/* * 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/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 /* if the next desired timer is more than 4 seconds in the future * then round the timer to whole seconds */ if (dst_gc_timer_expires > 4*HZ) mod_timer(&dst_gc_timer, round_jiffies(jiffies + dst_gc_timer_expires)); else mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); out: spin_unlock(&dst_lock); } static int dst_discard(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_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_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->output = dst_discard; } 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);