286 lines
6.3 KiB
C
286 lines
6.3 KiB
C
/*
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* net/core/dst.c Protocol independent destination cache.
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*
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* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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*
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*/
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#include <linux/bitops.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/netdevice.h>
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#include <linux/sched.h>
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#include <linux/skbuff.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <net/dst.h>
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/* Locking strategy:
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* 1) Garbage collection state of dead destination cache
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* entries is protected by dst_lock.
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* 2) GC is run only from BH context, and is the only remover
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* of entries.
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* 3) Entries are added to the garbage list from both BH
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* and non-BH context, so local BH disabling is needed.
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* 4) All operations modify state, so a spinlock is used.
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*/
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static struct dst_entry *dst_garbage_list;
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#if RT_CACHE_DEBUG >= 2
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static atomic_t dst_total = ATOMIC_INIT(0);
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#endif
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static DEFINE_SPINLOCK(dst_lock);
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static unsigned long dst_gc_timer_expires;
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static unsigned long dst_gc_timer_inc = DST_GC_MAX;
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static void dst_run_gc(unsigned long);
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static void ___dst_free(struct dst_entry * dst);
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static struct timer_list dst_gc_timer =
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TIMER_INITIALIZER(dst_run_gc, DST_GC_MIN, 0);
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static void dst_run_gc(unsigned long dummy)
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{
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int delayed = 0;
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int work_performed;
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struct dst_entry * dst, **dstp;
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if (!spin_trylock(&dst_lock)) {
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mod_timer(&dst_gc_timer, jiffies + HZ/10);
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return;
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}
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del_timer(&dst_gc_timer);
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dstp = &dst_garbage_list;
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work_performed = 0;
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while ((dst = *dstp) != NULL) {
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if (atomic_read(&dst->__refcnt)) {
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dstp = &dst->next;
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delayed++;
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continue;
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}
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*dstp = dst->next;
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work_performed = 1;
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dst = dst_destroy(dst);
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if (dst) {
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/* NOHASH and still referenced. Unless it is already
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* on gc list, invalidate it and add to gc list.
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*
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* Note: this is temporary. Actually, NOHASH dst's
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* must be obsoleted when parent is obsoleted.
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* But we do not have state "obsoleted, but
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* referenced by parent", so it is right.
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*/
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if (dst->obsolete > 1)
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continue;
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___dst_free(dst);
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dst->next = *dstp;
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*dstp = dst;
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dstp = &dst->next;
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}
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}
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if (!dst_garbage_list) {
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dst_gc_timer_inc = DST_GC_MAX;
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goto out;
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}
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if (!work_performed) {
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if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
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dst_gc_timer_expires = DST_GC_MAX;
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dst_gc_timer_inc += DST_GC_INC;
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} else {
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dst_gc_timer_inc = DST_GC_INC;
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dst_gc_timer_expires = DST_GC_MIN;
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}
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dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
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#if RT_CACHE_DEBUG >= 2
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printk("dst_total: %d/%d %ld\n",
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atomic_read(&dst_total), delayed, dst_gc_timer_expires);
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#endif
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add_timer(&dst_gc_timer);
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out:
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spin_unlock(&dst_lock);
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}
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static int dst_discard_in(struct sk_buff *skb)
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{
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kfree_skb(skb);
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return 0;
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}
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static int dst_discard_out(struct sk_buff *skb)
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{
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kfree_skb(skb);
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return 0;
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}
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void * dst_alloc(struct dst_ops * ops)
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{
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struct dst_entry * dst;
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if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
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if (ops->gc())
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return NULL;
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}
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dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC);
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if (!dst)
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return NULL;
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memset(dst, 0, ops->entry_size);
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atomic_set(&dst->__refcnt, 0);
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dst->ops = ops;
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dst->lastuse = jiffies;
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dst->path = dst;
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dst->input = dst_discard_in;
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dst->output = dst_discard_out;
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#if RT_CACHE_DEBUG >= 2
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atomic_inc(&dst_total);
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#endif
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atomic_inc(&ops->entries);
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return dst;
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}
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static void ___dst_free(struct dst_entry * dst)
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{
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/* The first case (dev==NULL) is required, when
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protocol module is unloaded.
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*/
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if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
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dst->input = dst_discard_in;
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dst->output = dst_discard_out;
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}
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dst->obsolete = 2;
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}
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void __dst_free(struct dst_entry * dst)
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{
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spin_lock_bh(&dst_lock);
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___dst_free(dst);
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dst->next = dst_garbage_list;
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dst_garbage_list = dst;
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if (dst_gc_timer_inc > DST_GC_INC) {
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dst_gc_timer_inc = DST_GC_INC;
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dst_gc_timer_expires = DST_GC_MIN;
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mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
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}
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spin_unlock_bh(&dst_lock);
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}
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struct dst_entry *dst_destroy(struct dst_entry * dst)
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{
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struct dst_entry *child;
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struct neighbour *neigh;
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struct hh_cache *hh;
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smp_rmb();
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again:
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neigh = dst->neighbour;
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hh = dst->hh;
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child = dst->child;
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dst->hh = NULL;
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if (hh && atomic_dec_and_test(&hh->hh_refcnt))
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kfree(hh);
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if (neigh) {
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dst->neighbour = NULL;
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neigh_release(neigh);
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}
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atomic_dec(&dst->ops->entries);
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if (dst->ops->destroy)
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dst->ops->destroy(dst);
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if (dst->dev)
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dev_put(dst->dev);
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#if RT_CACHE_DEBUG >= 2
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atomic_dec(&dst_total);
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#endif
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kmem_cache_free(dst->ops->kmem_cachep, dst);
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dst = child;
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if (dst) {
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int nohash = dst->flags & DST_NOHASH;
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if (atomic_dec_and_test(&dst->__refcnt)) {
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/* We were real parent of this dst, so kill child. */
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if (nohash)
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goto again;
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} else {
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/* Child is still referenced, return it for freeing. */
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if (nohash)
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return dst;
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/* Child is still in his hash table */
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}
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}
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return NULL;
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}
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/* Dirty hack. We did it in 2.2 (in __dst_free),
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* we have _very_ good reasons not to repeat
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* this mistake in 2.3, but we have no choice
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* now. _It_ _is_ _explicit_ _deliberate_
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* _race_ _condition_.
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*
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* Commented and originally written by Alexey.
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*/
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static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev,
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int unregister)
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{
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if (dst->ops->ifdown)
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dst->ops->ifdown(dst, dev, unregister);
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if (dev != dst->dev)
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return;
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if (!unregister) {
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dst->input = dst_discard_in;
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dst->output = dst_discard_out;
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} else {
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dst->dev = &loopback_dev;
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dev_hold(&loopback_dev);
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dev_put(dev);
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if (dst->neighbour && dst->neighbour->dev == dev) {
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dst->neighbour->dev = &loopback_dev;
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dev_put(dev);
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dev_hold(&loopback_dev);
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}
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}
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}
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static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
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{
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struct net_device *dev = ptr;
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struct dst_entry *dst;
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switch (event) {
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case NETDEV_UNREGISTER:
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case NETDEV_DOWN:
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spin_lock_bh(&dst_lock);
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for (dst = dst_garbage_list; dst; dst = dst->next) {
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dst_ifdown(dst, dev, event != NETDEV_DOWN);
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}
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spin_unlock_bh(&dst_lock);
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break;
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}
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return NOTIFY_DONE;
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}
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static struct notifier_block dst_dev_notifier = {
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.notifier_call = dst_dev_event,
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};
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void __init dst_init(void)
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{
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register_netdevice_notifier(&dst_dev_notifier);
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}
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EXPORT_SYMBOL(__dst_free);
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EXPORT_SYMBOL(dst_alloc);
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EXPORT_SYMBOL(dst_destroy);
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