net/core/flow.c

   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 <asm/atomic.h>
  26 #include <asm/semaphore.h>
  27 #include <linux/security.h>
  28
  29 struct flow_cache_entry {
  30         struct flow_cache_entry *next;
  31         u16                     family;
  32         u8                      dir;
  33         struct flowi            key;
  34         u32                     genid;
  35         void                    *object;
  36         atomic_t                *object_ref;
  37 };
  38
  39 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  40
  41 static u32 flow_hash_shift;
  42 #define flow_hash_size  (1 << flow_hash_shift)
  43 static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
  44
  45 #define flow_table(cpu) (per_cpu(flow_tables, cpu))
  46
  47 static kmem_cache_t *flow_cachep __read_mostly;
  48
  49 static int flow_lwm, flow_hwm;
  50
  51 struct flow_percpu_info {
  52         int hash_rnd_recalc;
  53         u32 hash_rnd;
  54         int count;
  55 } ____cacheline_aligned;
  56 static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
  57
  58 #define flow_hash_rnd_recalc(cpu) \
  59         (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
  60 #define flow_hash_rnd(cpu) \
  61         (per_cpu(flow_hash_info, cpu).hash_rnd)
  62 #define flow_count(cpu) \
  63         (per_cpu(flow_hash_info, cpu).count)
  64
  65 static struct timer_list flow_hash_rnd_timer;
  66
  67 #define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)
  68
  69 struct flow_flush_info {
  70         atomic_t cpuleft;
  71         struct completion completion;
  72 };
  73 static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
  74
  75 #define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
  76
  77 static void flow_cache_new_hashrnd(unsigned long arg)
  78 {
  79         int i;
  80
  81         for_each_possible_cpu(i)
  82                 flow_hash_rnd_recalc(i) = 1;
  83
  84         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  85         add_timer(&flow_hash_rnd_timer);
  86 }
  87
  88 static void __flow_cache_shrink(int cpu, int shrink_to)
  89 {
  90         struct flow_cache_entry *fle, **flp;
  91         int i;
  92
  93         for (i = 0; i < flow_hash_size; i++) {
  94                 int k = 0;
  95
  96                 flp = &flow_table(cpu)[i];
  97                 while ((fle = *flp) != NULL && k < shrink_to) {
  98                         k++;
  99                         flp = &fle->next;
 100                 }
 101                 while ((fle = *flp) != NULL) {
 102                         *flp = fle->next;
 103                         if (fle->object)
 104                                 atomic_dec(fle->object_ref);
 105                         kmem_cache_free(flow_cachep, fle);
 106                         flow_count(cpu)--;
 107                 }
 108         }
 109 }
 110
 111 static void flow_cache_shrink(int cpu)
 112 {
 113         int shrink_to = flow_lwm / flow_hash_size;
 114
 115         __flow_cache_shrink(cpu, shrink_to);
 116 }
 117
 118 static void flow_new_hash_rnd(int cpu)
 119 {
 120         get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
 121         flow_hash_rnd_recalc(cpu) = 0;
 122
 123         __flow_cache_shrink(cpu, 0);
 124 }
 125
 126 static u32 flow_hash_code(struct flowi *key, int cpu)
 127 {
 128         u32 *k = (u32 *) key;
 129
 130         return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
 131                 (flow_hash_size - 1));
 132 }
 133
 134 #if (BITS_PER_LONG == 64)
 135 typedef u64 flow_compare_t;
 136 #else
 137 typedef u32 flow_compare_t;
 138 #endif
 139
 140 extern void flowi_is_missized(void);
 141
 142 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 143  * important assumptions that we can here, such as alignment and
 144  * constant size.
 145  */
 146 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 147 {
 148         flow_compare_t *k1, *k1_lim, *k2;
 149         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 150
 151         if (sizeof(struct flowi) % sizeof(flow_compare_t))
 152                 flowi_is_missized();
 153
 154         k1 = (flow_compare_t *) key1;
 155         k1_lim = k1 + n_elem;
 156
 157         k2 = (flow_compare_t *) key2;
 158
 159         do {
 160                 if (*k1++ != *k2++)
 161                         return 1;
 162         } while (k1 < k1_lim);
 163
 164         return 0;
 165 }
 166
 167 void *flow_cache_lookup(struct flowi *key, u16 family, u8 dir,
 168                         flow_resolve_t resolver)
 169 {
 170         struct flow_cache_entry *fle, **head;
 171         unsigned int hash;
 172         int cpu;
 173
 174         local_bh_disable();
 175         cpu = smp_processor_id();
 176
 177         fle = NULL;
 178         /* Packet really early in init?  Making flow_cache_init a
 179          * pre-smp initcall would solve this.  --RR */
 180         if (!flow_table(cpu))
 181                 goto nocache;
 182
 183         if (flow_hash_rnd_recalc(cpu))
 184                 flow_new_hash_rnd(cpu);
 185         hash = flow_hash_code(key, cpu);
 186
 187         head = &flow_table(cpu)[hash];
 188         for (fle = *head; fle; fle = fle->next) {
 189                 if (fle->family == family &&
 190                     fle->dir == dir &&
 191                     flow_key_compare(key, &fle->key) == 0) {
 192                         if (fle->genid == atomic_read(&flow_cache_genid)) {
 193                                 void *ret = fle->object;
 194
 195                                 if (ret)
 196                                         atomic_inc(fle->object_ref);
 197                                 local_bh_enable();
 198
 199                                 return ret;
 200                         }
 201                         break;
 202                 }
 203         }
 204
 205         if (!fle) {
 206                 if (flow_count(cpu) > flow_hwm)
 207                         flow_cache_shrink(cpu);
 208
 209                 fle = kmem_cache_alloc(flow_cachep, SLAB_ATOMIC);
 210                 if (fle) {
 211                         fle->next = *head;
 212                         *head = fle;
 213                         fle->family = family;
 214                         fle->dir = dir;
 215                         memcpy(&fle->key, key, sizeof(*key));
 216                         fle->object = NULL;
 217                         flow_count(cpu)++;
 218                 }
 219         }
 220
 221 nocache:
 222         {
 223                 void *obj;
 224                 atomic_t *obj_ref;
 225
 226                 resolver(key, family, dir, &obj, &obj_ref);
 227
 228                 if (fle) {
 229                         fle->genid = atomic_read(&flow_cache_genid);
 230
 231                         if (fle->object)
 232                                 atomic_dec(fle->object_ref);
 233
 234                         fle->object = obj;
 235                         fle->object_ref = obj_ref;
 236                         if (obj)
 237                                 atomic_inc(fle->object_ref);
 238                 }
 239                 local_bh_enable();
 240
 241                 return obj;
 242         }
 243 }
 244
 245 static void flow_cache_flush_tasklet(unsigned long data)
 246 {
 247         struct flow_flush_info *info = (void *)data;
 248         int i;
 249         int cpu;
 250
 251         cpu = smp_processor_id();
 252         for (i = 0; i < flow_hash_size; i++) {
 253                 struct flow_cache_entry *fle;
 254
 255                 fle = flow_table(cpu)[i];
 256                 for (; fle; fle = fle->next) {
 257                         unsigned genid = atomic_read(&flow_cache_genid);
 258
 259                         if (!fle->object || fle->genid == genid)
 260                                 continue;
 261
 262                         fle->object = NULL;
 263                         atomic_dec(fle->object_ref);
 264                 }
 265         }
 266
 267         if (atomic_dec_and_test(&info->cpuleft))
 268                 complete(&info->completion);
 269 }
 270
 271 static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
 272 static void flow_cache_flush_per_cpu(void *data)
 273 {
 274         struct flow_flush_info *info = data;
 275         int cpu;
 276         struct tasklet_struct *tasklet;
 277
 278         cpu = smp_processor_id();
 279
 280         tasklet = flow_flush_tasklet(cpu);
 281         tasklet->data = (unsigned long)info;
 282         tasklet_schedule(tasklet);
 283 }
 284
 285 void flow_cache_flush(void)
 286 {
 287         struct flow_flush_info info;
 288         static DEFINE_MUTEX(flow_flush_sem);
 289
 290         /* Don't want cpus going down or up during this. */
 291         lock_cpu_hotplug();
 292         mutex_lock(&flow_flush_sem);
 293         atomic_set(&info.cpuleft, num_online_cpus());
 294         init_completion(&info.completion);
 295
 296         local_bh_disable();
 297         smp_call_function(flow_cache_flush_per_cpu, &info, 1, 0);
 298         flow_cache_flush_tasklet((unsigned long)&info);
 299         local_bh_enable();
 300
 301         wait_for_completion(&info.completion);
 302         mutex_unlock(&flow_flush_sem);
 303         unlock_cpu_hotplug();
 304 }
 305
 306 static void __devinit flow_cache_cpu_prepare(int cpu)
 307 {
 308         struct tasklet_struct *tasklet;
 309         unsigned long order;
 310
 311         for (order = 0;
 312              (PAGE_SIZE << order) <
 313                      (sizeof(struct flow_cache_entry *)*flow_hash_size);
 314              order++)
 315                 /* NOTHING */;
 316
 317         flow_table(cpu) = (struct flow_cache_entry **)
 318                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 319         if (!flow_table(cpu))
 320                 panic("NET: failed to allocate flow cache order %lu\n", order);
 321
 322         flow_hash_rnd_recalc(cpu) = 1;
 323         flow_count(cpu) = 0;
 324
 325         tasklet = flow_flush_tasklet(cpu);
 326         tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
 327 }
 328
 329 #ifdef CONFIG_HOTPLUG_CPU
 330 static int flow_cache_cpu(struct notifier_block *nfb,
 331                           unsigned long action,
 332                           void *hcpu)
 333 {
 334         if (action == CPU_DEAD)
 335                 __flow_cache_shrink((unsigned long)hcpu, 0);
 336         return NOTIFY_OK;
 337 }
 338 #endif /* CONFIG_HOTPLUG_CPU */
 339
 340 static int __init flow_cache_init(void)
 341 {
 342         int i;
 343
 344         flow_cachep = kmem_cache_create("flow_cache",
 345                                         sizeof(struct flow_cache_entry),
 346                                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC,
 347                                         NULL, NULL);
 348         flow_hash_shift = 10;
 349         flow_lwm = 2 * flow_hash_size;
 350         flow_hwm = 4 * flow_hash_size;
 351
 352         init_timer(&flow_hash_rnd_timer);
 353         flow_hash_rnd_timer.function = flow_cache_new_hashrnd;
 354         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 355         add_timer(&flow_hash_rnd_timer);
 356
 357         for_each_possible_cpu(i)
 358                 flow_cache_cpu_prepare(i);
 359
 360         hotcpu_notifier(flow_cache_cpu, 0);
 361         return 0;
 362 }
 363
 364 module_init(flow_cache_init);
 365
 366 EXPORT_SYMBOL(flow_cache_genid);
 367 EXPORT_SYMBOL(flow_cache_lookup);