[PATCH] md: Allow resync_start to be set and queried via sysfs

     simply a number that is interpretted differently by different

     levels.  It can be written while assembling an array.

  resync_start

     The point at which resync should start.  If no resync is needed,

     this will be a very large number.  At array creation it will

     default to 0, though starting the array as 'clean' will

     set it much larger.

   new_dev

     This file can be written but not read.  The value written should

     be a block device number as major:minor.  e.g. 8:0

static struct md_sysfs_entry md_chunk_size =

__ATTR(chunk_size, 0644, chunk_size_show, chunk_size_store);

static ssize_t

resync_start_show(mddev_t *mddev, char *page)

{

	return sprintf(page, "%llu\n", (unsigned long long)mddev->recovery_cp);

}

static ssize_t

resync_start_store(mddev_t *mddev, const char *buf, size_t len)

{

	/* can only set chunk_size if array is not yet active */

	char *e;

	unsigned long long n = simple_strtoull(buf, &e, 10);

	if (mddev->pers)

		return -EBUSY;

	if (!*buf || (*e && *e != '\n'))

		return -EINVAL;

	mddev->recovery_cp = n;

	return len;

}

static struct md_sysfs_entry md_resync_start =

__ATTR(resync_start, 0644, resync_start_show, resync_start_store);

/*

 * The array state can be:

 *

	&md_raid_disks.attr,

	&md_chunk_size.attr,

	&md_size.attr,

	&md_resync_start.attr,

	&md_metadata.attr,

	&md_new_device.attr,

	&md_safe_delay.attr,

		mddev->array_size = 0;

		mddev->size = 0;

		mddev->raid_disks = 0;

		mddev->recovery_cp = 0;

		disk = mddev->gendisk;

		if (disk)