[deliverable/linux.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
	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, SLAB_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
7c91767a	102	mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
1da177e4 LT	103
	104	out:
	105	spin_unlock(&dst_lock);
	106	}
	107
	108	static int dst_discard_in(struct sk_buff *skb)
	109	{
	110	kfree_skb(skb);
	111	return 0;
	112	}
	113
	114	static int dst_discard_out(struct sk_buff *skb)
	115	{
	116	kfree_skb(skb);
	117	return 0;
	118	}
	119
	120	void * dst_alloc(struct dst_ops * ops)
	121	{
	122	struct dst_entry * dst;
	123
	124	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
	125	if (ops->gc())
	126	return NULL;
	127	}
	128	dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC);
	129	if (!dst)
	130	return NULL;
	131	memset(dst, 0, ops->entry_size);
	132	atomic_set(&dst->__refcnt, 0);
	133	dst->ops = ops;
	134	dst->lastuse = jiffies;
	135	dst->path = dst;
	136	dst->input = dst_discard_in;
	137	dst->output = dst_discard_out;
	138	#if RT_CACHE_DEBUG >= 2
	139	atomic_inc(&dst_total);
	140	#endif
	141	atomic_inc(&ops->entries);
	142	return dst;
	143	}
	144
	145	static void ___dst_free(struct dst_entry * dst)
	146	{
	147	/* The first case (dev==NULL) is required, when
	148	protocol module is unloaded.
	149	*/
	150	if (dst->dev == NULL \|\| !(dst->dev->flags&IFF_UP)) {
	151	dst->input = dst_discard_in;
	152	dst->output = dst_discard_out;
	153	}
	154	dst->obsolete = 2;
	155	}
	156
	157	void __dst_free(struct dst_entry * dst)
	158	{
	159	spin_lock_bh(&dst_lock);
	160	___dst_free(dst);
	161	dst->next = dst_garbage_list;
	162	dst_garbage_list = dst;
	163	if (dst_gc_timer_inc > DST_GC_INC) {
	164	dst_gc_timer_inc = DST_GC_INC;
	165	dst_gc_timer_expires = DST_GC_MIN;
	166	mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
167	}
168	spin_unlock_bh(&dst_lock);
169	}
170
171	struct dst_entry dst_destroy(struct dst_entry dst)
172	{
173	struct dst_entry *child;
174	struct neighbour *neigh;
175	struct hh_cache *hh;
176
177	smp_rmb();
178
179	again:
180	neigh = dst->neighbour;
181	hh = dst->hh;
182	child = dst->child;
183
184	dst->hh = NULL;
185	if (hh && atomic_dec_and_test(&hh->hh_refcnt))
186	kfree(hh);
187
188	if (neigh) {
189	dst->neighbour = NULL;
190	neigh_release(neigh);
191	}
192
193	atomic_dec(&dst->ops->entries);
194
195	if (dst->ops->destroy)
196	dst->ops->destroy(dst);
197	if (dst->dev)
198	dev_put(dst->dev);
199	#if RT_CACHE_DEBUG >= 2
200	atomic_dec(&dst_total);
201	#endif
202	kmem_cache_free(dst->ops->kmem_cachep, dst);
203
204	dst = child;
205	if (dst) {
6775cab9 HX	206	int nohash = dst->flags & DST_NOHASH;
6775cab9 HX	207
1da177e4 LT	208	if (atomic_dec_and_test(&dst->__refcnt)) {
1da177e4 LT	209	/* We were real parent of this dst, so kill child. */
6775cab9	210	if (nohash)
1da177e4 LT	211	goto again;
	212	} else {
	213	/* Child is still referenced, return it for freeing. */
6775cab9	214	if (nohash)
1da177e4 LT	215	return dst;
	216	/* Child is still in his hash table */
	217	}
	218	}
	219	return NULL;
	220	}
	221
	222	/* Dirty hack. We did it in 2.2 (in __dst_free),
	223	* we have _very_ good reasons not to repeat
	224	* this mistake in 2.3, but we have no choice
	225	* now. _It_ _is_ _explicit_ _deliberate_
	226	* _race_ _condition_.
	227	*
	228	* Commented and originally written by Alexey.
	229	*/
	230	static inline void dst_ifdown(struct dst_entry dst, struct net_device dev,
	231	int unregister)
	232	{
	233	if (dst->ops->ifdown)
	234	dst->ops->ifdown(dst, dev, unregister);
	235
	236	if (dev != dst->dev)
	237	return;
	238
	239	if (!unregister) {
	240	dst->input = dst_discard_in;
	241	dst->output = dst_discard_out;
	242	} else {
	243	dst->dev = &loopback_dev;
	244	dev_hold(&loopback_dev);
	245	dev_put(dev);
	246	if (dst->neighbour && dst->neighbour->dev == dev) {
	247	dst->neighbour->dev = &loopback_dev;
	248	dev_put(dev);
	249	dev_hold(&loopback_dev);
	250	}
	251	}
	252	}
	253
	254	static int dst_dev_event(struct notifier_block this, unsigned long event, void ptr)
	255	{
	256	struct net_device *dev = ptr;
	257	struct dst_entry *dst;
	258
	259	switch (event) {
	260	case NETDEV_UNREGISTER:
	261	case NETDEV_DOWN:
	262	spin_lock_bh(&dst_lock);
	263	for (dst = dst_garbage_list; dst; dst = dst->next) {
	264	dst_ifdown(dst, dev, event != NETDEV_DOWN);
	265	}
	266	spin_unlock_bh(&dst_lock);
	267	break;
	268	}
	269	return NOTIFY_DONE;
	270	}
	271
	272	static struct notifier_block dst_dev_notifier = {
	273	.notifier_call = dst_dev_event,
	274	};
	275
	276	void __init dst_init(void)
	277	{
	278	register_netdevice_notifier(&dst_dev_notifier);
279	}
280
281	EXPORT_SYMBOL(__dst_free);
282	EXPORT_SYMBOL(dst_alloc);
283	EXPORT_SYMBOL(dst_destroy);