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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> | |
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 struct timer_list dst_gc_timer = | |
43 | TIMER_INITIALIZER(dst_run_gc, DST_GC_MIN, 0); | |
44 | ||
45 | static void dst_run_gc(unsigned long dummy) | |
46 | { | |
47 | int delayed = 0; | |
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 | ||
56 | del_timer(&dst_gc_timer); | |
57 | dstp = &dst_garbage_list; | |
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 | ||
66 | dst = dst_destroy(dst); | |
67 | if (dst) { | |
68 | /* NOHASH and still referenced. Unless it is already | |
69 | * on gc list, invalidate it and add to gc list. | |
70 | * | |
71 | * Note: this is temporary. Actually, NOHASH dst's | |
72 | * must be obsoleted when parent is obsoleted. | |
73 | * But we do not have state "obsoleted, but | |
74 | * referenced by parent", so it is right. | |
75 | */ | |
76 | if (dst->obsolete > 1) | |
77 | continue; | |
78 | ||
79 | ___dst_free(dst); | |
80 | dst->next = *dstp; | |
81 | *dstp = dst; | |
82 | dstp = &dst->next; | |
83 | } | |
84 | } | |
85 | if (!dst_garbage_list) { | |
86 | dst_gc_timer_inc = DST_GC_MAX; | |
87 | goto out; | |
88 | } | |
89 | if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX) | |
90 | dst_gc_timer_expires = DST_GC_MAX; | |
91 | dst_gc_timer_inc += DST_GC_INC; | |
92 | dst_gc_timer.expires = jiffies + dst_gc_timer_expires; | |
93 | #if RT_CACHE_DEBUG >= 2 | |
94 | printk("dst_total: %d/%d %ld\n", | |
95 | atomic_read(&dst_total), delayed, dst_gc_timer_expires); | |
96 | #endif | |
97 | add_timer(&dst_gc_timer); | |
98 | ||
99 | out: | |
100 | spin_unlock(&dst_lock); | |
101 | } | |
102 | ||
103 | static int dst_discard_in(struct sk_buff *skb) | |
104 | { | |
105 | kfree_skb(skb); | |
106 | return 0; | |
107 | } | |
108 | ||
109 | static int dst_discard_out(struct sk_buff *skb) | |
110 | { | |
111 | kfree_skb(skb); | |
112 | return 0; | |
113 | } | |
114 | ||
115 | void * dst_alloc(struct dst_ops * ops) | |
116 | { | |
117 | struct dst_entry * dst; | |
118 | ||
119 | if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) { | |
120 | if (ops->gc()) | |
121 | return NULL; | |
122 | } | |
123 | dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC); | |
124 | if (!dst) | |
125 | return NULL; | |
126 | memset(dst, 0, ops->entry_size); | |
127 | atomic_set(&dst->__refcnt, 0); | |
128 | dst->ops = ops; | |
129 | dst->lastuse = jiffies; | |
130 | dst->path = dst; | |
131 | dst->input = dst_discard_in; | |
132 | dst->output = dst_discard_out; | |
133 | #if RT_CACHE_DEBUG >= 2 | |
134 | atomic_inc(&dst_total); | |
135 | #endif | |
136 | atomic_inc(&ops->entries); | |
137 | return dst; | |
138 | } | |
139 | ||
140 | static void ___dst_free(struct dst_entry * dst) | |
141 | { | |
142 | /* The first case (dev==NULL) is required, when | |
143 | protocol module is unloaded. | |
144 | */ | |
145 | if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) { | |
146 | dst->input = dst_discard_in; | |
147 | dst->output = dst_discard_out; | |
148 | } | |
149 | dst->obsolete = 2; | |
150 | } | |
151 | ||
152 | void __dst_free(struct dst_entry * dst) | |
153 | { | |
154 | spin_lock_bh(&dst_lock); | |
155 | ___dst_free(dst); | |
156 | dst->next = dst_garbage_list; | |
157 | dst_garbage_list = dst; | |
158 | if (dst_gc_timer_inc > DST_GC_INC) { | |
159 | dst_gc_timer_inc = DST_GC_INC; | |
160 | dst_gc_timer_expires = DST_GC_MIN; | |
161 | mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires); | |
162 | } | |
163 | spin_unlock_bh(&dst_lock); | |
164 | } | |
165 | ||
166 | struct dst_entry *dst_destroy(struct dst_entry * dst) | |
167 | { | |
168 | struct dst_entry *child; | |
169 | struct neighbour *neigh; | |
170 | struct hh_cache *hh; | |
171 | ||
172 | smp_rmb(); | |
173 | ||
174 | again: | |
175 | neigh = dst->neighbour; | |
176 | hh = dst->hh; | |
177 | child = dst->child; | |
178 | ||
179 | dst->hh = NULL; | |
180 | if (hh && atomic_dec_and_test(&hh->hh_refcnt)) | |
181 | kfree(hh); | |
182 | ||
183 | if (neigh) { | |
184 | dst->neighbour = NULL; | |
185 | neigh_release(neigh); | |
186 | } | |
187 | ||
188 | atomic_dec(&dst->ops->entries); | |
189 | ||
190 | if (dst->ops->destroy) | |
191 | dst->ops->destroy(dst); | |
192 | if (dst->dev) | |
193 | dev_put(dst->dev); | |
194 | #if RT_CACHE_DEBUG >= 2 | |
195 | atomic_dec(&dst_total); | |
196 | #endif | |
197 | kmem_cache_free(dst->ops->kmem_cachep, dst); | |
198 | ||
199 | dst = child; | |
200 | if (dst) { | |
201 | if (atomic_dec_and_test(&dst->__refcnt)) { | |
202 | /* We were real parent of this dst, so kill child. */ | |
203 | if (dst->flags&DST_NOHASH) | |
204 | goto again; | |
205 | } else { | |
206 | /* Child is still referenced, return it for freeing. */ | |
207 | if (dst->flags&DST_NOHASH) | |
208 | return dst; | |
209 | /* Child is still in his hash table */ | |
210 | } | |
211 | } | |
212 | return NULL; | |
213 | } | |
214 | ||
215 | /* Dirty hack. We did it in 2.2 (in __dst_free), | |
216 | * we have _very_ good reasons not to repeat | |
217 | * this mistake in 2.3, but we have no choice | |
218 | * now. _It_ _is_ _explicit_ _deliberate_ | |
219 | * _race_ _condition_. | |
220 | * | |
221 | * Commented and originally written by Alexey. | |
222 | */ | |
223 | static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev, | |
224 | int unregister) | |
225 | { | |
226 | if (dst->ops->ifdown) | |
227 | dst->ops->ifdown(dst, dev, unregister); | |
228 | ||
229 | if (dev != dst->dev) | |
230 | return; | |
231 | ||
232 | if (!unregister) { | |
233 | dst->input = dst_discard_in; | |
234 | dst->output = dst_discard_out; | |
235 | } else { | |
236 | dst->dev = &loopback_dev; | |
237 | dev_hold(&loopback_dev); | |
238 | dev_put(dev); | |
239 | if (dst->neighbour && dst->neighbour->dev == dev) { | |
240 | dst->neighbour->dev = &loopback_dev; | |
241 | dev_put(dev); | |
242 | dev_hold(&loopback_dev); | |
243 | } | |
244 | } | |
245 | } | |
246 | ||
247 | static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr) | |
248 | { | |
249 | struct net_device *dev = ptr; | |
250 | struct dst_entry *dst; | |
251 | ||
252 | switch (event) { | |
253 | case NETDEV_UNREGISTER: | |
254 | case NETDEV_DOWN: | |
255 | spin_lock_bh(&dst_lock); | |
256 | for (dst = dst_garbage_list; dst; dst = dst->next) { | |
257 | dst_ifdown(dst, dev, event != NETDEV_DOWN); | |
258 | } | |
259 | spin_unlock_bh(&dst_lock); | |
260 | break; | |
261 | } | |
262 | return NOTIFY_DONE; | |
263 | } | |
264 | ||
265 | static struct notifier_block dst_dev_notifier = { | |
266 | .notifier_call = dst_dev_event, | |
267 | }; | |
268 | ||
269 | void __init dst_init(void) | |
270 | { | |
271 | register_netdevice_notifier(&dst_dev_notifier); | |
272 | } | |
273 | ||
274 | EXPORT_SYMBOL(__dst_free); | |
275 | EXPORT_SYMBOL(dst_alloc); | |
276 | EXPORT_SYMBOL(dst_destroy); |