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_talloc_value {
31 void *ptr;
32 size_t len;
33 };
34
35 struct memcache_element {
36 struct rb_node rb_node;
37 struct memcache_element *prev, *next;
38 size_t keylength, valuelength;
39 uint8_t n; /* This is really an enum, but save memory */
40 char data[1]; /* placeholder for offsetof */
41 };
42
43 struct memcache {
44 struct memcache_element *mru;
45 struct rb_root tree;
46 size_t size;
47 size_t max_size;
48 };
49
50 static void memcache_element_parse(struct memcache_element *e,
51 DATA_BLOB *key, DATA_BLOB *value);
52
memcache_is_talloc(enum memcache_number n)53 static bool memcache_is_talloc(enum memcache_number n)
54 {
55 bool result;
56
57 switch (n) {
58 case GETPWNAM_CACHE:
59 case PDB_GETPWSID_CACHE:
60 case SINGLETON_CACHE_TALLOC:
61 case SHARE_MODE_LOCK_CACHE:
62 case GETWD_CACHE:
63 case VIRUSFILTER_SCAN_RESULTS_CACHE_TALLOC:
64 result = true;
65 break;
66 default:
67 result = false;
68 break;
69 }
70
71 return result;
72 }
73
memcache_destructor(struct memcache * cache)74 static int memcache_destructor(struct memcache *cache) {
75 struct memcache_element *e, *next;
76
77 for (e = cache->mru; e != NULL; e = next) {
78 next = e->next;
79 TALLOC_FREE(e);
80 }
81 return 0;
82 }
83
memcache_init(TALLOC_CTX * mem_ctx,size_t max_size)84 struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
85 {
86 struct memcache *result;
87
88 result = talloc_zero(mem_ctx, struct memcache);
89 if (result == NULL) {
90 return NULL;
91 }
92 result->max_size = max_size;
93 talloc_set_destructor(result, memcache_destructor);
94 return result;
95 }
96
memcache_set_global(struct memcache * cache)97 void memcache_set_global(struct memcache *cache)
98 {
99 TALLOC_FREE(global_cache);
100 global_cache = cache;
101 }
102
memcache_node2elem(struct rb_node * node)103 static struct memcache_element *memcache_node2elem(struct rb_node *node)
104 {
105 return (struct memcache_element *)
106 ((char *)node - offsetof(struct memcache_element, rb_node));
107 }
108
memcache_element_parse(struct memcache_element * e,DATA_BLOB * key,DATA_BLOB * value)109 static void memcache_element_parse(struct memcache_element *e,
110 DATA_BLOB *key, DATA_BLOB *value)
111 {
112 key->data = ((uint8_t *)e) + offsetof(struct memcache_element, data);
113 key->length = e->keylength;
114 value->data = key->data + e->keylength;
115 value->length = e->valuelength;
116 }
117
memcache_element_size(size_t key_length,size_t value_length)118 static size_t memcache_element_size(size_t key_length, size_t value_length)
119 {
120 return sizeof(struct memcache_element) - 1 + key_length + value_length;
121 }
122
memcache_compare(struct memcache_element * e,enum memcache_number n,DATA_BLOB key)123 static int memcache_compare(struct memcache_element *e, enum memcache_number n,
124 DATA_BLOB key)
125 {
126 DATA_BLOB this_key, this_value;
127
128 if ((int)e->n < (int)n) return 1;
129 if ((int)e->n > (int)n) return -1;
130
131 if (e->keylength < key.length) return 1;
132 if (e->keylength > key.length) return -1;
133
134 memcache_element_parse(e, &this_key, &this_value);
135 return memcmp(this_key.data, key.data, key.length);
136 }
137
memcache_find(struct memcache * cache,enum memcache_number n,DATA_BLOB key)138 static struct memcache_element *memcache_find(
139 struct memcache *cache, enum memcache_number n, DATA_BLOB key)
140 {
141 struct rb_node *node;
142
143 node = cache->tree.rb_node;
144
145 while (node != NULL) {
146 struct memcache_element *elem = memcache_node2elem(node);
147 int cmp;
148
149 cmp = memcache_compare(elem, n, key);
150 if (cmp == 0) {
151 return elem;
152 }
153 node = (cmp < 0) ? node->rb_left : node->rb_right;
154 }
155
156 return NULL;
157 }
158
memcache_lookup(struct memcache * cache,enum memcache_number n,DATA_BLOB key,DATA_BLOB * value)159 bool memcache_lookup(struct memcache *cache, enum memcache_number n,
160 DATA_BLOB key, DATA_BLOB *value)
161 {
162 struct memcache_element *e;
163
164 if (cache == NULL) {
165 cache = global_cache;
166 }
167 if (cache == NULL) {
168 return false;
169 }
170
171 e = memcache_find(cache, n, key);
172 if (e == NULL) {
173 return false;
174 }
175
176 if (cache->size != 0) {
177 DLIST_PROMOTE(cache->mru, e);
178 }
179
180 memcache_element_parse(e, &key, value);
181 return true;
182 }
183
memcache_lookup_talloc(struct memcache * cache,enum memcache_number n,DATA_BLOB key)184 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
185 DATA_BLOB key)
186 {
187 DATA_BLOB value;
188 struct memcache_talloc_value mtv;
189
190 if (!memcache_lookup(cache, n, key, &value)) {
191 return NULL;
192 }
193
194 if (value.length != sizeof(mtv)) {
195 return NULL;
196 }
197
198 memcpy(&mtv, value.data, sizeof(mtv));
199
200 return mtv.ptr;
201 }
202
memcache_delete_element(struct memcache * cache,struct memcache_element * e)203 static void memcache_delete_element(struct memcache *cache,
204 struct memcache_element *e)
205 {
206 rb_erase(&e->rb_node, &cache->tree);
207
208 DLIST_REMOVE(cache->mru, e);
209
210 if (memcache_is_talloc(e->n)) {
211 DATA_BLOB cache_key, cache_value;
212 struct memcache_talloc_value mtv;
213
214 memcache_element_parse(e, &cache_key, &cache_value);
215 SMB_ASSERT(cache_value.length == sizeof(mtv));
216 memcpy(&mtv, cache_value.data, sizeof(mtv));
217 cache->size -= mtv.len;
218 TALLOC_FREE(mtv.ptr);
219 }
220
221 cache->size -= memcache_element_size(e->keylength, e->valuelength);
222
223 TALLOC_FREE(e);
224 }
225
memcache_trim(struct memcache * cache,struct memcache_element * e)226 static void memcache_trim(struct memcache *cache, struct memcache_element *e)
227 {
228 struct memcache_element *tail = NULL;
229
230 if (cache->max_size == 0) {
231 return;
232 }
233
234 for (tail = DLIST_TAIL(cache->mru);
235 (cache->size > cache->max_size) && (tail != NULL);
236 tail = DLIST_TAIL(cache->mru))
237 {
238 if (tail == e) {
239 tail = DLIST_PREV(tail);
240 if (tail == NULL) {
241 break;
242 }
243 }
244 memcache_delete_element(cache, tail);
245 }
246 }
247
memcache_delete(struct memcache * cache,enum memcache_number n,DATA_BLOB key)248 void memcache_delete(struct memcache *cache, enum memcache_number n,
249 DATA_BLOB key)
250 {
251 struct memcache_element *e;
252
253 if (cache == NULL) {
254 cache = global_cache;
255 }
256 if (cache == NULL) {
257 return;
258 }
259
260 e = memcache_find(cache, n, key);
261 if (e == NULL) {
262 return;
263 }
264
265 memcache_delete_element(cache, e);
266 }
267
memcache_add(struct memcache * cache,enum memcache_number n,DATA_BLOB key,DATA_BLOB value)268 void memcache_add(struct memcache *cache, enum memcache_number n,
269 DATA_BLOB key, DATA_BLOB value)
270 {
271 struct memcache_element *e;
272 struct rb_node **p;
273 struct rb_node *parent;
274 DATA_BLOB cache_key, cache_value;
275 size_t element_size;
276
277 if (cache == NULL) {
278 cache = global_cache;
279 }
280 if (cache == NULL) {
281 return;
282 }
283
284 if (key.length == 0) {
285 return;
286 }
287
288 e = memcache_find(cache, n, key);
289
290 if (e != NULL) {
291 memcache_element_parse(e, &cache_key, &cache_value);
292
293 if (value.length <= cache_value.length) {
294 if (memcache_is_talloc(e->n)) {
295 struct memcache_talloc_value mtv;
296
297 SMB_ASSERT(cache_value.length == sizeof(mtv));
298 memcpy(&mtv, cache_value.data, sizeof(mtv));
299 cache->size -= mtv.len;
300 TALLOC_FREE(mtv.ptr);
301 }
302 /*
303 * We can reuse the existing record
304 */
305 memcpy(cache_value.data, value.data, value.length);
306 e->valuelength = value.length;
307
308 if (memcache_is_talloc(e->n)) {
309 struct memcache_talloc_value mtv;
310
311 SMB_ASSERT(cache_value.length == sizeof(mtv));
312 memcpy(&mtv, cache_value.data, sizeof(mtv));
313 cache->size += mtv.len;
314 }
315 return;
316 }
317
318 memcache_delete_element(cache, e);
319 }
320
321 element_size = memcache_element_size(key.length, value.length);
322
323 e = talloc_size(cache, element_size);
324 if (e == NULL) {
325 DEBUG(0, ("talloc failed\n"));
326 return;
327 }
328 talloc_set_type(e, struct memcache_element);
329
330 e->n = n;
331 e->keylength = key.length;
332 e->valuelength = value.length;
333
334 memcache_element_parse(e, &cache_key, &cache_value);
335 memcpy(cache_key.data, key.data, key.length);
336 memcpy(cache_value.data, value.data, value.length);
337
338 parent = NULL;
339 p = &cache->tree.rb_node;
340
341 while (*p) {
342 struct memcache_element *elem = memcache_node2elem(*p);
343 int cmp;
344
345 parent = (*p);
346
347 cmp = memcache_compare(elem, n, key);
348
349 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
350 }
351
352 rb_link_node(&e->rb_node, parent, p);
353 rb_insert_color(&e->rb_node, &cache->tree);
354
355 DLIST_ADD(cache->mru, e);
356
357 cache->size += element_size;
358 if (memcache_is_talloc(e->n)) {
359 struct memcache_talloc_value mtv;
360
361 SMB_ASSERT(cache_value.length == sizeof(mtv));
362 memcpy(&mtv, cache_value.data, sizeof(mtv));
363 cache->size += mtv.len;
364 }
365 memcache_trim(cache, e);
366 }
367
memcache_add_talloc(struct memcache * cache,enum memcache_number n,DATA_BLOB key,void * pptr)368 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
369 DATA_BLOB key, void *pptr)
370 {
371 struct memcache_talloc_value mtv;
372 void **ptr = (void **)pptr;
373
374 if (cache == NULL) {
375 cache = global_cache;
376 }
377 if (cache == NULL) {
378 return;
379 }
380
381 mtv.len = talloc_total_size(*ptr);
382 mtv.ptr = talloc_move(cache, ptr);
383 memcache_add(cache, n, key, data_blob_const(&mtv, sizeof(mtv)));
384 }
385
memcache_flush(struct memcache * cache,enum memcache_number n)386 void memcache_flush(struct memcache *cache, enum memcache_number n)
387 {
388 struct rb_node *node;
389
390 if (cache == NULL) {
391 cache = global_cache;
392 }
393 if (cache == NULL) {
394 return;
395 }
396
397 /*
398 * Find the smallest element of number n
399 */
400
401 node = cache->tree.rb_node;
402 if (node == NULL) {
403 return;
404 }
405
406 /*
407 * First, find *any* element of number n
408 */
409
410 while (true) {
411 struct memcache_element *elem = memcache_node2elem(node);
412 struct rb_node *next;
413
414 if ((int)elem->n == (int)n) {
415 break;
416 }
417
418 if ((int)elem->n < (int)n) {
419 next = node->rb_right;
420 }
421 else {
422 next = node->rb_left;
423 }
424 if (next == NULL) {
425 break;
426 }
427 node = next;
428 }
429
430 /*
431 * Then, find the leftmost element with number n
432 */
433
434 while (true) {
435 struct rb_node *prev = rb_prev(node);
436 struct memcache_element *elem;
437
438 if (prev == NULL) {
439 break;
440 }
441 elem = memcache_node2elem(prev);
442 if ((int)elem->n != (int)n) {
443 break;
444 }
445 node = prev;
446 }
447
448 while (node != NULL) {
449 struct memcache_element *e = memcache_node2elem(node);
450 struct rb_node *next = rb_next(node);
451
452 if (e->n != n) {
453 break;
454 }
455
456 memcache_delete_element(cache, e);
457 node = next;
458 }
459 }
460