/*
     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.
  
     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, or (at your option)
     any later version.
     
     You should have received a copy of the GNU General Public License
     (for example /usr/src/linux/COPYING); if not, write to the Free
     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
  */

  #include <linux/blkdev.h>

  #include <linux/seq_file.h>

  #include <linux/module.h>

  #include <linux/slab.h>

  #include "md.h"

  #include "raid0.h"

  #include "raid5.h"

  static int raid0_congested(void *data, int bits)
  {

  	struct mddev *mddev = data;

  	struct r0conf *conf = mddev->private;

  	struct md_rdev **devlist = conf->devlist;

  	int raid_disks = conf->strip_zone[0].nb_dev;

  	int i, ret = 0;

  	if (mddev_congested(mddev, bits))
  		return 1;

  	for (i = 0; i < raid_disks && !ret ; i++) {

  		struct request_queue *q = bdev_get_queue(devlist[i]->bdev);

  
  		ret |= bdi_congested(&q->backing_dev_info, bits);
  	}
  	return ret;
  }

  /*
   * 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;
  	char b[BDEVNAME_SIZE];

  	struct r0conf *conf = mddev->private;

  	int raid_disks = conf->strip_zone[0].nb_dev;

  	printk(KERN_INFO "md: RAID0 configuration for %s - %d zone%s
  ",
  	       mdname(mddev),
  	       conf->nr_strip_zones, conf->nr_strip_zones==1?"":"s");

  	for (j = 0; j < conf->nr_strip_zones; j++) {

  		printk(KERN_INFO "md: zone%d=[", j);

  		for (k = 0; k < conf->strip_zone[j].nb_dev; k++)

  			printk(KERN_CONT "%s%s", k?"/":"",

  			bdevname(conf->devlist[j*raid_disks

  						+ k]->bdev, b));

  		printk(KERN_CONT "]
  ");

  
  		zone_size  = conf->strip_zone[j].zone_end - zone_start;

  		printk(KERN_INFO "      zone-offset=%10lluKB, "
  				"device-offset=%10lluKB, size=%10lluKB
  ",

  			(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;
  	}

  	printk(KERN_INFO "
  ");

  }

  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;
  	char b[BDEVNAME_SIZE];

  	char b2[BDEVNAME_SIZE];

  	struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);

  	bool discard_supported = false;

  
  	if (!conf)
  		return -ENOMEM;

  	rdev_for_each(rdev1, mddev) {

  		pr_debug("md/raid0:%s: looking at %s
  ",
  			 mdname(mddev),
  			 bdevname(rdev1->bdev, b));

  		c = 0;

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

  		rdev_for_each(rdev2, mddev) {

  			pr_debug("md/raid0:%s:   comparing %s(%llu)"
  				 " with %s(%llu)
  ",
  				 mdname(mddev),
  				 bdevname(rdev1->bdev,b),
  				 (unsigned long long)rdev1->sectors,
  				 bdevname(rdev2->bdev,b2),
  				 (unsigned long long)rdev2->sectors);

  			if (rdev2 == rdev1) {

  				pr_debug("md/raid0:%s:   END
  ",
  					 mdname(mddev));

  				break;
  			}

  			if (rdev2->sectors == rdev1->sectors) {

  				/*
  				 * Not unique, don't count it as a new
  				 * group
  				 */

  				pr_debug("md/raid0:%s:   EQUAL
  ",
  					 mdname(mddev));

  				c = 1;
  				break;
  			}

  			pr_debug("md/raid0:%s:   NOT EQUAL
  ",
  				 mdname(mddev));

  		}
  		if (!c) {

  			pr_debug("md/raid0:%s:   ==> UNIQUE
  ",
  				 mdname(mddev));

  			conf->nr_strip_zones++;

  			pr_debug("md/raid0:%s: %d zones
  ",
  				 mdname(mddev), conf->nr_strip_zones);

  		}
  	}

  	pr_debug("md/raid0:%s: FINAL %d zones
  ",
  		 mdname(mddev), conf->nr_strip_zones);

  	err = -ENOMEM;

  	conf->strip_zone = kzalloc(sizeof(struct strip_zone)*

  				conf->nr_strip_zones, GFP_KERNEL);
  	if (!conf->strip_zone)

  		goto abort;

  	conf->devlist = kzalloc(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) {
  			printk(KERN_ERR
  			       "md/raid0:%s: remove inactive devices before converting to RAID0
  ",
  			       mdname(mddev));
  			goto abort;
  		}
  		if (j >= mddev->raid_disks) {

  			printk(KERN_ERR "md/raid0:%s: bad disk number %d - "
  			       "aborting!
  ", mdname(mddev), j);

  			goto abort;
  		}

  		if (dev[j]) {

  			printk(KERN_ERR "md/raid0:%s: multiple devices for %d - "
  			       "aborting!
  ", mdname(mddev), j);

  			goto abort;
  		}

  		dev[j] = rdev1;

  		disk_stack_limits(mddev->gendisk, rdev1->bdev,
  				  rdev1->data_offset << 9);

  		if (rdev1->bdev->bd_disk->queue->merge_bvec_fn)
  			conf->has_merge_bvec = 1;

  		if (!smallest || (rdev1->sectors < smallest->sectors))

  			smallest = rdev1;
  		cnt++;

  
  		if (blk_queue_discard(bdev_get_queue(rdev1->bdev)))
  			discard_supported = true;

  	}
  	if (cnt != mddev->raid_disks) {

  		printk(KERN_ERR "md/raid0:%s: too few disks (%d of %d) - "
  		       "aborting!
  ", 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
  ", 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 %s ... nope
  ",
  					 mdname(mddev),
  					 bdevname(rdev->bdev, b));

  				continue;
  			}

  			pr_debug("md/raid0:%s: checking %s ..."
  				 " contained as device %d
  ",
  				 mdname(mddev),
  				 bdevname(rdev->bdev, b), c);

  			dev[c] = rdev;

  			c++;
  			if (!smallest || rdev->sectors < smallest->sectors) {
  				smallest = rdev;

  				pr_debug("md/raid0:%s:  (%llu) is smallest!.
  ",
  					 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
  ",
  			 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
  ",
  			 mdname(mddev),
  			 (unsigned long long)smallest->sectors);

  	}

  	mddev->queue->backing_dev_info.congested_fn = raid0_congested;
  	mddev->queue->backing_dev_info.congested_data = mddev;

  	/*
  	 * 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) % queue_logical_block_size(mddev->queue)) {

  		printk(KERN_ERR "md/raid0:%s: chunk_size of %d not valid
  ",

  		       mdname(mddev),

  		       mddev->chunk_sectors << 9);

  		goto abort;
  	}

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

  	if (!discard_supported)
  		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
  	else
  		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);

  	pr_debug("md/raid0:%s: done.
  ", 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 perfromance
  */
  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)];
  }

  /**

   *	raid0_mergeable_bvec -- tell bio layer if two requests can be merged

   *	@q: request queue

   *	@bvm: properties of new bio

   *	@biovec: the request that could be merged to it.
   *
   *	Return amount of bytes we can accept at this offset
   */

  static int raid0_mergeable_bvec(struct request_queue *q,
  				struct bvec_merge_data *bvm,
  				struct bio_vec *biovec)

  {

  	struct mddev *mddev = q->queuedata;

  	struct r0conf *conf = mddev->private;

  	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);

  	sector_t sector_offset = sector;

  	int max;

  	unsigned int chunk_sectors = mddev->chunk_sectors;

  	unsigned int bio_sectors = bvm->bi_size >> 9;

  	struct strip_zone *zone;
  	struct md_rdev *rdev;
  	struct request_queue *subq;

  	if (is_power_of_2(chunk_sectors))

  		max =  (chunk_sectors - ((sector & (chunk_sectors-1))
  						+ bio_sectors)) << 9;
  	else
  		max =  (chunk_sectors - (sector_div(sector, chunk_sectors)
  						+ bio_sectors)) << 9;

  	if (max < 0)
  		max = 0; /* bio_add cannot handle a negative return */

  	if (max <= biovec->bv_len && bio_sectors == 0)
  		return biovec->bv_len;

  	if (max < biovec->bv_len)
  		/* too small already, no need to check further */
  		return max;
  	if (!conf->has_merge_bvec)
  		return max;
  
  	/* May need to check subordinate device */
  	sector = sector_offset;
  	zone = find_zone(mddev->private, &sector_offset);
  	rdev = map_sector(mddev, zone, sector, &sector_offset);
  	subq = bdev_get_queue(rdev->bdev);
  	if (subq->merge_bvec_fn) {
  		bvm->bi_bdev = rdev->bdev;
  		bvm->bi_sector = sector_offset + zone->dev_start +
  			rdev->data_offset;
  		return min(max, subq->merge_bvec_fn(subq, bvm, biovec));
  	} else

  		return max;
  }

  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
  ", __func__);

  	rdev_for_each(rdev, mddev)

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

  
  	return array_sectors;
  }

  static int raid0_stop(struct mddev *mddev);

  static int raid0_run(struct mddev *mddev)

  {

  	struct r0conf *conf;

  	int ret;

  	if (mddev->chunk_sectors == 0) {

  		printk(KERN_ERR "md/raid0:%s: chunk size must be set.
  ",
  		       mdname(mddev));

  		return -EINVAL;
  	}

  	if (md_check_no_bitmap(mddev))
  		return -EINVAL;

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

  	blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);

  	blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);

  	/* 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;

  
  	/* calculate array device size */

  	md_set_array_sectors(mddev, raid0_size(mddev, 0, 0));

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

  	/* calculate the max read-ahead size.
  	 * For read-ahead of large files to be effective, we need to
  	 * readahead at least twice a whole stripe. i.e. number of devices
  	 * multiplied by chunk size times 2.
  	 * If an individual device has an ra_pages greater than the
  	 * chunk size, then we will not drive that device as hard as it
  	 * wants.  We consider this a configuration error: a larger
  	 * chunksize should be used in that case.
  	 */
  	{

  		int stripe = mddev->raid_disks *
  			(mddev->chunk_sectors << 9) / PAGE_SIZE;

  		if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
  			mddev->queue->backing_dev_info.ra_pages = 2* stripe;
  	}

  	blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);

  	dump_zones(mddev);

  
  	ret = md_integrity_register(mddev);
  	if (ret)
  		raid0_stop(mddev);
  
  	return ret;

  }

  static int raid0_stop(struct mddev *mddev)

  {

  	struct r0conf *conf = mddev->private;

  
  	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/

  	kfree(conf->strip_zone);

  	kfree(conf->devlist);

  	kfree(conf);

  	mddev->private = NULL;

  	return 0;
  }

  /*
   * Is io distribute over 1 or more chunks ?
  */

  static inline int is_io_in_chunk_boundary(struct mddev *mddev,

  			unsigned int chunk_sects, struct bio *bio)
  {

  	if (likely(is_power_of_2(chunk_sects))) {

  		return chunk_sects >=
  			((bio->bi_iter.bi_sector & (chunk_sects-1))

  					+ bio_sectors(bio));

  	} else{

  		sector_t sector = bio->bi_iter.bi_sector;

  		return chunk_sects >= (sector_div(sector, chunk_sects)

  						+ bio_sectors(bio));

  	}
  }

  static void raid0_make_request(struct mddev *mddev, struct bio *bio)

  {

  	struct strip_zone *zone;

  	struct md_rdev *tmp_dev;

  	struct bio *split;

  	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
  		md_flush_request(mddev, bio);

  		return;

  	}

  	do {

  		sector_t sector = bio->bi_iter.bi_sector;

  		unsigned chunk_sects = mddev->chunk_sectors;
  
  		unsigned sectors = chunk_sects -
  			(likely(is_power_of_2(chunk_sects))
  			 ? (sector & (chunk_sects-1))
  			 : sector_div(sector, chunk_sects));
  
  		if (sectors < bio_sectors(bio)) {
  			split = bio_split(bio, sectors, GFP_NOIO, fs_bio_set);
  			bio_chain(split, bio);
  		} else {
  			split = bio;
  		}

  		zone = find_zone(mddev->private, &sector);
  		tmp_dev = map_sector(mddev, zone, sector, &sector);
  		split->bi_bdev = tmp_dev->bdev;
  		split->bi_iter.bi_sector = sector + zone->dev_start +
  			tmp_dev->data_offset;
  
  		if (unlikely((split->bi_rw & REQ_DISCARD) &&
  			 !blk_queue_discard(bdev_get_queue(split->bi_bdev)))) {
  			/* Just ignore it */
  			bio_endio(split, 0);
  		} else
  			generic_make_request(split);
  	} while (split != bio);

  }

  static void raid0_status(struct seq_file *seq, struct mddev *mddev)

  {

  	seq_printf(seq, " %dk chunks", mddev->chunk_sectors / 2);

  	return;
  }

  static void *raid0_takeover_raid45(struct mddev *mddev)

  {

  	struct md_rdev *rdev;

  	struct r0conf *priv_conf;

  
  	if (mddev->degraded != 1) {

  		printk(KERN_ERR "md/raid0:%s: raid5 must be degraded! Degraded disks: %d
  ",
  		       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) {

  			printk(KERN_ERR "md/raid0:%s: raid5 must have missing parity disk!
  ",
  			       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;
  
  	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)) {

  		printk(KERN_ERR "md/raid0:%s:: Raid0 cannot takover layout: 0x%x
  ",
  		       mdname(mddev),

  		       mddev->layout);
  		return ERR_PTR(-EINVAL);
  	}
  	if (mddev->raid_disks & 1) {

  		printk(KERN_ERR "md/raid0:%s: Raid0 cannot takover Raid10 with odd disk number.
  ",
  		       mdname(mddev));

  		return ERR_PTR(-EINVAL);
  	}
  	if (mddev->degraded != (mddev->raid_disks>>1)) {

  		printk(KERN_ERR "md/raid0:%s: All mirrors must be already degraded!
  ",
  		       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;
  
  	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) {
  		printk(KERN_ERR "md/raid0:%s: (N - 1) mirrors drives must be already faulty!
  ",
  		       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;
  
  	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) {
  		printk(KERN_ERR "md/raid0: %s: cannot takeover array with bitmap
  ",
  		       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);

  		printk(KERN_ERR "md/raid0:%s: Raid can only takeover Raid5 with layout: %d
  ",
  		       mdname(mddev), ALGORITHM_PARITY_N);

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

  	if (mddev->level == 1)
  		return raid0_takeover_raid1(mddev);
  
  	printk(KERN_ERR "Takeover from raid%i to raid0 not supported
  ",
  		mddev->level);

  	return ERR_PTR(-EINVAL);
  }

  static void raid0_quiesce(struct mddev *mddev, int state)

  {
  }

  static struct md_personality raid0_personality=

  {
  	.name		= "raid0",

  	.level		= 0,

  	.owner		= THIS_MODULE,
  	.make_request	= raid0_make_request,
  	.run		= raid0_run,
  	.stop		= raid0_stop,
  	.status		= raid0_status,

  	.size		= raid0_size,

  	.takeover	= raid0_takeover,
  	.quiesce	= raid0_quiesce,

  };
  
  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");