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