[linux-2.6-block.git] / net / core / dst.c

/*
 * net/core/dst.c	Protocol independent destination cache.
 *
 * Authors:		Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 */

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/sched.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>

#include <net/dst.h>

/* Locking strategy:
 * 1) Garbage collection state of dead destination cache
 *    entries is protected by dst_lock.
 * 2) GC is run only from BH context, and is the only remover
 *    of entries.
 * 3) Entries are added to the garbage list from both BH
 *    and non-BH context, so local BH disabling is needed.
 * 4) All operations modify state, so a spinlock is used.
 */
static struct dst_entry 	*dst_garbage_list;
#if RT_CACHE_DEBUG >= 2 
static atomic_t			 dst_total = ATOMIC_INIT(0);
#endif
static DEFINE_SPINLOCK(dst_lock);

static unsigned long dst_gc_timer_expires;
static unsigned long dst_gc_timer_inc = DST_GC_MAX;
static void dst_run_gc(unsigned long);
static void ___dst_free(struct dst_entry * dst);

static DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0);

static void dst_run_gc(unsigned long dummy)
{
	int    delayed = 0;
	int    work_performed;
	struct dst_entry * dst, **dstp;

	if (!spin_trylock(&dst_lock)) {
		mod_timer(&dst_gc_timer, jiffies + HZ/10);
		return;
	}

	del_timer(&dst_gc_timer);
	dstp = &dst_garbage_list;
	work_performed = 0;
	while ((dst = *dstp) != NULL) {
		if (atomic_read(&dst->__refcnt)) {
			dstp = &dst->next;
			delayed++;
			continue;
		}
		*dstp = dst->next;
		work_performed = 1;

		dst = dst_destroy(dst);
		if (dst) {
			/* NOHASH and still referenced. Unless it is already
			 * on gc list, invalidate it and add to gc list.
			 *
			 * Note: this is temporary. Actually, NOHASH dst's
			 * must be obsoleted when parent is obsoleted.
			 * But we do not have state "obsoleted, but
			 * referenced by parent", so it is right.
			 */
			if (dst->obsolete > 1)
				continue;

			___dst_free(dst);
			dst->next = *dstp;
			*dstp = dst;
			dstp = &dst->next;
		}
	}
	if (!dst_garbage_list) {
		dst_gc_timer_inc = DST_GC_MAX;
		goto out;
	}
	if (!work_performed) {
		if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
			dst_gc_timer_expires = DST_GC_MAX;
		dst_gc_timer_inc += DST_GC_INC;
	} else {
		dst_gc_timer_inc = DST_GC_INC;
		dst_gc_timer_expires = DST_GC_MIN;
	}
#if RT_CACHE_DEBUG >= 2
	printk("dst_total: %d/%d %ld\n",
	       atomic_read(&dst_total), delayed,  dst_gc_timer_expires);
#endif
	/* if the next desired timer is more than 4 seconds in the future
	 * then round the timer to whole seconds
	 */
	if (dst_gc_timer_expires > 4*HZ)
		mod_timer(&dst_gc_timer,
			round_jiffies(jiffies + dst_gc_timer_expires));
	else
		mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);

out:
	spin_unlock(&dst_lock);
}

static int dst_discard_in(struct sk_buff *skb)
{
	kfree_skb(skb);
	return 0;
}

static int dst_discard_out(struct sk_buff *skb)
{
	kfree_skb(skb);
	return 0;
}

void * dst_alloc(struct dst_ops * ops)
{
	struct dst_entry * dst;

	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
		if (ops->gc())
			return NULL;
	}
	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
	if (!dst)
		return NULL;
	memset(dst, 0, ops->entry_size);
	atomic_set(&dst->__refcnt, 0);
	dst->ops = ops;
	dst->lastuse = jiffies;
	dst->path = dst;
	dst->input = dst_discard_in;
	dst->output = dst_discard_out;
#if RT_CACHE_DEBUG >= 2 
	atomic_inc(&dst_total);
#endif
	atomic_inc(&ops->entries);
	return dst;
}

static void ___dst_free(struct dst_entry * dst)
{
	/* The first case (dev==NULL) is required, when
	   protocol module is unloaded.
	 */
	if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
		dst->input = dst_discard_in;
		dst->output = dst_discard_out;
	}
	dst->obsolete = 2;
}

void __dst_free(struct dst_entry * dst)
{
	spin_lock_bh(&dst_lock);
	___dst_free(dst);
	dst->next = dst_garbage_list;
	dst_garbage_list = dst;
	if (dst_gc_timer_inc > DST_GC_INC) {
		dst_gc_timer_inc = DST_GC_INC;
		dst_gc_timer_expires = DST_GC_MIN;
		mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
	}
	spin_unlock_bh(&dst_lock);
}

struct dst_entry *dst_destroy(struct dst_entry * dst)
{
	struct dst_entry *child;
	struct neighbour *neigh;
	struct hh_cache *hh;

	smp_rmb();

again:
	neigh = dst->neighbour;
	hh = dst->hh;
	child = dst->child;

	dst->hh = NULL;
	if (hh && atomic_dec_and_test(&hh->hh_refcnt))
		kfree(hh);

	if (neigh) {
		dst->neighbour = NULL;
		neigh_release(neigh);
	}

	atomic_dec(&dst->ops->entries);

	if (dst->ops->destroy)
		dst->ops->destroy(dst);
	if (dst->dev)
		dev_put(dst->dev);
#if RT_CACHE_DEBUG >= 2 
	atomic_dec(&dst_total);
#endif
	kmem_cache_free(dst->ops->kmem_cachep, dst);

	dst = child;
	if (dst) {
		int nohash = dst->flags & DST_NOHASH;

		if (atomic_dec_and_test(&dst->__refcnt)) {
			/* We were real parent of this dst, so kill child. */
			if (nohash)
				goto again;
		} else {
			/* Child is still referenced, return it for freeing. */
			if (nohash)
				return dst;
			/* Child is still in his hash table */
		}
	}
	return NULL;
}

/* Dirty hack. We did it in 2.2 (in __dst_free),
 * we have _very_ good reasons not to repeat
 * this mistake in 2.3, but we have no choice
 * now. _It_ _is_ _explicit_ _deliberate_
 * _race_ _condition_.
 *
 * Commented and originally written by Alexey.
 */
static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev,
			      int unregister)
{
	if (dst->ops->ifdown)
		dst->ops->ifdown(dst, dev, unregister);

	if (dev != dst->dev)
		return;

	if (!unregister) {
		dst->input = dst_discard_in;
		dst->output = dst_discard_out;
	} else {
		dst->dev = &loopback_dev;
		dev_hold(&loopback_dev);
		dev_put(dev);
		if (dst->neighbour && dst->neighbour->dev == dev) {
			dst->neighbour->dev = &loopback_dev;
			dev_put(dev);
			dev_hold(&loopback_dev);
		}
	}
}

static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
{
	struct net_device *dev = ptr;
	struct dst_entry *dst;

	switch (event) {
	case NETDEV_UNREGISTER:
	case NETDEV_DOWN:
		spin_lock_bh(&dst_lock);
		for (dst = dst_garbage_list; dst; dst = dst->next) {
			dst_ifdown(dst, dev, event != NETDEV_DOWN);
		}
		spin_unlock_bh(&dst_lock);
		break;
	}
	return NOTIFY_DONE;
}

static struct notifier_block dst_dev_notifier = {
	.notifier_call	= dst_dev_event,
};

void __init dst_init(void)
{
	register_netdevice_notifier(&dst_dev_notifier);
}

EXPORT_SYMBOL(__dst_free);
EXPORT_SYMBOL(dst_alloc);
EXPORT_SYMBOL(dst_destroy);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* net/core/dst.c Protocol independent destination cache.
	3	*
	4	* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
	5	*
	6	*/
	7
	8	#include <linux/bitops.h>
	9	#include <linux/errno.h>
	10	#include <linux/init.h>
	11	#include <linux/kernel.h>
	12	#include <linux/mm.h>
	13	#include <linux/module.h>
	14	#include <linux/netdevice.h>
	15	#include <linux/sched.h>
	16	#include <linux/skbuff.h>
	17	#include <linux/string.h>
	18	#include <linux/types.h>
	19
	20	#include <net/dst.h>
	21
	22	/* Locking strategy:
	23	* 1) Garbage collection state of dead destination cache
	24	* entries is protected by dst_lock.
	25	* 2) GC is run only from BH context, and is the only remover
	26	* of entries.
	27	* 3) Entries are added to the garbage list from both BH
	28	* and non-BH context, so local BH disabling is needed.
	29	* 4) All operations modify state, so a spinlock is used.
	30	*/
	31	static struct dst_entry *dst_garbage_list;
	32	#if RT_CACHE_DEBUG >= 2
	33	static atomic_t dst_total = ATOMIC_INIT(0);
	34	#endif
	35	static DEFINE_SPINLOCK(dst_lock);
	36
	37	static unsigned long dst_gc_timer_expires;
	38	static unsigned long dst_gc_timer_inc = DST_GC_MAX;
	39	static void dst_run_gc(unsigned long);
	40	static void ___dst_free(struct dst_entry * dst);
	41
8d06afab	42	static DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0);
1da177e4 LT	43
	44	static void dst_run_gc(unsigned long dummy)
	45	{
	46	int delayed = 0;
f0098f78	47	int work_performed;
1da177e4 LT	48	struct dst_entry * dst, **dstp;
	49
	50	if (!spin_trylock(&dst_lock)) {
	51	mod_timer(&dst_gc_timer, jiffies + HZ/10);
	52	return;
	53	}
	54
1da177e4 LT	55	del_timer(&dst_gc_timer);
1da177e4 LT	56	dstp = &dst_garbage_list;
f0098f78	57	work_performed = 0;
1da177e4 LT	58	while ((dst = *dstp) != NULL) {
	59	if (atomic_read(&dst->__refcnt)) {
	60	dstp = &dst->next;
	61	delayed++;
	62	continue;
	63	}
	64	*dstp = dst->next;
f0098f78	65	work_performed = 1;
1da177e4 LT	66
	67	dst = dst_destroy(dst);
	68	if (dst) {
	69	/* NOHASH and still referenced. Unless it is already
	70	* on gc list, invalidate it and add to gc list.
	71	*
	72	* Note: this is temporary. Actually, NOHASH dst's
	73	* must be obsoleted when parent is obsoleted.
	74	* But we do not have state "obsoleted, but
	75	* referenced by parent", so it is right.
	76	*/
	77	if (dst->obsolete > 1)
	78	continue;
	79
	80	___dst_free(dst);
	81	dst->next = *dstp;
	82	*dstp = dst;
	83	dstp = &dst->next;
	84	}
	85	}
	86	if (!dst_garbage_list) {
	87	dst_gc_timer_inc = DST_GC_MAX;
	88	goto out;
	89	}
f0098f78 DL	90	if (!work_performed) {
	91	if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
	92	dst_gc_timer_expires = DST_GC_MAX;
	93	dst_gc_timer_inc += DST_GC_INC;
	94	} else {
	95	dst_gc_timer_inc = DST_GC_INC;
	96	dst_gc_timer_expires = DST_GC_MIN;
	97	}
1da177e4 LT	98	#if RT_CACHE_DEBUG >= 2
	99	printk("dst_total: %d/%d %ld\n",
	100	atomic_read(&dst_total), delayed, dst_gc_timer_expires);
	101	#endif
f5a6e01c AV	102	/* if the next desired timer is more than 4 seconds in the future
	103	* then round the timer to whole seconds
	104	*/
	105	if (dst_gc_timer_expires > 4*HZ)
	106	mod_timer(&dst_gc_timer,
	107	round_jiffies(jiffies + dst_gc_timer_expires));
	108	else
	109	mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
1da177e4 LT	110
	111	out:
	112	spin_unlock(&dst_lock);
	113	}
	114
	115	static int dst_discard_in(struct sk_buff *skb)
	116	{
	117	kfree_skb(skb);
	118	return 0;
	119	}
	120
	121	static int dst_discard_out(struct sk_buff *skb)
	122	{
	123	kfree_skb(skb);
	124	return 0;
	125	}
	126
	127	void * dst_alloc(struct dst_ops * ops)
	128	{
	129	struct dst_entry * dst;
	130
	131	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
	132	if (ops->gc())
	133	return NULL;
	134	}
54e6ecb2	135	dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
1da177e4 LT	136	if (!dst)
	137	return NULL;
	138	memset(dst, 0, ops->entry_size);
	139	atomic_set(&dst->__refcnt, 0);
	140	dst->ops = ops;
	141	dst->lastuse = jiffies;
	142	dst->path = dst;
	143	dst->input = dst_discard_in;
	144	dst->output = dst_discard_out;
	145	#if RT_CACHE_DEBUG >= 2
	146	atomic_inc(&dst_total);
	147	#endif
	148	atomic_inc(&ops->entries);
	149	return dst;
	150	}
	151
	152	static void ___dst_free(struct dst_entry * dst)
	153	{
	154	/* The first case (dev==NULL) is required, when
	155	protocol module is unloaded.
	156	*/
	157	if (dst->dev == NULL \|\| !(dst->dev->flags&IFF_UP)) {
	158	dst->input = dst_discard_in;
	159	dst->output = dst_discard_out;
	160	}
	161	dst->obsolete = 2;
	162	}
	163
	164	void __dst_free(struct dst_entry * dst)
	165	{
	166	spin_lock_bh(&dst_lock);
	167	___dst_free(dst);
	168	dst->next = dst_garbage_list;
	169	dst_garbage_list = dst;
	170	if (dst_gc_timer_inc > DST_GC_INC) {
	171	dst_gc_timer_inc = DST_GC_INC;
	172	dst_gc_timer_expires = DST_GC_MIN;
	173	mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
	174	}
	175	spin_unlock_bh(&dst_lock);
	176	}
	177
	178	struct dst_entry dst_destroy(struct dst_entry dst)
	179	{
	180	struct dst_entry *child;
	181	struct neighbour *neigh;
	182	struct hh_cache *hh;
	183
	184	smp_rmb();
	185
	186	again:
	187	neigh = dst->neighbour;
	188	hh = dst->hh;
	189	child = dst->child;
	190
	191	dst->hh = NULL;
	192	if (hh && atomic_dec_and_test(&hh->hh_refcnt))
	193	kfree(hh);
	194
	195	if (neigh) {
	196	dst->neighbour = NULL;
	197	neigh_release(neigh);
	198	}
	199
200	atomic_dec(&dst->ops->entries);
201
202	if (dst->ops->destroy)
203	dst->ops->destroy(dst);
204	if (dst->dev)
205	dev_put(dst->dev);
206	#if RT_CACHE_DEBUG >= 2
207	atomic_dec(&dst_total);
208	#endif
209	kmem_cache_free(dst->ops->kmem_cachep, dst);
210
211	dst = child;
212	if (dst) {
6775cab9 HX	213	int nohash = dst->flags & DST_NOHASH;
6775cab9 HX	214
1da177e4 LT	215	if (atomic_dec_and_test(&dst->__refcnt)) {
1da177e4 LT	216	/* We were real parent of this dst, so kill child. */
6775cab9	217	if (nohash)
1da177e4 LT	218	goto again;
	219	} else {
	220	/* Child is still referenced, return it for freeing. */
6775cab9	221	if (nohash)
1da177e4 LT	222	return dst;
	223	/* Child is still in his hash table */
	224	}
	225	}
	226	return NULL;
	227	}
	228
	229	/* Dirty hack. We did it in 2.2 (in __dst_free),
	230	* we have _very_ good reasons not to repeat
	231	* this mistake in 2.3, but we have no choice
	232	* now. _It_ _is_ _explicit_ _deliberate_
	233	* _race_ _condition_.
	234	*
	235	* Commented and originally written by Alexey.
	236	*/
	237	static inline void dst_ifdown(struct dst_entry dst, struct net_device dev,
	238	int unregister)
	239	{
	240	if (dst->ops->ifdown)
	241	dst->ops->ifdown(dst, dev, unregister);
	242
	243	if (dev != dst->dev)
	244	return;
	245
	246	if (!unregister) {
	247	dst->input = dst_discard_in;
	248	dst->output = dst_discard_out;
	249	} else {
	250	dst->dev = &loopback_dev;
	251	dev_hold(&loopback_dev);
	252	dev_put(dev);
	253	if (dst->neighbour && dst->neighbour->dev == dev) {
	254	dst->neighbour->dev = &loopback_dev;
	255	dev_put(dev);
	256	dev_hold(&loopback_dev);
	257	}
	258	}
	259	}
	260
	261	static int dst_dev_event(struct notifier_block this, unsigned long event, void ptr)
	262	{
	263	struct net_device *dev = ptr;
	264	struct dst_entry *dst;
	265
	266	switch (event) {
	267	case NETDEV_UNREGISTER:
	268	case NETDEV_DOWN:
	269	spin_lock_bh(&dst_lock);
	270	for (dst = dst_garbage_list; dst; dst = dst->next) {
	271	dst_ifdown(dst, dev, event != NETDEV_DOWN);
	272	}
	273	spin_unlock_bh(&dst_lock);
	274	break;
	275	}
	276	return NOTIFY_DONE;
	277	}
	278
	279	static struct notifier_block dst_dev_notifier = {
	280	.notifier_call = dst_dev_event,
	281	};
	282
	283	void __init dst_init(void)
	284	{
	285	register_netdevice_notifier(&dst_dev_notifier);
286	}
287
288	EXPORT_SYMBOL(__dst_free);
289	EXPORT_SYMBOL(dst_alloc);
290	EXPORT_SYMBOL(dst_destroy);