summaryrefslogtreecommitdiff
path: root/drivers/md/raid0.c
blob: c50a7abda744ad13262378a83fec2dbde0e00b9a (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
   raid0.c : Multiple Devices driver for Linux
	     Copyright (C) 1994-96 Marc ZYNGIER
	     <zyngier@ufr-info-p7.ibp.fr> or
	     <maz@gloups.fdn.fr>
	     Copyright (C) 1999, 2000 Ingo Molnar, Red Hat

   RAID-0 management functions.

*/

#include <linux/blkdev.h>
#include <linux/seq_file.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <trace/events/block.h>
#include "md.h"
#include "raid0.h"
#include "raid5.h"

static int default_layout = 0;
module_param(default_layout, int, 0644);

#define UNSUPPORTED_MDDEV_FLAGS		\
	((1L << MD_HAS_JOURNAL) |	\
	 (1L << MD_JOURNAL_CLEAN) |	\
	 (1L << MD_FAILFAST_SUPPORTED) |\
	 (1L << MD_HAS_PPL) |		\
	 (1L << MD_HAS_MULTIPLE_PPLS))

/*
 * inform the user of the raid configuration
*/
static void dump_zones(struct mddev *mddev)
{
	int j, k;
	sector_t zone_size = 0;
	sector_t zone_start = 0;
	struct r0conf *conf = mddev->private;
	int raid_disks = conf->strip_zone[0].nb_dev;
	pr_debug("md: RAID0 configuration for %s - %d zone%s\n",
		 mdname(mddev),
		 conf->nr_strip_zones, conf->nr_strip_zones==1?"":"s");
	for (j = 0; j < conf->nr_strip_zones; j++) {
		char line[200];
		int len = 0;

		for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
			len += scnprintf(line+len, 200-len, "%s%pg", k?"/":"",
				conf->devlist[j * raid_disks + k]->bdev);
		pr_debug("md: zone%d=[%s]\n", j, line);

		zone_size  = conf->strip_zone[j].zone_end - zone_start;
		pr_debug("      zone-offset=%10lluKB, device-offset=%10lluKB, size=%10lluKB\n",
			(unsigned long long)zone_start>>1,
			(unsigned long long)conf->strip_zone[j].dev_start>>1,
			(unsigned long long)zone_size>>1);
		zone_start = conf->strip_zone[j].zone_end;
	}
}

static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
{
	int i, c, err;
	sector_t curr_zone_end, sectors;
	struct md_rdev *smallest, *rdev1, *rdev2, *rdev, **dev;
	struct strip_zone *zone;
	int cnt;
	struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
	unsigned blksize = 512;

	*private_conf = ERR_PTR(-ENOMEM);
	if (!conf)
		return -ENOMEM;
	rdev_for_each(rdev1, mddev) {
		pr_debug("md/raid0:%s: looking at %pg\n",
			 mdname(mddev),
			 rdev1->bdev);
		c = 0;

		/* round size to chunk_size */
		sectors = rdev1->sectors;
		sector_div(sectors, mddev->chunk_sectors);
		rdev1->sectors = sectors * mddev->chunk_sectors;

		blksize = max(blksize, queue_logical_block_size(
				      rdev1->bdev->bd_disk->queue));

		rdev_for_each(rdev2, mddev) {
			pr_debug("md/raid0:%s:   comparing %pg(%llu)"
				 " with %pg(%llu)\n",
				 mdname(mddev),
				 rdev1->bdev,
				 (unsigned long long)rdev1->sectors,
				 rdev2->bdev,
				 (unsigned long long)rdev2->sectors);
			if (rdev2 == rdev1) {
				pr_debug("md/raid0:%s:   END\n",
					 mdname(mddev));
				break;
			}
			if (rdev2->sectors == rdev1->sectors) {
				/*
				 * Not unique, don't count it as a new
				 * group
				 */
				pr_debug("md/raid0:%s:   EQUAL\n",
					 mdname(mddev));
				c = 1;
				break;
			}
			pr_debug("md/raid0:%s:   NOT EQUAL\n",
				 mdname(mddev));
		}
		if (!c) {
			pr_debug("md/raid0:%s:   ==> UNIQUE\n",
				 mdname(mddev));
			conf->nr_strip_zones++;
			pr_debug("md/raid0:%s: %d zones\n",
				 mdname(mddev), conf->nr_strip_zones);
		}
	}
	pr_debug("md/raid0:%s: FINAL %d zones\n",
		 mdname(mddev), conf->nr_strip_zones);

	/*
	 * now since we have the hard sector sizes, we can make sure
	 * chunk size is a multiple of that sector size
	 */
	if ((mddev->chunk_sectors << 9) % blksize) {
		pr_warn("md/raid0:%s: chunk_size of %d not multiple of block size %d\n",
			mdname(mddev),
			mddev->chunk_sectors << 9, blksize);
		err = -EINVAL;
		goto abort;
	}

	err = -ENOMEM;
	conf->strip_zone = kcalloc(conf->nr_strip_zones,
				   sizeof(struct strip_zone),
				   GFP_KERNEL);
	if (!conf->strip_zone)
		goto abort;
	conf->devlist = kzalloc(array3_size(sizeof(struct md_rdev *),
					    conf->nr_strip_zones,
					    mddev->raid_disks),
				GFP_KERNEL);
	if (!conf->devlist)
		goto abort;

	/* The first zone must contain all devices, so here we check that
	 * there is a proper alignment of slots to devices and find them all
	 */
	zone = &conf->strip_zone[0];
	cnt = 0;
	smallest = NULL;
	dev = conf->devlist;
	err = -EINVAL;
	rdev_for_each(rdev1, mddev) {
		int j = rdev1->raid_disk;

		if (mddev->level == 10) {
			/* taking over a raid10-n2 array */
			j /= 2;
			rdev1->new_raid_disk = j;
		}

		if (mddev->level == 1) {
			/* taiking over a raid1 array-
			 * we have only one active disk
			 */
			j = 0;
			rdev1->new_raid_disk = j;
		}

		if (j < 0) {
			pr_warn("md/raid0:%s: remove inactive devices before converting to RAID0\n",
				mdname(mddev));
			goto abort;
		}
		if (j >= mddev->raid_disks) {
			pr_warn("md/raid0:%s: bad disk number %d - aborting!\n",
				mdname(mddev), j);
			goto abort;
		}
		if (dev[j]) {
			pr_warn("md/raid0:%s: multiple devices for %d - aborting!\n",
				mdname(mddev), j);
			goto abort;
		}
		dev[j] = rdev1;

		if (!smallest || (rdev1->sectors < smallest->sectors))
			smallest = rdev1;
		cnt++;
	}
	if (cnt != mddev->raid_disks) {
		pr_warn("md/raid0:%s: too few disks (%d of %d) - aborting!\n",
			mdname(mddev), cnt, mddev->raid_disks);
		goto abort;
	}
	zone->nb_dev = cnt;
	zone->zone_end = smallest->sectors * cnt;

	curr_zone_end = zone->zone_end;

	/* now do the other zones */
	for (i = 1; i < conf->nr_strip_zones; i++)
	{
		int j;

		zone = conf->strip_zone + i;
		dev = conf->devlist + i * mddev->raid_disks;

		pr_debug("md/raid0:%s: zone %d\n", mdname(mddev), i);
		zone->dev_start = smallest->sectors;
		smallest = NULL;
		c = 0;

		for (j=0; j<cnt; j++) {
			rdev = conf->devlist[j];
			if (rdev->sectors <= zone->dev_start) {
				pr_debug("md/raid0:%s: checking %pg ... nope\n",
					 mdname(mddev),
					 rdev->bdev);
				continue;
			}
			pr_debug("md/raid0:%s: checking %pg ..."
				 " contained as device %d\n",
				 mdname(mddev),
				 rdev->bdev, c);
			dev[c] = rdev;
			c++;
			if (!smallest || rdev->sectors < smallest->sectors) {
				smallest = rdev;
				pr_debug("md/raid0:%s:  (%llu) is smallest!.\n",
					 mdname(mddev),
					 (unsigned long long)rdev->sectors);
			}
		}

		zone->nb_dev = c;
		sectors = (smallest->sectors - zone->dev_start) * c;
		pr_debug("md/raid0:%s: zone->nb_dev: %d, sectors: %llu\n",
			 mdname(mddev),
			 zone->nb_dev, (unsigned long long)sectors);

		curr_zone_end += sectors;
		zone->zone_end = curr_zone_end;

		pr_debug("md/raid0:%s: current zone start: %llu\n",
			 mdname(mddev),
			 (unsigned long long)smallest->sectors);
	}

	if (conf->nr_strip_zones == 1 || conf->strip_zone[1].nb_dev == 1) {
		conf->layout = RAID0_ORIG_LAYOUT;
	} else if (mddev->layout == RAID0_ORIG_LAYOUT ||
		   mddev->layout == RAID0_ALT_MULTIZONE_LAYOUT) {
		conf->layout = mddev->layout;
	} else if (default_layout == RAID0_ORIG_LAYOUT ||
		   default_layout == RAID0_ALT_MULTIZONE_LAYOUT) {
		conf->layout = default_layout;
	} else {
		pr_err("md/raid0:%s: cannot assemble multi-zone RAID0 with default_layout setting\n",
		       mdname(mddev));
		pr_err("md/raid0: please set raid0.default_layout to 1 or 2\n");
		err = -EOPNOTSUPP;
		goto abort;
	}

	if (conf->layout == RAID0_ORIG_LAYOUT) {
		for (i = 1; i < conf->nr_strip_zones; i++) {
			sector_t first_sector = conf->strip_zone[i-1].zone_end;

			sector_div(first_sector, mddev->chunk_sectors);
			zone = conf->strip_zone + i;
			/* disk_shift is first disk index used in the zone */
			zone->disk_shift = sector_div(first_sector,
						      zone->nb_dev);
		}
	}

	pr_debug("md/raid0:%s: done.\n", mdname(mddev));
	*private_conf = conf;

	return 0;
abort:
	kfree(conf->strip_zone);
	kfree(conf->devlist);
	kfree(conf);
	*private_conf = ERR_PTR(err);
	return err;
}

/* Find the zone which holds a particular offset
 * Update *sectorp to be an offset in that zone
 */
static struct strip_zone *find_zone(struct r0conf *conf,
				    sector_t *sectorp)
{
	int i;
	struct strip_zone *z = conf->strip_zone;
	sector_t sector = *sectorp;

	for (i = 0; i < conf->nr_strip_zones; i++)
		if (sector < z[i].zone_end) {
			if (i)
				*sectorp = sector - z[i-1].zone_end;
			return z + i;
		}
	BUG();
}

/*
 * remaps the bio to the target device. we separate two flows.
 * power 2 flow and a general flow for the sake of performance
*/
static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
				sector_t sector, sector_t *sector_offset)
{
	unsigned int sect_in_chunk;
	sector_t chunk;
	struct r0conf *conf = mddev->private;
	int raid_disks = conf->strip_zone[0].nb_dev;
	unsigned int chunk_sects = mddev->chunk_sectors;

	if (is_power_of_2(chunk_sects)) {
		int chunksect_bits = ffz(~chunk_sects);
		/* find the sector offset inside the chunk */
		sect_in_chunk  = sector & (chunk_sects - 1);
		sector >>= chunksect_bits;
		/* chunk in zone */
		chunk = *sector_offset;
		/* quotient is the chunk in real device*/
		sector_div(chunk, zone->nb_dev << chunksect_bits);
	} else{
		sect_in_chunk = sector_div(sector, chunk_sects);
		chunk = *sector_offset;
		sector_div(chunk, chunk_sects * zone->nb_dev);
	}
	/*
	*  position the bio over the real device
	*  real sector = chunk in device + starting of zone
	*	+ the position in the chunk
	*/
	*sector_offset = (chunk * chunk_sects) + sect_in_chunk;
	return conf->devlist[(zone - conf->strip_zone)*raid_disks
			     + sector_div(sector, zone->nb_dev)];
}

static sector_t raid0_size(struct mddev *mddev, sector_t sectors, int raid_disks)
{
	sector_t array_sectors = 0;
	struct md_rdev *rdev;

	WARN_ONCE(sectors || raid_disks,
		  "%s does not support generic reshape\n", __func__);

	rdev_for_each(rdev, mddev)
		array_sectors += (rdev->sectors &
				  ~(sector_t)(mddev->chunk_sectors-1));

	return array_sectors;
}

static void free_conf(struct mddev *mddev, struct r0conf *conf)
{
	kfree(conf->strip_zone);
	kfree(conf->devlist);
	kfree(conf);
}

static void raid0_free(struct mddev *mddev, void *priv)
{
	struct r0conf *conf = priv;

	free_conf(mddev, conf);
}

static int raid0_run(struct mddev *mddev)
{
	struct r0conf *conf;
	int ret;

	if (mddev->chunk_sectors == 0) {
		pr_warn("md/raid0:%s: chunk size must be set.\n", mdname(mddev));
		return -EINVAL;
	}
	if (md_check_no_bitmap(mddev))
		return -EINVAL;

	/* if private is not null, we are here after takeover */
	if (mddev->private == NULL) {
		ret = create_strip_zones(mddev, &conf);
		if (ret < 0)
			return ret;
		mddev->private = conf;
	}
	conf = mddev->private;
	if (mddev->queue) {
		struct md_rdev *rdev;

		blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
		blk_queue_max_write_zeroes_sectors(mddev->queue, mddev->chunk_sectors);

		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
		blk_queue_io_opt(mddev->queue,
				 (mddev->chunk_sectors << 9) * mddev->raid_disks);

		rdev_for_each(rdev, mddev) {
			disk_stack_limits(mddev->gendisk, rdev->bdev,
					  rdev->data_offset << 9);
		}
	}

	/* calculate array device size */
	md_set_array_sectors(mddev, raid0_size(mddev, 0, 0));

	pr_debug("md/raid0:%s: md_size is %llu sectors.\n",
		 mdname(mddev),
		 (unsigned long long)mddev->array_sectors);

	dump_zones(mddev);

	ret = md_integrity_register(mddev);
	if (ret)
		free_conf(mddev, conf);

	return ret;
}

/*
 * Convert disk_index to the disk order in which it is read/written.
 *  For example, if we have 4 disks, they are numbered 0,1,2,3. If we
 *  write the disks starting at disk 3, then the read/write order would
 *  be disk 3, then 0, then 1, and then disk 2 and we want map_disk_shift()
 *  to map the disks as follows 0,1,2,3 => 1,2,3,0. So disk 0 would map
 *  to 1, 1 to 2, 2 to 3, and 3 to 0. That way we can compare disks in
 *  that 'output' space to understand the read/write disk ordering.
 */
static int map_disk_shift(int disk_index, int num_disks, int disk_shift)
{
	return ((disk_index + num_disks - disk_shift) % num_disks);
}

static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
{
	struct r0conf *conf = mddev->private;
	struct strip_zone *zone;
	sector_t start = bio->bi_iter.bi_sector;
	sector_t end;
	unsigned int stripe_size;
	sector_t first_stripe_index, last_stripe_index;
	sector_t start_disk_offset;
	unsigned int start_disk_index;
	sector_t end_disk_offset;
	unsigned int end_disk_index;
	unsigned int disk;
	sector_t orig_start, orig_end;

	orig_start = start;
	zone = find_zone(conf, &start);

	if (bio_end_sector(bio) > zone->zone_end) {
		struct bio *split = bio_split(bio,
			zone->zone_end - bio->bi_iter.bi_sector, GFP_NOIO,
			&mddev->bio_set);
		bio_chain(split, bio);
		submit_bio_noacct(bio);
		bio = split;
		end = zone->zone_end;
	} else
		end = bio_end_sector(bio);

	orig_end = end;
	if (zone != conf->strip_zone)
		end = end - zone[-1].zone_end;

	/* Now start and end is the offset in zone */
	stripe_size = zone->nb_dev * mddev->chunk_sectors;

	first_stripe_index = start;
	sector_div(first_stripe_index, stripe_size);
	last_stripe_index = end;
	sector_div(last_stripe_index, stripe_size);

	/* In the first zone the original and alternate layouts are the same */
	if ((conf->layout == RAID0_ORIG_LAYOUT) && (zone != conf->strip_zone)) {
		sector_div(orig_start, mddev->chunk_sectors);
		start_disk_index = sector_div(orig_start, zone->nb_dev);
		start_disk_index = map_disk_shift(start_disk_index,
						  zone->nb_dev,
						  zone->disk_shift);
		sector_div(orig_end, mddev->chunk_sectors);
		end_disk_index = sector_div(orig_end, zone->nb_dev);
		end_disk_index = map_disk_shift(end_disk_index,
						zone->nb_dev, zone->disk_shift);
	} else {
		start_disk_index = (int)(start - first_stripe_index * stripe_size) /
			mddev->chunk_sectors;
		end_disk_index = (int)(end - last_stripe_index * stripe_size) /
			mddev->chunk_sectors;
	}
	start_disk_offset = ((int)(start - first_stripe_index * stripe_size) %
		mddev->chunk_sectors) +
		first_stripe_index * mddev->chunk_sectors;
	end_disk_offset = ((int)(end - last_stripe_index * stripe_size) %
		mddev->chunk_sectors) +
		last_stripe_index * mddev->chunk_sectors;

	for (disk = 0; disk < zone->nb_dev; disk++) {
		sector_t dev_start, dev_end;
		struct md_rdev *rdev;
		int compare_disk;

		compare_disk = map_disk_shift(disk, zone->nb_dev,
					      zone->disk_shift);

		if (compare_disk < start_disk_index)
			dev_start = (first_stripe_index + 1) *
				mddev->chunk_sectors;
		else if (compare_disk > start_disk_index)
			dev_start = first_stripe_index * mddev->chunk_sectors;
		else
			dev_start = start_disk_offset;

		if (compare_disk < end_disk_index)
			dev_end = (last_stripe_index + 1) * mddev->chunk_sectors;
		else if (compare_disk > end_disk_index)
			dev_end = last_stripe_index * mddev->chunk_sectors;
		else
			dev_end = end_disk_offset;

		if (dev_end <= dev_start)
			continue;

		rdev = conf->devlist[(zone - conf->strip_zone) *
			conf->strip_zone[0].nb_dev + disk];
		md_submit_discard_bio(mddev, rdev, bio,
			dev_start + zone->dev_start + rdev->data_offset,
			dev_end - dev_start);
	}
	bio_endio(bio);
}

static void raid0_map_submit_bio(struct mddev *mddev, struct bio *bio)
{
	struct r0conf *conf = mddev->private;
	struct strip_zone *zone;
	struct md_rdev *tmp_dev;
	sector_t bio_sector = bio->bi_iter.bi_sector;
	sector_t sector = bio_sector;

	md_account_bio(mddev, &bio);

	zone = find_zone(mddev->private, &sector);
	switch (conf->layout) {
	case RAID0_ORIG_LAYOUT:
		tmp_dev = map_sector(mddev, zone, bio_sector, &sector);
		break;
	case RAID0_ALT_MULTIZONE_LAYOUT:
		tmp_dev = map_sector(mddev, zone, sector, &sector);
		break;
	default:
		WARN(1, "md/raid0:%s: Invalid layout\n", mdname(mddev));
		bio_io_error(bio);
		return;
	}

	if (unlikely(is_rdev_broken(tmp_dev))) {
		bio_io_error(bio);
		md_error(mddev, tmp_dev);
		return;
	}

	bio_set_dev(bio, tmp_dev->bdev);
	bio->bi_iter.bi_sector = sector + zone->dev_start +
		tmp_dev->data_offset;

	if (mddev->gendisk)
		trace_block_bio_remap(bio, disk_devt(mddev->gendisk),
				      bio_sector);
	mddev_check_write_zeroes(mddev, bio);
	submit_bio_noacct(bio);
}

static bool raid0_make_request(struct mddev *mddev, struct bio *bio)
{
	sector_t sector;
	unsigned chunk_sects;
	unsigned sectors;

	if (unlikely(bio->bi_opf & REQ_PREFLUSH)
	    && md_flush_request(mddev, bio))
		return true;

	if (unlikely((bio_op(bio) == REQ_OP_DISCARD))) {
		raid0_handle_discard(mddev, bio);
		return true;
	}

	sector = bio->bi_iter.bi_sector;
	chunk_sects = mddev->chunk_sectors;

	sectors = chunk_sects -
		(likely(is_power_of_2(chunk_sects))
		 ? (sector & (chunk_sects-1))
		 : sector_div(sector, chunk_sects));

	if (sectors < bio_sectors(bio)) {
		struct bio *split = bio_split(bio, sectors, GFP_NOIO,
					      &mddev->bio_set);
		bio_chain(split, bio);
		raid0_map_submit_bio(mddev, bio);
		bio = split;
	}

	raid0_map_submit_bio(mddev, bio);
	return true;
}

static void raid0_status(struct seq_file *seq, struct mddev *mddev)
{
	seq_printf(seq, " %dk chunks", mddev->chunk_sectors / 2);
	return;
}

static void raid0_error(struct mddev *mddev, struct md_rdev *rdev)
{
	if (!test_and_set_bit(MD_BROKEN, &mddev->flags)) {
		char *md_name = mdname(mddev);

		pr_crit("md/raid0%s: Disk failure on %pg detected, failing array.\n",
			md_name, rdev->bdev);
	}
}

static void *raid0_takeover_raid45(struct mddev *mddev)
{
	struct md_rdev *rdev;
	struct r0conf *priv_conf;

	if (mddev->degraded != 1) {
		pr_warn("md/raid0:%s: raid5 must be degraded! Degraded disks: %d\n",
			mdname(mddev),
			mddev->degraded);
		return ERR_PTR(-EINVAL);
	}

	rdev_for_each(rdev, mddev) {
		/* check slot number for a disk */
		if (rdev->raid_disk == mddev->raid_disks-1) {
			pr_warn("md/raid0:%s: raid5 must have missing parity disk!\n",
				mdname(mddev));
			return ERR_PTR(-EINVAL);
		}
		rdev->sectors = mddev->dev_sectors;
	}

	/* Set new parameters */
	mddev->new_level = 0;
	mddev->new_layout = 0;
	mddev->new_chunk_sectors = mddev->chunk_sectors;
	mddev->raid_disks--;
	mddev->delta_disks = -1;
	/* make sure it will be not marked as dirty */
	mddev->recovery_cp = MaxSector;
	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);

	create_strip_zones(mddev, &priv_conf);

	return priv_conf;
}

static void *raid0_takeover_raid10(struct mddev *mddev)
{
	struct r0conf *priv_conf;

	/* Check layout:
	 *  - far_copies must be 1
	 *  - near_copies must be 2
	 *  - disks number must be even
	 *  - all mirrors must be already degraded
	 */
	if (mddev->layout != ((1 << 8) + 2)) {
		pr_warn("md/raid0:%s:: Raid0 cannot takeover layout: 0x%x\n",
			mdname(mddev),
			mddev->layout);
		return ERR_PTR(-EINVAL);
	}
	if (mddev->raid_disks & 1) {
		pr_warn("md/raid0:%s: Raid0 cannot takeover Raid10 with odd disk number.\n",
			mdname(mddev));
		return ERR_PTR(-EINVAL);
	}
	if (mddev->degraded != (mddev->raid_disks>>1)) {
		pr_warn("md/raid0:%s: All mirrors must be already degraded!\n",
			mdname(mddev));
		return ERR_PTR(-EINVAL);
	}

	/* Set new parameters */
	mddev->new_level = 0;
	mddev->new_layout = 0;
	mddev->new_chunk_sectors = mddev->chunk_sectors;
	mddev->delta_disks = - mddev->raid_disks / 2;
	mddev->raid_disks += mddev->delta_disks;
	mddev->degraded = 0;
	/* make sure it will be not marked as dirty */
	mddev->recovery_cp = MaxSector;
	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);

	create_strip_zones(mddev, &priv_conf);
	return priv_conf;
}

static void *raid0_takeover_raid1(struct mddev *mddev)
{
	struct r0conf *priv_conf;
	int chunksect;

	/* Check layout:
	 *  - (N - 1) mirror drives must be already faulty
	 */
	if ((mddev->raid_disks - 1) != mddev->degraded) {
		pr_err("md/raid0:%s: (N - 1) mirrors drives must be already faulty!\n",
		       mdname(mddev));
		return ERR_PTR(-EINVAL);
	}

	/*
	 * a raid1 doesn't have the notion of chunk size, so
	 * figure out the largest suitable size we can use.
	 */
	chunksect = 64 * 2; /* 64K by default */

	/* The array must be an exact multiple of chunksize */
	while (chunksect && (mddev->array_sectors & (chunksect - 1)))
		chunksect >>= 1;

	if ((chunksect << 9) < PAGE_SIZE)
		/* array size does not allow a suitable chunk size */
		return ERR_PTR(-EINVAL);

	/* Set new parameters */
	mddev->new_level = 0;
	mddev->new_layout = 0;
	mddev->new_chunk_sectors = chunksect;
	mddev->chunk_sectors = chunksect;
	mddev->delta_disks = 1 - mddev->raid_disks;
	mddev->raid_disks = 1;
	/* make sure it will be not marked as dirty */
	mddev->recovery_cp = MaxSector;
	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);

	create_strip_zones(mddev, &priv_conf);
	return priv_conf;
}

static void *raid0_takeover(struct mddev *mddev)
{
	/* raid0 can take over:
	 *  raid4 - if all data disks are active.
	 *  raid5 - providing it is Raid4 layout and one disk is faulty
	 *  raid10 - assuming we have all necessary active disks
	 *  raid1 - with (N -1) mirror drives faulty
	 */

	if (mddev->bitmap) {
		pr_warn("md/raid0: %s: cannot takeover array with bitmap\n",
			mdname(mddev));
		return ERR_PTR(-EBUSY);
	}
	if (mddev->level == 4)
		return raid0_takeover_raid45(mddev);

	if (mddev->level == 5) {
		if (mddev->layout == ALGORITHM_PARITY_N)
			return raid0_takeover_raid45(mddev);

		pr_warn("md/raid0:%s: Raid can only takeover Raid5 with layout: %d\n",
			mdname(mddev), ALGORITHM_PARITY_N);
	}

	if (mddev->level == 10)
		return raid0_takeover_raid10(mddev);

	if (mddev->level == 1)
		return raid0_takeover_raid1(mddev);

	pr_warn("Takeover from raid%i to raid0 not supported\n",
		mddev->level);

	return ERR_PTR(-EINVAL);
}

static void raid0_quiesce(struct mddev *mddev, int quiesce)
{
}

static struct md_personality raid0_personality=
{
	.name		= "raid0",
	.level		= 0,
	.owner		= THIS_MODULE,
	.make_request	= raid0_make_request,
	.run		= raid0_run,
	.free		= raid0_free,
	.status		= raid0_status,
	.size		= raid0_size,
	.takeover	= raid0_takeover,
	.quiesce	= raid0_quiesce,
	.error_handler	= raid0_error,
};

static int __init raid0_init (void)
{
	return register_md_personality (&raid0_personality);
}

static void raid0_exit (void)
{
	unregister_md_personality (&raid0_personality);
}

module_init(raid0_init);
module_exit(raid0_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RAID0 (striping) personality for MD");
MODULE_ALIAS("md-personality-2"); /* RAID0 */
MODULE_ALIAS("md-raid0");
MODULE_ALIAS("md-level-0");