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Linux/net/core/flow.c

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  1 /* flow.c: Generic flow cache.
  2  *
  3  * Copyright (C) 2003 Alexey N. Kuznetsov (kuznet@ms2.inr.ac.ru)
  4  * Copyright (C) 2003 David S. Miller (davem@redhat.com)
  5  */
  6 
  7 #include <linux/kernel.h>
  8 #include <linux/module.h>
  9 #include <linux/list.h>
 10 #include <linux/jhash.h>
 11 #include <linux/interrupt.h>
 12 #include <linux/mm.h>
 13 #include <linux/random.h>
 14 #include <linux/init.h>
 15 #include <linux/slab.h>
 16 #include <linux/smp.h>
 17 #include <linux/completion.h>
 18 #include <linux/percpu.h>
 19 #include <linux/bitops.h>
 20 #include <linux/notifier.h>
 21 #include <linux/cpu.h>
 22 #include <linux/cpumask.h>
 23 #include <linux/mutex.h>
 24 #include <net/flow.h>
 25 #include <linux/atomic.h>
 26 #include <linux/security.h>
 27 
 28 struct flow_cache_entry {
 29         union {
 30                 struct hlist_node       hlist;
 31                 struct list_head        gc_list;
 32         } u;
 33         struct net                      *net;
 34         u16                             family;
 35         u8                              dir;
 36         u32                             genid;
 37         struct flowi                    key;
 38         struct flow_cache_object        *object;
 39 };
 40 
 41 struct flow_cache_percpu {
 42         struct hlist_head               *hash_table;
 43         int                             hash_count;
 44         u32                             hash_rnd;
 45         int                             hash_rnd_recalc;
 46         struct tasklet_struct           flush_tasklet;
 47 };
 48 
 49 struct flow_flush_info {
 50         struct flow_cache               *cache;
 51         atomic_t                        cpuleft;
 52         struct completion               completion;
 53 };
 54 
 55 struct flow_cache {
 56         u32                             hash_shift;
 57         struct flow_cache_percpu __percpu *percpu;
 58         struct notifier_block           hotcpu_notifier;
 59         int                             low_watermark;
 60         int                             high_watermark;
 61         struct timer_list               rnd_timer;
 62 };
 63 
 64 atomic_t flow_cache_genid = ATOMIC_INIT(0);
 65 EXPORT_SYMBOL(flow_cache_genid);
 66 static struct flow_cache flow_cache_global;
 67 static struct kmem_cache *flow_cachep __read_mostly;
 68 
 69 static DEFINE_SPINLOCK(flow_cache_gc_lock);
 70 static LIST_HEAD(flow_cache_gc_list);
 71 
 72 #define flow_cache_hash_size(cache)     (1 << (cache)->hash_shift)
 73 #define FLOW_HASH_RND_PERIOD            (10 * 60 * HZ)
 74 
 75 static void flow_cache_new_hashrnd(unsigned long arg)
 76 {
 77         struct flow_cache *fc = (void *) arg;
 78         int i;
 79 
 80         for_each_possible_cpu(i)
 81                 per_cpu_ptr(fc->percpu, i)->hash_rnd_recalc = 1;
 82 
 83         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 84         add_timer(&fc->rnd_timer);
 85 }
 86 
 87 static int flow_entry_valid(struct flow_cache_entry *fle)
 88 {
 89         if (atomic_read(&flow_cache_genid) != fle->genid)
 90                 return 0;
 91         if (fle->object && !fle->object->ops->check(fle->object))
 92                 return 0;
 93         return 1;
 94 }
 95 
 96 static void flow_entry_kill(struct flow_cache_entry *fle)
 97 {
 98         if (fle->object)
 99                 fle->object->ops->delete(fle->object);
100         kmem_cache_free(flow_cachep, fle);
101 }
102 
103 static void flow_cache_gc_task(struct work_struct *work)
104 {
105         struct list_head gc_list;
106         struct flow_cache_entry *fce, *n;
107 
108         INIT_LIST_HEAD(&gc_list);
109         spin_lock_bh(&flow_cache_gc_lock);
110         list_splice_tail_init(&flow_cache_gc_list, &gc_list);
111         spin_unlock_bh(&flow_cache_gc_lock);
112 
113         list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
114                 flow_entry_kill(fce);
115 }
116 static DECLARE_WORK(flow_cache_gc_work, flow_cache_gc_task);
117 
118 static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
119                                      int deleted, struct list_head *gc_list)
120 {
121         if (deleted) {
122                 fcp->hash_count -= deleted;
123                 spin_lock_bh(&flow_cache_gc_lock);
124                 list_splice_tail(gc_list, &flow_cache_gc_list);
125                 spin_unlock_bh(&flow_cache_gc_lock);
126                 schedule_work(&flow_cache_gc_work);
127         }
128 }
129 
130 static void __flow_cache_shrink(struct flow_cache *fc,
131                                 struct flow_cache_percpu *fcp,
132                                 int shrink_to)
133 {
134         struct flow_cache_entry *fle;
135         struct hlist_node *tmp;
136         LIST_HEAD(gc_list);
137         int i, deleted = 0;
138 
139         for (i = 0; i < flow_cache_hash_size(fc); i++) {
140                 int saved = 0;
141 
142                 hlist_for_each_entry_safe(fle, tmp,
143                                           &fcp->hash_table[i], u.hlist) {
144                         if (saved < shrink_to &&
145                             flow_entry_valid(fle)) {
146                                 saved++;
147                         } else {
148                                 deleted++;
149                                 hlist_del(&fle->u.hlist);
150                                 list_add_tail(&fle->u.gc_list, &gc_list);
151                         }
152                 }
153         }
154 
155         flow_cache_queue_garbage(fcp, deleted, &gc_list);
156 }
157 
158 static void flow_cache_shrink(struct flow_cache *fc,
159                               struct flow_cache_percpu *fcp)
160 {
161         int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);
162 
163         __flow_cache_shrink(fc, fcp, shrink_to);
164 }
165 
166 static void flow_new_hash_rnd(struct flow_cache *fc,
167                               struct flow_cache_percpu *fcp)
168 {
169         get_random_bytes(&fcp->hash_rnd, sizeof(u32));
170         fcp->hash_rnd_recalc = 0;
171         __flow_cache_shrink(fc, fcp, 0);
172 }
173 
174 static u32 flow_hash_code(struct flow_cache *fc,
175                           struct flow_cache_percpu *fcp,
176                           const struct flowi *key,
177                           size_t keysize)
178 {
179         const u32 *k = (const u32 *) key;
180         const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);
181 
182         return jhash2(k, length, fcp->hash_rnd)
183                 & (flow_cache_hash_size(fc) - 1);
184 }
185 
186 /* I hear what you're saying, use memcmp.  But memcmp cannot make
187  * important assumptions that we can here, such as alignment.
188  */
189 static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
190                             size_t keysize)
191 {
192         const flow_compare_t *k1, *k1_lim, *k2;
193 
194         k1 = (const flow_compare_t *) key1;
195         k1_lim = k1 + keysize;
196 
197         k2 = (const flow_compare_t *) key2;
198 
199         do {
200                 if (*k1++ != *k2++)
201                         return 1;
202         } while (k1 < k1_lim);
203 
204         return 0;
205 }
206 
207 struct flow_cache_object *
208 flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
209                   flow_resolve_t resolver, void *ctx)
210 {
211         struct flow_cache *fc = &flow_cache_global;
212         struct flow_cache_percpu *fcp;
213         struct flow_cache_entry *fle, *tfle;
214         struct flow_cache_object *flo;
215         size_t keysize;
216         unsigned int hash;
217 
218         local_bh_disable();
219         fcp = this_cpu_ptr(fc->percpu);
220 
221         fle = NULL;
222         flo = NULL;
223 
224         keysize = flow_key_size(family);
225         if (!keysize)
226                 goto nocache;
227 
228         /* Packet really early in init?  Making flow_cache_init a
229          * pre-smp initcall would solve this.  --RR */
230         if (!fcp->hash_table)
231                 goto nocache;
232 
233         if (fcp->hash_rnd_recalc)
234                 flow_new_hash_rnd(fc, fcp);
235 
236         hash = flow_hash_code(fc, fcp, key, keysize);
237         hlist_for_each_entry(tfle, &fcp->hash_table[hash], u.hlist) {
238                 if (tfle->net == net &&
239                     tfle->family == family &&
240                     tfle->dir == dir &&
241                     flow_key_compare(key, &tfle->key, keysize) == 0) {
242                         fle = tfle;
243                         break;
244                 }
245         }
246 
247         if (unlikely(!fle)) {
248                 if (fcp->hash_count > fc->high_watermark)
249                         flow_cache_shrink(fc, fcp);
250 
251                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
252                 if (fle) {
253                         fle->net = net;
254                         fle->family = family;
255                         fle->dir = dir;
256                         memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
257                         fle->object = NULL;
258                         hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
259                         fcp->hash_count++;
260                 }
261         } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
262                 flo = fle->object;
263                 if (!flo)
264                         goto ret_object;
265                 flo = flo->ops->get(flo);
266                 if (flo)
267                         goto ret_object;
268         } else if (fle->object) {
269                 flo = fle->object;
270                 flo->ops->delete(flo);
271                 fle->object = NULL;
272         }
273 
274 nocache:
275         flo = NULL;
276         if (fle) {
277                 flo = fle->object;
278                 fle->object = NULL;
279         }
280         flo = resolver(net, key, family, dir, flo, ctx);
281         if (fle) {
282                 fle->genid = atomic_read(&flow_cache_genid);
283                 if (!IS_ERR(flo))
284                         fle->object = flo;
285                 else
286                         fle->genid--;
287         } else {
288                 if (!IS_ERR_OR_NULL(flo))
289                         flo->ops->delete(flo);
290         }
291 ret_object:
292         local_bh_enable();
293         return flo;
294 }
295 EXPORT_SYMBOL(flow_cache_lookup);
296 
297 static void flow_cache_flush_tasklet(unsigned long data)
298 {
299         struct flow_flush_info *info = (void *)data;
300         struct flow_cache *fc = info->cache;
301         struct flow_cache_percpu *fcp;
302         struct flow_cache_entry *fle;
303         struct hlist_node *tmp;
304         LIST_HEAD(gc_list);
305         int i, deleted = 0;
306 
307         fcp = this_cpu_ptr(fc->percpu);
308         for (i = 0; i < flow_cache_hash_size(fc); i++) {
309                 hlist_for_each_entry_safe(fle, tmp,
310                                           &fcp->hash_table[i], u.hlist) {
311                         if (flow_entry_valid(fle))
312                                 continue;
313 
314                         deleted++;
315                         hlist_del(&fle->u.hlist);
316                         list_add_tail(&fle->u.gc_list, &gc_list);
317                 }
318         }
319 
320         flow_cache_queue_garbage(fcp, deleted, &gc_list);
321 
322         if (atomic_dec_and_test(&info->cpuleft))
323                 complete(&info->completion);
324 }
325 
326 /*
327  * Return whether a cpu needs flushing.  Conservatively, we assume
328  * the presence of any entries means the core may require flushing,
329  * since the flow_cache_ops.check() function may assume it's running
330  * on the same core as the per-cpu cache component.
331  */
332 static int flow_cache_percpu_empty(struct flow_cache *fc, int cpu)
333 {
334         struct flow_cache_percpu *fcp;
335         int i;
336 
337         fcp = per_cpu_ptr(fc->percpu, cpu);
338         for (i = 0; i < flow_cache_hash_size(fc); i++)
339                 if (!hlist_empty(&fcp->hash_table[i]))
340                         return 0;
341         return 1;
342 }
343 
344 static void flow_cache_flush_per_cpu(void *data)
345 {
346         struct flow_flush_info *info = data;
347         struct tasklet_struct *tasklet;
348 
349         tasklet = &this_cpu_ptr(info->cache->percpu)->flush_tasklet;
350         tasklet->data = (unsigned long)info;
351         tasklet_schedule(tasklet);
352 }
353 
354 void flow_cache_flush(void)
355 {
356         struct flow_flush_info info;
357         static DEFINE_MUTEX(flow_flush_sem);
358         cpumask_var_t mask;
359         int i, self;
360 
361         /* Track which cpus need flushing to avoid disturbing all cores. */
362         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
363                 return;
364         cpumask_clear(mask);
365 
366         /* Don't want cpus going down or up during this. */
367         get_online_cpus();
368         mutex_lock(&flow_flush_sem);
369         info.cache = &flow_cache_global;
370         for_each_online_cpu(i)
371                 if (!flow_cache_percpu_empty(info.cache, i))
372                         cpumask_set_cpu(i, mask);
373         atomic_set(&info.cpuleft, cpumask_weight(mask));
374         if (atomic_read(&info.cpuleft) == 0)
375                 goto done;
376 
377         init_completion(&info.completion);
378 
379         local_bh_disable();
380         self = cpumask_test_and_clear_cpu(smp_processor_id(), mask);
381         on_each_cpu_mask(mask, flow_cache_flush_per_cpu, &info, 0);
382         if (self)
383                 flow_cache_flush_tasklet((unsigned long)&info);
384         local_bh_enable();
385 
386         wait_for_completion(&info.completion);
387 
388 done:
389         mutex_unlock(&flow_flush_sem);
390         put_online_cpus();
391         free_cpumask_var(mask);
392 }
393 
394 static void flow_cache_flush_task(struct work_struct *work)
395 {
396         flow_cache_flush();
397 }
398 
399 static DECLARE_WORK(flow_cache_flush_work, flow_cache_flush_task);
400 
401 void flow_cache_flush_deferred(void)
402 {
403         schedule_work(&flow_cache_flush_work);
404 }
405 
406 static int flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
407 {
408         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
409         size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);
410 
411         if (!fcp->hash_table) {
412                 fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
413                 if (!fcp->hash_table) {
414                         pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
415                         return -ENOMEM;
416                 }
417                 fcp->hash_rnd_recalc = 1;
418                 fcp->hash_count = 0;
419                 tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
420         }
421         return 0;
422 }
423 
424 static int flow_cache_cpu(struct notifier_block *nfb,
425                           unsigned long action,
426                           void *hcpu)
427 {
428         struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
429         int res, cpu = (unsigned long) hcpu;
430         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
431 
432         switch (action) {
433         case CPU_UP_PREPARE:
434         case CPU_UP_PREPARE_FROZEN:
435                 res = flow_cache_cpu_prepare(fc, cpu);
436                 if (res)
437                         return notifier_from_errno(res);
438                 break;
439         case CPU_DEAD:
440         case CPU_DEAD_FROZEN:
441                 __flow_cache_shrink(fc, fcp, 0);
442                 break;
443         }
444         return NOTIFY_OK;
445 }
446 
447 static int __init flow_cache_init(struct flow_cache *fc)
448 {
449         int i;
450 
451         fc->hash_shift = 10;
452         fc->low_watermark = 2 * flow_cache_hash_size(fc);
453         fc->high_watermark = 4 * flow_cache_hash_size(fc);
454 
455         fc->percpu = alloc_percpu(struct flow_cache_percpu);
456         if (!fc->percpu)
457                 return -ENOMEM;
458 
459         for_each_online_cpu(i) {
460                 if (flow_cache_cpu_prepare(fc, i))
461                         goto err;
462         }
463         fc->hotcpu_notifier = (struct notifier_block){
464                 .notifier_call = flow_cache_cpu,
465         };
466         register_hotcpu_notifier(&fc->hotcpu_notifier);
467 
468         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
469                     (unsigned long) fc);
470         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
471         add_timer(&fc->rnd_timer);
472 
473         return 0;
474 
475 err:
476         for_each_possible_cpu(i) {
477                 struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
478                 kfree(fcp->hash_table);
479                 fcp->hash_table = NULL;
480         }
481 
482         free_percpu(fc->percpu);
483         fc->percpu = NULL;
484 
485         return -ENOMEM;
486 }
487 
488 static int __init flow_cache_init_global(void)
489 {
490         flow_cachep = kmem_cache_create("flow_cache",
491                                         sizeof(struct flow_cache_entry),
492                                         0, SLAB_PANIC, NULL);
493 
494         return flow_cache_init(&flow_cache_global);
495 }
496 
497 module_init(flow_cache_init_global);
498 

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