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 2 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, write to the Free Software
26 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
29 #include "tdb_private.h"
31 /* a byte range locking function - return 0 on success
32 this functions locks/unlocks 1 byte at the specified offset.
34 On error, errno is also set so that errors are passed back properly
37 note that a len of zero means lock to end of file
39 int tdb_brlock_len(struct tdb_context *tdb, tdb_off_t offset,
40 int rw_type, int lck_type, int probe, size_t len)
45 if (tdb->flags & TDB_NOLOCK) {
49 if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
50 tdb->ecode = TDB_ERR_RDONLY;
55 fl.l_whence = SEEK_SET;
61 ret = fcntl(tdb->fd,lck_type,&fl);
62 } while (ret == -1 && errno == EINTR);
65 /* Generic lock error. errno set by fcntl.
66 * EAGAIN is an expected return from non-blocking
68 if (errno != EAGAIN) {
69 TDB_LOG((tdb, 5, "tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d: %s\n",
70 tdb->fd, offset, rw_type, lck_type, len,
72 } else if (!probe && lck_type != F_SETLK) {
73 /* Ensure error code is set for log fun to examine. */
74 tdb->ecode = TDB_ERR_LOCK;
75 TDB_LOG((tdb, 5,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d\n",
76 tdb->fd, offset, rw_type, lck_type));
78 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
85 upgrade a read lock to a write lock. This needs to be handled in a
86 special way as some OSes (such as solaris) have too conservative
87 deadlock detection and claim a deadlock when progress can be
88 made. For those OSes we may loop for a while.
90 int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
95 if (tdb_brlock_len(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
98 if (errno != EDEADLK) {
101 /* sleep for as short a time as we can - more portable than usleep() */
104 select(0, NULL, NULL, NULL, &tv);
110 /* a byte range locking function - return 0 on success
111 this functions locks/unlocks 1 byte at the specified offset.
113 On error, errno is also set so that errors are passed back properly
114 through tdb_open(). */
115 int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
116 int rw_type, int lck_type, int probe)
118 return tdb_brlock_len(tdb, offset, rw_type, lck_type, probe, 1);
121 /* lock a list in the database. list -1 is the alloc list */
122 int tdb_lock(struct tdb_context *tdb, int list, int ltype)
124 if (list < -1 || list >= (int)tdb->header.hash_size) {
125 TDB_LOG((tdb, 0,"tdb_lock: invalid list %d for ltype=%d\n",
129 if (tdb->flags & TDB_NOLOCK)
132 /* Since fcntl locks don't nest, we do a lock for the first one,
133 and simply bump the count for future ones */
134 if (tdb->locked[list+1].count == 0) {
135 if (tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list,ltype,F_SETLKW, 0)) {
136 TDB_LOG((tdb, 0,"tdb_lock failed on list %d ltype=%d (%s)\n",
137 list, ltype, strerror(errno)));
140 tdb->locked[list+1].ltype = ltype;
143 tdb->locked[list+1].count++;
147 /* unlock the database: returns void because it's too late for errors. */
148 /* changed to return int it may be interesting to know there
149 has been an error --simo */
150 int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
154 if (tdb->flags & TDB_NOLOCK)
158 if (list < -1 || list >= (int)tdb->header.hash_size) {
159 TDB_LOG((tdb, 0, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
163 if (tdb->locked[list+1].count==0) {
164 TDB_LOG((tdb, 0, "tdb_unlock: count is 0\n"));
168 if (tdb->locked[list+1].count == 1) {
169 /* Down to last nested lock: unlock underneath */
170 ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK, F_SETLKW, 0);
175 tdb->locked[list+1].count--;
178 TDB_LOG((tdb, 0,"tdb_unlock: An error occurred unlocking!\n"));
184 /* lock/unlock entire database */
185 int tdb_lockall(struct tdb_context *tdb)
189 /* There are no locks on read-only dbs */
190 if (tdb->read_only || tdb->traverse_read)
191 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
192 for (i = 0; i < tdb->header.hash_size; i++)
193 if (tdb_lock(tdb, i, F_WRLCK))
196 /* If error, release locks we have... */
197 if (i < tdb->header.hash_size) {
200 for ( j = 0; j < i; j++)
201 tdb_unlock(tdb, j, F_WRLCK);
202 return TDB_ERRCODE(TDB_ERR_NOLOCK, -1);
207 void tdb_unlockall(struct tdb_context *tdb)
210 for (i=0; i < tdb->header.hash_size; i++)
211 tdb_unlock(tdb, i, F_WRLCK);
214 /* lock/unlock one hash chain. This is meant to be used to reduce
215 contention - it cannot guarantee how many records will be locked */
216 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
218 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
221 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
223 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
226 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
228 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
231 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
233 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
238 /* record lock stops delete underneath */
239 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
241 return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0) : 0;
245 Write locks override our own fcntl readlocks, so check it here.
246 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
247 an error to fail to get the lock here.
249 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
251 struct tdb_traverse_lock *i;
252 for (i = &tdb->travlocks; i; i = i->next)
255 return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1);
259 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
260 an error to fail to get the lock here.
262 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
264 return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0);
267 /* fcntl locks don't stack: avoid unlocking someone else's */
268 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
270 struct tdb_traverse_lock *i;
275 for (i = &tdb->travlocks; i; i = i->next)
278 return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0) : 0);