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 #define TDB_NEXT_LOCK_ERR ((tdb_off_t)-1)
32 /* Uses traverse lock: 0 = finish, TDB_NEXT_LOCK_ERR = error,
33 other = record offset */
34 static tdb_off_t
tdb_next_lock(struct tdb_context
*tdb
, struct tdb_traverse_lock
*tlock
,
35 struct tdb_record
*rec
)
37 int want_next
= (tlock
->off
!= 0);
39 /* Lock each chain from the start one. */
40 for (; tlock
->hash
< tdb
->header
.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.
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
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.
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).
70 tdb
->methods
->next_hash_chain(tdb
, &tlock
->hash
);
71 if (tlock
->hash
== tdb
->header
.hash_size
) {
76 if (tdb_lock(tdb
, tlock
->hash
, tlock
->lock_rw
) == -1)
77 return TDB_NEXT_LOCK_ERR
;
79 /* No previous record? Start at top of chain. */
81 if (tdb_ofs_read(tdb
, TDB_HASH_TOP(tlock
->hash
),
85 /* Otherwise unlock the previous record. */
86 if (tdb_unlock_record(tdb
, tlock
->off
) != 0)
91 /* We have offset of old record: grab next */
92 if (tdb_rec_read(tdb
, tlock
->off
, rec
) == -1)
94 tlock
->off
= rec
->next
;
97 /* Iterate through chain */
100 if (tdb_rec_read(tdb
, tlock
->off
, rec
) == -1)
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"));
110 if (!TDB_DEAD(rec
)) {
111 /* Woohoo: we found one! */
112 if (tdb_lock_record(tdb
, tlock
->off
) != 0)
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)
124 tdb_unlock(tdb
, tlock
->hash
, tlock
->lock_rw
);
127 /* We finished iteration without finding anything */
128 tdb
->ecode
= TDB_SUCCESS
;
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
;
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
143 static int tdb_traverse_internal(struct tdb_context
*tdb
,
144 tdb_traverse_func fn
, void *private_data
,
145 struct tdb_traverse_lock
*tl
)
148 struct tdb_record rec
;
149 int ret
= 0, count
= 0;
152 /* This was in the initializaton, above, but the IRIX compiler
153 * did not like it. crh
155 tl
->next
= tdb
->travlocks
.next
;
157 /* fcntl locks don't stack: beware traverse inside traverse */
158 tdb
->travlocks
.next
= tl
;
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
) {
167 /* now read the full record */
168 key
.dptr
= tdb_alloc_read(tdb
, tl
->off
+ sizeof(rec
),
169 rec
.key_len
+ rec
.data_len
);
172 if (tdb_unlock(tdb
, tl
->hash
, tl
->lock_rw
) != 0)
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"));
178 key
.dsize
= rec
.key_len
;
179 dbuf
.dptr
= key
.dptr
+ rec
.key_len
;
180 dbuf
.dsize
= rec
.data_len
;
182 tdb_trace_1rec_retrec(tdb
, "traverse", key
, dbuf
);
184 /* Drop chain lock, call out */
185 if (tdb_unlock(tdb
, tl
->hash
, tl
->lock_rw
) != 0) {
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"));;
202 tdb_trace(tdb
, "tdb_traverse_end");
204 tdb
->travlocks
.next
= tl
->next
;
213 a write style traverse - temporarily marks the db read only
215 int tdb_traverse_read(struct tdb_context
*tdb
,
216 tdb_traverse_func fn
, void *private_data
)
218 struct tdb_traverse_lock tl
= { NULL
, 0, 0, F_RDLCK
};
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
)) {
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
--;
232 tdb_transaction_unlock(tdb
, F_RDLCK
);
238 a write style traverse - needs to get the transaction lock to
241 WARNING: The data buffer given to the callback fn does NOT meet the
242 alignment restrictions malloc gives you.
244 int tdb_traverse(struct tdb_context
*tdb
,
245 tdb_traverse_func fn
, void *private_data
)
247 struct tdb_traverse_lock tl
= { NULL
, 0, 0, F_WRLCK
};
250 if (tdb
->read_only
|| tdb
->traverse_read
) {
251 return tdb_traverse_read(tdb
, fn
, private_data
);
254 if (tdb_transaction_lock(tdb
, F_WRLCK
)) {
258 tdb
->traverse_write
++;
259 tdb_trace(tdb
, "tdb_traverse_start");
260 ret
= tdb_traverse_internal(tdb
, fn
, private_data
, &tl
);
261 tdb
->traverse_write
--;
263 tdb_transaction_unlock(tdb
, F_WRLCK
);
269 /* find the first entry in the database and return its key */
270 TDB_DATA
tdb_firstkey(struct tdb_context
*tdb
)
273 struct tdb_record rec
;
276 /* release any old lock */
277 if (tdb_unlock_record(tdb
, tdb
->travlocks
.off
) != 0)
279 tdb
->travlocks
.off
= tdb
->travlocks
.hash
= 0;
280 tdb
->travlocks
.lock_rw
= F_RDLCK
;
282 /* Grab first record: locks chain and returned record. */
283 off
= tdb_next_lock(tdb
, &tdb
->travlocks
, &rec
);
284 if (off
== 0 || off
== TDB_NEXT_LOCK_ERR
) {
285 tdb_trace_retrec(tdb
, "tdb_firstkey", tdb_null
);
288 /* now read the key */
289 key
.dsize
= rec
.key_len
;
290 key
.dptr
=tdb_alloc_read(tdb
,tdb
->travlocks
.off
+sizeof(rec
),key
.dsize
);
292 tdb_trace_retrec(tdb
, "tdb_firstkey", key
);
294 /* Unlock the hash chain of the record we just read. */
295 if (tdb_unlock(tdb
, tdb
->travlocks
.hash
, tdb
->travlocks
.lock_rw
) != 0)
296 TDB_LOG((tdb
, TDB_DEBUG_FATAL
, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
300 /* find the next entry in the database, returning its key */
301 TDB_DATA
tdb_nextkey(struct tdb_context
*tdb
, TDB_DATA oldkey
)
304 TDB_DATA key
= tdb_null
;
305 struct tdb_record rec
;
306 unsigned char *k
= NULL
;
309 /* Is locked key the old key? If so, traverse will be reliable. */
310 if (tdb
->travlocks
.off
) {
311 if (tdb_lock(tdb
,tdb
->travlocks
.hash
,tdb
->travlocks
.lock_rw
))
313 if (tdb_rec_read(tdb
, tdb
->travlocks
.off
, &rec
) == -1
314 || !(k
= tdb_alloc_read(tdb
,tdb
->travlocks
.off
+sizeof(rec
),
316 || memcmp(k
, oldkey
.dptr
, oldkey
.dsize
) != 0) {
317 /* No, it wasn't: unlock it and start from scratch */
318 if (tdb_unlock_record(tdb
, tdb
->travlocks
.off
) != 0) {
319 tdb_trace_1rec_retrec(tdb
, "tdb_nextkey",
324 if (tdb_unlock(tdb
, tdb
->travlocks
.hash
, tdb
->travlocks
.lock_rw
) != 0) {
328 tdb
->travlocks
.off
= 0;
334 if (!tdb
->travlocks
.off
) {
335 /* No previous element: do normal find, and lock record */
336 tdb
->travlocks
.off
= tdb_find_lock_hash(tdb
, oldkey
, tdb
->hash_fn(&oldkey
), tdb
->travlocks
.lock_rw
, &rec
);
337 if (!tdb
->travlocks
.off
) {
338 tdb_trace_1rec_retrec(tdb
, "tdb_nextkey", oldkey
, tdb_null
);
341 tdb
->travlocks
.hash
= BUCKET(rec
.full_hash
);
342 if (tdb_lock_record(tdb
, tdb
->travlocks
.off
) != 0) {
343 TDB_LOG((tdb
, TDB_DEBUG_FATAL
, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno
)));
347 oldhash
= tdb
->travlocks
.hash
;
349 /* Grab next record: locks chain and returned record,
350 unlocks old record */
351 off
= tdb_next_lock(tdb
, &tdb
->travlocks
, &rec
);
352 if (off
!= TDB_NEXT_LOCK_ERR
&& off
!= 0) {
353 key
.dsize
= rec
.key_len
;
354 key
.dptr
= tdb_alloc_read(tdb
, tdb
->travlocks
.off
+sizeof(rec
),
356 /* Unlock the chain of this new record */
357 if (tdb_unlock(tdb
, tdb
->travlocks
.hash
, tdb
->travlocks
.lock_rw
) != 0)
358 TDB_LOG((tdb
, TDB_DEBUG_FATAL
, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
360 /* Unlock the chain of old record */
361 if (tdb_unlock(tdb
, BUCKET(oldhash
), tdb
->travlocks
.lock_rw
) != 0)
362 TDB_LOG((tdb
, TDB_DEBUG_FATAL
, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
363 tdb_trace_1rec_retrec(tdb
, "tdb_nextkey", oldkey
, key
);