All places where we do blkdev_size_in_bytes(sb->s_dev) are bogus - we
can get the same information from ->s_bdev without messing with kdev_t,
major/minor, etc.

There will be more patches of that kind - in the long run I'd expect
only one caller of blkdev_size_in_bytes() to survive.  One if
fs/block_dev.c, that is - called when we open device.