summaryrefslogtreecommitdiff
path: root/drivers/md/dm-table.c
blob: e8361b191b9b223baef941bfc14212dc052d127f (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
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
/*
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/namei.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <asm/atomic.h>

#define DM_MSG_PREFIX "table"

#define MAX_DEPTH 16
#define NODE_SIZE L1_CACHE_BYTES
#define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t))
#define CHILDREN_PER_NODE (KEYS_PER_NODE + 1)

/*
 * The table has always exactly one reference from either mapped_device->map
 * or hash_cell->new_map. This reference is not counted in table->holders.
 * A pair of dm_create_table/dm_destroy_table functions is used for table
 * creation/destruction.
 *
 * Temporary references from the other code increase table->holders. A pair
 * of dm_table_get/dm_table_put functions is used to manipulate it.
 *
 * When the table is about to be destroyed, we wait for table->holders to
 * drop to zero.
 */

struct dm_table {
	struct mapped_device *md;
	atomic_t holders;

	/* btree table */
	unsigned int depth;
	unsigned int counts[MAX_DEPTH];	/* in nodes */
	sector_t *index[MAX_DEPTH];

	unsigned int num_targets;
	unsigned int num_allocated;
	sector_t *highs;
	struct dm_target *targets;

	unsigned barriers_supported:1;

	/*
	 * Indicates the rw permissions for the new logical
	 * device.  This should be a combination of FMODE_READ
	 * and FMODE_WRITE.
	 */
	fmode_t mode;

	/* a list of devices used by this table */
	struct list_head devices;

	/*
	 * These are optimistic limits taken from all the
	 * targets, some targets will need smaller limits.
	 */
	struct io_restrictions limits;

	/* events get handed up using this callback */
	void (*event_fn)(void *);
	void *event_context;
};

/*
 * Similar to ceiling(log_size(n))
 */
static unsigned int int_log(unsigned int n, unsigned int base)
{
	int result = 0;

	while (n > 1) {
		n = dm_div_up(n, base);
		result++;
	}

	return result;
}

/*
 * Returns the minimum that is _not_ zero, unless both are zero.
 */
#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))

/*
 * Combine two io_restrictions, always taking the lower value.
 */
static void combine_restrictions_low(struct io_restrictions *lhs,
				     struct io_restrictions *rhs)
{
	lhs->max_sectors =
		min_not_zero(lhs->max_sectors, rhs->max_sectors);

	lhs->max_phys_segments =
		min_not_zero(lhs->max_phys_segments, rhs->max_phys_segments);

	lhs->max_hw_segments =
		min_not_zero(lhs->max_hw_segments, rhs->max_hw_segments);

	lhs->hardsect_size = max(lhs->hardsect_size, rhs->hardsect_size);

	lhs->max_segment_size =
		min_not_zero(lhs->max_segment_size, rhs->max_segment_size);

	lhs->max_hw_sectors =
		min_not_zero(lhs->max_hw_sectors, rhs->max_hw_sectors);

	lhs->seg_boundary_mask =
		min_not_zero(lhs->seg_boundary_mask, rhs->seg_boundary_mask);

	lhs->bounce_pfn = min_not_zero(lhs->bounce_pfn, rhs->bounce_pfn);

	lhs->no_cluster |= rhs->no_cluster;
}

/*
 * Calculate the index of the child node of the n'th node k'th key.
 */
static inline unsigned int get_child(unsigned int n, unsigned int k)
{
	return (n * CHILDREN_PER_NODE) + k;
}

/*
 * Return the n'th node of level l from table t.
 */
static inline sector_t *get_node(struct dm_table *t,
				 unsigned int l, unsigned int n)
{
	return t->index[l] + (n * KEYS_PER_NODE);
}

/*
 * Return the highest key that you could lookup from the n'th
 * node on level l of the btree.
 */
static sector_t high(struct dm_table *t, unsigned int l, unsigned int n)
{
	for (; l < t->depth - 1; l++)
		n = get_child(n, CHILDREN_PER_NODE - 1);

	if (n >= t->counts[l])
		return (sector_t) - 1;

	return get_node(t, l, n)[KEYS_PER_NODE - 1];
}

/*
 * Fills in a level of the btree based on the highs of the level
 * below it.
 */
static int setup_btree_index(unsigned int l, struct dm_table *t)
{
	unsigned int n, k;
	sector_t *node;

	for (n = 0U; n < t->counts[l]; n++) {
		node = get_node(t, l, n);

		for (k = 0U; k < KEYS_PER_NODE; k++)
			node[k] = high(t, l + 1, get_child(n, k));
	}

	return 0;
}

void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size)
{
	unsigned long size;
	void *addr;

	/*
	 * Check that we're not going to overflow.
	 */
	if (nmemb > (ULONG_MAX / elem_size))
		return NULL;

	size = nmemb * elem_size;
	addr = vmalloc(size);
	if (addr)
		memset(addr, 0, size);

	return addr;
}

/*
 * highs, and targets are managed as dynamic arrays during a
 * table load.
 */
static int alloc_targets(struct dm_table *t, unsigned int num)
{
	sector_t *n_highs;
	struct dm_target *n_targets;
	int n = t->num_targets;

	/*
	 * Allocate both the target array and offset array at once.
	 * Append an empty entry to catch sectors beyond the end of
	 * the device.
	 */
	n_highs = (sector_t *) dm_vcalloc(num + 1, sizeof(struct dm_target) +
					  sizeof(sector_t));
	if (!n_highs)
		return -ENOMEM;

	n_targets = (struct dm_target *) (n_highs + num);

	if (n) {
		memcpy(n_highs, t->highs, sizeof(*n_highs) * n);
		memcpy(n_targets, t->targets, sizeof(*n_targets) * n);
	}

	memset(n_highs + n, -1, sizeof(*n_highs) * (num - n));
	vfree(t->highs);

	t->num_allocated = num;
	t->highs = n_highs;
	t->targets = n_targets;

	return 0;
}

int dm_table_create(struct dm_table **result, fmode_t mode,
		    unsigned num_targets, struct mapped_device *md)
{
	struct dm_table *t = kzalloc(sizeof(*t), GFP_KERNEL);

	if (!t)
		return -ENOMEM;

	INIT_LIST_HEAD(&t->devices);
	atomic_set(&t->holders, 0);
	t->barriers_supported = 1;

	if (!num_targets)
		num_targets = KEYS_PER_NODE;

	num_targets = dm_round_up(num_targets, KEYS_PER_NODE);

	if (alloc_targets(t, num_targets)) {
		kfree(t);
		t = NULL;
		return -ENOMEM;
	}

	t->mode = mode;
	t->md = md;
	*result = t;
	return 0;
}

static void free_devices(struct list_head *devices)
{
	struct list_head *tmp, *next;

	list_for_each_safe(tmp, next, devices) {
		struct dm_dev_internal *dd =
		    list_entry(tmp, struct dm_dev_internal, list);
		kfree(dd);
	}
}

void dm_table_destroy(struct dm_table *t)
{
	unsigned int i;

	while (atomic_read(&t->holders))
		msleep(1);
	smp_mb();

	/* free the indexes (see dm_table_complete) */
	if (t->depth >= 2)
		vfree(t->index[t->depth - 2]);

	/* free the targets */
	for (i = 0; i < t->num_targets; i++) {
		struct dm_target *tgt = t->targets + i;

		if (tgt->type->dtr)
			tgt->type->dtr(tgt);

		dm_put_target_type(tgt->type);
	}

	vfree(t->highs);

	/* free the device list */
	if (t->devices.next != &t->devices) {
		DMWARN("devices still present during destroy: "
		       "dm_table_remove_device calls missing");

		free_devices(&t->devices);
	}

	kfree(t);
}

void dm_table_get(struct dm_table *t)
{
	atomic_inc(&t->holders);
}

void dm_table_put(struct dm_table *t)
{
	if (!t)
		return;

	smp_mb__before_atomic_dec();
	atomic_dec(&t->holders);
}

/*
 * Checks to see if we need to extend highs or targets.
 */
static inline int check_space(struct dm_table *t)
{
	if (t->num_targets >= t->num_allocated)
		return alloc_targets(t, t->num_allocated * 2);

	return 0;
}

/*
 * See if we've already got a device in the list.
 */
static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev)
{
	struct dm_dev_internal *dd;

	list_for_each_entry (dd, l, list)
		if (dd->dm_dev.bdev->bd_dev == dev)
			return dd;

	return NULL;
}

/*
 * Open a device so we can use it as a map destination.
 */
static int open_dev(struct dm_dev_internal *d, dev_t dev,
		    struct mapped_device *md)
{
	static char *_claim_ptr = "I belong to device-mapper";
	struct block_device *bdev;

	int r;

	BUG_ON(d->dm_dev.bdev);

	bdev = open_by_devnum(dev, d->dm_dev.mode);
	if (IS_ERR(bdev))
		return PTR_ERR(bdev);
	r = bd_claim_by_disk(bdev, _claim_ptr, dm_disk(md));
	if (r)
		blkdev_put(bdev, d->dm_dev.mode);
	else
		d->dm_dev.bdev = bdev;
	return r;
}

/*
 * Close a device that we've been using.
 */
static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
{
	if (!d->dm_dev.bdev)
		return;

	bd_release_from_disk(d->dm_dev.bdev, dm_disk(md));
	blkdev_put(d->dm_dev.bdev, d->dm_dev.mode);
	d->dm_dev.bdev = NULL;
}

/*
 * If possible, this checks an area of a destination device is valid.
 */
static int check_device_area(struct dm_dev_internal *dd, sector_t start,
			     sector_t len)
{
	sector_t dev_size = dd->dm_dev.bdev->bd_inode->i_size >> SECTOR_SHIFT;

	if (!dev_size)
		return 1;

	return ((start < dev_size) && (len <= (dev_size - start)));
}

/*
 * This upgrades the mode on an already open dm_dev, being
 * careful to leave things as they were if we fail to reopen the
 * device and not to touch the existing bdev field in case
 * it is accessed concurrently inside dm_table_any_congested().
 */
static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
			struct mapped_device *md)
{
	int r;
	struct dm_dev_internal dd_new, dd_old;

	dd_new = dd_old = *dd;

	dd_new.dm_dev.mode |= new_mode;
	dd_new.dm_dev.bdev = NULL;

	r = open_dev(&dd_new, dd->dm_dev.bdev->bd_dev, md);
	if (r)
		return r;

	dd->dm_dev.mode |= new_mode;
	close_dev(&dd_old, md);

	return 0;
}

/*
 * Add a device to the list, or just increment the usage count if
 * it's already present.
 */
static int __table_get_device(struct dm_table *t, struct dm_target *ti,
			      const char *path, sector_t start, sector_t len,
			      fmode_t mode, struct dm_dev **result)
{
	int r;
	dev_t uninitialized_var(dev);
	struct dm_dev_internal *dd;
	unsigned int major, minor;

	BUG_ON(!t);

	if (sscanf(path, "%u:%u", &major, &minor) == 2) {
		/* Extract the major/minor numbers */
		dev = MKDEV(major, minor);
		if (MAJOR(dev) != major || MINOR(dev) != minor)
			return -EOVERFLOW;
	} else {
		/* convert the path to a device */
		struct block_device *bdev = lookup_bdev(path);

		if (IS_ERR(bdev))
			return PTR_ERR(bdev);
		dev = bdev->bd_dev;
		bdput(bdev);
	}

	dd = find_device(&t->devices, dev);
	if (!dd) {
		dd = kmalloc(sizeof(*dd), GFP_KERNEL);
		if (!dd)
			return -ENOMEM;

		dd->dm_dev.mode = mode;
		dd->dm_dev.bdev = NULL;

		if ((r = open_dev(dd, dev, t->md))) {
			kfree(dd);
			return r;
		}

		format_dev_t(dd->dm_dev.name, dev);

		atomic_set(&dd->count, 0);
		list_add(&dd->list, &t->devices);

	} else if (dd->dm_dev.mode != (mode | dd->dm_dev.mode)) {
		r = upgrade_mode(dd, mode, t->md);
		if (r)
			return r;
	}
	atomic_inc(&dd->count);

	if (!check_device_area(dd, start, len)) {
		DMWARN("device %s too small for target", path);
		dm_put_device(ti, &dd->dm_dev);
		return -EINVAL;
	}

	*result = &dd->dm_dev;

	return 0;
}

void dm_set_device_limits(struct dm_target *ti, struct block_device *bdev)
{
	struct request_queue *q = bdev_get_queue(bdev);
	struct io_restrictions *rs = &ti->limits;
	char b[BDEVNAME_SIZE];

	if (unlikely(!q)) {
		DMWARN("%s: Cannot set limits for nonexistent device %s",
		       dm_device_name(ti->table->md), bdevname(bdev, b));
		return;
	}

	/*
	 * Combine the device limits low.
	 *
	 * FIXME: if we move an io_restriction struct
	 *        into q this would just be a call to
	 *        combine_restrictions_low()
	 */
	rs->max_sectors =
		min_not_zero(rs->max_sectors, q->max_sectors);

	/*
	 * Check if merge fn is supported.
	 * If not we'll force DM to use PAGE_SIZE or
	 * smaller I/O, just to be safe.
	 */

	if (q->merge_bvec_fn && !ti->type->merge)
		rs->max_sectors =
			min_not_zero(rs->max_sectors,
				     (unsigned int) (PAGE_SIZE >> 9));

	rs->max_phys_segments =
		min_not_zero(rs->max_phys_segments,
			     q->max_phys_segments);

	rs->max_hw_segments =
		min_not_zero(rs->max_hw_segments, q->max_hw_segments);

	rs->hardsect_size = max(rs->hardsect_size, q->hardsect_size);

	rs->max_segment_size =
		min_not_zero(rs->max_segment_size, q->max_segment_size);

	rs->max_hw_sectors =
		min_not_zero(rs->max_hw_sectors, q->max_hw_sectors);

	rs->seg_boundary_mask =
		min_not_zero(rs->seg_boundary_mask,
			     q->seg_boundary_mask);

	rs->bounce_pfn = min_not_zero(rs->bounce_pfn, q->bounce_pfn);

	rs->no_cluster |= !test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
}
EXPORT_SYMBOL_GPL(dm_set_device_limits);

int dm_get_device(struct dm_target *ti, const char *path, sector_t start,
		  sector_t len, fmode_t mode, struct dm_dev **result)
{
	int r = __table_get_device(ti->table, ti, path,
				   start, len, mode, result);

	if (!r)
		dm_set_device_limits(ti, (*result)->bdev);

	return r;
}

/*
 * Decrement a devices use count and remove it if necessary.
 */
void dm_put_device(struct dm_target *ti, struct dm_dev *d)
{
	struct dm_dev_internal *dd = container_of(d, struct dm_dev_internal,
						  dm_dev);

	if (atomic_dec_and_test(&dd->count)) {
		close_dev(dd, ti->table->md);
		list_del(&dd->list);
		kfree(dd);
	}
}

/*
 * Checks to see if the target joins onto the end of the table.
 */
static int adjoin(struct dm_table *table, struct dm_target *ti)
{
	struct dm_target *prev;

	if (!table->num_targets)
		return !ti->begin;

	prev = &table->targets[table->num_targets - 1];
	return (ti->begin == (prev->begin + prev->len));
}

/*
 * Used to dynamically allocate the arg array.
 */
static char **realloc_argv(unsigned *array_size, char **old_argv)
{
	char **argv;
	unsigned new_size;

	new_size = *array_size ? *array_size * 2 : 64;
	argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);
	if (argv) {
		memcpy(argv, old_argv, *array_size * sizeof(*argv));
		*array_size = new_size;
	}

	kfree(old_argv);
	return argv;
}

/*
 * Destructively splits up the argument list to pass to ctr.
 */
int dm_split_args(int *argc, char ***argvp, char *input)
{
	char *start, *end = input, *out, **argv = NULL;
	unsigned array_size = 0;

	*argc = 0;

	if (!input) {
		*argvp = NULL;
		return 0;
	}

	argv = realloc_argv(&array_size, argv);
	if (!argv)
		return -ENOMEM;

	while (1) {
		start = end;

		/* Skip whitespace */
		while (*start && isspace(*start))
			start++;

		if (!*start)
			break;	/* success, we hit the end */

		/* 'out' is used to remove any back-quotes */
		end = out = start;
		while (*end) {
			/* Everything apart from '\0' can be quoted */
			if (*end == '\\' && *(end + 1)) {
				*out++ = *(end + 1);
				end += 2;
				continue;
			}

			if (isspace(*end))
				break;	/* end of token */

			*out++ = *end++;
		}

		/* have we already filled the array ? */
		if ((*argc + 1) > array_size) {
			argv = realloc_argv(&array_size, argv);
			if (!argv)
				return -ENOMEM;
		}

		/* we know this is whitespace */
		if (*end)
			end++;

		/* terminate the string and put it in the array */
		*out = '\0';
		argv[*argc] = start;
		(*argc)++;
	}

	*argvp = argv;
	return 0;
}

static void check_for_valid_limits(struct io_restrictions *rs)
{
	if (!rs->max_sectors)
		rs->max_sectors = SAFE_MAX_SECTORS;
	if (!rs->max_hw_sectors)
		rs->max_hw_sectors = SAFE_MAX_SECTORS;
	if (!rs->max_phys_segments)
		rs->max_phys_segments = MAX_PHYS_SEGMENTS;
	if (!rs->max_hw_segments)
		rs->max_hw_segments = MAX_HW_SEGMENTS;
	if (!rs->hardsect_size)
		rs->hardsect_size = 1 << SECTOR_SHIFT;
	if (!rs->max_segment_size)
		rs->max_segment_size = MAX_SEGMENT_SIZE;
	if (!rs->seg_boundary_mask)
		rs->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
	if (!rs->bounce_pfn)
		rs->bounce_pfn = -1;
}

int dm_table_add_target(struct dm_table *t, const char *type,
			sector_t start, sector_t len, char *params)
{
	int r = -EINVAL, argc;
	char **argv;
	struct dm_target *tgt;

	if ((r = check_space(t)))
		return r;

	tgt = t->targets + t->num_targets;
	memset(tgt, 0, sizeof(*tgt));

	if (!len) {
		DMERR("%s: zero-length target", dm_device_name(t->md));
		return -EINVAL;
	}

	tgt->type = dm_get_target_type(type);
	if (!tgt->type) {
		DMERR("%s: %s: unknown target type", dm_device_name(t->md),
		      type);
		return -EINVAL;
	}

	tgt->table = t;
	tgt->begin = start;
	tgt->len = len;
	tgt->error = "Unknown error";

	/*
	 * Does this target adjoin the previous one ?
	 */
	if (!adjoin(t, tgt)) {
		tgt->error = "Gap in table";
		r = -EINVAL;
		goto bad;
	}

	r = dm_split_args(&argc, &argv, params);
	if (r) {
		tgt->error = "couldn't split parameters (insufficient memory)";
		goto bad;
	}

	r = tgt->type->ctr(tgt, argc, argv);
	kfree(argv);
	if (r)
		goto bad;

	t->highs[t->num_targets++] = tgt->begin + tgt->len - 1;

	/* FIXME: the plan is to combine high here and then have
	 * the merge fn apply the target level restrictions. */
	combine_restrictions_low(&t->limits, &tgt->limits);

	if (!(tgt->type->features & DM_TARGET_SUPPORTS_BARRIERS))
		t->barriers_supported = 0;

	return 0;

 bad:
	DMERR("%s: %s: %s", dm_device_name(t->md), type, tgt->error);
	dm_put_target_type(tgt->type);
	return r;
}

static int setup_indexes(struct dm_table *t)
{
	int i;
	unsigned int total = 0;
	sector_t *indexes;

	/* allocate the space for *all* the indexes */
	for (i = t->depth - 2; i >= 0; i--) {
		t->counts[i] = dm_div_up(t->counts[i + 1], CHILDREN_PER_NODE);
		total += t->counts[i];
	}

	indexes = (sector_t *) dm_vcalloc(total, (unsigned long) NODE_SIZE);
	if (!indexes)
		return -ENOMEM;

	/* set up internal nodes, bottom-up */
	for (i = t->depth - 2; i >= 0; i--) {
		t->index[i] = indexes;
		indexes += (KEYS_PER_NODE * t->counts[i]);
		setup_btree_index(i, t);
	}

	return 0;
}

/*
 * Builds the btree to index the map.
 */
int dm_table_complete(struct dm_table *t)
{
	int r = 0;
	unsigned int leaf_nodes;

	check_for_valid_limits(&t->limits);

	/*
	 * We only support barriers if there is exactly one underlying device.
	 */
	if (!list_is_singular(&t->devices))
		t->barriers_supported = 0;

	/* how many indexes will the btree have ? */
	leaf_nodes = dm_div_up(t->num_targets, KEYS_PER_NODE);
	t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);

	/* leaf layer has already been set up */
	t->counts[t->depth - 1] = leaf_nodes;
	t->index[t->depth - 1] = t->highs;

	if (t->depth >= 2)
		r = setup_indexes(t);

	return r;
}

static DEFINE_MUTEX(_event_lock);
void dm_table_event_callback(struct dm_table *t,
			     void (*fn)(void *), void *context)
{
	mutex_lock(&_event_lock);
	t->event_fn = fn;
	t->event_context = context;
	mutex_unlock(&_event_lock);
}

void dm_table_event(struct dm_table *t)
{
	/*
	 * You can no longer call dm_table_event() from interrupt
	 * context, use a bottom half instead.
	 */
	BUG_ON(in_interrupt());

	mutex_lock(&_event_lock);
	if (t->event_fn)
		t->event_fn(t->event_context);
	mutex_unlock(&_event_lock);
}

sector_t dm_table_get_size(struct dm_table *t)
{
	return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
}

struct dm_target *dm_table_get_target(struct dm_table *t, unsigned int index)
{
	if (index >= t->num_targets)
		return NULL;

	return t->targets + index;
}

/*
 * Search the btree for the correct target.
 *
 * Caller should check returned pointer with dm_target_is_valid()
 * to trap I/O beyond end of device.
 */
struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
{
	unsigned int l, n = 0, k = 0;
	sector_t *node;

	for (l = 0; l < t->depth; l++) {
		n = get_child(n, k);
		node = get_node(t, l, n);

		for (k = 0; k < KEYS_PER_NODE; k++)
			if (node[k] >= sector)
				break;
	}

	return &t->targets[(KEYS_PER_NODE * n) + k];
}

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
{
	/*
	 * Make sure we obey the optimistic sub devices
	 * restrictions.
	 */
	blk_queue_max_sectors(q, t->limits.max_sectors);
	q->max_phys_segments = t->limits.max_phys_segments;
	q->max_hw_segments = t->limits.max_hw_segments;
	q->hardsect_size = t->limits.hardsect_size;
	q->max_segment_size = t->limits.max_segment_size;
	q->max_hw_sectors = t->limits.max_hw_sectors;
	q->seg_boundary_mask = t->limits.seg_boundary_mask;
	q->bounce_pfn = t->limits.bounce_pfn;

	if (t->limits.no_cluster)
		queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q);
	else
		queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);

}

unsigned int dm_table_get_num_targets(struct dm_table *t)
{
	return t->num_targets;
}

struct list_head *dm_table_get_devices(struct dm_table *t)
{
	return &t->devices;
}

fmode_t dm_table_get_mode(struct dm_table *t)
{
	return t->mode;
}

static void suspend_targets(struct dm_table *t, unsigned postsuspend)
{
	int i = t->num_targets;
	struct dm_target *ti = t->targets;

	while (i--) {
		if (postsuspend) {
			if (ti->type->postsuspend)
				ti->type->postsuspend(ti);
		} else if (ti->type->presuspend)
			ti->type->presuspend(ti);

		ti++;
	}
}

void dm_table_presuspend_targets(struct dm_table *t)
{
	if (!t)
		return;

	suspend_targets(t, 0);
}

void dm_table_postsuspend_targets(struct dm_table *t)
{
	if (!t)
		return;

	suspend_targets(t, 1);
}

int dm_table_resume_targets(struct dm_table *t)
{
	int i, r = 0;

	for (i = 0; i < t->num_targets; i++) {
		struct dm_target *ti = t->targets + i;

		if (!ti->type->preresume)
			continue;

		r = ti->type->preresume(ti);
		if (r)
			return r;
	}

	for (i = 0; i < t->num_targets; i++) {
		struct dm_target *ti = t->targets + i;

		if (ti->type->resume)
			ti->type->resume(ti);
	}

	return 0;
}

int dm_table_any_congested(struct dm_table *t, int bdi_bits)
{
	struct dm_dev_internal *dd;
	struct list_head *devices = dm_table_get_devices(t);
	int r = 0;

	list_for_each_entry(dd, devices, list) {
		struct request_queue *q = bdev_get_queue(dd->dm_dev.bdev);
		char b[BDEVNAME_SIZE];

		if (likely(q))
			r |= bdi_congested(&q->backing_dev_info, bdi_bits);
		else
			DMWARN_LIMIT("%s: any_congested: nonexistent device %s",
				     dm_device_name(t->md),
				     bdevname(dd->dm_dev.bdev, b));
	}

	return r;
}

void dm_table_unplug_all(struct dm_table *t)
{
	struct dm_dev_internal *dd;
	struct list_head *devices = dm_table_get_devices(t);

	list_for_each_entry(dd, devices, list) {
		struct request_queue *q = bdev_get_queue(dd->dm_dev.bdev);
		char b[BDEVNAME_SIZE];

		if (likely(q))
			blk_unplug(q);
		else
			DMWARN_LIMIT("%s: Cannot unplug nonexistent device %s",
				     dm_device_name(t->md),
				     bdevname(dd->dm_dev.bdev, b));
	}
}

struct mapped_device *dm_table_get_md(struct dm_table *t)
{
	dm_get(t->md);

	return t->md;
}

int dm_table_barrier_ok(struct dm_table *t)
{
	return t->barriers_supported;
}
EXPORT_SYMBOL(dm_table_barrier_ok);

EXPORT_SYMBOL(dm_vcalloc);
EXPORT_SYMBOL(dm_get_device);
EXPORT_SYMBOL(dm_put_device);
EXPORT_SYMBOL(dm_table_event);
EXPORT_SYMBOL(dm_table_get_size);
EXPORT_SYMBOL(dm_table_get_mode);
EXPORT_SYMBOL(dm_table_get_md);
EXPORT_SYMBOL(dm_table_put);
EXPORT_SYMBOL(dm_table_get);
EXPORT_SYMBOL(dm_table_unplug_all);