[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/workqueue.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <net/net_namespace.h>
#include <linux/sched.h>

#include <net/dst.h>

/*
 * Theory of operations:
 * 1) We use a list, protected by a spinlock, to add
 *    new entries from both BH and non-BH context.
 * 2) In order to keep spinlock held for a small delay,
 *    we use a second list where are stored long lived
 *    entries, that are handled by the garbage collect thread
 *    fired by a workqueue.
 * 3) This list is guarded by a mutex,
 *    so that the gc_task and dst_dev_event() can be synchronized.
 */
#if RT_CACHE_DEBUG >= 2
static atomic_t			 dst_total = ATOMIC_INIT(0);
#endif

/*
 * We want to keep lock & list close together
 * to dirty as few cache lines as possible in __dst_free().
 * As this is not a very strong hint, we dont force an alignment on SMP.
 */
static struct {
	spinlock_t		lock;
	struct dst_entry 	*list;
	unsigned long		timer_inc;
	unsigned long		timer_expires;
} dst_garbage = {
	.lock = __SPIN_LOCK_UNLOCKED(dst_garbage.lock),
	.timer_inc = DST_GC_MAX,
};
static void dst_gc_task(struct work_struct *work);
static void ___dst_free(struct dst_entry * dst);

static DECLARE_DELAYED_WORK(dst_gc_work, dst_gc_task);

static DEFINE_MUTEX(dst_gc_mutex);
/*
 * long lived entries are maintained in this list, guarded by dst_gc_mutex
 */
static struct dst_entry         *dst_busy_list;

static void dst_gc_task(struct work_struct *work)
{
	int    delayed = 0;
	int    work_performed = 0;
	unsigned long expires = ~0L;
	struct dst_entry *dst, *next, head;
	struct dst_entry *last = &head;
#if RT_CACHE_DEBUG >= 2
	ktime_t time_start = ktime_get();
	struct timespec elapsed;
#endif

	mutex_lock(&dst_gc_mutex);
	next = dst_busy_list;

loop:
	while ((dst = next) != NULL) {
		next = dst->next;
		prefetch(&next->next);
		cond_resched();
		if (likely(atomic_read(&dst->__refcnt))) {
			last->next = dst;
			last = dst;
			delayed++;
			continue;
		}
		work_performed++;

		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 = next;
			next = dst;
		}
	}

	spin_lock_bh(&dst_garbage.lock);
	next = dst_garbage.list;
	if (next) {
		dst_garbage.list = NULL;
		spin_unlock_bh(&dst_garbage.lock);
		goto loop;
	}
	last->next = NULL;
	dst_busy_list = head.next;
	if (!dst_busy_list)
		dst_garbage.timer_inc = DST_GC_MAX;
	else {
		/*
		 * if we freed less than 1/10 of delayed entries,
		 * we can sleep longer.
		 */
		if (work_performed <= delayed/10) {
			dst_garbage.timer_expires += dst_garbage.timer_inc;
			if (dst_garbage.timer_expires > DST_GC_MAX)
				dst_garbage.timer_expires = DST_GC_MAX;
			dst_garbage.timer_inc += DST_GC_INC;
		} else {
			dst_garbage.timer_inc = DST_GC_INC;
			dst_garbage.timer_expires = DST_GC_MIN;
		}
		expires = dst_garbage.timer_expires;
		/*
		 * if the next desired timer is more than 4 seconds in the future
		 * then round the timer to whole seconds
		 */
		if (expires > 4*HZ)
			expires = round_jiffies_relative(expires);
		schedule_delayed_work(&dst_gc_work, expires);
	}

	spin_unlock_bh(&dst_garbage.lock);
	mutex_unlock(&dst_gc_mutex);
#if RT_CACHE_DEBUG >= 2
	elapsed = ktime_to_timespec(ktime_sub(ktime_get(), time_start));
	printk(KERN_DEBUG "dst_total: %d delayed: %d work_perf: %d"
		" expires: %lu elapsed: %lu us\n",
		atomic_read(&dst_total), delayed, work_performed,
		expires,
		elapsed.tv_sec * USEC_PER_SEC + elapsed.tv_nsec / NSEC_PER_USEC);
#endif
}

int dst_discard(struct sk_buff *skb)
{
	kfree_skb(skb);
	return 0;
}
EXPORT_SYMBOL(dst_discard);

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

	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
		if (ops->gc(ops))
			return NULL;
	}
	dst = kmem_cache_zalloc(ops->kmem_cachep, GFP_ATOMIC);
	if (!dst)
		return NULL;
	atomic_set(&dst->__refcnt, 0);
	dst->ops = ops;
	dst->lastuse = jiffies;
	dst->path = dst;
	dst->input = dst->output = dst_discard;
#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->output = dst_discard;
	}
	dst->obsolete = 2;
}

void __dst_free(struct dst_entry * dst)
{
	spin_lock_bh(&dst_garbage.lock);
	___dst_free(dst);
	dst->next = dst_garbage.list;
	dst_garbage.list = dst;
	if (dst_garbage.timer_inc > DST_GC_INC) {
		dst_garbage.timer_inc = DST_GC_INC;
		dst_garbage.timer_expires = DST_GC_MIN;
		cancel_delayed_work(&dst_gc_work);
		schedule_delayed_work(&dst_gc_work, dst_garbage.timer_expires);
	}
	spin_unlock_bh(&dst_garbage.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;
}

void dst_release(struct dst_entry *dst)
{
	if (dst) {
               int newrefcnt;

		smp_mb__before_atomic_dec();
               newrefcnt = atomic_dec_return(&dst->__refcnt);
               WARN_ON(newrefcnt < 0);
	}
}
EXPORT_SYMBOL(dst_release);

/* 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->output = dst_discard;
	} else {
		dst->dev = dev_net(dst->dev)->loopback_dev;
		dev_hold(dst->dev);
		dev_put(dev);
		if (dst->neighbour && dst->neighbour->dev == dev) {
			dst->neighbour->dev = dst->dev;
			dev_hold(dst->dev);
			dev_put(dev);
		}
	}
}

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

	switch (event) {
	case NETDEV_UNREGISTER:
	case NETDEV_DOWN:
		mutex_lock(&dst_gc_mutex);
		for (dst = dst_busy_list; dst; dst = dst->next) {
			last = dst;
			dst_ifdown(dst, dev, event != NETDEV_DOWN);
		}

		spin_lock_bh(&dst_garbage.lock);
		dst = dst_garbage.list;
		dst_garbage.list = NULL;
		spin_unlock_bh(&dst_garbage.lock);

		if (last)
			last->next = dst;
		else
			dst_busy_list = dst;
		for (; dst; dst = dst->next) {
			dst_ifdown(dst, dev, event != NETDEV_DOWN);
		}
		mutex_unlock(&dst_gc_mutex);
		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>
86bba269	12	#include <linux/workqueue.h>
1da177e4 LT	13	#include <linux/mm.h>
	14	#include <linux/module.h>
	15	#include <linux/netdevice.h>
1da177e4 LT	16	#include <linux/skbuff.h>
	17	#include <linux/string.h>
	18	#include <linux/types.h>
e9dc8653	19	#include <net/net_namespace.h>
2fc1b5dd	20	#include <linux/sched.h>
1da177e4 LT	21
	22	#include <net/dst.h>
	23
86bba269 ED	24	/*
	25	* Theory of operations:
	26	* 1) We use a list, protected by a spinlock, to add
	27	* new entries from both BH and non-BH context.
	28	* 2) In order to keep spinlock held for a small delay,
	29	* we use a second list where are stored long lived
	30	* entries, that are handled by the garbage collect thread
	31	* fired by a workqueue.
	32	* 3) This list is guarded by a mutex,
	33	* so that the gc_task and dst_dev_event() can be synchronized.
1da177e4	34	*/
4ec93edb	35	#if RT_CACHE_DEBUG >= 2
1da177e4 LT	36	static atomic_t dst_total = ATOMIC_INIT(0);
1da177e4 LT	37	#endif
1da177e4	38
86bba269 ED	39	/*
	40	* We want to keep lock & list close together
	41	* to dirty as few cache lines as possible in __dst_free().
	42	* As this is not a very strong hint, we dont force an alignment on SMP.
	43	*/
	44	static struct {
	45	spinlock_t lock;
	46	struct dst_entry *list;
	47	unsigned long timer_inc;
	48	unsigned long timer_expires;
	49	} dst_garbage = {
	50	.lock = __SPIN_LOCK_UNLOCKED(dst_garbage.lock),
	51	.timer_inc = DST_GC_MAX,
	52	};
	53	static void dst_gc_task(struct work_struct *work);
1da177e4 LT	54	static void ___dst_free(struct dst_entry * dst);
1da177e4 LT	55
86bba269	56	static DECLARE_DELAYED_WORK(dst_gc_work, dst_gc_task);
1da177e4	57
86bba269 ED	58	static DEFINE_MUTEX(dst_gc_mutex);
	59	/*
	60	* long lived entries are maintained in this list, guarded by dst_gc_mutex
	61	*/
	62	static struct dst_entry *dst_busy_list;
	63
	64	static void dst_gc_task(struct work_struct *work)
1da177e4 LT	65	{
1da177e4 LT	66	int delayed = 0;
86bba269 ED	67	int work_performed = 0;
	68	unsigned long expires = ~0L;
	69	struct dst_entry dst, next, head;
	70	struct dst_entry *last = &head;
	71	#if RT_CACHE_DEBUG >= 2
	72	ktime_t time_start = ktime_get();
	73	struct timespec elapsed;
	74	#endif
1da177e4	75
86bba269 ED	76	mutex_lock(&dst_gc_mutex);
86bba269 ED	77	next = dst_busy_list;
1da177e4	78
86bba269 ED	79	loop:
	80	while ((dst = next) != NULL) {
	81	next = dst->next;
	82	prefetch(&next->next);
2fc1b5dd	83	cond_resched();
86bba269 ED	84	if (likely(atomic_read(&dst->__refcnt))) {
	85	last->next = dst;
	86	last = dst;
1da177e4 LT	87	delayed++;
	88	continue;
	89	}
86bba269	90	work_performed++;
1da177e4 LT	91
	92	dst = dst_destroy(dst);
	93	if (dst) {
	94	/* NOHASH and still referenced. Unless it is already
	95	* on gc list, invalidate it and add to gc list.
	96	*
	97	* Note: this is temporary. Actually, NOHASH dst's
	98	* must be obsoleted when parent is obsoleted.
	99	* But we do not have state "obsoleted, but
	100	* referenced by parent", so it is right.
	101	*/
	102	if (dst->obsolete > 1)
	103	continue;
	104
	105	___dst_free(dst);
86bba269 ED	106	dst->next = next;
86bba269 ED	107	next = dst;
1da177e4 LT	108	}
1da177e4 LT	109	}
86bba269 ED	110
	111	spin_lock_bh(&dst_garbage.lock);
	112	next = dst_garbage.list;
	113	if (next) {
	114	dst_garbage.list = NULL;
	115	spin_unlock_bh(&dst_garbage.lock);
	116	goto loop;
1da177e4	117	}
86bba269 ED	118	last->next = NULL;
	119	dst_busy_list = head.next;
	120	if (!dst_busy_list)
	121	dst_garbage.timer_inc = DST_GC_MAX;
	122	else {
	123	/*
	124	* if we freed less than 1/10 of delayed entries,
	125	* we can sleep longer.
	126	*/
	127	if (work_performed <= delayed/10) {
	128	dst_garbage.timer_expires += dst_garbage.timer_inc;
	129	if (dst_garbage.timer_expires > DST_GC_MAX)
	130	dst_garbage.timer_expires = DST_GC_MAX;
	131	dst_garbage.timer_inc += DST_GC_INC;
	132	} else {
	133	dst_garbage.timer_inc = DST_GC_INC;
	134	dst_garbage.timer_expires = DST_GC_MIN;
	135	}
	136	expires = dst_garbage.timer_expires;
	137	/*
	138	* if the next desired timer is more than 4 seconds in the future
	139	* then round the timer to whole seconds
	140	*/
	141	if (expires > 4*HZ)
	142	expires = round_jiffies_relative(expires);
	143	schedule_delayed_work(&dst_gc_work, expires);
f0098f78	144	}
86bba269 ED	145
	146	spin_unlock_bh(&dst_garbage.lock);
	147	mutex_unlock(&dst_gc_mutex);
1da177e4	148	#if RT_CACHE_DEBUG >= 2
86bba269 ED	149	elapsed = ktime_to_timespec(ktime_sub(ktime_get(), time_start));
	150	printk(KERN_DEBUG "dst_total: %d delayed: %d work_perf: %d"
	151	" expires: %lu elapsed: %lu us\n",
	152	atomic_read(&dst_total), delayed, work_performed,
	153	expires,
	154	elapsed.tv_sec * USEC_PER_SEC + elapsed.tv_nsec / NSEC_PER_USEC);
1da177e4	155	#endif
1da177e4 LT	156	}
1da177e4 LT	157
352e512c	158	int dst_discard(struct sk_buff *skb)
1da177e4 LT	159	{
	160	kfree_skb(skb);
	161	return 0;
	162	}
352e512c	163	EXPORT_SYMBOL(dst_discard);
1da177e4 LT	164
	165	void * dst_alloc(struct dst_ops * ops)
	166	{
	167	struct dst_entry * dst;
	168
	169	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
569d3645	170	if (ops->gc(ops))
1da177e4 LT	171	return NULL;
1da177e4 LT	172	}
c3762229	173	dst = kmem_cache_zalloc(ops->kmem_cachep, GFP_ATOMIC);
1da177e4 LT	174	if (!dst)
1da177e4 LT	175	return NULL;
1da177e4 LT	176	atomic_set(&dst->__refcnt, 0);
	177	dst->ops = ops;
	178	dst->lastuse = jiffies;
	179	dst->path = dst;
c4b1010f	180	dst->input = dst->output = dst_discard;
4ec93edb	181	#if RT_CACHE_DEBUG >= 2
1da177e4 LT	182	atomic_inc(&dst_total);
	183	#endif
	184	atomic_inc(&ops->entries);
	185	return dst;
	186	}
	187
	188	static void ___dst_free(struct dst_entry * dst)
	189	{
	190	/* The first case (dev==NULL) is required, when
	191	protocol module is unloaded.
	192	*/
	193	if (dst->dev == NULL \|\| !(dst->dev->flags&IFF_UP)) {
c4b1010f	194	dst->input = dst->output = dst_discard;
1da177e4 LT	195	}
	196	dst->obsolete = 2;
	197	}
	198
	199	void __dst_free(struct dst_entry * dst)
	200	{
86bba269	201	spin_lock_bh(&dst_garbage.lock);
1da177e4	202	___dst_free(dst);
86bba269 ED	203	dst->next = dst_garbage.list;
	204	dst_garbage.list = dst;
	205	if (dst_garbage.timer_inc > DST_GC_INC) {
	206	dst_garbage.timer_inc = DST_GC_INC;
	207	dst_garbage.timer_expires = DST_GC_MIN;
f262b59b	208	cancel_delayed_work(&dst_gc_work);
86bba269	209	schedule_delayed_work(&dst_gc_work, dst_garbage.timer_expires);
1da177e4	210	}
86bba269	211	spin_unlock_bh(&dst_garbage.lock);
1da177e4 LT	212	}
	213
	214	struct dst_entry dst_destroy(struct dst_entry dst)
	215	{
	216	struct dst_entry *child;
	217	struct neighbour *neigh;
	218	struct hh_cache *hh;
	219
	220	smp_rmb();
	221
	222	again:
	223	neigh = dst->neighbour;
	224	hh = dst->hh;
	225	child = dst->child;
	226
	227	dst->hh = NULL;
	228	if (hh && atomic_dec_and_test(&hh->hh_refcnt))
	229	kfree(hh);
	230
	231	if (neigh) {
	232	dst->neighbour = NULL;
	233	neigh_release(neigh);
	234	}
	235
	236	atomic_dec(&dst->ops->entries);
	237
	238	if (dst->ops->destroy)
	239	dst->ops->destroy(dst);
	240	if (dst->dev)
	241	dev_put(dst->dev);
4ec93edb	242	#if RT_CACHE_DEBUG >= 2
1da177e4 LT	243	atomic_dec(&dst_total);
	244	#endif
	245	kmem_cache_free(dst->ops->kmem_cachep, dst);
	246
	247	dst = child;
	248	if (dst) {
6775cab9 HX	249	int nohash = dst->flags & DST_NOHASH;
6775cab9 HX	250
1da177e4 LT	251	if (atomic_dec_and_test(&dst->__refcnt)) {
1da177e4 LT	252	/* We were real parent of this dst, so kill child. */
6775cab9	253	if (nohash)
1da177e4 LT	254	goto again;
	255	} else {
	256	/* Child is still referenced, return it for freeing. */
6775cab9	257	if (nohash)
1da177e4 LT	258	return dst;
	259	/* Child is still in his hash table */
	260	}
	261	}
	262	return NULL;
	263	}
	264
8d330868 IJ	265	void dst_release(struct dst_entry *dst)
	266	{
	267	if (dst) {
ef711cf1 ED	268	int newrefcnt;
ef711cf1 ED	269
8d330868	270	smp_mb__before_atomic_dec();
ef711cf1 ED	271	newrefcnt = atomic_dec_return(&dst->__refcnt);
ef711cf1 ED	272	WARN_ON(newrefcnt < 0);
8d330868 IJ	273	}
	274	}
	275	EXPORT_SYMBOL(dst_release);
	276
1da177e4 LT	277	/* Dirty hack. We did it in 2.2 (in __dst_free),
	278	* we have _very_ good reasons not to repeat
	279	* this mistake in 2.3, but we have no choice
	280	* now. _It_ _is_ _explicit_ _deliberate_
	281	* _race_ _condition_.
	282	*
	283	* Commented and originally written by Alexey.
	284	*/
	285	static inline void dst_ifdown(struct dst_entry dst, struct net_device dev,
	286	int unregister)
	287	{
	288	if (dst->ops->ifdown)
	289	dst->ops->ifdown(dst, dev, unregister);
	290
	291	if (dev != dst->dev)
	292	return;
	293
	294	if (!unregister) {
c4b1010f	295	dst->input = dst->output = dst_discard;
1da177e4	296	} else {
c346dca1	297	dst->dev = dev_net(dst->dev)->loopback_dev;
de3cb747	298	dev_hold(dst->dev);
1da177e4 LT	299	dev_put(dev);
1da177e4 LT	300	if (dst->neighbour && dst->neighbour->dev == dev) {
5a3e55d6	301	dst->neighbour->dev = dst->dev;
64b7d961	302	dev_hold(dst->dev);
1da177e4	303	dev_put(dev);
1da177e4 LT	304	}
	305	}
	306	}
	307
	308	static int dst_dev_event(struct notifier_block this, unsigned long event, void ptr)
	309	{
	310	struct net_device *dev = ptr;
86bba269	311	struct dst_entry dst, last = NULL;
1da177e4 LT	312
	313	switch (event) {
	314	case NETDEV_UNREGISTER:
	315	case NETDEV_DOWN:
86bba269 ED	316	mutex_lock(&dst_gc_mutex);
	317	for (dst = dst_busy_list; dst; dst = dst->next) {
	318	last = dst;
	319	dst_ifdown(dst, dev, event != NETDEV_DOWN);
	320	}
	321
	322	spin_lock_bh(&dst_garbage.lock);
	323	dst = dst_garbage.list;
	324	dst_garbage.list = NULL;
	325	spin_unlock_bh(&dst_garbage.lock);
	326
	327	if (last)
	328	last->next = dst;
	329	else
	330	dst_busy_list = dst;
	331	for (; dst; dst = dst->next) {
1da177e4 LT	332	dst_ifdown(dst, dev, event != NETDEV_DOWN);
1da177e4 LT	333	}
86bba269	334	mutex_unlock(&dst_gc_mutex);
1da177e4 LT	335	break;
	336	}
	337	return NOTIFY_DONE;
	338	}
	339
	340	static struct notifier_block dst_dev_notifier = {
	341	.notifier_call = dst_dev_event,
	342	};
	343
	344	void __init dst_init(void)
	345	{
	346	register_netdevice_notifier(&dst_dev_notifier);
	347	}
	348
	349	EXPORT_SYMBOL(__dst_free);
	350	EXPORT_SYMBOL(dst_alloc);
	351	EXPORT_SYMBOL(dst_destroy);