[PATCH] md: allow chunk_size to be settable through sysfs

     will be empty.  If an array is being resized (not currently

     possible) this will contain the larger of the old and new sizes.

  chunk_size

     This is the size if bytes for 'chunks' and is only relevant to

     raid levels that involve striping (1,4,5,6,10). The address space

     of the array is conceptually divided into chunks and consecutive

     chunks are striped onto neighbouring devices.

     The size should be atleast PAGE_SIZE (4k) and should be a power

     of 2.  This can only be set while assembling an array

As component devices are added to an md array, they appear in the 'md'

directory as new directories named

      dev-XXX

static struct md_sysfs_entry md_raid_disks = __ATTR_RO(raid_disks);

static ssize_t

chunk_size_show(mddev_t *mddev, char *page)

{

	return sprintf(page, "%d\n", mddev->chunk_size);

}

static ssize_t

chunk_size_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 n = simple_strtoul(buf, &e, 10);

	if (mddev->pers)

		return -EBUSY;

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

		return -EINVAL;

	mddev->chunk_size = n;

	return len;

}

static struct md_sysfs_entry md_chunk_size =

__ATTR(chunk_size, 0644, chunk_size_show, chunk_size_store);

static ssize_t

action_show(mddev_t *mddev, char *page)

{

static struct attribute *md_default_attrs[] = {

	&md_level.attr,

	&md_raid_disks.attr,

	&md_chunk_size.attr,

	NULL,

};