[linux.git] / net / core / dst.c

/*
 * net/core/dst.c	Protocol independent destination cache.
 *
 * Authors:		Alexey Kuznetsov, <[email protected]>
 *
 */

#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;
	}
	dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
#if RT_CACHE_DEBUG >= 2
	printk("dst_total: %d/%d %ld\n",
	       atomic_read(&dst_total), delayed,  dst_gc_timer_expires);
#endif
	add_timer(&dst_gc_timer);

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