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                 SAFE_FREE(e);
  67         }
  68         return 0;
  69 }
  70
  71 struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
  72 {
  73         struct memcache *result;
  74
  75         result = TALLOC_ZERO_P(mem_ctx, struct memcache);
  76         if (result == NULL) {
  77                 return NULL;
  78         }
  79         result->max_size = max_size;
  80         talloc_set_destructor(result, memcache_destructor);
  81         return result;
  82 }
  83
  84 void memcache_set_global(struct memcache *cache)
  85 {
  86         TALLOC_FREE(global_cache);
  87         global_cache = cache;
  88 }
  89
  90 static struct memcache_element *memcache_node2elem(struct rb_node *node)
  91 {
  92         return (struct memcache_element *)
  93                 ((char *)node - offsetof(struct memcache_element, rb_node));
  94 }
  95
  96 static void memcache_element_parse(struct memcache_element *e,
  97                                    DATA_BLOB *key, DATA_BLOB *value)
  98 {
  99         key->data = ((uint8 *)e) + offsetof(struct memcache_element, data);
 100         key->length = e->keylength;
 101         value->data = key->data + e->keylength;
 102         value->length = e->valuelength;
 103 }
 104
 105 static size_t memcache_element_size(size_t key_length, size_t value_length)
 106 {
 107         return sizeof(struct memcache_element) - 1 + key_length + value_length;
 108 }
 109
 110 static int memcache_compare(struct memcache_element *e, enum memcache_number n,
 111                             DATA_BLOB key)
 112 {
 113         DATA_BLOB this_key, this_value;
 114
 115         if ((int)e->n < (int)n) return 1;
 116         if ((int)e->n > (int)n) return -1;
 117
 118         if (e->keylength < key.length) return 1;
 119         if (e->keylength > key.length) return -1;
 120
 121         memcache_element_parse(e, &this_key, &this_value);
 122         return memcmp(this_key.data, key.data, key.length);
 123 }
 124
 125 static struct memcache_element *memcache_find(
 126         struct memcache *cache, enum memcache_number n, DATA_BLOB key)
 127 {
 128         struct rb_node *node;
 129
 130         node = cache->tree.rb_node;
 131
 132         while (node != NULL) {
 133                 struct memcache_element *elem = memcache_node2elem(node);
 134                 int cmp;
 135
 136                 cmp = memcache_compare(elem, n, key);
 137                 if (cmp == 0) {
 138                         return elem;
 139                 }
 140                 node = (cmp < 0) ? node->rb_left : node->rb_right;
 141         }
 142
 143         return NULL;
 144 }
 145
 146 bool memcache_lookup(struct memcache *cache, enum memcache_number n,
 147                      DATA_BLOB key, DATA_BLOB *value)
 148 {
 149         struct memcache_element *e;
 150
 151         if (cache == NULL) {
 152                 cache = global_cache;
 153         }
 154         if (cache == NULL) {
 155                 return false;
 156         }
 157
 158         e = memcache_find(cache, n, key);
 159         if (e == NULL) {
 160                 return false;
 161         }
 162
 163         if (cache->size != 0) {
 164                 /*
 165                  * Do LRU promotion only when we will ever shrink
 166                  */
 167                 if (e == cache->lru) {
 168                         cache->lru = e->prev;
 169                 }
 170                 DLIST_PROMOTE(cache->mru, e);
 171                 if (cache->mru == NULL) {
 172                         cache->mru = e;
 173                 }
 174         }
 175
 176         memcache_element_parse(e, &key, value);
 177         return true;
 178 }
 179
 180 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 181                              DATA_BLOB key)
 182 {
 183         DATA_BLOB value;
 184         void *result;
 185
 186         if (!memcache_lookup(cache, n, key, &value)) {
 187                 return NULL;
 188         }
 189
 190         if (value.length != sizeof(result)) {
 191                 return NULL;
 192         }
 193
 194         memcpy(&result, value.data, sizeof(result));
 195
 196         return result;
 197 }
 198
 199 static void memcache_delete_element(struct memcache *cache,
 200                                     struct memcache_element *e)
 201 {
 202         rb_erase(&e->rb_node, &cache->tree);
 203
 204         if (e == cache->lru) {
 205                 cache->lru = e->prev;
 206         }
 207         DLIST_REMOVE(cache->mru, e);
 208
 209         if (memcache_is_talloc(e->n)) {
 210                 DATA_BLOB cache_key, cache_value;
 211                 void *ptr;
 212
 213                 memcache_element_parse(e, &cache_key, &cache_value);
 214                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 215                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 216                 TALLOC_FREE(ptr);
 217         }
 218
 219         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 220
 221         SAFE_FREE(e);
 222 }
 223
 224 static void memcache_trim(struct memcache *cache)
 225 {
 226         if (cache->max_size == 0) {
 227                 return;
 228         }
 229
 230         while ((cache->size > cache->max_size) && (cache->lru != NULL)) {
 231                 memcache_delete_element(cache, cache->lru);
 232         }
 233 }
 234
 235 void memcache_delete(struct memcache *cache, enum memcache_number n,
 236                      DATA_BLOB key)
 237 {
 238         struct memcache_element *e;
 239
 240         if (cache == NULL) {
 241                 cache = global_cache;
 242         }
 243         if (cache == NULL) {
 244                 return;
 245         }
 246
 247         e = memcache_find(cache, n, key);
 248         if (e == NULL) {
 249                 return;
 250         }
 251
 252         memcache_delete_element(cache, e);
 253 }
 254
 255 void memcache_add(struct memcache *cache, enum memcache_number n,
 256                   DATA_BLOB key, DATA_BLOB value)
 257 {
 258         struct memcache_element *e;
 259         struct rb_node **p;
 260         struct rb_node *parent;
 261         DATA_BLOB cache_key, cache_value;
 262         size_t element_size;
 263
 264         if (cache == NULL) {
 265                 cache = global_cache;
 266         }
 267         if (cache == NULL) {
 268                 return;
 269         }
 270
 271         if (key.length == 0) {
 272                 return;
 273         }
 274
 275         e = memcache_find(cache, n, key);
 276
 277         if (e != NULL) {
 278                 memcache_element_parse(e, &cache_key, &cache_value);
 279
 280                 if (value.length <= cache_value.length) {
 281                         if (memcache_is_talloc(e->n)) {
 282                                 void *ptr;
 283                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 284                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 285                                 TALLOC_FREE(ptr);
 286                         }
 287                         /*
 288                          * We can reuse the existing record
 289                          */
 290                         memcpy(cache_value.data, value.data, value.length);
 291                         e->valuelength = value.length;
 292                         return;
 293                 }
 294
 295                 memcache_delete_element(cache, e);
 296         }
 297
 298         element_size = memcache_element_size(key.length, value.length);
 299
 300
 301         e = (struct memcache_element *)SMB_MALLOC(element_size);
 302
 303         if (e == NULL) {
 304                 DEBUG(0, ("malloc failed\n"));
 305                 return;
 306         }
 307
 308         e->n = n;
 309         e->keylength = key.length;
 310         e->valuelength = value.length;
 311
 312         memcache_element_parse(e, &cache_key, &cache_value);
 313         memcpy(cache_key.data, key.data, key.length);
 314         memcpy(cache_value.data, value.data, value.length);
 315
 316         parent = NULL;
 317         p = &cache->tree.rb_node;
 318
 319         while (*p) {
 320                 struct memcache_element *elem = memcache_node2elem(*p);
 321                 int cmp;
 322
 323                 parent = (*p);
 324
 325                 cmp = memcache_compare(elem, n, key);
 326
 327                 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
 328         }
 329
 330         rb_link_node(&e->rb_node, parent, p);
 331         rb_insert_color(&e->rb_node, &cache->tree);
 332
 333         DLIST_ADD(cache->mru, e);
 334         if (cache->lru == NULL) {
 335                 cache->lru = e;
 336         }
 337
 338         cache->size += element_size;
 339         memcache_trim(cache);
 340 }
 341
 342 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 343                          DATA_BLOB key, void *ptr)
 344 {
 345         void *p = talloc_move(cache, &ptr);
 346         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 347 }
 348
 349 void memcache_flush(struct memcache *cache, enum memcache_number n)
 350 {
 351         struct rb_node *node;
 352
 353         if (cache == NULL) {
 354                 cache = global_cache;
 355         }
 356         if (cache == NULL) {
 357                 return;
 358         }
 359
 360         /*
 361          * Find the smallest element of number n
 362          */
 363
 364         node = cache->tree.rb_node;
 365         if (node == NULL) {
 366                 return;
 367         }
 368
 369         /*
 370          * First, find *any* element of number n
 371          */
 372
 373         while (true) {
 374                 struct memcache_element *elem = memcache_node2elem(node);
 375                 struct rb_node *next;
 376
 377                 if ((int)elem->n == (int)n) {
 378                         break;
 379                 }
 380
 381                 if ((int)elem->n < (int)n) {
 382                         next = node->rb_right;
 383                 }
 384                 else {
 385                         next = node->rb_left;
 386                 }
 387                 if (next == NULL) {
 388                         break;
 389                 }
 390                 node = next;
 391         }
 392
 393         if (node == NULL) {
 394                 return;
 395         }
 396
 397         /*
 398          * Then, find the leftmost element with number n
 399          */
 400
 401         while (true) {
 402                 struct rb_node *prev = rb_prev(node);
 403                 struct memcache_element *elem;
 404
 405                 if (prev == NULL) {
 406                         break;
 407                 }
 408                 elem = memcache_node2elem(prev);
 409                 if ((int)elem->n != (int)n) {
 410                         break;
 411                 }
 412                 node = prev;
 413         }
 414
 415         while (node != NULL) {
 416                 struct memcache_element *e = memcache_node2elem(node);
 417                 struct rb_node *next = rb_next(node);
 418
 419                 if (e->n != n) {
 420                         break;
 421                 }
 422
 423                 memcache_delete_element(cache, e);
 424                 node = next;
 425         }
 426 }