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/*
   md.c : Multiple Devices driver for Linux
	  Copyright (C) 1998, 1999, 2000 Ingo Molnar

     completely rewritten, based on the MD driver code from Marc Zyngier

   Changes:

   - RAID-1/RAID-5 extensions by Miguel de Icaza, Gadi Oxman, Ingo Molnar
   - RAID-6 extensions by H. Peter Anvin <hpa@zytor.com>
   - boot support for linear and striped mode by Harald Hoyer <HarryH@Royal.Net>
   - kerneld support by Boris Tobotras <boris@xtalk.msk.su>
   - kmod support by: Cyrus Durgin
   - RAID0 bugfixes: Mark Anthony Lisher <markal@iname.com>
   - Devfs support by Richard Gooch <rgooch@atnf.csiro.au>

   - lots of fixes and improvements to the RAID1/RAID5 and generic
     RAID code (such as request based resynchronization):

     Neil Brown <neilb@cse.unsw.edu.au>.

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   - persistent bitmap code
     Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.

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   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/module.h>
#include <linux/config.h>
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#include <linux/kthread.h>
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#include <linux/linkage.h>
#include <linux/raid/md.h>
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#include <linux/raid/bitmap.h>
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#include <linux/sysctl.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/buffer_head.h> /* for invalidate_bdev */
#include <linux/suspend.h>
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#include <linux/poll.h>
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#include <linux/init.h>

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#include <linux/file.h>

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#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

#include <asm/unaligned.h>

#define MAJOR_NR MD_MAJOR
#define MD_DRIVER

/* 63 partitions with the alternate major number (mdp) */
#define MdpMinorShift 6

#define DEBUG 0
#define dprintk(x...) ((void)(DEBUG && printk(x)))


#ifndef MODULE
static void autostart_arrays (int part);
#endif

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static LIST_HEAD(pers_list);
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static DEFINE_SPINLOCK(pers_lock);

/*
 * Current RAID-1,4,5 parallel reconstruction 'guaranteed speed limit'
 * is 1000 KB/sec, so the extra system load does not show up that much.
 * Increase it if you want to have more _guaranteed_ speed. Note that
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 * the RAID driver will use the maximum available bandwidth if the IO
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 * subsystem is idle. There is also an 'absolute maximum' reconstruction
 * speed limit - in case reconstruction slows down your system despite
 * idle IO detection.
 *
 * you can change it via /proc/sys/dev/raid/speed_limit_min and _max.
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 * or /sys/block/mdX/md/sync_speed_{min,max}
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 */

static int sysctl_speed_limit_min = 1000;
static int sysctl_speed_limit_max = 200000;
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static inline int speed_min(mddev_t *mddev)
{
	return mddev->sync_speed_min ?
		mddev->sync_speed_min : sysctl_speed_limit_min;
}

static inline int speed_max(mddev_t *mddev)
{
	return mddev->sync_speed_max ?
		mddev->sync_speed_max : sysctl_speed_limit_max;
}
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static struct ctl_table_header *raid_table_header;

static ctl_table raid_table[] = {
	{
		.ctl_name	= DEV_RAID_SPEED_LIMIT_MIN,
		.procname	= "speed_limit_min",
		.data		= &sysctl_speed_limit_min,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= DEV_RAID_SPEED_LIMIT_MAX,
		.procname	= "speed_limit_max",
		.data		= &sysctl_speed_limit_max,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec,
	},
	{ .ctl_name = 0 }
};

static ctl_table raid_dir_table[] = {
	{
		.ctl_name	= DEV_RAID,
		.procname	= "raid",
		.maxlen		= 0,
		.mode		= 0555,
		.child		= raid_table,
	},
	{ .ctl_name = 0 }
};

static ctl_table raid_root_table[] = {
	{
		.ctl_name	= CTL_DEV,
		.procname	= "dev",
		.maxlen		= 0,
		.mode		= 0555,
		.child		= raid_dir_table,
	},
	{ .ctl_name = 0 }
};

static struct block_device_operations md_fops;

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static int start_readonly;

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/*
 * We have a system wide 'event count' that is incremented
 * on any 'interesting' event, and readers of /proc/mdstat
 * can use 'poll' or 'select' to find out when the event
 * count increases.
 *
 * Events are:
 *  start array, stop array, error, add device, remove device,
 *  start build, activate spare
 */
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static DECLARE_WAIT_QUEUE_HEAD(md_event_waiters);
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static atomic_t md_event_count;
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static void md_new_event(mddev_t *mddev)
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{
	atomic_inc(&md_event_count);
	wake_up(&md_event_waiters);
}

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/*
 * Enables to iterate over all existing md arrays
 * all_mddevs_lock protects this list.
 */
static LIST_HEAD(all_mddevs);
static DEFINE_SPINLOCK(all_mddevs_lock);


/*
 * iterates through all used mddevs in the system.
 * We take care to grab the all_mddevs_lock whenever navigating
 * the list, and to always hold a refcount when unlocked.
 * Any code which breaks out of this loop while own
 * a reference to the current mddev and must mddev_put it.
 */
#define ITERATE_MDDEV(mddev,tmp)					\
									\
	for (({ spin_lock(&all_mddevs_lock); 				\
		tmp = all_mddevs.next;					\
		mddev = NULL;});					\
	     ({ if (tmp != &all_mddevs)					\
			mddev_get(list_entry(tmp, mddev_t, all_mddevs));\
		spin_unlock(&all_mddevs_lock);				\
		if (mddev) mddev_put(mddev);				\
		mddev = list_entry(tmp, mddev_t, all_mddevs);		\
		tmp != &all_mddevs;});					\
	     ({ spin_lock(&all_mddevs_lock);				\
		tmp = tmp->next;})					\
		)


static int md_fail_request (request_queue_t *q, struct bio *bio)
{
	bio_io_error(bio, bio->bi_size);
	return 0;
}

static inline mddev_t *mddev_get(mddev_t *mddev)
{
	atomic_inc(&mddev->active);
	return mddev;
}

static void mddev_put(mddev_t *mddev)
{
	if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
		return;
	if (!mddev->raid_disks && list_empty(&mddev->disks)) {
		list_del(&mddev->all_mddevs);
		blk_put_queue(mddev->queue);
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		kobject_unregister(&mddev->kobj);
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	}
	spin_unlock(&all_mddevs_lock);
}

static mddev_t * mddev_find(dev_t unit)
{
	mddev_t *mddev, *new = NULL;

 retry:
	spin_lock(&all_mddevs_lock);
	list_for_each_entry(mddev, &all_mddevs, all_mddevs)
		if (mddev->unit == unit) {
			mddev_get(mddev);
			spin_unlock(&all_mddevs_lock);
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			kfree(new);
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			return mddev;
		}

	if (new) {
		list_add(&new->all_mddevs, &all_mddevs);
		spin_unlock(&all_mddevs_lock);
		return new;
	}
	spin_unlock(&all_mddevs_lock);

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	new = kzalloc(sizeof(*new), GFP_KERNEL);
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	if (!new)
		return NULL;

	new->unit = unit;
	if (MAJOR(unit) == MD_MAJOR)
		new->md_minor = MINOR(unit);
	else
		new->md_minor = MINOR(unit) >> MdpMinorShift;

	init_MUTEX(&new->reconfig_sem);
	INIT_LIST_HEAD(&new->disks);
	INIT_LIST_HEAD(&new->all_mddevs);
	init_timer(&new->safemode_timer);
	atomic_set(&new->active, 1);
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	spin_lock_init(&new->write_lock);
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	init_waitqueue_head(&new->sb_wait);
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	new->queue = blk_alloc_queue(GFP_KERNEL);
	if (!new->queue) {
		kfree(new);
		return NULL;
	}

	blk_queue_make_request(new->queue, md_fail_request);

	goto retry;
}

static inline int mddev_lock(mddev_t * mddev)
{
	return down_interruptible(&mddev->reconfig_sem);
}

static inline void mddev_lock_uninterruptible(mddev_t * mddev)
{
	down(&mddev->reconfig_sem);
}

static inline int mddev_trylock(mddev_t * mddev)
{
	return down_trylock(&mddev->reconfig_sem);
}

static inline void mddev_unlock(mddev_t * mddev)
{
	up(&mddev->reconfig_sem);

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	md_wakeup_thread(mddev->thread);
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}

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static mdk_rdev_t * find_rdev_nr(mddev_t *mddev, int nr)
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{
	mdk_rdev_t * rdev;
	struct list_head *tmp;

	ITERATE_RDEV(mddev,rdev,tmp) {
		if (rdev->desc_nr == nr)
			return rdev;
	}
	return NULL;
}

static mdk_rdev_t * find_rdev(mddev_t * mddev, dev_t dev)
{
	struct list_head *tmp;
	mdk_rdev_t *rdev;

	ITERATE_RDEV(mddev,rdev,tmp) {
		if (rdev->bdev->bd_dev == dev)
			return rdev;
	}
	return NULL;
}

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static struct mdk_personality *find_pers(int level, char *clevel)
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{
	struct mdk_personality *pers;
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	list_for_each_entry(pers, &pers_list, list) {
		if (level != LEVEL_NONE && pers->level == level)
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			return pers;
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		if (strcmp(pers->name, clevel)==0)
			return pers;
	}
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	return NULL;
}

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static inline sector_t calc_dev_sboffset(struct block_device *bdev)
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{
	sector_t size = bdev->bd_inode->i_size >> BLOCK_SIZE_BITS;
	return MD_NEW_SIZE_BLOCKS(size);
}

static sector_t calc_dev_size(mdk_rdev_t *rdev, unsigned chunk_size)
{
	sector_t size;

	size = rdev->sb_offset;

	if (chunk_size)
		size &= ~((sector_t)chunk_size/1024 - 1);
	return size;
}

static int alloc_disk_sb(mdk_rdev_t * rdev)
{
	if (rdev->sb_page)
		MD_BUG();

	rdev->sb_page = alloc_page(GFP_KERNEL);
	if (!rdev->sb_page) {
		printk(KERN_ALERT "md: out of memory.\n");
		return -EINVAL;
	}

	return 0;
}

static void free_disk_sb(mdk_rdev_t * rdev)
{
	if (rdev->sb_page) {
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		put_page(rdev->sb_page);
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		rdev->sb_loaded = 0;
		rdev->sb_page = NULL;
		rdev->sb_offset = 0;
		rdev->size = 0;
	}
}


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static int super_written(struct bio *bio, unsigned int bytes_done, int error)
{
	mdk_rdev_t *rdev = bio->bi_private;
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	mddev_t *mddev = rdev->mddev;
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	if (bio->bi_size)
		return 1;

	if (error || !test_bit(BIO_UPTODATE, &bio->bi_flags))
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		md_error(mddev, rdev);
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	if (atomic_dec_and_test(&mddev->pending_writes))
		wake_up(&mddev->sb_wait);
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	bio_put(bio);
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	return 0;
}

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static int super_written_barrier(struct bio *bio, unsigned int bytes_done, int error)
{
	struct bio *bio2 = bio->bi_private;
	mdk_rdev_t *rdev = bio2->bi_private;
	mddev_t *mddev = rdev->mddev;
	if (bio->bi_size)
		return 1;

	if (!test_bit(BIO_UPTODATE, &bio->bi_flags) &&
	    error == -EOPNOTSUPP) {
		unsigned long flags;
		/* barriers don't appear to be supported :-( */
		set_bit(BarriersNotsupp, &rdev->flags);
		mddev->barriers_work = 0;
		spin_lock_irqsave(&mddev->write_lock, flags);
		bio2->bi_next = mddev->biolist;
		mddev->biolist = bio2;
		spin_unlock_irqrestore(&mddev->write_lock, flags);
		wake_up(&mddev->sb_wait);
		bio_put(bio);
		return 0;
	}
	bio_put(bio2);
	bio->bi_private = rdev;
	return super_written(bio, bytes_done, error);
}

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void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
		   sector_t sector, int size, struct page *page)
{
	/* write first size bytes of page to sector of rdev
	 * Increment mddev->pending_writes before returning
	 * and decrement it on completion, waking up sb_wait
	 * if zero is reached.
	 * If an error occurred, call md_error
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	 *
	 * As we might need to resubmit the request if BIO_RW_BARRIER
	 * causes ENOTSUPP, we allocate a spare bio...
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	 */
	struct bio *bio = bio_alloc(GFP_NOIO, 1);
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	int rw = (1<<BIO_RW) | (1<<BIO_RW_SYNC);
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	bio->bi_bdev = rdev->bdev;
	bio->bi_sector = sector;
	bio_add_page(bio, page, size, 0);
	bio->bi_private = rdev;
	bio->bi_end_io = super_written;
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	bio->bi_rw = rw;

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	atomic_inc(&mddev->pending_writes);
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	if (!test_bit(BarriersNotsupp, &rdev->flags)) {
		struct bio *rbio;
		rw |= (1<<BIO_RW_BARRIER);
		rbio = bio_clone(bio, GFP_NOIO);
		rbio->bi_private = bio;
		rbio->bi_end_io = super_written_barrier;
		submit_bio(rw, rbio);
	} else
		submit_bio(rw, bio);
}

void md_super_wait(mddev_t *mddev)
{
	/* wait for all superblock writes that were scheduled to complete.
	 * if any had to be retried (due to BARRIER problems), retry them
	 */
	DEFINE_WAIT(wq);
	for(;;) {
		prepare_to_wait(&mddev->sb_wait, &wq, TASK_UNINTERRUPTIBLE);
		if (atomic_read(&mddev->pending_writes)==0)
			break;
		while (mddev->biolist) {
			struct bio *bio;
			spin_lock_irq(&mddev->write_lock);
			bio = mddev->biolist;
			mddev->biolist = bio->bi_next ;
			bio->bi_next = NULL;
			spin_unlock_irq(&mddev->write_lock);
			submit_bio(bio->bi_rw, bio);
		}
		schedule();
	}
	finish_wait(&mddev->sb_wait, &wq);
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}

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static int bi_complete(struct bio *bio, unsigned int bytes_done, int error)
{
	if (bio->bi_size)
		return 1;

	complete((struct completion*)bio->bi_private);
	return 0;
}

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int sync_page_io(struct block_device *bdev, sector_t sector, int size,
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		   struct page *page, int rw)
{
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	struct bio *bio = bio_alloc(GFP_NOIO, 1);
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	struct completion event;
	int ret;

	rw |= (1 << BIO_RW_SYNC);

	bio->bi_bdev = bdev;
	bio->bi_sector = sector;
	bio_add_page(bio, page, size, 0);
	init_completion(&event);
	bio->bi_private = &event;
	bio->bi_end_io = bi_complete;
	submit_bio(rw, bio);
	wait_for_completion(&event);

	ret = test_bit(BIO_UPTODATE, &bio->bi_flags);
	bio_put(bio);
	return ret;
}
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EXPORT_SYMBOL_GPL(sync_page_io);
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static int read_disk_sb(mdk_rdev_t * rdev, int size)
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{
	char b[BDEVNAME_SIZE];
	if (!rdev->sb_page) {
		MD_BUG();
		return -EINVAL;
	}
	if (rdev->sb_loaded)
		return 0;


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	if (!sync_page_io(rdev->bdev, rdev->sb_offset<<1, size, rdev->sb_page, READ))
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		goto fail;
	rdev->sb_loaded = 1;
	return 0;

fail:
	printk(KERN_WARNING "md: disabled device %s, could not read superblock.\n",
		bdevname(rdev->bdev,b));
	return -EINVAL;
}

static int uuid_equal(mdp_super_t *sb1, mdp_super_t *sb2)
{
	if (	(sb1->set_uuid0 == sb2->set_uuid0) &&
		(sb1->set_uuid1 == sb2->set_uuid1) &&
		(sb1->set_uuid2 == sb2->set_uuid2) &&
		(sb1->set_uuid3 == sb2->set_uuid3))

		return 1;

	return 0;
}


static int sb_equal(mdp_super_t *sb1, mdp_super_t *sb2)
{
	int ret;
	mdp_super_t *tmp1, *tmp2;

	tmp1 = kmalloc(sizeof(*tmp1),GFP_KERNEL);
	tmp2 = kmalloc(sizeof(*tmp2),GFP_KERNEL);

	if (!tmp1 || !tmp2) {
		ret = 0;
		printk(KERN_INFO "md.c: sb1 is not equal to sb2!\n");
		goto abort;
	}

	*tmp1 = *sb1;
	*tmp2 = *sb2;

	/*
	 * nr_disks is not constant
	 */
	tmp1->nr_disks = 0;
	tmp2->nr_disks = 0;

	if (memcmp(tmp1, tmp2, MD_SB_GENERIC_CONSTANT_WORDS * 4))
		ret = 0;
	else
		ret = 1;

abort:
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	kfree(tmp1);
	kfree(tmp2);
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	return ret;
}

static unsigned int calc_sb_csum(mdp_super_t * sb)
{
	unsigned int disk_csum, csum;

	disk_csum = sb->sb_csum;
	sb->sb_csum = 0;
	csum = csum_partial((void *)sb, MD_SB_BYTES, 0);
	sb->sb_csum = disk_csum;
	return csum;
}


/*
 * Handle superblock details.
 * We want to be able to handle multiple superblock formats
 * so we have a common interface to them all, and an array of
 * different handlers.
 * We rely on user-space to write the initial superblock, and support
 * reading and updating of superblocks.
 * Interface methods are:
 *   int load_super(mdk_rdev_t *dev, mdk_rdev_t *refdev, int minor_version)
 *      loads and validates a superblock on dev.
 *      if refdev != NULL, compare superblocks on both devices
 *    Return:
 *      0 - dev has a superblock that is compatible with refdev
 *      1 - dev has a superblock that is compatible and newer than refdev
 *          so dev should be used as the refdev in future
 *     -EINVAL superblock incompatible or invalid
 *     -othererror e.g. -EIO
 *
 *   int validate_super(mddev_t *mddev, mdk_rdev_t *dev)
 *      Verify that dev is acceptable into mddev.
 *       The first time, mddev->raid_disks will be 0, and data from
 *       dev should be merged in.  Subsequent calls check that dev
 *       is new enough.  Return 0 or -EINVAL
 *
 *   void sync_super(mddev_t *mddev, mdk_rdev_t *dev)
 *     Update the superblock for rdev with data in mddev
 *     This does not write to disc.
 *
 */

struct super_type  {
	char 		*name;
	struct module	*owner;
	int		(*load_super)(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version);
	int		(*validate_super)(mddev_t *mddev, mdk_rdev_t *rdev);
	void		(*sync_super)(mddev_t *mddev, mdk_rdev_t *rdev);
};

/*
 * load_super for 0.90.0 
 */
static int super_90_load(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version)
{
	char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
	mdp_super_t *sb;
	int ret;
	sector_t sb_offset;

	/*
	 * Calculate the position of the superblock,
	 * it's at the end of the disk.
	 *
	 * It also happens to be a multiple of 4Kb.
	 */
	sb_offset = calc_dev_sboffset(rdev->bdev);
	rdev->sb_offset = sb_offset;

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	ret = read_disk_sb(rdev, MD_SB_BYTES);
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	if (ret) return ret;

	ret = -EINVAL;

	bdevname(rdev->bdev, b);
	sb = (mdp_super_t*)page_address(rdev->sb_page);

	if (sb->md_magic != MD_SB_MAGIC) {
		printk(KERN_ERR "md: invalid raid superblock magic on %s\n",
		       b);
		goto abort;
	}

	if (sb->major_version != 0 ||
	    sb->minor_version != 90) {
		printk(KERN_WARNING "Bad version number %d.%d on %s\n",
			sb->major_version, sb->minor_version,
			b);
		goto abort;
	}

	if (sb->raid_disks <= 0)
		goto abort;

	if (csum_fold(calc_sb_csum(sb)) != csum_fold(sb->sb_csum)) {
		printk(KERN_WARNING "md: invalid superblock checksum on %s\n",
			b);
		goto abort;
	}

	rdev->preferred_minor = sb->md_minor;
	rdev->data_offset = 0;
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	rdev->sb_size = MD_SB_BYTES;
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	if (sb->level == LEVEL_MULTIPATH)
		rdev->desc_nr = -1;
	else
		rdev->desc_nr = sb->this_disk.number;

	if (refdev == 0)
		ret = 1;
	else {
		__u64 ev1, ev2;
		mdp_super_t *refsb = (mdp_super_t*)page_address(refdev->sb_page);
		if (!uuid_equal(refsb, sb)) {
			printk(KERN_WARNING "md: %s has different UUID to %s\n",
				b, bdevname(refdev->bdev,b2));
			goto abort;
		}
		if (!sb_equal(refsb, sb)) {
			printk(KERN_WARNING "md: %s has same UUID"
			       " but different superblock to %s\n",
			       b, bdevname(refdev->bdev, b2));
			goto abort;
		}
		ev1 = md_event(sb);
		ev2 = md_event(refsb);
		if (ev1 > ev2)
			ret = 1;
		else 
			ret = 0;
	}
	rdev->size = calc_dev_size(rdev, sb->chunk_size);

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	if (rdev->size < sb->size && sb->level > 1)
		/* "this cannot possibly happen" ... */
		ret = -EINVAL;

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 abort:
	return ret;
}

/*
 * validate_super for 0.90.0
 */
static int super_90_validate(mddev_t *mddev, mdk_rdev_t *rdev)
{
	mdp_disk_t *desc;
	mdp_super_t *sb = (mdp_super_t *)page_address(rdev->sb_page);

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	rdev->raid_disk = -1;
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	rdev->flags = 0;
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	if (mddev->raid_disks == 0) {
		mddev->major_version = 0;
		mddev->minor_version = sb->minor_version;
		mddev->patch_version = sb->patch_version;
		mddev->persistent = ! sb->not_persistent;
		mddev->chunk_size = sb->chunk_size;
		mddev->ctime = sb->ctime;
		mddev->utime = sb->utime;
		mddev->level = sb->level;
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		mddev->clevel[0] = 0;
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		mddev->layout = sb->layout;
		mddev->raid_disks = sb->raid_disks;
		mddev->size = sb->size;
		mddev->events = md_event(sb);
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		mddev->bitmap_offset = 0;
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		mddev->default_bitmap_offset = MD_SB_BYTES >> 9;
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		if (sb->state & (1<<MD_SB_CLEAN))
			mddev->recovery_cp = MaxSector;
		else {
			if (sb->events_hi == sb->cp_events_hi && 
				sb->events_lo == sb->cp_events_lo) {
				mddev->recovery_cp = sb->recovery_cp;
			} else
				mddev->recovery_cp = 0;
		}

		memcpy(mddev->uuid+0, &sb->set_uuid0, 4);
		memcpy(mddev->uuid+4, &sb->set_uuid1, 4);
		memcpy(mddev->uuid+8, &sb->set_uuid2, 4);
		memcpy(mddev->uuid+12,&sb->set_uuid3, 4);

		mddev->max_disks = MD_SB_DISKS;
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		if (sb->state & (1<<MD_SB_BITMAP_PRESENT) &&
		    mddev->bitmap_file == NULL) {
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			if (mddev->level != 1 && mddev->level != 5 && mddev->level != 6
			    && mddev->level != 10) {
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				/* FIXME use a better test */
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				printk(KERN_WARNING "md: bitmaps not supported for this level.\n");
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				return -EINVAL;
			}
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			mddev->bitmap_offset = mddev->default_bitmap_offset;
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		}

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	} else if (mddev->pers == NULL) {
		/* Insist on good event counter while assembling */
		__u64 ev1 = md_event(sb);
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		++ev1;
		if (ev1 < mddev->events) 
			return -EINVAL;
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	} else if (mddev->bitmap) {
		/* if adding to array with a bitmap, then we can accept an
		 * older device ... but not too old.
		 */
		__u64 ev1 = md_event(sb);
		if (ev1 < mddev->bitmap->events_cleared)
			return 0;
	} else /* just a hot-add of a new device, leave raid_disk at -1 */
		return 0;

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	if (mddev->level != LEVEL_MULTIPATH) {
		desc = sb->disks + rdev->desc_nr;

		if (desc->state & (1<<MD_DISK_FAULTY))
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			set_bit(Faulty, &rdev->flags);
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		else if (desc->state & (1<<MD_DISK_SYNC) &&
			 desc->raid_disk < mddev->raid_disks) {
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			set_bit(In_sync, &rdev->flags);
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			rdev->raid_disk = desc->raid_disk;
		}
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		if (desc->state & (1<<MD_DISK_WRITEMOSTLY))
			set_bit(WriteMostly, &rdev->flags);
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	} else /* MULTIPATH are always insync */
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		set_bit(In_sync, &rdev->flags);
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	return 0;
}

/*
 * sync_super for 0.90.0
 */
static void super_90_sync(mddev_t *mddev, mdk_rdev_t *rdev)
{
	mdp_super_t *sb;
	struct list_head *tmp;
	mdk_rdev_t *rdev2;
	int next_spare = mddev->raid_disks;
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	/* make rdev->sb match mddev data..
	 *
	 * 1/ zero out disks
	 * 2/ Add info for each disk, keeping track of highest desc_nr (next_spare);
	 * 3/ any empty disks < next_spare become removed
	 *
	 * disks[0] gets initialised to REMOVED because
	 * we cannot be sure from other fields if it has
	 * been initialised or not.
	 */
	int i;
	int active=0, working=0,failed=0,spare=0,nr_disks=0;

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	rdev->sb_size = MD_SB_BYTES;

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	sb = (mdp_super_t*)page_address(rdev->sb_page);

	memset(sb, 0, sizeof(*sb));

	sb->md_magic = MD_SB_MAGIC;
	sb->major_version = mddev->major_version;
	sb->minor_version = mddev->minor_version;
	sb->patch_version = mddev->patch_version;
	sb->gvalid_words  = 0; /* ignored */
	memcpy(&sb->set_uuid0, mddev->uuid+0, 4);
	memcpy(&sb->set_uuid1, mddev->uuid+4, 4);
	memcpy(&sb->set_uuid2, mddev->uuid+8, 4);
	memcpy(&sb->set_uuid3, mddev->uuid+12,4);

	sb->ctime = mddev->ctime;
	sb->level = mddev->level;
	sb->size  = mddev->size;
	sb->raid_disks = mddev->raid_disks;
	sb->md_minor = mddev->md_minor;
	sb->not_persistent = !mddev->persistent;
	sb->utime = mddev->utime;
	sb->state = 0;
	sb->events_hi = (mddev->events>>32);
	sb->events_lo = (u32)mddev->events;

	if (mddev->in_sync)
	{
		sb->recovery_cp = mddev->recovery_cp;
		sb->cp_events_hi = (mddev->events>>32);
		sb->cp_events_lo = (u32)mddev->events;
		if (mddev->recovery_cp == MaxSector)
			sb->state = (1<< MD_SB_CLEAN);
	} else
		sb->recovery_cp = 0;

	sb->layout = mddev->layout;
	sb->chunk_size = mddev->chunk_size;

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	if (mddev->bitmap && mddev->bitmap_file == NULL)
		sb->state |= (1<<MD_SB_BITMAP_PRESENT);

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	sb->disks[0].state = (1<<MD_DISK_REMOVED);
	ITERATE_RDEV(mddev,rdev2,tmp) {
		mdp_disk_t *d;
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		int desc_nr;
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		if (rdev2->raid_disk >= 0 && test_bit(In_sync, &rdev2->flags)
		    && !test_bit(Faulty, &rdev2->flags))
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			desc_nr = rdev2->raid_disk;
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		else
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			desc_nr = next_spare++;
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		rdev2->desc_nr = desc_nr;
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		d = &sb->disks[rdev2->desc_nr];
		nr_disks++;
		d->number = rdev2->desc_nr;
		d->major = MAJOR(rdev2->bdev->bd_dev);
		d->minor = MINOR(rdev2->bdev->bd_dev);
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		if (rdev2->raid_disk >= 0 && test_bit(In_sync, &rdev2->flags)
		    && !test_bit(Faulty, &rdev2->flags))
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			d->raid_disk = rdev2->raid_disk;
		else
			d->raid_disk = rdev2->desc_nr; /* compatibility */
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		if (test_bit(Faulty, &rdev2->flags)) {
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			d->state = (1<<MD_DISK_FAULTY);
			failed++;
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		} else if (test_bit(In_sync, &rdev2->flags)) {
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			d->state = (1<<MD_DISK_ACTIVE);
			d->state |= (1<<MD_DISK_SYNC);
			active++;
			working++;
		} else {
			d->state = 0;
			spare++;
			working++;
		}
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		if (test_bit(WriteMostly, &rdev2->flags))
			d->state |= (1<<MD_DISK_WRITEMOSTLY);
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	}
	/* now set the "removed" and "faulty" bits on any missing devices */
	for (i=0 ; i < mddev->raid_disks ; i++) {
		mdp_disk_t *d = &sb->disks[i];
		if (d->state == 0 && d->number == 0) {
			d->number = i;
			d->raid_disk = i;
			d->state = (1<<MD_DISK_REMOVED);
			d->state |= (1<<MD_DISK_FAULTY);
			failed++;
		}
	}
	sb->nr_disks = nr_disks;
	sb->active_disks = active;
	sb->working_disks = working;
	sb->failed_disks = failed;
	sb->spare_disks = spare;

	sb->this_disk = sb->disks[rdev->desc_nr];
	sb->sb_csum = calc_sb_csum(sb);
}

/*
 * version 1 superblock
 */

static unsigned int calc_sb_1_csum(struct mdp_superblock_1 * sb)
{
	unsigned int disk_csum, csum;
	unsigned long long newcsum;
	int size = 256 + le32_to_cpu(sb->max_dev)*2;
	unsigned int *isuper = (unsigned int*)sb;
	int i;

	disk_csum = sb->sb_csum;
	sb->sb_csum = 0;
	newcsum = 0;
	for (i=0; size>=4; size -= 4 )
		newcsum += le32_to_cpu(*isuper++);

	if (size == 2)
		newcsum += le16_to_cpu(*(unsigned short*) isuper);

	csum = (newcsum & 0xffffffff) + (newcsum >> 32);
	sb->sb_csum = disk_csum;
	return cpu_to_le32(csum);
}

static int super_1_load(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version)
{
	struct mdp_superblock_1 *sb;
	int ret;
	sector_t sb_offset;
	char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
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	int bmask;
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	/*
	 * Calculate the position of the superblock.
	 * It is always aligned to a 4K boundary and
	 * depeding on minor_version, it can be:
	 * 0: At least 8K, but less than 12K, from end of device
	 * 1: At start of device
	 * 2: 4K from start of device.
	 */
	switch(minor_version) {
	case 0:
		sb_offset = rdev->bdev->bd_inode->i_size >> 9;
		sb_offset -= 8*2;
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		sb_offset &= ~(sector_t)(4*2-1);
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		/* convert from sectors to K */
		sb_offset /= 2;
		break;
	case 1:
		sb_offset = 0;
		break;
	case 2:
		sb_offset = 4;
		break;
	default:
		return -EINVAL;
	}
	rdev->sb_offset = sb_offset;

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	/* superblock is rarely larger than 1K, but it can be larger,
	 * and it is safe to read 4k, so we do that
	 */
	ret = read_disk_sb(rdev, 4096);
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	if (ret) return ret;


	sb = (struct mdp_superblock_1*)page_address(rdev->sb_page);

	if (sb->magic != cpu_to_le32(MD_SB_MAGIC) ||
	    sb->major_version != cpu_to_le32(1) ||
	    le32_to_cpu(sb->max_dev) > (4096-256)/2 ||
	    le64_to_cpu(sb->super_offset) != (rdev->sb_offset<<1) ||
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	    (le32_to_cpu(sb->feature_map) & ~MD_FEATURE_ALL) != 0)
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		return -EINVAL;

	if (calc_sb_1_csum(sb) != sb->sb_csum) {
		printk("md: invalid superblock checksum on %s\n",
			bdevname(rdev->bdev,b));
		return -EINVAL;
	}
	if (le64_to_cpu(sb->data_size) < 10) {
		printk("md: data_size too small on %s\n",
		       bdevname(rdev->bdev,b));
		return -EINVAL;
	}
	rdev->preferred_minor = 0xffff;
	rdev->data_offset = le64_to_cpu(sb->data_offset);
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	atomic_set(&rdev->corrected_errors, le32_to_cpu(sb->cnt_corrected_read));
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	rdev->sb_size = le32_to_cpu(sb->max_dev) * 2 + 256;
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	bmask = queue_hardsect_size(rdev->bdev->bd_disk->queue)-1;
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	if (rdev->sb_size & bmask)
		rdev-> sb_size = (rdev->sb_size | bmask)+1;

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	if (refdev == 0)
		return 1;
	else {
		__u64 ev1, ev2;
		struct mdp_superblock_1 *refsb = 
			(struct mdp_superblock_1*)page_address(refdev->sb_page);

		if (memcmp(sb->set_uuid, refsb->set_uuid, 16) != 0 ||
		    sb->level != refsb->level ||
		    sb->layout != refsb->layout ||
		    sb->chunksize != refsb->chunksize) {
			printk(KERN_WARNING "md: %s has strangely different"
				" superblock to %s\n",
				bdevname(rdev->bdev,b),
				bdevname(refdev->bdev,b2));
			return -EINVAL;
		}
		ev1 = le64_to_cpu(sb->events);
		ev2 = le64_to_cpu(refsb->events);

		if (ev1 > ev2)
			return 1;
	}
	if (minor_version) 
		rdev->size = ((rdev->bdev->bd_inode->i_size>>9) - le64_to_cpu(sb->data_offset)) / 2;
	else
		rdev->size = rdev->sb_offset;
	if (rdev->size < le64_to_cpu(sb->data_size)/2)
		return -EINVAL;
	rdev->size = le64_to_cpu(sb->data_size)/2;
	if (le32_to_cpu(sb->chunksize))
		rdev->size &= ~((sector_t)le32_to_cpu(sb->chunksize)/2 - 1);
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	if (le32_to_cpu(sb->size) > rdev->size*2)
		return -EINVAL;
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	return 0;
}

static int super_1_validate(mddev_t *mddev, mdk_rdev_t *rdev)
{
	struct mdp_superblock_1 *sb = (struct mdp_superblock_1*)page_address(rdev->sb_page);

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	rdev->raid_disk = -1;
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	rdev->flags = 0;
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	if (mddev->raid_disks == 0) {
		mddev->major_version = 1;
		mddev->patch_version = 0;
		mddev->persistent = 1;
		mddev->chunk_size = le32_to_cpu(sb->chunksize) << 9;
		mddev->ctime = le64_to_cpu(sb->ctime) & ((1ULL << 32)-1);
		mddev->utime = le64_to_cpu(sb->utime) & ((1ULL << 32)-1);
		mddev->level = le32_to_cpu(sb->level);
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		mddev->clevel[0] = 0;
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		mddev->layout = le32_to_cpu(sb->layout);
		mddev->raid_disks = le32_to_cpu(sb->raid_disks);
		mddev->size = le64_to_cpu(sb->size)/2;
		mddev->events = le64_to_cpu(sb->events);
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		mddev->bitmap_offset = 0;
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		mddev->default_bitmap_offset = 1024;
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		mddev->recovery_cp = le64_to_cpu(sb->resync_offset);
		memcpy(mddev->uuid, sb->set_uuid, 16);

		mddev->max_disks =  (4096-256)/2;
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		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
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		    mddev->bitmap_file == NULL ) {
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			if (mddev->level != 1 && mddev->level != 5 && mddev->level != 6
			    && mddev->level != 10) {
				printk(KERN_WARNING "md: bitmaps not supported for this level.\n");
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				return -EINVAL;
			}
			mddev->bitmap_offset = (__s32)le32_to_cpu(sb->bitmap_offset);
		}
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	} else if (mddev->pers == NULL) {
		/* Insist of good event counter while assembling */
		__u64 ev1 = le64_to_cpu(sb->events);
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		++ev1;
		if (ev1 < mddev->events)
			return -EINVAL;
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	} else if (mddev->bitmap) {
		/* If adding to array with a bitmap, then we can accept an
		 * older device, but not too old.
		 */
		__u64 ev1 = le64_to_cpu(sb->events);
		if (ev1 < mddev->bitmap->events_cleared)
			return 0;
	} else /* just a hot-add of a new device, leave raid_disk at -1 */
		return 0;
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	if (mddev->level != LEVEL_MULTIPATH) {
		int role;
		rdev->desc_nr = le32_to_cpu(sb->dev_number);
		role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
		switch(role) {
		case 0xffff: /* spare */
			break;
		case 0xfffe: /* faulty */
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			set_bit(Faulty, &rdev->flags);
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			break;
		default:
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			set_bit(In_sync, &rdev->flags);
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			rdev->raid_disk = role;
			break;
		}
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		if (sb->devflags & WriteMostly1)
			set_bit(WriteMostly, &rdev->flags);
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	} else /* MULTIPATH are always insync */
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		set_bit(In_sync, &rdev->flags);
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	return 0;
}

static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
{
	struct mdp_superblock_1 *sb;
	struct list_head *tmp;
	mdk_rdev_t *rdev2;
	int max_dev, i;
	/* make rdev->sb match mddev and rdev data. */

	sb = (struct mdp_superblock_1*)page_address(rdev->sb_page);

	sb->feature_map = 0;
	sb->pad0 = 0;
	memset(sb->pad1, 0, sizeof(sb->pad1));
	memset(sb->pad2, 0, sizeof(sb->pad2));
	memset(sb->pad3, 0, sizeof(sb->pad3));

	sb->utime = cpu_to_le64((__u64)mddev->utime);
	sb->events = cpu_to_le64(mddev->events);
	if (mddev->in_sync)
		sb->resync_offset = cpu_to_le64(mddev->recovery_cp);
	else
		sb->resync_offset = cpu_to_le64(0);

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	sb->cnt_corrected_read = atomic_read(&rdev->corrected_errors);

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	if (mddev->bitmap && mddev->bitmap_file == NULL) {
		sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_offset);
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		sb->feature_map = cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);
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	}

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	max_dev = 0;
	ITERATE_RDEV(mddev,rdev2,tmp)
		if (rdev2->desc_nr+1 > max_dev)
			max_dev = rdev2->desc_nr+1;
	
	sb->max_dev = cpu_to_le32(max_dev);
	for (i=0; i<max_dev;i++)
		sb->dev_roles[i] = cpu_to_le16(0xfffe);
	
	ITERATE_RDEV(mddev,rdev2,tmp) {
		i = rdev2->desc_nr;
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		if (test_bit(Faulty, &rdev2->flags))
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			sb->dev_roles[i] = cpu_to_le16(0xfffe);
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		else if (test_bit(In_sync, &rdev2->flags))
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			sb->dev_roles[i] = cpu_to_le16(rdev2->raid_disk);
		else
			sb->dev_roles[i] = cpu_to_le16(0xffff);
	}

	sb->recovery_offset = cpu_to_le64(0); /* not supported yet */
	sb->sb_csum = calc_sb_1_csum(sb);
}


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static struct super_type super_types[] = {
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	[0] = {
		.name	= "0.90.0",
		.owner	= THIS_MODULE,
		.load_super	= super_90_load,
		.validate_super	= super_90_validate,
		.sync_super	= super_90_sync,
	},
	[1] = {
		.name	= "md-1",
		.owner	= THIS_MODULE,
		.load_super	= super_1_load,
		.validate_super	= super_1_validate,
		.sync_super	= super_1_sync,
	},
};
	
static mdk_rdev_t * match_dev_unit(mddev_t *mddev, mdk_rdev_t *dev)
{
	struct list_head *tmp;
	mdk_rdev_t *rdev;

	ITERATE_RDEV(mddev,rdev,tmp)
		if (rdev->bdev->bd_contains == dev->bdev->bd_contains)
			return rdev;

	return NULL;
}

static int match_mddev_units(mddev_t *mddev1, mddev_t *mddev2)
{
	struct list_head *tmp;
	mdk_rdev_t *rdev;

	ITERATE_RDEV(mddev1,rdev,tmp)
		if (match_dev_unit(mddev2, rdev))
			return 1;

	return 0;
}

static LIST_HEAD(pending_raid_disks);

static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev)
{
	mdk_rdev_t *same_pdev;
	char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
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	struct kobject *ko;
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	if (rdev->mddev) {
		MD_BUG();
		return -EINVAL;
	}
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	/* make sure rdev->size exceeds mddev->size */
	if (rdev->size && (mddev->size == 0 || rdev->size < mddev->size)) {
		if (mddev->pers)
			/* Cannot change size, so fail */
			return -ENOSPC;
		else
			mddev->size = rdev->size;
	}
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	same_pdev = match_dev_unit(mddev, rdev);
	if (same_pdev)
		printk(KERN_WARNING
			"%s: WARNING: %s appears to be on the same physical"
	 		" disk as %s. True\n     protection against single-disk"
			" failure might be compromised.\n",
			mdname(mddev), bdevname(rdev->bdev,b),
			bdevname(same_pdev->bdev,b2));

	/* Verify rdev->desc_nr is unique.
	 * If it is -1, assign a free number, else
	 * check number is not in use
	 */
	if (rdev->desc_nr < 0) {
		int choice = 0;
		if (mddev->pers) choice = mddev->raid_disks;
		while (find_rdev_nr(mddev, choice))
			choice++;
		rdev->desc_nr = choice;
	} else {
		if (find_rdev_nr(mddev, rdev->desc_nr))
			return -EBUSY;
	}
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	bdevname(rdev->bdev,b);
	if (kobject_set_name(&rdev->kobj, "dev-%s", b) < 0)
		return -ENOMEM;
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	list_add(&rdev->same_set, &mddev->disks);
	rdev->mddev = mddev;
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	printk(KERN_INFO "md: bind<%s>\n", b);
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	rdev->kobj.parent = &mddev->kobj;
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	kobject_add(&rdev->kobj);

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	if (rdev->bdev->bd_part)
		ko = &rdev->bdev->bd_part->kobj;
	else
		ko = &rdev->bdev->bd_disk->kobj;
	sysfs_create_link(&rdev->kobj, ko, "block");
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	return 0;
}

static void unbind_rdev_from_array(mdk_rdev_t * rdev)
{
	char b[BDEVNAME_SIZE];
	if (!rdev->mddev) {
		MD_BUG();
		return;
	}
	list_del_init(&rdev->same_set);
	printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b));
	rdev->mddev = NULL;
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	sysfs_remove_link(&rdev->kobj, "block");
	kobject_del(&rdev->kobj);
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}

/*
 * prevent the device from being mounted, repartitioned or
 * otherwise reused by a RAID array (or any other kernel
 * subsystem), by bd_claiming the device.
 */
static int lock_rdev(mdk_rdev_t *rdev, dev_t dev)
{
	int err = 0;
	struct block_device *bdev;
	char b[BDEVNAME_SIZE];

	bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE);
	if (IS_ERR(bdev)) {
		printk(KERN_ERR "md: could not open %s.\n",
			__bdevname(dev, b));
		return PTR_ERR(bdev);
	}
	err = bd_claim(bdev, rdev);
	if (err) {
		printk(KERN_ERR "md: could not bd_claim %s.\n",
			bdevname(bdev, b));
		blkdev_put(bdev);
		return err;
	}
	rdev->bdev = bdev;
	return err;
}

static void unlock_rdev(mdk_rdev_t *rdev)
{
	struct block_device *bdev = rdev->bdev;
	rdev->bdev = NULL;
	if (!bdev)
		MD_BUG();
	bd_release(bdev);
	blkdev_put(bdev);
}

void md_autodetect_dev(dev_t dev);

static void export_rdev(mdk_rdev_t * rdev)
{
	char b[BDEVNAME_SIZE];
	printk(KERN_INFO "md: export_rdev(%s)\n",
		bdevname(rdev->bdev,b));
	if (rdev->mddev)
		MD_BUG();
	free_disk_sb(rdev);
	list_del_init(&rdev->same_set);
#ifndef MODULE
	md_autodetect_dev(rdev->bdev->bd_dev);
#endif
	unlock_rdev(rdev);
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	kobject_put(&rdev->kobj);
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}

static void kick_rdev_from_array(mdk_rdev_t * rdev)
{
	unbind_rdev_from_array(rdev);
	export_rdev(rdev);
}

static void export_array(mddev_t *mddev)
{
	struct list_head *tmp;
	mdk_rdev_t *rdev;

	ITERATE_RDEV(mddev,rdev,tmp) {
		if (!rdev->mddev) {
			MD_BUG();
			continue;
		}
		kick_rdev_from_array(rdev);
	}
	if (!list_empty(&mddev->disks))
		MD_BUG();
	mddev->raid_disks = 0;
	mddev->major_version = 0;
}

static void print_desc(mdp_disk_t *desc)
{
	printk(" DISK<N:%d,(%d,%d),R:%d,S:%d>\n", desc->number,
		desc->major,desc->minor,desc->raid_disk,desc->state);
}

static void print_sb(mdp_super_t *sb)
{
	int i;

	printk(KERN_INFO 
		"md:  SB: (V:%d.%d.%d) ID:<%08x.%08x.%08x.%08x> CT:%08x\n",
		sb->major_version, sb->minor_version, sb->patch_version,
		sb->set_uuid0, sb->set_uuid1, sb->set_uuid2, sb->set_uuid3,
		sb->ctime);
	printk(KERN_INFO "md:     L%d S%08d ND:%d RD:%d md%d LO:%d CS:%d\n",
		sb->level, sb->size, sb->nr_disks, sb->raid_disks,
		sb->md_minor, sb->layout, sb->chunk_size);
	printk(KERN_INFO "md:     UT:%08x ST:%d AD:%d WD:%d"
		" FD:%d SD:%d CSUM:%08x E:%08lx\n",
		sb->utime, sb->state, sb->active_disks, sb->working_disks,
		sb->failed_disks, sb->spare_disks,
		sb->sb_csum, (unsigned long)sb->events_lo);

	printk(KERN_INFO);
	for (i = 0; i < MD_SB_DISKS; i++) {
		mdp_disk_t *desc;

		desc = sb->disks + i;
		if (desc->number || desc->major || desc->minor ||
		    desc->raid_disk || (desc->state && (desc->state != 4))) {
			printk("     D %2d: ", i);
			print_desc(desc);
		}
	}
	printk(KERN_INFO "md:     THIS: ");
	print_desc(&sb->this_disk);

}

static void print_rdev(mdk_rdev_t *rdev)
{
	char b[BDEVNAME_SIZE];
	printk(KERN_INFO "md: rdev %s, SZ:%08llu F:%d S:%d DN:%u\n",
		bdevname(rdev->bdev,b), (unsigned long long)rdev->size,
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	        test_bit(Faulty, &rdev->flags), test_bit(In_sync, &rdev->flags),
	        rdev->desc_nr);
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	if (rdev->sb_loaded) {
		printk(KERN_INFO "md: rdev superblock:\n");
		print_sb((mdp_super_t*)page_address(rdev->sb_page));
	} else
		printk(KERN_INFO "md: no rdev superblock!\n");
}

void md_print_devices(void)
{
	struct list_head *tmp, *tmp2;
	mdk_rdev_t *rdev;
	mddev_t *mddev;
	char b[BDEVNAME_SIZE];

	printk("\n");
	printk("md:	**********************************\n");
	printk("md:	* <COMPLETE RAID STATE PRINTOUT> *\n");
	printk("md:	**********************************\n");
	ITERATE_MDDEV(mddev,tmp) {

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		if (mddev->bitmap)
			bitmap_print_sb(mddev->bitmap);
		else
			printk("%s: ", mdname(mddev));
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		ITERATE_RDEV(mddev,rdev,tmp2)
			printk("<%s>", bdevname(rdev->bdev,b));
		printk("\n");

		ITERATE_RDEV(mddev,rdev,tmp2)
			print_rdev(rdev);
	}
	printk("md:	**********************************\n");
	printk("\n");
}


static void sync_sbs(mddev_t * mddev)
{
	mdk_rdev_t *rdev;
	struct list_head *tmp;

	ITERATE_RDEV(mddev,rdev,tmp) {
		super_types[mddev->major_version].
			sync_super(mddev, rdev);
		rdev->sb_loaded = 1;
	}
}

static void md_update_sb(mddev_t * mddev)
{
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	int err;
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	struct list_head *tmp;
	mdk_rdev_t *rdev;
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	int sync_req;
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repeat:
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	spin_lock_irq(&mddev->write_lock);