// SPDX-License-Identifier: GPL-2.0-only
/*
 * net/sched/sch_mq.c           Classful multiqueue dummy scheduler
 *
 * Copyright (c) 2009 Patrick McHardy <kaber@trash.net>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/netlink.h>
#include <net/pkt_cls.h>
#include <net/pkt_sched.h>
#include <net/sch_generic.h>

struct mq_sched {
        struct Qdisc            **qdiscs;
};

static int mq_offload(struct Qdisc *sch, enum tc_mq_command cmd)
{
        struct net_device *dev = qdisc_dev(sch);
        struct tc_mq_qopt_offload opt = {
                .command = cmd,
                .handle = sch->handle,
        };

        if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
                return -EOPNOTSUPP;

        return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_MQ, &opt);
}

static int mq_offload_stats(struct Qdisc *sch)
{
        struct tc_mq_qopt_offload opt = {
                .command = TC_MQ_STATS,
                .handle = sch->handle,
                .stats = {
                        .bstats = &sch->bstats,
                        .qstats = &sch->qstats,
                },
        };

        return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_MQ, &opt);
}

static void mq_destroy(struct Qdisc *sch)
{
        struct net_device *dev = qdisc_dev(sch);
        struct mq_sched *priv = qdisc_priv(sch);
        unsigned int ntx;

        mq_offload(sch, TC_MQ_DESTROY);

        if (!priv->qdiscs)
                return;
        for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
                qdisc_put(priv->qdiscs[ntx]);
        kfree(priv->qdiscs);
}

static int mq_init(struct Qdisc *sch, struct nlattr *opt,
                   struct netlink_ext_ack *extack)
{
        struct net_device *dev = qdisc_dev(sch);
        struct mq_sched *priv = qdisc_priv(sch);
        struct netdev_queue *dev_queue;
        struct Qdisc *qdisc;
        unsigned int ntx;

        if (sch->parent != TC_H_ROOT)
                return -EOPNOTSUPP;

        if (!netif_is_multiqueue(dev))
                return -EOPNOTSUPP;

        /* pre-allocate qdiscs, attachment can't fail */
        priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
                               GFP_KERNEL);
        if (!priv->qdiscs)
                return -ENOMEM;

        for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
                dev_queue = netdev_get_tx_queue(dev, ntx);
                qdisc = qdisc_create_dflt(dev_queue, get_default_qdisc_ops(dev, ntx),
                                          TC_H_MAKE(TC_H_MAJ(sch->handle),
                                                    TC_H_MIN(ntx + 1)),
                                          extack);
                if (!qdisc)
                        return -ENOMEM;
                priv->qdiscs[ntx] = qdisc;
                qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
        }

        sch->flags |= TCQ_F_MQROOT;

        mq_offload(sch, TC_MQ_CREATE);
        return 0;
}

static void mq_attach(struct Qdisc *sch)
{
        struct net_device *dev = qdisc_dev(sch);
        struct mq_sched *priv = qdisc_priv(sch);
        struct Qdisc *qdisc, *old;
        unsigned int ntx;

        for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
                qdisc = priv->qdiscs[ntx];
                old = dev_graft_qdisc(qdisc->dev_queue, qdisc);
                if (old)
                        qdisc_put(old);
#ifdef CONFIG_NET_SCHED
                if (ntx < dev->real_num_tx_queues)
                        qdisc_hash_add(qdisc, false);
#endif

        }
        kfree(priv->qdiscs);
        priv->qdiscs = NULL;
}

static int mq_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct net_device *dev = qdisc_dev(sch);
        struct Qdisc *qdisc;
        unsigned int ntx;
        __u32 qlen = 0;

        sch->q.qlen = 0;
        memset(&sch->bstats, 0, sizeof(sch->bstats));
        memset(&sch->qstats, 0, sizeof(sch->qstats));

        /* MQ supports lockless qdiscs. However, statistics accounting needs
         * to account for all, none, or a mix of locked and unlocked child
         * qdiscs. Percpu stats are added to counters in-band and locking
         * qdisc totals are added at end.
         */
        for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
                qdisc = netdev_get_tx_queue(dev, ntx)->qdisc_sleeping;
                spin_lock_bh(qdisc_lock(qdisc));

                if (qdisc_is_percpu_stats(qdisc)) {
                        qlen = qdisc_qlen_sum(qdisc);
                        __gnet_stats_copy_basic(NULL, &sch->bstats,
                                                qdisc->cpu_bstats,
                                                &qdisc->bstats);
                        __gnet_stats_copy_queue(&sch->qstats,
                                                qdisc->cpu_qstats,
                                                &qdisc->qstats, qlen);
                        sch->q.qlen             += qlen;
                } else {
                        sch->q.qlen             += qdisc->q.qlen;
                        sch->bstats.bytes       += qdisc->bstats.bytes;
                        sch->bstats.packets     += qdisc->bstats.packets;
                        sch->qstats.qlen        += qdisc->qstats.qlen;
                        sch->qstats.backlog     += qdisc->qstats.backlog;
                        sch->qstats.drops       += qdisc->qstats.drops;
                        sch->qstats.requeues    += qdisc->qstats.requeues;
                        sch->qstats.overlimits  += qdisc->qstats.overlimits;
                }

                spin_unlock_bh(qdisc_lock(qdisc));
        }

        return mq_offload_stats(sch);
}

static struct netdev_queue *mq_queue_get(struct Qdisc *sch, unsigned long cl)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned long ntx = cl - 1;

        if (ntx >= dev->num_tx_queues)
                return NULL;
        return netdev_get_tx_queue(dev, ntx);
}

static struct netdev_queue *mq_select_queue(struct Qdisc *sch,
                                            struct tcmsg *tcm)
{
        return mq_queue_get(sch, TC_H_MIN(tcm->tcm_parent));
}

static int mq_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
                    struct Qdisc **old, struct netlink_ext_ack *extack)
{
        struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
        struct tc_mq_qopt_offload graft_offload;
        struct net_device *dev = qdisc_dev(sch);

        if (dev->flags & IFF_UP)
                dev_deactivate(dev);

        *old = dev_graft_qdisc(dev_queue, new);
        if (new)
                new->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
        if (dev->flags & IFF_UP)
                dev_activate(dev);

        graft_offload.handle = sch->handle;
        graft_offload.graft_params.queue = cl - 1;
        graft_offload.graft_params.child_handle = new ? new->handle : 0;
        graft_offload.command = TC_MQ_GRAFT;

        qdisc_offload_graft_helper(qdisc_dev(sch), sch, new, *old,
                                   TC_SETUP_QDISC_MQ, &graft_offload, extack);
        return 0;
}

static struct Qdisc *mq_leaf(struct Qdisc *sch, unsigned long cl)
{
        struct netdev_queue *dev_queue = mq_queue_get(sch, cl);

        return dev_queue->qdisc_sleeping;
}

static unsigned long mq_find(struct Qdisc *sch, u32 classid)
{
        unsigned int ntx = TC_H_MIN(classid);

        if (!mq_queue_get(sch, ntx))
                return 0;
        return ntx;
}

static int mq_dump_class(struct Qdisc *sch, unsigned long cl,
                         struct sk_buff *skb, struct tcmsg *tcm)
{
        struct netdev_queue *dev_queue = mq_queue_get(sch, cl);

        tcm->tcm_parent = TC_H_ROOT;
        tcm->tcm_handle |= TC_H_MIN(cl);
        tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
        return 0;
}

static int mq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
                               struct gnet_dump *d)
{
        struct netdev_queue *dev_queue = mq_queue_get(sch, cl);

        sch = dev_queue->qdisc_sleeping;
        if (gnet_stats_copy_basic(&sch->running, d, sch->cpu_bstats,
                                  &sch->bstats) < 0 ||
            qdisc_qstats_copy(d, sch) < 0)
                return -1;
        return 0;
}

static void mq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned int ntx;

        if (arg->stop)
                return;

        arg->count = arg->skip;
        for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
                if (arg->fn(sch, ntx + 1, arg) < 0) {
                        arg->stop = 1;
                        break;
                }
                arg->count++;
        }
}

static const struct Qdisc_class_ops mq_class_ops = {
        .select_queue   = mq_select_queue,
        .graft          = mq_graft,
        .leaf           = mq_leaf,
        .find           = mq_find,
        .walk           = mq_walk,
        .dump           = mq_dump_class,
        .dump_stats     = mq_dump_class_stats,
};

struct Qdisc_ops mq_qdisc_ops __read_mostly = {
        .cl_ops         = &mq_class_ops,
        .id             = "mq",
        .priv_size      = sizeof(struct mq_sched),
        .init           = mq_init,
        .destroy        = mq_destroy,
        .attach         = mq_attach,
        .dump           = mq_dump,
        .owner          = THIS_MODULE,
};