2 Unix SMB/CIFS implementation.
4 trivial database library
6 Copyright (C) Andrew Tridgell 1999-2005
7 Copyright (C) Paul `Rusty' Russell 2000
8 Copyright (C) Jeremy Allison 2000-2003
10 ** NOTE! The following LGPL license applies to the tdb
11 ** library. This does NOT imply that all of Samba is released
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.
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.
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/>.
28 #include "tdb_private.h"
30 /* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
31 static int tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
32 struct list_struct *rec)
34 int want_next = (tlock->off != 0);
36 /* Lock each chain from the start one. */
37 for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {
38 if (!tlock->off && tlock->hash != 0) {
39 /* this is an optimisation for the common case where
40 the hash chain is empty, which is particularly
41 common for the use of tdb with ldb, where large
42 hashes are used. In that case we spend most of our
43 time in tdb_brlock(), locking empty hash chains.
45 To avoid this, we do an unlocked pre-check to see
46 if the hash chain is empty before starting to look
47 inside it. If it is empty then we can avoid that
48 hash chain. If it isn't empty then we can't believe
49 the value we get back, as we read it without a
50 lock, so instead we get the lock and re-fetch the
53 Notice that not doing this optimisation on the
54 first hash chain is critical. We must guarantee
55 that we have done at least one fcntl lock at the
56 start of a search to guarantee that memory is
57 coherent on SMP systems. If records are added by
58 others during the search then thats OK, and we
59 could possibly miss those with this trick, but we
60 could miss them anyway without this trick, so the
61 semantics don't change.
63 With a non-indexed ldb search this trick gains us a
64 factor of around 80 in speed on a linux 2.6.x
65 system (testing using ldbtest).
67 tdb->methods->next_hash_chain(tdb, &tlock->hash);
68 if (tlock->hash == tdb->header.hash_size) {
73 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
76 /* No previous record? Start at top of chain. */
78 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
82 /* Otherwise unlock the previous record. */
83 if (tdb_unlock_record(tdb, tlock->off) != 0)
88 /* We have offset of old record: grab next */
89 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
91 tlock->off = rec->next;
94 /* Iterate through chain */
97 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
100 /* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
101 if (tlock->off == rec->next) {
102 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
106 if (!TDB_DEAD(rec)) {
107 /* Woohoo: we found one! */
108 if (tdb_lock_record(tdb, tlock->off) != 0)
113 /* Try to clean dead ones from old traverses */
114 current = tlock->off;
115 tlock->off = rec->next;
116 if (!(tdb->read_only || tdb->traverse_read) &&
117 tdb_do_delete(tdb, current, rec) != 0)
120 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
123 /* We finished iteration without finding anything */
124 return TDB_ERRCODE(TDB_SUCCESS, 0);
128 if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
129 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
133 /* traverse the entire database - calling fn(tdb, key, data) on each element.
134 return -1 on error or the record count traversed
135 if fn is NULL then it is not called
136 a non-zero return value from fn() indicates that the traversal should stop
138 static int tdb_traverse_internal(struct tdb_context *tdb,
139 tdb_traverse_func fn, void *private_data,
140 struct tdb_traverse_lock *tl)
143 struct list_struct rec;
146 /* This was in the initializaton, above, but the IRIX compiler
147 * did not like it. crh
149 tl->next = tdb->travlocks.next;
151 /* fcntl locks don't stack: beware traverse inside traverse */
152 tdb->travlocks.next = tl;
154 /* tdb_next_lock places locks on the record returned, and its chain */
155 while ((ret = tdb_next_lock(tdb, tl, &rec)) > 0) {
157 /* now read the full record */
158 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
159 rec.key_len + rec.data_len);
162 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
164 if (tdb_unlock_record(tdb, tl->off) != 0)
165 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
168 key.dsize = rec.key_len;
169 dbuf.dptr = key.dptr + rec.key_len;
170 dbuf.dsize = rec.data_len;
172 /* Drop chain lock, call out */
173 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
178 if (fn && fn(tdb, key, dbuf, private_data)) {
179 /* They want us to terminate traversal */
181 if (tdb_unlock_record(tdb, tl->off) != 0) {
182 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
191 tdb->travlocks.next = tl->next;
200 a write style traverse - temporarily marks the db read only
202 int tdb_traverse_read(struct tdb_context *tdb,
203 tdb_traverse_func fn, void *private_data)
205 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
208 /* we need to get a read lock on the transaction lock here to
209 cope with the lock ordering semantics of solaris10 */
210 if (tdb_transaction_lock(tdb, F_RDLCK)) {
214 tdb->traverse_read++;
215 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
216 tdb->traverse_read--;
217 tdb_trace(tdb, "tdb_traverse_read = %i\n", ret);
219 tdb_transaction_unlock(tdb);
225 a write style traverse - needs to get the transaction lock to
228 WARNING: The data buffer given to the callback fn does NOT meet the
229 alignment restrictions malloc gives you.
231 int tdb_traverse(struct tdb_context *tdb,
232 tdb_traverse_func fn, void *private_data)
234 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
237 if (tdb->read_only || tdb->traverse_read) {
238 return tdb_traverse_read(tdb, fn, private_data);
241 if (tdb_transaction_lock(tdb, F_WRLCK)) {
245 tdb->traverse_write++;
246 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
247 tdb->traverse_write--;
248 tdb_trace(tdb, "tdb_traverse = %i\n", ret);
250 tdb_transaction_unlock(tdb);
256 /* find the first entry in the database and return its key */
257 TDB_DATA tdb_firstkey(struct tdb_context *tdb)
260 struct list_struct rec;
262 /* release any old lock */
263 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
265 tdb->travlocks.off = tdb->travlocks.hash = 0;
266 tdb->travlocks.lock_rw = F_RDLCK;
268 /* Grab first record: locks chain and returned record. */
269 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0) {
270 tdb_trace(tdb, "tdb_firstkey = ENOENT\n");
273 /* now read the key */
274 key.dsize = rec.key_len;
275 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
277 tdb_trace(tdb, "tdb_firstkey = ");
278 tdb_trace_record(tdb, key);
279 tdb_trace(tdb, "\n");
281 /* Unlock the hash chain of the record we just read. */
282 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
283 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
287 /* find the next entry in the database, returning its key */
288 TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
291 TDB_DATA key = tdb_null;
292 struct list_struct rec;
293 unsigned char *k = NULL;
295 /* Is locked key the old key? If so, traverse will be reliable. */
296 if (tdb->travlocks.off) {
297 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
299 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
300 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
302 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
303 /* No, it wasn't: unlock it and start from scratch */
304 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
305 tdb_trace(tdb, "tdb_nextkey ");
306 tdb_trace_record(tdb, oldkey);
307 tdb_trace(tdb, "= ENOENT\n");
311 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
315 tdb->travlocks.off = 0;
321 if (!tdb->travlocks.off) {
322 /* No previous element: do normal find, and lock record */
323 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
324 if (!tdb->travlocks.off) {
325 tdb_trace(tdb, "tdb_nextkey ");
326 tdb_trace_record(tdb, oldkey);
327 tdb_trace(tdb, "= ENOENT\n");
330 tdb->travlocks.hash = BUCKET(rec.full_hash);
331 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
332 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
336 oldhash = tdb->travlocks.hash;
338 /* Grab next record: locks chain and returned record,
339 unlocks old record */
340 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
341 key.dsize = rec.key_len;
342 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
344 /* Unlock the chain of this new record */
345 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
346 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
348 /* Unlock the chain of old record */
349 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
350 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
351 tdb_trace(tdb, "tdb_nextkey ");
352 tdb_trace_record(tdb, oldkey);
353 tdb_trace(tdb, "= ");
354 tdb_trace_record(tdb, key);
355 tdb_trace(tdb, "\n");