Just FYI:

In message <20010711213834.A240@antioche.eu.org>
	on Wed, 11 Jul 2001 21:38:34 +0200,
	Manuel Bouyer <bouyer@antioche.lip6.fr> wrote:
> As far as I know there's no way to reassign a bad block on IDE disk (no IDE
> command for that). The drive should do it by itself, if it can't maybe
> there's no spare blocks left.
In my experience, IDE disk drive reassigns a bad block with spare one
when writing to the bad block occured (but not when reading).

In my real world, I added "write to a sector when it can't read"
function to FreeBSD 2.2.8's bad144(8) which has an option doing bad
block scan check for registering to bad144 table.

So, implementing "write to a sector when it can't read" tool might be
useful.  (Device driver itself could it, but I don't think it is good
thing.)

--
Takahiro Kambe <taca@sky.yamashina.kyoto.jp>