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 <net/flow.h>
  24 #include <asm/atomic.h>
  25 #include <asm/semaphore.h>
  26
  27 struct flow_cache_entry {
  28         struct flow_cache_entry *next;
  29         u16                     family;
  30         u8                      dir;
  31         struct flowi            key;
  32         u32                     genid;
  33         void                    *object;
  34         atomic_t                *object_ref;
  35 };
  36
  37 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  38
  39 static u32 flow_hash_shift;
  40 #define flow_hash_size  (1 << flow_hash_shift)
  41 static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
  42
  43 #define flow_table(cpu) (per_cpu(flow_tables, cpu))
  44
  45 static kmem_cache_t *flow_cachep __read_mostly;
  46
  47 static int flow_lwm, flow_hwm;
  48
  49 struct flow_percpu_info {
  50         int hash_rnd_recalc;
  51         u32 hash_rnd;
  52         int count;
  53 } ____cacheline_aligned;
  54 static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
  55
  56 #define flow_hash_rnd_recalc(cpu) \
  57         (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
  58 #define flow_hash_rnd(cpu) \
  59         (per_cpu(flow_hash_info, cpu).hash_rnd)
  60 #define flow_count(cpu) \
  61         (per_cpu(flow_hash_info, cpu).count)
  62
  63 static struct timer_list flow_hash_rnd_timer;
  64
  65 #define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)
  66
  67 struct flow_flush_info {
  68         atomic_t cpuleft;
  69         struct completion completion;
  70 };
  71 static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
  72
  73 #define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
  74
  75 static void flow_cache_new_hashrnd(unsigned long arg)
  76 {
  77         int i;
  78
  79         for_each_cpu(i)
  80                 flow_hash_rnd_recalc(i) = 1;
  81
  82         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  83         add_timer(&flow_hash_rnd_timer);
  84 }
  85
  86 static void __flow_cache_shrink(int cpu, int shrink_to)
  87 {
  88         struct flow_cache_entry *fle, **flp;
  89         int i;
  90
  91         for (i = 0; i < flow_hash_size; i++) {
  92                 int k = 0;
  93
  94                 flp = &flow_table(cpu)[i];
  95                 while ((fle = *flp) != NULL && k < shrink_to) {
  96                         k++;
  97                         flp = &fle->next;
  98                 }
  99                 while ((fle = *flp) != NULL) {
 100                         *flp = fle->next;
 101                         if (fle->object)
 102                                 atomic_dec(fle->object_ref);
 103                         kmem_cache_free(flow_cachep, fle);
 104                         flow_count(cpu)--;
 105                 }
 106         }
 107 }
 108
 109 static void flow_cache_shrink(int cpu)
 110 {
 111         int shrink_to = flow_lwm / flow_hash_size;
 112
 113         __flow_cache_shrink(cpu, shrink_to);
 114 }
 115
 116 static void flow_new_hash_rnd(int cpu)
 117 {
 118         get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
 119         flow_hash_rnd_recalc(cpu) = 0;
 120
 121         __flow_cache_shrink(cpu, 0);
 122 }
 123
 124 static u32 flow_hash_code(struct flowi *key, int cpu)
 125 {
 126         u32 *k = (u32 *) key;
 127
 128         return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
 129                 (flow_hash_size - 1));
 130 }
 131
 132 #if (BITS_PER_LONG == 64)
 133 typedef u64 flow_compare_t;
 134 #else
 135 typedef u32 flow_compare_t;
 136 #endif
 137
 138 extern void flowi_is_missized(void);
 139
 140 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 141  * important assumptions that we can here, such as alignment and
 142  * constant size.
 143  */
 144 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 145 {
 146         flow_compare_t *k1, *k1_lim, *k2;
 147         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 148
 149         if (sizeof(struct flowi) % sizeof(flow_compare_t))
 150                 flowi_is_missized();
 151
 152         k1 = (flow_compare_t *) key1;
 153         k1_lim = k1 + n_elem;
 154
 155         k2 = (flow_compare_t *) key2;
 156
 157         do {
 158                 if (*k1++ != *k2++)
 159                         return 1;
 160         } while (k1 < k1_lim);
 161
 162         return 0;
 163 }
 164
 165 void *flow_cache_lookup(struct flowi *key, u16 family, u8 dir,
 166                         flow_resolve_t resolver)
 167 {
 168         struct flow_cache_entry *fle, **head;
 169         unsigned int hash;
 170         int cpu;
 171
 172         local_bh_disable();
 173         cpu = smp_processor_id();
 174
 175         fle = NULL;
 176         /* Packet really early in init?  Making flow_cache_init a
 177          * pre-smp initcall would solve this.  --RR */
 178         if (!flow_table(cpu))
 179                 goto nocache;
 180
 181         if (flow_hash_rnd_recalc(cpu))
 182                 flow_new_hash_rnd(cpu);
 183         hash = flow_hash_code(key, cpu);
 184
 185         head = &flow_table(cpu)[hash];
 186         for (fle = *head; fle; fle = fle->next) {
 187                 if (fle->family == family &&
 188                     fle->dir == dir &&
 189                     flow_key_compare(key, &fle->key) == 0) {
 190                         if (fle->genid == atomic_read(&flow_cache_genid)) {
 191                                 void *ret = fle->object;
 192
 193                                 if (ret)
 194                                         atomic_inc(fle->object_ref);
 195                                 local_bh_enable();
 196
 197                                 return ret;
 198                         }
 199                         break;
 200                 }
 201         }
 202
 203         if (!fle) {
 204                 if (flow_count(cpu) > flow_hwm)
 205                         flow_cache_shrink(cpu);
 206
 207                 fle = kmem_cache_alloc(flow_cachep, SLAB_ATOMIC);
 208                 if (fle) {
 209                         fle->next = *head;
 210                         *head = fle;
 211                         fle->family = family;
 212                         fle->dir = dir;
 213                         memcpy(&fle->key, key, sizeof(*key));
 214                         fle->object = NULL;
 215                         flow_count(cpu)++;
 216                 }
 217         }
 218
 219 nocache:
 220         {
 221                 void *obj;
 222                 atomic_t *obj_ref;
 223
 224                 resolver(key, family, dir, &obj, &obj_ref);
 225
 226                 if (fle) {
 227                         fle->genid = atomic_read(&flow_cache_genid);
 228
 229                         if (fle->object)
 230                                 atomic_dec(fle->object_ref);
 231
 232                         fle->object = obj;
 233                         fle->object_ref = obj_ref;
 234                         if (obj)
 235                                 atomic_inc(fle->object_ref);
 236                 }
 237                 local_bh_enable();
 238
 239                 return obj;
 240         }
 241 }
 242
 243 static void flow_cache_flush_tasklet(unsigned long data)
 244 {
 245         struct flow_flush_info *info = (void *)data;
 246         int i;
 247         int cpu;
 248
 249         cpu = smp_processor_id();
 250         for (i = 0; i < flow_hash_size; i++) {
 251                 struct flow_cache_entry *fle;
 252
 253                 fle = flow_table(cpu)[i];
 254                 for (; fle; fle = fle->next) {
 255                         unsigned genid = atomic_read(&flow_cache_genid);
 256
 257                         if (!fle->object || fle->genid == genid)
 258                                 continue;
 259
 260                         fle->object = NULL;
 261                         atomic_dec(fle->object_ref);
 262                 }
 263         }
 264
 265         if (atomic_dec_and_test(&info->cpuleft))
 266                 complete(&info->completion);
 267 }
 268
 269 static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
 270 static void flow_cache_flush_per_cpu(void *data)
 271 {
 272         struct flow_flush_info *info = data;
 273         int cpu;
 274         struct tasklet_struct *tasklet;
 275
 276         cpu = smp_processor_id();
 277
 278         tasklet = flow_flush_tasklet(cpu);
 279         tasklet->data = (unsigned long)info;
 280         tasklet_schedule(tasklet);
 281 }
 282
 283 void flow_cache_flush(void)
 284 {
 285         struct flow_flush_info info;
 286         static DECLARE_MUTEX(flow_flush_sem);
 287
 288         /* Don't want cpus going down or up during this. */
 289         lock_cpu_hotplug();
 290         down(&flow_flush_sem);
 291         atomic_set(&info.cpuleft, num_online_cpus());
 292         init_completion(&info.completion);
 293
 294         local_bh_disable();
 295         smp_call_function(flow_cache_flush_per_cpu, &info, 1, 0);
 296         flow_cache_flush_tasklet((unsigned long)&info);
 297         local_bh_enable();
 298
 299         wait_for_completion(&info.completion);
 300         up(&flow_flush_sem);
 301         unlock_cpu_hotplug();
 302 }
 303
 304 static void __devinit flow_cache_cpu_prepare(int cpu)
 305 {
 306         struct tasklet_struct *tasklet;
 307         unsigned long order;
 308
 309         for (order = 0;
 310              (PAGE_SIZE << order) <
 311                      (sizeof(struct flow_cache_entry *)*flow_hash_size);
 312              order++)
 313                 /* NOTHING */;
 314
 315         flow_table(cpu) = (struct flow_cache_entry **)
 316                 __get_free_pages(GFP_KERNEL, order);
 317         if (!flow_table(cpu))
 318                 panic("NET: failed to allocate flow cache order %lu\n", order);
 319
 320         memset(flow_table(cpu), 0, PAGE_SIZE << 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,
 347                                         NULL, NULL);
 348
 349         if (!flow_cachep)
 350                 panic("NET: failed to allocate flow cache slab\n");
 351
 352         flow_hash_shift = 10;
 353         flow_lwm = 2 * flow_hash_size;
 354         flow_hwm = 4 * flow_hash_size;
 355
 356         init_timer(&flow_hash_rnd_timer);
 357         flow_hash_rnd_timer.function = flow_cache_new_hashrnd;
 358         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 359         add_timer(&flow_hash_rnd_timer);
 360
 361         for_each_cpu(i)
 362                 flow_cache_cpu_prepare(i);
 363
 364         hotcpu_notifier(flow_cache_cpu, 0);
 365         return 0;
 366 }
 367
 368 module_init(flow_cache_init);
 369
 370 EXPORT_SYMBOL(flow_cache_genid);
 371 EXPORT_SYMBOL(flow_cache_lookup);