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 DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0); 43 44 static void dst_run_gc(unsigned long dummy) 45 { 46 int delayed = 0; 47 int work_performed; 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 del_timer(&dst_gc_timer); 56 dstp = &dst_garbage_list; 57 work_performed = 0; 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 work_performed = 1; 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 } 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 } 98 #if RT_CACHE_DEBUG >= 2 99 printk("dst_total: %d/%d %ld\n", 100 atomic_read(&dst_total), delayed, dst_gc_timer_expires); 101 #endif 102 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); 103 104 out: 105 spin_unlock(&dst_lock); 106 } 107 108 static int dst_discard_in(struct sk_buff *skb) 109 { 110 kfree_skb(skb); 111 return 0; 112 } 113 114 static int dst_discard_out(struct sk_buff *skb) 115 { 116 kfree_skb(skb); 117 return 0; 118 } 119 120 void * dst_alloc(struct dst_ops * ops) 121 { 122 struct dst_entry * dst; 123 124 if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) { 125 if (ops->gc()) 126 return NULL; 127 } 128 dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC); 129 if (!dst) 130 return NULL; 131 memset(dst, 0, ops->entry_size); 132 atomic_set(&dst->__refcnt, 0); 133 dst->ops = ops; 134 dst->lastuse = jiffies; 135 dst->path = dst; 136 dst->input = dst_discard_in; 137 dst->output = dst_discard_out; 138 #if RT_CACHE_DEBUG >= 2 139 atomic_inc(&dst_total); 140 #endif 141 atomic_inc(&ops->entries); 142 return dst; 143 } 144 145 static void ___dst_free(struct dst_entry * dst) 146 { 147 /* The first case (dev==NULL) is required, when 148 protocol module is unloaded. 149 */ 150 if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) { 151 dst->input = dst_discard_in; 152 dst->output = dst_discard_out; 153 } 154 dst->obsolete = 2; 155 } 156 157 void __dst_free(struct dst_entry * dst) 158 { 159 spin_lock_bh(&dst_lock); 160 ___dst_free(dst); 161 dst->next = dst_garbage_list; 162 dst_garbage_list = dst; 163 if (dst_gc_timer_inc > DST_GC_INC) { 164 dst_gc_timer_inc = DST_GC_INC; 165 dst_gc_timer_expires = DST_GC_MIN; 166 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); 167 } 168 spin_unlock_bh(&dst_lock); 169 } 170 171 struct dst_entry *dst_destroy(struct dst_entry * dst) 172 { 173 struct dst_entry *child; 174 struct neighbour *neigh; 175 struct hh_cache *hh; 176 177 smp_rmb(); 178 179 again: 180 neigh = dst->neighbour; 181 hh = dst->hh; 182 child = dst->child; 183 184 dst->hh = NULL; 185 if (hh && atomic_dec_and_test(&hh->hh_refcnt)) 186 kfree(hh); 187 188 if (neigh) { 189 dst->neighbour = NULL; 190 neigh_release(neigh); 191 } 192 193 atomic_dec(&dst->ops->entries); 194 195 if (dst->ops->destroy) 196 dst->ops->destroy(dst); 197 if (dst->dev) 198 dev_put(dst->dev); 199 #if RT_CACHE_DEBUG >= 2 200 atomic_dec(&dst_total); 201 #endif 202 kmem_cache_free(dst->ops->kmem_cachep, dst); 203 204 dst = child; 205 if (dst) { 206 int nohash = dst->flags & DST_NOHASH; 207 208 if (atomic_dec_and_test(&dst->__refcnt)) { 209 /* We were real parent of this dst, so kill child. */ 210 if (nohash) 211 goto again; 212 } else { 213 /* Child is still referenced, return it for freeing. */ 214 if (nohash) 215 return dst; 216 /* Child is still in his hash table */ 217 } 218 } 219 return NULL; 220 } 221 222 /* Dirty hack. We did it in 2.2 (in __dst_free), 223 * we have _very_ good reasons not to repeat 224 * this mistake in 2.3, but we have no choice 225 * now. _It_ _is_ _explicit_ _deliberate_ 226 * _race_ _condition_. 227 * 228 * Commented and originally written by Alexey. 229 */ 230 static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, 231 int unregister) 232 { 233 if (dst->ops->ifdown) 234 dst->ops->ifdown(dst, dev, unregister); 235 236 if (dev != dst->dev) 237 return; 238 239 if (!unregister) { 240 dst->input = dst_discard_in; 241 dst->output = dst_discard_out; 242 } else { 243 dst->dev = &loopback_dev; 244 dev_hold(&loopback_dev); 245 dev_put(dev); 246 if (dst->neighbour && dst->neighbour->dev == dev) { 247 dst->neighbour->dev = &loopback_dev; 248 dev_put(dev); 249 dev_hold(&loopback_dev); 250 } 251 } 252 } 253 254 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr) 255 { 256 struct net_device *dev = ptr; 257 struct dst_entry *dst; 258 259 switch (event) { 260 case NETDEV_UNREGISTER: 261 case NETDEV_DOWN: 262 spin_lock_bh(&dst_lock); 263 for (dst = dst_garbage_list; dst; dst = dst->next) { 264 dst_ifdown(dst, dev, event != NETDEV_DOWN); 265 } 266 spin_unlock_bh(&dst_lock); 267 break; 268 } 269 return NOTIFY_DONE; 270 } 271 272 static struct notifier_block dst_dev_notifier = { 273 .notifier_call = dst_dev_event, 274 }; 275 276 void __init dst_init(void) 277 { 278 register_netdevice_notifier(&dst_dev_notifier); 279 } 280 281 EXPORT_SYMBOL(__dst_free); 282 EXPORT_SYMBOL(dst_alloc); 283 EXPORT_SYMBOL(dst_destroy); 284