source/lib/memcache.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    In-memory cache
   4    Copyright (C) Volker Lendecke 2007
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "memcache.h"
  21 #include "rbtree.h"
  22
  23 static struct memcache *global_cache;
  24
  25 struct memcache_element {
  26         struct rb_node rb_node;
  27         struct memcache_element *prev, *next;
  28         size_t keylength, valuelength;
  29         uint8 n;                /* This is really an enum, but save memory */
  30         char data[1];           /* placeholder for offsetof */
  31 };
  32
  33 struct memcache {
  34         struct memcache_element *mru, *lru;
  35         struct rb_root tree;
  36         size_t size;
  37         size_t max_size;
  38 };
  39
  40 static void memcache_element_parse(struct memcache_element *e,
  41                                    DATA_BLOB *key, DATA_BLOB *value);
  42
  43 static bool memcache_is_talloc(enum memcache_number n)
  44 {
  45         bool result;
  46
  47         switch (n) {
  48         case GETPWNAM_CACHE:
  49         case PDB_GETPWSID_CACHE:
  50         case SINGLETON_CACHE_TALLOC:
  51                 result = true;
  52                 break;
  53         default:
  54                 result = false;
  55                 break;
  56         }
  57
  58         return result;
  59 }
  60
  61 static int memcache_destructor(struct memcache *cache) {
  62         struct memcache_element *e, *next;
  63
  64         for (e = cache->mru; e != NULL; e = next) {
  65                 next = e->next;
  66                 if (memcache_is_talloc((enum memcache_number)e->n)
  67                     && (e->valuelength == sizeof(void *))) {
  68                         DATA_BLOB key, value;
  69                         void *ptr;
  70                         memcache_element_parse(e, &key, &value);
  71                         memcpy(&ptr, value.data, sizeof(ptr));
  72                         TALLOC_FREE(ptr);
  73                 }
  74                 SAFE_FREE(e);
  75         }
  76         return 0;
  77 }
  78
  79 struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
  80 {
  81         struct memcache *result;
  82
  83         result = TALLOC_ZERO_P(mem_ctx, struct memcache);
  84         if (result == NULL) {
  85                 return NULL;
  86         }
  87         result->max_size = max_size;
  88         talloc_set_destructor(result, memcache_destructor);
  89         return result;
  90 }
  91
  92 void memcache_set_global(struct memcache *cache)
  93 {
  94         TALLOC_FREE(global_cache);
  95         global_cache = cache;
  96 }
  97
  98 static struct memcache_element *memcache_node2elem(struct rb_node *node)
  99 {
 100         return (struct memcache_element *)
 101                 ((char *)node - offsetof(struct memcache_element, rb_node));
 102 }
 103
 104 static void memcache_element_parse(struct memcache_element *e,
 105                                    DATA_BLOB *key, DATA_BLOB *value)
 106 {
 107         key->data = ((uint8 *)e) + offsetof(struct memcache_element, data);
 108         key->length = e->keylength;
 109         value->data = key->data + e->keylength;
 110         value->length = e->valuelength;
 111 }
 112
 113 static size_t memcache_element_size(size_t key_length, size_t value_length)
 114 {
 115         return sizeof(struct memcache_element) - 1 + key_length + value_length;
 116 }
 117
 118 static int memcache_compare(struct memcache_element *e, enum memcache_number n,
 119                             DATA_BLOB key)
 120 {
 121         DATA_BLOB this_key, this_value;
 122
 123         if ((int)e->n < (int)n) return 1;
 124         if ((int)e->n > (int)n) return -1;
 125
 126         if (e->keylength < key.length) return 1;
 127         if (e->keylength > key.length) return -1;
 128
 129         memcache_element_parse(e, &this_key, &this_value);
 130         return memcmp(this_key.data, key.data, key.length);
 131 }
 132
 133 static struct memcache_element *memcache_find(
 134         struct memcache *cache, enum memcache_number n, DATA_BLOB key)
 135 {
 136         struct rb_node *node;
 137
 138         node = cache->tree.rb_node;
 139
 140         while (node != NULL) {
 141                 struct memcache_element *elem = memcache_node2elem(node);
 142                 int cmp;
 143
 144                 cmp = memcache_compare(elem, n, key);
 145                 if (cmp == 0) {
 146                         return elem;
 147                 }
 148                 node = (cmp < 0) ? node->rb_left : node->rb_right;
 149         }
 150
 151         return NULL;
 152 }
 153
 154 bool memcache_lookup(struct memcache *cache, enum memcache_number n,
 155                      DATA_BLOB key, DATA_BLOB *value)
 156 {
 157         struct memcache_element *e;
 158
 159         if (cache == NULL) {
 160                 cache = global_cache;
 161         }
 162         if (cache == NULL) {
 163                 return false;
 164         }
 165
 166         e = memcache_find(cache, n, key);
 167         if (e == NULL) {
 168                 return false;
 169         }
 170
 171         if (cache->size != 0) {
 172                 /*
 173                  * Do LRU promotion only when we will ever shrink
 174                  */
 175                 if (e == cache->lru) {
 176                         cache->lru = e->prev;
 177                 }
 178                 DLIST_PROMOTE(cache->mru, e);
 179                 if (cache->mru == NULL) {
 180                         cache->mru = e;
 181                 }
 182         }
 183
 184         memcache_element_parse(e, &key, value);
 185         return true;
 186 }
 187
 188 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 189                              DATA_BLOB key)
 190 {
 191         DATA_BLOB value;
 192         void *result;
 193
 194         if (!memcache_lookup(cache, n, key, &value)) {
 195                 return NULL;
 196         }
 197
 198         if (value.length != sizeof(result)) {
 199                 return NULL;
 200         }
 201
 202         memcpy(&result, value.data, sizeof(result));
 203
 204         return result;
 205 }
 206
 207 static void memcache_delete_element(struct memcache *cache,
 208                                     struct memcache_element *e)
 209 {
 210         rb_erase(&e->rb_node, &cache->tree);
 211
 212         if (e == cache->lru) {
 213                 cache->lru = e->prev;
 214         }
 215         DLIST_REMOVE(cache->mru, e);
 216
 217         if (memcache_is_talloc(e->n)) {
 218                 DATA_BLOB cache_key, cache_value;
 219                 void *ptr;
 220
 221                 memcache_element_parse(e, &cache_key, &cache_value);
 222                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 223                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 224                 TALLOC_FREE(ptr);
 225         }
 226
 227         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 228
 229         SAFE_FREE(e);
 230 }
 231
 232 static void memcache_trim(struct memcache *cache)
 233 {
 234         if (cache->max_size == 0) {
 235                 return;
 236         }
 237
 238         while ((cache->size > cache->max_size) && (cache->lru != NULL)) {
 239                 memcache_delete_element(cache, cache->lru);
 240         }
 241 }
 242
 243 void memcache_delete(struct memcache *cache, enum memcache_number n,
 244                      DATA_BLOB key)
 245 {
 246         struct memcache_element *e;
 247
 248         if (cache == NULL) {
 249                 cache = global_cache;
 250         }
 251         if (cache == NULL) {
 252                 return;
 253         }
 254
 255         e = memcache_find(cache, n, key);
 256         if (e == NULL) {
 257                 return;
 258         }
 259
 260         memcache_delete_element(cache, e);
 261 }
 262
 263 void memcache_add(struct memcache *cache, enum memcache_number n,
 264                   DATA_BLOB key, DATA_BLOB value)
 265 {
 266         struct memcache_element *e;
 267         struct rb_node **p;
 268         struct rb_node *parent;
 269         DATA_BLOB cache_key, cache_value;
 270         size_t element_size;
 271
 272         if (cache == NULL) {
 273                 cache = global_cache;
 274         }
 275         if (cache == NULL) {
 276                 return;
 277         }
 278
 279         if (key.length == 0) {
 280                 return;
 281         }
 282
 283         e = memcache_find(cache, n, key);
 284
 285         if (e != NULL) {
 286                 memcache_element_parse(e, &cache_key, &cache_value);
 287
 288                 if (value.length <= cache_value.length) {
 289                         if (memcache_is_talloc(e->n)) {
 290                                 void *ptr;
 291                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 292                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 293                                 TALLOC_FREE(ptr);
 294                         }
 295                         /*
 296                          * We can reuse the existing record
 297                          */
 298                         memcpy(cache_value.data, value.data, value.length);
 299                         e->valuelength = value.length;
 300                         return;
 301                 }
 302
 303                 memcache_delete_element(cache, e);
 304         }
 305
 306         element_size = memcache_element_size(key.length, value.length);
 307
 308
 309         e = (struct memcache_element *)SMB_MALLOC(element_size);
 310
 311         if (e == NULL) {
 312                 DEBUG(0, ("malloc failed\n"));
 313                 return;
 314         }
 315
 316         e->n = n;
 317         e->keylength = key.length;
 318         e->valuelength = value.length;
 319
 320         memcache_element_parse(e, &cache_key, &cache_value);
 321         memcpy(cache_key.data, key.data, key.length);
 322         memcpy(cache_value.data, value.data, value.length);
 323
 324         parent = NULL;
 325         p = &cache->tree.rb_node;
 326
 327         while (*p) {
 328                 struct memcache_element *elem = memcache_node2elem(*p);
 329                 int cmp;
 330
 331                 parent = (*p);
 332
 333                 cmp = memcache_compare(elem, n, key);
 334
 335                 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
 336         }
 337
 338         rb_link_node(&e->rb_node, parent, p);
 339         rb_insert_color(&e->rb_node, &cache->tree);
 340
 341         DLIST_ADD(cache->mru, e);
 342         if (cache->lru == NULL) {
 343                 cache->lru = e;
 344         }
 345
 346         cache->size += element_size;
 347         memcache_trim(cache);
 348 }
 349
 350 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 351                          DATA_BLOB key, void *ptr)
 352 {
 353         void *p = talloc_move(cache, &ptr);
 354         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 355 }
 356
 357 void memcache_flush(struct memcache *cache, enum memcache_number n)
 358 {
 359         struct rb_node *node;
 360
 361         if (cache == NULL) {
 362                 cache = global_cache;
 363         }
 364         if (cache == NULL) {
 365                 return;
 366         }
 367
 368         /*
 369          * Find the smallest element of number n
 370          */
 371
 372         node = cache->tree.rb_node;
 373         if (node == NULL) {
 374                 return;
 375         }
 376
 377         /*
 378          * First, find *any* element of number n
 379          */
 380
 381         while (true) {
 382                 struct memcache_element *elem = memcache_node2elem(node);
 383                 struct rb_node *next;
 384
 385                 if ((int)elem->n == (int)n) {
 386                         break;
 387                 }
 388
 389                 if ((int)elem->n < (int)n) {
 390                         next = node->rb_right;
 391                 }
 392                 else {
 393                         next = node->rb_left;
 394                 }
 395                 if (next == NULL) {
 396                         break;
 397                 }
 398                 node = next;
 399         }
 400
 401         if (node == NULL) {
 402                 return;
 403         }
 404
 405         /*
 406          * Then, find the leftmost element with number n
 407          */
 408
 409         while (true) {
 410                 struct rb_node *prev = rb_prev(node);
 411                 struct memcache_element *elem;
 412
 413                 if (prev == NULL) {
 414                         break;
 415                 }
 416                 elem = memcache_node2elem(prev);
 417                 if ((int)elem->n != (int)n) {
 418                         break;
 419                 }
 420                 node = prev;
 421         }
 422
 423         while (node != NULL) {
 424                 struct memcache_element *e = memcache_node2elem(node);
 425                 struct rb_node *next = rb_next(node);
 426
 427                 if (e->n != n) {
 428                         break;
 429                 }
 430
 431                 memcache_delete_element(cache, e);
 432                 node = next;
 433         }
 434 }