[PATCH] md: expose md metadata format in sysfs

     the array if the personality supports it (raid1, raid5, raid6),

     and if the component drives are large enough.

  metadata_version

     This indicates the format that is being used to record metadata

     about the array.  It can be 0.90 (traditional format), 1.0, 1.1,

     1.2 (newer format in varying locations) or "none" indicating that

     the kernel isn't managing metadata at all.

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_size =

__ATTR(component_size, 0644, size_show, size_store);

/* Metdata version.

 * This is either 'none' for arrays with externally managed metadata,

 * or N.M for internally known formats

 */

static ssize_t

metadata_show(mddev_t *mddev, char *page)

{

	if (mddev->persistent)

		return sprintf(page, "%d.%d\n",

			       mddev->major_version, mddev->minor_version);

	else

		return sprintf(page, "none\n");

}

static ssize_t

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

{

	int major, minor;

	char *e;

	if (!list_empty(&mddev->disks))

		return -EBUSY;

	if (cmd_match(buf, "none")) {

		mddev->persistent = 0;

		mddev->major_version = 0;

		mddev->minor_version = 90;

		return len;

	}

	major = simple_strtoul(buf, &e, 10);

	if (e==buf || *e != '.')

		return -EINVAL;

	buf = e+1;

	minor = simple_strtoul(buf, &e, 10);

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

		return -EINVAL;

	if (major >= sizeof(super_types)/sizeof(super_types[0]) ||

	    super_types[major].name == NULL)

		return -ENOENT;

	mddev->major_version = major;

	mddev->minor_version = minor;

	mddev->persistent = 1;

	return len;

}

static struct md_sysfs_entry md_metadata =

__ATTR(metadata_version, 0644, metadata_show, metadata_store);

static ssize_t

action_show(mddev_t *mddev, char *page)

{

	&md_raid_disks.attr,

	&md_chunk_size.attr,

	&md_size.attr,

	&md_metadata.attr,

	NULL,

};