summaryrefslogtreecommitdiff
path: root/source3/locking/locking.c
blob: 97366a1f9b76cb704bb4ea4a96d34793721671f7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
/* 
   Unix SMB/CIFS implementation.
   Locking functions
   Copyright (C) Andrew Tridgell 1992-2000
   Copyright (C) Jeremy Allison 1992-2000
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   Revision History:

   12 aug 96: Erik.Devriendt@te6.siemens.be
   added support for shared memory implementation of share mode locking

   May 1997. Jeremy Allison (jallison@whistle.com). Modified share mode
   locking to deal with multiple share modes per open file.

   September 1997. Jeremy Allison (jallison@whistle.com). Added oplock
   support.

   rewrtten completely to use new tdb code. Tridge, Dec '99

   Added POSIX locking support. Jeremy Allison (jeremy@valinux.com), Apr. 2000.
*/

#include "includes.h"
uint16 global_smbpid;

/* the locking database handle */
static TDB_CONTEXT *tdb;

/****************************************************************************
 Debugging aid :-).
****************************************************************************/

static const char *lock_type_name(enum brl_type lock_type)
{
	return (lock_type == READ_LOCK) ? "READ" : "WRITE";
}

/****************************************************************************
 Utility function called to see if a file region is locked.
 If check_self is True, then checks on our own fd with the same locking context
 are still made. If check_self is False, then checks are not made on our own fd
 with the same locking context are not made.
****************************************************************************/

BOOL is_locked(files_struct *fsp,connection_struct *conn,
	       SMB_BIG_UINT count,SMB_BIG_UINT offset, 
	       enum brl_type lock_type, BOOL check_self)
{
	int snum = SNUM(conn);
	BOOL ret;
	
	if (count == 0)
		return(False);

	if (!lp_locking(snum) || !lp_strict_locking(snum))
		return(False);

	ret = !brl_locktest(fsp->dev, fsp->inode, fsp->fnum,
			     global_smbpid, sys_getpid(), conn->cnum, 
			     offset, count, lock_type, check_self);

	DEBUG(10,("is_locked: brl start=%.0f len=%.0f %s for file %s\n",
			(double)offset, (double)count, ret ? "locked" : "unlocked",
			fsp->fsp_name ));

	/*
	 * There is no lock held by an SMB daemon, check to
	 * see if there is a POSIX lock from a UNIX or NFS process.
	 */

	if(!ret && lp_posix_locking(snum)) {
		ret = is_posix_locked(fsp, offset, count, lock_type);

		DEBUG(10,("is_locked: posix start=%.0f len=%.0f %s for file %s\n",
				(double)offset, (double)count, ret ? "locked" : "unlocked",
				fsp->fsp_name ));
	}

	return ret;
}

/****************************************************************************
 Utility function called by locking requests.
****************************************************************************/

NTSTATUS do_lock(files_struct *fsp,connection_struct *conn, uint16 lock_pid,
		 SMB_BIG_UINT count,SMB_BIG_UINT offset,enum brl_type lock_type)
{
	NTSTATUS status;

	if (!lp_locking(SNUM(conn)))
		return NT_STATUS_OK;

	/* NOTE! 0 byte long ranges ARE allowed and should be stored  */


	DEBUG(10,("do_lock: lock type %s start=%.0f len=%.0f requested for file %s\n",
		  lock_type_name(lock_type), (double)offset, (double)count, fsp->fsp_name ));

	if (OPEN_FSP(fsp) && fsp->can_lock && (fsp->conn == conn)) {
		status = brl_lock(fsp->dev, fsp->inode, fsp->fnum,
				  lock_pid, sys_getpid(), conn->cnum, 
				  offset, count, 
				  lock_type);

		if (NT_STATUS_IS_OK(status) && lp_posix_locking(SNUM(conn))) {

			/*
			 * Try and get a POSIX lock on this range.
			 * Note that this is ok if it is a read lock
			 * overlapping on a different fd. JRA.
			 */

			if (!set_posix_lock(fsp, offset, count, lock_type)) {
				status = NT_STATUS_LOCK_NOT_GRANTED;
				/*
				 * We failed to map - we must now remove the brl
				 * lock entry.
				 */
				(void)brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
								lock_pid, sys_getpid(), conn->cnum, 
								offset, count);
			}
		}
	}

	return status;
}

/****************************************************************************
 Utility function called by unlocking requests.
****************************************************************************/

NTSTATUS do_unlock(files_struct *fsp,connection_struct *conn, uint16 lock_pid,
		   SMB_BIG_UINT count,SMB_BIG_UINT offset)
{
	BOOL ok = False;
	
	if (!lp_locking(SNUM(conn)))
		return NT_STATUS_OK;
	
	if (!OPEN_FSP(fsp) || !fsp->can_lock || (fsp->conn != conn)) {
		return NT_STATUS_INVALID_HANDLE;
	}
	
	DEBUG(10,("do_unlock: unlock start=%.0f len=%.0f requested for file %s\n",
		  (double)offset, (double)count, fsp->fsp_name ));

	/*
	 * Remove the existing lock record from the tdb lockdb
	 * before looking at POSIX locks. If this record doesn't
	 * match then don't bother looking to remove POSIX locks.
	 */

	ok = brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
			lock_pid, sys_getpid(), conn->cnum, offset, count);
   
	if (!ok) {
		DEBUG(10,("do_unlock: returning ERRlock.\n" ));
		return NT_STATUS_LOCK_NOT_GRANTED;
	}

	if (!lp_posix_locking(SNUM(conn)))
		return NT_STATUS_OK;

	(void)release_posix_lock(fsp, offset, count);

	return NT_STATUS_OK;
}

/****************************************************************************
 Remove any locks on this fd. Called from file_close().
****************************************************************************/

void locking_close_file(files_struct *fsp)
{
	pid_t pid = sys_getpid();

	if (!lp_locking(SNUM(fsp->conn)))
		return;

	/*
	 * Just release all the brl locks, no need to release individually.
	 */

	brl_close(fsp->dev, fsp->inode, pid, fsp->conn->cnum, fsp->fnum);

	if(lp_posix_locking(SNUM(fsp->conn))) {

	 	/* 
		 * Release all the POSIX locks.
		 */
		posix_locking_close_file(fsp);

	}
}

/****************************************************************************
 Initialise the locking functions.
****************************************************************************/

static int open_read_only;

BOOL locking_init(int read_only)
{
	brl_init(read_only);

	if (tdb)
		return True;

	tdb = tdb_open_log(lock_path("locking.tdb"), 
		       0, TDB_DEFAULT|(read_only?0x0:TDB_CLEAR_IF_FIRST), 
		       read_only?O_RDONLY:O_RDWR|O_CREAT,
		       0644);

	if (!tdb) {
		DEBUG(0,("ERROR: Failed to initialise locking database\n"));
		return False;
	}
	
	if (!posix_locking_init(read_only))
		return False;

	open_read_only = read_only;

	return True;
}

/*******************************************************************
 Deinitialize the share_mode management.
******************************************************************/

BOOL locking_end(void)
{

	brl_shutdown(open_read_only);
	if (tdb) {

		if (tdb_close(tdb) != 0)
			return False;
	}

	return True;
}

/*******************************************************************
 Form a static locking key for a dev/inode pair.
******************************************************************/

static TDB_DATA locking_key(SMB_DEV_T dev, SMB_INO_T inode)
{
	static struct locking_key key;
	TDB_DATA kbuf;

	memset(&key, '\0', sizeof(key));
	key.dev = dev;
	key.inode = inode;
	kbuf.dptr = (char *)&key;
	kbuf.dsize = sizeof(key);
	return kbuf;
}

static TDB_DATA locking_key_fsp(files_struct *fsp)
{
	return locking_key(fsp->dev, fsp->inode);
}

/*******************************************************************
 Lock a hash bucket entry.
******************************************************************/

BOOL lock_share_entry(connection_struct *conn,
		      SMB_DEV_T dev, SMB_INO_T inode)
{
	return tdb_chainlock(tdb, locking_key(dev, inode)) == 0;
}

/*******************************************************************
 Unlock a hash bucket entry.
******************************************************************/

void unlock_share_entry(connection_struct *conn,
			SMB_DEV_T dev, SMB_INO_T inode)
{
	tdb_chainunlock(tdb, locking_key(dev, inode));
}

/*******************************************************************
 Lock a hash bucket entry. use a fsp for convenience
******************************************************************/

BOOL lock_share_entry_fsp(files_struct *fsp)
{
	return tdb_chainlock(tdb, locking_key(fsp->dev, fsp->inode)) == 0;
}

/*******************************************************************
 Unlock a hash bucket entry.
******************************************************************/

void unlock_share_entry_fsp(files_struct *fsp)
{
	tdb_chainunlock(tdb, locking_key(fsp->dev, fsp->inode));
}

/*******************************************************************
 Print out a share mode.
********************************************************************/

static char *share_mode_str(int num, share_mode_entry *e)
{
	static pstring share_str;

	slprintf(share_str, sizeof(share_str)-1, "share_mode_entry[%d]: \
pid = %u, share_mode = 0x%x, port = 0x%x, type= 0x%x, file_id = %lu, dev = 0x%x, inode = %.0f",
	num, e->pid, e->share_mode, e->op_port, e->op_type, e->share_file_id,
	(unsigned int)e->dev, (double)e->inode );

	return share_str;
}

/*******************************************************************
 Print out a share mode table.
********************************************************************/

static void print_share_mode_table(struct locking_data *data)
{
	int num_share_modes = data->u.num_share_mode_entries;
	share_mode_entry *shares = (share_mode_entry *)(data + 1);
	int i;

	for (i = 0; i < num_share_modes; i++) {
		share_mode_entry *entry_p = &shares[i];
		DEBUG(10,("print_share_mode_table: %s\n", share_mode_str(i, entry_p) ));
	}
}

/*******************************************************************
 Get all share mode entries for a dev/inode pair.
********************************************************************/

int get_share_modes(connection_struct *conn, 
		    SMB_DEV_T dev, SMB_INO_T inode, 
		    share_mode_entry **pp_shares)
{
	TDB_DATA dbuf;
	struct locking_data *data;
	int num_share_modes;
	share_mode_entry *shares = NULL;

	*pp_shares = NULL;

	dbuf = tdb_fetch(tdb, locking_key(dev, inode));
	if (!dbuf.dptr)
		return 0;

	data = (struct locking_data *)dbuf.dptr;
	num_share_modes = data->u.num_share_mode_entries;
	if(num_share_modes) {
		int i;
		int del_count = 0;

		shares = (share_mode_entry *)memdup(dbuf.dptr + sizeof(*data),	
						num_share_modes * sizeof(share_mode_entry));

		if (!shares) {
			SAFE_FREE(dbuf.dptr);
			return 0;
		}

		/*
		 * Ensure that each entry has a real process attached.
		 */

		for (i = 0; i < num_share_modes; ) {
			share_mode_entry *entry_p = &shares[i];
			if (process_exists(entry_p->pid)) {
				DEBUG(10,("get_share_modes: %s\n", share_mode_str(i, entry_p) ));
				i++;
			} else {
				DEBUG(10,("get_share_modes: deleted %s\n", share_mode_str(i, entry_p) ));
				memcpy( &shares[i], &shares[i+1],
					sizeof(share_mode_entry) * (num_share_modes - i - 1));
				num_share_modes--;
				del_count++;
			}
		}

		/* Did we delete any ? If so, re-store in tdb. */
		if (del_count) {
			data->u.num_share_mode_entries = num_share_modes;
			
			if (num_share_modes)
				memcpy(dbuf.dptr + sizeof(*data), shares,
						num_share_modes * sizeof(share_mode_entry));

			/* The record has shrunk a bit */
			dbuf.dsize -= del_count * sizeof(share_mode_entry);

			if (tdb_store(tdb, locking_key(dev, inode), dbuf, TDB_REPLACE) == -1) {
				SAFE_FREE(shares);
				SAFE_FREE(dbuf.dptr);
				return 0;
			}
		}
	}

	SAFE_FREE(dbuf.dptr);
	*pp_shares = shares;
	return num_share_modes;
}

/*******************************************************************
 Fill a share mode entry.
********************************************************************/

static void fill_share_mode(char *p, files_struct *fsp, uint16 port, uint16 op_type)
{
	share_mode_entry *e = (share_mode_entry *)p;
	void *x = &e->time; /* Needed to force alignment. p may not be aligned.... */

	memset(e, '\0', sizeof(share_mode_entry));
	e->pid = sys_getpid();
	e->share_mode = fsp->share_mode;
	e->op_port = port;
	e->op_type = op_type;
	memcpy(x, &fsp->open_time, sizeof(struct timeval));
	e->share_file_id = fsp->file_id;
	e->dev = fsp->dev;
	e->inode = fsp->inode;
}

/*******************************************************************
 Check if two share mode entries are identical, ignoring oplock 
 and port info. 
********************************************************************/

BOOL share_modes_identical( share_mode_entry *e1, share_mode_entry *e2)
{
#if 1 /* JRA PARANOIA TEST - REMOVE LATER */
	if (e1->pid == e2->pid &&
		e1->share_file_id == e2->share_file_id &&
		e1->dev == e2->dev &&
		e1->inode == e2->inode &&
		(e1->share_mode & ~DELETE_ON_CLOSE_FLAG) != (e2->share_mode & ~DELETE_ON_CLOSE_FLAG)) {
			DEBUG(0,("PANIC: share_modes_identical: share_mode missmatch (e1 = %u, e2 = %u). Logic error.\n",
				(unsigned int)(e1->share_mode & ~DELETE_ON_CLOSE_FLAG),
				(unsigned int)(e2->share_mode & ~DELETE_ON_CLOSE_FLAG) ));
		smb_panic("PANIC: share_modes_identical logic error.\n");
	}
#endif

	return (e1->pid == e2->pid &&
		(e1->share_mode & ~DELETE_ON_CLOSE_FLAG) == (e2->share_mode & ~DELETE_ON_CLOSE_FLAG) &&
		e1->dev == e2->dev &&
		e1->inode == e2->inode &&
		e1->share_file_id == e2->share_file_id );
}

/*******************************************************************
 Delete a specific share mode. Return the number
 of entries left, and a memdup'ed copy of the entry deleted (if required).
 Ignore if no entry deleted.
********************************************************************/

ssize_t del_share_entry( SMB_DEV_T dev, SMB_INO_T inode,
			share_mode_entry *entry, share_mode_entry **ppse)
{
	TDB_DATA dbuf;
	struct locking_data *data;
	int i, del_count=0;
	share_mode_entry *shares;
	ssize_t count = 0;

	if (ppse)
		*ppse = NULL;

	/* read in the existing share modes */
	dbuf = tdb_fetch(tdb, locking_key(dev, inode));
	if (!dbuf.dptr)
		return -1;

	data = (struct locking_data *)dbuf.dptr;
	shares = (share_mode_entry *)(dbuf.dptr + sizeof(*data));

	/*
	 * Find any with this pid and delete it
	 * by overwriting with the rest of the data 
	 * from the record.
	 */

	DEBUG(10,("del_share_entry: num_share_modes = %d\n", data->u.num_share_mode_entries ));

	for (i=0;i<data->u.num_share_mode_entries;) {
		if (share_modes_identical(&shares[i], entry)) {
			DEBUG(10,("del_share_entry: deleted %s\n",
				share_mode_str(i, &shares[i]) ));
			if (ppse)
				*ppse = memdup(&shares[i], sizeof(*shares));
			data->u.num_share_mode_entries--;
			memmove(&shares[i], &shares[i+1], 
				dbuf.dsize - (sizeof(*data) + (i+1)*sizeof(*shares)));
			del_count++;

			DEBUG(10,("del_share_entry: deleting entry %d\n", i ));

		} else {
			i++;
		}
	}

	if (del_count) {
		/* the record may have shrunk a bit */
		dbuf.dsize -= del_count * sizeof(*shares);

		count = (ssize_t)data->u.num_share_mode_entries;

		/* store it back in the database */
		if (data->u.num_share_mode_entries == 0) {
			if (tdb_delete(tdb, locking_key(dev, inode)) == -1)
				count = -1;
		} else {
			if (tdb_store(tdb, locking_key(dev, inode), dbuf, TDB_REPLACE) == -1)
				count = -1;
		}
	}
	DEBUG(10,("del_share_entry: Remaining table.\n"));
	print_share_mode_table((struct locking_data *)dbuf.dptr);
	SAFE_FREE(dbuf.dptr);
	return count;
}

/*******************************************************************
 Del the share mode of a file for this process. Return the number
 of entries left, and a memdup'ed copy of the entry deleted.
********************************************************************/

ssize_t del_share_mode(files_struct *fsp, share_mode_entry **ppse)
{
	share_mode_entry entry;

	/*
	 * Fake up a share_mode_entry for comparisons.
	 */

	fill_share_mode((char *)&entry, fsp, 0, 0);
	return del_share_entry(fsp->dev, fsp->inode, &entry, ppse);
}

/*******************************************************************
 Set the share mode of a file. Return False on fail, True on success.
********************************************************************/

BOOL set_share_mode(files_struct *fsp, uint16 port, uint16 op_type)
{
	TDB_DATA dbuf;
	struct locking_data *data;
	char *p=NULL;
	int size;
	BOOL ret = True;
		
	/* read in the existing share modes if any */
	dbuf = tdb_fetch(tdb, locking_key_fsp(fsp));
	if (!dbuf.dptr) {
		/* we'll need to create a new record */
		pstring fname;

		pstrcpy(fname, fsp->conn->connectpath);
		pstrcat(fname, "/");
		pstrcat(fname, fsp->fsp_name);

		size = sizeof(*data) + sizeof(share_mode_entry) + strlen(fname) + 1;
		p = (char *)malloc(size);
		if (!p)
			return False;
		data = (struct locking_data *)p;
		data->u.num_share_mode_entries = 1;
	
		DEBUG(10,("set_share_mode: creating entry for file %s. num_share_modes = 1\n",
			fsp->fsp_name ));

		pstrcpy(p + sizeof(*data) + sizeof(share_mode_entry), fname);
		fill_share_mode(p + sizeof(*data), fsp, port, op_type);
		dbuf.dptr = p;
		dbuf.dsize = size;
		if (tdb_store(tdb, locking_key_fsp(fsp), dbuf, TDB_REPLACE) == -1)
			ret = False;

		print_share_mode_table((struct locking_data *)p);

		SAFE_FREE(p);
		return ret;
	}

	/* we're adding to an existing entry - this is a bit fiddly */
	data = (struct locking_data *)dbuf.dptr;

	data->u.num_share_mode_entries++;
	
	DEBUG(10,("set_share_mode: adding entry for file %s. new num_share_modes = %d\n",
		fsp->fsp_name, data->u.num_share_mode_entries ));

	size = dbuf.dsize + sizeof(share_mode_entry);
	p = malloc(size);
	if (!p)
		return False;
	memcpy(p, dbuf.dptr, sizeof(*data));
	fill_share_mode(p + sizeof(*data), fsp, port, op_type);
	memcpy(p + sizeof(*data) + sizeof(share_mode_entry), dbuf.dptr + sizeof(*data),
	       dbuf.dsize - sizeof(*data));
	SAFE_FREE(dbuf.dptr);
	dbuf.dptr = p;
	dbuf.dsize = size;
	if (tdb_store(tdb, locking_key_fsp(fsp), dbuf, TDB_REPLACE) == -1)
		ret = False;
	print_share_mode_table((struct locking_data *)p);
	SAFE_FREE(p);
	return ret;
}

/*******************************************************************
 A generic in-place modification call for share mode entries.
********************************************************************/

static BOOL mod_share_mode( SMB_DEV_T dev, SMB_INO_T inode, share_mode_entry *entry,
			   void (*mod_fn)(share_mode_entry *, SMB_DEV_T, SMB_INO_T, void *),
			   void *param)
{
	TDB_DATA dbuf;
	struct locking_data *data;
	int i;
	share_mode_entry *shares;
	BOOL need_store=False;

	/* read in the existing share modes */
	dbuf = tdb_fetch(tdb, locking_key(dev, inode));
	if (!dbuf.dptr)
		return False;

	data = (struct locking_data *)dbuf.dptr;
	shares = (share_mode_entry *)(dbuf.dptr + sizeof(*data));

	/* find any with our pid and call the supplied function */
	for (i=0;i<data->u.num_share_mode_entries;i++) {
		if (share_modes_identical(entry, &shares[i])) {
			mod_fn(&shares[i], dev, inode, param);
			need_store=True;
		}
	}

	/* if the mod fn was called then store it back */
	if (need_store) {
		if (data->u.num_share_mode_entries == 0) {
			if (tdb_delete(tdb, locking_key(dev, inode)) == -1)
				need_store = False;
		} else {
			if (tdb_store(tdb, locking_key(dev, inode), dbuf, TDB_REPLACE) == -1)
				need_store = False;
		}
	}

	SAFE_FREE(dbuf.dptr);
	return need_store;
}

/*******************************************************************
 Static function that actually does the work for the generic function
 below.
********************************************************************/

static void remove_share_oplock_fn(share_mode_entry *entry, SMB_DEV_T dev, SMB_INO_T inode, 
                                   void *param)
{
	DEBUG(10,("remove_share_oplock_fn: removing oplock info for entry dev=%x ino=%.0f\n",
		  (unsigned int)dev, (double)inode ));
	/* Delete the oplock info. */
	entry->op_port = 0;
	entry->op_type = NO_OPLOCK;
}

/*******************************************************************
 Remove an oplock port and mode entry from a share mode.
********************************************************************/

BOOL remove_share_oplock(files_struct *fsp)
{
	share_mode_entry entry;
	/*
	 * Fake up an entry for comparisons...
	 */
	fill_share_mode((char *)&entry, fsp, 0, 0);
	return mod_share_mode(fsp->dev, fsp->inode, &entry, remove_share_oplock_fn, NULL);
}

/*******************************************************************
 Static function that actually does the work for the generic function
 below.
********************************************************************/

static void downgrade_share_oplock_fn(share_mode_entry *entry, SMB_DEV_T dev, SMB_INO_T inode, 
                                   void *param)
{
	DEBUG(10,("downgrade_share_oplock_fn: downgrading oplock info for entry dev=%x ino=%.0f\n",
		  (unsigned int)dev, (double)inode ));
	entry->op_type = LEVEL_II_OPLOCK;
}

/*******************************************************************
 Downgrade a oplock type from exclusive to level II.
********************************************************************/

BOOL downgrade_share_oplock(files_struct *fsp)
{
	share_mode_entry entry;
	/*
	 * Fake up an entry for comparisons...
	 */
	fill_share_mode((char *)&entry, fsp, 0, 0);
	return mod_share_mode(fsp->dev, fsp->inode, &entry, downgrade_share_oplock_fn, NULL);
}

/*******************************************************************
 Get/Set the delete on close flag in a set of share modes.
 Return False on fail, True on success.
********************************************************************/

BOOL modify_delete_flag( SMB_DEV_T dev, SMB_INO_T inode, BOOL delete_on_close)
{
	TDB_DATA dbuf;
	struct locking_data *data;
	int i;
	share_mode_entry *shares;

	/* read in the existing share modes */
	dbuf = tdb_fetch(tdb, locking_key(dev, inode));
	if (!dbuf.dptr)
		return False;

	data = (struct locking_data *)dbuf.dptr;
	shares = (share_mode_entry *)(dbuf.dptr + sizeof(*data));

	/* Set/Unset the delete on close element. */
	for (i=0;i<data->u.num_share_mode_entries;i++,shares++) {
		shares->share_mode = (delete_on_close ?
                            (shares->share_mode | DELETE_ON_CLOSE_FLAG) :
                            (shares->share_mode & ~DELETE_ON_CLOSE_FLAG) );
	}

	/* store it back */
	if (data->u.num_share_mode_entries) {
		if (tdb_store(tdb, locking_key(dev,inode), dbuf, TDB_REPLACE)==-1) {
			SAFE_FREE(dbuf.dptr);
			return False;
		}
	}

	SAFE_FREE(dbuf.dptr);
	return True;
}

/****************************************************************************
 Traverse the whole database with this function, calling traverse_callback
 on each share mode
****************************************************************************/

static int traverse_fn(TDB_CONTEXT *the_tdb, TDB_DATA kbuf, TDB_DATA dbuf, 
                       void* state)
{
	struct locking_data *data;
	share_mode_entry *shares;
	char *name;
	int i;

	SHAREMODE_FN(traverse_callback) = (SHAREMODE_FN_CAST())state;

	data = (struct locking_data *)dbuf.dptr;
	shares = (share_mode_entry *)(dbuf.dptr + sizeof(*data));
	name = dbuf.dptr + sizeof(*data) + data->u.num_share_mode_entries*sizeof(*shares);

	for (i=0;i<data->u.num_share_mode_entries;i++) {
		traverse_callback(&shares[i], name);
	}
	return 0;
}

/*******************************************************************
 Call the specified function on each entry under management by the
 share mode system.
********************************************************************/

int share_mode_forall(SHAREMODE_FN(fn))
{
	if (!tdb)
		return 0;
	return tdb_traverse(tdb, traverse_fn, (void*)fn);
}