Merge tag 'gpio-v3.13-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[linux-2.6.git] / drivers / md / raid0.c

/*
   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\n",
               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 "]\n");

                zone_size  = conf->strip_zone[j].zone_end - zone_start;
                printk(KERN_INFO "      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;
        }
        printk(KERN_INFO "\n");
}

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\n",
                         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)\n",
                                 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\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);
        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\n",
                               mdname(mddev));
                        goto abort;
                }
                if (j >= mddev->raid_disks) {
                        printk(KERN_ERR "md/raid0:%s: bad disk number %d - "
                               "aborting!\n", mdname(mddev), j);
                        goto abort;
                }
                if (dev[j]) {
                        printk(KERN_ERR "md/raid0:%s: multiple devices for %d - "
                               "aborting!\n", 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!\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 %s ... nope\n",
                                         mdname(mddev),
                                         bdevname(rdev->bdev, b));
                                continue;
                        }
                        pr_debug("md/raid0:%s: checking %s ..."
                                 " contained as device %d\n",
                                 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!.\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);
        }
        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\n",
                       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.\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 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\n", __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.\n",
                       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.\n",
               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_sector & (chunk_sects-1))
                                        + bio_sectors(bio));
        } else{
                sector_t sector = bio->bi_sector;
                return chunk_sects >= (sector_div(sector, chunk_sects)
                                                + bio_sectors(bio));
        }
}

static void raid0_make_request(struct mddev *mddev, struct bio *bio)
{
        unsigned int chunk_sects;
        sector_t sector_offset;
        struct strip_zone *zone;
        struct md_rdev *tmp_dev;

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

        chunk_sects = mddev->chunk_sectors;
        if (unlikely(!is_io_in_chunk_boundary(mddev, chunk_sects, bio))) {
                sector_t sector = bio->bi_sector;
                struct bio_pair *bp;
                /* Sanity check -- queue functions should prevent this happening */
                if (bio_segments(bio) > 1)
                        goto bad_map;
                /* This is a one page bio that upper layers
                 * refuse to split for us, so we need to split it.
                 */
                if (likely(is_power_of_2(chunk_sects)))
                        bp = bio_split(bio, chunk_sects - (sector &
                                                           (chunk_sects-1)));
                else
                        bp = bio_split(bio, chunk_sects -
                                       sector_div(sector, chunk_sects));
                raid0_make_request(mddev, &bp->bio1);
                raid0_make_request(mddev, &bp->bio2);
                bio_pair_release(bp);
                return;
        }

        sector_offset = bio->bi_sector;
        zone = find_zone(mddev->private, &sector_offset);
        tmp_dev = map_sector(mddev, zone, bio->bi_sector,
                             &sector_offset);
        bio->bi_bdev = tmp_dev->bdev;
        bio->bi_sector = sector_offset + zone->dev_start +
                tmp_dev->data_offset;

        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
                     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
                /* Just ignore it */
                bio_endio(bio, 0);
                return;
        }

        generic_make_request(bio);
        return;

bad_map:
        printk("md/raid0:%s: make_request bug: can't convert block across chunks"
               " or bigger than %dk %llu %d\n",
               mdname(mddev), chunk_sects / 2,
               (unsigned long long)bio->bi_sector, bio_sectors(bio) / 2);

        bio_io_error(bio);
        return;
}

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\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) {
                        printk(KERN_ERR "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;

        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\n",
                       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.\n",
                       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!\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;

        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!\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;

        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->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\n",
                       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\n",
                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");