xref: /linux/drivers/md/raid0.c (revision b85d45947951d23cb22d90caecf4c1eb81342c96)
1 /*
2    raid0.c : Multiple Devices driver for Linux
3 	     Copyright (C) 1994-96 Marc ZYNGIER
4 	     <zyngier@ufr-info-p7.ibp.fr> or
5 	     <maz@gloups.fdn.fr>
6 	     Copyright (C) 1999, 2000 Ingo Molnar, Red Hat
7 
8    RAID-0 management functions.
9 
10    This program is free software; you can redistribute it and/or modify
11    it under the terms of the GNU General Public License as published by
12    the Free Software Foundation; either version 2, or (at your option)
13    any later version.
14 
15    You should have received a copy of the GNU General Public License
16    (for example /usr/src/linux/COPYING); if not, write to the Free
17    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18 */
19 
20 #include <linux/blkdev.h>
21 #include <linux/seq_file.h>
22 #include <linux/module.h>
23 #include <linux/slab.h>
24 #include "md.h"
25 #include "raid0.h"
26 #include "raid5.h"
27 
28 static int raid0_congested(struct mddev *mddev, int bits)
29 {
30 	struct r0conf *conf = mddev->private;
31 	struct md_rdev **devlist = conf->devlist;
32 	int raid_disks = conf->strip_zone[0].nb_dev;
33 	int i, ret = 0;
34 
35 	for (i = 0; i < raid_disks && !ret ; i++) {
36 		struct request_queue *q = bdev_get_queue(devlist[i]->bdev);
37 
38 		ret |= bdi_congested(&q->backing_dev_info, bits);
39 	}
40 	return ret;
41 }
42 
43 /*
44  * inform the user of the raid configuration
45 */
46 static void dump_zones(struct mddev *mddev)
47 {
48 	int j, k;
49 	sector_t zone_size = 0;
50 	sector_t zone_start = 0;
51 	char b[BDEVNAME_SIZE];
52 	struct r0conf *conf = mddev->private;
53 	int raid_disks = conf->strip_zone[0].nb_dev;
54 	printk(KERN_INFO "md: RAID0 configuration for %s - %d zone%s\n",
55 	       mdname(mddev),
56 	       conf->nr_strip_zones, conf->nr_strip_zones==1?"":"s");
57 	for (j = 0; j < conf->nr_strip_zones; j++) {
58 		printk(KERN_INFO "md: zone%d=[", j);
59 		for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
60 			printk(KERN_CONT "%s%s", k?"/":"",
61 			bdevname(conf->devlist[j*raid_disks
62 						+ k]->bdev, b));
63 		printk(KERN_CONT "]\n");
64 
65 		zone_size  = conf->strip_zone[j].zone_end - zone_start;
66 		printk(KERN_INFO "      zone-offset=%10lluKB, "
67 				"device-offset=%10lluKB, size=%10lluKB\n",
68 			(unsigned long long)zone_start>>1,
69 			(unsigned long long)conf->strip_zone[j].dev_start>>1,
70 			(unsigned long long)zone_size>>1);
71 		zone_start = conf->strip_zone[j].zone_end;
72 	}
73 	printk(KERN_INFO "\n");
74 }
75 
76 static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
77 {
78 	int i, c, err;
79 	sector_t curr_zone_end, sectors;
80 	struct md_rdev *smallest, *rdev1, *rdev2, *rdev, **dev;
81 	struct strip_zone *zone;
82 	int cnt;
83 	char b[BDEVNAME_SIZE];
84 	char b2[BDEVNAME_SIZE];
85 	struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
86 	unsigned short blksize = 512;
87 
88 	if (!conf)
89 		return -ENOMEM;
90 	rdev_for_each(rdev1, mddev) {
91 		pr_debug("md/raid0:%s: looking at %s\n",
92 			 mdname(mddev),
93 			 bdevname(rdev1->bdev, b));
94 		c = 0;
95 
96 		/* round size to chunk_size */
97 		sectors = rdev1->sectors;
98 		sector_div(sectors, mddev->chunk_sectors);
99 		rdev1->sectors = sectors * mddev->chunk_sectors;
100 
101 		blksize = max(blksize, queue_logical_block_size(
102 				      rdev1->bdev->bd_disk->queue));
103 
104 		rdev_for_each(rdev2, mddev) {
105 			pr_debug("md/raid0:%s:   comparing %s(%llu)"
106 				 " with %s(%llu)\n",
107 				 mdname(mddev),
108 				 bdevname(rdev1->bdev,b),
109 				 (unsigned long long)rdev1->sectors,
110 				 bdevname(rdev2->bdev,b2),
111 				 (unsigned long long)rdev2->sectors);
112 			if (rdev2 == rdev1) {
113 				pr_debug("md/raid0:%s:   END\n",
114 					 mdname(mddev));
115 				break;
116 			}
117 			if (rdev2->sectors == rdev1->sectors) {
118 				/*
119 				 * Not unique, don't count it as a new
120 				 * group
121 				 */
122 				pr_debug("md/raid0:%s:   EQUAL\n",
123 					 mdname(mddev));
124 				c = 1;
125 				break;
126 			}
127 			pr_debug("md/raid0:%s:   NOT EQUAL\n",
128 				 mdname(mddev));
129 		}
130 		if (!c) {
131 			pr_debug("md/raid0:%s:   ==> UNIQUE\n",
132 				 mdname(mddev));
133 			conf->nr_strip_zones++;
134 			pr_debug("md/raid0:%s: %d zones\n",
135 				 mdname(mddev), conf->nr_strip_zones);
136 		}
137 	}
138 	pr_debug("md/raid0:%s: FINAL %d zones\n",
139 		 mdname(mddev), conf->nr_strip_zones);
140 	/*
141 	 * now since we have the hard sector sizes, we can make sure
142 	 * chunk size is a multiple of that sector size
143 	 */
144 	if ((mddev->chunk_sectors << 9) % blksize) {
145 		printk(KERN_ERR "md/raid0:%s: chunk_size of %d not multiple of block size %d\n",
146 		       mdname(mddev),
147 		       mddev->chunk_sectors << 9, blksize);
148 		err = -EINVAL;
149 		goto abort;
150 	}
151 
152 	err = -ENOMEM;
153 	conf->strip_zone = kzalloc(sizeof(struct strip_zone)*
154 				conf->nr_strip_zones, GFP_KERNEL);
155 	if (!conf->strip_zone)
156 		goto abort;
157 	conf->devlist = kzalloc(sizeof(struct md_rdev*)*
158 				conf->nr_strip_zones*mddev->raid_disks,
159 				GFP_KERNEL);
160 	if (!conf->devlist)
161 		goto abort;
162 
163 	/* The first zone must contain all devices, so here we check that
164 	 * there is a proper alignment of slots to devices and find them all
165 	 */
166 	zone = &conf->strip_zone[0];
167 	cnt = 0;
168 	smallest = NULL;
169 	dev = conf->devlist;
170 	err = -EINVAL;
171 	rdev_for_each(rdev1, mddev) {
172 		int j = rdev1->raid_disk;
173 
174 		if (mddev->level == 10) {
175 			/* taking over a raid10-n2 array */
176 			j /= 2;
177 			rdev1->new_raid_disk = j;
178 		}
179 
180 		if (mddev->level == 1) {
181 			/* taiking over a raid1 array-
182 			 * we have only one active disk
183 			 */
184 			j = 0;
185 			rdev1->new_raid_disk = j;
186 		}
187 
188 		if (j < 0) {
189 			printk(KERN_ERR
190 			       "md/raid0:%s: remove inactive devices before converting to RAID0\n",
191 			       mdname(mddev));
192 			goto abort;
193 		}
194 		if (j >= mddev->raid_disks) {
195 			printk(KERN_ERR "md/raid0:%s: bad disk number %d - "
196 			       "aborting!\n", mdname(mddev), j);
197 			goto abort;
198 		}
199 		if (dev[j]) {
200 			printk(KERN_ERR "md/raid0:%s: multiple devices for %d - "
201 			       "aborting!\n", mdname(mddev), j);
202 			goto abort;
203 		}
204 		dev[j] = rdev1;
205 
206 		if (!smallest || (rdev1->sectors < smallest->sectors))
207 			smallest = rdev1;
208 		cnt++;
209 	}
210 	if (cnt != mddev->raid_disks) {
211 		printk(KERN_ERR "md/raid0:%s: too few disks (%d of %d) - "
212 		       "aborting!\n", mdname(mddev), cnt, mddev->raid_disks);
213 		goto abort;
214 	}
215 	zone->nb_dev = cnt;
216 	zone->zone_end = smallest->sectors * cnt;
217 
218 	curr_zone_end = zone->zone_end;
219 
220 	/* now do the other zones */
221 	for (i = 1; i < conf->nr_strip_zones; i++)
222 	{
223 		int j;
224 
225 		zone = conf->strip_zone + i;
226 		dev = conf->devlist + i * mddev->raid_disks;
227 
228 		pr_debug("md/raid0:%s: zone %d\n", mdname(mddev), i);
229 		zone->dev_start = smallest->sectors;
230 		smallest = NULL;
231 		c = 0;
232 
233 		for (j=0; j<cnt; j++) {
234 			rdev = conf->devlist[j];
235 			if (rdev->sectors <= zone->dev_start) {
236 				pr_debug("md/raid0:%s: checking %s ... nope\n",
237 					 mdname(mddev),
238 					 bdevname(rdev->bdev, b));
239 				continue;
240 			}
241 			pr_debug("md/raid0:%s: checking %s ..."
242 				 " contained as device %d\n",
243 				 mdname(mddev),
244 				 bdevname(rdev->bdev, b), c);
245 			dev[c] = rdev;
246 			c++;
247 			if (!smallest || rdev->sectors < smallest->sectors) {
248 				smallest = rdev;
249 				pr_debug("md/raid0:%s:  (%llu) is smallest!.\n",
250 					 mdname(mddev),
251 					 (unsigned long long)rdev->sectors);
252 			}
253 		}
254 
255 		zone->nb_dev = c;
256 		sectors = (smallest->sectors - zone->dev_start) * c;
257 		pr_debug("md/raid0:%s: zone->nb_dev: %d, sectors: %llu\n",
258 			 mdname(mddev),
259 			 zone->nb_dev, (unsigned long long)sectors);
260 
261 		curr_zone_end += sectors;
262 		zone->zone_end = curr_zone_end;
263 
264 		pr_debug("md/raid0:%s: current zone start: %llu\n",
265 			 mdname(mddev),
266 			 (unsigned long long)smallest->sectors);
267 	}
268 
269 	pr_debug("md/raid0:%s: done.\n", mdname(mddev));
270 	*private_conf = conf;
271 
272 	return 0;
273 abort:
274 	kfree(conf->strip_zone);
275 	kfree(conf->devlist);
276 	kfree(conf);
277 	*private_conf = ERR_PTR(err);
278 	return err;
279 }
280 
281 /* Find the zone which holds a particular offset
282  * Update *sectorp to be an offset in that zone
283  */
284 static struct strip_zone *find_zone(struct r0conf *conf,
285 				    sector_t *sectorp)
286 {
287 	int i;
288 	struct strip_zone *z = conf->strip_zone;
289 	sector_t sector = *sectorp;
290 
291 	for (i = 0; i < conf->nr_strip_zones; i++)
292 		if (sector < z[i].zone_end) {
293 			if (i)
294 				*sectorp = sector - z[i-1].zone_end;
295 			return z + i;
296 		}
297 	BUG();
298 }
299 
300 /*
301  * remaps the bio to the target device. we separate two flows.
302  * power 2 flow and a general flow for the sake of performance
303 */
304 static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
305 				sector_t sector, sector_t *sector_offset)
306 {
307 	unsigned int sect_in_chunk;
308 	sector_t chunk;
309 	struct r0conf *conf = mddev->private;
310 	int raid_disks = conf->strip_zone[0].nb_dev;
311 	unsigned int chunk_sects = mddev->chunk_sectors;
312 
313 	if (is_power_of_2(chunk_sects)) {
314 		int chunksect_bits = ffz(~chunk_sects);
315 		/* find the sector offset inside the chunk */
316 		sect_in_chunk  = sector & (chunk_sects - 1);
317 		sector >>= chunksect_bits;
318 		/* chunk in zone */
319 		chunk = *sector_offset;
320 		/* quotient is the chunk in real device*/
321 		sector_div(chunk, zone->nb_dev << chunksect_bits);
322 	} else{
323 		sect_in_chunk = sector_div(sector, chunk_sects);
324 		chunk = *sector_offset;
325 		sector_div(chunk, chunk_sects * zone->nb_dev);
326 	}
327 	/*
328 	*  position the bio over the real device
329 	*  real sector = chunk in device + starting of zone
330 	*	+ the position in the chunk
331 	*/
332 	*sector_offset = (chunk * chunk_sects) + sect_in_chunk;
333 	return conf->devlist[(zone - conf->strip_zone)*raid_disks
334 			     + sector_div(sector, zone->nb_dev)];
335 }
336 
337 static sector_t raid0_size(struct mddev *mddev, sector_t sectors, int raid_disks)
338 {
339 	sector_t array_sectors = 0;
340 	struct md_rdev *rdev;
341 
342 	WARN_ONCE(sectors || raid_disks,
343 		  "%s does not support generic reshape\n", __func__);
344 
345 	rdev_for_each(rdev, mddev)
346 		array_sectors += (rdev->sectors &
347 				  ~(sector_t)(mddev->chunk_sectors-1));
348 
349 	return array_sectors;
350 }
351 
352 static void raid0_free(struct mddev *mddev, void *priv);
353 
354 static int raid0_run(struct mddev *mddev)
355 {
356 	struct r0conf *conf;
357 	int ret;
358 
359 	if (mddev->chunk_sectors == 0) {
360 		printk(KERN_ERR "md/raid0:%s: chunk size must be set.\n",
361 		       mdname(mddev));
362 		return -EINVAL;
363 	}
364 	if (md_check_no_bitmap(mddev))
365 		return -EINVAL;
366 
367 	/* if private is not null, we are here after takeover */
368 	if (mddev->private == NULL) {
369 		ret = create_strip_zones(mddev, &conf);
370 		if (ret < 0)
371 			return ret;
372 		mddev->private = conf;
373 	}
374 	conf = mddev->private;
375 	if (mddev->queue) {
376 		struct md_rdev *rdev;
377 		bool discard_supported = false;
378 
379 		blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
380 		blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
381 		blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
382 
383 		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
384 		blk_queue_io_opt(mddev->queue,
385 				 (mddev->chunk_sectors << 9) * mddev->raid_disks);
386 
387 		rdev_for_each(rdev, mddev) {
388 			disk_stack_limits(mddev->gendisk, rdev->bdev,
389 					  rdev->data_offset << 9);
390 			if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
391 				discard_supported = true;
392 		}
393 		if (!discard_supported)
394 			queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
395 		else
396 			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
397 	}
398 
399 	/* calculate array device size */
400 	md_set_array_sectors(mddev, raid0_size(mddev, 0, 0));
401 
402 	printk(KERN_INFO "md/raid0:%s: md_size is %llu sectors.\n",
403 	       mdname(mddev),
404 	       (unsigned long long)mddev->array_sectors);
405 
406 	if (mddev->queue) {
407 		/* calculate the max read-ahead size.
408 		 * For read-ahead of large files to be effective, we need to
409 		 * readahead at least twice a whole stripe. i.e. number of devices
410 		 * multiplied by chunk size times 2.
411 		 * If an individual device has an ra_pages greater than the
412 		 * chunk size, then we will not drive that device as hard as it
413 		 * wants.  We consider this a configuration error: a larger
414 		 * chunksize should be used in that case.
415 		 */
416 		int stripe = mddev->raid_disks *
417 			(mddev->chunk_sectors << 9) / PAGE_SIZE;
418 		if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
419 			mddev->queue->backing_dev_info.ra_pages = 2* stripe;
420 	}
421 
422 	dump_zones(mddev);
423 
424 	ret = md_integrity_register(mddev);
425 
426 	return ret;
427 }
428 
429 static void raid0_free(struct mddev *mddev, void *priv)
430 {
431 	struct r0conf *conf = priv;
432 
433 	kfree(conf->strip_zone);
434 	kfree(conf->devlist);
435 	kfree(conf);
436 }
437 
438 /*
439  * Is io distribute over 1 or more chunks ?
440 */
441 static inline int is_io_in_chunk_boundary(struct mddev *mddev,
442 			unsigned int chunk_sects, struct bio *bio)
443 {
444 	if (likely(is_power_of_2(chunk_sects))) {
445 		return chunk_sects >=
446 			((bio->bi_iter.bi_sector & (chunk_sects-1))
447 					+ bio_sectors(bio));
448 	} else{
449 		sector_t sector = bio->bi_iter.bi_sector;
450 		return chunk_sects >= (sector_div(sector, chunk_sects)
451 						+ bio_sectors(bio));
452 	}
453 }
454 
455 static void raid0_make_request(struct mddev *mddev, struct bio *bio)
456 {
457 	struct strip_zone *zone;
458 	struct md_rdev *tmp_dev;
459 	struct bio *split;
460 
461 	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
462 		md_flush_request(mddev, bio);
463 		return;
464 	}
465 
466 	do {
467 		sector_t sector = bio->bi_iter.bi_sector;
468 		unsigned chunk_sects = mddev->chunk_sectors;
469 
470 		unsigned sectors = chunk_sects -
471 			(likely(is_power_of_2(chunk_sects))
472 			 ? (sector & (chunk_sects-1))
473 			 : sector_div(sector, chunk_sects));
474 
475 		/* Restore due to sector_div */
476 		sector = bio->bi_iter.bi_sector;
477 
478 		if (sectors < bio_sectors(bio)) {
479 			split = bio_split(bio, sectors, GFP_NOIO, fs_bio_set);
480 			bio_chain(split, bio);
481 		} else {
482 			split = bio;
483 		}
484 
485 		zone = find_zone(mddev->private, &sector);
486 		tmp_dev = map_sector(mddev, zone, sector, &sector);
487 		split->bi_bdev = tmp_dev->bdev;
488 		split->bi_iter.bi_sector = sector + zone->dev_start +
489 			tmp_dev->data_offset;
490 
491 		if (unlikely((split->bi_rw & REQ_DISCARD) &&
492 			 !blk_queue_discard(bdev_get_queue(split->bi_bdev)))) {
493 			/* Just ignore it */
494 			bio_endio(split);
495 		} else
496 			generic_make_request(split);
497 	} while (split != bio);
498 }
499 
500 static void raid0_status(struct seq_file *seq, struct mddev *mddev)
501 {
502 	seq_printf(seq, " %dk chunks", mddev->chunk_sectors / 2);
503 	return;
504 }
505 
506 static void *raid0_takeover_raid45(struct mddev *mddev)
507 {
508 	struct md_rdev *rdev;
509 	struct r0conf *priv_conf;
510 
511 	if (mddev->degraded != 1) {
512 		printk(KERN_ERR "md/raid0:%s: raid5 must be degraded! Degraded disks: %d\n",
513 		       mdname(mddev),
514 		       mddev->degraded);
515 		return ERR_PTR(-EINVAL);
516 	}
517 
518 	rdev_for_each(rdev, mddev) {
519 		/* check slot number for a disk */
520 		if (rdev->raid_disk == mddev->raid_disks-1) {
521 			printk(KERN_ERR "md/raid0:%s: raid5 must have missing parity disk!\n",
522 			       mdname(mddev));
523 			return ERR_PTR(-EINVAL);
524 		}
525 		rdev->sectors = mddev->dev_sectors;
526 	}
527 
528 	/* Set new parameters */
529 	mddev->new_level = 0;
530 	mddev->new_layout = 0;
531 	mddev->new_chunk_sectors = mddev->chunk_sectors;
532 	mddev->raid_disks--;
533 	mddev->delta_disks = -1;
534 	/* make sure it will be not marked as dirty */
535 	mddev->recovery_cp = MaxSector;
536 
537 	create_strip_zones(mddev, &priv_conf);
538 	return priv_conf;
539 }
540 
541 static void *raid0_takeover_raid10(struct mddev *mddev)
542 {
543 	struct r0conf *priv_conf;
544 
545 	/* Check layout:
546 	 *  - far_copies must be 1
547 	 *  - near_copies must be 2
548 	 *  - disks number must be even
549 	 *  - all mirrors must be already degraded
550 	 */
551 	if (mddev->layout != ((1 << 8) + 2)) {
552 		printk(KERN_ERR "md/raid0:%s:: Raid0 cannot takover layout: 0x%x\n",
553 		       mdname(mddev),
554 		       mddev->layout);
555 		return ERR_PTR(-EINVAL);
556 	}
557 	if (mddev->raid_disks & 1) {
558 		printk(KERN_ERR "md/raid0:%s: Raid0 cannot takover Raid10 with odd disk number.\n",
559 		       mdname(mddev));
560 		return ERR_PTR(-EINVAL);
561 	}
562 	if (mddev->degraded != (mddev->raid_disks>>1)) {
563 		printk(KERN_ERR "md/raid0:%s: All mirrors must be already degraded!\n",
564 		       mdname(mddev));
565 		return ERR_PTR(-EINVAL);
566 	}
567 
568 	/* Set new parameters */
569 	mddev->new_level = 0;
570 	mddev->new_layout = 0;
571 	mddev->new_chunk_sectors = mddev->chunk_sectors;
572 	mddev->delta_disks = - mddev->raid_disks / 2;
573 	mddev->raid_disks += mddev->delta_disks;
574 	mddev->degraded = 0;
575 	/* make sure it will be not marked as dirty */
576 	mddev->recovery_cp = MaxSector;
577 
578 	create_strip_zones(mddev, &priv_conf);
579 	return priv_conf;
580 }
581 
582 static void *raid0_takeover_raid1(struct mddev *mddev)
583 {
584 	struct r0conf *priv_conf;
585 	int chunksect;
586 
587 	/* Check layout:
588 	 *  - (N - 1) mirror drives must be already faulty
589 	 */
590 	if ((mddev->raid_disks - 1) != mddev->degraded) {
591 		printk(KERN_ERR "md/raid0:%s: (N - 1) mirrors drives must be already faulty!\n",
592 		       mdname(mddev));
593 		return ERR_PTR(-EINVAL);
594 	}
595 
596 	/*
597 	 * a raid1 doesn't have the notion of chunk size, so
598 	 * figure out the largest suitable size we can use.
599 	 */
600 	chunksect = 64 * 2; /* 64K by default */
601 
602 	/* The array must be an exact multiple of chunksize */
603 	while (chunksect && (mddev->array_sectors & (chunksect - 1)))
604 		chunksect >>= 1;
605 
606 	if ((chunksect << 9) < PAGE_SIZE)
607 		/* array size does not allow a suitable chunk size */
608 		return ERR_PTR(-EINVAL);
609 
610 	/* Set new parameters */
611 	mddev->new_level = 0;
612 	mddev->new_layout = 0;
613 	mddev->new_chunk_sectors = chunksect;
614 	mddev->chunk_sectors = chunksect;
615 	mddev->delta_disks = 1 - mddev->raid_disks;
616 	mddev->raid_disks = 1;
617 	/* make sure it will be not marked as dirty */
618 	mddev->recovery_cp = MaxSector;
619 
620 	create_strip_zones(mddev, &priv_conf);
621 	return priv_conf;
622 }
623 
624 static void *raid0_takeover(struct mddev *mddev)
625 {
626 	/* raid0 can take over:
627 	 *  raid4 - if all data disks are active.
628 	 *  raid5 - providing it is Raid4 layout and one disk is faulty
629 	 *  raid10 - assuming we have all necessary active disks
630 	 *  raid1 - with (N -1) mirror drives faulty
631 	 */
632 
633 	if (mddev->bitmap) {
634 		printk(KERN_ERR "md/raid0: %s: cannot takeover array with bitmap\n",
635 		       mdname(mddev));
636 		return ERR_PTR(-EBUSY);
637 	}
638 	if (mddev->level == 4)
639 		return raid0_takeover_raid45(mddev);
640 
641 	if (mddev->level == 5) {
642 		if (mddev->layout == ALGORITHM_PARITY_N)
643 			return raid0_takeover_raid45(mddev);
644 
645 		printk(KERN_ERR "md/raid0:%s: Raid can only takeover Raid5 with layout: %d\n",
646 		       mdname(mddev), ALGORITHM_PARITY_N);
647 	}
648 
649 	if (mddev->level == 10)
650 		return raid0_takeover_raid10(mddev);
651 
652 	if (mddev->level == 1)
653 		return raid0_takeover_raid1(mddev);
654 
655 	printk(KERN_ERR "Takeover from raid%i to raid0 not supported\n",
656 		mddev->level);
657 
658 	return ERR_PTR(-EINVAL);
659 }
660 
661 static void raid0_quiesce(struct mddev *mddev, int state)
662 {
663 }
664 
665 static struct md_personality raid0_personality=
666 {
667 	.name		= "raid0",
668 	.level		= 0,
669 	.owner		= THIS_MODULE,
670 	.make_request	= raid0_make_request,
671 	.run		= raid0_run,
672 	.free		= raid0_free,
673 	.status		= raid0_status,
674 	.size		= raid0_size,
675 	.takeover	= raid0_takeover,
676 	.quiesce	= raid0_quiesce,
677 	.congested	= raid0_congested,
678 };
679 
680 static int __init raid0_init (void)
681 {
682 	return register_md_personality (&raid0_personality);
683 }
684 
685 static void raid0_exit (void)
686 {
687 	unregister_md_personality (&raid0_personality);
688 }
689 
690 module_init(raid0_init);
691 module_exit(raid0_exit);
692 MODULE_LICENSE("GPL");
693 MODULE_DESCRIPTION("RAID0 (striping) personality for MD");
694 MODULE_ALIAS("md-personality-2"); /* RAID0 */
695 MODULE_ALIAS("md-raid0");
696 MODULE_ALIAS("md-level-0");
697