source: trunk-3.0/source/tdb/common/traverse.c@ 103

Last change on this file since 103 was 44, checked in by Paul Smedley, 18 years ago

Update source to 3.0.25b
File size: 10.8 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 2 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, write to the Free Software
26 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27*/
28
29#include "tdb_private.h"
30
31/* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
32static int tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
33 struct list_struct *rec)
34{
35 int want_next = (tlock->off != 0);
36
37 /* Lock each chain from the start one. */
38 for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {
39 if (!tlock->off && tlock->hash != 0) {
40 /* this is an optimisation for the common case where
41 the hash chain is empty, which is particularly
42 common for the use of tdb with ldb, where large
43 hashes are used. In that case we spend most of our
44 time in tdb_brlock(), locking empty hash chains.
45
46 To avoid this, we do an unlocked pre-check to see
47 if the hash chain is empty before starting to look
48 inside it. If it is empty then we can avoid that
49 hash chain. If it isn't empty then we can't believe
50 the value we get back, as we read it without a
51 lock, so instead we get the lock and re-fetch the
52 value below.
53
54 Notice that not doing this optimisation on the
55 first hash chain is critical. We must guarantee
56 that we have done at least one fcntl lock at the
57 start of a search to guarantee that memory is
58 coherent on SMP systems. If records are added by
59 others during the search then thats OK, and we
60 could possibly miss those with this trick, but we
61 could miss them anyway without this trick, so the
62 semantics don't change.
63
64 With a non-indexed ldb search this trick gains us a
65 factor of around 80 in speed on a linux 2.6.x
66 system (testing using ldbtest).
67 */
68 tdb->methods->next_hash_chain(tdb, &tlock->hash);
69 if (tlock->hash == tdb->header.hash_size) {
70 continue;
71 }
72 }
73
74 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
75 return -1;
76
77 /* No previous record? Start at top of chain. */
78 if (!tlock->off) {
79 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
80 &tlock->off) == -1)
81 goto fail;
82 } else {
83 /* Otherwise unlock the previous record. */
84 if (tdb_unlock_record(tdb, tlock->off) != 0)
85 goto fail;
86 }
87
88 if (want_next) {
89 /* We have offset of old record: grab next */
90 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
91 goto fail;
92 tlock->off = rec->next;
93 }
94
95 /* Iterate through chain */
96 while( tlock->off) {
97 tdb_off_t current;
98 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
99 goto fail;
100
101 /* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
102 if (tlock->off == rec->next) {
103 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
104 goto fail;
105 }
106
107 if (!TDB_DEAD(rec)) {
108 /* Woohoo: we found one! */
109 if (tdb_lock_record(tdb, tlock->off) != 0)
110 goto fail;
111 return tlock->off;
112 }
113
114 /* Try to clean dead ones from old traverses */
115 current = tlock->off;
116 tlock->off = rec->next;
117 if (!(tdb->read_only || tdb->traverse_read) &&
118 tdb_do_delete(tdb, current, rec) != 0)
119 goto fail;
120 }
121 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
122 want_next = 0;
123 }
124 /* We finished iteration without finding anything */
125 return TDB_ERRCODE(TDB_SUCCESS, 0);
126
127 fail:
128 tlock->off = 0;
129 if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
130 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
131 return -1;
132}
133
134/* traverse the entire database - calling fn(tdb, key, data) on each element.
135 return -1 on error or the record count traversed
136 if fn is NULL then it is not called
137 a non-zero return value from fn() indicates that the traversal should stop
138 */
139static int tdb_traverse_internal(struct tdb_context *tdb,
140 tdb_traverse_func fn, void *private_data,
141 struct tdb_traverse_lock *tl)
142{
143 TDB_DATA key, dbuf;
144 struct list_struct rec;
145 int ret, count = 0;
146
147 /* This was in the initializaton, above, but the IRIX compiler
148 * did not like it. crh
149 */
150 tl->next = tdb->travlocks.next;
151
152 /* fcntl locks don't stack: beware traverse inside traverse */
153 tdb->travlocks.next = tl;
154
155 /* tdb_next_lock places locks on the record returned, and its chain */
156 while ((ret = tdb_next_lock(tdb, tl, &rec)) > 0) {
157 count++;
158 /* now read the full record */
159 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
160 rec.key_len + rec.data_len);
161 if (!key.dptr) {
162 ret = -1;
163 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
164 goto out;
165 if (tdb_unlock_record(tdb, tl->off) != 0)
166 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
167 goto out;
168 }
169 key.dsize = rec.key_len;
170 dbuf.dptr = key.dptr + rec.key_len;
171 dbuf.dsize = rec.data_len;
172
173 /* Drop chain lock, call out */
174 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
175 ret = -1;
176 SAFE_FREE(key.dptr);
177 goto out;
178 }
179 if (fn && fn(tdb, key, dbuf, private_data)) {
180 /* They want us to terminate traversal */
181 ret = count;
182 if (tdb_unlock_record(tdb, tl->off) != 0) {
183 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
184 ret = -1;
185 }
186 SAFE_FREE(key.dptr);
187 goto out;
188 }
189 SAFE_FREE(key.dptr);
190 }
191out:
192 tdb->travlocks.next = tl->next;
193 if (ret < 0)
194 return -1;
195 else
196 return count;
197}
198
199
200/*
201 a write style traverse - temporarily marks the db read only
202*/
203int tdb_traverse_read(struct tdb_context *tdb,
204 tdb_traverse_func fn, void *private_data)
205{
206 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
207 int ret;
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 (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_RDLCK, F_SETLKW, 0, 1) == -1) {
212 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_traverse_read: failed to get transaction lock\n"));
213 tdb->ecode = TDB_ERR_LOCK;
214 return -1;
215 }
216
217 tdb->traverse_read++;
218 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
219 tdb->traverse_read--;
220
221 tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
222
223 return ret;
224}
225
226/*
227 a write style traverse - needs to get the transaction lock to
228 prevent deadlocks
229*/
230int tdb_traverse(struct tdb_context *tdb,
231 tdb_traverse_func fn, void *private_data)
232{
233 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
234 int ret;
235
236 if (tdb->read_only || tdb->traverse_read) {
237 return tdb_traverse_read(tdb, fn, private_data);
238 }
239
240 if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
241 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_traverse: failed to get transaction lock\n"));
242 tdb->ecode = TDB_ERR_LOCK;
243 return -1;
244 }
245
246 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
247
248 tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
249
250 return ret;
251}
252
253
254/* find the first entry in the database and return its key */
255TDB_DATA tdb_firstkey(struct tdb_context *tdb)
256{
257 TDB_DATA key;
258 struct list_struct rec;
259
260 /* release any old lock */
261 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
262 return tdb_null;
263 tdb->travlocks.off = tdb->travlocks.hash = 0;
264 tdb->travlocks.lock_rw = F_RDLCK;
265
266 /* Grab first record: locks chain and returned record. */
267 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0)
268 return tdb_null;
269 /* now read the key */
270 key.dsize = rec.key_len;
271 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
272
273 /* Unlock the hash chain of the record we just read. */
274 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
275 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
276 return key;
277}
278
279/* find the next entry in the database, returning its key */
280TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
281{
282 u32 oldhash;
283 TDB_DATA key = tdb_null;
284 struct list_struct rec;
285 char *k = NULL;
286
287 /* Is locked key the old key? If so, traverse will be reliable. */
288 if (tdb->travlocks.off) {
289 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
290 return tdb_null;
291 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
292 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
293 rec.key_len))
294 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
295 /* No, it wasn't: unlock it and start from scratch */
296 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
297 SAFE_FREE(k);
298 return tdb_null;
299 }
300 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
301 SAFE_FREE(k);
302 return tdb_null;
303 }
304 tdb->travlocks.off = 0;
305 }
306
307 SAFE_FREE(k);
308 }
309
310 if (!tdb->travlocks.off) {
311 /* No previous element: do normal find, and lock record */
312 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
313 if (!tdb->travlocks.off)
314 return tdb_null;
315 tdb->travlocks.hash = BUCKET(rec.full_hash);
316 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
317 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
318 return tdb_null;
319 }
320 }
321 oldhash = tdb->travlocks.hash;
322
323 /* Grab next record: locks chain and returned record,
324 unlocks old record */
325 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
326 key.dsize = rec.key_len;
327 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
328 key.dsize);
329 /* Unlock the chain of this new record */
330 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
331 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
332 }
333 /* Unlock the chain of old record */
334 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
335 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
336 return key;
337}
Note: See TracBrowser for help on using the repository browser.