[PATCH] hfs: don't dirty unchanged inode

[linux-2.6/openmoko-kernel/knife-kernel.git] / net / sched / sch_generic.c

/*
 * net/sched/sch_generic.c      Generic packet scheduler routines.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
 *              - Ingress support
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <net/sock.h>
#include <net/pkt_sched.h>

/* Main transmission queue. */

/* Main qdisc structure lock. 

   However, modifications
   to data, participating in scheduling must be additionally
   protected with dev->queue_lock spinlock.

   The idea is the following:
   - enqueue, dequeue are serialized via top level device
     spinlock dev->queue_lock.
   - tree walking is protected by read_lock_bh(qdisc_tree_lock)
     and this lock is used only in process context.
   - updates to tree are made under rtnl semaphore or
     from softirq context (__qdisc_destroy rcu-callback)
     hence this lock needs local bh disabling.

   qdisc_tree_lock must be grabbed BEFORE dev->queue_lock!
 */
DEFINE_RWLOCK(qdisc_tree_lock);

void qdisc_lock_tree(struct net_device *dev)
{
        write_lock_bh(&qdisc_tree_lock);
        spin_lock_bh(&dev->queue_lock);
}

void qdisc_unlock_tree(struct net_device *dev)
{
        spin_unlock_bh(&dev->queue_lock);
        write_unlock_bh(&qdisc_tree_lock);
}

/* 
   dev->queue_lock serializes queue accesses for this device
   AND dev->qdisc pointer itself.

   dev->xmit_lock serializes accesses to device driver.

   dev->queue_lock and dev->xmit_lock are mutually exclusive,
   if one is grabbed, another must be free.
 */


/* Kick device.
   Note, that this procedure can be called by a watchdog timer, so that
   we do not check dev->tbusy flag here.

   Returns:  0  - queue is empty.
            >0  - queue is not empty, but throttled.
            <0  - queue is not empty. Device is throttled, if dev->tbusy != 0.

   NOTE: Called under dev->queue_lock with locally disabled BH.
*/

int qdisc_restart(struct net_device *dev)
{
        struct Qdisc *q = dev->qdisc;
        struct sk_buff *skb;

        /* Dequeue packet */
        if ((skb = q->dequeue(q)) != NULL) {
                unsigned nolock = (dev->features & NETIF_F_LLTX);
                /*
                 * When the driver has LLTX set it does its own locking
                 * in start_xmit. No need to add additional overhead by
                 * locking again. These checks are worth it because
                 * even uncongested locks can be quite expensive.
                 * The driver can do trylock like here too, in case
                 * of lock congestion it should return -1 and the packet
                 * will be requeued.
                 */
                if (!nolock) {
                        if (!spin_trylock(&dev->xmit_lock)) {
                        collision:
                                /* So, someone grabbed the driver. */
                                
                                /* It may be transient configuration error,
                                   when hard_start_xmit() recurses. We detect
                                   it by checking xmit owner and drop the
                                   packet when deadloop is detected.
                                */
                                if (dev->xmit_lock_owner == smp_processor_id()) {
                                        kfree_skb(skb);
                                        if (net_ratelimit())
                                                printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
                                        return -1;
                                }
                                __get_cpu_var(netdev_rx_stat).cpu_collision++;
                                goto requeue;
                        }
                        /* Remember that the driver is grabbed by us. */
                        dev->xmit_lock_owner = smp_processor_id();
                }
                
                {
                        /* And release queue */
                        spin_unlock(&dev->queue_lock);

                        if (!netif_queue_stopped(dev)) {
                                int ret;
                                if (netdev_nit)
                                        dev_queue_xmit_nit(skb, dev);

                                ret = dev->hard_start_xmit(skb, dev);
                                if (ret == NETDEV_TX_OK) { 
                                        if (!nolock) {
                                                dev->xmit_lock_owner = -1;
                                                spin_unlock(&dev->xmit_lock);
                                        }
                                        spin_lock(&dev->queue_lock);
                                        return -1;
                                }
                                if (ret == NETDEV_TX_LOCKED && nolock) {
                                        spin_lock(&dev->queue_lock);
                                        goto collision; 
                                }
                        }

                        /* NETDEV_TX_BUSY - we need to requeue */
                        /* Release the driver */
                        if (!nolock) { 
                                dev->xmit_lock_owner = -1;
                                spin_unlock(&dev->xmit_lock);
                        } 
                        spin_lock(&dev->queue_lock);
                        q = dev->qdisc;
                }

                /* Device kicked us out :(
                   This is possible in three cases:

                   0. driver is locked
                   1. fastroute is enabled
                   2. device cannot determine busy state
                      before start of transmission (f.e. dialout)
                   3. device is buggy (ppp)
                 */

requeue:
                q->ops->requeue(skb, q);
                netif_schedule(dev);
                return 1;
        }
        BUG_ON((int) q->q.qlen < 0);
        return q->q.qlen;
}

static void dev_watchdog(unsigned long arg)
{
        struct net_device *dev = (struct net_device *)arg;

        spin_lock(&dev->xmit_lock);
        if (dev->qdisc != &noop_qdisc) {
                if (netif_device_present(dev) &&
                    netif_running(dev) &&
                    netif_carrier_ok(dev)) {
                        if (netif_queue_stopped(dev) &&
                            (jiffies - dev->trans_start) > dev->watchdog_timeo) {
                                printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n", dev->name);
                                dev->tx_timeout(dev);
                        }
                        if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
                                dev_hold(dev);
                }
        }
        spin_unlock(&dev->xmit_lock);

        dev_put(dev);
}

static void dev_watchdog_init(struct net_device *dev)
{
        init_timer(&dev->watchdog_timer);
        dev->watchdog_timer.data = (unsigned long)dev;
        dev->watchdog_timer.function = dev_watchdog;
}

void __netdev_watchdog_up(struct net_device *dev)
{
        if (dev->tx_timeout) {
                if (dev->watchdog_timeo <= 0)
                        dev->watchdog_timeo = 5*HZ;
                if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
                        dev_hold(dev);
        }
}

static void dev_watchdog_up(struct net_device *dev)
{
        spin_lock_bh(&dev->xmit_lock);
        __netdev_watchdog_up(dev);
        spin_unlock_bh(&dev->xmit_lock);
}

static void dev_watchdog_down(struct net_device *dev)
{
        spin_lock_bh(&dev->xmit_lock);
        if (del_timer(&dev->watchdog_timer))
                __dev_put(dev);
        spin_unlock_bh(&dev->xmit_lock);
}

/* "NOOP" scheduler: the best scheduler, recommended for all interfaces
   under all circumstances. It is difficult to invent anything faster or
   cheaper.
 */

static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
{
        kfree_skb(skb);
        return NET_XMIT_CN;
}

static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
{
        return NULL;
}

static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        if (net_ratelimit())
                printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
                       skb->dev->name);
        kfree_skb(skb);
        return NET_XMIT_CN;
}

struct Qdisc_ops noop_qdisc_ops = {
        .id             =       "noop",
        .priv_size      =       0,
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .requeue        =       noop_requeue,
        .owner          =       THIS_MODULE,
};

struct Qdisc noop_qdisc = {
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .flags          =       TCQ_F_BUILTIN,
        .ops            =       &noop_qdisc_ops,        
        .list           =       LIST_HEAD_INIT(noop_qdisc.list),
};

static struct Qdisc_ops noqueue_qdisc_ops = {
        .id             =       "noqueue",
        .priv_size      =       0,
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .requeue        =       noop_requeue,
        .owner          =       THIS_MODULE,
};

static struct Qdisc noqueue_qdisc = {
        .enqueue        =       NULL,
        .dequeue        =       noop_dequeue,
        .flags          =       TCQ_F_BUILTIN,
        .ops            =       &noqueue_qdisc_ops,
        .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
};


static const u8 prio2band[TC_PRIO_MAX+1] =
        { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };

/* 3-band FIFO queue: old style, but should be a bit faster than
   generic prio+fifo combination.
 */

#define PFIFO_FAST_BANDS 3

static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
                                             struct Qdisc *qdisc)
{
        struct sk_buff_head *list = qdisc_priv(qdisc);
        return list + prio2band[skb->priority & TC_PRIO_MAX];
}

static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        struct sk_buff_head *list = prio2list(skb, qdisc);

        if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
                qdisc->q.qlen++;
                return __qdisc_enqueue_tail(skb, qdisc, list);
        }

        return qdisc_drop(skb, qdisc);
}

static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
                if (!skb_queue_empty(list + prio)) {
                        qdisc->q.qlen--;
                        return __qdisc_dequeue_head(qdisc, list + prio);
                }
        }

        return NULL;
}

static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        qdisc->q.qlen++;
        return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
}

static void pfifo_fast_reset(struct Qdisc* qdisc)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
                __qdisc_reset_queue(qdisc, list + prio);

        qdisc->qstats.backlog = 0;
        qdisc->q.qlen = 0;
}

static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
{
        struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };

        memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
        RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
        return skb->len;

rtattr_failure:
        return -1;
}

static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
                skb_queue_head_init(list + prio);

        return 0;
}

static struct Qdisc_ops pfifo_fast_ops = {
        .id             =       "pfifo_fast",
        .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
        .enqueue        =       pfifo_fast_enqueue,
        .dequeue        =       pfifo_fast_dequeue,
        .requeue        =       pfifo_fast_requeue,
        .init           =       pfifo_fast_init,
        .reset          =       pfifo_fast_reset,
        .dump           =       pfifo_fast_dump,
        .owner          =       THIS_MODULE,
};

struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
{
        void *p;
        struct Qdisc *sch;
        unsigned int size;
        int err = -ENOBUFS;

        /* ensure that the Qdisc and the private data are 32-byte aligned */
        size = QDISC_ALIGN(sizeof(*sch));
        size += ops->priv_size + (QDISC_ALIGNTO - 1);

        p = kmalloc(size, GFP_KERNEL);
        if (!p)
                goto errout;
        memset(p, 0, size);
        sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
        sch->padded = (char *) sch - (char *) p;

        INIT_LIST_HEAD(&sch->list);
        skb_queue_head_init(&sch->q);
        sch->ops = ops;
        sch->enqueue = ops->enqueue;
        sch->dequeue = ops->dequeue;
        sch->dev = dev;
        dev_hold(dev);
        sch->stats_lock = &dev->queue_lock;
        atomic_set(&sch->refcnt, 1);

        return sch;
errout:
        return ERR_PTR(-err);
}

struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
{
        struct Qdisc *sch;
        
        sch = qdisc_alloc(dev, ops);
        if (IS_ERR(sch))
                goto errout;

        if (!ops->init || ops->init(sch, NULL) == 0)
                return sch;

errout:
        return NULL;
}

/* Under dev->queue_lock and BH! */

void qdisc_reset(struct Qdisc *qdisc)
{
        struct Qdisc_ops *ops = qdisc->ops;

        if (ops->reset)
                ops->reset(qdisc);
}

/* this is the rcu callback function to clean up a qdisc when there 
 * are no further references to it */

static void __qdisc_destroy(struct rcu_head *head)
{
        struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
        struct Qdisc_ops  *ops = qdisc->ops;

#ifdef CONFIG_NET_ESTIMATOR
        gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
#endif
        write_lock(&qdisc_tree_lock);
        if (ops->reset)
                ops->reset(qdisc);
        if (ops->destroy)
                ops->destroy(qdisc);
        write_unlock(&qdisc_tree_lock);
        module_put(ops->owner);

        dev_put(qdisc->dev);
        kfree((char *) qdisc - qdisc->padded);
}

/* Under dev->queue_lock and BH! */

void qdisc_destroy(struct Qdisc *qdisc)
{
        struct list_head cql = LIST_HEAD_INIT(cql);
        struct Qdisc *cq, *q, *n;

        if (qdisc->flags & TCQ_F_BUILTIN ||
                !atomic_dec_and_test(&qdisc->refcnt))
                return;

        if (!list_empty(&qdisc->list)) {
                if (qdisc->ops->cl_ops == NULL)
                        list_del(&qdisc->list);
                else
                        list_move(&qdisc->list, &cql);
        }

        /* unlink inner qdiscs from dev->qdisc_list immediately */
        list_for_each_entry(cq, &cql, list)
                list_for_each_entry_safe(q, n, &qdisc->dev->qdisc_list, list)
                        if (TC_H_MAJ(q->parent) == TC_H_MAJ(cq->handle)) {
                                if (q->ops->cl_ops == NULL)
                                        list_del_init(&q->list);
                                else
                                        list_move_tail(&q->list, &cql);
                        }
        list_for_each_entry_safe(cq, n, &cql, list)
                list_del_init(&cq->list);

        call_rcu(&qdisc->q_rcu, __qdisc_destroy);
}

void dev_activate(struct net_device *dev)
{
        /* No queueing discipline is attached to device;
           create default one i.e. pfifo_fast for devices,
           which need queueing and noqueue_qdisc for
           virtual interfaces
         */

        if (dev->qdisc_sleeping == &noop_qdisc) {
                struct Qdisc *qdisc;
                if (dev->tx_queue_len) {
                        qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops);
                        if (qdisc == NULL) {
                                printk(KERN_INFO "%s: activation failed\n", dev->name);
                                return;
                        }
                        write_lock_bh(&qdisc_tree_lock);
                        list_add_tail(&qdisc->list, &dev->qdisc_list);
                        write_unlock_bh(&qdisc_tree_lock);
                } else {
                        qdisc =  &noqueue_qdisc;
                }
                write_lock_bh(&qdisc_tree_lock);
                dev->qdisc_sleeping = qdisc;
                write_unlock_bh(&qdisc_tree_lock);
        }

        if (!netif_carrier_ok(dev))
                /* Delay activation until next carrier-on event */
                return;

        spin_lock_bh(&dev->queue_lock);
        rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
        if (dev->qdisc != &noqueue_qdisc) {
                dev->trans_start = jiffies;
                dev_watchdog_up(dev);
        }
        spin_unlock_bh(&dev->queue_lock);
}

void dev_deactivate(struct net_device *dev)
{
        struct Qdisc *qdisc;

        spin_lock_bh(&dev->queue_lock);
        qdisc = dev->qdisc;
        dev->qdisc = &noop_qdisc;

        qdisc_reset(qdisc);

        spin_unlock_bh(&dev->queue_lock);

        dev_watchdog_down(dev);

        while (test_bit(__LINK_STATE_SCHED, &dev->state))
                yield();

        spin_unlock_wait(&dev->xmit_lock);
}

void dev_init_scheduler(struct net_device *dev)
{
        qdisc_lock_tree(dev);
        dev->qdisc = &noop_qdisc;
        dev->qdisc_sleeping = &noop_qdisc;
        INIT_LIST_HEAD(&dev->qdisc_list);
        qdisc_unlock_tree(dev);

        dev_watchdog_init(dev);
}

void dev_shutdown(struct net_device *dev)
{
        struct Qdisc *qdisc;

        qdisc_lock_tree(dev);
        qdisc = dev->qdisc_sleeping;
        dev->qdisc = &noop_qdisc;
        dev->qdisc_sleeping = &noop_qdisc;
        qdisc_destroy(qdisc);
#if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
        if ((qdisc = dev->qdisc_ingress) != NULL) {
                dev->qdisc_ingress = NULL;
                qdisc_destroy(qdisc);
        }
#endif
        BUG_TRAP(!timer_pending(&dev->watchdog_timer));
        qdisc_unlock_tree(dev);
}

EXPORT_SYMBOL(__netdev_watchdog_up);
EXPORT_SYMBOL(noop_qdisc);
EXPORT_SYMBOL(noop_qdisc_ops);
EXPORT_SYMBOL(qdisc_create_dflt);
EXPORT_SYMBOL(qdisc_alloc);
EXPORT_SYMBOL(qdisc_destroy);
EXPORT_SYMBOL(qdisc_reset);
EXPORT_SYMBOL(qdisc_restart);
EXPORT_SYMBOL(qdisc_lock_tree);
EXPORT_SYMBOL(qdisc_unlock_tree);