source: branches/samba-3.2.x/source/lib/tdb/common/traverse.c

Last change on this file was 136, checked in by Paul Smedley, 17 years ago

Update trunk to 3.2.0rc1
File size: 10.7 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/* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
31static int tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
32 struct list_struct *rec)
33{
34 int want_next = (tlock->off != 0);
35
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.
44
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
51 value below.
52
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.
62
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).
66 */
67 tdb->methods->next_hash_chain(tdb, &tlock->hash);
68 if (tlock->hash == tdb->header.hash_size) {
69 continue;
70 }
71 }
72
73 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
74 return -1;
75
76 /* No previous record? Start at top of chain. */
77 if (!tlock->off) {
78 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
79 &tlock->off) == -1)
80 goto fail;
81 } else {
82 /* Otherwise unlock the previous record. */
83 if (tdb_unlock_record(tdb, tlock->off) != 0)
84 goto fail;
85 }
86
87 if (want_next) {
88 /* We have offset of old record: grab next */
89 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
90 goto fail;
91 tlock->off = rec->next;
92 }
93
94 /* Iterate through chain */
95 while( tlock->off) {
96 tdb_off_t current;
97 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
98 goto fail;
99
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"));
103 goto fail;
104 }
105
106 if (!TDB_DEAD(rec)) {
107 /* Woohoo: we found one! */
108 if (tdb_lock_record(tdb, tlock->off) != 0)
109 goto fail;
110 return tlock->off;
111 }
112
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)
118 goto fail;
119 }
120 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
121 want_next = 0;
122 }
123 /* We finished iteration without finding anything */
124 return TDB_ERRCODE(TDB_SUCCESS, 0);
125
126 fail:
127 tlock->off = 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"));
130 return -1;
131}
132
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
137 */
138static int tdb_traverse_internal(struct tdb_context *tdb,
139 tdb_traverse_func fn, void *private_data,
140 struct tdb_traverse_lock *tl)
141{
142 TDB_DATA key, dbuf;
143 struct list_struct rec;
144 int ret, count = 0;
145
146 /* This was in the initializaton, above, but the IRIX compiler
147 * did not like it. crh
148 */
149 tl->next = tdb->travlocks.next;
150
151 /* fcntl locks don't stack: beware traverse inside traverse */
152 tdb->travlocks.next = tl;
153
154 /* tdb_next_lock places locks on the record returned, and its chain */
155 while ((ret = tdb_next_lock(tdb, tl, &rec)) > 0) {
156 count++;
157 /* now read the full record */
158 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
159 rec.key_len + rec.data_len);
160 if (!key.dptr) {
161 ret = -1;
162 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
163 goto out;
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"));
166 goto out;
167 }
168 key.dsize = rec.key_len;
169 dbuf.dptr = key.dptr + rec.key_len;
170 dbuf.dsize = rec.data_len;
171
172 /* Drop chain lock, call out */
173 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
174 ret = -1;
175 SAFE_FREE(key.dptr);
176 goto out;
177 }
178 if (fn && fn(tdb, key, dbuf, private_data)) {
179 /* They want us to terminate traversal */
180 ret = count;
181 if (tdb_unlock_record(tdb, tl->off) != 0) {
182 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
183 ret = -1;
184 }
185 SAFE_FREE(key.dptr);
186 goto out;
187 }
188 SAFE_FREE(key.dptr);
189 }
190out:
191 tdb->travlocks.next = tl->next;
192 if (ret < 0)
193 return -1;
194 else
195 return count;
196}
197
198
199/*
200 a write style traverse - temporarily marks the db read only
201*/
202int tdb_traverse_read(struct tdb_context *tdb,
203 tdb_traverse_func fn, void *private_data)
204{
205 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
206 int ret;
207 bool in_transaction = (tdb->transaction != NULL);
208
209 /* we need to get a read lock on the transaction lock here to
210 cope with the lock ordering semantics of solaris10 */
211 if (!in_transaction) {
212 if (tdb_transaction_lock(tdb, F_RDLCK)) {
213 return -1;
214 }
215 }
216
217 tdb->traverse_read++;
218 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
219 tdb->traverse_read--;
220
221 if (!in_transaction) {
222 tdb_transaction_unlock(tdb);
223 }
224
225 return ret;
226}
227
228/*
229 a write style traverse - needs to get the transaction lock to
230 prevent deadlocks
231
232 WARNING: The data buffer given to the callback fn does NOT meet the
233 alignment restrictions malloc gives you.
234*/
235int tdb_traverse(struct tdb_context *tdb,
236 tdb_traverse_func fn, void *private_data)
237{
238 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
239 int ret;
240 bool in_transaction = (tdb->transaction != NULL);
241
242 if (tdb->read_only || tdb->traverse_read) {
243 return tdb_traverse_read(tdb, fn, private_data);
244 }
245
246 if (!in_transaction) {
247 if (tdb_transaction_lock(tdb, F_WRLCK)) {
248 return -1;
249 }
250 }
251
252 tdb->traverse_write++;
253 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
254 tdb->traverse_write--;
255
256 if (!in_transaction) {
257 tdb_transaction_unlock(tdb);
258 }
259
260 return ret;
261}
262
263
264/* find the first entry in the database and return its key */
265TDB_DATA tdb_firstkey(struct tdb_context *tdb)
266{
267 TDB_DATA key;
268 struct list_struct rec;
269
270 /* release any old lock */
271 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
272 return tdb_null;
273 tdb->travlocks.off = tdb->travlocks.hash = 0;
274 tdb->travlocks.lock_rw = F_RDLCK;
275
276 /* Grab first record: locks chain and returned record. */
277 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0)
278 return tdb_null;
279 /* now read the key */
280 key.dsize = rec.key_len;
281 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
282
283 /* Unlock the hash chain of the record we just read. */
284 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
285 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
286 return key;
287}
288
289/* find the next entry in the database, returning its key */
290TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
291{
292 uint32_t oldhash;
293 TDB_DATA key = tdb_null;
294 struct list_struct rec;
295 unsigned char *k = NULL;
296
297 /* Is locked key the old key? If so, traverse will be reliable. */
298 if (tdb->travlocks.off) {
299 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
300 return tdb_null;
301 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
302 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
303 rec.key_len))
304 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
305 /* No, it wasn't: unlock it and start from scratch */
306 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
307 SAFE_FREE(k);
308 return tdb_null;
309 }
310 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
311 SAFE_FREE(k);
312 return tdb_null;
313 }
314 tdb->travlocks.off = 0;
315 }
316
317 SAFE_FREE(k);
318 }
319
320 if (!tdb->travlocks.off) {
321 /* No previous element: do normal find, and lock record */
322 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
323 if (!tdb->travlocks.off)
324 return tdb_null;
325 tdb->travlocks.hash = BUCKET(rec.full_hash);
326 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
327 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
328 return tdb_null;
329 }
330 }
331 oldhash = tdb->travlocks.hash;
332
333 /* Grab next record: locks chain and returned record,
334 unlocks old record */
335 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
336 key.dsize = rec.key_len;
337 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
338 key.dsize);
339 /* Unlock the chain of this new record */
340 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
341 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
342 }
343 /* Unlock the chain of old record */
344 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
345 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
346 return key;
347}
348
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