Patch from Hugh Dickins <hugh@veritas.com>

Fix premature -EIO from blkdev_get_block: bdget initialize
bd_block_size consistent with bd_inode->i_blkbits (assigned by
new_inode).  Otherwise, subsequent set_blocksize can find bd_block_size
doesn't need updating, and skip updating i_blkbits, leaving them
inconsistent.