lib/util/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 "replace.h"
  21 #include <talloc.h>
  22 #include "../lib/util/debug.h"
  23 #include "../lib/util/samba_util.h"
  24 #include "../lib/util/dlinklist.h"
  25 #include "../lib/util/rbtree.h"
  26 #include "memcache.h"
  27
  28 static struct memcache *global_cache;
  29
  30 struct memcache_element {
  31         struct rb_node rb_node;
  32         struct memcache_element *prev, *next;
  33         size_t keylength, valuelength;
  34         uint8_t n;              /* This is really an enum, but save memory */
  35         char data[1];           /* placeholder for offsetof */
  36 };
  37
  38 struct memcache {
  39         struct memcache_element *mru;
  40         struct rb_root tree;
  41         size_t size;
  42         size_t max_size;
  43 };
  44
  45 static void memcache_element_parse(struct memcache_element *e,
  46                                    DATA_BLOB *key, DATA_BLOB *value);
  47
  48 static bool memcache_is_talloc(enum memcache_number n)
  49 {
  50         bool result;
  51
  52         switch (n) {
  53         case GETPWNAM_CACHE:
  54         case PDB_GETPWSID_CACHE:
  55         case SINGLETON_CACHE_TALLOC:
  56         case SHARE_MODE_LOCK_CACHE:
  57         case GETWD_CACHE:
  58         case VIRUSFILTER_SCAN_RESULTS_CACHE_TALLOC:
  59                 result = true;
  60                 break;
  61         default:
  62                 result = false;
  63                 break;
  64         }
  65
  66         return result;
  67 }
  68
  69 static int memcache_destructor(struct memcache *cache) {
  70         struct memcache_element *e, *next;
  71
  72         for (e = cache->mru; e != NULL; e = next) {
  73                 next = e->next;
  74                 TALLOC_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(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_t *)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                 DLIST_PROMOTE(cache->mru, e);
 173         }
 174
 175         memcache_element_parse(e, &key, value);
 176         return true;
 177 }
 178
 179 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 180                              DATA_BLOB key)
 181 {
 182         DATA_BLOB value;
 183         void *result;
 184
 185         if (!memcache_lookup(cache, n, key, &value)) {
 186                 return NULL;
 187         }
 188
 189         if (value.length != sizeof(result)) {
 190                 return NULL;
 191         }
 192
 193         memcpy(&result, value.data, sizeof(result));
 194
 195         return result;
 196 }
 197
 198 static void memcache_delete_element(struct memcache *cache,
 199                                     struct memcache_element *e)
 200 {
 201         rb_erase(&e->rb_node, &cache->tree);
 202
 203         DLIST_REMOVE(cache->mru, e);
 204
 205         if (memcache_is_talloc(e->n)) {
 206                 DATA_BLOB cache_key, cache_value;
 207                 void *ptr;
 208
 209                 memcache_element_parse(e, &cache_key, &cache_value);
 210                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 211                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 212                 TALLOC_FREE(ptr);
 213         }
 214
 215         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 216
 217         TALLOC_FREE(e);
 218 }
 219
 220 static void memcache_trim(struct memcache *cache)
 221 {
 222         if (cache->max_size == 0) {
 223                 return;
 224         }
 225
 226         while ((cache->size > cache->max_size) && DLIST_TAIL(cache->mru)) {
 227                 memcache_delete_element(cache, DLIST_TAIL(cache->mru));
 228         }
 229 }
 230
 231 void memcache_delete(struct memcache *cache, enum memcache_number n,
 232                      DATA_BLOB key)
 233 {
 234         struct memcache_element *e;
 235
 236         if (cache == NULL) {
 237                 cache = global_cache;
 238         }
 239         if (cache == NULL) {
 240                 return;
 241         }
 242
 243         e = memcache_find(cache, n, key);
 244         if (e == NULL) {
 245                 return;
 246         }
 247
 248         memcache_delete_element(cache, e);
 249 }
 250
 251 void memcache_add(struct memcache *cache, enum memcache_number n,
 252                   DATA_BLOB key, DATA_BLOB value)
 253 {
 254         struct memcache_element *e;
 255         struct rb_node **p;
 256         struct rb_node *parent;
 257         DATA_BLOB cache_key, cache_value;
 258         size_t element_size;
 259
 260         if (cache == NULL) {
 261                 cache = global_cache;
 262         }
 263         if (cache == NULL) {
 264                 return;
 265         }
 266
 267         if (key.length == 0) {
 268                 return;
 269         }
 270
 271         e = memcache_find(cache, n, key);
 272
 273         if (e != NULL) {
 274                 memcache_element_parse(e, &cache_key, &cache_value);
 275
 276                 if (value.length <= cache_value.length) {
 277                         if (memcache_is_talloc(e->n)) {
 278                                 void *ptr;
 279                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 280                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 281                                 TALLOC_FREE(ptr);
 282                         }
 283                         /*
 284                          * We can reuse the existing record
 285                          */
 286                         memcpy(cache_value.data, value.data, value.length);
 287                         e->valuelength = value.length;
 288                         return;
 289                 }
 290
 291                 memcache_delete_element(cache, e);
 292         }
 293
 294         element_size = memcache_element_size(key.length, value.length);
 295
 296         e = talloc_size(cache, element_size);
 297         if (e == NULL) {
 298                 DEBUG(0, ("talloc failed\n"));
 299                 return;
 300         }
 301         talloc_set_type(e, struct memcache_element);
 302
 303         e->n = n;
 304         e->keylength = key.length;
 305         e->valuelength = value.length;
 306
 307         memcache_element_parse(e, &cache_key, &cache_value);
 308         memcpy(cache_key.data, key.data, key.length);
 309         memcpy(cache_value.data, value.data, value.length);
 310
 311         parent = NULL;
 312         p = &cache->tree.rb_node;
 313
 314         while (*p) {
 315                 struct memcache_element *elem = memcache_node2elem(*p);
 316                 int cmp;
 317
 318                 parent = (*p);
 319
 320                 cmp = memcache_compare(elem, n, key);
 321
 322                 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
 323         }
 324
 325         rb_link_node(&e->rb_node, parent, p);
 326         rb_insert_color(&e->rb_node, &cache->tree);
 327
 328         DLIST_ADD(cache->mru, e);
 329
 330         cache->size += element_size;
 331         memcache_trim(cache);
 332 }
 333
 334 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 335                          DATA_BLOB key, void *pptr)
 336 {
 337         void **ptr = (void **)pptr;
 338         void *p;
 339
 340         if (cache == NULL) {
 341                 cache = global_cache;
 342         }
 343         if (cache == NULL) {
 344                 return;
 345         }
 346
 347         p = talloc_move(cache, ptr);
 348         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 349 }
 350
 351 void memcache_flush(struct memcache *cache, enum memcache_number n)
 352 {
 353         struct rb_node *node;
 354
 355         if (cache == NULL) {
 356                 cache = global_cache;
 357         }
 358         if (cache == NULL) {
 359                 return;
 360         }
 361
 362         /*
 363          * Find the smallest element of number n
 364          */
 365
 366         node = cache->tree.rb_node;
 367         if (node == NULL) {
 368                 return;
 369         }
 370
 371         /*
 372          * First, find *any* element of number n
 373          */
 374
 375         while (true) {
 376                 struct memcache_element *elem = memcache_node2elem(node);
 377                 struct rb_node *next;
 378
 379                 if ((int)elem->n == (int)n) {
 380                         break;
 381                 }
 382
 383                 if ((int)elem->n < (int)n) {
 384                         next = node->rb_right;
 385                 }
 386                 else {
 387                         next = node->rb_left;
 388                 }
 389                 if (next == NULL) {
 390                         break;
 391                 }
 392                 node = next;
 393         }
 394
 395         /*
 396          * Then, find the leftmost element with number n
 397          */
 398
 399         while (true) {
 400                 struct rb_node *prev = rb_prev(node);
 401                 struct memcache_element *elem;
 402
 403                 if (prev == NULL) {
 404                         break;
 405                 }
 406                 elem = memcache_node2elem(prev);
 407                 if ((int)elem->n != (int)n) {
 408                         break;
 409                 }
 410                 node = prev;
 411         }
 412
 413         while (node != NULL) {
 414                 struct memcache_element *e = memcache_node2elem(node);
 415                 struct rb_node *next = rb_next(node);
 416
 417                 if (e->n != n) {
 418                         break;
 419                 }
 420
 421                 memcache_delete_element(cache, e);
 422                 node = next;
 423         }
 424 }