tin *tin,
                         fq_skb_free_t free_func)
{
        struct list_head *head;
        struct fq_flow *flow;

        for (;;) {
                head = &tin->new_flows;
                if (list_empty(head)) {
                        head = &tin->old_flows;
                        if (list_empty(head))
                                break;
                }

                flow = list_first_entry(head, struct fq_flow, flowchain);
                fq_flow_reset(fq, flow, free_func);
        }

        WARN_ON_ONCE(!list_empty(&tin->tin_list));
        WARN_ON_ONCE(tin->backlog_bytes);
        WARN_ON_ONCE(tin->backlog_packets);
}

static void fq_flow_init(struct fq_flow *flow)
{
        INIT_LIST_HEAD(&flow->flowchain);
        __skb_queue_head_init(&flow->queue);
}

static void fq_tin_init(struct fq_tin *tin)
{
        INIT_LIST_HEAD(&tin->new_flows);
        INIT_LIST_HEAD(&tin->old_flows);
        INIT_LIST_HEAD(&tin->tin_list);
        fq_flow_init(&tin->default_flow);
}

static int fq_init(struct fq *fq, int flows_cnt)
{
        int i;

        memset(fq, 0, sizeof(fq[0]));
        spin_lock_init(&fq->lock);
        INIT_LIST_HEAD(&fq->tin_backlog);
        fq->flows_cnt = max_t(u32, flows_cnt, 1);
        fq->quantum = 300;
        fq->limit = 8192;
        fq->memory_limit = 16 << 20; /* 16 MBytes */

        fq->flows = kvzalloc_objs(fq->flows[0], fq->flows_cnt);
        if (!fq->flows)
                return -ENOMEM;

        fq->flows_bitmap = bitmap_zalloc(fq->flows_cnt, GFP_KERNEL);
        if (!fq->flows_bitmap) {
                kvfree(fq->flows);
                fq->flows = NULL;
                return -ENOMEM;
        }

        for (i = 0; i < fq->flows_cnt; i++)
                fq_flow_init(&fq->flows[i]);

        return 0;
}

static void fq_reset(struct fq *fq,
                     fq_skb_free_t free_func)
{
        int i;

        for (i = 0; i < fq->flows_cnt; i++)
                fq_flow_reset(fq, &fq->flows[i], free_func);

        kvfree(fq->flows);
        fq->flows = NULL;

        bitmap_free(fq->flows_bitmap);
        fq->flows_bitmap = NULL;
}

#endif