[mirror_ubuntu-zesty-kernel.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 struct timer_list dst_gc_timer =
	TIMER_INITIALIZER(dst_run_gc, DST_GC_MIN, 0);

static void dst_run_gc(unsigned long dummy)
{
	int    delayed = 0;
	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;
	while ((dst = *dstp) != NULL) {
		if (atomic_read(&dst->__refcnt)) {
			dstp = &dst->next;
			delayed++;
			continue;
		}
		*dstp = dst->next;

		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 ((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;
	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, <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
	42	static struct timer_list dst_gc_timer =
	43	TIMER_INITIALIZER(dst_run_gc, DST_GC_MIN, 0);
	44
	45	static void dst_run_gc(unsigned long dummy)
	46	{
	47	int delayed = 0;
	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
	55
	56	del_timer(&dst_gc_timer);
	57	dstp = &dst_garbage_list;
	58	while ((dst = *dstp) != NULL) {
	59	if (atomic_read(&dst->__refcnt)) {
	60	dstp = &dst->next;
	61	delayed++;
	62	continue;
	63	}
	64	*dstp = dst->next;
65
66	dst = dst_destroy(dst);
67	if (dst) {
68	/* NOHASH and still referenced. Unless it is already
69	* on gc list, invalidate it and add to gc list.
70	*
71	* Note: this is temporary. Actually, NOHASH dst's
72	* must be obsoleted when parent is obsoleted.
73	* But we do not have state "obsoleted, but
74	* referenced by parent", so it is right.
75	*/
76	if (dst->obsolete > 1)
77	continue;
78
79	___dst_free(dst);
80	dst->next = *dstp;
81	*dstp = dst;
82	dstp = &dst->next;
83	}
84	}
85	if (!dst_garbage_list) {
86	dst_gc_timer_inc = DST_GC_MAX;
87	goto out;
88	}
89	if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
90	dst_gc_timer_expires = DST_GC_MAX;
91	dst_gc_timer_inc += DST_GC_INC;
92	dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
93	#if RT_CACHE_DEBUG >= 2
94	printk("dst_total: %d/%d %ld\n",
95	atomic_read(&dst_total), delayed, dst_gc_timer_expires);
96	#endif
97	add_timer(&dst_gc_timer);
98
99	out:
100	spin_unlock(&dst_lock);
101	}
102
103	static int dst_discard_in(struct sk_buff *skb)
104	{
105	kfree_skb(skb);
106	return 0;
107	}
108
109	static int dst_discard_out(struct sk_buff *skb)
110	{
111	kfree_skb(skb);
112	return 0;
113	}
114
115	void * dst_alloc(struct dst_ops * ops)
116	{
117	struct dst_entry * dst;
118
119	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
120	if (ops->gc())
121	return NULL;
122	}
123	dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC);
124	if (!dst)
125	return NULL;
126	memset(dst, 0, ops->entry_size);
127	atomic_set(&dst->__refcnt, 0);
128	dst->ops = ops;
129	dst->lastuse = jiffies;
130	dst->path = dst;
131	dst->input = dst_discard_in;
132	dst->output = dst_discard_out;
133	#if RT_CACHE_DEBUG >= 2
134	atomic_inc(&dst_total);
135	#endif
136	atomic_inc(&ops->entries);
137	return dst;
138	}
139
140	static void ___dst_free(struct dst_entry * dst)
141	{
142	/* The first case (dev==NULL) is required, when
143	protocol module is unloaded.
144	*/
145	if (dst->dev == NULL \|\| !(dst->dev->flags&IFF_UP)) {
146	dst->input = dst_discard_in;
147	dst->output = dst_discard_out;
148	}
149	dst->obsolete = 2;
150	}
151
152	void __dst_free(struct dst_entry * dst)
153	{
154	spin_lock_bh(&dst_lock);
155	___dst_free(dst);
156	dst->next = dst_garbage_list;
157	dst_garbage_list = dst;
158	if (dst_gc_timer_inc > DST_GC_INC) {
159	dst_gc_timer_inc = DST_GC_INC;
160	dst_gc_timer_expires = DST_GC_MIN;
161	mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
162	}
163	spin_unlock_bh(&dst_lock);
164	}
165
166	struct dst_entry dst_destroy(struct dst_entry dst)
167	{
168	struct dst_entry *child;
169	struct neighbour *neigh;
170	struct hh_cache *hh;
171
172	smp_rmb();
173
174	again:
175	neigh = dst->neighbour;
176	hh = dst->hh;
177	child = dst->child;
178
179	dst->hh = NULL;
180	if (hh && atomic_dec_and_test(&hh->hh_refcnt))
181	kfree(hh);
182
183	if (neigh) {
184	dst->neighbour = NULL;
185	neigh_release(neigh);
186	}
187
188	atomic_dec(&dst->ops->entries);
189
190	if (dst->ops->destroy)
191	dst->ops->destroy(dst);
192	if (dst->dev)
193	dev_put(dst->dev);
194	#if RT_CACHE_DEBUG >= 2
195	atomic_dec(&dst_total);
196	#endif
197	kmem_cache_free(dst->ops->kmem_cachep, dst);
198
199	dst = child;
200	if (dst) {
6775cab9 HX	201	int nohash = dst->flags & DST_NOHASH;
6775cab9 HX	202
1da177e4 LT	203	if (atomic_dec_and_test(&dst->__refcnt)) {
1da177e4 LT	204	/* We were real parent of this dst, so kill child. */
6775cab9	205	if (nohash)
1da177e4 LT	206	goto again;
	207	} else {
	208	/* Child is still referenced, return it for freeing. */
6775cab9	209	if (nohash)
1da177e4 LT	210	return dst;
	211	/* Child is still in his hash table */
	212	}
	213	}
	214	return NULL;
	215	}
	216
	217	/* Dirty hack. We did it in 2.2 (in __dst_free),
	218	* we have _very_ good reasons not to repeat
	219	* this mistake in 2.3, but we have no choice
	220	* now. _It_ _is_ _explicit_ _deliberate_
	221	* _race_ _condition_.
	222	*
	223	* Commented and originally written by Alexey.
	224	*/
	225	static inline void dst_ifdown(struct dst_entry dst, struct net_device dev,
	226	int unregister)
	227	{
	228	if (dst->ops->ifdown)
	229	dst->ops->ifdown(dst, dev, unregister);
	230
	231	if (dev != dst->dev)
	232	return;
	233
	234	if (!unregister) {
	235	dst->input = dst_discard_in;
	236	dst->output = dst_discard_out;
	237	} else {
	238	dst->dev = &loopback_dev;
	239	dev_hold(&loopback_dev);
	240	dev_put(dev);
	241	if (dst->neighbour && dst->neighbour->dev == dev) {
	242	dst->neighbour->dev = &loopback_dev;
	243	dev_put(dev);
	244	dev_hold(&loopback_dev);
	245	}
	246	}
	247	}
	248
	249	static int dst_dev_event(struct notifier_block this, unsigned long event, void ptr)
	250	{
	251	struct net_device *dev = ptr;
	252	struct dst_entry *dst;
	253
	254	switch (event) {
	255	case NETDEV_UNREGISTER:
	256	case NETDEV_DOWN:
	257	spin_lock_bh(&dst_lock);
	258	for (dst = dst_garbage_list; dst; dst = dst->next) {
	259	dst_ifdown(dst, dev, event != NETDEV_DOWN);
	260	}
	261	spin_unlock_bh(&dst_lock);
	262	break;
	263	}
	264	return NOTIFY_DONE;
	265	}
	266
	267	static struct notifier_block dst_dev_notifier = {
	268	.notifier_call = dst_dev_event,
	269	};
	270
	271	void __init dst_init(void)
	272	{
	273	register_netdevice_notifier(&dst_dev_notifier);
274	}
275
276	EXPORT_SYMBOL(__dst_free);
277	EXPORT_SYMBOL(dst_alloc);
278	EXPORT_SYMBOL(dst_destroy);