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 dst_gc_timer.expires = jiffies + dst_gc_timer_expires; 99 #if RT_CACHE_DEBUG >= 2 100 printk("dst_total: %d/%d %ld\n", 101 atomic_read(&dst_total), delayed, dst_gc_timer_expires); 102 #endif 103 add_timer(&dst_gc_timer); 104 105 out: 106 spin_unlock(&dst_lock); 107 } 108 109 static int dst_discard_in(struct sk_buff *skb) 110 { 111 kfree_skb(skb); 112 return 0; 113 } 114 115 static int dst_discard_out(struct sk_buff *skb) 116 { 117 kfree_skb(skb); 118 return 0; 119 } 120 121 void * dst_alloc(struct dst_ops * ops) 122 { 123 struct dst_entry * dst; 124 125 if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) { 126 if (ops->gc()) 127 return NULL; 128 } 129 dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC); 130 if (!dst) 131 return NULL; 132 memset(dst, 0, ops->entry_size); 133 atomic_set(&dst->__refcnt, 0); 134 dst->ops = ops; 135 dst->lastuse = jiffies; 136 dst->path = dst; 137 dst->input = dst_discard_in; 138 dst->output = dst_discard_out; 139 #if RT_CACHE_DEBUG >= 2 140 atomic_inc(&dst_total); 141 #endif 142 atomic_inc(&ops->entries); 143 return dst; 144 } 145 146 static void ___dst_free(struct dst_entry * dst) 147 { 148 /* The first case (dev==NULL) is required, when 149 protocol module is unloaded. 150 */ 151 if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) { 152 dst->input = dst_discard_in; 153 dst->output = dst_discard_out; 154 } 155 dst->obsolete = 2; 156 } 157 158 void __dst_free(struct dst_entry * dst) 159 { 160 spin_lock_bh(&dst_lock); 161 ___dst_free(dst); 162 dst->next = dst_garbage_list; 163 dst_garbage_list = dst; 164 if (dst_gc_timer_inc > DST_GC_INC) { 165 dst_gc_timer_inc = DST_GC_INC; 166 dst_gc_timer_expires = DST_GC_MIN; 167 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); 168 } 169 spin_unlock_bh(&dst_lock); 170 } 171 172 struct dst_entry *dst_destroy(struct dst_entry * dst) 173 { 174 struct dst_entry *child; 175 struct neighbour *neigh; 176 struct hh_cache *hh; 177 178 smp_rmb(); 179 180 again: 181 neigh = dst->neighbour; 182 hh = dst->hh; 183 child = dst->child; 184 185 dst->hh = NULL; 186 if (hh && atomic_dec_and_test(&hh->hh_refcnt)) 187 kfree(hh); 188 189 if (neigh) { 190 dst->neighbour = NULL; 191 neigh_release(neigh); 192 } 193 194 atomic_dec(&dst->ops->entries); 195 196 if (dst->ops->destroy) 197 dst->ops->destroy(dst); 198 if (dst->dev) 199 dev_put(dst->dev); 200 #if RT_CACHE_DEBUG >= 2 201 atomic_dec(&dst_total); 202 #endif 203 kmem_cache_free(dst->ops->kmem_cachep, dst); 204 205 dst = child; 206 if (dst) { 207 int nohash = dst->flags & DST_NOHASH; 208 209 if (atomic_dec_and_test(&dst->__refcnt)) { 210 /* We were real parent of this dst, so kill child. */ 211 if (nohash) 212 goto again; 213 } else { 214 /* Child is still referenced, return it for freeing. */ 215 if (nohash) 216 return dst; 217 /* Child is still in his hash table */ 218 } 219 } 220 return NULL; 221 } 222 223 /* Dirty hack. We did it in 2.2 (in __dst_free), 224 * we have _very_ good reasons not to repeat 225 * this mistake in 2.3, but we have no choice 226 * now. _It_ _is_ _explicit_ _deliberate_ 227 * _race_ _condition_. 228 * 229 * Commented and originally written by Alexey. 230 */ 231 static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, 232 int unregister) 233 { 234 if (dst->ops->ifdown) 235 dst->ops->ifdown(dst, dev, unregister); 236 237 if (dev != dst->dev) 238 return; 239 240 if (!unregister) { 241 dst->input = dst_discard_in; 242 dst->output = dst_discard_out; 243 } else { 244 dst->dev = &loopback_dev; 245 dev_hold(&loopback_dev); 246 dev_put(dev); 247 if (dst->neighbour && dst->neighbour->dev == dev) { 248 dst->neighbour->dev = &loopback_dev; 249 dev_put(dev); 250 dev_hold(&loopback_dev); 251 } 252 } 253 } 254 255 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr) 256 { 257 struct net_device *dev = ptr; 258 struct dst_entry *dst; 259 260 switch (event) { 261 case NETDEV_UNREGISTER: 262 case NETDEV_DOWN: 263 spin_lock_bh(&dst_lock); 264 for (dst = dst_garbage_list; dst; dst = dst->next) { 265 dst_ifdown(dst, dev, event != NETDEV_DOWN); 266 } 267 spin_unlock_bh(&dst_lock); 268 break; 269 } 270 return NOTIFY_DONE; 271 } 272 273 static struct notifier_block dst_dev_notifier = { 274 .notifier_call = dst_dev_event, 275 }; 276 277 void __init dst_init(void) 278 { 279 register_netdevice_notifier(&dst_dev_notifier); 280 } 281 282 EXPORT_SYMBOL(__dst_free); 283 EXPORT_SYMBOL(dst_alloc); 284 EXPORT_SYMBOL(dst_destroy); 285