source: vendor/current/lib/tdb/common/traverse.c

Last change on this file was 988, checked in by Silvan Scherrer, 9 years ago

Samba Server: update vendor to version 4.4.3
File size: 11.3 KB
Line 
1 /*
2 Unix SMB/CIFS implementation.
3
4 trivial database library
5
6 Copyright (C) Andrew Tridgell 1999-2005
7 Copyright (C) Paul `Rusty' Russell 2000
8 Copyright (C) Jeremy Allison 2000-2003
9
10 ** NOTE! The following LGPL license applies to the tdb
11 ** library. This does NOT imply that all of Samba is released
12 ** under the LGPL
13
14 This library is free software; you can redistribute it and/or
15 modify it under the terms of the GNU Lesser General Public
16 License as published by the Free Software Foundation; either
17 version 3 of the License, or (at your option) any later version.
18
19 This library is distributed in the hope that it will be useful,
20 but WITHOUT ANY WARRANTY; without even the implied warranty of
21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22 Lesser General Public License for more details.
23
24 You should have received a copy of the GNU Lesser General Public
25 License along with this library; if not, see <http://www.gnu.org/licenses/>.
26*/
27
28#include "tdb_private.h"
29
30#define TDB_NEXT_LOCK_ERR ((tdb_off_t)-1)
31
32/* Uses traverse lock: 0 = finish, TDB_NEXT_LOCK_ERR = error,
33 other = record offset */
34static tdb_off_t tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
35 struct tdb_record *rec)
36{
37 int want_next = (tlock->off != 0);
38
39 /* Lock each chain from the start one. */
40 for (; tlock->hash < tdb->hash_size; tlock->hash++) {
41 if (!tlock->off && tlock->hash != 0) {
42 /* this is an optimisation for the common case where
43 the hash chain is empty, which is particularly
44 common for the use of tdb with ldb, where large
45 hashes are used. In that case we spend most of our
46 time in tdb_brlock(), locking empty hash chains.
47
48 To avoid this, we do an unlocked pre-check to see
49 if the hash chain is empty before starting to look
50 inside it. If it is empty then we can avoid that
51 hash chain. If it isn't empty then we can't believe
52 the value we get back, as we read it without a
53 lock, so instead we get the lock and re-fetch the
54 value below.
55
56 Notice that not doing this optimisation on the
57 first hash chain is critical. We must guarantee
58 that we have done at least one fcntl lock at the
59 start of a search to guarantee that memory is
60 coherent on SMP systems. If records are added by
61 others during the search then thats OK, and we
62 could possibly miss those with this trick, but we
63 could miss them anyway without this trick, so the
64 semantics don't change.
65
66 With a non-indexed ldb search this trick gains us a
67 factor of around 80 in speed on a linux 2.6.x
68 system (testing using ldbtest).
69 */
70 tdb->methods->next_hash_chain(tdb, &tlock->hash);
71 if (tlock->hash == tdb->hash_size) {
72 continue;
73 }
74 }
75
76 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
77 return TDB_NEXT_LOCK_ERR;
78
79 /* No previous record? Start at top of chain. */
80 if (!tlock->off) {
81 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
82 &tlock->off) == -1)
83 goto fail;
84 } else {
85 /* Otherwise unlock the previous record. */
86 if (tdb_unlock_record(tdb, tlock->off) != 0)
87 goto fail;
88 }
89
90 if (want_next) {
91 /* We have offset of old record: grab next */
92 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
93 goto fail;
94 tlock->off = rec->next;
95 }
96
97 /* Iterate through chain */
98 while( tlock->off) {
99 tdb_off_t current;
100 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
101 goto fail;
102
103 /* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
104 if (tlock->off == rec->next) {
105 tdb->ecode = TDB_ERR_CORRUPT;
106 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
107 goto fail;
108 }
109
110 if (!TDB_DEAD(rec)) {
111 /* Woohoo: we found one! */
112 if (tdb_lock_record(tdb, tlock->off) != 0)
113 goto fail;
114 return tlock->off;
115 }
116
117 /* Try to clean dead ones from old traverses */
118 current = tlock->off;
119 tlock->off = rec->next;
120 if (!(tdb->read_only || tdb->traverse_read) &&
121 tdb_do_delete(tdb, current, rec) != 0)
122 goto fail;
123 }
124 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
125 want_next = 0;
126 }
127 /* We finished iteration without finding anything */
128 tdb->ecode = TDB_SUCCESS;
129 return 0;
130
131 fail:
132 tlock->off = 0;
133 if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
134 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
135 return TDB_NEXT_LOCK_ERR;
136}
137
138/* traverse the entire database - calling fn(tdb, key, data) on each element.
139 return -1 on error or the record count traversed
140 if fn is NULL then it is not called
141 a non-zero return value from fn() indicates that the traversal should stop
142 */
143static int tdb_traverse_internal(struct tdb_context *tdb,
144 tdb_traverse_func fn, void *private_data,
145 struct tdb_traverse_lock *tl)
146{
147 TDB_DATA key, dbuf;
148 struct tdb_record rec;
149 int ret = 0, count = 0;
150 tdb_off_t off;
151
152 /* This was in the initialization, above, but the IRIX compiler
153 * did not like it. crh
154 */
155 tl->next = tdb->travlocks.next;
156
157 /* fcntl locks don't stack: beware traverse inside traverse */
158 tdb->travlocks.next = tl;
159
160 /* tdb_next_lock places locks on the record returned, and its chain */
161 while ((off = tdb_next_lock(tdb, tl, &rec)) != 0) {
162 if (off == TDB_NEXT_LOCK_ERR) {
163 ret = -1;
164 goto out;
165 }
166 count++;
167 /* now read the full record */
168 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
169 rec.key_len + rec.data_len);
170 if (!key.dptr) {
171 ret = -1;
172 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
173 goto out;
174 if (tdb_unlock_record(tdb, tl->off) != 0)
175 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
176 goto out;
177 }
178 key.dsize = rec.key_len;
179 dbuf.dptr = key.dptr + rec.key_len;
180 dbuf.dsize = rec.data_len;
181
182 tdb_trace_1rec_retrec(tdb, "traverse", key, dbuf);
183
184 /* Drop chain lock, call out */
185 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
186 ret = -1;
187 SAFE_FREE(key.dptr);
188 goto out;
189 }
190 if (fn && fn(tdb, key, dbuf, private_data)) {
191 /* They want us to terminate traversal */
192 tdb_trace_ret(tdb, "tdb_traverse_end", count);
193 if (tdb_unlock_record(tdb, tl->off) != 0) {
194 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
195 ret = -1;
196 }
197 SAFE_FREE(key.dptr);
198 goto out;
199 }
200 SAFE_FREE(key.dptr);
201 }
202 tdb_trace(tdb, "tdb_traverse_end");
203out:
204 tdb->travlocks.next = tl->next;
205 if (ret < 0)
206 return -1;
207 else
208 return count;
209}
210
211
212/*
213 a read style traverse - temporarily marks the db read only
214*/
215_PUBLIC_ int tdb_traverse_read(struct tdb_context *tdb,
216 tdb_traverse_func fn, void *private_data)
217{
218 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
219 int ret;
220
221 /* we need to get a read lock on the transaction lock here to
222 cope with the lock ordering semantics of solaris10 */
223 if (tdb_transaction_lock(tdb, F_RDLCK, TDB_LOCK_WAIT)) {
224 return -1;
225 }
226
227 tdb->traverse_read++;
228 tdb_trace(tdb, "tdb_traverse_read_start");
229 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
230 tdb->traverse_read--;
231
232 tdb_transaction_unlock(tdb, F_RDLCK);
233
234 return ret;
235}
236
237/*
238 a write style traverse - needs to get the transaction lock to
239 prevent deadlocks
240
241 WARNING: The data buffer given to the callback fn does NOT meet the
242 alignment guarantees malloc gives you.
243*/
244_PUBLIC_ int tdb_traverse(struct tdb_context *tdb,
245 tdb_traverse_func fn, void *private_data)
246{
247 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
248 enum tdb_lock_flags lock_flags;
249 int ret;
250
251 if (tdb->read_only || tdb->traverse_read) {
252 return tdb_traverse_read(tdb, fn, private_data);
253 }
254
255 lock_flags = TDB_LOCK_WAIT;
256
257 if (tdb->allrecord_lock.count != 0) {
258 /*
259 * This avoids a deadlock between tdb_lockall() and
260 * tdb_traverse(). See
261 * https://bugzilla.samba.org/show_bug.cgi?id=11381
262 */
263 lock_flags = TDB_LOCK_NOWAIT;
264 }
265
266 if (tdb_transaction_lock(tdb, F_WRLCK, lock_flags)) {
267 return -1;
268 }
269
270 tdb->traverse_write++;
271 tdb_trace(tdb, "tdb_traverse_start");
272 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
273 tdb->traverse_write--;
274
275 tdb_transaction_unlock(tdb, F_WRLCK);
276
277 return ret;
278}
279
280
281/* find the first entry in the database and return its key */
282_PUBLIC_ TDB_DATA tdb_firstkey(struct tdb_context *tdb)
283{
284 TDB_DATA key;
285 struct tdb_record rec;
286 tdb_off_t off;
287
288 /* release any old lock */
289 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
290 return tdb_null;
291 tdb->travlocks.off = tdb->travlocks.hash = 0;
292 tdb->travlocks.lock_rw = F_RDLCK;
293
294 /* Grab first record: locks chain and returned record. */
295 off = tdb_next_lock(tdb, &tdb->travlocks, &rec);
296 if (off == 0 || off == TDB_NEXT_LOCK_ERR) {
297 tdb_trace_retrec(tdb, "tdb_firstkey", tdb_null);
298 return tdb_null;
299 }
300 /* now read the key */
301 key.dsize = rec.key_len;
302 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
303
304 tdb_trace_retrec(tdb, "tdb_firstkey", key);
305
306 /* Unlock the hash chain of the record we just read. */
307 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
308 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
309 return key;
310}
311
312/* find the next entry in the database, returning its key */
313_PUBLIC_ TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
314{
315 uint32_t oldhash;
316 TDB_DATA key = tdb_null;
317 struct tdb_record rec;
318 unsigned char *k = NULL;
319 tdb_off_t off;
320
321 /* Is locked key the old key? If so, traverse will be reliable. */
322 if (tdb->travlocks.off) {
323 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
324 return tdb_null;
325 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
326 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
327 rec.key_len))
328 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
329 /* No, it wasn't: unlock it and start from scratch */
330 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
331 tdb_trace_1rec_retrec(tdb, "tdb_nextkey",
332 oldkey, tdb_null);
333 SAFE_FREE(k);
334 return tdb_null;
335 }
336 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
337 SAFE_FREE(k);
338 return tdb_null;
339 }
340 tdb->travlocks.off = 0;
341 }
342
343 SAFE_FREE(k);
344 }
345
346 if (!tdb->travlocks.off) {
347 /* No previous element: do normal find, and lock record */
348 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
349 if (!tdb->travlocks.off) {
350 tdb_trace_1rec_retrec(tdb, "tdb_nextkey", oldkey, tdb_null);
351 return tdb_null;
352 }
353 tdb->travlocks.hash = BUCKET(rec.full_hash);
354 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
355 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
356 return tdb_null;
357 }
358 }
359 oldhash = tdb->travlocks.hash;
360
361 /* Grab next record: locks chain and returned record,
362 unlocks old record */
363 off = tdb_next_lock(tdb, &tdb->travlocks, &rec);
364 if (off != TDB_NEXT_LOCK_ERR && off != 0) {
365 key.dsize = rec.key_len;
366 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
367 key.dsize);
368 /* Unlock the chain of this new record */
369 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
370 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
371 }
372 /* Unlock the chain of old record */
373 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
374 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
375 tdb_trace_1rec_retrec(tdb, "tdb_nextkey", oldkey, key);
376 return key;
377}
378
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