linux/drivers/md/raid0.c
Kent Overstreet 5b83636ae3 block: Change bio_split() to respect the current value of bi_idx
In the current code bio_split() won't be seeing partially completed bios
so this doesn't change any behaviour, but this makes the code a bit
clearer as to what bio_split() actually requires.

The immediate purpose of the patch is removing unnecessary bi_idx
references, but the end goal is to allow partial completed bios to be
submitted, which along with immutable biovecs enables effecient bio
splitting.

Some of the callers were (double) checking that bios could be split, so
update their checks too.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: Lars Ellenberg <drbd-dev@lists.linbit.com>
CC: Neil Brown <neilb@suse.de>
CC: Martin K. Petersen <martin.petersen@oracle.com>
2013-03-23 14:15:30 -07:00

764 lines
20 KiB
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);
}
}
/* 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");