mdadm: bad block support for external metadata - initialization

mdadm: bad block support for external metadata - initialization

If metadata handler provides support for bad blocks, tell md by writing
'external_bbl' to rdev state file (both on create and assemble),
followed by a list of known bad blocks written via sysfs 'bad_blocks'
file.

Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Reviewed-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>